摘要:

This study investigated isokinetic peak‐ and angle‐specific hamstring/quadriceps strength ratios (conventional H/Q ratio) obtained during concentric and eccentric muscle contraction and examined the influence of joint angular velocity and the effect of gravity correction on these ratios. Also, a ‘functional’ H/Q ratio was defined by calculating eccentric hamstring strength relative to concentric quadriceps strength (Heee/Qeonrepresentative for knee extension) and calculating concentric hamstring strength relative to eccentric quadriceps strength (Heon/Qeeerepresentative for knee flexion). TheH/Qratio was calculated based on isokinetic peak moment and 50o‐moment (0o= full extension) obtained at joint angular velocities 30, 120 and 240os‐1. Gravity corrected conventional H/Q ratio remained constant across speeds and contraction mode, ranging from 0.47 to 0.54 and from 0.49 to 0.56 based on peak and 50omoment, respectively. In contrast, non‐correctedH/Q_ratio increased during concentric contraction from 0.58 at 30os‐1to 0.74 at 240os‐1(P<0.01). For knee extension at 240os‐1an Heee/Qeonof 1.05 (peak) and 0.89 (50o) was observed while for flexion at 240os‐1an Heon/Qeeeof 0.27 (peak) and 0.28 (50o) was observed. In conclusion, gravity correction had high influence on the change inH/Qratio with variation in extension velocity. A potential 1:1 hamstring/quadriceps strength relationship was demonstrated for fast knee extension, indicating a significant functional capacity of the hamstring muscles for providing muscular stability at the knee joi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09927.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In order to evaluate adaptational changes in vascular function in congestive heart failure (CHF), we studied the contractile responses of isolated arterial and venous blood vessels from rats suffering from CHF induced by coronary artery ligature, resulting in a myocardial infarction. The contractile responses of the basilar, femoral and renal arteries and of the iliac vein were examined in relation to adrenergic and neuropeptide Y (NPY) receptor function by the action of the α1agonist phenylephrine, the α2agonist clonidine and NPY. The contractile force was measured (in mN) and in% of K+‐induced contraction as well as pD2to each agonist. When stimulated by a 60 mM K+‐buffer solution, the femoral and renal arteries from CHF rats responded with a stronger contraction (Emax; 9.4 ± 0.6 and 9.8 ± 0.6mN) than the corresponding Sham vessels (Emax; 6.2 ± 0.7 and 5.6 ± 0.4 mN respectively,P<0.001). On the contrary, the iliac vein of CHF responded less to K+than the Sham iliac vein (Emas2.5 ± 0.2 and 3.7 ± 0.5 mN,P<0.01). The CHF iliac vein responded with a weaker contraction when stimulated with phenylephrine (Emax1.9 ± 0.4 mN) and showed a lower sensitivity (pD25.6 ± 0.1) than the corresponding sham vessel (Emax5.7 ± 2.3mN and pD26.3 ± 0.5,P<0.05). The CHF renal artery was less sensitive to clonidine (pD26.4 ± 0.6) than the Sham renal artery (pD27.2 ± 0.1,P<0.05). The results indicate differences between CHF and Sham vessel segments according to both contractile capacity induced by K+‐depolarization and to agonist induced contractile capacity and sensitivity. The differences are not of general nature but vary according to the va

