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Proton flux measurements from tissues in buffered solution   总被引:4,自引:1,他引:4  
Proton movement across plant cell membranes is part of many important physiological processes. The net proton flux to or from tissues can be determined non-invasively by measuring the proton electrochemical potential gradient in the adjacent solution. In buffered solution, some of the protons crossing the tissue boundary diffuse as proto-nated buffer whose flux is not included in the flux calculated from the proton (hydrogen ion) electrochemical gradient. In this theoretical paper, it is shown how experimenters can calculate the protonated buffer flux from the measured proton flux in solution. The ratio of these two components of total proton flux depends on the pH of the solution and on the concentration and pK of the buffer. For a given concentration of a buffer which has a single pK, the flux ratio rises with pH when the solution pH is lower than the buffer pK. The slope is about 2 on a log10 scale. As the pH increases above the pK, the flux ratio levels off to approach its maximum. With mixed buffers, or one having two or more pK values, the flux ratios are additive: each buffer acts independently based on its concentration and its pK value. Unbuffered solutions always have the buffering effects of water itself and also of carbonates due to carbon dioxide dissolved from the atmosphere. In unbuffered solutions at pH 6, the flux carried by water and carbonate is about 1 % of the measured proton flux. This validates measurements of proton flux from tissues, made by a number of workers, in unbuffered solutions below pH 6.  相似文献   

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Ten experiments were done in oligotrophic North Pacific waters to examine the effects of small-volume, short-period containment (6–24 h) on plankton and their implications for productivity measurements. Effects of pre-filtering samples were also considered. Chlorophyll α and adenosine triphosphate were measured, but the major emphasis was on changes in the taxonomic composition and abundance of the microplankton.Chlorophyll α measurements indicate the variability of replicate samples increased significantly during incubation; the coefficient of variation of duplicate productivity measurements ranged between 3 % and 40 %. A large fraction of this may be due to increasing heterogeneity of the phytoplankton during incubation.Pre-filtering samples through 202, 102, 35 and 15μm mesh filters removed a small but consistent fraction of phytoplankton (as estimated by chlorophyll α) but a highly variable amount of total biomass (as estimated by ATP). The effect of pre-filtration on primary production was very inconsistent between experiments, varying both in magnitude and direction.The composition of the contained microplankton changed markedly during incubation. Nearly all components decreased in abundance regardless of pre-filtration treatment and some ciliate groups completely disappeared.  相似文献   

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Regression models play a significant role for appropriate interpretations of complex phenomena of biomedical sciences. In the present paper an attempt has been made to critically review the applications of regression models in physiological research pertaining to the solutions of various defence oriented problems of indirect estimation of human endurances, fitness, physical work capacity, energy expenditure at different work rates, body density and lean body mass from body measurements at high altitude, ventilatory 'norms' for wider age groups from physical characteristics, heat output and index finger temperature from ambient temperature, leg muscle volume and fat free mass from X-ray radiographs and stature, total body volume from anthropometric measurements, thermoregulatory efficiency at different environmental situations etc. These regression models are of practical significance for screening personnel in defence services, mines, industrial work, sports and the like.  相似文献   

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By J.C. Kolar and E.M. Salter. Springfield, IL: Charles C. Thomas. 1996. xxiii + 334 pp. ISBN 0-398-06616-7. $69.95 (cloth).  相似文献   

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Heat of reaction measurements for hydrothermal carbonization of biomass   总被引:2,自引:0,他引:2  
This paper presents a set of calorimetric measurements with the aim of better understanding the calorific nature of hydrothermal carbonization. Presented values so far show an inadequately high scatter to do so, preventing a well funded assessment of the energetic feasibility of this process.The heat released during hydrothermal carbonization at 240 °C measured with the applied differential calorimetry setup is −1.06 MJ/kgglucose,daf with a standard deviation of 14%, −1.07 MJ/kgcellulose,daf with a standard deviation of 9%, and −0.76 MJ/kgwood,daf with a standard deviation of 32%. These results are in good agreement with the theoretically derived maximum heat release. Despite the comparably high experimental standard deviation of these results, their accuracy is considerably higher than previously published results.  相似文献   

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Normal physiological values for conscious pigs used in biomedical research   总被引:8,自引:0,他引:8  
Although the domestic pig is rapidly becoming an animal of choice in certain areas of biomedical research requiring a large animal model, effective utilization of the species is often encumbered by a lack of reference values for common functional variables. To address this problem, normal data for over 100 physiologic or related variables were collected from conscious chronically instrumented animals that were maintained under near basal conditions. Included were measurements of body composition, fluid volumes, blood physical and biochemical characteristics, blood gas and acid-base status, plasma hormone levels, energy metabolism, renal function, hemodynamics and pulmonary function. Most porcine values were similar to those collected under comparable conditions from humans. Compared to adult man, however, pigs had higher values for extracellular space, plasma volume, arterial pH, plasma bicarbonate, cardiac output, arterial pressure, expired ventilation, heat production, and core temperature, and lower values for red cell volume, hemoglobin level, plasma osmotic and oncotic pressure, arterial O2 content, renal blood flow and glomerular filtration rate. Many of these deviations were due to immaturity. Nevertheless, we have found pigs to be an excellent large animal model for a variety of functional studies.  相似文献   

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Proteomics is the comprehensive and systematic study of proteins, which are functional molecules. Although proteins are products of gene expression, there are more proteins than genes due to the posttranslational modifications of proteins, making the study of proteins difficult. Protein expression is tissue specific, and its function is modulated by variety of factors, including other proteins, phosphates, sulfates, carbohydrates, and lipids, as well as other metabolites. Because of the dynamic nature of protein expression and posttranslational modifications, identification and quantification of proteins alone are not sufficient to understand functional changes. Emerging technologies will allow investigators to perform a combination of metabolic labeling and identification as well as quantification and measurement of the synthesis rates of a large number of proteins in a tissue. This offers the opportunity to better understand the regulation of tissue functions. Rapid advances in mass spectrometry, protein purification techniques, isotope labeling of proteins, and bioinformatics are likely to improve our understanding of physiological states and altered functions in diseased states. Such mechanistic information will improve the ability to perform early diagnosis of tumors and other diseases and develop prognostic indexes and novel therapies.  相似文献   

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Background

Owing to recent discoveries of many hydrogen sulfide-mediated physiological processes, sulfide biology is in the focus of scientific research. However, the promiscuous chemical properties of sulfide pose complications for biological studies, which led to accumulation of controversial observations in the literature.

Scope of review

We intend to provide an overview of fundamental thermodynamic and kinetic features of sulfide redox- and coordination-chemical reactions and protonation equilibria in relation to its biological functions. In light of these chemical properties we review the strengths and limitations of the most commonly used sulfide detection methods and recently developed fluorescent probes. We also give a personal perspective on blood and tissue sulfide measurements based on proposed biomolecule–sulfide interactions and point out important chemical aspects of handling sulfide reagent solutions.

Major conclusions

The diverse chemistries of sulfide detection methods resulted in orders of magnitude differences in measured physiological sulfide levels. Investigations that were aimed to dissect the underlying molecular reasons responsible for these controversies made the important recognition that there are large sulfide reserves in biological systems. These sulfide pools are tightly regulated in a dynamic manner and they are likely to play a major role in regulation of endogenous-sulfide-mediated biological functions and avoiding toxic side effects.

General significance

Working with sulfide is challenging, because it requires considerable amounts of chemical knowledge to adequately handle reagent sulfide solutions and interpret biological observations. Therefore, we propose that a rigorous chemical approach could aid the reconciliation of the increasing number of controversies in sulfide biology. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.  相似文献   

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A new, heat shock-inducible expression system based on an endogenous hsp16+ promoter was developed for use in the fission yeast Schizosaccharomyces pombe. Analysis of GFP expression profiles indicated that a 1.2-kb segment of the hsp16+ promoter region was sufficient to drive expression of heterologous protein. The hsp16+ promoter was found to be activated not only by heat shock but also by other stresses including cadmium, ethanol, and oxidative stress. Two expression vectors, pHIL and pHIU, were constructed using the 1.2-kb hsp16+ promoter for inducible gene expression in Sch. pombe. This new expression system utilizes a simple induction protocol and promises to be a useful tool for analyzing gene expression in Sch. pombe.  相似文献   

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