Biomedical subjects

M Tamura

Publications and source records attributed to M Tamura.

At least 73 records · Page 4Linked to original sources

PubMed2001

Fused p47phox and p67phox truncations efficiently reconstitute NADPH oxidase with higher activity and stability than the individual components.

Activation of the neutrophil NADPH oxidase occurs via assembly of the cytosolic regulatory proteins p47(phox), p67(phox), and Rac with the membrane-associated flavocytochrome b(558). Following cell-free activation, enzymatic activity is highly labile (Tamura, M., Takeshita, M., Curnutte, J. T., Uhlinger, D. J., and Lambeth, J. D. (1992) J. Biol. Chem. 267, 7529-7538). To try to stabilize the activity and investigate the nature of the complex, fusion proteins between p47N-(1-286) and p67N-(1-210) were constructed. In a cell-free system, a fusion protein, p67N-p47N, had an 8-fold higher efficiency and produced a higher activity than the individual proteins, and also resulted in an 8-fold improved efficiency for Rac and a lowered K(m) for NADPH. O(2) generating activity was remarkably stabilized by using p67N-p47N. The cytosolic proteins fused in the opposite orientation, p47N-p67N, showed similar activity and stability as individual proteins, but with a 4-fold improved efficiency compared with the individual cytosolic factors. In the system efficiency for Rac and affinity for NADPH were also higher than those with the nonfused components. Interestingly, the p67N-p47N showed nearly full activation in the absence of an anionic amphifile in a cell-free system containing cytochrome b(558) relipidated with phosphatidylinositol- or phosphatidylserine-enriched phospholipid mixtures. From the results we consider multiple roles of anionic amphifiles in a cell-free activation, which could be substituted by our system. The fact that a fusion produces a more stable complex indicates that interactions among components determine the longevity of the complex. Based on the findings we propose a model for the topology among p47N, p67N, and cytochrome b(558) in the active complex.

Cell-Free System↗

PubMed2001

A polyrotaxane series containing alpha-cyclodextrin and naphthalene-modified alpha-cyclodextrin as a light-harvesting antenna system.

Supramolecular light-harvesting antenna systems were constructed by using polyrotaxanes, in which cyclodextrin (CD) rings of alpha-CD and naphthalene (energy donor)-appended alpha-CD are threaded by a poly(ethylene glycol) chain with anthracene (energy acceptor) units at both ends (5-8). The effects of the component ratio of the polyrotaxanes on the efficiencies of energy migration and energy transfer were examined by fluorescence emission and excitation spectra and anisotropy and by fluorescence decay measurements. The observed results were explained by using the Forster mechanism.

Journal Article↗

PubMed2001

Stimulation of beta1 integrin down-regulates ICAM-1 expression and ICAM-1-dependent adhesion of lung cancer cells through focal adhesion kinase.

Adhesion molecules are involved in intracellular signaling in various physiological and pathological processes including metastasis and growth of tumor cells. Tumor cells interact with various host cells as well as with extracellular matrices through certain adhesion molecules such as integrins. We here propose that stimulation of beta1 integrin reduces intercellular adhesion molecule (ICAM)-1-mediated interaction of lung cancer cells with CTLs. This concept is based on the following findings: (a) engagement of beta1 integrins on certain lung cancer cells by a specific antibody or by ligand matrices such as fibronectin and collagen markedly reduced ICAM-1 expression on the cell surface and induced sICAM-1; (b) down-regulation of ICAM-1 by stimulation of beta1 integrins was abrogated by tyrosine kinase inhibitors or by transfection of dominant negative truncations of focal adhesion kinase (FAK); (c) engagement of beta1 integrins also reduced ICAM-1-dependent adhesion of lung cancer cells to T cells, a process completely inhibited by tyrosine kinase inhibitors and by transfection of dominant negative forms of FAK; and (d) stimulation of beta1 integrins prevented killing of lung cancer cells by autologous CTLs. In malignant tumors, cancer cells, including lung cancer cells, are surrounded by extracellular matrix proteins such as fibronectin and collagen. This suggests that the engagement of beta1 integrins by matrix proteins potentially occurs in cancer cells in vivo and that continuous stimulation via beta1 integrins reduces ICAM-1-expression, ICAM-1-mediated adhesion of cancer cells to CTLs and their killing by CTLs. Our results suggest that such processes can lead to the escape of lung cancer cells in vivo from immunological surveillance.

Antibodies, Monoclonal↗

PubMed2001

Destabilization of neutrophil NADPH oxidase by ATP and other trinucleotides and its prevention by Mg(2+).

Neutrophil NADPH oxidase (O(2)(-) generating enzyme) activated in a cell-free system was deactivated by dilution. When ATP was included in dilution the deactivation was further accelerated. The deactivation by dilution was biphasic, and the half-life of the enzyme was significantly shortened by ATP in each phase. ADP and AMP had little effect on the enzyme longevity while GTP and CTP had a similar effect to ATP. Staurosporine, a wide-range inhibitor of protein kinases, had no effect on ATP-induced deactivation, suggesting that the effect was not due to a protein phosphorylation. Mg(2+) addition largely prevented the deactivation by ATP. Chemical crosslinking of the activated oxidase prevented the deactivation by dilution and ATP, suggesting that the deactivation is caused by dissociation of the oxidase complex. Estimation of actin filament (F-actin) showed that the F-actin level was markedly reduced by addition of ATP. The ATP effect on the deactivation was not prominent in a semi-recombinant system which does not contain cytosol. These results suggest that ATP-induced deactivation is largely due to the chelation of Mg(2+) and are consistent with the concept that Mg(2+) stabilizes the oxidase complex by stabilizing F-actin.

Actins↗

PubMed2001

Cerebroprotective action of a Na+/Ca2+ channel blocker NS-7. I. Effect on the cerebral infarction and edema at the acute stage of permanent middle cerebral artery occlusion in rats.

The effect of a novel Na+/Ca2+ channel blocker NS-7 [4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy)pyrimidine hydrochloride] on the cerebral infarction, edema and brain energy metabolism was investigated in rats after permanent middle cerebral artery occlusion (MCAO). The infarction and brain water content were evaluated at 48 h and 24 h after MCAO, respectively. A single bolus injection of NS-7 (0.03125-0.25 mg/kg) immediately after MCAO produced a dose-dependent reduction in the infarct volume as well as edema both in the cerebral cortex and striatum. Glycerol (4 g/kg) also decreased water content both in the occluded and non-occluded brain, but it did not reduce the size of cerebral infarction. Unlike glycerol, NS-7 did not change the water content in non-occluded brain. Moreover, a significant protective action was still observed even when NS-7 was injected once at 12 h after occlusion. In addition, NS-7 significantly reversed the decrease in tissue ATP content observed at 3 h but not at 0.5 h after MCAO. These findings suggest that a Na+/Ca2+ channel blocker NS-7 protects cerebral tissues against ischemic insults by improving the disturbance of cerebral energy metabolism and suppressing the cerebral edema.

Adenosine Diphosphate↗

PubMed2001

Cerebroprotective action of a Na+/Ca2+ channel blocker NS-7. II. Effect on the cerebral infarction, behavioral and cognitive impairments at the chronic stage of permanent middle cerebral artery occlusion in rats.

We have previously shown that NS-7 [4-(4-fluorophenyl)-2-methyl-6-(5-piperidinopentyloxy)pyrimidine hydrochloride] reduces the size of cerebral infarction measured by 2,3,5-triphenyltetrazolium chloride staining at 48 h after permanent middle cerebral artery occlusion (MCAO) in rats. To determine whether NS-7 improves the pathological and behavioral changes at the chronic stage of MCAO, the effect of this compound on the cerebral infarction as well as the neurological and cognitive impairments was investigated 7 days after MCAO. Single or five daily injections of NS-7 (0.125-0.5 mg/kg, i.v.) significantly reduced the infarct volume and improved the neuronal dysfunction including the hind leg paralysis, walking disability and motor incoordination, and the deficit of passive avoidance task, although the neuroprotective efficacy was not different among these dosing regimens. On the other hand, the effects of single versus repeated injections of NS-7 at 0.1 or 0.2 mg/kg on the neurological symptoms were compared at 4 weeks after MCAO. At a lower dose, repeated but not single injection of NS-7 significantly improved the neurological symptoms, although the single injection was effective at a higher dose. From these findings, it is suggested that NS-7 reverses the behavioral and cognitive dysfunction observed at the chronic stage of cerebral ischemia by suppressing the cerebral infarction.

Animals↗

PubMed2001

Microenvironment of endosomal aqueous phase investigated by the mobility of microparticles using fluorescence correlation spectroscopy.

Temporal observation of the dynamic behavior of molecules in cells gives information about the physiological environment at the region of interest. Here we report the direct measurement of the mobility of rhodamine-labeled microparticles (14 and 35 nm in diameter) ingested in endosomes of cultured bovine aortic endothelial cells using fluorescence correlation spectroscopy (FCS). The fluctuation of fluorescent signals from microparticles were measured by FCS. Obtained autocorrelation functions (FAFs) were analyzed by the 2-D multicomponent model according to an evaluation procedure we newly developed. It was found that microparticles moved freely in endosomes with average diffusion coefficients of 4.3 x 10(-8) and 2.7 x 10(-8) cm2 s(-1) for 14 and 35 nm, which were 45% slower than in water. This result implies that the endosomal aqueous phase is homogeneous with the viscosity about 2.2 times of water. Our study also proposes the new use of FCS for investigation of the internal space of organelles.

