S. R. Ramesh

Brain aging, memory impairment and oxidative stress: A study in Drosophila melanogaster

Memory impairment during aging is believed to be a consequence of decline in neuronal function and increase in neurodegeneration. Accumulation of oxidative damage and reduction of antioxidant defense system play a key role in organismal aging and functional senescence. In our study, we examined the age-related memory impairment (AMI) in relation to oxidative stress using Drosophila model. We observed a decline in cognitive function in old flies with respect to both short-lived and consolidated forms of olfactory memory. Light and electron microscopy of mushroom bodies revealed a reduction in the number of synapses and discernible architectural defects in mitochondria. An increase in neuronal apoptosis in Kenyon cells was also evident in aged flies. Biochemical investigations revealed a comparable age-associated decrease in the activity of antioxidant enzymes such as catalase and superoxide dismutase as well as the GSH level, accompanied by an increase in the level of lipid peroxidation and generation of reactive oxygen species in the brain. There was no significant difference in the activity level of AChE and BChE enzymes between different age groups while immunohistochemical studies showed a significant decrease in the level of ChAT in 50-day-old flies. RNAi-mediated silencing of cat and sod1 genes caused severe memory impairment in 15-day-old flies, whereas, over-expression of cat gene could partially rescue the memory loss in the old flies. We demonstrated that a Drosophila long-lived strain, possessing enhanced activity of antioxidant enzymes and higher rate of resistance to oxidative stress, shows lower extent of AMI compared to normal lifespan strain. Present study provides evidence for involvement of oxidative stress in AMI in Drosophila.

ATTENUATION OF NEUROMOTOR DEFICITS BY NATURAL ANTIOXIDANTS OF DECALEPIS HAMILTONII IN TRANSGENIC DROSOPHILA MODEL OF PARKINSON'S DISEASE

Oxidative stress is believed to be a major factor for the onset of Parkinsons disease (PD). In this study, we have investigated oxidative status in transgenic Drosophila model of PD. Our results revealed elevated levels of reactive oxygen species (ROS) and lipid peroxidation (LPO) in A30P and A53T α-synuclein PD model flies compared to control. We have demonstrated for the first time the ameliorating potential of natural antioxidants characterized from the roots of Dh in A30P and A53T α-synuclein PD model flies. Feeding of transgenic flies with aqueous Dh root extract for 21 days significantly improved their climbing ability and circadian rhythm of locomotor activity which was associated with reduction in levels of ROS and LPO and enhancement in the activities of catalase (CAT) and superoxide dismutase (SOD). Dh protected against paraquat (PQ) sensitivity in α-synuclein transgenic flies and delayed the onset of PD-like symptoms which appears to be mediated by suppression of oxidative stress.

Male accessory gland secretory proteins in nasuta subgroup of Drosophila: synthetic activity of Acp.

Abstract The quantity of male accessory gland secretory proteins in relation to the number of cells in the gland, size of the gland and the duration of copulation has been studied in seven members of the nasuta subgroup of Drosophila. The study revealed that the difference in the quantity of secretions is independent of the number of secretory cells in the gland. However, a positive correlation exists between the quantity of secretions and size of the gland; while there is no correlation between the copulation duration and the quantity of secretions. Further, there is an increase in the values of all the parameters studied, with increasing distance of the species from the ancestor.

Decalepis hamiltonii root extract attenuates the age-related decline in the cognitive function in Drosophila melanogaster.

Age-associated accumulation of oxidative damage linked to decline of antioxidant defense mechanism, leads to impairment of cognitive function in many organisms. These damages can pass through generations and affect the cognitive quality of progenies. In Drosophila, classical olfactory conditioning results in the formation of different types of memory. Age-related memory impairment (AMI) causes reduction in middle term memory (MTM) and parental senescence causes decline in short-term memory (STM) of the offspring. We have further examined the neuromodulatory effect of Decalepis hamiltonii (Dh) root extract, which is a cocktail of novel antioxidant molecules, on the biochemical oxidative defenses in relation to cognitive ability of the aged flies and their offspring. There is a strong correlation between the age-related decline in the activity of the antioxidant enzymes and the lower cognitive ability of the aged flies and their offspring. Feeding of aged flies in the diet containing 0.1% Dh, markedly enhances the cognitive ability of both aged flies and their offspring which is associated with enhanced antioxidant defenses as evident for the activity of superoxide dismutase (SOD) and catalase. Our findings, for the first time, show that the antioxidant-rich Dh root extract attenuates the age-related decline in cognitive ability of Drosophila, and also shows ameliorative effect on the memory of the offspring.

Modulatory effect of Decalepis hamiltonii on ethanol-induced toxicity in transgenic Drosophila model of Parkinson's disease

Overexpression of human α-synuclein gene in Drosophila can reduce lifespan, and we have performed lifespan assay for A30P and A53Tα-synuclein transgenic and control (elav-GAL4, UAS-A30P, UAS-A53T) flies. Our results showed reduced lifespan of transgenic flies compared to controls. We have also investigated behavioral responses, levels of reactive oxygen species (ROS) and lipid peroxidation (LPO) and activities of catalase (CAT) and superoxide dismutase (SOD) in a combined genetic-toxin model (Ethanol-A30P or A53Tα-synuclein models) and controls. Our results showed that sedation time (ST50) of A30P or A53Tα-synuclein PD model flies was significantly lower while recovery time (RC50) of them was remarkably higher compared to control flies. The levels of oxidative markers (ROS and LPO) were significantly higher and the activities of CAT and SOD were lower in transgenic flies that underwent ethanol exposure compared to control. Based on our earlier studies on antioxidant properties of isolated and characterized molecules from Decalepis hamiltonii (Dh) root extract, its protective effect in this combined toxicity model has been investigated. Surprisingly, Dh treatment increased ST50 and decreased RC50 values of transgenic flies. Moreover, we showed that Dh pre-treatment could decrease the levels of ROS and LPO and increase the activities of CAT and SOD in the ethanol-α-synuclein model. This is the first report on protective effects of natural antioxidants in A30P or A53Tα-synuclein PD model flies against oxidative stress induced by ethanol.

In Silico Studies of (2E,5E)-2,5-bis(3-methoxy-4-hydroxy-benzylidene) Cyclopentanone on Proteins AChE and BChE Involved in Alzheimer's disease and Ameliorative Effects on Paraquat Induced Oxidative Stress Markers in Drosophila melanogaster

In the present study, the ameliorative effect of a bischalcone (2E,5E)-2,5-bis(3-methoxy-4-hydroxy-benzylidene) cyclopentanone (CA), a curcumin analog was studied on Drosophila melanogaster (oregon K strain) in vivo by inducing oxidative stress using paraquat. Curcumin (CU) was taken as standard for studies. In negative geotaxis assay it was found that CA was able to rescue the flies significantly from deteriorating locomotor dysfunctions. A docking study for antialzeimers activity of CA was carried out by targeting the proteins Acetylcholinesterase (AChE) and Butyrylcholinesterase (BChE). It binds effectively to the target proteins.

Male Accessory Gland Secretory Proteins in a Few Members of the Drosophila nasuta Subgroup

Male accessory gland secretory proteins in seven members of the Drosophila nasuta subgroup have been analyzed by SDS-PAGE. The study revealed remarkable simplicity in the patterns. The protein fractions, which migrate in three groups, could be categorized as “major” and “minor.” The number of major fractions varies from a maximum of eight to a minimum of four. Group I consists of high molecular weight fractions, and group III, low molecular weight fractions. Among different members analyzed, the variation with respect to pattern and the number of fractions are confined largely to group III protein fractions, while group I and II fractions are found to be conserved to a greater extent. These proteins are PAS positive and group III fractions are not sensitive to silver staining. Analysis of these tissue specific proteins in the F1 and F2 of interspecific crosses and backcross progeny as well as volume analysis revealed that a 26-kD fraction in D. n. nasuta follows an autosomal pattern of inheritance, while a 55-kD and a 25-kD fraction in D. n. albomicans and a 24-kD fraction in D. n. kepulauana follow an X-linked pattern of inheritance.

Genetic and biochemical analysis of brown eye mutation in Drosophila nasuta nasuta and Drosophila nasuta albomicans

AbstractBy analyzing the progeny of crosses involving brown eye mutants and the wild types in two members of Drosophila nasuta subgroup namely D. n. nasuta and D. n. albomicans we could show that the mutant gene is recessive, located in the chromosome 2 and the alleles of this gene are present at different loci. A study of fitness in the eye color mutants in comparison with the wild types revealed that D. n. nasuta mutant has higher viability at both 25 ± 1°C and ambient temperatures; while D. n. albomicans mutant has faster rate of development only at 25 ± 1°C. Quantitative analysis of eye pigments in the mutants revealed that there is biosynthesis of both pteridines and xanthommatins unlike in bw/bw of D. melanogaster, where only xanthommatins are synthesized. In both the species, the pteridine quantities in mutants are similar; whereas xanthommatin quantity in

Male accessory gland secretory protein polymorphism in natural populations of Drosophila nasuta nasuta and Drosophila sulfurigaster neonasuta

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