Post introductory risk assessment studies on Zygogramma bicolorata (Coleoptera: Chrysomelidae), a classical biological control agent of Parthenium hysterophorus (Asteraceae) in India

Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), a biological control agent of Parthenium hysterophorus L. (Asteraceae), was feeding on leaves of Helianthus annuus in India, raising concerns of its host range. Based on the age grading technique, it was shown that the majority of Z. bicolorata on sunflower plants at any time were reproductively immature. This establishes that Z. bicolorata does not pose any risk to sunflower in India.     

Characterization of a beta-D-(1-->3)-glucan from the marine diatom Chaetoceros mülleri by high-resolution magic-angle spinning NMR spectroscopy on whole algal cells

High-resolution magic-angle spinning (hr-MAS) NMR spectroscopy was used to record NMR spectra of a cell paste from the marine diatom Chaetoceros mülleri. This gave information on a cellular storage polysaccharide identified as a beta-D-(1-->3)-linked glucan, using hr-MAS one-dimensional 1H and 13C, two-dimensional 1H,1H-COSY and 13C,1H-correlation spectroscopy. The same structural information was deduced from the liquid state NMR data on the glucan extracted from C. mülleri. The extracted glucan proved to be a beta-D-(1-->3)-linked glucan with a degree of polymerization of 19 and a degree of beta-D-(1-->6) branching of 0.005. The hr-MAS spectrum of the diatom showed several nonglucan resonances in the carbohydrate region of the NMR spectrum (60-103 ppm) that were shown to be noncarbohydrate resonances by means of two-dimensional 13C,1H- and 1H,1H-correlated NMR data.     

Substrate Dependent Reversibility of Inhibition by β-Thujaplicin of Glucose and Acetate Respiration in Saccharomyces cerevisiae

Attempts to determine the rate of uptake of β-thujaplicin (TH) and its 1:1 rupric chelate (CuT⁺) in yeast cells showed in both cases a very rapid equilibration. In the concentration range where respiration is inhibited, most of the TH added was still present in the extracellular fluid, while CuT⁺ was almost completely removed. The inhibition of glucose respiration by TH was Completely removed when the cells were repeatedly washed, while inhibition of acetate respiration remained. Washing of CuT⁺ inhibited cells did not release the inhibition of either glucose or acetate respiration. The succinic acid dehydrogenase activity was the same in homogenates of both CuT⁺ and TH inhibited cells as in homogenates of non-inhibited cells. Prior to homogenization acetate respiration was inhibited by 60 to 70 per cent by both inhibitors. Alcohol dehydrogenase activity was likewise not affected by TH and CuT⁺. The formation of acetyl coenzyme A was inhibited by both TH and CuT⁺ to about the same extent as the respiration of acetate. It is concluded that TH inhibits the acetate respiration by inhibiting the formation of acetyl coenzyme A from acetate. The same site of action is plausible also for CuT⁺ but in that case, additional sites of inhibition may also be located in the reactions in the Krebs cycle.