ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09497.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The effects of intracellular and extraceIlular superoxide dismutase and heparin administration on oxygen radical formation after ischaemia in the rabbit kidney were studied. Radicals were measured with ESR and spin trapping. At reperfusion after 60 min of renal ischaemia there was a significant increase in the production of free radicals in the venous effluent from the kidney. Administration of either intracellular superoxide dismutase or extracellular superoxide dismutase before ischaemia and before reperfusion prevented approximately 85 % of the radical formation seen in the untreated control group. Administration of heparin 5 min before recirculation resulted in a 65% decrease in radical production compared to the control group.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09498.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

There is an increasing demand for non‐invasive methods for the assessment of left ventricular function. Ultrasound Doppler methods are promising, and the early systolic flow velocity signal immediately distal to the aortic valve has been used clinically for this purpose. However, the signal is influenced not only by left ventricular ejection but also by systemic vascular characteristics. Their relative contribution to the timevelocity signal has not been analysed in depth previously. A theoretical analysis, based on a three‐element Windkessel model, neglecting peripheral outflow in early systole and assuming linear pressure rise, was therefore tested in computer and hydraulic model simulations where peripheral outflow was included. Significant changes in early aortic flow velocity parameters were found when vascular characteristics were altered. As predicted by the theory, with a standardized aortic valve area and aortic pressure change, the simulations confirmed that maximal flow velocity is related to compliance of the aorta and the large arteries, and that maximal acceleration is inversely related to the characteristic impedance of the aorta. Therefore, maximal velocity and acceleration can be used for assessment of left ventricular function only in situations where vascular characteristics can be considered relatively constant or where they can be estima

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09499.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The threshold body core temperature for selective brain cooling (SBC) as well as the slope of brain cooling were determined in three Norwegian reindeer (Rangifer tarandus tarandus) during rest and during exercise. Brain temperature was measured in the hypothalamus (Thypo) and blood temperature (Tblood) was measured either in the right carotid artery or in a few cases in the right atrium of the heart. During rest the animals were subjected to ramp‐like increases of Tbloodby means of a thermostatically controlled water circulated heat exchanger (HE) introduced into the rumen via a chronically implanted rumen cannula. During exercise the animals ran on a treadmill at a speed of between 5.5–8.0 km hr‐1and a slope of 13.5° for periods of 30–60 min. The elevation of Tbloodduring both rest and exercise resulted in significant amounts of SBC. The mean threshold for SBC (Thypo= Tblood) during rest was 38.7°C. The threshold for SBC was elevated significantly to 39.5°C during exercise. The mean slope of SBC (increase of SBC per degree increase of Tblood) was 0.82 both during rest an

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09500.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Hydrolysis of inositol phospholipids caused by muscarinic agonists was studied in the guinea‐pig parotid gland (PG) and cerebral cortex (CX). The present study describes the effect of two muscarinic agonists, carbachol and oxotremorine, on stimulation of phosphoinositide hydrolysis and on binding of [3H]NMS in the presence of the irreversible muscarinic antagonist benzilyl choline mustard (BCM).Carbachol and oxotremorine stimulated the formation of inositol phosphates in PG, pD2(Carb) = 5.3 ± 0.1, pD2(Oxo) = 5.9 ± 0.1 and in CX, pD2(Carb) = 4.3 ± 0.2, pD2(Oxo) = 5.8 ± 0.2. In the present study slices from both tissues have been exposed to 0.1 μM BCM for 2, 5 and 10 min. Treatment for 10 min caused a 75–85%, reduction in specific [3H]N‐methyl scopolamine ([3H]NMS) binding sites in both PG and CX. Following 2 min BCM treatment of PG a marked decrease in pD2value of the carbachol‐stimulated inositol phosphate formation was found. This effect was not found in CX. The results showed that a 30–40% reduction in binding sites shifted the carbachol concentration response curve to the right by one order of magnitude and reduced the oxotremorine‐induced release of inositol phosphates by approximately 20%. In PG, the BCM‐induced reduction of the carbachol‐stimulated inositol phosphate formation was paralleled by the reduction in receptor binding sites. Similar treatment, but in CX, showed a lower reduction of the carbachol‐stimulated inositol phosphate formation as compared to the reduction in receptor‐binding sites.The results from the present study indicate that stimulation of phosphoinositide hydrolysis in PG involves a receptor reserve, mainly via stimulation of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09501.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The charge density of renal interstitium was analysed from the volume of distribution of negative native albumin as compared with neutralized albumin, labelled with125I and131I, respectively. The experiments were conducted by infusing the two probes intravenously at a rate which kept the plasma concentrations stable. The concentration in renal hilar lymph, Clymph(t), will then obey the function Clymph(t) = Clymph(tx) (1‐exp—Kt), where Clymph(tx) is the steady state Concentration andKthe time constant for passage of the tracer through the renal interstitium ‐ the former is dependent on the permeability of the peritubular capillary membrane, whereas the time constant is inversely related to the interstitial distribution volume of the tracers. The lymph‐to‐plasma concentration ratio (L/P‐ratio) of negative, native albumin was found to be lower than that of neutralized albumin, a finding suggesting that the peritubular capillary membrane is negatively charged. Regarding the interstitium, it was calculated from the respective time constants,K, that the interstitium/lymph concentration ratio of negative native albumin was 0.96 ± 0.06 of that of neutralized albumin. This suggests the presence of negative fixed charges repelling negative native albumin. However, since the calculated charge density of — 1.8 ± 1.2 mEq 1‐‐1was not significantly different from zero, it is concluded that the renal interstitium is uncharged. This does not, however, rule out the possibility that, for example, negative groups are fixed to the interstitial matrix, merely that the average fixed charge density of renal interstitial

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09502.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

It is believed that chloride transport through the macula densa (MD) cells is a factor involved in the tubuloglomerular feedback (TGF) mechanism and in MD‐mediated renin release. In this study isolated and perfused rabbit kidney cortical thick ascending limb (cTAL) segments containing MD plaques and attached glomeruli were loaded with chloride (CL‐sensitive) 6 methoxy‐l‐fluorophore (sulphanate‐propyl) quinolinium (SPQ). MD and cTAL intracellular chloride concentration ([Cl‐]i) was determined by using image‐intensified video microscopy and digital image‐processing for measuring the intensity of the emitted SPQfluorescence. With 150 mM NaCl in lumen and bath the [Cl‐], in MD and cTAL cells was 58.8 ± 7.2 mm (n= 20) and 68.7 ± 9.8 mm (n= 14), respectively. When the presumed luminal Na+‐2Cl‐‐K+co‐transporter was blocked by adding 10‐‐4m furosemide, the [Cl‐]iwas reduced in both, MD and cTAL cells from 55.5 ± 11.9 to 28.6 ± 10.0mm (n= 10) and from 43.8± 2.6 to 13.1± 4.5mm (n= 5), respectively. A reduction in luminal NaCl from 150 to 30 mm also decreased both, MD and cTAL [Cl‐]ifrom 69.4± 9.1 to 36.5± 5.1 mm (n= 9) and from 82.9 ±14.5 to 49.4± 8.0 mm (n= 8), respectively. Basolateral addition of the Cl‐‐channel blocker NPPB increased MD [Cl‐], from 31.1± 2.0 to 100.7± 17.0 mm (n= 5) and cTAL [Cl‐]ifrom 44.4 ± 12.9 to 89.7 ± 11.7 mm (n= 5). These results show the existence of a luminal Na+‐2C1‐K+cotransporter and a basolateral Cl‐conductance, and that chloride transport is directed from the luminal to the basolateral side during symmetrical conditions. They also indicate that sensing of luminal NaCl by the MD cells could be of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09503.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In the present study we have investigated the cardiovascular effects and peptide‐releasing actions of different capsaicin doses in the absence and presence of the inhibitor of Ca2+fluxes, ruthenium red, in the pigin vivo. Bolus injections of capsaicin (10, 100 and 1000μg kg‐1i.v.) evoked a concentration‐dependent increase in mean arterial pressure and heart rate (HR), while in the bronchial and nasal circulations, a fall in vascular resistance was observed. At the highest capsaicin dose used, there was, in addition, a marked increase in arterial levels of calcitonin gene‐related peptide (CGRP)‐and neuropeptide Y (NPY)‐like immunoreactivity (LI). Ruthenium red (RR) significantly reduced the CGRP‐LI release, but not the outflow of NPY‐LI, at the highest dose of capsaicin as well as the functional effects evoked by low dose capsaicin administration. The inhibitory effects of RR were reversible, i.e. 30 min after ruthenium red administration, bolus injections of capsaicin (10 and 100 μg kg‐1) induced responses similar to those seen in controls.It is concluded that capsaicin given intravenously to the pig produces profound haemodynamic effects and release of CGRP‐ and NPY‐LI through direct activation of a population of C‐fibre endings and increased autonomic discharge. RR inhibits not only the local peptide‐releasing properties of capsaicin, but also the centrally directed discharge activity leading to reflex responses, with the latter

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09504.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Lactate accumulation in skeletal muscle is reduced after a period of endurance training. Explanations for this phenomena include the increased oxidative capacity of the muscle, a reduction in lactate production, and increased lactate clearance. Muscle membrane transport of lactate can be seen to be a fundamental aspect of such clearance, and transmembrane lactate flux may well be an important aspect of the training response in skeletal muscle. Therefore, the lactate transport capacity in skeletal muscle sarcolemmal membranes in endurance‐trained and sedentary rats was investigated. Training consisted of 6 weeks of progressively increased treadmill exercise. Twenty‐four hours before being killed, both the trained and sedentary animals completed a brief exercise bout. Studies of lactate transport (zero‐trans) were conducted using highly purified sarcolemmal vesicles. When low concentrations of L‐lactate (1 mm) were used a 59.4% increase in lactate transport was observed (P0.05). Several interpretations are possible for these observations: (1) that there is an alteration in the Kmbut not the Vmaxof the lactate transport system in skeletal muscle membranes; and (2) that specific changes occur in selected isoforms of the lactate transport protein which may co‐exist

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09505.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The output of hyaluronan in mesenteric lymph was studied in anaesthetized rats to allow estimation of the turnover rate. The duodenum/jejunum contained 45,μgof this glycosaminoglycan per g wet tissue weight. In fasted rats the concentration of hyaluronan in postnodal lymph averaged 15 μgml‐1and the mean efflux was 2.1 μg h‐1, corresponding to a daily removal of 10% of the intestinal hyaluronan content. An intravenously injected bolus of 0.9% saline 4 ml 100 g‐1followed by an infusion of the same amount per hour increased the hyaluronan concentration in lymph transiently to 22 μg ml‐1. During the 8‐h i.v. infusion the hyaluronan output remained five times above control due to the high lymph flow. Water and hyaluronan content of the small intestine remained unaltered despite the saline load, the maintained tissue level of hyaluronan suggests an increased rate

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1993.tb09506.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY