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Biomedical subjects

D Schmitt

Publications and source records attributed to D Schmitt.

At least 91 records · Page 5Linked to original sources
PubMed1999

The kinetics of translocation and cellular quantity of protein kinase C in human leukocytes are modified during spaceflight.

Protein kinase C (PKC) is a family of serine/threonine kinases that play an important role in mediating intracellular signal transduction in eukaryotes. U937 cells were exposed to microgravity during a space shuttle flight and stimulated with a radiolabeled phorbol ester ([3H]PDBu) to both specifically label and activate translocation of PKC from the cytosol to the particulate fraction of the cell. Although significant translocation of PKC occurred at all g levels, the kinetics of translocation in flight were significantly different from those on the ground. In addition, the total quantity of [3H]PDBu binding PKC was increased in flight compared to cells at 1 g on the ground, whereas the quantity in hypergravity (1.4 g) was decreased with respect to 1 g. Similarly, in purified human peripheral blood T cells the quantity of PKCdelta varied in inverse proportion to the g level for some experimental treatments. In addition to these novel findings, the results confirm earlier studies which showed that PKC is sensitive to changes in gravitational acceleration. The mechanisms of cellular gravisensitivity are poorly understood but the demonstrated sensitivity of PKC to this stimulus provides us with a useful means of measuring the effect of altered gravity levels on early cell activation events.

Biological Transport↗
PubMed1999

Fragrance and contact allergens in vitro modulate the HLA-DR and E-cadherin expression on human epidermal Langerhans cells.

BACKGROUND: Epidermal Langerhans cells (LCs) play a critical role in the induction of contact hypersensitivity. The LCs leave the skin, move to the regional lymph nodes and present the allergens embedded in the HLA-DR molecule to naive T-lymphocytes. To allow LC emigration from the epidermis, E-cadherin must be downregulated. In this study, we have examined the early events that occur in the human epidermis after exposure to three strong contact sensitizers and two commonly used fragrances by examining alterations of E-cadherin and HLA-DR expression. METHODS: To determine whether E-cadherin and HLA-DR levels were modulated by allergens, flow cytometry was utilized to evaluate E-cadherin and HLA-DR expression on human epidermal LCs exposed to the different chemicals for 4 h at 37 degrees C. RESULTS: In vitro stimulation with the contact sensitizers isoeugenol, cinnamaldehyde, 2,4, 6-trinitrobenzenesulfonic acid, Bandrowski'sbase, or p-phenylene diamine resulted in a dose-dependent decrease of HLA-DR expression on the surface of LCs without affecting the number of positive cells. These contact allergens induced a downregulation of E-cadherin expression as well as a significant decrease of the percentage of E-cadherin-positive cells. Incubation with an irritant, sodium lauryl sulfate, did not significantly change HLA-DR and E-cadherin expression. CONCLUSIONS: Based on the alteration of E-cadherin and HLA-DR expression of human LCs under short-term exposure conditions, there was a clear difference between contact sensitizers and a well-characterized irritant. For the first time, the ability of fragrance allergens in dipropylene glycol, a widely used vehicle in fragrance and cosmetic industries, was demonstrated to induce human LC phenotypic alterations. In combination with a series of in vitro tests, this rapid and simple method should help to detect the sensitizing potential of a substance to be applied onto the human skin as an alternative to animal testing.

Acrolein↗
PubMed1999

Expression of substance P receptors in normal and psoriatic skin.

Recently, substance P receptors (SPR) have been detected in neonatal foreskin. Our purpose was to determine the expression of SPR in other localizations than neonatal foreskin. As SP has been implicated in the pathogenesis of inflammatory cutaneous lesions, we wondered whether SPR localization was modified in psoriatic lesions. In normal skin, SP binding sites were detected using biotinylated SP and abrogated by a specific NK1 antagonist (spantide) on blood vessels, sweat glands and hair follicles. In the normal epidermis, SPR were usually observed on granular layers but may also be observed on other cell layers. The SP binding processed on cultured keratinocytes demonstrated that SPR were expressed in the epidermis, except basal cell layers, confirming that keratinocytes constitutively express SPR. In skin lesions of psoriatic patients, SP binding sites were expressed on the uppermost keratinocytes which are not granular cells, and seem to be overexpressed. Our results raise the question of the role of SPR on psoriatic keratinocytes.

Adult↗
PubMed1999

Myeloperoxidase-generated reactive nitrogen species convert LDL into an atherogenic form in vitro.

Oxidized LDL is implicated in atherosclerosis; however, the pathways that convert LDL into an atherogenic form in vivo are not established. Production of reactive nitrogen species may be one important pathway, since LDL recovered from human atherosclerotic aorta is enriched in nitrotyrosine. We now report that reactive nitrogen species generated by the MPO-H2O2-NO2- system of monocytes convert LDL into a form (NO2-LDL) that is avidly taken up and degraded by macrophages, leading to massive cholesterol deposition and foam cell formation, essential steps in lesion development. Incubation of LDL with isolated MPO, an H2O2-generating system, and nitrite (NO2-)-- a major end-product of NO metabolism--resulted in nitration of apolipoprotein B 100 tyrosyl residues and initiation of LDL lipid peroxidation. The time course of LDL protein nitration and lipid peroxidation paralleled the acquisition of high-affinity, concentration-dependent, and saturable binding of NO2-LDL to human monocyte-derived macrophages and mouse peritoneal macrophages. LDL modification and conversion into a high-uptake form occurred in the absence of free metal ions, required NO2-, occurred at physiological levels of Cl-, and was inhibited by heme poisons, catalase, and BHT. Macrophage binding of NO2-LDL was specific and mediated by neither the LDL receptor nor the scavenger receptor class A type I. Exposure of macrophages to NO2-LDL promoted cholesteryl ester synthesis, intracellular cholesterol and cholesteryl ester accumulation, and foam cell formation. Collectively, these results identify MPO-generated reactive nitrogen species as a physiologically plausible pathway for converting LDL into an atherogenic form.

Animals↗
PubMed1999

Human normal dermal fibroblasts express somatostatin receptors.

The hormone/neuropeptide somatostatin (SOM) exerts multiple functions in the central nervous system, the immune system, the hypothalamo-pituitary axis, the gastrointestinal tract, and the pancreas. Endogenous SOM occurs in 2 biologically active forms, with 14 or 28 amino acids. Five subtypes of SOM receptors have been cloned. SOM is present in human skin. We have investigated the expression of SOM receptors on human dermal normal fibroblasts. Biotinyl-SOM allowed the visualization of SOM receptors on human dermal fibroblasts. Radioligand binding studies with (3-[125I]iodotyrosyl11)-SOM-14 were performed on these cells and the effect of SOM-14 on the DNA synthesis by fibroblasts was evaluated by measuring [3H]-methyl thymidine incorporation. Saturation curve, and Scatchard plot showed a homogeneous class of receptors with a Bmax of 0.055 +/- 0.023 nM and KD of 2.0 +/- 0.4 nM (values: mean +/- SEM). Fibroblasts expressed 3,317 +/- 1,385 binding sites per cell. Competitive displacement experiments showed that SOM-14 IC50 was 69.3 +/- 4.5 nM (mean +/- SEM), for SOM-28 33.2 +/- 6.0 nM and for octreotide 36.5 +/- 3.3 nM. The KI values calculated from these IC50 were, respectively: 62.4 +/- 4.1 nM; 29.9 +/- 5.4 nM; 32.9 +/- 2.9 nM. We conclude that subtype 2 or 3 SOM receptors is present on human normal dermal fibroblasts. A weak effect of SOM-14 on DNA synthesis was observed with SOM concentrations of 10(-7) and 10(-6) M.

Animals↗
PubMed1998

Stratum corneum, corneodesmosomes and ex vivo percutaneous penetration.

The stratum corneum is composed of cornified keratinocytes, joined together with corneodesmosomes and embedded in the relatively hydrophobic intercellular substance. Formation of this horny layer and its constant desquamation are fundamental processes leading to the establishment of an efficient epidermal barrier. We examined structural changes occurring in the stratum corneum ex vivo, in order to better understand the mechanisms regulating corneocyte desquamation at the epidermal surface and influencing percutaneous penetration of exogenous substances. Morphologic modifications were induced by occlusion, increasing the tissue hydration, or by application of propylene glycol, a hydrophilic solvent of small molecular size. Distribution of the major epidermal antigens, markers of terminal differentiation, was studied immunohistochemically and showed no modification related to the tissue alteration. Skin samples were fixed in paraformaldehyde and either postfixed in OsO4 and embedded in Epon or postfixed in RuO4 and embedded in epoxy and acrylic resins. Structural composition and spatial organization of the elements present in the intercorneocyte spaces were evaluated ultrastructurally, with special attention paid to the fate of corneodesmosomes. Our results suggest that the spontaneous organization of lipids excreted into the intercellular spaces and constitution of the lamellar multilayers in the lower stratum corneum are at the origin of partition of the intercellular compartment to the hydrophobic and hydrophilic domains. The latter, compatible with the proteinic contents, seem to be displaced by the hydrophobic components undergoing reorganization, towards the invariable hydrophilic foci represented by corneodesmosomes. This mechanism may be involved in the delivery of proteolytic enzymes, thus contributing to the progressive degradation of corneodesmosomal proteins.

Desmosomes↗
PubMed1998

Cholesteryl hydroperoxyoctadecadienoate from oxidized low density lipoprotein inactivates platelet-derived growth factor.

Both oxidized low density lipoprotein (ox-LDL) and platelet-derived growth factor (PDGF) have been implicated in the genesis of various inflammatory responses, including atherosclerosis. We demonstrate here a novel interaction between specific oxidized lipids derived from ox-LDL and PDGF. The lipid moieties of ox-LDL caused concentration-dependent inactivation of PDGF as measured by loss of its mitogenic activity and its binding to high affinity receptors. Reverse-phase and normal-phase HPLC were used to purify the inactivating component in the lipid mixture. By fast atom bombardment mass spectrometry and infrared spectroscopy, we identified the inactivating lipids as the 9- and 13-hydroperoxy derivatives of cholesteryl linoleate, cholesteryl hydroperoxyoctadecadienoate. When a series of cholesteryl esters were subjected to oxidizing conditions, only those containing two or more double bonds caused inactivation of PDGF; the extent of inactivation increased with increased levels of oxidation. Exposing PDGF to cumene hydroperoxide, t-butyl hydroperoxide, or hydrogen peroxide did not affect the activity of the mitogen. The oxidized lipid had no effect on the mitogenic activity of epidermal growth factor but did abolish the mitogenic activity of basic fibroblast growth factor and the antiproliferative activity of transforming growth factor beta1. The inactivation of PDGF and other cytokines by lipid hydroperoxides may occur in such processes as vascular disease, inflammation, and wound healing.

Arteriosclerosis↗
PubMed1998

Circulating vascular endothelial growth factor (VEGF) is not a prognostic indicator in malignant melanoma.

Among angiogenic peptides, vascular endothelial growth factor (VEGF) is associated with growth and metastasis of solid tumours. In order to determine whether VEGF could be involved in the clinical course of malignant melanoma, we studied 96 patients with primary or metastatic melanoma and we reported the follow-up of nine cases who initially presented with a primary melanoma and further developed metastasis over a period of 12-25 months. Circulating VEGF levels quantified by enzyme-linked immunosorbent assay were found to be elevated in patients with primary or metastatic melanoma compared to a control group (P < 0.001), but no significant difference occurred between primary and metastatic melanoma. The follow-up of patients who developed metastasis showed high initial VEGF levels (in five out nine cases) which remained increased with the course of the disease. It is conceivable that increased VEGF levels reflect an intense activation of the host immune system but the variations in the concentration of circulating VEGF were not considered as an indicator of disease evolution in malignant melanoma.

Adult↗
PubMed1998

The relation between hand morphology and quadrupedalism in primates.

Primate hands can be classified into two broad categories on the basis of ray proportions and other features. Ectaxonic hands are characterized by a longer fourth ray and are found in most strepsirhines. Most haplorhines possess mesaxonic hands which are characterized by a longer third ray. Preuschoft et al. ([1993] in H. Preuschoft and D.J. Chivers (eds.): Hands of Primates. Berlin: Springer-Verlag, pp. 21-30) proposed a biomechanical model which predicts that, during quadrupedalism, a mesaxonic hand should be held in a more neutral position with respect to the forearm, whereas an ectaxonic hand should be more ulnarly deviated. The relation between hand positioning and the mesaxony/ectaxony categorization is investigated for 27 primate taxa. Videotapes were recorded for each species walking quadrupedally on arboreal supports. Several species were also videotaped during ground quadrupedalism. The degree of deviation of the hand relative to the substrate and the grips utilized were quantified for 18 species from the videotapes. Primates with mesaxonic hands use deviated hand positions and grips, especially when walking quadrupedally on small poles. Several species with ectaxonic hands use neutral hand positions and grips when walking quadrupedally on similar supports. Also, several primates, with either ectaxonic or mesaxonic hands, display a combination of deviated hand positions and grips when on arboreal substrates and neutral hand positioning when on the ground. The statistical results indicate that hand positioning during quadrupedal walking is more variable than expected based on the mesaxony/ectaxony classification. Furthermore, radiographic data suggest that primates evolved at least two different mechanisms of hand ulnar deviation.

Animals↗
PubMed1998

Human epidermal Langerhans cells express the mannose-fucose binding receptor.

Sugar receptors are being increasingly implicated in host-pathogen interactions because of their specific recognition of carbohydrates of microorganisms. The aim of this study was to identify sugar receptors expressed on the surface of human epidermal Langerhans cells (LC). To this end, binding of a panel of fluorescent neoglycoproteins to human epidermal LC was analyzed by quantitative flow cytofluorometry after standardization with calibrated beads. We demonstrate that fresh human LC are the only cells isolated from healthy epidermis which express a membrane receptor specific for fucose-bovine serum albumin (BSA) and mannose-BSA. Quantitative analysis of mannose-BSA or fucose-BSA binding showed non-linear Scatchard plots, denoting the presence of high and moderate affinity binding on the LC surface. The binding parameters of these two ligands were not significantly different. Mannan, the yeast mannose-rich polysaccharide, fucose-BSA, mannose-BSA and free fucose are strong competitors of the three known ligands of the mannose receptor, i.e. fucose-BSA, mannose-BSA and fluorescein isothiocyanate dextran. The amount of mannose-BSA and fucose-BSA bound to LC was 1.5-fold higher at 37 degrees C than at 4 degrees C, suggesting an internalization process. Antibodies raised against the human macrophage mannose receptor strongly stained CD1a-positive LC but not CD1a-negative population. Taken together, our data demonstrate that fresh human LC are the only cells in the epidermis to express a fucose-mannose receptor on their surface.

Animals↗
PubMed1998

Monocyte-derived dendritic cells have a phenotype comparable to that of dermal dendritic cells and display ultrastructural granules distinct from Birbeck granules.

Most monocyte-derived dendritic cells (DC) display CD1a, like Langerhans cells (LC) and some dermal DC, but their relationship with these skin DC remains unclear. To address this issue, we studied the expression of different antigens characteristic of skin DC and of monocyte/macrophages in CD1a+ and CD1a- monocyte-derived DC. Their phenotype indicated that they may be related to dermal DC rather than to LC, i.e., they were all CD11b-positive, and 72% were Factor XIIIa-positive, but they did not express E-cadherin nor VLA-6. It is interesting that CD1a+ and CD1a-cells showed intracytoplasmic granules that were different from LC Birbeck granules. These phenotypical and ultrastructural features are comparable to those of CD14-derived DC obtained from cord blood precursors [C. Caux et al. J. Exp. Med. 184, 695-706]. These results show a close relationship between these two in vitro models, which are both related to dermal DC.

Antigens, CD↗
PubMed1998

EMG of the human flexor pollicis longus muscle: implications for the evolution of hominid tool use.

Modern humans possess a distinct and well-developed flexor pollicis longus muscle, an extrinsic thumb flexor which is "either rudimentary or absent" in great apes (Straus, 1942, p. 228). Previous workers (e.g., Napier, 1962; Susman, 1988) have related the origin of a well-developed flexor pollicis longus muscle to the acquisition of precision grasping and stone tool making capabilities in early hominids. The proposed functional association between flexor pollicis longus activity, precision grasping, and stone tool manufacture has, however, never been tested experimentally. This study uses electromyographic techniques (EMG) to investigate the role of flexor pollicis longus during a variety of tool making, tool using, and manipulatory behaviors in order to determine the functional and evolutionary significance of the human flexor pollicis longus muscle. Our results indicate that flexor pollicis longus is recruited during forceful tool using and stone tool making behaviors, regardless of the power or precision grip used to hold the tool. In particular, both stone tool use and stone tool making employing three- and four-jaw chuck precision grips elicit consistently high levels of FPL activity. Flexor pollicis longus activity increases most when resistance is increased to the thumb's volar pad during these hammering, cutting, and knapping behaviors. In contrast, we observed relatively low levels of flexor pollicis longus activity during the fine manipulation of food items, the making of slender wooden probes, and the use of these probes as tools. The paleontological, archaeological, and experimental data suggest that a well-developed flexor pollicis longus muscle functioned initially in the hominid lineage to stabilize the terminal pollical phalanx against loads applied to the thumb's apical pad during the frequent and forceful use of unmodified stones as tools.

Animals↗
PubMed1998

Effects of CD40 ligation on human keratinocyte accessory function.

CD40/CD40 ligand interactions are known to play a key role in the development of immune reactions, especially by enhancing the costimulatory function of professional antigen-presenting cells (APC). Little is known, however, about the role this receptor plays on occasional APC, i.e. cells that are induced to express MHC class II molecules following an inflammatory process. In this study, we used CD40 ligand-transfected cells to analyze the effect of CD40 ligation on the phenotype, as well as accessory function, of human keratinocytes. We found that CD40 ligation enhanced ICAM-1 expression and did not upregulate HLA-DR, CD80 or CD86 expression on IFN-gamma-treated keratinocytes. CD40 triggering was not sufficient to generate primary allogeneic T-cell responses even in the presence of anti-CD28 monoclonal antibody (mAb). Moreover, CD40 ligation, in the presence or not of IFN-gamma, did not alter the accessory function of keratinocytes in PHA- or superantigen-induced T-cell activation. The lack of effect on the T-cell response was confirmed in blocking experiments using anti-CD40 mAbs. Collectively, these results suggest that CD40-CD40 ligand interactions on nonprofessional APC may amplify the inflammatory reaction without providing a mitogenic signal to the T cells.

3T3 Cells↗
PubMed1998

Detection of low copy numbers of HPV DNA by fluorescent in situ hybridization combined with confocal microscopy as an alternative to in situ polymerase chain reaction.

In genital lesions infected by human papillomavirus (HPV), histological criteria and HPV DNA typing are of prognostic value. Therefore, non-radioactive methods such as in situ hybridization are used extensively since they preserve the histological organization of the tissue, and allow the detection and characterization of HPV DNA. However, the sensitivity of these methods is often limited to detection of low copy numbers of HPV DNA in isolated cells or in tissue sections, and therefore alternative techniques have been explored. In the present study, 1-2 copies of HPV DNA were visualized in SiHa cells either by in situ amplification of nucleic acid sequences with the polymerase chain reaction (PCR) or by fluorescent in situ hybridization (FISH) associated with observation by laser scanning confocal microscopy (LSCM). The latter procedure was evaluated for use on histological tissue sections to identify low copy numbers of HPV DNA. Genital lesions which were negative by enzymatic in situ hybridization and FISH but histologically suspected of HPV infection were investigated, and intense signals were obtained both with in situ PCR and with the combined use of FISH and LSCM. Therefore, the combination of FISH with LSCM examination may be as valuable as in situ PCR to detect viral genes present in small amounts in isolated cells and in tissue sections.

Condylomata Acuminata↗
PubMed1998

IL-4 addition during differentiation of CD34 progenitors delays maturation of dendritic cells while promoting their survival.

Dendritic cells (DC) are the most effective cells for antigen presentation in primary immune responses. Human cord blood CD34+ progenitors cultured in the presence of GM-CSF and TNF alpha generate a heterogeneous population of DC including Langerhans-like DC (LLDC) and monocytes. We describe here that IL-4 exerts different effecs in such culture according to the cells considered. Thus, IL-4 favors DC components at the expense of monocytic development, and permits long-time persistence of DC which can be maintained up to one month in culture. These results show an IL-4-dependent inhibition of proliferation and emergence of CD14+ cells. Notably, however, IL-4 also acts on the DC precursors. Thus, IL-4 enhances survival and delays maturation of LLDC from CD1a+ CD14- precursors. In addition, IL-4 also favors orientation of CD14+ CD1a- DC/monocyte precursors towards dermal-type CD1a+ DC. DC recovered from IL-4 treated cultures display reduced allostimulatory capacity, but this function is restored upon IL-4 weaning. Finally, a short (48h) IL-4 pulse is sufficient to favor DC development. The present study demonstrates that IL-4 positively regulates DC development at several levels on distinct precursor cells.

Antigens, CD1↗
PubMed1998

Utility of serum progesterone and prolactin analysis for assessing reproductive status in the Asian elephant (Elephas maximus).

Concentrations of serum progesterone and prolactin were assessed during the perioestrous period and throughout gestation in the Asian elephant (Elephas maximus) as a means of generating information of potential use to managers. In > 95% of perioestrous periods (n=35), behavioural oestrus (as determined by bull interest, mounting and/or breeding) coincided with the onset of increased serum progesterone concentrations at the beginning of the luteal phase and continued through Day 7 (Day 1 = first significant serum progesterone rise). Within individuals, 1- to 2-day transient decreases (P < 0.05) in serum progesterone occurred between Days 2 and 9. Notably, no sexual behaviour was observed in any female after this transient fall in progesterone. Prolactin concentrations fluctuated randomly throughout the perioestrous period, with no clear pattern. During the study, four females conceived (one conceived twice), and two delivered three viable offspring. Serum progesterone was elevated above baseline throughout gestation, and then declined precipitously 2-3 days before parturition. Serum prolactin concentrations were significantly elevated above baseline (P < 0.05) after 5-6 months of gestation and remained high until after parturition. This study confirms that serum progesterone and prolactin analyses are useful tools for monitoring the reproductive status of Asian elephant females. Specifically, the transition from low to high progesterone secretion during the late interluteal/early luteal phase is predictive of oestrus and can be used to coordinate breeding efforts. Pregnancy can be confirmed by elevated serum prolactin after 6 months postbreeding, whereas the late gestational decrease in progesterone is predictive of impending parturition.

Animals↗
PubMed1998

In vitro dermal intoxication by bis(chloroethyl)sulfide. Effect on secondary epidermization.

Skin intoxication by bis(beta-chloroethyl)sulfide (BCES; sulfur mustard) induces cutaneous lesions similar to thermal burns, characterized by slowness of skin healing. We have developed an in vitro model of skin equivalent to investigate mechanisms involved in this delay. Direct intoxication of dermal equivalent produced dose- and time-dependent cytotoxicity. A decrease of macroscopic retraction of collagen gels was observed, parallel to the toxic concentration with, at histological level, absence of collagen fiber reorganization. Fibroblast synthesis of fibronectin was also inhibited by intoxication, as demonstrated at an immunobiochemical and immunohistochemical level. These dermal alterations were correlated with secondary modifications of epithelial maturation of nonintoxicated normal human keratinocytes. Cellular adhesion was perturbed, as visualized by a delay in expression and reorganization of basement membrane components, laminen, collagen IV, and fibronectin. Epidermal terminal differentiation was also affected, as shown by the absence of profilaggrin/filaggrin biosynthesis. We demonstrated in vitro, that direct dermal alterations secondarily induce disturbance of epithelial maturation. Taken together, these data show the fundamental role of dermal-epidermal interactions in a normal skin reconstruction. Clinical slowness of wound healing observed after cutaneous intoxication by BCES may thus be explained by direct alkylation of some structures and further disturbances of their biosynthesis.

Basement Membrane↗