Domain: Healthcare — Pathophysiology
Target concept: Neurogenic tumor tissue

Video generation prompt: Take nerve-derived tumor tissue samples, perform S-100 protein immunohistochemical staining, develop with DAB, and observe the tumor cells under an optical microscope.

Evaluation guide:
(i) Target concept: Immunohistochemical confirmation of neural differentiation in tumor tissue via S-100/DAB staining.
Minimum mechanism: Antibody binding requires antigen preservation (fixed tissue), specific primary antibody incubation, enzyme-linked secondary antibody, and DAB oxidation producing insoluble brown precipitate at antigen site.
(ii)Storyline: [0–2s] Tissue section on slide visible (spindle cells, fascicular pattern); [2–4s] Pipette dispenses clear S-100 reagent onto tissue (liquid contact visible); [4–6s] DAB solution applied → immediate onset of brown precipitate formation localized to tumor cells; [6–10s] Microscope eyepiece view shows high-magnification field: brown-stained spindle cells with blue nuclei, aligned fascicles, no background staining, all viewed from fixed optical axis with stable focus and lighting.

Manual:
Experimental Procedure
1. Place neurogenic tumor tissue section on glass slide.
2. Apply S-100 primary antibody solution to tissue.
3. Develop with DAB substrate solution → brown precipitate forms in S-100+ cells.
4. Observe under optical microscope: spindle-shaped tumor cells show brown cytoplasmic/membranous staining against blue nuclei.
Observation of Experimental Phenomena
Brown DAB reaction product appears selectively in tumor cell cytoplasm and/or membranes; nuclei remain blue; background matrix is pale pink; spindle cells align in fascicles.
Summary of Experimental Principles
S-100 protein is a calcium-binding marker highly expressed in neural crest-derived cells (e.g., Schwann cells); immunohistochemical detection using S-100 antibody + DAB enzymatic development confirms neurogenic origin of tumor tissue.

Prompt Grounding rubric:
level_1: No neurogenic tumor-tissue section on a slide appears; no S-100 antibody application is shown; no DAB development step appears; no microscope view of stained cells appears; none of the four steps (tissue sampling, S-100 staining, DAB development, microscopic observation) are shown.
level_2: Exactly one of the four steps appears (for example, only a microscope view), and even that one is wrong in some basic way: the tissue looks like a different organ, or the slide never shows any brown staining at all; the other three steps are missing entirely.
level_3: At least three of the four steps are recognizable: a tumor-tissue section on a slide with spindle-shaped cells, a labeled S-100 reagent bottle or a pipette tip touching the tissue, DAB solution visibly applied to the tissue before any brown color appears, and a microscope eyepiece view of the cells, but one of these is missing its key visual feature, such as the microscope view showing only blue-stained nuclei with no brown signal at all.
level_4: All four steps appear with their key visual features: spindle-shaped tumor cells arranged in fascicles on the slide, S-100 reagent visibly applied (liquid contact or a labeled vial and pipette), DAB development shown underway or complete with brown reaction product on the tissue, and a microscope view showing cell-level detail, but something is slightly off, such as the microscope view appearing to show a different area of tissue than was just stained, or the brown color appearing to already be present before the DAB step is shown.
level_5: All four steps appear in the correct order (sampling, then S-100 application, then DAB development, then microscopic observation), with the same tissue section recognizably carried through each step (or clearly and logically linked across cuts); every label is legible, every container is properly identified, and the microscope view clearly matches the same tissue location and staining outcome shown earlier, with no unrelated objects appearing in any shot.

Scientific and Causal Correctness rubric:
level_1: No brown DAB signal appears anywhere on the tissue; the section instead looks uniformly pink (as in a plain H&E stain) or uniformly blue (hematoxylin only), or a brown color appears on tissue that was never shown receiving DAB, or on tissue that clearly is not the neurogenic tumor section.
level_2: Brown precipitate appears, but in the wrong place: on a tissue type that clearly is not the neurogenic tumor section, or only in necrotic/stromal debris rather than in the tumor cells themselves; or the brown color shows up before the DAB step is ever depicted; or the tumor cells stay unstained while the surrounding background picks up a strong brown tint instead.
level_3: Brown DAB precipitate appears specifically inside the tumor cells' cytoplasm and/or along their membranes, in a pattern consistent with S-100 positivity (diffuse or granular brown within the spindle-shaped cells); but either the blue hematoxylin nuclear counterstain is missing or hidden, or the brown staining is too blurry, overdeveloped, or faint to make out individual cells, or the fascicular arrangement of the tumor cells is not visible.
level_4: The brown DAB signal sits clearly inside the tumor cells' cytoplasm/membranes and contrasts clearly against blue-stained nuclei; the cells show the expected spindle shape arranged in parallel fascicles; there is no brown staining in the surrounding stroma or background; but staining intensity varies unevenly between cells for no biological reason, or a single artifact (an air bubble, a torn fold in the tissue, or a stray fleck of precipitate outside the tissue) is visible somewhere in the field.
level_5: Brown DAB staining fills the cytoplasm/membranes of at least 90% of the tumor cells in view, sharply set off from their blue nuclei and from the pale pink background; the cells keep an intact spindle shape in neat, parallel fascicles; there is no staining outside the tumor cells, no artifacts, and no over- or under-developed patches; the whole field looks like a textbook S-100-positive schwannoma or neurofibroma.

Spatiotemporal Consistency rubric:
level_1: The clip cuts abruptly with no continuity: the tissue slide disappears and reappears in a different orientation; the pipette tip teleports across the frame; the light source flips direction between frames for no reason.
level_2: At least one major break appears: the tissue section changes size or shape between shots without any visible cause (shrinking or expanding unnaturally); the microscope view suddenly shows a different magnification or focal plane than the previous step implied; the DAB reagent looks full in one frame and empty in the next with no dispensing shown; a hand or tool enters the frame from a different direction than in the preceding action.
level_3: The slide, pipette, and microscope stay consistent in size, position, and orientation relative to one another across the clip; the light stays even with no unexplained flicker; motion is continuous with no jumps or freezes; small flaws are allowed, such as brief blur during the pipetting motion, or the slide appearing to shift very slightly between two shots without a visible hand moving it.
level_4: Everything required at the 3-point level holds, and additionally the pipette consistently approaches the slide from the same direction every time, and the microscope stage stays put once the slide is positioned; focus and magnification stay stable through the DAB development and the microscope-view steps; at most one small perceptual hiccup is present (e.g., a glare reflection appears and fades once with no light change, or the background shows a faint parallax shift during a zoom).
level_5: No spatiotemporal flaws remain: the slide stays in the same position and orientation across every shot; the pipette moves along one continuous, evenly paced path as it dispenses; the microscope image's sharpness and field of view change only when a focus or zoom action is shown, and match that action exactly; lighting, reflections, and perspective stay stable and physically coherent from the first frame to the last, with no dropped frames or motion that looks faster or slower than the hand/tool action performed.