Circadian rhythms in hot flashes in natural and surgically-induced menopause

The aim of this study was to investigate circadian and ultradian variations in menopausal hot flash. The number of hot flashes per 2-hr period was collected from 25 diurnally-active, perimenopausal women for 1 week in January or February of each year for 3 consecutive years. Fourteen women were experiencing natural menopause (NM) (mean age 51.9 years) and 11 were experiencing surgically-induced menopause (SIM) (mean age 52.0 years). The difference in the number of hot flashes between the two types of menopause at each clock time was not statistically significant; neither was the mean number of hot flashes per 24 hr different between the two groups (Student's t-test). Data when normalized for each woman and placed end-to-end revealed by cosinor analysis circadian rhythmicity in the SIM group (P = 0.02) but not in the NM group. A 12-hr periodicity was detected in both groups (P less than 0.001 for both). An 8-hr rhythm was detected only for the NM group (P = 0.04). Both groups combined exhibited statistically significant rhythmicities with periods of 24 hr (P = 0.003), 12 hr (P less than 0.001) and 8 hr (P = 0.005). Regardless of the type of menopause, the women could be separated into two groups based on the temporal pattern of hot flashes during the day. One group was defined by the occurrence of peak frequency of flashes during the morning (0400-0959), while the second group was defined by the occurrence of the peak in the evening (1600-2159).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Season and Light Treatment Upon Hot Flashes in a Perimenopausal SAD Patient

A perimenopausal woman with seasonal affective disorder (SAD, winter depression) presented with a 2-year history of hot flashes occurring only in the wintertime. Prospectively documented hot flashes appeared to follow a seasonal rhythm and a bimodal circadian rhythm. The hot flashes decreased with morning, but not evening, light therapy. These observations are discussed in the context of the literature regarding light's possible role in animal and human reproductive functioning.     

Therapeutic advantage of unequal dosing of theophylline in patients with nocturnal asthma

Two theophylline treatments were compared in a randomized, multiple-dose, crossover study on 20 patients present with nonallergic bronchial asthma. Both products (E = Euphyllin CR, A = Afonilum Retard) were capsules containing micropellets. They were administered according to the recommendations of the manufactures and differed in the total daily theophylline dose (642 mg versus 500 mg), the partition of this dose (1/3 in the morning and 2/3 in the evening versus equal amounts in the morning and evening) and the timing of the evening dose (2200 hr versus 2000 hr). The patients were off oral theophyllines at least 2 days prior to study onset and no other drugs were allowed to be administered during the testing periods. On the 4th day of each study period, serum theophylline concentrations (STC) and peak expiratory flow rate (PEF) were determined every 2 hr. Compared with the 24-hr PEF reference profile taken prior to study onset, both theophylline treatments produced a significantly higher 24-hr PEF average (mesor). Treatment E resulted in significantly higher mesor than A; in addition, the PEF amplitude relative to the mesor was reduced by treatment E when compared with placebo.     

Day-night differences in effects of cosmetic treatments on facial skin. Effects on facial skin appearance

Two groups of 24 healthy caucasian women, similar with regard to age classes (from 19 to 55) as well as fair and dark complexion of skin and hair, volunteered to use during a 14-day span a conventional facial cream (active placebo: AP) and thereafter, during a 21-day span Noctosome (Noctos). The latter is a new generation of liposome made with non-ionic lipids leading to microspheres which include glycopeptides in the aqueous compartment of the vesicle, alpha-tocopherol ester in the membrane-like structure and sphingo-ceramides at the surface of the microspheres. The aim of the study was to test the beneficial effects of Noctos (vsAP) with respectively morning (7-9-hr) and evening (21-23-hr) applications as facial ointments. Observed differences were validated using several statistical tests: ANOVA, cosinor, etc. Subjects were socially synchronized with a diurnal activity from 7 hr to 23 hr and a nocturnal rest. Each day, at fixed clock hours (7, 10, 20 and 23 hr), each subject used visual analogue scales to self-rate a set of variables characterizing facial aspects. Brilliance of complexion and texture of skin exhibited a circadian rhythm (peak time at 10 hr), both with AP and Noctos. The latter produces a beneficial effect with regard to reference values (AP). The evening application of Noctos is more efficient than the morning one. However, the magnitude of this beneficial effect is related both to age (greater for the age class 25-35 years than for younger and older subjects) and to skin complexion (greater for fair than dark complexioned subjects). Major beneficial effects of Noctos in the evening hours are related neither to fatigue nor to mood of the women since the respective circadian rhythms of these variables appear to vary independently from those of facial skin characteristics.     

Effect of oral gamolenic acid from evening primrose oil on menopausal flushing.

OBJECTIVE--To evaluate the efficacy of gamolenic acid provided by evening primrose oil in treating hot flushes and sweating associated with the menopause. DESIGN--Randomised, double blind, placebo controlled study. SETTING--District general hospital and teaching hospital. SUBJECTS--56 menopausal women suffering hot flushes at least three times a day. INTERVENTION--Four capsules twice a day of 500 mg evening primrose oil with 10 mg natural vitamin E or 500 mg liquid paraffin for six months. MAIN OUTCOME MEASURES--Change in the number of hot flushes or sweating episodes a month. RESULTS--56 diaries were analysed, 28 from women taking gamolenic acid and 28 from those taking placebo. Only 18 women given gamolenic acid and 17 given placebo completed the trial. The mean (SE) improvement in the number of flushes in the last available treatment cycle compared with the control cycle was 1.9 (0.4) (P < 0.001) for daytime flushes and 0.7 (0.3) (P < 0.05) for night time flushes in women taking placebo; the corresponding values for women taking gamolenic acid were 0.5 (0.4) and 0.5 (0.3). In women taking gamolenic acid the only significant improvement was a reduction in the maximum number of night time flushes (1.4 (0.6); P < 0.05). CONCLUSION--Gamolenic acid offers no benefit over placebo in treating menopausal flushing.     

Geographical distribution of hot flash frequencies: considering climatic influences

Laboratory studies suggest that hot flashes are triggered by small elevations in core body temperature acting within a reduced thermoneutral zone, i.e., the temperature range in which a woman neither shivers nor sweats. In the present study, it was hypothesized that women in different populations develop climate-specific thermoneutral zones, and ultimately, population-specific frequencies of hot flashes at menopause. Correlations were predicted between hot flash frequencies and latitude, elevation, and annual temperatures. Data on hot flash frequencies were drawn from 54 studies. Pearson correlation analyses and simple linear regressions were applied, first using all studies, and second using a subset of studies that included participants only to age 60 (n = 36). Regressions were repeated with all studies, controlling for method of hot flash assessment. When analyses were restricted to studies that included women up to age 60, average temperature of the coldest month was a significant predictor of hot flash frequency (P < 0.01), explaining 29.2% of the variation in hot flash frequency. In a separate equation, the difference between hottest and coldest temperatures was also a significant predictor (P < 0.01), explaining 26.4% of the variation in hot flash frequency. When regressions used all studies but controlled for method of hot flash assessment, average temperature of the coldest month, difference between hottest and coldest temperatures, and mean annual temperature were significant predictors of hot flash frequency. Women reported fewer hot flashes in warmer temperatures, and more hot flashes with increasing seasonality. These results suggest that acclimatization to coldest temperatures or sensitivity to seasonality may explain part of the population variation in hot flash frequency.     

The effects of time of day-specific resistance training on adaptations in skeletal muscle hypertrophy and muscle strength: A systematic review and meta-analysis

The present paper endeavored to elucidate the topic on the effects of morning versus evening resistance training on muscle strength and hypertrophy by conducting a systematic review and a meta-analysis of studies that examined time of day-specific resistance training. This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines with searches conducted through PubMed/MEDLINE, Scopus, and SPORTDiscus databases. The Downs and Black checklist was used for the assessment of the methodological quality of the included studies. Studies that examined the effects of time of day-specific resistance training (while equating all other training variables, such as training frequency and volume, between the groups) on muscle strength and/or muscle size were included in the present review. The random effects model was used for the meta-analysis. Meta-analyses explored (1) the differences in strength expression between morning and evening hours at baseline; (2) the differences in strength within the groups training in the morning and evening by using their post-intervention strength data from the morning and evening strength assessments; (3) the overall differences between the effects of morning and evening resistance training (with subgroup analyses conducted for studies that assessed strength in the morning hours and for the studies that assessed strength in the evening hours). Finally, a meta-analysis was also conducted for studies that assessed muscle hypertrophy. Eleven studies of moderate and good methodological quality were included in the present review. The primary findings of the review are as follows: (1) at baseline, a significant difference in strength between morning and evening is evident, with greater strength observed in the evening hours; (2) resistance training in the morning hours may increase strength assessed in the morning to similar levels as strength assessed in the evening; (3) training in the evening hours, however, maintains the general difference in strength across the day, with greater strength observed in the evening hours; (4) when comparing the effects between the groups training in the morning versus in the evening hours, increases in strength are similar in both groups, regardless of the time of day at which strength assessment is conducted; and (5) increases in muscle size are similar irrespective of the time of day at which the training is performed.     

Heart Rate Orcadian Rhythm as a Biological Marker of Desynchronization in Major Depression: A Methodological and Preliminary Report

Heart rate (HR) was continuously monitored during successive 24-hr periods in 19 healthy subjects and 26 major depressed patients (DSM III-R). Recordings were performed after a 2-week wash-out period and the morningness or eveningness typology of each subject was determined. The chronobiological parameters and rhythm percentage (RP) were calculated by the single cosinor method from the smoothed HR curves of each subject. In normal subjects, HR follows a circadian rhythm (RP > 65%) with the lowest values at night. Morning type subjects have an earlier peak time (13:30) than evening type subjects (17:30). Major depressive patients were split into two groups; in the first one HR circadian rhythm was still present (RP > 63%) with a decrease in amplitude (24%) while in the second group, no circadian rhythm of HR could be detected (RP < 25%, decrease in amplitude > 70%). In the group of patients with a persisting HK circadian rhythm, no veritable phase advance was observed. Our results suggest that circadian HR rhythm, which can be easily studied with non-invasive methods, might represent a chronobiological marker of some depressions. Given the lag that exists between the rhythms of morning type and evening type subjects, our study also stresses the importance of taking into account this behavioural trait in chronobiological studies.     

Dosing Time Optimizes Sustained-Release Ketoprofen Treatment of Osteoarthritis

A double-blind randomized parallel-group trial was undertaken to evaluate the influence of the dosing time of sustained-release ketoprofen (SRK) on its acceptability and efficacy. The SRK was prescribed for 2 weeks (200 mg once a day) to 117 outpatients with osteoarthritis of the knee and/ or hip. One group received SRK in the morning (at 8 a.m.) and the other group in the evening (at 8 p.m.). The principal aim of the trial concerned the acceptability, whereas efficacy was its secondary aim. The principal trial criterion was defined as the number of spontaneous recordings of adverse effects. Results showed clearly that the acceptability of SRK in the SRK morning group was worse than that in the evening group (39% of patients with one or more adverse effects in the SRK morning group versus 19% in the evening group; p = 0.019). It is important to stress the difference concerning the number of adverse effects (48 for SRK morning group versus 23 for SRK evening group; p = 0.0234). The analgesic efficacy seemed to be similar, but one criterion was statistically significant: The duration of analgesic efficacy was more important for the SRK evening group than for the morning group (9.37 and 5.47 h, respectively; p = 0.001). To increase its acceptability, evening administration of SRK seems to be preferred over morning administration in osteoarthritis. However, other trials of the same type, assessing other antiinflammatory agents, are necessary before a general extrapolation of such results can be undertaken.     

Treatment of Nocturnal Asthma: the Role of Sustained-Release Theophylline and Oral β-2-Mimetics

In two double-blind, multiple-dose cross-over studies the therapeutic effects of SR theophylline preparations given once each night (mean 11.2mg/kg per day) versus twice daily in equal doses (mean 10.3 mg/kg per day) (study I) and SR-terbutaline in equal doses (mean 0.25 mg/kg per day) versus SR theophylline in unequally divided daily doses (mean 5.3 mg/kg morning dose, 10.6 mg/kg evening dose) study II) were compared in 19 patients with nocturnal asthma. At the end of each treatment period drug serum concentrations and PEFR were measured every 2 hr over a 24-hr period. With the twice-daily, equally divided regimen, serum theophylline concentrations were lower at night than during the day (mean 9.4 ±0.9 versus 11.3± 1.0mg/l). With the single evening administration, serum theophylline concentrations were considerably higher at night (C_max16.3 ±1.4 mg/1) and the circadian variation of PEFR was significantly reduced. PEFR was higher during night and early morning (283 ±14 versus 217 ± 11 l/min, P< 0.005). During daytime in study II, PEFR values were slightly higher with theophylline than terbutaline. There was no significant difference in peak flow between either treatment during the night and early morning. However, additional use of inhaled β-2-mimetics because of asthmatic attacks occurred more often during terbutaline (79 times in 8/10 patients) than theophylline treatment (29 times in 5/10 patients). Symptom scores, number of attacks and side-effects clearly favor the theophylline regimen. We conclude that for patients with nocturnal asthma a once-nightly dose of SR theophylline can be sufficient for stabilization of the airways.     

Combination of meal and exercise timing with a high-fat diet influences energy expenditure and obesity in mice

In mice, obesity has been observed not only in those freely fed a high-fat diet (HFD) but also in those fed while physically inactive. In contrast, a HFD during physically active periods protects against obesity and the impairments in the circadian rhythm induced by free feeding of a HFD. Although exercise is known to be effective for obesity prevention and management, the optimal timing of exercise has not yet been determined. In the present experiments, we aimed to determine the best combination of daily timing of HFD consumption and exercise for the prevention of HFD-induced weight gain in mice. In this experiment, “morning” refers to the beginning of the active phase (the “morning” for nocturnal animals). Increases in body weight related to free feeding of a HFD was significantly reduced with 4?h of exercise during the late (evening) or middle (noon) active period compared to 4?h of exercise during the early (morning) active period or free access to exercise, which resulted in hours of exercise similar to that of morning exercise. These results suggested that eating in the morning or at noon followed by exercise in the evening could prevent weight gain more effectively than exercise in the morning followed by eating at noon or in the evening. The group fed a HFD for 4?h in the morning had lower body weight than the group fed a HFD for 4?h in the evening without exercise. The last group of experiments tested the hypothesis that there would be an interaction between mealtime and exercise time (i.e. time of day) versus order (i.e. which comes first) effects. We compared groups that exercised for 4?h at noon and were fed either in the morning or evening and groups that were fed for 4?h at noon and either exercised in the morning or evening. We found that the groups that were fed before exercise gained less body and fat weight and more skeletal muscle weight compared to the groups that exercised before eating. Corresponding to the body and fat weight changes, the respiratory exchange ratio (RER) was lower and energy expenditure was higher in the groups fed before exercise than in the groups fed after exercise, and these effects on energy metabolism were also observed in the early stage of HFD feeding before obesity. When obese mice fed a HFD for 12 weeks were exposed to a combination of feeding and exercise timing in an effort to reduce body weight, eating followed by exercise resulted in greater weight loss, similar to the experiments conducted to prevent weight gain. These results demonstrate that a combination of daily timing of eating and exercise may influence weight gain and that eating followed by exercise may be effective for minimizing increases in body and fat weight as well as maximizing increases in skeletal muscle weight.     

A Behavioral Group Treatment Program for Menopausal Hot Flashes: Results of a Pilot Study

In the present study, we tested the effectiveness of a cognitive-behavioral group treatment (CBGT) for hot flashes in menopausal women. Treatment was administered over 8, 90 min weekly sessions and consisted of education, relaxation training and cognitive restructuring. Nineteen women meeting STRAW staging criteria for the menopause transition (stages –1 to +1) were randomly assigned to immediate or delayed treatment (wait list) and were asked to monitor their hot flashes and night sweats prospectively. They also completed questionnaires, including the Womens Health Questionnaire and the Menopause Specific Quality of Life Questionnaire to determine psychosocial benefits of treatment. Results suggested that the CBGT was moderately successful in reducing the frequency of total vasomotor symptoms [F (1, 17) = 6.16, p < .01], as measured by daily symptom diaries. While there were arithmetic improvements in psychosocial functioning in this sample, these results were not significant. Despite the limitations of small sample size and possible placebo effect, this pilot study supports the notion that cognitive-behavioral interventions aimed at reducing vasomotor symptoms may be of value for menopausal hot flashes when administered in a small-group format.     

Circadian Variation in Human Performance Evaluated By the Walter Reed Performance

-As part of a two clock-time (0830 versus 2030) evaluation of administration-time dependent effects of dexedrine (S mg) and triazolam (0.25 mg) on human cognitive performance, placebo (control) studies were conducted on 12 diurnally active (0700-2300) male adults (23-38 yrs) using a double-blind, randomized crossover design. Testing was conducted hourly during a series of sleepless 13-hr spans commencing in the morning or evening, using the Walter Reed computer controlled and scored multi-task cognitive performance assessment battery. For the placebo condition, Single and Group Cosinor analyses documented circadian rhythms in performance for most tasks (reaction time, logical reasoning, serial add/subtract and spatial orientation) both for individuals and the group. Overall, performance was worse overnight, when sleepiness was greatest, and best between 1830 and 2030. It was most variable around 0600-0700. The day-night variation in performance over all cognitive tests amounted to 21% of the 24-hr mean.     

Theophylline Steady-State Pharmacokinetics: Recent Concepts and Their Application in Chronotherapy of Reactive Airway Diseases

With the introduction of sustained-release theophyllíne formulations for once-daily dosing or for unequally divided twice-daily dosing, comparison with conventional equally divided twice-daily dosing has been focused on nocturnal serum theophylline concentrations (STCs), plateau properties and peak-trough fluctuation. The merits of various steady-state characteristics such as nocturnal excess, plateau time, residual concentration, peak-trough fluctuation, swing and AUC fluctuation are illustrated by 15 data sets from 7 multiple-dose studies, each including either 10–12 healthy volunteers or 12–20 COPD-patients. In all of the studies, STCs were determined at least every 2 hr over a 24-hr period in steady-state. Included in the studies were 7 sustained-release theophylline formulations which were administered either once daily (in the morning or in the evening), or twice daily (either equally divided, or unequally divided with one-third of the dose being given in the morning and two-thirds in the evening).     

Circadian Rhythm of Gastric Acid Secretion in Active Duodenal Ulcer: Chronobiological Statistical Characteristics and Comparison of Acid Secretory and Plasma Gastrin Patterns with Healthy Subjects and Post-Vagotomy and Pyloroplasty Patients

Twenty-one male patients with active duodenal ulcer underwent hourly 24-hr gastric acid collections under controlled, calorically deprived conditions. The 24-hr hourly acid secretory output for the group displayed a statistically significant (p < 0.001) rhythm, with peak rates occurring during the evening hours and low rates during the early morning hours, by population-mean cosinor statistical analysis. Population-mean cosinor analysis also verified the occurrence of a significant (p=0.034) circadian rhythm in unstimulated acid secretion in a group (N=14) of healthy male subjects similarly studied and reported previously. In contrast, population-mean cosinor analysis confirmed the absence of any detectable circadian rhythm in unstimulated acid secretion in a group (N=17) of post-vagotomy and pyloroplasty patients studied 2-11 years after surgery. Population-mean cosinor analysis of 4-hr plasma gastrin determinations, obtained in all groups during the 24-hr gastric acid collection, revealed an absence of any detectable circadian rhythm in plasma gastrin. This latter finding is compatible with the interpretation that the circadian rhythm of unstimulated gastric acid secretion, observed in the clinically healthy and active ulcer groups, is unrelated to changes in plasma gastrin levels. The employment of quantitative chronobiological inferential statistical techniques is important to the analysis of any time-dependent measurement in gastrointestinal function, of which gastric acidity is one example.     

Chronotype and postmenopausal breast cancer risk among women in the California Teachers Study

ABSTRACT

Chronotype is the behavioral manifestation of an individual’s underlying circadian rhythm, generally characterized by one’s propensity to sleep at a particular time during the 24 hour cycle. Evening chronotypes (“night owls”) generally suffer from worse physical and mental health compared to morning chronotypes (“morning larks”) – for reasons that have yet to be explained. One hypothesis is that evening chronotypes may be more susceptible to circadian disruption, a condition where the coordinated timing of biologic processes breaks down. The role of chronotype as an independent or modifying risk factor for cancer has not been widely explored. The objective of the current study was to evaluate the risk of breast cancer associated with chronotype in a case-control study nested within the California Teachers Study (CTS) cohort. The study population consisted of 39686 post-menopausal CTS participants who provided information on chronotype by completing a questionnaire in 2012–2013. 2719 cases of primary invasive breast cancer diagnosed from 1995/1996 through completion of the chronotype questionnaire were identified by linkage of the CTS to the California Cancer Registry. 36967 CTS participants who had remained cancer-free during this same time period served as controls. Chronotype was ascertained by responses to an abbreviated version of the Horne-Ostberg Morningness-Eveningness Questionnaire (MEQ) and was characterized into five categories: definite morning, more morning than evening, neither morning or evening, more evening than morning, definite evening. Multivariable unconditional logistic regression analyses were performed to estimate the odds ratios (ORs) and 95% confidence intervals (95% CIs) for each of the chronotypes, adjusted for established breast cancer risk factors. Compared to definite morning types, definite evening types had an increased risk of breast cancer with elevated ORs that were statistically significant in both the crude (OR = 1.24, 95% CI: 1.10–1.40) and fully-adjusted models (OR = 1.20, 95% CI: 1.06–1.35). The risk estimates in the fully-adjusted model for all other chronotypes did not significantly differ from one. These results suggest that evening chronotype may be an independent risk factor for breast cancer among a population of women who are not known to have engaged in any substantial night shift work. Further research in other populations of non-shift workers is warranted.     

Circadian Variation in Human Performance Evaluated By the Walter Reed Performance

–As part of a two clock-time (0830 versus 2030) evaluation of administration-time dependent effects of dexedrine (S mg) and triazolam (0.25 mg) on human cognitive performance, placebo (control) studies were conducted on 12 diurnally active (0700–2300) male adults (23–38 yrs) using a double-blind, randomized crossover design. Testing was conducted hourly during a series of sleepless 13-hr spans commencing in the morning or evening, using the Walter Reed computer controlled and scored multi-task cognitive performance assessment battery. For the placebo condition, Single and Group Cosinor analyses documented circadian rhythms in performance for most tasks (reaction time, logical reasoning, serial add/subtract and spatial orientation) both for individuals and the group. Overall, performance was worse overnight, when sleepiness was greatest, and best between 1830 and 2030. It was most variable around 0600–0700. The day-night variation in performance over all cognitive tests amounted to 21% of the 24-hr mean.     

Should obstetricians see women with normal pregnancies? A multicentre randomised controlled trial of routine antenatal care by general practitioners and midwives compared with shared care led by obstetricians.

OBJECTIVE--To compare routine antenatal care provided by general practitioners and midwives with obstetrician led shared care. DESIGN--Multicentre randomised controlled trial. SETTING--51 general practices linked to nine Scottish maternity hospitals. SUBJECTS--1765 women at low risk of antenatal complications. INTERVENTION--Routine antenatal care by general practitioners and midwives according to a care plan and protocols for managing complications. MAIN OUTCOME MEASURES--Comparisons of health service use, indicators of quality of care, and women''s satisfaction. RESULTS--Continuity of care was improved for the general practitioner and midwife group as the number of carers was less (median 5 carers v 7 for shared care group, P<0.0001) and the number of routine visits reduced (10.9 v 11.7, P<0.0001). Fewer women in the general practitioner and midwife group had antenatal admissions (27% (222/834) v 32% (266/840), P<0.05), non-attendances (7% (57) v 11% (89), P<0.01) and daycare (12% (102) v 7% (139), P<0.05) but more were referred (49% (406) v 36% (305), P<0.0001). Rates of antenatal diagnoses did not differ except that fewer women in the general practitioner and midwife group had hypertensive disorders (pregnancy induced hypertension, 5% (37) v 8% (70), P<0.01) and fewer had labour induced (18% (149) v 24% (201), P<0.01). Few failures to comply with the care protocol occurred, but more Rhesus negative women in the general practitioner and midwife group did not have an appropriate antibody check (2.5% (20) v 0.4% (3), P<0.0001). Both groups expressed high satisfaction with care (68% (453/663) v 65% (430/656), P=0.5) and acceptability of allocated style of care (93% (618) v 94% (624), P=0.6). Access to hospital support before labour was similar (45% (302) v 48% (312) visited labour rooms before giving birth, P=0.6). CONCLUSION--Routine specialist visits for women initially at low risk of pregnancy complications offer little or no clinical or consumer benefit.     

Aging alters properties of the circadian pacemaker controlling the locomotor activity rhythm in males of Drosophila nasuta

Effects of aging on the circadian rhythm of locomotor activity in males of Drosophila nasuta were investigated. The adult life of males was divided in 1-3 stages according to spontaneous changes in free-running period x in constant darkness (DD): stage 1, days 1-19; stage 2, days 20-36; stage 3, days 37-43. Stage 1 was characterized by a bimodal activity pattern with a short light-induced morning peak and a prolonged evening peak when the flies were entrained to light-dark cycles of 12 hours of light, 12 hours of darkness (LD 12:12). The morning peak had a phase angle difference Ψ_m (Ψ, the time from lights on in LD 12:12 cycles to the onset of morning peak) of about 0.1h, while Ψ_e (Ψ of evening peak) was about 9h at stage 1. The transient morning peak was curtailed at the end of stage 1. At stage 2, the Ψ_e was about 10h, and the activity end was delayed by an addition of about 3h of activity in the scotophase. The changes in W during DD free runs were determined in two groups of flies: flies reared in LD 12:12 and flies reared in DD. In both groups, W increased from about 23h at stage 1 to about 25h at stage 2. Stage 3 was characterized by arrhythmicity associated with highest mean activity level (total number of passes/fly/day) in the entrained and both free-running groups. The mean activity level increased significantly from stage 1 to stage 3 in all three groups of flies.