Tesi sul tema "Nitrogen Metabolism"
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1
Fulayfil, Nada. "Nitrogen metabolism of Archaeoglobus fulgidus". Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270335.
2
Stevens, Carol Jean. "Nitrogen metabolism by Thiobacillus ferrooxidans /". The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487597424138725.
3
Silva, Cesar José da [UNESP]. "Efeito de diferentes relações folha/grãos sobre o metabolismo do nitrogênio em diferentes partes da planta de milho". Universidade Estadual Paulista (UNESP), 2002. http://hdl.handle.net/11449/96968.
Abstract (sommario):
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silva_cj_me_jabo.pdf: 651711 bytes, checksum: 6f7b9a354cd661de53615cc81e866c62 (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Embora esteja bem estabelecido pelos experimentos clássicos, qual são os fatores que limitam a produção, o funcionamento da planta na fase reprodutiva que envolve um complexo relacionamento tanto entre órgãos fonte e dreno de fotossintatos como do metabolismo do nitrogênio em ambos os tipos de órgãos, ainda permanece pouco esclarecido. Assim sendo, na fase de polinização foram impostas diferentes proporções de folhas (% de fonte) e de grãos (% de dreno) em plantas de milho para estudar o efeito destes tratamentos sobre o comportamento do metabolismo do nitrogênio em grãos, folhas e colmos, em diferentes etapas da fase reprodutiva da cultura e suas relações com a produção de massa seca, desenvolvimento de grãos, bem como desenvolvimento e senescência das folhas. Avaliou-se atividade de algumas enzimas, o teor dos principais metabólitos nitrogendados nas folhas, nos colmos e nos grãos em formação, bem como os reflexos destas variáveis sobre algumas características agronômicas aos 2, 10, 20 e 30 dias após a polinização (dap). Os resultados do presente trabalho permitiram esclarecer que a atividade da redutase do nitrato na folha não foi afetada pelas alterações nas proporções de fonte e dreno de fotossintatos. Os teores de N-total, N-nitrato e N-aminoácidos livres, nas folhas, colmos e endospermas foram mais intensamente afetados quanto mais drásticas foram as reduções de folhas ou grãos. As reduções da fonte e dreno promoveram aumentos significativos nos teores de N-total, N-nitrato e N-aminoácidos livres nas partes remanescentes analisadas. Os teores de proteína solúvel foram mais afetados nos grãos, onde os maiores valores foram encontrados aos 10 dap., nos tratamentos sem folhas e sem grãos...
Although it is well very established, for the classic experiments, which are the factors that limit the production, the operation of the plant in the reproductive phase that involves a compound so much relationship between organs source and fotossintatos drain as of the metabolism of the nitrogen in both types of organs, it remains unclear. Like this being, in the pollination phase different proportions of leaves were imposed (% of source) and of grains (% of drain) in corn plants to study the effect of these treatments on the behavior of nitrogen metabolism in grains, leaves and stems, in different stages during reproductive phase of the culture and your relationships with the production of dry mass, development of grains, as well as development and senescence of leaves. Enzymes activity were evaluated (NR, TGO and TGP), the level of main metabolites (N-total, N-nitrate, free amino acids and soluble protein) in the leaves, in the stems and in the grains in formation, as well as the reflexes of these varied on the agronomic characteristics (mass evaporates of leaves stems and grains), to the 2, 10, 20 and 30 days after the pollination (dap). The results of the present work allowed to clear that the activity of the nitrate reductase in the leaf was not affected by the alterations in the source proportions and photoassimilated drain. The levels of N-total, N-nitrate and free N-amino acids, in the leaves, stems and endosperms were more intensely affected the more drastic they were the reductions of leaves or grains. The reductions of the source and drain promoted significant increases in the levels of N-total, N-nitrate and free N-amino acids in the analyzed remaining parts. The soluble protein concentration was more affected in the grains, where the largest values were found to the 10 dap, in the treatments without leaves and grains... (Complete abstract, click eletronic address below).
4
Laberge, MacDonald Tammy. "Molecular Aspects of Nitrogen Metabolism in Fishes". Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/668.
Abstract (sommario):
Molecular aspects of nitrogen metabolism in vertebrates is an interesting area of physiology and evolution to explore due to the different ways in which animals excrete nitrogenous waste as they transition from an aquatic to a terrestrial lifestyle. Two main products of nitrogen metabolism in fishes are ammonia and urea. Ammonia is produced during protein catabolism and build up of ammonia is toxic. Some aquatic vertebrates convert ammonia into a less toxic compound urea via de novo synthesis through the ornithine-urea cycle (O-UC). Five enzymes are involved in the O-UC: carbamoyl phosphate synthetase (CPS), ornithine carbamoyl transferase (OCT), argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL), and arginase (ARG). An accessory enzyme, glutamine synthetase (GS) also participates in the "fish-type" O-UC. Teleosts excrete ammonia passively over their gills into the aquatic environment. The teleost, Opsanus beta, has been shown to increase urea production after 48 hours of crowding. This thesis explored how crowding stress affected nitrogen metabolite levels of ammonia and urea and O-UC gene expression and enzyme activity in O. beta. Lungfishes while in an aquatic environment avoid ammonia toxicity by releasing excess ammonia across their gills, but when stranded on land they produce urea through the O-UC. Urea production via the O-UC has a metabolic cost of at least four ATP molecules. This thesis explored the response of a lungfish, Protopterus annectens, to six days of aerial exposure and re-immersion conditions by measuring concentrations of O-UC mRNA expression and enzyme activity and nitrogen metabolites ammonia and urea. CPS acts as the entry point to the O-UC and based on enzymatic studies, most aquatic vertebrates utilize one isoform of this enzyme (CPSIII) while terrestrial vertebrates utilize a different isoform of this enzyme (CPSI). Lungfishes are a particularly interesting group of air-breathing fishes, not only because of their link to the origins of tetrapods, but also because CPS I may have originated within this group. Both CPS III and CPS I have been enzymatically described within this group. This thesis uses phylogenetics to investigate how CPS nucleotide sequences in lungfishes evolved compared to other vertebrates.
5
Dixon, G. K. "The inorganic nitrogen metabolism of marine dinoflagellates". Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636452.
Abstract (sommario):
Nitrogen-replete cells of Amphidinium carterae took up ammonium in the light at a rate 5 - 6 times that of nitrate even though exponential growth rates were similar on these two N-sources. A. carterae exhibited a capability for enhanced initial ammonium uptake, particularly when deprived of nitrogen. Enhanced initial rates of ammonium uptake were also observed in a natural population of Gyrodinium aureolum. Initially ammonium accumulated within the cells of A. carterae but was assimilated into organic-N within a matter of hours; increases in total cellular-N, total free amino acids, glutamine and cellular protein were observed 4 h after an ammonium addition. In comparison, very little nitrate was accumulated. Ammonium (250 μM) inhibited reversibly the uptake of nitrate; the rapidity of the response suggests a direct effect on uptake. Prior nitrogen deprivation of the cells did not affect this inhibition. Rates of ammonium uptake were similar in the light and dark but nitrate uptake was completely inhibited by darkness in nitrogen replete cells of A. carterae and in a natural population of G. aureolum. Dark uptake of nitrate was stimulated by a period of nitrogen deprivation. Ammonium uptake in darkness by A. carterae was accompanied by the utilization of cellular polysaccharide, mainly glucose polysaccharide. Most of this carbon was unavailable for the assimilation of nitrate in the dark. It is suggested that a control mechanism is in operation, via a product of ammonium assimilation, on one or more of the enzymes concerned with polysaccharide breakdown, e.g. α-amylase or phosphorylase. Ammonium addition caused a marked enhancement of dark CO2 fixation in several nitrogen-replete dinoflagellates. Nitrate addition produced little enhancement in comparison. The amount of enhancement was dependent on species, age of culture and period of diel cycle. Nitrogen deprivation caused a 2-3 fold increase in enhancement in all species tested. The measurement of dark 14CO2 fixation shows promise as a technique for determining the nitrogen status of phytoplankton in both the laboratory and in the field. A natural population of Gyrodinium aureolum appeared to be slightly N-limited using this technique, an observation supported by other field data. The use of this technique as a tool to determine the nitrogen status of phytoplankton in culture and in the field is discussed.
6
Allison, Clive. "Nitrogen metabolism of human large-intestinal bacteria". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306357.
7
Schulz, Anton A. "Nitrogen metabolism in Corynebacterium glutamicum ATCC 13032". Doctoral thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/4329.
Abstract (sommario):
Bibliography: leaves 125-146.Corynebacterium glutamicum is extensively used for the commercial production of a host of amino acids including lysine, glutamate, and threonine. Consequently, much research has been directed at analyzing nitrogen metabolism in this bacterium. In particular, our research focused on investigating the regulation of nitrogen assimilation. Initially, we searched for homologs of the Streptomyces glnR, glnII, and glnE genes in C. glutamicum. These studies, however, were met with limited success, and we therefore decided to use promoter probe vectors in order to identify nitrogen-responsive promoters.
8
Sabag-Daigle, Anice. "Nitrogen Metabolism of the Haloarchaeon Haloferax volcanii". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250008417.
9
Mos, Magdalena. "The control of nitrogen metabolism in Aspergillus nidulans". Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539565.
10
Alvarado, Adriana Delgado. "Interactions between carbon and nitrogen metabolism in legumes". Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274992.
11
Bon, E. P. S. "Glucoamylase production and nitrogen metabolism in Aspergullus awamori". Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306324.
12
Ng, Doris Hui Lan. "Nitrogen metabolism and health of people with ileostomy". Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427418.
13
Tolonen, Andrew Carl. "Prochlorococcus genetic transformation and genomics of nitrogen metabolism". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/43721.
Abstract (sommario):
Thesis (Ph. D.)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005.Includes bibliographical references.
Prochlorococcus, a unicellular cyanobacterium, is the most abundant phytoplankton in the oligotrophic, oceanic gyres where major plant nutrients such as nitrogen (N) and phosphorus (P) are at nanomolar concentrations. Nitrogen availability controls primary productivity in many of these regions. The cellular mechanisms that Prochlorococcus uses to acquire and metabolize nitrogen are thus central to its ecology. One of the goals of this thesis was to investigate how two Prochlorococcus strains responded on a physiological and genetic level to changes in ambient nitrogen. We characterized the N-starvation response of Prochlorococcus MED4 and MIT9313 by quantifying changes in global mRNA expression, chlorophyll fluorescence, and Fv/Fm along a time-series of increasing N starvation. In addition to efficiently scavenging ambient nitrogen, Prochlorococcus strains are hypothesized to niche-partition the water column by utilizing different N sources. We thus studied the global mRNA expression profiles of these two Prochlorococcus strains on different N sources. The recent sequencing of a number of Prochlorococcus genomes has revealed that nearly half of Prochlorococcus genes are of unknown function.
(cont.) Genetic methods such as reporter gene assays and tagged mutagenesis are critical tools for unveiling the function of these genes. As the basis for such approaches, another goal of this thesis was to find conditions by which interspecific conjugation with Escherichia coli could be used to transfer plasmid DNA into Prochlorococcus MIT9313. Following conjugation, E. coli were removed from the Prochlorococcus cultures by infection with E. coli phage T7. We applied these methods to show that an RSF1010-derived plasmid will replicate in Prochlorococcus MIT9313. When this plasmid was modified to contain green fluorescent protein (GFP) we detected its expression in Prochlorococcus by Western blot and cellular fluorescence. Further, we applied these conjugation methods to show that Tn5 will transpose in vivo in Prochlorococcus. Collectively, these methods provide a means to experimentally alter the expression of genes in the Prochlorococcus cell.
by Andrew Carl Tolonen.
Ph.D.
14
Li, Mengmeng. "Modeling Nitrogen and Energy Metabolism in the Bovine". Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/87090.
Abstract (sommario):
The objectives of this research were to: 1) evaluate the accuracy of the Molly cow model predictions of ruminal metabolism and nutrient digestion when simulating dairy and beef cattle diets, 2) advance representations of N recycling between blood and the gut and urinary N excretion in the model, 3) improve the representation of pH and to refit parameters related to ruminal metabolism and nutrient digestion in the model, 4) investigate how ruminal pH affects the microbial community, expression of carbohydrate-active enzyme transcripts (CAZymes), fiber degradation, and short chain fatty acid (SCFA) concentrations. To achieve the first objective, a total of 229 studies (n = 938 treatments) including dairy and beef cattle data, published from 1972 through 2016, were collected from the literature and used to assess the model accuracy and precision based on root mean squared errors (RMSE) and concordance correlation coefficients (CCC). Only slight mean and slope bias were exhibited for ruminal outflow of NDF, starch, lipid, total N, and non-ammonia N, and for fecal output of protein, NDF, lipid, and starch. However, ruminal pH was poorly simulated and contributed to problems in ruminal nutrient degradation and VFA production predictions. To achieve the second objective, representations including ruminal ammonia outflow, intestinal urea entry, microbial protein synthesis in the hindgut, and fecal urea N excretion, were added in the model. Total urea entry, gut urea entry, and urinary urea elimination rates collected from 15 published urea kinetics studies were used to derive related parameters. Significant improvements in predictions of variables describing ruminal N metabolism, blood urea metabolism and urinary N secretion were exhibited after the modifications. To achieve the third objective, a dataset assembled from the literature containing 284 peer reviewed studies with 1223 treatment means was used to derive parameter estimates for ruminal metabolism and nutrient digestions. After refitting the parameters, the model is even more robust in representing ruminal nutrient degradation compared to the initial model. Adding ammonia concentration as a driver to the pH equation increased the precision of predicted ruminal pH, and thereby, the precision of predicted VFA concentrations due to an improved representation of pH regulation of VFA production rates. To achieve the fourth objective, six cannulated Holstein heifers with an initial BW of 362 ± 22 kg (mean ± SD) were subjected to 2 treatments in a cross-over design. The treatments were 10 days of intraruminal infusions of both 1) distilled water (Control), and 2) a dilute blend of hydrochloric and phosphoric acids to achieve a pH reduction of 0.5 units (LpH). Statistical analyses indicated 19 bacterial genera and 4 protozoal genera were affected by low ruminal pH. We observed significant correlations between 54 microbes (43 bacterial and 11 protozoal genera) and 25 enzymes, of which 8 key enzymes participated in reactions leading to SCFA production, suggesting that the ruminal microbial community alters fiber catalysis and fermentation in response to altered pH through a shift in carbohydrate-active enzyme transcripts (CAZymes) expression. Overall, after the modifications and reparameterizations, 19.7 to 37.5% of RMSE with essentially no slope bias and minor mean bias were exhibited for of ruminal and fecal outflow of ADF, NDF, fat, and protein, suggesting the model is properly to represent nutrient degradation and digestion in the bovine. Considering ruminal microbes and CAZymes in predicting ruminal volatile fatty acid concentrations could explain more variance of observations.Ph. D.
The purpose of this research was to improve ruminal nutrient metabolism and nutrient digestion representations in the Molly cow model. First, the model accuracy and precision were assessed using a dataset including 229 studies (n = 938 treatments) conducted with dairy and beef cattle. The model evaluation results indicated the mechanisms encoded in the model relative to ruminal and total tract nutrient digestion are properly represented. However, ruminal pH was very poorly represented in the model with a RMSE of 4.6% and a concordance correlation coefficient (CCC) of 0.0. Although VFA concentrations had negligible mean (2.5% of MSE) and slope (6.8% of MSE) bias, the CCC was 0.28 implying that further modifications with respect to VFA production and absorption are required to improve model precision. As identified by the residual analyses, the representations of N recycling between blood and the gut were improved by considering ruminal ammonia outflow, intestinal urea entry, microbial protein synthesis in the hindgut, and fecal urea N excretion in the model. Observations of total urea entry, gut urea entry, and urinary urea elimination rates were collected from 15 published urea kinetics studies were used to derive related parameters. After the modifications, prediction errors for ruminal outflows of total N, microbial N, and non-ammonia non-microbial N were 39.5, 27.8 and 35.9% of the respective observed mean values. Prediction errors of each were approximately 10% units less than the corresponding values before model modifications and fitting due primarily to decreased slope bias. The revised model predicted ruminal ammonia and blood urea concentrations with substantially decreased overall error and reductions in slope and mean bias. After that, ammonia concentration as a driver was added to the pH equation, and a dataset assembled from the literature containing 284 peer reviewed studies with 1223 treatment means was used to derive parameter estimates for ruminal metabolism and nutrient digestions. Refitting the parameters significantly improved the accuracy and precision of the model predictions for ruminal nutrient outflow (ADF, NDF, total N, microbial N, non-ammonia N, and non-ammonia, non-microbial N), ammonia concentrations, and fecal nutrient outflow (protein, ADF, and NDF). Therefore, the improved model can be used to simulate nutrient degradation and digestion in the bovine. Although minor mean and slope bias were observed for ruminal pH and VFA concentrations, the small values for concordance correlations indicated much of the observed variation in these variables remains unexplained. To further explain variance in ruminal metabolism and understand how ruminal pH affects the microbial community, expression of carbohydrate-active enzyme transcripts (CAZymes), fiber degradation, and short chain fatty acid (SCFA) concentrations, six cannulated Holstein heifers with an initial BW of 362 ± 22 kg (mean ± SD) were subjected to 2 treatments in a cross-over design. We observed 19 bacterial genera and 4 protozoal genera were affected by low ruminal pH, and significant correlations between 54 microbes (43 bacterial and 11 protozoal genera) and 25 enzymes, of which 8 key enzymes participated in reactions leading to SCFA production. In summary, after the modifications and reparameterizations, the model is even more robust to represent nutrient degradation and digestion in bovine compared to the initial model. More variance of observations of ruminal volatile fatty acid concentrations could be explained by considering ruminal microbes and CAZymes expressions in further study.
15
Oelberg, Thomas Jonathan. "Meal patterns and nitrogen metabolism in dairy cows /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259580262914.
16
Poll, Marcel Coenraad Gerhard van de. "Nitrogen metabolism and hepatocellular injury during liver resection". Maastricht : Maastricht : Universitaire Pers ; University Library, Universiteit Maastricht [host], 2008. http://arno.unimaas.nl/show.cgi?fid=13094.
17
Silva, Cesar José da. "Efeito de diferentes relações folha/grãos sobre o metabolismo do nitrogênio em diferentes partes da planta de milho /". Jaboticabal : [s.n.], 2002. http://hdl.handle.net/11449/96968.
Abstract (sommario):
Orientador: Jairo Osvaldo CazettaBanca: Antonio Álvaro Corsetti Purcino
Banca: Marcelo Murad Magalhães
Resumo: Embora esteja bem estabelecido pelos experimentos clássicos, qual são os fatores que limitam a produção, o funcionamento da planta na fase reprodutiva que envolve um complexo relacionamento tanto entre órgãos fonte e dreno de fotossintatos como do metabolismo do nitrogênio em ambos os tipos de órgãos, ainda permanece pouco esclarecido. Assim sendo, na fase de polinização foram impostas diferentes proporções de folhas (% de fonte) e de grãos (% de dreno) em plantas de milho para estudar o efeito destes tratamentos sobre o comportamento do metabolismo do nitrogênio em grãos, folhas e colmos, em diferentes etapas da fase reprodutiva da cultura e suas relações com a produção de massa seca, desenvolvimento de grãos, bem como desenvolvimento e senescência das folhas. Avaliou-se atividade de algumas enzimas, o teor dos principais metabólitos nitrogendados nas folhas, nos colmos e nos grãos em formação, bem como os reflexos destas variáveis sobre algumas características agronômicas aos 2, 10, 20 e 30 dias após a polinização (dap). Os resultados do presente trabalho permitiram esclarecer que a atividade da redutase do nitrato na folha não foi afetada pelas alterações nas proporções de fonte e dreno de fotossintatos. Os teores de N-total, N-nitrato e N-aminoácidos livres, nas folhas, colmos e endospermas foram mais intensamente afetados quanto mais drásticas foram as reduções de folhas ou grãos. As reduções da fonte e dreno promoveram aumentos significativos nos teores de N-total, N-nitrato e N-aminoácidos livres nas partes remanescentes analisadas. Os teores de proteína solúvel foram mais afetados nos grãos, onde os maiores valores foram encontrados aos 10 dap., nos tratamentos sem folhas e sem grãos... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Although it is well very established, for the classic experiments, which are the factors that limit the production, the operation of the plant in the reproductive phase that involves a compound so much relationship between organs source and fotossintatos drain as of the metabolism of the nitrogen in both types of organs, it remains unclear. Like this being, in the pollination phase different proportions of leaves were imposed (% of source) and of grains (% of drain) in corn plants to study the effect of these treatments on the behavior of nitrogen metabolism in grains, leaves and stems, in different stages during reproductive phase of the culture and your relationships with the production of dry mass, development of grains, as well as development and senescence of leaves. Enzymes activity were evaluated (NR, TGO and TGP), the level of main metabolites (N-total, N-nitrate, free amino acids and soluble protein) in the leaves, in the stems and in the grains in formation, as well as the reflexes of these varied on the agronomic characteristics (mass evaporates of leaves stems and grains), to the 2, 10, 20 and 30 days after the pollination (dap). The results of the present work allowed to clear that the activity of the nitrate reductase in the leaf was not affected by the alterations in the source proportions and photoassimilated drain. The levels of N-total, N-nitrate and free N-amino acids, in the leaves, stems and endosperms were more intensely affected the more drastic they were the reductions of leaves or grains. The reductions of the source and drain promoted significant increases in the levels of N-total, N-nitrate and free N-amino acids in the analyzed remaining parts. The soluble protein concentration was more affected in the grains, where the largest values were found to the 10 dap, in the treatments without leaves and grains... (Complete abstract, click eletronic address below).
Mestre
18
Reeder, Trista. "DIETARY LYSINE:CALORIE RATIOS AND THEIR INFLUENCE ON NITROGEN METABOLISM AND DIGESTIBILITY IN MODERATELY OBESE MATURE DOGS". UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_theses/183.
Abstract (sommario):
This experiment was conducted to determine if changing the amount of ideal aminoacids (meaning the amount of amino acids necessary to supply all the animal's needswithout excesses or deficiencies of any single amino acid), in relation to caloric intakewill change nitrogen metabolism and weight loss in obese mature dogs. Informationprovided by this experiment can be used to formulate canine diets emphasizing weightloss in older animals.Six moderately obese mature female crossbred hounds were fed diets varying in theirratio of lysine:calories (Lysine % : Mcal ME/g) (2.2, 3.0, and 3.8) in a 3 x 3 replicatedLatin square design. Increasing the lysine:calorie of the diets linearly increased theamount of nitrogen absorbed. It did not, however, significantly affect blood chemistryvalues. Protein turnover exhibited a positive linear trend with increasing ratio and proteindegradation showed a strong quadratic change with the lowest point of degradationoccurring with the diet containing a 3.0 lysine:calorie ratio. Plasma urea and creatinineexcretion demonstrated quadratic tendencies with the two highest values occurring withthe diets containing lysine:calorie of 2.2 and 3.8, reflecting changes in muscle proteinbreakdown while nitrogen was retained in the body. Caloric restriction did not result inloss of lean mass as much as a loss of fat mass. By increasing the quality of protein fedas a percentage of caloric intake, lean muscle mass was conserved during periods ofcaloric restriction.
19
Rajab, T. M. A. "Studies on carbon metabolism and nitrogen fixation by Gloeothece". Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638610.
Abstract (sommario):
When cultures of Gloeothece grown under constant light, were transferred to dark anerobic conditions, the rate of acetylene reduction dropped within 1h to 25-30% of that in the light, and reached a minimum after 10-12h. The only source at ATP for nitrogenase, under such conditions, is substrate level phosphorylation utilising endogenous material. All attempts to support N2-fixation by an exogenous source of energy proved unsuccessful. Although Gloeothecewas able to fix nitrogen under dark anaerobic conditions, no nitrogenase synthesis was observed. Gloeothece survived under dark anaerobic conditions for at least 96h, but they appeared to lose the ability to protect nitrogenase against inactivation by O2 over this period. Thus, when cultures of Gloeothece maintained under dark anaerobic conditions for more than 12h, were transferred to the light under anaerobic conditions, the nitrogenase activity which subsequently appeared was oxygen-sensitive. ATP is a necessary source of energy for N2-fixation. On the other hand, ADP inhibits nitrogenase activity. Therefore, the relative amounts of ADP and ATP may control nitrogenase activity. A routine method for measuring adenine nucleotides in Gloeothece, based on the luciferin-luciferase technique, was developed as existing methodology was found unsuitable. Under constant illumination, the observed fluctuations in nitrogenase activity in Gloeothece were not found to be related to changes in the ADP/ATP ratio. However, the ADP/ATP ratio had an indirect effect, possibly via synthesis, on the nitrogenase activity in Gloeothece grown under an alternating cycle of 12h light and 12h darkness. On the other hand, acetylene reduction was inversely related to the ADP/ATP ratio when cultures of Gloeothece were transferred from dark anaerobic conditions to dark aerobic and then to light aerobic conditions.
20
Lodwig, Emma Mary. "Regulation of carbon and nitrogen metabolism in Rhizobium leguminosarum". Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368874.
21
Dewhurst, R. J. "Studies on energy and nitrogen metabolism in the rumen". Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234566.
22
Cavan, Graeme Patrick. "Interaction of carbon and nitrogen metabolism in Schizosaccharomyces pombe". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259573.
23
Kirsten, Catriona Jane. "Nitrogen metabolism and the regulation thereof in Mycobacterium smegmatis". Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/17991.
Abstract (sommario):
Thesis (PhD (Med))--University of Stellenbosch, 2011.ENGLISH ABSTRACT: The nitrogen metabolic pathway is essential for growth and survival of all living organisms including prokaryotes. Certain components of the pathway, such as the enzyme glutamine synthetase (GS), have been studied; however, little information is available regarding the pathway in the mycobacteria. Our in silico studies revealed that many of the components and mechanisms involved in the pathway appear to be conserved between closely related Actinomycetales. Therefore, we investigated three aspects of nitrogen metabolic control in Mycobacterium smegmatis; namely, transcriptional regulation of nitrogen metabolism-related genes, control of enzyme activity and the signalling cascade governing the nitrogen metabolic response. At the transcriptional level, it was found that nitrogen metabolism-related genes were regulated in response to ammonium availability. Two possible transcriptional regulators, AmtR and GlnR, which are the regulators responsible for control of nitrogen-related gene transcription in Streptomyces coelicolor and Corynebacterium glutamicum respectively, were identified in M. smegmatis. Through generation of amtR and glnR deletion mutants, we found that both potential regulators played a role in the control of nitrogen-related gene expression in M. smegmatis. GlnR acted as both an activator and repressor of gene transcription whilst AmtR appeared to activate gene expression which is different to the role its homolog plays in C. glutamicum. On a protein level we found that both GS and glutamate dehydrogenase (GDH) were responsible for ammonium assimilation in M. smegmatis and were regulated in response to ammonium availability. Two GDH isoforms (NAD+- and NADP+-specific) were identified in M. smegmatis and whereas only an NAD+-GDH was detected in M. tuberculosis. The M. tuberculosis GDH also played a largely anabolic role with regard to ammonium assimilation which is in contrast to the belief that ammonium can only be assimilated via GS in this pathogen. The signaling cascade was investigated through generation of a glnD deletion mutant in M. smegmatis. We were able to show that this pivotal protein (GlnD) was able to relay the cellular nitrogen status to the transcriptional machinery as well as to GS. The data presented in this study has advanced our understanding of the nitrogen metabolic pathway in the mycobacteria. Through elucidation of such pathways, our knowledge of mycobacterial physiology and thus infection and survival improves, which could ultimately lead to the discovery of novel mechanisms to aid in the eradication of the disease.
AFRIKAANSE OPSOMMING: Stikstof metabolisme is noodsaaklik vir die oorlewing en groei van alle organismes, prokariote ingesluit. Sekere sellulêre komponente, soos die ensiem glutamine sintetase (GS), is al tevore bestudeer, maar baie min verdere inligting is beskikbaar oor stikstof metabolisme in die mycobacteria. Ons in silico studies het gewys dat baie van die komponente en meganismes gekonserveerd gebly het tussen nou-verwante Actinomycetales. Dus het ons drie aspekte in die beheer van stikstof metabolisme ondersoek; naamlik, die transkriptionele regulering van stikstof metabolisme-verwante gene, die beheer van ensiem aktiwiteit en die sein-meganisme wat die reaksie op stikstof konsentrasie reageer. Op transkripsionele vlak het ons gevind dat stikstof metabolisme-verwante gene gereguleer word in reaksie op stikstof beskikbaarheid. AmtR en GlnR is twee moontlike transkripsie reguleerders wat verantwoordelik is vir transkripsionele beheer in onderskeidelik Streptomyces coelicolor en Corynebacterium glutamicum. Beide hierdie proteïene is geïdentifiseer in M. smegmatis. Deur die konstruksie van amtR en glnR mutante, het ons gevind dat beide potensiële reguleerders ‘n rol gespeel het in die beheer van stikstof-verwante transkripsie in M. smegmatis. GlnR het opgetree as beide ‘n aktiveerder en ‘n onderdrukker van transkripsie terwyl AmtR net ‘n aktiverende rol gespeel het. Die funksie van AmtR in M. smegmatis is dus verskillend van sy homoloog in C. glutamicum. Op proteïen-vlak het ons gevind dat beide GS en glutamaat dehidrogenase (GDH) verantwoordelik was vir die assimilasie van ammonium in M. smegmatis en albei was gereguleer in reaksie op ammonium beskikbaarheid. Twee vorme van GDH (NAD+- spesifieke- en NADP+-spesifieke GDH) was geïdentifiseer in M. smegmatis terwyl net ‘n NAD+- spesifieke GDH in M. tuberculosis gevind is. Die M. tuberculosis GDH het ook ‘n anaboliesie rol gespeel met betrekking tot ammonium assimilasie wat in teenstelling is met die huidige opvatting dat ammonium alleenlik deur GS ge-assimileer kan word. Die sein-meganisme is ondersoek deur ‘n glnD M. smegmatis mutant te konstrueer. Ons het bewys dat hierdie deurslaggewende proteïen (GlnD) die sellulêre stikstof status aan die transkripsionele masjinerie, en aan GS kon oordra. Die data wat in hierdie studie voorgelê word, het ons kennis van stikstof metabolisme in die mycobacteria gevorder. Sodanige metaboliese studies verbreed ons kennis van mycobacteriële fisiologie en dus M. tuberculosis infeksie en oorlewing en kan uiteindelik lei tot die ontdekking van unieke teiken meganismes om te help met die beheer van die siekte en nuwe middelontwikkeling.
24
Takahashi, Cassia Ayumi. "Assimilação do nitrogênio em diferentes regiões foliares de uma bromélia epífita com tanque". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/41/41132/tde-06112008-174416/.
Abstract (sommario):
A folha é o principal órgão de absorção e assimilação de nutrientes dos membros epífitos com tanque da família Bromeliaceae. Pouco se conhece sobre a nutrição dessas bromélias, entretanto algumas evidências (TAKAHASHI, 2007) indicaram a possibilidade de haver uma absorção preferencial do nitrogênio na porção basal e a assimilação desse nutriente na porção apical foliar. Para se compreender melhor os mecanismos de assimilação do nitrogênio utilizados pelas bromélias epífitas com tanque, foi proposto neste trabalho dois principais objetivos: 1) verificar possíveis diferenças quanto à capacidade de assimilação do nitrogênio em diferentes porções foliares de uma bromélia epífita com tanque; 2) constatar possível preferência em assimilar fonte nitrogenada orgânica ou inorgânica, quando ambas estão disponíveis no interior do tanque. A estratégia utilizada para o primeiro objetivo foi cultivar bromélias da espécie Vriesea gigantea, cultivadas em casa de vegetação e registrar em suas folhas as variações temporais das atividades enzimáticas da urease, redutase do nitrato (NR), sintetase da glutamina (GS), desidrogenase do glutamato dependente de NADH (GDH-NADH) e arginase após o fornecimento, no interior do tanque das bromélias, de uma solução nutritiva contendo NO3-/NH4+ (3:2) ou uréia (5mM de N total), como fontes de nitrogênio. Foram analisadas as atividades enzimáticas nas porções apical e basal foliar de Vriesea gigantea nos seguintes tempos: 0, 1, 3, 6, 9, 12, 24, 48, 51, 54, 57, 60 e 73 horas após a rega. Além disso, também foram quantificadas as concentrações do amônio e da uréia endógenos presentes nos tecidos foliares de ambas as porções. Os resultados mostraram que, independente do tratamento, as atividades de GS, GDH e arginase foram mais altas na porção apical em todos os tempos de coleta. Já as atividades da NR e urease, foram crescentes e mais intensas na porção basal, da mesma forma como foi visto para as concentrações endógenas de amônio durante as primeiras 24 horas. As maiores concentrações de uréia endógenas também foram registradas principalmente na porção basal foliar. Esses resultados permitem inferir que a região apical pode estar envolvida, preferencialmente, com a assimilação do nitrogênio, enquanto que a basal, com a sua absorção, redução do nitrato e hidrólise da uréia. Além disso, sugere-se também que ocorra o transporte de amônio da base para a região de sua assimilação em aminoácidos (ápice) através do xilema e apoplasto. Em relação ao segundo objetivo, a estratégia utilizada foi fornecer à bromélia Vriesea gigantea com uma solução nutritiva que continha 5mM de nitrogênio total, disponível na forma inorgânica + orgânica (NH4+/NO3- + uréia nas proporções 1:1 ou 1:3, respectivamente). Como controle foram empregados os seguintes tratamentos: ausência de nitrogênio e presença de somente fontes inorgânicas (5mM de nitrogênio total). As porções apical e basal das folhas foram coletadas 9 horas após o fornecimento das soluções nutritivas e, posteriormente, utilizadas nas análises enzimáticas referentes às atividades da urease, NR, GS, e GDH-NADH. Além disso, foram quantificados em ambas as porções os teores endógenos de amônio, uréia, amido, açúcares totais e clorofila total. Também foram determinados as densidades de tricomas e estômatos nas duas regiões foliares. Verificou-se que as maiores atividades da GS (porção apical) e GDH (porção basal) foram registradas nos dois tratamentos com uréia (1:1 e 1:3) quando comparadas com as dos dois controles. As maiores concentrações de amônio endógeno na porção basal também foram detectadas nos mesmos tratamentos com uréia (1:1 e 1:3). Já a atividade da NR apresentou os maiores valores nos tratamentos de proporção 1:1 e no controle 2 (com somente fontes inorgânicas) na porção basal foliar. De modo interessante, a GS não mostrou o mesmo desempenho nos dois tratamentos (1:1 e controle 2), sendo que, no tratamento de proporção 1:1, a atividade foi o dobro daquela registrada no controle 2. Todos esses resultados analisados em conjunto permitem inferir que a bromélia Vriesea gigantea pode ter preferência por assimilar o nitrogênio proveniente da uréia quando essa fonte se encontra disponível no interior do tanque, mesmo quando também há a presença de formas inorgânicas (nitrato e amônio).The leaf is considered the most important vegetative organ of tank epiphytic bromeliads due to its ability to absorb and assimilate nutrients. Little is known about the nutrition of these bromeliads, but there are evidences that the basal region of the leaf may be preferentially involved with the absorption of nutrients, whereas the apical region may be involved with its assimilation (TAKAHASHI, 2007). In order to better understand the mechanisms utilized by these tank epiphytic bromeliads to optimize the nitrogen acquisition and assimilation, it was proposed in this study two main objectives: 1) verify the existence of a differential capacity to assimilate nitrogen in different leaf portions of a tank epiphytic bromeliad; 2) analyze the nitrogen assimilation preference between inorganic and organic nitrogen sources when both are available in the tank water. The experiments of the first objective were conducted using Vriesea gigantea plants, a typical specie of tank epiphytic bromeliad, cultivated in greenhouse. Nutrient solution containing NO3-/NH4+ (3:2) or urea as nitrogen source (5mM of total N) was supplied into the tank of these plants and the activities of urease, nitrate reductase (NR), glutamine synthetase (GS), NADH-dependent glutamate dehydrogenase (GDH-NADH) and arginase were quantified in apical and basal leaf portions after 0, 1, 3, 6, 9, 12, 24, 48, 51, 54, 57, 60 and 73 hours. The ammonium and urea present in the tissues were also analyzed. Independent of the nitrogen source utilized, GS, GDH and arginase activities were higher in the apical portions of leaves in all the period analyzed. On the other hand, the opposite was observed in relation to NR and urease activities. The highest activities were detected in the basal portion of leaves at all harvest times, with increasing values during the first 24 hours of experiment. Interestingly, this same pattern was also observed in relation to the endogenous ammonium and urea: the highest contents were detected in the basal portion of leaves, with a gradual increase of ammonium in the first 24 hours of analysis. These results suggest that the basal portion of leaves was preferentially involved in nitrogen uptake, nitrate reduction and urea hydrolysis, while the apical portion was the main responsible for nitrogen assimilation. Moreover, it was possible to infer that the ammonium may be transported from the base (uptake region) to the apex of the leaves (the main nitrogen assimilation region) through the xylem and apoplast. In order to analyze the nitrogen assimilation preference of Vriesea gigantea, a nutrient solution containing 5mM of nitrogen containing a mixture of inorganic and organic sources (NH4+/NO3- + urea in the proportion 1:1 or 1:3, respectively) were supplied into the tank of the bromeliads. As a control, a nutrient solution containing no nitrogen source (control 1) or 5mM of inorganic nitrogen sources (control 2) were used. The basal and apical leaf tissues were collected after 9 hours and the activities of urease, NR, GS and GDH-NADH were analyzed. Endogenous ammonium, urea, starch, total soluble carbohydrates and total chlorophyll were also quantified. Furthermore, the density of trichomes and stomata were also analyzed on the abaxial leaf surface of both regions. The highest activities of GS (apex) and GDH (base), as well as the endogenous ammonium content (base), were registered in both treatments with urea (1:1 and 1:3) in comparison with both controls. A different pattern was obtained analyzing NR: the highest activities were observed in plants that received nutrient solutions containing only inorganic nitrogen (control 2) or a mixture of inorganic and organic nitrogen in the proportion 1:1. Moreover, an interesting behavior was observed in relation to the GS activity: it was detected the double activity of this enzyme when Vriesea gigantea was in contact with a mixture of inorganic and organic nitrogen (1:1) in comparison to the plants in the presence of only inorganic nitrogen sources. All results suggest that Vriesea gigantea may have preference to assimilate organic nitrogen source (urea), when the inorganic nitrogen sources (ammonium and nitrate) are also available in the tank water.
25
Biggs, Ian Maxwell. "An investigation of sugarcane nitrogen physiology : sources, uptake, and metabolism /". St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17647.pdf.
26
Larson, Tony Robert. "Storage lipid metabolism during nitrogen assimilation in a marine diatom". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq27184.pdf.
27
Frick, Natasha Therese. "Nitrogen metabolism and excretion in the mangrove killifish, Rivulus marmoratus". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ56324.pdf.
28
Kosma, Dylan K. "Interaction of cyanide with nitrogen metabolism in wheat (Triticum aestivum) /". Available to subscribers only, 2005. http://proquest.umi.com/pqdweb?did=1075707051&sid=17&Fmt=2&clientId=1509&RQT=309&VName=PQD.
29
Couper, Andrew David. "Aspects of nitrogen metabolism in temperate and tropical crab species". Thesis, University of Hull, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250833.
30
Maltby, Susan A. "Nutritional regulation of splanchnic nitrogen and energy metabolism in cattle". Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241630.
31
Gorgens, Johann Ferdinand. "Quantitative yeast physiology and nitrogen metabolism during heterologous protein production". Thesis, Stellenbosch : University of Stellenbosch, 2003. http://hdl.handle.net/10019.1/16051.
Abstract (sommario):
Dissertation (PhD)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: QUANTITATIVE YEAST PHYSIOLOGY AND NITROGEN METABOLISM DURING HETEROLOGOUS PROTEIN PRODUCTION By Johann F. Görgens The physiology and nitrogen metabolism of the yeast, Saccharomyces cerevisiae, during heterologous xylanase production in a defined medium was quantified by the comparison of isogenic yeast strains, whereby several potential limitations in the production of the heterologous xylanase could be identified. The presence of global sensing and regulatory mechanisms, by which the yeast is able to actively regulate both heterologous gene expression and the physiological response to the process, was also investigated. The deleterious effects of heterologous xylanase production on the physiology of the recombinant host were disproportionately large with respect to the amount of foreign protein produced. The cellular processes involved in this response were identified by the transcriptional profiling of isogenic recombinant strains, in a novel analytical approach to investigating foreign protein production by S. cerevisiae. Heterologous gene expression affected a combination of cellular processes and induced the yeast stringent stress response. The corresponding loss of metabolic functionality resulted in the disproportionate physiological effects of foreign protein production, similar to previous observations in recombinant Escherichia coli, and a possible reduction in attainable production levels. Reducing the propensity of recombinant gene expression to introduce metabolic stress may therefore increase production levels of foreign proteins by yeast. The metabolic vitality of transformed strains was also reduced by the presence of multiple copies of active, plasmid-based PGK1-promoters in the cell without expression of the heterologous gene. The negative effect was caused by an increase in the biosynthetic and glycolytic capacity of the strain at the expense of other processes. Production levels of heterologous xylanase were influenced by expression vector selection and the presence of auxotrophic mutations in transformed strains of S. cerevisiae. The increased transcription levels obtained with the multicopy plasmidbased YEp-type expression system, compared to the integrative YIp-type expression system, resulted in higher levels of xylanase production. Heterologous xylanase production thus did not saturate the secretory capacity of the host strain. The genetic stability of the autoselective YEp-type expression system in long-term chemostat culture was also demonstrated. High levels of heterologous xylanase production by transformed S. cerevisiae strains containing auxotrophic markers required the stabilisation of nitrogen metabolism via saturation of yeast cells with an excess of imported amino acids. By the removal of excessive auxotrophic markers, high levels of xylanase production by a prototrophic transformant in defined medium without amino acid addition could be obtained. Heterologous xylanase production by the prototrophic transformant was further enhanced by increasing the availability of preferred amino acids or succinate in the defined medium, indicating an additional requirement for metabolic precursors and building blocks for foreign protein synthesis. Comparable levels of heterologous xylanase production were obtained in high cell density cultures of the alternative yeast, Pichia stipitis, by the proper induction of the native ADH2-promoter, the control of oxygenation, and addition of an amino acid mixture to the defined medium, indicating the presence of generic limitations in transcription, nutrient availability and the yeast biosynthetic capacity for foreign protein production by various yeasts. The presence of global sensing and regulatory mechanisms was confirmed by the physiological response of S. cerevisiae to heterologous protein production, which included the downregulation of biosynthesis and growth, and the induction of various processes involved in the stringent stress response. Additionally, heterologous xylanase production was actively regulated on a posttranscriptional level by the auxotrophic transformants in response to the level of amino acid availability. The biosynthetic capacity for foreign protein production by both recombinant S. cerevisiae and P. stiptis was also regulated in response to the physiological state of the yeast and the availability of nutrients. The presence of these regulatory mechanisms complicated the manipulation of cellular biosynthesis at will.
AFRIKAANSE OPSOMMING: KWANTITATIEWE GIS-FISIOLOGIE EN -STIKSTOF METABOLISME GEDURENDE HETEROLOË PROTEÏEN PRODUKSIE Deur Johann Ferdinand Görgens Die fisiologie en stikstof-metabolisme van die gis, Saccharomyces cerevisiae, gedurende heteroloë xilanase produksie in ‘n gedefiniëerde medium is gekarakteriseer deur isogeniese gis-rasse te vergelyk, waardeur verskeie moontlike beperkings in die produksie van die heteroloë xilanase uitgewys kon word. Die teenwoordigheid van globale sensoriese- en beheer-meganismes, wat die gis in staat stel om beide heteroloë geen uitdrukking en die fisiologiese respons op die proses aktief te reguleer, is ook ondersoek. Die nadelige effekte van heteroloë xilanase produksie op die fisiologie van die rekombinante gasheer-organisme was uitermatig groot in vergelyking met die hoeveelheid vreemde proteïen wat geproduseer is. Die sellulêre prosesse verantwoordelik vir hierdie respons is identifiseer deur die transkripsionele profiele van isogeniese rekombinante rasse te vergelyk, in ‘n nuwe analitiese benadering tot die bestudering van vreemde proteïen produksie deur S. cerevisiae. Heteroloë geen uitdrukking het ‘n kombinasie van sellulêre prosesse geaffekteer en die gis se algemene voedingstres-respons geaktiveer. Die gepaardgaande verlies aan metaboliese funksie het die uitermatige fisiologiese effek van vreemde proteïen produksie veroorsaak, soortgelyk aan vorige waarnemings met rekombinante Escherichia coli. Die haalbare produksie-vlakke is moontlik ook verlaag deur hierdie respons. ‘n Verlaging van die geneigdheid van rekombinante geen uitdrukking om metaboliese stres te veroorsaak, mag dus die produksievlakke van vreemde proteïene in gis verbeter. Die metaboliese groei-potensiaal van die getransformeerde rasse is ook verlaag deur die teenwoordigheid van etlike aktiewe kopieë van plasmied-gebaseerde PGK1-promotors in die sel, sonder uitdrukking van die heteroloë geen, deur ‘n toename in die biosintetiese en glikolitiese kapasiteit ten koste van die ander sellulêre prosesse. Die produksievlakke van heteroloë xilanase is deur die keuse van uitdrukkings-sisteem en die teenwoordigheid van autotrofiese mutasies in die getransformeerde rasse van S.cerevisiae beïnvloed. Die verhoogde transkripsie vlakke wat met die multi-kopie, plasmied-gebaseerde YEp-tipe uitdrukkingsisteem, eerder as die geïntegreerde YIp-tipe sisteem, verkry is, het tot verhoogde xilanase produksie gelei. Heteroloë xilanase produksie het dus nie die uitskeidingskapasiteit van die gasheer versadig nie. Die genetiese stabiliteit van die autoselektiewe, YEp-tipe uitdrukkingsisteem in langtermyn chemostaat-kulture is ook gedemonstreer. Hoë vlakke van xilanase produksie deur getransformeerde S. cerevisiae rasse met autotrofiese merkers het die stabilisering van die stikstof metabolisme, deur die versadiging van die sel met ingevoerde aminosure, vereis. Die verwydering van oormatige autotrofiese merkers het tot hoë vlakke van xilanase produksie deur die prototrofiese transformant in gedefinieerde medium sonder aminosuur byvoeging gelei. Heteroloë xilanase produksie deur die prototrofiese transformant kon verder verbeter word deur die byvoeging van voorkeur-aminosure of suksinaat tot die gedefinieerde medium, en ‘n addisionele behoefte aan metaboliese voorloper-molekules en bou-blokke vir vreemde proteïensintese het dus bestaan. Vergelykbare vlakke van heteroloë xilanase produksie is in kulture met hoë sel-digthede van die alternatiewe gis, Pichia stipitis, verkry deur die doeltreffende induksie van die eiesoortige ADH2-promotor en die byvoeging van ‘n aminosuur-mengsel tot die gedefinieerde medium, wat die teenwoordigheid van generiese beperkinge in transkripsie, voedingstof-beskikbaarheid en biosintetiese kapasiteit van die gis vir vreemde proteïen produksie deur verskeie giste uitgewys het. Die teenwoordigheid van globale sensoriese- en beheer-meganismes is bevestig deur die fisiologiese respons van S. cerevisiae tot heteroloë proteïen produksie, wat die afwaartse regulering van biosintese en groei, en die induksie van verskeie prosesse betrokke by die algemene voedingstres-respons, ingesluit het. Heteroloë xilanase produksie is ook op ‘n na-transkripsionele vlak aktief gereguleer deur die autotrofiese transformante in reaksie tot die vlak van aminosuur beskikbaarheid. Die biosintetiese kapasiteit vir vreemde proteïen-produksie van beide rekombinante S. cerevisiae en P. stipitis is ook in reaksie tot die fisiologiese toestand van die gis en die beskikbaarheid van voedingstowwe gereguleer. Die teenwoordigheid van hierdie regulatoriese meganismes het die willekeurige manipulasie van sellulêre proteïen-biosintese bemoeilik.
32
Kasap, Murat. "Nitrogen Metabolism and Solvent Production in Clostridium Beijerinckii Nrrl B593". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28446.
Abstract (sommario):
The onset of solvent production by the clostridia involves regulation at the transcriptional level. The signal triggering the onset has not been identified, but redox and energetic states have been suggested as possible factors. Because several solvent-producing clostridia, including Clostridium acetobutylicum and Clostridium beijerinckii, are nitrogen-fixing organisms and both nitrogen-fixation and alcohol production (n-butanol, isopropanol and ethanol) are reductant-dependent processes, the effect of nitrogen fixation on the onset and progression of solvent production in C. beijerinckii NRRL B593 and vice versa was investigated. For this purpose, a defined growth medium containing three amino acids was developed for C. beijerinckii NRRL B593, and this medium was used for growing solvent-producing and nitrogen-fixing cultures. The nitrogen-fixing cultures produced solvents with a solventogenic shift, which appeared to coincide with a decrease in nitrogen-fixing activity. Measurement of specific activities of acetoacetate decarboxylase and aldehyde dehydrogenase and Northern blot analysis of the mRNA of the solvent-producing genes in samples harvested periodically from a nitrogen-fixing culture of C. beijerinckii showed the presence of both enzyme activities and the mRNA carrying the solvent-production genes throughout incubation. A 2.5-fold increase in the specific activity of acetoacetate decarboxylase and a 4.5-fold increase in the specific activity of aldehyde dehydrogenase were observed when the activities in the latest cell-free extract was compared with the activities in the earliest cell-free extract. When C. beijerinckii was grown in the medium containing 4 mM ammonium acetate, the onset of nitrogen fixation coincided with the onset of solvent production and prevented accumulation of solvents to high levels, which suggested competition between alcohol-producing enzymes and nitrogenase for the reductant.
Recently, a 20-kb region of the genomic DNA of C. beijerinckii NRRL B593 that contained the nif genes and ORFs with other putative functions was sequenced in our laboratory. An examination of the nif clusters of C. beijerinckii, C. acetobutylicum and C. pasteurianum revealed apparent differences in the intervening ORFs which suggested differences in the regulation of nitrogen fixation in these organisms. Transcriptional analysis of genes in the nif cluster of C. beijerinckii by Northern blotting revealed four different transcripts. The absence of mRNAs of the nif-associated ORFs in RNA samples isolated from non-nitrogen-fixing cells indicated that the nif-associated ORFs are regulated in parallel to the nif genes. By studying the effect of ammonia addition on nitrogen-fixing activities of C. beijerinckii and C. pasteurianum, significant differences in the regulation of nitrogen-fixation in the two species were observed. C. beijerinckii NRRL B593, but not C. pasteurianum, showed a rapid decrease in nitrogen-fixing activity in vivo upon ammonium acetate addition. However, measurement of nitrogen-fixing activities in vitro before and after ammonium acetate addition showed the presence of active nitrogenase throughout growth in both organisms. The results suggest that the nitrogenase activity in C. beijerinckii NRRL B593 is inhibited when ammonia is available.
A second nifH-hybridizing mRNA was detected in Northern blots during studies of the expression of nifH1 in C. pasteurianum. The mRNA was identified as that from either the nifH2 or nifH6 gene after sequencing the cDNA strands, which were generated by RT (Reverse Transcriptase)-PCR. In addition, Western blot analysis of the cell-free extracts of nitrogen-fixing cells of C. pasteurianum indicated the presence of a second NifH-related polypeptide. The two NifH-related polypeptides were separated by preparative gel electrophoresis and characterized by MALDI-TOF (Matrix-assisted Laser Desorption Ionization Time-Of-Flight) mass spectrometry. The results suggested the expression of NifH2/H6 protein in nitrogen-fixing cells of C. pasteurianum. The physiological significance of the expression of the nifH2 or nifH6 gene or both is yet to be determined.Ph. D.
33
Farmer, Ryan Michael. "Coordination of Carbon Dioxide and Nitrogen Metabolism in Rhodobacter sphaeroides". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365519943.
34
Qiao, ZhengDao. "Interactions between NO2 absorption and nitrogen metabolism in soyabean plants". Thesis, Qiao, ZhengDao (1998) Interactions between NO2 absorption and nitrogen metabolism in soyabean plants. PhD thesis, Murdoch University, 1998. https://researchrepository.murdoch.edu.au/id/eprint/51679/.
Abstract (sommario):
NO2 is a common atmospheric pollutant. It can enter plants through leaf absorption and participate in general N metabolism to ameliorate N-deficiency in plants. However, NO2 exposure sometimes exerts detrimental effects on plant growth. The hypotheses to explain the mechanism of these detrimental effects have remained inconsistent.
Besides formation of nitrate and nitrite as an additional N supply to plants, NO2 absorption by leaves also brings H+ into plants. Almost every process of nitrogen uptake and assimilation, (such as uptake of nitrate and ammonium, fixation of N2, absorption of NO2, reduction of nitrate and nitrite, and synthesis of amino acids from ammonium), involves production or consumption of H+. Therefore NO2 absorption and N metabolism may interfere with each other through changes in concentration of H+, which take part in reactions of N metabolism and influence activity of the enzymes catalyzing biochemical reactions in N metabolism of plants.
This study aims to specify the effects of NO2 exposure on nitrogen uptake and metabolism in soybean plants, and to explore the mechanistic links between the acidity changes caused by NO2 absorption and N metabolism, and the effects of NO2 on N metabolism and growth of plants.
The study was conducted mainly through exposure experiments. Plants were supplied with ammonium or 15N-labelled nitrate, and exposed to NO2 or clean air. H+ concentrations and concentrations of the products of N uptake and metabolism in plants and growth mediums were measured and compared between exposed plants and control plants.
These exposure experiments have explored the effects and relevant mechanisms of NO2 exposure on uptake and metabolism of nitrate and ammonium, on translocation and distribution of N within plant organs, on activity of N2-fixation, as well as the effects of N supplies to roots on NO2 absorption by leaves. In addition, two new calculation methods were proposed to improve the estimation methods for NO2 absorption by plants.
Exposing soybean plants, supplied with nitrate, to high levels of NO2 (1.1 µl 1-1) caused accumulations of ammonium and nitrate in leaves, decreases in nitrate uptake by roots and in the amount of organic N per plant, and increases in the acidities of both leaves and nutrient solution. These results suggest that an increase in H+ from NO2 absorption in exposed plants may inhibit ammonium assimilation, and convert HCO3- to H2CO3 in roots, causing the decrease in nitrate uptake by roots. The H+ from NO2 absorption may be neutralized by the OH- produced from nitrate reduction, or it may exude into the growth medium through roots. If the H+ cannot be promptly removed from exposed plants, the H+ accumulation may inhibit general assimilation and uptake of nitrate.
NO2 absorption, as a supplement to N supply, can partly meet the N demand of plants; and the N derived from NO2 absorbed by leaves was mainly located in leaves. Consequently NO2 exposure of plants supplied with nitrate usually decreases the nitrate transport from roots to leaves and the redistribution of N within plants.
Exposing the soybean plants, grown with ammonium, to 0.2 - 0.25 µl 1-1 of NO2 increased ammonium concentration in leaves, slowed down the rise in leaf acidity from ammonium assimilation, and decreased ammonium uptake by roots. These results suggest that reduction of the nitrate and nitrite, produced from N02 absorption, consumes H+ and competes for energy with ammonium assimilation which produces H+. It inhibits the increase in concentration of H+ from ammonium assimilation in exposed plants. As plants take up ammonium through exchange of the H+ in roots with the ammonium in nutrient solution, the lower H+ concentration in exposed plants decreases ammonium uptake by roots, compared with control plants. This inhibition of ammonium uptake may further restrict ammonium assimilation and H+ increase in exposed plants.
Long-term exposure of soybean plants to 0.2 µl 1-1 of NO2 increased concentrations of nitrite and H+ in root nodules, and inhibited activity of nitrogenase. Nitrate supply to roots intensified the nitrite accumulation, decreased the acidity in nodules, and alleviated the inhibition of nitrogenase activity. These results suggest that the H+ from N02 absorption accelerates reduction of nitrite to NO and conversion of LHb to LHbNO, resulting in inhibition of nitrogenase activity. Reduction of nitrate in plants consumes H+, which may be the reason why nitrate supply can alleviate the inhibitory effects of NO2 on nitrogenase activity.
Leaf pH and absorption rate of NO2 of the plants growing in a nitrate solution were higher than those of the plants growing in ammonium. The absorption rates of NO2 of both sets of plants decreased with increasing the duration of NO2 exposure. These results suggest that accumulation of H+ in leaves, caused by NO2 absorption and ammonium assimilation, may slow down the dissolution of NO2 in extracellular fluid of leaves, and result in the decrease in absorption rate of NO2. The decline in NO2 absorption with increasing exposure time, which is analogous to a decline in exposure concentration of NO2, may be one of the reasons why plants show some acclimation to long-term exposure.
The popular methods for quantitative estimation of NOx absorption by leaves of plants supplied with 15N-labelled fertilizer, the 15N dilution method and the difference method, were compared with the classical mass balance (MB) method and/or the 15NOx method. Neglect of the influence of NOx exposure on N uptake by roots results in an overestimation in NO2 absorption calculated using the 15N dilution method. Two new alternative calculation methods, the TNF method and the TWF method, are proposed on different prerequisites. The TNF method can reduce the error of 15N dilution method, and give closer results to the MB method or 15NOx method. The TWF method is suitable to calculate NOx-N in organs (leaf, stem, root) of exposed plants. The estimation error of these methods are found to increase with decreasing concentration of 15N-labelled fertilizer supplied to roots.
The results of these exposure experiments suggest that the acid-alkali balance plays a fundamental role in determining the interactions between NO2 absorption and N metabolism in exposed plants. H+ not only take part in the reactions of uptake and assimilation of various forms of nitrogen, it also affects the activity of the enzymes catalyzing reduction of oxidized N and synthesis of organic N. NO2 and other forms of N interact on each other through production or consumption of H+ in their uptake and assimilation. Whether the concentration of the H+ produced from NO2 absorption and N assimilation in exposed plants can be kept at a suitably low level, may determine whether the effects of NOx exposure on plants are beneficial or detrimental.
According to the role of H+ in uptake and metabolism of N, two conclusions are possible:
1. Susceptibility of plants to NO2 exposure may depend on the acidity of the growth medium.
2. Velocities of uptake and assimilation of nitrogen in plants may fluctuate cyclically.
Further experiments to test these inferences are recommended.
35
Grantley-Smith, M. P. "Nitrogen cycling in growing cattle fed maize silage". Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370353.
36
Woodend, John J. "Genetic and physiological studies on potassium and nitrogen uptake and utilization in wheat". Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27653.
Abstract (sommario):
Experiments were undertaken to examine the extent of variation for potassium and nitrogen uptake and utilization in wheat and also to address some issues of relevance to the improvement of these traits. These issues included the inheritance of these traits and the difficulties that could arise due to (1) the methodology that is used to measure ion fluxes and utilization, (2) ontogenetic variation in the expression of these traits, and (3) the growth stage at which nutrient utilization is evaluated. To compare varieties developed during different periods in the history of wheat breeding, the varieties were assigned to five groups on the basis of height and origin.
Nutrient fluxes were measured either as average net fluxes or short-term net fluxes. Nutrient utilization was expressed as shoot fresh weight per plant, efficiency ratio or utilization efficiency.
Substantial variation was observed for all traits except potassium and nitrogen efficiency ratios. Although short-term net potassium fluxes were negatively correlated with root potassium concentration, some of the differences in flux were not associated with differences in root potassium concentration. These differences must therefore be heritable. Due to the complexity of the regulation of nitrate uptake, genotypic differences in short-term net nitrate flux were not examined in relation to root nitrate concentration. Therefore, some of the variation in nitrate flux could be due to differences in root nitrate concentration or some other factor(s) which regulates nitrate uptake.
Significant differences between groups were also observed. The tall varieties had the highest potassium and nitrate fluxes but were not significantly different from the triple dwarfs. The double dwarfs were the poorest performers for both nutrient uptake and utilization. In general, the tall traditional varieties were more vigorous and hence showed the highest shoot weight per plant and utilization efficiencies. These findings are examined in relation to the contention that plant breeding under high fertility conditions may have resulted in a decline in the ability of plants to acquire and utilize mineral nutrients.
The inheritance of short-term net potassium flux, shoot weight per plant, potassium efficiency ratio and potassium utilization efficiency was studied in four crosses. Complex modes of inheritance were observed for all the traits. For one of the crosses significant reciprocal effects were observed for shoot weight per plant, efficiency ratio and utilization efficiency. Narrow sense heritabilities for the two traits most likely to be selected for, namely short-term net potassium flux and shoot weight per plant, indicated that selection for these traits should be carried out amongst families rather than amongst single plants. Diallel analysis for nitrate uptake and utilization indicated that both additive and dominance gene effects are important in the determination of these traits.
The effect of developmental changes in potassium uptake and utilization on varietal comparisons and genetic studies was investigated by comparing the performance of six varieties at different stages of growth over a five-week period. The rankings of the varieties for short-term net potassium flux and shoot weight per plant were found to be fairly consistent. Correlations between average net fluxes for different time periods as well between short-term and average net fluxes were poor. These findings indicate that selection for differences in uptake should be based on fluxes obtained from solutions identical in concentration to the growth solution rather than on perturbation fluxes obtained by depletion of a solution much more concentrated than the growth solution.
All measures of potassium utilization based on vegetative growth were poorly correlated with performance at the adult stage. Significant negative rank correlations between shoot fresh weight per plant and grain weight per plant were obtained most likely due to differences in harvest index. This finding casts some doubt on the usefulness of vegetative measures of nutrient utilization as indicators of nutrient-use efficiency for a crop in which the economic product consists of grain.Science, Faculty of
Botany, Department of
Graduate
37
Dunstan, R. H. "A GC-MS approach to carbon and nitrogen metabolism in Paracoccus denitrificans". Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370248.
38
Chénier, Martin. "Impact of seasonal variations, nutrients, pollutants and dissolved oxygen on the microbial composition and activity of river biofilms". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85144.
Abstract (sommario):
Biofilm communities were cultivated in rotating annular bioreactors using water from the South Saskatchewan River. The impacts of seasonal variations, nutrients, pollutants and dissolved oxygen on the activity and composition of the biofilms were assessed by using a combination of microcosm assays and molecular biology techniques.The seasonal pattern in nitrification, denitrification and hexadecane mineralization, and in the occurrence of nirK in the South Saskatchewan River biofilms was: fall greater than winter, which was equivalent to spring. Hexadecane mineralization was higher in fall 1999 than in fall 2001, denitrification was similar in these two years, and no seasonal pattern of nitrification was observed.
The addition of combined nutrients (C, N, and P) resulted in significant increases in the measured bacterial activities and in the predominance of alkB, nirS and nirK in all seasons and years. The addition of individual nutrients did not stimulate hexadecane mineralization, denitrification, and the PCR amplification of nirS and nirK. In fall 1999, CNP and, to a lesser extent P, stimulated nitrification, whereas in fall 2001, no pattern was observed. The results showed that nutrients, especially P, were limiting for bacterial activities, and that the biofilm activities and composition varied with nutrient availability and time of year.
At the concentration assessed (1 ppb), hexadecane partially inhibited denitrification to similar extents in both years, had a negative impact on nitrification and hexadecane mineralization in fall 1999, and a positive impact on these two latter activities in fall 2001. Nickel (0.5 mg liter-1 ) negatively affected denitrification but had no effect on hexadecane mineralization. The alkB and nirS genes were less predominant and absent, respectively, in biofilms grown in the presence of nickel. DGGE analyses indicated that nickel reduced the biofilm bacterial diversity.
The results presented herein provide much needed information on the microbial ecology of river biofilms, and on the impact and interactive effects of pollutant and nutrient inputs on these biofilms. These results and the techniques used in this project can be applied to monitor environmental effects of anthropogenic activities on aquatic biofilms, and can contribute to establish or revise environmental regulations.
39
Mikhael, Marc Raymond. "The role of nitrogen monoxide in macrophage and reticulocyte iron metabolism". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66688.
Abstract (sommario):
The human body contains about three to four grams of iron, a metal of vital importance for almost all forms of life. The majority of body iron is used by developing red blood cells for hemoglobin production. Macrophages digest senescent red blood cells, break down heme and then return heme-derived iron to the circulation. Macrophages also produce an immense amount of reactive oxygen species, including nitrogen monoxide (NO), which in turn severely reduces pathogen vitality and proliferation, in response to inflammatory stimuli. In addition, to its cytotoxic effects on pathogens and tumor cells, NO regulates macrophage iron metabolism in numerous ways. Furthermore, NO derived from bone-marrow macrophages may also expose developing red blood cells to the modulating effects of NO. In anemia of chronic disease (ACD), the perturbation of macrophage iron export during inflammatory conditions leads to iron-restricted erythropoiesis. ACD is usually present in patients suffering from tumors, chronic infections, or chronic inflammatory conditions and results from retention of macrophage iron, thus leading to anemia. In this thesis we examine the effects of NO on macrophage and reticulocyte iron metabolism and suggest that NO could contribute to the pathogenesis of ACD by increasing macrophage iron storage and impairing hemoglobin synthesis in developing red blood cells. In chapter 2 we investigated the effects of NO on the synthesis of the iron storing protein, ferritin, in macrophages. We showed that the increase in ferritin synthesis by NO occurs independently of the ferritin-translation regulatory proteins, known as iron regulatory proteins (IRPs). Moreover, we demonstrated that sodium nitroprusside (SNP) greatly increases the efficiency of ferritin mRNA translation. In chapter 3 we examined the possibility that ferritin-iron could be used for the macrophage's own metabolic needs. Indeed, we show that stimulation of heme synthesLe corps humain contient entre 3 et 4 grammes de fer. Ce métal est d'une importance vitale pour presque toute forme de vie. La majorité du fer contenu dans le corps est utilisé par les globules rouges en développement pour la production d'hémoglobine. Les macrophages digèrent les globules rouges sénèscents, décomposent l'hème et remettent en circulation le fer qui en dérive. Les macrophages produisent aussi une immense quantité d'espèces oxygénées réactives, incluant le monoxyde d'azote (NO), qui en retour réduit sévèrement la vitalité et la prolifération des agents pathogènes, en réponse aux signaux inflammatoires. Additionnellement à ses effects cytotoxiques sur les pathogènes et les cellules tumorales, le NO régule le métabolisme du fer dans les macrophages de nombreuses façons. Le NO qui dérive des macrophages de la moëlle osseuse pourrait aussi exposer les globules rouges en développement à l'effet modulateur du NO. Dans l'anémie des maladies chroniques (AMC), la perturbation de l'exportation du fer par les macrophages au cours de conditions inflammatoires mène à l'erythropoïèse restreinte au fer. L'AMC est habituellement présente chez les patients souffrant de tumeurs, d'infections chroniques, ou d'inflammation chronique, elle aboutit à la rétention du fer par les macrophages, conduisant ainsi à l'anémie. Dans cette thèse, nous examinons l'effet du NO sur le métabolime du fer dans les macrophages et les réticulocytes. Nous suggèrons que le NO pourrait contribuer à la pathogenèse de l'AMC en augmentant le stockage du fer dans les macrophages et en affectant la synthèse d'hémoglobine dans les globules rouges en développement. Dans le chapître 2, nous étudions les effects du NO sur la synthèse de la ferritine, protéine de stockage du fer, dans les macrophages. Nous avons montré que l'augmentation de la synthèse de ferritine par le NO apparaît indépendement de
40
Holder, Vaughn B. "THE EFFECTS OF SLOW RELEASE UREA ON NITROGEN METABOLISM IN CATTLE". UKnowledge, 2012. http://uknowledge.uky.edu/animalsci_etds/6.
Abstract (sommario):
The objective of this research was to investigate the effects of slow release urea on N metabolism in cattle. The ruminal behavior of Optigen®II and the effect of basal diet on the in situ degradability of urea and Optigen®II were evaluated. The effect of slow release urea and its interaction with degradable intake protein (DIP) level in the diet on N retention and excretion was evaluated utilizing 8 Holstein steers in a 4 x 4 Latin square experiment. In addition, the effect of slow release urea and DIP level on ruminal and systemic urea kinetics was evaluated using stable isotope techniques with 8 Holstein steers in a 4 x 4 Latin square experiment. Finally, slow release urea was evaluated under a practical beef production setting. The performance of slow release urea was compared to regular feed grade urea in a 42 day receiving study (288 Angus cross steers) as well as a 70 day growing study (240 Angus cross steers). High forage diets increased the ruminal degradation rate of both urea and slow release urea an increased the extent of degradation of slow release urea when compared to high concentrate diets. Lower DIP concentrations in the diet reduced systemic urea production, ruminal ammonia and plasma urea concentrations and urinary urea excretion under most circumstances but also led to a reduction in N retention, reduced diet digestibility, lower feed intake, lower growth rate and decreased feed efficiency. High DIP intakes increased N retention, growth rate, diet digestibility and improved feed efficiency but also lead to increased excretion on urea N in the urine. Slow release urea improved N retention and efficiency of N retention in high DIP diets when compared to urea and generally reduced plasma urea and ruminal ammonia concentrations. Compared to urea, slow release urea did not significantly improve the production of receiving cattle. However Optigen®II improved the feed efficiency when compared to urea on high concentrate diets but reduced feed efficiency on high forage diets.
41
Pedro, Roig Laia. "GlnK regulatory proteins and their role in Haloferax mediterranei nitrogen metabolism". Doctoral thesis, Universidad de Alicante, 2012. http://hdl.handle.net/10045/27319.
42
Hutchins, David Allen. "Nitrogen and iron interactions in filamentous cyanobacteria". PDXScholar, 1989. https://pdxscholar.library.pdx.edu/open_access_etds/3934.
Abstract (sommario):
The investigations described in this paper are an attempt to further define and quantify the interrelationship of nitrogen fixation and iron nutritional physiology in these two species. Chapter II will present and compare data on nutritional ratios of field collected Trichodesmium colonies and laboratory Anabaena cultures, with the intent of examining possible correlations between observed iron levels and protein nitrogen and chlorophyll concentrations, as well as nitrogen fixation rates. Chapter Ill is an examination of nitrogen fixation and siderophore production in Anabaena with emphasis on the possible implications of hypothesized synergistic effects of these two physiological capabilities on cyanobacterial dominance and bloom formation. Chapter IV will deal with the possibility of gratuitous manganese repression of Anabaena siderophore production in the manner described by Hantke (1987) for regulation of siderophore production in E. coli. The Conclusions chapter (Chapter V) will present a discussion of the results of these experiments in the context of current problems in cyanobacterial physiology, ecology and evolution. It is hoped that a significant contribution can be made to our understanding of the related problems of cyanobacterial dominance in freshwater ecosysytems and the scarcity of cyanobacterial nitrogen fixation in marine ecosystems.
43
Burity, Helio Almeida. "Nitrogen fixation, transfer and competition in alfalfa-grass mixtures". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73959.
44
Rius, Agustin Gregorio. "Nitrogen Efficiency and Regulation of Protein Synthesis in Lactating Dairy Cows". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37780.
Abstract (sommario):
Dairy herds are major contributors to N pollution because 70% of the N intake is lost to the environment and 30% or less is retained in milk protein. Plasma amino acids (AA) that are not used for protein synthesis in mammary glands (MG) are catabolized in post splanchnic tissues (liver plus gastrointestinal tract, pancreas, spleen, portal system, and associated adipose tissue) and two thirds of the net supply of essential AA (EAA) are cleared in splanchnic tissues. Thus, increasing AA capture in MG would be expected to reduce AA catabolism and thereby increase efficiency of AA utilization. The objectives of the work presented in this dissertation were to test the effect of energy and N intake on cell regulatory mechanisms, nutrient kinetics, milk, milk protein yield, and N efficiency in dairy cows.
The aim of the first study was to test whether metabolizable protein (MP) and dietary energy exerted independent effects on milk protein synthesis and postabsorptive N efficiency. Forty mid-lactation cows (32 multiparous Holstein and 8 primiparous Holstein x Jersey cross-breds) were used in a complete randomized design with a 2 x 2 factorial arrangement of diets. Cows were assigned to one of four dietary treatments: high-energy, high-protein (HE/HP); high-energy, low-protein (HE/LP); low-energy, high-protein (LE/HP); and low-energy, low-protein (LE/LP). Energy concentrations were 1.55 (HE/HP and HE/LP) or 1.44 (LE/HP and LE/LP) Mcal NEL/kg DM according to the NRC model. Changes in predicted MP were achieved by feeding diets with 6.6 (HE/HP and LE/HP) or 4.6% (HE/LP and LE/LP) ruminally undegradable protein (DM basis). Ruminally degradable protein was held constant at 10.1% of DM. All cows were fed HE/HP diet from day 1 to 21 followed by the respective treatments from day 22 to 43 (n=10). Milk protein yield was reduced as dietary energy was reduced. There were no interactions between dietary energy and protein for either milk or protein yield. Milk urea N was significantly affected by energy and protein with an interaction (HE/HP=17.2, HE/LP=12.2, LE/HP=21.0, LE/LP=12.2 mg/dl). Nitrogen efficiency was affected by energy and protein supplies with no interaction and ranged from a low of 31% (LE/HP) to a high of 43% (HE/LP). Although energy and protein independently affected milk and protein yield the tissue and cellular mechanisms that regulate milk production were not studied.
The second experiment studied cellular mechanisms in MG that contributed to the regulation of protein synthesis in the presence of energy or protein supply. We hypothesized that metabolism of AA in the MG is controlled by systemic and local tissue adaptations and when combined with altered mammary cell function controlled milk protein yield. Six primiparous mid-lactation Holstein cows with rumen cannulas were randomly assigned to abomasal infusions of casein and starch using a 2 x 2 factorial arrangement. The design was a replicated incomplete 4 x 4 Latin-square. All animals received the same basal diet (17.6% CP and 1.58 Mcal NEL/kg DM) throughout the study. Cows were restricted to 70% of ad libitum intake and infused abomasally for 36 h with water, starch (2 kg/d), casein (0.86 kg/d), or the combination (2 kg/d starch + 0.86 kg/d casein) using peristaltic pumps. Milk weights, milk samples, and arterial and venous blood samples were collected during the last 8 h of infusions. Mammary biopsy samples were collected and tissue protein prepared to evaluate cell signaling. Animals infused with casein had increased arterial concentrations of NEAA and EAA, as well as net uptake and clearance; however, milk protein yield did not increase. Animals infused with starch however, exhibited reduced arterial concentrations of NEAA and EAA but increased clearance and net uptake of most AA. Additionally, infusions of starch increased circulating concentration of insulin, IGF-I, and glucose as well as the rate of mammary plasma flow. Abomasal infusions of starch activated mammary activity of ribosomal protein S6 irrespective of other treatments. However, mammary tissue mTOR increased activity in response to casein only when starch was present during the infusions. These results suggest that cell signaling activation responded to different nutritional stimuli. Milk and protein yield increased in animals infused with starch. Therefore, MG positively responded to energy supply and engaged local and intracellular regulatory mechanisms to achieve that response. Understanding these adaptations could be beneficial in the development of mathematical representations for nutrients utilization in lactating animals. These two studies supported our hypotheses that regulatory mechanism are activated during limiting supply of AA to sustain protein synthesis in MG. The accuracy of mathematical models for lactating animals would increase if effects of energy on AA metabolism and cell signaling related to protein synthesis were included in the representation of milk protein synthesis.Ph. D.
45
Beltran, Casellas Gemma. "Effect of low temperature fermentation and nitrogen content on wine yeast metabolism". Doctoral thesis, Universitat Rovira i Virgili, 2005. http://hdl.handle.net/10803/8651.
Abstract (sommario):
Les fermentacions a baixes temperatures (13ºC o inferiors) són interessants en l'elaboració de vins blancs i rosats, ja que augmenten la retenció i la producció dels aromes, i per tant la qualitat del producte final. Però aquestes baixes temperatures també tenen certs desavantatges, com una disminució en la velocitat de consum de sucres, obtenint fermentacions més llargues i amb risc de parades.Per intentar millorar el procés fermentatiu i la qualitat del producte final es van fixar els següents objectius:
- L'estudi del metabolisme del llevat a baixes temperatures de fermentació (13ºC), i la seva influència en aspectes com la cinètica fermentativa, el creixement dels llevats; el metabolisme lipídic; la producció dels aromes, i la expressió gènica global del llevat.
- El coneixement del metabolisme nitrogenat del llevat en la fermentació alcohòlica, així com en les addicions de nitrogen realitzades a diferents moments de la fermentació.
Els resultats obtinguts mostren que les baixes temperatures, a part d'augmentar la durada de fermentació, augmenten la viabilitat dels llevats al llarg del procés, provoquen canvis en la composició lipídica, augmentant la fluïdesa de la membrana, i milloren la composició aromàtica del vi, incrementant la producció d'aromes beneficiosos i disminuint-ne la de compostos perjudicials pel la qualitat vi final.
Amb l'objectiu d'identificar els mecanismes moleculars que causen aquests canvis metabòlics a baixes temperatures, vam utilitzar la tècnica de "chips de DNA" o "microarrays" per comparar l'expressió global dels gens del llevat fermentant a 13ºC i fermentant a 25ºC. En general, aquest anàlisis de l'expressió global del llevat dut a terme per primer cop en condicions industrials rebel·la importants canvis en la expressió d'alguns gens tant al llarg de la fermentació com entre les dos temperatures. La fermentació a 13ºC presenta l'avantatge d'induir una ràpida resposta al estrès que podria aportar més resistència al llevat al llarg de la fermentació, i per això augmentar-ne la seva viabilitat.
En l'estudi del metabolisme nitrogenat del llevat al llarg de la fermentació, vam observar que en la fermentació alcohòlica les cèl·lules evolucionen d'una situació de repressió per nitrogen al començament de la fermentació, quan hi ha compostos nitrogenats en el medi, a una situació de de-repressió quan el nitrogen ha estat consumit pel llevat. Aquestes situacions de repressió/de-repressió determinen el perfil de consum de l'amoni i dels aminoàcids, els quals determinen a la vegada la producció d'alguns compostos aromàtics. La repressió dels gens de les permeases GAP1 i MEP2, la baixa activitat arginasa o la inhibició en la captació de l'arginina, poden ser considerats bons marcadors de Repressió Catabòlica per Nitrogen (NCR).
