Northern blotting analysis of tRNA-Val-CAC halves in mouse serum. (A) RNA extracted from 0.4 ml of mouse whole serum, from supernatant or pellet after ultracentrifugation of 0.4 ml of mouse serum at 110000g and analyzed with northern blotting by hybridization to a 32P 5′-end labeled oligonucleotide probe complementary to the 5′ end of tRNA-Val-CAC. (B) RNA extracted from 0.2 ml serum mixed with 1.8 ml PBS subjected to ultrafiltration with Vivaspin 2 columns with 30, 100, and 300 kDa MW cut-off. Total RNAs were extracted from filtrate (f) and concentrate (c) fractions. Blot was hybridized to a 32P 5′-end labeled oligonucleotide probe complementary to the 5′ end of tRNA-Val-CAC. The positions of full length tRNAs and tRNA halves are indicated on the right. DM: decade markers.