M. De Visscher

MEASUREMENT OF PREALBUMIN AS INDEX OF PROTEIN-CALORIE MALNUTRITION

Abstract Measurement of prealbumin (thyroxine-binding prealbumin, T.B.P.A.) appears to be a sensitive indicator of protein deficiency and of its improvement by nutritional treatment. It also allows the detection of pre-kwashiorkor and the differential diagnosis of various forms of protein-calorie malnutrition. This sensitivity seems to be due to three factors: ( a ) biosynthesis of T.B.P.A. by the liver, which reacts promptly to protein deficiency, ( b ) the richness of T.B.P.A. in tryptophan; and ( c ) the rapid turnover-rate of this protein. Measurement by a micromethod, using radial immunodiffusion, is simple, reproducible, accurate, and inexpensive.

Hormonal and nutritional status: Critical conditions for endemic goiter epidemiology?

Recent advances in protein metabolism and in glycoprotein synthesis bring further insight into endemic goiter epidemiology. Retinol circulates in the blood stream in close parallelism with retinol-binding protein and prealbumin (RBP-PA), a protein complex whose liver secretory rate is dependent upon hormonal and nutritional status. On the other hand, normal glycosylation reaction occurs through the formation of a retinol-linked sugar complex. It is suggested that the relative drop of serum retinol levels, as a result of modified hormonal climate and/or declining protein status, might constitute a critical factor capable of inducing a defective incorporation of mannose into native thyroglobulin, leading to an early depression of the full glycoprotein production. This concept affords a comprehensive explanation of the following unresolved data recorded in goitrous areas: (1) clinical and biochemical discrepancies between subjects living in the same morbid territory, (2) persistence of endemicity in spite of appropriate iodine supplementation, (3) similar prevalence of goiter hypertrophy in male and female prepubertal children, (4) increased frequency of goiter enlargement in the four most vulnerable groups, namely preschool children of both sexes, adolescent girls, pregnant women, and elderly persons, (5) decreased impact of thyroid swelling accompanying improved socio-economic status, even without iodine addition, and (6) resurgence of goitrous hyperplasia as an effect of seasonal or sporadic deterioration of nutritional habits, even when iodine supply remains unchanged.

Synthesis of thyroglobulin subunits in oocytes injected with thyroidal ribonucleic acid.

Abstract Oocytes from Xenopus laevis were injected with RNA extracted from bovine thyroid polyribosomes. The analysis of the labelled products performed on SDS-polyacrylamide gels revealed the presence of a radioactive peak with a migration distance corresponding to a protein of about 85,000 daltons. Immunoprecipitation of the labelled products allowed us to single out this specifically induced protein. Sucrose density ultracentrifugation showed that translation of m-RNA for thyroglobulin (Tg) by oocytes did not result in the assembly of the subunits into the complete 19 S Tg molecule in the soluble phase of the homogenate.