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Biomedical subjects

R G Olsen

Publications and source records attributed to R G Olsen.

At least 37 records · Page 2Linked to original sources
PubMed1989

In vitro infection of cell lines with HTLV-I and SIVmac results in altered intracellular free calcium concentration and increased membrane polarization.

This study was designed to determine whether retrovirus infection alters basal concentrations of intracellular free calcium, the magnitude of intracellular free calcium change upon receptor-mediated cell-stimulation, and cell membrane polarization. Two retrovirus-infected cell lines were utilized: HTLV-I-infected MT-2 cells and SIV-infected H-9 cells. Uninfected H-9 cells were used as controls. The results show that the retrovirally-infected cells had an increased basal concentration of intracellular free calcium when compared with the control cells and also a reduced magnitude of intracellular free calcium response to receptor-mediated cell stimulants. The retrovirally-infected cell membranes were also hyperpolarized when compared with the control cells.

Calcium↗
PubMed1989

Outdoor measurement of SAR in a full-sized human model exposed to 29.9 MHz in the near field.

Localized and averaged specific absorption rates (SARs) were obtained in a full-size muscle-equivalent human model exposed to near-field 29.9 MHz irradiation at an outdoor facility. The model was positioned erect on a metallic groundplane 1.22 m (4 ft) from the base of a 10.8-m (35 ft) whip antenna with an input power of 1.0 kW. For whole-body SAR, a mean value of 0.83 W/kg was determined using two gradient-layer calorimeters in a twin-well configuration. The localized SARs at 12 body locations were measured using nonperturbing temperature probes and were highest in the ankle region. We conclude that averaged SAR measurements in a full-size phantom are feasible using a twin-calorimeter approach; measurements in the field are practical when human-size (183 x 61 x 46 cm) calorimeters are used.

Absorption↗
PubMed1989

Simple nonperturbing temperature probe for microwave/radio frequency dosimetry.

We present a simple readout device that fills the void produced by the gradual disappearance of the Vitck model 101 Electrothermia Monitor. The new device uses commercially available probes that are similar to Bowman's (IEEE Trans Microwave Theory Tech MTT-24:43-45, 1976) original design. As described, the device covers the range of 7 degrees to 45 degrees C with an accuracy and resolution of better than 0.1 degree C throughout. The digital readout (3 1/2 digits) is proportional to the thermistor resistance in the tip of the probe; it is converted to temperature through a formula or printed table. Outdoor dosimetric comparisons between the new and Vitek devices were conducted. Results showed no significant difference in the calculated specific absorption rates (SARs); moreover, variance was lower in the data collected from the new device.

Equipment Design↗
PubMed1989

Immunodeficiency in latent feline leukemia virus infections.

Challenge of naive experimental animals with a retroviral inoculum may result in one of two broad sequelae. The first is the establishment of an appropriate humoral and cellular immune response leading to a condition of immunity to subsequent infection with the retrovirus. Alternatively, the host may fail to develop a successful immune response, resulting in a chronic viremia associated with immunosuppression and ultimately death due to secondary pathogens. An alternate disease course is the establishment of a latent infection characterized by the presence of neutralizing antibody and strong cellular immune reactivity. Recent data from the feline leukemia virus (FeLV) system suggest that cats infected with this virus may develop immunosuppression in the form of persistent neutrophil dysfunction. The potential effect of this cellular dysfunction is the possible susceptibility of the host to the same opportunistic pathogens which are responsible for the increased mortality noted in chronic FeLV infections. These data demonstrate that persistent retroviremia is not essential for the establishment of immunosuppression. This overview presents data accumulated from the feline model of the human acquired immunodeficiency syndrome (AIDS) and discusses its relationship to human retroviral infections.

Acquired Immunodeficiency Syndrome↗
PubMed1989

FeLV-induced immunosuppression through alterations in signal transduction: changes in intracellular free calcium levels.

Feline leukemia virus (FeLV) is a retrovirus with immunosuppressive properties. The mechanism(s) of immunosuppression is unknown. Calcium has been shown to be a second messenger in cellular activation and regulation. This study was designed to determine whether FeLV alters intracellular free calcium (IFC) levels in an FeLV-infected feline lymphoid cell line. Control cells and FeLV-infected cells were exposed to Concanavalin A, formyl-L-methionyl-L-leucyl-L-phenylalanine, and leukotriene B4. The basal IFC and post-stimulation IFC levels were recorded using Fura 2 AM and a luminescence spectrometer. Data collected indicate that FeLV-infected cells have a higher basal level of IFC and a reduced amount of increase in IFC after stimulation when compared to the control cells. The results would seem to indicate retrovirus-mediated interference occurring in the intracellular calcium signaling process.

Animals↗
PubMed1989

FeLV-induced immunosuppression through alterations in signal transduction: down regulation of protein kinase C.

Activation of protein kinase C by a phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), was shown to stimulate the respiratory burst in normal cat neutrophils. Neutrophils from feline leukemia virus (FeLV)-exposed viremic and nonviremic cats had significant suppression of their respiratory burst when stimulated with TPA. The addition of whole ultraviolet light-inactivated FeLV and FeLV proteins to normal cat neutrophils produced no significant suppression of the respiratory burst. These data suggest two possible mechanisms for suppression. The first is partially due to viral alterations of the neutrophil as seen in viremic cats, but, because exogenously applied FeLV or FeLV proteins had no effect on the respiratory burst, an additional mechanism is present. The second mechanism may be caused by a latent FeLV infection residing in nonviremic cat bone marrows which alters their immune system, resulting in immunosuppression.

Animals↗
PubMed1989

Radio frequency (13.56 MHz) energy enhances recovery from mild hypothermia.

The rate of warming after hypothermia depends on the method of rewarming. This study compared the effectiveness of radio frequency (RF) energy against hot (41 degrees C) water immersion (HW) and an insulated cocoon (IC) for rewarming hypothermic men. Six men fasted overnight and were rewarmed for 1 h after attaining a 0.5 degree C reduction in rectal temperature (Tre). Tre and esophageal (Tes) temperature were recorded every 5 min with nonmetallic thermal probes. The base-line value for Tre and Tes just before rewarming was subtracted from each 5 min Tre and Tes during rewarming to give delta Tre and delta Tes. The 12 delta Tes values were averaged for each individual and were compared using analysis of variance. The average delta Tes for RF (1.15 +/- 0.22 degrees C/h) was faster (P less than 0.001) than either IC (0.37 +/- 0.16 degrees C/h) or HW (0.18 +/- 0.09 degree C/h). The present study shows the superiority of RF energy for rewarming mildly hypothermic men.

Adult↗
PubMed1988

Parameters of production and partial characterization of feline interleukin 2.

The conditions for the production of feline interleukin 2 (IL-2) from peripheral blood leukocytes (PBL) and splenocytes by concanavalin A (Con A) stimulation are described. Feline IL-2 was quantitated by measuring DNA synthesis in the murine IL-2-dependent cell line, CTLL-20. In addition, feline IL-2 was generated for the maintenance of long-term cultures of Con A-stimulated feline PBL and for biochemical characterization. Finally, IL-2 production was evaluated from the PBL of feline leukemia virus (FeLV)-infected cats. Con A at 9.6 micrograms/ml produced a plateau of peak IL-2 activity from 24 to 48 h following stimulation. The tumor promoter, phorbol myristic acetate, stimulated feline IL-2 production and enhanced Con A-stimulated feline IL-2 production. Fetal calf serum (FCS) was not required for IL-2 production; however, FCS at 5% (v/v) allowed for maximal Con A-stimulated IL-2 production. Feline IL-2 generated from Con A-stimulated splenocytes migrated with an apparent molecular size of 13.7 to 23 kD by gel filtration chromatography and supported the proliferation of Con A-activated feline PBL at a final concentration of 0.3 to 0.9 units/ml.

Animals↗
PubMed1988

Evidence that 8-methoxypsoralen (8-MOP) is a T-lymphocyte immunomodulatory agent.

This study was designed to characterize the effects of the anti-psoriatic compound 8-methoxypsoralen (8-MOP) on human lymphocyte function in vitro. Normal human peripheral blood mononuclear cells were stimulated with an optimal (1%) or a suboptimal (0.05%) concentration of phytohemagglutinin (PHA). At the optimal concentration of PHA, 8-MOP (140 microM) caused a delay in lymphocyte proliferation, interleukin-2 (IL-2) production/accumulation and IL-2 receptor expression. Addition of exogenous IL-2 to cultures stimulated with an optimal concentration of PHA did not overcome the delay of lymphocyte proliferation and IL-2 receptor expression. At the suboptimal concentration of PHA, 8-MOP (140 microM) caused a sustained inhibition of lymphocyte proliferation, IL-2 production/accumulation and IL-2 receptor expression. Addition of exogenous IL-2 under these conditions restored the magnitude of lymphocyte proliferation and IL-2 receptor expression. However, the responses displayed the delayed lymphocyte proliferation and IL-2 receptor expression typical of cells incubated with 8-MOP and an optimal concentration of PHA.

Adjuvants, Immunologic↗
PubMed1988

Suppression of feline bone marrow fibroblast colony-forming units by feline leukemia virus.

Bone marrow fibroblast colony-forming units (CFU-F) were evaluated in cats experimentally infected with feline leukemia virus (FeLV). Cats that developed persistent viral infection and anemia (progressor cats) had a progressive decrease in the number of CFU-F at 2, 4, 6, 8, and 10 weeks after inoculation with FeLV. This suppression of CFU-F number in progressor cats ranged from 16 to 44% of the preinoculation CFU-F value. Cats that did not develop persistent viral infection or anemia (regressor cats) had decreased numbers of CFU-F (24% of the preinoculation CFU-F value) at 2 weeks after inoculation, but normal CFU-F numbers at 4, 6, 8, and 10 weeks after inoculation. In vitro incubation of bone marrow mononuclear cells from healthy cats with the 15,000-dalton envelope protein of FeLV resulted in decreased number of CFU-F (21% of that of untreated cultures). The number of CFU-F from bone marrow mononuclear cells incubated with the 27,000-dalton core protein of FeLV was similar to that from untreated cultures.

Animals↗
PubMed1988

Enhancement of murine mixed lymphocyte response by 1,1-dimethylhydrazine: characterization and possible mechanism.

Treatment of mice with 1,1-dimethylhydrazine (UDMH) resulted in enhancement of the one-way mixed lymphocyte response (MLR); this effect was seen when both responder and stimulator mice were treated as well as when just the stimulator or just the responder mice were treated. Experiments in which splenocytes were exposed to UDMH in vitro indicated that exposure of the stimulator cells alone resulted in an enhanced MLR; exposure of the responder cells alone had no effect; and addition of UDMH to the assay (exposure of both populations) resulted in suppression of the response at higher concentrations. A possible mechanism for the enhancement of the MLR by UDMH was suggested by further experiments showing that UDMH inhibited prostaglandin E2 production by adherent splenocytes.

Animals↗
PubMed1988

Expression, release, and characterization of soluble human T-lymphotropic virus-I (HTLV-I) antigens from an infected cell line.

The Human T-lymphotropic virus type I (HTLV-I) infected cell line MT-2 was studied to obtain HTLV-I or related proteins for the purpose of producing an effective vaccine for HTLV-I infection. The cells were characterized as to HTLV-I antigen expression during the cell cycle and antigens released into the culture fluids. MT-2 cell grown in fetal calf supplemented media produced more HTLV-I related antigens during the G2/M phase of the cell cycle. To determine the conditions for maximal release and harvest of HTLV-I associated proteins, the MT-2 cells were grown in RPMI 1640 medium supplemented with serum-free medium. Cell- and virus-free supernatants were collected on day 4, lyophilized, and concentrated 50-fold. The proteins in these supernatants were characterized using SDS-PAGE and western blot using rabbit anti-HTLV-I sera and human adult T-cell leukemia sera. The western-blot analysis indicated that the supernatants obtained from the MT-2 cells grown in serum-free supplemented medium contained detectable amounts of proteins which reacted with human ATL and rabbit anti-HTLV-I sera. The molecular weights of these proteins observed are 68kd, 46kd, 28kd, 24kd, 19kd, and 15kd indicating that gag, env, and pX gene products are present.

Blotting, Western↗
PubMed1988

Oral use of human alpha interferon in cats.

Low doses (0.5 or 5.0 U) of human alpha interferon (HuIFN alpha) given orally prevented the experimental development of fatal feline leukemia virus (FeLV)-related disease. Twenty-one FeLV-susceptible cats were inoculated with the Rickard strain of FeLV. Cats given oral HuIFN alpha survived significantly (p less than 0.001) longer than untreated FeLV-infected cats. Moreover, only 4 of 13 (30.8%) HuIFN alpha-treated cats developed clinical disease during the course of the study, whereas 100% of the untreated control cats developed fatal FeLV-related disease. Thus, in experimental retroviral disease, heterologous species HuIFN alpha provided significant clinical benefits.

Administration, Oral↗
PubMed1988

Reduced temperature afterdrop in rhesus monkeys with radio frequency rewarming.

Rhesus monkeys were anesthetized and rendered hypothermic by icewater immersion. Rewarming by radio frequency (RF) energy at 13.56 MHz or by a surgical heating pad was initiated either immediately after removal from the icewater or after a delay of 20-26 min. Rectal temperature (Tre) was monitored during each experiment, and RF energy, initially applied at a specific absorption rate (SAR) of 10 W.kg-1, was able to raise Tre an average of 3 degrees C in 20 min. For an equivalent period of rewarming with the heating pad, Tre had not yet recovered from the immersion-induced afterdrop. It is concluded that RF rewarming offers a special advantage when applied to the treatment of immersion hypothermia.

Animals↗
PubMed1987

Rewarming of the hypothermic rhesus monkey with electromagnetic radiation.

To obtain more detailed information relative to the potential usefulness of using radio frequency (RF) energy in treating hypothermia, anesthetized rhesus monkeys were used in a rewarming study that compared a conventional method (heating pad) with an RF induction coil system. Rectal temperature (Tre) of each subject was monitored, and enzyme and isoenzyme levels were determined from blood samples collected before, during, and up to 48 h after hypothermia in order to assess the effects of each rewarming method. The previously observed postprocedure rise in serum enzymes (most visible at 24 h) was again seen, with no statistically significant difference in the time course of serum enzyme levels between the two treatments for comparable durations of hypothermia. To test the limits of the ability of the RF induction coil system, successively more severe hypothermia was induced in the subjects to the point of cardiovascular collapse (Tre less than 20 degrees C); RF energy was successful in resuscitating the profoundly hypothermic subjects without discernible harmful effects.

Alanine Transaminase↗