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Biomedical subjects

M Michel

Publications and source records attributed to M Michel.

At least 55 records · Page 3Linked to original sources
PubMed1999

Characterization of a new tissue-engineered human skin equivalent with hair.

We designed a new tissue-engineered skin equivalent in which complete pilosebaceous units were integrated. This model was produced exclusively from human fibroblasts and keratinocytes and did not contain any synthetic material. Fibroblasts were cultured for 35 d with ascorbic acid and formed a thick fibrous sheet in the culture dish. The dermal equivalent was composed of stacked fibroblast sheets and exhibited some ultrastructural organization found in normal connective tissues. Keratinocytes seeded on this tissue formed a stratified and cornified epidermis and expressed typical markers of differentiation (keratin 10, filaggrin, and transglutaminase). After 4 wk of culture, a continuous and ultrastructurally organized basement membrane was observed and associated with the expression of laminin and collagen IV and VII. Complete pilosebaceous units were obtained by thermolysin digestion and inserted in this skin equivalent in order to assess the role of the transfollicular route in percutaneous absorption. The presence of hair follicles abolished the lag-time observed during hydrocortisone diffusion and increased significantly its rate of penetration in comparison to the control (skin equivalent with sham hair insertion). Therefore, this new hairy human skin equivalent model allowed an experimental design in which the only variable was the presence of pilosebaceous units and provided new data confirming the importance of hair follicles in percutaneous absorption.

Adult↗
PubMed1999

The calcium-activated neutral protease calpain I is present in normal foetal skin and is decreased in neonatal harlequin ichthyosis.

Calcium concentration is a critical factor for epidermal differentiation and is implicated in the expression and post-translational modification of numerous proteins in suprabasal cells of the epidermis. Calpains (calcium-activated neutral proteases) are believed to participate in signal transduction via highly regulated cytoplasmic protease activity. Here we investigate the expression of calpain I in normal human skin development and in neonatal harlequin ichthyosis (HI), a disorder of altered epidermal differentiation, especially the transition from the granular to the fully differentiated cornified layer. Calpain I was detected in developing foetal epidermis at 54 days estimated gestational age in the basal layer and the periderm of the developing foetal epidermis. By 125 days, calpain I was also detected in the granular layer. This pattern was maintained in newborn skin, but expression was significantly weaker in HI biopsies (n = 7). Reduced expression of calpain was specific to HI and was not observed in other skin diseases. Calpain was also normally expressed in the outer root sheath of hair follicles, in sebaceous glands and in sweat ducts and glands. Immunoblots of epidermal and keratinocyte extracts showed that the 78-kDa and 76-kDa active forms were generated via limited proteolysis of the 80-kDa inactive subunit; however, all forms were diminished in HI, consistent with findings in tissue sections. Our results show that calpain is present throughout the epidermis and is expressed from the early stages of development. These findings implicate calcium-mediated signalling events in the alteration of differentiation that occurs in HI.

Biomarkers↗
PubMed1999

The outcomes of an inpatient treatment program for geriatric patients with dementia and dysfunctional behaviors.

This study evaluated outcomes of an inpatient program designed to reduce severe agitated behavior in geriatric patients with dementia who could not be successfully treated on an outpatient basis. An individualized treatment plan was created for each patient (N = 250) that involved pharmacological and nonpharmacological interventions with behavioral, environmental, and psychological components. Assessment of behavioral, cognitive, and functional status was conducted for each patient on admission to the program and at discharge. Significant improvements on these assessments were observed. We conclude that the longitudinal, multidisciplinary approach used in this study was effective in significantly reducing intrusive and dangerous behaviors while preserving or enhancing patients' cognitive and functional abilities.

Aged↗
PubMed1999

Hypersensitivity syndrome due to 2 anticonvulsant drugs.

Drug-induced hypersensitivity syndrome is a multiorgan-system reaction characterized by fever, pleomorphic eruption, lymphadenopathy, eosinophilia, lymphocytosis and hepatitis. We report a drug hypersensitivity syndrome in a 6-year-old Tunisian child treated for epileptic absences with sodium valproate and ethosuximide. Imputability of these 2 drugs is probable because of the chronological and clinical features. Positive rechallenge with ethosuximide confirmed the toxicity of this drug. Sodium valproate was also responsible because patch testing was positive and followed by a generalized eruption. Human herpesvirus 6 (HHV6) antibody titers increased significantly within 15 days. There was a favourable outcome after discontinuation of the drugs and corticosteroid therapy. Our case is interesting because this drug hypersensitivity syndrome occurred with non-aromatic anticonvulsant drugs. It is the 1st case with ethosuximide and the 2nd with sodium valproate. We also observed a reactivation of HHV6 infection that may contribute to the development of this hypersensitivity syndrome.

Antibodies, Viral↗
PubMed1999

Are vaccination rates higher if providers receive free vaccines and follow contraindication guidelines?

BACKGROUND AND OBJECTIVES: Economics has been suggested as a barrier to vaccination, but data that link clinician reports to actual immunization rates are limited. This study examined the relationship between clinicians' self-report regarding likelihood of vaccinating and actual age at vaccination from a registry of children seen by the clinicians. METHODS: Standardized telephone survey results of 29 providers were compared to the immunization records of children seeing these providers, using analysis of contingency tables (on time versus late) and conditional hierarchical linear models with log age at diphtheria-tetanus-pertussis (DTP)#3, DTP#4, and measles-mumps-rubella (MMR)#1 as the dependent variables. RESULTS: Children seeing providers likely to refer an uninsured child for immunization were vaccinated at a later log age at DTP#4 but not for DTP#3 or MMR#1 than children seeing providers unlikely to refer. Vaccination rates were higher for MMR#1 (77% versus 48%), DTP#3 (84% versus 71%), and DTP#4 (82% versus 66%) among providers who received free vaccine, compared with children seen by providers who did not receive free vaccine. These results remained significant in the hierarchical analyses. Providers likely to vaccinate an 18-month-old with watery diarrhea had higher vaccination rates than those unlikely to vaccinate for MMR#1, DTP#3, and DTP#4; the results were also significant in the hierarchical analyses. CONCLUSION: Children are vaccinated later in the practices of providers who are likely to refer uninsured children to a public vaccine clinic for vaccination, who do not receive free vaccine supplies, or who overinterpret contraindications.

Age Factors↗
PubMed1998

[Immunogenetic bases of systemic lupus erythematosus in humans].

INTRODUCTION: Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown pathogenesis. Familial studies and concordance rates among affected twins suggest that human SLE has a strong genetic basis. CURRENT KNOWLEDGE AND KEY POINTS: Recent studies have emphasized that SLE, like other autoimmune diseases, is a complex genetic trait with contributions of both major histocompatibility complex (MHC) associated genes and multiple non-MHC genes. Recent significant advances have been made in the genetic analysis of complex traits, which allow the identification of new candidate genes in SLE. Among the genes reviewed in this article, some polymorphisms of Fc gamma receptor genes and other genes or loci localized on the long arm of the human chromosome 1 appear to be very promising. FUTURE PROSPECTS AND PROJECTS: The identification of new susceptibility genes in SLE will certainly provide important insights into the breakdown of self-tolerance mechanisms leading to autoimmune diseases. To achieve this objective, the recruitment of a large number of genetic traits of multiplex families presenting with SLE is therefore essential. More than 125 multiplex families have been collected to date in France.

Animals↗
PubMed1997

Gliotoxicity, reverse transcriptase activity and retroviral RNA in monocyte/macrophage culture supernatants from patients with multiple sclerosis.

In investigating a possible link between a novel retroviral agent (provisionally called MSRV), recently characterised in multiple sclerosis (MS), and the neuropathology of MS, it was found that there was a significant correlation between gliotoxicity and reverse transcriptase activity in monocyte/macrophage culture supernatants (MMCS) unique to MS patients. MMCS from healthy controls and patients with other neurological diseases did not display either gliotoxicity or reverse transcriptase activity. The observed gliotoxic effect was an initial, intermediate filament network disorganization and subsequent cell death which was specific to astrocytes and oligodendrocytes. The reverse transcriptase activity and MSRV-specific RNA were observed during the first 2 weeks of culture in MMCS from patients with active MS. The further elucidation of the molecular form(s) of this gliotoxic factor and its original source may be crucial in elucidating important etiopathogenic mechanisms in MS.

Animals↗
PubMed1997

Methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci: therapeutic realities and possibilities.

