Determination of okadaic acid content of dinoflagellate cells: a comparison of the HPLC-fluorescent method and two monoclonal antibody ELISA test kits.

Total okadaic acid (okadaic acid plus methylokadaic acid) in acclimated clones of the dinoflagellates Prorocentrum hoffmannianum and P. lima was determined using the HPLC-fluorescent method, UBE ELISA test kit, and Rougier ELISA test kit. The nonokadaic acid-producing species. Amphidinium klebsii, Prorocentrum mexicanum, P. micans, P. cassubicum, and Gambierdiscus toxicus were examined using the same methods of analysis. All three methods yielded consistent results for P. hoffmannianum which produces only okadaic acid. However, results of the three methods were not consistent for P. lima which produces both okadaic acid and methylokadaic acid. The UBE ELISA demonstrated little or no cross-reactivity with methylokadaic acid; whereas, the Rougier ELISA demonstrated varying degrees of cross-reactivity with that analog. Analyses of nonokadaic acid producing-species yielded negative results, with one exception. The Rougier ELISA demonstrated reactivity with extracts of G. toxicus. Since outbreaks of DSP may be caused by okadaic acid, methylokadaic acid, or a combination of these toxins, both ELISA kits may underestimate total toxin present in toxic shellfish.

Interactions of maitotoxin with voltage-sensitive calcium channels in cultured neuronal cells.

The dinoflagellate toxin maitotoxin (MTX) stimulated 45Ca2+ uptake in cultured NG108-15 neuroblastoma X glioma cells. Depolarizing stimuli (e.g., 50 mM K+) produced an immediate stimulation in Ca2+ uptake, whereas that produced by MTX occurred only after a lag period of about 2 min. MTX did not stimulate Ca2+ uptake into fibroblasts. Both 50 mM K+- and MTX-stimulated Ca2+ uptake was blocked by organic calcium channel antagonists (nitrendipine, D-600, diltiazem) at very low concentrations. Cd2+ was also a potent blocker. The novel dihydropyridine BAY K8644 enhanced Ca2+ uptake in the presence of 50 mM K+ but had no effect in 5 mM Ca2+. However, in the presence of MTX, BAY K8644 stimulated Ca2+ uptake in 5 mM K+. The effects of MTX were not blocked by tetrodotoxin but were decreased in Na+-free medium. MTX did not stimulate Na+ uptake into NG108-15 cells and did not alter [3H]nitrendipine binding to rat brain cortical synaptosomes. It is concluded that MTX may alter the voltage dependence of calcium-channel activation.

Ion metabolism in a halophilic blue-green alga, Aphanothece halophytica.

The intracellular ion content of the halophilic blue-green alga, Aphanthece halophytica was studied as a function of age, external sodium and external potassium concentration. Intracellular Na+ was found to be about 0.38 millimoles/g dry mass. Intracellular K+ concentrations were as high as 1 M and varied directly with external salinity. Intracellular Ca++ and Mg++ were in the range previously reported for fresh water blue-green algae despite their extremely high extracellular concentrations. Average cell size is consistent at room temperature with two exceptions. When the outside K+ is lower than 6.5 mM the cells tend to be smaller with less intracellular K+ and high Ca++. In stationary phase cultrues the cells are larger with high intracellular Mg++ and low K+.

A NEW SPECIES OF NITELLA (CHARACEAE) BELONGING TO THE NITELLA FLEXILIS SPECIES GROUP IN NORTH AMERICA(1) (2).

A new species of Nitella belonging to the N. flexilis species group is described. The neiu species shows definite relationships to N. flexilis, N. opaca, N. missouriensis, and N. mirabilis. Relationships of the new species to N. acuminata are also discussed.