Leishmania donovani affects antigen presentation of macrophage by disrupting lipid rafts

Leishmania donovani-infected splenic macrophages and P388D1 (P388D1(I)) failed to activate T cells in response to low dose of exogenous peptide. The membrane fluidity of P388D1(I) was greater than that of the normal counterpart P388D1(N), but could be reduced either by exposing the cell below phase transition point or by loading cholesterol into membrane (L-P388D1(I)), and this was associated with enhanced Ag-presenting ability of P388D1(I). Presentation of endogenous leishmanial Ag, kinetoplastid membrane protein-11, was also defective, but could be corrected by loading cholesterol into membrane. Because membrane rafts are important for Ag presentation at a low peptide dose, raft architecture of P388D1(I) was studied using raft (CD48 and cholera toxin-B) and non-raft (CD71) markers in terms of their colocalization with I-A(d). Binding of anti-CD48 mAb and cholera toxin B subunit decreased significantly in P388D1(I), and consequently, colocalization with I-A(d) was not seen, but this could be restored in L-P388D1(I). Conversely, colocalization between I-A(d) and CD71 remained unaffected regardless of the presence or the absence of intracellular parasites. P388D1(N) and L-P388D1(I), but not P388D1(I), formed peptide-dependent synapse with T cells quite efficiently and this was found to be corroborated with both intracellular Ca2+ mobilization in T cells and IL-2 production. This indicated that intracellular parasites disrupt the membrane rafts, possibly by increasing the membrane fluidity, which could be corrected by making the membrane rigid. This may be a strategy that intracellular L. donovani adopts to evade host immune system.     

Light-induced inhibition of papain by a {Mn-NO}6 nitrosyl: identification of papain-SNO adduct by mass spectrometry

Modification of Cys25 at the active site of the cysteine protease papain by S-nitrosylation inhibits its hydrolytic ability. Previous studies have demonstrated that NO donors N-nitrosoanilines inhibit papain activity via formation of S-NO bond formation at the active site while NO donors such as S-nitroso-N-acetyl-penicillamine (SNAP), N-nitrosoaniline derivatives, and S-nitroso-glutathione (GSNO) inhibit the enzyme via S-thiolation by thiyl radicals generated from the S-nitrosothiols. In this study, we report papain inactivation by a photosensitive {Mn-NO}(6) nitrosyl [(PaPy(3))Mn(NO)](ClO(4)) (1) where PaPy(3)(-) is the anion of the designed ligand N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide. This nitrosyl releases NO upon exposure to visible light of low intensity (50W tungsten lamp). With N(alpha)-benzoyl-l-arginine-p-nitroanilide (l-BApNA) as the substrate, the dissociation constant for the breakdown of the enzyme-inactivator complex (K(I)) and the overall inactivation rate constant (k(i)) were calculated to be 2.46mM and 64.8min(-1), respectively. The papainS-NO adduct has been identified using electrospray mass spectrometry (ESI-MS). The results demonstrate that controlled inactivation of papain can be achieved with the {Mn-NO}(6) nitrosyl 1 and light. The reaction is clean and the extent of inactivation is directly proportional to the exposure time.     

The carboxy-terminal end of the peptide deformylase from Mycobacterium tuberculosis is indispensable for its enzymatic activity

The peptide deformylase in bacteria is involved in removal of N-formyl group from newly synthesized proteins. The gene encoding this enzyme from Mycobacterium tuberculosis was cloned and expressed in Escherichia coli. The enzyme activity of the recombinant protein (mPDF) was insensitive to modulation by common monovalent/divalent cations. Kinetic analysis, using N-formylmethionine-alanine as the substrate, yielded K(cat)/K(m) of approximately 1220 M(-1)s(-1). Actinonin, a naturally occurring antibiotic, and 1,10-ortho-phenanthroline strongly inhibited the enzyme activity. The mPDF was very stable at 30 degrees C with a half-life of approximately 4h and exhibited resistance to oxidizing agents, like H(2)O(2). Thus, the mPDF achieved distinction in its behavior among any reported iron-containing peptide deformylases. Furthermore, amino acid sequence analysis of mPDF revealed the presence of an unusually long carboxy-terminal end (residues 182-197), which is atypical for any gram-positive bacteria. Our results, through deletion analysis, for the first time established the role of this region in mPDF enzyme activity.     

Anthelmintic efficacy of genistein, the active principle of Flemingia vestita (Fabaceae): alterations in the free amino acid pool and ammonia levels in the fluke, Fasciolopsis buski

The crude root-peel extract of Flemingia vestita, its active principle genistein and the reference flukicide oxyclozanide were tested against Fasciolopsis buski, the giant intestinal trematode. The amino acid composition of F. buski was demonstrated using HPLC and it was observed that the free amino acid (FAA) pool of the control worm consisted of aspartate, threonine, serine, glutamic acid, glutamine, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, lysine, histidine, arginine, phosphoserine, taurine, citrulline, ornithine, β-alanine, and γ-amino butyric acid (GABA). Of the amino acids detected valine was found to be the maximum in quantitative analysis. In qualitative analysis the FAA pool of the parasites under various treatments remained same as that of the control; however, quantitatively the level of various FAAs in the parasite was significantly affected. The treated parasites showed a marked decrease in the levels of arginine, ornithine, tyrosine, leucine, isoleucine, valine, alanine, glycine, proline, serine, threonine, and taurine following treatment with 20 mg/ml of crude peel extract, 0.5 mg/ml of genistein and 20 mg/ml of the reference drug, though an increase in the levels of glutamic acid, glutamine, phosphoserine, citrulline and GABA was noticeable. Enhanced levels of GABA and citrulline under the influence of genistein may be implicated in alterations of nitric oxide release and consequent neurological change (e.g. paralysis) in the parasite. Ammonia in the tissue homogenate as well as in the incubation medium showed a quantitative increase compared to the controls after treatment with the various test materials. The ammonia level increased by 40.7%, 66.4% and 18.16% in treatments with F. vestita, genistein and oxyclozanide, respectively, at the mentioned dosages. The changes in the levels of the amino acids and nitrogen components post treatment suggest that the amino acid metabolism in the parasite may have been altered under the influence of the test materials.     

Neue diterpene und sesquiterpene aus südafrikanischen Helichrysum-arten

The investigation of several South African Helichrysum species afforded in addition to known compounds two new kaurenic acid derivatives, three new labdane derivatives, three aromadendrene derivatives and geranylterpinene. The structures are elucidated mainly by extensive ¹H NMR-studies. The chemotaxonomic importance of these findings is discussed briefly.     

Severe Sepsis in Severely Malnourished Young Bangladeshi Children with Pneumonia: A Retrospective Case Control Study

BackgroundIn developing countries, there is no published report on predicting factors of severe sepsis in severely acute malnourished (SAM) children having pneumonia and impact of fluid resuscitation in such children. Thus, we aimed to identify predicting factors for severe sepsis and assess the outcome of fluid resuscitation of such children.MethodsIn this retrospective case-control study SAM children aged 0–59 months, admitted to the Intensive Care Unit (ICU) of the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh from April 2011 through July 2012 with history of cough or difficult breathing and radiologic pneumonia, who were assessed for severe sepsis at admission constituted the study population. We compared the pneumonic SAM children with severe sepsis (cases = 50) with those without severe sepsis (controls = 354). Severe sepsis was defined with objective clinical criteria and managed with fluid resuscitation, in addition to antibiotic and other supportive therapy, following the standard hospital guideline, which is very similar to the WHO guideline.ResultsThe case-fatality-rate was significantly higher among the cases than the controls (40% vs. 4%; p<0.001). In logistic regression analysis after adjusting for potential confounders, lack of BCG vaccination, drowsiness, abdominal distension, acute kidney injury, and metabolic acidosis at admission remained as independent predicting factors for severe sepsis in pneumonic SAM children (p<0.05 for all comparisons).

Conclusion and Significance

We noted a much higher case fatality among under-five SAM children with pneumonia and severe sepsis who required fluid resuscitation in addition to standard antibiotic and other supportive therapy compared to those without severe sepsis. Independent risk factors and outcome of the management of severe sepsis in our study children highlight the importance for defining optimal fluid resuscitation therapy aiming at reducing the case fatality in such children.     

Cissampelos pareira Linn: Natural Source of Potent Antiviral Activity against All Four Dengue Virus Serotypes

Background

Dengue, a mosquito-borne viral disease, poses a significant global public health risk. In tropical countries such as India where periodic dengue outbreaks can be correlated to the high prevalence of the mosquito vector, circulation of all four dengue viruses (DENVs) and the high population density, a drug for dengue is being increasingly recognized as an unmet public health need.

Methodology/Principal findings

Using the knowledge of traditional Indian medicine, Ayurveda, we developed a systematic bioassay-guided screening approach to explore the indigenous herbal bio-resource to identify plants with pan-DENV inhibitory activity. Our results show that the alcoholic extract of Cissampelos pariera Linn (Cipa extract) was a potent inhibitor of all four DENVs in cell-based assays, assessed in terms of viral NS1 antigen secretion using ELISA, as well as viral replication, based on plaque assays. Virus yield reduction assays showed that Cipa extract could decrease viral titers by an order of magnitude. The extract conferred statistically significant protection against DENV infection using the AG129 mouse model. A preliminary evaluation of the clinical relevance of Cipa extract showed that it had no adverse effects on platelet counts and RBC viability. In addition to inherent antipyretic activity in Wistar rats, it possessed the ability to down-regulate the production of TNF-α, a cytokine implicated in severe dengue disease. Importantly, it showed no evidence of toxicity in Wistar rats, when administered at doses as high as 2g/Kg body weight for up to 1 week.

Conclusions/Significance

Our findings above, taken in the context of the human safety of Cipa, based on its use in Indian traditional medicine, warrant further work to explore Cipa as a source for the development of an inexpensive herbal formulation for dengue therapy. This may be of practical relevance to a dengue-endemic resource-poor country such as India.     

Are Protected Areas Required to Maintain Functional Diversity in Human-Modified Landscapes?

The conversion of forest to agriculture across the world’s tropics, and the limited space for protected areas, has increased the need to identify effective conservation strategies in human-modified landscapes. Isolated trees are believed to conserve elements of ecological structure, providing micro-sites for conservation in matrix landscapes, and facilitating seed dispersal and forest restoration. Here we investigate the role of isolated Ficus trees, which are of critical importance to tropical forest ecosystems, in conserving frugivore composition and function in a human-modified landscape in Assam, India. We surveyed the frugivorous birds feeding at 122 isolated Ficus trees, 33 fruit trees, and 31 other large trees across a range of 32 km from the nearest intact forest. We found that Ficus trees attracted richer and more abundant assemblages of frugivores than the other tree categories. However, incidence function estimates revealed that forest specialist species decreased dramatically within the first kilometre of the forest edge. Despite this, species richness and functional diversity remained consistent across the human-modified landscape, as habitat generalists replaced forest-dependent frugivores, and accounted for most of the ecological function found in Ficus trees near the forest edge. We recommend that isolated Ficus trees are awarded greater conservation status, and suggest that their conservation can support ecologically functional networks of frugivorous bird communities.