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Biomedical subjects

C L Seidel

Publications and source records attributed to C L Seidel.

47 records · Page 3Linked to original sources
PubMed1980

Mechanical and biochemical alterations of aorta induced by hydralazine hypotension.

Previous experiments from this laboratory indicated that the actomyosin content of aorta from spontaneously hypertensive (SHR) rats was greater than that from normotensive (WKY) rats. The purpose of the present experiments was to determine the effect of hydralazine-induced hypotension on actomyosin content and mechanical properties of aorta from SHR and WKY rats. Ten-week-old WKY and SHR rats were given to tap water or tap water containing 80 mg/l of hydralazine for 2 weeks and at the end of this time the actomyosin content (sodium dodecyl sulfate-polyacrylamide gel electrophoresis), the contractile responses to potassium chloride and phenylephrine and the passive stress-strain properties of the aorta were determined. Hydralazine-treated rats had a significantly lower systolic pressure after 1 week which remained lower for the remainder of the treatment period. Treated WKY and SHR rats exhibited a reduced actomyosin content relative to total protein content of cell number (based on DNA determination). Mechanically, aorta from treated animals showed no change in their passive elastic properties or in their sensitivity (ED50) to either agonist; however, the maximum contractile response to both agonists was significantly reduced. Normalization of force development to actomyosin content indicated: 1) that aorta from SHR rats develop less force for a given amount of actomyosin than WKY aorta; 2) a 2-week period of hydralazine hypotension results in a reduction in force development in both WKY and SHR aorta that can be accounted for by a reduction in cellular actomyosin content; and 3) this period of hydralazine hypotension does not return the contractile effectiveness of actomyosin from SHR aorta to that of actomyosin from WKY aorta.

Actomyosin↗
PubMed1979

Effect of ionophore RO 2-2985 on the contractile response of canine coronary, renal and femoral arteries.

The effects of the ionophore, RO 2-2985 (X537A, RO) were studied on isolated coronary, renal and femoral arteries in two types of experiments: (1) the effect of RO as a modulator of various contractile effects of KCl and phenylephrine (PE), and (2) the effect of RO itself as a contractile agonist. The effect of the ionophore A23187 was observed in similar experiments to help determine the nature of the RO response. In the first type of experiment, RO was found to have a differential effect upon the arteries contracted with KCl. The coronary arteries relaxed upon addition of the ionophore, whereas, the femoral and renal arteries did not. A23187 had only a transient effect on KCl-contracted coronary arteries. RO relaxed femoral and renal arteries contracted with PE, and A23187 had only a transient effect. RO attenuated ED50 values and maximum tension developments to both KCl and PE, and A23187 had no effect on these parameters. In the second type of experiment, RO (only at 10-5 M) was found to contract femoral and coronary arteries, but had no effect on renal arteries. Experiments with alpha-blocking agents and calculations using association constants of RO for catecholamines suggest that RO is not acting via catecholamine chelation. The dissimilarity between the effects of RO and A23187 suggest that RO may not be working through a specific effect on Ca++. These differential responses to RO suggest variations in intervessel regulation of PE- AND KCl-induced contradictions and can explain, in part, the in vivo effects of RO on regional blood flow.

Animals↗
PubMed1979

Changes in rat aortic actomyosin content with maturation.

It has been reported by several investigators that the maximum active force generating ability (i.e., force/tissue cross-sectional area) of the aorta increases as the animal matures and then declines later in life. The purpose of this work was to determine if changes in the actomyosin content of the aorta occur during maturation which could contribute to the observed changes in force generating ability. The actin and myosin contents of rat thoracic aorta obtained from animals 3, 5, 7, 16 and 43 weeks of age were determined by quantitative gel electrophoresis, and were normalized with respect to tissue mass and protein and DNA contents. The results indicate that the amount of actomyosin (i.e., actin + myosin heavy chains) per tissue mass, protein and DNA increases rapidly during the first 5 weeks after birth and then remains constant. These observations suggest that the increasing actin and myosin heavy chain content of aorta observed early in life could explain in part the increasing force generating ability reported during this period, but that a loss of contractile material is not responsible for the reduction in force generating ability seen later in life.

Actomyosin↗
PubMed1976

Radio and microwave radiation and experimental atherosclerosis.

