The predatory mite Hypoaspis miles: biological and demographic characteristics on two prey species, the mushroom sciarid fly, Lycoriella solani, and the mould mite, Tyrophagus putrescentiae

The biology of Hypoaspis miles Berlese (Acarina: Hypoaspidae) fed on mushroom sciarid larvae (Lycoriella solani Winnertz) (Diptera: Lycoriidae) and mould mites (Tyrophagus putrescentiae Schrank) (Acari: Acaridae), was investigated by laboratory experiments at 20 °C, 75% r.h. and LD16:D8 hours. H. miles had a significantly shorter development time and a significantly lower juvenile mortality when fed on sciarid larvae than on mould mites, the development time being 14.5 days and the mortality 3.5% on the former prey. The preoviposition and postoviposition periods of H. miles were not uninfluenced by the prey species and were 5–9 and 32–37 days, respectively. Oviposition periods of 53.2 and 68.5 days and female longevities of 82 and 109.6 days were observed on diets of sciarid larvae and mould mites, respectively. Male longevity (168–219 days) was uninfluenced by the prey species. The egg production of H. miles on sciarid larvae was estimated to be 44.4 ± 4.33 eggs per female, as compared to 22.43 ± 1.79 eggs per female on mould mites. The sex-ratio of the offspring was significantly influenced by the prey species, the ratios (/(+)) being 0.66 on sciarid larvae and 0.54 on mould mites. The net reproductive rate (R₀) for H. miles fed on sciarid larvae was approximately 27 which was three times higher than for mites feeding on mould mites. The innate capacity of increase (r_m) was highest (0.0747 day^–1) when sciarid larvae served as food, giving a doubling time of 9.3 days as compared to 12.8 days on mould mites. The generation times were 44.28 on sciarid larvae and 40.67 days on mould mites. The daily food consumption rate of juvenile and adult H. miles was 0.24 and 0.86 sciarid larvae and 10.8 and 21.7 mould mites, respectively. In terms of weight consumed, however, the consumption of sciarid larvae was 2–3.5 times the weight of mould mites. The ratio of females to males influenced the oviposition period and egg production of H. miles, with virgin females laying fewer eggs over a longer period of time as compared with females with access to males. The egg production in relation to the sex-ratio was described by models predicting a maximum number of eggs per female of 22.3 to be attained at a sex ratio of 0.69 (/(+)) and a maximum daily number of eggs per female of 0.33 to be attained at a sex ratio of 0.37 (/(+)).     

Effects of long-term exposure to 900 megahertz electromagnetic field on heart morphology and biochemistry of male adolescent rats

The pathological effects of exposure to an electromagnetic field (EMF) during adolescence may be greater than those in adulthood. We investigated the effects of exposure to 900 MHz EMF during adolescence on male adult rats. Twenty-four 21-day-old male rats were divided into three equal groups: control (Cont-Gr), sham (Shm-Gr) and EMF-exposed (EMF-Gr). EMF-Gr rats were placed in an EMF exposure cage (Plexiglas cage) for 1 h/day between postnatal days 21 and 59 and exposed to 900 MHz EMF. Shm-Gr rats were placed inside the Plexiglas cage under the same conditions and for the same duration, but were not exposed to EMF. All animals were sacrificed on postnatal day 60 and the hearts were extracted for microscopic and biochemical analyses. Biochemical analysis showed increased levels of malondialdehyde and superoxide dismutase, and reduced glutathione and catalase levels in EMF-Gr compared to Cont-Gr animals. Hematoxylin and eosin stained sections from EMF-Gr animals exhibited structural changes and capillary congestion in the myocardium. The percentage of apoptotic myocardial cells in EMF-Gr was higher than in either Shm-Gr or Cont-Gr animals. Transmission electron microscopy of myocardial cells of EMF-Gr animals showed altered structure of Z bands, decreased myofilaments and pronounced vacuolization. We found that exposure of male rats to 900 MHz EMF for 1 h/day during adolescence caused oxidative stress, which caused structural alteration of male adolescent rat heart tissue.     

Genetic Manipulation of Leishmania donovani to Explore the Involvement of Argininosuccinate Synthase in Oxidative Stress Management

Reactive oxygen and nitrogen species (ROS and RNS) produced by the phagocytic cells are the most common arsenals used to kill the intracellular pathogens. However, Leishmania, an intracellular pathogen, has evolved mechanisms to survive by counterbalancing the toxic oxygen metabolites produced during infection. Polyamines, the major contributor in this anti-oxidant machinery, are largely dependent on the availability of L-arginine in the intracellular milieu. Argininosuccinate synthase (ASS) plays an important role as the rate-limiting step required for converting L-citrulline to argininosuccinate to provide arginine for an assortment of metabolic processes. Leishmania produce an active ASS enzyme, yet it has an incomplete urea cycle as it lacks an argininosuccinate lyase (ASL). There is no evidence for endogenous synthesis of L-arginine in Leishmania, which suggests that these parasites salvage L-arginine from extracellular milieu and makes the biological function of ASS and the production of argininosuccinate in Leishmania unclear. Our previous quantitative proteomic analysis of Leishmania promastigotes treated with sub-lethal doses of ROS, RNS, or a combination of both, led to the identification of several differentially expressed proteins which included ASS. To assess the involvement of ASS in stress management, a mutant cell line with greatly reduced ASS activity was created by a double-targeted gene replacement strategy in L. donovani promastigote. Interestingly, LdASS is encoded by three copies of allele, but Western blot analysis showed the third allele did not appear to express ASS. The free thiol levels in the mutant LdASS^-/-/+ cell line were decreased. Furthermore, the cell viability in L-arginine depleted medium was greatly attenuated on exposure to different stress environments and was adversely impacted in its ability to infect mice. These findings suggest that ASS is important for Leishmania donovani to counterbalance the stressed environments encountered during infection and can be targeted for chemotherapeutic purpose to treat visceral leishmaniasis.     

Deprivation of L-Arginine Induces Oxidative Stress Mediated Apoptosis in Leishmania donovani Promastigotes: Contribution of the Polyamine Pathway

The growth and survival of intracellular parasites depends on the availability of extracellular nutrients. Deprivation of nutrients viz glucose or amino acid alters redox balance in mammalian cells as well as some lower organisms. To further understand the relationship, the mechanistic role of L-arginine in regulation of redox mediated survival of Leishmania donovani promastigotes was investigated. L-arginine deprivation from the culture medium was found to inhibit cell growth, reduce proliferation and increase L-arginine uptake. Relative expression of enzymes, involved in L-arginine metabolism, which leads to polyamine and trypanothione biosynthesis, were downregulated causing decreased production of polyamines in L-arginine deprived parasites and cell death. The resultant increase in reactive oxygen species (ROS), due to L-arginine deprivation, correlated with increased NADP+/NADPH ratio, decreased superoxide dismutase (SOD) level, increased lipid peroxidation and reduced thiol content. A deficiency of L-arginine triggered phosphatidyl serine externalization, a change in mitochondrial membrane potential, release of intracellular calcium and cytochrome-c. This finally led to DNA damage in Leishmania promastigotes. In summary, the growth and survival of Leishmania depends on the availability of extracellular L-arginine. In its absence the parasite undergoes ROS mediated, caspase-independent apoptosis-like cell death. Therefore, L-arginine metabolism pathway could be a probable target for controlling the growth of Leishmania parasites and disease pathogenesis.     

Inheritance of fruit-coat colours in Trichosanthes anguina Linn.

Summary In Trichosanthes anguina Linn. (Cucurbitaceae), reciprocal crosses among three naturally occurring fruit-coat colour varieties (deep green, green and white) and two yellow fruit-coat colour mutants isolated in the M₁ generation showed that a multiple allelic series control the fruit-coat colours. In the F₂ generation the fruit-coat colours segregated in a monohybrid ratio with deep green dominant over green, yellow and white, green dominant over yellow and white, and yellow dominant over white. Two yellow fruit-coat colour mutants used in this study were isolated from X-ray- and EMS-treated populations of a white fruit-coat colour variety.     

Arsenic and Heavy Metal Concentrations in Drinking Water in Pakistan and Risk Assessment: A Case Study

The present study was performed to assess drinking water quality and potential health risk in the Nowshera District, Khyber Pakhtunkhwa, Pakistan. For this purpose drinking water samples were collected from local available sources and analyzed for physico-chemical characteristics, arsenic (As) and heavy metals. Results revealed high levels of toxic heavy metals such as chromium (Cr), nickel (Ni), lead (Pb), cadmium (Cd), and As contaminations in the drinking water. Results were evaluated for chronic risk including average daily intake (ADI) and hazard quotient (HQ). Among heavy metals the HQ values were highest for Cd (5.80) and As (2.00). Therefore, populations in the study area may be at a low level of chronic toxicity and carcinogenic risk. Statistical analyses showed that contribution of different drinking water sources to the mean contaminant levels in the study area was insignificant (p =.53). Correlation analysis further revealed that anthropogenic activities were the main sources of contamination, rather than geogenic. This study strongly recommends the treatment of urban and industrial wastewater in the vicinity of the study area and provision of safe drinking water.     

TGF-β1 re-programs TLR4 signaling in L. donovani infection: enhancement of SHP-1 and ubiquitin-editing enzyme A20

Visceral leishmaniasis (VL), caused by Leishmania donovani, is a major health concern in India. It represents T-helper type 2 (Th2) bias of cytokines in active state and Th1 bias at cure. However, the role of the parasite in regulating Toll-like receptor (TLR)-mediated macrophage activation in VL patients remains elusive. In this report, we demonstrated that later stages of L. donovani infection rendered tolerance to macrophages, leading to incapability for the production of inflammatory cytokines like tumor necrosis factor (TNF)-α and interleukin (IL)-1β in response to TLR stimulation. Overexpression of transforming growth factor (TGF)-β(1), but not IL-10, resulted in suppressed lipopolysaccharide (LPS)-induced production of TNF-α and downregulation of TLR4 expression in L. donovani-infected macrophages. Recombinant human (rh)TGF-β(1) markedly enhanced tyrosine phosphatase (Src homology region 2 domain-containing phosphatase-1) activity, but inhibited IL-1 receptor-activated kinase (IRAK)-1 activation. Addition of neutralizing TGF-β(1) antibody reversed these effects, and thus suggesting the pivotal role of TGF-β(1) in promoting refractoriness for LPS in macrophages. Surprisingly, the use of a tyrosine phosphatase inhibitor (sodium orthovanadate, Na(3)VO(4)) promoted IRAK-1 activation, confirming the negative inhibitory role of tyrosine phosphatase in macrophage activation. Furthermore, rhTGF-β(1) induced tolerance in infected macrophages by reducing inhibitory protein (IκBα) degradation in a time-dependent manner. In addition, short interfering RNA studies proved that overexpression of A20 ubiquitin-editing protein complex induced inhibitory activity of TGF-β(1) on LPS-mediated nuclear factor-κB activation. Thus, these findings suggest that TGF-β(1) promotes overexpression of A20 through tyrosine phosphatase activity that ensures transient activation of inflammatory signaling pathways in macrophages in active L. donovani infection.     

Effect of Long-term Fluoride Exposure on Growth, Nutrient Utilization and Fluoride Kinetics of Calves Fed Graded Levels of Dietary Protein

In order to assess the influence of dietary protein levels on the fluoride (F) bioavailability, 30 crossbred calves (6-8 months; approximately 104 kg BW) initially exposed to different dietary protein levels were allotted into six groups in a 3?×?2 factorial design. The factors included three different levels of protein viz. normal (100%; NP), low (75%; LP), and high (125%; HP) as per Kearl recommendations besides two levels of supplemental fluorine (as sodium fluoride) at 0 or 200 mg/kg diet. The animals were fed on the respective concentrate mixture and wheat straw for 210 days. A metabolism trial was conducted at 200 days post-feeding to study digestibility, plane of nutrition, and nutrient balances. The final body weight at the end of 210 days was lower (p?<?0.01) in animals fed 200 mg/kg F (164.2?±?8.92 kg) compared to those fed no F (200.7?±?8.05 kg). Calves on LP diets attained lower (p?<?0.05) average daily gain in comparison to NP or HP fed calves. The F-supplemented calves exhibited lower (p?<?0.01) voluntary feed intake than their non-supplemented control. The digestibility of proximate nutrients other than ether extract exhibited higher (p?<?0.01) values in F-fed calves attributable chiefly to reduced consumption of dry matter. The calves fed extra F retained lower mean daily nitrogen; calcium, and phosphorus compared to the calves fed no F. The mean daily intake, excretion, and retention of F were higher (p?<?0.01) in the F-supplemented calves. A significant (p?<?0.01) interaction between protein levels and F was evident in the urinary excretion of F; calves on LP diet exhibiting lower urinary excretion. Consequently, the bioavailability of F tended to be higher on LP than NP or HP diets. From the results, it is concluded that protein levels in the diet do not impart significant influence on susceptibility to fluorosis in crossbred calves. However, the bioavailability of F tended to increase on diets low in protein.     

EhMAPK, the mitogen-activated protein kinase from Entamoeba histolytica is associated with cell survival

Mitogen Activated Protein Kinases (MAPKs) are a class of serine/threonine kinases that regulate a number of different cellular activities including cell proliferation, differentiation, survival and even death. The pathogen Entamoeba histolytica possess a single homologue of a typical MAPK gene (EhMAPK) whose identification was previously reported by us but its functional implications remained unexplored. EhMAPK, the only mitogen-activated protein kinase from the parasitic protist Entamoeba histolytica with Threonine-X-Tyrosine (TXY) phosphorylation motif was cloned, expressed in E. coli and functionally characterized under different stress conditions. The expression profile of EhMAPK at the protein and mRNA level remained similar among untreated, heat shocked and hydrogen peroxide-treated samples in all cases of dose and time. But a significant difference was obtained in the phosphorylation status of the protein in response to different stresses. Heat shock at 43°C or 0.5 mM H(2)O(2) treatment enhanced the phosphorylation status of EhMAPK and augmented the kinase activity of the protein whereas 2.0 mM H(2)O(2) treatment induced dephosphorylation of EhMAPK and loss of kinase activity. 2.0 mM H(2)O(2) treatment reduced parasite viability significantly but heat shock and 0.5 mM H(2)O(2) treatment failed to adversely affect E. histolytica viability. Therefore, a distinct possibility that activation of EhMAPK is associated with stress survival in E. histolytica is seen. Our study also gives a glimpse of the regulatory mechanism of the protein under in vivo conditions. Since the parasite genome lacks any typical homologue of mammalian MEK, the dual specificity kinases which are the upstream activators of MAPK, indications of the existence of some alternate regulatory mechanisms of the EhMAPK activity is perceived. These may include the autophosphorylation activity of the protein itself in combination with some upstream phosphatases which are not yet identified.