Anselmo Velázquez

Amino Acid Pools in the Feto-Maternal System

The determinations of the amino acid pools, including tryptophan (by fluorescence spectrometry), in the arterial and venous blood of the mother, the arterial and venous blood of the fetus (cord blood), the amniotic fluid and the placenta was done in eight women at the moment of delivery. Only nine amino acids (asp, try, met, phe, ser, cys, lys, gly, thr) were significantly retained and four (arg, glu, pro and glu-NH2) were significantly released by the fetal tissues. In contrast with this behavior most amino acids were retained by the maternal tissue, try, phe and hist showing the highest retention. When the amino acids are grouped as essential and nonessentials, the maternal tissues retained both categories without apparent discrimination, while the fetal tissues retained essential amino acids preferentially. Our results emphasize the importance of the placenta as the regulating system of the fetal milieu under normal conditions. Thus human fetal blood levels of amino acids are patterned after the placental ones and not after the maternal values obtained at the same time. It is apparent that the placenta seems to function as a nonspecific retention filter for outgoing amino acids, but that its function is selective in respect to the release of amino acids into the fetal circulation.

Amino Acid and Protein Concentrations of Human Follicular Fluid

The amino acid and protein composition of human follicular fluid, obtained during surgery from women with polycystic ovaries, and of a simultaneously obtained sample of blood plasma were studied. In general, amino acid concentrations were higher in follicular fluid than in blood plasma: only the concentration of Cys was significantly lower in follicular fluid than in plasma, while Asp, Thr, Glu, Glu-NH2, Gly, Ala, and Met showed concentrations that were not significantly different in either biologic fluid. The concentration of basic amino acids, taken as group, was almost twice as high in follicular fluid as in plasma. The total protein concentration in follicular fluid was not significantly different from that in blood plasma. However, the follicular fluid albumin concentration was higher and globulin concentration lower than the respective concentrations in plasma. Polyacrylamide gel disc electrophoresis of follicular fluid showed some consistent differences, particularly in the alpha-globulin region, with the pattern observed in blood plasma. These findings are discussed in relation to the possible role of follicular fluid in capacitation and egg segmentation.

Monosodium l-glutamate-induced convulsions—II. Changes in catecholamine concentrations in various brain areas of adult rats

Norepinephrine (NE) and dopamine (DA) levels in various brain regions were measured in a model of experimentally produced convulsions by monosodium L-glutamate (MSG) administration to adult rats. Stress by injection of all solutions produced a 60% decrease in NE level in forebrain, recovering its basal value at 15 min after injection. A significant reduction of brain NE and DA levels of MSG-injected animals was found in the preconvulsive stage, particularly in the forebrain. No significant variations in catecholamine levels were seen in brain stem and cerebellum as a result of MSG injection. It is suggested that the changes found in endogenous catecholamine concentration in the forebrain may play a physiological role in the mechanisms of production of convulsions in the MSG model.

Taurine content and amino acid composition of human acrosome.

The presence and concentration of taurine was determined by amino acid analysis in human spermatozoa acrosomes isolated by the method of Srivastava. Taurine is one of the four amino acids whose concentration is higher in the acrosomal extracts, being only lower than histidine, methionine and lysine. It is worth mentioning that these four amino acids constituted 50% the free amino acid concentration in this organelle. The role that this high concentration of taurine, and also the presence of considerable amounts of methyl histidine may have in the functioning of the acrosome, is discussed.

Cyclic changes in salivary activity of N-acetyl-beta-D-glucosaminidase. A possible efficient indicator for predicting ovulation and pregnancy.

Salivary activity of N-acetyl-beta-D-glucosaminidase showed a characteristic pattern of changes during the normal menstrual cycle with a distinct peak on Day 13, 14, or 15 before the next menstruation. This peak of enzyme activity occurred withing one day of the nadir of basal body temperature and was absent in women with spontaneous or iatrogenic anovulatory cycles. These results are stongly suggestive that the salivary determination of this activity may be convenient indicatior for determining the day of ovulation.

Endogenous serotonin release from rat cerebellar slices

Endogenous serotonin (5-HT) content in cerebellar slices and in the incubation medium was measured before and after depolarizing stimulus with high-K+ concentration in the medium. Small amount of 5-HT was spontaneously released from tissue slices incubated in low-K+ and Ca2+-free medium. A significant increase of endogenous 5-HT release was obtained after depolarizing stimulus with high-K+ plus Ca2+ in the medium. It is suggested that the endogenous 5-HT release in cerebellum induced by depolarizing stimuli is a Ca2+-dependent phenomenon.