No abstract

Removal of pyrimidine dimers was measured in defined sequences in human cells amplified for the dihydrofolate reductase (DHFR) gene. We quantitated repair in specific restriction fragments by using the dimer-specific bacteriophage T4 endonuclease V and analysis by Southern blotting. Within 4 hr after 5-or 10-J/m2 UV irradiation, more than 60% of the dimers had been removed from a 20-kilobase fragment that lies entirely within the transcription unit of the DHFR gene and from a 25-kilobase fragment located in the 5' flanking region of the gene. Repair in the overall genome was measured by analyzing cellular DNA treated with T4 endonuclease V in alkaline sucrose gradients. Sixty-nine percent of the dimers were removed from the genome overall within 24 hr after irradiation, but only 25% were removed within 4 hr and 38% were removed within 8 hr. These results demonstrate a strong preferential rate of removal of dimers from the 50-kilobase region that includes the transcriptionally active DHFR gene compared to that in total cellular DNA. We confirmed that DHFR-containing DNA is repaired more rapidly than bulk DNA by using an approach that provides a direct comparison between repair in specific sequences and repair in total cellular DNA. We also show that the DHFR-containing sequences are repaired more rapidly than the nontranscribed repetitive ar DNA sequences. Our finding of preferential early repair in a transcriptionally active region in overall repair-proficient cells suggests that selective dimer removal from active sequences may be a general characteristic of mammalian DNA repair.

Public Health Biiefs reports to the NMHED. The high rates of reporting of laboratory-confirmed cases documented in this study demonstrate that the system is working efficiently.Connell, etal, have described the opportunities and hazards in the use for research of datasets designed and compiled for other purposes.6 Our study exemplifies such limitations. Although ICD-9-CM code assignments were not sensitive for detection and surveillance ofthe notifiable infectious diseases we chose for this study, they were congruent with the clinical picture and may have identified potential cases not detected by laboratorybased surveillance. Conditions whose diagnoses rely predominantly on clinical evidence (e.g., injuries) are likely to be more accurately identified by ICD-9-CM code surveillance. Although further studies on the feasibility of inpatient and outpatient data systems for surveillance are needed, access to a dataset combining laboratory, inpatient, and outpatient information holds potential for disease surveillance. O

No abstract

Many of the viruses which infect Bacillus subtilis require glucosylated polyglycerol teichoic acid for adsorption. These mutants can be divided into three classes on the basis of enzymatic defects and growth on galactose-minimal medium. Transduction with phage PBS1 reveals that two of these, gtaA and gtaB, are linked to hisAl, whereas the gtaC locus is linked to argC. Analysis by deoxyribonucleic acid-mediated transformation indicates that these loci exist in a cluster between the hisAI and argC4 loci. Anomalies in mapping in the group II region of the chromosome exist. The basis of these anomalies is discussed. ' Presented at the Annual Meeting of the American Society for Microbiology, Detroit, Mich., May 1968.