Pinitol, a larval growth inhibitor for Heliothis zea in soybeans

A search for insect growth inhibitors in methanol extracts of soybean leaves resulted in isolation of pinitol. Pinitol caused a 50% reduction in weight gain (ED50) of Heliothis zea larvae at about 0.7% when added to a synthetic diet. Although myo-inositol is a normal component of the insect diet, it also caused growth inhibition at higher concentrations; ED50 4%.     

Differential sensitivity of the two phases of ear artery contraction to intimal and adventitial norepinephrine

Summary The biphasic contraction of the rabbit ear artery to norepinephrine (NE) was investigated in the normal (adventitial stimulation) and the everted (intimal stimulation) segment of ear artery. The 2nd phase response showed an intimal ED₅₀ of 8.2×10^–8 M which was significantly (p<0.05) lower than the adventitial ED₅₀ of 42.6×10^–8 M. This difference was abolished by inhibition of neuronal and extraneuronal uptake for NE. The 1st phase response also showed an ED₅₀ for the intimal stimulation (6.9×10^–8 M) which was significantly (p<0.05) lower than adventitial (65.5×10^–8 M). This difference was reduced but not abolished by NE uptake inhibition. This suggsets that some feature of the adrenergic neuroeffector apparatus is asymmetrically arranged to favor fast responses to blood borne NE.Supported by American Heart Association-Greater Los Angeles Affiliate Grant No. 602. We wish to thank Dr John Bevan and Dr Alasdair MacLean for helpful advice.     

Antifeedant activity of precocenes and analogs onRhodnius prolixus

Summary Precocene and analogs added to the meal of 4th instar larvae ofRhodnius prolixus were tested as antifeedants. While precocene II had a strong antifeedant effect (ED₅₀=48 g/ml), the other compounds showed no drastic inhibition of feeding (ED₅₀>140 g/ml). ATP, a phagostimulant, did not reverse the antifeedant action of precocene II. The mechanism of feeding inhibition is discussed.Acknowledgments. This research was supported by funds from Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, and National Science Foundation grants PCM-76-09647 and PCM-79-03245.     

Photoreactivation of UV damage in culturedDrosophila cells

Summary Cell survival and photoreactivation of 254 nm ultraviolet (UV) light damage in a wild typeDrosophila cell line was assayed by colony formation in liquid medium. F_o, F_q, and extrapolation number for the exponential portion of survival curves are 21 J/m², 3.6 J/m², and 1.5 for non-photoreactivated cells and 110 J/m², 11.2 J/m², and 1.3 for those exposed to photoreactivating light. Maximal photoreactivation occurs at the 100 J/m² region of the curve. At 10 and 50% survival, 75–80% of the UV damage was photoreactivable.     

Dynamic insulin secretion from perifused rat pancreatic islets

Insulin secretion from isolated pancreatic islets of 8- to 12-day-old rats was investigated in a dynamic in vitro (perifusion) system. The aims of the study were (i) to describe a carefully controlled in vitro method to study the mechanism of insulin secretion and to analyse the effects and dynamic interactions of bioactive compounds on isolated rat pancreatic islets, (ii) to validate the method by comparing fundamental data on the functions of the islets obtained with this method to those collected with other techniques; and (iii) to find novel features of the control of insulin secretion. The method was carefully designed to maintain the functional capacity of the explanted cells. A functional standardization system was elaborated consisting of (i) analysis of the changes in the basal hormone secretion of the cells; (ii) evaluating responses to a standard, specific stimuli (50 mM glucose for 3 min); (iii) determining the alteration of the momentary size of the hormone pool with responses to KCl; and (iv) direct determination of the total intracellular hormone content from the extract of the column. The technique provides accurate quantitative data on the dynamic responses to biologically active compounds that act directly on the pancreatic islets. The islets maintained their full responsiveness for up to 7 days, and responses as close as in 1-min intervals could be distinguished. A linear dose-response relationship was found on the glucose-induced insulin release in case of 3-min stimulation with 4 and 500 mM of glucose (lin-log graph). Utilizing this method, we showed that no desensitization to glucose-induced insulin release can be observed if the responsiveness of the cells is properly maintained and the parameters of the stimulation are carefully designed. Exposure of the explanted islets to 10 μM acetylcholine or 30 mM arginine (Arg) induced a transitory elevation of insulin release similar in shape to that experienced after glucose stimulation. Norepinephrine (NE), dopamine (DA) and somatostatin (SS) did not induce any detectable alteration on the basal insulin secretion of the islets. However, 100 nM SS given together with 50 mM glucose, 30 mM Arg or 10 μM acetylcholine significantly reduced the insulin-releasing effect of these substances (by 75.5, 71.5 and 72.5%, respectively). At the same time, SS did not alter the insulin response of the islets to 100 mM elevation of K⁺ concentration. SS also inhibited glucose-induced insulin release in a dose-dependent way (ED₅₀ = 22 nM). A similar dose-dependent inhibitory effect on glucose-induced insulin release was found with NE (ED₅₀ = 89 nM) and DA (ED₅₀ = 2.2 μM). γ-Aminobutyric acid (GABA) did not influence insulin release under similar circumstances. Received 16 January 1998; received after revision 6 May 1998; accepted 8 May 1998     

Serotoninantagonismus an der Placenta

Summary The placentae of 17 to 19 days pregnant mice respond to subcutaneous serotonin (15 mg/kg) with vascular changes which lead to the death of the fetuses in 3–4 h. Pretreatment of the females withd-lysergic acid derivatives preserves the life of the young. Thus, LSD showed an ED₅₀ of only 30 g/kg, while UML (Deseril®) gave an ED₅₀ of 3.7 g/kg. PML takes an intermediate position. At a 50% efficiency level, UML (Deseril®) antagonises the effect of a 4000 times higher dose of serotonin.     

Effects of diflubenzuron and tunicamycin on N-acetylglucosaminyl transferases in prepupae of the stable fly (Stomoxys calcitrans)

Summary Tunicamycin, an antibiotic, and diflubenzuron, an insect growth regulator, were tested to determine their effects on N-acetylglucosaminyl transferase fromS. calcitrans prepupae. Diflubenzuron had no effect, but tunicamycin inhibited the transfer of GlcNAc-1-P from UDP-GlcNAc to dolicholmonophosphate with an I₅₀ of 1.5–4 ng/ml.     

Diterpene acids as larval growth inhibitors

Summary Kaurenoic and trachylobanoic acids from sunflower inhibited larval development in several Lepidoptera species. The tricyclic resin acids were also effective in curtailing growth ofPectinophora gossypiella and either reduction to carbinol or esterification of the carboxyl group lowered activity. Partial reversal of growth inhibition in the presence of relatively large amounts of cholesterol suggests an interaction with the insects' hormonal system.Acknowledgment. We wish to thankM. Rose andJ. Baker for insect bioassays.     

Resveratrol-type oligostilbenes from Iris clarkei antagonize 20-hydroxyecdysone action in the Drosophila melanogaster B(II) cell line

Bioassay-guided high-performance liquid chromatography analysis of a MeOH extract of Iris clarkei seeds yielded the resveratrol-type oligomeric stilbenes, ampelopsin B and α-viniferin, which antagonize the action of 20-hydroxyecdysone; with a 20-hydroxyecdysone concentration of 50 nM, the ED₅₀ values were 33 μM and 10 μM, respectively. The structures of these compounds were determined by spectroscopic analysis, notably ultraviolet, liquid secondary ion mass spectrometry and modern one- and two-dimensional nuclear magnetic resonance techniques. Received 4 November 1999; accepted 13 December 1999     

Morphogenetic effect of precocene I and II onSchistocerca gregaria (Forsk)

Summary 4th instar nymphs ofSchistocerca gregaria exposed to precocene I and II by topical application metamorphosed precociously. The ED₅₀ of both compounds were evaluated and, unexpectedly, precocene I was found to be more active than precocene II. All adultiforms were identical and in an advanced form.Acknowledgments. This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada and the Ministère de l'Education du Québec. We are grateful to Gaston Grégoire for rearing the insects.     

Über den Vitamin-B12-Gehalt von Organen verschieden ernährter Ratten

Summary Adult, male rats bred for over 10 generations on a soy meal-corn-diet had vitamin B₁₂ values of liver and kidney about 10 times lower than the controls. If the deficient ration was supplemented with 5µg/kg of B₁₂, these values were still about 1/5 of the controls. 3 weeks on the deficient diet lowered the B₁₂ levels in the livers and kidneys of previously undepleted rats to about 1/2, and a similar diet containing 0.1% of iodized casein lowered these levels to about 1/3 of the normal values but did not lower the B₁₂-concentration of organs of already deficient rats.Rats bred on the deficient diet and receiving for 1 month a supplement of 30µg/kg of vitamin B₁₂ or the stock diet with a similar B₁₂-content, had normal B₁₂-levels in livers and kidneys.     

Activity of precocene analogs onLocusta migratoria migratorioides (R. and F.)

Summary Several analogs of precocene have been synthesized and evaluated as potential inhibitors of juvenile hormone onLocusta migratoria. Only 5,7-dimethoxy-2,2-dimethylchromene was active; its ED₅₀ and LD₅₀ were measured and compared to those of precocene I and II.Acknowledgments. This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada and the Ministère de l'Education du Québec. We are grateful to Gaston Grégoire for rearing the insects.     

Drosophila melanogaster does not dealkylate [14C]sitosterol

Summary Drosophila melanogaster was unable to dealkylate and convert [¹⁴C]sitosterol to cholesterol and no evidence was found for conversion of [¹⁴C]desmosterol to cholesterol. Therefore,D. melanogaster is incapable of dealkylating and converting C₂₈ and C₂₉ phytosterols to cholesterol.The authors thank O. J. Duncan III, and H. S. Symonds for technical assistance. Mention of a company name or proprietary product does not imply endorsement by the U.S. Department of Agriculture.     

Anti-feedant activity of the polyacetylene,phenylheptatriyne (PHT), from the Asteraceae toEuxoa messoria (Lepidoptera: Noctuidae)

Summary Phenylheptatriyne (PHT), a polyacetylene from various species of Asteraceae reduced feeding and weight gain of larvae of the polyphagous insectEuxoa messoria when incorporated into an artificial diet at concentrations of 10–300 ppm. These results suggest a role as insect antifeedants for the widely distributed polyacetylenes of the Asteraceae.Acknowledgment. This work was supported by NSERC and Agriculture Canada (E.M.R.) We thank Dr R. J. Byers (Agriculture Canada) for eggs ofEuxoa. To whom reprint requests should be addressed.     

High sensitivity of porcine cerebral arteries to endothelin

Summary The threshold concentration of endothelin to induce contractions in porcine cerebral arteries (anterior cerebral, Willis ring and basilar artery) was lower than those for coronary and renal arteries. The median effective concentrations (ED₅₀) of endothelin in cerebral arteries were also significantly lower than those for coronary and renal arteries. There was no significant difference in the sensitivity to endothelin among cerebral arteries, or between coronary and renal arteries. The maximal percentage of contractions induced by endothelin, as compared to that induced by 10^–1 M potassium chloride, was not significantly different between the arteries.     

Oxidative stress in the moderately halophilic bacteriumDeleya halophila: Effect of NaCl concentration

The sensitivity ofDeleya halophila to oxidative stress caused by hydrogen peroxide (H₂O₂) was found to vary, depending on the NaCl concentration of the growth medium. Pretreatment of the bacteria at a low concentration of H₂O₂ (50 M) protected the cells against the lethal effects of higher levels (1–2 mM) of H₂O₂. Exposure ofD. halophila cells to 50 M H₂O₂ resulted in the induction of several proteins (hydrogen peroxide-inducible proteins, hips). However, the kinetics of induction, the extent of induction and the number of hips appear to be influenced by the salt concentration of the growth medium. Five of the hips exhibited apparent molecular masses identical to those of five heat shock proteins (hsps).     

