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Biomedical subjects

T R Ames

Publications and source records attributed to T R Ames.

At least 19 recordsLinked to original sources
PubMed1995

Aneurysm of the cranial mesenteric artery in a cow.

Exploratory laparotomy of an adult dairy cow, examined because of acute signs of persistent abdominal pain, revealed a firm pulsatile mass with associated fremitus just distal to the origin of the cranial mesenteric artery. The cow died acutely 2.5 days after surgery. A dilated, thin-walled, sacculated aneurysm, which had ruptured, was located along the proximal portion of the cranial mesenteric artery. It was postulated that the aneurysm developed secondary to structural defects in the arterial wall, but caused no clinical signs until enlargement and local tissue stretching or circulatory disturbances caused intestinal ischemia, resulting in abdominal pain. Aneurysms of visceral arteries in cattle should be considered as another differential diagnosis for signs of abdominal pain after more common causes such as severe bloat, mesenteric root volvulus, intussusception, cecal dilatation/volvulus, and uterine torsion have been excluded.

Abdominal Pain↗
PubMed1995

Purified Pasteurella haemolytica leukotoxin induces expression of inflammatory cytokines from bovine alveolar macrophages.

We obtained biologically active purified leukotoxin (Lkt) from Pasteurella haemolytica serotypel, strain 12296 using preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Three species of Lkt of molecular masses 95, 100, and 104 kDa were obtained. Purity of all three species of Lkt was confirmed by analytical SDS-PAGE and Western blot (immunoblot) analysis. Results from the chromogenic Limulus amebocyte lysate assay and silver staining of SDS-PAGE patterns indicated that the preparations were free of contaminating lipopolysaccharide. We then studied the kinetics of TNF alpha and IL-1 beta mRNA expression in bovine alveolar macrophages stimulated with the purified 104 kDa Lkt. Subcytolytic concentrations of Lkt induced TNF alpha and IL-1 beta gene expression and peak induction was observed at a concentration of 1 leukotoxin unit/ml. Both TNF alpha and IL-1 beta mRNA expression were detectable at 1 h after stimulation with 1 leukotoxin unit/ml. The expression peaked at 2 h, steadily declining up to 6 h, and was undetectable by 10 h. Secreted TNF alpha measured by bioassay peaked at 4-6 h and accumulated at a lesser concentration after 6 h. By contrast, secreted IL-1 peaked at 6 h and decreased significantly by 10 h. The ability of purified Lkt to induce TNF alpha and IL-1 beta gene expression and secretion of bioactive proteins was suppressed by Ca2+ chelating agents, 5 mM EDTA and 5 mM EGTA, but not polymyxin B. Heat-inactivation of the purified Lkt that had lost its cytocidal property completely abrogated induction of TNF alpha and IL-1 beta gene expression and secretion in bovine AMs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Induction of inflammatory cytokines in bovine alveolar macrophages following stimulation with Pasteurella haemolytica lipopolysaccharide.

Bovine tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) cDNAs were generated by reverse transcription and then by PCR amplification from lipopolysaccharide (LPS)-stimulated alveolar macrophage RNA. The amplified cDNAs were cloned into pPow and expressed in Escherichia coli DH5 alpha. The expressed proteins were confirmed as TNF-alpha and IL-1 beta by Western blot (immunoblot) analysis and bioassays. We then used the cloned genes as probes in Northern (RNA) blots and investigated the kinetics of TNF-alpha and IL-1 beta mRNA expression in bovine alveolar macrophages stimulated with purified LPS from Pasteurella haemolytica 12296. The effect of LPS on TNF-alpha and IL-1 beta gene expression was dose dependent, and induction was observed at a concentration of 0.01 microgram/ml. Both TNF-alpha and IL-1 beta mRNA expression were detectable within 0.5 h after stimulation with 1 microgram of LPS per ml, peaked at 1 to 2 h, steadily declined up to 16 h, and were undetectable by 24 h. Secreted TNF-alpha measured by bioassay peaked at 4 h and accumulated at a lesser concentration in conditioned medium throughout the 24 h. By contrast, secreted IL-1 beta was induced at 8 h and reached a maximal concentration at 24 h after stimulation. The ability of LPS to induce TNF-alpha and IL-1 beta gene expression and secretion of bioactive proteins were suppressed by polymyxin B. Our findings support a role for LPS from P. haemolytica in the induction of inflammatory cytokines in bovine pneumonic pasteurellosis.

Animals↗
PubMed1994

Interaction of bovine respiratory syncytial virus with bovine alveolar macrophages in vivo: effects of virus infection upon selected cell functions.

The effect of bovine respiratory syncytial virus (BRSV) upon alveolar macrophage (AM) function was investigated using an in vivo calf inoculation model. Alveolar macrophages were collected sequentially from live calves at multiple time points during the 14 day period following viral inoculation. Alveolar macrophages from bronchoalveolar lavage fluids were purified by density gradient centrifugation (> 95% AM) prior to in vitro evaluation of cell functions. There were significant but variable and inconsistent differences in the functions of AM from the BRSV inoculated calves compared to the control calves. Fc-receptor mediated phagocytosis was either increased or unchanged by BRSV inoculation. Nonopsonized phagocytosis was decreased during the early postinoculation period and later increased. There was a variable effect on AM phagosome lysosome fusion with increased fusion activity on postinoculation days 2 through 5, 7 and 12 but reduced activity on days 6 and 10. The AM respiratory burst, as measured by nitroblue tetrazolium dye reduction, was essentially unaffected with a reduction in activity on day 10 only. In this model, BRSV inoculation of calves primarily resulted in an alteration of the membrane associated phagocytic functions of the alveolar macrophages (p < 0.05).

Animals↗
PubMed1992

Fecalith impaction in four miniature foals.

Four miniature foals admitted with signs of progressive nonresponsive abdominal pain and no fecal production had fecalith impaction of the small colon. Duration of clinical signs ranged from 10 hours to 5 days. Removal of the fecalith via small colon enterotomy was a successful treatment in all 4 cases. Miniature foals may be predisposed to fecalith impaction of the small colon. If a miniature foal has signs of progressive nonresponsive abdominal pain, fecalith impaction needs to be considered. Surgical correction may be required.

Animals↗
PubMed1991

Morphological and morphometrical analysis of the acute response of the bovine alveolar wall to Pasteurella haemolytica A1-derived endotoxin and leucotoxin.

Endotoxin or leucotoxin derived from Pasteurella haemolytica biotype A serotype 1 or saline was deposited by fibreoptic bronchoscopy into the caudal segment of the right anterior lung lobe of calves, and the lesions were characterized by light and transmission electron microscopy. Morphometric techniques were used to determine if changes in the arithmetic mean thickness of the alveolar wall occurred. Group 1 calves (n = 2) were inoculated with 6 ml saline, groups 2 calves (n = 3) received 6 ml of a partially purified leucotoxin preparation, group 3 calves (n = 3) received 96 micrograms of endotoxin in 6 ml of saline and group 4 calves (n = 3) received 2.5 mg of endotoxin in 6 ml of saline. Calves were killed 4 h after inoculation. Lesions in groups 2, 3 and 4 were similar and we found that (a) endotoxin alone is capable of initiating an inflammatory response in the bovine lung, (b) leucotoxin causes cytotoxic changes in alveolar macrophages but not in parenchymal cells of the lung, (c) neutrophil sequestration and platelet aggregation occur in alveolar capillaries in association with pulmonary intravascular macrophages, (d) neutrophils and fibrin were found in the alveolus in close association with alveolar macrophages, (e) disruption of the alveolar epithelial layer occurred in association with neutrophils and (f) there were no significant increases in the arithmetic mean thickness of the alveolar wall.

Animals↗
PubMed1991

Therapy of bovine bacterial pneumonia.

Practical strategies for developing rational therapeutic regimens based on in vitro sensitivity and pharmacokinetic disposition are presented. Special attention is given to Pasteurella haemolytica, which is regarded as the most frequent cause of bovine bacterial pneumonia. Bacterial-dependent and host-dependent causes of therapeutic failure and potentially valuable novel therapies and drug combinations are considered.

Animals↗
PubMed1991

Alterations in pulmonary morphology and peripheral coagulation profiles caused by intratracheal inoculation of live and ultraviolet light-killed Pasteurella haemolytica A1 in calves.

Eighteen male Holstein calves were divided into groups of three and inoculated intratracheally with 5 x 10(9) logarithmic phase or ultraviolet light-killed Pasteurella haemolytica biotype A serotype 1. Serial coagulation profiles were done on one calf from each group during the first 24 hours after inoculation. One calf from each group was necropsied at 4, 12, and 24 hours after inoculation and lesions were characterized with light and transmission electron microscopy. We found that 1) the pulmonary intravascular macrophage may have an important role in the early intravascular inflammatory events; 2) there was morphologic evidence for local initiation of the coagulation cascade in the lung early in the disease process but it was not a consumptive process; and 3) killed-bacteria were capable of causing fibrin exudation, platelet aggregation and alveolar epithelial damage similar to live bacteria, but the degenerative changes in neutrophils, endothelial cells and intravascular fibrin formation that occur with live bacteria were not seen.

Animals↗
PubMed1991

Changes in blood and bronchoalveolar lavage fluid components in calves with experimentally induced pneumonic pasteurellosis.

Pneumonic pasteurellosis was experimentally induced in calves by inoculation of 5 x 10(8) Pasteurella haemolytica organisms into the right diaphragmatic lung lobe. Blood and bronchoalveolar lavage fluid samples were obtained prior to inoculation and at postinoculation hour (PIH) 2, 4, and 6. Calves developed acute lung injury, characteristic of pneumonic pasteurellosis. Lesions were found only in the right diaphragmatic lobe. By PIH 4, significant (P less than 0.01) increases were detected in lavage fluid total cell count, neutrophil count, total protein and albumin concentrations, and alkaline phosphatase (ALP) and lactic dehydrogenase (LD) activities. Myeloperoxidase and elastase activities did not increase. Neutrophil depletion ameliorated the lung lesions and prevented the increase in lavage fluid cell count, total protein, and albumin concentrations and ALP and LD activities. Treatment with the iron chelator, deferoxamine mesylatehydroxyethyl starch, attenuated the increase in total protein and albumin concentrations and ALP and LD activities at PID 4, but not PIH 6. Treatment with a neutrophil function inhibitor, pentoxifylline, prevented the increase in lavage fluid neutrophil numbers, but accentuated the increase in total protein and albumin concentrations, and ALP, LD, myeloperoxidase, and elastase activities.

Animals↗
PubMed1990

Serodiagnosis of equine monocytic ehrlichiosis in selected groups of horses in Minnesota.

Antibody titer to Ehrlichia risticii was determined, in 2,549 equine serum samples, using an indirect fluorescent antibody assay. During 1986, samples were obtained from the Minnesota State-Federal Equine Infectious Anemia Diagnostic Laboratory, the Minnesota Racing Laboratory, from horses admitted to the University of Minnesota Veterinary Teaching Hospital, and as a result of field investigations of horses with acute diarrhea. Results of the study revealed antibody prevalence of 33, 24, 47, and 25% for the respective groups. There was no statistical association between seropositive status and age, sex, breed, or clinical problem of horses referred to the teaching hospital. There was an increase in the total percentage of seropositive samples over the duration of the sample collection period, suggesting a seasonal exposure pattern, and E risticii was associated with clinical and subclinical infections in horses of Minnesota.

Animals↗
PubMed1990

Immunohistochemical localization of Pasteurella haemolytica A1-derived endotoxin, leukotoxin, and capsular polysaccharide in experimental bovine Pasteurella pneumonia.

Six, 5- to 10-week-old male Holstein calves were inoculated intratracheally with 5 x 10(9) logarithmic growth phase Pasteurella haemolytica biotype A serotype 1 (A1). Immunohistochemical techniques in conjunction with the use of monoclonal antibodies directed against P. haemolytica A1-derived lipopolysaccharide (LPS), capsular polysaccharide, and a polyclonal rabbit anti-leukotoxin antibody were used to localize their respective antigens in tissue sections of pneumonic lung at the light and electron microscopic levels. We found the following: 1) LPS, capsular polysaccharide, and leukotoxin were released into the inflammatory exudate; 2) LPS was found within the cytoplasm of neutrophils (located in the alveolus and alveolar wall), alveolar macrophages, endothelial cells, pulmonary intravascular macrophages, and on epithelial cell surfaces; 3) capsular polysaccharide was found in the alveolus and alveolar macrophages but not in cells of the alveolar wall; and 4) leukotoxin was associated with cell membranes of degenerating inflammatory cells located in the alveolus. This is the first study that demonstrates the presence of leukotoxin in the pulmonary inflammatory lesions caused by P. haemolytica A1 and implicates endotoxin as an important factor in the genesis of the pulmonary lesions.

Animals↗
PubMed1989

Diagnostic investigation of bovine viral diarrhea infection in a Minnesota dairy herd.

Bovine viral diarrhea (BVD) virus infection was diagnosed in neonatal calves with enteritis. Successful diagnostic procedures included direct immunofluorescence of frozen tissue sections, histopathology, and virus isolation. Virus isolation from buffy coats and serum was successful in detecting infected animals, whereas direct immunofluorescence of buffy coat samples was found to be less reliable. Virus was not isolated from any fecal samples. Booster vaccinations and the culling of animals shedding virus resulted in improved calf viability in this herd. It is suggested that procedures for the diagnosis of BVD virus infection should always be included in the diagnosis of neonatal calf enteritis.

Animals↗
PubMed1988

Adrenocorticotropin-containing neoplastic cells in a pars intermedia adenoma in a horse.

Pituitary-dependent hyperadrenocorticism was diagnosed in a 14-year-old Arabian mare with chronic weight loss, hirsutism, polyuria, and polydipsia. The mare had a stress leukogram, glucosuria, and consistent hyperglycemia. Plasma glucose concentrations were resistant to suppression by insulin. Plasma cortisol concentrations were within normal limits, but did not respond to dexamethasone suppression and had an exaggerated response to ACTH stimulation. At necropsy, a chromophobe adenoma of the pars intermedia of the pituitary gland was found. The zona fasciculata of the adrenal cortex and the pancreatic islets of Langerhans were hypertrophied. An immunohistologic staining technique was used to demonstrate ACTH-containing neoplastic cells in the pituitary mass. These cells released ACTH and other peptides that initiated the chain of endocrinologic events leading to clinical disease.

Adenoma↗
PubMed1988

Production and partial characterization of monoclonal antibodies to Pasteurella haemolytica A1 capsular polysaccharide and lipopolysaccharide.

Hybridoma-derived monoclonal antibodies (MAB) against the cell surface antigens of Pasteurella haemolytica serotype 1 were obtained by the fusion of murine myeloma cells (P3 X 63 - Ag 8.653) with splenocytes of BALB/c mice immunized with crude logarithmic growth-phase culture supernatant. Initial screening was performed, using an ELISA, with the same bacterial growth culture supernatant as coating antigens. Further selection was done, using a panel of purified antigens--either capsular polysaccharide or lipopolysaccharide--as the coating antigen in an ELISA, and then performing a leukotoxin-neutralization assay. Two MAB, designated IIB-6 and H-2, reacted specifically with the capsular polysaccharide and the other 3, designated IVG-3, IH-3, and IIC-2, reacted with the lipopolysaccharide. One MAB, designated IH-6, did not react with leukotoxin, capsular polysaccharide, or lipopolysaccharide. The MAB to the capsular polysaccharide (IIB-6 and H-2) were characterized further; both antibodies belonged to the IgM class and were agglutinating. In addition, they promoted neutrophil-mediated opsonophagocytosis and complement-mediated immune bacteriolysis of P haemolytica serotype 1. Results from 3 studies indicated that the MAB IIB-6 and H-2 were specific only to the capsular polysaccharide of serotype 1 of P haemolytica. The MAB to the lipopolysaccharide (IVG-3, IH-3, and IIC-2) were of the IgG1, IgG3, and IgM classes, respectively and were not characterized further. The availability of a MAB identifying a serotype-specific, surface-exposed determinant on the capsule of P haemolytica serotype 1 should facilitate and expand studies concerning the role of the capsular material and lipopolysaccharide in the pathogenicity of P haemolytica infection in cattle.

Animals↗