动物模型 z-bo 2020-08-10 611

　　Frostbite refers to a symptom of partial damage to a part of the body's tissues from cold. Freezing methods include immersing rabbit feet at -25°C, freezing with 80%-95% ethanol, and freezing rabbit ears caused by solid carbon dioxide.

　　1 Alcohol-induced freezing model

　　First cut the rabbit’s right hind foot, inject 3% pentobarbital sodium through the rabbit ear vein at a dose of 1ml/kg body weight for anesthesia, draw a freezing line along the fourth metatarsal tuberosity, and then disinfect with 75% ethanol. A needle equipped with a thermocouple is inserted into the palm surface from above the midpoint of the freezing line, and inserted subcutaneously to the junction of the second and third metatarsophalangeal joints to record the temperature of the freezing zone. Then the rabbit feet were immersed and frozen in -25°C and 95% ethanol. After the temperature dropped to -5°C, it was immersed for 7 minutes and then taken out, placed in 20°C water to reheat until the tissue temperature was close to the water temperature. 1 day after freezing, the frozen area of rabbit foot was swollen obviously, and the living area of the frozen area was less than 25%.

　　2 Liquid nitrogen freezing model

　　(1) Copy method Fix the experimental rabbit with a fixed frame, and use curved scissors to close the skin to roughly cut off the coat on both sides of the back of the experiment, apply 10% sodium sulfide to further dehair, and rinse thoroughly with warm water. The silver circle (diameter 39mm) was immersed in liquid nitrogen at -196°C, cooled sufficiently and taken out, and immediately pressed against the experimental sites on both sides of the rabbit's back, causing local frostbite.

　　(2) Model characteristics 24 hours after injury, skin histology observations showed that: after freezing lasting 3s, the skin epidermis of the frozen part of the animal was locally necrosis, inflammatory cell infiltration, superficial dermal vesicle formation, and superficial hair follicle necrosis (second degree frostbite); After 5s of freezing, local necrosis of the skin epidermis, basophilic change, inflammatory cell infiltration in the superficial dermis, stasis of small blood vessels, exudative hemorrhage in the deep dermis, inflammatory cell infiltration, edema (11 degrees to deep second degree frostbite) 10s after freezing, local necrosis of the skin epidermis at the freezing site, a large number of inflammatory cell infiltration and edema in the superficial dermis, and coagulation and necrosis of the fibrous tissue around the superficial hair follicle. Inflammatory cells in the deep dermis are infiltrated, blisters are formed, collagen fibers are degenerated, shortened, broken, and arranged disorderly, and the striated muscle of the muscle layer becomes basophilic (deep frostbite above second degree).

　　(3) Comparative medicine Using liquid nitrogen as the cold source and using silver balls with good heat transfer performance to cause freezing, animal models with different degrees of frostbite can be made according to different experimental purposes and different time of injury. After 5s of freezing, the skin of the frozen part of the model animal is still in the pathological changes of deep second degree frostbite after 4d, which is very suitable for the observation experiment of drug efficacy.