摘要:

The effects of bromide, nitrate, iodide, and thiocyanate ions on the neurally evoked fast and slow contractions of a crab muscle were investigated. Both types of contraction were depressed in bromide and nitrate. In iodide and thiocyanate, the slow contraction was often depressed but the fast contraction was potentiated. The foreign anions increased muscle fiber membrane resistance and the amplitudes of both fast and slow postsynaptic potentials. Records of tension development in single muscle fibers showed that more stimulating current was required to produce a given tension in nitrate than in the standard bathing fluid; this change was related to hyperpolarization of the muscle fiber membrane in nitrate. Potassium contractures also were inhibited by nitrate, because of the less effective depolarization of the cell membrane by potassium ion in the presence of nitrate. No marked shift in the membrane potential threshold for contraction occurred after treatment with the foreign anions.

ISSN:0008-4212    

DOI:10.1139/y68-001

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A single subcutaneous injection of 40 units of renin to uninephrectomized rats about triples aldosterone secretion. Chronic injections of renin cause hypertension and a stimulation of the zona glomerulosa, whether the animals are given tap water or 1% saline to drink. On the 12th day aldosterone secretion is about four times the normal rate. The appearance of the zona glomerulosa is like that after sodium deficiency, with cellular hypertrophy and watery vacuoles.

ISSN:0008-4212    

DOI:10.1139/y68-002

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Four young male subjects were exposed for 1 h to environmental temperatures of 8.5 °C, 14.0 °C, and 20.0 °C while lying on a rope mesh cot. During exposure they wore swimming trunks only. Heat production, skin temperature at seven locations, and rectal temperature were measured. Mean body temperatures (MBT) and heat debts were calculated from Burton's equations and also from equations determining radiative, convective, and evaporative heat losses. It was found that a linear equation with constant coefficients, such as Burton's, for measuring MBT does not allow for the fact that in the non-steady state the body continues to lose heat even though the skin temperature is relatively constant. During the initial period of cold exposure the coefficient of skin temperature when calculating MBT should be much smaller than at later stages in the cooling.

ISSN:0008-4212    

DOI:10.1139/y68-003

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Male rats of the Wistar strain were fed either a control (20% casein) or a low-protein (5% casein) diet. Following the intraperitoneal injection of glucose solution it was observed from the blood glucose curve that low-protein fed rats had a delayed or impaired utilization of this carbohydrate. Resting oxygen consumption was not significantly different, and after glucose injection the slight increase in both groups was not significant. On refeeding after fasting, the colonic temperature of low-protein fed rats rose to a greater extent than did that of controls. Administration of protamine zinc insulin (PZI) decreased colonic temperature during fasting particularly in low-protein fed animals, and also during refeeding following a brief fasting period. From the results of these several experiments, it would appear that low-protein fed rats may have (a) an impairment in utilization of carbohydrate, and (b) a defect in immediate energy dissipation or an increased rate of energy production from ingested food. These two abnormalities may contribute to the reduced food intake of such animals. The association of a greater increase in colonic temperature on feeding and the hypophagia of rats fed a low-protein diet, as well as the hypothermic effect of PZI associated with an increase in food intake are suggestive of a thermostatic control of food intake in addition to a glucostatic control.

ISSN:0008-4212    

DOI:10.1139/y68-004

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The relation of cell Na and K to vascular smooth muscle tension was studied in the isolated, perfused rat tail artery. Glass electrodes were used to measure ion exchanges; cooling and rewarming were used to modify cell ion content and exchange rates. The cells, made Na-rich and K-poor by overnight cooling of the artery at 2 °C, responded weakly to vasoactive agents (norepinephrine, L-8 vasopressin, and angiotensin) and characteristically showed a slow rate of rise followed by a still slower rate of fall in tension. Within minutes of initiating rewarming to 37 °C the rate of rise was accelerated even in the presence of metabolic inhibitors. The degree of rise depended on the degree of restoration of ionic gradients; it increased progressively with the time allowed for extrusion of Na and reaccumulation of K, a process which could be blocked by iodoacetate. During rewarming, the Na/K exchange rate rose from zero at 2 °C to reach a maximum toward the end of the first hour of rewarming, and in this interval the rate of relaxation following stimulation returned to normal. Stimulation of the cold artery with angiotensin enhanced subsequent Na outflow during rewarming without affecting K inflow, and the tissue was unable to respond to a second stimulus.

ISSN:0008-4212    

DOI:10.1139/y68-005

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The hypothesis that the limiting factor controlling the noradrenaline-releasing activity of a sympathomimetic amine is the ability of the nerve ending to take up the amine, i.e. the affinity of the amine for the postulated amine carrier in the sympathetic nerve ending, was tested on perfused rat hearts labelled with tritiated noradrenaline (NA). Experiments were done to determine whether cocaine and desmethylimipramine (DMI) would block the releasing action of sympathomimetic amines (SMA) and to determine whether the ranking order of the releasing activity of a series of SMA corresponds to the order of affinity for the amine carrier as reported by Iversen. The releasing activity of NA was found to be a saturable process, reaching a maximum rate estimated to be 2.6% of the amount present in the heart per minute. In addition, cocaine and DMI competitively blocked the releasing activity of infused NA, adrenaline, and dopamine, but this inhibition could be overcome by increasing the dose of the SMA. The ranking order of releasing activity of this series of amines wasl-noradrenaline, dopamine,l-adrenaline,p-tyramine,d-noradrenaline,d-adrenaline,l-isoproterenol, phenylethylamine,d-isoproterenol, which was approximately the same as their order of affinity for the amine carrier. Our results indicate that uptake by a membrane carrier is probably the limiting factor in the releasing activity of SMA which are catechols and have a β-OH group. However, those amines studied which do not have these structural properties, i.e. dopamine, tyramine, and phenylethylamine, are further limited in their releasing activity, possibly owing to a less rapid exchange at the binding site on the storage granule.

ISSN:0008-4212    

DOI:10.1139/y68-006

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Ten dogs were anesthetized with pentobarbital, and after a control period of at least 1 h, during which three blood samples were taken, adrenaline (2–4 μg/kg per min) was infused intravenously for 1 h. Blood samples were taken at 15- or 30-min intervals during the infusion and for 2 h thereafter. These were analyzed for calcium, inorganic phosphate, and glucose. The plasma calcium level did not change significantly during or following the infusion; however, the plasma glucose rose and the plasma phosphate fell during adrenaline administration. The glucose level returned to normal within 2 h of termination of the infusion; in some dogs the plasma phosphate also returned to the control level, whereas in others it remained depressed at this time.

ISSN:0008-4212    

DOI:10.1139/y68-007

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Acetylsalicylic acid was administered orally in doses from 0.2 to 1.9 g/kg with pentobarbital or thiopental, given intraperitoneally 1 h later, in doses ranging from 25 to 55 mg/kg, to overnight-fasted, male, albino rats. Both sleeping time and mortality were significantly increased with acetylsalicylic acid – barbiturate combinations. A dose-response relationship was observed in both sleeping time and mortality after acetylsalicylic acid and thiopental but only with the former after acetylsalicylic acid and pentobarbital. Starvation prolonged thiopental sleeping time. At equal doses, thiopental was more toxic than pentobarbital, when given separately and in combination with acetylsalicylic acid.

ISSN:0008-4212    

DOI:10.1139/y68-008

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Most of the significant changes in the mean weight and water content of 18 organs of albino rats at 18 h after the rectal administration of an LD50of acetylsalicylic acid were found to be dose-dependent. Variations in the dose of drug and in the interval after drug administration selected for measurements were factors which affected the relation between mean changes and close–response correlations. Most mean changes in organ weights and water contents in an acute drug toxicity study will probably be dose–dependent. A dose–response correlation of changes in organ weights and water contents is not necessarily indicated in routine acute toxicity studies on new drugs. Gastric ulcers were found in albino rats 18 h after the rectal administration of 0.8 g of acetylsalicylic acid per kg; and over. It is concluded that measurement of organ weights and water contents in representative groups of animals at death and at intervals in survivors of specified doses of the drug under study will provide probably as much information as the more expensive dose–response studies.

ISSN:0008-4212    

DOI:10.1139/y68-009

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Dietary administration ofo,p′-DDD (2,2-bis(2-chlorophenyl, 4-chlorophenyl)-1,1-dichloroethane) at 1.0 and 3.0 g/kg food for 6 weeks increased the thyroid weight of male albino rats by 62 and 81% respectively. The rate of oxygen consumption (measured at 30 °C) and gain in body weight were unaffected by treatment. The rate of loss of131I from the thyroid gland was significantly faster for both treated groups than for controls. These results suggest that the chronic administration ofo,p′-DDD at the doses used resulted in a compensated hypothyroidism in rats. In another experiment, the thyroid weight of female hooded rats givenm,p′-DDD (1.0 g/kg food) andp,p′-DDD (1.0 and 3.0 g/kg food) for 24 weeks also increased 112, 94, and 113% respectively above control weight. Ninety-six hours after the administration of thyroxine-131I, significantly greater fecal and less urinary excretion of radioactivity was observed for all treated groups than for the control group. The increase in thyroid weight of the treated rats may be associated with increased hepatic metabolism of thyroxine, but specific effects on the thyroid gland have not been excluded. Although isomers of DDD are reported to induce atrophy of the adrenal cortex and to reduce glucocorticoid secretion in dogs, no effect of the chronic administration of isomers of DDD on adrenal weight or production of either total Δ4-3 ketosteroids or corticosterone in vitro was observed in the case of rats. The rate of metabolism of desoxycorticosterone in vitro by rat liver slices was also unaffected by chronic treatment witho,p′-DDD.

ISSN:0008-4212    

DOI:10.1139/y68-010

出版商:NRC Research Press    

年代:1968

数据来源: NRC