摘要:

AbstractIsometric and isotonic length‐tension relations of longitudinal smooth muscle from rabbit urinary bladder were studied together with muscle cell length and tissue structure as revealed histologically. In vivo strip length at a bladder volume of 10 ml is referred to as L10. The smooth muscle was relaxed by Ca2+‐free solution and contracted by K+‐high solution with different Ca2+‐concentrations. Maximal active force, 12.5±0.4 N/cm2(S.E., n ‐ 11), for whole strips was attained at a length of 206±4% (S.E., n 5) of L10. Passive tension at this length was about 15% of total tension. After correction for amount of connective tissue, maximal active tension of pure muscle bundles was 19 N/cm2. Up to about 165% of L10isometric and isotonic length‐tension relations were identical; if the muscle was stretched beyond this, it failed to shorten isotonically to the same length as when contracting from a shorter starting length. This decreased shortening capacity was reversible if the muscle was shortened passively. The extent of shortening against zero load was dependent on degree of activation suggesting an internal resistance to shortening. A linear relationship was found between bladder radius and muscle cell length, indicating that no slippage occurs between the cells when the bladder is filled. Mean cell diameter in the nuclear region at L10was 7.2±0.2 μm (S.D., n = 10). Mean maximal active tension per cell was calculated to be 2.3·10‐6N and occurred at a cel

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10230.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractIt has been demonstrated that cardiac receptors, most likely of the left ventricular type, are present also in the duck's heart. These receptors and their reflex responses (i.e.bradycardia and hypotension) could be blocked by intrapericardial administration of lidocaine. Initially, such receptor blockade did not affect efferent vagal control of heart rate, as revealed by undiminished bradycardia in response to a standardized vagal stimulation. After cardiac receptor blockade, however, the duck's normal bradycardia response to head immersion was greatly reduced. The cardiovascular response to submersion was now instead characterized by a marked rise in arterial pressure, with superimposed bouts of intensified bradycardia and pressure reduction, evidently induced reflexly from the arterial baroreceptors. Meanwhile, the bradycardia response to standardized efferent vagal stimulation was still the same as before intrapericardial lidocaine injection. These results suggest that the marked rise in cardiac filling pressure following the intense chemo‐receptor‐induced constriction of both resistance and capacitance vessels, activates ventricular stretch receptors signalling in vagal afferents. Apparently, the activation of these receptors contributes crucially to the bradycardia and reduction of cardiac output, which balance off the greatly increased peripheral resistance in the diving d

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10231.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe synthesis of S‐100 protein and that of soluble and total proteins was investigated using cerebral slices from rats fed a 20% or 3% protein containing diet for 6 days. Incorporation of radioactive amino acids into S‐100 protein was significantly higher when rats were fed a diet containing 20% protein. No significant differences were obtained in the radioactivity incorporated into total or soluble proteins between the 2 dietary groups.14C‐leucine of a specific radioactivity of 55 mCi/mmol or 3.2 mCi/mmol incorporated with time into total protein was similar for the 2 dietary groups. The time‐dependent uptake of14C‐leucine by the slices and the inulin space remained unaffected by the dietary conditions used; and amino acid analyser estimates of the free amino acid pool showed no significant differences. Brain wet weight was 1.54 ± 0.02 g and 1.39 ± 0.02 g for protein‐fed and protein‐restricted rats respectively. The corresponding body weight increased by 7.8 g/day or fell by 0.5 g/day. Although the differences observed in total protein synthesis were small the synthesis of a nervous tissue specific protein S‐100 was markedly affected by short‐term

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10232.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe voltage dependencies of Na and CI fluxes were investigated in the isolated toad skin. With Cl‐Ringer's on both sides Cl outflux varied very little with clamping voltage. The same was true for the influx of Cl at depolarizing voltages (ψi‐ ψo<0 mV). whereas hyperpolarization led to a marked increase in this flux. A net chloride influx under short circuit conditions indicated active transport of chloride. The outflux of Cl was a saturable function of outside Cl concentration. The outflux of urea was hardly affected by raising outside Cl concentration, and the effect of varying outside nitrate concentration on Cl outflux was likewise small. Both influx and outflux could be inhibited partially by acetazolamide. The outflux of Na varied with the clamping voltage as would be expected for an ion transported by electrodiffusion, and it was shown that amiloride had no effect on Na outflux, so it was concluded that the Na outflux route is paracellular. In the absence of Cl in the outside solution a small outflux of Cl persists. Also this flux varied with the clamping voltage according to laws for electrodiffusion. The variation of the ratio of sodium outflux to chloride outflux with clamping voltage indicated free passive diffusion of both these ions under the conditions mentioned. A comparison of the outfluxes of Na and Cl in skins bathed with gluconate Ringer's outside showed that the outflux route of these two ions was cation selective (PNa/Pcl= 1.88). When the paracellular leak pathway of the skins was opened by exposing the outside to hyperosmolar urea solutions, the ratio of the transport numbers was found to be TNa/Tcl= 1.71. The roles of the two ions in determining the steady state current‐voltage relationships were compared. At hyperpolarizing voltages most or all of the clamping current was carried by an inward Cl flux. By depolarization sodium influx plays an increasing role with increasing depolarization. Under short circuit conditions active chloride transport was found to contribute to the short circuit

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10233.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe effect of sympathetic nerve stimulation (NS) and injected noradrenaline (NA) or isoprenaline (Iso) on PvO2, V̇osand PtO2was studied in isolated canine subcutaneous adipose tissue. These effects were compared to those produced by mechanical blood flow reduction (clamping). Resting V̇o2measured 13.0 ± 2.3 μmol × min‐1× 100 g‐1. When blood flow was reduced by 20% or less there was no significant change of V̇o2. Reducing blood flow to 50% of control or less by NS caused a parallel reduction in V̇o2, while clamping reduced V̇o2significantly less. NA gave effects similar to those of NS. After NS or NA there was a period of hyperemia and increased oxygen extraction which more than compensated for the decrease in V̇o2during vasoconstriction. Such a net increase in V̇o2was not produced by clamping. Control PtO2averaged 29±2 mmHg. NA reduced it by 70% and clamping to the same blood flow level only by 14% (p<0.01). Thus, a mere reduction in blood flow has little effect on PtO2, while blood flow reduction combined with redistribution of blood flow and an increased oxygen demand can lead to

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10234.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractIsolated rabbit hearts were perfused according to Langendorff. The bilateral sympathetic nerve supply to the organ was stimulated at intervals, and the overflow of noradrenaline and of prostaglandins of the E series in the effluent was assayed, using fluorimetric and bioassay methods, respectively. The synthesis of prostaglandins in the organ was stimulated, either by perfusing the heart at a low pO2, or by infusing nicotinic acid. Hypoxia increased the coronary flow, provided the prostaglandin synthesis was not inhibited, probably as a consequence of hypoxia stimulation of the endogenous formation of prostaglandins. The release of NA in response to nerve stimulation was, however, unaffected by hypoxia. Nicotinic acid also stimulated prostaglandin formation, doubling the overflow of the lipid in response to nerve stimulation. In this series, too, the release of NA induced by nerve stimulation was unaffected by stimulation of prostaglandin synthesis. It is concluded that local variations in the rate of prostaglandin synthesis are unable to change the degree to which the release of sympathetic neurotransmitter is inhibited. Furthermore, it is suggested that the prostaglandin synthesis in rabbit heart takes place in compartments, separated functionally or morphologically.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10235.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe occurrence of impulse block was studied in single unit recordings and related to impulse shape when peripheral nerves were impaled with tungsten needle electrodes. Exposed nerves were exploited in frog and cat and non‐exposed nerves in man. Three different impulse shapes were seen: 1. Negative spikes of very short durations which nearly all propagated. 2. Positive double peaked spikes which all propagated. 3. Positive single peaked spikes which were of two different natures: one which propagated and one which did not. The findings suggest that unitary impulses recorded with a needle electrode impaling the myelin are positive and single peaked when the injury is minimal. Gradually a propagation delay might develop at the site of impalement giving rise to a double peak. Later the propagation may be blocked which is seen as a drop out of the second peak. The collected sample of observations indicates that it was possible to predict in practically all cases whether the propagation was blocked or not from the shapes of the single unit impulses and their alterations as seen by the tungsten needle electrod

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10236.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractBlood flow in the external carotid artery (ECBF) and dental pulp (PBF) was measured during arterial infusion of vasodilators (isoprenaline, papaverine, acetylcholine and bradykinin). Systemic arterial pressure (AP) and local arterial pressure of the teeth (LAP) were recorded in a femoral and the lateral nasal artery respectively. All four vasodilators were found to increase ECBF and simultaneously reduce lateral nasal arterial pressure—or in other words—to “steal” perfusion pressure from the teeth. AP remained practically unchanged whereas PBF was variably affected. During infusion of isoprenaline PBF decreased on average by 19% of control. Papaverine nearly doubled PBF, while bradykinin caused no consistent change. Great pulpal flow variations were often recorded during constant acetylcholine infusion rate. The variable effect of the four vasodilators on PBF could partly be explained by the fall in LAP. Calculated pulpal resistance (LAP/PBF) showed no consistent change during isoprenaline infusion, bradykinin caused a slight fall and papaverine reduced LAP/PBF by 49%. The experiments demonstrate that due to the “stealing” of dental perfusion pressure caused by vasodilation in the neighbouring tissues, the effect of vasodilators on pulpal resistance vessels cannot be estimated without knowledge of the pressure in the small arteries directly feedin

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10237.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractIsolated superfused biopsy specimens of human peripheral arteries and veins, preincubated with3H‐(‐)‐noradrenaline (NA) to label the neural stores of NA, were used to study the β‐adrenoceptors previously found to increase the secretion of3H‐NA evoked by electrical field stimulation of the adrenergic nerves of this tissue. The increase in nerve stimulation induced secretion of3H‐NA caused by 0.04μM isoprenaline was prevented by 1 μM propranolol. This&bT‐blocking drug by itself slightly but significantly depressed the secretion of3H‐NA caused by nerve stimulation in the absence of isoprenaline. While the secretion of3H‐NA was not affected by two known β1‐agonists, it was dose‐dependently and reversibly increased by two different β2‐agonists. The effect of isoprenaline on3H‐NA secretion was not altered by a selective β‐antagonist, but strongly reduced or abolished by a β2‐blocking drug. The results indicate that the β‐adrenoceptors involved in the control of NA secretion from the vasoconstrictor nerves of human omental blood vessels are only to a minimal extent stimulated by NA secreted from the nerves, and therefore do probably not mainly serve to mediatelocalpositive feedback control of transmitter secretion;

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10238.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractIntravascular platelet aggregation induced in cats by i.v. infusions of collagen caused a transient increase in pulmonary vascular resistance (PVR) and in non‐elastic pulmonary resistance (RL), and a transient decrease in dynamic lung compliance (dyn CL). PVR, dyn CLand platelet aggregation after collagen infusions were unaffected by bilateral cervical vagotomy and atropinization, whereas these procedures reduced the post‐infusion rise in RLby about 50 per cent. The administration of indomethacin inhibited platelet aggregation as well as bronchoconstriction after collagen infusion. The present investigation indicates that intravascular platelet aggregation will cause reflex bronchoconstriction mediated by vagal efferent fib

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10239.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY