Looplure

Fluorescence in situ hybridization detects specific DNA or RNA sequences inside fixed cells or tissue sections by hybridizing fluorescently labeled nucleic-acid probes to complementary target sequences, allowing the target’s copy number, chromosomal position, spatial distribution, or transcript abundance to be visualized microscopically. DNA-FISH detects genomic loci, chromosomal gains/losses, amplifications, deletions, and rearrangements, while RNA-FISH detects RNA molecules or transcript localization; in cancer cells, mouse tumors, neurons, organoids, macrophages, or drug-screening samples, the readout is fluorescent puncta, fusion/split signals, or localized RNA signal interpreted relative to validated controls.

Acute systemic toxicity studies evaluate adverse effects occurring after a single exposure, or repeated exposure within a short acute window, and the main in vivo readouts are mortality, moribund condition, clinical signs, body-weight change, and gross pathological findings; acute oral toxicity methods were developed to replace classical LD50 testing with reduced-animal designs such as fixed-dose procedure, acute toxic class method, and up-and-down procedure. The fixed-dose procedure classifies acute toxicity by administering predefined dose levels and observing evident toxicity rather than using death as the primary endpoint, whereas the acute toxic class method uses sequential groups of three animals per step and the up-and-down procedure doses animals sequentially to estimate an LD50 with fewer animals than conventional LD50 testing.