摘要:

Micro‐electrode multi‐unit recordings of muscle nerve sympathetic activity (MSA) involved in cardiovascular homeostasis or skin nerve sympathetic activity (SSA) involved in thermoregulation were made in the right peroneal nerve of 48 healthy volunteers during performance of the cold pressor test, i.e. immersion of one hand in ice water (zko.5 “C) for I min. Eleven subjects underwent the same procedure on a second MSA recording occasion. As a rule, immersion evoked an increase in MSA, with a gradual decrease on emersion. The response showed a wide range of variation between and within subjects; the intra‐individual difference between first and second immersion on the same recording occasion was up to sevenfold, and from first to second recording up to fivefold. The increase in MSA correlated with the degree of discomfort from the ice water. In nine subjects with a large increase in MSA on ice water immersion, intracutaneous painful electrical stimulation to a level equalling the discomfort from the ice water was added, but it was not accompanied by any change in MSA. The increase in MSA was accompanied by and correlated quite well with an increase in blood pressure. Intra‐arterial blood pressure recordings showed that MSA occurred at pressure levels normally associated with total inhibition of MSA, and that an inverse linear relationship between diastolic blood pressure and MSA at rest was abolished during the ice water immersion. SSA showed no consistent change with ice water immersion.I t is concluded that the cold pressor test is a powerful activator of MSA, i.c. baroreceptor‐governed vasoconstrictor outflow; that MSA contributes to the blood pressure elevation with this manoeuvre; that MSA operates at another blood pressure level during the manoeuvre and that the baroreflex inhibitory level consequently is changed; and that the response is not a reaction t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08760.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

By the use of invasive techniques, skeletal muscle has been shown to contribute to thermogenesis induced by glucose in humans. In an attempt to study this phenomenon by a non‐invasive method, this study investigated intracellular high‐energy phosphorous compounds in calf muscle by “P MR spectroscopy during an oral glucose load in healthy lean subjects. The inorganic phosphate concentration increased gradually (P<0.0;) after glucose intake. The phosphocreatine/inorganic phosphate rate decreased (P<0.0;) and the estimated ADP concentration increased. ATP and intracellular pH remained unchanged after the glucose administration. N o changes were seen in the control experiments. The processes responsible for the decreased energy‐ state of the skeletal muscle cell may be an obligatory conversion of glucose to glycogen. Also, facultative processes, such as sodium/potassium pumping and substrate cycles stimulated by the sympatho‐adrenal system, may be partly re

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08761.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

HellstnWesting, Y., Ekblom, B.&Sjödin, R. 1989. The metabolic relation between hypoxanthine and uric acid in man following masimal short‐distance running.Acta Physiol Scand1–37, 341–345. Received 10 March 1989, accepted 24 June 1989. ISSN 0001–0772. Department of Physiology III, Karolinska Institute, and Swedish Defence Research Establishment, Stockholm, Sweden.This study was performed to asscss the metabolic relation between hypoxanthine and uric acid following short‐distance maximal running. Eleven trained males, mean age 22 years (16–31), were instructed to run 800 m in the shortest time possible. Bood samples were collected before warm‐up, before the run, immediately after the run and periodically up to 24 h following the run. Blood lactate was determined after warm‐up, and at 5, 10, and 30 min following the run. MeanVo2mas for the subjects was 65.8 (4.7) (SD) ml kg‐1min‐1and mean oxygen demand for the running was 118 (8)%, of Vo2may. Plasma hl‐poxanthine levels rose from 3.3 (1.4) to a peak of 48.2 (19.0)μmol l‐1at to min following the run and at 180 min had almost returned to pre‐tun levels Plasma uric acid levels rose from a pre‐run value of 267 (34) to a peak value of 131 (87) μmol l‐1at 45 min following the run. Uric acid concentrations had not returned to normal at 10 h following the run. The hlood lactate level peaked at j min with 13.7 (2.0) mmol l‐1. The results obtained in this study indicate a metabolic relationship between the formation of hypoxanthine and the formation of uric acid. The data also indicate that xanthine osidase is active followin

