A type of biodegradable microsphere (DSM), approximately 45 microns in diameter, made of polymerized potato starch (Pharmacia, Sweden) was intravenously injected into rats to observe the state of DSM in small blood vessels in the kidney and liver at the electron microscopic level. Prior to their digestion with amylase, individual DSM changed their round shape to an irregularly folded one to occupy almost the whole area of the lumen. At the transmission electron microscopic level, DSM were impregnated with colloidal iron and were easily identified. Interaction of the iron labelled DSM with the surface of endothelial cells was unexpectedly loose and no adherence or fusion of this surface was observed. The starch substance was not visible in the pinocytotic vesicles of the endothelium. These findings suggest the independent profile of DSM in situ.

Further to our previous reports on the combination of CRYO-SEM and WET-SEM, this is application of another type of cryo-SEM device(SP2000 Sputter cryo, ST2000 Semtran, and SC2000 Semcool of Emscope Lab,England) attached to WET- SEM(W-40,Akashi Beam Technol.Tokyo) and SEM(DS130,ABT.Tokyo) to observe unfixed tissues of rats. The main check points of this system were how its cryotransfer device could prevent frost and ample space of cryo chamber which is independent to SEM chamber could safely utilized.Briefly preparation steps before observation were as follows;To insert thin specimen into two metalic tubies and install this assembly in specimen holderFor rapid freezing immerse this whole assembly into semi-solid nitrogen.Enclose this frozen specimen within a small chamber of transfer device and evacuate the chamber.Transfer to precooled (less than-170°C) specimen preparation chamber.By a stroke of handle,crack two metalic tubes in which frozen samples are contained. Alternatively scrach the surface of samples by a surgical knife.