Wildlife ecological risk assessment in the 21st century: Promising technologies to assess toxicological effects

Despite advances in toxicity testing and the development of new approach methodologies (NAMs) for hazard assessment, the ecological risk assessment (ERA) framework for terrestrial wildlife (i.e., air-breathing amphibians, reptiles, birds, and mammals) has remained unchanged for decades. While survival, growth, and reproductive endpoints derived from whole-animal toxicity tests are central to hazard assessment, nonstandard measures of biological effects at multiple levels of biological organization (e.g., molecular, cellular, tissue, organ, organism, population, community, ecosystem) have the potential to enhance the relevance of prospective and retrospective wildlife ERAs. Other factors (e.g., indirect effects of contaminants on food supplies and infectious disease processes) are influenced by toxicants at individual, population, and community levels, and need to be factored into chemically based risk assessments to enhance the "eco" component of ERAs. Regulatory and logistical challenges often relegate such nonstandard endpoints and indirect effects to postregistration evaluations of pesticides and industrial chemicals and contaminated site evaluations. While NAMs are being developed, to date, their applications in ERAs focused on wildlife have been limited. No single magic tool or model will address all uncertainties in hazard assessment. Modernizing wildlife ERAs will likely entail combinations of laboratory- and field-derived data at multiple levels of biological organization, knowledge collection solutions (e.g., systematic review, adverse outcome pathway frameworks), and inferential methods that facilitate integrations and risk estimations focused on species, populations, interspecific extrapolations, and ecosystem services modeling, with less dependence on whole-animal data and simple hazard ratios. Integr Environ Assess Manag 2024;20:725-748. © 2023 His Majesty the King in Right of Canada and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Toxicological effects assessment for wildlife in the 21st century: Review of current methods and recommendations for a path forward

Model species (e.g., granivorous gamebirds, waterfowl, passerines, domesticated rodents) have been used for decades in guideline laboratory tests to generate survival, growth, and reproductive data for prospective ecological risk assessments (ERAs) for birds and mammals, while officially adopted risk assessment schemes for amphibians and reptiles do not exist. There are recognized shortcomings of current in vivo methods as well as uncertainty around the extent to which species with different life histories (e.g., terrestrial amphibians, reptiles, bats) than these commonly used models are protected by existing ERA frameworks. Approaches other than validating additional animal models for testing are being developed, but the incorporation of such new approach methodologies (NAMs) into risk assessment frameworks will require robust validations against in vivo responses. This takes time, and the ability to extrapolate findings from nonanimal studies to organism- and population-level effects in terrestrial wildlife remains weak. Failure to adequately anticipate and predict hazards could have economic and potentially even legal consequences for regulators and product registrants. In order to be able to use fewer animals or replace them altogether in the long term, vertebrate use and whole organism data will be needed to provide data for NAM validation in the short term. Therefore, it is worth investing resources for potential updates to existing standard test guidelines used in the laboratory as well as addressing the need for clear guidance on the conduct of field studies. Herein, we review the potential for improving standard in vivo test methods and for advancing the use of field studies in wildlife risk assessment, as these tools will be needed in the foreseeable future. Integr Environ Assess Manag 2024;20:699-724. © 2023 His Majesty the King in Right of Canada and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Gas-Liquid Chromatographic Determination of T-2 Toxin in Plasma

The gas-liquid chromatographic method for the determination of T-2 toxin in plasma is described. The toxin is extracted with benzene, washed with aqueous sodium hydroxide, and chromatographed on a small Florisil column; the heptafluorobutyryl derivative is prepared by reaction with heptafluorobutyrylimidazole. The T-2 HFB derivative is chromatographed onOV-1 at 230°C and measured with an electron capture detector. Iso-T-2, an isomer of T-2 toxin, is added to samples as an internal standard before extraction. Recoveries averaged 98.0 ± 5.5% at levels ranging from 50 to 1000 ng/m L. The limit of detection is 25 ng/mL.

Transdisciplinary and social-ecological health frameworks-Novel approaches to emerging parasitic and vector-borne diseases

Ecosystem Health, Conservation Medicine, EcoHealth, One Health, Planetary Health and GeoHealth are inter-related disciplines that underpin a shared understanding of the functional prerequisites of health, sustainable vitality and wellbeing. All of these are based on recognition that health interconnects species across the planet, and they offer ways to more effectively tackle complex real-world challenges. Herein we present a bibliometric analysis to document usage of a subset of such terms by journals over time. We also provide examples of parasitic and vector-borne diseases, including malaria, toxoplasmosis, baylisascariasis, and Lyme disease. These and many other diseases have persisted, emerged or re-emerged, and caused great harm to human and animal populations in developed and low income, biodiverse nations around the world, largely because of societal drivers that undermined natural processes of disease prevention and control, which had developed through co-evolution over millennia. Shortcomings in addressing drivers has arisen from a lack or coordinated efforts among researchers, health stewards, societies at large, and governments. Fortunately, specialists collaborating under transdisciplinary and socio-ecological health umbrellas are increasingly integrating established and new techniques for disease modeling, prediction, diagnosis, treatment, control, and prevention. Such approaches often emphasize conservation of biodiversity for health protection, and they provide novel opportunities to increase the efficiency and probability of success.

One health-Transdisciplinary opportunities for SETAC leadership in integrating and improving the health of people, animals, and the environment

One Health is a collaborative, transdisciplinary effort working locally, nationally, and globally to improve health for people, animals, plants, and the environment. The term is relatively new (from ∼2003), and it is increasingly common to see One Health included by name in interinstitutional research partnerships, conferences, communications, and organizational frameworks, particularly those championed by the human health and veterinary medical communities. Environmental quality is arguably the least developed component within the One Health framework, but can be guided by expertise within the Society of Environmental Toxicology and Chemistry (SETAC). Despite SETAC's long history of tripartite (academic, government, business) interdisciplinary environmental science activities, the term "One Health" is seldom used in SETAC communications (i.e., many of SETAC's activities are guided by One Health, but it is called by other names in SETAC's journals, newsletters, and presentations). Accordingly, the objective of this Focus article is to introduce the One Health concept to the SETAC membership. The article discusses the origins, evolution, and utility of the One Health approach as an organizational framework and provides key examples of ways in which SETAC expertise can benefit the One Health community. The authors assert that One Health needs SETAC and, to be most effective, SETAC needs One Health. Given that One Health to date has focused too little on the environment, on ecosystems, and on contaminants, SETAC's constructive involvement in One Health presents an opportunity to accelerate actions that will ultimately better protect human and ecosystem health. Environ Toxicol Chem 2016;35:2383-2391. © 2016 SETAC.

One health and cyanobacteria in freshwater systems: animal illnesses and deaths are sentinel events for human health risks

Harmful cyanobacterial blooms have adversely impacted human and animal health for thousands of years. Recently, the health impacts of harmful cyanobacteria blooms are becoming more frequently detected and reported. However, reports of human and animal illnesses or deaths associated with harmful cyanobacteria blooms tend to be investigated and reported separately. Consequently, professionals working in human or in animal health do not always communicate findings related to these events with one another. Using the One Health concept of integration and collaboration among health disciplines, we systematically review the existing literature to discover where harmful cyanobacteria-associated animal illnesses and deaths have served as sentinel events to warn of potential human health risks. We find that illnesses or deaths among livestock, dogs and fish are all potentially useful as sentinel events for the presence of harmful cyanobacteria that may impact human health. We also describe ways to enhance the value of reports of cyanobacteria-associated illnesses and deaths in animals to protect human health. Efficient monitoring of environmental and animal health in a One Health collaborative framework can provide vital warnings of cyanobacteria-associated human health risks.

The feline thyroid gland: a model for endocrine disruption by polybrominated diphenyl ethers (PBDEs)?

The role of polybrominated diphenyl ethers (PBDE) was investigated in the occurrence of feline hyperthyroidism (FH) by evaluating 15 PBDE congeners in serum from 62 client-owned (21 euthyroid, 41 hyperthyroid) and 10 feral cats. Total serum PBDE concentrations in euthyroid cats were not significantly different from those of hyperthyroid cats. Total serum PBDE in feral cats were significantly lower than in either of the groups of client-owned cats. Total serum PBDE did not correlate with serum total T4 concentration. Ten samples of commercial canned cat food and 19 dust samples from homes of client-owned cats were analyzed. Total PBDE in canned cat food ranged from 0.42 to 3.1 ng/g, and total PBDE in dust from 510 to 95,000 ng/g. Total PBDE in dust from homes of euthyroid cats ranged from 510 to 4900 ng/g. In dust from homes of hyperthyroid cats, total PBDE concentrations were significantly higher, ranging from 1100 to 95,000 ng/g. Dust PBDE and serum total T4 concentration were also significantly correlated. Estimates of PBDE exposures calculated from canned cat food and dust data suggest that domestic cats are primarily exposed through ingestion of household dust. These findings indicate further study of the role of PBDE is needed in the development of FH, which might identify the cat as a model and sentinel for humans with toxic nodular goiter (TNG).

Demasculinization and feminization of male gonads by atrazine: consistent effects across vertebrate classes

Atrazine is the most commonly detected pesticide contaminant of ground water, surface water, and precipitation. Atrazine is also an endocrine disruptor that, among other effects, alters male reproductive tissues when animals are exposed during development. Here, we apply the nine so-called "Hill criteria" (Strength, Consistency, Specificity, Temporality, Biological Gradient, Plausibility, Coherence, Experiment, and Analogy) for establishing cause-effect relationships to examine the evidence for atrazine as an endocrine disruptor that demasculinizes and feminizes the gonads of male vertebrates. We present experimental evidence that the effects of atrazine on male development are consistent across all vertebrate classes examined and we present a state of the art summary of the mechanisms by which atrazine acts as an endocrine disruptor to produce these effects. Atrazine demasculinizes male gonads producing testicular lesions associated with reduced germ cell numbers in teleost fish, amphibians, reptiles, and mammals, and induces partial and/or complete feminization in fish, amphibians, and reptiles. These effects are strong (statistically significant), consistent across vertebrate classes, and specific. Reductions in androgen levels and the induction of estrogen synthesis - demonstrated in fish, amphibians, reptiles, and mammals - represent plausible and coherent mechanisms that explain these effects. Biological gradients are observed in several of the cited studies, although threshold doses and patterns vary among species. Given that the effects on the male gonads described in all of these experimental studies occurred only after atrazine exposure, temporality is also met here. Thus the case for atrazine as an endocrine disruptor that demasculinizes and feminizes male vertebrates meets all nine of the "Hill criteria".

Effects of wetland vs. landscape variables on parasite communities of Rana pipiens: links to anthropogenic factors

The emergence of several diseases affecting amphibian populations worldwide has prompted investigations into determinants of the occurrence and abundance of parasites in frogs. To understand the spatial scales and identify specific environmental factors that determine risks of parasitism in frogs, helminth communities in metamorphic frogs of the northern leopard frog (Rana pipiens) were examined in relation to wetland and landscape factors at local (1 km) and regional (10 km) spatial extents in an agricultural region of Minnesota (USA) using regression analyses, ordination, and variance partitioning techniques. Greater amounts of forested and woody wetland habitats, shorter distances between woody wetlands, and smaller-sized open water patches in surrounding landscapes were the most consistently positive correlates with the abundances, richness, and diversity of helminths found in the frogs. Wetland and local landscape variables were suggested as most important for larval trematode abundances, whereas local and regional landscape variables appeared most important for adult helminths. As previously reported, the sum concentration of atrazine and its metabolite desethylatrazine, was the strongest predictor of larval trematode communities. In this report, we highlight the additional influences of landscape factors. In particular, our data suggest that anthropogenic activities that have resulted in the loss of the availability and connectivity of suitable habitats in the surrounding landscapes of wetlands are associated with declines in helminth richness and abundance, but that alteration of wetland water quality through eutrophication or pesticide contamination may facilitate the transmission of certain parasite taxa when they are present at wetlands. Although additional research is needed to quantify the negative effects of parasitism on frog populations, efforts to reduce inputs of agrochemicals into wetlands to limit larval trematode infections may be warranted, given the current high rates of amphibian declines and extinction events.

Ribeiroia ondatrae cercariae are consumed by aquatic invertebrate predators

Trematodes amplify asexually in their snail intermediate hosts, resulting in the potential release of hundreds to thousands of free-living cercariae per day for the life of the snail. The high number of cercariae released into the environment undoubtedly increases the probability of transmission. Although many individual cercariae successfully infect another host in their life cycle, most fail. Factors that prevent successful transmission of cercariae are poorly understood. Microcrustaceans and fish have been observed to eat cercariae of some species, although the possibility that predation represents a significant source of mortality for cercariae has been largely unexplored. We tested the cercariophagic activity of several freshwater invertebrates on Ribeiroia ondatrae, a trematode that causes limb deformities in amphibians. Individuals of potential predators were placed into wells of multiwell plates with 10-15 cercariae, and numbers of cercariae remaining over time were recorded and compared with numbers in control wells that contained no predators. Of the species tested, Hydra sp., damselfly (Odonata, Coenagrionidae) larvae, dragonfly (Odonata, Libellulidae), larvae, and copepods (Cyclopoida) consumed cercariae. In some cases, 80-90% of the cercariae offered to damselfly and dragonfly larvae were consumed within 10 min. In most cases, predators continued to consume cercariae at the same average rates when offered cercariae together with individuals of an alternate prey item. Hydra sp. ate fewer cercariae in these trials. Our findings suggest the need for field and laboratory studies to further explore the effects of predators on transmission of R. ondatrae to amphibian larvae. In addition, the results suggest that conservation of the biodiversity and numbers of aquatic predators may limit adverse impacts of trematode infections in vertebrate hosts.

Microcystin-LR and kinetics of cytoskeletal reorganization in hepatocytes, kidney cells, and fibroblasts

Microcystin-LR (MCLR) is a cyanobacterial hepatotoxin that inhibits protein phosphatases 1 and 2A. To characterize cytoskeletal changes over time, hepatocytes were incubated with the toxin at 13.3 microM for 0, 2, 4, 6, 8, 16, 32, or 64 minutes. Changes in the hepatocytes were compared to those in cultured kidney cells and skin fibroblasts incubated with the toxin at 133 microM for 0, 2, 4, 8, 12, 16, or 24 hours. Cells were fixed and incubated with rhodamine-conjugated phalloidin, or primary antibodies against beta-tubulin and either vimentin or cytokeratin intermediate filaments (IFs), followed by fluorescein-conjugated secondary antibodies. The number of affected cells per 400 counted (NAC) with alterations in a specific cytoskeletal element were determined at each time point. In fibroblasts as well as kidney cells, changes occurred first in IFs, followed by microtubules (MTs), and later microfilaments (MFs). In some hepatocytes, IFs were affected first, but after 16 minutes, the NAC with altered MTs exceeded the NAC with alterations in other cytoskeletal elements. In both hepatocytes and non-hepatocytes, IFs and MTs condensed and collapsed around the nucleus. MFs similarly collapsed, but some of the actin radiated outward, producing a star-like appearance. The similarity of the cytoskeletal changes induced by MCLR in hepatocytes and non-hepatocytes suggests a common mechanism of action. Differences among cell types in sequential cytoskeletal alterations may be due to differences in phosphorylation of intracellular proteins.

HEMATOLOGY, PLASMA BIOCHEMISTRY, AND ANTIBODIES TO SELECT VIRUSES IN WILD-CAUGHT EASTERN MASSASAUGA RATTLESNAKES (SISTRURUS CATENATUS CATENATUS) FROM ILLINOIS

During the 2004 field season, blood was collected from Eastern massasauga rattlesnakes (Sistrurus catenatus catenatus) in the Carlyle Lake (Carlyle, Illinois, USA) and Allerton Park (Monticello, Illinois, USA) populations to derive baseline complete blood count and plasma biochemistry data and to assess the prevalence of antibodies to West Nile virus (WNV) and ophidian paramyxovirus (OPMV). Massasaugas were located for sampling through visual encounter surveys. Body weight, snout-vent length, total protein, globulins, sodium, and potassium were normally distributed among the survey population. Aspartate aminotransferase, creatine kinase, albumin, calcium, uric acid, white blood cell count, heterophils, lymphocytes, monocytes, eosinophils, and basophils were non-normally distributed within these animals. Female snakes had significantly shorter tail lengths; lower blood glucose, packed cell volumes, and absolute azurophil counts; and higher plasma calcium and phosphorus concentrations than did males. None of the snakes tested (n=21) were seropositive for WNV, whereas all (n=20) were seropositive for OPMV.

Fate of tritiated didemnin B in mice: excretion and tissue concentrations after an intraperitoneal dose

Didemnin B has undergone trials in cancer patients, and has antiviral and immunosuppressive properties. [(3)H]didemnin B was administered intraperitoneally (i.p.) to mice at 320 or 1280 microg/kg. Urine and feces were collected until 168 h, at which time the mice were killed and tissues collected. Additionally, [(3)H]didemnin B was given i.p. at 320 microg/kg, and mice were killed at 1-120 h post-dosing. Radiolabel increased rapidly in blood then rapidly declined. Most radiolabel in urine, feces and tissues represented parent compound. Concentrations of [(3)H]didemnin B were greatest in the liver > gallbladder > lower digestive tract congruent with pancreas > spleen > kidney congruent with adipose tissue congruent with urinary bladder with urine. The pancreas had the longest terminal half-life of the tissues and the highest radioactivity at 7 days. Intermediate concentrations were in the duodenum congruent with jejunum > lung > iliopsoas > stomach congruent with testes congruent with skin > heart. Low concentrations were in the humerus congruent with femur congruent with quadriceps congruent with triceps >> brain. Fecal excretion accounted for 45.9%-58.3% of the dose and declined after 24 h, followed by an increase, suggesting possible enterohepatic recycling or an impact of circadian rhythms. Urinary excretion accounted for 18.4%-25.2% of the dose, but was minimal after 24 h. The concentrations were highest in organs previously found to be sensitive in animals and humans. Didemnin B should be evaluated in animal models for treatment of pancreatic cancer.

Intersexuality and the cricket frog decline: historic and geographic trends

Exposure to anthropogenic endocrine disruptors has been listed as one of several potential causes of amphibian declines in recent years. We examined gonads of 814 cricket frogs (Acris crepitans) collected in Illinois and deposited in museum collections to elucidate relationships between the decline of this species in Illinois and the spatial and temporal distribution of individuals with intersex gonads. Compared with the preorganochlorine era studied (1852-1929), the percentage of intersex cricket frogs increased during the period of industrial growth and initial uses of polychlorinated biphenyls (PCBs) (1930-1945), was highest during the greatest manufacture and use of p,p-dichlorodiphenyltrichloroethane (DDT) and PCBs (1946-1959), began declining with the increase in public concern and environmental regulations that reduced and then prevented sales of DDT in the United States (1960-1979), and continued to decline through the period of gradual reductions in environmental residues of organochlorine pesticides and PCBs in the midwestern United States (1980-2001). The proportion of intersex individuals among those frogs was highest in the heavily industrialized and urbanized northeastern portion of Illinois, intermediate in the intensively farmed central and northwestern areas, and lowest in the less intensively managed and ecologically more diverse southern part of the state. Records of deposits of cricket frog specimens into museum collections indicate a marked reduction in numbers from northeastern Illinois in recent decades. These findings are consistent with the hypothesis that endocrine disruption contributed to the decline of cricket frogs in Illinois.

Prevalence of skeletal and eye malformations in frogs from north-central United States: estimations based on collections from randomly selected sites

Skeletal malformation rates for several frog species were determined in a set of randomly selected wetlands in the north-central USA over three consecutive years. In 1998, 62 sites yielded 389 metamorphic frogs, nine (2.3%) of which had skeletal or eye malformations. A subset of the original sites was surveyed in the following 2 yr. In 1999, 1,085 metamorphic frogs were collected from 36 sites and 17 (1.6%) had skeletal or eye malformations, while in 2000, examination of 1,131 metamorphs yielded 16 (1.4%) with skeletal or eye malformations. Hindlimb malformations predominated in all three years, but other abnormalities, involving forelimb, eye, and pelvis were also found. Northern leopard frogs (Rana pipiens) constituted the majority of collected metamorphs as well as most of the malformed specimens. However, malformations were also noted in mink frogs (R. septentrionalis), wood frogs (R. sylvatica), and gray tree frogs (Hyla spp.). The malformed specimens were found in clustered sites in all three years but the cluster locations were not the same in any year. The malformation rates reported here are higher than the 0.3% rate determined for metamorphic frogs collected from similar sites in Minnesota in the 1960s, and thus, appear to represent an elevation of an earlier baseline malformation rate.

Relationship of tadpole stage to location of echinostome cercariae encystment and the consequences for tadpole survival

The effect of echinostome infections on the survival of Rana pipiens tadpoles was examined in relation to developmental stage of tadpoles. Individual tadpoles of Gosner stages 25, 27, 32-33, and 37-39 were exposed to 1 of 4 levels of cercariae (0, 20, 50, or 100). Only tadpoles at stage 25, the earliest stage infected, died within a 5-day experimental period. This stage-specific mortality rate could be explained, in part, by the stage-specific location of encystment of cercariae, which was documented in a separate experiment. In accordance with kidney development, cercariae predominately encysted in the pronephroi during early stages of tadpole development (stages 25 through 31-32) and only in the mesonephroi and associated ducts at later stages (stages 37 through 46). As the mesonephros develops, renal capacity presumably increases. Thus, tadpoles died only when metacercariae concentrated in the functional portion of the kidney with the most limited renal capacity. As tadpoles aged, they also became less susceptible to infections. On average, 69.5% of cercariae that were exposed to stage 25-26 tadpoles successfully encysted. compared with only 8.4% of cercariae exposed to stage 37-38 tadpoles. Exposures of metamorphic frogs (poststage 46) to cercariae revealed that these individuals can become infected with echinostomes. Collectively, our data highlight the host stage-dependent dynamics of tadpole-echinostome interactions.

Toxic and feeding deterrent effects of native aquatic macrophytes on exotic grass carp (Ctenopharyngodon idella)

Declines of amphibians have been attributed to many factors including habitat degradation. The introduction of grass carp (Ctenopharyngodon idella) as a biological agent for aquatic plant control in ponds and lakes managed narrowly for human recreation has likely contributed to amphibian declines through massive plant removal and associated habitat simplification and thus degradation. This research examined the interactions among grass carp and three Midwestern aquatic plants (Jussiaea repens, Ranunculus longirostris, and R. flabellaris) that may be of value in rehabilitation of habitats needed by amphibians. The feeding preference study found that C. idella avoided eating both J. repens and R. longirostris. Ranunculus species studied to date contain a vesicant toxin called ranunculin that is released upon mastication. The study that compared the effects of R. flabellaris, J. repens and a control food administered by tube feeding to C. idella found significant lesions only in the mucosal epithelium of the individuals exposed to R.flabellaris. The avoidance by C. idella of J. repens and R. longirostris in the feeding preference study, and the significant toxicity of R. flabellaris demonstrated by the dosing study, indicate these plants warrant further examination as to their potential effectiveness in aquatic amphibian habitat rehabilitation.

Distribution of inorganic mercury in liver and kidney of beluga and bowhead whales through autometallographic development of light microscopic tissue sections

Inorganic mercury was localized through autometallography (AMG) in kidney and liver of free-ranging, subsistence-harvested beluga (Delphinapterus leucus: n = 20) and bowhead (Balaena mysticetrus: n = 5) whales. AMG granules were not evident in bowhead tissues, confirming nominal mercury (Hg) concentrations (range = 0.011 to 0.038 microg/g ww for total Hg). In belugas, total Hg ranged from 0.30 to 17.11 and from 0.33 to 82.47 microg/g ww in liver and kidney, respectively. AMG granules were restricted to cortical tubular epithelial cytoplasm in belugas with lower tissue burdens; whales with higher tissue burdens had granules throughout the uriniferous tubular epithelium. In liver, AMG granular densities differed between lobular zones, concentrating in stellate macrophages and bile cannalicular domains of hepatocytes. AMG granules aggregated in periportal regions in belugas with lower hepatic Hg concentrations, yet among whales with higher Hg, AMG granule deposition extended to pericentral and midzonal regions of liver lobules. Mean areas occupied by AMG granules correlated well with hepatic Hg concentrations and age. In beluga livers, AMG staining density was not associated with lipofuscin quantity (an index of oxidative damage). Occasionally, AMG granules and lipofuscin were colocalized, but more often were not, implying that Hg was not a prominent factor in hepatic lipofuscin deposition in belugas.

Concentrations and interactions of selected essential and non-essential elements in bowhead and beluga whales of arctic Alaska

In this study, we evaluated concentrations of twelve essential and non-essential elements (As, Cd, Co, Cu, Pb, Mg, Mn, Hg, Mo, Se, Ag, and Zn) in tissues of bowhead (Balaena mysticetus) and beluga (Delphinapterus leucas) whales from arctic Alaska (USA) and northwestern Canada. Tissue samples were collected between 1983 and 1997, mostly in 1995-97. The essential elements are reported to develop reference ranges for health status determination, and to help assess known or suspected interactions affecting toxicoses of cadmium (Cd) and mercury (Hg). In some tissues, Cd, Hg, and selenium (Se) were present at concentrations that have been associated with toxicoses in some domestic animals. Nevertheless, tissue levels of all elements were within ranges that have been reported previously in marine mammals. While mean Ag concentrations in beluga whale liver were relatively high (15.91 micrograms/g ww), Ag was not associated with hepatic Se levels or age, contrary to previous findings. Significant associations included: Cd with age, Zn, or Cu; Cu with age, Zn or Ag; and Hg with age, Se, Zn, or Cu. This study found hepatic Hg:Se molar ratios to be consistently lower than unity and different between species. Possible explanations for observed elemental correlations (i.e., interactions) and ancillary mechanisms of Cd and Hg detoxification are discussed.

Concentrations and interactions of selected essential and non-essential elements in ringed seals and polar bears of arctic Alaska

In this study, we evaluated concentrations of twelve essential and non-essential elements (As, Cd, Co, Cu, Pb, Mg, Mn, Hg, Mo, Se, Ag, and Zn) in tissues of ringed seals (Phoca hispida) and polar bears (Ursus maritimus) of arctic Alaska (USA). All samples were collected between 1995-97 in conjunction with subsistence harvests. The essential elements are reported to help develop reference ranges for health status determination and to help assess known or suspected interactions affecting toxicoses of cadmium (Cd) and mercury (Hg). In some tissues, Cd, Hg, and selenium (Se) were present at concentrations that have been associated with toxicoses in some domestic animals. Nevertheless, tissue levels of all elements were within ranges that have been reported previously in other pinnipeds and polar bears. Significant associations included: Cd with Zn or Cu; Cu with Zn or Ag; and Hg with Se, Zn, or Cu. This study found hepatic Hg:Se molar ratios to be lower than unity and different between the two species. Based upon significant differences in mean tissue elemental concentrations for polar bear versus ringed seal, we concluded that biomagnification factors (bear/seal) were significant for: Cu in liver and muscle; Pb in kidney; Se in kidney and muscle; Zn in liver and muscle; and Hg in liver. Possible explanations for observed elemental correlations (i.e., interactions) and ancillary mechanisms of Cd and Hg detoxification are discussed.

Microcystin-LR decreases hepatic and renal perfusion, and causes circulatory shock, severe hypoglycemia, and terminal hyperkalemia in intravascularly dosed swine

Cross-bred, anesthetized female swine were given intravascularly a lethal (72 microg/kg; n = 6) or toxic-sublethal (25 microg/kg; n = 6) dose of microcystin-LR (MCLR), from Microcystis aeruginosa, or the vehicle (n = 4). At the high dose, from 12 to 18 min after administration, central venous pressure and hepatic perfusion were significantly lower, and shortly thereafter, portal venous pressure was significantly higher and aortic mean pressure was significantly lower than controls. By 45 min postdosing, serum bile acids, lactate, potassium, and total bilirubin, as well as blood pO2, were significantly higher, while hematocrit, platelet count, and blood bicarbonate, pCO2, and base excess were significantly lower than controls. By 90 min, serum arginase, urea nitrogen, inorganic phosphorus, and creatinine were significantly higher, while glucose and blood pH were significantly lower than in controls. By 150 min, serum alanine and aspartate aminotransferases, alkaline phosphatase, lactate dehydrogenase, and creatinine phosphokinase activities were significantly higher than controls. At the low dose, significant differences from controls occurred in hemodynamic, organ perfusion, and serum chemistry parameters, but such changes generally took longer to occur and were of a lesser magnitude than at the high dose. Livers of the high-dose swine were swollen and dark red-purple, and exuded excessive blood on the cut surface. Based on increases in liver weight and liver hemoglobin, 38% of the total blood volume was lost into the liver. Terminally, all high-dose swine experienced hyperkalemia, and most had severe hypoglycemia. Death due to acute MCLR toxicosis in intravascularly dosed swine appears to result from severe intrahepatic hemorrhage, partial obstruction of blood flow through the liver, circulatory shock, severe hypoglycemia, and/or terminal hyperkalemia.

Organochlorine pesticide and polychlorinated biphenyl residues in Canada geese (Branta canadensis) from Chicago, Illinois

Breast muscle samples, with or without overlying adipose tissue and skin, were obtained from Canada geese collected in northeastern illinois while undergoing feather molt. Specimens were evaluated for contaminant concentrations to determine if they would be acceptable as human food provided through government-subsidized programs. Samples were baked, allowing fat to drip free, and assayed for persistent organochlorine pesticides and polychlorinated biphenyls. Residues of heptachlor epoxide, dieldrin, DDE and PCBs (as Arochlor 1248) were detected. The specimens contained relatively low concentrations of contaminants, such that US Department of Agriculture residue limits for meat were exceeded in only 1 sample. Baking of breast muscle without the overlying skin and adipose tissue resulted in reductions in concentrations of detectable compounds. Fewer samples baked with the skin attached had detectable concentrations of heptachlor epoxide, dieldrin and PCB then samples cooked without skin; however, the converse was true for DDE. Periodic monitoring for environmental contaminants such as PCBs, exclusion of geese from localities where samples have contaminants such as PCBs, exclusion of geese from localities where samples have contaminants at concentrations that exceed recommended dietary limits, the use of processing and/or cooking methods which remove large amounts of lipid, and advisories that provide information on known health risks are recommended if wild resident Canada geese from the Chicago area are provided as food for underprivileged humans.

Development of fumonisin-induced hepatotoxicity and pulmonary edema in orally dosed swine: morphological and biochemical alterations

The fumonisin (FB) mycotoxins induce liver injury in all species but induce fatal pulmonary edema (PE) only in pigs. They inhibit ceramide synthase in the sphingolipid biosynthetic pathway. To study the pathogenesis of PE, we examined the early events in the development of FB-induced PE and hepatotoxicity in pigs. Pigs were fed FB-contaminated culture material at 20 mg fumonsin B1 (FB1)/kg body weight/day. Groups of 4 pigs were to be euthanatized on 0, 1, 2, 3, 4, or 5 days after initial exposure to FB or when PE developed. Pigs developed PE beginning on day 3; none survived beyond day 4. Progressive elevations in hepatic parameters, including serum enzymes, bile acids, total bilirubin, and histologic changes, began on day 2. Early histologic changes in the lung (day 2) consisted of perivascular edema followed by interlobular and peribronchial edema. Ultrastructurally, alveolar endothelial cells contained unique accumulations of membranous material in the cytocavitary network beginning on day 2. Marked elevations in sphinganine, sphingosine, and their ratio began on day 1 for all tissues whether affected morphologically (lung, liver) or not (kidney, pancreas). The membranous material in endothelial cells may be accumulations of sphingoid bases with damage to the cytocavitary network. Thus, FB induces early elevations in sphingolipids and hepatic injury, followed by alveolar endothelial damage, which may be the critical event in the pathogenesis of PE in pigs.

Neutral red assay modification to prevent cytotoxicity and improve reproducibility using E-63 rat skeletal muscle cells

Cellular uptake of neutral red dye (NR) is currently used as an indirect measure of viable cells in cultures. We used E-63 rat skeletal muscle cells to identify causes of NR assay variability and to develop modifications that substantially reduce it. Three methods of NR preparation and/or addition to cells were used. When NR medium was prepared, incubated overnight, and filtered to remove precipitates, the amount of dye precipitated varied greatly. Coefficients of variation (CVs) in NR uptake were greater than 25% between assays. Higher NR concentrations, longer incubation times, increased pH, and decreased temperature promoted NR precipitation in media. NR media prepared and filtered just prior to use or direct addition of prefiltered NR stock solution to cell cultures resulted in much smaller CVs between assays. NR was cytotoxic to E-63 rat muscle and primary quail myoblasts in a time- and concentration-dependent manner. NR exposure to E-63 cells for greater than 1.25 and 2 hr at 157 or 127 microg/ml, respectively, was associated with swelling and rupture of lysosomes. By contrast, there was no evidence of cytotoxicity when E-63 cells were exposed to NR for 1 hr at either 127 or 157 microg/ml. Primary quail myoblasts developed lysosomal swelling and ruptured more rapidly than E-63 cells when exposed to NR at either 127 or 157 microg/ml. For confluent 10-day cultures of E-63 cells exposed to NR at 127 microg/ml for 1 hr, the CVs within assay and between assays were 3.3-3.9% and 5.1%, respectively. For similarly exposed, actively replicating 3-day cultures of E-63 cells, the CVs within and between assays were 6.2-9.6% and 2.4%, respectively. NR uptake by the E-63 cells was linear with respect to viable cell number.

Forms and prevalence of intersexuality and effects of environmental contaminants on sexuality in cricket frogs (Acris crepitans)

Cricket frogs (Acris crepitans) from several different sites in Illinois were collected to assess the effects of environmental contamination on the prevalence of intersex gonads. Of 341 frogs collected in 1993, 1994, and 1995, 2.7% were intersex individuals. There was no statistically significant relationship between the chemical compounds detected and cricket frog intersexuality. However, there was an association approaching significance (p = 0.07) between the detection of atrazine and intersex individuals. A comparison of reference sites with sites that had point polychlorinated biphenyl (PCB) and polychlorinated dibenzofuran (PCDF) contamination revealed a significant relationship between sex-ratio reversal and contamination with PCBs and PCDFs. The sex ratio of juvenile frogs studied from three sites with PCB and PCDF point contamination favored males over females, which was the opposite of the sex ratio in control ponds (p = 0.0007). The statistically significant correlation between organochlorine contamination and sex-ratio reversal suggests PCBs and PCDFs can influence cricket frog sexual differentiation. The current study suggests that in cricket frogs, sex ratios and the prevalence of intersex gonads are altered by environmental contamination.

Forms and prevalence of intersexuality and effects of environmental contaminants on sexuality in cricket frogs (Acris crepitans)

Cricket frogs (Acris crepitans) from several different sites in Illinois were collected to assess the effects of environmental contamination on the prevalence of intersex gonads. Of 341 frogs collected in 1993, 1994, and 1995, 2.7% were intersex individuals. There was no statistically significant relationship between the chemical compounds detected and cricket frog intersexuality. However, there was an association approaching significance (p = 0.07) between the detection of atrazine and intersex individuals. A comparison of reference sites with sites that had point polychlorinated biphenyl (PCB) and polychlorinated dibenzofuran (PCDF) contamination revealed a significant relationship between sex-ratio reversal and contamination with PCBs and PCDFs. The sex ratio of juvenile frogs studied from three sites with PCB and PCDF point contamination favored males over females, which was the opposite of the sex ratio in control ponds (p = 0.0007). The statistically significant correlation between organochlorine contamination and sex-ratio reversal suggests PCBs and PCDFs can influence cricket frog sexual differentiation. The current study suggests that in cricket frogs, sex ratios and the prevalence of intersex gonads are altered by environmental contamination.

Rhamnus cathartica (buckthorn) hepatocellular toxicity in mice

The toxicity of the plant Rhamnus cathartica was assessed in mice after the plant was identified as a potential cause of an idiopathic neurologic disease in horses. Another member of the Rhamnaceae family, Karwinskia humboldtiana, is neurotoxic to mammals and birds and can induce hepatic degeneration and necrosis. To investigate the toxicity of R. cathartica, a 34-day feeding trial in mice was conducted using a complete rodent diet with 0, 5, or 25% added R. cathartica. No clinical signs or gross lesions were seen, and all major tissues were histologically normal except the liver. The livers of mice fed R. cathartica had marked hepatocellular swelling. Results from periodic acid-Schiff reaction staining and from electron microscopy confirmed that the swelling was due to deposits of monoparticulate glycogen (beta particles) in the cytoplasm. Glycogen deposition is an uncommon toxic change in cells. Apparently, compound(s) in R. cathartica directly or indirectly interfered with glycogen metabolism (either glycogenesis or glycogenolysis). Mechanistic and chronicity studies with R. cathartica are needed to investigate the pathophysiology of the glycogen disturbance and to determine if hepatic injury progresses and if other organs will be injured.

Distribution of tritiated dihydromicrocystin in swine

The distribution of tritiated dihydromicrocystin [3H]2H-MCLR was studied in anesthetized specific-pathogen-free pigs. Two doses were administered i.m. and one dose was given via an isolated ileal loop. At 4 hr after i.v. administration of the toxin at 25 micrograms/kg, 64.6% of the total dose (%TD) was located in the liver, with smaller amounts distributed to the kidneys (1.2% TD), lungs (1.75% TD), heart (0.22% TD), ileum (0.13% TD) and spleen (0.04% TD). A similar distribution was found at 4 hr postdosing in pigs given 75 micrograms/kg, although the liver contained a lower fraction of the total dose, at 46.99% TD, and the kidneys had somewhat more, at 2.19% TD, than the low dose. At the high dose, the fractions of the amount given accounted for by the lungs (0.55% TD), heart (0.23% TD), ileum (0.20% TD) and spleen (0.07% TD) were similar to those at the low dose. The livers of the pigs given 75 micrograms/kg via the ileal loop, at 5 hr postdosing, contained 49.5% TD and the ileum had 33.94% TD. Smaller amounts were distributed to kidneys (1.04% TD), lungs (0.65% TD), heart (0.81% TD) and spleen (0.16% TD). The livers of both groups dosed at 75 micrograms/kg contained higher concentrations of toxin, but lower percentages of the total dose, than the livers of pigs dosed at 25 micrograms/kg. Larger increases in serum arginase in the two 75 micrograms/kg groups were associated with histological evidence of more severe liver damage than at the 25 micrograms/kg dose. Analysis of radiolabeled compounds from hepatic tissue using fast atom bombardment mass spectrometry determined that the primary constituent was [3H]2H-MCLR, but two minor radioactive components were also isolated. These findings indicate that [3H]2H-MCLR is rapidly concentrated in the liver of swine, whether given i.v. or via an isolated ileal loop, that at extremely toxic doses uptake is slowed, and that it is as toxicologically active as the parent compound.

Toxicokinetics of tritiated dihydromicrocystin-LR in swine

The toxicokinetics of tritiated dihydromicrocystin-LR ([3H]2H-MCLR) were studied in anesthetized, specific-pathogen-free pigs. Pigs were dosed with radiolabeled plus non-labeled 2H-MCLR at 25 or 75 micrograms/kg i.v., or via an isolated ileal loop at 75 micrograms/kg. The i.v. doses were rapidly removed from the blood. At either i.v. dose, more than half the radiolabel from [3H]2H-MCLR present in the blood at 1 min postdosing was cleared by 6 min. The blood clearance at the 75 micrograms/kg dose was slower than at the 25 micrograms/kg dose. Accordingly, at the high dose, the concentrations of the toxin in blood were disproportionately higher from 10 min after dosing until the study ended 4 hr later. The decreased clearance is presumably due to decreased elimination from the blood as a consequence of the hepatic injury that was observed histologically. Following administration of [3H]2H-MCLR at 75 micrograms/kg via the ileum, the maximal toxin concentration in blood was achieved at 90 min after dosing. At that time the [3H]2H-MCLR concentration in portal venous blood was 3.6 times higher than in peripheral venous blood. Although bile production varied, following i.v. dosing radioactivity was detected in bile as early as 12 min postdosing in one animal. This study demonstrated that [3H]2H-MCLR is rapidly removed from the blood of anesthetized swine and that excretion of the radiolabel into bile may begin within 30 min of dosing.

Alterations in microtubules, intermediate filaments, and microfilaments induced by microcystin-LR in cultured cells

Microcystin-LR (MCLR) is a cyanobacterial hepatotoxin that inhibits intracellular serine/threonine protein phosphatases causing disruption of actin microfilaments (MFs) and intermediate filaments (IFs) in hepatocytes. This study compared the effects of MCLR on the organization of MFs, IFs, and microtubules (MTs) in hepatocytes and nonhepatocyte cell lines and determined the sequence of toxin-induced changes in these cytoskeletal components. Rat renal epithelial cells and fibroblasts were incubated with MCLR at 100 or 200 microM for 6-18 hr. Rat hepatocytes in primary culture were exposed to the toxin at 1 or 10 microM for 2-64 min. Cells were fixed and incubated with primary antibodies against beta-tubulin, actin, and vimentin or cytokeratin IFs, followed by gold-labeled secondary antibodies with silver enhancement of the gold probe. The fraction of fibroblasts and hepatocytes with altered cytoskeletal morphology was evaluated as a function of MCLR dose and exposure time to assess the sequence of changes in cytoskeletal components. Changes in fibroblasts and some hepatocytes were characterized initially by disorganization of IFs, followed rapidly by disorganization of MTs, with the progressive collapse of both cytoskeletal components around cell nuclei. Many hepatocytes exhibited MT changes prior to effects on IF structure. Alterations in MFs occurred later and included initial aggregation of actin under the plasma membrane, followed by condensation into rosette-like structures and eventual complete collapse into a dense perinuclear bundle. The similarity of effects among different cell types suggests a common mechanism of action, but the independent kinetics of IF and MT disruption in hepatocytes suggests that there may be at least 2 sites of phosphorylation that lead to cytoskeletal alterations.

Effects of intravenous fumonisin B1 in rabbits: nephrotoxicity and sphingolipid alterations

Fumonisin B1 is hepatotoxic in all species, but nephrotoxicity has only been reported in rats. It is a specific inhibitor of sphinganine N-acyltransferase. Our objective was to determine the target organs for fumonisin toxicosis in the rabbit. We administered fumonisin B1 ( > 95% pure) intravenously to adult rabbits and examined selected clinical, biochemical, and histological parameters for up to 5 days. In a pilot study, rabbits were given fumonisin B1 at 1, 0.5, 0.3, 0.15, or 0 mg/kg daily for 4 or 5 days and then euthanized. Additional rabbits were given a single dose of fumonisin B1 at 1 mg/kg and euthanized on day 2 or 4. In the formal time-course study, rabbits were given a single dose of fumonisin B1 at 0 or 1.25 mg/kg and euthanized on days 1, 3, or 5. Rabbits given multiple doses of fumonisin B1 were lethargic and anorectic, and had decreased urine production. Liver- and renal-associated clinical chemistry parameters were elevated. Renal lesions consisted of severe proximal tubular necrosis. Liver lesions were variable and consisted of mild necrosis, hepatocyte vacuolation, and bile stasis. The sphinganine-to-sphingosine ratio, in both target and nontarget tissues, was markedly elevated in treated rabbits. A single dose of fumonisin B1 induced renal but not hepatic injury. Therefore, the target organs for fumonisin B1 toxicity in rabbits are kidney and liver, with the kidney being more sensitive.

Comparative pathology of microcystin-LR in cultured hepatocytes, fibroblasts, and renal epithelial cells

The cyanobacterial toxin microcystin-LR (MCLR) is a potent inhibitor of protein phosphatases 1 and 2A, and is selectively toxic to the liver in vivo and to isolated hepatocytes in vitro. This selectivity is believed to be due to toxin uptake via bile acid carriers. We investigated at the light and ultrastructural levels the effects of high concentrations of MCLR and long incubation times to determine in vitro whether fibroblasts and kidney cells (non-target cells) respond in the same manner as do hepatocytes (target cells) at low concentrations and short incubation times. Cultured rat skin fibroblasts (ATCC 1213) and rat kidney epithelial cells (ATCC 1571) were incubated with with MCLR at 133 microM for 1-24 hr. Lesions in these cells were compared with those in cultured hepatocytes incubated MCLR at 13.3 microM from 1 to 32 min. Lesions in hepatocytes, kidney cells, and fibroblasts were noted at 4 min, 1 hr, and 8 hr, respectively, after initial exposure to MCLR. Lesions in all three cell types progressed and included plasma membrane blebbing, loss of cell-to-cell contact, clumping and rounding of cells, cytoplasmic vacuolization, and redistribution of cytoplasmic organelles. Loss of microvilli, whorling of rough endoplasmic reticulum, dense staining and dilated cristae in mitochondria, and pinching off of membrane blebs were noted only in hepatocytes. Nuclear changes typical of apoptosis were observed only in fibroblasts and kidney cells. Similarities in responses of different cell types to MCLR exposure probably reflect a common biochemical mechanism of action, i.e., inhibition of protein phosphatases 1 and 2A as described by others.(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal and dose-response features in swine fed corn screenings contaminated with fumonisin mycotoxins

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium moniliforme and F. proliferatum, induces liver damage and pulmonary edema in swine. We examined the temporal and dose-response features of FB1 toxicosis in male weanling crossbred pigs fed nutritionally balanced diets, containing corn screenings naturally contaminated with fumonisins, for 14 days. Total fumonisins (FB1 and FB2) in diets 1 through 6 were assayed at 175, 101, 39, 23, 5, and < 1 ppm (below detectable concentrations), respectively. Clinical signs, serum biochemical alterations, and morphologic changes were evaluated. Pigs were weighed, and bled for hematologic and clinical chemistry evaluation on days 5 and 14. They were euthanized on day 14, or earlier if respiratory distress was observed. Respiratory distress developed in 3/5 pigs fed diet 1 between days 4 and 6 due to severe pulmonary edema and pleural effusion. Histologic evidence of hepatic injury was present in all pigs fed diets 1 and 2, 3/5 on diet 3, and 1/5 on diet 4. Serum bilirubin and cholesterol concentrations, gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and arginase (ARG) activities were elevated in pigs fed diets 1 and 2. Based on liver histopathology, the no observed adverse effect level (NOAEL) for fumonisin toxicity in swine was < 23 ppm total fumosins for the 14-day period. Based on regression analyses of the clinical chemistry profiles at 14 days, the NOAEL was < 12 ppm, with ALP being the most sensitive parameter. In conclusion, pulmonary edema occurred only at the highest fumonisin concentration (175 ppm), while liver damage occurred at much lower concentrations with a NOAEL of < 12 ppm.

Chemical study of the hepatotoxins from Microcystis aeruginosa collected in California

Four cyclic peptide toxins were purified and quantified from the aqueous extract of algal cell material utilizing high performance liquid chromatography, thin layer chromatography, and fast atom bombardment mass spectrometry. The cyclic peptide toxins appear to be similar structurally to hepatotoxins from previously identified blooms of the blue-green alga Microcystis aeruginosa.

Structural modifications imparting reduced toxicity in microcystins from Microcystis spp

A cyanobacterial (blue-green algal) bloom containing Microcystis aeruginosa (dominant), M. viridis, and M. wesenbergii, was collected from Homer Lake (Illinois, U.S.A.) in the summer of 1988 and microcystins were isolated. One microcystin of substantially reduced toxicity was isolated, together with ten hepatotoxic microcystins. The compound with reduced toxicity was nonlethal at 1 mg/kg (i.p. mouse) and was determined to have a (C3H7O2) mono-ester of the alpha-carboxyl on the Glu unit of microcystin-LR. The other nine microcystins apart from MCLR had approximate LD50S ranging from 97 micrograms/kg to 750 micrograms/kg.

Denatonium benzoate as a deterrent to ingestion of toxic substances: toxicity and efficacy

When ingested at 10 ppm by human beings, denatonium benzoate has an extremely bitter, unpleasant taste. The addition of denatonium benzoate to liquid dish detergents and orange juice reduces the amount ingested by children. The toxicity of denatonium benzoate is low with acute po LD50's in rats of 485-740 mg/kg. The use of bittering agents, such as denatonium benzoate, could reduce the ingestion of toxic substances by dogs, cats, other animals and children and warrants further investigation.

Alteration of tissue and serum sphinganine to sphingosine ratio: an early biomarker of exposure to fumonisin-containing feeds in pigs

Fumonisins are a group of naturally occurring compounds produced by the fungus Fusarium moniliforme. They are believed to be the etiologic agent of several animal diseases associated with consumption of corn-based feeds including porcine pulmonary edema. Recently it was shown in vitro that fumonisins are specific inhibitors of sphingosine and sphinganine N-acyltransferases. Inhibition of these enzymes in cultured cells results in the accumulation of free long chain sphingoid bases, specifically sphingosine and sphinganine, and the depletion of complex sphingolipids. In this study, tissues and serum from male SPF pigs fed a nutritionally balanced diet containing corn or corn screenings naturally contaminated with fumonisins for up to 14 days were analyzed for free sphingoid bases and complex sphingolipids. Total fumonisins (B1 and B2) in the diets were analyzed at 0 (< 1), 5, 23, 39, 101, and 175 ppm. Pulmonary edema only occurred at 175 ppm, while histologic liver damage was present at > or = 23 ppm, and serum liver enzymes were significantly elevated at > or = 101 ppm. The results of this study show that free sphinganine is elevated in liver, lung, and kidney, from pigs consuming feeds containing fumonisins at total fumonisin concentrations of 23 ppm or greater. Sphingosine is also elevated in a dose-dependent manner, but to a lesser extent than sphinganine. The consequence of this differential inhibition is that the ratio of sphinganine to sphingosine increases, suggesting that sphinganine N-acyltransferase is the preferred target for fumonisins. Elevation of free sphinganine and free sphingosine in serum paralleled the increases in tissues. Statistically significant increases in the ratio were observed at feed concentrations as low as 5 ppm total fumonisins and in pigs (at higher concentrations) in which other serum biochemistry parameters and tissue morphology were not altered. Elevated ratios were also observed in serum from pigs fed pure fumonisin B1. The sensitivity of the ratio indicates that it could serve as an effective biomarker for consumption of fumonisin-containing feeds. In addition, the data supports the hypothesis that inhibition of sphingosine and sphinganine N-acyltransferase plays an important role in the pathogenesis of animal diseases associated with consumption of feed containing fumonisins.

Characterization of fumonisin toxicity in orally and intravenously dosed swine

Fumonisin B1 (FB1), a recently identified mycotoxin produced by Fusarium moniliforme in corn, has been shown to cause death in swine due to pulmonary edema, an apparently species specific effect, and to interfere with sphingolipid metabolism in vitro. Here we characterize the toxicity of fumonisins, using female cross-bred swine weighing 6 to 13 kg, and present a hypothesis regarding the mechanism of fumonisin-induced pulmonary edema in swine. FB1 was given daily intravenously (IV) to pig 1 for 9 days for a total of 72 mg (7.9 mg/kg) and to pig 2 for 4 days for a total of 67 mg (4.6 mg/kg). Pig 3 (control) was given saline IV for 9 days. Corn screenings naturally contaminated with FB1 (166 ppm) and FB2 (48 ppm) were fed to pigs 4, 5, and 6, and ground corn was fed to pigs 7 and 8 (controls). Pigs 4 and 7 were killed on day 5; pig 5 was found dead on day 6; and pigs 6 and 8 were killed on day 15. Pigs 4 and 5 had ingested 187 and 176 mg total fumonisins, respectively, while pig 6 had ingested 645 mg. Feed consumption had decreased in pigs fed corn screenings, with an additional sharp decrease prior to onset of clinical signs. Increases in serum liver enzymes, total bilirubin, and cholesterol were present, but electrocardiograms, heart rate, and body temperature were unaffected. Pigs dosed IV with FB1, developed mild intermittent respiratory abnormalities, while those fed screenings developed respiratory distress within 5 days. Mild interstitial pulmonary edema was observed in pig 1. Severe interstitial pulmonary edema, pleural effusion, and increased lung wet/dry weight ratio were observed in pigs 4 and 5. All pigs given fumonisin (either IV or orally) had hepatic changes characterized by hepatocyte disorganization and necrosis; pancreatic acinar cell degeneration was also observed. Ultrastructural changes in orally dosed swine included loss of sinusoidal hepatocyte microvilli; membranous material in hepatic sinusoids; and multilamellar bodies in hepatocytes, Kupffer cells, pancreatic acinar cells and pulmonary macrophages. Pulmonary intravascular macrophages (PIMs) contained large amounts of membranous material. Thus, the target organs of fumonisin in the pig are the lung, liver, and pancreas. At lower doses, slowly progressive hepatic disease is the most prominent feature, while at higher doses, acute pulmonary edema is superimposed on hepatic injury and may cause death. We hypothesize that altered sphingolipid metabolism causes hepatocellular damage resulting in release of membranous material into the circulation.(ABSTRACT TRUNCATED AT 400 WORDS)

2,4-D toxicosis.II: A pilot study of clinical pathologic and electroencephalographic effects and residues of 2,4-D in orally dosed dogs

English pointer dogs dosed po with encapsulated 2,4-dichlorophenoxyacetic acid (2,4-D) at 1.3, 8.8, 43.7, 175 or 220 mg/kg body weight failed to exhibit abnormalities in hematologic, serum biochemical, urinalysis, or electrocardiographic parameters. At the 3 lowest doses, no changes were noted in electro-encephalograms (EEGs). In the dog given 175 mg/kg, at 24 h postdosing mild sedation was accompanied by excessive slowing in the EEG with loss of low voltage fast activity. In the dog given 220 mg/kg, nonspecific alterations in the EEG suggestive of irritation and mild seizure activity was detected 7 h, but the EEG returned to normal by 24 h. A maximum 2,4-D concentration in serum of 1075 ppm was detected 5 h after a po dose of 220 mg/kg. A maximum 2,4-D, concentration in urine of 1792 ppm was detected 2 h after a po dose of 175 mg/kg, while 25 h after that dose kidney issue contained 271 ppm.

2,4-D toxicosis.III: An attempt to produce 2,4-D toxicosis in dogs on treated grass plots

Eighteen English pointer dogs were randomly assigned to 3 outdoor grass-plot enclosures (6/enclosure) uniformly sprayed once with either the 2,4-dichlorophenoxyacetic acid (2,4-D) dimethylamine formulation (DMA-4) at the maximum recommended application rate, DMA-4 at 4 times the maximum recommended application rate, or the DMA-4 vehicle alone at 4 times the maximum recommended application rate. A heavy rain shower occurred 24 h after application. The dogs were observed for clinical signs and evaluated using an electroencephalograph, electrocardiograph (lead I), and electromyograph prior to exposure, and either 1 or 7 d after continuous exposure. Clinical examination, hematologic and serum biochemical data were obtained, and serum, urine and kidney 2,4-D were quantified. Half of the dogs from each group were killed after 1 d of continuous exposure, while the other half were killed after 7 d. Gross postmortem and histologic examinations were conducted on each dog. No obvious 2,4-D effects were detected in any of the dogs.

Actin filament alterations in rat hepatocytes induced in vivo and in vitro by microcystin-LR, a hepatotoxin from the blue-green alga, Microcystis aeruginosa

The morphologic effects of microcystin-LR (MCLR) were examined in vitro and in vivo to identify the specific cell type(s) affected and to characterize the actin filament changes occurring in hepatocytes. Male Sprague Dawley rats were used for all studies. For in vitro studies, hepatic cells were isolated by collagenase perfusion of liver, while parenchymal cells (hepatocytes) and nonparenchymal cells were prepared by pronase digestion and metrimazide gradient centrifugation. Cell suspensions and and primary hepatocyte monolayer cultures were treated with MCLR at doses up to 10 micrograms/ml; cultured hepatocytes were also treated with phalloidin or cytochalasin B at a dose of 10 micrograms/ml; and rats were treated intraperitoneally with MCLR at 180 mg/kg. Cultured hepatocyte preparations and frozen liver sections were stained with rhodamine-labeled phalloidin for filamentous actin. In cell suspensions, MCLR did not affect nonparenchymal cells but caused rapid, progressive, blebbing of the plasma membrane in hepatocytes. In cultured hepatocytes, MCLR caused plasma membrane blebbing as well as marked reorganization of actin microfilaments. These alterations were dose and time dependent. Cultured hepatocytes treated with phalloidin or cytochalasin B also showed extensive plasma membrane blebbing and actin filament alterations; however, actin filament changes were morphologically distinct from those induced by MCLR. In vivo, MCLR-induced hepatocyte actin alterations occurred at the same time as, or slightly preceded, histologic changes that began 30 minutes after dosing. These studies suggest that early MCLR-induced morphologic changes occurring both in vivo and in vitro are due to alterations in hepatocyte actin filaments.