摘要:

A review of the literature on the relationship of exercise to mental health strongly suggests that the two are closely linked. Thus, physical activity has been reported to reduce depression symptoms and anxiety, and to improve coping with stress. Logically, many investigators have then tried to determine the physiological mechanisms that are responsible for this mood‐elevating effect of exercise. Among the current hypotheses, those regarding the endorphin and the monoamine systems have received a great deal of attention. On that basis, the respective effects of physical exercise on brain dopamine, noradrenaline and serotonin transmission are reviewed herein. In addition, suggestions are advanced for future research in this fiel

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08715.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The rate of glycogen resynthesis was examined in different muscle fibre types after prolonged exhaustive exercise. Six subjects exercised to exhaustion at 75% ofVo2max, and muscle hiopsies were taken after 0, 90 and 180 niin of recovery. Glucose drinks (1.4, 0.7 and 0.7 g kg‐1body wt) were taken at time 0, 60 and 120 min. Photometric determination of periodic acid‐Schiff stain intensity revealed a 65% faster rate of glycogen resynthesis in type IIA and IIAB as compared to type I fibres during the first 90 min. Thereafter no differences between the various fibre types were detected. No digerences in the rate of glycogen resynthesis were observed between the subgroups of type II muscle fibres. These results suggest that there was a slower acceleration of glycogen resynthesis in type I compared to type II fibres. In all fibre types a positive relationship between rate of synthesis and glycogen concentration was observed. It is suggested that the size of the glycogen molecule and hence the number of available terminal glucospl units is a major determinant of rate of resynthe

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08716.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effect of ageing on human skeletal muscle was investigated using needle biopsies from young and aged subjects and from aged subjects trained with different activity patterns. Histochemical staining for myofibrillar ATPase of ageing m. vastus lateralis demonstrated an unchanged fibre type distribution but a selective atrophy of type IIa and type IIb fibres. Analysis of myosin heavy chain (MHC) composition showed that type I MHC increased with ageing (P<0.05). The relative content of the MHC isoforms correlated with the relative area of the respective fibre types. Sarcoplasmic reticulum (SR) proteins were investigated in muscle extracts by electrophoretic and immunoblotting techniques. When compared to a young control group (28 0.1 years old,n =7) blots of post‐myofibrillar supernatant proteins probed with polyclonal antibodies to the rabbit fast SR Ca‐ATPase, a marker of extrajunctional SR, showed that the content of Ca‐ATPase was significantly lower (P<0.05) in the old control group (68 ± 0.5 years old,n= 8). On the other hand the content of calsequestrin (CS), the major intraluminal protein of SR terminal cisternae (TC), and of the 350‐kDa ryanodine‐binding protein, which is localized in the junctional regions of TC, did not show a concomitant decrease. These results suggest that ageing differentially affects extrajunctional and junctional SR of human skeletal muscle. These age‐related changes were not observed within a group of old strength‐tr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08717.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Lactate transport across the sarcolemma of isolated mouse muscles was studied with a14C tracer technique. The cellular tracer uptake could be inhibited by unlabelledl‐lactate (and pyruvate) and to a lesser extent by d‐lactate. The stereospecific fraction had aKmof 3.5 mm, and made up 50% of the total transport. The tracer uptake was unaffected by 0.05 mM DIDS and 0.2 mM amiloride, but was inhibited by cinnamate (Ki= 8 mm) and PCMBS (Ki=0.8 mm). With high concentrations of the latter inhibitor compounds or with high concentrations of unlabelledl‐lactate, the tracer uptake was inhibited 80%, which indicates that the main part of the transport involves facilitated diffusion. The remaining fraction (20%) was non‐saturable, reduced at high pH, and could not be inhibited; it is probably mediated by diffusion of undissociated lactic acid. Lactate transport was pH‐dependent, which is consistent with a lactate‐H+symport. The maximal transport capacity, as calculated from the pH changes measured with pH‐sensitive micro‐electrodes while the lactate gradient was 30 mM, was 11.8 mmol kg

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08718.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Metabolic regulation of contractility in vascular smooth muscle was studied in the spontaneously active rat portal vein using respiratory depression by cyanide (0.2–2.0 mm) as a model for tissue hypoxia. Intracellular recordings of electrical activity were done with concomitant registration of force development. Average membrane potential in the absence of cyanide was ‐ 61 ± 1 mV (n =27). Addition of cyanide to normal Krebs solution resulted in a reduction of force amplitude and the number of action potentials per burst, with a relatively more pronounced effect on the mechanical activity. At moderate levels of inhibition of force amplitude the frequency of spontaneous bursts of action potentials transiently increased concomitant with a slight depolarization, but after prolonged (15–20 min) exposure to cyanide the membrane repolarized to the level prior to cyanide addition and the burst frequency decreased to be equal to or lower than that in the absence of cyanide. Higher concentrations of cyanide totally inhibited spontaneous mechanical and electrical activity. In contrast to the results with glucose, it was found that when p‐hydroxybutyrate was used as substrate the addition of 2 mmcyanide led to a marked hyperpolarization (13 ± 1 mV) after total inhibition of spontaneous activity. The hyperpolarization was not prevented by administration of 4‐aminopyridine (2.5 mm) or tetraethylammonium (44 mm) prior to the addition of cyanide. To investigate the effects of increased metabolic demand on the relation between force and membrane potential in cyanide‐treated muscle, high‐K+(40 mm) contractures were studied. Contractures were associated with depolarization of 34 ± 3 mV (n =5). I mmcyanide reduced the amplitude of the contractures to about 904 of control with a moderate reduction in the amount of depolarization (28 ± 1 mV,n= 5).Ihd is concluded that the decrease of mechanical activithd during respiratory inhibition may partly reflect a reduction in the number of spikes per burst but that other mechanisms, independent of membrane activity, also contribute to the inhibition. The increase of glycolysis during respiratory inhibition seems to prevent more pronounced changes in m

