ABSTRACT
Microphysiological techniques and computer-based methods of data acquisition and analysis were used to investigate the dynamics of neurochemical action on spontaneous contractions of continuously perfused oviducts and hindguts isolated from female mosquitoes (Aedes aegypti). Proctolin, leucomyosuppressin (LMS), serotonin and octopamine, which are known to modulate insect muscle contractions, and a mosquito neuropeptide, Aedes Head Peptide I (Aea-HP-I), which inhibits host-seeking behavior, were tested in the bioassays. LMS depressed contractile activity in oviducts at concentrations above 10(-12) mol l-1, but hindguts did not respond to concentrations below 10(-6) mol l-1. Hindgut contractions spontaneously restarted in 10(-6) mol l-1 LMS, but only washing out LMS restored activity in oviducts. LMS changed the amplitude of the oviduct contractions, but the dynamics of contraction remained steady. Following recovery of contractions in LMS, hindgut tissues contracted with a more regular pattern. Serotonin and octopamine had an identical action on oviduct and hindgut tissues. At concentrations greater than 10(-8) mol l-1, serotonin eliminated the refractory period between contractions and thus increased the contraction frequency of oviducts. Though the contractions appeared chaotic, state-series analysis proved that serotonin-treated oviducts contracted rhythmically. Above 10(-6) mol l-1, serotonin extinguished normal hindgut peristalsis and induced regular fluttering of the anteriormost portion of the hindgut, an effect possibly related to diuresis following the blood meal. Proctolin failed to stimulate both oviduct and hindgut contractions at concentrations up to 10(-6) mol l-1, but at 10(-8) mol l-1 induced contractions of cricket hindgut preparations. Aea-HP-I had no effect on either tissue at 10(-6) mol l-1 or lower concentrations. State-series analysis, based on simple manipulations of experimental data, permitted direct observation of the dynamics of oviduct and hindgut contractile activity.
Subject(s)
Aedes/physiology , Neuropeptides/pharmacology , Oviducts/physiology , Animals , Female , Insect Hormones/pharmacology , Muscle Contraction/drug effects , Muscle Contraction/physiologyABSTRACT
Originally isolated fromDipterocarpus kerrii, the two previously uncharacterized sesquiterpenes,1 and20, were synthesized from α-gurjunene. A novel process involvingm-chloroperoxybenzoic acid oxidation ofα-gurjunene produced20 in one step. Spectroscopic studies determined that the diene moiety in20 is nonconjugated and also found the C-4 tertiary alcohol center to have theα-configuration, while the other stereocenters have configurations matching the corresponding centers inα-gurjunene. Bioassays with termites demonstrated that20 was more toxic than1, resulting in a 50% mortality in seven days when offered toNeotermes ?dalbergiae on filter papers. The chemicals appear to result from biotransformation ofα-gurjunene. In view of its similarity to the known sesquiterpeneγ-gurjunene, we suggest that20 be referred to asγ-gurjunenol.
ABSTRACT
Selective removal of symbiotic hindgut microorganisms by chemical treatments reduced methane emission by the termiteZootermopsis angusticollis. Methane emission from untreated termites incubated in 25% H2 increased 123%, from 10.3 nmol/termite/hour (U) to 22.9 U. Though linear with time, methane emission was not correlated with termite mass. Hyperbaric oxygen treatments reduced methane emission to unquantifiable levels and eliminated all but the protozoaTricercomitus andHexamastix. Exogenous H2 restored 5% of methane emission to 1.3 U. 2-bromoethanesulfonic acid, fed on filter papers to termites, eliminated methane production. Epifluorescence microscopy showed that this treatment selectively removed methanogens from symbioses withTricercomitus, Hexamastix, andTrichomitopsis, but the protozoa did not appear to be affected. The insect molting hormone 20-hydroxyecdysone reduced methane production 86% to 1.6 U from an initial level of 11.4 U. Hydrogen incubation increased this rate to 77% of the initial rate, 8.8 U. Hormone treatment reduced the number ofTrichonympha in the hindgut and induced sexuality in these protozoa. A model suggests thatTrichonympha evolve most of the hydrogen and that methanogenic bacteria symbiotic withTrichomitopsis produce most of the methane in this hindgut ecosystem.
ABSTRACT
Four sesquiterpenoids (2, 4, 7, and9) have been isolated and characterized from the termiticidal fraction ofDipterocarpus kerrii resin. The major constituent of this resin is α-gurjunene (1).
