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Y Gomez

Publications and source records attributed to Y Gomez.

6 recordsLinked to original sources
PubMed2004

Analysis of purity in 19 drug product tablets containing clopidogrel: 18 copies versus the original brand.

In this study, 18 copies of PLAVIX tablets containing clopidogrel hydrogensulfate were compared to the innovator drug product for uniformity of mass, impurity profile, content, dissolution properties and stability. In order to be able to separate the R-enantiomer of clopidogrel, an enantiospecific liquid chromatographic method was used to determine the impurities and to perform the assay. The paddle method was used for dissolution testing. Most of the copies were not similar compared to the original drug product: their amount of impurities was higher, the content of clopidogrel lower, the dissolution profiles different and after 3 months under stress conditions in the original packaging, the results for the samples and the reference were significantly different in most of the cases.

Chromatography, High Pressure Liquid↗
PubMed2000

Sex steroids and parasitism: Taenia crassiceps cisticercus metabolizes exogenous androstenedione to testosterone in vitro.

Sex hormones are known to modulate immune responses and may be implicated in sex associated susceptibilities to infections. Taenia crassiceps cysticerci grow to larger numbers in female mice than in males. Gonadectomy alters the course of this infection and hormone replacement with 17beta-estradiol increases the parasite numbers. However, in chronic Taenia crassiceps cysticercosis the sex-hormone profile of males becomes more like that of the females' and progressively loose their sexual behavior. To have further insight in these outstanding endocrinological effects induced by the parasite upon the host, we investigated the parasite's capacity to produce sex steroids. In vitro experiments showed that Taenia crassiceps cysticerci transform 3H-Androstenedione to 3(H)-Testosterone, but not 3H-Pregnenolone. The production of 3H-Testosterone increased when the parasite numbers doubled. A recrystallisation procedure demonstrated that the metabolite identified by TLC was in fact testosterone. Thus, the cysticercus has the ability to use 3H-Androstenedione to make Testosterone possibly by a 17beta-Hydroxysteroid deshidrogenase-like activity in the parasite. In vivo, the parasite could use steroid precursors from the host to produce sex hormones, either accidentally or as needed for its own development, and thus alters the host's normal environment with sexual and immunological repercussions.

Androstenedione↗
PubMed1993

Ascorbic acid regeneration by bovine iris-ciliary body.

Ocular tissues appear to require high levels of ascorbic acid and the elucidation of the mechanisms by which those tissues maintain the vitamin in its reduced state remains an important objective. The regeneration of ascorbate from its oxidative by-product, dehydroascorbic acid (DHAA), was studied in bovine iris-ciliary body. Iris-ciliary body was removed by scalpel, weighed, minced, and homogenized in 20 mM MOPS, 62 mM sucrose, and 0.1 mM EDTA at pH 7.0. The homogenate was centrifuged and precipitated with ammonium sulfate such that maximal DHAA reducing activity was enhanced in a 50-75% ammonium sulfate fraction. This fraction was employed for subsequent characterization of DHAA reduction by iris-ciliary body. Results indicate that the iris-ciliary body enzymatically reduces DHAA to ascorbate at a rate significantly greater than can be accounted for by a nonenzymatic glutathione-dependent mechanism. In addition, saturation kinetics are observed, and the enzymatic activity is dependent on protein concentration, DHAA concentration, and reduced glutathione (GSH) concentration. The activity is sensitive to pH, to high temperature, and to digestion by trypsin and is greatest in the presence of both GSH and NADPH. The reducing activity is therefore attributed to one or more proteins that are distinct from the known ascorbate regenerating enzyme, GSH-dependent DHAA reductase (EC 1.8.5.1).

Animals↗