Comparative action of 1,4-phenylenebis(methylene)selenocyanate and its metabolites against 7,12-dimethylbenz[a]anthracene-DNA adduct formation in the rat and cell proliferation in rat mammary tumor cells

1,4-phenylenebis(methylene)selenocyanate (p-XSC) inhibits 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis and DMBA-DNA binding in the rat mammary gland. Tetraselenocyclophane (TSC) was identified in rat feces as a metabolite of p-XSC. This led us to postulate the metabolic pathway: p-XSC-->glutathione conjugate (p-XSeSG)-->aromatic selenol (p-XSeH)-->TSC. Whether p-XSC or one of its metabolites is responsible for cancer prevention is the focus of this study. We utilized the DMBA-DNA binding assay with p-XSC as a positive control to evaluate the chemopreventive potential of p-XSC metabolites at dietary selenium levels of 10 ppm. Rats were fed AIN-76A diet supplemented with various selenium compounds for 1 week prior to the oral administration of a single dose of [3H]DMBA (5 mg per rat, specific activity 51.3 mCi/mmol). The rats were sacrificed 24 h later and DNA was isolated from the mammary fat pads. Relative levels of total binding were: [pmol/mg DNA, mean +/- S.D., n=6]; DMBA [7.2 +/- 1.6]; DMBA+p-XSC [3.5 +/- 2.7]; DMBA+p-XSeSG [2.2 +/- 1.1]; DMBA+TSC [5.6 +/- 2.9]. All selenium compounds, except TSC, significantly inhibited DMBA-DNA adduct formation; however, the difference between p-XSC and p-XSeSG was not statistically significant. The inhibition of total binding was attributed to a reduction in the formation of the three major adducts derived from bay-region diol epoxides of DMBA. On the basis of their chromatographic characteristics, these were identified as anti-diol-epoxide:deoxyguanosine, syn-diol-epoxide:deoxyadenosine, and anti-diol-epoxide:deoxyadenosine. Our results suggest that p-XSeSG, but not TSC, is the likely inhibitor of mammary cancer. Selenium levels measured by atomic absorption spectroscopy in the target organ (mammary fat pads) and in plasma following the dietary administration of selenium compounds were in the order of p-XSeSG congruent with p-XSC>TSC. These results appear to be consistent with their order of inhibitory effects on total DMBA-DNA binding. Further in vitro studies of the effect of selenium compounds on cell proliferation suggest that, depending on the dose and time point selected, p-XSC is comparable to or better than p-XSeSG; but both are more effective than TSC. Collectively, our in vivo and in vitro results indicate that p-XSC and its conjugate are better candidates than TSC for future studies on mammary cancer chemoprevention.     

Cellular and molecular pathways that lead to progression and regression of renal fibrogenesis

Renal fibrosis is a common consequence and often a central feature of all the progressive renal diseases that lead to end-stage renal failure. In comparison to wound healing, during kidney fibrosis the length of the post-inflammatory phase often exceeds and continues unchecked resulting in scar formation. Infiltrating immune cells and a heterogeneous colony of interstitial cells derived from a variety of cellular origins such as resident mesenchymal cells, tubular epithelial cells, circulating fibrocytes, and bone marrow derived stem cells, communicate with each other and with inflamed and surviving parenchymal cells via a network of cytokines and adhesion molecules to populate the renal tubulointerstitial space during early fibrogenesis. Such fibroblasts subsequently secrete abundant extracellular matrix to achieve architectural remodeling in parallel with functional deterioration. Renal fibrosis is a dominant determinant of the clinical outcome of patients and yet for the most part, current therapies are ineffective or only marginally effective. This review highlights recent advances in our understanding of the cellular and molecular events leading to the progression of renal fibrosis.     

A simple method for efficient extraction and purification of C-phycocyanin from Spirulina platensis Geitler

Phycocyanin is a major light harvesting accessory pigment of red algae and cyanobacteria. In the light of its many commercial applications in food and pharmaceutical industry, purity of the pigment plays a major role. Pharmaceutical industry demands a highly pure phycocyanin with A620/280 ratio of 4 and food industry a ratio of 2. In the present study phycocyanin was extracted in sodium phosphate buffer (pH 7) after macerating in liquid nitrogen. The crude phycocyanin thus extracted was precipitated with 50% ammonium sulphate, purified by dialysis and finally by gel filtration chromatography. Pure phycocyanin was finally obtained with an A620/A280 value of 4.98.     

Bone morphogenic protein-7 induces mesenchymal to epithelial transition in adult renal fibroblasts and facilitates regeneration of injured kidney

In the kidney, a unique plasticity exists between epithelial and mesenchymal cells. During kidney development, the metanephric mesenchyme contributes to emerging epithelium of the nephron via mesenchymal to epithelial transition (MET). In the injured adult kidney, renal epithelia contribute to the generation of fibroblasts via epithelial-mesenchymal transition, facilitating renal fibrosis. Recombinant human bone morphogenic protein (BMP)-7, a morphogen that is essential for the conversion of epithelia from condensing mesenchyme during kidney development, enhances the repair of tubular structures in the kidney. In this setting, BMP-7 inhibits epithelial-mesenchymal transition involving adult renal epithelial tubular cells and decreases secretion of type I collagen by adult renal fibroblasts. In search of a mechanism behind the ability of BMP-7 to repair damaged renal tubules, we hypothesized that systemic treatment with BMP-7 might induce MET involving adult renal fibroblasts in the injured kidney, generating functional epithelial cells. Here we report that BMP-7 induces formation of epithelial cell aggregates in adult renal fibroblasts associated with reacquisition of E-cadherin expression and decreased motility, mimicking the effect of BMP-7 on embryonic metanephric mesenchyme to generate epithelium. In addition, we provide evidence that BMP-7-mediated repair of renal injury is associated with MET involving adult renal interstitial fibroblasts in mouse models for renal fibrosis. Collectively, these findings suggest that adult renal fibroblasts might retain parts of their original embryonic imprint and plasticity, which can be re-engaged by systemic administration of BMP-7 to mediate repair of tubular injury in a fibrotic kidney.     

Reduced DNA gap repair in aging rat neuronal extracts and its restoration by DNA polymerase beta and DNA-ligase

Synthetic deoxy-oligo duplexes containing short gaps of 1 and 4 nucleotides were used as model substrates to assess the DNA gap repair ability of the neuronal extracts prepared from cerebral cortex of rats of different ages. Our results demonstrate that gap repair activity in neurons decreases markedly with age. The decreased activity could be restored by supplementing the neuronal extracts with pure recombinant rat liver DNA polymerase beta. High levels of DNA polymerase beta supplementation resulted in gap-filling activity that proceeded essentially through addition of nucleotides through a slow distributive strand displacement mode to achieve full template length (32-mer). However, at lower concentrations of DNA polymerase beta, the gap repair takes place quickly through gap filling followed by ligation to downstream primer, in an energy efficient manner. For this to happen, the conditions required are the presence of 5'-PO4 on the downstream primer and supplementation of aging neuronal extracts with DNA-ligase in addition to recombinant DNA polymerase beta. These results demonstrate that aging neurons are unable to affect base excision repair (BER) due to deficiency of DNA polymerase beta and DNA-ligase and fortifying aged neuronal extracts with these two factors can restore the lost BER activity.     

Decreased expression of vesicular GABA transporter, but not vesicular glutamate, acetylcholine and monoamine transporters in rat brain following focal ischemia

In nerve terminals, vesicular transporters pack neurotransmitters into synaptic vesicles, which is an essential prerequisite for transmitter release. To date, three distinct families of vesicular transporters have been identified which are specific for (a) excitatory amino acids (glutamate and aspartate), (b) inhibitory amino acids (GABA and glycine) and (c) acetylcholine and monoamines. The present study evaluated the effect of transient focal cerebral ischemia on the expression of these vesicular transporters in adult rat brain. Ischemia was induced by a 1 h transient middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats. At various reperfusion periods (3-72 h), mRNA levels of the vesicular transporters were estimated in the contralateral and the ipsilateral cerebral cortex by real-time PCR analysis. Following transient focal ischemia, mRNA expression of the vesicular GABA transporter (VGAT) decreased significantly by 3 h of reperfusion and remained at a significantly lower level than sham until at least 72 h of reperfusion. Western blotting showed a significant decrease in the VGAT immunoreactive protein levels in the ipsilateral cortex of rats subjected to focal ischemia and 24 h reperfusion. Immunohistochemistry demonstrated many VGAT immunopositive puncta in the contralateral cortex, which were significantly decreased in the ipsilateral cortex at 24 h reperfusion. Focal ischemia had no effect on the mRNA levels of the vesicular transporters specific for glutamate/aspartate, acetylcholine and monoamines at either 6 h or 24 h of reperfusion.     

A systematic approach to biological control agent exploration and prioritisation for prickly acacia (Acacia nilotica ssp. indica)

Abstract  Agent selection for prickly acacia has been largely dictated by logistics and host specificity. Given that detailed ecological information is available on this species in Australia, we propose that it is possible to select agents based on agent efficacy and desired impact on prickly acacia demography. We propose to use the 'plant genotype' and 'climatic' similarities as filters to identify areas for future agent exploration; and plant response to herbivory and field host range as 'predictive' filters for agent prioritisation. Adopting such a systematic method that incorporates knowledge from plant population ecology and plant–herbivore interactions makes agent selection decisions explicit and allow more rigorous evaluations of agent performance and better understanding of success and failure of agents in weed biological control.     

Microbial mediation of fruit fly–host plant interactions: is the host plant the “centre of activity”?

Insects utilize resources in their environment with the aid of mutualistic or symbiotic mediation by microorganisms. Some insect species such as ants and termites often have complex ecological and evolutionary associations with their symbionts, while the nature and functional significance of such associations in non-social insects is often unclear. In the Dacinae (Diptera: Tephritidae), specific Enterobacteriaceae ( Erwinia herbicola , Enterobacter cloacae , Klebsiella oxytoca ) are believed to mediate interactions between the adult fruit flies and the larval host plant. This bacterial mediation is hypothesized as being integral to the larval host plant being the "centre of activity" of the fly. Using a non-pest, monophagous fruit fly ( Bactrocera cacuminata [Hering]), we tested this hypothesis by manipulating the fruiting state of its larval host plant ( Solanum mauritianum Scopoli) and subsequently assessing insect behaviour and phylloplane microflora on those hosts. On host plants that had never fruited, few flies or bacterial colonies were recorded, consistent with hypothesis expectations. On fruiting host plants or plants that had had their fruit removed, bacterial colonies were present; again consistent with expectation. However, few flies were recorded on fruit-removed plants and all fly behaviours, other than resting or oviposition, were rare or absent on any hosts; inconsistent with expectation. The general pattern of results suggested that female flies coming to oviposit on fruiting hosts were spreading Enterobacteriaceae, but such spread was incidental and not part of some mutualistic interaction between fruit flies and bacteria.     

Trichoderma sp. as a microbial suppressive agent of Sclerotium rolfsii on vegetables

World Journal of Microbiology and Biotechnology -     

Nature and type of gene action governing resistance to Helminthosporium turcicum leaf blight in maize (Zea mays L.)

Six generations, consisting of three resistant parents, three susceptible parents, their 15 possible F₁ crosses, 15 F₂'s, 15 BC₁'s (F₁ x resistant female parent) and 15 BC₂'s (F₁ x susceptible male parent) were analysed following Hayman (Heredity 12: 371–390, 1958) to evaluate the nature and type of gene action governing resistance to H. turcicum. The results showed that all types of gene effects, viz., additive, dominance and epistasis (i.e., additive x additive, additive x dominance and dominance x dominance) were operating in one cross or the other in controlling resistance. However, it was additive gene action and dominance x dominance type of epistasis with duplicate nature that were important in controlling resistance in most crosses. Depending upon the final objectives, one of the breeding methods, viz., recurrent selection, heterosis breeding, back-cross method or full-sib selection (bi-parental mating) may be followed.