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Mode of Action of a Specific Insecticidal Protein from Bacillus thuringiensis
Sakai,Hiroshi 한국생명과학회 2000 한국생명과학회 학술발표회 Vol.29 No.-
Bacillus thuringiensis (Bt) is a gram-positive soil bacterium that produces, during sporulation, crystalline inclusions consisting of highly specific insecticidal proteins called insecticidal crystal protein (ICP), δ-endotoxin or Cry protein, which are toxic to the larvae of lepidopteran, dipteran, and coleopteran insects. An outline of the action of ICPS is as follows. The ICPS are ingested by susceptible insect larvas and dissolved in the midgut under generally alkaline and reducing conditions. The solubilized ICPS are processed by gut processes into the active forms, which bind to the surface of midgut epithelial cells and form a leakage channel in the cel membrane. Colloid-osmotic swelling and lysis of the cell result in death of the larvae. Thus, B. thuringiensis has been used, as bioinsecticides, in agriculture, forest management and mosquito control. B. thuringiensis produces different ICPS among subspecies. B. thuringiensis subsp. israelensis produces dipteran-specific ICPS, CryfA, Cry4B and Cry11A, and non-specifically cytotoxic Cyt1A. A 130--kDa protoxin of Cry4A, a dipteran-specific ICP, was processed into 20- and 45-kDa fragments through a 60-kDa intermediate by the midgut proteases of larvae of mosquito Culex pipiens both in vitro and in vivo. Neither the 20-kDa nor the 40-kDa fragment was toxic against C. pipiens larvae but the significant toxicity was observed when both the fragments coexisted. The two fragments are associated with each other. Thus, it is demonstrated that the complex consisting of the 20- and 45-kDa fragments is an active form of Cry4A. Some ICPS including Cry4A bind to the surface of epithelial cells of the larval midguts of mosquito and silkworm. They also bind brush border membrane vesicle (BBMV) from the larval midguts. However, their insecticidal specificities are not necessarily interpretable based on their characteristics in the initial binding step mentioned above. Another binding state should be involved in determining the insecticidal specificities of the ICPs. Production of ICP in B. thuringiensis cells is regulated promarily at the transcriptional level. The transcriptional regulation of the cry4A gene is somewhat more complicated than other cry genes. It is strongly suggested that the cry4A transcription is under the control of three types of δ factors.
E . coli cryptic miniplasmid p 15A 에서 유래하는 플라스미드 pACYC 184 의 ssi 시그날에 관한 연구
박정동,Sakai Hiroshi,Tohru Komano ( Jeong Dong Bahk,Hiroshi Sakai,Tohru Komano ) 생화학분자생물학회 1990 BMB Reports Vol.23 No.1
Single-strand DNA initiation (ssi) signals are DNA requirements for initiation of DNA synthesis on the single-strand DNA templates. For primary screening of ssi signal function, we used plaque morphology method. Plasmid pACYCl84 derived from E. coli minicryptic plasmid p15A had only one ssi signal which consists of 119-nt stretch. This segment played critical roles in ss DNA phage growth activity and performed primase-dependent replication instead of RNA polymerase-dependent one. Three kinds of energetically stable stem and loop structures were expected. Especially, the orientation and location of this 119-nt stretch, when compared with those of the origin of p15A, favor that this ssi signal might be taken part in the lagging strand replication of plasmid pACYCl84.
Conclusions and Suggestions on Low-Dose and Low-Dose Rate Radiation Risk Estimation Methodology
Sakai, Kazuo,Yamada, Yutaka,Yoshida, Kazuo,Yoshinaga, Shinji,Sato, Kaoru,Ogata, Hiromitsu,Iwasaki, Toshiyasu,Kudo, Shin'ichi,Asada, Yasuki,Kawaguchi, Isao,Haeno, Hiroshi,Sasaki, Michiya The Korean Association for Radiation Protection 2021 방사선방어학회지 Vol.46 No.1
Background: For radiological protection and control, the International Commission on Radiological Protection (ICRP) provides the nominal risk coefficients related to radiation exposure, which can be extrapolated using the excess relative risk and excess absolute risk obtained from the Life Span Study of atomic bomb survivors in Hiroshima and Nagasaki with the dose and dose-rate effectiveness factor (DDREF). Materials and Methods: Since it is impossible to directly estimate the radiation risk at doses less than approximately 100 mSv only from epidemiological knowledge and data, support from radiation biology is absolutely imperative, and thus, several national and international bodies have advocated the importance of bridging knowledge between biology and epidemiology. Because of the accident at the Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi Nuclear Power Station in 2011, the exposure of the public to radiation has become a major concern and it was considered that the estimation of radiation risk should be more realistic to cope with the prevailing radiation exposure situation. Results and Discussion: To discuss the issues from wide aspects related to radiological protection, and to realize bridging knowledge between biology and epidemiology, we have established a research group to develop low-dose and low-dose-rate radiation risk estimation methodology, with the permission of the Japan Health Physics Society. Conclusion: The aim of the research group was to clarify the current situation and issues related to the risk estimation of low-dose and low-dose-rate radiation exposure from the viewpoints of different research fields, such as epidemiology, biology, modeling, and dosimetry, to identify a future strategy and roadmap to elucidate a more realistic estimation of risk against low-dose and low-dose-rate radiation exposure.
