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M Niwa

Publications and source records attributed to M Niwa.

At least 253 records · Page 14Linked to original sources
PubMed1994

Microglia with an endothelin ETB receptor aggregate in rat hippocampus CA1 subfields following transient forebrain ischemia.

We examined endothelin (ET) receptors in the hippocampus CA1 subfields of stroke-prone spontaneously hypertensive rats subjected to a 10-min bilateral carotid occlusion and reperfusion. When delayed neuronal death had occurred in the pyramidal cell layer at 7 days after transient forebrain ischemia, the quantitative receptor autoradiographic method we used revealed a dramatic increase in number of 125I-ET-1 binding sites in the hippocampus CA1 subfields. The highest number of de novo binding sites appeared in the area corresponding anatomically to the pyramidal cell layer with neuronal death. These binding sites were characteristically the ETB receptor. The de novo 125I-ET-1 binding was mainly present on microglia aggregating with a high density in the damaged pyramidal cell layer. As ET-1- and ET-3-like immunoreactivities were highly expressed within astrocytes in damaged neural tissue, the possibility that microglia with the ETB receptor are activated to participate in the pathophysiology of ischemia-related neural tissue damage by astrocytic ET-1 and ET-3 produced in response to transient forebrain ischemia would have to be considered.

Amino Acid Sequence↗
PubMed1994

Enhanced expression of an endothelin ETA receptor in capillaries from human glioblastoma: a quantitative receptor autoradiographic analysis using a radioluminographic imaging plate system.

We identified and characterized 125I-endothelin-1 (125I-ET-1) binding sites in tumor capillaries isolated from human glioblastomas, using the quantitative receptor autoradiographic technique with pellet sections. Quantification was done using the computerized radioluminographic imaging plate system. High-affinity ET receptors were localized in capillaries from glioblastomas and the surrounding brain tissues (KD = 4.7 +/- 1.0 x 10(-10) and 1.6 +/- 0.3 x 10(-10) M, respectively; Bmax = 161 +/- 38 and 140 +/- 37 fmol/mg, respectively; mean +/- SEM, n = 5). BQ-123, a selective antagonist for the ETA receptor, potently competed for 125I-ET-1 binding to sections of the microvessels with IC50 values of 5.1 +/- 0.3 and 5.1 +/- 1.5 nM, and 10(-6) M BQ-123 displaced 84 and 58% of ET binding to capillaries from tumors and brains, respectively. In addition, competition curves obtained in the presence of increasing concentrations of ET-3 showed two components (IC50 = 5.7 +/- 2.5 x 10(-10) and 1.4 +/- 0.2 x 10(-6) M for tumor microvessels, 1.8 +/- 0.6 x 10(-10) and 1.1 +/- 0.3 x 10(-6) M for brain microvessels, respectively). Our results indicate that (a) the method we used is simple and highly sensitive for detecting and characterizing various receptors in tumor capillaries, especially in the case of a sparse specimen, and (b) capillaries in glioblastomas express specific high-affinity ET binding sites, candidates for biologically active ET receptors, which predominantly belong to the ETA subtype.

Adult↗
PubMed1994

The induction of interleukin-6 (IL-6) and colony-stimulating factors (CSFs) by FK565 and its thrombopoietic activity following in vivo administration.

The induction of macrophage colony-stimulating factor (M-CSF) in monkey plasma following administration of FK565 was observed within 2 h of injection peaked at 4 h, and remained high after 24 h. Interleukin-6 (IL-6) and M-CSF levels increased in monkeys treated with FK565, even at doses as low as 0.01 mg/kg. Granulocyte CSF (G-CSF) levels increased slightly following a dose of 1 mg/kg, but granulocyte macrophage CSF (GM-CSF) was not detected at any doses of FK565 studied. To examine the thrombopoietic activity of FK565 in vivo, single doses of drug (0.01, 0.1 or 1.0 mg/kg) were administered i.v. to cynomolgus monkeys or normal mice on day 0. The promotes platelet (PLT) count after FK565 injection decreased transiently on days 1 and 2, and then increased in a dose-dependent manner on day 5 and was still high on day 14. The experiment using anti-PLT antibody showed that the increased PLT count was not simply due to a rebound phenomenon after the transient decrease in PLT. The effect of i.v. FK565 was studied in mice myelosuppressed with a single dose of mitomycin C (MMC) (5.6 mg/kg). The fall in PLT count was suppressed on day 7 by 0.1 and 1.0 mg/kg FK565. Although intact cells or tissues are necessary for an increase in PLT following FK565 treatment, FK565 suppressed the impaired hematopoietic function seen after chemotherapy. FK565 is proposed as a drug to restore reduced neutrophil and platelet counts found in AIDS or cancer therapy.

Animals↗
PubMed1994

[Quantitative receptor autoradiography].

The quantitative receptor autoradiographic method has been developed to determine the precise location and kinetic properties of receptors for biologically active transmitters, based on the original technique for benzodiazepine receptors in the rat brain with a 3H-labeled ligand. The autoradiography with hyperfilm-3H of cryostat sections (10- to 20-microns thick) incubated with appropriate 3H- or 125I-labeled ligands and analysis of the autoradiogram by computerized microdensitometry makes feasible quantitative determinations and complete characterization of receptors in tissues from a single animal and in human tissues obtained at autopsy. Furthermore, the autoradiographic technique has advantages over receptor binding assays with partially purified membrane preparations because it enables precise anatomical localization and has high sensitivity. In some cases, the autoradiogram can be quantitated with a computerized radioluminographic imaging-plate system. Special care has to be taken when a 3H-labeled ligand is used, since tissue quenching of the radioisotope energy of 3H is linked to the failure to attain precise quantitation of receptors in myelin-rich areas such as brain white matter. In combination with quantitative radioimmunohistochemical and in situ hybridization techniques, the quantitative receptor autoradiographic method should enable investigators to elucidate the roles of receptors for biologically active transmitters.

Animals↗
PubMed1994

Incidental white matter lesions identified on magnetic resonance images of normal Japanese individuals--correlation with age and hypertension.

Incidental white matter high-intensity lesions are frequently seen on T2-weighted magnetic resonance (MR) images of the brain in older people. The incidence increases with advancing age or hypertension. Brain MR images of 59 normal individuals were examined to analyze this phenomenon. The total number of white matter high-intensity lesions correlated significantly with age (p = 0.004) or systolic blood pressure (p = 0.03). The 60- to 69-year-old group demonstrated a very close correlation of white matter lesions with systolic (p = 0.02) and diastolic blood pressure (p = 0.01), in contrast to the 50- to 59-year-old group. Hypertensive subjects in their 60s are thought to develop more white matter lesions than subjects in their 50s.

Adult↗
PubMed1994

Early changes in volume and non-enhanced volume of acoustic neurinoma after stereotactic gamma-radiosurgery.

The effectiveness of stereotactic gamma-radiosurgery for treating acoustic neurinoma was evaluated by measuring the volumes of the tumor, non-enhanced tumor, and cerebellar edema in 13 patients with acoustic neurinoma who were followed up for 9 to 15 months (median 12.7 mos) after treatment. The tumor volume and non-enhanced volume tended to reach a maximum after 6 months, and cerebellar edema volume after 9 months, then decreased gradually thereafter. Hearing loss tended to increase gradually, but involvement of the facial nerve was transient.

Aged↗
PubMed1994

Effect of suramin on 125I-insulin-like growth factor-I binding to human meningiomas and on proliferation of meningioma cells.

Suramin, a polyanionic compound, has been shown to inhibit the binding of various growth factors to cell surface receptors. The effects of suramin on 125I-insulin-like growth factor (IGF)-I binding to human meningioma tissues and IGF-I-induced deoxyribonucleic acid (DNA) synthesis in cultured meningioma cells were examined using the quantitative receptor autoradiographic method and 3H-thymidine incorporation, respectively. Suramin inhibited specific 125I-IGF-I binding to meningioma tissue sections in concentration-dependent manner, with a 50% inhibiting concentration (IC50) of 8.7 +/- 0.5 x 10(-5) M. The addition of 10(-3) M suramin to the incubation buffer potently dissociated 125I-IGF-I previously bound to meningioma tissue as a function of time (dissociation half-life (T1/2) 6.8 minutes). After preincubation of tissue sections with 10(-3) M suramin for 120 minutes, there was no inhibition of the subsequent 125I-IGF-I binding to meningiomas. Suramin inhibited the IGF-I-induced incorporation of 3H-thymidine into meningioma cells in a dose-dependent manner, with an IC50 of 4.6 +/- 1.4 x 10(-5) M. The growth rate of meningioma cells (determined 4 days after seeding) was reduced by 10%, 20%, and 50% of the control culture in the presence of 10(-6), 10(-5), and 10(-4) M suramin, respectively. These results suggest that suramin interferes with IGF-I binding to meningioma tissue and inhibits proliferation of cells, at least partially by preventing IGF-I-induced DNA synthesis and probably by interacting with IGF-I directly rather than with its binding sites.

Aged↗
PubMed1994

Expression of a functional endothelin (ETA) receptor in human meningiomas.

Endothelin (ET) receptor subtypes (ETA and ETB) in human meningiomas were characterized using quantitative receptor autoradiography. A single class of high-affinity 125I-ET-1 binding sites was localized in all meningioma tissue studied (dissociation constant: 2.4 +/- 0.3 nM, maximum binding capacity: 319 +/- 66 fmol/mg (mean +/- standard error of the mean for 13 tumors)). Unlabeled ET-1 showed a strong affinity for 125I-ET-1 binding to tissue sections of the tumors with a 50% inhibiting concentration (IC50) of 2.9 +/- 0.7 x 10(-9) M, whereas ET-3 showed a much lower affinity (IC50: 8.4 +/- 2.5 x 10(-6) M). Sarafotoxin S6c, a selective agonist for the ETB receptor, could not compete for 125I-ET-1 binding to meningiomas. Endothelin-1 significantly stimulated deoxyribonucleic acid (DNA) synthesis in a dose-dependent manner in cultured human meningioma cells. In contrast, no significant stimulation of DNA synthesis occurred with an S6c concentration up to 10(-7) M. Pretreatment of the meningioma cells with pertussis toxin, a bacterial toxin that adds adenosine 5'-diphosphate-ribose to the alpha subunit of guanine nucleotide binding (G) proteins such as Gi or G(o), induced a concentration-dependent reduction in ET-stimulated DNA synthesis in meningioma cells, but did not affect the epidermal growth factor-induced DNA synthesis. These observations suggest that the ETA receptor is predominantly expressed in human meningioma tissue and that ET may act as a growth factor on the meningioma cells by interacting with the ETA receptor and by pertussis toxin-sensitive mechanisms.

Adolescent↗
PubMed1994

Helicobacter pylori infection in gastric carcinoma.

PURPOSE: This study was undertaken to compare the pathoclinical findings in gastric adenocarcinoma with serum IgG antibody to Helicobacter pylori. MATERIALS AND METHODS: We examined 185 patients with histologically established gastric cancer. The presence of immunoglobulin (Ig)G antibody in the high molecular cell-associated antigen of H. pylori was determined by enzyme-linked immunosorbent assay. Pepsinogens I and II were measured by radioimmunoassay. The distribution of H. pylori on the gastric mucosa was assessed by the Campylobacter-like organism test and phenol red dye spraying. RESULTS: H. pylori IgG antibody was detected in 93.1% of patients with gastric cancer (mean age 61.7 years), 94.3% of patients with early gastric cancer and 91.2% with advanced gastric cancer. No statistical difference in serology was observed between type of gastric cancer, depth of cancer invasion, tumor size or histology. Only in patients with diffuse-type cancer of the cardia was there a lower percentage of positive results (80.0%). The ratio of pepsinogen I to pepsinogen II was higher in the patients who exhibited no H. pylori antibodies. CONCLUSIONS: H. pylori antibodies were common in patients with gastric cancer, and were not correlated with histological type nor stage of cancer. In the Niigata district, a higher percentage of patients with gastric carcinoma displayed H. pylori antibodies compared with other districts in Japan.

Adenocarcinoma↗
PubMed1994

GABA receptor function in the parasympathetic ganglia.

The criteria required to establish gamma-aminobutyric acid (GABA) as a neurotransmitter have been fulfilled in the enteric nervous system of the mammalian intestine. In the intestine, GABA-A receptors are located on somato-dendritic regions of the postganglionic cholinergic neurons and mediate the release of acetylcholine (ACh). GABA-B receptors are located on nerve terminals of the cholinergic neurons and mediate inhibition of nerve-stimulated release of ACh. In the urinary bladder, GABA is possibly a noncholinergic, nonadrenergic inhibitory neurotransmitter. Both GABA-A and GABA-B receptors seem to be present in the parasympathetic ganglia and mediate inhibition of ACh release from the cholinergic neurons. Thus, the functional property of GABA-A receptor is different between the intestine and urinary bladder. GABA-A receptors are also located on the GABAergic nerve terminals as an autoreceptor, and mediate inhibition of GABA release both in the intestine and urinary bladder.

Animals↗
PubMed1994

[An enzyme-linked immunosorbent assay for the detection of IgG antibodies against urease of Helicobacter pylori].

We have developed an enzyme-linked immunosorbent assay (ELISA) for the detection of IgG antibodies against Helicobacter pylori (HP) using purified HP urease as an antigen. The urease was purified from ultrasonicated extract of HP by NaCl linear gradient system on DEAE-Sepharose 4B chromatography. Two molecular weight bands, 65kD and 27kD were observed on a SDS-PAGE gel in the purified urease sample. The urease antigen did not crossreact to rabbit antibodies prepared against Campylobacter coli and Campylobacter jejuni. Out of 93 gastric biopsy patients, sixty nine patients (74.2%) were positive in HP culture test. Serum HP antibody titers (AU: arbitrary unit) of HP culture positive and negative patients were 42.9 +/- 47.4 and 16.7 +/- 25.7 (mean +/- SD), respectively (p < 0.05). The ELISA system have sensitivity of 72.5% and specificity of 70.8%. We believe that the ELISA system is useful for diagnosis and monitoring of HP infection.

Adolescent↗
PubMed1993

Identification of three forms of the gamma subunit of G proteins isolated from bovine spleen.

We reported previously that G proteins from bovine spleen contain at least five forms of the gamma subunit (designated S1 through S5), among which S1 and S5 have been identified as novel gamma and gamma 2 subunits, respectively. In this study, we identified the other three forms of the gamma subunit, namely, S2, S3 and S4. Amino acid sequences of proteolytic fragments obtained from S2, S3 and S4 coincided exactly with internal sequences of gamma 7, gamma 5 and gamma 2, respectively. However, sequence analysis of undigested S4 revealed that S4 was an N-terminally truncated form of gamma 2, while analysis of the C-terminal fragment by fast atom bombardment mass spectrometry revealed that the C-terminus of S4 seemed to be geranylgeranylated and carboxymethylated as is that of intact gamma 2. Thus, the three types of gamma subunit obtained from bovine spleen were identified as gamma 7, gamma 5, and an N-terminally truncated gamma 2.

Amino Acid Sequence↗
PubMed1993

Clinical usefulness of computer-assisted diagnosis using combination assay of tumor markers for pancreatic carcinoma.

BACKGROUND: There has been extensive use of serum tumor markers in diagnosing pancreatic adenocarcinoma. There is no tumor marker, however, that alone has sufficient diagnostic accuracy. It is necessary to know which combination of tumor markers should be used to detect pancreatic cancer, with respect to clinical usefulness and cost effectiveness. METHODS: Serum levels of 17 kinds of tumor markers were determined in 145 patients and 40 healthy volunteers. Thirty-five patients with proven pancreatic adenocarcinoma, and 32 with benign pancreatobiliary disease (14 chronic pancreatitis and 18 biliary stones) were selected. For analysis of the usefulness of each tumor marker to differentiate these two groups, scatterplot and relative operating characteristic (ROC) analyses were used. A multivariate discriminant system to differentiate these two groups was developed using stepwise discriminant analysis by backward elimination selection. RESULTS: The significance of each tumor marker varied according to the tumor volume. By ROC analysis, the markers were divided into four subgroups according to their usefulness in discriminating pancreatic adenocarcinoma from benign pancreatobiliary disease. A discriminant system consisting of two different discriminant functions using nine tumor markers (CA 19-9, DUPAN-2, TPA, elastase-1, lipase, amylase, gamma-glutamyl transpeptidase, alkaline phosphatase, and lactate dehydrogenase) was developed and designated CAMPAS-P; it could differentiate between all 35 cases of pancreatic adenocarcinoma and 32 cases of benign pancreatobiliary disease. On the other hand, CAMPAS-P showed a low positive rate in pancreatic tumors of unusual histologic type, and poor organ-specific diagnostic ability in various digestive organ malignancies. CONCLUSIONS: CAMPAS-P may be very useful for differential diagnosis between pancreatic adenocarcinoma and benign pancreatobiliary disease.

Adenocarcinoma↗
PubMed1993

Purification and molecular cloning of mouse renal dipeptidase.

Mouse renal dipeptidase (mouseRDP, EC 3.4.13.11) was purified from the membrane fraction of kidney. The molecular mass of the enzyme was 115 kDa by size-exclusion HPLC and SDS-PAGE under non-reduced conditions and 58 kDa by SDS-PAGE under reduced conditions. The mouseRDP cDNA fragment was amplified from mouse kidney total RNA by reverse transcription-polymerase ŏffin reaction (RT-PCR). The mouseRDP cDNA was isolated from a kidney cDNA library using the probe. The primary structure of mouseRDP deduced from the cDNA showed a high homology with renal dipeptidase from various mammals, except for the amino-terminal and carboxy-terminal domains. Recombinant mouseRDP obtained from transfected mouse L929 cells containing the expression plasmids has the same Km value and molecular mass as native mouse renal dipeptidase. From Northern blotting analysis, expression of the mouseRDP gene was recognized in both kidney and liver.

Amino Acid Sequence↗
PubMed1993

Involvement of cholinergic neurons in intestinal contraction caused by vasoactive intestinal contractor.

The mechanism of the contractile response to vasoactive intestinal contractor (VIC) was examined in the isolated guinea-pig small intestine. VIC at 10(-9) to 10(-7) M produced a transient relaxation followed by a contraction, and this contraction was partially inhibited, to the same degree, by either atropine or tetrodotoxin. VIC (10(-8) M) induced an increase in the release of [3H]acetylcholine from the ileum preloaded with [3H]choline. The VIC-induced acetylcholine release was dependent on external Ca2+. Thus, the VIC-induced contractions may relate to stimulation of cholinergic neurons and smooth muscle cells.

Acetylcholine↗
PubMed1993

Cloning and structural analysis of genomic DNA for human renal dipeptidase.

A genomic DNA for human renal dipeptidase was isolated from a human genomic library using probes for human renal dipeptidase cDNA. The human renal dipeptidase gene, containing ten exons and nine introns, had a total length of approx. 6 kbp. The DNA sequence of these exons was slightly different from that of the human renal dipeptidase cDNA reported by Adachi et al. [1]. From the results of a comparison of the deduced amino acid sequence of each exon with various mammalian renal dipeptidases, the fourth exon was found to be highly conserved (90%).

Amino Acid Sequence↗
PubMed1993

Biphasic effects of suramin on 125I-epidermal growth factor binding to human meningiomas.

1. We studied the effects of suramin, a nonspecific growth factor antagonist, on epidermal growth factor (EGF) binding to cell surface receptors in surgically excised human meningiomas, using quantitative receptor autoradiographic methods with radioluminography. 2. High concentrations (10(-4) - 10(-2) M) of suramin inhibited 125I-EGF binding to meningioma sections with IC50's of 3.2 +/- 0.4 x 10(-4) M, whereas lower concentrations (10(-5) - 10(-4) M) of the drug significantly enhanced EGF binding to the tumor. Scatchard analysis of EGF binding profile revealed significant increases in binding affinity following incubation in the presence of 5 x 10(-5) M suramin, without significant alterations in maximal binding capacity. 3. The addition of 10(-3) M suramin to the incubation buffer rapidly dissociated 125I-EGF previously bound to meningioma tissues as a function of time (dissociation half-life, T1/2 = 12.4 min). 4. Preincubation in the presence of 5 x 10(-5) M suramin resulted in significant increases in the subsequent binding of 125I-EGF to meningiomas, compared to findings in the control. 5. Our data indicate that (a) suramin exerts biphasic effects on EGF binding to the tissue sections of meningiomas in vitro, depending on the concentration of the drug; and (b) low concentrations of suramin enhance the affinity of the EGF receptor in the tumor sections, probably by interacting with the EGF receptor molecule rather than with the EGF peptide. 6. The functional role of increased EGF receptor affinity in meningioma sections in the presence of lower concentrations of suramin remains to be determined.

Aged↗