Biomedical subjects

M Molero

Publications and source records attributed to M Molero.

4 recordsLinked to original sources

PubMed1999

Cloning of the human thiamine transporter, a member of the folate transporter family.

We have isolated a cDNA from human placenta, which, when expressed heterologously in mammalian cells, mediates the transport of the water-soluble vitamin thiamine. The cDNA codes for a protein of 497 amino acids containing 12 putative transmembrane domains. Northern blot analysis indicates that this transporter is widely expressed in human tissues. When expressed in HeLa cells, the cDNA induces the transport of thiamine (K(t) = 2.5 +/- 0.6 microM) in a Na(+)-independent manner. The cDNA-mediated transport of thiamine is stimulated by an outwardly directed H(+) gradient. Substrate specificity assays indicate that the transporter is specific to thiamine. Even though thiamine is an organic cation, the cDNA-induced thiamine transport is not inhibited by other organic cations. Similarly, thiamine is not a substrate for the known members of mammalian organic cation transporter family. The thiamine transporter gene, located on human chromosome 1q24, consists of 6 exons and is most likely the gene defective in the metabolic disorder, thiamine-responsive megaloblastic anemia. At the level of amino acid sequence, the thiamine transporter is most closely related to the reduced-folate transporter and thus represents the second member of the folate transporter family.

Amino Acid Sequence↗

PubMed1999

[Candida in biological human samples].

Infections by Candida have been raising in the last decades, and risk factors, mainly immunosuppression and the appearance of Candida no albicans, are determinants in the prognosis of these mycoses. The purpose of this investigation was to identify and establish the prevalence of C. albicans and Candida spp. in candidiases, in patients to the Hospital Universitario de Maracaibo, whose biological samples were processed for both direct examination and cultures, needed for the proper identification. From October 1996 to October 1998, isolation and identification of yeasts of Candida were performed in 177 biological samples: 73 (41.24%) Candida albicans and 104 (58.75%) Candida spp. Both blastoconidias and pseudohyphae were found in 34 samples (19.21%), 24 of which (70.5%) were diagnosed as C. albicans and 10 (29.5%), as Candida spp. Blastoconidias identified by direct method were distributed as C. albicans 34.2% and Candida spp. 65.7%. C. albicans was found more often in intertrigo, sputum and in bronquial lavage samples. Candida spp. was more frequent in nails. Candidiasis is a frequently diagnosed mycosis in hospitals, mainly among immunossuppresed patients. It is very important to use direct microscopical evaluation and cultures, in order to establish the presence of blastoconidias and pseudohyphae, that will help to diagnose the aethiology and prevalence of candidiasis. It is also important to recognize subungueal candidiasis in hospital staff, that could spread the infection to inpatients.

Adult↗

PubMed1998

Modulation by nitric oxide of gastric acid secretion in toads.

Nitric oxide (NO) is a novel chemical messenger that mediates a variety of biological actions. This study was undertaken to investigate the effects of NO on parietal cell function. The rate of [3H]arginine conversion to [3H]citrulline, a parameter of NO synthase activity, and NO formation (as NO2-), were inhibited by the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), in a concentration-dependent manner in the non-stimulated toad gastric mucosa. This range of concentrations of L-NAME provoked stimulation of H+ secretion in a similar fashion, which was blocked by L-arginine but not by D-arginine. Pre-treatment with carbachol plus ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra-acetic acid (EGTA) prevented the effect of L-NAME on H+ secretion and drastically reduced NO synthase activity. L-arginine had an inhibitory effect on H+ secretion in non-stimulated and carbachol-stimulated gastric mucosa, which was reversed by L-NAME. Carbachol and pentagastrin, but not histamine, significantly increased NO formation in the toad gastric mucosa. The results suggest that changes in NO synthesis in the gastric mucosa may modulate parietal cell function and that a calcium-dependent mechanism may be involved.

1-Methyl-3-isobutylxanthine↗

PubMed1989

Quiescent human lymphocytes do not contain DNA strand breaks detectable by alkaline elution.

On the basis of qualitative assays, quiescent lymphocytes have previously been reported to have numerous DNA strand breaks, which are thought to be repaired after mitogenic stimulation by a process associated with poly(ADP-ribosyl)ation. Using alkaline elution, a very sensitive assay for quantifying DNA single-strand breakage, we found no evidence for a high frequency of DNA strand breaks in unstimulated human peripheral blood lymphocytes. No differences in elution profiles were observed between unstimulated lymphocytes and lymphocytes 4 or 48 h after addition of the mitogen phytohemagglutinin (PHA). Furthermore, addition of 3-aminobenzamide (3AB), an inhibitor of poly(ADP-ribose) synthetase, or aphidicolin, an inhibitor of DNA polymerase alpha, did not increase the amount of DNA eluting from the filter after PHA stimulation. In contrast to reported studies of mouse splenic lymphocytes, we found that human lymphocytes were able to replicate and divide in the presence of the ADP-ribosylation inhibitor. Human lymphocytes were also capable of proliferating in nicotinamide-free medium, with or without 3AB, indicating that ADP-ribosylation is not a requirement for lymphocyte differentiation. We therefore consider it unlikely that peripheral human lymphocytes contain significant numbers of strand breaks that play any role in their stimulation or differentiation in response to PHA.

Aphidicolin↗