Ralph B. March

Toxicological properties of phosphorothioate and related esters present as impurities in technical organophosphorus insecticides

O,O,S-Trimethyl phosphorothioate, an impurity in several technical organophosphorus insecticides, when administered orally to rats at single doses as low as 15 mg/kg caused delayed mortality, with death occurring 4-22 d after treatment. Delayed toxic signs were also observed in mice, but mice were generally less sensitive than rats. O,O,S-triethyl phosphorothioate and O,S,S-trimethyl phosphorodithioate induced the same signs of intoxication at slightly higher doses. Rats treated with O,O,S-trimethyl phosphorothioate refused food and water within 24 h after treatment and did not eat or drink until the time of death. Neither injection of nutrient solution nor atropine served to reduce or block intoxication. However, the isomeric O,O,O-trimethyl phosphorothioate was a potent antagonist of the toxicity of O,O,S-trimethyl phosphorothioate. As little as 1% of the O,O,O-trimethyl isomer protected rats from the intoxicating effects of the O,O,S-trimethyl isomer at doses as high as 200 mg/kg. Rat serum carboxylesterase and cholinesterase were inhibited for prolonged periods after a single oral dose of O,O,S-trimethyl phosphorothioate, but the duration of inhibition was significantly less when the toxicant contained 1% O,O,O-trimethyl isomer.

Effects of water stress and rehydration on hemolymph volume and amino acid content in the blister beetle, Cysteodemus armatus

1. 1. Hemolymph volume, osmolality, amino acid concentrations and fecal amino acid concentrations were measured in a desert blister beetle, Cysteodemus armatus LeConte, which were not desiccated, 10% desiccated (% of body mass), or rehydrated. 2. 2. Desiccation and rehydration had significant effects on the hemolymph volume in this species but not hemolymph osmolality. 3. 3. Total amino acid concentrations were significantly affected by hydration state. 4. 4. Hemolymph urea, asparagine, methionine and histidine were significantly affected by hydration state, but other ninhydrin positive substances (NFS) were not affected. 5. 5. While production of fecal material (frass) decreased with desiccation, the concentration of most amino acids increased, indicating excretion as an avenue of hemolymph osmoregulation.

Insecticidal properties, antiesterase activities, and metabolism of methamidophos

Abstract Methamidophos is highly toxic to insects but at best is a moderate cholinesterase inhibitor. Evaluation of the kinetics of its housefly cholinesterase inhibition showed that its affinity for the enzyme and its phosphorylation and bimolecular inhibition rates are all relatively low. In vivo metabolism studies in houseflies provided evidence that it is not activated to a more effective cholinesterase inhibitor and indirect evidence also was obtained for its slow degradation. In vitro metabolism studies in housefly and mouse tissues provided additional evidence for its lack of activation and slow metabolic degradation. Compared to other effective organophosphorus insecticides, methamidophos was slow in producing acute symptoms of poisoning and cholinesterase inhibition and required the accumulation of comparatively high internal levels for toxic effects. However, in vivo cholinesterase inhibition studies provided evidence for the interrelationships of cholinesterase inhibition and toxic effects. Thus, its relative stability and low in vivo degradation appeared to be of critical importance in accumulating and maintaining a sufficient internal concentration for a sufficiently long period of time to permit the development of its slowly expressed toxicity.

The activation and inhibition of adenyl cyclase from the brain of the madagascar cockroach (gromphadorhina portentosa)

Abstract 1. 1. The enzyme adenyl cyclase has been demonstrated for the first time in insect nerve tissue. 2. 2. The assay employed is linear with time for 20 min. A plot of activity against protein concentration reveals a non-linear response very similar to that previously reported for rat pineal gland adenyl cyclase. 3. 3. Known mammalian adenyl cyclase activators, norepinephrine and epinephrine significantly stimulate insect adenyl cyclase; however, isoproterenol is not effective. Fluoride ion is a very potent stimulator. 4. 4. Ecdysterone and 4-aminobutyric acid both appear to inhibit cockroach brain adenyl cyclase.

Delayed acute toxicity of O,S,S-trimethyl phosphorodithioate and O,O,S-trimethyl phosphorothioate to the rat

Abstract The toxicity and LD 50 of O,S,S -trimethyl phosphorodithioate were reexamined in the rat. Animals treated orally (single dose) with this compound exhibited early cholinergic signs followed at approximately 5 hr by delayed toxic signs, with an LD 50 of 43 mg/kg. Contamination of O,S,S -trimethyl phosphorodithioate by as much as 5% (w/w) O,O,O -trimethyl phosphorothioate provided only limited antagonism to the dithioates toxicity. In contrast, the addition of 5% O,O,S -trimethyl phosphorodithioate to O,O,S -trimethyl phosphorothioate gave protection against the toxic effects of the latter compound up to 80 mg/kg of toxicant. Pretreatment of rats with as little as 5% O,O,O -trimethyl phosphorothioate, 24 hr prior to treatment with 200 mg/kg O,O,S -trimethyl phosphorothioate, gave complete protection against the toxic effects of this compound. Conversely, administration of 10% (w/w) O,O,O -trimethyl phosphorothioate 4 or 24 hr after treatment with 60 or 80 mg/kg of O,O,S -trimethyl phosphorothioate provided only partial protection at 4 hr and no protection from the effects of the toxicant at 24 hr. The ability of O,O,O -trimethyl phosphorothioate to antagonize the toxicity of this compound depended markedly on the route of administration (oral, intravenous, or intraperitoneal). At 4 hr past treatment with toxicant, only oral administration of the antagonist provided full protection. Intraperitoneal and intravenous administration of antagonist 4 hr after treatment with toxicant were partially effective and completely ineffective, respectively, in halting the toxic effects of this compound.

Water Relations of the Desert Blister Beetle Cysteodemus armatus (Leconte) (Coleoptera: Meloidae)

Several parameters of the xeric adaptiveness of the desert blister beetle Cysteodemus armatus were studied in the field and laboratory. Field measurements demonstrated that these beetles were most active during warmer parts of the day with exposure to high air (>35 C) and soil (>55 C) temperatures. Beetles had body temperatures consistently higher than ambient air temperatures but less than substrate temperatures. Rates of water loss (173 mg day⁻¹, including fecal losses), gravimetrically determined in the laboratory at 30 C, were higher than field-determined tritiated water turnover (125 mg day⁻¹). The Q10s for water loss were highest (5.4) at 25-30 C and lowest at 30-35 C (1.6). Cysteodemus armatus is subjected to stressful conditions and compensates for water losses with water-rich food (creosote flowers with 85% water content). However, the voracious feeding habits of these beetles are most likely devoted to energy accommodation rather than the water balance. Females ingest a mean of 185 cal day⁻¹, with a fecal output of 41 cal day⁻¹ and a metabolic output of 71 cal day⁻¹, providing about 73 cal day⁻¹ for egg production, with a batch of 100 eggs produced every 3.2 days. Under stress with no food available the beetles have higher rates of water loss than any other desert species studied. The major water saving displayed by stressed animals is through reduction of fecal water output. A total water budget showed a gain of 200 mg day⁻¹ and losses of 184 mg day⁻¹, excluding reproductive losses.

Insecticide cyclic nucleotide interactions: I. Quinoxalinedithiol derivatives: A new group of potent phosphodiesterase inhibitors

Abstract The direct effects of tepp, methyl paraoxon, DDT, dieldrin, aldicarb, dimetilan, rotenone, allethrin, and oxythioquinox were surveyed on cockroach brain adenyl cyclase and phosphodiesterase in vitro . The most striking result of this survey was the observation that oxythioquinox is a potent inhibitor of phosphodiesterase. The inhibitory activities of seven different quinoxalinedithiol derivatives were compared with those of methyl-xanthines and SQ 65,442 on phosphodiesterases from cockroach brain, rat brain, and beef heart. Although I 50 values of the quinoxaline inhibitors were found to be in the μ M range, solubility deficiencies apparently limit their effectiveness with inhibition reaching limiting values of about 70–90% as concentrations are increased. Evaluation of the quinoxaline inhibitors to enhance the accumulation of cyclic AMP in the assay of adenyl cyclase did not demonstrate any significant advantage over the use of aminophylline, a standard inhibitor for this purpose. A new assay for phosphodiesterase, involving separation of substrate from product on aluminum oxide columns, was developed by modification of similar techniques utilized in the assay of adenyl cyclase.

Characteristics of cyclic 3′,5′-nucleotide phosphodiesterase from the brain of the madagascor cockroach (gromphadorhina portentosa)

Abstract 1. 1. The presence of the enzyme phosphodiesterase has been demonstrated in different tissues of the Madagascar cockroach by various assay techniques. The brain had the highest level of enzyme activity and was most thoroughly studied. 2. 2. A temperature optimum at approximately 53°C was observed. Storage for 7 months at —30°C resulted in an activity loss of only 20%. A pH optimum of 8·5 was found. Stimulation by imidazole was pH dependent. Mg 2+ was the only divalent cation among those tested which increased activity. Other divalent cations were inhibitory. 3. 3. Theophylline and caffeine were competitive inhibitors, the former being more effective than the latter. A K m of 2·6−3·0×10 −5 M was observed for 3′,5′-cyclic adenosine monophosphate (cAMP). 3′,5′-Cyclic guanosine monophosphate (cGMP) was hydrolyzed at 70% of the rate of cAMP. Adenosine triphosphate (ATP), citrate, pyrophosphate, reserpine and SQ 65,442 were all inhibitory.

The Coinage of Common Names for Insecticides

The need for standardized common names for pest control chemicals is well recognized, national and international organizations having been set up to promote their development. The problems involved in coining and standardizing common names are complex, however, particularly for proprietary compounds that are marketed in numerous countries, and therefore the development of common names sometimes lags far behind the need. The Entomological Society of America, through its Committee on Insecticide Terminology, endeavors to promote the development of common names for insecticides when the need becomes evident, and periodically publishes a list of the common names that have been approved for use in the publications of the Society.