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J Sampedro

Publications and source records attributed to J Sampedro.

13 recordsLinked to original sources
PubMed2001

Cloning and expression pattern of a gene encoding an alpha-xylosidase active against xyloglucan oligosaccharides from Arabidopsis.

An alpha-xylosidase active against xyloglucan oligosaccharides was purified from cabbage (Brassica oleracea var. capitata) leaves. Two peptide sequences were obtained from this protein, the N-terminal and an internal one, and these were used to identify an Arabidopsis gene coding for an alpha-xylosidase that we propose to call AtXYL1. It has been mapped to a region of chromosome I between markers at 100.44 and 107.48 cM. AtXYL1 comprised three exons and encoded a peptide that was 915 amino acids long, with a potential signal peptide of 22 amino acids and eight possible N-glycosylation sites. The protein encoded by AtXYL1 showed the signature regions of family 31 glycosyl hydrolases, which comprises not only alpha-xylosidases, but also alpha-glucosidases. The alpha-xylosidase activity is present in apoplastic extractions from Arabidopsis seedlings, as suggested by the deduced signal peptide. The first eight leaves from Arabidopsis plants were harvested to analyze alpha-xylosidase activity and AtXYL1 expression levels. Both increased from older to younger leaves, where xyloglucan turnover is expected to be higher. When this gene was introduced in a suitable expression vector and used to transform Saccharomyces cerevisiae, significantly higher alpha-xylosidase activity was detected in the yeast cells. alpha-Glucosidase activity was also increased in the transformed cells, although to a lesser extent. These results show that AtXYL1 encodes for an apoplastic alpha-xylosidase active against xyloglucan oligosaccharides that probably also has activity against p-nitrophenyl-alpha-D-glucoside.

Amino Acid Sequence↗
PubMed1994

Developmental consequences of unrestricted expression of the abd-A gene of Drosophila.

The abdominal-A (abd-A) gene of Drosophila specifies abdominal segments two through eight (A2-A8). We have found that the uniform expression of the abd-A protein under heat shock control transforms embryonic segments anterior to the abd-A domain into an abdominal segment of the A2-A6 type. Posterior abdominal segments and telson undergo little or no transformation, that is, the abd-A product is phenotypically suppressed posterior to its realm of expression. The comparison of wildtype embryos with embryos carrying the heat shock-abd-A construct but no abd-A endogenous product indicate that some elements of the pattern-like shape of denticle belts or ventral pits depend on the amount of abd-A protein. The concurrent expression of abd-A and other homeotic genes suggest competition for common downstream genes. This competition has been studied by looking at the expression on the visceral mesoderm of a gene downstream of abd-A, decapentaplegic, when two homeoproteins with opposing effects on its transcription are simultaneously induced.

Abdomen↗
PubMed1994

Neoplastic colonic polyps in acromegaly.

A high prevalence of neoplastic colorectal polyps has been described in acromegalic patients. The aim of the present report was to confirm the high prevalence of neoplastic colorectal polyps in acromegaly and the existence of special risk factors for this type of polyps among acromegalic patients. A fiberoptic colonoscopy was performed in 27 active acromegalic patients, followed by both polypectomy and biopsy when indicated. Several prognostic variables were analysed a potential risk factors, in all cases. The prevalence of neoplastic colorectal polyps found in our series (22.2%) was similar to that in previous studies, and did not show any apparent increment compared to that in the populations in which it is known. None of the prognostic variables studied were related to the presence of neoplastic colorectal polyps.

Acromegaly↗
PubMed1994

Subcellular localization of the segment polarity protein patched suggests an interaction with the wingless reception complex in Drosophila embryos.

The product of the segment polarity gene patched is a transmembrane protein involved in the cell communication processes that establish polarity within the embryonic segments of Drosophila. Monoclonal antibodies have been raised against the patched protein, and by immunoelectron microscopy part of the patched staining is found associated with discrete regions of the lateral plasma membrane of the embryonic epidermal cells. Using a mutation affecting endocytosis (shibire) we find that patched is a membrane-bound protein, which is internalized by endocytosis, and that the preferential sites of accumulation resemble the described localization of the cell-cell adhesive junctions of the epidermal cells. patched partially co-localizes with the wingless protein in the wingless-expressing and nearby cells, in structures that seem to be endocytic vesicles. These data suggest the interaction of patched protein with elements of the reception complex of wingless, as a way to control the wingless expression.

Animals↗
PubMed1993

A role for wingless in the segmental gradient of Drosophila?

The wild-type functions of the Wnt family of genes are still little understood (for review see Nusse and Varmus, Cell 69, 1073-1087, 1992). In Drosophila, the wingless (D-Wnt-1) protein is expressed in segmental stripes: its absence leads to a complete failure of segmentation, loss of engrailed expression and lack of pattern in the cuticle. A predominating hypothesis is that the spatial distribution of wingless is crucial to pattern; it might carry an instructive signal from cells that secrete the protein to cells nearby, or it might form a concentration gradient which acts as a morphogen. We tested these hypotheses by expressing wingless ubiquitously in wingless- embryos. The distribution of wingless protein in these embryos is uniform. Despite this, engrailed expression persists, is confined to the most anterior third of the parasegment, and delineates the parasegment border. The cuticle shows a segmentally reiterated pattern and, dorsally, the denticles are normally distributed and oriented. Because all these position-specific features cannot have been placed by a local source or a differential distribution of wingless protein, we conclude that, in the early embryo, the role of wingless is neither to act as a local instructive signal, nor as a morphogen. We propose an alternative hypothesis that the wild-type function of the wingless protein is to maintain and 'seal' the parasegment borders; in its absence the borders fail to isolate abutting segmental gradients.

Animals↗
PubMed1992

D-penicillamine therapy associated with rapidly progressive glomerulonephritis.

A 55-year-old woman with advanced rheumatoid arthritis developed rapidly progressive glomerulonephritis with epithelial crescents and pulmonary hemorrhage following treatment with D-penicillamine. D-penicillamine was then withdrawn and a pulse therapy with methylprednisolone halted the progression of kidney and lung damage. We review the other cases previously reported and discuss pathogenesis and treatment of this rare condition.

Arthritis, Rheumatoid↗
PubMed1991

Unrestricted expression of the Drosophila gene patched allows a normal segment polarity.

In the Drosophila embryo, mutations in the segment polarity gene patched (ptc) cause the replacement of the middle region of each segment by a mirror-image duplication of the remaining structures, including the parasegmental border. This gene, which encodes a transmembrane protein, is initially expressed in a generalized way at blastoderm, but later stops being transcribed in cells expressing the engrailed gene, and even later in cells in the middle of the parasegment. The genes engrailed (en) and wingless (wg) are also segment-polarity genes, and they are expressed in adjacent stripes flanking the parasegment borders in the embryo; in ptc mutants wg expression extends anteriorly and an ectopic stripe of en expression is induced. The suggestion has been made that ptc must be transcribed in a specific subset of cells to prevent en expression anterior to the wg-expressing stripe. Here we report that unrestricted expression of ptc from a heat-shock promoter has no adverse effect on development of Drosophila embryos. The heat-shock construct can also rescue ptc mutants, restoring wg expression to its normal narrow stripe. The ectopic en stripe fails to appear, but the normal one remains unaffected. The results imply that, despite its localized requirement, the restricted expression of ptc does not itself allocate positional information.

Animals↗
PubMed1991

[The value of endoscopic biopsy in the diagnosis of carcinoma of Vater's ampulla].

In a series of 23 ampullary carcinomas, confirmed by the pathological examination of the duodenopancreatectomy specimens, 17 were biopsied during the previous ERCP examination. Biopsies were diagnostic of carcinoma in 12 (70.5%). Among 11 exophytic tumours biopsy was positive in 8 (72.7%) while in 6 tumours growing inside the papilla biopsies were positive in 4 (66.6%) (NS). It is concluded that endoscopic biopsy may be diagnostic in two-thirds of ampullary carcinomas.

Adenocarcinoma↗
PubMed1990

Transcription at the ecdysone-inducible locus 2B5 in Drosophila.

The Broad-Complex (BR-C) of D. melanogaster, mapping at the 2B5 early ecdysone puff, mediates ecdysone-induced processes. We present here the transcriptional analysis of the locus in both wild type and representative mutants. Two well defined regions are transcribed, only one of which has a pattern consistent with the proposed 2B5 located BR-C function. The 2B5 region is actively transcribed in early third instar larvae before ecdysone levels increase. Ecdysone switches this early pattern to a complex late type which requires the presence of functional BR-C product. Therefore, BR-C self-regulates its own ecdysone-induced transcription. The effect of 2B5 mutations on transcription at several intermolt, early and late puffs is also described. Null mutations at the 2B5 locus prevents ecdysone inducible transcription. This evidence supports the fact that 2B5 codes for an ecdysone-dependent transcriptional regulator.

Animals↗
PubMed1989

Mutation mapping of the 2B5 ecdysone locus in Drosophila melanogaster reveals a long-distance controlling element.

Mutations at the Broad-Complex, a key gene triggering metamorphosis in Drosophila melanogaster, were mapped at the DNA level. The Broad-Complex includes two mutually complementing allelic classes, br and l(1)2Bc, both of which can associate to insertions at the same intron. Alterations spreading over 50 kilobases upstream from the transcription unit also disrupt br but not l(1)2Bc function.

Animals↗
PubMedDate not supplied

Evaluation of total IgE in diverse allergosis. Comparative study with other techniques. Part I.

Three hundred patients whose ages ranged between 10 and 50 years were studied. They were classified, according to the number of sensitizing allergens, their sensitization frequency, the clinical syndrome diagnosed, and the therapy followed by each one of them. Intracutaneous tests with twenty-nine groups of allergens and the determination of total IgE, were carried out on each of them. A statistical evaluation was performed on the results obtained, for the purpose of proving mathematically the certainty of these values. The results obtained lead to the following conclusions: 1) The mean values of IGE found coincide with those discovered by other authors, except in the cases of parasytosis and atopic dermatitis. 2) The expression "mean value of IgE" is incorrect for comparative effects with respect to normal levels, since a great diffusion of individual values with respect to this mean value, were observed in all the circumstances studied. 3) A different reaginic response is noticed in the patients studied: from 50 to 70% presented extremely elevated values of serum IgE. Points 1) and 3) are being submitted to an exhaustive re-examination.

Absorption↗