The density of the cricoid cartilage from 29 equine larynges collected from an abattoir was determined by dual photon absorptiometry (DPA). Densities of the right and left cricoid cartilages were highly correlated. No correlation was found between age of the horse and the density of the cricoid cartilage.

Two experiments were performed to study the relationship between leukotriene B4 (LTB4) synthesis and placental separation and uterine involution in the cow. In experiment I, the concentration and synthesis of LTB4 by caruncular tissue was lower in cows with retained fetal membranes (RFM cows, n = 11) than in cows that expelled the fetal membranes normally (NFM cows, n = 19). The presence of bacterial cell wall, especially of alpha-hemolytic streptococci and coagulase positive staphylococci enhanced LTB4 synthesis by allantochorion only in NFM cows. In the RFM group, Escherichia coli lipopolysaccharide decreased allantochorionic LTB4 synthesis. With caruncle, only epidermal growth factor increased LTB4 production in NFM cows. In experiment II, the caruncular and endometrial secretion of LTB4 was lower in cows with subuterine involution (SUI cows, n = 5) or cows with SUI and RFM (SUI+RFM cows, n = 4) than in cows with normal uterine involution (NUI cows, n = 8). This decrease was especially noticeable in the previously gravid horn. In the three uterine involution groups, there were no differences in LTB4 synthesis by caruncular tissue taken from the previously gravid horn. However, progesterone and a bacterial suspension of E. coli reduced the synthesis of LTB4. Estradiol had no effect on LTB4 synthesis at the end of the postpartum period. These results suggest that LTB4 may play an important role in both placental separation and uterine involution in cattle and LTB4 synthesis may be modulated by endocrine and bacterial factors.

Selective parathyroidectomy (PTX) is preferred to thyroparathyroidectomy (TPTX) when specific effects of parathyroid hormone depletion are being studied. However, because of the anatomic proximity of thyroid and parathyroid glands, TPTX often is performed, leaving animals depleted of thyroxine (T4) and calcitonin as well as parathyroid hormone (PTH). In the present study, six normal dogs had parathyroid tissue and about seven-eighths of thyroid tissue removed. This quantity of thyroid tissue was inadequate to maintain normal serum T4 concentrations, despite allowance of 168 days for thyroid recovery. Five of six dogs with reduced renal mass had successful selective PTX and normal serum T4 concentrations at 28 days, when one-half or more of thyroid tissue was spared. We conclude that with attention to the surgical technique, selective PTX can be achieved in a high percentage of dogs and sufficient thyroid tissue spared to maintain euthyroidism.

Two experiments were undertaken to evaluate whether porcine reproductive and respiratory syndrome (PRRS) virus was able to cross the placenta and infect midgestation fetuses following intranasal inoculation of sows and whether PRRS virus directly infected fetuses following in utero inoculation. In experiment 1, eight sows between 45 and 50 days of gestation were intranasally inoculated with PRRS virus (ATCC VR-2332), and four control sows were inoculated with uninfected cell culture lysate. Virus inoculated sows were viremic on postinoculation (PI) days 1, 3, 5, 7 and 9, shed virus in their feces and nasal secretions, and became leukopenic. Sixty-nine of 71 fetuses from principal sows euthanized on PI day 7, 14 or 21 were alive at necropsy and no virus was isolated from any of the fetuses. Two principal sows that farrowed 65 and 67 days PI delivered 25 live piglets and three stillborn fetuses. The PRRS virus was isolated from two live piglets in one litter. In experiment 2, laparotomies were performed on five sows between 40 and 45 days of gestation and fetuses were inoculated in utero with either PRRS virus alone, PRRS virus plus a swine serum containing PRRS antibodies, or uninfected cell culture lysate. Three sows were euthanized on PI day 4 and two sows on PI day 11. Viral replication occurred in fetuses inoculated with virus alone and was enhanced in fetuses inoculated with virus plus antibody. No virus was isolated from control fetuses. The results indicate that sows and fetuses are susceptible to PRRS virus infection in mid-gestation, that viral replication is enhanced by the addition of serum with PRRS virus antibody, and that the virus does not readily cross the placental barrier during mid-gestation.

Virulence of three Canadian poultry strains of Salmonella enteritidis, namely phagetypes (PT) 4, 8 and 13, and one Salmonella heidelberg strain was assessed in orally and intraperitoneally inoculated one-day old chickens and compared to the virulence of a human S. enteritidis PT 4 strain from the United Kingdom (UK). The two PT 4 strains were also compared in orally inoculated adult laying hens. In addition, orally inoculated Balb/c mice were used to evaluate virulence of the above strains and two strains of Salmonella typhimurium containing different plasmids. In orally inoculated one-day old chickens, the UK S. enteritidis PT 4 strain was more virulent than the Canadian PT 4 strain. The UK PT 4 strain was also more virulent and invasive in adult laying hens than the Canadian PT 4 strain. The S. enteritidis PT 8 strain and one S. typhimurium strain isolated from a chicken hatchery were the most virulent for orally inoculated Balb/c mice. This strain of S. typhimurium contained the 60 megadalton plasmid associated with virulence for Balb/c mice which was not present in the S. typhimurium strain isolated from a pig with septicemic disease.

A simple and humane model of inflammation, induced by the intradermal injection of 0.3 mL of sterile 2% carrageenan, was characterized in calves by measuring the volume of skin swelling plus histological analysis of skin biopsies. Carrageenan produced a biphasic increase in skin swelling, with an early edematous response followed by a more chronic cellular infiltrate. The swelling and sensitivity to pressure observed in the early response were suitable for testing the antiedematous and analgesic activity of a new nonsteroidal anti-inflammatory drug (NSAID), oxindanac. Pretreatment with intravenous oxindanac at doses from 0.5 to 8.0 mg/kg reduced the volume of swelling and this reached statistical significance (p < 0.05) at 2 mg/kg. The ED50 and ED90 values for inhibition of the peak swelling volume (4 h) were estimated to be 1 mg/kg and 2 mg/kg, respectively. These compare with an ED90 of 2.0 mg/kg for inhibition of serum TxB2 production, an index of platelet cyclo-oxygenase activity. The dose of oxindanac required for antiedematous activity correlated, therefore, with maximal inhibition of serum TxB2. The analgesic activity of oxindanac reached no clear maximum response, but statistically significant difference (p < 0.05) from placebo was reached with doses of 2 mg/kg and above. It is concluded that intradermal carrageenan produced a simple, humane and useful model for dose estimation of a new NSAID in calves.

Withdrawal periods required when doses of 24,000 IU and 66,000 IU of procaine penicillin G/kg body weight were administered to yearling beef steers by intramuscular injection daily for five consecutive days were investigated. These dosages are in excess of product label recommendations, but are in the range of procaine penicillin G dosages that have been administered for the treatment of some feedlot bacterial diseases. The approved dose in Canada is 7,500 IU/kg body weight intramuscularly, once daily, with a withdrawal period of five days. Based on the tissue residue data from this study, the appropriate withdrawal period is ten days for the 24,000 IU/kg body weight dose and 21 days for the 66,000 IU/kg body weight dose when administered intramuscularly to yearling beef steers. In a related study, 18 yearling beef steers received 66,000 IU of procaine penicillin G/kg body weight administered by subcutaneous injection, an extra-label treatment in terms of both dose and route of administration, typical of current practice in some circumstances. Deposits of the drug were visible at subcutaneous injection sites up to ten days after injection, with more inflammation and hemorrhage observed than for intramuscular injections of the same dose. These results suggest that procaine penicillin G should not be administered subcutaneously at high doses; and therefore a withdrawal period was not established for subcutaneous injection.

The prevalence of feline leukemia virus (FeLV) antigen and DNA was assessed in formalin-fixed, paraffin-embedded tumor tissues from 70 cats with lymphosarcoma (LSA). Tissue sections were tested for FeLV gp70 antigen using avidinbiotin complex (ABC) immunohistochemistry (IHC); DNA was extracted and purified from the same tissue blocks for polymerase chain reaction (PCR) amplification of a 166 base pair region of the FeLV long terminal repeat (LTR). Results were related to antemortem FeLV enzyme-linked immunosorbent assay (ELISA) for serum p27 antigen, anatomic site of LSA, and patient age. Viral DNA was detected by PCR in 80% of cases and viral antigen by IHC in 57% of cases. Seventeen cases were PCR-positive and IHC-negative; one case was PCR-negative and IHC-positive. Clinical records included FeLV ELISA results for 30 of 70 cats. All 19 ELISA-positive cats were positive by PCR and IHC; of the 11 ELISA-negative cats that were negative by IHC, seven were positive by PCR. When evaluated according to anatomic site, FeLV DNA and antigen were detected less frequently in intestinal LSAs than in multicentric and mediastinal tumors. Lymphosarcoma tissues from cats < 7 yr were several fold more likely to be positive for FeLV antigen by IHC than were tumors from cats > or = 7 yr. However, there was no significant difference in PCR detection of FeLV provirus between LSAs from cats < 7 yr and those > or = 7 yr. These proviruspositive, antigen-negative cases may represent infection with latent or replication-defective FeLV.

Two cytopathic agents were isolated on porcine alveolar macrophages following inoculation with homogenates of lung tissues from pigs showing respiratory problems. These isolates were identified as porcine reproductive and respiratory syndrome (PRRS) virus isolates by indirect immunofluorescence using a PRRS virus (PRRSV) specific monoclonal antibody (MAb) and were designated as LHVA-92-1 and LHVA-92-2. Immunogold electron microscopy using a porcine PRRS positive serum pool and protein A-gold resulted in an intense labelling of aggregates of viral particles. Dark specific cytoplasmic staining of porcine alveolar macrophages infected with both virus isolates could be observed by immunogold silver staining (IGSS) using the specific MAb. This method proved effective in detecting PRRSV antigens in several ethanol-fixed tissues of piglets intranasally inoculated with the supernatants of macrophages infected with each isolate. Immunogold silver staining was also successfully used for the detection of PRRSV antigens on sections of formalin-fixed paraffin-embedded lung tissues and on frozen sections of lungs. The present results indicate that colloidal gold may be useful for the identification and immunohistochemical detection of PRRSV in tissues.

A field study involving 325 calves from 17 dairy herds in Saskatchewan was conducted to determine the risk of enzootic pneumonia and to assess its association with a number of factors. Two different case definitions of pneumonia were used in the analyses: the first was based on producers' treatment risk (CASE1) and the second was based on semimonthly clinical examinations of calves by the research veterinarian (CASE2). The risk of pneumonia based on CASE1 was 39% and on CASE2 was 29%. The measure of agreement between CASE1 and CASE2 at the calf level of analysis was poor (kappa = 0.24, SE = 0.02) and at the herd level of analysis was moderate (kappa = 0.40, SE = 0.12). The mortality risk from pneumonia was 1.8% and a variety of infectious organisms were isolated from pneumonic lungs. Twenty-seven percent of the calves had inadequate (total IgG < or = 800 mg/dL) levels of passively acquired antibodies as measured by radial immunodiffusion. The proportion of seropositive titers in calves within the first two weeks of age was 94% to parainfluenza 3 virus (PI3V) and bovine respiratory syncytial virus (BRSV), 73% to Pasteurella haemolytica (Ph), 68% to bovine viral diarrhea virus (BVDV), 67% to infectious bovine rhinotracheitis virus (IBRV), 46% to Mycoplasma dispar (Md), 44% to Haemophilus somnus (Hs), and 21% to Mycoplasma bovis (Mb). At the calf level of analysis and after adjusting for clustering, there was a negative association (p = 0.10) between the diagnosis of pneumonia based on CASE2 and total IgG levels and Ph titers (rPh).