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  • Author: T. J. Lauterio x
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T. J. Lauterio and C. G. Scanes

ABSTRACT

The possible role of thyroid hormones in the rise in plasma GH observed in protein-restricted chicks was examined. Increased sensitivity of protein-restricted chicks to secretagogue challenge (TRH or GH-releasing factor) appears to account, at least in part, for increased GH concentrations in protein-restricted chicks. Thyroid hormones administered acutely were able to suppress plasma GH concentrations in protein-restricted chicks. Further, chronic thyroid hormone supplementation to low protein diets normalized circulating thyroid hormone concentrations and also normalized the response to GH secretagogue challenge. This decreased sensitivity to TRH provocation occurred without an accompanying change in plasma concentrations of insulin-like growth factor-I, a reputed inhibitor of GH secretion in the chicken.

J. Endocr. (1988) 117, 223–228

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J. Rabii, L. Knapp, A. De La Guardia, P. Zafian, T. J. Lauterio, and C. G. Scanes

ABSTRACT

To study brain sites involved in the regulation of GH secretion in the domestic fowl, lesions were placed in and around the hypothalamus of 1-week-old cockerels. Circulating concentrations of GH were then measured at weekly intervals for 4 weeks after the placement of lesions. At the termination of the experiment, histological procedures were used to determine the exact site of the lesion in each bird. Although a fair degree of overlap existed between the lesion sites leading to stimulation and those causing an inhibition of GH secretion, a clear distinction could be made in the overall distribution of stimulatory and inhibitory sites of GH control. A high concentration of lesion sites resulting in GH decline (presumed GH-releasing factor-rich areas) appeared to reside in the general area of the ventromedial and the arcuate nucleus of the hypothalamus. Lesion sites causing a GH rise (presumed somatostatin-rich areas), on the other hand, seemed to have a more caudal distribution. In addition, some evidence of an anterior hypothalamic distribution of these presumed 'somatostatin' neurones was observed. These agree with the existing immunohistochemical data on the distribution of somatostatin and constitute experimental evidence for localization of presumed GH-releasing factor sites within the avian brain.

J. Endocr. (1984) 103, 327–332

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L. M. Huybrechts, D. B. King, T. J. Lauterio, J. Marsh, and C. G. Scanes

ABSTRACT

The application of a human somatomedin-C radioimmunoassay for the determination of somatomedin-C in chicken plasma has been examined. Parallel inhibition of binding of 125I-labelled somatomedin-C to antisera raised against somatomedin-C was observed with acid-treated human and chicken plasma. The concentration of immunoreactive (IR)-somatomedin-C in the plasma of the domestic fowl appears to be GH dependent. Plasma concentrations of IR-somatomedin-C were reduced after hypophysectomy and partially restored by replacement therapy with chicken GH. The age/development pattern of circulating concentrations of IR-somatomedin-C has been determined in normal and dwarf strains of domestic fowl. Increases in the plasma concentration of IR-somatomedin-C were observed between 1 and 6 weeks of age in control male domestic fowl of either heavy (broiler type) or light (White Leghorn) strains. Thereafter, the plasma concentrations of IR-somatomedin-C remained constant in the heavy strain birds but declined in White Leghorn chicks. Plasma concentrations of IR-somatomedin-C were reduced in sex-linked dwarf chickens, in both light and heavy strains of fowl, but were unaffected in autosomal dwarf chickens.

J. Endocr. (1985) 104, 233–239