Faculty Bibliography

The effectiveness of beta-histine-HCL in modifying the size of developing myocardial infarcts was tested in the surgically ligated dog. Branches of the left coronary artery were ligated and a 6-hour continuous intravenous infusion of 0.24 mg/kg/min of beta-histine was administered from 0 to 120 min after ligation. The effect of this treatment was evaluated histologically in studies on acute ischemia by the use of the hematoxylin-basic fuchsin-picric acid stain for early myocardial ischemia. The treatment was also evaluated grossly in a study on chronic ischemia where the dogs were permitted to survive for 30 days before sacrifice. In these experiments the size of infarcts found in the beta-histine-treated animals was compared with those found in the saline controls. Both studies showed that the control ligations produced a large uniform area of ischemia or infarction that was greatly reduced or prevented by immediate treatment with beta-histine. Also, beta-histine was capable of significantly reducing the size of developing infarcts for up to 120 min after ligation.

A dependable method for freeze-drying tissues for electron microscopy has been developed. Thin slices of fresh tissue were frozen by bringing them into direct contact with a polished copper bar at liquid nitrogen temperature. The tissue was transferred to a copper specimen block equipped with a thermocouple and heating circuit for accurate control of the environmental temperature of the tissue, and evacuated in a glass freeze-drier using clean high vacuum techniques for keeping the system free of hydrocarbons. The tissue was dried by increasing the temperature of the specimen block 10 degrees C each hour while monitoring the rate of water removal from the tissue with a partial pressure analyzer. The dry tissue was fixed with OsO4 vapor, vacuum embedded in a low viscosity epoxy resin, sectioned, stained, and viewed with the electron microscope. Tissue processed in this manner exhibits excellent morphological preservation at both cellular and organellar levels without prefixation or the use of cryoprotective agents. The results of the experiments using the partial pressure analyzer indicate that small blocks of tissue can be dried in a short time at low temperature.