Biomedical subjects

M Darmon

Publications and source records attributed to M Darmon.

At least 73 records · Page 4Linked to original sources

PubMed1986

Onset of epidermal differentiation in rapidly proliferating basal keratinocytes.

Stratified epithelia such as epidermis are classically considered to comprise 2 cell compartments, one consisting of undifferentiated proliferative cells occupying the basal layer, and the other consisting of differentiated postmitotic cells occupying the suprabasal layers. It is also generally assumed that the 58K basic-50K acidic couple of keratins is expressed in basal cells, while the 67K basic-56K acidic couple appears in suprabasal cells. In the present work we demonstrate that the population of basal keratinocytes is heterogeneous, since 8% of them are found to express the 67-56K "suprabasal" set of keratins. The morphology of these transitional cells suggests that they are in the process of detaching from the basement membrane to move upward to the epidermis. Cytoflow-fluorometric studies showed that the fraction of cells in S plus G2/M phases is 4 times higher in transitional keratinocytes than in basal or suprabasal keratinocytes. Altogether, these results suggest that the onset of terminal differentiation occurs in human epidermis in a subpopulation of keratinocytes which are still located in the basal layer, and that a transient increase in proliferation occurs when the cells engage in terminal differentiation and are ready to move toward the suprabasal layers.

Adult↗

PubMed1986

Mesenchymal-epithelial conversions induced by 5-azacytidine: appearance of cytokeratin Endo-A messenger RNA.

When mouse-teratocarcinoma-derived fibroblasts (1246 cell line) are subjected to treatment with the inhibitor of DNA methylation, 5-Azacytidine (5 AzaC), they transiently express at 55-kilodalton intermediate-filament protein recognized by the epithelial-specific monoclonal antibody, TROMA-1, although they retain a fibroblastic morphology. However, rare clones (e.g., the 1339 cell line) that permanently express the antigen recognized by TROMA-1 can be derived from the 5 AzaC-treated 1246 population, and these clones have an epithelial phenotype. In the present study, we used cloned DNA probes to demonstrate that, in 1246 fibroblasts, 5 AzaC induces the appearance of Endo-A mRNA. High levels of Endo-A mRNA were also detected in the epithelial derivative, cell line 1339. In both cases, the capping site of the Endo-A mRNA was found to be the same as that in epithelial cells which normally express this RNA.

Animals↗

PubMed1985

Co-expression of specific acid and basic cytokeratins in teratocarcinoma-derived fibroblasts treated with 5-azacytidine.

Epithelial cells always co-express acidic and basic keratin polypeptides. Mesenchymal cells, which do not normally contain keratins, can be induced by the inhibitor of DNA methylation 5-azacytidine to synthesize the basic keratin Endo A. In the present paper we show that the acidic keratins Endo B and Endo C can also be induced by 5-azacytidine in teratocarcinoma-derived fibroblasts. Furthermore, individual cells in which Endo B and/or Endo C keratins are found, always co-express the basic polypeptide Endo A. Other cytokeratins are not or very rarely found. Interestingly, Endo A, B, and C are usually associated in vivo and are known to be the first keratin polypeptides appearing during the development of the mouse embryo.

Animals↗

PubMed1985

Epidermal morphogenesis and induction of the 67 kD keratin polypeptide by culture of human keratinocytes at the liquid-air interface.

Culture in the presence of delipidized serum (i.e., in the absence of vitamin A) has been shown to allow terminal differentiation of human keratinocytes, both in terms of morphological appearance and in terms of 67 kD keratin polypeptide synthesis (Fuchs, E & Green, H, Cell 25 (1981) 617) [2]. Culture at the liquid-air interface is known to induce morphological differentiation in a variety of culture systems designed for keratinocytes (Pruniéras, M et al., J invest dermatol 81 (1983) 28s) [3]. We report here that human keratinocytes grown on a dermal equivalent (or lattice) in the presence of total serum are able to express the 67 kD keratin polypeptide, provided that the culture is raised at the liquid-air interface. Loss of contact with air results in switching off this synthesis.

Cell Differentiation↗

PubMed1985

Abnormal maturation pathway of keratinocytes in psoriatic skin.

We compared the maturation pathway of normal and psoriatic epidermis using three different markers: (1) Involucrin, which is normally detected in the stratum granulosum in normal skin, was detected in all but the basal layer of involved psoriatic skin; (2) an antigen, recognized by the murine monoclonal antibody psi 3, was present in all but the basal layer of involved psoriatic skin but was absent from uninvolved and normal skin; (3) fibronectin, which normally localizes in the dermis and the epidermal-dermal junction, was also detected intra- and extracellularly in the psoriatic epidermis. These results indicate that the alterations in keratinocyte maturation found in psoriasis do not arise from a truncation of the normal maturation pathway but rather reflect the onset of an abnormal pathway of differentiation characterized by the expression of psi 3 antigen and fibronectin and the premature appearance of involucrin.

Antibodies, Monoclonal↗

PubMed1985

Merkel cells express desmosomal proteins and cytokeratins.

Indirect immunofluorescence experiments performed on various mammalian tissues rich in Merkel cells show that these cells contain keratin intermediate filaments and desmosomal proteins, which demonstrates their epithelial nature. Although they share desmosomes with neighbouring keratinocytes, Merkel cells differ from them, since they contain keratin polypeptides usually found in simple epithelia. In that respect, Merkel cells resemble fetal keratinocytes.

Animals↗

PubMed1985

Reexpression of fetal characters in simian virus 40-transformed human keratinocytes.

Normal human keratinocytes are able to stratify, form cornified squames, and terminally differentiate in tissue culture. These properties are frequently impaired by malignant transformation. In the present paper, we show that, in addition, transformation by SV40 results in the coordinate reexpression of a whole set of fetal characters. Moreover, a comparison of two SV40-transformed human keratinocyte cell lines, one still showing a certain degree of stratification and terminal differentiation (HE-SV) and the other almost completely unable to differentiate (SVK14), suggests that the impairment of differentiation and the intensity of reexpression of fetal markers are correlated. Particularly, a set of three keratin polypeptides, absent in adult stratified epithelia but normally found in the nonstratified fetal epidermis, is present in much larger amounts in SVK14 cells than in HE-SV cells. On the other hand, the inability of SVK14 cells, in contrast to HE-SV cells, to form cornified envelopes seems to be due to the inability of those cells to accumulate involucrin.

Basement Membrane↗

PubMed1985

[Factors in recurrence of perforated duodenal ulcer after simple suture. Therapeutic deductions].

Objective predisposing factors leading to relapse after simple suture for perforated duodenal ulcer were evaluated by a retrospective study of 80 cases. Statistical analysis showed 3 main factors to be involved: age under 45 years, presence of a previous ulcer ano smoking, and these were attributed a coefficient of severity. A simple method will enable a population at high risk of recurrence to be selected, for which immediate radical treatment can be applied when vital risk factors, also analyzed in this study, are lacking.

Adult↗

PubMed1984

5-Azacytidine is able to induce the conversion of teratocarcinoma-derived mesenchymal cells into epithelia cells.

The inhibitor of DNA-methylation, 5-azacytidine (5- AzaC ) induced the appearance of cytokeratin-containing cells in several mesenchymal cell lines such as teratocarcinoma-derived fibroblasts, preadipocytes and myoblasts, NIH-3T3 fibroblasts and human embryonic fibroblasts. At optimal 5- AzaC concentrations the proportion of such cells was in the range of 10(-1) compared with 10(-6) -10(-4) in non-treated cultures. Dose-response curves indicated that the induction of cytokeratin was the result of an interaction of the drug with few targets. Stable, mature, keratinocyte cell lines, as well as lines of myoblasts and astrocytes, could be isolated from a teratocarcinoma-derived preadipocyte line, showing that 5- AzaC is able to provoke a wide range of complete phenotypic conversions. In these cell lines, the intermediate filaments corresponded to the morphological phenotype. Altogether, the results suggest that 5- AzaC preferentially activates certain genes.

Adipose Tissue↗

PubMed1984

A keratin of fetal skin is reexpressed in human keratinocytes transformed by SV40 virus or treated with the tumor promoter TPA.

SV40-transformation as well as treatment with tumor promoters produce alterations in morphology, differentiation and keratinization of human keratinocytes. Two cell lines of SV40-transformed keratinocytes and primary cultures of keratinocytes treated with the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA) were found to contain an additional protein of 52.5 kD molecular weight (MW). This protein was identified by its reactivity with the monoclonal antibody TROMA-I as being keratin no. 8, a keratin normally present only in simple epithelia. Since this keratin is present in fetal epidermis but disappears gradually when fetal skin becomes multilayered after week 13 of development (Moll et al., Differentiation 23 (1982) 170. [23]), it suggests that SV40 virus and TPA are able to induce in human keratinocytes the reexpression of fetal characters.

Cell Line↗

PubMed1983

Changes in pattern and accessibility for 125I-labelling of cell-surface proteins after mesenchymal differentiation of embryonal carcinoma cells.

Cell-surface proteins of the embryonal carcinoma line C17-S1 1003 (1003) and of some of its mesenchymal derivatives were studied. The surface proteins were labelled with 125I using the lactoperoxidase-glucose-glucose oxidase system either on the cells attached to the culture dishes or after their dissociation. Iodinated proteins were analyzed by two-dimensional gel electrophoresis. The patterns obtained with embryonal carcinoma cells 1003 and with two mesenchymal cell types derived from them, namely embryonic mesenchymal cells (line 10035) and fibroblastic cells (line 10031), were different one from the other, especially when considering the group of proteins labelled on the attached cells. The pattern of cell-surface proteins of the myoblastic line 1168, also derived from C17-S1, was found to be similar to that of 10031 fibroblastic cells. This result is discussed in the light of the phenotypic transition toward myogenesis, which can be obtained with 10031 fibroblastic cells but not with 10035 embryonic mesenchymal cells. A direct method of detection of lectin-binding proteins permitted us to identify the major concanavalin A-binding proteins. Two of them are common to all cell lines studied. They were labeled with 125I on the attached undifferentiated 1003 cells, while in all differentiated derivatives they became available for labelling after the cell detachment only.

Animals↗

PubMed1983

Two specific markers for neural differentiation of embryonal carcinoma cells.

Two multipotential embryonal carcinoma (EC) cell lines, 1003 and 1009, can be induced to form preferentially neural derivatives in vitro. Synthesis of specific proteins during neural differentiation was followed by two-dimensional gel electrophoresis. The comparison of protein patterns obtained with neural and non-neural derivatives of these EC cell lines indicates that two changes are specific for the neural pathway: (i) the appearance of a new beta-tubulin isoform and (ii) the accumulation of the brain isozyme of creatine phosphokinase already present in small amounts in EC stem cells. These changes were found to take place early in the course of differentiation and to occur even when neurite outgrowth was prevented.

Animals↗

PubMed1982

Control by the extracellular environment of differentiation pathways in 1003 embryonal carcinoma cells: study at the level of specific intermediate filaments.

1003 is a multipotential embryonal carcinoma (EC) clonal cell line which can be induced to follow different developmental pathways by altering the composition of the culture medium. When grown in serum-containing medium the great majority of 1003 cells remain undifferentiated; they express the ECMA 7 cell-surface embryonic antigen and very low amounts of vimentin. In serum-free medium, most 1003 cells differentiate into neuroepithelial cells. The majority of these cells are still labelled with ECMA 7 antibodies. They contain higher amounts of vimentin than EC cells, but no neurofilament proteins. Neuroepithelial cells then differentiate into neurons through a stage of preneurons containing both vimentin and the 70-K neurofilament protein. Fully differentiated neurons contain 70-K neurofilament protein but no vimentin. The 200-K neurofilament protein is detected later in the neurons. Mesenchymal cells (induced by re-adding serum) express high amounts of vimentin organized in networks. Preneurons , neurons, and mesenchymal cells do not express ECMA 7 antigen.

Animals↗

PubMed1982