The Ionoregulatory Responses to Hypoxia in the Freshwater Rainbow Trout<i>Oncorhynchus mykiss</i>
Bibliographic record
Abstract
We utilized the rainbow trout, a hypoxia-intolerant freshwater teleost, to examine ionoregulatory changes at the gills during hypoxia. Progressive mild hypoxia led first to a significant elevation (by 21%) in J(Na)(influx) (measured with 22Na), but at 4-h hypoxia when PCO2 reached approximately 110 mmHg, there was a 79% depression in J(Na)(influx). Influx remained depressed during the first hour of normoxic recovery but was restored back to control rates thereafter; there were no significant changes in J(Na)(efflux) or J(Na)(net). A more prolonged (8 h) and severe hypoxic (approximately 80 mmHg) exposure induced a triphasic response whereby J(Na)(influx) was significantly elevated during the first hour, as during mild hypoxia, but returned to control rates during the subsequent 3 h. Thereafter, rates started to gradually increase and remained significantly elevated by about 38% through to 8 h of hypoxia. A similar triphasic trend was observed with J(Na)(efflux) but with larger changes than in J(Na)(influx), such that negative Na+ balance occurred during the hypoxic exposure. Net K+ loss rates to the water approximately doubled. There were no significant alterations in ammonia excretion rates in either of the hypoxia regimes. Branchial Na+/K+-ATPase activity did not change during 4 h at PO2 approximately 80 mmHg or return to normoxia; H+-ATPase activity also did not change during hypoxia but was significantly depressed by approximately 75% after 6 h of normoxic recovery. Scanning electron microscopy revealed that within 1 h of exposure to PO2 approximately 80 mmHg, exposed mitochondria-rich cell (MRC) numbers increased by 30%, while individual MRC exposed surface area and total MRC surface area both increased by three- to fourfold. MRC numbers had decreased below control levels by 4 h of hypoxia, but surface exposure remained elevated by approximately twofold, a response that persisted through 6 h of normoxic recovery. Environmental hypoxia induces complex changes in gill ionoregulatory function in this hypoxia-intolerant species that are very different from those recently reported in the hypoxia-tolerant Amazonian oscar.
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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 | 0.000 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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".