The effect of vitamin E supplementation on discoloration of injection-site lesions in retail cuts and the greening reaction observed in injection-site lesions in muscles of the chuck

Concern has been raised about green discoloration of injection-site lesions in chuck muscles in modified-atmosphere packages. Objectives were: 1) to recreate green lesions, 2) to compare the severity of discoloration of injection-site lesions in chucks from carcasses of control or vitamin E-supplemented steers, and 3) to identify pigment(s) responsible for discoloration via in vitro color reactions. In Exp. 1, 23 steers (BW = 415 kg; 37 d before harvest) were injected with one of 12 pharmaceuticals, following label directions for route and dose, with the exception of a 5-mL maximum dose, to identify a product that could result in discoloration. Two vaccines (Products A and B) resulted in greening. In Exp. 2, 50 steers were injected (i.m.) with Product A and assigned to the control or vitamin E (1,000 IU/steer daily for 60 d) group. After retail display, 80 and 72% of steaks from the control and treatment groups, respectively, were discolored. Although vitamin E did not reduce (P = 0.53) greening, there was a trend (P = 0.10) toward delay discoloration of lesions from the treatment group. In Phase I of Exp. 3, pigments extracted from green lesions obtained from Exp. 2 were compared with solutions, exposed to a high partial pressure of oxygen (ppO), of myoglobin (Mb), copper sulfate, hydrogen peroxide (H2O2), vaccine, and aluminum hydroxide either alone or in combination. In Phase II of Exp. 3, solutions of two or more of Mb, Cu, sodium sulfide, sodium sulfite, sodium sulfate (Na2SO4), and H2O2 were made at pH 7.2 or 5.5 and exposed to low or high ppO. Normal muscle tissue displayed a 3.2 and 56.7% decrease in absorbance/microg of protein as wavelength changed from 654 to 656 nm and 656 to 658 nm, respectively. Pigments from control and treatment group green tissue displayed a 164.5 and 621.3% increase, respectively, in absorbance/microg of protein as wavelength changed from 654 to 656 nm. As wavelength changed from 656 to 658 nm, the absorbance/microg of protein for control and treatment group lesions decreased by 75 and 109%, respectively. The Mb+Cu+Na2SO4 solution, at pH 5.5 and high ppO, exhibited similar absorbance trends as green lesions indicating that greening may result from a Mb, Cu, and Na2SO4 interaction. Results indicated that greening varies with pharmaceuticals and oxidation of tissue cannot be controlled with vitamin E supplementation. Research on the causative agents of green discoloration, with an emphasis on compounds containing sulfate or Cu, is needed.

Association of 3-methyleneindolenine, a toxic metabolite of 3-methylindole, with acute interstitial pneumonia in feedlot cattle

OBJECTIVE

To compare concentrations of 3-methyleneindolenine (3MEIN) in lung tissues obtained from feedlot cattle that died as a result of acute interstitial pneumonia (AIP) and cattle that died as a result of other causes and to compare blood concentrations of 3MEIN in healthy feedlot cattle and feedlot cattle with AIP.

STUDY POPULATION

Blood samples and lung tissues collected from 186 cattle housed in 14 feedlots in the western United States.

PROCEDURE

Samples of lung tissues were collected during routine postmortem examination and submitted for histologic, microbiologic, and toxicologic examination. Blood samples were collected from cattle with clinical manifestations of AIP and healthy penmates. Histologic diagnoses were categorized as AIP, bronchopneumonia (BP), control samples, and other disorders. Concentrations of 3MEIN were determined in lung tissues and blood samples, using an ELISA.

RESULTS

Concentrations of 3MEIN in lung tissues were significantly greater in AIP and BP samples, compared with control samples. Absorbance per microgram of protein did not differ between BP and AIP samples. Blood concentrations of 3MEIN were significantly greater in cattle with AIP, compared with healthy cattle or cattle with BP. Odds of an animal with AIP being a heifer was 3.1 times greater than the odds of that animal being a steer.

CONCLUSIONS AND CLINICAL RELEVANCE

Increased pulmonary production of 3MEIN may be an important etiologic factor in feedlot-associated AIP.

Involvement of microbial respiratory pathogens in acute interstitial pneumonia in feedlot cattle

OBJECTIVE

To evaluate viral and bacterial respiratory pathogens and Mycoplasma spp isolated from lung tissues of cattle with acute interstitial pneumonia (AIP) and cattle that had died as a result of other causes.

SAMPLE POPULATION

186 samples of lung tissues collected from cattle housed in 14 feedlots in the western United States.

PROCEDURE

Lung tissues were collected during routine postmortem examination and submitted for histologic, microbiologic, and toxicologic examinations. Histologic diagnoses were categorized for AIP, bronchopneumonia (BP), control samples (no evidence of disease), and other disorders.

RESULTS

Cattle affected with AIP had been in feedlots for a mean of 1272 days before death, which was longer than cattle with BP and control cattle. Detection of a viral respiratory pathogen (eg, bovine respiratory syncytial virus [BRSV], bovine viral diarrhea virus, bovine herpesvirus 1, or parainfluenza virus 3) was not associated with histologic category of lung tissues. Bovine respiratory syncytial virus was detected in 8.3% of AIP samples and 24.0% of control samples. Histologic category was associated with isolation of an aerobic bacterial agent and Mycoplasma spp. Cattle with BP were at greatest risk for isolation of an aerobic bacterial agent and Mycoplasma spp.

CONCLUSIONS AND CLINICAL RELEVANCE

Analysis of these results suggests that AIP in feedlot cattle is not a consequence of infection with BRSV. The increased, risk of isolation of an aerobic bacterial agent from cattle with AIP, compared with control cattle, may indicate a causal role or an opportunistic infection that follows development of AIP.

Radiculomeningomyelitis due to Halicephalobus gingivalis in a horse

An adult horse was euthanatized following a clinical diagnosis of cauda equina neuritis. Significant gross postmortem and histopathologic findings were limited to the sacral spinal cord and cauda equina. The sacral spinal cord, meninges, and spinal nerve roots were expanded and partially effaced by sclerosing granulomatous inflammation with necrosis. The lesion contained numerous nematode larvae and fewer adults with a rhabditiform esophagus having a corpus, isthmus, and valved bulb. Female nematodes were amphidelphic and didelphic with reflexed ovaries. These morphologic features confirm Halicephalobus gingivalis as a novel cause of clinical signs in this case of cauda equina neuritis.

Cutaneous metastases of a mammary carcinoma in a llama

An 8-year-old, female llama was evaluated for nonhealing, ulcerative, cutaneous lesions, which also involved the mammary gland. Biopsies of the lesions distant from and within the mammary gland area revealed an aggressive carcinoma. The tumor was confirmed at necropsy to be a mammary gland adenocarcinoma with cutaneous metastasis.

Bovine abortions associated with Bacteroides fragilis fetal infection

Two Santa Gertrudis cattle from a herd of 105 aborted within a 24-hour period. Bacteroides fragilis was isolated from tissues of each aborted fetus. Histopathologic lesions included placentitis and bronchopneumonia in which gram-negative, rod-shaped organisms were visible. The diagnostic workup failed to reveal other causes of abortion. Anaerobes are rarely implicated in bovine abortions, and no other report was found that described abortion in cattle due to B. fragilis.

Lymphosarcoma with leukemic blood profile in a Savannah monitor lizard (Varanus exanthematicus)

A 6-mo-old male Savannah monitor lizard (Varanus exanthematicus) was presented for lethargy and anorexia of 7 days duration. Physical examination revealed a slightly raised subcutaneous mass (1 cm diameter) in the left scapular area. Fine-needle aspiration cytology of the mass revealed a population of immature, pleomorphic lymphoid cells consistent with lymphosarcoma. A hemogram indicated marked leukocytosis (465,000 cells/microl) characterized by extreme lymphocytosis and many circulating lymphoid blast cells. The lizard was euthanized at the owner's request. Necropsy revealed severe hepatomegaly and multiple raised, ulcerated mural masses in the gastrointestinal tract. There were many raised, poorly demarcated tan foci in all the parenchymal organs. Histopathologic examination confirmed infiltration of all parenchymal organs by neoplastic lymphoid cells. Transmission electron microscopic examination failed to identify viruses within the neoplastic cells. A literature review revealed few reports of squamate leukemia and lymphosarcoma and none in Savannah monitor lizards.

Nitric oxide production and expression of inducible nitric oxide synthase by bovine alveolar macrophages

Alveolar macrophages play a central role in host defense in the lower respiratory tract. Production of the reactive intermediate nitric oxide (NO), via expression of inducible nitric oxide synthase (iNOS) is an important microbicidal effector mechanism possessed by macrophages. In this study, cytokine regulation of NO production by bovine alveolar macrophages (bAM) was evaluated. Bovine alveolar macrophages were exposed to one or more of the following: recombinant human (rh) and recombinant bovine (rb) IFN gamma, rh- and rbIL-1 beta, rbGM-CSF, rhTNF alpha, rhIL-4, endotoxin (LPS), fetal bovine serum (FBS), mitogen-stimulated bovine splenic supernatant (SS), and purified human TGF beta-1. LPS alone, or in combination with SS, rbIFN gamma, or rbIL-1 beta stimulated production of NO in a time and dose dependent fashion. Recombinant bovine IFN gamma, rbIL-1 beta, and rhTNF alpha in combination produced maximal stimulation which was not further enhanced by LPS. Recombinant human IFN gamma, rhIL-1 beta, and rbGM-CSF had minimal effect either as single stimuli, or in combination with LPS, rbIFN gamma, rbIL-1 beta, or rhTNF alpha. Nitric oxide production was inhibited by rhIL-4, and the L-arginine analogue antagonists of iNOS, N-G-monomethyl-L-arginine (NGMMA) and aminoguanidine (AG). Purified human TGF beta-1 did not inhibit NO production. Messenger RNA for iNOS was maximally expressed by 8 h and remained detectable for at least 48 h. Expression of iNOS mRNA induced by cytokines and LPS varied with strength of the stimulus as determined by nitrite production in culture supernatant.

Bacterial lipopolysaccharide-stimulated nitric oxide generation is unrelated to concurrent cytotoxicity of bovine alveolar macrophages

Nitric Oxide (NO) is a reactive metabolite produced by stimulated macrophages, and it has been demonstrated to exert cytotoxic actions on a number of microbes, parasites, and tumor cells. In addition, NO has been reported to have an autotoxic effect on murine macrophages, its site of synthesis. We have investigated the relationship of NO generation to cytotoxicity of bovine alveolar macrophages (AM) in vitro, and have also assessed the effects of several modulators of cellular function on this relationship. NO was generated in cultures of AM using sodium nitroprusside (SNP) and measured as [nitrite]. Cellular viability of AM reflected a strong, negative correlation with the concentration of NO/nitrite in supernatants (r = -0.987). Supernatants with nitrite concentrations in excess of 30 microMs were correlated with cytotoxicity. AM stimulated with the potent combination of endotoxin (Lipopolysaccharide, LPS; 10 ng/ml) and recombinant bovine IFN gamma (100 U/ml) also exhibited cytotoxicity over a 48-hour incubation period, and cells deteriorated to an average viability of 72.3% as compared to unstimulated control macrophages. In some cases the viability of macrophages was much lower. Even though LPS-mediated cytotoxicity occurred, the [nitrite] produced in supernatants during the 48-hour period (12.23 microMs) was well below the minimum concentration of SNP-generated NO required to induce cytotoxicity to macrophages. N(G)-monomethyl-L-arginine (N(G)MMA, 2 mM) is a competitive inhibitor of NO synthesis and was found to reduce nitrite concentrations from 12.23 microMs to 1.56 microMs in supernatants of LPS-stimulated AM, but this reduction did not promote increased viability of AM. Other modulators of cellular function including phenylbutazone (PBZ, 100 microMs), flunixin meglumine (FM, 100 microMs) and interleukin-4 (IL-4, 100 ng/ml) modestly inhibited synthesis of NO, but did not improve cellular viability. These results suggest that relatively high concentrations of exogenously-generated NO are toxic to AM in vitro, but the quantity of endogenously-generated NO synthesized by LPS-stimulated bovine AM is usually below the threshold for toxicity. Cytotoxicity occurs independently of NO synthesis, and factors other than NO are apparently responsible for LPS-related cytotoxicity to bovine macrophages.

Analysis of the CD14 receptor associated with bovine alveolar macrophages

Previous studies have suggested the existence of a bovine homolog of the membrane-associated CD14 receptor (mCD14) on macrophages, and functional similarity of bovine mCD14 receptor activity to that reported for other species. Bovine alveolar macrophages (bAM) reportedly possess two mRNA transcripts of 1.5 and 3.1 kb for CD14, rather than a single 1.5 kb transcript as reported for other species. The purpose of this study was to determine the molecular mass of the bovine CD14 receptor, and to determine if the two mRNA transcripts for bovine CD14 yield either a single or two different gene products. Culture supernatant from 125I-surface-labeled bAM was examined for the existence of bovine CD14 using SDS-PAGE and autoradiography. A single protein band of 49 kD was immunoprecipitated from the supernatant using anti-CD14 monoclonal antibodies (MAb). Macrophage-derived mRNA was subjected to hybrid-selection using a human CD14 cDNA probe immobilized on a nitrocellulose filter. The resultant, selected bovine mRNA was then utilized for in vitro translation, and protein of 38-40 kD was synthesized. This size is consistent with an unglycosylated CD14 receptor protein. Protein was also synthesized from total RNA by in vitro translation, and was immunoprecipitated with anti-CD14 monoclonal antibodies. A doublet-band of protein was seen at 38 kD using SDS-PAGE and autoradiography. Anti-CD14 antibodies were also used to inhibit serum- and LPS-dependent bovine macrophage activation as measured by tissue factor expression, which is compatible with the presence and function of CD14 receptors on macrophages. These results collectively demonstrate that a receptor consistent with CD14 is present on bovine macrophages, the form of the receptor released into supernatants is 49 kD, and that it functions as an LPS receptor on these cells.

Regulation of superoxide anion generation in bovine alveolar macrophages by bacterial lipopolysaccharide, serum proteins, and modulators of signal transduction

The respiratory burst of phagocytes in an important leukocyte function which results in generation of oxygen species that are both microbicidal and potentially damaging to host tissues. We investigated regulation of the respiratory burst of alveolar macrophages in response to lipopolysaccharide (LPS) derived from gram-negative bacteria, serum proteins, and several modulators of signal transduction. When employed as a single stimulus, LPS (E. coli 055:B5, 10 ng/ml-1 microgram/ml) was a weak stimulus for generation of superoxide anion (O2-) as compared to the potent effect of the protein kinase C activator, phorbol 12-myristate 13-acetate (PMA; 500 ng/ml). However, when LPS was combined with fetal bovine serum (FBS; 0.4-1.0% vol/vol, equivalent to 128-320 micrograms protein/ml), O2- generation was enhanced approximately two-fold over LPS alone. A chromatographically-derived bovine serum fraction which contained bovine lipopolysaccharide-binding protein (bLBP; 0.25-1.0 microgram/ml) was an effective substitute for FBS at a much lower protein concentration than whole FBS, and a similar synergistic effect with LPS on O2- generation was observed. Stimulation of macrophages for generation of O2- either with LPS alone or with LPS plus serum/serum fraction was suppressed by the protein tyrosine kinase inhibitor heribimycin A (0.2 ng/ml), and the calcium chelator BAPTA (12 microM), but not by modulators of G-proteins, including pertussis toxin (10 ng/ml) and cholera toxin (5 micrograms/ml protein). Essentially complete inhibition of O2- synthesis by herbimycin A and BAPTA occurred in the presence of LPS and the bLBP-containing serum fraction (1 microgram/ml protein), but only partial inhibition (46.7% and 64.1%, respectively) was observed in the presence of LPS plus FBS (256 micrograms/ml protein). These results indicate that when LPS is used as a sole stimulus it induces modest respiratory burst activity. However, when LPS is combined with appropriate serum components, it stimulates alveolar macrophages to generate larger amounts of O2-. Cellular signaling pathways important in stimulation of macrophages by LPS and serum components are protein tyrosine kinase- and Ca(++)-dependent, but do not relay on G-protein-mediated signaling.