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Biomedical subjects

S Gauthier

Publications and source records attributed to S Gauthier.

At least 19 recordsLinked to original sources
PubMed1996

Comparative ontogenic profile of cholinergic markers, including nicotinic and muscarinic receptors, in the rat brain.

The ontogenic profiles of several cholinergic markers were assessed in the rat brain by using quantitative in vitro receptor autoradiography. Brain sections from animals at different stages of development were processed with [3H]AH5183 (vesamicol; vesicular acetylcholine transport sites), [3H]N-methylcarbamylcholine (alpha(4)beta(2) nicotinic receptor sites), [3H]hemicholinium-3 (high-affinity choline uptake sites), [3H]3-quinuclidinyl benzilate (total population of muscarinic receptor sites), [3H]4-DAMP (muscarinic M1/M3 receptor sites), [3H]pirenzepine (muscarinic M1 receptor sites), and [3H]AF-DX 116 and [3H]AF-DX 384 (muscarinic M2 receptor sites) as radiolabeled probes. The results revealed that, by the end of the prenatal period (embryonic day 20), the densities of nicotinic receptor and vesicular acetylcholine transport sites already represented a considerable proportion of those observed in adulthood (postnatal day 60) in different laminae of the frontal, parietal, and occipital cortices, in the layers of Ammon's horn fields and the dentate gyrus of the hippocampal formation, as well as in the amygdaloid body, the olfactory tubercle, and the striatum. In contrast, at that stage, the densities of total muscarinic, M1/M3, M1, and possibly M2 receptor and high-affinity choline uptake sites represent only a small proportion of levels seen in the adult. Differences were also observed in the postnatal ontogenic profiles of nicotinic, muscarinic, vesamicol, and high-affinity choline uptake sites. For example, between postnatal weeks 3 and 5, the levels of M1/M3 and M1 sites were at least as high as in the adult, whereas M2 and high-affinity choline uptake site densities appeared to be delayed and to reach adult values only after postnatal week 5. With regard to cholinergic innervation in the developing rat brain, the present findings suggest a temporal establishment of several components of the cholinergic systems. The first components are the vesicular acetylcholine transporter and nicotinic sites; these are followed by M1/M3 and M1 sites and, finally, by M2 and high-affinity choline uptake sites.

Acetylcholine↗
PubMed1996

Effects of the phosphatase inhibitors calyculin A and okadaic acid on acetylcholine synthesis and content of rat hippocampal formation.

The biochemical mechanisms involved in the regulation of acetylcholine (ACh) turnover are poorly understood. In the experiments reported here, we examined whether inhibition of the serine/threonine phosphatases 1 and 2A by calyculin A or okadaic acid alters ACh synthesis by rat hippocampal preparations. With hippocampal slices, calyculin A (50 nM) and okadaic acid (50 nM) reduced significantly (p < 0.01) the synthesis of [3H]ACh from [3H]choline. Both calyculin A and okadaic acid produced significant depletion of endogenous tissue ACh in a concentration-dependent manner (p < 0.01). This depletion was not the result of a drug-induced increase of spontaneous ACh release, which was not changed significantly (p > 0.7) by either drug. Choline acetyltransferase (ChAT) activity from tissue exposed to calyculin A or okadaic acid was reduced in a concentration-dependent manner (p < 0.05), but these phosphatase inhibitors did not act directly on ChAT in vitro; i.e., enzymatic activity was not altered significantly (p > 0.4) in the presence of calyculin A or okadaic acid. Both high-affinity and low-affinity [3H]choline uptake by hippocampal synaptosomes were reduced significantly in a concentration-dependent manner in the presence of calyculin A or okadaic acid; these agents reduced Vmax values for high- and low-affinity choline uptake (p < 0.01) with no significant change in Km values (p > 0.1), indicating a noncompetitive inhibition. Taken together, these data suggest that phosphatase activity plays a role in presynaptic central cholinergic nerve terminal function, in particular in the modulation of ACh synthesis.

Acetylcholine↗
PubMed1996

The Bcg/Ity/Lsh locus: genetic transfer of resistance to infections in C57BL/6J mice transgenic for the Nramp1 Gly169 allele.

The murine Bcg/Ity/Lsh locus determines the susceptibilities of inbred strains to infection with unrelated intracellular parasites, such as Mycobacterium bovis, Salmonella typhimurium, and Leishmania donovani. A candidate for Bcg/Ity/Lsh, designated Nramp1, has been recently identified and shown to encode a novel integral membrane protein that is expressed exclusively in professional phagocytes but whose function remains unknown. In inbred strains, the susceptibility to infection is associated with a single glycine-to-aspartic acid substitution at position 169 (G169D) in the predicted TM4 of the protein. To confirm the candidacy of Nramp1 as Bcg/Ity/Lsh and to determine the importance of the G169D mutation on Nramp1 function, we constructed transgenic mice in which the G169 allele of Nramp1 was transferred onto the background of a homozygous D169 allele. These transgenic mice were analyzed for their sensitivity to infections under the control of Bcg/Ity/Lsh. The transgene constructed for these studies contained the entire Nramp1G169 gene together with approximately 5 kb of sequences upstream of the transcription initiation site of this gene. We observed that these sequences were sufficient to direct Nramp1G169 expression in transgenic macrophages, resulting in the appearance of a mature protein of 90 to 100 kDa over a background of Nramp1G169 characterized by the complete absence of the mature Nramp1 polypeptide. The appearance of the Nramp1G169-encoded protein in transgenic macrophages was concomitant with the emergence of resistance to infection by M. bovis BCG, as measured by the extent of bacteria] replication in the spleen, and by S. typhimurium, as measured by survival after an intravenous challenge. The gain of function detected in transgenic Nramp1G169 animals establishes unambiguously that Nramp1 and Bcg/Ity/Lsh are allelic.

Alleles↗
PubMed1995

Apolipoprotein E4 allele as a predictor of cholinergic deficits and treatment outcome in Alzheimer disease.

Apolipoprotein E (apoE) is critical in the modulation of cholesterol and phospholipid transport between cells of different types. Human apoE is a polymorphic protein with three common alleles, APO epsilon 2, APO epsilon 3, and APO epsilon 4. ApoE4 is associated with sporadic and late-onset familial Alzheimer disease (AD). Gene dose was shown to have an effect on risk of developing AD, age of onset, accumulation of senile plaques in the brain, and reduction of choline acetyltransferase (ChAT) activity in the hippocampus of AD subjects. To characterize the possible impact of the apoE4 allele on cholinergic markers in AD, we examined the effect of apoE4 allele copy number on pre- and postsynaptic markers of cholinergic activity. ApoE4 allele copy number showed an inverse relationship with residual brain ChAT activity and nicotinic receptor binding sites in both the hippocampal formation and the temporal cortex of AD subjects. AD cases lacking the apoE4 allele showed ChAT activities close or within age-matched normal control values. The effect of the apoE4 allele on cholinomimetic drug responsiveness was assessed next in a group (n = 40) of AD patients who completed a double-blind, 30-week clinical trial of the cholinesterase inhibitor tacrine. Results showed that > 80% of apoE4-negative AD patients showed marked improvement after 30 weeks as measured by the AD assessment scale (ADAS), whereas 60% of apoE4 carriers had ADAS scores that were worse compared to baseline. These results strongly support the concept that apoE4 plays a crucial role in the cholinergic dysfunction associated with AD and may be a prognostic indicator of poor response to therapy with acetylcholinesterase inhibitors in AD patients.

Age of Onset↗
PubMed1995

The Ity/Lsh/Bcg locus: natural resistance to infection with intracellular parasites is abrogated by disruption of the Nramp1 gene.

In mice, natural resistance or susceptibility to infection with intracellular parasites is determined by a locus or group of loci on chromosome 1, designated Bcg, Lsh, and Ity, which controls early microbial replication in reticuloendothelial organs. We have identified by positional cloning a candidate gene for Bcg, Nramp1, which codes for a novel macrophage-specific membrane transport protein. We have created a mouse mutant bearing a null allele at Nramp1, and we have analyzed the effect of such a mutation on natural resistance to infection. Targeted disruption of Nramp1 has pleiotropic effects on natural resistance to infection with intracellular parasites, as it eliminated resistance to Mycobacterium bovis, Leishmania donovani, and lethal Salmonella typhimurium infection, establishing that Nramp1, Bcg, Lsh, and Ity are the same locus. Comparing the profiles of parasite replication in control and Nramp1-/- mice indicated that the Nramp1Asp169 allele of BcgS inbred strains is a null allele, pointing to a critical role of this residue in the mechanism of action of the protein. Despite their inability to control parasite growth in the early nonimmune phase of the infection, Nramp1-/- mutants can overcome the infection in the late immune phase, suggesting that Nramp1 plays a key role only in the early part of the macrophage-parasite interaction and may function by a cytocidal or cytostatic mechanism distinct from those expressed by activated macrophages.

Alleles↗
PubMed1995

Active site residues in m-calpain: identification by site-directed mutagenesis.

Site-directed mutagenesis was used to alter putative active site residues in the large subunit of calpain, and the activity of the mutants was measured following coexpression in E. coli of both calpain subunits and purification of the resultant dimers. Mutants Cys105Ser, His262Ala and Asn286Ala had no activity. Together with sequence comparisons among cysteine proteinases, the results suggest that these residues constitute the catalytic triad in calpain. Mutants Asn286Asp and Trp288Tyr had low activity, consistent with interaction of these residues with His262.

Animals↗
PubMed1995

Polymerase chain reaction quantification of lymphoid amyloid precursor protein mRNAs in Alzheimer's disease and Down's syndrome.

Amyloid beta-protein, the major constituent of Alzheimer's disease (AD) brain amyloid deposits, is encoded by several alternatively spliced amyloid precursor protein (APP) mRNAs. The well-established associated in Down's syndrome (DS) between APP overproduction and premature development of AD, as well as the recent demonstration of an increase in APP transcripts from lymphoblastoid cells of familial AD cases, suggest aberrant transcriptional regulation of some genes in AD. We assayed steady-state expression of the APP gene transcripts in peripheral blood mononuclear cells (PBMC) of AD and DS patients using quantitative polymerase chain reaction of reverse-transcribed mRNAs, and we compared their levels of PBMC APP expression with those of young and age-matched healthy controls. Results indicate APP mRNAs were of comparable abundance in PBMC obtained from 9 AD patients, 7 young controls and 12 age-matched controls. These data suggest regulation of APP mRNAs is normal in AD and DS PBMC.

Adult↗
PubMed1995

Factors predictive of the need for levodopa therapy in early, untreated Parkinson's disease. The Parkinson Study Group.

OBJECTIVE: To identify characteristics of patients with early, untreated Parkinson's disease that are the most important predictors of rapid functional decline. DESIGN: Prospective observational study of a cohort of 800 patients with early, untreated Parkinson's disease who were involved in a multicenter, randomized, double-blind, controlled clinical trial of selegiline hydrochloride (L-deprenyl) and vitamin E (alpha-tocopherol). PRIMARY OUTCOME VARIABLE: Time from randomization to the onset of disability that necessitated levodopa therapy (end point), as judged by the enrolling investigator. METHODS: Stepwise Cox regression was used in combination with clinical judgment to identify the most important independent baseline predictors of the primary end point among a host of variables, including treatment with selegiline and vitamin E, global and specific clinical measures of disease severity, demographic variables, and neuropsychological test results. RESULTS: In addition to selegiline treatment and global disease severity measures, such as the stage according to the criteria of Hoehn and Yahr, impaired domestic capacity, and the activities of daily living score, the complex of postural instability/gait difficulty and bradykinesia were found to be the factors that were most highly associated with the risk of reaching the end point. CONCLUSIONS: The findings suggest that patients with Parkinson's disease whose early clinical presentation includes either postural instability/gait difficulty or bradykinesia are at high risk for rapid functional decline.

Adult↗
PubMed1995

Plasma hormones and metabolites in cattle in relation to breed (Belgian Blue vs Holstein) and conformation (double-muscled vs dual-purpose type).

Four Belgian Blue double-muscled type (BBDM) bulls, four Belgian Blue dual-purpose type (BBDP) bulls and four Holstein bulls were used in a fattening trial in order to relate differences in the extent of muscle development and adiposity to differences in digestibility, endocrine status, protein and lipid metabolism. The larger muscle development in BBDM animals was associated with a trend to higher nitrogen retention, higher food conversion efficiency (p < 0.05) and lower apparent digestibility (p < 0.05). No difference was found between the groups for plasma glucose concentration. Higher creatinine, lower alpha-amino nitrogen, lower triglycerides and higher non-esterified fatty acid plasma levels were observed in BBDM as compared to Holstein bulls (p < 0.05), the BBDP group being intermediate. A trend to a higher cholesterol plasma level was found in BBDM animals. There was no difference between the three groups in plasma fatty acid composition, except for the C14:0 content. Some of the differences in plasma metabolites were related to carcass composition and endocrine regulation, a decrease in muscle development and an increase in adiposity being associated with lower growth hormone production (p < 0.05) and higher insulin (p < 0.05) and IGF secretions. The insulin/growth hormone ratio at the end of the fattening period was 0.0011, 0.0018 and 0.0069 in BBDM, BBDP and Holstein bulls, respectively, and was directly associated with fat deposition.

Adipose Tissue↗
PubMed1995

Cholinergic markers in aged cognitively impaired Long-Evans rats.

Aged Long-Evans rats (24-25 months old) were classified into cognitively impaired or unimpaired subgroups based on their performances in the Morris Swim Maze task compared to young controls. Using quantitative in vitro receptor autoradiography, we investigated the status of various cholinergic markers in these two groups and in young adults (six months) animals. The apparent density of [3H]pirenzepine (muscarinic M1) sites was similar in the three groups of rats in various cortical areas, subfields of the hippocampus, medial septum and striatum. Similarly, choline acetyltransferase activity and the density of [3H]hemicholinium-3 (high-affinity choline uptake) and [3H]cytisine (nicotinic) binding sites were also unchanged in the brain regions studied between the aged cognitively impaired, unimpaired and young adult rats. In contrast, significant increases in [3H]AF-DX 384 (muscarinic M2) binding density were observed in various cortical areas and in the molecular layer of the dentate gyrus of aged cognitively impaired versus unimpaired rats and in few cortical regions of old as compared to young animals. Therefore, a selective alteration in the regulation of putative M2 receptor sites is apparent, particularly in the aged cognitively impaired rats. Increases in M2 binding sites could lead to a decrease in the capacity to release acetylcholine, as some of the M2 receptors are believed to act as negative autoreceptors. This could influence cognitive functions as selective M2 blockers have recently been reported to facilitate spatial memory in aged impaired rats [Doods et al. (1993) Life Sci. 52, 497-503: Quirion et al. (1995) J. Neurosci. 15, 1455-1462.

Aging↗
PubMed1995

Canadian guidelines for the development of antidementia therapies: a conceptual summary.

The magnitude of the problems faced by Canadian society as a result of an aging population has been identified. Perhaps the most important concern related to this greying of Canada is the increasing incidence of dementia and Alzheimer's disease. Therapeutic options for these disorders have been limited to date. Advances in biotechnology and molecular biology will offer novel approaches to treatment. These and the expansion of more traditional therapeutic avenues require guidelines with the aim of optimizing their development.

Aged↗
PubMed1995

Recombinant calpain II: improved expression systems and production of a C105A active-site mutant for crystallography.

The bacterial production of recombinant rat calpain II has been improved greatly by the use of two compatible plasmids for the two subunits. The calpain small subunit C-terminal fragment (21 kDa) was expressed from a new A15-based vector created by cloning T7 control elements into pACYC177. This vector is compatible with the ColE1-based pET-24d(+) vector containing the calpain large subunit, and the yield of calpain activity was increased at least 16-fold by co-expression from these two vectors. A high level of activity was also obtained from a bicistronic construct containing both subunit cDNAs under the control of one T7 promoter. The addition of a C-terminal His-tag to the large subunit simplified purification without affecting subunit association or enzyme activity. The active-site cysteine 105 was mutated to alanine, causing complete loss of activity. The yield of purified C105A-calpain II (80 + 21 kDa) dimer following three column chromatography steps was 10 mg/l of cell culture. This provides a purified calpain, stable to autolysis and oxidation, which is likely to facilitate crystallization in both the presence and absence of calcium.

Amino Acid Sequence↗
PubMed1994

Active recombinant rat calpain II. Bacterially produced large and small subunits associate both in vivo and in vitro.

cDNA for the C-terminal Ca(2+)-binding domain of rat calpain small subunit was cloned by means of the polymerase chain reaction. The encoded protein (21 kDa), which corresponds closely to the natural autolysis product of the small subunit, was produced in soluble form in Escherichia coli at a level of 20 mg/liter of cell culture. Rat calpain II large subunit (80 kDa) was produced from a cDNA clone in E. coli in soluble form at a level of approximately 1 mg/liter. The 80-kDa subunit alone had no proteinase activity, with or without Ca2+, but Ca(2+)-dependent proteinase activity was obtained following association of the two subunits, which was achieved either by co-expression of the two subunit cDNAs in E. coli, or by mixing the two partially purified subunits in the presence of 1 M NaSCN followed by dialysis. The heterodimeric (80 + 21 kDa) proteinase had a Ca2+ requirement for 50% activity of 0.35 mM and a specific activity at 2 mM Ca2+ of approximately 1 unit/microgram, values essentially identical to those of natural (80 + 30 kDa) calpain II. The results establish association and biological activity of the bacterially produced subunits and provide a system for studying structure-function relationships in calpain by means of mutagenesis.

Amino Acid Sequence↗
PubMed1994

Health of family members caring for elderly persons with dementia. A longitudinal study.

OBJECTIVE: To estimate the change in depression and physical symptoms during a 1-year period in a group of caregivers for elderly persons with dementia and in a group of comparison participants. DESIGN: Cohort study with a comparison group. SETTING: Outpatient geriatric assessment unit and ophthalmology service in an acute care hospital. PARTICIPANTS: 218 close family members of a consecutive sample of patients with dementia and patients having cataract surgery were interviewed to obtain a baseline assessment. Of these, 86 caregivers (family members of patients with dementia) and 95 comparison participants (family members of patients with cataracts) were interviewed again approximately 1 year later. MAIN OUTCOME MEASURES: Center for Epidemiologic Studies depression scale and Aday and Andersen's 24-item physical symptom checklist. RESULTS: For the Center for Epidemiologic Studies depression score, the difference between caregivers and comparison participants with respect to change during the 1-year study period was 2.1 (95% CI, 1.0 to 5.2); for physical symptoms, the difference was 0.4 (CI, -0.3 to 1.1). A higher level of behavioral disturbance in the patients with dementia at time 1 and institutionalization of the patient between time 1 and time 2 were predictive of worsening caregiver depression and physical symptoms during the study period. The magnitude and direction of changes in caregiver health varied considerably. CONCLUSIONS: Overall mean changes in depression and physical symptoms during 1 year were small. The observed variability in the individual response to the caregiving situation suggests that future research should focus on the identification of salient prognostic factors.

Aged↗
PubMed1994

Predictive value of apolipoprotein E genotyping in Alzheimer's disease: results of an autopsy series and an analysis of several combined studies.

Apoliprotein E (apoE) is associated with Alzheimer's neurofibrillary tangles and beta-amyloid protein in senile plaques. Recent studies have shown an increased frequency of the epsilon 4 allele of the apoE gene in familial and sporadic cases of Alzheimer's disease (AD). In the present case control study, we have determined the apoE genotype by allele-specific extension of 113 postmortem cases of sporadic AD and 77 control brains shown to be free of AD neuropathological features and then calculated the frequency of the various allelic forms of apoE (epsilon 2, epsilon 3, epsilon 4). The odds ratio associating epsilon 4 with AD was 15.5 (95% confidence interval [CI] 6.2-38.5), and the population attributable risk was 0.53. We have also combined the results of our study and several others to calculate these same parameters in a larger population (570 controls and 961 AD subjects); the odds ratio for this larger group was 6.2 (95% CI 4.9-7.8) and the population attributable risk was 0.57. These results further substantiate and strengthen the association between the epsilon 4 allele of apoE gene and AD. We have also used these results to investigate the usefulness of the determination of epsilon 4 carrier status in the diagnosis of AD.

Aged↗
PubMed1994

Cross-national interrater agreement on the clinical diagnostic criteria for dementia. WHO-PRA Age-Associated Dementia Working Group, WHO-Program for Research on Aging, Health of Elderly Program.

We assessed the interobserver agreement on the clinical diagnosis of dementia syndrome and dementia subtypes as part of a cross-national project on the prevalence of dementia. Fourteen clinicians from the participating countries (Canada, Chile, Malta, Nigeria, Spain, and the United States) independently assessed the diagnosis of 51 patients whose clinical information was in standard records written in English. We used the DSM-III-R and ICD-10 criteria for dementia syndrome, the NINCDS-ADRDA criteria for Alzheimer's disease (AD), and the ICD-10 criteria for other dementing diseases, and measured interobserver agreement. We found comparable levels of agreement on the diagnosis of dementia using the DSM-III-R (kappa = 0.67) as well as the ICD-10 criteria (kappa = 0.69). Cognitive impairment without dementia was a major source of disagreement (kappa = 0.10). The kappa values were 0.58 for probable AD, 0.12 for possible AD, and rose to 0.72 when the two categories were merged. The interrater reproducibility of the diagnosis of vascular dementia was 0.66 in terms of kappa index; the diagnoses of other dementing disorders as a whole reached a kappa value of 0.40. This study suggests that clinicians from different cultures and medical traditions can use the DSM-III-R and the ICD-10 criteria for dementia effectively and thus reliably identify dementia cases in cross-national research. The interrater agreement on the diagnosis of dementia might be improved if clear-cut guidelines in the definition of cognitive impairment are provided. To improve the reliability of AD diagnosis in epidemiologic studies, we suggest that the NINCDS-ADRDA "probable" and "possible" categories be merged.

Aged↗