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Biomedical subjects

O J Fletcher

Publications and source records attributed to O J Fletcher.

At least 19 recordsLinked to original sources
PubMed1990

Effect of cold acclimation on the broiler chicks' resistance to dietary aflatoxin.

The effect of acclimation to environmental temperatures of 10 to 12 or 28 to 30 C on the resistance of broiler chicks to dietary aflatoxin was examined. Broiler chicks were acclimated from day-of-age for 2 wk to environmental temperatures of 10 to 12 or 28 to 30 C. On Day 14, a single oral dose of aflatoxin (8 mg per kg of body weight) was administered to 50 chicks in each environment. An increase in aflatoxin resistance, as assessed by survival rate, was conveyed by acclimation to cold temperatures. In each environmental chamber, a separate group of chicks was maintained for 2 additional wk, but those groups received 5 mg of aflatoxin per kg feed. By the end of the study, aflatoxicosis was characterized by: 1) a significant (P less than or equal to .05) decrease in body weight; 2) increases in spleen weight, liver weight, liver lipid, and liver dry-matter content; 3) changes in the serum levels of total protein, albumin, glucose, cholesterol, uric acid, potassium, phosphorus, iron and calcium; and 4) increased hepatic hyperplasia. Acclimation to 10 to 12 C was characterized by: 1) an increase in body weight, liver weight, spleen weight and bursa weight; 2) changes in the serum glucose and potassium levels; and 3) a decrease in glutamic-oxaloacetic transaminase activity. Significant aflatoxin by temperature interactions were evident only in serum levels of glucose and phosphorus, and in the serum activity of glutamic-oxaloacetic transaminase. These data suggest that acclimation to cool temperatures does not play a significant role in the resistance by broiler chickens to chronic aflatoxin exposure.

Adaptation, Physiological↗
PubMed1990

Effects of dietary aflatoxin in aflatoxin-resistant and control lines of chickens.

The resistance to a single oral dose (12 mg of aflatoxin per kg of BW) and 4 wk of dietary aflatoxin (2.5 mg per kg of feed) were investigated in chicks selected for five generations for resistance to acute aflatoxicosis (AR) and unselected control (C) chicks. The AR chicks were more resistant to a single oral dose of aflatoxin and had significantly decreased sodium pentobarbital sleeping time compared to C chicks. Four-weeks exposure to dietary aflatoxin did not result in any significant change in BW or feed conversion ratios of chicks from either the C or AR line. However, more sensitive indicators of aflatoxicosis including plasma total protein, albumin, cholesterol concentrations, and gamma glutamyl transferase activity were significantly altered in C chicks but not in AR chicks fed aflatoxin. Percentages of liver lipid and liver hyperplasia score were also significantly altered as a result of dietary aflatoxin treatment in C but not AR chicks. These data indicate that selection-associated differences exist between the C and AR lines of chickens that convey resistance to not only a single oral dose of aflatoxin but also to a more chronic dietary exposure to aflatoxin.

Aflatoxins↗
PubMed1989

Marek's disease virus-induced transient paralysis in chickens: demonstration of vasogenic brain oedema by an immunohistochemical method.

The presence of vasogenic brain oedema and its distribution in Marek's disease virus (MDV)-induced transient paralysis (TP) were determined in genetically resistant and susceptible inbred White Leghorn chickens. MDV-inoculated TP-susceptible chickens with nervous signs (9 days post-inoculation) had severe vacuolation of cerebellar white matter and associated diffuse leakage of albumin and IgG. The serum protein leakage was associated morphologically with a vasculitis and intramural pseudocyst formation in the walls of blood vessels cuffed by mononuclear cells. This transient vasculitis and resulting vasogenic oedema coincided with the temporary neurological signs seen in TP-susceptible chickens. The vasculitis and vasogenic oedema were not present in brain tissue from recovered MDV-inoculated TP-susceptible chickens, MDV-inoculated TP-resistant chickens, or uninoculated control chickens from either line.

Animals↗
PubMed1988

Marek's disease virus-induced transient paralysis in chickens: alterations in brain density.

The presence of brain edema and its distribution in Marek's disease virus (MDV)-induced transient paralysis (TP) was determined in genetically resistant and susceptible inbred White Leghorn chickens. Density measurements on samples from the cerebellum, cerebral cortex, optic chiasm, and optic lobe were determined on continuous density Percoll gradients. At 9 days post inoculation of MDV, the cerebellums from the susceptible line of chickens were significantly less dense than cerebellums from the resistant line or the controls of either line. The cerebellar edema, as measured by tissue density, coincided with the transient neurological symptoms and was not present in brain tissue from clinically recovered TP birds.

Animals↗
PubMed1987

Feed refusal in swine fed ochratoxin-contaminated grain sorghum: evaluation of toxicity in chicks.

In an episode of feed refusal in a swine herd, feed specimens were found to be contaminated with mycotoxin. Grain sorghum, the chief ingredient of the swine diet, was found to be the source of contamination and contained 5 mg of ochratoxin/kg of feed. Incorporation of the grain into poultry diets induced renal and hepatic lesions, reduced weight gains, decreased feed utilization, and altered serum uric acid, blood urea nitrogen, and serum creatinine concentrations in chicks.

Animal Feed↗
PubMed1987

Suppression of humoral immunity in chickens with carrageenans.

Carrageenans (CGN), sulphated polygalactans, have been reported to be cytotoxic for macrophages in vitro. On this basis, the effect of the 3 major CGN types on humoral immune responses in chickens was investigated. Carrageenan had no effect on body and lymphoid organ weights. Histologically, CGN produced a significant proliferation of reticuloendothelial cells in liver and spleen, but no changes were observed in lymphocyte populations of the bursa of Fabricius, thymus, or spleen. Intracoelomic pretreatment with high doses of CGN induced a marked suppression of primary responses to sheep red blood cells (SRBC) given by the same route. However, if SRBC were injected intravenously into chickens already treated intracoelomically with CGN, no evidence of suppression was demonstrated. Antibody responses to Brucella abortus (BA), a T-independent antigen, were not affected by intracoelomic treatment with CGN. Intravenous pretreatment with CGN did not alter antibody responses to SRBC and BA given by the same route.

Animals↗
PubMed1986

Influence of ochratoxin A and vanadium on various parameters in growing chicks.

The effects of ochratoxin A (OA) and vanadium (V) singly and in combinations, at levels that could be encountered under field conditions, were determined in male Leghorn chicks. The chicks were fed a control diet containing the following additives: none; 12.5 mg V/kg; 25.0 mg V/kg; 2.5 mg OA/kg; 2.5 mg OA plus 12.5 mg V/kg; and 2.5 mg OA plus 25.0 mg V/kg. These data show that V, singly at levels of 12.5 or 25.0 mg/kg of diet, did not adversely affect body weight gain at 1, 2, 3, or 4 weeks of age. Body weight gains of the chicks receiving the diets containing OA singly were significantly lower than the controls except during the 1- to 7-day period. Body weight gains of chicks receiving the OA in combination with either level of V were significantly lower than any of the other groups during the 1- to 7- and 22- to 28-day periods. The quantity of feed required per unit of gain was increased slightly by the addition of OA at 2.5 mg/kg and the addition of V at 12.5 or 25.0 mg/kg and, to a greater extent, by the OA-V combinations. The relative liver and kidney weights were higher in the groups receiving OA singly or in combination with V. When compared to the controls, relative gizzard weights were significantly higher in the two combination groups; whereas the relative proventriculus weights were significantly higher only in the group receiving the 2.5 mg OA plus 25.0 mg V/kg combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Toxicity of ochratoxin A and vanadium to growing chicks.

The effects of ochratoxin A (OA) and vanadium (V), singly and in combination, were determined in male Leghorn chicks from 1 to 28 days of age. The chicks were fed a control diet containing the following additives: A) none; B) 2.5 mg OA/kg; C) 50 mg V/kg; D) 2.5 mg OA plus 50 mg V/kg. These data show that body weight gains were significantly reduced by OA and V singly, and a toxicity-enhancing synergism exists between OA and V, which caused a further reduction in performance. The OA-V combination caused a significant increase in the relative weights of the liver, kidney, gizzard, and proventriculus and a significant decrease in the relative weights of the bursa of Fabricius. This decrease in bursal weight was due to atrophy of lymphoid follicles as indicated by the increase in the histologic lesion score. Uric acid in serum was increased, and albumin, calcium, and phosphorus were decreased in the OA-V combination group. There were also small but significant changes in the hematological parameters measured. Distribution of OA to the liver and kidney was not altered, nor was the distribution of V to the liver, kidney, or muscle tissue. Histologic lesions in kidneys were mild but were more prevalent in chicks in the OA-V combination group.

Animal Feed↗
PubMed1985

Performance of broiler progeny of breeder flocks vaccinated with inactivated oil emulsion malabsorption syndrome virus vaccine.

Broiler breeder pullets were vaccinated at 20 to 24 weeks of age with an inactivated, oil emulsion vaccine containing the CO8 strain of avian reovirus. The vaccination induced a high and uniform antibody response that peaked 4 to 5 months postvaccination and persisted up to 11 months postvaccination. Broiler production parameters in progeny of vaccinated breeders were compared weekly with parameters of the total broiler production. There was a consistent improvement in body weight at processing time and a reduction in total production cost in progeny of vaccinated parents. There was also a reduction of percent of parts condemned during the first part of the trial. There were no consistent differences in feed conversion or condemnation of whole carcasses. Progeny of vaccinated parents had reduced livability. This effect was interpreted to be due to the smaller egg size of young breeder flocks.

Animals↗
PubMed1985

Evaluation of cytopathologic changes induced in chicken tracheal epithelium by Mycoplasma gallisepticum in vivo and in vitro.

Changes in tracheal epithelial surfaces induced by Mycoplasma infection in vivo and in vitro included release of mucous granules followed by exfoliation of ciliated and nonciliated epithelial cells. Light microscopy, scanning electron microscopy, and transmission electron microscopy confirmed that the loss of cilia from individual cells was infrequent. Epithelial cells typically lost their intercellular connections, rounded up, exfoliated, and then lysed--giving rise to a population of cellular organelles, such as mitochondria and cilia intermixed with mucus to form the exudate found within the tracheal lumen. Repair of the epithelial surface was effected by basilar epithelial cells differentiating and filling in the spaces formed by exfoliated cells. These cells were hypertrophied, nonciliated at 14 days after infection in vivo, and covered with microvilli. In sectioned material obtained during the infection, there was increasing epithelial thickness due to cellular infiltration and edema. Tracheal rings in vitro showed similar changes to those seen in vivo, except that exfoliation was more severe and occurred earlier. In addition, there were no cellular infiltration due to the lack of a vascular supply and only a small amount of mucus due to the smaller number of mucous cells available to release into the tracheal lumen.

Animals↗
PubMed1985

Variation in histology and growth characteristics of transplantable Marek's disease lymphomas.

A comparative study was made of the histology and growth characteristics of three different Marek's disease virus-induced transplantable lymphomas. These lymphomas were developed previously in related inbred chicken lines G-B1 and G-B2. The UG1 lymphoma was developed by serial i.m. passage in G-B1 chickens, and the UG2 and UG4 lymphomas were developed similarly in G-B2 chickens. While all three lymphomas grow progressively and cause rapid death in syngeneic hosts, differences in pathogenicity exist. For equivalent passage levels, the mean time to death of syngeneic chickens inoculated with 10(5) lymphoma cells was 10.8, 12.8, and 16.3 days postinoculation for UG1, UG2, and UG4, respectively. Histological features examined at the light microscopic level included tumor necrosis, muscle invasion, mitotic activity, and presence of heterophils (comparable to mammalian neutrophils). The UG2 lymphoma was characterized by a high degree of necrosis during all stages of growth. This feature was least pronounced in UG4 lymphomas, which generally grow to a much larger size than UG1 or UG2 lymphomas. Vascular invasion was a feature of UG2 lymphoma cells in skeletal muscle and may account for the necrosis. The UG2 cells, which are somewhat larger than UG4 cells, occasionally contained cytoplasmic vacuoles. While the number of heterophils was highest in early stages of UG2 tumors, the role of these cells is unclear. The findings provide the basis for utilizing the transplantable lymphomas as a model to study mechanisms underlying variable pathogenicity of malignant tumors.

Animals↗
PubMed1978

Comparative study of experimental inclusion body hepatitis of chickens caused by two serotypes of avian adenovirus.

Twenty 1-day-old specific-pathogen-free chickens each were given an intraabdominal inoculation of either a type-8 avian adenovirus, [AMG 5 (2a], or a type-5 avian adenovirus, inclusion body hepatitis virus (IBHV). The diseases produced were similar. High (60-100%) mortality and statistically significant depression of body weights occurred in both infections. There were necrotizing hepatitis and pancreatitis, lymphoid depletion in the spleen, bursa of Fabricius and thymus, hydropericardium, nephritis and enteritis. Intranuclear inclusions occurred in affected organs. Fluorescent-antibody staining, the Feulgen reaction for deoxyribonucleic acid and electron microscopic studies, as well as studies from the literature, indicated that basophilic inclusions consisted of assembled adenovirions.

Adenoviridae Infections↗
PubMed1977

In vivo function tests of the effect of tilorone and niridazole on cell-mediated immunity in chickens.

The need for effective, safe, specific cellular immune suppression in avian research led to the study of effects of tilorone and niridazole on cell-mediated immunity of chickens. Two in vivo tests for cell-mediated immunity function were used--the graft-vs-host (GvH) test and the delayed hypersensitivity (DH) test. Humoral immunity was evaluated by measuring natural hemagglutination (HA) titers against rabbit red blood cells. Intraperitoneal administration of tilorone to young chickens appeared to have severe toxic side effects and was of little value as an immune suppressant. Oral administration of tilorone to 6-week-old chickens caused DH suppression, but no marked effect was seen on GvH reactions or HA titers. Toxicosis appeared less severe. Oral administration of niridazole to 6-week-old birds caused nearly complete loss of GvH and DH reactivity but caused an increase in HA titers. General toxic effects of niridazole were not apparent.

Animals↗
PubMed1977

Dose response, prevention, and treatment of a transplantable lymphoid tumor.

Transplantable lymphoid tumor (TLT) cells in doses ranging from 10(2.43) to 10(6.80) were transplanted into 3-week-old chicks. A total of 199 chicks in 31 dosage groups was included in this 2-year study. Overall mortality was nearly 100% and analysis of the results revealed no significant differences in mortality among the groups. A significant (P less than 0.001) linear relationship existed between log10 of the TLT cell dose and mean survival time. Serum obtained from chickens which survived TLT growth, regression, and challenge inoculation was administered to chicks 4, 7, or 11 days before TLT induction. Of the chickens in each of these 3 groups, 80 to 100% survived compared with 0 to 20% in those given control serum. In chicks with actively growing TLT that were treated with 2 injections of plasma from TLT-resistant chickens, mean survival time was lengthened and survival was increased by 36%. Lymphocytes from resistant chickens or plasma od and survival was increased by 36%. Lymphocytes from resistant chickens or plasma or lymphocytes from control chickens did not affect survival time or percentage of survival. In the present study, results demonstrated a similarity to the TLT model studied 30 years ago and established the usefulness of this model in the study of serum immunotherapy.

Animals↗
PubMed1976

Histology of air sac lesions induced in chickens by contact exposure to Mycoplasma synoviae.

Chickens were housed when 1 day old with chickens experimentally infected with Mycoplasma synoviae. Air sacs from 16 of the 2-week-old and eight of the 3-week-old contact-exposed chickens were given gross lesion scores and embedded in glycol methacrylate for slide preparation. Histologic lesions in air sacs with gross scores of 0-2 were mild edema resulting in a two to eightfold increase in air sac thickness, capillary proliferation, and exudate consisting largely of heterophils and necrotic debris. Histologic lesions in air sacs with gross scores of 3 and 4 were marked hyperplasia of epithelial cells and diffuse infiltration of the air sac connective tissue by mononuclear cells. Nine of 10 air sacs with gross scores of 0 had no histologic evidence of inflammation. The most severe histologic lesions were in those air sacs with gross scores of 4. The glycol methacrylate procedure resulted in 2-mum sections with excellent cellular detail.

Air Sacs↗