Weanling mice were given intraperitoneal inoculations of the neurotropic, JHM strain of mouse hepatitis virus, the virulence of which had been altered by repeated mouse passages. Five to seven days later many animals developed hind leg paralysis. The pathology consisted of an acute encephalomyelitis with patchy demyclinating lesions in the brain stem and spinal cord. Virus particles, consistent with the appearance of corona viruses, were found in the cytoplasm of cells that were identified as oligondendrocytes by demonstrating connections of their plasma membranes with myelin lamellae. Following the degeneration of oligodendrocytes the myelin sheaths disintegrated or were stripped off intact axons by cytoplasmic tongues of polymorpho-and mononuclear leucocytes that intruded between myelin lamellae. The findings indicate that JHM virus has an affinity for oligodendroeytes in weanling mice and that demyelination occurs subsequently to the degeneration of the infected oligodendrocytes.

A cell line derived from normal fetal canine thymus (Cf2Th) has been in culture since 1967. During cultivation the cells have changed morphologically from a fibroblast-like to flat, fusiform appearance and karyologically from diploid (2n=78) with 76 telocentric autosomes to hypodiploid with newly formed atelocentric chromosomes. The cells retain canine characteristic enzyme activity (G6PD and LDH) as well as cell membrane fluorescence and are free of mycoplasma. High passage cells produce tumors in ATST mice. No endogenous viruses have been detected in these cells. No original publication exists, to date, on the origin of this line, but seed stocks thereof have been distributed to many laboratories and the cells have served as experimental substrates in a number of published works on oncology albeit under different designations. The present information is offered in order to establish the provenance of this valuable cell line and to list characteristics which may serve to monitor for its purity and to distinguish it from other existing cell lines of dog origin also in common use.

This investigation employed a viral screening method detect endogenous bovine virus contaminants in commercially supplied fetal bovine serum. Fifty-one lots of fetal bovine serum from 14 suppliers were examined. Over 30% of the lots tested were found to contain bovine viruses; they included bovine virus diarrhea virus, parainfluenza type3-like virus, bovine herpesvirus-1, bovine enterovirus type 4, and an unidentified cytopathogenic agent. Of the 51 lots, 20 had been pretested by the suppliers and were considered to be free of known viral contaminants. Our viral screening methods revealed that five of these pretested lots, or 25%, contained endogenous bovine viruses.

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