摘要:

AbstractThe effects of α‐adrenergic (Phenoxybenzamine) and parasympathetic (Atropin) blockade on the cardiovascular response to diving in the duck has been studied. With no significant reduction in the immediate, slight fall in heart rate, a‐adrenergic blockade caused peripheral vasodilatation, and virtually abolished the more delayed phase of profound bradycardia during diving. Atropinization eliminated both elenients of the diving bradycardia., while the arterial and venous pressure greatly increased, suggesting that intense activation of the vasoconstrictor fibres was maintained during submersion. It is concluded that the gradual but profound intensification of the initial, slight bradycardia in the dividing duck is a matter of a secondary reflex adjustment to the pressure l

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05591.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractMuscle biopsy samples were obtained from the thigh muscle of 4 subjects before and after 2 h of work and at selected intervals during the following 46 h when a carbohydrate enriched diet was consumed. Mean glycogen content declined 103 (from 125 to 22) mmol glucose units × kg‐lfollowing exercise. 5 and 10 h after consuming the carbohydrate enriched diet muscle glycogen increased to 64 and 86 mmol glucose units × kg‐l, respectively. During the first 5 h there was a marked storage of glycogen in the muscle which was related to the carbohydrate intake, but pre‐exercise concentrations of muscle glycogen were observed first after 46 h. The increase in glycogen occurred in both fibre types, but the fast twitch fibres replinished their glycogen somewhat faster than did the slow twitch fibres suggesting a higher glycogen synthetase activity. At glycogen concentrations above 80–90 mmol no differences in the glycogen content of the two fibre types could be discerned with histochemica

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05592.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractImpulses in single muscle spindle afferents from the antebrachial finger flexor muscles were recorded from the median nerve of waking human subjects. The discharge frequency in the steady state was measured as the metacarpo‐phalangeal joint angles were passively changed in steps. At a comfortable resting position of the hand, less than ten percent of the spindle primaries were discharging. Within intermediate ranges of muscle lengths the discharge frequency of the single units did not exceed 20 impulse per second (ips). The response to joint movements was that expected from muscle stretch and muscle release alone and there was no indication of fusimotor adjustments as a result of joint movement. The frequency of the single units increased linearly with joint extension, the mean sensitivity of the primaries being 0.18 ips per degree which is about 5 times lower than the sensitivity of de‐efferented spindles in cat ankle extensors. The afferent discharge from the secondaries was in most respects very similar to that of the primaries. The low discharge frequency, the low percentage of active units and the low position sensitivity all indicate an insignificant fusimotor outflow to relaxed human hand muscles and a comparatively poor ability of the spindles to measure muscle length under these conditi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05593.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractDuring isometric voluntary contractions, the impulse frequency in muscle spindle afferents was analysed in relation to the contraction intensity in man. Single unit impulses from the finger flexor muscles were recorded with percutaneously inserted tungsten needle electrodes from the median nerve. The spindle frequency increased with the contraction intensity. For very weak contractions the increase was steep but levelled off to attain an average slope of 32.8 ips/Nm at the metacarpo‐phalangeal joint for the primaries and 22.8 ips/Nm for the secondaries when the muscles to a single finger were activated. The close relation between spindle frequency and torque suggests parallel modulations of the skeletomotor and the fusimotor outputs during voluntary contractions. The dominating type of fusimotor outflow was of the static type but clear indications of increased dynamic fusimotor outflow were also seen. Quantitative considerations of the spindle frequency as a function of contraction intensity and as a function of muscle length suggest that the muscle spindles and their central connections do not constitute a very powerful mechanism for holding the muscle at constant length when the load varie

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05594.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractRegional cerebral blood flow and cerebral arteriovenous differences in oxygen content were studied in rats provided with a porta‐caval shunt. The arteriovenous oxygen differences decreased, while cerebral blood flow was unchanged. It is concluded that rats with a porta‐caval anastomosis have a reduction in cerebral metabolic rate for oxygen, possibly due to reduced functional dema

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05595.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe influence of arterial hypotension upon the energy state of thc brain was studied in rats with porta‐caval anastomosis by bleeding the animals to mean arterial blood pressures of 45 and 30 mm Hg, respectively. Reduction of blood pressure to 45 mm Hg in shunted rats gave no or only very moderate accumulation of lactate and there were no changes in the contents of ATP, ADP and AMP in frontal lobe or brainstem. At a mean blood pressure of 30 mm Hg shunted animals and controls showed similar values for glycolytic and citric acid cycle intermediates, amino acids and adenine nucleotides in frontal lobe, parietal cortex and Drainstem. It is concluded that the shunting procedure, and the ensuing hyperammonemia, does not adversely affect the sensitivity of the cerebral energy state to arterial hypotensio

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05596.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractRespiratory and circulatory responses to electrical brain stimulation were studied in 30 anesthetized chicken from about 850 histologically verified loci in an attempt 1) to delineate the limits and characterize the response patterns of a thalaniic cardioinhibitory area (Putkonen 1967) and 2) to extend exploration of respiratory and circulatory functions of the avian brain to telecephalic and mesencephalic levels. Apnea or partial respiratory inhibition were obtained from; 1) an anterolateral thalamic field in front and around the nurotundus, 2) the entire course of the quinto‐frontal tract, which was the only forebrain site yielding apnea and from 3) a medial and a lateral mesencephalic area. The apnea from the antero‐lateral thalamus was associated with progressive bradycardia and fall in blood pressure which both could be almost abolished during tracheal infusion of oxygen. Apneic bradycardia from the mesencephalic quinto‐frontal tract was associated with hypertension thus mimicking the “diving reflex”. Varying patterns of respiratory and circulatory activation, often with vocalizations, were obtained from; 1) septal and preoptic areas, 2) medial archistriatal regions, 3) the occipito‐mesencephalic tract and from 4) a large field in the mesencephalic lateral reticular formation. The results are discussed in relation to pertinent literature from birds and mammals with an emphasis on inhibitory

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05597.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effects of denervation on acetylcholine sensitivity and on the electrical properties of frog tonic and phasic muscle fibres were examined by the use of iontophoretic micro‐application of acetylcholine and conventional intracellular techniques for recording and stimulation. In tonic fibres extrajunctional cholinergic sensitivity appeared 4 days after sectioning of the nerve and by 2 weeks the entire membrane had attained a high level of acetylcholine sensitivity. The sensitivity of former end‐plate regions also increased with time. In phasic fibres cholinergic sensitivity appeared about one week later but otherwise followed the same pattern as in tonic fibres. Innervated tonic fibres are incapable of generating action potentials but this property is induced upon denervation. After one week of denervation small spikes were observed in response to depolarizing current pulses and by 2 weeks large action potentials, sometimes followed by repetitive discharges were recorded. Denervation failed to affect the action potential in phasic fibres. Tetrodotoxin completely blocked action potentials in tonic and in phasic fibres. Denervation reduced the effective resistance and the time constant of tonic fibres but had no effect on these properties in phasic fibres. Actinornycin D injected i.p. in a single dose (7.5 or 9.0 μg) failed to prevent the appearance of extrajunctional cholinergic receptors but almost completely blocked the induction of action potentials in denervated tonic fi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05598.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe autonomic mechanisms controlling cardio‐vascular adjustments to diving have been studied in ducks using drugs which block adrenergic a‐receptors (phentolamine) or deplete catechol‐amine stores (reserpine). In animals thus treated there was a marked change in the cardiovascular reflex pattern upon diving. The vasoconstrictor response regularly seen in normal, submerged animals appeared to be abolished, and the diving bradycardia was only poorly developed. As a consequence, the treated animals had lost their capability to endure submersion for prolonged periods of time, the catecholamine depleter being more effective in this respect than the α‐receptor blocking agent. However, if noradrenaline was administered to a submerged animal pre‐treated with reserpine, peripheral vasoconstriction and bradycardia took place momentarily. It is concluded that the initial, quick slowing of the heart, which takes place upon submersion, results from an immediate parasympathetic activity associated with the reflex apnoea. The profound diving bradycardia gradually developing may be due to baroreceptor stimulation related to the peripheral vasoco

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05599.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractMembrane potentials and contraction curves of different types of rat muscle fibre have been studied at body and room temperatures with special regard to the effects of repetitive stimulation. Fast fibres (from the surface of the extensor muscles of the antebrachium) have a higher resting membrane potential, a higher amplitude and shorter duration of the spike of the action potential and a larger early negative after‐potential than soleus fibres. In the fast fibres stimulation at 10 Hz for 30 s produced a decicase of the resting membrane potential, a decrease in the amplitude of the spike of the action potential and an increase in its duration, as well as an increase in the early negative after‐potential. In soleus fibres such changes were rare. These findings indicate that there are differences in the membrane properties between the two types of muscle fibres in addition to previously known differences in mechanical properties. Repetitive stimulation of fast fibres at body temperature caused a rapid increase in the twitch amplitude (staircase phenomenon). This increase occurred before any appreciable change in the action potential. Stimulation at room temperature caused only small changes in the twitch amplitude but marked increase in the twitch duration. This suggests that repetitive stimulation may alter both the amplitude and the duration of the active state cu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1974.tb05600.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY