Membrane-Active Macromolecules Resensitize NDM-1 Gram-Negative Clinical Isolates to Tetracycline Antibiotics

Gram-negative ‘superbugs’ such as New Delhi metallo-beta-lactamase-1 (bla _NDM-1) producing pathogens have become world’s major public health threats. Development of molecular strategies that can rehabilitate the ‘old antibiotics’ and halt the antibiotic resistance is a promising approach to target them. We report membrane-active macromolecules (MAMs) that restore the antibacterial efficacy (enhancement by >80-1250 fold) of tetracycline antibiotics towards bla _NDM-1 Klebsiella pneumonia and bla _NDM-1 Escherichia coli clinical isolates. Organismic studies showed that bacteria had an increased and faster uptake of tetracycline in the presence of MAMs which is attributed to the mechanism of re-sensitization. Moreover, bacteria did not develop resistance to MAMs and MAMs stalled the development of bacterial resistance to tetracycline. MAMs displayed membrane-active properties such as dissipation of membrane potential and membrane-permeabilization that enabled higher uptake of tetracycline in bacteria. In-vivo toxicity studies displayed good safety profiles and preliminary in-vivo antibacterial efficacy studies showed that mice treated with MAMs in combination with antibiotics had significantly decreased bacterial burden compared to the untreated mice. This report of re-instating the efficacy of the antibiotics towards bla _NDM-1 pathogens using membrane-active molecules advocates their potential for synergistic co-delivery of antibiotics to combat Gram-negative superbugs.     

Studies on collagen-tannic acid-collagenase ternary system: Inhibition of collagenase against collagenolytic degradation of extracellular matrix component of collagen

We report the detailed studies on the inhibitory effect of tannic acid (TA) on Clostridium histolyticum collagenase (ChC) activity against degradation of extracellular matrix component of collagen. The TA treated collagen exhibited 64% resistance against collagenolytic hydrolysis by ChC, whereas direct interaction of TA with ChC exhibited 99% inhibition against degradation of collagen and the inhibition was found to be concentration dependant. The kinetic inhibition of ChC has been deduced from the extent of hydrolysis of N-[3-(2-furyl) acryloyl]-Leu-Gly-Pro-Ala (FALGPA). This data provides a selective competitive mode of inhibition on ChC activity seems to be influenced strongly by the nature and structure of TA. TA showed inhibitor activity against the ChC by molecular docking method. This result demonstrated that TA containing digalloyl radical possess the ability to inhibit the ChC. The inhibition of ChC in gaining new insight into the mechanism of stabilization of collagen by TA is discussed.     

On the role of TolC in multidrug efflux: the function and assembly of AcrAB–TolC tolerate significant depletion of intracellular TolC protein

TolC channel provides a route for the expelled drugs and toxins to cross the outer membrane of Escherichia coli. The puzzling feature of TolC structure is that the periplasmic entrance of the channel is closed by dense packing of 12 α‐helices. Efflux pumps exemplified by AcrAB are proposed to drive the opening of TolC channel. How interactions with AcrAB promote the close‐to‐open transition in TolC remains unclear. In this study, we investigated in vivo the functional and physical interactions of AcrAB with the closed TolC and its conformer opened by mutations in the periplasmic entrance. We found that the two conformers of TolC are readily distinguishable in vivo by characteristic drug susceptibility, thiol modification and proteolytic profiles. However, these profiles of TolC variants respond neither to the in vivo stoichiometry of AcrAB:TolC nor to the presence of vancomycin, which is used often to assess the permeability of TolC channel. We further found that the activity and assembly of AcrAB–TolC tolerates significant changes in amounts of TolC and that only a small fraction of intracellular TolC is likely used to support efflux needs of E. coli. Our findings explain why TolC is not a good target for inhibition of multidrug efflux.     

Implications of the genetic epidemiology of globin haplotypes linked to the sickle cell gene in southern Iran

To determine the origin of sickle cell mutation in different ethnic groups living in southern Iran, we studied the haplotype background of the betaS and betaA genes in subjects from the provinces of Fars, Khuzestan, Bushehr, Hormozgan, and Kerman and from the islands of Khark and Qeshm. beta-globin gene cluster haplotypes were determined using the PCR-RFLP technique. Detection of -alpha 3.7 deletion and beta-thalassemia mutations were defined by PCR and reverse dot blot techniques, respectively. The framework of the beta-globin gene was determined using denaturing gradient gel electrophoresis. We found that the betaS mutation in southern Iran is associated with multiple mutational events. Most of the patients were from two ethnic groups: Farsi speakers (presumably Persian in origin) from Fars province and patients of Arab origin from Khuzestan province. In both ethnic groups the Arab-Indian haplotype was the most prevalent. The frequencies of the Arab-Indian and African haplotypes in sickle cell anemia patients from the provinces of Fars and Khuzestan were similar. Among betaA chromosomes the Bantu A2 haplotype was the most prevalent. The decrease in alpha-globin production in SS patients and AS individuals appeared to be related to the reduction in mean cell volume and mean cell hemoglobin. The Arab-Indian haplotype gene flow into this region of Iran can be traced to the Sassanian Empire. It is likely that the influx of betaS genes linked to the Benin and Bantu haplotypes, of African origin, must have occurred during the Arab slave trade.     

Biological control of citrus mealybug,Planococcus citri with an introduced parasite,Leptomastix dactylopii in India

Planococcus citri (Risso) is one of the major pests of citrus orchards in India. For the control ofP. citri, an encyrtid parasite,Leptomastix dactylopii How. was introduced from West Indies in 1983. The parasite was mass bred and inoculative releases were made in 2 selected citrus orchards where infestation of mealybug on fruits (sweet orange, seedless lime and acid lime) ranged from 38 to 65 per cent. Establishment of the parasite in the 2 release orchards resulted in complete control of the mealybug within 3 to 4 months. No insecticidal sprays were required subsequently for the control ofP. citri in the following seasons. Contribution No. 152/85 of the IIHR, Bangalore — 560089.     

Re-irradiation after stereotactic body radiotherapy for spine metastases from hepatocellular carcinoma: a case report

Modern radiotherapy machines with refinements in planning software and image-guidance apparatuses have made stereotactic body radiotherapy (SBRT) more widely available as an effective tool in the management of spine metastases. In conventional palliative radiotherapy, the aim has traditionally been pain relief and short-term local control. In contrast, SBRT aims to deliver an ablative dose to enhance local control, with a smaller number of fractions while sparing the organs at risk (OAR), especially the spinal cord. Recently, trials have asserted the role of spine SBRT as an effective modality for durable local control, in addition to achieving pain relief. The quality of evidence for spine SBRT data is maturing, while prospective published trials on re-irradiation SBRT in spine remain sparse. The purpose of the present case report is to share the challenges faced while salvaging a dorsal spine metastasis and ablating a new right adrenal metastatic lesion in proximity of the transplanted liver.     

Nutrient uptake by paddy during the main three stages of growth

Summary Uptake of mineral nutrients and production of carbohydrates by paddy during the vegetative, the reproductive, and the ripening stage of growth were determined in a pot experiment.From 59 to 84 per cent of the nutrients present in the ripe plants were absorbed between tillering and flowering. More than 90 per cent of the N and K, 80 per cent of the P and Ca, and 65 per cent of the Mg were absorbed prior to flowering, and the remainder after heading.More than 60 per cent of the carbohydrates present in the ripe stage was produced after flowering.     

Activation of c-Kit in dendritic cells regulates T helper cell differentiation and allergic asthma

Dendritic cells (DCs) are integral to the differentiation of T helper cells into T helper type 1 T(H)1, T(H)2 and T(H)17 subsets. Interleukin-6 (IL-6) plays an important part in regulating these three arms of the immune response by limiting the T(H)1 response and promoting the T(H)2 and T(H)17 responses. In this study, we investigated pathways in DCs that promote IL-6 production. We show that the allergen house dust mite (HDM) or the mucosal adjuvant cholera toxin promotes cell surface expression of c-Kit and its ligand, stem cell factor (SCF), on DCs. This dual upregulation of c-Kit and SCF results in sustained signaling downstream of c-Kit, promoting IL-6 secretion. Intranasal administration of antigen into c-Kit-mutant mice or neutralization of IL-6 in cultures established from the lung-draining lymph nodes of immunized wild-type mice blunted the T(H)2 and T(H)17 responses. DCs lacking functional c-Kit or those unable to express membrane-bound SCF secreted lower amounts of IL-6 in response to HDM or cholera toxin. DCs expressing nonfunctional c-Kit were unable to induce a robust T(H)2 or T(H)17 response and elicited diminished allergic airway inflammation when adoptively transferred into mice. Expression of the Notch ligand Jagged-2, which has been associated with T(H)2 differentiation, was blunted in DCs from c-Kit-mutant mice. c-Kit upregulation was specifically induced by T(H)2- and T(H)17-skewing stimuli, as the T(H)1-inducing adjuvant, CpG oligodeoxynucleotide, did not promote either c-Kit or Jagged-2 expression. DCs generated from mice expressing a catalytically inactive form of the p110delta subunit of phosphatidylinositol-3 (PI3) kinase (p110(D910A)) secreted lower amounts of IL-6 upon stimulation with cholera toxin. Collectively, these results highlight the importance of the c-Kit-PI3 kinase-IL-6 signaling axis in DCs in regulating T cell responses.