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E Piña

Publications and source records attributed to E Piña.

At least 37 records · Page 2Linked to original sources
PubMed1991

Stimulation of L-ornithine uptake and L-citrulline and urea biosynthesis by D-arginine.

The action of D-arginine on isolated cells and mitochondria obtained from rat liver was studied. The D-amino acid at 200 microM stimulated by 40% the rate of urea biosynthesis by isolated hepatocytes. Citrulline formation was increased 60-70% in rat liver mitochondria incubated with 10 microM D-arginine. In these mitochondria, ornithine uptake was enhanced 204% with 1 microM D-arginine. Inhibition in urea and citrulline synthesis and in ornithine uptake was recorded with high concentrations of the D-amino acid. Respiratory control in liver mitochondria with glutamate-malate was inhibited 32% by 100 microM D-arginine. In isolated mitochondria loaded with Fluo-3-acetoxymethyl (AM) ester, 50 microM D-arginine diminished the matrix free calcium concentration.

Adenosine Triphosphate↗
PubMed1989

"Hormone-like" effect of adenosine and inosine on gluconeogenesis from lactate in isolated hepatocytes.

In isolated rat hepatocytes adenosine and inosine showed a dose-dependent increase in the rate of glucose synthesis from lactate with a Ka of 7.5 x 10(-8) and 9 x 10(-8) M, respectively. Absence of this action was recorded with: IMP, xanthosine, adenine, hypoxanthine, and uric acid. A reciprocal inhibition of individual gluconeogenic stimulation was found in cells incubated with glucagon or epinephrine and adenosine, but not with inosine. 5'-(N-ethyl) carboxamido adenosine was more potent than adenosine, whereas N6-(L-2-phenylisopropyl)-adenosine antagonized the stimulation of gluconeogenesis by adenosine. Neither of the analogs used modified the stimulatory role of inosine on the studied pathway. Adenosine and inosine may be involved in the short term regulation of gluconeogenesis.

Adenosine↗
PubMed1989

A simplified purification method of aminoacylase I.

Taking advantage that the stability of aminoacylase I increases in the presence of Co2+, a simplified method of its purification, which includes a heating step, is described. This method is easy, fast, and gives a good yield of the enzyme. The properties of aminoacylase I thus prepared are similar to those described in the literature.

Amidohydrolases↗
PubMed1987

Effect of adenosine and inosine on ureagenesis in hepatocytes.

Adenosine and inosine produced a dose-dependent stimulation of ureagenesis in isolated rat hepatocytes. Hypoxanthine, xanthine and uric acid were without effect. Half-maximally effective concentrations were 0.08 microM for adenosine and 5 microM for inosine. Activation of ureagenesis by both nucleosides had the following characteristics: (a) it was observed with either glutamine or (NH4)2CO3, provided that glucose was present; (b) it was not detected when glucose was replaced by lactate plus oleate; (c) it was mutually antagonized by glucagon, but not by adrenaline; and (d) it was dependent on Ca2+. We suggest that the action of adenosine and inosine on ureagenesis might be of physiological significance.

Adenosine↗
PubMed1987

Accumulation of D-arginine by rat liver mitochondria.

The permeability of the inner mitochondrial membrane from rat liver to D-arginine was studied. By using safranin as a probe of the membrane potential, depolarization of energized liver mitochondria occurred in a dose-dependent fashion starting at 3.3 mmol/L of D- or DL-arginine. When ethidium bromide fluorescence was employed, a decrease in the membrane potential due to D- or DL-arginine was observed. A parallel significant change in succinate-induced respiration in rat liver mitochondria was found in response to osmotic swelling in 125 mmol/L of D-arginine salts. L-Arginine, L-glutamine, L-asparagine, L-ornithine, D-ornithine, and L-lysine did not modify the membrane potential at the concentrations tested. D-Arginine was not transformed into citrulline, but 1.0 mmol/L of the D-amino acid inhibited, by 42%, the state 3 of mitochondrial respiration using succinate as substrate. When D-arginine was used in combination with nigericin, a 40% inhibition of mitochondrial respiration in state 3 was recorded with succinate and with glutamate-malate as substrates.

Amino Acids↗
PubMed1987

Ornithine uptake by rat liver mitochondria: effect of calcium and arginine.

The effect of calcium and L-arginine on ornithine uptake by rat liver mitochondria was studied. In the absence of arginine, calcium ions at a concentration of 0.36 microM increase ornithine uptake 218% above control, but at metal concentrations higher than 1.0 microM the amino acid uptake is diminished. Keeping calcium concentration constant in the medium (0.36 microM), ornithine transport was maximal at 5.0 microM L-arginine and decreased at higher concentrations of arginine. The possible role of calcium and arginine as physiological regulators of ornithine transport is discussed.

Animals↗
PubMed1982

In vivo effect of adenosine on adenine nucleotides and inorganic phosphate in rat blood.

The effect of adenosine and the time response on adenine nucleotide and Pi levels in rat blood was investigated. An increase in adenine nucleotide with a concomitant decrease in Pi concentration 30, 60, and 90 minutes after the nucleoside administration were observed. Though the 100 mg/Kg dose showed the highest effect on nucleotide concentration, the maximal response on Pi content was achieved with the 50 mg/Kg dose. The results are discussed at the light of previous data obtained in hepatocytes, and using as indicators the energy charge and the phosphorylation potential.

Adenine Nucleotides↗
PubMed1980

Disappearance of nystatin resistance in Candida mediated by ergosterol.

Two nystatin-resistant mutants of Candida were isolated in vivo and identified as C. albicans and C. krusei. Analysis of the sterol composition of these cells indicated a total absence of ergosterol and an increased level of a possible precursor. Successive cultures of the resistant strains in a medium supplemented with 10 microgram ergosterol ml-1 induced in 5d a sensitivity to nystatin identical to that of the wild-type strain. These ergosterol-supplemented strains had an ergosterol content similar to that of the wild-type strain cultured in the absence of ergosterol. Resistance to nystatin was recovered after 5d subculture in medium without ergosterol.

Candida↗
PubMed1977

Stimulatory action of cycloheximide on glucose metabolism in the rat epididymal fat pad.

The action of cycloheximide on some parameters of glucose and lipid metabolism was studied in vitro in epidiymal fat pads from fasted rats. Incubation of fat pads with cycloheximide (1 mug/ml) for 2 hours resulted in a two-fold increase in glucose uptake, glucose oxidation, incorporation of glucose into lipids, and reesterification of free fatty acid. The increase in glucose oxidation was evident in experiments in which [U-14C], [1-14C], or [6-14C]glucose was added to the media, but it was absent when the media were supplemented with pyruvate. Incorporation of glucose into glycogen and accumulation of lactate in the medium were not seriously modified by the presence of cycloheximide. The stimulatory effect of cycloheximide on incorporation of glucose into lipids was absent when insulin or cortisol was added to the medium. A cycloheximide-mediated increase in glucose uptake seems to be responsible for the subsequent changes in glucose metabolism, and would seem to be independent of an inhibition in protein synthesis; puromycin and actinomycin D did not mimic the cycloheximide action on glucose incorporation into lipids.

Adipose Tissue↗
PubMed1975

The regulation of myo-inositol-1-phosphate-synthase activity from Neurospora crassa by pyrophosphate and some cations.

The effect of several cations on the inhibition by PPi of the enzyme myo-inositol-1-phosphate synthase (1L-myo-inositol-1-phosphate lyase (isomerizing) EC 5.5.1.4) from Neurospora crassa was studied. The study wastol biosynthesis can occur in the presence of an intracellular PPi concentration which exceeds the Ki for the enzyme by 350-fold. The inhibition of enzyme activity by PPi,at pH 7.7, was reversed, in decreasing order of effectiveness, by Mn-2, Fe-3

Ammonia↗