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Biomedical subjects

O Gauthier

Publications and source records attributed to O Gauthier.

At least 37 records · Page 2Linked to original sources
PubMed1998

Growth hormone-loaded macroporous calcium phosphate ceramic: in vitro biopharmaceutical characterization and preliminary in vivo study.

Calcium phosphate ceramics recently have been used for administering therapeutic agents in bone. The present work investigated the efficacy of macroporous biphasic calcium phosphate (MBCP) implants as a matrix for local delivery of human growth hormone (hGH). An initial study showed that the release of 5 microg of hGH loaded onto MBCP cylinders was rapid during the first 48 h and sustained for a total of 11 days. The biological integrity of hGH (88.2%) was checked using a specific bioassay (cellular proliferation of hGH-sensitive Nb2 cells) in comparison with a radioimmunoassay to calculate the proportion of bioactive hGH released. MBCP cylinders then were loaded with 1, 10, and 100 microg of hGH and implanted into rabbit femurs (n = 16) to determine hGH effects on bone ingrowth and ceramic resorption, as evaluated by scanning electron microscopy and image analysis. Results indicated that hGH increased bone ingrowth and ceramic resorption significantly in comparison with contralateral and control implants. Biochemical parameters monitored in rabbit plasma showed that hGH did not produce detectable systemic effects. Thus the use of MBCP appears to be effective for local delivery of hGH and for increasing bone ingrowth.

Absorption↗
PubMed1998

Transmission FT-IR microspectroscopy of mineral phases in calcified tissues.

Fourier-transform infrared microspectroscopy (FT-IRM) was used to study bone mineralization processes in an in vivo model and in enamel in osteogenesis imperfecta. Finally, the ability of FT-IRM to map new bone formed in implanted macroporous calcium phosphate biomaterial from sections was reported for the first time. FT-IRM allowed the correlation of the microstructure of bone formation in the in vivo model with modifications in carbonate and phosphate environments of the mineral phases during maturation. FR-IRM analysis on enamel sections revealed changes in the mineral environment of carbonate and phosphate ions and probably in the size of enamel crystals. These modifications contributed to the fragility of enamel in osteogenesis imperfecta. The infrared functional group imaging of a part of implanted biomaterial and the bone ingrowth provided the visualization of chemical modifications occurring in biomaterial implants at 20 microns spatial resolution. The use of FT-IRM, in conjunction with appropriate sampling methods and data analysis should provide further insight into the molecular structure of mineral phases of calcified tissues and help to elucidate mineralization processes, skeletal disorders and properties of the biomaterials used as bone substitute.

Animals↗
PubMed1998

Human growth hormone locally released in bone sites by calcium-phosphate biomaterial stimulates ceramic bone substitution without systemic effects: a rabbit study.

Calcium-phosphate bone replacement biomaterial has been used as a drug carrier for therapeutic agents. This study investigated the efficacy of local administration of human growth hormone (hGH) by macroporous biphasic calcium phosphate (MBCP) implants in improving the bone substitution qualities of ceramics. hGH release from MBCP implants loaded with 1 microg of hGH was rapid during the first 48 h and then sustained for a total of 9 days. Immunolocalization of hGH in vitro and in vivo by transmission electron microscopy showed its presence inside the material, indicating that it was able to penetrate within the porosity of the ceramic during the adsorption process. MBCP cylinders (6 x 6 mm) were loaded with 0.1, 1, and 10 microg of hGH and implanted into rabbit femurs (n = 40). The effects of locally released hGH on bone ingrowth and ceramic resorption were evaluated by scanning electron microscopy and image analysis. The results indicated that hGH increased bone ingrowth (+65%) and ceramic resorption (+140%) significantly in comparison with control implants and that the increase was dose dependent. Biochemical parameters monitored in rabbit plasma and urine, as well as the absence of any significant difference between contralateral implants and the control, indicated that hGH did not produce detectable systemic effects. Thus, the use of MBCP appears to be effective for local delivery of hGH, resulting in improved bone substitution.

Animals↗
PubMed1996

[Atrophic collodion-like skin in long-term treatments with hydroxyurea].

INTRODUCTION: Despite good general and hematological tolerance, hydroxyurea frequently causes polymorphous skin lesions when given as long-term therapy. Distal skin atrophy, pseudodermatomyositis, pseudolichen and ulcerations have been observed. CASE REPORT: We report three cases of diffuse atrophic collodion skin in patients given long-term hydroxyurea. Histology findings demonstrated atrophy and the same signs located at the dermo-epidermal junction as seen in acute toxidermia due to hydroxyurea. Examination of the ultrastructure showed abnormalities in the proliferative epidermal layer which was disrupted by edema and a multiple, irregular basal membrane. DISCUSSION: The chronology of the lesions and partial resolution after treatment withdrawal together with clinical and histological signs demonstrating hydroxyurea impregnation would implicate hydroxyurea as the cause of this case of diffuse atrophic collodion skin. Cells in the epidermal layer of the skin, the most external layer in the organism, have a high turnover rate and would be more vulnerable to the cytostatic action of hydroxyurea than other tissues. The effect of hydroxyurea on keratinocytes implicated in the production and maintenance of the basal membrane would be one of the causes.

Aged↗
PubMed1978

[Hypomelanosis of the skin and malignant melanoma (author's transl)].

8 patients suffering from malignant melanoma have been found to have various degrees of hypomelanoses of the skin. Depigmentation of the skin and/or hair associated with malignant melanoma may take several forms. Schematically six clinical types are described: - vitiligo-like hypomelanoses distant from cutaneous tumors; - vitiligo-like depigmentation associated with uveitis (incomplete Vogt-Koyanagi); - hypomelanoses in the primary tumor and/or its metastases; - "halo melanoma" in which the hypomelanoses encircles the primary tumor and/or its metastases; - halo nevi around preexisting benign nevocellular nevi; - "non-specific depigmentary phenomen" distant from the primary tumor or its metastases. Histological and ultrastructural studies of the depigmented skin show an absence of melanocytes. The association of hypomelanoses of the skin with malignant melanoma is probably not coincidental. Various hypothesis are discussed as well as the prognostic significance of such an association.

Adult↗
PubMed1975

Ultrastructure of halo nevi.

An ultrastructural study was conducted on eight halo nevi. Some of them were of recent onset. Others had an evolution of several months. The distribution of the population of the dendritic cells in the depigmented epidermis of the halo was more polymorphous at the early stage when few melanocytes with abundant cytofilaments and some Langerhans cells were seen. At an advanced clinical stage, only Langerhans cells were present in the basal layer. In the dermis abnormal nerves as in vitiligo were observed. The inflammatory infiltrate does not seem to appear at the early stage of involution of the nevus. At the advanced clinical stage, small mononuclear cells were also noticed among the inflammatory cells (lymphocyte-like cells, macrophages, mast cells). It is suggested that an initial stage of inhibition of both the melanocytes and the nevus cells may be responsible for the development of the depigmented halo. This stage precedes the appearance of a dermal lymphomacrophagic infiltrate that leads to the destruction of the nevus.

Adolescent↗
PubMed1975

[Lepromatous leprosy after BCG vaccination].

The authors describe an eruption of cutaneons nodules after a BCG vaccination. Investigation demonstrated that the lesions were caused by Lepromata. An increased number of B lymphocytes was observed in the bloodstream. Ryphampycin was used with good results.

Adolescent↗
PubMed1975

[4 years of use of a linear accelerator in dermatology].

A recent acquisition in external radiotherapy, electrontherapy is the direct use of electrons which are essential in radiobiology. By their physical characteristics, the rapid fall in absorbed dosage in deep tissues, the electron beam is especially well adapted to dermatological practice. Four years use of a Bordeaux linear accelerator permitted the authors to determine the indications for the technique, its limits and practical details of its use. Carcinomas are the main indications, especially extensive lesions, advanced, relapsing, or even after other methods of radiotherapy, and in certain localisations. Wide or total irradiation raises new prospects in the treatment of hematodermia, perhaps, hope of a cure.

Electrons↗
PubMed1972

[Herpes gestationis].

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Dermatitis Herpetiformis↗