Fidelity of synthesis of preribosomal RNA in isolated nucleoli and nucleolar chromatin.

Comparisons were made of the T1 ribonuclease digests of 32P-labeled nucleolar 45S RNA of intact Novikoff hepatoma cells and the RNA synthesized in vitro by isolated nucleoli. Approximately 200 oligonucleotide spots were found in the two-dimensional chromatogram of 45S nucleolar RNA labeled in vivo, which includes fragments of 18S and 28S rRNA and nonconserved spacer regions; four spots containing 2'-O-methyl nucleotides were not found in the corresponding pattern of RNA labeled in vitro. This high degree of fidelity was retained in the patterns of spots from the RNA produced with nucleolar chromatin as template. This specific expression of rDNA was lost when the nucleolar chromatin was completely deproteinized. Specific spots found in the control patterns were absent and many nonspecific oligonucleotides were found to be labeled. A similar nonspecific chromatogram pattern was found when nucleolar chromatin was transcribed with RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) of Escherichia coli. These results show that specificity of genetic expression in vitro of isolated chromatin of eukaryotic systems is dependent on the chromatin-associated proteins and the type of RNA polymerase present.

Platelet dysfunction in migraine: effect of self-medication with aspirin.

Circulating microembolic index (CMI) was determined by drawing one blood sample into EDTA-formalin and the other into DTA alone in patients with migraine and compared with matched normal controls. Platelet aggregates, if any, are fixed in EDTA-formalin but disaggregated by EDTA. Ratios of these two counts approximate "unity" in normals and are proportionately less than unity, depending on the number of platelet aggregates. 26 untreated migraineurs and 19 migraineurs with history of self-medication with aspirin taken within 72 hours of the test, were studied in headache-free intervals. Results were compared with those from 20 healthy, age and sex matched volunteers, without migraine, who were medication-free for at least one week. Mean CMI in untreated migraineurs (0.77 +/- 0.03 SEM) was significantly lower than the mean in normal controls (0.94 +/- 0.02, p. less than 0.002). Migraineurs with self administration of aspirin had mean CMI of 0.88 +/- 0.02, differing significantly from untreated migraineurs (p less than 0.01) but not from normal controls (0.1 less than p less than 0.2). Results suggest excessive platelet aggregation in migraineurs which tends to be corrected by treatment with platelet inhibitors such as aspirin.