Minimal endocrine alterations in rodents after consumption of lake trout (Salvelinus namaycush).

Polychlorinated biphenyls (PCBs) and dioxins are known to cause disruptions in circulating hormone concentrations, which may influence fertility and normal fetal development. Structure activity relationships have been determined for individual congeners, but it is unclear what impacts occur due to exposure to complex mixtures of chemicals found in the environment. Most laboratory studies of PCB exposure have used commercial mixtures in high doses, which may not be representative of environmental concentrations of individual congeners, nor accurately represent complex interactions of multiple contaminants. The present study investigated endocrine alterations in rats associated with the consumption of lake trout collected from three specific locations in the Great Lakes. Composite fish samples were analyzed for PCBs, organochlorines, and mercury and ranged from 415 ppb to 1,275 ppb for individual contaminants. Fillet composites were fed to timed-pregnant Long-Evans rats as 30% of their diet. Concentrations of total thyroxine and estrogen were not significantly different in offspring of dosed dams from that of controls. However, aromatase activity was lowered in all dosed groups as compared with controls. This may represent a lowered expression of the CYP 19 gene in exposed rats or may be due to the presence of one or more substances in the contaminants that are capable of altering the affinity of the aromatase enzyme for its normal endogenous substrate. It is also possible that the number of maturing follicles in the lake trout-fed rats may be fewer than controls, which would result in an overall reduction in the enzyme activity. Data regarding the endocrine effects of environmental contaminant mixtures found in fish from the Great Lakes Basin are still controversial. Additionally, information is scarce with respect to the F1 generation of laboratory animals following environmental maternal exposures, therefore, we investigated the reproductive-endocrine alterations in rat offspring associated with the consumption of lake trout (Salvelinus namaycush) collected from three areas in the Great Lakes.

Concentrations and frequencies of polychlorinated biphenyl congeners in a Native American population that consumes Great Lakes fish.

OBJECTIVE: Polychlorinated biphenyl congener profiles were examined in serum samples from 61 Native American (Ojibwa) volunteers who regularly consumed fish harvested from the Great Lakes region. A total of 93 peaks are reported which represent 126 individual chlorobiphenyls. RESULTS: When ranked by frequency, 13 peaks comprising single or co-eluting chlorobiphenyls occurred in all 61 samples (a frequency of 100%). These included chlorobiphenyls 138 + 158 + 163, 105 + 132 + 153, 180, 118, 196 + 203, 74, 182 + 187, 199, 183, 114 + 134, 195 + 208, 206, and 194. These 13 peaks also occurred at concentrations higher than those of all other measured chlorobiphenyls, except for the addition of the peak containing chlorobiphenyls 170 and 190, which was below detection in 15% of the samples and ranked fifth in average concentration. The highly chlorinated chlorobiphenyls resembled human serum profiles previously reported in the literature. METHODS: Individual chlorobiphenyls were identified using a gas chromatograph equipped with a 60-meter DB-5 capillary column and electron capture detection. CONCLUSION: When compared to other human residue analyses for fish-eating populations, the Ojibwa samples contained higher proportions of lightly chlorinated and labile chlorobiphenyls such as 8, 16 + 32, 17, 18, 25, 41 + 64 + 71, 33, 52, 110, and 129. These proportions were similar to those found in carp, whitefish, or whitefish livers harvested from the Great Lakes region. These data indicate that regular meals of lower trophic level fish, such as whitefish from the Great Lakes, may distort steady-state human chlorobiphenyl profiles with respect to certain lightly chlorinated or labile chlorobiphenyls.

Age- and gender-adjusted comparison of Wisconsin native mortality with general Wisconsin population, for diabetes and diabetes-related causes of death--1986-1995.

UNLABELLED: To compare mortality for diabetes and diabetes-related causes in Native American (NA) with total mortality for Wisconsin population by age, and gender. METHODS: Adjusting for age and sex, standardized mortality ratios (SMRs) were calculated for Wisconsin Native Americans for 1986-1995, using the 1990 total Wisconsin population as a reference and death certificate data to count and categorize deaths. RESULTS: Statistically significant high NA SMRs were found for total deaths (SMR = 1.28, p < .005), diabetes (SMR = 2.87, p < .005), heart disease (SMR = 1.16, p < .005), and kidney disease (SMR = 2.72, p < .005). There was substantial concordance in SMRs between men and women. NA SMRs were above 1 for all five year age groups below 75. Comparisons are provided with national data. CONCLUSION: Mortality due to diabetes mellitus, heart disease and kidney disease are higher among Native Americans in Wisconsin for all age groups below 75 and in both genders.

Concentrations of blood and hair mercury and serum PCBs in an Ojibwa population that consumes Great Lakes region fish.

OBJECTIVE: This paper describes an exposure assessment of an American Indian population using blood and hair samples as indicators of mercury and polychlorinated biphenyl exposure from the consumption of fish taken from the Great Lakes region. METHODS: Questionnaires regarding fish consumption were completed by 89 Ojibwa tribal members. Mercury concentrations were determined in human hair and blood samples, and polychlorinated biphenyl concentrations were determined in serum. RESULTS: Fish were consumed at the highest rates in April, May, June, and July. Lake trout, whitefish, and walleye were the preferred fish consumed by 91.4% of the respondents. Concentrations of blood mercury were all below 55 micrograms/L (ppb), while concentrations of mercury in hair were all less than 3 mg/L (ppm). Hair mercury concentrations were correlated with the previous year's fish consumption (p = .05). Dental amalgams and blood mercury concentrations were also significantly correlated (p < .002). Serum polychlorinated biphenyl concentrations, determined as the sum of 89 congeners, were all below 9.6 ppb total polychlorinated biphenyls. Subject age and total serum polychlorinated biphenyls were correlated (p < .001). CONCLUSIONS: The concentrations of mercury and polychlorinated biphenyls in this Ojibwa population were relatively low, but several individuals were identified as having elevated concentrations and additional testing may be warranted. Since the accumulation of contaminants was related to fish consumption and age, a long-term monitoring program that assesses chronic exposure to fish diets would be beneficial.

The Ojibwa Health Study: fish residue comparisons for Lakes Superior, Michigan, and Huron.

The Ojibwa Health Study is a descriptive epidemiology study of six Ojibwa reservations in the Upper Great Lakes. Fish consumption habits, contaminant (mercury [Hg], polychlorinated biphenyls [PCBs], and other organochlorines [OCs]) residues in dietary fish and humans, and chronic disease outcomes currently are being documented. Four hundred and fifty questionnaires and approximately 200 biological samples had been collected as of December 1994. Fish collections from reservations included lake trout, walleye, lake whitefish, and lake herring from Lakes Superior (three sites), Michigan, and Huron. Hg and OC residue analyses have been completed for the fish composite samples. A preliminary examination of the data has revealed regional differences in the contaminant burdens of the fish. Lake Michigan and Lake Huron whitefish composite samples had approximately twice the OC concentrations of Lake Superior whitefish samples. In general, the whitefish composite samples were far below the U.S. Food and Drug Administration or any state advisory limits for OC or Hg residues. Lake trout samples contained higher amounts of all residues than did the whitefish samples.

Retina, brain and blood cholinesterase levels in cats treated with oral dichlorvos.

Dichlorvos (DDVP) is used as an antihelmetic, principally in dogs, cats, pigs and horses. Retina, whole blood, erythrocyte, plasma and brain cholinesterase (ChE) activities were monitored following DDVP exposure in cats to establish their use as indicators of exposure to a ChE inhibitor. Following DDVP exposure, whole blood ChE activity was 16.8% of preexposure, erythrocyte ChE activity was 33% of preexposure, and plasma ChE was 19% of preexposure values. Brain and retinal ChE activities were reduced to 45% and 43% of control values. Retinal ChE paralleled brain activity.

Pharmacologic challenges for establishing interspecies extrapolation models in neurotoxicology.

Pharmacologic challenges and dose/response studies are discussed as tools for aiding in the extrapolation of nonhuman animal models to human neurotoxicology. Specific experiments conducted using humans, baboons, rhesus monkeys, and dogs are cited as examples of the use of pharmacologic methods for neurotoxicology applications. Respiratory sinus arrhythmias are quantified following atropine sulfate administration and the resulting vagolytic blockade is used as a pharmacologic challenge technique. Dose/response studies in humans and rhesus monkeys are cited as an example for interspecies comparisons using ED50 calculations for a 30% decrease in the respiratory sinus arrhythmias following atropine. Pharmacologic challenges with drugs of relevant mechanisms of action are useful for demonstrating relative physiologic responses for interspecies extrapolations.

Regional brain cholinesterase activity in rats injected intraperitoneally with anatoxin-a(s) or paraoxon.

Adult male Long-Evans rats were injected intraperitoneally with 1.5, 3.0 or 9.0 micrograms/kg of anatoxin-a(s) that had been extracted from laboratory-grown Anabaena flos-aquae NRC-525-17, 800 micrograms/kg of paraoxon, or a control solution. Blood, anterior spinal cord, and brain cerebellar, cortical, medullary, midbrain, hippocampal, hypothalamic, olfactory and striatal cholinesterase activity was determined in rats that died prior to 2 hours or were anesthetized and killed at 2 hours. Unlike paraoxon, anatoxin-a(s) did not cause detectable inhibition of cholinesterase in the central nervous system, but did cause inhibition of cholinesterase in blood, suggesting that anatoxin-a(s) is strictly a peripheral cholinesterase inhibitor.

Comparing the cardiac vagolytic effects of atropine and methylatropine in rhesus macaques.

Atropine and methylatropine (190 nmol/kg) were compared in rhesus monkeys (Macaca mulatta) for their ability to produce a cardiac vagal blockade using a noninvasive estimate of respiratory sinus arrhythmia (RSA). Twelve monkeys received both drugs via intravenous (IV) and intramuscular (IM) routes of administration and were monitored for 3 hr after treatment. Both drugs, regardless of the route of administration, reduced RSA amplitude. At this dose, methylatropine was more effective than atropine in its ability to reduce RSA amplitude, heart period (HP; beat-to-beat interval), and overall heart period variability (HPV). Estimated RSA amplitude and HPV returned to basal levels significantly earlier after IM atropine administration than after IV treatment. Methylatropine did not exhibit any route effects. In addition, the mean decrease in RSA amplitude and HPV for the IM route of atropine sulfate was significantly less than that for the IV route. Serum atropine concentrations correlated significantly with all variables after IM treatment but only with RSA and HPV after IV treatment. Methylatropine may therefore be more useful than atropine as a pharmacologic challenge drug for detecting organophosphorus (OP) exposure because of its longer duration of action, lack of route of administration differences, and less likelihood of crossing the blood-brain barrier. Further studies are needed to fully evaluate methylatropine's potential in the challenge method of OP detection.

Quantifying the altered cardiac response to atropine following pyridostigmine in rhesus macaques.

An estimate of the amplitude of respiratory sinus arrhythmia (V) has been proposed as a noninvasive measure of parasympathetic activity. This experiment monitored V in response to a subclinical dose of pyridostigmine bromide (PYR) and a pharmacological challenge of atropine sulfate (ATR). Twelve male rhesus macaques received 200 micrograms/kg of PYR 30 min prior to an injection of 0, 14, 44, or 140 micrograms/kg ATR. The decrease in V after both the 44 and 140 micrograms/kg ATR doses was similar to the response to ATR alone in a previous experiment. The 14 micrograms/kg dose of ATR did not significantly decrease V in this experiment, which is in contrast with the large decrease of V after ATR alone in a previous experiment. Neither drug affected respiration. The dose of ATR which would be effective in causing a 30% decrease of V in the presence of PYR was estimated to be 18.3 micrograms/kg of ATR. This is twice the dose of ATR calculated to have the same effect without PYR. The attenuated response of V after a pharmacological challenge of ATR may be used to quantify the latent muscarinic effects from exposure to anticholinesterase agents. The attenuated response to ATR may also be useful for evaluating the return of normal cholinergic function after disruption by cholinesterase inhibitors.

Vagal tone monitoring: a potential indicator of anti-cholinesterase exposure in Macaca mulatta.

A vagal tone monitor (VTM) was used to evaluate cardiac rhythm changes in Rhesus monkeys (Macaca mulatta) after intramuscular (i.m.) administration of an anti-cholinergic (atropine sulfate), two carbamates (pyridostigmine bromide and physostigmine salicylate), and combinations of pyridostigmine and atropine. Twelve monkeys were studied in 4 experiments using Latin Square blind designs. Experiment I tested the VTM responses to atropine sulfate injections of 0, 14, 44 and 140 micrograms/kg. Experiment II tested the responses to 0, 100, 200 and 400 micrograms/kg pyridostigmine injections. Experiment III tested the responses to physostigmine injections of 0, 25, 50 and 100 micrograms/kg. Experiment IV tested the same atropine sulfate treatments as Experiment I 30 min after a pyridostigmine pretreatment of 200 micrograms/kg. The VTM analysis produced an estimate of vagal tone (V) every 30 s, and V was averaged over 15 min. The results indicated that V responded more to physostigmine and atropine than pyridostigmine. There was also an attenuated response to atropine following pyridostigmine pretreatment. The attenuated response had been demonstrated earlier in organophosphate (OP) treated dogs. The results suggest that V may be used as a non-invasive indicator of cholinergic drug effects.

Effects of atropine on respiratory sinus arrhythmia (RSA) in the rhesus macaque.

Twelve juvenile to adult rhesus macaques were administered atropine sulfate (0, 14, 44, and 140 mcg/kg IM). The amplitude of the respiratory sinus arrhythmia (RSA) in the rhesus macaque was estimated using a Vagal Tone Monitor (VTM). The estimate of RSA (termed V; vagal tone) was significantly reduced for nearly 3 hr after all doses of atropine, suggesting possible central nervous system effects. Heart period (R-R interval) was reduced briefly after dosing. Overall heart period variability (HPV) was depressed after all doses of atropine. The amount of atropine required to decrease HPV and V by 30% was similar to that reported for the human. The rhesus monkey was determined to have little resting vagal tone as estimated by V. A large slow wave oscillation contributed to the overall variability in heart period. It is concluded that the rhesus monkey exhibits a similar sensitivity to atropine as did the human and, therefore, provides a useful model for the study of cholinergic drug actions and their effects on RSA.

Comparison of effects of anatoxin-a(s) and paraoxon, physostigmine and pyridostigmine on mouse brain cholinesterase activity.

Anatoxin-a(s), an alkaloid neurotoxin from the freshwater cyanobacterium, Anabaena flos-aquae NRC-525-17, was compared to paraoxon, physostigmine and pyridostigmine for effects on brain cholinesterase after i.p. injection into Balb/c mice. The duration of clinical signs in mice injected with anatoxin-a(s) persisted longer than in mice given the carbamates and was comparable with that of paraoxon. Anatoxin-a(s) did not inhibit brain cholinesterase activity suggesting that this toxin is unable to cross the blood-brain barrier.

Latent dichlorvos neurotoxicity detected by vagal tone monitoring in dogs.

Dichlorvos (dimethyl 2,2-dichlorovinyl phosphate) was administered orally to German Shorthair Pointer dogs at approximately 60 mg/kg (twice the usual clinical dose). Plasma and erythrocyte cholinesterase (ChE) was monitored prior to, 90 min, and 180 min post-ingestion. 2-PAM (20 mg/kg IV) and atropine sulfate (0.022 mg/kg IM) were administered 90 min after the dichlorvos to paired treated and control dogs. The telemetered electrocardiographic (ECG) signal was analyzed by a Vagal Tone Monitor (VTM) to yield mean heart period (msec) and an estimate of the amplitude of respiratory sinus arrhythmia (V in natural log values of msec2) for five min intervals. Dichlorvos did not cause cholinomimetic symptoms even though blood cholinesterase was significantly inhibited (plasma -51.3% and erythrocyte -43.7%). The atropine sulfate treatment resulted in the expected vagolytic effects in both the control and the dichlorvos treated dogs, but the atropine effects were attenuated in the latter dogs. Three weeks later, ChE activity was not significantly depressed in the dichlorvos treated dogs, and their V responses to atropine were more similar to the responses in control dogs.

In vivo interactions of aluminum with hepatic cytochrome P-450 and metallothionein.

Male Sprague-Dawley rats (three per treatment group) were administered 0, 2, 10, 20, or 40 mg aluminum per kilogram ip per day for 3 days as aluminum chloride in saline. Animals were killed 24 hr later. Aluminum was found to inhibit hepatic drug metabolism in a dose-dependent fashion. The lowest dose (2 mg or 75 mumol/kg) had no effect on the parameters measured, whereas the highest dose (40 mg or 1.5 mmol/kg) caused a 52% decrease in cytochrome P-450, a 71% decrease in p-nitrophenetole O-deethylase activity, and a 77% decrease in ethylmorphine N-demethylase activity. Hepatic glutathione levels were unaffected by aluminum, whereas metallothionein (MT) was induced in both liver and kidney. The distribution of endogenous metals normally associated with MT was altered by aluminum administration. At the highest dose of aluminum (40 mg/kg), zinc levels were increased in liver cytosol (154%), while copper levels were unchanged in liver, but decreased in kidney (70%). Aluminum was present in the liver and kidney. Of the aluminum in the liver, less than 5% was in the cytosol, bound to a MT-like protein. It is concluded that acute ip administration of aluminum adversely effects hepatic drug metabolism and that aluminum induces and binds to MT or a MT-like protein.

Atropine sulfate effects on aviator performance and on respiratory-heart period interactions.

In this study, 20 human volunteers received a placebo and atropine doses of 0.5, 1.0, 2.0, and 4.0 mg X 75 kg-1 in a Latin Square double blind design, and effects were monitored for 3 h postinjection. The 2.0 mg and the 4.0 mg doses resulted in significant flight simulator performance decrements beginning at 1 h postinjection with only minimal recovery by 3 h postinjection. Electrocardiogram data were used to estimate the amplitude of respiratory sinus arrhythmia (RSA) which was more sensitive than mean heart period or mean heart period variance to the effects of atropine. These parasympathetic effects were relatively rapid in onset and peaked within the first 40-min period for the 2.0 and 4.0 mg doses. The onset of performance effects were delayed 1 h 40 min for the 2.0 mg and 1 h 00 min for the 4.0 mg treatment.

Comparison of the effects of atropine sulfate and ethanol on performance.

The flight simulator performance decrements resulting from atropine injections were compared to similar decrements resulting from ethanol toxicosis. There were 20 volunteers that received 0.0, 0.5, 1.0, 2.0, and 4.0 X 75 kg-1 of atropine sulfate under double-blind conditions. The performance decrements at each atropine sulfate treatment level for each subject were determined by computing root mean square (RMS) deviations for five flight performance variables. The data set from a previous study concerned with the effects of ethanol on pilot performance was reanalyzed, and the decrements for the five variables at the 0.082% blood alcohol level (BAL) were computed. Probit analysis was used to estimate the effective dose (ED50) at which 50% of the subjects in the atropine sulfate experiment were expected to display decrements in excess of those observed for the 0.082% BAL. The ED50 was 3.12 mg of atropine sulfate.

Monitoring the chronic effects of anticholinesterase pesticides in aerial applicators.

Four pilots were monitored over a six month period for physiological signs of anticholinesterase exposures in this preliminary study. Two pilots were controls and two were aerial applicators whose spraying activities included the application of ethyl parathion on more than 85% of their total acreages. Erythrocytic and plasma cholinesterase assays, plus dark-adapted pupil dilation, and a measure of the amplitude of respiratory sinus arrhythmia (RSA), were measured pre-seasonally and near the end of the spraying season. Comparisons between the controls and the two aerial applicators indicated that one aerial applicator displayed organophosphorus toxicosis symptoms. Dark-adapted pupil dilation and RSA more clearly indicated the chronic exposure than did the blood cholinesterase assays. The alleged exposure was linked by post-study interviews to flight pattern and residue cleaning procedures.