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Biomedical subjects

P Lopez

Publications and source records attributed to P Lopez.

At least 19 recordsLinked to original sources
PubMed1992

A population of early fetal thymocytes expressing Fc gamma RII/III contains precursors of T lymphocytes and natural killer cells.

We have identified a dominant fetal thymocyte population at day 14.5 of gestation in the mouse that lacks CD4 and CD8 but expresses Fc gamma RII/III several days prior to acquisition of the T cell receptor (TCR) in vivo. If maintained in a thymic microenvironment, this population of CD4-CD8-TCR-Fc gamma RII/III+ thymocytes differentiates first into CD4+CD8+TCRlowFc gamma RII/III- thymocytes and subsequently CD4+CD8-TCRhighFc gamma RII/III- and CD4-CD8+TCRhighFc gamma RII/III- mature Ti alpha-beta lineage T cells. However, if removed from the thymus, the CD4-CD8-TCR-Fc gamma RII/III+ thymocyte population selectively generates functional natural killer (NK) cells in vivo as well as in vitro. These findings show that a cellular pool of Fc gamma RII/III+ precursors gives rise to T and NK lineages in a microenvironment-dependent manner. Moreover, they suggest a hitherto unrecognized role for Fc receptors on primitive T cells.

Animals↗
PubMed1992

Analysis of clinical course and prognosis of culture-positive spontaneous bacterial peritonitis and neutrocytic ascites. Evidence of the same disease.

The clinical significance and prognosis of culture-negative neutrocytic ascites in cirrhotic patients is a controversial topic. In the present study, the clinical and humoral presentation and the short- and long-term prognosis were analyzed in 36 patients with cirrhosis and culture-positive spontaneous bacterial peritonitis and in 28 patients with cirrhosis and ascitic fluid polymorphonuclear count greater than 250/mm3, a negative ascitic fluid culture, and without previous antibiotic therapy. On admission there were no significant differences between groups related to age, sex, alcoholism, fever, abdominal pain, serum albumin, serum urea, serum creatinine, Child-Pugh score, polymorphonuclear count, and total protein concentration in ascitic fluid. A greater frequency of positive blood culture was found in patients with spontaneous bacterial peritonitis (15/21 vs 2/18) (P < 0.001). Mortality during the first episode was 36% in patients with spontaneous bacterial peritonitis and 46% in patients with culture-negative neutrocytic ascites (NS). Mortality during follow-up was high and survival probability at 12 months was 32% in spontaneous bacterial peritonitis and 31% in culture-negative neutrocytic ascites. The probability of recurrence at 12 months was 33% in spontaneous bacterial peritonitis and 34% in culture-negative neutrocytic ascites. Our results show that spontaneous bacterial peritonitis and culture-negative neutrocytic ascites are variants of the same disease with a high mortality and poor prognosis.

Aged↗
PubMed1992

Alterations induced by fascioliasis and cirrhosis on the biliary excretion of cefmetazole in Wistar rats.

1. Alterations induced by fascioliasis and cirrhosis on the biliary excretion of cefmetazole have been studied in Wistar rats. 2. Both infestation with Fasciola hepatica and experimental cirrhosis originated a significant decrease in the biliary excretion and in bile flow increase induced by the drug. 3. Administration of the beta-lactam antibiotic induced a lower degree of uncoupling of biliary lipid secretion in the cirrhotic and fasciolotic animals, but the effect was evident in all experimental groups.

Animals↗
PubMed1992

Streptococcus pneumoniae DNA polymerase I lacks 3'-to-5' exonuclease activity: localization of the 5'-to-3' exonucleolytic domain.

