摘要:

High levels (110–120 cmH2O) of lower body negative pressure (LBNP) were used in male volunteers (n =7) to produce pronounced hypovolaemic circulatory stress in an attempt to reveal the potential in man for compensatory absorption of extra vascular fluid from skeletal muscle and skin as studied in the upper arm by plethysmographic technique. LBNP evoked clear‐cut hypovolaemic symptoms or even accidental syncope as well as a marked tachycardiac response and a significant fall in systolic blood pressure. In the studied arm there was concomitantly a very rapid net transcapillary absorption of extravascular fluid into the circulation at an average rate of 0.35 ml min‐1100 mr1soft tissue during 5 min of LBNP exposure. These data demonstrate an amazingly great potential to increase plasma volume by ‘autotransfusion’ of fluid from tissue to blood, as may be visualized by extrapolation of the data from the arm to apply to the whole mass of skeletal muscle and skin in the body. The observed absorption rate would then correspond to a total fluid gain of no less than 700 ml within a period no longer than 5 min. At present, however, there is no evidence to indicate that such impressive fluid volumes can be rapidly transferred from the extra‐ to the intravascular space after actual

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08623.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The capillary filtration coefficient (CFC) in the human forearm, determined with the ‘venous occlusion’ method, was found to be about 0.005 ml rnin‐1100 mh‐1soft tissue mmHg‐1when capillary pressure (Pc) was raised by about 30 mmHg, a finding in accordance with previous literature. With gradually smaller increments ofPc, however, the calculated CFC became gradually larger to reach maximal values of about 0.05 ml min‐1100 ml‐1mmHg‐1at increases in venous pressure that raisedPcby only 1.5–2 mmHg. It is suggested that these high CFC values, obtained at increases of intravascular pressure so low as to ensure minimal interference with the normal circulation, reflect the true prevailing transcapillary hydrodynamic conductivity in the tissue. The low CFC values during high increases in capillary (microvascular) pressure, on the other hand, seem to represent serious underestimations of the true CFC as a result of experimentally induced undesired active smooth muscle constrictor responses and/or passive deterioration of capillary exchange function. The conclusion is therefore reached that CFC in skeletal muscle and skin in man might be about 10 times higher than pr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08624.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In 1985 both Pendergastet al.and Piiperet al.described a major regional heterogeneity in blood flow within single skeletal muscles both at rest and during exercise. Based on the microsphere method they described large variations in blood flow between muscle samples as large as 1 g each.The aims of the present study were:1 To test this notion of regional heterogeneity in microsphere deposition within single skeletal muscles both at rest and during exercise.2 To compare the distribution of microspheres with other blood flow tracers.3 To test whether or not any heterogeneity was due to vasomotion in small arteries or arterioles.Microspheres were infused into anaesthetized rabbits over either 10, 30 or 120 s, or 10 min. Exercise was mimicked by tetanic contractions obtained by electrical stimulation of the motor nerves. Three hindleg muscles were divided into samples of 0.25 g each. Regional heterogeneity was expressed as the coefficient of variation corrected for statistical distribution of microspheres (CVc). The CVc at rest was about 0.34. The CVc was unaffected by the various infusion periods and did not change during exercise. Simultaneous infusions of microspheres and86Rb+or antipyrine gave high correlations between the two blood flow tracers, with allrvalues exceeding 0.83 (n= 18).We conclude that the microsphere method provides reliable estimates for regional blood flow within single skeletal muscles. The distribution of blood flow was markedly heterogeneous both at rest and during exercise. The heterogeneity in blood flow was apparently not a result of vasom

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08625.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The quadriceps muscles from 20–30‐ and 70‐year‐old clinically healthy men and women were studied regarding maximal isometric and isokinetic muscle torque in Newton metres (Nm), morphology and enzyme activity. Biopsy specimens were taken from the vastus lateralis muscle and freeze‐dried, and individual fibres were dissected out and identified as type I or type II. The activities of citrate synthase (CS), 3‐OHacyl‐coA dehydrogenase (HAD), lactate dehydrogenase (LDH), myokinase (MK) and creatine phosphokinase (CPK) were determined in pools of type I and type II fibres. In both age groups a higher oxidative (CS, HAD, 1.3–1.5 x) and a lower glycolytic (LDH, 0.7 x) capacity was found in type I than in type II fibres. The myokinase activity was higher in type II (2 x) than in type I, whereas CPK activity was similar. The young men showed higher CS activity in both type I and type II fibres (1.5 x) and higher CPK activity in type I fibres (1.4 x) than the young women. There were only minor changes in oxidative or glycolytic capacities in relation to age. Myokinase was the only enzyme that decreased markedly with age in both pools of fibre types. Type II fibre area and mean fibre area correlated significantly to muscle torque in both sexes. In men, myokinase activity in type II fibres was significantly correlated to type II fibre area and to maxima

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08626.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The contractile effects of amrinone were studied on twitch and tetanus responses of mouse lumbrical muscles. Amrinone (1.1 mM) increased the maximum force level during the tetanus, reduced the rate of rise of force during the onset of tetanus and prolonged the time from the last stimulus to half‐relaxation. The rate of redevelopment of force after a release during the tetanus plateau was likewise reduced. Amrinone (I.I 0.5 mM) increased the time to peak twitch force and the time to half‐relaxation during the twitch. The peak twitch force was not significantly changed. The force‐velocity relation was markedly affected by amrinone: there was a decrease in maximum velocity of shortening, an increase in maximum isometric force and a decrease in curvature of the force–velocity relation. The results suggest that amrinone modulates the kinetic properties of the myosin cross‐bridges by exerting a specific effect upon the myofilament system. The latter effects are mainly responsible for the contractile changes produced by amrinone in mouse skeletal muscle. Amrinone appears to have little effect on the metabolism of activator calcium in this particular pr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08627.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The co‐ordination between muscles controlling the primary movement and associated postural adjustments during fast trunk extension movements was studied in six male subjects. Myoelectrical activity (EMG) was recorded from antagonistic muscle pairs at the trunk, hip, knee and ankle. Horizontal displacements of the upper trunk, hip and knee were recorded with an opto‐electronic system (Selspot).A backward displacement of the trunk was accompanied by a forward displacement of the hip and knee. In general, the trunk started to move 30 ms before the hip and knee. Muscle activity first appeared in the ankle extensors (soleus/gastrocnemius) up to 150 ms prior to onset of prime mover muscles (trunk extensor, erector spinae; and hip extensors/knee flexors, hamstrings). This pre‐activation was seldom followed by any detectable ankle joint movement. Prime mover muscles were activated simultaneously followed by the hip extensor gluteus maximus. Time to activation of muscles braking the movement (rectus abdominis, rectus femoris and vastus lateralis) was correlated with the amplitude of the primary movement (r =0.63–0.75,P0.01). Onset of activity in vastus lateralis was highly correlated with the amplitude of the forward displacement of the knee (r= 0.93,P0.01). An associated postural adjustment appeared as an ankle flexion accompanied by activity in the ankle flexor tibialis anterior, and often also in the ankle extensors. This co‐activation of antagonistic ankle muscles can under certain conditions have interesting functional implications for the control o

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08628.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Pharmacological experiments were carried out on isolated basilar arteries (BA) from the brain vasculature of guinea‐pig and rat in order to characterize post‐junctional serotonergic receptors mediating contraction by the use of selective agonists and antagonists. The sensitivity to 5‐HT was higher, but the intrinsic activity lower, in guinea‐pig compared to rat vessels. The contractile potency of the 5‐HT1agonist, 5‐carboxamidotryptamine (5‐CT), was three times higher than 5‐HT in guinea‐pig but 16 times lower in rat BA. In arteries from both species the 5‐HT1Aagonist, 8‐hydroxy‐2‐(di‐n‐propylamino)‐tetralin (8‐OH‐DPAT), only caused weak contraction. In rat BA, where the serotonergic contractile receptors are ketanserin‐sensitive, mesulergine inhibited the contraction in doses high enough to block 5‐HT2receptors, and also propranolol slightly inhibited the contraction, probably due to its binding to these receptors. Methiothepin, a potent antagonist of the 5‐HT1‐like receptors, affected the contraction in a non‐competitive manner. The antagonist profile was different in guinea‐pig BA: propranolol was ineffective, mesulergine caused a slight, non‐surmountable inhibition, whereas methiothepin acted as a true, competitive antagonist. The data support previous suggestions that the serotonergic contraction in rat BA is mediated by 5‐HT2receptors, whereas the present data show tha

