Sridhar V

References (4)

Title : Evidence-based insecticide resistance in South American tomato leaf miner, Phthorimaea absoluta (Meyrick) under laboratory selection - Prasannakumar_2023_Bull.Entomol.Res__1
Author(s) : Prasannakumar NR , Jyothi N , Prasadbabu K , Ramkumar G , Asokan R , Saroja S , Sridhar V
Ref : Bull Entomol Res , :1 , 2023
Abstract : The South American tomato moth, Phthorimaea absoluta (Meyrick), is one of the key pests of tomato in India. Since its report in 2014, chemical control has been the main means of tackling this pest, both in the open field and protected cultivation. Despite regular insecticidal sprays, many outbreaks were reported from major tomato-growing regions of South India during 2019-2020. A study was conducted to investigate the effect of insecticide resistance on biology, biochemical enzymes, and gene expression in various P. absoluta field populations viz., Bangalore, Kolar, Madurai, Salem, and Anantapur to commonly used insecticides such as flubendiamide, cyantraniliprole, and indoxacarb. Increased levels of insecticide resistance ratios (RR) were recorded in P. absoluta populations of different locations. A significant increase in cytochrome P450 monooxygenase (CYP/MFO) and esterase levels was noticed in the resistant population compared to susceptible one. Through molecular studies, we identified four new CYP genes viz., CYP248f (flubendiamide), CYP272c, CYP724c (cyantraniliprole), and CYP648i (indoxacarb). The expression levels of these genes significantly increased as the folds of resistance increased from G1 to G20 (generation), indicating involvement of the identified genes in insecticide resistance development in P. absoluta. In addition, the resistant populations showed decreased fecundity, increased larval development period, and adult longevity, resulting in more crop damage. The information generated in the present study thus helps in understanding the development of insecticide resistance by P. absoluta and suggests the farmers and researchers to use insecticides wisely by adopting insecticide resistance management as a strategy under integrated pest management.
ESTHER : Prasannakumar_2023_Bull.Entomol.Res__1
PubMedSearch : Prasannakumar_2023_Bull.Entomol.Res__1
PubMedID: 36920057

Title : Toxicity of organophosphates on morphology and locomotor behavior in brine shrimp, Artemia salina - Venkateswara_2007_Arch.Environ.Contam.Toxicol_53_227
Author(s) : Venkateswara Rao J , Kavitha P , Jakka NM , Sridhar V , Usman PK
Ref : Archives of Environmental Contamination & Toxicology , 53 :227 , 2007
Abstract : The acute toxicity and hatching success of four organophosphorus insecticides--acephate (ACEP), chlorpyrifos (CPP), monocrotophos (MCP), and profenofos (PF)--was studied in a short-term bioassay using brine shrimp, Artemia salina. Fifty percent hatchability inhibition concentration and median lethal concentration (LC(50)) values were calculated after probit transformation of the resulting data. Among the insecticides tested, CPP is found to be the most toxic and also to inhibit hatching success of A. salina cysts in a concentration-dependent manner. In addition, the effect of these pesticides on locomotor behavior (swimming speed) and morphologic differences were studied in LC(50)-exposed nauplii after 24 hours. The in vivo effect of these insecticides on acetylcholinesterase (Enzyme commission number (EC activity was also determined in LC(50)-exposed nauplii after 24 hours. Maximum percent decrease in their swimming speed and significant morphologic alterations were noticed in CPP-exposed brine shrimps. The order of toxicity was CPP > PF > MCP > ACEP in all the parameters studied.
ESTHER : Venkateswara_2007_Arch.Environ.Contam.Toxicol_53_227
PubMedSearch : Venkateswara_2007_Arch.Environ.Contam.Toxicol_53_227
PubMedID: 17549541

Title : Sublethal effects of monocrotophos on locomotor behavior and gill architecture of the mosquito fish, Gambusia affinis - Rao_2005_J.Environ.Sci.Health.B_40_813
Author(s) : Rao JV , Begum G , Sridhar V , Reddy NC
Ref : J Environ Sci Health B , 40 :813 , 2005
Abstract : Subacute studies of monocrotophos [Dimethyl (E)-1-methyl-2-(methyl-carbamoyl) vinyl phosphate] on mosquito fish, Gambusia affinis, were carried out in vivo for 24 days to assess the locomotor behavior, structural integrity of gill, and targeted enzyme acetylcholinesterase (AChE, EC: interactions. Monocrotophos (MCP) can be rated as moderately toxic to G. affinis, with a median lethal concentration (LC(50)) of 20.49 +/- 2.45 mgL(-1). The fish exposed to sublethal concentration of LC(10) (7.74 mgL(-1)) were under stress and altered their locomotor behavior, such as distance traveled per unit time (m min(-1)) and swimming speed (cm sec(-1)) with respect to the length of exposure. Inhibition in the activity of brain AChE and deformities in the primary and secondary lamellae of gill may have resulted in failure of exchange of gases. The maximum inhibition of 95% of AChE activity was observed on days 20 and 24. Morphological aberrations in the gills were also studied during exposure to the sublethal concentration of monocrotophos for a period ranging from 8 to 24 days. The extent of damage in gill was dependent on the duration of exposure. The findings revealed that inhibition in brain AChE activity and structural alteration in gill were responsible for altering the locomotor behavior of exposed fish.
ESTHER : Rao_2005_J.Environ.Sci.Health.B_40_813
PubMedSearch : Rao_2005_J.Environ.Sci.Health.B_40_813
PubMedID: 16194919

Title : Structural and kinetic analysis of the substrate specificity of human fibroblast activation protein alpha - Aertgeerts_2005_J.Biol.Chem_280_19441
Author(s) : Aertgeerts K , Levin I , Shi L , Snell GP , Jennings A , Prasad GS , Zhang Y , Kraus ML , Salakian S , Sridhar V , Wijnands R , Tennant MG
Ref : Journal of Biological Chemistry , 280 :19441 , 2005
Abstract : Fibroblast activation protein alpha (FAPalpha) is highly expressed in epithelial cancers and has been implicated in extracellular matrix remodeling, tumor growth, and metastasis. We present the first high resolution structure for the apoenzyme as well as kinetic data toward small dipeptide substrates. FAPalpha exhibits a dipeptidyl peptidase IV (DPPIV)-like fold, featuring an alpha/beta-hydrolase domain and an eight-bladed beta-propeller domain. Known DPPIV dipeptides are cleaved by FAPalpha with an approximately 100-fold decrease in catalytic efficiency compared with DPPIV. Moreover, FAPalpha, but not DPPIV, possesses endopeptidase activity toward N-terminal benzyloxycarbonyl (Z)-blocked peptides. Comparison of the crystal structures of FAPalpha and DPPIV revealed one major difference in the vicinity of the Glu motif (Glu(203)-Glu(204) for FAPalpha; Glu(205)-Glu(206) for DPPIV) within the active site of the enzyme. Ala(657) in FAPalpha, instead of Asp(663) as in DP-PIV, reduces the acidity in this pocket, and this change could explain the lower affinity for N-terminal amines by FAPalpha. This hypothesis was tested by kinetic analysis of the mutant FAPalpha/A657D, which shows on average an approximately 60-fold increase in the catalytic efficiency, as measured by k(cat)/K(m), for the cleavage of dipeptide substrates. Furthermore, the catalytic efficiency of the mutant is reduced by approximately 350-fold for cleavage of Z-Gly-Pro-7-amino-4-methylcoumarin. Our data provide a clear understanding of the molecular determinants responsible for the substrate specificity and endopeptidase activity of FAPalpha.
ESTHER : Aertgeerts_2005_J.Biol.Chem_280_19441
PubMedSearch : Aertgeerts_2005_J.Biol.Chem_280_19441
PubMedID: 15809306
Gene_locus related to this paper: human-FAP