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Biomedical subjects

J A Rodriguez

Publications and source records attributed to J A Rodriguez.

At least 109 records · Page 6Linked to original sources
PubMed1980

Plasma aldosterone response to angiotensin II and potassium chloride infusions in hypopituitary patients.

The acute adrenal response to potassium chloride and angiotensin II (A II) infusions was studied in hypopituitary patients and compared with normal subjects. The peripheral plasma levels of aldosterone (PAC), cortisol (F), potassium (K), and plasma renin activity (PRA), were measured at 09.00 h and after 60 and 120 min of infusion. All subjects were recumbent ad under balance conditions, receiving a daily dietary intake of 180 mmol of sodium and 80 mmol of potassium. Basal PAC in hypopituitary patients was not significantly different from that observed in the control group. Both normal and hypopituitary patients respond to A II infusion with significant increments. Under potassium chloride stimulus the PAC response in hypopituitary patients was only observed when cortisol (20 mg) was given 2 h prior to the infusion. When cortisol replacement was omitted the response KCl was not detected. These results suggest a permissive role of cortisol on glomerulosa response to potassium.

Adrenal Glands↗
PubMed1979

Experimental phenylketonuria: replacement of carboxyl terminal tyrosine by phenylalanine in infant rat brain tubulin.

In the brains of newborn rats, about half of the tubulin molecules are modified posttranslationally by the addition of an aromatic amino acid at the carboxyl terminus of the alpha chain. Of the added residues, 96 percent are tyrosine and 4 percent are phenylalanine. After induction of hyperphenylalaninemia, the proportion of tubulin molecules containing carboxyl terminal phenylalanine increases up to eightfold and the pool of tyrosine-containing molecules decreases by an equivalent amount.

Amino Acid Sequence↗
PubMed1975

Incorporation of L-tyrosine, L-phenylalanine and L-3,4-dihydroxyphenylalanine as single units into rat brain tubulin.

The product of the incorporation of [14C]tyrosine as single unit into a protein of the soluble fraction of rat brain homogenate was purified by following a procedure used to purify tubulin. Sodium dodecylsulphate-polyacrylamide gel electrophoresis of the purified material showed a single protein band containing all the radioactivity. Purification data indicate that this protein accounts for 10.2% of the total protein of the supernatant fraction. This is in good agreement with the amount found for tubulin by the [3H]colchicine-binding method (10.5% of the total protein). The incorporated [14C]-tyrosine was found in the alpha-subunit of tubulin. Protein labelled with [3H]colchicine and [14C]tyrosine was precipatated with vinblastine sulphate and the radioactivity of 3H and that of 14C were quantitatively recovered in the precipitate (98%). Sodium dodecylsulphate-polyacrylamide gel electrophoresis of the vinblastine precipitate showed that the 14C radioactivity moved with the tubulin band. Results obtained in experiments with phenylalanine and 3,4-dihydroxyphenylalanine were identical to those obtained for tyrosine. Bineing of colchicine did not interfere with the incorporation of tyrosine. About 30% of tubulin from rat brain supernatant fraction can incorporate tyrosine as single unit.

Animals↗
PubMed1975

The reciprocal exclusion by L-dopa (L-3,4-dihydroxyphenylalanine) and L-tyrosine of their incorporation as single units into a soluble rat brain protein.

Several compounds, structurally and metabolically related to phenylalanine and tyrosine, were tested for their effects on the incorporations of phenylalanine and tyrosine as single units into a protein of the soluble subcellular fraction of rat brain. Of the compounds tested, only L-dopa (L-3,4-dihydroxyphenylalanine) inhibited these incorporations. Further, L-dopa was incorporated into a protein of the same fraction in such a way that it excluded the incorporation of tyrosine as a single unit. Conversely, tyrosine inhibited and excluded the incorporation of L-dopa. The incorporation of L-dopa required ATP (apparent Km = 0.23mM), KCl (apparent Km = 20mM) and MgCl2 (optimal concentration range, 5-16mM). These requirements were similar to those previously determined for the incorporation of tyrosine and phenylalanine. The inactivation rate of the enzymic systems for L-tyrosine and L-dopa incorporations, when kept at 37 degrees C, was the same for both amino acids (half-life = 80 min). It is suggested that the acceptor for the incorporation of dopa is the same as that for the incorporation of tyrosine.

Adenosine Triphosphate↗