The comparative cytotoxicity of riddelliine in primary mouse, rat and chick hepatocytes

Dehydropyrrolizidine alkaloid (DHPA) producing plants commonly poison livestock, wildlife and humans. Poisoning occurs when DHPAs are ingested as feed or food, or when they contaminate medicinal or herbal products. Direct toxicologic comparison of individual DHPAs is essential to estimate their actual health risks. This has been problematic due to varying models and difficulties in DHPA isolation or synthesis. In contrast, the macrocyclic DHPA riddelliine is readily isolated and it has been used as a benchmark to characterize different models of toxicity and carcinogenicity. Following earlier work with immortalized cell lines, the objective of this study was to characterize the effect of riddelliine on primary mouse, rat and chick hepatocyte cultures with the aim of developing a suitable, sensitive model for assessing DHPA-related cytotoxicity. After establishing viable cultures, the hepatocytes were exposed for 24 hours to riddelliine (from 0.1µM to 1.2mM) and cytotoxicity (CT­­50) was estimated using a mitochondrial function assay (MTT). Despite a biphasic response, possibly attributable to a sub-population of resistant chick hepatocytes, chick hepatocyte cultures were highly sensitive (CT50 0.9 µM) to riddelliine cytotoxicity relative to rat (CT50 289 µM) and mouse (CT50 627 µM) hepatocytes. Chick, mouse and rat hepatocyte cytochrome P450 3A4 activities did not correlate with riddelliine-induced cytotoxicity. With further development to utilize the highly sensitive primary chick hepatocytes, this model may be useful to directly compare panels of DHPAs, including rare or difficult to isolate alkaloids

Broom Snakeweed Extracts Dosed to Late-Term Pregnant Cattle Do Not Cause Premature Parturition

Broom snakeweed [Gutierrezia sarothrae (Pursh) Britton and Rusby] and threadleaf snakeweed [G. microcephala (DC.) A. Gray] are found on many rangelands in western North America. Snakeweeds are generally unpalatable; however, animals will graze them when other forage is not available and there are field reports that pregnant cows that graze snakeweeds may abort calves. Subsequent feeding studies using fresh cut snakeweed, ground and gavaged into pregnant cattle have failed to reproduce abortions, though it was evident that at high doses snakeweed quickly damaged the rumen microflora resulting in severe rumen atony, bloating and acidosis. We report here an attempt to solvent extract the snakeweeds, mix the extracts with ground alfalfa hay, and test the extracts for abortifacient activity in late-term pregnant cattle. The dosed extracts again appear to be unable to reproduce snakeweed induced abortions in cattle. Extracts from snakeweed chemotype 1 plant appear to be quite toxic to the rumen and caused complete rumen stasis after 2-3 days. In contrast, cattle receiving chemotype 2 extracts were able to tolerate over twice the dosage as that given for chemotype 1 extracts. We conclude that broom snakeweed plants are unlikely to be directly responsible for cattle abortions observed in cattle grazing snakeweed infested rangelands. It is more likely that cattle may be affected by rumen toxicity and/or might suffer from poor nutritional factors given the lack of quality forage that might be available on rangelands with high snakeweed infestation

THE ISOLATION AND IDENTIFICATION OF STEROIDAL SAPOGENINS IN SWITCHGRASS

Switchgrass (Panicum virgatum L.) has been reported to be hepatotoxic, causing photosensitization in lambs and horses. In this study we show the presence of steroidal saponins in two samples of switchgrass that has been implicated in the poisonings of sheep and horses. After hydrolysis of the saponins, diosgenin was determined to be the major sapogenin in both switchgrass samples. We also confirmed the presence of diosgenin in kleingrass after hydrolysis of saponins extracted from it

North American Hard Yellow Liver Disease: An Old Problem Readdressed

Hard yellow liver disease or fatty cirrhosis periodically affects cattle, sheep, goats, pronghorn antelope (Antilocapra americana) and whitetail deer (Odocoileus virginianus texanus) within several Texas counties in the United States. Clinically it presents as chronic liver disease with progressive hepatic necrosis and fibrosis, icterus and liver failure. The damaged livers are yellow and many have multiple firm, often gritty foci that are scattered throughout all lobes. Early investigations included feeding studies using potential toxic plants, climate and forage studies, infectious disease surveys and various mycotoxin studies and analyses. None have definitively reproduced the disease or identified the inciting cause. However, the problem continues and recent outbreaks have allowed the collection of additional frozen tissues, and numerous paraffin tissue blocks and slides for additional studies. The objectives for this work are to evaluate and compare the microscopic changes, special histochemical studies, microbial and fungal surveys and chemical assays for dehyro-pyrrolizidine alkaloid (DHPA) metabolites of these additional cases with historical reports. These bovine livers had a spectrum of lesions including lipid degeneration and necrosis, eosinophilic granulomatous hepatitis, focal follicular lymphoid proliferation and chronic fibrosing hepatitis with dystrophic mineralization. No pyrrolizidine alkaloid metabolites were detected in any of the livers and select special stains did not reveal any fungal, bacterial or parasitic etiologies. The lack of findings and mixed histologic presentation suggest that this syndrome is a collection of chronic diseases probably of various etiologies. Earlier animal surveillance work is needed in endemic areas to better understand the etiology and pathogenesis of this syndrome

Pyrrolizidine Alkaloid– Containing Toxic Plants (\u3ci\u3eSenecio, Crotalaria, Cynoglossum, Amsinckia, Heliotropium, \u3c/i\u3e and \u3ci\u3eEchium\u3c/i\u3e spp.)

Many problematic pyrrolizidine alkaloid (PA)-containing plants are foreign invasive weeds that invade pastures, fields, and ranges, and contaminate feeds and food. Others are native plants that may increase or expand on field edges or in disturbed areas. Most are unpalatable, only becoming a problem for livestock when alternative forages are unavailable, or when they are included in hay and other harvested feeds. Human poisoning is most often a result of contaminated grain or flour, although several poisonings have resulted from the use of PA-containing herbal preparations. Major PA plants and their specific health-related characteristics are discussed individually

A study of the genetic alterations in the progression of plutonium-239-induced rat lung cancer

Specific molecular alterations have been detected in many neoplasms and their presence may be pivotal in neoplastic transformation. Our objective was to sequentially evaluate the molecular alterations in \sp{239}Pu-induced proliferative lesions in rat lungs. Three-hundred-sixty Fischer F344/N female rats were exposed by inhalation to a \sp{239}PuO\sb2 aerosol and one-hundred-forty control animals were exposed to a sham aerosol. Proliferative and neoplastic pulmonary lesions were evaluated by immunohistochemistry, in situ hybridization, Western blot immunochemistry, Northern and Southern hybridization, oligonucleotide hybridization, and direct nucleic acid sequencing for activation or altered expression of Ki-ras, TGF$\alpha$, EGFR, and p53. Specific Ki-ras point mutations were present in about 40% of the radiation-induced and spontaneous malignant neoplasms. We found similar mutation frequencies in adenomas and foci of epithelial hyperplasia. No Ki-ras mutations were identified in normal lung tissue. Ras expression in hyperplastic lesions and neoplasms was similar to that observed in normal pulmonary epithelia. Many pulmonary proliferative lesions and neoplasms had increased expression of TGF$\alpha$. Some of the same neoplasms also had increased expression of EGFR. TGF$\alpha$ was present in lavage fluid of normal and neoplastic lungs and normalized TGF$\alpha$ concentrations in lavages from lungs with squamous cell carcinomas were significantly higher than concentrations in lavages of normal lung. No alterations were found in expression or Southern blot analysis of p53. Preliminary sequence analysis suggests that 2-of-8 neoplasms examined have point mutations in the p53 gene. These findings suggest the following: (1) Ki-ras mutation, not alterations in ras expression, and increased TGF$\alpha$ expression are early lesions associated with many radiation-induced, proliferative pulmonary lesions. (2) Increased or concomitant expression of EGFR and TGF$\alpha$ may provide proliferative and neoplastic cells growth advantages and promote neoplastic progression. (3) Small numbers of neoplasms may have mutational alterations in the p53 gene. And (4) the frequency of these alterations suggests these are important components of radiation-induced pulmonary carcinogenesis. However, there were many neoplasms in which we did not detect altered expression or mutational activation of any of these genes, suggesting there are additional molecular lesions and transforming factors, that as yet, remain unidentified

Effects of Xenobiotics and Phytotoxins on Reproduction in Food Animals

The influence of natural toxicants and anthropogenic compounds on reproduction in food animals is significant in its economic impact, and the subject requires more research and further experimental substantiation. Confounding factors such as stress, nutritional status, season of the year, animal species involved, genetic variability, disease conditions, management factors, and so forth exacerbate the difficulty of making an accurate diagnosis and thereby may impede progress to improve reproductive performance on an individual operation. The interaction between the reproductive system and xenobiotics (reproductive toxicology) is a relatively new area of study and a subject of increasing interest, especially in the area of environmental exposures and potential work place toxicants affecting human health and reproduction.1 Much of the experimental literature about this subject comes from rodent models designed to replicate human exposure; however, the extrapolation to food-producing animals is limited at best. The list of compounds in this article with known effects on reproductive function is extensive and represents most classes of chemicals in the environment; however, this list is not intended to be exhaustive. Investigation of reproductive dysfunction, especially infertility, abortions, and teratogenesis, should center on a thorough examination of animal condition and health, management practices, and infectious agents while potential toxicants are sought. This method requires a systematic approach including individual animal and herd/ flock history, veterinary examination of individual animals, testing of blood, urine, feces, or tissues, gross and pathologic/histologic postmortem examination, and toxicologic screening of samples of feed and or tissue. In livestock production systems, these investigations are often limited by economics, and the extent of the battery of tests must be determined in consultation between the animal producer, veterinarian, and diagnostician. Reproductive dysfunction includes all facets of reproduction, and when such dysfunction occurs failure to conceive, abortion, stillbirths, and anomalous fetuses may result. Although the following discussion focuses on abnormal embryonic and fetal development (teratogenesis), many of the principles and methods outlined in this article may be used to investigate the other causes of reproductive dysfunction

THE ISOLATION AND IDENTIFICATION OF STEROIDAL SAPOGENINS IN SWITCHGRASS

Switchgrass (Panicum virgatum L.) has been reported to be hepatotoxic, causing photosensitization in lambs and horses. In this study we show the presence of steroidal saponins in two samples of switchgrass that has been implicated in the poisonings of sheep and horses. After hydrolysis of the saponins, diosgenin was determined to be the major sapogenin in both switchgrass samples. We also confirmed the presence of diosgenin in kleingrass after hydrolysis of saponins extracted from it

Livestock Poisoning With Pyrrolizidine-Alkaloid–Containing Plants (Senecio, Crotalaria, Cynoglossum, Amsinckia, Heliotropium, and Echium spp.)

The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 2020Legacy DOIs that must be preserved: 10.2458/azu_rangelands_v31i1_stegelmier

Toxicokinetics and pathology of plant-associated acute selenium toxicosis in steers

Sixteen of approximately 500 yearling steers died of acute selenium (Se) toxicosis after grazing on a Secontaminated range for only a few days. Field studies and chemical analyses identified the predominant toxic plant as western aster (Symphyotrichum ascendens, previously Aster ascendens), which contained over 4,000 ppm Se (dry weight). Several dead animals that were necropsied had acute severe myocardial necrosis characterized by edema and myocyte swelling, with hypereosinophilia, clumping, and coagulation of myocardial proteins. Whole blood from 36 surviving steers was collected and analyzed, and 10 steers with elevated Se concentrations were selected for close monitoring and clinical evaluations. Each steer was weighed, and serum, blood, liver, skeletal muscle, and hair were regularly collected after removal from the Secontaminated range. One animal that died 18 days after exposure was necropsied and exhibited severe multifocal myocardial fibrosis with extensive hepatic congestion, degeneration, and hemosiderosis. At 180 days postexposure, 2 of the 10 steers were euthanized, and tissue samples were collected. Both steers had rare, small fibrotic foci in their hearts. The Se elimination halflives from serum, whole blood, liver, and muscle of the recovering steers were 40.5 ± 8.2, 115.6 ± 25.1, 38.2 ± 5.0, and 98.5 ± 19.1 days, respectively. The Se concentration in hair reached a peak of 11.5 ± 5.3 ppm at 22 days postexposure. The findings indicate that cattle are sensitive to acute Se toxicosis caused by ingestion of Se-accumulator plants, with myocardial necrosis as the primary lesion. Some poisoned animals may develop congestive heart failure weeks after the toxic exposure, and in the current study, Se was slowly excreted requiring a relatively long withdrawal time