Biochemical characterization of serum thyroglobulin from patients with bone metastases from follicular carcinoma of the thyroid.

The biochemical properties of serum thyroglobulin obtained from six patients with follicular carcinoma of the thyroid and distant metastases to bone(s) have been studied. Since it is difficult to isolate sufficient thyroglobulin from serum samples, in vivo radioiodinated serum thyroglobulin obtained after radioiodine administration was used. In contrast to a sharp salting-out pattern observed with native thyroglobulin isolated from normal thyroid tissue, a broad salting-out curve was seen with metastatic serum thyroglobulin. The metastatic serum thyroglobulin eluted with low ionic strength from ion-exchange column. More than 95% of metastatic serum thyroglobulin could be bound to concanavalin-A sepharose and be eluted with 0.5 M alpha-methyl mannoside. The reactivity of metastatic serum thyroglobulin and native thyroglobulin towards concanavalin-A was comparable. Both types of thyroglobulins showed identical mobilities on sucrose linear density gradient centrifugation. The metastatic serum thyroglobulin from follicular carcinoma of the thyroid thus appears to be 19 S thyroglobulin with near normal concanavalin-A binding sugars but altered surface charges.

Malic enzyme activity in the developing rat brain in relation to thyroid status.

Malic enzyme activity in the soluble fraction of neonate brains from mothers fed with propylthiouracil (0.015% w/v) in drinking water from day 12 of the gestation period was significantly lowered (P less than 0.01) as compared to the offspring of normal mothers. Supplementation of triiodothyronine to the neonates from experimental mothers restored the malic enzyme activity to normal levels. However, administration of triiodothyronine to adult control rats did not influence malic enzyme activity in the brains of these animals. Our data suggest that during the initial critical period of brain maturation, malic enzyme is under the control of thyroid hormones. The response of malic enzyme towards thyroid hormones is lost once the brain has matured.

Malic enzyme response to triiodothyronine in the brain of neonatal rats.

Malic enzyme activity in the soluble fraction of the neonatal brain of hypothyroid rats was observed to be lowered as compared to that of the control animals (p less than 0.01). Administration of triiodothyronine to the neonates of control animals resulted in significant enhancement (p less than 0.001) in the activity of the Malic enzyme. Our studies show that brain malic enzyme which is involved in lipogenesis and hence in myelination responds to triiodothyronine in the early stage of life.

Immunoreactive thyroglobulin-like material derived from saliva.

The presence of an immunoreactive thyroglobulin-like material in saliva from normal subjects and from 35 patients with thyroid carcinoma was detected by radioimmunoassay. The levels of this material in saliva were markedly elevated in patients with extensive metastases. Concentrated saliva samples from normal subjects and from patients with thyroid carcinoma were fractioned on Sepharose-6B and each fraction was assayed from thyroglobulin content by RIA. Several protein peaks of varying molecular size with thyroglublin-like immunoreactivity were observed. The physiological significance of these molecules in saliva remains to be established.