Chronobiologia最新文献

Genetic risk is a primary contributing factor to the predisposition of a newborn child to elevated blood pressure later in life. An index for this factor is needed to assess in the neonate the success or failure of preventive interventions instituted for the pregnant woman. This index could be based on characteristics describing the variability of blood pressure and heart rate during the first days after birth. In the search for such an index, the systolic and diastolic blood pressures and heart rates of 150 newborn babies were automatically monitored at about 30-minute intervals for 48h with a Nippon Colin device, starting early after birth. On the basis of questionnaires given to the parents, the neonates were assigned to a group of either a negative or positive family history of high blood pressure, according to the absence or presence of high blood pressure and/or related cardiovascular disease in two generations (those of the newborn's parents and grandparents). Circadian characteristics and descriptive statistics for the three circulatory variables were used for classification by a so-called "monotest", an all-subsets variable selection technique for biomedical discriminant analysis. For a particular combination of variables, the "monotest" performs as many steps of separate analyses as the total number of subjects, each subject's data being compared as a set with those of all others ("leave-one-out" approach). When the circadian amplitude of systolic blood pressure was used as classifier, the "monotest" yielded a 63% classification equivalent to prior criteria, the latter being based on a negative or a positive family history of high blood pressure. The "monotest" complements rhythmometric procedures and defines a set of individualized criteria for risk assessment. The combined use of automatic hardware for time-specified sampling with proper software for signal processing and discriminant analysis allows to recognize parameters of blood pressure circadian variability as a source of information for neonatal classification according to cardiovascular disease risk.

Twelve adult patients with indwelling common bile duct T-tube were selected for the study of circadian fluctuation of biliary excretion. From the 10th postoperative day on when the enterohepatic circulation was well reestablished a 5 ml bile sample was collected at the end of each 4-h interval for 3 to 4 days for determination of the concentrations of various biliary constituents. This was followed by measurement of bile flow rate by collecting the bile continuously through the T-tube at 4-h intervals for another 3 to 4 days. One quarter of the twelve patients showed no persistent daily fluctuation of all the variables studied. A circadian rhythm was demonstrated by single cosinor rhythmometry in the biliary concentrations of bile acid, cholesterol, phospholipid, bilirubin, alkaline phosphatase, and lactate dehydrogenase in the remaining nine patients. Among them six also showed a circadian fluctuation of hepatic bile flow. The lack of synchronization of the rhythm of the concentrations of various biliary constituents with the bile flow rate resulted in undetectability of a circadian rhythm for their excretory rate in the great majority of patients. Those few patients in whom a rhythm remained to be detectable had a much reduced amplitude but the same acrophase. We concluded that bile flow rate played a major role in the circadian rhythm of biliary excretion and might coordinate the fluctuation of the concentrations of various biliary constituents. However, a true circadian rhythm for their concentrations also existed at least in certain subjects.

Forty-eight subjects, divided into 4 equal groups (young and older female, young and older male), reproduced 19 time intervals varying in logarithmic steps between 1.3 and 20 s. The durations were indicated by noise of 50 dB SL. To assess Type A and Type B behavior, the subjects were administered a Swedish version of Jenkins Activity Survey with 21 items. It was found that 1. reproductions of durations by older subjects are longer than those by younger subjects, and 2. reproductions by male subjects are shorter than those by female, although an interaction was also detected between gender and the standard durations. Type A and Type B behavior did not show any main effect. The data were treated in accordance with the "parallel-clock model", whereby the parameters of the psychophysical power function are determined from duration reproduction data. As in previous experiments, the data showed a break in the function, entailing two segments. The effect of both age and gender could be explained by the weight coefficient of the upper relative to the lower segment of the psychophysical function, the coefficient being lower for male and higher for older subjects.

A 35-year-old cardiologist monitored himself with an automatic ABPM-630 (Colin Electronics) monitor, mostly at 15-minute intervals around-the-clock for three years with a few interruptions. In this subject with a family history of high blood pressure and stroke, a cross-spectral analysis revealed a statistically significant coherence at 27.7 days between systolic and diastolic blood pressure and heart rate vs. the geomagnetic disturbance index, Kp. A lesser peak in coherence was found for systolic blood pressure with Kp at a trial period of 4.16 days (P = 0.046). These results suggest that changes in geomagnetism may influence the human circulation, at least in the presence of familial cardiovascular disease risk, and they may do so at frequencies that have no precise human-made cyclic worldwide match.

The aim of this study is to assess the mode of release of renin, angiotensin II and aldosterone during in vitro superfusion of the human adrenal gland using a non-parametric combination of four randomness tests. Five normal adrenals and four aldosteronomas superfused over 270 mins were found to concomitantly release renin, angiotensin II and aldosterone. The pattern of this release exhibited a significantly non-random pulsatile character in 17 out of 23 single hormone series (p < 0.05). A further statistical combination-test analyzing the release of each hormone for all experiments with normal and pathological tissue, respectively, showed significant pulsatility (p < 0.01) in 5 out of 6 groups. The pulsatile mode of in vitro hormone release by the human adrenals indicates an active secretory process rather than a discharge of tissue-stored forms. The source of such intra-adrenal intrinsic pulse-generating mechanism could reflect the periodic course of a negative biological feedback reaction.

The scope and the details of a newly developed actometer were introduced. We are able to select a desired threshold of gravity(g)-forces between 0.01g and 0.50g and to simultaneously monitor 3 kinds of activity along with an averaged g-force every minute. As a routine study, we monitored at settings of 0.01g, 0.05g and 0.20g and averaged on one channel. Part of the time, physical activity was monitored together with ambulatorily monitored blood pressure (BP) and the ECG, or at least heart rate (HR). Physical activity showed a circasemiseptan and circaseptan periodicity as well as the circadian component, especially in subjects with an irregular sleep-wakefulness life style. On the average, physical activity was greater on a working day than on a holiday. Everyday physical activity reflects in part the ability to exercise, and it is expected that this actometer can contribute or provide an objective individualized quality-of-life index. The effect of physical activity on circadian profiles of BP, HR and HR variability is also examined. We observed that BP started to increase several hours before getting up. This fact likely shows that there is an endogenous circadian rhythm in BP, independently of the sleep-wakefulness cycle. Lastly, we investigated the relationship between physical activity and HR in patients permanently paced; we confirmed that the DDDR pacing mode was more physiological than the VVI or VVIR mode. This newly developed actometer will bring about further progress in chronobiology.