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T Dohi

Publications and source records attributed to T Dohi.

At least 91 records · Page 5Linked to original sources
PubMed1995

Flow visualization study on centrifugal blood pump using a high speed video camera.

Flow visualization is widely applied to evaluate rotary blood pumps; however, it is very difficult to visualize flow near the vanes of centrifugal blood pumps because the rotational speed of the impeller is usually several thousand rpm. In this study, a tracer method with a high speed video camera that can take more than 2,000 frames/s was utilized for flow visualization together with computer-assisted image measurement. This method visualized the complex secondary flow pattern near the vanes of the impeller, such as the vortex and recirculation. It also visualized the enhanced washout effect by the secondary washout vanes on the backside of the impeller. The proposed method was effective to analyze the flow pattern in the centrifugal blood pump by providing useful information for better design of the pump hemolysis and thrombus formation.

Blood Flow Velocity↗
PubMed1995

[Fucosyltransferase producing sialyl Le(a) and sialyl Le(x) carbohydrate antigen in gastrointestinal cancer].

Sialyl Lea and sialyl Lex are cancer-associated carbohydrate antigens. The biosynthesis of these antigens is completed by fucosyltransferases. We measured the activity of alpha 1-->4 fucosyltransferase (sialyl Lea synthase) and alpha 1-->3 fucosyltransferase (sialyl Lex synthase) in gastrointestinal cancer tissues. alpha 1-->4 fucosyltransferase activity was similarly detected in most normal or malignant tissues. alpha 1-->3 fucosyltransferase activity in gastric cancer was higher than in the normal mucosa. In colonic cancer, although the enhanced expression of sialyl Lex was observed in 86% of cases, the elevated activity of alpha 1-->3 fucosyltransferase was observed in only 58%. In conclusion, the expression of sialyl Lea and sialyl Lex antigens in the stomach and colon was not controlled solely by fucosyltransferases.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1994

Phorbol esters alter functions of the expressed dopamine transporter.

Recent elucidation of the amino acid sequences of the neurotransmitter transporters reveals several consensus sequences for phosphorylation by kinases including protein kinase C. Protein kinase C activation did modulate the function of the rat dopamine transporter expressed in COS cells. Cell treatment with the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) reduced the affinity of binding of the radiolabeled cocaine analog [3H](-)-2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (WIN 35,428) without affecting its Bmax. The uptake of [3H]dopamine was reduced by treatment with PMA in a staurosporine-sensitive manner. Kinetic analysis revealed that the inhibitory effect of PMA on [3H]dopamine uptake was due to reduced uptake velocity and a small reduction of affinity for Na+, without changed affinity for dopamine. 1-Oleoyl-2-acetyl-sn-glycerol (OAG) mimicked these actions of PMA. These results demonstrate that activation of protein kinase C alters dopamine transporter functions in both ligand recognition and substrate translocation. These phosphorylation phenomena in vitro suggest the possibility that phosphorylation could modulate the activity of this important dopaminergic synaptic regulator under physiological conditions.

Animals↗
PubMed1994

Major defect of carbohydrate-deficient-glycoprotein syndrome is not found in the synthesis of dolichyl phosphate or N-acetylglucosaminyl-pyrophosphoryl-dolichol.

The contents of dolichyl phosphate and UDP-N-acetylglucosamine:dolichyl phosphate N-acetylglucosamine 1-phosphate transferase (GlcNAc-1-P transferase) activity in fibroblasts from patients with carbohydrate-deficient-glycoprotein (CDG) syndrome were analyzed. The amount of dolichyl phosphate and GlcNAc-1-P transferase activity in CDG syndrome fibroblasts were similar to those in normal fibroblasts, suggesting that CDG syndrome may not be due to a deficiency of a biosynthetic enzyme for dolichol-oligosaccharide intermediates, but to a metabolic error in assembly of asparagine-linked oligosaccharide.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1994

Fucosyltransferase-producing sialyl Le(a) and sialyl Le(x) carbohydrate antigen in benign and malignant gastrointestinal mucosa.

BACKGROUND: Sialyl Le(a) antigen and sialyl Le(x) antigen are cancer-associated carbohydrate antigens. Previous immunohistologic and immunochemical studies have shown that these antigens are preferentially expressed in gastric cancer and colonic cancer and that they possibly are related to the metastatic potential of the cancer cells. The biosynthesis of these antigens is completed by fucosyltransferases, but it has not been reported how fucosyltransferases control the expression of these carbohydrate antigens concerning the invasive potential of the cancer. METHODS: The authors established an assay system for measuring the activity of alpha 1-->4 fucosyltransferase (sialyl Le(a) synthase) and alpha 1-->3 fucosyltransferase (sialyl Le(x) synthase) with a high-pressure liquid chromatography system (HPLC). The activity was measured in various parts of normal and cancerous gastric and colonic tissue and compared with the expression of sialyl Le(a), sialyl Le(x), Le(a), and Le(x) antigens determined in a solid-phase enzyme-linked immunosolvent assay (EIA). RESULTS: Sialyl Le(a) synthase was detected in most normal or malignant mucosa of gastric and colonic tissues, regardless of anatomic locations. Sialyl Le(x) synthase activity generally was low in the normal gastric mucosa, whereas the activity was higher in 77% (7 of 9) of gastric cancer tissues than in corresponding normal tissues with enhanced expression of sialyl Le(x) antigen in most patients (5 of 7). In the large intestine, the activity of sialyl Le(a) synthase and sialyl Le(x) synthase was correlated. Although enhanced expression of sialyl Le(x) in colonic cancer was observed in 86% (12 of 14) of all patients, concomitant higher sialyl Le(x) synthase activity than that in normal tissue was observed in only 58% (7 of 12) of patients. CONCLUSIONS: The expression of sialyl Le(a) and sialyl Le(x) antigens in the stomach and the colon was not controlled solely by fucosyltransferases but by a more complicated system involving other glycosyltransferases.

Adenocarcinoma↗
PubMed1994

Cyclic AMP-induced depolarization measured by bis-oxonol fluorescence in bovine adrenal medullary chromaffin cells.

Effects of cyclic AMP on membrane potentials were examined by measuring the changes of bis-oxonol fluorescence in bovine adrenal medullary chromaffin cells. 8-Bromo cyclic AMP (8Br-cAMP) or forskolin caused a gradual and long lasting increase of the fluorescence intensity. The effects of 8br-cAMP was blocked by cyclic AMP-dependent protein kinase inhibitor, adenosine-3', 5'-cyclic monophosphothioate, Rp-diastereomer (Rp-cAMPS) and there was no further increase in the fluorescence by 8br-cAMP in the cells depolarized with 56 mM KC1 or gramicidin D. Ouabain or the removal of extracellular K+ ([K+]0 free) which block Na+, K+-ATPase also increased the fluorescence. The effect of 8br-cAMP on the fluorescence was counteracted by ouabain or [K+]0 free and was blocked in the absence of extracellular Na+ but not by tetrodotoxin or the removal of Ca2+ from the medium. These results may suggest that cyclic AMP causes the membrane depolarization by accumulating Na+ through the inhibition of Na+, K+-ATPase in adrenal chromaffin cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

An image-guided stereotactic system for neurosurgical operations.

A new simulation system utilizing digital images (CT/MRI/SPECT) and an ultrasound/laser navigation system has been developed for image-guided surgery. Preoperative CT/MRI imaging does not always indicate the actual location of the lesion during intracranial operation, because the lesion may be displaced or distorted by operative procedures or CSF flowout. The authors developed an image integration system including an intraoperative ultrasonogram, which provides accurate information not only on the location of the deep-seated lesions but also surrounding anatomical structures during operation. The rationale of the system is to coordinate the three-dimensional axes of each image with the aid of a stereotactic subframe. Our simulation system has two ways. One simulation system works on a SUN workstation. At the preoperative simulation study: the entry point on the brain surface and the access route to the lesion are decided on from the three-dimensional CT/MRI images on the computer display. Then the configuration of the lesion from the operative view is displayed as an expected ultrasound image by reconstructing the CT and/or SPECT image. Another simulation system (HyperCAS) works on the HyperCard of a MacIntosh. The target point, the entry point and the trajectory are decided on and the three-dimensional location of these points is measured from serial CT images on the LCD display. At the time of operation, stereotactic craniotomy is performed using the laser navigator. The extent of the lesion at every depth in the surgical process is predicted from these images, and the access route to the lesion is easily corrected with the intraoperative ultrasound navigator.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Simulation↗
PubMed1994

Possible involvement of nitric oxide in acetylcholine-induced increase of intracellular Ca2+ concentration and catecholamine release in bovine adrenal chromaffin cells.

The role of nitric oxide (NO) in neurotransmitter release was studied using bovine adrenal medullary chromaffin cells. L-Arginine and sodium nitroprusside (SNP) slightly increased the intracellular free calcium concentration ([Ca2+]i), and the effects of the agents were dependent on the presence of the extracellular Ca2+ ([Ca2+]o), but were not blocked by verapamil (30 microM) or diltiazem (30 microM). SNP enhanced the acetylcholine (ACh)-induced rise in [Ca2+]i in the presence but not in the absence of [Ca2+]o. The effects of L-arginine but not those of SNP were inhibited by N omega-nitro-L-arginine (L-NNA). L-NNA significantly reduced the ACh-induced rise in [Ca2+]i and catecholamine (CA) release, and the reduction was restored by L-arginine but not by D-arginine. These results suggest a possible involvement of NO in ACh-induced [Ca2+]i rise and CA release in bovine adrenal chromaffin cells.

Acetylcholine↗
PubMed1994

Regulation by protein kinase C of platelet-activating factor- and thapsigargin-induced calcium entry in rabbit neutrophils.

12-O-Tetradecanoylphorbol-13-acetate (TPA) time-dependently inhibited the platelet-activating factor (PAF)-induced rise in cytosolic free calcium concentration ([Ca2+]i) in rabbit neutrophils, whereas staurosporine significantly enhanced it. Inositol 1,4,5-trisphosphate (IP3) induced Ca2+ release in digitonin-permeabilized cells but not in PAF-pretreated permeabilized cells. IP3-induced Ca2+ release was not affected by protein kinase C activators or inhibitors. In the cells pretreated with PAF and thapsigargin in Ca(2+)-deficient medium, stimulated Ca2+ entry was evoked by the subsequent addition of CaCl2. TPA inhibited the Ca2+ entry induced by PAF and thapsigargin in a staurosporine-reversible manner but not thapsigargin-induced [Ca2+]i elevation. These results suggest that protein kinase C negatively regulates PAF- and thapsigargin-induced rise in [Ca2+]i possibly by inhibiting Ca2+ store depletion-induced Ca2+ entry.

Alkaloids↗
PubMed1994

Effect of 12-hydroxyeicosatetraenoic acid on cytosolic calcium in human neutrophils.

12-Hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) has been reported to be a chemoattractant for human neutrophils. To assess its cellular mechanism, we focused on the effect of 12-HETE on cytosolic Ca2+ ([Ca2+]i) and characterized the effect of 12-HETE on [Ca2+]i in human neutrophils. 12(S)- and 12(R)-HETE increased [Ca2+]i in the presence and absence of extracellular Ca2+ in a concentration-related fashion. The elevation of [Ca2+]i by 12(R)-HETE was completely abolished by pertussis toxin treatment. U-73122, a selective phospholipase C inhibitor, depressed the 12(S)- and 12(R)-HETE-induced rise in [Ca2+]i in the presence and absence of extracellular Ca2+. 12(R)-HETE resulted in the rapid production of inositol 1,4,5-trisphosphate (IP3). Furthermore, 12(R)-HETE elicited slight depolarization of neutrophils as assessed using the fluorescent dye bis-oxonol. These results provide evidence demonstrating the signal transduction pathway in human neutrophils after stimulation with 12-HETE and suggest that 12-HETE causes a rapid rise of [Ca2+]i by mobilizing Ca2+ from an IP3-sensitive intracellular Ca2+ pool in human neutrophils.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1994

Plasmenylethanolamine in human intestinal mucosa detected by an improved method for analysis of phospholipid.

Analysis of phospholipid and their fatty acid composition of human intestinal mucosa was performed by an method elaborated to analyze the limited amount of sample with 2-dimensional TLC followed by lipid-phosphorus determination. Using this method, plasmenylethanolamine was detected in human intestinal mucosa and accounted for about 7% of phospholipid in small and large intestinal mucosa. The amounts of polyunsaturated fatty acids of phosphatidylethanolamine were higher than those of other phosphoglycerides in intestinal mucosa, hence, inflammation-related eicosanoids may originate from ethanolamine containing phospholipid.

Arachidonic Acid↗
PubMed1993

Expression cloning of a novel Gal beta (1-3/1-4) GlcNAc alpha 2,3-sialyltransferase using lectin resistance selection.

This report describes the isolation of a cDNA encoding a novel human Gal beta (1-3/1-4)GlcNac alpha 2,3-sialyl-transferase involved in the biosynthesis of the sialyl Lewis x determinant (NeuAc alpha 2-3 Gal beta 1-4(Fuc alpha 1-3)GlcNAc). A cDNA library of the human melanoma cell line WM266-4 was constructed in an Epstein-Barr virus-based cloning vector. Selection of the B-cell line Namalwa expressing transfected cDNAs in the presence of the cytotoxic lectin Ricinus communis agglutinin 120 gave a cDNA encoding a protein with type II transmembrane topology, as found for mammalian glycosyltransferases. The use of this lectin, which is specific to galactose residues (especially the Gal beta 1-4GlcNAc structure), originates from our prediction that the modification of the Gal beta 1-4GlcNAc structure (a backbone of the sialyl Lewis x structure) by glycosyltransferases may increase the levels of resistance to this lectin. Comparison of this cDNA sequence with those of three other cloned sialyltransferases revealed two conserved regions shared by all four enzymes. Expression of the COOH-terminal catalytic domain of this protein showed alpha 2,3-sialyltransferase activity with substrate specificity different from that of CMP-N-acetylneuraminate:N-acetyllactosaminide alpha-2,3-sialyltransferase (Gal-beta 1-3(4)GlcNAc alpha 2,3-sialyltransferase, EC 2.4.99.6). Furthermore, expression of this cDNA in Namalwa cells increased the level of sialyl Lewis x antigens. The cloning approach based on lectin resistance may be useful for the isolation of cDNAs encoding other mammalian glycosyltransferases.

Amino Acid Sequence↗
PubMed1993

Induction of the fundic mucosa-specific glycolipid with dimethylformamide in gastric-cancer cell lines.

We have previously reported that a glycolipid GalNAc beta 1-4[NeuAc alpha 2-3]Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-Cer named NGM-1 is present specifically in the human gastric fundic mucosa, but not in other organs. In gastric-cancer tissue and cancer cell lines, this glycolipid completely disappears. These findings imply that NGM-1 is expressed only in well-differentiated fundic mucosa. The purpose of this study is to examine the expression of NGM-1 as a differentiation-related molecule. A gastric cell line AZ521 was cultured in the medium with various reagents which had been reported to induce differentiation in cancer cells. The growth of AZ521 was suppressed by the addition of 0.8% dimethylformamide (DMF) to the medium, but not by addition of dimethylsulfoxide (DMSO), retinoic acid or butyric acid. In the ganglioside fraction of the cells cultured with DMF, a glycolipid regarded as NGM-1 which had not been present before treatment was detected using a monoclonal antibody. Suppression of the proliferation of AZ521 by eliminating the serum from the medium could not induce the expression of NGM-1. A colonic cell line treated with DMF also failed to express the glycolipid. The synthase activity of NGM-1 was elevated in the AZ521 cells treated with DMF, but not with DMSO. These results demonstrate that the expression of NGM-1 is induced by DMF specifically in gastric-cancer cells, and suggest the possibility that NGM-1 is a differentiation-related molecule.

Butyrates↗
PubMed1993

12-Lipoxygenase product as an inhibitor of the action of chemoattractant peptide fMet-Leu-Phe in rat neutrophils.

1. 12-Hydroxyeicosatetraenoic acid (12-HETE) has been evaluated for its capacities to modulate neutrophil migration and cytosolic Ca2+ ([Ca2+]i) using compounds prepared by chemical synthesis and tissue extract from dog gingiva. 2. 12-HETE inhibited N-formyl-Met-Leu-Phe (fMLP)-stimulated neutrophil migration in a concentration-dependent fashion. 3. The tissue extract from dog gingiva mimicked the actions of 12-HETE. 4. Although 12-HETE failed to increase [Ca2+]i, preincubation of neutrophils with 12-HETE led to a suppression of [Ca2+]i when the cells were subsequently stimulated by fMLP. 5. Again tissue extract from dog gingiva mimicked the action of 12-HETE on [Ca2+]i. 6. These results suggest the possible correlation of the inhibitory activities of 12-HETE on the regulation of neutrophil migration and Ca2+ mobilization, and this may be important for the role of 12-HETE in pathogenesis in periodontal tissues.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1993

Water transport model during CAPD: determination of parameters.

To minimize the total amount of glucose required for removing the same volume of water as a bolus, a continuous infusion of glucose during CAPD was proposed and studied. Both a computer simulation of water transport through the peritoneal membrane and in vivo assessment with rats were carried out to evaluate the feasibility of the newly proposed mathematical model in which lymphatic drainage of dialysate from the peritoneal cavity to lymphatic system was considered in addition to conventional water transport. Mass transport area coefficients (KA) of 0.041 to 0.063 ml/min/100 g body wt and 0.045 to 0.066 ml/min/100 g body wt were measured for glucose and urea during CAPD with male Wistar rats. Hydraulic conductivity of peritoneal membrane (Lc) was 7.9 x 10(-5) to 1.5 x 10(-4) ml/min/mm Hg/100 g body wt, which was calculated by a linear relationship between volume and osmotic pressure. Simulated water transport model using determined parameters indicated that the ratio of lymphatic transport to convective transport would be changeable in CAPD with glucose infusion at varying infusion rates, while up to 16% of the glucose uptake could be reduced compared with that of the common CAPD at the same dwell time.

Animals↗
PubMed1993

Involvement of brain serotonergic function in lidocaine-induced convulsions in mice.

Influences of drug-induced manipulations of central serotonergic function on lidocaine- and pentylenetetrazol (PTZ)-induced convulsions were examined in mice. Agents that suppressed serotonergic transmission increased, whereas drugs that facilitated serotonin (5-HT) function decreased the incidence of lidocaine-induced convulsions. These treatments had similar influences on the incidence of PTZ-induced convulsions. Lidocaine (10(-5)-10(-3) M) reduced the stimulation evoked [3H]5-HT release from cortical slices, followed with an increased spontaneous [3H] overflow at higher concentrations. These results may suggest that brain 5-HT neurons are causally involved as inhibitory neurons in lidocaine-induced convulsions as in the case of PTZ-induced convulsions.

5-Hydroxytryptophan↗