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Biomedical subjects

A Baird

Publications and source records attributed to A Baird.

At least 235 records · Page 13Linked to original sources
PubMed1983

Immunohistochemical evidence that brain enkephalins arise from a precursor similar to adrenal preproenkephalin.

We have examined rat brains by immunohistochemistry with an antiserum raised against BAM22P, a synthetic fragment of the adrenomedullary precursor of Leu- and Met-enkephalin, in order to determine whether preproenkephalin derived peptides are detectable in the central nervous system. BAM22P antiserum stained fibers, nerve endings and cell bodies in many areas of the brain, especially the striatum, the septum and the hypothalamus. Comparative topographical studies showed that neurons recognized by anti-BAM22P overlapped structures found immunoreactive for enkephalins in the present study. In addition, BAM22P antiserum stained cell bodies in cerebral cortex and in caudate putamen. The presence of BAM22P immunoreactivity in presumptive enkephalin neurons suggests that some brain enkephalins arise from a precursor identical or closely related to the preproenkephalin A found in the bovine adrenal medulla. This does not preclude the possibility of enkephalins also arising from other precursor molecules.

Adrenal Medulla↗
PubMed1983

Androstenedione-mediated inhibition of 11 beta-hydroxylation in monolayer cell cultures of fetal calf adrenals.

The possibility that the formation of androstenedione by fetal calf adrenal cells in culture is linked to their decreased ability to form cortisol and corticosterone was investigated. Fetal calf adrenal cells metabolise radioactive adrostenedione to two major products which coelute on thin layer chromatography with 11 beta-hydroxyandrostenedione and 11 beta-hydroxytestosterone. When the cells are incubated with 11-deoxycortisol or 11-deoxycorticosterone in the presence of androstenedione there is a dose dependant inhibition of cortisol and corticosterone formation. Further studies with progesterone showed an accumulation of 11-deoxycortisol and 11-deoxycorticosterone in cells incubated simultaneously with androstenedione. The results demonstrate that exogenous androstenedione can have dramatic effects on steroidogenesis in the fetal calf adrenal and suggest that the accumulation of androstenedione in the medium of cultured andrenocortical cells is responsible, at least in part, for the decreased formation of cortisol and corticosterone.

Adrenal Glands↗
PubMed1983

Inhibitory effects of cysteamine on neuroendocrine function.

The action of cysteamine on anterior pituitary hormone secretion was studied in vivo using conscious, freely moving male rats and in vitro using anterior pituitary cells in monolayer culture. Administration of 500 micrograms cysteamine into the lateral cerebral ventricles of normal rats caused the complete inhibition of pulsatile GH secretion for a minimum of 6 h. This treatment also significantly decreased plasma concentrations of LH for at least 6 h in orchiectomized rat, TSH in short-term (0.5 month) thyroidectomized rats, and PRL in long-term (6 months) thyroidectomized rats. The in vivo stimulation of GH, LH, TSH and PRL with their respective releasing hormones 60 min after administration of cysteamine was not different from the response observed in rats pretreated with saline except for PRL where cysteamine pretreatment significantly inhibited the expected PRL increase. In vitro, 1 mM cysteamine decreased basal and TRH stimulated PRL release while not affecting basal or stimulated GH, LH, TSH and ACTH secretion. These data demonstrate the dramatic and wide-ranging effects of cysteamine on anterior pituitary hormone secretion. This action appears to be mediated through hypothalamic pathways for GH, LH and TSH and through a pituitary pathway for PRL.

Animals↗
PubMed1983

Gestational changes in the metabolism of progesterone by the fetal calf adrenal.

The metabolism of [3H]progesterone by the fetal calf adrenal was examined in homogenates and microsomal fractions of adrenals obtained from mid- or late gestational fetal calves. Throughout the course of gestation, there was no detectable difference in the formation of corticosterone from progesterone by adrenal homogenates. In contrast, cortisol production in these same homogenates increased 7-fold from 0.3-2.2% at the end of gestation. Similar results were obtained using microsomal fractions prepared from these homogenates: the 17 alpha-hydroxylation of progesterone (i.e. 17 alpha-hydroxyprogesterone and 11-deoxycortisol) increased from 0.7% to 26% at the end of gestation. The results suggest that the increased cortisol observed in the fetal circulation toward the end of gestation is the result of a rapid increase in the capacity of the fetal calf adrenal to form 17 alpha-hydroxycorticosteroids. The underlying mechanism for this change is discussed.

17-alpha-Hydroxyprogesterone↗
PubMed1983

Role of pro-opiomelanocortin-derived peptides in the regulation of steroid production by human fetal adrenal cells in culture.

Synthetic (1-39)ACTH, (1-24)ACTH, (18-39)ACTH, alpha-MSH, met-enkephalin and alpha-, beta- and gamma-endorphin were tested for their ability to stimulate steroidogenesis by human fetal adrenal cells in culture. Adrenal cells were incubated with peptide hormones for two periods of 24h. On the third day of the experiment the cells were incubated with progesterone (4 micrograms/2 ml) for 8 h. At the doses tested only (1-39)ACTH, (1-24)ACTH and alpha-MSH stimulated steroidogenesis. None of the other peptides had any corticotrophic effect on the formation of cortisol, corticosterone or dehydroepiandrosterone sulphate (DHAS). At the highest doses tested, alpha-MSH (100 micrograms/2 ml) had a corticotrophic effect that was not different from that obtained with 20 ng (1-39)ACTH or (1-24)ACTH. At the lower doses (0.2-2 micrograms/2 ml), alpha-MSH stimulated the formation of DHAS (P less than 0.01) without stimulating the formation of cortisol.

Adrenal Glands↗
PubMed1982

Molecular forms of the putative enkephalin precursor BAM-12P in bovine adrenal, pituitary, and hypothalamus.

A highly specific radioimmunoassay for one of the putative adrenomedullary [Met]enkephalin precursors, BAM-12P (Tyr-Gly-Gly-Phe-Met-Arg-Arg-Val-Gly-Arg-Pro-Glu-OH), has been developed. The BAM-12P antibodies recognize the COOH-terminal fragment of the peptide from Arg7 to Glu12 and do not crossreact with [Met5]- or [Leu5]enkephalin or any of their COOH-terminal lysine or arginine extended analogs. Specificity for the COOH-terminal Glu-OH is suggested by the 100% crossreactivity with BAM-12P5-12 and 0.3% crossreactivity with BAM-12P5-12 amide. Using these antibodies, we have measured three forms of BAM-12P-like immunoreactivity in extracts of bovine adrenal medulla, of which the major form (greater than 90%) corresponds to BAM-12P by molecular weight. Extracts of bovine adrenal cortex contain 1% the amount of a BAM-12P-like material (Mr approximately 1400; 20 ng per gland), possibly due to crosscontamination with adrenomedullary tissue. The major form of BAM-12P-like material in extracts of bovine neurointermediate pituitaries is of higher molecular weight than authentic BAM-12P (Mr approximately 4000); the remaining material (10%) corresponds to BAM-12P by molecular weight. There is no detectable BAM-12P-like immunoreactivity in crude or purified extracts of bovine anterior pituitaries. Extracts of bovine hypothalamic tissues contain small amounts of BAM-12P immunoreactivity (approximately 2 ng per fragment) which can be detected as one molecular form corresponding to a 1400-dalton molecule. The results indicate that the enkephalin precursor found in the adrenal medulla also may be present in the pituitary and hypothalamus. Furthermore, the processing of this molecule appears to be tissue-specific.

Adrenal Cortex↗
PubMedDate not supplied

Inhibition of aldosterone production in the adrenal glomerulosa by atrial natriuretic factor.

Several forms of the polypeptide atrial natriuretic factor (ANF) have been isolated recently from rat and human atria and identified; they are probably associated with the secretory granules of atrial tissue. The potent ability of ANFs to increase urine sodium content is mediated by their direct action on the kidney. We report here the high intrinsic activity of a synthetic replicate of one form of this molecule, ANF(8-33)(ref. 7), to inhibit directly basal aldosterone secretion and its ability to antagonize the stimulatory effects of adrenocorticotropin (ACTH) and angiotensin II (AN-II) on the secretion of aldosterone by rat adrenoglomerulosa cells in vitro. Our results suggest that ANF is of clinical importance in the management of aldosterone-dependent hypertension by modifying the adrenocortical response to endogenous ACTH and AN-II.

Adrenal Glands↗
PubMedDate not supplied

Pneumococcal vaccine in general practice.

A practice nurse discusses the need for pneumococcal vaccine for at risk patients, and charts the innovation of the vaccine programme in her practice.

Bacterial Vaccines↗