Domain: Healthcare — Pathophysiology
Target concept: Obstructive Ventilation Impairment: Changes in Airway Resistance

Video generation prompt: In the isolated tracheal specimen, histamine solution was applied, and the tracheal diameter changes were continuously recorded by filming the specimen.

Evaluation guide:
(i) Target concept: Histamine-induced bronchoconstriction in isolated airway tissue as a model of obstructive ventilation impairment.
Minimum mechanism: Intact, viable smooth-muscle layer in the tracheal wall responsive to histamine via H1 receptors; histamine reaches the smooth muscle by bathing/superfusing the outer surface of the isolated specimen (standard isolated-trachea organ-bath methodology); contraction narrows the lumen, which is visible externally as the tracheal wall's contour draws inward and the gap along the posterior (membranous) wall between the cartilage-ring ends narrows; absence of tissue damage or swelling that would confound the interpretation.
(ii)Storyline: Frame 0–t1: Static isolated trachea specimen in a bath or on a stage, in a neutral resting state (cartilage rings evenly spaced, tracheal contour at its resting width). t1: Histamine solution contacts the outer surface of the specimen (visible liquid application or bath-level change). t1–t2: Smooth, progressive narrowing of the tracheal contour (no lag, no oscillation), with the posterior wall drawing inward while the cartilage rings keep their shape and spacing. t2–end: Sustained narrowed state (no recovery). Perspective: Fixed frontal view, perpendicular to the tracheal axis, with enough magnification to resolve the ring morphology and the outer contour; no occlusion, no parallax shift.

Manual:
Experimental Procedure
1. Place isolated tracheal specimen (intact, C-shaped cartilage rings visible) horizontally under a fixed camera.
2. Apply histamine solution onto the outer surface of the specimen (e.g., via dropper or bath immersion), consistent with standard isolated-tissue organ-bath methodology.
3. Record continuously from before application through the visible narrowing.
Observation of Experimental Phenomena
The trachea's visible diameter narrows evenly after histamine contact; the wall draws inward — most visibly along the posterior (membranous) portion between the cartilage-ring ends — while the cartilage rings retain their shape and spacing; the narrowing persists without reversal.
Summary of Experimental Principles
Histamine binds H1 receptors on tracheal smooth muscle → Gq-protein activation → IP3-mediated Ca²⁺ release → actin-myosin cross-bridge formation → sustained contraction of the smooth muscle in the tracheal wall → visible narrowing of the airway → increased airway resistance → obstructive ventilation impairment.

Prompt Grounding rubric:
level_1: No tracheal specimen is visible; no histamine solution or application method (bath, dropper) is shown; there is no fixed-camera filming of the specimen; nothing in the scene matches the posted_prompt's demonstration.
level_2: A tracheal specimen appears but is not isolated (e.g., still attached to lungs or blood vessels); histamine solution is visible but is never applied to the specimen; the camera setup is missing or unstable (e.g., handheld shake, no consistent viewpoint).
level_3: An isolated tracheal specimen sits centered in the frame; a container of histamine solution and its means of application (e.g., dropper, pipette, or bath) are visible; the histamine solution visibly reaches the specimen's surface; the camera holds a fixed viewpoint throughout; filming starts before the application and continues afterward.
level_4: All elements from score 3 are present AND the trachea is anatomically recognizable, with visible C-shaped cartilage rings and a discernible smooth-muscle wall between them; the histamine solution is visibly a clear or pale-yellow liquid (not opaque or gel-like); the solution is applied to the outer surface of the specimen (e.g., bathing or dropping onto the trachea from outside), consistent with standard isolated-tissue histamine exposure, rather than requiring the inner lumen to be opened or exposed.
level_5: All elements from score 4 are present AND the specimen stays completely still (no translation or rotation) for the whole video; the histamine solution is applied in one continuous motion (no pausing, repositioning, or multiple separate applications); the specimen fills at least 70% of the frame's vertical height with steady focus and lighting throughout.

Scientific and Causal Correctness rubric:
level_1: The tracheal specimen's visible diameter does not change after the histamine solution is applied; the specimen appears rigid or swells rather than narrowing; or the trachea's contour widens instead of narrowing.
level_2: The specimen's shape changes, but not in a way consistent with obstructive airway narrowing: e.g., it shortens along its length without the diameter narrowing, or it buckles or collapses in an irregular, unstable way that doesn't track a consistent narrowing pattern, or its color changes (e.g., redness, discoloration) unrelated to an acute histamine response.
level_3: The trachea's visible diameter narrows following the histamine application and does not reverse into widening at any point; the narrowing begins only after the solution contacts the specimen and lasts until the end of the video.
level_4: All elements from score 3 are present AND the narrowing is visibly driven by the wall drawing inward, most noticeably along the posterior (membranous) portion between the ends of the C-shaped cartilage rings, while the cartilage rings themselves keep their shape and spacing; nothing suggests the specimen is leaking, tearing, or otherwise falling apart.
level_5: All elements from score 4 are present AND the narrowing proceeds continuously with no reversal, stutter, or back-and-forth motion; the degree of narrowing increases steadily from start to end of the visible response; nothing else competes for attention on screen (no bubbling, precipitation, or visible condensation on the specimen).

Spatiotemporal Consistency rubric:
level_1: The specimen's position or size jumps abruptly between frames rather than moving continuously; the lighting swings from full brightness to near-darkness within a single frame; the camera's zoom or crop changes suddenly; the trachea disappears and reappears; the specimen shows a structural break (e.g., a ring appearing to float free, or mismatched cut ends).
level_2: The specimen repeatedly shifts position by more than about a quarter of the frame's width between consecutive frames; the image loses focus for two or more frames in a row; the lighting flickers with three or more abrupt brightness changes; or the trachea rotates by more than about 15 degrees with no smooth transition.
level_3: There is no abrupt jump or structural break; the specimen stays fully within the frame for the whole video; the lighting stays steady with no sudden on/off or color shift; focus stays acceptably sharp on the tracheal wall throughout; any motion is gentle and physically plausible (e.g., a slight sway of no more than about 5 degrees, with no jerking).
level_4: All elements from score 3 are present AND the specimen shows no visible shaking or wobble from one frame to the next; the lighting is even across the specimen's surface, with no glare washing out the visible contour and no shadow that would make the rings look broken; the background stays still and unchanging.
level_5: All elements from score 4 are present AND the motion between frames looks perfectly continuous, with no visibly skipped or repeated frames; the cartilage rings keep a consistent relative size and spacing as the camera's implied depth stays constant; the image stays clear and free of visible glitches such as blurring or garbled patches that would distort the tracheal shape.