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G Ayala

Publications and source records attributed to G Ayala.

At least 55 records · Page 3Linked to original sources
PubMed1993

Pathologic features of epidermoid carcinoma of the penis. A prospective study of 66 cases.

We report a whole-organ-section pathologic study of 66 cases of epidermoid carcinoma of the penis. Specimens were divided into three compartments: glans (G), coronal sulcus (COS), and foreskin (F) with 24, 4, and 12 histologic sections each. Four types of carcinomas were found: (a) superficially spreading (42%), a biphasic infiltrating and extensive carcinoma in situ usually involving more than one compartment and radially growing along the surface of G, BPS, F, or even urethra; (b) vertical growth (32%), unifocal high-grade, deeply invasive neoplasms with minimal or no carcinoma in situ component; (c) verrucous (18%), low-grade papillary or endophytic; and (d) multicentric (8%), two or more independent primary tumors separated by non-neoplastic mucosa. Inguinal lymph node metastasis were found in 82, 42, and 33% of pathologic types vertical growth, superficially spreading, and multicentric carcinomas, respectively; verrucous tumors did not show metastasis. The morphologic diversity of penile cancer may be related to different causative factors. Metastatic involvement suggests a distinctive biological behavior of the tumor. The widespread extension of superficially spreading and multicentric carcinomas to anatomical compartments indicate penile mucosa as one "field" prone to malignant transformation. These findings may be important for the selection of appropriate therapy and emphasize the need for a close follow-up of patients undergoing less than a complete removal of the three compartments.

Carcinoma, Squamous Cell↗
PubMed1992

Solubilization and activity of proteins in compressible-fluid based microemulsions.

We have used the pressure dependency of density in near critical propane to design a novel protein extraction system. Active, structurally intact, proteins have been extracted from an aqueous phase into subcritical propane containing the non-ionic detergent polyoxyethylene sorbitan trioleate (Tween-85). The pressure dependence of protein transfer from the aqueous to organic phase is described for cytochrome C and subtilisin. The effect of the microemulsion and compressible propane on protein structure and function is also discussed. The first determinations of kinetic constants for an enzyme-catalyzed reaction in such a system are also presented.

Cytochrome c Group↗
PubMed1990

Stability and activity of 20 beta-hydroxysteroid dehydrogenase in microemulsion of non-ionic detergents.

We report here the formation of a microemulsion with non-ionic detergents and cyclohexane. The activity and stability of 20 beta-hydroxysteroid dehydrogenase solubilized in all water systems and in microemulsions of Nonidet P-40: Triton X-35/water/cyclohexane was investigated. In the microemulsion the activity depended on the molecular ratio of water to surfactant (Wo); maximal activity was obtained at Wo of 8.4. The stability in the microemulsion was higher at Wo = 11.75 i.e. the enzyme, retained about 50% of activity after eight days.

Buffers↗
PubMed1989

Catalytic activity of cytochrome oxidase and cytochrome c in apolar solvents containing phospholipids and low amounts of water.

Cytochrome c and cytochrome oxidase, in bovine heart submitochondrial particles and in their purified forms, were transferred to a ternary system that contained phospholipids (10 mg/ml toluene), the apolar solvent toluene, and water at concentrations of 13-15 microliters (high water) and 3 microliters (low water) per milliliter of toluene. When the enzymes were transferred back to an all water system, they exhibited full catalytic capacity. In the low water ternary system, cytochrome c could be reduced by ascorbate introduced via inverted micelles. Also in this system, cytochrome oxidase was reduced by ascorbate and cytochrome c but its oxidation was highly impaired. Data on the kinetics of reduction by ascorbate of cytochrome c and cytochrome oxidase under these conditions are presented. Cytochrome oxidase reduced in the organic solvent by ascorbate failed to form a complex with CO, but formed a complex with cyanide introduced via inverted micelles. The oxidized and the ascorbate-reduced cytochrome oxidase-cyanide complex exhibited a trough at 415 nm and a peak at 433 nm. The extent and rate of formation of the cyanide complex were higher with the reduced form of cytochrome oxidase. To achieve protein-protein interactions (cytochrome c-cytochrome oxidase) in the ternary system, it was necessary to extract the two proteins together. There was no functional interaction when they were extracted separately and mixed. In the high water ternary system reduced cytochrome oxidase was not detected, and it oxidized ascorbate at a higher rate than in the low water system; however, this rate was several orders of magnitude lower than in aqueous media.

Animals↗
PubMed1987

Vibrational spectra and structure of myelin membranes.

Raman and infrared spectroscopy have been simultaneously applied, for the first time, to the study of myelin membranes and their proteolipid protein (PLP) so as to obtain information on the secondary structure of proteins and the ordering of lipid chains. The vibrational spectra were recorded at physiological pH using a non-denaturing detergent (n-octyl-beta-D-glucopyranoside) in phosphate buffer. Neither the buffer nor the detergent interfere spectroscopically with the amide bands from proteins. The spectra reveal that the predominant secondary structure in the polypeptide backbone in myelin is the helix. The proteolipid protein was found to be more disordered than the polypeptide arrangement of the myelin membrane, as deduced from the relative intensities and halfwidths of characteristic infrared amide I bands. beta-form and turns are also present, the amount of these structures being higher in PLP. The study of the Raman spectra of vC-C and vC-H regions made it possible to obtain information on the lipid chain order.

Animals↗
PubMed1986

Thermostability of membrane systems in organic solvents.

Two multisubunit enzymes of the inner mitochondrial membrane, cytochrome oxidase and the H+-ATPase may be transferred into highly apolar solvents as protein-lipid complexes. At 70 degrees C and an initial water concentration of 13 microliters per ml organic solvent (toluene), the half-life of the ATPase was approx. 11 h, whereas that of cytochrome oxidase was about 100 s. Thermostability of cytochrome oxidase could be increased more than 100-times by decreasing the water concentration to 3 microliters per ml toluene. At this latter concentration of water the half-life of the ATPase at 90, 80 and 70 degrees C was 5, 48 and 96 h, respectively.

Animals↗
PubMed1985

Extraction of mitochondrial membrane proteins into organic solvents in a functional state.

Protein-lipid complexes in organic solvents can be used as the starting material in the reassembly of functional planar and spherical bilayers (Montal, M., Darszon, A. and Schindler, H. (1981) Q. Rev. Biophys. 14, 1-79). The transfer of three enzymes of the inner mitochondrial membrane into organic solvents as protein-lipid complexes has been studied to understand better the extraction process. The enzymes studied were cytochrome c oxidase, ATPase and succinate dehydrogenase. These enzymes were transferred into hexane and diethyl ether in an active state, however, the activities extracted varied quantitatively, depending on the amount of protein of the starting preparation, the concentration of phospholipids and the cation employed. In all conditions cytochrome c oxidase was extracted with the highest yield and specific activity, and it was actually enriched in the organic extract. The values for succinate dehydrogenase and ATPase were lower, but their specific activities were similar to those of the starting material. This indicates that some membrane proteins are preferentially extracted into organic solvents in a functional state. The enzymes, as protein-lipid complexes, are fairly stable in organic solvents; in a month of storage at 4 degrees C in hexane some enzymes loose less than 50% of their activity.

Adenosine Triphosphatases↗
PubMed1985

Transitional cell carcinoma of the prostate.

5 cases of transitional cell carcinoma of the prostate, which represent 1.5% of a series of 323 consecutive prostatic carcinomas, are presented. The cases with possible prostatic involvement by contiguity from a bladder carcinoma as well as those tumors with a transitional pattern which contain prostatic acid phosphatase in the cellular cytoplasm have been ruled out to make the diagnosis. The mean age of the tumoral onset is 70 years with an identical symptomatology to that of the adenocarcinoma. In 20% of the cases it is associated with an adenocarcinoma and in 40% with a bladder carcinoma without contiguity. The mean survival is 10.6 months with 60% succumbing within the first 6 months. Our findings agree with all authors in considering this type of tumor an urothelial neoplasia.

Acid Phosphatase↗
PubMed1984

Oxidative phosphorylation and the Pi-ATP exchange reaction of submitochondrial particles under the influence of organic solvents.

The effect of some organic solvents, in particular dimethyl sulfoxide, on oxidative phosphorylation, the Pi-ATP exchange reaction, and ATP hydrolysis has been studied in submitochondrial particles from bovine heart. The three reactions are inhibited by dimethyl sulfoxide, but with a different sensitivity. Oxidative phosphorylation takes place at considerable rates in the presence of concentrations of dimethyl sulfoxide that completely inhibit the Pi-ATP exchange reaction. The sensitivity of the Pi-ITP exchange reaction to dimethyl sulfoxide measured in the presence of electron transport is also higher than that of oxidative phosphorylation. Dimethyl sulfoxide inhibits an electrochemical H+ gradient-dependent stimulating effect of inorganic phosphate on ATP hydrolysis which is linked to the Pi-ATP exchange reaction. In the absence of phosphate or in the presence of phosphate plus uncoupler, dimethyl sulfoxide does not inhibit hydrolysis. These findings, together with the observation that electron transport increases the rate of the Pi-ITP exchange reaction, suggest that electrochemical H+ gradients modify the kinetic characteristics of particulate Fi-ATPase. Glycerol and methanol, but not dimethylformamide, induce effects similar to those of dimethyl sulfoxide on oxidative phosphorylation and the Pi-ATP exchange reaction. This suggests that the described effects of solvents could be due to alterations of water structure.

