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Biomedical subjects

E H Bowman

Publications and source records attributed to E H Bowman.

6 recordsLinked to original sources
PubMed1998

Retroviral recombination rates do not increase linearly with marker distance and are limited by the size of the recombining subpopulation.

Recombination occurs at high frequencies in all examined retroviruses. The previously determined homologous recombination rate in one retroviral replication cycle is 4% for markers 1.0 kb apart in spleen necrosis virus (SNV). This has often been used to suggest that approximately 30 to 40% of the replication-competent viruses with 7- to 10-kb genomes undergo recombination. These estimates were based on the untested assumption that a linear relationship exists between recombination rates and marker distances. To delineate this relationship, we constructed three sets of murine leukemia virus (MLV)-based vectors containing the neomycin phosphotransferase gene (neo) and the hygromycin phosphotransferase B gene (hygro). Each set contained one vector with a functional neo and an inactivated hygro and one vector with a functional hygro and an inactivated neo. The two inactivating mutations in the three sets of vectors were separated by 1.0, 1.9, and 7.1 kb. Recombination rates after one round of replication were 4.7, 7.4, and 8.2% with markers 1.0, 1.9, and 7.1 kb apart, respectively. Thus, the rate of homologous recombination with 1.0 kb of marker distance is similar in MLV and SNV. The recombination rate increases when the marker distance increases from 1.0 to 1.9 kb; however, the recombination rates with marker distances of 1.9 and 7.1 kb are not significantly different. These data refute the previous assumption that recombination is proportional to marker distance and define the maximum recombining population in retroviruses.

Genome, Viral↗
PubMed1997

Homologous recombination occurs in a distinct retroviral subpopulation and exhibits high negative interference.

Homologous recombination and deletions occur during retroviral replication when reverse transcriptase switches templates. While recombination occurs solely by intermolecular template switching (between copackaged RNAs), deletions can occur by an intermolecular or an intramolecular template switch (within the same RNA). To directly compare the rates of intramolecular and intermolecular template switching, two spleen necrosis virus-based vectors were constructed. Each vector contained a 110-bp direct repeat that was previously shown to delete at a high rate. The 110-bp direct repeat was flanked by two different sets of restriction site markers. These vectors were used to form heterozygotic virions containing RNAs of each parental vector, from which recombinant viruses were generated. By analyses of the markers flanking the direct repeats in recombinant and nonrecombinant proviruses, the rates of intramolecular and intermolecular template switching were determined. The results of these analyses indicate that intramolecular template switching is much more efficient than intermolecular template switching and that direct repeat deletions occur primarily through intramolecular template switching events. These studies also indicate that retroviral recombination occurs within a distinct viral subpopulation and exhibits high negative interference, whereby the selection of one recombination event increases the probability that a second recombination event will be observed.

Animals↗
PubMed1996

Efficient initiation and strand transfer of polypurine tract-primed plus-strand DNA prevent strand transfer of internally initiated plus-strand DNA.

A critical step in retroviral reverse transcription is the initiation of plus-strand DNA synthesis at the polypurine tract (PPT) and strand transfer of the PPT-primed strong-stop DNA to the 5' end of the viral DNA. An attachment site (att) immediately 3' to the PPT is essential for proper integration of proviral DNA into the host chromosome. Plus-strand DNA synthesis is discontinuous in many retroviruses, indicating that sequences upstream of the PPT are also used to initiate plus-strand DNA synthesis (internally initiated DNA). Strand transfer of internally initiated DNA would result in "dead" viral DNA that lacks the att site needed for integration. Strand transfer of the internally initiated DNA could occur if DNA synthesis failed to initiate at the PPT or if the PPT-primed DNA was displaced before strand transfer. We sought to determine the efficiency of DNA synthesis initiating at the PPT and the proportions of PPT-primed DNA and internally initiated DNAs that are utilized for strand transfer. We constructed spleen necrosis virus-based retroviral vectors containing an internal PPT and an att site 5' of the normal PPT and att site. After one replication cycle of the retroviral vectors, the structures of the resulting proviruses were determined by Southern blotting. The analysis suggested that the PPT is an efficient and rapid initiator of plus-strand DNA synthesis and that internally initiated DNAs are rarely utilized for strand transfer. We hypothesize that efficient synthesis and strand transfer of PPT-primed DNA evolved to prevent lethal strand transfers of internally initiated DNAs.

Animals↗
PubMed1986

Managing information systems: still a CFO function.

This article represents the first in a series examining the information management needs, both now and in 1988, of hospital CFOs. Future articles will focus on the management concerns of CFOs in relation to information, their current and projected use of information management products for long-range, strategic planning, and criteria for systems design. All these articles are based on HFMA members' opinions as voiced in a recent national poll. In all, more than 600 CFOs and data processing professionals responded to a recent survey sponsored by HFMA, HBO & Company, and Amherst Associates.

Computers↗
PubMed1986

Information systems for the value management era.

Health care is entering into the era of value management--delivering high quality products and services at a reasonable price. This concept of delivery will have a definite effect on an organization's management strategies and tactics, especially in the area of information systems. Much re-evaluation of an organization's requirements for its information systems wil happen. As a result, a value-managed organization will place a greater demand on its information systems.

Data Collection↗