Toxicity of abamectin to cockroaches (Dictyoptera: Blattellidae, Blattidae).

Abamectin was fed to German cockroaches, Blattella germanica (L.), in non-choice tests. LT50s and LC50s were estimated by probit analysis. The LT50s for the German cockroach ranged from 4.4 to 1.7 d for males, from 9.0 to 2.4 d for females, and from 4.4 to 1.6 d for nymphs for bait concentrations of abamectin between 0.0025 and 0.0500%. The LC50s of abamectin were 0.0110 and 0.0040% from males, 0.0240 and 0.0090% for females, and 0.0200 and 0.0080% for nymphs at 3 and 6 d, respectively. The LT50 values of 0.0550% abamectin bait were 3.4, 3.4, 2.4, 7.5, 2.9, and 4.5 d for Periplaneta americana (L.), P. fuliginosa (Serville), P. brunnea Burmeister, P. australasiae (F.), Blatta orientalis L., and Supella longipalpa (Serville). Although the bait was effective against various cockroach species, time to death for the larger species was longer than for the German cockroach. In preference tests in which male German cockroaches were allowed to feed on rat chow or abamectin bait, all died within 5 d of exposure to abamectin bait. Abamectin bait consumption was not significantly lower than that of untreated rat chow. Arena tests with 0.0550% abamectin bait resulted in 31-75% mortality of German cockroaches after 9 d, with most control being achieved by treating harborages with the bait. The hydramethylnon standard resulted in 65% mortality after 9 d.     

Spectra and structure of alpha-tocopherol radicals produced in anoxic media.

Electron spin resonance and flash photolysis studies have been combined to determine, amid conflicting reports from radiolysis studies, the spectrum for the phenoxyl radical of alpha-tocopherol. Triplet state ketones were used to abstract the alpha-tocopherol phenolic hydrogen in order to obtain both the transient ESR spectrum and optical spectrum. Analysis of the ESR data yields g = 2.00469, a(H, 5-CCH3) = 6.04G, a(H,7-CCH3) = 4.51G, a(H, CH2) = 1.38G, a(H', CH2) = 1.49G, and a(H,8-CCH3) = 0.89G. The g factor shows large spin population on oxygen in this radical and demonstrates conclusively involvement of the phenoxyl radical. Both spectra were in agreement with those produced by radiolysis of alpha-tocopherol in N2 saturated EtOH. While the spectral characteristics of the phenoxyl radical now appear to be clarified, uncertainties remain concerning optical spectra for radiolysis of alpha-tocopherol in air- and oxygen-containing systems.     

Bovine dopamine beta-hydroxylase cDNA. Complete coding sequence and expression in mammalian cells with vaccinia virus vector.

We have isolated cDNA clones for bovine dopamine beta-hydroxylase from an adrenal medulla cDNA library and have determined the complete coding sequence. The largest cDNA clone isolated from the library is 2.4 kilobase pairs (kb) and contains an open reading frame of 1788 bases, coding for a protein of 597 amino acids and Mr = 66,803. The predicted amino acid sequence of the bovine cDNA contains 85% identity with human dopamine beta-hydroxylase (Lamouroux, A., Vingny, A., Faucon Biquet, N., Darmon, M. C., Franck, R., Henry, J.P., and Mallet, J. (1987) EMBO J. 6, 3931-3937; Kobayashi, K., Kurosawa, Y., Fujita, K., and Nagatsu, T. (1989) Nucleic Acids Res. 17, 1089-1102). Northern blot analysis reveals that the cDNA hybridizes to an mRNA of 2.4 kb present in bovine adrenal medulla, but not in kidney, heart, or liver. In addition, the cDNA hybridizes to a second RNA species of 5.5 kb, which is 4-fold less abundant than the 2.4-kb RNA. In vitro translation of a synthetic RNA transcribed from the 2.4-kb cDNA produces a 68-kDa protein, which is specifically immunoprecipitated by antiserum to bovine dopamine beta-hydroxylase. The 2.4-kb cDNA was cloned into a vaccinia virus vector, and the recombinant virus was used to infect the rat pheochromocytoma PC12 and monkey BSC-40 fibroblast cell lines. In both cell lines, infection with recombinant virus produces a protein of Mr = 75,000, which reacts with antiserum to bovine dopamine beta-hydroxylase. These results indicate that the 2.4-kb cDNA contains the genetic information necessary to code for the bovine dopamine beta-hydroxylase subunit.     

Plasminogen activator: The major secreted neutral protease of cultured skeletal muscle cells

Clonal mouse skeletal muscle cells which differentiate in culture and from synpases with neuronal cells were found to secrete high levels of protease activity as measured with an ¹²⁵I-fibrin assay. The secreted proteolytic activity was more than 90% dependent upon the presence of plasminogen in the medium, and had a pH optimum at 7 to 8. This activity was not inhibited by n-ethylmaleimide, pepstatin, EDTA, or EGTA. At millimolar concentrations, greater than 90% inhibition was obtained with either soybean typsin inhibitor, epsilon aminocaproic acid, Trasylol, or leupeptin. Almost complete inhibition occured with 1 mM diisopropylfluorophosphate suggesting the presence of a serine residue at the catalytic site. In contrast to the high levels of secreted activity, a lower steady-state level of cell-associated protease activity was detected in cell lysates. The high level of plasminogen activator secreted into the medium of cultured muscle cells suggests a role for such extracellular protease activity in myogenesis during development and remodeling following muscle injury. Such information may be useful in understanding the initial degeneration of neuromusclar contacts in experimental and pathologic denervation.     

Sensitive gas chromatographic assay for the quantitation of bretylium in plasma,urine and myocardial tissue

A sensitive analytical method has been developed for the quantitation of bretylium in plasma, urine and myocardial tissue. Bretylium and the internal standard, UM-360 (o-iodobenzyltrimethylammonium), are extracted and isolated as the iodide salts. Sodium benzenethiolate is added and the mixture heated to 100° for one hour. This results in the formation of 2-bromobenzyl phenyl thioether and 2-iodobenzyl phenyl thioether, which can be separated and quantitated by gas chromatography. Good reliability and reproducibility can be obtained using electron-capture detection with quantities of bretylium as small as 1 ng.     

Involvement of smooth and coated vesicles in the function of the contractile vacuole complex of some cryptophycean flagellates

The contractile vacuole complex of cryptophycean flagellates comprises the contractile vacuole, a pore and a vesicular spongiome. A minority of spongiome vesicles bear a 15-nm coat on the cytoplasmic surface of the membrane. The coat superficially resembles a clathrin coat. The majority of vesicles are smooth surfaced. Both types of vesicles are found at the same time. Smooth vesicles can be seen in profile suggesting vesicle-vesicle and vesicle-vacuole fusion. It is suggested that smooth vesicles are involved in the segregation of fluid from the cytoplasm and in filling the vacuole. Coated elements exist only as independent vesicles and as coated pits in the contractile vacuole membrane. There is no evidence of fusion of coated vesicles. It is suggested that coated vesicles function to retrieve specific membrane components from the contractile vacuole.     

Hydrogen peroxide causes the fatal injury to human fibroblasts exposed to oxygen radicals

Oxygen radicals are suspected as being a cause of the cellular damage that occurs at sites of inflammation. The phagocytic cells that accumulate in areas of inflammation produce superoxide, hydrogen peroxide, hydroxyl radical, and probably singlet oxygen in the extracellular fluid. The mechanism by which these oxygen molecules kill cells is unknown. To determine which of the oxygen species is responsible for the cellular killing, we exposed human fibroblasts in culture to oxygen radicals generated by the enzymatic action of xanthine oxidase upon acetaldehyde. Using the amount of chromium-51 released from labeled fibroblasts as an index of cellular death, we found that cells were protected only by interventions that reduce hydrogen peroxide concentration. Agents that inactivate superoxide, hydroxyl radical, and singlet oxygen were ineffective in limiting oxygen radical-induced cellular death.     

Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism: isolation and characterization of a mutant deficient in the activity of phosphoribosylaminoimidazole synthetase.

A new purine-requiring mutant of Chinese hamster ovary cells (CHO-Kl) is described. This mutant, Ade-G, grows on aminoimidazole carboxamide, hypoxanthine, or adenine. It complements all eight of our other previously described Ade- mutants. Biochemical analysis of de novo purine synthesis in whole cells suggests that Ade-G is capable of the first four reactions of de novo purine biosynthesis and that it synthesizes and accumulates phosphoribosylformylglycinamidine (FGAM). Direct enzyme assay in cell-free extracts confirms that Ade-G is defective in phosphoribosylaminoimidazole synthetase activity and does not convert FGAM to phosphoribosylaminoimidazole (AIR), the next intermediate in the de novo biosynthetic pathway.