Quinone and oxyradical scavenging properties of N-acetylcysteine prevent dopamine mediated inhibition of Na+, K+-ATPase and mitochondrial electron transport chain activity in rat brain: implications in the neuroprotective therapy of Parkinson's disease

Dopamine oxidation products such as H2O2 and reactive quinones have been held responsible for various toxic actions of dopamine, which have implications in the aetiopathogenesis of Parkinson's disease. This study has shown that N-acetylcysteine (0.25-1 mm) is a potent scavenger of both H2O2 and toxic quinones derived from dopamine and it further prevents dopamine mediated inhibition of Na+,K+-ATPase activity and mitochondrial respiratory chain function. The quinone scavenging ability of N-acetylcysteine is presumably related to its protective effect against dopamine mediated inhibition of mitochondrial respiratory chain activity. However, both H2O2 scavenging and quinone scavenging properties of N-acetylcysteine probably account for its protective effect against Na+,K+-ATPase inhibition induced by dopamine. The results have important implications in the neuroprotective therapy of sporadic Parkinson's disease since inactivation of mitochondrial respiratory activity and Na+,K+-ATPase may trigger intracellular damage pathways leading to the death of nigral dopaminergic neurons.     

Resonance Raman studies on xanthine oxidase: observation of Mo<Superscript>VI</Superscript>-ligand vibrations

Resonance Raman spectra were investigated for the sulfo and desulfo forms of cow's milk xanthine oxidase, with various visible excitation lines between 400 and 650 nm, and Mo(VI)-ligand vibrations were observed for the first time. The Mo(VI)=S stretch was identified at 474 and 462 cm(-1 )for the (32)S- and (34)S-sulfo forms, respectively, but was absent in the reduced state and in the desulfo form. The Mo(VI)=O stretch was weakly observed at 899 cm(-1 )for the sulfo form and shifted to 892 cm(-1) with very weak intensity for the dioxo desulfo form. In measurements of an excitation profile, the two bands at 474 and 899 cm(-1) showed maximum intensity at similar excitation wavelengths, suggesting that the Raman intensity of the metal-ligand modes is due to the Mo(VI)<--S charge transfer transition, and that this is the origin of the intrinsically weak features of the Mo(VI)-ligand Raman bands. When the sulfo form was regenerated from the desulfo form, the 899 cm(-1) band reappeared. However, the band at 899 cm(-1) showed no frequency shift when regeneration was conducted in H(2)(18)O, or after several turnovers in the presence of xanthine in H(2)(18)O. When the sulfo form was reduced and reoxidized in H(2)(18)O buffer, the 899 cm(-1) band reappeared without any frequency shift. These observations suggest that the oxo oxygen in the Mo center of xanthine oxidase is not labile. Low-frequency vibrations of the Mo center were observed together with those of the Fe(2)S(2) center with some overlaps, while FAD modes were observed clearly. The absence of dithiolene modes in XO is in contrast to the Mo(VI) centers of DMSO reductase and sulfite oxidase.     

Molecular recognition of plant DNA: Does it differ from conventional animal DNA?

The recognition mechanism of DNA with small drugs/ligands is an important field of research from pharmacological point of view. Such studies are ample with DNAs extracted from animal cells, but are rare for those extracted from plant cells. However, such a study is strongly demanding for the formulation of pesticides and other agrochemicals. In this contribution, for the first time, we report the interaction of two well-known DNA binder ethidium bromide (EB) and Hoechst 33258 (H33258) with two genomic DNAs extracted from the leaves of Ricinus communis L. (castor bean) and Mangifera indica (mango) using steady-state and picosecond-resolved fluorescence spectroscopy. The purity of the extracted DNAs is confirmed from gel electrophoresis and optical absorption studies. As evidenced from the circular dichroism (CD) measurements the DNAs retain physiologically relevant B forms. The well-known DNA intercalator EB has been found to show an additional electrostatic mode of binding with the DNAs, which is not present in the conventional animal DNAs. The binding affinity of EB is found to be even weaker for the DNA extracted from M. indica compared to that in R. communis L. On the other hand, the binding affinity of H33258 with the plant DNAs is found to be comparable to that of animal DNAs. The difference in interaction could be rationalized from the possible differences in the base sequences.     

Characterization and evaluation of methyl methacrylate-acetylated Saccharum spontaneum L. graft copolymers prepared under microwave

Hybridization of the natural polymers with synthetic polymers is of great interest because of its application to biomedical and biodegradable materials. Synthesis of graft copolymers of methyl methacrylate (MMA) onto acetylated Saccharum spontaneum L. fiber using ferrous ammonium sulphate–potassium per sulphate (FAS–KPS) redox initiator under the influence of microwave radiation (MWR) was carried-out. Different reaction parameters such as time, initiator molar ratio, monomer concentration, microwave power, pH and solvent were optimized to get maximum graft yield (72.2%). On grafting, percentage crystallinity decreases rapidly with reduction in its stiffness and hardness. The graft copolymers thus formed were characterized by FTIR, SEM, XRD, TGA, DTA and DTG techniques. Moreover, graft copolymers have been found to be more moisture resistant and also showed higher chemical and thermal resistance.     

Inhibitory effect of Abrus abrin-derived peptide fraction against Dalton's lymphoma ascites model

Peptides derived from larger molecules that are important modulators in cancer regression are becoming leads for development of therapeutic drugs. It has been reported that Abrus abrin, isolated from the seeds of Abrus precatorius, showed in vitro and in vivo antitumor properties by the induction of apoptosis. The present study was designed to evaluate the in vivo therapeutic effectiveness of abrin-derived peptide (ABP) fraction in Dalton's lymphoma (DL) mice model. The lethal dose (LD₅₀) of ABP was found to be 2.25 mg/kg body weight and further the acute toxicity was determined with sublethal doses in normal mice. The acute toxicity like body weight, peripheral blood cell count, lympho-hematological and biochemical parameters remained unaffected till 200 μg/kg body weight of ABP. The sublethal doses of ABP showed very significant growth inhibitory properties in vivo DL mice model. There were 24%, 70.8% and 89.7% reductions in DL cell survival in 25, 50 and 100 μg/kg body weight of ABP, respectively. Analysis of the growth inhibitory mechanism in DL cells revealed nuclear fragmentation, and condensation with the appearance of the sub-G₀/G₁ peak is indicative of apoptosis. Further, the Western blotting showed that apoptosis was mediated by the reduction in the ratio of Bcl-2 and Bax protein expression, and activation of caspase-3 through the release of cytochrome c in DL cells. Kaplan–Meier survival analysis showed an effective antitumor response (104.6 increase in life span (ILS) %) with a dose of 100 μg/kg body weight.     

In vitro immunostimulatory properties of Abrus lectins derived peptides in tumor bearing mice

In vitro immunostimulatory effect of Abrus lectins derived peptide fractions (AGP and ABP) was investigated in DL bearing mice. Both AGP and ABP were found to activate splenocytes and induced production of cytokines like IL-2, IFN-γ and TNF-α indicating a Th1 type of immune response. Analysis of in vitro treated splenocytes by flow cytometry revealed an increase in percentage of T and B cell with high expression of activation markers (CD25⁺ and CD71⁺). At the same time, expression of co-stimulatory markers was significantly high compared to tumor control. The tumor associated macrophages were able to stimulate NO production, IL-1 secretion, increased phagocytosis and decreased expression of mannose receptor. It was also observed that NK cell was activated by AGP and ABP. These results suggest that both AGP and ABP act as immunostimulants in vitro in DL bearing mice.     

Evaluation of RAPD-PCR and protein profile analysis to differentiate <Emphasis Type="Italic">Vibrio harveyi</Emphasis> strains prevalent along the southwest coast of India

Sixty five isolates of Vibrio harveyi were subjected to random amplified polymorphic DNA (RAPD)-PCR analysis and protein profiling to investigate the genetic variability among V. harveyi prevalent along the coast and also assess the discriminating ability of these two molecular methods. A total of 10 RAPD primers were assayed for their specificity in detecting V. harveyi, of which only two primers: PM3 and CRA25 were highly reproducible and found suitable for use in RAPD-PCR. The genetic diversity among V. harveyi isolates assessed by RAPD-PCR using PM3 primer yielded 35 different RAPD patterns which clustered the isolates into 15 groups at 72% similarity level. Similarly, RAPD-PCR with CRA25 clustered the 38 patterns into 10 groups at 74% similarity. The discriminatory index (D) value calculated for RAPD fingerprints generated with PM3 and CRA25 were 0.90 and 0.85, respectively. On the other hand, molecular typing of V. harveyi using whole cell proteins generated profiles that showed no major difference indicating the technique to be not useful in typing strains of this bacterium. However, a few of the isolates showed the presence of unique band of 28 kDa that needs to be further investigated to understand the role of the protein in disease process if any.     

Biophysical aspects and biological implications of the interaction of benzophenanthridine alkaloids with DNA

Benzophenanthridine alkaloids represent a very interesting and significant group of natural products that exhibit a broad range of biological and pharmacological properties. Among this group of alkaloids, sanguinarine, nitidine, fagaronine, and chelerythrine have the potential to form molecular complexes with DNA structures and have attracted recent attention for their possible clinical and pharmacological utility. This review focuses on the interaction of these alkaloids with polymorphic DNA structures (B-form, Z-form, H^L-form, and triple helical form) reported by several research groups employing various physical techniques such as spectrophotometry, spectrofluorimetry, circular dichroism, NMR spectroscopy, thermal melting, viscometry as well as thermodynamic analysis by isothermal titration calorimetry and differential scanning calorimetry to elucidate the mode and mechanism of action at the molecular level to determine the structure-activity relationship. DNA binding properties of these alkaloids are interpreted in relation to their biological activity.     

Synthesis and structure-activity studies of novel benzocycloheptanone oxazolidinone antibacterial agents

We describe a novel class of benzocycloheptanone derived oxazolidinone antibacterial agents. The synthesis and antibacterial activities with structure variation is discussed.