ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09802.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Cells in posterior parts of the cat thalamus were investigated. Responses in single units excited by electrical stimulation in the lateral funiculus (LF), the dorsal column nucleus (DCN) or the canine tooth pulp (TP) were analysed. All cells had a spontaneous resting activity which could be increased by extracellular iontophoretic application of DL‐homocysteic acid (DLH) and decreased by gamma‐aminobutyric acid (GABA). No effect on the spontaneous firing rate was observed following iontophoresis of the selective GABA‐antagonists, picrotoxin (GABA‐A receptor antagonist) or saclofen (GABA‐B receptor antagonist). However, the decreased firing following GABA application was partially blocked by picrotoxin but not by saclofen. A phasic inhibition induced by DCN stimulation in nociceptive thalamic cells is indicated since simultaneous administration of picrotoxin increased the evoked response. This type of inhibitory mechanism could not be detected following LF or TP stimulation. The extracellular activity evoked by electrical stimulation of LF or TP was significantly depressed by preceding electrical stimulation in the DCN. This inhibition was reversed by simultaneous administration of picrotoxin, indicating an involvement of GABA‐A receptors. The reversal of the DCN‐induced depression of the late responses following LF stimulation occurred after application of saclofen. It is suggested that this effect is partly mediated via GABA‐B receptors. Results from the present study indicate an interaction in the thalamus between presumed low‐threshold (DCN) and presumed nociceptive afferents (LF and TP) similar to that previously described i

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09803.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In humans, cardiovascular adjustment to simulated diving causes a marked increase in sympathetic outflow to intramuscular vessels and muscle vasoconstriction. Skin vasoconstriction in the hand also occurs during diving in humans. Skin nerve sympathetic activity (SSA), containing vasoconstrictor signals to glabrous skin, unexpectedly was reduced during diving in a previous study of SSA recorded in the peroneal nerve. SSA was recorded by microneurography in the median nerve in 13 healthy volunteers during simulated diving. Skin blood flow in the hand and one finger was monitored. The typical SSA response, irrespective of duration of diving and water temperature, was an increase during the control period immediately prior to immersion of the face and a sudden reduction of SSA when the face was immersed. The increase in SSA preceding the dive was accompanied by vasoconstriction, which continued during the dive, but re‐dilation regularly occurred before the end of the dive. Inhibition of SSA was not total. Mental arithmetic during diving evoked strong bursts of SSA, similar to those seen normally during mental stress. It is concluded that the true response of SSA to simulated diving is an inhibition of the immediately preceding outflow, in agreement with observations of cutaneous blood flow in animals. The skin vasoconstriction recorded during simulated diving is a consequence of an SSA increase before the procedure, suggested to be a stress response before the forthcoming manoeuvre. The SSA response during simulated diving is the opposite to that of sympathetic outflow to muscle, which emphasizes the diversity of sympathetic regulation of different organ system

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09804.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

We tested the hypothesis that palmar and plantar sweating has a thermoregulatory role and is mediated by the same thermoregulatory mechanisms that control sweating in the rest of the body surface. In a series of empirical tests involving 34 participants (five of whom exhibited palmar hyperhydrosis), the effect of high environmental temperature on sweating was examined. Wilcott's finding, that effects at the palm are of considerable magnitude, was confirmed only in subjects who were in a state of excitement. In relaxed subjects, the effect of high environmental temperature on palmar and plantar sweating was negligible. We conclude that the palms and soles do not directly participate in thermoregulation.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09805.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

This study investigated changes in intramuscular fluid pressure (IMP), torque and swelling related to delayed onset muscle soreness (DOMS) of the vastus lateralis muscle. IMP was measured via catheterization in the unstretched (0°, full extension) and stretched (90° of knee flexion) muscle at rest; then IMP and knee extension torque were determined during maximal contractions pre and 2 d after (post) repetitive eccentric activity in one leg for eight male subjects. DOMS of the vastus lateralis muscle was associated with a significant elevation in IMP at rest as indicated by pre (0°: 5.4 mmHg, 90°:80mmHg) and post (0°:8.4mmHg, 90°: 13.2 mmHg) comparisons (P =0.02). Soreness symptoms were aggravated when the muscle was stretched and this was accompanied by a significantly higher post IMP at 90° vs. 0° (P= 0.01). During maximal contractions, peak torque declined by 15% relative to pre and peak IMP declined by 26%; DOMS symptoms, however, were most severe during this manoeuvre. Biopsies from the sore vastus lateralis muscle revealed significantly larger fibre areas for all fibre types as compared with contralateral controls (P<0.01); however, no differences were detected for extracellular volume percent comparisons. This study shows that DOMS of the vastus lateralis muscle is associated with extensive intracellular swelling and with elevated IMP. In line with previous studies, fibre swelling may be a common subsequence to repetitive eccentric activity; the ability of IMP measurements to detect this swelling at rest and during various manoeuvres for other muscles may depend on compartmental com

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09806.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

This study examined the influence of reduced oxygen availability on the ability to perform repeated bouts of high intensity exercise on a cycle ergometer. Seven male physical education students performed 10 exercise bouts (of 6 s each), interspersed with 30‐s recovery periods, under hypoxic and normoxic conditions. The hypoxic condition was carried out in a low pressure chamber at 526 mmHg. Subjects were instructed to try to maintain a target pedalling speed of 140 rev min‐1during each exercise period. The mean power output of the first exercise bout was ˜ 950 W. In both experimental conditions, all subjects were able to maintain the target speed for the first 3 s of each of the 10 exercise bouts. During the last 3‐s interval of each exercise period the target speed was not maintained in both conditions over the 10 sprints. However, the reduction was greater in the hypoxic condition (P<0.05). Post‐exercise blood lactate accumulation was higher with hypoxia [10.3 (0.7) vs. 8.5 (0.8) mmol 1‐1P<0.05]. Oxygen uptake, measured during the exercise and recovery periods of sprints 6–9, was lower in the hypoxic condition [3.03 (0.2) vs. 3.19 (0.2) 1 min‐1,P<0.05], These results indicate that a reduction in oxygen availability during high intensity intermittent exercise results in a higher accumulation of blood lactate and a lower oxygen uptake. The ability to maintain a high power outp

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09807.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In a stretch‐shortening cycle (SSC) the concentric muscle action is enhanced by a preceding eccentric muscle action. The hypothesis of the present study is that a preceding isometric action can also have an effect on a following concentric action, but to a lesser degree. A KINetic‐COMmunicator II dynamometer was used to test muscle strength of the plantar flexion of the right foot in 20 healthy women. Maximal voluntary torque measurements were made at different angular velocities (120os‐1and 240os‐1) and the range of motion of the ankle joint was 78–125o. The assessment was based on concentric torque output and EMG recording from the gastrocnemius muscle under three different types of testing conditions (concentric actions with and without preceding eccentric or isometric actions, all with maximal efforts). The results showed that preceding muscle actions led to greater concentric torque output (P<0.01) between 90 and 99oplantar flexion. However, the increase in the concentric action was significantly (P<0.01) larger with eccentric than with isometric preceding action, regardless of velocity. The EMG activity of the concentric action showed unchanged or lower values when preceded by a muscle action. In this model our conclusion is that the main reason for larger concentric torque values after a preceding muscle action is that time is sufficient for maximal muscle tension development; in addition, elastic energy is stored, particularly during the preceding eccentric action. Our results show that the effect of preceding muscle actions should be taken into account when measuring isokinetic muscle strength at relatively small angular

