CYTOCHEMICAL AND IMMUNOCYTOCHEMICAL CHARACTERIZATION OF KINETOCHORES IN THE HOLOCENTRIC CHROMOSOMES OF GRAPHOSOMA-ITALICUM

In the present paper we have analyzed the trilaminar kinetochores pres ent in the mitotic holocentric chromosomes of the heteropteran Graphos oma italicum by means of different cytochemical and immunocytochemical techniques at the ultrastructural level. The results obtained after E DTA and osmium tetroxide/p-phenylenediamine, both cytochemical methods for preferential detection of ribonucleoproteins, show that the inner and outer kinetochore layers are selectively contrasted. These result s agree with those previously reported for the kinetochores of monocen tric chromosomes. Additionally, using cytochemical techniques such as ethanolic phosphotungstic acid staining and silver impregnation, which recognize proteins, we report a different response of the inner kinet ochore layer compared with those obtained in the middle and enter laye rs. Finally, our immunoelectron microscopic results employing monoclon al antibodies against DNA indicate the absence of this component from the kinetochore plates in holocentric chromosomes. Although the trilam inar appearance of kinetochores in holocentric chromosomes is very sim ilar to that of the localized kinetochores in mammals, our observation s imply the existence of significant differences on the macromolecular organization of both types of kinetochores.