DEVELOPMENT OF POLYPLOIDY IN B-CELLS OF NORMAL AND DIABETIC MICE

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Abstract
The relationship between pancreatic B[bone marrow-derived]-cell polyploidization and the progress of the diabetic syndrome in genetically diabetic (C57BL/Ks-db/db) and normal control mice (C57BL/KsJ) of matched age groups was studied. Nuclear volume was confirmed to be a proper index of the polyploid class of the B-cell by correlation with Feulgen-DNA content as measured by microdensitometry. Nuclei of B-cells, identified by aldehyde fuchsin positive cytoplasmic granules, were traced by camera lucida and their volumes determined by semiautomatic particle size analysis. The age groups studied were 4.5, 7, 9.5, 12, 14.5 and 17 wk. The percentage of tetraploid nuclei in normal mice was consistently between 1.0-2.0% from 4.5-14.5 wk of age and increased to approximately 3.0% at 17 wk of age. The significance of this increase are as yet unknown. In all age groups studied, percentages of polyploid nuclei are significantly greater in diabetic than in control mice. The percentage of tetraploid nuclei in diabetic animals is elevated 220% over controls at 4.5 wk of age, remains constant until 12 wk (while other parameters such as blood glucose level and body weight continue to rise) and increases significantly at 12-14.5 wk of age. Implications of both the increased polyploidy observed at the onset of disease symptoms, and the dramatic increase occurring during the later stages of the disease, are discussed.