L. Huybrechts

The synthesis of 5-carboxamido-4-hydroxy-3-(β-D-ribofuranosyl)-thiophene derivatives, analogues of pyrazofurin

Abstract Methyl 5-carboxamido-4-hydroxy-3(β-D-ribofuranosyl)-2-thiophene carboxylate 2 a and the corresponding 2,5-thiophene dicarboxamide 2 b, two new analogues of the antiviral compound pyrazofurin, were synthesized. A base mediated condensation method with dimethyl thiodiacetate and methyl 2(2,3,5,-tri-O- t -butyldimethylsilyl-β-D-ribofuranosyl)-2-oxoacetate 5 was used. The structure of these compounds and their intermediates was determined spectroscopically.

Effects of dietary T3 on growth parameters and hormone levels in normal and sex-linked dwarf chickens

Tri-iodothyronine (T3) has been administered in the diet, from day of hatch until 8 weeks of age, to sex-linked dwarf and normal chicks of both sexes from a brown-egg slow-growing strain. Feed was supplemented with either 0.1 ppm or 0.5 ppm T3. A significant genotype by treatment interaction was observed on body weight: the effect of T3 in males was significantly positive for dwarfs and null for normals, the effect in females was null for dwarfs and significantly negative for normals. Feed efficiency was rather decreased by the treatment in both genotypes. Abdominal fatness was decreased in a dose-dependent manner in both genotypes, while rectal temperature was raised in dwarf chicks only. Plasma T3 was raised to normal levels in dwarfs receiving 0.1 ppm exogenous T3, while the 0.5 ppm dose yielded hyperthyroid levels. Plasma GH levels were decreased in a dose-dependent manner by the T3 treatment, the effect being larger in dwarfs. Surprisingly, plasma IGF-I was unchanged in spite of the GH decrease, whatever the genotype or the sex. It was concluded that exogenous T3 alone can have a stimulatory effect on growth in dwarfs but can not fully restore a normal growth rate. Both T3 and IGF-I are important for a normal growth and the relationship between T3 and IGF-I production should be further investigated in order to better understand the physiological modifications due to the sex-linked dwarf gene.

Effect of triiodothyronine supplementation on thyrotropin-releasing hormone-induced growth-hormone secretion in sex-linked dwarf and normal chicks

The effect of a dietary triiodothyronine (T3) supplement, of either 0.1 or 0.5 microgram/g of feed, was studied on the thyrotropin-releasing hormone (TRH)-induced growth hormone (GH) secretion in sex-linked dwarf (dw) or normal (Dw) chicks of both sexes. In normal chicks, 0.1 microgram/g T3 decreased plasma GH levels before TRH as well as the GH increase after TRH, and 0.5 microgram/g T3 totally suppressed any response to TRH, either at 4 or at 7 weeks of age. Dwarf chicks were more sensitive to TRH than normals when receiving either 0 or 0.1 microgram/g T3; 0.5 microgram/g T3 abolished the difference between genotypes at 4 weeks of age but not so clearly at 7 weeks of age, where dwarf females showed a slight but still significant GH increase after TRH. Interactions between genotype, TRH injection, and T3 treatments were often significant at 4 weeks of age and even more at 7 weeks of age. Dwarf chicks receiving 0.1 microgram/g T3, expected to have normal plasma T3 levels, showed a higher GH response after TRH. This suggests that other hormones may be involved in the regulation of this response, particularly IGF-I, which is known to remain at a low level in T3-treated dwarf chicks.