ISSN:0022-1945    

DOI:10.1080/09291018409359827

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Separate groups of banded killifish,Fundulus diaphanus,were maintained on a LD 12:12 photoregime at either 5° or 20°C for a total duration of 16 days. Following this acclimation period, blood samples were taken by cardiac puncture at six different times of day and analyzed for serum cortisol by radioimmunoassay. Fish acclimated to 20°C had a unimodal daily pattern of serum cortisol with the peak concentration occurring during the four hour period before the onset of light. The daily pattern of cortisol of the fish acclimated to 5°C was bimodal with peak cortisol values measured at the onset and the offset of light. These thermally induced changes in cortisol hormone patterns may be related to other temperature dependent seasonal changes such as the annual cycle of reproductive development or changes in the time of daily locomotor activity.

ISSN:0022-1945    

DOI:10.1080/09291018409359828

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A group of 11 healthy subjects aged 32–48 years was studied by dynamic electrocardiography. Electrocardiogram (ECG) was recorded on CM5 lead for 14 sec every 15 min during 24 h. All the subjects were under a different sleep‐wakefulness cycle, sleeping at different hours of the day. The time of midsleep was used to reference the chronobiologic evaluation of the parameters studied. Single cosinor analysis of the data revealed statistically significant circadian rhythms in: (a) heart rate (HR) and duration of QT interval for all the subjects studied; (b) ST segment displacement for the 2 subjects who were found to have it; (c) R and T waves voltage for 10 and 7 subjects, respectively. On the contrary, population mean cosinor analysis of the same data revealed statistically significant circadian rhythms only in HR and in the duration of QT interval. We conclude that only HR and QT interval relate to the sleep‐wakefulness schedule.

ISSN:0022-1945    

DOI:10.1080/09291018409359829

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The period length of the running wheel activity rhythm of cockroaches(Leucophaea maderae),which is lengthened by Li+, was found to be shortened by 0.7% by administering 50 mM RbCl in the drinking water. Replacing the Rb+solution by H2O for four weeks did not bring the period length back to the control value. This is probably due to the long biological half life of Rb+in the cells. The phenomenon is another instance in which the effect of Rb+is opposite to that of Li+.

ISSN:0022-1945    

DOI:10.1080/09291018409359830

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

To determine the effects of acute plasma volume expansion and heat exposure on the periodic oscillations of selected hormones, two doses of albumin were administered intravenously followed by exposure to heat stress (37°C, 25–30% RH). Plasma volume was previously established by a dye dilution technique using indocyanine green. During heat exposure blood samples were taken from antecubital catheters at 1, 3, 6, 9, 12, and 24 hours following completion of albumin or saline (control) infusion, and the plasma analyzed. No significant effects of heat stress or albumin administration were noted on circulating cortisol concentrations or on the diurnal/nocturnal periodicity of cortisol and aldosterone levels. There did occur a significant reduction in plasma levels of aldosterone as a result of albumin‐induced plasma volume expansion. We concluded that the duration and intensity of heat stress used in these studies had no effects on plasma hormonal levels and periodicities, but plasma volume expansion elicited a significant decrement in aldosterone concentrations.

ISSN:0022-1945    

DOI:10.1080/09291018409359831

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Cold sensitivity of last instarGalleria mellonellalarvae was investigated by measuring (1) the number of extra‐larval molts, (2) the number of larvae retaining ability to secrete silk, and (3) the number of larvae showing arrested development, after 2 h exposure to 0°C. Daily changes refer to the production of extra‐larval molts only, which are not generated by photoperiod. These variations result from (a) the time of day at which larvae molt from the penultimate into the last larval instar, (b) the sex of larvae, (c) the age of larvae at cooling, and (d) the time of day at which cooling stress was given.

ISSN:0022-1945    

DOI:10.1080/09291018409359832

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The circadian behavioral rhythm in a population ofParamecium multimicronucleatumwas examined by means of a computer/video system. A parameter, “traverse frequency”;, was introduced to index a locomotor activity of the specimens. The frequency is the average number of paramecia images per hour which individually traversed underneath photo‐cells placed on the CRT‐screen of the TV monitor. The traverse frequency was entrained and phase‐shifted by light‐dark (LD) cycles. It was highest at about 4 h after the beginning of the dark period and lowest at about 4 h after the beginning of the light period in LD 12:12 (20°C). Its rhythm free‐ran in DD and LL with about a 24 h period, the LL rhythm being relatively less stable than the DD rhythm. The free‐running period of DD rhythm was temperature‐compensated for 15–25°C. The circadian rhythmicity in the traverse frequency implies that the daily locomotor behavior ofParameciumis controlled by its circadian pacemaker.

ISSN:0022-1945    

DOI:10.1080/09291018409359833

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

An increase in body temperature (Tb) observed in pinealectomized (Px) early winter pigeons as opposed to sham‐operated (SPx) ones, at two as well as three weeks post‐surgery, was found to have disappeared when examined one year later during corresponding season. Following this one‐year post‐surgery period under 12‐h daily photoperiod and 25°C ambient temperature (Ta), neither a 3‐week exposure to continuous light nor a 1‐week exposure to continuous darkness was found to produce any difference in Tbbetween Px and SPx pigeons.

ISSN:0022-1945    

DOI:10.1080/09291018409359834

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Three different patterns were found in the locomotor activity rhythm of the cockroachLeucophaea maderae,when exposed to cycles of 12 h red light: 12 h dark (RD) at constant temperature: en trainment, relative coordination, and free‐run. The different reactions were only weakly correlated with the energy ranges of the red light. Instead, the free‐running period and the previous state of the rhythm were most decisive. Entrainment to RD occurred when the free‐running period in constant conditions was close to 24 h (23.8±0.07h, SE), while animals showing shorter average period lengths in constant conditions (23.0±0.06 h or 23.0 h±0.11 h) exhibited in RD relative coordination or an unaffected free‐run, respectively. Following stepwise reduction of the red light energy to 0.5μW/cm2, rhythms remained entrained in all cases as long as they had been entrained before, and the RD cycle was not phaseshifted. After a shift, however, re‐entrainment failed, even when the light energies were one log unit higher (5μW/cm2). The results are consistent with properties of a system of unilaterally coupled non‐linear oscillators: the circadian rhythm reacts to RD like a driven self‐sustained pacemaker does, which is weakly coupled to a forcing oscillation.

ISSN:0022-1945    

DOI:10.1080/09291018409359835

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0022-1945    

DOI:10.1080/09291018409359826

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor