Thesis (MSc (Paravet Studies))--University of Pretoria, 2005. / Includes bibliographical references.

The pathogenesis of hepatotoxic and hepatocarcinogenic actions of the mycotoxin aflatoxin B1 (AFB1) involves initial bioactivation by microsomal cytochrome P450s (P450) to a reactive and electrophilic intermediate, exo-aflatoxin B1-8,9-epoxide (exo-AFBO). Poultry, especially turkeys, are extremely sensitive to AFB1, a condition associated with efficient epoxidation by P450s. The purpose of this research was to 1) discover and characterize the P450s in turkey liver responsible for AFB1 bioactivation, and 2) determine the relative importance of these P450s in turkey liver. Initial investigations led to the discovery of CYP1A5. We then identified CYP3A37, a human CYP3A4 homologue from turkey liver, which along with CYP1A5 plays an important role in the bioactivation of AFB1 to exo-AFBO. The E. coli-expressed CYP3A37 possessed striking similarities to human CYP3A4, in terms of its catalytic activities and the kinetics of AFB1 oxidation. After the discovery of CYP3A37, further research evaluated its relative importance to CYP1A5, with respect to the epoxidation of AFB1, to determine which of the homologues bioactivated relatively low "real world" AFB1 concentrations, reflective of the potential dietary exposure. Using antibodies directed to both the enzymes as tools in immuno-inhibition experiments, we determined that CYP1A5 contributes to about 98% of the exo-AFBO formation at the low AFB1 concentrations (0.1 µM), which led us to conclude that CYP1A5 is likely the dominant homologue involved in the extreme sensitivity of the turkeys to AFB1. CYP3A37 also efficiently epoxidated AFB1, but only at high concentrations of this mycotoxin, not likely to be achievable in turkey liver in vivo. Our research has helped shed light on the relative importance of CYP1A5 and CYP3A37 in the bioactivation of AFB1 to the toxic exo-AFBO, and thus on the mechanisms of the extreme sensitivity of turkeys to AFB1. Given that AFB1 is a ubiquitous component of corn-based poultry feed and contamination is practically unavoidable, we conducted further studies evaluating the chemopreventive action of probiotic bacteria, Lactobacillus, on AFB1 toxicity in turkeys. Probiotic bacteria are known to bind AFB1, thus reducing its bioavailability. A mix of probiotic bacteria provided protection against key endpoints of aflatoxicosis, like AFB1-induced reduction in body and liver weights. Our data demonstrate that Lactobacillus was protective against aflatoxicosis in turkeys, thus validating its use as a possible chemopreventive, thereby helping alleviate the significant annual losses to the poultry industry due to feed contamination by AFB1.

In the 19th century, halothane hepatitis became a sensitive and well-known subject in human anesthesiology due to the production of a noxious metabolite further discovered, trifluoroacetic acid. Subsequently, isoflurane, enflurane, and desflurane were also investigated for potentially causing hepatitis through the same metabolite. Sevoflurane, however, does not generate trifluoroacetic acid and is quickly conjugated and excreted. For more than four decades these anesthetics have been experimentally developed for intravenous injection by having added either a lipid or fluorocarbon-based carrier to produce general anesthesia with less drug and faster onset of action. The use of intravenous emulsified halogenated anesthetics as an alternative to inhalation brought contradictory findings, therefore they are still not utilized in the clinical settings of veterinary and human anesthesia. The high solubility of these anesthetic emulsions increases their tissue uptake, volume of distribution, and potency. By this means, the amount of anesthetic necessary to establish general anesthesia could be significantly reduced but would still carry the risk of causing hepatic toxicity. On the other hand, because the emulsified anesthetics have a higher tissue uptake and are liposoluble, they remain for longer periods in the cellular membrane providing cellular pre- and postconditioning effects by minimizing cellular deleterious responses to a critical environment. Emulsified isoflurane and sevoflurane are the most investigated anesthetics for this purposein the heart, brain, kidneys, liver, and central nervous system of laboratory animals and human volunteers. The focus of this study is to evaluate the cellular effects of the loaded-lipid emulsified isoflurane and sevoflurane at different concentrations on cultured primary canine hepatocytes considering their viability and apoptosis response. Specifically, the overall objective is to establish a basis for in vitro metabolism of these emulsified anesthetics on canine hepatocytes under normal oxygen tension and on canine hepatocytes exposed to extreme hypoxia (1% O2). Thus, this study is sectioned into three major chapters followed by conclusions and future studies to determine the safety and indication of these anesthetic formulations in canine hepatocytes to be further explored in the clinical setting with live animals.

Call number: LD2668 .T4 1984 C68 / Master of Science

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-04T23:14:49Z No. of bitstreams: 1 EXPEDITO KENNEDY ALVES CAMBOIM - TESE PPGMV 2012..pdf: 1710872 bytes, checksum: c527311a481ea2baaf5080340bd08c0c (MD5) / Made available in DSpace on 2018-09-04T23:14:49Z (GMT). No. of bitstreams: 1 EXPEDITO KENNEDY ALVES CAMBOIM - TESE PPGMV 2012..pdf: 1710872 bytes, checksum: c527311a481ea2baaf5080340bd08c0c (MD5) Previous issue date: 2012-11-09 / O objetivo deste trabalho foi isolar e identificar bactérias capazes de degradar fluoroacetato de sódio (FS) em amostras de solo e plantas, coletadas em áreas onde são encontradas plantas que contêm fluoroacetato tais como Mascagnia rigida e Palicourea aenofusca. As amostras foram cultivadas em meio mineral acrescido de 20 mmol L−1 de fluoroacetato de sódio. Através do sequenciamento do gene 16S rRNA os sete isolados foram identificados como Paenibacillus sp. (ECPB01), Burkholderia sp. (ECPB02), Cupriavidus sp. (ECPB03), Staphylococcus sp. (ECPB04), Ancylobacter sp. (ECPB05), Ralstonia sp. (ECPB06), e Stenotrophomonas sp. (ECPB07). Todos os sete isolados degradaram o FS contido no meio, alcançando uma taxa de degradação de 20 mmol L−1 de íon flúor. Dos isolados, seis são descritos pela primeira vez como capazes de degradar FS. No futuro, alguns destes microorganismos podem ser utilizados para estabelecer no rúmen uma população bacteriana capaz de degradar o fluoroacetato de sódio e proteger ruminantes de intoxicações por este composto.

Intra-articular glucocorticoid injections are commonly used to treat synovitis and osteoarthritis in horses. These agents are highly effective at relieving pain, swelling, and other symptoms of joint inflammation. The drugs also have therapeutic benefits by down regulating the expression of cytokines and protease enzymes that participate in the degradation of articular cartilage. However, detrimental effects on chondrocyte function and cell viability that is independent of osteoarthritis pathogenesis have been described and linked to glucocorticoid use. These side effects are both drug- and dose-dependent. This study tested the hypothesis that manufacture recommended dosage levels of methylprednisolone, betamethasone, and triamcinolone that are widely used in equine clinical practice are cytotoxic to articular chondrocytes. Drug-induced chondrocyte cytotoxicity was evaluated in monolayer cultures, cartilage explants, and equine fetlock joints. Total RNA was isolated from control and IL-1β stimulated primary chondrocytes and synoviocytes in culture. Changes in steady state mRNA for targeted gene transcripts related to inflammation and normal cell function were measured using reverse transcription and quantitative PCR. Inducible nitric oxide synthase activity was evaluated using nitrite production. Drug-induced chondrocyte cytotoxicity occurred at drug dosage levels frequently used in equine clinical practice. Both drug- and dose-dependent effects on chondrocyte and synoviocyte gene expression were observed. Maximum anti-inflammatory activities for the glucocorticoids were observed at in vitro concentrations below manufacturer-recommended levels. Results from this study suggest that lower glucocorticoid dose ranges for intra-articular therapy in horses should be validated to maximize the ratio of their therapeutically beneficial anti-inflammatory efficacy against detrimental effects on cell function and viability.

Bovine viral diarrhea (BVD) is an economically important disease of cattle. Calves persistently infected (PI) with the bovine viral diarrhea virus (BVDV) are a powerful agent for spread of the virus. A total of 24,423 southeast origin beef cattle comingled at three Warren County, Kentucky locations were tested from November 2007 to June 2010 for PI BVDV. A total of 97 head tested positive for PI BVDV, giving an average overall prevalence of 0.397%. Calves tested were subdivided into categories for additional calculations of dependence. A total of 8,910 were categorized by weight range upon testing (300-399 lbs, 400-499 lbs, 500-599 lbs, and 600-699 lbs). Prevalence does show a dependence on weight, with a higher prevalence found in lower weight classes, especially 300-399 lb calves (P<0.001). A total of 24,423 were categorized by season at time of testing (Fall, Winter, Spring, Summer). Prevalence does not show a dependence on season (P>0.05). Although eradication programs are not likely to be organized in the United States, several control programs have been developed. These findings can be used as additional support for PI testing of calves, especially those in lighter weight classes, as part of a BVD control program.

Kentucky 31 tall fescue (KY31) infected with the common toxic endophyte strains of Epichloё coenophiala produces toxic alkaloids that improve plant vigor, but cause numerous adverse effects in grazing animals. Researchers developed a variety of KY31 containing an alternative strain of E. coenophiala, termed novel endophyte (NE). Adverse health effects in mares have not been evaluated. Experiments in this thesis tested the hypothesis that the NE pasture does not cause adverse effects typically associated with KY31. Specific aims were to: 1) compare forage ergovaline concentrations between KY31 vs NE pastures; 2) evaluate palmar artery diameters in mares grazing KY31, NE, or orchardgrass-bluegrass (OGBG) pastures; 3) determine mare serum prolactin, estradiol, and progesterone concentrations associated with ingesting each pasture type over time; and 4) measure foaling outcomes, including percentage of live foals, foal birth weights, and foal growth rates. In 2015, six nonpregnant mares grazed KY31, six pregnant mares grazed NE and six pregnant mares grazed OGBG pastures. In 2016, eighteen mares were used; six mares grazed each pasture type. Study results showed that ergovaline did not appear to be produced by NE. Novel endophyte pasture did not have negative effects on palmar artery diameter, reproductive hormones, or foaling outcomes.

The objectives of this thesis were: (1) to evaluate the downregulation of the stallion hypothalamic-pituitary-gonadal (HPG) axis by a GnRH antagonist (acyline) based upon endocrine, seminal, testicular and behavioral effects, and (2) to assess recovery after treatment. Stallions were treated for 50 days (n=4; 330µg/kg acyline q 5d) and controls (n=4) received vehicle alone. Stallions were assessed pre-treatment and for 72 days after last treatment. Treatment induced declines (p<0.05) in FSH, LH, testosterone (to castrate levels) and estrone sulfate. Gonadotropins and testosterone returned to control values within nine days and estrone sulfate by 14 days after treatment discontinuation. Acyline-treated stallions failed to respond with FSH, LH and testosterone increase after exogenous GnRH stimulation (25µg gonadorelin, IV) compared to pre-treatment and control stimulation. Total sperm numbers and motility were reduced in acyline-treated stallions, as well as total seminal plasma protein and testicular volume (p<0.05). Time to ejaculation was increased in acyline group (p<0.5). Testicular, sexual behavior and most seminal parameters regained normal levels within 72 days after treatment ceased. Sperm output of acyline-treated stallions was regained within seven months after ending treatment. Acyline reversibly suppressed the stallion HPG axis, thus has potential for treating the androgen-dependent Equine-Arteritis-Virus carrier state and as behavior modulator.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-04T22:56:45Z No. of bitstreams: 1 AMÉLIA LIZZIANE LEITE DUARTE - TESE PPGMV 2012..pdf: 637832 bytes, checksum: 8a08b402027d942419996459bd5d8dfd (MD5) / Made available in DSpace on 2018-09-04T22:56:45Z (GMT). No. of bitstreams: 1 AMÉLIA LIZZIANE LEITE DUARTE - TESE PPGMV 2012..pdf: 637832 bytes, checksum: 8a08b402027d942419996459bd5d8dfd (MD5) Previous issue date: 2012 / Capes / Esta tese inclui três artigos sobre plantas tóxicas que causam ou são suspeitas de causarem morte súbita associada ao exercício em animais domésticos, intoxicação que se caracteriza por evolução superaguda, sem alterações cardíacas morfológicas significativas. O primeiro capítulo é uma revisão bibliográfica, detalhando recentes mudanças que ocorreram na identificação das diferentes espécies tóxicas de Amorimia (anteriormente referidas como Mascagnia) encontradas no Brasil e diferenciando-as quanto à epidemiologia e toxicidade. São descritos, também, os sinais clínicos, achados de necropsia e histológicos, diagnóstico e medidas de prevenção e/ou controle das intoxicações por Amorimia spp. No segundo capítulo é descrita, em caprinos, a indução de resistência à intoxicação por Amorimia septentrionalis, mediante administração repetida de doses não-tóxicas desta planta, e a transmissão da resistência de caprinos resistentes para caprinos susceptíveis através da transfaunação de líquido ruminal. Neste estudo, observou-se que os caprinos que recebiam doses não tóxicas e os que receberam a transfaunação foram mais resistentes que os que nunca ingeriram a planta previamente ou apenas coabitavam com os resistentes. O terceiro capítulo é uma comunicação científica que avaliou, experimentalmente, a toxicidade de Callaeum psilophyllum (sinônimo Mascagnia psilophylla) em coelhos e caprinos, assim como a possibilidade da ocorrência de intoxicação espontânea por esta planta em ruminantes. Foi comprovado que, em coelhos, C. psilophyllum causa um quadro clínico semelhante aos das plantas que causam morte súbita; no entanto, em caprinos, causa sinais digestivos, principalmente diarreia. Não há evidências de que C. psilophyllum cause intoxicações espontâneas em ruminantes. / This thesis includes three papers on toxic plants that cause or are suspected of causing sudden death associated with exercise in domestic animals, poisoning characterized by a per acute course without significant morphological heart changes. The first chapter is a literature review, detailing recent changes that have occurred in the identification of different species of toxic Amorimia (formerly referred as Mascagnia) found in Brazil. We also report the epidemiology, toxicity, clinical signs, necropsy and histologic findings, diagnosis, and prevention and control of the poisoning by Amorimia spp. The second chapter reports the induction of resistance to poisoning by Amorimia septentrionalis by the repeated administration of non toxic doses, and also by transfaunation of ruminal contents from resistant to susceptible goats. In this study, we observed that animals receiving non-toxic doses and transfaunation of ruminal content were more resistant than goats that never ingested the plant. The third chapter is a short communication that evaluated experimentally the toxicity of Callaeum psilophyllum (synonym Mascagnia psilophylla) in rabbits and goats, as well as the possibility of the occurrence of poisoning by this plant in ruminants. It was demonstrated that, in rabbits, this plant causes similar clinical signs than those caused by plants causing sudden death; however, in goats, C. psilophyllum causes digestive signs, mainly diarrhea. There is no evidence that C. psilophyllum causes spontaneous poisoning in ruminants.