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Biomedical subjects

P Robert

Publications and source records attributed to P Robert.

At least 109 records · Page 6Linked to original sources
PubMed1976

Association of a ribonuclease with the purified influenza virus.

Purified influenza virus contains ribonuclease activity. The enzyme does not hydrolyze viral RNA but both 28 S and 18 S host cell RNA are degraded forming large (about 16 S) and small (about 5 S) fragments with the release of the acid-soluble material. It has an optimum temperature of 37 degrees C, requires no divalent ions, and is inhibited by 0.1 M EDTA and 1% SDS. Treatment with 4 M urea increases enzymatic activity considerably (42%) but is not a prerequisite for eliciting ribonuclease activity suggesting that the enzyme is probably located near the surface of the virus particle. Results show that the observed enzyme activity is virus-associated as no host cell protein is detectable in the purified virus.

Cell-Free System↗
PubMed1976

Vestibular habituation in flightcrew.

Vestibular habituation is a general reaction to any repetitive sensory stimulation. It can be characterized by four main features: acquisition, retention, loss or dishabituation, and transfer. This study concerns three groups of subjects: The first group consists of a) 27 pilots at present serving in the French Air Force, b) 12 pilots at present serving in the major civil airlines, c) 8 navigators, radio-navigators, and crew mechanics, some of whom are flying club pilots, and d) 3 professional pilots trained in flying clubs. All of these subjects had more than 2000 h flying time. They were from 27 to 50 years old. The second group consists of airline stewards. The third group consists of trainee pilots still in flying school. All of these subjects were examined for their suitability, in particular undergoing a damped swing test. The first oscillation was in an anticlockwise direction and the damping extended over 20 periods. The following parametre was measured: the ratio of total left nystagmus frequency to total right nystagmus frequency. In "normal" control subjects the ratio is greater than 1. The results were: The first group: In 41 out of 50 subjects, the ratio of left tremors frequency to right tremors frequency was less than or approximately equal to 1. In the second group: The results showed no significant differences in comparison with a control group of subjects. In the third group: Zero flying time--the results were identical with those of control subjects; 40 h flying time--the ratio approached 1; 100 h flying time--the ratio was less than 1. Vestibular habituation, that is inversion of the preponderance of the total number of left tremors over the total number of right tremors, was observed in the technical flightcrew. The appearance of this inversion during the pilots' training was studied and its retention tested. This test for showing vestibular habituation may be of use for monitoring the function of equilibrium and the development of habituation during flight training. In this report, we shall first review the definition and characteristics of vestibular habituation, and the main body of recent work on this phenomenon in flightcrew. Our own findings will be then presented.

Aerospace Medicine↗
PubMedDate not supplied

Computerized localization of brain structures in single photon emission computed tomography using a proportional anatomical stereotactic atlas.

An accurate identification of cerebral structures is necessary to perform quantification of single photon emission computed tomography (SPECT). We have developed an anatomical localization system that accounts for individual brain shapes and sizes by using the Talairach proportional grid system. The locations of the commissural lines, which define the stereotactic coordinate system, are calculated from the external landmarks provided by the canthomeatal line. This is validated on MRI images. When applied to SPECT data, the use of a neuroanatomical atlas data along with the automaticity of the processing guarantees a high degree of objectivity and inter-observer reproducibility.

Anatomy, Artistic↗
PubMedDate not supplied

[Morningness-Eveningness for Children Scale: psychometric properties and month of birth effect].

There is strong evidence that individuals can be arranged on a continuum from Eveningness to Morningness reflecting their preferred time range for different activities. This preference, which mostly reflects the phase of the circadian pacemaker, is determined in part by mutations on the CLOCK gene, and by environmental factors such as the month of birth. It has been suggested that eveningness might be a susceptibility factor for depressive disorders. Two self-rated questionnaires are available (the Morningness-Eveningness Questionnaire, MEQ, and the Composite Scale for Morningness) and have been adapted for use with youngsters: the Junior-MEQ and the Morningness-Eveningness Scale for Children (MESC), respectively. Most studies concern adult samples, but it is accepted that puberty is associated with a phase delay in the circadian pacemaker die a shift towards eveningness) occuring around age 12 in both genders. In this study, we examined the psychometric properties of the French version of the MESC in 3 independent samples of adolescents (total n = 392) recruited in the community or during hospitalization in paediatric department, most of them after they attempted suicide. A three-way ANCOVA showed no gender or age effect but rather a strong group effect: hospitalized adolescents scored about 3 points below the community samples (ie towards an eveningness tendency). In each sample, the internal consistency for this 10-item measure was satisfactory (mean alpha = 0.76) and the same two-factor structure was found (Morningness and Planification) as shown by procrustes rotations. As expected, there was a negative correlation between the MESC scores and reported times of rising, of going to bed, of best intellectual and physical performances, but no correlation with the number of minutes of sleep needed. The test-retest stability was acceptable within a 8-month delay although the sample size was limited (n = 20). In line with literature data, we found a modest negative correlation about -0.20 in 2 of the samples with two depression measures (MADRS and CES-D). Finally, we assessed the effect of the month of birth on the MESC total score by a non-linear regression adjusted for age and gender that included a one-cycle cosinus function. We found that birth in March-April was associated with eveningness while birth in September-October was associated with morningness. The peak and nadir occur two months before those found in a large sample of young adults. However, this result could not be replicated in the sample of hospitalized adolescents suggesting that the effect might have been smoothed by a "pathological" factor. Reasons for this descrepancy and implications for developmental psychiatry are discussed. More precisely, we postulate a relationship between morningness and impulsivity-related personality traits. In conclusion, the MESC is a psychometrically sound instrument in need of further validity assessment.

Adolescent↗
PubMedDate not supplied

[Causes and consequences of elderly's agitated and aggressive behavior].

Agitation and aggressiveness are frequent in the elderly and often related to dementia. As a result of the ageing of the general population this is becoming a major public health concern. No or little epidemiological data, during primary health care, about symptoms, co-morbidity, nor medical and social consequences of elderlys' disruptive behavior have been gathered or published in the French literature. Thus, in order to describe these disorders, a survey in cooperation with general practitioners (GP) was conducted. A representative sample of 212 French GP's, all with preferential geriatric activity were asked to conduct a study by including retrospectively their two most recent patients older than 65, who had exhibited agitation and/or aggressiveness. From this cross sectional study, 410 patients (female: 61%, male: 39%) were included. The mean age was 81 years (sd: 7.65). The patients suffered from change in verbal behavior (80%), verbal aggressiveness (71%), physical agitation (60%), wandering (48%), and/or physical aggressiveness (31%). The average of disruptive behavior symptoms per patient was 2.9. The symptoms appeared progressively in 81% of patients, the mean duration was two years and it was the first episode in 40% of patients. Disruptive behaviors may be explained in view of organic illness in 62% of patients (cardiovascular disease: 37%, neurologic: 12%, diabetes: 7%, dehydratation: 5%), dementia (Alzheimer disease: 20%, vascular dementia: 18%, mixed dementia: 14%). In 54% of patients disruptive behavior may be explained in view of depression: 34%, and anxiety disorder: 31%. A triggering factor was observed in 57% of cases (psychosocial stress: 39%). Somatic consequences of the symptoms were frequently identified: decrease of alimentary intake: 39%, weight loss: 27%, dehydratation: 11%, falls: 32%, and irregular medication intake: 31%. Limitation of daily life activities: 85%, and family life: 97% were also noted. Acceptability of patient's symptoms by the family was good (no discomfort or transitory and mild irritability) in 61% of cases, and very bad (reactions of exhaustion, hospitalization requirement) in 13%. This study carried out during primary care, showed that the elderly's disruptive behaviors cause severe medical consequences and familial and social distress.

Age Factors↗
PubMedDate not supplied

[Contribution of zolpidem in the management of sleep disorders].

Zolpidem is a nonbenzodiazepine hypnotic agent belonging to a new class of psychotropic drugs the imidazopyridines which enhance the GABAA receptor function by interacting with a specific receptor population. Zolpidem binds selectively to the Omega-1 receptor subtype and from a pharmacological point of view differs from benzodiazepines (BZD) by producing a strong sedative and hypnotic profile which predominates over the anticonvulsivant and anxiolytic activity and moreover appears practically devoid of myorelaxant properties. From a pharmacodynamic point of view, these results suggest that zolpidem facilitates more selectively than BZD, GABAA function and produces a selective hypnotic effect. Though if the role played by receptors in tolerance and dependence has not been yet fully elucidated, it could be described as an adaptative process to sustained stimulation of GABA function. Animal data obtained with zolpidem differs substantially from that of the BZD and indicates that repeated zolpidem administration may not lead to phenomena of tolerance and withdrawal syndrome after abrupt drug discontinuation. In human following oral intake, zolpidem is very rapidly (Tmax: 30-40 min) absorbed. The clearance is essentially metabolic and less than 1% is recovered in urine. The apparent plasma half-life is of 2.0-2.5 hours in most adult subjects and metabolites are totally inactive. The hypnotic activity of zolpidem and its effects on sleep architecture have been assessed in polysomnographic studies: 11 studies in 579 healthy volunteers and 12 studies in 202 insomniac patients. From all the patient studies, it emerges clearly that zolpidem at the dose of 10 mg significantly decreases sleep onset latency, the number and the duration of nocturnal awakenings, and concomitantly increases total sleep time. Furthermore, at variance with what observed with reference benzodiazepine hypnotics, zolpidem does not alter patient sleep architecture: it increases only moderately stage 2, it increases, when reduced, stages 3 and 4 (slow wave sleep) and it does not decrease REM sleep. Clinical studies conducted on more than 4,000 insomniac patients have clearly shown that at the dose of 10-20 mg, zolpidem induces from the first night a definite hypnotic effect in all types of insomnia. In elderly subjects an initial dose of 5 mg should be considered. The possible presence of residual effects during the day following administration of zolpidem has been assessed in 535 healthy volunteers and in 133 insomniac patients according to a double blind (versus placebo and/or benzodiazepine) controlled design.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