摘要:

Viscosity of blood was measured in the absence of anticoagulants by means of an improved cone-in-cone viscometer. Data obtained in a study of a series of patients suffering from venous thrombosis and coronary occlusion were compared with data from a control group of healthy subjects. The probability that the large difference in viscosity observed between normal and abnormal blood is due to chance is approximately 1 in 1,000,000. The viscosity of blood remains constant, at any rate of shear, during the first two to four minutes after removal of blood. Clotting starts after various time periods, depending not only on the intrinsic properties of the particular blood sample, but also on the velocity gradient at which such clotting takes place.The following general trends were established: at 36°C the onset of clotting is much more rapid at high rates of shear than at low rates of shear. It appears, however, that at lowered temperatures this trend is reversed.The causes of aggregation of red cells, and the role of this aggregation in clotting, are discussed. It is emphasized that blood is thixotropic, i.e., that its viscosity is both time and rate-of-shear dependent. Thixotropy of blood is due, mainly, to a reversible aggregation of red cells. This suggests the existence of intermittent sedimentation of red cell aggregates during flow in blood vessels. Owing to the existence of a velocity profile, in which the axial region is under zero or near-zero rate of shear, such aggregates should be present especially in large veins and arteries. It appears that an increased thixotropy and viscosity are symptomatic of some thrombotic states.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Evidence is presented for an extra-adrenal factor which is necessary for aldosterone or DCA to produce chronic renal Na retention. To study this factor, the left kidney was transplanted to the neck, both adrenal glands and the right kidney were removed and the thoracic inferior vena cava was constricted in six dogs. For a period of two to three weeks, injection of 25 mg/day of DCA resulted in marked Na retention by the transplanted kidney and ascites formed. Neither renal venous hypertension nor the renal nerves were essential for renal Na retention under these circumstances since the transplanted kidney was denervated and its venous drainage was into the external jugular vein with a normal venous pressure. Removal of the caval ligature in four of the dogs was followed by a diuresis and loss of ascites in spite of continued injection of 25 mg/day of DCA. Similar changes occurred during the injection of aldosterone instead of DCA. Measurements of renal hemodynamic function, first, during Na retention and ascites formation and, later, after removal of the caval ligature showed levels of GFR and RPF during Na retention as high as or higher than those observed during the diuresis and subsequent Na balance. In three hypophysectomized dogs with a very low GFR and RPF, Na retention failed to occur during injection of 25 mg/day of DCA. Also, in three adrenalectomized dogs, administration of a large dose of DCA failed to produce chronic Na retention. Finally, four dogs with a large aortic-caval fistula were given 25 mg/day of DCA; sustained Na retention occurred in all four animals and ascites developed in two of the four dogs. A low rate of Na excretion in these animals was present despite a large postprandial rise in GFR. Available evidence indicates that the extra-adrenal factor is either 1) a humoral agent, or 2) some as yet undefined renal functional change.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Repeatedly bred male and female rats of several strains develop arteriosclerosis spontaneously, irrespective of diet. The severity of the lesions differs between male and female breeders. The morphology and pathogenesis of these lesions have been found to be the same in all of the strains examined. Once the process of arteriosclerosis has been initiated within the abdominal aorta, the subendocardial and medium-sized myocardial coronary arteries also show degenerative changes. The large epicardial coronary arteries become arteriosclerotic only when the process of arteriosclerosis has become severe and generally distributed throughout the aorta.The smaller subendocardial lesions are characterized by occlusive swelling of medial muscle cells and by the presence of vacuoles. These vacuoles react negatively to lipid stains but stain positively for mucopolysaccharide. The myocardial arteries show endothelial hyperplasia, elastosis and accumulations of mucopolysaccharides, especially in the region of fragmented elastic elements. The mucopolysaccharide-rich endothelial cushions eventually become fibrosed. The epicardial arteries show intense accumulations of calcium-mucopolysaccharide complexes. These arteries become greatly distended and can be detected grossly because of their size and tortuosity.Acute and chronic myocardial infarct-like lesions are found but these cannot be associated with specific coronary thrombi or arteriosclerotic lesions. Valvular scarring, calcification of the papillary muscles and disappearance of myocardial mast cells has been correlated with advancing arteriosclerosis.The relation between the intensity of coronary arteriosclerosis and the frequency of breeding, the sex of the animal, and the strain indicates that the pathogenesis of this disease in breeder rats is probably governed by hormonal factors, e.g., sex and adrenal steroids, as well as by genetic factors.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Recovery of excitability of ventricular muscle was measured at numerous points in exposed dog ventricles at varying distances along six radial axes from a primary point of stimulation. Temporal dispersion of recovery of excitability at various points equidistant from the point of stimulation was minimal after a basic beat but was increased after an early premature beat. The degree of dispersion following a basic beat was increased by stimulation of the cardiac sympathetic nerves, administration of chloroform, ouabain intoxication, administration of higher doses of quinidine, myocardial ischemia, and hypothermia, but it was decreased by administration of sympathomimetic amines.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

An experiment was conducted to compare the effects of feeding cholesterol alone, thiouracil alone, and cholesterol and thiouracil combined, on the serum lipids and arteries of dogs. These substances were added to a basal diet rich in linoleic acid. Serum cholesterol and total serum lipids were determined periodically during the four-month period of feeding, and serum and tissue lipids obtained at necropsy were fractionated and analyzed by silicic acid column and gas chromatography.During the period of feeding the experimental diets, three levels of hypercholesterolemia and hyperlipemia were produced. The smallest increase over control levels occurred in the animals receiving cholesterol alone; an intermediate increase was produced in those receiving thiouracil alone; and the greatest increase occurred in the group receiving both cholesterol and thiouracil. The lipemia was proportional to the cholesterolemia in each of the experimental groups. Only those dogs receiving both cholesterol and thiouracil developed arterial lesions.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

The influence of cardiac sympathetic nerve stimulation on certain aspects of ventricular excitation was examined in dogs at constant heart rate. Bipolar electrodes were used to record electrical activity from atrium, His bundle, right Purkinje papillary muscle junction, basal interventricular septum and the epicardial surface of the ventricles. Stimulation of the left stellate ganglion reduced markedly the A-V nodal delay, but produced little or no change of conduction velocity in the Purkinje system or in the pattern of epicardial depolarization. Conduction in muscle was enhanced slightly by stellate stimulation and appears to account for the observed decrease of 2 to 3 msec in ventricular activation time. These data indicate that cardiac sympathetic nerve stimulation does not result in major changes in the sequence of ventricular excitation.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID