Functional relationship between ammonia and gangliosides in brain

The functional significance of ammonia production in brain under physiological or pathological conditions is not clearly known. NH₄ ⁺ stimulates Na⁺, K⁺ activated ATPase causing stabilization of neuronal membranes of which gangliosides are major structural components. Moreover ammonia is known to inhibit lysosomal enzymes which include enzymes degrading gangliosides. Gangliosides have been shown to stimulate neuritogenesis in neuronal cultures and prevent the damage of the neurons from glutamate toxicity particularly in areas of brain ischemia. Hyperammonemia without any behavioural changes was induced in experimental rats by intraperitoneal administration of either a single dose (0.8 mmol/100 g wt.) or by six hourly doses (0.6 mmol/100 g wt.) of ammonium acetate. An increase in the content of gangliosides along with a rise in the content of GD_1A and GD_1B without any change in -galactosidase and N-acetylhexosaminidase was observed in cerebral cortex, cerebellum, and brain stem, following the administration of single dose of ammonium acetate. Gangliosides, after extraction from the different brain regions, were estimated by the thiobarbituric acid method and expressed in terms of sialic acid. Individual gangliosides were separated and estimated by thin layer chromatography using resorcinol as the staining agent. These results suggest that ammonia production in the neuronal pathways in brain either as a result of repeated stimulation under physiological conditions or as a result of focal ischemia or injury, may likewise cause an increase in the content of gangliosides which may help in neuritic growth (physiological conditions facilitating synaptic plasticity) and may exert a protective effect on the neurons in the ischemic area against glutamate toxicity.Former Professor of Biochemistry, OMC, Hyderabad.     

Poly-3-hydroxybutyrate production byAzotobacter chroococcum

Thirty-seven soil isolates and mutants ofAzotobacter chroococcum tested for poly-3-hydroxybutyrate (PHB) production using Sudan black B staining method were found to be positive. One mutant showed a higher number of PHB-producing cells and maximum number of granules per cell. Using 2% glucose and 15 mmol/L ammonium acetate, PHB production was found to be maximum at 36 and 48 h of growth under submerged cultivation and under stationary cultivation, respectively. PHB production was found to be higher on sucrose and commercial sugar (as carbon sources) as compared to glucose and mannitol. As commercial sugar is cheaper than sucrose it was selected as carbon source for PHB production, that being found to be maximum at 1% concentration. Inorganic nitrogen sources seemed to have no stimulatory effect on the production of PHB. However, ammonium acetate (15 mmol/L) was found to be best for PHB production. Peptone (0.2 %) gave a better yield of PHB under both growth conditions. Using all optimized conditions, PHB production was studied in ten selected strains. Two of them were found to be best PHB producers under both growth conditions, one producing 621 and 740 μg/g dry mass under submerged cultivation and under stationary cultivation, respectively, while the second one produced 589 and 733 μg/g.     

Design, synthesis, and antiproliferative and CDK2-cyclin a inhibitory activity of novel flavopiridol analogues

The design and synthesis of a small library of 8-amidoflavone, 8-sulfonamidoflavone, 8-amido-7-hydroxyflavone, and heterocyclic analogues of flavopiridol is reported. The potential activity of these compounds as kinase inhibitors was evaluated by cytotoxicity studies in MCF-7 and ID-8 cancer cell lines and inhibition of CDK2-Cyclin A enzyme activity in vitro. The antiproliferative and CDK2-Cyclin A inhibitory activity of these analogues was significantly lower than the activity of flavopiridol. Molecular docking simulations were carried out and these studies suggested a different binding orientation inside the CDK2 binding pocket for these analogues compared to flavopiridol.     

Oxygen isotope enrichment (delta18O) as a measure of time-averaged transpiration rate

Experimental evidence is presented to show that the 18O enrichment in the leaf biomass and the mean (time-averaged) transpiration rate are positively correlated in groundnut and rice genotypes. The relationship between oxygen isotope enrichment and stomatal conductance (g(s)) was determined by altering g(s) through ABA and subsequently using contrasting genotypes of cowpea and groundnut. The Peclet model for the 18O enrichment of leaf water relative to the source water is able to predict the mean observed values well, while it cannot reproduce the full range of measured isotopic values. Further, it fails to explain the observed positive correlation between transpiration rate and 18O enrichment in leaf biomass. Transpiration rate is influenced by the prevailing environmental conditions besides the intrinsic genetic variability. As all the genotypes of both species experienced similar environmental conditions, the differences in transpiration rate could mostly be dependent on intrinsic g(s). Therefore, it appears that the delta18O of leaf biomass can be used as an effective surrogate for mean transpiration rate. Further, at a given vapour pressure difference, delta18O can serve as a measure of stomatal conductance as well.     

An efficient and universal Agrobacterium-mediated transformation protocol in rice

For development of transgenic varieties of interest in rice, we have developed a simple, efficient and universal Agrobacterium mediated transformation protocol. Mature seeds of two indica (IR64 and Jaya), one each from japonica (AC41039) and aromatic (Basmati370) varieties were used as explants in the present study. Agrobacterium tumefaciens strain EHA 105 carrying Ti plasmid (pBI121) with the selectable marker npt ^II along with the reporter gene uidA encoding ??-glucuronidase (GUS) was successfully integrated with rice genome without use of acetosyringone. Sterile distilled water washing in place of cefotaxime in the elimination process has been used to control excess growth of Agrobacterium. All the material after transformation germinated in 2 to 3?days of co-cultivation on MS basal medium. Germinated seeds transferred to the selection medium i.e. plain MS medium with 50?mg/l of kanamycin, produced two to three primary tillers within 2?weeks. Mesocotyls from 2?week old in vitro grown plants were taken and cultured in the multiplication medium (MS supplemented with 0.5?mg/l BA and 50?mg/l Kanamycin) where within 6?C8?days they produced 3?C4 secondary tillers. All the five to six tiller shoots so produced in the process developed roots on plain MS and grew well when transferred to pots containing autoclaved soil and vermicompost in the proportion of 4:1. Transient expression of GUS was observed in all the tissues of recipient plants. Integration of the transgene was confirmed by employing southern blotting and real-time PCR technique. The transformation protocol developed can be efficiently used across the two major subspecies/ecotypes of the Asian rice cultivar Oryza sativa.     

Nature and role of plasmids in Azotobacter chroococcum

Summary Heavy metal, antibiotic resistance and hydrocarbon utilization properties were studied inAzotobactor chroococcum to investigate the nature and role of plasmids in different soil isolates. There is wide prevalence of heavy metal resistance, antibiotic resistance and utilization of hydrocarbons; the heavy metal resistance property seems to be conferred by plasmids.     

Tricyclic 4,4-dimethyl-3,4-dihydrochromeno[3,4-d]imidazole derivatives as microsomal prostaglandin E2 synthase-1 (mPGES-1) inhibitors: SAR and in vivo efficacy in hyperalgesia pain model

A series of substituted tricyclic 4,4-dimethyl-3,4-dihydrochromeno[3,4-d]imidazole derivatives have been synthesized and their mPGES-1 biological activity has been disclosed in detail. Structure-activity relationship (SAR) optimization provided inhibitors with excellent mPGES-1 potency and low to moderate PGE₂ release A549 cell potency. Among the mPGES-1 inhibitors studied, 7, 9 and 11l provided excellent selectivity over COX-2 (>200-fold) and >70-fold selectivity for COX-1 except 11l, which exhibited dual mPGES-1/COX-1 activity. Furthermore, the above tested mPGES-1 inhibitors demonstrated good metabolic stability in liver microsomes, high plasma protein binding (PPB) and no significant inhibition observed in clinically relevant CYP isoforms. Besides, selected mPGES-1 tool compounds 9 and 11l provided good in vivo pharmacokinetic profile and oral bioavailability (%F = 33 and 85). Additionally, the representative mPGES-1 tool compounds 9 and 11l revealed moderate in vivo efficacy in the LPS-induced thermal hyperalgesia guinea pig pain model.