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08762.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The adaptation in activation patterns of the ankle extensor muscles to different functional demands a‐as studied in adult men (n =10) and 9‐year‐old boys (n= 10). The relative magnitude of the activation of the slow soleus (SOL) and the relatively fist medial gastrocnemius (MG) muscle was measured during various postures and hopping tasks on a force plate. In addition, the myo‐electric activity was quantificd in three different phases of the stretchbshortening cycles during hopping. Major differences between boys and adults were observed in the postul‐al tasks, where the boys appeared to utilize the MG to a relatively larger extent. During maximal height hopping there was a clearly larger potentiation of the MG activity in the adults, particularly in the eccentric phase. On the other hand, there were striking similarities between boqs and adults aith respect to the degree of pre‐activation of both muscles during the different hopping regimes as Hell as potentiation of muscle activity during the concentric phase ot maximal height hopping. Thus, sonic aspects of the selectivc ncural control of the ankle extenson muscles appear to be manifested in pre‐pubertal boys. However, the data also indicate that other factors, such as utilization of stored elastic energy in the muscles and stretch reflex potentiation, will still continue to develop from th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08763.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Experiments were performed on rats anaesthetized with chloralose. A duodenal segment was perfused with recirculating isotonic saline, and alkalinization of this perfusate (HCO‐3secretion) was measured by continuous pH‐stat titration. Stereotaxic electric unipolar stimulations were performed in the perifornical region of the hypothalamus. Stimulation points eliciting an increased arterial pressure were stimulated for a period of 15 min. Duodenal HCO‐3secretion decreased in 19 out of 25 experiments and increased in four out of 25 experiments. Inhibitory responses to hypothalamic stimulation were blocked either by thoracic epidural anaesthesia or by the adrenolytic agent guanethidine, suggesting a spinal pathway to the duodenum, presumably in the thoracic splanchnic nerves, and involvement of adrenergic ne

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08764.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The aim of this study was to elucidate the mechanisms behind the absorptive response to mesenteric nerve stimulation (MNS). Segments of rat jejunum were mounted with intact blood circulation in an‘in‐vivochamber’, allowing parallel registration of net fluid transport rate (NFT) and electrical parameters of the tissue. All segments secreted fluid spontaneously, and the secretion rate was inversely correlated to the corresponding potential difference (PD) across the segment. The secretion was not inhibited by atropine. The nicotinic antagonist hexamethonium (Hx) inhibited the secretion and changed the relationship between PD and NFT. MNS reversed the secretion into an absorption (absorptive response) and decreased PD and short‐circuit current (SCC) (electrogenic response). Total tissue resistance (Rt) was not significantly changed. The absorptive response increased at high control secretion rates and the electrogenic response increased at high control PD levels. The electrogenic response was inversely related to the absorptive response; however, the presence of Hx reversed this correlation. Guanetbidine, a sympatholytic agent, eliminated all effects of MNS. Phentolamine eliminated the absorptive response but not the electrogenic response, and the remaining electrogenic response was not sensitive to propranolol (a β‐adrenergic antagonist). Hx induced similar but smaller effects than MNS, and after Hx treatment the MNS effects were reduced. We conclude:1Fluid secretion in our model involves a mechanism other than electrogenic Cl‐secretion.2MNS activates sympathetic nerve fibres, which enhance fluid absorption and decrease PD and SCC.3The absorptive and electrogenic responses involve partly separate transport mechanisms.4Both responses are partly due to the inhibition of intramural secretory nervous pathways.5Some sympathetic nerve fibres interact directly with th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08765.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Regional administration of VIP elicited a dose‐dependent relaxation of the feline sphincter of Oddi and gall‐bladder. Relaxatory motor responses of these regions at efferent electrical stimulation of the vagal nerves were unmasked after atropine (resistant to propranolol but sensitive to hexamethonium). These findings in combination with the presence of a rich VIP‐ergic innervation, including intrinsic VIP neurons, have made VIP a tentative post‐ganglionic non‐adrenergic, non‐cholinergic neurotransmitter to these regions. The relaxatory motor responses elicited by VIP or vagal activation were selectively antagonized using regional administration of specific VIP antisera in support of this

