Dermal exposure to weathered MC252 crude oil results in echocardiographically identifiable systolic myocardial dysfunction in double-crested cormorants (Phalacrocorax auritus).

During the Deepwater Horizon Natural Resource Damage Assessment, gross morphologic cardiac abnormalities, including softer, more distensible musculature, were noted upon gross necropsy in hearts from laughing gulls and double-crested cormorants exposed to weathered MC252 crude oil. A species specific, echocardiographic technique was developed for antemortem evaluation of function that was used to evaluate and better characterize cardiac dysfunction. Control (n=12) and treated (n=13) cormorant groups of similar sex-ratio and ages were dermally treated with approximately 13ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages. This resulted in a low to moderate external exposure. Upon visualization and clinical assessment of the hearts of all test subjects, comprehensive diagnostic cardiographic measurements were taken twice, prior to oil application and after a 21day dermal oil exposure. Oil-treated birds showed a decrease in cardiac systolic function, as characterized by an increased left ventricular internal dimension-systole and left ventricular stroke volume as well as concurrent decreased left ventricular ejection fraction and left ventricular fractional shortening when compared to both control birds' and the treated birds' time zero values. These changes are indicative of a possible dilative cardiomyopathy induced by oil exposure, although further elucidation of possible collagen damage is recommended. Arrhythmias including tachycardia in two treated birds and bradycardia in all treated birds were documented, indicating further clinically significant abnormalities induced by MC252 oil that warrant further investigation. A statistically significant increase in free calcium concentration, important to muscular and neurologic function in treated birds was also noted. This study documents that weathered MC252 oil caused clinically significant cardiac dysfunction that could result in mortality and decrease recruitment.

Toxic effects of orally ingested oil from the Deepwater Horizon spill on laughing gulls.

The explosion of the Deepwater Horizon oil rig released, millions of gallons of oil into the environment, subsequently exposing wildlife, including numerous bird species. To determine the effects of MC252 oil to species relevant to the Gulf of Mexico, studies were done examining multiple exposure scenarios and doses. In this study, laughing gulls (Leucophaeus atricilla, LAGU) were offered fish injected with MC252 oil at target doses of 5 or 10mL/kg bw per day. Dosing continued for 27 days. Of the adult, mixed-sex LAGUs used in the present study, ten of 20 oil exposed LAGUs survived to the end of the study; a total of 10 of the oil exposed LAGUs died or were euthanized within 20 days of initiation of the study. Endpoints associated with oxidative stress, hepatic total glutathione (tGSH), oxidized glutathione (GSSG) and reduced glutathione (rGSH) significantly increased as mean dose of oil increased, while the rGSH:GSSG ratio showed a non-significant negative trend with oil dose. A significant increase in 3-methyl histidine was found in oil exposed birds when compared to controls indicative of muscle wastage and may have been associated with the gross observation of diminished structural integrity in cardiac tissue. Consistent with previous oil dosing studies in birds, significant changes in liver, spleen, and kidney weight when normalized to body weight were observed. These studies indicate that mortality in response to oil dosing is relatively common and the mortality exhibited by the gulls is consistent with previous studies examining oil toxicity. Whether survival effects in the gull study were associated with weight loss, physiologic effects of oil toxicity, or a behavioral response that led the birds to reject the dosed fish is unknown.

Reprint of: Overview of avian toxicity studies for the Deepwater Horizon Natural Resource Damage Assessment.

The Oil Pollution Act of 1990 establishes liability for injuries to natural resources because of the release or threat of release of oil. Assessment of injury to natural resources resulting from an oil spill and development and implementation of a plan for the restoration, rehabilitation, replacement or acquisition of natural resources to compensate for those injuries is accomplished through the Natural Resource Damage Assessment (NRDA) process. The NRDA process began within a week of the Deepwater Horizon oil spill, which occurred on April 20, 2010. During the spill, more than 8500 dead and impaired birds representing at least 93 avian species were collected. In addition, there were more than 3500 birds observed to be visibly oiled. While information in the literature at the time helped to identify some of the effects of oil on birds, it was not sufficient to fully characterize the nature and extent of the injuries to the thousands of live oiled birds, or to quantify those injuries in terms of effects on bird viability. As a result, the US Fish and Wildlife Service proposed various assessment activities to inform NRDA injury determination and quantification analyses associated with the Deepwater Horizon oil spill, including avian toxicity studies. The goal of these studies was to evaluate the effects of oral exposure to 1-20ml of artificially weathered Mississippi Canyon 252 oil kg bw-1 day-1 from one to 28 days or one to five applications of oil to 20% of the bird's surface area. It was thought that these exposure levels would not result in immediate or short-term mortality but might result in physiological effects that ultimately could affect avian survival, reproduction and health. These studies included oral dosing studies, an external dosing study, metabolic and flight performance studies and field-based flight studies. Results of these studies indicated changes in hematologic endpoints including formation of Heinz bodies and changes in cell counts. There were also effects on multiple organ systems, cardiac function and oxidative status. External oiling affected flight patterns and time spent during flight tasks indicating that migration may be affected by short-term repeated exposure to oil. Feather damage also resulted in increased heat loss and energetic demands. The papers in this special issue indicate that the combined effects of oil toxicity and feather effects in avian species, even in the case of relatively light oiling, can significantly affect the overall health of birds.

Overview of avian toxicity studies for the Deepwater Horizon Natural Resource Damage Assessment.

The Oil Pollution Act of 1990 establishes liability for injuries to natural resources because of the release or threat of release of oil. Assessment of injury to natural resources resulting from an oil spill and development and implementation of a plan for the restoration, rehabilitation, replacement or acquisition of natural resources to compensate for those injuries is accomplished through the Natural Resource Damage Assessment (NRDA) process. The NRDA process began within a week of the Deepwater Horizon oil spill, which occurred on April 20, 2010. During the spill, more than 8500 dead and impaired birds representing at least 93 avian species were collected. In addition, there were more than 3500 birds observed to be visibly oiled. While information in the literature at the time helped to identify some of the effects of oil on birds, it was not sufficient to fully characterize the nature and extent of the injuries to the thousands of live oiled birds, or to quantify those injuries in terms of effects on bird viability. As a result, the US Fish and Wildlife Service proposed various assessment activities to inform NRDA injury determination and quantification analyses associated with the Deepwater Horizon oil spill, including avian toxicity studies. The goal of these studies was to evaluate the effects of oral exposure to 1-20ml of artificially weathered Mississippi Canyon 252 oil kg bw-1 day-1 from one to 28 days or one to five applications of oil to 20% of the bird's surface area. It was thought that these exposure levels would not result in immediate or short-term mortality but might result in physiological effects that ultimately could affect avian survival, reproduction and health. These studies included oral dosing studies, an external dosing study, metabolic and flight performance studies and field-based flight studies. Results of these studies indicated changes in hematologic endpoints including formation of Heinz bodies and changes in cell counts. There were also effects on multiple organ systems, cardiac function and oxidative status. External oiling affected flight patterns and time spent during flight tasks indicating that migration may be affected by short-term repeated exposure to oil. Feather damage also resulted in increased heat loss and energetic demands. The papers in this special issue indicate that the combined effects of oil toxicity and feather effects in avian species, even in the case of relatively light oiling, can significantly affect the overall health of birds.

Testing of an oral dosing technique for double-crested cormorants, Phalacocorax auritus, laughing gulls, Leucophaeus atricilla, homing pigeons, Columba livia, and western sandpipers, Calidris mauri, with artificially weather MC252 oil.

Scoping studies were designed to determine if double-crested cormorants (Phalacocorax auritus), laughing gulls (Leucophaues atricilla), homing pigeons (Columba livia) and western sandpipers (Calidris mauri) that were gavaged with a mixture of artificially weathered MC252 oil and food for either a single day or 4-5 consecutive days showed signs of oil toxicity. Where volume allowed, samples were collected for hematology, plasma protein electrophoresis, clinical chemistry and electrolytes, oxidative stress and organ weigh changes. Double-crested cormorants, laughing gulls and western sandpipers all excreted oil within 30min of dose, while pigeons regurgitated within less than one hour of dosing. There were species differences in the effectiveness of the dosing technique, with double-crested cormorants having the greatest number of responsive endpoints at the completion of the trial. Statistically significant changes in packed cell volume, white cell counts, alkaline phosphatase, alanine aminotransferase, creatine phosphokinase, gamma glutamyl transferase, uric acid, chloride, sodium, potassium, calcium, total glutathione, glutathione disulfide, reduced glutathione, spleen and liver weights were measured in double-crested cormorants. Homing pigeons had statistically significant changes in creatine phosphokinase, total glutathione, glutathione disulfide, reduced glutathione and Trolox equivalents. Laughing gulls exhibited statistically significant decreases in spleen and kidney weight, and no changes were observed in any measurement endpoints tested in western sandpipers.

Embryo toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin to the wood duck (Aix sponsa).

We examined the sensitivity of the wood duck (Aix sponsa) embryo to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by injecting the toxicant into their eggs. Six groups of wood duck eggs (n = 35 to 211 per trial) were injected with 0 to 4600 pg TCDD/g egg between 2003 and 2005. Injections were made into yolk prior to incubation, and eggs were subsequently incubated and assessed weekly for mortality. Significant TCDD-induced mortality was not observed through day 25 (90% of incubation). Liver, heart, eye, and brain histology were generally unremarkable. Hepatic ethoxyresorufin-O-deethylase activity, a biomarker of dioxin-like compound exposure, was induced by 12-fold in the 4600 pg/g treatment relative to controls. The median lethal dose for chicken (Gallus domesticus) eggs we dosed identically to wood duck eggs was about 100 pg/g, similar to other assessments of chickens. Among dioxin-like compound embryo lethality data for 15 avian genera, the wood duck 4600 pg/g no-observed-effect level ranks near the middle. Because no higher doses were tested, wood ducks may be like other waterfowl (order Anseriformes), which are comparatively tolerant to embryo mortality from polychlorinated dibenzo-p-dioxins and dibenzofurans when exposed by egg injection.

Organophosphorus-induced neurotoxicity in the absence of neuropathy target esterase inhibition: the effects of triphenyl phosphine in the European ferret.

Abou-Donia et al. (in Toxicologist, Vol. 30, 1996) have reported that repeated oral administration of the organo-phosphorus compound triphenyl phosphine (TPPn) to the domestic chicken results in neuropathological changes in the spinal cord and peripheral nerves, accompanied by ataxia and paralysis. This study also noted that single doses of TPPn resulted in no inhibition of the enzymes neuropathy target esterase (NTE) and acetylcholinesterase (AChE). We undertook the present study to determine the biochemical, neuropathological, and clinical effects of single doses of TPPn in the European ferret, a mammalian species shown to be susceptible to organophosphorus-induced neurotoxicity. Eight 12-week-old ferrets were each injected subcutaneously with either 250 mg TPPn/kg bw or 500 mg TPPn/kg bw, or with the peanut oil/ethyl ether vehicle. Twenty-four h after dosing, the brains of 5 animals from each dose group were examined for NTE and AChE activities. The remaining 3 animals in each group were observed for 6 days for the development of clinical signs, after which their brains were processed for the presence of axonal degeneration using the Fink-Heimer silver impregnation method. Single injections of TPPn had no effect on the activities of whole-brain NTE or AChE 24 h after injection. The animals observed for clinical signs showed increasing trunk and hindlimb ataxia beginning 4 days after injection, culminating in fore-and hindlimb paralysis 6 days after injection. All brains exposed to either dose of TPPn showed widespread axonal degeneration extending from the brainstem and cerebellum into midbrain and forebrain areas. The results of this study support the hypothesis that TPPn-induced neurotoxicity is a separate and distinct form of organophosphorus-induced neurotoxicity not dependent on NTE inhibition, and therefore not a variant of organophosphorus-induced delayed neurotoxicity (OPIDN).

Degeneration patterns in the chicken central nervous system induced by ingestion of the organophosphorus delayed neurotoxin tri-ortho-tolyl phosphate. A silver impregnation study.

Exposure to certain organophosphorus compounds results in a neurological condition known as organophosphorus-induced delayed neurotoxicity (OPIDN). OPIDN is characterized clinically by an initial post-exposure delay period of 8-14 days after which signs of progressively developing ataxia and paralysis of the hindlimbs are observed. Although several studies have reported the presence of degeneration induced by organophosphorus delayed neurotoxins in specific central nervous system (CNS) structures, none have systematically examined CNS changes seen in the most frequently studied animal model for OPIDN--the domestic fowl. In the present study, we assessed the location and extent of anterograde degeneration in the chicken CNS following exposure to tri-o-tolyl phosphate (TOTP). All birds were dosed with 500 mg TOTP/kg body weight and killed after post-exposure periods of 1, 2, 3, or 4 weeks. The brains and spinal cords were processed with Fink-Heimer and Nissl stains. In the spinal cord, axon degeneration was noted in the fasciculus gracilis at cervical levels two weeks after exposure to TOTP. At 3 weeks, degeneration was also present in the cervical part of the dorsal spinocerebellar tract, in the lumbar part of the medial pontine-spinal tract, and in lamina VII in the lumbar ventral horn. In the medulla, moderate amounts of terminal and preterminal degeneration appeared at two weeks in the lateral vestibular, gracile, external cuneate, and lateral cervical nuclei. Lesser amounts of degeneration were noted in the solitary, inferior olivary, and raphae nuclei, in the medial, descending and lateral vestibular nuclei, and in the lateral paragigantocellular, gigantocellular, and lateral reticular nuclei. Fiber degeneration was also present in the medullary portions of the dorsal and ventral spinocerebellar tracts and spinal lemniscus. In the cerebellum, moderate amounts of terminal degeneration appeared in the deep cerebellar nuclei at one week while moderate mossy fiber degeneration was first noted in the granular layers of cerebellar folia I-V at 3 weeks. These results indicate (1) that, in the CNS, axonal and terminal degeneration resulting from TOTP intoxication appears to be confined to the spinal cord, medulla and cerebellum, (2) that the time of onset of degeneration in different fiber tracts and nuclei ranges from one to three weeks post-exposure, and (3) that the delay in the appearance of clinical signs of OPIDN is consistent with the delayed onset of degeneration in many of the affected CNS fiber systems.

Selective axonal and terminal degeneration in the chicken brainstem and cerebellum following exposure to bis(1-methylethyl)phosphorofluoridate (DFP).

Utilizing a variation of the Fink-Heimer method, we examined the extent and location of axonal and terminal degeneration within the chicken cervical spinal cord, brainstem and cerebellum resulting from a single subcutaneous dose of bis(1-methylethyl)phosphorofluoridate (DFP). The effects of DFP on the activities of whole-brain neuropathy target esterase (NTE) and cholinesterase (ChE) were also assessed as were the development and severity of clinical signs characteristic of organophosphorus-induced delayed neuropathy (OPIDN). Both whole brain NTE and ChE activities were maximally inhibited during the first 24 h post-exposure, showing gradual recovery over a period of 3 weeks. OPIDN clinical signs were not observed at 7 days post-DFP but progressed to severe ataxia by day 14 and paralysis by day 21. There was a relative absence of degeneration at 7 days, a dramatic increase in degeneration density at 14 days, and high density degeneration at both 21 and 28 days. Cervical spinal and medullary tracts containing axonal degeneration included the fasciculus gracilis, dorsal and ventral spinocerebellar tracts, spinal lemniscus, and the intramedullary portions of the glossopharyngeal and vagus nerves. Brainstem nuclei containing terminal degeneration included the lateral cervical, gracile-cuneate, external cuneate, and inferior olivary nuclei, the nucleus tractus solitarius, and the lateral and paragigantocellular lateral reticular nuclei. Mossy fiber degeneration was also present in cerebellar folia I-Vb. These results show that exposure to DFP causes axonal and terminal degeneration in ascending spinal tracts, brainstem nuclei and cerebellar folia associated with the transmission of somatic and visceral sensory information.

Exposure to triphenyl phosphite results in widespread degeneration in the mammalian central nervous system.

Previous studies in mammals have found that exposure to triphenyl phosphite results in cellular and axonal degeneration in the spinal cord and medulla. However, the nature of concomitant clinical signs suggested that other areas of the central nervous system might also be affected. In this study, the brains of ferrets receiving single subcutaneous injections of triphenyl phosphite were examined 8-12 days after dosing. Widespread areas of axonal, terminal, and somatic degeneration were seen in medullary, pontine, and thalamic nuclei. Extensive axonal and terminal degeneration were also noted in the cerebellar granule cell layer and in the cerebral cortical primary visual and sensorimotor areas. These data indicate that triphenyl phosphite exerts a potent neurotoxic effect, not only in the medulla and spinal cord, but also in the cerebellum, thalamus, and cerebral cortex.

Neurochemical alterations induced by manganese chloride in neonatal rats.

Male rats were exposed to manganese at doses of 1, 10, and 20 microg/g body weight/day from birth to day 24 post-partum. Animals were weighed and examined daily. The animals showed no visible signs of toxicity and exhibited normal weight gain. On day 25 the animals were killed by decapitation and the hypothalamic area and corpus striatum were removed and analyzed for several neurochemical components. Chronic manganese administration (10 and 20 microg/g) caused a significant reduction in the concentration of endogenous dopamine in the hypothalamic area. The concentration of endogenous norepinephrine in the hypothalamic area was unaffected at all levels of manganese administration. The depletion of dopamine induced by alpha-methyl-p-tyrosine was less in the hypothalamic area of chronic manganese-treated rats suggesting that dopamine turnover was reduced. No significant changes in neurochemical components occurred in the corpus striatum. Manganese at a dose of 20 microg/g caused a significant decrease in hypothalamic tyrosine hydroxylase activity and a significant increase in hypothalamic monoamine oxidase activity. The dosing regimen of 10 and 20 microg/g caused a significant elevation in tissue levels of manganese in both the hypothalamic area and corpus striatum. The results of this study indicate that minor alterations in the manganese content of the developing rat brain can lead to neurochemical alterations in specific brain regions.

An investigation into the effects of manganese and other divalent cations on tyrosine hydroxylase activity.

The activity of tyrosine hydroxylase (TH) was measured in homogenates of hypothalamic tissue and corpus striatum obtained from 24 day old rats. The addition of manganese to the preparations had no direct effect on TH activity in either brain region. Similarly, the addition of calcium, magnesium and lead at concentrations of 1.0 mM did not affect TH activity. Cadmium and zinc (1.0 mM) significantly reduced TH activity in both the hypothalamic area and corpus striatum. Iron (1.0 mM) significantly stimulated TH activity in the corpus striatum but did not affect TH activity in the hypothalamic area. At conentrations of 1.0 mM, neither disodium ethylenediamine tetra-acetic acid (EDTA) nor ethylene glycol bis (beta-amino-ethyl ether)-N,N'-tetraacetic acid (ECTA) affected directly TH activity in either brain region. Cyclic adenosine 3',5'-monophosphate (cAMP) at a concentration of 1.0 mM did not affect TH activity in either the hypothalamic area or corpus striatum. Results from these in vitro studies show clearly that manganese does not inhibit directly TH activity and that manganese does not compete with other physiologically important divalent cations to cause the reduction in TH activity seen in vivo after chronic exposure.

Delayed neurotoxic effects of bis (1-methylethyl) phosphorofluoridate (DFP) in the European ferret: a possible mammalian model for organophosphorus-induced delayed neurotoxicity.

This study examined the effects of the organophosphorus delayed neurotoxicant bis (1-methylethyl) phosphorofluoridate (DFP) on the central nervous system of the European ferret. Animals received subcutaneous injections of either 2 or 4 mg DFP/kg b.w. The extent of neuropathology was determined by the Fink-Heimer method, the activities of neuropathy target esterase (NTE) and cholinesterase (ChE) by enzyme assay methods, and the severity of clinical signs by a graded scale. In ferrets injected with 4 mg DFP/kg b.w., dense axonal and terminal degeneration were noted at 21 and 28 days post-DFP in the gracile, inferior vestibular, and lateral reticular nuclei, medial and dorsal accessory nuclei of the inferior olive, and in cerebellar folia I-IV. Degeneration was also noted in laminae VI-VII throughout most of the spinal cord and in the ventral motor nucleus at the level of the cervical enlargement. Both NTE and ChE activities were maximally inhibited at 6 hr post-dosing. NTE activity returned to control levels by 4 days while ChE activities reached control levels at 21 days. Clinical signs at 21 and 28 days post-DFP ranged from slight hindlimb weakness to severe ataxia or hindlimb paralysis. Less severe degeneration and clinical signs were noted in the animals exposed to 2 mg DFP/kg b.w. These findings indicate that the European ferret may be a model species for assessing the effects of organophosphorus delayed neurotoxicants.

Triphenyl phosphite-induced neuropathy in the avian forebrain: a silver impregnation study of the visual and auditory systems of the Japanese quail.

Single subcutaneous injections of triphenyl phosphite (TPP) (62.5-500 mg/kg body weight) were made in the Japanese quail (Coturnix coturnix japonica). The extent and density of resultant central nervous system degeneration were mapped by using the Fink-Heimer silver impregnation method to selectively impregnate degenerating axons and terminals. In addition to resulting in degeneration in the medulla and cerebellum, exposure to TPP also resulted in axonal and terminal degeneration in specific midbrain and forebrain nuclei and tracts related to the auditory and visual systems. Auditory system nuclei containing axonal and terminal degeneration included the lateral mesencephalic nucleus, pars dorsalis, the nucleus ovoidalis, and area L of Rose in the caudal neostriatum. Anterograde degeneration was also noted in nuclei and tracts related to the visual tectofugal system-the brachium of the superior colliculus, nucleus rotundus, pretectal nuclei, and the ectostriatum. Additional degeneration was noted in the paleostriatum primitivum, dorso-intermediate posterior thalamic nucleus, lateral spiriform nucleus, and the pedunculopontine tegmental nucleus, all of which are related to visuomotor control. These results indicate that in the Japanese quail, exposure to TPP yields anterograde degeneration in nuclei and tracts involved with the transmission and processing of higher order visuomotor, visual sensory, and auditory sensory information.

Organophosphorus-induced delayed neurotoxicity: a comparative study of the effects of tri-ortho-tolyl phosphate and triphenyl phosphite on the central nervous system of the Japanese quail.

The neurotoxic effects of single oral doses of tri-ortho-tolyl phosphate (TOTP) (500 mg/kg body weight) or single subcutaneous injections of triphenyl phosphite (TPP) (62.5-500 mg/kg body weight) were investigated in the Japanese quail (Coturnix coturnix japonica). Oral doses of TOTP resulted in no detectable clinical signs while injections of TPP resulted in mild ataxia to severe paralysis depending upon the dosage level. At 24 hr postdosing, whole-brain activity of neuropathy target esterase (NTE) was inhibited by 90% in birds exposed to TOTP and by 11-87% in birds injected with TPP. Oral doses of TOTP resulted in only sparse Fink-Heimer silver-impregnated degeneration in the white matter of the cerebellum with no degeneration noted in any other region of the brain. Injections of TPP resulted in widespread degeneration in large numbers of brainstem nuclei and tracts and in all cerebellar foliae and deep nuclei. These results indicate that the Japanese quail responds differentially to exposure to TOTP and TPP. Oral doses of TOTP do not result in clinical signs or in significant amounts of degeneration in the brain even though NTE activity is inhibited by 90%. In contrast, injections of TPP at higher dosage levels yield severe clinical signs, widespread axonal and terminal degeneration in the CNS, and significant inhibition of NTE activity. This sharp dichotomy in relative sensitivity to TOTP and TPP in the Japanese quail suggests that each compound may have its own unique effect on CNS structure and function. In addition, the relationship between levels of NTE inhibition and the onset of clinical signs or neuropathology remains unclear.

The effects of diisopropylphosphorofluoridate (DFP) on the ganglioside profile in the chicken (Gallus domesticus) hindbrain.

The ameliorative effect(s) of exogenous gangliosides on the development of organophosphorus ester-induced delayed neurotoxicity (OPIDN) suggests that administration of an organophosphorus delayed neurotoxicant could alter the endogenous ganglioside composition of nervous system tissue. To investigate this possibility, White Leghorn hens were injected subcutaneously with diisopropylphosphorofluoridate (DFP) at a dose of 1 mg/kg body weight and hindbrains (cerebella and brainstems) were removed for analysis of ganglioside concentrations at 4, 7, 14, or 21 days post-dosing. Treatment with DFP resulted in an increase in the proportion of GQ1b from day 4 to day 21 post-dosing which was significantly (p < 0.05) different from the control value at day 21. The proportion of GT1b increased in a similar manner over the 21 day period while the proportion of GD3 decreased over time. These progressive changes in ganglioside composition paralleled increasing hindlimb ataxia characteristic of OPIDN. In addition, the concentrations of protein, total lipid, total cholesterol, and lipid phosphorus in the chicken hindbrain were not affected by administration of DFP, indicating that the changes in ganglioside concentrations were not due to a non-specific effect on lipids.

Mating behavior and brain biogenic amine concentrations in chickens treated with parachlorophenylalanine (PCPA).

Four experiments were conducted to determine the effect of parachlorophenylalanine (PCPA) on the male mating behavior of a line of chickens genetically selected for low mating frequency and to determine the effect on brain concentrations of 5-hydroxytryptamine, dopamine (DA) and norepinephrine (NE). Mating behavior was not affected by moderate levels (less than 64 mg/kg) of PCPA, and decreased significantly when higher levels (100 mg/kg) of the drugs were administered. Results suggest that elevated brain serotonin titers were not causing the low mating frequency associated with the selected line. Birds receiving higher levels of PCPA exhibited a lethargy which persisted for approximately ten days after withdrawal of the drug. Serotonin, DA, and NE were all significantly reduced in the brains of birds receiving PCPA (30 mg/kg).

The effect of triorthocresyl phosphate, a delayed neurotoxin, on the testes of young broilers.

Broiler chickens were raised in brooder batteries. At 6 weeks of age 10 chickens were given either a single oral dose of triorthocresyl phosphate (TOCP) at 500 mg/kg body wt. or corn oil as a vehicle. The testes of both groups were examined morphologically and histologically. Changes in characteristics of testicular atrophy in the TOCP-treated group were clearly evident. The results also suggest that TOCP, a delayed neurotoxin, may induce sterility in young male chickens by an unknown mechanism.

Effects of dark-rearing on triphenyl phosphate-induced neuropathy in the visual system of the developing European ferret (Mustela putorius furo).

Results of a previous study in our lab (Tanaka et al., 1994) suggested that the onset of susceptibility to the organophosphorus compound triphenyl phosphite (TPP) in the developing ferret visual system might be closely related to eye opening and the onset of light stimulation. In order to explore this idea further, TPP was administered to ferret kits that had been raised for varying periods of time in total darkness to assess whether a delay in the onset of light stimulation to the visual system might also result in a delay in its susceptibility to TPP. Ferret kits were raised from birth either in total darkness or in open-sided sheds exposed to ambient light, injected subcutaneously with TPP (888 mg/kg body weight) at 5.5, 7.5, 9.5, or 21.5 wk of age, euthanized, and perfused transcardially with a 10% formalin-saline solution 4 d after injection. Brains were sectioned parasagittally at a thickness of 40 microm and subsequently processed with the Fink-Heimer silver impregnation technique to reveal the presence of degenerating axons and terminals, and with cresyl violet stain to delineate nuclear boundaries and cell soma morphology. Comparisons among degeneration patterns present in light-reared and dark-reared kits at the four ages examined revealed that the time of onset, extent, and density of TPP-induced axonal and terminal degeneration seen in the lateral geniculate nucleus and primary visual cortex did not differ significantly between light- and dark-reared groups, with the possible exception of dark-reared kits exposed to TPP at 7.5 wk of age. In addition, neurons in the primary visual cortex showed shrinkage and increased packing densities in kits exposed to TPP in both light and dark environments, as well as in dark-reared non-injected kits. The results of this study indicate that dark-rearing does not delay the onset or lessen the severity of TPP-induced axonal and terminal degeneration in the developing visual system of the ferret. Data suggest that light activation and stimulation of the retino-geniculo-striatal visual pathway is not a necessary prerequisite for the onset of visual system susceptibility to the axonopathic effects of triphenyl phosphite.

Multigenerational study of the effects of consumption of PCB-contaminated carp from Saginaw Bay, Lake Huron, on mink. 3. Estrogen receptor and progesterone receptor concentrations, and potential correlation with dietary PCB consumption.

Mink (Mustela vison) were fed diets containing ocean fish (control diet, 0.0 ppm polychlorinated biphenyls, PCBs) or Saginaw Bay carp to provide 0.25, 0.5, or 1.0 ppm PCBs to examine the effect of PCBs on homeostasis of binding sites for ovarian steroid hormones. Ranch-raised mink fed Great Lakes fish contaminated with PCBs, or treated with PCBs directly, have demonstrated reproductive impairment including anovulation, fetal resorption, delayed ovulation, increased gestation, and decreased litter size. Previous studies have demonstrated that estrogen and progesterone levels are unaltered in mink treated with PCBs, suggesting that the effect of PCBs on reproduction is not mediated through alterations in hormone homeostasis. In vitro studies have demonstrated that the most likely means by which PCBs exert antiestrogenic ability is through a down-regulation of the estrogen receptor in normally estrogen-responsive tissues such as liver and uterus. Hepatic and uterine estrogen binding site concentrations were measured in female mink consuming diets containing PCBs for up to 18 mo at up to 1 ppm. Hepatic estrogen binding site concentrations generally decreased with increasing dietary PCB concentrations. Uterine estrogen binding site concentration did not decrease in these animals. Uterine progesterone receptor concentration also did not change with increasing PCB consumption. In total, the response of hepatic and uterine estrogen and uterine progesterone binding sites in mink fed diets containing Saginaw Bay carp suggests that concentrations of PCBs available to uterine tissue may not have been sufficient to decrease uterine estrogen receptor, despite their effect on hepatic estrogen receptor.