During the past decade much effort has been devoted worldwide to limiting the spread of methicillin-resistant Staphylococcus aureus. However, the recent emergence of almost untreatable vancomycin-resistant enterococci has led to a new and unexpected public health problem in hospitals and the community. Moreover, the threat of transfer of glycopeptide resistance to S aureus means that development of alternative antimicrobial strategies has become urgent. Whereas major advances have been made in our understanding of methicillin and vancomycin resistance mechanisms, we still need to identify the sources and reservoirs of the genetic determinants of resistance and to discover how they disseminate in the environment. The outcome of the battle between antimicrobials and bacteria is still uncertain, but the challenge is worth meeting.

Anti-Bacterial Agents↗
PubMed1997

Ultrastructure of adult human articular cartilage matrix after cryotechnical processing.

The ultrastructure of adult human articular cartilage matrix is reexamined in tissue processed according to recently improved cryotechniques [Studer et al. (1995) J. Microsc., 179:321-332]. In truely vitrified tissue, a network of fine cross-banded filaments (10-15 nm in diameter) with a periodicity characteristic of collagen fibrils is seen throughout the extracellular substance, even within the pericellular compartment, which has hitherto been deemed free of such components. Proteoglycans fill the interstices between these entities as a homogeneously distributed granular mass; they do not manifest a morphologically identifiable reticular structure. Longitudinally sectioned collagen fibrils exhibit variations in thickness and kinking; they tend to align with their periodic banding in register and are frequently seen to split or fuse along their longitudinal course. The tendency of fibrils to form bundles is greater in deeper zones than in more superficial ones. A duality in the orientation of fibrils and fibril bundles is observed within the interterritorial matrix compartment: superimposed upon the well-characterized arcade-like structure formed by one subpopulation is another, more randomly arranged one. The classical concepts of matrix organization thus need to be modified and refined to encompass these findings.

Cartilage, Articular↗
PubMed1997

From newborn to adult: phenotypic and functional properties of skin equivalent and human skin as a function of donor age.

The skin's most important function is to act as a barrier against fluid loss, microorganism infections, and percutaneous absorption. To fulfill this role, keratinocytes proliferate and differentiate to produce a protective layer: the stratum corneum. Because stem cells are responsible for the production of differentiated progeny and stem cells (K19-expressing cells) are less abundant in skin from older donors, the purpose of this study was to establish whether histological and functional properties of differentiating skin is influenced by donor age. The in vitro model developed for the evaluation of skin properties (Michel et al., 1995) was used to produce skin equivalents from newborn, child, and adult keratinocytes. Throughout maturation, skin equivalents were compared with corresponding skin biopsies for keratin, filaggrin, and transglutaminase expression. Percutaneous absorptions of hydrocortisone also were measured and correlated with lipid content. After 1 wk of immersed culture, the epidermal layer of newborn skin equivalents was thicker than child and adult epidermis. As expected, a greater proportion of cutaneous stem cells was present in newborn compared with children and adult skin equivalents. No age-related difference was observed for differentiation markers. When skin equivalents were cultured at the air-liquid interface, cell differentiation and stratum corneum formation were induced, and the age-related variation in the thickness of the epidermal layer disappeared. Percutaneous absorption through these matured skin equivalents did not vary with age. Their lipid density and profile were similar. Accordingly, skin biopsies exhibited comparable percutaneous absorption profiles independently of donor age. In conclusion, although newborn skin equivalents, or skin biopsies, contained more stem cells than child and adult counterparts, no age-related histological difference was observed in the differentiated tissues. Moreover, the functional barrier property of skins and matured skin equivalents did not vary with age. Therefore, both newborn and adult keratinocytes produce useful in vitro models to study epidermal differentiation processes involved in both normal and pathological states.

Absorption↗
PubMed1997

Two Encephalitozoon cuniculi strains of human origin are infectious to rabbits.

The microsporidian Encephalitozoon cuniculi can infect a wide variety of mammals including man. In this study, E. cuniculi isolates of animal origin were compared with 6 isolates obtained from HIV-infected patients. Based on results of Western blot analysis, random amplified polymorphic DNA (RAPD) and the sequence of the rDNA internal transcribed spacer (ITS) the isolates were classified into 3 groups with the repeated element 5'GTTT-3' in the ITS being a reliable genetic marker. Five isolates from Swiss patients were found to be homologous to isolates from Swiss rabbits (strain I). The sixth isolate from a patient from Mexico differed by all methods and could be attributed to E. cuniculi strain III that has been described from 2 dogs from the USA. All of these isolates were distinguished from isolates from blue foxes from Norway (strain II). Intraspecific nucleotide divergence of the SSU rRNA gene of E. cuniculi belonging to the 3 strains was in the same low range (0.00-0.15%) as was found for the corresponding sequence of 2 E. hellem isolates. Groups of 2 rabbits were infected by oral inoculation of 10(7) E. cuniculi spores (2 isolates from strain I of human and rabbit origin, 1 from strain III) as shown by antibody responses and the re-isolation of the parasites from brain material. The results provide further evidence that per oral transmission of the parasite between various hosts is feasible.

Animals↗
PubMed1997

[Congenital toxoplasmosis and seroconversion at the end of pregnancy: clinical observations].

We report seven cases of subclinical congenital toxoplasmosis secondary to maternal primary infections. Mothers were infected between two and four weeks prior to delivery. The diagnostic criteria of congenital infections included: IgM antibody (Ab) (1 case); IgM and IgA Ab (1 case); a real IgG seroconversion in the neonatal and postnatal samples (3 cases); persistence of IgG Ab beyond 6 months post-delivery (2 cases). A treatment was initiated, including a combination of pyrimethamine + sulfadiazine (6 cases); trimethoprim + sulfamethoxazole (1 case). This retrospective study suggests that it is important to screen the non-immune pregnant women until delivery. We confirmed the usefulness of a combination of isotypes of antibodies for the accurate assessment of congenital infection. Finally, infected infants have to be treated and monitored clinically and immunologically during the first year of life.

Adult↗
PubMed1997

Cell cultures and associated retroviruses in multiple sclerosis. Collaborative Research Group on MS.

Retroviral particles associated with reverse transcriptase (RT) activity in cell-cultures from MS patients have been reported by different groups. Cell-cultures have been used for the study and characterization of the corresponding retroviral genome which we have shown is related to ERV9 in the pol region. Previously unpublished details of a study with monocyte cultures are presented together with observations on leptomeningeal and choroid-plexus cultures. The generation of self-transformed cultures after inhibition of interferon, followed by the loss of retroviral expression and recurrent apoptosis, is analyzed. Retroviral particles with RT-activity are produced in monocyte cultures with an apparent correlation with MS disease activity. However, though leptomeningeal and choroid plexus cells from MS can be passaged for a limited period, their evolution in vitro is not compatible with stable retroviral expression. These culture limitations greatly hampered progress on the elucidation of the retroviral genome sequence.

Adult↗
PubMed1997

Skin reactions to hydroxyzine.

Sensitivity to histamine H1-antagonists has mainly been observed with phenothiazine and ethylenediamine, and is very rare with hydroxyzine. We report 3 cases of sensitization to hydroxyzine, which was prescribed to treat urticaria and atopic dermatitis. A generalized maculopapular eruption appeared shortly after taking the drug. Patch tests with Atarax tablet were positive +3, and +2 or +3 with different dilutions of hydroxyzine. Patch tests with ethylenediamine, piperazine and other antihistamines were negative; therefore, there is no cross-allergy. We believe these rapid systemic reactions to hydroxyzine after the initial dose may have been due to prior systemic sensitivity to this drug, which cannot be used topically. Allergy to antihistamines must be considered when cutaneous lesions worsen on such therapy.

Adult↗
PubMed1997

Photodermatitis from ketoprofen with cross-reactivity to fenofibrate and benzophenones.

The aim of this study was to evaluate the possibility of cross-reactivity between ketoprofen, fenofibrate and benzophenones because of their structural similarities. Seven patients presenting photodermatitis from ketoprofen underwent patch and photopatch tests. Ketoprofen, fenofibrate, benzophenone 3, benzophenone 10, benzophenone 4, personal medications and topical creams were tested. All patients had positive patch or photopatch tests to ketoprofen and fenofibrate, four patients had positive UVA photopatch tests to benzophenone 3, and two to benzophenone 10. Patients presenting photosensitization to ketoprofen may also have cross-reactivity to fenofibrate and some benzophenones.

Adult↗