Sequences of 18S ribosomal DNA (rDNA) are increasingly being used to infer phylogenetic relationships among living taxa. Although the 18S rDNA belongs to a multigene family, all its copies are kept homogeneous by concerted evolution (Dover 1982; Hillis and Dixon 1991). To date, there is only one well-characterized exception to this rule, the protozoan Plasmodium (Gunderson et al. 1987; Waters, ...

Biodiversity studies are commonly conducted using 18S rRNA genes. In this study, we compared the inter-species divergence of variable regions (V1-9) within the copepod 18S rRNA gene, and tested their taxonomic resolutions at different taxonomic levels. Our results indicate that the 18S rRNA gene is a good molecular marker for the study of copepod biodiversity, and our conclusions are as follows...

We report here that the mature 5' terminus of human 18S rRNA is generated in vitro by a two-step processing reaction. In the first step, SP6 transcripts were specifically cleaved in HeLa cell nucleolar extract at three positions near the external transcribed spacer (ETS)-18S boundary. Of these cleavage sites, two were major and the other was minor. RNase T1 fingerprint and secondary nuclease an...

Pancreatic acinar cells express proteinase-activated receptor-2 (PAR2) that is activated by trypsin-like serine proteases and has been shown to exert model-specific effects on the severity of experimental pancreatitis, i.e., PAR2(-/-) mice are protected from experimental acute biliary pancreatitis but develop more severe secretagogue-induced pancreatitis. P2pal-18S is a novel pepducin lipopepti...

We have determined the sequences of the 3'-terminal approximately 100 nucleotides of [5' -32P]pCp-labeled wheat mitochondrial, wheat cytosol, and E. coli small sub-unit rRNAs. Sequence comparison demonstrates that within this region, there is a substantially greater degree of homology between wheat mitochondrial 18S and E. coli 16S rRNAs than between either of these and wheat cytosol 18S rRNA. ...

Considering the importance of Theileria equi infection in horse breeding industry and marketing, in the present study, we aimed to determine the prevalence of T. equi among dromedaries in central Iran, where a considerable number of camels and horses are raised and equine theileriosis is quite prevalent. For this purpose, a total of 161 blood samples from camels were examined in terms of T. equ...

The 18S rRNA sequences of 12 molluscs, representing the extant classes Gastropoda, Bivalvia, Polyplacophora, Scaphopoda, and Caudofoveata, were determined and compared with selected known 18S rRNA sequences of Metazoa, including other Mollusca. These data do not provide support for a close relationship between Platyhelminthes (Turbellaria) and Mollusca, but rather suggest that the latter group ...

Virus-specific ribonucleic acid (RNA), synthesized in influenza virus-infected cells from 3.5 to 7.5 hr after infection, was studied. After velocity centrifugation in sucrose, three peaks of virus-specific RNA could be identified: 34S, 18S, and 11S. These RNA species are predominantly single-stranded and consist of 90% viral (plus) and 10% complementary (minus) RNA strands. Most (75%) of the co...