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Biomedical subjects

Toshiaki Hasegawa

Publications and source records attributed to Toshiaki Hasegawa.

11 recordsLinked to original sources
PubMed2006

Observations of unstained biological specimens using a low-energy, high-resolution STEM.

Low-energy, high-resolution scanning transmission electron microscopy (STEM) is introduced as a convenient method for observing unstained biological specimens. By reducing the electron energy, the cross section for light elements becomes comparable to that of conventional electron microscopy observations. The STEM mode exhibited the advantage that the induced energy loss and charge build-up in the sample affected the image to a lesser extent than in the TEM or SEM mode. Furthermore, the efficiency of an STEM detector is high, and the total radiation damage can be reduced if thermal damage due to localized heating at a slow scan operation can be overcome. We applied this method for observations of biological samples that were in the form of thin slices, fine fibers and small particles. When the supporting film for samples is absent, the resolution and the contrast of STEM images can be maintained similar to SEM and TEM images, respectively.

Animals↗
PubMed2006

Bioactive dibenzylbutyrolactone and dibenzylbutanediol lignans from Peperomia duclouxii.

Six new dibenzylbutyrolactone (6-11) and two new dibenzylbutanediol lignans (12, 13) were obtained from Peperomia duclouxii. The structures were elucidated mainly by the analysis of NMR and MS data. The anticancer activity against a normal (WI-38) and a simian virus 40-transformed human lung fibroblast cell (VA-13) and a hepatoma G2 cell (HepG2) and the MDR reversal activity of the isolated compounds were examined. Compound 7 showed moderate inhibitory activity against VA-13 and HepG2 with IC(50) values of 23.2 and 26.4 microM, respectively. Compound 2 inhibited the growth of HepG2 cells with an IC(50) of 42.8 microM. Compounds 2 and 13 exhibited stronger MDR reversal activity than verapamil, at 25 and 2.5 microg/mL, respectively, and 4, 5, and 7 showed comparable activity with verapamil, at 25, 25, and 2.5 microg/mL, respectively.

Antineoplastic Agents, Phytogenic↗
PubMed2006

Bioactive secolignans from Peperomia dindygulensis.

Thirteen secolignans, including eight new ones (1-8), were isolated from the EtOAc extract of Peperomia dindygulensis. The structures were mainly elucidated by 1D and 2D NMR and MS experiments, the relative configurations were determined by NOE correlations, and the absolute configurations were established by the optical rotations and CD spectra. Cytotoxicity and MDR (multidrug resistance) reversal activity of the isolated compounds were examined. Compounds 6 and 7, peperomins B (10) and E (12), showed moderate to strong growth inhibitory activity against a malignant lung tumor cell (VA-13) with IC(50) values of 15.2, 13.5, 13.9, and 1.93 microM, respectively, and also inhibited the growth of a normal lung fibroblast cell (WI-38) at the same levels. Compound 7 and peperomin E (12) exhibited inhibitory activity against a liver tumor cell (HepG2) with IC(50) values of 22.3 and 12.1 microM. Compounds 5 and 7 and peperomins A, B, C, and E (9-12) enhanced calcein accumulation in MDR 2780 cells at 25 microg/mL. Compounds 2, 3, 7, and peperomin E (12) showed inhibitory activity on induction of the intercellular adhesion molecule-1 (ICAM-1).

Antineoplastic Agents, Phytogenic↗
PubMed2006

Taraxasterane- and ursane-type triterpenes from Nerium oleander and their biological activities.

Two new taraxasterane-type triterpenes, 20beta,28-epoxy-28alpha-methoxytaraxasteran-3beta-ol (1) and 20beta,28-epoxytaraxaster-21-en-3beta-ol (2), were isolated from an ethyl acetate extract of the leaves of Nerium oleander, together with ursane-type triterpenes, 28-nor-urs-12-ene-3beta,17beta-diol (3) and 3beta-hydroxyurs-12-en-28-aldehyde (4). The structures of 1 and 2 were established on the basis of their spectroscopic data. Anti-inflammatory activity of 1-4 was examined on the basis of inhibitory activity against the induction of intercellular adhesion molecule-1 (ICAM-1). Cytotoxic activity of 1-4 was evaluated against four human cell lines, A-549, WI-38, VA-13, and HepG2 cells.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Bioactive guaianolides from siyekucai (Ixeris chinensis).

Two new guaianolides, named chinensiolides D (5) and E (6), were isolated from Ixeris chinensis Nakai, and their structures were determined to be 10alpha-hydroxy-3-oxoguaia-11(13)-eno-12,6alpha-lactone (5) and 10alpha-hydroxy-3beta-O-[2,6-di(p-hydroxyphenylacetyl)-beta-glucopylanosyl]guaia-4(15),11(13)-dieno-12,6alpha-lactone (6). The first isolation of (11S)-10alpha-hydroxy-3-oxoguaia-4-eno-12,6alpha-lactone (4) from natural sources and its characterization are also reported. Chinenciolide E (6) showed significant growth inhibitory activity toward VA-13 malignant lung tumor cells (IC50 = 0.72 microM).

Antineoplastic Agents, Phytogenic↗
PubMed2006

A new taxoid from a callus culture of Taxus cuspidata as an MDR reversal agent.

A new taxoid, 5alpha,13alpha-diacetoxy-10beta-cinnamoyloxy-4(20),11-taxadien-9alpha-ol (1) along with its 9,10-isomer, taxinine NN-11 (2) were isolated from the callus cultures of Taxus cuspidata. The structures were identified by the analyses of the spectral data and chemical method. Their in vitro cytotoxicity against 3 cell lines (HepG2, WI-38 and VA-13) and multidrug resistance (MDR) reversal activity toward 2780AD tumor cells were preliminarily evaluated, the low cytotoxicities and potent MDR reversal activities suggested that they might be good lead compounds of tumor MDR reversal agent.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Asymmetrically modified silica particles: a simple particulate surfactant for stabilization of oil droplets in water.

Spherical silica particles that are able to assemble at a phase boundary of a dual-phase mixture of water and an immiscible organic solvent were prepared by a partial modification of their surface hydroxyl groups with an alkylsilylation agent. Scanning electron microscopic observation of these particles in which their remaining surface hydroxyl groups had been selectively modified with colloidal gold particles revealed that each particle has an asymmetric surface structure: one side of the surface is hydrophilic and the other is hydrophobic. We found that these particles could form a micellar structure in water in the presence of an organic solution of a toluene/polystyrene mixture. The micellar structure was evidenced by formation of golf-ball-like polystyrene particles with dimples imprinting morphologies of the hydrophobic part of modified silica particles.

Journal Article↗
PubMed2005

Three new triterpenes from Nerium oleander and biological activity of the isolated compounds.

New ursane-type triterpene 1, oleanane-type triterpene 2, and dammarane-type triterpene 15 were isolated from the leaves of Nerium oleander together with 12 known triterpenes, 3beta-hydroxy-12-ursen-28-oic acid (ursolic acid, 3), 3beta,27-dihydroxy-12-ursen-28-oic acid (4), 3beta,13beta-dihydroxyurs-11-en-28-oic acid (5), 3beta-hydroxyurs-12-en-28-aldehyde (6), 28-norurs-12-en-3beta-ol (7), urs-12-en-3beta-ol (8), urs-12-ene-3beta,28-diol (9), 3beta-hydroxy-12-oleanen-28-oic acid (oleanolic acid, 10), 3beta,27-dihydroxy-12-oleanen-28-oic acid (11), 3beta-hydroxy-20(29)-lupen-28-oic acid (betulinic acid, 12), 20(29)-lupene-3beta,28-diol (betulin, 13), and (20S,24R)-epoxydammarane-3beta,25-diol (14). On the basis of their spectroscopic data, the structures of the new compounds 1, 2, and 15 were established as 3beta,20alpha-dihydroxyurs-21-en-28-oic acid, 3beta,12alpha-dihydroxyoleanan-28,13beta-olide, and (20S,24S)-epoxydammarane-3beta,25-diol, respectively. The anti-inflammatory activity of the seven isolated compounds and methyl esters of ursolic acid and oleanoic acid in vitro was examined on the basis of inhibitory activity against the induction of the intercellular adhesion molecule-1 (ICAM-1). The anticancer activity of the 14 isolated compounds, including 1, 2, 15, and methyl esters of ursolic acid and oleanolic acid in vitro was examined on the basis of the cell growth inhibitory activities toward three kinds of human cell lines.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2005

Bioactive tetrahydrofuran lignans from Peperomia dindygulensis.

Five new tetrahydrofuran lignans (1-5), accompanied by four known compounds, were isolated from the ethyl acetate extract of Peperomia dindygulensis. Structures were elucidated mainly using 1D NMR, 2D NMR, and mass spectroscopic studies. The relative configurations of 1-5 were determined by NOE correlations. Several of the compounds showed weak growth inhibitory activity against three cell lines (WI-38, VA-13, and HepG2). Compound 5 exhibited stronger MDR (multidrug resistance) reversal activity than verapamil at 2.5 microg/mL in a cellular calcein accumulation assay. Compounds 4 and 5 showed weak inhibitory activity against induction of the intercellular adhesion molecule-1 (ICAM-1) in anti-inflammatory activity experiments.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2004

Structural analysis of human hair fibers under the ultra-high voltage electron microscope.

Three-dimensional structural analyses of human hair fibers and comparison of the different fibers were tried by using the Ultra-high Voltage Electron Microscope (UHVEM). The analysis condition, sample preparation, and a machine state were adjusted to the suitable condition for tilting observation of from -70 degree to +70 degree, at 2 degrees intervals. The tomography of hair fiber was successfully reconstructed from the different angle pictures with IMODE software in a computer. By using UHVEM, the various human hair fibers from Japanese and Caucasians were investigated and discussed about their structures.

Hair↗