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Biomedical subjects

A Fairbrother

Publications and source records attributed to A Fairbrother.

25 records · Page 2Linked to original sources
PubMed1987

Experimental infection and horizontal transmission of Modoc virus in deer mice (Peromyscus maniculatus).

Deer mice (Peromyscus maniculatus) were inoculated with a sublethal dose of a field strain of Modoc virus to determine patterns of viral persistence, shedding, and transmission. Blood, serum, urine, fecal, and oral swab samples were collected at selected intervals until 63 days postinoculation (PI) after which lung, liver, spleen, kidney, and salivary glands were explanted. Viral assays were conducted by intracranial inoculations of suckling mice and antibody titers were determined by the micro-complement-fixation test. Viremias lasted for up to 4 days PI. Antibody titers were present by day 8 PI, peaked at day 13-20 PI, and persisted until day 63 PI. There was no evidence of viral shedding in urine, fecal, or oral swab samples. Virus was detected in explanted lungs only. In a separate experiment, deer mice were inoculated with virus and lungs were removed from five mice per wk for 10 wk. Indirect fluorescent antibody (IFA) techniques were used to determine the location of virus in lung tissue and to examine fixed tissue for lesions. IFA showed virus in lung parenchymal cells beginning 42 days PI and persisting at least 70 days PI. No histopathologic changes were seen. Horizontal transmission of the virus was studied by placing uninoculated mice with inoculated mice for 42 days and determining if the test animals developed antibodies or had virus in their lungs. Fifty-percent of the uninoculated mice developed antibody. One of these animals had virus in its lungs. Therefore, Modoc virus may be transmitted by direct contact.

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PubMed1984

Toxicant-disease-environment interactions associated with suppression of immune system, growth, and reproduction.

The effects of marginal malnourishment , infections, and environmental chemicals on growth and reproductive success in Swiss-Webster white mice and wild deer mice were studied with fractional factorial designs. Interaction effects were discovered. For example, malnourished mice were more sensitive to virus exposure and environmental chemicals (a plant growth regulator or polychlorinated biphenyls). Since several commercial plant growth regulators also appear to suppress the immune system, these results cast doubt on the adequacy of current toxicity testing procedures in which factors are studied individually and not in combination.

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PubMed1984

Effects of ingestion of chlorocholine chloride and cyclophosphamide on Venezuelan equine encephalitis virus infections in deer mice (Peromyscus maniculatus).

We investigated the effects of chlorocholine chloride (CCC), a plant growth regulator, and cyclophosphamide (CP), a known immunosuppressant, on the ability of deer mice (Peromyscus maniculatus) to resist challenge with a sublethal dose of Venezuelan equine encephalitis virus ( VEEV ). The toxicants were continuously delivered in low doses in the feed; CP at 20 mg/kg body wt/day and CCC at 1, 10, 20 or 40 mg/kg body wt/day. Mice were inoculated with 3 X 10(4) plaque forming units (pfu) of VEEV after eating experimental feed for 23 days. Mice were bled daily for 7 days and at selected intervals from 8 to 63 days post inoculation (PI) for viremia and antibody titer determinations. CP treatment increased the duration of viremia and significantly (P less than or equal to 0.05) decreased mean viremia titers. Antibody titers were significantly (P less than or equal to 0.05) depressed in CP-treated mice compared to controls. CP treatment increased mortality. CCC had no effect on viremia duration or titer except when given in doses of 1 mg/kg body wt/day when it significantly (P less than or equal to 0.05) decreased mean viremia titers compared to controls. Early antibody responses were increased by CCC treatment except in the 10 mg/kg body wt/day treatment group in which titers were decreased. By 30 days PI antibody titers of CCC-treated mice were no different from controls.

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PubMedDate not supplied

Glucocorticoid effects on natural and humoral immunity in mallards.

Two studies were conducted to determine the effects of dexamethasone (DEX) on immune function in mallard ducks. Each day ducks were injected intramuscularly with DEX at doses ranging from 0.2-4.0 mg/kg for 28-30 days. Physiologic effects consistent with high dose glucocorticoid (GC) treatment were observed at the 4 mg/kg dose, and included significant body weight loss, lowered hematocrit, and elevated alanine aminotransferase (ALT) activity. At all doses, effects of DEX on the immune system were observed. When DEX was given at 0.2 mg/kg/day, significant suppression of primary IgG antibody titers to sheep erythrocytes (SRBC) was observed. At 1 mg/kg/day, primary IgM and secondary IgM and IgG titers were suppressed as well. These doses of DEX also produced significant elevation in natural killer cell (NKC) activity of peripheral blood mononuclear cells (PBMNC). Removal of adherent cells from the PBMNC prior to NKC assay eliminated the enhancement in NKC activity. Based on these results, it was postulated that the elevation in NKC activity may be due to suppression by DEX of monocyte production of prostaglandin-E2 (PGE-2) resulting in the release of NKC activity from the inhibitory effects of PGE-2. This hypothesis was supported by a measured decrease in PGE-2 production during the NKC assay by cells from DEX-treated birds. Furthermore, an enhanced NKC activity could be reproduced in vitro with the addition of indomethacin or DEX to NKC cultures containing adherent cells from PBMNC. Direct effects of DEX on nonadherent cell NKC activity and lymphocyte viability were only observed at high concentrations (10(-4) M) of DEX, while the phagocytic activity of adhered blood monocytes was inhibited at 10(-6) M DEX. The suppressed phagocytic activity may contribute to the suppressed antibody responses observed in DEX-treated birds. Together, these results support an indirect immunomodulatory effect of DEX on NKC activity and perhaps antibody responses in vivo via altered monocyte function in mallard ducks.

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PubMedDate not supplied

Pathogenicity of Salmonella pullorum in northern bobwhite quail and mallard ducks.

Ten-day-old northern bobwhite quail and mallard ducks were inoculated orally and intravenously with Salmonella pullorum at selected concentrations (10(3) to 10(10) colony-forming units). Mortality in bobwhites ranged from 65% to 100%, whereas no mallards died or exhibited any signs of morbidity. Significantly (P less than 0.05) increased values for serum calcium, uric acid, and lactate dehydrogenase were observed in mallards inoculated with live S. pullorum, and antibody titers were detected as early as 1 week postinoculation. Viable bacteria were cultured from feces, liver, lungs, heart, kidneys, pancreas, and spleen of bobwhites and from livers of four mallards. Bacterial colonies were frequently found in the capillaries of various organs of the quail, particularly in the heart and kidneys, with slight-to-moderate diffuse or multifocal necrotizing inflammation present in all organs examined. Bobwhites are susceptible to infection from S. pullorum, with morbidity and mortality rates similar to those of chicks and poults, whereas mallards undergo a short, subclinical infection that is resolved without lasting tissue damage.

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