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Biomedical subjects

M Hébert

Publications and source records attributed to M Hébert.

At least 37 records · Page 2Linked to original sources
PubMed1998

Seasonal and diurnal patterns of human illumination under natural conditions.

Little is known about the natural pattern of seasonal and diurnal illumination to which normal people are exposed, especially in northern latitudes. In this study, ambient illumination of normal volunteers living at a latitude of 45 degrees 31' N was recorded with ambulatory photosensors worn for 5 to 6 days in winter and summer. Results from 12 normal subjects (6 men, 6 women) aged 18 to 35 years were included in the analyses. The mean daily duration of time awake was similar in both seasons: 14.6h in the summer and 14.9h in the winter. However, the phase of the sleep-wake cycle was advanced in the summer compared to the winter, as shown by an earlier average waketime and bedtime in the summer. Illumination recorded by the ambulatory monitor between waketime and bedtime was categorized according to four ranges of light intensities: very dim (< 1 lux), dim (1-100 lux), moderate (100-1000 lux), and bright (> 1000 lux) illumination. There was no seasonal difference for the time spent in illumination lower than 1000 lux, but the duration of daily exposure to bright light averaged 2.6h in the summer compared to only 0.4h in the winter (p = 0.0004). To evaluate the diurnal distribution of ambient illumination, time spent awake was divided into four time intervals: morning (waketime to 12:00), afternoon (12:00 to 16:00), early evening (16:00 to 20:00), and late evening (20:00 to bedtime). Except for late evening, the time spent in bright illumination was significantly longer during the summer for all time intervals, but the relative distribution of bright light exposure throughout the day was the same in both seasons. The subjects spent more than 50% of their time awake in illumination dimmer than 100 lux, even in the summer. More naturalistic studies are needed to determine whether very short exposure to bright light or longer exposure to light of moderate intensity (100-1000 lux) are sufficient to maintain circadian entrainment and euthymia in normal young subjects.

Adult↗
PubMed1996

Body temperature and the return of slow wave activity in extended sleep.

The time courses of slow wave sleep (SWS) and EEG slow wave activity (SWA) were examined in relation to core body temperature (CBT) during extended sleep periods of 15 h. Ten subjects (4 male, 6 female; aged 18-29 years) slept in the laboratory for 3 consecutive nights (2 of 8 h, and the last of 15 h). Bedtime was as close as possible to subjects' habitual bedtimes, but was always between 23.00 h and 1.00 h, and was the same on all nights. Standard polysomnographic measures as well as rectal temperature were collected continuously each night. Using 3 h blocks, SWS and SWA declined with time asleep, then showed a significant increase in the final 3 h. Using a more specific measure with 15 min means, 8 of the 10 subjects showed SWA returns late in sleep, that were not related to preceding amounts of waking after sleep onset (WASO), rapid eye movement sleep (REMS), or WASO+REMS. The timing and magnitude of the SWA return was significantly associated with the phase of CBT as indexed by delay from sleep onset to CBT minimum. The findings are consistent with a 12 h rhythm of SWS and SWA that is related to the phase of the CBT rhythm, with the minor pole of SWS/SWA occurring independently of WASO and/or REMS.

Adolescent↗
PubMed1995

An occupational therapy course on community practice.

This article outlines a course on occupational therapy community practice offered at the University of Ottawa and discusses its assets and limitations in terms of preparing students for the shift to community-based health services. The shift to community services in the health care systems of Ontario and Québec is described. Then the curricular components needed to prepare students for community practice are summarized. Finally, the community practice course at the University of Ottawa including its goal, objectives, class topics and evaluations is outlined. The strength of the community practice course described is that it includes many of the curricular components needed for community practice. On the other hand, limitations include the lack of skill training in some areas, its place in the last year of the programme, and its optional nature. Changes planned for the course and other recommendations for curricula are also discussed.

Community Health Services↗
PubMed1994

Possible dual role of anti-idiotypic antibodies in combined passive and active immunotherapy in honeybee sting allergy.

BACKGROUND: Passive infusion of beekeepers' plasma was shown to protect patients against systemic reactions occurring during active immunotherapy by mechanisms still to be clarified. It is tempting to speculate that anti-idiotypic antibodies could play a role because they are found in beekeepers' plasma and are involved in the regulation of IgE synthesis. METHODS: In this report we studied the effects of passive infusion of a beekeeper's plasma rich in anti-idiotypic antibodies to a patient who experienced systemic reactions to honeybee venom. RESULTS: We reported, during the days after the infusion, a decrease of clinical sensitivity to the honeybee venom. Indeed, the patient tolerated a cumulative dose of 280 micrograms of venom without adverse reactions. We also observed decreases in skin mast cell and in basophil sensitivity. After the plasma infusion, a modified rush immunotherapy with honeybee venom was initiated in our patient. In the following 76 weeks, increased levels of anti-idiotypic antibodies in the serum of the patient were associated with a diminution of specific antibodies (IgG and IgE) to honeybee venom. CONCLUSION: These results suggest a dual role of anti-id in our combined protocol of passive and active immunotherapy: an immediate action on clinical sensitivity along with a decrease of skin mast cell and basophil sensitivity and an immunoregulatory role on specific antibody production.

Adult↗
PubMed1988

Megarectum.

Evaluation of the rectum by barium enema does not correlate well with rectometrographic studies and is not predictive of bowel function. The purpose of the present study was to describe clinical and functional data in patients with chronic idiopathic constipation, where a megarectum was diagnosed by a rectometrogram. Among 355 patients who underwent rectal elasticity studies, 35 were found to have a megarectum (maximum tolerable volume above 320 ml in women and 440 in men) for which no specific etiology was recognized. They, and a group of 11 healthy controls who were not sensitive to stress, underwent studies of stool frequency, colonic transit time of radiopaque markers, rectal elasticity, and anorectal pressures and reflexes. The elasticity coefficient of the rectal wall was decreased in patients as compared to controls (P less than 0.01). Seven patients had onset of symptoms at birth, with maximum tolerable volume in the rectum between 460 and 900 ml, and all were incontinent for feces. Studies of colonic transit times demonstrated normal function in the right and left colon, but there was rectosigmoid stagnation (transit time of 122 +/- 17 hr vs 8 +/- 2 in stress-free controls; X +/- SE; P less than 0.001). In the other 28 patients (late-onset megarectum), in contrast to the congenital group, there was a marked female preponderance, and their recorded stool frequency (4 +/- 0.7/week) was greater than the recalled frequency (1.4 +/- 0.2/week; P less than 0.001). Only half suffered from fecal incontinence. They did not have a greater rectal capacity when colonic transit times were prolonged (455 +/- 27 ml) than when normal (422 +/- 27). Rectal pressure was similar at the level of conscious sensation of filling, regardless of rectal capacity, suggesting a motor, rather than a sensory, abnormality. The amplitude of the rectoanal inhibitory reflex was decreased (P less than 0.001) as compared to controls, sometimes mimicking the findings of Hirschsprung's disease, but increasing rectal distension always induced a relaxation of the internal anal sphincter. The notion of a megarectum, which tolerates large amounts of fluid without sensation, lacks elasticity, and is accompanied by an abnormal rectoanal inhibitory reflex, provides an explanation for one of the mechanisms of constipation by outlet obstruction.

Adult↗
PubMed1988

Effects of rest, stress, and food on myoelectric spiking activity of left and sigmoid colon in humans.

The great variability which is known to affect colonic motility may partly be the result of changes in physiological conditions. In order to test this hypothesis, 40 subjects were sequentially put in conditions of vigilance, rest, stress, and feeding while colonic motility was monitored. The myoelectric spiking activity of the left colon was recorded with a 50-cm-long silastic tube equipped with four bipolar ring electrodes (located 10 cm apart) introduced into the left colon by flexible sigmoidoscopy. Tracings were performed while the subjects were kept awake (by conversation) for 1 hr, put at rest (quiet) for another 1 hr, submitted to a stress (by alternatively immersing and removing one hand from 2-4 degrees C cold water) for 20 min, and finally recorded for 2 hr after a 800-kcal meal. In 18 other subjects, the sequences of vigilance and rest were randomized. The results showed that colonic spiking activity was made of sporadic bursts that are known to be associated with intraluminal propulsion and of stationary bursts that probably play no role in colonic peristalsis. The duration of sporadic spiking activity was respectively 13.6 +/- 1.2 min/hr (mean +/- SEM) during the period of vigilance, 5.4 +/- 0.6 min/hr during the period of rest (P less than 0.001), 14.3 +/- 1.0 min/hr during the period of stress (NS), and 16.8 +/- 1.2 min/hr after a meal (P less than 0.05). The duration of stationary spiking activity did not change significantly throughout the four periods, respectively, 6.6 +/- 4.9, 4.4 +/- 3.7 (NS), 5.2 +/- 3.9 (NS), and 3.3 +/- 2.8 min/hr (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Sexual abuse of children under 12 years of age: a review of 511 cases.

In a retrospective study of 511 cases of alleged sexual abuse in children 12 years of age and under, data were analyzed with respect to the victim's age, sex, and the type of sexual abuse (intra- or extrafamilial). A total of 85.5% of the victims were female and 14.5% were male with ages ranging from 2 months to 12 years. The mean age of female victims was 6.8 years and that of male victims, 7.4 years. Most victims (68%) presented with histories of single assault by a known perpetrator (78%). Characteristics of abuse were found to be associated with the victim's age, sex, and relationship to the assailant. School-age victims were more likely to be abused by an individual outside the family or by a complete stranger. Older victims were also more likely to be involved in severe forms of sexual abuse (penetration, attempted penetration or oral-genital contact), associated with acts of abduction and with reports to the police. Male victims were more likely to be assaulted by a stranger, outside the home environment, and to suffer a more severe form of sexual abuse than female victims. Finally, extrafamilial sexual abuse was distinguished from intrafamilial sexual abuse insofar as it was more often a single episode, occurring outside the home environment, involving an act of abduction and physical force, and being reported to the police.

Age Factors↗
PubMed1986

How does morphine work on colonic motility? An electromyographic study in the human left and sigmoid colon.

The effect of morphine on colonic motility was investigated by recording the colonic myoelectric spiking activity by means of a 50 cm long silastic tube equipped with 4 bipolar AgAgCl ring electrodes fixed at 10 cm intervals that was introduced into the left colon in 8 healthy subjects by flexible sigmoidoscopy. Tracings were obtained for 1 hour in the fasting state and for another 1 hour after i.m. injection of morphine sulphate 0.15 mg/kg. The different types of spike bursts were compared before and after morphine injection. The control tracings showed that the spiking activity of the colon was made of 2 types: 1)- Rhythmic Stationary Spike Bursts (RSB), that were seen at only one electrode site; 2)- Sporadic Bursts, that were either propagating over all 4 electrodes (SPB) or non propagating (SNPB). Injection of morphine was followed by 1)- a considerable increase in the number of RSB from 107 +/- 43 bursts/hour (mean +/- SEM) to 491 +/- 23 bursts/hour; 2)- the complete disappearance of the SPB dropping from 7.3 +/- 2.0 bursts/hour to 0.3 +/- 0.2 bursts/hour; 3)- no significant change in SNPB (from 52 +/- 4 bursts/hour to 57 +/- 5 bursts/hour). These results indicate that 1)- stimulation of colonic smooth muscle activity by morphine seems to result from an increase in the number of rhythmic stationary bursts; 2)- however inhibition of colonic transit may be related to the decrease in the number of sporadic propagating bursts.

Action Potentials↗
PubMed1986

Myoelectrical activity and intraluminal flow in human sigmoid colon.

Myoelectric spike bursts were recorded in the sigmoid colon by means of an intraluminal silastic tube equipped with 3 Ag-AgCl ring electrodes fixed 15 cm apart on the tube that was introduced by flexible sigmoidoscopy. In six subjects, the tube was also equipped with three catheters whose tip opened 1 cm aborad from each electrode, for pressure recordings. In six other subjects, the tube was equipped with both electrodes and a catheter opening at the tip of the probe for infusing fluids at a rate of 12 ml/min into the colonic lumen. The fluid was collected with another tube inserted in the rectum and the volume was measured at 1-min intervals. Colonic spiking activity was made of rhythmic stationary bursts (RSB) and of sporadic bursts that were either propagating (SPB) or not propagating (SNPB). All sporadic bursts were associated with intraluminal pressure waves whose amplitude was significantly higher than that associated with rhythmic bursts. In the infusion experiments, the volume of fluid collected did not change significantly whether rhythmic bursts were present or not (3.9 +/- 1.7 ml/min and 3.3 +/- 1.9 ml/min respectively) (mean +/- SD). However, the volume was significantly higher when sporadic nonpropagating bursts were present (9.4 +/- 4.1 ml/min), and even higher when the sporadic bursts were propagating (21.6 +/- 8.8 ml/min). These results indicate that the occurrence of sporadic bursts, particularly when propagating, is associated with intraluminal pressure waves that lead to significant propulsive movements; and rhythmic bursts do not seem to be involved in colonic propulsive activity.

Colon, Sigmoid↗
PubMed1986

Changes in colonic myoelectric spiking activity during stimulation by bisacodyl.

The purpose of this study was to determine some relationships between colonic myoelectric spiking activity and intraluminal propulsion when colonic peristalsis was stimulated by bisacodyl. Myoelectric recordings were obtained in 12 subjects by means of a 50 cm long Silastic tube equipped with four bipolar electrodes fixed at 10-cm intervals. The tube was introduced into the left colon by flexible sigmoidoscopy and the electrodes were located at 50, 40, 30, and 20 cm from the anal verge. A small polyethylene catheter opening at the proximal end of the Silastic tube was used for introducing the laxative into the colon. One hour recording sessions were obtained before and after bisacodyl administration (5 mL of 0.4% solution). The control tracings showed that colonic spiking activity was made of rhythmic stationary bursts that occurred at only one electrode site and of sporadic bursts that were either propagating over the whole colonic segment or nonpropagating. Administration of bisacodyl was followed by complete suppression of the rhythmic stationary activity; a considerable increase in the sporadic spiking activity, propagating as well as nonpropagating; the occurrence of abdominal cramps and urgency to defecate, both associated with the propagating sporadic spike bursts. It is concluded that colonic propulsion induced by bisacodyl may be dependent upon the production of the sporadic bursts, particularly the propagating ones, while the rhythmic stationary bursts do not seem to play a significant role in colonic transit.

Action Potentials↗