Influence of dietary arginine on the anabolic effects of androgens.

Feeding mice an arginine-deficient diet decreased plasma concentrations of arginine, citrulline and ornithine in the females and arginine in the males, abolishing the sexual dimorphic pattern of these amino acids found in mice fed the standard diet. In addition, the restriction of dietary arginine produced a marked decrease in body and renal weights as well as in the activity of renal ornithine decarboxylase, decreases that were gender dependent since they were observed exclusively in males. The fact that these changes were not associated with the decrease in the circulating levels of testosterone and that the dietary arginine restriction prevented the body weight gain induced by testosterone treatment of female mice fed the standard diet indicates that dietary arginine is required for the anabolic action of androgens.

Gender-related differences in carnosine, anserine and lysine content of murine skeletal muscle.

The aminoacyl-imidazole dipeptides carnosine (beta-alanyl-L-histidine) and anserine (beta-alanyl-1-methyl-histidine) are present in relatively high concentrations in excitable tissues, such as muscle and nervous tissue. In the present study we describe the existence of a marked sexual dimorphism of carnosine and anserine in skeletal muscles of CD1 mice. In adult animals the concentrations of anserine were higher than those of carnosine in all skeletal muscles studied, and the content of aminoacyl-imidazole dipeptides was remarkably higher in males than in females.

Influence of dietary arginine on sexual dimorphism of arginine metabolism in mice.

We have studied the influence of dietary arginine on tissue arginine content, and arginine metabolism in CD1 mice. Dietary arginine restriction produced by feeding mice with a low arginine diet (0.06%) produced a marked decrease in arginine concentrations in the plasma, skeletal muscle and kidney of female mice (72%, 67% and 54%, respectively) while in male mice the decreases were smaller (58% in blood and 18% in the skeletal muscle).

Effects of potassium deficiency on potassium, polyamines and amino acids in mouse tissues.

Sexual dimorphism in potassium content was found in plasma, kidney, heart and skeletal muscle of CD1 mice. We observed that feeding mice with a K(+)-deficient diet had an uneven and gender-dependent effect on organ weight and tissue potassium concentrations. Treatment produced a marked decrease in plasma, pancreas and skeletal muscle K(+) levels in both sexes, and a reduction in kidney, liver and heart potassium concentrations in females.

Interference of the antihormone RU486 in the determination of testosterone and estradiol by enzyme-immunoassay.

The antihormone RU486 (mifepristone, 11beta-(4-dimethylaminophenyl)-17beta-hydroxy-17alpha-(prop- 1-ynyl)-estra-4,9-dien-3-one) is currently used in many endocrinological studies and in clinical practice as a contraceptive agent. The results presented here indicate that the synthetic steroid RU486 may interfere in determinations of testosterone and estradiol when using some commercial kits. Although the cross reactivity is low (0.

Neuronal regulation of ornithine decarboxylase induced by androgens in the mouse kidney.

1. Neuronal, but not circulating catecholamines, regulate the induction of ornithine decarboxylase (ODC) by testosterone in the mouse kidney. 2.

The effect of glycine administration on taurine concentration in the rat liver.

1. The treatment of rats with glycine (2 mg/g) produced a marked decrease in the hepatic taurine content of neonate rats but not of adult rats. 2.

Monosodium glutamate induced convulsions in rats: Influence of route of administration, temperature and age.

Treatment of developing rats with monosodium glutamate (MSG) produces an increase of glutamate levels in the brain, being this elevation dependent on both route of administration and animal's age. The capacity of exogenous MSG to induce convulsions seems to be related to the rate of glutamate elevation in the brain, rather than to the absolute value of glutamate concentration reached. Short exposure of MSG-treated rats to moderate hyperthermia potentiated the convulsive incidence and extended the brain damage to areas not affected by treatment with MSG alone, suggesting that the synergic effect of hyperthermia on glutamate neurotoxicity may be related to an increase in the permeability of the blood-brain barrier in the hyperthermic developing rats.

Glycine administration decreases hepatic taurine content in mice.

The administration of glycine (2 mg/g) to mice showed marked increases in the hepatic content of some amino acids, specially glycine, serine and citrulline, but produced a notorious decrease in the concentration of taurine and aspartic acid. The depletion of taurine was higher than 50% after one hour of treatment, and was observed both in neonate and adult mice. The effect produced by the glycine treatment on hepatic taurine content was not observed in the heart, even after a larger amount of glycine administration.

Free amino acids in the cerebrospinal fluid of children with febrile seizures.

The content of free amino acids in the cerebrospinal fluid from 52 children in different age groups with febrile seizures were determined and compared to 88 age matched children without seizures. We found that the concentrations of some amino acids in CSF in the control group decreased slowly with age, reaching the concentrations found in adults at the age of 3 to 6 years, and that the free amino acid levels were no significantly altered by temperature. The free amino acids in the CSF from patients with febrile seizures showed a different pattern of change with age.

Hyperthermia and the neurotoxicity of exogenous glutamate in infant rats.

A substantial elevation of the excitatory neurotransmitter glutamate can be produced in the brain of 3-day old rats, either after subcutaneous injection of monosodium glutamate (4 mg/g), or by hyperthermic treatment (40 degrees C, 3 h). In the glutamate-treated animals a large increase in the GABA levels has also been observed while the elevation of this amino acid in the hyperthermic animals is insignificant. Although the magnitude of the increase of glutamate in both cases is rather similar, in the hyperthermic animals no cerebral lesions such as those produced in the glutamate-treated animals could be observed.

Activatory action of trypsin on epidermis dopa-oxidase.

Trypsin activated the Dopa-oxidase enzyme of frog epidermis, while carboxypeptidase "a" achieved only 50% of this activation. The enzyme can be activated by passing it through a column of insoluble trypsin coupled to Sepharose. Some properties of inactive and active dopa-oxidase are compared: a) Apparent molecular weight and Stokes radius of active enzyme are higher than those of the inactive one.