FINE-STRUCTURE OF HYDROUS CHROMOSOMES OBSERVED BY LOW VACUUM SCANNINGELECTRON-MICROSCOPY

Chinese hamster metaphase chromosomes were stained with platinum (Pt) blue and observed in the hydrous state with low vacuum scanning electr on microscopes (LVSEM). The coiled structure of the chromatin fibers i n the chromosomes was well recognized through the surrounding perichro mosomal substances in the backscattered electron (BSE) mode at acceler ating voltages of over 20 kV. Findings indicated that chromatin fibers in native chromosomes have a structure similar to the hierarchic coil ed model. The present study also demonstrated that not only surface st ructures but also subsurface structures can be studied in the BSE mode of LVSEM, when the subsurface structures have been stained with heavy metal salts such as Pt blue.