Blot hybridization analysis of poly(A+) RNAs isolated from various mouse tissues (A) and from rat and mouse brains of different ages (B). Experimental details are described in Materials and Methods. The poly(A+) RNAs used were isolated from the following tissues: mouse in A, lane 1, cerebral cortex;lane 2, cerebellum; lane 3, testis;lane 4, heart; lane 5, large intestine; and lane 6, liver; in B, whole brain of rat (top) or mouse (bottom) age 7 d (7d), 15 d (15d), and 35 d (35d). The hybridization was carried out with probes from NTRL in A and B (top) and from NTRH in B (bottom).