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Biomedical subjects

L Rey

Publications and source records attributed to L Rey.

At least 37 records · Page 2Linked to original sources
PubMed1998

Susceptibility of Nectomys rattus (Pelzen, 1883) to experimental infection with Schistosoma mansoni (Sambon, 1907): a potential reservoir in Brazil.

The aim of the present research was to evaluate the potential of Nectomys rattus, the "water rat", to develop Schistosoma mansoni infection. Comparison with N. squamipes was carried out. Both species of rodents were submitted to transcutaneous infection using different infective cercariae loads: 50, 100 or 500. N. rattus showed high susceptibility to S. mansoni, with an infection rate of 71%. Rodents were able to excrete viable eggs of S. mansoni in the faeces during all infection period. For both species, the small intestine, followed by the liver and the large intestine, presented the highest concentration of eggs among the surveyed organs. Infection caused no animal death. Moreover, N. rattus accomplished the parasite's life cycle, by infecting the snails Biomphalaria glabrata and later Mus musculus. These evidences indicate that both N. rattus, as for N. squamipes are potential reservoirs for schistosomiasis in Brazil. Considering the fact that N. rattus and N. squamipes exist in the same natural ecosystems of S. mansoni, we suggest that these rodents must be regarded as influential factors in epidemiology surveys.

Animals↗
PubMed1998

An uncommon false aneurysm of the left ventricle.

An 83-year-old woman with previous closed transventricular commissurotomy was admitted for congestive heart failure. Echocardiogram and angiography demonstrated a mitral restenosis and a large-mouthed false aneurysm of the left ventricle.

Aged↗
PubMed1997

Hydrogenase genes from Rhizobium leguminosarum bv. viciae are controlled by the nitrogen fixation regulatory protein nifA.

Rhizobium leguminosarum bv. viciae expresses an uptake hydrogenase in symbiosis with peas (Pisum sativum) but, unlike all other characterized hydrogen-oxidizing bacteria, cannot express it in free-living conditions. The hydrogenase-specific transcriptional activator gene hoxA described in other species was shown to have been inactivated in R. leguminosarum by accumulation of frameshift and deletion mutations. Symbiotic transcription of hydrogenase structural genes hupSL originates from a -24/-12 type promoter (hupSp). A regulatory region located in the -173 to -88 region was essential for promoter activity in R. leguminosarum. Activation of hupSp was observed in Klebsiella pneumoniae and Escherichia coli cells expressing the K. pneumoniae nitrogen fixation regulator NifA, and in E. coli cells expressing R. meliloti NifA. This activation required direct interaction of NifA with the essential -173 to -88 regulatory region. However, no sequences resembling known NifA-binding sites were found in or around this region. NifA-dependent activation was also observed in R. etli bean bacteroids. NifA-dependent hupSp activity in heterologous hosts was also absolutely dependent on the RpoN sigma-factor and on integration host factor. Proteins immunologically related to integration host factor were identified in R. leguminosarum. The data suggest that hupSp is structurally and functionally similar to nitrogen fixation promoters. The requirement to coordinate nitrogenase-dependent H2 production and H2 oxidation in nodules might be the reason for the loss of HoxA in R. leguminosarum and the concomitant NifA control of hup gene expression. This evolutionary acquired control would ensure regulated synthesis of uptake hydrogenase in the most common H2-rich environment for rhizobia, the legume nodule.

Bacterial Proteins↗
PubMed1997

Cytochrome c terminal oxidase pathways of Azotobacter vinelandii: analysis of cytochrome c4 and c5 mutants and up-regulation of cytochrome c-dependent pathways with N2 fixation.

The Azotobacter vinelandii cytochrome c5 gene (termed cycB) was cloned and sequenced. Mutants in this c-type cytochrome as well as cytochrome c4 mutants (mutations in cycA) and double mutants in both of the c-type respiratory pathways were characterized. Spectral and heme staining experiments on membranes from the mutants were consistent with the anticipated characteristics of all the gene-directed mutants. Membranes of the individual cytochrome c4 or c5 mutants had normal respiratory rates with physiological substrates but respiration significantly lower than the wild-type rate with ascorbate-N,N,N',N',-tetramethyl-p-phenylenediamine (TMPD) as a reductant. The growth rates of the individual cytochrome c4 or c5 mutants were not markedly different from that of the wild-type strain, but the cycA cycB double-mutant strain was noticeably growth retarded at and below 7.5% O2 on both N-containing and N-free media. The double-mutant strain was unable to grow on agar plates at O2 tensions of 2.5% or less on N-free medium. As the wild-type growth was unaffected by varying the O2 tension, the results indicate that the role of the cytochrome c-dependent pathways is to provide respiration at intermediate (5 to 10%) and low (below 5%) O2 tensions. The two c-type cytochrome genes are transcriptionally up-regulated with N2 fixation; N starvation caused 2.8-fold and 7- to 10-fold increases in the promoter activities of cycA and cycB, respectively, but these activities were affected little by the O2 level supplied to the cultures.

Amino Acid Sequence↗
PubMed1996

The hydrogenase gene cluster of Rhizobium leguminosarum bv. viciae contains an additional gene (hypX), which encodes a protein with sequence similarity to the N10-formyltetrahydrofolate-dependent enzyme family and is required for nickel-dependent hydrogenase processing and activity.

Plasmid pAL618 contains the genetic determinants for H2 uptake (hup) from Rhizobium leguminosarum bv. viciae, including a cluster of 17 genes named hupSLCDEFGHIJK-hypABFCDE. A 1.7-kb segment of insert DNA located downstream of hypE has now been sequenced, thus completing the sequence of the 20441-bp insert DNA in plasmid pAL618. An open reading frame (designated hypX) encoding a protein with a calculated M(r) of 62300 that exhibits extensive sequence similarity with HoxX from Alcaligenes eutrophus (52% identity) and Bradyrhizobium japonicum (57% identity) was identified 10 bp downstream of hypE. Nodule bacteroids produced by hypX mutants in pea (Pisum sativum L.) plants grown at optimal nickel concentrations (100 microM) for hydrogenase expression, exhibited less than 5% of the wild-type levels of hydrogenase activity. These bacteroids contained wild-type levels of mRNA from hydrogenase structural genes (hupSL) but accumulated large amounts of the immature form of HupL protein. The Hup-deficient mutants were complemented for normal hydrogenase activity and nickel-dependent maturation of HupL by a hypX gene provided in trans. From expression analysis of hypX-lacZ fusion genes, it appears that hypX gene is transcribed from the FnrN-dependent hyp promoter, thus placing hypX in the hyp operon (hypBFCDEX). Comparisons of the HypX/HoxX sequences with those in databases provided unexpected insights into their function in hydrogenase synthesis. Similarities were restricted to two distinct regions in the HypX/HoxX sequences. Region I, corresponding to a sequence conserved in N10-formyltetrahydrofolate-dependent enzymes involved in transferring one-carbon units (C1), was located in the N-terminal half of the protein, whereas region II, corresponding to a sequence conserved in enzymes of the enoyl-CoA hydratase/isomerase family, was located in the C-terminal half. These similarities strongly suggest that HypX/HoxX have dual functions: binding of the C1 donor N10-formyltetrahydrofolate and transfer of the C1 to an unknown substrate, and catalysis of a reaction involving polarization of the C = O bond of an X-CO-SCoA substrate. These results also suggest the involvement of a small organic molecule, possibly synthesized with the participation of an X-CO-SCoA precursor and of formyl groups, in the synthesis of the metal-containing active centre of hydrogenase.

Amino Acid Sequence↗
PubMed1996

Breeding of the water rat (Nectomys squamipes) in the laboratory.

The water rat, Nectomys squamipes, is reported as a natural host of Schistosoma mansoni in Brazil. This paper presents some reproductive, growth and developmental data, and laboratory management of a breeding programme for N. squamipes. The colony was derived from animals captured at Sumidouro, Rio de Janeiro state. The animals' diploid number was 56, conception rate was 66.7% and gestation period was 30 days. Litter size ranged from 1 to 6, with a mean of 4.1 (SD +/- 1.2) and a mode of 4 and 5. Sex ratio at birth and at weaning was not significantly different from the expected ratio of 1:1. There were no significant differences between mean body weights at birth for males and females. The minimum age for weaning was between 20-25 days. The growth curves of body weight, head-body length and tail length, for both sexes, comprise at least three linear segments representing different phases of approximately constant growth rates. Facilities for colony maintenance and its potential for use as experimental model are reported.

Animal Husbandry↗
PubMed1996

[Enteroparasitosis in pregnant and post-partem women in Rio de Janeiro]

From November 1989 to May 1991, in Rio de Janeiro, Brazil, the prevalence of intestinal parasitosis was investigated in 795 women coming from the Public Health Services, who were divided into three groups: 490 pregnant women in pre-natal care period, 104 after-delivery women and 201 non-pregnant women (control). Coproparasitologic tests were run using the Sedimentation through Centrifugation, Faust, Kato-Katz and Baermann-Moraes methods. Positivities were found ranging from 37.6% to 53.6% for pregnant women, 38.3% for non-pregnant women and 69.2% for after-delivery women, with statistically significant differences between the rates of pregnant women and after-delivery women, and with no statistic difference between the groups of pregnant and non-pregnant women. The most frequent parasites found were A. lumbricoides and T. trichiura. The conclusion was that the control of intestinal parasitosis is not a priority in the pregnant population studied because, in spite of the regular assistance provided during the pre-natal care period, they keep on infected.

Journal Article↗
PubMed1995

Immunopathological characteristics of in situ T-cell subpopulations in human immunodeficiency virus-associated nephropathy.

Human immunodeficiency virus-associated nephropathy (HI-VAN) is a common form of nephropathy present in HIV-infected individuals that clinically presents with proteinuria that is frequently in the nephrotic range, less often with hematuria, and with a course that may evolve to irreversible azotemia ultimately resulting in renal failure. Pediatric and adult HIV-positive patients both experience HIVAN morphologically after displaying focal segmental glomerulosclerosis, diffuse mesangial hyperplasia, microcystic tubular dilatation, interstitial inflammation, edema, and fibrosis. There is minimal information regarding the interstitial inflammatory cell infiltrate, despite the possibility that these cells may play an important role in the etiology of HIVAN. This study was designed to characterize and compare several morphological and immunopathological features of clearly established HIVAN, particularly the hematopoietic cell markers present on the interstitial inflammatory cells and the state of T-lymphocyte activation (ie, class II expression). Quantitative grading of HIVAN kidneys showed that CD4-positive and CD8-positive T cells comprised the major cell populations in the interstitium, often with CD4-positive T cells exceeding or being equivalent in number to CD8-positive T cells. B cells and macrophages were negligible components of the infiltrate. Human leukocyte antigen-DR class II molecules were found to be increased on the interstitial T cells as well as on all glomerular cells and endothelial cells. There was no significant relationship established between the immunophenotype of the interstitial inflammatory cells and other morphological, ultrastructural, immunofluorescent, or clinical features. These data imply that the inflammatory infiltrate in HIVAN is largely composed of activated T cells. At this point the role of these interstitial T cells in HIVAN is undetermined, although it can be speculated that they may be participating as antiviral or autoreactive immune effector cells imparting renal injury in this entity.

AIDS-Associated Nephropathy↗
PubMed1994

Purification of Rhizobium leguminosarum HypB, a nickel-binding protein required for hydrogenase synthesis.

The products of the Rhizobium leguminosarum hyp gene cluster are necessary for synthesis of a functional uptake [NiFe] hydrogenase system in symbiosis with pea plants, and at least for HypB and HypF, a role in hydrogenase-specific nickel metabolism has been postulated (L. Rey, J. Murillo, Y. Hernando, E. Hidalgo, E. Cabrera, J. Imperial, and T. Ruiz-Argüeso, Mol. Microbiol. 8:471-481, 1993). The R. leguminosarum hypB gene product has been overexpressed in Escherichia coli and purified by immobilized nickel chelate affinity chromatography in a single step. The purified recombinant HypB protein was able to bind 3.9 +/- 0.1 Ni2+ ions per HypB monomer in solution. Co2+, Cu2+, and Zn2+ ions competed with Ni2+ with increasing efficiency. Monospecific HypB antibodies were raised and used to show that HypB is synthesized in R. leguminosarum microaerobic vegetative cells and pea bacteroids but not in R. leguminosarum aerobic cells. HypB protein synthesized by R. leguminosarum microaerobic vegetative cells could also be isolated by immobilized nickel chelate affinity chromatography. A histidine-rich region at the amino terminus of the protein (23-HGHHHH DGHHDHDHDHDHHRGDHEHDDHHH-54) is proposed to play a role in nickel binding, both in solution and in chelated form.

Aerobiosis↗
PubMed1993

Molecular analysis of a microaerobically induced operon required for hydrogenase synthesis in Rhizobium leguminosarum biovar viciae.

The nucleotide sequence (6138 bp) of a microaerobically inducible region (hupV/VI) from the Rhizobium leguminosarum bv. viciae hydrogenase gene cluster has been determined. Six genes, arranged as a single operon, were identified, and designated hypA, B, F, C, D and E based on the sequence similarities of all of them, except hypF, to genes from the hydrogenase pleiotropic operon (hyp) from Escherichia coli. The gene products from hypBFCDE were identified by in vivo expression analysis in E. coli, and their molecular sizes were consistent with those predicted from the nucleotide sequence. Transposon Tn5 insertions into hypB, hypF, hypD and hypE resulted in R. leguminosarum mutants that lacked any hydrogenase activity in symbiosis with peas, but still were able to synthesize the polypeptide for the hydrogenase large subunit. The gene products HypA, HypB, HypF and HypD contained CX2C motifs characteristic of metal-binding proteins. In addition, HypB bore a long histidine-rich stretch of amino acids near the N-terminus, suggesting a possible role in nickel binding for this protein. The gene product HypF, which was translationally coupled to HypB, presented two cysteine motifs (CX2CX18CX2C) with a capacity to form zinc finger-like structures in the N-terminal third of the protein. A role in nickel metabolism in relation to hydrogenase synthesis is postulated for proteins HypB and HypF.

Aerobiosis↗
PubMed1993

[3 families with a congenital factor X deficiency, one of them with an associated factor XII deficiency].

Factor X deficiency constitutes one of the most uncommon congenital bleeding disorders. Here we report three families with Factor X deficiency, one of them with an associated deficit of Factor XII. Family I presented Red variant deficiency (low functional and antigenic activity, the latter in higher levels than the former). In Family II functional activity was low but antigenic one was normal (Prower defect). Besides, an heterozygous deficiency of factor XII was diagnosed. Although genetic analysis supports the hypothesis of combined deficiency, the study was possible in only two generations of the propositus, so a multiple familial deficiency could not be discarded. Finally, Family III suffered from a "classic" or Mr. Stuart deficiency (low levels in functional and immunological assays). Besides, crossed immunoelectrophoresis showed a grossly pathological pattern.

Adult↗
PubMed1992

Nucleotide sequence and organization of an H2-uptake gene cluster from Rhizobium leguminosarum bv. viciae containing a rubredoxin-like gene and four additional open reading frames.

The nucleotide sequence of a 3.2 kb region following the hydrogenase structural operon (hupSLCDEF) in the H2-uptake gene cluster from Rhizobium leguminosarum by viciae strain 128C53 has been determined. Five closely linked genes encoding products of 16.3 (HupG), 30.5 (HupH), 8.0 (HupI), 18.4 (HupJ) and 38.7 (HupK) kDa were identified 166 bp downstream from hupF. Transposon insertions into hupG, hupH, hupJ and hupK suppress the H2-oxidizing capability of the wild-type strain. The amino acid sequence deduced from hupI contains two Cys-X-X-Cys motifs, characteristic of rubredoxins, separated by 29 amino acid residues showing strong sequence homology with other bacterial rubredoxins. The amino acid-derived sequence from hupG and hupH showed homology to products from genes hyaE and hyaF of the operon encoding hydrogenase 1 from Escherichia coli, and hupJ and hupK were related to open reading frames identified in Rhodobacter capsulatus and Azotobacter vinelandii hydrogenase gene clusters. An involvement of the hupGHIJK gene cluster in redox reactions related to hydrogenase synthesis or activity is predicted on the basis of the function as electron carrier attributed to rubredoxin.

Amino Acid Sequence↗
PubMed1992

Thromboxane augmentation of alloreactive T cell function.

Thromboxane (Tx) plays a vital role in the dysfunction and ultimate rejection of MHC-disparate renal allografts. In addition to its potent vasoconstrictory properties, in vivo studies have implied that Tx is capable of promoting immune cytotoxic T cell function within transplants. In this study, we have examined the in vitro effect of Tx inhibition on alloreactive immune cells using MHC-disparate mouse strain combinations. Coculture of either Tx-synthetase or Tx-receptor inhibitors modified the response of unprimed mouse lymphoid populations in a primary MLR, implying that Tx inhibition and not endoperoxide shunting was responsible for the modulatory effects seen. For example, B10.S lymphoid cells displayed decreased proliferation to H-2 disparate B10.A cells with Tx inhibitors present during the MLR, at pharmacologically active drug concentrations. Moreover, in vitro addition of TxA2 had an augmentory effect on the response in the primary and secondary MLR. Interleukin 2 production and percentages of T cell populations in the primary MLR were not affected by the presence of these compounds, although CD4 and CD8 expression was often increased in the treated populations. Finally, alloreactive primed effector cells also displayed reduced proliferation to specific alloantigen in a secondary MLR when Tx inhibitors were also present, although responses to IL-2 by T cells were not influenced by thromboxane inhibition. These data imply that thromboxane is an important immunoregulatory mediator capable of potentiating the function of naive and primed alloreactive immune T cell populations crucial to the rejection of the transplant.

Animals↗