Adenosine Triphosphate↗
PubMed1983

Regulation of the synthesis and hydrolysis of ATP by mitochondrial ATPase. Role of Mg2+.

ATP hydrolysis, the exchange of inorganic phosphate with ATP, and ATP synthesis have been studied as a function of Mg2+ concentration in bovine heart submitochondrial particles. The rate of exchange is low at concentrations of Mg2+ below 3 mM, at higher concentrations, the exchange is several times higher. ATP hydrolysis shows a different pattern with respect to the concentration of Mg2+. The ratio of ATP hydrolyzed to ATP exchanged is above 20 at Mg2+ concentrations below 3 mM and about 5 at high Mg2+ concentrations; ADP induces a further drop of the ratio (2-3). By assays of the sensitivity of the hydrolytic reaction to organic solvents (dimethyl sulfoxide), it has been possible to determine the rate-limiting step of ATP hydrolysis. At 3 mM Mg2+, the rate-limiting step is the release of ADP in the soluble, but not in the particulate enzyme. However at higher Mg2+ concentrations, the rate-limiting step in the particulate enzyme is also ADP release. Therefore, the decrease in the ratio of ATP hydrolysis to inorganic phosphate incorporated into ATP coincides with a change in the kinetics of the enzyme, i.e. when the terminal step of ATP hydrolysis becomes rate-limiting, the inorganic phosphate-ATP exchange increases. Ca2+ induces an increase in the phosphate-ATP exchange at low Mg2+ concentrations.

Adenosine Diphosphate↗
PubMed1983

Regulation of the synthesis and hydrolysis of ATP by mitochondrial ATPase. Role of the natural ATPase inhibitor protein.

The action of the natural ATPase inhibitor protein of Pullman and Monroy (Pullman, M. E., and Monroy, G. C. (1963) J. Biol. Chem. 238, 3762-3769) on the mechanisms of energy conservation of heart mitochondria has been explored. The synthesis and hydrolysis of ATP and the Pi-ATP exchange reaction were studied in submitochondrial particles that possess the ATPase-inhibitor protein complex in two distinguishable states. In addition to their different rates of hydrolysis, the two states of the complex have been identified from their different accessibility to antibodies directed against the inhibitor protein, and from the different action of antibodies and trypsin on the ATPase activity of the two types of particles studied. The steady state rates of hydrolysis and of the Pi-ATP exchange reaction of the particles are determined by the state in which the ATPase-inhibitor complex exists. Apparently by modifying the rate of one of the steps involved in the catalytic reaction of the ATPase, the inhibitor protein determines the extent to which the enzyme is able to catalyze ATP hydrolysis and the Pi-ATP exchange reaction. This action of the inhibitor protein also reflects the rate at which the particles carry out oxidative phosphorylation.

Adenosine Triphosphate↗
PubMed1981

[Polyorchidism (author's transl)].

The authors describe two new cases of polyorchidism. In the first case, they removed a testis which had a better seminal line than the testis preserved. In the other case, a conservative attitude was adopted. A review of the literature is followed by a discussion of the benefits of conservative therapy.

Adolescent↗
PubMed1977

Electrical stimulation of the rectal ampulla causing reflex voiding.

Electrical stimulation of the rectal ampulla resulted in a desire to void and defecate in 11 patients with an intact nervous system. There was a contraction of the detrusor and the rectal ampulla with relaxation of the anal sphincter. Electrical stimulation of the rectal ampulla and anal sphincter has clinical applications in patients with incontinence of, or inability to empty, the lower urinary tract or fecal system.

Anal Canal↗
PubMed1976

Role of calcium and beta-adrenergic system in control of parathyroid hormone secretion.

In the rat, EDTA and isoproterenol stimulated PTH secretion, whereas high calcium and propranolol inhibited it. The stimulatory effects of EDTA and isoproterenol were still evident and unaltered in the presence of blocks induced by propranolol and high calcium, respectively. The findings suggest that: (i) both calcium and beta-adrenergic stimuli affect PTH secretion; and (ii) the two influences affect the PTH secretion by separate initial pathways.

Animals↗