PubMed Health⌕ Search

Biomedical subjects

Kenichi Kato

Publications and source records attributed to Kenichi Kato.

At least 19 recordsLinked to original sources
PubMed2006

Accurate structure factors and experimental charge densities from synchrotron X-ray powder diffraction data at SPring-8.

Accurate structure factors of silicon and diamond have been experimentally determined from powder diffraction data measured at the third-generation synchrotron-radiation source SPring-8, BL02B2. The accuracy of the obtained structure factors has been evaluated by comparing with structure factors in the literature measured by the Pendellösung method and with some from theoretical calculations. The results indicate that the structure factors from powder data are accurate enough to discuss the experimental charge-density distributions of these materials. The number of structure factors of silicon determined in the present study is 104, which is three times more than that of previous Pendellösung data. The experimental charge densities have been obtained by the maximum-entropy method from the present structure factors. The charge densities at bond mid-points for silicon and diamond show good agreement with different kinds of theoretical calculations. The present study proved that the powder diffraction at SPring-8 is a promising method for determination of experimental charge density for a wider range of materials.

Data Interpretation, Statistical↗
PubMed2006

Chemical reaction-inspired crystal growth of a coordination polymer toward morphology design and control.

This paper reports a novel crystal growth system of a coordination framework {[Cu3(CN)3{hat-(CN)3(OEt)3}]}n (1) (hat-(CN)3(OEt)3 = 2,6,10-tricyano-3,7,11-triethoxy-1,4,5,8,9,12-hexaazatriphenylene). The coordination polymer is crystallized through the reaction of 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (hat-(CN)6), ethanol, and copper(I) complex, involving the breaking and forming of covalent bonds. The crystal morphologies obtained in the present system contain dumbbells, cogwheels, and superlattices. Moreover, in the growth perpendicular to the c-axis, periodic ramification at regular interval is observed, affording superlattice morphologies. Observation of the growth of dumbbell crystals shows that the growth rates parallel and perpendicular to the crystallographic c-axis are quite different: the former shows a drastic change with the reaction duration, while the latter is almost constant. These results are reproduced as a simple reaction-diffusion system, indicating that chemical reactions on crystal surfaces play an important role in determining the macroscopic crystal morphologies.

Journal Article↗
PubMed2006

High-spin- and low-spin-state structures of [Fe(chloroethyltetrazole)6](ClO4)2 from synchrotron powder diffraction data.

The spin-crossover complex [Fe(teec)(6)](ClO(4))(2) (teec = chloroethyltetrazole) exhibits a 50 % incomplete spin crossover in the temperature range 300-30 K. Time-resolved synchrotron powder diffraction experiments have been carried out to elucidate its structural behavior. We report crystal structure models of this material at 300 K (high spin) and 90 K (low spin), as solved from synchrotron powder diffraction data by using Genetic Algorithm and Parallel Tempering techniques and refined with Rietveld refinement. During short synchrotron powder diffraction experiments (five minutes duration) two distinguishable lattices were observed the quantities of which vary with temperature. The implication of this phenomenon, that is interpreted as a structural phase transition associated with the high-to-low spin crossover, and the structural characteristics of the high-spin and low-spin models are discussed in relation to other compounds showing a similar type of spin-crossover behavior.

Journal Article↗
PubMed2006

Tissue preferential expression of estrogen receptor gene in the marine snail, Thais clavigera.

Sex steroid hormones have been widely detected in molluscs, and experiments have shown the importance of sex steroids in sex determination, gonadal tissue maturation and gametogenesis. Nevertheless, the signaling pathways of sex steroids in invertebrates have not yet been elucidated. In order to gain insights into the mechanism of sex steroid signaling in molluscs, we have, therefore, tried to isolate molluscan estrogen receptors from the prosobranch mollusc Thais clavigera. Cerebral ganglia of T. clavigera (Mollusca, Gastropoda, Prosobranchia) were subjected to RNA extraction, and degenerate primers for amino acid sequences conserved in vertebrate estrogen receptors were designed. PCR amplification using cerebral RNA and degenerate primers followed by 5'- and 3'-RACE identified the cDNA encoding T. clavigera estrogen receptor 1 (tcER1). The deduced amino acid sequence showed 93% identity in the DNA-binding domain and 72% identity in the ligand binding domain when compared to Aplysia estrogen receptor. Reporter gene assay revealed that tcER1 is constitutively active and unresponsive to estrogen. Quantitative analysis of the tcER1 mRNA level demonstrated the preferential expression in the ovary. Furthermore, cerebral ganglia expressed tcER1 at a high level in the spring followed by subsequent enlargement of the ovary in later seasons. These results suggest importance of tcER1 in the seasonal development of reproductive organs in T. clavigera.

Amino Acid Sequence↗
PubMed2006

Synthesis, structure, and magnetic properties of Li-doped manganese-phthalocyanine, Li(x)[MnPc] (0 < or = x < or = 4).

We report on the first synthesis of Li-intercalated manganese-phthalocyanine (MnPc) in the bulk form and on the evolution of the structural and magnetic properties as a function of Li concentration, x. We find that solid beta-MnPc, which comprises rodlike assemblies of individual planar molecules, is best described as a glassy one-dimensional ferromagnet without three-dimensional ordering and that it can be quasi-continuously intercalated with Li up to x = 4, forming an isosymmetrical series of Li(x)[MnPc] phases. Inserted Li+ ions strongly bond to pyrrole-bridging nitrogen atoms of the Pc rings, thereby disrupting the ferromagnetic Mn-N(a)...Mn superexchange pathways. This gradually induces a crossover of the intrachain exchange interactions from ferromagnetic to antiferromagnetic as the doping level, x, increases coupled with a spin-state transition of the Mn2+ ions from intermediate spin, S = 3/2, to high spin, S = 5/2.

Indoles↗
PubMed2006

Difference in the characteristics of ETA-receptor-stimulated response between rat small pulmonary and renal arteries.

We investigated the difference in the characteristics of endothelin-1 (ET-1)-induced contraction and the responses of intracellular Ca(2+) concentration ([Ca(2+)](i)) between rat small pulmonary artery and renal artery. ET-1 (30 nM) failed to elicit any contraction in renal arteries pretreated with 3 microM BQ-123, an ETA blocker. However, in the pulmonary artery a combination of BQ-123 and BQ-788, an ETB blocker (5 microM each), only partially inhibited the ET-1-induced contraction (by 25%). To focus on the ETA receptor, in the presence of 5 microM BQ-788, nitric oxide donors (sodium nitroprusside and (+/-)-S-nitroso-N-acetylpenicillamine) and forskolin reduced both the ET-1-induced contraction and increase in [Ca(2+)](i) in both pulmonary and renal arteries. However, the effects were stronger in the renal than in the pulmonary artery. ET-1-induced increase in [Ca(2+)](i) was only partially attenuated by 10 microM verapamil (to 81% of control) in pulmonary arteries but was reduced to 56.1% of control in renal arteries. Our results provide evidence that ET-1 may activate ET receptor(s) insensitive to both BQ-123 and BQ-788 in rat small pulmonary artery, at least under these conditions. Furthermore, the effects of relaxants such as L-type Ca(2+) channel blocker and nitric oxide donors on the ET-1-induced contraction were studied.

Animals↗
PubMed2006

Osteopontin expression in vascular smooth muscle cells in patients with end-stage renal disease.

beta-glycerophosphate, a phosphate donor, and uremic sera induce osteopontin (OPN) expression in bovine vascular smooth muscle cells (VSMCs). However, the correlations of serum phosphorus level with OPN expression, and blood urea nitrogen (BUN) level with OPN expression in humans have not previously been reported. The purpose of the current study is to compare the expression of OPN in VSMCs with clinical data in patients with end-stage renal disease (ESRD). The radial arteries of 33 patients (21 male and 12 female patients) were examined to determine the expression of OPN and collagen type I (Col I) by immunohistochemistry. The correlation of the expression of bone matrix proteins with clinical data was analyzed. Between the low-serum phosphorus (<6 mg/dL) group and high-serum phosphorus (> or =6 mg/dL) group, significant differences were detected in the expression of OPN (P = 0.0049) and the levels of BUN (P = 0.0005), serum phosphorus (P < 0.0001) and calcium x phosphorus products (P < 0.0001). Moreover, between the low-BUN (<70 mg/dL, N = 19) group and high-BUN (> or =70 mg/dL) group, significant differences were detected in the expression of OPN (P = 0.0039) and the levels of BUN (P = 0.0002), serum phosphorus (P = 0.0002) and calcium x phosphorus products (P = 0.0003). We have shown that hyperphosphatemia or azotemia is associated with the expression of OPN in VSMCs in patients with ESRD.

Aged↗
PubMed2005

Structure basis for antitumor effect of aplyronine a.

Aplyronine A, isolated from the sea hare Aplysia kurodai, possesses an exceedingly potent antitumor effect in vivo and it is one of the promising candidates as an anticancer drug. This macrolide is known to depolymerize F-actin and inhibit the polymerization of actin by forming a 1:1 complex with monomeric actin. The first complex structure of actin-aplyronine A was determined via a synchrotron X-ray analysis at a 1.45 A resolution. As expected, aplyronine A binds to a hydrophobic cleft composed of subdomains 1 and 3 of actin by intercalating its aliphatic tail part into the actin molecule as do the other reported F-actin depolymerizing agents. Unexpectedly, this complex structure shows the specific structural features around the trimethylserine moiety, revealed as an important moiety of aplyronine A for cytotoxicity against HeLa cells. Combining this result and our previous one, the moiety should strongly relate to the specific biological activity of aplyronine A; i.e. a potent antitumor effect.

Actins↗
PubMed2005

Resistin SNP-420 determines its monocyte mRNA and serum levels inducing type 2 diabetes.

Resistin, secreted from adipocytes, causes insulin resistance in rodents. Its roles and main source in humans remain unknown. The G/G genotype of resistin single nucleotide polymorphism, SNP-420, induces type 2 diabetes mellitus (T2DM) by increasing promoter activity. We elucidated factors correlated with serum resistin and effects of SNP-420 on monocyte resistin mRNA. In 198 T2DM and 157 controls, fasting serum resistin was higher in T2DM. Multiple regression analysis revealed that SNP-420 genotype was the strongest determinant of serum resistin. In T2DM, 1-year duration of T2DM and 1% HbA1c was also correlated with 0.19 and 0.54 ng/ml serum resistin, respectively. Logistic regression analysis revealed that serum resistin was an independent factor for T2DM. In 23 healthy volunteers, monocyte resistin mRNA was positively correlated with its simultaneous serum levels and was higher in G/G genotype. Thus, SNP-420 determines monocyte mRNA and serum levels of resistin, which could induce T2DM.

Adipocytes↗
PubMed2005

Adjuvant-induced macrophage-dominant nephrotoxic serum nephritis in rats.

BACKGROUND: To investigate cellular mechanisms responsible for the development of crescentic glomerular lesions, we have studied the effects of complete adjuvant (CA) on subnephritogenic nephrotoxic serum (NTS) nephritis (NTS-N) in Brown Norway rats. METHODS: A subnephritogenic dose of NTS, 0.02 ml per rat, was intravenously injected into rats that were previously (14 days earlier) treated intradermally with CA, incomplete adjuvant, or PBS. RESULTS: Proteinuria developed by day 2 only in CA-treated rats. Also, severe glomerular lesions associated with cellular crescent formation developed by day 2 only in the CA-treated rats. The glomerular extent of infiltration of IL-1beta-positive cells, MCP-1 expression level, and the number of ED1 and PCNA double-positive activated macrophages peaked on day 4 and decreased thereafter. The numbers of T lymphocytes and polymorphonuclear neutrophils did not significantly increase throughout the experiments. CONCLUSIONS: These results indicate that CA can potently induce crescentic NTS-N characterized by the infiltration of activated macrophages, which presumably bind to rabbit IgG on the glomerular basement membrane and may play a critical role in the development of severe NTS-N associated with crescent formation.

Animals↗
PubMed2005

Catheter ablation of tachycardias after undergoing a surgical atriotomy using a multipolar electrode catheter: conventional mapping method without an electroanatomical mapping system.

BACKGROUND: A variety of supraventricular tachyarrhythmias may occur in patients after undergoing a surgical atriotomy. The purpose of this study was to characterize them and determine the role of conventional mapping. METHODS AND RESULTS: In 45 patients after a surgical atriotomy, 68 atrial tachyarrhythmias were observed. A conventional mapping system with a 20-pole electrode catheter used in the electrophysiological study detected 39 atrial tachycardias (ATs). Type 1 atrial flutter (AFL) was observed in 23 and reverse type 1 AFL in 4. AT was classified into 3 subgroups, namely, incisional macroreentrant AT (n=31), incisional focal AT (n=1) and non-incisional AT (n=7). In the patients with incisional macroreentrant AT after the standard right atriotomy, the 20-pole electrode catheter placed on the incision could easily record the entire sequence of the atrial activation. Successful catheter ablation was achieved in all patients with incisional reentrant AT. The ablation site of incisional reentrant AT was the isthmus between the incision and the superior vena cava cannulation scar in 4, between the incision and the inferior vena cava cannulation scar in 22, and the area at the septal incision in 3. The remaining 2 incisional ATs were left atrial AT and right atrial transincisional AT. CONCLUSIONS: The conventional mapping system is still very useful for making an electrophysiological diagnosis in patients after a standard right atriotomy.

Adult↗
PubMed2005

[Case of paroxysmal nocturnal hemoglobinuria complicated with IgA nephropathy who developed acute renal failure induced by hemolytic crisis].

A 60-year-old man, who had been diagnosed as having paroxysmal nocturnal hemoglobinuria(PNH) in 1994, was admitted to our hospital with general fatigue, and dark urine after a common-cold in January 2001. In the peripheral blood, the red blood cell count was 136 x 10(4)/microl, hemoglobin 4.0 g/dl and hematocrit 12.4%. The serum creatinine level was 9.9 mg/dl. Kidney biopsy revealed focal and segmental proliferation of mesangial cells, mesangial matrix expansion, acute tubular necrosis, interstitial fibrosis and hemosiderine deposits in the tubular epithelial cells confirmed by Berlin-blue staining. Immunofluorescence microscopy showed IgA and C3 deposition in the mesangium. Electron microscopy revealed electron dense deposits in the mesangial area and heavy electron-dense hemosiderin pigments in proximal tubular epithelial cells. After the transfusion of six units of washed red blood cells and two sessions of hemodialysis, the renal function returned to the levels before admission.

Acute Kidney Injury↗
PubMed2004

Structures of Fe(II) spin-crossover complexes from synchrotron powder-diffraction data.

Crystal structure determination and analysis have been carried out for the two spin-crossover compounds [Fe(teeX)(6)](BF(4))(2) (teeX is haloethyltetrazole; X = I: teei; X = Br: teeb), in both their high-spin (near 300 K) and their low-spin states (T = 90 K), using high-resolution powder-diffraction data collected at the ESRF (Grenoble, France) and SPring8 (Japan) synchrotron radiation facilities. The structures of teei have been solved using various direct-space structure determination techniques (grid search, genetic algorithm and parallel tempering) and refined with the Rietveld method using geometrical restraints. In the case of teeb, a structural model was found but a full refinement was not successful because of the presence of a significant amount of an amorphous component. Analysis of the structures (space group P2(1)/c, Z = 2) and diffraction data, and the absence of phase transitions, show the overall structural similarity of these compounds and lead to the conclusion that the gradual spin-crossovers are likely to be accompanied by small structural changes only.

Journal Article↗