Albert S. Perry

The effect of aroclor 1254 (PCB) on the physiology of reproduction in the female rat—I

Daily oral exposure of rats to 30 mg/kg of Aroclor 1254 for 1 month caused deleterious effects on the reproductive process, which were reflected in a decrease in the reproductive potential. The following disturbances were observed: prolongation of the estrous cycle; decrease in sexual receptivity; delay in timing of copulation; vaginal bleeding during gestation; decrease in litter size and delay in the time of parturition. The offspring, whether exposed to PCBs either prenatally and/or postnatally, showed a slower rate of body weight gain than controls. This was accompanied by high mortality until weaning of treated pups. Vaginal opening in the PCB-treated (as young) females occurred precociously, while other reproductive parameters were not affected at adulthood. Discontinuance of PCB treatment reversed the above symptoms.

Acetylcholinesterase of Aphis citricola: Properties and significance in determining toxicity of systemic organophosphorus and carbamate compounds☆

Abstract In apterous adults of the spirea aphid, Aphis citricola van der Goot, the optimum conditions for determining acetylcholinesterase (AChE) activity consist of reaction mixture of 0.1 M phosphate buffer (pH 7.5), 10 −3 M acetylthiocholine (ASCh), and enzyme extract equivalent to 80 ± 3 μg protein incubated for 15 min at 30°C. The K m value for ASCh (6.7 × 10 −5 M ) was much lower than that of butyrylthiocholine (BuSCh) (1.25 × 10 −2 M ). The enzyme activity was almost completely inhibited by 10 −6 M paraoxon or 10 −5 M eserine and was 84% inhibited by 10 −5 M BW284C51 (a specific AChE inhibitor). DTNB was found to inhibit the enzyme activity and was therefore added at the end of the reaction. AChE activity of A. citricola was inhibited in vitro and in vivo by dimethoxon > dimethoate, and aldicarb sulfoxide > aldicarb > aldicarb sulfone. The in vivo effect correlates well with the toxicity level of the various toxicants. A neurotoxicity index which combines both mortality and in vivo inhibition of the aphid AChE activity is suggested as a measure for determining the toxicity of organophosphorus and carbamate compounds toward aphids.

Monooxygenase activity of rat liver microsomes immobilized by entrapment in a crosslinked prepolymerized polyacrylamide hydrazide.

Rat liver microsomes were immobilized by entrapment in a chemically crosslinked synthetic gel obtained by crosslinking prepolymerized polyacrylamide-hydrazide with glyoxal. Approximately 88% of the microsomal fraction was entrapped in the gel. The specific rate of O-demethylation of p-nitroanisole was used to assay the microsomal cytochrome P-450 activity of the immobilized microsomal preparations. The gel entrapped microsomes showed monooxygenase activity at 37 degrees C of Vmax = 2.3 nmol p-nitrophenol/min per nmol cytochrome P-450, similar to that of microsomes in suspension. The Km value for the p-nitroanisole-immobilized microsomal cytochrome P-450 system (1.2 X 10(-5) M) was rather close to that of microsomes in suspension (0.8 X 10(-5) M). Under the experimental conditions used the pH activity curve of the immobilized preparation was shifted towards more alkaline values by approx. 0.5 pH unit in comparison with microsomes in suspension. The rate of cytochrome c reduction by the immobilized microsomal system (11.7 nmol/min per mg protein) at 25 degrees C was considerably lower than that of the control (microsomes in suspension, 78 nmol/min per mg protein). Enzyme activity in both preparations showed the same temperature dependence at the temperature range of 10 to 37 degrees C. The immobilized microsomal monooxygenase system could be operated continuously for several hours at 37 degrees C provided that adequate amounts of an NADPH-generating system were added periodically. Under similar conditions a control microsomal suspension lost its enzymic activity within 90 min.

Detoxification and synergism of diflubenzuron and chlorfluazuron in the red flour beetle Tribolium castaneum

