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Biomedical subjects

J F Nicolas

Publications and source records attributed to J F Nicolas.

At least 127 records · Page 7Linked to original sources
PubMed1991

Activator-dependent and activator-independent defective recombinant retroviruses from bovine leukemia virus.

The replication-competent bovine leukemia virus (BLV) has been modified for use as a vector for foreign genes. The gag, pol, env, and pX regions of the virus were replaced by an exogenous nuclear location signal LacZ (nlsLacZ) or SVnlsLacZ gene. Transfection of the ovine cell line FLK-BLV, which expresses all BLV proteins from a wild-type provirus, with this viral DNA resulted in a viral titer of 10(4) CFU/ml. The inclusion of a large portion of the gag region did not significantly increase the titer. Both activator-dependent and activator-independent retroviruses were constructed. In activator-dependent vectors, the expression of the insert was dependent on the presence of the Tax protein, which activated the BLV long terminal repeat. In activator-independent vectors, the expression of the insert was constitutive because of the presence of an internal promoter. Infections with the recombinant retrovirus were inhibited by specific neutralizing antibodies. The structure of the transduced genetic material was not rearranged. BLV vectors encoding a reporter nlsLacZ gene, the product of which can be detected in single cells, greatly simplified studies of their biological properties. Determination of the host range of BLV vectors established that BLV-based recombinant retroviruses are effective in the transduction of genes in a variety of species and cell types.

Animals↗
PubMed1991

Interleukin-4 stimulates collagen synthesis by normal and scleroderma fibroblasts in dermal equivalents.

Interleukin-4 (IL-4) is one of the products of T-lymphocytes and mast cells, inflammatory cells which accumulate in connective tissues at early stages of fibrosis. We tested the effects of IL-4 on human fibroblasts from normal and scleroderma skin seeded in three dimensional collagen lattices ("dermal equivalents"). IL-4 (10 and 100 U/ml) stimulated collagen synthesis in a dose-dependent manner. No significant alteration of lattice retraction and cell proliferation was observed. At the concentration 100 U/ml, Il-4 was approximately twice more efficient on collagen synthesis than Transforming Growth Factor beta (10 ng/ml). IL-4 secretion in connective tissues might be an important factor for the development of fibrotic processes.

Cells, Cultured↗
PubMed1990

Xenotropic and amphotropic pseudotyped recombinant retrovirus to transfer genes into cells from various species.

The ability to transfer genes into cells from different species with murine recombinant retroviruses was evaluated with the SVnls LacZ reporter gene. Mouse and cat packaging cell lines can be used to transfer amphotropic pseudotype, in human, mouse, cat, rabbit, sheep, horse and beef cells and with a very low efficiency in pig and avian cells. Xenotropic pseudotype recombinant retroviruses, produced in cat and rabbit packaging cell lines, transferred genes with the same efficiency as amphotropic retroviruses in human, cat, rabbit and sheep cells. In contrast to amphotropic retroviruses, xenotropic retroviruses infect beef, pig and horse cells with a high efficiency. These results emphasize the need to determine carefully the producer cell line (the type of helper virus and the species origin of the cell) for efficient transfer of genes in cells and embryos.

Animals↗
PubMed1990

Porphyria cutanea tarda after allogeneic bone marrow transplantation for chronic myelogenous leukemia.

A case of porphyria cutanea tarda (PCT) occurring after bone marrow transplantation (BMT) is reported. A 43-year-old male with chronic myelogenous leukemia received an human leukocyte antigen (HLA)-identical allogeneic transplantation with T-cell depleted marrow. Because of graft rejection, a second transplant was performed 4 months later. A grade II acute graft- vs.-host disease and a cytomegalovirus (CMV) infection were subsequently observed. Two years after the second transplant, cutaneous symptoms of PCT with typical biochemical abnormalities developed. Liver biopsy revealed signs of hepatitis with iron overload. CMV was isolated from liver tissue. The possible roles of underlying disease, BMT, and CMV liver disease are discussed in view of the recently reported cases of PCT in patients with AIDS or hematological disorders.

Bone Marrow Transplantation↗
PubMed1990

Patterns of expression of position-dependent integrated transgenes in mouse embryo.

The abilities to introduce foreign DNA into the genome of mice and to visualize gene expression at the single-cell level underlie a method for defining individual elements of a genetic program. We describe the use of an Escherichia coli lacZ reporter gene fused to the promoter of the gene for hypoxanthine phosphoribosyl transferase that is expressed in all tissues. Most transgenic mice (six of seven) obtained with this construct express the lacZ gene from the hypoxanthine phosphoribosyltransferase promoter. Unexpectedly, however, the expression is temporally and spatially regulated. Each transgenic line is characterized by a specific, highly reproducible pattern of lacZ expression. These results show that, for expression, the integrated construct must be complemented by elements of the genome. These elements exert dominant developmental control on the hypoxanthine phosphoribosyltransferase promoter. The expression patterns in some transgenic mice conform to a typological marker and in others to a subtle combination of typology and topography. These observations define discrete heterogeneities of cell types and of certain structures, particularly in the nervous system and in the mesoderm. This system opens opportunities for developmental studies by providing cellular, molecular, and genetic markers of cell types, cell states, and cells from developmental compartments. Finally this method illustrates that genes transduced or transposed to a different position in the genome acquire different spatiotemporal specificities, a result that has implications for evolution.

Animals↗
PubMed1990

Response of discoid and subacute cutaneous lupus erythematosus to recombinant interferon alpha 2a.

Ten patients suffering from discoid lupus erythematosus (DLE) or subacute cutaneous lupus erythematosus (SCLE) were treated with interferon alpha 2a. A marked improvement or clearing of cutaneous lupus erythematosus lesions was observed in eight of them. However, the response to interferon was of short duration and within a few weeks after interferon withdrawal all patients who were improved or cleared relapsed. This study suggests that interferon alpha 2a represents a new interesting approach in the treatment of DLE and SCLE. Ongoing trials will define the optimal treatment schedule for the maintenance of interferon-induced improvement of cutaneous lupus erythematosus.

Dose-Response Relationship, Drug↗
PubMed1990

Recombinant interferon alpha 2a is effective in the treatment of discoid and subacute cutaneous lupus erythematosus.

Ten patients suffering from either discoid lupus erythematosus (DLE) or subacute cutaneous lupus erythematosus (SCLE) were treated with interferon alpha 2a. Eight received low or intermediate doses (18-45 x 10(6) U/week) for a short period of time (4-8 weeks), with marked improvement of skin lesions in six, an exacerbation in one patient and no change in the other. Two patients with SCLE received high doses (100-120 x 10(6) U/week) over 12 weeks, with complete clearing of the lesions in one and a marked improvement in the other. The responses were of short duration and within a few weeks of stopping treatment all who had improved or cleared relapsed. The side-effects in all the patients were fever and a flu-like syndrome which necessitated a reduction of the dose in one case. In two patients there were increases in the liver enzyme levels, but no haematological toxicity was noted.

Adult↗
PubMed1990

Skin ageing and immune competence.

Ageing is associated with impairment of immune function, the most significant changes being a decrease in T-cell-mediated immunity and antibody-mediated effector functions, and an increase in autoantibodies and other dysregulatory phenomena, such as an abnormal production of monoclonal antibodies and other immune complexes. Elderly subjects are increasingly susceptible to cutaneous pathological changes that are known to correlate with immune deficiencies, such as viral and fungal infections, and skin cancers. Antigenic responses in skin may be an indicator of immune status. The recall antigens elicit fewer delayed-type hypersensitivity reactions in the elderly, particularly in subjects over 75 years old. Sensitivity to contact allergens, such as dinitrochlorobenzene, and inflammatory responses and the cutaneous response to histamine are reduced in the elderly. The pathophysiology of deficiencies in the skin's immune system in the elderly is not clear; it probably reflects not only a general decline in the immune system but also more specific changes. Age-related changes in epidermal immune functions have been observed, such as morphological and functional changes in Langerhans cells and decreased production of various cytokines. Evaluation of these changes is difficult and the results may be disputed, but it is probable that sun-induced ageing plays an important role. Few substances seem to be capable of stimulating the immunoactive cells of the skin or of modifying the production of epidermal cytokines. One possibility may be vitamin A and its derivatives, and studies of other molecules such as interferons are being carried out.

Aged↗
PubMed1990

Activation of a beta-galactosidase recombinant provirus: application to titration of human immunodeficiency virus (HIV) and HIV-infected cells.

A quantitative bioassay for human immunodeficiency viruses has been developed on the basis of the ability of the tat gene to transactivate the expression of an integrated beta-galactosidase gene in a HeLa-CD4+ cell line. Infection by a single virion of HIV-1 or HIV-2 corresponds to a unique blue syncytium or a cell cluster detected after fixation and addition of 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (a beta-galactosidase substrate). The number of infected lymphoid cells in a culture (stimulated human peripheral blood lymphocytes and cell lines) can also be quantified by cell-to-cell transmission of HIV into the HeLa-CD4(+)-beta-galactosidase monolayer. Infections by simian immunodeficiency viruses are similarly detected. This assay has been used to determine the dose response of drugs, the half-life of HIV at 37 degrees C, and the appearance of infectious particles after virus infection.

Blotting, Southern↗
PubMed1990

Hox-2.3 upstream sequences mediate lacZ expression in intermediate mesoderm derivatives of transgenic mice.

The mouse Hox-2.3 gene contains an Antp-like homeobox sequence and is expressed in a spatially restricted anteroposterior domain during development. To study the molecular basis of this differential gene regulation, we set out to characterize the cis-regulatory elements mediating Hox-2.3 expression during embryogenesis. We show that a fragment extending 1316 base pairs (bp) upstream of the transcription start site, thus corresponding to the Hox-2.4/Hox-2.3 intergenic sequences is capable of mediating luciferase gene transcription in transfected cells in vitro and lacZ expression in transgenic mice. The beta-galactosidase-staining pattern in embryos was found to be strikingly similar to the Hox-2.3 in situ hybridization pattern in intermediate mesoderm derivatives: high levels of both Hox-2.3 transcripts and beta-galactosidase activity were found in the mesonephric duct-derived epithelium of the meso- and metanephric kidney and associated ducts, from the time these structures first appeared on throughout development. The transgene apparently lacks sequences needed for correct Hox-2.3 expression in somitic and lateral plate mesoderm and in neurectoderm. These results document the involvement of distinct regulatory elements in Hox gene expression in subsets of cells with distinct developmental fate, situated at similar positions along the anteroposterior axis of the embryo.

Animals↗
PubMed1990

Syncytium induction by fresh HIV isolates: quantitative analysis using a transactivation beta-gal assay.

We used a quantitative bioassay (the beta-gal assay) to visualize and quantify syncytium induction by fresh HIV isolates. This bioassay is based on the transactivation by tat of a chimeric gene comprising an HIV-1 long terminal repeat (LTR) fused to a modified lacZ gene of Escherichia coli. The chimeric gene encodes a beta-galactosidase which is translocated to the nucleus. It allows the enzymatic staining of all nuclei from HIV-induced syncytia. Using this unequivocal assay (the beta-gal assay), we could assess the syncytium-inducing properties of fresh HIV isolates after only 4 days of coculture of patient lymphocytes with activated normal lymphocytes. Syncytium-inducing HIV isolates were detected in 11 out of 40 seropositive patients studied. They were isolated mainly from AIDS patients: eight out of 17 grade IV (according to Centers for Disease Control criteria) patients were infected with syncytium-inducing strains. However, of 23 grade II and III patients tested, syncytium-inducing HIV strains were isolated from three cases. These three patients displayed no detectable p24 antigenaemia and had a CD4+ cell count of greater than 300 cells/microliter. The in vitro replication rate of HIV grown from 36 patient blood samples was then examined by sequential p24 antigen measurements in coculture supernatants. The 10 samples leading to syncytium formation also exhibited the highest replication rate. The possibility of unequivocally detecting syncytium-inducing strains after only a few days of coculture will make this detection routine and rapid. In addition, the limited period of amplification required is a significant advantage as it minimizes the emergence of HIV variants selected during long-term in vitro cultures.

Acquired Immunodeficiency Syndrome↗