Biomedical subjects

A Yamaguchi

Publications and source records attributed to A Yamaguchi.

At least 55 records · Page 3Linked to original sources

PubMed2001

Two KaiA-binding domains of cyanobacterial circadian clock protein KaiC.

kaiABC, a gene cluster, encodes KaiA, KaiB and KaiC proteins that are essential to circadian rhythms in the unicellular cyanobacterium Synechococcus sp. strain PCC 7942. Kai proteins can interact with each other in all possible combinations. This study identified two KaiA-binding domains (C(KABD1) and C(KABD2)) in KaiC at corresponding regions of its duplicated structure. Clock mutations on the two domains and kaiA altered the strength of C(KABD)-KaiA interactions assayed by the yeast two-hybrid system. Thus, interaction between KaiA and KaiC through C(KABD1) and C(KABD2) is likely important for circadian timing in the cyanobacterium.

Adenosine Triphosphate↗

PubMed2001

Identification of genes upregulated in the inflamed colonic lesions of Crohn's disease.

To identify the molecular mechanism which primarily plays a role in the pathogenesis of Crohn's disease (CD) without prior hypothesis, differential display method was employed to detect differentially expressed genes between the inflamed and uninflamed colonic samples from one patient with CD. The mRNA levels of these genes were subsequently semi-quantitated in affected and unaffected tissues from six patients using reverse transcriptase polymerase chain reaction (RT-PCR). Six genes including long form FLICE inhibitory protein (FLIP(L)) were found to be consistently overexpressed in the inflamed colonic CD tissues. Immunohistochemical studies revealed that FLIP(L) expressing cells were lamina propria lymphocytes (LPLs). The present study suggested that overexpression of FLIP(L) in the LPLs may be involved in the pathogenesis of CD through defective activation-induced cell death. In addition, this study provided evidence for a possible role of several previously unsuspected genes in the pathogenesis of CD.

Adult↗

PubMed2001

Genes highly expressed in the early phase of murine graft-versus-host reaction.

Graft-versus-host reaction (GVHR) is a complex process initiated upon allorecognition. For detection of early molecular events in GVHR, we first assessed time courses with respect to symptoms and serum interferon (IFN)-gamma levels and then used the differential display method to compare gene transcript patterns during the early phase between acute lethal GVHR mice and syngeneic controls. In the GVHR mice, high expression levels of seven genes encoding the following molecules were detected: TGTP/Mg21 (an IFN-gamma-related signaling molecule), vitronectin, Nedd5 (a mammalian septin), manganese superoxide dismutase, activin betaC subunit, PRCC (a papillary renal cell carcinoma-associated molecule), and an uncharacterized gene corresponding to a mouse expressed sequence tag (EST). The expression levels of most genes peaked before the symptomatological onset and the peak of IFN-gamma levels. Thus, gene expression monitoring may characterize the inductive process of GVHR and aid in the development of gene-based diagnostics and therapies.

Animals↗

PubMed2001

Time-resolved energy-dispersive XAFS study on the reduction process of Cu-ZSM-5 catalysts.

The time-resolved reduction process of copper cations in ZSM-5 during temperature-programmed reduction (300-700 K) was studied by energy dispersive X-ray absorption fine structure (DXAFS). The Cu K-edge DXAFS spectra for isolated Cu2+ species in the channels of ZSM-5 were recorded at an interval of 1 s during the reduction. The curve fitting analysis of the EXAFS data and the XANES analysis revealed that the isolated Cu2+ species in the channels were reduced stepwise. They were reduced to isolated Cu+ species at 400-450 K and the Cu+ species to Cu0 metallic clusters at 550-650 K. Small clusters like Cu4 were initially formed, followed by particle growth. A small part of them went out to the outer surfaces of ZSM-5 during the reduction.

Journal Article↗

PubMed2001

DXAFS study on the decarbonylation process of Mo(CO)6 in NaY supercages.

The decarbonylation process of Mo(CO)6 in the NaY supercages was studied by means of a time resolved dispersive XAFS method during temperature programmed decarbonylation. XANES analysis demonstrated that the decarbonylation proceeded through two steps and that a stable intermediate existed between 440-490 K. The curve fitting analysis revealed that the intermediate was a molybdenum monomer subcarbonyl species coordinated by three CO ligands and three oxygen atoms of zeolite framework. Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that DXAFS technique is a powerful method to study the dynamic behaviour of the Mo carbonyl species during decarbonylation process.

Journal Article↗

PubMed2001

Complete cysteine-scanning mutagenesis and site-directed chemical modification of the Tn10-encoded metal-tetracycline/H+ antiporter.

Bacterial Tn10-encoded metal-tetracycline/H(+) antiporter was the first found drug exporter and has been studied as a paradigm of antiporter-type major facilitator superfamily transporters. Here the 400 amino acid residues of this protein were individually replaced by cysteine except for the initial methionine. As a result, we could obtain a complete map of the functionally or structurally important residues. In addition, we could determine the precise boundaries of all the transmembrane segments on the basis of the reactivity with N-ethylmaleimide (NEM). The NEM binding results indicated the presence of a transmembrane water-filled channel in the transporter. The twelve transmembrane segments can be divided into three groups; four are totally embedded in the hydrophobic interior, four face a putative water-filled channel along their full length, and the remaining four face the channel for half their length, the other halves being embedded in the hydrophobic interior. These three types of transmembrane segments are mutually arranged with a 4-fold symmetry. The competitive binding of membrane-permeable and -impermeable SH reagents in intact cells indicates that the transmembrane water-filled channel has a thin barrier against hydrophilic molecules in the middle of the transmembrane region. Inhibition and stimulation of NEM binding in the presence of tetracycline reflects the substrate-induced protection or conformational change of the Tn10-encoded metal-tetracycline/H(+) antiporter. The mutations protected from NEM binding by tetracycline were mainly located around the permeability barrier in the N-terminal half, suggesting the location of the substrate binding site.

Amino Acid Sequence↗

PubMed2001

Indirect micromanipulation of single molecules in water-in-oil emulsion.

Based on real-time observation and micromanipulation, analytical methods for single DNA molecules have been under development for some time. Precise manipulation, however, is still difficult because single molecules are too small for conventional techniques. We have developed a chemical reaction system that uses water droplets in oil as containers of materials. The water droplets can be manipulated by optical force. The manipulation of the water droplets permits the fusion of two selected droplets. This process corresponds to mixing of different samples. We designate this system as "w/o (water-in-oil emulsion) microreactor system", and each droplet can be thought of as a "microreactor". In this system, single molecules can be manipulated readily, as a molecule can be contained in a microm-sized microreactor. The microreactor utilizes extremely small quantities of samples, therefore, reactions are rapid, as diffusion times in the microreactor are very short. The manipulation technique of the microreactors based on optical force has been applied to induce fusion between microreactors loaded with DNA and YOYO, a fluorescent dye that binds to DNA. This fusion induced a rapid binding of YOYO.

Benzoxazoles↗

PubMed2001

Cardiac displacement after lobectomy in a patient with a congenital complete left-sided pericardial defect.

A 74-year-old man underwent left upper lobectomy for a suspected lung cancer. At thoracotomy, the pericardium was found to be completely absent. The heart was fixed in a central position with an artificial patch to prevent displacement. However, the heart became displaced just after closure of the thoracotomy. The thoracotomy was immediately reopened. The anchor points of the patch on the adventitia of the descending aorta had pulled through. The heart was fixed to the surrounding mediastinal tissues with a larger patch using pledget-reinforced mattress sutures. Because simple closure may result in cardiac herniation due to the cardiac pulsations, congenital pericardial defects should be securely repaired when encountered.

Aged↗

PubMed2001

Viability of liver grafts from fasted donor rats: relationship to sinusoidal endothelial cell apoptosis.

Previous studies have shown that livers from fasted donors appear to tolerate long-term preservation better than livers from fed donors, but the mechanism is not clear. Some studies have shown that the apoptosis of sinusoidal endothelial cells (SEC) appeared to be a pivotal mechanism of ischemia/reperfusion injury in liver transplantation. The purpose of the present investigation was to evaluate the relation of SEC apoptosis to liver viability in rats after liver transplantation, comparing findings for fasted and fed donors. Wistar rats were used as donors and recipients. The fed group had access to solid feed and water ad libitum. The fasted group was allowed access only to water for 4 days prior to liver harvest. All rat livers were preserved with University of Wisconsin (UW) solution at 2 degrees C for 24 h. After preservation, the livers were orthotopically transplanted, and survival time was measured. Apoptosis was determined by in-situ staining for apoptotic cells, using a TdT-mediated dUTP-digoxigenin nick-end labeling (TUNEL) assay and electron microscope (EM) examination separately. The 14-day survival rates after 24-h preservation were 0% (0/11) for recipients of livers from fed donors and 91% (10/11) for recipients of livers from fasted donors. There was no significant difference in the numbers of TUNEL-positive SEC after 24-h preservation between the two groups. However, at 6 h after transplantation, the number of TUNEL-positive SEC was significantly higher in the fed group than in the fasted group. These results suggest that donor fasting decreases SEC apoptosis after reperfusion alone, and that this may be related to the protection of the liver graft from reperfusion injury.

Analysis of Variance↗

PubMed2001

Long-Term surgical outcomes following intraluminal sutureless graft insertion for type A aortic dissection.

The long-term outcome of sutureless intraluminal graft insertion remains unclarified. Therefore, we reviewed the late surgical outcomes of patients who underwent this procedure for acute type A dissection. Between March 1990 and May 2000, 80 patients aged from 36 to 92 years underwent isolated replacement of the ascending aorta for type A acute aortic dissection. The surgical procedures performed were replacement with an intraluminal sutureless graft in 18 patients (group 1) and suturing of the aorta with a conventional Dacron prosthesis in 62 patients (group 2). The cross-clamp, extracorporeal circulation, circulatory arrest, and operation times were significantly shorter in group 1 than in group 2, and the amount of total blood transfusion was also significantly less in group 1 than in group 2. The hospital mortality rates were 11.1% (2/18) in group 1 and 9.7% (6/62) in group 2 (P > 0.999). The 5-year actuarial survival rates (including operative mortality) were 71% +/- 11% in group 1 and 77% +/- 9% in group 2 (P = 0.268). The event-free survival rates at 5 years were 80% +/- 10% in group 1, and 67% +/- 13% in group 2 (P = 0.780). Regarding graft-related complications, long-term follow-up revealed one graft-related death and one reoperation in group 1 (12.5%), and no graft-related complications in group 2 (0%) (P = 0.047). In conclusion, intraluminal sutureless grafts required less blood transfusion, and shorter cross-clamp, extracorporeal circulation, circulatory arrest, and surgery times. However, the procedure did not improve the hospital mortality or long-term outcome. In fact, the rate of graft-related complications was significantly higher in the intraluminal sutureless group than in the sutured group. Therefore, the intraluminal graft insertion technique should be used only under exceptional circumstances.

Acute Disease↗

PubMed2001

Ossification of tracheal cartilage in aged humans: a histological and immunohistochemical analysis.

Tracheal cartilage has been considered as permanent cartilage without endochondral ossification. We examined ossification of the tracheal cartilage in 25 adults (mean age 67.8 years; range 20-87 years; male:female = 17:8). Thirteen cases (52%) demonstrated ossification of the tracheal cartilage, accompanied by the formation of lamellar bones with fatty bone marrow. Ossification was observed at the lateral peripheral region of the tracheal cartilage, while vascular invasion into the cartilage was seen even where no ossification was present. Twenty-two cases (88%) showed marked hyalinization in the central region of the tracheal cartilage. Type II collagen was immunolocalized in the cartilage matrix, except for in the central hyalinized area, while type I collagen was immunolocalized around the perichondrium and ossified areas in the tracheal cartilage. Type X collagen immunolocalized on territorial matrices around the lacunae near the ossified regions. These results suggest that tracheal cartilage in aged humans frequently ossifies physiologically, and that aging promotes osteogenesis, even in permanent cartilage.

Adult↗

PubMed2001

Cartilage-specific matrix protein chondromodulin-I is associated with chondroid formation in salivary pleomorphic adenomas: immunohistochemical analysis.

Chondromodulin-I (ChM-I) is a novel cartilage-specific matrix protein. In the growth plates of the long bones, ChM-I was shown to be expressed in mature to upper hypertrophic chondrocytes, and to be deposited in the cartilage matrix. As ChM-I strongly inhibits angiogenesis, cartilage is avascular. Also, ChM-I has bifunctional activity against chondrocyte proliferation. On the other hand, pleomorphic adenomas of the salivary glands frequently have chondroid elements. To elucidate the relationship between chondroid formation and hypovascularity in salivary pleomorphic adenomas, we immunohistochemically examined the expression and localization of ChM-I in 35 cases of this tumor. ChM-I was immunolocalized to the lacunae in the chondroid elements of pleomorphic adenomas (100%). Type II collagen and aggrecan were immunolocalized throughout the matrix around lacuna cells of the chondroid element (100%, 91.7%), and ChM-I was infrequently immunolocalized to the spindle-shaped myoepithelial cells in the myxoid element (37.5%). Fibroblast growth factor-2 was strongly immunolocalized to the lacuna cells in the chondroid element (100%), among the neoplastic myoepithelial cells in the myxoid elements (96.9%), and on the basement membranes around the solid nests of neoplastic myoepithelial cells (71.4%). Although CD34 is a marker of endothelial cells, CD34 was expressed in the endothelial cells in only a few areas around the epithelial elements and in the fibrous element of pleomorphic adenomas. No signals for CD34 were observed in chondroid elements in pleomorphic adenomas (P < 0.001), but a few signals were seen in the myxoid elements (P < 0.05). These findings suggested that lacuna cells and neoplastic myoepithelial cells expressed ChM-I, and that this molecule may play an important role in hypovascularity and chondroid differentiation in pleomorphic adenoma. In conclusion, pleomorphic adenoma expressed ChM-I, which is involved in hypovascularity and chondroid formation in this type of tumor.

Adenoma, Pleomorphic↗

PubMed2001

Preoperative risk factors for hospital mortality in acute type A aortic dissection.

BACKGROUND: Acute type A dissection is associated with postoperative complications and a high mortality rate. This study was performed to determine the perioperative risk factors leading to hospital mortality in patients with acute type A aortic dissection. METHODS: One hundred twenty-two patients with acute type A aortic dissection treated surgically within 48 hours after onset were enrolled in this study. Thirty-two perioperative risk factors were used in statistical analysis for prediction of mortality. Risk factors for hospital death were investigated with univariate and multiple logistic regression analysis. RESULTS: The in-hospital mortality rate including operative death was 12.3% (15 of 122 patients) and the actuarial survival rate (including in-hospital death) was 72%+/-6% at 5 years. Univariate analysis revealed 10 risk factors to be statistically significant predictors of hospital death: age, year of operation (1990 to 1995), Marfan syndrome, preoperative ST segment elevation, heart failure from aortic regurgitation, preoperative shock, preoperative coma, long operation time (> 6 hours), long cardiopulmonary bypass time (> 4 hours), and massive blood transfusion (> 20 units) (p < 0.05). Multiple logistic regression analysis confirmed preoperative ST-T segment elevation and massive blood transfusion to be statistically significant independent risk factors for hospital death (p < 0.05). CONCLUSIONS: Preoperative ST-T elevation and massive blood transfusion during operation were identified as significant independent risk factors for hospital mortality after operation for acute type A aortic dissection. Our findings should contribute to estimation of operative risk in individual patients.

Acute Disease↗

PubMed2001

The effects of transplantation of osteoblastic cells with bone morphogenetic protein (BMP)/carrier complex on bone repair.

We investigated the effects of transplantation of osteoblastic cells with a bone morphogenetic protein (BMP)/carrier complex on bone repair by in vitro and in vivo experiments. Poly-D,L-lactic-co-glycolic acid/gelatin sponge (PGS) was used as a carrier for cell transplantation. In the in vitro experiments, three cell types, C3H10T1/2 cells, MC3T3-E1 cells, and primary osteoblastic cells, isolated from newborn rat calvariae (ROB cells), were cultured for 2 weeks on PGS alone or PGS containing BMP-2 (PGS/BMP). C3H10T1/2 cells cultured on PGS/BMP expressed several markers related to differentiation of both osteoblasts and chondrocytes, such as alkaline phosphatase (ALP) activity and mRNAs for osteocalcin and aggrecan, whereas the cells cultured on PGS alone expressed no such markers. MC3T3-E1 cells cultured on PGS/BMP exhibited a more ALP-positive cells than those cultured on PGS alone. PGS/BMP promoted ROB cell differentiation into both osteoblasts and chondrocytes. In the in vivo experiments, we transplanted ROB cells, which had been cultured on PGS alone or PGS/BMP in vitro for 2 weeks, into bone defects created in rat calvariae. Transplantation of ROB cells cultured on PGS alone generated little new bone. Transplantation of ROB cells cultured on PGS, which absorbed a low dose (10 ng) of rhBMP-2,; induced significantly higher bone mineral content than PGS/BMP alone, although application of a high dose (1 microg) of rhBMP-2 induced no difference in bone mineral content between transplantation of PGS/BMP with or without ROB cells. These results show that transplantation of osteoblastic cells after induction of osteoblast maturation in vitro by cultivation on PGS/BMP is a potent technique for cell therapy of bone repair.

Aggrecans↗

PubMed2001

Dose-dependent conjugation of sulfobromophthalein and hepatic transit time in bile fistula rats: role of the microtubule-dependent vesicle pathway.

Sulfobromophthalein (BSP) is selectively taken up by the liver and secreted into the bile as unconjugated and conjugated forms. Our previous study demonstrated that unconjugated BSP, but not conjugated BSP, caused the dissociation of biliary lipid secretion from that of bile acids, suggesting that the hepatic BSP conjugation rate partly regulated biliary lipid secretion. To evaluate the mechanisms through which biliary lipid secretion is regulated by exogenous organic anions, we intravenously administered BSP to male Sprague-Dawley rats at various doses either continuously or as a bolus. Then the relationship of the dose of BSP to its conjugation rate, hepatic transit time, and biliary lipid secretion was determined. BSP decreased biliary secretion of cholesterol and phospholipids in a dose-dependent manner without affecting bile acid secretion. In contrast, the proportion of conjugated BSP in bile was associated with the dose. Although the serum clearance of BSP after bolus infusion was constant regardless of the dose administered (50 or 200 nmol/100 g), BSP secretion was delayed with increasing doses: unconjugated BSP was secreted predominantly in the early phase (0-15 min after bolus injection), and conjugated BSP was the predominant form in the late phase (15-30 min). Pretreatment with colchicine reduced the conjugation rate and hepatic transit time of BSP, suggesting that the microtubule-dependent vesicle pathway plays a role in biliary excretion and conjugation of BSP. We conclude that biliary lipid secretion is influenced by organic anions with an affinity for bile acids such as BSP and that this effect is dependent upon the hepatic metabolic rate, i.e., conjugation rate. The hepatic transit time also plays a key role in this process by influencing metabolism.

Animals↗

PubMed2001

Phospholipid alterations in hepatocyte membranes and transporter protein changes in cholestatic rat model.

Biliary components are transported by hepatic adenosine triphosphate-binding cassette (ABC) transporters that are located in canalicular membranes. Physiological transporter function is related to membrane fluidity, which is modulated by the phospholipid composition of the lipid bilayer. We hypothesized that cholestasis may alter transporter function by modifying phospholipid species to protect the cell from cholestatic damage. Therefore, we examined the expression of ABC transport proteins and their mRNA levels in canalicular membrane vesicles isolated from rat liver 6 hr or three days after bile duct ligation. Membrane lipid composition and membrane fluidity of both sinusoidal and canalicular membrane vesicles were also examined. By 6 hr after bile duct ligation, we found a clear increase of mdr2 and bsep mRNA. These changes were associated with an increase of mdr-Pgp and with a clear decrease of mrp2 protein, and small decrease of bsep protein. In addition, mdrlb mRNA showed a strong increase by three days after bile duct ligation. Canalicular membrane fluidity decreased in a marked time-dependent manner, whereas sinusoidal membranes showed biphasic changes: increased fluidity at 6 hr and a decrease at three days. These changes were closely related to the changes of membrane lipid constitution; the saturated/unsaturated fatty acid ratio increased for phosphatidylcholine in canalicular membrane and the reverse occurred in sinusoidal membrane, and those for sphingomyelin showed the opposite pattern. We conclude that cholestasis causes modulation of ABC transporters as well as that of the lipid constitution in lipid bilayer. These may confer cytoprotective resistance to hepatocytes against cholestatic stress.

ATP-Binding Cassette Transporters↗

PubMed2001

Adenomatoid odontogenic tumour: immunohistochemical demonstration of transferrin, ferritin and alpha-one-antitrypsin.

Three cases of adenomatoid odontogenic tumour (AOT) were examined by morphological and immunohistochemical methods, to define the nature of tumour cells and to determine the correlation between the occurrence of extracellular eosinophilic amorphous material and epithelial tumour cells. The epithelial tumour cell components observed in this study were divided into three cell types (cell type I: small compact cells in a solid nodule and pseudoglandular cells in a duct-like structure; cell type II: peripheral elongated cells and spindle-shaped cells in a cribriform pattern; and cell type III: metaplastic squamous cells). The mesenchymal components consisted of eosinophilic amorphous material and calcified material. Immunohistochemically, the type I cells reacted positively with antibodies to transferrin, ferritin and alpha-one-antitrypsin (alpha1-AT), whereas the type II cells constantly indicated intense expression only for transferrin and alpha1-AT. All types of epithelial tumour cells reacted negatively with lactoferrin, alpha-one-antichymotrypsin, S-100 protein, S-100alpha subunit and S-100beta subunit. Moreover, the eosinophilic amorphous material and calcified material examined were positive for the antibody against alpha1-AT. These materials expressed immunophenotypes similar to those of the epithelial tumour cells, except for metaplastic squamous cells. The present study showed that iron-binding proteins and proteinase inhibitor might be related to the pathogenesis of AOT. Furthermore, we indicated that the formation of eosinophilic amorphous material was associated with type I and type II cells.

Adolescent↗

PubMed2001

Immunohistochemical localization of members of the transforming growth factor (TGF)-beta superfamily in normal human salivary glands and pleomorphic adenomas.

Although pleomorphic adenoma is the most common type of salivary gland epithelial tumor, it frequently contains "mesenchymal"-like components, including myxoid or chondroid tissues. We reported previously that chondroid tissue formation in pleomorphic adenoma was associated with overexpression of bone morphogenetic proteins (BMPs) by neoplastic myoepithelial cells. BMPs belong to the transforming growth factor (TGF)-beta superfamily, so we hypothesized that pleomorphic adenoma may express TGF-betas and that these molecules may regulate mesenchymal-like tissue formation. To evaluate this hypothesis, we immunohistochemically examined TGF-beta1, -beta2 and -beta3 expression and localization in normal salivary glands and in 43 cases of pleomorphic adenomas. There was no evidence of TGF-beta1 expression in normal salivary glands or pleomorphic adenomas. Signals for TGF-beta2 in the normal salivary glands were observed in the intercalated ducts, while in pleomorphic adenomas they were observed in the inner ductal cells of the tubulo-glandular structures. Signals for TGF-beta3 in the normal salivary glands were observed in mucous cells, whereas in pleomorphic adenomas they were observed in the solid nests of neoplastic myoepithelial cells, in the portion showing squamous metaplasia, and in the inner ductal cells of tubulo-glandular structures. TGF-betas induce ectopic cartilage formation in vivo, but chondroid tissues in pleomorphic adenomas showed only weak TGF-beta3 expression. TGF-beta may be related to differentiation of the inner ductal cells and the neoplastic myoepithelial cells. In conclusion, pleomorphic adenomas expressed TGF-beta2 and -beta3, which may be associated with differentiation of the inner ductal cells and neoplastic myoepithelial cells.

Adenoma, Pleomorphic↗