摘要:

The Korotkoff sounds which serve as criteria for sphygmomanometry are composed of at least two components, (1) an initial transient (Ki), and (2) a more prolonged “compression murmur” (Kc). In this experimental survey, the Doppler flow detection device was used to acquire evidence indicating that Kioccurs at the very onset of flow under the cuff and probably represents an acceleration transient producing abrupt displacement of the arterial wall and surrounding tissues distal to the point of compression. It is nonspecific in nature and can be simulated by tapping the skin of the hand. Kcfollows the initial transient and appears to represent audible sounds from turbulence or eddies in the blood flowing from the constricted artery under the cuff. Muffling seems attributable to the attenuation of frequencies between 60 and 180 cycle/sec, as the initial transient sound disappears, leaving the “compression murmur” as the muffled sound. Studies of cineangiograms and casts of arteries demonstrated that the arterial lumen under the cuff is primarily tapered and that the circumference of the artery shrinks considerably as the wall is unloaded by decreased transmural pressure. In contrast, rubber tubes become unstable and flatten into a binodal configuration when externally compressed. It seems doubtful that rubber tubes constitute adequate models for arteries in situ in the study of the genesis of Korotkoff sounds.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

Indicator dilution techniques were used to determine the vascular and extravascular volumes of the normal human kidney. Renal volumes were corrected to 1.73 m2and refer to one kidney. The renal blood volume (VIG) averaged 34.8±3.1 ml; the water contained in the distribution volume of labeled inulin (VINW) averaged 48.8±9.0 ml, and that of tritiated water (VTHOW) 152±20 ml. VINWwas used as an index of the extracellular space of the kidney exclusive of the tubular lumina. VTHOWwas interpreted to represent the total exchangeable water content of the kidney. The interstitial volume (ΔVINTW) and tubular-cellular volume (ΔVCW) were derived and averaged 27.4±6.2 ml and 93.7±14.3 ml, respectively.Correction for recirculation by exponential extrapolation was studied and appears satisfactory. Evidence is presented for the existence of significant fluctuations in renal blood flow during the indicator collection intervals, and it is suggested that renal volumes be based on flows determined from the recoveries of each indicator.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

The critical opening pressure (COP) of digital vessels after digital nerve block and the change in COP caused by angiotensin at 4 mμg/kilo per min intravenously after the block were compared in 9 normotensive subjects, 8 patients with essential hypertension and 7 patients with various kinds of renal hypertension. The COP after nerve block was less than 20 mm Hg in the normotensives and in 6 renal hypertensives, but more than 20 mm Hg in 7 essential hypertensives. The angiotensin reduced the COP in 7 of the normotensives, increased it substantially in 7 essential hypertensives, but had little effect in 6 renal hypertensives. A significantly greater increase in systemic blood pressure occurred in the essential hypertensives than in the normotensive subjects. In normotensive subjects doses of intravenous angiotensin from 2 to 16 mμg/kilo per min decreased the COP whether preceded by digital nerve block or not. Angiotensin at 8 mμg/kilo per min increased total digital vascular resistance as estimated by venous occlusion plethysmography. The results indicated that angiotensin relaxed smooth muscle in digital vessels of normal subjects but increased vascular resistance. In patients with essential hypertension angiotensin caused contraction of the smooth muscle, a response apparently qualitatively different from normal. In renal hypertensives the smooth muscle had little response to the exogenous angiotensin.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

Pressures were measured in lobar pulmonary arteries, veins, and left atria of anesthetized open-chest dogs. Observations were made before and after snaring the lobar vessels and before and after infusing dextran to raise the mean pressure. Pressure waves were subjected to harmonic analysis. Forward (artery to vein) and backward (vein to artery) transmission (output/input pressure) and transmission ratios (forward/backward transmission) were calculated for each harmonic.At low frequencies, forward transmission was increased by dextran, but backward transmission was unaffected. At low frequencies and high mean pressures the bed was nonsymmetrical, forward transmission being several times greater than backward at the same mean pressure (transmission ratio >1).The findings were analyzed with the aid of simple models. Nonsymmetry at low frequencies and high mean pressures appears to be due to arterial exceeding venous compliance. The findings and resulting theory are pertinent to the understanding of the shape and amplitude of arterial “wedge”-pressure traces.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

Renal medullary heat clearance was investigated in anesthetized dogs to evaluate countercurrent exchange of heat. Sudden changes in the temperature of renal arterial blood were induced by infusion of 3 to 7 ml/min of saline at room temperature. The resulting changes in medullary temperature, measured with fine thermocouples, started with increasing delay from cortex towards the papilla. Average rate constant for heat uptake in the inner medulla was 0.61 min−1. In the outer medulla, rate constants from 0.6 to 5.0 min−1were observed, with the higher values in the subcortical zone. Inner medullary clearance rose during diuresis, but was practically uninfluenced by lowering perfusion pressure to 35 mm Hg. Calculated heat conduction (diffusion) from cortex into medulla was close to observed clearances, which are thus mainly determined by heat conduction. Clearance due to flow in vasa recta and loops of Henle was small, presumably due to efficient countercurrent heat exchange, whereas urine flow in collecting ducts is not subject to this effect. Formulas for countercurrent exchange not taking into account length diffusion (parallel to the vasa recta) are not valid for medullary heat exchange. The present heat clearance technique cannot be used for estimating medullary blood flow.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

Simultaneous left and right atrial surface electrograms were obtained from the right and left atria of 30 chick embryos. These were divided into 3 equal groups that were studied at 15 to 16, 10 to 11, and 5 to 7 days of incubation. The embryos were removed from the shell with their circulation intact and temperature maintained constant. In an early stage of development (5 to 6 days), the left atrium and its appendage were larger than the right, and left preceded right atrial depolarization. At and after 7 days of incubation, the right atrium and its appendage were larger than the left, and right preceded left atrial depolarization. The intervals for interatrial conduction and for atrio-ventricular conduction were about the same at all stages of development. Since the length and width of the heart at 15 to 16 days of incubation were about 3 times those of a heart at 5 to 7 days of incubation, it is proposed that the higher the stage of development of the chick embryo the greater must be the conduction velocity between the two atria and from atrium to ventricle. This was assumed to be related to the degree of development of the specialized conduction pathways that are probably absent or underdeveloped in early stages of development.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

Changes in left ventricular performance, stroke volume, and peripheral vascular resistance were studied in dogs after combined and separate stimulation of the aortic and carotid chemoreceptors. Selective stimulation of the aortic chemoreceptors produced an immediate increase in myocardial contractility as judged by the force developed by a strain gauge arch sewn into the left ventricular myocardium and by changes in the first derivative of the left ventricular pressure. Similar results were seen when heart rate changes were prevented by prior administration of atropine, when changes in outflow impedance were prevented by previous blockade of the alpha-adrenergic receptors, and when there was combined chemoreceptor stimulation. Beta-adrenergic blockade prevented the increase in myocardial contractility observed after chemoreceptor stimulation. With selective carotid chemoreceptor stimulation there was no significant change in contractility. Aortic chemoreceptor stimulation increased the heart rate and peripheral vascular resistance, while stroke volume decreased; carotid chemoreceptor stimulation slowed the heart rate and increased the stroke volume, but not change peripheral vascular resistance.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

In anesthetized dogs the vagus nerve was stimulated for 2 min; during the first minute the ventricles were driven at a rate higher than the control sinus rate; after discontinuation of the drive, the duration of asystole was prolonged. When the ventricles were driven at a rate lower than the sinus rate during vagal stimulation the subsequent asystole was shortened. Slowing sinus activity by graded vagal stimulation before maximal vagal stimulation led to a shorter asystole. Driving the ventricles at a rate higher than the sinus node rate before vagal stimulation resulted in longer asystole. In animals with chronic atrioventricular block, “overdriving” the ventricles resulted in subsequent temporary inhibition of ventricular pacemakers. In dogs with atrioventricular block, coronary sinus plasma potassium increased during the period of ventricular overdriving, and the magnitude of the rise was a function of the driving rate. These results support the concept that ventricular asystole results from the suppressive action of the fast rate imposed by the sinus node upon the slowly discharging ventricular pacemakers. Suppression of sinus node activity by the vagus reveals the rate-dependent inhibition of ventricular pacemakers. The mechanism of inhibition may be related to changes in ionic concentration gradients.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

Thirty dogs were made hyperthyroid by feeding them 1 g/kg USP thyroid powder or injecting 1.2 mg/kg of 1-thyroxine/day. Seven of the 30 dogs used had surgically induced mild valvular lesions of the right heart to determine whether preexistent organic disease was a requisite to the induction of failure in hyperthyroidism.At 2 to 27 months the animals were subjected to cardiac catheterization for measurement of cardiac work and metabolism in vivo. The animals were then killed and the levels of the high energy phosphate compounds creatine phosphate (CP) and the adenine nucleotides (ATP+ADP) in the heart were measured as an index of the net efficiency of the processes of oxidative phosphorylation.By hemodynamic or histopathologic criteria, 13 dogs showed signs of failure, only 3 of which had preexistent valvular lesions. The failure was not accompanied by a decreased efficiency of oxidative phosphorylation. Net levels of CP and ATP + ADP in the myocardium were normal. Preliminary studies with sarcosomes isolated from 5 animals also revealed normal P/O ratios in 3 dogs with and in 2 without signs of cardiac failure. Liver mitochondria isolated from these same 5 animals all demonstrated decreased P/O ratios. Decreased myocardial extractions of both glucose and pyruvate occurred with failure, suggesting some degree of myocardial hypoxia with increased intracellular glycolysis. Areas of relative hypoxia may exist in a hypertrophied myocardium of the hyperthyroid animal.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID

摘要:

The effects of beta-adrenergic receptor stimulants (nylidrin and isoproterenol) on the hemorrhagic shock state of anesthetized dogs were measured and compared to those of phenoxybenzamine to determine the therapeutic effectiveness of the combined cardiac stimulatory and peripheral vasodilatory actions of the former drugs. Anesthetized dogs were subjected to 3 hours of hypovolemia followed by the return of the shed blood. Nylidrin, isoproterenol (continuous infusion), and phenoxybenzamine were administered 1 hour after bleeding the animals and heart rate, arterial blood pressure, venous hematocrit, coronary blood flow, cardiac output, ventricular contractility, and survival rates were measured. Nylidrin and isoproterenol afforded significant protection against shock deaths, whereas phenoxybenzamine did not increase survival over control values. Mild to moderate intestinal hemorrhage and distention were noted in the isoproterenol- and phenoxybenzamine-treated animals, but not in the nylidrin-treated animals. Phenoxybenzamine gradually decreased the arterial blood pressure and additional quantities of blood had to be infused to maintain cardiac output and blood pressure. Ventricular contractile force progressively decreased in the phenoxybenzamine-treated animals, whereas isoproterenol and nylidrin enhanced the force of ventricular contractions. In the presence of existing hypotension, isoproterenol and nylidrin maintained cardiac output. These agents deserve further consideration as potentially useful therapeutic agents in the management of shock states.

ISSN:0009-7330    

出版商:OVID    

年代:1967

数据来源: OVID