Insecticidal activities of methyleugenol and β-asarone,from the herbal medicines Saishin and Sekishōkon,and other alkoxy-propenyl-benzene derivatives against the cigarette beetle <Emphasis Type="Italic">Lasioderma serricorne</Emphasis> (Coleoptera: Anobiidae)

The principal insecticidal compounds from the herbal medicines Saishin, the root of Asarum sieboldii Miquel, and Sekishōkon, the rhizome of Acorus gramineus Soland, were isolated by successive silica gel column chromatography and high performance liquid chromatography. The active components, which work against larvae of the cigarette beetle, Lasioderma serricorne (F.), were identified as methyleugenol (4-allyl-1,2-dimethoxybenzene) and β-asarone {1,2,4-trimethoxy-5-[(Z)-prop-1-enyl]benzene} by gas chromatography and gas chromatography/mass spectrometry analyses. These two compounds share some structural features, such as a benzene ring with o-dimethoxy groups and a propenyl group in the opposite position. Consequently, the insecticidal activities of 20 structurally related compounds were tested to evaluate their structure–activity relationship. We found myristicin (5-allyl-1-methoxy-2,3-methylenedioxybenzene) exhibited comparable insecticidal activity to methyleugenol and β-asarone, but the other tested compounds were less active. The lack of insecticidal activity of compounds with a hydrogen, hydroxy, or acetoxy substituent in place of one methoxy group indicates that o-dimethoxy groups are essential for insecticidal activity. The position and configuration of a double bond in the propenyl side chain affected the toxicity, but there was a lack of consistency in the structure–activity relationship for this.     

Onset of amnesia is delayed with a decrease in inhibition of protein synthesis during odor-taste associative learning in the terrestrial slug Limax valentianus

Slugs can retain odor-taste associative memory for several weeks, and this requires protein synthesis. We examined the dose-dependency of the onset time of amnesia caused by the protein synthesis inhibitor anisomycin, and showed that with reduced dose, the onset is shifted from 2 days to 3 days after conditioning; we could not shift the onset delay later than 3 days. Our results suggest that the mechanism underling memory retention is different in the period up to 3 days, versus the period later than 3 days. Our results also suggest that sustained inhibition of protein synthesis in the period from zero to 3 hr after conditioning is necessary to cause amnesia.     

Identification of the gravitropism-related rice gene LAZY1 and elucidation of LAZY1-dependent and -independent gravity signaling pathways

We identified the gene responsible for three allelic lazy1 mutations of Japonica rice (Oryza sativa L.) by map-based cloning, complementation and RNA interference. Sequence analysis and database searches indicated that the wild-type gene (LAZY1) encodes a novel and unique protein (LAZY1) and that rice has no homologous gene. Two lazy1 mutants were LAZY1 null. Confirming and advancing the previously reported results on lazy1 mutants, we found the following. (i) Gravitropism is impaired, but only partially, in lazy1 coleoptiles. (ii) Circumnutation, observed in dark-grown coleoptiles, is totally absent from lazy1 coleoptiles. (iii) Primary roots of lazy1 mutants show normal gravitropism and circumnutation. (iv) LAZY1 is expressed in a tissue-specific manner in gravity-sensitive shoot tissues (i.e. coleoptiles, leaf sheath pulvini and lamina joints) and is little expressed in roots. (v) The gravitropic response of lazy1 coleoptiles is kinetically separable from that absent from lazy1 coleoptiles. (vi) Gravity-induced lateral translocation of auxin, found in wild-type coleoptiles, does not occur in lazy1 coleoptiles. Based on the genetic and physiological evidence obtained, it is concluded that LAZY1 is specifically involved in shoot gravitropism and that LAZY1-dependent and -independent signaling pathways occur in coleoptiles. It is further concluded that, in coleoptiles, only the LAZY1-dependent gravity signaling involves asymmetric distribution of auxin between the two lateral halves and is required for circumnutation.     

小鼠生精细胞染色质与染色体构筑的扫描电镜研究（简报）

It remains unclear about the intermediate construction of chromosome due to its highly compact nature and the limitation in methods. The present study was designed to investigate the construction of chromatin and mitotic chromosome in situ with scanning electron microscopy. Mouse testes were selected as the material, because of in which the spermatogenic cells divide actively and successively to form the sperm. Such a feature would be able to study the structure of mammalian chromatin and chromosomes along with the change of nuclear cycle. The animal were perfused with 200 ml of 0.075 mol/L KCl hypotonic solution to remove blood and placed for 15-20 min on ice followed by 0.5% glutaraldehyde and 0.5% formaldehyde for fixing. Through treated by the routine process of fractured and freeze dried with t-butyl alcohol, the specimens were then coated with a 3 nm thick platinum and observed with Hitachi S-430 scanning electron microscopy. It was found that the hypotonic treatment with 0.075 mol/L KCl solution was suit for demonstrating the nuclear structure, when the organelles were well preserved. The chromatin fibers of 10-30 nm and 80-125 nm in diameter could be recognized in the interphase nuclei, which were arranged losely at the region of euchromatin, and folded with each other into chromatin masses at the region of heterochromatin, while the chromatin fibers with the diameter of 80-125 nm often could be viewed on the mitotic chromosomes. Since its presence in interphase nuclei and mitotic chromosomes, it was considered that the chromatin fibers with 80-125 nm in diameter might play a role in the condensation of chromosome, serve as a type of the intermediate structure.     

Stiffness of γ subunit of F1-ATPase

F₁-ATPase is a molecular motor in which the γ subunit rotates inside the α₃β₃ ring upon adenosine triphosphate (ATP) hydrolysis. Recent works on single-molecule manipulation of F₁-ATPase have shown that kinetic parameters such as the on-rate of ATP and the off-rate of adenosine diphosphate (ADP) strongly depend on the rotary angle of the γ subunit (Hirono-Hara et al. 2005; Iko et al. 2009). These findings provide important insight into how individual reaction steps release energy to power F₁ and also have implications regarding ATP synthesis and how reaction steps are reversed upon reverse rotation. An important issue regarding the angular dependence of kinetic parameters is that the angular position of a magnetic bead rotation probe could be larger than the actual position of the γ subunit due to the torsional elasticity of the system. In the present study, we assessed the stiffness of two different portions of F₁ from thermophilic Bacillus PS3: the internal part of the γ subunit embedded in the α₃β₃ ring, and the complex of the external part of the γ subunit and the α₃β₃ ring (and streptavidin and magnetic bead), by comparing rotational fluctuations before and after crosslinkage between the rotor and stator. The torsional stiffnesses of the internal and remaining parts were determined to be around 223 and 73 pNnm/radian, respectively. Based on these values, it was estimated that the actual angular position of the internal part of the γ subunit is one-fourth of the magnetic bead position upon stalling using an external magnetic field. The estimated elasticity also partially explains the accommodation of the intrinsic step size mismatch between F_o and F₁-ATPase.     

Ribonucleic Acid Polymerase Mutant of Escherichia coli Defective in Flagella Formation

Escherichia coli K-12 mutants that are resistant to bacteriophage chi, defective in motility, and unable to grow at high temperature (42 degrees C) were isolated from among those selected for rifampin resistance at low temperature (30 degrees C) after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Genetic analysis of one such mutant indicated the presence of two mutations that probably affect the beta subunit of ribonucleic acid (RNA) polymerase: one (rif) causing rifampin resistance and the other (Ts-74) conferring resistance to phage chi (and loss of motility) and temperature sensitivity for growth. Observations with an electron microscope revealed that the number of flagella per mutant cell was significantly reduced, suggesting that the Ts-74 mutation somehow affected flagella formation at the permissive temperature. When a mutant culture was transferred from 30 to 42 degrees C, deoxyribonucleic acid synthesis accelerated normally, but RNA or protein synthesis was enhanced relatively little. The rate of synthesis of beta and beta' subunits of RNA polymerase was low even at 30 degrees C and was further reduced at 42 degrees C, in contrast to the parental wild-type strain. Expression of the lactose and other sugar fermentation operons, as well as lysogenization with phage lambda, occurred normally at 30 degrees C, suggesting that the mutation does not cause general shut-off of gene expression regulated by cyclic adenosine 3',5'-monophosphate.     

In vitro synthesis of phase-specific flagellin of Salmonella

Chromatography of Salmonella flagellin at pH 8 on DEAE-cellulose separated at least four serologically distinct kinds of flagellin, a, enx, i and 1,2, eluting in that order with increasing concentration of sodium chloride. By this chromatographic technique, the preincubated cell-free extract of Escherichia coli given saltprecipitable RNA of Salmonella was shown to synthesize flagellin characteristic of the flagellar antigen type of the cells from which the RNA was derived. Two of the in vitro synthesized flagellins specifically reacted with their corresponding antiserum.When RNA was extracted from the cells of the diphasic strain propagated from a single colony, expressing either phase 1 or phase 2, the in vitro synthesized flagellin was predominantly the same as that produced by the original colony. Translation of messenger RNA specific for phase 1 flagellin was not inhibited by the presence of messenger RNA specific for phase 2. RNA extracted from the cells of a diphasic strain without any selection directed synthesis of both phase 1 and phase 2 flagellins in the ratio expected if the culture was at equilibrium with respect to phase variation. Experimental evidence is presented to support the hypothesis that phase variation is due to the alternative synthesis of phase-specific messenger RNA.