Pathway of human AS3MT arsenic methylation

A synthetic gene encoding human As(III) S-adenosylmethionine (SAM) methyltransferase (hAS3MT) was expressed, and the purified enzyme was characterized. The synthetic enzyme is considerably more active than a cDNA-expressed enzyme using endogenous reductants thioredoxin (Trx), thioredoxin reductase (TR), NADPH, and reduced glutathione (GSH). Each of the seven cysteines (the four conserved residues, Cys32, Cys61, Cys156, and Cys206, and nonconserved, Cys72, Cys85, and Cys250) was individually changed to serine. The nonconserved cysteine derivates were still active. None of the individual C32S, C61S, C156S, and C206S derivates were able to methylate As(III). However, the C32S and C61S enzymes retained the ability to methylate MAs(III). These observations suggest that Cys156 and Cys206 play a different role in catalysis than that of Cys32 and Cys61. A homology model built on the structure of a thermophilic orthologue indicates that Cys156 and Cys206 form the As(III) binding site, whereas Cys32 and Cys61 form a disulfide bond. Two observations shed light on the pathway of methylation. First, binding assays using the fluorescence of a single-tryptophan derivative indicate that As(GS)3 binds to the enzyme much faster than inorganic As(III). Second, the major product of the first round of methylation is MAs(III), not MAs(V), and remains enzyme-bound until it is methylated a second time. We propose a new pathway for hAS3MT catalysis that reconciles the hypothesis of Challenger ((1947) Sci. Prog., 35, 396-416) with the pathway proposed by Hayakawa et al. ((2005) Arch. Toxicol., 79, 183-191). The products are the more toxic and more carcinogenic trivalent methylarsenicals, but arsenic undergoes oxidation and reduction as enzyme-bound intermediates

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Hydrological conditions of marine fish culture ponds and adjacent inshore waters of Palk Bay near Mandapam during the North-East Monsoon period

In recent years, attempts were being made in India to utilise the coastal lagoons, estuaries and other water bodies for fish culture practices by which the protein uptake of our masses could be increased. Tampi (1960) has proved that the coastal lagoons with low biological productivity can be developed into fish farm

Rearing of prawn larvae for seed production

Rearing the newly hatched prawn larvae is the most demanding of the procedures in hatchery production of seeds. Freshly spawned eggs of the penaeid prawn hatch out into nauplii which pass through protozoea and mysis stages before metamorphosing into post larvae

Artemether resistance in vitro is linked to mutations in PfATP6 that also interact with mutations in PfMDR1 in travellers returning with Plasmodium falciparum infections.

BACKGROUND: Monitoring resistance phenotypes for Plasmodium falciparum, using in vitro growth assays, and relating findings to parasite genotype has proved particularly challenging for the study of resistance to artemisinins. METHODS: Plasmodium falciparum isolates cultured from 28 returning travellers diagnosed with malaria were assessed for sensitivity to artemisinin, artemether, dihydroartemisinin and artesunate and findings related to mutations in pfatp6 and pfmdr1. RESULTS: Resistance to artemether in vitro was significantly associated with a pfatp6 haplotype encoding two amino acid substitutions (pfatp6 A623E and S769N; (mean IC50 (95% CI) values of 8.2 (5.7 - 10.7) for A623/S769 versus 623E/769 N 13.5 (9.8 - 17.3) nM with a mean increase of 65%; p = 0.012). Increased copy number of pfmdr1 was not itself associated with increased IC50 values for artemether, but when interactions between the pfatp6 haplotype and increased copy number of pfmdr1 were examined together, a highly significant association was noted with IC50 values for artemether (mean IC50 (95% CI) values of 8.7 (5.9 - 11.6) versus 16.3 (10.7 - 21.8) nM with a mean increase of 87%; p = 0.0068). Previously described SNPs in pfmdr1 are also associated with differences in sensitivity to some artemisinins. CONCLUSIONS: These findings were further explored in molecular modelling experiments that suggest mutations in pfatp6 are unlikely to affect differential binding of artemisinins at their proposed site, whereas there may be differences in such binding associated with mutations in pfmdr1. Implications for a hypothesis that artemisinin resistance may be exacerbated by interactions between PfATP6 and PfMDR1 and for epidemiological studies to monitor emerging resistance are discussed

Handbook of training programmes

The Indian Council of Agricultural Research has established specialised Trainers' Training Centres in order to meet the demand of adequately trained teachers and trainers in agriculture and allied subjects to impart training on the principles of learning by doing. The TTCs offer in-service training courses for the trainers/instructors of the extension training centres, agricultural schools and teachers dealing with work experience and vocational courses in high schools and higher secondary schools. In addition to these programmes, the TTCs also offer skill oriented training programmes to entrepreneurs and progressive farmer

Floral development and potential pollinators of Syzygium myhendrae (Bedd. ex Brandis) Gamble, a wild endemic tree of the Southern Western Ghats, India

Syzygium myhendrae, is a semi-evergreen, endemic and endangered tree species of the Southern Western Ghats, India which exhibits bi-annual mode of flowering and fruiting behaviour. This research is specifically aimed to observe the sequence of morphological processes occurring during floral development and to identify the potential pollinators from the different floral visitors. These aims are achieved by examining the individual trees of candidate species during their flowering season. Sticky traps, bee bowls, sweep nets and pan traps were used to capture floral visitors at the anthesis stage. Visitation frequency and visitor activity index were calculated to distinguish effective pollinators from visitor insects. The results showed nine stages in flower development starting from flower bud emergence to fruit ripening, which took 6-9 weeks. Nine species of insects were recorded as visitors. Honey bees (Apis cerana, ApisMdorsata and Tetragonula iridipennis), butterflies (Hypolimnas misippus,pachilopta pandiana), wasp species, beetle species, fly species were exclusively visiting the flowers of the candidate species. Among the honey bees, Apis dorsata showed high visitation frequency (0.40±0.01) followed by Apis cerana (0.31±0.02) and Tetragonula iridipennis (052±0.02). As per the visitation frequency, it can be concluded that Apis dorsata was the most frequent and effective pollinator