摘要:

Cardiovascular performance was studied in 18 α‐chloralose anaesthetized pigs when arterial potassium ([K+]a) was raised to levels observed in heavy exercise. The effects of hyperkalaemia were then studied during cardiac sympathetic nerve stimulation or during an infusion of noradrenaline. Elevation of [K+]aup toca.10 mM caused a progressive decline in cardiovascular performance. However, right cardiac sympathetic nerve stimulation elevated all cardiovascular parameters in the presence of raised [K+]aand offset the negative cardiac effects of hyperkalaemia. Electrical pacing of the right atrium to heart rates (HRs) equivalent to those observed during right cardiac sympathetic nerve stimulation did not offset the depressive effects of hyperkalaemia and, indeed, hastened the decline in cardiovascular performance. Infusion of noradrenaline (1m̀g kg min‐1i. v.) during hyperkalaemia caused an increase in all cardiovascular parameters similar to that seen during sympathetic nerve stimulation. After propranolol (0.5 mg kg‐1i. v.), sympathetic nerve stimulation slightly increased HR, systolic blood pressure (SBP) and dP/dtmax. Elevation of [K+]aoccurred more rapidly after propranolol, but the heart was still protected from hyperkalaemia during cardiac sympathetic stimulation. Infusion of noradrenaline elicited arrhythmias in six pigs. Infusion of KCI reduced the incidence of arrhythmias and in some cases abolished them. These findings may be related to how the heart is protected from exercise‐induced changes in potassium and catec

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09828.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The influence of coronary venous retroinfusion and a vasoselective calcium antagonist felodipine on the microsphere loss in a porcine model of myocardial ischaemia and reperfusion was studied.Sixteen open‐chest pigs underwent 45 min of myocardial ischaemia induced by occlusion of the left anterior descending coronary artery followed by 4 h of reperfusion. Either felodipine (felo‐retro group, 7 nmol kg‐1,n= 6) or the corresponding amount of vehicle (vehicle‐retro group,n= 5) was infused retrogradely into the coronary veins over 30 min, starting 5 min before reperfusion. In a third group, the same amount of felodipine was administered intravenously (felo‐iv group,n= 5). Myocardial regional blood flow was measured with radiolabelled microspheres (ø= 15 μm) injected before ischaemia to investigate a possible loss during ischaemia.In the felo‐retro group, the apparent blood flow in the ischaemic areas, expressed as a percentage of the corresponding values in the non‐ischaemic areas (%‐flow), were 73±15, 73±11 and 75±19 in the subendocardial, midmyocardial and subepicardial layers, respectively. The corresponding percentage flows were 64±11, 70±11 and 62±9 in the vehicle‐retro group and 75±18, 77±15 and 76±11 in the felo‐iv group. The differences between the groups were not satistically significant.It is concluded that in this open‐chest preparation microsphere loss observed in the ischaemic and reperfused myocardium is not increased by coronary venous retroinfusion or by a concomitantly administered va

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09829.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The excitability of the soleus Hoffmann (H) reflex was measured in five healthy male subjects during graded treadmill walking. Uphill and downhill walking at an 8% grade as well as level walking were used to vary the demands for lengthening and shortening contractions of the soleus muscle. These changes were assumed to cause differences in control of the afferent input in the spinal cord and the voluntary output to the soleus muscle.The H reflex was strongly modulated in all three walking conditions, high during the stance phase and low or absent during the swing phase. The shape of the modulations was, however, different. At uphill walking the reflex increased gradually during the whole stance phase and seemed to follow the soleus electromyogram (EMG) pattern closely. In the downhill condition the reflex excitability increased rapidly at heel strike like the soleus EMG and co‐contraction of the anterior tibial muscle was observed. At level walking a fast rise in reflex excitability was seen just after heel strike with low or absent soleus EMG.Mean soleus EMG was lower during downhill than during uphill or level walking, but the mean H reflex amplitude was similar in all three conditions. However, when the H reflex was related directly to the EMG activity by linear regression the reflex gain was lower during uphill walking than in the two other conditions. Furthermore, the ratio between H reflex and EMG amplitude was high during the first half of the stance phase at level walking indicating an elevated reflex excitability independent of the voluntary motor output. It is therefore concluded that the modulation of reflexes during walking cannot be interpreted in terms of the idea of automatic gain compensation. The reflexes must be controlled specifically and independently during the different phases of the motor output to meet the mechanical requirements of the movement task. Most explicitly this was seen during downhill walking, where an elevated reflex excitability together with co‐contraction at the ankle joint seem to provide increased joint stiffness and security, when the kinetic energy of the body has to be brought under control at heel str

