A search for Drosophila mutants with phenotypes similar to human diseases might help to unravel evolutionary conserved genes implicated in polygenic human disorders. Among these are neurodegenerative diseases, characterized by a late onset disturbance of memory, synaptic and glial pathology, structural brain impairments and altered content of the intermediates of the kynurenine pathway, the modulators of glutamate excito- and oxidative toxicity. This pathway is conserved in insects, in rodents, and in humans. We tested the Drosophila mutants cardinal (3-hydroxykynurenine excess) and cinnabar (kynurenic acid excess) for age-dependent changes in memory, synaptic pathology, structural brain plasticity and glial immunoreactivity. The mutant cardinal demonstrated a decline in learning and memory from the 12th to the 29th day of life in a paradigm of conditioned courtship suppression. Memory decline was accompanied by a sharp decrease in immunoreactivity to the synaptic cysteine string protein, and alterations in volumetric parameters of the mushroom bodies, the brain structures implicated in memory.
Mechanisms modifying the structural-functional organization of polytene chromosomes were studied in a Drosophila line in which the activating properties of calmodulin were altered and learning ability was increased, by treating mutants with homeopathic preparations which affect Ca2+ and F- ion metabolism. The results indicated a dominant role for Ca2+ ions and calmodulin in determining the chromocentric organization of the nucleus. F- ions, which stimulate the adenylate cyclase complex, were found not to have a role.
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