Rozprawy doktorskie na temat „Cell ultrastructure”
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Chao, Ying L. (Ying Liang). "Ultrastructure of Azotobacter vinelandii". Thesis, North Texas State University, 1993. https://digital.library.unt.edu/ark:/67531/metadc798461/.
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The purpose of this research was to reveal the morphological and cytological characteristics of Azotobacter vinelandii cells cultured in dialyzed soil medium. Culture samples taken at two, four, eight, sixteen and thirty-two days were prepared and examined with the electron microscope. Comparisons of the morphology of Azotobacter vinelandii grown in dialyzed soil medium with those grown in Burk's nitrogen-free, chemically-defined medium were done.
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Goss, Steven Philip Allan. "Ultrastructure and Mitosis of Glaucosphaera vacuolata". W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539625804.
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Hudson, Liam. "Ultrastructure of the A-band unit cell in relaxed muscle". Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310340.
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Ridden, John. "Studies on the cell biology of the human sebaceous gland". Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258034.
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Fahlén, Jesper. "The cell wall ultrastructure of wood fibres : effects of the chemical pulp fibre line". Doctoral thesis, KTH, Fiber- och polymerteknik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-129.
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Knowledge of the ultrastructural arrangement within wood fibres is important for understanding the mechanical properties of the fibres themselves, as well as for understanding and controlling the ultrastructural changes that occur during pulp processing. The object of this work was to explore the use of atomic force microscopy (AFM) in studies of the cell wall ultrastructure and to see how this structure is affected in the kraft pulp fibre line. This is done in order to eventually improve fibre properties for use in paper and other applications, such as composites. On the ultrastructural level of native spruce fibres (tracheids), it was found that cellulose fibril aggregates exist as agglomerates of individual cellulose microfibrils (with a width of 4 nm). Using AFM in combination with image processing, the average side length (assuming a square cross-section) for a cellulose fibril aggregate was found to be 15–16 nm although with a broad distribution. A concentric lamella structure (following the fibre curvature) within the secondary cell wall layer of native spruce fibres was confirmed. These concentric lamellae were formed of aligned cellulose fibril aggregates with a width of about 15 nm, i.e. of the order of a single cellulose fibril aggregate. It was further found that the cellulose fibril aggregates had a uniform size distribution across the fibre wall in the transverse direction. During the chemical processing of wood chips into kraft pulp fibres, a 25 % increase in cellulose fibril aggregate dimension was found, but no such cellulose fibril aggregate enlargement occurred during the low temperature delignification of wood into holocellulose fibres. The high temperature in the pulping process, over 100 ºC, was the most important factor for the cellulose fibril aggregate enlargement. Neither refining nor drying of kraft or holocellulose pulp changed the cellulose fibril aggregate dimensions. During kraft pulping, when lignin is removed, pores are formed in the fibre cell wall. These pores were uniformly distributed throughout the transverse direction of the wood cell wall. The lamellae consisting of both pores and matrix material (“pore and matrix lamella”) became wider and their numeral decreased after chemical pulping. In holocellulose pulp, no such changes were seen. Refining of kraft pulp increased the width of the pore and matrix lamellae in the outer parts of the fibre wall, but this was not seen in holocellulose. Upon drying of holocellulose, a small decrease in the width of the pore and matrix lamellae was seen, reflecting a probable hornification of the pulp. Refining of holocellulose pulp led to pore closure probably due to the enhanced mobility within the fibre wall. Enzymatic treatment using hemicellulases on xylan and glucomannan revealed that, during the hydrolysis of one type of hemicellulose, some of the other type was also dissolved, indicating that the two hemicelluloses were to some extent linked to each other in the structure. The enzymatic treatment also decreased the pore volume throughout the fibre wall in the transverse direction, indicating enzymatic accessibility to the entire fibre wall. The results presented in this thesis show that several changes in the fibre cell wall ultrastructure occur in the kraft pulp fibre line, although the effects of these ultrastructural changes on the fibre properties are not completely understood.QC 20101012
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Fahlén, Jesper. "The cell wall ultrastructure of wood fibres : effects of the chemical pulp fibre line /". Stockholm : Fibre and Polymer technology, KTH, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-129.
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Stander, Cornelia Steynberg. "An ultrastructural and light microscopic study of melanocyte differentiation in chick embryos". Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/27149.
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The embryonic source and chemical nature of those factor/s directing the in vivo differentiation of melanocytes from crest cells are as yet unknown. To begin to address this issue, it is important to establish exactly when and where these signa/s first exert their effects. Therefore, in the present study, overtly differentiated melanocytes containing melanin were quantitated in developing Black Australorp X New Hampshire Red chick embryos. In contrast to previous studies, it was found that embryos synthesize melanin from as early as Day 5 of development, and that at this stage, the melanocytes are predominantly dermally located. Between 5 and 8 days, the numbers of both dermal and epidermal melanocytes increase, after which the dermal melanocyte population declines rapidly while the number of epidermal melanocytes continues to increase. These findings suggest that premelanocytes do not have to be epidermally located to initiate terminal differentiation and implicate the dermis as a possible source of melanocyte inducing factor/s. The next step was to examine stages of development prior to the onset of pigment production. For this reason, tyrosinase was purified for use as antigen in the production of a polyclonal antibody. The antibody was tested for specificity by western blotting, - immunocytochemistry and immunoinhibition procedures. Lack of specificity was demonstrated, rendering it unsuitable as an antibody marker for early melanocytes. Fowl melanocytes are thought to differentiate into either eumelanosome- or pheomelanosome synthesizing cells. To test the validity of this concept, embryonic skin of the red/black cross breed were screened for possible mixed type melanocytes by electron microscopy. The melanocytes contained melanosomes with a matrix of irregularly arranged filaments amongst typical eumelanogenic melanosomes. This suggests that these chick melanocytes may synthesize both eumelanosomes and pheomelanosomes in single cells. In a further study on pure breeding New Hampshire Reds, it was found that the melanocytes contained a mixture of typical and less typical pheomelanosomes. Outer membrane indentations in the latter melanosome type suggest that tyrosinase may enter these pheomelanosomes by a mechanism related to that proposed for the melanosomes of goldfish.
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au, jeremy shaw@uwa edu, i Jeremy Shaw. "Biomineralisation processes in the radula teeth of the chiton Acanthopleura hirtosa (Mollusca: Polyplacophora)". Murdoch University, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20080703.163505.
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A detailed row by row investigation of major lateral tooth cusp mineralisation, together with the concomitant development of the superior epithelial tissue surrounding the teeth of the chiton Acanthopleura hirtosa has been undertaken using a combination of light microscopy, and scanning and transmission electron microscopy. A holistic approach has been adopted that encompasses observations over a range of spatial scales, from whole radula mineralisation processes to those occurring within individual tooth cusps at various stages of development. In addition, mineralisation in radulae from freshly collected animals has been compared to that of animals maintained for extensive periods within a newly developed iron limited system, which restricts radula mineralisation without impeding the formation of the organic matrix.
An evaluation of the iron limitation technique has revealed that maintaining specimens of A. hirtosa within an iron poor environment results in a significant departure from the normal pattern of mineralisation in these animals. As a consequence of iron limitation, there is an obvious increase in the number of unmineralised tooth rows in addition to associated alterations in structure and composition at all stages of tooth development.
In normal specimens of A. hirtosa, the onset of mineralisation in the tooth cusps occurs following the prior accumulation of iron at the junction zone and the sudden accumulation of iron containing granules in the cusp epithelium at tooth row 13. The superior epithelium surrounding the tooth cusps undergoes a series of developmental changes leading up to, and following, the onset of mineralisation. In particular, the abundance of mitochondria within the apical cusp epithelium increases, presumably in order to provide the ideal conditions of pH, and thus solubility, needed for the supersaturation of iron and its nucleation at row 13. Once mineralisation has commenced, the microvilli attached to the cusps develop rapidly, and are suggested to do so in order to facilitate the transport of iron, and thereby ensure that a high concentration gradient of this element into the cusps is maintained.
The delivery of iron into the cusps occurs from two fronts, the first from the superior epithelium via the posterior surface, and the second from the junction zone via an internal pathway situated along the lepidocrocite boundary between the magnetite and core regions of the tooth. The existence of a plume of elements between this internal mineralisation pathway and the junction zone, provides the first direct evidence that the junction zone is involved in the storage and release of elements for cusp mineralisation. Data from iron limited radulae also indicate that iron continues to be deposited at the junction zone in preference to the superior epithelium or cusps, despite the disruption of mineralisation, highlighting the importance of this region in the mineralisation process.
Iron reinstatement experiments have also shown that the internal pathways of iron delivery within the organic matrix remain viable, despite prolonged periods of iron limitation. In addition, the reinstatement of iron has revealed that the plumes, situated between the junction zone and internal mineralising pathway of the cusp, stem from the centre of the plate like junction zone, directly above the stylus canal, a tube like cavity situated within the styli of each major lateral tooth.
An in depth study of the stylus canal has revealed that cells within the canal are remarkably similar to those of the epithelium surrounding the cusps, suggesting that this structure may also be involved in the delivery of ions to the junction zone. The stylus canal is shown to be present in the major lateral tooth cusps of 38 chiton species distributed worldwide, and is therefore likely to be a feature common to all chitons. The presence of the canal, and indeed its absence from the bases of all remaining non iron mineralised teeth, irrespective of chiton species, also points strongly to a functional relationship between the stylus canal and tooth cusp mineralisation.
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Merced-Alejandro, Amelia. "Evolution of stomata in mosses (Bryophyta): From molecules to form and function". OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1038.
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As one of the first land plant groups to diversify, mosses are central in understanding the origin, diversification, and early function of stomata. Unlike tracheophytes that have stomata on anatomically complex leaves and stems, mosses bear stomata exclusively on spore-bearing organs (capsules). However, stomata do not occur in all mosses and, indeed, are absence in the earliest-divergent mosses (Takakia, Andreaea, Andreaeobryum and Sphagnum), suggesting that stomata originated in mosses independently of other plants. The occurrence of structurally unique pseudostomata in Sphagnum further confounds the resolution of homology of moss stomata with those of other plants. The five studies included in this dissertation are aimed at clarifying the structure, development and evolution of moss stomata. The first study focuses on the sporophyte anatomy and stomatal ultrastructure in two structurally and phylogenetically divergent mosses, Oedipodium and Ephemerum. Oedipodium is the sister to peristomate mosses and the first extant moss with true stomata. This monospecific genus has an elaborated capsule with an extended apophysis bearing numerous long-pored stomata. In contrast, Ephemerum nests within the peristomate mosses and has a reduced capsule that lacks an apophysis and has a few round-pored stomata. Ultrastructure of stomata is similar in these two mosses and comparable to that of tracheophytes, except that the stomata of mosses are not as structurally distinct from epidermal cells as are tracheophyte stomata. Anatomical features such as the presence of a cuticle, water-conducting cells, and spongy tissues with large areas for gas exchange are more pronounced in Oedipodium sporophytes and support the role of stomata in gas exchange and water transport during development and maturation. The second study examines changes in pectin composition during development in the model moss Funaria. Stomatal movement in tracheophytes requires guard cell walls to be strong, yet flexible, because they have to undergo reversible deformation to open and close the pore. Pectins are necessary for wall flexibility and proper stomatal functioning in seed plants. In this study of Funaria, immunogold-labeling using five antibodies to pectin epitopes was conducted on guard cell walls during development to relate these features to the limited movement of stomata in moss. Movement of Funaria stomata coincides with capsule expansion when guard cell walls are thin and pectinaceous. Walls dramatically increase in thickness after pore formation and the pectin content significantly decreases in mature guard cell walls, suggesting that a decrease in flexibility is responsible for the inability to open a close previously reported in older moss guard cells. Because this was the first study to demonstrate changes in pectin composition during stomatal development in any plant, a similar study was done on Arabidopsis to identify the main types of pectins in guard cell walls. Localization of pectins in guard cell walls of Arabidopsis is similar to mosses in the stage they can move, with homogeneous walls rich in arabinan pectins that are required for wall flexibility. This study extends knowledge of pectin composition from stomata of the moss Funaria with limited stomatal movement to an angiosperm in which stomatal activity is crucial to the physiological health of the plant. The fourth study describes stomata development and internal changes in sporophyte anatomy that lead to formation of air spaces in the moss Funaria. Developing sporophytes at different stages were examined using light, fluorescence and electron microscopy; immunogold-labeling was used to investigate the presence of pectin in the newly formed cavities. Stomata in mosses do not develop from a self-generating meristemoid like in Arabidopsis, but instead they originate from a protodermal cell that differentiates directly into a guard mother cell. Epidermal cells develop from protodermal or other epidermal cells, i.e., there are no stomatal lineage ground cells. This developmental pattern is congruent with the presence of a gene ortholog of FAMA, but not SPCH and MUTE, in Physcomitrella. The final study in this dissertation focuses on the enigmatic Sphagnum. Although true stomata are absent in early-divergent mosses, Sphagnum has specialized epidermal cells, pseudostomata, that partially separate but do not open to the inside. To further understand the structure, function and evolution of pseudostomata, capsule anatomy and ultrastructure of pseudostomata were detailed. As in moss stomata, pseudostomata wall architecture and behavior facilitate capsule dehydration, shape change, and dehiscence, supporting this common function. Unlike other moss stomata, pseudostomata collapse along their ventral walls and they lack a substomatal cavity. Similarities to true stomata include two modified epidermal cells with specialized cell walls that separate by cuticle deposition and respond to drying. Pseudostomata may be interpreted as modified stomata that suppressed substomatal cavity formation, which in turn eliminated pore development. However, clarification of the homology of pseudostomata and moss stomata will require genomic studies integrated with physiological and structural data. The studies described in this dissertation significantly advance our understanding of moss stomatal development and structure, and provide a comparison point to better evaluate the evolution of stomata. Moss capsule anatomy coupled with the exclusive existence of stomata on capsules supports the concept that stomata in moss are involve in gas exchange but also facilitate drying and dispersal of spores. Changes in wall architecture coupled with a decrease in total pectin explain the inability of mature stomata to move. Development and distribution of stomata in Funaria provides evidence of a direct and less elaborated mechanism for stomatal development than described in Arabidopsis. Resolving relationships among early land plants, especially hornworts and mosses, the only bryophyte groups with stomata, is critical to understanding stomata evolution. Evaluated together, the results of this dissertation are consistent with a single origin of stomata in land plants.
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Kamakura, Tsukasa. "Ultrastructural Maturation of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes in a Long-Term Culture". Kyoto University, 2015. http://hdl.handle.net/2433/199202.
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Stevanic, Srndovic Jasna. "Ultrastructure of the Primary Cell Wall of Softwood Fibres Studied using Dynamic FT-IR Spectroscopy". Licentiate thesis, KTH, Fibre and Polymer Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4614.
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The primary cell wall is a complex multipolymer system whose composite structure has been mostly determined from chemical and biochemical studies. Although the primary cell wall serves a central role, with regard to the connective properties of fibres, knowledge about the interactions among the polymers, when it comes to the mechanical properties, is very limited. The physical properties of the polymers, i.e. their elastic and viscous deformations, as well as the ultrastructure of the polymers, i.e. the interactions among the polymers in the outer fibre wall layers that lead to this behaviour, are still not fully understood.
The aim of this study was to examine how the different wood polymers, viz. lignin, protein, pectin, xyloglucan and cellulose, interact in the outer fibre wall layers of the spruce wood tracheid. The initial objective was to separate an enriched primary cell wall material from a first stage TMP, by means of screening and centri-cleaning. From this material, consisting of the primary cell wall (P) and outer secondary cell wall (S1) materials, thin sheets were prepared and analysed using a number of different analytical methods. The major measuring technique used was dynamic Fourier transform infra-red (FT-IR) spectroscopy in combination with dynamic 2D FT-IR spectroscopy. This technique is based on the detection of small changes in molecular absorption that occur when a sinusoidally stretched sample undergoes low strain. The molecular groups affected by the stretching respond in a specific way, depending on their environment, while the unaffected molecular groups provide no response to the dynamic spectra, by producing no elastic or viscous signals. Moreover, the dynamic 2D FT-IR spectroscopy provides useful information about various intermolecular and intramolecular interactions, which influence the reorientability of functional groups in a polymer material.
Measurements of the primary cell wall material, using dynamic FT-IR spectroscopy, indicated that strong interactions exist among lignin, protein and pectin, as well as among cellulose, xyloglucan and pectin in this particular layer. This was in contrast to the secondary cell wall, where interactions of cellulose with glucomannan and of xylan with lignin were dominant. It was also indicated that the most abundant crystalline cellulose in the primary cell wall of spruce wood fibres is the cellulose Iβ allomorph, which was also in contrast to the secondary cell wall, where the cellulose Iα allomorph is more dominant. The presence of strong interactions among the polymers in the primary cell wall and, especially, the relatively high content of pectin and protein, showed that there is a very good possibility of selectively attacking these polymers in the primary cell wall. The first selective reaction chosen was a low degree of sulphonation, applied by an impregnation pretreatment of chips with a very low charge of sodium sulfite (Na2SO3). This selective reaction caused some structural modification of the lignin, a weakening of the interactions between lignin;pectin, lignin;protein and pectin;protein, as well as an increased softening of the sulphonated primary cell wall material, when compared to the unsulphonated primary cell wall material. All this resulted in an increased swelling ability of the material.
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Stevanic, Srndovic Jasna. "Ultrastructure of the primary cell wall of softwood fibres studied using dynamic FT-IR spectroscopy /". Stockholm : Fiber- och polymerteknologi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4614.
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Kokinos, John Peter. "Studies on the cell wall of dinoflagellate resting cysts : morphological development, ultrastructure, and chemical composition". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17366.
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Mansouri, Katayoun. "COMPARATIVE ULTRASTRUCTURE OF APICAL CELLS AND DERIVATIVES IN BRYOPHYTES, WITH SPECIAL REFERENCE TO PLASMODESMATA". OpenSIUC, 2012. https://opensiuc.lib.siu.edu/dissertations/484.
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This study focused on the primary cell wall constituents and plasmodesmata (PD) density in three mosses and four liverwort apical cells (AC) and immediate derivatives. The three mosses have tetrahedral apical cells and the liverworts possess tetrahedral, hemidiscoid and lenticular AC geometries. The primary cell wall in the studied taxa is comprised of two layers. A fibrillar layer, which is the outer wall layer, contains compacted cellulosic fibrils, and represents the two adjacent primary walls and middle lamella, the latter of which is rarely discernible. An electron-lucent inner wall layer abuts the plasma membrane. This layer has faint fibrous materials that extend from the plasma membrane to the fibrillar layer. Generally, as the cell wall ages it thickens, the fibrillar layer increases in width while the electron-lucent wall stays more or less consistent in width. In the four liverworts, the most recent wall of the AC has the highest PD density in the apical region regardless of AC geometry. As the walls elongate, primary wall is laid down between PD, separating them and resulting in lower densities and wider PD diameters in older walls. The season of fixation and whether plants were studied from nature or culture have an influence on AC ultrastructure. A developmental study of Physcomitrella patents gametophores in four stages, bud, 2-leaved, 7-8-leaved and ~20-leaved, reveals that the primary cell wall constituents change slightly during development. Specifically, LM5 a RG-I pectin antibody against the galactan branch epitope is only localized in the fibrillar layer of young water-conducting cells in the 7-8-leaved and 20-leaved gametophores. LM20, an antibody against HG esterified pectins, does not localize in any of the cell walls during development. The distribution patterns for AGPs (JIM13 and LM2) are consistent during gametophore development and predominantly localize on the electron-lucent layer and wall/plasma membrane interface. However, LM2 is mainly localized on the fibrillar layer in 7-8-leaved cell walls. AGPs also localize on element of the cytoplasm. LM6, an antibody against an RG-I pectin with arabinan branch epitopes, also localizes AGPs and because it expressed similar distribution patterns as JIM13 and LM2 on the cell wall, it likely localizes AGP in Physcomitrella. In addition, LM6 localizes pectins on the fibrillar layer similar to LM5 and LM19 for HG unesterified pectins. Callose predominantly localizes at the PD neck region. This study provides the first documentation of changes in size and shape of AC with age in Physcomitrella patens gametophores. The PD densities of gametophytes examined in this study fall into the lineage-specific network of PD (LPD) group designated for sporophytes of monilophytes and Selaginella (heterosporous lycophyte) with single ACs. Takakia lepidozioides leafy shoot has a tetrahedral AC with a highly curved free surface. This peculiar moss has mucilage hair (MH) associated with axil of phyllids. Mucilage hair in both species are 3-celled with a forth epidermal cell as the base. However, occasional 2-celled MH is seen in T. ceratophylla. The ultrastructure of MH has similarities with other mosses and liverworts.
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Stanley, MacIsaac Sarah. "Ultrastructure of the visceral ganglion in the ascidian larva Ciona intestinalis, cell circuitry and synaptic distribution". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0017/MQ57329.pdf.
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Usher-Smith, Juliet Alexandra. "An in vitro reconstruction of the influence of exercise on skeletal muscle cell volume and ultrastructure". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612748.
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Schultes, Klaus. "Ultrastructural characterization of ultraviolet induced corneal disease : an animal model". Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/27046.
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The majority of ancient people worshipped the sun and viewed it as a health - bringing deity. During the eighteenth and nineteenth century therapeutic benefits of sunlight exposure were beginning to be understood and by the end of the nineteenth century the importance of ultraviolet radiation was being realized. Danish physician Niels Finsen, whom many regard as the father of ultraviolet phototherapy, also stressed that it was ultraviolet radiation in the solar spectrum which cause sunburn. We now recognize that the small portion of ultraviolet radiation which reaches the earth's surface is not necessarily therapeutic, but in fact could be harmful to humans. There are numerous accounts of the harmful effects of UV radiation to the skin and the eye as a whole. These effects may be caused by either acute or chronic exposure to UV radiation. For example, some acute effects of UV-B radiation include conjunctivitis and photokeratitis. "Snow blindness" and "arc welders eye" are further examples of acute ultraviolet damage specifically to the surface of the cornea. On the other hand, chronic exposure to ultraviolet radiation is thought to be responsible for pterygia, climatic droplet keratopathy Hill and Maske (1989), cancers of the external eye, cataracts and various types of retinal diseases. The present study is an extension of ongoing studies on ultraviolet radiation damage to the cornea in the Department of Ophthalmology, University of Cape Town and Groote Schuur Hospital. Their specific interest lies in the causes and treatment of climatic droplet keratopathy. The aims of the present study are: 1) Establish a possible role of ultraviolet B radiation in human corneal diseases such as climatic droplet keratopathy and pterygium using the rabbit as an animal model. 2) Determine by means of SEM the initial effects and subsequent recovery of the epithelium after a 3-hour dose of ultraviolet B radiation. We refer to this study as "acute" response to ultraviolet B radiation. 3) To try and confirm the effects observed by SEM with ultrastructural studies using TEM. 4) In addition, we are also looking at the possible effects after exposing rabbit cornea to a daily dose of low level ultraviolet B radiation, over a long period of time. We refer to this as chronic exposure to ultraviolet B radiation. It is hoped that by exposing rabbits to ultraviolet light, principally ultraviolet B radiation, diseases similar to those found in humans could be simulated and disease progression studied. People are generally exposed to substantial amounts of UV radiation for a very long time. Since people generally live longer they will be exposed to an ever-increasing amount of solar UV radiation and subsequently, there is an increasing risk of developing corneal diseases. The possible threat to the ozone is also a real possibility and could lead to increased levels of ultraviolet radiation reaching the earth's surface. This will require a greater understanding of the very nature of corneal damage due to acute and chronic exposure. This study focusses mainly on the acute response to UV-B radiation since most studies have investigated effects of prolonged exposure to UV light. Accordingly, much less is known about acute exposure. Many people suffering from acute UV B radiation effects probably never visit the ophthalmologist or wait for a couple of days. This could also contribute to the fact that effects of short-term damage is not well documented.
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Silva, Thiago Pereira da. "Bacteria from freshwater ecosystems: structural aspects and programmed cell death". Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/6145.
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Bacteria are important components of the food web structure in aquatic ecosystems in which they influence the flow of carbon and energy. Populations of bacteria in these ecosystems comprise a diverse spectrum of individual cells able to respond to many factors such as nutrient supply, temperature and virus infection, which regulate bacterial life and death. Bacterial death is a key cellular event involved in the control and production of bacteria in aquatic ecosystems with functional meaning in the carbon and nutrient cycles. Therefore, the study of bacterial structural features and cellular mechanisms underlying bacterial death is crucial to understand processes affecting the entire population. However, both bacterial structure and cellular events of death in aquatic ecosystems are still poorly understood. In the present work, we used single cell approaches to study the structural organization of bacteria as well as to characterize cellular processes of death in these organisms. First, by using fluorescence and transmission electron microscopy (TEM), we provided a general panorama of how microscopy techniques, especially TEM, are powerful tools to understand bacterial structure and their responses to environmental stresses. We showed that bacteria from aquatic ecosystems have remarkable ultrastrutural diversity with components such as bacterial envelope of individual cells differing in structure within the same population. Second, we sought to identify and characterize mechanisms of bacterial cell death. Because our TEM analyses revealed morphological signs of apoptosis, a type of program cell death (PCD), in aquatic bacteria directly collected from natural ecosystems, we applied different techniques to detect apoptosis in bacteria cultured from natural samples. We used TEM as well as different probes to detect this type of PCD in cultured bacteria exposed to increased temperature and viral infection, which are recognized inducers of bacterial death. TEM showed, in both situations, ultrastructural changes indicative of apoptosis, such as cell retraction and condensation, similar to those reported for eukaryotic cells. Assays for membrane permeability, DNA fragmentation, phosphatidilserine exposition and caspase activation were significantly increased in treated bacteria compared to the control group. Altogether, our data demonstrate, for the first time, that PCD occur in aquatic bacteria, and that this event may be a basic mechanism for regulation of bacterial communities in these ecosystems.
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Wester, Brock Andrew. "Development and characterization of mechanically actuated microtweezers for use in a single-cell neural injury model". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39645.
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Traumatic brain injury (TBI) affects 1.4 million people a year in the United States alone and despite the fact that 96% of people survive a TBI, the health and socioeconomic consequences can be grave, partially due to the fact that very few clinical treatments are available to reduce the damage and subsequent dysfunction following TBI. To better understand the various mechanical, electrical, and chemical events during neural injury, and to elucidate specific cellular events and mechanisms that result in cell dysfunction and death, new high-throughput models are needed to recreate the environmental conditions during injury.
This thesis project focuses on the creation of a novel and clinically relevant single-cell injury model of traumatic brain injury (TBI). The implementation of the model requires the development of a novel injury device that allows specialized micro-interfacing functionality with neural micro environments, which includes the induction of prescribed strains and strain rates onto neural tissue, such as groups of cells, individual cells, and cell processes.
The device consists of a high-resolution micro-electro-mechanical-system (MEMS) microtweezer microactuator tool that is introducible into both biological and aqueous environments and can be proximally positioned to specific targets in neural tissue and neural culture systems. This microtweezer, which is constructed using traditional photolithography and micromachining processes, is controllable by a custom developed software-automated controller that incorporates a high precision linear actuator and utilizes a luer-based microtool docking interface.
The injury studies will include examination of intracellular calcium concentration over the injury time course to evaluate neuronal plasma membrane permeability, which is a significant contributor to secondary injury cascades following initial mechanical insult. Mechanical strain and strain rate input tolerance criteria will also be used to determined thresholds for cellular dysfunction and death.
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Fremont, Patrick. "Differenciation en culture in vitro de myoblastes d'ebauches musculaires lentes et rapides de l'embryon d'oiseau : influence de l'innervation et de l'activite mecanique". Nantes, 1987. http://www.theses.fr/1987NANT2028.
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Berger, Bruno [UNESP]. "Controles do desenvolvimento ovariano em abelhas africanizadas adultas, Apis mellifera Linné, 1758 (Hymenoptera, Apidae)". Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/100574.
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berger_b_dr_rcla.pdf: 1800024 bytes, checksum: b803c12973aa74cd00fe939959c8d1f1 (MD5)Os ovários das rainhas diferem dos de operárias de Apis mellifera quanto ao número e comprimento dos ovaríolos. Tanto o número, como o comprimento destes, é muito maior na rainha que nas operárias. No entanto, em ambos os casos os ovários são funcionais, isto é, capazes de produzir óvulos maduros. Apesar disso, operárias e rainhas diferem muito quanto à fertilidade e aos mecanismos controladores/estimuladores da vitelogênese, ou seja, da maturação dos óvulos. Em condições normais da colônia, nas rainhas a vitelogênese é desencadeada pelo acasalamento e nas operárias, pela ausência da rainha ou do recebimento de informações sobre sua presença na colônia. Passada a ocasião própria para o acasalamento no caso da rainha, e em idade avançada das operárias, os ovários entram em degeneração. O objetivo do presente trabalho foi o de avaliar como se comporta o desenvolvimento do ovário em rainhas e operárias mantidas fora dos condicionamentos da colônia e o efeito do tratamento destas com CO2, prática corrente na apicultura. Para tanto, operárias e rainhas foram mantidas aprisionadas em caixas com candy e água durante 15 dias e seguida a seqüência de desenvolvimento de seus ovários. O efeito do não acasalamento na época própria e do tratamento com CO2 foi feito estudando a morfologia do desenvolvimento da ovogênese, usando TUNEL e reação de fosfatase acida para caracterizar possíveis alterações celulares. As células do filamento terminal apresentaram-se empilhadas em fila única. Na transição para o germário as células tornam-se piramidais com a base apoiada sobre a lâmina própria e o ápice voltado para o centro do ovaríolo. São encontradas células esféricas, provavelmente ovogônias. No germário estão presentes células somáticas e germinativas, sendo da linhagem germinativa, os cistoblastos, os cistócitos, os ovócitos e as futuras...
The ovaries of queens and workers of Apis mellifera differs in number and length of the ovarioles. Length and number of ovarioles are larger in queen than in workers. However, in both cases, the ovaries are functional, i.e., it is able of produce mature eggs. Despite of that, workers and queens differ very in fertility and mechanisms of controlling/inducing vitellogenesis. In colony conditions, queen’s vitellogenesis is triggered by the matting and in workers by the absence of the queen or of the receipt of information about its presence in the colony. After the age proper to mate or in workers advanced age, the ovaries enter in degeneration. The objective of the present work was the evaluating of the ovary development in queens and workers maintained caged outside of the colony conditionings and the effect of the narcosis with CO2, practice current in the beekeeping. Newly emerged queens and workers were caged with candy and water during 15 days. For the queens the effect of the mate delay and CO2 narcosis were studied using TUNEL and acid fosfatase reaction to evaluate cell damages. The cells of the terminal filament appear as rows of one single cell, with a rectangular shape, poor in organelles and with a big central nucleus. In the transition for the germarium the cells present a pyramidal form with their base widened resting on tunica propria and the apex directed to center of the ovariole. Below the region of transition to the germarium are spherical cells, probably the oogonia. In the germarium are found somatic (pre-follicular cells) and germinative (cystoblasts, the cystocists, the oocytes and the future nurse cells) cells. The queen’s ovaries develop normally until the mating age, 5 days old queens. About the 10 days, the virgin queen beginning to presents an ovariolar disorganization with big incidence of injured cells with characteristics of apoptosis and autofagic death... (Complete abstract click electronic access below)
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Berger, Bruno. "Controles do desenvolvimento ovariano em abelhas africanizadas adultas, Apis mellifera Linné, 1758 (Hymenoptera, Apidae) /". Rio Claro : [s.n.], 2009. http://hdl.handle.net/11449/100574.
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Orientador: Carminda da Cruz-LandimBanca: Karina Patrício
Banca: José Lino Neto
Banca: José Chaud Netto
Banca: Daniela Carvalho dos Santos
Resumo: Os ovários das rainhas diferem dos de operárias de Apis mellifera quanto ao número e comprimento dos ovaríolos. Tanto o número, como o comprimento destes, é muito maior na rainha que nas operárias. No entanto, em ambos os casos os ovários são funcionais, isto é, capazes de produzir óvulos maduros. Apesar disso, operárias e rainhas diferem muito quanto à fertilidade e aos mecanismos controladores/estimuladores da vitelogênese, ou seja, da maturação dos óvulos. Em condições normais da colônia, nas rainhas a vitelogênese é desencadeada pelo acasalamento e nas operárias, pela ausência da rainha ou do recebimento de informações sobre sua presença na colônia. Passada a ocasião própria para o acasalamento no caso da rainha, e em idade avançada das operárias, os ovários entram em degeneração. O objetivo do presente trabalho foi o de avaliar como se comporta o desenvolvimento do ovário em rainhas e operárias mantidas fora dos condicionamentos da colônia e o efeito do tratamento destas com CO2, prática corrente na apicultura. Para tanto, operárias e rainhas foram mantidas aprisionadas em caixas com candy e água durante 15 dias e seguida a seqüência de desenvolvimento de seus ovários. O efeito do não acasalamento na época própria e do tratamento com CO2 foi feito estudando a morfologia do desenvolvimento da ovogênese, usando TUNEL e reação de fosfatase acida para caracterizar possíveis alterações celulares. As células do filamento terminal apresentaram-se empilhadas em fila única. Na transição para o germário as células tornam-se piramidais com a base apoiada sobre a lâmina própria e o ápice voltado para o centro do ovaríolo. São encontradas células esféricas, provavelmente ovogônias. No germário estão presentes células somáticas e germinativas, sendo da linhagem germinativa, os cistoblastos, os cistócitos, os ovócitos e as futuras... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The ovaries of queens and workers of Apis mellifera differs in number and length of the ovarioles. Length and number of ovarioles are larger in queen than in workers. However, in both cases, the ovaries are functional, i.e., it is able of produce mature eggs. Despite of that, workers and queens differ very in fertility and mechanisms of controlling/inducing vitellogenesis. In colony conditions, queen's vitellogenesis is triggered by the matting and in workers by the absence of the queen or of the receipt of information about its presence in the colony. After the age proper to mate or in workers advanced age, the ovaries enter in degeneration. The objective of the present work was the evaluating of the ovary development in queens and workers maintained caged outside of the colony conditionings and the effect of the narcosis with CO2, practice current in the beekeeping. Newly emerged queens and workers were caged with candy and water during 15 days. For the queens the effect of the mate delay and CO2 narcosis were studied using TUNEL and acid fosfatase reaction to evaluate cell damages. The cells of the terminal filament appear as rows of one single cell, with a rectangular shape, poor in organelles and with a big central nucleus. In the transition for the germarium the cells present a pyramidal form with their base widened resting on tunica propria and the apex directed to center of the ovariole. Below the region of transition to the germarium are spherical cells, probably the oogonia. In the germarium are found somatic (pre-follicular cells) and germinative (cystoblasts, the cystocists, the oocytes and the future nurse cells) cells. The queen's ovaries develop normally until the mating age, 5 days old queens. About the 10 days, the virgin queen beginning to presents an ovariolar disorganization with big incidence of injured cells with characteristics of apoptosis and autofagic death... (Complete abstract click electronic access below)
Doutor
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Lemullois, Michel. "Etude ultrastructurale et immunocytochimique de la ciliogenese dans l'oviducte de caille". Paris 6, 1988. http://www.theses.fr/1988PA066360.
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Description del a ciliogenese dans l'oviducte de caille, differenciation qui est specifiquement induite par les oestrogenes. Analyse de la mise en place de certains constituants du cytosquelette par des techniques immunocytochimiques
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Santana, Júlio César de Oliveira 1985. "Relações suprafamiliares em Erythrinoidea (Teleostei: Characiformes) com base em caracteres moleculares e da morfologia das células espermáticas = Suprafamilial relationships of the Erythrinoidea (Teleostei: Characiformes) based on molecular and spermatic cell data". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/317601.
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Orientadores: Irani Quagio Grassiotto, Daniela CalcagnottoTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A superfamília Erythrinoidea é uma das oito famílias que compõem a ordem Characiformes e foi proposta como um grupo monofilético para abrigar as famílias neotropicais Ctenoluciidae, Erythrinidae e Lebiasinidae, e a família africana Hepsetidae. Após a proposição da superfamília, estudos filogenéticos recentes com base em caracteres morfológicos, como osteologia e morfologia de partes moles, e caracteres moleculares tem refutado a ideia de monofiletismo do grupo. Além disso, diferentes autores divergem quanto às relações suprafamiliares de Erythrinoidea. Além dos caracteres tradicionais, o emprego dos caracteres oriundos da análise da ultraestrutura da ontogenia dos espermatozoides e sua forma final tem sido uma importante fonte na complementação dos estudos filogenéticos. O estudo apresentado teve como objetivo realizar uma análise filogenética para testar a monofiletismo de Erythrinoidea e verificar os padrões de relacionamento suprafamiliares em Characiformes, e testar o posicionamento filogenético da família Crenuchidae, supostamente relacionada à superfamília. As análises filogenéticas foram realizadas com base em dados moleculares e dados morfológicos independentemente, e de maneira conjunta (evidência total) através do método de Parcimônia. A ultraestrutura da espermiogênese e dos espermatozoides dos gêneros incluídos em Erythrinoidea, mais a família Crenuchidae e outras possivelmente relacionadas, foram descritos e codificados em uma matriz de dados. Nas três análises realizadas a superfamília Erythrinoidea não é recuperada como monofilética. A família Crenuchidae posiciona-se na base da subordem Characoidei e não está estreitamente relacionada à Erythrinoidea. As análises com dados moleculares e de evidência total apresentaram uma topologia muito semelhante ao nível mais inclusivo e os valores de suporte dos principais clados apresentaram-se maiores na evidência total, mostrando a influência positiva da inserção dos caracteres da morfologia das células espermáticas nas análises filogenéticas
Abstract: The superfamily Erythrinoidea is one of eight superfamilies within the order Characiformes and was proposed to include a monophyletic group composed of the Neotropical fish families Ctenoluciidae, Erythrinidae and Lebiasinidae, and African family Hepsetidae. Current phylogenetic studies based on morphological data, such as osteology and morphology of soft structures, and molecular data have refuted the hypothesis of monophyly of this group. In addition, the suprafamilial relationships in Erythrinoidea have diverged among the authors. In combination with more traditional characters, the analyses of the ultrastructure of sperm ontogeny and its final shape have become an interesting source of characters to complement phylogenetic studies. The goal of this study was to perform a phylogenetic analysis to test the monophyly of the Erythrinoidea and to assess the phylogenetic position of the family Crenuchidae, a group supposed to be closely related to the superfamily. The phylogenetic analyses were performed using molecular and morphological data separately, and in a combined approach (total evidence) through the Parsimony method. The ultrastructure of the spermiogenesis and the sperm shape of Erythrinoidea genera, plus the family Crenuchidae and other species possibly related to the superfamily were described and coded in a matrix data. In all three analyses Erythrinoidea was not recovered as monophyletic. The family Crenuchidae was placed in a basal position within the suborder Characoidei in molecular and total evidence analysis, and was not closely related to the Erythrinoidea. The analyses using only molecular data and total evidence showed a very similar topology for the more inclusive relationship levels. The support values were higher for the total evidence tree when compared to the one resulting of only molecular data possibly pointing to a positive influence of the combination of the spermatic cell data in phylogenetic analyses
Doutorado
Biologia Celular
Doutor em Biologia Celular e Estrutural
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Menzel, Lorenzo P. "Aspects of the Innate Immune System in the Caribbean Octocoral Swiftia exserta". FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/1025.
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The immune systems of cnidaria are important to study for two reasons: to gain a better understanding of the evolution of immune responses, and to provide a basis to partially redress the precipitous world-wide die-offs of reef corals, some of which have been attributed to diseases and stress. Many immune responses share ancient evolutionary origins and are common across many taxa.
Using Swiftia exserta, an azooxanthellate ahermatypic local octocoral, as a proxy model organism to study aspects of innate immunity in corals and cnidaria allows us to address both of the reasons listed above while not using endangered species. Utilizing a coral that does not contain symbiotic dinoflagellates (zooxanthellae) simplifies the system by restricting the source of proteins to a single genome. The lack of zooxanthellae in Swiftia exserta also allows the animal’s simple adaptation to lab settings.
This study of the innate immune system of an octocoral demonstrates: 1) a novel understanding of the microanatomy of octocoral tissues; 2) that Swiftia exserta has at least two cell types that function as constitutive immunocytes; and 3) the presence of two potent antibacterial peptides, one with a mass between 4694 and 4696 Daltons. My report on the microanatomy of the coenenchyme, the tissue between polyps, advances the understanding of octocoral anatomy by systematically comparing histology sections with electron micrographs. Applying various techniques of enzyme histochemistry, coupled with cryo-preservation, to the coenenchyme I have identified at least two populations of constitutive immunocytes in Swiftia exserta. Two antibacterial proteins are identified by protein purification and antimicrobial testing techniques. The more active protein is partially characterized with modern hyphenated mass-spectrometry techniques, and can be the focus of future study.
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Mosiniak-Bessoles, Michèle. "Contribution a l'etude des oscillations spontanees de l'assemblage cellulosique dans les parois des cellules vegetales". Paris 6, 1987. http://www.theses.fr/1987PA066189.
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Un systeme oscillatoire tres caracteristique des parois cellulaires des cellules vegetales est constitue par l'assemblage helicoidal. Par des recherches methodologiques de demasquage et de dissection des edifices microfibrillaires, par une analyse stereoscopique et par une modelisation des variations dans l'espace et dans le temps, on etablit la dynamique, la gamme et les modalites d'adaptation du systeme en fonction de la differenciation cellulaire afin de mieux comprendre la morphogenese parietale
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Cohen, Edith. "Etude cytologique de la cellule neuro-epitheliale, chez l'embryon de souris, au stade initial de la differenciation neuronale". Paris 6, 1987. http://www.theses.fr/1987PA066155.
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Sarkar, Purbasha. "Cell death mechanisms leading to vascular cavity formation in pea (Pisum sativum) L. ‘Alaska’) primary roots". Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1218090008.
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Seilhean, Véronique. "La cellule apicale d'une pteridophyte, nephrolepis biserrata (sw. ) schott : modifications de la structure nucleaire en fonction de l'activite cellulaire". Paris 6, 1987. http://www.theses.fr/1987PA066621.
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Une etude detaillee de la structure a ete entreprise afin d'examiner les relations existant entre l'organisation nucleaire et l'activite cellulaire. Les noyaux de nephrolepis biserrata ont une structure chromerique sans chromocentre. L'analyse cytologique en microscopie phtonique et electronique montre que la structure chromaticienne du noyau de l'apicale est tres diffuse. L'application de la cytophotometrie a balayage permet d'obtenir des donnees quantitatives. Dans les cellules mitotiquement actives, la proportion d'adn condense ne varie pas au cours du cycle mais la densite moyenne augmente lors du passage en phase g2. La proportion d'adn condense, en volume et en teneur, est plus faible dans les nouyaux de la cellule apicale et des derivees que dans ceux des autres cellules du meristelme. Une relation entre l'organisation de la chromatine et les fonctions du noyau a pu etre degagee. L'ensemble de ces resultats permet de rapprocher les proprietes de l'apicale de celles des cellules zygotiques
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Landemore, Gérard. "Contribution a l'etude biochimique et cytochimique de la cellule de kurloff". Caen, 1987. http://www.theses.fr/1987CAEN2046.
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Lelong-Rebel, Isabelle. "Etude de l'evolution de l'architecture membranaire des neurones d'embryons de poulet en culture : composition et topologie des proteines et des lipides polaires au cours du developpement cellulaire". Université Louis Pasteur (Strasbourg) (1971-2008), 1989. http://www.theses.fr/1989STR13089.
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L'isolement d'une fraction hautement purifiee de membranes plasmiques et l'emploi de radioiodations enzymatiques ont permis de suivre la composition des proteines et de certains lipides polaires, ainsi que leur representation a la surface cellulaire
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Tourmente, Sylvette. "Evolution des mitochondries pendant l'ovogenese de drosophile : morphologie, distribution, replication et expression du genome". Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF21073.
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Benmoussa, Nemcha. "Effets de l'hydrocortisone sur la morphogénèse du tégument du pied chez l'embryon de poulet : analyse morphologique, ultrastructurale, immunohistochimique et expérimentale à l'aide de recombinaisons dermo-épidermiques". Grenoble 1, 1986. http://www.theses.fr/1986GRE10011.
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Porter, Heidi Sue. "The Effect of Febrile Temperature on Plasmodium falciparum". BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1573.
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Previously it has been shown that cultures of Plasmodium falciparum died following exposure to a febrile temperature of 40°C, as demonstrated by a decrease in parasitemia of the following generation. In the current study, the effect of 40°C treatment on culture media, erythrocytes, and parasite glucose consumption, were ruled out as possible influences on parasite death, demonstrating that 40°C impacted the parasites directly. Metabolic profiling of DNA synthesis, protein synthesis, and glucose utilization during exposure to 40°C clearly indicated that febrile temperatures had direct effect on major metabolic pathways and parasite development, beginning 20-24 hr after erythrocyte invasion. The ring stages were relatively refractory to heat and recovered completely if returned to 37°C. The mechanism of parasite death was investigated for evidence of an apoptosis-like pathway in cells treated with 40°C, chloroquine, and staurosporine. Lack of typical physiological hallmarks, namely, caspase activation, characteristic mitochondrial membrane potential changes, and DNA degradation as indicated by DNA laddering, eliminated ‘classical’, apoptosis as a mechanism of parasite death. Parasites dying under the influence of 40°C, staurosporine, and chloroquine initially appeared pyknotic in light and electron microscopy, as in apoptosis, but eventual swelling and lysis of the food vacuole membrane led to secondary necrosis. Initially, chloroquine did induce DNA laddering, but it was later attributed to occult white blood cell contamination. While not apoptosis, the results do not rule out other forms of temperature-induced programmed cell death.
35
Metivier, Christine. "La motilité chez le dinoflagellé évolué Noctiluca Scintillans Mccartney : organisation structurale, régulation ionique, caractérisation biochimique et immunologique des protéines corticales". Paris 6, 1986. http://www.theses.fr/1986PA066243.
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La motilité du tentacule du dinoflagellé Noctiluca Scintillans et les mouvements du cytostome dépendent d'un épiplasme fibreux périphérique, d'un réseau microtubulaire longitudinal sous-jacent à l'épiplasme et de myonèmes transversaux striés contractiles. L'étude de l'organisation de ce cytosquelette et de la contractilité des myonèmes du tentacule et du cytostome ont été réalisées en microscopie électronique. Le rôle des microtubules des myonèmes, du magnésium, de l'ATP extracellulaires et plus particulièrement celui du calcium au cours de la motilité ont été précisées ainsi que la recherche de la présence d'actine intracellulaire et la caractérisation biochimique et immunologique des 3 protéines majoritaires du cytosquelette (45, 80 et 140 KD).
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Sève, Annie-Pierre. "Lectines nucleaires". Orléans, 1987. http://www.theses.fr/1987ORLE2020.
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PERRIN-WALDEMER, CLAUDE GILBERT. "Etude des glandes accessoires du male de drosophila melanogaster (meigen) : cytophysiologie et cytochimie". Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF2E359.
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Harper, John D. I. "Genetical and ultrastructural analysis of the Chlamydomonas cell cycle". Thesis, Queen's University Belfast, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236312.
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Ambert, Katia. "Étude ultrastructurale de la dégradation des fibres lignocellulosiques par le champignon filamenteux Phlebia radiata". Grenoble 1, 1996. http://www.theses.fr/1996GRE10036.
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Phlebia radiata est un basidiomycete du groupe des champignons de la pourriture blanche, seuls microorganismes connus capables de degrader totalement la lignine du bois. A l'aide de la microscopie electronique a transmission associee a des techniques cytochimiques, nous avons pu mettre en evidence differents modes de degradation provoques par le champignon au cours de l'attaque d'echantillons de bouleau et de peuplier: il peut soit attaquer selectivement la lignine, en provoquant un amincissement progressif des parois secondaires des fibres et / ou en degradant les lamelles mitoyennes, soit degrader simultanement tous les constituants du bois, en perforant les parois et / ou en degradant specifiquement la couche s1 de la paroi. Une etude originale utilisant des anticorps diriges contre des lignines synthetiques nous a permis de visualiser la distribution heterogene des lignines au sein des differentes couches des parois cellulaires. Il apparait que la nature de la lignine a une influence sur le type de degradation. P. Radiata produit des enzymes ligninolytiques, lignine-peroxydases, manganese-peroxydases et laccases, que nous avons localisees au cours de la degradation du bois, grace a des marquages immunocytochimiques. Afin de suivre les enzymes ligninolytiques a un stade tres precoce de leur formation, une approche en biologie moleculaire utilisant des sondes arn a ete engagee pour localiser les arnm codant pour une lignine-peroxydase et pour une laccase de p. Radiata. Ce champignon, comme les autres champignons de la pourriture blanche, presente, par sa capacite a delignifier le bois, un interet potentiel pour l'industrie papetiere. Nous avons montre que la mnp isolee provoque une defibrillation de pates kraft ecrues. Par ailleurs, l'ion manganese complexe a un acide organique, agit egalement en defibrillant les pates. Il apparait que le complexe mniii-oxalate est plus efficace que le complexe mniii-pyrophosphate a blanchir la pate kraft
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Sheffield, Edward Alexander. "The ultrastructural features of developing epithelioid cell granulomas in man". Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259692.
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Patrone, Laura May. "Ultrastructural Analysis of Vegetative and Mitotic Cells of the Unicellular Red Alga Rhodella violacea". W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539625447.
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Dorgans, Kevin. "Ultrastructural, molecular and functional heterogeneities of cerebellar granule cell presynaptic terminals". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAJ083/document.
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Le cervelet est une structure cérébrale impliquée dans la régulation motrice. Dans le cortex cerebelleux, les informations sensorimotrices sont transmises par les cellules en grain. Mon travail de thèse démontre que les connections synaptiques de ces neurones ont des propriétés hétérogènes. D’une synapse à l’autre, j’ai pu observer des variations d’ultrastructure, de composition moléculaire et de fonctionnement au cours de trains de potentiels d’action à haute fréquence. Plus particulièrement, j’ai caractérisé les propriétés de « plasticité à court terme » des synapses unitaires des cellules en grain : 1) Elles sont très différentes d’une synapse à l’autre et peuvent être classées en différentes sous-catégories. 2) Certaines catégories de fonctionnement synaptique reposent sur l’expression de molécules telles que la Synapsine2. 3) La réponse d’un neurone post-synaptique à de hautes fréquences de stimulation dépend de la nature de la synapse activéeCerebellum is a brain structure involved in motor regulation and motor learning. In the cerebellar cortex, sensorimotor information is transmitted by granule cells. During my PhD, I demonstrated that the properties of individual granule cell synaptic connections are highly heterogeneous. From one synapse to another, I observed ultrastructural, molecular and functional variability at unitary contacts. More precisely, I assessed the properties of short term plasticity at individual synapses during high frequency trains of stimulation :1) Short term plasticities are highly heterogeneous from one synapse to another and can be classified in sub-categories.2) Some categories of short-term plasticity profiles relie on the expression of molecules such as Synapsin2.3) The response of post-synaptic neuron to high-frequency inputs is dependent on the nature of the activated synaptic contact
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Moreira-de-Sousa, Cristina. "Avaliação dos impactos gerados pela vinhaça bruta e após ajuste de pH, em representantes da fauna edáfica". Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/158310.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A cana-de-açúcar é uma das principais culturas mundialmente difundida e a alta produtividade resulta na geração de inúmeros resíduos. A vinhaça, resíduo da produção do etanol tem chamado a atenção devido suas características e propriedades, quando empregada na fertirrigação das culturas de cana-de-açúcar. Diversos benefícios foram descritos, ganhos na fertilização e enriquecimento do solo, bem como aumentos na produtividade. Entretanto, a vinhaça também apresenta substâncias que podem ser nocivas, afetando negativamente a fauna existente nos locais de aplicação do resíduo. Frente a essa problemática, diversos estudos foram desenvolvidos com o intuito de melhor compreender os impactos da vinhaça no meio ambiente e, mesmo diante dos benefícios que a fertirrigação com a vinhaça implica economicamente ainda há a necessidade de maiores cuidados com a utilização do resíduo no campo. Nesse contexto, o objetivo deste trabalho foi propor um tratamento para a vinhaça, ajustando seu pH em 7,0 (neutro) utilizando cal (CaO), com a intenção de amenizar sua toxicidade para posterior uso no solo, visto que, um dos grandes problemas apresentados pela vinhaça é o pH ácido. O uso de cal foi escolhido por ser este produto utilizado em campo para correção do solo. Foi associado o uso de diversos biomarcadores à bioindicadores de solo, além de testes ecotoxicológicos para avaliar o efeito da vinhaça bruta em comparação à vinhaça tratada. Diplópodos da espécie Rhinocricus padbergi foram expostos à vinhaça em sua forma bruta e tratada com CaO, na concentração estabelecida pela Norma da CETESB, e ao dobro desta mesma concentração, simulando uma situação de super dosagem. A análise do intestino médio destes animais por meio das ferramentas ultraestruturais, imunohistoquímica e marcação de morte celular revelou que a vinhaça bruta pode ocasionar danos nos tecidos dos animais expostos e que o tratamento desta vinhaça surtiu efeito na diminuição desses danos. Testes ecotoxicológicos de fuga e reprodução, padronizados mundialmente pela Organização Internacional de Normalização (ISO), foram realizados com as espécies Eisenia andrei, Enchytraeus crypticus e Folsomia candida; de um modo geral, observou-se que as espécies E. crypticus e F. candida não tiveram seus comportamentos influenciados pela vinhaça bruta e nem pela vinhaça tratada, mas a espécie E. andrei apresentou-se mais sensível a presença da vinhaça no solo demonstrando comportamento de fuga em concentrações mais elevadas de vinhaça bruta e tratada, e, no teste de reprodução, respondeu a exposição à vinhaça tratada, com aumento no número de juvenis em relação a vinhaça bruta. Logo, o emprego da vinhaça na fertirrigação ainda requer cuidados, uma vez que seus efeitos nocivos são notórios, e nesse sentido, a alternativa de neutralizar seu pH pode representar uma medida de emprego desse resíduo com menos impacto.
Sugarcane is one of the main crops worldwide and the high productivity results in the generation of many wastes. Vinasse, the residue of ethanol production, has attracted attention because of its characteristics and properties, when used in the fertirrigation of sugarcane crops. Several benefits have been described, gains in fertilization and soil enrichment, as well as increases in productivity. However, the vinasse also presents substances that can be harmful, negatively affecting the fauna existing in the places of application of the residue. Faced with this problem, several studies were developed with the purpose of better understanding the impacts of vinasse in the environment and, even in view of the benefits that fertirrigation with vinasse implies economically, there is still a need for greater care with the use of the residue in the field. In this context, the objective of this work was to propose a treatment for vinasse, adjusting its pH to 7.0 (neutral) using lime (CaO), with the intention of mitigating its toxicity for later use in the soil, since one of the great problems presented by vinasse is acid pH. The use of lime was chosen because this product is used in field for soil correction. It was associated the use of several biomarkers to soil bioindicators, as well as ecotoxicological tests to evaluate the effect of raw vinasse in comparison to the treated vinasse. Diplopods of the species Rhinocricus padbergi were exposed to vinasse in their raw form and treated with CaO, at the concentration established by the CETESB Standard, and at twice the same concentration, simulating a super dosage situation. The analysis of the midgut of these animals using ultrastructural tools, immunohistochemistry and cell death marking revealed that raw vinasse can cause damage to the tissues of the exposed animals and that the treatment of this vinasse had an effect in reducing these damages. Ecotoxicological tests of the avoidance and reproduction tests, standardized worldwide by the International Organization for Standardization (ISO), were carried out with the species Eisenia andrei, Enchytraeus crypticus and Folsomia candida; in general, E. crypticus and F. candida were not influenced by raw vinasse or treated vinasse, but the E. andrei species was more sensitive to the presence of vinasse in the soil, demonstrating in the higher concentrations of raw and treated vinasse, and in the reproduction test, the exposure to treated vinasse responded, with an increase in the number of juveniles in relation to raw vinasse. Therefore, the use of vinasse in fertigation still requires care, since its harmful effects are notorious, and in this sense, the alternative of neutralizing its pH can represent a measure of the use of this residue with less impact.
CAPES: 001
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Daniels, Alison. "Microscopic and computer analysis of ultrastructural changes accompanying isolation and manipulation of tobacco protoplasts". Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278755.
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Choi, Jiwon 1977. "The role of fibulin-5 : in the ultrastructural and biomechanical properties of skin". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81611.
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Properly assembled elastic fibers play an important role in providing skin with the properties of elasticity and resilience to allow for considerable mobility, but the mechanisms involved in elastic fiber assembly remains unknown. Fibulin-5 is an extracellular 66kDa glycoprotein synthesized and secreted by fibroblasts in skin, and has the ability to bind to tropoelastin. This study addresses (1) the role of fibulin-5 in the ultrastructure of elastic fibers in skin, and (2) its function in the cutaneous mechanical properties by using wild type and fibulin-5 null mice. In the first part, skin of fibulin-5 null mice as well as wild type mice was investigated in order to gain insight into the function of fibulin-5 in elastic fiber assembly. Using light and electron microscopy, the dramatic defects of dermal elastic fibers in the absence of fibulin-5 were analyzed. Interestingly, in the immunoelectron microscopy for LOXL-1, an enzyme responsible for the elastin cross-links, fibulin-5 null mouse skin exhibited similar immunoreactivity for LOXL-1 to wild type skin. Moreover, in the wild type skin, fibulin-5 localized to the microfibril-elastin interface at the edges and within the elastic fiber. In the second part of this study, the function of fibulin-5 in skin biomechanics was studied in order to determine its role in skin strength and elasticity. By using tensile tests, fibulin-5 null mouse skin was found to be significantly stiffer and weaker than wild type skin. Taken together, the defective elastic fibers in the absence of fibulin-5 suggest that fibulin-5 is involved in a secondary step of cutaneous elastic fiber assembly and in the mechanical properties of adult mouse skin.
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Bairaktaris, George. "Ultrastructural investigation of matrix and cell surface factors in corneal transplantation, refractive surgery and stem-cell grafting". Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340515.
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Damerval, Marc. "Identification et rôle physiologique des inclusions contenues dans le système nerveux central de la moule Mytilus edulis et de la crépidule Crepidula fornicata". Caen, 1985. http://www.theses.fr/1985CAEN2004.
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Les inclusions des cellules gliales et des neurones des ganglions cérébroïdes de crépidule et cérépleuraux de la moule ont été examinés. Une première approche a permis de distinguer les granules de neurosécretion de type neuroendocrine des inclusions pigmentées. L'ultrastructure de ces inclusions permet de les caracteriser avec précision. L'étude biochimique révèle la présence de carotènes et de différentes xanthophylles. On précise enfin le rôle de ces inclusions dans des conditions d'hypoxie et d'anoxie du milieu
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Mak, Kai-yu, i 麥啟宇. "Substratum effects of micro- and nano-structures on cellular behavior". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/202233.
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Substratum effects of micro- and nano-scaled structures on mammalian cell lines have experienced rapid developments during past decades. Tremendous studies have shown that micro- and nano- scaled surface morphology has great influences on cellular behavior and has great potential application in medical device design and organs regeneration. Although a variety of cell types have been used in cell-substrate studies for different purposes, information about how the cellular response of hepatic cells to the nanoporous and microgrooved structures is still insufficient The effects of groove/ridge width of the microgrooved structures on the mammalian cell culturing is usually overlooked. In this thesis, the cellular response of hepatic cells to the nanoporous and microgrooved is studied, including the cell spreading, cell elongation, cell alignment, and cell motility. Also, the effects of groove/ridge width are addressed on three mammalian cell lines (BEL-7402, MIHA, and HeLa). Three experiments were performed.
Firstly, the effect of nanoporous surface on hepatic cell line, BEL-7402, was studied. The nanoporous surface (140 nm) was fabricated by anodize alumina membrane and microcontact printing techniques on PDMS surface. Cellular behaviors were analyzed with scanning electron microscope and time-lapse imaging. The results showed that cell projected area was reduced with cell migration speed was promoted on porous surface when compared with flat control surface.
Secondly, the effect of microgrooves surface (10 μm, 30 μm and 50μm, with equal ridge and groove width) on hepatic cell line, BEL-7402, was studied. The microgrooved surface was fabricated by microcontact printing on PDMS. Cellular behaviors were analyzed with scanning electron microscope and time-lapse imaging. The results showed that cell elongation, alignment and directional migration was promoted by the groove structure when comparing with flat surface.
Thirdly, the effect of microgrooved PDMS surfaces with varied ridge width and groove width on three mammalian cell lines (BEL-7402, MIHA, and HeLa)was studied. Microgrooved PDMS surfaces with nine combination of ridge width (5 μm, 10 μm and 30 μm) and groove width (5 μm, 10 μm and 30 μm) were fabricated using photolithography and soft lithography. The results showed that all grooved structures have almost same affection on the cellular response, independent of the cell type. Also, our result showed that the cell elongation displayed same pattern on all micrgrooved surfaces, independent of the groove/ridge width changes. In addition, our result showed that microgrooved surface that contained 10 μm ridge or groove were less effective in aligning cells. On the other hand, microgrooved surface 5×5, 5×30, 30×5 and 30×30 showed most effective in aligning cell when compare with other grooved surface and flat control surface.
Our result provide information on how cell response to surface morphology at nano-scale and micro-scale. These informations are highly conducive for the liver regeneration, cancer metastasis study, and other tissue engineering research.published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
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Beswetherick, John T. "An ultrastructural study of host and non-host resistance reactions in plant cells". Thesis, Open University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292658.
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Mutasa, H. C. F. "Cytology, cytochemistry and ultrastructure of blood cells with special reference to myeloid leukaemias". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335133.
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