OBJECTIVE: To test the effect of female sex hormone depletion and replacement on the distensibility and geometry of the saphenous vein in female rats. DESIGN: Twenty Sprague-Dawley rats were pharmacologically ovariectomized by triptorelin. Ten of these animals received combined hormone replacement with estradiol and medroxyprogesterone acetate. The rest were given vehicle. Ten animals kept parallel without pharmacological ovariectomy served as controls. After 3 months of treatment, a segment of the saphenous vein was dissected. Pressure-diameter curves were recorded in relaxed, contracted, and control states using a microangiograph. RESULTS: Pharmacological ovariectomy lowered venous wall distensibility measured in contraction (at P=8 mm Hg: 4.41+/-1.21*10(-3) m2/N vs. control: 0.79+/-0.14*10(-3) m2/N; p < 0.05). Hormone replacement partially restored this value (1.8+/-0.49*10(-3) m2/N). No alterations in distensibility were found in the relaxed state. After adjusting for body weight, we found that pharmacological ovariectomy lowered venous inner radius significantly compared with control (p < 0.05), whereas hormone replacement increased it compared with pharmacological ovariectomy (p < 0.05) and more significantly compared with control (p < 0.01). CONCLUSION: Sex hormone depletion induces significant alterations in venous distensibility, presumably by inducing initial remodeling of the venous wall. Hormone dependency of distensibility differed in relaxed and contracted states of the vein, so some alterations of contractile elements of the wall may be hypothesized. Lower distensibility of the venous wall found after pharmacological ovariectomy could be part of the mechanism of predisposition for postmenopausal hypertension. This can be reversed by female sex hormone replacement.

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PubMedDate not supplied

Segmental differences in geometric, elastic and contractile characteristics of small intramural coronary arteries of the rat.

The depedence of elastic and contractile properties on the caliber of small intramural coronary arteries was investigated in the rat in vitro. Different segments of the left anterior descending coronary artery branching system were prepared for microarteriography. The segments were cannulated at both ends, immersed in oxygenated normal Krebs Ringer (nKR) solution. Intraluminal pressure was changed at a rate of about 0.5 mm Hg/s between 0 and 150 mm Hg in repeated cycles. The outer diameter was continuously measured with microangiometry. Pressure-diameter curves were recorded after preconditioning pressure cycles in nKR, with PGF2alpha in the bath (7.5 x 10(-6) M), and in maximal relaxation with papaverine (2.8 x 10(-4) M). Biomechanical parameters were computed for vessels grouped according to their calibers (inner diameters: 50-150, 150-250, 250-350, >350 microm). Distensibility and contractility decreased with increasing caliber of the vessels, while the elastic modulus increased. Spontaneous tone was (at 100 mm Hg in mechanically preconditioned vessels) 18.8 +/- 4.5, 8.4 +/- 4.4, 9.7 +/- 3.7 and 8.3 +/- 3.8% in the four groups, respectively. PGF2alpha contraction was maximal around the 300- microm caliber. Our study is the first direct demonstration that intramural small coronary arteries exhibit characteristic variability in their elastic and contractile properties as a function of their caliber. Such differences may be important in segmentally specific control processes of the coronary microcirculation.

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PubMedDate not supplied

Sterically inhomogenous viscoelastic behavior of human saccular cerebral aneurysms.

To clarify the mechanism leading to the development and rupture of intracranial aneurysms, tensile strength and viscoelastic parameters of 22 human saccular aneurysms were investigated. Meridional and circumferential strips from the thin and the thick part of the aneurysm sack and 18 control strips from the basilar artery of 8 patients with pathologies not affecting the cerebral arterial system were studied. The length of the strips was increased in 200- microm steps, while distending force was recorded. Tensile strength and viscoelastic parameters were computed. In both directions, tensile strength of thick strips was significantly lower than that of controls. In the meridional direction, tensile strength of thin strips was significantly larger than that of thick ones (14.5 +/- 4.1 x 10(6) vs. 7.5 +/- 2.0 x 10(6) dyn/cm2, p < 0.05). In the circumferential direction, thin strips tore at lower strain values than thick ones (29 +/- 4 vs. 55 +/- 16%, p < 0.05). Viscoelastic parameters changed in parallel. In circumferential direction, values of thick and thin strips were significantly lower than those of controls. In the meridional direction, values of thin strips were significantly higher than those of the thick ones. These observations show that characteristic mechanical deterioration and steric inhomogeneities accompany the loss of smooth muscle cells and the derangement of connective tissue elements in the wall of intracranial aneurysms, which may explain certain steps in their initiation, enlargement and rupture.

Adult↗

PubMedDate not supplied

Physiology in the oeuvre of a prominent Hungarian medical scientist--Endre H"ogyes.

Endre Hógyes, one of the most prominent and internationally-renown leaders in the field of medical research, especially the treatment of rabies, was born one hundred and fifty years ago in Hungary. E. Hógyes had started his medical and research carrier in 1870. In 1889 he had become vice-president of the Royal Hungarian Society of Natural Sciences and was elected as a member of the Hungarian Academy of Sciences (MTA) and that member of the National Council of Public Health. Scientific carrier of E. Hógyes has always been closely linked to physiological sciences. E Hógyes made a significant contribution to different areas of physiological sciences; his most important scientific publications in this field deal with renal physiology, respitary mechanics, cerebellar function, and associated eye movement. Endre Hógyes was the first to organize Hungarian physiologists into a community. The "Special Physiological Conferences" were initiated within the Hungarian Royal Society of Natural Sciences in 1891. As a token of appretiation, Hungarian physiologists and other medical professionals have announced the year of 1997 as a memorial year of Dr. Endre Hógyes.

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PubMedDate not supplied

Hormone replacement reduces elevated in vivo venous tone in hypertensive ovariectomized rats.

OBJECTIVE: The venous system may play a role in the development and progression of postmenopausal hypertension. In the present study, we investigated the effect of chronic angiotensin II-induced hypertension on the geometric, elastic, and contractile properties of the saphenous vein in sex hormone deficient and replaced female rats. METHODS: Thirty Sprague-Dawley rats were ovariectomized (n = 10), ovariectomized and angiotensin-infused (n = 10), or ovariectomized plus angiotensin-infused and hormone replaced with estradiol and medroxyprogesterone (n= 10). After 4 weeks, the saphenous veins were removed and cylindrical segments of the vessels were placed into a microangiograph and cannulated at both ends. Intraluminal pressure versus outer diameter curves were registered in Krebs-Ringer solution, in maximal norepinephrine contraction, and in full papaverine relaxation. RESULTS: In vivo venous tone of the saphenous vein in ovariectomized plus angiotensin-infused animals was significantly higher than in ovariectomized animals without angiotensin treatment (27.2 +/- 3.7% versus 5.3 +/- 2.1%, respectively; P <.05). Hormone replacement restored venous tone (9.6 +/- 3.4%; P <.01). In vitro pressure-induced myogenic tone was markedly reduced by chronic angiotensin infusion, which was partially reversed by hormone replacement. Passive incremental distensibility was lowered after angiotensin infusion independently of the sex hormone state. CONCLUSION: Hormone replacement improved venous contractility (rapid adaptation response), which was seen as decreased in vivo venous tone, but venous distensibility (chronic adaptation) was not improved by hormone replacement in our short-term study. We demonstrate beneficial short-term effects of hormone replacement on the venous system in our model of postmenopausal hypertension. Further studies might be warranted to see whether long-term benefits can be achieved.

Angiotensin II↗