Location and staining properties of axial core structures in grasshopper spermatocytes

Abstract

Location of axial core structures in mitotic and meiotic chromosomes in Chorthippus brunneus and Mecostethus grossus were studied, and the results were compared with those gained by N-banding procedure. In Chorthippus, axial cores are located centrally in mitotic chromosomes and in chromosomes at the second meiotic division, while their location is lateral in chromosomes at the first meiotic division, where they can be stained also with N-banding procedure. Exceptionally, N-banding reveals axial core also in mitotic chromosomes. This stainability was attributed to the tight coiling of a fine gyred axial filament facilitating its demonstration as axial core. In Mecostethus, axial cores are located centrally both in mitotic and meiotic divisions, and N-banding reveals only centromeric dots. Thus, it was confirmed that when located laterally in the chromatid, the axial core can be stained as well with Giemsa as with silver nitrate, but when centrally located it is stainable, with rare exceptions, only with silver nitrate. The observations support the idea of axial filament being always stainable with Giemsa aside silver nitrate, only the dimensions of axial filament generally limiting its demonstration with Giemsa staining. It is concluded, that both variations in the location of axial core in chromosomes and its specific staining properties attributable to specific proteins confirm its reality as a structural element of chromosomes. Thus, by staining axial filament, the elucidation of details in chromosome structure can be achieved with light microscope with great accuracy.