Induction of the mixed-function oxidase system in the liver of the barn owl Tyto alba by PCBs

Injection of 30 mg/kg body wt of polychlorinated biphenyl (Aroclor 1254) into liver parenchymal tissue of nestling and adult barn owls Tyto alba resulted in increases in the level of cytochrome P-450. Concomitantly, there were increases in catalytic activity of the microsomal enzyme system as measured by aldrin epoxidation and aminopyrine N-demethylation. However, the ratio $\text{455}\text{430}\text{nm}$ in the ethylisocyanide-difference spectrum remained unchanged. Of particular interest is the sudden drop in the level and catalytic activity of cytochrome P-450 in nestling owls at age 40 days. Treatment with Aroclor 1254 produced small hemorrhages in the liver of nestling owls and the liver appeared much enlarged (hepatomegaly), indicating a toxic effect and resulting in little induction of microsomal enzymes. In adult owls the inductive effect was much greater. Aroclor 1254 produced a spectral shift in the cytochrome P-450-difference spectrum from 450 to 448 nm and in the ethylisocyanide-difference spectrum from 455 to 453 nm and from 430 to 427 nm.     

Induced hydrogen ion transport in lipid membranes as origin of toxic effect of pentachlorophenol in an alga

Pentachlorophenol (PCP) decreases the rate of carbon assimilation in the alga Selenastrum capricornutum. In parallel with the reduction of carbon assimilation in this alga there is a decrease of electrical resistance of lipid membranes and development of negative membrane surface charge. The experimental results suggest that PCP toxicity to algae is due to adsorption of negatively charged PCP ions at the membrane surface that act as carriers of hydrogen ion across the membrane. This protonophoretic action of PCP causes the decrease of membrane electrical resistance and the dissipation of hydrogen ion electrochemical potential gradients across cellular and subcellular membranes, which reduces the ability of algae to assimilate carbon.     

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.     

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.     

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.     

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.     

Structure-activity relationships of DDT-type analogs based on in vivo toxicity to the sensory nerves of the cockroach, Periplaneta americana L

Forty-three DDT-type compounds were applied in saline suspension to the crural nerve of Periplaneta americana L. and the threshold concentration (ED₅₀) to produce trains of impulses was determined together with the frequency of appearance of repetitive afterdischarge. These quantitative neurological measures were evaluated in multiple regression analyses of structural parameters including van der Waal's volume, the F and R components of Hammet's σ, and the hydrophobic constant Π. This structure-activity analysis provides an accurate estimation of the intrinsic toxicity of the DDT analogs. The results affirm previous working theories that the bulk of the functional groups within the DDT framework is the primary factor relating to activity. However, conformation is also an important parameter.     

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.     

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.     

Membrane damage in human erythrocytes caused by captan and captafol

Treatment of human erythrocytes with 5 × 10^?5M captan or captafol caused a rapid increase in the efflux of intracellular potassium. Captafol had a more pronounced effect than captan on cation permeability. Captafol also decreased anion permeability whereas captan did not affect this process. Glutathione (5 × 10^?4M) had little effect in reducing potassium efflux when added to the cells after they were incubated for 1 h with captan or captafol, but it was effective in reducing the potassium loss when added to the cells prior to their treatment with the fungicides. Captafol caused an increase in osmotic fragility of the cells. Incubation of the cell membranes with captafol resulted in the liberation of a small fraction of membrane phospholipids, whereas captan produced no effect. Both the fungicides readily reacted with the sulfhydryl groups in the isolated membrane; 31.5 and 45.7% of the membrane sulfhydryl groups had disappeared following treatment with captan and captafol, respectively. It is suggested that the reaction of captan or captafol and/or their reaction products with the sulfhydryl and amino groups of the red cell membrane protein produces changes in the structure of the membrane with consequent alteration in its permeability.     

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.     

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.     

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.     

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.     

The toxicological significance of paraoxon deethylation

The in vivo formation of deethylation and hydrolytic products of paraoxon degradation after parathion or paraoxon administration was nearly equal in control male rats, and the relative abundance of metabolites was not appreciably altered by pretreatment of rats with enzymeinducing agents. However, pretreatment with inducers dramatically increased the oxidative paraoxon O-deethylase of male rat liver while having little effect on hydrolytic enzymes. Prior to induction, the hepatic O-deethylase activity was greatly inferior to the various hydrolytic enzymes, but nearly equal levels of both enzyme systems were found after induction. These results indicate that a large portion of the hepatic hydrolases detected in vitro is not active in vivo. It also appears that the majority of the induced hepatic deethylase was not involved in vivo at the dosage levels employed. The in vivo metabolism of monoethyl paraoxon was also demonstrated. The predominant metabolite of ethyl-[1-¹⁴C]monoethyl paraoxon is ¹⁴CO₂, while phenyl-[1-¹⁴C]monoethyl paraoxon yielded 4-nitro[1-¹⁴C]phenol. Paraoxon deethylation was also shown to be an important detoxication mechanism in female rats and male mice and must be considered in interpreting the toxicological properties of parathion and paraoxon.     

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.     

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.     

The mechanism of resistance to lindane and hexadeuterated lindane in the Third Yumenoshima strain of house fly

The factors which cause lindane resistance in the Third Yumenoshima strain, a strain of house flies highly resistant to insecticides, were studied using hexadeuterated lindane. Hexadeuterated lindane has the same physicochemical properties as lindane, but the former is much less biodegradable than the latter. The LD₅₀ ratio of lindane to hexadeuterated lindane in this strain, deuterium isotope effect on LD₅₀ values, was larger than that in S_NAIDM, a susceptible (nonresistant) strain. The penetration rates of labeled and nonlabeled lindane through the insect cuticle were about the same for both strains. Thus, penetration rate does not cause resistance. The metabolic degradation of lindane in the resistant strain in vivo occurred much faster than in the susceptible strain. This was also the case for lindane degradation processes in vitro such as microsomal oxidation and glutathione conjugation. In both strains, significant isotope effects were observed in the degradation rates in vitro of labeled and nonlabeled lindane. Therefore, principal biodegradation and detoxication pathways should include reactions which cleave the CH bonds. When the much less biodegradable d₆ counterpart of lindane was applied to both strains, the susceptible strain became much more highly intoxicated than the other within 20 to 30 min. This indicates that a combination of both greater degradability and probably lower sensitivity at the action site are the main factors underlying resistance in the Third Yumenoshima strain.     

Differential inhibition of potassium ion absorption by difenzoquat in wild oat and cereals

Over a concentration range of 5.0 × 10^?6?7.5 × 10^?4M, the selective herbicide difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) caused more pronounced inhibition of potassium ion (K⁺) absorption by excised seedling roots of susceptible wild oat (Avena fatua L.) compared to those of tolerant barley (Hordeum vulgare L. cv. Bonanza) or wheat (Triticum aestivum L. cv. Neepawa). At 2.5 × 10^?5M difenzoquat, the relative inhibition of K⁺ (⁸⁶Rb) absorption by wild oat root segments inceased from 30% with a 10-min uptake period to 75% with an uptake period of 90 min, whereas no inhibition at all was evident for wheat root segments even after a 90-min exposure to the herbicide. An ion efflux compartmental analysis procedure demonstrated that difenzoquat did not affect the passive permeability properties of the plasma membrane of wild oat root cells. The experimental findings indicated that difenzoquat interfered directly with the process of active ion transport across the plasma membrane of root cells.     

Dichloroacetamide herbicide antidotes enhance sulfate metabolism in corn roots

The herbicide antidotes N,N-diallyl-2,2-dichloroacetamide (R25788) and 3-dichloroacetyl-2,2,5-trimethyloxazolidine (R29148) at ppm levels slightly enhance the uptake of [³⁵S]sulfate in corn roots and greatly increase its metabolism to “bound sulfide”, cysteine, and glutathione (GSH). The decrease in free sulfate content of the roots with R25788 is closely associated with an increase in GSH level. The sulfate content is decreased with an 8-hr exposure to R25788 and R29148 at 3 ppm and its decline continues through 48 hr to about 5% of the control level. Effects on sulfate content are evident at 24 hr even with 0.3–1 ppm of these antidotes. Several other mono- or dichloroacetamide antidotes at 30 ppm also decrease the free sulfate content of corn roots to about 34–60% of control levels within 24 hr. R25788 at 30 ppm has little or no effect at 24 hr on sulfate levels in corn leaves whether the plants are grown in the light or in the dark. R25788 and R29148 decrease sulfate levels in the leaves of milo and in whole pigweed plants, but not in barley, lambsquarters, water grass, wheat, or wild mustard. In increasing GSH biosynthesis, the antidote acts in corn prior to the reduction step to form bound sulfide; in fact, R25788 increases the specific activity of ATP sulfurylase, the first enzyme involved in sulfate assimilation. Thus, dichloroacetamides such as R25788 and R29148 provide a means to experimentally, and perhaps even practically, manipulate sulfate utilization in corn and some other plants.