Non-target effects of three biorationale insecticides on two endolarval parasitoids of Liriomyza sativae (Dipt., Agromyzidae)

Abstract:  Side effects of two azadirachtin formulations [NeemAzal-U (17% azadirachtin) and NeemAzal^®-T/S (1% azadirachtin)] and two biorationale pesticides – Success^® (Spinosad) and Abamectin (Avermectin) – on two endoparasitoids Opius ( Opiothorax ) chromatomyiae and Neochrysocharis formosa of Liriomyza sativae were investigated under laboratory conditions. The eggs of O. chromatomyiae , and the eggs, larvae and pupae of N. formosa within the host or within the plant/host complex were exposed to NeemAzal, Success and Abamectin at different dose rates. Adult emergence of O. chromatomyiae from parasitized L. sativae in NeemAzal-U (0.75, 1.5, 2.25 and 3 g/l water) drenched soil was only slightly lower than from untreated control hosts. In contrast, adult emergence of unparasitized L. sativae was almost completely inhibited by NeemAzal-U, indicating a high, direct toxicity. Development of O. chromatomyiae within L3 of L. sativae was very much affected from topical applications of NeemAzal^®-T/S, Success^® and Abamectin at particular dose rates. Spraying of tomato leaves with NeemAzal^®-T/S revealed no detrimental effect on the adult emergence of N. formosa developing in mining L2 of L. sativae . This was in contrast to Success^® and Abamectin which strongly affected N. formosa adult emergence when applied at different immature developmental stages of N. formosa .     

Seasonal Variation in the Prevalence of Sand Flies Infected with Leishmania donovani

Background

Visceral Leishmaniasis (VL) is a life threatening neglected infectious disease in the Indian subcontinent, transmitted by the bite of female sand flies. Estimation of the infectivity in the vector population, collected in different seasons, may be useful to better understanding the transmission dynamics of VL as well as to plan vector control measures.

Methodology

We collected sand flies from highly endemic regions of Bihar state, India for one year over three seasons. The species of the sand flies were confirmed by species-specific PCR-RFLP. Leishmania donovani infection was investigated in 1397 female Phlebotomus argentipes using PCR, targeting the Leishmania specific minicircle of the kDNA region. Further, the parasitic load in the infected sand flies was measured using quantitative PCR.

Conclusion

Though sand flies were most abundant in the rainy season, the highest rate of infection was detected in the winter season with 2.84% sand flies infected followed by the summer and rainy seasons respectively. This study can help in vector elimination programmes and to reduce disease transmission.     

Divalent metal cation requirements of phosphofructokinase-2 from E. coli. Evidence for a high affinity binding site for Mn

The reaction catalyzed by E. coli Pfk-2 presents a dual-cation requirement. In addition to that chelated by the nucleotide substrate, an activating cation is required to obtain full activity of the enzyme. Only Mn²⁺ and Mg²⁺ can fulfill this role binding to the same activating site but the affinity for Mn²⁺ is 13-fold higher compared to that of Mg²⁺. The role of the E190 residue, present in the highly conserved motif NXXE involved in Mg²⁺ binding, is also evaluated in this behavior. The E190Q mutation drastically diminishes the kinetic affinity of this site for both cations. However, binding studies of free Mn²⁺ and metal–Mant-ATP complex through EPR and FRET experiments between the ATP analog and Trp88, demonstrated that Mn²⁺ as well as the metal–nucleotide complex bind with the same affinity to the wild type and E190Q mutant Pfk-2. These results suggest that this residue exert its role mainly kinetically, probably stabilizing the transition state and that the geometry of metal binding to E190 residue may be crucial to determine the catalytic competence.     

Strong Association between Serological Status and Probability of Progression to Clinical Visceral Leishmaniasis in Prospective Cohort Studies in India and Nepal

Introduction

Asymptomatic persons infected with the parasites causing visceral leishmaniasis (VL) usually outnumber clinically apparent cases by a ratio of 4–10 to 1. We assessed the risk of progression from infection to disease as a function of DAT and rK39 serological titers.

Methods

We used available data on four cohorts from villages in India and Nepal that are highly endemic for Leishmania donovani. In each cohort two serosurveys had been conducted. Based on results of initial surveys, subjects were classified as seronegative, moderately seropositive or strongly seropositive using both DAT and rK39. Based on the combination of first and second survey results we identified seroconvertors for both markers. Seroconvertors were subdivided in high and low titer convertors. Subjects were followed up for at least one year following the second survey. Incident VL cases were recorded and verified.

Results

We assessed a total of 32,529 enrolled subjects, for a total follow-up time of 72,169 person years. Altogether 235 incident VL cases were documented. The probability of progression to disease was strongly associated with initial serostatus and with seroconversion; this was particularly the case for those with high titers and most prominently among seroconvertors. For high titer DAT convertors the hazard ratio reached as high as 97.4 when compared to non-convertors. The strengths of the associations varied between cohorts and between markers but similar trends were observed between the four cohorts and the two markers.

Discussion

There is a strongly increased risk of progressing to disease among DAT and/or rK39 seropositives with high titers. The options for prophylactic treatment for this group merit further investigation, as it could be of clinical benefit if it prevents progression to disease. Prophylactic treatment might also have a public health benefit if it can be corroborated that these asymptomatically infected individuals are infectious for sand flies.     

Immunomodulatory efficacy of nisin—a bacterial lantibiotic peptide

Nisin is a peptide bacteriocin, grouped under the category of lantibiotics. It is naturally produced by Lactococcus lactis to eliminate other competing gram‐positive bacteria from its vicinity. Moreover under certain conditions it is reported to be effective against a broad range of gram‐negative bacteria as well. Thus, it has been widely used as a safe food preservative especially in the dairy industry. Because of its wide‐scale consumption, its effect on eukaryotic cells should be of great concern. Here we examine the immunomodulatory efficacy of nisin in vitro. MTT‐based cytotoxicity assay demonstrated nisin's cytotoxicity on human T‐cell lymphoma Jurkat cells, Molt‐4 cells and freshly cultured human lymphocytes at over 200 µM concentration (IC₅₀225 µM ). The cell death mechanism induced by nisin in all these lymphocyte types was independent of oligonucleosomal DNA fragmentation, as analyzed by agarose gel electrophoresis and comet assay. Additionally, scanning electron microscope and fluorescence microscopy demonstrated the ability of nisin to activate human PMNs in vitro. Nisin‐activated neutrophils extruded intact nuclear chromatin to form NETs, well known for neutralization of virulence factors and extermination of bacterial pathogens. Nisin's presence also elevated neutrophil intracellular superoxide levels, normally produced by activated NADPH oxidase and prerequisite to NET formation. These nisin‐induced responses in cellular representatives of two separate branches of human immune system—adaptive and innate—although leading to cell death, did not include DNA fragmentation. From these findings, we propose that nisin might trigger similar AICD mechanisms in lymphocytes and neutrophils, different from conventional apoptosis which involves DNA fragmentation. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Antarctic terrestrial ecosystem and role of pigments in enhanced UV-B radiations

The terrestrial ecosystem of Antarctica are among the most extreme on earth, challenging the communities and making their existence difficult by rapidly increasing annual summer influx of solar ultraviolet radiations (UV-R), extremely cold conditions and lesser availability of nutrients. Spring time ozone depletion is due to release of chlorofluorocarbons in the earth atmosphere and is a serious cause of concern among environmentalists. Antarctic continent is mostly dominated by cryptogamic plants with limited distribution in different parts of the icy continent however; their distribution is mostly confined to Sub-Antarctic region. By the virtue of light requirement, cryptogams are exposed to extreme seasonal fluctuation in photosynthetically active radiation (PAR), and ultraviolet (UV) radiation which are closely associated with photosynthetic pigments in photoautotrophic organisms. Antarctic cryptogams cope up the stress imposed by UV radiation by the development of efficient systems for repairing damage by synthesis of screening compounds such as UV-B absorbing pigments and anthocyanin compounds. A major part of the UV absorbing compounds are appeared to be constitutive in lichens which are usnic acid, perlatolic acid and fumarphotocetraric acid which is particularly induced by UV-B. Secondary metabolites such as phenolics, atranorin, parietin and melanin also enhance the plant defense, by different molecular targets in specific solar irradiance and potential for increased antioxidative protection to UV induced vulnerability.     

Curcuminoids modulates oxidative damage and mitochondrial dysfunction in diabetic rat brain

Diabetes exacerbates neuronal injury induced by hyperglycemia mediated oxidative damage and mitochondrial dysfunction. The aim of the present study is to investigate the effects of curcuminoids, polyphenols of Curcuma longa (L.) on oxidative stress and mitochondrial impairment in the brain of streptozotocin (STZ)-induced diabetic rats. A marked increase in lipid peroxidation and nitrite levels with simultaneous decrease in endogenous antioxidant marker enzymes was observed in the diabetic rat brain, which was restored to normal levels on curcuminoids treatment. Down-regulation of mitochondrial complex I and IV activity caused by STZ induction was also up-regulated on oral administration of curcuminoids. Moreover, curcuminoids administration profoundly elevated the ATP level, which was earlier reduced in the diabetic brain. These results suggest that curcuminoids exhibit a protective effect by accelerating antioxidant defense mechanisms and attenuating mitochondrial dysfunction in the brain of diabetic rats. Curcuminoids thus may be used as a promising therapeutic agent in preventing and/or delaying the progression of diabetic complications in the brain.     

Expanded Monomeric Intermediate upon Cold and Heat Unfolding of Phosphofructokinase-2 from Escherichia coli

Folding studies have been focused mainly on small, single-domain proteins or isolated single domains of larger proteins. However, most of the proteins present in biological systems are composed of multiple domains, and to date, the principles that underlie its folding remain elusive. The unfolding of Pfk-2 induced by GdnHCl has been described by highly cooperative three-state equilibrium (N₂↔2I↔2U). This is characterized by a strong coupling between the subunits’ tertiary structure and the integrity of the dimer interface because “I” represents an unstructured and expanded monomeric intermediate. Here we report that cold and heat unfolding of Pfk-2 resembles the N₂↔2I step of chemically induced unfolding. Moreover, cold unfolding appears to be as cooperative as that induced chemically and even more so than its heat-unfolding counterpart. Because Pfk-2 is a large homodimer of 66 kDa with a complex topology consisting of well-defined domains, these results are somewhat unexpected considering that cold unfolding has been described as a special kind of perturbation that decouples the cooperative unfolding of several proteins.     

Nickel transport in nickel-resistant strains ofNeurospora crassa

Transport of Ni²⁺ has been studied in three Ni²⁺-resistant strains ofNeurospora crassa (Ni^R1, Ni^R3) and Ni^R3) and in the parent wild strainN. crassa Em 5297a. Several strainspecific differences have been found. Rates of Ni²⁺ uptake were Ni^R2>Ni^R1>Em>>Ni^R3. While K_m for Ni²⁺ uptake was similar, V_max values were sharply different, with Ni^R3 having the lowest value. Observed uptake was entirely due to transport into the intracellular phase. Transport was strongly pH dependent only in Em, Ni^R1, and Ni^R2, which had a pH optimum at 4; optimum was at pH 5 for Ni^R3. Mg²⁺ was powerfully inhibitory to Ni²⁺ uptake in Ni^R1 and Ni^R2, but was less efficient in Ni^R3; in contrast, Mn²⁺ was most inhibitory in Ni^R3. It has been suggested that Ni²⁺ resistance in Ni^R3 is specifically due to lowered levels of the Ni²⁺ transport system herein.