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Biomedical subjects

J Lambert

Publications and source records attributed to J Lambert.

At least 37 records · Page 2Linked to original sources

Fatigue effects on muscle excitability.

Repeated isometric or shortening contractions of skeletal muscle cause muscle fatigue but several prior studies have reported an apparent absence of muscle fatigue when humans performed up to 70 lengthening contractions. We pursued the hypothesis that perhaps muscle excitability is a factor that aids force preservation with repeated eccentric actions. Soleus compound muscle action potential (M-wave) latency, peak-to-peak amplitude (PPA), duration, and area under the curve were examined in 12 subjects (mean age 24.3 y) over 4 testing days that included: no exercise, isometric exercise (neutral ankle angle), isokinetic (0.5 rad.s-1) concentric and eccentric exercise of the plantar flexors in the seated position on a Biodex dynamometer. Supramaximal shocks were delivered to the tibial nerve in the popliteal fossa at baseline (3 shocks, 1 min apart), during exercise (1 shock-after each of 5 bouts/10 contractions), and during 10-min recovery. From initial to final contractions, concentric, isometric, and eccentric fatigue was -32, -41 and + 2% (Condition by Trial Interaction, F2,22 = 25.1, p = 0.000). No changes occurred in latency or duration (p > 0.05), but PPA (Condition by Time interaction, F51,561 = 3.7, p = 0.000) increased during isometric and eccentric exercise and remained elevated during recovery. Area increased (F51,561 = 3.1, p = 0.000) significantly during all three exercise conditions and approximated baseline by minute 8 of recovery. It was concluded that although the potentiation of the action potential of individual muscle fibers seems to be the common mechanism underlying the increase in muscle excitability during plantar flexion exercise, it is possible that different factors could cause such a non-specific response.

Action Potentials

Sexual risk and HIV-testing behaviour by gay and bisexual men in Canada.

Behavioural epidemiology is an important aspect of HIV research, particularly among marginalized populations where measurement of rates of infection have not been conducted. This Canadian study provides a country-wide analysis of the characteristics and behaviours of gay and bisexual men, and examines the influence of geographic, socio-demographic and lifestyle influences on sexual behaviour and test-seeking. A purposive sample of 4,803 men was recruited through gay-identified venues. In order to provide national representation seven sampling strata were defined. Data were collected by self-completed questionnaire. A three-level hierarchical logistic regression analysis is used to model two behaviours, unprotected anal intercourse and test-seeking. The results showed that, nationally, 22.9% of respondents reported at least one episode of unprotected anal intercourse in the previous 3 months, and 63% had been tested. Characteristics and behaviours of men varied across the country. Geographic differences appear to be less important in explaining unprotected anal intercourse than test-seeking. In conclusion, policy, programmes and social environment appear to exert an important influence on test-seeking, whereas cultural and psychosocial dimensions appear to have a greater influence on sexual behaviour.

AIDS Serodiagnosis

Evaluation of two-point discrimination in children: reliability, effects of passive displacement and voluntary movements.

Two-point discrimination (2-PD) thresholds were studied at three sites (tip of index finger, thenar eminence, external malleolus) and under various testing conditions (dynamic vs static, with and without displacement of instrument on skin; and active vs passive, with and without voluntary movement of subject) in 47 healthy children between 6 and 13 years of age. Reliability was fair to moderate, with slightly better perception (learning effect) during the second testing session. The threshold values of these children were similar to those of adults. For the passive conditions, the threshold values were lower for dynamic than for static tests at all sites. For the active condition at the index finger, there were no differences between dynamic and static values and there was no active/passive main effect. It is concluded that: (1) the hand is more sensitive than the ankle, with the finger being the most sensitive area, (2) the 2-PD test procedure used was most reliable at the index finger and least reliable at the external malleolus and (3) displacement of the instrument on the skin can improve 2-PD threshold values in children but the discrimination thresholds are not changed by active movement of the subject.

Adolescent

A survey of midwives in Quebec: what are their similarities and differences?

BACKGROUND: Until recently, Canada was the only industrialized country that had not legalized midwifery. In the province of Quebec the government adopted a law to evaluate midwifery in eight pilot projects before generalizing the practice. This study examined the similarities and differences among midwives in Quebec. METHODS: Using data from a 1991 mail survey, we compared 31 nurse-midwives, 12 professional midwives, and 27 lay midwives to assess professional background and opinions about selected maternity care issues and aspects of future midwifery practice, such as midwife training options, responsibilities, setting for midwifery care, relationship to other maternity caregivers, autonomy, and control over their profession. RESULTS: Midwives largely shared the same philosophy of care but had different viewpoints on two main professional aspects: compared with professional midwives and nurse-midwives, lay midwives preferred to deliver antepartum, intrapartum, and postpartum care at a client's home or an independent birthing center; like professional midwives, they rejected nursing as a prerequisite to midwifery training. Other interrelated personal, social, political, and legal factors were also associated with different beliefs. CONCLUSIONS: Despite the differences among the three groups, the process under way in Canada is to recognize a single profession of midwife. Creating a unified profession is a challenge that Canadian midwives with different backgrounds face in the 1990s.

Health Knowledge, Attitudes, Practice

Greater initial adaptations to submaximal muscle lengthening than maximal shortening.

The purpose of this study was to compare the short-term strength and neural adaptations to eccentric and concentric training at equal force levels. Forty-two sedentary women (age = 21.5 yr) were ranked based on the initial quadriceps strength score, and trios of subjects were randomly assigned to either an eccentric (n = 14), a concentric (n = 14), or a nonexercising control group (n = 14). Training involved a total of 824 eccentric or concentric quadriceps actions at 1.05 rad.s-1 administered in four sets of 6-10 repetitions, four times per week for 6 wk. Before and after training, all subjects were tested for unilateral maximal isometric and eccentric and concentric actions at 1.05 rad.s-1 and for a 40-repetition eccentric and concentric fatigue series of the left and right quadriceps. Surface electromyographic activity of the vastus lateralis and medialis was monitored during testing. Concentric training increased concentric (36%, P < 0.05), isometric (18%, P < 0.05), and eccentric strength (13%), and eccentric training increased eccentric (42%, P < 0.05), isometric (30%, P < 0.05), and concentric (13%) strength. Eccentric training improved eccentric and isometric strength more (P < 0.05) than did concentric training. The electromyographic adaptations were greater with eccentric training. Cross-education was 6%, and neither training mode modified fatigability. The data suggest that training of the quadriceps muscle with submaximal eccentric actions brings about greater strength adaptations faster than does training with maximal-level concentric actions in women. This greater adaptation is likely to be mediated by both mechanical and neural factors.

Adaptation, Physiological

Endothelium-dependent and -independent vasodilation of large arteries in normoalbuminuric insulin-dependent diabetes mellitus.

Vascular complications in diabetes mellitus are associated with endothelial dysfunction. Whether endothelium-dependent vasodilation is impaired in normoalbuminuric patients with insulin-dependent diabetes mellitus (IDDM) is controversial. Using a noninvasive echo-Doppler method, we investigated endothelium-dependent and endothelium-independent vasodilation in the brachial artery of IDDM patients. There were 52 normoalbuminuric and normotensive patients with IDDM (aged 31.9 +/- 9.8 years; diabetes duration, 14.9 +/- 7.9 years; glycated hemoglobin, 7.9 +/- 1.2%) and 52 healthy control group (C) subjects comparable for age and sex studied. Brachial artery diameter was measured at baseline, during postocclusion reactive hyperemia (flow-mediated, endothelium-dependent dilation [FMD]), and after 400 micrograms glyceryl trinitrate (GTN) sublingually (endothelium-independent vasodilation). Vasodilation was expressed as the percentage change relative to the baseline diameter. Baseline flow and blood pressure were similar for IDDM patients and C. Baseline vessel diameter was slightly larger in IDDM patients (3.10 +/- 0.52 mm) compared with C (2.89 +/- 0.55 mm, P = 5.0). FMD in IDDM patients was decreased (12.0 +/- 9.1% versus 15.7 +/- 9.5% in C, P = .046), as was GTN-induced vasodilation (14.9 +/- 8.2% versus 18.3 +/- 8.5% in C, P = .045). After correction for the difference in baseline diameter, FMD and GTN-induced dilation were not different between the groups. GTN-induced vasodilation decreased slightly with increasing diabetes duration. There was no relation between the vasodilatory responses and HbA1c. In normoalbuminuric IDDM patients, endothelium-dependent as well as endothelium-independent vasodilation are normal when the difference in baseline diameter is taken into account.

Adult

Treatment of familial hypercholesterolemia in children and adolescents: effect of lovastatin. Canadian Lovastatin in Children Study Group.

OBJECTIVE: Familial hypercholesterolemia (FH), an inherited autosomal dominant disorder of lipoprotein metabolism, is associated with premature atherosclerosis. The recommended pediatric therapy consists of dietary intervention and, when necessary, treatment with bile acid-binding resins. However, compliance has been poor in many children. Therefore, our objectives were to determine the efficacy, safety, and tolerance of the short-term use of lovastatin, a 3-hydroxy 3-methylglutaryl coenzyme A reductase inhibitor, in the control of severe FH in a male pediatric population and to evaluate the dose-response relationship. METHODS: Sixty-nine male patients with FH 12.9 +/- 2.4 years of age (mean +/- SD) participated in this multicenter, randomized, double-blind trial. After a 4-week placebo period, the patients were allocated to four treatment groups (lovastatin 10, 20, 30, 40 mg/d) for 8 weeks. Plasma lipid and apolipoprotein (Apo) concentrations were measured every 2 weeks. Clinical and laboratory evidence of adverse events was monitored periodically throughout the study. RESULTS: All lovastatin doses reduced total cholesterol (-17% to -29%), low density lipoprotein cholesterol (-21% to -36%), and ApoB (-19% to -28%) concentrations. A dose-response relationship was seen, and between-group comparisons showed that results were significantly improved up to a dose of 30 mg/d. We observed a 7% increase in high-density lipoprotein cholesterol and a 4% increase in ApoA1 concentrations. The medication was well tolerated by all patients. No serious clinical adverse experience was reported. Lovastatin increased aspartate aminotransferase concentrations, but there was no evidence of a dose-response relationship, and no value exceeded two times the upper limit of normal. No significant change in alanine aminotransferase was observed. Three patients had marked (more than three times the upper limit of normal) asymptomatic elevations in their creatine kinase values, which returned spontaneously to normal, and no action was required regarding the drug.

Adolescent

[Neuro-cognitive models of spelling and Alzheimer disease: mutual clarification].

The neuro-cognitive models developed over the last twenty years have considerably added to the understanding of disorders of spelling and writing resulting from brain lesions. These models differentiate between central processes, damage to which explains linguistic disorders, and peripheral processes, damage to which results in praxia and related disorders. This article analyses studies which have applied these distinctions to disorders observed in Alzheimer's disease. This disease causes unusual pathological situations which show certain types of agraphia rarely seen in the relevant literature, particularly certain peripheral forms. Several studies considered demonstrate the frequency of lexical agraphia in Alzheimer's disease. These lexical disorders of written expression seem to be independent of the lexico-semantic disorders found in other areas of the intellectual processes, Central writing disorders-lexical but also phonological-would appear to be the result of relatively focussed dysfunctionings, the left gyrus angularis and left gyrus supramarginalis respectively, as is suggested in brain metabolism studies. Moreover, certain patients develop peripheral writing disorders which are at present less well known, on a cognitive and neurobiological point of view. Inferences from other pathological contexts reveals that these disorders are often associated with diffuse cerebral lesions. Therefore disorders of written expression in Alzheimer's disease may be the result of two different pathological mechanisms: central disorders arising from localized areas of dysfunctioning at the left temporo-parietal intersection; peripheral disorders linked to the dysfunctioning of a much wider network involving the parietal and frontal regions of both cerebral hemispheres. To account for the diversity of clinical pictures, we suggest a physiopathological hypothesis which could also be used as a therapeutic model in Alzheimer's disease.

Agraphia

Randomized trial of intake of fat, fiber, and beta carotene to prevent colorectal adenomas.

BACKGROUND: Epidemiologic evidence of associations between the high intake of fat and low intake of dietary fiber, beta carotene, and other dietary constituents and the risk of colorectal neoplasia has been inconsistent and has not provided a sufficient basis for recommendations concerning the dietary prevention of large-bowel cancer in humans. PURPOSE: We conducted a clinical trial to assess the effects on the incidence of adenomas of reducing dietary fat to 25% of total calories and supplementing the diet with 25 g of wheat bran daily and a capsule of beta carotene (20 mg daily). METHODS: We performed a randomized, partially double-blinded, placebo-controlled factorial trial in which half the patients were assigned to each intervention, resulting in seven intervention groups and one control group. Eligibility criteria included histologic confirmation of at least one colorectal adenoma and confidence expressed by the colonoscopist that all polyps had been removed. Dietary changes were individually initiated and monitored by dietitians and research nurses. At surveillance colonoscopy, the size and location of all polyps were recorded, and their histology was later centrally reviewed. Among 424 patients who were randomly assigned in the trial, 13 were found to be ineligible upon histologic review. Among the remaining 411, complete outcome data were collected from 390 at 24 months and from 306 at 48 months. All P values are from two-sided tests of statistical significance. RESULTS: There was no statistically significant prevention of total new adenomas with any of the interventions. We found a statistically non-significant reduced risk of large adenomas (> or = 10 mm) with the low-fat intervention: At 24 months, the odds ratio (OR) adjusted for potential confounders = 0.4 and 95% confidence interval (CI) = 0.1-1.1; at 48 months, OR = 0.3 and 95% CI = 0.1-1.0. Less and statistically nonsignificant reductions in the risk of large adenomas were found with wheat bran: At 24 months, OR = 0.8 and 95% CI = 0.3-2.2; at 48 months, OR = 0.8 and 95% CI = 0.3-2.5. Patients on the combined intervention of low fat and added wheat bran had zero large adenomas at both 24 and 48 months, a statistically significant finding (P = .03). CONCLUSIONS: Because only small numbers of patients were studied, our finding that the combination of fat reduction and a supplement of wheat bran reduced the incidence of large adenomas in this randomized, controlled trial must be treated with caution. The results do suggest, however, that these interventions may reduce the transition from smaller to larger adenomas, a step that may critically define those adenomas most likely to progress to malignancy.

Adenoma

Coronary artery disease in heterozygous familial hypercholesterolemia patients with the same LDL receptor gene mutation.

BACKGROUND: Familial hypercholesterolemia (FH), an autosomal codominant disease, is characterized by high levels of LDL cholesterol and a high incidence of coronary artery disease (CAD). To date, genetic heterogeneity has hindered the proper assessment of the relation between risk factors and CAD in FH patients. METHODS AND RESULTS: We studied the association between CAD and common risk factors in a sample of 263 French Canadian FH patients (147 women, 116 men) carrying the same > 10-kb deletion of the LDL receptor gene. Thirty-five women and 54 men had CAD. The mean age of onset of CAD was 45.6 +/- 12.7 years in women and 38.8 +/- 9.4 years in men. Multiple logistic regression analyses were performed to test the association between CAD and age, tendon xanthomas, cigarette smoking, hypertension, diabetes mellitus, apolipoprotein E polymorphism, total plasma cholesterol, triglycerides, VLDL cholesterol, LDL cholesterol, HDL cholesterol, and lipoprotein(a) [Lp(a)]. In FH women, significant multivariate predictors were age (odds ratio, 1.10 for 1 year; P < .0001), VLDL cholesterol (odds ratio, 3.85 for 1 natural log unit; P < .002), and LDL cholesterol (odds ratio, 1.42 for 1 mmol/L; P < .02). In FH men, age (odds ratio, 1.08 for 1 year; P < .0001) and HDL cholesterol (odds ratio, 0.14 for 1 mmol/L; P = .05) were significant predictors of disease. Lp(a) was not a significant predictor in univariate or multivariate analyses. CONCLUSIONS: This study suggests that increased risk of CAD in FH is not solely due to elevated LDL cholesterol levels and demonstrates a sex-specific lipoprotein influence on CAD in a large sample of FH patients carrying the same LDL receptor gene defect.

Adult

Insect immunity. The inducible antibacterial peptide diptericin carries two O-glycans necessary for biological activity.

A bacterial challenge of larvae of the dipteran insect Phormia terranovae induces the rapid synthesis of diptericin, an antibacterial polypeptide, previously characterized at the amino acid level and indirectly by cDNA cloning studies. This 82-residue polypeptide consists of an N-terminal proline-rich domain and a central and C-terminal glycine-rich domain. Using liquid chromatography coupled to electrospray ionization-mass spectrometry, we demonstrate here that this molecule is more complex than anticipated and carries two O-substitutions on threonine residues, one in the proline-rich domain (residue 10) and one in the glycine-rich domain (residue 54). These substitutions consist of identical trisaccharides: glucose-->galactose-->N-acetylgalactosamine-->(threonine). Treatment of diptericin with O-glycosidase, which selectively removes the substitutions without altering the polypeptide proper, abolishes the antibacterial activity, indicating that this posttranslational modification is essential for biological activity of the polypeptide. We also show that diptericin is posttranslationally modified by a C-terminal amidation.

Amino Acid Sequence

Topographic EEG activations during timbre and pitch discrimination tasks using musical sounds.

Successive auditory stimulation sequences were presented binaurally to 18 young normal volunteers. Five conditions were investigated: two reference tasks, assumed to involve passive listening to couples of musical sounds, and three discrimination tasks, one dealing with pitch, and two with timbre (either with or without the attack). A symmetrical montage of 16 EEG channels was recorded for each subject across the different conditions. Two quantitative parameters of EEG activity were compared among the different sequences within five distinct frequency bands. As compared to a rest (no stimulation) condition, both passive listening conditions led to changes in primary auditory cortex areas. Both discrimination tasks for pitch and timbre led to right hemisphere EEG changes, organized in two poles: an anterior one and a posterior one. After discussing the electrophysiological aspects of this work, these results are interpreted in terms of a network including the right temporal neocortex and the right frontal lobe to maintain the acoustical information in an auditory working memory necessary to carry out the discrimination task.

Adolescent

Disorders of auditory identification in dementia of the Alzheimer type.

Fifteen patients with probable DAT and 18 matched controls were given tests that required the identification of verbal (phonemes and words) and non verbal (sounds and melodies) stimuli. In all tests, DAT patients made significantly more errors than controls. Errors predominated in non verbal tests in both groups. DAT patients (and, to a lesser degree, control subjects) made almost exclusively acoustic errors in word-identification, while errors in the identification of sounds and melodies could be either semantic or acoustic. Some categories of errors were observed predominantly in DAT patients. These results suggest that, in addition to their cognitive impairment, DAT patients have a specific deficiency of central auditory perception.

Aged

Food habits of French Canadians in Montreal, Quebec.

OBJECTIVES: Since the 1960's, marked sociocultural and economic changes have affected lifestyle, religious practices, and family structure among French Canadians in Quebec. Recent nutritional assessment was unavailable, despite indications of change. METHODS: A survey was carried out in 1988 in a representative sample living in Greater Montreal, to obtain current data on food habits, nutrient intakes and sociodemographic factors, using interviewer-administered questionnaires and seven-day food records. RESULTS: Some 845 families (1450 individuals from different age groups) were studied in two phases: summer/fall and winter/spring. Mean household size in the study population was 2.7. Among adults, extremes of educational level were observed, with 33% having elementary school only and 28% having completed university. On average, each household spent $CAN 89.90 a week for food, $26.00 for tobacco, and $13.50 for alcohol. Breakfast was eaten regularly by 90% of subjects while 96% ate lunch and 99% ate dinner. Morning snacks were consumed by 36% and afternoon snacks were taken by 50%. Milk was consumed with breakfast by 24% of respondents, with lunch by 19%, and with dinner by 24%. On weekdays, 81% of subjects ate their main meals at home, while on weekends this figure was 95%. Time spent for meals varied by meal, and was slightly longer on weekends. Specialty diets, including vegetarianism, were followed by 7% of the study subjects, while 22% adhered to health-related diets. CONCLUSIONS: The food record analyses revealed adequate nutrient intakes overall in relation to the 1990 Canadian Recommended Nutrient Intakes, although further investigation is needed before addressing dietary quality in specific age-sex groups. Protein comprised 16% of energy, fat 38%, and carbohydrates composed 45% or 46% for males and females, respectively. Subsequent analyses will evaluate nutrient intakes in relation to health and sociodemographic indicators in this population.

Adolescent

Availability of 0.3% ofloxacin ointment and solution in human conjunctiva and aqueous humor.

Ofloxacin 0.3% ophthalmic solution or ointment was administered preoperatively to 13 patients undergoing cataract surgery. Mean drug concentrations in conjunctival biopsies were 2.62 and 6.55 micrograms/gm and in aqueous humor samples were 0.36 micrograms/mL and 0.43 micrograms/mL, for ointment and solution respectively. Mean conjunctival concentrations of ofloxacin achieved MIC90 values for 419 gram-positive and gram-negative organisms previously analyzed.

Aged

A PET study of the functional neuroanatomy of writing impairment in Alzheimer's disease. The role of the left supramarginal and left angular gyri.

A dissociation in the central processes of spelling, with preferentially lexical over phonological impairment, frequently affects patients with early Alzheimer's disease. The aim of this work was to test whether dissociations in the language domain in Alzheimer's disease can be exploited with PET to assess the neural basis of cognition. To this end, we studied the functional neuroanatomy of writing impairment in Alzheimer's disease by means of PET measurements of the local cerebral glucose utilization and neuropsychological tests specially designed to assess the phonological and lexical components of writing. We analysed the performance in written spelling of irregular words and non-words of 11 right-handed patients with mild-to-moderate Alzheimer's disease. For each patient, we calculated a residual phonological score and a residual lexical score, based on a cognitive interpretation of the errors according to the item category. In each of these 11 patients, using PET, we measured the resting-state utilization of glucose in the left supramarginal gyrus and the left angular gyrus, two cortical regions selected a priori because of their presumed role in the central processes for spelling, and identified on CT scans obtained according to stereotaxic references and coregistered with PET. To assess the relationships between the neuropsychological scores and the metabolic data, we used the 'ratio paradigm', the sensitivity of which has been previously documented in cognitive-metabolic correlative PET studies of Alzheimer's disease that were less focused than the present study in both cognitive and anatomical terms. We found a highly significant positive correlation between phonological score:lexical score neuropsychological ratios and corresponding supramarginal gyrus:angular gyrus metabolic ratios. These findings further support the role of these two left-sided temporo-parietal regions in the central processes of writing and show that the neuropsychological dissociations in early Alzheimer's diseases can be exploited to further our understanding of the functional neuroanatomy of cognitive operations. The role of focal, as compared with more diffuse, brain damage in the development of impaired written language of central origin in Alzheimer's disease is also discussed.

Aged

Effect of the inhibitor of nitric oxide synthase, NG-nitro-L-arginine methyl ester, on cerebral and myocardial blood flows during hypoxia in the awake dog.

The increase in cerebral blood flow (CBF) elicited by moderate hypoxia in anesthetized animals is little attenuated by nitric oxide (NO) synthase inhibitors. However, in previous studies, the effects of NO synthase inhibitors may have been altered by anesthetics. Consequently, we studied the effects of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), on cerebral and myocardial blood flows during hypoxia in the awake dog. Regional CBF and myocardial blood flows (MBF) were measured under normoxia and hypoxia in 16 beagle dogs after an intravenous (IV) injection of either saline (control, n = 8) or L-NAME 20 mg/kg (n = 8). One week after thoracotomy for catheter insertion, awake dogs were studied during three periods: normoxia and after 2 and 4 h of normocapanic hypoxia in an environmental chamber (FIO2 = 0.10, FICO2 = 0.035, balance N2). At each stage, a bolus injection of L-NAME or saline was followed 15 min later by left atrial injection of radiolabeled microspheres (141Ce, 103Ru, 46Sc) for regional CBF and MBF. After the dogs were killed, the brain and the heart were fixed in 10% formaldehyde, dissected by region and weighed, and radioactivity was measured in a gamma counter. During hypoxia, Pao2 was approximately 45 mm Hg with normal Paco2. In the control group, CBF increased by 45% after 2 h and 48% after 4 h of hypoxia; MBF increased by 69% and 60%, respectively. L-NAME prevented the CBF increase during hypoxia and the MBF increase after 2 h of hypoxia; after 4 h of hypoxia the measurement of MBF was confounded by cardiac dysfunction. These results suggest that NO plays a role in cerebral vasodilation during hypoxia in the awake animal.

Animals