Characterization of branchial lead-calcium interaction in the freshwater rainbow trout <i>Oncorhynchus mykiss</i>
Bibliographic record
Abstract
The mechanism of branchial lead uptake and interplay with Ca(2+) transport was investigated in the freshwater rainbow trout Oncorhynchus mykiss. Lead significantly reduced Ca(2+) influx by approximately 40% and 30% after exposure to 2.3+/-0.1 and 1.4+/-0.2 micromol l(-1) dissolved lead, respectively, for 0-48 h. Acute inhibition of Ca(2+) influx by lead exhibited typical Michaelis-Menten kinetics with an approximate 16-fold increase in K(m), whereas J(max) values did not significantly change, yielding an inhibitor constant (K(i,Pb)) of 0.48 micromol l(-1). Alternative analyses suggest the possibility of a mixed competitive/non-competitive interaction at the highest lead concentration tested (4.8 micromol l(-1)). Branchial lead accumulation was reduced with increasing waterborne Ca(2+) concentrations, suggesting a protective effect of Ca(2+) against lead uptake at the gill. The apical entries of Ca(2+) and lead were both inhibited (55% and 77%, respectively) by the addition of lanthanum (1 micromol l(-1)) to the exposure water. The use of cadmium (1 micromol l(-1)) and zinc (100 micromol l(-1)) as voltage-independent calcium channel competitors also reduced branchial lead uptake by approximately 56% and 47%, respectively. Nifedipine and verapamil (up to 100 micromol l(-1)), both voltage-dependent calcium channel blockers, had no effect on gill lead accumulation. CaCl(2) injection reduced both Ca(2+) and lead uptake by the gills. This suggests transport of lead through apical voltage-independent calcium channels, similar to the entry of Ca(2+). High-affinity Ca(2+)-ATPase activity was not acutely affected by lead, but a significant 80% reduction in activity occurred during exposure for 96 h to 5.5+/-0.4 micromol l(-1) dissolved lead, indicating a possible non-competitive component to lead-induced Ca(2+) disruption. The effect of lead on Ca(2+) efflux was investigated and found to be insignificant. We conclude that uptake of lead occurs, at least in part, by the same mechanism as Ca(2+), which results in disruption of Ca(2+) influx and ultimately Ca(2+) homeostasis.
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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".