A brief description is given of neurofibrillary changes of the paired helical filament type in a variety of chronic neurological diseases. These include subacute sclerosing panencephalitis, lead encephalopathy, tuberous sclerosis, Down syndrome, Hallervorden-Spatz disease, and lipofuscinosis. In these conditions, with the exception of Hallervorden-Spatz disease neurofibrillary changes were previously recognized but paired helical filaments were identified only in some cases. Moreover, in the present series, the age of patients at death was often younger than in previously recorded cases.

Several inbred strains of mice were injected with different scrapie agents and their total body weight was monitored throughout the incubation period. As a control, mice were injected with normal mouse brain homogenate. For most combinations of scrapie agent and mouse strain, weights during the preclinical phase were similar to or lower than the average weight of controls. For some combinations there was a significant increase in weight (compared to controls) during the latter part of the preclinical phase of disease. The effect was dependent on both agent and mouse strain, i. e., in some cases a mouse strain showed the increase with one scrapie agent but not another and some scrapie agents caused the increase in one inbred strain of mouse but not in another strain. The increase in weight was due to accumulations of fat rather than a generalized increase in weight of various organs. With one mouse strain (SJL), there was increased vacuolation seen in the hypothalamus of mice injected with scrapie agents that showed the increase in weight compared to the lesion intensity with an agent which did not cause the weight increase.

Dietary taurine deprivation adversely affects feline pregnancy and is associated with the frequent occurrence of fetal resorption, abortion, stillbirth, and low birthweight of live kittens at term. Taurine-deprived, live-born kittens have a poor postnatal survival rate and grow less well than kittens from taurine-supplemented queens. The postnatal dietary taurine intake of such kittens is reduced if they are nursed by their biologic mothers; the concentration of taurine in milk of taurine-deprived mothers is less than 10% of that in milk from taurine-supplemented queens. Surviving kittens from taurine-deprived mothers exhibit a constellation of neurological abnormalities (abnormal hind leg development, a peculiar gait characterized by excessive abduction and paresis, and thoracic kyphosis readily visible by X-ray). These findings suggest the presence of a developmental cerebellar deficit. Histological examination of the pre- and postnatally taurine-deprived kitten's cerebellum reveals a persistence of the external granule cell layer, which was confirmed by electron-microscopic examination. Numerous mitotic figures are present in the cells in the external granule cell layer of the cerebellum of kittens born from the nursed by taurine-deprived queens, but not in those from taurine-supplemented mothers. These findings suggest a maturational delay.

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