摘要:

Dogs with complete heart block were used to explore the dependence of the intrinsic rhythmicity of the heart on catecholamine activity. By the use of reserpine, hexamethonium, and surgical sympathectomy, it was demonstrated that, while reduction in catecholamine activity slows both the atrial and the ventricular rates, the ventricular pace maker was always affected to a greater degree. The effect of a combination of reserpine and hexamethonium on the ventricle was greater than when either agent was administered alone, suggesting that the greater the sympathetic blockade, the greater the depression in pacemaker rhythmicity. Since the course of its action on the heart paralleled that of catecholamine depletion, it seems probable that the effect of reserpine on rhythmicity was due to its catecholamine depleting action. It was thought unlikely that prolonged hypotension contributed to the reserpine action on the heart. It is indicated that disturbances in electrolyte balance and blood pH did not play a role in the effects observed.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The present experiments show that the adsorption of antibodies to the guinea pig heart can be achieved by perfusing the heart with rabbit antiovalbumin solutions. The amount of radioactive antibody remaining on the tissue is a definite function of the concentration of antibody in the bulk phase instilled into the coronary circulation. When the antibody-loaded organ is challenged with ovalbumin, the efflux rate of antibody is increased; it is also increased in response to such nonspecific agents as histamine and epinephrine. Since the output rate is not affected when the heart fails to react to rechallenge with antigen, the release of antibody may be entirely dependent upon the mechanical response.The maximal amount.it of histamine-like material that can be produced by the heart undergoing anaphylaxis was found to be 1 × 10−smoles/Gm./min., estimated as histamine; the minimal amount of antibody necessary to release this quantity was calculated to be 0.343 μg. of specific antiovalbumin/100 mg. of heart. This load can be achieved by perfusing the heart with an antibody solution containing 30 μg. of specific γ-globulin. Perfusion with an antibody solution containing 50 μg./ml. showed the amount of histamine subsequently liberated by the same dose of ovalbumin to be reduced by 50 per cent.The rate and amplitude of contraction were increased to the same absolute values in all cases in which either ovalbumin or histamine was employed to set off the reaction, suggesting that the release of active material at even the low sensitizing doses of antibody used exceeded the ceiling of the physiological response. The decrease in coronary flow was inversely related to the dose of sensitizing antibody and bore little relation to the changes in this parameter induced by the subsequent administration of histamine.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

An experimental model of canine endotoxin shock was employed for evaluating therapeutic agents that are used in the management of peripheral vascular collapse. An important feature of the present study was that an agent or agents were not administered until hypotension and oligulria were present. Progressive endotoxin shock was not reversed by the infusion of large amounts of canine plasma. Large doses of hydrocortisone did not prevent a lethal outcome. Even though the blood pressure was stabilized near normotensive levels with the vasopressor drug, metaraminol, progressive shock occurred. The most significant finding was that lethal endotoxin shock was prevented in six of the 10 animals studied by the simultaneous use of hydrocortisone and metaraminol. Only one-eighth the amount of metaraminol was necessary to maintain normotensive levels of blood pressure if a large dose of hydrocortisone was administered before the infusion of the pressor drug.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The effects of intravenous administration of angiotensin on the arterial pressure and on the renal, carotid, iliac, uterine, and femoral blood flows were investigated in dogs and sheep through the use of implanted electromagnetic flowmeters. The rise in arterial pressure was immediate and, within the range of doses employed, presented little relation ship to the dose. The pressor effect of angiotensin was accompanied by a consistent fall in the renal blood flow and a rise in the femoral, iliac, and uterine flows. Carotid flow was less affected. These studies demonstrate the specificity of flow response to a given change in pressure in the various areas of the body.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The existence of concealed conduction of atrial beats has been demonstrated. Concealed conduction within the atrioventricular node has been studied by recording the transmembrane potential of single nodal fibers. Conduction block in this part of the specialized conducting system depends more upon decremental conduction within certain nodal fibers than upon differences in action-potential duration. Also, the extreme delay of activation that results from such decremental conduction explains certain changes in atrioventricular delay associated with premature atrial beats as well as a prolonged refractoriness of atrioventricular transmission after concealed nodal conduction of an atrial extrasystole.In the in situ dog heart, local bipolar electrograms recorded from various parts of the bundle of His, bundle branches, and peripheral Purkinje fibers have shown that con cealed conduction may extend through the atrioventricular node and the bundle of His and that block may occur between common bundle and bundle branches or between the latter and the peripheral Purkinje fiber. Block in these locations, which results from local differences in the action-potential duration, has been compared to decremental conduction within the atrioventricular node.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

Cholesterol-fed chickens have been injected subcutaneously for eight weeks with the following drugs: estradiol, diethylstilbestrol, estriol, androstanolone, δ5-androstenediol and androstanediol. Aortic and coronary atherosclerosis, blood and aortic cholesterol, as well as several endocrine structures have been studied. Coronary atherosclerosis has been prevented by estradiol and by diethylstilbestrol, while the other steroids have been ineffective at the dosage used here. When birds were considered individually, no correlation was found between antiatherogenic activity and endocrine changes, thus confirming that testicular depression is not necessary for arterial protection. An attempt to correlate molecular structure and arterial changes has been carried out.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

摘要:

The production of acute necrotic lesions of the myocardium and concomitant changes in myocardial and skeletal muscle potassium concentrations were investigated in rats. Lesions were induced by the administration of 2α inethyl-9α-chlorocortisol plus oral Na2SO4(which caused a profuse catharsis), steroid plus an irritant cathartic (croton oil), steroid plus low-potassium diet, and low-potassium diet alone. Lesions in the various groups were grossly and microscopically indistinguishable. Their incidence and severity were well correlated with the degree of myocardial potassium depletion below a threshold value of approximately 72 mEq./Kg. wet weight. Skeletal muscle potassium was decreased roughly parallel to that of the myocardium, but some what more variably. Other treatments, including steroid or oral Na2SO4alone and steroid plus subcutaneous Na2SO4which failed to produce comparable reductions in myocardial potassium, failed to induce morphological lesions. Any specific interaction between steroid and electrolyte in the production of the myocardial lesions appears to be ruled out by the ineffectiveness of Na2SO4administered sub cutaneously. It is concluded that the “electro lyte-steroid-cardiopathy” results from a simple intracellular potassium deficiency and its sequelae, and that the roles of the steroid-cathartic electrolyte, and other agents and procedures are to induce potassium depletion by various mechanisms.

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1961

数据来源: OVID