Figure 1

A, Age-dependent changes of β-galactosidase (β-Gal) expression in the brain slice cultures from mice of different ages after murine cytomegalovirus (MCMV) infection. The brain slice cultures from 0-day-old (a and b), 7-day-old (c and d), 14-day-old (e and f), and 21-day-old (g and h) BALB/c mice were infected with recombinant MCMV (RM461) (5 × 10⁶ PFU/ml) by whole immersion, and cultured for 3 days (a, c, e, and g) or 5 days (b, d, f, and h). In the 0-day-old slices (a and b), virus-infected cells are scattered throughout the slices. In the 7-day-old slices (c and d), virus-infected cells tend to be localized in the subventricular zone (SVZ) and the marginal regions of the cortex, and thereafter tend to be confined more to the ventricular wall than the marginal regions. B, Quantitative analysis of infection rates in brain slices after 5 days of infection by estimation of the X-Gal-stained area per whole brain slice area using Photoshop image software. The infection ratio was the highest in the 0-day-old slices and became progressively lower in 7-, 14-, and 21-day-old slices. There was no significant difference between the ratios in the brain slices from BALB/c mice and those from C57BL/6 mice. Data are expressed as the mean ± sd of at least three independent experiments. ★ or ⋆ p < 0.05 compared with 0-day-old slices. C, The SVZ is susceptible to MCMV infection after injection of virus. a, MCMV solution supplemented with fast green dye was injected into portions of the SVZ, cerebral cortex (C) or striatum (ST) using a microcapillary pipette. b, Only the injected SVZ portion expressed β-Gal 5 days after injection.