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Biomedical subjects

C Bonnet

Publications and source records attributed to C Bonnet.

At least 73 records · Page 4Linked to original sources
PubMed1995

Deficits of cognitive executive functions in patients with sleep apnea syndrome.

Impairment of cognitive executive functions previously has been suspected to occur in association with sleep apnea syndrome (SAS), as suggested by some neuropsychological studies. However, such functions have not been assessed directly. In the present study, 17 patients with SAS were evaluated with various focused frontal lobe-related tests in comparison with 17 normal controls. Such tasks explored attention, short-term memory spans, learning abilities, planning and programming capacities, categorizing activities and verbal fluency. Patients were found to have a significantly decreased ability to initiate new mental processes and to inhibit automatic ones, in conjunction with a tendency for preservative errors. They were also affected with deficits of verbal and visual learning abilities and had reduced memory spans. Such defects were further evaluated via logistic regression against two criteria of the severity of the disease: the number of apneas and hypopneas per hour of sleep and the level of nocturnal hypoxemia. Memory deficits were rather related to the former, whereas typical frontal lobe-related abnormalities seemed rather consistent with the latter. These findings are discussed in light of data from the literature concerning cognitive impairments described for patients with isolated daytime sleepiness versus hypoxemia, as illustrated in other pathological or physiological circumstances.

Adult↗
PubMed1994

Immunocytochemical study of the CLIP/ACTH-immunoreactive nerve fibres in the dorsal raphe nucleus of the rat.

The injection of corticotrophin-like intermediate lobe peptide (CLIP) in the lateral ventricle or the dorsal raphe nucleus (DRN) of the rat is followed by a significant increase in the amount of paradoxical sleep. In the DRN, CLIP would act through a somatic and/or dendritic release of serotonin. To establish the anatomical basis of these effects, the nerve fibres immunoreactive for CLIP/ACTH were labelled and their fine anatomical relationships with the neuronal elements of the DRN were studied at the ultrastructural level. Half of the profiles of labelled varicosities were 'free' in the neuropile, the other half was in close contact with dendrites, either shafts or spines. It was interesting to note that few contacts with dendritic shafts were under the form of a synapse, whereas a large number of the contacts with spines were synaptic. The chemical nature of these dendritic targets remains to be determined but preliminary results indicate that they are partly serotoninergic.

Adrenocorticotropic Hormone↗
PubMed1994

Circadian changes of left ventricular ejection fraction in normal subjects.

Sleep has a specific physiology with related cardiovascular changes. We have previously found in respiratory patients [chronic obstructive pulmonary disease (COPD) and sleep apnea syndrome (OSAS)] an unexpected decrease in left ventricular ejection fraction (LVEF) at waking in the morning when compared with the rest period during the day. Whether this observation was linked to the consequences of the respiratory abnormalities or reflected physiological fluctuations related to the changes in autonomic nervous system tone remained unknown. Thus, we have set out to analyze the changes in LVEF with sleep in normal individuals. Eight healthy young men had LVEF measured before and after submaximal exercise, at rest before bedtime, and on waking in the morning. Technetium-99m with in vivo red cell labelling was used. Sleep parameters were assessed using classical polysomnography. In order to detect any influence of autonomic nervous system stimulation on LVEF, sympathovagal tone (SVT) was also assessed during night-time LVEF measurements using spectral analysis of RR intervals. LVEF at rest was within the normal limits for all the subjects (range 51-62%). On submaximal exercise, the LVEF increased in four subjects, was unchanged in two, and decreased in two. The main result concerns the changes in LVEF overnight. In the morning, LVEF decreased dramatically in three subjects and reached a level of < 30% in four. These decreases in LVEF were not related to changes in SVT or sleep structure. LVEF values returned to normal in 30 min. The LVEF changes during exercise are in accordance with previous data in the literature. The dramatic decrease in LVEF observed in the morning could be related either to vascular resistance changes or to nocturnal variations in cardiac contractility, which both need further studies to be established.

Adult↗
PubMed1994

Idiopathic retroperitoneal fibrosis with systemic manifestations.

We describe a previously unreported association of idiopathic retroperitoneal fibrosis with mesenteric, pulmonary and perhaps periarticular fibrotic involvement, and panniculitis resembling Weber-Christian panniculitis. The onset of the disease was uncommon with arthritis. Then, several episodes of migratory panniculitis appeared; biopsy showed septal panniculitis without necrosis of adipose tissue. Considering the patient's anamnesis, it is tempting to speculate that these manifestations all originate from the same mechanism.

Adult↗
PubMed1993

Perceived speed of moving lines depends on orientation, length, speed and luminance.

In this study, the perceived speed of a tilted line translating horizontally (for a duration of 167 msec) is evaluated with respect to a vertical line undergoing the same translation. Perceived speed of the oblique line is shown to be underestimated when compared to the vertical line. This bias increases: (1) when the line is further tilted, (2) with greater line lengths, (3) with lower contrasts, and finally (4) with a speed of 2.1 deg/sec as compared to a higher speed of 4.2 deg/sec. These results may be accounted for by considering that two velocity signals are used by the visual system to estimate the speed of the line: the translation of this line (this signal does not depend on the line's orientation) and the motion component normal to the line (this signal depends on orientation). We suggest that these two signals are encoded by different types of units and that the translation signal is specifically extracted at the line endings. We further suggest that these signals are integrated by a weighted average process according to their perceptual salience. Other interpretations are considered at the light of current models dealing with the two-dimensional integration of different velocity signals.

Differential Threshold↗
PubMed1993

The inverse intensity effect is not lost with stimuli in apparent motion.

The inverse relationship between the visible persistence of a briefly presented stimulus and its intensity is well established for static displays. However, with non-static displays, this relationship is only partially reported by previous studies. In order to clarify this topic, we investigated the effect of luminance on the visible persistence of a stimulus in apparent motion. Assuming that persistence duration is a normally distributed random variable, we studied whether the mean persistence of a stimulus could be systematically varied by varying its luminance. Our paradigm permits evaluation of this effect without changing the temporal interval between two successive presentations of the stimulus, thus avoiding the potential influence of this latter factor on persistence. Our results show that the inverse intensity effect still occurs at each of the successive locations of a stimulus in apparent motion. In addition, we provide evidence that increasing the spatial separation between the successive presentations, and decreasing the background luminance, result both in longer persistence duration. Altogether, these findings favour the hypothesis that persistence is actively suppressed by inhibitory interactions between adjacent neural zones.

Afterimage↗
PubMed1993

Sugar composition of dietary fibre and short-chain fatty acid production during in vitro fermentation by human bacteria.

The aim of the present study was to assess the relationship between the disappearance of dietary fibre sugars and the production of individual short-chain fatty acids (SCFA). The bacterial degradation of five dietary fibres whose sugars were quantified was investigated in vitro using a human faecal inoculum. Involvement of the main fibre sugars in SCFA production was evaluated by a stepwise multiple linear regression. The results show first that the nature and chiefly the associations between the fibre sugars were key variables in the fermentability. Second, the nature and the amounts of SCFA produced were closely related to the in vitro fermentation of the main sugars available: uronic acids seemed to be principally involved in the production of acetic acid whereas the production of propionic acid could be promoted by the fermentation of glucose and, to a lesser extent, by that of xylose and arabinose. Xylose tended to have a greater impact than uronic acids and glucose on the production of butyric acid. Thus, it would be possible to predict which SCFA could be specifically produced during the fermentation of a fibre, as far as the chemical composition and structure of this fibre are known.

Acetates↗
PubMed1993

Properties of curvilinear vection.

Approximately linear relationships were observed between contrast, spatial frequency, temporal frequency, or velocity of stimulation and perceived velocity of curvilinear vection--that is, a visually induced self-motion in a curved path. Similarly, linear relationships were also found between the perceived degree of curvature of curvilinear vection and spatial frequency or velocity of stimulation. Since the perceived velocity of curvilinear vection varies with contrast, spatial frequency, temporal frequency, and angular velocity, and the perceived degree of curvature of curvilinear vection varies only with spatial frequency and angular velocity, peripheral vision is not sufficient for computing accurately the curvilinear component of induced self-motion in a curved path. Concurrently, it was shown that the perceived direction of curvilinear vection is not always unambiguously perceived (Sauvan & Bonnet, 1989). Consequently, it is suggested that two different types of visual processing, which involve the peripheral or the central vision, underlie the processing of curvilinear vection.

Adult↗
PubMed1992

Adolescent osteoporosis disclosing familial osteopenia.

The observations of familial juvenile osteoporosis, presumably of genetic origin are exceptional. The authors report the observation of a 16-year old adolescent suffering from osteoporosis, confirmed by histomorphometry and decrease in bone density (lumbar vertebrae 0.79 g/cm2 and femoral neck 0.88 g/cm2: LUNAR DPX). We prescribed fluorine and calcium therapy. Lumbar bone density increases by 11% and bone density of the thighbone neck by 7.6%. We cannot rule out growth as a factor in the changes observed, given that the propositus is only 16. A densitometric investigation performed in 4 of his 12 brothers shows a decrease in the lumbar bone mineral content (from 61 to 94% expressed as Z score). A genotypic origin seems to be conceivable, especially since no other cause could be considered (endocrinal, alimentary...). On the other hand, there is no argument in favour of osteogenesis imperfecta disease. The bone densitometry is a useful diagnostic means to detect familial forms of osteoporosis.

Adolescent↗
PubMed1992

[Nicardipine vs trinitrin for controlled hypotension in maxillo-facial surgery].

In this study we examined perioperative blood losses during maxillo-facial surgery comparing 2 techniques for controlled hypotension using nitroglycerin (NTG) and nicardipine (NICAR). 37 ASA I and II patients electively scheduled for rhinoseptoplasties under general anaesthesia were randomly divided into 2 groups. General anaesthesia was induced with intravenous thiopental and vecuronium following a neuroleptanalgesia consisting of fentanyl (0.053 +/- 0.004 microgram.kg-1.min-1) IV and droperidol (1.98 +/- 0.35 microgram.kg-1.min-1) IV given in bolus doses. The patients were intubated and ventilated (N2O in O2) to maintain normocarbia. Controlled hypotension to maintain a mean arterial pressure (MAP) between 50 and 55 mmHg was induced using an IV infusion of NTG 6 micrograms.kg-1.min-1 in group I and NICAR 10 micrograms.kg-1.min-1 over 10 minutes followed by an infusion at 4 mg.kg-1.min-1 for group II. Measurements of heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), MAP using an automated blood-pressure cuff and end tidal carbon dioxide (ETCO2) were recorded prior to induction (PREIND), intraoperatively (PEROP) at 15, 30, 40 and 120 minutes post-induction, and at 15, 30 and 60 minutes postoperatively (POSTOP). Blood loss, graded as minimal or frank, was assessed by the surgeon during the operative period, post-extubation and 3 days postoperatively at dressing removal. The surgeon was unaware of the randomization schedule. Student's test was applied for statistical analysis of measured variables and Fisher's test for qualitative parameters. No statistically significant differences were noted between both groups with respect to demographic data, duration of surgery and total doses of anaesthetic agents (Table I).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