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08629.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

We investigated the effect of glucose and glucose polymer ingestion on plasma arginine vasopressin (pAVP) levels, on plasma osmolality (p‐osm), and on performance during two prolonged endurance events. The study subjects were 37 Finnish elite endurance athletes, of whom 18 were orienteers and 19 cross‐country skiers. Plasma AVP increased in both combined glucose and glucose polymer groups, but the increase in the glucose polymer group was significantly smaller (P0.001) than that in the glucose group. A significant change in p‐osm caused a significant change in pAVP and vice versa. Both the orienteers and the skiers on glucose polymer tended to have more success in the competition; the orienteers on glucose polymer ran the last third of the competition significantly faster than those on glucose (P0.05). It is suggested, in the light of the smaller pAVP response, that after glucose polymer ingestion the physical stress in prolonged endurance exercise is smaller than after ingestion of gl

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08630.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The concentration of 3,4‐dihydroxyphenylalanine (DOPA) was low in the pancreas, liver, kidney, spleen, salivary glands, heart and adrenal glands of untreated mice, but increased following inhibition of DOPA decarboxylase by 3‐hydroxybenzylhydrazine. The ratio of the accumulation of DOPAtothe concentration of noradrenaline (i.e. the density of sympathetic nerves) was greater in the kidney, liver and, particularly, pancreas than in the other organs studied, suggesting that DOPA occurred outside sympathetic nerves in these organs. The tyrosine hydroxylase inhibitor α‐methyltyrosine almost completely inhibited the accumulation of DOPA in all organs. The DOPA accumulation was enhanced in all organs by the α‐adrenoceptor antagonists phenotolamine and yohimbine. The results indicate that the DOPA was formed in the sympatho‐adrenal system. In the pancreas, liver and kidney, most of the DOPA accumulated might have been formed outside these organs and transferred there via the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08631.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The roles of endothelium‐derived relaxing factor (EDRF) and endothelin in the regulation of vascular tone are intensely studied at present. Since factors which directly affect vascular tone also frequently modulate sympathetic transmitter release, we found it of interest to study whether EDRF or endothelin displays such modulatory activity as well. Isolated rabbit hearts were perfused according to Langendorff, and the release of transmitter induced by sympathetic nerve stimulation was estimated by analysis of the effluent content of noradrenaline (NA) with liquid chromatography. The activity of EDRF spontaneously formed in the heart was counteracted by addition of haemoglobin (Hb, 2.4–15 g l‐1) or facilitated by addition of superoxide dismutase (SOD, 14–140 U ml‐1), to the perfusion solution. In other experiments authentic endothelin (0.1–10 nM) was given to the heart. Nerve stimulation (5 Hz for 30 s) elicited a release of NA into the cardiac effluent amounting to 319 ± 28 pmol (n= 53). Hb lowered the coronary flow to 68± 9% (P0.01) and impaired the outflow of NA to 62 ± 9% of control (P0.01). SOD facilitated coronary flow by 11 ± 4% (P0.005), and augmented the outflow of NA by 15±6% (P0.05). Endothelin dose‐dependently inhibited the coronary flow, with an IC50of about 1 nM, and in parallel decreased the efflux of NA. Mechanical obstruction of the coronary flow induced an attenuation of the efflux of NA that was quantitatively similar to the flow reduction. The data indicate that the efflux of NA from this rabbit heart preparation is closely dependent on the coronary flow rate. EDRF and endothelin seem to affect the efflux of NA by changing coronary flow, but not by direct interference with the process of sympathetic t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08632.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY