Biomedical subjects

P Jolicoeur

Publications and source records attributed to P Jolicoeur.

At least 73 records · Page 4Linked to original sources

PubMed1996

Effect of adoptive transfer of CD4, CD8 and B cells on recovery from MHV3-induced immunodeficiencies.

A chronic viral infection can occur when the host fails to mount an effective immune response to clear the virus. Mouse hepatitis virus type 3 (MHV3) appears to be an excellent model for the study of the relationship between viral-induced immunodeficiency and chronic disease development. (C57BL/6 x A/J)F1 mice surviving acute hepatitis develop a chronic disease characterized by T- and B-cell immunodeficiencies, viral persistence in various organs including the brain, spleen and thymus, and death within 3 months postinfection (p.i.). We have reported that T- or B-cell deficiencies, observed in MHV3 chronically infected (C57BL/6 x A/J)F1 mice, can be partially or totally thwarted by adoptive transfer of CD4+, CD8+ and/or B cells, at 15 days p.i. in mice surviving the acute phase of the disease. Adoptive transfer of syngeneic CD4+ and/or CD8+ allowed a partial restoration of the T-cell deficiencies, as characterized by thymic atrophy, decrease in splenic T cells, and in all thymocyte subpopulations. B-cell immunodeficiency, as defined by a decrease in splenic B cells, as well as in the bone marrow pre-B- and B-cell compartments, and the occurrence of abnormally larger forms of bone marrow pre-B and B cells, were partially thwarted by B-cell treatment only. Splenic B cells and the bone marrow B-cell compartment, respectively, returned partially or totally to normal values, whereas the pre-B-cell compartment remained depleted in infected mice treated with B cells. Levels of all immunoglobulin classes returned to normal values in MHV3 chronically infected mice when treated with CD4+ in combination with CD8+ cells. All T- and/or B-cell treatments, however, were sufficient to thwart the process of the chronic disease, and favoured the survival of mice for up to 6 months p.i.

Animals↗

PubMed1996

Evidence that the murine AIDS defective virus does not encode a superantigen.

The T-cell receptor repertoire was analyzed in C57BL/6 mice upon infection with helper-free stocks of the pathogenic murine AIDS (MAIDS) defective virus in order to demonstrate if, as previously reported, this virus encodes a superantigen. A polyclonal T-cell stimulation involving T cells expressing multiple V beta subsets occurred within the first week of infection, while late in the disease we could note only a 50% deletion of V beta 5 CD8+ cells. Transfection of the MAIDS virus genomic DNA into fibroblasts and B cells expressing major histocompatibility complex class II molecules failed to show any stimulation of cells expressing the specific V beta (V beta 5) previously reported to respond to MAIDS virus-infected cells. In addition, mice lacking V beta 5 cells did not show any significant decrease in susceptibility to the disease compared with mice expressing V beta 5 and bred on the same genetic background. Our in vivo and in vitro results fail to demonstrate a role for a superantigen encoded by the MAIDS defective viral genome in the pathogenesis of MAIDS.

Animals↗

PubMed1996

The prion protein gene is dispensable for the development of spongiform myeloencephalopathy induced by the neurovirulent Cas-Br-E murine leukemia virus.

The Cas-Br-E murine leukemia virus (MuLV) induces paralysis in susceptible mice that is accompanied by a severe spongiform myeloencephalopathy. These neurodegenerative lesions are very similar to those observed in prion diseases. To determine whether the prion protein gene (Prn-p) product was a downstream effector of this neurovirulent MuLV, we inoculated Prn-p(-/-) knockout homozygote and control heterozygote or wild-type mice with this retrovirus. All groups developed typical paralysis and spongiform encephalopathy, and no differences in clinical or histological phenotypes were observed between these groups. These results indicate that the Cas-Br-E MuLV does not require the prion protein to induce lesions. Thus, MuLV and prion proteins may induce a very similar disease through distinct pathways, or the viral Env protein, which harbors the primary determinant of pathogenicity, may act in a common pathway but downstream of the prion protein.

Animals↗

PubMed1995

Fos proteins can act as negative regulators of cell growth independently of the fos transforming pathway.

The proto-oncogene c-fos is known to be an important positive regulator of cell growth and notably of the G0/G1 transition. However, we observed that v-fos or c-fos-transformed rat-1 fibroblasts paradoxically had a low growth rate as compared to control untransformed rat-1 cells. We determined that this slow growth mainly reflects an increase of the G1 phase of the cell cycle (up to fourfold). In addition, the G0 --> S progression of serum-starved fos-expressing rat-1 cells refed with serum was found to be also delayed as compared to rat-1 cells. The delayed G0 --> S progression in fos-expressing cells was accompanied by the inappropriate levels or kinetics of expression of several cell cycle-regulated genes (cyclin D1, cdc2, cdk2, cdk4 and rb). Furthermore, a clear uncoupling of the pRb hyperphosphorylation with the entry into S phase was found in these fos-expressing rat-1 cells. Interestingly, the effect of the Fos proteins on the cell cycle was independent of the fos transforming pathway, indicating that the effector genes for Fos proteins are likely to be different for each process. In conclusion, our results indicate that Fos proteins may act as negative regulators of cell growth in some cell types, independently of the fos transforming pathway.

Animals↗

PubMed1995

Establishment of leukemic T-cell lines from mice inoculated with the MAIDS defective virus.

Mice inoculated with replication-competent stocks of the murine acquired immunodeficiency syndrome (MAIDS) virus are severely immunocompromised and proned to the development of T- and B-cell lymphomas. We have studied the development of T-cell lymphomas in C57BL/6 and RF/J mice inoculated with helper-free stocks of the MAIDS defective virus. We observed the expansion of T cell clones (detected by TCR gene rearrangements and by transplantation) only rarely in diseased C57BL/6 mice and slightly more frequently in RF/J mice. We succeeded in establishing four transplantable T cell tumors and malignant cell lines. The three cell lines from RF/J mice were immature T-cells (Thy-1+, CD3-, CD4+, CD8+, Mac-1+), while the line from the C57BL/6 mouse had the phenotype of mature T-cells (Thy-1+, CD3+, CD4+, CD8-). All lines were virus-producers despite the fact that helper-free stocks of the virus were inoculated. These helper MuLVs most likely originated from endogenous MuLV sequences. Also, the defective viral genome was clearly detectable in one cell line and was rearranged in two other lines. These established cell lines may be useful to determine whether they share some of the characteristics of the anergic T-cells in vivo and to study the role of the MAIDS defective virus in T cell transformation.

Animals↗

PubMed1995

Impairment of bone marrow pre-B and B cells in MHV3 chronically-infected mice.

Mouse hepatitis virus type 3 (MHV3) appears to be an excellent model for the study of the relationship between viral-induced immunodeficiency and the development of chronic disease. Animal surviving acute hepatitis develop a chronic disease characterized by viral persistency in various organs, by a humoral immunodeficiency, and eventually die within the next three months postinfection. To verify if B cell immunodeficiency occurs during the chronic disease, percentage and absolute number of bone marrow B lineage cell subpopulations were recorded at various times postinfection (p.i.) in pathogenic L2-MHV3-infected (C57BL/6 x A/J) F1 mice. Absolute numbers of B (cmu+smu+) cells decreased as early as three days p.i. up to 15 days p.i., and then gradually returned toward normal values in L2-MHV3-infected mice during the chronic disease. In contrast, pre-B (cmu+smu-) cells were less significantly decrease during the chronic disease. In addition, abnormally enlarged cells (> 13 microns) were detected either in bone marrow pre-B or B cells from L2-MHV3-infected mice.

Animals↗

PubMed1995

Rotated object identification with and without orientation cues.

The time to name two-dimensional line drawings of objects increases linearly for object rotations between 0 degrees and 120 degrees from the upright. Several theories attribute these effects of orientation to finding the top or the top-bottom axis of objects. By this account, prior knowledge of the location of the top or the top-bottom axis of objects should diminish effects of object orientation when they are named. When this hypothesis was tested by cuing the top or the top-bottom axis, no reduction in the effects of orientation on object naming was found. This result is inconsistent with effects of orientation on object naming being due to finding the top or the top-bottom axis. Instead, the top may be found prior to rotational normalization of the object image.

Humans↗

PubMed1995

Prevention of breast tumour development in vivo by downregulation of the p185neu receptor.

Certain strains of transgenic mice that express the rat neu oncogene (neuT) in mammary epithelial cells develop breast tumours at an average of 44 weeks of age. In this study, intraperitoneal injection of a monoclonal anti-receptor antibody specific for the rat neuT oncogene product dramatically affected tumour development in these transgenic mice in a dose-dependent manner. A significant proportion (50%) of mice, when injected with anti-receptor antibodies, did not develop tumours even after 90 weeks of age. The phosphotyrosine levels of the membrane fraction of breast tissues in the anti-receptor antibody-treated mice were almost completely abolished when a higher dose of antibodies was used. This study demonstrates, for the first time, that immunologic manipulation of an oncogene product can effectively prevent the development of tumours in a rodent transgenic model.

Animals↗

PubMed1995

Mutational analysis of the murine AIDS-defective viral genome reveals a high reversion rate in vivo and a requirement for an intact Pr60gag protein for efficient induction of disease.

Pr60gag appears to be the only protein encoded by the murine AIDS (MAIDS)-defective virus. To study the role of Pr60gag or some other sequences of the viral genome in the pathogenicity of the virus, we have generated mutants of the defective viral genome. These mutant defective viruses, prepared as helper-free stocks, were inoculated into susceptible C57BL/6 mice. Mutant Du5H-A virus, which had a stop codon within gag MA(p15), did not induce target cell proliferation or MAIDS. Mutants Du5H-B and -C encoded truncated Pr60gag proteins containing, respectively, MA(p15)-p12 or MA(p15)-p12 and part of CA(p30). These mutants showed a very limited capacity to induce early cell expansion and were poorly pathogenic. Only recombinant (revertant) viruses were recovered from organs of diseased mice inoculated with these two mutants. Mutant Du5H-D was generated by deleting 1.4 kbp of the 3'-end sequences, outside the gag coding region. The levels of RNA and proteins made by this mutant were low. This mutant also reverting frequently but was nevertheless able to induce MAIDS at a low efficiency without reverting. Our results indicate that the Pr60gag protein is necessary and sufficient to induce MAIDS. These data also suggest that the Pr60gag protein needs to be relatively intact to be fully pathogenic. In addition, our study shows a very high reversion rate of some mutants and emphasizes the need to check for the presence of revertant (recombinant) viruses in diseased organs when working with mutants of the MAIDS-defective virus.

Animals↗

PubMed1995

The murine AIDS defective provirus acts as an insertional mutagen in its infected target B cells.

In susceptible mice, the murine AIDS (MAIDS) defective virus can induce marked expansion of its target cells, the majority of which belong to the B-cell lineage. This expansion, which appears to be critical for the development of the immunodeficiency syndrome, is initially polyclonal but becomes oligoclonal late in the disease, suggesting the involvement of a secondary genetic event(s) during this proliferation. To determine whether integration of the MAIDS defective provirus into particular regions of the cellular genome contributes to this oligoclonal expansion, we searched for common provirus integration sites in enlarged lymphoid organs of MAIDS mice. We identified two common proviral integration sites, Dis-1 and Dis-2, which were occupied by a defective provirus at frequencies of 20 and 13%, respectively. Our analysis revealed that the Dis-1 region corresponds to the Sfpil1 (Spi-1, PU.1) locus, which maps on chromosome 2, and encodes a transcription factor. Insertion of the MAIDS defective provirus into this region led to a two- to threefold increase in the expression of Sfpi1 RNA. The Dis-2 locus was found to map to mouse chromosome 11, between Hox2 and Scya. It appears to be a novel locus probably harboring a gene involved in B-cell proliferation. The present study indicates that the MAIDS defective provirus can act as an insertional mutagen, thus contributing to the oligoclonal expansion of infected cells. The detection of two common proviral integration sites, each of which targetted at a low frequency in diseased organs, suggests that the deregulation of a unique gene through provirus insertion is essential for neither proliferation of infected B cells nor development of the immunodeficiency syndrome.

Animals↗

PubMed1994

Impaired T and B cell subpopulations involved in a chronic disease induced by mouse hepatitis virus type 3.

A chronic viral infection can occur when the host immune system fails to detect the viruses. Mouse hepatitis virus type 3 (MHV3) seems to be an excellent model for the study of the relationship between viral-induced immunodeficiency and the development of chronic disease. Animals that survive acute hepatitis develop a chronic disease characterized by viral persistency in various organs, including the brain, spleen, and thymus, and they eventually die within the next 3 mo postinfection (p.i.). To verify whether T and B cell immunodeficiency occurs either in the acute or chronic phase of the disease, the percentage and absolute number of splenic T and B lymphocytes, thymic T, or bone marrow B-lineage cell subpopulations were recorded at various times p.i. in pathogenic L2-MHV3-infected and nonpathogenic YAC-MHV3-infected (C57BL/6 x A/J) F1 mice. Splenic T and B cells were depleted as early as 48 h p.i., and maintained at low levels for up to 3 mo until death of mice. Such depletions resulted from thymic depletion in all T cell subpopulations, and in B (cytoplasmic micro-chain+ and surface micro-chain+) lymphocytes only in the bone marrow of pathogenic L2-MHV3-infected mice. In vitro studies of purified thymic stromal cells have produced a nonproductive L2-MHV3 replication with a low viral transmission to complexed thymocytes. However, pre-B and B cells have supported a productive viral replication, generating abnormal forms, which leads to cell lysis. These results are discussed in relation to viral persistency in the brain and lymphoid cells, which results from a chronic impairment of cellular and humoral immune mechanisms that are involved in the viral elimination process.

Animals↗

PubMed1994

Herpes simplex virus type 1 pathogenicity in mice expressed by lytic infection in pre-B and B cells.

The outcome of herpes simplex virus type 1 (HSV-1) infection in human or in the murine model can be influenced by host immunocompetency. We postulate in this work that HSV-1 infection alters bone marrow B lymphopoiesis in genetically determined susceptible mice. To verify this hypothesis, resistant C57BL/6 or susceptible A/J adult mice were intraperitoneally infected with HSV-1 (McIntyre strain). At various postinfection times, spleen and bone marrow were collected from both infected mouse strains. B lineage cell subpopulations were identified by double immunofluorescence assays using mAbs to terminal deoxynucleotidyl transferase (TdT), 220-kDa surface membrane glycoprotein (detected by mAb 14.8), and cytoplasmic (c mu) or surface (s mu) IgM chains. Results revealed a decrease in both percentage and absolute number of splenic B (c mu+, s mu+) cells and bone marrow pre-B (c mu+, s mu-) and B cells isolated only from susceptible A/J mice. No effect was observed on pro-B (14.8+, c mu-) or TdT+ precursor cells from both mouse strains. Intracellular viral proteins were detected in pre-B and B cells in in vivo-infected susceptible A/J mice. In vitro studies also revealed that virus-induced cell lysis occurred in purified splenic and bone marrow pre-B or B cells derived only from susceptible A/J mice. Viral tropism for pre-B and B cells represents another immunodeficiency mechanism involved in the genetic sensitivity to HSV-1.

Animals↗

PubMed1994

The Myb and Ahi-1 genes are physically very closely linked on mouse chromosome 10.

Ahi-1 has previously been identified as a common helper provirus integration site on mouse Chromosome (Chr) 10 in 16% of Abelson pre-B-cell lymphomas and shown to be closely linked to the Myb protooncogene. By using long-range restriction mapping, we have mapped the Myb and Ahi-1 regions within a 120-kbp DNA fragment. The Ahi-1 region is located approximately 35 kbp downstream of the Myb gene. A further confirmation of this finding was obtained by screening a mouse YAC library. The three positive clones obtained contained both the Myb and Ahi-1 gene sequences. To test whether provirus integration in the Ahi-1 region enhances the expression of Myb by a cis-acting mechanism, we have also examined Myb gene expression in A-MuLV-induced pre-B-lymphomas. Our data have revealed that there is no clear evidence for such activation in the tumors we have tested, indicating that provirus insertion in the Ahi-1 region is activating a novel gene, apparently involved in tumor formation.

Animals↗

PubMed1994

Early expression of human CD4 delays thymic differentiation in transgenic mice.

CD4 is a cell surface molecule expressed mostly on cells of the T-cell lineage. Studies have shown that this molecule plays an important role in positive and negative selection of T cells in the thymus. It is not surprising therefore, that in T-cell ontogeny, CD4 starts to be expressed on thymocyte subpopulations about to undergo these selection processes. The human CD4 molecule was expressed in mouse thymus ontogeny using a promoter, MMTVD, which targets expression as early as day 14 of ontogeny, prior to expression of endogenous TCR, CD4 and CD8. Thymic ontogeny is delayed in foetal MMTVD-CD4 mice. Human CD4-expressing thymuses show a twofold reduction in cellularity at days 17 and 18 of ontogeny compared with non-transgenic control littermate thymuses, and paradoxically, MMTVD-CD4 thymuses contain more cells in the S and G2/M stages of the cell cycle than control thymuses do. At the cell surface marker level, MMTVD-CD4 thymocytes show a delay in surface expression of CD3, murine CD4 and murine CD8, along with persistent expression of IL2R alpha compared with foetal non-transgenic littermates. Biochemical studies show that, although MMTVD-CD4 thymocytes do not express surface CD3, cytoplasmic CD3 epsilon proteins as well as TCR beta incomplete and complete transcripts are present in foetal day-17 thymocytes. Low levels of surface CD3/TCR expression, however, could partly be due to the low levels of zeta mRNA and proteins detected in these cells. These results suggest that CD4 is not expressed until a certain stage of differentiation not only because it is not yet required for selection processes, but because it can lead to a reversible deregulation of thymocyte development.

Animals↗

PubMed1994

Evidence against early selection: stimulus quality effects in previewed displays.

H. Pashler (1984) reported that when subjects identified a probed letter in a display of 8 characters, the effect of stimulus quality on reaction time persisted full blown even when subjects had 300 ms to preprocess the display. Pashler argued that these results are incompatible with theories of late selection but that they are naturally accommodated by theories of early selection. The authors report 14 experiments using Pashler's methodology in which the effects of stimulus quality were reliably attenuated with a preview of the letter array. Pashler's results were also replicated, but only under a narrow set of conditions. Several "early selection" accounts of the interaction of probe delay with stimulus quality were examined and rejected in favor of a late selection account.

Adult↗

PubMed1994

Can mental rotation occur before the dual-task bottleneck?

The effect of character disorientation on mirror-normal judgments was found to be partially attenuated with increasing task overlap with a preceding tone-frequency discrimination judgment. These results suggest that orientation-sensitive processing, used to prepare disoriented stimuli for mirror-normal discrimination, can be initiated and proceed in parallel with mental activities required for a tone-frequency discrimination task. The attenuation indicates that at least some of the orientation effect on mirror-normal discriminations has its locus prior to the dual-task processing bottleneck. The possibility that the partial attenuation of the orientation effect was due to attenuation of the effect of orientation on character identification, but not on the mental rotation required for mirror-normal judgments, was examined and rejected.

Adolescent↗

PubMed1994

Manipulating the shape of distance effects in visual curve tracing: further evidence for the zoom lens model.

The time required to determine that two dots occur on the same curve in a visual display increases with increasing interdot curve distance. McCormick and Jolicoeur (1991) presented a model of visual curve tracing in which a local operator with a variable size receptive field tracks the curve segment intervening the two dots. In this model, human response time can be predicted by counting the number of shifts of the receptive field needed to trace the curve segment. The present study re-examined the predictive power of the zoom lens curve tracing model by selectively manipulating distractor proximity in four conditions and regressing the predictions of the model on human response time. The model was compared with two other curve tracing models, pixel by pixel tracing, and Jolicoeur, Ullman and MacKay's (1991) bipartite receptive field operator. The results provided strong support for McCormick and Jolicoeur's (1991) visual attention based zoom lens operator.

Adult↗

PubMed1994

Impact of quality of the image, orientation, and similarity of the stimuli on visual search for faces.

Evidence from a series of visual-search experiments suggests that detecting an upright face amidst face-like distractors elicits a pattern of reaction times that is consistent with serial search. In four experiments the impact of orientation, number of stimuli in the display, and similarity of stimuli on search rates was examined. All displays were homogeneous. Trials were blocked by distractor type for three experiments. In the first experiment search rates for faces amidst identical faces rotated by 180 degrees were examined. No advantage was evidenced in searching for an upright face. The impact of the quality of the face representation was examined in the second experiment. Search rates are reported for a line-drawn and a digitized image of a face amidst identical faces rotated by 180 degrees. Search was faster for digitized than for line-drawn faces. The findings of the first experiment for orientation were replicated. In the third and fourth experiments the impact of disrupting the facial configuration in distractors was examined and performance was contrasted for blocked and mixed trials, respectively, with the same stimulus set. Reaction times increased with the number of distractors in the display in all but the nonface condition, which produced a shallow slope suggestive of parallel search. Search amidst other distractors appeared to involve the conjoining of a specific set of features with specific spatial relations. The hierarchy of relevant configural dimensions was inconsistent across these two experiments, suggesting that the symmetry, top-down order of features, orientation of the face, and predictability of the distractor type may have an interactive effect on search strategies.

Agnosia↗