摘要:

Measurements of the intracellular pH of mammalian hearts by means of ordinary sealed electrodes are difficult mainly because of the small diameter of most of these muscle fibres. An open-tip pH micro-electrode was designed. The difference between the measurements with this electrode and measurements with a control pyrex glass electrode of the same resistance, filled with the same medium, and immersed in the same solution, is specific for the pH variations of this solution. The new pH electrode, if filled with 0.5 M KCl, has an electrical resistance of 30 to 100 megohms and a sensitivity of about 30 mv/pH unit. The sensitive head of the device has a diameter of about half a micron and a length of one to two microns. The intracellular pH value of isolated rat atria, beating at 200/min in a Krebs-Ringer solution maintained at 30°C and at a pH value of 7.4, was measured with this method and found to be 6.9.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

No differences were found between the sedimentation coefficients, intrinsic viscosities, amino acid contents, and peptide patterns resulting from tryptic digestion of rabbit cardiac and skeletal tropomyosins. From sedimentation and viscosity data, the molecular weights of cardiac and skeletal tropomyosins were estimated to be 54,800 for both. This value is similar to previous estimates of the molecular weight of rabbit skeletal tropomyosin.No evidence was obtained for the existence in heart muscle of tropomyosin A. Of the three more abundant contractile proteins of the heart, myosin, actin, and tropomyosin, only myosin appears to differ from its skeletal counterpart.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Continuous closed-chest massage (mechanized and manual) and ventilation with pure oxygen were performed for 15 and 30-minute periods, to maintain viability in 43 dogs with electrically induced ventricular fibrillation. External countershocks were applied and 32 of the animals lived more than 48 hours. The return of electrical and hemodynamic functions of the heart, as well as the function of the central nervous system, were graded arbitrarily to characterize recovery from poor to excellent. Electrocardiographic changes (lead II) were studied in detail and compared with the gross result of survival or death, and also with more quantitative characterization of recovery.When the initial electrocardiogram after defibrillation contained a P wave, the prognosis was most favorable. When the P wave was absent the amount of ST segment depression in the initial complex differentiated the better from the poorer results.During the first hour following defibrillation, a variety of arrhythmias was noted, as well as varying degrees of change in the R, T, and ST portions of the electrocardiogram. The most serious arrhythmias, in decreasing severity, were idioventricular rhythm, atrio-ventricular block, and multiple premature ventricular contractions. Recovery was poorest when multiple arrhythmias occurred. Changes in the voltage of the R and T waves could not be correlated with prognosis. However, more favorable recoveries were noted in animals without significant changes in the ST segment than in animals having ST segment depression greater than 4 mm.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

In the isolated, perfused dog's tongue, alterations of pulse pressure, at constant mean pressure, can produce parallel or oppositely directed changes in blood flow or can leave the flow unaffected. Parallel changes occur when the vascular bed is passively distensible; opposite changes occur when active contraction of smooth muscle overcomes the effects of passive distensibility, and no change is found when the two effects balance. The first is seen at mean pressures below 80 mm Hg or peak pressures above 155 to 165 mm Hg. The other reactions are produced in the mean pressure range in which autoregulatory reactions occur, viz. opposite changes when the pulse pressure is low and no change under conditions close to in situ mean and pulse pressure. Even when pulse pressure has no observable influence on flow, therefore, it modifies vascular tone.The active response of vascular smooth muscle to pulse pressure persists in part after the removal of the stimulus, opposing stress-relaxation of resistance vessels. Tissue weight changes reflect alterations in capacitance vessel volume which may vary in direction from the volume changes occurring in resistance vessels.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

The effects of altered hepatic blood flow, of splanchnic and hepatic nerve stimulation, and of injecting epinephrine and vasopressin (Pitressin) were studied by perfusing canine livers in vitro. Controlled hepatic arterial perfusions demonstrated a linear relationship between arterial pressure and hepatic arterial inflow. It was found that increases of hepatic artery flow slightly increased portal vein pressure and vascular resistance of the portal vein, and that increases of portal vein flow slightly increased hepatic artery vascular resistance. Splanchnic nerve stimulation caused vasoconstriction of the hepatic artery, portal vein, and mesenteric vasculature. Hepatic nerve stimulation caused constriction of only the hepatic artery and portal vein vasculature. Similar results were obtained by the administration of epinephrine. Pitressin caused marked vasoconstriction of the mesenteric vasculature, vasodilatation of the portal vein vascular bed, and slightly increased hepatic artery vasomotor tone. It was noted that the rise in portal vein vasomotor tone with sympathetic stimulation was due in part to constriction of the “postjunctional” resistance.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Cocainization of a segment of the right or left bundle branch in the canine heart permitted observation of the phenomenon of incomplete bundle branch block in its dual expressions, namely, alterations in the action potential of the respective bundle branch and alterations in the ventricular complexes of the limb-lead electrocardiogram. As the effects of cocainization waned, the bundle action potential reflected intermediate stages between complete block of conduction and normal conduction. Likewise, the attendant ventricular complexes reflected intermediate stages between that form traditionally associated with complete block of the corresponding bundle and normal form. Characteristic shift in direction of the near-terminal QRS axis occurred with and without significant prolongation in QRS.Cocainization of a segment of the common bundle resulted in first, second, or third degree atrioventricular block, unattended by changes in form of associated ventricular complexes. As in bundle branch block, regression of common bundle block occurred also in stepwise fashion.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

The relationships between lateral intravascular pressure, vessel radius, and vessel length were evaluated in the common carotid artery in vivo in thirteen patients during treatment by surgery. Strain was measured in the wall of the carotid artery by means of an electrical caliper sutured to the vessel wall. Lateral intravascular pressure was measured directly with either an 18-gauge needle or a short polyethylene catheter connected to a Statham, P23Db, strain gauge. The results indicate that circumferential and longitudinal strains in the common carotid artery were both small. The mean systolic change in cross-sectional area was 2.10% (±SD 1.08) of the end diastolic area. In three patients a negative circumferential strain was produced by making the cross section of the vessel elliptical. During systole, longitudinal strain increased in four patients and decreased in six patients. The average change in vessel segment length during systole was approximately 1.0% of the end diastolic length.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

The effects of cocaine on the responses of arteries, veins, and small vessels to norepinephrine were studied. Intra-arterial norepinephrine was injected or infused into perfused forelegs of dogs. Angiotensin and serotonin were used as agonists. The effects of postganglionic sympathetic stimulation and of intra-arterial tyramine were tested also.Cocaine in doses of 0.5, 5.0, and 10 mg/kg IV sensitized the arterial and venous segments to norepinephrine; the responses of small vessels were not augmented significantly. The effects of angiotensin and serotonin were not increased. The vasoconstrictor effect of weak and strong submaximal postganglionic sympathetic nerve stimulations was reduced and that of intra-arterial tyramine was suppressed after cocaine.The results allow us to conclude that vascular supersensitivity to norepinephrine after cocaine is not a uniform phenomenon but it is restricted to certain vascular segments. The reason for the sensitization of arteries and veins but not small vessels is unknown. The observations are discussed in light of the recent hypothesis proposed by Furchgott et al on the mechanism of action of cocaine.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

A very high powered amplifier for experimental transthoracic ventricular defibrillation has been described. The effectiveness of both one-half-cycle unidirectional and one-cycle bidirectional square waves in terminating ventricular fibrillation first increases, then reaches a maximum and finally decreases as the duration of the shock is increased. With 10- and 20-ampere unidirectional shocks and 10-ampere bidirectional shocks, a maximal effectiveness of substantially 100% was found under the chosen experimental conditions. Five-ampere unidirectional and bidirectional shocks yielded maximal effectiveness of 70%. The effectiveness of a 128-millisecond, 5-ampere, multicycle square-wave shock is a strong function of frequency and has a maximal value of approximately 70%.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID

摘要:

Using the vinyl acetate corrosion cast technique devised by Tepperman and Pearlman, it has been demonstrated that, in the rat, forced physical exercise (treadmill or swimming) causes an increase in apparent coronary tree size provided the exercise is not too strenuous or frequent.

ISSN:0009-7330    

出版商:OVID    

年代:1964

数据来源: OVID