摘要:

Well-expressed endogenous circadian rhythms inAcetabularia acetabulumwere spectrally analyzed and recorded in time-period distributions. The stability of the circadian periods under constant conditions and their changes could be monitored continually in step sizes close to the circadian period length. The resolution of period estimates of the circadian component was increased by a factor of 4–10 by adapting analyzed interval lengths to full period sizes of the corresponding main component. Methodological aspects of the applied algorithms are discussed by means of examples that measure the temperature dependency of the circadian period.

ISSN:0742-0528    

DOI:10.3109/07420529409057226

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Pineal melatonin production was estimated by means of urinary 6-sulfatoxymelatonin (aMT6s) determination in two groups of female rats for 1 year each. Seasonal changes of nocturnal aMT6s excretion were found with peak levels in summer despite constant photoperiods. We hypothesize that the horizontal component H of the geomagnetic field may act as a seasonal zeitgeber because H shows a similar seasonal rhythm, and changes in the direction and intensity of H can affect pineal activity. The observed seasonal changes of pineal melatonin production stress that despite constant environmental conditions, endocrine experiments require consideration of season, neglect of which may lead to contradictory results.

ISSN:0742-0528    

DOI:10.3109/07420529409057227

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Tryptophan hydroxylase activity has been measured in synaptosomal preparations from rat brain. A significant circadian variation in enzyme activity was apparent in corpus striatum, (p<0.001), brainstem and cortex (p<0.01). A single dose of clomipramine or mianserin (20 mg/kg) had no effect on brainstem enzyme activity measured at mid-light or mid-dark. Chronic administration (7.5 mg/kg i.p. twice daily for 2 weeks) of either clomipramine or mianserin significantly increased enzyme activity. There was no significant difference between the drug effects measured at mid-light or mid-dark.

ISSN:0742-0528    

DOI:10.3109/07420529409057228

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

To evaluate whether circadian rhythms in blood pressure and heart rate are influenced by age, we analyzed 24-h ambulatory blood pressure and heart rate recordings from 31 patients with primary hypertension. Data were collected during hospitalization, after a drug-free run-in period. Set times were administered for lights-on, meals, and lights-off. Daytime napping was prohibited. The patients were divided into sex-matched groups of young (group I: 25-45 years, n = 9), middle-aged (group II: 47-57 years, n = 11), and old (group III: 57-74 years, n = 11) subjects. Hourly data were analysed by fitting a two-component cosine function (24- and 12-h periods). Amplitudes of the circadian rhythms in systolic blood pressure and heart rate were significantly reduced with age. This finding could be partly attributed to the recording of higher nocturnal values in older patients. Elderly hypertensives also evidenced a significantly greater ultradian component (12-h period) in the systolic blood pressure rhythm than did young patients, with the secondary afternoon decline in blood pressure being more pronounced in groups II and III. The 24-h acrophase of heart rate was found to occur 1.6 h earlier than that of systolic blood pressure in the young group (p<0.01). This phase advance of heart rate compared with systolic blood pressure was reduced to 1 h in group II (p0.1). These results indicate that circadian blood pressure and heart rate profiles of primary hypertensives change with age. Since measures were obtained in a typical clinical setting, these findings have implications for the diagnosis and treatment of hypertension in the elderly. The marked afternoon decline in blood pressure for the elderly patients may also render conventional cosinor analysis inappropriate for accurate description of the circadian rhythms of geriatric hypertensives.

ISSN:0742-0528    

DOI:10.3109/07420529409057229

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Two different medications, one assumed to be a tranquilizer and the other an antifatigue agent, were tested. Both were found to be ineffective and thus were viewed as placebos and named P1 and P2. The effect of P1 and P2 on the circadian rhythms of a set of variables (e.g., sleep/wake, oral temperature and grip strength of both hands) were monitored by five to 10 measurements per day over three consecutive 8- to 10-day spans. The first documented span was a control (no medication), and the second and third spans (in randomized order) were under P1 and P2. Healthy subjects volunteered for the studies: nine men and seven women (median age 28 years) in study 1 and 12 men and 12 women (median age 36 years) in study 2. They were synchronized with diurnal activity from 07:00 h (±30 min) to 00:00 h (±1 h) and nocturnal rest. De Prins' method was used to obtain the prominent periodτin each (control, P1, and P2) individual time series. Theχ2test was used to test group and subgroup differences. All 40 subjects exhibited a significant sleep/wake rhythm with a±= 24 h in control, P1, and P2 series. During the control span a gender-related statistically significant difference was observed: fewer men than women exhibited a temperature rhythm desynchronized from 24 h. In addition, more women than men had aτ<24 h during control. The gender-related difference was obliterated by placebos. Similarly desynchronized circadian rhythms of left and right hand-grip strength were observed in both men and women during the control span, which were all obliterated by placebo but only in men. Results are discussed with regard to a genetic model of human dyschronism as proposed by the authors.

ISSN:0742-0528    

DOI:10.3109/07420529409057230

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

To provide an objective measure of the effects of on-call stress on the blood pressure (BP) of a group of pediatric residents, we used a Space Labs Ambulatory Blood Pressure Monitor (ABPM) to compare 37 pediatric residents' on- and off-call BPs. Residents wore the ABPM for 24 h (once on call and again off call) to assess systolic and diastolic BPs every 30 min during the day and hourly overnight. We found significantly higher MESOR (an acronym for midline estimating statistic of rhythm, which yields a mean value more representative of the true mean than an average of a series of measurements) BPs and BP loads (%BP readings>135 mm Hg for systolic and/or 85 mm Hg diastolic) during the on-call period. Some residents became hypertensive on call, and the normal 24-h pattern of lower nighttime blood pressures was altered during this period. ABPM monitoring may prove useful in evaluating the effectiveness of interventions to reduce the stress of residency training.

ISSN:0742-0528    

DOI:10.3109/07420529409057231

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

ISSN:0742-0528    

DOI:10.3109/07420529409057232

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor