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J F Nicolas

Publications and source records attributed to J F Nicolas.

At least 163 records · Page 9Linked to original sources
PubMed1988

[Severe psoriasis induced by chloroquine (nivaquine)].

The adverse effects of a variety of drugs on psoriasis are well documented, and they generally result in aggravation of the disease. We report the case of a 75-year old man who developed a psoriatic erythroderma and a generalized pustular psoriasis two weeks after the beginning of an antimalarial treatment. The psoriasis responded poorly to etretinate alone, and an etretinate-methotrexate combination was needed to cure the patient. Some psoriasis vulgaris plaques persisted for six months after the acute complication. Thus, chloroquine should be entered in the list of drugs which may induce psoriasis.

Aged↗
PubMed1988

[Toward an unpublished method of detecting human retroviruses: activation of HIV-1 LacZ recombinant provirus by the tat gene product].

For a few of retroviruses, the level of synthesis of viral proteins is greatly increased in the presence of a transactivator gene which is encoded by the virus. For instance, for HIV, TAT acts on target sequences present in the viral long terminal repeat (LTR). HIV-1 recombinant retrovirus (RRV), where the gag, pol and part of env genes have been exchanged for the reporter nlsLacZ gene, expresses the reporter gene only in presence of TAT. When the RRV is tat defective, this activity can be complemented by tat present on a second molecule. The expression of nlsLacZ can then be detected by a simple histochemical staining. If this complementation can also be provided by a wild type virus, then their detection and titration would be greatly simplified.

Genes, Viral↗
PubMed1987

Relationship of B cell Fc receptors to T cell recognition of Mls antigen.

The Mls locus on chromosome 1 controls the expression of cellular determinants that are responsible for stimulating mixed lymphocyte reactions between H-2-identical strains. However, the biochemical nature of Mls antigenic determinants remains undefined. It has been proposed that Ly-17 lymphoid cell surface antigens (also known as Ly.m.20.2 and LyM-1) and Mls antigens could be identical because they are both encoded by loci on chromosome 1 and display similar tissue distribution. The Ly-17 locus encodes polymorphic alleles of the IgG Fc receptor (Fc gamma R). In the present study, two approaches were used to address the question of whether Fc gamma R are involved in T cell recognition of Mls antigen. In the first approach we tested the effect of Fc gamma R blockade by heat-aggregated mouse IgG or anti-Fc gamma R monoclonal antibodies (2.4.G2) on the ability of an Ia+, Fc gamma R+ Mlsa-expressing B cell hybrid (LBB.3.4.16) to stimulate interleukin 2 secretion by an anti-Mlsa-specific T cell hybrid. We show that blockade of Fc gamma R does not inhibit the Mlsa-specific stimulation of T cells during a 24-h culture period in which Fc gamma R remain blocked. In the second approach, we derived irradiation-induced variants of LBB.3.4.16 to dissociate Fc gamma R expression and Mls antigen expression. We describe 2 LBB variants which no longer stimulate Mlsa-reactive T cells but do express Fc gamma R. Compared to parental LBB cells, the capacity of variant LBB cells to present soluble antigen to Ia-restricted T cells is unaffected. Collectively, these results indicate that Fc gamma R expression and Mlsa antigen stimulation can be dissociated. We conclude that Fc gamma R expression may be necessary, but not sufficient for T cell recognition of Mls antigen.

Animals↗
PubMed1987

A beta-galactosidase hybrid protein targeted to nuclei as a marker for developmental studies.

The Escherichia coli lacZ gene has been used as an indicator gene for the study of cell lineage in vivo. To adapt this marker for gene expression studies, a sequence encoding a modified beta-galactosidase and including the simian virus 40 large tumor nuclear location signal (nls-beta-Gal) has been introduced into vectors. In differentiated cells, multipotential cells, and embryos, the constructs led to the expression of an enzymatically active protein. Its location was examined by its beta-galactosidase activity or by using antibodies and electron microscopy. The results show that the nls-beta-Gal protein remains mainly located at the nuclear periphery (probably at the nuclear pores) but does not reach the nucleoplasm. It suggests that an interaction with the nuclear membrane is necessary but not sufficient for protein uptake into the nucleus. In multipotential cells, the expression of nuclear location signal LacZ (nls-LacZ) interferes neither with cell growth nor with differentiation. Using various lacZ constructs, the transcriptional activity of embryos was studied. At the two-cell stage, the promoters of the Rous sarcoma virus, simian virus 40, and the beta-actin gene are functional but the Moloney murine leukemia virus long terminal repeat is not. Thus, transcriptional specificity must already be present at the stage of activation of the embryonic genome.

Animals↗
PubMed1987

Epidermal cell-derived lymphocyte differentiating factor (ELDIF) inhibits in vitro lymphoproliferative responses and interleukin 2 production.

We have examined the biologic characteristics and immunologic properties of epidermal cell-derived lymphocyte differentiating factor (ELDIF), a lymphocyte differentiating factor produced by cultured human keratinocytes. The ELDIF was semipurified by a gel filtration procedure. This factor, which is distinct from prostaglandins, epidermal cell-derived thymocyte activating factor (ETAF), and the well-known thymic hormones (thymulin, thymopoietin, and thymosin alpha 1) did not exhibit any interleukin (IL)-1, IL-2, or IL-3 activity. It strongly inhibited in vitro lymphoproliferative responses of normal mouse spleen cells to phytohemagglutinin, concanavalin A, and lipopolysaccharide. This dose-dependent phenomenon was associated with a suppression of IL-2 production rather than any toxic effect. It can be concluded that ELDIF, a product of human epidermal cells, which displays in vitro T-cell differentiation and regulatory activities, could be of major importance in vivo in the control of cutaneous inflammatory reactions.

Animals↗
PubMed1986

Use of a recombinant retrovirus to study post-implantation cell lineage in mouse embryos.

We show that a gene introduced into cells of mouse embryos by a retrovirus can serve as a heritable marker for the study of cell lineage in vivo. We constructed a defective recombinant retrovirus in which the Escherichia coli beta-galactosidase (lacZ) gene is inserted in the genome of a Muloney murine leukemia virus (M-MuLV). Expression of lacZ was detected with a histochemical stain that can be applied to cultured cells and embryonic tissue. Infection of cultured cells showed that lacZ has no detectable deleterious effects on cell viability or growth, that the enzyme is stably expressed in the progeny of infected cells for many generations in the absence of selective pressure, and that the virus can induce lacZ in a variety of cell types. Following injection of the virus into mid-gestation mouse embryos, clones of lacZ-positive cells were detected in skin, skull, meninges, brain, visceral yolk sac, and amnion. We identified the cell types comprising a series of lacZ-positive clones in the visceral yolk sac and skin to learn the lineage relationships of the labelled cells. In each tissue, we obtained evidence that several cell types have a pluripotential ancestor and that cell fate is progressively restricted as development proceeds.

Animals↗
PubMed1986

Epithelial cell heterogeneity in the guinea pig thymus: immunohistochemical characterization of four thymic epithelial subsets defined by monoclonal anti-keratin antibodies.

Keratins are a family of related polypeptides constitutive of the cytoskeleton of epithelial cells and are never found in nonepithelial tissues. Thymic epithelial cells (TEC), known to induce T cell differentiation, are the keratin-containing cells within the thymus. Using four monoclonal anti-keratin antibodies (KL1, KL4, AE2, AE3) directed against keratins of different molecular weight, we have investigated the guinea pig thymic epithelium. The immunohistochemical analysis of thymic cryostatic sections revealed that the keratin expression of TEC varied according to their location in the thymic lobula; the thymic cortex was specifically stained by AE3 whereas the thymic medulla and the subcapsular cortex were recognized by KL4. In addition, KL1 and AE2 exclusively labeled Hassall's corpuscles. The biochemical analysis of keratins extracted from the thymus showed that each TEC subset was characterized by an unique pattern of keratin polypeptides. This study extends the concept of thymic epithelium heterogeneity and suggests that anti-keratin antibodies which allow the typing of TEC subsets may be valuable tools for studying the differentiation of thymic epithelium and its in vitro function on T lymphocytes.

Animals↗
PubMed1986

Introduction of genes into preimplantation mouse embryos by use of a defective recombinant retrovirus.

Two-cell and four-cell preimplantation mouse embryos were cocultured in vitro with fibroblasts producing the recombinant retrovirus M-MuLV-neo. No wildtype helper virus was detected in these cultures. Of the embryos that survived the in vitro cultivation and the reimplantation into foster mothers, 2 of 15 that were tested contained the proviral genome. The provirus integrated as a single copy at a unique site. We estimate that approximately equal to 20% of the cells in each of the two transgenic fetuses contained the provirus.

Animals↗
PubMed1985

Single channel currents in mouse embryonal multipotential carcinoma cells.

Electrical membrane properties of embryonal non-differentiated carcinoma cells which have been extensively used for the study of early mammalian embryogenesis were investigated by using patch clamp techniques. These multipotential cells were found to contain a restricted repertoire of a small number of ionic channels on the whole cell membrane. The most abundant type was a voltage- and calcium-activated potassium channel with characteristics similar to those described in fully differentiated cells.

Animals↗
PubMed1985

Production of a lymphocyte differentiating factor (ELDIF) by cultured human epidermal cells.

T lymphocyte maturation activity of supernatants from cultured human epidermal cells was investigated using a biological rosette assay based upon Thy 1 induction on T cell precursors. Between days 5 and 18 of keratinocyte cultures, supernatants exhibited Thy 1-inductive properties. Optimal activity was found between days 10 and 14 of culture, which correspond to the beginning of epidermal cell stratification. This activity was independent of the presence of prostaglandin E. Absorption experiments using monoclonal and polyclonal antibodies showed that ELDIF was different from other recognized thymic hormones (thymulin, thymopoietin, thymosin alpha 1), produced by thymic epithelial cells and known to induce T cell markers.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1985

Heterogeneity of thymic epithelial cell (TEC) keratins--immunohistochemical and biochemical evidence for a subset of highly differentiated TEC in the mouse.

The mouse thymic epithelial network was studied using three different anti-keratin antibodies. One of these antibodies, KL1, exclusively recognized a small subset of medullary epithelial cells characterized by its content of a high molecular weight keratin (63 kD). Since epithelial differentiation is known to be associated with the acquisition of high molecular weight keratins, KL1-positive cells, which express the Ia antigen and secrete thymulin, may represent a subset of highly differentiated cells among mouse thymic epithelial cells (TEC). These data reflect the heterogeneity of the thymic epithelium and support the concept that distinct TEC subsets might provide the thymus with different microenvironments.

Animals↗