摘要:

AbstractThe chemical course in a multi‐membrane system with interacting H+and HCO3ions has been described phenomenologically as an analogy of the neutralisation reaction between secreted H+ and filtered HCO3ions in the proximal tubules of the kidney. It was shown that the produced CO2gave the highest PCO2in the asymmetrically placed reaction centre, which favours a build‐up of a high intratubular PCO2. The CO2transport was dependent on the rate‐limiting permeation of the reacting ions, and the permeation could be increased by the influence of solutions of macro molecules such as carbonic anhydrase, albumin and de

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06324.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractRecordings in vivo of the carbon dioxide tension of the proximal tubular fluid and of the efferent arteriolar blood were performed with PCO2microelectrodes in the rat kidney. The buffer lines of the efferent arteriolar blood and systemic arterial blood were determined with an ultramicro equilibration system and the acid‐base status of the systemic arterial blood was measured. The intratubular PCO2was significantly higher than the PCO2of the arterial blood, and the PCO2of the efferent arteriolar blood was significantly lower than that of the arterial blood. The buffer capacity was higher and the bicarbonate concentration slightly lower for the efferent arteriolar blood than for the arterial blood. It is concluded that a PCO2difference exists across the tubular wall and that the high intratubular PCO2favours a chemical equilibrium of the carbonic acid‐bicarbonate system in the proximal tubular fluid. It is supposed that the slightly lowered bicarbonate concentration in the efferent arteriolar blood is an effect of the glomerular ultrafiltration proc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06325.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe proximal intratubular pH of the rat kidney was measured in vivo with an antimony electrode system. PCO2and bicarbonate concentration of the proximal tubular fluid were determined with an ultramicro equilibration system. The tubular fluid to plasma inulin concentration ratio was evaluated by a microscope fluorometric method. The acid‐base parameters and the inulin concentrations were determined under control conditions and during acetazolamide treatment. The intratubular PCO2., was higher than the PCO2of the systemic arterial blood under control conditions and the difference in PCO2was increased during acetazolamide treatment. In acetazolamide treated rats the rate of fractional bicarbonate reabsorption was decreased in the early part of the proximal tubule, while it was of about the same in the middle and late parts as compared with control rats. The total bicarbonate reabsorption in the proximal tubule was reduced by 50% due to the carbonic anhydrase inhibition. It seems possible that the bicarbonate is still reabsorbed as CO2after carbonic anhydrase inhibition, as hydrogen ion secretion is not totally stopped by this treatment. The increase in intratubular PCO2after acetazolamide treatment is assumed to be due to an inhibition of the carbonic anhydrase facilitating effect on outward diffusion of CO2from the tubular lumen across the cell wal

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06326.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe distribution of the labels of [35S]taurine, [3H]lysine, [14C]glutamate and [11C]norleucine in mouse brain subcellular fractions was followed after intracerebral injectionin vivo.[35S]taurine, [3H]lysine and [14C]gluta‐mate and its metabolites accumulated in the nerve terminals, lysine and glutamate also occurring in the synaptic vesicles, while taurine remained mainly in the soluble synaptoplasm. [14C]norleucine penetrated the brain cell membranes slowly, but was still bound to the synaptic vesicles to a greater extent than taurin

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06327.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe effects of 15 days of detraining and 15 days of retraining were studied in 6 well‐trained runners. Detraining resulted in significant decreases in the mean activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) of 24 % and 13 %, respectively, but no significant increases in these enzyme activities occurred with retraining. Maximal oxygen uptake (VO2max) decreased by 4% with detraining (p<0.05), and increased by a similar amount with retraining. Performance time in an intense submaximal run decreased by 25% (p<0.05) with inactivity, but still averaged 9% below the initial level after retraining. Maximal heart rate and peak heart rate during the performance run were higher after detraining by 4 and 9 beats per min, respectively (p<0.05). With retraining, these heart rate values were decreased by 7 and 9 beats per min (p<0.05). Blood lactate concentrations after the VO2max and performance run were approximately 20% lower after detraining and retraining (p<0.05). Muscle fibre areas for three subjects tended to be larger in biopsy samples taken after detraining and retraining. These data suggest that even short periods of detraining result in significant changes in indices of physiological capacity and function in subjects near their upper limit of adaptation, and that a longer period of retraining is necessary for muscle to re‐adapt to its original trained st

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06328.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract‘Initial’ clearance of radiolabeled serum albumin was measured in the perfused, maximally vasodilated muscle vascular bed of rat hindquarters during tissue cooling, during increases in filtration and during changes in serum colloid osmotic pressure. Albumin clearance during ordinary serum perfusion at iso‐gravimetry amounted to 0.03 ml/min x 100 g, increasing linearly with filtration rate to some 0.07 ml/minx 100 g at 0.5 ml/minx 100 g of filtration. During cooling from 36°C to 14°C both CFC and initial albumin clearance at isogravimetry decreased some 40%, in due proportion to the increased viscosity of the fluid. Increases of the colloid osmotic pressure of the perfusate correspondingly increased both the isogravimetric capillary pressure and ‘initial’ albumin clearance during isogravimetry. – It is concluded that even during isogravimetry the transmicrovascular albumin passage is to about 70 per cent due to filtration, and only some 30 per cent of transport at ordinary serum colloid osmotic pressures takes place by diffusion, both events presumably via ‘large pores’. There was no evidence that transendothelial vesicular transport should to any significant extent contribute to the passage of albumin from

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06329.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractRats were kept either on a standard laboratory diet or a high cholesterol, olive oil diet for periods ranging from 1 day to 22 weeks. The effect of the high cholesterol, olive oil diet on the concentrations of cholesterol, glycosaminoglycans (GAGs) and collagen in aortic intima‐media, were studied and the developing hyper‐lipidemia was characterized. The concentration of cholesterol in rat aorta was increased after 22 weeks' high cholesterol, olive oil diet, while collagen concentration was not affected. On the contrary, the concentration of aortic sulphated GAGs was significantly increased already after one week's high cholesterol, olive oil diet. The diet increased the formation of a cholesterol‐rich very low density lipoprotein (VLDL), decreased high density lipoprotein (HDL)‐associated cholesterol and phospholipids, but had virtually no effect on low density lipoprotein (LDL)‐lipids. The concentrations of VLDL‐cholesterol and ‐phospholipids showed positive correlations with the concentration of aortic GAGs (r = 0.89 and 0.83, respectively, P<0.05 for both). Stronger (negative) correlations were found between aortic GAGs and HDL‐cholesterol and ‐phospholipids (r = ‐0.94 for both, P<0.01) suggesting that HDL may have a role in the control of arterial sulphate

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06330.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractProgressive changes in the S‐T interval of the fetal electrocardiogram (FECG) were studied in 14 lamb fetuses, acutely exteriorized and subjected to graded hypoxia. The aims of the study were to investigate whether beta‐adrenoceptor stimulation and hypoxia exerted additive or potentiating effects on the FECG and several cardiovascular parameters and whether the hypoxic changes of the FECG could be blocked by beta‐adrenoceptor blocking agents. The FECG changes were studied in order to correlate them with cardiovascular function, as measured by heart rate, mean arterial pressure, end diastolic pressure, maximum dP/dt and combined cardiac output, estimated by the thermodilution method, as well as with blood gases, acid base status, blood lactate and glucose. Injections of small doses (0.02 to 0.4 μgkg‐1min‐1) of isoprenaline induced the same pattern of changes in the FECG as we have previously recorded during hypoxia. By increasing the isoprenaline dose an increase in the duration of the FECG changes and amplitude of the T‐wave changes was obtained. Propranolol was found to completely abolish the FECG changes induced by isoprenaline, as well as by mild hypoxia. During severe hypoxia the FECG changes could not be abolished by propranolol. Our previous findings indicated that the hypoxic changes could be regarded as a sign of myocardial glycolysis. Thus, the present finding that even small doses of isoprenaline given to the fetus, initiates the same pattern of FECG changes corroborate thi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06331.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractTo investigate the effects of sustained positive‐pressure breathing (PPB) on the adaptation of respiratory and circulatory functions to exercise, 8 healthy volunteers were exposed to PPB of air at 15 and 30 cm H2O in the supine position at rest and while performing leg exercise at 50% of individual maximal working capacity. PPB was both subjectively and objectively better tolerated when combined with exercise than it was at rest. PPB at 30 cm HaO resulted in marked hyperventilation with alkalosis in the resting condition, but did not significantly affect respiratory minute volume, blood gases or acid‐base balance during exercise. Cardiac output and left ventricular work were reduced by about one fifth and one third, respectively, both at rest and during exercise. In contrast to the case at normal airway pressure, exercise‐induced increase in cardiac output was accompanied by an increment in stroke volume during PPB. Although mean arterial pressure (relative to atmospheric) was elevated by PPB at rest and during exercise, the driving pressure in systemic circuits (arterial minus central venous pressure) was reduced in both conditions. It is concluded that dynamic exercise counteracts deleterious effects of PPB by normalizing respiratory function and by improving cardiac filling by activation of the leg muscle and the abdominal

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06332.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe effects of growth hormone (G H)in vitroon phenylalanine‐14C incorporation to assess protein synthesis and on a‐aminoisobutyric‐l‐3H accumulation to measure amino acid transport in the diaphragm muscle of the rat were investigated 2, 6 and 24 h after hypophysectomy or sham‐operation. In hypophysectomized animals protein synthesis was depressed. GHin vitrowas without effect 2 h after hypophysectomy but stimulated protein synthesis 6 and 24 h after the operation. Six hours after hypophysectomy amino acid transport was enhanced and further stimulated by GH. After 24 h amino acid transport was depressed but was stimulated to normal levels by GH. Six hours after sham‐operation protein synthesis was depressed, but was stimulated by GH. After 24 h protein synthesis was normalized and GH was without effect. GH did not influence amino acid transport after sham‐operation. Plasma levels of GH were undetectable after hypophysectomy, markedly depressed 2 and 6 h after sham‐operation, but normal after 24 h. It is concluded that tissue responsiveness to GH develops a few hours after

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06333.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY