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D Schmitt

Publications and source records attributed to D Schmitt.

At least 145 records · Page 8Linked to original sources
PubMed1996

Differences of reactivity to interferon gamma in HeLa and CaSki cells: a combined immunocytochemical and flow-cytometric study.

We characterized the changes induced by treatment for 48 h with 100 U/ ml interferon gamma (IFN-gamma) on HeLa and CaSki cells, derived from human uterine carcinomas and containing human papillomavirus (HPV) type 16 and HPV type 18 respectively, by studying cell growth, cell morphology, the cell cycle and expression of epidermal growth factor (EGF) receptor, filaggrin-profilaggrin and MHC class II antigen, HLA-DR. The response of the two cell lines to IFN gamma differed in some cases. In both cell lines, the cells remained viable; cell growth was similarly inhibited as shown by cell counts. Signs of morphological changes were essentially observed in HeLa cells. The cell cycle phases, analyzed by flow cytometry were more disturbed in CaSki than in HeLa cells; the proportion of CaSki cells in S phase increased and those in G2 + M decreased. Expression of EGF receptors related to proliferation increased only in CaSki cells while expression of filaggrin-profilaggrin, a marker of differentiation, and HLA-DR, a marker of epithelial cell immune response, was enhanced in both cell lines. The presence of filaggrin-profilaggrin being unexpected in these cells, the specificity of the reaction with the monoclonal antibody AKH1 was confirmed by immunoblotting. In conclusion, our results show that the two cell lines reacted differently to IFN gamma although they are of similar origin and the different antigens studied may be useful to predict the progression of lesions infected with HPV towards malignancy or the reactivity to IFN gamma of such lesions. However, enhanced synthesis of EGF receptors is probably independent of the antiproliferative effect of IFN gamma but an increase in HLA-DR antigen expression by epithelial cells, which corresponds to an immune response favored by IFN gamma, could act synergistically with cell growth inhibition and differentiation to exclude tumoral and/or HPV-infected cells.

Biomarkers, Tumor↗
PubMed1996

Substance P and keratinocyte activation markers: an in vitro approach.

Substance P (SP) released by cutaneous C fibres is involved in the physiopathology of cutaneous lesions. As normal human keratinocytes have been reported to express SP receptors, we studied the effects of SP on keratinocyte activation markers such as ICAM-1 induction and cytokine production. Human keratinocytes derived from skin obtained during plastic surgery were cultured in defined medium (MCDB 153) and were stimulated by SP. Flow cytometry analysis showed that SP (10(-7) and 10(-5) M) as well as the specific NK1 agonist Sar9Met(O2)11SP (Sar Met) induced a slight but significant expression of ICAM-1 at the cell surface during treatment periods of 24 h and 48 h. SP (10(-5) M) also induced a significant but transient increase in the production of IL-1alpha, IL-1beta, IL-1 receptor antagonist and IL-8 which was detectable by ELISA techniques 6 h after stimulation. This elevation returned to constitutive levels 24 or 48 h postinduction. TNFalpha secretion was detected in stimulated cells only after 48 h. These results suggest that SP can activate keratinocytes and support its role in the local inflammatory reaction.

Adolescent↗
PubMed1996

Glucocorticoid receptor localization in human epidermal cells.

Glucocorticoids, which are widely used in therapy, exert their immunosuppressive actions through specific receptors. These receptors have been characterized in cultured human skin fibroblasts and keratinocytes, but their localization in vitro and in vivo has not been established. To determine the tissue and cellular distribution of glucocorticoid receptors (GR), two specific polyclonal rabbit anti-human GR antibodies were used to detect these receptors in skin biopsy specimens, in freshly isolated and cultured human epidermal cells and in keratinocyte cell lines. Immunoreactive GR were only faintly detected in normal and abnormal differentiated cells and as well as those in the stratum granulosum and corneocytes. These immunolocalization studies were confirmed by fluorescence cell sorter analysis of isolated basal and suprabasal keratinocytes. Immunoreactive GR were highly expressed in normal cultured human keratinocytes, Langerhans cells and several cell lines whereas they were less expressed in melanocytes. Based upon these results the main targets of glucocorticoids in the epidermis appear to be basal and Langerhans cells.

Animals↗
PubMed1996

Tumour necrosis factor (TNF) soluble receptors in malignant melanoma: correlation with soluble ICAM-1 levels.

It has been recently suggested that soluble tumour necrosis factor receptors (sTNF-Rs) may represent prognostic factors in cancer. In malignant melanoma, the intercellular adhesion molecule (ICAM-1) has been described as involved in progression of the disease and is upregulated by TNF alpha. We report in this study the serum concentrations of sTNF-R1 and sTNF-R2 in 32 patients with primary melanoma and in 21 patients with metastatic melanoma, in correlation with those of soluble ICAM-1 (sICAM-1). Significantly raised sTNF-R1 levels were detected only in patients with metastatic melanoma compared with normal controls (P < 0.002), whereas sTNF-R2 levels were increased both in primary and metastatic melanoma (P < 0.001). The ratio of type 2 to type 1 proteins increased in malignant melanoma compared with the controls but remained constant with the progression of the disease. A correlation between sTNF-Rs and sICAM-1 concentrations in patients' sera was observed in metastatic melanoma. The combined adverse effects of these soluble proteins on normal immune effector functions may contribute to tumour progression.

Adult↗
PubMed1996

Molecular and biochemical characterization of tomato farnesyl-protein transferase.

The prenylation of membrane-associated proteins involved in the regulation of eukaryotic cell growth and signal transduction is critically important for their subcellular localization and biological activity. In contrast to mammalian cells and yeast, however, the function of protein prenylation in plants is not well understood and only a few prenylated proteins have been identified. We partially purified and characterized farnesyl-protein transferase from tomato (Lycopersicon esculentum, LeFTase) to analyze its biochemical and molecular properties. Using Ras- and G gamma-specific peptide substrates and competition assays we showed that tomato protein extracts have both farnesyl-protein transferase and geranylgeranyl-protein transferase 1 activities. Compared with the heterologous synthetic peptide substrates, the plant-specific CaaX sequence of the ANJ1 protein is a less efficient substrate for LeFTase in vitro. LeFTase activity profiles and LeFTase beta-subunit protein (LeFTB) levels differ significantly in various tissues and are regulated during fruit development. Partially purified LeFTase requires Zn2+ and Mg2+ for enzymatic activity and has an apparent molecular mass of 100 kD Immunoprecipitation experiments using anti-alpha LeFTB antibodies confirmed that LeFTB is a component of LeFTase but not of tomato geranylgeranyl-protein transferase 1. Based on their conserved bio-chemical activities, we expect that prenyltransferases are likely integrated with the sterol biosynthesis pathway in the control of plant cell growth.

Alkyl and Aryl Transferases↗
PubMed1996

Interkeratinocyte adherens junctions: immunocytochemical visualization of cell-cell junctional structures, distinct from desmosomes, in human epidermis.

Vinculin and beta-catenin are intracellular attachment proteins linking transmembrane adhesion molecules (E-cadherin) to the actin microfilament cytoskeleton, thus participating in formation of cell-cell adherens junctions, or zonulae adherentes. This type of junction was only recently described in human epidermis due to the imprecise morphological criteria for its recognition. In this study, we investigated the relationship between the expression of the zonula adherens-associated proteins vinculin, beta-catenin, E-cadherin, and actin, on the one hand, and the presence of electron microscopically discernable structures in normal human epidermis on the other. Mouse jejunal epithelium with its orderly arrangement of various junctional structures served as a positive control. Simple and dual post-embedding immunogold labeling was performed on ultrathin sections of Lowicryl K4M and Lowicryl K11M embedded tissues. The overall distribution of the antigens in human epidermis was evaluated on frozen tissue sections using immunofluorescence and laser confocal scanning microscopy. Antibodies against proteins associated with desmosomes (i.e., keratins, desmoglein 1, and plakoglobin) were used as controls. Vinculin and beta-catenin were localized to junctional structures distinct from desmosomes, thus defining the presence of zonulae adherentes. Labeling of actin and E-cadherin was less clearly restricted to the junctions, but these two proteins were also co-expressed at zonulae adherentes and not at desmosomes. In human epidermis, zonula adherens-associated labeling was consistently detected near desmosomes, indicating the possibility of a functional relationship between the two types of junctions.

Actins↗
PubMed1996

Inhibition of human peripheral blood mononuclear cell proliferative response by glycosphingolipids from metacestodes of Echinococcus multilocularis.

The effect on human peripheral blood mononuclear cells (PBMCs) of neutral glycosphingolipids extracted from metacestodes of the parasite Echinococcus multilocularis was investigated. Neutral glycosphingolipids inhibited [3H]thymidine uptake by human PBMCs upon stimulation by mitogens such as phytohemagglutinin A and pokeweed mitogen or by allogeneic Burkitt B cells. This effect was dose dependent and was related to a decrease in interleukin 2 (IL-2) synthesis, the expression of IL-2 receptors (CD25) being unmodified. Addition of exogenous recombinant IL-2 restored the cell proliferation. Partial inhibition of immunoglobulin G (IgG), IgA, and IgM synthesis was observed in the supernatant of cell culture in association with the inhibitory effect. Identification of active subfractions contained in the neutral glycosphingolipid fraction was also studied in relation to cell viability. The free ceramide fraction had an inhibitory effect, in part related to cell lysis, particularly at high concentration, while the monogalactosylceramides had a paradoxical effect: as an activator at low concentrations and as an inhibitor at high concentrations, with limited cell survival. The immunogenic neutral glycosphingolipids containing at least two carbohydrate residues, all having a structure based on Gal beta 1-->6Gal, were inhibitors of PBMC proliferation and showed good cell survival. These results suggest that parasite neutral glycosphingolipids may play an immunologically relevant role in alveolar hydatid disease.

Animals↗
PubMed1996

Diversity of the envelope glycoprotein among human immunodeficiency virus type 1 isolates of clade E from Asia and Africa.

Human immunodeficiency virus type 1 isolates of clade E, known to be largely responsible for the fulminating epidemic in Southeast Asia, have been derived exclusively from Asia and Africa. Here we provide full or partial sequences of the envelope glycoprotein gene from 13 additional clade E isolates from Asia representing patients in both early and late stages of disease. More extensive comparison of isolates within clade E by geographic locale, stage of disease, and year of isolation is now possible. The genetic diversity of clade E isolates from Asia, particularly among those derived from early-stage patients, is restricted compared with African isolates (mean interisolate distances in gp120, 5.4 and 20.2%, respectively). However, patients hospitalized with AIDS-related illnesses in Thailand harbored clade E isolates exhibiting broader interisolate diversity and with highly heterogeneous third hypervariable loop sequences. An additional pair of cysteine residues, predicting a novel disulfide bridge and present in 80% of clade E isolates from Asia, was uniformly absent from six African isolates. Clade E isolates in Thailand from early-stage subjects continue to be genetically similar to potential vaccine prototype strains, providing a favorable environment for the evaluation of genotype E candidate vaccines. However, evidence of increasing interisolate diversity is appearing among late-stage patients in Asia. This diversification of the clade E virus, if sustained, may impact preventive vaccine development strategies.

Africa↗
PubMed1996

Humeral head shape as an indicator of locomotor behavior in extant strepsirhines and Eocene adapids.

Postcranial material from Notharctus, Smilodectes and Cantius is abundant and well studied, but debate continues over whether the locomotor repertoire of these animals included a substantial component of vertical leaping. Here, the shape of the humeral head of 11 genera of extant strepsirhines, Notharctus, Smilodectes and Cantius was quantified using serial mediolateral and proximodistal contours. Univariate and multivariate analyses of these data show that vertically leaping strepsirhines have a distally relatively high narrow humeral head compared to arboreal quadrupeds and it places Notharctus and Smilodectes in a group with Hapalemur griseus, while Cantius is grouped with Eulemur macaco, suggesting that a quadrupedal form preceded the appearance of vertical leaping.

Analysis of Variance↗
PubMed1996

Expression of gastrin-releasing peptide receptor in human skin.

Bombesin-related peptides are expressed in the skin of batrachians and mammals. As gastrin-releasing peptide belongs to this family, we searched for the presence and distribution of gastrin-releasing peptide receptors (GRPr) in the skin of healthy human adults by immunohistochemistry, flow cytometry and electron microscopy. The results indicated that GRPr are expressed on nerves and vessels in the dermis, on eccrine sweat glands, sebaceous glands and erector pili muscle. Within epidermis, staining was localized only on basal and suprabasal layer cells, or in the whole epidermis, according to the samples studied. Interestingly, suprabasal epidermal dendritic cells occasionally showed a strong labelling. Some of these epidermal dendritic cells were identified as Langerhans' cells by immunoelectron microscopy studies. Flow cytometry analysis of crude epidermal cell suspensions resulted in the expression of GRPr on about 43% of the cells. Therefore, we investigated whether human GRPr could modulate Langerhans' cells antigen-presenting functions. For this purpose, we added increasing concentrations of GRP (10(-12) to 10(-5) M) to mixed epidermal cell lymphocyte reactions. Allogeneic T-cell proliferation was not significantly modified when added to GRP-pretreated epidermal cells. In conclusion, we demonstrated the presence of GRPr in human skin, suggesting that GRP may modulate epidermal cell functions but does not modify antigenic presentation.

Adult↗
PubMed1996

In vitro primary sensitization of hapten-specific T cells by cultured human epidermal Langerhans cells--a screening predictive assay for contact sensitizers.

BACKGROUND: The need to develop predictive tests which could identify potential allergens has been recognized for many years. There is as yet no accepted in vitro method for the assessment of contact sensitizers. OBJECTIVE: We have tested the ability of a range of contact allergens to induce in vitro primary sensitization of autologous T cells. METHOD: T-cell proliferation induced by haptens using 2-day cultured human Langerhans cells as antigen-presenting cell was assessed by 3H thymidine incorporation. Antigen specific stimulation was calculated as stimulation indexes. RESULTS: Strong allergens induced in vitro a primary T-cell response in all (trinitrophenyl, TNP: 13/13) or in the majority (fluorescein isothiocyanate, FITC: 7/10) of experiments. An irritant, sodium dodecyl sulfate (SDS), failed to generate a significant T-cell proliferation in any of the experiments (0/10). We obtained a significant lymphoproliferative response to weak sensitizers only in a limited number of experiments: (coumarin: 1/12, citronellal: 0/10, hydroxycitronellal: 2/8). p-Phenylenediamine (PPDA), a prohapten and highly sensitizing chemical in vivo, generated primary sensitization in vitro in only one of six experiments, while Bandrowski's base (BB), a metabolization product of PPDA induced a significant T-cell response in all six experiments. CONCLUSION: The present in vitro model allows discrimination between two groups of substances: strong contact sensitizers (TNP, FITC, BB) on the one hand and weak sensitizers (coumarin, citronellal and hydroxycitronellal) and irritants (SDS) on the other hand. It could be used as a screening in vitro assay to eliminate strong contact allergens before further predictive animal tests have to be performed.

Coumarins↗
PubMed1996

Ready for the road.

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Accidents, Occupational↗
PubMed1996

A possible role for human papillomaviruses and c-myc, c-Ha-ras, and p53 gene alterations in malignant cutaneous lesions from renal transplant recipients.

Several years after transplantation, renal transplant recipients develop numerous cutaneous squamous cell carcinomas (SCC), in which human papillomaviruses (HPV) may be detected. Alterations in c-myc, c-Ha-ras, and p53 genes were studied in 34 SCC, in correlation with the presence of HPV. In situ hybridization (ISH) and polymerase chain reaction (PCR) showed that many SCC contained several HPV types infecting different foci of epithelial cells. Using Southern blot and ISH, c-myc and/or c-Ha-ras gene amplification was detected in 7/13 SCC tested. With PCR and oligoprobe hybridization, a GGC -> GAC mutation was found at codon 12 of c-Ha-ras gene in 1/21 SCC tested, while no mutation was detected at codon 61. Using immunohistochemistry, p53 protein expression was detected either along the basal cell layer or spotted in foci of basal cells. Our results show an abnormal distribution of HPV types in SCC from renal transplant recipients, and alterations of c-myc, c-Ha-ras, and p53 genes without any direct link with the presence of any studied HPV type. Thus, viral infection and oncogene activation may represent factors involved in the etiology of skin SCC from transplant recipients.

Base Sequence↗
PubMed1996

A longitudinal study of a harlequin infant presenting clinically as non-bullous congenital ichthyosiform erythroderma.

Over the past 8 years, we have followed a child born as a harlequin baby, who survived due to treatment with retinoids. His condition evolved clinically towards the erythrodermic form of lamellar ichthyosis (non-bullous congenital ichthyosiform erythroderma, NBCIE). According to ultrastructural and biochemical criteria, our patient originally presented with type II harlequin ichthyosis. Investigations showed an abnormal keratinosome structure and extrusion, a keratin pattern characteristic for epidermal hyperproliferation, and an absence of conversion of profilaggrin to filaggrin. Persisting keratinocyte hyperproliferation, associated with the presence of a dermal infiltrate, is in agreement with the present clinical picture of severe NBCIE. However, abnormal lamellar body production and defective filaggrin processing, which is not one of the diagnostic criteria of NBCIE, persist in the patient's skin. Further studies of the epidermal lipid composition, and of possible mutations of the keratinocyte transglutaminase gene performed on epidermal cell cultures of harlequin ichthyosis, will be necessary before type II harlequin ichthyosis can be accepted as an extremely severe form of NBCIE.

Etretinate↗