Domain: Healthcare — Pathophysiology
Target concept: Epithelial-derived tumor

Video generation prompt: Take sections of epithelial-derived tumor tissue, perform cytokeratin (CK) immunohistochemical staining, develop with DAB, and observe the staining results.

Evaluation guide:
(i) Target concept: Immunohistochemical confirmation of epithelial lineage via CK-DAB detection.
Minimum mechanism: CK antibody must bind specifically to cytokeratin proteins in the epithelial cell cytoskeleton; an HRP-conjugated secondary antibody (or HRP-polymer detection reagent) is implicit in the CK staining step even when not shown as a separately depicted action; DAB must undergo HRP-catalyzed oxidation to form an insoluble brown polymer exclusively where CK is expressed.
(ii)Storyline: [Frame 1–3] Tissue section placed on slide → [Frame 4–6] CK reagent applied as a coherent liquid film covering tissue → [Frame 7–8] DAB reagent applied atop the CK layer → [Frame 9–10] Stable microscope view revealing brown-stained epithelial structures against unstained stroma; all events occur in fixed lateral view with no camera repositioning; epithelial morphology must be visually legible before staining and preserved after development.

Manual:
Experimental Procedure
1. Place epithelial-derived tumor tissue section on glass slide.
2. Apply cytokeratin (CK) primary antibody reagent evenly over tissue.
3. Apply DAB developer solution to the same tissue area.
Observation of Experimental Phenomena
Brown DAB precipitate appears selectively within epithelial tumor cells, outlining cytoplasm and cell membranes; stroma, blood vessels, and inflammatory cells remain unstained.
Summary of Experimental Principles
Cytokeratins are intermediate filament proteins expressed exclusively in epithelial cells; CK immunohistochemistry uses antibody binding (via an implicit HRP-conjugated secondary antibody or polymer detection system) followed by enzyme-mediated DAB oxidation to generate an insoluble brown reaction product — confirming epithelial origin of tumor.

Prompt Grounding rubric:
level_1: No tissue section is shown; no CK antibody reagent is applied; no DAB developer appears; none of the required steps (section placement, CK application, DAB development) occur.
level_2: A slide, tissue section, or brown coloring appears but the required steps are missing or out of order: e.g., DAB is applied before CK, a reagent is applied with no tissue on the slide, or the CK step or the DAB step is skipped entirely.
level_3: All three required elements appear in order: a tissue section sits on a slide, CK primary antibody reagent is applied over it, and DAB developer is applied after the CK reagent; the sequence runs section then CK then DAB, with no reversal.
level_4: Everything required for a 3 holds, and additionally: after DAB application the clip shows a steady microscope view of the stained tissue; the slide never changes position between steps; the whole sequence plays out in one continuous scene from a single, unchanging viewpoint.
level_5: Everything required for a 4 holds, and additionally: the tissue clearly shows epithelial architecture (cohesive glandular or layered sheets of cells, not loose spindle-shaped cells); the CK reagent spreads as an even film over the tissue rather than pooling off to one side; the final microscope view clearly shows brown coloring localized to the epithelial structures against tissue that stayed unstained elsewhere.

Scientific and Causal Correctness rubric:
level_1: No plausible brown color develops anywhere; or brown color shows up before DAB is even applied; or brown color appears uniformly across regions that never received the CK reagent, with no visible link between CK application and the coloring.
level_2: Brown color appears but is unrelated to where CK was applied: e.g., it also covers areas that had no CK reagent on them, or the tissue shows no epithelial-like clustering at all (only scattered single or spindle-shaped cells) so there is nothing recognizable as epithelium to stain selectively.
level_3: Brown color only shows up after DAB is applied and only over tissue that received the CK reagent; the tissue has recognizable epithelial structure (clustered cells forming sheets, nests, or gland-like spaces); regions clearly outside the tissue, such as bare slide or surrounding stroma, do not turn brown, though faint uneven background tint elsewhere is tolerated.
level_4: Everything required for a 3 holds, and additionally: the brown color sits specifically over the epithelial-looking clusters (the polygonal, tightly-packed cells) and not over the looser, spindle-shaped stromal tissue around them; there is no scattered brown coloring appearing in gaps between epithelial clusters.
level_5: Everything required for a 4 holds, and additionally: the whole visible epithelial region takes on a similarly even brown tone rather than some clusters staining darkly while neighboring ones stay pale or blank; the surrounding stroma stays visibly unstained by comparison; the epithelial clusters keep their clustered shape rather than looking dissolved or broken apart after staining.

Spatiotemporal Consistency rubric:
level_1: The tissue section vanishes and reappears, or the slide spins more than 90 degrees with no motion shown getting it there, or the brown color flashes fully into view in a single frame with no build-up, or the scene suddenly jumps from bright to dark with no adjustment to explain it.
level_2: The slide's position jumps between the CK step and the DAB step with nothing shown moving it there; the microscope view cuts to a different zoom level with no zooming motion shown; the brown color appears already fully formed in one frame rather than building up; the CK liquid disappears from the tissue the instant it is applied.
level_3: The tissue section stays in the same spot on the slide throughout; the CK reagent and then the DAB reagent both land on and spread across the same tissue region; the microscope view stays trained on the same patch of tissue; there is no jump in the slide's position, no warping of the tissue shape, and no sudden flash or dimming of the lighting.
level_4: Everything required for a 3 holds, and additionally: each applied liquid spreads outward continuously from where it was applied rather than jumping to cover new areas; the microscope field holds completely still with no panning, zooming, or rotating; the tissue's edges stay crisp and stable rather than shimmering or warping between frames.
level_5: Everything required for a 4 holds, and additionally: each reagent flows and settles in a way consistent with a thin film under gravity, not as a rigid instantly-appearing layer; the brown coloring spreads outward gradually from where it first appears rather than filling in all at once; if the microscope refocuses, it does so as a gradual blur-to-sharp transition rather than an instant snap; no frame repeats or freezes anywhere in the clip.