Granulocyte colony-stimulating factor (G-CSF) mRNA contains two distinct types of cis-acting mRNA destabilizing elements in the 3-untranslated region. In addition to several copies of the AU-rich element the G-CSF mRNA also contains a destabilizing region that includes several predicted stem-loop structures. We report here that the destabilizing activity resides in a single stem-loop structure within this region. A consensus sequence for the active structure has been derived by site-directed mutagenesis, revealing that a three-base loop of sequence YAU and unpaired bases either side of the stem contribute to the activity. The helical nature of the stem is essential and the stem must be less than 11 bp in length, but the destabilizing activity is relatively insensitive to the sequence within the helix. The stem-loop increases the rate of mRNA deadenylation, most likely by enhancing the processivity of the deadenylation reaction. A protein that binds the stem-loop, but not an inactive mutant form, has been detected in cytoplasmic lysates.

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Karyotypic analysis of concepti spontaneously aborted in the first trimester shows approximately 50% of these concepti contain abnormal chromosomes. In order to determine whether cytomegalovirus (CMV) infection may play a role in the early loss of pregnancies with either normal or abnormal chromosomes, we have developed an assay to amplify CMV DNA in DNA extracts from spontaneously aborted concepti using the polymerase chain reaction (PCR). Using PCR, we were unable to detect CMV DNA in any of 350 spontaneously aborted concepti. Viral cultures were also negative when 36 of these were tested. Our results suggest that CMV infection is an unlikely cause of pregnancy loss in the first trimester of pregnancy.

Semiautomated rapid broth elution (Autobac Multi-Test System; General Diagnostics, Div. Warner-Lambert Co., Morris Plains, N.J.) and disk diffusion tests were compared with an agar dilution breakpoint method to determine the antibiotic susceptibility of 147 methicillin-resistant Staphylococcus aureus isolates from our hospital. Although the disk diffusion method, in general, correlated well with the agar dilution tests, the overall agreement of the Autobac tests with agar dilution tests was only 79%, with many very major discrepancies occurring with clindamycin (88%), gentamicin (33%), and methicillin (15%). When we used a 10-fold higher inoculum for the Autobac tests, all isolates were shown to be resistant to methicillin, but significant numbers of major and minor discrepancies occurred with chloramphenicol, fusidic acid, and neomycin. The majority of isolates were shown to belong to three biotypes, distinguishable by lactose fermentation, lipolysis, hemolysis, and pigment production. The antibiotic susceptibility profile of one biotype was found to be markedly different from those of the other biotypes and contained a high incidence of clindamycin susceptibility and neomycin, gentamicin, and kanamycin resistance. In contrast, the other two biotypes had a high incidence of clindamycin, gentamicin, and kanamycin resistance and neomycin susceptibility and accounted for most of the very major discrepancies in the clindamycin and aminoglycoside tests. In these methicillin-resistant S. aureus strains, discrepancies possibly may arise from partial expression of methicillin resistance, dissociated or inducible clindamycin resistance, and instability of gentamicin resistance.