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Biomedical subjects

H Ramirez

Publications and source records attributed to H Ramirez.

33 records · Page 2Linked to original sources
PubMed1983

3-hydroxy-3-methylglutaryl-CoA reductase from neonatal chick.

The optimal conditions for identification of mevalonic acid as the product of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase are described, as well as the effect of different buffer constituents on the enzyme activity. Under the chosen assay conditions, reductase activity from neonatal chick liver increased with the incubation time up to 60 min and was proportional to the amounts of protein added in a range of 0.1-0.5 mg. The specific activity was maximal in brain and liver and lower in intestine of 6-day-old chicks. Thermostability of hepatic reductase was studied. When microsomal preparations were maintained at 4 degrees C, reductase activity remained unchanged for 6 hr and decreased afterwards. Addition of 50 mM KF to the homogenization medium had no effect on the reductase activity. Similarly, preincubation of microsomal preparations with 105,000 g supernatants in the presence or absence of KF did not significantly increase the reductase activity. These results suggest that HMG-CoA reductase was isolated from neonatal chick in the fully activated form.

Animals↗
PubMed1983

Computed tomographic identification of calcified optic nerve drusen.

Four cases of optic disk drusen were accurately diagnosed with orbital computed tomography (CT). The radiologist should be aware of the characteristic CT finding of discrete calcification within an otherwise normal optic disk. This benign process is easily differentiated from lesions such as calcific neoplastic processes of the posterior globe. CT identification of optic disk drusen is essential in the evaluation of visual field defects, migraine-like headaches, and pseudopapilledema.

Calcinosis↗
PubMed1982

Development of the diurnal rhythm of chick 3-hydroxy-3-methylglutaryl-CoA reductase.

Chick liver and intestine 3-hydroxy-3-methylglutaryl-CoA reductase did not show diurnal rhythm at hatching. Differences in activity between light and dark periods appeared during the first week and remained more or less constant between 10-14 days after hatching. Hepatic and intestinal reductase activities were maximal during the light period and minimal during the dark period. Amplitude of the rhythm was practically similar in both tissues (about 3-fold) although specific activities and differences between peak and nadir values were always higher in liver. Chick brain reductase did not show significant diurnal variations in the age range assayed.

Aging↗
PubMed1981

Different thermal behavior of neonatal hepatic and cerebral 3-hydroxy-3-methylglutaryl-CoA reductase.

The Arrhenius plots of hepatic and cerebral 3-hydroxy-3-methylglutaryl-CoA reductase activity were studied in neonatal chicks fed with a standard diet. Supplementation of the diet with 2% cholesterol from hatching has no effect on the thermal characteristics of the brain enzyme. The Arrhenius plot of brain reductase was practically similar to that found in control chicks. However, hepatic reductase was inhibited by cholesterol feeding. Dietary cholesterol increased the cholesterol/lipidic phosphorus molar ratio in liver microsomes, whereas no significant differences were observed in brain microsomes. These results are in agreement with the hypothesis that activity of hepatic reductase is regulated by the fluidity of microsomal membrane and show that cholesterol feeding does not alter the fluidity of microsomal membranes in neonatal chick brain having, thus, no effect on the thermal behavior of cerebral reductase.

Animals↗
PubMed1981

Different developmental patterns of 3-hydroxy-3-methylglutaryl-CoA reductase in chick tissues according to their role in cholesterogenesis.

The developmental pattern of microsomal 3-hydroxy-3-methylglutaryl-CoA reductase activity was different in liver, intestine and brain of neonatal chicks. Hepatic reductase activity sharply increased between 5 and 9 days after hatching. This pattern agrees with changes in acetate incorporation into non-saponifiable lipids by liver slices. Both enzyme activity and acetate incorporation seem to be related to the hepatic uptake of cholesterol from the yolk sac during the first days after hatching and to the new synthesis of cholesterol commencing in the second week. Changes in intestinal reductase suggest that the enzyme was less sensitive to the cholesterol in yolk sac. Brain reductase did not change within the age assayed (1-15 days), being independent from the levels of yolk sac or serum cholesterol during the later steps of myelination.

Animals↗
PubMedDate not supplied

Computer tomography in children with electrophysiological abnormalities.

A computed tomography examination was carried out in a group of 43 children, of whom 15 had learning disabilities (LD). Children were selected with electrophysiological abnormalities in the routine EEG, in the quantitative EEG analysis and/or in the visual cortical and auditory brainstem evoked responses. Seven children, 1 control and 6 LD, had abnormalities in the computed tomography. The most frequent localization of the lesion was the left temporal lobe. This localization might explain the origin of the learning disorder, since the left temporal lobe is involved in reading and writing processes. There was a great concordance between the anatomical localization of the lesion by the computed tomography and the place of electrical abnormalities in the quantitative EEG and the visual evoked responses. These results strongly support the indication of a computed tomography examination in LD children.

Adolescent↗
PubMedDate not supplied

Abdominal aortic aneurysms. Risk factors and complications and their influence on indication for operation.

From January 1982 to June 1986 475 patients underwent operation for abdominal aortic aneurysm (AAA) with reconstruction by tube graft or bifurcation graft. Patients were subdivided into 2 groups, those operated upon either electively or those operated upon urgently. The overall hospital mortality following elective intervention was 4.9%, following emergency intervention 36.5%. In patients operated upon electively preoperative risk factors such as history of myocardial infarction or coronary artery disease did not influence mortality. In patients operated upon urgently, however, the postoperative mortality was significantly higher (p less than 0.005) in those with a history of myocardial infarction or coronary artery disease. Postoperative morbidity in the emergency group (2.7 complications per patient) was significantly higher than in the elective group (0.94 complications per patient). These results show that early elective operation on asymptomatic aneurysms and younger patients with few risk factors can prevent rupture and reduce postoperative mortality to an acceptable level.

Aged↗