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Nuclear and chromatin fractions were prepared from cerebral cortex of 34 human and 37 animal brains. Chromatin was separated into a heavy heterochromatin fraction and two euchromatin fractions: intermediate euchromatin and light euchromatin. Compared to age-matched controls, aluminum content expressed per gram of DNA was significantly increased in nuclear and heterochromatin fractions in pre-senile Alzheimer's disease. In contrast nuclear preparations from brains of patients who had died with dialysis encephalopathy contained less aluminum than controls, although whole tissue concentrations were elevated ten to fifteen times above the control concentrations. Direct injection of aluminum into the cerebrospinal fluid of cats resulted in a progressive encephalopathy with neurofibrillary degeneration and increased intranuclear aluminum content. It is speculated that in Alzheimer's disease the normal blood-brain and cytoplasmic barriers for this neurotoxic metal are defective permitting aluminum to gain access to DNA-containing constitutents of the nuclei.

The term "nuclear rotation" refers to a motion of nucleoli within interphase nuclei of several cell types. No mechanism or function has been ascribed to this phenomenon, and it was unknown whether nuclear structures in addition to nucleoli participate in this motion. Moreover, it was unclear whether nuclear rotation occurs independent of concurrent motion of juxtanuclear cytoplasm. The work reported here presents quantitative evidence, for three-dimensional intranuclear, tandem motion of fluorescently labeled chromatin domains associated with nucleoli and those remote from nucleoli. The results show that such motion is curvilinear, that it is not restricted to nucleoli, and, moreover, that it occurs independently of motion of juxtanuclear, cytoplasmic structures. These results suggest that this motion represents karyoplasmic streaming and its function is to transpose to nuclear pores those chromatin domains actively transcribed.

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