摘要:

Abstract13 male subjects were studied and placed in 3 groups. Each group exercised one leg with sprint (S), or endurance (E) training and the other leg oppositely or not at all (NT). Oxygen uptake (Vo2), heart rate and blood lactate were measured for each leg separately and for both legs together during submaximal and maximal bicycle work before and after 4 weeks of training with 4–5 sessions per week. Muscle samples were obtained from the quadriceps muscle and assayed for succinate dehydrogenase (SDH) activity, and stained for myofibrillar AT Pase. In addition eight of the subjects performed after the training two‐legged exercise at 70% Vo2max for one hour. The measurements included muscle glycogen and lactate concentrations of the two legs as well as the blood flow and the a‐v difference for O2, glucose and lactate.The improvement in Vo2max, the lowered heart rate and blood lactate response at submaximal work levels were only found when exercising with a trained leg (E or S). Part of the variables studied were markedly more changed with E as compared with S‐training. Although muscle fibre composition did not change a pronounced muscle adaptation took place with the training with enhancement of the SDH activity of the S and E legs while the NT‐leg did not change. Blood flow and oxygen uptake were similar in NT and S–E legs while femoral vein oxygen content was slightly lower in the trained as compared to the NT‐leg. Glycogen utilization was lowest in the trained leg with similar glucose uptake in all legs regardless of training status. Moreover, lactate was only continuously released from the NT‐leg. It is concluded that training induces marked local adaptations which not only affects the metabolic response to exercise but also are of importance eliciting an improved cardiova

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10200.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe function of the suggested hypothalamic osmoreceptors was investigated in dogs during light chloralose anesthesia. The dogs were subjected to an i.v. load of 40 ml/kg b.wt. of a hypo‐osmolar solution of sodium chloride and glucose. This degree of hydration was kept constant by a specially constructed servo system based on the weight of the animal. During water diuresis the renal free water clearance remained essentially constant for several hours (mean about 0.2 ml/kg b.wt.‐min). Renal sodium excretion was low (mean 0.82 μmol/kg b.wt. · min) and decreased continuously throughout the experimental period. I.v. infusion of hyper‐osmolar sodium chloride solution (1.33 mmol/kg b.wt. in 30 min) was followed by prolonged parallel increases in free water clearance and sodium excretion, without any detectable change in the excretion of osmoles and potassium. The renal response to bilateral infusion of hyper‐osmolar NaCl (1.33 mmol/kg b.wt. in 30 min) into the common carotid arteries was identical to the response to i.v. infusion. The estimated increase in the osmolality of the carotid blood was 2.2 %. In seven out of eight experiments intracarotid infusion of NaCl (1.33 mmol/kg b.wt. in 8 min) did not elicit any reduction in free water clearance. On the contrary, an increase was found similar to that obtained after i.v. infusion. The estimated increase in the osmolality of the carotid blood was 8.4%. The present results question the validity of the currently held view that hypothalamic osmoreceptors play an important role in the control of the osmolality

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10201.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe effects of iso‐osmolar and hypo‐osmolar volume expansion on renal water and sodium excretion were studied in dogs during light chloralose anesthesia. Saline or a hypo‐osmolar solution of glucose and urea was given i.v. (20 ml/kg b.wt. in 60 min). From the start of this infusion the combined weight of the hydration infusate and the dog was maintained constant by a servo system, which controlled the rate of infusion of a hypo‐osmolar solution. Consequently the degree of hydration increased linearly during the infusion period after which it remained constant throughout the experiment. No increase in free water clearance was seen after iso‐osmolar volume expansion. The rate of excretion of sodium increased considerably. Hypo‐osmolar volume expansion provoked a water diuresis during which the rate of excretion of sodium fell to less than 0.1 μmol/kg b.wt. min. It is concluded that under the present circumstances infusion of iso‐osmolar saline is not associated with a decrease in the rate of secretion

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10202.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe effects of PCO2and body temperature on the time course and peak amplitude of the central inspiratory activity (CIA) and the inspiratory ‘off‐switch’ threshold was studied in apneustic and non‐apneustic cats. Apneusis resulted from lesions of the inspiratory inhibiting structures of the medial parabrachial nucleus (NPBM) and by interrupting vagal volume feedback. The cats were paralyzed and ventilated either proportionally to their phrenic output or at predetermined rate and volume. The dependence of the rate of rise and maximal amplitude of phrenic activity on PCO2, and body temperature were comparable in apneustic and non‐lesioned animals. The Hering‐Breuer volume threshold for inspiratory termination was increased following the rostral pontine lesions. Both hyperthermia and hypercapnia caused augmentation of the absolute rate of rise of inspiratory activity but hypercapnia, in contrast to hyperthermia, caused virtually no change in the fractional increment per unit time. With hypercapnia the inspiratory ‘off‐switch’ threshold was raised in the apneustic animals as in intact ones, whereas hyperthermia did not seem to influence this threshold. In apneustic conditions expiratory duration remained constant, independent of the large variations in the inspiratory durations. Our results suggest that the NPBM merely provides an excitatory, threshold‐lowering input to the inspiratory ‘

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10203.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractIn order to obtain further information on the mechanisms controlling expiratory duration (TE) we have studied the effects of changes in body temperature on reflex characteristics of the TE‐prolonging inflation reflex. In cats under light pentobarbitone anesthesia controlled volume changes were applied at various times in expiration and the changes in TEwere measured from records of phrenic activity. Inflations falling in the last 20% of the control expiratory time were without effect. This reflex insensitive phase remained a constant fraction of expiratory time when respiratory rate was changed with temperature. The relative reflex responsiveness increased, and the volume threshold was reduced with increasing respiratory rate. The inflation reflex characteristics showed integration of the incoming pulmonary stretch receptor activity. The integrating mechanism exhibited a ‘leaky’ character, the decay rate of which changed with body temperature. Functionally the duration of the inspiration‐inhibiting activity controlling expiratory duration can be regarded as dependent on 3 main factors 1) the initial peak level of the inhibitory activity, 2) the amount and timing of the vagal afferent activity which adds to this inhibition, and 3) its rate of decay. The results suggest that all these factors are influenced by changes in temp

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10204.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractInterneurones identified as mediating the disynaptic reciprocal Ia inhibition of motoneurones (referred to as “Ia inhibitory interneurones”) were recorded in the lumbar spinal cord of the cat. Volleys in ipsilateral and contralateral high threshold muscle afferents, cutaneous afferents and high threshold joint afferents evoked a mixture of polysynaptic excitation and inhibition. These effects were ascribed to pathways activated by flexor reflex afferents (FRA) and in addition a specific ipsilateral low threshold cutaneous pathway. Ia inhibitory interneurones excited monosynaptically from flexor nerves received stronger net excitation by volleys in ipsilateral FRA than did extensor coupled interneurones, while the opposite pattern was seen from the contralateral FRA. These patterns are similar to those found in flexor and extensor motoneurones respectively. The FRA inhibition in Ia inhibitory interneurones was partly mediated by “opposite” Ia inhibitory interneurones,i.e.those which are mediating the Ia inhibition of la inhibitory interneurones. The extent to which the FRA inhibition is transmitted by Ia inhibitory interneurones was roughly estimated by its susceptibility to recurrent depression by antidromic ventral root stimulation. The main conclusion is that most segmental pathways seem to evoke their effects in parallel to motoneurones and Ia inhibitory interneurones which are monosynaptically linked to the same muscle. The functional importance of this conclusion is discussed in a following

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10205.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractSupraspinal effects were investigated in interneurones identified as mediating the disynaptic reciprocal Ia inhibition of motoneurones (referred to as “Ia inhibitory interneurones”). It was revealed that volleys in the vestibulospinal tract may evoke mono‐ and disynaptic EPSPs in interneurones monosynaptically excited from extensor muscles,i.e.extensor coupled Ia inhibitory interneurones. Flexor coupled interneurones instead received disynaptic inhibition. Volleys in the rubrospinal tract evoked a dominating polysynaptic excitation, usually mixed with inhibition, in flexor as well as extensor coupled interneurones. Disynaptic rubrospinal EPSPs and IPSPs were also revealed. The pyramidal tract also gives rise to a dominating polysynaptic excitation, usually mixed with inhibition, in flexor as well as extensor coupled Ia inhibitory interneurones. Rubrospinal and pyramidal volleys were shown to facilitate transmission in various segmental reflex pathways to the Ia inhibitory interneurones. A detailed comparison reveals a striking parallelism of segmental and supraspinal effects on α‐motoneurones and Ia inhibitory interneurones connected to the same muscles. This considerably strengthens the hypothesis of an “α–γ‐linkage in the recipr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10206.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractProgressive strength training was performed 3 times a week for 8 weeks by 14 healthy male students (19–31 yrs). The training program consisted mainly of dynamic exercises for the leg extensors with maximal or close to maximal loads. The training caused significant improvements in dynamic and isometric strength. One repetition maximum in squats increased with 67%, Sargent jump with 22%, and maximal voluntary isometric contraction (MVC) with 13 %, respectively. Body weight and leg muscle circumferences remained unchanged after training, whereas total body potassium, lean body mass and calculated total muscle mass increased, suggesting a change in body composition with training. Muscle biopsies were obtained from vastus lateralis for fibre analyses and determination of enzyme activities. There were no changes in muscle fibre composition or fibre area with training. The activities of Mg2+stimulated ATPase, creatine phosphokinase and phosphofructokinase remained unchanged, whereas myokinase activity was increased after training (from 1.41 to 1.52 moles × 10‐4× g‐1× min‐1, p>0.05). After training significant correlations (p>0.01) were demonstrated between Mg2+stimulated ATPase activity and % fast twitch fibres (% FT) (r = 0.67), as well as between myokinase activity and % F

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10207.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractHuman fetuses, rabbit fetuses and newborn rats have a relatively high concentration of protein in cerebrospinal fluid (csf) as compared with the adult. The present study was undertaken in an attempt to evaluate whether this high protein concentration in newborn rats is caused by a high permeability of the blood‐brain‐csf barrier to protein or by a low production rate of csf. The results suggest that the high concentration of protein in csf in newborn rats is due to a low rate of production of csf rather than to an increased transfer of protein across the blood‐brain‐csf

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10208.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe effect of reserpine, guanethidine and imipramine on the uptake of tritiated 5‐hydroxytryptamine by rat peritoneal mast cells was studiedin vitro.The Kmvalue for uptake of 5‐hydroxytryptamine was 3 × 10‐7M in this study. Kinetic analysis of the data obtained suggests that the drugs inhibit the uptake in a competitive manner, in the order of decreasing potency: reserpine, imipramine, guanethidine. For reserpine the Dixon plot resulted in two curves, each composed of 2 linear components suggesting inhibition of uptake of 5‐hydroxytryptamine at 2 different levels or by 2 different mechanisms with different K1values. It is suggested that the higher K1value, representing an immediate effect of reserpine, stands for inhibition of uptake at the cell membrane. The lower K1value possibly represents inhibition at the level of the membranes surrounding the intracellular storage or

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1976.tb10209.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY