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Biomedical subjects

C Varela

Publications and source records attributed to C Varela.

At least 19 recordsLinked to original sources
PubMed1991

Influence of hypothyroidism duration on developmental changes in the hypothalamic factors implicated in growth hormone secretion in the male rat.

The effects of hypothyroidism duration on several factors implicated in GH secretion control were studied in the male rat at different maturity stages, ranging from the peripuberal period to adulthood. Thyroid ablation was performed on 22-day-old Wistar male rats maintained on a low iodine diet (T group). Age-paired controls (C group) were fed with the same diet, supplemented with potassium iodide. Subgroups of T and C animals (aged 32, 42, 52, 82 and 112 days) were studied 10, 20, 30, 60 and 90 days after surgery. After pentobarbital anesthesia, jugular blood was withdrawn before and 5 min after an intravenous TRH stimulus, for GH assay. Hypothalamic and pituitary tissues were obtained in order to measure GH, immunoreactive somatostatin (IR-SRIF) and growth hormone-releasing factor (IR-GRF). Growth rate and serum testosterone confirmed that C rats reached sexual maturity by day 30 of the study. Mean +/- SE serum GH (ng/ml) increased (p less than 0.05) in C animals from day 10 (38.5 +/- 5) to day 30 (67.4 +/- 7.3), with no significant variations thereafter. The same time sequence pattern was observed in pituitary GH concentrations. In T rats, both serum and pituitary GH decreased progressively from day 10 to 90, being significantly lower than in C at all times of the study. No GH response to TRH could be found in C groups. In contrast, GH increased significantly (p less than 0.05) in T animals after TRH at days 20 and 30.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Ectopic Cushing's syndrome with periodic hormonogenesis--a case suggesting a pathogenetic mechanism.

We report on a case of ectopic Cushing's syndrome due to a thymic carcinoid tumour with periodic hormonogenesis. Periods of hormonal production averaged 27 days. Prior to bilateral adrenalectomy, mean (s.d) values of ACTH and cortisol were 202.1 (50.3) pg/ml and 46 (14.7) micrograms/dl, ACTH rising to 3996 +/- 425 pg/ml (P less than 0.01) and cortisol falling to 6.3 +/- 1.5 micrograms/dl (P less than 0.01) in the immediate postoperative period. During the late postoperative period (2-13 months following surgery) ACTH levels fell to 509.3 (123.8) pg/ml (P less than 0.01), but remaining even higher (P less than 0.01) than before adrenalectomy. The pattern of ACTH in the present case suggests the existence of a negative feedback exerted by the cortisol over tumoral ACTH.

ACTH Syndrome, Ectopic↗
PubMed1986

Interaction of thyrotrophin releasing hormone and the enkephalin analogue DAMME on pituitary hormone secretion.

Because TRH counteracts the inhibitory effect of opiate peptides on LH secretion in cultured cells from normal pituitaries, six normal postmenopausal women were studied to determine whether TRH interacts in vivo with opioid peptides in the regulation of pituitary hormone secretion. At two different times a constant 3 h infusion of either saline or TRH (5 micrograms/min) was initiated. At 60 min a 250 micrograms bolus of the opiate agonist peptide D-Ala2-MePhe4-met-enkephalin-0-ol (DAMME) was injected in one of the two saline and TRH infusion tests. The four treatments, i.e. saline infusion alone, saline infusion with a DAMME bolus, TRH infusion alone; and TRH infusion with DAMME bolus were given at random with an interval of at least 7 d. Blood samples were taken every 15 min during the 3 h study. DAMME induced a significant fall (P less than 0.05) in serum LH (from 35 +/- 8.5 to 18.3 +/- 5.1 mIU/ml) (mean +/- SEM) without significantly affecting FSH levels (from 29 +/- 11.2 to 26.9 +/- 12.4 mIU/ml). These changes were not antagonized by the continuous infusion of TRH. PRL had a monophasic response pattern to continuous isolated TRH infusion; the basal levels increased from 4.2 +/- 1.2 to 24.5 +/- 6.8 ng/ml at 30 min and then slowly decreased with a plateau from 90 min until the end of the study. DAMME administration at 60 min induced a significant second peak of PRL secretion (44 +/- 6.5 ng/ml) 30 min later (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