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M Faure

Publications and source records attributed to M Faure.

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

Involvement of Na and Cl in ouabain-induced cell swelling in thick ascending limb of rat kidney.

Changes in the volume of isolated segments of rat medullary thick ascending limb (MAL) were studied by a photographic technique, after tubule incubation in isotonic solutions in the absence or presence of ouabain and/or K. When segments were incubated at 30 degrees C in NaCl solution, their volume increased by 75% after removal of external K, and by 170% after removal of external K plus addition of 1 mmol/l ouabain. At steady state, tubular volume was a function of the external K concentration. Resting volume was obtained with external K concentrations higher than 0.1 and 1.0 mmol/l in the absence and presence of ouabain respectively. When MAL samples were incubated in isotonic K-free Na2SO4 or K-free choline Cl solution, their volume per unit of length was similar to that determined in NaCl medium, but there was no swelling after the addition of ouabain. The ouabain-induced swelling was shown to depend on both the Na and Cl concentrations in the incubate (apparent Km of 87 and 80 mmol/l for Na and Cl respectively). Swollen tubules recovered their resting volume when ouabain, Na or Cl was removed from the incubation medium. Recovery of resting volume was also observed after addition of K into the incubation medium. These observations indicate that rat MAL cell volume is the result of coupled passive net fluxes of Na and Cl, which depend on the respective electrochemical gradients for Na or Cl across the cell membranes and the Na-pump activity which continuously extrudes Na.

Animals↗
PubMed1988

Relationship between cell volume and cation content in thick ascending limb of rat kidney.

We examined the relationship between the cell volume and cation concentration ([Nai] and [Ki]) of isolated segments of rat medullary thick ascending limb (MAL) after incubation at 30 degrees C in various isotonic solutions. When the tubules were incubated in a normal NaCl solution containing 5 mmol/l K+, addition of 1 mmol/l of ouabain increased [Nai] and decreased [Ki] but did not change the total ([Nai] + [Ki]) concentration (about 90 mEq/l) or tubular volume. After incubation in various K+-free solutions, the tubules were almost fully K+-depleted; their volume per unit of length was similar in the three solutions, although the choline Cl-treated tubules had a very low sodium content compared to the NaCl- and Na2SO4-treated tubules (8 vs. 97 and 95 mEq/l respectively). Ouabain altered neither volume nor [Nai] of tubules incubated in choline Cl or Na2SO4 solution. Transfer of tubules from K+-free Na2SO4 or K+-free choline Cl solution into K+-free NaCl solution resulted in an increase in [Nai] (by 29 and 97 mEq/l respectively) without much increase in tubular volume. A marked swelling of the tubules was only observed when the K+-free NaCl solution contained also ouabain. Under this condition, [Nai] was comparable to the Na+ concentration of the incubation medium. After washing and incubation in a normal NaCl solution containing K+, the swollen tubules recovered their initial volume and restored Na+ and K+ concentration gradients across the cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Developmental control of the expression of the dihydroorotate dehydrogenase and UMP synthase genes in Dictyostelium discoideum.

Developmental variations in the expression of two genes of the de novo pyrimidine biosynthetic pathway have been examined in Dictyostelium discoideum. One gene, DdPYR4, encodes the dihydroorotate dehydrogenase (EC 1.3.3.1); the other, DdPYR5-6, encodes the UMP synthase which in D. discoideum is a bifunctional enzyme harboring both the orotate phosphoribosyl transferase activity (EC 2.4.2.10) and the OMP decarboxylase activity (EC 4.1.1.23). The relative amount of mRNA for both genes has been estimated by hybridization with the previously cloned DNAs and compared with the amount of actin mRNA. The level of both mRNAs is dramatically reduced after 4 h of development and remains at a low level later in development. In contrast to these variations, the specific activity of the enzymes encoded by these genes during development is similar to that measured during exponential growth. These results lead us to propose that DdPYR4 and DdPYR5-6 genes encode for relatively stable proteins and that their synthesis is reduced to maintain a constant level of enzymes in non-growing cells. This mode of regulation could apply to a large number of housekeeping genes.

Animals↗
PubMed1988

Disruption of Dictyostelium discoideum morphogenesis by overproduction of cAMP phosphodiesterase.

The development and cellular differentiation of Dictyostelium discoideum are disrupted in transformants secreting high levels of the cyclic nucleotide phosphodiesterase. The aggregation of these cells in the early stage of development proceeds rapidly and without the formation of organized streams. The later stages of development, in which differentiation into stalk and spore cells normally takes place, are completely blocked so that the transformants remain in spherical clusters of undifferentiated cells that do not elaborate the tip structure that regulates morphogenesis. These effects are due to overproduction of extracellular phosphodiesterase and demonstrate the role of cAMP during the aggregation phase of development as well as in the control of differentiation and pattern formation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1988

Epithelial differentiation of human skin equivalents after grafting onto nude mice.

Human skin equivalents were developed in vitro with a unidimensionally retracted dermal equivalent made of human type I + III collagen and human MRC5 fibroblasts, and a multilayered epithelium grown in liquid medium from normal human keratinocytes in suspension. We investigated the degree of epidermal differentiation that could be achieved after in vivo grafting onto nude mice by means of light and electronmicroscopy as well as by immunohistochemistry. All transplanted grafts showed a primary take. The grafts formed an epidermis with a stratum corneum and from day 7 to 14 after transplantation a distribution of a 56.5 Kd keratin protein, involucrin, profilaggrin/filaggrin, and MHC-I antigens that was similar to what is noted in normal human epidermis. These data indicate that a full terminal differentiation was only achieved after in vivo transplantation of the cultured epithelium. Pigmentation was present, but no marker of Langerhans cells was seen at 4 weeks. Although there was no evidence of the dermal equivalent after 2 weeks, we noted a strong adherence of the graft to the wound bed, with the presence of type-IV collagen, laminin, and bullous pemphigoid antigen at the dermo-epidermal junction (day 7) and hemidesmosomes, a lamina lucida and a lamina densa (day 30). No epithelial damage was noted in spite of an inflammatory infiltrate in the underlying tissue. This represents a preliminary step in the use of such a skin-equivalent in the treatment of human patients with wounds.

Animals↗
PubMed1988

[Use of cultured epidermis of human origin for demonstrating the acantholytic action of staphylococcal exfoliatin A].

Cultured human epithelia obtained from epidermal cells in vitro were used to assay the activity of staphylococcal epidermolytic toxin and develop an in vitro experimental model for the staphylococcal scalded skin syndrome. Human epidermal cells were grown from single epidermal cell suspensions obtained through trypsinization of adult normal skin into multilayered epithelia (with a basal cell layer, several intermediate and one or two upper layers) on mouse 3T3 feeder cells. First passage cultures were incubated with exfoliative toxin A from phage Group II staphylococci at various concentrations in DMEM. They were examined at various time intervals by direct microscopic and histological examination of respectively the culture plates or the epidermal sheets after their detachment from the plates with dispase grad II. A total exfoliation could be obtained at 24 hour at concentrations of Img and 500 micrograms/ml, only local areas of epidermolysis noted at 100 micrograms/ml. The intraepithelial separation was noted to occur between the basal layer and the lowest intermediate layer. No exfoliation could be observed at lower concentrations. Up to 4-5 hours few changes were evident, but at this time small areas of epidermolysis developed. With exfoliatin 100 micrograms/ml, intraepidermal blisters were clearly visible, occurring either between the basal cells and the lowest intermediate layer or between the first two intermediate cell layers. At the ultrastructural level, desmosomes were sparse and altered, with enlargement of the intercellular spaces and condensation of tonofilaments. These data indicate that human epidermal cell cultures, although their differentiation in culture only mimics what occurs in vivo, can be used as an in vitro model of the staphylococcal TEN to further investigate the site of action of such a toxin and the cellular mechanism responsible for the syndrome.

Adult↗
PubMed1987

Growth and differentiation of human keratinocytes on extracellular matrix.

Extracellular matrices (ECM) have been reported to enhance epithelial cell attachment and proliferation as well as to induce differentiation in vitro. Since ECM components are physiological constituents of the dermoepidermal basement membrane, we studied the growth and differentiation of human keratinocytes on ECM in order to determine the benefits of culturing epidermal epithelial cells (keratinocytes) on reconstituted basement membranes. Disaggregated epidermal cells were grown in primary and subcultures in liquid medium; the attachment of the cells was greatly enhanced by ECM and noted within the first few hours after seeding; cells formed small islets that reached confluence within 2-12 days depending upon the plating density and the type of culture (primary or passages). Histological and ultrastructural cross-sections of the cultures clearly indicated that a multilayered epithelium can be obtained including a basal cell layer, several intermediate cell layers with cytoplasmic organelles, intermediate size filaments, desmosomes, and keratohyaline granules, and an upper layer of anucleated cells. Using immunofluorescence, both pemphigus and pemphigoid (basal membrane zone) antigens were expressed. The keratin pattern noted indicated that these epithelia differentiate and keratinize but do not express a complete program of keratinization, a finding usually noted when cells are grown submersed. These data show that ECM favor epidermal cell proliferation and differentiation and suggest that they may be used to obtain large amounts of epidermal equivalent suitable for grafting and/or in vitro studies.

Adult↗
PubMed1987

Ultrastructural studies of cultured human epithelial sheets used as skin allografts.

In this work the ultrastructural features of cultured epithelial sheets (CES) used as skin allografts in humans are described, before and at various times after grafting. Prior to grafting, CES consisted of 4-5 layers of keratinocytes of a low to moderate degree of differentiation. However, after grafting, the CES developed progressively but rapidly features of a well-differentiated epidermis (including melanocytes and Langerhans' cells) and a dermal-epidermal junction. No evidence of rejection was observed. These results demonstrate the key role of normal dermis in the maturation of the surface epithelium and prove the suitability of CES as skin allografts.

Cells, Cultured↗
PubMed1987

Functional effects of epidermal cell culture supernatants (ECCS) on human B-cell activation.

Epidermal cells (EC) were cultured without stimulation and the effect of these EC culture supernatants (ECCS) on human in vitro B-cell response was determined. Supernatants obtained between Days 5 and 7 were able to replace monocytes in the antibody response to the particulate antigen trinitrophenyl-polyacrylamide (TNP-PAA). These results were obtained when highly monocyte-depleted cultures (less than 0.5% peroxidase-positive cells) were used and were reproduced with supernatants from several different EC cultures. ECCS could not substitute for T cells in the T-dependent response to TNP-PAA. They contained an interleukin 1 (IL-1) activity but no interleukin 2 or B-cell growth factor (BCGF) activities. We tested the effect of ECCS on the proliferative response of highly monocyte-depleted B cells cultured at low cell density costimulated with anti-u antibody and BCGF. ECCS had no BCGF-like activity of its own but did potentiate the effect of BCGF. Thus EC cultures produce IL-1-like factor(s) which act directly on the early stages of B-cell activation.

Antibody Formation↗
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↗
PubMed1987

Growth and differentiation of human epidermal cultures used as auto- and allografts in humans.

Human keratinocytes from small skin specimens were grown on mouse 3T3 cell feeder layers into epidermal sheets free from Langerhans cells and MHC class II antigen. These were found to be suitable for the permanent coverage of wounds when used as autografts or allografts. We report here the ultrastructural differentiation of this cultured epidermis after grafting onto autologous or allogeneic recipients. The cultured epidermis was a thin but multilayered Malpighian epithelium composed of keratinocytes at different stages of differentiation. The dermo-epidermal basement membrane was newly synthesized during the first few days following transplantation onto de-epidermized wounds. The analysis of keratins and examination of various keratinocyte membrane antigens by immunofluorescence indicated that full terminal epithelial differentiation was only achieved after in vivo transplantation of the cultured epidermis. Langerhans cells, absent in cultures, progressively colonized the grafts, while melanocytes, not detectable in sections of the cultures, were identified among the keratinocytes 2 weeks after grafting.

Adolescent↗