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Biomedical subjects

D L Walker

Publications and source records attributed to D L Walker.

120 records · Page 7Linked to original sources
PubMed1971

Comparison of cytocidal and noncytocidal strains of Shope rabbit fibroma virus.

Seven strains of Shope fibroma virus were compared for their effect on rabbit cells in vitro. All but one of the naturally occurring strains examined in this study produced a similar response in the infected cultures. This consisted of continued cell multiplication together with changes in cell morphology and growth pattern. In contrast, a recently isolated strain of fibroma virus, the M1 strain, was found to produce a gradual cell destruction under the same cultural conditions. A comparison of the cytocidal M1 strain with a representative noncytocidal strain in vitro showed no differences in the rate of multiplication, plaque type, antigenic composition, or heat lability. Only minor differences were found in the tumors produced in rabbits by these strains.

Animals↗
PubMed1970

Effect of persistent fibroma virus infection on susceptibility of cells to other viruses.

Shope fibroma virus establishes a persistent cytoplasmic infection in primary (RK) and serially cultivated (DRK(3)) rabbit kidney cells which is accompanied by a morphological alteration of the cells. The response of such cells to superinfection by other viruses was compared with that of control cells by determining plaque production and virus yield of superinfecting viruses. It was found that the growth of other poxviruses, myxoma and vaccinia, was greatly inhibited in the fibroma virus-infected cells, but that of pseudorabies and herpes simplex viruses, which are unrelated deoxyribonucleic acid viruses, was virtually unaffected. The ribonucleic acid (RNA) viruses, poliovirus 1 and coxsackievirus B1, did not produce plaques on either RK or fibroma virus-infected (F-RK) monolayers. However, the growth of several other RNA viruses, vesicular stomatitis virus, encephalomyocarditis virus, Sindbis virus, and Newcastle disease virus, was enhanced in F-RK cells. None of these latter RNA viruses produced any infectious progeny in DRK(3) cells, but they all plaqued on and produced good yields in DRK(3) cells persistently infected with fibroma virus. This phenomenon is termed facilitation. Facilitation results from the infection of DRK(3) cells by fibroma virus. Neither interference nor facilitation were due to changes in the adsorption or eclipse of the superinfecting virus.

Adenoviridae↗
PubMed1969

The role of individual spleen cells in the interferon response of the intact mouse.

A method is described for the detection of interferon production by individual spleen cells of mice after intravenous virus infection. Although mouse spleen plays a major role in the total interferon response to Newcastle disease virus, the number of spleen cells participating is a small fraction of the total, suggesting that interferon formation is to some extent a specialized cell function. Monolayers of mouse embryo cells, after brief contact with agar-suspended spleen cells from interferon-producing mice, have roughly circular foci of cells remaining after removal of agar and vesicular stomatitis virus challenge. The numbers of such foci correlate directly with the number of spleen cells, concentration of inducing virus in the inoculum, duration of contact of cells with mouse-embryo indicator monolayers, time after interferon induction, and serum interferon titer. With this technique, evolution of the interferon-forming cell response in spleens of virus-infected mice has been studied.

Animals↗
PubMed1969

Cellular deoxyribonucleic acid synthesis and loss of contact inhibition in irradiated and contact-inhibited cell cultures infected with fibroma virus.

Cultural changes that follow infection of rabbit kidney cells with fibroma virus were studied. Characteristic alterations of cell morphology and development of multilayered piles and cords of cells were found to occur in infected cultures in which cell division was blocked by gamma radiation or by cell crowding and serum deprivation, thus indicating no dependence upon cell division. Fibroma virus infection did not remove blocks to cell division, but it did exert distinct effects upon nuclear deoxyribonucleic acid synthesis in cells blocked by radiation or cell crowding. Use of tritium-labeled thymidine and autoradiography demonstrated that after infection initial inhibition of nuclear incorporation was followed by sharply increased nuclear labeling at a time that coincided with beginning alterations of cell morphology and development of cell piling.

Animals↗
PubMed1968

Enhancement of infectivity of murine cytomegalovirus in vitro by centrifugal inoculation.

Centrifugation of murine cytomegalovirus inocula from a variety of sources onto secondary mouse embryo cell monolayers at 1,900 x g for 30 min regularly revealed 10- to 100-fold more infectious virus than could be found in the same materials using standard inoculation methods. Virus demonstrable only by centrifugation was present throughout the entire growth cycle in a constant proportion to virus measured without centrifugation. Extracellular growth curves of both populations revealed an 18- to 21-hr latent period, followed by a long-linear increase over the next 12 hr; final yield was 30 plaque-forming units (PFU) per cell. Centrifugation of cells prior to inoculation or after standard adsorption and removal of inoculum failed to result in any significant change in measured virus titer. However, even after 4-hr adsorption, the supernatant inoculum could be transferred and centrifuged onto a fresh monolayer resulting in the same increment of measurable virus. Neutralizing antibody and interferon were equally efficacious against 100 PFU of virus as defined by either method. Thus, this newly identified population of cytomegalo-virus represents the vast majority of potentially infectious units and appears to differ solely in ease of adsorption onto cell monolayers.

Adsorption↗
PubMed1966

Persistent, noncytocidal viral infection: nonsynchrony of viral and cellular multiplication.

Walker, Duard L. (University of Wisconsin Medical School, Madison), Ping-Ping Chang, Robert L. Northrop, and Harry C. Hinze. Persistent, noncytocidal viral infection: nonsynchrony of viral and cellular multiplication. J. Bacteriol. 92:983-989. 1966.-In cultures of human conjunctive cells persistently infected with mumps virus (C-M cultures), the degree to which viral multiplication is linked to cell multiplication was examined. First, cell multiplication was inhibited. This resulted in a 10-fold increase in virus-excreting cells in the culture and an 80-fold increase in virus in the medium as compared with vigorously growing control cultures. Second, by use of elevated incubation temperature, virus multiplication was inhibited without slowing multiplication of the cells, and uninfected cells that appeared in the culture were protected by virus antiserum. This resulted in accumulation of antigen-free cells and, in one experiment, in elimination of the virus. Evidence indicated that uninfected cells accumulated as a result of dilution of virus by repeated cell divisions, but not as a result of selection of uninfected cells. These data indicate that viral multiplication in the C-M system is not closely linked to cell multiplication and that each can proceed at a rate different from the other.

Antigens↗
PubMedDate not supplied

Measuring resource utilization in medical group practice.

The staff seems so busy every time you walk by the front office or pass through the nurses' station. The office seems to brim with patients whenever you stop by to chat with the medical director. "Seems" is the operative word--analyzing reality versus appearance may lead to some important insights about the utilization of resources in your practice. This article serves to define and analyze resource utilization in a medical practice by considering examples of staff and facility utilization.

Benchmarking↗
PubMedDate not supplied

Survival and in vitro fertilization potential of sperm following washing and incubation with different protein supplements.

Three protein supplements, preovulatory donor serum (PDS), Cohn Fr V human serum albumin (HSA), and highly purified HSA were used for washing sperm. The ability of the different protein supplements to support sperm survival and in vitro fertilization of zona-free hamster oocytes was compared following 18 hours of incubation. Sperm motility, velocity, linearity, and motility index were the same for the various proteins. The percentage of sperm with a functional plasma membrane was significantly greater (P less than .02) for highly purified HSA than for PDS or Cohn Fr V HSA. The percentage of zona-free hamster oocytes penetrated and penetrations per oocyte were two times greater (P less than .0001) for PDS and Cohn Fr V HSA compared with highly purified HSA. These data indicate that (1) proteins can possess an equal ability to support sperm survival, yet differ in their ability to support capacitation and the acrosome reaction; (2) HSA preparations derived from dissimilar purification methods may differ in their ability to support in vitro fertilization; (3) PDS and certain types of HSA possess an equal ability to support in vitro fertilization.

Blood Proteins↗