Mary M. Walser

Pain threshold changes in adjuvant-induced inflammation: A possible model of chronic pain in the mouse

A chronic hyperalgesic condition was induced in mice by the injection of Freunds complete adjuvant (FCA) into the lower lumbar region or directly into the hind footpads. Although little or no visible inflammation was observed after a single intradermal injection of FCA into the lower lumbar area of rats or mice, significant alterations in nociceptive thresholds occurred in each species as determined by decreases in response latency in tail-flick and hot-plate assays. Unilateral intraplantar administration of FCA in mice resulted in visible inflammation in the area of the tibiotarsal (ankle) joint. Changes in the response latency to a noxious stimulus in the areas surrounding the inflamed joint were similar to those observed in non-inflamed limbs, suggesting that changes in sensitivity to noxious stimuli were not merely the result of local hypersensitivity of the inflamed tissue, but may also be due to alterations in nociception at the level of the central nervous system (CNS). When the chronic inflammatory condition induced in the mouse tibiotarsal joint was evaluated by histological and morphological techniques, it was found to have the same characteristics as described in the early stages of FCA-induced arthritis in rats. The similarities between the response to FCA in rat and mouse suggest that injection of FCA in mice may prove to be a useful model for the study of chronic pain in mice as well as in rats.

An Antiviral Effect of Nitric Oxide: Inhibition of Reovirus Replication

We have previously shown that macrophages from chickens infected with avian reovirus are primed to produce nitric oxide (NO) in response to T cell cytokines and bacterial lipopolysaccharide (LPS). We now show that NO exerts potent antireovirus effects. Reovirus replication was substantially reduced in a chicken macrophage cell line, HD11, induced to make NO by stimulation with LPS or conditioned medium from concanavalin A-stimulated spleen cells. The use of a competitive inhibitor of nitric oxide synthase, NG-monomethyl-L-arginine, reduced the antiviral effect of LPS-stimulated HD11 cells. Cytostatic effects were concurrent with the observed antiviral effects of NO. Among these cytostatic effects were reduction in DNA synthesis, protein synthesis, and mitochondrial metabolism. These results indicated that a potential consequence of macrophage priming following virus infection is the protection of cells against virus-induced replication and cytopathic effects, and this protection may be mediated by the cytostatic effects of NO on the host cell.

Osseous Development and Tibial Dyschondroplasia in Five Lines of Turkeys

Tibiotarsi and femurs from five genetic lines of turkeys from 8 to 39 weeks of age were examined to define the characteristics of normal bones. Bone lengths and body weights are presented. Tibial dyschondroplasia (TD) frequently was detected on gross examination and by high-detail radiography. The incidence of TD peaked at 12 weeks of age, when 79% of the toms were affected. This incidence rate dropped until the age of closure of the proximal tibial physis (22 to 24 weeks in toms) but remained 5 to 15%. Deformities of the tibiotarsi were frequently associated with TD in older toms. The incidence of TD and tibiotarsal deformities was highest in toms of the heaviest line.

Suppressor macrophages mediate depressed lymphoproliferation in chickens infected with avian reovirus

A previous study indicated that spleens from reovirus-infected chickens contained macrophages that were primed to produce nitric oxide (NO). The presence of these primed macrophages correlated with depressed in vitro T cell mitogenesis. The current studies indicated that splenic adherent macrophages from virus-exposed chickens inhibited concanavalin A (ConA) induced proliferation of normal spleen cells. ConA-stimulated spleen cells from uninfected chickens, but not virus-exposed chickens, produced large quantities of interleukin-2 (IL-2) and a factor that induced NO production. This factor was tentatively named NO inducing factor (NOIF). The removal of macrophages from the spleens of virus-exposed chickens by plastic adherence resulted in partial recovery of ConA-induced proliferation and the production of normal levels of IL-2 and increased levels of NOIF, although these remained below normal. However, nonadherent spleen cells produced substantial quantities of NO, which indicated an incomplete removal of macrophages. Because removal by plastic adherence did not result in the depletion of all macrophages, spleen cells were panned with anti-CD3 antibody to obtain an almost pure population of T cells. Fractionated T cells from virus-exposed chickens proliferated vigorously to ConA and produced normal levels of IL-2 and NOIF. When splenic adherent cells from virus-exposed chickens were added to purified T cells, the T cells failed to respond to ConA. Addition of splenic adherent cells from virus-free chickens did not induce mitogenic inhibition. Further, the addition of purified T cells from the spleens of reovirus-infected chickens to T cells from virus-free birds did not adversely affect T cell mitogenesis. These data indicated that reovirus infection in chickens does not compromise the functional capabilities of T cells but induces suppressor macrophages that inhibit T cell functions.

Presence of Lesions without Virus Replication in the Thymus of Chickens Exposed to Infectious Bursal Disease Virus

Specific-pathogen-free (SPF) chickens were exposed to the IM and VA isolates of virulent infectious bursal disease virus (IBDV). Both viruses induced rapidly progressing lymphoid cell depletion in the bursa. The bursal lesions persisted through the observation period of 16 days. The virus-exposed birds also had histologic lesions in the thymus. Thymic lesions peaked at 3-4 days postinoculation (PI) and then subsided. Immunofluorescence (IF) and antigen-capture enzyme-linked immunosorbent assay (ELISA) detected abundant viral antigen in the bursa, but not in the thymus, of chickens during the first week after infection with IM-IBDV or VA-IBDV. This result indicated that the presence of histologic lesions in the thymus was not associated with active infection and replication of the virus in thymic cells. Inoculation of homogenates of bursal and thymic tissues from virus-exposed chickens into embryonated chicken eggs revealed the presence of infectious virus from both tissues. We speculated that the virus recovered from thymus may have been contributed by virus-infected cells that were circulating through the thymus at the time when this tissue was homogenized.

Effect of dietary selenium on the development of Fusarium-induced tibial dyschondroplasia in broiler chickens.

A trial was conducted to determine the effects of dietary level of selenium on the pathogenesis of Fusarium-induced tibial dyschondroplasia (FITD) in broiler chicks, and to assess the applicability of FITD as an animal model of Kashin-Beck disease of humans. Day-old female broilers were fed diets that were deficient in selenium (0.02 ppm Se), adequate in selenium (0.15 ppm Se), or generous in selenium (0.50 ppm Se). TDP-1, the toxic component of the fungus, was administered to 15 of 26 chicks in each dietary group starting at 1 week of age and continuing until the chicks were killed at 24-30 days of age. Plasma selenium levels and hepatic glutathione peroxidase activity were significantly lower in the selenium-deficient group than in other dietary groups; these parameters were not affected by treatment with TDP-1. The mortality rate of the TDP-1-treated selenium-generous group was significantly less than that in the other TDP-1-treated groups, but there were no differences in the incidence, severity, or character of the FITD lesions among the groups. Thus, the interaction of selenium and TDP-1 did not include an effect on FITD.

Acid Phosphatase Activity of Chondroclasts from Fusarium-Induced Tibial Dyschondroplastic Cartilage

Tibial dyschondroplasia was induced in broiler chickens by oral administration of fusarochromanone, the toxic component of Fusarium equiseti. In two experiments, the activity of acid phosphatase in chondroclasts was assessed histochemically. Chicks were examined at 7, 14, 21, and 28 days of treatment in Expt. 1 and at 2, 4, and 6 days of treatment in Expt. 2. The staining for acid phosphatase was consistently lower in fusarochromanone-treated chicks after 2 days of treatment than in age-matched controls, and the onset of this difference corresponded to the onset of lesions. However, the decrease in acid phosphatase staining intensity was significant only at day 21 in Expt. 1 and at day 6 in Expt. 2. The deficiency of acid phosphatase in chondroclasts was judged to be of insufficient magnitude to account for the accumulation of growth plate cartilage that characterizes tibial dyschondroplasia.

In vitro characterization of field isolants of Pasteurella multocida from Georgia turkeys

Field isolants of Pasteurella multocida from fowl cholera outbreaks in Georgia turkeys were characterized by three sets of criteria: differential biochemical reactions, in vitro drug sensitivity, and serology. Of the 30 isolants studied, 28 exhibited identical biochemical patterns. These were similar to previously described patterns for turkey isolants of P. multocida. The two exceptions were isolants recovered from the same farm at different times. They differed only in ability to ferment arabinose. The isolants were generally sensitive to broad-spectrum antibiotics in vitro. The majority were also sensitive to the sulfonamides tested. Variation was sufficient, however, to warrant recommending in vitro sensitivity testing as a guide to selection of the proper therapeutic regimen in individual cases. Of the 30 isolants tested, 57% were of Heddlestons serotype 3, 3% were of his type 4, and 40% precipitated with antisera against both types 3 and 4. The large proportion of cross-reactors is unique to Georgia isolants. The biochemical patterns, drug sensitivities, and serological types had no apparent relationship to each other.

Immunohistochemical Detection of Lymphocyte Subpopulations in the Tarsal Joints of Chickens with Experimental Viral Arthritis

We characterized the lymphocytes in the tarsal joint synovium of chickens inoculated with an arthrotropic strain of avian reovirus. Cryostat sections of whole joints taken from 2 days to 35 days postinoculation were analyzed using monoclonal antibodies directed against B lymphocytes, T lymphocytes, and chicken Ia antigen. Plasma cells were morphologically identified using stained sections of whole joints. Time-dependent changes were found in the type and number of positively staining cells. Synoviocytes and cells with a dendritic morphology stained positive for Ia in normal joint sections. T cells, mostly CD8 positive, were present in low numbers in acute phase arthritis (2-6 days postinfection) in the perivascular and superficial regions of the synovium. Subacute arthritis (8-14 days postinfection) was characterized by increased numbers of CD4 and CD8 T cells in the perivascular and superficial regions. The perivascular T cells began to organize into aggregates, with IgM-positive B cells and plasma cells on the periphery of these aggregates. Some CD8-positive cells were detected on the surface of the articular cartilage. Cells staining positively for Ia were not lymphocytes. Chronic arthritis (> 14 days postinfection) was characterized by large numbers of T cells in the perivascular and superficial regions, with the CD4-positive T cells found primarly in the lymphoid aggregates of the perivascular regions. IgM-positive B cells were fewer, but more plasma cells, few of which stained positive for IgM, were present. Lymphocytes in chronic arthritis stained positively for Ia. These data suggest that the types, numbers, and activation level of lymphocytes present in the tarsal joints are similar but not identical to those seen in rheumatoid arthritis.

Field Rickets in Turkey Poults: Biochemical Findings

Two clinical cases of field rickets and one of nutritional rickets in turkey poults were studied. Plasma levels of calcium, phosphorus, alkaline phosphatase, and vitamin D metabolites were determined. Concentrations of calcium, phosphorus, and alkaline phosphatase in affected poults were typical of nutritional rickets. The mean plasma calcium concentration in rachitic poults was not significantly different from that in controls. Mean values for plasma phosphorus were 1.5 to 2.4 mg/dl lower in the rachitic poults, and values for alkaline phosphatase activity were 1.3-1.7 times greater. In assays of vitamin D metabolites, mean 24, 25 dihydroxyvitamin D3 values were consistently lower in rachitic poults.