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S Kondo

Publications and source records attributed to S Kondo.

At least 451 records · Page 25Linked to original sources
PubMed1996

N3-phenacyluridine, a novel hypnotic compound, interacts with the benzodiazepine receptor.

N3-Phenacyluridine (3-phenacyl-1-beta-D-ribofuranosyluracil) has potent sedative and hypnotic activities following intracerebroventricular injection in mice. To study the mechanism of action of N3-phenacyluridine, the interaction of this compound with the benzodiazepine receptor has been investigated. Results obtained showed that this compound inhibited specific binding of [3H]flunitrazepam to synaptic membranes of bovine cortex in a concentration-dependent fashion (IC50 = 129 microM). Scatchard analysis of [3H]flunitrazepam binding revealed that N3-phenacyluridine interacted with the ligand at the benzodiazepine receptor binding site in a competitive manner. Ro15-1788 (8-fluoro-3-carboethoxy-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a ]1, 4-benzodiazepine), a benzodiazepine receptor antagonist, also inhibited the specific binding of [3H]flunitrazepam in the presence of the compound. The results suggest that the pharmacological activity of N3-phenacyluridine may be partially mediated through the benzodiazepine receptor.

Analysis of Variance↗
PubMed1996

Transacylase-mediated and phosphodiesterase-mediated synthesis of N-arachidonoylethanolamine, an endogenous cannabinoid-receptor ligand, in rat brain microsomes. Comparison with synthesis from free arachidonic acid and ethanolamine.

The levels of N-arachidonoylethanolamine (anandamide), an endogenous cannabinoid-receptor ligand, and a relevant molecule, N-arachidonoylphosphatidylethanolamine (N-arachidonoylPtdEtn), in rat brain were investigated using a newly developed sensitive analytical method. We found that rat brain contains small but significant amounts of these two types of N-arachidonoyl lipids (4.3 pmol/g tissue and 50.2 pmol/g tissue, respectively). Then, we investigated how N-arachidonoylethanolamine (anandamide) is produced in the brain. We found that anandamide can be formed enzymatically via two separate synthetic pathways in the brain: enzymatic condensation of free arachidonic acid and ethanolamine; and formation of N-arachidonoylPtdEtn from PtdEtn and arachidonic acid esterified at the 1-position of phosphatidyl-choline (PtdCho), and subsequent release of anandamide from N-arachidonoylPtdEtn through the action of a phosphodiesterase. We confirmed that rat brain contains both the enzyme activities and lipid substrates involved in these reactions. Several lines of evidence strongly suggest that the second pathway, rather than the first one, meets the requirements and conditions for the synthesis of various species of N-acylethanolamine including anandamide in the brain.

Acyltransferases↗
PubMed1996

Characterization of a ligand for receptor protein-tyrosine kinase HTK expressed in immature hematopoietic cells.

HTK is a receptor tyrosine kinase that belongs to the Eph subfamily. An extensive screening using BIAcore system revealed that a colon cancer cell line, C-1, expressed the ligand for HTK. From the conditioned medium of C-1 cells, a soluble form of ligand was purified by receptor affinity chromatography, and the isolation of full-length cDNA revealed that this ligand is identical to the human HTK ligand (HTKL) previously reported. HTK receptor tyrosine phosphorylation was induced by membrane-bound or clustered soluble HTKL but not by unclustered soluble HTKL, indicating that HTKL requires cell-to-cell interaction for receptor activation. Binding analysis demonstrated that HTKL binds to HTK with a much higher affinity (Kd: 1.23 nM) than the other transmembrane-type ligand for Eph family, LERK-2/ELKL (Kd: 135 nM). The expression of HTK in cord blood cells was upregulated after the culture in the presence of stem cell factor. Clustered soluble HTKL stimulated the proliferation of sorted HTK+ cord blood cells and a hematopoietic cell line, UT-7/EPO from which HTK was isolated. These findings suggest the involvement of HTK-HTKL system in the proliferation of HTK+ hematopoietic progenitor cells in the hematopoietic environment.

Amino Acid Sequence↗
PubMed1996

Concanamycin A, a powerful tool for characterization and estimation of contribution of perforin- and Fas-based lytic pathways in cell-mediated cytotoxicity.

Perforin- and Fas-based cytolytic pathways are two major mechanisms of cell-mediated cytotoxicity. Recently, we have shown that an inhibitor of vacuolar type H+-ATPase, concanamycin A (CMA), inhibits perforin-based cytotoxic activity, mostly due to accelerated degradation of perforin by an increase in the pH of lytic granules. Here we show that CMA failed to inhibit the cytolytic activity of CD4+ CTL clone and perforin-deficient CD8+ CTL clone, which exclusively mediate Fas-based cytotoxicity, although CMA inhibited acidification and induced drastic vacuolation of cytoplasmic granules in these clones. In a wide range of alloantigen-specific CTL, a significant amount of the lysis of Con A blasts from normal mice and of Fas-positive tumor cells remained unaffected even in excess concentrations of CMA. However, CMA almost completely inhibited the lysis of Con A blasts from lpr mice and of Fas low expressing or negative tumor cells. Cytolysis by alloantigen-specific CD8+ CTL derived from gld mice was completely prevented by CMA. Furthermore, CMA-insensitive cytolysis exerted by CD8+ CTL clone was completely inhibitable by soluble Fas molecules. Thus, these data clearly indicate not only that CMA-insensitive cytolysis mediated by alloantigen-specific CTL is Fas dependent, but also that CMA is a selective inhibitor to block only the perforin-based killing pathway. In contrast, brefeldin A blocked the Fas-based cytotoxicity, but only marginally reduced the perforin-based cytotoxicity. Moreover, CMA and brefeldin A in combination completely abrogated all cytolytic activity of alloantigen-specific CTL. Taken together, these results reveal that CTL mainly exert perforin-based cytotoxicity and complementary Fas-based cytotoxicity, and that CMA is a powerful tool to clarify the contributions of the two distinct cytolytic pathways.

Animals↗
PubMed1996

Concentration of vascular endothelial growth factor in the serum and tumor tissue of brain tumor patients.

Vascular endothelial growth factor (VEGF) has been investigated as a potent mediator of brain tumor angiogenesis, vascular permeability, and glioma growth. Using a VEGF ELISA, we determined the concentration of VEGF in the sera and tumor extracts of 19 brain tumor patients including glioblastoma, anaplastic astrocytoma, low grade astrocytoma, meningioma, malignant lymphoma, and metastatic brain tumor as well as normal brain. Although VEGF concentration of the serum was not correlated with that of the tissue, VEGF concentrations of glioblastoma cyst fluid were 200-300-fold higher than those of serum in the patients. VEGF concentration in the tumors was significantly correlated with the vascularity measured by counting vessels stained with von Willebrand factor antibody. VEGF protein localized to the cytoplasm of tumor cells and vasculature in gliomas, predominantly in the peripheral microvessel "hot spots" as well as around the necrosis in glioblastomas. VEGF immunopositivities were well reflected with VEGF concentration determined by ELISA. VEGF ELISA demonstrated time-dependent increase of the VEGF concentration in the serum-free conditioned medium of various glioma cell lines. The conditioned medium with high VEGF concentration induced endothelial cell migration. These observations suggest that VEGF represents a useful marker and measurable element of glioblastoma angiogenesis. The measurement of VEGF concentration by ELISA in tumor and tumor cyst fluid may allow for the assessment of vascularity in gliomas.

Adult↗
PubMed1996

Vascular endothelial growth factor is induced by long-term high glucose concentration and up-regulated by acute glucose deprivation in cultured bovine retinal pigmented epithelial cells.

Vascular endothelial growth factor (VEGF) is closely correlated to diabetic retinopathy. Its basal production in three types of cultured retinal cells (endothelial cells, pericytes and retinal pigment epithelial cells; RPE) was examined. RPE production of VEGF was markedly higher than the rest of the cells. VEGF production in RPE was significantly elevated by 10-day, but not by 1- or 3-day exposure to 16.5 mM glucose compared to a 5.5 mM glucose group. Transient deterioration of diabetic retinopathy is frequently observed during rapid correction of glycemic control. To determine whether VEGF is up-regulated following a sharp drop in the glucose concentration or not, we examined the changes in VEGF production in RPE before and after a sudden drop in the glucose concentration. VEGF production was significantly increased by a glucose concentration decrease from 5.5 to 0.5 mM, but not by a decrease from 33 or 16.5 to 5.5 mM. These findings suggest that up-regulation of VEGF may contribute to the development of diabetic retinopathy and its worsening by hypoglycemia.

Animals↗
PubMed1996

Regulation of mitochondrial pyruvate dehydrogenase activity by tau protein kinase I/glycogen synthase kinase 3beta in brain.

According to the amyloid hypothesis for the pathogenesis of Alzheimer disease, beta-amyloid peptide (betaA) directly affects neurons, leading to neurodegeneration and tau phosphorylation. In rat hippocampal culture, betaA exposure activates tau protein kinase I/glycogen synthase kinase 3beta (TPKI/GSK-3beta), which phosphorylates tau protein into Alzheimer disease-like forms, resulting in neuronal death. To elucidate the mechanism of betaA-induced neuronal death, we searched for substrates of TPKI/GSK-3beta in a two-hybrid system and identified pyruvate dehydrogenase (PDH), which converts pyruvate to acetyl-CoA in mitochondria. PDH was phosphorylated and inactivated by TPKI/GSK-3beta in vitro and also in betaA-treated hippocampal cultures, resulting in mitochondrial dysfunction, which would contribute to neuronal death. In cholinergic neurons, betaA impaired acetylcholine synthesis without affecting choline acetyltransferase activity, which suggests that PDH is inactivated by betaA-induced TPKI/GSK-3beta. Thus, TPKI/GSK-3beta regulates PDH and participates in energy metabolism and acetylcholine synthesis. These results suggest that TPKI/GSK-3beta plays a key role in the pathogenesis of Alzheimer disease.

Animals↗
PubMed1996

Quantitative analysis of vascular endothelial growth factor in primary breast cancer.

BACKGROUND: Recent clinical studies have demonstrated that tumor angiogenesis is a potent prognostic indicator for breast cancer patients. The quantitation of endothelial growth factors is thought to be useful to assess angiogenic phenotype in the tumor. Among the many new endothelial growth factors, vascular endothelial growth factor (VEGF) is known to be particularly responsible for promoting the neovascularization in human breast cancer. METHODS: Intratumoral protein levels of VEGF were measured by enzymatic immunoassay in 135 primary breast cancer tissues. The VEGF levels were compared with the microvessel density evaluated by immunostaining the endothelial antigen and also were compared with intratumoral protein levels of other endothelial growth factors, including basic fibroblast growth factor (bFGF) and hepatocyte growth factor (HGF). RESULTS: Intratumoral VEGF concentrations varied from 3.3 pg/mg protein to 2032 pg/mg protein (average 148 pg/mg protein). An immunocytochemical analysis using anti-VEGF antibody confirmed that VEGF was located mainly in the cytoplasm of the tumor cells. The VEGF concentrations were significantly higher in vascularly rich tumors than in vascularly poor tumors. No significant association was found between VEGF concentrations and the two other endothelial growth factor concentrations. CONCLUSIONS: The quantitation of intratumoral VFGF levels seems to be useful for assessing the activity of tumor angiogenesis.

Breast Neoplasms↗
PubMed1996

Molecular and cellular basis for type I heparin cofactor II deficiency (heparin cofactor II Awaji).

Heparin cofactor II (HCII) is a serine proteinase inhibitor in human plasma that rapidly inhibits thrombin in the presence of dermatan sulfate or heparin. To understand the molecular mechanism for HCII deficiency in a patient with reduced circulating HCII antigen, we studied a Japanese patient with type I HCII deficiency who suffered from angina pectoris and coronary artery disease. Polymerase chain reaction (PCR)-based sequence analysis showed that the propositus' gene for HCII (HCII Awaji gene) had a thymine insertion after codon (GAT) for Asp88 in exon II, resulting in a frameshift mutation. Consequently, the abnormal HCII Awaji protein was suggested to have an altered amino acid sequence from position 89 and terminate at 107, thus being composed of the NH2-terminal one fifth of normal HCII and dysfunctional for thrombin inhibition. The molecular weight and pI value of HCII Awaji were calculated to be 12,040 and 3.6, respectively, without posttranslational modification. Mutagenic PCR followed by the Tsp509I digestion showed that a half of the PCR products derived from the propositus and his sister was cleaved, suggesting that his sister also has the same mutant allele. Crossed-immunoelectrophoresis and Western blot analyses of plasma and urine from the the propositus and of plasma from his sister did not provide evidence for the existence of the abnormal HCII, suggesting that little truncated HCII was circulating in the patient's blood. However, stable expression assay using human kidney 293 cells transfected with the expression vector containing cDNA encoding wild-type or Awaji-type HCII showed that mutant as well as wild-type HCII was secreted into culture medium normally. These results suggest that the abnormal HCII Awaji protein is secreted normally, but rapidly degraded in the circulating blood.

Amino Acid Sequence↗
PubMed1996

Enzymatic synthesis of anandamide, an endogenous cannabinoid receptor ligand, through N-acylphosphatidylethanolamine pathway in testis: involvement of Ca(2+)-dependent transacylase and phosphodiesterase activities.

Rat testis was shown to contain significant amounts of both N-acylethanolamine, including N-arachidonoylethanolamine (anandamide), and N-acylphosphatidylethanolamine (N-acylPE), including N-arachidonoylPE. The fatty acid profiles of the N-acyl moieties of the two classes resembled each other. We confirmed that testis microsomes contain a phosphodiesterase activity catalyzing the release of anandamide from N-arachidonoylPE. They also contain an enzyme activity catalyzing the transfer of arachidonic acid from the 1-position of diacylphospholipids to PE to form N-arachidonoylPE. These results suggest that the N-acylPE pathway is important in the synthesis of anandamide in this tissue.

Acyltransferases↗
PubMed1996

Mannosylated superoxide dismutase inhibits hepatic reperfusion injury in rats.

Superoxide anion radical (O2-) is one factor related to ischemia/reperfusion injury to the liver. The sites of O2- production and injury have yet to be determined. Superoxide dismutase (SOD), a specific scavenger for O2-, has an inhibitory effect on injury caused by O2-. SOD is of low molecular weight; hence, it has a short half-life in the circulating blood. Mannosylated SOD is taken up in sinusoidal endothelial cells of the liver by receptor-mediated endocytosis. In rats with an occluded inflow against 70% of the liver for 30 min followed by reperfusion there were elevations of serum aspartate aminotransferase and alanine aminotransferase, and lipid peroxide concentrations in liver tissue were significantly inhibited by intravenous administration of mannosylated SOD compared to treatment with normal saline. Electron microscopic examination showed that mannosylated SOD protected against damage to the sinusoidal endothelial cells caused by ischemia/reperfusion and that conventional SOD had no such protective effect. Thus, O2- produced by ischemia/reperfusion apparently damages sinusoidal endothelial cells, and damage to hepatic parenchymal cells is secondary. Mannosylated SOD deserves further study for possible use in surgical resection of the liver and for liver transplantations.

Alanine Transaminase↗
PubMed1996

Postprandial responses of liver blood flow prior to and following hepatectomy in conscious dogs.

The responses of the portal and hepatic arterial blood flows to various diets and nutrients were measured simultaneously in conscious dogs prior to and following hepatic resection. Prior to hepatectomy, the increase in the portal blood flow was significantly larger in response to an elemental diet, fats, or amino acids than to glucose or water. The peak increase was 60.2 +/- 14.4 ml for water, 144.7 +/- 22.1 ml for a 150-cal elemental diet, 168.5 +/- 16.1 ml for a 300-cal elemental diet, 86.7 +/- 14.0 ml for a glucose solution, 159.3 +/- 16.7 ml for an amino acid meal, and 188.5 +/- 25.3 ml for a fat meal. Following partial hepatectomy, fats and amino acids induced an increase in the portal blood flow similar to that prior to hepatectomy. Glucose and the elemental diet, on the other hand, induced a significantly larger increase in portal blood flow following the surgery although water did not. The peak increase was 144.4 +/- 27.8 ml for glucose (166% of the peak increase prior to hepatectomy) and 221.8 +/- 32.5 ml for the 300-cal elemental diet (132%). The postprandial response of the hepatic artery to every diet was quite different among the dogs and there were no significant changes both prior to and following surgery. The different response of the portal flow to intraluminal glucose following partial hepatectomy may be due to alterations in glucose metabolism following hepatectomy. We have shown that the postprandial response of the portal blood flow varies with the type of nutrient, and it can be altered by hepatectomy.

Animals↗
PubMed1996

Changes in liver blood flow after hepatectomy in conscious dogs.

Hepatic circulation after hepatectomy was investigated in conscious dogs under fasting and feeding conditions. After a 40% hepatectomy, both the hepatic arterial and portal blood flow were measured simultaneously using ultrasonic transit time flowmeters. During fasting, the total hepatic blood flow (i.e., the sum of arterial and portal blood flow) changed in a biphasic pattern after hepatectomy. The first peak (517.9 +/- 42.7 ml/min; 130.1% of preoperative flow) was seen on the 1st postoperative day (POD) and the second peak (444.8 +/- 25.6 ml/min; 112.7% of preoperative flow) occurred on the 7th POD. The portal flow demonstrated the same biphasic changes as the total hepatic flow, although the hepatic arterial flow showed only the first peak. A heart rate analysis suggested that the first peak was probably due to hyperdynamic circulatory conditions, as has been previously reported. In addition, the existence of the second peak was established by the present study. The postprandial hepatic blood flow decreased during the first 2 weeks postoperatively, but exceeded the presurgical levels on PODs 21 and 28.

Animals↗
PubMed1996

99mTc-DTPA-HSA uptake in a case of splenic hamartoma.

Primary splenic tumors are very rare. The authors present a case of splenic hamartoma in which positive 99mTc-DTPA-HSA uptake was recognized with ultrasound, CT, MR and angiographic images. This case showed the need to consider hamartoma as well as hemangioma in the differential diagnosis of 99mTc-DTPA-HSA uptake in splenic tumors.

Female↗
PubMed1996

Progesterone induces vascular endothelial growth factor on retinal pigment epithelial cells in culture.

Diabetic retinopathy is known to frequently deteriorate during pregnancy but the cause remains obscure. Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), is a potent vascular endothelial cell mitogen which is mainly up-regulated by hypoxia, and is closely associated with the development and progression of diabetic retinopathy. To examine the influence of the drastic hormonal alterations during pregnancy on the worsening of diabetic retinopathy, we examined the effects of estradiol (E2) and progesterone (P4) on the production of VEGF/VPF in bovine retinal pigment epithelial cells in culture. The VEGF/VPF production was significantly elevated (214.5 +/- 28.3 ng/g protein, P < 0.01) by 48 h of exposure to a high concentration of P4(10 microM), which is still within the physiological range during pregnancy, compared to that of the control group (147.7 +/- 17.9 ng/g protein). However, E2 significantly stimulated the production of VEGF/VPF only at concentrations (100 microM) much higher than normally encountered during pregnancy. These two hormones were not observed to have a synergistic effect, at least at physiological concentrations. As the increase in serum P4 levels during pregnancy is reported to be greater in pregnant diabetic patients with progressive retinopathy, our findings suggest that P4 may contribute to the worsening of diabetic retinopathy during pregnancy by up-regulating intraocular VEGF levels.

Animals↗
PubMed1996

Expression of CD26/dipeptidyl peptidase IV in adult T cell leukemia/lymphoma (ATLL).

The association of CD26/dipeptidyl peptidase IV (DPPIV) and human T lymphotropic virus type I (HTLV-I) was studied by two approaches. First, we examined the expression of CD26 in peripheral blood mononuclear cells (PBMC) from the patients with adult T cell leukemia/lymphoma (ATLL), an HTLV-I-related malignancy. The expression of CD26 on the surface of PBMC was decreased in all 20 patients with ATLL compared with those from normal individuals (P < 0.01) and the expression of the CD26 gene transcript was not detectable in seven out of eight patients with ATLL. Then we compared the quantity of viral DNA in CD26-negative (CD26-) and CD26-positive (CD26+) cells obtained from 17 HTLV-I healthy carries by using a polymerase chain reaction method. The CD26-cells had a higher copy number of viral DNA than CD26+ cells. These findings indicate that HTLV-I has in vivo tropism to CD26- cells, suggesting that some phenotypes of ATLL cells reflect the in vivo cellular tropism of HTLV-I.

Adult↗
PubMed1996

Inhibition of human immunodeficiency virus type 1 infectivity by a new amine bellenamine.

Bellenamine, (R)-3,6-diamino-N-(aminomethyl)hexanamide (molecular weight 174), produced by Streptomyces nashvillensis, which has been reported to have weak antibacterial activity and to slightly enhance the immune response, showed potent activity against human immunodeficiency virus type 1 (HIV-1). Its mode of action was investigated. Bellenamine inhibited de novo infection of human T cells with HIV-1, at a 50% effective concentration (EC50) of 0.62 micrograms/ml (3.6 microM). Its 50% cytotoxic concentration (CC50) was over 2000 micrograms/ml (11.5 mM) and thus its cytotoxicity was quite low. When HIV-1-infected cells were treated with bellenamine or glycosylation inhibitors, they produced virus with reduced infectivity, and thus bellenamine inhibited the secondary spread of HIV-1 in vitro similarly to glycosylation inhibitors. However, bellenamine did not change the apparent molecular weights of env or gag proteins, unlike glycosylation inhibitors. Bellenamine showed no significant activity against virus adsorption, reverse transcriptase, viral protease or the glycosylation process. The antiviral mechanism of bellenamine remains to be examined further.

Antiviral Agents↗