Biomedical subjects

N Boucher

Publications and source records attributed to N Boucher.

9 recordsLinked to original sources

PubMed2002

A +2138InsCAGACC polymorphism of the melanocortin receptor 3 gene is associated in human with fat level and partitioning in interaction with body corpulence.

BACKGROUND: The melanocortin system includes five receptors (MC1R to MC5R), and mouse and human MC4R has been shown to be involved in the regulation of feeding, and mouse MC3R in body composition. To verify a possible similar effect of MC3R in humans, we analyzed one insertion and one single nucleotide polymorphism by restriction fragment length polymorphisms (RFLP), and a microsatellite (D20S32e) in relation to body composition and glucose metabolism. METHODS: Eight hundred twelve subjects of the Québec Family Study (QFS) cohort were analyzed for body composition, food intake, and energy metabolism phenotypes. Southern Blot with the complete MC3R cDNA was used to detect a new +2138InsCAGACC variant by Pst1 restriction. PCR-RFLP with BsaJ1 was used to type amino acid polymorphism V81I arising from a G241A nucleotide change. PCR and automatic DNA sequencers were used for the analysis of the TG dinucleotide repeat D20S32e located between -1933/-1892 of MC3R. In a covariance analysis among genotypes, phenotypes were adjusted for age and sex as covariates. Food intake and energy metabolism phenotypes were also adjusted for body mass index (BMI), and leptin and abdominal fat, as assessed by a computed tomography scan, for fatness using six skinfold thicknesses. RESULTS: An association between the +2138InsCAGACC MC3R polymorphism was observed with fat mass (FM), percent body fat (%FAT), and total abdominal fat (ATF). Homozygote subjects for the +2138 insertion variant allele in normal weight (BMI < 25 kg/m(2)) and overweight (25 < or = BMI < 30 kg/m(2)) subjects showed a similar level of fatness despite the overall difference in BMI. In normal weight, homozygotes for the insertion allele showed higher mean values than heterozygotes and homozygotes for wild-type allele without insertion (%FAT: 24.0 +/- 1.1 versus 19.3 +/- 0.9 and 20.5 +/- 0.8, p = 0.0005; FM: 15.7 +/- 0.9 kg versus 11.7 +/- 0.7 kg and 12.6 +/- 0.6 kg, p = 0.0003). In contrast, overweight subjects homozygote for the variant allele showed lower mean values (%FAT: 27.0 +/- 1.2 versus 31.4 +/- 0.8 and 30.9 +/- 0.7, p = 0.002; FM: 18.3 +/- 1.0 kg versus 22.8 +/- 0.8 kg and 22.0 +/- 0.6 kg, p = 0.0001). This resulted in a similar level of body fat between both BMI groups for subjects homozygote for the insertion allele versus wild-type allele carriers (%FAT: +/-2-3% versus +/-10-12%; FM: +/-2 kg versus +/-9-11 kg). In obese subjects (BMI > or = 30 kg/m(2) ), a lower level of ATF was seen (-15%, p = 0.002). Other polymorphisms and phenotypes tested showed no association. CONCLUSION: A new 12138InsCAGACC MC3R polymorphism is associated with the level of adiposity and with body fat partitioning in interaction with corpulence in humans.

Adipose Tissue↗

PubMed2001

Electrophysiological and behavioral output of the rat basal ganglia after intrastriatal infusion of d-amphetamine: lack of support for the basal ganglia model.

Dopamine, by acting upon D1 and D2 dopamine receptors located on striatonigral and striatopallidal neurons, respectively, has been postulated to inhibit output from the substantia nigra pars reticulata (SNpr) and internal pallidal segment (GPi). The inhibition of the SNpr/GPi should, in turn, disinhibit the thalamus to facilitate movement. The present study tests this prediction in intact (unlesioned) rats by attempting to correlate changes in the single unit activities of SNpr neurons with motor (i.e. behavioral) responses in the 20-30 min after infusions of d-amphetamine into the striatum. Unilateral injections of amphetamine (20 microg/microl) into either the dorsal-rostral, central, or ventral-lateral striatum failed to appreciably alter behavior and, in parallel electrophysiological studies, failed to consistently or significantly alter the activities of SNpr neurons in either chloral hydrate-anesthetized rats or awake locally anesthetized rats. However, when amphetamine was infused bilaterally into the ventral-lateral striatum (VLS; 20 microg/microl per side), a robust behavioral activation ensued (increased locomotor activity, oral movements, and sniffing) with an onset ranging from immediate to 20 min post-infusion and persisting for at least 40 min. In parallel studies, bilateral amphetamine infusions into VLS also caused changes in the firing frequency of a majority of SNpr neurons. However, the changes in firing were extremely variable and, contrary to expectation, the net population response of SNpr neurons was an increase in firing which corresponded in time with the period of peak behavioral activation. These results show that (i) bilateral but not unilateral activation of striatal dopamine receptors is needed to elicit behavioral and electrophysiological output from the basal ganglia, and (ii) motor activation is apparently not signaled by a generalized inhibition of SNpr firing, as is predicted by the basal ganglia model.

Animals↗

PubMed2001

Intratester and intertester reliability of the Cybex electronic digital inclinometer (EDI-320) for measurement of active neck flexion and extension in healthy subjects.

This study examined the intratester and intertester reliability of the electronic digital goniometer EDI-320 for the measurement of active neck flexion and extension in healthy subjects. In the context of evidence-based practice, the EDI-320 instrument has the potential to improve patient assessment, provide a clearer picture of patient progress, and confirm the effectiveness of physiotherapy interventions. However, the psychometric properties of the EDI-320 have not yet been documented for cervical spine range of motion. Forty-four individuals with no known history of cervical disorder within the three months prior to the testing, voluntarily consented to participate in this study. Repeated measurements with the EDI-320 were taken by two trained testers (TH1 and TH2) and data were recorded by two separate observers. Subjects performed a standardized warm-up. Testers were required to repeat palpation of bony landmarks prior to each trial. Measurements were taken at the end-range of active cervical flexion and extension for each subject. Both testers measured each subject twice. The intraclass correlation coefficients (ICC) were derived from one-way ANOVA for intratester reliability and a two-way ANOVA for intertester reliability. Paired t -tests were then applied to verify for systematic error. Moderate intratester reliability was found for both testers for flexion (TH1: ICC=0.77; 95% CI: 0.62-0.87; TH2: ICC=0.77; 95% CI: 0.58-0.87). As for extension, high intratester reliability was found for TH1 (ICC=0.79; 95% CI: 0.65-0.88) and moderate for TH2: (ICC=0.83; 95% CI: 0.63-0.92). Intertester reliability results showed a moderate reliability for both flexion and extension (ICC=0.66; 95% CI: 0.24-0.84) on the first trial. On the second trial, reliability was moderate for flexion (ICC=0.73; 95% CI: 0.53-0.85) and high for extension (ICC=0.80; 95% CI: 0.64-0.89). The t -test analysis revealed the inclusion of systematic error by Tester 2 for intratester reliability. This error was also found for all but one of the intertester reliability calculations. This study has shown that the EDI-320 is a moderately reliable instrument for quantifying cervical flexion and extension range of motion. The presence of systematic error in the study highlights the importance of following standardized procedures and suggests that the EDI-320 could be more reliable than reported in this study. Further psychometric studies investigating the validity of the EDI and reliability with subjects affected by cervical pathology is warranted.

Adult↗

PubMed1999

Expression of the GALalpha(1-3)GAL epitope on pig islets.

Expression of Galalpha(1-3)Gal on endothelium has been implicated in the rejection of porcine xenografts. The aim of this study was to determine whether expression of Galalpha(1-3)Gal on pig islets varies between pigs aged 5, 12 and 24 weeks, and to investigate whether it is expressed on islets isolated by collagenase digestion or islets maintained in tissue culture. Samples of pancreas were obtained from pigs aged 5, 12 and 24 weeks. Islets were isolated by manual collagenase digestion and density gradient separation. Samples were taken immediately after isolation or after maintenance in tissue culture. Pancreas and islet samples were processed, sectioned and stained with the lectin BS1-B4 (which binds to Galalpha(1-3)Gal residues), and anti-insulin antibody using a double staining technique. There was no significant difference in the staining patterns to sections of pancreas obtained from 5, 12 and 24 week old pigs. Vascular endothelium, connective tissue and the luminal surface of duct epithelial cells stained with BS1-B4 in all sections; endocrine and exocrine cells did not stain. Preliminary experiments showed that lectin staining to isolated islets was inconsistent between preparations, but expression did not appear to differ significantly between ages: lectin staining of some beta-cells was evident in the majority of freshly isolated preparations, but was not detectable on beta-cells following tissue culture. In conclusion, expression of Galalpha(1-3)Gal did not differ significantly in pancreata from 5, 12 and 24 week old pigs. Preliminary experiments showed that Galalpha(1-3)Gal was expressed by beta-cells immediately following isolation, but not after maintenance in culture.

Aging↗

PubMed1998

CD28 expression in T cell aging and human longevity.

Functional decrements of the immune system have a major contribution to aging and age-related diseases. Here, we further characterize the decline in proportion of CD28-positive T cells previously identified in centenarians. Cohorts of 97 centenarians, 40 subjects aged 70-90 (ELD group), and 40 young adults (under age 40) were phenotyped for T cell surface expression of CD28, CD4, and CD8 antigens. The significant decline in T cells expressing CD28 (p < 10(-4) for comparisons between adults and either ELD or centenarians) affects preferentially the CD8+ subset of T cells. This decline accounts largely for the age-related diminution of T cell responsiveness to mitogenic signals. CD28 expression is modulated in T cell cultures in a growth-related fashion and this modulation is dampened in cultures from centenarians. We propose that the decrease in CD28 expression reflects a compensatory adaptation of the immune system during aging in the face of chronic stimulation.

Adult↗

PubMed1995

[Cellular senescence and survival of T lymphocytes].

In order to study cellular senescence in T lymphocytes and its link with aging, we have undertaken long-term cultures from adult individuals (aged from 20 to 40) and centenarians. The proliferative advantage of CD4+ over CD8+ T cells is reversed after the second stimulation. Periodically stimulated cultures remained exponentially growing during nearly 200 days, whereas 2 of them that were continued for 300 days stopped proliferating. However, once this phase of senescence is reached, the cells do not die out. Six other cultures remained viable for 34 months without proliferation but with conservation of the cell number. Three of these cultures have clonal karyotypic abnormalities: trisomy 2 and telomeric fusions.

Adult↗

PubMedDate not supplied

Decline in CD28+ T cells in centenarians and in long-term T cell cultures: a possible cause for both in vivo and in vitro immunosenescence.

The dramatic decline in immune function with age, especially in T cell proliferative activity, has been documented extensively in experimental animal models and in clinical studies of the elderly. A similar proliferative decline is also seen in long-term T lymphocyte cultures used to study in vitro cellular senescence. We have compared the peripheral blood T lymphocytes of centenarians and younger controls for the cell surface expression of CD28, a costimulatory molecule that is required for optimal activation and proliferation following engagement of the T cell receptor. Our analysis shows a significant decrease (p < 0.001) in the percentage of T cells expressing CD28 in the elderly cohort, with values ranging from 44% to 90%, as compared to the mean control value of 91%. The decline in the percentage of CD28+ T cells correlates with a reduction in the CD4/CD8 ratio (r2 = 0.695, p < 0.0001). Concommitantly, experiments using an in vitro T cell culture system showed a progressive loss of CD28 expression with culture "age." The concordance of proliferative decline and loss of CD28 in the centenarians and in the in vitro cultures suggest that a Hayflick phenomenon may operate in vivo leading to immunosenescence.

Adult↗

PubMedDate not supplied

Heat-stress stimulation of electron flow in a photosystem I submembrane fraction.

Oxygen uptake using methyl viologen as the terminal electron acceptor was recorded in digitonin-derived photosystem I submembrane fractions incubated at either 25 or 50 degrees C. A two- to four-fold heat-stress stimulation of electron flow was detected at 50 degrees C when reduced 2,6-dichlorophenol-indophenol was used as the primary electron donor. However, no stimulation was seen with N,N,N',N'-tetramethylphenylenediamine as the donor. The stimulation was enhanced by specific cations (Mg2+, Na+, K+), but not by Mn2 or Ca2+. The enhancement obtained with Mg2+ could be eliminated by incubating for a prolonged period. It is proposed that the observed heat-stress stimulation is due to a conformational change at the level of the cytochrome b6-f complex. This change increased the affinity of the protein complex for 2,6-dichlorophenol-indophenol at its oxidation sites. The involvement of a conformational modification is demonstrated by the absence of heat-stress stimulation in submembrane fractions immobilized in an albumin-glutaraldehyde cross-linked matrix.

2,6-Dichloroindophenol↗

PubMedDate not supplied

Development of a very sensitive luminescence assay for the measurement of paclitaxel and related taxanes.

A rapid and very sensitive enzyme immunoassay was developed for the measurement of paclitaxel and related taxanes in crude extracts of Taxus sp., in human serum and in culture medium of paclitaxel-producing microorganisms such as Erwinia taxi. For the ELISA, paclitaxel was chemically modified by the introduction of an amine to enable coupling with biotin. The presence of paclitaxel or related taxanes competitively inhibited the binding of paclitaxel-biotin to anti-taxane monoclonal antibody. This method detected paclitaxel in concentrations as low as 33 pM; the affinity of the antibody was higher for paclitaxel than for cephalomanine, baccatin and DAB. The sensitivity of this assay makes it useful for estimating the paclitaxel and taxanes content of Taxus sp. extracts, monitoring the paclitaxel serum level of paclitaxel treated patients and in other biological fluids.

Antibodies, Monoclonal↗