Further Studies on the Incubation of Tyrosine-UL-C14 with Beef Thyroid Tissue Slices.

Abstract

only ones through which feed-back control of immunoglobulin synthesis can operate. Therefore, under physiological conditions, the combined effect on regulation of antibody synthesis of all these structural features, might still be sufficiently specific without involving the antibody combining sites.Sunzmary. Regulation of immunoglobulin synthesis by feed-back inhibition was investigated so as to test whether the specificity of feed-back inhibition depends on recognition of allotypic specificities. This inhibition was observed in rabbits which were pretreated by neonatal injections with antiserum directed against their paternal allotypic specificity. As a result of this pretreatment, synthesis of immunoglobulin of paternal type was reduced (suppressed) for 3-4 months. After this time, some of the pretreated rabbits were injected with normal rabbit serum, containing immunoglobulin of the suppressed type. This resulted in an inhibition of the synthesis of this allotypic immunoglobulin lasting from 50 to 150 days. I t was concluded that feed-back inhibition of immunoglobulin synthesis may operate through recognition of allotypic specificities and possibly through recognition of other structural features of immunoglobulins as well.

The Biosynthesis of Thyroxine: Incorporation of [U-14c]tyrosine Into Thyroglobulin by Mouse Thyroid Glands in Vivo and in Vitro

“…3c) is an indication of the normal metabo¬ lism of tyrosine by the thyroid gland. The suggestion by Dillard et al (1966) that the thyroid gland may show an abnormal tyrosine metabolism is unlikely in view of these experiments with mice in vivo (Text- fig. 1) and in vitro (Text- fig.…”

“…Their yields were low and Dillard, Hollingsworth & Bondy (1966) suggested that the thyroid gland may metabolize tyrosine abnormally. This suggestion was supported by the findings of Mosier (1966) who was unable to incorporate [14C]tyrosine into thyroglobulin although in his invitro system 131I incorporated into DIT and T4 was recovered from hydrolysed thyroglobulin.…”