The effect of radio and microwave radiation on dietary atherosclerosis of rabbits was tested. 16 New Zealand white rabbits were exposed to microwave (2.45 GHz) radiation at a power density of 20--30 mW/cm2 for 4 h a day, 5 days a week for 8 to 10 weeks. Irradiated animals had serum cholesterol concentrations, aortic wall cholesterol concentrations and percentage of intimal surface involved in atherosclerotic lesions which were not different from age and weight matched controls. Continuous radio frequency irradiation (1 MHz) for 8 to 11 weeks with a field strength of 30 V/cm also failed to change these indices of atherogenesis. We conclude that under the conditions of these experiments radio and microwave irradiation do not affect the course of diet induced atherogenesis.

Animals↗
PubMed1976

Stress relaxation in hog carotid artery as related to contractile activity.

The purpose of this work was to test the hypothesis that stress relaxation (SR) in vascular smooth muscle is related to the amount of contractile activity (developed stress) and perhaps a property of the contractile element (CE). Using medial-intimal strips from the hog carotid artery, a strain (delta 1/l0, where l0 equals optimal length for force development) of 2% was applied at two different rates in the presence of various levels of developed or passive stress. Developed stress was altered either by changing the extracellular K-ion concentration with the strip length equal to l0 or by stimulating with a salt solution containing 30 mM KCl at various strip lengths. Passive stress was altered by varying strip length. At each level of developed or passive stress the magnitude of the increment in stress due to the strain (induced stress) and the SR were noted. SR varied directly with the magnitude of the developed stress, but there was a small and relatively unchanging amount of SR when passive stress was varied. At a given level of developed stress, the magnitude of SR was greater at a strain rate of 0.016 than at 0.001 l0/sec. When developed stress was altered, the magnitude of SR was essentially equal to the amount of induced stress; however, when passive stress was varied, SR was always less than induced stress. These observations are consistent with the hypothesis that, in the presence of developed stress, a large fraction of the SR represents the lengthening of the CE. This increased CE length allows a reequilibration of stress between the series elastic element and the contractile element. In the absence of developed stress, SR may represent a passive, physical property of this heterogeneous tissue.

Animals↗
PubMed1975

Coronary artery cyclic AMP content during adrenergic receptor stimulation.

The purpose of this study was to test the hypothesis that the mechanical response of coronary smooth muscle following adrenergic receptor stimulation was mediated by changes in cyclic AMP content. Dibutyryl cyclic AMP caused relaxation of coronary artery strips. Aminophyline caused relaxation and a 254% elevation of cyclic AMP content (P less than 0.005). Phenylephrine caused contraction but no significant change in cyclic AMP content (P greater than 0.4). Epinephrine alone caused contraction and a 99% elevation of cyclic AMP content (P less than 0.001). The alpha blocker, phentolamine, reversed the mechanicaal response to epinephrine, but it did not significantly (P greater than 0.15) reduce the effect of epinephrine on cyclic AMP content. Propranolol enhanced the contractile response to epinephrine and attenuated the epinephrine-induced increase in cyclic AMP content. These results suggest that the contraction of coronary arteries associated with alpha-receptor stimulation is not mediated by changes in cyclic AMP content; however, relaxation associated with beta-receptor stimulation may be mediated by an increase in cyclic AMP content.

Aminophylline↗
PubMedDate not supplied

Hydralazine: effect on contraction mechanics of WKY and SHR rat heart muscle.

Chronic hydralazine treatment (2 weeks) in 22-week-old normotensive (WKY) and spontaneously hypertensive rats (SHR) significantly lowered the systolic blood pressure in both groups. Left ventricular papillary muscles from nontreated and treated WKY and SHR were placed in an isometric myography, and contractile indices monitored. Nontreated WKY and SHR were not statistically different comparing: tension, maximum contraction and relaxation rates, time to maximum tension, total contraction time, or passive and active length-tension curves. Hydralazine-treated WKY and SHR had significantly reduced tension and maximum rates of tension development and relaxation; passive length-tension characteristics were not altered. Stressing the papillary muscles with increased frequency of electrical stimulation (0.1-2 Hz) did not differentiate the various groups. Significant (p less than 0.05) alteration with isoproterenol (10(-9)-10(-5) M) occurred with the hydralazine-treated WKY, which responded with a greater increase in relaxation rate than the hydralazine-treated SHR. It is suggested that the clinically very useful drug, hydralazine, causes a distinct contractile state alteration in rat myocardium after treatment sufficient to lower SHR blood pressure to a normal range.

Animals↗