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Biomedical subjects

A Simon

Publications and source records attributed to A Simon.

At least 361 records · Page 20Linked to original sources
PubMed1990

Effects of muscarinic and beta-adrenergic blockade on the aortic elastic response to epinephrine induced acute hypertension in conscious dogs.

To determine the effects of parasympathetic blockade and beta-blockade on the elastic response of aortic stiffness to vasopressive interventions, we studied 5 unanesthetised adult mongrel dogs by means of a pressure microtransducer and two ultrasonic crystals positioned at opposing sites in the proximal descending thoracic aorta which were used for diameter measurements. Systolic and diastolic changes in pressure and diameter were used to calculate Peterson and incremental elastic moduli. Acute hypertension was induced using infusions of epinephrine during the control period and later propranolol (1.5 mg/kg) plus atropine (0.2 mg/kg). Percent variations of mean aortic diameter were correlated to percent variations in mean aortic pressure in the control period and after autonomic blockade (P less than .001). The slopes of these correlations in the control group were higher than after autonomic blockade (P less than .05). Correlations were also found between Peterson and incremental elastic moduli and mean pressure in the control group and after autonomic blockade (P less than .001). The slopes of the correlations of incremental elastic modulus and Peterson's modulus versus mean aortic pressure were lower in the control group than after blockade (P less than .001). We conclude that in conscious dogs, autonomic blockade with propranolol and atropine decreased the distension and increased the stiffness of the aortic wall in response to acute hypertension mediated by epinephrine.

Acute Disease↗
PubMed1990

Preovulatory luteinization during induction of follicular maturation with menotrophin and menotrophin--clomiphene combination.

Late follicular phase levels of 17 beta-oestradiol (E2) and progesterone (P) in serum were studied during the induction of follicular maturation with human menopausal gonadotrophin (HMG) (n = 23) and HMG-clomiphene citrate (CC) (n = 18). For each patient one hormonal profile was studied between 6 days to 2 h before administration of human chorionic gonadotrophin (HCG). Ultrasonographic follicular measurement at the time of evaluation demonstrated preovoulatory ovarian follicles of various number and size in all patients studied. Sixteen endometrial biopsies were performed at the time of evaluation (eight for each subgroup), before HCG administration. Mean late follicular phase levels of E2 did not differ significantly between the two groups (436 +/- 348 and 475 +/- 267 pg/ml for the HMG and HMG-CC groups respectively). The mean progesterone levels in the HMG-CC group (1.233 +/- 0.67 ng/ml) was significantly higher than that for the HMG group of (0.86 +/- 0.55 ng/ml, P less than or equal to 0.04). The mean time interval between ovulation and HCG administration for the two groups was 2.5 and 2.4 days for the HMG and HMG-CC groups, respectively. In all eight biopsies taken from the HMG group, various stages of endometrial proliferation were demonstrated. Premature glandular secretory transformation and oedematous stroma were observed in three out of eight biopsy specimens obtained from the HMG-CC group. Taken together, these results demonstrate that subtle or full premature luteinization in the late follicular phase occurs more frequently with the use of HMG-CC for induction of follicular maturation.

Adult↗
PubMed1990

Chronic progressive changes in brachial and carotid artery circulations under the combined effects of aging and hypertension.

Brachial and carotid artery diameters, blood velocities and blood flows were determined by a pulsed-Doppler flowmeter in 22 normotensive and 74 mild to moderate essential hypertensive subjects, aged 46 +/- 8 years. The product age x MAP/1000 (where MAP is mean arterial blood pressure), called 'arterial age' (expressed in years x mmHg/1000), was used to assess the progress of age and blood pressure. The moving-mean method was first used to explore the chronic hemodynamic changes in the two circulations with a progressive increase in arterial age. The method indicated that an arterial age of about 4-4.5 units a noticeable decrease in both brachial and carotid blood velocities occurred, and at an arterial age of about 5 units an important increase in brachial artery diameter occurred. In order to test these findings, the total sample (n = 96) was divided into three groups of equal size with low, median and high arterial ages. Brachial blood velocity decreased significantly in groups 2 (P less than 0.05) and 3 (P less than 0.05) compared with group 1, and carotid blood velocity decreased significantly from group 1 to group 2 (P less than 0.02) and from group 2 to group 3 (P less than 0.05). Brachial artery diameter did not change from group 1 to group 2, but increased significantly from group 2 to group 3 (P less than 0.05). Over the whole arterial age range, the carotid artery diameter remained identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Blood viscosity as a chronic contributing factor of vasodilatation in humans.

Since resistance to flow is theoretically determined by arteriolar geometry and blood viscosity, we studied these two factors in 44 normal and 106 hypertensive subjects. Brachial bed vascular resistance was calculated as the ratio between mean pressure and brachial artery flow. Systemic blood viscosity in vitro was determined at 96 per s, while microvessel blood viscosity in vivo was estimated from the haematocrit-viscosity relationship at 240 per s. A resistive radius index was calculated which was only related to the microvessel viscosity: resistance ratio. Compared to normal subjects, hypertensive subjects had higher systemic in vitro blood viscosity (4.75 +/- 0.47 versus 4.50 +/- 0.43 mPa.s; P less than 0.005) and microvessel blood viscosity (2.60 +/- 0.21 versus 2.43 +/- 0.16 mPa.s; P less than 0.001). Hypertensive subjects also had a higher brachial vascular resistance (161 +/- 89 versus 124 +/- 58 mmHg/ml per s; P less than 0.01), but showed a similar resistive radius index (2.47 +/- 0.36 versus 2.57 +/- 0.35) compared to normal subjects. There was a positive correlation between systemic viscosity and brachial artery diameter and a negative correlation between microvessel viscosity and vascular resistance in the normotensive (P less than 0.05 and P less than 0.001, respectively) and hypertensive groups (P less than 0.001 and P less than 0.005, respectively). The resistive radius index was positively related to viscosity in normal and in hypertensive groups (P less than 0.001) but these relationships were significantly different (P less than 0.001), showing that, at the highest viscosities, arterial radius increased less in hypertensive than in normal subjects. Thus, the level of blood viscosity might influence arterial diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Contrary effects of hypertension and cigarette smoking on the conditions of wall shear in large arteries].

Systolic wall shear conditions were studied in the brachial artery of 4 groups of subjects including 11 non-smokers normotensives (NSNT), 25 non smokers hypertensives (NSHT), 21 smokers normotensives (SNT) and 10 smokers hypertensives (SHT). Brachial artery diameter (D) and systolic centerline blood velocity (VCLS) were measured with a pulsed Doppler device and blood viscosity at 96 sec-1 was measured with a coaxial cylinder viscometer. The wall shear rate (gamma S) corresponding to systolic velocity was calculated using a Womersley model of pulsatile flow according to the formula: alpha = (D/2) (omega/mu) 1/2, omega being the angular pulse frequency and mu the kinematic viscosity. The wall shear stress was then calculated as the product between wall shear rate and viscosity. The analysis of results in the 4 groups showed that both hypertension and smoking increased blood viscosity bu their effects on wall shear were opposite since hypertension decreased shear and stress while smoking did not change it. However, in hypertensive patients, smoking induced a clear elevation in wall shear rate and stress, whereas in smokers hypertension did not change shear conditions. Thus, opposite and interactive effects of hypertension and smokers exist on large artery wall shear phenomena which could induce differences in response of functional and structural endothelial cells to these two vascular risk factors.

Adult↗
PubMed1990

[A new hemodynamic endothelial approach using non-invasive evaluation of instantaneous wall shear in human arteries. Application in arterial hypertension].

A new non-invasive methodology of measurement of pulsatile wall shear in superficial large arteries in man is presented from simple determinations of internal diameter of large artery and centerline instantaneous blood velocity (pulsed Doppler apparatus) and asymptotic blood viscosity (coaxial cylinder viscometer). Pulsatile distribution of velocity across the arterial lumen has been represented by a Womersley model enabling to define and calculate wall shear rate as the slope at the wall to the velocity profile at each cardiac time. These complex mathematical calculations have been performed on micro-computer by means of appropriate programmation according to the following steps (1) Digitization and processing of instantaneous centerline blood velocity (2) Decomposition of velocity signal into Fourier series as a sum of elementary velocity sinusoids of increasing frequency (3) computation of velocity profile and slope at the wall to the profile for each harmonic (4) Resynthetization of instantaneous wall shear rate as function in time (5) calculation of wall shear stress by multiplying wall shear rate by blood viscosity. Taking the brachial artery as model of peripheral large artery, pulsatile wall shear rate and stress curves were determined in individual subjects and analysed by means of several characteristic indices including: maximum, minimum and mean values; time of systolic increase and time of systolic relaxation; and oscillating index defined from the positive and negative surfaces of the shear curve. This original methodology open new way for studying hemodynamical conditions at the interface between blood and endothelium surface of large arteries and might be applied to the physiopharmacological approach of vascular disease such as hypertension.

Adult↗
PubMed1990

Prolonged paresis in a primigravida during and after caesarean section.

A primigravida, who had a Caesarean section because of cervical dystocia and relative cephalo-pelvic disproportion, in Nov. 1988 in Yekatit 12 Hospital, Addis Ababa, remained relaxed and without spontaneous respiration for about four hours after the completion of the operation, requiring assisted respiration. This condition is the result of a decreased plasma cholinesterase (PCE) activity which is responsible for the breaking down of succinylcholine used in general anaesthesia as a muscle relaxant. Although the incidence of PCE deficiency in our population is not known, it should be remembered that such a complication may be seen in hospitals where operations are carried out using succinylcholine as a muscle relaxant.

Adult↗
PubMed1990

Quantitative and qualitative finger dermatoglyphics in the Basque Valley of Urola, Spain.

Digital dermatoglyphics of an indigenous sample of 87 males and 101 females from the Urola Valley in the Spanish Basque Country are compared with those from the nine other Basque valleys previously analyzed. In both sexes of the Urola Valley, there is a very high frequency of radial loops; the mean found in this valley extends the range of variation for South European-Mediterranean populations, and it is in the superior limit of all Caucasian populations. There are bimanual and sex differences in the frequencies of whorls and loops. Contrary to what occurs normally in populations, in the Urola Valley the frequency of whorls is higher in females and the quantitative value of digital patterns is lower in males. The results of this study show the existence of heterogeneity among valleys for digital trait frequencies and for finger ridge count, and this heterogeneity is more marked in females.

Cross-Cultural Comparison↗
PubMed1990

[Emergency intubation and ventilation therapy in severe bronchial asthma].

37 patients were treated with emergency intubation because of severe asthma bronchiale. In 30 patients the usual bronchospasmolytic therapy was ineffective, 12 patients were under permanent treatment. Halothane produced immediate and unequivocal improvement of respiratory global insufficiency and resolution of bronchospasm in 8 out of 13 patients, ketamine in 6 of 18 and a combination of both drugs in 4 of 9 patients. Both drugs are an efficient complement to conventional emergency treatment. A step-by-step schema for anaesthesia in severe asthma bronchiale requiring intubation is presented.

Aged↗