摘要:

AbstractThe mechanisms behind the autoregulation of the total renal blood flow and the glomerular filtration rate are unclear. In this investigation a modified microsphere technique was applied to measure the blood flow at different depths in the renal cortex during normotensive and hypotensive conditions. No autoregulation was found in the outer cortex while it was well pronounced in the inner one. During similar conditions, glomerular capillary pressure, welling point pressure and intratubular pressure were recorded. By combining these results with the blood flow data, the preglomerular and postglomerula resistances were calculated. It was then found that the preglomerular resistance decreased and the postglomerular resistance increased when the blood pressure was lowered. The results indicate a redistribution of blood flow from the outer parts to the inner parts of the cortex when the blood pressure is decreased. The redistribution of the blood flow might explain the well known linear relationship between the arterial pressure and the urine flow. The single nephron filtration rate of the outermost glomeruli could be calculated and the results seem to indicate a non‐equilibrium at the end of the glomerular capillarie

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05888.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThis paper handles a model of the capillary function in the exchange of uncharged molecules between the blood and the tissue. The capillary system is subdivided into a filtering and a reabsorbing part. The exchange is assumed to occur through channels which are described in operational terms as pores. Through these pores there is a transport of solutes by concomitantly acting convection and diffusion influenced by a steric hinderance (restricted convection‐diffusion). The outflux of glucose and raffinose is enhanced in the filtering pores, raffinose relatively more than glucose. In the reabsorbing pores the outward diffusion is hindered to some extent, raffinose relatively more than glucose. It is shown that the net effect of filtration and reabsorption is to increase the outflux of raffinose as compared to that of glucose. This mechanism may explain why glucose and raffinose and other small molecules appear to pass across capillary walls in proportion to their free diffusion coefficients and not in proportion to their restricted diffusion coefficient

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05889.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractIf a sudden rise in solute concentration travels through a capillary system, a diffusible neutral solute passes the walls of the exchange vessels. If then the rate of passage depends on a chemical potential gradient (diffusion) and a hydrodynamical potential gradient (diffusion) and a hydrodynamical potential gradient (convection) and is sterically restricted (restricted convection‐diffusion), water and low molecular weight solvents leave the filtering part of the capillary at a higher rate than the solute, causing a relative increase in its concentration. This phenomenon and the effect of an increasing pore size along the capillary is investigated in a model for an impermeable solute and two diffusible solutes, corresponding to glucose and raffinose. It is shown that in the model, the concentration fall along the capillary tends to become rectilinea

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05890.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractSprint type strength training was performed 3–4 times a week for 8 healthy male students (16–18 yrs). The training was carried out on a treadmill at high speed and with high inclination. Muscle biopsies were obtained from vastus lateralis before and after the training period for histochemical classification of slow and fast twitch muscle fibres and for biochemical determination of metabolites and enzyme activities. Muscle fibre type distribution was unchanged. whereas fibre area indicated an increase for both fibre types in 3 subjects after training. The muscle enzyme activities of Mg2+stimulated ATPase, myokinase and creatine phosphokinase increased 30, 20, and 36 percent, pespectively. Muscle concentration of ATP and creatine phosphate (CP) did not change with training. Sargent's jump increased with on average 4 cm (from 47 to 51 cm), maximal voluntary contraction (MVC) with 19 kp (from 165 to 184 kp), andurance at 50 percent of MVC with 9 s (from 47 to 56 s), respectively. After training all subjects showed a gain in body weight (mean 1.4 kg) and in thigh circumference (mean 1.5 cm) indicating a larger leg muscle volume and consequently also an increase in total ATP and

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05891.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThe effects of 2 prostaglandin synthetase inhibitors, indomethacin and eicoa‐5, 8, 11, 14‐terraynoic acid (ETA) and of the prostaglandin antagonist, polyphloretin phosphate (PPP), on the tone of the isolated human umbilical artery and on the responses of this preparation to 5‐hydroxytryptamine (5‐HT) and prostaglandin F2α(PGF2α) were investigated. Indomethacin (8μg/ml), ETA (5 μg/ml) or PPP (40 μ/ml) reduced the tone of human umbilical arteries but had no influence on the responses to 5‐HT. In these concentrations ETA and PPP but not indomethacin antagonized the action of PGF2α. When the concentration of indomethacin or PPP was increased 5‐fold both 5‐HT‐ and PGF2α‐induced contractios were antagonized indicating a non‐specific inhibition at these concentration levels. A 10‐fold increase in the concentration of ETA had no antagonizing action on 5‐HT‐induced contractions suggesting a more selective inhibition of the PGF2αaction than displayed by the other compounds. The effects on the tone of the human umbilical artery of the compounds studied might reflect inhibition of prostaglandin biosynthesis and/or antagonism of prostaglandins contributes to the maintenance of tone of th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05892.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThe respective effects of pentobarbital‐sodium, enibumal‐sodium, urethane, urethane‐chloralose and lidocaine on the function of the acoustic middle ear reflex in the rabbit were studied. The response of the middle ear muscles was measured by recording changes in both ears' acoustic impedance when the reflex was elicited by applying pure tone stimuli (2000 Hz) to the two ears one at a time. In that way both the crossed and the uncrossed reflexes were studied. All the drugs were found to depress the reflex in such a way that a higher sound intensity was required after administration to achieve the same impedance change as before. The effect of the anesthetics was roughly proportional to their known anesthetic power. Lidocaine produced only a slight depression of the reflex. The crossed reflex showed a greater susceptibility to the general anesthetics than did the uncrossed reflex which suggests a greater complexity of the crossed reflex. Because the method of recording the reflex response does not require any surgery and is equally well applicable in unrestrained rabbits and in humans, it is suggested as a way of testing the effect of drugs on the central nervous s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05893.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThe capillaries of the counter‐current capillary organ,rete mirabile,have been studied by light microscopy and electron microscopy. The vasculature of thisretewas found to have a cross‐sectional area of about 5.25 mm2, and it consisted of 34000 efferent(= arterial)and 22 000 afferent(= venous) capillaries. The total surface area was the same for the two types of capillaries. The capillary endothelial cells showed numerous pinocytotic vesicles, scattered giant vacuoles and cytoplasmic extrusions (microvilli) at the luminal surface. The majority of the intercellular junctions appeared to have patent gaps with a width of 110–120 Å. The arterial capillaries appeared in many ways to be morphologically similar to skeletal muscle capillaries of mammals, whereas the fenestrated venous capillaries resembled those in the intestinal mucosa of mammals. Measurements of the ionic composition of theretetissue indicated that the endothelial cells contained much less K+than other cells, theretecontaining approximately equimolar amounts of K+and Na+. The functional significance of the structural and chemical observations are dis

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05894.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractBehavioural, cardiovascular and gastric responses induced by fastigial stimulation wereobserved in conscious cats with gastric fistulas, indwelling fastigial electrodes and arterial catheters. Fastigial stimulation elicited oral behaviours,e.g.grooming and chewing, together with tachycardia and pressor responses, while gastric motility was unaffected in most cases as was gastric hydrochloric secretion. In subsequent experiments on the anesthetized animals it was found that the same fastigial area could suppress the intestino‐gastric inhibitory reflex. Fastigial influences on small intestinal motility were investigated in anesthetized cats, well recovered from surgical isolation of intestinal loops whose motility could therefore be recorded without laparotomy. Fastigial stimulation either depressed or did not influence ileal motility before laparotomy but after this procedure excitatory responses were uniformly recorded. This reversal is explained by a fastigial suppression of inhibitory intestinal reflexes, elicited by the laparotom

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05895.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractIn acute experiments on chloralosed cats gastric motility, blood pressure and heart rate were investigated for influences exerted by the fastigial nucleus. Besides pressor responses, fastigial stimulation could produce either gastric excitation or relaxation and the background of these responses was analysed by selective nerve sectioning and administration of suitable autonomic blocking agents. Suppression of prevailing gastric motility was found to be mediated mainly by increased discharge in adrenergic nerve fibres but also by adrenal catecholamine release.–Gastric excitation could be induced in three different ways, first via increased activity in vagal cholinergic fibres, second, by fastigial suppression of the vago‐vagal non‐adrenergic relaxatory reflex. In addition, when laparotomy or other noxious abdominal stimuli had induced inhibitory gastric reflexes, the consequent sympathetic discharge could be suppressed by fastigial stimulation resulting in enhanced gastric motility.–The importance of background activity in the various nervous pathways for the fastigially induced gastric responses is di

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05896.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractAfter complete cardiovascular denervation mean arterial pressure (MAP) falls to almost equally low levels in spontaneously hypertensive rats (SHR) and normotensive control rats (NCR). This has earlier been suggested to indicate a dominance of neurogenic mechanisms in established SHR hypertension.–In the present study, total peripheral resistance (TPR) remains, however, some 35 per cent higher in adult SHR than in NCR after pithing while cardiac output (CO), and stroke volume, is 35 per cent lower in SHR. These opposite differences in TPR and CO after denervation, resulting in equal MAP levels in SHR and NCR, seem rather to be a consequence of the rapidly established structural adaptation that affects all SHR high‐pressure cardiovascular sections. Thus, the SHR precapillary resistance vessels display thick‐ ened walls and luminal narrowing, which keeps TPR higher than in NCR even during maximal vaso‐ dilatation. Due to hypertrophy, the SHR left ventricle exhibits a reduced myocardial stretch for a given filling pressure and stroke volume is consequently reduced more than in NCR after complete denervation.–Paradoxically, therefore, rather than reflecting any dominance of neurogenic mechanisms in established SHR hypertension the MAP equalization in SHR and NCR after cardiovascular denervation emphasizes the hemodynamic importance of cardiovascular structural changes present in hyp

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1975.tb05897.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY