摘要:

Abstract:This study was performed in order to elucidate the mechanism behind the decreased responsiveness to β‐adrenergic stimulation occuring in uterine muscle after prolonged treatment with isoprenaline. Pretreatment of rats with isoprenaline, 20 nmol/kg, three times daily during four days, significantly decreased the myometrial relaxing effect of the β‐agonist. There was also a significant decrease of the β‐receptor binding capacity of the myometrial membranes measured by the (minus;)‐(3H) DHA binding technique. In the animals pretreated with isoprenaline no significant increase of the adenylate cyclase activity could be observed after isoprenaline stimulationin vitro. The uterine cAMP level was diminished in the desensitized rats. The phosphodiesterase activity was increased. Thus both decreased production and increased degradation contribute to the lower level of uterine cAMP content. The activity of cAMP dependent protein kinase was also depressed. In this work, where low concentrations of isoprenaline have been administeredin vivo, several biochemical parameters have been shown to contribute to the β‐adrenergic desensitization in myom

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00901.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The effects of lofepramine on the isolated guinea pig atrial trabeculae were compared with those of desipramine. The preparations were taken from the same animal and mounted in the same tissue bath. All parameters were recorded in parallel. Lofepramine 10 μM was shown to exhibit minor changes in the transmembrane action potential duration only. The action potentials of the atrial trabeculae were prolonged, whereas they were shortened in the papillary muscles. Desipramine was about ten times more potent than lofepramine, but produced similar qualitative changes. Desipramine 10 μM and lofepramine 100 μM showed local anaesthetic properties: a decreased overshoot without a decreased resting potential, a decreased and rate‐dependent Vmax, and a decrease in propagation velocity. After the addition of either drug in a lower concentration, a transient increase in force development and a concomitant increase in repolarization phase height (atrial trabeculum) or plateau length (papillary muscle) were recorded. The steady state effect on the force development was a decrease accompanied by a shortening of the action potential duration (papillary muscle). It is suggested that the actions of lofepramine 100 μM and desipramine 10 μM on phase 0 of the action potential are produced by blockage of the fast sodium channel. The transient increase in developed force and the increase in repolarization phase height (atrial trabeculum) or plateau length (papillary muscle) could be caused by inhibition of the membrane re‐uptake system for released noradrenaline. The steady state shortening and flattening of the plateau (papillary muscle) and the decrease in force development could be the cause of a block in the slow channe

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00902.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The role of intestinal flora in the decomposition and faecal excretion of methyl mercury was studied in mice treated with antibiotics. The antibiotics, neomycin sulfate and chloramphenicol, were given to mice in drinking water for six days before intraperitoneal administration of methyl mercuric chloride (MMC), and intestinal microorganisms were thereby reduced. Inorganic and organic mercury were determined separately for faeces, intestinal contents and organs. On the fourth day after the mercury administration, the percentage ratios of inorganic mercury to total mercury in the contents of the caecum and large intestine were less in the mice treated with antibiotics, at 37% and 39%, respectively, than in the control mice (66% and 65%, respectively). Administration of the antibiotics reduced the excretion of inorganic mercury in the faeces to 26% of that of control mice and also reduced the excretion of total mercury to 60%. Reduction of intestinal microorganisms by the antibiotics was assumed to have caused the reduced decomposition of methyl mercury in the caecal contents and the reduced excretion of total mercury in the faeces.

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00903.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Exposure of the Indian catfish (Heteropneustes fossilis) to a sublethal concentration of 0.14 p.p.m. aldrin for 3, 6, 12, 48, and 96 hrs affected carbohydrate metabolism. Muscle glycogenolysis and glycogenesis were obtained at 3 and 12 hrs, respectively. Hepatic glycogenolysis occurred at 3, 48, and 96 hrs. The treatment caused hyperglycaemia at 3, 6, 48, and 96 hrs, and hypoglycaemia at 12 hrs. Blood pyruvate values increased significantly at 3, 6, and 96 hrs. Hyperlacticaemia was observed at 3 and 12 hrs but hypolacticaemia developed at 96 hrs. The results are discussed in relation to acute stress syndrome. Also, impairment of carbohydrate metabolism by aldrin may be involved in the biochemical mechanism for its toxic action. It is concluded that evaluation of carbohydrate metabolites in fish could prove useful as a rapid method for assessing acute toxicity of pesticides.

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00904.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Three different nitro compounds glyceryl mononitrate (GMN), glyceryl dinitrate (GDN) and ethylene glycol dinitrate (EGDN) were tested on histamine contracted bovine mesenteric artery. GDN and EGDN caused a dose‐dependent relaxation which was accompanied by an increase in the endogenous cGMP level. The ED50‐value for GDN and EGDN with regard to the relaxant action was 1.06×10−6M and 4.20×10−8, respectively. GMN was almost completely ineffective as a relaxing agent and did not cause any significant change in cGMP. Regression analysis revealed a significant correlation between relaxation and increase in cGMP for both GDN and EGDN. The regression model for EGDN could be significantly improved by including the squared cGMP change, indicating a non‐linear relationship. With regard to GDN a hyperbolic relationship between relaxation and cGMP increase was found. A slight improvement of the regression model was found for EGDN when the change in cAMP was included. For GMN and GDN no improvement of the regression model could be revealed by including the change of cAMP. It is suggested that the present data give further evidence for cGMP as a mediator of vascular smooth muscle relaxation induced by nitr

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00905.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The 5‐HT uptake mechanism in human platelets was studied in undiluted and diluted platelet‐rich plasma (PRP). The kinetic data obtained, which were based on 5‐HT concentrations ranging from 0.17 to 1.7 μmol/1, were analyzed according to Lineweaver‐Burk, Eadie‐Hofstee, Scatchard and Sips. In undiluted PRP all the analyses revealed a strict linearity between 5‐HT concentrations and initial uptake velocities. Only one site for active transport seemed to be involved and no passive diffusion was present. The apparent Kmand Vmaxin a 95 per cent confidence interval (n = 25) were 1.20 ± 0.14 μmol/1 and 1.40 ± 0.15 pmol/106platelets and minutes, respectively. Dilution of PRP with autologous platelet‐poor plasma or Ringer's solution markedly influenced the active 5‐HT transport mechanism. The addition of minute amounts of supernatant from lysed autologous platelets to PRP totally impaired the active 5‐HT uptake. It is concluded that relevant studies on the active 5‐HT transport can be performed only in fresh undiluted PRP. The commonly used Lineweaver‐Burk analysis does not discriminate sufficiently between fully saturable and non‐saturable transport mechanism and therefore cannot be used for the detection of irregular

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00906.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The effect of furosemide 8×10−4mol/l and 8×10−5mol/l on parathyroid hormone stimulated adenylate cyclase was studied in renal tissue slices from guinea pigs. Furosemide caused a dose‐dependent inhibition of the effect of parathyroid hormone on production of cyclic AMP, without having any significant effect on the basal cyclic AMP production. Furosemide in similar concentrations did not inhibit the stimulatory effect of thyrotrophin and fluoride in human thyroid homogenates suggesting that furosemide is not an universal inhibitor of adenylate cyclase and that the inhibition is not caused by a direct action of furosemide on the adenylate cyclase enzyme. Furosemide did not interfere with binding of cyclic AMP to cyclic AMP binding protein kinase from rabbit muscle. The results indicate that furosemide exerts an inhibitory influence either upon binding of parathyroid hormone to renal receptors or upon transmission of impulse from receptor to adenylate cyclase. The inhibitory influence of furosemide on parathyroid hormone action in kidney could explain the value of furosemide in the acute treatment of hypercalcaemia, but also suggest that chronic treatment with furosemide might interfere with normal calcium met

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00907.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:LS 1727, a nitroso‐chloroethyl carbamate of 19‐nortestosterone, given intraperitoneally had a high cytostatic activity against some experimental tumours.In vitrostudies showed that the tested tumours differed in their ability to hydrolyze LS 1727. The hydrolytic capacity was related to the sensitivity to treatment with LS 1727. Distribution studies with double‐labelled LS 1727 demonstrated that the chloroethyl‐part of the molecule was retained in dimethylbenz(a)anthracene‐induced mammary tumours in the rat. Our findings suggest that the antitumour activity of LS 1727 is exerted by alkylating metabolites released at hydrolysis of the compound. LS 1727 had no oral antitumour activity probably due to pre‐systemic hydrolysis. When given intravenously, hydrolysis of LS 1727 in lungs caused severe pulmonary toxicity already a

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00908.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:Zinc concentrations, determined with atomic absorption spectrophotometry, did not differ significantly in plasma from manic‐depressive patients about to start lithium treatment and in patients having been in lithium treatment for six months or 1‐2 years. Plasma zinc concentrations and zinc concentrations in liver, muscle, kidney, bone, and skin did not differ in control rats and rats given lithium with the food for four we

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00909.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract:The oral absorption of pc V in different preparations, given at various times before and after a meal, was investigated in children with upper respiratory infections. The best absorption with respect to peak concentration was observed when potassium pc V (Calciopen®) was given after at least two hours of fasting with no food intake within the following hour. Shorter periods of fasting (1,1/2,0 hrs) before drug intake resulted in significantly lower plasma concentrations. When drug intake was followed by a meal, the absorption was also decreased to some extent. When pc V was given in an oil suspension (Fenoxypen®), or in a small volume (Roscopenin®) together with a meal, the peak concentration was significantly lower than when pc V was given in an aqueous solution with a larger volume (Calciopen

ISSN:0001-6683    

DOI:10.1111/j.1600-0773.1981.tb00910.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY