A quantitative decatenation assay for type II topoisomerases

Type II topoisomerases catalyze decatenation of the catenated network of kinetoplast DNA [J. C. Marini, K. G. Miller, and P. T. Englund (1980) J. Biol. Chem. 255, 4976-4979]. The individual DNA circles and small catenanes produced during the decatenation reaction can be separated from the large network of substrate DNA by 5 min centrifugation at 13,000g and quantitated. The appearance of these decatenated DNA molecules which appear in the supernatant first showed a lag, whose duration depended on the enzyme concentration, and then increased linearly with time until it reached a plateau. The slope of the linear part of the kinetic curve was directly proportional to the enzyme concentration, whether a purified or crude preparation of type II topoisomerase from mammalian cells was used. These findings led us to a rapid quantitative assay of type II topoisomerases not involving electrophoresis. The method was developed with purified enzyme but was also useful for assay of the activity in crude extracts. Surprisingly, the type I topoisomerase, even when present in large excess, failed to decatenate the nicked DNA circles often present in the kinetoplast DNA. This renders the assay virtually free from interference by type I enzyme. The method is sensitive and allowed quantitative estimation of the enzyme activity present in the crude extracts corresponding to that derived from 500 to 700 cultured mammalian cells. Since various type II topoisomerases from procaryotic, eucaryotic, and viral sources decatenate kinetoplast DNA and generate similar DNA products, the assay method is likely to be generally applicable.     

Distribution of C3 phenotypes in North India: A pilot study

Summary A patient with partial trisomy 22 (PT22) is presented. Inheritance is presumed to be due to secondary nondisjunction in her mother, who has a balanced translocation t(11;22)(q25;q13). The problem of the phenotypic heterogeneity observed with this chromosome change is discussed.     

Reproductive biology of two species of Canavalia DC. (Fabaceae)—A non-conventional wild legume

The reproductive biology of two important species of Canavalia, i.e. Canavalia gladiata and Canavalia virosa, was investigated in detail by studying floral phenology, floral biology including fruit and seed set, breeding system and pollinator's activity. Both the species flower and set their seed primarily from August to December. The study of pollen–-pistil interaction indicated the existence of morphological protandry in both species, and pollen germination occurred only after rupture of the stigmatic surface. This suggests that some form of self-incompatibility operates in these species. Ants were the common vectors tripping the stigma and transporting some foreign pollen. Campylomma verbasci (large black ants) were only seen on the flowers of C. virosa, while Monomorium minimum (small black ants) were restricted to the flowers of C. gladiata. Inadequacy of reliable pollinators and high rate of bud/flower drop may be the main factors for low fruit and seed set in both the species.     

Lack of response of (Ca2+ + Mg2+) ATPase to atrial natriuretic peptide in basolateral membranes from kidney cortex of chronic diabetic rats

Incubation of basolateral membranes obtained from control rat kidney cortex in the presence of atrial natriuretic peptide (ANP) increased (Ca2+ + Mg2+) ATPase activity in a dose-dependent manner. Such response was absent in membranes obtained from animals made diabetic by streptozotocin injection (65 mg/kg, iv). The differential responses in the ATPase activity were not due to changes in the affinity for Ca2+ and insulin treatment in the diabetic animals completely reversed the situation. Our data suggest that ANP may mediate its cellular effects in part by changes in cellular Ca2+ homeostasis in kidney cortex and the lack of response of (Ca2+ + Mg2+) ATPase to ANP in chronic diabetes may contribute to the development of intracellular Ca2+ overload and nephropathy.     

Osteogenic activity of constituents from Butea monosperma

Phytochemical investigation from the stem bark of Butea monosperma, led to the isolation and identification of three new compounds named buteaspermin A (1), buteaspermin B (2) and buteaspermanol (3), along with 19 known compounds. The structure of compounds 1–22 were established on the basis of their spectroscopic data. The isolated compounds 2–17 were evaluated using neonatal (1–3 day old) rat calvaria derived primary osteoblast cultures. Five of these compounds 7, 10–13 showed promising osteogenic activity, attributed to increased osteoblast proliferation, differentiation and mineralization as evidenced by marked increase in expression of alkaline phosphatase, an early phase differentiation marker, and alizarin Red S staining of osteoblasts cultured for 48 h and von Kossa silver staining of nodules formed 15 days after culture with these compounds. Quantification of mineralization by optical density measurement of Alizarin Red S extracted from stained osteoblasts cultured for 7 days in presence of these compounds showed significant (P < 0.05, vs corresponding vehicle control group) increase in mineralization. On the basis of biological results, structure–activity relationships are discussed.     

Genetic algorithm-based medium optimization for enhanced production of fluorescent pseudomonad R81 and siderophore

Fluorescent pseudomonad R81, a root-colonizing bacterium, is a potential bio-inoculant due to its plant growth promoting characteristics. It produces hydroxamate-type siderophore which is involved in disease suppression in plants. Genetic algorithm (GA) methodology was applied for the optimization of siderophore and cell mass production simultaneously in shake flask experiments. A total of 10 medium components were optimized within 80 experiments. A high siderophore concentration of 1.9 g/L and cell mass concentration of 2.8 g/L was achieved in the optimized medium. The application of GA was well suited for determination of optimum concentration levels of the medium constituents for a bi-objective function. GA was able to increase the siderophore concentration by 2.8-fold when compared to RSM-based optimization. Further, the batch fermentation of the GA-optimized medium in 14 L bioreactor without pH control produced 2.2 g/L siderophore in 36 h, the highest reported so far. GA was also successfully used to estimate the kinetic parameters of the mathematical models of the batch fermentation.