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Biomedical subjects

A Simon

Publications and source records attributed to A Simon.

At least 289 records · Page 16Linked to original sources
PubMed1993

Intrinsic effect of antihypertensive treatment with isradipine and metoprolol on large artery geometric and elastic properties.

The effects of isradipine and metoprolol were studied on the brachial arteries of two groups of 14 patients with hypertension, 90 minutes after the first dose and after 3 months of treatment. Diameter (pulsed Doppler) and compliance (pulse-wave velocity) were measured and calculated in isobaric conditions by way of a model that allowed discrimination of the active intrinsic drug action. Isradipine increased measured and isobaric diameter during short-term (p < 0.05) and long-term administration (p < 0.05), whereas metoprolol did not change it. Active diameter effects were different between drugs during short-term administration (p < 0.05). Isaradipine increased measured and isobaric compliance during short-term (p < 0.05) and long-term administration (p < 0.05). Short-term administration of metoprolol decreased measured compliance (p < 0.01). Metoprolol decreased isobaric compliance during short-term (p < 0.01) and long-term (p < 0.05) administration. Active compliance effects were different between drugs during short- and long-term administration (p < 0.01). These arterial intrinsic drug effects, independent of the pressure-lowering influence, suggested different mechanisms, consisting of a large artery smooth muscle relaxation for isradipine and an isometric arterial constriction for metoprolol.

Adult↗
PubMed1993

[Methodical studies of metabolism oriented methionine requirement determination in broiler chicks. 2. Effect of feeding frequency on methionine utilization].

The effect of feeding frequency (daily 2 times feeding for 1 hour or 6 times feeding for 30 minutes) and a different methionine content of the diet on weight gain, N-balance and metabolic 35S-methionine degradation was investigated in broiler chickens. Weight gain and N-balance were not improved by increased feeding frequency. At the high feeding frequency, weight gain and N-balance were even depressed when diets with methionine deficiency (without methionine supplementation) were fed. No effects of feeding frequency and the amount of DL-methionine supplementation on the level of excreted 35S after i.v. injection of 35S-methionine were observed.

Animal Feed↗
PubMed1993

Preventive effect of chronic converting enzyme inhibition on aortic stiffening induced by renovascular hypertension in conscious dogs.

OBJECTIVE: The aim was to assess the influence of the renin-angiotensin system on the geometrical and elastic properties of the aorta in conscious dogs, using a model of renovascular hypertension, and to examine the effects of inhibition of the system by the angiotensin converting enzyme inhibitor spirapril. METHODS: The aortic elastic behaviour in response to renovascular hypertension was studied in 15 conscious dogs instrumented with a pressure microtransducer and a pair of ultrasonic diameter dimension gauges in the upper descending thoracic aorta. Renovascular hypertension was induced by surgical occlusion of one renal artery and stenosis of the other. One day after renal surgery, dogs were randomly assigned to two groups receiving for two months either the new angiotensin converting enzyme inhibitor spirapril (n = 8) or a placebo capsule (n = 7). The two groups of dogs were compared to a control group of normotensive dogs (n = 7). After two months of treatment the elastic properties of the aorta were studied by computation of the beat to beat pressure-diameter hysteresis loops obtained during transient increase of pressure induced by bolus doses of angiotensin. The aortic pressure-diameter (P-D) relationship, obtained over a wide range, was fitted by an exponential fit (P = alpha.e beta D), where beta is the stiffness index. A decomposition of the P-D curve according to a biphasic model of the parallel arrangement of elastin and collagen enabled two pressure-diameter elastic moduli to be obtained, one representing the resistance to stretch at low pressure levels (elastic fibres and smooth muscle), and the other representing the resistance to stretch at the highest pressures (collagen fibres). RESULTS: The pressure-diameter curve of the placebo group was shifted to the left compared to the curves of the control and spirapril groups, showing that renovascular hypertension was associated with isobaric reduction of aortic diameter. The stiffness index beta was higher (p < 0.05) in the placebo group [0.605(SD 0.304) mm-1] than in either the control group [0.362(0.126) mm-1] or the spirapril group [0.348(0.083) mm-1], suggesting that renovascular hypertension was associated with aortic stiffening. The biphasic analysis showed that the collagen pressure-diameter elastic modulus was unaffected by spirapril, whereas the elastin pressure-diameter elastic modulus was significantly reduced by converting enzyme inhibitor with respect to the placebo (p < 0.05). CONCLUSIONS: Chronic converting enzyme inhibition by spirapril prevents the isobaric aortic diameter reduction induced by renovascular hypertension in conscious dogs and decreases aortic stiffness, in particular by changing the elastic behaviour of the elastin fibres rather than of the collagen fibres.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

In vivo shear flow and erythrocyte membrane fluidity in hypertensive patients.

1. To evaluate the response of red blood cells subjected to the shear flow in hypertension, the relationships between wall shear phenomena determined in vivo in the brachial artery of hypertensive patients and the modifications of the membrane dynamics measured in vitro in erythrocyte ghosts of 32 patients were investigated. 2. Two fluorescent probes, diphenylhexatriene (DPH) and its trimethylamino-derivative (TMA-DPH), localized respectively in the lipid membrane core and at the lipid-water interface, were used. 3. Shear rate, shear stress and blood velocity were positively correlated with TMA-DPH anisotropy (P = 0.015, 0.005 and 0.026, respectively), but not with that of DPH. This indicates that wall shear forces were associated with the microviscosity of the outer part of the cell membrane. 4. The changes in wall shear forces and erythrocyte membrane microviscosity probed by TMA-DPH or DPH were observed to vary in parallel under nitrendipine therapy. 5. These results suggest that in vivo shear forces participate in the control of erythrocyte membrane fluidity or that erythrocytes adapt their membrane properties to blood flow conditions.

Antihypertensive Agents↗
PubMed1993

In vitro cultivation and immunogenicity of human cardiac valve endothelium.

Endothelial cells were derived from aortic and mitral valves (n = 17) by collagenase digestion and subsequently cultivated in RPMI medium supplemented with 20% fetal calf serum. The cells were stained in an alkaline phosphatase-anti-alkaline phosphatase stain for the expression of MHC Class I and Class II antigens, ICAM-1, ELAM-1, F VIII, and H/Y. The endothelium showed a strong expression of Class I, H/Y, and ICAM-1 molecules, and weak expression of MHC Class II molecules. In contrast to vascular endothelium that is known to express F VIII constitutively, cardiac valve endothelium was found to be negative. F VIII and ELAM-1 were only expressed after stimulation with recombinant interferon-gamma. To analyze the immunogenicity of valve endothelium, cells were used as stimulator cells in a mixed cell culture reaction using lymphocytes as responder cells. Endothelial cells had a 2 to 3 times higher stimulatory effect than peripheral blood lymphocytes. These data allow speculation on whether the observed degeneration of homografts can be reduced if HLA matching is performed prior to valve implantation.

Cell Adhesion Molecules↗
PubMed1993

Evidence for in vivo carotid and femoral wall thickening in human hypertension. Groupe de Prévention Cardio-vasculaire en Médecine du Travail.

Little is known of the in vivo structural changes of large arteries in uncomplicated hypertension. Therefore, we measured the intima-media thickness and lumen diameter of common carotid and femoral arteries by a computerized ultrasonographic technique in 25 normotensive and 25 never treated hypertensive men of similar age (from 25 to 72 years). The intraobserver variability of carotid and femoral wall thicknesses was 4.3% and 5.6%, respectively. Moreover, an in vitro study of 13 human arterial segments removed at autopsy demonstrated a strong correlation (r = .989, P < .001) between computerized ultrasonic and histological intima-media thickness measurements. Compared with control subjects, hypertensive patients had similar arterial diameters but higher carotid and femoral intima-media thicknesses (P < .001) as well as higher ratios of carotid and femoral intima-media thickness to lumen (P < .001, P < .01). The carotid thickness was correlated with age in control subjects (r = .48, P < .05) but not in hypertensive patients. The femoral thickness was correlated with age both in control subjects (r = .55, P < .01) and in hypertensive patients (r = .46, P < .05). Thus, carotid and femoral arterial walls of hypertensive patients were thickened. This thickening was not due to age, although aging also thickened both vessels in control subjects and the femoral artery only in hypertensive patients. Such a wall thickening associated with a normal diameter provides direct evidence of vascular growth and represents a new target to monitor noninvasively in vivo for large artery changes in human hypertension.

Adult↗
PubMed1993

Assessment of smooth muscle contribution to descending thoracic aortic elastic mechanics in conscious dogs.

Early investigators found contradictory evidence that vascular smooth muscle activation reduces the elastic modulus of the arterial wall under isotonic conditions but increases it under isometric conditions, concomitant with increased pulse-wave velocity. We examined the individual contributions of aortic constituents to the elastic modulus of the aortic wall to determine if isobaric analysis produces an accurate assessment of vascular smooth muscle activation. We used a modified Maxwell model assuming an incremental elastic modulus (Einc) composed of the elastic modulus of elastin fibers (EE), the elastic modulus of collagen fibers (EC) affected by the fraction of collagen fibers (fC) recruited to support wall stress, and the elastic modulus of the vascular smooth muscle (ESM) according to the following formula: Einc = EE+EC x fC+ESM.Einc was assessed in eight conscious dogs using descending thoracic aortic pressure (microtransducer) and diameter (sonomicrometry) measurements. Stress-strain relations in the control state and during activation of smooth muscle by continuous administration of phenylephrine (5 micrograms.kg-1 x min-1) were obtained by transient occlusions of the descending aorta and inferior vena cava. Results were as follows: EE was 4.99 +/- 1.58 x 10(6) dynes/cm2 (mean +/- SD), and EC was 965.8 +/- 399.8 x 10(6) dynes/cm2, assessed during the control state. Phenylephrine administration increased the theoretical pulse-wave velocity (Moens-Korteweg equation) from 5.25 +/- 1.03 m/s during the control state to 7.57 +/- 2.53 m/s (P < .005). Active muscle exhibited a unimodal stress-strain curve with a maximum stress of 0.949 +/- 0.57 x 10(6) dynes/cm2 at a corresponding strain value of 1.299 +/- 0.083. The maximum value observed corresponded, on the pressure-diameter curve of the active artery, to a pressure of 234.28 +/- 46.6 mm Hg and a diameter of 17.94 +/- 1.6 mm. The maximum ESM derived from the stress-strain relation of the active muscle was 8.345 +/- 7.56 x 10(6) dynes/cm2 at a strain value of 1.283 +/- 0.079. This point was located at 208.01 +/- 40.8 mm Hg and 17.73 +/- 1.41 mm on the active pressure-diameter curve. During activation of vascular smooth muscle, Einc decreased (P < .05) when plotted against internal pressure but increased (P < .05) when plotted against strain, over the operative range.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Early detection of subclinical atherosclerosis in asymptomatic subjects at high risk for cardiovascular disease.

Subclinical atherosclerosis can be non-invasively detected via calcifications, thickening and stiffening of arteries. Coronary calcifications seen with ultrafast computed tomography are frequent in hypertension or hypercholesterolemia and synonymous of coronary atherosis but not of coronary stenosis. Wall thickening detectable by extracoronary ultrasonography may be characterized by an intimamedia thickening shown in hypertension or by a focalized plaque whose the presence in the aortic or femoral level seem influenced by systolic pressure. Extracoronary wall thickening may be an aid in the diagnosis of coronary atherosclerosis, a predictor of coronary event, and a therapeutic target. Wall stiffening, which reflects sclerosis, is detected by pulse wave velocity. Its increase in hypertension may be an indicator of atherosclerosis and can be reversed by certain antihypertensive agents. Clinical care of at risk individuals might profit from subclinical atherosclerosis which adds objectivity and sensitivity in the individualization of risk and the decision to treat.

Arteriosclerosis↗
PubMed1993

[Estradiol and progesterone physiological substitution effects on the hemodynamics of the humeral artery in women with inactive ovaries].

To determine the effects of female hormones on peripheral vasculature we studied the brachial artery circulation. Nine young women (27-37 yrs) having inactive ovaries received transdermal estradiol (E2) (0.1-0.4 mg/d) and vaginal progesterone (P) (300 mg/d) to duplicate the menstrual cycle levels of E2 and P. Brachial artery diameter, blood velocity and flow were measured by bidimensional pulsed Doppler in basal conditions, and during hand exclusion by a cuff inflated at suprasystolic pressure. Vascular resistance was calculated by the ratio of mean blood pressure over mean flow. Measurements were obtained before hormonotherapy (d0), on day 14 (d14, after E2), and on day 28 (d28, after E2 and P). The increase of brachial artery diameter began at d14 (3.73 +/- 0.12 mm, vs 3.66 +/- 0.11 mm; NS) to become significant at d28 (3.91 +/- 0.10 mm, p < 0.05). Blood velocity and flow increased at d28 (4.78 +/- 0.55 cm/s, vs 3.55 +/- 0.65 cm/s; P < 0.05 and 35.2 +/- 5.2 ml/mn vs 22.2 +/- 3.6 ml/mn, P < 0.05 respectively). No change was noted in mean blood pressure. The decrease of resistance began at d14, in order to be significant at d28 (158 +/- 17 mmHg/ml/s at d0 vs 263 +/- 31 mmHg/ml/s at d28; P < 0.05). Brachial vasoconstriction during hand exclusion, in response to low flow state disappeared at d14 with estradiol. In conclusion, in women deprived of ovarian function, physiological E2 and P replacement vasodilates small and large arteries, whereas E2 alone attenuates the large artery vasoconstriction in acute response to low flow state.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Cutaneous↗
PubMed1993

[Epidemiology of hand injuries based on surveys in Vas County].

Authors have found in a 1 year survey in the county Vas 7580 hand injuries. The major proportion of young men and adolescents in the material was conspicuous. The types of accidents were investigated together with the place of the accident and types of the injury. The material shows that in contrary to the accidents of the work in the recent past the number of the accidents at home has increased--and so their prophylaxis became the main point.

Accident Prevention↗
PubMed1993

[The Basel dependence study].

In a survey of 177 patients of several outpatient departments and private practices in the area of Basel there were 23% with a dependence syndrome according to the diagnostic guidelines of ICD-10. Sedatives and hypnotics were the mostly mentioned psychotropic substances in this group. In a second survey six to twelve months later 80% of the initial study group were reassessed, focusing on referrals of the patients with a dependence syndrome to institutions specialized for the treatment of addiction. In most cases these patients were still treated at the previous institution; there were only a few referrals. Improvements concerning the increase of the referral rate to competent specialized institutions for patients with addiction seems possible by implementation of a decentralized consultation liaison service for outpatient departments, hospitals and also private practitioners in a mobile form.

Adaptation, Psychological↗
PubMed1993

Plasma norepinephrine, plasma renin activity, and congestive heart failure. Relations to survival and the effects of therapy in V-HeFT II. The V-HeFT VA Cooperative Studies Group.

BACKGROUND: Congestive heart failure is a clinical syndrome characterized by neuroendocrine activation. Measurements of plasma norepinephrine and plasma renin activity were performed in the Vasodilator-Heart Failure Trial II (V-HeFT II) to characterize the effect of therapy on neuroendocrine activation and to examine the responses to therapy among patients with different degrees of activation. METHODS AND RESULTS: The baseline median plasma norepinephrine value (n = 743) was 490 pg/mL and the baseline median plasma renin activity (n = 737) was 6.9 ng.mL-1 x hr-1. Baseline plasma renin activity and plasma norepinephrine correlated poorly with each other (r = 0.12), implying that these two neuroendocrine systems are being activated by separate processes. By univariate analysis, the logarithms of the plasma norepinephrine (p < 0.0001) and the plasma renin activity (p = 0.01) were significantly related to all-cause mortality. In a multivariate analysis that included other significant univariate prognostic variables (i.e., baseline ejection fraction, peak oxygen consumption during exercise, and cardiothoracic ratio), log plasma norepinephrine but not plasma renin activity remained a significant (p = 0.02) predictor of mortality. Baseline plasma norepinephrine correlated poorly with baseline left ventricular ejection fraction (r = -0.18), peak oxygen consumption (r = -0.15), and cardiothoracic ratio (r = 0.11). Neither the plasma norepinephrine (r = 0.09) nor the plasma renin activity (r = 0.18) was closely associated with a quality of life assessment at baseline. The baseline plasma norepinephrine level in patients randomized to enalapril (mean, 593 +/- 388 [SD] pg/mL; n = 372) and to hydralazine and isosorbide dinitrate (mean, 544 +/- 297 pg/mL; n = 371) were similar. Thirteen weeks after randomization, plasma norepinephrine did not change (-5 +/- 393 pg/mL) in 312 patients randomized to enalapril but increased significantly by 74 +/- 311 pg/mL (p < 0.0001) in 300 patients assigned to hydralazine-isosorbide dinitrate. The plasma norepinephrine increased significantly more in patients assigned to hydralazine-isosorbide dinitrate than those on enalapril at both 13 weeks (p = 0.01) and at 1 year (p = 0.04) (90 +/- 302 pg/mL [n = 240] versus 14 +/- 376 pg/mL [n = 265]). Based on previous reports and examination of survival among several plasma norepinephrine strata, the baseline plasma norepinephrine data were grouped into three relatively homogeneous strata for further analysis. The cumulative mortality was significantly different between the three strata (p < 0.0001). The patients with plasma norepinephrine > 900 pg/mL had a higher mortality than those with corresponding values from 601 to 900 pg/mL or < 600 pg/mL. The survival benefit of enalapril compared with hydralazine-isosorbide dinitrate was most evident in those patients with a plasma norepinephrine value > 900 pg/mL. Although the plasma renin activity was not strongly associated with survival, patients in the upper quartile (> 16 ng.mL-1 x hr-1) had the worst prognosis. Among this group, the patients on enalapril demonstrated significantly better survival than those on hydralazine-isosorbide dinitrate (p = 0.02). CONCLUSIONS: This study confirms that plasma norepinephrine is an independent predictor of prognosis in patients with congestive heart failure. Hydralazine-isosorbide dinitrate treatment, unlike enalapril treatment, was associated with increased plasma norepinephrine concentration during the first year of follow-up. The enalapril group had a significantly lower mortality, and this survival benefit of enalapril as compared with hydralazine-isosorbide dinitrate was most evident among patients with the most marked neuroendocrine activation. Neuroendocrine activation is an important prognostic factor for patients with congestive heart failure and is an important determinant of the differential response to vasodilators.

Drug Therapy, Combination↗
PubMed1992

Inhibition of lipoxygenase activity and HL60 leukemic cell proliferation by ursolic acid isolated from heather flowers (Calluna vulgaris).

A compound was isolated and purified from heather flowers (Calluna vulgaris) based on its ability to inhibit lipoxygenase activity. This molecule was characterized as ursolic acid by GC-MS. Ursolic acid was found to be an inhibitor of both potato tuber 5-lipoxygenase and soybean 15-lipoxygenase with IC50 values of 0.3 mM. Ursolic acid also inhibits lipoxygenase activity in mouse peritoneal macrophages at 1 microM and HL60 leukemic cells growth (IC50 = 0.85 microM) as well as their DNA synthesis (IC50 = 1 microM). The possible role of lipoxygenase inhibition in the proliferation of leukemic cells is discussed.

Animals↗
PubMed1992

Angiotensin-I-converting enzyme and its correlation with human follicular fluid steroids.

Angiotensin-I-converting enzyme (ACE) is a peptidyl-dipeptide hydrolase which splits off the dipeptide His-Leu from the decapeptide angiotensin I and thus converts it to angiotensin II. We determined ACE activity in human preovulatory follicular fluid to further establish the intraovarian activity of the renin angiotensin system. Follicular fluids (n = 18) were obtained from eight patients undergoing in vitro fertilization (IVF) and embryo transfer (ET). ACE activity in follicular fluid and serum was determined by fluorescent spectrophotometry. The median follicular fluid ACE activity was 1.12 (range: 0.19-1.56) nmol/min/ml. This value was significantly lower than ACE activity in serum, 1.50 (range: 1.22-1.57) nmol/min/ml (P less than 0.001). In contrast to this 3:4 ratio between follicular fluid and serum ACE when expressed per ml fluid, the values were very similar when expressed per mg of protein: 0.025 vs. 0.023 nmol/min/mg in follicular fluid and serum, respectively. Correlations were sought between follicular fluid ACE activity and both serum and follicular fluid E2 and P4. A highly significant correlation (P less than 0.0005, r = 0.73) was found between ACE activity in follicular fluid and follicular fluid P4. The presence of significant ACE activity in human follicular fluid further supports the local-ovarian activity of the renin angiotensin cascade.

Embryo Transfer↗