In conventionally processed specimens, the nucleoplasm of plant reticulate interphase nuclei consists of a mixture of fibrils and granules of varying sizes. The degree of granularity of the nucleoplasm varies, however, with the fixative used. The finest texture of the nucleoplasm is provided by osmium tetroxide fixation, but judging by its greater transparency, material is undoubtedly extracted. In specimens fixed with glutaraldehyde only evidence of clumping of the nucleoplasm is observed. The nucleoplasm exhibits a finer, less granular texture following postfixation with osmium tetroxide. Although extraction of nucleoplasmic material is noted in samples fixed in formaldehyde, a much improved preservation is obtained when this fixative is used with osmium tetroxide. Following preservation with these two fixatives and stainingen blocwith bismuth the ultrastructural characteristics of the nucleoplasm are particularly well revealed. Apart from fine fibrillar material permeating the nucleoplasmic zones, a large population of granules of different sizes is also observed. Part of the material may be shown, using phosphotungstic acid staining, to consist of diffuse chromatin. The fact, however, that the nucleoplasm also contains much RNA-containing structural elements is revealed by the persistence of a coarse interchromatin reticulum after extraction of specimens with deoxyribonuclease and staining with 3,3prime;-diaminobenzidine.
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