摘要:

AbstractThe lactate and pyruvate concentrations in cisternal cerebrospinal fluid (CSF), and the lactate, pyruvate, ATP, ADP, phosphocreatine, and creatine concentrations in brain tissue were measured in cats during hyper‐ and hypocapnia. (PaCO210–100 mm Hg). Both the CSF and the tissue concentrations of lactate and pyruvate varied inversely with the arterial CO2tension. In hypercapnia the tissue lactate/pyruvate ratio increased in accordance with a theoretical curve, calculated for a pH dependent equilibrium between the lactate/pyruvate and the NADH/NAD+ systems. In hypocapnia, however, there was no corresponding decrease in the CSF and tissue lactate/pyruvate ratios but a progressive increase at arterial CO2tensions below 25–20 mm Hg. The inter‐pretation of these results, which indicate the presence of tissue hypoxia at such low CO2tensions, were complicated by the presence of unchanged tissue levels of ATP and phosphocreatine. The results also showed that in hypocapnia, pyruvate, but not lactate, was distributed between the extra‐ and intracellular spaces according to the pH gradient, while in hypercapnia, lactate, but not pyruvate, had this distribution. The similarity of the changes in CSF and tissue lactate and pyruvate concentrations lend further support to the assumption that the CSF lactate/pyruvate system reflects cellular red

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04379.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe effects of increased cerebrospinal fluid (CSF) pressure on cerebral blood flow and on cerebral venous pO2, pCO2, pH, lactate, and pyruvate were studied in dogs by infusing an artificial CSF into the cisterna magna. With moderate and rapid increases in the CSF pressure, which did not lower cerebral perfusion pressure below 60–70 mm Hg, the cerebral blood flow was not measurably lowered, although there were sometimes detectable metabolic changes in cerebral venous blood suggestive of a transient reduction of the cerebral blood flow. That is, cerebral venous pO2and pH decreased slightly, and there were increases in the cerebral venous pCO2, in the lactate and pyruvate concentrations, and in the lactate/ pyruvate ratios, indicating an anaerobic glucolysis. When the pressure was released there was usually no reactive hyperemia, and no persisting metabolic changes in the cerebral venous blood. When the CSF pressure was markedly increased, and the cerebral perfusion pressure accordingly reduced to 30–50 mm Hg there were marked metabolic changes in cerebral venous blood, the pO2often approaching 10 mm Hg. In this case, a sudden reduction of the CSF pressure was almost invariably followed by a significant reactive hyperemia, which was paralleled by an arterialization of cerebral venous blood with a high pO2and a low pCO2. The changes in pO2usually expressed the changes in flow. During and after the reactive hyperemia there were no lactate/pyruvate changes to indicate the preceding period of anaerobic glucoly

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04380.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA method has been worked out by which one of the closed control circuits in the blood‐pressure‐regulating system in the dog can be reversibly interrupted for varying periods of time. Careful studies of the chemistry of the carotid‐sinus blood, using this method, as well as of other conditions described in the literature, make it probable that the chemoreceptor mechanism in the carotid‐sinus region and the C.N.S. remain unaffected in this connection. The method provides the pre‐requisite conditions for on‐line simulation of the regulatory properties of the carotid‐sinus reflex, as regards the barorece

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04381.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA method has been worked out by which one of the closed control circuits in the blood‐pressure‐regulating system of the dog can be reversibly opened and closed again with the aid of an on‐line analog computer. This makes it possible to study the regulatory properties of the carotid‐sinus reflex, as regards the baroreceptor function, in the regulation of the systemic blood pressure. Proportional characteristics in the analog produce marked instability in the blood‐pressure regulation, while with increasing proportional‐plus‐derivative characteristics the stability is increased. The electronic analog can be given characteristics that produce the same step‐function response in the systemic pressure as the bi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04382.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractTetrodotoxin in concentrations of 0.8–1.0 × 10‐7g/ml completely blocked conducted activity of the afferent nerve of isolated frog muscle spindle without affecting the receptor potential. Development of block was characterized by an increase in threshold of the nerve, a gradual delay of the onset of the impulse response and a reduction and decomposition of the individual action potentials into smaller spikes. The spike decomposition appeared to be due to a de‐synchronization of the conducted activity in the branched afferent terminals. After block by tetrodotoxin for up to 20 min the normal response could be restored by washing the preparation with Ringer's solution. The blocking action of tetrodotoxin was delayed and reduced by increasing calcium; removal of calcium had the opposite effect. Tetrodotoxin (1000 ng/ml) had no significant effect on the receptor potential. With low sodium plus tetrodotoxin the receptor potential was reduced by about 50 %; this reduction was reversed by addition of normal sodium. It is suggested that the sodium carrying system of the generator potential differs from that underlying the regenerative ac

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04383.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractIt has been shown in a previous work that sodium influx is trebled, whereas potassium efflux is slightly reduced, when erythrocytes are suspended in a 142 mM bicarbonate medium containing ouabain. The present work deals with the active transport of sodium and potassium occurring in the presence of 142 mM bicarbonate (38° C, pH 7.40). Sodium influx and potassium efflux were unaffected by the removal of ouabain, whereas sodium efflux, potassium influx, and glucose metabolism were all strongly stimulated. The relation between ouabain sensitive ion transport and the calculated extra formation of ATP was 3.1 moles Na/mole ATP and 2.3 moles K/mole ATP, in agreement with values previously found on red cells transporting Na and K in plasma. Red cells incubated in the bicarbonate medium accumulated potassium until extracellular potassium concentration had been reduced to 1.8–2 mM. The normal volume regulation of the cells was severely interfered with, because accumulation of sodium and potassium was accompanied by a net flux of water of 6 g per meq cation. All effects observed could be interpreted to be secondary to the increased sodium influx, leading to an increase of intracellular sodium concentration, which in turn stimulated active cation transport, thereby accelerating the rate of ATP turn‐over. The properties of the ouabain sensitive transport mechanism were not affected by the presence of bicarbonate.Both potassium efflux and sodium influx are increased by 200–300 per cent in the presence of 120 mM thiocyanate. It was found, however, that active cation transport is not stimulated in a 120 mM thiocyanate medium. On the contrary the ouabain sensitive ion transport was steadily decreasing during incubation in spite of conditions otherwise favouring transport of Na and K,i.e.increasing extracellular potassium and intracellular sodium concentr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04384.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe construction of a sound‐attenuating, electrically shielded chamber for experiments in sensory physiology is reported in short. The values of sound attenuation are given. Electrical shielding and connection to the laboratory computer are explaine

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04385.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractAddition of propranolol to a suspension of human red cells was found to cause outflow of K+ ions and, to a lesser degree, inflow of Na+ ions, until a new stationary state was reached in which their cell/medium concentration ratios did not deviate much from unity. The cell volume decreased. Lactic acid production increased slightly. Against the outflow of bulk K+ ions, tracer K+ and Rb+ ions accumulated very rapidly in the cells and then began to flow out. The ratio of inward to outward rate constant of K+ tracer immediately decreased, while that of Na+ tracer increased, transiently exceeding the medium/cell concentration ratio of Br‐ tracer, in which no abrupt change occurred. In the propranolol‐induced stationary state the cationic tracer rate constants were higher than in the untreated cell, but not so high as just after addition of propranolol. Their order was K.+>Rb+>Cs+>Li+>Na+. It is suggested that an accelerated “carrier”‐mediated exchange diffusion of cations across the cell membrane, driven by the flow of bulk ions down their gradients, would explain the rapid tracer ion

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04386.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe cerebral perfusion pressure was reduced in dogs by infusing an artificial cerebrospinal fluid (CSF) into the cisterna magna, or by reducing the mean arterial pressure by means of arterial bleeding, and the effects of the reduced perfusion pressure on the CSF concentrations of lactate, pyruvate and bicarbonate were studied. Even relatively small reductions (25–40 mm Hg) of the cerebral perfusion pressure were found to be accompanied by an increased CSF lactate concentration and an increased lactate / pyruvate ratio, and by a decreased bicarbonate concentration, suggesting the appearance of a slight hypoxic lactacidosis in spite of a normal, or near‐normal flow in the autoregulation range. When the cerebral perfusion pressure was markedly, or repeatedly, reduced a longlasting and often very marked lactacidosis was seen in the CSF. With a moderate lactacidosis in the CSF there was a good agreement between the increase in the lactate, and the decrease in the bicarbonate concentration, but with a marked and longlasting lactacidosis the decrease in the bicarbonate concentration could exceed the lactate accumulated. The possible coupling between the lactacidosis and the decrease in the cerebrovascular resistance is discus

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04387.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractWhen arterial PO2is increased to supra‐atmospheric tensions approximating 500 mm Hg in the dog, the PO2of the renal cortex rises from under 50 mm Hg to the range of 130 mm Hg, in contrast with that of the outer medulla which may even fall; there is little absolute change in the already extremely low PO2of the inner medulla. These observations are interpreted to support the idea of a homeostatic mechanism operating to regulate medullary blood flow as already suggested by observations of urine PO2at various arterial O2tensions. This mechanism helps to maintain the hypoxic state of the medulla appropriate to its relatively anaeroboic metabolis

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1969.tb04388.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY