Biological Rhythm Research

Valentinuzzi, Verónica S.; Diniz, Gabriela Pestana; Menna-Barreto, Luiz; Xavier, Gilberto F.

doi: 10.1080/09291010601044165pmid: N/A

Abstract Wistar rats maintained in cages with running wheels and submitted to a skeleton photoperiod or to a light – dark cycle were tested in the Morris water maze. Half of the animals were exposed to the task during their active phase while the other half was exposed during their inactive phase. The effect of the experience in the water maze, a strong arousing event, on the rhythm of wheel-running activity was evaluated. In the first experiment, a group of animals submitted to a skeleton photoperiod was trained every day in the reference memory version of the task. The novel experience in the water maze had a strong phase-dependent masking effect: it produced an intense post-training bout of activity in the animals tested during their inactive phase. Another experiment was run using single working memory sessions in the water maze and with animals submitted to a light – dark cycle. The circadian rhythm of locomotor activity was evaluated on undisturbed days and compared with testing days. The experience in the water maze produced a significant increase in variability of activity onset during both circadian phases. Taken together, the data suggest that there is a modulating effect of the arousing experience in the pool on the overt circadian rhythm of locomotor activity.

Essa, M. Mohamed; Subramanian, P.

doi: 10.1080/09291010600981789pmid: N/A

Abstract In this study, the influences of Pongamia pinnata, an indigenous medicinal plant used in Ayurvedic and traditional Medicine in India, on the circadian variations of liver marker enzymes in ammonium chloride (AC) induced hyperammonemic rats were studied. Experimental rats (160 – 180 g) were divided into control, AC (daily i.p. injection of AC (100 mg kg−1 body weight)) treated, AC + P. pinnata ethanolic leaf extract (PPEt) (300 mg kg−1 body weight) treated and PPEt treated groups. Temporal characteristics (acrophase, amplitude and mesor) of liver marker enzymes; alkaline phosphatase (ALP), aspartate and alanine transaminases (ALT and AST) and γ-glutamyl transferase (GGT) were analyzed. Elevated liver marker enzymes (increased mesor and delayed acrophase of AST, ALT, ALP and GGT) were found in hyperammonemic rats. Administration of PPEt significantly alters these changes. Variations in acrophase, amplitude and r values were also found in control and experimental rats. The detectable circadian rhythms of hepatic marker enzymes and their alterations during AC/PPEt treatments, in the present study, deserve further investigation for the diagnosis and for the therapeutic efficacy of hyperammonemia.

Satralkar, Moses K.; Keny, V. L.; Khare, P. V.; Vanlalnghaka, C.; Kasture, M. S.; Shivagaje, A. J.; Barnabas, R. J.; Iyyer, S. B.; Joshi, D. S.

doi: 10.1080/09291010601048711pmid: N/A

Abstract Parameters of light pulse induced phase response curves (PRCs) for the circadian rhythm of oviposition in three latitudinal strains of Drosophila ananassae originating from 0°N on the equator at Pontianak (the PK strain), 11.94°N at Kannur (the KR strain) and 22.29°N at Dwaraka (the DA strain) were variable and latitude dependent. The PRC for the PK strain had a low amplitude, dead zone of 8 h and the ratio for the advance to delay region (A/D) < 1, but the PRC for the DA strain had a high amplitude, absence of dead zone and ratio of A/D > 1, while the PRC for the KR strain had intermediate values for these parameters. Thus, the lower latitude was correlated with low amplitude and protracted dead zone in the PRC for oviposition rhythm of D. ananassae.

Yang, Bo; Liu, Yanyou; Wang, Yuhui; Wang, Yueqi; Ling, Yanyal; Jiang, Zhou; Wang, Zhengrong; Cornelissen, G.; Halberg, F.

doi: 10.1080/09291010601049040pmid: N/A

Abstract Objective. This study investigates how the shortening or lengthening of the circadian period of the environmental lighting schedule affects the circadian and extra-circadian structure of locomotor activity in mice, with particular focus on the circasemiseptan, circaseptan, and circadecadian components with anticipated periods of about 3.5, 7, and 10 days, respectively. Methods. The locomotor activity of mice kept on different light – dark (LD) cycles was automatically monitored around the clock for about five weeks. The data were analyzed by linear – nonlinear rhythmometry. Results. As anticipated, in LD12:12, a prominent circadian rhythm was observed, with a marked 12-hour component qualifying the circadian waveform. By comparison, in LD10:10 and in LD14:14, the circadian rhythm had a reduced amplitude and a period close to that of the environmental synchronizer. Extra-circadian variation was then also demonstrated. In conclusion, circadian lighting schedules affect a broader-than-circadian time structure of locomotor activity in mice.

Esposito, Maria J.; Natale, Vincenzo; Martoni, Monica; Occhionero, Miranda; Fabbri, Marco; Cicogna, Piercarla

doi: 10.1080/09291010601068776pmid: N/A

Abstract The aim of the present study was to investigate the time of night effect on prospective time estimation efficiency. Fifty-four participants took part in six consecutive experimental sessions from 10:00 p.m. to 8:00 a.m. at intervals of 2 h, during which they had to carry out two kinds of tasks (simple reaction time and prospective time estimation), give an evaluation of their subjective alertness, and record body temperature. In agreement with previous data on body temperature, subjective alertness and performance in simple reaction time showed a significant decrease during the night, while performance in prospective time estimation did not change over the night. Taking into account circadian typology we found that morning-types tended to produce significantly shorter time intervals and less time estimation accuracy than evening-types. With reference to recent cognitive timing models and data derived from free-running conditions, it is hypothesised that internal pace-makers pulse at different rates between the extreme chronotypes.