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D Bergeron

Publications and source records attributed to D Bergeron.

At least 37 records · Page 2Linked to original sources
PubMed1997

Combinatorial tools for the analysis of transcriptional regulation.

In this paper, we discuss virtual experiments for the study of major regulatory processes such as translation, signalization or transcription pathways. An essential part of these processes is the formation of protein clusters held together by a small number of binding domains that can be shared by many different proteins. Analysis of these clusters is complicated by the vast number of different arrangements of proteins that can trigger a specific reaction. We propose combinatorial tools that can help predict the effects on the rate of transcription of either changes in transcriptional factors concentration, or due to the introduction of chimeras combining domains not usually present on a protein.

Computer Simulation↗
PubMed1996

In vitro characterization of purified human thymic dendritic cells infected with human immunodeficiency virus type 1.

In the thymus, dendritic cells (DC) are functionally associated with thymocytes and are recognized to play a major role in the intrathymic differentiation of T cells. Several studies have previously investigated the role of DC during HIV-infection, but the status of thymic DC in HIV-1 pathogenesis remains unclear. In this study, we investigated the susceptibility of purified human thymic DC to HIV-1 infection in vitro. HIV-1 was not detected in cell-free supernatants collected from HIV-infected DC. However, these cultures were shown to transmit HIV-1 infection since coculture with permissive MT4 cells resulted in virus production. The exposure of DC in culture to HIV-1 was shown to promote severe DC morphological changes and killing. We also found that one or several heat labile soluble cytotoxic agents present in the HIV-1-infected DC supernatant mediated the killing of thymocytes. Our observations raise the possibility that (1) the HIV-1-induced DC killing, (2) the capacity of DC to transmit viral infection, and/or (3) the release of HIV-1-mediated cytotoxic agent(s) from DC may contribute to AIDS pathogenesis in vivo.

Animals↗
PubMed1996

Characterization of the human and mouse Fli-1 promoter regions.

Overexpression of the Fli-1 gene has been shown to be involved in retrovirus-induced mouse tumors. Cloning of the 5' flanking sequence of the mouse and human Fli-1 exon 1 was performed. At least two major transcription initiation sites were localized respectively at 143 and 114 nucleotides upstream of the previously defined mouse Fli-1 cDNA 5' end. The sequences flanking the CAP sites show good conservation between human and mouse (94%). The promoter region contains a potential TATA box lying 30 bp from one of the major identified CAP sites. Several conserved elements, such as GATA, EBS, GC rich, AP-2, AP-3 elements and a repetition of GA were observed next to the two major CAP sites. Furthermore, this latter was shown to form a H-DNA structure in vitro by S1 nuclease sensitivity experiments. The highly conserved 5' non-translated region of exon 1 is predicted to form a very stable hairpin structure which could regulate the Fli-1 expression at the post-transcriptional level. In Cas-Br-E-induced tumors, all the proviruses are found clustered within 35 nucleotides directly upstream the Fli-1 ATG start codon, thus deleting the hairpin structure from the transcript. Promoter activity was tested using the CAT reporter gene transfected in mouse and human erythroid cell lines. No promoter activity could be detected with various mouse Fli-1 promoter-CAT constructs containing 600 bp of the 5' flanking region, the complete exon 1, the 5' end of intron 1 and/or retroviral LTR sequence. Constructions of the human homologue containing nearly 1.5 kbp of Fli-1 5' flanking region was also inactive in transfected cells. These results suggest that multiple levels of regulation might control the Fli-1 expression.

Animals↗
PubMed1996

Regulation of leukocyte interleukin 2 and interleukin 2 receptor gene expression by rabbit blastocoelic fluid.

The mechanisms underlying the inhibition of lymphocyte proliferative response by rabbit blastocoelic fluid collected on day 12 of embryonic development were investigated. Treatment with blastocoelic fluid, even in the presence of concanavalin A, maintains lymphocytes in a quiescent state by preventing cell entry into the S phase of the cell cycle. Gene expression of interleukin 2 receptor is completely blocked by treatment with blastocoelic fluid as are the secretion and gene expression of interleukin 2. Addition of interleukin 2 to prestimulated interleukin 2 receptor positive lymphocytes failed to downregulate the expression of high-affinity interleukin 2 receptor and completely abolished the embryonic fluid-mediated inhibitory effect on [3H]thymidine incorporation. Taken together, these results suggest that embryonic fluid has differential inhibitory effects, depending on the activation state of the lymphocytes. Nevertheless, inhibition of interleukin 2 and interleukin 2 receptor expression by embryonic fluid restrains immune cell activity and therefore can be implicated in the survival of the fetal semi-allograft.

Animals↗
PubMed1995

Incorporation of Vpr into human immunodeficiency virus type 1: role of conserved regions within the P6 domain of Pr55gag.

The 96-amino acid Vpr protein is the only virion-associated regulatory protein encoded by the human immunodeficiency virus type 1 (HIV-1). Vpr incorporation into the viral particle is most likely due to an interaction with a viral structural protein. Recent data have shown that DNA encoding for the p55 Gag precursor protein (Pr55gag) is the minimal viral genetic information necessary for Vpr incorporation. Other studies have suggested that the p6 portion of Pr55gag, which is unique to lentiviruses, is involved in Vpr incorporation. To investigate the mechanism of incorporation of Vpr into HIV-1 virions, COS-7 cells were cotransfected with ptrENV, an expression vector that encodes all of the HIV-1 regulatory proteins including Rev and Vpr, and different constructs of pIIIgagCAR, a rev-dependent Gag expression plasmid that encodes Pr55gag and the viral protease. Virions produced from gag constructs containing a premature p6 termination codon at positions Leu-1, Ser-17, Tyr-36, or Leu-44 lacked detectable Vpr. In contrast, gag constructs with double Pro-10-Pro-11 substitutions for Leu-10-Leu-11 or a premature termination codon at position Pro-49 of p6 were still able to incorporate Vpr, however, with lower efficiency than wild type. The mutations described in this study affected directly two short regions within the p6 domain, which are highly conserved among primate immunodeficiency viruses. Our results suggest that the conserved (P-T/S-A-P-P) and (L-X-S-L-F-G) motifs located near the N-terminus and C-terminus, respectively, of the p6 domain of Gag are critical for Vpr incorporation into HIV-1 virions.

Amino Acid Sequence↗
PubMed1995

An improved method for purifying human thymic dendritic cells.

Thymic dendritic cells (DC) play a prominent role in the immune response as they constitute a key element involved in the maturation of thymocytes in the thymus. Human thymic DC, like DC from other lymphoid organs, represent a minor cell population (< 2%) of the thymus. Since these cells cannot replicate in vitro, the development of efficient purification methods is an essential prerequisite for extensive functional studies. DC express high levels of HLA-DR, a cell surface marker of the MHC class II antigen which is not exclusive to DC. Since no specific human thymic DC marker has been identified so far, DC purification methods are mainly based on depletion of particular subgroups of cells. We report here an improved method for purifying human thymic dendritic cells. In contrast to prior work, CD2+ thymocytes were first depleted by rosetting with neuraminidase treated sheep red blood cells. The nonrosetted cells were separated in a Percoll gradient, and the low-density cells were subsequently depleted of nondendritic cells by using thymocyte and macrophage specific monoclonal antibodies and either magnetic bead depletion or cytofluorometry. Cell populations (18-55 x 10(6) cells) obtained following magnetic bead purification were at least 80% HLA-DR+/CD2- and exhibited ultrastructural morphological features and functional activities such as those described previously for thymic DC. This improved method was compared with different purification approaches that use various combinations of cell density-based separation techniques and cell surface specific markers antibody reactivity. The magnetic beads depletion approach provided higher yields.

Antibodies, Monoclonal↗
PubMed1995

Mutagenic analysis of human immunodeficiency virus type 1 Vpr: role of a predicted N-terminal alpha-helical structure in Vpr nuclear localization and virion incorporation.

The Vpr gene product of human immunodeficiency virus type 1 is a virion-associated protein that is important for efficient viral replication in nondividing cells such as macrophages. At the cellular level, Vpr is primarily localized in the nucleus when expressed in the absence of other viral proteins. Incorporation of Vpr into viral particles requires a determinant within the p6 domain of the Gag precursor polyprotein Pr55gag. In the present study, we have used site-directed mutagenesis to identify a domain(s) of Vpr involved in virion incorporation and nuclear localization. Truncations of the carboxyl (C)-terminal domain, rich in basic residues, resulted in a less stable Vpr protein and in the impairment of both virion incorporation and nuclear localization. However, introduction of individual substitution mutations in this region did not impair Vpr nuclear localization and virion incorporation, suggesting that this region is necessary for the stability and/or optimal protein conformation relevant to these Vpr functions. In contrast, the substitution mutations within the amino (N)-terminal region of Vpr that is predicted to adopt an alpha-helical structure (extending from amino acids 16 to 34) impaired both virion incorporation and nuclear localization, suggesting that this structure may play a pivotal role in modulating both of these biological properties. These results are in agreement with a recent study showing that the introduction of proline residues in this predicted alpha-helical region abolished Vpr virion incorporation, presumably by disrupting this secondary structure (S. Mahalingam, S. A. Khan, R. Murali, M. A. Jabbar, C. E. Monken, R. G. Collman, and A. Srinivasan, Proc. Natl. Acad. Sci. USA 92:3794-3798, 1995). Interestingly, our results show that two Vpr mutants harboring single amino acid substitutions (L to F at position 23 [L23F] and A30F) on the hydrophobic face of the predicted helix coded for relatively stable proteins that retained their ability to translocate to the nucleus but exhibited dramatic reduction in Vpr incorporation, suggesting that this hydrophobic face might mediate protein-protein interactions required for Vpr virion incorporation but not nuclear localization. Furthermore, a single mutation (E25K) located on the hydrophilic face of this predicted alpha-helical structure affected not only virion incorporation but also nuclear localization of Vpr. The differential impairment of Vpr nuclear localization and virion incorporation by mutations in the predicted N-terminal alpha-helical region suggests that this region of Vpr plays a role in both of these biological functions of Vpr.

Amino Acid Sequence↗
PubMed1995

Neuroleptic associated tardive dyskinesias in young people with psychoses.

BACKGROUND: Apart from ageing, the factors associated with vulnerability to the emergence of tardive dyskinesia are poorly defined. METHOD: Risk factors associated with the presence of a chronic choreic or dystonic disorder were assessed in a cross-sectional comparison of anamnestic and clinical data in a homogeneous group of 64 young psychotic patients (under 40 years of age) on chronic low to moderate doses of neuroleptics. RESULTS: Dyskinetic subjects presented more indirect indicators of occult brain damage, such as a perinatal event or traumatic brain injuries in infancy and early childhood; neurological examination showed more anomalies in dyskinetic patients than in nondyskinetics, with a higher prevalence of facial release reflexes. CONCLUSION: These data may support the hypothesis that occult acquired brain damage is important in the genesis of this 'drug-induced' disorder.

Adult↗
PubMed1995

Rural Minnesota family physicians' attitudes toward telemedicine.

This study reports the results of an assessment of the attitudes and opinions of rural Minnesota family physicians toward telemedicine. The results of 52 mail surveys and 32 telephone interviews were compiled to determine existing attitudes and levels of awareness concerning aspects of telemedicine. Surveyed physicians overwhelmingly agreed that they do not have sufficient information about telemedicine. Their awareness of telemedicine's applications and capabilities is minimal. Also, responding physicians indicated little knowledge regarding such important issues as cost-effectiveness, reimbursement, liability, and potential primary care benefits. In general, however, physicians' attitudes toward telemedicine were favorable. This information should be important to funders, suppliers, and potential users of telemedicine. This study suggests a need to educate medical students, residents, and practicing physicians about telemedicine and issues related to its use.

Attitude of Health Personnel↗
PubMed1995

Retirement of senior physicians in rural Minnesota. Factors influencing physicians' plans to retire.

The demand for physicians in rural Minnesota is likely to increase significantly over the next few years. Nearly 20% of all rural physicians in Minnesota are older than age 65. This paper reports the results of a survey of rural Minnesota physicians over age 60 on their current practices and their plans for retirement. Of the 33 physicians questioned, 25 (75%) currently had plans to retire and more than half of the 25 planned to retire in the next two years. Factors that these physicians perceived as important in determining their decisions to retire or continue practice are described, and implications for the delivery of health care in rural communities are discussed.

Aged↗
PubMed1995

Experimental bias in the evaluation of the cellular transient expression in DNA co-transfection experiments.

beta-Galactosidase (beta-gal) expressing vectors are commonly used to standardize the transfection efficiency in transient expression experiments. In the Chinese hamster ovary (CHO) cell line, we transfected beta-gal expressing vectors in combination with different plasmid DNAs. We reported here that the presence of specific DNAs led to statistically significant variations in the beta-gal expression level. Therefore, the measure of beta-gal activity is not necessarily an accurate method to monitor transfection efficiency, and its use to normalize the expression from reporter genes could be questionable.

Animals↗
PubMed1994

Recruitment of family physicians in rural practice.

We report the results of a study to find out how rural family physicians choose their practice location--information that could allow physicians and practices to be more appropriately and easily matched. We interviewed rural family physicians who completed a Minnesota residency in 1990 or 1991 to determine what factors influenced their final practice selection. The survey revealed that partners in practice are physicians' greatest concern, followed by geographic location, recreational activities, call schedule, and opportunities for spouse and children. Despite numerous available practice options, it was difficult for physicians to find practices and communities that met the majority of their personal, professional, and familial needs. This study suggests a need for a physician placement network that would increase retention and help ease the current health care provider shortage in rural Minnesota.

Career Choice↗
PubMed1993

Sequence and expression of a gene encoding a protein with RNA-binding and glycine-rich domains in Brassica napus.

A cDNA clone and its genomic counterpart were isolated from Brassica napus. The encoded protein, BnGRP10, is composed of two modules, the first one is homologous to many RNA-binding domains of ribonucleoproteins, and the second is 73% glycine rich. Northern analysis shows that this gene is expressed only in roots and stems and is slightly induced by different stress conditions.

Amino Acid Sequence↗
PubMed1993

Long-range mapping of the 11q23 region involved in chromosome aberrations in human tumors by pulsed-field gel electrophoresis with a yeast artificial chromosome.

We have previously demonstrated that the RCK gene involved in t(11;14)(q23;q32) and the more centromeric MLL/ALL1 gene involved in t(4;11)(q21;q23) and t(11;19)(q23;p13) are localized on different adjacent NotI fragments by using pulsed-field gel electrophoresis (PFGE) analysis with the yeast artificial chromosome (YAC) clone yB22B2. The PFGE analysis using the YACs of YTY17 containing the prophobilinogen deaminase (PBGD), CBL2 and THY1 genes and yB22B2 allowed the following ordering of genes and breakpoints from CD3 to THY1 on 11q23: cent-CD3-ALL/MLL1-RCK-PBGD-CBL2-THY1, and the establishment of a long-range restriction map covering these genes. In addition, we showed that the FLI1 region involved in the t(11;22)(q24;q12) in Ewing's sarcoma was more telomeric region that the THY1 gene by analyzing somatic cell hybrids carrying the 11q- and/or 14q+ chromosome of the t(11;14)(q23;q32) translocation, and by PFGE analysis of the YAC clone YTY17.

Acute Disease↗
PubMed1993

Biochemical and morphological characterizations of DU-145 cell mortality in rabbit embryo-fetal fluid.

