Induction of mitochondrial nitrative damage and cardiac dysfunction by chronic provision of dietary omega-6 polyunsaturated fatty acids

Increased awareness of obesity has led to a dietary shift toward "heart-friendly" vegetable oils containing omega-6 polyunsaturated fatty acid (omega-6 PUFA). In addition to its beneficial effects, omega-6 PUFA also exhibits proinflammatory and prooxidative properties. We hypothesized that chronic dietary omega-6 PUFA can induce free radical generation, predisposing the cardiac mitochondria to oxidative damage. Male Wistar rats were fed a diet supplemented with 20% w/w sunflower oil, rich in omega-6 PUFA (HP) or normal laboratory chow (LP) for 4 weeks. HP feeding augmented phospholipase A(2) activity and breakdown of cardiolipin, a mitochondrial phospholipid. HP hearts also demonstrated elevated inducible nitric oxide synthase expression, loss of Mn superoxide dismutase, and increased mitochondrial nitrotyrosine levels. In these hearts, oxidative damage to mitochondrial DNA (mDNA) was demonstrated by 8-hydroxyguanosine immunopositivity, overexpression of DNA repair enzymes, and a decrease in the mRNA expression of specific respiratory subunits encoded by the mDNA. Functionally, at higher workloads, HP hearts also demonstrated a greater decline in cardiac work than LP, suggesting a compromised mitochondrial reserve. Our study, for the first time, demonstrates that consumption of a high fat diet rich in omega-6 PUFA for only 4 weeks instigates mitochondrial nitrosative damage and causes cardiac dysfunction at high afterloads.     

Importance of Native Grassland Habitat for Den-Site Selection of Indian Foxes in a Fragmented Landscape

Fragmentation of native habitats is now a ubiquitous phenomenon affecting wildlife at various scales. We examined selection of den-sites (n = 26) by Indian foxes (Vulpes bengalensis) in a highly modified short-grassland landscape in central India (Jan-May, 2010). At the scale of the home-range, defined by an 800 m circular buffer around den sites, we examined the effect of land-cover edges and roads on selection of sites for denning using a distance-based approach. At the smaller den-area scale, defined by a 25 m x 25 m plot around den and paired available sites, the effect of microhabitat characteristics was examined using discrete-choice models. Indian foxes selected den-sites closer to native grasslands (t = -9.57, P < 0.001) and roads (t = -2.04, P = 0.05) than random at the home-range scale. At the smaller scale, abundance of rodents and higher visibility increased the odds of selection of a site by eight and four times respectively, indicating resource availability and predator avoidance to be important considerations for foxes. Indian foxes largely chose to den in human-made structures, indicated by the proportion of dens found in earthen bunds (0.69) and boulder piles (0.27) in the study area. With agricultural expansion and human modification threatening native short-grassland habitats, their conservation and effective management in human-dominated landscapes will benefit the Indian fox. The presence of some human-made structures within native grasslands would also be beneficial for this den-dependent species. We suggest future studies examine the impact of fragmentation and connectivity of grasslands on survival and reproductive success of the Indian fox.     

Snake venom hyaluronidase: An evidence for isoforms and extracellular matrix degradation

The present study attempts to establish the isoforms of hyaluronidase enzyme and their possible role in the spreading of toxins during envenomation. Screening of venoms of 15 snakes belonging to three different families revealed varied hyaluronidase activity in ELISA-like assay, but with relatively similar pH and temperature optima. The zymograms of individual venoms showed varied activity banding patterns and indicated the presence of at least two molecular forms of the enzyme. During envenomation, activity of hyaluronidase is considered crucial for the spreading of toxins and is presumed to distort the integrity of extracellular matrix through the degradation of hyaluronic acid in it. This property has been addressed through localization of hyaluronic acid in human skin and muscle tissue sections using the probe, biotinylated hyaluronic acid binding protein. Faint and discontinuous staining pattern of hyaluronidase treated tissue sections over intense staining of untreated tissue sections confirm the selective degradation of hyaluronic acid in extracellular matrix and thus provide an evidence for the spreading property of the enzyme.     

Isolation and characterization of hyaluronidase a "spreading factor" from Indian cobra (Naja naja) venom

Hyaluronidase, ubiquitous enzyme in snake venoms, known originally as "spreading factor", has not been well studied. The present study describes the purification and characterization of hyaluronidase from Indian cobra (Naja naja) venom and provides systematic evaluation of the spreading property of the enzyme. Hyaluronidase (NNH1) has been purified through gel permeation and ion exchange chromatography. The molecular mass was found to be 70.406 kDa by MALDI-TOF mass spectrometry and with the (p)i pI of 9.2. The amino acid sequence of the N-terminus was found to be NEQSTHGAYV. The enzyme shows absolute specificity for hyaluronan and belongs to the group of neutral active enzymes. Tetrasaccharides are the final product of hyaluronan digestion. The enzyme cleaves beta 1,4-glycosidic linkage and belongs to a group of endo-beta-N-acetyl hexosaminidases. Hyaluronidase indirectly potentiates the myotoxicity of VRV-PL-VIII, a phospholipolytic myotoxin, and also the hemorrhagic potency of a hemorrhagic complex-I. Localization of hyaluronan in human skin section and selective degradation by venom hyaluronidase (NNH1) corroborate the plausible in vivo degradation of hyaluronan in the extracellular matrix (ECM) resulting in easy dissemination of VRV-PL-VIII myotoxin and hemorrhagic complex-I.     

Gγ1, a Downstream Target for the hmgcr-Isoprenoid Biosynthetic Pathway, Is Required for Releasing the Hedgehog Ligand and Directing Germ Cell Migration

The isoprenoid biosynthetic pathway leading from the production of mevalonate by HMGCoA reductase (Hmgcr) to the geranylation of the G protein subunit, Gγ1, plays an important role in cardiac development in the fly. Hmgcr has also been implicated in the release of the signaling molecule Hedgehog (Hh) from hh expressing cells and in the production of an attractant that directs primordial germ cells to migrate to the somatic gonadal precursor cells (SGPs). The studies reported here indicate that this same hmgcr→Gγ1 pathway provides a novel post-translational mechanism for modulating the range and activity of the Hh signal produced by hh expressing cells. We show that, like hmgcr, gγ1 and quemao (which encodes the enzyme, geranylgeranyl diphosphate synthetase, that produces the substrate for geranylation of Gγ1) are components of the hh signaling pathway and are required for the efficient release of the Hh ligand from hh expressing cells. We also show that the hmgcr→Gγ1 pathway is linked to production of the germ cell attractant by the SGPs through its ability to enhance the potency of the Hh signal. We show that germ cell migration is disrupted by the loss or gain of gγ1 activity, by trans-heterozygous combinations between gγ1 and either hmgcr or hh mutations, and by ectopic expression of dominant negative Gγ1 proteins that cannot be geranylated.     

Synthesis and Biological Activity of 6-Hydroxyguanidino-and 6-Hydroxyureidopurine And Their Ribonucleosides

Abstract

N ⁶ ?(1-hydroxyguanidino)purine IIa, and its 9-β-D-ribonucleoside derivative IIb were prepared by reacting at room temperature 6-hydroxyadenine Ia and 6-hydroxyadenosine Ib, with 1-guanyl-3,5-dimethylpyrazole nitrate in DMF. Refluxing IIa and IIb in 95% ethanol gave N⁶?(1-hydroxyureido)purine and its ribonucleoside derivative respectively; the latter compound was also obtained by refluxing Ib with 1-guanyl-3,5-dimethylpyrazole nitrate in ethanol. The two base analogs were inactive against L1210 cells in vitro, but the nucleoside derivatives inhibited the growth of these cells by 50% at 5 × 10 ^-6 and 6 × 10^?7 M respectively. Compound IIb, at 200 mg/kg/day × 5, increased the life span of L1210-bearing DBA/2N mice by 57%. Cytofluorometric determinations showed that IIb inhibited cell growth in the G₂ phase of the cell cycle. also found to inhibit adenosine deaminase activity with a K_i = 3.47 μM.