摘要:

This study was performed to provide information on the determinants of lymph flow by comparing the effect of venous stasis and hypoproteinaemia in the rat tail. This low‐compliant tissue was chosen in an attempt to induce preferential changes in interstitial pressure or volume. The removal rate (kAIb) of1251‐labelled human serum albumin (I‐HSA) injected subcutaneously was monitored with external gamma‐counting equipment and used as a measure of lymph flow. Interstitial fluid hydrostatic pressure (Pi) was measured with wick‐in‐needle technique, and interstitial fluid was collected post mortem by dry wicks. Colloid osmotic pressure of plasma (COPp) and wick fluid (COPi) was measured with a colloid osmometer. In a separate group of experiments,51Cr‐EDTA and [125I]HSA were used to measure the interstitial fluid volume. Venous stasis, induced by bilateral ligation of the external tail veins, increased interstitial fluid hydrostatic pressure from 1.7 to 16 mmHg and A/bfrom 0.030 to 0.063 h‐1, whereas tail circumference was nearly constant. Interstitial volume averaged 1.17 ml/g dry weight in control animals and 1.27 ml/g during increased venous pressure. Daily injections of aminonucleoside in salt‐loaded rats (0.3yo NaCl as drinking water) reduced colloid osmotic pressure of plasma from 19.1 to 8.5 mmHg and of wick fluid from 11.2 to 2.9 mmHg, while interstitial fluid hydrostatic pressure increased to 5.2 mmHg. The removal rate of125I‐labelled human serum albumin increased to 0.113 h‐1, compared to 0.051 h‐1in salt‐loaded controls. The interstitial volume showed a marked increase in salt‐loaded hypoproteinaemic rats, 1.75 ml/g dry weight, compared to 1.30 ml/g in salt‐loaded controls. The results indicate that absolute interstitial fluid pressure is not the main determinant of lymph flow and rather support the hypothesis that an increase of interstitial volume promotes lymph formation by pulling open the initial lymphatics thro

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09122.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The aim of this study was to evaluate a possible humoral β2‐adrenergic effect on the capillary pressure autoregulation capacity in cat skeletal muscle during bleeding. For this purpose capillary pressure autoregulation in response to graded decrease in arterial pressure was studied in sympathectomized muscle in the control state, and during haemorrhagic hypovolaemia in the presence and absence of selective β2‐adrenoceptor blockade (ICI 118,551). The study was performed with a technique that permits continuous recordings of average capillary pressure in absolute terms and of the regional pre‐ and postcapillary vascular resistance, from which the pre‐ to post capillary resistance ratio could be determined. In the pre‐haemorrhagic control state, an experimental decrease in arterial pressure from 100 to 50 mmHg caused a fall of capillary pressure from 17.6 by only 1.7 mmHg (ΔPA/ΔPc= 29), demonstrating an efficient capillary pressure autoregulation. This autoregulation was accomplished by a decrease in pre‐ to post capillary resistance ratio in turn being a result of active precapillary dilatation and a passive increase in post capillary vascular resistance. Haemorrhageper se, via a humoral α‐adrenergic preferentially precapillary vaso‐constriction, caused a decrease in capillary pressure to 16.8 mmHg at arterial pressure 100 mmHg. A superimposed decrease in arterial pressure to 50 mmHg resulted in a capillary pressure fall by 3.7 mmHg (ΔPA/ΔPe=14), indicating impaired autoregulation capacity. This attenuation to a great extent could be ascribed to adrenaline‐induced B2‐adrenoceptor stimulation, since β2‐blockade restored the Δ arterial pressure/capillary pressure ratio to 20. Low‐dose isoprenaline infusion in the control state similarly caused marked impairment of capillary pressure autoregulation. The β2‐adrenergic attenuation of capillary pressure autoregulation appears to be a beneficial effect in haemorrhagic hypotension, since it lowers capillary pressure passively in relation to the arterial pressure fall, thereby reinforcing the a‐adrenergic active capillary pressure decrease, leading to more effective transcapillary fluid absorption and, hence, im

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09123.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Effects of cervical sympathetic nerve stimulation (SNS) at 10 Hz and intravenous infusion of neuropeptide Y (NPY), 10 and 100 pmol×kg body wt‐1×min‐1for 5 min, on regional blood flow in the cat were investigated with radioactive microspheres.Sympathetic nerve stimulation caused significant reductions in blood flows in the facial tissues including the eye. Alpha‐adrenoceptor blockade with phenoxybenzamine and combined beta‐ and alpha‐adrenoceptor blockade with propranolol and phenoxybenzamine abolished the effects of sympathetic nerve stimulation in most facial tissues except in the tongue, upper eyelid and masseter muscle.In most cranial tissues, neuropeptide Y reduced regional blood flow and increased vascular resistance. No effect of neuropeptide Y on vascular resistance was observed in the choroid.In the present study, evidence for a non‐adrenergic component in sympathetic vasoconstriction was found in the tongue, upper eyelid and masseter muscle but not in the majority of feline facial tissues. Neuropeptide Y was a potent vasoconstrictor in many cranial tissues, while in parts of the area, the effects of neuropeptide Y were le

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09124.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Heart rate, stroke volume, cardiac output and mean arterial blood pressure were followed from the resting primal situation and for 2 hours after intake of standardized meals in four healthy individuals. Continuous records of stroke volume and cardiac output were achieved with an improved method of Doppler ultrasonography. A smallish meal and one 2 1/2 times larger were both given twice and in random order to each of the four test persons.The consumption of a meal invariably resulted in a cardiac output increase, which developed gradually to reach a maximum level 30 to 60 min after end of the meal. The postprandial cardiac output increase resulted from significant increases in both heart rate and stroke volume.There were distinct and significant differences between the circulatory responses to small and large meals. The increase in cardiac output after a large meal was considerably larger and lasted for longer than the increase after a small meal. Two hours after a small meal cardiac output was nearly or fully back to pre‐meal values, while cardiac output was still markedly elevated 2 hours after a large meal. Consequently, the total ‘extra’ amount of blood delivered by the heart over 2 post‐meal hours was significantly — about 100%— larger after the large meal than after the small one.Mean arterial blood pressure either fell or remained almost unchanged in the hour after a meal, so that total peripheral resistance was consistently and significantly reduced in the postprandial period — and considerably more so after a large meal than afte

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09125.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

We have determined the vascular pressure profile in lungs of adult ferrets utilizing an anaesthetized open chested preparation and have compared the pressure profilein vivowith that in isolated, perfused lungs. Ten adult ferrets, mean body weight 980 ± 108 g, were studied. Forin vivomeasurements, five ferrets were anaesthetized, mechanically ventilated and the left chest wall resected. Pressures were measured in the pulmonary artery, left atrium and by micropuncture, in 20–50μmdiameter subpleural arterioles and venules. During micropuncture, ventilation was stopped for 1–2 min and the lungs kept distended at an airway pressure of 6 cmH2O. Left atrial pressure was raised to ˜ 8 cmH2O with saline infusion so that lungs were in Zone 3. Cardiac output was measured by thermodilution. Lungs of five other ferrets were isolated and perfused with a steady flow roller pump. In these lungs blood flow was adjusted so that pulmonary artery pressure was similar to that in anaesthetized ferrets, with airway and left atrial pressures at 6 and 8 cmH2O respectively (Zone 3). Blood haematocrit (35 ± 7%) was similar in the two groups. In lungs of anaesthetized ferrets total arteriovenous pressure drop was 12.l ± 1.9 cmH2O, with cardiac output being 210 ± 80 ml kg body weight‐1min‐1. Fractional resistance in arteries was 37%, 37% in microvessels and 26% in veins. In isolated ferret lungs, though blood flow was only 48 ± 10 ml kg body wt‐1min‐1for the same total arteriovenous pressure drop asin vivo, the longitudinal distribution of vascular resistance was similar to that in live ferrets. We conclude that in the ferret, the contribution of arteries, microvessels and veins to total vascular resistance is similar in isolated lung

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09126.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Measurements of tracheal wall blood flow were made in anaesthetized, ventilated dogs during resting ventilatory conditions, during application of positive end‐expiratory pressure (PEEP) and during eucapnic hyperventilation of dry air, using laser Doppler flowmetry and the radiolabelled microsphere reference flow technique. Six regions of the trachea were studied in each dog, and the average laser Doppler flowmetry measurement derived from 12 sites within each region was compared with the reference flow measurement, obtained using 15 micron diameter microspheres labelled with113Sn,103Ru,141Ce or151Gd. Under each set of ventilatory conditions, there was a weak, but significant, correlation between laser Doppler flowmetry and reference flow values (baseliner =0.44, hyperventilationr =0.44, and PEEPr= 0.74). Average laser‐Doppler flowmetry and reference flow values showed a similar reduction from baseline during application of PEEP. The mean (SD) change from baseline, expressed as a percentage, was ‐63 (15)% for laser‐Doppler flowmetry values, and ‐63 (21)% for reference flow values. However, there was no correlation between the magnitude of change measured in individual regions using the two techniques. During hyperventilation, laser Doppler flowmetry measurements showed variable changes from baseline, and the mean change was ‐12 (45)%, which was not significantly different from zero. Reference flow values increased during hyperventilation, the mean change being 87 (77)%. The results indicate that laser Doppler flowmetry and reference flow measurements of airway wall blood flow are not directly

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09127.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The aim of the present study was to follow local potassium homeostasis during and after exhaustive contractions. Eight subjects performed static handgrip with their right forearm at 10% 25% and 40% maximal voluntary contraction. Blood flow (venous occlusion plethysmography) and the venous effluent plasma potassium concentration were followed during the contractions and during a 60‐min recovery period. Electro‐myography was registered during exercise (frequency analysis). With all three protocols the blood flow increased significantly during the contractions and the same was true of the effluent plasma potassium concentrations. In the recovery period blood flow and the venous effluent plasma potassium concentration returned to base values within 30 min following 40% maximal voluntary contraction while following 10% and 25% maximal voluntary contraction, venous effluent plasma potassium concentration was still significantly below resting values one hour after the exercise had ceased, indicating a long‐lasting uptake of potassium from the blood into the muscles. In line with this a significant potassium deficit was still seen after 1 hour of recovery following 10% and 25% maximal voluntary contraction. It is concluded that the recovery of potassium homeostasis following prolonged low‐intensity contractions is a slow process. This may be duetoeither sequestration of potassium in other tissues with a subsequent slow release and/or insufficient sodium/potassium pump activation. The contraction induced potassium loss may play a major role in muscle performance since it may impair mechanical force production, and it is hypothesized that this may be the origin of low‐frequenc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09128.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The outward current was analysed in the rapidly adapting stretch receptor neuron of the crayfishPacifastacus leniusculuswith a two‐micropipette potential clamp technique and K+‐selective microelectrodes in an attempt to establish if the properties of this current could explain the difference in adaptive behaviour compared to the slowly adapting receptor. A fast activating outward current carried by K+was revealed. The time constant of activation (tn) was dependent on potential and had a mean value of 0.5 ms at potential steps to 0 mV. Activation followed a second‐order process according to the Hodgkin‐Huxley model. The potential dependence of activation (n∞) followed by a sigmoid curven∞=l/{l + exp[(E —En)/a]}with a half maximal activation potentialEn= ‐44 mV anda =‐13 mV.When long pulses were applied the outward potassium current decreased with two time constants, one that was potential independent (0.2 s) and one that was potential dependent (2–8 s). The latter could be explained by accumulation of K+in the extracellular space of the neuron. The potential dependence of inactivation followed a sigmoid functionk∞=1/{1 +exp[(E —Ek)/+ a]} withEk= ‐36 mV anda =13 mV. The inactivation properties are different from those of the classical fast transient (IA) current. The transport system for the outward potassium current during depolarizing potential steps in the rapidly adapting stretch receptor is similar to the current found in the slowly adapting receptor neuron. However, the activation is faster and seems to occur at potentials more negative than in the slowly adapting receptor. These differences can contribute to but not entirely explain the difference in adaptive behaviour between the slowly and

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09129.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The relaxant effects of some isozyme‐selective phosphodiesterase inhibitors were evaluated in isolated human and rat coronary, lung and renal arteries. Milrinone and OPC 3911, inhibitors of a cGMP‐inhibited cAMP phosphodiesterase (cGI‐PDE), were shown to have distinct vasodilator actions. These agents were less potent as relaxants in rat lung and renal arteries than in the corresponding human tissues. OPC 3911, the more potent cGMP‐inhibited cAMP phosphodiesterase inhibitor, was found to be the more potent vasorelaxant. Rolipram, a selective inhibitor of a cGMP‐noninhibited cAMP phosphodiesterase, had small effects on coronary and lung arteries, but produced a slightly more pronounced relaxation of renal arteries from both man and rat. In human preparations contracted by 30 mm K+, milrinone and OPC 3911 had similar relaxant profiles, and were as potent in coronary as in renal arteries. These results do not support the notion that milrinone has reduced effects on renal vessels in man and show that there may be species differences in vascular responsiveness to cGMP‐inhibited cAMP phosphodiesterase

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09130.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Dopamine was shown to affect Na+, K+‐ATPase activity in basolateral membranes of the rat kidney via a pertussis toxin dependent mechanism. In order to examine if some form of pertussis toxin sensitive G‐protein is present exclusively in the basolateral membrane of the rat renal cortex we examined the G‐protein composition of both apical and basolateral membrane vesicles. Western blots showed an essentially uniform distribution of Gαtotal,Gαsand Gβ over the two membranes. Gocould not be detected with western blot technique in the vesicle preparations. By contrast, the distribution of ADP‐ribosylation with the bacterial toxins pertussis toxin and cholera toxin depended on the amount of detergent in the assay and perhaps other factors, and thus could not be used to evaluate the relative amounts of G‐protein subunits. Thus, in contrast to the situation in cultured renal cells, unequal distribution of receptor and G‐protein substrates is apparently not paralleled by an unequal distribution of the detected forms of G‐proteins under physiolo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09131.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY