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Biomedical subjects

C Bonnet

Publications and source records attributed to C Bonnet.

At least 37 records · Page 2Linked to original sources
PubMed1999

Group and individual gustatory reaction times and Piéron's law.

Simple reaction times (SRT) to eight substances belonging to the four classical taste families were evaluated. The same eight subjects participated in all experiments. The functional relationship between SRT and concentration for group and for individual data were examined. Equations presented by different authors to describe RT data are discussed. The Piéron function [(SRT - t0) = betaI-alpha] best fits the gustatory data collected in the present experiments. These results, together with others taken from previous studies, show that the exponent of salt and acid taste functions is lower than 1.0 with a relatively short t0. Sweet and bitter exponents were equal t0 or higher than 1, with a larger t0. Individual performances correlated with taste families for salt and acid. However, the limited samples of some solutions sets some limits to the interpretation of RT to taste substances.

Adult↗
PubMed1999

One spatial filter limits speed of detecting low and middle frequency gratings.

Reaction times for detecting sinusoidal gratings depend jointly on grating contrast and spatial frequency. We examine whether the effect of spatial frequency results from low-pass filtering in a single channel or reflects processing of different frequencies by two or more different processing streams. Observers performed a speeded two-alternative spatial forced-choice detection. Errors and reaction times were measured. Contrasts varied from 0.05 to 0.67, and spatial frequencies from 0.72 to 6.51 cpd. No effect of uncertainty about spatial frequency was found, arguing against multiple channels. The data are well fit by a single channel model driven by a low pass filter.

Adult↗
PubMed1999

Influence of stress duration on the sleep rebound induced by immobilization in the rat: a possible role for corticosterone.

In rats, recovery from short intense stress usually involves a sleep rebound characterized by an increase in slow-wave sleep and paradoxical sleep duration. However, a large body of evidence indicates that stressful situations lasting for several days or weeks can have deleterious effects on sleep quantity and quality, probably leading to an impairment of the sleep rebound. In this study, using immobilization as a stress model in the rat, we sought to determine the stress duration beyond which the sleep rebound disappears, as well as the mechanisms responsible for this suppression. In a first series of experiments, rats were immobilized for 30 min, 1h, 2h or 4 h. Slow-wave sleep rebounds evidenced after the different immobilization periods were, respectively, +32%, +25%, +9% and -0.2% and paradoxical sleep rebounds +57%, +88%, +103% and +21% compared with control recordings of the same animals. The sleep rebound thus disappeared when the duration of immobilization reached 4 h. In a second series of experiments, adrenalectomized rats were subjected to a 1 h immobilization, and showed an increased slow-wave sleep rebound ( + 44% compared to intact ones), whereas the paradoxical sleep rebound was slightly decreased and delayed. When glucocorticoid action was replaced by an intramuscular injection of dexamethasone, a glucocorticoid receptor agonist, the sleep rebound was suppressed (-3% in slow-wave sleep and -37% in paradoxical sleep). Lastly, in a third series of experiments, plasma corticosterone concentration was evaluated at different times in rats immobilized for 1 h or 4 h. Corticosterone concentration was higher in stressed animals than in control ones (+92%) and returned to baseline 4 h earlier in animals immobilized for 1 h compared with those stressed for 4 h. Therefore, corticosterone is probably involved in the suppression of the sleep rebound after long immobilization periods since (i) dexamethasone suppressed the stress-induced sleep rebound, and (ii) corticosterone was elevated for a longer period in the 4 h immobilization group. It is concluded that the reparative sleep rebound is suppressed after long and intense stress periods and that a prolonged glucocorticoid secretion could be one of the factors responsible for this effect. This deleterious effect on sleep could impair normal recovery and quick adaptation to a new situation, and could participate in the development of stress-related pathologies in humans.

Adrenalectomy↗
PubMed1999

Response times to Ehrenstein illusions of varying subjective magnitude: complementarity of psychophysical measures.

The following experiments investigate the effects of contrast polarity, inducer spacing, and inducer type on three dependent variables measuring the perception of an illusory surface in Ehrenstein figures: subjective magnitude, response time, and frequency of perception. It was found that response time generally decreased when the other two behavioral indicators increased. However, it was also shown that subjective magnitude provided more discriminating measures of relatively strong illusory percepts, whereas frequency of perception and response time provided more discriminating measures of relatively weak illusory percepts. The findings generally confirm earlier work on the effect of inducer spacing and contrast polarity on the perceived strength of brightness illusions, and in particular reveal the complementarity of subjective magnitude, response time, and frequency of perception as critical measures of configurational effects in the perceptual processing of these phenomena.

Adult↗
PubMed1999

Long-term cyclosporin continuation rates in rheumatoid arthritis patients.

OBJECTIVE: To evaluate the continuation rate of cyclosporin therapy in rheumatoid arthritis patients followed for at least three years. METHODS: Retrospective medical chart review of rheumatoid arthritis patients on cyclosporin. Treatment efficacy was assessed based on a visual analog scale pain score, Ritchie's articular index, and Lee's functional index. Nonparametric Kaplan-Meier survival curves were used to evaluate continuation rates. RESULTS: 24 cyclosporin-treated patients with a mean age of 58 years and a mean disease duration of ten years were included in the study; 87% had received three second-line drugs prior to cyclosporin. Mean cyclosporin treatment duration was 28 months (range, 1-103 months). Overall cyclosporin continuation rates were 75% after four months and 50% after 36 months. Toxicity and inefficacy caused 33% and 13% of cyclosporin discontinuations, respectively. CONCLUSION: The continuation rate of cyclosporin was satisfactory and similar to that reported for other second-line drugs.

Adult↗
PubMed1999

Longitudinal determination of antiphospholipid antibodies in lupus patients without previous manifestations of antiphospholipid syndrome. A prospective study.

OBJECTIVE: To investigate whether serial anticardiolipin determination contributes to the clinical management of patients with systemic lupus erythematosus (SLE) with no previous sign of the antiphospholipid syndrome (APS). METHODS: In 90 patients with SLE with no previous clinical manifestations of the APS, repeated clinical evaluations were performed, and serial blood samples (obtained over a 30 month period, range 13-53 mo) were screened for antiphospholipid antibodies (aPL). Anticardiolipin antibodies (aCL) were detected using an ELISA and considered positive if the result was >25 GPL on 2 separate occasions. Patients were not required to be on a specific treatment regimen during the study. RESULTS: Thirty-four patients (37%) had at least one positive ELISA and 11 (11/90, 12%) 2 positive ELISA for IgG aCL during the study. Lupus anticoagulant (LAC) was found in 16 patients, and a false positive VDRL in 5. At study completion, the total number of clinical or laboratory events associated with APS was 30. In univariate analysis, aCL was significantly associated only with LAC (p<0.012). Presence of aCL also correlated with hemoglobin level, anti-DNA antibody, leukocyte count, and the SLE Disease Activity Index (SLEDAI). LAC and aCL were significantly associated with each other (OR 5.17; 95% CI 1.5-17.7), but LAC had a better positive predictive value than aCL for arterial thrombosis and neurological events. CONCLUSION: Among our patients with SLE without previous clinical manifestations of APS, positive aCL did not predict the occurrence of APS within the next 3 years, but was statistically related to the clinical disease activity (SLEDAI).

Adolescent↗
PubMed1998

[Male osteoporosis].

AN UPCOMING PUBLIC HEALTH PROBLEM: There has been a considerable focus on osteoporosis in men recently. Bone mass is high in men who have larger bones than women. The frequency of fractures is also higher due to post-trauma lesions. Femoral neck fractures have also increased over the last few years although the F/M ratio remains about 2.8. Overall, there is a trend towards an increased incidence of masculine osteoporosis (and vertebral fractures) due to population aging. FAVORING FACTORS IN MEN: The most important factors are hypoandrogenism, hypoestrogenism (pre or post-puberty), the alcohol-smoking association, malnutrition, lack of sun exposure and chronic liver disease. Other causes of osteoporosis (hyperthyroidism, Cushing's disease, hemochromatosis, gastrectomy, inflammatory rheumatic disease, tubulopathy, hypercalciuria and iatrogenic causes) should also be taken into consideration. PRETHERAPY WORK-UP: All the different possible etiologies should be investigated. Therapeutic protocols should provide hormone replacement when required, withdrawal of causal drugs, better nutrition and reduced alcohol and tobacco use.

Bone Density↗
PubMed1998

In vivo voltammetric detection of rat brain lactate with carbon fiber microelectrodes coated with lactate oxidase.

To allow rat brain lactate measurement in vivo, a specific sensor based on a carbon fiber (phi = 30 microns) microelectrode coated with lactate oxidase was prepared. Combined with the differential normal pulse voltammetry measurement method, such a sensor, with a sensitivity of 9.15 +/- 0.91 mA.M-1.cm-2, provided a lactate linear response in concentrations ranging from 0.1 to 2.0 mM. The measurements performed appeared to be essentially insensitive to usual interference caused by the electroactive compounds present in the brain (ascorbic acid and peptides). In vivo detection performed in the cortex of the anesthetized rat led to the determination of a lactate concentration of 0.41 +/- 0.02 mM. Moreover, to validate the results obtained in vivo, an ex vivo determination of the lactate level was also performed in samples of brain tissue, plasma, and cerebrospinal fluid, using both voltammetry and a clinical analyzer with colorimetric-based detection. A good correlation was observed between the sets of data established by both methods.

Animals↗
PubMed1998

Cognitive executive dysfunction in patients with obstructive sleep apnea syndrome (OSAS) after CPAP treatment.

We have previously described impairments of cognitive executive functions in 17 patients with OSAS in comparison with 17 normal controls, as assessed by various frontal-lobe-related tests. In the present study, 10 of these OSAS patients treated with continuous positive airway pressure (CPAP) were reevaluated after 4-6 months of treatment. Neuropsychological tasks explored attention, short-term memory span, learning abilities, planning capacities, categorizing activities, and verbal fluency. Patients were found to have normalized most of their cognitive executive and learning disabilities, but all the short-term memory tests remained unchanged. These findings are discussed in light of the contribution of the frontal-lobe-related systems to short-term memory functions, and the eventual pathogenic role played by sleep fragmentation and nocturnal hypoxemia, which are related to the occurrence of apneic and hypopneic events. In conclusion, short-term memory impairment was persistent in OSAS patients despite CPAP treatment for 4-6 months.

Adult↗
PubMed1998

Learning difficulties of diabetic patients: a survey of educators.

This study was designed to shed light on the learning difficulties of diabetic patients. An open-ended questionnaire was sent to 85 health care professionals working in the field of diabetes and nutrition who had been trained in patient education techniques. They were asked to describe the skills that were the easiest to teach patients and those that patients mastered the best, as well as the skills they found hardest to teach patients, those that patients mastered the least and those that gave rise to errors persisting after the patients education was completed. On the whole, the results showed that the educators found it easy to teach techniques: patients mastered procedures well and made few mistakes. In contrast, diabetic patients seem to have problems learning skills, such as insulin dose adjustment, that require complex problem-solving (involving multiple variables). Based on these findings, the authors discuss the notions of learning complexity and the time needed for successful patient education.

Attitude of Health Personnel↗
PubMed1998

Expression of growth factors and their receptors in the postnatal rat cochlea.

RT-PCR was used to assay for growth factors and receptors from seven different protein families in cochlea tissues of the juvenile rat. There was a broad representation of the growth factor families in all the cochlea tissues examined, though the organ of Corti and stria vascularis expressed a greater variety than the spiral ganglion. This broad expression suggests that a variety of known growth factors play significant roles in the development, maintenance, and repair of the inner ear. The results of this survey serve as a basis for the design of future in vitro experiments that will address the ability of growth factors to protect hair cells from damage and to evoke a repair-regeneration response by injured hair cells.

Animals↗
PubMed1998

Is there an optimal time to administer methotrexate in the treatment of rheumatoid arthritis?

OBJECTIVE: To determine the optimal time to administer methotrexate (MTX) in rheumatoid arthritis (RA). METHODS: In a crossover study 23 patients were administered MTX intramuscularly at either 10 AM or 6 PM. A 2 week interval separated the 2 injections. MTX concentrations were measured using a fluorescence polarization immunoassay. Pharmacokinetic variables were estimated using a Bayesian approach. The morning and evening schedules were compared using analysis of variance to determine the optimal time of injection. RESULTS: No statistical difference was found in the pharmacokinetics of MTX according to hour of injection. A difference in the creatinine clearance, however, was observed in the samples obtained at noon and 8 PM, but clearance of MTX was unchanged. CONCLUSION: Pharmacokinetic variables suggest that MTX can be administered either in the morning (10 AM) or evening (6 PM) in the treatment of RA.

Adult↗
PubMed1997

Influence of a 1 h immobilization stress on sleep states and corticotropin-like intermediate lobe peptide (CLIP or ACTH18-39, Ph-ACTH18-39) brain contents in the rat.

A 1 h immobilization stress (IS) was imposed to rats at the beginning of the dark period, i.e., when the animals start to be active. The IS was accompanied by an intense polygraphic waking and followed, over 12 h of the dark period, by a significant rebound of slow-wave sleep (SWS, +17%) and paradoxical sleep (PS, +57%). In order to estimate the IS-related changes in the endogenous concentrations of corticotropin-like intermediate lobe peptide (CLIP, ACTH18-39) and related compounds, a specific radioimmunoassay (RIA) was used. Assays performed in cerebral biopsies taken from arcuate (AN) and raphe dorsalis (nRD) nuclei led to the obtention of 2 main immunoreactive peaks, corresponding to CLIP and its phosphorylated form Ph-CLIP. Just after end of the IS and within the nRD. Ph-CLIP immunoreactivity increased by about 95%. Four hours later, i.e., when PS rebound was maximal, a 37% increase in Ph-CLIP immunoreactivity was measured in the AN. These observations have never been described before. In the blood, at the end of the restraint, CLIP/ACTH1-39 total immunoreactivity was increased by 330%. It returned to baseline level 4 h later. Blood concentration of corticosterone was also increased by 56% at the end of the IS and was close to baseline level 4 h later. Data reported here indicate that the IS first triggers an increase in Ph-CLIP within the nRD. Since the nRD contains sleep permissive components, this increase might be determinant for the SWS and PS rebound induction. The changes observed in the blood as regards CLIP/ACTH1-39 total immunoreactivity and corticosterone concentration testify to the efficacy of the IS and are part of the conventional picture accompanying such a situation. Finally, the increase in Ph-CLIP, occurring in the AN 4 h after the end of the restraint, might be part of the restorative processes necessary to compensate the stress overshoot.

Adrenocorticotropic Hormone↗
PubMed1997

Ultrastructural relationships of the pro-opiomelanocortin axons with the serotoninergic neurons in the dorsal raphe nucleus of the rat.

The relationships of the corticotropin-like intermediate lobe peptide (CLIP)/ACTH-immunoreactive axons with the serotoninergic and non-serotoninergic neurons in the dorsal raphe nucleus of the rat were examined by means of a double label immunocytochemical method. It is suggested that the rare contacts established by the CLIP/ACTH-immunoreactive fibers with serotoninergic neurons (cell bodies and dendrites) are not under a synaptic from. In contrast, the contacts with non-serotoninergic neurons were predominantly formed with dendrites and showed a substantial number of synapses.

Adrenocorticotropic Hormone↗
PubMed1997

Hemispheric asymmetries of visual evoked potentials in relation to spatial frequency, handedness and familial left-handedness.

The effects of handedness and of familial left-handedness on the asymmetry of the cerebral hemispheres were investigated by means of visual evoked potentials. Square gratings of different spatial frequencies were presented, at 1 Hz in ON-OFF mode to 60 subjects: 30 right-handers and 30 left-handers, 15 with familial handedness and 15 without in each group. The results show that the patterns of hemispheric asymmetry differ in right- and left-handers. They also show that in left-handers these patterns depend on the presence or absence of familial left-handedness, whereas in right-handers the role of this genetic factor is less evident.

Adolescent↗