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08719.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effect of eaminopyridine (4‐AP) on the potassium currents in the node of Ranvier in myelinated nerve fibres was investigated with the voltage‐clamp technique. The potential and time dependence of the currents in solutions with a high potassium concentration (114.5 mm) were studied. The block of the tail current was found to be less than that of the corresponding current during a potential step. Also, the time‐course of the tail current was modified. In order to explain these findings, kinetic models of the 4‐AP action were constructed and analysed numerically. A simple four‐state model, in which 4‐AP interacts only with open channels and where the binding is diphasically potential dependent, was found to account for

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08720.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In few systems has the release of coexisting classical and peptide neurotransmitters been studied. Here the release of substance P‐like immunoreactivity (SP‐LI), thyrotropin releasing hormone‐like immunoreactivity (TRH‐LI) and [3H]serotonin ([3H]5‐HT) from tissue slices of rat ventral spinal cord was investigated in a superfusion system. The slices were stimulated electrically with field stimulation (900 pulses, 2 ms duration, 36 V) at frequencies between 0.25 Hz and 40 Hz. The evoked fractional release of SP‐LI increased significantly from 0.46 to 1.24% of the total tissue store when the frequency of stimulation was changed from 3 to 10 Hz, while the evoked fractional release of TRH‐LI increased significantly from 0.28 to 0.71% of the total tissue store with increasing frequency of stimulation between 0.5 and 3 Hz. The evoked fractional release of [3H]5‐HT did not show any significant change when the frequency of stimulation was changed in the frequency range of 0.25–40 Hz but remained between 5.6 and 7.2% of the total tissue store. It appears that at frequencies lower than 0.5–1 Hz these 5‐HT/SP/TRH neurons may function predominantly as serotonergic neurons. At 3 Hz stimulation with 900 pulses the extracellular Ca2+concentration required for half‐maximal release of [3H]5‐HT was 1.2 mmol 1‐‐1, while for half‐maximal release of SP‐LI significantly higher concentrations of Ca2+(4.2 mmol 1‐‐1) would be required. The results demonstrate that the coexisting neurotransmitters substance P, thyrotropin releasing hormone and [3H]serotonin show different dependence on frequency of stimulation for the electrically evokedin‐vitrorelease and suggest that the mechanism of release of these coexisting neurotr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08721.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Unmyelinated C‐fibre responses to electrical stimulation were recorded in common peroneal, sural and tibial nerves of rabbits. Three distinct C elevations, here called C1, C2 and C3, were recorded. C2 is prohbly of somatic origin because it was depressed due to collision by peripheral stimulation of cutaneous receptors. The conduction velocity of C3 corresponded to that of sympathetic post‐ganglionic fibres. During sympathetic trunk stimulation the A‐fibre responses were not significantly changed while C responses, especially C2, were reduced in amplitude and slightly delayed. The C‐fibre responses were also influenced by intra‐arterial infusion of noradrenaline. In most cases, the latency of the response was increased. The effect of sympathetic stimulation was completely blocked by hexamethonium, and partly blocked by phentolamine, an adrenergic a‐receptor blocking agent which also blocked the effect of noradrenaline. The findings suggest that there are adrenergic receptors distributed along unmyelinated somatic afferent fibres. Sympathetic activity may release noradrenaline in the peripheral nerve, resulting in changed conductive properties in unmyelinated fibres transmitting sensory

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08722.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Single afferent unmyelinated fibres were dissected from the otherwise intact sural nerve in anaesthetized rabbits. The sympathetic trunk could be stimulated via electrodes implanted through the abdomen. The response in single C fibres was elicited by electrical stimulation in the cutaneous innervation area of the fibre. Sympathetic stimulation (8 Hz, I ms pulses, 5 mA for 60 s) increased the latency in all tested C fibres (2.0%± 0.87%, mean ± SD,n= 17). In 48% of the units the amplitude of the action potential decreased (26.4% 12.3%) during sympathetic stimulation. Infusion of noradrenaline (5 μg min‐1) increased (7.7%±4.1%) the latency in all units and increased (36.9%± 29.8%) the amplitude of 25% of the units. The effects of sympathetic stimulation and noradrenaline infusion were blocked by pre‐treatment with phentolamine (3 mg kg‐1i. v.). The results suggest that catecholamines change the membrane properties of unmyelina

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08723.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A non‐invasive technique was developed to measure single‐nephron glomerular blood flow (SNGBF) inNecturus maculosus. Erythrocytes labelled with rhodamine, a fluorescent dye, were injected systemically and the frequency at which labelled cells entered an arteriole was measured. Frequency was converted to flow by measuring the concentration of labelled erythrocytes in whole blood. Dependence of SNGBF on flow rate in early distal tubules was used to assess tubuloglomerular feedback (TGF). SNGBF decreased with increasing flow in the early distal tubule in a pattern typical of TGF; SNGBF decreased 25% at the highest flow rates. SNGBF increased when bumetanide was added to the perfusate, but the TGF response to flow rate persisted. IC50(concentration that produces half‐maximal inhibition) was 2.4 × 10‐10, 9.8 × 10‐10and 1.2 × 10‐9m bumetanide at distal perfusion rates of 5, 10 and 20 nl min‐1respectively. These results are consistent with modulation of SNGBF according to the rate of luminal entry of NaCl into early distal tubule cells. This transport rate depends on the luminal concentration of NaCl, which is tubular flow rate‐dependent; NaCl and

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08724.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY