Biomedical subjects

K Nagata

Publications and source records attributed to K Nagata.

At least 91 records · Page 5Linked to original sources

PubMed2001

Biphasic changes in left ventricular end-diastolic pressure during dynamic exercise in patients with nonobstructive hypertrophic cardiomyopathy.

OBJECTIVES: The aim of this study was to clarify the serial changes in left ventricular (LV) end-diastolic pressure (LVEDP) during dynamic exercise in patients with hypertrophic cardiomyopathy (HCM). BACKGROUND: Although HCM is characterized by impaired resting LV diastolic function, serial changes in LVEDP during exercise have not been characterized. METHODS: We simultaneously measured LV pressure and LV dimensions during symptom-limited supine bicycle exercise in 5 healthy individuals and 20 patients with HCM. Exercise thallium-201 scintigraphic studies were also performed. RESULTS: The LVEDP (baseline: 12 +/- 5 mm Hg) progressively increased to a maximum value at peak exercise (28 +/- 8 mm Hg) in 11 patients with HCM (group I). In the remaining nine patients with HCM (group II), changes in LVEDP during exercise were biphasic, with an initial progressive increase and a subsequent gradual decline up to peak exercise (14 +/- 4 mm Hg at baseline, 27 +/- 5 mm Hg at the critical heart rate, 16 +/- 3 mm Hg at peak exercise). Exercise-induced changes in LV dimensions and LV peak systolic pressures were similar in both groups. However, the maximum first derivative of LV pressure was greater and the LV pressure half-time was shorter in group II than in group I at a similar peak exercise heart rate. The biphasic changes in LVEDP disappeared by pretreatment with propranolol. The LV hypertrophy scores were higher in group I than in group II. Exercise thallium-201 images showed more severe perfusion defects in group I than in group II patients. CONCLUSIONS: The biphasic changes in LVEDP seen during exercise may be related to improved coronary microcirculation in response to beta-adrenergic stimulation in patients with mild to moderate HCM.

Adult↗

PubMed2001

Activated brain regions in musicians during an ensemble: a PET study.

As in visual processing, we speculated that, in music processing, different brain regions would activate according to the mode of music listening. Using motets by a famous composer, we studied changes in regional cerebral blood flow (rCBF) with positron emission tomography associated with concentrating on the alto-part within the harmony (alto-part-listening condition) compared to listening to the harmony as a whole (harmony-listening condition). The alto-part-listening condition was associated with bilateral increases of rCBF in superior parietal lobules, precunei, premotor areas and orbital frontal cortices. Superior parietal lobules are likely to be responsible for auditory selective attention to the alto part within the harmony and the analysis of tone pitch on a mental score. The precuneus possibly participated in writing tones of the alto part on a mental score. Based on our findings, we propose that both auditory selective attention and analytic processing play an important role in concentrating on a certain vocal part within a harmony. During the harmony-listening condition, temporal poles, the anterior portion of the cingulate gyrus, occipital cortex and the medial surface of the cerebellum were bilaterally activated. Further studies are necessary to clarify the difference in music processing between musicians and nonmusicians.

Adult↗

PubMed2001

2-Alkynyl-8-aryladenines possessing an amide moiety: their synthesis and structure-activity relationships of effects on hepatic glucose production induced via agonism of the A(2B) adenosine receptor.

A series of 2-alkynyl-8-aryladenine derivatives bearing an amide moiety at the 9-position of adenine was synthesized. These analogues were evaluated for inhibitory activity on N-ethylcarboxamidoadenosine (NECA)-induced glucose production in primary cultured rat hepatocytes. The m-primary benzamide derivative 15f was the most potent compound (IC(50)=0.017 microM), being 15-fold more active than the corresponding 9-methyl derivative (1). Compound 15f showed 72- and 5.2-fold selectivity for human A(2B) receptor versus human A(1) and A(2A) receptors, respectively. Structure-activity relationship (SAR) studies of the synthesized compounds indicated that a three-carbon linker, fixed in the form of a benzene ring, between the adenine core and the amide moiety is important for both A(2B) antagonistic activity and selectivity. The IC(50) values in rat hepatocyte glucose assay correlated well with the IC(50) values in cAMP assay using Chinese hamster ovary cells stably transfected with human A(2B) receptors (r(2)=0.94). The A(1) and A(2A) affinities showed no correlation with the potency to inhibit NECA-induced glucose production. These results strongly support our previous conclusion that adenosine agonist-induced hepatic glucose production in rat hepatocytes is mediated through the A(2B) receptor.

Adenine↗

PubMed2001

A novel surface molecule of Th2- and Tc2-type cells, CRTH2 expression on human peripheral and decidual CD4+ and CD8+ T cells during the early stage of pregnancy.

It has been demonstrated that pregnancy induces the immunomodulation of cytokine responses away from the Th1 paradigm and towards the Th2 paradigm. In this study, we examined the expression of CRTH2 (chemoattractant receptor-homologous molecule expressed on Th2) on decidual CD4+ and CD8+ T cells during the early stages of pregnancy. Examination of the cytokine profile revealed that CRTH2 was expressed on CD4+-type-2 T helper (Th2-type) and CD8+-type 2 T cytotoxic (Tc2-type) cells. The percentages of CRTH2+ cells in CD3+/CD4+ T cells and CD3+/CD8+ T cells were significantly higher in the decidua than in the peripheral blood. These results indicate the significance of Th2- and Tc2-type cells of the decidua in the maternal immune system, presumably through their production of cytokines which may contribute to the maintenance of pregnancy.

Adult↗

PubMed2001

A decade of site- and phosphorylation state-specific antibodies: recent advances in studies of spatiotemporal protein phosphorylation.

From 1990 to 2001, numerous site- and phosphorylation state-specific antibodies have been developed and many are now commercially available. These antibodies have facilitated understanding of the cytoskeletal organization, signal transduction and transcriptional mechanisms as well as clinical diseases. This review is an attempt to cover all these aspects.

Animals↗

PubMed2001

Coordination structures of Ca2+ and Mg2+ in Akazara scallop troponin C in solution. FTIR spectroscopy of side-chain COO- groups.

FTIR spectroscopy has been applied to study the coordination structures of Mg2+ and Ca2+ ions bound in Akazara scallop troponin C (TnC), which contains only a single Ca2+ binding site. The region of the COO- antisymmetric stretch provides information about the coordination modes of COO- groups to the metal ions: bidentate, unidentate, or pseudo-bridging. Two bands were observed at 1584 and 1567 cm-1 in the apo state, whereas additional bands were observed at 1543 and 1601 cm-1 in the Ca2+-bound and Mg2+-bound states, respectively. The intensity of the band at 1567 cm-1 in the Mg2+-bound state was identical to that in the apo state. Therefore, the side-chain COO- group of Glu142 at the 12th position in the Ca2+-binding site coordinates to Ca2+ in the bidentate mode but does not interact with Mg2+ directly. A slight upshift of COO- antisymmetric stretch due to Asp side-chains was also observed upon Mg2+ and Ca2+ binding. This indicates that the COO- groups of Asp131 and Asp133 interact with both Ca2+ and Mg2+ in the pseudo-bridging mode. Therefore, the present study directly demonstrated that the coordination structure of Mg2+ was different from that of Ca2+ in the Ca2+-binding site. In contrast to vertebrate TnC, most of the secondary structures remained unchanged among apo, Mg2+-bound and Ca2+-bound states of Akazara scallop TnC, as spectral changes upon either Ca2+ or Mg2+ binding were very small in the infrared amide-I' region as well as in the CD spectra. Fluorescence spectroscopy indicated that the spectral changes upon Ca2+ binding were larger than that upon Mg2+ binding. Moreover, gel-filtration experiments indicated that the molecular sizes of TnC had the order apo TnC > Mg2+-bound TnC > Ca2+-bound TnC. These results suggest that the tertiary structures are different in the Ca2+- and Mg2+-bound states. The present study may provide direct evidence that the side-chain COO- groups in the Ca2+-binding site are directly involved in the functional on/off mechanism of the activation of Akazara scallop TnC.

Animals↗

PubMed2001

Transcriptional activation of p21 by vitamin D(3) or vitamin K(2) leads to differentiation of p53-deficient MG-63 osteosarcoma cells.

p21 (WAF1/CIP1) is a downstream effector of p53 and mediates growth arrest by inhibiting the action of G(1) cyclin-dependent kinases. However, it has been reported that the p21 expression was triggered by multiple differentiation-inducing agents by a p53-independent pathway. These agents induced expression of p21 by binding to specific DNA elements and modulating transcriptional initiation. We demonstrated that the gene encoding p21 was not only a vitamin D(3) target gene but also a vitamin K(2) target gene in the cells and that their differentiation was well related to the transcriptional activation of the p21 gene. Transient overexpression of p21, using adenovirus-driven p21 expression plasmid, in MG-63 cells in the absence of vitamins D(3) and K(2) resulted in their differentiation. The transcriptional activation of p21 by vitamin D(3) or vitamin K(2) in p53-deficient osteosarcoma cells demonstrated the p53-independent role of p21 in human osseous differentiation. HUM PATHOL 32:410-416.

Bone Neoplasms↗

PubMed2001

Etoposide prevents apoptosis in mouse liver with D-galactosamine/lipopolysaccharide-induced fulminant hepatic failure resulting in reduction of lethality.

D-Galactosamine (GalN)/lipopolysaccharide (LPS)-induced liver injury is an experimental model of fulminant hepatic failure in which tumor necrosis factor alpha (TNF-alpha) plays a pivotal role. We examined the effects of etoposide on GalN/LPS-induced fulminant hepatic failure. Mice were given an intraperitoneal dose of GalN (800 microg/g body weight)/LPS (100 ng/g body weight) with and without intraperitoneal etoposide (10 microg/g body weight) treatment. Liver injury was assessed biochemically and histologically. TNF-alpha levels in the serum, and apoptosis of hepatocytes and CPP32/caspase-3 in the liver, were determined. GalN/LPS treatment caused lethal liver injury in 87% of animals (13 of 15). The effect was associated with significant increases in TNF-alpha and alanine transaminase (ALT) levels in serum, the number of apoptotic hepatocytes, CPP32/caspase-3 activity, and TNF receptor 1 (TNFR1) mRNA expression in the liver. Etoposide (10 microg/g body weight) was given 3 times (at 50, 26, and 4 hours before GalN/LPS administration). Treatment of GalN/LPS-treated mice with etoposide reduced apoptosis of hepatocytes, resulting in reduction of lethality (13% [2 of 15]), while another topoisomerase II inhibitor, IRCF-193, showed no significant effect. The antilethal effect of etoposide was also confirmed in GalN/TNF-alpha-induced fulminant hepatic failure. Etoposide treatment reduced CPP32/caspase-3 activity in the liver, although it did not alter the serum TNF-alpha levels or hepatic TNFR1 mRNA expressions. In addition, etoposide treatment enhanced the mRNA and protein expression of Bcl-xL, an antiapoptotic molecule in the liver. The present findings suggest that etoposide prevents endotoxin-induced lethal liver injury by up-regulation of Bcl-xL, and that etoposide could be useful for the treatment of TNF-alpha-mediated liver diseases.

Animals↗

PubMed2001

Reversal of human allergen-specific CRTH2+ T(H)2 cells by IL-12 or the PS-DSP30 oligodeoxynucleotide.

BACKGROUND: The chemoattractant receptor homologous molecule expressed on T(H)2 cells (CRTH2) is a receptor for prostaglandin D(2), which among human T cells is selectively expressed by T(H)2 and type 2 cytotoxic effectors. OBJECTIVE: Our purpose was to assess whether the cytokine production profile of T(H)2 effectors could be reversed by exploiting their selective expression of CRTH2. METHODS: CRTH2(+) T cells were purified from the blood of allergic subjects, stimulated with the specific allergen in the absence or presence of IL-12, and assessed by flow cytometry at the single-cell level for their ability to produce IL-4 and/or IFN-gamma after antigen or polyclonal stimulation. RESULTS: Both IL-12 and the PS-DSP30 oligodeoxynucleotide enabled CRTH2(+) allergen-stimulated T(H)2 cells to produce IFN-gamma. This change in the profile of cytokine production by T(H)2 cells from allergic subjects was related to the upregulation of IL-12 receptor beta2 chain and was associated with the loss of CRTH2. CONCLUSIONS: These data demonstrate that the cytokine production pattern of fully differentiated T(H)2 effectors can be changed to a less polarized profile, thus providing the physiologic basis for new immunotherapeutic strategies in allergic disorders.

Allergens↗

PubMed2001

Naproxen particle design using porous starch.

Naproxen (Nap) was embedded in porous starch by preferential grinding, and we examined the physicochemical properties of these particles, including pore diameter, pore volume, and dissolution of naproxen. Porous starch (PS) particles made by preferential grinding with a Mechanofusion system had a higher content of naproxen than those made using the Mechanomill as determined using a mercury porosimeter. Neither sample showed any significant changes in crystallization state of naproxen in particles as determined by powder X-ray diffraction and differential scanning calorimetry (DSC). No interactions occurred between naproxen and porous starch due to preferential grinding as determined by powder X-ray diffraction and DSC. The dissolution rate of drug from particles prepared by preferential grinding was faster than that from physical mixtures.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

A novel ER alpha-mannosidase-like protein accelerates ER-associated degradation.

The quality control mechanism in the endoplasmic reticulum (ER) discriminates correctly folded proteins from misfolded polypeptides and determines their fate. Terminally misfolded proteins are retrotranslocated from the ER and degraded by cytoplasmic proteasomes, a mechanism known as ER-associated degradation (ERAD). We report the cDNA cloning of Edem, a mouse gene encoding a putative type II ER transmembrane protein. Expression of Edem mRNA was induced by various types of ER stress. Although the luminal region of ER degradation enhancing alpha-mannosidase-like protein (EDEM) is similar to class I alpha1,2-mannosidases involved in N-glycan processing, EDEM did not have enzymatic activity. Overexpression of EDEM in human embryonic kidney 293 cells accelerated the degradation of misfolded alpha1-antitrypsin, and EDEM bound to this misfolded glycoprotein. The results suggest that EDEM is directly involved in ERAD, and targets misfolded glycoproteins for degradation in an N-glycan dependent manner.

Alkaloids↗

PubMed2001

Bruton's tyrosine kinase is required for signaling the CD79b-mediated pro-B to pre-B cell transition.

Formation of the pre-BCR complex is a critical check point during B cell development and induces the transition of pro-B to pre-B cells. CD79b (Igbeta) is a signaling component in the pre-BCR complex, since differentiation to the pre-B phenotype is induced by cross-linking the CD79b expressed on developmentally arrested pro-B cells from recombination-activating gene (RAG)-2-deficient mice. Bruton's tyrosine kinase (BTK) plays important roles in B cell development. However, its molecular mechanisms in early B cell development are not fully understood. To examine whether BTK functions in CD79b-mediated signaling for the pro-B/pre-B transition, we utilized RAG2/BTK double-knockout (DKO) mice. Pro-B cells from RAG2/BTK-DKO mice did not differentiate into pre-B cells following CD79b cross-linking, although tyrosine phosphorylation of cellular proteins including Erk1/2 and phospholipase C-gamma2 was induced in the same manner as RAG2-KO mice. BTK is phosphorylated after cross-linking of CD79b on RAG2-deficient pro-B cells. These findings suggest that BTK-dependent pathways downstream of CD79b are critical for the pro-B/pre-B transition and BTK-independent signaling pathways are also activated via the pre-BCR complex.

Agammaglobulinaemia Tyrosine Kinase↗

PubMed2001

A single-chain Fv fragment 2A3 specific for native lysozyme: isolation from a human synthetic phage display antibody library and characterization.

We have isolated from a human synthetic phage display library a clone, 2A3, which discriminates native lysozyme from denatured forms. Binding of single-chain Fv fragments (scFvs) of the clone to native hen egg white lysozyme was competitively inhibited by native hen egg white (hew) and human (h) lysozymes. Dot blotting analysis indicated that scFv of the clone did not react with denatured lysozymes. The K(d) values for scFv of 2A3 binding to native hew- and h-lysozymes were 3.78 x 10(-9) and 9.31 x 10(-9) M, respectively, indicating that 2A3 binds more strongly to native hew-lysozyme than to native h-lysozyme. The deduced amino acid sequence of the V(H) chain-CDR3 region of 2A3 was RRYALDY, of which the Arg residues at positions 1 and 2 of the CDR3 region were observed to be extremely rare in other antibodies by homology analysis. Based on these observations, site-directed mutagenesis of the RRYALDY-coding region was carried out. The results, combined with biomolecular analyses, demonstrated that Arg residues at positions 1 and 2 of this region were important for native lysozyme-binding.

Amino Acid Sequence↗

PubMed2001

Presence of interleukin-4-producing cells for human bone regeneration after application of guided tissue regeneration membranes.

To study the process of bone regeneration we examined three samples of periapical regenerative tissue obtained from two patients under a guided tissue regeneration treatment in endodontic surgery by the immunohistochemical and enzyme histochemical methods. The regenerative tissue consisted of a large number of fibroblast-like cells and a small number of mononuclear cells. Fibroblast-like cells stained positively for alkaline phosphatase and osteopontin, whereas mononuclear cells stained positively for CD4. Interleukin-4-producing cells could be detected in adjacent sections. However, interferon-y-producing cells could not be detected. These findings suggest that interleukin-4-producing cells may be one of the elements associated with success in the human bone regeneration process in vivo.

Adult↗

PubMed2001

Effects of blockade of the renin-angiotensin system on tissue factor and plasminogen activator inhibitor-1 synthesis in human cultured monocytes.

OBJECTIVES: To clarify the pathophysiological significance of the renin-angiotensin system (RAS) in monocytes, we examined the effect of its blockade on tissue factor and plasminogen activator inhibitor-1 (PAI-1) synthesis in human cultured monocytes. METHODS: Monocytes were isolated from healthy volunteers and cultured. Tissue factor and PAI-1 antigens in culture medium and cells were measured by enzyme-linked immunosorbent assay and Western blotting, and mRNA levels were assessed by reverse-transcriptase polymerase chain reaction. RESULTS: We show that the RAS is present in isolated human peripheral blood monocytes. Exogenous angiotensin II increased the levels of tissue factor antigen and mRNA in cultured monocytes, but not of PAI-1 synthesis. An angiotensin converting enzyme (ACE) inhibitor (captopril) and an angiotensin II type 1 (AT1) receptor antagonist (candesartan) decreased the levels of tissue factor protein and mRNA in cultured monocytes. These alterations were accompanied by a reduction in the levels of tumour necrosis factor-alpha protein and mRNA. The levels of PAI-1 protein were reduced by captopril, but not by candesartan. A bradykinin B2 receptor antagonist abolished the suppressive effect of captopril on PAI-1 antigen. CONCLUSIONS: An ACE inhibitor and an AT1 receptor antagonist reduced tissue factor synthesis in these cells. We show different actions of these agents on PAI-1 synthesis. ACE inhibition decreased PAI-1 synthesis mediated by bradykinin production, but AT1 receptor inhibition had no effect.

Angiotensin II↗

PubMed2001

Increased plasminogen activator inhibitor-1 and apolipoprotein (a) in coronary atherectomy specimens in acute coronary syndromes.

BACKGROUND: Although increased tissue factor expression is known in vulnerable plaques, there is no reported study to compare plaque fibrinolysis in stable and unstable plaques. This study investigates the extent of plasminogen activator inhibitor-1 (PAI-1) and apolipoprotein (a) [apo(a)] in the plaques of different types of coronary artery disease as well as the correlation between these molecules and infiltration of macrophages to plaques. METHODS: Using immunohistochemical staining, we examined PAI-1 expression and apo(a) deposition in coronary atherosclerotic specimens obtained by directional coronary atherectomy from 19 patients with acute myocardial infarction (AMI), 12 with unstable angina pectoris (UAP), and 13 with stable angina pectoris (SAP). The percentages of the total areas of specimens stained with PAI-1 or apo(a) were estimated by an NIH image program. The proportion of macrophages as a percentage of all cells in plaques was calculated as the macrophage density. RESULTS: We found significantly higher percentages of total areas of specimens stained with PAI-1 in AMI (25.5 +/- 8.6%, P < 0.001) and UAP (22.2 +/- 10.4%, P < 0.005) than in SAP (9.5 +/- 5.0%), as well as with apo(a) (AMI; 11.7 +/- 7.1%, P < 0.005, UAP; 11.1 +/- 5.5%, P < 0.01 versus SAP; 3.9 +/- 1.5%). Linear regression analysis of all the samples showed a correlation between PAI-1 or apo(a) and macrophage density (PAI-1: r = 0.75, P < 0.001 and apo(a): r = 0.56, P < 0.001). CONCLUSIONS: Our results suggest a possible contribution of increased PAI-1 and apo(a) in plaques to the pathogenesis of acute coronary syndromes including impaired fibrinolysis.

Aged↗

PubMed2001

Inhibitory activities of lansoprazole against respiration in Helicobacter pylori.

Lansoprazole and its derivative AG-1789 dose-dependently inhibited cellular respiration by an endogenous substrate and decreased the ATP level in Helicobacter pylori cells. The inhibitory action of lansoprazole and AG-1789 against respiration was specific to substrates such as pyruvate and alpha-ketoglutarate and similar to the inhibitory action of rotenone, which is an inhibitor for the mitochondrial respiratory chain. Growth inhibition by lansoprazole and AG-1789 as well as by rotenone was augmented at high oxygen concentrations under atmospheric conditions. Since the 50% inhibitory concentrations of these compounds for the respiration were close to their MICs for H. pylori growth, the growth inhibition might be due to respiratory inhibition by these compounds.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2001

Identification of an antigenic epitope in Helicobacter pylori urease that induces neutralizing antibody production.

We previously reported a mouse monoclonal antibody (MAb), termed L2, specific for Helicobacter pylori urease strongly inhibited its enzymatic activity. Here, to gain insight into how this antibody affects urease activity, the epitope that was recognized by the antibody was determined. By screening a panel of overlapping synthetic peptides covering the entire sequence of the two subunits (UreA and UreB), we identified a stretch of UreB-derived 19 amino acid (aa) residues (UB-33; aa 321 to 339, CHHLDKSIKEDVQFADSRI) that was specifically recognized by the L2 antibody. Further sequential amino acid deletion of the 19-mer peptide from either end allowed us to determine the minimal epitope as 8 amino acid residues (F8; SIKEDVQF) for L2 reactivity. This epitope appears to lie exactly on a short sequence which formed a flap over the active site of urease, suggesting that binding of the L2 antibody sterically inhibits access of urea, the substrate of urease. Finally, immunization of rabbits with either the 19-mer peptide or the 8-mer minimal epitope resulted in generation of antiurease antibodies that were capable of inhibiting the enzymatic activity. Since urease is critical for virulence of H. pylori, antigenic peptides that induce production of antibodies to inhibit its enzymatic activity may potentially be a useful tool as a vaccine for prevention and treatment of H. pylori infection.

Amino Acid Sequence↗