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09808.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effects of sprint training on the contractile properties of human muscle fibres obtained by needle biopsy were investigated. Individual fibres were mechanically skinned and activated by Ca2+‐ and Sr2+‐buffered solutions at pH 7.1, and allocated to distinct populations on the basis of their contractile characteristics. The majority of fibres sampled pre‐training could be separated into the three major fibre groups: Populations I (24/70, 34%), II (25/70, 36%) and III (18/70, 26%), which exhibited characteristics similar to those of histochemically classified type I, IIA and IIB fibres, respectively. The remainder (3/70, 4%) represented another fibre group, with intermediate characteristics. The muscle fibres were also activated by Ca2+at a reduced pH of 6.6, to mimic the intracellular acidification that occurs during intense exercise. Lowering pH increased the threshold for contraction by Ca2+, reduced Ca2+sensitivity, and increased the steepness of the force‐pCa relationship, in all fibres sampled from the three major fibre groups. Maximum force was not significantly reduced in any fibre population. In the post‐training sample, the three major fibre types were present in different proportions: Populations I (10/52, 19%), II (20/52, 38.5%) and III (11/52, 21%). Three other fibre groups sampled in low numbers exhibited contractile characteristics intermediate between Population I and Population II. Following sprint training all of the three main fibre populations exhibited higher thresholds for contraction by, and lower sensitivities to, Sr2+but not Ca2+, compared with the fibres sampled pre‐training. Maximum force was significantly lower in Population II fibres after sprint training. At pH 6.6, post‐trained Population III fibres exhibited even lower Ca2+sensitivity, with concomitant increases in the threshold for contraction and force‐pCa

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09809.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

This reports presents the changing morphological characteristics of collagen and fibroblasts in the soleus and gastrocnemius muscle tendon of female Japanese white rabbits with ageing. The fibroblasts decreased in number per 37 μm2with ageing in each group, and their morphology became longer and more slender through ageing. The mean fibril area and diameter of the collagen fibrils of soleus muscle tendon (SMT) and lateral gastrocnemius muscle tendon (GMT) in 8‐ to 10‐month old rabbits were significantly higher than those of 3‐wk‐old rabbits during growth (P<0.01). The mean area and diameter of collagen fibrils of SMT and GMT decreased during senescence: the values for 4‐ to 5‐yr‐old rabbits were lower than those for 8‐ to 10‐month‐old rabbits, but the difference was not significant. Statistically significant differences in fibril area and diameter between the SMT and GMT were not found during ageing. The number of thick fibrils increased during growth, but decreased in senescence. There were more thin fibrils (30–60 nm) in the 3‐wk‐old rabbits than in the 8‐ to 10‐month old and 4 to 5‐yr‐old groups, and the large‐diameter collagen (300–360 nm) was more abundant in the 8‐ to 10‐month‐old group than in the 3‐wk‐old and 4‐ to 5‐yr‐old groups. Differences in fibril size between slow a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09810.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The role of nerve‐induced release of nitric oxide (NO) as a modulator of neuroeffector transmission was studied in the longitudinal muscle of the guinea pig colon. The biological activity of a vascular relaxing factor released by nerve stimulation was examined in a bioassay cascade system. Furthermore, biochemical measurements of nerve‐induced release of the NO metabolite nitrite (NO2‐) were made with a chemiluminescence technique. Transmural nerve stimulation elicited contractile responses that were partly blocked by atropine and further inhibited after additional application of the tachykinin receptor antagonist CP‐96, 345. The NO‐synthase inhibitorNw‐nitro‐L‐arginine (NOARG) enhanced the nerve‐induced contractions and concomitantly increased the basal degree of contraction (‘tone’). The relaxations obtained by nerve stimulation after treatment with atropine and histamine were inhibited by NOARG. Electrical stimulation of the guinea pig colon released a non‐adrenergic non‐cholinergic (NANC) vascular relaxing factor into the tissue superfusate. The half‐life of this factor down the cascade was the same as that observed with exogenous application of NO NOARG and tetrodotoxin (TTX) inhibited the release of the relaxing factor. During transmural nerve stimulation there was a significant increase in NO/NO2‐release. This increase was inhibited by TTX andNw‐nitro‐L‐arginine methyl ester (L‐NAME). In conclusion, pharmacological analysis as well as bioassay and biochemical measurements suggest that NO is released during nerve stimulation in the guinea pig colon, where

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09811.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY