Synthesis and processing of bone sialoproteins during de novo bone formation in vitro
Bibliographic record
Abstract
Bone sialoprotein (BSP) and osteopontin (OPN) are sulphated and phosphorylated sialoglycoproteins that regulate the formation of hydroxyapatite crystals during de novo bone formation. To gain insights into the relationship between the synthesis and posttranslational modification of BSP and OPN and the mineralization of bone, pulse-chase studies were conducted on cultures of newly forming bone nodules produced by fetal rat calvarial cells in vitro. Cultures were pulse labelled with 35SO4, or with either 32PO4 or [gamma-32P]ATP to study intracellular and extracellular phosphorylation, respectively, and chased in isotope-free medium for various times up to 24 h. The presence of radiolabelled BSP and OPN was determined in the cells, in culture medium, and in various tissue compartments obtained by dissociative extraction with 4 M GuHCl (G1), 0.5 M EDTA (E), and again with 4 M GuHCl (G2) and a bacterial collagenase digestion of the demineralized collagenous tissue residue. With each isotope employed, radiolabelled BSP and OPN were detected in the E extract within the 1-h chase period and increased in amount with time. Similarly, 35SO4- and 32PO4-labelled BSP increased in the G2 extract, but OPN was not detected. In the G1 extract the 35SO4-labelled BSP decreased with chase time, whereas the 32PO4-labelled BSP increased. No differences were evident in the profiles of BSP labelled with 32PO4 or [gamma-32P]ATP. In the absence of beta-glycerophosphate, which is required for optimal mineralization of the bone nodules, 35SO4-labelled BSP was increased in the medium and G1 extract and decreased in the E extract and G2 extract after 3 h. In addition to differences in the tissue compartmentalization of BSP and OPN, these studies indicate that 35SO4 is lost from BSP during mineralization and that isoforms of BSP exist with a selective affinity for the organic and mineral phases. Moreover, the additional phosphorylation of BSP and OPN catalyzed by ectokinase activity does not appear to alter the distribution of these sialoproteins.
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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 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".