Nitrogenase activity associated with codium species from New Zealand marine habitats

Nitrogenase activity, measured as acetylene reduction, was recorded at rates up to 1028 nmol.h \g * dry weight for Codium adhaerens (Cabr.) Ag. var. convolutum Dellow and Codium fragile (Sur.) Hariot subsp. tomentosoides (Van Goor) Silva collected from New Zealand habitats. In both species the ability to reduce acetylene is invariably associated with the presence of a heterocystous blue-green alga, Calothrix sp., epiphytic or embedded in the Codium thallus. A highly significant (P < 0.001) correlation between heterocyst frequency and nitrogenase activity was found. Nitrogenase and net photosynthesis of the Codium-Calothrix system have different steady-state responses to light intensity, and the kinetics of the two processes also differ in that nitrogenase is slow to respond to illumination or darkening. Glucose additions to Codium did not significantly increase nitrogenase activity. Nitrogenase is relatively insensitive to oxygen tension over the range 0-1.0 atm (0-1.033 kgf.cnT2) and still occurs at 1.5 atm (1.55 kgf.cm"2); this condition is unique in all nitrogenase systems thus far reported. Collectively these facts suggest that Calothrix is the agent primarily responsible for nitrogenase activity in these Codium species

Pulsational frequencies of the eclipsing delta-Scuti star HD 172189

The eclipsing delta-Scuti star HD 172189 is a probable member of the open cluster IC 4756 and a promising candidate target for the CoRoT mission. The detection of pulsation modes is the first step in the asteroseismological study of the star. Further, the calculation of the orbital parameters of the binary system allows us to make a dynamical determination of the mass of the star, which works as an important constraint to test and calibrate the asteroseismological models. From a detailed frequency analysis of 210 hours of photometric data of HD 172189 obtained from the STEPHI XIII campaign we have identified six pulsation frequencies with a confidence level of 99% and a seventh with a 65% confidence level in the range between 100-300 uHz. In addiction, three eclipses were observed during the campaign, allowing us to improve the determination of the orbital period of the system.Comment: 6 pages, 7 figure

A review on combined effects of moniliformin and co-occurring Fusarium toxins in farm animals

International audienceCo-occurrence of mycotoxins in food and feed represents the rule rather than the exception. Information about combinatory toxic effects of co-occurring mycotoxins is scarce, in particular the effects that mixtures of mycotoxins in feed may have on farm animals. This review focusses on studies on the combined effects of moniliformin and co-occurring mycotoxins in feed on farm animals. Moniliformin is a mycotoxin of emerging scientific interest, which may co-occur with many other mycotoxins, especially Fusarium mycotoxins. Oral exposure to moniliformin reduces feed consumption and body weight gain in poultry, in pigs and catfish, and induces cardiotoxic effects and/or alterations in serum biochemical and haematological parameters. In this review only experiments comparing effects as a result of the exposure to a combination of mycotoxins with effects due to the exposure to single mycotoxins were considered. Identified published studies on combined toxicity have been limited to combinations of moniliformin with either fumonisin B-1 or deoxynivalenol, and were performed with poultry, pigs, and catfish. Most of the moniliformin/fumonisin B-1 investigations involved poultry and focussed on adverse effects on feed intake, weight gain and immune response, as well as organ lesions. These studies mainly reported an interactive toxicity of moniliformin and fumonisin B-1 but did not allow identification of the type of interaction. Likewise, no indication could be given for the interaction detected for both mycotoxins on weight gains of catfish. For the moniliformin/deoxynivalenol combination, only one study with broiler chickens was found relevant. This study concluded additive or less than additive toxicity, using kidney lesions and renal tubular epithelial degeneration as endpoints. While possible interactions between moniliformin and fumonisin B-1 or deoxynivalenol were identified, the conclusions are based on limited studies and experimental designs. Further studies on the combined toxicity of moniliformin with other mycotoxins and other animal species would be needed