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Biomedical subjects

C Costa

Publications and source records attributed to C Costa.

At least 217 records · Page 12Linked to original sources
PubMed1975

Effect of phototherapy on the urinary excretion of tryptophan metabolites in neonatal hyperbilirubinemia.

The 24 hours urinary excretion of tryptophan metabolites after an aminoacid loading (50 mg/Kg body-weight) was studied in a group of hyperbilirubinemic infants with or without light exposure treatment, in comparison to normal newborn babies. Kynurenine was the main metabolite in the urine of the control subjects. In the hyperbilirubinemic infants a high urinary excretion of kynurenine and 3-hydroxyanthranilic acid was observed. In the ones treated with phototherapy these two substances were markedly decreased. Besides 3-hydroxykynurenine was almost always absent. The effect of the light exposure was studied on kynurenine and 3-hydroxykynurenine "in vitro". Kynurenine did not present any photodecomposition. On the contrary, 3-hydroxykynurenine was easily decomposed. This fact can explain the decreased excretion of 3-hydroxykynurenine and 3-hydroxyanthranilic acid observed in urine of hyperbilirubinemic newborn infants treated with phototherapy. The decrease of kynurenine in these infants probably is a consequence of the photodecomposition of 3-hydroxykynurenine.

Fluorescence↗
PubMed1975

Studies on melanogenesis of tryptophan in Harding-Passey mouse melanoma.

D,L-tryptophan[benzene ring-14C (U)] and D,L-tryptophan (methylene-14C) are incorporated significantly into melanin of Harding-Passey mouse melanoma. D,L-5-hydroxytryptophan (methylene-14C) and 5-hydroxytryptamine-3-14C (serotonin) gave an incorporation of radioactivity into melanin significantly lower than tryptophan. D,L-tyrosine-2-14C was incorporated into melanin as well as tryptophan. Therefore tryptophan must be considered an important precursor in the biogenesis of melanins too.

Animals↗
PubMed1975

Studies on 3-hydroxykynureninase from rat liver.

Kynureninase (L-kynurenine hydrolase E.C. 3.7.1.3.) was purified about 200 times from rat liver. The purified enzyme catalyzes the L-3-hydroxykynurenine leads to 3-hydroxyanthranilate reaction more favorably than the L-kynurenine leads to anthranilate reaction, with Km values of 1.67 x 10(-6) M for L-3-hydroxykynurenine and of 1.67 x 10(-4) M for L-kynurenine. Besides, this enzyme did not produce 5-hydroxyanthranilate from D,L-5-hydroxykynurenine. Therefore we think it is mainly a 3-hydroxykynureninase regulating the tryptophan degradation towards the formation of nicotinic acid necessary to NAD synthesis, rather than towards the accumulation of anthranilate.

Animals↗
PubMed1975

Relationship between tryptophan metabolism and vitamin B6 and nicotinamide in aged subjects.

The urinary excretion of tryptophan metabolites was studied in 20 aged subjects (over 70 years) after oral tryptophan loading (100 mg/kg body weight). All the subjects considered showed an abnormal excretion of metabolites with mean values of 24.67% in men and 25.83% in women in comparison to 6.77% in young controls. Among the metabolites the highest excretion was from kynurenine; moreover kynurenic acid and N-alpha-acetylkynurenine were also excreted in signficantly high amounts. The other metabolites too showed increased values. As the abnormal tryptophan metabolism in aging seemed to be in connection with vitamin B6 and nicotinamide, in a group of 7 aged sugjects the urinary excretion of tryptophan metabolites was studied after aminoacid loading with or without simultaneous administration of these two vitamins. The results show that the abnormal excretory pattern is normalized after vitamin administration (from 16.49% to 7.42% total mean metabolite values).

Adult↗
PubMed1975

Studies on tryptophan metabolism in ethylism.

The urinary excretion of the metabolites "via kynurenine" was studied in a group of patients with chronic alcoholism after a L-tryptophan loading (100 mg/kg body-weight) with or without simultaneous administration of vitamin B6 or nicotinamide or both. In these subjects an abnormal tryptophan metabolism was obtained with excretion total mean values of 9 metabolites of 15.34% against 6.86% in healthy controls. The treatment with vitamin B6 or nicotinamide in 5 patients decreased the total average excretion from 14.41% to 9.47% and to 9.92% respectively without normalizing, however, the excretory pattern produced from the aminoacid loading. The simultaneous administration of these two vitamins in 9 chronic alcoholic men corrected completely the metabolic defect (from 15.34% to 6.55%).

Adult↗