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09830.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effects of handling and handling combined with phencyclidine (PCP) treatment on GABAergic neurotransmission were studied in Sprague‐Dawley rats. The animal material consisted of handling‐habituated (HH, for 11 d), acutely handled (naive, N), handling‐habituated and PCP‐treated (10 mg kg‐1i. p., HH+PCP) and acutely handled (naive) PCP‐treated (N+PCP) and unhandled ‘control’ rats. The binding of [3]GANA and [3H]flunitrazepam (FLU) was studied with membrances and the release of [3H]GABA with slices prepared from the striatum and frontal cortex. In the striatum the maximal binding capacity (Bmax) and the binding constant (KDwas lower in N rats. KDconstants of [3H]FLU were significantly lower in both brain areas in N rats than in HH rats. After PCP treatment both Bmaxand KDfor [3H]GAGA diminished. Neither handlign nor PCP had any effect on [3H]GABA release from striatal and frontal cortical slices. Handling prior to killing thus affects differently the GABAergic parameters studied and modulates the PCP

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09831.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Renal effects of acute renal denervation (DNX) were studied in anaesthetized rats. In a first series, whole kidney clearance measurements were made 120 and 240 min after unilateral DNX. At 240 min, urine production was 3.59±0.87 μL min‐1in control kidneys and 7.74±1.97 μL min‐1in denervated kidneys. The corresponding values for sodium excretion were 0.56±0.17 and 1.41±0.34 μmol min‐1, potassium excretion 0.48±0.08 and 0.97±0.37 μmol min‐1and glomerular filtration rate (GFR) 0.83±0.08 and 1.05±0.16 mL min‐1, respectively. In a second series, tubuloglomerular feedback (TGF) characteristics were determined with the stop‐flow pressure (Psf) technique. With increasing time, the sensitivity of the TGF mechanism diminished in denervated rats, as indicated by an increased turning point (TP). TP was significantly increased 2 h after DNX from 19.1±1.13 in control to 25.9±1.10 nL min‐1. TP was further increased 4 h after DNX to 37.3±3.12 nL min‐1. However, the maximal TGF response to increased flow in the late proximal tubule was not altered. But, Pstwas significantly higher in DNX rats than in the controls (47.4±1.01 vs. 43.0±1.53 mmHg) in spite of a lower blood pressure (107±2.9 vs. 119±2.2 mmHg). We conclude that intact renal nerves are essential for the setting of the TGF sensitiv

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09832.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The metabolic pathways of denatured collagen (gelatin) and hyaluronan were studied by injecting labelled macromolecules into the mesentery of rats. The label, [125I]tyraminecellobiose is trapped intracellularly after endocytosis, allowing localization of the site of uptake. Mesenteric and thoracic lymph was sampled for 6 h in anaesthetized rats. Separate rats were investigated after an awake period of 6 or 24 h. About 30% of the gelatin remained at the site of injection and of the remaining activity 1.7% was recovered in lymph, 11 yo in the liver and 15% in the kidneys, whereas 3 h after an intravenous injection of gelatin>70% was recovered in the liver. The change in preferable site of uptake from the liver to the kidney was attributed to local degradation in the mesentery as confirmed by chromatography of tissue extracts and lymph.Following hyaluronan injection and 6 h lymph sampling approximately 30% was left at the site of injection and of the remaining activity 5.7% was recovered in lymph. After an awake period of 6 or 24 h, 30% was regained in the liver. The recoveries in other organs were negligible and mesenteric lymph nodes seem quantitatively unimportant in the uptake of hyaluronan or gelatin from lymph or blood.The liver has a central role in intestinal hyaluronan metabolism, while denatured collagen is more prone to local degradation with remote uptake shared between the liver and the kidney.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09833.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Six minke whales (BaLaenoptera acutorostrata) were instrumented with VHF‐radio transmitters and four with sonic speed‐depth transmitters off the west coast of northern Norway and Svalbard and followed within view for up to 24 h. During such periods their respiratory rate was continuously recorded and their energy expenditure estimated according to Folkow&Blix (1992) at different swimming speeds and types of activity. We found that cost of swimming is remarkably low in these large animals and that their estimated daily energy expenditure on average only amounts to 80 kJ kg‐1

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09834.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effects of long‐term exposure (7 wk) to hyperinsulinaemia on insulin sensitivity were studied in female rats. The rats were made hyperinsulinaemic by implantation of osmotic minipumps that were changed once a week. Elevated adrenergic activity and secretion of glucocorticoids were controlled by another minipump with propranolol and adrenalectomy with corticosterone substitution, respectively. This resulted in hyperinsulinaemia and moderate hypoglycaemia, the latter probably counteracted by overeating and increased glucagon secretion, as indicated by increased body weight and lower liver glycogen contents, respectively. Euglycaemic, hyperinsulinaemic clamp measurements showed a significantly higher glucose disposal rate (P<0.05) in the hyperinsulinaemic rats 18.8± 1.1 mg kg‐1min‐1compared with the control groups 14.6±0.4 and 15.4±0.9 mg kg‐1min‐1. Insulin stimulation of 2‐deoxyglucose as well as glycogen synthesis was measured in the extensor digitorum longus muscle, the red and white part of the gastrocnemius, the soleus muscle, the liver and in parametrial, retroperitoneal, and inguinal adipose tissue. No differences were found between the groups in the insulin response of the 2‐deoxyglucose uptake. Glycogen synthesis was significantly elevated in all muscles in the insulin treated compared with the control rats but no differences were found in the liver. Capillary density was significantly elevated per unit muscle surface area in the soleus and extensor digitorum longus muscles of the insulin‐exposed rats. These results suggest that long‐term exposure to insulin is followed by increased insulin sensitivity, apparently localized to the insulin regulation of glycogen synthesis in muscles. Muscle capillary density is

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09835.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Raising the sodium concentration in the third cerebral ventricle increases renal sodium, potassium and water excretion. The identification and characterization of the factor(s) mediating the centrally evoked natriuresis would be greatly facilitated if the exact intrarenal effector site were known. We have assessed the importance of inner medullary structures for the effects of CNS stimulation by examining its ability to alter renal excretion in rats with papillary necrosis, induced 2 d earlier with 2‐bromoethylamine hydrobromide (BEA), 250 mg kg‐1body wt i. v. Male Lewis x DA rats were divided into a BEA‐treated group (n = 6) and a control group receiving vehicle alone (n = 6). In contrast to the white papillae normally seen, the papillae of BEA‐treated animals were bright red and showed a clear line of demarcation at their base. The rats were anaesthetized i. p. with Inactin (120 mg kg‐lbody wt). Artificial cerebrospinal fluid (CSF) was infused (520 nL min‐1) via a cannula into the left lateral ventricle. After 45 min CSF containing 1 M NaCl was used. Stimulation of the control rats with hypertonic CSF increased urine flow rate five‐fold (5.4± 0.8 to 27.1±6.1 μL min‐1), Na excretion 23‐fold (0.4±0.1 to 7.6±1.8 μmol min‐1) and K excretion fourfold (0.6±0.18 to 3.8±O.5 pmol min‐1). When the concentration mechanisms were damaged with BEA, the basal excretion rates of water and Na increased. The natriuretic response to ICV stimulation was severely impaired in these rats, but the kaliuretic effect was sustained. In conclusion, the natriuretic effect of ICV stimulation with hypertonic CSF is dependent on an intact renal inner medulla, which is not the case for the less pronounced kaliuretic response. Thus, either the juxtamedullary nephrons possess marked natriuretic responsiveness, not present in the cortical ones, or the responsiveness lies mainly in the papillary collecting ducts. However, it cannot be excluded that a disturbance of salt balance co

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09836.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09837.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY