摘要:

AbstractThe egg‐larval parasitoidChelonussp. induces the precocious onset of metamorphosis in the 4th (penultimate) stadium of its hostTrichoplusia ni, emerges from the prepupa, and then feeds on it. Qualitative and quantitative changes in ecdysteroids and juvenile hormone were measured. Hemolymph of 3rd‐to 4th‐instar host larvae and the parasitoids they contained, as well as nonparasitized and parasitized eggs, were analyzed. In the host hemolymph a broad peak of ecdysteroids during molting into the 4th stadium and a continuous increase from day 2 (onset of precocious wandering) until day 4 (emergence of parasitoid) were observed; 20‐hydroxyecdysone and 20,26‐dihydroxyecdysone were predominant. The juvenile hormone titer fluctuated in the 3rd and early 4th stadium and fell to undetectable levels shortly before the precocious onset of wandering. The parasitoid's ecdysteroids started to increase on the molt to the 2nd instar ( = early 4th instar of the host) and thereafter fluctuated on a high level, 20‐hydroxyecdysone, 20,26‐dihydroxy‐ecdysone, and ecdysone being predominant. The juvenile hormone titer was high in late 1st‐instar parasitoids, decreased to low levels at ecdysis into the 2nd instar, and increased again to high levels in the 2nd‐instar larvae at the time when their shape changed from flat to cylindrical. After ecdysis to the 3rd instar the juvenile hormone titer fell. A comparison revealed that both ecdysteroids and juvenile hormone fluctuate independently in parasitoid and host at most stages, suggesting that the parasitoid produces its own hormones.The first data on ecdysteroids and juvenile hormones in the egg stage of a parasitoid/host system are reported. At the stage of eye pigmentation parasitized eggs contained more immunoreactive midpolar ecdysteroids than nonparasitized ones. 20‐Hydroxyecdysone and 20,26‐dihydroxyecdysone were the predominant ecdysteroids in both nonparasitized and parasitized eggs, but the latter contained several additional ecdysteroids which were not seen in nonparasitized egges. The titer of juvenile hormone was similar in both. Shortly before hatching the ecdysteroids were low in parasitized and nonparasitized egges, but the content of juvenile hormone was much higher in the former. At this stage the majority of parasitoids have already eclosed and teratocytes are released. The results of HPLC analysis indicated the presence of juvenile hormone lll together with juvenile hormones l and ll in parasitized eggs, but only juvenile hormones l and ll

ISSN:0739-4462    

DOI:10.1002/arch.940140402

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn crude extracts of eggs of the soft tickOrnithodoros moubata, maximum degradation of vitellin is at pH 3–3, 3.5, whereas no proteolysis is detected at neutral or weakly acidic pHs. Acidic proteolysis is maintained at high level throughout embryonic development, and rapidly decreases in the larva, during the high phase of yolk degradation. Proteinase, acid phosphatase, andN‐acetylglucosaminidase are localized within the yolk spheres; these can be considered as lysosomal‐like organelles containing both substrate (vitellin) and the degradative machinery. Proteolytic activity has been essentially attributed to a cathepsin L‐like enzyme through substrate specificity and inhibitors. The molecular weight is 37,000 to 39,000 as shown using gelatin‐containing SDS‐PAGE activity gels. At neutral pH the enzyme binds to vitellin, as demonstrated by gel filtration and PAGE under nondenaturing conditions. Acid proteinase activity at pH 5–6 is undetectable both with proteins and synthetic substrates, but is strongly increased after preincubation at pH 3–4. Activation at low pH could be important in the regulation of y

ISSN:0739-4462    

DOI:10.1002/arch.940140403

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

年代:1990

数据来源: WILEY

摘要:

AbstractCathepsin L–like proteinase found in the eggs of the tickOrnithodoros moubatais latent during embryogenesis, but can be activated by acid treatment. In crude extracts as well as in partially purified fractions, activation requires reducing conditions and is inhibited by leupeptin, which indicates that it is mediated by a thiol proteinase, probably by the cathepsin L itself. Latency disappears in vivo at the time of the acute phase of yolk digestion, which takes place during late embryonic development and larval life. When egg cathepsin L is localized through its gelatinolytic activity on SDS‐PAGE, the activated enzyme migrates as lower Mr bands than the latent form. Disappearance of the higher Mr bands corresponding to the latent form is directly related to appearance of the lower Mr bands characteristic of the active one; transition from one pattern to the other and enzymatic activation are in perfect agreement with regard to kinetics and sensitivity to inhibitors. The same pattern change occurs in vivo, parallel to latency removal and intense yolk degradation. These results strongly suggest that egg cathepsin L is stored in the yolk as a proenzyme which is activated by partial proteolysis at low

ISSN:0739-4462    

DOI:10.1002/arch.940140404

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

年代:1990

数据来源: WILEY

摘要:

AbstractA protocol has been developed for the purification of vitellogenin from the honey bee,Apis mellifera. Purification allows for the first characterization of a vitellogenin from the large order Hymenoptera. Hymenopteran vitellogenins are unusual among insect vitellogenins in that they contain only one type of apoprotein. The honey bee vitellogenin was isolated from hemolymph of honey bee queens by a combination of density gradient ultracentrifugation, ion‐exchange chromatography, and affinity chromatography. The native vitellogenin particle is a very high density glycolipoprotein containing approximately 91% protein, 7% lipid, and 2% carbohydrate. Phospholipid and diacylglycerol are the major lipid components. The equilibrium density (1.28 g/ml) is the same as that forManduca sextavitellogenin, which contains a much higher proportion of lipid. The covalently bound carbohydrate moiety of the particle is high in mannose. The amino acid composition of vitellogenin is similar to those of vitellogenins from other insect species. The N‐terminal amino acid sequence of the apoprotein was determined, the first such sequence for any insect vitellogenin. When analyzed by sodium dodecyl sulfate (SDS)‐gel electrophoresis A.melliferavitellogenin resolved into a single band with an apparent Mrof 180,000. Gel filtration under reducing and native conditions yielded estimated Mrvalues of about 30

ISSN:0739-4462    

DOI:10.1002/arch.940140405

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

年代:1990

数据来源: WILEY

摘要:

AbstractVitellogenic follicles ofHyalophora cecropiawere incubated in metabolically radiolabeled, high‐density lipophorin isolated from pharate adult hemolymph by KBr density gradient centrifugation. The follicles transferred this probe from the incubation medium to the cortical yolk spheres in the oocyte by an energy‐dependent and saturable mechanism. Vitellogenin and high‐density lipophorin competed with each other for uptake, and are therefore concentrated by the follicle with a common mechanism. Microvitellin and lipophorin, in contrast, did not compete for uptake. The Kuptakefor the accumulation of high‐density lipophorin was substantially higher than the value estimated earlier for vitellogenin (133 μM vs. 18 μM). This relationship helps explain why the shared concentrating mechanism does not deplete the lipid transport capacity of the hemolymph, and how a low vitellogenin: lipophorin molar ratio in the hemolymph yields a high ratio in the m

ISSN:0739-4462    

DOI:10.1002/arch.940140406

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

年代:1990

数据来源: WILEY

ISSN:0739-4462    

DOI:10.1002/arch.940140401

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

年代:1990

数据来源: WILEY