ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

摘要:

The dynamic geometry of the left ventricle was assessed with the use of chronically implanted pulse-transit ultrasonic dimension transducers. The orientation of the transducers allowed the measurement of left ventricular minor and major axis diameters and equatorial wall thickness in the conscious dog. The left ventricle was modeled as a three-dimensional, prolate ellipsoidal shell. Left ventricular and pleural pressures were measured with high fidelity micTomanometers. Aortic blood flow was obtained with electromagnetic flow probes. To test the assumptions inherent in this technique, left ventricular mass, internal volume, stroke volume, and peak aortic flow were computed from the dimension data and compared to directly measured values. Correlation coefficients of 0.95 or greater were obtained for each of these comparisons. In addition, the calculated left ventricular mass was constant to within ±6% of the mean value throughout the cardiac cycle. We found that the dynamic contraction pattern of the left ventricle was dependent on the physiological state of the dog. Furthermore, in the conscious state, shortening of the minor axis diameter, lengthening of the major axis diameter, and slight thickening or thinning of the wall were noted during isovolumic contraction (isovolumic ellipticalization pattern). In the open-chested, anesthetized state, however, marked rearrangements in geometry were observed during isovolumic contraction manifested by lengthening of the minor axis diameter, shortening of the major axis diameter, and significant thickening of the wall (isovolumic sphericalization pattern). We also observed that left ventricular volume was significantly diminished in the open-chested state. The isovolumic contraction pattern in open-chested dogs could be changed from sphericalization to ellipticalization by increasing end-diastolic volume with the infusion of saline. During a vena caval occlusion in the conscious state, the contraction pattern changed from isovolumic ellipticalization to isovolumic sphericalization as the end-diastolic volume decreased. Thus, the exact pattern of left ventricular contraction was found to be a function of left ventricular volume.

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

摘要:

Twenty-one dogs were studied under conditions of normal oxygenation and hypoxia with the mlcrosphere distribution method to determine the effect of arterial oxygen saturation on the regional distribution of cardiac output. The dogs were anesthetized and artificially ventilated. Cannulas were placed in the left ventricle to administer microspheres and in a peripheral artery to determine cardiac output. Each dog received two microsphere injections: (1) while normally oxygenated (room air), and (2) under hypoxia (10% oxygen-90% nitrogen in 10 dogs and 5% oxygen-95% nitrogen in 11 dogs). Absolute cardiac output increased from 87 ± 15 ml/min per kg to 101 ± 14 ml/mln per kg during mild hypoxia (10% oxygen) (P< 0.05), and from 73 ± 17 ml/min per kg to 120 ± 24 ml/min per kg during severe hypoxia (5% oxygen) (P< 0.01). Absolute Mood flow increased to all organs except skin and muscle during hypoxia, although there were decreases in the fractional distribution of cardiac output to the splanchnic bed and kidney. Striking changes were found in coronary, hepatic, and cerebral circulation, and the organ with greatest response to hypoxia was tbe heart, with increased coronary flows of 37% and 285% during exposure to 10% and 5% oxygen, respectively. Hence, low oxygen levels in blood cause redistribution of cardiac output and arterial content plays an important role in blood flow regulation.

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

摘要:

Cardiac myosin from thyrotoxic animals (myosin-T) exhibits elevated Ca2+-ATPase activity which is resistant to further stimulation by sulfhydryl modification. In the present study, we bare compared the enzymatic properties of myosin-T with those of myosin from eutbyroid rabbits (myosin-N) and toe derivatives of myosin-T and myosin-N formed by Mocking tile most rapidly reacting class of thiols (SH,) with yV-ethylmalelmlde (NEM). Vmaxfor Ca2+-ATPase of myosin-T was about 250% greater than myosin-N and was nearly the same as NEM-modified myosin-N. Values for tbe apparent Kmof myosin-T and NEM-modified myosin-N were 200% greater than tbe value for unmodified myosin-N. Vmaxand Kmfor K+(EDTA)-ATPase activity of NEM-modified myosin-T and myosin-N were identical. The Ca2+saturation, pH, and salt-dependency curves for tbe ATPase activity of myosin-T were parallel to the curves for myosin-N and differed from tbose for tbe NEM-modified myoslns. Myosin-T exhibited an increased rate of hydrolysis of ATP, CTP, and UTP in both low (0.05 m) and high (0.5 m) KC1 medium. NEM-modified myosin-N showed increased hydrolysis of ATP and CTP in low KCI medium and increased hydrolysis of ATP, CTP, and UTP in high KCI medium. These results support tbe hypothesis that the enzymatic behavior of myosin-T may be caused by an alteration in tbe active site near the SH, thiols. Tbe unique enzymatic properties of myosin-T did not seem to be the result of a major change in structure. The electropboretic pattern of light chains from myosin-T and myosin-N was tbe same in polyacrylamide gels containing either 8 M urea at pH 8.6 or sodium dodecyl sulfate. Also, myosin-T had a normal amino acid composition and lacked 3-methyl-histidine and hot acid-stable phosphate.

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

摘要:

Abnormally low plasma flow to renal papilla characterizes Dahl hypertension. When eating a normal Na diet (0.3% NaCl) both hypertension-seiisitive (S) rats and hypertension-resistant (R) rats, 16 weeks old, have fairly normal blood pressure (BP), averaging 144 and 129 mm Hg, respectively. However, even in this barely hypertensive state, 18 S rats bad a 31% lower papillary plasma flow (LilienTield method) than 22 R rats, 19.2 ml/100 g of papilla per min compared to 25.6 (P< 0.001). When a high (8%) NaCl diet was fed for 7 days, R rats increased papillary plasma flow from 25.6 on 0.3% NaCl to 33.8 on 8% NaCl, a 32% rise (P< 0.001). S rats increased papillary flow from 20.4 to 24.8, a 22% rise (P< 0.05). When a high (8%) NaCl diet was fed for 4 weeks, R rats increased papillary plasma flow from 25.7 ml/100 g per min on 0.3% NaCl to 29.5 ml/100 g per min on 8% NaCl, a 15% rise (P < 0.025). S rats increased papillary flow from 17.7 to 20.0 ml/100 g per min (not significant). S rats on 8% NaCl had a papillary flow 32% lower than R rats on 8% NaCl (P< 0.001). BP of S rats rose to 162 mm Hg after 4 weeks on 8% NaCl; in R rats, BP did not rise at all. S rats on 0.3% NaCl hare a low papillary flow even in a borderline hypertensive slate. When challenged with 8% NaCl, R rats increased papillary flow, an adaptation possibly important for the natriuresis. S rats failed to achieve this same high papillary flow. Lacking this adaptation, hypertension may then conceivably occur in S rats to accomplish natriuresis through a "pressure natriuresis" mechanism. Papillary flow also decreased by 11% in 26 Kyoto 17-week-old spontaneously hypertensives (BP, 182 mm Hg) compared to 24 Kyoto nonnotensives (BP, 118 mm Hg), 29.5 vs. 33.2 ml/100 g per min (P< 0.001). Thus, low papillary flow exists in both hypertensions.

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

摘要:

The left or right cardiac sympathetic nenes in open-chest, anesthetized dogs were stimulated at mean frequencies of 2 or 4 Hz. The stimuli were applied intermittently, in patterns with repetition rates of either 60/min or 15/min, to simulate the spontaneous patterns of sympathetic neural activity that occur synchronously with the cardiac or respiratory cycles, respectively. With either repetition rate, intermittent stimulation of the left sympathetic nerves was about 10-20% less effective in enhancing myocardial contractile force (CF) and about 10% less effective in increasing coronary sinus blood flow than was steady stimulation at the same mean frequency. With right-sided stimulation, there was no appreciable difference between steady and intermittent stimulation patterns with respect to the effect on heart rate. With either left-or right-sided stimulation, the rate of norepinephrine (NE) overflow into the coronary sinus blood was 20-40% less with intermittent than with steady stimulation. Cocaine administration did not materially affect this difference in NE overflow. It was concluded that the higher instantaneous frequencies that prevail during intermittent stimulation result in a reduction in the rate of NE release at the sympathetic postganglionic nerve endings in the heart.

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

摘要:

We measured steady state capillary hydrostatic pressure (P,ci). plasma and lymph protein concentrations, lymph and blood flow, and capillary filtration coefficients in an in situ loop of cat small intestine at venous outflow pressures (Pv) of 0, 5, 10, 15, 20, 25, and 30 mm Hg. The data were used to calculate colloid osmotic pressure of lymph and plasma, interstitial fluid pressure (PT), preand postcapillary resistances, and a tissue pressure-volume curve of the intestinal interstitium. When Pvwas derated from 0 to 30 mm Hg, lymph protein concentration decreased from 3.8 to 1.9 g/100 ml (representing a change in colloid osmotic pressure of 6.2 mm Hg), lymph flow increased 7-fold (or an equivalent imbalance in Starling forces of 4.3 mm Hg), and the calculated PTincreased from -1.8 to +5.3. Because lymph flow draining the loop decreased during the determination of Pc,iat venous pressures between 15 and 30 mm Hg, the corresponding calculated PTmay be in error by 1-2 mm Hg. The tissue pressure-volume relationship calculated from the data indicates that the intestinal interstitial volume expands nonlioearly and this expansion is characterized by two distinctly different compliant components: (1) tissue compliance is low at Pvbetween 0 and 15 mm Hg (0.4 ml/mm Hg), and (2) at Pvgreater than 15 mm Hg the tissue compliance is relatively high (4 ml/mm Hg). We found that when Pvwas elevated from 0 to 15 mm Hg, increases in PTare the major tissue adjustments that oppose the increased filtration pressures. Furthermore, at Pvof 20-30 mm Hg, tissue protein concentration decreases, lymph flow relative to the filtration coefficient ΔPdrop) increases and, to a much lesser extent, PTincreases. Finally, the combination of these changes in tissue force at high filtration pressures represent a maximum tissue edema "safety factor" of 10 mm Hg; further increases in filtration pressures result in large volume movements into the intestinal lumen.

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID

摘要:

The transcapillary escape rate of albumin (TERalb), i.e., tbe fraction of intravascular mass of albumin that passes to the extravascular space per unit of time, was determined from tbe disappearance of intravenously injected "M-labeled human serum albumin during the first 60 minutes after injection in 10 subjects with chronic right heart failure. The investigation was repeated after sodium and water depletion. Before treatment TERalbwas significantly elevated (mean 83 ± 1.6% (SD)/hour, in comparison to values for normal subjects (mean 5.4 ± 1.1%/hour,P< 0.001). With treatment TERalbdecreased significantly (mean 5.9 ± 1.2%/hour,P< 0.01). Right atrial pressure decreased from an average of 10 mm Hg to 6 mm Hg during treatment. A statistically significant, positive correlation was found between TERalband right atrial pressure (r- 0.77,P< 0.001). Our results best can be explained by increased filtration, mainly through the venous end of the micro-vasculature, due to the increased venous pressure in heart failure.

ISSN:0009-7330    

出版商:OVID    

年代:1976

数据来源: OVID