Oxidative metabolism by <i>Thalassiosira weissflogii</i> (Bacillariophyceae) of a diol‐ester of okadaic acid, the diarrhetic shellfish poisoning
Bibliographic record
Abstract
Previous investigations into the comparative toxicity of the diarrhetic shellfish poisoning (DSP) toxins to Thalassiosira weissflogii (Grun.) Fryxell et Hasle found that this diatom oxidatively metabolized okadaic acid diol‐ester (OA diol‐ester) to a more water‐soluble product. This oxidative transformation of OA diol‐ester by the diatom is significant for two reasons. First, it is known that dinophysistoxin‐4 (DTX‐4), the primary DSP toxin produced by the dinoflagellate Exuviaella lima (Ehr.) Butschli, will be hydrolyzed to the diol‐ester following cell rupture (e.g. ingestion by a predator). Second, it implies that the ester, an uncharged, lipophilic intermediate, can easily enter cells and therefore may play an important role in the uptake and transfer of DSP toxins through the food web. It has been suggested that the water soluble DTX‐4 may also be the form in which DSP toxins are excreted from the producing cell. Therefore, the stability of DTX‐4 was examined when incubated either in fresh seawater medium into which washed cells of E. lima were introduced or in seawater medium conditioned by E. lima cells. Rapid hydrolysis of DTX‐4 to the diol‐ester took place in both cases. Thus, regardless of the route by which DTX‐4 is liberated from the cell, either by cell disruption or excretion, the diol‐ester will be the dominant form of the toxin to challenge associated organisms. To examine the metabolism of OA diol‐ester by T. weissflogii in more detail, serial cultures of the diatom were challenged with OA diol‐ester at a concentration of 2.0 μg·mL −1 . The metabolism and fate of the diol‐ester in both cellular and medium fractions were monitored over 3 days using liquid chromatography with either ultraviolet (LC‐UV) or mass spectrometric (LC‐MS) detection. During the course of the experiment, all of the diol‐ester was metabolized. LC‐MS analysis revealed the presence of multiple oxidative products of OA diol‐ester in the medium fraction, including a carboxylic acid derivative. The major metabolites were isolated in sufficient quantity to permit structural elucidation by NMR and MS. All the metabolites identified resulted from oxidation of the diol‐ester side chain with the primary sites of attack at the terminal, subterminal, and unsaturated carbons. OA was found in both cellular and medium fractions, and its production was directly correlated with the metabolism of the diol‐ester. The relative partitioning of both OA diol‐ester and its oxidation products between cells and medium supports the contention that OA diol‐ester can readily enter cells, be metabolized, and then excreted in more water‐soluble forms.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.013 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".