摘要:

AbstractFive subjects performed submaximal and maximal bicycle and maximal treadmill exercise in normalcy and after carbon monoxide inhalation, giving different levels of carboxyhemoglobin (COHb) in the blood. During maximal treadmill exercise work time on a fixed work load and maximal oxygen uptake were decreased with increasing level of COHb (r = 0.79 and r = 0.85, respectively). Peak blood lactate concentration and pulmonary ventilation were unchanged. Highest measured heart rate was lower in parallell with the increased COHb level compared to control studies. During submaximal work heart rate was increased and oxygen uptake was unchanged at the various levels of COHb. At low submaximal work loads blood lactate concentrations and oxygen deficit was unchanged but increased as work load and COHb‐level increase

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05350.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractEffects of adrenaline on amino acid transport in the isolated perfused rat heart was investigated using the non‐utilizable amino acidsα‐aminoisobutyric acid (AIB) and 1‐aminocyclopentanecarboxylic acid (cycloleucine). Adrenaline, addedin vitro, caused a dose dependent increase in the uptake of AIB and cycloleucine, and a significant stimulation was seen after 15 min of perfusion. The minimal effective concentration was 5 × 10‐8M, and an effect was obtained when hearts were perfused with glucose or palmitate as substrate and when no exogenous substrate was added. Adrenaline increased the uptake in hearts arrested with high [K+] or tetrodotoxin, and the accelerated uptake was not dependent upon the chronotropic effect of adrenaline. Under conditions when adrenaline increased amino acid uptake, protein synthesis was either unaffected or decreased. The data of the present study show that adrenaline directly stimulates amino acid transport in the heart and it is concluded that increased uptake of amino acids could be an energy‐generating system for the heart during adrenergic

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05351.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe presence of an electrogenic Na, K‐pump has been demonstrated in identified neurons of the snail,Helix pomatiaby the observation of ouabain sensitive hyperpolarizations following increases of intracellular sodium concentration. A contribution of the pump to the resting membrane potential (RMP) has been measured at varying extracellular potassium concentration as the depolarizing effect of ouabain upon RMP. The contribution was found to have a value of – 7 mV at 4 mM external potassium and to decline with increasing and decreasing K‐concentrations. The electrogenic flux has been calculated by two independent methods from measurements of membrane resistance and the electrogenic contribution to the RMP. Agreement was found when the flux was computed both from modified constant field equations and from Ohm's law. The flux increased from zero at 0 mM external potassium concentration to –10 peq cm–2s–1at 6 mM and stayed at this level with rising concentrations of K. It is concluded that the decrease of the electrogenic contribution to RMP observed at low K‐concentrations is caused by inhibition of the electrogenic flux whereas the decline of the contribution seen at higher K‐concentrations is due to a diminution of the membrane resistance (increment of potassium permeability) rather than to a fall of the el

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05352.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractArterial hypotension was induced by bleeding lightly anesthetized rats to mean arterial blood pressures of 60 and 45 mm Hg, respectively, with subsequent measurements of arterial and cerebral venous gas tensions, of extra‐ and intracellular acid‐base parameters, as well as of parameters necessary for an evaluation of the energy state of the brain tissue. In none of the groups were there significant changes in extra‐ or intracellular pH, indicating that a non‐chemical mechanism was responsible for the autoregulation of flow. Most of the animals in the 60 mm Hg group, and about half of those with a blood pressure of 45 mm Hg, showed a normal metabolic pattern in the brain. In the remaining animals, there were moderate in‐creases in lactate and, simultaneously, slight decreases in the charge potential of the adenine nucleotides of the tissue due to moderate increases in ADP and AMP. Such changes occurred at a venous Po, of about 25 mm Hg. Since other results indicate that the cerebral energy state fails at higher mean arterial blood pressures, and at higher Pvo, values, provided that the tissue is acidotic, it is concluded that the efficient energy homeostasis observed in the present experiments may have been due to the fact that no tissue acidosis

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05353.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe effect of bilateral carotid artery ligation upon acid‐base parameters and substrate levels in the brain were studied in lightly anesthetized rats, either at normal blood pressure or after a reduction in blood pressure to 100 and 70 mm Hg, respectively. As evaluated arteriovenous differences the tissue CO2tension was consistently higher than the Pco2in cisternal CSF. At low blood pressures most animals showed a marked to excessive elevation of the tissue lactate content but since the CSF lactate content was only moderately increased it is concluded that a larger reduction in blood flow occurred in the supratentorial than in the infratentorial parts of the brain. At low perfusion pressures the tissue contents of glucose, α‐ketoglutarate and glutamate were considerably reduced. The results suggest that the experimental model used gave rise to an inhomogenous decrease in flow in the tissue, and a correlation between the increase in the lactate and the decrease in the bicarbonate contents suggests that a mixture of perfused and non‐perfused tissue areas may have e

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05354.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractAn increase of the total activity of choline acetyltransferase occurs in the dog's parotid and in the submaxillary glands of the golden hamster and mouse after a surgical postganglionic sympathetic denervation. No such increase was found in the guinea‐pig's submaxillary gland; nor was it found in the rat's parotid and sublingual glands. A gradual enzyme increase was shown to begin after about 15 days in the rat's submaxillary gland. A chemical sympathectomy with 6‐hydroxydopamine had a similar effect as a surgical denervation; an enzyme increase was noticed in the rat's submaxillary but not in the sublingual gland. It is concluded that in the same species one type of gland may show the enzyme increase, while another type remains unchanged. A low enzyme concentration and a high density of adrenergic nerve fibres seem to favour the increase of the activity of choline acetyltransfer

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05355.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractMotoneurone models were developed by modifications of the Frankenhaeuser‐Huxley equations (1964) for voltage clamp data amphibian nerve fibre. The major modifications were: (i) that the subthreshold sodium inactivation was decreased, and (ii) that the Frankenhaeuser‐Huxley model was provided with a long‐lasting after‐hyperpolarization due to potassium permeability changes. Besides, model versions were developed that also had passive membrane properties (e. g. a resting membrane time constant) similar to those of spinal motoneurones. For various model versions, single spikes and the associated afterpotentials were shown in the present paper. The main aim was to use the motoneurone models for studies of repetitive impulse firing. This will be done in a subsequent paper (Kernell and Sjohol

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05356.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe effect of inhibition of prostaglandin synthesis on the release of noradrenaline induced by sympathetic nerve stimulation was studied in the isolated perfused rabbit heart. It was found that indomethacin (Indomeé®, Merck, Sharp and Dohme), a drug known to inhibit prostaglandin synthesis, decreased the outflow of prostaglandins normally induced by nerve stimulation. Simultaneously the outflow of noradrenaline in response to nerve stimulation was augmented. Since indomethacin neither caused any release of noradrenaline heart in the absence of nerve stimulation, nor affected the uptake of exogenous noradrenaline, it is concluded, that the increased noradrenaline release reflects disinhibition of a feed‐back mechanism, using endogenously formed prostaglandins for limitation of noradrenaline rele

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05357.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05358.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05359.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY