Christina R. Wilson

Taxines: a review of the mechanism and toxicity of yew (Taxus spp.) alkaloids.

This literature review summarizes relevant information and recent progress regarding the scientific investigations of taxine alkaloids. Taxines are the active, poisonous constituents in yew plants (Taxus spp.) and have been implicated in animal and human poisonings. Several taxine alkaloids have been isolated and characterized through the use of high performance liquid chromatography, mass spectroscopy, and nuclear magnetic resonance. Recently, as a result of electrophysiological investigations, significant progress has been made with regard to their pharmacological and toxicological mechanisms of action. Current investigations suggest that their chief action is on cardiac myocytes resulting in heart failure and death in instances of animal and human poisoning.

A Retrospective Immunohistochemical Study Reveals Atypical Scrapie has Existed in the United Kingdom since at Least 1987

Atypical scrapie is a relatively recent discovery, and it was unknown whether it was a new phenomenon or whether it had existed undetected in the United Kingdom national flock. Before 1998, the routine statutory diagnosis of transmissible spongiform encephalopathy (TSE) in sheep relied on the presence of TSE vacuolation in the brainstem. This method would not have been effective for the detection of atypical scrapie. Currently, immunohistochemistry (IHC) and Western blot are commonly used for the differential diagnosis of classical and atypical scrapie. The IHC pattern of PrP d deposition in atypical scrapie is very different from that in classical scrapie using the same antibody. It is thus possible that because of a lack of suitable diagnostic techniques and awareness of this form of the disease, historic cases of atypical scrapie remain undiagnosed. Immunohistochemistry was performed on selected formalin-fixed, paraffin-embedded (FFPE) blocks of ovine brain from the Veterinary Laboratories Agency archives that were submitted for various reasons, including suspect neurological disorders, between 1980 and 1989. It was found that PrP d deposits in a single case were consistent with atypical scrapie. A method was developed to obtain a PrP genotype from FFPE tissues and was applied to material from this single case, which was shown to be AHQ/AHQ. This animal was a scrapie suspect from 1987, but diagnosis was not confirmed by the available techniques at that time.

Tremetone and Structurally Related Compounds in White Snakeroot (Ageratina altissima): A Plant Associated with Trembles and Milk Sickness

Ingestion of white snakeroot ( Ageratina altissima ) can cause trembles in livestock and milk sickness in humans. The toxicity has been associated with tremetol, a relatively crude, multicomponent lipophilic extract of the plant. In this study, 11 different compounds were isolated from white snakeroot-derived lipophilic extracts from 18 collections. Six of the isolated compounds have not been previously reported to be found in white snakeroot. High-performance liquid chromatography (HPLC) analysis indicated that there are three different chemotypes of white snakeroot from the plant samples analyzed. Elucidation of these chemotypes may explain the sporadic and unpredictable toxicity of white snakeroot to livestock and humans.

Toxicity of Yew (Taxus spp.) Alkaloids

Yew plant intoxication has been implicated in numerous animal and human poisoning cases. The poisonous nature of the yew plant ( Taxus spp.) is attributed to the presence of cardiotoxic taxine alkaloids. The mechanism of action of taxine alkaloids involves calcium channel antagonism in cardiac myocytes. Ultimately, these toxins cause cardiac dysrhythmias and rapid onset of adverse clinical signs, often ending in death. Diagnosis of yew poisoning is frequently based on history of exposure or identification of yew plant fragments in the digestive tract; however, improvements in analytical toxicology have made chemical confirmation of the taxine alkaloids in diagnostic cases possible. In suspect cases of yew intoxication, the primary treatment for exposed mammals primarily involves symptomatic and supportive care.

Species comparison of vitamin K1 2,3-epoxide reductase activity in vitro: kinetics and warfarin inhibition

A comparative study of vitamin K(1) 2,3-epoxide reductase (VKOR) activity in vitro was conducted across species. The apparent kinetic constants K(m app), V(max), and Cl(int app) were determined in bovine, canine, equine, human, murine, ovine, porcine, and rat hepatic microsomes. In addition to these enzyme kinetic constants, the IC(50) of warfarin for VKOR was determined in human, murine, porcine, and rat hepatic microsomes. Interspecies differences were observed when comparing the K(m app) (range, 2.41-6.46 microM), V(max) (range, 19.5-85.7 nmol/mg/min), and Cl(int app) (range, 8.2-18.4 ml/mg/min) values. Comparison of the IC(50) values of warfarin, across the four species tested, revealed a significant species difference between murine microsomes (0.17 microM) and rat microsomes (0.07 microM). Overall, this study indicates that there are interspecies differences regarding the in vitro reduction of vitamin K(1) 2,3-epoxide by the warfarin-sensitive enzyme vitamin K(1) 2,3-epoxide reductase. Significant differences between the IC(50) values of murine and rat microsomes suggest differences in the susceptibility of these species to warfarin.

Effects of storage conditions and hemolysis on vitamin E concentrations in porcine serum and liver.

Vitamin E (α-tocopherol) is an antioxidant vitamin important in protecting unsaturated fatty acids in lipid membranes from peroxidation. Variation in collection, storage, and shipping conditions of samples can potentially lead to breakdown of vitamin E prior to analysis. Therefore, the purposes of this project were 1) to determine the stability of vitamin E in refrigerated and frozen porcine liver and serum and 2) to evaluate the effects of red blood cell (RBC) hemolysis on porcine serum vitamin E concentrations. Porcine liver and nonhemolyzed serum were collected and stored refrigerated or frozen. Samples were analyzed for vitamin E immediately or on days 2, 3, 7, or 14. In addition, porcine RBCs were added to normal serum at concentrations from 1 × 106 to 1 × 109 RBC/ml and hemolyzed by freeze-thaw prior to analysis for vitamin E or products of lipid peroxidation.

Myocardial fibrosis associated with previous ingestion of yew (Taxus sp.) in a Holstein heifer evidence for chronic yew toxicity in cattle

Twenty-six 5-month-old Holstein calves were accidentally exposed to discarded branches of yew bushes (Taxus sp.). Several calves were found dead approximately 24 hr after exposure; however, a few calves died several days after exposure. One calf died 18 days after the initial exposure to Taxus sp. and was examined on the farm via necropsy. Gross lesions included ascites, and dilated and flaccid myocardial ventricles. Sections of formalin-fixed heart were submitted to the Indiana Animal Disease Diagnostic Laboratory for histopathologic examination; fresh rumen contents were submitted for toxicologic testing. Histologically, large areas of myocardium were replaced by fibrous connective tissue, suggesting previous myocardial necrosis. Taxus alkaloids were identified in the rumen contents using gas chromatography–mass spectrometry. Based on the clinical history, the gross and histologic lesions, the identification of Taxus alkaloids in the rumen contents, and lack of exposure to other known cardiotoxic agents, yew toxicity was considered the cause of death in this calf. Ingestion of taxines is known to cause acute and subacute toxicity in human beings and animals; however, a chronic clinical course and severe histologic lesions have not been previously associated with yew toxicity. Although only 1 calf was examined, this case suggests that yew toxicity can result in a prolonged clinical course in cattle and can cause histologic myocardial lesions.

Glycoproteomics Based on Lectin Affinity Chromatographic Selection of Glycoforms

Publisher Summary This chapter explores the use of structure-specific affinity selection as a way to look at a portion of a proteome. This can be done in several ways. One is to derivatize a specific functional group in proteins with an affinity selectable reagent that can be targeted with an affinity chromatography column. Avidin selection of proteins or peptides in which sulfhydryl or carbonyl groups have been derivatized with biotin is an example. A second approach is to directly select proteins or peptides based on shared structural features. For instance, direct selection of histidine containing peptides with copper-loaded immobilized metal affinity chromatography (Cu 2+ -IMAC) columns. Selection of phosphorylated peptides with either Fe 3+ -IMAC or Ga 3+ -IMAC columns is another. An additional powerful approach is to select a subset of proteins which have a common post-translational modification (PTM) related to the disease being studied. For example, lectins can be used to select for specific protein glycosylation associated with inflammation or cancer. Taken together there are more than a dozen ways to target structural features in proteomics.

Development of a gas chromatography-mass spectrometry technique to diagnose white snakeroot (Ageratina altissima) poisoning in a cow.

An 8-year-old, crossbred beef cow was referred to the Indiana Animal Disease Diagnostic Laboratory at Purdue University for a complete necropsy in October 2009. The cow was the sixth to die in a 7-day period. Affected cows were reportedly stumbling and became weak, excitable, and recumbent. Histologically, myonecrosis was severe in the skeletal muscles and mild in the heart and tongue. According to the submitter, exposure to a poisonous plant was suspected, and a plant specimen received from this case was identified as white snakeroot (Ageratina altissima). Using the white snakeroot specimen, a gas chromatography–mass spectrometry analytical method for the detection of tremetone and dehydrotremetone (2 components of white snakeroot) was developed. Both tremetone and dehydrotremetone were detected in the plant specimen. Dehydrotremetone was recovered from the liver, while neither component was recovered in the rumen content. In the past, because of the lack of standard reference material, the diagnosis of white snakeroot poisoning was based mainly on history of exposure and the presence of the plant in the rumen. The analytical method described herein can be used to document exposure to tremetone or dehydrotremetone in cases of suspected white snakeroot poisoning when coupled with the appropriate clinical signs and lesions.

Quantitative assessment of the percent fat in domestic animal bone marrow.

Abstract:  Measurement of the amount of fat in femoral bone marrow can provide a quantitative assessment of the nutritional status of an individual animal. An analytical method is presented for quantitating the percent fat in bone marrow from three domestic species: bovine, canine, and equine. In this procedure, fat is extracted from bone marrow using pentane, and the percent fat recovered is determined gravimetrically. Based on analyses from adult animals (normal body condition scores), the average percentage of fat in the bone marrow was >80%. In cases in which animals have been diagnosed as emaciated or exhibit serous atrophy of fat (body scores of 1 or 2), the femoral bone marrow fat was less than 20%. In domestic animals, bone marrow fat analysis can be a useful, quantitative measure that, when used in conjunction with all other data available, can support a diagnosis of starvation or malnutrition.