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1.
In Vitro Retina as an Experimental Model of the Central Nervous System   总被引:8,自引:3,他引:8  
Abstract Methods are described for isolating adult rabbit retina and maintaining it in a medium designed to resemble CSF. Morphologic, metabolic, and electrophysiologic measurements obtained on the in vitro retinas showed that they remained in a nearly physiological state for at least 8 h, and even after 2 days in vitro they still exhibited a high level of metabolic activity and electrical responsiveness to light. Physiological activity was modified by photic stimulation, and data are presented to document changes in metabolism in response to the changes in function. The isolated retina appears to offer a number of unusual advantages for studying relationships between function and metabolism in organized mammalian central nervous tissue  相似文献   

2.
Erdem Akbal  Levent Filik 《Gerodontology》2012,29(2):e1261-e1262
doi: 10.1111/j.1741‐2358.2010.00408.x
Unnoticed ingestion of dislodged fixed prosthesis in an elderly patient  相似文献   

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To facilitate analysis and understanding of biological systems, large-scale data are often integrated into models using a variety of mathematical and computational approaches. Such models describe the dynamics of the biological system and can be used to study the changes in the state of the system over time. For many model classes, such as discrete or continuous dynamical systems, there exist appropriate frameworks and tools for analyzing system dynamics. However, the heterogeneous information that encodes and bridges molecular and cellular dynamics, inherent to fine-grained molecular simulation models, presents significant challenges to the study of system dynamics. In this paper, we present an algorithmic information theory based approach for the analysis and interpretation of the dynamics of such executable models of biological systems. We apply a normalized compression distance (NCD) analysis to the state representations of a model that simulates the immune decision making and immune cell behavior. We show that this analysis successfully captures the essential information in the dynamics of the system, which results from a variety of events including proliferation, differentiation, or perturbations such as gene knock-outs. We demonstrate that this approach can be used for the analysis of executable models, regardless of the modeling framework, and for making experimentally quantifiable predictions.  相似文献   

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Tupaias, or tree shrews, are small mammals that are similar in appearance to squirrels. The morphological and behavioral characteristics of the group have been extensively characterized, and despite previously being classified as primates, recent studies have placed the group in its own family, the Tupaiidae. Genomic analysis has revealed that the genus Tupaia is closer to humans than it is to rodents. In addition, tupaias are susceptible to hepatitis B virus and hepatitis C virus. The only other experimental animal that has been demonstrated to be sensitive to both of these viruses is the chimpanzee, but restrictions on animal testing have meant that experiments using chimpanzees have become almost impossible. Consequently, the development of the tupaia for use as an animal infection model could become a powerful tool for hepatitis virus research and in preclinical studies on drug development.  相似文献   

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By reason nonlinear relations founded between selection differential and realised selection response we have been made investigations about variants of the genetic-statistical model, which include this nonlinearity. The variations of the model would not only referred to the postulate pattern of the connection between phenotype, genotype and environment but also enclosed the postulate assumption about the distribution of the variates. In an investigated special case the linear model equation P = G ± e was held, however the distributions of P and G were defined over a limited range in one direction. For P we have defined a modified normal distribution and the distribution of the random vector (G, e) non normal regarded with cov (G, e) ≠ 0, By means of a solution set of an integral equation a density function of the random vector (P, G) has been received, in which the expectation of the selection response of the usual genetic-statistical model approximate is included as a special case. The genetical parameters has been derived, which result from changed model. However their representation was only possible partially as an integral function. A subsequent paper informs of the examination this mode! variants, which depend on a parameter of the nonlinearity c.  相似文献   

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A growing bulk of recent data from different fields as molecular biology, developmental biology, genetics, paleontology and phylogenetics shows that organisms play a more active role in their evolution than what postulated by the random variation-natural selection paradigm of the neo-Darwinian synthesis. Organisms show during development and morphogenesis autopoietic processes which are related to their body-plan potentialities. These potentialities are expressed through regulatory networks in which a plastic genome participates together with proteins and other substances in an epigenetic space. The epigenetic systems which arise from this interaction may be inherited and then assume a significant role in evolution becoming the source of new acquired characters. The acquisition of new traits through the epigenetic systems is influenced directly by environmental cues. If this process is coherent with the environmental demands it co-operates with natural selection in organism adaptation. An outstanding role in this context may be played by phenotypic plasticity if, as emerges in recent views, it may constitute a general basis for genetic assimilation processes.  相似文献   

9.
Kamenev  G. K.  Sarancha  D. A.  Polyanovsky  V. O. 《Biophysics》2020,65(6):1007-1016
Biophysics - An autonomous model of a phenomenological type was designed for a biological population of lemmings in complex studies of tundra communities. The population dynamics is described in...  相似文献   

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While insulin induced hypoglycemia is the principle method of producing hypothalamic-pituitary-adrenal stress response, the mechanism by which this occurs may be different from that produced by other stressors. In a pilot study, we explored ways to standardize lower body negative pressure (LBNP), as a simulator of hemorrhage, to determine its utility for future studies of hypothalamic-pituitary-adrenal (HPA) axis function. Reduced atmospheric pressure of -40 mmHg applied at the level of the iliac crests during LBNP rapidly lowers blood pressure in most subjects, simulating acute hemorrhage. In 6 normal subjects, ACTH and cortisol values were measured before, during and after the application LBNP at 0800, 1600 and 2300 hours in the baseline state and at 1600 hours on the day following 1 mg of dexamethasone. Peak ACTH values of 60-250 pg/ml occurred 2 to 10 minutes after the cessation of the stimulus in subjects experiencing presyncope or having a systolic or diastolic blood pressure decrease of greater than 20 mmHg with a rise in pulse of 30 beats per minute or more. There was no significant difference between ACTH responses at different times of day. Peak cortisol values of 25-30 micrograms/dl occurred 15-20 minutes after cessation of the stimulus. In all subjects, administration of dexamethasone greatly attenuated the ACTH response and decreased but did not ablate the cortisol response. In conclusion, these data indicate that LBNP may be used to simulate hemorrhage as a stimulus of the HPA axis. HPA axis changes occur only when physiologic evidence of hypovolemic stress is present. Dexamethasone may be used to modulate the response to this stress paradigm.  相似文献   

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To preserve organic materials in the sludge required for denitrification, a study was made with a contact process. The contactor, when operated with a short retention time (30 min), gave incomplete metabolism of organic matter. With 64% of the influent soluble COD (SCOD) was adsorbed to activated sludge within 30 min. The specific mass of organic matter uptaken was 55 mg SCOD/g Mixed Liquor Suspended Solids that enhanced the denitrification efficiency up to 63% in the following denitrification step.  相似文献   

14.

Background

In nature, deuterium/hydrogen ratio is ~1/6600, therefore one of ~3300 water (H2O) molecules is deuterated (HOD + D2O). In body fluids the ratio of deuterons to protons is ~1/15000 because of the lower ionization constant of heavy water. The probability of deuteronation rather than protonation of Asp 61 on the subunit c of F0 part of ATP synthase is also ~1/15000. The contribution of deuteronation to the pKa of Asp 61 is 0.35.

Theory and Discussion

In mitochondria, the release of a deuteron into the matrix side half-channel of F0 is likely to be slower than that of a proton. As another example, deuteronation may slow down electron transfer in the electron transport chain (ETC) by interfering with proton coupled electron transport reactions (PCET), and increase free radical production through the leakage of temporarily accumulated electrons at the downstream complexes.

Conclusion

Deuteronation, as exemplified by ATP synthase and the ETC, may interfere with the conformations and functions of many macromolecules and contribute to some pathologies like heavy water toxicity and aging.  相似文献   

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In this study the interaction of the antitumoral drug daunorubicin with egg phosphatidylcholine (EPC) liposomes, used as a cell membrane model, was quantified by determination of the partition coefficient (K p). The liposome/aqueous-phase K p of daunorubicin was determined by derivative spectrophotometry and measurement of the zeta-potential. Mathematical models were used to fit the experimental data, enabling determination of K p. In the partition of daunorubicin within the membrane both superficial electrostatic and inner hydrophobic interactions seem to be involved. The results are affected by the two types of interaction since spectrophotometry measures mainly hydrophobic interactions, while zeta-potential is affected by both interpenetration of amphiphilic charged molecules in the bilayer and superficial electrostatic interaction. Moreover, the degree of the partition of daunorubicin with the membrane changes with the drug concentration, due mainly to saturation factors. Derivative spectrophotometry and zeta-potential variation results, together with the broad range of concentrations studied, revealed the different types of interactions involved. The mathematical formalism applied also allowed quantification of the number of lipid molecules associated with one drug molecule.  相似文献   

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Experiments are described in which we used a mass spectrometer to monitor O2 uptake of enclosed soil samples as a function of temperature. We found that an Arrhenius plot of the rate of O2 uptake showed pronounced local maxima attributable to biological activity, whereas similar plots of rates obtained with abiotic soils yielded straight lines. This procedure thus provides a basis for distinguishing biological from chemical activity for reactions, such as O2 uptake, that can occur via either biological or chemical pathways.  相似文献   

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