1,2,3,4,7,8,9-Heptachlorodibenzofuran

By lysing cells, releasing RNA, and removing impurities such as proteins and DNA, high-purity RNA products are finally obtained. The commonly used traditional method is the guanidine isothiocyanate/phenol/chloroform method (Trizol), which is suitable for a variety of animal materials including animal tissues, microorganisms, cultured cells, etc., and most plant materials.

A subchronic/chronic oral toxicity study detects systemic adverse effects caused by repeated administration of a test article, using mortality, clinical signs, body weight, food/water intake, ophthalmology, urinalysis, hematology, serum biochemistry, organ weights, gross necropsy, and histopathology as integrated readouts. The readout reflects dose-related physiological injury, target-organ pathology, reversibility after recovery, and derivation of NOAEL, LOAEL, or related point-of-departure values when the dataset supports them.

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.