摘要:

AbstractMicrovitellogenin and vitellogenin cDNA fromManduca sexta(tobacco horn‐worm) were tested for use as molecular probes to investigate the expression of genes coding for vitellogenins inSpodoptera frugiperda(fall armyworm) andLymantria dispar(gypsy moth). Cross‐hybridization was not observed between theM. sextacDNAs andS. frugiperdaDNA and mRNA. Vitellogenin cDNA fromM. sextadid not hybridize toL. disparDNA or mRNA. However, the 834 bp microvitellogenin cDNA fromM. sextahybridized to an approximately 850 bp transcript inL. disparmRNA.A 2.5 kb cDNA clone, pz64, was isolated from late last instar larvae of femaleL. disparby differential screening. This clone has 38% amino acid sequence (deduced) and 55% nucleic acid sequence similarities with the 3′‐end of high molecular weight vitellogenin inBombyx mori(silkworm). When used as a probe in northern analysis ofL. disparmRNA, this cDNA hybridized to a 5.3 kb transcript in female last instar larvae, pupae, and adults, but not to male last instar larvae and adults. This cDNA did not hybridize to mRNA fromM. sextaorS. frugiperda.Expression of the 5.3 kb vitellogenin transcript hybridizing to the 2.5 kb cDNA clone was suppressed in 5‐day‐old last instar larvae of femaleL. dispartreated on day 2 with doses of the juvenile hormone analog, methoprene, greater than 10 nmol. Apparently, the high in vivo titer of juvenile hormone during the first 2 days of the last instar represses the transcription of vitellogenin mRNA. © 1996 Wil

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<237::AID-ARCH1>3.0.CO;2-V

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe development of resistance toBacillus thuringiensistoxic proteins is a growing concern because it could threaten both conventional and gene transfer use of this environmentally safe biological insecticide. The most common mechanism of resistance involves changes in binding affinity of toxin receptors in the insect midgut membrane. This has not been the case inHeliothis virescens. We have investigated changes in midgut proteolytic activity as a possibility to explain the resistance observed in this insect species.We have developed an improvement of known methods to demonstrate proteolytic activity in crude extracts. Using this method we have found differences in the proteolytic activity profile of midgut extracts of a susceptible and a resistantH. virescensstrain. We also have studied the in vitro processing of CrylA(b) toxin and protoxin by midgut contents of both strains. SDS‐PAGE of the in vitro degradation products showed differences between the strains. The resistant strain degrades protoxin more slowly and processes the active toxin more quickly than the susceptible strain. © 1996 Wiley‐Liss,

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<257::AID-ARCH2>3.0.CO;2-V

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractA female specific protein was isolated from eggs and female hemolymph of cochineal insects, using density gradient ultracentrifugation, ammonium sulfate precipitation, and size exclusion column chromatography. The protein was found to consist of four different subunits with apparent molecular weights (Mr) 45,000, 49,000, 53,000, and 56,000, respectively. All four subunits were found to be glycosylated; no association of lipids was detected. Size exclusion column chromatography and non‐denaturing polyacrylamide gel electrophoresis demonstrated that the native yolk protein exists as large polymers. Electron microscopy showed that these molecules are long, helical ribbons of variable size which are found in both hemolymph and eggs. Using cryo‐electron microscopy, it was shown that the ribbons were 14.6 ± 1.5 nm wide; the helix they form has a repeat distance of 104.9 ± 11.3 nm and a diameter of 42.1 ± 5 nm. A clear substructure of the ribbons was recognized.The newly identified protein is the major yolk protein ofDactylopius confususand no other proteins resembling the more familiar vitellins of other insect species were detected. Moreover, theD. confususyolk protein appears to be unique both in its subunit structure and in its polymerizing qualities. Thus, the cochineal yolk protein (CYP) is suggested to represent a new type of insect yolk protein. © 1996 Wiley‐

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<273::AID-ARCH3>3.0.CO;2-Z

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractLipophorin was isolated from homogenized adultDrosophila melanogaster. It is stained by Sudan Black and has a native molecular mass of 640 kD and a density of 1.12 g/ml. It consists of two glycosylated apoproteins of 240 and 75 kDa. Gas chromatography and mass spectrometry showed that lipophorins isolated separately from virgin 3‐day‐old male and female flies were associated with specific hydrocarbons, and that these were the same hydrocarbons found in male and female cuticles, respectively. Moreover, a pool of internal hydrocarbons was demonstrated for the first time, with chain lengths similar to those of the cuticular pool. Studies on the fate of the hydrocarbons synthesized de novo after topical applications of radiolabelled fatty acid precursors showed a decrease of the internal pool of hydrocarbons with time, concomitant with an increase of the cuticular pool. These results suggest that hydrocarbons synthesized at an internal site, possibly in oenocytes, may be transported to the cuticle of the flies by lipophorin. © 1996 Wiley‐Lis

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<289::AID-ARCH4>3.0.CO;2-T

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe larval midgut of the tobacco hornworm,Manduca sexta, has high ecdysone 20‐monooxygenase (E20MO) activity, located both in the mitochondria and in the microsomes. The apparent kinetic parameters for E20MO in mitochondria and microsomes were determined. The Km5(for ecdysone) of the mitochondrial and microsomal enzymes were 1.63 × 10−5and 3.67 × 10−7M, respectively. The Vmaxwas 82.7 pmol/min/mg protein for mitochondria and 32.0 pmol/min/mg protein for microsomes. Although the mitochondrial E20MO has the higher Vmax, at physiological ecdysone concentrations (10−7− 10−8M) it is only one‐eighth to one‐tenth as active as the microsomal enzyme. It is concluded that the microsomal E20MO is the primary, if not the only, enzyme involved in ecdysone 20‐hydroxylation inM. sextamidgut. © 1996 Wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the Un

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<305::AID-ARCH5>3.0.CO;2-W

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractCytochrome P450tpris a xenobiotic metabolizing P450 that is found in house flies (Musca domestica). To better understand the regulation of cytochrome P450tpr, the effects of 21 potential monooxygenase inducers were examined for their ability to induce total cytochromes P450 and cytochrome P450tprlevels in adult flies. Six compounds caused induction of total cytochromes P450 per mg protein in adult susceptible (CS) house flies: ethanol (1.6‐fold), phenobarbital in food (1.5‐fold) or water (1.5‐fold), naphthalene (1.3‐fold), DDT (1.3‐fold), xanthotoxin (1.4‐fold), and α‐pinene (1.2‐fold). Six compounds were found to be inducers of cytochrome P450tpr: piperonyl butoxide in food (1.9‐fold), phenobarbital in food (1.4‐fold) and water (3.4‐fold), clofibrate (1.3‐fold), xanthotoxin (1.3‐fold), methohexital (1.3‐fold), and isosafrole (1.3‐fold). Comparison of our results with house fly P450 6A1 indicates that there are specific inducers for each of these individual P450s as well as compounds that induce both P450s.Total P450s were inducible by PB in CS house fly larvae, but not in LPR larvae. Immunoblotting revealed no detectable P450tprin control or PB‐treated larvae in either strain. Thus, although total P450s are inducible in the susceptible strain larvae, P450tprdoes not appear to be normally present or inducible with PB in larvae of either strain.Northern blots of phenobarbital (in water) treated CS flies indicated that there was a 4.2‐fold increase in the P450tpr(i.e., CYP6D1) mRNA levels over the untreated flies. In the multiresistant LPR strain there was no apparent induction of CYP6D1 mRNA by phenobarbital. Following phenobarbital induction, the level of CYP6D1 mRNA in the CS strain was about half of the level in the

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<313::AID-ARCH6>3.0.CO;2-Y

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe pathway for the synthesis of sn‐1,2‐diacylglycerol stimulated by the action of adipokinetic hormone (AKH) in the insect fat body is unknown. Previous results from this laboratory suggested that the hydrolysis of stored triacylglycerol to sn‐2‐monoacylglycerol followed by the stereospecific acylation of sn‐2‐monoacylglycerol catalyzed by a monoacylglycerol‐acyltransferase (MGAT) could be the major route of AKH‐stimulated sn‐1,2‐diacylglycerol synthesis. Thus, MGAT might represent a key enzyme of this pathway. In this study we characterized the MGAT activity from theManduca sextafat body. The activity, which was assayed by acylation of 2‐monoolein using radioactive labeled palmitoyl‐CoA, was found to be primarily a microsomal enzyme. The products of the acylation of 2‐monoolein were 1,2‐diacylglycerol (40–50%), 1,3‐diacylglycerol (20–30%), and triacylglycerol (30–40%). The presence of triacylglycerol as a product revealed the presence of diacylglycerol‐acyltransferase activity in the fat body microsomes. The pH optimum of MGAT activity was 7.0, and the dependence of the activity on the concentration of 2‐monoolein showed saturation kinetics. An endogenous MGAT activity, which represented 20% of the maximal activity observed with added substrate, was detected. Optimal concentrations of palmitoyl‐CoA ranged between 0.10–0.20 mM. The specific activity of MGAT, measured under optimal conditions, was about 0.6 nmol DG formed/min‐mg protein. MGAT activity was greatest with 2‐monoolein, and lower activity was observed when a saturated 2‐monoacylglycerol was employed. The activity observed with sn‐1‐monoacylglycerol was lower than that observed with sn‐2‐monoacylglycerol. AKH did not stimulate MGAT activity, suggesting that either the enzyme is not under hormonal regulation or the monoacylglycerol pathway is not involved in the AKH‐stimulated production of sn‐1,2

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<325::AID-ARCH7>3.0.CO;2-W

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe increase in the juvenile hormone (JH) III titer in the hemolymph ofLymantria disparlarvae that were parasitized by the endoparasitoid braconid,Glyptapanteles liparidis, during the host's premolt to third instar, coincided with the molt of the parasitoid larvae to the second instar between day 5 and 7 of the fourth host instar. It reached a maximum mean value of 89 pmol/ml on day 7 of the fifth instar while it remained below 1 pmol/ml in unparasitized larvae. Only newly molted fifth instar hosts showed a low JH III titer similar to that of the unparasitized larvae. JH II, which is the predominant JH homologue in unparasitized gypsy moth larvae, also increased relative to controls in the last two samples (days 7 and 9) from parasitized fourth and fifth instars. Compared to unparasitized larvae, a generally reduced activity of JH esterase (JHE) was found in parasitized larvae throughout both larval stages. The reduction in enzyme activity at the beginning and at the end of each instar, when the JHE activity in unparasitized larvae was high, may be in part responsible for the increased JH II and JH III titers in parasitized larvae. Ester hydrolysis was the only pathway of JH metabolism in the hemolymph of unparasitized and parasitized gypsy moth larvae as detected by chromatographic assays. © 1996 Wiley‐Liss, I

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)31:3<337::AID-ARCH8>3.0.CO;2-U

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

ISSN:0739-4462    

DOI:10.1002/1520-6327(1996)31:3<353::AID-ARCH940310302>3.0.CO;2-8

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

ISSN:0739-4462    

DOI:10.1002/1520-6327(1996)31:3<::AID-ARCH940310301>3.0.CO;2-1

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY