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Biomedical subjects

M Velasco

Publications and source records attributed to M Velasco.

At least 271 records · Page 15Linked to original sources
PubMed1978

Clinical and pathological study of asymptomatic HBsAg carriers in Chile.

A clinical, biochemical, and pathological study was performed in 38 chronic HBsAg carriers. The study group is a part of 393 carriers found among 117 705 voluntary blood donors at the National Blood Bank, Hospital del Salvador, Santiago, Chile. None of the 38 carriers had a past history of illicit drug abuse, hepatitis, or work involving a high risk of hepatitis B virus infection. Ten individuals had a normal liver biopsy, 17 reactive non-specific hepatitis, one fatty changes, four chr onic persistent hepatitis, one aggressive hepatitis, two post-necrotic cirrhosis, and three alcoholic cirrhosis. There was not a close correlation between liver function test and liver histology. The most significant laboratory finding was the postivity of alpha fetoprotein in two cases. During the follow-up the two alpha fetoprotein patients presented a hepatocarcinoma 12 and 14 months after admission to the study.

Adolescent↗
PubMed1977

Physiologic mechanisms of bupicomide- and hydralazine-induced increase in plasma renin activity in hypertensive patients.

A study was made of the possible mechanisms underlying bupicomide- and hydralazine-induced increase of plasma renin activity. Six patients with mild to moderate hypertension were treated with both bupicomide and hydralazine on separate occasions in random order. Bupicomide lowered mean arterial pressure from 124.2 +/- 3.7 mm Hg (mean +/- SE) to 107.2 +/- 3.9 mm Hg (P less than 0.001). The associated increase in plasma renin activity was 1.27 ng/ml per hour and the increase in heart rate was 16.5 beats/min. Hydralazine reduced mean arterial pressure from 124.2 +/- 3.7 mm Hg to 107.0 +/- 2.0 mm Hg (P less than 0.01). The associated increase in plasma renin activity was 2.20 ng/ml per hour and the increase in heart rate was 22.4 beats/min. Plasma renin activity during bupicomide and hydralazine administration correlated positively with control plasma renin activity (r = 0.98, P less than 0.001). The log of plasma renin activity correlated positively with heart rate (r = 0.51, P less than 0.02) and negatively with mean arterial pressure (r = -0.62, P less than 0.005). We conclude that control plasma renin activity is a major determinant of change in plasma renin activity during administration of bupicomide or hydralazine. Both an increase in sympathetic activity and a decrease in perfusion pressure may contribute to the bupicomide- and hydralazine-induced increase in plasma renin activity, possibly by a baroreceptor-mediated increase in adrenergic tone.

Adult↗
PubMed1976

Mechanism of the interaction of propranolol and a potent vasodilator antihypertensive agent - minoxidil.

A study, using non-invasive techniques, was carried out in ten patients with essential hypertension to examine the mechanism of the hypotensive effect of propranolol when used in combination with a potent vasodilator antihypertensive - minoxidil. The hypotensive effect of minoxidil, a mean (+/- SEM) decrease of 42.4 +/- 4.3 mm Hg, was accompanied by a marked increase in heart rate, cardiac index and plasma renin activity and a significant decrease in total peripheral resistance, limb vascular resistance and pre-ejection period. Addition of propranolol further reduced mean arterial pressure by an average of 12.9 +/- 2.0 mm Hg. Propranolol returned cardiac index to control values and total peripheral resistance index rose but not to control levels. Plasma renin activity was significantly reduced by propranolol. By multiple regression analysis no correlation was found between propranolol-induced decrease in mean arterial pressure and changes in cardiac index, total peripheral resistance index or plasma renin activity. Quantitatively, the reduction in cardiac index observed probably accounted for the hypotensive effect of propranolol. The role of plasma renin activity reduction in the hypotensive effect of propranolol in this situation remains to be clarified. The findings in the present study were consonant with the known actions of vasodilator antihypertensive agents and propranolol and indicate the applicability of non-invasive methodology to the investigation of cardiovascular drugs in man.

Adult↗
PubMed1976

A sliding intravenous dose schedule for clonidine in hypertensive patients.

Cumulative doses of clonidine were administered intravenously to 8 hypertensive patients to a maximal dose of 100 mug or a blood pressure fall to normal. There was a reduction in mean arterial pressure of 35.6 mm Hg (p less than 0.001), accompanied by a decrease in heart rate of 11.8 bpm (p less than 0.001). There was also a significant linear relationship between the reduction in blood pressure and the intravenous log dose of clonidine with 6.5-fold difference in delta MAP/dose potency. There was no correlation between the baseline blood pressure and the slopes of dose-blood pressure response curves or the reduction in mean arterial pressure; the rate of the decline of the hypotensive effect of clonidine varied widely between patients and was not related to baseline blood pressure.

Adult↗
PubMed1976

Specific and nonspecific multiple unit activities during the onset of pentylenetetrazol seizures. II. Acute lesions interrupting nonspecific system connections.

Nonspecific cortical, thalamic, mesencephalic, and pontine multiple unit activities (MUA) and changes in EEG and MUS of the sciatic nerve after threshold pentylenetetrazol activation were studied in three groups of animals in which neuronal connections were interrupted at three different levels of the central nervous system: spinal, mesencephalic, and prethalamic. Maximal increments of nonspecific MUA and maximal increments and maximal decrements of sciatic MUA after pentylenetetrazol from each group of lesioned animals were statistically compared with tose observed in intact animals. 1. Pentylenetetrazol threshold for producing cortical tonic-clonic EEG discharges was increased in animals with nesencephaic and prethalamic lesions but was not modified in animals with spinal transection. 2. Cortical MUA maximal increment was significantly decreased in mesencephalic and prethalamic lesioned animals, whereas thalamic MUA maximal increment was significantly decreased in mesencephalic and significantly increased in prethalamic lesioned animals. Pontine MUA maximal increment was significantly increased in spinal, mesencephalic, and prethalamic lesioned animals, and mesencephalic M-A maximal increment was not significantly modified in either prethalamic lesioned or in spinal transected animals. 3. Sciatic MUA maximal increment and maximal decrement were significatly decreased in spinal transected animals, whereas only maximal increment was significantly decreased in mesencephalic and only maximal decrement was significantly decreased in prethalamic lesioned animals. These results based on lesion experiments permit us to infer than under normal cinditions the development of generalized seizures induced by threshold pentylenetetrazol injection is highly dependent upon the neuronal interactions between nonspecific structures at different levels of the central nervous system. The possible nature of these neuronal interactions in the intact animals is discussed.

Animals↗
PubMed1976

Improvement of intractable idiopathic epilepsy with chlormadinone acetate. A case report.

A 10-year-old boy with idiopathic epilepsy refractory to treatment from age 4 and with clinical signs of hyperandrogenism was treated with chlormadinone acetate (24 mg/day) during two alternate periods of 3 months. The administration of chlormadinone was associated with a marked clinical and electroencephalographic improvement as well as a concomitant decrease in the levels of plasma testosterone and delta4 androstenedione. No changes in plasma gonadotropins were observed. Placebo had no effect neither in seizures nor in the concentration of hormones in the plasma. Since chlormadinone acetate is not a very potent gonadotropin inhibitor in males, it is suggested that the clinical and electroencephalographic improvement associated with the use of this compound, might be the consequence of a decrease in the plasma levels of androgens, mainly testosterone.

Androstenedione↗
PubMed1976

[Identification and lesion of prelemniscal radiation in the surgical treatment of tremor].

In a group of 40 patients operated on for the relief of tremor using stereotaxic techniques, the radiological location and electrophysiological characteristics of the optimum target were studied. The optimum target was defined as the place where the minimal lesion produced by the insertion of a 1.5 mm diameter electrode produced immediate cessation of tremor in the contralateral extremities. It was found that the optimum target is located in the subthalamus. Within this area electrical stimulation did not elicit sensory of pyramidal responses, but increased the amplitude of tremor. The study of somatic evoked potentials produced by stimulation of contralateral median nerve confirmed that the area does not correspond to a specific sensory system (medial lemniscus). By recording multiple unit activity a spontaneous 5 cycle per second rhythmic pattern, similar to that described for the VL thalamic nucleus, was occasionally seen. Finally, through an IBM 1130 computer the radiological location of those electrodes in the target area was approximated to a line, representing a vector whose orientation in space could be compared with that of different anatomical structures, and corresponded to the prelemniscal radiation. We concluded that the target area herein described is part of a reticulothalamic system that conveys tremogrogenic impulses to the pyramidal system and from here to the periphery.

Computers↗