摘要:

The effect of vein pump activation upon superficial venous pressure and blood flow in human skeletal muscle tissue was studied in 7 healthy subjects. Blood flow was measured in the anterior tibia muscle by the local133Xe washout technique. The subjects were placed on a steeply tilted couch in nearly erect position. The vein pump in gastroenemius‐soleus muscles was activated by heel‐raisings. and the anterior tibial muscle remained relaxed during this procedure. Blood flow in the resting anterior tibial muscle was constant before, during and after 20 heel‐raisings per min. A more heavy exercise with 40 heel‐raisings per min increased blood flow about 100%. This increase in blood flow was absent during venous stasis (40 mmHg), and in areas infiltrated with lidocaine. It is concluded, that intense dynamic exercise in gastrocnemius‐soleus muscles, in erect humans, increased blood flow considerably in another crural muscle remaining in the resting state. The present study strongly suggests, that the observed increase in blood flow, was associated with a decrease in regional subfascial venous pressure to below the threshold level of the local sympathetic veno‐arteri

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07015.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The time course of the stiffness during the relaxation period following tetanic stimulation was studied in isolated single muscle fibres of the frog. The stiffness was measured by subjecting the fibres to a sudden stretch at constant velocity from an initial sarcomere length of 2.2 μm, and related to the tension carried by the muscle fibre immediately before the stretch. Both stiffness and tension fell close to the resting level during the first second (4°C) after the end of stimulation. While stiffness and tension fell proportionally during the phase of almost exponential decline in tension following the shoulder in the tension recording, the relative drop in stiffness was less than the relative drop in tension during the preceding phase of almost linear decline in tension corresponding to the first 300–400 ms after the end of stimulat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07016.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

NORESSON, E., THORÉN, P.&HALLBÄCK‐NORLANDER, M.: Performance of the hypertrophied left ventricle in spontaneously hypertensive rats. Effects of adrenergic stimulation. Acta Physiol Scand 1982, 114:497–504. Received 22 May 1981. ISSN 0001–6772. Department of Physiology. University of Goteborg. Sweden.The performance of isolated hearts from adult male spontaneously hypertensive rats (SHR) and matched normotensive controls (NCR) was investigated in an antegrade perfusion system, where preload and afterload could be varied independently. During electrical pacing of the heart to constant heart rate. increases in afterload, but not in preload, considerably raised cardiac contractility, measured as left ventricular max dP/dt. At after‐loads equalling their respective in vivo ones. max dP/dt was similar in SHR and NCR. This indicates that the SHR hearts by myocardial hypertrophy are so well adapted to their raised afterload that an increased inotropic state of the heart is not required. Upon adrenaline addition, SHR and NCR did not differ concerning either “chronotropic sensitivity”, i.e. per cent increase in heart rate of the spontaneously beating heart or in “inotropic sensitivity”, measured as increase in max dP/dt. However, in this in vitro situation adrenaline increased stroke volume only when the hearts worked at reduced inotropism, induced by lowered temperature (30°C). At maximal inotropic stimulation by adrenaline and occluded outflow, the SHR hearts produced higher systolic pressures than the NCR ones. This reveals an increased maximal contractile capacity of the hypertrophied SHR left ventricle, rather than a reduced one as s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07017.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Cardiac output (CO) and blood flow to major organs were investigated in pentobarbital‐anesthetized rats usingH5Sr and141Celabelled mierospheres (MS) of 15mUmdiameter injected into the left ventricle. Changes in organ blood flow and CO were measured after intraventricular dextran (3.4 μmol/kg/min) and intravenous neurotensin (NT) at two differ ent rates, 2.5 nmol/kg/min and 0.125 nmol/kg/min. Dextran, known to give anaphylactoid response in rats, reduced the mean arterial pressure (MAP) from 118±17 to 55±8 mmHg (p<0.001) concomitant with a 56% decline in CO and significant decreases in blood flow to most organs. At 2.5 nmol/kg/min, NT caused a pattern of changes in MAP. CO and organ blood flow similar to that obtained with dextran, and thus consistent with an indirect response via mast cell stimulation. NT injected at 0.125 nmol/kg/min resulted in a significant increase (30%) in blood flow to the small intestine (p<0.01) without changes in MAP or CO. Vascular resistance decreased by 30% in the small intestine (p<0.01) and by 20% in the large intestine (p<0.05). The results show that circulating NT, at concentrations below those eliciting hypotension, enhances intestinal blood flow without significant changes in other or

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07018.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The distribution volumes of125l‐labelled IgG (γ‐immunoglobulin).32P‐labelled VLDL (very light density lipoproteina) (d

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07019.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The contractile properties of twitch muscle fibres in the iliofibularis muscle ofXenopus laeviswith characteristic differences in light‐microscopical appearance have been studied under isometric and isotonic conditions. Type 1 fibres (large. pale) have a short contraction time (te), a shoulder in the relaxation phase, and a high twitch‐tetanus ratio. In type 2 fibres (medium‐to‐large with abundant mitochondria and lipid droplets) teis longer, half‐relaxation time equals te, and the twitch‐tetanus is lower. The capillary density is about 4 times higher for type 2 than for type 1. Computer‐fitted hyperbolic force‐velocity curves gave the following Hill constants (20°C) for type 1 (2) fibres:Po*/Po1.03 (l.15),a/Po*0.48 (0.26),b3.51 (133) Io/s; extrapolated Vmax(0–0.8Po) was 7.60 (6.27) Io/s. Lowered temperature (10°C) increases the curvature of the P‐V relation in type 1 fibres, little effect was seen in type 2. Increased Pco2depressed the isometric tension in both types; in type I fibres theP‐Vrelation became less curved, in type 2 fibres no change in curvature was observed. The results suggest that type 1 and type 2 fibres might contain myosin isozymes with slightly different temperatur

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07020.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

In response to mild stress the levels of immunoreactive β‐endorphin in rat anterior pituitary, hypothalamus and pineal fell within 10 minutes from 210 to 129 pmol/lobe, 1.47 to 0.89 pmol/mg protein and 2.53 to 0.41 pmol/gland, respectively. No alterations were found to take place in β‐endorphin levels in posterior pituitary or plasma. Dexamethasone pre‐treatment given 18 h prior to stress resulted in significantly greater reduction of β‐endorphin levels in hypothalamus and pineal than stress alone—hypothalamic levels fell to 0.73 pmol/mg protein and pineal to 0.07 pmol/gland. Plasma β‐endorphin levels in dexamethasone pretreated stressed rats were significantly lower than in intact rats (42 fmol/ml vs. 98 fmol/ml). The almost complete disappearance of β‐endorphin from the pineal in response to stress and dexamethasone suggests that pineal does not itself synthesize the hormone but only utilizes and/or stores it. Gel filtration analysis of the β‐endorphin im‐munoreactivity in tissue extracts and plasma showed that anterior pituitary and plasma contain three immunoreactive components, eluting like β‐endorphin,βP‐Epotropin and pro‐opiocortin, whereas only β‐endorphin‐like material was detected in posterio

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07021.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The influence of prestretch amplitude on the mechanical efficiency was examined with 5 subjects, who performed 5 different series of vertical jumps, each of which differed with respect to the mechanics of the knee joint action during the prestretch (eccentric) phase of the contact on the floor. Electromyographic activity was recorded from the major extensor muscles during the entire work period of 1 min per series. In addition, expired air was collected during the test and recovery for determination of energy expenditure. Mechanical work was calculated from the vertical displacement of the body during the jumps. The results indicated that high net efficiency of 38.7% was observed in condition where amplitude of knee bending in eccentric phase was small. In large range motion the corresponding net efficiency was 30.1%. In jumps where no prestretching of extensor muscles ocurred the net efficiency was 19.7%. The high efficiency of small amplitude jumps was characterized by low myoelectrical activity of the leg extensor muscles during the positive (concentric) work phase. In addition, the small amplitude jumps had shorter transition time in the stretch‐shortening cycle, high average eccentric force and high stretching speed. Therefore the results suggest that the restitution of elastic energy, which was also related to the length change and stiffness of the muscles during stretch, plays an important role in regulating the mechanical efficiency of wor

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07022.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The tissue fluid equilibration pressure in central and peripheral regions of rat calf muscles has been measured by needles with large smoothed sideholes. Short equilibration periods were normally achieved although saline was not infused. Tissue fluid pressure during rest remained constant at ‐2 to 0 mmHg. During sustained isometric contraction the average tissue fluid pressure rose almost linearly with increasing force of contraction. The average pressure in the central inner zone of the muscle reached 220±80 mmHg during maximal force, whereas the average pressure in the outer peripheral zone increased to 85±56 mmHg, markedly less than in the central zone. Thus, this difference in regional tissue pressure may possibly explain the greater impediment to blood flow in central than in peripheral regions during contraction shown previously by Wisnes&Kirkebø (1976). Although a corresponding regional pressure difference was observed during passive stretch of the muscle, the absolute tissue pressures were much smaller. However, the heterogeneous pattern of muscle fiber directions and relative displacement of various muscle elements during work, may induce shear forces causing focal vessel obstructions that are different during contraction and str

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07023.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

In addition to the utilization of muscle's elastic energy enhancement of performance in exercise involving stretch‐shortening cycle might be also due to simultaneous increase of myoelectrical activity. This hypothesis was tested by examining three athletes during jumping exercise on force‐platform. Vertical jumps were performed with and without preliminary counter‐movement, and the jumps were called counter‐movement jump (CMJ) and squatting jump (SJ), respectively. In both conditions several jumps were performed also with extra loads on the shoulders (15–220% of b. wt.). Additional droppingjumps (DJ) were executed from different heights (20–100 cm). During jumping exercise myoelectrical activity of selected muscles from the quadriceps femoris was monitored with surface electrodes. The results obtained were similar to those reported in isolated muscle and as expected, the prestretch in CMJ shifted the force‐velocity curve of concentric work to the right. In two cases enhancement of performance was attributed primarily to restitution of elastic energy because myoelectrical activity was similar to that observed in SJ. In one subject increased myoelectrical activity was observed during the concentric phase of CMJ. In DJ condition the EMG activity during eccentric phase was much higher than in SJ. Therefore the high performance in this condition was attributed to both elastic energy and reflex potentiation. In eccentric work of CMJ the average force decreased with the increase of stretching speed. This phenomenon was associated with a light increase of EMG activity. The observed results emphasize that both elastic energy and reflex potentiation may operate effectively during stretch‐shortening

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07024.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY