摘要:

Blood flow distribution in the renal cortex was investigated in control and during i.a. infusion of dopamine (DA) and acetylcholine (Ach) in dogs. Local blood flow in outer cortex (OCF) and in inner cortex (ICF) was measured by platinum electrodes detecting hydrogen washout rate in tissue. Mean cortical blood flow measured by hydrogen washout rate in the renal vein (CFV) was compared with renal arterial blood flow (RAF) measured by electromagnetic flowmeter. With electrodes of 0.05–0.2 mm diameter control blood flow rates in outer and inner cortex were 4.57± (S.D.) 1.73 ml/min g and 4.35±0.57 ml/min g, which is higher than found using 0.2–0.5 mm electrodes in this and previous studies. OCF and ICF increased proportionally during intraarterial infusion of DA or Ach. The increase in local blood flow per unit volume was about 20% less than the increase in RAF, most likely due to an increase in renal volume and a reduced vasodilatory response in the surrounding of some electrodes. CFV rose almost to the same degree as RAF, showing a diffusion equilibrium for hydrogen gas even at maximal flow rate. During vasoconstriction induced by high doses of DA, OCF and ICF fell proportionately. Thus, equal vascular responses in outer and inner cortex were observed during both vasodilator and vasoconstrictor infusion. This indicates that changes in sodium excretion with renal blood flow may not be associated with a redistribution of cortical peritubular blood

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06418.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Isometric force and membrane action potential were recorded simultaneously in rabbit papillary muscles (36.5o–37.5oC). One to three test stimuli were given at various intervals (0.20–10.0 s) after a series of control contractions at constant stimulation intervals (1.0–1.5 s). Optimum peak force always occurred when the preceding test interval was 0.80 s. When this interval was>0.80 s, time to peak force was a linear function of the action potential duration. Furthermore, under these conditions the action potential duration (AP1) and peak force (F1,) of the test contraction could be used to predict peak force (F2) of the subsequent contraction elicited after a fixed interval (0.80–1.50 s) according to the equation (regression plane):F2=BApAPt+BFF,+A.ConstantsBAPandflFare interpreted to provide information about calcium influx during the action potential and of the recirculation of calcium between contractions, respectively.F2deviated towards higher values than predicted from the equation when the preceding test contraction was triggered to occur at an interval&0.80 s. This may be due to an intensified calcium transport into the cell during the action potential after these short intervals. The action potential duration was inversely related to both the inotropic state of the muscle (representing a feed–back mechanism) and the preceding stimulation

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06419.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The recently described static and dynamic myogenic responses in the sympathectomized skeletal muscle microvessels to a given transmural pressure (PT) change applied at different rates (dPTldt) (Grände&Mellander 1978), were further analysed in this study with a mathematical approach. The hypothesis that myogenic reactions are triggered by and related to wall tension was also tested. The mathematical model was based on a force–equilibrium in the microvessel wall including passive forces related to vascular transmural pressure, elasticity, and wall–viscosity, and active myogenic forces related to wall tension and its rate of change. Great resemblance was demonstrated between microvascular resistance curves obtained with the model and corresponding curves observed in vivo, indicating that the model quite adequately can describe myogenic microvascular resistance responses to transmural pressure stimuli. The results support the myogenic hypothesis in general and, in particular, the concept of an important rate–sensitivity in myogenic microvascular control and are compatible with the view that myogenic reactions are triggered by and related to change of wall tension. The model, in addition, provided data for certain microvascular variables which are difficult to assess by in vivo observations, e.g. Young's modulus of elasticity, wall tension, its rate of change, and internal vessel radius, and it offered a means to define more precisely the role of physical factors like effects of Poiseuille's and Laplace's laws in vascular resistance regu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06420.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Transcapillary movements of22Na,51Cr–EDTA and125I–myogIobin were studied in the cat choroid by means of the single injection technique, using labelled albumin as the reference tracer. By an external shunting of blood, recirculation of tracer was delayed and complete venous outflow curves became available for analysis. The initial extractions observed were 0.66, 0.35 and 0.08 respectively. The extractions decreased with time. Within 20–25 s the extracted fractions of the tracers had almost completely returned to the blood. The results indicate high permeability coefficients and small extravascular volumes of distribution. The retinal pigment epithelium seems to have a very low permeability to all three substances. Extraction of tritiated water at 20–25 s was about 0.30 probably due to rapid penetration of labelled water into the retina. Evidence for a stereo–specific transport system for glucose in the retinal pigment epithelium was found in experiments with labelled D–glucose and 3–O–methyl–D–glucose. The total amount of glucose delivered by the choroid was calculated from measurements of the a–v differences fo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06421.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Duct ligation was found to cause a decrease in the weights of submaxillary and parotid glands examined 3 weeks postoperatively. Choline acetyltransferase activity in ligated glands was compared with that in unligated contralateral glands. The enzyme activity was also measured in the glands from both sides of unoperated control animals. Interference in the assay of choline acetyltransferase by other acetylated compounds was avoided by introducing suitable control incubations. Ligated submaxillary glands showed a small decrease in the activity of choline acetyltransferase both when compared with contralateral glands and with glands of control rats. In parotid glands the enzyme activity was found to be lower only when ligated and contralateral glands were compared. Structural changes in the nerves and reduced traffic of impulses in them may have to be considered as explanations for the reduction in enzyme activity in duct–ligated gland

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06422.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A new approach for measuring blood flow in bone is presented. It consists of the local injection of133Xe into the proximal femur of adult beagles and the external measurement of isotope washout curves. The curves were analyzed using a two–compartment exponential model. The half–times for the tracer washout from the fast and slow compartment were 3.34±0.48 min and 33.6±11.7 min (mean ±1 S.D.) respectively. Blood flow was calculated using a measured blood to bone partition coefficient of 1.55 ml/g. The mean blood perfusion in proximal femur of the dog was 10.8±4.3 ml/100 g/min (mean ± 1 S.D.). This value agrees well with most estimates of bone circulation. Due to rapid disappearance of133Xe the method is easy to repeat and is thus suitable for physiological studies of local blood flow

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06423.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The capacity of human skeletal muscle and kidney homogenates to synthetize prostaglandins (PGs) from exogenous precursor was investigated. Low–speed supernatants of muscle as well as renal medullary and cortical homogenates were incubated with14C–labelled arachidonic acid (14C–AA) prepared as a sodium salt.14C–PGs in the incubates were extracted, separated with thin–layer chromatography (TLC) and quantified by radioscanning. In the skeletal muscle incubates14C–AA was converted into14C–PGs with a time–dependent yield, most effectively after 10–15 min incubation. Well–defined radiopeaks parallel to unlabelled standards of PGD2, PGE2, PGF2αand 6–keto–PGF1αwere obtained in the chromatograms. PGE2was the main PG formed, constituting over 50% of14C–activity, whereas 6–keto–PGF1α, PGD2and PGF2αwere found in considerably lower proportions. In the renal medullary incubates, PGE2likewise accounted for the largest part of14C–PGs formed, but significant relative amounts of PGF2αand PGD2were also found. A minor peak, corresponding to 6–keto–PGF,aand thus indicating formation of PGI2, was also obtained. In contrast to the medulla, no14C–PGs could be found in the renal cortical incubates. The results demonstrate the existence of a considerable tissue specificity in the quantitative and qualit

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06424.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Hemodynamic changes during the development of sodium–induced hypertension were investigated in male Sprague–Dawley rats after about 70% of the renal mass was removed. Throughout the four experimental weeks, subtotally nephrectomized rats on a high sodium diet (750 mEq/kg) showed a continuous rise in blood pressure up to the mean value of 178±9 mmHg. In sham–operated animals on the high sodium supply the blood pressure did not increase, as compared to sham–operated controls on the standard sodium diet (150 mEq/kg). In the hypertensive group, the primary changes were urea retention and a concomitant increase of serum osmolality, but the serum sodium concentration remained at the normal level. These changes were followed by sustained enlargement of extracellular fluid and relative intravascular volumes, together with a simultaneous increase of heart rate and blood pressure. During high sodium intake, the plasma renin activity in subtotally nephrectomized rats was suppressed to one fifth of that in sham–operated animals, but the renin substrate activity did not increas

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06425.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Analysis of myogenic microvascular reactivity in terms of its recently described prominent dynamic component was performed before and during graded sympathetic stimulation and catecholamine infusion. Phenoxybenzamine and propranolol were used to differentiate between α– and β–adrenoceptor effects. The study first confirmed previous findings of a β–adrenergic inhibitory component in the neural control of microvascular resistance which attenuated the a–adrenergic constriction. The results concerning the interaction between adrenergic and myogenic control mechanisms corroborated the conclusion that the sympathoadrenal system, via its β–adrenergic link, exerts effective inhibitory action on myogenic excitatory reactions. As regards the neural control, its –adrenergic component seemed to quite precisely compensate for the reinforcing effect on the myogenic constrictor response which results from increased vascular tone per se (in this case caused by a–adrenergic constriction), interpreted as a physical ‘gain’ effect inherent in the inverse fourth power relationship between radius and resistance. The latter complicating factor, which implies non–linearity in integrated peripheral resistance control, was thus revealed only after β–blockade, but not on the vascular bed with intact adrenoceptors, where a given transmural pressure stimulus evoked an almost equally large myogenic constrictor response irrespective of the prevailing level of vascular tone. The β–inhibitory action of blood–borne noradrenaline was similar to the neural one, whereas that of adrenaline was more effective, causing decline of my

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06426.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Force–velocity and power–velocity curves in a vertical jump involving movements around several joints were derived from vertical ground reaction forces and knee angular velocities. The jumps were performed with weights from 10 to 160 kg added on the shoulders. The obtained curves from a semi–squatting static starting position resembled those reported for isolated muscles or single muscle groups. Vertical jumps were also performed in the conditions where the shortening of the leg extensors was preceded by prestretching of the active muscles either through a preparatory counter–movement or dropping down on the force–platform from the various heights ranging from 20 to 100 cm. Prestretching modified through a range of velocities the force–velocity and power–velocity curves by increasing both the ground reaction forces and the calculated mechanical power. Thus the results are similar to those reported in isolated muscles. In studies with isolated muscle preparation the nervous connections have not been intact and therefore it is suggested that increase in the performance of the skeletal muscles through prestretching, in the conditions of the present study, was attributed to the combined effects of the utilization of stored elastic energy and the reflex potentiation of musc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06427.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY