Biomedical subjects

T Ikeda

Publications and source records attributed to T Ikeda.

At least 217 records · Page 12Linked to original sources

PubMed2000

Netrin-G1: a novel glycosyl phosphatidylinositol-linked mammalian netrin that is functionally divergent from classical netrins.

UNC-6/netrins compose a small phylogenetically conserved family of proteins that act as axon guidance cues. With a signal sequence trap method, we isolated a cDNA encoding a novel member of the UNC-6/netrin family, which we named netrin-G1. Unlike classical netrins, netrin-G1 consists of at least six isoforms of which five were predominantly anchored to the plasma membrane via glycosyl phosphatidyl-inositol linkages. Netrin-G1 transcripts were first detected in midbrain and hindbrain regions by embryonic day 12 and reached highest levels at perinatal stages in various brain regions, including olfactory bulb mitral cells, thalamus, and deep cerebellar nuclei. Its expression was primarily restricted to the CNS. Interestingly, netrin-G1 proteins did not show appreciable affinity to any netrin receptor examined. Unlike netrin-1, a secreted form of netrin-G1 consistently failed to attract circumferentially growing axons from the cerebellar plate. Our findings suggest that netrin-G1 and its putative receptors have coevolved independently from the classical netrins. The expression pattern of netrin-G1 and its predicted neuronal membrane localization suggest it may also have novel signaling functions in nervous system development.

Amino Acid Sequence↗

PubMed2000

Ru(II)- and Pt(II)-catalyzed cycloisomerization of omega-aryl-1-alkynes. Generation Of carbocationic species from alkynes and transition metal halides and its interception by an aromatic ring

The treatment of aryl-1-alkynes, such as 4-aryl-1-butyne, 5-aryl-1-pentyne, and 6-aryl-1-hexyne, with catalytic amounts of transition metal chlorides, such as PtCl(2) and [RuCl(2)(CO)(3)](2), at 80 degrees C in toluene results in cycloisomerization to give dihydronaphthalenes or dihydrobenzocycloheptenes, in which the cyclization mode is dependent on the length of the tethers. The reaction is limited to substrates containing terminal alkynes. A key step of the reaction is the intramolecular interception by an aromatic ring of the vinylmetal complex 2, which contains a cation center at the beta-position, generated from the electrophilic addition of transition metal halides toward an alkyne. The more electron-rich aryl systems are more reactive.

Journal Article↗

PubMed2000

Elevation of soluble thrombomodulin antigen levels in the serum and urine of streptozotocin-induced diabetes model rats.

The present study was designed to evaluate the serum thrombomodulin (TM) antigen levels, the TM content in several tissues, and vascular endothelium injury in a streptozotocin-induced diabetic mellitus model of rats with the basic observations concerning soluble serum TM antigen. The soluble TM antigen levels in the serum of 1-week-old Sprague-Dawley rats were 1028.7+/-56.8 ng/mL in the immunoassay using rabbit anti-rat TM IgG. The levels gradually decreased to about 400 ng/mL within 11 weeks during the development, and the levels in 11-week-old rats were preserved up to 31 weeks of age (experimental period). Identical patterns of five kinds of TM antigen subspecies (105, 52, 46, 31, and 28 kDa) in the serum were observed during normal development from 1 to 31 weeks in the Western blotting under reducing conditions. Soluble TM antigen levels in the serum and urine of the model rats were significantly increased to 1. 3 times the levels in the buffer-administrated control rats without an increase in the serum creatinine levels. In contrast to the TM antigen levels in the serum and urine, the TM content in several tissues including the lung, pancreas, kidney, and spleen of the model rats significantly decreased by 47% to 10% of those in the buffer-administrated control rats. Flattening of the longitudinal ridges in the endothelium, crevasse-like endothelial sloughing, platelet activation and aggregation, and/or leukocyte adherence on the endothelium were observed in the aorta of the model rats based on scanning electron microscopic observations, indicating endothelium injury. The present results indicate that the serum TM antigen levels increased with injury to the endothelium in the model, even when renal dysfunction was not present. It is suggested that increased TM antigen levels in diabetic patients could reflect endothelium injury as observed in this diabetic model experiment.

Animals↗

PubMed2000

Organ-dependent modifying effects of oltipraz on N-nitrosobis(2-oxopropyl)amine (BOP)-initiation of tumorigenesis in hamsters.

5-(2-Pyrazinyl)-4-methyl-1,2-dithiole-thione (oltipraz), a substituted 1,2-dithiole-3-thione, is known to inhibit tumorigenesis induced by variety of carcinogens in several animal model systems. In the present experiment, the modifying effects of dietary oltipraz, given during N-nitrosobis(2-oxopropyl)amine (BOP) initiation of carcinogenesis, were investigated in Syrian hamsters. A total of 120 six-week-old females were divided into six groups. Groups 1-3 (30 animals each) were thrice given subcutaneous injections of BOP (10 mg/kg, body weight) at 1 week intervals and fed diets supplemented with 400 or 200 ppm of oltipraz or basal diet alone, starting 1 week prior and finishing 1 week after the carcinogen exposure. Groups 4-6 (10 animals each) were similarly treated without application of BOP. At the end of the 52nd experimental week, all surviving animals were autopsied and examined histopathologically for proliferative lesions of the major target organs for BOP tumorigenicity, including pancreas, liver, kidney, and lung. The incidences and multiplicity of adenocarcinomas of the pancreas were higher in groups 1 and 2 than in group 3 although without statistical significance. The incidence of pancreatic duct dysplasias was significantly (P<0.05) increased in group 2 (62.0%) but not in group 1 (50.0%) as compared with group 3 (46.6%). While the incidences of alveolar adenomas and carcinomas were significantly (P<0.05) decreased by the high dose, the multiplicities of hepatocellular adenomas, cholagiocellular carcinomas and gall bladder adenomas were elevated in the BOP/oltipraz groups (P<0.05). The results of the present study suggest that oltipraz exerts organ-dependent modifying effects on BOP-induced carcinogenesis in hamsters when given in the initiation stage.

Animals↗

PubMed2000

Design and synthesis of a more highly selective ammonium ionophore than nonactin and its application as an ion-sensing component for an ion-selective electrode

A novel ammonium ionophore, which exhibits superior NH4+ selectivity compared with that of the natural antibiotic nonactin, was successfully designed and synthesized based on a 19-membered crown compound (TD19C6) having three decalino subunits in the macrocyclic system. This bulky decalino subunit is effective for (1) increasing the structural rigidity of the cyclic compound, (2) introducing the "block-wall effect", which prevents forming a complex with a large ion, and (3) increasing the lipophilicity of the ionophore molecule. In the ammonium ionophore design, the first factor contributes to increasing the NH4+ selectivity relative to smaller ions such as Li+, Na+, or even the closest size, K+, and the second factor increases the NH4+ selectivity over larger ions such as Rb+ and Cs+. The X-ray structural analysis proved that TD19C6 forms a size-fit complexwith NH4+ in its crown ring cavity. As an application of this ionophore, an ion sensor (ion-selective electrode) was prepared, which exhibited NH4+ to K+ and Na+ selectivity of 10 and 3,000 times, respectively. This electrode showed a better performance compared to the electrode based on nonactin, which is the only ammonium ionophore presently used in practical applications.

Journal Article↗

PubMed2000

Fluid shear stress induces lipocalin-type prostaglandin D(2) synthase expression in vascular endothelial cells.

Ligands for peroxisome proliferator-activated receptor gamma, such as the thiazolidinedione class of antidiabetic drugs and 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), modulate various processes in atherogenesis. In search of cells that generate prostaglandin D(2) (PGD(2)), the metabolic precursor of 15d-PGJ(2), we identified PGD(2) from culture medium of endothelial cells. To study how PGD(2) production is regulated in endothelial cells, we investigated the role of fluid shear stress in the metabolism of PGD(2). Endothelial cells expressed the mRNA for the lipocalin-type PGD(2) synthase (L-PGDS) both in vitro and in vivo. Loading laminar shear stress using a parallel-plate flow chamber markedly enhanced the gene expression of L-PGDS, with the maximal effect being obtained at 15 to 30 dyne/cm(2). The expression began to increase within 6 hours after loading shear stress and reached the maximal level at 18 to 24 hours. In contrast, shear stress did not alter the expression levels of PGI(2) synthase and thromboxane A(2) synthase. In parallel with the increase in the expression level of L-PGDS, endothelial cells released PGD(2) and 15d-PGJ(2) into culture medium. These results demonstrate that shear stress promotes PGD(2) production by stimulating L-PGDS expression and suggest the possibility that a peroxisome proliferator-activated receptor gamma ligand is produced in vascular wall in response to blood flow.

Arteries↗

PubMed2000

Alpha-thujone (the active component of absinthe): gamma-aminobutyric acid type A receptor modulation and metabolic detoxification.

Alpha-thujone is the toxic agent in absinthe, a liqueur popular in the 19th and early 20th centuries that has adverse health effects. It is also the active ingredient of wormwood oil and some other herbal medicines and is reported to have antinociceptive, insecticidal, and anthelmintic activity. This study elucidates the mechanism of alpha-thujone neurotoxicity and identifies its major metabolites and their role in the poisoning process. Four observations establish that alpha-thujone is a modulator of the gamma-aminobutyric acid (GABA) type A receptor. First, the poisoning signs (and their alleviation by diazepam and phenobarbital) in mice are similar to those of the classical antagonist picrotoxinin. Second, a strain of Drosophila specifically resistant to chloride channel blockers is also tolerant to alpha-thujone. Third, alpha-thujone is a competitive inhibitor of [(3)H]ethynylbicycloorthobenzoate binding to mouse brain membranes. Most definitively, GABA-induced peak currents in rat dorsal root ganglion neurons are suppressed by alpha-thujone with complete reversal after washout. alpha-Thujone is quickly metabolized in vitro by mouse liver microsomes with NADPH (cytochrome P450) forming 7-hydroxy-alpha-thujone as the major product plus five minor ones (4-hydroxy-alpha-thujone, 4-hydroxy-beta-thujone, two other hydroxythujones, and 7,8-dehydro-alpha-thujone), several of which also are detected in the brain of mice treated i.p. with alpha-thujone. The major 7-hydroxy metabolite attains much higher brain levels than alpha-thujone but is less toxic to mice and Drosophila and less potent in the binding assay. The other metabolites assayed are also detoxification products. Thus, alpha-thujone in absinthe and herbal medicines is a rapid-acting and readily detoxified modulator of the GABA-gated chloride channel.

Absinthe↗

PubMed2000

Increased formation of oxidative DNA damage, 8-hydroxy-2'-deoxyguanosine, in human breast cancer tissue and its relationship to GSTP1 and COMT genotypes.

Reactive oxygen species (ROS) induced damage to DNA plays a major role in carcinogenesis. In order to estimate the level of oxidative damage and its role in breast cancer, 8-hydroxy-2'-deoxyguanosine (8-OHdG) was determined in DNA isolated from human breast tissue. Furthermore, we investigated whether polymorphisms in genes for enzymes involved in generation and elimination of ROS had any association with the level of 8-OHdG in breast tissue. In this study, the level of 8-OHdG in DNA was measured by the high performance liquid chromatography-electrochemical detector (HPLC-ECD) method. Genotypes of cytochrome P450 (CYP)1A1, glutathione S-transferase (GST)M 1, GSTP1 and catechol O-methyltransferase (COMT) were determined by PCR-based restriction fragment length polymorphism analysis. A total of 61 Japanese patients were included in the study. The mean level of 8-OHdG in DNA of breast cancer tissues was 2.07 +/- 0.95 per 10(5) dG residues, while the mean level of 8-OHdG in DNA of non-cancerous breast tissues was 1.34 +/- 0.46 per 10(5) dG residues. The 8-OHdG levels in DNA of breast cancer tissues were significantly higher than those of their corresponding non-cancerous breast tissues (P < 0.0001). There was negative correlation between the clinical stage and the mean level of 8-OHdG in DNA of breast cancer tissues. Furthermore, patients with genotype of high GSTP1 activity had lower level of 8-OHdG in DNA of breast cancer tissues than others. On the contrary, the mean level of 8-OHdG in DNA of breast cancer tissues was higher among patients with genotype of high COMT activity. Our findings support the assumption that cancer cells are more exposed to oxidative stress than adjacent non-cancerous tissue. Genetic polymorphisms in enzymes involved in ROS metabolism may have a role in individual susceptibility to oxidant-related breast disease. At the same time, reduction of oxidative stress is thought to be a very important measure for primary prevention of breast cancer.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2000

Inhibitory effect of metformin on intestinal glucose absorption in the perfused rat intestine.

To investigate the effect of metformin on intestinal glucose absorption, a perfusion study of the intestine was performed in the rat. Male Wistar albino rats (8 weeks old) were used in the present study. The glucose absorption by the perfused intestine (788.1+/-81.9 micromol/30 min) was not changed significantly by the direct addition of metformin (90 microg/mL) to the perfusing medium (737.0+/-118.2 micromol/30 min) or by intraduodenal metformin (250 mg/kg in saline solution) infusion (772.8+/-106.3 micromol/30 min). In rats orally administered metformin (250 mg/kg) for 5 days, glucose absorption by the perfused intestine (375.0+/-164.3 micromol/30 min) was significantly (P<0.001) lower than that in control rats (811.0+/-83.1 micromol/30 min). These results indicate that metformin had a significant effect on the digestive tract, and that metformin treatment exerted an inhibitory effect on intestinal glucose absorption in the rat.

Animals↗

PubMed2000

Potent protective effects of melatonin on experimental spinal cord injury.

STUDY DESIGN: Experimental biochemical, behavioral, and histologic investigations of spinal cord injury in rats. OBJECTIVE: To investigate the effects of melatonin, a pineal hormone, in compression ischemic-induced spinal cord injury. SUMMARY OF BACKGROUND DATA: The implication of activated neutrophils in the worsening of spinal cord injury has been shown. Melatonin was shown to play an important role in protecting animal cells from neutrophil-induced toxicity and damage by free radicals. There is no report on using melatonin for spinal cord injury. METHODS: Spinal cord injury was induced by placing 25 g of weight extradurally on the rat spinal cord at T12 for 20 minutes. The rats were randomly divided into three groups. Sham rats had only laminectomy. Melatonin rats were injected with melatonin (2.5 mg/kg) intraperitoneally (intraperitoneal) five times: at 5 minutes, then 1, 2, 3, and 4 hours after the injury. Correspondingly, the control rats were injected with saline. Measured levels of lipid peroxidation estimated thiobarbituric acid reactive substances (TBARS) and the accumulation of leukocytes at the site of trauma, which were evaluated by measuring tissue myeloperoxidase activity. The recovery was assessed by using three clinical scoring systems, and histologic changes of the damaged spinal cord were examined. RESULTS: The thiobarbituric acid reactive substances content in the spinal cord increased after the injury, with two peaks (at 1 and 4 hours), and nitrogen mustard-induced leukocytopenia significantly attenuated the thiobarbituric acid reactive substances content in four 4 after injury. Also in these 4 hours, myeloperoxidase activity increased and melatonin injection reduced thiobarbituric acid reactive substances content and myeloperoxidase activity, which attenuated the motor deficits as well. Histologic findings showed that the melatonin group had less cavity formation than the control group. CONCLUSION: Results showed that injection of melatonin reduced thiobarbituric acid reactive substances content and myeloperoxidase activity, facilitating recovery of the damaged spinal cord.

Animals↗

PubMed2000

Progression of human breast cancers to the metastatic state is linked to genotypes of catechol-O-methyltransferase.

There is increasing evidence that catecholestrogens may contribute to the development of breast cancer. Specifically, inactivation of catecholestrogens may prevent the genesis and arrest the progression of the disease. Catechol-O-methyltransferase (COMT), Glutathione S-transferase (GST) M1 and GSTP1 are responsible for the detoxification of catecholestrogens, and are polymorphic in the human population. In this study, a PCR-based restriction fragment length polymorphism analysis was performed to determine genotypes of the COMT, GSTM1 and GSTP1 genes. We investigated the relationship between the germline polymorphism of these genes and clinico-pathological characteristics in 140 patients with breast cancer. Among 73 patients with the low activity COMT allele, 49 (67%) had regional lymph node metastasis. On the other hand, only 27 (40%) of 67 patients without the low activity allele had lymph node metastasis. The COMT genotype was significantly associated with clinical stage and the extent of regional lymph node metastasis of breast cancer (P<0.05). However, polymorphisms of the GSTM1 and GSTP1 gene were not associated with clinico-pathological factors. Our findings suggest that the allele encoding for low activity COMT may contribute to the progression of breast cancer.

Adult↗

PubMed2000

Combined assessment of T-wave alternans and late potentials used to predict arrhythmic events after myocardial infarction. A prospective study.

OBJECTIVES: The aim of the present study was to determine whether the combination of two markers that reflect depolarization and repolarization abnormalities can predict future arrhythmic events after acute myocardial infarction (MI). BACKGROUND: Although various noninvasive markers have been used to predict arrhythmic events after MI, the positive predictive value of the markers remains low. METHODS: We prospectively assessed T-wave alternans (TWA) and late potentials (LP) by signal-averaged electrocardiogram (ECG) and ejection fraction (EF) in 102 patients with successful determination results after acute MI. The TWA was analyzed using the power-spectral method during supine bicycle exercise testing. No antiarrhythmic drugs were used during the follow-up period. The study end point was the documentation of ventricular arrhythmias. RESULTS: The TWA was present in 50 patients (49%), LP present in 21 patients (21%), and an EF <40% in 28 patients (27%). During a follow-up period of 13 +/- 6 months, symptomatic, sustained ventricular tachycardia or ventricular fibrillation occurred in 15 patients (15%). The event rates were significantly higher in patients with TWA, LP, or an abnormal EF. The sensitivity and the negative predictive value of TWA in predicting arrhythmic events were very high (93% and 98%, respectively), whereas its positive predictive value (28%) was lower than those for LP and EF. The highest positive predictive value (50%) was obtained when TWA and LP were combined. CONCLUSIONS: The combined assessment of TWA and LP was associated with a high positive predictive value for an arrhythmic event after acute MI. Therefore, it could be a useful index to identify patients at high risk of arrhythmic events.

Arrhythmias, Cardiac↗

PubMed2000

Differential neurotrophin levels in cerebrospinal fluid and their changes during development in newborn rat.

Cerebrospinal fluid concentration of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) was measured in normal developing rat from birth to postnatal day (PND) 21 by enzyme-linked immunosorbent assay. NGF levels were significantly higher than those of BDNF and NT-3 from PND 1-21. NGF levels decreased from PND 1-3 to PND 9. At PND 15 and 17, NGF levels peaked a second time and rapidly decreased to PND 21. BDNF peaked at PND 13-15, while NT-3 levels peaked at PND 7-9. Each of the three neurotrophins has its own characteristic pattern in changes in cerebrospinal fluid levels.

Aging↗

PubMed2000

Specific and chemoselective multi-alpha-arylation reaction of benzoylformic acid with or without decarbonylation in P(2)O(5)-MsOH and related acidic media

In P(2)O(5)-MsOH, or related acidic media, benzoylformic acid (1) undergoes three types of di- or mono-alpha-arylation reactions with or without decarbonylation ((1) decarbonylative alpha, alpha-diarylation, yielding triarylmethanols 6, (2) decarbonylative alpha-monoarylation, giving benzophenone derivatives 7, and (3) alpha,alpha-diarylation without decarbonylation, affording diarylated carboxylic acids 5) and one simple decarbonylation, without arylation, to form benzoic acid (8), instead of the conventional Friedel-Crafts acylation type reaction. The product ratios are governed by the capability of the acidic medium to form mixed anhydrides with carboxylic acids and the ability of the arenes to accept electrophiles.

Journal Article↗

PubMed2000

Protein redox potential measurements based on kinetic analysis with mediated continuous-flow column electrolytic spectroelectrochemical technique. Application to TTQ-containing methylamine dehydrogenase.

Kinetic determination of protein redox potentials with a mediated continuous-flow column electrolytic spectroelectrochemical technique (CFCESET) is described. In this method, the redox state of the mediator is completely regulated by the continuous-flow column electrolysis, and the homogeneous redox reaction between the mediator and a protein sample in the column is monitored spectroscopically at the downstream of the column. The protein/mediator reaction is in the pseudo-first-order kinetics, and then the rate equation is analytically solved. The kinetic analysis provides the protein redox potential as well as the homogeneous rate constant. In the kinetic measurements, equilibration of the system within the column is not required, which allows the use of increased kinds of mediators. This method was successfully applied to quinoprotein methylamine dehydrogenase containing tryptophan tryptophylquinone (TTQ) as a prosthetic group. The kinetic aspect is also valuable for the thermodynamic analysis with the mediated CFCESET. The half-life time of the kinetics can be utilized to optimize the system for the attainment of the equilibrated state within the column and can provide the assurance that the system is in equilibrium.

Electrochemistry↗

PubMed2000

HTLV-1 unrelated adult T-cell leukemia/lymphoma with unique phenotype and karyotype.

We describe a unique case of adult T-cell leukemia/lymphoma (ATL). The patient had typical clinicohematological features as ATL, but showed a lack of antibody to human T-cell leukemia virus type-1 (HTLV-1) and was negative for HTLV-1 proviral DNA in the peripheral mononuclear cells by means of polymerase chain reaction. The phenotype of tumor cells revealed CD7+, CD5+, CD2+, CD3+, WT31-, TcR delta 1-, CD4-, CD8-, CD25-, and the karyotype showed a 5q-, t(12;18). HTLV-1 unrelated ATL is very rare, and the karyotype as in our case has not been reported previously.

Aged↗

PubMed2000

IL-4, but not vitamin D(3), induces monoblastic cell line UG3 to differentiate into multinucleated giant cells on osteoclast lineage.

The formation of multinucleated giant cells (MGCs) from monocytes/macrophages is controlled by various cytokines, the roles of which are not fully understood. Both interleukin (IL)-4 and 1alpha,25(OH)(2) vitamin D(3) (D(3)) are known to induce MGC formation from monocytes/macrophages. D(3) is also known as a stimulator of osteoclast formation in the presence of stroma cells, and IL-4 as an inhibitor. Previously, we showed that IL-4-induced MGCs from monocytes/macrophages expressed tartrate resistant acid phosphatase (TRAP) activity and hydroxyapatite-resorptive activity in the presence of M-CSF without stroma cells. In this study, we examined the effects of D(3) and/or IL-4 on MGC formation and the characteristics of these MGCs using a monoblastic cell line (UG3), to elucidate the involvement of these factors in osteoclast development without stroma cells. D(3)-induced MGCs showed none of the markers of osteoclasts, such as TRAP activity, calcitonin receptor (cal-R) expression, hydroxyapatite-resorptive activity, and bone-resorptive activity. A low concentration of D(3) synergistically stimulated IL-4-induced TRAP-positive MGC formation, whereas a high concentration of D(3) inhibited it. When IL-4 was added on day 7 of the 2-week culture with D(3), TRAP positivity reached maximum. On the other hand, delayed addition of D(3) on day 7 of culture did not increase the TRAP positivity. Although the fusion rate increased during the first week of the 2-week culture in the presence of D(3), it increased further in the second week following the addition of IL-4 on day 7. Furthermore, IL-4-induced, or IL-4- and D(3)-induced MGCs differentiated into functional osteoclasts with bone-resorptive activity following coculture with osteoblastic cells, whereas D(3)-induced MGCs did not acquire bone-resorptive activity even after coculture with osteoblastic cells in the presence of D(3). These findings suggest that IL-4 initiates osteoclast development of UG3 cells, although stroma cells were necessary for development of functional osteoclasts. On the other hand, D(3) had only a "supportive" effect on this differentiation. IL-4 and direct contact with stroma cells may regulate different stages in the multistep process of osteoclastogenesis of UG3 cells.

3T3 Cells↗

PubMed2000

Polar Thin Films Produced by Phosphonium Liquid Crystals: Two-Dimensional Self-Assembled Ionic Layers with Spontaneous Polarization.

Nonlinear optical properties are shown by the smectic phase formed by simple dialkyl phosphonium salts. The molecules form into layers, featuring ion pairs separated by insulating glassy alkyl coating to produce a spontaneous polarization (P(s)) in the sheets (see picture). Applications of this material are currently leading to the development of novel electrical and electrooptical devices.

Journal Article↗