摘要:

AbstractPyrithiamine (50 mg/kg), a thiamine antagonist, decreased the muscle twitches of the rat masseter muscle at stimulation frequencies above 1 Hz 40–80 min after an i.v. injection. The post‐tetanic potentiation (PTP) induced by nerve stimulation of the masseter muscle was abolished by pyrithiamine. Administration of thiamine restored the muscle twitches at stimulation frequencies above 1 Hz and the PTP. The muscle twitches elicited by direct muscle stimulation were not affected by pyrithiamine treatment. The abolishment of the PTP was accompanied by a decrease in thiamine and thiamine‐diphosphate. The pyruvate level in the blood was unchanged after pyrithiamine treatment. Oxythiamine, on the other hand, had no effect on the PTP but increased the pyruvate level in the blood. Fern extract which contains thiaminase I also abolished the PTP–an effect reversible by the addition of thiamine. The frequency‐induced depression of the muscle twitches induced by pyrithiamine was similar to the effect of low doses of d‐tubocurarine (8 μg/kg). The results support the hypothesis that thiamine may play a role in neuromuscular

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06309.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractParallel functional and ultrastructural studies were performed in maturing rats in order to elucidate factors determining the development of proximal tubular fluid reabsorption. Three groups of hydropenic animals, which were 22 to 24, 28 to 32 and 40 to 45 days old, were studied. Nephron function was evaluated at the single nephron level by micropuncture technique. The ultrastructure of the developing proximal tubules was analysed by morphometric techniques following fixation of single nephrons. Kidney weight, proximal convoluted tubule length and diameter increased during postnatal development. SNGFR increased from 2.98 to 8.57 and to 20.5 nl/min in respective group of rats whereas proximal tubular fluid reabsorption Jv (a) increased from 0.15 to 0.22 and 0.34 μm3μm_2‐s_1. Parallel to the functional development the relative area of lateral and basal cell membrane increased, resulting in a constant relationship between net fluid reabsorption and the lateral and basal cell membrane area during the fourth postnatal week and then only a slight increase in this relation during the further development. The results suggest that net fluid transport during hydropenia is determined by the amount of available lateral and basal cell membranes where the transporting enzyme for sodium is loca

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06310.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractSteady‐state responses to hyperoxic hypercapnia and eucapnic hypoxia were measured both as minute ventilation (VE) and as inspiratory mouth occlusion pressure (P0.1) with and without 25 cm H2O/l/s added resistance (R). Reduction in slope of the ventilatory response to CO2with R was highly significant in all 3 subjects whereas the response to hypoxia was barely significantly reduced in 1 subject and not significantly decreased in two. Although P0.1was higher with than without R under all conditions, the slope of the P0.1response to CO2with R was not increased in two subjects and only slightly increased in the third. The slope of the P0.1response to hypoxia was significantly greater in all subjects with R. Expiratory reserve volume was increased with R but the change was the same with hypoxia and hypercapnia. We conclude that ventilation is better maintained with resistive loading during hypoxia than during hypercapnia and that this results from a greater force output of inspiratory muscles as reflected by a higher P0.1. This suggests a greater neural output to these muscle

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06311.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe pancreatic secretion of fluid, bicarbonate and protein in response to electrical stimulation of the vagus and splanchnic nerves, to exogenous and endogenous secretin and to various pharmacological agents was studied in anesthetized young pigs (21 kg). Vagal stimulation increased flow, bicarbonate output and protein output in a frequency dependent manner; the half maximal effective frequency was 2–4 Hz and the maximal effective frequency 12 Hz. The secretory response to vagal stimulation was potentiated by physiological elevations of the arterial concentration of secretin brought about by injection of secretin or by acidification of the duodenal bulb. Simultaneous stimulation of the splanchnic nerves strongly inhibited the response to vagal stimulation; splanchnic nerve stimulation alone had no demonstrable effect. The flow and bicarbonate response to vagal stimulation was unaffected by atropine, but abolished by hexa‐methonium. Protein output was strongly inhibited by both agents. The response to intraarterial infusion of acetylcholine resembled that elicited by vagal stimulation but it was smaller and it was completely abolished by atropine and unaffected by hexamethonium. Alpha‐ and beta‐adrenergic blockade stimulated rather than inhibited the secretory response to vagal stimulation. The portal vein plasma concentration of secretin was not affected by vagal stimulation. The results indicate that the protein response, and the flow and bicarbonate response to vagal stimulation are not brought about by the same mechanism. An increased release of secretin is not involved. Peptidergic (VIP‐containing) nerves may c

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06312.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe response amplitude in the chorda tympani proper nerve of rats to taste stimulation has been studied at different times after interruption of the nerve in the middle ear. The results show that the response in the nerve declined and disappeared completely within 15 h after the nerve was interrupted. As a first sign of deteriorating function a stage of hypersensitivity was observed. Results obtained during applications of local anesthetic or colchicine and section at different distances from the tongue indicate that the decreased response was the result of an interruption of axoplasmic flow from the nerve cell bodies in the geniculate ganglion to the taste buds.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06313.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractIt is confirmed that while noradrenaline stimulates release of submaxillary as well as renal renin, isoprenaline only stimulates renal renin release. The effects of these two adrenergic agonists differ in several other ways. The kidneys respond to isoprenaline with a dose dependant renin release. As a contrast the submaxillary glands respond to noradrenaline by no or by non‐dose‐dependant release. After single doses of the agonists the isoprenaline induced renin release is of short duration, contrasting with a prolonged renin release after injection of noradrenaline. The kidneys are able to respond to repeated doses of both agonists, while the submaxillary glands most often only respond to the first dose. While the effect of noradrenaline is blocked by pretreatment with phenoxybenzamine, this blocker is without effect when given after noradrenaline. The two agonists do not provoke any increase in plasma renin in mice which have been both sialoadenectomized and nephrectomi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06314.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractIn mice aggressive behaviour causes a vast release of renin, which can result in about 600‐fold increase in plasma renin concentration, reaching 6 Goldblatt Units, corresponding to 15μg renin per ml. This increase is mainly due to release of submaxillary renin, but there is also a significantly increased renal renin release. The degree of renin release is influenced by the duration of the aggression and by previous contact with other mice. Contrasting with the vast increase in plasma renin the blood pressure is normal or only moderately increased. This disproportion is not due to the depletion of renin substrate, caused by the increased renin, as shown by the increased calculated renin activity, as well as by decrease in blood pressure elicited by blockade of the renin system. Nor is the disproportion due to change in the sensitivity of the vessels to angiotensin II, the cause of this lack of tachyphylaxis being unknown. By way of exclusion the lack of pronounced increase in blood pressure can be explained by homeostatic function of the cardiovascular reflexes, which may also account for the fact that the pressor response after injection of pure submaxillary renin is only short, contrasting with a prolonged marked increase in plasma renin concentrati

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06315.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractKinetic analysis of residue and outflow curves of y‐emitting indicators such as chromium‐51‐EDTA and iodide‐131‐thalamate from skeletal muscle gives the possibility to determine the extraction fraction and the plasma flow, and from these two values the capillary diffusion capacity can be calculated (Sejrsen 1970, preliminary report). This is possible both for the transport from blood to tissue and from tissue to blood. This alternative method has been compared in the autoperfused cat gastrocnemius preparation with the indicator diffusion method based on venous registration of a diffusible test indicator and an intravascular reference indicator (Chinardet at.1955, Crone 1963). The results of the five independent measurements show good agreement. Calculation of the permeability Pdbased on a capillary surface area of 7 000 cm2/100 g of tissue gives values of 1.05–10‐5, 1.10–10‐5, and 1.16–10‐5cm/s, which is in agreement with results obtained by other investigators. The permeability was equal in both directions, and thus the capillary membrane seems to function as a symmetrical membrane. Using an area of 5 000 cm2/100 g which presumably is more realistic at the plasma flow range used gives Pdvalues around 1.5–10‐6cm/s. The effective pore area is calculated to constitute 1/50 000 of the capillary surface area. Calculation of volumes of distribution in the muscle tissue gave intravascular plasma volumes of 1.8 to 2.0 ml/100 g, an extravascular volume of 12.4 and 15.2 ml/100 g and a final monoexponential component constituting a compartment of 5.4 and 7.0 ml/100 g from residue and venous curves, respectively. The last mentioned compartment constitutes nearly 50 per cent of the extravascular space, and it is suggested, that it is located inside the sarcoplasmic reticulum, which anatomically constitutes about 50 per cent of the interstitial space. The total area of contact between the longitudinal and the transversal tubules in this subsystem, which is the membrane of the lateral saccus, is estimated to about 6 times the capillary surface area at a plasma flow of 15 ml/100 g min which gives a permeability about 60 times lower for this membrane compared

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06316.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractGastric acid secretion was measured in unanaesthetized codfish surgically equipped with a catheter draining the stomach. The pylorus was ligated. Without perfusion of the intestine, or during perfusion with pure sea water (100% SW) or slightly diluted (67%) SW, gastric acid secretion was low (<10 μmol H+/kg‐h) and the fishes became dehydrated during the experiment. Perfusion of the intestine with 50% or 33% SW enabled the fishes to compensate for the water loss to the environment and greatly enhanced gastric acid secretion. Acid secretion was elevated also in fishes in which the dehydration was prevented by an intramuscular infusion of saline. Perfusion of the intestine (8.5 ml/h) decreased the hourly effluent volume (‘drinking rate’) from the stomach to almost zero within 2 h. The effect was independent of the degree of dilution of the perfusing SW, but was less pronounced when the perfusion rate was lowered. Intra‐muscular saline also depressed ‘drinking rate’. The acid secretion prevailing during perfusion of the intestine with SW at a dilution preventing dehydration–suggested to represent the basal acid secretion of the codfish– was inhibited by atropine, hexamethoniu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06317.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractElectrical field stimulation was applied to the rabbit lacrimal gland during incubationin vitrowith3H‐choline, after which the efflux of tritiated metabolites was studied. In the presence of physostigmine3H‐acetylcholine was released into the incubation medium when the gland was stimulated electrically. The identity of the3H‐acetylcholine synthesized by the preparation was established by its identical ion exchange chromatographic properties to native acetylcholine. The tissue contents of3H‐acetylcholine and3H‐choline were 14.4 and 3.6%, respectively, of the total activities found in the gland. This study demonstrates that the rabbit lacrimal gland is innervated cholinergically. It is suggested that the method developed might be of value for studying effects of drugs on cholinergic neurotransmission in t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1979.tb06318.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY