Aerospace medicine and biology. A continuing bibliography (supplement 231)

This bibliography lists 284 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1982

A novel image analysis approach to characterise the effects of dietary components on intestinal morphology and immune system in Atlantic salmon

The intestinal tract of salmonids provides a dynamic interface that not only mediates nutrient uptake but also functions as the first line of defence against ingested pathogens. Exposure of the immune system to beneficial microorganisms and different dietary immunostimulants via the intestine has been shown to prime the immune system and help in the development of immune competence. Furthermore, the morphology and function of teleostean intestines are known to respond to feed components and to ingested and resident bacterial communities. Histological appraisal is still generally considered to be the gold standard for sensitive assessment of the effects of such dietary modulation. The aim of the present study was to improve understanding of salmonid intestinal function, structure and dynamics and to use the knowledge gained to develop a model for analysis, which would allow intestinal health to be assessed with respect to different intestinal communities and feed components. Virtual histology, the process of assessing digital images of histological slides, is gaining momentum as an approach to supplement traditional histological evaluation methodologies and at the same time, image analysis of digitised histological sections provides a practical means for quantifiable assessment of structural and functional changes in tissues, being both objective and reproducible. This project focused on the development of a rapid, practical analytical methodology based on advanced image analysis, that was able to measure and characterise a range of features of the intestinal histology of Atlantic salmon in a quantitative manner. In the first research chapter, the development of a novel histological assessment system based upon advanced image analysis was described, this being developed with the help of a soybean feed model known to induce enteropathy in Atlantic salmon. This tool targeted the evaluation of the extent of morphological changes occurring in the distal intestine of Atlantic salmon following dietary modulation. The final analytical methodology arrived at, could be conducted with minimal user-interaction, allowing rapid and objective assessment of 12 continuous variables per histological frame analysed. The processing time required for each histological frame was roughly 20-25 min, which greatly improved the efficiency of conducting such a quantitative assessment with respect to the time taken for a subjective semi-quantitative alternative approach. Significant agreement between the fully automated and the manual morphometric image segmentation was achieved, however, the strength of this quantitative approach was enhanced by the employment of interactive procedures, which enabled the operator / observer to rectify preceding automated segmentation steps, and account for the specimen’s variations. Results indicated that image analysis provided a viable alternative to a pathologist’s manual scoring, being more practical and time-efficient. In the second research chapter, feeding Atlantic salmon a high inclusion level of unrefined SBM (25 %) produced an inflammatory response in the distal intestine as previously described by other authors. The model feed trial successfully generated differentiable states, although these were not, for the most part, systemically differentiable through the majority of standard immunological procedures used, being only detectable morphologically. Quantitation of morphometric parameters associated with histological sections using the newly developed image analysis tool successfully allowed identification of major morphological changes. Image analysis was thus shown to provide a powerful tool for describing the histomorphological structure of Atlantic salmon distal intestine. In turn, the semi-automated image analysis methods were able to distinguish normal intestinal mucosa from those affected by enteritis. While individual parameters were less discriminatory, use of multivariate techniques allowed better discrimination of states and is likely to prove the most productive approach in further studies. Work described in the third research chapter sought to validate the semi-automated image analysis system to establish that it was measuring the parameters it was purported to be measuring, and to provide reassurance that it could reliably measure pre-determined features. This study, using the same sections for semi-quantitative and quantitative analyses, demonstrated that the quantitative indices performed well when compared to analogous semi-quantitative descriptive parameters of assessment for enteritis prognosis. The excellent reproducibility and accuracy performance levels indicated that the image analysis system was a useful and reliable morphometric method for the quantification of SB-induced enteritis in salmon. Other characteristics such as rapidity, simplicity and adaptability favour this method for image analysis, and are particularly useful where less experienced interpreters are performing the analysis. The work described in the fourth research chapter characterised changes in the morphology of the intestinal epithelial cells occurring as a result of dietary modulation and aspects of inflammatory infiltration, using a selected panel of enzyme and IHC markers. To accomplish this, image analysis techniques were used to evaluate and systematically optimise a quantitative immunolabelling assessment protocol. Digital computer-assisted quantification of labelling for cell proliferation and regeneration; programmed cell death or apoptosis; EGCs and t-cell like infiltrates; mobilisation of stress-related protein regenerative processes and facilitation of nutrient uptake and ion transport provided encouraging results. Through the description of the intestinal cellular responses at a molecular level, such IHC expression profiling further characterised the inflammatory reaction generated by the enteropathic diet. In addition, a number of potential diagnostic parameters were described for fish intestinal health e.g. the relative levels of antigenicity and the spatial distribution of antigens in tissues. Work described in the final research chapter focused on detailed characterisation of intestinal MCs / EGCs in order to try to elucidate their functional role in the intestinal immune responses. Through an understanding of their distribution, composition and ultrastructure, the intention was to better characterise these cells and their functional properties. The general morphology, histochemical characteristics and tissue distribution of these cells were explored in detail using histochemical, IHC and immunogold staining / labelling, visualised using light, confocal and TEM microscopy. Despite these extensive investigations, their physiological function and the content of their granules still remain somewhat obscure, although a role as immunodulatory cells reacting to various exogeneous signals through a finely regulated process and comparable to that causing the degranulation of mammalian MCs is suggested. The histochemical staining properties demonstrated for salmonid MCs / EGCs seem to resemble those of mammalian mucosal mast cells, with both acidophilic and basophilic components in their granules, and a granule content containing neuromodulator / neurotransmitter-peptides such as serotonin, met-enkephalin and substance-p. Consequently, distinguishable bio-chromogenic markers have been identified that are of utility in generating a discriminatory profile for image analysis of such cells

Stress-strain analysis of skull implant

Lebeční implantáty se používají jako náhrady částí lebečních kosti, které v důsledku zranění nebo nemoci ztratili svou funkci. Důležitým faktorem, který ovlivňuje funkci celé soustavy implantátu, jsou jeho mechanické projevy. Tato práce stručně shrnuje současné znalosti v oblasti rekonstrukce lebečních defektů a popisuje srovnání různých tvarů stěn implantátu vytvořených z různých materiálů, na základě deformační napěťové analýzy modelu neurocrania s umístěným implantátem, zatíženým nitrolebečním tlakem a vnějším zatížením.Cranial implants are used as a substitute for parts of cranial bones that lost its function due to trauma or disease. An important factor, that influences function of the cranial implant structure, is its mechanical behavior. This thesis briefly summarizes current knowledge in the field of cranial defect reconstruction and provides comparison of different types of materials and implant wall shapes, based on stress-strain analysis of Computer Tomography based neurocranial model with placed implant and loaded by intracranial pressure and external load.

Aerospace medicine and biology: A continuing bibliography with indexes, supplement 183

This bibliography lists 273 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1978

Microglia-neuron interactions in the electrophysiological domain : can microglia respond directly to electrical signals?

A microglia é um tipo de célula com um comportamento dinâmico, que está constantemente a analisar a sua vizinhança e a alterar a sua morfologia para se adaptar ao microambiente onde está inserida. Apesar de serem conhecidas como células eletricamente não excitáveis, as funções da microglia parecem estar extremamente coordenadas com o estado funcional das redes neuronais, o que sugere a existência de uma íntima comunicação com os neurónios. Embora esta comunicação, através de sinais químicos, já ter sido alvo de muitos estudos, ainda não é claro se a microglia tem a capacidade de monitorizar outro tipo de sinais, nomeadamente sinais elétricos. In vivo, a microglia estabelece contactos regulares e transientes (durante 4-5 min) com as estruturas pré- e pós-sinápticas neuronais, sendo a duração destes contactos regulada pelo perfil de atividade neuronal. Além disso, a sua morfologia e o perfil de expressão genética também são modulados pelo nível de atividade neuronal. Estes factos indicam que a comunicação microglia-neurónio é sincronizada de modo a manter a funcionalidade e a homeostasia do SNC. Um elemento relevante, é que a microglia expressa diferentes tipos de canais iónicos dependentes de voltagem, tendo alguns destes canais, funções focadas na regulação do potencial de repouso da membrana e concentrações iónicas intracelulares. Estes canais iónicos dependentes de voltagem deixam em aberto a possibilidade de deteção direta de potenciais elétricos neuronais. Esta interação elétrica continua, porém, inexplorada. Portanto, este trabalho tem como objetivo investigar de que forma as propriedades elétricas do microambiente, para além da sinalização química, afetam a dinâmica da microglia. Por outras palavras, pretende-se decifrar se a microglia consegue detetar a atividade elétrica neuronal, e explorar os mecanismos envolvidos nessa deteção. Para investigar essa possível capacidade, foram utilizadas câmaras de galvanotaxia, para estudar as mudanças de comportamento da microglia quando sujeitas a campos elétricos compatíveis com as condições fisiológicas. Campos elétricos de 40 e 400 V/m foram aplicados à microglia durante 6 ou 24 horas, e as mudanças morfológicas observadas na microglia foram quantificadas através de análise de imagem. Para o campo elétrico de 40 V/m, observou-se um aumento da área e uma diminuição da irregularidade da membrana da microglia, ao longo do tempo. Por sua vez, o campo elétrico de 400 V/m, em ambos os períodos de tempo estudados, causou um aumento das protusões citoplasmáticas e nenhuma alteração na área da microglia O impacto de compostos bioativos (secretoma) resultante de diferentes perfis de atividade neuronal na microglia foi igualmente investigado. O meio condicionado neuronal (NCM) foi extraído de culturas neuronais funcionalmente ativas, em diferentes estados de maturação in vitro, e foi exposto à microglia durante 24 ou 48 horas. O tratamento com NCM resultou num aumento da área da microglia e numa tendência para um aumento da ramificação destas células. Em conclusão, este estudo mostrou que a microglia, tem a capacidade de detetar campos elétricos. Os mecanismos que levam à sua alteração morfológica na presença de campos elétricos ainda está por ser investigada. Trabalhos futuros poderão explorar estes mecanismos através do estudo da expressão de marcadores de ativação.Microglia are highly dynamic cells that constantly scan their surroundings and undergo changes in their morphology to adapt to their microenvironment. Although known as nonexcitable cells, microglia functions seem to be highly coordinated with the neuronal activity levels, suggesting the existence of a very close signaling crosstalk with neurons. This communication in terms of chemical signals, has been the focus of many studies but, it is still unknown if microglia have the capacity to detect other kind of signals, namely electrical signals. In vivo, microglia regularly establish transient contacts (for 4-5 min) with pre- and postsynaptic neuronal structures, being the frequency and duration of such contacts dependent on neuronal activity profile. Their morphology and gene expression profile are also shaped by neuronal activity. This indicates that microglia-neuron work in synchrony to maintain the functional and structural CNS homeostasis. Moreover, microglia express different types of voltage-gated ion channels. Some of these channels have the function of regulating the membrane rest potential and intracellular ionic concentrations. These voltage-gated ion channels open the possibility of microglia to be able to sense directly the neuronal electrical activity. Yet, this interaction remains unexplored in what regards its electrical dependence. Therefore, this work aims to investigate how the electrophysiological microenvironment, beyond the chemical signaling, impacts microglia dynamics. In other words, one aims to decipher if microglia can perceive the electrical activity per se and, explore the mechanisms by which it may occur. To investigate this capacity, it were used galvanotaxis chambers to study the microglia behavior changes when exposed to electric fields (EF) compatible with the physiologic conditions. EFs of 40 or 400 V/m were applied to microglia for 6 or 24 h and the microglia morphological changes were quantified by image analysis. For the 40 V/m applied EF, one observed an increase in microglia area and a decrease in cell membrane irregularity, with time. The EF of 400 V/m, at both time points, resulted in an increase of the cytoplasmatic protrusions in the microglia but no change in the microglia cell area. The impact of bioactive compounds (secretome) resultant from different neuronal network activity profiles on microglia behavior were also investigated. Neuronconditioned medium (NCM) was extracted from functionally active neuron cultures, at different stages of maturation in vitro, and exposed to microglia for 24 or 48h. NCMviii treatment resulted in an increase in microglia area and a tendency to these cells to become more ramified. In conclusion, this study showed that microglial cells are capable of detecting EFs. The mechanisms by which microglia change their morphology in the presence of EFs are still under investigation. Future work may explore these mechanisms by evaluating the expression of microglia activation markers

Space Station needs, attributes and architectural options. Volume 2, book 1, part 2, task 1: Mission requirements

Mission areas analyzed for input to the baseline mission model include: (1) commercial materials processing, including representative missions for producing metallurgical, chemical and biological products; (2) commercial Earth observation, represented by a typical carry-on mission amenable to commercialization; (3) solar terrestrial and resource observations including missions in geoscience and scientific land observation; (4) global environment, including representative missions in meteorology, climatology, ocean science, and atmospheric science; (5) materials science, including missions for measuring material properties, studying chemical reactions and utilizing the high vacuum-pumping capacity of space; and (6) life sciences with experiments in biomedicine and animal and plant biology