The Streptococcus pneumoniae polA gene was altered at various positions by deletions and insertions. The polypeptides encoded by these mutant polA genes were identified in S. pneumoniae. Three of them were enzymatically active. One was a fused protein containing the first 11 amino acid residues of gene 10 from coliphage T7 and the carboxyl-terminal two-thirds of pneumococcal DNA polymerase I; it possessed only polymerase activity. The other two enzymatically active proteins, which contained 620 and 351 amino acid residues from the amino terminus, respectively, lacked polymerase activity and showed only exonuclease activity. These two polymerase-deficient proteins and the wild-type protein were hyperproduced in Escherichia coli and purified. In contrast to the DNA polymerase I of Escherichia coli but similar to the corresponding enzyme of Thermus aquaticus, the pneumococcal enzyme appeared to lack 3'-to-5' exonuclease activity. The 5'-to-3' exonuclease domain was located in the amino-terminal region of the wild-type pneumococcal protein. This exonuclease activity excised deoxyribonucleoside 5'-monophosphate from both double- and single-stranded DNAs. It degraded oligonucleotide substrates to a decameric final product.

Bacterial Proteins↗
PubMed1991

[Lumbar disk herniation with no surgical treatment. Clinical and x-ray computed tomographic follow-up study].

The authors have studied the clinical and computed tomographic (CT) follow-up of 50 patients with nerve root symptoms and herniated nucleus pulposus (HNP) who received only a conservative medical treatment. The clinical follow-up showed that after 23 months 38 patients (76 percent) did not require surgery and 63 percent of these had good or very good results. Follow-up CT scans, performed in 20 patients, found spontaneous disappearance of NP in 10 cases and partial regression in 3 cases. Several mechanisms may explain this regression, including fragmentation and sequestration of the disc fragment, dehydration and shrinkage of the HNP and its reintegration into the annulus. On the other hand, HNP persisted in some patients who had become asymptomatic, and it was also found in an asymptomatic control subject. These data demonstrate that clinical and CT findings may be dissociated. Not all CT scan-documented HNPs require interventional therapy. Except in case of emergency, surgical treatment should be considered only after failure of conservative medical treatment and whenever clinical and CT data are concordant. CT and other imaging procedures, such as myelography and nuclear magnetic resonance, should only be used preoperatively in patients with appropriate clinical findings.

Adult↗
PubMed1991

Concomitant delineation of surface Ig, B-cell differentiation antigens, and HLADR on lymphoid proliferations using three-color immunocytometry.

Accurate and consistent enumeration of B-cell subpopulations in lymphoid tissue was achieved through multiparameter three-color immunofluorescence and flow cytometric analysis (FCM). Phycoerythrin (PE)-anti-CD19 (Leu12) and biotinylated anti-HLADr/streptavidin-Duochrome (PE/Texas Red), used in conjunction with polyclonal fluorescein isothiocyanate (FITC) conjugated anti-surface immunoglobulin (SIg) antibodies, effectively separated non-specific binding and background fluorescence from true B-cell surface FITC immunofluorescence, while concomitantly analyzing for HLADr and CD19 phenotypic expression/deletion. Autofluorescence was measured to establish a fluorescence threshold. A second control measured non-specific binding of isotypic control mouse Ig and non-immune rabbit IgG. Cell suspensions from 128 samples of various lymphoid proliferations were studied. In 116 of the 128 samples, kappa/lambda ratios determined by flow cytometry correlated well with immunocytology results obtained using cytospins from the same cell suspension and with histopathologically established diagnosis. Clonality and lineage as defined immunotypically by flow cytometry was concordant with genotypic results in 64 of the 67 cases evaluated. SIg, HLADr, and CD19 deletions were demonstrated by flow cytometry in 8, 4, and 1 case(s), respectively. Discordance was usually attributable to selective loss of large neoplastic cells in flow cytometry specimens or absent expression of SIg by some cytoplasmic Ig (CIg+) lymphomas.

Antigens, CD↗
PubMed1991

Treatment of pruritus of primary biliary cirrhosis with rifampin.

Pruritus can be a debilitating symptom in patients with chronic cholestasis. Based on previous reports of its efficacy, we evaluated the impact of rifampin on the pruritus associated with primary biliary cirrhosis. Fourteen patients were included in a randomized, crossover study. After a 15-day washout period, subjects were followed for three weeks. During the first and third week, patients received 600 mg of rifampin or placebo; no treatment was administered during the second week. Pruritus was subjectively scored on a scale from 0 to 100. With rifampin, pruritus disappeared in 11 patients and partially improved in three; with placebo, only two had a partial response (P less than 0.001). Six patients with a prior poor or no response to cholestyramine improved with rifampin. No changes in biochemical tests or side effects were observed during this period. We conclude that short-term administration of rifampin relieves pruritus in primary biliary cirrhosis. When administered over a period of eight months in an open study, the relief of pruritus was maintained, while one individual developed an allergic reaction. Rifampin appears to be a safe drug in the management of the pruritus of primary biliary cirrhosis.

Adult↗
PubMed1991

Hepatic disposition of organic anions in rats infested with Fasciola hepatica.

This study was undertaken to investigate the effects of subclinical fascioliasis at various stages of its development (3, 6, and 11 weeks after infestation with an oral dose of 20 metacercariae of Fasciola hepatica) on the hepatobiliary transport of organic anions in rats. Basal bile acid secretion was not significantly modified in infested rats as compared to the controls but there was a significantly increased bile flow in the 11-week group. In all infested rats, maximal biliary excretion and cumulative excretion of bromosulphthalein was significantly reduced, although there was a tendence to recovery in the 11-week infested group. Decreased biliary secretion was accompanied by increased plasma and liver concentrations of bromosulphthalein. Glutathione S-transferase activity was significantly reduced by Weeks 3 and 6 postinfestation. Liver glutathione concentration was significantly reduced in all infested rats. Maximal excretion of dibromosulphthalein, a compound not biotransformed in the liver, fell by Week 6 postinfestation and recovered a normal value thereafter. These results indicate that effects of experimentally induced fascioliasis on hepatic disposition of organic anions depend upon the stage of its development and that are a consequence of both metabolism and transport related factors.

Animals↗
PubMed1991

Fiber digestibility and breath-hydrogen excretion in subjects consuming rural and urban Mexican diets.

Apparent digestibility of dietary fiber and its effect on breath-hydrogen excretion and gastrointestinal symptoms were determined in 16 subjects consuming a plant-based rural Mexican diet (RMD) and a more refined urban Mexican diet (UMD). Neutral-detergent-fiber intake and digestibility were 40.2 and 22.7 g/d (56%) for the RMD and 12.1 and 8.9 g/d (70%), respectively, for the UMD. Apparent digestibilities of hemicellulose, cellulose, and lignin were 40%, 63%, and 53% from the RMD and 73%, 75%, and 58%, respectively, from the UMD. Total breath-hydrogen excretion during 10 postprandial h was similar after both diets, showing that the breath-hydrogen test is of limited value for comparing carbohydrate fermentation from mixed diets. Mouth-to-colon transit time was 5.7 and 6.5 h for the RMD and UMD, respectively (P less than 0.05). There were significantly more gastrointestinal symptoms with the RMD (P less than 0.01); however, neither diet caused symptoms indicative of serious gastrointestinal discomfort.

Adolescent↗
PubMed1991

[Proposal for a radiologic classification of disorders of the pelvi-rectal angle based on measurement of the posterior rectal inclination. Value of dynamic digitalized rectography].

The difficulties for evaluation of the perineal descent have always been linked to the choice of references and mostly with the incertitude of the measurement of length on the radiographic film. This present study was carried out to evaluate the perineal descent on the choice of an angular measurement: the posterior rectal inclination. The dynamic digitalized rectography was used to investigate the pelvic floor status of 134 women: 115 patients complaining of idiopathic constipation, and 19 healthy volunteers. Results have shown 3 populations with an increasing graduation of perineal impairment and led to propose a radiologic classification of pelvic floor impairment: stage I, or solid perineum, stage II, or descending perineum and stage III or descended perineum. This study has brought up that the first sign of a pelvic floor abnormality may be increased descent during straining, only later followed by perineal descent at rest. The relationship linking abnormal perineal descent and excessive opening of the ano-rectal angle suggested logically that fecal incontinence may be the end complication of the Descending Perineum Syndrom.

