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S Vidal

Publications and source records attributed to S Vidal.

At least 109 records · Page 6Linked to original sources
PubMed1994

Expression of the plasmodial pfmdr1 gene in mammalian cells is associated with increased susceptibility to chloroquine.

Chloroquine (CQ)-resistant (CQR) Plasmodium falciparum malaria parasites show a strong decrease in CQ accumulation in comparison with chloroquine-sensitive parasites. Controversy exists over the role of the plasmodial pfmdr1 gene in the CQR phenotype. pfmdr1 is a member of the superfamily of ATP-binding cassette transporters. Other members of this family are the mammalian multidrug resistance genes and the CFTR gene. We have expressed the pfmdr1-encoded protein, Pgh1, in CHO cells and Xenopus oocytes. CHO cells expressing the Pgh1 protein demonstrated an increased, verapamil-insensitive susceptibility to CQ. Conversely, no increase in drug susceptibility to primaquine, quinine, adriamycin, or colchicine was observed in Pgh1-expressing cells. CQ uptake experiments revealed an increased, ATP-dependent accumulation of CQ in Pgh1-expressing cells over the level in nonexpressing control cells. The increased CQ accumulation in Pgh1-expressing cells coincided with an enhanced in vivo inhibition of lysosomal alpha-galactosidase by CQ. CHO cells expressing Pgh1 carrying two of the CQR-associated Pgh1 amino acid changes (S1034C and N1042D) did not display an increased CQ sensitivity. Immunofluorescence experiments revealed an intracellular localization of both mutant and wild-type forms of Pgh1. We conclude from our results that wild-type Pgh1 protein can mediate an increased intracellular accumulation of CQ and that this function is impaired in CQR-associated mutant forms of the protein. We speculate that the Pgh1 protein plays an important role in CQ import in CQ-sensitive malaria parasites.

ATP-Binding Cassette Transporters↗
PubMed1994

An immunogenetic study of familial scleroderma.

OBJECTIVE: To study the role of the HLA system in the genetic susceptibility to familial systemic sclerosis (SSc). METHODS: HLA class I antigens were determined by classic serological methods and HLA-DRB, -DQA and -DQB genes were analysed by genetic typing in 36 individuals belonging to two families with several individuals affected by SSc. RESULTS: The results did not show any association of the inheritance to SSc with any particular HLA allele in these families but revealed a striking frequency of ANA autoantibodies in healthy spouses of the members of these families. CONCLUSION: The otherwise infrequent familial incidence of SSc does not appear to be primarily linked to the HLA system in this study but it is suggested that other unknown exogenous environmental factors could be implicated in the development of the disease in families.

Adolescent↗
PubMed1993

Physical delineation of the minimal chromosomal segment encompassing the murine host resistance locus Bcg.

The host resistance locus Bcg determines resistance of mice to infection with intracellular pathogens such as certain species of Mycobacteria, Salmonella typhimurium, and Leishmania donovani. Bcg maps on the proximal portion of mouse chromosome 1, very tightly linked to villin (Vil), with the gene order and intergene distances Tp-1-(1 cM)-D1Mcg105-(0.1 cM)-lambda Mm1C165/Vil/Bcg-(0.2 cM)-lambda Mm1C136-(0.3 cM)-Des-(0.1 cM)-Inha. In an effort to clone genomic sequences overlapping Bcg, we have used pulsed-field gel electrophoresis (PFGE) and fluorescence in situ hybridization to construct a physical map of the 3.9-Mb segment of proximal mouse chromosome 1, near Bcg. In situ hybridization to metaphase mouse chromosomes indicates that the mapped region is within band C5. Physical mapping of the Tp-1-Vil and lambda Mm1C136-Inha intervals was carried out by PFGE analysis, whereas the Vil-Des interval was estimated by in situ hybridization to interphase nuclei. Results of these combined analyses indicate the following locus order and maximal interlocus distances: Tp-1-(1000 kb)-D1Mcg105-(160 kb)-lambda Mm1C165-(180 kb)-Vil-(800 kb)-lambda Mm1C136-(290 kb)-Des-(130 kb)-Inha. Detailed restriction mapping of this region identifies numerous putative CpG islands, suggesting that several transcription units are present in the vicinity of Bcg.

Animals↗
PubMed1991

Regulation of neurotransmitter synthesis: from neuron to gene.

We are interested in the molecular mechanisms of the regulation of neurotransmitter related gene expression by neurotrophic factors and neuronal activity. Previous work has shown that conditioned medium of muscle cells induces choline acetyltransferase (CAT) activity and represses tyrosine hydroxylase, dopamine-beta-hydroxylase and aromatic L-amino acid decarboxylase (AADC) activities in cultured sympathetic neurons. Here, we show that a new muscle-derived cell line secretes two factors which induce CAT activity in spinal cord cultures; one of those is related to LIF, a CAT inducing factor for sympathetic neurons. Preliminary data are presented on the structure of the human AADC and CAT genes. Putative promoter regions have been coupled to reporter genes; transient transfection experiments will allow us to determine the promoter elements responsible for the regulation by neurotrophic factors. We also summarize the distribution of AADC-immunoreactive cells in rat and cat brain, which will be used as a reference for the study of the specificity of expression of AADC promoter in transgenic mice.

Animals↗
PubMed1990

Induction of the vesicular monoamine transporter by elevated potassium concentration in cultures of rat sympathetic neurons.

The expression of the vesicular monoamine transporter was studied in newborn rat sympathetic neurons and compared to that of the catecholamine biosynthesis enzymes tyrosine hydroxylase and dopamine-beta-hydroxylase. The vesicular monoamine transporter was assayed using the specific ligand [3H]dihydrotetrabenazine. In cultures grown for 10 days in the presence of 35 mM K+, tyrosine hydroxylase activity and the density of [3H]dihydrotetrabenazine binding sites were increased by a similar 2-3-fold factor, while dopamine-beta-hydroxylase activity and protein level were unchanged. Under these conditions, choline acetyltransferase activity was depressed by 90%. The induction of the vesicular monoamine transporter by high K+ was dependent upon Ca2+ entry through slow calcium channels since it was inhibited by the diphenylbutylpiperidine antagonist fluspirilene and by 20 mM Mg2+, and was enhanced by the dihydropyridine agonist, Bay K8644. The induction of the vesicular monoamine transporter by neuronal depolarization indicates the existence of a Ca2(+)-dependent mechanism of coregulation for this intrinsic component of monoaminergic synaptic vesicles and tyrosine hydroxylase. On the other hand, the apparent absence of dopamine-beta-hydroxylase induction is probably due to the continuous secretion of this intravesicular enzyme by the depolarized sympathetic neurons, an effect already observed in trans-synaptically stimulated adult sympathetic ganglion and adrenal medulla.

Animals↗
PubMed1990

A stuttering model for paramyxovirus P mRNA editing.

Paramyxovirus P genes are transcribed into two mRNAs which differ from each other by either one (measles and Sendai virus) or two (SV5 and mumps virus) G insertions, and which code for either the P or V proteins. The G insertions always occur within a short run of Gs, and a stuttering mechanism for the insertions has been suggested in which the viral polymerase reiteratively copies a template C residue during mRNA synthesis. Support for this mechanism was obtained by varying the reaction conditions during Sendai virus mRNA synthesis in vitro. A stuttering model is proposed which accounts for how the ratio of inserted to uninserted mRNAs is controlled, and why some paramyxoviruses insert one G and others two Gs when insertions occur.

Base Sequence↗
PubMed1990

Different strains of donor parental lymphoid cells induce different models of chronic graft-versus-host disease in murine (Balb/c x A/J)F1 hybrid hosts.

The induction of a chronic graft-versus-host (cGVH) disease in (Balb/c x A/J)F1 mice by the intravenous injection of either Balb/c or A/J parental lymphoid cells led to the development of two different models of disease. In this paper we compared the clinical aspects and the antigen specificities which recognized the autoantibodies developed by the animals of these two models of cGVH disease. Renal disease, alopecia, and purpura lesions were common in both models, although their frequency and intensity varied between groups. The models were differentiated by two main characteristics. When donor cells were of Balb/c origin, a joint disease similar to rheumatoid arthritis developed in 50% of the animals, and when donor cells were of A/J origin, 25% of the animals developed edema of the front feet, occasionally with loss of the nails, similar to that of scleroderma. Differences among the autoantibodies found in the sera of these two groups of mice were also observed. After the injection of Balb/c lymphoid cells, rheumatoid factors reactive with human and murine IgG were characteristically present (69 and 75%, respectively) and a statistically significant correlation was found between high titers of rheumatoid factor and arthritis (P less than 0.001). Antinuclear antibodies (ANAs) were present in all animals. Anti-dsDNA and anti-histones were positive in 50 and 25%, respectively. Anti-snRNP were detected at a low titer in 35% of the animals. When donor cells were of A/J origin, ANAs were also present in all mice. Anti-dsDNA, anti-histones, and anti-snRNPs antibodies were present in 90, 15, and 65%, respectively. The most outstanding characteristics among anti-snRNPs were the high titers of anti-U1 and anti-U3 detected in 50 and 30%, respectively. Rheumatoid factors reactive with human and murine IgG were positive in 15 and 42% of animals, respectively, but no significant correlation was found between these factors and disease. Our results indicate that the graft-versus-host disease induced in the same F1 strain of mice can be manifested in different forms of connective tissue disease, depending on whether the cells come from one or the other of the parental strains. Furthermore, in this paper the occurrence of rheumatoid factors in mice with cGVH is described for the first time.

Animals↗
PubMed1990

Identification of protein components reactive with anti-PM/Scl autoantibodies.

The PM/Scl antigen from mammalian cells has been characterized as a nucleolar and nucleoplasmic molecular complex containing at least 16 polypeptides ranging in molecular weight from 110 to 20 kD. Of these polypeptides, we have found those of 68, 39 and 20 kD to be in a phosphorilated form. Whereas the entire complex was precipitated by all the anti-PM/Scl sera tested, in immunoblots the antibodies specifically recognized determinants on the 110-kD protein. This protein was immunoprecipitated more preferentially from nucleoli extracts than from total cell extracts. Moreover, this protein disappeared from the immunoprecipitates when treated with DNAse. Likewise, the immunoblot reaction of the specific antibodies with the 110-kD protein was abolished by treatment of the extracts with DNAse and trypsin, and was resistant when extracts were treated with RNAse. Affinity-purified antibodies from this protein selectively stained the nucleoli and the nucleoplasm of the mammalian cells. Moreover, when the cultured cells used in immunofluorescence were treated with DNAse, the affinity purified antibodies from the 110-kD protein gave negative fluorescence. However, when whole anti-PM/Scl sera were used, a nucleolar and nucleoplasmic staining was found. We conclude that the 110-kD protein has at least one of the autoimmunogenic epitopes of the PM/Scl antigen, recognized by all anti-PM/Scl sera tested. Other epitopes differing in their DNAse sensitivity may also be present in the PM/Scl antigen.

Antibody Specificity↗
PubMed1990

Editing of the Sendai virus P/C mRNA by G insertion occurs during mRNA synthesis via a virus-encoded activity.

Two forms of the Sendai virus P/C mRNA have been predicted: one an exact copy of the viral genome, and the other with a single G insertion within a run of three G's. We directly cloned the mRNA or portions of it containing the insertion site and screened the resulting colonies with oligonucleotides that could distinguish the presence of three or four G's at this position. We found that 31% of the mRNAs did in fact contain the predicted insertion, whereas the viral genomes contained no heterogeneity at this position. A smaller fraction (7%) of the mRNA contained two to eight G's inserted at this position. The insertions also took place during RNA synthesis in vitro with purified virions but were not detected when the mRNA was expressed in vivo via a vaccinia virus recombinant. When the Sendai virus- and vaccinia virus-derived P/C mRNAs were coexpressed in the same cells under conditions in which each could be distinguished, those from the Sendai genome were altered as before, but those from the vaccinia virus genome remained unaltered. The activity that alters the mRNA is therefore likely to be coded for by the virus and cannot function in trans.

Animals↗
PubMed1989

The role of Ca2+ channels of the L-type in neurotransmitter plasticity of cultured sympathetic neurons.

We have studied the effects of Ca2+ antagonists and agonists on the development of choline acetyltransferase (ChAT), tyrosine hydroxylase (TOH) and acetylcholinesterase (AChE) in cultures of rat sympathetic neurons maintained for 6-9 days in low K+ (5 mM) or high K+ (35 mM) medium. Previous experiments have shown that high K+ medium increases TOH activity and TOH-mRNA level up to 3.5-fold and depresses the development of AChE, in particular of its asymmetric A12 form. Moreover, high K+ medium inhibits ChAT induction by 90% in muscle-conditioned medium (Raynaud et al., Dev. Biol., 119 (1987) 305-312; 121 (1987) 548-558). None of the Ca2+ antagonists tested affected the development of ChAT, TOH or AChE in low K+ medium. In high K+ medium, nitrendipine (3 microM) or fluspirilene (1 microM) fully restored ChAT induction by conditioned medium to the level observed in low K+ medium. Other drugs (1 microM) gave partial reversion: flunarizine greater than (+)-PN 200-110 greater than (-)-D-888 greater than cinnarizine = lidoflazine. On the other hand, ChAT induction was not restored by a calmodulin inhibitor, calmidazolium (1 microM). Fluspirilene, PN 200-110, and nitrendipine also totally abolished TOH induction by high K+ medium; fluspirilene (1 microM) suppressed the inhibitory effect of high K+ medium on AChE development and restored the development of A12 AChE. Conditioned medium also depresses AChE and blocks the development of A12 AChE (Swerts et al., Dev. Biol., 103 (1984) 230-234), but these effects were insensitive to fluspirilene. The Ca2+ agonist Bay K 8644 (1 microM) potentiated the effects of elevated K+ on both ChAT and TOH. The data suggest that the effects of long-term depolarization on ChAT, TOH and AChE are mediated by Ca2+ entry specifically through voltage-sensitive channels of the L-type. Our results on cultured sympathetic neurons raise the possibility that Ca2+ antagonists, which are widely used clinically, may affect the expression of neurotransmitter phenotypic traits in vivo and interfere with trans-synaptic induction of enzymes.

Acetylcholinesterase↗
PubMed1989

Addition of high-mannose sugars must precede disulfide bond formation for proper folding of Sendai virus glycoproteins.

The role of glycosylation and of disulfide bonds in the formation of the native structure of the Sendai virus hemagglutinin-neuraminidase (HN) and fusion (F0) glycoproteins was studied. In contrast to the HN and F0 synthesized in vivo, the proteins made from pSP6 transcripts in reticulocyte lysates, whether glycosylated or not, were not recognized by monoclonal antibodies or polyclonal rabbit sera raised against the native proteins; they efficiently reacted only with rabbit antisera raised against the reduced sodium dodecyl sulfate-denatured proteins. These in vitro-made proteins, however, did not contain disulfide bonds. The proteins made in vivo in the presence of tunicamycin, which were also not recognized by the anti-native protein antibodies, did contain disulfide bonds, but they were mainly incorrect interchain disulfide bonds. Moreover, while F0 acquired proper disulfide bonds as soon as it was synthesized under normal conditions in vivo, the disulfides were formed in HN only after a lag of 10 to 30 min. This lag coincides with the delay observed in HN native structure formation. We therefore conclude that the maturation of the HN and F0 proteins depends on the formation of proper intramolecular disulfide bonds, which in turn depends on the previous addition of high-mannose sugars.

Cystine↗
PubMed1989

Modified model for the switch from Sendai virus transcription to replication.

RNase mapping was used to estimate the levels of unencapsidated Sendai virus plus-strand RNAs which cross the leader-NP junction relative to NP mRNA. Significant amounts of leader readthrough RNAs were found in Z strain-infected cells, similar to that described for the polR mutant of vesicular stomatitis virus, even though this strain is considered wild type. The levels of the readthrough RNAs detected fell sharply when progressively longer probes were used, unlike that of NP mRNA. These studies suggest that polymerases which read through the first junction terminate shortly afterwards in the absence of concurrent assembly of the nascent chain, whereas those which reinitiate at NP continue efficiently to the next junction. Reinitiation appears to be necessary to convert the polymerase to a mode in which elongation is independent of concurrent assembly. Concurrent assembly appears to be required not only for the polymerase to read through the junction efficiently, but also for it to continue elongation between junctions.

Cell Line↗
PubMed1988

Mapping of monoclonal antibodies to the Sendai virus P protein and the location of its phosphates.

The epitopes of a panel of five monoclonal antibodies to the Sendai virus P protein were mapped by generating modified forms of the P mRNA via SP6 expression followed by in vitro translation. The epitopes were found to be clustered in the C-terminal region of the protein. Two epitopes were within the last 30 residues, two were within the next 65, and one was between residues 308 and 451 of this 568-residue-long protein. By a combination of partial proteolysis and Western immunoblotting with one of these antibodies, the sites at which phosphates are added in vitro by the virion-associated kinase were mapped to the second quarter of the molecule from the N terminus.

Antibodies, Monoclonal↗
PubMed1988

Regulation of neurotransmitter metabolic enzymes and tyrosine hydroxylase mRNA level by nerve growth factor in cultured sympathetic neurones.

The survival of new-born rat sympathetic neurones in culture was increased in a dose-dependent manner by 7S nerve growth factor (NGF). NGF also increased, in a parallel manner, the specific activities of tyrosine hydroxylase (TOH) and choline acetyltransferase (CAT). Total acetylcholinesterase (AcChE) activity increased with NGF concentration, although less distinctly than TOH and CAT. However, NGF caused a large induction of the asymmetric A12 form of AcChE, and to a lesser extent of the globular G1 and G2 forms, whereas the globular G4 form was little affected. This suggests that NGF differentially regulates the synthesis and/or assembly of the various AcChE molecular forms. The levels of TOH mRNA in neurone cultures grown with increasing NGF concentrations were measured by Northern blot analysis with a rat cDNA probe. To correct for variations in the total mass of RNA per neurone, the filters were rehybridized with an 18S rRNA probe. The level of TOH mRNA, measured by the ratio (TOH:18S) of the hybridization signals increased 3.4-fold between 92 and 740 ng ml-1 7S NGF. Increases of TOH specific activity of the same order of magnitude were observed in sister cultures. The deficit in the level of mature TOH mRNA at low NGF concentration was not accompanied by a compensatory accumulation in unprocessed TOH transcripts. As TOH induction is insensitive to RNA polymerase inhibitors, we suggest that NGF regulates the maturation of TOH pre-mRNAs, and that the unprocessed transcripts are rapidly degraded. The long-term regulation of TOH by NGF may thus constitute a case of process-versus-discard control, as defined by J.E. Darnell.

Acetylcholinesterase↗