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11.
E. É. Kolesnikova 《Neurophysiology》2008,40(1):48-52
Results of a comparative study of the sensitivity of the system of respiratory control to increases in the CO2 concentration and the intensity of free-radical processes in young and elderly subjects are described. It is shown that normal
(natural) aging is accompanied by a decrease in the sensitivity of the respiratory system to hypercapnic stimulation and a
parallel significant decrease in the activity of catalase in the blood of examined subjects. Mechanisms responsible for the
modifications of the sensitivity of the system of respiratory control to hypercapnia are discussed; these shifts can be at
least partly related to changes in the intensity of production of free radicals observed in elderly subjects.
Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 53–57, January–February, 2008. 相似文献
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K.G. Raghu Richa Singh A. Prathapan Govind Kumar Yadav 《Chemico-biological interactions》2009,180(3):454-459
Haloperidol (HPL), well known antipsychotic drug can induce a marked QT prolongation and polymorphic arrhythmias. In this study we evaluated the influence of various induced risk factors such as electrolyte imbalance (hypokalemia and hypomagnesemia), gender difference, low pacing frequency, ischemia reperfusion insult on electrophysiological effect by haloperidol on electrically driven action potentials recorded from guinea pig papillary muscle. The doses of HPL ranging from 1 to 16 μM were used in this investigation. Action potentials (APs) were elicited electrically and recorded by classical microelectrode technique. HPL caused dose dependent prolongation of APD90 the final stage of repolarization, increased triangulation, and led into dispersion of action potential, conduction delay and conduction block. Magnitude of the effect of haloperidol was amplified significantly by most of the risk factors. Among the various risk factors, electrolyte imbalance (hypokalemia, hypomagnesemia) caused more amplification of HPL effect. Most of the risk factors amplified prolongation of APD90 by HPL. This effect is mainly due to the influence of these electrolytes and sex hormone on various ion channels involved in the repolarization phase of cardiac AP. This is the first report which provides an experimental evidence of amplification of electrophysiological effects of HPL in the presence of various risk factors. 相似文献
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Respiration, which is the second most important carbon flux in ecosystems following gross primary productivity, is typically represented in biogeochemical models by simple temperature dependence equations. These equations were established in the 19th century and have been modified very little since then. Recent applications of these equations to data on soil respiration have produced highly variable apparent temperature sensitivities. This paper searches for reasons for this variability, ranging from biochemical reactions to ecosystem‐scale substrate supply. For a simple membrane‐bound enzymatic system that follows Michaelis–Menten kinetics, the temperature sensitivities of maximum enzyme activity (Vmax) and the half‐saturation constant that reflects the affinity of the enzyme for the substrate (Km) can cancel each other to produce no net temperature dependence of the enzyme. Alternatively, when diffusion of substrates covaries with temperature, then the combined temperature sensitivity can be higher than that of each individual process. We also present examples to show that soluble carbon substrate supply is likely to be important at scales ranging from transport across membranes, diffusion through soil water films, allocation to aboveground and belowground plant tissues, phenological patterns of carbon allocation and growth, and intersite differences in productivity. Robust models of soil respiration will require that the direct effects of substrate supply, temperature, and desiccation stress be separated from the indirect effects of temperature and soil water content on substrate diffusion and availability. We speculate that apparent Q10 values of respiration that are significantly above about 2.5 probably indicate that some unidentified process of substrate supply is confounded with observed temperature variation. 相似文献
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The turnover of organic carbon in rivers could represent a large source of greenhouse gases to the atmosphere and studies have suggested that of the order of 70% of the dissolved organic carbon exported from soils could be lost in rivers before it flows to continental seas. The Environmental Change Network (ECN) monitoring of the dominantly peat-covered Trout Beck catchment within the Moor House site enabled the amount of dissolved organic carbon (DOC) lost within a stream over a 20-year period to be estimated. The study compared DOC concentrations of precipitation, shallow and deep soil waters with those at the catchment outlet. The mass balance between source and outlet was reconstructed by two methods: a single conservative tracer; and based upon a principal component analysis (PCA) using multiple tracers. The study showed the two methods had different outcomes, with the PCA showing a DOC gain and the single tracer showing a DOC loss. The DOC gain was attributed to an unmeasured groundwater contribution that dominates when the river discharge is lower. The DOC loss was related to the in-stream residence time, the soil temperature and month of the year, with longer in-stream residence times, warmer soils and summer months having larger DOC losses. The single tracer study suggested a 10 year average loss of 8.77 g C m−2 year−1, which is 33.1 g CO2eq m−2 year−1, or 29% of the DOC flux from the source over a mean in-stream residence time of 4.33 h. 相似文献
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Symbiotic fungi and clonal plant physiology 总被引:2,自引:1,他引:1
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L. Ferreira 《Journal of cellular biochemistry》2009,108(4):746-752
The use of nanoparticles in stem cell research is relatively recent, although very significant in the last 5 years with the publication of about 400 papers. The recent advances in the preparation of some nanomaterials, growing awareness of material science and tissue engineering researchers regarding the potential of stem cells for regenerative medicine, and advances in stem cell biology have contributed towards the boost of this research field in the last few years. Most of the research has been focused in the development of new nanoparticles for stem cell imaging; however, these nanoparticles have several potential applications such as intracellular drug carriers to control stem cell differentiation and biosensors to monitor in real time the intracellular levels of relevant biomolecules/enzymes. This review examines recent advances in the use of nanoparticles for stem cell tracking, differentiation and biosensing. We further discuss their utility and the potential concerns regarding their cytotoxicity. J. Cell. Biochem. 108: 746–752, 2009. © 2009 Wiley‐Liss, Inc. 相似文献