Thesis (Ph. D.)--University of Florida, 1970. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 103-110).

The incidence of cleft palate was observed in 1361 F₁, 1531 F₂, and 2275 backcross embryos and chicks from a reciprocal cross between an inbred Leghorn line selected for high incidence (30 to 50%) of cleft palate and a non-cleft palate (New Hampshire; zero %) line. Cleft palate appeared in the F₁ at frequencies less than 1%, in the F₂ at approximately 1%, and in the backcrosses at approximately 8%. When dams were fed a diet deficient in riboflavin, the incidence of cleft palate was shown to increase for the F₂ and backcross progeny to 4% and 12% respectively. The response of cleft palate incidence to riboflavin deficiency was shown to be in large part a genetic characteristic of the embryo itself and not the dam. The reduced hatchability of eggs during maternal riboflavin deficiency was shown to be similar to earlier reports. No evidence of any unusual response of cleft palate line hens to riboflavin deficiency was found for hatchability, chick body weight, nor maternal effect on cleft palate. The cleft palate condition was shown to be semi-lethal, the lethality being partially due to severe expression of the trait. Genetic models were considered and it was suggested that the model to be further tested should be that of 3 recessive loci, one of which involves a fault in the normal metabolism of riboflavin, and a few additive loci controlling penetrance and expressivity of the trait. / Land and Food Systems, Faculty of / Graduate

The study of thyroid metabolism usually involves the employment of antithyroid compounds and exogenous thyroid hormones in order to elucidate the thyroid function through the understanding of the effects of these compounds. In this study, the effects of die thiouracil and rapeseed meal goitrogens were examined in chicks. The goitrogenic effects of the thiouracil were manifested rapidly by increased thyroid weight, thyroid epithelium and uptake of radioiodine. The goitrogenic effects of rapeseed meal were similar to the effect of thiouracil except that at the level of meal fed, the effects were less pronounced and evident only after prolonged feeding. When an iodine deficient diet was fed to growing chicks, the goitrogenic effect was less than when thiouracil or rapeseed meal was fed. Histological studies of the thyroid glands of adult birds fed an iodine deficient diet showed slight hyperplasia without thyroidal enlargement and with persistence of colloid,whereas growing chicks fed an iodine deficient diet displayed severe hyperplasia and loss of colloid. By contrast, the effects of thiouracil were independent of the age of chicks. A combination of thiouracil and rapeseed meal produced goitrogenic effects greater than those occurring when thiouracil or rapeseed meal was fed singly. Thiouracil fed in an iodine deficient diet, on the other hand, showed no goitrogenicity for chicks. High doses (4.0 μg) of thyroxine administered daily to thiouraci1-treated chicks alleviated the antithyroid effects of thiouracil as indicated by the decrease in thyroid weight, thyroid epithelium and radioiodine uptake. Low doses (1.0 ug or less) of thyroxine administration, however, produced the opposite effects. Nevertheless, high doses of thyroxine did not relieve the growth depressing effects of thiouracil completely. Autoradiographic studies on thyroids of thiouraci1-treated or rapeseed meal-fed chicks showed a uniform distribution of radioiodine in the colloid within five hours of administration of tracer. Differences in activity were observed among the individual follicles in each gland. The smaller follicles concentrated more iodine than the larger ones. Furthermore, very little iodine was observed in the epithelial cells. These findings, together with previous reports that inorganic iodine was present in the thyroid after its administration, suggested that iodination did not occur in the apical membrane of the follicular cells bordering the colloid. Different rapeseed cultivars contain different amounts of glucosinolates which are responsible for the goitrogenic effect of the rapeseed meal. Goitrogenicity of three different kinds of rapeseed meals was compared in growing chicks and the results indicated that Candle meal had the least goitrogenic activity than the Tower and Span meal. / Land and Food Systems, Faculty of / Graduate

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.