E . coli cryptic miniplasmid p 15A 에서 유래하는 플라스미드 pACYC 184 의 ssi 시그날에 관한 연구
박정동,Sakai, Hiroshi,Komano, Tohru 생화학분자생물학회 1993 BMB Reports Vol.17 No.3
Single-strand DNA initiation (ssi) signals are DNA requirements for initiation of DNA synthesis on the single-strand DNA templates. For primary screening of ssi signal function, we used plaque morphology method. Plasmid pACYCl84 derived from E. coli minicryptic plasmid p15A had only one ssi signal which consists of 119-nt stretch. This segment played critical roles in ss DNA phage growth activity and performed primase-dependent replication instead of RNA polymerase-dependent one. Three kinds of energetically stable stem and loop structures were expected. Especially, the orientation and location of this 119-nt stretch, when compared with those of the origin of p15A, favor that this ssi signal might be taken part in the lagging strand replication of plasmid pACYCl84.
Ohta, Eisuke,Kobayashi, Hitoshi,Sakai, Atsushi,Matsui, Yasunori,Sato, Hiroyasu,Ikeda, Hiroshi Korean Society of Photoscience 2015 Rapid communication in photoscience Vol.4 No.2
Fluorescence (FL) properties of a novel donor-acceptor dyad, comprised of mesitylene and 1,4-dicyano-2-methylnaphthalene (DCMN) subunits connected by an ether linkage, were elucidated. The dyad in cyclohexane exhibits FL arising from an intramolecular exciplex. In the crystalline state, the dyad does not emit light from intra- and inter-molecular exciplexes but rather displays FL that is nearly equivalent to that of 2-methoxymethyl-substituted DCMN. However, the emission spectrum of the crystalline dyad contains a shoulder in the long wavelength region, suggesting that weak intercolumnar charge-transfer interactions take place between columns consisting of the mesitylene and DCMN subunits.
( Takashi Nonaka ),( Yusuke Sekino ),( Hiroshi Iida ),( Eiji Yamada ),( Hidenori Ohkubo ),( Eiji Sakai ),( Takuma Higurashi ),( Kunihiro Hosono ),( Hiroki Endo ),( Tomoko Koide ),( Hirokazu Takahashi 대한소화기기능성질환·운동학회 2013 Journal of Neurogastroenterology and Motility (JNM Vol.19 No.2
The gastrointestinal motility effects of endogenous incretin hormones enhanced by dipeptidyl peptidase-IV (DPP-IV) inhibitors have not yet been sufficiently investigated. The aim of this study was to determine whether single pre-prandial sitagliptin, the DPP-IV inhibitor, administration might have an effect on the rate of liquid gastric emptying using the 13C-acetic acid breath test. Methods Ten healthy male volunteers participated in this randomized, two-way crossover study. The subjects fasted for overnight and were randomly assigned to receive 50 mg sitagliptin 2 hours before ingestion of the liquid test meal (200 kcal per 200 mL, containing 100 mg 13C-acetate) or the test meal alone. Under both conditions, breath samples were collected for 150 minutes following the meal. Liquid gastric emptying was estimated by the values of the following parameters: the time required for 50% emptying of the labeled meal (T1/2), the analog to the scintigraphy lag time for 10% emptying of the labeled meal (Tlag), the gastric emptying coefficient and the regression-estimated constants (β and k), calculated by using the 13CO2 breath excretion curve using the conventional formulae. The parameters between the 2 test conditions were compared statistically. Results No significant differences in the calculated parameters, including T1/2, Tlag, gastric emptying coefficient or β and k, were observed between the 2 test conditions. Conclusions The present study revealed that single-dose sitagliptin intake had no significant influence on the rate of liquid gastric emptying in asymptomatic volunteers.
Atmospheric Polycyclic and Nitropolycyclic Aromatic Hydrocarbons in an Iron-manufacturing City
Kazuichi Hayakawa,Ning Tang,Hiroshi Morisaki,Akira Toriba,Tomoko Akutagawa,Shigekatsu Sakai 한국대기환경학회 2016 Asian Journal of Atmospheric Environment (AJAE) Vol.10 No.2
Total suspended particulates (TSP) in the atmosphere were collected for 2 weeks during winter in Muroran, Hokkaido, Japan, a typical iron-manufacturing city. The concentrations of polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) in TSP were determined by high-performance liquid chromatography (HPLC) using fluorescence and chemiluminescence detectors, respectively. No relationship was observed between the atmospheric PAH and NPAH concentration, or the atmospheric PAH and TSP concentration. However, there was a tendency that the atmospheric PAH concentration was higher when the wind blew from the coke-oven plant. Furthermore, the concentration ratios of 1-nitropyrene to pyrene, which is a suitable indicator of the contribution made by automobiles and coal combustion systems to urban air particulates, were smaller in Muroran and the values were close to those observed in particulates from coal combustion systems. Therefore, these results show that the PAH and NPAH compositions for Muroran are characteristic of an iron-manufacturing city.