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Biomedical subjects

J Lecomte

Publications and source records attributed to J Lecomte.

At least 91 records · Page 5Linked to original sources
PubMed1987

Comparison of methods for concentration and purification of bovine viral diarrhea virus.

The NADL strain of bovine viral diarrhea virus (BVDV) was concentrated by hollow fiber ultrafiltration or polyethylene glycol and purified by centrifugation through sucrose or potassium tartrate gradients. The protein content of polyethylene glycol concentrates was much lower than that of ultrafiltration concentrates. Conversely, recoveries of infectivity were greater using polyethylene glycol (100%) as compared to ultrafiltration (50%). Sucrose or potassium tartrate density gradients appeared comparable in purification of BVD virus. Peak infectivity fractions in both gradients corresponded quite well, having densities of 1.12-1.14 g/cm3, and showed a 150-fold reduction of protein when compared to crude viral supernate. Further examination by negative stain electron microscopy revealed integral pleomorphic, roughly spherical particles in both purified virus preparations. Small knob-like projections could be seen on viral particles.

Centrifugation, Density Gradient↗
PubMed1987

Cell-protective monoclonal antibodies to bovine enterovirus-3 and partial or no activity against other serotypes.

Preparation of monoclonal antibodies to bovine virus diarrhea virus (BVDV) yielded some hybridoma cells that secreted monoclonal antibodies against the Madin-Darby bovine kidney cells. The anti-cellular monoclonal antibodies reacted with other bovine cells (bovine turbinate and testicle) but not with cell lines derived from other animal species. Subclones derived from one hybridoma partially blocked the infectivity of BVDV, possibly through the binding of the monoclonal antibodies with an epitope close to the receptor site of BVDV and not by way of steric hindrance. Unexpectedly, these same subclones completely blocked the infectivity of bovine enterovirus-3 (BEV-3) strain 240A and partially blocked the infectivity of BEV-2 and BEV-3 (ATCC strain) but not that of other serotypes. Other subclones derived from two other hybridomas, although cell membrane specific, did not have a protective activity against BEV or BVDV.

Animals↗
PubMed1987

Production and characterization of monoclonal antibodies showing a different spectrum of reactivity to human breast tissue.

We have generated three hybridoma-producing monoclonal antibodies (MAs) that show a different spectrum of reactivity to human mammary tissues. Two of these antibodies, 1F10B4 and 1F10G2, recognize a cytoplasmic determinant highly expressed in most of the primary and metastatic breast carcinomas studied, and weakly (or not at all) in normal breast and nonbreast tissues. 3C6F9 detected a surface determinant common to both normal and neoplastic mammary epithelium. Five hundred hybridomas were obtained from the fusion of NS-1 myeloma cells with spleen cells of mice hyperimmunized with the well-characterized human breast carcinoma cell line BT-20. After the initial screenings and clonings, three monoclonal antibodies (1F10B4, 1F10G2, and 3C6F9) showing a restricted range of reactivity were selected for further investigation. These three antibodies recognized a panel of neoplastic mammary cell lines; however, the degree of reactivity could not be correlated to any of the various characteristics of these epithelial cell lines. Moreover, immunofluorescence analysis of acetone-fixed cryostat section showed that 1F10B4 and 1F10G2 recognize the vast majority of the 37 primary and metastatic breast cancers tested, binding strongly to 47% and 67% of them respectively. Only one of the primary carcinomas was not recognized by 1F10B4. On the other hand, these two MAs reacted weakly or not at all with normal breast and nonbreast tissues showing only few focal reactivities with the luminal pole of some ducts of the breast; very weak staining in renal tubular epithelial cells, in few keratinocytes and epithelial cells lining some sebaceous glands in the skin; and a moderate staining in biliary ducts of the liver. All mesenchymal structures including smooth and striated muscle tissues, lymph nodes, and connective tissue were negative. On the other hand, 3C6F9 recognized a more limited number of human mammary tumors and reacted with normal ductal epithelium in the breast and with nonbreast tissues. Because of their wide spectrum of reactivity with breast cancer cells and restricted recognition of normal mammary tissues, their cytoplasmic localization, and their heterogeneous distribution within a single neoplasm, 1F10B4 and 1F10G2 are now being used to characterize antigenic phenotypes of tumor-associated antigens in retrospective studies performed on conventional formalin-fixed, paraffin-embedded human mammary carcinomas.

Animals↗
PubMed1987

[Effects of the addition of carbon dioxide on manifestations of acute hypoxia in rats].

In pentobarbitalized rats, hypoxia induced by inhalation of O2 8%-N2 92%, produces a transient hyperventilation which is followed by a respiratory depression and an apnea. A cardiovascular collapse is then observed. Correction of the hypocapnia depending on the initial hyperventilation, by inhalation of a gas mixture containing 4% CO2 maintains the hyperventilation and suppresses the cardiovascular collapse. Carbon dioxide activity is both a direct one by stimulation of respiratory centers and an indirect one by increasing the sensitivity of the peripheral arterial chemoreceptors to hypoxia. Four percent carbon dioxide just compensating hypocapnia are sufficient to prevent apnea and vascular collapse. The increase of this concentration up to hypercapnia complicates the interpretation of the results by addition of hypoxic and hypercapnic effects.

Acute Disease↗
PubMed1986

Immunocytochemical localization of a medullary thymic epithelial glycoprotein.

The thymic microenvironment is known to play a key role in T-cell differentiation, but the exact nature of the interactions between epithelial and lymphoid cells has not been fully elucidated. With a monoclonal antibody to a thymic epithelial glycoprotein, we report the localization of an antigen specific for medullary epithelial cells of the mouse thymus. This antigen is found in the Golgi apparatus of epithelial cells, and on their borders with adjoining lymphocytes. This location is compatible with the previously reported observation that differentiation signals transmitted to thymic lymphocytes by thymic epithelial cells require actual contact between these two cell types.

Animals↗
PubMed1986

[Stimulation of rat mastocytes and molecular oxygen].

Free peritoneal mast-cells of the rat are stimulated in vitro by molecular oxygen as well as by hydrogen peroxide. Histamine release is also observed in vivo when molecular oxygen or diluted solutions of hydrogen peroxide are injected into the peritoneal cavity of the rat. Inflammatory lesions are produced (vascular congestion, oedema, exudate) which are suppressed by pretreatment with anti-H1 antihistaminics. When hydrogen peroxide solutions are more concentrated, inflammation is also provoked but antihistaminics are no more inhibitory. Mast-cells of the skin and of the lungs are not stimulated neither by molecular oxygen, nor by hydrogen peroxide.

Animals↗
PubMed1986

[Mast cell heterogeneity in normal man].

Thermographic analysis of the skin of the forearm of normal men submitted to nasal instillation of 1 ml of a solution of 48/80, 1 X 10(-2), demonstrates that the skin vessels undergo local vasodilatation. Erythema and wheals sometimes appear, due to the stimulation of the dermal mast cells. Mast cells of the nasal mucosa are never stimulated by such instillation. The differences between dermal and nasal mast cell reactions are in accordance with the concept of mast cell heterogeneity.

Adult↗
PubMed1986

Adherence of gram-positive and gram-negative bacterial strains to human lung fibroblasts in vitro.

The adherence to eukaryotic cells of Escherichia coli, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis and the yeast Candida albicans was studied by light microscopy with an in vitro micromethod involving different cell lines. The method is inexpensive, consumes little time and material, and is reproducible. It was used to show that the gram-positive Cowan I strain of S. aureus, which naturally forms protein A on its surface, adheres in much larger numbers to human lung fibroblasts than the protein A-free Wood 46 strain, the strain of S. epidermidis, and the encapsulated Smith strain. The presence of a capsule on the latter strain apparently prevented its attachment to the fibroblasts. Among the gram-negative species studied, a piliated clinical isolate of N. gonorrhoeae, displaying the opaque colonial phenotype, adhered in larger numbers than another isolate lacking pili and displaying the transparent phenotype. E. coli K12 attached slightly to the cell line, whereas P. aeruginosa adhered to it moderately. One strain of C. albicans tested did not attach in any detectable numbers. No clear correlation between bacterial cell surface hydrophobicity, as evaluated by the hexadecane assay, and adherence to eukaryotic cells could be demonstrated for these microorganisms. With our method, bacterial attachment proceeded best at 37 degrees C and did not require more than 1 h of contact with the cell monolayer. The method described revealed differences in the adherence to eukaryotic cells, not only among species, but also between strains of the same species.

Candida albicans↗