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Biomedical subjects

L Bourgeois

Publications and source records attributed to L Bourgeois.

10 recordsLinked to original sources
PubMed1999

Boron nitride cones: structure determination by transmission electron microscopy.

A form of turbostratic boron nitride containing a large percentage of micrometre-size conically shaped particles was investigated by transmission electron microscopy. Electron diffraction patterns revealed the presence of correlations between adjacent boron nitride layers. The diffraction patterns were also used to determine the cone apex angle of many cone-like objects. The apex angles exhibited a broad distribution from 84 to 130 degrees with an ill defined peak in the 92-95 degrees region. These results could be accounted for by a structure model in which conical boron nitride layers are helically wound about a disclination axis, according to overlap angles that correspond to high densities of coincidental lattice sites between successive layers. The clustering of the apex angles near 93 degrees was attributed to the formation of a square ring during the nucleation stage. This appears to be specific to the boron nitride system.

Journal Article↗
PubMed1999

[MRI].

Explore the source record for details and available documents.

France↗
PubMed1998

[Female fertility prognosis and diethylstilbestrol. Personal data and review of the literature].

Diethylstilbestrol (DES) exposure in utero in females is a cause of clear-cell adenocarcinoma of the cervix and of several anatomical and functional disorders of the genital tract. DES exposure must be evoked whenever counselling women for reproductive disorders. In France around 80,000 women have had in utero DES exposure. The cases of 4 young women who consulted our Reproduction Center for reproductive disorders illustrate the usual difficulties faced by these patients. In spite of their difficult past reproductive history (uterine malformations, repeated miscarriages, ectopic pregnancies) and low fertility rate, all four women conceived successfully, either after spontaneous or induced ovulation. We stress the need for adapted psychological and medical care which can lead to successful childbearing in the vast majority of these high-risk patients.

Adult↗
PubMed1997

Serpin-derived peptide substrates for investigating the substrate specificity of human tissue kallikreins hK1 and hK2.

The third human tissue kallikrein to be identified, hK2, could be an alternate or complementary marker to kallikrein hK3 (prostate-specific antigen) for prostate diseases. Most of the hK2 in seminal plasma forms an inactive complex with protein C inhibitor (PCI), a serpin secreted by seminal vesicles. As serpin inhibitors behave as suicide substrates that are cleaved early in the interaction with their target enzyme, and kallikreins have different sensitivities to serpin inhibitors, we prepared a series of substrates with intramolecularly quenched fluorescence based on the sequences of the serpin reactive loops. They were used to compare the substrate specificities of hK1 and hK2, which both have trypsin-like specificity, and thus differ from chymotrypsin-like hK3. The serpin-derived peptides behaved as kallikrein substrates whose sensitivities reflected the specificity of the parent inhibitory proteins. Substrates derived from PCI were the most sensitive for both hK1 and hK2 with specificity constants of about 10(7) M-1. s-1. Those derived from antithrombin III and alpha2-antiplasmin were more specific for hK2 while a kallistatin-derived substrate was specifically cleaved by hK1. hK1 and hK2 substrates of greater specificity were obtained using chimeric peptides based on the sequence of serpin reactive loops. The main difference between specificities of hK1 and hK2 arise because hK2 can accommodate positively charged as well as small residues at P2 and requires an arginyl residue at P1. Thus, unlike hK1, hK2 does not cleave kininogen-derived substrates overlapping the region of N-terminal insertion of bradykinin in human kininogens.

Amino Acid Sequence↗
PubMed1990

Predictive validity of therapeutic alliance in group marital therapy.

The relation between marital distress, therapeutic alliance formation, and treatment outcome was investigated in a group marital skills training program in which 63 couples met for 9 weekly 3-hr sessions. Treatment outcome was assessed before and after completion of treatment through a series of self-report measures. The quality of the therapeutic alliance as viewed by the couples and the therapists was monitored at the 3rd session. Results indicate that levels of marital distress neither impaired nor facilitated alliance formation. In addition, it was demonstrated that patients' and therapists' ratings of the strength of the therapeutic alliance constitute a determinant of successful treatment. It appears, however, that the strength of the alliance is a more powerful predictor of therapeutic success among men than among women.

Adult↗
PubMed1981

Variations in properties of Nocardia asteroides resulting from growth in the cell wall-deficient state.

Several revertants possessing a cell wall were obtained from L-forms of Nocardia asteroides 10905. These L-form revertants differed from the parent in respect to colonial and cellular morphology, pigmentation, metabolic, capacities, cell wall structure, and mycolic acid composition. These data suggest a possible mechanism for the taxonomic heterogeneity and phenotypic diversity observed among N. asteroides strains.

Carbohydrate Metabolism↗
PubMed1976

In vitro spheroplast and L-form induction within the pathogenic nocardiae.

Six strains of Nocardia asteroides, two strains of N. caviae, and two strains of N. braziliensis were grown in medium supplementted with glycine, lysozyme, D-cycloserine, glycine plus lysozyme, and glycine plus D-cycloserine. It was shown that three strains of N. asteroides, and two strains of N. caviae, readily formed spheroplasts and/or protoplasts when grown in the presence of glycine plus either lysozyme or D-cycloserine. This process was studied by both phase contrast microscopy and electron microscopy. The induced cultures were then plated on hypertonic medium for the isolation of L-forms. It was shown that the organisms differed greatly in their ability to produce spheroplasts and subsequently grew as L-forms or transitional-phase variants.

Culture Media↗
PubMed1974

Probable L-forms of Nocardia asteroides induced in cultured mouse peritoneal macrophages.

Mouse peritoneal macrophages were infected with varying numbers of Nocardia asteroides 10905, and the fate of the ingested organisms was determined by viable plate count (VPC), light microscopy (LM), immunofluorescent microscopy (IM), and electron microscopy (EM). The results obtained with these methods differed. VPC indicated that intracellular Nocardia decreased in numbers during the first 12 days, followed by significant increases after 16 days. LM suggested that N. asteroides 10905 was slowly degraded by macrophages with no subsequent increases observed. In contrast, IM demonstrated large numbers of intracellular Nocardia throughout the experiment. EM studies of infected macrophages failed to demonstrate intact bacteria after 8 days; however, wall-less and spheroplast-like organisms were seen. These results suggested that N. asteroides 10905 was present within the macrophages in an altered form. By using hypertonic culture medium, we were able to isolate, from infected macrophages, organisms which exhibited many of the properties of bacterial L-forms. IM demonstrated these variants to be of nocardial origin. These altered forms also reverted to typical nocardial cells either spontaneously or upon transfer into broth. These findings indicate that N. asteroides 10905 is capable of existing within macrophages in an altered state. Further investigation is in progress to determine whether these altered forms represent L-forms or transitional-phase variants.

Animals↗
PubMedDate not supplied

Potential involvement of kallikrein hK2 in the hydrolysis of the human seminal vesicle proteins after ejaculation.

We have recently demonstrated in liquefied human seminal plasma the presence of the novel kallikrein hK2 in association with protein C inhibitor (PCI) as a 75-kDa complex. In the present study, we showed that hK2, immediately after ejaculation, was recovered only in its free form but complex formation with PCI occurred rapidly thereafter and was completed within 10 minutes. That reaction required an enzymatically active kallikrein. In order to determine the patterns of hydrolysis of major seminal vesicle proteins, semenogelins and fibronectin were exposed to hK2 and to hK3 (prostate-specific antigen or PSA) and cleavage sequences were identified by N-terminal sequencing. Free hK2 was able to hydrolyze semenogelins and fibronectin in vitro. Most of cleavage sites were at the carboxyl-side of arginyl residues. Semenogelins were hydrolyzed to a similar extent by catalytic (and similar) concentration of either hK2 or PSA though no common cleavage sites was identified for both proteinases. Unlike semenogelins, fibronectin was hydrolyzed much more efficiently by hK2 than by PSA. These results show that hK2 is enzymatically active during a short period of time after ejaculation, that major seminal vesicle proteins can be the target of this proteolytic activity, and that hK2 and PSA have different substrate specificities.

Antibody Specificity↗