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Biomedical subjects

T Sakurai

Publications and source records attributed to T Sakurai.

At least 397 records · Page 22Linked to original sources
PubMed1994

Interactions with tenascin and differential effects on cell adhesion of neurocan and phosphacan, two major chondroitin sulfate proteoglycans of nervous tissue.

We have studied interactions of tenascin with two chondroitin sulfate proteoglycans, neurocan and phosphacan. Neurocan is a multi-domain proteoglycan with a 136-kDa core protein that is synthesized by neurons and binds to hyaluronic acid, whereas the 173-kDa core protein of phosphacan, which is synthesized by glia, represents an extracellular variant of the receptor-type protein tyrosine phosphatase RPTP zeta/beta. Keratan sulfate-containing glycoforms of phosphacan (designated phosphacan-KS) are also present in brain. Immunocytochemical studies of early postnatal rat cerebellum demonstrated that the localization of neurocan, phosphacan, and phosphacan-KS all overlap extensively with that of tenascin, an extracellular matrix protein that modulates cell adhesion and migration. Binding studies using purified proteins covalently attached to fluorescent microbeads demonstrated that proteoglycan-coated beads co-aggregated with differently fluorescing beads coated with tenascin. The co-aggregation was specifically inhibited by Fab' fragments of antibodies against tenascin or the proteoglycans and by soluble neurocan, phosphacan, and tenascin. A solid phase radioligand binding assay confirmed that neurocan, phosphacan, and phosphacan-KS bind to tenascin but not to laminin and fibronectin. Chondroitinase treatment of the proteoglycans or addition of free chondroitin sulfate had no significant effect, indicating that the binding activity is mediated largely via the core glycoproteins. Scatchard analysis demonstrated high affinity binding of 125I-phosphacan, phosphacan-KS, and neurocan to a single site in tenascin, and neurocan and various glycoforms of phosphacan all inhibited binding of 125I-phosphacan to tenascin. In studies of cell adhesion to proteins adsorbed to Petri dishes, phosphacan inhibited adhesion of C6 glioma cells to tenascin whereas neurocan had no effect. Our results suggest that tenascin binds phosphacan and neurocan in vivo and that interactions between chondroitin sulfate proteoglycans and tenascin may play important roles in nervous tissue histogenesis, possibly by modulating signal transduction across the plasma membrane.

Animals↗
PubMed1994

Human endothelin receptor ETB. Amino acid sequence requirements for super stable complex formation with its ligand.

ETB type endothelin receptor (ETBR) forms a stable complex with its ligand endothelin-1 (ET-1). The ligand-receptor complex can survive in the presence of 2% SDS and migrate in SDS-polyacrylamide gel electrophoresis at reduced temperature. This is not the case for the ETA type endothelin receptor (ETAR). Most of ETBR from various animals, except rat, can form such a stable complex. Examination of stability in the ligand-receptor complex which was formed by chimeric receptors constructed from human ETBR and rat ETBR demonstrated that the region containing 29 amino acids in the N-terminal extracellular domain is responsible for the formation of such a stable complex. Site-directed mutagenesis focused on this particular region revealed that Asp75 and Pro93 are involved in the formation of the stable complex. This unique observation contributes to the elucidation of the structure of the stable ETBR.ET-1 complex at the molecular level.

Amino Acid Sequence↗
PubMed1994

Differential expression of bovine adseverin in adrenal gland revealed by in situ hybridization. Cloning of a cDNA for adseverin.

Adseverin is a Ca(2+)-dependent actin filament-severing protein that is presumed to have a regulatory function in exocytosis by affecting the organization of the microfilament network underneath the plasma membrane. As the first step to investigate whether adseverin has the expected function in vivo, we have cloned a cDNA for bovine adseverin. Analysis of the nucleotide sequence revealed the following points. 1) Adseverin consisted of 715 amino acid residues, and its predicted molecular mass was 80.5 kDa. 2) Adseverin belonged to the gelsolin family of proteins, which consists of six homologous segments. 3) Adseverin had two putative polyphosphoinositide binding sequences, very similar to but distinct from those in gelsolin. Adseverin was produced in Escherichia coli and purified to homogeneity. The adseverin reacted with adseverin-specific antibody and showed Ca(2+)-dependent actin filament severing activity like authentic adseverin. In situ hybridization demonstrated that adseverin mRNA was differentially expressed in the bovine adrenal gland; it was expressed in the adrenal medulla but not in most parts of the adrenal cortex, although both have a secretory function. The observation strongly suggested that adseverin is not involved in secretory processes in general but is specifically involved in exocytosis.

Adrenal Glands↗
PubMed1994

Electron transfer reaction of stellacyanin at a bare glassy carbon electrode.

Direct (unmediated) electrochemistry of Rhus vernicifera stellacyanin at a glassy carbon electrode has been briefly investigated in phosphate buffer. The voltammetry was practically independent of the buffer concentration, suggesting that the interaction between stellacyanin and the glassy carbon electrode is mainly realized through the hydrophobic interaction. The quasi-reversible process was found to be diffusion controlled at a sweep rate < 80 mVs-1. From stellacyanin concentration dependence, a transformation from linear diffusion to radial diffusion was observed. Two-step voltammetry was affected by translocations of the active site (rotation of the protein molecule on the electrode surface and diffusion). Activation energies for reduction and oxidation processes were determined to be 24 kJmol-1 and 54 kJmol-1, respectively, by the stationary method, and 15 kJmol-1 and 66 kJmol-1, respectively, by cyclic voltammetry. The considerable difference in the activation energies is supposedly due to the reduction and oxidation which are performed utilizing different electron-transfer pathways or because only one electron-transfer pathway (probably through His92) is significantly changed during the reorganization between the oxidized and reduced forms. The fact that the diffusion constant estimated from one-step voltammetry (Dox = 4.2 x 10(-9) cm2 s-1 for 484 microM stellacyanin) is much smaller than that determined from cyclic voltammetry (7.5 x 10(-7) cm2 s-1) derives from the fact that motions of the stellacyanin molecule (rotation leading to translocation of the active site and diffusion) are not fast enough to allow data from potential step voltammetry to be treated as the reversible process, but are fast enough to allow data from cyclic voltammetry to be treated as a diffusion-controlled process.

Carbon↗
PubMed1994

Identification of collagen and laminin receptor integrins on murine T lymphocytes.

In this study we investigated the receptors by which murine lymphocytes bind to collagen and laminin. To identify the collagen and laminin receptors, we generated three monoclonal antibodies, two of which (HM alpha 1 and HM alpha 2) could inhibit adhesion of activated T cells to collagen and laminin and one of which (HM alpha 6) could inhibit that to laminin. Biochemical studies showed that the antigens recognized by HM alpha 1, HM alpha 2, and HM alpha 6 are the mouse homologues of human VLA-1, VLA-2, and VLA-6, respectively. Finally, we demonstrated that both VLA-1 and VLA-2 contribute to the functional interaction between collagen and activated T cells, since HM alpha 1 and HM alpha 2 specifically inhibited collagen-induced TNF secretion from activated T cells. These results indicate that VLA-1 and VLA-2 play an important role in regulating adhesion and cytokine production of activated T cells.

Animals↗
PubMed1994

Endothelin-1 acts as an autocrine growth factor for normal human keratinocytes.

Endothelin-1 (ET-1) is an endothelium-derived 21 amino acid vasoconstrictor peptide possessing two intrachain disulfide bridges. Recently it has become evident that isoforms of ET (ET-1, -2, and -3) have a wide range of pharmacological effects in various tissues and act as autocrine/paracrine factors. We demonstrate here that ET-1 is secreted from normal human keratinocytes and may work as an autocrine growth factor through a specific receptor. In this study, human foreskin keratinocytes were cultured in serum-free MCDB 153 medium. Cell growth and [3H] thymidine incorporation in low and high Ca++ concentration media was stimulated by ET-1, -2, and -3 with similar potencies. The strongest response was observed at 10 nM ETs, whereas stimulatory activity was reduced at 100 nM. ETs suppressed keratinocyte differentiation as measured by reactivity with involucrin antibody. Plasminogen activator activity (mainly urokinase) in the medium was also stimulated by the addition of 10 nM ETs. ET-1-like immunoreactivity measured by radioimmunoassay was 1.4 fmol/day/10(6) cells in non-treated condition medium. Among the various cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha, and transforming growth factor-beta stimulated ET-1 secretion in a dose-dependent manner. The strongest response (ten-fold) was observed upon the addition of 10 ng/ml TNF-alpha. Scatchard plot analysis of [125I] ET-1 binding to keratinocytes revealed the presence of a single class of high affinity receptors (KD 50 pM, 9 x 10(3) sites/cell). Binding was competitively inhibited by the addition of unlabeled ET-1 and -2 with similar affinities and by ET-3 with weaker affinity. ET-1 mRNA expression in keratinocytes was detected by reverse transcription-polymerase chain reaction and was increased by treatment with 10 ng/ml TNF-alpha. These results suggest that ET-1 acts as an autocrine growth factor for keratinocytes through a specific receptor.

Base Sequence↗
PubMed1994

Anti-oncogene product p53 binds DNA helicase.

An oncogene product, p53, interacts with a simian virus 40-encoded T-antigen, which is an initiation protein for the viral DNA replication and also works as DNA helicase during elongation. Here we examine the interaction of p53 with cellular DNA helicase. A recombinant human wild type p53 fused with glutathione S-transferase was immobilized on glutathione-agarose as a ligand for affinity column. Hela cell extract was applied to the p53 column and the adsorbed proteins were eluted with buffers containing salt, 50% ethylene glycol, and glutathione. The ethylene glycol fraction contained a number of p53 binding proteins, and this fraction showed a DNA helicase activity measured by the displacement of DNA fragment from partially duplexed M13 DNA. The DNA helicase translocated in a 5'-to-3' direction on the single-stranded DNA using ATP as an energy source. The glutathione fraction that contained the p53 glutathione S-transferase fused protein also showed the same activity. The corresponding fractions from a control column carrying glutathione S-transferase showed only a trace amount of activity of DNA helicase. Therefore, the binding may be specific. Furthermore, an anti-p53 antibody column retained a p53-DNA helicase complex when the crude extracts of human placenta and of osteosarcoma cells were applied. These results indicate that p53 physically interacts with DNA helicase in vitro as well as in vivo.

Chromatography, Affinity↗
PubMed1994

The ter primordial germ cell deficiency mutation maps near Grl-1 on mouse chromosome 18.

A single recessive gene, ter (teratoma), causes germ cell deficiency and a high incidence of congenital testicular teratomas in the 129/Sv-ter strain of the mouse. Linkage analyses between the ter gene and 36 marker genes of 19 chromosomes were performed with matings between the C57BL/6J-ter congenic strain and four inbred strains. Results showed that the ter gene was linked to D18Mit9, D18Mit14, and D18Mit17 on Chromosome (Chr) 18. Gene order estimated on the basis of recombination distance (in centimorgans) was [centromere-D18Mit14-5.1 (cM)-ter-0 (cM)-D18Mit17-23.8 (cM)-D18Mit9]. D18Mit17 is the microsatellite DNA of the Grl-1 (glucocorticoid receptor-1) locus. We conclude that the ter gene is closely linked to Grl-1 on Chr 18 and is a new mutation involving the developmental modification of primordial germ cells in mice.

Animals↗
PubMed1994

Three-dimensional architecture of the tubular endocytic apparatus and paramembranous networks of the endoplasmic reticulum in the rat visceral yolk-sac endoderm.

The three-dimensional architecture of the tubular endocytic apparatus and the endoplasmic reticulum in the rat yolk-sac endoderm was investigated after loading with horseradish peroxidase-conjugated concanavalin A by intrauterine administration. After 30 min, small vesicles (50-150 nm in diameter), small tubules (80-100 nm in diameter) and large vacuoles (0.2-1.0 microns in diameter) in the apical cytoplasm were labeled with the tracer, but lysosomes (1.0-3.5 microns in diameter) in the supranuclear cytoplasm were not labeled until 60 min after loading. Stereo-viewing of the labeled small tubules in thick sections revealed that they were not isolated structures but formed three-dimensional anastomosing networks, which were also confirmed by scanning electron microscopy after maceration with diluted osmium tetroxide. Their earlier labeling with the endocytic tracer, localization in the apical cytoplasm and three-dimensional network formation indicated that the labeled small tubules represented tubular endosomes (tubular endocytic apparatus). These well-developed membranous networks provided by the tubular endosomes are suggested to facilitate the receptor-mediated endocytosis and transcytosis of the maternal immunoglobulin in the rat yolk-sac endoderm. Scanning electron microscopy further revealed lace-like networks of the smooth endoplasmic reticulum near the lateral plasma membrane. Their possible involvement in transport of small molecules or electrolytes is discussed.

Animals↗
PubMed1994

Nefiracetam enhances acetylcholine outflow from the frontal cortex: in vivo microdialysis study in the rat.

The effects of nefiracetam [DM-9384; N-(2, 6-dimethylphenyl)-2-(2-oxo-1-pyrrolidinyl)acetamide], a cognitive enhancer, on extracellular acetylcholine and glutamic acid in the frontal cortex were studied using brain microdialysis in freely moving rats. Nefiracetam administration (1 mg/kg, p.o.) doubled the amount of acetylcholine in the dialysate. When tetrodotoxin was added to the perfusion solution, the basal level of acetylcholine decreased and nefiracetam caused no increase in acetylcholine outflow. The amount of glutamic acid in the dialysates was not affected by nefiracetam. These results suggest that nefiracetam increases the amount of acetylcholine within the cholinergic synaptic clefts.

Acetylcholine↗
PubMed1994

Clinical course and long-term prognosis of Crohn's disease in Japan.

The long-term outcome of Crohn's disease was reviewed in 74 patients who had a history of more than 10 years (range 10.8-27.3) since disease onset. The observation period was between 4.3 and 18.5 years, the mean and SD being 10.6 +/- 3.1 years. The means and SD of age at onset and final observation were 21 +/- 7 and 37 +/- 8 years, respectively. Fifty-eight of the 74 patients had not undergone bowel resection at the time of diagnosis; of these 58, 31 (53.4%) had an operation for the disease during the follow-up period. Thus, of the 74 patients, 47 (63.5%) (these 31, plus the 16 who had undergone bowel resection at the time of diagnosis) had an operation at least once during a follow-up period of 10 years or more. The cumulative operation rates 5, 10, and 15 years after onset in the 74 and 58 patients above were 18.9%, 6.9%, and 40.8%, and 34.8%, 49.1%, and 46.0%, respectively. The corresponding figures 5 and 10 years after diagnosis in all 74 patients and the 58 patients were 32.3% and 28.6% and 47.3% and 46.3%, respectively. There were no significant differences in the incidence of operation rate in relation to anatomical involvement. Cumulative reoperation rates 1, 3, 5, and 10 years after the first operation in the 31 patients who were operated on during the follow-up period were 3.4%, 6.9%, 25.5%, and 51.7%, respectively. Three patients died, the causes of death in one being directly related to Crohn's disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Intestinal and extraintestinal complications of Crohn's disease: predictors and cumulative probability of complications.

Of 238 patients with Crohn's disease seen at our clinics from April 1973 to August 1988, 203 patients were selected for this study, since they fulfilled the following criteria: they had been followed up for more than 6 months as outpatients or had been treated as inpatients for more than 1 month. They were studied to elucidate: (a) the different types and incidence of various complications, (b) the factors related to complications present at the time of diagnosis, (c) predictors of new complications arising after diagnosis, and (d) the cumulative incidence of complications occurring during the course of the disease from the times of onset and diagnosis. Of the intestinal complications, perianal fistula was most common (33%), followed by strictures with dilatations of the proximal bowel (21%), and internal fistula (14%). Of the extraintestinal complications, menstrual disturbance was the most common (18% of the female patients), followed by arthritis (10%), and aphthous stomatitis (10%). As for the factors influencing complications present at the time of diagnosis, the pattern of bowel involvement was significantly correlated with the presence of intestinal stricture, while the erythrocyte sedimentation rate was significantly correlated with the presence of perianal fistula. A significant predictor of new complications arising after diagnosis was the general well-being of patients at the time of diagnosis. Patients who, at diagnosis, already have complications such as stricture, abdominal abscess, internal or external fistula, massive hemorrhage, and free perforation or anal lesions are more likely to develop new complications in addition to those present at diagnosis, compared with patients without any complications at diagnosis (P = 0.055).

Adult↗
PubMed1994

Noninvasive identification of anthracycline cardiotoxicity: comparison of 123I-MIBG and 123I-BMIPP imaging.

To test the feasibility of myocardial 123I-MIBG and 123I-BMIPP imaging for the early detection of anthracycline cardiotoxicity, 13 patients who had received anthracycline anticancer chemotherapeutic agents were studied. Two-dimensional echocardiography and myocardial imaging with both 123I-MIBG and 123I-BMIPP were performed in 13 patients treated with anthracycline (group A) and 10 normal control subjects (group C). Anterior myocardial images were obtained 15 minutes and 3 hours after the injection of isotopes. The heart-to-mediastinum ratio (H/M ratio) was used to quantify cardiac 123I-MIBG and 123I-BMIPP uptake. The left ventricular shortening fraction (%SF) and the ratio of peak mitral flow velocity in early diastole to that at the time of atrial systole (E/A ratio) were measured by echocardiography. The H/M ratio of 123I-MIBG was lower in group A than in group C (1.5 +/- 0.2 vs. 1.9 +/- 0.2, p < 0.01). The patients in group A had faster clearance of 123I-MIBG from the myocardium than those in group C (27 +/- 10% vs. 22 +/- 4%, p < 0.05). However, the H/M ratio and clearance of 123I-BMIPP were similar between the two groups (H/M ratio: 2.1 +/- 0.2 vs. 2.0 +/- 0.2, clearance: 24 +/- 6% vs. 26 +/- 6%). The %SF (37 +/- 8% vs. 36 +/- 7%) and E/A ratio (1.4 +/- 0.4 vs. 1.6 +/- 0.3) were comparable in groups A and C. The present findings indicated that myocardial imaging with 123I-MIBG could detect myocardial damage in patients treated with anthracycline in the early stage when cardiac systolic and diastolic function was still preserved. Early detection of anthracycline cardiotoxicity by 123I-MIBG would reduce the incidence and severity of heart failure.

3-Iodobenzylguanidine↗
PubMed1994

The effect of anti-tumor necrosis factor (TNF)-alpha monoclonal antibody on allergic cutaneous late phase reaction in mice.

Biphasic cutaneous reaction with peak response at 1 (early phase) and 24 to 48 hour (late phase) was elicited by epicutaneous challenge with antigen in actively and passively sensitized mice. Mice were actively immunized with dinitrophenylated (DNP) ascaris antigen and challenged with dinitrofluorobenzene (DNFB). Passively sensitization was carried out by the injection of monoclonal anti-DNP-IgE antibody into mice and challenge was elicited with DNFB. Prednisolone at doses of 3 to 10 mg/kg clearly inhibited both early and late phase reactions in either sensitized mice. Monoclonal anti-tumor necrosis factor (TNF)-alpha antibody inhibited the late phase cutaneous reaction in actively sensitized mice. Anti-interleukin-5 (IL-5) monoclonal antibody has no effect on both phase reactions in either actively and passively sensitized animals. These results indicate the possible participation of TNF-alpha in allergic cutaneous late phase reaction in actively sensitized mice.

Animals↗
PubMed1994

Intraoral computed radiography using the Fuji computed radiography imaging plate. Correlation between image quality and reading condition.

The quality of images obtained by a new method of intraoral computed radiography using three types of imaging plates and a drum scanner designed exclusively for use with an imaging plate was investigated. The aperture size for reading of radiographic data from the imaging plate and for film recording was 50, 100, or 150 microns 2. The results indicated that high resolution type imaging plate for mammography produced the best image quality. For each imaging plate, it was also found that the image quality improved as the aperture size was decreased. However, the high resolution type IP even at the aperture size of 100 microns 2 showed diagnostic accuracy as high as the image processing of conventional periapical radiographs. This finding suggests that this new imaging system using an imaging plate at the reading and recording aperture size 100 microns 2 has promise for use in intraoral radiography.

Evaluation Studies as Topic↗
PubMed1994

Pharmacological studies of platelet-activating factor (PAF)-induced augmentation of response to histamine in guinea-pigs.

An acute increase in airway response to histamine produced by platelet activating factor (PAF) was investigated pharmacologically in guinea-pigs. (1) The airway response to histamine (3 micrograms/kg) measured as pulmonary pressure was increased 8 min after injection of PAF at a dose of 25 ng/kg without affecting the numbers of leukocytes (macrophages, eosinophils, neutrophils and lymphocytes) in bronchoalveolar lavage fluid and airway capillary permeability. (2) To investigate the mechanism responsible for the PAF (25 ng/kg)-induced airway hyperresponsiveness to histamine, the effects of CV-3988 (a PAF-antagonist), ONO-1078 (a leukotriene (LT) antagonist), AA-861 (a 5-lipoxygenase inhibitor), indomethacin (a cyclooxygenase inhibitor), OKY-046 (a thromboxane A2 (TXA2) synthetase inhibitor) and S-1452 (a TXA2 receptor antagonist) were examined. Simultaneously, to investigate the direct antagonistic effects of these drugs on PAF-induced response, the effects of above agents on PAF (150 ng/kg) induced bronchoconstriction were examined. CV-3988 completely inhibited both reactions, while ONO-1078 and AA-861 had no effect on both reactions. OKY-046, S-1452 and indomethacin inhibited PAF-induced bronchoconstriction more potently than PAF-induced airway hyperresponsiveness. These results indicate that inflammatory response is not involved in the onset of PAF-induced acute airway hyperreactivity. Results also suggest that TXA2 but not LT may play a role in the onset of this airway hyperreactivity and the role of TXA2 in hyperreactivity is less important than in PAF-induced bronchoconstriction.

Animals↗