Umbilical vein infusion of prostaglandin I<sub>2</sub> increases ductus venosus shunting of oxygen‐rich blood but does not increase cerebral oxygen delivery in the fetal sheep
Bibliographic record
Abstract
Key points The ductus venosus (DV) is a dynamic fetal shunt that allows substrate‐rich blood from the umbilical vein to bypass the hepatic circulation. In vitro studies suggest a direct role of prostaglandin I 2 (PGI 2 ) in the regulation of DV tone; however, the extent of this regulation has not been determined in utero . 4D flow and T 2 oximetry magnetic resonance imaging can be combined to determine blood flow and oxygen delivery within the fetal circulation. PGI 2 increases DV shunting of substrate‐rich blood but this does not increase cerebral oxygen delivery. Abstract During fetal development, the maintenance of adequate oxygen and nutrient supply to vital organs is regulated through specialized fetal shunts. One of these shunts, the ductus venosus (DV), allows oxygen‐rich blood to preferentially stream from the placenta toward the heart and brain. Herein, we combine magnetic resonance imaging (MRI) techniques that measure blood flow (4D flow) and oxygen saturation (T 2 oximetry) in the fetal circuit to determine whether umbilical vein infusion of prostaglandin I 2 (PGI 2 , regulator of DV tone ex utero ) directly dilates the DV and thus increases the preferential streaming of oxygen‐rich blood toward the brain. At 114–115 days gestational age (dGA; term = 150 days), fetal sheep ( n = 6) underwent surgery to implant vascular catheters in the fetal femoral artery, femoral vein, amniotic cavity and umbilical vein. Fetal MRI scans were performed at 119–124 dGA. 4D flow and T 2 oximetry were performed to measure blood flow and oxygen saturation across the fetal circulation in both a basal state and whilst the fetus was receiving a continuous infusion of PGI 2 . The proportion of oxygenated blood that passed through the DV from the umbilical vein was increased by PGI 2 . Cerebral oxygen delivery was unchanged in the PGI 2 state. This may be a result of decreased flow from the right to left side of the heart as blood flow through the foramen ovale was decreased by PGI 2 . We have shown that although PGI 2 acts on the DV to increase the proportion of oxygen‐rich blood that bypasses the liver, this does not increase cerebral oxygen delivery in the fetal sheep.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".