摘要:

An experimental model used with the intention of mimicking the ischaemic condition in patients with arterial obliterative disease was evaluated. The influence of reduced effective perfusion pressure by increased external pressure on leg blood flow and metabolism was determined during exercise in 10 healthy subjects. Catheters were inserted into the right femoral artery and vein and into the left femoral vein. Supine one‐legged (n= 5) or two‐legged (n= 5) cycle exercise was performed with the subject's legs in a pressure chamber. Zero and three different levels of local supra‐atmospheric pressure were applied over the legs: 30, 50 and 60 mmHg. Three submaximal work loads were used: 24, 48 and 72 W/leg. Leg blood flow was measured by the constant‐infusion dye‐dilution technique. Samples were also drawn from the femoral artery and vein for oxygen saturation and lactate determinations and arterial pressure was recorded. Exercise blood flow decreased progressively with increasing chamber pressure (P<0.001). Exposure to 50 mmHg over the working leg led to a mean reduction of blood flow by 16% and venous oxygen saturation by 12 percentage units (P<0.05). Lactate release increased with increasing pressure (P<0.05). In summary, local application of moderate positive external pressure over the working leg reduces blood flow in a ‘dose‐dependent’ manner, and as a consequence, femoral venous oxygen saturation decreases and lactate release increases. Thus, this method makes it possible to induce graded ischaemia in human skeletal muscle during exercise in a con

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09386.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

[31P]magnetic resonance spectroscopy was used to study the metabolic sequelae of intense muscular activity in gastrocnemius of seven subjects 1–2 days after a 67‐mile bicycle ride. The muscle was examined at rest, during a test exercise and during recovery from test exercise. Post‐ride and pre‐ride results were compared. At rest, the ratio of phosphocreatine to ATP (PCr/ATP) was increased post‐ride; during test exercise PCr/(PCr + Pi) was lower post‐ride; and the recoveries of PCr, Pi and PCr/(PCr + Pi) after test exercise were delayed, with decreased ‘overshoot’ of PCr/(PCr + Pi) (which is due to recovery of Pi to below its resting value). Mild mitochondrial damage (perhaps due to exposure to high cytosolic [Pi]during the bicycle ride) may explain some of these results. In contrast to reports of largely eccentric exercise there was no increase in resting Pi/ATP. We have thus demonstrated perturbations of muscle bio‐energetics 1–2 days after strenuous exercise, in the absence of convincing enzymological eviden

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09387.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

We used31P magnetic resonance spectroscopy to study changes in phosphorus metabolite concentrations in rat skeletal muscle during respiratory acidosis (14 and 20% inspired CO2) and recovery. As intracellular pH fell (from 7.05 to 6.75 after 20 min of 20% CO2), intracellular [Pi] increased by up to 50% while phosphocreatine concentration decreased by up to 8%. The sum of all intracellular phosphates remained constant. [ADP]decreased by up to 40% in accordance with the creatine kinase equilibrium but the phosphorylation potential [ATP]/([ADP][Pi]) was preserved as a result of increased [Pi]. This adjustment may be a mechanism for maintaining mitochondrial ATP synthesis despite low pH. Eventually this increase in cellular [Pi] could lead to slow efflux of Pifrom the skeletal muscle cell contributing to the hyperphosphataemia of acute respiratory acidosis.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09388.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

This study analyses the effects of Amrinone (bipyridine derivative with phosphodiesterase inhibitor properties) on the myofibrillar apparatus of rat myocardium.Thin trabeculae were isolated from the right ventricle and chemically demembranated. Force development and shortening velocity were measured during maximal calcium activations (pCa = 4.45) in control conditions and in the presence of 1–3 mM Amrinone. Maximum shortening velocity was obtained both from extrapolation of the force‐velocity curve and with the slack test method. Amrinone was found to significantly reduce maximum shortening velocity and force development.Myofibrils and myosin were prepared from rat ventricular myocardium and their ATPase activity was assessed in control conditions and in the presence of Amrinone (0.3–6 mM). Ca–Mg dependent myofibrillar ATPase activity which was determined at low ionic strength was depressed by Amrinone in a dose‐dependent way. Ca‐stimulated ATPase activity determined at high ionic strength in myofibril or myosin preparations was not affected. Furthermore, Amrinone did not influence the pCa‐ATPase activity curve of the myofibrillar preparations. A comparison between the inhibitory effects of Amrinone on myofibrils prepared from euthyroid rats and myofibrils prepared from hypothyroid rats was carried out. The ATPase activity was significantly less depressed in myofibrils prepared from hypothyroid rats than in those prepared from euthyroid rats.These results provide the first evidence of an effect of Amrinone on ATP splitting and force generation in the myofilament system of c

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09389.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Human atrial muscle preparations obtained during open heart surgery were mounted in a sucrose gap. Force and membrane currents were recorded during voltage clamp. After a 20‐s rest, 10 clamps from a holding potential of –40 to 0 mV at 1.0 Hz were given. This was followed by a test clamp (called 1) of a varied duration and amplitude and two more test clamps (called 2 and 3) as during the priming period. Peak force of contraction 1 (Fl) was independent of clamp duration from 2 s to about 100 ms but declined at shorter durations. Peak force of contraction 2 (F2) and 3 (F3) increased with the duration and became potentiated. Increasing the clamp amplitude raised F1 to an optimum value at about + 10 mV and there was a decline at higher voltages. Both F2 and F3 increased at higher amplitudes. A conventional bell‐shaped current‐voltage relation for the second inward current was obtained during clamp 1 with maximum inward current around –10 mV. In control experiments on isolated human myocytes peak current was recorded at somewhat more positive potentials. The relation between F3 and F2 was linear both when duration and amplitude of clamp 1 was varied. The slope of the line, interpreted as a measure of recirculation of activator calcium, was 0.4. It is concluded that force during voltage clamp in human atrial muscle is similarly related to membrane voltage as previously reported for guinea pig and ferret pre

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09390.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A study was performed to elucidate how different impulse frequencies and impulse patterns in cutaneous nociceptive fibres influence the subjective magnitude of pain. Groups of nociceptive Aδand C fibres were co‐activated by electrical intraneural stimulation at constant intensity in cutaneous fascicles of the peroneal nerve in healthy human subjects. The resulting pain sensations were rated on a modified visual analogue scale. Five‐second trains were administered randomly at irregular intervals of at least 30 s. Five of the stimulus patterns had regular interpulse intervals, corresponding to frequencies of 1, 2, 4, 10 and 15 Hz, and three other patterns were constructed to mimic to some extent the initially phasic and subsequently slowly adapting discharge patterns which may be encountered in recordings from human nociceptors. The results from these experiments using stimulation frequencies within physiological discharge ranges for human nociceptors indicate that the subjective magnitude of pain increases monotonously as a function of stimulus frequency, and that patterns mimicking nociceptor discharges in response to natural stimuli give rise to greater peak magnitudes of pain than artificial regular patterns with a corresponding number of impu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09391.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Field potentials and single cell activity evoked by tooth pulp (TP) stimulation were studied in the ventrobasal (VB) complex of the cat. The experiments were performed using a conditioning‐test paradigm. Evoked cell activity or field potentials following TP stimulation was used as a test. Conditioning stimulus was given to different regions of the thalamic central lateral nucleus (CL). Conditioning electrical stimulation in medial (ML 2.8‐3.6 mm) parts of CL induced a depression of the TP evoked response in 10 cells. Stimulation sites in lateral CL (ML 3.6‐4.2 mm) induced facilitation in eight cells and decreased activity in seven cells. Tooth pulp evoked field potentials in thalamus were facilitated by a preceding stimulation in lateral CL. Cells in the lateral parts of CL are suggested to induce an increased activity in cells in the VB complex which mediate nociceptive information. This effect is suggested to be mediated via a CL induced disinhibition at a reticular thalamic (RE) or at a VB complex level. The medial parts of CL seem to give a traditional feedback inhibition on VB cells. Such an effect is also suggested to be mediated via the RE complex. The importance of these findings are discussed with relation to changes in the thalamus that may occur following long lasting nociceptive stimul

