Mouse neuroblastoma (NB) cells in culture were more sensitive to sodium L-ascorbate than were rat glioma cells by the criterion of growth inhibition (due to cell death and reduction in cell division). Sodium L-ascorbate at nonlethal concentrations potentiated the effect of 5-fluorouracil (FUra), x-irradiation, bleomycin, R020-1724, prostaglandin El, and sodium butyrate on NB cells but did not produce such an effect on glioma cells. Sodium L-ascorbate did not enhance the effect of vincristine, 6-thioguanine, or 1-2-chloroethyl--cyclohexyl-1-nitrosourea (CCNU) except at higher drug doses and it reduced the cytotoxic effect of methotrexate and 5-3,3-dimethyl-1-triazeno)imidazole4-carboxamide (DTIC) on NB cells. Sodium D-ascorbate produced effects similar to those produced by sodium L-asco ate on NB cells. L-Ascorbic acid-2-sulfate (barium salt) affected neither the growth rate nor the effect of 5-FUra on NB cells. Glutathione, a reducing agent, was more toxic to NB cells in comparison to D-or L-ascorbate; however, at a similar concentration it failed to potentiate the effect of 5-FUra on NB cells.The beneficial effect of high doses of ascorbic acid in advanced human neoplasms has been reported (1-3). Because of its potential significance as a chemotherapeutic agent, the effects of sodium ascorbate in combination with some tumor therapeutic agents were studied to ascertain if sodium ascorbate would potentiate their growth inhibitory effect (due to cell death and reduction of cell division). We report that sodium ascorbate at nonlethal concentrations potentiates the growth inhibitory effect of 5-fluorouracil (5-FUra), bleomycin sulfate, sodium butyrate, cyclic AMP stimulating agents, and x-irradiation on neuroblastoma (NB) cells, but it does not produce a similar effect on rat glioma cells in culture. MATERIALS AND METHODSThe procedures for culturing and maintaining mouse neuroblastoma (NBP2) cells have been described (4). Rat glioma (C-6, passage number 24-38) cells developed by Benda et al. (5), were maintained in Eagle's minimal essential medium containing 10% fetal calf serum, penicillin (100 units/ml), and streptomycin (100 ,g/ml). Mouse fibroblasts (L cells) were grown under conditions described for NB cells. L-Ascorbic acid (Sigma) or D-isoascorbic acid (Sigma) was dissolved in water at a concentration of 10 mg/ml and the pH was adjusted to 7.0 with sodium hydroxide. Sodium ascorbate in solution is unstable (6, 7) and light sensitive; therefore, a fresh solution was made every week, and the vials were wrapped with aluminum foil to protect the solution against light. Beef liver catalase suspended in 0.1% thymol (Sigma) was diluted with water at a concentration of 5 mg/ml. The concentration of the original stock solution was 50 mg/ml (33,300 units/ml). One unit decomposes 1 umol of hydrogen peroxide per min at pH 7.0 at 250C. 5-FUra, 5-(3,3-dimethyl-btriazeno)-imidazole-4-carboxamide (DTIC), 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), bleomycin sulfate, adriamycin sulfate, 6-thioguanine, vincris...

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Elevated UV-B radiation (12.2 kJ m -2 d -1 ) as against the ambient level of 10 kJ m -2 d -1 affected flowering, productivity and biomass partitioning of green gram [Vigna radiata (L.) Wilczek cv. KM-2]. UV-B stress delayed flowering initiation and achievement of 50 % flowering, reduced flower retention by 25 %, potential yield by 18 % and all yield attributes such as pod number (25 %), pod mass (41 %), seed number (32 %) and seed mass (45 %). Harvest index and shelling percentage were also reduced by 31 and 7 %, respectively. Application of triadimefon (20 mg dm -3 ) to unstressed plants accelerated flowering and enhanced flower retention (21 %), potential yield (15 %) and yield attributes (7 to 44 %). The partitioning of biomass between plant parts also showed improvement over the control plants. In UV-Bstressed plants, triadimefon treatment compensated the inhibitions to varying extents.