Domain: Healthcare — Pathophysiology
Target concept: Skin color changes in hemogenous hypoxia

Video generation prompt: Intravenous injection of a sodium nitrite solution into rabbits, with continuous observation of the ear margin skin and conjunctiva of the eyes.

Evaluation guide:
(i) Target concept: Methemoglobinemia-induced central cyanosis in hemogenous hypoxia.
Minimum mechanism: Sodium nitrite must enter systemic circulation via intravenous route → oxidize Fe²⁺ in heme to Fe³⁺ → form methemoglobin → reduce oxygen-carrying capacity → increase concentration of blue-tinted hemoglobin derivatives in arteriolar-capillary beds of thin tissues (ear margin, conjunctiva).
(ii)Storyline: Frame 1–2: Rabbit in stable lateral view, ear margin extended, eyes open, marginal vein visible. Frame 3–4: Syringe approaches ear margin; needle aligns with vein. Frame 5–6: Needle contacts and penetrates skin; skin indents. Frame 7–8: Plunger depresses; fluid flows visibly in syringe barrel. Frame 9–10: Bluish hue emerges first in ear margin (vascular bed), then appears in conjunctiva; both changes are uniform, continuous, and confined to vascularized tissue; no occlusion, lighting shift, or motion artifact disrupts visibility of either site throughout.

Manual:
Experimental Procedure
1. Restrain conscious rabbit in lateral recumbency with ear extended.
2. Identify marginal vein on ear margin; disinfect site.
3. Insert needle into marginal vein; inject sodium nitrite solution slowly.
4. Observe ear margin skin and conjunctiva continuously for color change.
Observation of Experimental Phenomena
- Ear margin skin changes from pink/red to uniform bluish hue within seconds of injection.
- Conjunctiva changes from pink/red to uniform bluish hue shortly after ear margin change.
Summary of Experimental Principles
Sodium nitrite oxidizes hemoglobin to methemoglobin, which cannot bind O₂; this causes functional hypoxia and cyanosis—bluish discoloration due to increased concentration of deoxygenated hemoglobin and methemoglobin in cutaneous and mucosal microvasculature.

Prompt Grounding rubric:
level_1: No rabbit appears; no intravenous injection equipment is shown; neither the ear margin nor the conjunctiva is shown; no sodium nitrite solution container or syringe appears; no procedural sequence (approach, contact, injection) is depicted at all.
level_2: A rabbit is shown but stays static and is mostly hidden from view; a syringe or needle appears without ever touching the rabbit; the ear margin or conjunctiva appear in an anatomically wrong place (e.g., the ear floats detached from the rabbit, or conjunctiva-like tissue appears on a surface that isn't the eye); a solution container appears but is never linked to the injection action.
level_3: The rabbit is shown with a visible ear margin and eyes; a syringe or needle appears near the ear's marginal vein; a sodium nitrite solution container is shown and visually linked to the syringe (matching liquid color, or shown being drawn into the syringe); the needle is shown approaching the skin, but there is no clear moment of contact or insertion.
level_4: The rabbit is shown with a clearly visible ear margin and open eyes showing the conjunctiva; the syringe makes visible contact with the ear margin at the vein site; the sodium nitrite container is visually consistent with the syringe's contents and clearly connected to it; the needle is shown entering the skin and the plunger being pressed, but there is no accompanying view of any color change at the ear margin or conjunctiva.
level_5: The rabbit is shown in a fixed side view with both the ear margin and open eyes visible; the syringe contacts the ear margin at the marginal vein; the sodium nitrite container is clearly labeled or otherwise unambiguous and directly connected to the syringe; the needle insertion and plunger depression happen in sequence; the ear margin and conjunctiva stay continuously visible throughout the entire ~10-second sequence, without being blocked from view or losing the camera's framing.

Scientific and Causal Correctness rubric:
level_1: The ear margin and conjunctiva stay their normal pink-red color throughout, with no bluish tint appearing anywhere; or a bluish tint appears only in some irrelevant part of the frame (fur, background, syringe) rather than in the ear margin or conjunctiva.
level_2: A color shift appears only in a non-target spot (fur, background, or the syringe itself) rather than in the ear margin or conjunctiva; or the ear margin or conjunctiva turns yellow, brown, purple, black, or gray instead of blue, colors that don't match methemoglobin-driven cyanosis; or any color shift happens before the injection or only after the sequence has ended.
level_3: The ear margin, the conjunctiva, or both turn bluish during or after the injection, but only one of the two sites changes color, or the bluish tint appears patchy and speckled rather than as an even wash over the vascular tissue, or it appears over non-vascular parts (cartilage, sclera) instead.
level_4: Both the ear margin and the conjunctiva turn bluish during or after the injection, with an even tint across each site; the ear margin appears to change before the conjunctiva, or both change within the same continuous shot, but which one changes first is hard to tell because the frames don't clearly separate the two moments.
level_5: The ear margin turns bluish first and clearly, followed by the conjunctiva turning bluish as well; both color changes look even and are confined to the vascular tissue (the ear margin's blood vessels and the conjunctival membrane) rather than cartilage, fur, or the white of the eye; no other color shift (paleness, redness, yellowing) appears at either site.

Spatiotemporal Consistency rubric:
level_1: The rabbit disappears and reappears between frames; the ear margin or conjunctiva abruptly cuts away or distorts into an unrecognizable shape; the scene suddenly flashes bright then dark with no visible cause; the syringe jumps from one position to another with no motion shown in between; the needle appears to pierce the skin with no dimple or indentation of the skin at the contact point.
level_2: The rabbit stays in view but its size or angle changes unnaturally between frames; the ear margin or conjunctiva flickers or breaks into visual noise; the syringe moves in a jerky, stop-start way or appears to skip between two positions; the needle enters the skin but the skin shows no dent and no sign of the fluid moving inside the syringe.
level_3: The rabbit stays in a stable position and pose; the ear margin and conjunctiva stay visible throughout; the syringe approaches the ear smoothly; the needle makes contact and enters with a visible skin indentation and slight tissue movement; however, the plunger being pressed and the fluid moving inside the syringe barrel do not clearly line up in time with the needle entering the skin, or the fluid movement inside the clear barrel is never actually visible.
level_4: Everything in the 3-point level holds, and additionally: the rabbit, ear, and syringe all keep a consistent size and position relative to one another as the needle moves in; the skin dents inward at the injection site and then settles back; pressing the plunger clearly coincides with visible fluid movement inside the syringe barrel; there is no visible leaking or backflow of fluid around the needle.
level_5: Everything in the 4-point level holds with no exceptions: the rabbit's posture, ear position, and open eyes stay steady throughout; every motion (the syringe's approach, the needle's contact, the skin's indentation, the plunger's depression, and the fluid's movement) flows smoothly and in the correct time order from start to finish; there is no repeated or frozen frame, no ghost-image doubling of the rabbit or syringe, and no warping of the ear or eye shapes at any point across the entire ~10-second sequence.