Cyclic AMP phosphodiesterase in human lymphocytes and lymphoblasts

Cyclic nucleotide phosphodiesterase activities were examined in lymphocytes from 12 transformed human B cell lines, two T cell lines, six patients with lymphocytic leukemia, and 10 normal donors. A consistent difference bwtween cells from the normal and leukemic state was observed. The cyclic AMP phosphodiesterase activity from normal lymphocytes is inhibited greater than 80% by muM cyclic GMP while this concentration of nucleotide has little or no effect on the enzyme from transformed lymphocytic cell lines or from lymphocytic cells of leukemia patients. The reported lack of cyclic GMP phosphodiesterase in human lymphocytes from several sources is confirmed. The apparent absence of a cyclic GMP degradation mechanism and of cyclic GMP control of cyclic AMP hydrolysis may be related to defective lymphocyte growth control.

Value of simultaneous T3, T4, and TSH measurements for management of graves' disease in children

One hundred simultaneous determinations of serum T4 and T3 were performed during the course of treatment of 23 children and adolescents with Graves' disease. Five patients were previously untreated and six were experiencing relapse after treatment was discontinued. During relapse, increased T3 concentration is frequently present when serum T4 concentration is normal and T3 measurement is therefore more reliable for early detection of relapse. During therapy with thionamides, T4 measurement alone is often misleading in assessing adequacy of control achieved by therapy. Commonly, patients who clinically have hyperthyroidism have serum T4 concentrations within the normal range but continue to have elevated T3 concentrations (T3 toxicosis). Similarly, T4 can be suppressed into the hypothyroid range in the clinically euthyroid patient with either a normal or high T3 concentration. In these patients, determination of serum T3 often prevents premature reduction of thionamide dosage. When T4 and T3 concentrations do not clearly demonstrate presence or absence of hypothyroidism, measurement of serum thyroid stimulating hormone can be of value.