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08766.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The plasminogen activator in parotid saliva has recently been characterized as a tissue‐type plasmhogen activator (t‐PA). In this study stimulated parotid saliva from 21 healthy volunteers was analysed for (a) t‐PA activitl‐ using the fibrin plate assay or a bioimmunoassay coupled to the plasmin‐specific chromogenic substrate S‐2251, (b) t‐PA antigen using an enzyme‐linked immunospecific assay and (c) activity of the specific fast‐acting plasminogen activator inhibitor (t‐PA inhibitor) assayed by its inhibitory effect on one‐chain t‐PA added to the samples. In parotid saliva the median t‐PA activity was 0.2 IU ml‐1(normal range 0.05–0.35 IU ml‐1), but activity of free t‐PA could not be demonstrated by bioimmunoassay in any sample. The mean antigen concentration of t‐PA was 2.2 IU ml‐1in the 10 samples with levels above the detection limit (0.5 IU ml‐1). High activity of t‐PA inhibitor was demonstrated in all parotid salivas, and the mean inhibitory effect on t‐PA was 13.2 IU t‐PA quenched per millilitre. This study thus demonstrates a fibrinolytic system in parotid saliva characterized by high t‐PA inhibitor activity and relatively low concentration of inactive, probably complex‐bound,

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08767.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effects of systemic administration of morphine (4.0 mg kg‐1) and clonidine (‐2.5–10.0 μg kg‐1), as well as the peripherally active α2‐adrenoceptor agonist oxymetazoline (2.8–11.2 μg kg‐1), were studied on the migrating myo‐electric complexes (MMCs) of the small intestine in conscious, naive rats. Furthermore, the effects of naloxone (1.0 mgkg‐l) and the peripherally acting opioid antagonist, methylbromide naloxone (1.0–2.0 mg kg‐1) were studied on the MMCs in morphine‐dependent animals. Similar doses of clonidine or oxymetazoline inhibited the MMCs of the small intestine, which suggests a peripheral site of action of clonidine. Since naloxone (1.0 mg kg‐1) did not antagonize the effect of clonidine, and yohimbine (1.0 mg kg‐1) failed to antagonize the effect of morphine on the MMC, the inhibitory effects on intestinal motility of clonidine and morphine are mediated through different receptors. Morphine‐dependent rats showed a prolonged interval between activity fronts and decreased propagation velocity of the activity fronts. Both naloxone (1.0 mg kg‐1) and methylbromide naloxone (1.0–2.0 mg kg‐1) induced intense spiking activity and profuse diarrhoea. Clonidine (5.0–10.0 μg kg‐1) as well as oxymetazoline (5.6–11.0 μg kg‐1) given prior to naloxone prevented the intense spiking as well as the concomitant diarrhoea. We conclude that the potent inhibition of small intestinal myoelectric activity by α2‐adrenoceptor agonists is mainly executed via peripheral mechanisms. This effect may contribute to their beneficial action in morphine withdrawal diarrhoea, and partly underlie a general antidiarrhoeal action. Thus, peripherally acting α2‐adrenoceptor agonists, lacking side effects of clonidine such as sedation and hypotension, may

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08768.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A new technique was designed to analyse whether pancreatic islet cells are able to regulate their volume in anisotonic media. The projected cell area of individual cells was continuously observed, and the corrcsponding volume calculated during microperifusion with media of diffrent osmolarities. In isotonic medium (317 niosmol) the cell volume was stable during perifusion and decreased by 17 or 25% when the osmolarity was increased (sucrose) to 417 or 517 mosmol. Reducing the medium osmolariti to 285 mosmol resulted in a volume reduction of ahout 7%. No evidence for cell volume regulation was observed in these media. Homever, reducing the medium osmolarity to 262 niosmol induced an immediate and rapid cell swelling of approximately 14% after which the initial cell volume was regained Mithin 9 min. The data suggest that the pancreatic islet cells are equipped with mechanisms for regulatory volume decrease that appear to he actibated when the cell volume is increased above a certain limit.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08769.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY