Effects of the bipyridylium herbicides diquat dibromide and paraquat dichloride on growth and development of Neobellieria bullata (Diptera: Sarcophagidae) larvae.

Diet containing diquat dibromide (1,000 or 2,000 ppm) caused an extension of the first-instar stadium of Neobellieria bullata (Parker); the first molt was primarily disturbed. Pupariation was delayed when early-wandering larvae had been injected with diquat dibromide (18 micrograms/larva; approximately to 150 ppm). This effect of diquat dibromide was eliminated by simultaneous injection of 20-OH ecdysone (0.02 micrograms/larva). After larvae in the red spiracle stage were injected with diquat dibromide (5 micrograms/larva; approximately 42 ppm), evagination of the pupal head was inhibited. Paraquat dichloride was less active than diquat dibromide and appears to be a safer herbicide for use around decomposer fly species.

Effects of precocene analogs on the nematode Caenorhabditis remanei (var. Bangaloreiensis). I. Structure/activity relations.

Precocenes (PI and PII) and 114 of their analogs (PAs) were synthetized and tested on C. remanei embryos for their precocene-like (P-like) activities resulting in unusual development at sublethal doses. The P-like activity was quantitated by plotting the probit of the percentage of the developmentally affected survivors against the (log) dose to obtain the EC plot and the half effective concentration (EC50). All five PAs (PI, PII, 7-ethoxy-PII, 7-(prop-2-ynyloxy)-PI, and 6-methoxy-7-(prop-2-ynyloxy)-PII) which exert both antiallatal activity in insects and P-like activity in nematodes are 7-alkoxy-substituted 2,2-dimethylchromenes. Both activities can be enhanced by an additional 6-MeO-substitution or by an asymmetric 6,7-dialkoxy-substitution, on condition that R-7 is longer than R-6. There are many more similarities than dissimilarities in the structural requirements needed for antiallatal and P-like activities. All but three nonantiallatal PAs effective in nematodes are 7-prop-2-ynyloxy-subsituted; two are symmetrically 6,7-disubstituted, and one is heterosubstituted (thio-PI). All PAs with antiallatal but without P-like activity are 7-monosubstituted with a relatively long alkoxy group. Certain substitutions favor antiallatal activity and others P-like activity. The severe nematocidal effect of 6,7-methylenedioxy-2,2-dimethylchromene (inert in insects) is not accompanied by P-like activity. The present findings lend some indirect support to the supposition that JH-producing cells and/or JH-dependent function(s) might exist in the nematodes.

Effects of precocene analogs on the nematode Caenorhabditis remanei (var. Bangaloreiensis). II. Competitions with a juvenile hormone analog (Methoprene).

Fourteen 7-alkoxy-2,2-dimethychromenes were synthetized and studied in JH competition experiments: precocenes (Ps) PI and PII, and synthetic analogs (PAs) including (i) three with both antiallatal and P-like activities: 7-ethoxy-PII (7-EPII); 7-(prop-2-ynyloxy)-2,-2-dimethylchromene (PPI); and 6-methoxy-7-(prop-2-ynyloxy)-2,2-dimethylchromene (PPIII); (ii) six without antiallatal activity, exerting P-like activity in nematodes; and (iii) three without either antiallatal or P-like activity, but with a strong nematocidal effect. Within the dose range 8-1000 micrograms/ml, different concentrations of each PA were applied to nematode growth medium which did or did not contain 1000 micrograms methoprene (a juvenile hormone analog JHA)/ml. Plates inoculated with Caenorhabditis embryos were incubated and scored for developmentally affected survivors. The JHA did not compete with any PA mentioned as (iii). It competed moderately with some nonantiallatal PAs (8-Me-PPI, 8-MeO-PPI, and 3,4-diCl-PPI) with strong P-like and nematocidal activities. The JHA competed most efficiently with all Ps, antiallatal PAs, and two nonantiallatal PAs (PPII and thio-PI) which exerted severe P-like activities in nematodes. Parameters assumed to be indicators of the P-like (rather than nematocidal) activity of the PAs proved more sensitive to the JHA than those of nematocidal activity. Whether the JH-compensable P-like activity of some PAs can be regarded as a real anti-JH action needs further clarification.

The antiallatal effects on locusts and lethal effects on nematodes of synthetic precocene-1 derivatives differing at the carbon 7 position.

Fourteen precocene-1 (P1) derivatives differing at C-7 were synthetized and tested for their antiallatal activities on Locusta migratoria (in vitro and in vivo) and nematocidal effects on Caenorhaditis elegans. An outstanding antiallatal effect was produced by 7-propargyloxy-P1 in vitro. It caused an elevated rate of mortality when applied in vivo to locusts or nematodes. The antiallatal effect of 7-cyclopentyloxy-P1 was not accompanied by toxicity. Aralkyloxy substitution at C-7 eliminated the precocene activity.

Swelling of nuclei and decondensation of chromatin in a multinuclear model.

Rat liver nuclei were isolated in the presence of a nonionic detergent, and the soluble proteins were extracted from them using low-salt solution. The isolated nuclei were then embedded in a fibrin clot which was cut into 4 to 5 mm3 pieces and placed into an AMICON pressure cell in the presence and absence of the soluble nuclear proteins. When the soluble nuclear proteins were present and when their concentrations reached 40 mg/ml, the nuclei were significantly larger and their chromatin more decondensed than in the absence of added proteins. Our findings suggest that the soluble nuclear proteins play a role in the regulation of nuclear volume and the hydration of chromatin.