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P Lopez

Publications and source records attributed to P Lopez.

At least 109 records · Page 6Linked to original sources
PubMed1990

[Solitary rectal ulcer syndrome: clinical features, clinical course and treatment. Apropos of 22 cases].

Rectopexy associated with anterior prolepsectomy was performed for 22 patients (19 females, 3 males), with solitary rectal ulcer syndrome (SRUS) surrounding internal rectal prolapse. The different lesions of SRUS were distributed among 3 main groups (G) according to the macroscopic appearance: G1: solitary ulcer (n = 7); G2: ulcerated proctitis (n = 7); G3: muco-hemorroidal prolapse (n = 3). A significant difference (P less than 0.05) was observed between each group, concerning mean age (G1: 34 years, G2 = 49, G3: 65) and the degree of perineal descent, which was more important in G3 and G2. Posterior intersphincteric rectopexy was performed for 6 patients in G3, with descending perineum and faecal incontinence, treated in the same time by perineoplasty (Parks). Abdominal rectopexy, mainly by the antero-posterior technique (Nicholls), was performed for the other patients (n = 6). Large anterior prolapsectomy reaching the top of the mucosal prolapse (4-7 cm), allowing ulcer resection in 3 cases, was combined with rectopexy. Associated operations were: sphincterotomy (n = 8) for narrow fibrous anal canal, sigmoidectomy (n = 4) for dolichocolon. Mean healing time for the solitary ulcer group (G1) was 2 months, 1 month for lesion of G2 and G3. Failures concerned 1 solitary ulcer after abdominal rectopexy and 1 ulcerative proctitis after rectopexy without prolapsectomy. Anorectal pain (81%), rectal bleeding (76%), faecal incontinence (27%), straining (81%), were cured or improved in 80% of cases. These results tend to confirm the efficacy of rectopexy, specially using the antero-posterior technique, for the treatment of SUSR with internal rectal prolapse. Nevertheless, rectopexy seems to be insufficient to correct the mucosal component of internal rectal prolapse, bearing the ulcerated lesion which needs to be treated by associated anterior prolapsectomy. Similarly all functional or organic disorders involving the perineum, anal canal or colon leading to anorectal dysfunction must also be considered to ensure complete treatment.

Adult↗
PubMed1989

A new probe for affinity labelling pancreatic cholecystokinin receptor with minor modification of its structure.

Biochemical studies on receptors for peptides are most often carried out on affinity-labelled (peptide-receptor) complexes. Necessarily, the assumption is made that a covalent (peptide-receptor) complex behaves as the native receptor. The validity of this assumption is dependent on both the affinity-labelling technique and the resolution of the analytical method used for biochemical characterization. We designed a new affinity-labelling probe in order to minimize structural modifications occurring within the affinity-labelled cholecystokinin (CCK) receptor protein. The probe was 125I-labelled 2-(p-azidosalicylamido)-1,3-dithiopropionate-[Thr28,Ahx31 ]CCK-25-33, (125I-ASD-[Thr28,Ahx31]CCK-25-33), the peptide moiety of which was released from its binding site by reduction. It was obtained by coupling a photoactivable chemical to [Thr28,Ahx31]CCK-25-33 via its N-terminus. The resulting peptide was HPLC purified and radioiodinated in the presence of chloramine T. Binding of 125I-ASD-[Thr28,Ahx31]CCK-25-33 was time- and temperature-dependent and reversible. At 25 degrees C, a steady-state level was reached after 60 min and half-maximal dissociation after 38 min. Binding was inhibited by [Thr28,Ahx31]CCK-25-33 and L-364-718 antagonist with IC50 0.4 nM and 0.9 nM, respectively. Photoaffinity labelling of pancreatic plasma membranes by 125I-ASD-[Thr28,Ahx31]CCK-25-33 identified a glycoprotein of Mr 85,000-100,000 which was retained on immobilized wheat germ agglutinin. Enzyme cleavage by endoproteinase Glu-C generated a main fragment of Mr 30,000-34,000. The same glycoprotein was photoaffinity labelled with 125I-DTyr-Gly-[Ahx28,31,pNO2Phe33]CCK-26-33 (Ahx, 2-aminohexanoic acid; pNO2Phe,p-nitrophenylalanine) an intrinsic probe having its photolabile group sited in the binding domain of cholecystokinin. 125I-ASD-[Thr28,Ahx31]CCK-25-33 is a potentially powerful tool for biologically and biochemically studying cholecystokinin receptors.

