Seasonal upregulation of fatty acid transporters in flight muscles of migratory white-throated sparrows (<i>Zonotrichia albicollis</i>)
Bibliographic record
Abstract
Endurance flights of birds, some known to last several days, can only be sustained by high rates of fatty acid uptake by flight muscles. Previous research in migratory shorebirds indicates that this is made possible in part by very high concentrations of cytosolic heart-type fatty acid binding protein (H-FABP), which is substantially upregulated during migratory seasons. We investigated if H-FABP and other components of muscle fatty acid transport also increase during these seasons in a passerine species, the white-throated sparrow (Zonotrichia albicollis). Fatty acid translocase (FAT/CD36) and plasma-membrane fatty acid binding protein (FABPpm) are well characterized mammalian proteins that facilitate transport of fatty acid through the muscle membrane, and in this study they were identified for the first time in birds. We used quantitative PCR to measure mRNA of FAT/CD36, FABPpm and H-FABP and immunoblotting to measure protein expression of FABPpm and H-FABP in the pectoralis muscles of sparrows captured in migratory (spring, fall) and non-migratory (winter) seasons. During migratory seasons, mRNA expression of these genes increased 70-1000% above wintering levels, while protein expression of H-FABP and FABPpm increased 43% and 110% above wintering levels. Activities of key metabolic enzymes, 3-hydroxyacyl-CoA-dehydrogenase (HOAD), carnitine palmitoyl transferase II (CPT II), and citrate synthase (CS) also increased (90-110%) in pectoralis muscles of migrant birds. These results support the hypothesis that enhanced protein-mediated transport of fatty acids from the circulation into muscle is a key component of the changes in muscle biochemistry required for migration in birds.
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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".