Basolateral ion transport mechanisms during fluid secretion by<i>Drosophila</i>Malpighian tubules: Na+ recycling,Na+:K+:2Cl– cotransport and Cl– conductance
Bibliographic record
Abstract
Mechanisms of ion transport during primary urine formation by the Malpighian tubule of Drosophila melanogaster were analyzed through measurements of fluid secretion rate, transepithelial ion flux, basolateral membrane potential (V(bl)) and intracellular activities of K(+) (a(K)(i)) and Cl(-) (a(Cl)(i)). Calculation of the electrochemical potentials for both ions permitted assessment of the possible contributions of K(+) channels, Na(+):K(+):2Cl(-) cotransport, and K(+):Cl(-) cotransport, to net transepithelial ion secretion across the basolateral membrane. The data show that passive movement of both K(+) and Cl(-) from cell to bath is favoured across the basolateral membrane, indicating that both ions are actively transported into the cell. Contributions of basolateral K(+) channels or K(+):Cl(-) cotransporters to net transepithelial ion secretion can be ruled out. After prior exposure of tubules to ouabain, subsequent addition of bumetanide reduced fluid secretion rate, K(+) flux and Na(+) flux, indicating a role for a Na(+):K(+):2Cl(-) cotransporter in fluid secretion. Addition of the K(+) channel blocker Ba(2+) had no effect on a(K)(i) or a(Cl)(i). Addition of Ba(2+) unmasked a basolateral Cl(-) conductance and the hyperpolarization of V(bl) in response to Ba(2+) was Cl(-)-dependent. A new model for fluid secretion proposes that K(+) and Cl(-) cross the basolateral membrane through a Na(+)-driven Na(+):K(+):2Cl(-) cotransporter and that most of the Na(+) that enters the cells is returned to the bath through the Na(+)/K(+)-ATPase.
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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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 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".