Affinity Labels↗
PubMed1989

Dissection of the human CD2 intracellular domain. Identification of a segment required for signal transduction and interleukin 2 production.

To evaluate those residues in the 117 amino acids of the CD2 cytoplasmic domain required for transduction of T lymphocyte activation signals, a full-length human CD2 cDNA and a series of deletion and substitution mutants were inserted into the ovalbumin-specific, I-Ad-restricted murine T cell hybridoma 3DO54.8 using a retroviral system. The resulting cells express surface CD2 protein and unlike the parental murine line, are reactive with murine anti-human CD2 antibodies. Anti-T11(2) plus anti-T11(3) antibody stimulation of cells expressing a full-length CD2 cDNA results in a characteristic rise in cytosolic-free calcium [( Ca2+]i), and subsequent IL-2 secretion that accompany CD2 stimulation in human T lymphocytes. Transfectants expressing CD2 delta C98 and CD2 delta C77, partially deleted CD2 molecules containing the entire extracellular and transmembrane CD2 segments but only 98 and 77 amino acids of the cytoplasmic domain, respectively, are also activated by anti-CD2 mAbs. In contrast, clones expressing more severely truncated CD2 structures, CD2 delta C43 and CD2 delta C18, are not stimulated. These data show that the cytoplasmic domain plays an essential role in transduction of activation signals via CD2, and that the segment between amino acid residues 253 and 278 is necessary for activation. This region contains two tandem repeats of the sequence PPPGHR, thought to form part of a putative cationic site. Disruption of the latter by site-directed mutagenesis does not affect IL-2 gene induction, suggesting that only one of the repeats is required for activating this function of the CD2 molecule.

Amino Acid Sequence↗
PubMed1989

Characterization of the polA gene of Streptococcus pneumoniae and comparison of the DNA polymerase I it encodes to homologous enzymes from Escherichia coli and phage T7.

The DNA sequence of the polA gene of Streptococcus pneumoniae was determined, and the DNA polymerase I encoded by the gene was purified to homogeneity. Determination of the amino-terminal amino acid sequence of the protein showed it to correspond to the Mr 99,487 polypeptide predicted from the nucleotide sequence. The mRNA transcript was mapped with respect to its sites of initiation and termination in the DNA. Inasmuch as the mRNA begins only two nucleotides before the first codon, it lacks a typical ribosome binding site. Nevertheless, 500 molecules of the protein are produced per cell. Like the Escherichia coli DNA polymerase I, the protein from S. pneumoniae has 5'- and 3'-exonuclease as well as polymerase activities, and it also undergoes a single cleavage on mild proteolysis. Alignment of the two different polymerase I proteins shows 40% of their amino acid residues to be identical. Homology is evident also with the DNA polymerase encoded by phage T7 gene 5. In addition, the amino-terminal regions of the bacterial polymerase I proteins are homologous to the separate 5'-exonuclease protein encoded by phage T7 gene 6. Analysis of the patterns of homology suggests that the bacterial polymerase I may represent the accretion of at least six separate genetic regions.

Base Sequence↗
PubMed1989

Immunohistochemical characterization of the histiocytes in sinus histiocytosis with massive lymphadenopathy: analysis of an extranodal case.

We studied the morphologic, antigenic, and enzymatic characteristics of the histiocytes in an isolated extranodal case of sinus histiocytosis with massive lymphadenopathy (SHML) involving the CNS. To our knowledge, this represents the first immunohistochemically documented case of CNS SHML. The histiocytes exhibited the S-100(+), CD11c(+), alpha-1-antichymotrypsin(+) immunophenotype, which suggests that the histiocytes of SHML coexpress phenotypic characteristics of histiocytes of the mononuclear phagocytic system, and histiocytes of the interdigitating reticulum cell and Langerhan cell lineages. To examine the argument that the histiocytes in SHML may represent ordinary tissue macrophages of granulomatous inflammation, we compared the immunophenotypic characteristics of the histiocytes found in SHML to those found in xanthogranulomatous pyelonephritis (XP). We found that the histiocytes of XP have immunophenotypic characteristics of histiocytes belonging to the mononuclear phagocytic system lineage. The present study demonstrates that the histiocytes of SHML are distinct from the histiocytes of another xanthogranulomatous disorder, supporting the concept that SHML is a distinct clinicopathologic entity.

Adult↗
PubMed1989

Plasmid structural instability associated with pC194 replication functions.

The hybrid plasmid pJS37 is composed of the streptococcal plasmid pLS1, which confers tetracycline resistance, and the staphylococcal plasmid pC194, which confers chloramphenicol resistance. When gram-positive bacteria containing pJS37 were grown in the presence of chloramphenicol, four different deleted derivatives accumulated. The deletions in the plasmid enhanced resistance to chloramphenicol by placing the cat gene of pC194 near promoters of pLS1. All four deletions shared a common endpoint that corresponded to the putative target site for DNA strand nicking by the pC194 replication protein, RepH. At the other, variable endpoint, the DNA sequence was similar to the putative RepH target sequence. Alteration of the RepH protein, by in vitro modification of the gene encoding it, eliminated this class of deletions. By extending a previously proposed model for the generation of a different but related class of deletions (B. Michel and S.D. Ehrlich, EMBO J. 5:3691-3696, 1986), a comprehensive model that could generate both classes of deletions is suggested. It proposes that a nicking-closing activity of the plasmid replication protein at its normal target site and, aberrantly, at sites with similar sequence can generate deletions either proximal or distal to the aberrant site during rolling-circle replication of the plasmid.

Bacterial Proteins↗
PubMed1989

[Anteroposterior rectopexy for disorders of rectal stasis: clinical and radiologic results. Value of digital subtraction rectography. Apropos of 30 cases].

We report the results of 30 antero-posterior rectopexies (APR) for rectal kinetic disorders with descending perineum syndrome. All patients were investigated by digital subtraction defecography and ano-rectal manometry. The associated surgical procedures were: sphincterotomy (n = 13) for outlet obstruction demonstrated by anal manometry or balloon expulsion test: hypertonic sphincter (n = 7), narrow fibrous sphincter (n = 6); 10 cases of prolapsectomy with extended anterior mucosectomy to reduce anterior rectal prolapse; 2 sigmoidectomy for dolichosigmoid. Best results (mean follow-up: 12 months, 3-26) were observed for ano-rectal or pelvic pain and rectal bleeding, which were cured in more than 80% of cases. Faecal incontinence (n = 5) was cured in all cases. Although normalisation of bowel movements and easier defecation were observed in 78% of cases, improvement in the dyschezic syndrome was differently perceived by the patients. Postoperative investigation demonstrated the probable cause of surgical failures (23%): impairment of rectal sensitivity (n = 2), anismus (n = 3), motor constipation (n = 4), with dolichosigmoid (n = 3). Severe perineal deficiency was also noted in 4 cases. Solitary ulcer (n = 6), anterior proctitis (n = 8), were cured within 2 months. Postoperative defecography showed correction of rectal intussusception without impairment of anterior rectal motility during defecation. These results confirm the efficacy of ARP for treatment of rectal intussusception or anterior rectocele. This functional rectopexy avoids the rectal "sling effect" of standard rectopexy which usually increases rectal dysfunction. Nevertheless, ARP alone seems to be insufficient when the associated functional or organic disorders implicated in rectal dysfunction are not also corrected, essentially outlet obstruction and dolichosigmoid.

Adult↗
PubMed1989

Reference values for trabecular and cortical vertebral bone density in single and dual-energy quantitative computed tomography.

The validity of reference values for vertebral bone mineral density (BMD) reported in the literature has frequently been questioned. The introduction of dual-energy methods, new calibration systems, and automated image evaluation algorithms, has also made it necessary for us to re-evaluate BMD values in a normal population. We present patient selection criteria, CT measurement and evaluation protocols and results of single energy (SEQCT) and dual energy quantitative CT (DEQCT) for trabecular (tBMD) and cortical (cBMD) bone density in 135 males and 139 females. For SEQCT, tBMD loss rates of 1.7 and 1.8 mg/ml per year for males and females, respectively, were determined by linear regression. The respective DEQCT data show smaller decrements with age. Different statistical models for tBMD in females were tested; models based on a multiphase variation of tBMD yielded an improvement of the fit. For cBMD the percent rate of loss with age is much smaller than for tBMD; females showed a significantly higher loss rate than males, however. A comparison of our results with published data is included.

Absorptiometry, Photon↗
PubMed1988

Interdependence of CD3-Ti and CD2 activation pathways in human T lymphocytes.

Human T lymphocytes can be activated through either the antigen/MHC receptor complex T3-Ti (CD3-Ti) or the T11 (CD2) molecule to proliferate via an IL-2 dependent mechanism. To investigate the relationship of these pathways to one another, we generated and characterized Jurkat mutants which selectively express either surface CD3-Ti or CD2. Here we show that CD3-Ti- mutants fail to be stimulated by either pathway to increase phosphoinositide turnover, mobilize calcium or induce the IL-2 gene. The activation capacity of these mutants via CD2 as well as CD3-Ti can be restored following reconstitution of surface CD3-Ti expression upon appropriate DNA transfer (e.g. Ti beta subunit cDNA into Ti beta- Jurkat variants). Collectively, these results demonstrate that CD3-Ti and CD2 pathways are interdependent and that phosphoinositide turnover is linked to the CD3-Ti complex.

Antigens, Differentiation↗
PubMed1988

Accommodative spasm.

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Accommodation, Ocular↗
PubMed1987

Complementation of Bacillus subtilis polA mutants by DNA polymerase I from Streptococcus pneumoniae.

The polA gene of Streptococcus pneumoniae cloned in the recombinant plasmid pSM22 is expressed in Bacillus subtilis. Extracts of B. subtilis polA mutants containing pSM22 showed 6 times more DNA polymerase activity than extracts of wild-type cells without the plasmid. Complete complementation of the B. subtilis polA5 and polA59 mutations with respect to in vivo resistance to UV irradiation and methyl methanesulfonate was observed when four copies of the pneumococcal polA gene were present in each cell. Ectopic integration of the polA gene together with a cat marker into the chromosome of B. subtilis gave chromosomal insertions containing single and double doses of the pneumococcal polA gene. Correlation with gene dosage was observed for both chloramphenicol acetyltransferase and DNA polymerase activities measured in vitro. Depending on the number of copies of the S. pneumoniae polA gene present, restoration of DNA repair functions in polA mutants of B. subtilis was either partial or complete.

Bacillus subtilis↗
PubMed1987

Human isolates of Enterobacter intermedium.

The phenotypic characters of four clinical strains of Enterobacter intermedium (a species usually isolated from surface water and soil) are described and compared to those of E. cloacae and E. asburiae.

Child, Preschool↗
PubMed1987

Sulfonamide resistance in Streptococcus pneumoniae: DNA sequence of the gene encoding dihydropteroate synthase and characterization of the enzyme.

A chromosomal gene of Streptococcus pneumoniae carrying a spontaneous mutation to sulfonamide resistance was identified. Comparison of its DNA sequence with the wild-type sequence showed that the mutation, sul-d, consisted of an insert of 6 base pairs, a repeat of an adjacent 6-base-pair segment. The gene encoded a 34-kilodalton polypeptide, SulA, which as a dimer or trimer constituted the enzyme dihydropteroate synthase. This was shown by enzyme activity measurements, expression in minicells of Bacillus subtilis, and the amino-terminal sequence of the polypeptide product. Subcloning of the gene in an Escherichia coli expression vector allowed purification of the enzyme to 80% homogeneity in a single step and at high yield. Although a deleted plasmid, pLS83, produced the mutant dihydropteroate synthase, it did not confer sulfonamide resistance in vivo. It is suggested that the SulA polypeptide is also a component of an enzyme that acts in another step of folate biosynthesis and that this step is inhibited in vivo by either free or conjugated sulfonamides.

Bacillus subtilis↗
PubMed1986

Identification and analysis of genes for tetracycline resistance and replication functions in the broad-host-range plasmid pLS1.

The streptococcal plasmid pMV158 and its derivative pLS1 are able to replicate and confer tetracycline resistance in both Gram-positive and Gram-negative bacteria. Copy numbers of pLS1 were 24, 4 and 4 molecules per genome in Streptococcus pneumoniae, Bacillus subtilis and Escherichia coli, respectively. Replication of the streptococcal plasmids in E. coli required functional polA and recA genes. A copy-number mutation corresponding to a 332 base-pair deletion of pLS1 doubled the plasmid copy number in all three species. Determination of the complete DNA sequence of pLS1 revealed transcriptional and translational signals and four open reading frames. A putative inhibitory RNA was encoded in the region deleted by the copy-control mutation. Two putative mRNA transcripts encoded proteins for replication functions and tetracycline resistance, respectively. The repB gene encoded a trans-acting, 23,000 Mr protein necessary for replication, and the tet gene encoded a very hydrophobic, 50,000 Mr protein required for tetracycline resistance. The polypeptides corresponding to these proteins were identified by specific labeling of plasmid-encoded products. The tet gene of pLS1 was highly homologous to tet genes in two other plasmids of Gram-positive origin but different in both sequence and mode of regulation from tet genes of Gram-negative origin.

Bacillus subtilis↗
PubMed1986

Cloning of a gene encoding a DNA polymerase-exonuclease of Streptococcus pneumoniae.

A procedure was developed for cloning and characterizing genes that encode proteins with nuclease activity in the Streptococcus pneumoniae [pLS1] host/vector system. Clones are screened for nuclease activity by a DNase colony assay and the nucleases that they produce are characterized by detection of enzyme activity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The method was used to clone the gene encoding a DNA polymerase (Pol)-exonuclease of S. pneumoniae. The activity of this enzyme, the predominant DNA Pol of S. pneumoniae, is tenfold greater in cells carrying the multicopy recombinant plasmid than in cells without the plasmid. The enzyme corresponds to a 100-kDa polypeptide, and its properties are similar to PolI of Escherichia coli. A restriction map of the pSM22 plasmid containing the pneumococcal polA gene was obtained. The gene was transferred into Bacillus subtilis and E. coli, and it was expressed in both species. Its direction of transcription was determined by placement of the gene in both orientations in an E. coli hyperexpression plasmid. In one of the orientations the pneumococcal PolI enzyme was produced at a level 50-fold greater than normally found in S. pneumoniae, and it comprised 5% of the total protein.

Bacillus subtilis↗
PubMed1986

Selective advantage of deletions enhancing chloramphenicol acetyltransferase gene expression in Streptococcus pneumoniae plasmids.

A hybrid plasmid, pJS37, was made by combining pLS1, which confers tetracycline (Tc) resistance, and pC194, which confers chloramphenicol (Cm) resistance. Both pJS37 (7.3 kb) and its derivative pJS140 (6.0 kb), from which pC194 replication genes were removed, were structurally and segregationally stable when introduced into Streptococcus pneumoniae and grown either in the presence of Tc or in the absence of drug. However, both hybrid plasmids underwent systematic deletion when grown in the presence of Cm. One of the deleted forms, pJS4 (3.4 kb), could not be maintained in the absence of a helper plasmid; two others, pJS3 (4.1 kb) and pJS5 (3.8 kb), lost the tet gene but retained the replication functions of pLS1. They both expressed very high levels of Cm acetyltransferase (CAT), which, in the case of pJS5, were constitutive. Nucleotide sequence determination of the deletion junctions in pJS3 and pJS5 indicated that the deletions occurred, presumably by recombination, between short direct repeats of 6 and 9 bp, respectively. In both cases the tet promoter was juxtaposed to the cat gene. In the case of pJS5, the deletion removed a sequence that sequestered the ribosome-binding site (RBS) for cat, thereby rendering constitutive the production of CAT. The increased resistance to Cm afforded by the hyperexpression of the cat gene apparently provided a positive selective advantage for the accumulation of the deleted forms in the plasmid pool.

Acetyltransferases↗
PubMed1986

Inhibition of transformation of Bacillus subtilis by ethidium bromide.

Incubation of donor DNA with ethidium bromide before addition to competent cells, strongly inhibited chromosomal transformation, plasmid transfer and phage-SPP1 DNA mediated transfection. There was no effect of the dye on the binding and entry of DNA into the cells. Analysis of the fate of transforming DNA treated with ethidium bromide showed a reduction in the amount of donor DNA associated with the recipient chromosome. The formation of this donor-recipient complex seems to be slowed down by the dye.

Bacillus subtilis↗