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09928.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Skeletal muscle metabolic abnormalities exist in chronic heart failure. The influence of physical training on muscle metabolism after myocardial infarction was studied in a rat model.31P magnetic resonance spectroscopy and enzyme assays were performed in Wistar rats 12 weeks after coronary artery ligation. Infarcted rats were allocated randomly to either 6 weeks of training or non‐training. Spectra were collected from the calf muscles during sciatic nerve stimulation at 2 Hz. Fibre typing and enzymatic assays were performed on the muscles of the contralateral non stimulated leg. Post‐mortem rats were also divided into severe and moderate heart failure according to the lung weight per body weight. At 200 g twitch tension, phosphocreatine and pH were found to be significantly lower in the non‐trained severe heart failure group compared with the other groups. Phosphocreatine recovery half‐time was significantly longer in the non‐trained group with severe heart failure and correlated with the citrate synthase activity in the muscle. The training did not induce a change in the enzyme activities in the infarcted animals with moderate heart failure but did correct the lower citrate synthase activity in the non‐trained severe heart failure animals. This normalization of muscle metabolism was achieved by training without any change in calf muscle mass, making atrophy unlikely to be the sole cause of the metabolic changes in heart failure. Training in rats with severe heart failure can reverse the abnormalities of skeletal muscle metabolism, implicating decreased physical activity in the aetiology of th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09929.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The binding of fluorescein‐labelled recombinant human platelet factor 4 (rhPF4) to the vasculature of the hamster cheek pouchin vivowas compared with that to cultured endothelial cells (EC) from human umbilical veins (HUVEC) and arteries (HUAEC) and from human aorta (HAEC).In vivodata: systemically injected rhPF4 rapidly disappeared from plasma in a biphasic pattern (t1= 2 and 41 min). High intensity non‐uniform binding of rhPF4 occurred at short specific sites along both arterioles and venules. The length of the intense sites was 76 + 46/xm and their frequency was 10 ± 4 per cm2cheek pouch. Heparin was injected at 4 and 9 min, but not 30 min, post‐rhPF4 displaced most of the high intensity labelling indicating internalization with time. Neither pretreatment with more than 50‐fold excess of unlabelled rhPF4 nor histamine‐ or LTB4‐induced vascular macromolecular leakage changed the frequency of short intense sites.In vitrodata: uniform time‐dependent intense binding of rhPF4 occurred in a similar fashion in subconfluent HUVEC, HUAEC and HAEC. All cell types showed nuclear staining, demonstrating internalization. When heparin was given to EC prior to rhPF4, binding was delayed in time but not blocked.In conclusion, rhPF4 does not bind uniformly with high intensity along pre‐ and post‐capillary vessels of the hamster cheek pouchin vivoas predicted by the rhPF4‐labelling of subconfluent (migrating/proliferating) human ECin vitro.The short infrequent sites of intense rhPF4‐labellingin vivomay represent regions of endothelial cell migration/proliferation similar to subc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09930.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effects of pre‐treatment with mannitol and the iron chelator desferrioxamine on oxygen radical formation and glomerular and tubular function 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 mannitol or desferrioxamine given before ischaemia and before recirculation reduced the radical production significantly. The iron chelator appeared to be more effective. Glomerular function measured 48 h after reperfusion was significantly better after pretreatment with desferrioxamine and mannitol compared with mannitol alone. Tubular function did not differ between the two pre‐treatment gro

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09931.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The electrically evoked isokinetic torque‐velocity relationship of the triceps surae of eight elderly and four non‐trained young men was examined in relation to the isomyosin composition of the soleus and the gastrocnemius muscles, determined under non‐denaturing conditions using pyrophosphate gel electrophoresis. The angle specific torque‐velocity properties of the triceps surae were measured using maximal percutaneous electrical stimulation at 50 Hz and a release technique. The elderly subjects generated significantly (P<0.05) less absolute torque at all angular velocities when compared with the young subjects. When the isokinetic data were normalized to the isometric torque, the lower normalized torques generated by the elderly subjects were not statistically different from the young. The total fast isomyosin (FM) content of the soleus and gastrocnemius in the elderly subjects was 22 ± 13 and 35 ± 18%, respectively. This compared with 29 ± 8 (n.s.) and 44 ± 8% (n.s.) in the young subjects. When the gastrocnemius and soleus muscles were given an equal weighting and considered together to represent the whole triceps surae, the normalized torque at the fixed angular velocity of 5 rad s‐1was significantly associated with%FM (r = 0.90,P<0.01), and the isomyosin bands%FM1 (r = 0.90,P<0.01) and%FM2 (r = 0.93,P<0.001) when only the elderly subjects were considered. No relationships were observed between contractile characteristics and contractile protein profile when only the young subjects were considered. This was despite the inclusion of a further two sprint and three endurance trained athletes to increase the range of contractile characteristics and differences in muscl

