摘要:

To examine the factors contributing to the rise in systemic blood pressure during α‐ and β‐ adrenergic stimulation, phenylephrine, an α‐adrenergic agonist, and norepinephrine, an α‐ and β‐adrenergic agonist, were infused intravenously to anesthetized dogs until mean aortic blood pressure was raised equally by 40–60 mmHg. Changes in preload were estimated by changes in left ventricular end‐diastolic pressure or segment length recorded by an ultrasonic technique. By obstructing the inferior vena cava (IVC), the increase in preload could be reduced to control level during phenylephrine and norepinephrine infusions without altering peripheral resistance (mean aortic blood pressure/cardiac output). Normalization of preload reduced the pressure response by 2/3 during phenylephrine infusion and by 1/4 during norepinephrine infusion. However, after β‐adrenergic blockade by propranolol, normalization of preload reduced the pressure response by 2/3 during both phenylephrine and norepinephrine infusions. Thus, during α‐adrenergic stimulation, the increase in preload is a more important factor than the increase in peripheral resistance. Norepinephrine raised stroke volume by 24±5%. When the increase in stroke volume was prevented by IVC obstruction, the pressure response to norepinephrine was halved. Thus, during norepinephrine infusion the rise in stroke volume caused by β‐adrenergic stimulation is as important as α‐adrenergic stimul

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07216.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The effect of electrical vagal stimulation (5 V, 2 ms, 2, 5 and 10 Hz) on gastric acid secretion and on the intragastric release of gastrin and somatostatin was studied in anesthetized rats. The gastric lumen was perfused with Dextrane T 70 (21 g/1) at 3 different rates (2.0, 0.15 and 0.035 ml/min). pH as well as gastrin and somatostatin levels were measured in the perfusate. At a perfusion rate of 2 ml/min electrical vagal stimulation (10 Hz) reduced pH of the perfusate from 3.8 to 2.6. Neither gastrin nor somatostatin levels were influenced. At a perfusion rate of 0.15 ml/min pH fell to 1.87 during vagal stimulation at 10 Hz. During this period the somatostatin levels in the perfusate increased approximately 7‐fold. No effect on gastrin release was observed. When the stomach was perfused with Dextrane at a rate of 0.035 ml/min. pH was lowered to 1.20 during vagal stimulation at 5 Hz. The somatostatin level increased approximately 14‐fold and the gastrin levels 6‐fold. In order to study the effect of low pH per se the stomach was perfused with 0.1 M HCl. Perfusion of the stomach with 0.1 M HCI (pH1.2) at a rate of 0.035 ml/min caused a small (3‐fold) increase in somatostatin levels. In conclusion, electrical vagal stimulation or low antral pH alone had minor effects on somatostatin or gastrin release. However, when intragastric pH was<2, electrical vagal stimulation increased the intraluminal release of somatostatin and to a lesser extent that of gastrin. We suggest that both somatostatin and gastrin cells are activated by vagal stimulation at low antral pH. Less gastrin was found to be released in comparison to somatostatin, which may be due to inhibition of the gastrin cells by the somatostatin simultaneously

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07217.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A procedure is described which, with good resolution, separates viable rat liver parenchymal cells from other cell populations present in crude suspensions of liver cells. Fractionation is carried out by vertical rotor centrifugation in a self‐generated Percoll gradient. Kupffer cells can be separated from other sinusoidal cells, resulting in a separate peak of peroxidase negative non‐parenchymal cells, composed mainly of endothelial ce

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07218.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

To study the possible influence of sympathetic adrenergic tone on the blood‐brain barrier function during acute hypertension in conscious unrestrained rats with indwelling catheters in the aorta and a jugular vein the blood pressure was increased by noradrenaline, 6‐hydroxydopamine (6‐OHDA) or baclofen. One or 60 min later the rats were sacrificed and the extravasation of125I labelled albumin determined in the brain. After i. v. injection of noradrenaline the baroreceptor reflex will decrease the sympathetic tone whereas the blood pressure increase induced by the other two drugs is accompanied by an increased sympathetic activity. One minute after a corresponding rise in blood pressure the albumin content in the brain was considerably lower in rats given 6‐OHDA than in those given noradrenaline. 60 min after the injection of 6‐OHDA or baclofen the extravasation in the brain did not differ despite a considerably more rapid increase in pressure after 6‐OHDA. Pretreatment with clonidine increased the blood‐brain barrier dysfunction in rats given 6‐OHDA but not in those given baclofen, probably because the slower rise in pressure facilitates myogenic autoregulation. It is concluded that neurogenic influences on vessel tone can modify the response of the blood‐brain barrier during acute hypertension

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07219.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Bidirectional axonal transport of radioactivity was demonstrated in frog sciatic nerve in vitro and in vivo after local application of the thallium isotope204Tl+1to the nerve. The transport rate was similar in both directions and about 30 mm/day at 18°C. The transport was depressed by 2.4‐DNP, low‐temperature and vinblastine. A somewhat larger amount of radioactivity was transported in the retrograde than in the anterograde direction. The possibility that K+ is in part replaced by Tl+, which is transported bound to organelles, e. g. mitochondria, will be considered. Thallium might be a useful tool for future studies of axonal trans

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07220.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The reversible effect of dietary lysine deficiency was studied in young adult rats. During 6 days on a lysine deficient diet the rats maintained the same body weight. During 2 days of recovery body weight gain was that of the controls. Liver nuclei were isolated, incubated with micrococcus nuclease and chromatin fractionated into a 2000 ×gpellet. 102 000 ×gpellet and supernatant fraction. Chromatin‐bound RNA polymerase I plus III activity decreased by 15% per mg of fractional and nuclear DNA and by 30% per total liver. The corresponding decrease of RNA polymerase II activity was 30% and 40%. Recovery from lysine deficiency was complete after 2 days of refeeding the amino acid. Chromatin proteins of the 102000 ×gpellet were characterized by polyacrylamide gel electrophoresis in sodium dodecylsulfate and by 2‐dimensional gel electrophoresis. Quantitative but no qualitative differences between the proteins of the dietary groups were observed. Relative to DNA the non‐histone proteins decreased in the lysine deficient group by 43% and histones by 10%. It is concluded that RNA synthesis is restored to its original level within 2 days of refeeding lysine after 6 days of lysine de

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07221.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The effect of indomethacin, a prostaglandin (PG) synthesis inhibitor, on some cardiovascular reflexes was studied in healthy subjects. Heart rate (HR) and respiratory sinus arrhythmia (RSA) in the basal state and during carotid stimulation (neck suction), Valsalva ratio, and changes in heart rate and blood pressure (BP) during an orthostatic test were measured before and one hour after administration of indomethacin (1.5 mg/kg). The efficacy of the PG synthesis inhibitor was monitored by analysis of platelet aggregation induced by arachidonic acid. Following indomethacin no change was observed in basal HR. Carotid stimulation depressed the HR and this effect was of the same amplitude before and after indomethacin. The amplitude of RSA was not affected by indomethacin, either in the basal state or during carotid stimulation. The Valsalva ratio and the changes in HR and BP during the orthostatic test were similar before and after the drug. Circulating levels of noradrenaline were unaffected by indomethacin. These data demonstrate that inhibition of PG bioformation in man does not affect major cardiovascular reflexes. Consequently they disfavour the hypothesis that endogenously formed PG would be involved in the normal activity of the afferent, central or efferent pathways for cardiovascular regulation.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07222.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The contractile effects of diazepam (10–200 μM) were studied on twitch and tetanus responses of isolated fibres of the semitendinosus muscle of Rana temporaria (3.5‐5.0°C). Diazepam (100–200 μM) enhanced the twitch amplitude to 95–100 % of maximum tetanic force and increased the rate of rise of force, the time to peak twitch force and the total duration of the relaxation phase. The maximum tetanic output was unaffected by diazepam but the drug increased the rate of rise of the tetanic force and delayed the onset of force decay after the last stimulus. However, the kinetics of relaxation was unaffected by the drug. Diazepam had no effect on either threshold, submaximum or maximum contracture responses to caffeine and to increased potassium concentration. Diazepam in concentrations producing full twitch potentiation caused only a moderate (ca 30%) increase in action potential duration. The results are in line with the idea that I: diazepam enhances the twitch response by increasing the rate of release of activator calcium without affecting the rate of calcium resequestration and 2: diazepam acts by modulating a mechanism in the excitation‐contraction coupling that responds specifically to membran

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07223.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The dependence of Ca2+ for different modes of activation has been investigated in the rat portal vein in vitro by evaluating the effects of substituting Sr2+ for Ca2+ in the extracellular fluid. For the spontaneous contractile activity as well as for contractures induced by depolarizing (high‐K+) solution Sr2+ can to a large extent replace Ca2+. Sr2+ is however a poor Ca2+‐substitute for the contractile response induced by α‐stimulation (noradrenaline). The inhibition of spontaneous contractions by β‐stimulation (isoprenaline) is markedly less pronounced in Sr2+ solutions. Available data in the literature suggest that agonist interaction with α‐receptors, in contrast to β‐receptors, is Ca2+ independent. Our results thus suggest that there exists a Ca2+ specific step between the α‐receptor agonist occupancy and m

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07224.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Maximally dilated renal vascular beds of 13‐month‐old NCR and SHR were compared to explore how aging respectively longstanding primary hypertension structurally alters total renal resistance, pre‐/postglomerular resistance ratio and maximal glomerular filtration capacity, as measured per unit kidney weight. According to comparisons of 1.5‐ and 3.5‐month‐old NCR and SHR (Folkow et al. 1977). a structurally increased pre‐/postglomerular resistance ratio rapidly resets the renal “longterm barostat function” in SHR to match the 30–40% pressure rise, thereby increasing total renal resistance 15–20%, while filtration capacity is unaltered so far. In NCR aging to 13 months hardly alters arterial pressure, but increases total renal resistance 10–15%, mainly affecting postglomerular vessels, while filtration capacity is reduced 25%. 13‐month‐old SHR show an additional 15% pressure rise and–relative to agematched NCR–a further 35% reduction of filtration capacity with a 30–35% increase of total renal resistance, which mainly affects the postglomerular vessels as the resistance ratio is now barely above that in NCR. Thus, advancing SHR hypertension seems to start a renal vicious circle, because accentuated reductions of filtration capacity are parallelled by structuralpostglomerular resistance increases, apparently to maintain GFR by raised filtration pressure which, however, acc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07225.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY