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Biomedical subjects

N Igarashi

Publications and source records attributed to N Igarashi.

At least 19 recordsLinked to original sources
PubMed2001

Regulation of mammalian phospholipase D2: interaction with and stimulation by G(M2) activator.

We have previously reported that a heat-stable activator for ganglioside metabolism, G(M2) activator, potently stimulates ADP-ribosylation factor (ARF)-dependent phospholipase D (PLD) activity (presumably PLD1) in an in vitro system [Nakamura, Akisue, Jinnai, Hitomi, Sarkar, Miwa, Okada, Yoshida, Kuroda, Kikkawa and Nishizuka (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 12249-12253]. However, little is known about the regulation of PLD2. In the present studies we have investigated the regulation of PLD2 by G(M2) activator and various other regulators including ARF. PLD2 was potently stimulated in vitro by G(M2) activator in a time- and dose-dependent manner. Neither ARF nor protein kinase C caused any significant changes in PLD2 activity. Importantly, PLD2 responsiveness to ARF was greatly enhanced by G(M2) activator, suggesting a possible role for G(M2) activator as a coupling factor. G(M2) activator was also demonstrated to physically associate with PLD2 in a stoichiometric manner. Further, PMA stimulation of COS-7 cells overexpressing both G(M2) activator and PLD2 resulted in a marked increase in the association of the two molecules. Interestingly, ARF association with PLD2 was greatly increased by G(M2) activator. Moreover, G(M2) activator enhanced PMA-induced PLD activity in a synergistic manner with ARF in streptolysin-O-permeabilized, cytosol-depleted HL-60 cells, suggesting that G(M2) activator may regulate PLD in a concerted manner with other factors, including ARF, inside the cells.

Amino Acid Sequence↗
PubMed2001

Systematic analysis of supersaturation and lysozyme crystal quality.

A systematic study of the correlation between supersaturation and protein crystal quality was carried out employing atomic force microscopy (AFM) and X-ray crystallography with synchrotron radiation (SR). The surface morphology and growth rates of hen egg-white (HEW) lysozyme crystals soaked in various supersaturated solutions were first investigated by AFM. The results showed that the formation of two-dimensional islands increased as a function of supersaturation. The growth rate (molecule intake speed) also increased as a function of supersaturation. In order to examine the correlation between the surface morphology, growth rate and the crystal quality, X-ray diffraction experiments were performed. It was confirmed that crystals grown at lower supersaturations diffracted better with higher signal-to-noise ratios, including better agreement between symmetry-related reflections. The results strongly suggested that the molecular misorientation at high supersaturation affected the crystal quality.

Animals↗
PubMed2001

Differential cellular targets of Epstein-Barr virus (EBV) infection between acute EBV-associated hemophagocytic lymphohistiocytosis and chronic active EBV infection.

Unusual Epstein-Barr virus (EBV) infection into T or natural killer cells plays a pivotal role in the pathogenesis of acute EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) and chronic active EBV infection (CAEBV). The precise frequency and localization of EBV genome in lymphocyte subpopulations especially within T-cell subpopulations are unclear in these EBV-related disorders. This study analyzed the frequency of EBV-infected cells in circulating lymphocyte subpopulations from 4 patients with acute EBV-HLH and 4 with CAEBV. EBV- encoded small RNA-1 in situ hybridization examination of peripheral blood lymphocytes showed a significantly higher frequency of EBV-infected cells of 1.0% to 13.4% in EBV-HLH and 1.6% to 25.6% in CAEBV, respectively. The patterns of EBV infection in lymphocyte subpopulations were quite different between acute EBV-HLH and CAEBV. EBV infection was predominant in CD8(+) T cells in all EBV-HLH patients, whereas the dominant EBV-infected cell populations were non-CD8(+) lymphocyte subpopulations in CAEBV patients. Phenotypical analysis revealed that EBV-infected cell populations from both EBV-HLH and CAEBV were activated. There was no predominance of any EBV substrain of latent membrane protein-1, EBV-associated nuclear antigen (EBNA)-1, and EBNA-2 genes between the 2 abnormal EBV-associated disorders, and self-limited acute infectious mononucleosis. These results showing differential virus-cell interactions between acute EBV-HLH and CAEBV indicated different pathogenic mechanisms against EBV infection between the 2 EBV-associated diseases, which accounts for the difference in clinical manifestations between the 2 diseases.

Acute Disease↗
PubMed2001

Crystallization and preliminary X-ray analysis of catalase-peroxidase from the halophilic archaeon Haloarcula marismortui.

Catalase-peroxidases are bifunctional enzymes found in many microorganisms. Crystals of catalase-peroxidase from the halophilic archaeon Haloarcula marismortui were obtained using the hanging-drop vapour-diffusion method. The rhombic plate-shaped crystals were grown from purified protein solution using (NH(4))(2)SO(4) as precipitant at 293 K. The crystal belongs to the monoclinic system, space group C2, and diffracted beyond 2.0 A resolution.

Archaeal Proteins↗
PubMed2001

Follicle-stimulating hormone promotes the growth of human epithelial ovarian cancer cells through the protein kinase C-mediated system.

We have previously described that follicle-stimulating hormone (FSH) stimulated the growth of human epithelial ovarian cancer tissues and cells. In order to determine the signaling pathway on FSH action in ovarian cancer, we used an epithelial ovarian cancer cell line (HRA line) which constitutively FSH receptors (FSHRs). FSH significantly increased cell proliferation (230.1 +/- 20.5%, P < 0.05) and (3)H-thymidine uptake (443.5 +/- 35.1%, P < 0.01). 1-(5-Isoquinolinesulfonyl)-2-methyipiperazine (H7, 1 5 nM), staurosponine (STR, 5 nM) and calphostin C (5 nM), specific protein kinase C (PKC) inhibitors, significantly suppressed the FSH-stimulated cell growth (120.2-140.2%, P < 0.05) and (3)H-thymidine uptake (140.5-173.9%, P < 0.05), whereas N-(2-guanidinoethyl)-5-isoquinoline-sulfon-amide (HA1004, l5 nM), which is a derivant of H7 and inhibits most of protein kinases except PKC, showed no effect on the FSH-stimulated cell growth and (3)H-thymidine uptake. A pretreatment with 12-0-tetradecanoylphorbol-13 acetate (TPA, 100 ng/ml) or STR (20 nM) significantly suppressed the subsequent FSH-stimulated cell growth (TPA; 152.3 +/-10.3%, STR; 160.4 +/- 15.9%, P < 0.05) and (3)H-thymidine uptake (TPA; 250.4 +/-18.3%, STR; 208.7 +/- 15.9%, P < 0.05). STR abolished the suppression of TPA preincubation on the subsequent FSH-stimulated cell growth and (3)H-thymidine uptake. HRA cells constitutively expressed PKCalpha but not PKCbeta nor PKCgamma. The levels of either expression of PKCalpha protein and mRNA were significantly amplified by FSH. These data suggest that stimulation of PKCalpha transcription is involved in the FSH-stimulated cell growth and DNA synthesis in epithelial ovarian cancer cells.

Cell Division↗
PubMed2001

Horizontal transfer of the photosynthesis gene cluster and operon rearrangement in purple bacteria.

A 37-kb photosynthesis gene cluster was sequenced in a photosynthetic bacterium belonging to the beta subclass of purple bacteria (Proteobacteria), Rubrivivax gelatinosus. The cluster contained 12 bacteriochlorophyll biosynthesis genes (bch), 7 carotenoid biosynthesis genes (crt), structural genes for photosynthetic apparatuses (puf and puh), and some other related genes. The gene arrangement was markedly different from those of other purple photosynthetic bacteria, while two superoperonal structures, crtEF-bchCXYZ-puf and bchFNBHLM-lhaA-puhA, were conserved. Molecular phylogenetic analyses of these photosynthesis genes showed that the photosynthesis gene cluster of Rvi. gelatinosus was originated from those of the species belonging to the alpha subclass of purple bacteria. It was concluded that a horizontal transfer of the photosynthesis gene cluster from an ancestral species belonging to the alpha subclass to that of the beta subclass of purple bacteria had occurred and was followed by rearrangements of the operons in this cluster.

Amino Acid Sequence↗
PubMed2000

Head movements and neck muscle activities associated with the jaw movement during mastication in the rabbit authors.

Rhythmical head movements and neck muscle activities associated with the masticatory jaw movement were investigated in rabbits. In natural mastication, head movements and neck muscle activities showed a rhythmical feature synchronized with jaw movement. During cortically induced rhythmical jaw movements, some neck muscle showed rhythmical activity induced by biting a wooden stick. Neck muscles may contribute to the rhythmical head movement after loading the tooth with food.

Animals↗
PubMed2000

Activation of matrix metalloproteinase-2 in head and neck squamous cell carcinoma: studies of clinical samples and in vitro cell lines co-cultured with fibroblasts.

We undertook this present study to investigate the activation of matrix metalloproteinase-2 (MMP-2) in human head and neck squamous cell carcinomas (HNSCC) tissues and cell lines. Gelatinolytic activities of active MMP-2 were significantly higher in carcinoma samples than in normal portions. Furthermore, the activation ratio of proMMP-2 significantly correlated with cervical lymph node metastasis. In vitro studies revealed an HNSCC cell line, HEp-2, to produce neither the pro form nor the active form of MMP-2, but human fibroblasts were found to produce proMMP-2. However, coculture of HEp-2 cells with fibroblasts resulted in the production of not only proMMP-2 but also activeMMP-2 in the culture medium. Northern blot analysis revealed a stronger expression of membrane-type 1 matrix metalloproteinase (MT1-MMP),which is a specific activator of MMP-2, mRNA in HEp-2 cells than in fibroblasts. These results suggest the activation of proMMP-2 as an important event in the process of HNSCC metastasis. They also suggest MMP-2 is secreted in its pro form by stromal fibroblasts surrounding the cancer cells and activated by MT1-MMP localized on the cancer cells.

Aged↗
PubMed2000

Matrix metalloproteinase expression in cultured human gastric wall fibroblasts--interactions with Helicobacter pylori isolated from patients with ulcers.

BACKGROUND: Matrix metalloproteinases (MMPs), enzymes capable of degrading collagens and other extracellular matrix components, have been implicated in gastric ulcer formation. However, the effect on MMP expression of Helicobacter pylori, also implicated in these lesions, has not been studied to our knowledge. AIM: To seek links between H. pylori and MMP expression likely to affect gastric ulcer formation. After fibroblasts from human gastric wall were cocultured with H. pylori. concentrations of MMP-1 and -2 in the medium were determined by enzyme-linked immunosorbent assays. RESULTS: Whereas MMP-1 was not detected in media from fibroblasts or H. pylori culture alone, MMP-1 was detected in cocultures (P<0.01). Similar amounts of MMP-2 were detected in medium from fibroblasts cultured alone and with H. pylori. No MMP-2 production by H. pylori cultured alone was detected. CONCLUSIONS: MMP-1 appears to be important in gastric ulcer pathogenesis, and MMP-1 induction by H. pylori may impede gastric ulcer healing.

Cells, Cultured↗
PubMed2000

Enhancement in the perfection of orthorhombic lysozyme crystals grown in a high magnetic field (10 T).

Orthorhombic crystals of hen egg-white (HEW) lysozyme were grown in a homogeneous and static magnetic field of 10 T. All crystals grown at 10 T were oriented such that their crystallographic c axes were parallel to the magnetic field direction and showed a narrower average full-width at half-maximum (FWHM) of the rocking curve than those grown at 0 T. Rocking-width measurements were made at the BL-10A station at the Photon Factory, Tsukuba, Japan, using a high-resolution vertical-type four-circle diffractometer. Crystal perfection was evaluated using the FWHM of the rocking curve; the effects of the magnetic field on the quality of the crystals were examined by comparison of the FWHM of seven crystals grown at 10 and 0 T. The FWHMs of the reflections along the a, b and c axes decreased by 23.5, 35.3 and 27.8%, respectively, and those of other general reflections decreased by 17.4-42.2% in the crystals grown at high magnetic field. These results clearly showed that a magnetic field of 10 T improved the crystal perfection of the orthorhombic lysozyme crystals. As a result, the maximum resolution of X-ray diffraction increased from 1.3 A at 0 T to 1.13 A at 10 T. The magnetic field also affected the dimensions of the unit cell, increments being 0.2% for the a and c axes and 0.1% for the b axis, respectively. These facts suggest that the application of a high magnetic field during crystallization might result in remarkable enhancements in the diffraction power of protein crystals having magnetic anisotropy.

Animals↗
PubMed2000

Laparoscopic wedge resection of gastric submucosal tumors.

Minimally invasive surgery has revolutionized the treatment of gastrointestinal tumors. Submucosal tumors (SMTs) of the stomach can be resected using laparoscopic techniques. Between 1993 and 1997, laparoscopic wedge resection was performed in 34 patients with an SMT of the stomach. The tumors ranged from 8 to 60 mm in diameter. All surgical margins were clear. The average operative time was 131 minutes. Most of the patients began eating on the first postoperative day and were discharged within 5 to 7 days. Histopathologic examination of the tumors showed gastrointestinal stromal tumor (n = 14), ectopic pancreas (n = 7), leiomyosarcoma (n = 4), schwannoma (n = 3), carcinoid (n = 2), leiomyoma (n = 2), an inflammatory lesion caused by parasites (n = 1), and cyst (n = 1). No recurrences were observed over the 5-year follow-up period. A solid SMT of the stomach larger than 20 mm in diameter can be treated using laparoscopic wedge resection.

Adult↗
PubMed1999

Predictive value of Ki-67, p53 protein, and DNA content in the diagnosis of gastric carcinoma.

BACKGROUND: The ability to make a precise preoperative diagnosis is a valuable and effective method in improving the prognosis of patients with gastric carcinoma. The authors examined retrospectively whether preoperative histopathologic analysis with p53 protein, Ki-67 labeling index, and DNA ploidy along with preoperative radiographic and endoscopic findings led to a precise preoperative diagnosis of patients with gastric carcinoma. METHODS: Histopathologic analysis of p53 protein, Ki-67 labeling index, and DNA content was performed on formalin fixed, paraffin embedded tissue. Tissue sections from endoscopic and surgically resected specimens were stained immunohistochemically for p53 protein and Ki-67 labeling index, and the cell nuclear DNA content of the surgically resected primary lesion was measured using a microspectrophotometer. These analyses were performed on 16 patients with early gastric carcinoma (EGC) who were diagnosed with advanced gastric carcinoma (AGC) based on the preoperative imaging findings and on 15 patients with AGC who were diagnosed preoperatively with EGC. RESULTS: Overexpression of p53 in the AGC group was significantly more frequent compared with that in the EGC group (P = 0.0386). With regard to the correlation between lymph node metastases and p53 overexpression, there was no apparent relation in either the AGC group (P = 0.648) or the EGC group (P = 0.726). The AGC group had significantly higher Ki-67 labeling indices compared with the EGC group (P = 0.0195). There was complete concordance between endoscopic and surgically resected specimens with regard to the p53 and Ki-67 labeling index findings. DNA ploidy in the primary tumor did not differ between the AGC and EGC groups. The survival rates for the EGC group were significantly superior to those for the AGC group (P = 0.0312). CONCLUSIONS: The findings of the current study suggest that in routine clinical practice, the combination of preoperative imaging findings in addition to Ki-67 labeling indexes, and p53 protein analyses may be useful for the accurate diagnosis of EGC; however, DNA ploidy did not appear to reflect the growth potential of gastric carcinoma.

Aged↗
PubMed1999

Effective control of Epstein-Barr virus-related hemophagocytic lymphohistiocytosis with immunochemotherapy. Histiocyte Society.

The familial form of hemophagocytic lymphohistiocytosis (HLH) is a lethal disorder. Although the prognosis for Epstein-Barr virus-associated HLH (EBV-HLH) remains uncertain, numerous reports indicate that it can also be fatal in a substantial proportion of cases. We therefore assessed the potential of immunochemotherapy with a core combination of steroids and etoposide to control EBV-HLH in 17 infants and children who met stringent diagnostic criteria for this reactive disorder of the mononuclear phagocyte system. Treatment of life-threatening emergencies was left to the discretion of participating investigators and typically included either intravenous Ig or cyclosporin A (CSA). Five patients (29%) entered complete remission during the induction phase (1 to 2 months), whereas 10 others (57%) required additional treatment to achieve this status. In 2 cases, immunochemotherapy was ineffective, prompting allogeneic bone marrow transplantation. Severe but reversible myelosuppression was a common finding; adverse late sequelae were limited to epileptic activity in one child and chronic EBV infection in 2 others. Fourteen of the 17 patients treated with immunochemotherapy have maintained their complete responses for 4+ to 39+ months (median, 15+ months), suggesting a low probability of disease recurrence. These results provide a new perspective on EBV-HLH, showing effective control (and perhaps cure) of the majority of EBV-HLH cases without bone marrow transplantation, using steroids and etoposide, with or without immunomodulatory agents.

Child↗
PubMed1999

Preventive effect of matrix metalloproteinase inhibitor, R-94138, in combination with mitomycin C or cisplatin on peritoneal dissemination of human gastric cancer cell line TMK-1 in nude mice.

R-94138, a matrix metalloproteinase inhibitor, was examined for the ability to prevent peritoneal dissemination of a human gastric cancer xenograft, TMK-1. When the supernatant of a co-culture of TMK-1 cells and human normal fibroblast cells was subjected to gelatin zymography, it was clear that the protein expression of MMP-2 had been inhibited by R-94138. When TMK-1 was injected intraperitoneally (i.p.) into nude mice at 5 x 10(5) cells/body, the resulting peritoneal dissemination mimicked clinical carcinomatous peritonitis. When the maximum tolerated dose of mitomycin C (MMC) or cisplatin (DDP) was given 12 h after the tumor inoculation, peritoneal dissemination was completely inhibited, while the effect of R-94138 was limited when it was given i.p. at a dose of 20 mg/kg in a schedule of q.d. x 5 starting 12 h after tumor injection. MMC and DDP also suppressed peritoneal dissemination when they were administered 1 week after the tumor inoculation at a single dose of 2 and 3 mg/kg i.p., respectively. R-94138 inhibited peritoneal dissemination when it was administered i.p. at a dose of 30 mg/kg in a schedule of q.d. x 5 starting from 1 week after tumor injection. The combination of MMC and R-94138 increased the preventive effect on peritoneal dissemination. R-94138 seems to be a promising candidate to prevent peritoneal dissemination of gastric cancer.

Acetamides↗
PubMed1999

Oxidative stress causes enhanced endothelial cell injury in human heme oxygenase-1 deficiency.

The first known human case of heme oxygenase-1 (HO-1) deficiency is presented in this report. The patient is a six-year-old boy with severe growth retardation. He has been suffering from persistent hemolytic anemia characterized by marked erythrocyte fragmentation and intravascular hemolysis, with paradoxical increase of serum haptoglobin and low bilirubin. An abnormal coagulation/fibrinolysis system, associated with elevated thrombomodulin and von Willebrand factor, indicated the presence of severe, persistent endothelial damage. Electron microscopy of renal glomeruli revealed detachment of endothelium, with subendothelial deposition of an unidentified material. Iron deposition was noted in renal and hepatic tissue. Immunohistochemistry of hepatic tissue and immunoblotting of a cadmium-stimulated Epstein-Barr virus-transformed lymphoblastoid cell line (LCL) revealed complete absence of HO-1 production. An LCL derived from the patient was extremely sensitive to hemin-induced cell injury. Sequence analysis of the patient's HO-1 gene revealed complete loss of exon-2 of the maternal allele and a two-nucleotide deletion within exon3 of the paternal allele. Growth retardation, anemia, iron deposition, and vulnerability to stressful injury are all characteristics observed in recently described HO-1 targeted mice. This study presents not only the first human case of HO-1 deficiency but may also provide clues to the key roles played by this important enzyme in vivo.

Animals↗
PubMed1998

Effects of food consistency on the modulatory mode of the digastric reflex during chewing in freely behaving rabbits.

Effects of food consistency on the mode of the phase-linked modulation in the digastric reflex amplitude were examined in naturally chewing rabbits. Two test foods with different textures (bread as a soft food, pellet as a hard food) were used. The digastric reflex was elicited by electrical stimulation (10 train pulses at 2 kHz) of the inferior alveolar nerve. The amplitude of the digastric reflex measured was divided into three categories depending on the chewing phases in which the stimulus was delivered and each value was compared with the control response obtained when the animal was resting. The reflex was strongly inhibited in the jaw-opening phase and no difference was observed in the inhibitory effect between the foods. In the jaw-closing phase, larger digastric reflexes than those in the opening phase were elicited with both foods. This was the case in both the fast-closing and slow-closing phases. Reflex amplitude was significantly larger during chewing of the hard food than the soft food and, thereafter, inhibition of the reflex was observed only during chewing of the soft food in the closing phase. The results suggest the following: (1) food consistency may affect the central mechanism which regulates the digastric reflex and (2) the reflex may contribute to the regulation of masticatory force during chewing particularly hard food.

Animal Feed↗