James B. Patterson

Specific-Locus Mutational Assay Systems for Mouse Lymphoma Cells

For several years, it was generally believed that tissue culture cells derived from mammalian sources could not be mutagenized by exposure to known mutagens (Szybalski et al., 1964; Morrow, 1964). However, in 1968, independent studies by Chu and Mailing (1968a b) and Kao and Puck (1968) revealed that gene mutations are induced when Chinese hamster cells are incubated for short periods in the presence of alkylating agents. Additional studies proved that the spontaneous mutation rate for mammalian tissue culture cells is actually several orders of magnitude lower than that assumed in the 1964 reports. Based on this knowledge, it became easy to understand how Szybalski and Morrow failed to demonstrate an enhancement of mutant frequency upon treatment of cells with mutagens; i.e., the background mutant frequency was too high to observe an increase arising from the induction of new mutants.

Pemphigus Vulgaris of the Esophagus

Excerpt Because skin and esophagus have in common a lining of stratified squamous epithelium, it is not surprising that certain diseases affecting this epithelium can involve both organs. Thus vesi...

Mumps Outbreak in a Highly Vaccinated University-Affiliated Setting Before and After a Measles-Mumps-Rubella Vaccination Campaign—Iowa, July 2015–May 2016

Background In response to a mumps outbreak at the University of Iowa and surrounding community, university, state, and local health officials implemented a vaccination campaign targeting students <25 years of age with an additional dose of measles-mumps-rubella (MMR) vaccine. More than 4700 vaccine campaign doses were administered; 97% were documented third doses. We describe the epidemiology of the outbreak before and after the campaign, focusing on cases in university students. Methods Mumps cases were identified from reportable disease databases and university health system records. Detailed information on student cases was obtained from interviews, medical chart abstractions, university and state vaccination records, and state public health laboratory results. Pre- and postcampaign incidence among students, university faculty/staff, and community members <25 vs ≥25 years old were compared using Fisher exact test. Multivariable regression modeling was performed to identify variables associated with a positive mumps polymerase chain reaction test. Results Of 453 cases in the county, 301 (66%) occurred in university students. Student cases were primarily undergraduates (90%) and highly vaccinated (86% had 2 MMR doses, and 12% had 3 MMR doses). Fewer cases occurred in students after the campaign (75 [25%]) than before (226 [75%]). Cases in the target group (students <25 years of age) declined 9% postcampaign (P=.01). A positive mumps polymerase chain reaction test was associated with the presence of parotitis and early sample collection, and inversely associated with recent receipt of MMR vaccine. Conclusions Following a large additional dose MMR vaccination campaign, fewer mumps cases occurred overall and in the target population.

RHEUMATOID SPONDYLITIS: A CLINICAL AND SOCIO-ECONOMIC STUDY

Excerpt The purpose of this paper is to describe the clinical manifestations of rheumatoid spondylitis and its impact upon the social and economic life of the individual. Inferences as to its preci...

Effect of mercuric and silver ions on cesium sulfate equilibrium buoyant densities of synthetic polydeoxyribonucleotides

The effect of Hg2+ and Ag+ on the buoyant density (rho) of four synthetic DNA polymers, poly[d(A-T)]; poly(dA) - poly(dT); oikt[d(G-C)]; and poly(dG) - poly(dC), was investigated. The buoyant density of poly[d(A-T)] in Cs2SO4 increased dramatically after complexing with Hg2+, but little change in the buoyant density of other polymers resulted except at very high molar ratios of Hg2+/DNA-P (rf). Hg2+ raised the thermal transition temperature (Tm) of alternating polymers and lowered the Tm of homopolymers. Measurements in the preparative ultracentrifuge indicated that lowered Tm correlated with Hg2+-induced strand separation of one homopolymer [poly(dA) - poly(dT)], but strand separation was not observed with another homopolymer [poly(dG) - poly(dC)] complexed with Hg2+. When Ag+ was mixed with the polymers, the buoyant density of poly(dG) - poly(dC) increased most markedly. A substantial increase in the buoyant density of poly[d(A-T)] and a small increase in the buoyant density of poly[d(G-C)] were also observed. The Tm changes induced by Ag+ were not related in any obvious way to buoyant density changes. These findings indicate that nucleotide sequence as well as overall base composition is of importance in understanding the buoyant density changes induced by metal ions. Although these data do not allow construction of a detailed molecular model of polymer-metal ion interactions, they may be used to explain much of the behavior of naturally occurring DNA sequences, such as heterochromatic satellite sequences and 5 S and rRNA sequences, in Hg2+/Cs2SO4 and Ag+/Cs2SO4 gradients.