Chronobiologia最新文献

The neocortical and hippocampal electrical activities were studied in 8, 15, 22, and 29-day-old rats. Segments of EEG recorded for 4 hours were analyzed by means of fast Fourier transformation. The sleep-wake activity stages were determined. The developments in the neocortical and hippocampal EEG activities were characterized by the gradual appearance of adult-like EEG waves and a shift towards higher frequencies in the theta wave range of the hippocampal electrical activity. The power value in the theta range, however, exhibited age-invariant rhythmicities with cycle lengths of about 9.5-11 and 16-22 min. The manifestation of such an age-invariant rhythm can be interpreted as an electrical manifestation of the rest-activity cycle originally described by KLEITMAN25.

The relationships between the circadian variation of abnormal heart beats and the circadian variation in sudden cardiac death warrant further discussion for the high correlations demonstrated here are difficult to ignore. In the healthy group abnormal beats showed a high correlation of their circadian variation with that of sudden cardiac death which is independent of heart rate. As a result the conclusion that the relationship of the circadian variations of abnormal heart beats and sudden cardiac death is merely dependent on a mutual dependence on activity is not supported here. The present data illustrates a strong association between arrhythmias and sudden cardiac death. The relationship of sudden cardiac death with abnormal heart beats demonstrated here, however, cannot confirm a causal role of the latter on the former for both may be responding to circadian variations of some underlying mechanism such as ischemia. Additionally the population studied here, although relatively comparable in terms of living conditions and other significant factors, was not strictly age-matched with those from the sudden cardiac death study warranting further caution in interpreting the association demonstrated here. The results from the unhealthy group, although somewhat limited, indicate that cardiovascular morbidity may alter the relationship of sudden cardiac death and abnormal heart beats. Such a result could be explained by the presence of other forms of heart disease which could be responsible for sudden cardiac death in the unhealthy group. An interesting question to ask concerning the data presented above is whether or not significant circadian variations in in the frequency of abnormal heart beats could have been demonstrated when exogenous factors such as meal times and activity were altered. The data on in hospital sudden cardiac death indicates that the circadian variation in sudden cardiac death is significantly altered by the radical changes in routine which accompany hospitalization. If the relationship between the circadian variation of sudden cardiac death and abnormal heart beats is as strong as the results presented here indicate, it is likely that the alteration of such exogenous factors would also change the circadian variation of abnormal heart beats. The results of the present study indicate that both the circadian variation in abnormal heart beats, and its relationship to sudden cardiac death, warrant further study.

The hypothesis that nonprotein and protein sulfhydryls in gastric mucosa may play some role in the defensive and offensive processes of gastric epithelium was tested in this study in the intact rat gastric mucosa. Both sulfhydryl compounds presented statistically significant changes during the 24-hour day. The content of nonprotein sulfhydryls was less during the dark span than during the light span, while the circadian acrophase of protein sulfhydryls occurred during dark span. These results may offer a new interpretation of the greater vulnerability to ulcerogenic agents of the gastric mucosa of rats during their usual activity span.

Twenty-four-hour blood pressure (BP) profiles of 56 patients diagnosed as 'hypertensive' by WHO criteria were analyzed by the fit of a 24-hour cosine curve according to the single cosinor method. A left ventricular mass index (LVMI) was also assessed by two-dimensional echocardiography on each patient as a gauge of target organ involvement. LVMI and the BP MESOR correlates positively for systolic, S (r = 0.324), mean arterial, MA (r = 0.334) and diastolic, D (r = 0.267) BP (P less than 0.05), yet no statistically significant linear correlation between LVMI and the circadian BP amplitude (one-half of predictable change) was found. When a second-degree polynomial regression was fitted to the circadian BP amplitudes, an association was found (SBP: R2 = 0.138, P = 0.02; MAP: R2 = 0.167, P = 0.01; DBP: R2 = 0.128, P less than 0.01). The corresponding curves were characterized by peaks in the circadian amplitudes of SBP, MAP and DBP around a value of LVMI between 110 and 120 g/m2. For further scrutiny, three subgroups had been formed on the basis of literature, a priori with respect to the LVMI (group 1: LVMI less than 100); group 2: 100 less than LVMI less than 130; group 3: 130 less than LVMI). For MESORs, there was no difference between groups 1 and 2, whereas the MESOR of group 3 were larger than the other two groups. The circadian BP amplitudes of group 2 were larger than those of the other two groups for SBP, MAP and DBP. An increasing LVMI precedes a definitive increase of BP MESOR and coincides with an increase in the circadian BP amplitude; thus an increase in extent of circadian changes can alert the self-monitoring population of a target organ involvement.

In the present study we determined the nocturnal profile of serum melatonin (MT) concentrations in 10 short normal children at Tanner stage I-II of pubertal development (12.5-14.9 yrs) and in 6 young adults (24-29 yrs). Blood was collected every 30 min from 00(00) to 06(00). We did not find any significant difference in the nocturnal profile of serum MT, as gauged by the comparison of MT concentrations at any time-point tested as well as of the transverse means (84.2 +/- 36.0 pg/ml [M +/- SD] in the children vs 78.7 +/- 10.8 pg/ml in the adults). Mean serum melatonin concentration was not correlated to sex hormone concentration or body surface area. Our findings do not support the view that MT concentrations fall at the beginning of pubertal development and that changes in body size may be the reason for age-dependent changes of serum MT concentrations.