摘要:

AbstractIn the eggs of the cockroachBlattella germanica, vitellin (Vt) utilization is initiated 4 days postovulation by the proteolytic processing of its three subunits. These reactions yield a specific set of peptides that are consumed by the developing embryo. A yolk proteinase activity, believed central to this processing event, has been investigated. First expressed at day 3 postovulation, just prior to Vt's processing, its specific activity with synthetic substrates increased four‐fold to 18‐fold through day 6. In addition, a mixing experiment showed that these proteinases(s) can also process Vt's large subunits in vitro. A relationship between Vt processing and proteinase specific activity was also noted with twoB. germanicatranslocation heterozygotes, which displayed differences in the extent of Vt processing. One group of eggs (group A) failed to process any Vt subunit. A second group (B) processed the Mr102,000 subunit but not the Mr95,000. A third group (C) processed their Vt normally. Proteinase specific activities in the yolk of translocant's eggs at day 6 mirrored the extent of processing, being highest in group C eggs and effectively absent from the yolk of group A eggs. Eggs defective in Vt processing also contained arrested embryos. It is concluded that the yolk proteinase activity described here participates in Vt processing at day 4 postovulation. Microscopic examination of yolk obtained from eggs of wild type females showed that, as processing began in vivo (day 4), the yolk granules also underwent an abrupt decrease in size from diameters of 15–30 μm to 3–10 μm. Yolk granules of those translocant's eggs that were defective in Vt processing did not undergo this size decrease, suggesting that granule reorganization and Vt proteolysis may be linked fun

ISSN:0739-4462    

DOI:10.1002/arch.940150302

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

年代:1990

数据来源: WILEY

摘要:

AbstractA chitin‐synthesizing cockroach cell line (UMBGE‐4) previously shown to secrete ecdysteroids was analyzed for its ability to metabolize potential precursors of ecdysone (e.g., 2‐deoxyecdysone, 2,22‐dideoxyecdysone, 2,22,25‐trideoxyecdysone, and cholesterol). All, except cholesterol, were actively metabolized by UMBGE‐4 cells. However, all but 2‐deoxyecdysone were converted to polar and hydrolyzable metabolites, and not to ecdysone. Labeling with cholesterol was unsuccessful. Labeling experiments with molting hormones, i.e., ecdysone and 20‐hydroxyecdysone, confirmed that this cell line can metabolize ecdysteroids and allowed identification of some of the products. Molting hormones were converted into acetate conjugates and polar conjugates which were often double‐conjugates, i.e., polar conjugates of acetate conjugates. Labeling experiments with ecdysone demonstrated that this cell line possesses a low ecdysone 20‐hydroxylase activity. The capacity of UMBGE‐2 cells, which do not synthesize chitin or ecdysteroids, was also examined. Neither ecdysone nor 20‐hydroxyecdysone was significantly metabolized by UMBGE‐2 cells. 2‐Deoxyecdysone and 2,22‐dideoxyecdysone were very slowly metabolized respect

ISSN:0739-4462    

DOI:10.1002/arch.940150303

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

年代:1990

数据来源: WILEY

摘要:

AbstractAminopeptidase activity was partially characterized from midguts ofAnopheles stephensiListon which had been dissected 30 h after blood feeding. In crude midgut homogenate supernatants the aminopeptidases showed optimum activity at pH 8.0 and preferentially hydrolyzed alanine‐ and leucine‐terminal amino acid substrates. Methionine, proline, lysine, and arginine terminal substrates were hydrolysed, but not glutamic acid. Activity was stimulated by Mg2+, EDTA, and low Ca2+concentrations, while Mn2+, Tris, 1,10 phenanthroline, and higher Ca2+concentrations were inhibitory.Supernatants from midguts homogenized in 1% Triton X‐100 showed a twofold increase in activity. Differential centrifugation of midgut homogenates demonstrated 45% of the total activity in a putative microvillar pellet and 32% in a soluble fraction. More than 92% of the total activity was solubilized after homogenization in Triton X‐100.Activity in homogenate supernatants was restricted to one major peak (Mr= 552,000) with a higher molecular weight shoulder. Three distinct peaks of aminopeptidase activity were observed forllowing Triton X‐100 treatment: a minor high molecular weight peak (Mr= 552,000), and two major peaks atMr= 123,000 andMr= 32,000 respectively.The activity of aminopeptidase increased after a blood meal, in parallel to the post‐feeding changes in trypsin activity, indicating its important role in secondary digestion of blood me

ISSN:0739-4462    

DOI:10.1002/arch.940150304

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe phenoloxidase system responsible for the sclerotization of cockroach ootheca is found to be present as an inactive form in the left colleterial gland ofPeriplaneta americana. The supernatant fraction obtained by centrifugation of the milky white secretions contained the inactive phenoloxidase which required both sodium dodecyl sulfate (SDS) and the insolubel sediment for exhibiting enzyme activity. Bovine serum albumin could replace the sediment in the activation process. Proteins separated from the supernatant fraction by molecular sieve chromatography on Sephadex G‐25 did not require either albumin or the sediment, but required SDS for exhibiting the phenoloxidase activity. Among the detergents tested, SDS (anionic) and cetylpyridinium chloride (cationic) activated the phenoloxidase, but CHAPS (zwitterionic) or nonionic detergents failed to activate the enzyme. The activation caused by SDS occurred well below the critical micellar concentration of SDS indicating that SDS is causing the activation by binding to the protein and altering its conformation. Chloroform‐methanol extracts of vestibulum or right gland could replace SDS confirming the presence of endogenous activator(s) of phenoloxidase system. A variety of exogenously added lipids could activate the latent enzyme, among which linoleate, oleate, laurate, linolenate, phosphatidylethanolamine, and phosphatidylglycerol proved to be the effective activators of the latent phenoloxidase.Partially purified phenoloxidase was found to be extremely labile and lost its activity on (a) freezing and thawing, (b) dialysis, and (c) heating for 10 min at 55°C. It exhibited a pH optimum of 7 and was inhibited drastically by phenylthiourea and diethyldithiocarbamate. It readily oxidized a number ofo‐diphenols such as 3,4‐dihydroxybenzylalcohol, 3,4‐dihydroxyphenethyl alcohol, catechol, N‐acetyldopamine, N‐acetylnorepinephrine, dopa, dopamine, etc., but failed to oxidize both 3,4‐dihydroxybenzoic acid and 3,4‐dihydroxybenzaldehyde. It neither converted the typical laccase substrate syringaldazine to its quinone methide product, nor oxidized thep‐diphenols, hydroquinone and methylhydroquinone. Therefore, the enzyme participating in the quinone tanning of cockroach ootheca appears to be a typical o‐diphenol oxidase and not a laccase

ISSN:0739-4462    

DOI:10.1002/arch.940150305

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

年代:1990

数据来源: WILEY

摘要:

AbstractVitellogenesis occurs during the late pharate adult stage in the Indianmeal moth,Plodia interpunctella. Repeated treatment of pharate adult females with doses of 20‐hydroxyecdysone (20HE) from 10 to 250 ng per pupa suppressed oocyte growth and inhibited yolk protein accumulation in the oocytes. Treatment of the pharate adults with a biologically inactive ecdysteroid analogue, 22–isoecdysone, had no effect on egg maturation or yolk protein accumulation. The hormonal action of 20HE was not through the inhibition of the corpora allata or juvenile hormone levels, because treatment with a juvenile hormone analogue did not reverse the inhibition by 20HE treatment. Exposure of early vitellogenic ovaries to 20HE in organ cultures in vitro showed that 20HE had a direct effect on the ovarian synthesis of YP2. At 20HE concentrations below 10 nM, YP2 synthesis was minimal, at 10 nM 20HE YP2 synthesis was maximal, and at concentrations higher than 10 nM YP2 synthesis was suppressed to 35% of the maximal level. Synthesis of most other ovarian proteins remained constant with the changing 20HE concentrations. Ovarian RNA from treated females translated in a reticulocyte lysate demonstrated that the hormonal effect of 20HE on the ovarian tissues was on the specific accumulation of translatable YP2 transcript as well as transcripts for a few other polypeptides. This study shows that 20HE controls the rate of egg development during metamorphosis and that declining titers of 20HE regulate the expression of adult ge

ISSN:0739-4462    

DOI:10.1002/arch.940150306

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.940150301

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

年代:1990

数据来源: WILEY