Biological Rhythm Research

Tabuchi, Hitoshi; Kiuchi, Yoshiaki; Nakakura, Shunsuke; Ohhara, Zaigen

doi: 10.1080/09291016.2011.599649pmid: N/A

The purpose of the article is to investigate the diurnal variation of intraocular pressure (IOP) in glaucoma patients by periodic regression analyses using two-way analysis of variance (ANOVA). Seventy-two open-angle glaucoma patients participated in this study and IOP measurements were taken in this group every 2 h during waking hours. Patients were categorized based on the Glaucoma staging system (GSS) into “severe” (GSS > stage 2) and “less severe” (GSS ≤ stage 2) groups. They were also categorized into high tension (IOP ≥ 19 mmHg) and low tension (IOP < 19 mmHg) groups. Diurnal IOP curves were plotted and analyzed for all patients and for each subgroup by periodic regression analysis with two-way ANOVA. Results showed that all diurnal IOP curves from all patients and all subgroups statistically fitted periodic regression curves within a 24-h period (p < 0.0001, two-way ANOVA for all categories). It is concluded that IOP exhibits a 24-h circadian rhythm in glaucoma patients during waking hours.

Sun, Nan; Qu, Chen; Zhao, Shaochen; Yu, Liyan; Zheng, Xifu

doi: 10.1080/09291016.2011.605626pmid: N/A

Hormonal cycle modulates arousal circuitry. Animal experiments suggested that progesterone enhanced fear-potentiated startle. At present, direct electrophysiological evidence of a gender difference in novel and unpredictive stimuli is still sparse. Ten men and 23 women at one of two different stages of the menstrual cycle (menses phase, WM, and luteal phase, WL) were examined for event-related potential evidence of attention allocation in the oddball task phase (OTP) and predictive task phase (PTP). We used two tones, 1 kHz 80% as standard stimuli and 2 kHz 20%, as novel stimuli presented randomly in OTP. In PTP, every novel stimuli fixed followed a white noise, but 1 kHz tones never followed white noise. The results showed: (1) In OTP, the P3 amplitude in the WL group during the 350–400-ms time window was higher than that of the other two groups. (2) In PTP, no difference was observed between the groups with respect to the amplitude of contingent negative variation during the 1080–1180 ms and 1320–1360 ms time windows. Thus, it is concluded that women in WL present modulated autonomic arousal, but no difference to predictive negative stimuli than women in WM and men.

Vaidya, Nishtha; Pati, Atanu Kumar; Parganiha, Arti

doi: 10.1080/09291016.2011.605629pmid: N/A

Blood pressure variability (BPV) is one of the recognized risk factors for different types of cardiovascular diseases (CVDs). Several physiological, behavioral and ethnic factors are known to modulate blood pressure (BP). Such studies on the population of southeast India are altogether absent. It is worthwhile, therefore, to examine the circadian variability in systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) and nocturnal dipping pattern in BP in apparently healthy human subjects as a function of gender. Sixty females and 40 males voluntarily participated in the study. All subjects wore an Ambulatory Blood Pressure Monitor (ABPM, TM 2430) for two to four consecutive days. SBP, DBP and HR was measured every 15 and 30 minutes between 07:00–22:00 and 22:00–07:00 hrs, respectively. In addition, double product (DP) and mean arterial pressure (MAP) were also computed. Data were analyzed using A&D, Cosinor and Spectre software. Prevalence of extreme dipper, dipper and non-dipper was 13%, 63% and 24%, respectively. A statistically significant circadian rhythm was validated in all studied variables, irrespective of gender and dipping pattern in BP. However, the rhythm detection ratio was low among non-dippers. Chi-square test revealed a statistically significant association of the frequency of prominent periods of SBP and MAP with nocturnal dipping categories. Further, significant differences for the circadian Mesors of SBP, DBP, HR, DP and MAP and acrophase of DBP and MAP were noticed between males and females. Dipping pattern produced a significant effect on the rhythm characteristics of all the studied variables. On the basis of our findings we can conclude that variability in BP may be associated with factor gender to some extent, whereas nocturnal dipping in BP is independent of gender. Interestingly in the present study about 24% subjects are non-dippers, which may be an indication of higher risk of CVDs among individuals belonging to younger generation of this region. However, further extensive study is desirable to strengthen the above conjecture.

Danielsson, Katarina; Markström, Agneta; Stridsberg, Mats; Broman, Jan-Erik

doi: 10.1080/09291016.2011.605631pmid: N/A

Dim light melatonin onset (DLMO) is defined as the start of the melatonin production in the evening during dim light conditions and has become a reliable phase marker of the circadian clock. The aim of the study was to investigate DLMO and its association with sleep timing and diurnal preferences in healthy working adults during real-life conditions. Fourteen adults were investigated. A sleep diary was kept during the preceding week, but no fixed sleep–wake schedule was implemented. Diurnal preferences were measured with the Horne–Östberg Morningness–Eveningness Questionnaire. DLMO was defined as the time point when melatonin in saliva exceeded a threshold of 3 ng/L. Results showed that DLMO appeared in the expected time interval but was not significantly associated with sleep timing or diurnal preference. The results illustrate the complexity of monitoring sleep patterns in real-life settings.

Ding, Yi; Jia, YanYan; Liu, WenXing; Lu, ChengTao; Zhu, YanRong; Yang, Jing; Ding, LiKun; Yang, Lin; Wen, AiDong

doi: 10.1080/09291016.2011.605639pmid: N/A

Few researches were conducted on the circadian variation of β-lactam antibiotics in humans. The aim of the present study was to determine whether circadian variation of cefalexin pharmacokinetics exists in postprandial or fasting male volunteers. Cefalexin was given orally to subjects under postprandial conditions or after an 8-h fast, at 08:00 or 20:00 h. In experiment 1, after the oral dose under postprandial conditions, time-dependent changes in cephalexin pharmacokinetics were significant. The elimination half-life (t 1/2) was prolonged obviously and thepeak serum concentration (C max) was higher after the 20:00 h compared to the 08:00 h administration. However, in experiment 2, no significant differences were found in the main pharmacokinetic parameters of cephalexin administered at two occasions after fasting. It is concluded that in this study, time of administration may affect the pharmacokinetics of cephalexin under the postprandial condition, and fasting may suppress the diurnal variations in cefalexin pharmacokinetics.

Ayari, Amel; Nasri-Ammar, Karima

doi: 10.1080/09291016.2011.613620pmid: N/A

The locomotor activity rhythm of the supralittoral sandhoppers, Talitrus saltator and Talorchestia deshayesii, was investigated over four seasons to reveal the impact of environmental variation on these sympatric species collected from Bizerte beach (37°19′N–9°51′E). For each season, thirty adult individuals were collected by hand and transferred to individual actographs equipped with an infrared recording system, where they were subjected to two consecutive experimental light/dark regimens (natural light/dark cycle (LD) and continuous darkness (DD)) in a controlled environment cabinet at 18°C ± 0.5°C. Periodogram analysis of the resulting actograms indicates a predominantly circadian rhythm with a period close to 24 h, with a less predictable semi-diurnal component of about 12 h in both T. saltator and T. deshayesii. A seasonal comparison of the various rhythm characteristics showed that the greater mortality was observed in winter (36.6%) and in spring (70%), respectively, among the population of T. saltator and T. deshayesii; whereas, in summer, this rate was equal to zero whatever the species. Moreover, irrespective of the season and the photoperiodic regimen, circadian rhythmicity was more important than the semi-diurnal one for all seasons and both under natural Light/Dark (nLD) cycle and free-running conditions. In addition, the stability of the circadian rhythm was better defined in spring, whatever the photoperiodic regimen imposed and the species. Similarities and differences observed between T. saltator and T. deshayesii over four seasons reflect an ecological plasticity of their biological clock adapted to different changing environmental conditions.

Pan, J.-Y.; Chou, M.-F.; Zhang, J.; Liu, Y.-P.

doi: 10.1080/09291016.2011.614791pmid: N/A

There was limited data on sleep patterns, insomnia, and daytime sleepiness in both south China adolescents and Macau adolescents. A school-based epidemiologic study (861 from Guangdong site and 618 from Macau) was conducted among high school adolescents from both sites. We found that Macau adolescents had slightly shorter nocturnal sleep duration during weekdays [mean (SD) = 7:24 (1:06) vs. 7:31 (0:35), p = 0.008] but longer nocturnal sleep duration during weekends [mean (SD) = 9:56 (1:40) vs. 8:48 (1:23)] than Guangdong adolescents. The rates of overall insomnia were 16.5% and 22.9% for Macau adolescents and Guangdong adolescents respectively (p < 0.001). Macau adolescents had higher scores in modified Epworth Sleepiness Scale than Guangdong adolescents. Multivariate analysis showed that study site was the most robust predictors for most of these variables of interest. Adolescents in Guangdong had shorter sleep duration, increased rates of insomnia, and habitual napping but were less sleepy than adolescents in Macau.

Nikkhah, A.

doi: 10.1080/09291016.2011.614792pmid: N/A

The objective of the first experiment was to determine effects of feeding time and dietary forage to concentrate ratio on diurnal averages and rhythms of blood urea (BU). Four multiparous (body weight, BW = 652 ± 14 kg, mean ± SD; body condition score, BCS = 2.87 ± 0.14; days in milk, DIM = 83 ± 22) and four primiparous (BW = 667 ± 110 kg; BCS = 3.19 ± 0.66; DIM = 81 ± 23) Holstein cows were utilized in a 4 × 4 Latin square design study with a 2 × 2 factorial arrangement of feeding time and diet type. A higher concentrate (forage to concentrate ratio = 38.5:61.5) or a lower concentrate (forage to concentrate ratio = 50.6:49.4) total mixed ration (TMR) was offered at either 2100 h or 0900 h. The study had four 21-d periods, with 14 d of adaptation. Blood was sampled every 2 h for two 24-h periods during sampling weeks. Feeding at 2100 h vs. 0900 h increased feed consumed within 3 h of feeding time, from 26% to 37% of total daily intake. Total daily dry matter intake (DMI) was similar among treatments. BU exhibited significant diurnal rhythms in both groups, which depended on diet type and its interactions with sampling hour and time of feeding (TF). The objective of the second experiment was to establish diurnal and post-feeding responses in BU levels to feeding time in lactating cows following 28-d adaptation periods. Four multiparous and four primiparous lactating Holstein cows (82 DIM) were used in a cross-over design study with two 6-wk periods. Each period had 4 wk of adaptation. A TMR with 49.8% concentrate was offered at either 0900 or 2100 h to permit 5–10% feed refusals. Jugular blood was sampled via catheters every 2 h for two 24-h period during wk 5 of each period. The proportion of daily TMR intake consumed within 3 h of feeding time was 55% in cows fed at 2100 h, and 46% in cows fed at 0900 h (P < 0.05). Rumen ammonia was higher at 2 h but lower at 6 h post-feeding and remained lower between 6 and 20 h post-feeding in cows fed at 2100 h vs. 0900 h. Feeding time did not affect daily averages of BU. BU increased shortly after feeding in morning-fed cows but not in evening-fed cows. BU was higher for about 12 h pre-feeding in evening- vs. morning-fed cows. Results establish that TF alters postprandial and diurnal patterns of feed intake, rumen ammonia, and peripheral BU. Time of eating and its interaction with diet type can therefore affect splanchnic and peripheral nitrogen metabolism and efficiency in lactating cows. Considering the comparative nature of the splanchnic metabolism in optimal mechanistic understanding of the gut function in any given species, these data could serve as a theoretical and in several aspects as an applied metabolic model for other high-producing ruminants and humans.

Robillard, R.; Lambert, T.J.R.; Rogers, N.L.

doi: 10.1080/09291016.2011.614794pmid: N/A

This study assessed the validity of using an energy expenditure actimeter for sleep–wake monitoring. Twelve participants underwent five to nine days of continuous actigraphy, simultaneously wearing an actimeter measuring energy expenditure (Actical) and an actimeter commonly used for sleep–wake assessment (Actiwatch-L) on their non-dominant wrist. Sleep timing variables measured with the two actimeters correlated above 0.90 and the correlation for sleep consolidation variables was above 0.75. Significant positive correlations between the two monitors were also found for an actigraphy based index assessing circadian rhythms. These results support the use of energy expenditure based actimeters to monitor sleep–wake patterns.

Chen, C.; Jiang, Z.; Cheng, S.; Zou, Y.; Liu, Y.; Wang, Y.; Xiao, J.; Guo, H.; Tebbutt, S.J.; Wang, Z.

doi: 10.1080/09291016.2011.614795pmid: N/A

Clock is a core, well-established, circadian gene, and clif is a newly discovered circadian gene, both of which not only maintain the circadian rhythm of cells but also regulate some organic functions. The purpose of this study was to determine whether genetic variations (single nucleotide polymorphisms – SNPs) in clock and/or clif genes associate with coronary artery disease (CAD). We silenced the clock and clif genes in cells and mice. The mRNA levels of clock, clif, pai-1, and tm of mice were examined using Reverse transcription polymerase chain reaction (RT-PCR). Plasminogen activator inhibitor 1 (PAI-1) and thrombomodulin (TM) levels will be examined using enzyme-linked immunosorbent assay. The clock SNPs (rs3840267, rs3749474, and rs1402963), and clif SNPs (rs62758860 and rs2289709) were analyzed in 116 patients with CAD and 95 healthy controls by sequence-specific primer-polymerase chain reaction. Data were analyzed by χ2 analysis. The mRNA levels of pai-1 and tm was decreased in the clock or clif gene silenced groups, and their protein levels were accordingly decreased. The blood serum PAI-1 and TM levels were significantly lower in CAD patients than that in healthy control. There showed significant association between clock SNPs (rs3840267) and CAD. And there was no significant association between clock SNPs (rs3749474 and rs1402963), clif SNPs (rs62758860 and rs2289709) and CAD. The data support an association between clock/clif and CAD. The clock SNPs (rs3840267) is associated with CAD. The clock gene could influence the expressions of PAI-1and TM in both cell and mice, and the blood levels had differences of PAI-1 and TM between CAD human recruitments and health controls. The process of PAI-1/TM influencing CAD may be under control by clock and clif gene.