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An amino-derivative of parathion was prepared and conjugated to human serum albumin (HSA) and bovine thyroglobulin (BTG) via diazonium condensation. Spleen cells producing high titer antibody were removed and fused with myeloma cells of SP2/0 origin. Using a conventional immunization protocol, we generated nine stable murine monoclonal antibodies (MAbs) producing cell lines to parathion. After four successive limiting dilutions, antibodies produced by nine clones had high affinities, ranging from 10(9) to 10(12) M(-1). These clones were found to be of IgG class and IgM class with k light chain. Subclass determination showed that the clones produced IgG(1), IgG(2a), IgG(2b), and IgM types of antibody. One clone (2H(9)) was used to establish the calibration curve with a sensitivity of 26 ng/mL, a practical working range of 46.8-6000 ng/mL parathion.

Spiking of tomato and apple fruits with parathion at different levels of about 1-4 mg/kg irradiation and under simulated sunlight conditions resulted in nearly complete photodegradation within 13 h, but extractable parathion degradation products could not be found in any case. However, after irradiation of an unrealistically spiked apple (134 mg/kg) different photoproducts including aminoparathion (AP) were detectable by HPLC, proving that the hitherto postulated photochemistry of parathion indeed takes place in the fruit cuticle environment. Besides the photoreduction pathway it was shown for the first time that AP is also easily formed by reduction of the primary photoproduct nitrosoparathion with thiols (cysteine, glutathione), while ascorbic acid only leaves hydroxylaminoparathion. In the presence of polyphenols, AP was effectively bound to quinone intermediates formed by both silver oxide and polyphenol oxidases. For pyrocatechol, a disubstituted o-quinone derivative could be isolated as a dark red addition product and structurally be elucidated. However, in the presence of caffeic acid, catechol, naringin, and quercetin, respectively, insoluble dark colored polymers precipitated within 48 h, while in the supernatants AP was not detectable any more. Polymer-bound and nonextractable AP was proven by transesterification with sodium ethoxide releasing O,O,O-triethyl thiophosphate which was determined by GC. Additionally, AP itself was a substrate for polyphenol oxidases, resulting in a quinone imine intermediate which in turn reacted with excessive AP yielding deep red colored di- and trimerization products.

Though little attention has been given to the possibility that glial cells may represent a target for the developmental neurotoxicity of organophosphorus (OP) insecticides, recent evidence, obtained in particular with chlorpyrifos (CP), suggests that developmental exposure to this compound may indeed target astrocytes. To substantiate and expand these observations, we carried out a series of in vitro studies utilizing fetal rat astrocytes and a human astrocytoma cell line, 1321N1 cells, to investigate the effect of the OPs CP, diazinon (DZ) and parathion (P), their oxygen analogs chlorpyrifos oxon (CPO), diazoxon (DZO) and paraoxon (PO), and their metabolites 3,5,6-trichloro-2-pyridinol (TCP), 2-isopropyl-6-methyl-4-pyrimidol (IMP) and para-nitrophenol (PNP), on cell proliferation. In fetal rat astrocytes and astrocytoma cells maintained in serum, CP, DZ, P, CPO, DZO, and PO induced a concentration-dependent inhibition in [(3)H]thymidine incorporation with a very similar potency (IC(50) between 45 and 57 microM). Among the other metabolites, PNP was the most potent (IC(50)=70-80 microM), while TCP and IMP were much less effective (IC(50)>100 microM). Cytotoxicity appears to account only for a small part of the effect on DNA synthesis. OP insecticides and their oxons were three- to six-fold more potent in inhibiting [(3)H]thymidine incorporation when cells were synchronized in the G(0)/G(1) phase of the cell cycle and re-stimulated by carbachol or epidermal growth factor. These results suggest that OP insecticides and their oxons affect astroglial cell proliferation and that the transition from the G(0)/G(1) to the S/G(2) phase of the cell cycle may be particularly sensitive to the action of these compounds.

An in vitro model, the aggregating brain cell culture of fetal rat telencephalon, has been used to study the maturation-dependent sensitivity of brain cells to two organophosphorus pesticides (OPs), chlorpyrifos and parathion, and to their oxon derivatives. Immature (DIV 5-15) or differentiated (DIV 25-35) brain cells were treated continuously for 10 days. Acetylcholinesterase (AChE) inhibitory potency for the OPs was compared to that of eserine (physostigmine), a reversible AChE inhibitor. Oxon derivatives were more potent AChE inhibitors than the parent compounds, and parathion was more potent than chlorpyrifos. No maturation-dependent differences for AChE inhibition were found for chlorpyrifos and eserine, whereas for parathion and paraoxon there was a tendency to be more effective in immature cultures, while the opposite was true for chlorpyrifos-oxon. Toxic effects, assessed by measuring protein content as an index of general cytotoxicity, and various enzyme activities as cell-type-specific neuronal and glial markers (ChAT and GAD, for cholinergic and GABAergic neurons, respectively, and GS and CNP, for astrocytes and oligodendrocytes, respectively) were only found at more than 70% of AChE inhibition. Immature compared to differentiated cholinergic neurons appeared to be more sensitive to OP treatments. The oxon derivates were found to be more toxic on neurons than the parent compounds, and chlorpyrifos was more toxic than parathion. Eserine was not neurotoxic. These results indicate that inhibition of AChE remains the most sensitive macromolecular target of OP exposure, since toxic effects were found at concentrations in which AChE was inhibited. Furthermore, the compound-specific reactions, the differential pattern of toxicity of OPs compared to eserine, and the higher sensitivity of immature brain cells suggest that the toxic effects and inhibition of AChE are unrelated.

This laboratory study investigated the effectiveness of selected detergents and the phenomenon of simulated environmental conditions (weathering) on the removal of a commercial-grade mixture of parathion and methyl parathion from a three-layer laminated fabric. The weathering treatment consisted of exposure and non-exposure to simulated environmental conditions of heat, light, and humidity. Contaminated fabric samples were laundered in one of three detergents containing an anionic, a nonionic, and a combined anionic and nonionic surfactant. The test fabric, a three-layer fabric containing an impermeable microporous film laminated between two layers of nylon, was pipette-contaminated with 400 microliters of field strength pesticide solution and allowed to dry. Half of the contaminated samples were weathered in an Atlas Fade-Ometer. All of the contaminated samples were subsequently laundered in a Launder-Ometer. Percent of pesticide residue was determined by gas chromatography. Weathering did significantly reduce both parathion and methyl parathion residues remaining in the test fabric. No statistically significant difference was found among the three detergents. High amounts of both parathion and methyl parathion remained in the test fabric after weathering and laundry treatments. Before the test fabric can be recommended for use in protective garments further research is needed to develop more effective decontamination procedures.

Physiologically based pharmacokinetic (PBPK) modeling of foreign chemicals is dependent on the accurate determination of their tissue/blood distribution coefficients, Kp (partition coefficients). The present study was undertaken to evaluate the validity of the in vitro estimation of the Kp values of the organothiophosphate insecticides parathion and methyl parathion by equilibrium dialysis. Data derived from previously published studies that utilized single-pass perfusions of mouse livers in situ with parathion or methyl parathion were analyzed to determine liver/perfusate Kp values from the equation Kp = (t 1/2ss) (Q)/(0.693) (VH), where Kp is the liver/perfusate distribution ratio, t 1/2ss is the half-life for approach to steady state of the chemical, VH is the liver volume, and Q is the perfusate flow rate. Kp values for methyl parathion were calculated to be 16.4 +/- 7.5 and 9.5 +/- 2.7 (mean +/- SD) for perfused livers and equilibrium dialysis, respectively, while estimates of Kp for parathion were 15.6 +/- 6.3 and 19.5 +/- 5.5 for perfused livers and equilibrium dialysis, respectively. These results indicate that equilibrium dialysis can be utilized to give an accurate estimate of tissue partitioning of parathion and methyl parathion from perfusate into perfused mouse livers.

The behavioral effects of subchronic exposure of male Wistar rats to the organophosphorus compound parathion-methyl (for 6 weeks 1/50 or 1/100 of LD50, PO) were studied. Open-field (OF) and elevated plus-maze (EPM) tasks were used to decide whether or not the compound can affect behavior. Significant effects were measured in the OF activity during the first minute, on the activity of crossing outer squares, increasing latencies to leave center, start of rearing, grooming, and defecation. EPM parameters showed an increased amount of time spent in the open arms and a clear tendency to enter more frequently open arms. The defecation rate in the EPM was significantly decreased. Results are discussed in terms of effects on emotional behavioral components (arousal) and on physiological functioning of the peripheral nervous system (lengthening of latencies).

Regulation of gonadal function by gonadotropic hormone (GtH) and gonadotropin-releasing hormone (GnRH) in Channa punctatus was significantly affected by nonlethal levels of Metacid-50 and Carbaryl. Under laboratory conditions, the time-dependent decrease in serum GtH level was higher in Carbaryl-treated fish than in Metacid-50-treated fish. The situation was reversed in the field, with a higher inhibitory effect of Metacid-50 being recorded. On the other hand, pituitary GtH content and GnRH activity were inhibited to a greater extent by Metacid-50 than by Carbaryl under both field and laboratory conditions. The present findings highlight that even low doses of Metacid-50 and Carbaryl are effective enough to cause reproductive damage, as evidenced by homeostatic unbalance of the reproductive regulatory system.

The genotoxic effect of methyl parathion, an organophosphorus insecticide commercially available as Metacid 50, was studied in Swiss albino mice using bone marrow and peripheral blood micronucleus tests. Single acute oral doses of the insecticide at concentrations of 75.0, 37.5, 18.75 and 9.375 mg/kg body weight, equivalent to 1/2 LD50, 1/4 LD50, 1/8 LD50 and 1/16 LD50, administered to female mice, elicited positive responses in bone marrow and peripheral blood micronuclei tests. Statistically significant increases in the frequency of micronuclei were observed at higher doses in both the tests performed. The data obtained for our experiments suggest that methyl parathion is a potent mutagen and so it is also likely to have a genotoxic effect in humans.

In a first experiment, the potential effectiveness of three cream formulations (A, B, C) against skin irritation due to n-hexane was evaluated using a guinea pig model. Semi-quantitative histopathological assessment of skin lesions were carried out. Due to interesting protective effects, cream formulation A (Travabon) was selected and further investigated. In a second series of experiments, this cream showed some protective effects against irritation due to toluene, but was not found efficacious against trichlorethylene irritation.

Rats were subjected to physical exercise in the form of a single race in a treadmill. Unexercised animals and those immediately or 1 h after the exercise were given oil or oily solution of parathion-methyl in a dose of 10 mg/kg by stomach gauge. At 1 h after pesticide administration the activity of cholinesterase (ChE) was determined in the serum, of paraoxonase--in the serum and liver, and that of beta-glucuronidase (beta-gluc)--in the serum, liver and intestine. Single physical exercise increased ChE activity in the serum, inhibited paraoxonase activity in the serum and liver; on the other hand, it did not affect significantly beta-gluc activity in the serum, but inhibited that enzyme in a transient manner in the liver and activated it in the intestine. In acute poisoning with parathion-methyl it was observed that ChE and paraoxonase activities were inhibited, while beta-gluc activity was enhanced in the serum. Single physical exercise either diminished or had no effect on enzymatic changes observed in acute poisoning with parathion-methyl.

When compared with non-exposed controls, a group of pesticide plant workers chronically exposed to methyl-parathion did not show an increased frequency of chromosome aberrations in lymphocyte cultures. Although methyl-parathion increased chromosome aberrations in cases of intoxication, a chronic exposure to small doses in the work place did not seem to produce the same effect.

The effects of culture filtrates, mixed populations, and common microbial exudates on bacterial transformations of three agricultural and industrial chemicals were investigated. Test chemicals included methyl parathion, diethyl phthalate, and 2,4-dichlorophenoxyacetic acid butoxyethyl ester. The presence of various cultures, filtrates, or exudates of algae, fungi, or other bacteria either stimulated or inhibited bacterial transformation rates. Inhibition resulted from treatments that lowered the pH, and stimulation resulted from an increase in cell biomass (based on plate counts) and from a different process whereby rates of transformation per bacterial cell rapidly increased as much as 10-fold.

The ability of human placental glutathione S-transferase (GSHTr) to metabolize methyl parathion (MeP) was examined. MeP was found to be a substrate for both partially purified pre-term and highly purified term placental GSHTr. The characterization of the reaction by high performance liquid chromatography revealed the presence of desmethyl parathion (DesMeP) as the sole metabolite. Term placental GSHTr activity towards MeP ranged from 2.22 to 3.53 nmoles DesMeP formed X min-1 X mg-1 while an activity of 0.60 to 1.12 nmoles DesMeP formed X min-1 X mg-1 was observed with the pre-term placental enzyme. The absence of the O-dearylation reaction by pre-term and term placental GSHTr represents a major species- and/or tissue-specific difference.

The mechanisms for the lower toxicity of fenitrothion as compared with methylparathion were investigated in male rats. The difference in the acute toxicity of the insecticides could be the more rapid decomposition of fenitrothion and fenitrooxon in rat liver than that of methylparathion and methylparaoxon. In particular, the decomposition of fenitrothion by hepatic microsomes was accelerated by increasing the insecticide concentration as the substrate. The oxygen analogues of both insecticides, fenitrooxon and methylparaoxon, were not detected in the brain after the administration of their parent compounds. From these results, it is concluded that the lower toxicity of fenitrothion as compared with methylparathion could be due to the greater rate of the decomposition of fenitrothion to its less toxic metabolites, rather than to the relative rate of penetration of the oxygen analogues into brain.

The inhibition of acetylcholinesterase, E.C.3.1.1.7, (AChE) activity in the ventral nerve cord of pink shrimp (Penaeus duorarum) by methyl parathion (MPT) and methyl paraoxon (MPO) was investigated. When the animals were exposed to these compounds in water (in vivo), AChE activity of the isolated nerve cord was significantly depressed by MPT only in moribund shrimp after exposure for six hr to 1.3 micrograms/L (96 hr LC50 = 1.9 micrograms/L). Methyl paraoxon (96 hr LC50 = 13.6 micrograms/L) did not depress AChE activity in surviving animals after exposure for 74 hr to 0.98 micrograms/L. Exposure of the excised ventral nerve cord directly (in vitro) resulted in inhibition of 100% after exposure for one hr to 60 mg/L MPT, 100% after exposure for one hr to 300 micrograms/L MPO. Implications with regard to the use of AChE activity as a monitor of water pollution by inhibitors of this enzyme are discussed.

The levels of proteins, glucose and glucose-6-phosphate dehydrogenase activity were studied in muscle, gill and liver tissues of the fish Tilapia mossambica under sublethal methyl parathion toxicity. Tissue glucose levels decreased with increased soluble protein content and the activity levels of glucose-6-phosphate dehydrogenase were elevated considerably. These results are discussed in relation to the involvement of glucose-6-phosphate dehydrogenase in both synthetic and detoxification processes as an adaptive response against methyl parathion toxicity.

Effects in vitro of methyl parathion on some kinetic constants of succinic dehydrogenase (SDH) in hepatopancreas of freshwater mussel, L. marginalis were studied. Altered pH vs. specific activity curves for SDH demonstrated significant inhibition by methyl parathion in buffered acidic, neutral and alkaline ranges. At high pH ranges IC50 (12.5 microM) of methyl parathion did not cause 50% inhibition enzyme as it did at neutral and acidic pHs. Activation energies (delta E) were found to be increased suggesting decreased efficiency of enzyme in presence of methyl parathion. Non-competitive inhibition with respect to activation by succinate was indicated by decreased maximal velocity (V) without change in Michaelis Menten constant (Km). Pyridine-2-aldoxime (25 microM), pyridine-4-aldoxime (15 microM) and L-cysteine (40 microM) neutralized the inhibition of SDH by methyl parathion (12.5 microM). The kinetic data suggests that inhibition of SDH by methyl parathion was pH and temperature independent.

Clearly pronounced changes in plasma enzyme activities were observed 24 hours after one and two applications of parathion methyl (PM). The most strongly pronounced rise was in activity of aspartate-amino transferase and was recorded from both sexes. PM application caused sizeable changes in male rats. Comparison between reactions after one and two applications revealed more intensive changes in males after the 1st application. Somewhat larger differences were recordable in some cases between the 1st and 2nd applications. Closer agreement between reaction intensities after the 1st and 2nd PM applications was recordable from female rats. In either sex in response to one single and repeated application parameters returned to normal within nearly one and the same period of time. No secured relationships between activities prior to and after application of PM could be derived from the assays of gamma-glutamyl transpeptidase (gamma-GT). Both increase and decrease of determined enzyme activities were actually recorded. Activities were highly variable in the control groups. Extreme rises were recordable in some cases from both control and experimental groups. No conclusions so far can be drawn as to "normal values" in rat plasma, possible sex-related differences, and behaviour of enzyme activity in response to one single or repetitive applications. Hence, within common investigations of acute toxicity of alkylphosphates, gamma-GT was found to be not suitable for detection of damage to the liver or other organs.

Nitrophenolic and alkyl phosphate metabolites of methyl and ethyl parathion in the urine of human subjects soon after doses of 1 to 4 mg have been ingested. Particular alkyl phosphates can serve as specific indices of absorption of the respective parathions. Paranitrophenol and diethyl thiophosphate are rapidly eliminated in the urine, while excretions of dimethyl phosphate, and particularly diethyl phosphate, are more protracted. Cumulative excretions of paranitrophenol and alkyl phosphates exhibit sufficient dose-dependence at convenient intervals following parathion ingestion to encourage use of metabolite measurements in estimating occupational absorption of the parathion insecticides.

A radio gas-chromatographic system consisting of a gas chromatograph, combustion furnace, proportional counter and guard scintillation counter has been studied for the analysis of trace amounts of 14C-labelled organophosphorus insecticides. The proportional detector is a concentration sensitive detector requiring strict flow control. Sensitivity depends on the concentration of the quenching gas used. Using 14C-ethyl parathion and 14C-metamidophos as model compounds a linear range of 3500-5000 was measured. A sensitivity of 0.98 cpm/pCi and a detection limit of 24pCi were obtained which allows the detection of 0.33 ng if the specific activity of the insecticide is 21.5 mCi/mMol. The system must be decontaminated in order to achieve optimum detection levels by passage of oxygen through the combustion tube and by periodically injecting the corresponding non-labelled compound into the column. A solvent effect was found to interfere in the analysis due to the sudden production and expansion of CO2. This effect was eliminated by choosing column conditions to prevent elution near the solvent. The system was tested by analyzing a mixture of 37 ppb and 23 ppb of ethyl parathion and its oxygen analog in orange juice.

Acetylcholinesterase (AChE) activity and acetylcholine (ACh) content of muscle, gill, liver and brain tissues of control and methyl parathion-exposed (MPE) fish were determined. In addition, in vitro concentrations of eserine necessary to produce inhibition of AChE equivalent to in vivo inhibition by sublethal amounts of methyl parathion (MP) were also investigated. AChE activity decreased in all tissues, while ACh content showed a corresponding increase. These observations indicate disruption of nerve impulse conduction. The in vitro effect of eserine on AChE activity differed with the type of MP action. These results are discussed in relation to the sensitivity and extent of innervation of various tissues.

Male mice (Q strain) received a single i.p. injection of 3 organophosphorus compounds: ethylparathion (10 mg/kg), its methyl analogue (methylparathion, 10 mg/kg), or its phosphate derivative (ethylparaoxon, 0.3 mg/kg). The number of chromosome aberrations observed in bone marrow cells and spermatogonia, and the frequency of pre- and postimplantation foetal lethality obtained in a dominant lethal mutation assay, did not conclusively prove that the tested compounds produced a mutagenic effect.

The dimethyl-substituted organothiophosphate insecticides methyl parathion and azinphos-methyl are thought to undergo glutathione-mediated detoxification in mammals. In the present study, depletion of hepatic glutathione in the mouse by pretreatment with diethyl maleate potentiated the acute toxicities of methyl parathion and azinphos-methyl, whereas depletion of hepatic glutathione by pretreatment with buthionine sulfoximine did not. Furthermore incubation of 50 microM methyl parathion with mouse hepatic microsomes for 5 min in the presence of 1 mM diethyl maleate led to significantly greater (p less than 0.05) production of methyl paraoxon, compared to incubations in the absence of diethyl maleate. Conversely, 1 mM diethyl maleate had no effect on metabolic activation of azinphos-methyl by mouse hepatic microsomes, while 10 mM inhibited slightly production of azinphos-methyl oxon from azinphos-methyl. These results suggest normal levels of hepatic glutathione are not required for detoxification of methyl parathion or azinphos-methyl in the mouse. Moreover the potentiation of the acute toxicity of methyl parathion following diethyl maleate pretreatment could result, at least in part, from enhanced production of methyl paraoxon. However, diethyl maleate likely acts through another mechanism(s) as well since it did not enhance the metabolic activation of azinphos-methyl in vitro. These data raise serious doubts about the participation of glutathione in the detoxification of methyl parathion and azinphos-methyl in vivo in the mouse.

Teratogenic effects of methylparathion / Wofatox 50 EC/ and Parathion 20 WP as positive control material were tested in pheasant embryos. On the 12th day of incubation 0.1 ml of the emulsions or suspensions of the insecticides at different concentrations was inoculated into the air space of embryonated eggs. The following dose levels were employed: 27 and 270 mg/kg egg of Wofatox 50 EC, and 10 mg/kg of Parathion 20 WP. Morphological changes were evaluated by macroscopic, skeletal staining and light microscopic examinations of the embryos. Primary hypoplasia or atrophy developed in the cervical musculature /m. longus colli/ accompanied by lordosis and scoliosis of the cervical spine. In most cases we also found cyllosis .

Higher yield and performance in plant and animal production will depend on reinforced use of pesticides, particularly alkyl phosphate esters and insecticidal carbamates. Prenatal toxic action of the pesticides used today may be detrimental to human and animal health. Prenatal-toxicological tests, using parathion-methyl, were conducted on the basis of known but modified experimental methods. The vulnerability of a rat strain was tested by applying to it teratogenic model substances (trypan blue and cyclophosphamide). Several oral applications of parathion-methyl (3 ppm) during the sensitive phases of germ formation and growth (fifth to ninth and eleventh to fifteenth or eleventh to nineteenth days from conception) were followed by clear embryotoxic effects, such as retardation and increased resorption. The average number of resorption sites grew from nine in the control group to 20 in the experimental group. Postnatal malformations were not observed.

Methyl parathion (1, 3, 10 and 30 mg.kg-1) was injected intravenously in dogs and the serum concentrations were followed in function of time. For each dose the serum level data were fitted to a two- or tri-exponential equation by means of a non-linear least-squares regression analysis computer program. During the first hours after injection a rapid and important decrease of the serum levels was observed, whereas afterwards the levels decreased more slowly with a harmonic mean terminal half-life of 7.2 h (range 6.6-8.8 h) for the 10 mg.kg-1 dose. Simulations using the kinetic parameters obtained for the dose of 10 mg.kg-1 show that elimination of methyl parathion from the body is fast (5 h after injection only 30% of the dose is still present in the body) and that the fraction remaining is mainly located in the peripheral compartments.

Liquid chromatography with ultraviolet detection (LC-UV) and positive and negative ion mode (PI and NI, respectively) thermospray LC-mass spectrometry (LC-MS) were used for the analysis of the organophosphorus pesticides azinphos-methyl, diazinon and parathion-methyl and their corresponding breakdown products obtained after basic hydrolysis (pH 7-11). LC analysis was performed in the reversed-phase mode using methanol-water (80:20) or methanol-water (70:30) + 0.1 M ammonium acetate for LC-UV or LC-MS, respectively. By employing NI thermospray LC-MS the identification of p-nitrophenol, showing the [2M-H]- ion as the base peak, was feasible and confirmed the LC-UV chromatogram at 220 nm. When the PI mode was used, [M + NH4]+ and [M + H]+ ions were obtained as base peaks for azinphos-methyl and diazinon, respectively. The degradation rates varied from diazinon, which showed no degradation during a period of ten days, to azinphos-methyl and parathion-methyl, for which degradation occurred rapidly when the pH was increased from 7 to 11.

Pesticide workers usually contaminate their cigarettes with less than 100 microgram per cigarette by handling them, but in some instances such contamination has been found to be over 200 microgram. To obtain values for potential exposure resulting from smoking contaminated filter tip and nonfilter cigarettes, from 10 to 200 microgram of parathion was applied to the cigarette surface area found to be most often contaminated by hands. This was followed in two separate experiments by simulated smoking using a special apparatus to determine (1) passage of toxic material through cigarettes in mainstream smoke, (2) amount found in sidestream smoke, (3) amount trapped in the filter or equivalent butt end, and (4) amount recovered in ashes. The amount of parathion passing through cigarettes as a potential for inhalation exposure ranged up to 28% of dosing levels. No paraoxon or S-ethyl parathion was detected. Although there was an indication that slightly more pesticide was recovered from filters than from equivalent butt ends, the amount recovered in mainstream smoke of filter type cigarettes was not significantly lower than for nonfilter cigarettes. Location of contamination on a cigarette had minimal effect on the amount found in mainstream smoke.

With regard to brain acetylcholinesterase and acetylcholine and serum triiodothyronine (T3) and thyroxine (T4) profiles, a biphasic response pattern was elicited in Channa punctatus chronically exposed to nonlethal doses of locally used pesticides, namely, Metacid-50 and Carbaryl. Data revealed that these xenobiotics caused significant inhibition of brain acetylcholinesterase activity and a decrease in thyroxine level accompanied by a concurrent increase in acetylcholine accumulation and T3 level. It is surmised that Metacid-50 and Carbaryl influence both neural and hormonal functions.