Synthesis and metabolism of vertebrate-type steroids by tissues of insects: A critical evaluation

Summary This review covers the synthesis and the metabolism of vertebrate-type steroids (progesterone, testosterone, estradiol, corticosteroids) by insect tissues and discusses the significance of the reactions for insect physiology. Biosynthesis of vertebrate-type steroids from cholesterol hitherto has been demonstrated in only two insect species, i.e. the water beetleAcilius sulcatus (Coleoptera) and the tobacco hornwormManduca sexta (Lepidoptera). InAcilius, steroid synthesis is associated with exosecretion (chemical defense). Nothing, however, is known about a physiological role of the C₂₁ steroid conjugate present in ovaries and eggs ofManduca. No synthesis of vertebrate-type steroids was observed in any other insect investigated to date. Most metabolic conversions of steroids by insects concerned oxidoreduction of oxygen groups (hydroxysteroid dehydrogenase activity) and (polar and apolar) conjugate formation. All important enzymatic steps involved in synthesis and catabolism, as known from studies with tissues of vertebrates, were not, or hardly observed. The conclusion is drawn that typical vertebrate-type (C₂₁, C₁₉ and C₁₈) steroids probably do not act as physiologically active substances in insects.     

Regulation of grasshopper fecundity,longevity and egg viability by plant growth hormones

Summary Abscisic acid, a plant growth hormone, added in water to the grass diet of a grasshopper, greatly reduces the reproductive rate, as does gibberellin A₃ at doses 10 times greater. Reciprocal seasonal variations in quantities of these hormones could synchronize the growth and reproduction of insects with their host plants in the field.Acknowledgments. I thank Drs J. Pickett, G. Strobel, D. Meyers, I. Mills, L. Jackson and J. Bradbury for helpful consultations; Dr R. Lund and Ms W. Whitmore for statistical analyses, and S. Baril, M. Gaudet, D. Wrobetz, J. Cotter and W. Wallace for technical assistance. This research was supported by the Montana Agricultural Experiment Station, Project 420, and is published as Journal Paper No. 865.     

Enantiomeric cannabinoids: stereospecificity of psychotropic activity

Summary The 1,1-dimethylheptyl homolog of (–)-(3R,4R)-7-hydroxy-delta-6-tetrahydrocannabinol (compoundII) is highly psychotropic in mice, rats and pigeons. The (+)-(3S,4S) enantiomer (III) was found to be psychotropically inactive at doses up to several thousand times those of the ED₅₀ of (II).We thank Dr A. Breuer and Mrs H. Amsalem for help with the syntheses. The research reported above was supported in Tucson by NIH grant NS 15441; in Uppsala by grants from the Swedish Medical Research Council (5757) and the Swedish Council for the Planning and Coordination of Research (84/2082); in Jerusalem by the Szold Foundation.Presented in part at a meeting at the US National Institute on Drug Abuse, Washington, D.C., October 1986, see NIDA Research Monographs79 (1987) 15.     

Occurrence of retinal and 3-hydroxyretinal in a possible photoreceptor of the silkworm brain involved in photoperiodism

Summary Deficiency of dietary carotenoid and vitamin A caused an absence of photoperiodic response of diapause induction in the silkworm,Bombyx mori, and an addition of vitamin A to the diet restored the response. By high pressure liquid chromatography (HPLC) a possible photoperiodic receptor of the silkworm brain was found to contain both retinal and 3-hydroxyretinal which are chromophores of insect visual pigments. These pieces of evidence suggest that a retinoid protein might function in the photoperiodic response of the silkworm.