摘要:

Isolated soleus muscle of rat was stimulated electrically (2 Hz) for 7 min under anaerobic conditions. Isometric twitch tension decreased progressively and was 30% of the initial value at the end of stimulation. The decline in relative force was similar to that previously observed in fast twitch muscle and soleus can thus not be termed fatigue‐resistant under anaerobic conditions. Phosphocreatine (PCr) decreased from (x̄± SD) 61.1 ± 4.4 at rest to 4.0 ± 1.8 mmol kg‐1dry muscle (d.m.) after 7 min of stimulation, while lactate increased from 3.7 ± 1.6 to 30 ± 8 mmol kg‐1d.m. Energy was thus derived from complete utilization of PCr and a low rate of glycolysis resulting in an almost unchanged calculated intracellular pH. It is concluded that tension decline in soleus muscle is not due to decreased intracellular pH but is more related to the capacity to regenerate ATP at a sufficient rate. Contraction and relaxation time of the twitch remained practically constant during the stimulation period. In contrast prolonged activation of fast‐twitch muscle results in a slowing of the relaxation of the twitch (Sahlinet al.1981) and it has been suggested that this is caused by the decrease of intracellular pH. The constancy of both relaxation time and calculated pH in the fatigued soleus muscle is consistent with the hypothesis that there is a connection between these two parameters. In contrast to the twitch, relaxation of tension after a tetanus was prolonged in soleus. Hence, it appears that the rate limiting step for relaxation is different for a twitch than for a teta

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08033.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08102.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The expression of insulin‐like growth factor I (IGF‐I, somatomedin C) was studied in regenerating skeletal muscle. Irreversible damage to skeletal muscle cells was induced in the extensor digitorum longus muscle (EDL) of adult rats by ischaemia, preceded by glycogen depletion, and the regeneration process was studied for periods up to 14 days after injury. The IGF‐I was demonstrated by indirect immunofluorescence. Immunoreactivity against ribonucleotide reductase (RR) was used as a marker for DNA synthesis, that is, cell proliferation. Increased IGF‐I immunoreactivity could be demonstrated within 24h after injury in satellite cells, intramuscular nerves and in blood vessels. The IGF‐I immunoreactivity remained virtually unchanged in the contralateral, undamaged EDL. An increasing number of satellite cells, expressing high IGF‐I immunoreactivity, could be demonstrated in the injured EDL, and within 72 h myoblasts, expressing high IGF‐I and RR immunoreactivity, were formed. Small immature muscle cells, displaying high IGF‐I immunoreactivity, were observed 4 days after injury. Increased IGF‐I immunoreactivity was still obvious in the regenerated muscle cells 14 days after injury while RR immunoreactivity was seen only in scattered satellite cells. It is concluded that IGF‐I may act as a trophic factor during regeneration of skeletal

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08034.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08103.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The purpose of the study was to examine the effects of naloxone on signs of cerebral ischaemia during hypotensive haemorrhage in unanaesthetized spontaneously hypertensive rats. Mean arterial blood pressure (MAP), heart rate (HR) and somatosensory evoked potentials (SEP) were recorded. Arousal tests were also performed and the behavioural responses quantified. The SEP alone were a poor indicator of cerebral function in these unanaesthetized rats, because they were markedly influenced by changes in activity and arousal of the animals. Hypotensive haemorrhage resulted in a biphasic tachycardia response, an attenuation of the first SEP component and a reduction of the behavioural response score. Naloxone, 5 mg kg‐1i.v., induced transient bradycardia and a dramatic improvement in arousal test responses, while SEP were not clearly altered. The MAP was kept constant after naloxone injection by adjustments of bleeding and transfusion. Injection of naloxone in unbled control SHR also induced bradycardia but without any changes in SEP and the behavioural responses. The results indicate that naloxone can have beneficial effects in cerebral ischaemia. Possible mechanisms are discusse

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08036.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

During continuous infusion of ethacrynic acid in dogs, changes in glomerular filtration rate (GFR) andPco2at constant plasma bicarbonate concentration (PHCO3) alter bicarbonate and chloride reabsorption in a ratio of 1: 2. This ratio did not apply whenPHCO3was raised by bicarbonate loading in 11 anaesthetized volume‐expanded dogs. A rise inPHCO3from 30 to 54 mM at constantPco2and GFR reduced sodium reabsorption during ethacrynic acid infusion from 3586 ± 725 to 2449 ± 403 μmol min‐1. Bicarbonate and chloride reabsorption were reduced in a ratio of 1: 10. When plasma pH was restored from 7.8 to 7.5 by raisingPco2, the inhibitory effect on chloride reabsorption was halved. At constant plasma pH 7.5 a rise inPHCO3from 20 to 30 mM reduced chloride reabsorption by 20%. A further 30% inhibition was caused by raisingPHCO3from 30 to 54 mM. Bicarbonate reabsorption was highest atPHCO354 suggesting a large capacity for bicarbonate reabsorption ifPHCO3is raised at constant plasma pH 7.5. Water and NaCI reabsorption remaining during ethacrynic acid infusion is almost equally inhibited by alkalosis and by an osmotic effect of unreabsorbed

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08037.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Increasing the haemoglobin concentration ([Hb]) improves the oxygen transport capacity but it also increases the viscosity of the blood. The influence of changes in [Hb]and viscosity on submaximal exercise capacity and maximal aerobic power was investigated in eight healthy males in varying states of training and with a normal resting [Hb] ([Hb]r), ranging from 123 to 178 g]‐1. The subjects were venesected five times (450 ml per unit) and exercise tests were performed in the anaemic state. After 5–7 weeks, when [Hb] had returned to the ‘normal’ value, a stepwise re‐transfusion of three to five units of blood was performed with exercise tests after each transfusion. The [Hb]rwas 137 ± 15 g l‐1in the anaemic state (A) and 170 ± 16 g l‐1after the last re‐transfusion (LT). TheVo2maxrose from 3.94 ± 0.35 in A to 4.68 ± 0.30 1 min‐1after LT. Individual regression lines for [Hb] andVo2maxrevealed a mean increase inVo2maxof 19 ± 6 ml min‐1per g l‐1change in [Hb]. This value did not differ between individuals with high and low normal [Hb]. Furthermore, in intra‐individual comparisons the relationship between [Hb] andVo2maxin high and low individual [Hb] ranges was not found to be statistically different despite a 40% increase in thein vitroviscosity from the anaemic to the polycythaemic state. The average individual correlation (based on five to seven measurements) between [Hb] at rest and after exercise andVo2maxwasr= 0.89 (P>0.01) in the former case andr= 0.92 (P>0.01) in the latter. The running velocity corresponding to a blood lactate concentration of 4 mM (VHla4.0) increased from 15.3 ± 2.3 in the control state to 15.6±2.3 km h1after the last transfusion (P>0.01). A leftward shift of the blood lactate curve, expressed as a percentage ofVo2max, was found. In conclusion, the results obtained indicate a close relationship betweenVo2maxand [Hb] up to at least 170 g l‐1. Furthermore, both inter‐and intra‐individual comparisons suggest that the influence of viscosity as such onVo2maxdoes no

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08038.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The effect of D‐Arg‐1, D‐Trp7,9, Leu11‐substance P (SP) (spantide), a putative SP antagonist, on SP‐induced facilitation of the flexion reflex was examined. The drugs were injected intrathecally (i.t.) in decerebrate, spinalized, unanaesthetized rats. Substance P (10 ng) caused an increase in reflex magnitude for about 5 min. Spantide (10 ng and 100 ng) also caused a facilitation of the reflex that was similar to SP. Spantide (10 ng) plus SP (10 ng) also had a similar excitatory effect. One microgramme of spantide totally blocked the flexion reflex, which could not be reversed by SP, L‐glutamate, L‐aspartate or naloxone. It is concluded that spantide does not have an antagonistic effect on SP‐induced changes in spinal reflex excitability. Some of the effects of i.t. spantide observed in behavioural studies may be due to a non‐specific spinai motor block. It is suggested that the flexion reflex in the decerebrate, spinalized rat is a useful physiological model in studies of the effects of algesic and analgesic drug

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08039.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Beaded dendrites of 1α‐motoneurons intracellularly labelled with horseradish peroxidase (HRP) were studied ultrastructurally in eight adult cats. For comparison, adjacent unlabelled beaded dendrites of unknown origin were also included in the study. Electron microscopy revealed no signs of degeneration or poor fixation according to common criteria. With the exception of the HRP‐reaction product no difference in structure was observed between labelled and unlabelled beaded dendrites. Both the beads and their interconnecting segments were postsynaptic to boutons of normal appearance containing spherical (S‐type boutons) or flattened vesicles (F‐type boutons). The values for synaptic covering and synaptic packing density of the beaded dendritic regions, which usually were located in the periphery of the dendritic trees, were clearly lower than values obtained previously for cell bodies and proximal dendrites of a‐m

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08040.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Plasma concentrations of immunoreactive atrial natriuretic peptide (ANP) was measured in spontaneously hypertensive rats (SHR) during chronic salt loading (1.5% NaCl in drinking water). During the 3‐week experimental period mean arterial blood pressure, heart rate, urinary sodium excretion and body weight was assessed in salt‐loaded as well as in control rats. The sodium excretion was more than lo‐fold increased in the rats on the high salt diet. The plasma ANP concentration was significantly increased only 24h after the start of the high salt intake. Thereafter plasma ANP concentrations were not significantly different from values obtained in control rats. The blood pressure was significantly increased after 3, weeks on the high salt diet. At the end of the 3‐week experimental period the rats were subjected to a 10 and 20% acute volume expansion with homologous whole blood. During this intervention the increase in plasma ANP concentrations was blunted in the high salt rats compared to the control group. It is concluded that during chronic salt loading in SHR there is an initial rise in plasma ANP levels and that other hormonal and neuronal systems are more important in the long term maintenance of fluid and electrolyte

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1987.tb08041.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY