Physiological characterisation of a pH- and calcium-dependent sodium uptake mechanism in the freshwater crustacean,<i>Daphnia magna</i>
Bibliographic record
Abstract
Daphnia are highly sensitive to sodium metabolism disruption caused by aquatic acidification and ionoregulatory toxicants, due to their finely balanced ion homeostasis. Nine different water chemistries of varying pH (4, 6 and 8) and calcium concentration (0, 0.5 and 1 mmol l(-1)) were used to delineate the mechanism of sodium influx in Daphnia magna. Lowering water pH severely inhibited sodium influx when calcium concentration was high, but transport kinetic analysis revealed a stimulated sodium influx capacity (J(max)) when calcium was absent. At low pH increasing water calcium levels decreased J(max) and raised K(m) (decreased sodium influx affinity), while at high pH the opposite pattern was observed (elevated J(max) and reduced K(m)). These effects on sodium influx were mirrored by changes in whole body sodium levels. Further examination of the effect of calcium on sodium influx showed a severe inhibition of sodium uptake by 100 micromol l(-1) calcium gluconate at both low (50 micromol l(-1)) and high (1000 micromol l(-1)) sodium concentrations. At high sodium concentrations, stimulated sodium influx was noted with elevated calcium levels. These results, in addition to data showing amiloride inhibition of sodium influx (K(i)=180 micromol l(-1)), suggest a mechanism of sodium influx in Daphnia magna that involves the electrogenic 2Na(+)/1H(+) exchanger.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".