Characterization of Two Distinct Populations of Epididymosomes Collected in the Intraluminal Compartment of the Bovine Cauda Epididymis1
Bibliographic record
Abstract
During their transit along the epididymis, mammalian spermatozoa acquire new proteins that are necessary for their acquisition of forward motility and fertility. By using the bovine model, we previously showed that small membranous vesicles named epididymosomes are secreted in the epididymal intraluminal compartment. Epididymosomes from caput and cauda are different, and interact sequentially with the transiting spermatozoa. In fact, selected proteins of epididymosomes are transferred to different subcompartments of the maturing spermatozoa. In this study, we investigate the possibility that different subpopulations of epididymosomes are present in the caudal portion of the epididymis. Through the use of discontinuous sucrose gradient ultracentrifugation, we isolated two distinct populations that differ in their protein and lipid compositions. Although they have similar diameters, the ultrastructural appearance of these two populations was very different. The low-density (Ld) vesicles are enriched in cholesterol, sphingomyelin, and ganglioside M1, suggesting the existence of detergent-resistant membrane domains or rafts. The high-density (Hd) vesicles show a high protein concentration, including ACTB and VAMP8. When each subpopulation of biotinylated cauda epididymosomes was coincubated with caput spermatozoa, a subset of biotinylated proteins was transferred to the sperm; the Ld and Hd vesicles transferring the same pattern of proteins. In vitro competition assays of protein transferred from Ld or Hd epididymosomes to sperm confirm the similarity in the selected transferred proteins. Electrospray tandem mass spectrometry (ES-MS/MS) analysis of proteins associated with the two populations of vesicles confirm the epididymal origin of some of them, the possible involvement of others in transmembrane signaling systems, and the identification of proteins for which functions in sperm physiology remain to be determined. Mass spectrometry analysis also revealed that ELSPBP1 and GBB2 were transferred from epididymosomes to spermatozoa. Results are discussed with regard to the functions of these two cauda epididymosome populations in sperm physiology.
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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) | 0.001 | 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 | 0.000 |
| 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".