Dynamics of C2 toxin and chlorophyll-a formation in the dinoflagellate Alexandrium tamarense during large scale cultivation.

The production of paralytic shellfish toxins (PSTs) by the dinoflagellate Alexandrium tamarense ATCI01, a toxigenic strain isolated from South China coastal waters, was studied in batch cultures in relatively large volumes (20l). Under nutrient-replete conditions, this strain produced C2 toxin (C2T) as a predominant PST. In a 15-day production culture, phosphate was depleted by day 4, the stationary phase began at day 6, and the toxin productivity peaked at day 10, in which the cell content of C2T reached 76 fmol per cell. Much of the toxin was produced after the depletion of phosphate in the medium suggesting that C2T is a secondary metabolite. Aeration with small bubbles was useful in increasing cell mass and toxin yield. Chlorophyll-a (Chl-a) was formed in algal cells until the culture entered the stationary phase, after which Chl-a began to disappear rapidly from the culture while the C2T content continued to rise. These results suggest a metabolic relationship between Chl-a and C2T.

Cytotoxicity assessment of Ma-huang (Ephedra) under different conditions of preparation.

Ma-huang is a traditional Chinese medicinal herb derived from EPHEDRA: sinica Stapf and other EPHEDRA: species, used to treat asthma, nose and lung congestion, and fever with anhidrosis. It contains 0.5-2.5% by weight of total alkaloids, of which ephedrine accounts for 30 to 90%. Recently, large amounts of ma-huang were used as a source of ephedrine in many dietary supplements formulated for weight reduction, because ephedrine has been found effective in inducing weight loss in diet-restricted obese patients. However, indiscriminate consumption of ma-huang-containing products has resulted in many cases of poisoning, some of which were fatal. The objective of this study is to investigate the relative toxicity of ma-huang extracted under different conditions. The toxicities of various extracts were assayed using MTT colorimetry on a battery of cell lines, while ephedrine alkaloids were analyzed with HPLC. The results are summarized as follows. (1) The cytotoxicity of all ma-huang extracts could not be totally accounted for by their ephedrine contents, suggesting the presence of other toxins in the extracts. (2) Grinding was a significant condition enhancing the toxicity of the extracts. (3) The relatively high sensitivity of the Neuro-2a cell line to the toxicity of ma-huang extracts suggests that the toxic principles were acting on neuronal cells. (4) One condition to produce a ma-huang extract with high ephedrine-to-toxins ratio would be to boil the whole herb for two h.

Effect of selenium on aflatoxin hepatocarcinogenesis in the rat.

The effects of selenium (Na2SeO3) on aflatoxin B1 (AFB1)-induced hepatic neoplasia were studied in the rat. Putative preneoplastic foci and nodules composed of basophilic, eosinophilic, and clear cells developed early. Basophilic foci were seen first; in the later stages basophilic and eosinophilic nodules predominated. At each stage the AFB1 + Se groups showed fewer and smaller foci and nodules than the AFB1 - Se group. The number of foci in the AFB1 + 3 ppm Se group and their mean area were smaller than those in the 6 ppm Se + AFB1 group. At the end of the experiment hepatocellular carcinoma (HCC) was found in 11/18 rats (61%) of the AFB1 - Se group. HCC was not found in either of the groups given AFB1 + Se. We conclude that Se had an inhibitory effect on the initiation and promotion stages of AFB1-induced preneoplastic foci and nodules. Se also prevented progression of these nodules to HCC even after cessation of AFB1 administration. The inhibitory effect of Se at 3 ppm was greater than at 6 ppm. The 6 ppm Se group also showed evidence of toxicity.