Basic studies for the practical use of bitterness inhibitors: selective inhibition of bitterness by phospholipids.

Purpose: We examined the effects of phospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol (PI), and phosphatidic acid (PA) on human taste sensation to various substances.

Methods: The effects were evaluated psychophysically using paid volunteers.

Results: PA inhibited the bitterness of various substances dissolved in water without affecting sweetness, saltiness, and sourness, although its inhibitory activity was less than that of PA-LG.

Quantitative histochemistry of the primate skin. III. Glyceraldehyde-3-phosphate dehydrogenase.

Glyceraldehyde-3-phosphate dehydrogenase activities were assayed with a fluorometric micromethod in various parts of the skin and its appendages. Enzyme activity was abundant, particularly in the epidermis and mucous membrane (4.2 to 11.

Quantitative histochemistry of the primate skin.

Fructoaldolase activity in primate skin and appendages has been assayed with a highly sensitive fluorometric method. Epidermal fructoaldolase has characteristics similar to the fructoaldolases obtained from animal sources. The fructoaldolase activities of various skin structures are remarkably high; all glandular structures (except for apocrine sweat glands which have the highest activity of 2400 mmoles/hr/kg dry wt.

Enzymatic basis for active transport of Na+ in the sweat gland unit.

The presence of specific adenosine triphosphatase (ATPase) is demonstrated in the eccrine sweat gland units in the scalp of the rhesus monkey (0.2 moles/kg dry wt/hr) and in the sole of the pigtail macaque (1 mole/kg dry wt/hr). This ATPase is activated by combination of Na+ and K+, and this activation is counteracted by ouabain (10(-5) M) which is a specific inhibitor of Na+ transport.

Quantitative histochemistry of the primate skin. I. Hexokinase.

A fluorometric micromethod, applicable to 0.5 to 5.0 μg skin samples, for the determination of hexokinase is described.