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Biomedical subjects

J A Andrada

Publications and source records attributed to J A Andrada.

At least 19 recordsLinked to original sources
PubMed1991

Biosynthesis of testicular steroids in the immature, adult and senescent guinea-pig.

The potential biosynthetic capacity of testicular hormones was studied in immature, pubertal and aging guinea-pig. In their sexual development towards puberty, changes in the relationship of the steroids involved in the steroidogenic pathways were observed. The testosterone/androstenedione ratio changes markedly, showing an important increase with pubertal proximity. The testosterone in equilibrium androstenedione sequence, reversibly catalyzed by 17 beta-hydroxysteroid oxidoreductase (17 beta-oxido-reductase), clearly shifted towards androstenedione in immature animals irrespective of the precursor utilized. Post-pubertal animals showed a greater enzymatic activity in the 5-ene and 4-ene testicular synthesis pathways, testosterone production being greatest. In the aging animal, hormonal biosynthetic capacity falls. Reversion of the 17 beta-oxido-reductase activity could be one of the mechanisms responsible for the decrease in testosterone, as in immature guinea-pigs. In order to investigate the in vitro steroidogenic capacity of glands at different ages, minces of testicular tissue were incubated with labelled precursors. The studies were conducted in triplicate at 35 degrees C. For equal quantities of incubated tissue the non-metabolized amount of [3H]pregnenolone and [14C]progesterone, utilized as precursors, was different in post-pubertal and senescent animals: 55.7 +/- 3 vs 59.3 +/- 2.3% (P less than 0.01) for pregnenolone, and 50.1 +/- 3.3 vs 56.3 +/- 2.9% (P less than 0.01) for progesterone, respectively. Testosterone production was 12 +/- 2% in adult and 6.7 +/- 2.7% in senescent animals (P less than 0.01). The testosterone/androstenedione ratio was not significantly different in post-pubertal and senescent animals: 2.8 +/- 0.5 vs 2.4 +/- 0.4, but consistently higher than found in immature animals: 0.3 +/- 0.1. The lesser potential capacity of the aging tissue to synthesize testosterone could be explained by a decline in the glands capacity to metabolize the hormonal precursors.

Aging↗
PubMed1990

Alpha-interferon induces cortisol release by human adrenals in vitro.

It is at present not clear whether alpha interferon (INF-alpha) can participate in the control of glucocorticoid blood levels through direct action on the adrenal gland. In this study, the possible action of INF-alpha on cortisol release by adrenal tissue was tested in vitro. Slices of normal human adrenals were incubated with INF-alpha for 3 h at 37 degrees C in 95% air and 5% CO2. Cortisol release by adrenal tissue was stimulated by INF-alpha, showing a dose-response curve from 20 IU/ml, the lowest dose that gave a response, to a maximal dose of 60 IU/ml when the response reached a plateau. The effect of INF-alpha on cortisol liberation by adrenal tissue in vitro may be implied in neuroimmune regulatory interactions.

Adrenal Glands↗
PubMed1990

Immunologic studies of male infertility.

The immunological basis of male sterility, as previously described, is related to alterations of spermatogenesis or impairment of seminal plasma formation. Both may be developed independently or may be related. Acute or subacute lesions of the genital tract or gonads may be more closely related to the presence of autosensitization than are chronic inflammatory processes or endocrine diseases of the testis. Oligo- or azoospermia may reflect the destruction of cells or halting of spermatogenesis. Immobilization and agglutination of sperm cells would depend predominantly on an allergic reaction that originates in the adnexal glands. Antibodies against testis do not affect adnexal glands but may immobilize epididymal spermatozoa, whereas antiseminal plasma antibodies react only with adnexal glands and seminal spermatozoa, but not with testicular cells. The pathogenic role of detectable antispermatic antibodies in sterile male or female patients are not sufficiently clarified. Their presence apparently correlate with unexplained cases of infertility, but this does not necessarily mean that they are specifically responsible for this abnormality; furthermore, they might be only an epiphenomenon of the immunological process involved.

Animals↗
PubMed1989

[Eclampsia induced by skin allografts in spontaneously hypertensive rats].

In order to develop an experimental model for eclampsia, 22 female inbred Spontaneously Hypertensive Rats (SHR) were grafted with skin from Holtzman males. The implantation of four sequential grafts took place at an interval of ten days. Each SHR was mated with its corresponding skin donor ten days after the last graft. Five non grafted SHR mated with Holtzman males were used as controls. In most of the experimental rats that became pregnant we found changes which consisted in: low number of offspring, stillborn fetuses, abortions and growth delay. Renal function was evaluated before and during pregnancy showing a physiological increase in glomerular filtration of 7.5% (basal = 0.93 +/- 0.12 ml/min, peak = 1.00 +/- 0.12 ml/min) as compared with an increase of 166% (basal = 0.68 +/- 0.22 ml/min, peak = 1.85 +/- 0.33 ml/min) in the control group. Renal histology showed lesions corresponding to disseminated intravascular coagulation. These results indicate that the association of skin grafts and hypertension in these rats affects the normal development of pregnancy and suggest that immunological factors could be involved in experimental eclampsia.

Animals↗
PubMed1979

Cushing's syndrome and autoimmunity.

Is Cushing's syndrome ever caused by adrenal stimulating autoantibodies? Specific antiadrenal antibodies were found in the serum of three of seven patients with Cushing's syndrome. The immunologic techniques that showed positive results were complement fixation, tanned RBC hemagglutination, and immunofluorescence. Lymphocytic infiltration of the adrenal was present in two cases, in one of which nodular hyperplasia seemed to be of primary adrenal origin with autoimmunity as a possible cause. However, in cases with clear-cut pituitary origin, the lymphocytic adrenalitis and circulating adrenal antibodies are likely secondary to antigen leaking from damaged tissue.

Adrenal Glands↗
PubMed1976

Immunologic response to A and B erythrocytic antigen.

Immunologic response to A and B erythrocytic antigen stimulation was studied in patients with pemphigus, in patients with systemic lupus erythematosus (SLE), and in normal subjects. Patients with pemphigus and normal subjects demonstrated a similar specific response (isohemagglutinins). A comparison between patients with pemphigus and SLE showed higher titers in the latter. Intercellular antibody titers increased after stimulation; corresponding titers were unaffected by isohemagglutinin absorption. Direct immunofluorescent studies showed IgG deposits in the intercellular spaces of the skin of the patients with pemphigus. However, C3 was found in the same sites in only three cases of pemphigus erythematosus. Immunofluorescent studies for IgG at the basal membrane were positive in only two cases of pemphigus erythematosus. Immunologic response of patients with pemphigus was similar to that of controls; however, it differed from that of patients with SLE.

ABO Blood-Group System↗
PubMed1975

Androgen biosynthesis in experimental cryptorchidism.

This study was conducted to investigate the effects of unilateral cryptorchidism on androgen production and testicular maturation. Experimental cryptorchidism was produced in small and large prepuberal guinea pigs by forcing the testis to remain in the abdomen for a period of 30 days. Small prepuberal animals, which did not reach sexual maturity, showed discrete reductions in the size and weight of the ectopic testes when compared with the scrotal testes. Immaturity of germinal line, tubular size, and intertubular spaces were more pronounced in the ectopic tissue. Both glands produced 4-androstenedione as a primary metabolic product of pregnenolone. Large prepuberal animals, puberal at the time of operation, showed tubular size, spermatic line, and interstitial tissue completely developed in the scrotal gland. Testosterone production was quite similar to that produced in postpuberal testes. The ectopic organ showed only Sertolic cells, some vacuolated, and a few spermatogonia in the tubules. The spaces contained Leydig cells. A significant accumulation of 4-adrenostenedione and a lower testosterone production, compared with that found in the scrotal gland, were observed. The histologic immaturity and the hormonal biosynthesis of the puberal cryptorchid testis parallel findings in scrotal glands from sexually immature guinea pigs.

17-alpha-Hydroxypregnenolone↗