[A comparative study of nocturnal sleep duration and timetable of children between five- and ten-years-old according to their age and socio-economic environment]. / Etude comparative des durées et des horaires du sommeil nocturne d'enfants de cinq à dix ans selon leur âge et leur environnement socio-économique.

AIM: This study was conducted on a sample of 644 pupils between the ages of five and ten years at school in the Orléans-Tours education authority with the aim of studying the nocturnal sleep duration and timetable of young children according to age and socio-economic environment. METHOD: In order to find out about children's sleeping habits (duration, time of going to bed and getting up, and weekly variations) a standard grid was used to carry out a cross-sectional survey in the children's families. This was filled in each day from Monday to Sunday during the same school week for all the children. RESULTS: Sleep duration decreased with age from maternelle to CM2 (nursery to last year of primary education). Data relating to sleep duration from CE2 (third year of primary school - 8-year-old -) showed differences according to whether the school belonged to an Educational Priority Zone (EPZ) or not. It was noticed that between five- and ten-year-old children from EPZ lost 62 minutes of sleep, whereas those not from EPZ only lost 29 minutes. These results would suggest that in addition to developmental factors, environmental factors also play a role in sleep duration. The differences observed were due to later bed times for children from EPZ. Weekly variations in sleep were generally very similar for all the children. At the weekend all the children tended to go to bed later, however this was more noticeable Saturday night for children not living in EPZ. Children slept the longest on Tuesday night due to the fact they got up later Wednesday morning (Wednesday is a day off in the majority of French schools). However, children from the age of nine (CM1 - forth year of primary education -) in EPZ did not benefit from this recuperation time, as they went to bed later but still got up early the next morning. CONCLUSION: This study showed that in addition to the physiological and developmental factors that influence children's sleep, the socio-economic context also plays a role. These results as a whole highlight the importance that practitioners and families should pay to maintaining a regularity in the child's routine and in the amount of sleep necessary at each age.

Role of school schedule, age, and parental socioeconomic status on sleep duration and sleepiness of Parisian children.

The aim of the study was to assess the duration and quality of sleep of prepubertal (Tanner Scale level 1) physically and mentally healthy children as a function of school schedule (4 versus 4.5 days per week), age and grade (median age of 9.5 years for 4th grade versus median age of 10.5 years for 5th grade), school district (wealthy versus nonwealthy) in Paris, France, and parental socioeconomic status (high, medium, or low). We studied 51 girl and 44 boy volunteer pupils with written parental consent. The study lasted 2 weeks during the month of March. During the first study week, the children attended school 4.5 days, and during the second week, they attended school only 4 days without difference in the length of the school day. A sleep log was used to ascertain time of lights off for sleep and lights on at awakening, nighttime sleep duration, and self-rated sleep quality. A visual analog scale (VAS) was also used by pupils to self-rate the level of perceived sleepiness at four specific times of the school day. Conventional statistical methods (e.g., t and chi2 tests) were used to examine differences in mean values. Sleep duration, self-rated sleepiness, and subjective sleep quality were comparable (P > .05) by gender, school schedule, school district, and parental socioeconomic status. Overall, the sleep of this sample of Parisian children around 10 years of age was rather stable in its duration and timing, suggesting flexibility to adjust to the different school schedules.

Time-of-day and day-of-week effects on mnemonic performance.

The present study attempts to determine whether diurnal variations in memory performance like the ones observed by Folkard et al. (1977) are independent of the testing day (Monday or Thursday) and the type of material (story or word list). In the experiment, 103 pupils aged 10 and 11 had to listen to a story and learn a list of 14 nouns at 09:00 or 15:00 on Monday or Thursday. Immediately after presentation of the information and then again 1 week later the pupils had to answer questions about the story and recall the list of nouns. The results showed that the type of task had no effect on memory performance, but immediate and delayed recall scores were dependent on both the time and the day the information was presented. Moreover, memory performance was also affected by the time at which the delayed recall test took place. On Monday and especially on Thursday, better performance was obtained at 09:00. This data only partially confirms the findings of Folkard et al.

[Biological, behavioral and intellectual rhythms in pupils during the school-day]. / Rythmicités biologiques, comportementales et intellectuelles de l'élève au cours de la journée scolaire.

We report in this paper the data separately collected for 15 years by the research teams of Montagner and Testu on the daily fluctuations of the periodical type and ultradian and circadian rhythms of biological, behavioural and mental variables which are or could be linked to or correlated with the fluctuations of intellectual activity in pupils throughout the school-day. The variables under study are the behaviours which are considered to be indicators of vigilance and non vigilance (arousal and drowsiness), corporal activation, heart rate, blood pressure, performances in tests of vigilance, targeted attention, spatial structuration and logical construction, and also in usual school tasks. Studies were carried out on different children populations at all ages (in this article we only report data on children attending primary school and partly kindergarten) in different French schools and, with regard to Testu's studies, several european schools in England, Germany and Spain. The main data collected by both teams are comparable in many respects: 1) the vigilance level and intellectual performances of pupils of all ages are weak or relatively weak at the beginning of the school activities, i.e. from 8 to 9 or 9:30 according to the studies and measured variables, as the biological constraints are not at a high level (heart rate and blood pressure); 2) the same items or patterns significantly increase throughout school time up to 11:30 or noon according to the studies with the exception of the 11:00-11:30 span in Montagner's research in children attending the first level of primary school, as the biological constraints decrease; 3) in most studies the vigilance level and intellectual performances are weak or relatively weak at the beginning of the school-time following the lunch, and the biological constraints are the strongest of the day (from 13:30 to 15:00) ; 4) the vigilance level and intellectual performances are always higher in the middle of the school-day (i.e. from 15:00 to 17:00) than at the beginning of the afternoon, and the biological constraints are weaker.

Diurnal variation in mental activities of French pupils and influence of test protocol.

The aim of the study was to determine the influence of the test protocol (individual vs. group) on the diurnal variations in mental activity of 18 11-year-old pupils. Number cancellation, a spatial orientation test, and mathematical problems were tested four times on three successive Fridays at 08:45, 11:15, 13:45 and 16:45 h. On the first and third Fridays the tests were performed on the group of subjects, whereas individual subjects were tested on the second Friday. Results indicated a possible influence of the test protocol (individual vs. group) on intellectual rhythmicity. Only in the group protocol did we find the psychological profile which is normally observed, namely, a performance increase during the morning, a postlunch fall, and then an increase in the afternoon. We suggest the existence of some group effect in these performance tests.

Identification of centrosomal proteins in a human lymphoblastic cell line.

Highly enriched preparations of centrosomes from human T-lymphoblasts KE 37 were analyzed for their protein content. The specific pattern of polypeptides was characterized by an abundant subset of high mol. wt proteins and a major group of proteins with mol. wt ranging from 50 to 65 kd. Several immunoreactive proteins were identified, using a rabbit serum spontaneously reacting with human centrosomes. They include a family of high mol. wt ranging from 180 to 250 kd, a 130-kd protein and a 60-65 kd doublet. These antigens have the following properties: they are localized within the pericentriolar material; their abundance, as judged by centrosome labelling, changes significantly during the cell cycle, the maximum being observed at the pole of the metaphasic spindle; in Taxol-treated cells where the centrosome is no longer acting as a nucleating center, they redistribute at one end of the microtubule arrays in both mitotic and interphasic cells, as expected for nucleating, or capping, proteins. All these properties are compatible with their involvement in microtubule nucleation.

Diurnal variations of performance and information processing.

The aim of the study was to establish whether performance of a task in which controlled search is required fluctuates during the day or, on the other hand, performance of a task in which the automatic detection is required does not fluctuate during the day. The material and the procedure for setting the subject with an automatic detection set and for controlled search were determined as experimental paradigms and based on the results of the studies published by Shiffrin and Schneider. Eighteen volunteers from first and second year students of Psychology (9 boys and 9 girls) took part in the study. The study was done in January and February 1985 in the Laboratory of experimental psychology of Tours (France) on Tuesdays, Thursdays and Fridays. Each subject individually participated in 4 sessions on the same day, at 08(30); 11(45); 13(45) and 17(00). The results indicate that the performances (number of the targets correctly detected and the reaction time) only fluctuate in the course of the day when the controlled search is required. We suggest that the independence or the dependence of performance variation may be linked to the use of one or another of the two information processes described by Shiffrin and Schneider: controlled search and automatic detection.

A protein of Mr 80,000 is associated with the nucleolus organizer of human cell lines.

A rabbit serum which had previously been reported to have an immunological affinity for centrosomes of human cell lines was shown also to be specific for the nucleus. Optical and ultrastructural immunolocalization in HeLa cells showed that this specificity is restricted to the fibrillar centre of nucleoli either in untreated or actinomycin D treated interphase cells. In mitotic cells discrete labelling was observed on chromosomes and shown to correspond, on spread metaphase plates, to the short arms of acrocentric chromosomes, i.e. to the nucleolar organizer regions (NORs). Using independent cell fractionation procedures in the human T-lymphoblastic KE 37 cell line and purification of immunoglobulins by affinity to antigens detected by electrophoresis and blotting, a strict correlation between immunoreactive proteins and cytological staining was established. The nucleolar specificity was shown to correspond to a protein with an Mr of 80,000 while the centrosomal specificity corresponded principally to a protein doublet of 60,000-65,000. These antigens share common epitopes as shown by the staining of both NOR and centrosome by immunoglobulins purified by affinity to either type of protein.

Restriction map of Tn7.

Tn7, a transposon of 14 kb, encodes resistance to trimethoprim (Tp) and streptomycin (Sm). A cleavage site map of this transposon for twenty-two different restriction enzymes as determined by comparison of restriction enzyme cleavage patterns of the plasmids ColE1 and ColE1::Tn7 is presented. The precise localization of these sites was facilitated by the use of two deletion derivatives of ColE1::Tn7: pGB2 and ColE1::Tn7 delta 6, and by the use of pOB14 and pOB15 which contain a part of Tn7 cloned into the plasmid pBR322. This map should aid in the study of the structural and genetic organization of this transposon.