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R B Chiasson

Publications and source records attributed to R B Chiasson.

24 records · Page 2Linked to original sources
PubMed1975

The effect of hypothalamic lesions on thyroid-stimulating hormone concentration in the chicken pituitary.

Studies of thyroid activity following hypothalamic lesions have provided indirect evidence of TSH influence on the pars distalis of birds. The present study examined the influence of hypothalamic lesions on TSH assays of the rostral and caudal lobes of the pars distalis. Lesions of the septomesencephalic tract increased TSH levels in the rostral lobe but had no influence on the caudal lobe. Lesions of the supraoptic or ventrolateral nuclei neither stimulated nor depressed TSH in either lobe of the pars distalis.

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PubMedDate not supplied

Comparative effects of three goitrogenic treatments on White Leghorn chickens.

White Leghorn chickens respond to dietary goitrogenic compounds by forming either colloidal or hyperplastic goiters. Thiourea does not cause increases in DNA above that seen in controls, although thyroid weight increases. This may be due to a secondary toxic effect of thiourea on the chick thyroid, which inhibits cellular replication. Both methimazole- and propylthiouracil- (PTU) fed birds exhibit cellular hyperplasia and increases in DNA amounts beyond control levels. The rapid thyroid growth in methimazole-treated birds from 30 to 70 days of age is partially due to follicular colloid accumulation. Growth of the thyroid in PTU-fed birds is thought to be due to cellular hyperplasia and hypertrophy, since DNA values are greatest in these glands. Histological studies of the thyroid glands confirm the results of DNA and protein assays for all three goitrogen-treated groups. The ultrastructural changes associated with prolonged stimulation of the chick thyroid are an increase in the amount of primary and secondary lysosomes, microvilli, and mitochondria, and a dilation of the endoplasmic reticulum and Golgi apparatus. It is thought that micropinocytosis is a more important endocytotic process during goiter development in the chick than is phagocytosis.

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PubMedDate not supplied

Muscle fiber types in the dystrophic puboischiofemoralis of commercial broilers.

Muscle fiber types, their diameters, lipid content, and nuclei distributions were studied in normal and necrotic puboischiofemoral muscles from commercial broiler chickens of the Hubbard strain. Three categories of puboischiofemoral fiber morphology (alpha R, beta R, and alpha W) occur in the cranial and caudal portions of the pars lateralis and in the cranial, medial, and caudal portions of the pars medialis. The greatest amount of necrosis occurred in the caudal portion of the pars medialis of the puboischiofemoralis. A fiber type characterized by a greatly enlarged and rounded or oval cross-section, decreased fat content, and internalized and clustered nuclei was present in necrotic muscle but not in normal muscle.

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