Abstract Chlorfluazuron (CFA), a benzoylphenyl urea insecticide, was found to be more potent than diflubenzuron (DFB) against Tribolium castaneum larvae. CFA was 37-fold more toxic than DFB against the fourth instar larvae but only 4-fold more against the first instar. While DFB had no effect on the pupal stage, CFA treatment resulted in a high level of pupa-adult intermediates. DFB was detoxified more rapidly than CFA in the larvae. Of the total amount applied to the larvae, 9% of the DFB could be detected in the pupae as compared with 40% of the CFA. No metabolites of CFA could be detected in either the larvae or the pupae, as compared with a high level of DFB metabolites, i.e., 4-chlorophenyl urea (4-CPU), 4-chloroaniline (4-CA), and polar materials. Hence, the retention time of CFA in the larval body ( T 1 2 > 100 hr ) was much higher than that of DFB ( T 1 2 ⋍ 7 hr ). The major metabolites of DFB in the larvae, determined as the percentage of the total recovery, were 4-CPU (6.6%), polar materials (1.8%), and 4-CA (3.6%). Simultaneous treatment of insects with DFB and esterase inhibitors such as phenyl saligenin cyclic phosphonate and S,S,S-tributylphosphorotrithioate resulted in decreased DFB metabolism and an increase in its T 1 2 to 9 and 18 hr, respectively. These inhibitors synergized considerably (2- to 3-fold) the larvicidal effect of DFB, but they did not alter the toxicity of CFA. Hence, efficient synergists to DFB, based on inhibition of detoxification, might improve its toxicity and help maintain its rapid biodegradable property in the environment.

Cadmium uptake and toxicity to water hyacinth: Effect of repeated exposures under controlled conditions

Water hyacinth, Eichornia crassipes has drawn attention as a plant of rapid growth and high biomass production, and capable of removing pollutants from domestic and industrial waste effluents. Most of the studies were static assays of short duration (1 to 3 days) and with a single exposure of the plants to cadmium. The authors presumed that repeated exposures to Cd might change the rate of uptake of the metal as well as the growth and physiological state of the plant. This prompted us to undertake the present study in order to evaluate the potential capacity of water hyacinth to remove Cd from solution under conditions of repeated exposures but otherwise favorable growth conditions and without interference from other toxic compounds. Removal of metal from effluents by plants is expected to be compounded by the influence of specific conditions of the medium such as temperature, pH, ionic strength, presence of other metals or complexing ligands. The results of the present study will serve as a comparative reference for evaluating the effect of effluent conditions on CD toxicity to water hyacinth and the plants capacity for metal removal.

Metabolism of parathion and brain cholinesterase inhibition in four species of wild birds

Abstract Rates of activation and degradation of parathion by the microsomal fraction and the 12,000g supernatant of cell-free preparations were measured in four species of wild birds. Cholinesterase activity and K i values for cholinesterase inhibition by paraoxon were also determined. Cytochrome P -450 content was lowest in the African bulbul and house sparrow, intermediate in the barn owl, and highest in the blackbird. Microsomal fractions of the bulbul and the sparrow metabolized parathion to paraoxon and p -nitrophenol at higher rates than those of the blackbird and the barn owl, but arylesterase activity was lower in the two former species than in the latter two. Cholinesterase activity was lowest in the barn owl which also exhibited the lowest K i value toward cholinesterase inhibition by paraoxon. These manifestations coupled with the high rate of arylesterase activity might afford the barn owl and the blackbird with a potential defense mechanism against the toxic action of parathion and related compounds.

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

Abstract 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 455 430 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.

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

Abstract 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 430 455 - 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.

Postnatal development of the mixed function oxidase system in nestling barn owls and baby chicks and induction of this system in the mature forms by Aroclor 1254

Postnatal changes in content and activity of the mixed-function oxidase system in nestling barn owls and baby chicks showed the following: 1. Increase in liver weight in both. 2. Significantly higher cytochrome P-450 level in 1-day old chicks but lower in 1-day old owls than at any other age. 3. Ratio of cytochrome b5 to P-450 was lower than one in nestling owls but higher than one in chicks. 4. Aroclor 1254 (PCBs) increased the level and catalytic activity of cytochrome P-450 more in the owl than in the chick. 5. The ratio 455:430 nm characteristic of ethylisocyanide binding was not altered in the barn owl due to PCB treatment but changed significantly in the treated chicken.

Spectral and catalytic properties of cytochrome P-450 from four wild bird species☆

Abstract 1. The n -octylamine difference spectra in all bird species were analogous to the high-spin form of cytochrome P -450 obtained in mammalian species after induction with 3-methylcholanthrene. 2. Differences between species were obtained in the ratios of the 430/455 nm peaks in the Soret region for the ethyl isocyanide difference spectra. 3. An atypical type I spectral change with methylaniline as ligand was found in one species and the reverse form of this spectral change was obtained in three other species. 4. Significant differences between species were also found in the K s values for aniline and ethyl isocyanide spectral changes and in catalytic activity with different substrates.