Cellular concentrations of glutamine synthetase in murine organs
Bibliographic record
Abstract
Glutamine synthetase (GS) is the only enzyme that can synthesize glutamine, but it also functions to detoxify glutamate and ammonia. Organs with high cellular concentrations of GS appear to function primarily to remove glutamate or ammonia, whereas those with a low cellular concentration appear to primarily produce glutamine. To validate this apparent dichotomy and to clarify its regulation, we determined the GS concentrations in 18 organs of the mouse. There was a >100-fold difference in GS mRNA, protein, and enzyme-activity levels among organs, whereas there was only a 20-fold difference in the GS protein:mRNA ratio, suggesting extensive transcriptional and posttranscriptional regulation. In contrast, only small differences in the GS enzyme activity : protein ratio were found, indicating that posttranslational regulation is of minor importance. The cellular concentration of GS was determined by relating the relative differences in cellular GS concentration, detected using image analysis of immunohistochemically stained tissue sections, to the biochemical data. There was a >1000-fold difference in cellular concentrations of GS between GS-positive cells in different organs, and cellular concentrations were up to 20x higher in subpopulations of cells within organs than in whole organs. GS activity was highest in pericentral hepatocytes (approximately 485 micromol.g(-1).min-(1), followed in descending order by epithelial cells in the epididymal head, Leydig cells in the testicular interstitium, epithelial cells of the uterine tube, acid-producing parietal cells in the stomach, epithelial cells of the S3 segment of the proximal convoluted tubule of the kidney, astrocytes of the central nervous tissue, and adipose tissue. GS activity in muscle amounted to only 0.4 micromol.g(-1).min(-1). Our findings confirmed the postulated dichotomy between cellular concentration and GS function.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".