L'addició de nitrogen és una pràctica habitual en bodega per evitar problemes fermentatius. Els nostres estudis demostren que el moment de dur a terme aquesta addició condiciona no només la cinètica fermentativa i el creixement del llevat, sinó també el perfil de consum d'amoni i aminoàcids, i la producció de compostos secundaris.
L'assimilació de nitrogen per part dels llevats també depèn de la temperatura de fermentació, la qual determina tant la qualitat com la quantitat dels requeriments nitrogenats dels llevats. A baixa temperatura de fermentació, l'amoni i la glutamina són menys consumits, mentre que els aminoàcids regulats per NCR ho són més.
Aquesta tesi és una aproximació global al comportament del llevat a baixes temperatures i al metabolisme nitrogenat, i ens obra moltes possibilitats d'estudi, punts on s'hauria d'aprofundir per un millor coneixement i millora d'aquestes fermentacions.
Wines produced at low temperatures (10-15ºC) are known to develop certain characteristics of taste and aroma, not only related to primary aroma retention. However, low temperature fermentations have also some disadvantages that comprise an increase of the duration of the process and a higher risk of stuck and sluggish fermentation.
In order to improve the fermentation performance and the quality of wine, we established the following objectives:
- The study of wine yeast metabolism at low temperature fermentation (13ºC), and its influence in aspects as the fermentation kinetic, the yeast growth, the yeast lipid metabolism, the production of aromatic compounds, and the global yeast gene expression.
- The study of nitrogen metabolism of yeast in alcoholic fermentation, as well as the study of nitrogen supplementations at different points of the fermentation.
Our results showed that low temperatures increased the length of fermentation, the yeast viability along the process, but also modified the lipid composition of yeast cells, increasing the membrane fluidity, and improved the aromatic composition of the wine, increasing the flavour-active compounds and decreasing the unpleasant ones such as acetic acid and fusel alcohols.
To identify the molecular mechanism that causes these changes in aroma profiles and to verify that 13°C-fermentation does not hinder other cellular properties, we compared the expression programs during wine fermentation at 13ºC and 25°C (using Microarrays technology), and tentatively correlated the differential genes expression with changes in intracellular lipid content, and in the production of flavour-active metabolites
This genome-wide analysis carried out for the first time with a commercial yeast strain under true industrial conditions revealed many major differential genes expression both during the course of the wine fermentation and between two fermentation temperatures. With respect to industrial output, wine fermentation conducted at 13°C presents the advantage to induce an early cold stress response that apparently does not penalize the wine fermentation process, further than the longest fermentation length.
In the study of the nitrogen metabolism of yeast along the fermentation we observed that in wine fermentations the cells evolve from a nitrogen-repressed situation at the beginning of the process to a nitrogen-derepressed situation as the nitrogen is consumed. These nitrogen-repressed/derepressed conditions determined the different patterns of ammonium and amino acid consumption. Arginine and alanine were hardly used under the repressed conditions, while the uptake of branched-chain and aromatic amino acids increased. The repression of GAP1 and MEP2 genes in the cells, low arginase activity or inhibition of arginine uptake could be considered as a good Nitrogen Catabolite Repression markers.
Winemakers systematically supplement grape musts with diammonium phosphate to prevent nitrogen-related fermentation problems. The timing of the nitrogen additions influenced the biomass yield, the fermentation performance, the patterns of ammonium and amino acid consumption, and the production of secondary metabolites. These nitrogen additions induced a nitrogen-repressed situation in the cells, and this situation determined which nitrogen sources were selected.
Nitrogen assimilation also depends on fermentation temperature. Fermentation temperature is an important factor determining utilization of nitrogen sources during fermentation of grape juice, and influences the quantity and the quality of nitrogen requirement. Ammonium and glutamine, the preferred source for biomass production, are less consumed at low temperature. Likewise amino acids that are only taken up under derepressed conditions (arginine, alanine, asparagine, etc.) are more consumed at low temperature.
The information provided by this thesis represents a starting point for deciphering the regulatory circuits during wine fermentation, overall at low temperature, and should help us to understand the properties of wine yeasts. Our results open up a lot of interesting perspectives that will further our knowledge of wine yeast metabolism during wine fermentations.
46
Sinclair, Liam Archibald. "Energy and nitrogen synchronisation and its effect on rumen metabolism in sheep". Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303959.
47
Davis, Daniel. "A study of nitrogen metabolism and lipopeptide biosurfactant production by Bacillus species". Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394224.
48
Vera, Juan Carlos Ku. "Energy and nitrogen metabolism in cattle nourished by intragastric infusion of nutrients". Thesis, University of Aberdeen, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238728.
Abstract (sommario):
Two open-circuit indirect-calorimetry ventilated hoods were built for measuring the energy exchanges of cattle nourished wholly be continuous intragastric infusions of mixtures of volatile fatty acids and casein. In Expt. 1 the energy costs of eating and ruminating oat husks were measured. The energy costs of eating and rumination were estimated to be 11.4 J/kg live weight and 9.3 J/kg live weight per minute spent eating and ruminating respectively. The energy cost of standing above that of lying was calculated to be 6.6 kJ/kg live weight per day. In the subsequent four experiments, the effect of abomasal infusions of various amount of glucose on the heat production, nitrogen metabolism and blood metabolites of Friesian steers was investigated. In Expt. 2, the abomasal infusion of 350 g of glucose/d after a five day fast, decreased the urinary nitrogen excretion to the endogenous nitrogen loss values. In Expt. 3 the infusion of glucose at low rates (16, 25 or 50 kJ/kg W0.75/d) had virtually no nitrogen-sparing effect. In Expts. 4 and 5 the response in heat production to abomasal infusions of glucose differed between steers. Two steers had consistent heat decrements whereas one steer showed mostly heat increments. Fasting urinary nitrogen excretion was gradually reduced by glucose infusion, demonstrating the nitrogen-sparing effect of glucose. Plasma insulin was decreased during the fast in Expt. 4, but it was not affected by glucose infusion in both Expts. 4 and 5, suggesting that nitrogen-sparing is not mediated by insulin. Plasma free fatty acids and β-hydroxybutyrate concentrations were increased several-fold during the fast and were decreased by the infusion of glucose. It is concluded that the increased loss of nitrogen in fasting cattle is unrelated to a specific requirement for glucose precursors during the fast.
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Conlon, Helen Elizabeth. "The characterization of 'areB', encoding a novel GATA factor of 'A. nidulans'". Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272780.
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Van, der Merwe George K. (George Karel)1968. "NCR-sensitive gene expression and regulation of nitrogen interconversion by VID30 in Saccharomyces cerevisiae". Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52952.
Abstract (sommario):
Dissertation (PhD)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: Saccharomyces cerevisiae uses the nitrogenous compounds in its environment selectively. The basis of this phenomenon is the transcriptional regulation of genes whose products are required for nitrogen catabolism. A rich nitrogen source represses the expression of genes required for the degradation of poor nitrogen sources via the action of the target of rapamyein (TOR) signaling cascade. If only a poor nitrogen source is available, these genes are derepressed. This process is known as nitrogen catabolite repression (NCR) or nitrogen regulation. The DALI and DAL4 genes of S. cerevisiae are transcribed divergently from the 829 bp intergenic region. The five known UASNTR elements (GATAI-5) were mutated in the full context of the intergenic promoter. All five elements are required for the transcriptional activation of DAL4. The two elements most proximal to DAL4 (GATA4 and GATA5) contributed the most and the one most distal (GATAI) contributed the least to its expression. In contrast, three of the five elements (GATA2-4) are required for DALI activation. In addition, analyses revealed that no single element is shared equally between these two genes. Predictions as to the function of known nitrogen-regulating elements based on their sequence and location proved to be inaccurate in some cases. Mutation analyses of the three UISALL elements present in the intergenic promoter region revealed that UIS8, which does not share a high degree of homology with the consensus UISALL sequence, is required the most for transcriptional induction of both DALI and DAL4. Also, UIS7, which shares the most similarity with the UISALL consensus sequence, has the phenotype of a repressor-like element when mutated. These observations therefore portray the opposite phenotypes of what was expected. We identified a regulator, Vid30p, which is required for the transcriptional response of S. cerevisiae in low ammonia conditions. Genetic analyses of the vid30/j, mutant indicate that Vid30p functions by regulating the expression of genes required for the production and degradation of glutamate. The transcription of VID30 is NCR-sensitive, highly induced by low concentrations of ammonia, and rapamycin-sensitive. In addition, the vid30/j, mutant is hypersensitive to rapamycin, indicating that this protein is, directly or indirectly, controlled by the TOR signaling pathway.
AFRIKAANSE OPSOMMING: Saccharomyces cerevisiae het die vermoeë om stikstofbronne vanuit die omgewing selektief te benut. Die basis van hierdie verskynsel is die transkripsionele regulering van gene wat vir proteïene kodeer wat stikstof katabolisme bemiddel. 'n Goeie stikstofbron onderdruk die transkripsie van gene wat met die degradering van swak stikstofbronne gemoeid is. Hierdie onderdrukking word deur die teiken-van-rapamisien (TVR)-seintransduksiepad bewerkstellig. Wanneer slegs 'n swak stikstofbron beskikbaar is, word hierdie gene geaktiveer. Hierdie verskynsel staan as stikstofkatabolietonderdrukking (SKR) of stikstofregulering bekend. Die DALI- en DAL4-gene van S. cerevisiae word divergent vanaf 'n 829 bp intergeniese area getranskribeer. Vyf UASNTR-elemente (GATAI-5) is in die volle konteks van die intergeniese promotor gemuteer. Al vyf elemente word vir DAL4 transkripsionele aktivering benodig. Die twee elemente mees proksimaal tot DAL4 (GATA4 en GATA5) lewer die grootste bydrae tot DAL4-geenuitdrukking, terwyl die mees distale element (GATAI) die kleinste bydrae lewer. In teenstelling hiermee lewer slegs drie van die vyf elemente (GATA2-4) 'n noemenswaardige bydrae tot DALI se uitdrukking. Nie een van die vyf elemente lewer 'n gelykwaardige bydrae tot die uitdrukking van DALI en DAL4 nie. Voorspellings betreffende die bydrae van die onderskeie UASNTR-elemente tot die uitdrukking van die DALI- en DAL4-gene, gebaseer op die sekwens en die posisie van die element in die promotor, was meestal onakkuraat. Die drie U/SALL-elemente in die intergeniese area is gemuteer en toon dat U/S8, wat nie 'n groot mate van homologie met die U/SALL konsensus sekwens deel nie, die mees kritiese element vir transkripsionele induksie van beide DALI en DAL4 is. UIS7, wat 'n hoër mate van homologie met die UISALL konsensus sekwens deel, toon die fenotipe van 'n onderdrukkingselement wanner dit gemuteer word. Hierdie waarnemings is dus die teenoorgestelde van wat verwag is. Ons het 'n reguleerder, Vid30p, geïdentifiseer wat benodig word VIr die transkripsionele response van stikstofgereguleerde gene in lae konsentrasie ammonium. Genetiese analises van die vid3011 mutant toon dat Vid30p funksioneer deur die transkripsie van gene gemoeid met die vorming en degradering van glutamaat te reguleer. Die transkripsie van V/D30 is SKO-sensitief, word sterk deur lae konsentrasies ammonium geïnduseer, en is rapamisien-sensitief. Die vid30t!. mutant is ook hipersensitief vir rapamisien, wat aandui dat Vid30p, direk of indirek, deur die TVR-seintransduksiepad gereguleer word.