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Biomedical subjects

A Lebrun

Publications and source records attributed to A Lebrun.

At least 19 recordsLinked to original sources
PubMed1992

Effects of sub-MICs of antibiotics on cell surface characteristics and virulence of Pasteurella multocida.

The effects of sub-MICs of certain antibiotics, namely, penicillin G, tetracycline, and trimethoprim-sulfamethoxazole, on the cell surface characteristics and the virulences of two toxigenic isolates of Pasteurella multocida representing capsular types A and D were evaluated. Expression of proteins, in particular, outer membrane proteins and iron-regulated proteins, was not affected by exposure of bacterial cells to low concentrations of antibiotics. However, exposition of surface antigens was modified by sub-MICs of the antibiotics tested. The lipopolysaccharide profile of one isolate (capsular type D) was altered by penicillin G. Sub-MICs of penicillin G and tetracycline diminished the virulence of the capsular type A isolate and adherence to porcine tracheal rings of the capsular type D isolate. Production of dermonecrotic toxin was not affected by sub-MICs of the antibiotics tested. Our results indicate that growth of P. multocida in the presence of low concentrations of antibiotics seems to have, depending on the isolate, profound effects on cell surface characteristics, with concomitant effects on adherence or virulence. Our results also indicate that production of dermonecrotic toxin, an important virulence factor of P. multocida isolates associated with porcine atrophic rhinitis, was not affected by sub-MICs of the antibiotics studied.

Animals↗
PubMed1991

Effects of antibiotics on the growth and morphology of Pasteurella multocida.

The effects of subminimal inhibitory concentrations (subMICs) of certain antibiotics, namely penicillin G, tetracycline and trimethoprim/sulphamethoxazole, on the growth and morphology of Pasteurella multocida were evaluated. SubMICs of penicillin markedly reduced the growth of P. multocida. Tetracycline and trimethoprim/sulphamethoxazole had no effect on its growth. SubMICs of penicillin greatly affected the morphology of P. multocida. At the highest concentrations tested (1/2 and 1/4 MIC) cells were acapsulate, and long filamentous cells (4-6 microns) were observed with some isolates. There was no correlation between the observed differences in the penicillin-binding proteins of the P. multocida isolates, and the extent of cell filamentation induced by penicillin G. SubMICs of tetracycline and trimethoprim/sulphamethoxazole did not seem to affect capsule production although filamentation was observed. Our results indicate that subMICs of penicillin can reduce growth of P. multocida. Furthermore, results also indicate that subMICs of antibiotics can affect the production of capsular material and the morphology of P. multocida.

Animals↗
PubMed1990

Hemagglutination properties of Streptococcus suis.

A total of 49 strains (23 reference strains and 26 field isolates) of Streptococcus suis were tested for their ability to agglutinate erythrocytes from different animal species. Ten different hemagglutination patterns were established. Thirty-three strains (67%) did not agglutinate any of the erythrocytes tested; sixteen strains (33%) agglutinated erythrocytes from one or more animal species. Different strains belonging to the same capsular type presented different hemagglutination patterns. No correlation was found between the tissue origin and/or the virulence (evaluated in 4-week-old mice) of different field isolates and their hemagglutination activity. Hydrophobic surface properties were also evaluated. All S. suis strains studied appeared to possess a hydrophilic cell surface. Morphologically similar fimbriae were observed on hemagglutinating as well as on nonhemagglutinating strains of S. suis. This study provides evidence that certain strains of S. suis possess hemagglutinating properties which do not appear to involve hydrophobic interactions. The possible role of fimbriae in hemagglutination remains unclear.

Animals↗
PubMed1986

HLA antigens in narcolepsy and idiopathic central nervous system hypersomnolence.

Several studies have shown familial incidence of narcolepsy and idiopathic central nervous system (CNS) hypersomnia. HLA antigen studies performed in mongoloid and caucasoid narcoleptic patients on the A, B, and C loci have yielded conflicting results. The aim of this study is to document a possible association between the HLA system, including the DR locus and excessive daytime somnolence. Thirty-one narcoleptic patients and 10 idiopathic hypersomniac patients were selected and typed for 54 HLA antigens. A family with narcoleptic members in 3 generations was also studied. HLA-DR2 was found in 100% of narcoleptic patients. The frequency of HLA-A3 and B7, which are in linkage disequilibrium with DR2 was also increased in this group. Idiopathic hypersomniac patients showed an increase of HLA-Cw2, DR5, and B27, three antigens known to be in linkage disequilibrium. In the family study, narcoleptic patients were also HLA-DR2; moreover, 3 subjects, one of whom was narcoleptic, were HLA-DR2 as a result of recombination (i.e., genetic crossing-over). These results locate the hypothetic gene associated with narcolepsy more precisely, and indicate that narcolepsy and idiopathic CNS hypersomnolence are two different entities.

Adult↗
PubMed1981

Relative lack of Epstein Barr virus (EBV) receptors on B cells from persistently EBV seronegative adults.

Viral receptors are essential for the entry of the virus into the cell. EBV receptors can be detected on fresh lymphocytes by a technique that uses EBV-coupled tanned red blood cells that form rosettes with lymphocyte-bearing receptors. This technique was found to detect viral receptors only and not surface immunoglobulins. T cell depletion of the lymphocyte population showed that these receptors were present on B lymphocytes. Study of the presence of these EBV receptors on the surface of fresh lymphocytes from 66 subjects (age 2 to 66), selected out of a group of over 2000 individuals, showed that the majority of these donors had receptors for the virus. However, a few of these adults persistently failed to develop anti-EBV antibodies, even if they were in close contact with the infectious agent. The lymphocytes of 11 such individuals were found to be lacking EBV receptors. Transformation assay of these lymphocytes did not give rise to lymphoblastoid cell lines whereas lymphocytes from 4 individuals, who were EBV seropositive or seronegative but receptor positive, yielded permanent lymphoblastoid cell lines. This would suggest that a few EBV seronegative adults (less than 0.5%) display natural resistance to EBV transformation of their lymphoid cells as a result of absolute or relative lack of EBV receptors on these cells.

Adolescent↗
PubMed1979

[Hypopituitarism and hyperlipidemia. Protective effect of growth hormone deficiency against atherosclerosis (author's transl)].

Twelve cases of hypopituitarism (Sheehan's syndrome, pituitary adenoma, idiopathic) associated with hyperlipidemia (type IIb in general) are reported. It is suggested that: 1 - Growth hormone deficiency seems to have a protective effect against atherosclerosis in hyperlipidemia because there are no cardiovascular signs in 10 cases with a history of growth hormone deficiency lasting from 5 to 57 years and a patent hyperlipidemia (lasting a mean of 23 years), and there is stabilisation or improvement of ischemic signs in 2 other cases. 2 - Lipid abnormalities are frequently seen in hypopituitarism even after thyroid replacement therapy. 3 - The hyperlipidemia can be familial or can result from growth hormone deficiency alone.

Adult↗
PubMed1979

[Hypopituitarism and hyperlipidemia. Protective effect of growth hormone deficiency against atherosclerosis (author's transl)].

A serie of 12 cases of hypopituitarism (Sheehan's syndrome, pituitary adenoma, idiopathic) associated with hyperlipidemia (type IIb in general), is reported. It is suggested that: 1--Growth hormone deficiency seems to have a protective effect against atherosclerosis in hyperlipidemia because there are no cardiovascular signs in 10 cases with a history of growth hormone deficiency lasting from 5 to 57 years and a manifesting hyperlipidemia (lasting a mean of 23 years), and there is stabilisation or improvement of ischemic signs in 2 other cases. 2--Lipid abnormalities are frequently seen in hypopituitarism even after thyroid replacement therapy. 3--The hyperlipidemia can be familial or can result from growth hormone deficiency alone.

Adult↗