Cdc25 phosphatases are essential for the activation of mitotic cyclin–Cdks, but the precise roles of the three mammalian isoforms (A, B, and C) are unclear. Using RNA interference to reduce the expression of each Cdc25 isoform in HeLa and HEK293 cells, we observed that Cdc25A and -B are both needed for mitotic entry, whereas Cdc25C alone cannot induce mitosis. We found that the G2 delay caused by small interfering RNA to Cdc25A or -B was accompanied by reduced activities of both cyclin B1–Cdk1 and cyclin A–Cdk2 complexes and a delayed accumulation of cyclin B1 protein. Further, three-dimensional time-lapse microscopy and quantification of Cdk1 phosphorylation versus cyclin B1 levels in individual cells revealed that Cdc25A and -B exert specific functions in the initiation of mitosis: Cdc25A may play a role in chromatin condensation, whereas Cdc25B specifically activates cyclin B1–Cdk1 on centrosomes.

A spontaneous neurological disease in cats characterized by behavioural and motor disturbances was investigated by clinical, morphological and immunological methods. Neuropathological examination showed a marked inflammatory reaction in the cerebral leptomeninges and the grey matter of the brain. In the white matter, the reaction was moderate. The changes consisted of perivascular cuffing by mononuclear cells and neuronal damage. The brain stem (thalamus, mesencephalon, caudal colliculus) was most severely affected. The spinal cord and its leptomeninges were involved to a lesser degree. The histopathological picture as well as the laboratory findings suggests a viral cause of the disease. The morphology of the disease and serological as well as immunohistochemical results indicate that this disorder is different from previously known feline viral encephalitides.

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Summary In 24 cats (Uppsala, Sweden) with neurological signs of “staggering disease” and typical neuropathology, 44% had Borna disease virus (BDV)‐specific antibodies. In 173 cat sera (Berlin, Germany) of animals with unknown record, 7% were BDV positive. Out of 24 cats with undefined neurological disorders, 13% were BDV positive. Similarities in staggering disease of cats and Borna disease of horses and sheep suggest related etiological agents.