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Biomedical subjects

K Takagi

Publications and source records attributed to K Takagi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Structure of a quinohemoprotein amine dehydrogenase with an uncommon redox cofactor and highly unusual crosslinking.

The crystal structure of the heterotrimeric quinohemoprotein amine dehydrogenase from Paracoccus denitrificans has been determined at 2.05-A resolution. Within an 82-residue subunit is contained an unusual redox cofactor, cysteine tryptophylquinone (CTQ), consisting of an orthoquinone-modified tryptophan side chain covalently linked to a nearby cysteine side chain. The subunit is surrounded on three sides by a 489-residue, four-domain subunit that includes a diheme cytochrome c. Both subunits sit on the surface of a third subunit, a 337-residue seven-bladed beta-propeller that forms part of the enzyme active site. The small catalytic subunit is internally crosslinked by three highly unusual covalent cysteine to aspartic or glutamic acid thioether linkages in addition to the cofactor crossbridge. The catalytic function of the enzyme as well as the biosynthesis of the unusual catalytic subunit is discussed.

Amino Acid Sequence↗
PubMed2001

Bifurcation of osteoclasts and dendritic cells from common progenitors.

Osteoclasts and dendritic cells are derived from monocyte/macrophage precursor cells; however, how their lineage commitment is regulated is unknown. This study investigated the differentiation pathways of osteoclasts and dendritic cells from common precursor cells at the single-cell level. Osteoclastogenesis induced by macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-kappaB ligand (RANKL) or tumor necrosis factor-alpha (TNF-alpha) is completely inhibited by addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 at early stages of differentiation. GM-CSF-treated cells express both c-Fms and RANK and also low levels of CD11c and DEC205, which are detected on dendritic cells. Addition of GM-CSF also reduces expression of both c-Fos and Fra-1, which is an important event for inhibition of osteoclastogenesis. Overexpression of c-Fos by retroviral infection or induction in transgenic mice can rescue a failure in osteoclast differentiation even in the presence of GM-CSF. By contrast, differentiation into dendritic cells is inhibited by M-CSF, indicating that M-CSF and GM-CSF reciprocally regulate the differentiation of both lineages. Dendritic cell maturation is also inhibited when c-Fos is expressed at an early stage of differentiation. Taken together, these findings suggest that c-Fos is a key mediator of the lineage commitment between osteoclasts and dendritic cells. The lineage determination of osteoclast progenitors seen following GM-CSF treatment functions through the regulation of c-Fos expression.

Animals↗
PubMed2001

Adrenomedullin and proadrenomedullin N-terminal 20 peptide induce histamine release from rat peritoneal mast cell.

Adrenomedullin (ADM)-induced histamine release from rat peritoneal mast cells was investigated. We compared the ability of full-length ADM to induce histamine release to the fragments ADM-(1-25) and ADM-(22-52), as well as proadrenomedullin N-terminal 20 peptide (PAMP). ADM (10(-8) to 10(-5) M) and PAMP (10(-8) to 10(-5) M) dose-dependently increased histamine release from peritoneal mast cell preparations. The effect of ADM-(1-25) was similar to ADM, whereas ADM-(22-52) did not show any effects. These data suggest the relative importance of the ADM C-terminal fragment, which contains a six-membered ring structure. Histamine release, induced by ADM, was significantly and dose-dependently inhibited by the addition of ADM-(22-52) (10(-5) M), Ca(2+) (0.5 to 2.0 mM), and benzalkonium chloride (3 to 7 microM), a selective inhibitor of Gi type G proteins. In contrast, PAMP (10(-5) M)-induced histamine release was not inhibited by Ca(2+). These results suggest that ADM induce histamine release via a putative ADM receptor in a manner sensitive to Gi-protein function and extracellular Ca(2+) concentration, and that PAMP might produce its effect by a different mechanism than ADM.

Adrenomedullin↗
PubMed2001

Activated astrocytes with glycogen accumulation in ischemic penumbra during the early stage of brain infarction: immunohistochemical and electron microscopic studies.

Brain infarction was induced in rats by injection of microspheres through the right internal carotid artery, and structural changes in the astrocytes were observed during the early period following the infarction. Necrotic foci, varying in size and shape, were found in the right hemisphere. After immunohistochemical staining for GFAP, GFAP-positive astrocytes in the perinecrotic area known as the ischemic penumbra had distinctly increased in number and size with elongation of cytoplasmic processes 3 days after infarction. Electron microscopic observation revealed that glycogen granules had markedly accumulated in the cytoplasm of astrocytes located in the ischemic penumbra 3 and 5 days after infarction. Seven days after infarction, however, the glycogen granules disappeared from the astrocytes. Intermediate filaments increasingly appeared in the protoplasmic astrocytes after 3 days and were abundant in the activated and hypertrophied astrocytes after 7 days. As a result of our present study, we conclude that: (1) the function of glucose uptake from blood vessels was not impaired in the astrocytes under hypoxic conditions; (2) the astrocytes actively ingested blood glucose through the endothelial cells and accumulated it as glycogen for activation of their functions, and the cell volume increased under hypoxic conditions; (3) the depression of energy metabolism and the decrease in the uptake of energy sources in the nerve cells promoted glycogen accumulation in the astrocytes under hypoxic conditions; (4) intermediate filaments (GFAP filaments) increased in number, coincident with the activation and enlargement of the astrocytes; and (5) protoplasmic astrocytes were transformed into fibrous astrocytes in the ischemic penumbra of the brain infarction.

Animals↗
PubMed2001

Ca(2+) stabilizes the semiquinone radical of pyrroloquinoline quinone.

Spectroelectrochemical studies were performed on the interaction between Ca(2+) and pyrroloquinoline quinone (PQQ) in soluble glucose dehydrogenase (sGDH) and in the free state by applying a mediated continuous-flow column electrolytic spectroelectrochemical technique. The enzyme forms used were holo-sGDH (the holo-form of sGDH from Acinetobacter calcoaceticus) and an incompletely reconstituted form of this, holo-X, in which the PQQ-activating Ca(2+) is lacking. The spectroelectrochemical and ESR data clearly demonstrated the generation of the semiquinone radical of PQQ in holo-sGDH and in the free state in the presence of Ca(2+). In contrast, in the absence of Ca(2+) no semiquinone was observed, either for PQQ in the free state (at pH 7.0) or in the enzyme (holo-X). Incorporation of Ca(2+) into the active site of holo-X, yielding holo-sGDH, caused not only stabilization of the semiquinone form of PQQ but also a negative shift (of 26.5 mV) of the two-electron redox potential, indicating that the effect of Ca(2+) is stronger on the oxidized than on the reduced PQQ. Combining these data with the observations on the kinetic and chemical mechanisms, it was concluded that the strong stimulating effect of Ca(2+) on the activity of sGDH can be attributed to facilitation of certain kinetic steps, and not to improvement of the thermodynamics of substrate oxidation. The consequences of this conclusion are discussed for the oxidative as well as for the reductive part of the reaction of sGDH.

Acinetobacter calcoaceticus↗
PubMed2001

Decreasing of p27(Kip1)and cyclin E protein levels is associated with progression from superficial into invasive bladder cancer.

The p27(Kip1)(p27) protein is a cyclin-dependent kinase inhibitor of the transition from G1 to S phase. It has been reported that decreased p27 protein level is a negative prognostic indicator in human tumours including bladder cancer. We studied the relationship between protein levels of p27, cyclin E and Ki-67 and clinicopathological features of 145 consecutive Japanese patients with transitional cell carcinoma of the bladder using immunohistochemical staining. Low protein levels of p27 were associated with low staining of cyclin E (P = 0.0302), high Ki-67 index (P = 0.0306), poorly differentiated grade (P = 0.0006), muscle invasion (P = 0.0019) and lymph node metastsis (P = 0.0002). Low staining of cyclin E and high Ki-67 index correlated with poorly differentiated grade, muscle invasion and lymph node metastsis. Cyclin E protein levels was inversely related with Ki-67 index (P = 0.0002). Kaplan-Meier plots of survival rate in patients with low versus high p27 staining showed that low protein levels of p27 were associated with a shortened disease-free and overall survival (P< 0.0001 and P< 0.0001, respectively). Similarly, low staining of cyclin E and high Ki-67 index correlated with a shortened disease-free and overall survival. On multivariate analysis using Cox proportional hazards model, low protein levels of p27 and high Ki-67 index were independent predictors of shortened disease-free (P< 0.0001, P = 0.0031, respectively), and low protein levels of p27, low staining of cyclin E and high Ki-67 index of overall survival (P = 0.0017, P = 0.0009, P = 0.0003, respectively). In superficial bladder tumours (Ta, T1; 86 patients), significant correlations were observed between low p27 staining and high Ki-67 index and early recurrence (P = 0.0048, P = 0.0178, respectively). Among the recurrenced superficial tumours (35 patients), the tumours which remained at a low stage showed high protein levels of p27 and cyclin E, and the tumours which progressed to invasive disease showed a gradual decrease in p27 and cyclin E protein levels over time. Our findings suggest that decreased protein levels of p27 and cyclin E play a role in the progression of bladder cancer and to evaluate these protein levels may be useful in management of the diseases.

Aged↗
PubMed2001

Measurement of liquid surface properties by laser-induced surface deformation spectroscopy.

We developed a technique of picking up the liquid surface in a noncontact manner by a cw-laser radiation. The momentum change of light at the laser transmission through the air-liquid interface appears as the radiation pressure, which deforms the liquid surface into the shape determined by the balance between the Laplace force of the curved surface and the radiation pressure. The displacement of the liquid surface is inversely proportional to the surface tension, which was measured by an optical probe. The dynamic response of the liquid surface deformation was theoretically derived under the periodical modulation of the radiation pressure. The experimentally observed spectra were in good agreement with the theory giving the dynamic properties of the liquid surface. The technique of the laser induced surface deformation has potential as a measurement tool of the surface dynamic properties, such as the time-dependent surface tension and surface viscoelasticity.

Journal Article↗
PubMed2001

Abnormal nucleotide repeat sequence in the TGF-betaRII gene in hepatocellular carcinoma and in uninvolved liver tissue.

Replication error (RER)-related genetic alterations are associated with a subset of hepatocellular carcinomas (HCCs) with multiple primary cancers. This study investigated whether mutations in the nucleotide repeats of three putative target genes of RER are associated with hepatocarcinogenesis. The genes examined were those encoding transforming growth factor beta type II receptor (TGF-betaRII), BCL-2-associated X protein (BAX), and insulin-like growth factor II receptor (IGF-IIR). Tumour and non-tumour hepatic tissues were examined in 48 HCC patients, 34 with solitary HCC and 14 who had double cancer with gastric cancer. Four double-cancer cases showed an abnormal signal in the single nucleotide repeat (A)10 of the TGF-betaRII gene. These four were among the six RER-positive cases in this series. The genotypes of the poly A tract of the TGF-betaRII gene in the liver tumour tissue of the four cases with an abnormal signal were (A)9/10, (A)9/10, (A)9/10, and (A)9/9. Five uninvolved liver tissue specimens from these four patients showed (A)9/10 and (A)9/9, (A)9/10, (A)10/10 and (A)9/9, respectively. The genotype in the stomach cancer specimens of these four patients was (A)10/10, indicating no germline mutation of the TGF-betaRII gene. There were no mutations in the nucleotide repeats of the BAX and IGF-IIR genes in any of the liver tissue specimens. Abnormality of the nucleotide repeat in the TGF-betaRII gene occurred in the uninvolved liver tissue as well as the HCC tissue in some HCC patients. Such genetic instability may be gene-specific and tissue-specific in carcinogenesis.

Carcinoma, Hepatocellular↗
PubMed2001

Increased ischemia-reperfusion blood flow impairs the skeletal muscle contractile function.

BACKGROUND: The ultimate aim of replantations and transplantations of skeletal muscle is to improve impaired function. The purpose of this study was to examine the contribution of varying durations of ischemia to postischemic blood flow in the skeletal muscle and the contribution of modulation of postischemic blood flow to skeletal muscle function and viability, using an ischemic revascularized hind limb model in rats. MATERIALS AND METHODS: Warm ischemia produced by vascular pedicle clamping was sustained for 90 min, 3 h, or 6 h. Postischemic blood flow was measured by a Doppler flowmeter or microsphere technique. In another series of experiments of 3-h ischemia, either saline or N(G)-methyl-l-arginine acetate (l-NMMA) was infused for the first 2 h of reperfusion. Postischemic blood flow was also measured. Muscle contractile function and viability were determined after 24 h of reperfusion. RESULTS: Postischemic blood flow was significantly increased during the first 10 min of reperfusion in the 90-minute ischemic group and during the first 2 h in the 3-h ischemic group compared with contralateral control blood flow. No significant increase in postischemic blood flow was noted in the 6-h ischemic group. Postischemic blood flow was significantly decreased by the l-NMMA infusion. Contractile function and viability of the tibialis anterior muscle and contractile function of the gastrocnemius muscle in the l-NMMA group were significantly increased. CONCLUSION: Reperfusion blood flow increased time dependently until 3 h of warm ischemia. Hyperemia deteriorated skeletal muscle contractile function, although it was well preserved by l-NMMA infusion to restrict the postischemic hyperemia.

Animals↗
PubMed2001

Effect of perfusion during ischemia on skeletal muscle.

BACKGROUND: Despite the established preservation method for major organs of perfusion followed by immersion at hypothermia, a standard preservation technique for skeletal muscle is still a matter of controversy. The purpose of this study is to examine the effect of perfusion on the preservation of skeletal muscle in amputated limbs. MATERIALS AND METHOD: The rat hindlimb was amputated for perfusion with Euro-Collins (EC) or University of Wisconsin (UW) solution at different perfusion pressures (40 or 100 cm-gravity). After certain ischemic periods (4 or 5 h), the skeletal muscle viability was determined by measuring the tissue content of adenosine triphosphate (ATP). RESULT: The UW solution perfusion group maintained better ATP levels than the EC solution group when the ischemic period was extended to 5 h. The perfusion pressure of 100 cm-gravity was more effective for preserving muscle viability than 40 cm-gravity with both EC and UW solutions. CONCLUSION: UW solution might be adequate to preserve muscle viability and perfusion pressure is recommended at 100 cm-gravity rather than at minimal pressure (40 cm-gravity), which washes out stagnant blood.

Adenosine↗
PubMed2001

Effects of a novel, selective, sigma1-ligand, MS-377, on phencyclidine-induced behaviour.

Phencyclidine (PCP)-induced head-weaving is inhibited by a novel selective sigma1-ligand, (R)-(+)-1-(4-chlorophenyl)-3-[4-(2-methoxyethyl)piperazin-1-yl]methyl-2-pyrrolidinone L-tartrate (MS-377), but not by dopamine D2 antagonists. In the present study, we examined the effects of two potent and selective sigma1-ligands, MS-377 and N,N-dipropyl-2-(4-methoxy-3-(2-phenylethoxy)phenyl) ethylamine (NE-100), on PCP-induced rearing behaviour, hyperlocomotion and ataxia in comparison with the currently available antipsychotic agents with affinity for D2 receptors, haloperidol, sultopride and risperidone. Male Wistar rats or ddY mice were administered MS-377, NE-100, haloperidol, sultopride or risperidone, and PCP was administered 60 min later (in the case of NE-100 10 min later). Rearing behaviour, hyperlocomotion and ataxia were examined 10 min after PCP administration. MS-377, haloperidol, sultopride and risperidone dose-dependently inhibited PCP-induced rearing and hyperlocomotion, but did not antagonize PCP-induced ataxia. In contrast, the other selective sigma1-ligand, NE-100, did not affect any of the PCP-induced behaviour patterns in this study. These results suggest that there are at least two types of ligands for sigma1-receptors and that some sigma1-ligands, including MS-377, have more comprehensive effects against PCP-induced abnormal behaviour than other sigma1-ligands or D2 antagonists.

Animals↗
PubMed2001

Identification of receptor-binding sites of monocyte chemotactic S19 ribosomal protein dimer.

The S19 ribosomal protein (RP S19) cross-linked homo-dimer attracts monocyte migration by binding to C5a receptor on monocytes (H Nishiura, Y Shibuya, T Yamamoto, Laboratory Investigation, 1998, 78:1615-1623). Using site-directed mutants of recombinant RP S19 and synthetic peptides mimicking RP S19 molecular regions, we currently identified the binding sites of the RP S19 dimer to the C5a receptor. The RP S19 dimer activated the receptor by a two-step binding mechanism as in the case of C5a. The first binding site was a basic cluster region containing a -Lys41-His42-Lys43- sequence. The second one was the -Leu131-Asp132-Arg133- moiety, localized 12 residues upstream from the COOH-terminal. The second binding triggered the chemotactic response. The first binding would have a role in achieving a high-binding affinity between the ligand and receptor. The first and second ligand-binding sites of C5a receptor seem to be shared by C5a and the RP S19 dimer, although overall homology between the amino acid sequences of these ligands is only 4%.

Amino Acid Sequence↗
PubMed2001

Incident-angle dependence of the phase conjugate reflectivity by nonlinear piezoelectric interaction in PZT ceramics.

The reflectivity of an acoustic phase conjugator by nonlinear piezoelectric interaction in PZT ceramics was measured as a function of the incident angle. The phase conjugator was designed as a solid block with a flat surface for the acoustic incidence from water. The phase conjugate reflectivity showed incident angle dependence, which is mainly determined by the transmissivity of the acoustic waves, together with some effects of anisotropy. The field-reconstructing ability of this phase conjugator was simulated for focused incident beams.

Acoustics↗
PubMed2001

Physician's attitudes towards disclosure of cancer diagnosis to elderly patients: a report from Tokyo, Japan.

Physicians' attitudes towards the disclosure of a cancer diagnosis to 114 consecutive patients (age range, 65-93 years; median 78 years) admitted to the Tokyo Metropolitan Tama Geriatric Hospital from April 1994 to May 1995 were analyzed utilizing a questionnaire administered to the attending physicians. Eighty-seven patients (76%) had been informed of their diagnosis before the initiation of cancer treatment, while 27 patients (24%) were not told. 'To carry out the treatment under patient's understanding' and 'consideration for patient's quality of life' were the major reasons for diagnosis disclosure, while 'lack of patient's ability to understand the information' and 'family's wish that the patient not be informed of the truth' were the major reasons for non-disclosure. Dementia, deteriorated performance status, and non-curability were major factors related to non-disclosure. Even with decisional ability, 15% of patients were not told their cancer diagnosis because wishes of their families were preferred. The current results suggest that telling cancer diagnosis to the elderly patients will not yield negative attitude of the patients and that there is no rationale for physicians to hesitate to disclose cancer diagnosis merely because of patient's high age.

Journal Article↗
PubMed2001

Surgical approach to pleural diffuse mesothelioma in Japan.

The current status of the surgical treatment of patients with pleural diffuse mesothelioma in Japan was surveyed from the results of a questionnaire sent to members of The Japanese Association for Chest Surgery. Physicians at 57 institutions returned the questionnaire, and a total of 189 surgical cases of diffuse mesothelioma between 1987 and 1996 were analyzed. The age of the patients ranged between 18 and 80 years. They consisted of 154 males and 33 females (the gender of two patients was not indicated). By histological type, 104 cases had the epithelial type, 29 cases had the sarcomatous type, and 46 cases had the mixed type of diffuse mesothelioma (the histology of 10 patients was not indicated). As to the type of surgery, pleuropneumonectomy was performed in 116 cases (61%), and limited resection [including decortication (5 cases) and tumorectomy (68 cases)] was performed in 73 cases (39%). The goal of pleuropneumonectomy is radical resection of the tumor, which often requires combined resection of adjacent structures. The tumor was completely removed macroscopically in 84 (72%) of the 116 cases who underwent pleuropneumonectomy; however, among those with an epithelial-type tumor that was completely removed by pleuropneumonectomy, the tumor recurred postoperatively in 43% of these patients. Perioperative adjuvant therapy was performed in 83 of the 116 patients who underwent pleuropneumonectomy. The 2-year and 5-year survival rates of those who had undergone pleuropneumonectomy were 29.7 and 9.1%, respectively, and the perioperative mortality rate of this procedure was 6%. Limited resection, on the other hand, did not involve radical resection of the tumor. The 2-year and 5-year survival rates of the patients who had undergone limited resection were 26.1 and 9.5%, respectively, and the perioperative mortality rate was 6%. The survival rates and perioperative mortality rate of the patients who had undergone pleuropneumonectomy or limited resection did not significantly differ. The prognostic factors for survival included gender (P=0.0019) and adjuvant therapy (P=0.0034) by Cox's Regression Analysis. The goals of surgical treatment of pleural diffuse mesothelioma are relief of symptoms and prolongation of survival time. Selecting the appropriate surgical procedure and more effective adjuvant therapy for each particular case is necessary under a new, accurate staging system for diffuse mesothelioma.

Adolescent↗
PubMed2001

Proteasome inhibitor enhances growth hormone-binding protein release.

We used murine Ba/F3 cells transfected with human growth hormone receptor (hGHR) cDNA to investigate the regulatory mechanisms of human growth hormone-binding protein (hGH-BP) release. The extracellular domain of hGHRs were cleaved and released as hGH-BPs (a soluble form of hGHR). The hGH-BP release was enhanced by phorbol 12,13-dibutyrate (PDBu), and suggested to be mediated by activation of PKC, the same as in human IM-9 cells. Thus, Ba/F3 cells have hGH-BP-releasing pathways similar to those of human cells. The proteasome inhibitors MG-132 and clasto-lactacystin beta-lactone also increased hGH-BP release from Ba/F3-hGHR cells, and MG-132 and PDBu synergistically increased hGH-BP release. The results obtained by using three PKC inhibitors Gö 6976, GF 109203X and Gö 6983 suggest that the enhancement of hGH-BP release by MG-132 and PDBu is mediated by different mechanisms probably involving different PKC isozymes.

Animals↗