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Studies of the congenitally goitrous sheep. Composition and metabolism of goitrous thyroid tissue.

ABSTRACT: 1. Normal and congenitally goitrous thyroid tissue was examined to identify the defective mechanism in the goitrous glands. 2. The uptake of [(131)I]iodide from the blood stream into the goitrous glands (average 74.9%) was significantly greater than normal (average 43.5%; P < 0.005), as was the rate of [(131)I]iodide release (goitrous t((1/2)) average 72.3hr., normal t((1/2)) average 198.7hr.; P0.025). 3. The l-[(131)I]-iodotyrosine-deiodinase activity was significantly (P0.02) greater than normal in goitrous-thyroid slices. 4. The 0.9%-sodium chloride-soluble proteins of [(131)I]-iodide-labelled thyroid glands were fractionated with ammonium sulphate: 68.7+/-4.0% of the total radioactivity appeared in the 35-45%-saturation precipitate from normal gland extracts, but less than 20% of the total radioactivity was in in this fraction from goitre extracts. 5. Ultracentrifugal analysis of 0.9%-sodium chloride-soluble proteins of goitrous glands showed no protein of S(20,w) 19-20s (thyroglobulin) even when the animals had previously received 0.1-2.0mg. of l-thyroxine/day intramuscularly for 40 days. The major proteins of goitrous glands had S(20,w) 3.2-7.6s. 6. The incorporation in incubated slices of [(14)C]proline and [(14)C]leucine into soluble proteins precipitated by 35-42%-saturated ammonium sulphate was markedly lower in goitrous tissue. 7. It was concluded that the goitrous tissue exhibited defective biosynthesis of thyroglobulin.

SUBMITTER: Falconer IR

PROVIDER: S-EPMC1265110 | biostudies-other | 1966 Jul

REPOSITORIES: biostudies-other

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Project description:1. Congenitally goitrous thyroid tissue was obtained from South Australian Merino sheep. Ultrastructural studies of the secretory cells in this tissue showed active cells of normal appearance, containing apical protein droplets. 2. (125)I-labelling in vivo of goitre tissue was used to investigate the iodoproteins, in which the major proportion of (125)I appeared in the cell protein fraction soluble in 0.9% sodium chloride (average 62% in goitres from untreated sheep). 3. Ammonium sulphate fractionation showed two clear peaks of iodoprotein precipitation, one at 35-40% saturation and the other at 50-55% saturation. Both iodoprotein fractions contained iodotyrosines and iodothyronines, which were identified chromatographically after enzymic hydrolysis of the protein. 4. Polyacrylamide-gel electrophoresis at pH9.4, at either 7.5 or 5.0% acrylamide concentration, was used to characterize the iodoproteins. Two major fractions were observed, the fastest-migrating fraction coincident with serum albumin, and a slower-migrating, less-well-defined zone. This fraction migrated in 7.5% acrylamide gel, which excluded normal thyroglobulin. 5. Density-gradient (10-40% sucrose) centrifugation was used to determine the approximate sedimentation coefficients of the iodoproteins, which showed major components at s(20,w) 8-9S and s(20,w)<5S. 6. Immunoprecipitation with rabbit anti-(sheep thyroglobulin) failed to sediment (125)I-labelled proteins from goitre extracts. 7. Ouchterlony-type double diffusion in agar plates demonstrated immunoprecipitation lines between rabbit anti-(sheep thyroglobulin) and both the concentrated goitre extract and its Sephadex G-200-excluded fraction, which were confluent with that obtained on reaction with purified normal thyroglobulin. 8. It was concluded that both major iodoprotein fractions were capable of supplying thyroid hormones to the animal, and that the fraction of s(20,w)<5S was iodinated serum albumin. As (125)I-labelled thyroglobulin was not detected in goitre tissue from untreated or thyroxine-treated animals, it was possible that the genetic defect causing goitre resulted in an abnormal thyroglobulin, incapable of being iodinated but immunologically reactive.

Project description:Higher dietary energy is often used to achieve better animal performance in mutton sheep production. Notably, changing the diet formula affects rumen fermentation and the microbiota of ruminants. In this study, we investigated the effect of dietary energy on rumen fermentation and ruminal microbiota in fattening sheep. Fifteen 2-month-old white-headed Suffolk sheep (♂) × Hu sheep (♀) crossbred lambs were randomly divided into three treatments based on the dietary energy of the feeds fed: 8.67 MJ/kg (Low energy (LE); n = 5), 10.38 MJ/kg (standard energy (CON); n = 5), and 12.31 MJ/kg (high energy (HE); n = 5) groups. After 70 days of feeding, sheep were slaughtered and the ruminal fluids were collected and analyzed to determine fermentation parameters. Microbiota was determined using metagenomics sequencing. Notably, the microbial cell protein (MCP) and butyric acid concentrations were significantly high in the HE group. Metagenomic sequencing revealed that ACE and Chao indexes of the HE group were significantly decreased. Four genera among the major classified taxa across all the kingdoms differed in relative abundance in the three dietary energy levels. The relative abundances of Prevotella_brevis, Succiniclasticum_ruminis, Prevotellace-ae_bacterium, and Lachnospiraceae_bacterium were significantly correlated with rumen fermentation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis further revealed that a high-energy diet increased lipid metabolism of microbiota. The Carbohydrate Active enzymes (CAZy) gene, which participates in energy metabolism, was upregulated, while genes regulating plant cell wall degradation were downregulated in the HE group. These results suggest that a high-energy diet had minimal influence on the rumen fermentation pattern but altered the composition of the rumen microbiota, enhancing microbial lipid metabolism and limiting crude fiber metabolism. The findings of this study provide scientific evidence of the effect of dietary energy on ruminant fermentation and fattening sheep production.

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Studies of the congenitally goitrous sheep. Composition and metabolism of goitrous thyroid tissue.

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