Adult↗
PubMed1990

Assembly and function of the T cell antigen receptor. Requirement of either the lysine or arginine residues in the transmembrane region of the alpha chain.

The T cell receptor (TCR) for antigen consists, on the majority of peripheral lymphocytes, of an immunoglobulin-like, disulfide-linked heterodimeric glycoprotein: the alpha and beta chain. These proteins are noncovalently linked to at least four nonvariant proteins which comprise the CD3 complex: CD3 gamma, delta, epsilon, and zeta. Whereas the TCR alpha and beta proteins have positively charged residues in the transmembrane region, all the CD3 proteins have similarly placed negatively charged amino acid residues. It has been suggested that these basic and acidic amino acid residues may play an important role in TCR.CD3 complex assembly and/or function. In this paper, the structural and functional role of the lysine and arginine residues of the TCR alpha chain was addressed using oligonucleotide mediated site directed mutagenesis. The Arg256 and Lys261 residues of the TCR alpha cDNA of the HPB-ALL cell line were mutated to either Gly256 and/or Ile261. The altered cDNAs were transfected into a TCR alpha negative recipient mutant cell line of REX, clone 20A. Metabolic labeling of the T cell transfectants showed that mutation of either the Arg256 or Lys261 amino acid residues had no effect on the ability of the TCR alpha chain to form either a heterodimer with the TCR beta chain or a complex with the CD3 gamma, delta, and epsilon proteins. Consequently, the Arg256 to Gly256 and Lys261 to Ile261 mutations did not prevent the formation of a mature, functional TCR.CD3 complex on the cell surface as determined by immunofluorescence, cell surface radioiodination, and the ability of the transfectants to mobilize intracellular calcium after stimulation with a mitogenic anti-CD3 epsilon monoclonal antibody. In contrast, a mutant cDNA in which both the Arg256 and Lys261 residues were mutated to Gly256 and Ile261, respectively, failed to reconstitute the cell surface expression of the TCR.CD3 complex and, consequently, the ability to respond to mitogenic stimuli. In the absence of both the Arg256 and Lys261 residues, TCR alpha beta heterodimer formation was not observed. Cotransfection studies in COS cells showed that the failure of assembly of a heterodimer was likely due to an inability of the mutated TCR alpha chain to form a subcomplex with either the CD3 gamma, delta, epsilon, or zeta proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1990

DNA sequence of folate biosynthesis gene sulD, encoding hydroxymethyldihydropterin pyrophosphokinase in Streptococcus pneumoniae, and characterization of the enzyme.

A cloned segment of the chromosome of Streptococcus pneumoniae, in which mutations to sulfonamide resistance occur, contains several genes encoding enzymes for folate biosynthesis. Determination of the DNA sequence of parts of this segment and identification of a putative promoter and terminator of transcription indicate an operon composed of four genes. The first, sulA, encodes the enzyme dihydropteroate synthase. The functions of the second and third possible genes, sulB and sulC, are not known. The last gene, sulD, encodes a 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase. The product of this enzyme is the substrate for dihydropteroate synthetase. The enzyme protein was partially purified and shown to consist of a single subunit of 31 kilodaltons, encoded by sulD. On the basis of gel filtration behavior, the native protein appears to be a trimer or tetramer. Subcloning of the sulD gene in an Escherichia coli expression vector increased expression of the pyrophosphokinase 1,000-fold over the level produced by a single copy of the chromosomal gene.

Amino Acid Sequence↗
PubMed1990

[Intestinal obstruction and pregnancy. Diagnostic and therapeutic approach. Apropos of 3 cases].

The etiological diagnosis of obstruction is difficult during pregnancy. The authors report 3 cases of this rare association: obstruction due to adhesions [1], volvulus of the transverse colon on a common mesentery [1] and obstruction due to an appendix abscess [1]. Complementary investigations, obviously limited under these circumstances, were based on plain abdominal X-rays, repeated if necessary. The diagnosis must be made early and appropriate treatment given in order to ensure a good materno-fetal prognosis as was obtained in these 3 cases.

Adult↗