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D Hanau

Publications and source records attributed to D Hanau.

At least 91 records · Page 5Linked to original sources
PubMed1988

Epinephrine potentiates human platelet activation but is not an aggregating agent.

Epinephrine can in certain in vitro conditions induce the aggregation of human platelets and could play an important role in vivo in the appearance of thrombotic disorders when catecholamine levels are increased. This study examines some functional and biochemical responses to epinephrine. Epinephrine induces the aggregation and serotonin secretion of human platelets in citrated plasma. This is not due to a direct effect of citrate itself, such as the lowering of plasma free Ca2+ but more likely to the generation of traces of thrombin during blood collection, as suggested by abrogation of these platelet responses when hirudin was added before citrate. When washed human platelets suspended in Tyrode buffer containing 2 mM Ca2+, 0.35% albumin and apyrase, and 0.1-100 microM epinephrine were used, no shape change, aggregation, or secretion of serotonin was observed, nor was the platelet ultrastructure modified. Epinephrine does not modify platelet membrane fluidity, as studied with the lipophilic fluorescent probe trimethylammonium-diphenylhexatriene. It has no direct effect on fibrinogen binding to intact platelets, intracellular Ca2+ levels measured by quin2, or protein phosphorylation. Epinephrine potentiates the action of all types of aggregating agents on aggregation, secretion, intracellular Ca2+ levels, membrane fluidity, fibrinogen binding, or protein phosphorylation. These effects are mediated by alpha 2-adrenergic agonists and inhibited by alpha 2-adrenergic antagonists. This study shows that epinephrine alone does not induce modifications of morphology, metabolism, or function of intact and functional washed human platelets and that it cannot be considered per se as an aggregating agent. However, epinephrine interacts with alpha 2-adrenergic receptors on human platelets and potentiates biochemical and aggregatory responses induced by other platelet agonists.

Adenosine Diphosphate↗
PubMed1987

Human epidermal Langerhans cells cointernalize by receptor-mediated endocytosis "nonclassical" major histocompatibility complex class I molecules (T6 antigens) and class II molecules (HLA-DR antigens).

HLA-DR and T6 surface antigens are expressed only by Langerhans cells and indeterminate cells in normal human epidermis. We have previously demonstrated that T6 antigens are internalized in Langerhans cells and indeterminate cells by receptor-mediated endocytosis. This process is induced by the binding of BL6, a monoclonal antibody directed against T6 antigens. In the present study, using a monoclonal antibody directed against HLA-DR antigens, on human epidermal cells in suspension, we show that the surface HLA-DR antigens are also internalized by receptor-mediated endocytosis in Langerhans and indeterminate cells. Moreover, using immunogold double labeling, we demonstrate that T6 and HLA-DR antigens are internalized through common coated regions of the membrane of Langerhans or indeterminate cells. The receptor-mediated endocytosis that is induced involves coated pits and vesicles, receptosomes, lysosomes, and also, in Langerhans cells, the Birbeck granules. Thus, T6 antigens, which are considered to be "unusual" or "nonclassical" major histocompatibility complex class I molecules, and the major histocompatibility complex class II molecules, HLA-DR, are internalized in Langerhans and indeterminate cells through common receptor-mediated endocytosis organelles.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1987

Human epidermal Langerhans cells internalize by receptor-mediated endocytosis T6 (CD1 "NA1/34") surface antigen. Birbeck granules are involved in the intracellular traffic of the T6 antigen.

Using immunogold staining of a suspension of living human epidermal cells to identify the Langerhans cell membrane-associated antigen T6 (revealed by the monoclonal antibody BL6), we have observed internalization of T6 antigen in Langerhans cells. This phenomenon is at least partly due to receptor-mediated endocytosis involving coated pits, coated vesicles, endosomes, the smooth endoplasmic reticulum, and lysosomes. These ultrastructural results suggest that T6 antigen may be part of a receptor site. Following receptor-mediated endocytosis, the appearance in the cell center of the first labeled Birbeck granules suggests that Birbeck granules could represent T6 intracellular transport organelles carrying T6 from the central part of the cell to an unknown destination.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1987

Internalization by receptor-mediated endocytosis of T6 (CD1 "NA1/34") surface antigen in T6 positive human cord blood cells (Langerhans cell precursors?).

A subset of T6 positive cells was recently separated from normal human cord blood mononuclear cells. It was shown to coexpress HLA-DR and myeloid differentiation antigens (Mo1, MY4). The phenotype and ultrastructure of the cells suggested that these T6 positive cells might be the precursors of the Langerhans cells of the skin. We have previously demonstrated by immunogold labeling techniques that the T6 surface antigen of human Langerhans cells of the skin is internalized in unfixed Langerhans cells or indeterminate cells by a process of receptor-mediated endocytosis. This process involved the formation of coated pits, coated vesicles, endosomes and lysosomes. Following this process, in Langerhans cells, gold labeled Birbeck granules appeared in the cell center often in continuity with endosomes. In the present study, we used an indirect immunogold labeling technique to reveal the T6 antigen present on the surface of living T6 positive cord blood mononuclear cells. We observed the internalization of the T6 surface antigen by a process of receptor-mediated endocytosis similar to that described in Langerhans cells of the skin. This process, however, was not followed by the appearance of intracytoplasmic Birbeck granules.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1986

ATPase Langerhans cell staining: a technique allowing progression from light to electron microscope observation.

A technique which enables good visualization of the membranous ATPase activity of epidermal Langerhans cells is described. The method has the advantage of keeping intact most of the ultrastructural details. It may allow the observation, under pathologic conditions, of ultrastructural modifications in ATPase-negative Langerhans cells still recognizable by their Langerhans cell granules.

Adenosine Triphosphatases↗
PubMed1985

Induction of tolerance to urushiol by epicutaneous application of this hapten on dinitrofluorobenzene-treated skin.

The application of a sensitizing dose of urushiol on a dinitrofluorobenzene (DNFB)-treated skin area significantly diminished the intensity of the urushiol challenge test in guinea pigs. Furthermore, the animals which had been first exposed to urushiol through DNFB-treated skin failed to become sensitized in a second sensitization attempt even when painted on a previously untreated area. This tolerance is hapten-specific and may be reversed by treatment with cyclophosphamide (200 mg/kg) shortly before another contact sensitization attempt to urushiol. In a previous work, we have shown that most of the Langerhans cells present in the DNFB-treated skin area are ATPase-negative and that there exists a link between the membranous ATPase system and the formation of Langerhans cell granules. The latter seem to develop in the course of a mechanism of adsorptive pinocytosis during which ATPase activity "disappears." Thus we suggest that the "unavailability" of ATPase-negative Langerhans cells for adequate processing a second hapten may result from the incapacity of cells lacking their ATPase system to activate the intracellular events that depend on this system and that normally lead to sensitization.

Adenosine Triphosphatases↗
PubMed1985

ATPase and morphologic changes induced by UVB on Langerhans cells in guinea pigs.

We have devised, in guinea pigs, an improved ATPase technique which enables one to proceed from light to electron microscope study while preserving, on the ultrastructural level, the various membranous structures, in particular the Langerhans cell (LC) granules. Using this method, we have been able to confirm the action of acute, low-dose UVB on the surface enzymatic marker, ATPase. Moreover, this study has shown that the ATPase-negative LC contain abnormal LC granules or, more often, are deficient in LC granules. In a previous work, we have shown that, after epicutaneous application of a hapten, one successively observes an extensive adsorptive pinocytosis process, the disappearance of the membranous ATPase system, and the appearance of LC granules in the cytoplasm. Therefore we may suppose that, after UVB irradiation, the disappearance of the ATPase system and/or the possible alteration of the adsorptive pinocytosis process interrupts or alters the formation of LC granules. These successive events might play a vital role in the formation of the hapten--carrier protein-Ia antigen complex. In their absence in a large number of LC, following UV irradiation, epicutaneous application of a hapten would lead to the development of a state of immune tolerance.

Adenosine Triphosphatases↗
PubMed1985

[Formation of Langerhans granules seems linked to membrane ATPase activity of epidermal Langerhans cells].

The epidermis contains a population of dendritic cells, Langerhans cells (LC), derived from cells originating from bone marrow, bearing receptors for the Fc fragment of IgG and for the C3 fraction of complement and expressing at their surface Ia antigens of the major histocompatibility system. These cells with multiple immunological functions are capable of presenting antigens to immunocompetent cells. The labeling of LC through revelation of their membranous ATPase activity constitutes one of the best available techniques for their visualization. Moreover, the presence of this ATPase activity appears to be a prerequisite for the induction of contact sensitivity, since in the absence of such activity, the epicutaneous application of a hapten induces a state of immunological tolerance. Applying, at a sensitizing dose, 2,4-dinitrofluorobenzene (DNFB) on an untreated guinea-pig skin surface results in a momentary drop in the number of ATPase positive LC in the application zone. Using an improved technique for ATPase labeling (Hanau et coll. submitted for publication, 1985)--which allows one to extend the study from optical to electron microscopy--we observed by electron microscopy the formation, within the LC, of numerous Langerhans granules, concurrent with the loss of ATPase membranous activity. These granules, first described by Birbeck et coll. and specific to LC in the epidermis, have a complex structure. On a section, they may display either a linear aspect (rod-like)--with sometimes a vesicular portion at one extremity (racket-like)--or a circular shape. Whatever their shape, they always show a central striation, which gives them a zipper-like appearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1984

A complex poroma-like adnexal adenoma.

Hidroacanthoma simplex, eccrine poroma, and dermal duct tumor are benign adenomas that develop from excretory ducts of eccrine glands and all three are variants of eccrine acrospiroma. To date, counterparts in apocrine or sebaceous glands have not been reported, but in this study we describe an adnexal, poroma-like adenoma that showed apocrine and sebaceous differentiations. Apocrine structures have the same embryonic origin as does the pilosebaceous system; both are derived from the primary epithelial germ. We suggest that the lesion we describe is truly a sebaceous and apocrine poroma. It must be distinguished from an infundibular adenoma whose pattern reproduces that of follicular poroma.

Adenoma↗
PubMed1984

Perforating lichen planus.

We describe a case of perforating lichen planus. The foreign material eliminated by this path appears to be represented by the numerous hyaline bodies present at the base of the perforation. This unusual variant may be added to the many variants of lichen planus previously described: atrophic, hypertrophic, planopilaris, bullous, etc. . .

Biopsy↗