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Biomedical subjects

L Simar

Publications and source records attributed to L Simar.

At least 19 recordsLinked to original sources
PubMed2004

Analysis of the expenses linked to hospital stays: how to detect outliers.

When hospital financing depends on a budget which in turn depends on the pathologies being treated, it is necessary to detect hospital stays which show discrepancies between the resources they consume and the medical characteristics they present. Deterministic nonparametric frontier models are used to rank hospital stays according to their expenses taking into account the severity of the patients' conditions. As these models are very sensitive to the extreme stays, a robust frontier model, the order-m frontier is used. The too-efficient stays are highlighted and described. The mean expenses are estimated after excluding too-efficient and inefficient stays. This mean is higher than the mean estimated by using classical trimming rules.

Belgium↗
PubMed1991

Invasion of reconstituted basement membrane matrix is not correlated to the malignant metastatic cell phenotype.

Interactions between tumor cells and basement membranes represent a critical step in the progression of neoplasia and in the metastatic process. Reconstituted basement membrane matrix, matrigel, has been recently used with the aim of developing an in vitro assay of tumor cell invasiveness. We have extended these studies by comparing the invasiveness of a large series of normal and malignant epithelial and mesenchymal cells of human and animal origin cultured on matrigel. Normal cells (fibroblasts, glomerular mesangial cells, keratinocytes), human fibrosarcoma cells (HT1080), and reticular sarcoma cells (M5076) clearly established invasive capabilities in the matrix. However, all the other tested cell lines, malignant or virally transformed cells invasive in vivo (MCF7, T47D, SA52, SW613, MO4, A431, BeWo), as well as normal nontransformed cells (MOH22) were incapable of penetration. The morphological features of matrigel invasion by normal fibroblasts and HT1080 cells are described at the light and electron microscope levels. The extent of degradation of a radiolabeled matrigel is minimal and similar in several cell lines reported to be noninvasive or invasive in vivo. Our data suggest that matrigel does not provide a universal model to correlate the invasiveness of cells in vivo and in vitro.

Animals↗
PubMed1989

Localization of interleukin 6 mRNA in human tonsils by in situ hybridization.

We have investigated which areas produce interleukin 6 (IL 6) in human tonsils. This growth factor is required for the terminal differentiation of B lymphocytes into plasmocytes. Using 35S-labeled IL 6 cDNA we demonstrated IL 6 gene expression over various areas of the tonsils, with consistent exception of the follicles, by in situ hybridization. It is, therefore, proposed that B cells are stimulated during their migration out of the follicles.

B-Lymphocytes↗
PubMed1988

[Preliminary study on nerve regeneration through an autologous venous tube].

Large posttraumatic defects in the peripheral nervous system bring up serious problems to the surgeon. There is no definitive answer yet. The authors present a model for nervous regeneration studies; venous autograft was used to bridge defects in a divided rat sciatic nerve; the venous tube guided the regenerating axons towards the distal stump over up to 1.9 cm length. Preliminary studies about nervous regeneration stimulation with autologous Schwann cells are discussed.

Animals↗
PubMed1984

Precise localization of antigens on follicular dendritic cells.

Horse-spleen ferritin or bovine serum albumin conjugated to colloidal gold (BSA-gold) were injected subcutaneously in preimmunized mice. In draining lymph nodes both antigens were located in macrophages or between the cytoplasmic processes of follicular dendritic cells (FDC). Some of the antigens remained trapped on FDC until day 31 after injection. Simultaneous injection of both antigens showed that they were located between the infoldings of the same FDC. These cells are thus able to retain at least two different antigens on their surface. The peculiar arrangement of ferritin between the cytoplasmic infoldings suggests that this antigen is fixed on both cell membranes by specific antibodies. The trapped immune complexes could thus stabilize the FDC membrane system. The antigen retention requires the presence of specific antibodies since BSA-gold or ferritin injected without preimmunization were not found between FDC processes. Nonantigenic materials, such as colloidal gold or carbon particles, are not trapped by FDC, except when injected in large amounts. The antigens were trapped on the surface of FDC, however unfrequently in close contact with lymphocytes. FDC might protect lymphocytes against an excess of immune complexes and act as regulators of contacts between lymphocytes and immune complexes.

Animals↗
PubMed1982

[Relation between immunogenicity and differentiation of metastasis in an experimental murine melanoma].

The graft into the footpad of Jackson mice of B16 melanoma cells which are only slightly pigmented, induces the simultaneous appearance of achromatic and well-pigmented metastatics. We have analysed histologically both types of metastases from the 8th to the 20th day after the resection of the primary tumor. The percentages of mitoses are higher in the achromatic metastases than in the pigmented ones. Both are infiltrated by lymphocytes and by a small number of macrophages and polymorphonuclears. A statistical analysis demonstrates however that the percentage of lymphocytes is not related to the importance of the metastase pigmentation. The discussion is devoted to the relations between the infiltration by lymphocytes, the immunogenicity and the differentiation of the tumor.

Animals↗
PubMed1980

[Immunogenicity of nerve allografts in rats].

The state of sensitization of rats after nerve or skin allograft was studied in vitro by using spleen cells or peripheral blood leukocytes (PBL) as responding cells and particulate alloantigen for stimulation, in culture conditions requiring or not supernatant from mixed lymphocytes culture. It is shown that 2-4 weeks after nerve or skin grafting a small number of PBL generates similar cytotoxic lymphocytic responses. However the state of sensitization induced by the nerve allografts is shorter compared to the one exhibited after skin allografts. On the other hand, no significant differences were observed at the level of the humoral response between both groups of grafted rats.

Animals↗
PubMed1978

Cobalt thiocyanate as a stain for basic proteins and other organic bases on thin sections.

Thin sections in mouse mast cells and thymic cells are stained with cobalt thiocyanate a compound known to form insoluble complexes with organic bases. Chromatin, nucleolus, ribosomes and mast cell granules are contrasted. Different blockade reactions and enzymatic digestions indicate the staining corresponds to the basic protein amino-groups. The silver methenamine reaction stains the same cellular structures. However, the specificity control reactions show the staining mainly corresponds to protein sulphydryle groups and in a lesser extent to aldehyde and polyanions.

Animals↗
PubMed1975

Transport of amylase across the apical membrane of the pancreatic exocrine cells. Quantitative analysis of zymogen granules.

The number or the size of the zymogen granules was calculated in a determined volume slice of pigeon pancreas and in a total cellular fraction of zymogen granules isolated from a part of this organ having the same volume. The obtained values were not significantly different. These results are discussed in relation to the mechanism of digestive enzyme secretion. They confirm that amylase can be transported molecule by molecule across the intact apical membrane of the pancreatic exocrine cells.

Amylases↗