Intracellular Glucose and Binding of Hexokinase and Phosphofructokinase to Particulate Fractions Increase under Hypoxia in Heart of the Amazonian Armored Catfish (<i>Liposarcus pardalis</i>)
Bibliographic record
Abstract
Armored catfish (Liposarcus pardalis), indigenous to the Amazon basin, have hearts that are extremely tolerant of oxygen limitation. Here we test the hypothesis that resistance to hypoxia is associated with increases in binding of selected glycolytic enzymes to subcellular fractions. Preparations of isolated ventricular sheets were subjected to 2 h of either oxygenated or hypoxic (via nitrogen gassing) treatment during which time the muscle was stimulated to contract. The bathing medium contained 5 mM glucose and was maintained at 25 degrees C. Initial experiments revealed increases in anaerobic metabolism. There was no measurable decrease in glycogen level; however, hypoxic treatment led to a twofold increase in heart glucose and a 10-fold increase in lactate content. It is suggested that the increase in heart glucose content is a result of an enhanced rate of facilitated glucose transport that exceeds the rate of phosphorylation of glucose. Further experiments assessed activities of metabolic enzymes in crude homogenates and subsequently tracked the degree of enzyme binding associated with subcellular fractions. Total maximal activities of glycolytic enzymes (hexokinase [HK], phosphofructokinase [PFK], aldolase, pyruvate kinase, lactate dehydrogenase), and a mitochondrial marker, citrate synthase, were not altered with the hypoxic treatment. A substantial portion (>/=50%) of HK is permanently bound to mitochondria, and this level increases under hypoxia. The amount of HK that is bound to the mitochondrial fraction is at least fourfold higher in hearts of L. pardalis than in rat hearts. Hypoxia also resulted in increased binding of PFK to a particulate fraction, and the degree of binding is higher in hypoxia-tolerant fish than in hypoxia-sensitive mammalian hearts. Such binding may be associated with increased glycolytic flux rates through modulation of enzyme-specific kinetics. The binding of HK and PFK occurs before any significant decrease in glycogen level.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".