An investigation of the role of carbonic anhydrase in aquatic and aerial gas transfer in the African lungfish<i>Protopterus dolloi</i>
Bibliographic record
Abstract
Experiments were performed on bimodally breathing African lungfish Protopterus dolloi to examine the effects of inhibition of extracellular vs total (extracellular and intracellular) carbonic anhydrase (CA) activity on pulmonary and branchial/cutaneous gas transfer. In contrast to previous studies on Protopterus, which showed that the vast majority of CO(2) is excreted into the water through the gill and/or skin whereas O(2) uptake largely occurs via the lung, P. dolloi appeared to use the lung for the bulk of both O(2) uptake (91.0+/-2.9%) and CO(2) excretion (76.0+/-6.6%). In support of the lung as the more important site of CO(2) transfer, aerial hypercapnia (P(CO(2))=40 mmHg) caused a significant rise in partial pressure of arterial blood CO(2) (Pa(CO(2))) whereas a similar degree of aquatic hypercapnia was without effect on Pa(CO(2)). Intravascular injection of low levels (1.2 mg kg(-1)) of the slowly permanent CA inhibitor, benzolamide, was without effect on red blood cell CA activity after 30 min, thus confirming its suitability as a short-term selective inhibitor of extracellular CA. Benzolamide treatment did not affect CO(2) excretion, blood acid-base status or any other measured variable within the 30 min measurement period. Injection of the permeant CA inhibitor acetazolamide (30 mg kg(-1)) resulted in the complete inhibition of red cell CA activity within 10 min. However, CO(2) excretion (measured for 2 h after injection) and arterial blood acid-base status (assessed for 24 h after injection) were unaffected by acetazolamide treatment. Intra-arterial injection of bovine CA (2 mg kg(-1)) caused a significant increase in overall CO(2) excretion (from 0.41+/-0.03 to 0.58+/-0.03 mmol kg(-1) h(-1)) and an increase in air breathing frequency (from 19.0+/-1.3 to 24.7+/-1.8 breaths min(-1)) that was accompanied by a slight, but significant, reduction in Pa(CO(2)) (from 21.6+/-1.6 to 19.6+/-1.8 mmHg). The findings of this study are significant because they (i) demonstrate that, unlike in other species of African lungfish that have been examined, the gill/skin is not the major route of CO(2) excretion in P. dolloi, and (ii) suggest that CO(2) excretion in Protopterus may be less reliant on carbonic anhydrase than in most other fish species.
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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".