Chronobiology international
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The present study is part of a broader body of research concerning the ontogeny and regulations of the young child's sleep-wake rhythm. It was carried out with 12 children admitted to a day-care center from 4 or 5 months of age. None of the children showed any anomalies or functional disorders. ⋯ The main findings are (a) the circadian rhythm of wakefulness and sleep is clearly set up as early as at 4 months of age and consolidates between 6 and 7 months; (b) some ages are characterized by significant changes in the daily distribution and duration of sleep spans: 6 to 7 months; 10 to 12 months; 13 to 15 months; (c) these changes suggest the existence of several ultradian rhythmicities which become successively prevailing from one age to the next throughout child development. The longitudinal study of the young child's sleep-wakefulness rhythm allows better evaluation of the influence of developmental factors in its structuralization and formulation of new hypotheses on its disorders and dysfunction. Individual factors are under study.
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The amplitude and phasing of circadian rhythms are under discussion as possible predictors of tolerance to night work. In a field study, subjective sleepiness and oral temperature of 147 female nurses were measured at 2-hour intervals during a period with one morning shift and two consecutive night shifts. The nurses also filled out a questionnaire. ⋯ However, with regard to the sleepiness index, the corresponding difference between the groups with good or poor tolerance was not significant. The data did not confirm the hypothesis that predicts a quick adjustment of the circadian rhythm when the circadian amplitude is small before the change to night work. The contradictory results found in this and in other studies do not yet permit prediction of tolerance to night work.
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Because a eutectic mixture of lidocaine and procaine (EMLA cream) is used to treat pain in children who are undergoing venipuncture for screening clinical presurgery laboratory tests, this study was designed to investigate the influence of the time of application of EMLA cream on lidocaine transcutaneous absorption in children. The same phenomenon was also studied in rats. Local application of EMLA (right and left cubital fossae) was performed 1 hour before venipuncture in two groups of children (0.5 g/kg body weight at two sites), at 08:15 or 16.15 h; blood samples were performed 1 h later. ⋯ Plasma lidocaine levels were assayed according to an immunoenzymatic method (Abbott). Our data indicate that the lidocaine plasma levels were significantly different: higher in the evening for the children or in the morning for the rats. The plasma level of the local anesthetics (LA) represents an elimination route and thus may be inversely correlated to the skin amount of the LA.
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Twenty-three diurnally active (0705-2333), healthy persons between 22 and 54 years of age and without history of sleep abnormality were monitored continuously for 120 consecutive hr (five days) by wrist actigraphy. Circadian rhythms of high amplitude were detected by cosinor analysis for each participant and for the groups of 10 males and 13 females with the average span of heightened activity timed between approximately 1330 and 1605. The circadian peak-trough difference in wrist movement was marked, equalling approximately 75% of the 24-hr mean level. ⋯ With respect to the daytime span of activity, the mean wrist movement of individual participants ranged from 155-265 movements/min, with the majority (20/23) varying between 185-245 movements/min. During nocturnal sleep the mean wrist activity level was quite low, varying between individuals from 5 to 25 movements/min for 21 of 23 persons. Wrist actigraphy proved to be well-accepted and was a most reliable means of monitoring aspects of body movement during activity and sleep in ambulatory persons adhering to usual life habits and pursuits.
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Circadian and circatrigintan time series of salivary progesterone levels in premenarchal and adolescent girls and healthy mature premenopausal women have been investigated as a possible determinant for breast cancer risk. Circadian variations in progesterone appear to be more random than systematic and estimates of total daily progesterone output are better represented by samples pooled from several 2-hr specimens. Different patterns of circatrigintan progesterone secretion in girls are recognised and relate to those experienced in infertile and fertile women, though their relation to chronological or menarchal age is as yet uncertain. These data suggest that the measurement of salivary progesterone at premenarche, adolescence and maturity is a feasible, though statistically difficult, study for prospective identification of individuals at risk for breast cancer.