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09392.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The aim of the study was to evaluate from the ethical point of view the importance of transient muscular jerks commonly exhibited by swine at an early stage of pre‐slaughter CO2anaesthesia.The influence of 5 min restraint upon plasma concentrations of adrenaline (A) and noradrenaline (NA) was studied in swine (n= 6) before and after bilateral lesioning of the amygdaloid region of the brain, as were the motor reactions of the same and three other animals during 1 min exposure to 80% CO2. The A and NA responses to the restraint became almost extinguished after amygdaloid lesioning in three of the animals, were reduced by about 50% in one swine, whereas no reduction was seen in the other two animals investigated. The amygdaloid lesioning did not visibly influence the latency for, and the duration and intensity of the muscular jerks manifested by the swine during the CO2‐exposure.The results do not favour the possibility that transient motor reactions exhibited by swine during pre‐slaughter CO2‐exposure are manifestations of emotional stress. Instead, the study indirectly supports the idea that the cause of the muscular jerks may be disinhibition of subcortical motor centres being inactivated by the CO2‐anaesthesia somewhat later than neocortical cells normally exerting the i

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09393.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effects of 4‐aminopyridine (4‐AP) and tetraethylammonium (TEA) on the outward potassium currents in the rapidly and slowly adapting stretch receptor neurons (SRNs) of the crayfish (Pacifastacus leniusculus) were studied using a two micro‐electrode voltage‐clamp technique. The leakage current was not affected by either 4‐AP or TEA. External 4‐AP blocked the peak outward current in a dose‐dependent manner (1:1 stoichiometry) with an apparent dissociation constant (Kd) of 2.3 ± 0.2 mm (mean ± SEM) in the slowly and 1.4 ± 0.2 mm in the rapidly adapting SRN, the block being voltage dependent. External application of TEA resulted in a block of the steady state current enhancing the transient characteristics of the current response. The block appeared to deviate from a 1: 1 stoichiometry and the apparentKdfor TEA was 9.6 ± 3.4 mm with a cooperativity factorn= 0.43 ± 0.03 in the slowly adapting SRN and 34.5 ± 9.2 mm and 0.37 ± 0.03 respectively in the rapidly adapting SRN. Low Ca2+, apamin and charybdotoxin, which are known to block Ca2+‐dependent K‐currents, had no effects on the outward current as was also the case with catechol.It is concluded that the different effects of TEA and 4‐AP on the outward current in the two types of SRNs can be explained by the presence of at least two, probably heteromultimeric, channel populations having similar sensitivity to 4‐AP but different sensitivity to TEA. One channel has a high affinity (Kd= 0.8–1.6 mm) for TEA and the other a low affinity (Kd= 173–213 mm) for TEA. The low‐affinity channel seems to dominate in the slowly adapting SRN while both channels are equally common in the rapidly adapting SRN. Further, the present results do not support the existence of a macroscopic Ca

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09394.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Binding of iodinated IGF‐I to tissue sections from regenerating muscle was studied by autoradiography in normal and in hypophysectomized rats. Binding of IGF‐I was low in control muscle in both groups of animals, but increased transiently about 10‐fold during regeneration after injury. Maximal binding occurred later in hypophysectomized rats than in control rats, and there was also a slower regeneration process in these animals. IGF‐I, as demonstrated by immunohistochemistry, and IGF‐I mRNA, as demonstrated byin situhybridization, were expressed by the regenerating muscle cells in both groups of animals. It is concluded that locally produced IGF‐I is the most likely ligand for IGF‐I receptors during muscle

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1992.tb09395.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY