Base changes at position 792 of Escherichia coli 16S rRNA affect assembly of 70S ribosomes

To investigate the function of base 792 of 16S rRNA in 30S ribosomes of Escherichia coli, the wild-type (adenine) residue was changed to guanine, cytosine, or uracil by oligonucleotide-directed mutagenesis. Each base change conferred a unique phenotype on the cells. Cells containing plasmid pKK3535 with G792 or T792 showed no difference in generation time in LB broth containing ampicillin, whereas cells with C792 exhibited a 20% increase in generation time in this medium. To study the effect on cell growth of a homogeneous population of mutant ribosomes, the mutations were cloned into the 16S rRNA gene on pKK3535 carrying a spectinomycin-resistance marker (thymine at position 1192), and the cells were grown with spectinomycin. Cells containing G792 or C792 showed 16% and 56% increases in generation time, respectively, and a concomitant decrease in 35S assimilation into proteins. Cells with T792 did not grow in spectinomycin-containing medium. Maxicell analyses indicated decreasing ability to form 70S ribosomes from 30S subunits containing guanine, cytosine, or uracil at position 792 in 16S rRNA. It appeared that C792-containing 30S ribosomes had lost the ability to bind initiation factor 3.

[Epidemiologic survey of migraine in six cities of China]

A door-to-door survey was carried out in six cities of China. A total of 63,195 individuals were sampled during 1983 to determine the prevalence of major neurological disorders including migraine. The survey involved a complete census, together with a pretested interview and brief screening examination with a high level of sensitivity for detecting individuals with migraine. All those with responses suggestive of severe headaches were requested to be examined by a senior neurologist using defined clinical criteria to establish the final diagnosis. Based on 396 prevalent cases of migraine, the crude and age-adjusted (to the 1960) total population of the United States point prevalence rate were 6.3 per 1000, and 5.4 per 1000 respectively. The prevalence among the females was nearly 3.5 times the figure for the males. For individuals above the age of 40, the age-specific prevalence rate declined with increasing age. The survey was followed by a case-control pairs matched by age, sex and geographic regions. A family history with "similar headache" seemed to be a significant risk factor while smoking and alcohol consumption appeared to be other relevant factors associated with the occurrence of migraine were also investigated. It seemed to the authors that the most frequently associated factors were psychological and hormonal factors.