Hypoxia Tolerance in Sculpins Is Associated with High Anaerobic Enzyme Activity in Brain but Not in Liver or Muscle
Bibliographic record
Abstract
We assessed hypoxia tolerance in 11 species of fish from the superfamily Cottoidea (commonly called sculpins) that are known to differ in their critical O(2) tensions (P(crit)) and examined whether hypoxia tolerance correlated with larger substrate stores and higher maximal activity of enzymes associated with anaerobic adenosine triphosphate production (especially glycolysis). Among the sculpins studied, there was large variation in time to loss of equilibrium (LOE(50)) at 6.4 ± 0.1 torr, with values ranging between 25 and 538 min, and the variation in LOE(50) was correlated with P(crit). Our measures of time to LOE(50) and P(crit) were regressed against maximal enzyme activities of lactate dehydrogenase (LDH), pyruvate kinase (PK), creatine phosphokinase (CPK), and citrate synthase (CS) as well as the concentrations of glycogen, glucose, and creatine phosphate in the brain, liver, and white muscle. In the brain, there was a phylogenetically independent relationship between P(crit) and tissue LDH, PK, CPK, and CS activities expressed relative to tissue mass. Hypoxia-tolerant sculpins (those with low P(crit) values) had higher levels of brain LDH, PK, CPK, and CS than did hypoxia-sensitive sculpins. Similarly, LOE(50) regressed against brain LDH, PK, and CPK activities expressed relative to tissue mass, with the more hypoxia-tolerant species (i.e., those with higher LOE(50)) having higher enzyme activities. However, when the phylogenetic relationship among our sculpins was taken into account, only the relationship between hypoxia tolerance and LDH activity remained significant. When enzyme activities were expressed relative to total soluble protein in the tissue, the only relationships that remained were between brain LDH activity and P(crit) and LOE(50). In liver and white muscle, there were no relationships between the measures of hypoxia tolerance and enzyme activity or metabolite content. Overall, our analysis suggests that hypoxia-tolerant sculpins maintain higher maximal activities of some of the enzymes involved in anaerobic metabolism in the brain, and this may be an adaptation to hypoxia.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| 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 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".