Biomedical subjects

Akira Miyazaki

Publications and source records attributed to Akira Miyazaki.

43 records · Page 3Linked to original sources

PubMed2002

Bulk weak ferromagnet in ferrimagnetic chains of organic-inorganic hybrid materials based on BDH-TTP and paramagnetic thiocyanato complex anions: (BDH-TTP)[M(isoq)(2)(NCS)(4)], M = Cr(III), Fe(III).

The preparation, X-ray crystal structures, and magnetic properties of two new isostructural charge transfer salts, (BDH-TTP)M(isoq)(2)(NCS)(4) (M = Cr(III) (1), Fe(III) (2), BDH-TTP = 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, isoq = isoquinoline), are reported. Crystal data for 1: monoclinic, space group C2/c (#15), a = 16.1363(9) A, b = 19.0874(12) A, c = 12.5075(6) A, beta = 95.70(4) degrees, V = 3833.2(4) A(3), Z = 4, R = 0.0516 for 2844 reflections with I > 2 sigma(I); for 2: monoclinic, C2/c (#15), a = 16.1938(8) A, b = 19.1117(11) A, c = 12.5100(10) A, beta = 94.265(3) degrees, V = 3861.0(4) A(3), Z = 4, R = 0.0479 for 2969 reflections with I > 2 sigma(I). The crystal structure consists of zigzag mixed organic and inorganic layers, and each layer is formed by mixed columns of BDH-TTP radical cations and paramagnetic metal complex anions. Short intermolecular atomic contacts between donor and anion are observed within the column in the c-direction. The two compounds have weak room-temperature electrical conductivities. ESR measurements show a single signal without separating the donor and anion spins, suggesting a pi interaction between the d and pi electrons. For both compounds ferrimagnetic interactions are observed between the nonequivalent donor and anion spins. These materials exhibit bulk canted weak ferromagnetism below 7.6 K for both 1 and 2.

Journal Article↗

PubMed2002

New tetrathiapentalene-derived charge transfer salts with paramagnetic transition metal complex anion: kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2).

The preparation, crystal structures, and optical and magnetic properties of two new charge-transfer salts kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) (1) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2) (2), where phen = 1,10- phenanthroline, EDDH-TTP = 2-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, and BDH-TTP = 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, are reported. Crystal data: (1) monoclinic P2(1)/a, a = 25.0752(5) A, b = 10.6732(3) A, c = 28.1601(6) A, beta = 95.195(2) degrees, Z = 4, R = 0.0585 for 6741 independent reflections with I > 3 sigma(I); (2) monoclinic P2(1)/a, a = 23.8275(4) A, b = 9.1015 (2) A, c = 27.0420(1) A, beta = 99.9297(8) degrees, Z = 4, R = 0.0530 for 4565 independent reflections with I > 2 sigma(I). The crystal structures for both compounds consist of alternating organic and inorganic layers. The organic layer in compound 1 is characterized as kappa-type, while the organic layer in 2 resembles the kappa-type but it contains orthogonal dimers and monomers, and it is therefore called kappa(21). Compound 1 shows metallic behavior down to low temperature. Salt 2 shows semiconductive behavior, which is explained as the result of either charge ordering owing to the kappa(21)-type structure or Peierls distortion due to the one-dimensional electronic nature. However, weak metallic behavior could be observed at 10 kbar above ca. 150 K and at 15 kbar above 170 K. The magnetic susceptibilities for both compounds show Curie-Weiss behavior, showing that the exchange interactions between the magnetic anions are weak. Polarized reflectance spectra of single crystals were measured over the spectral range from 650 to 7000 cm(-1). Moreover, absorption and diffusion reflectance spectra of powdered crystals dispersed in KBr (from 400 to 7000 cm(-1)) were recorded. Vibrational and electronic features are discussed.

Journal Article↗

PubMed2002

Lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) serves as an endothelial receptor for advanced glycation end products (AGE).

Advanced glycation end products (AGE) are known to serve as ligands for the scavenger receptors such as SR-A, CD36 and SR-BI. In the current study, we examined whether AGE is recognized by lectin-like oxidized low density lipoprotein receptor-1 (LOX-1). Cellular binding experiments revealed that AGE-bovine serum albumin (AGE-BSA) showed the specific binding to CHO cells overexpressing bovine LOX-1 (BLOX-1), which was effectively suppressed by an anti-BLOX-1 antibody. Cultured bovine aortic endothelial cells also showed the specific binding for AGE-BSA, which was suppressed by 67% by the anti-BLOX-1 antibody. Thus, LOX-1 is identified as a novel endothelial receptor for AGE.

Animals↗

PubMed2002

Positive family history for coronary heart disease and 'midband lipoproteins' are potential risk factors of carotid atherosclerosis in familial hypercholesterolemia.

Patients with heterozygous familial hypercholesterolemia (FH) were examined with B-mode ultrasound in order to determine intima-media thickness (IMT) in the common carotid artery, and to uncover potential risk factors responsible for the development of IMT. Ninety seven FH subjects and 132 non FH type IIa hyperlipidemic subjects were involved in the present study. Age was found to correlate positively with IMT in both FH and non FH groups. FH individuals showed a higher IMT, along with elevated low density lipoprotein (LDL) cholesterol levels, compared with age-matched non FH individuals. To clarify potential factors contributing to the formation and development of carotid atherosclerosis, we divided the FH subjects into two subgroups, namely FH with high IMT group (HIG), and those with low IMT group (LIG). We investigated those two subgroups on the presence of angiographically documented coronary heart disease (CHD), of family history of CHD and of 'midband lipoproteins' by polyacrylamide gel electrophoresis (PAGE) analysis, by matching for age and LDL-cholesterol (LDL-C) level. Fifty percent of FH men in HIG was found to have CHD, whereas only 14% of those in LIG had CHD (P<0.05). Thirty-three percent of FH women in HIG was found to have CHD, whereas only 12% of those in LIG had CHD (P<0.05). Fifty percent of FH men in HIG was found to have 'midband lipoproteins', whereas only 7% of those in LIG had 'midband lipoproteins' (P<0.01). Seventy-three percent of FH women in HIG had 'midband lipoproteins', whereas only 21% of those in LIG had 'midband lipoproteins' (P<0.0005). Fifty-five percent of FH men in HIG was had positive family history for CHD, whereas only 14% of those in LIG had positive family history for CHD (P<0.05). Sixty-three percent of FH women in HIG was found to have positive family history for CHD, whereas only 29% of those in LIG had positive family history for CHD (P<0.05). Based on these findings, we propose that, besides age and elevated levels of LDL-C, positive family history for CHD and 'midband lipoproteins' are important determinants for the development of carotid atherosclerosis in FH individuals in Japanese population.

Carotid Artery Diseases↗

PubMed2002

Scavenger receptors that recognize advanced glycation end products.

Scavenger receptors recognize modified low-density lipoproteins (LDLs) such as acetylated LDL and oxidized LDL. Advanced glycation end products (AGE), which are generated through long-term exposure of proteins to glucose, also behave as active ligands for some scavenger receptors, including class A scavenger receptor (SR-A) and class B scavenger receptors such as CD36 and scavenger receptor, class B, type I (SR-BI). SR-BI, the first identified high-density lipoprotein (HDL) receptor, plays key roles in reverse cholesterol transport by promoting selective uptake of cholesteryl esters (CE) in HDL by hepatocytes, and cholesterol efflux of unesterified cholesterol from peripheral cells to HDL. Using Chinese hamster ovary cells overexpressing SR-BI (CHO-SR-BI cells), it was demonstrated that AGE-bovine serum albumin binds to SR-BI and inhibits selective uptake of HDL-CE by CHO-SR-BI cells as well as cholesterol efflux from CHO-SR-BI cells to HDL, suggesting potential roles of AGE in diabetic dyslipidemia and accelerated atherosclerosis in diabetes.

Animals↗

PubMed1998

Synthesis, Crystal and Network Structures, and Magnetic Properties of a Hybrid Layered Compound: [K(18-cr)(2-PrOH)(2)][{Mn(acacen)}(2){Fe(CN)(6)}] (18-cr = 18-Crown-6-ether, acacen = N,N'-Ethylenebis(acetylacetonylideneiminate)).

A hybrid layered compound [{K(18-cr)(2-PrOH)(2)}{Mn(acacen)}(2){Fe(CN)(6)}] has been prepared by the reaction of [Mn(acacen)(Cl)] with [K(18-cr)(H(2)O)(2)](3)[Fe(CN)(6)].3H(2)O in an ethanol/2-propanol mixed solvent (18-cr = 18-crown-6-ether, acacen = N,N'-ethylenebis(acetylacetonylideneiminate)). It crystallizes in the monoclinic space group P2(1)/a with cell dimensions of a = 13.272(3) Å, b = 15.768 (2) Å, c = 14.771(2) Å, beta = 105.64(1) degrees, Z = 2. It assumes a hybrid layered structure of alternating arrays of two types of layers. One of the layers is formed by the anionic part [{Mn(acacen)}(2){Fe(CN)(6)}](n)()(n)()(-), where [Fe(CN)(6)](3)(-) coordinates through its four cyanide groups on a plane to the axial sites of four [Mn(acacen)](+) entities. The two-dimensional layer consists of the cyclic octamer [-Mn-NC-Fe-CN-](4) having the Fe ions at the corners and the Mn ions on the edges of a deformed square. Another layer is formed by the cationic part [K(18-cr)(2-PrOH)(2)](+) that has a hexagonal-bipyramidal geometry about the metal with two 2-PrOH molecules at the apexes of the nearly planar [K(18-cr)](+). The anionic and cationic layers are combined by the hydrogen bond between the cyanide groups (free from coordination) of the anionic layer and the 2-propanol groups of the cationic layer with bond distance of N.O = 2.861(5) Å. Magnetic studies (magnetic susceptibility vs T, field-cooled magnetization vs T, saturation magnetization vs H) indicate that the compound is a metamagnet with a Néel temperature T(N) = 5.0 K, showing the onset of ferromagnetic ordering within the anionic layer and an antiferromagnetic interlayer interaction. Magnetization as a function of the applied magnetic field indicates a spin-flipping from antiferromagnetic arrangement to ferromagnetic arrangement between the layers around 1200 Oe and exhibits hysteresis behavior.

Journal Article↗

PubMedDate not supplied

CD36, serves as a receptor for advanced glycation endproducts (AGE).

Interaction of advanced glycation endproducts (AGE) with AGE receptors induces several cellular phenomena relating potentially to diabetic complications. Five AGE receptors identified so far are receptor for AGE (RAGE), 80 K-H, OST-48, galectin-3, and macrophage scavenger receptor, types I and II (SR-A) [Eur. J. Biochem. 230 (1995) 408; Nature 386 (1997) 292.]. Since SR-A is known to belong to the class A scavenger receptor family and the scavenger receptor collectively represents a family of multiligand lipoprotein receptors, it is possible that CD36 belonging to class B scavenger receptor family (SR-B) can recognize AGE proteins as a ligand. This was tested in the present study at the cellular level by using Chinese hamster ovary (CHO) cells overexpressing human CD36 (CHO-CD36 cells). 125I-AGE-bovine serum albumin (BSA) was endocytosed in a dose-dependent fashion and underwent lysosomal degradation by CHO-CD36, but not wild-type CHO cells. Endocytic uptake of 125I-AGE-BSA by these cells was inhibited 50% by oxidized low-density lipoprotein (Ox-LDL) and 60% by FA6-152, an anti-CD36 antibody inhibiting cellular binding of Ox-LDL. Our results indicate that CD36 expressed by these cells mediates endocytic uptake and subsequent intracellular degradation of AGE proteins. Since CD36 is one of the major Ox-LDL receptors and is up-regulated in macrophage- and smooth muscle cell-derived foam cells in human atherosclerotic lesions, the present results suggest that, like Ox-LDL, AGE proteins generated in situ are recognized by CD36, which might contribute to the pathogenesis of diabetic macrovascular complications.

Animals↗