R. Sivaperumal

Constant light influences the circadian oscillations of circulatory lipid peroxidation, antioxidants and some biochemical variables in rats

Abstract Temporal oscillations of circulatory thiobarbituric acid reactive substances (TBARS), antioxidants such as reduced glutathione (GSH), superoxide dismutase (SOD), and catalase and glucose, cholesterol, total protein and aspartate transaminase (AST) were studied under LD (12:12 h) and constant light (LL) (500 lux) conditions after exposing the animal for 21 days. Advances in the acrophase of GSH, SOD, catalase, glucose, total protein and (AST) rhythms and delays in TBARS and cholesterol were found; amplitude and mesor values of these rhythms were found to be altered during constant light treatment. The above said circadian alterations during LL exposure may be due to (1) formation of photooxidants and stress mediated lipid peroxidation, suppression of melatonin (2) modulation of neuroendocrine and neurotransmitters rhythm (3) suppression of sleep – wake cycle (4) feeding and locomotion rhythm. The exact mechanism still remains to be explored and further research needed.

Aspartate modulates the circadian patterns of a few biochemical variables in Wistar rats

Abstract D-aspartate was used to demonstrate possible sources of excitatory input to the suprachiasmatic nucleus (SCN) in rats. Aspartate (50 mg/kg bodyweight) was orally administrated chronically for 60 days to Wistar rats and 24 h rhythmic patterns of glucose, cholesterol, total protein and aspartate transaminase (AST) were studied under light – dark (LD 12:12 h) cycle. Our results showed acrophase advances in glucose and delays in cholesterol and AST rhythms. Increased mesor and altered amplitude values were found in all rhythms; aspartate levels in the brain were found to be significantly increased in aspartate treated animals. We hypothesised that the altered biochemical rhythms in aspartate treated rats could be due to (1) modulation of neurotransmission in SCN, (2) behavioural rhythms and (3) feeding rhythms.

Rhythmic expression patterns of locomotor activity in mutants of Drosophila melanogaster under different wavelengths of light

It is a well known fact that light is the major environmental cue for the expression of overt circadian rhythms in a wide variety of living organisms including Drosophila. In this study, we have analyzed the period length (τ), amount of activity (α) and phase angle difference (ψ) in wild type, vestigial (vg) and cry b mutants (synthesizing functionless cryptochrome) of Drosophila under different light regime treated (12:12 - white light:dark (LD), blue (450 nm):dark (BD), green (550 nm):dark and red (650 nm):dark (RD)) conditions. Under red light (RD 12:12), period length, amount of activity and phase angle difference were significantly decreased in wild type and mutants, indicating that red light could be less effective on the expression of locomotor rhythms. Further, under blue (BD 12:12) and green (GD 12:12) light, the amount of activity was significantly decreased in vg and cry b mutants than wild type; period length, phase angle difference were significantly decreased in cry b mutants, in blue light, raising the possibility that blue light could mimic darkness in cry b mutants of Drosophila.

Analysis of circadian locomotor rhythms in vg and cry b mutants of Drosophila melanogaster under different light:dark regimens

The fruit fly (Drosophila melanogaster) offers an extremely useful system to study circadian clock function at the behavioral, molecular, cellular, and organismal levels. We reared wild type (Oregon R+) and mutant flies – vestigial (vg) and cryptochrome depleted (cryb ) flies in 12:12 light:dark cycles (LD 12:12) from the embryo to adult stage. Later, the locomotor activity rhythms of these newly eclosed flies were monitored in different light:dark (LD) regimens such as T20 (LD 10:10), T22 (LD 11:11), T24 (LD 12:12), T26 (LD 13:13), T28 (LD 14:14), continuous light (LL), and continuous darkness (DD) for seven to eight cycles. The circadian locomotor characteristics, such as period length, percentage activity, day and nighttime activity, anticipation index (AI), and phase relationships, were analyzed. Under these LD regimens, the above-mentioned characteristics were altered in these mutants when compared to wild-type (WT) flies. Altered circadian locomotor rhythms in vg mutants under these LD regimens might be due to its reduced wing structure. cryb flies have defective photic input to clock and it showed altered circadian locomotor activity rhythms when compared to WT flies under all these LD regimens. From this study, we suggest that under different LD regimens blue-light component cryptochrome as well as wing structure play an important role for the expression of circadian locomotor rhythms in D. melanogaster.

Influence of Withania somnifera on circadian rhythms of lipid peroxidation products and antioxidants in Gentamicin induced nephrotoxicity

In the present study, we investigated the protective effect of Withania somnifera root (W. somnifera) powder, an indigenous medicinal herb used in ayurvedic traditional systems for over 3000 years in India, on the circadian variations of gentamicin (GEN) induced nephrotoxicity. The circadian characteristics of 24 h variations such as acrophase, amplitude and mesor of lipid peroxidation products [Thiobarbituric acid reactive substances (TBARS)] and antioxidants [superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH) and glutathione peroxidase (GPx)] were analyzed. Administration of GEN delayed TBARS (increased mesor) and advanced antioxidants (decreased mesor) acrophases. Treatment with W. somnifera alters these changes. Variations in amplitude and ‘r’ values were also found in between the nephrotoxic rats and other experimental groups. From this study, we conclude that W. somnifera would work in a dynamic way in modulating the temporal redox status by directly scavenging the radicals by enhancing the antioxidant defense system during nephrotoxic conditions.

Influence of Withania somnifera on 24 h oscillations of biomarkers in gentamicin induced nephrotoxicity

The medicinal value of Withania somnifera root powder on the circadian variations of gentamicin (GEN)-induced nephrotoxicity was explored in this study. The circadian characterstics of 24 h rhythms such as acrophase, amplitude and mesor of renal biomarkers (urea and creatinine), blood glucose, protein and cholesterol were analyzed. In GEN treated rats, elevated levels of circulatory biomarkers-glucose, protein and cholesterol (increased mesor) were observed. In contrast treatment with W. somnifera significantly restored these levels (decreased mesor). Variations in amplitude and ‘r’ values also were observed in between the nephrotoxic rats and other experimental groups. Therefore, we conclude that W. somnifera alter the circadian variations directly with its valuable bioactive compounds, which could pave a way for future investigation for therapeutic approach.

Circadian expression patterns of vrille in peripheral tissues of mutants in Drosophila melanogaster

The circadian clock of Drosophila (fruit fly) has been extensively studied as a model system in molecular chronobiology. In Drosophila melanogaster, several clock genes are necessary for the generation and regulation of overt rhythms. Among these, vrille (vri) is a clock gene as well as a clock-controlled gene and its oscillation is essential for circadian rhythms at both molecular and behavioral levels. In this study, we have investigated the rhythmic expression patterns of vri at six time points (ZT 02, ZT 06, ZT 10, ZT 14, ZT 18 and ZT 22) over the 24 h period in peripheral tissues such as intestine and salivary glands of wild type (WT) and mutants [vestigial (vg) and cryptochrome absent (cryb )] of D. melanogaster under LD (12:12) condition. At ZT 14, vri expression was most pronounced in WT and mutants in both tissues compared to other time points. At ZT 22 and ZT 02, the expression was almost nil in both tissues. A definite temporal pattern in the levels of vri expression was observed at ZT 06, ZT 10 and ZT 18 in both tissues (of WT and other mutants). vg flies have greatly reduced wings, their gross locomotor activity was poorer and levels of its expression were also lower than WT flies. In cryb mutant, vri expression was less intensive than WT and vg mutants; this indicates that photic transduction to central/peripheral clock(s) is defective in cryb flies compared to other two types. In this study, we observed the presence of circadian expression patterns of vri in the peripheral oscillators during the developmental stages of Drosophila melanogaster.