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Biomedical subjects

J Herrera

Publications and source records attributed to J Herrera.

At least 145 records · Page 8Linked to original sources
PubMed1982

Zinc, prolactin, gonadotropins, and androgen levels in uremic men.

This study correlates plasma levels of Zinc (Zn) and some pituitary and testicular hormones in 20 uremic men (aged 17-58 years) on a weekly peritoneal dialysis program. Patients were compared to 12 healthy male volunteers (aged 28-40 years). In uremic men, plasma androstenedione (A) was elevated, while testosterone (T), dihydrotestosterone (DHT), and Zn were low. On a group basis, plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH) were normal while prolactin was increased. A negative correlation was observed between plasma A and LH levels, as well as between the A/T+DHT ratio and plasma Zn concentrations. Our results suggest a diminished A-to-T conversion and point to the possible role of Zn in the enzyme activity of the 17 beta-hydroxysteroid dehydrogenase.

Adolescent↗
PubMed1982

Endocrine profile in patients with chronic renal failure under zinc replacement.

The plasma levels of androstenedione (A), testosterone (T), dihydrotestosterone (DHT), follicle stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL) were studied in 15 men (aged 24-50 years) with chronic renal failure under periodic peritoneal dialysis, before and after 50 mg of elemental zinc (Zn) orally, twice a day for three weeks. Before treatment, they were divided into three groups: group I, plasma A above normal and PRL less than 100 ng/ml; group II, low or normal A levels with PRL less than 100 ng/ml; and group III, normal or high A levels with PRL greater than 100 ng/ml. After oral Zn, plasma FSH, LH, and PRL were unchanged in all groups; however, in groups I and II plasma A was within normal T and DHT rose significantly, the A/(T+DHT) ratio decreased to normal, and the T/DHT ratio rose above normal. In group III plasma androgens remained low and androgen ratios were unchanged. Oral Zn seems to improve the conversion of A to T and also uncovered the possibility that plasma PRL levels greater than 100 ng/ml might cause a blockade in the 5 alfa-reductase.

Adult↗
PubMed1982

Testicular function in men with chronic renal failure and transplant recipients under bromoergocriptine therapy.

Plasma zinc (Zn), follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and androgens concentrations were determined in 15 male patients with chronic renal failure who were successful recipients of kidney transplant. After 25 +/- 8.5 months of the renal transplant, Zn levels were (88 +/- 4 g/dl) lower than in the control group (116 +/- 5 micrograms/dl). Normal concentrations for androstenedione (A) (0.63 +/- 0.05 ng/ml) and testosterone (T) (3.31 +/- 0.15 ng/ml) were found. Dihydrotestosterone (DHT) levels (0.38 +/- 0.01 ng/ml) were lower than normal (1.11 +/- 0.09 ng/ml), suggesting a blockade in the conversion of T to DHT. Eleven of the 15 patients showed higher PRL levels (9.5 +/- 0.8 ng/ml) in contrast with the normal group (3.6 +/- 0.3 ng/ml). Ten patients received orally 2-alpha-bromoergocriptine (BEC) 2.5 mg/day for ten days. Plasma PRL decreased to 2.6 +/- 1.0 ng/ml (p less than 0.001), but A and T levels did not significantly change; however, DHT increased from 0.38 +/- 0.02 ng/ml to 0.72 +/- 0.04 ng/ml (p less than 0.01). All patients showed an increase in both gonadotropins before BEC without significant changes after treatment. The high PRL levels may be responsible for the impaired conversion of T to DHT, possibly by interference with the enzyme 5 alpha-reductase.

Adult↗
PubMed1979

Elimination of nadolol by patients with renal impairment.

1 Nadolol excretion was studied in 24 patients with chronic renal failure. 2 The amount of nadolol excreted during the 120-h period after receiving the drug ranged from less than 1% in functionally anephric, patients up to 11.5% in patients with average creatinine clearance of 57.9 +/- 3.6 ml/min/1.73 m2. 3 Renal clearance of nadolol was found to correlate with creatinine clearance; nadolol elimination is retarded in patients with renal failure. 4 Nadolol serum half-life is prolonged in proportion to the remaining renal function. Therefore, dosage intervals in renal patients receiving nadolol should be adjusted to creatinine clearance. 5 Haemodialysis effectively reduced serum concentration of the drug; it may therefore be a useful therapy for drug intoxication.

Adolescent↗
PubMed1978

[Specific protection by sulfhydryl groups against inhibition of urease by hypoglycaemic drugs (author's transl)].

The effect of oral hypoglycaemic drugs, derivatives of sulphonylurea, upon urease has been studied. These compounds, structurally connected to urea, produce a competitive inhibition of enzyme activity with respect to substrate. Glutathioné (reduced form) and cysteine prevent inactivation of enzyme by sulphonylurea, whereas-oxidated glutathione and cysteine do not. The same phenomenon occurs in enzyme preparations inhibited by p-hydroxymercuribenzoate. The role of sulfhydryl groups in the formation of enzyme-substrate complex is discussed.

Chlorpropamide↗
PubMed1977

Retrolental fibroplasia: I. Clinical observations.

The changes occurring in retrolental fibroplasia were studied in 97 premature infants with fundus photography and fluorescein angiography. The macrovascular lesion of proliferative retrolental fibroplasia was identified as a functioning arteriovenous shunt. The microvascular abnormalities were capillary tufts, collaterals, capillary-free zones, and neovascular membranes. Regression was signaled by the ingrowth of capillaries from the shunt into the avascular retina. Cicatrization was characterized by persistence of the vascular abnormalities of the proliferative phase and organization of the avascular retina into a contracting scar.

Fluorescein Angiography↗
PubMed1977

[Inhibition of urease by hypoglycaemic drugs (author's transl)].

The effect of oral hypoglycaemic drugs (derived from sulphonylurea) on urease activity in the quantitative determination of urea has been studied. These compounds have been found to produce a competitive inhibition of enzyme activity with respect to substrate. Possible interference of these antidiabetic agents upon urea analysis is discussed.

Chlorpropamide↗
PubMed1975

[Quick radioimmunoassay method for the determination of estrogens].

The aim of this report is to describe a quick method for measuring plasma estrogens by radio immunoassay in one day. Briefly, 1000 cpm of estradiol-3-H were added to 0.1 to 1.5 ml of plasma or serum to calculate losses during the procedure. After ether extraction and without any purification step, aliquots for tracer recoveries and the radioimmunoassay were taken. The antiserum working dilution was 1:100,000. The incubation of the antiserum at 37degreesC with the tritiated and cold estradiol lasts one hour. The free and bound fractions were separated with charcoal/dextran. With this method, 95% of estradiol, 16% of estrone and 6% of estriol are quantified. Other steroids normally present in plasma produce no interference. The minimal detectable level is 10 pg. Pasma and water blanks are indistinguishable of zero (C.V. 1%). Intra-analysis coefficient of variation is 6.1%. Mass recovery of estradiol (5 ng), estrone (5 ng) and estriol (5ng) are 4.75, 0.83 and 0.31 ng, respectively. Tracer recoveries are 92.6%. When plasma levels of estradiol are determined during menstrual cycle, normal and/or pathological pregnancy, by either the method described herein or measured selectively, the results show no significant differences. Finally, practical usefulness of this method is stressed, inasmuch results are obtained in six hours and one person can easily perform 200 samples in one week.

Blood Specimen Collection↗