Pre and Post Natal Exposure of Fluoride Induced Oxidative Macromolecular Alterations in Developing Central Nervous System of Rat and Amelioration by Antioxidants

The effect of fluoride exposure during gestation and post gestation periods were studied to check the status of oxidant, antioxidant and macromolecular changes in CNS and ameliorative role of antioxidants. The pregnant Wistar albino rats were exposed to 50 and 150 ppm fluoride in drinking water and the pups born to them were used for experimentation. After postpartum, the pups were administered daily selected antioxidants through oral gavage. On 21st postnatal day pups were sacrificed and biochemical parameters were assessed. Fluoride exposure substantially increased the activity/levels of fluoride, LPO, protein oxidation, MAO-B, GOT, GPT and decreased protein thiols, RNA and total proteins in discrete regions of CNS. The findings evidenced fluoride induced dyshomeostasis caused on antioxidants, enzymes, macromolecules and governed the pathophysiological events leading to functional loss in a dose dependent manner. The administration of antioxidants remedied the disquiet caused by high fluoride exposure at extreme vulnerable periods of life.     

3D-QSAR and molecular docking studies of 2-pyrimidinecarbonitrile derivatives as inhibitors against falcipain-3

The three dimensional-quantitative structure activity relationship (3D-QSAR) studies were performed on a series of falcipain-3 inhibitors using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques. A training set containing 42 molecules served to establish the QSAR models. The optimum CoMFA and CoMSIA models obtained for the training set were statistically significant with cross-validated correlation coefficients r(cv)(2) (q(2)) of 0.549 and 0.608, and conventional correlation coefficients (r(2)) of 0.976 and 0.932, respectively. An independent test set of 12 molecules validated the external predictive power of both models with predicted correlation coefficients (r(pred)(2)) for CoMFA and CoMSIA as 0.697 and 0.509, respectively. The docking of inhibitors into falcipain-3 active site using GOLD software revealed the vital interactions and binding conformation of the inhibitors. The CoMFA and CoMSIA field contour maps agree well with the structural characteristics of the binding pocket of falcipain-3 active site, which suggests that the information rendered by 3D-QSAR models and the docking interactions can provide guidelines for the development of improved falcipain-3 inhibitors.     

A conserved patch near the C terminus of histone H4 is required for genome stability in budding yeast

A screen of Saccharomyces cerevisiae histone alanine substitution mutants revealed that mutations in any of three adjacent residues, L97, Y98, or G99, near the C terminus of H4 led to a unique phenotype. The mutants grew slowly, became polyploid or aneuploid rapidly, and also lost chromosomes at a high rate, most likely because their kinetochores were not assembled properly. There was lower histone occupancy, not only in the centromeric region, but also throughout the genome for the H4 mutants. The mutants displayed genetic interactions with the genes encoding two different histone chaperones, Rtt106 and CAF-I. Affinity purification of Rtt106 and CAF-I from yeast showed that much more H4 and H3 were bound to these histone chaperones in the case of the H4 mutants than in the wild type. However, in vitro binding experiments showed that the H4 mutant proteins bound somewhat more weakly to Rtt106 than did wild-type H4. These data suggest that the H4 mutant proteins, along with H3, accumulate on Rtt106 and CAF-I in vivo because they cannot be deposited efficiently on DNA or passed on to the next step in the histone deposition pathway, and this contributes to the observed genome instability and growth defects.     

Effect of maternal exposure of fluoride on oxidative stress markers and amelioration by selected antioxidants in developing central nervous system of rats

Fluoride has been implicated as a pathologic mediator of fluorosis. Interestingly neuronal destruction, synaptic injury occurs by a mechanism involving oxidative stress, however, its effects in developmental stages of life, during maternal fluoride exposure and amelioration are not elucidated. In the present study, pregnant Wistar albino rats were exposed to 50 and 150 ppm fluoride in drinking water during gestation and post gestation. After parturition the pups born to the experimental animals were administered daily with selected antioxidants for 21 consecutive days. Fluoride administration substantially enhanced fluoride accumulation, lipid peroxidation and decreased the activity of superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione levels in discrete regions of central nervous system. The results significantly (P < 0.05) demonstrated the effect of fluoride through exacerbated oxidative damage and disrupted antioxidant homeostasis, leading to altered neuronal integrity. The administration of antioxidants vitamin E, vitamin C, selenium and zinc produced a promising accost and timely intervention to the aggravated impairment during highly vulnerable early stage of life.     

Manipulating the edge of instability

We investigate the integration of visual and tactile sensory input for dynamic manipulation. Our experimental data and computational modeling reveal that time-delays are as critical to task-optimal multisensory integration as sensorimotor noise. Our focus is a dynamic manipulation task "at the edge of instability." Mathematical bifurcation theory predicts that this system will exhibit well-classified low-dimensional dynamics in this regime. The task was using the thumbpad to compress a slender spring prone to buckling as far as possible, just shy of slipping. As expected from bifurcation theory, principal components analysis gives a projection of the data onto a low dimensional subspace that captures 91-97% of its variance. In this subspace, we formulate a low-order model for the brain+hand+spring dynamics based on known mechanical and neurophysiological properties of the system. By systematically occluding vision and anesthetically blocking thumbpad sensation in 12 consenting subjects, we found that vision contributed to dynamic manipulation only when thumbpad sensation was absent. The reduced ability of the model system to compress the spring with absent sensory channels closely resembled the experimental results. Moreover, we found that the model reproduced the contextual usefulness of vision only if we took account of time-delays. Our results shed light on critical features of dynamic manipulation distinct from those of static pinch, as well as the mechanism likely responsible for loss of manual dexterity and increased reliance on vision when age or neuromuscular disease increase noisiness and/or time-delays during sensorimotor integration.     

Short-strong hydrogen bonds and a low barrier transition state for the proton transfer reaction in RNase A catalysis: a quantum chemical study

There is growing evidence that some enzymes catalyze reactions through the formation of short-strong hydrogen bonds as first suggested by Gerlt and Gassman. Support comes from several experimental and quantum chemical studies that include correlation energies on model systems. In the present study, the process of proton transfer between hydroxyl and imidazole groups, a model of the crucial step in the hydrolysis of RNA by the enzymes of the RNase A family, is investigated at the quantum mechanical level of density functional theory and perturbation theory at the MP2 level. The model focuses on the nature of the formation of a complex between the important residues of the protein and the hydroxyl group of the substrate. We have also investigated different configurations of the ground state that are important in the proton transfer reaction. The nature of bonding between the catalytic unit of the enzyme and the substrate in the model is investigated by Bader's atoms in molecule theory. The contributions of solvation and vibrational energies corresponding to the reactant, the transition state and the product configurations are also evaluated. Furthermore, the effect of protein environment is investigated by considering the catalytic unit surrounded by complete proteins--RNase A and Angiogenin. The results, in general, indicate the formation of a short-strong hydrogen bond and the formation of a low barrier transition state for the proton transfer model of the enzyme.     

Modeling of angiogenin - 3-NMP complex

Angiogenin belongs to the Ribonuclease superfamily and has a weak enzymatic activity that is crucial for its biological function of stimulating blood vessel growth. Structural studies on ligand bound Angiogenin will go a long way in understanding the mechanism of the protein as well as help in designing drugs against it. In this study we present the first available structure of nucleotide ligand bound Angiogenin obtained by computer modeling. The importance of this study in itself notwithstanding, is a precursor to modeling a full dinucleotide substrate onto Angiogenin. Bovine Angiogenin, the structure of which has been solved at a high resolution, was earlier subjected to Molecular Dynamics simulations for a nanosecond. The MD structures offer better starting points for docking as they offer lesser obstruction than the crystal structure to ligand binding. The MD structure with the least serious short contacts was modeled to obtain a steric free Angiogenin - 3' mononucleotide complex structure. The structures were energetically minimized and subjected to a brief spell of Molecular Dynamics. The results of the simulation show that all the ligand-Angiogenin interactions and hydrogen bonds are retained, redeeming the structure and docking procedure. Further, following ligand - protein interactions in the case of the ligands 3'-CMP and 3'-UMP we were able to speculate on how Angiogenin, a predominantly prymidine specific ribonuclease prefers Cytosine to Uracil in the first base position.