Subchronic toxicity and reproduction effects of tri-n-butyltin oxide in Japanese quail

A subchronic toxicity/reproduction study was performed in Japanese quails that were fed a diet containing 0, 24, 60, and 150 mg tri-n-butyltin oxide (TBTO) per kg basal diet for 6 weeks. Eggs produced during the 6 weeks of treatment were incubated and hatched, and chicks hatched from eggs collected in weeks 5 and 6 of exposure were reared for 2 weeks. In parent quail, neither diminished food consumption nor any overt toxic or histopathologic signs were observed following exposure to TBTO. A statistically significant decrease in hatchability and increase in percent of chicks found dead in the shell were observed following TBTO exposure at concentrations of 60 and 150 mg/kg food. However, no significant, adverse effects were recorded on total egg production, eggshell thickness and cracked eggs. Blood chemistry parameters of birds measured at the last day of TBTO treatment revealed a statistically significant decrease in serum aspartate aminotransferase (ASAT) enzyme activity among both sexes in all treatment groups. In addition, a statistically significant dose-related decrease in serum calcium level was observed in females only, while serum follicle stimulating hormone (FSH) levels were statistically significantly reduced in male birds in all treatment groups (approximately 50% of the controls).Moreover, a significant decrease in hepatic microsomal 7-ethoxyresorufin (EROD) activity was recorded in females fed 24 and 60 mg TBTO/kg diet and males fed 60 and 150 mg TBTO/kg diet, whereas pentoxyresorufin-o-deetylase (PROD) activity was only significantly decreased in males fed 150 mg TBTO/kg diet. No TBTO related effects were found on serum alanine aminotransferase (ALAT), serum total thyroxine (TT₄), luteinizing hormone (LH) or retinol levels in both sexes. In summary, TBTO affected mainly reproduction in Japanese quail at a dose where no overt toxicity is observed.     

Hematology and serum biochemistry of Japanese quail fed dietary tri-n-butyltin oxide during reproduction

During a subchronic toxicity and reproduction study with tri-n-butyltin oxide (TBTO) concentrations of 0, 24, 60, and 150 mg/kg diet in Japanese quail, preliminary data on hematology and serum biochemistry were obtained. The absence of serious effects in blood parameters in both adult quail and developing chicks are discussed in view of the adverse effects of TBTO on reproduction.     

Lack of Developmental and Reproductive Toxicity of 2,3,3′,4,4′-Pentachlorobiphenyl (PCB 105) in Ring-Necked Pheasants

Mono-ortho PCBs are global contaminants of wildlife with the potential to produce toxicity by an aryl hydrocarbon receptor (AhR)–mediated mechanism. To determine the potency of 2,3,3′,4,4′-pentachlorobiphenyl (PCB 105) for producing reproductive and developmental toxicity, adult ring-necked pheasant hens (Phasianus colchicus) were orally dosed with 0, 0.06, 0.6, or 6 mg PCB 105/kg hen/week for 10 weeks to achieve cumulative doses of 0, 0.6, 6, or 60 mg PCB 105/kg hen after which hens were bred with untreated roosters once per week for 8 weeks. Except at week 6 of the egg-laying period when cumulative egg production in the 6 mg PCB 105/kg hen group was greater than controls, fertilized egg production was not significantly different between treatment groups. Embryo mortality and chick mortality were not significantly different between treatment groups. Total body and heart weights of all chicks 1 day posthatch (dph) were not different between groups, however, liver weights of chicks from the 60 mg/kg treatment group were greater than controls at 1 dph. The first chick to hatch from each hen was reared to 21 dph and among these birds, the total body, liver, and heart weights were not different between groups. There were no dose-related malformations of the beak or limbs, and no signs of subcutaneous edema, ascites, or pericardial edema in chicks at 1 or 21 dph. Hepatic microsomal monooxygenase activities [ethoxyresorufin-O-dealkylase (EROD), benzyloxyresorufin-O-dealkylase (BROD), and methyloxyresorufin-O-dealkylase (MROD)] were significantly elevated in chicks at 1 dph from hens given a cumulative PCB 105 dose of 6 mg/kg and in chicks at 21 dph from hens given a cumulative PCB dose of 60 mg/kg. These results indicate that a cumulative PCB 105 dose up to 60 mg/kg hen does not decrease the production of fertilized eggs or increase embryo or chick mortality in ring-necked pheasants, but does increase chick hepatic monooxygenase activity. Received: 6 January 1998/Accepted: 1 July 1998     

Toxicity of bis (tri-n-butyltin) oxide on learning and development in the rat

The toxicity of bis (tri-n-butyltin) oxide (TBTO) was studied in THA rats. Doses of 0 (control), 10 or 15 mg/kg/day of TBTO were administered to adult rats for 12 consecutive days, and 0, 5 or 10 mg/kg/day was given to pregnant rats from day 6 to day 20 of gestation by gastric intubation. In the adult rat exposure experiment, the 15 mg/kg group showed slightly decreased body weight and spontaneous motor activity, and a low avoidance rate in the Sidman avoidance test in the early stage of administration. In the pregnant-rat exposure experiment, no effect of TBTO was seen in either the 5 mg/kg or 10 mg/kg groups in dams while all pups in the 10 mg/kg group died by postnatal day 3. Little effect of TBTO on body weight, pinna detachment, incisor eruption, eye opening, surface righting, cliff avoidance, pivoting, negative geotaxis and auditory startle was found in the 5 mg/kg pups. In the Sidman avoidance test, the avoidance rate of the 5 mg/kg pups was lower than that of control pups in the early stage of the session. In a water E-maze test, the swimming time to the goal and the number of errors were increased in the 5 mg/kg pups. In a reversal water E-maze test, increases of the swimming time to the goal and the number of errors made by the 5 mg/kg pups were marked. These results suggest that TBTO administration disrupts the learning acquisition of rats, and that the toxicity of TBTO is greater in prenatally exposed pups than in adult rats.     

Amelioration of oral copper toxicity in chicks by dietary additions of ascorbic acid, cysteine and zinc

Four experiments were conducted to evaluate the interrelationship of L-ascorbic acid, L-cysteine and Zn for amelioration of Cu toxicity in chicks. Chicks were fed a corn-soybean meal diet with 1,000 mg Cu (CuSO₄ · 5H₂O)/kg to produce Cu toxicity. Single dietary additions and two-way combinations of ascorbic acid (1,000 mg/kg), cysteine (0.5 g/100 g) and Zn (1,000 mg/kg) reduced liver Cu accumulation, with cysteine resulting in the largest response. Although supplemental Zn from ZnSO₄ · 7H₂O reduced liver Cu concentrations, it also reduced chick weight gain and food intake. Experiment 2 tested a range of cysteine and Zn levels to determine their effects on Cu toxicity in chicks. Supplemental Zn levels as low as 500 mg/kg reduced growth, but a cysteine level as low as 0.1 g/100 g increased chick weight gain and reduced liver Cu. Experiment 3 evaluated two Zn sources to determine if Zn source was affecting weight gain of chicks fed high Cu diets. There was a reduction in chick weight gain with 1,000 mg Zn/kg from Zn sulfate, but no reduction in weight gain with the same level of Zn from Zn oxide. In Experiment 4, 1,000 mg ascorbic acid/kg, 0.05 g/100 g cysteine and 1,000 mg Zn/kg from Zn oxide were tested in a 2 x 2 x 2 factorial. As in Experiment 1, ascorbic acid, cysteine and Zn were all effective in reducing liver Cu. The results suggested that L-cysteine was more effective than either L-ascorbate or Zn in ameliorating Cu toxicity, but a lower dose of cysteine together with pharmacologic additions of ascorbate and Zn (from ZnO) may be just as effective.     

Macrophage Secretory Function Is Enhanced by Low Doses of Tributyltin-Oxide (TBTO), But Not Tributyltin-Chloride (TBTCl)

Numerous studies suggest that tributyltin (TBT) is a potent immunotoxicant in nontarget organisms with lymphoid atrophy being a hallmark response. Two of the most common formulations of TBT are bis (tri-n-butyl)-tin oxide (TBTO) and tri-n-butyl-tin chloride (TBTCl). Most of studies investigating TBT-related immunotoxicity have used relatively high doses of both compounds, but little is known about the effects of very low doses. In addition, no studies have directly compared the effects of both formulations on immune function(s). We exposed female B6C3F1 mice to a single dose of TBTO or TBTCl at 0.3, 3.0, 30 mM/kg or corn oil as a carrier control. Forty-eight h later mice received a 4% solution of thioglycolate intraperitoneally to elicit peritoneal macrophages. Ninety-six h later macrophages were harvested and stimulated with a mixture of gamma-interferon (IFN-γ) and lipopolysaccharide (LPS). Nitric oxide (NO), tumor necrosis factor-α (TNF-α), transforming growth factor beta-1 (TGF-β₁), and phorbol ester-stimulated oxidative burst activity were then measured. Nitric oxide and TNF-α production were significantly elevated in the 0.3 and 3.0 mM TBTO/kg–treated groups but not in those treated by TBTCl. Background TNF-α production (without stimulation) was also elevated at these two doses but suppressed in TBTCl-treated animals. Oxidative burst activity was elevated at 0.3 mM TBTO/kg but not by TBTCl. TGF-β₁ production was not altered by either treatment, nor were body wts and organ-body wt ratios. To further evaluate the difference between the effects of TBTO and TBTCl on macrophage function, the in vitro toxicity of the two was determined using elicited peritoneal macrophages from untreated mice. Following a 24-h exposure to increasing concentrations of TBTO or TBTCl, functional viability was evaluated using the MTT assay. There were no differences between the two compounds in terms of treatment-related viability except that at the very highest concentrations (10⁻⁶ M) TBTO was more toxic than TBTCl. Received: 25 June 1997/Accepted: 6 November 1997     

Oral iodine toxicity in chicks can be reversed by supplemental bromine

Four chick bioassays were conducted to quantify iodine (I) toxicity and its amelioration in young chicks. A supplemental I level from KI of 600 mg/kg depressed growth in chicks fed methionine-deficient diets but not in those fed methionine-adequate diets. An I dose level >or= 900 mg/kg was required to cause growth depression in chicks fed a methionine-adequate corn-soybean meal diet. Iodine intoxicated chicks also displayed neurological symptoms and extreme malaise, but dose levels up to 1200 mg I/kg had no effect on blood hemoglobin or hematocrit. Supplemental I levels of 1000-1500 mg/kg caused severe growth depressions that could be totally reversed by dietary addition of 50 or 100 mg/kg bromine provided as NaBr. Nuclear accidents or terrorist actions that result in I toxicity and thyroid cancer or goiter may benefit from use of NaBr as a therapeutic agent.     

Waterborne and sediment-source toxicities of six organic chemicals to grass shrimp (Palaemonetes pugio) and amphioxus (Branchiostoma caribaeum)

Grass shrimp (Palaemonetes pugio) were exposed to either waterborne or sediment-source concentrations of fenvalerate, cypermethrin, 1,2,4-trichlorobenzene (TCB), tributyltin oxide (TBTO), triphenyltin oxide, and di-n-butylphthalate in static or flow-through test systems. Similarly, amphioxus (Branchiostoma caribaeum) were tested with fenvalerate, TCB, and TBTO. The LC50 and no-effect and 100% mortality concentrations are reported from 96-hr and 10-day tests. The toxicity of contaminated sediments could be explained by chemical partitioning into overlying or interstitial water. Amphioxus is not recommended as a routine test species because of (1) difficulty in distinguishing severely affected from dead individuals, (2) inability to determine the status of burrowed animals without disrupting sediment, (3) their relative lack of sensitivity in acute exposures to toxic chemicals, and (4) difficulty in routine collection of sufficient numbers of animals. Grass shrimp, however, are useful as an epibenthic test species for waterborne and sediment-source toxicants.     

A long-term toxicity test comprising reproduction and growth of zebrafish with 4-chloroaniiine

This study describes a long-term test over three generations, using zebrafish (Brachydanio rerio) as the test species and concentrations of 1, 0.2, and 0.04 mg/L 4-chloroaniline (CA) as a model substance. The effect of the compound on the ecologically important parameters reproduction and growth was the focus of interest. Reduction in egg release by fish raised under CA was the most sensitive parameter in the test. Compared to the toxic threshold concentration for growth (0.4 mg/L), egg release was affected by a ten-fold lower concentration (0.04 mg/L). This study demonstrates that a long-term test is still the most appropriate method to assess the chronic toxicity of a substance on fish. A chronic toxicity test is proposed which comprises two generations, with the zebrafish as test species.     

Relative toxicity and metabolic effects of cholecalciferol and 25-hydroxycholecalciferol in chicks.

The relative toxicity and metabolic effectiveness of cholecalciferol (CC) and 25-hydroxycholecalciferol (25-HCC) in chicks were evaluated by feeding six graded levels of each and observing gross and microscopic pathology as well as several metabolic parameters of calcium metabolism. Renal tubular calcification was observed when CC was fed at the rate of 10.0 mg/kg of diet and when 25-HCC was fed at the rate of 0.1 mg/kg diet. Thus, 100-fold increase in toxicity results when the hydroxylated form of CC is fed. Both microscopic renal lesions and increased renal calcium and inorganic phosphate concentrations occurred in chicks with normal serum calcium concentrations.     

Reproductive and morphological effects of o,p′-dicofol on two generations of captive American kestrels

A two-generation laboratory study was conducted on a captive population of American kestrels (Falco sparverius) to investigate the possible reproductive and teratogenic effects of the pesticide dicofol. Paired females were exposed to three levels of dicofol: 0, 5, and 20 mg/kg. Integrity of the reproductive tract of the resulting embryos was examined. Viable eggs were hatched, and these birds were permitted to breed the following year. Breeding performance for these birds was measured based on their ability to form pair bonds and exhibit normal behavior in the presence of a mate. Clutch completion, fertility, hatchability, and number of hatchlings reared to the fledging were used as reproductive parameters. Females dosed with 20 mg/kg of dicofol laid eggs with shells that were significantly (p<0.05) thinner than those of the control birds. Residue levels of dicofol in the form of dichlorobenzophenone were detected in the first and second clutch eggs of the 20-mg/kg dose group only. Male embryos from females dosed with 5 and 20 mg/kg of dicofol had gonads that were significantly different (p<0.05) from the control chicks. Feminization of male embryos was confirmed by the presence of primordial germ cells in the male gonad. Second-generation adult 5-mg/kg females showed a significantly (p<0.05) greater number of eggs and hatched chicks lost when compared to second-generation control females. Similar results were found in second-generation 5-mg/kg males paired with normal females and had a significant (p<0.05) number of chicks die posthatching. Results of second-generation breeding parameters indicate a negative effect on reproductive behavior.     

Predator–Prey Relationships in a Two-Species Toxicity Test System

In a two-species toxicity test system survival and reproduction of both the predatorHypoaspis aculeifer(Gamasida) and the preyFolsomia fimetaria(Collembola) were studied after 21 days of residual exposure to a soil contamination of the insecticide dimethoate. Additional experiments were run to analyze which species–species and compound–species relationships determine the outcome of this two–species experiment. Number of adultF. fimetariawere reduced by both predation and dimethoate exposure, whereas mites preyed less efficiently on adults than on juveniles. At 0.357 mg dimethoate/kg soil, numbers of juvenileF. fimetariawere mainly reduced by predation on adults and juveniles. At 0.7 mg/kg, an additional dimethoate effect was found, which was attributed to an effect on the reproduction ofF. fimetaria, mainly due to lethality of adults. It was reasoned that lethal effects on juvenile springtails are less important. AdultH. aculeiferwas not affected by dimethoate exposure, whereas numbers of juvenileH. aculeiferdemonstrated a decline only at the highest concentration of 0.7 mg/kg. It is hypothesized that this latter effect is possibly due to food depletion caused by a decreased availability of prey, rather than to the lethal effects of dimethoate on juvenile mites. Such a secondary effect of a pesticide application could not have been derived from a single-species toxicity experiment and demonstrates the additional value of a two-species toxicity test system.     

Acute toxicity and cholinesterase inhibition in chicks dosed orally with organophosphate insecticides

Acute toxic effects of three commonly used insecticidal preparations of the organophosphates chlorpyrifos, diazinon, and dichlorvos were examined in mixed breed broiler chicks, and cholinesterase activity in plasma and brain were measured. The acute (24 h) oral median lethal doses (LD50) of chlorpyrifos, diazinon, and dichlorvos were 10.79 mg kg(-1), 6.32 mg kg(-1), and 6.30 mg kg(-1), respectively, as determined by the up-and-down method in chicks. Signs of cholinergic toxicosis in the chicks appeared within two hours after dosing, and they included salivation, lacrimation, gasping, frequent defecation, drooping of wings, tremors, convulsions, and recumbency before death. Halving the oral LD50 of chlorpyrifos (5 mg kg(-1)), diazinon (3 mg kg(-1)), and dichlorvos (3 mg kg(-1)) caused immobility and wing drooping, but not the clinical signs of cholinergic toxicity. However, at full LD50 doses of these insecticides, chicks showed clinical signs of cholinergic toxicity similar to those seen in the LD50 experiments. Two out of six chicks died within two hours after treatment with LD50 doses of chlorpyrifos and dichlorvos, whereas LD50 dosing with diazinon caused death in three out of six chicks. Compared to control values, the insecticides reduced plasma and whole brain cholinesterase activities by 29% to 84% and 18% to 77%, respectively, depending on the dose. The decrease in plasma cholinesterase correlated well (r=0.82) with that of the brain. These data suggest that organophosphate insecticides administered orally at LD50 doses induce clinical signs of cholinergic poisoning and concurrently reduce brain and plasma cholinesterase activities in chicks.     

氨糖胶囊的安全性毒理学试验

目的观察氨糖胶囊毒性。方法最大耐受量试验（MTD）,遗传毒性试验（Ames、骨髓细胞微核及精子畸变试验）,30 d喂养试验。结果氨糖胶囊大鼠、小鼠MTD〉10.0 g/kg.bw。Ames试验、小鼠骨髓细胞微核试验及小鼠精子畸变试验结果为阴性。大鼠30 d喂养试验,在雌、雄性大鼠高剂量组为4.0 g/kg.bw（相当于人体推荐量的100倍）时各项检测指标与对照组比较差异无统计学意义。结论本试验条件下,氨糖胶囊未见明显毒性。     

Chronic toxicity of copper to a partial life cycle of the midge,Chironomus decorus

The development and hatchability ofChironomus decorus eggs were not affected by 0.1 to 5 mg/L of copper in water. The embryos developed normally and hatched at about the same time (after 55 hr of incubation). All larvae survived the duration of the test (72 hr) except those subjected to 5 mg/L of copper in water, which died after only partial emergence from the egg shell. Apparently, eggs were protected by their shell from copper. Growth ofC. decorus larvae was reduced significantly when they were reared in copper-spiked food-substrate (bound copper) from the age 1 to 15 days old (900–4,500 mg/kg of copper). The substrate copper concentration at which larval growth was reduced to 50% (EC50) was 1,602 mg/kg. Substrate copper caused deformities in the epipharyngeal plate of larval mouthparts and copper concentration higher than 1,800 mg/kg delayed adult emergence. The copper concentration in pupal exuviae and adults were positively correlated to copper concentration in the substrate in which they had been reared as larvae. Larval stage appeared to be the most sensitive to copper toxicity, while eggs were the least sensitive. Larval growth was the best indicator in detecting copper pollution, since it could detect copper at relatively low concentrations. The time to adult emergence was not considered a very good indicator, while larval deformities offered a quick tool to evaluate copper pollution.     

Effect of bis (tributyl tin) oxide on permeability of the blood-brain barrier: a transient increase.

OBJECTIVES--To study the effect of bis (tributyl tin) oxide (TBTO) on permeability of the blood-brain barrier. METHODS--Electron microscopy and an x ray microanalyser with lanthanum chloride as a tracer were used, and blood tin concentrations were determined with an atomic absorption spectrophotometer. Adult male wistar rats received 0.05 ml/kg body weight of TBTO orally. RESULTS--A transient increase in paracellular permeability at the blood-brain barrier was found 2 h after the dose of TBTO. Electron dense lanthanum deposits penetrated tight junctions of the endothelia and permeated the subendothelial space. The x ray microprobe data showed an accumulation of TBTO at the tight junctions at 2 h. Leakage of tracer did not occur at 4 h, but oedematous changes in the surrounding glial cells were prominent between 4 and 8 h and had almost returned to normal by 24 h. By atomic absorption analysis, it was seen that blood tin concentrations rapidly increased at 1 h and rose to a maximum peak at 8 h, then gradually decreased to reach zero at 24 h. CONCLUSIONS--Accumulated TBTO at tight junctions could have caused the temporary replacement of calcium ion by tin, which induces a transient increase in paracellular permeability throughout the blood-brain barrier.     

异丙威的毒性研究

目的　研究异丙威的毒性 ,制订卫生标准 ,保护生产和使用者的健康。　方法　毒性试验按文献 [1 ] 进行 ;全血胆碱酯酶测定采用盐酸羟胺—三氯化铁法。　结果　大鼠和小鼠经口 L D50 分别为 2 5 9.2和 2 99.4g/ kg.bw;家兔眼粘膜刺激试验可致结合膜轻度充血和瞳孔缩小 ;小鼠浸尾试验为阴性。Ames试验、小鼠骨髓嗜多染红细胞微核试验、小鼠精子畸形试验均为阴性。蓄积系数 >5 .3。对全血胆碱酯酶 (Ch E)有抑制作用 ,其慢性最大无作用剂量为 73 .5 mg/ kg.bw。慢性毒作用的靶器官是肝脏 ,最大无作用剂量为 49mg/ kg.bw。致畸试验虽未见仔鼠畸形 ,但有一定的早期胚胎毒性。致癌试验为阴性。根据对肝脏的慢性最大无作用剂量 ,推算出日容许摄入量 (ADI)为 2 9.4m g。　结论　异丙威的急性毒性属中等毒 ;对眼粘膜有轻度刺激作用 ;无致突变和致癌作用 ;对全血 Ch E有抑制作用 ;有一定的胚胎毒性 ;慢性毒作用的靶器官是肝脏 ,最大无作用剂量为 49mg/ kg.bw,日许摄入量为 2 9.4mg     

Availability to chicks of biotin from dried egg products

Two feeding experiments were conducted with duplicate groups of five chicks each to study the availability of biotin in spray-dried egg products. In the first experiment chicks that were fed diets containing 43% dried whole egg (DWE) grew poorly and developed perosis and dermatitis. The signs were prevented and growth improved progressively with supplementation of 0.5 and 1.0 mg biotin/kg diet. In the second experiment dried egg yolk (DEY) and dried egg white (DEW) were compared with DWE at equivalent levels of egg components. Signs of biotin deficiency and reduced growth were slightly more severe with DEW than with DWE, although liver biotin content was slightly lower at 0 and 0.5 mg biotin/kg with DWE than with DEW. Growth with DEY and no added biotin was not different from that with DEY and 500 or 1000 mg biotin/kg diet, although liver biotin was lower than when supplemental biotin was added. Liver fat was approximately five times greater in the groups receiving DWE and DEY than in the groups receiving DEW. The results show that the biotin contained in egg yolk is inadequate to counteract the deficiency of biotin caused by the avidin in egg white so that unheated dried whole egg is deficient in this vitamin.     

Soil sorption of bis-(tributylin) oxide

A statistical method was used to study the sorption of bis-(tributyltin) oxide (TBTO) by liquid versus solid soil phases. The concentration of TBTO was studied for its effect on the rate of soil sorption. The soil sorption of TBTO was found to be 99.9% of its administered amount that was in the range of 5.7-22.8 mg/g.     

Acute toxicity of veterinary and agricultural formulations of organophosphates dichlorvos and diazinon in chicks

Formulation components of organophosphate insecticidal preparations might affect their toxic action in animals. The objective of this study was to examine and compare the acute toxicity and cholinesterase inhibition in seven to 14-day-old chicks dosed orally with dichlorvos and diazinon in standard veterinary and agricultural formulations. The acute (24 h) oral median lethal doses (LD50) of the formulations were determined using the up-and-down method. Respective LD50 of dichlorvos of the veterinary and agricultural formulations in chicks were 11.1 mg kg(-1) and 6.51 mg kg(-1) and those of diazinon 6.4 mg kg(-1) and 6.7 mg kg(-1). Plasma and brain cholinesterase activities were measured by electrometry after in vivo and in vitro exposure to organophosphates. The chicks showed signs of cholinergic toxicosis within one hour of dosing. Dichlorvos (8 mg kg(-1)) and diazinon (4 mg kg(-1)) in the veterinary and agricultural formulation significantly reduced both plasma and brain cholinesterase activities in the chicks. The veterinary formulation of dichlorvos reduced plasma ChE by 60% and agricultural by 40% and brain ChE by 93% and 87%, respectively. In contrast, ChE inhibition by diazinon in the agricultural formulation of diazinon was stronger than by the veterinary formulation; 72% vs. 64% in plasma and 97% vs. 80% in the brain, respectively. The highest in vitro inhibitions were observed with dichlorvos in the agricultural formulation (50%) in the brain samples and with diazinon in the agricultural formulation (52%) in the plasma samples. While they exist, differences between formulations cannot be taken as a rule and further investigations should inventory the toxicity of standard veterinary and agricultural organophosphate formulations in addition to the known data for pure forms.