Animals↗

PubMed2001

Recognition of the Lck tyrosine kinase as a tumor antigen by cytotoxic T lymphocytes of cancer patients with distant metastases.

The Lck protein (p56(lck)), a src family tyrosine kinase that is essential for T cell development and function, is aberrantly expressed in metastatic colon cancers. p56(lck) seems to facilitate the malignant transformation of epithelial cells through initiation of anchorage-independent proliferation. We demonstrate that the lck gene encodes antigenic epitopes recognized by the HLA class I-restricted and tumor-specific CTL of metastatic cancer patients. Lck peptides augmented CTL activity in peripheral blood mononuclear cells (PBMC) of colon and other epithelial cancer patients with distant metastases, but not those without distant metastases. CTL precursors recognizing the Lck peptide were identified in freshly prepared PBMC of patients with distant metastases, and their frequency was significantly augmented by stimulation with the peptide. Thus, Lck peptides could be useful in developing a specific immunotherapy for cancer patients with distant metastases.

Antigens, Neoplasm↗

PubMed2001

Different forms of dizziness occurring after cochlear implant.

Dizziness after cochlear implant (CI) was studied in a series of 94 consecutive adult patients receiving a cochlear implant, 46 (49.0%) of whom experienced dizziness post-operatively. In 29 patients, post-operative dizziness occurred soon after surgery and subsided within one month. Dizziness of the continuous type, lasting more than 6 months, was a complaint in only two patients. In addition to these already known forms of dizziness, spells of vertigo occurring later than one month after cochlear implant were experienced by 15 patients (delayed-V). The spells of delayed-V occurred suddenly and persisted for several hours. Moreover, 85.7% of delayed-V patients complained of hearing and tinnitus abnormalities during these spells. The clinical features of delayed-V were similar to those in patients with Meniere's disease. The preoperative bithermal caloric test showed a significantly higher response for the delayed-V group than the other groups (ANOVA: P < 0.05) in terms of slow phase eye velocity of caloric nystagmus. These findings suggest that inner ear lesions due to cochlear implant surgery develop gradually. Similarities in clinical features between delayed-V and Ménière's disease indicate the presence of labyrinthine hydrops.

Adolescent↗

PubMed2001

Analysis of photochemical pollution in summer and winter using a photochemical box model in the center of Tokyo, Japan.

In order to give an effective and rapid analysis of the photochemical pollution and information for emission control strategies, a photochemical box model (PBM) was applied to one moderate summer episode, 11 July 1996, and one typical winter episode, 3 December 1996, in the center of Tokyo, Japan. The box model gave a good prediction of the photochemical pollution with minimal investment. As expected, the peak ozone in summer is higher than in winter. The NOx concentrations in winter are higher than those in summer. In summer, NO and NO2 have one peak in the morning. In winter, NO and NO2 show two peaks during the day. Three model runs including no reactions, a zero ozone boundary condition and dark reactions were conducted to understand the photochemical processes. The effects of emission reduction on the formation of the photochemical pollution in the center of Tokyo have been studied. The results show that the reduction of NMHC emission can decrease the ozone, however, the reduction of NOx emission can increase the ozone. It can be concluded that if the NOx emission are reduced, the reduction of NMHC should be more emphasized in order to decrease the ozone concentration in the center of Tokyo, Japan, especially the reduction of the NMHC from stationary source emission.

Air Pollution↗

PubMed2001

Circular polarisation in star-forming regions: possible implications for homochirality.

Our discovery of high degrees of circular polarisation in some star-forming regions provides an attractive mechanism for the origin of homochirality. The largest degrees of circular polarisation, so far observed at near-infrared wavelengths, are thought to arise from the scattering of stellar radiation from aligned dust grains and are calculated to extend down to UV wavelengths. The extent of the region where circularly polarised light (CPL) of a single handedness originates is very large, and it is likely that the whole of a planetary system would see a single handedness of CPL also. We present the observational data, models of the scattering that leads to the production of CPL, and a model for the origin of homochirality. We also discuss briefly future laboratory and space-based experiments.

Astronomical Phenomena↗

PubMed2001

Functional analyses of MeCP2 mutations associated with Rett syndrome using transient expression systems.

Rett syndrome, an X-linked neurodevelopmental disorder, is a major cause of mental retardation in females. Recent genetic analyses have revealed that mutations in the methyl-CpG-binding protein gene encoding MeCP2 are associated with Rett syndrome. In this study, we used transient expression systems to investigate the functional significance of mutations seen in patients with Rett syndrome. Missense mutations in the methyl-CpG-binding domain were analyzed by the transfection in mouse L929 cells and Drosophila SL2 cells. The L929 cells were utilized to investigate the effects of mutations on the affinity for heterochromatin, where methylated CpG dinucleotides are extremely enriched. The SL2 cells were utilized to analyze their effects on transcriptional repression activities. R106W and F155S mutations led to the substantial impairment of MeCP2 functions, showing the loss of accumulation of the mutated protein to mouse heterochromatin and the reduction of the transcriptional repressive activity in Drosophila SL2 cells. Intriguingly, the R133C mutant retained the functionality equivalent to MeCP2 in these analyses. On the other hand, the T158M mutation exhibited the intermediate level of the impairment of functions in both analyses. Thus, these functional assays are useful to evaluate the consequences of mutation in the methyl-CpG-binding domain of MeCP2 and provide an insight into the relationship between the genotype and the severity of Rett syndrome.

Animals↗

PubMed2001

An increase of mature type skin collagen cross-link, histidinohydroxylysinonorleucine, in the sclerotic skin of morphea.

Histidinohydroxylysinonorleucine (HHL) is a trivalent cross-link of type I collagen that is stable and has physiologic properties. In this study, we conducted a biochemical quantification of HHL in five patients with morphea. We compared the quantity of HHL contained in the lesional skin and the adjacent normal skin. The molar ratio of HHL to collagen in the sclerotic lesion was significantly higher than that of the adjacent normal skin (0.36 +/- 0.09 vs. 0.28 +/- 0.10, P<0.01). We could find no relationship between an increase of HHL content and the duration of the disease. The results indicate that an increased amount of HHL may play a certain role to inducing the sclerotic skin change characteristic of morphea.

Adult↗

PubMed2001

Pod-1/Capsulin shows a sex- and stage-dependent expression pattern in the mouse gonad development and represses expression of Ad4BP/SF-1.

Mammalian sex-determination and differentiation are controlled by several genes, such as Sry, Sox-9, Dax-1 and Mullerian inhibiting substance (MIS), but their upstream and downstream genes are largely unknown. Ad4BP/SF-1, encoding a zinc finger transcription factor, plays important roles in gonadogenesis. Disruption of this gene caused disappearance of the urogenital system including the gonad. Ad4BP/SF-1, however, is also involved in the sex differentiation of the gonad at later stages, such as the regulation of steroid hormones and MIS. Pod-1/Capsulin, a member of basic helix-loop-helix transcription factors, is expressed in a pattern closely related but mostly complimentary to that of the Ad4BP/SF-1 expression in the developing gonad. In the co-transfection experiment using cultured cells, overexpression of Pod-1/Capsulin repressed expression of a reporter gene that carried the upstream regulatory region of the Ad4BP/SF-1 gene. Furthermore, forced expression of Pod-1/Capsulin repressed expression of Ad4BP/SF-1 in the Leydig cell-derived I-10 cells. These results suggest that Pod-1/Capsulin may play important roles in the development and sex differentiation of the mammalian gonad via transcriptional regulation of Ad4BP/SF-1.

Animals↗

PubMed2001

Role of aromatase in endometrial disease.

Aromatase is the key enzyme for estrogen biosynthesis. It is normally expressed in the human ovary, skin, adipose tissue and brain. Aromatase activity is not detectable in normal endometrium. In contrast, aromatase is expressed aberrantly in endometriosis and is stimulated by PGE2. This results in local production of estrogen, which induces PGE2 formation and establishes a positive feedback cycle. Another abnormality in endometriosis, i.e. deficient 17beta-hydroxysteroid dehydrogenase (17beta-HSD) type 2 expression, impairs the inactivation of estradiol to estrone. These molecular aberrations collectively favor accumulation of increasing quantities of estradiol and PGE2 in endometriosis. The clinical relevance of these findings was exemplified by the successful treatment of an unusually aggressive case of post-menopausal endometriosis using an aromatase inhibitor.

Aromatase↗

PubMed2001

Development of a minimally immunogenic variant of humanized anti-carcinoma monoclonal antibody CC49.

Monoclonal antibody (MAb) CC49 reacts with a pancarcinoma antigen, tumor associated glycoprotein (TAG)-72. To circumvent human anti-murine antibody (HAMA) responses in patients, we earlier developed a humanized CC49 (HuCC49) by grafting the complementarity-determining regions (CDRs) of MAb CC49 onto variable light (VL) and variable heavy (VH) frameworks of the human MAbs LEN and 21/28'CL, respectively. With the aim of minimizing its immunogenicity further, we have now generated a variant HuCC49 MAb by grafting the specificity-determining residues (SDRs) of MAb CC49 onto the frameworks of the human MAbs. Based on the evaluation of its binding affinity for TAG-72 and its reactivity with anti-idiotypic antibodies present in sera from patients who have been treated with murine CC49, this variant retains its antigen-binding activity and shows minimal reactivity with anti-idiotypic antibodies in patients' sera. Development of this variant, which is a potentially useful clinical reagent for diagnosis and therapy of human carcinomas, demonstrates that for humanization of a xenogeneic antibody grafting of the potential SDRs should be sufficient to retain its antigen-binding properties.

Animals↗

PubMed2001

A comparison of tissue Doppler imaging and velocities of transmitral flow in children with elevated left ventricular preload.

Compared with transmitral velocities of flow, myocardial wall velocities obtained by tissue Doppler imaging are less influenced by left atrial pressure. The data supporting this assumption, however, are limited in patients with congenital cardiac disease. The aim of this study was to compare the effects of left ventricular preload on transmitral inflow and velocities assessed by tissue Doppler imaging. Tissue Doppler imaging, and conventional Doppler echocardiography with simultaneous invasive hemodynamic studies, were performed in 33 patients with a simple ventricular septal defect or patency of the arterial duct. Transmitral velocities (E, A) and mitral annular velocities (Ea, Aa) were measured, permitting calculation of the ratio of E to Ea. The ratio of pulmonary to systemic flows, and mean left atrial pressure, were also measured. In 10 of 33 patients, echocardiographic and hemodynamic studies were performed 4 to 5 months after surgery. The E and A values in the patients were greater than those in the controls (p < 0.01). In contrast, neither Ea nor Aa differed between the two group. The ratio of E to Ea in the patients increased significantly compared with that in the controls (8.9+/-2.1 vs 7.3+/-1.3, p < 0.01). The E value was directly related to mean left atrial pressure and the ratio of pulmonary to systemic flows. The velocities measured by Tissue Doppler imaging, however, had no significant relationship to either of these measurements. The ratio of E to Ea correlated well with mean left atrial pressure (r = 0.75, p < 0.01). In 10 post-operative patients, the values for E and A decreased from 119+/-14 to 89+/-10 cm/sec (p < 0.01) and from 91+/-22 to 61+/-9 cm/sec (p < 0.01), respectively. No significant changes were noted in the values of Ea and Aa. The ratio of E to Ea, and mean left atrial pressure, decreased from 10.3+/-1.9 to 8.2+/-1.5 (p < 0.01) and from 11.0+/-1.8 to 7.4+/-1.0 mmHg (p < 0.01), respectively. The percentage change in left atrial pressure correlated with the percent change in the ratio of E to Ea (r = 0.64, p < 0.05). The present study showed that the velocities obtained with tissue Doppler imaging are less dependent on mean left atrial pressure in children with elevated left ventricular preload caused by a left-to-right shunt.

Blood Flow Velocity↗

PubMed2001

Abnormal venous structures in salivary gland tumors: vasculature characteristics of pleomorphic adenoma.

To clarify the diagnostic significance of abnormal venous structures present in salivary gland tumors, we examined 21 pleomorphic adenomas, 14 Warthin tumors, 1 oncocytic adenoma, 3 myoepitheliomas, 7 basal cell adenomas, 5 mucoepidermoid carcinomas, and 6 adenoid cystic carcinomas. Verhoeffvan Gieson staining was carried out and the morphology of the veins within the tumors was observed microscopically. Branching veins, thickened intima of the veins, discontinuous elastic membrane and multilayered elastic membrane were seen in 71.4%, 76.2%, 47.6% and 85.7% of pleomorphic adenomas, respectively, and were abundant and easily found in most cases. The abnormal venous structures were also found in other salivary gland tumors examined, but they were few in number and lacked variety. Elastic fibers extending radially into the surrounding stroma were seen in 66.7% of pleomorphic adenomas, and were not seen in other salivary gland tumors. Our results showed that a variety of abnormal venous structures are more abundant and more easily found in pleomorphic adenoma compared with other salivary gland tumors, and, in particular, that perivascular radiating elastic fibers are characteristic of pleomorphic adenoma. We emphasize that the presence of perivascular radiating elastic fibers may be helpful in diagnosing pleomorphic adenoma in small biopsy specimens.

Adenoma, Pleomorphic↗