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Biomedical subjects

R G Olsen

Publications and source records attributed to R G Olsen.

At least 19 recordsLinked to original sources
PubMed1992

Anti-human immunodeficiency virus (HIV) agents are also potent and selective inhibitors of feline immunodeficiency virus (FIV)-induced cytopathic effect: development of a new method for screening of anti-FIV substances in vitro.

The ability of several known anti-HIV substances to inhibit feline immunodeficiency virus (FIV) was tested. The results showed that FIV infection of feline T-cells was almost completely blocked in the presence of all of the agents tested. However, FIV-induced syncytium formation between a human T-cell line (MT-2 cells) and a FIV-infected feline lymphocyte cell line (3201/FIV) was inhibited only by dextran sulfate and pradimicin A. The assay used to measure syncytium inhibition was rapid and did not use potentially hazardous human immunodeficiency virus (HIV)-infected cells. The efficacy results coincided with those of HIV studies.

Animals↗
PubMed1992

Effect of 1,1-dimethylhydrazine (UDMH) on Corynebacterium parvum-associated immunosuppression in mice.

These studies further investigate the immunoenhancement properties of UDMH by utilizing Corynebacterium parvum-induced immunosuppressed mice as well as evaluating activated macrophage production of reactive oxygen intermediates or their effects. Forty-eight hour Con A-induced lymphoblastogenic responses from splenocytes isolated from C. parvum and UDMH-treated Balb/C mice were significantly increased compared with C. parvum alone, although less than normal control mice (no treatment). In vitro bioassay of IL-2 production in cell culture supernatant isolated from these same treatment groups exhibited a pattern of stimulation similar to that of lymphocyte blastogenesis. In addition, UDMH did not interfere with H2O2-mediated suppression of either Con A- or LPS-induced lymphocyte blastogenesis and actually enhanced suppression of Con A-induced lymphocyte cultures at 25 micrograms/ml. We also report that production of superoxide anion from TPA-activated peritoneal macrophages exposed to various concentrations of UDMH in vitro was not affected. Although in vivo exposure to UDMH partially reversed C. parvum-induced immunosuppression in mice, the exact mechanism by which UDMH acts to reverse this immune suppression is not clear. UDMH does not appear to interfere with either activated peritoneal macrophage production of superoxide anion or H2O2-induced suppression of lymphocyte blastogenesis to elicit immune enhancement.

Animals↗
PubMed1979

Enhancement of feline leukemia virus-induced leukemogenesis in cats exposed to methylnitrosourea.

The effect of methylnitrosourea (MNU), a potent resorptive carcinogen, was evaluated for its influence on the susceptibility of adult cats to infection and induction of oncornavirus disease by feline leukemia virus (FeLV). Young adult cats at an age previously demonstrated to be highly resistant to FeLV, were injected intravenously with moderately toxic doses (15-20 mg/kg) of MNU alone or with infections FeLV (Rickard strain). Following exposure to virus and chemical, cats were monitored for antibody to the feline oncornavirus-associated cell membrane antigen (FOCMA), viremia by direct infectivity and the presence of gsa in peripheral blood leukocytes, and for toxic effects of MNU by hemogram analyses on peripheral blood. Of 8 cats injected with MNU + FeLV, 6 developed persistent viremia, 5 of which became debilitated from thymic lymphoma. Only 1 of 6 non-MNU-treated and infected cats of the same age became transiently viremic. FOCMA antibody development was markedly depressed in MNU + FeLV inoculated cats compared with cats inoculated with FeLV alone. Results show that MNU was apparently responsible for the obliteration of age-related susceptibility in cats to FeLV infection and induction of FeLV-related disease, and suggest that in nature exposure to toxic chemical carcinogens may act as factors which determine susceptibility to feline oncornaviruses in the cat.

Age Factors↗
PubMed1979

The effects of methylnitrosourea on the immune system and hematopoietic system of adult specific pathogen free cats.

The effects of a single non-carcinogenic dose of 15 mg/kg methylnitrosourea (MNU) on the immune and hematopoietic systems of adult specific-pathogen-free (SPF) cats were determined. The cell-mediated-immune (CMI) system was markedly suppressed, as evidenced by: (i) Prolonged cutaneous allograft retention time (41-84 days); (ii) Decreased lymphocyte blast transformation response to mitogens (2% of pretreatment response to pokeweed mitogen or concanavalin A) and antigen (12% of untreated control cat response to keyhole limpet hemocyanin); (iii) Reduced number of absolute erythrocyte-rosetting T-cells in the peripheral blood. This immunosuppression lasted at least 3 months, the duration of the experiment. Suppression of the hematopoietic system was also noted as evidenced by: (i) Peripheral lymphopenia lasting 3 months and neutropenia lasting 3 weeks; (ii) Bone marrow hypocellularity lasting 3 weeks; (iii) Hypoplasia of neutrophilic precursors lasting 3 weeks and erythroid precursors lasting 4 days. It was concluded that a single non-carcinogenic dose of MNU induces a prolonged suppression of the CMI system and a brief suppression of hematopoiesis in adult SPF cats. The immunosuppression may in part be responsible for the previously observed increased susceptibility to feline leukemia virus infection and disease of adult SPF cats treated with MNU.

Animals↗
PubMed1979

Recovery of soluble feline oncornavirus-associated cell membrane antigen from large volumes of tissue culture fluids.

Feline oncornavirus-associated cell membrane antigen (FOCMA), which is released spontaneously in tissue culture, was harvested from large volumes of culture fluid. Continuous-flow molecular filtration was the method of choice for concentrating the component. The yield of antigen recovered, as determined by cytotoxicity inhibition, was equal to that recovered with concentration in cellulose membrane tubing against polyethylene glycol and half that obtained by lyophilization. The latter two techniques were found to be impractical for handling large volumes of material. However, lyophilization was used for the final concentration step following volume reduction to approximately 300 ml in the molecular filtration system. Antigen yields were equivalent when removing salt by constant-volume molecular washing, prior to concentration in the filtration system, or when removing salt by conventional diffusion through cellulose membrane tubing.

Animals↗
PubMed1979

Preliminary studies: far-field microwave dosimetric measurements of a full-scale model of man.

Measurements of microwave heating were made in a full-size, upright human model. The 75-Kg model, composed of electrically simulated muscle, was placed in the far-zone of a standard-gain horn inside an absorber-lined chamber. Pulsed energy at 1.29 GHz was obtained from a military radar transmitter (AN/TPS-1G) and produced radiation at 6-14 mW/cm2 average power density at the location of the model. Microwave heating at the front surface was measured at nine locations on the phantom. Measurements at several depths within the phantom were also made at a central location to gain information on the depth-of-penetration of the microwave energy. Results of the frontal surface measurements and of the penetration study permitted a calculation of the approximate whole-body average specific absorption rate (SAR) when the model's long axis was parallel to the E-field vector. For a normalized power density of 1 mW/cm2 at a frequency of 1.29 GHz, the whole-body average SAR approximated 0.03 W/Kg. This result agrees well with theoretical predictions based on absorption in prolate spheroidal models of man.

Humans↗
PubMed1979

Inhibition of human lymphocyte mitogen and antigen response by a 15,000-dalton protein from feline leukemia virus.

Peripheral blood lymphocyte response of normal human subjects to mitogens and antigens was suppressed by a 15,000-dalton protein (p15) from a C-type feline leukemia virus. Four of six subjects were suppressed 70 to 96% when responding to concanavalin A or phytohemagglutinin in the presence of 5.0 microgram of p15. The three subjects who responded to streptokinase-streptodornase and Candida were suppressed 68 to 91% when cultured with 5.0 microgram of p15. The subviral protein did not appear to be cytotoxic at doses reported. Lymphocyte membrane studies with fluorescein isothiocyanate-concanavalin A revealed a reduction in concanavalin A-induced cap formation of 51 to 91% in the presence of the same dose of p15. These results demonstrate that in vitro immunological dysfunction in human lymphocytes can be induced by a C-type virion protein.

Antigens↗
PubMed1979

Immunosuppressive properties of a virion polypeptide, a 15,000-dalton protein, from feline leukemia virus.

The 15,000-molecular-weight polypeptide (p15) of feline leukemia virus (FeLV) was shown to impair normal lymphocyte function in vitro and to abrogate immunity to feline oncornavirus disease in vivo. FeLVp15 suppressed concanavalin A-induced blast transformation of normal feline lymphocytes by 68%, while other virion proteins had no effect. p15 suppression was not due to toxicity, nor was p15 a competitive inhibitor of concanavalin A binding. Capping of receptors for concanavalin A on normal feline lymphocytes also was inhibited by either inactivated FeLV or FeLV p15. Groups of cats were immunized with either killed feline oncornavirus-associated cell membrane antigen bearing tumor cells or tumor cells plus FeLV p15. After challenge with feline sarcoma virus, three of four p15-treated cats developed progressive fatal fibrosarcoma as compared to one of five non-p15-treated cats. The cats receiving p15 also had lower cytotoxic antibody titers against feline oncornavirus-associated cell membrane antigen (mean peak titer, 1:6) than did the non-p15 group (1:74). These data support the hypothesis that the immunosuppression in cats infected with FeLV is mediated by FeLV p15.

Animals↗
PubMed1979

Mobility of lymphocyte surface membrane concanavalin A receptors of normal and feline leukemia virus-infected viremic felines.

The virus-associated depression of concanavalin A mitogenesis which accompanies feline leukemia virus-induced cat lymphoma was investigated by comparing lymphocyte surface receptor mobility of normal cats to that of viremic diseased animals. The mechanics of feline lymphocyte receptor mobility were studied using fluorescein-conjugated concanavalin A to quantitate lymphocyte capping. The results of a study of 21 disease-free animals showed that cat lymphocytes undergo appreciable concanavalin A capping, with a mean capping rate of 17% under conditions developed in this study. In contrast, morphologically normal peripheral blood lymphocytes of six feline leukemia virus-infected viremic cats, with or without lymphoma, exhibited a mean capping of only 7%, significantly less than that of the control animals (p less than 0.005). These findings suggest that a membrane-related lymphocyte deficiency accompanies the development of virus-induced lymphoma in the cat.

Animals↗
PubMed1979

Influence of adrenal corticosteroids on the susceptibility of cats to feline leukemia virus infection.

The natural resistance of adult specific-pathogen-free cats to feline leukemia virus (FeLV) was abrogated by treatment with various doses of a synthetic corticosteroid, methylprednisolone acetate (MPA), prior to either oral-nasal or i.p. inoculation of FeLV. Persistent viremia was induced in 82% (18 of 22) of MPA-treated cats versus 11% (1 of 9) of age-matched control cats. MPA-treated FeLV-inoculated cats developed prolonged lymphopenia (2 to 8 weeks postinoculation) and a delayed antibody response to the feline oncornavirus-associated cell membrane antigen. The distribution of FeLV group specific antigen in tissues of MPA-treated, FeLV-inoculated cats suggested that corticosteroids enhanced susceptibility to FeLV by impairing early viral containment in the reticuloendothelial and lymphoid tissues.

Animals↗
PubMed1979

Feline lymphocytes: observations on surface membrane concanavalin A receptor mobility.

The mechanics of concanavalin A receptor mobility of the feline lymphocyte surface membrane were investigated, utilizing fluorescein-labeled lectin to quantitate lymphocyte capping. The results of this study indicated that lectin concentration and buffer selection were critical for extensive receptor redistribution with cap formation of feline lymphocytes. Maximal capping was obtained with 50 microgram of concanavalin A/ml of minimal essential medium. The mean capping rate of peripheral blood lymphocytes increased significantly with colchicine exposure at 10(-7) M concentration. The mean values of capping increased slightly with advancing age of feline donors, although this difference was not statistically significant. Concurrent work has indicated that concanavalin A capping may be useful in the study of immunosuppression in feline leukemia virus-infected cats.

Age Factors↗
PubMed1978

Increased susceptibility to feline leukemia virus infection in cats exposed to methylnitrosourea.

Exposure of adult specific-pathogen-free cats to methylnitrosourea resulted in increased susceptibility to infection by feline leukemia virus. A greater proportion of cats exposed to methylnitrosourea and feline leukemia virus (69%) became persistently viremic than those exposed to feline leukemia virus alone (17%). Segmented neutrophils were reduced by 90 to 99% within 3 days following exposure to methylnitrosourea, (15 to 20 mg/kg) whereas the effects on lymphocytes and erythrocytes, although less obvious, were also detected.

Animals↗
PubMed1978

Influence of thymectomy on the susceptibility of cats to feline leukemia virus and lymphosarcoma.

Twelve cats were thymectomized at 5 weeks of age. Six of these cats were inoculated at 8 weeks of age and 6 at 4 months of age with the Rickard (R) strain of feline leukemia virus (FeLV), which produces a high incidence of thymic lymphosarcoma. Two groups of age-matched nonthymectomized cats were inoculated with the same FeLV-R stock. Thymectomy prior to FeLV infection had no influence on the induction of viremia or the incidence of lymphosarcoma. In the FeLV-inoculated nonthymectomized cats, lymphosarcoma developed in the thymus. In the thymectomized cats, lymphosarcoma developed in the intestine, mesenteric lymph nodes, and bone marrow, but the malignant lymphoblasts had surface markers characteristic of feline T lymphocytes. It was concluded that the presence of the thymus per se is not required for infection and oncogenesis by FeLV and that feline T lymphocytes may be transformed after peripheralization to other tissues.

Animals↗
PubMed1978

Modifications of the immunofluorescence assay for feline leukemia virus group-specific antigens.

Observations and minor modifications are presented concerning the immunofluorescence assay for feline leukemia virus (FeLV) group-specific antigens (GSA) in blood cells of cats. Data are given regarding absorption of goat FeLV GSA antiserum in vivo in cats, absorption of the antiserum in vitro with feline blood cells, and the comparative efficacy of various chemical fixatives in preservation of FeLV GSA for immunofluorescent staining. The best results were obtained with in vitro absorption of antiserum and methanol fixation of FeLV GSA in blood smears.

Animals↗
PubMed1978

Thymectomy in preweanling kittens: technique and immunologic consequences.

Thymectomy of 5-week-old kittens was accomplished by left parasternal thoracotomy, ligation of the left internal thoracic artery, and removal of the thymus from the mediastinum by traction and blunt dissection. Thymectomy had no adverse clinical effects, and neither the response of peripheral blood lymphocytes to phytomitogens nor the proportions of circulating lymphocytes bearing T- or B-cell markers differed substantially between thymectomized cats and nonthymectomized control cats. Skin allograft rejection times of the thymectomized cats (3 weeks after operation) were slightly longer than those of littermate nonthymectomized controls. We conclude that removal of the thymus in preweanling kittens does not have important physiologic or immunologic consequences.

Animals↗