Si-Kab Nho

β-Secretase (BACE1) inhibitors from Sanguisorbae Radix

In the course of screening anti-dementia agents from natural products, two β-secretase (BACE1) inhibitors were isolated from the ethyl acetate soluble fraction of Sanguisorbae Radix by the activity-guided purification using silica gel, Sephadex LH-20, and RP-HPLC. They were identified as 1,2,3-trigalloyl-4,6-hexahydroxydiphenoyl-β-d-glucopyranoside (Tellimagrandin II,1) and 1,2,3,4,6-pentagalloyl-β-d-glucopyranoside (2) and were shown to non-competitively inhibit β-secretase (BACE1) with the IC50 values of 3.10×10−6 M and 3.76×10−6 M, respectively. TheKi values of1 and2 were 6.84×10−6 M and 5.13×10−6 M. They were less inhibitory to α-secretase (TACE) and other serine proteases such as chymotrypsin, trypsin, and elastase, suggesting that they were relatively specific inhibitors of BACE1.

Gene Expression Profiling in the Silkworm, Bombyx mori, During Early Embryonic Development

Abstract We prepared a cDNA library for a microarray from eggs of the silkworm, Bombyx mori, at the germ-band formation (24 hours after fertilization) stage. Using a microarray constructed with 2,445 ESTs, we screened gene expression profiles during germ-band formation at six specific time points in the early embryonic stages (from the unfertilized egg to the formation of abdominal leg appendages), and determined 241 of these cDNAs to represent genes that were expressed differentially during the germ-band formation stage. These differentially expressed genes grouped into two clusters. In the early and late clusters, 203 and 38 genes were upregulated, respectively. In the upregulated clusters, we isolated several genes that were associated with development and cell communication, including egalitarian, RAD23b, innexin 2, and senescence-associated protein. Northern blot hybridization revealed that the expression patterns of 14 genes had changed in each of the stages. In this study, we assessed changes in the levels of gene expression in relation to the germ-band formation stages in whole Bombyx embryos.

Endoplasmic reticulum stress response of Bombyx mori calreticulin.

We isolated a calreticulin cDNA from the silkworm, Bombyx mori. The cDNA encodes 398 amino acid residues of B. mori calreticulin, with an endoplasmic reticulum retentional HDEL motif at its C-terminus and a predicted molecular mass of 45,801 Da. The B. mori calreticulin shows high protein homology with calreticulin from G. mellonella (88%), A. aegypti (71%), D. melanogaster (69%) and H. sapiens (63%). The highest level of mRNA expression of B. mori calreticulin was exhibited in the fat body of this insect. Although expression of B. mori calreticulin was affected by disturbances in intracellular calcium levels, other ER stress conditions such as inhibition of intracellular protein transport, reduction of disulfide formation, glycosylation inhibition, heat shock and oxidative stress did not disrupt induction of B. mori calreticulin.

Behavioral Attraction of Two Parasitoids, Venturia canescens and Bracon hebetor, to Silk Extracts of a Host Plodia interpunctella

Abstract Kairomonal activities of silk extracts of host Plodia interpunctella were determined by measuring the rates of behavioral responses of two parasitic wasps, Venturia canescens and Bracon hebetor. Silk of P. interpunctella larvae attracted both parasitic wasps but the cocoon silk of silkworm, Bombyx mori and the web silk of two-spotted spider mite, Tetranychus urticae did not. Silk components of P. interpunctella were extracted by using either hexane or methanol, and tested the rates of three serial responses of wasps; host location, antennal drumming and ovipositor probing behaviors. The patterns of each behavioral response were similar in two wasps. The rates of each response were increased at the higher concentrations of both extracts. Antennal drumming behavior was much more responsive to lower concentrations of both extracts than ovipositor probing behavior was. Furthermore, the rate of antennal drumming response was higher in hexane-extracts rather than methanol-extract in both wasps; V. canescens and B. hebetor for 20 and 17 times, respectively. However, ovipositor probing response was similar in two different extracts. Both extracts elicited 100% of antennal drumming response but ovipositor probing response was only 60 to 80% of all tested individuals. Our results were shown that silk extracts of host larvae elicited strong behavioral responses of two parasitic wasps and could be applied for practical application of parasitoids attraction in the biological control of agricultural pests.

Host Selection Behaviors and Progeny Suitability of Two Parasitic Wasps, Venturia canescens and Bracon hebetor, against Abnormal Host Conditions of Plodia interpunctella

Abstract Abilities of host search, oviposition and progeny development of both endoparasitoid, Venturia canescens , and ectoparasitoid, Bracon hebetor , were compared from four different abnormal host conditions of Plodia interpunctella. Wasps were allowed to parasitize normal, granulovirus-infected, frozen, tebufenozide-treated or multi-parasitized host larvae. Both wasps delayed at various times to locate most hosts that conditioned abnormally. The rates of antennal drumming and ovipositor probing of both wasps were reduced in frozen and multi-parasitized hosts. Particularly, V. canescens strongly avoided these behaviors in a host that previously parasitized by B. hebetor. Oviposition of V. canescens was completely absent in frozen and multi-parasitized hosts but suppressed in a tebufenozide-treated host. B. hebetor suppressed its oviposition only in a frozen host. In addition, the progeny development of both wasps was greatly reduced or absent in most abnormal conditions. However, B. hebetor successfully developed in a host that previously parasitized by V. canescens. Our results in overall indicate that each parasitic behaviors and progeny development are greatly dependent on different host conditions and provides a basis for studies on the mechanism underlying host-parasitoid interactions.