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J L Palacios

Publications and source records attributed to J L Palacios.

4 recordsLinked to original sources
PubMed2005

Helicobacter pylori vacA s1a and s1b alleles from clinical isolates from different regions of Chile show a distinct geographic distribution.

AIM: To establish the most common vacA alleles in Helicobacter pylori (H pylori) strains isolated from Chilean patients and its relationship with gastritis and gastroduodenal ulcers. METHODS: Two hundred and forty five H pylori clinical isolates were obtained from 79 biopsies from Chilean infected patients suffering from gastrointestinal diseases. An average of 2-3 strains per patient was isolated and the vacA genotype was analyzed by PCR and 3% agarose electrophoresis. Some genotypes were checked by DNA sequencing. RESULTS: The most prevalent vacA genotype in Chilean patients was s1b m1 (76%), followed by s1a m1 (21%). In contrast, the s2 m2 genotype was scarcely represented (3%). The s1b m1 genotype was found most frequently linked to gastropathies (P<0.05) rather than ulcers. Ulcers were found more commonly in male and older patients. Curiously, patients living in cities located North and far South of Santiago, the capital and largest Chilean city, carried almost exclusively strains with the s1b m1 genotype. In contrast, patients from Santiago and cities located South of Santiago carried strains with either one or both s1a m1 and s1b m1 genotypes. Regarding the s2 m2 genotype, comparison with GenBank sequences revealed that Chilean s2 sequence was identical to those of Australian, American, and Colombian strains but quite different from those of Alaska and India. CONCLUSION: Differences in geographic distribution of the s and m vacA alleles in Chile and a relationship of s1b m1 genotype with gastritis were found. Sequence data in part support a hispanic origin for the vacA genotype. Asymmetric distribution of genotypes s1b m1 and s2 m2 recedes H Pylori strain distribution in Spain and Portugal.

Adolescent↗
PubMed2001

Subset of hybrid eukaryotic proteins is exported by the type I secretion system of Erwinia chrysanthemi.

Erwinia chrysanthemi exports degradative enzymes by using a type I protein secretion system. The proteases secreted by this system lack an N-terminal signal peptide but contain a C-terminal secretion signal. To explore the substrate specificity of this system, we have expressed the E. chrysanthemi transporter system (prtDEF genes) in Escherichia coli and tested the ability of this ABC transporter to export hybrid proteins carrying C-terminal fragments of E. chrysanthemi protease B. The C terminus contains six glycine-rich repeated motifs, followed by two repeats of the sequences DFLV and DIIV. Two types of hybrid proteins were assayed for transport, proteins with the 93-residue-protease-B C terminus containing one glycine-rich repeat and both hydrophobic terminal repeats and proteins with the 181-residue C terminus containing all repeat motifs. Although the shorter C terminus is unable to export the hybrids, the longer C terminus can promote the secretion of hybrid proteins with N termini as large as 424 amino acids, showing that the glycine-rich motifs are required for the efficient secretion of these hybrids. However, the secretion of hybrids occurs only if these proteins do not carry disulfide bonds in their mature structures. These latter results suggest that disulfide bond formation can occur prior to or during the secretion. Disulfide bonds may prevent type I secretion of hybrids. One simple hypothesis to explain these results is that the type I channel is too narrow to permit the export of proteins with secondary structures stabilized by disulfide bonds.

ATP-Binding Cassette Transporters↗
PubMed1979

[Effect of intracerebroventricular injection of 6-hydroxydopamine and 5,6-dyhydroxytryptamine on the phasic secretion of luteinizing hormone (author's transl)].

In ovariectomized rats carrying an estradiol sylastic implant the effect of the intraventricular administration of the serotonin neurotoxin 5,6-dihydroxytryptamine and of the norepinephrine neurotoxin 6-hydroxydopamine on the circadian secretion of the luteinizing hormone (LH) was studied. The decrease of 5-HT after injection of 5,6-dihydroxytryptamine reduced the a.m. and p.m. values and suppressed the phasic rhythm of LH. The diminution of noradrenaline after administration of 6-hydroxydopamine increased the a.m. and did not alter the p.m. values, resulting in a partial abolition of the rhythm.

Animals↗