The effects of organophosphorus poisoning on dopamine and 5-hydroxytryptamine concentrations in the brain of the cricket, Acheta pennsylvanicus, and the cockroach, Periplaneta americana

Liquid chromatography with electrochemical detection was used to measure dopamine and 5-hydroxytryptamine concentrations in the brains of crickets (Acheta (Gryllus) pennsylvanicus) and cockroaches (Periplaneta america) treated with the organophosphate dicrotophos. Organophosphate treatment did not cause depletion in dopamine and 5-hydroxytryptamine concentrations although reserpine treatment caused a reduction in the concentrations of both amines in the brains of these insects. Fluorescent histochemical studies of cricket brains confirmed these observations.     

Structure-activity correlations of the insecticide Prolan and its analogs

Structure-activity correlations for 45 insecticidal diaryl nitropropanes (Prolan analogs) were analyzed by multiple regression analysis. Molecular bulk constants including van der Waal's radii, molar attraction constants, parachor, steric constants such as Taft's E₈ and Verloop's dimensional steric constants, hydrophobic constants such as II, and electronic parameters such as σ, F, and R were evaluated. It was concluded that the diaryl nitropropanes like the diaryl trichloroethanes fit into a receptor site which has an optimum volume for maximum interaction. The interaction between the insecticide and the receptor shows high correlation with steric constants for the aryl substituents and with intermolecular attractive forces. Highly asymmetrical compounds such as 1-(p-fluorophenyl)-1-(p-hexoxyphenyl)-2-nitropropane were surprisingly effective insecticides.     

Long-term effects of DDT on the behavior and central nervous system activity in Periplaneta americana

The effects of p,p′-DDT and four of its analogs on electrical activity in the central nervous system of the cockroach, Periplaneta americana (L.), were investigated. Cockroaches were injected intraabdominally with an organochlorine compound at LD₅₀ 96-hr doses (except for p,p′-DDE). Extracellular recordings were made from the central nervous system at 1 hr, 24 hr, or 3 weeks postinjection. p,p′-DDT, methoxychlor, and p,p′-DDD induced behavioral changes (tremors, jitters, hyperexcitability) and repetitive firing in the central nervous system prior to 1 hr postinjection. By 24 hr postinjection, most behavioral signs of poisoning had disappeared, though repetitive firing could still be readily elicited in the central nervous system. Cockroaches injected with o,p′-DDT, however, usually required about 48 hr before overt signs of poisoning became apparent. Cockroaches treated with p,p′-DDT or o,p′-DDT behaved normally at 3 weeks postinjection but still displayed a significant occurrence of repetitive firing in the central nervous system. A mechanism is proposed to explain how a cockroach might recover behaviorally from a sublethal dose of an organochlorine compound but still display repetitive firing in its central nervous system. A direct “cause and effect” relationship between repetitive firing in the central nervous system and mortality (and external signs of poisoning) is therefore questioned.     

Paraoxon-induced release of β-glucuronidase from rat hepatocytes in vitro

A suspension culture of isolated rat hepatocytes was used to reproduce in vitro the paraoxon-induced release of hepatic β-glucuronidase observed in vivo. After a short latent period, exposure of hepatocytes to paraoxon at 10^?7 to 10^?4M resulted in a typical dose-dependent response, with highest release occurring at 10^?4M paraoxon. With 10^?3M paraoxon, however, response was anomalous with a much-decreased enzyme release. As expected from earlier results in vivo, SV₁-oxon exhibited less effect than paraoxon.     

In vitro activity and binding characteristics of the hydroxybenzonitriles in chloroplasts isolated from Matricaria inodora and Viola arvensis

The electron transport inhibition, uncoupling, and binding of ioxynil and bromoxynil salts is compared in chloroplast fragments isolated from two weed species with contrasting responses to the hydroxybenzonitriles. Ioxynil Na was three to four times more inhibitory than bromoxynil K towards DCPIP and SiMo reduction in both Matricaria inodora and Viola arvensis. Ioxynil Na was also a more potent uncoupler of PSI-dependent electron transport from ascorbate/DCPIP to methyl viologen. Uncoupling occurred at concentrations higher than those that inhibited electron transport. Binding studies with [¹⁴C]bromoxynil K and [¹⁴C]ioxynil Na salts revealed slightly biphasic curves with no significant difference in the amounts of the two herbicides bound at a given concentration. The ratios of inhibition constant (K_i) and binding constant (K_b) were approximately one for ioxynil Na and three for bromoxynil K. Radiolabelled herbicide displacement studies revealed that ioxynil Na could partially displace bound [¹⁴C]bromoxynil K, but bromoxynil K could not displace bound ioxynil Na at biochemically active concentrations. Ioxynil Na may be a more effective inhibitor than bromoxynil K because it binds more strongly to the thylakoid membrane.     

The effect of O,S,S,-trimethyl phosphorodithioate on the in vivo metabolism of phenthoate in the rat

The in vivo metabolism of phenthoate (O,O-dimethyl S-[α-(carboethoxy)benzyl]phosphorodithioate) was followed in rats after oral administration of a nontoxic dose of 100 mg/kg. The same metabolic study was conducted following coadministration of 0.5% O,S,S-trimethyl phosphorodithioate (OSS-Me). When administered alone, phenthoate was metabolized principally by carboethoxy ester hydrolysis and cleavage of the PO and CS bonds, resulting in at least six metabolites. The primary urinary metabolite excreted was phenthoate acid. Coadministration of 0.5% OSS-Me did not alter the types of metabolites excreted. However, a reduction of the carboxylesterase-catalyzed product (phenthoate acid) was observed, indicating that the enzyme responsible for the major pathway of phenthoate detoxication was inhibited. Alternate detoxication processes did not compensate for the reduction in carboxylesterase-catalyzed detoxication. It was concluded that inhibition of the carboxylesterase enzymes is the major cause of the potentiation of phenthoate toxicity by OSS-Me.     

Enhancement of dye-sensitized phototoxicity to house fly larvae in vivo by dietary ascorbate,diazabicyclooctane, and other additives

Several reagents reported to be singlet oxygen quenchers and/or radical scavengers and to be protectants against photooxidative damage to isolated systems in vitro were examined, in vivo, for protective effect on the larvae of the house fly (Musca domestica L.; Diptera:Muscidae). A standardized erythrosine-sensitized phototoxic test procedure was used. β-Carotene appeared to show some protective effect. Other dietary additives exhibited no measurable degree of protection to the larvae in vitro; on the contrary, mortality increased in the presence of butylated hydroxytoluene, ascorbate, and diazabicyclooctane.     

The apparent in vivo neuromuscular effects of the δ-endotoxin of Bacillus thuringiensis var. israelensis in mice and insects of four orders

Alkaline-dissolved crystal δ-endotoxin from Bacillus thuringiensis var. israelensis (serovar H 14) was injected into mice and seven species of insects representing the orders Lepidoptera, Orthoptera, Coleoptera, Hemiptera, and Diptera. High in vivo toxicity, at 1 to 5 ppm (μg toxin/g body wet wt), was observed with mice and some insects, including some that are not sensitive to the toxin when administered orally. Neuromuscular effects were observed when the toxin was injected directly into the body cavity of the test animals. Biochemical studies suggested that different protein fragments within the crystal δ-endotoxin may be responsible for the majority of the mosquito larvacidal activity and the neurotoxic symptoms observed in larvae of Trichoplusia ni.     

Increased cyclic nucleotides in several tissues of the cockroach and mouse following treatment with toxaphene

Cylic AMP (cAMP) and cyclic GMP (cGMP) concentrations in toxaphene-treated cockroaches, Leucophaea maderae (Fab.), increased in all tissues sampled, with the greatest increases occurring at 24 hr for cAMP and 168 hr for cGMP. Asymptomatic mice treated with 112 mg/kg of toxaphene were not significantly different from controls. Symptomatic mice showed increased cAMP in all tissues examined and an increase in testicle cGMP. The greatest increases in cAMP occurred during the more advanced stages of toxaphene poisoning.     

Pyrethroid action on the nicotinic acetylcholine receptor/channel

The interactions of natural pyrethrins and nine pyrethroids with the nicotinic acetylcholine (ACh) receptor/channel complex of Torpedo electric organ membranes were studied. None caused significant reduction in [³H]ACh binding to the receptor sites, but all inhibited [³H]perhydrohistrionicotoxin ([³H]H₁₂-HTX) binding to the channel sites in presence of carbamylcholine. Allethrin inhibited [³H]H₁₂-HTX binding noncompetitively, but [³H]imipramine binding competitively, suggesting that allethrin binds to the receptor's channel sites that bind imipramine. The pyrethroids were divided into two types according to their actions: type I, which included pyrethrins, allethrin, bioallethrin, resmethrin, and tetramethrin, was more potent in inhibiting [³H]H₁₂-HTX binding and acted more rapidly (i.e., in <30 sec). Type II, which included permethrin, fluvalinate, cypermethrin and fenvalerate, was less potent and their potency increased slowly with time. Also, inhibition of the initial rate of [³H]H₁₂-HTX binding by type I compounds increased greatly by the presence of the agonist carbamylcholine, but this was not so with type II compounds. The receptor-regulated ⁴⁵Ca²⁺ flux into Torpedo microsacs was inhibited by pyrethrins and pyrethroids, suggesting that their action on this receptor function is inhibitory. There was very poor correlation between the potencies of pyrethrins and pyrethroids in inhibiting [³H]H₁₂-HTX binding and their toxicities to house flies, mosquitoes, and the American cockroach. However, the high affinities that several pyrethroids have for this nicotinic ACh receptor suggest that pyrethroids may have a synaptic site of action in addition to their well known effects on the axonal channels.     

The effect of diflubenzuron [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea] on soybean [Glycine max (L.) Merr.] photosynthesis,respiration, and leaf ultrastructure

The effect of the insecticide diflubenzuron [1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea] on photosynthesis, respiration, and leaf ultrastructure of soybean [Glycine max (L.) Merr., cv. Swift] was examined on plants treated at the second trifoliate leaf stage with 0, 0.067, and 0.269 kg of active ingredien/ha of diflubenzuron. Photosynthesis and respiration were measured with an infrared CO₂ analyzer in an open flow system prior to diflubenzuron application and at 4, 24, 48, and 96 hr after treatment with diflubenzuron. Diflubenzuron had no effect on soybean photosynthesis at any rate examined. Respiration was stimulated by the high rate (0.269 kg/ha) in a transitory manner. Tissue samples removed from both old and new leaves, 9 days after diflubenzuron application, were used for the ultrastructure study with the transmission electron microscope. The lower trifoliate leaves contained more starch grains than the upper ones being formed after treatment, but no aberrations or degradation of leaf ultrastructure due to diflubenzuron treatment were evident.     

Pyrethroid-hydrolyzing esterases in southern armyworm larvae: Tissue distribution,kinetic properties,and selective inhibition

Esterase activity hydrolyzing both [1RS,trans]- and [1RS,cis]-permethrin was detected in crude homogenates of the following southern armyworm (Spodoptera eridania Cramer) larval tissues: cuticle, gut, fat body, head capsule, Malpighian tubules, and silk gland. Neither substrate was detectably hydrolyzed by hemolymph. The highest esterase activities per insect equivalent of tissue were found in cuticle, gut, and fat body for the trans isomer and in cuticle and gut for the cis isomer. Each preparation hydrolyzed the trans isomer more rapidly, but the degree of specificity varied greatly between tissues. Differences in apparent K_m and V_max values between the three most active tissues were threefold or less for trans isomer hydrolysis, but differences between tissues of up to 100-fold were found for K_m and V_max values for cis isomer hydrolysis. Hydrolysis of the trans isomer in cuticle, gut, and fat body homogenates was only partially inhibited by α-naphthyl N-propylcarbamate (NPC). Concentrations of NPC giving maximal inhibition of trans isomer hydrolysis had little effect on the hydrolysis of the cis isomer. These results demonstrate that pyrethroid-hydrolyzing activity is broadly distributed in insect tissues and results from the combined activity of several esterases with different properties. It is likely that the trans and cis isomers of permethrin are hydrolyzed by separate enzymes in this insect.     

Rates of sulfide oxidation in cotton,carrot, and tobacco cultured plant cells measured with a model aromatic alkyl-sulfide

p-Chlorophenylmethylsulfide (PCPMS) was enzymatically sulfoxidized to p-chlorophenylmethylsulfoxide (PCPMSO) in aerobic cotton, carrot, and tobacco cell suspension cultures. Neither boiled nor freeze-killed cell cultures were competent to sulfoxidize PCPMS to PCPMSO. The sulfone, p-chlorophenylmethylsulfone (PCPMSO₂), was not produced in any of the three species. The rates of PCPMS sulfoxidation, were cotton > carrot > tobacco. The apparent K_m for carrot cells was 88 μM PCPMS (14 μg/ml), while the apparent V_max was 7 nmol PCPMSO/mg whole cell protein/hr. These rates of sulfide oxidation are higher than previously reported in intact plants.     

Pesticide action: Different response of erythrocyte membrane acetylcholinesterase to inhibition by organophosphorus compounds under varied dietary conditions

The inhibitory effect of malathion in conjunction with maloxon or other derivatives on the activity of rat erythrocyte membrane-bound acetylcholinesterase has been investigated after feeding diets known to affect the lipid composition of the membrane. The inhibition of AchE by preincubation of membrane preparations with this organophosphorus compound, possibly with contaminants, differed with the diet: the curve was sigmoidal after supplementation with corn oil and hyperbolic after supplementation with lard. In the latter case the kinetics of the inhibition became sigmoidal by assaying in the presence of cortisol or isoproterenol or by previous solubilization of the enzyme. These results indicate that some organophosphorus compounds can differentiate conformational states of acetylcholinesterase present in the erythrocyte membrane.     

Metabolism of fenitrothion in red-backed voles (Clethrionomys gapperi)

To estimate the impact of fenitrothion on small mammals, a breeding colony of wild southern red-backed voles (Clethrionomys gapperi) was successfully maintained. The red-backed vole is a nontarget species inhabiting coniferous forests that are subjected to aerial spraying of the pesticide for the control of spruce budworm infestations. The voles were used to examine toxicity and the metabolic pathways involved in the elimination of fenitrothion after intraperitoneal injection of the purified, undiluted organophosphate. The 96-hr LD₅₀ was 1330 mg/kg. Toxicities toward males and females were not significantly different. All observed symptoms of intoxication and 99% of the mortality occurred within 48 hr of dose application. All major metabolites of fenitrothion metabolism in nonruminant mammals were identified and quantified by gas chromatography. At all doses, fenitrothion was rapidly metabolized and excreted. No body accumulation of residues was implied. The toxicity of fenitrothion was not correlated with increasing proportion of the dose converted into fenitrooxon. The low toxicity to red-backed voles is probably due, in part, to rapid metabolic detoxication by the two mechanisms cleaving fenitrothion at the P-O-aryl and PO-alkyl bonds, the latter becoming more prominent at high dose levels.     

Differential inhibition responses caused by DDT on oligomycin-sensitive Mg2+-ATPase activity: Nature of the requirements for DDT sensitivity

Earlier communications from this laboratory have shown that DDT inhibited oligomycin-sensitive Mg²⁺-ATPase (EC 3.6.1.3) but that its active component, F₁, was not affected. In the present investigation evidence has been obtained to determine the nature of the requirements for DDT sensitivity. The results showed that DDT sensitivity was conferred to F₁ from pig heart mitochondrial preparations when it was bound to F₀ from the same preparation. The F₁ from house fly (Musca domestica L) thorax was able to bind to F₀ from pig heart. This combination showed similar sensitivity to that of the original F₁-F₀ combination from pig heart mitochondria. However, when F₁ from pig heart mitochondria was incorporated into F₀ depleted in oligomycin sensitivity-conferring protein (OSCP) from the same source, the resulting ATPase activity was insensitive to DDT. Addition of crude (50–200 μg) or purified (5–20 μg) OSCP in the above preparation restored DDT sensitivity. Presence of dioleyl or dipalmitoyl phosphatidyl choline or Triton X-100 in the reaction medium antagonized the DDT inhibitions. Depletion of phospholipids from submitochondrial membrane preparations (SMP) decreased ATPase activity. Addition of dioleyl or soybean phosphatidyl choline to this lipid-depleted preparation restored DDT sensitivity. Evidence presented suggests that DDT acted on F₁ in association with one or more membrane components and that OSCP and phospholipid were essential for DDT sensitivity.     

Effects of DDT on electrical properties of lecithin-decane bilayer membranes

Lecithin-decane bilayer membranes were treated with DDT and valinomycin, either by adding the compounds to the electrolyte around the membrane or by adding them directly to the lecithin-decane. Membrane capacitance was calculated using the dc transient technique. Specific capacitance was determined from capacitance versus area regressions and was not significantly altered by DDT. Specific K⁺ conductance was decreased by DDT, but only when DDT and the K⁺ carrier, valinomycin, were administered to the electrolyte where they may have interacted hydrophobically. It is concluded that the valinomycin-induced conductance of artificial membranes is inappropriate as a model for investigating the effects of DDT on the electrical properties of excitable membranes.     

Components of the electron transport system in the microsomal mixed-function oxidase system in wild birds

Notable differences were found among six species of wild-caught birds in the levels of cytochrome P-450, cytochrome b₅, NADPH-cytochrome c reductase, and NADH-cytochrome c reductase. Ethyl isocyanide difference spectra showed significant variations among the species in peak height and in the ratios of the $\text{430}\text{455}\text{-}\text{nm}$ peaks. Substantial aldrin epoxidase activity was found in all species, and the amounts of dieldrin produced compared favorably with pigeon and rat liver microsomes. Higher content of cytochrome P-450 was not always accompanied by a similar rise in specific catalytic activity. Thus, no correlation could be established between these two parameters. Aldrin epoxidase activity with NADH as the sole electron donor was 25–49% as effective as with the NADPH-generating system. Addition of both NADH and NADPH-generating systems to the incubation mixture produced a synergistic effect with liver microsomes of two species but not with two other species. DDE and polychlorinated biphenyls residues were found in the heart tissue of all species examined, and this might indicate a possible inductive effect on the microsomal mixed-function oxidase system by environmental contaminants.     

Herbicidal interference with the photochemical activities of chloroplasts (in vivo and in vitro) of certain crop and weed species

The independent modes of action of diuron and atrazine on the photochemical activities of chloroplasts (In vivo and in vitro) from the leaves of crop plants Pisum sativum and Pennisetum typhoides and the weeds Amaranthus viridis and Cyperus rotundus were investigated. Hill reaction activity (DCPIP photoreduction) of in vivo chloroplasts (chloroplasts isolated from herbicide-sprayed plants) was unaffected by treatment at sublethal or intermediate levels of diuron or atrazine while that of in vitro chloroplasts (chloroplasts incubated in the required herbicidal concentration) was severely inhibited. The ferricyanide catalyzed noncyclic photophosphorylation was markedly reduced in both the in vivo and in vitro chloroplast systems. N-Methyl phenozonium sulfate (PMS)-mediated cyclic photophosphorylation was inhibited in the in vivo system while a pronounced enhancement of activity was noticed in the in vitro chloroplasts. The rate of NADP⁺ photoreduction was severely inhibited in the in vitro chloroplasts. The unaffected in the in vivo system. The herbicidal effects on the photoreactions of isolated chloroplasts were compared with chloroplasts isolated from herbicide-sprayed plants.     

The action of formamidines on octopamine receptors in the locust

The actions of a range of formamidines have been investigated biochemically and physiologically on octopamine receptors in the locust Schistocerca gregaria. All the formamidines tested [chlordimeform (CDM), demethylchlordimeform (DCDM), amitraz, and UK 16353] mimicked the action of octopamine by (1) increasing the amplitude and relaxation rate of slow motorneurone tension in the extensor-tibiae muscle of the hind leg and (2) changing the levels of cyclic AMP in this muscle. UK 16353 was most effective in changing these parameters, followed by DCDM then amitraz and CDM. The formamidine-induced increase in cyclic AMP levels was reduced or completely blocked by phentolamine, an antagonist of insect octopamine receptors. The time course for the increase in cyclic AMP was followed for 30 min by incubating muscles in 10^?5M DCDM. The increase was potentiated by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. In the presence of this compound, the response peaked within 5 min, before declining to a lower plateau after 12 min. The response to 10^?5M CDM was lower and the maximum increase occurred after 7 min, then rapidly declined. Both formamidines increased cyclic AMP in a dose-dependent way with a threshold of between 5 × 10^?7 and 10^?8M. The results are discused in terms of the relationship between the biochemical and physiological actions of the formamidines in this preparation.