Rabbit embryo-fetal fluid (EFF) contains regulatory factors of cell proliferation which increase the duration of the cell cycle, induce a quiescent status in some cells and lead up to cell death in others. The objective of this study was to demonstrate which of the two processes, namely necrosis or apoptosis, was responsible for the cell death. Inhibitors of protein synthesis, and nuclease and phospholipase A2 activities did not restore the viability of the cells treated with EFF. Using a combination of DNA labelling and extraction, it was possible to show that a large proportion of DNA was fragmented in the cells released in the supernatant while only a very small portion of DNA was fragmented in the monolayer cells. EFF did not induce fragmentation of DNA into nucleosome-sized subunits as analysed using polyacrylamide gel electrophoresis. Nevertheless, using cytofluorometric analysis, it was possible to demonstrate that 50% of the cells released in the supernatant contained a lower quantity of DNA per cell than in the control cells. This was also observed with EFF-treated monolayer cells but not in the control monolayer cells. The reduction of the DNA content per monolayer cell became significant at 48 h of treatment with EFF. Electron microscopic analysis did not reveal blebbing of the cells. However, depletion of glycogen, condensation of mitochondria and increasing number of lysosomes and residual bodies were observed upon treatment with EFF. From these experiments we conclude that the DU-145 cells treated with EFF do not die by apoptosis, but rather seem to die by necrosis.

Animals↗
PubMed1993

Expression and DNA rearrangement of proto-oncogenes in Cas-Br-E-induced non-T-, non-B-cell leukemias.

The Cas-Br-E murine leukemia virus is a non-defective retrovirus that induces non-T-, non-B-cell leukemias in susceptible NIH/Swiss mice. A collection of tumors was examined for genomic DNA structure and RNA expression of known or putative proto-oncogenes and one tumor-suppressor gene, with the aim of identifying genes involved in Cas-Br-E-induced non-T-, non-B-cell leukemogenesis. Fli-1, p53, and Evi-1 were found to be rearranged in 72%, 23%, and 18% of the tumors, respectively, whereas no DNA alteration were detected for c-myc, c-myb, Pim-1, Evi-2, and EpoR genes. Evi-1 rearrangements are rarely associated with p53 or Fli-1 alterations. However, rearrangements of these last two genes are very often associated within the same tumor. Moreover, patterns of coordinated expression of critical cell growth-regulating genes are consistently associated with specific tumor types. These data suggest that Cas-Br-E can induce two types of hematopoietic neoplasias by different mechanisms.

Animals↗
PubMed1992

Analysis of proviruses integrated in Fli-1 and Evi-1 regions in Cas-Br-E MuLV-induced non-T-, non-B-cell leukemias.

The DNAs of the Cas-Br-E MuLV-induced leukemias always contain somatically acquired mink cell focus-forming (MCF) recombinant proviruses. MCF recombinants could be involved during leukemogenesis at both preleukemic times and in late-stage tumors. Among the Cas-Br-E-induced non-T-, non-B-cell leukemias, viral integrations were found in the Fli-1 and Evi-1 region in 71% (36 out of 51) and 22% (16 out of 72) of the tumors analyzed, respectively. As an approach to evaluate the contribution of Cas-Br-E MCF recombinant formation in cis-activation of proto-oncogenes, we analyzed the structure of the Fli-1- and Evi-1-associated proviruses by Southern blot hybridization. In Fli-1, we found that the proviruses, ecotropic as well as MCF, are all integrated within a very short DNA region immediately upstream of the initiator ATG, toward the 3' end of a 5' exon (Ben-David, Giddens, Letwin, and Bernstein, 1991, Genes Dev. 5, 908-918). All proviruses are oriented the same way, in the 5' to 3' transcriptional sense. Both provirus types are able to direct the Fli-1 expression to the same extent presumably via a promoter insertion mechanism. Most of the proviruses had no detectable deletion and contained both 5' and 3' LTR sequences with similar U3 sequences. MCF recombinants did not show any selective advantage over ecotropic proviruses for the Fli-1 locus since the frequency of ecotropic to MCF-recombinant virus at the Fli-1 locus was identical to that observed at any other locus. This suggests that the formation of these MCF recombinants is not essential for activation of Fli-1 and that ecotropic Cas-Br-E already possesses the required sequences for full cis-activation of Fli-1. On the other hand, in Evi-1, there is a strict selection for ecotropic proviruses. Presumably, viral genetic elements outside of the U3 region could be critical for the Evi-1 cis-activation.

Animals↗