Search PubMed⌕ Search

Biomedical subjects

L O Arthur

Publications and source records attributed to L O Arthur.

119 records · Page 7Linked to original sources
PubMed1978

Prevalence of murine mammary tumor virus antibody and antigens in normal and tumor-bearing feral mice.

Approximately 20% of normal male and female feral mice (Mus musculus) from areas with populations having either high [Lake Casitas (LC) and La Puente] or low (Bouquet Canyon) spontaneous lymphoma incidence expressed murine mammary tumor virus (MuMTV) gp52 in specific tissues. Sera from a low percentage (6%) of mice from the same trapping areas contained precipitating antibody specific for MuMTV. Although moderate to high levels of MuMTV gp52 were expressed in mammary tumor tissues of 3 of 7 LC mice and 3 of 3 (C57BL/10ScSn X LC)F1 mice, the same animals showed no detectable MuMTV-precipitating antibody. Neither MuMTV antibody nor tumor-associated MuMTV gp52 was defected in 10 LC mice bearing lymphomas or in 5 LC mice bearing hepatomas. Low levels of MuMTV gp52 expression and MuMTV antibody were also detected in subspecies of M. musculus and in the more distantly related species M. cervicolar. Compared with normal and tumor-bearing inbred mice of high (C3H/HeN) and low (C3H/HeN foster-nursed on NIH Swiss) mammary tumor strains, normal and tumor-bearing feral mice express MuMTV gp52 and MuMTV-precipitating antibodies at low frequency.

Animals↗
PubMed1976

Propagation of mouse mammary tumor cell lines and production of mouse mammary tumor virus in a serum-free medium.

Five different mouse mammary tumor cell lines were propagated in a serum free medium. Evaluation of growth characteristics, including logarithmic growth, cell population increase, protein production and days to confluency, showed serum-free medium comparable to serum-containing medium. Mouse mammary tumor virus expression and production, in C3H and GR tumor cell lines, as determined by virus particle counting and RNA dependent DNA polymerase assays, subsequent to dexamethasone stimulation revealed equivalent to higher levels of virus in serum-free medium as compared to serum-containing medium.

Animals↗
PubMed1976

Cell culture factors influencing in vitro expression of mouse mammary tumor virus.

Several cell culture factors were found to influence in vitro expression of mouse mammary tumor virus (MMTV) in the mouse adenocarcinoma cell line Mm5mt/c1. Cells were propagated in a variety of commercially available cell culture media to which dexamethasone (DXM) was added as a stimulator of MMTV production. Culture seeding density, culture medium type, and glucose concentration each influenced MMTV production when expressed on a per cell basis. Maximum cell growth occurred in cultures grown in RPMI-1640 medium containing insulin. Those media which provided good cell growth were not necessarily optimal for virus expression. Addition of insulin did not stimulate MMTV synthesis although dexamethasone alone was stimulatory in all media used; however, maximum MMTV expression was obtained when dexamethasone and insulin were used in concert. Equivalent levels of MMTV-specific cell membrane antigen, MMTV-specific protein, and virus particles were produced at incubation temperatures of 32 degrees, 34 degrees or 37 degrees C; however, higher levels of virus-related RNA-dependent DNA polymerase (RDDP) activity were recovered from cultures incubated at 32 degrees and 34 degrees C than at 37 degrees C. Decreased levels of RDDP were attributed to enzyme thermolability at 37 degrees C incubation.

Animals↗
PubMed1976

Surface localization of virus production on a glucocorticoid-stimulated oncornavirus-producing mouse mammary tumor cell line by scanning electron microscopy.

A chronically infected continuous mouse mammary tumor cell line containing virus particles of type B morphology, free of contaminating type C virions, has been grown in tissue culture. These cells were treated with dexamethasone, a synthetic glucocorticoid, a potent stimulator of mouse mammary tumor virus expression. Surfaces of untreated and dexamethasone-treated cells were investigated by scanning electron microscopy. Untreated cells demonstrated a moderate expression of mouse mammary tumor virus (80 particles/cell) distributed diffusely over the cell surface. However, virions on dexamethasone-treated cells were localized in clusters of 100 to greater than 2000 virus particles, often with more than one cluster per cell. Dexamethasone-treated cells typically showed a 10-fold increase in cell-associated virus over untreated cells. Concentrated extracellular fluids from untreated and dexamethasone-treated cultures were quantitated for free virus. Dexamethasone-treated culture fluids demonstrated a similar 10-fold increase of extracellular particles, in contrast to untreated cultures. This increase in virus particles on the cell surfaces as well as in the extracellular fluids supports the theory that dexamethasone has a stimulatory effect on viral replication, not just on the release of budding particles. The ultrastructure of budding mouse mammary tumor virus during dexamethasone stimulation, determined by scanning and transmission electron microscopy, and the significance of such an in vitro system for viral immunodiagnosis are discussed.

Cell Line↗
PubMed1976

Autogenous immunity to mouse mammary tumor virus in mouse strains of high and low mammary tumor incidence.

Specific radioimmune precipitation assays were utilized to demonstrate the presence of precipitating antibodies to mouse mammary tumor virus (MMTV) in the high-spontaneous mammary tumor strains of mice: C3H/HeN+, GR/N, BALB/cfC3H, and C57BL/6 X C3H F1 (hereafter called B6C3F1). Antibody titers in C3H/HeN+ mice increased with age, with highest titers observed in tumor-bearing animals. MMTV-precipitating antibodies were not detectable by radioimmune precipitation assay in low-mammary tumor strains (AKR, BALB/c C57BL/6, and C3H/HeN-) but were detectable in MMTV-inoculated BALB/c mice. Appearance of antibodies preceded palpable tumor formation, and antibody titers were directly correlated to virus dose. Natural antibody to MMTV in C3H/HeN+ and B6C3F1 mice coexists with the murine leukemia virus natural antibody as determined by competition radioimmunoassays.

Animals↗
PubMed1975

Carbohydrate catabolism of selected strains in the genus Agrobacterium.

Radiorespirometric and enzyme analyses were used to reveal the glucose-catabolizing mechanisms functioning in single strains of seven presumed Agrobacterium species. The Entner-Doudoroff and pentose cycle pathways functioned in A. radiobacter, A. tumefaciens, A. rubi, and A. rhizogenes. Whereas both catabolic pathways were utilized to an almost equal degree in the A. radiobacter and A. tumefaciens strains, use of the Entner-Doudoroff pathway predominated in the A. rubi and A. rhizogenes strains. A stellulatum catabolized glucose almost solely through the Entner-Doudoroff pathway. In A. pseudotsugae and A. gypsophilae, glucose was metabolized mainly through the Emden-Meyerhof-Parnas pathway; the pentose phosphate pathway was also utilized.

Aldehyde-Lyases↗
PubMed1974

In vitro system for production of mouse mammary tumor virus.

An in vitro system for production, purification, and concentration of mouse mammary tumor virus is described. Monolayer cultures of C(3)H mouse mammary tumor cells propagated at 34 C in roller bottles in the presence of dexamethasone, a glucocorticoid hormone, release B-type particles which possess ribonucleic acid and a ribonucleic acid-dependent deoxyribonucleic acid polymerase. One thousandfold concentration by ultracentrifugation with subsequent gradient fractionation yielded > 7 x 10(10) particles per ml in the 1.16- to 1.18-g/ml region. Mouse mammary tumor virus produced in this system was free of detectable C-type virus.

Animals↗
PubMed1973

Control of pantothenate accumulation in Agrobacterium tumefaciens.

Two pantothenate-requiring mutants of Agrobacterium tumefaciens have been isolated. One of them (strain WMP-1) is unusual in that growth levels equivalent to the parent strain are achieved only when the medium is additionally supplemented with aspartate or another compound related to the tricarboxylic acid cycle. Extracts of cells grown on limiting aspartate were found to contain four times more (14)C-pantothenate than those grown at optimal aspartate concentrations. This difference was found in both the perchloric acid-soluble and -insoluble fractions, presumably the coenzyme A pool and acyl carrier protein, respectively. These findings are discussed in terms of membrane integrity and the control of fatty acid biosynthesis.

Alanine↗
PubMed1973

Carbohydrate metabolism in Agrobacterium tumefaciens.

The activity of pentose cycling (PC) reactions in Agrobacterium tumefaciens is much greater than that normally found in bacteria, and in this regard the organism represents a unique category. Equations specifically derived from radiorespirometric data for bacteria with high PC activity in the presence of an alternate pathway are presented. A. tumefaciens utilizes d-glucose by strictly aerobic mechanisms involving the Entner-Doudoroff (ED) and PC pathways; relative participation by the ED pathway is 55% and by the PC cycle, 44%. The 3-ketoglycose-synthesizing system in the bacterium does not affect the relative participation of these two pathways. Radiorespirometric and enzymatic analyses clearly demonstrate that the Embden-Meyerhof-Parnas pathway does not function. Studies on the oxidation of pyruvic, acetic, succinic, and glutamic acids show that terminal respiration includes both the tricarboxylic acid and glyoxylic acid cycles.

Acetates↗
PubMedDate not supplied

Characterization and molecular cloning of a bovine lentivirus related to human immunodeficiency virus.

An infectious virus which causes persistent lymphocytosis, lymphadenopathy, lesions in the central nervous system (CNS), progressive weakness and emaciation was previously isolated from the leukocytes of cattle. Our present studies show that this virus encodes a reverse transcriptase (RT) with Mg2+ cation preference, replicates and induces syncytia in a variety of embryonic bovine tissues in vitro, and has a morphology most similar to the human immunodeficiency virus (HIV). Moreover, serologic analyses have demonstrated a conservation of epitopes between the major core protein of this bovine retrovirus and HIV. Shared antigenic determinants were also observed with other pathogenic retroviruses of the lentivirus subfamily. To resolve the phylogenetic relationship of this virus, proviral molecular clones were derived and used to determine the nucleotide sequence of the highly conserved RT domain. The sequence data and serologic analyses together show that this bovine retrovirus is a novel lentivirus related to HIV and other lentiviruses. We propose that this virus be tentatively named bovine immunodeficiency-like virus (BIV) to reflect its genetic relationship and biological similarity to HIV.

Animals↗