摘要:

AbstractJuvenile hormones play a crucial role in development, metamorphosis, and reproduction of insects. This mini‐review discusses the nature of the juvenile hormones identified in insects and their changes in concentration in the hemolymph during development and reproduction. The hemolymph titer is largely determined by the rate at which juvenile hormones are synthesized and released by the corpora allata, but other factors are also involved in titer regulation, such as the affinity and concentration of juvenile hormone binding proteins in the hemolymph and the rate of juvenile hormone degradation in hemolymph and tissues. Juvenile hormone specific esterases occur in hemolymph and tissues, whereas epoxide hydrolases, which may degrade the hormone, are exclusively tissue bound. The activities of these degradative enzymes and the concentration of binding proteins change during the insect life cycle and these changes are related to fluctuations in hormone titer. However, we are still a long way from understanding the subtle interactions between these components in regulation of juvenile hormone titers. In particular, our knowledge is hampered by lack of information about the types, concentrations, and affinities of intracellular juvenile hormone receptors. © 1996 Wiley‐Liss,

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)33:1<1::AID-ARCH1>3.0.CO;2-2

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

年代:1996

数据来源: WILEY

摘要:

AbstractCuticular phenoloxidase (Tyrosinase) in the larval stage of the coconut pestOryctes rhinoceroshas been extracted in the stable proform using cane sugar saline/borate buffer. The extracted prophenol oxidase can be activated by the addition of proteolytic enzymes such as trypsin, chymotrypsin, thermolysin, and subtilisin. Detergents such as SDS and Tween‐80 also activated the enzyme. Electrophoretical analysis revealed dissociation of the enzyme into two molecular forms after its activation by proteolytic enzymes. The functional significance of the enzyme is suggested to involve the generation of quinone compounds in the wound healing process: most phenoloxidase inhibitors prevented melanization when applied topically to surgical wounds. © 1996 Wiley‐Liss,

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)33:1<27::AID-ARCH2>3.0.CO;2-U

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe cytosolic free calcium was measured with Fura‐2 in single prothoracic gland cells ofGallerialarvae. During the last two larval instars calcium concentration correlated with ecdysone secretion by the glands. Addition of prothoracicotropic hormone (PTTH) from brains ofGallerialarvae to prothoracic glands in vitro induced a significant increase in calcium in the gland cells. This effect of PTTH was abolished by removal of extracellular calcium, or by the addition of lanthanum or of the calcium channel antagonists nicardipine and verapamil. The calcium channel agonist Bay K 8644 evoked an increase in intracellular calcium. TMB‐8, an inhibitor of intracellular calcium mobilization, did not block the PTTH‐stimulated rise in calcium concentration or ecdysone production, indicating that intracellular calcium stores are not involved in the calcium‐mediated ecdysone synthesis. Moreover, PTTH seems to exert its action by influencing dihydropyridine‐sensitive calcium channels in the plasma membrane. © 1996 Wiley

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)33:1<39::AID-ARCH3>3.0.CO;2-S

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe density of lipophorin was determined in individualManduca sextaduring development from the second day of the fifth larval instar to the second day of the pupal stage. Lipophorin formed defined bands when subjected to density gradient ultracentrifugation. All lipophorin observed was high density lipophorin; however, the densities varied from 1.100 to 1.184 g/ml, and 40% of the animals had more than one density form of lipophorin. The lipophorins were divided into five density classes: class 1 from 1.100 to 1.113 g/ml, class 2 from 1.114 to 1.132 g/ml, class 3 from 1.133 to 1.145 g/ml, class 4 from 1.146 to 1.162 g/ml, and class 5 from 1.163 to 1.184 g/ml. In feeding larvae, classes 2 and 3 were the most abundant. Larvae of the first day of wandering had either lipophorin in class 2 or in classes 2 and 5. Later during wandering the variation increased, but on the third day most of the lipophorin was in class 2. In first day pupae, only lipophorins of classes 4 and 5 were detected, while on the second day of the pupal stage, classes 2 and 3 were predominant.Class 1 lipophorin was abundant in larvae injected withManducaadipokinetic hormone (M‐AKH), and rare in young feeding larvae. In no other stage was class 1 lipophorin observed. Our results show that the density of lipophorin is much more variable than previously reported which makes it difficult to ascribe any lipophorin density to a developmental stage. These results also show that adipokinetic hormone decreases the density of lipophorin in larvae. © 1996 Wiley‐Liss,

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)33:1<53::AID-ARCH4>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:

AbstractOn the hypothesis that prostaglandins and other eicosanoids mediate nodulation responses to bacterial infections in insects, we describe an intracellular phospholipase A2(PLA2) in homogenates prepared from hemocytes collected from the tobacco hornworm,Manduca sexta. PLA2hydrolyzes fatty acids from thesn‐2 position of phospholipids. Some PLA2s are thought to be the first and rate‐limiting step in biosynthesis of prostaglandins and other eicosanoids. The hemocyte PLA2activity was sensitive to hemocyte homogenate protein concentration (up to 250 μg protein/reaction), pH (optimal activity at pH 8.0), and the presence of a Ca2+chelator. Like PLA2s from mammalian sources, the hemocyte PLA2was inhibited by the phospholipid analog oleyoxyethyl phosphorylcholine. Whereas most intracellular PLA2s require Ca2+for catalytic activity, some PLA2s, including the hemocyte enzyme, are Ca2+‐independent. The hemocyte PLA2exhibited a preference for arachidonyl‐associated substrate over palmitoyl‐associated substrate. These findings show thatM. sextahemocytes express a PLA2that shows a marked preference for hydrolyzing arachidonic acid from phospholipids. The biological significance of this enzyme relates to cellular immune responses to bacterial infections. The hemocyte PLA2may be the first biochemical step in synthesis of the eicosanoids that mediate cellular immunity in insects. © 1996 Wile

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)33:1<63::AID-ARCH5>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:

AbstractChromatographic conditions are reported for the efficient separation of fatty acyl precursors ofSpodoptera littoralissex pheromone by reversed‐phase high‐performance liquid chromatography. The procedure was optimized with a mixture of phenacyl derivative standards, using an octadecylsilane column, mixtures of acetonitrile‐water, methanol‐water, and methanol‐isopropanol‐water as mobile phases, and temperature control. This optimized method allowed the satisfactory separation of phenacyl esters obtained directly fromS. littoralissex pheromone gland extracts. © 1996 Wil

ISSN:0739-4462    

DOI:10.1002/(SICI)1520-6327(1996)33:1<75::AID-ARCH6>3.0.CO;2-W

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)33:1<82::AID-ARCH940330102>3.0.CO;2-9

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)33:1<::AID-ARCH940330101>3.0.CO;2-1

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

年代:1996

数据来源: WILEY