Effects of nitrogen dioxide on Mycoplasma pulmonis infection and humoral immune responses in mice

The effects of continuous exposure to nitrogen dioxide (NO2) on the pathologic and immunologic responses of ddY mice to the infection with Mycoplasma pulmonis were investigated. The organisms grew well in the trachea as early as 7 days after infection but barely grew in the lung even after 28 days, causing slight pneumonic lesions in only a few of the infected mice exposed to 1 and 5 ppm NO2. When mice were exposed to 10 ppm NO2 at or after the infection, however, mycoplasmal growth in the lung, but not in the trachea, was greatly enhanced, and pneumonic lesions were evident in the lung of almost all the mice examined. The serum antibody titers to M. pulmonis increased with time after infection regardless of the concentration of NO2 exposed or the mycoplasmal number in the respiratory tract in the infected mice. The in vitro immune responses of the spleen cells of the infected mice were significantly depressed by exposure to 10 ppm NO2 in not only mitogenic response to LPS and ConA but also antibody production to SRBC, whereas uninfected healthy mice were apparently not modulated except for a slight decrease in Con A response.     

Effect of prenatal N2O exposure on startle reflex reactivity

The teratogenic effect of N2O is of interest because thousands of pregnant women are exposed to this gaseous anesthetic each year. The effects of repeated N2O exposures were investigated for offspring of mice exposed to air or N2O (5%, 15%, or 35%) for 4 hours per day on days 6 through 15 of pregnancy. Ten litters per exposure group were studied. Exposures did not affect reproductive indices, survival, or physical milestones of development. Body weights showed significant exposure effects that could not be isolated to specific exposure groups; however, N2O-exposed mice tended to weigh more than air-exposed animals. Brain weights measured on postnatal day (PND) 126 or 127 were not different among exposure groups or between genders. Ability to stay on a rotating rod was not affected by prenatal N2O exposure. Prenatal exposure to N2O resulted in hyporeactivity of the startle reflex in response to acoustic or tactile stimuli. On PND 95 the results were statistically significant for all N2O-exposed groups compared with the air-exposed group. On PND 60, although not statistically significant, there was a definite trend toward hyporeactivity for the N2O groups. There was a significant age-related difference in startle response; control animals were significantly more reactive at 95 than at 60 days of age. Of the N2O-exposed groups, only the 15% group showed a statistically significant increase in reactivity from 60 to 95 days of age. The risk of behavioral or functional abnormalities for humans following in utero N2O exposure is unknown and cannot be directly extrapolated from the present study.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of postradiation chemical signals of mice on the humoral immune response in recipients in different time relative to antigenic stimulus

The influence of volatile urine chemosignals of irradiated (4 Gy) mice on the primary humoral immune response to sheep red blood cells in intact recipients was investigated. It was demonstrated that the direction of immunomodulatory effect is dependent upon the time at which the postradiation chemosignals was initially applied. The antibody response to antigen was markedly suppressed in mice that were exposed before antigen injection. When chemosignals applied immediately following inoculation of antigen the antibody response was unaffected. The immune response was increased when chemosignals was loadeded for 1-10 days after immunization. The possible mechanisms of immunomodulation are considered.     

Influence of 60-hertz magnetic fields on leukemia

Female DBA/2 mice at 8 weeks of age were implanted with P388 leukemia cells in groups of ten mice and exposed to a 60-Hz 1.4-μT, 200-μT, or 500-μT magnetic field 2-3 hours after the implant for 6 hours daily, 5 days/week until all the exposed P388-treated and nontreated mice died. Parallel exposed groups of non-P388-treated mice and P388-treated mice exposed at 0 μT were included for study. No statistically significant differences (P > .05) in survival, spleen weight, or body weight resulted between P388-treated or nontreated mice from exposure to the magnetic field. No effect on the incidence or progression of P388 leukemia was apparent.     

Fractionated, low-dose-rate ionizing radiation exposure and chronic ulcerative dermatitis in normal and Trp53 heterozygous C57BL/6 mice

The influence of low-dose-rate chronic radiation exposure and adaptive responses on non-cancer diseases is largely unknown. We examined the effect of low-dose/low-dose-rate fractionated or single exposures on spontaneous chronic ulcerative dermatitis in Trp53 normal or heterozygous female C57BL/6 mice. From 6 weeks of age, mice were exposed 5 days/week to single daily doses (0.33 mGy, 0.7 mGy/h) totaling 48, 97 or 146 mGy over 30, 60 or 90 weeks, and other Trp53+/- mice were exposed to a single dose of 10 mGy (0.5 mGy/min) at 20 weeks of age. The 90-week exposure produced an adaptive response, decreasing both disease frequency and severity in Trp53+/+ mice and extending the life span of older animals euthanized due to severe disease. The 30- or 60-week exposures had no significant protective or detrimental effect. In contrast, the chronic, fractionated exposure for 30 or 60 weeks significantly increased the frequency and severity of the disease in older Trp53+/- mice, significantly decreasing the life span of the animals required to be euthanized for disease. Similarly, the single 10-mGy exposure also increased disease frequency in older animals. However, the chronic, fractionated exposure for 90 weeks prevented these detrimental effects, with disease frequency and severity not different from unexposed controls. We conclude that very low-dose fractionated exposures can induce a protective adaptive response in both Trp53 normal and heterozygous mice, but that a lower threshold level of exposure, similar in both cases, must first be passed. In mice with reduced Trp53 functionality, doses below the threshold can produce detrimental effects.     

Lung development and the host response to influenza A virus are altered by different doses of neonatal oxygen in mice

Oxygen exposure in preterm infants has been associated with altered lung development and increased risk for respiratory viral infections later in life. Although the dose of oxygen sufficient to exert these changes in humans remains unknown, adult mice exposed to 100% oxygen between postnatal days 1-4 exhibit alveolar simplification and increased sensitivity to influenza virus infection. Additionally, two nonlinear thresholds of neonatal oxygen exposures were previously identified that promote modest (between 40% and 60% oxygen) and severe (between 80% and 100% oxygen) changes in lung development. Here, we investigate whether these two thresholds correlate with the severity of lung disease following respiratory viral infection. Adult mice exposed to 100% oxygen at birth, and to a lesser extent 80% oxygen, demonstrated enhanced body weight loss, persistent inflammation, and fibrosis following infection compared with infected siblings exposed to room air at birth. In contrast, the host response to infection was indistinguishable between mice exposed to room air and 40% or 60% oxygen. Interestingly, levels of monocyte chemoattractant protein (MCP)-1 were equivalently elevated in infected mice that had been exposed to 80% or 100% oxygen as neonates. However, reducing levels of MCP-1 using heterozygous Mcp-1 mice did not affect oxygen-dependent changes in the response to infection. Thus lung development and the host response to respiratory viral infection are disrupted by different doses of oxygen. Our findings suggest that measuring lung function alone may not be sufficient to identify individuals born prematurely who have increased risk for respiratory viral infection.     

Detection of genomic instability in offspring of male mice chronically exposed to gamma-radiation by the "adaptive response" test

The genomic instability (GI) in somatic cells of the progeny (F1 generation) of male mice chronically exposed to low-dose gamma-radiation was studied by comparative analysis of chromosome damage. BALB/C male mice exposed to 0.1 Gy (0.01 Gy/day) and 0.5 Gy (0.01 and 0.05 Gy/day) were mated with unirradiated females 15 days after irradiation. For comparison of radiosensitivity, two-month-old males, the descendants of irradiated and unirradiated animals, were subjected to irradiation with a dose of 1.5 Gy (0.47 Gy/min) from a 60Co source. GI was revealed by the standard scheme of adaptive response. The experiments indicated that, by using the test "adaptive response", it is possible to detect the transition of gamma-radiation-induced genomic instability in sex cells of male parent into somatic cells of mice (F1 generation) either from changes in radiosensitivity or by the absence of the adaptive response induced by a standard scheme.     

Alteration of circulating antibody response of mice exposed to 9-GHz pulsed microwaves

A significant increase was observed in the circulating antibody titers of mice exposed to 9-GHz pulsed microwaves at an average power density of 10 mW/ cm², two hours per day for five days compared with sham-irradiated animals. The mice were previously immunized with type III pneumococcal polysaccharide. Following irradiation, a portion of the immunized animals were challenged with virulent ^{Streptococcus pneumoniae}, type III. Ten days after challenge, mortality was essentially the same in the two groups, but during the ten day period, there was a noticeable increase in the survival time of the irradiated animals compared with the sham-irradiated animals, suggesting that the increased circulating antibody response afforded some degree of temporary protection to the animals.     

Role of tumor necrosis factor in oxygen toxicity.

mRNA from lungs of mice exposed to high-dose oxygen (greater than 95%) for 3 days demonstrated increased expression of the genes for tumor necrosis factor (TNF), interleukin-1, and interleukin-6 compared with mRNA from lungs of mice exposed to room air. Daily treatment of mice exposed to high-dose oxygen with an antibody to TNF improved survival compared with mice receiving a similar dose of control immunoglobulin G. Pretreatment of mice with repetitive sublethal intraperitoneal doses of recombinant human TNF for 3 days or a single intravenous dose followed by exposure to high-dose oxygen afforded a significant survival advantage compared with high-dose oxygen-exposed mice pretreated with vehicle or interleukin-1. The repetitive intraperitoneal TNF pretreatment reduced the development of interstitial pneumonitis, pulmonary edema, and lung weight gain associated with oxygen toxicity and enhanced expression of the gene for the free radical protective enzyme manganous superoxide dismutase in lung tissue, a gene that is augmented as mice are exposed to high-dose oxygen. Furthermore a single intravenous dose of TNF 24 h after oxygen exposure was still protective. The results suggest that the toxicity of oxygen therapy can be partially ameliorated by either treatment with anti-TNF antibody or pretreatment and early treatment with TNF. These findings are consistent with the hypothesis that oxygen exposure induces TNF, which causes part of the toxicity of high-dose oxygen, and that pretreatment or early treatment with TNF induces the gene for an enzyme that recently has been shown to be very effective in protecting mice from the toxicity of oxygen.     

Effects of acute and repeated exposure to stress on the hypothalamo-pituitary-adrenocortical activity in mice during postnatal development

Hypothalamo-pituitary-adrenocortical (HPA) response to a mild stressful procedure was investigated in mice at Days 8, 10, 12, and 14 of postnatal development. Pups that were removed from the dam and exposed to a novel odor (clean bedding) for 15 min showed higher plasma corticosterone levels than pups whose mother was removed from the cage for 15 min or unhandled pups at all ages, although statistically significant differences were only evident at Days 12 and 14. Lower HPA axis responding in younger mice was not due to immaturity since 8-day-old mice showed a significant and larger increase of plasma corticosterone levels when separated from the mother and isolated from littermates in the absence of bedding. Mice daily exposed to clean bedding (15 min) for the first 13 days of life did not show reduced plasma corticosterone response when reexposed to the stressor at 14 days of age. Conversely, increased plasma corticosterone levels in dams in response to removal of pups was not detectable after repeated exposure to this manipulation (14 days) regardless of the procedure their pups were submitted to, thus ruling out a role of maternal corticosterone passing through the milk on which the pups were fed. These results demonstrate that 15 min exposure to clean bedding is a noninvasive procedure able to elicit HPA axis response in developing mice over a wide age range without producing habituation.     

Effect of a single exposure to ultraviolet radiation on Mycobacterium bovis bacillus Calmette-Guerin infection in mice

BALB/c and C3H mice were exposed on the dorsal skin to 45 kJ/m2 of UVB radiation from FS-40 sunlamps 3 days before infection with 1 x 10(6) live units of Mycobacterium bovis bacillus Calmette-Guérin (BCG) (Tice strain) in the footpad. At regular intervals, groups of mice were tested for a delayed type hypersensitivity (DTH) response to the purified protein derivative (PPD) of tubercle bacilli, and the course of infection was monitored by measuring the size of the infected footpad, enlargement of the draining lymph node, and the number of bacteria in the spleen and lymph node. In both strains the DTH response to PPD was significantly delayed in UV-treated mice compared to unirradiated mice, when tested 21 and 42 days after BCG infection. By day 50, no significant difference was detected in the DTH response between irradiated and unirradiated mice. UV treatment reduced the size of the lymph node draining the site of BCG infection in both strains of mice and the size of the infected footpad in C3H mice but not in BALB/c mice. In both strains of mice the total number of bacteria in the spleen and the draining lymph node increased after UV irradiation. When irradiated 3, 5, 18, or 21 days after BCG infection, BALB/c mice also showed a significant decrease in their DTH response to PPD, indicating that the UV-induced suppression of BCG occurs both at the induction and the elicitation stages of the immune response. Thus, mice exposed to a single dose of UV radiation either before or after BCG infection showed an impaired DTH response to mycobacteria, which was accompanied by an increase in the multiplication of bacteria in the tissues, even though the organisms were introduced at an unirradiated site. These studies demonstrate that a systemic effect of UV irradiation can interfere with the development and expression of immunity to pathogenic bacteria in mice.     

Deficiency in immunocompetence of mice cured from large MOPC-315 plasmacytomas by melphalan therapy

Summary Mice cured from large MOPC-315 tumors by a single dose of melphalan, 7.5 mg/kg, were examined for up to 60 days after the drug treatment (71 days after the tumor inoculation) for their ability to respond to mitogenic stimulation, specific and nonspecific antigenic stimulation and for their susceptibility to inoculation with an unrelated tumor, L10 lymphoma. The response of spleen cells from cured mice to mitogenic stimulation by phytohemagglutinin or concanavalin A was slightly depressed at an early stage after the drug treatment. The allogeneic response against C57BL spleen cells and the antibody response against sheep red blood cells (SRBC) of spleen cells from cured mice remained below normal levels during the whole observation period. The deficiency in response to antigenic stimulation was found to be due to impairment in T-cell function. Cured mice were also deficient in their response to SRBC immunization (antibody and delayed-type hypersensitivity responses) and were more susceptible to inoculation with an unrelated tumor, L10 lymphoma, than normal, noninoculated mice. On the other hand, spleen cells of cured mice developed a highly specific cytotoxic response against target MOPC-315 tumor cells and the cured mice were resistant to challenge with an otherwise highly tumorigenic dose of MOPC-315. Thus, cured mice remained deficient for a long period of time in their response to MOPC-315-unrelated antigens but, at the same time, they showed a potent specific antitumor immunity potential in vivo and in vitro.Presented in part at the Ninth European Immunology Meeting, September 14–17, 1988, Rome, ItalyThe contribution of S. Shoval is in partial fullfillment of a PhD Thesis     

Effects of time-varying uniform magnetic fields on Natural Killer cell activity and antibody response in mice

Natural Killer cell activity and antibody response were studied in Balb/c mice which were exposed in vivo to uniform pulsed magnetic fields (square-wave, 0.8 Hz, 120 mT maximum field strength, 0.1 s rise-time) for 5 days, 10 h/day. No effects were found in antibody response to sheep red blood cell (SRBC) immunization as assayed by counting the plaque-forming cells (PFC) in the spleens of animals on the sixth day. Following 5-day exposures, the activity of Natural Killer (NK) cells was measured in vitro by challenge with YAC-1 cells, in experiments in which mice were not immunized. An increase of NK cytotoxic activity due to exposure was found which depended on the age of the mice (effect observed above 12 weeks) and on the strength of the applied field (effect observed above 30 mT). © 1993 Wiley-Liss. Inc.     

Progenitors Mobilized by Gamma-Tocotrienol as an Effective Radiation Countermeasure

The purpose of this study was to elucidate the role of gamma-tocotrienol (GT3)-mobilized progenitors in mitigating damage to mice exposed to a supralethal dose of cobalt-60 gamma-radiation. CD2F1 mice were transfused 24 h post-irradiation with whole blood or isolated peripheral blood mononuclear cells (PBMC) from donors that had received GT3 72 h prior to blood collection and recipient mice were monitored for 30 days. To understand the role of GT3-induced granulocyte colony-stimulating factor (G-CSF) in mobilizing progenitors, donor mice were administered a neutralizing antibody specific to G-CSF or its isotype before blood collection. Bacterial translocation from gut to heart, spleen and liver of irradiated recipient mice was evaluated by bacterial culture on enriched and selective agar media. Endotoxin in serum samples also was measured. We also analyzed the colony-forming units in the spleens of irradiated mice. Our results demonstrate that whole blood or PBMC from GT3-administered mice mitigated radiation injury when administered 24 h post-irradiation. Furthermore, administration of a G-CSF antibody to GT3-injected mice abrogated the efficacy of blood or PBMC obtained from such donors. Additionally, GT3-mobilized PBMC inhibited the translocation of intestinal bacteria to the heart, spleen, and liver, and increased colony forming unit-spleen (CFU-S) numbers in irradiated mice. Our data suggests that GT3 induces G-CSF, which mobilizes progenitors and these progenitors mitigate radiation injury in recipient mice. This approach using mobilized progenitor cells from GT3-injected donors could be a potential treatment for humans exposed to high doses of radiation.     

Relation between Enhanced Antibody Responses Elicited by Adjuvant Injection and Those Elicited by Secondary Antigenic Stimulation

An attempt was made to determine if there is any common mechanism in the enhanced antibody response caused either by injection of adjuvant, such as bacterial endotoxin (LPS) and complexed polynucleotides, or by secondary antigenic stimulation. LPS inoculated in mice 4 days before injection of sheep red blood cells (SRBC) and polyA:U invalidated the adjuvant effect of polyA:U injected together with SRBC, and the hemolysin plaque-forming cell (PFC) response of such mice was similar to that of the mice which received SRBC alone. When mice primed with SRBC 24 days in advance were injected with LPS and 4 days later re-stimulated with SRBC, their PFC response to the secondary stimulation was suppressed to less than one tenth of the normal secondary PFC response. The suppressive effect of LPS on the secondary antibody response was abolished if the serum collected from mice injected with LPS was given to the primed and LPS-injected mice at the time of the secondary antigenic stimulation. From these results we discussed the possibility that some common mediator might play a role in the enhanced antibody response elicited by either adjuvant injection or secondary injection of antigen.     

Effect of extremely high frequency electromagnetic radiation of low intensity on parameters of humoral immunity in healthy mice

The modification of indices of the humoral immune response to thymus-dependent antigen (sheep erythrocytes) after a whole-body exposure of healthy mice to low-intensity extremely-high-frequency electromagnetic radiation was studied. Male NMRI mice were exposed in the far-field zone of horn antenna at a frequency of 42.0 GHz and energy flux density of 0.15 mW/cm2 under different regimes: once for 20 min, for 20 min daily during 5 and 20 successive days before immunization, and for 20 min daily during 5 successive days after immunization throughout the development of the humoral immune response. The intensity of the humoral immune response was estimated on day 5 after immunization by the number of antibody-forming cells of the spleen and antibody titers. Changes in cellularity of the spleen, thymus and red bone marrow were also assessed. The indices of humoral immunity and cellularity of lymphoid organs changed insignificantly after acute exposure and series of 5 exposures before and after immunization of the animals. However, after repeated exposures for 20 days before immunization, a statistically significant reduction of thymic cellularity by 17.5% (p < 0.05) and a decrease in cellularity of the spleen by 14.5% (p < 0.05) were revealed. The results show that low-intensity extremely-high-frequency electromagnetic radiation with the frequency and energy flux density used does not influence the humoral immune response intensity in healthy mice but influences immunogenesis under multiple repeated exposures.     

Cytogenetic effects of microwave irradiation on male germ cells of the mouse

Hybrid male mice were exposed to 2.45 GHz microwaves for 30 min/day, 6 days a week for two consecutive weeks at power densities of 1.0, 100 or 400 W m-2, with sham-exposed controls. Rectal temperatures before and after exposure were measured on days 1, 6 and 12. Measurements made on day 1 were treated with caution because of heterogeneity in rectal temperatures taken before exposure between the groups of mice given different treatments. On days 6 and 12, rectal temperatures rose by approximately 1 degree C in mice sham exposed, or exposed to 1 W m-2 or 100 W m-2. Only in the group of mice exposed to 400 W m-2 was the mean rise in rectal temperature during exposure (about 3 degrees C) significantly increased above the sham value. In groups killed 2-3 days after treatment (mainly meiotic exposure) frequencies of chromosome aberrations in spermatocytes showed no significant heterogeneity although the highest frequency of 1.5 per cent was at the highest (400 W m-2) power density. Another group killed 30 days after 100 W m-2 exposures (spermatogonial sampling) showed no significant increase over controls in chromosome aberration frequency. There was a small but significant increase in sperm count with increasing power density in mice killed 12-13 days after exposure, but a non-significant one in those exposed as spermatogonia (killed 41 days later). Thus effects were markedly less severe than those reported previously by Manikowska-Czerska et al. (1985) with a very similar radiation regime and were probably caused by the temperature enhancement.     

Antibody responses of mice exposed to low-power microwaves under combined, pulse-and-amplitude modulation

Irradiation by pulsed microwaves (9.4 GHz, 1 microsecond pulses at 1,000/s), both with and without concurrent amplitude modulation (AM) by a sinusoid at discrete frequencies between 14 and 41 MHz, was assessed for effects on the immune system of Balb/C mice. The mice were immunized either by sheep red blood cells (SRBC) or by glutaric-anhydride conjugated bovine serum albumin (GA-BSA), then exposed to the microwaves at a low rms power density (30 microW/cm2; whole-body-averaged SAR approximately 0.015 W/kg). Sham exposure or microwave irradiation took place during each of five contiguous days, 10 h/day. The antibody response was evaluated by the plaque-forming cell assay (SRBC experiment) or by the titration of IgM and IgG antibodies (GA-BSA experiment). In the absence of AM, the pulsed field did not greatly alter immune responsiveness. In contrast, exposure to the field under the combined-modulation condition resulted in significant, AM-frequency-dependent augmentation or weakening of immune responses.     

Effects of intestinal contents from normal and immunized mice on sporozoites of Eimeria falciformis

The interaction of Eimeria falciformis sporozoites with the intestinal epithelium and with the intestinal contents from the cecum and colon of normal and specifically immunized mice was studied by light (LM) and scanning electron (SEM) microscopy. Fecal (FM) and enterocyte-associated (EAM) mucus were removed from the cecum and colon of normal mice and mice that had been immunized 1, 6, 12, or 20 days earlier with a series of oral inoculations of E. falciformis oocysts. Sporozoite-specific IgA, but neither IgM nor IgG, was detected by the immunofluorescent antibody test in FM and EAM from immunized mice. No sporozoite-specific immunoglobulin was detected in normal mice. When examined by LM, sporozoites exposed to all FM and EAM preparations exhibited greater motility and excystation from sporocysts. At 4 h after incubation in FM or EAM from normal or immune mice, about 10% of the sporozoites appeared damaged, being non-motile and non-refractile. Immune FM and EAM caused agglutination of sporozoites and sporocysts and oocyst walls of E. falciformis, but did not agglutinate those of E. ferrisi. Scanning electron microscopy of in vitro interactions between E. falciformis sporozoites and intestinal contents revealed that sporozoites exposed to immune EAM were coated with particulate material whereas those exposed to normal EAM were relatively clean. Sporozoites exposed to immune FM were usually embedded within the mucus whereas those exposed to normal FM were situated on top of the mucus. No significant differences occurred between the length/width (L/W) ratios of sporozoites incubated in normal and EAM or in PBS.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immune responsiveness and phagocytic activity of macrophages in streptozotocin (SZ)-induced diabetic mice

We succeeded in inducing different severities of diabetic state in C3H male mice by repeated intraperitoneal injections of various doses of SZ. SZ-induced diabetic mice were divided into four groups as follows: Group A, B, C and D. SZ, respectively, 3, 5 doses of 45 mg/kg, 5 doses of 60 mg/kg on consecutive days and one of a dose of 200 mg/kg BW. The degree of hyperglycemia and glycosuria were mild in group A and D. Group B was moderate and group C severe with ketonuria and loss of body weight. We investigated the immune response to anti-sheep red blood cells (SRBC) and the phagocytic activity of macrophages in the above mentioned various SZ-induced mice. Antibody forming activities (values of anti-SRBC plaque-forming cells (PFC) and serum agglutinin) were markedly depressed in all of SZ-diabetic groups. The degree of the suppression of antibody response to SRBC in SZ-diabetic mice corresponded with the severity of the diabetic state (C greater than B greater than A = D). However, the phagocytic activity of peritoneal macrophages in SZ-diabetic mice was as high as or higher than that in normal controls, using both latex beads and immune complex as test particles. Moreover, we observed that insulin treatment reversed the defect in the immune response in SZ-diabetic mice. These results indicate that the phagocytic activity of peritoneal macrophages was retained but the antibody response was impaired in the SZ-diabetic mice, and this suggested that the impaired antibody response may be a contributing cause of increased susceptibility to infections in a diabetic state.