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In seven obese female subjects undergoing a period of therapeutic starvation, the excretion of sodium, potassium and dopamine and plasma levels of renin and aldosterone were measured. Sodium excretion increased during starvation and was maximal on the 2nd day. The urinary excretion of dopamine was significantly higher on day 4 and it remained elevated till the end of the study. Plasma renin activity and plasma aldosterone levels were also higher on the 4th-6th days of starvation. These findings suggest that dopamine may not play a significant role in the natriuresis of starvation. 相似文献
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A D Edwards G C Brown M Cope J S Wyatt D C McCormick S C Roth D T Delpy E O Reynolds 《Journal of applied physiology》1991,71(5):1907-1913
The oxygenation of cerebral cytochrome oxidase in vivo was investigated in eight newborn preterm infants. Near-infrared spectroscopy was used to quantify changes in the concentration of oxidized cytochrome oxidase ([CytO2]) observed during alterations in arterial oxygen saturation (SaO2) in the range of 85-99% and of carbon dioxide tension (PaCO2) in the range of 4.3-9.6 kPa. No relation was found between changes in SaO2 and [CytO2]. Alterations in PaCO2 were positively related both to changes in [CytO2] and total cerebral hemoglobin concentration [( Hb]t). The changes in [CytO2] ranged from 0.09 to 0.33 (median 0.21) mumol.l-1.kPa-1. The ratio [CytO2]/[Hb]t ranged from 0.06 to 0.12 (median 0.08). The relation of delta [CytO2] to the change in cerebral blood volume (delta CBV) was calculated: delta [CytO2]/delta CBV ranged from 0.09 to 0.18 (median 0.11) mumol/ml. These results define a fraction of cerebral cytochrome oxidase in the newborn infant that is oxidized after an increase in PaCO2 but demonstrate that a change in SaO2 in the range studied was not sufficient by itself to change [CytO2]. They differ from results of studies in adults; this may reflect significant differences between adult and neonatal brain. 相似文献
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Summary The role of tubular mastigonemes in the reversal of thrust of the anterior flagellum ofPhytophthora cinnamomi was analysed using mastigoneme-specific monoclonal antibodies and immunoflu-orescence and video microscopy. Exposure of live zoospores ofP. cinnamomi to the mastigoneme-specific Zg antibodies caused alterations in the arrangement of mastigonemes on the flagellar surface and at Zg concentrations above 0.3 /ml, mastigonemes became detached from the flagellum. As a consequence of antibody binding to the mastigonemes there were concentration-dependent perturbations in zoospore swimming behaviour and anterior flagellum beat pattern. With increasing antibody concentration zoospores swam more slowly and other parameters of their swimming pattern, such as the wavelength of the swimming helix and the frequency of rotation, were also reduced. The effects of Zg antibodies were specific at two levels: control immunoglobulins or antibodies that bound to other flagellar surface components did not have an effect on motility, and Zg antibodies did not interfere with the motility of zoospores of oomycete species to which they did not bind. The effects of antibody-induced disruption of mastigoneme arrangement strongly support previous hypotheses that tubular mastigonemes are responsible for thrust reversal by the anterior flagellum, enabling it to pull the cell through the surrounding medium. 相似文献
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Summary A detailed stereological analysis has been made of the organelle content of rabbit acinar cells during the restoration of granule stores following extensive degranulation with isoprenaline (IPR). Rabbits were sacrificed 2, 4, 8, 12 and 16 h after IPR administration and the volumes and proportions of intracellular organelles were compared with those of untreated glands.At 2 h only 5% of cell volume was occupied by secretion granules, but there was already evidence of nascent granule formation. The volume per cell of secretion granules increased in sigmoid fashion and by 16 h amounted to 350 m3/cell, 36% of cell volume, which are values similar to those of the control replete glands. IPR treatment caused some initial swelling of the cells, and there were transient increases in the volumes of several compartments. However, the volume of mitochondrial and lysosomal compartments had returned to control levels by 4 h and that of the nucleus by 8 h. The greatest increase was in the volume of the rough endoplasmic reticulum which had increased by nearly 70% by 2 h and remained enlarged throughout the period of restitution. However, neither the volume nor the proportion of the smooth membraned compartment varied throughout the period of analysis.The results are analysed in the light of the overall response of the cells to IPR and the interaction of the organelles during the synthetic phase of the secretory cycle. They are presented as a basis for ensuing studies of the granule populations and the membrane composition of the cells during the restoration of granule stores. 相似文献