Search PubMed⌕ Search

Biomedical subjects

D Roche

Publications and source records attributed to D Roche.

At least 19 recordsLinked to original sources
PubMed2003

Questionnaire or objective assessment for studying exposure to tobacco smoke among asthmatic and healthy children: The French VESTA Study.

BACKGROUND: The underreporting of environmental tobacco smoke (ETS) exposure by parents of study children may depend on the instrument used and population studied, underlining the need for questionnaire validation in specific study settings. This study explores the validity of parent-reported ETS exposure in a French multicenter study on asthma. METHODS: The study population was composed of 313 children ages 4 to 14 years. Exposure to ETS was evaluated both by questionnaires on recent ETS exposure and by assessment of urinary cotinine by an enzyme immunoassay. RESULTS: According to parents' reports, about one-third of children were exposed to ETS within the past 2 days before cotinine measurement, and on average 14.9 +/- 15.4 cigarette-equivalent were smoked in their homes. The mean urinary cotinine was 435 +/- 530 nmol/mol creatinine and increased with the reported number of cigarette-equivalents smoked at home but it did not differ between children registered as being exposed to 1-10 cigarettes and children registered as unexposed. Agreement between questionnaire and urinary cotinine was moderate to poor according to our correlation coefficient (0.22) and kappa coefficient (0.09). CONCLUSION: These results show that our questionnaire is not discriminating enough to distinguish between nonexposure and mild exposure, but reveals gradients of higher exposure.

Adolescent↗
PubMed2001

Hydrophilic, pro-drug analogues of T138067 are efficacious in controlling tumor growth in vivo and show a decreased ability to cross the blood brain barrier.

The novel anticancer compound T138067 is an irreversible inhibitor of tubulin polymerization. Amides 3-6 were synthesized using standard methodologies and determined to be significantly less lipophilic than T138067 based on logP calculations. Tubulin polymerization and [(3)H]-T138067 competition assays revealed that these amides are pro-drugs for parent aniline 2. Amides 3-5 showed no detectable signs of crossing the blood brain barrier, while amide 6 was found in extremely small amounts (12 ng/g of brain tissue). Aniline 2, which was formed in vivo from these amides, was found in significantly smaller amounts (approximately 20 to >5000 times) in the brain than when 2 was administered directly. The in vivo efficacy of amide 6 approached that of T138067 and was better tolerated when administered to athymic nude mice bearing MX-1 human mammary tumor xenografts.

Aniline Compounds↗
PubMed2001

Total syntheses of bengamides B and E.

Total syntheses of the cytotoxic marine natural products bengamides B and E are described. Both bengamides are prepared via amide coupling of a protected polyhydroxylated lactone intermediate 9 with a suitably substituted aminocaprolactam intermediate. Lactone 9 is prepared in five steps from commercially available alpha-D-glucoheptonic gamma-lactone. The key reactions are a selective deprotection of a 1,2-acetonide in the presence of a 1,3-acetonide and an (E)-selective olefination of an unstable aldehyde using a gem-dichromium reagent. The bengamide B lactam intermediate 10 is prepared in seven steps from commercially available (5R)-5-hydroxy-L-lysine (12). The desired S-configuration at the gamma-OH lactam position is established using the Mitsunobu reaction.

Animals↗
PubMed2001

Reversible disruption of pericentric heterochromatin and centromere function by inhibiting deacetylases.

Histone modifications might act to mark and maintain functional chromatin domains during both interphase and mitosis. Here we show that pericentric heterochromatin in mammalian cells is specifically responsive to prolonged treatment with deacetylase inhibitors. These defined regions relocate at the nuclear periphery and lose their properties of retaining HP1 (heterochromatin protein 1) proteins. Subsequent defects in chromosome segregation arise in mitosis. All these changes can reverse rapidly after drug removal. Our data point to a crucial role of histone underacetylation within pericentric heterochromatin regions for their association with HP1 proteins, their nuclear compartmentalization and their contribution to centromere function.

Animals↗
PubMed2000

Postprandial concentrations and distribution of apo C-III in type 2 diabetic patients. Effect Of bezafibrate treatment.

Apo C-III plays a key role in the metabolism of triglyceride-rich lipoproteins. It has recently been implicated as a potential determinant of the triglyceride (TG) lowering effect of fibrates, which down-regulate its expression. This hypothesis has been explored in ten moderately hypertriglyceridemic (TG 4.50+/-2.40 mmol/l) male type 2 diabetic patients tested with a lipid load before and after 4 weeks of treatment with 400 mg bezafibrate daily. Treatment lowered apo C-III concentrations by 20%, mainly in VLDL. Postprandially, apo C-III was transferred to chylomicrons in proportion to their TG content exclusively from HDL. VLDL retained their apo C-III and the apo C-III:TG ratio decreased as TG contents increased. At the end of the absorptive period (8 h) HDL did not recover the totality of their apo C-III (net loss 19 and 28% respectively before and after treatment, P<0.0001 for time effect). Bezafibrate lowered apo E by 33% (P<0.03). The apo C-III:apo E ratio did not vary significantly under treatment but underwent a postprandial decrease: 13% before and 18% (P=0.01) after treatment. These results indicate that repression of apo C-III expression and lowering of the apo C-III:E ratio are not likely mechanisms for the lipid-lowering effects of fibrates in type 2 diabetic patients. The potent effects on postprandial lipemia are suggestive of an apo C-III-independent stimulation of lipolysis.

Aged↗
PubMed2000

Effects of centrally administered galanin (1-16) on galanin expression in the rat hypothalamus.

In the rat hypothalamic magnocellular neurons, galanin coexists with vasopressin and might be involved in hydro-osmotic regulation. In the present study, we investigated the ability of galanin to also regulate the osmotically stimulated expression of galanin itself in hypothalamic magnocellular neurons. Ten minutes after galanin injection, galanin mRNA rate decreased in salt-loaded rats whereas the level of galanin immunoreactivity increased. Both effects were suppressed by the injection of a galanin antagonist together with galanin. Moreover, electron microscope studies demonstrated synaptic contacts between galanin-containing fibers and magnocellular neurons. Galanin may exert inhibitory roles in the regulation of magnocellular neurons. However, galanin and vasopressin expression displayed differences upon galanin injection. Possible mechanisms underlying these discrepancies are further discussed.

Animals↗
PubMed1999

Duplication and maintenance of heterochromatin domains.

To investigate the mechanisms that assure the maintenance of heterochromatin regions, we took advantage of the fact that clusters of heterochromatin DNA replicate late in S phase and are processed in discrete foci with a characteristic nuclear distribution. At the light microscopy level, within these entities, we followed DNA synthesis, histone H4 acetylation, heterochromatin protein 1 (Hp1alpha and -beta), and chromatin assembly factor 1 (CAF-1). During replication, Hp1alpha and -beta domains of concentration are stably maintained, whereas heterochromatin regions are enriched in both CAF-1 and replication-specific acetylated isoforms of histone H4 (H4Ac 5 and 12). We defined a time window of 20 min for the maintenance of this state. Furthermore, treatment with Trichostatin A (TSA), during and after replication, sustains the H4Ac 5 and 12 state in heterochromatin excluding H4Ac 8 and 16. In comparison, early replication foci, at the same level, did not display any specific enrichment in H4Ac 5 and 12. These data emphasize the specific importance for heterochromatin of the replication-associated H4 isoforms. We propose that perpetuation of heterochromatin involves self-maintenance factors, including local concentration of Hp1alpha and -beta, and that a degree of plasticity is provided by the cycle of H4 acetylation/deacetylation assisted by CAF-1.

Acetylation↗
PubMed1999

Novel halogenated sulfonamides inhibit the growth of multidrug resistant MCF-7/ADR cancer cells.

In this report, we describe the synthesis of halogenated benzenesulfonamide compounds and their ability to inhibit the growth of HeLa, MCF-7 and MCF-7/ADR tumor cells in vitro. The multidrug resistance (MDR) phenotype of certain cells does not affect their sensitivity to these compounds. These agents belong to a family of compounds previously shown to bind irreversibly to cysteine-239 of beta-tubulin. Consistent with this mechanism of action, the cytotoxicities of these compounds appear to correlate with their ability to undergo nucleophilic aromatic substitution.

Drug Resistance, Multiple↗
PubMed1999

Short Communication: An apospory-specific genomic region is conserved between Buffelgrass (Cenchrus ciliaris L.) and Pennisetum squamulatum Fresen.

Twelve molecular markers linked to pseudogamous apospory, a form of gametophytic apomixis, were previously isolated from Pennisetum squamulatum Fresen. No recombination between these markers was found in a segregating population of 397 individuals (Ozias-Akins et al. 1998, Proc. Natl Acad. Sci. USA, 95, 5127-5132). The objective of the present study was to test if these markers were also linked to the aposporous mode of reproduction in two small segregating populations of Cenchrus ciliaris (= Pennisetum ciliare (L.)Link), another apomictic grass species. Among 12 markers (sequence characterized amplified regions, SCARs), six were scored as dominant markers between aposporous and sexual C. ciliaris genotypes (presence/absence, respectively). Five were always linked to apospory and one showed a low level of recombination in 84 progenies. Restriction fragment length polymorphisms (RFLPs) were observed between sexual and apomictic phenotypes for three of the six remaining SCARs from P. squamulatum when used as probes. No recombination was observed in the F1 progenies. Preliminary data from megabase DNA analysis and sequencing in both species indicate that an apospory-specific genomic region (ASGR) is highly conserved between the two species. Although C. ciliaris has a smaller genome size to P. squamulatum, a higher copy number for markers linked to apospory found in the former may impair the progress of positional cloning of gene(s) for apomixis in this species.

Journal Article↗
PubMed1999

Fas ligand and Fas receptor are coexpressed in normal human esophageal epithelium: a potential mechanism of apoptotic epithelial turnover.

Fas (CD95/Apo-1) receptor (FasR) is a cell-surface receptor that mediates apoptotic cell death upon triggering by Fas ligand (FasL). We sought to determine whether normal human esophageal epithelial cells express FasL and/or FasR and whether their localization is consistent with a role in the turnover of normal esophageal epithelium. Normal esophageal epithelium was immunohistochemically positive for FasL in upper prickle cell layers and in mature squamous cells, but the proliferative basal layer was negative. FasL mRNA was detected in the same epithelial cell layers by in situ hybridization. Co-localization of FasL mRNA and protein therefore confirmed that FasL expression is induced in esophageal epithelial cells as they reach terminal differentiation. FasR was immunohistochemically detected throughout the esophageal epithelium. Positive TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling) staining confirmed cell death of the FasL and FasR coexpressing mature epithelial cells. CD45-positive immunocytes were notably absent from FasL-expressing upper epithelial layers. The findings are consistent with a contributory role for Fas-mediated autocrine suicide or paracrine fratricide in the apoptotic turnover of normal esophageal epithelium.

Apoptosis↗
PubMed1999

Oxidative turnover of soybean root glutamine synthetase. In vitro and in vivo studies

Glutamine synthetase (GS) is the key enzyme in ammonia assimilation and catalyzes the ATP-dependent condensation of NH3 with glutamate to produce glutamine. GS in plants is an octameric enzyme. Recent work from our laboratory suggests that GS activity in plants may be regulated at the level of protein turnover (S.J. Temple, T.J. Knight, P.J. Unkefer, C. Sengupta-Gopalan [1993] Mol Gen Genet 236: 315-325; S.J. Temple, S. Kunjibettu, D. Roche, C. Sengupta-Gopalan [1996] Plant Physiol 112: 1723-1733; S.J. Temple, C. Sengupta-Gopalan [1997] In C.H. Foyer, W.P. Quick, eds, A Molecular Approach to Primary Metabolism in Higher Plants. Taylor & Francis, London, pp 155-177). Oxidative modification of GS has been implicated as the first step in the turnover of GS in bacteria. By incubating soybean (Glycine max) root extract enriched in GS in a metal-catalyzed oxidation system to produce the.OH radical, we have shown that GS is oxidized and that oxidized GS is inactive and more susceptible to degradation than nonoxidized GS. Histidine and cysteine protect GS from metal-catalyzed inactivation, indicating that oxidation modifies the GS active site and that cysteine and histidine residues are the site of modification. Similarly, ATP and particularly ATP/glutamate give the enzyme the greatest protection against oxidative inactivation. The roots of plants fed ammonium nitrate showed a 3-fold increase in the level of GS polypeptides and activity compared with plants not fed ammonium nitrate but without a corresponding increase in the GS transcript level. This would suggest either translational or posttranslational control of GS levels.

Journal Article↗
PubMed1999

Expression of Fas ligand by human gastric adenocarcinomas: a potential mechanism of immune escape in stomach cancer.

BACKGROUND: Despite being immunogenic, gastric cancers overcome antitumour immune responses by mechanisms that have yet to be fully elucidated. Fas ligand (FasL) is a molecule that induces Fas receptor mediated apoptosis of activated immunocytes, thereby mediating normal immune downregulatory roles including immune response termination, tolerance acquisition, and immune privilege. Colon cancer cell lines have previously been shown to express FasL and kill lymphoid cells by Fas mediated apoptosis in vitro. Many diverse tumours have since been found to express FasL suggesting that a "Fas counterattack" against antitumour immune effector cells may contribute to tumour immune escape. AIM: To ascertain if human gastric tumours express FasL in vivo, as a potential mediator of immune escape in stomach cancer. SPECIMENS: Thirty paraffin wax embedded human gastric adenocarcinomas. METHODS: FasL protein was detected in gastric tumours using immunohistochemistry; FasL mRNA was detected in the tumours using in situ hybridisation. Cell death was detected in situ in tumour infiltrating lymphocytes using terminal deoxynucleotidyl transferase mediated dUTP nick end labelling (TUNEL). RESULTS: Prevalent expression of FasL was detected in all 30 resected gastric adenocarcinomas examined. In the tumours, FasL protein and mRNA were co-localised to neoplastic gastric epithelial cells, confirming expression by the tumour cells. FasL expression was independent of tumour stage, suggesting that it may be expressed throughout gastric cancer progression. TUNEL staining disclosed a high level of cell death among lymphocytes infiltrating FasL positive areas of tumour. CONCLUSIONS: Human gastric adenocarcinomas express the immune downregulatory molecule, FasL. The results suggest that FasL is a prevalent mediator of immune privilege in stomach cancer.

Adenocarcinoma↗
PubMed1998

Novel antineoplastic agents with efficacy against multidrug resistant tumor cells.

A novel series of pentafluorobenzenesulfonamides has been shown to inhibit the growth of a variety of human tumor cell lines. Among the cell types against which these agents were evaluated were the multidrug resistant (MDR) cell lines MCF-7/ADR and P388/ADR. The cytotoxic activity of members of this series of compounds was not affected by the multidrug resistant pump in MCF-7/ADR or P388/ADR cells.

Antineoplastic Agents↗
PubMed1998

The Fas counterattack in vivo: apoptotic depletion of tumor-infiltrating lymphocytes associated with Fas ligand expression by human esophageal carcinoma.

Various cancer cell lines express Fas ligand (FasL) and can kill lymphoid cells by Fas-mediated apoptosis in vitro. FasL expression has been demonstrated in several human malignancies in vivo. We sought to determine whether human esophageal carcinomas express FasL, and whether FasL expression is associated with increased apoptosis of tumor-infiltrating lymphocytes (TIL) in vivo, thereby contributing to the immune privilege of the tumor. Using in situ hybridization and immunohistochemistry, respectively, FasL mRNA and protein were colocalized to neoplastic esophageal epithelial cells in all esophageal carcinomas (squamous, n = 6; adenocarcinoma, n = 2). The Extent of FasL expression was variable, with both FasL-positive and FasL-negative neoplastic regions occurring within tumors. TIL were detected by immunohistochemical staining for the leukocyte common Ag, CD45. FasL expression was associated with a mean fourfold depletion of TIL when compared with FasL-negative areas within the same tumors (range 1.6- to 12-fold, n = 6,p < 0.05). Cell death of TIL was detected by dual staining of CD45 (immunohistochemistry) and DNA strand breaks (TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling). There was a mean twofold increase in detectable cell death among TIL in FasL-positive areas compared with FasL-negative areas (range 1.6- to 2.4-fold, n = 6, p < 0.05). In conclusion, we demonstrate a statistically significant, quantitative reduction of TIL concomitant with significantly increased TIL apoptosis within FasL-expressing areas of esophageal tumors. Our findings suggest Fas-mediated apoptotic depletion of TIL in response to FasL expression by esophageal cancers, and provide the first direct, quantitative evidence to support the Fas counterattack as a mechanism of immune privilege in vivo in human cancer.

Adenocarcinoma↗
PubMed1998

Tight clustering and hemizygosity of apomixis-linked molecular markers in Pennisetum squamulatum implies genetic control of apospory by a divergent locus that may have no allelic form in sexual genotypes.

Apomixis is a naturally occurring mode of reproduction that results in embryo formation without the involvement of meiosis or fertilization of the egg. Seed-derived progeny of an apomictic plant are genetically identical to the maternal parent. We are studying a form of apomixis called apospory that occurs in the genus Pennisetum, a taxon in the grass family. A cultivated member of this genus, pearl millet (Pennisetum glaucum), reproduces sexually. A wild relative of pearl millet, Pennisetum squamulatum, that is an obligate aposporous species, is cross-compatible with pearl millet when used as a pollen donor in the interspecific cross. We present herein the genetic mapping of 13 molecular markers in an interspecific hybrid population of 397 individuals that segregates for apomixis and sexuality. Surprisingly, 12 of the 13 markers strictly cosegregated with aposporous embryo sac development, clearly defining a contiguous apospory-specific genomic region in which no genetic recombination was detected. Lack of or suppression of recombination may be coincidentally associated with the chromosomal context of the apomixis locus or it may be a consequence of its evolution that is essential for preservation of gene function as has been previously shown in studies of complex loci in both plant and animal species.

Aneuploidy↗