Effect of precocene II,applied independently or subsequent to hydroprene treatment,on the morphogenesis of female reproductive organs of Corcyra cephalonica

Application of precocene II, either independently or subsequent to hydroprene treatment to 0–24-hr-old last-instar larvae and 12–24 hr and 48–72 hr-old pupae of the rice moth Corcyra cephalonica brings about serious abnormalities in the histomorphology of female reproductive organs. The most sensitive organs are the ovaries, reservoir of accessory glands and the bursa copulatrix. After application of precocene II to hydroprene-treated individuals, some of the hydroprene-induced defects are retained while others do not appear. Similarly, some of the precocene-induced abnormalities are manifested. Finally, new disorders develop, which cannot be caused by either of the compounds independently. Precocene II can prevent the inhibitory effect of hydroprene on the rate of adult emergence of this insect quite considerably. But the juvenoid-induced effects cannot change the responsiveness of sensitive tissues of the system to precocene.     

Precocene II modifies maternal responsiveness in the burrower bug, Sehirus cinctus (Heteroptera)

Abstract. The anti-Juvenile Hormone agent precocene II was used to investigate the relationship of corpora allata activity to subsocial behaviour in a burrower bug Sehirus cinctus Palisot (Heteroptera: Cydnidae). Egg-brooding females treated with a range of dosages of precocene II exhibited reliably depressed maternal defensive behaviour when treated with at least 70 μg of precocene II, but attraction to eggs was only depressed at higher dosages. This effect was not due to precocene II toxicity, as demonstrated by the prevention of depression effects through simultaneous treatments of precocene II and the Juvenile Hormone analogue methoprene. Methoprene, however, failed to reinstate maternal responsiveness in maternally depressed females that had been previously treated with precocene II. This study provides the first clear evidence that insect parental behaviour can be modified by treatment with anti-Juvenile Hormone agents, and suggests that the role of the corpora allata in governing care in S. cinctus is different from that of other maternal insects, such as earwigs.     

Alteration of precocene II-induced hepatotoxicity by modulation of hepatic glutathione levels

Precocene II (6,7-dimethoxy-2,2-dimethyl-2H-benzo[b]pyran), an insect growth regulator that is structurally related to several naturally occurring carcinogenic and non-carcinogenic alkenylbenzenes, is genotoxic and produces hepatic centrolobular necrosis in rats. This investigation was conducted to evaluate the effects of modulation of hepatic glutathione levels on the toxicity of precocene II. Administration of a toxic dose of precocene II (175 mg/kg) to male Sprague-Dawley rats rapidly depleted hepatic GSH, produced histopathological changes in the liver, and induced increases in serum aminotransferase activity. Concurrent administration of the cysteine pro-drug L-2-oxothiazolidine-4-carboxylic acid (OTC) prevented these toxic effects of precocene II. In contrast, pretreatment of rats with DL-buthionine-SR-sulfoximine (BSO), an inhibitor of glutathione synthesis, potentiated the toxicity of an otherwise non-toxic dose of precocene II (100 mg/kg). These results indicate that glutathione is important for protection from precocene II-induced hepatotoxicity.     

Antijuvenile influence of the precocene on the development of adult antennae in the large fruit-tree tortrix Archips podana Scop. (Lepidoptera: Tortricidae)

The influence of precocene II, an antijuvenile agent, on the development of adult antennae in the large fruit-tree tortrix A. podana Scop. was demonstrated. Treatment of the fifth instar larvae and prepupae with different doses of precocene proved to cause different sensitivity of the specimens to the juvenile hormone deficit. Treatment with 450 and 600 ??g precocene per specimen during the first days after ecdysis to the fifth instar caused the death of larvae. Treatment with 300, 450, and 600 ??g per specimen on the third day of the fifth instar larvae and prepupae caused a delay in the development of adult antennae. The results are discussed with respect to the role of the juvenile hormone in the development of imaginal structures during metamorphosis.     

Morphogenetic effects of precocenes on three aphid species

The disruptive effects of precocenes I, II and III on metamorphosis were assessed in apterous viviparae of Acyrthosiphon pisum, Aphis fabae and Megoura viciae. Prenatally applied precocene I had no effect, precocene II caused supernumerary moulting (metathetely) in M. viciae but precocene III induced both precocious adult development (prothetely) and metathetely in all three species. the latter compound also promoted precocious adult development in alate virginoparae, males and ovipara-producers of M. viciae. However, gynoparae of A. fabae, and oviparae of M. viciae and A. pisum were resistant to this action. When topically applied to young adults of A. fabae or M. viciae none of the precocenes caused alate progeny to be produced but all did so in A. pisum. However, the previous supposition that precocene II promotes wing development because it decreases juvenile hormone titres should be viewed with caution as: (a) Precocene II was more potent than precocenes I and III when inducing wing formation but did not provoke precocious adult development, an overt indication of low juvenile hormone titres. (b) Precocene I and III were equally effective in inducing alate progeny but only the latter provoked precocious adult development. (c) Attempts to prevent or reduce the alata-inducing property of precocene II with juvenile hormone I were unsuccessful.     

Antigonadotropic and antiallatal effects of precocene II in the firebrat, Thermobia domestica (Thysanura,Lepismatidae)

The sensitivity of an apterygote insect to precocene II was investigated for the first time in females of Thermobia domestica. Topical applications of this compound, which has been said to possess anti-juvenile hormone activity, were carried out at various times in the postecdysial period of a reproductive cycle, during intense vitellogenesis in the terminal oöcytes. The effects of treatment were observed on mortality, fecundity, insemination and also on the ultrastructure of corpora allata; they depend on the dose used and on the day of treatment. A single application of 10 μg/insect at the beginning of the postecdysial period induces antigonadotropic effects in females reared both with and without males. The effects of precocene add to those of non-insemination, which also elicits inhibition of oöcyte maturation. In addition, the cytotoxic action of precocene, leading to degeneration of the corpora allata, which is most probably irreversible, was demonstrated.     

Synthesis and Anti-juvenile Hormone Activity of 2,2-Dimethyl-1,2-dihydroquinoline Derivatives,Nitrogen Analogues of Precocene I and II

A synthesis of nitrogen analogues of the natural insect anti-juvenile hormones precocene I and II is reported. The crucial step of this synthesis is thermal cyclization of the N-alkynylaniline 3 into the corresponding 1,2-dihydroquinoline when promoted by a copper catalyst. Biological testing of the anti-juvenile hormone activity was carried out against Callosobruchus chinensis by observing the inhibition of eclosion. The 7-methoxy analogue showed higher activity than the 6,7-dimethoxy analogue. However, the former showed lower activity than precocene I.     

Influence of precocene II on the sensory system of antennae and mouthparts in larvae of the fruit tree tortricid <Emphasis Type="Italic">Archips podana</Emphasis> Scop. (Lepidoptera: Tortricidae)

The influence of precocene II, an antijuvenile agent, on morphological characters of the chemoreceptor apparatus of antennae and mouthparts was studied in fifth instar A. podana larvae. Treatment with different doses of precocene was performed at the egg stage. It proved to cause changes in the form and number of basiconic sensilla on the maxillary palps and galea and in the size of basiconic sensilla on the second and third antennal segments. The results are discussed with respect to the influence of precocenes on the insect sensory system and the role of the juvenile hormone in regulation of its development.     

早熟素II对家蝇卵黄发生的影响

本实验通过卵巢发育分级的解剖观察、可溶性蛋白质和核酸的定量测定、火箭免疫电泳定量测定卵黄原蛋白及激素处理等方法,研究了早熟素对家蝇(Muscadomestica vicina)卵黄发生的影响。试验结果表明用20ug早熟素处理每头刚羽化家蝇时,家蝇卵黄发生处于不完全抑制状态,其卵黄发生过程比对照组“延迟”约12小时。处理后48小时,血淋巴中卵黄原蛋白的滴度为lo.5ug/ul,接近对照组,而其卵巢鲜重和发育等级明显低于对照组,这种不完全抑制状态表明卵母细胞对卵黄原蛋白的吸收作用受到抑制。当用高剂量100ug早熟素11处理每头刚羽化家蝇时,血淋巴中卵黄原蛋白滴度、卵巢鲜重及其发育均受到明显的抑制,这种抑制效应能自然恢复。 当早熟素11和保幼激素(JH-III)、20-羟基蜕皮酮共同处理时,保幼激素具有明显的去抑制作用,可使血淋巴中卵黄蛋白浓度成倍增加,20-羟基蜕皮酮的去抑制效应不明显。本文还对早熟素作用于双翅目昆虫的方式作了讨论。     

Age-dependent physiological responses of last instarHelicoverpa zea larvae to oral and topical application of precocene II

Newly-ecdysed last instar larvae ofH. zea grouped into 100-, 200-, 300-, or 400-mg categories were fed diet containing precocene II or given precocene II topically on the abdomen. The time for larvae to reach a maximal weight, time to pupation, growth rate, and the amount of precocene II excreted were calculated. Younger larvae of lower weights, which were fed or topically treated with precocene II required more time to reach their maximal weight, had a lower maximal weight, a lower growth rate, and required more time to pupate than control larvae. Older larvae represented by the largest weight category were less sensitive to precocene II, had a shorter delay in reaching maximal weight, and a shorter delay in the time to pupation than control larvae; larvae in the largest weight category that were fed precocene II also had smaller decreases in the growth rate. Growth rate declines for larvae given topical doses of precocene II, however, were largest for the oldest larvae. All larvae given a single topical dose excreted precocene II for several days and were most efficient at eliminating smaller doses; larger, older larvae excreted more precocene II than smaller, younger larvae. Age-dependent responses to precocene II indicate that growth and metabolic processes, as well as xenobiotic metabolism, change in last instar larvae.     

Behavioral changes and growth inhibition in last instar larvae of Heliothis zea induced by oral and topical application of precocene II

In diet choice tests, newly-ecdysed fifth instar Heliothis zea larvae randomly chose diet containing 4 mM precocene II or diet without precocene II but initially preferred to feed on diet without precocene II. After two days, however, they were found more frequently on diet containing precocene II. Nevertheless, larval growth and development were inhibited when forced to eat diet containing precocene II. Removal of the maxillae, the site of the primary gustatory receptors, did not prevent the growth inhibition caused by larval consumption of diet with precocene II. Topical treatments with precocene II also caused larval growth inhibition, and daily treatments were more detrimental to the larvae than a large single dose. Addition of methylenedioxyprecocene (6,7-methylenedioxy-2,2-dimethylchromene) to the diet did not reverse the observed larval growth inhibition and this compound was itself significantly toxic. These results indicate that larval growth and development are disrupted after precocene II ingestion, but not because of preingestive discrimination by olfaction and gustation.     

Involvement of an Inducible Cytochrome P-450 in Precocene II Oxidation by Streptomyces Griseus

Streptomyces griseus oxidizes the insecticide precocene II to its cis- and trans-dihydrodiols and 3-chromenol after growth on an enriched medium containing soybean flour. Oxidation of precocene II is dependent on the level of cytochrome P-450 in this organism. Extracts of cells grown on media lacking soybean flour were devoid of cytochrome P-450 and could not oxidize precocene II. In an in vitro reconstituted system containing NADPH, spinach ferredoxin reductase, spinach ferredoxin and ammonium sulfate fractions enriched in cytochrome P-450, precocene II was oxidized to its dihydrodiols. An aerial mycelium-negative variant of S. griseus (AMY mutant), that was unable to elicit cytochrome P-450 when grown on soybean flour-enriched medium, failed to oxidize precocene II.     

Juvenile hormone regulates the expression of the gene encoding ceratotoxin a,an antibacterial peptide from the female reproductive accessory glands of the medfly Ceratitis capitata

Ceratotoxin A is an antibacterial peptide produced by the reproductive female accessory glands of the medfly Ceratitis capitata. To investigate whether ceratotoxin A gene expression was affected by juvenile hormone, which has gonadotropic functions in adult insects, newly emerged female medflies were treated with precocene II, an antiallotropin compound capable of inhibiting juvenile hormone biosynthesis. Daily treatment of newly emerged flies with precocene II blocked ceratotoxin A gene expression in a dose-dependent manner. Ceratotoxin A gene expression could be recovered after withdrawl of precocene II treatment. Moreover, the effect of precocene II on ceratotoxin A gene expression could be countered by simultaneous treatment with methoprene, a juvenile hormone analogue. The effects of precocene II and methoprene treatments on the growth of both ovaries and accessory glands was also investigated. Our data suggest that ceratotoxin A gene expression is modulated by juvenile hormone.     

Biomorphogenetic changes caused by the application of precocene II in nymphs of Triatoma infestans (Klug, 1834) (Hemiptera, Reduviidae, Triatominae)

The morphogenetic effect of precocene II on 4th instar nymphs of Triatoma infestans was examined. Topical treatment with precocene II (200, 300 and 400 micrograms/nymph) induced the formation of adultoids with the following characteristics: rudimentary wings, three segmented tarsi, ocelli, deformed genitalia and mouth-parts and testes with intermediary development. Precocene II also increases the duration of the molting cycle. The survival of the adultoid insects was related to the inverse of the applied doses. These data extend our knowledge of the action of precocene II on triatominae species.     

Effect of precocene II on fatty acid metabolism in the pea aphid, Acyrthosiphon pisum, under cold stress

Pea aphids, Acyrthosiphon pisum (Harris), reared at 10 degrees C contain higher levels of fatty acids than those reared at 25 degrees C. This is primarily the result of an accumulation of triacylglycerols containing myristic acid. When aphids reared at 25 degrees C were transferred to 10 degrees C there was a gradual increase in triacylglycerol content that reached a maximum at 16 days post-transfer. Treatment of aphids with precocene II prior to transfer to 10 degrees C blocked the accumulation of fatty acids including myristic acid. A single application of 2 microg precocene II/aphid or two applications of 0.5 microg precocene II/ aphid administered on consecutive days resulted in aphids moved to 10 degrees C maintaining the same fatty acid profile as aphids maintained at 25 degrees C. Aphids that were treated with precocene II and maintained at 25 degrees C did not show changes in fatty acid profiles. Rearing aphids at 10 degrees C resulted in lower rates of reproduction and lower total numbers of progeny with longer longevity. Treatment with precocene II significantly decreased the total number of progeny produced at both temperatures. Precocene II did not reduce life span of aphids reared at 25 degrees C, however, the life span of treated aphids reared at 10 degrees C was decreased. The mechanism by which precocene II prevents the accumulation of myristic acid in aphids reared at 10 degrees C remains to be determined.     

Precocene II,a Trichothecene Production Inhibitor,Binds to Voltage-Dependent Anion Channel and Increases the Superoxide Level in Mitochondria of Fusarium graminearum

Precocene II, a constituent of essential oils, shows antijuvenile hormone activity in insects and inhibits trichothecene production in fungi. We investigated the molecular mechanism by which precocene II inhibits trichothecene production in Fusarium graminearum, the main causal agent of Fusarium head blight and trichothecene contamination in grains. Voltage-dependent anion channel (VDAC), a mitochondrial outer membrane protein, was identified as the precocene II-binding protein by an affinity magnetic bead method. Precocene II increased the superoxide level in mitochondria as well as the amount of oxidized mitochondrial proteins. Ascorbic acid, glutathione, and α-tocopherol promoted trichothecene production by the fungus. These antioxidants compensated for the inhibitory activity of precocene II on trichothecene production. These results suggest that the binding of precocene II to VDAC may cause high superoxide levels in mitochondria, which leads to stopping of trichothecene production.     

Precocene is not a specific antigonadotropic agent in adult female Aedes aegypti

ABSTRACT. In the mosquito, Aedes aegypti , other workers have shown that prior to blood-feeding a pre-vitellogenic period ensues manifested by the growth and differentiation of ovarian follicles. This results in resting stage follicles which will then complete ovarian development after the blood-meal. Allatectomy of newly emerged females prevents follicles from reaching their resting stage and such follicles do not undergo subsequent vitellogenesis after blood-feeding. Precocene II, a plant substance which effectively prevents ovarian development in Oncopeltus fasciatus by causing the irreversible degeneration of the corpus allatum, was applied to newly emerged mosquitoes, and at various times after blood-feeding. Sublethal doses of precocene applied 1 h after adult emergence had no effect on pre-vitellogenic follicular development and did not prevent yolk deposition after the blood-meal. Precocene applied after blood-feeding had two major effects. When administered early, it inhibited trypsin synthesis and retarded ovarian maturation. Animals exposed to it later, exhibited abnormal oviposition. It is proposed that precocene II does not act as an antigonadotropic agent in adult Aedes aegypti , but that it does induce a general toxic state in treated animals.     

Effects of juvenile hormone and precocene II on the metabolic rate of the digestive system, fat body and ovaries of the insect Oncopeltus fasciatus

The metabolic rate of midgut, fat body and ovaries from Oncopeltus fasciatus adult female has been studied, comparing the results with that from juvenile hormone or precocene II treated insects. Neither juvenile hormone nor precocene II had any effect on midgut and fat body. Precocene II treatment increased the oxygen consumption rate of ovaries, which in turn remained undeveloped. Juvenile hormone had no detectable effects on the metabolic rate of ovaries, other than accelerate their development.     

Precocenes as pro-allatocidins in adult female Diploptera punctata: A functional and ultrastructural study

Adult mated females of the viviparous cockroach Diploptera punctata are moderately sensitive to precocenes. Oöcyte growth is inhibited and oviposition is delayed in insects topically treated with precocene II or precocene III. C₁₆ juvenile hormone release by corpora allata of precocene-treated insects is markedly inhibited when compared to corpora allata of acetone-treated controls. Electron microscopy of the corpora allata reveals that precocene treatment results in a disorganisation of the intracellular organelles. Topically applied precocene II reaches a high concentration in the haemolymph (0.5 mM 2 hr after topical application of 250 μg). C₁₆ juvenile hormone release by isolated corpora allata is inhibited by precocenes in vitro; half-maximal inhibition over a 3 hr period is obtained at 0.4 mM precocene II. In vitro inhibition of corpora allata by precocene II concentrations higher than 1 mM rapidly destroys the glands as evidenced by electron microscopy (total disintegration of cellular organelles) and by the virtual cessation of C₁₆ juvenile hormone synthesis by the corpora allata. Inhibition of C₁₆ juvenile hormone release by precocene is time-dependent and is not reversible over the short-term incubation in vitro. This inhibition does not appear to be related to the spontaneous activity of the glands in vitro, and it can be reduced by two epoxidase inhibitors. Precocenes are pro-allatocidins in this species: they are bioactivated within the corpora allata to cytotoxic epoxides.     

Precocious metamorphosis of the aphid Myzus persicae induced by the precocene analogue 6-methoxy-7-ethoxy-2,2-dimethylchromene

For up to three days after being treated with the precocene analogue 6-methoxy-7-ethoxy-2,2-dimethylchromene, adult green peach aphids (Myzus persicae) gave birth to offspring (alate and apterous virginoparae, males) which underwent precocious metamorphosis. Only a few precocious gynoparae and no precocious oviparae were recorded. The precocious aphids became adultoid in the third or fourth-instar as a result of corpus allatum destruction. They were able to develop mature embryos, but could not deposit them because of incomplete differentiation of the reproductive tract. The treatment did not induce the production of alate virginoparae in the experimental clone of Myzus persicae. However, a few males were born late in the reproductive sequence of treated apterae. The corpora allata of the treated adults appeared on histological examination to be unaffected by precocene.