Biomedical subjects

S Koizumi

Publications and source records attributed to S Koizumi.

At least 163 records · Page 9Linked to original sources

PubMed1995

Inhibition by suramin and reactive blue 2 of GABA and glutamate receptor channels in rat hippocampal neurons.

Effects of suramin and reactive blue 2 (RB2), compounds known as antagonists at P2-purinoceptors, on ionic currents mediated through GABA and glutamate receptor channels were investigated in rat hippocampal neurons. Under whole-cell voltage-clamp, suramin (30 to 300 microM) and RB2 (10 to 100 microM) inhibited a current activated by 10 microM GABA in a concentration-dependent manner. Suramin (100 and 300 microM) and RB2 (10 and 30 microM) also inhibited an inward current activated by kainic acid (100 microM), an agonist at non-NMDA type glutamate receptor channels, and an inward current activated by N-methyl-D-aspartate (NMDA; 100 microM), an agonist at NMDA type glutamate receptor channels. The inhibition by suramin or RB2 did not exhibit voltage-dependence between -30 and -90 mV in the case of the GABA- or the kainate-evoked current. In contrast, the inhibition by these compounds of the NMDA-evoked current exhibited voltage-dependence and was enhanced by hyperpolarization. When the concentration of agonists was increased by 5- or 10-fold, the magnitude of the inhibition by suramin of the kainate-evoked current and the magnitude of the inhibition by RB2 of the NMDA-evoked current were attenuated. alpha,beta-Methylene ATP (100 microM) did not affect the GABA-, kainate- or NMDA-activated current. The results suggest that suramin and RB2 inhibit GABA receptor channels and glutamate receptor channels. The blockade of these channels must be taken into account when these compounds are used as pharmacological tools to examine an involvement of P2-purinoceptors, especially in preparations where GABAergic or glutamatergic neurotransmission is expected.

Animals↗

PubMed1995

Application of three-dimensional spiral computed tomographic angiography prior to hepatectomy for hepatocellular carcinoma.

A newly developed method of spiral computed tomography (CT) angiography was employed for 19 consecutive hepatocellular carcinoma (HCC) patients who underwent hepatectomy. Fine images of the intrahepatic vascular structure, portal venous branches and hepatic veins, and HCC nodules were obtained in 16 patients. A more accurate and easier understanding of the relationship between the intrahepatic vascular structure and the HCC nodules was provided by this spiral CT angiography compared with any other imaging modality.

Angiography↗

PubMed1995

Preventive effect of simultaneously infused lipid emulsion against thrombophlebitis during postoperative peripheral parenteral nutrition.

A prospective, randomized study was conducted to determine whether simultaneous infusion of lipid emulsion with an amino acid-dextrose-electrolyte solution would reduce the incidence of thrombophlebitis (TP) during postoperative peripheral parenteral nutrition (PPN). Thirty patients who had undergone gastric resection for adenocarcinoma were randomly divided into two groups according to whether they were infused with 10% lipid emulsion (group A) or 5% glucose solution (group B) simultaneously with the amino acid-glucose solutions. The total osmolarity of the infusion solutions in each group was 853 mOsm/l. The incidence of complications due to TP, namely, redness and/or edema beneath the cannula insertion site and/or pain, was investigated. There were no differences in the background characteristics of the patients in groups A and B, except regarding concurrent resection of other organs (P = 0.03). The incidence of edema in group A was significantly lower than in group B on postoperative days 2 and 4, although there was no difference in the incidence of redness and pain between the two groups. These findings suggest that the simultaneous infusion of lipid emulsion has a preventive effect against TP during postoperative PPN, and may be a practical means of providing PPN after gastrointestinal surgery.

Adenocarcinoma↗

PubMed1995

Reduction of acetylcholine-activated current by low concentrations of extracellular adenosine 5'-triphosphate.

Effects of adenosine 5'-triphosphate (ATP) on ionic currents activated by acetylcholine (ACh) were investigated using rat pheochromocytoma PC12 cells and Xenopus oocytes expressing nicotinic receptors. In PC12 cells, ATP (10 nM to 1 microM) inhibited an inward current activated by ACh in not all but about 60% of cell batches. The ACh-activated current was also inhibited by ATP in Xenopus oocytes and, with a subunit combination of alpha 3 plus beta 4, the inhibition was observed at concentration as low as 100 fM. Uridine 5'-triphosphate (UTP) induced a similar inhibition of the ACh-activated current both in PC12 cells and Xenopus oocytes. These and other properties suggest that the current reduction by ATP is not mediated through conventional P2-purinoceptors.

Acetylcholine↗

PubMed1995

Long-term enhancement of dopamine release by high frequency tetanic stimulation via a N-methyl-D-aspartate-receptor-mediated pathway in rat striatum.

We studied the effects of high frequency tetanic stimulation of the striatum on the KCl (20 mM)-evoked dopamine release in rat striatal slices. The KCl-evoked dopamine release was potentiated by high frequency tetanic stimulation (10-20 Hz) of the striatum including the corticostriatal fibers, and this potentiation was observed until 3 h after high frequency tetanic stimulation. Potentiation of dopamine release after high frequency tetanic stimulation was induced not only by KCl but also by glutamate in Mg(2+)-free medium, N-methyl-D-aspartate in Mg(2+)-free medium, and by DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid. 2-amino-5-phosphovalerate, 3-[(+/-)-2-carboxypiperazine-4-yl]-propyl-1-phosphonate or dibenzocycloheptaneimine, N-methyl-D-aspartate receptor inhibitors, abolished enhancement by tetanus, whereas, 6,7-dinitroquinoxaline-2,3-dione, an antagonist of DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid ionotropic receptors, or L-2-amino-4-phosphonobutyrate, an antagonist of glutamate metabotropic receptors, showed no effect. Moreover, pretreatment with glutamate or N-methyl-D-aspartate in the absence of Mg2+ also facilitated dopamine release evoked by KCl concentrations. When extracellular Ca2+ was removed from the medium during pretreatment, potentiation by glutamate disappeared. We conclude that activation of N-methyl-D-aspartate receptors on dopaminergic nerve terminals in the striatum produces the long-term changes in efficacy of the response to KCl or glutamatergic agents. That is, plastical phenomena could exist at presynaptic levels between glutamatergic neurons and dopaminergic neurons in striatum.

Animals↗

PubMed1995

Flow cytometric functional analysis of multidrug resistance by Fluo-3: a comparison with rhodamine-123.

Using four cell lines including drug-sensitive K562/Parent cells, P-glycoprotein (Pgp)-mediated multidrug resistant (MDR) K562/VCR, K562/ADR and revertant K562/ADR-R cells, two fluorescent agents, Fluo-3 and rhodamine-123 (Rh-123), were compared as indicators in a functional assay of MDR. Cells were incubated with 4 microM Fluo-3 or 1 microM Rh-123 for 45 min and then the intracellular accumulation of the agent was measured using a flow cytometer. Verapamil (20 microM) or cepharanthine (biscoclaurine alkaloid, 10 microM) was added just before the fluorescent agents. Efflux patterns were also studied 60 min after incubation with or without verapamil and cepharanthine. Increased intracellular accumulation and a delayed efflux pattern of Fluo-3 by verapamil and cepharanthine were demonstrated in multidrug resistant K562/VCR and K562/ADR cells, indicating that Fluo-3 is another good indicator of MDR. However, a similar, but lower, increase in uptake and a delayed efflux pattern of Fluo-3 by verapamil and cepharanthine were also demonstrated even in Pgp-non-overexpressed K562/Parent cells. In contrast, accumulation of Rh-123 was not affected by verapamil and cepharanthine. To further study the Pgp dependency of Fluo-3, another cell line, K562/NC16 expressing minimum MDR1 mRNA, was cloned. Increased uptake and a delayed efflux pattern of Fluo-3, but not Rh-123, with verapamil or cepharanthine were again demonstrated in K562/NC16 cells, indicating that intracellular accumulation of Fluo-3 may be non-specifically influenced by verapamil and cepharanthine at very low levels of Pgp-related MDR, while the influx and efflux patterns of Rh-123 may be specifically affected by Pgp overexpression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Inhibition by Zn2+ of uridine 5'-triphosphate-induced Ca(2+)-influx but not Ca(2+)-mobilization in rat phaeochromocytoma cells.

1. Uridine 5'-triphosphate (UTP)-evoked increase in intracellular Ca2+ concentration ([Ca]i) and release of dopamine were investigated in rat phaeochromocytoma PC12 cells. UTP (1-100 microM) evoked an increase in [Ca]i in a concentration-dependent manner. This response was decreased to about 30% by extracellular Ca(2+)-depletion, but not abolished. This [Ca]i rise was mimicked by 100 microM ATP but not by 100 microM 2-methyl-thio-ATP or alpha,beta-methylene-ATP in the absence of external Ca2+, suggesting that the response was mediated by P2U purinoceptors, a subclass of P2-purinoceptors. 2. The UTP-evoked [Ca]i rise consisted of two components; a transient and a sustained one. When external Ca2+ was removed, the sustained component was abolished while the transient component was decreased by about 70% but did not disappear. These results suggest that UTP induces Ca(2+)-mobilization and, subsequently, Ca(2+)-influx. 3. The UTP-evoked increase in [Ca]i was not affected by Cd2+ (100 and 300 microM) or nicardipine (30 microM), inhibitors of voltage-gated calcium channels, but was significantly inhibited by Zn2+ (10-300 microM) in the presence of external Ca2+. Zn2+, however, did not affect the Ca2+ response to UTP in the absence of external Ca2+. 4. UTP (30 microM-1 mM) evoked the release of dopamine from the cells in a concentration-dependent manner. This dopamine release was abolished by Ca(2+)-depletion or Zn2+ but not by Cd2+ or nicardipine. 5. Taken together, the data demonstrate that UTP stimulates P2U-purinoceptors and induces a rise in [Ca]i both by Ca(2+)-mobilization and Ca(2+)-influx in PC12 cells. The dopamine release evoked by UTP requires external Ca2+ which may enter the cells through pathways sensitive to Zn2+ but insensitive to Cd2+ or nicardipine.

Adenosine Triphosphate↗

PubMed1995

Characterization of inhibition by haloperidol and chlorpromazine of a voltage-activated K+ current in rat phaeochromocytoma cells.

1. Inhibition by haloperidol and chlorpromazine of a voltage-activated K+ current was characterized in rat phaeochromocytoma PC12 cells by use of whole-cell voltage-clamp techniques. 2. Haloperidol or chlorpromazine (1 and 10 microM) inhibited a K+ current activated by a test potential of +20 mV applied from a holding potential of -60 mV. The K+ current inhibition did not exhibit voltage-dependence when test potentials were changed between -10 and +40 mV or when holding potentials were changed between -120 and -60 mV. 3. Effects of compounds that are related to haloperidol and chlorpromazine in their pharmacological actions were examined. Fluspirilene (1 and 10 microM), an antipsychotic drug, inhibited the K+ current, but pimozide (1 and 10 microM), another antipsychotic drug did not significantly inhibit the K+ current. Sulpiride (1 or 10 microM), an antagonist of dopamine D2 receptors, did not affect the K+ current whereas (+)-SCH-23390 (10 microM), an antagonist of dopamine D1 receptors, reduced the K+ current. As for calmodulin antagonists, W-7 (100 microM), but not calmidazolium (1 microM), reduced the K+ current. 4. The inhibition by haloperidol or chlorpromazine of the K+ current was abolished when GTP in intracellular solution was replaced with GDP beta S. Similarly, the inhibition by pimozide, fluspirilene, (+)-SCH-23390 or W-7 was abolished or attenuated in the presence of intracellular GDP beta S. The inhibition by haloperidol or chlorpromazine was not prevented when cells were pretreated with pertussis toxin or when K-252a, an inhibitor of a variety of protein kinases, was included in the intracellular solution. 5. Haloperidol and chlorpromazine reduced a Ba2+ current permeating through Ca2+ channels. Inhibition by haloperidol or chlorpromazine of the Ba2+ current was not affected by GDP beta S included in the intracellular solution. 6. It is concluded that haloperidol and chlorpromazine inhibit voltage-gated K+ channels in PC12 cells by a mechanism involving GTP-binding proteins. The inhibition may not be related to their activity as antagonists of dopamine D2 receptors or calmodulin antagonists.

Animals↗

PubMed1995

[Fluctuations in serum antigens and antibodies in a patient with primary cutaneous aspergillosis associated with acute leukemia].

A 5-year-old girl developed cutaneous aspergillosis due to Aspergillus flavus while undergoing remission induction therapy for acute lymphocytic leukemia. Of six serum samples obtained during the acute stage of Aspergillus infection, four showed antigenemia (6.5-22.9 ng/ml) determined by enzyme-linked immunosorbent assay (ELISA). However, five serum samples obtained after treatment with amphotericin B and granulocyte-colony stimulating factor showed negative results for antigens. Sera obtained on day 17 after the detection of skin lesions showed seroconversion in precipitin antibody determined by an immunodiffusion test and in immunoglobulin (Ig) A class antibody determined by ELISA, while sera obtained on day 24 showed seroconversion of IgG and IgM class antibodies. The patient achieved complete remission of leukemia and was discharged on the 92nd day of hospitalization. No signs of disseminated or deep-seated fungal infections were present during the hospitalization. Assays for serum antigens may be of value for the early diagnosis of invasive aspergillosis. Moreover, persistently negative results for antigens in accordance with antibody responses may correlate with recovery from the infection.

Antibodies, Fungal↗

PubMed1995

Bronchial epithelial cells regulate fibroblast proliferation.

Chronic bronchitis frequently leads to irreversible airway obstruction. Alteration of airway architecture with abnormal airway connective tissue is thought to play an important role in this process. We hypothesized that the epithelial cells that line the airways modulate the development of peribronchial fibrosis and fixed airway obstruction by directing fibroblast proliferation. To assess this, we examined stimulatory activities for human lung fibroblast proliferation in bovine bronchial epithelial cell-conditioned medium. The conditioned medium stimulated the proliferation of fibroblasts in a serum-free culture system in a concentration-dependent manner. The fibroblast growth stimulatory activity was heterogenous, with molecular masses of > 50 and approximately 10 kDa. Bronchial epithelial cell-conditioned medium also contained fibroblast growth inhibitory factors, including both transforming growth factor (TGF)-beta and, based on indomethacin sensitivity, cyclooxygenase products. TGF-beta appeared to contribute to the morphological change of fibroblasts induced by the conditioned medium. Co-culture of human lung fibroblasts with bronchial epithelial cells resulted in a stimulation of fibroblast proliferation. In summary, airway epithelial cells appear to regulate fibroblast proliferation and may play a role in peribronchial fibrosis in chronic bronchitis.

Animals↗

PubMed1995

Graves' hyperthyroidism following transient thyrotoxicosis during interferon therapy for chronic hepatitis type C.

We report a case of Graves' hyperthyroidism induced by long-term interferon (IFN) therapy. A 52-year-old woman suffered from chronic active hepatitis type C and was treated with a total of 456 x 10(6) units of IFN-alpha for 23 weeks. During the 12th week of treatment she showed transient thyrotoxicosis. One week after the termination of IFN therapy, TSH-receptor antibodies became positive and subsequently she showed Graves' hyperthyroidism. This case showed sequential manifestation from transient thyrotoxicosis to the appearance of TSH-receptor autoantibodies, and then the occurrence of Graves' hyperthyroidism during IFN therapy. The course of this case may be useful in the understanding of the pathogenesis of autoimmune hyperthyroidism.

Autoantibodies↗

PubMed1995

[ATP as a neurotransmitter in the brain: its possibility based upon recent findings].

We discuss here possible neurotransmitter roles of extracellular ATP in the central nervous system. Important findings concerning the effects of ATP on central neurons have been made in the last few years. A fast neurotransmitter role of ATP in rat medial habenula reported by Edwards et al (1992) may be the best example. In rat cultured hippocampal neurons, we have found that ATP evokes postsynaptic currents, and increases the intracellular Ca2+ concentration. In addition, ATP also produces a "long-term potentiation like effect" in these cells. Receptors for ATP are generally divided into two classes: one class is coupled with ion channels and the other class is coupled with GTP-binding proteins. In cultured hippocampal neurons, the GTP-binding protein-coupled receptors are present and promote the inhibition of K+ channels. Although the channel-coupled receptors have not been identified in the hippocampal neurons, these channels have been found in nucleus solitarii and locus coeruleus. Several types of ATP receptors have been cloned very recently. These cloned receptors, combined with molecular biological techniques, will allow great progress in this field.

Adenosine Triphosphate↗

PubMed1995

Prospective monitoring of minimal residual disease during the course of chemotherapy in patients with acute lymphoblastic leukemia, and detection of contaminating tumor cells in peripheral blood stem cells for autotransplantation.

A prospective study for detecting minimal residual disease (MRD) was conducted on children with acute lymphoblastic leukemia (ALL). Thirty-nine patients (38 B-lineage ALL, one T-ALL) with TCR delta rearrangements could be followed for 21 to 44 months (mean 30.9 months) excluding four patients who died. One hundred and ninety four bone marrow (BM) samples and 13 peripheral blood stem cell (PBSC) grafts were available for detection of MRD. Initially 34 cases were treated prospectively according to the CCLSG risk-stratified protocols for ALL (ALL874 or ALL911), and five cases according to the other protocols. Conventional chemotherapy was replaced by autologous PBSC transplantation (PBSCT) in five patients, by allogenic BM transplantation (BMT) in one patient, or suspended in another patient. Twenty-nine of 32 children in whom conventional chemotherapy could be continued without interruption remain in complete remission (CR). In 24 of the 29 patients MRD became undetectable within 12 months of their diagnosis. In five cases, BM samples obtained during maintenance therapy exhibited residual leukemia cells, and yet none of them relapsed (mean follow-up period 28.6 months). Our results thus indicate that intensive maintenance therapy for patients with PCR-positive results during consolidation therapy may prevent subsequent relapse. Nine events of relapse were diagnosed in eight patients (five BM, two isolated central nervous system (CNS), one combined BM and CNS, one isolated skin relapse). An increase or a re-emergence of MRD was detected in BM samples obtained from patients prior to BM relapse, but one patient remained in CR despite reappearance of leukemic cells following a PCR-negative status. Monitoring of MRD failed to predict isolated CNS or skin relapse. PBSCT allows high-dose cytoreduction therapy for patients with refractory neoplasia. In our study, leukemic cells were identified in eight of 13 PBSC grafts harvested from five patients. Three of four children who received PBSC grafts containing leukemic cells relapsed within 6 months after PBSCT. Monitoring of MRD as part of quality control of PBSC grafts may ultimately contribute to improvements in PBSCT procedures.

Child↗

PubMed1995

[Fibroma of the bladder associated with a large diverticulum: a case report].

A 57-year-old woman was admitted with a chief complaint of difficult urination on June 7, 1993. A filling defect and a large diverticulum were revealed on the cystogram. Cystoscopy showed a tumor, obstructing the internal urethral orifice at the bladder neck and a diverticulum at the right posterior wall of the bladder. Under the preoperative diagnosis of a benign bladder tumor with a diverticulum, resection of the tumor and transvesical diverticulectomy were performed by a suprapubic approach. The resected tumor was smooth-surfaced, elastic soft and was measured 2.0 by 1.5 by 1.0 cm in size. Histologically, the tumor was diagnosed as a benign fibroma of the urinary bladder. The postoperative course was uneventful. Non-epithelial benign bladder tumors are rare. To our knowledge, this is the 18th case of bladder fibroma in the Japanese literature. The characteristics of bladder fibroma are briefly described.

Diverticulum↗

PubMed1994

ETB receptor involvement in stimulatory and neurotoxic action of endothelin on dopamine neurones.

We examined the role of endothelin (ET) receptor subtypes in mediating the transient and sustained release of dopamine (DA) evoked by ETs and ET-1-induced dopaminergic dysfunction in rat striatal slices. Both phases of the release of DA evoked by ET-1 and ET-3 were inhibited by RES-701-1 (ETB antagonist) but not BQ-123 (ETA antagonist). The high K(+)-evoked DA release from slices remained impaired following a brief exposure to ET-1, under conditions of hypoxia/hypoglycaemia. RES-701-1 but not BQ-123 led to a recovery from ET-1-induced striatal dysfunction. Therefore, ETB receptors are involved in the stimulatory and neurotoxic actions of ETs on the striatal dopaminergic system.

Animals↗

PubMed1994

Modulatory effect of plasminogen on NMDA-induced increase in intracellular free calcium concentration in rat cultured hippocampal neurons.

The effect of plasminogen on the intracellular Ca2+ concentration ([Ca]i) was examined in cultured rat hippocampal neurons. Plasminogen (100 nM) did not increase [Ca]i in the presence of tetrodotoxin (TTX, 3 microM) but increased [Ca]i in the absence of TTX. In all the cells which responded to plasminogen (100 nM), NMDA (5 microM) also increased [Ca]i in the presence of TTX. Furthermore, plasminogen (100 nM) enhanced the NMDA-evoked [Ca]i increase, and the potentiation by plasminogen was blocked by an NMDA receptor blocker, 2-amino-phosphonovalerate (APV). These data suggest that plasminogen enhances glutamate-evoked [Ca]i increase through modulation of NMDA receptor in hippocampal neurons.

2-Amino-5-phosphonovalerate↗

PubMed1994

Purification and characterization of a protein that binds to metal responsive elements of the human metallothionein IIA gene.

Metal responsive element (MRE) is a cis-acting DNA motif located in the upstream region of vertebrate metallothionein genes, which can confer metal responsiveness on downstream heterologous promoters. A protein that binds to the MRE sequence in a zinc-dependent manner (zinc regulatory factor; ZRF) was purified 16,000-fold from HeLa cell nuclear extracts by means of the avidin-biotin method, in which a complex formed between ZRF and a biotinylated probe containing MRE was trapped by streptavidin-agarose beads, and ZRF was recovered by salt extraction. By repeating the method three times, a homogeneous 116-kDa protein was obtained whose recovery was zinc-dependent and MRE sequence-specific. UV cross-linking analysis also revealed that a protein that specifically binds to MRE has the same molecular mass as the purified protein. Zinc-dependent and MRE sequence-specific footprints of ZRF were obtained on MREa and MREb in the upstream region of the human metallothionein IIA gene. The ZRF-MRE complex dissociates by the addition of chelating reagents, suggesting a direct role of zinc ions in the DNA binding of ZRF. Partial amino acid sequences of ZRF were found to be highly homologous to those of a mouse MRE-binding protein, mMTF-1.

Amino Acid Sequence↗

PubMed1994

Gastric carcinoma: monoclonal epithelial malignant cells expressing Epstein-Barr virus latent infection protein.

In 1000 primary gastric carcinomas, 70 (7.0%) contained Epstein-Barr virus (EBV) genomic sequences detected by PCR and Southern blots. The positive tumors comprised 8 of 9 (89%) undifferentiated lymphoepithelioma-like carcinomas, 27 of 476 (5.7%) poorly differentiated adenocarcinomas, and 35 of 515 (6.8%) moderately to well-differentiated adenocarcinomas. In situ EBV-encoded small RNA 1 hybridization and hematoxylin/eosin staining in adjacent sections showed that the EBV was present in every carcinoma cell but was not significantly present in lymphoid stroma and in normal mucosa. Two-color immunofluorescence and hematoxylin/eosin staining in parallel sections revealed that every keratin-positive epithelial malignant cell expressed EBV-determined nuclear antigen 1 (EBNA1) but did not significantly express CD45+ infiltrating leukocytes. A single fused terminal fragment was detected in each of the EBNA1-expressing tumors, thereby suggesting that the EBV-carrying gastric carcinomas represent clonal proliferation of cells infected with EBV. The carcinoma cells had exclusively EBNA1 but not EBNA2, -3A, -3B, and -3C; leader protein; and latent membrane protein 1 because of methylation. The patients with EBV-carrying gastric carcinoma had elevated serum EBV-specific antibodies. The EBV-specific cellular immunity was not significantly reduced; however, the cytotoxic T-cell target antigens were not expressed. These findings strongly suggest a causal relation between a significant proportion of gastric carcinoma and EBV, and the virus-carrying carcinoma cells may evade immune surveillance.

Antibodies, Viral↗