Tesi sul tema "Starvation"
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1
Robertson, Fiona E. "Starvation-survival in Escherichia coli". Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/63636/.
Testo completoAbstract (sommario):
The population dynamics of carbon-starved E. coli K12 cultures was investigated. It was found that less cell lysis occurred when cells were previously grown in low glucose concentrations. Exponential-phase cells grown previously in 0.05% (w/v) glucose had survival rates comparable with their stationary-phase counterparts, suggesting that the rate of growth is more important in determining the outcome of starvation than the phase of batch culture growth. Long-termstarved cells (18-24 months) showed very little protein, DNA and RNA synthesis. Methionine was shown to alter the de novo synthesis protein profiles of longterm- starved cells and growth was seen to occur in the presence of methionine. This suggests that radio-labelling of proteins with 35S-methionine in these cells should be interpreted with care as the cells have been subjected to a nutrient upshift. Radio-labelling of proteins with 3H-leucine did not have the same effect. The ATP content of cells during prolonged incubation was shown to decrease in the first 48 hours incubation, increase until 5-7 days incubation then decrease after 7-8 days. After 13 days a slow, steady increase occurred. The ATP content of cells incubated for 16 days was higher than that of 48 hour-incubated cells. The physiology of long-term-starved cells was investigated with respect to their permeability to routine bacteriological stains ( e.g. DAPI, saffranin, Geimsa) and it was found that very few of these dyes were able to penetrate the cells, indicating that a decrease in cell permeability may be an important factor in survival as is seen in endospores of Bacillus species and swarmer cells of Rhodomicrobium vannielii and Caulobacter crescentus. Resistance of long-term starved cells to heat and biocide challenge was increased in comparison with exponential- and short-term (48 hour) stationary-phase cells and the resistance to biocides was shown to be retained through subsequent generations. Examination of the nucleoids of long-term-starved cells revealed that a more condensed form was present in cultures incubated for over 14 days, suggesting that dehydration of the DNA had occurred, similar to the situation found in endospores of Bacillus species and suggestive of dormancy. Analysis of outer-membrane proteins and lipopolysaccharide of long-term-starved cells showed that alterations occurred to the surface of the cells and it was demonstrated that hydrophobicity changes occurred. Hydrophobicity reached a maximum after 48 hours incubation then subsequently declined between days 2 and 3 which corresponded with an increase in cell numbers. Cell surface hydrophobicity was shown to be a potential method for separating heterogeneous, carbon-starved populations into homogeneous subpopulations. The data suggest that E. coli produces a dormant survival cell type which is morphologically and physiologically distinct from the parent cell.
2
Dwivedi, Padmanabh. "Carbohydrate starvation and plant respiration". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624182.
Testo completo
3
Price-Bishop, G. P., e Phillip R. Scheuerman. "Effects of Starvation on Bacteria". Digital Commons @ East Tennessee State University, 1992. https://dc.etsu.edu/etsu-works/2891.
Testo completo
4
Howard, Jane Katherine. "Leptin, starvation and the immune system". Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396338.
Testo completo
5
Poursaitidis, I. "Identification of differential nutrient starvation responses". Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3019213/.
Testo completoAbstract (sommario):
To promote survival and proliferation cancer cells re-programme their metabolism, altering both uptake and utilisation of extracellular nutrients. To examine correspondences between nutrient supply and viability, in order to identify targetable requirements, I individually depleted amino acid nutrients from diploid Human Mammary Epithelial (HME) isogenic cells expressing commonly activated oncogenes. Cystine deprivation was found to induce massive-oxidative stress associated-cell death of HME cells expressing an activated epidermal growth factor receptor (EGFR). Cell death occurred via an iron-dependent mode, known as ferroptosis associated with increased generation of reactive oxygen species and lipid peroxidation. Pharmacological inhibition of EGFR or mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) signalling was found to block ferroptosis and ROS production and was associated with increased expression of glutathione peroxidase 4 (GPX4). Suppression of GPX4 expression in wild-type or gefitinib-treated HME-EGFR cells was sufficient to sensitise cells to ferroptosis. Importantly, MAPK signals were also important in suppressing cell-cell contact and communication that was found to provide an essential line of defence against ferroptosis induction and spread. In this way, microscopic observation of ferroptosis in wild-type HME cells identified a cell death spread phenotype that is consistent with necrosis phenotypes observed in ischemic models. Inhibition of ROS generation and lipid peroxidation effectively blocked the progression of necrosis indicating that counteracting lipid peroxidation might be beneficial for degenerative conditions where lipid peroxidation is evident. Additional therapeutic application of my findings was modelled using non-small lung cancer cell (NSCLC) lines with overactive ERK signalling. These cells were found to be sensitive to ferroptosis following deprivation of cystine in vitro as well as in vivo where in systemic deprivation of cystine was achieved in xenografted mice following administration of a cystine-degrading enzyme. Taken together, my results show that the presence of common oncogenic mutations can render cells sensitive to the depletion of a specific nutrient, and further suggest potentially novel anti-cancer therapies based on the inability of some MAPK-driven cancer cells to overcome oxidative stress following nutrient depletion, as well as therapies to limit the spreading phenotype of ferroptosis in cells associated with other diseases such as Alzheimer’s Disease, or that occur in normal cells in response to ischemic reperfusion and acute kidney injuries.
6
PORCILE, GAETANO. "Subaqueous sand dunes and sediment starvation". Doctoral thesis, Università degli studi di Genova, 2019. http://hdl.handle.net/11567/941829.
Testo completo
7
Thomas, Beth Elene Armstrong. "Regulation of phosphate starvation response in Arabidopsis". Texas A&M University, 2006. http://hdl.handle.net/1969.1/5029.
Testo completoAbstract (sommario):
Phosphate is an essential but limited macronutrient for all plants. In response to
limited levels of phosphate, plants have developed highly specialized developmental,
biochemical, and molecular responses. To further expand our knowledge of the
phosphate starvation induced signal transduction pathway in plants, the expression of the
phosphate starvation inducible Purple Acid Phosphatase 1 (PAP1) gene was studied in
transgenic Arabidopsis. While few components have been identified regulating gene
expression under phosphate starvation conditions in plants, one cis regulatory element
recognized by the MYB transcriptions factor Phosphate Starvation Response 1 (PHR1)
has been identified in many phosphate starvation induced (PSI) genes. PAP1 and many
other genes examined during the course of the mutant characterization contain this cis
element.
Using the GUS reporter gene under control of the PAP1 promoter, a mutant
screen was devised for plants showing abnormal PAP1 response to phosphate nutrition.
Three mutant lines were identified and subsequently characterized for the phosphate
starvation-induced signal-transduction pathway in Arabidopsis.
Two mutants, BT1 and BT2, both with dominant mutations, showed increased
GUS staining. The mutations in BT1 and BT2 are tightly linked to the transgene and to
each other, but complementation analysis suggested that they are in different genes.
Characterization of these mutants indicated that the PSI genes PAP1 and At4 (in BT1
roots), and RNS1 (in BT2 leaves) have alternative or additional methods of regulation
other than PHR, even though these genes all contain PHR1 binding sites. A third mutant, BT3, had a phenotype similar to the PAP1 null-mutant and did
not show PAP1 phosphatase activity under normal soil-grown conditions.
Characterization of BT3 indicates that PAP1, RNS1, and AtIPS1 are not exclusively
regulated by PHR1.
In an attempt to map the BT3 mutant in a Columbia background by crossing with
Landsberg erecta (Ler), it was discovered that the Ler ecotype does not show PAP1
phosphatase activity under normal soil-grown conditions. The PAP1 phosphatase
regulatory trait, named BT5, was mapped to a 15,562 bp-region area containing only two
genes between the GPA1 and ER markers on Chromosome 2.
8
Purdon, Scott Drummond. "Starvation survival response of sulphate-reducing bacteria". Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340595.
Testo completoAbstract (sommario):
This thesis aims to investigate how SRB endure long periods of nutrient deprivation in the oligotrophic conditions of the North Sea. The presence of small cells in the marine environment has been extensively documented. These small cells are termed ultramicrobacteria, and are defined as being less than 0.3 μm in diameter. The formation of small cells by SRB was postulated to facilitate penetration of SRB deep within oil reservoirs, during water injection, exacerbating SRB associated problems. These studies revealed that a maximum of 15% of starving SRB populations formed UMB. Cultures starved for up to 6 years did not demonstrate an increase in UMB formation. Cell size studies revealed that SRB demonstrated a maximum 62% cell size decrease during starvation. Total cell counts revealed a constant cell number throughout starvation studies indicating a decrease in cell size by cell dwarfing. Transmission electron microscopy revealed a decrease in cellular content during starvation. This is consistent with a decrease in cell diameter during starvation. There was no difference in cell size decrease when cells were starved in the presence or absence of sulphate. There appeared, however, to be enhanced recoverability of cells starved in the presence of sulphate. SRB were demonstrated to be able to withstand simultaneous periods of sulphate and carbon starvation. This may have serious consequences for the oil industry as sulphate is often limiting in oil reservoirs. This evidence suggests that SRB could endure such conditions and recover when sulphate becomes available. SRB appear to enter a dormant phase shortly after the onset of starvation. Metabolic studies indicated that the entry into starvation was characterised by an initial increase in metabolic activity followed by a sharp decrease in metabolic activity to negligible levels. Metabolic activity could be re-initiated following inoculation into fresh growth medium.
9
Bishop, G. P., e Phillip R. Scheuerman. "Physiological Changes in Bacteria During Starvation Stress". Digital Commons @ East Tennessee State University, 1990. https://dc.etsu.edu/etsu-works/2889.
Testo completo
10
Bishop, G. P., e Phillip R. Scheuerman. "Physiological Changes in Bacteria During Starvation Stress". Digital Commons @ East Tennessee State University, 1991. https://dc.etsu.edu/etsu-works/2890.
Testo completo
11
Landers, Evan. "CHARACTERIZATION OF THE CHLAMYDIAL PARTNER SWITCHING MECHANISM USING IN VITRO, IN VIVO, AND IN SILICO APPROACHES". OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2326.
Testo completoAbstract (sommario):
Chlamydia trachomatis is a Gram-negative, obligate intracellular pathogen that is the causative agent of sexually transmitted infections and the ocular disease trachoma. Chlamydia trachomatis undergoes a biphasic developmental cycle differentiating between the infectious elementary body (EB) and the replicative reticulate body (RB). Under certain stress conditions, C. trachomatis can stall its developmental cycle and enter an aberrant state termed persistence. While in a persistent state, C. trachomatis is refractory toward antibiotics, can evade the host immune response, and becomes undetectable using standard clinical detection methods. Environmental and other pathogenic microbes are known to utilize partner switching mechanisms (PSM) to regulate sigma factors used to initiate a stress response. For this reason, this study focuses on the chlamydial PSM, its role in regulating the availability of the housekeeping sigma factor σ66, and its role in the developmental cycle and stress response of C. trachomatis. The chlamydial PSM is composed of five known proteins: the anti-sigma factor RsbW, two anti-anti-sigma factors RsbV1 and RsbV2, a regulatory phosphatase RsbU, and a second phosphatase-like protein CTL0852. In order to test the role of the PSM in the chlamydial stress response, a panel of C. trachomatis rsbV1 mutants were generated, persistence inducing iron starvation and tryptophan starvation cell culture conditions were optimized, and growth of the rsbV1 mutants under iron starvation conditions were assayed. No significant differences were seen between rsbV1 mutants under iron starvation nor recovery conditions as determined by progeny production and inclusion size analysis. Furthermore, this study generated PSM protein producing Escherichia coli strains for in vitro protein work and performed operon mapping of the PSM genes of C. trachomatis to help aid in future studies of the chlamydial PSM by facilitating the development of new chlamydial PSM mutants. This study gives phylogenetic support to the classification of ctl0852 as a chlamydial PSM gene by comparing relative mutations rates of PSM genes across chlamydial species.
12
Laurila, M. (Mirja). "Thermoregulatory consequences of starvation and digestion in birds". Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514277147.
Testo completoAbstract (sommario):
Abstract
In homeothermic birds and mammals, several thermoregulatory adaptations have evolved for surviving in unstable, food-restricted conditions. This study focuses on two adaptive mechanisms in pigeons (Columba livia) and quails (Coturnix coturnix japonica): hypothermia and the adaptive use obligatory heat production connected with feeding and digestion. The plasticity of the hypothermic response in fed and fasted birds and birds with restricted feeding was studied in laboratory and outdoor winter conditions. The other objective was to study adaptive timing of digestion, and substitution of facultative thermogenesis by obligatory heat production in cold and at thermoneutrality.
The results showed that fasting has a strong influence on the level of nocturnal hypothermia in laboratory conditions: hypothermia becomes progressively deeper when fasting continues. In outdoor conditions, ambient temperature and predation risk modulated the daily body temperature (Tb) pattern of fasting pigeons. In very cold conditions, diurnal Tb of fasted birds also dropped below the normal level of the active phase. Predation risk prevented diurnal hypothermia but also attenuated the depth of nocturnal hypothermia in fasting pigeons. This study provides the first empirical effects of predation risk on hypothermia in starving birds.
The study suggests that the presence of crop in pigeons allows adaptive timing of digestion. At thermoneutrality, peak digestion appeared late in the dark phase in birds with fed in the morning. Because the Tb of the birds increases to diurnal levels late in the dark phase, this obligatory heat from digestion can be used to aid re-warming by such timing. On other hand, the results of this study were partly opposite to the classical model of thermoregulatory substitution. In line with the classical model, a postprandial increase in metabolic rate (heat increment of feeding, HIF) was seen at thermoneutrality but not in cold. However, electromyographic measurements showed that there was no postprandial decrease in the intensity of shivering in the fed birds in cold. This indicates that true thermoregulatory substitution may be less common than assumed and suggests a role for facultative thermogenesis in HIF.
13
Alley, M. R. K. "Molecular biological aspects of nitrogen starvation in cyanobacteria". Thesis, University of Warwick, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383376.
Testo completo
14
Dickson, Lorna Mary. "Translation during growth and starvation in Saccharomyces cerevisiae". Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320770.
Testo completoAbstract (sommario):
The translation of a series of cat mRNAs containing either the HSP26 5'- leader or various artificial 5'-leaders (Vega Laso et al., 1993) were analysed during growth. From this study, the relative translational efficiencies of these mRNAs were shown to vary from 2% to 100% during mid-exponential phase as observed previously (Vega Laso et al.,1993). However, upon analysing the translation of the various cat constructs during growth, their relative translational efficiencies did not change significantly as yeast cells approached stationary phase. A new set of lacZ mRNAs carrying different natural 5'-leaders (PGK1, PYK1, RpL3, Rp29, GDH1, HSP26, HSP12 and TH14) were constructed. These lacZ mRNAs were placed under the control of the promoters taken from genes expressed during different phases of growth (PGK1 and HSP26). Even though the various PGK1-lacZ and HSP26-lacZ mRNAs were translated differentially, the ability of these mRNAs to compete for the translational apparatus did not appear to change as cells entered stationary phase. The translation of a variety of natural mRNAs encoding a wide range of functions was then analysed by determining their polysomal distribution at various points during growth. Irrespective of the growth phase, a large proportion of each mRNA was detected in the polysomal fractions, suggesting that they continued to be translated in stationary phase. Overall, the data strongly suggest that, under the conditions tested, an excess translational capacity exists in stationary phase yeast cells. Hence gene expression may be largely regulated by transcription upon entry to stationary phase.
15
Porras, Vazquez Alberto. "Lubricant starvation in elastohydrodynamic large-size spinning contacts". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI109.
Testo completoAbstract (sommario):
Cette thèse est dédiée à l'étude des contacts pivotants de grandes dimensions situés à l'interface entre l'extrémité du rouleau et le collet de la bague des roulement. L'objectif principal de l'étude est d'évaluer l'influence de la sous-alimentation sur la distribution d'épaisseur de film du contact et d'analyser comment le pivotement pourrait affecter ce mécanisme. En raison de son importance dans la fiabilité et la performance du roulement, l'accent est mis sur l'épaisseur de film minimale locale située dans la région de faible vitesse de la zone de contact. Pour résoudre ce problème, une double approche numérique-expérimentale est proposée. La distribution de l'épaisseur de film des contacts pivotants est étudiée numériquement à l’aide d'un modèle d'éléments finis préalablement validé par deux bancs d'essai dédiés: Jerotrib et Tribogyr. La simulation de différentes conditions opératoires, cinématiques, géométriques et de lubrification permet d'écrire une expression analytique pour prédire l'épaisseur critique du film précédent. En même temps, de nouvelles techniques pour induire et contrôler expérimentalement la sous-alimentation au contact sont mises en œuvre dans les deux bancs d'essai et leurs résultats sont comparés à ceux de la simulation. Il est démontré que les effets du pivotement et de la sous-alimentation s’additionnent, de sorte que la distribution de l’épaisseur de film du contact pivotant reste asymétrique mais tend à une distribution plus hertzienne, et donc plus mince, lors de la limitation de l’alimentation en huile en amont de l’entrée du contactThis thesis is dedicated to the study of large-size spinning contacts located at the interface between the roller-end and the flange in rolling-element bearings. The main goal of the study is to evaluate the influence of lubricant starvation on the film thickness distribution of the contact and analyze how spinning might affect this mechanism. Due to its importance in the reliability and performance of the bearing, the focus is set of the local minimum film thickness found at the low velocity region of the contact area. To tackle this problem, a dual numerical-experimental approach is proposed. The film thickness distribution of spinning contacts is investigated numerically by means of a finite element model previously validated by two dedicated test rigs: Jerotrib and Tribogyr. The simulation of different operating, kinematic, geometric and lubrication conditions enables to write an analytic expression for predicting the aforementioned critical film thickness. At the same time, novel techniques to experimentally induce and control starvation in the contact are implemented into both test rigs and their results are contrasted with those of the simulation. It is demonstrated that the effects of spinning and starvation add up, so that the film thickness distribution of the spinning contact remains asymmetric but tends to a more Hertzian, and therefore thinner, distribution when limiting the oil supply upstream of the contact’s inlet
16
Busuioc, Monica. "Survival Strategies of Streptococcus mutans during Carbohydrate Starvation". Diss., Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/88876.
Testo completoAbstract (sommario):
Microbiology and ImmunologyPh.D.
Streptococcus mutans is a facultative member of the oral plaque and is associated with dental caries. It is able to survive long periods of sugar starvation. The purpose of this project was to explore specific avenues that S. mutans may use in order to cope with carbohydrate deprivation. Intracellular polysaccharide (IPS) is accumulated by S. mutans when grown in excess sugar, and can contribute towards the cariogenicity of S. mutans. Inactivation of the glgA gene, encoding a putative glycogen synthase, prevented accumulation of IPS in batch cultures grown with excess glucose or sucrose. Inactivation of the pul gene, encoding a putative pullulanase which is thought to be involved in IPS catabolism, did not prevent IPS accumulation. IPS was found to be important for the persistence of S. mutans grown in batch culture with excess glucose, and then starved of glucose. In these conditions, the IPS was largely used up within one day of starvation, and yet survival of the parental strain was extended by at least 15 days beyond that of the glgA and pul mutants; potentially, some feature of IPS metabolism, distinct from providing nutrients, is important for persistence. IPS was not needed for persistence when sucrose was carbon source or when mucin was present in batch cultures. IPS accumulation was not clearly demonstrated in biofilm conditions. When grown in condition permissive for IPS accumulation, biofilms of the glgA and pul mutants did not show decreased survival, compared to the parental strain. It is plausible that, within a biofilm, S. mutans can use alternative sources of energy (like the extracellular matrix) to compensate for the lack of IPS. To look at specific genes upregulated by sugar starvation, microarrays analysis was performed on S. mutans batch cultures. Some of the genes upregulated by starved, stationary phase bacteria, appeared to be organized in an operon, thought to encode components of the pyruvate dehydrogenase (PDH) complex. Northern Blot analysis showed that pdhD and the downstream genes, pdhA, pdhB and pdhC, form an operon that is transcribed predominantly in stationary phase. Inactivation of pdhD impaired survival of both batch cultures and biofilms. Analysis with fluorescent reporters revealed a distinct expression pattern for the pdh promoter, with less than 1% of stationary phase bacteria displaying pdh expression. When first detected, after one day of sugar starvation, expression was in individual bacteria. At later times, expressing bacteria were often in chains. The lengths of chains increased with time suggesting growth and division. It is likely that the pdh-expressing sub-population is able to persist for extend times in stationary phase.
Temple University--Theses
17
Man, Siu-yin. "Adrenomedullin in the rat digestive system response to starvation /". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32032298.
Testo completo
18
Klinger, Edward. "The mechanics of lubricant starvation in rolling element bearings /". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70222.
Testo completoAbstract (sommario):
This thesis investigates the mechanics of lubricant starvation in rolling element bearings. A hydrodynamic study is made which assumes incompressible, steady, isoviscous flow with body forces negligible. A cylinder on plate mathematical model is utilized to establish an analytical solution for low capillary numbers in sliding contacts. A complete load and stability analysis is obtained for this flow regime.The case of general capillary number is undertaken via a numerical method. A finite volume approach using curvilinear orthogonal coordinates is implemented. A complete grid generator and flow solver are developed and used to determine the velocity and pressure fields for general capillary number. Results of the numerical and analytical models are compared for low capillary numbers and show good correlation.
19
Guangteng, Gao. "A study of squeeze and starvation in elastohydrodynamic lubrication". Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388292.
Testo completo
20
Man, Siu-yin, e 文小燕. "Adrenomedullin in the rat digestive system: response to starvation". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B32032298.
Testo completo
21
Quan, Zhenzhen. "Regulation of starvation-induced gene expression in Saccharomyces cerevisiae". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610892.
Testo completo
22
Herbert, Kevin Craig. "Characterisation of the starvation-survival response in Listeria monocytogenes". Thesis, University of Sheffield, 2001. http://etheses.whiterose.ac.uk/12837/.
Testo completoAbstract (sommario):
Listeria monocytogenes is a food-borne pathogen able to adapt and survive in a wide range of habitats in addition to being able to overcome host defences. The need to prevent L. monocytogenes entering the food chain and the role that stress plays during the course of an infection, means that the starvation-survival and stress resistance mechanism of this organism are thus of significant interest. The starvation-survival response of L. monocytogenes EGD in a chemically defined medium was induced under glucose- or multiple nutrient-, but not amino acid-limitation. This resulted in 90 to 99.9% loss of viability within 2 days, with viability maintained during prolonged starvation. Surviving cells were reduced in size and developed increased general stress resistance. L. monocytogenes EGD demonstrated densitydependent starvation-survival under multiple nutrient- but not under glucose-limitation. Protein synthesis was required for long-term survival only for the first 8 hours of starvation and survival became independent of cell wall biosynthesis during long-term starvation. Strains bearing mutations in the gene regulators sigB (DESOII) or prfA (DES012) showed a to-fold reduction in starvation-survival compared to EGD after 20 days of glucose limitation. DESOl1 had reduced exponential phase acid stress resistance, but increased H202 resistance. Resistance to H20 2 in exponential phase and long-term starved DES012 cells was over 290- fold and 380-fold greater than in EGD (after 20 minutes and 50 minutes exposure respectively), whilst exponential- and post-exponential-phase acid resistance in the DESOl2 was at least 10-fold greater than in EGD. Both DESOII and DESOl2 also exhibited altered catalase expression. Four transposon insertion mutants (two pairs of siblings) defective in starvation-survival were isolated from a glucose-limitation screen. Both sets of mutations resulted in decreased starvation-survival and altered stress resistance properties. Characterisation of the transposon insertion sites in DES028 and DES029 revealed disruption of a putative ORF encoding for a homologue of YuIB, a DeoR-family transcriptional regulator from Bacillus subtilis. In the isolates DES035 and DES045, the transposon insertion was found to disrupt a putative ORF encoding for a homologue of PhaQ, a protein associated with inclusion bodies of the storage polymer polyhydroxyalkanoic acid in Bacillus megaterium. The roles of these two loci in the starvation-survival response and in stress resistance are discussed.
23
McConnellogue, D. M. "Set shifting, central coherence and starvation in eating disorders". Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1365984/.
Testo completoAbstract (sommario):
Aims: This review aims to evaluate and synthesise previous research on set shifting in eating disorders in order to determine whether individuals with eating disorders have impaired set shifting. It also aims to determine whether set shifting difficulties are a risk factor for eating disorders or a consequence of starvation. Method: A summary and critique of the 13 papers specifically exploring set shifting in eating disorders is presented and followed by a synthesis of the results. Results: There is evidence for set shifting difficulties in Anorexia Nervosa (AN) and Bulimia Nervosa (BN) however no research has been conducted into Binge Eating Disorder (BED). This review suggests that starvation may have a mediating or maintaining role in neuropsychological impairments, rather than causing them per se. Increased set shifting impairments in recovered AN participants and genetic relatives suggest that set shifting difficulties may be a predisposing trait, increasing vulnerability to eating disorders. However, there are various methodological limitations (such as no power analyses to estimate required sample sizes) which are discussed and should be kept in mind. Conclusions: Although there is evidence for set shifting difficulties in AN and BN, the evidence is still very mixed and there is a need for use of consistent measures and clear reporting of findings with equal importance given to non-significant results.
24
Karlén, Louise. "State Responsibility Regarding Starvation in Non-International Armed Conflicts". Thesis, Örebro universitet, Institutionen för juridik, psykologi och socialt arbete, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-81618.
Testo completo
25
Minzter, Beth Hillary 1958. "THE EFFECT OF STARVATION ON RECOMBINATION IN PHAGE T4". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276397.
Testo completo
26
Lee, Sonia Jean. "Body mass regulation in birds". Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336929.
Testo completo
27
Freitag, Kimberly A. "Effects of Acute Nutritional Deprivation on Lymphocyte Subsets and Membrane Function in Cats". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/46484.
Testo completoAbstract (sommario):
Identification of patients with suboptimal nutritional status allows for early treatment intervention. Currently, no definitive test of nutritional status exists. Therefore, this study was conducted to identify possible functional indicators of acute nutritional deprivation. The effects of total nutritional deprivation and subsequent refeeding on lymphocyte functions and subpopulations were examined in 23 healthy cats. Peripheral blood samples were analyzed at various times during fasting and refeeding periods. During the fasting period, decreases were observed in leukocyte number (day 4; p < 0.04), lymphocyte number (p < 0.02), CD4+ cells (day 4; p < 0.06), CD4:CD8 ratio (0 hours; p < 0.004), and mitogen stimulated CD4:CD8 ratio (72 hours; p < 0.15) during the fasting period as compared to baseline. Increases were seen in CD4+ cells (day 7; p < 0.09), CD8+ cells (day 7; p < 0.04) and intracellular calcium (day 4; p < 0.02) as compared to baseline. During the refeeding period increases (p < 0.05) were observed in leukocyte number, CD4+ cells, CD8+ cells, lymphocyte proliferation (p < 0.07) and lymphocyte number (p < 0.004) as compared to day 7. These findings suggest that 7 days starvation had immunosuppressive effects on cats which were alleviated during 7 days refeeding. The use of CD4:CD8 ratio in conjunction with intracellular calcium flux may be useful as indices of nutritional status.Master of Science
28
Canadell, i. Sala David. "Potassium starvation responses in yeast highlight novel potassium-related functions". Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/298180.
Testo completoAbstract (sommario):
Mantenir la homeòstasis de cations és essencial per la supervivència dels éssers vius, i en especial pels organismes unicel·lulars. El llevat Saccharomyces cerevisiae s’ha utilitzat al llarg dels anys com un organisme model per l’estudi del conjunt de processos que controlen els nivells intracel·lulars de cations. El potassi és el principal catió intracel·lular del llevat i està involucrat en diversos processos de la fisiologia d'aquest organisme. Per aquest motiu la seva homeòstasis està minuciosament controlada per un seguit de transportadors que permeten la seva captació, distribució intracel·lular i eliminació de la cèl·lula i per un conjunt de proteïnes reguladores d’aquests processos. Encara que es té constància de la rellevància del potassi en el llevat, les seves dianes específiques i les bases moleculars d’algunes de les seves funcions són poc conegudes.
En aquest treball, mitjançant aproximacions d’eliminació del potassi del medi de cultiu, s’han pogut determinar els mecanismes d’algunes de les funcions conegudes del potassi i descobrir-ne de noves. S’ha demostrat que la manca de potassi provoca profundes alteracions en el perfil transcripcional del llevat. Entre elles destaquen l’accentuada repressió del gens que codifiquen proteïnes ribosomals i elements necessaris per la síntesi del ribosoma, dotant d’explicació molecular al ja conegut bloqueig en la síntesi de proteïnes provocat per la manca de potassi. L’eliminació del potassi del medi també provoca una caiguda dels nivells dels aminoàcids cisteïna i metionina que condueix a una activació del gens relacionats amb el metabolisme del sulfat i la síntesi d’aminoàcids sulfurats. Igualment, la privació del potassi comporta una acumulació d’espècies reactives de l’oxigen que produeixen un estat d’estrès oxidatiu a la cèl·lula. Aquesta respon amb l’activació transcripcional dels gens necessaris per combatre l’estrès oxidatiu, eliminar els oxidants i retornar la cèl·lula a un correcte estat redox. El llevat creixent en un medi sense potassi i en presència d’amoni acumula grans quantitats d’amoni a l’interior cel·lular a través del transportador de potassi Trk1 aprofitant la similitud química d’ambdós cations. Aquesta acumulació d’amoni activa vies per la seva fixació i eliminació en forma d’aminoàcids com és la via retrograda mitocondrial. L’eliminació del potassi del medi atura la proliferació cel·lular. Els nostres resultats han demostrat que aquesta aturada podria ser deguda a la disminució de les ciclines i d’elements reguladors de la formació dels anells de septines que afecten la progressió del cicle cel·lular.
El potassi també l’hem relacionat amb la homeòstasi d’un nutrient essencial com és el fosfat. L’absència de potassi o la pertorbació de la entrada normal d’aquest catió indueix els gens involucrats en la obtenció i mobilització del fosfat, d’igual manera com ho faria la depleció o limitació del fosfat. En aquetes condicions, la resposta transcripcional d’aquets gens està regulada pels diferents elements que composen la via PHO. L’afectació en l’obtenció del potassi impacte en la normal homeòstasis del fosfat provocant la mobilització de les reserves emmagatzemades en forma de polifosfats. La limitació del potassi, però, no modifica els nivells de fosfat lliure intracel·lular però sí que provoca una caiguda del nivells d’ATP i d’ADP, que podrien ser el senyal d’activació de la via PHO. A més, la pertorbació de la homeòstasis del potassi afecta el creixement dels llevats en medis amb baixos nivells de fosfat.
El conjunt de dades obtingudes en aquest treball ha permès descobrir nous vincles entre la homeòstasis del potassi i diversos processos cel·lulars, a més de la connexió d’aquest catió amb la homeòstasis de nutrients com el nitrogen, el sulfat i el fosfat.The maintenance of cation homeostasis is essential for the survival of all living organisms and especially for microorganisms. The yeast Saccharomyces cerevisiae has been used over the years as a model organism for study the processes that control intracellular cation levels. Potassium is the major intracellular cation in yeast and it has been associated with various relevant cellular processes. For this reason, potassium homeostasis is tightly controlled by several transporters, that allow the cation uptake, intracellular traffic and efflux, and by a set of proteins regulating these processes. In spite of the importance of potassium for yeast physiology, not all relevant functional potassium-related targets have been identified. In this work, potassium starvation conditions are used to determine the mechanisms of some of the known potassium functions and to discover new ones. We show that lack of potassium causes major alterations in the transcriptional profile of yeast cells. These transcriptional changes include the marked repression of genes encoding ribosomal proteins and elements necessary for the synthesis and assembly of ribosomes, providing the molecular basis for previously observed halt in protein synthesis caused by potassium deprivation. The elimination of potassium from the medium also causes a drop in cysteine and methionine levels which lead to transcriptional activation of genes related to metabolism of sulfate and biosynthesis of sulfur-contain amino acids. Similarly, cells deprived for potassium accumulate reactive oxygen species which results in oxidative stress. Concomitantly, cells trigger the transcriptional activation of genes necessary to combat oxidative stress, eliminate oxidants and return cells to the proper redox state. Yeast cells growing on ammonium as nitrogen source but lacking potassium accumulate large amounts of intracellular ammonium, which is transported through Trk1 taking advantage of the chemical similarity of both cations. Ammonium accumulation activates the retrograde mitochondrial pathway, resulting in detoxification of ammonium by its integration into amino acids. The complete removal of potassium from the medium leads to growth arrest. Our results show that this arrest could be due to the decrease in cyclins levels and in proteins involved in the assembly of septin rings, elements that are necessary for cell cycle progression. We also have related potassium to the homeostasis of other essential nutrients such as phosphate. Depletion of potassium from the medium or disturbance of normal potassium uptake induces genes involved in the acquisition and release of phosphate, as it is usually observed in a situation of phosphate starvation. Under these conditions, the transcription of PHO-controlled genes is activated by different regulatory elements of the PHO pathway. Situations that impact on normal potassium homeostasis also cause mobilization of the phosphate reserves stored in form of polyphosphates. Potassium restrictions, however, does not alter the levels of intracellular free phosphate but it causes a drop in the levels of ATP and ADP, which could be the signal for the activation of the PHO pathway. In addition, on media with low levels of phosphate, disruption of normal potassium homeostasis effects yeast growth. The results obtained in this work have been crucial to uncover new links between potassium homeostasis and many important cellular processes, in particular establishing the link between the homeostasis of this cation with that of other essential nutrients such as nitrogen, sulfate, and phosphate.
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Albano, Caterina. "Representations of food and starvation in early modern English drama". Thesis, Birkbeck (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314188.
Testo completo
30
Bourne, Julie. "The response of cyanobacterium Synechococcus sp. WH7803 to phosphate starvation". Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306976.
Testo completo
31
Turner, Kirsty. "The effects of starvation on the survival of Salmonella typhimurium". Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367651.
Testo completo
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Walsh, Sally. "The isolation and starvation-survival of thermophilic sulphate-reducing bacteria". Thesis, University of Exeter, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307293.
Testo completo
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Matthus, Elsa. "Phosphate starvation alters calcium signalling in roots of Arabidopsis thaliana". Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290260.
Testo completoAbstract (sommario):
Low bioavailability of phosphate (P) due to low concentration and high immobility in soils is a key limiting factor in crop production. Application of excess amounts of P fertilizer is costly and by no means sustainable, as world-wide P resources are finite and running out. To facilitate the breeding of crops adapted to low-input soils, it is essential to understand the consequences of P deficiency. The second messenger calcium (Ca2+) is known to signal in plant development and stress perception, and most recently its direct role in signalling nutrient availability and deficiency has been partially elucidated. The use of Ca2+ as a signal has to be tightly controlled, as Ca2+ easily complexes with P groups and therefore is highly toxic to cellular P metabolism. It is unknown whether Ca2+ signals P availability or whether signalling is altered under P starvation conditions. The aim of this PhD project was to characterise the use of Ca2+ ions, particularly cytosolic free Ca2+ ([Ca2+]cyt), in stress signalling by P-starved roots of the model plant Arabidopsis thaliana. The hypothesis was that under P starvation and a resulting decreased cellular P pool, the use of [Ca2+]cyt may have to be restricted to avoid cytotoxic complexation of Ca2+ with limited P groups. Employing a range of genetically encoded Ca2+ reporters in Arabidopsis, P starvation but not nitrogen starvation was found to strongly dampen the root [Ca2+]cyt increases evoked by mechanical, salt, osmotic, and oxidative stress as well as by extracellular nucleotides. The strongly altered root [Ca2+]cyt response to extracellular nucleotides was shown to manifest itself during seedling development under chronic P deprivation, but could be reversed by P resupply. Fluorescent imaging elucidated that P-starved roots showed a normal [Ca2+]cyt response to extracellular nucleotides at the apex, but a strongly dampened [Ca2+]cyt response in distal parts of the root tip, correlating with high reactive oxygen species (ROS) levels induced by P starvation. Excluding iron, as well as P, rescued the altered [Ca2+]cyt response, and restored ROS levels to those seen under nutrient-replete conditions. P availability was not signalled through [Ca2+]cyt. In another part of this PhD project, a library of 77 putative Ca2+ channel mutants was compiled and screened for aberrant root hair growth under P starvation conditions. No mutant line showed aberrant root hair growth. These results indicate that P starvation strongly affects stress-induced [Ca2+]cyt modulations. The data generated in this thesis further understanding of how plants can integrate nutritional and environmental cues, adding another layer of complexity to the use of Ca2+ as a signal transducer.
34
Rahman, Muzna. "Speaking starvation : representations of bodily protest in contemporary postcolonial fiction". Thesis, University of Manchester, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570270.
Testo completoAbstract (sommario):
This thesis traces the forms and contexts of hunger strikes as they are represented in contemporary postcolonial fiction. I look specifically at three postcolonial novels: Kiran Desai’s The Inheritance of Loss (2006), J.M. Coetzee’s Life and Times of Michael K (1983), and Tsitsi Dangarembga’s Nervous Conditions (1988). The final work examined in this piece is a selection of prison writings by Bobby Sands, a non-fictional figure who underwent a hunger strike in 1981 in Long Kesh (otherwise known as the Maze Prison) in Northern Ireland.The historical and regional scope of this investigation is broad. The works presented are framed by very different socio-cultural backgrounds. The common thread that runs throughout the pieces is an engagement with the themes, motifs, and concerns of postcoloniality. The hunger strike is figured as a response to the pressures associated with the fractured form of postcolonial identity. This identity is informed by contemporary and historical engagements with colonial ideology. I utilise historical and sociological material in order to outline and trace an inherited legacy of this colonial ideology – specifically through a frame of hunger and deprivation as associated with imperial domination.The four chapters of this thesis examine one hunger-strike scenario apiece. In each instance, the bodily protest performed takes on a common form. The logic of the hunger strike relies on a division between mind and body. Using the four individuals analysed in this thesis I examine how the form of the hunger strike seeks to separate the realm of representation, which is associated with the mind, from the realm of the material, which is related to the body. The failure of each hunger strike is reflected in the indivisible relationship between representation and the material contexts they construct.Using this basic dichotomy, I consider how each text comments on, reacts to, and contains the categories of representation and the material. Through the lens of this oppositional binary I examine the relationship between historical colonial narratives and the texts and subjects that they produce, and are in turn produced by.
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Fox, Courtney. "Relationship between Semi-Starvation Symptoms, Self-Efficacy, and Weight Loss". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/42528.
Testo completoAbstract (sommario):
The purpose of this study was to explore whether overweight college dieters, engaged in self-structured weight loss efforts, experienced physical symptomatology that has previously been associated with severe caloric restriction. The relationships between physical symptomatology, self-efficacy, and future dieting behavior were also investigated. Forty college students (21 female, Mage = 19.58 years, SD= 1.85) self-reported caloric intake and completed self-efficacy measures and physical symptom reports for three weeks. Results indicated that weekly physical symptom reports were not associated with caloric deficit and did not predict future dieting behavior. Physical symptoms were negatively related to self-efficacy for dieting and exercise as predicted, but in several analyses, higher self-efficacy actually predicted less calorie restriction. Physical symptom reports were predicted by trait neuroticism and neuroticism was also significantly and negatively associated with eating and exercise self-efficacy. Results raised issues about the accuracy of caloric restriction reporting and suggested that personality characteristics may have an important impact on an individualâ s perception of dieting experiences and levels of self-efficacy during dieting.Master of Science
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PIGNATTA, SARA. "Starvation-dependent differential stress resistance: a new frontier for radiotherapy?" Doctoral thesis, Urbino, 2018. http://hdl.handle.net/11576/2664031.
Testo completo
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Raheb, Jamshid. "The molecular and physiological effects of starvation and other stresses on Flexibacter chinensis". Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300717.
Testo completo
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Stafford, Jeffrey. "Juvenile Hormone esterase is a conserved regulator of starvation-induced behavior". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/56249.
Testo completoAbstract (sommario):
Although feeding behavior is a matter of life and death for animals, the genetic factors that control it remain poorly understood. We have identified a novel regulator of hunger-induced behavior through comparison of transcriptomic changes in the fruit fly Drosophila melanogaster and the yellow fever mosquito Aedes aegypti. Head mRNA from each insect was sequenced at a roughly equivalent level of starvation. Using data gleaned from the protein orthology database OrthoDB, we looked for gene pairs in which both A. aegypti and D. melanogaster orthologs were significantly regulated by starvation. This identified Juvenile Hormone esterase (Jhe) as a possible modulator of hunger-induced behavior. Pan-neuronal knockdown of Jhe resulted in increased food consumption and caused enhancement of starvation-induced sleep suppression in Drosophila. These behavioral phenotypes were not caused by a developmental or metabolic defects, and were reproduced by feeding adult Drosophila methoprene, a synthetic Juvenile Hormone analog. Application of precocene I, an inhibitor of Juvenile Hormone biosynthesis, reversed the phenotype. Our analysis suggests that Jhe (and Juvenile Hormone by extension) is a novel and biologically relevant regulator of hunger-induced behavior.Science, Faculty of
Zoology, Department of
Graduate
39
Weldai, Lydia. "Do Major Facilitator Superfamily Domain Containing Proteins Respond to Glucose Starvation?" Thesis, Uppsala universitet, Institutionen för farmaceutisk biovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-348673.
Testo completoAbstract (sommario):
The human brain weighs around 2% of the total body mass, nevertheless it consumes about 20% of the total glucose intake. Glucose, the main energy source of the brain, is important for many processes, for instance as energy for synthesis of neurotransmitters. Therefore a stable glucose concentration in the brain is crucial. Unlike other macronutrients, glucose is able to cross the BBB through facilitated transport by glucose transporters (GLUTs) that belong to the solute carrier (SLC) superfamily. There are currently 65 SLC families with over 400 members in total. Out of 65 families, many belong to the protein family (Pfam) class major facilitator superfamily (MFS). There were 28 putative SLC transporters, 18 of them were called major facilitator domain containing proteins (MFSDs). Recently MFSD2A, MFSD2B, MFSD4A, MFSD4B and MFSD5 were grouped into SLC families making the total amount of current putative SLCs 23 In this project the effects of glucose starvation on MFSD6, MFSD6L, MFSD8, MFSD9 and MFSD10 in primary mouse cortex cultures were studied on protein and gene level through immunocytochemistry (ICC) and quantitative polymerase chain reaction (qPCR). All proteins except for MFSD10 were detected in the ICC. All except MFSD8 displayed a change in fluorescent intensity. MFSD6, MFSD6L and MFSD9 were upregulated after 3 h of glucose starvation compared with control. Gene expression was detected for all targets except for Mfsd6l. Gene expression alterations were found for Mfsd8, Mfsd9 and Mfsd10. The 3 h glucose starvation resulted in an acute response in the gene expression for Mfsd9 and Mfsd10 but was back to control levels after 12 h, while Mfsd8 respond after 12 h of glucose starvation. All of them were back at similar levels as controls when re-fed with glucose. In conclusion, all five MFSDs responded to glucose starvation at some point. For instance MFSD6 responds to glucose starvation on a protein level, Mfsd6 was however also the only gene out of the four tested that did not respond to glucose starvation on a gene level.
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McDougald, S. Diane School of Microbiology & Immunology UNSW. "Regulation of starvation and nonculturability in the marine pathogen, Vibrio vulnificus". Awarded by:University of New South Wales. School of Microbiology and Immunology, 2000. http://handle.unsw.edu.au/1959.4/19118.
Testo completoAbstract (sommario):
Vibrio vulnificus is a model environmental organism exhibiting a classical starvation response during nutrient limitation as well as a non-culturable state when exposed to low temperatures. In addition to these classic global responses, this organism is an opportunistic pathogen that exhibits numerous virulence factors. This organism was chosen as the model organism for the identification of regulators of the viable but nonculturable response (VBNC) and the starvation-induced maintenance of culturability (SIMC) that occurs when cells are starved prior to low temperature incubation. In order to accomplish this, three indirect approaches were used; proteomics, investigation of intercellular signalling pathways and genetic analysis of regulators involved in these responses. Two-dimensional gel electrophoresis was used to identify proteins expressed under conditions that induced SIMC. It was determined that carbon and long-term phosphorus starvation were important in the SIMC response. V. vulnificus was shown to possess genes, luxS and smcR, that are homologues of genes involved in signalling system system 2 in Vibrio harveyi. Signal molecules were produced upon starvation and the entry to stationary phase in V. vulnificus. Furthermore, a null mutation in smcR, a transcriptional regulator was shown to have pleiotropic effects in V. vulnificus, including up-regulation of numerous virulence factors and a defect in starvation survival and development of the SIMC response. We propose that V. vulnificus possesses a signalling system analogous to that of system 2 in V. harveyi, and that this system is involved in the regulation of stationary phase and starvation adaptation in this organism.
41
Popovici, Gheorghiță. "Effects of lubricant starvation on performance of elasto-hydrodynamically lubricated contacts". Enschede : University of Twente [Host], 2005. http://doc.utwente.nl/50845.
Testo completo
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Jones, Katherine. "The starvation-predation risk trade-off in the chaffinch Fringilla coelebs". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442521.
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Taylor, Ian. "'A period of orchestral starvation ?' : concert life in London, 1795-1813". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419117.
Testo completo
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Sivapathasundram, Sudhersha. "The effect of nitrogen starvation on PS2 in the cyanobacterium synechococcus". Thesis, Liverpool John Moores University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275823.
Testo completo
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Henricot, Beatrice. "A study of the starvation-induced genes of Cladosporium fulvum (Cooke)". Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267544.
Testo completo
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Kilpatrick, Kaylon Ann. "Starvation induces Polycystic Ovarian Syndrome (PCOS) like symptoms in Drosophila melanogaster". Thesis, Mississippi College, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10128977.
Testo completoAbstract (sommario):
Polycystic Ovarian Syndrome (PCOS) is a metabolic and endocrine disorder that is the most common cause of infertility. PCOS can manifest itself as a long and short term disability and is characterized by insulin resistance (IR), hyperandrogenism, anovulation, hyperinsulinaemia and polycystic ovaries. Our lack of understanding of this disorder and its long term effects has complicated the treatment of the disorder; yet, it is clear that PCOS involves the intricate interaction between genetics, environments and behaviors. To study this disease, scientists have used various animal models. Since the Drosophila model for PCOS has only been postulated,in this work, we determined whether starvation along with the addition of steroid hormones would induce a PCOS-like disorder in D. melanogaster after 24 hour exposure.
In women with PCOS, testosterone levels and the expression of the androgen receptor are elevated. In fruit flies, ecdysone (E) and its “active” form, 20-hydroxyecdysone (20E), are homologous to the human testosterone and 20-hydroxytestosterone, respectively. This hormone is required for circadian cycles, molting, and maturation in insects. More specifically, this hormone is also located in ovarian tissue and aids in follicular development. The receptor for ecdysone is the ecdysone receptor (EcR). In this work, we examined the expression of the ecdysone receptor (EcR) upon starvation for up to 24 hours by immunofluorescence microcopy. Using qRT-PCR, we determined the levels of expression of genes usually associated with inflammation. Ovarian dysfunction was examined by measuring the fecundity of the females. Starvation increases the expression of the EcR and pro-inflammatory gene expression and decreases fecundity, suggesting that Drosophila melanogaster is a potentially useful model organism in the study of PCOS.
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Murby, Fredrika. "Phosphorus reduction in wastewater using microalgae with different phosphorus starvation periods". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-82778.
Testo completoAbstract (sommario):
Anthropogenic induced nutrients in the Baltic Sea have led to 97% of it being eutrophic. Phosphorus is regarded the main regulating nutrient, and nearly 25% of the nutrients coming to the Baltic Sea originate from wastewater treatment plants. To reduce the nutrient concentrations in the effluents from treatment plants, tertiary treatment methods based on chemical dosing have been the principal answer. The chemicals create a sludge in addition to remediating the water, which needs disposal. Methods for remediating secondary wastewater with microalgae exist but are not common in conventional wastewater treatment. However, using microalgae could be beneficial, since they use inorganic carbon (from the atmosphere and wastewater) and inorganic nutrients, while producing biomass and oxygen. The biomass in turn has a potential to be used in production of bioenergy, food, and fertilizers. This thesis investigated whether pre-phosphorus starvation of five different microalgae strains enhanced the removal rate of phosphorus from secondary wastewater. The aim was to determine the optimal starvation period of different algae strains and to achieve wastewater effluent concentrations below 0.1 mg/L at the shortest possible time. Algae were transferred to a phosphorus-free media for five, three, one and zero days before entering the wastewater in a batch reactor at a temperature of 27°C and a 16:8 hours light and dark regime. Phosphate and nitrate concentrations as well as biomass production were monitored during a period of ten days. The experiment was repeated three times using Chlorella Vulgaris and two times using Tetradesmus Obliquus, Ankistrodesmus Falcatus, Botryococcus Braunii and one time using Desmodesmus Communis. The secondary wastewater was obtained from a small wastewater treatment plant from the village Roja in Latvia. Prior to the experiments, it was filtered three times through filters with different pore sizes (the smallest pore size was 0.2 µm), and the average nitrate and phosphate concentrations were 21.3 ± 1.1 mg/L and 17.8 ± 0.56 mg/L, respectively. The nitrate to phosphate ratio was 1.8:1. It was possible to remove the inorganic phosphorus to concentrations below 0.1 mg/L within ten days, although it did not happen in all the reactors. It was found that in most cases pre-phosphorus-starvation increased the removal rate of phosphorus. For two of the strains, Chlorella Vulgaris and Ankistrodesmus Falcatus, the three-day of pre-starvation period was optimal, while two to three days was optimal for Tetradesmus Obliquus, compared to other pre-starvation periods. For Botryococcus Braunii the one-day and the zero-days starved batches removed the phosphorus most efficiently. For Chlorella Vulgaris and Ankistrodesmus falcatus nearly a 100% of the phosphorus was removed within seven days after three days of pre-starvation. Without pre-starvation, these strains achieved the same result after ten days. It was also found that the nitrogen was the limiting nutrient in the wastewater and that the different strains responded differently to the changes in environment brought on by the experiment. When using microalgae in wastewater treatment, the choice of strain greatly impacts the removal rate, as the likeliness for them to survive in a specific environment varies among strains. It was concluded that using microalgae as a wastewater treatment method could pose great benefits. However, more experiments with colder climate, non-pre-filtered wastewater, a less nutrient rich media, greater initial biomass concentrations and pilot tests are recommended. Another insight from this thesis was that the method for transferring algae between different media needs to be refined to reach the target concentration in a reactor (or other setup).
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LENAGALA, ROSHAN M. S. "STUDY OF STARVATION ISSUES IN THE IEEE 802.11e MAC LAYER PROTOCOL". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1155326763.
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Flärdh, Klas. "Physiology of carbon starvation and recovery of a marine Vibrio sp". Göteborg, Sweden : Dept. of General and Marine Microbiology, University of Göteborg, 1994. http://catalog.hathitrust.org/api/volumes/oclc/34487576.html.
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Holmquist, Louise. "Phenotypic and molecular responses to starvation of a marine Vibrio sp". Göteborg, Sweden : Dept. of General and Marine Microbiology, Göteborg University, 1994. http://catalog.hathitrust.org/api/volumes/oclc/34487585.html.
Testo completo