摘要:

Structural and functional relationships underlying the blood flow distribution in the rabbit tenuissimus muscle were examined by means of intravital microscopy. A majority of the main feeding arterioles (transverse arterioles) continued into adjacent connective tissue, after giving off branches (terminal arterioles) within the muscle tissue to supply the muscle capillaries. The transverse arterioles thus supplied two vascular areas, although the major part of the arteriolar flow, under normal resting conditions, was distributed to the muscle capillaries—a flow fraction over which the terminal arterioles exerted ultimate control. The fractional distribution of the blood flow between muscle and connective tissue was determined by the relative contributions of the transverse and terminal arterioles to the vascular resistance. These arteriolar segments showed a differential response to an increase in oxygen availability (elevated ambient pO2), resulting in a total reduction of muscle capillary flow, but no concomitant change in the flow to connective tissue. A decrease in perfusion pressure, on the other hand, led to similar flow changes in the muscle and connective tissue circulation, which was attributed to proportionate resistance changes in the transverse and terminal arterioles. Differences between the larger transverse and smaller terminal arterioles in their sensitivity to various stimuli may form a functional basis for a differential control of arteriolar blood supply and capillary perfusion in this muscl

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07505.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Single nephron glomerular filtration rate (SNGFR) of superficial and juxtamedullary nephrons were measured at normal and reduced perfusion pressure in the left kidney of young Sprague Dawley rats. Perfusion pressure was lowered by constricting the aorta proximal to the branching of the left renal artery. The influence of the tubulo‐glomerular feedback mechanism on SNGFR was quantitated by measuring SNGFR during intact and interrupted urine flow to the macula densa region. By using a modified Hanssen technique, SNGFR was measured under free‐flow conditions. In other experiments, the urine flow to the distal nephron was blocked by a micropuncture technique, which was used for collection of the tubular fluid for measuring the filtration rate. All nephron populations autoregulated SNGFR from 70–80 to 130 mmHg, which was the upper limit of this investigation, when urine flow throughout the nephron was intact. The autoregulation in this pressure range was lost when tubular fluid was prevented from reaching the distal nephron. It was shown that the influence of negative feedback on SNGFR by the macula densa mechanism at normal blood pressure is greater in deep nephrons than in superficial

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07506.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of fatigue developed during 96 repeated rapid maximal voluntary finger muscle contractions (MVC), 12 contractions per minute, was followed in 4 control subjects and 4 myasthenic patients. The tension‐time integral (T‐TI) was determined during either the first 1 or 1.25 s of each contraction. Fatigue decreased the T‐TI by 21% in the control subjects and by 65% in the patients. While ordinary MVC showed a slow rate of rise of tension and gradually increasing electromyographic activity, rapid MVC from both groups showed a steep rate of rise of tension, a ‘notch’ after about 0.3‐0.4 s separating two relative maxima and a larger electromyographic activity during the first half second of the contraction. The mechanograms from rapid MVC were divided by an arbitrary straight line connecting the starting pint of the contraction curve and the notch. The line separated an area (N x s) above and to the left (a‐component) from an area below and to the right (β‐component) of the line. Fatigue affected the β‐component selectively in both control subjects and myasthenic patients. Only when the α‐component was reduced by more than 80%, was a reduction of the α‐component also seen. At any time during a sustained contraction, the patients could briefly increase their instantaneous strength, but for only about one half second. The results suggest that human muscle contractions can be divided into two parts with a different sensitivity to fatigue in both control subject

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07507.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Frog (Rana temporaria) skins were studied in an Ussing type lucite chamber adapted to diminish tissue edge damage. The transepithelial electrical potential difference, short circuit current and direct current (DC) resistance of skins mounted in this chamber were 56, 20 and 24% higher, respectively, than those of skins mounted in a conventional chamber. Amiloride, triamterene, ouabain and ortho‐vanadate inhibited short circuit current and net mucosal to serosal flux of22Na. Amiloride and triamterene had rapid onsets of action and were effective only when administered to the mucosal (pond) side of the skin. Ouabain and ortho‐vanadate had slower onsets of action and were effective only when administered to the serosal side of the skin. Steady state of effects of these drugs was not reached within the three‐hour period of the experiments. The inhibitory effect of ortho‐vanadate was blocked by adding a disulfonic stilbene derivative (DIDS) to the serosal side of the skin. Serosal prostaglandin E2stimulated the short‐circuit current and decreased the DC resistance. Thiazides, acetazolamide and loop diuretics had no effects on Na+transport by frog skin. Thus, frog skin seems to be a useful model only in studies of the mode of action and the structure‐activity relationship of diuretic which act by inhibiting sodium entry or Na+‐K+‐

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07508.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Neurotensin‐like immunoreactivity (NTLI) is released from the small intestine into the blood after enteral administration of fat and systemic administration of bombesin. The purpose of the present investigation in the rat was to study the effect of intravenously (i. v.) administered CaCl2on the plasma concentration of NTLI (pNTLI) and to investigate the effect of i. v. infusion of somatostatin on basal NTLI release, as well as that stimulated by fat, bombesin and CaCl2. Administration of CaCl2(5–25 mgxkg‐) increased p‐NTLI levels in a significant and dose‐dependent manner. In contrast, somatostatin 25–200 ngxmin‐1) reduced the basal p‐NTLI levels, as well as the increase in p‐NTLI levels induced by CaCl2(10 and 25 mgxkg‐1), fat (oleic acid, 0.5 ml) and bombesin (25 and 125 pmolxkg‐1), in a dose‐related manner. Injection of bombesin released immunoreactive material that was indistinguishable from synthetic bovine neurotensin (1–13) upon gel‐filtration. This material seemed to be rapidly converted to the more stable m

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07509.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The local cerebral blood flow in cerebral cortical and subcortical regions of the rat brain was studied with the14C‐iodoantipyrine autoradiographic technique at rest and during strong non‐noxious stimulation of the nose. Patterns of local blood flow changes evoked by stimulation with and without pretreatment of indomethacin, a potent cyclooxygenase inhibitor were determined. Stimulation produced a marked heterogeneous enhancement of CBF. Indomethacin did not prevent this effect although the absolute flow levels were considerably lower in indomethacin‐treated animals. Indomethacin was especially effective in reducing the cerebral cortical blood flow response to stimulation whereas the subcortical response was much less aff

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07510.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

An attempt was made to evaluate the possible metabolic interaction with myogenic vascular reactivity during autoregulation of blood flow in sympathectomized cat skeletal muscle. This was done by studying the extent to which a purely myogenic response, elicited by a standardized 2 s vascular transmural pressure impulse stimulus was altered when mean arterial inflow pressure was varied in the range from 160 down to 40 mmHg. The observations were made during the steady state blood flows encountered at the different pressure levels. The data were corrected for the effects of physical factors inherent in altered basal vascular tone and intravascular pressure with the aid of a mathematical model for purely myogenic responses. The results demonstrated a flow dependent decline in myogenic vascular reactivity during reduction of arterial pressure, even in the range where blood flow was autoregulated quite effectively. This suggested a significant metabolic interaction with myogenic reactivity, an interpretation corroborated by a similar decline in myogenic reactivity found during more defined activation of the vascular metabolic control system by graded light muscle exercise. The fact that a significant metabolic interaction was revealed even at such minute flow changes that occur in the autoregulatory range indicates a high ‘gain’ in the metabolic feedback interacting, directly or indirectly, with myogenic mechanisms in local vascular regulat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07511.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Ethacrynic acid inhibits energy‐requiring transcellular NaCl reabsorption without affecting NaHCO3reabsorption. Acetazolamide inhibits NaHCO3and most of the remaining NaCl reabsorption in the proximal tubules (bicarbonate‐dependent reabsorption) but raises distal transcellular NaCl reabsorption. After administration of both diuretics, the remaining bicarbonate‐dependent and transcellular reabsorptions become constant until glomerular filtration rate (GFR) is almost halved. The inhibitory effect of expanding the extracellular volume (ECV) until plasma volume and GFR increased 30–40% was examined in anesthetized dogs. Examinations at comparable GFR obtained by altering arterial perfusion pressure showed that the inhibitory effect of ECV expansion was attenuated by administering acetazolamide. Ethacrynic acid amplified the inhibitory effect which for sodium and chloride reabsorption amounted to 6–7% of the filtered load at comparable GFR. An inhibitory effect of ECV expansion of bicarbonate reabsorption was disclosed only after raising plasma bicarbonate concentration. Thus, the small inhibitory effect of massive ECV expansion is confined to proximal tubular bicarbonate‐dependent reabsorption and is of the same magnitude as previously demonstrated in experiments of similar design by raising plasma pH by only 0.07 unit. Since ouabain inhibits transcellular NaCl reabsorption, a natriuretic hormone is more likely to be an inhibitor of carbonic anhydrase than of N

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07512.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Previous measurements of the intracranial pressure in experimental animals suffer from acute and subacute effects of cannulation. In order to obtain reliable, repetitive or continuous values, we measured the intracranial pressures in awake rabbits with a new permanent adjustable ventricular cannula that included a separate entrance to the subarachnoid space. The mean intraventricular pressure ten days after the operation was 5.2±1.1 mmHg (SD) (70 animals). Manipulation of the cannula system and infusion of artificial cerebrospinal fluid did not damage the blood‐brain barrier (indicated by extravasation of Evans Blue). The intracranial pressure was constant for as long as 6 months and as many as 22 separate measurements and infusions. The cerebrospinal fluid cells and protein content did not change in animals with permanent cannulae and in animals perfused with 2–4 ml artificial cerebrospinal fluid. In 30 animals the ventricular cannula functioned for 10–180 (median 65) days and the subarachnoid entrance for 11–23 (median

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07513.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of close intrarterial administration of pentobarbital in the concentration of about 2times10‐4mol/1 on the venous stasis induced arteriolar constriction in the dog hindleg was studied in 6 neurolept anesthetized dogs. It was found that the blood flows and vascular resistances in the legs before pentobarbital infusion were equal and the vasoconstrictor responses to venous stasis were the same. Pentobarbital infusion into the femoral artery in one of the legs increased the total leg blood flow compared to the control leg and abolished the increase in vascular resistance during venous stasis. In another experimental series the effect of general pentobarbital anesthesia on the vasoconstrictor activity in response to venous stasis locally in subcutaneous and muscle tissue in the hind limb was examined in 6 dogs. It was found that during the first 2–3 h of anesthesia the vasoconstrictor response was present in both tissues although the response in muscle tissue exhibited a great variation between the dogs during this period. However, after 4–5 h of anesthesia the response was abolished in both tissues. During neurolept anesthesia with fentanyl/N2O the same vasoconstrictor response was demonstrated in the hindleg 1 h and 5 h after induction of the anesthesia. It is concluded that pentobarbital anesthesia abolishes the arteriolar constriction induced by venous stasis. The mechanism may be blockade of the local sympathetic vasoconstrictor fibres or interference with myogenic vasoconstrictor mechanism of the vascular smooth muscle cells or both. It is suggested that fentanyl/N2O anesthesia is better suited for this kind of st

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1984.tb07514.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY