Faculty Bibliography

Fourteen patients with unipolar depression who had a blunted thyroid-stimulating hormone (TSH) response to infusion of 500 micrograms of thyrotropin-releasing hormone (TRH) and who showed marked clinical improvement after pharmacotherapy and/or electroconvulsive therapy had the TRH test repeated after improvement. The mean (+/- SD) maximal TSH response to TRH (delta TSH) increased significantly from 4.0 +/- 1.9 to 9.1 3.5 micro IU/ml. The number of patients with delta TSH less than 7.0 micro IU/ml increased significantly from 0 to 9 of 14 after improvement. Eleven of the patients were followed for 5 to 19 months, and none showed clear relapse. The results suggest that the blunted TSH response to TRH has features of both a state marker for active unipolar depression and a trait marker for vulnerability to this illness, and support the suggestion that the TRH test may be useful in diagnosis and treatment planning.

Horseradish peroxidase (HRP) was used as a marker to determine the rate of ongoing pinocytosis in several fibroblast cell lines. The enzyme was interiorized in the fluid phase without evidence of adsorption to the cell surface. Cytochemical reaction product was not found on the cell surface and was visualized only within intracellular vesicles and granules. Uptake was directly proportional to the administered concentration of HRP and to the duration of exposure. The rate of HRP uptake was 0.0032-0.0035% of the administered load per 10(6) cells per hour for all cells studied with one exception: L cells, after reaching confluence, progressively increased their pinocytic activity two- to fourfold. After uptake of HRP, L cells inactivated HRP with a half-life of 6-8 h. Certain metabolic requirements of pinocytosis were then studied in detail in L cells. Raising the environmental temperature increased pinocytosis over a range of 2-38 degrees C. The Q(10) was 2.7 and the activation energy, 17.6 kcal/mol. Studies on the levels of cellular ATP in the presence of various metabolic inhibitors (fluoride, 2-desoxyglycose, azide, and cyanide) showed that L cells synthesized ATP by both glycolytic and respiratory pathways. A combination of a glycolytic and a respiratory inhibitor was needed to depress cellular ATP levels as well as pinocytic activity to 10-20% of control values, whereas drugs administered individually had only partial effects. In spite of the availability of an accurate quantitative assay for fluid and solute uptake, the function of pinocytosis in tissue culture cells remains unknown.