Circadian clock genes in Drosophila: recent developments.

Circadian rhythms provide a temporal framework to living organisms and are established in a majority of eukaryotes and in a few prokaryotes. The molecular mechanisms of circadian clock is constantly being investigated in Drosophila melanogaster. The core of the clock mechanism was described by a transcription-translation feedback loop model involving period (per), timeless (tim), dclock and cycle genes. However, recent research has identified multiple feedback loops controlling rhythm generation and expression. Novel mutations of timeless throw more light on the functions of per and tim products. Analysis of pdf neuropeptide gene (expressed in circadian pacemaker cells in Drosophila), indicate that PDF acts as the principal circadian transmitter and is involved in output pathways. The product of cryptochrome is known to function as a circadian photoreceptor as well as component of the circadian clock. This review focuses on the recent progress in the field of molecular rhythm research in the fruit fly. The gene(s) and the gene product(s) that are involved in the transmission of environmental information to the clock, as well as the timing signals from the clock outward to cellular functions are remain to be determined.

N-Phthaloyl gamma-aminobutyric acid affects biochemical circadian rhythms in Wistar rats.

N-Phthaloyl gamma-aminobutyric acid (P-GABA) was administered to Wistar rats and 24 hr rhythms of glucose, cholesterol, total protein and lactic acid levels in blood were studied under semi-natural light dark conditions. P-GABA administration caused desynchronisation of the rhythms; while glucose and lactic acid rhythms were advanced, cholesterol and total protein rhythms were delayed. Since GABA is being involved in conveying dark information to the clock, exogenous administration of P-GABA may reduce the photic information received by the clock. The results could be explained by slightly less than 1 hr daily delays (or) advances respectively which would bring the peak times to the points 21 days after the start of administration.

Temporal oscillations of phosphatases in N-phthaloyl gamma-aminobutyric acid treated rats.

N-pathaloyl gamma-aminobutyric acid (P-GABA) was administered to Wistar and 24 hr rhythms of acid and alkaline phosphatases were studied under light-dark conditions. P-GABA administration advanced the peak times of phosphatases. Since GABA is being involved in conveying dark information to the clock, exogenous administration of P-GABA might reduce the photic information received by the clock. The results could be explained by slight daily advances which would bring the peak times to the points 21 days after the start of administration.