In vitro and in vivo assessment of the effect of impurities and chirality on methamidophos-induced neuropathy target esterase aging.

In vitro and in vivo studies evaluated neuropathy target esterase (NTE) inhibition and aging (i.e., loss of reactivation potential) by analytical and technical grade racemic and resolved L-(-) and D-(+) isomers of methamidophos (O,S-dimethyl phosphoramidothioate). For studies in vitro, microsomal protein from phenobarbital-induced livers was isolated from chick embryos and NTE inhibition assays were performed using chick embryo brain homogenate treated with 1 or 5 mM methamidophos (with and without metabolic enzymes); for studies in vivo, hens received 30 to 35 mg/kg methamidophos injected into the pectoral muscle. NTE aging in hens was assessed 24 h later or after 30 min to 1 h incubation in vitro using solutions of potassium fluoride (KF) reactivator. Technical methamidophos produced significantly higher levels of aged-inhibited NTE than analytical methamidophos or isolated optical isomers. In vivo, technical methamidophos produced 61% total NTE inhibition with 18% aged and 43% unaged NTE; hens receiving analytical grade averaged 6% aged, 52% unaged, and 58% total NTE inhibition. Results for 1 mM analytical methamidophos in vitro were 5% aged, 54% unaged, and 59% total inhibition; for 1 mM technical methamidophos, values averaged 11% aged, 50% unaged, and 60% total NTE inhibition. The degree of NTE aging obtained both in vivo and in vitro for the isolated D-(+) and L-(-) isomers never exceeded that obtained using analytical grade. These data indicate that impurities in methamidophos could contribute to OPIDN potential. The in vitro methodology described could be applied to first tier screening for detection of NTE inhibition and aging, thus reducing the need for whole-animal testing for OPIDN.     

Cumulative risk assessment of the exposure to organophosphorus and carbamate insecticides in the Dutch diet

We report the acute cumulative exposure to organophosphorus insecticides (OPs) and carbamates in the Dutch population and young children (1-6 years) via the diet. Residue data were derived from Dutch monitoring programmes performed during 2003-2005, and food consumption levels from the Dutch National Food Consumption Survey 1997/1998. The relative potency factor (RPF) approach was used to cumulate the exposure to OPs and carbamates using acephate and oxamyl as index compound respectively. The exposure was estimated using the probabilistic approach, including unit variability and processing effects. We demonstrate that about 3% of the composite samples analysed for OPs and 0.2% for carbamates contain combinations of these pesticides. The P99.9 of exposure to OPs and carbamates in the total Dutch population equals 23 and 0.64mug/kg BW/d respectively. For young children the corresponding exposure levels are 57 and 1.47mug/kg BW/d. When comparing the P99.9 of exposure with the ARfD, 50 and 9mug/kg BW/d for acephate and oxamyl respectively, there is only a possible health risk for young children. Spinach contributed most to the exposure to OPs in both age groups, followed by orange and mandarin. For carbamates apple (sauce) was the main product determining the exposure.     

Exposure of California Quail to Organophosphorus Insecticides in Apple Orchards in the Okanagan Valley,British Columbia

We studied the exposure and effect of the organophosphate insecticides azinphos-methyl and diazinon on adult California quail (Callipepla californica) in an apple orchard in the Okanagan Valley, British Columbia. Cholinesterase activity was measured in plasma samples (n=65) collected from 54 individuals either prior to spraying, immediately (<24 hours) or 10 days after three spray events. Mean plasma cholinesterase levels declined significantly (P<0.05, n=12) to 61% of pre-spray mean activity (controls) immediately following the first spray event, but by ten days had recovered to 86% of mean control activity. Subsequent spray events caused no significant declines in mean plasma cholinesterase activity. Four of the 26 quail sampled within 24 h of a spray event exhibited plasma-ChE inhibition exceeding 50% inhibition. Radio-tagged quail (n=25) were monitored throughout the breeding season to determine use of orchards and detect changes in use patterns resulting from the spraying of insecticides. Use of orchards by quail varied over the summer, with the highest use occurring in May, declining to very low use by July. Quail exhibited a diurnal pattern, roosting in sparsely forested uplands at night, travelling to orchard areas to feed early each morning and returning to roosts at dusk. Orchard use by quail differed during spray events compared to non-spray times. During the three hour period immediately after spraying (0530–0800), 14–20% of observed quail were in the orchard, after which use declined to <4%, and returned to 12% by the next day. During non-spray times, 3–13% of radio-tagged the quail were observed in orchard habitat, with the heaviest use (13%) occurring later in the day (0830–1700 h). Seven radio-tagged quail were predated during the study period. However, no deaths could be attributed to insecticide poisoning as carcasses were not in suitable condition for testing. It was concluded that adult quail using orchard habitat early in the summer may be acutely poisoned by anti-cholinesterase insecticides, but the risk of exposure declined over the summer.     

Perinatal Methanol Exposure in the Rat: I. Blood Methanol Concentration and Neural Cell Adhesion Molecules

Although the acute toxicity of methanol is well documented,few studies have addressed the consequences of perinatal exposuresto the low concentrations that are expected to arise from itsproposed use as a component of automobile fuel. This reportdescribes the general research design of a series of studies,the effects of methanol exposures on blood concentrations indams and neonates, and indices of brain development. Four cohortsof Long-Evans pregnant rats, each cohort consisting of an exposure(n=12) and a control (n=12) group, were exposed whole-body to4500 ppm methanol vapor or air for 6 hr daily beginning on GestationDay 6. Both dams and pups were then exposed through PostnatalDay 21 (PND 21). Blood methanol concentrations determined bygas chromatography from samples obtained immediately followinga 6-hr exposure reached approximately 500–800 µg/mlin the dams during gestation and lactation. Average concentrationsfor pups attained levels about twice those of the dams. Selectedoffspring from Cohort 4 were exposed for one additional 6-hrsession at ages that extended out to PND 52. Regression analysesshowed that the blood methanol concentrations of the pups declineduntil about PND 48, at which time their levels approximatedthose of their dams. Such pharmacokinetic differences mightincrease the risks posed to developing organisms. Light-microscopicanalysis showed no significant abnormalities in the brains ofthe methanol-treated animals. However, assays of neural celladhesion molecules (NCAMs) in brains of pups sacrificed on PND4 showed staining for both the 140 and the 180 kDa isoformsto be less intense in the cerebellum of exposed animals. NCAMdifferences were not apparent in animals sacrificed 15 monthsafter their final exposure.     

Exposure to perfluorooctane sulfonate during pregnancy in rat and mouse. I: maternal and prenatal evaluations.

The maternal and developmental toxicities of perfluorooctane sulfonate (PFOS, C8F17SO3-) were evaluated in the rat and mouse. PFOS is an environmentally persistent compound used as a surfactant and occurs as a degradation product of both perfluorooctane sulfonyl fluoride and substituted perfluorooctane sulfonamido components found in many commercial and consumer applications. Pregnant Sprague-Dawley rats were given 1, 2, 3, 5, or 10 mg/kg PFOS daily by gavage from gestational day (GD) 2 to GD 20; CD-1 mice were similarly treated with 1, 5, 10, 15, and 20 mg/kg PFOS from GD 1 to GD 17. Controls received 0.5% Tween-20 vehicle (1 ml/kg for rats and 10 ml/kg for mice). Maternal weight gain, food and water consumption, and serum chemistry were monitored. Rats were euthanized on GD 21 and mice on GD 18. PFOS levels in maternal serum and in maternal and fetal livers were determined. Maternal weight gains in both species were suppressed by PFOS in a dose-dependent manner, likely attributed to reduced food and water intake. Serum PFOS levels increased with dosage, and liver levels were approximately fourfold higher than serum. Serum thyroxine (T4) and triiodothyronine (T3) in the PFOS-treated rat dams were significantly reduced as early as one week after chemical exposure, although no feedback response of thyroid-stimulating hormone (TSH) was observed. A similar pattern of reduction in T4 was also seen in the pregnant mice. Maternal serum triglycerides were significantly reduced, particularly in the high-dose groups, although cholesterol levels were not affected. In the mouse dams, PFOS produced a marked enlargement of the liver at 10 mg/kg and higher dosages. In the rat fetuses, PFOS was detected in the liver but at levels nearly half of those in the maternal counterparts, regardless of administered doses. In both rodent species, PFOS did not alter the numbers of implantations or live fetuses at term, although small deficits in fetal weight were noted in the rat. A host of birth defects, including cleft palate, anasarca, ventricular septal defect, and enlargement of the right atrium, were seen in both rats and mice, primarily in the 10 and 20 mg/kg dosage groups, respectively. Our results demonstrate both maternal and developmental toxicity of PFOS in the rat and mouse.     

Function of the Auditory and Visual Systems,and of Peripheral Nerve,in Rats after Long-Term Combined Exposure to n-Hexane and Methylated Benzene Derivatives. I. Toluene

Rats were exposed to n-hexane, toluene, or toluene together with n-hexane, each solvent 1000 p.p.m. (1000+ 1000 p.p.m. in combined exposure), 21 hr/day, 7 days/week during 28 days. Neurophysiological recordings were made 2 days, 3 months, and one year after end of exposure. A reduction in auditory sensitivity, recorded by click evoked auditory brainstem response, was observed 2 days after exposure to toluene alone, or to toluene together with n-hexane, but not after exposure to n-hexane alone. The reduction lasted one year after the exposure. Three months after combined exposure, a synergistic enhancement of loss of auditory sensitivity was observed in the mixed exposure group. One amplitude in the flash evoked potentials was lowered in the n-hexane exposed group 2 days after exposure. No such reduction was seen after simultaneous exposure to toluene. Exposure to n-hexane alone caused a marked decrease in peripheral nerve conduction velocity 2 days and 3 months after exposure, while exposure to n-hexane together with toluene had only a small effect on this velocity.     

Trends in Binge and Heavy Drinking,Alcohol-Related Problems,and Combat Exposure in the U.S. Military

Population-based Department of Defense health behavior surveys were examined for binge and heavy drinking among U.S. active duty personnel. From 1998–2008, personnel showed significant increases in heavy drinking (15% to 20%) and binge drinking (35% to 47%). The rate of alcohol-related serious consequences was 4% for nonbinge drinkers, 9% for binge drinkers, and 19% for heavy drinkers. Personnel with high combat exposure had significantly higher rates of heavy (26.8%) and binge (54.8%) drinking than their counterparts (17% and 45%, respectively). Heavy and binge drinking put service members at high risk for problems that diminish force readiness and psychological fitness.     

A small-volume bioassay for quantification of the esterase inhibiting potency of mixtures of organophosphate and carbamate insecticides in rainwater: development and optimization.

The goal of this study was to develop a sensitive in vitro bioassay for quantification of the total esterase inhibiting potency of low concentrations of organophosphate and carbamate insecticides in relatively small rainwater samples. Purified acetylcholinesterase (AChE) from electric eel (Electrophorus electricus) and carboxylesterases from a homogenate of honeybee heads (Apis mellifera) were used as esterases, each having different affinities for the substrates S-acetylthiocholine-iodide (ATC) and N-methylindoxylacetate (MIA). MIA hydrolysis by honeybee homogenate was more sensitive to inhibition by organophosphate insecticides than ATC hydrolysis by purified AChE, although the latter parameter is often used for in vitro monitoring of esterase inhibitors. The higher sensitivity of carboxylesterases is attributed to the instant formation of a reversible Michaelis-Menten complex with the inhibitor, which competes with MIA for the active sites of the free enzymes. This dose-dependent instant inhibition can be quantified with kinetics for competitive inhibition at dichlorvos concentrations < 16 nM. At similar concentrations, purified AChE was not instantly inhibited, whereas both AChE and carboxylesterases were irreversibly and progressively inhibited at higher dichlorvos concentrations (IC50(10min) >/= 0.1 microM). Honeybee homogenate mediated MIA hydrolysis was applied as the most sensitive enzyme-substrate combination for experiments with fractionated extracts of 4 rainwater samples collected in a natural conservation area. Most esterase inhibiting potency was found in the polar methanol fraction, with recalculated concentrations equivalent to 12-125 ng dichlorvos per liter rainwater.     

Barrier mechanisms in the brain, I. Adult brain

1. The adult brain functions within a well-controlled (internal) environment that is separate from that of the internal environment of the rest of the body as a whole. 2. The underlying mechanism of control of the brain's internal environment lies in the presence of tight junctions between the cerebral endothelial cells at the blood-brain interface (blood-brain barrier) and between choroid plexus epithelial cells (blood-cerebrospinal fluid (CSF) barrier). 3. The effect of tight junctions at the blood-brain and blood-CSF barriers is to convert the properties of the individual endothelial and epithelial cells into properties of these interfaces as a whole. 4. Superimposed on the diffusion restriction provided by the tight junctions in the blood-brain and blood-CSF barriers is a series of transport mechanisms into and out of the brain and CSF that determine and control the internal environment of the brain with respect to a wide range of molecules, such as electrolytes, amino acids, glucose, vitamins and peptides. 5. The physical characteristics of drugs, together with their interaction with the properties of the barriers between blood, brain and CSF, determine the extent to which drugs penetrate into the brain. 6. Drugs can be targeted to the brain by making use of knowledge of this interaction between the physical properties of a drug (which can be modified by manipulation of the structure of the molecule in predictable ways) and the influx/efflux mechanisms present in the blood-CSF and blood-brain interfaces.     

Therapeutic traditions in Northern Ireland,Norway and Sweden: I. Diabetes

Summary A questionnaire survey was carried out to explore differences in the approach to treatment of patients with Type II diabetes between physicians in Northern Ireland, Norway and Sweden, and to discover to what extent it could account for the three-fold difference in drug use between the countries. A representative sample of 400 physicians in each country was asked to give their opinions on the choice of therapy for three model cases designed to cover the spectrum of treatment — from diet alone to insulin. Significantly more Swedish (65%) than Northern Irish (51%) and Norwegian (52%) doctors suggested diet alone for uncomplicated diabetes recently discovered in a middle aged, overweight man. For symptomatic diabetes in a 76 year old overweight woman with few retinal microaneurysms, the majority of physicians in all three countries suggested treatment with sulphonylureas. Biguanides were here a more common alternative in Northern Ireland than in Scandinavia. For suspected secondary treatment failure in a 63 year old woman with no signs of complications, insulin was suggested by 71% of the Norwegian doctors but only by 44 and 49% of those in Northern Ireland and Sweden, respectively. General practitioners tended to suggest oral treatment earlier and to maintain it longer than hospital physicians. The study has demonstrated significant differences in the approach to treatment of Type II diabetes mellitus between physicians in the three countries. However, the differences were more prominent in the choice of drugs than in the threshold of drug treatment. The results also fit with qualitative but not with quantitative differences in drug sales between the countries, suggesting that important differences may exist in the prevalence of clinically recognized Type II diabetes.     

Perinatal toxicology of mirex administered in the diet: I. viability,growth, cataractogenicity and tissue levels

Mirex was administered at a concentration of 25 ppm in the diet to pregnant rats. Animals were allowed to give birth and the pups were cross-fostered. Prenatal exposure to mirex resulted in decreased postnatal viability. Growth was decreased in litters exposed postnatally. Postnatal exposure to the pesticide also resulted in a high incidence of cataracts and/or outlined lenses. Mirex crossed the placenta and significant quantities of the chemical were found in newborns. Following postnatal administration of mirex, tissue levels were found to rise through day 21 (weaning) and thereafter to slowly decline. Tissue levels (ppm) were generally found to be in the order of fat > liver > kidney > brain > eyes.     

Ochratoxins in Wines: A Review of Their Occurrence in the Last Decade,Toxicity, and Exposure Risk in Humans

Ochratoxins (OTs) are mycotoxins frequently found in wines, and their contamination can occur during any stage of the winemaking process. Ochratoxin A (OTA) has been the most widely reported and the only one whose concentrations are legislated in this beverage. However, ochratoxin B, ochratoxin A methyl ester, ochratoxin B methyl ester, ochratoxin A ethyl ester, ochratoxin B ethyl ester, ochratoxin α, ochratoxin β, OTα methyl ester, OTA ethyl amide, and OTA glucose ester have also been reported in wines. Thus, detecting only OTA would lead to the underestimation of ochratoxin levels, which is a risk to human health. Considering the threat represented by the presence of ochratoxins in wines and the long-term health problems that they can cause in wine drinkers, this paper aims to review reports of the last 10 years regarding the presence of different ochratoxins in wines and how the winemaking process influences the degree of contamination, mainly by OTA. Additionally, toxicity from human exposure due to the consumption of contaminated wines is addressed.     

Prenatal cocaine exposure in the Long-Evans rat: I. Dose-dependent effects on gestation, mortality, and postnatal maturation

Pregnant Long-Evans rats were injected daily with 40, 60, 80, or 100 mg/kg cocaine HCl (SC, 2% solution) from gestational days 7-20 (sperm positive = day 0). Daily doses were split evenly with half given between 9:00-10:00 a.m. and half between 3:00-4:00 p.m. An ad lib-fed group as well as nutritional control groups that were pair-fed to the 80 and 100 mg/kg cocaine dams were also evaluated (N = 11-18 liters/group). Cocaine had no effect on gestational length but did cause dose-dependent decreases in maternal food consumption and weight gain and increases in maternal mortality. Interestingly, cocaine-treated dams shows a significant increase in water consumption. In terms of offspring variables, there was a dose-dependent decrease in birth weight and postnatal weight gain in both the cocaine and pair-fed groups. There were also dose-dependent effects on litter size, stillbirths and postnatal mortality in the cocaine-treated groups as compared to the control groups. High dose cocaine treatment caused delays in several indices of physical maturation (pinna detachment, fur growth, ear opening, eye opening, vaginal opening) but not in others (incisor eruption, testicular descent). Physical anomalies and postnatal morbidity, while uncommon, were observed in animals prenatally exposed to the higher cocaine doses. Collectively, these data suggest that prenatal cocaine exposure can increase postnatal morbidity as well as increase pre-and postnatal mortality in animal offspring.