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The anaerobic photodissimilation of acetate by Chlamydomonas reinhardii F-60 adapted to a hydrogen metabolism was studied utilizing manometric and isotopic techniques. The rate of photoanaerobic (N2) acetate uptake was approximately 20 μmoles per milligram chlorophyll per hour or one-half that of the photoaerobic (air) rate. Under N2, cells produced 1.7 moles H2 and 0.8 mole CO2 per mole of acetate consumed. Gas production and acetate uptake were inhibited by monofluoroacetic acid (MFA), 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) and by H2. Acetate uptake was inhibited about 50% by 5% H2 (95% N2). H2 in the presence of MFA or DCMU stimulated acetate uptake and the result was interpreted to indicate a transition from oxidative to reductive metabolism. Carbon-14 from both [1-14C]- and [2-14C]acetate was incorporated under N2 or H2 into CO2, lipids, and carbohydrates. The methyl carbon of acetate accumulated principally (75-80%) in the lipid and carbohydrate fractions, whereas the carboxyl carbon contributed isotope primarily to CO2 (56%) in N2. The presence of H2 caused a decrease in carbon lost from the cell as CO2 and a greater proportion of the acetate was incorporated into lipid. The results support the occurrence of anaerobic and light-dependent citric acid and glyoxylate cycles which affect the conversion of acetate to CO2 and H2 prior to its conversion to cellular material. 相似文献
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The Journal of Membrane Biology - Methods were developed for estimation of the area of the microscopic and ultramicroscopic surface of the toad bladder epithelium at various degrees of stretch.... 相似文献
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Duane J Funk M Ruth Graham Linda G Girling James A Thliveris Bruce M McManus Elizabeth KY Walker Edward S Rector Craig Hillier J Elliott Scott W Alan C Mutch 《Respiratory research》2004,5(1):22
BackgroundBiologically variable ventilation (return of physiological variability in rate and tidal volume using a computer-controller) was compared to control mode ventilation with and without a recruitment manoeuvre – 40 cm H2O for 40 sec performed hourly; in a porcine oleic acid acute lung injury model.MethodsWe compared gas exchange, respiratory mechanics, and measured bronchoalveolar fluid for inflammatory cytokines, cell counts and surfactant function. Lung injury was scored by light microscopy. Pigs received mechanical ventilation (FIO2 = 0.3; PEEP 5 cm H2O) in control mode until PaO2 decreased to 60 mm Hg with oleic acid infusion (PaO2/FIO2 <200 mm Hg). Additional PEEP to 10 cm H2O was added after injury. Animals were randomized to one of the 3 modes of ventilation and followed for 5 hr after injury.ResultsPaO2 and respiratory system compliance was significantly greater with biologically variable ventilation compared to the other 2 groups. Mean and mean peak airway pressures were also lower. There were no differences in cell counts in bronchoalveolar fluid by flow cytometry, or interleukin-8 and -10 levels between groups. Lung injury scoring revealed no difference between groups in the regions examined. No differences in surfactant function were seen between groups by capillary surfactometry.ConclusionsIn this porcine model of acute lung injury, various indices to measure injury or inflammation did not differ between the 3 approaches to ventilation. However, when using a low tidal volume strategy with moderate levels of PEEP, sustained improvements in arterial oxygen tension and respiratory system compliance were only seen with BVV when compared to CMV or CMV with a recruitment manoeuvre. 相似文献