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Biomedical subjects

G Bélanger

Publications and source records attributed to G Bélanger.

At least 19 recordsLinked to original sources
PubMed2000

New approach to aphidicolin and total asymmetric synthesis of unnatural (11R)-(-)-8-epi-11-hydroxyaphidicolin by tandem transannular Diels-Alder/aldol reactions.

The 8-epiaphidicolane skeleton (3) was formed in one key reaction by highly diastereoselective tandem transannular Diels-Alder (TADA)-aldol reactions from the trans-trans-cis trienic macrocycle (4). The unnatural derivative (11R)-(-)-8-epi-11-hydroxyaphidicolin (2) was thus constructed, and an original solution to the C16 functionalization problem of many aphidicolin (1) syntheses is presented.

Aldehydes↗
PubMed2000

Total asymmetric synthesis of the aphidicolin derivative (11R)-(-)-8-epi-11-hydroxyaphidicolin using tandem transannular Diels-Alder/aldol reactions.

[reaction: see text] Aphidicolin unnatural derivative (2) was synthesized using a new tandem transannular Diels-Alder/aldol methodology. The 8-epi-aphidicolane skeleton is constructed in a highly diastereoselective manner and converted into (11R)-(-)-8-epi-11-hydroxyaphidicolin (2). An efficient method for the difficult C16 funtionalization is presented.

Acremonium↗
PubMed1999

Molecular cloning, expression and characterization of a monkey steroid UDP-glucuronosyltransferase, UGT2B19, that conjugates testosterone.

Although enzymatic processes involved in the formation of active steroids are well known, less information is available about the enzymes responsible for the metabolism of these hormones. Moreover, the expression of these catabolic enzymes, which include UDP-glucuronosyltransferases, may play a role in the regulation of the level and action of steroid hormones in steroid target tissues. Previous studies have shown that the cynomolgus monkey contains high levels of circulating androgen glucuronides, indicating that it represents the best animal model to study the glucuronidation of steroids in extrahepatic tissues. Two cDNA libraries were constructed from monkey liver and prostate mRNA, and a novel UDP-glucuronosyltransferase UGT2B cDNA, UGT2B19, was isolated from both libraries. The UGT2B19 cDNA is 2108 bp in length and contains an open reading frame of 1584 bp encoding a protein of 528 residues. The UGT2B19 cDNA clone was transfected into HK293 cells and a stable cell line expressing UGT2B19 protein was established. The activity of UGT2B19 on 3alpha-hydroxy and 17beta-hydroxy positions of steroids was demonstrated. The enzyme also conjugates xenobiotics including eugenol, 1-naphthol and p-nitrophenol. Kinetic analysis revealed that UGT2B19 glucuronidates steroids with Km values of 1.6, 2.6 and 4.3 microm for testosterone, etiocholanolone and 5beta-androstane-3alpha,17beta-diol, respectively. UGT2B19 transcript was detected, by specific reverse transcriptase-PCR analysis in the liver, ovary, prostate, colon, spleen, kidney, pancreas, brain, cerebellum, mammary gland and epididymis. The molecular characterization of simian UGT2B19 demonstrates relevance of using monkey as an animal model to study and understand steroid glucuronidation in extrahepatic target tissue.

Amino Acid Sequence↗
PubMed1999

Hepatitis C virus is related to progressive liver disease in human immunodeficiency virus-positive hemophiliacs and should be treated as an opportunistic infection.

The hypothesis was investigated that hepatitis C virus (HCV) infection behaves like an opportunistic infection in which progressive liver disease (PLD) is the principal manifestation. PLD in 81 hemophiliacs coinfected with HCV and human immunodeficiency virus (HIV) was compared with 53 HIV-seronegative HCV-infected hemophiliacs. Progression to AIDS and death in 22 HCV/HIV-coinfected hemophiliacs with PLD was also compared with 59 coinfected hemophiliacs who did not develop PLD. The risk of PLD occurrence associated with an HIV-positive status was 7.4 (95% confidence interval [CI], 2.2-25.5; Cox model). In the coinfected group, the risk of PLD occurrence was higher in subjects with severe AIDS-defining immunodeficiency than in those without (odds ratio, 3. 6; 95% CI, 1.3-10). Persons with PLD also had a faster progression to AIDS (P=.03, log rank test) than those without PLD. Thus, as with other chronic resident human viruses, HCV should be considered another opportunistic pathogen in HIV disease.

AIDS-Related Opportunistic Infections↗
PubMed1999

Production of probiotic cheese (cheddar-like cheese) using enriched cream fermented by Bifidobacterium infantis.

Probiotic cheeses (Cheddar-like cheese) were produced with microfiltered milk standardized with cream enriched with native phosphocaseinate retentate and fermented by Bifidobacterium infantis. During the manufacture and storage of cheeses, viability of the bifidobacteria was determined. Biochemical changes such as proteolysis, sugar metabolism, and organic acids production were estimated. No bifidobacteria growth was observed during cheese-making steps. Bifidobacteria survived very well in cheeses packed in vacuum sealed bags kept at 4 degrees C for 84 d and remained above 3 x 10(6) cfu/g of cheese. No significant difference was observed between cheeses produced with or without bifidobacteria for fat, protein, moisture, salt, ash, or pH. After 12 wk of storage, more than 56% of the as1-CN was hydrolyzed in cheeses that were produced with bifidobacteria and inoculated at 10(8) cfu/g in the cream, and > 45% of hydrolysis was observed in the control cheese. However, no significant differences in the electrophoretic sodium dodecyl sulfate-PAGE patterns were observed in cheeses at any period of storage. At the first day after manufacture, lactose was completely hydrolyzed in cheeses made with bifidobacteria, which suggested high beta-galactosidase activity by B. infantis. Small quantities of acetic acid were detected in bifidus cheeses. The results indicated that B. infantis introduced into hard pressed cheese exhibited excellent viability during storage for 12 wk and could be metabolically active.

Bifidobacterium↗
PubMed1999

Predicting the probability of meningioma recurrence based on the quantity of peritumoral brain edema on computerized tomography scanning.

OBJECT: The goal of this study was to determine whether the quantity of peritumoral brain edema displayed on computerized tomography (CT) scanning could be correlated with brain invasion and subsequent recurrence of meningiomas. METHODS: One hundred thirty-five patients who underwent resection of intracranial meningiomas at the Ottawa Civic Hospital were followed during the period 1980 to 1998. A complete resection was defined as one in which tumor, invaded bone, and involved dura were removed. Tumors were examined microscopically for evidence of brain invasion. The mean follow-up period was 9 +/- 4 years (standard deviation [SD]) and the mean time to recurrence was 5 +/- 4 years (SD). The authors used a simple grading system based on the average thickness (in centimeters) of edema seen on an axial CT slice showing the most tumor. Edema grade was linearly related to edema volume determined by digitizing the scans (r = 0.96; 29 cases). The chance of brain invasion increased by 20% for each centimeter of edema (r(s) = 1, p < 0.0001; 124 cases). The presence of brain invasion was predictive of recurrence after complete resection with an accuracy of 83%, a sensitivity of 89%, and a specificity of 82%. The chance of recurrence within 10 years after complete resection was given by the equation: percentage chance of recurrence = (centimeter of edema)3 x 0.7, which can be used to predict the chance of recurrence based on findings on CT scans (r(s) = 1, p < 0.0001; 86 patients). Statistical significance was confirmed using Kaplan-Meier and univariate and multivariate analyses. Completeness of resection was the most powerful predictor of recurrence (p < 0.00001, r = 0.6), followed by edema grade and brain invasion (both p = 0.02, r = 0.1). Patient age and gender and tumor location, size, and histological subtype were nonsignificant factors. CONCLUSIONS: Brain invasion causes peritumoral edema. Invaded brain tissue is also the source of residual cells in cases of tumor recurrence after gross-total resection.

Aged↗
PubMed1998

Isolation and characterization of a simian UDP-glucuronosyltransferase UGT2B18 active on 3-hydroxyandrogens.

A monkey cDNA, UGT2B18, encoding a UDP-glucuronosyltransferase (UGT) active on 3-hydroxyandrogens, has been isolated and characterized. Previous results suggested that the monkey represents the most appropriate animal model for studying the physiologic relevance of steroid UGTs. UGT2B18 was isolated from a cynomolgus monkey prostate cDNA library using human UGT2B7, UGT2B10 and UGT2B15 cDNA as probes. The cDNA is 1748 bp in length and contains an open reading frame of 1587 bp encoding a protein of 529 residues. The UGT2B18 cDNA clone was transfected into HK293 cells and a stable cell line expressing UGT2B18 protein was established. Western blot analysis of the UGT2B18-HK293 cell line using a human UGT2B17 polyclonal antibody (EL-93) revealed high expression of a 53 kDa UGT2B protein. The transferase activity of UGT2B18 was tested with over 60 compounds and was demonstrated to be principally active on C19 steroids having an hydroxyl group at position 3alpha of the steroid molecule. UGT2B18 was also active on planar phenols and bile acids. Kinetic analysis revealed that UGT2B18 glucuronidates 3-hydroxyandrogens with high velocity and affinity. Using cell homogenates, Km values of 5.1, 7.8 and 23 microM for androsterone (ADT), etiocholanolone and androstane-3alpha, 17beta diol (3alpha-diol) were obtained, respectively. Specific RT-PCR analysis demonstrated the expression of UGT2B18 transcripts in several tissues including liver, prostate, kidney, testis, adrenal, bile duct, bladder, colon, small intestine, cerebellum and pancreas suggesting a contribution of this isoenzyme to the high plasma levels of glucuronidated ADT and 3alpha-diol found in the cynomolgus monkey.

Amino Acid Sequence↗
PubMed1998

Characterization and regulation of UDP-glucuronosyltransferases in steroid target tissues.

Conjugation of compounds by glucuronidation is a pathway found in all vertebrates studied to date. Although, it is widely recognized that the liver is a major site of glucuronidation, it is now clear that extrahepatic tissues are also involved in the conjugation of compounds to which these tissues are exposed. High levels of androsterone glucuronide and androstane-3alpha,17beta-diol glucuronide found in the human prostate, breast cyst fluid and ovary follicular fluid suggest that glucuronidation of 5alpha-reduced C19 steroids occurs in these tissues. Recently, we have reported the tissue distribution of UGT2B15, which can conjugate steroids in several human extrahepatic steroid target tissues including the skin, breast and prostate. We have also isolated a new UGT2B cDNA encoding UGT2B17, that conjugates ADT which is the major 5alpha-reduced C19 steroid glucuronide in the circulation of humans. UGT2B17 is also widely distributed in several human steroid target tissues. This gene was mapped to human chromosome 4q13 and has an exon/intron structure similar to that of rat UGT2B1 and UGT2B2. Both UGT2B15 and UGT2B17, which are able to catalyze the glucuronidation of DHT, are expressed in LNCaP cells. Interestingly, glucuronidation of steroids is markedly regulated by several factors including androgens and growth factors. Treatment of LNCaP cells with dihydrotestosterone (DHT) and epidermal growth factor (EGF) caused a decrease of DHT glucuronidation and UGT2B mRNA levels. RNase protection assays showed a specific decrease of UGT2B17 transcript in LNCaP cells treated with DHT and EGF however, the level of UGT2B15 mRNA was not affected. As well, Western blot analysis demonstrated a diminution of UGT2B17 protein level in response to DHT and EGF. These results demonstrate a differential regulation of different isoforms of steroid conjugating UGTs present in human prostate LNCaP cells. In addition, UGT2B17 was shown to be more labile than UGT2B15 indicating that regulation of UGT2B17 expression would lead to a more rapid change in the level of glucuronidated steroids. Expression of exogenous UGT2B17 in LNCaP cells by gene transfer led to a significant decrease in the androgen response. This result indicates the ability of UGT enzymes to regulate the androgen response by conjugating androgens which abolishes their interaction with their receptor and facilitates their clearance from the cell. The glucuronidation of steroids by UGT enzymes is an important mechanism by which the levels of steroids is regulated in steroid target tissues.

Amino Acid Sequence↗
PubMed1997

Expression and characterization of a novel UDP-glucuronosyltransferase, UGT2B9, from cynomolgus monkey.

Uridine diphosphate glucuronosyltransferases (UGTs) are important phase II detoxification enzymes. Despite the expression of UGT proteins in many species, previous results have suggested that simians represent the most appropriate animal model to study the glucuronidation of steroids in extrahepatic steroid target tissues. Northern blot analysis using a pool of human UGT2B cDNA probes demonstrated the expression of homologous UGT2B transcripts in several tissues including the liver, kidney, adrenal, breast, testis, and prostate of the cynomolgus monkey (Macacafascicularis). Western blot analyses using a polyclonal antibody raised against human UGT2B17 protein also demonstrated expression of homologous UGT2B proteins in monkey tissues. cDNA libraries were constructed from monkey liver and prostate mRNA and a novel UGT2B cDNA, UGT2B9, was isolated from both libraries. The UGT2B cDNA from the prostate library is 2,648 bp in length and contains an open reading frame of 1,587 bp encoding a protein of 529 residues. In vitro transcription/translation of the cDNA clone produced a protein of 52 kD. The UGT2B9 cDNA clone was transfected into HK293 cells and a stable cell line expressing UGT2B9 protein was established. The activity of UGT2B9 was tested with over 60 compounds and was demonstrated to be active on C18, C19, and C21 steroids, bile acids, and several xenobiotics including eugenol, 1-naphthol, and p-nitrophenol. Kinetic analysis revealed that UGT2B9 glucuronidates steroids with high affinity and efficiency with Km values of 0.2, 3.2, 0.2, and 1.8 microM for dihydrotestosterone, testosterone, androsterone, and 1,3,5,10-estratrien-3,4-diol-17-one, respectively. It is apparent that this simian UGT2B enzyme is specific for more different classes of steroids than any other UGT enzyme characterized to date, and may be related to the high plasma levels of glucuronidated C19 steroids found in the cynomolgus monkey.

Amino Acid Sequence↗
PubMed1997

Glucuronidation of opioids, carboxylic acid-containing drugs, and hydroxylated xenobiotics catalyzed by expressed monkey UDP-glucuronosyltransferase 2B9 protein.

UDP-glucuronosyltransferase (UGT) 2B9, isolated from a cynomolgus monkey liver cDNA library, is 89% identical to human UGT2B7 in primary amino acid sequence, and the two expressed enzymes were previously shown to catalyze the glucuronidation of many common endogenous substrates. The purpose of the present study was to characterize the reactivity of expressed UGT2B9 with important therapeutic agents and other xenobiotics. UGT2B9, stably expressed in human embryonic kidney 293 cells, catalyzes the 3-O- and 6-O-glucuronidation of morphine and the 6-O-glucuronidation of codeine. A number of other morphinan (e.g. naloxone, naltrexone, and nalorphine) and oripavine (e.g. buprenorphine) derivatives are substrates for this enzyme. In general, morphinan derivatives are glucuronidated at higher rates, compared with oripavines; however, glucuronidation efficiency values (Vmax/KM) for the compounds are similar. Stably expressed UGT2B9 also catalyzes the glucuronidation of profen nonsteroidal anti-inflammatory drugs, fibrate hypolipidemic agents, and straight-chain fatty acids at the carboxylic acid moiety. Monoterpenoid alcohols and propanolol are glucuronidated at aliphatic hydroxyl positions. Expressed UGT2B9 exhibits enantioselective glucuronidation for (R/S)-ibuprofen, (R/S)-propanolol, and (+)/(-)-menthol. The data suggest that monkey UGT2B9 and human UGT2B7 are functionally similar.

Animals↗
PubMed1996

[Computerization and nursing: in search of an ideal!].

The computerized systems that are currently available are frequently incompatible with the specific information needs of nursing practice (Grassert, 1990). It is not currently possible to analyze the computerization requirements of nursing practice, since we do not know towards what ideal situation the process of computerizing nursing should be evolving. This makes it impossible to measure the gap between the status quo and the ideal situation. This methodological study described the desired situation by identifying 43 criteria for ideal management procedures and the handling of data needed in nursing practice. Criteria were validated using the DELPHI technique on a non-probablist sampling of 22 nurses who had developed some expertise in computerization in nursing. The study paves the way for conducting a needs assessment, then measuring the capacity of current systems to meet specific needs in terms of management and handling of nursing data.

Attitude of Health Personnel↗
PubMed1995

Expression of transcripts encoding steroid UDP-glucuronosyltransferases in human prostate hyperplastic tissue and the LNCaP cell line.

The UDP-glucuronosyltransferase (EC 2.4.1.17) enzymes transform many lipophilic compounds to more water-soluble products via conjugation with glucuronic acid. This conversion is responsible for enhancing the excretion of endogenous aglycones such as steroids. To date, several distinct isoforms of steroid UDP-glucuronosyltransferases (UGTs) have been isolated in the human liver. Among these UGTs, UGT2B7 is specific for estriol and 3,4-catechol estrogens, UGT2B15 glucuronidates 17beta-hydroxy-C19 steroids while UGT2B10 has as yet an undescribed activity. To further demonstrate the presence of UGTs in peripheral tissues we studied the expression of these enzymes in human prostate hyperplastic tissue and the LNCaP cell line. Metabolism studies using intact LNCaP cells in culture indicate the presence of UGT activities involved in the glucuronidation of 3alpha-hydroxysteroids (androsterone) and 17beta-hydroxysteroids (testosterone and dihydrotestosterone). Northern blot analysis of poly(A+) RNA from LNCaP cells and prostate using a UGT2B15 cDNA probe revealed two bands of 2.0 and 2.3 kb. In order to identify more specifically the mRNAs detected in Northern blot analysis we used RNase protection and RT-PCR, although, these approaches did not allow detection of UGT2B7 transcripts. Our studies demonstrate the presence of two UGT activities and at least two types of UGT transcripts in both the human prostate and the LNCaP.

Androsterone↗