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09932.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Endurance training is known to increase ventricular performance during exercise and to decrease resting heart rate. The aim of this study was to evaluate a model for endurance training in rabbits and to study the effects of endurance training on local myocardial performance in the left ventricle during resting conditions. One group of rabbits underwent a 10‐week exercise training programme. The rabbits trained 5 days a week on a treadmill. Training periods increased gradually from 15 min to 1 h with increments in speed from 0.5 to 1.2 km h1. After the training programme the rabbits were anaesthetized and studied as acute open‐chest preparations. A micro‐tip pressure transducer was introduced via apex to the left ventricle and two pairs of ultrasonic crystals were implanted in the left anterior wall to measure segment lengths. One pair measured shortening in the circumferential direction whereas the other pair measured shortening in the longitudinal direction. Heart rate was lower in the trained group (n = 5), 172 + 9 beats min“‘ (mean±SEM), compared with 235 ± 19 beats min ’ in the control group (n = 8) (P<0.02). Stroke volume, measured by radio‐nuclidelabelled microspheres, was greater in the trained rabbits compared with controls (P<0.03). Shortening in both segments was of similar magnitude for the trained and control groups. End‐systolic pressure‐length relations (ESPLR) obtained by occlusion of the descending aorta (balloon catheter) showed reduced slopes for longitudinal segments in the trained group compared with the control group (P<0.05). We conclude that this endurance training programme in rabbits can be used to study myocardial effects of endurance training. Furthermore, the less steep slope of ESPLRs for the longitudinal segment in the trained animals might indicate a structural myocardial remodelling and increased contractile reserve that might be recruited during adrenergic stimulation i

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09933.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Previous work has shown that the plasma levels of the potent vasoactive peptide endothelin (ET) are increased in pathophysiological conditions with increased pulmonary vascular resistance and it has been speculated that ET may play some part in hypoxic pulmonary hypertension. We have therefore evaluated the effects of ET‐infusion in the porcine pulmonary circulation after hypoxia‐induced hypertension.Pigs under general anaesthesia were artificially ventilated through an endotracheal tube and hypoxia was induced by decreasing the fraction inhaled 02from 0.21 to 0.10. Haemodynamic parameters were continuously recorded using a Swan‐Ganz catheter in combination with thermodilution for cardiac output measurements. ET‐1 or ET‐3 was given as an i.v. infusion through the Swan‐Ganz catheter in the right ventricle.Hypoxia induced a reproducible increase in pulmonary vascular resistance (PVR), mean pulmonary artery pressure (MPAP) and right ventricular stroke work (RVSW) while the systemic vascular resistance (SVR) slightly decreased. Cumulative infusion of ET‐1 (10, 25 and 50 ng kg‐1min‐1) dose‐dependently decreased MPAP and PVR; at a higher dose (100 ng kg‐1min‐1), the PVR returned to the level observed at hypoxia. ET‐infusions at 50 and 100 ng kg‐1min‐1evoked an increase in SVR and a decrease in cardiac output (CO) and stroke volume (SV). RVSW also gradually decreased during ET‐1 infusion. Infusion of ET‐3 evoked effects similar to those of ET‐1 infusions, although the response to ET‐3 was not that rapid in onset. In a second series of animals, repeated 15 min periods of hypoxia evoked a stable, reproducible response with a consistent increase in PVR, MPAP and RVSW which returned to baseline values during normoxia. Infusion of ET‐1 (25 ng kg‐1min‐1) evoked a rapidly developing decrease in PVR and MPAP which was quickly normalized upon cessation of the ET‐infusion. ET‐1 infusion at this concentration did notper seinfluence the haemodynamic parameters during normoxia.It is concluded that in the pig, short‐term ET‐infusion reduces the p

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09934.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The purpose of this study was to assess the effects of acclimatization to extreme altitude on the cardiovascular system, using vagal and adrenergic blockade and acute restoration of normoxia during exercise to maximum with one and two legs. Fourteen climbers on an expedition to the Himalayas were studied at a lower base camp (5250 m) following 56–81 days at altitudes between 5250 and 8700 m. After acclimatization, peak heart rate (HRpeak), oxygen uptake (o2k) and noradrenaline (NA) were similar during maximal one‐ and two‐legged cycling, whereas peak plasma lactate was higher during the one‐legged protocol. HRpeak(range 113–168 beats min“1) was lowest when subjects returned from the higher camps. The degree of partial restoration of HRpeakto more normal values within seconds of 60% 02inhalation (range 5–35 beats min˜lHRpeakincrease) was greatest in subjects with low HRpeak. HR responses to /?‐l blockade increased as a function of HRpeakand the HR responses to atropine were the least in subjects with high HRpeak‐ These findings suggest that (a) the reduction in HRpeakis linked to the duration and severity of the hypoxaemia, (b) the degree of restoration of HRpeakwith acute normoxia is dependent on the level of attenuation or down‐regulation of cardiac sympathetic activation (SNA), (c) cardiac vagal drive is masked to a lesser extent in chronic hypoxia because of attenuated SNA and lower HRpeakvalues, and (d) the lower blood lactate levels at altitude is a function of muscle mass involvement rather than adrenergic activation, as normal peak values were reached during exercise with

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09935.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.tb09936.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY