Biomedical subjects

T Kishi

Publications and source records attributed to T Kishi.

At least 73 records · Page 4Linked to original sources

PubMed1997

Nigral axon terminals are in contact with parvicellular reticular neurons which project to the motor trigeminal nucleus in the rat.

We examined whether in the rat the descending fibers from the substantia nigra pars reticulata (SNr) were in contact with premotor neurons projecting to the motor trigeminal nucleus (Vm), using a combined anterograde and retrograde tracing technique. After ipsilateral injections of cholera toxin B subunit (CTb) into the Vm and biotinylated dextranamine (BDA) into the SNr, numerous CTb-labeled neurons were distributed bilaterally with slightly ipsilateral dominance in the parvicellular reticular formation (RFp), where many BDA-labeled axons with bouton-like varicosities were found bilaterally with a clear-cut ipsilateral dominance. The overlapping distribution of these labeled axons and neurons was more prominent in the rostral RFp than in the caudal RFp. Within the neuropil of the RFp, some of the BDA-labeled axons made synapses with the somata and proximal dendrites of CTb-labeled neurons. Thus, the present study demonstrated the existence of an indirect pathway from the SNr to the Vm, relayed by the RFp.

Animals↗

PubMed1997

Enhancement of neurite outgrowth by the soluble form of human L1 (neural cell adhesion molecule).

L1, a neural cell adhesion molecule, is involved in neurite outgrowth, migration and fasciculation. Although L1 is a membrane glycoprotein expressed on neural cells, the soluble form of L1 is generated in vivo by proteolysis. In the present study, a stable transfectant of Chinese hamster ovary (CHO) cells secreting human L1 without cytoplasmic and membrane spanning domains was generated, and the function of the secreted L1 was examined. Explants from embryonic chick brain stem were cultured on a substrate coated with polyethylenimine (PEI) alone, on substrate-bound L1 or in medium containing soluble L1. The neurites induced by L1, both the substrate-bound form and the soluble form, were 2-3 times longer than those cultured on PEI. The ability of the soluble L1 to induce neurite formation was slightly greater than that of the substrate L1. The present results demonstrated that neurite outgrowth was induced not only by substrate-bound L1 but also by soluble L1. Soluble L1 could be a pharmaceutical candidate for the promotion of nerve regeneration.

Animals↗

PubMed1997

Isolation of a candidate gene, CAB1, for cholesterol transport to mitochondria from the c-ERBB-2 amplicon by a modified cDNA selection method.

An improved cDNA selection method was established to isolate expressed genes efficiently from an amplified chromosome region in human cancer. Biotinylated yeast artificial chromosome DNA containing c-ERBB-2 was hybridized in solution with PCR-amplifiable cDNAs of an esophageal cancer cell line bearing the c-ERBB-2 amplification. After capturing the hybrids on avidin-coated magnetic beads, the cDNAs were amplified by PCR. Four new genes (A39, C51, CAB1, and GRB-7) coamplified with c-ERBB-2 were isolated from the enriched cDNA library. CAB1, GRB-7, and c-ERBB-2 were overexpressed in gastric and esophageal cancer cells in correspondence with the amplification. The deduced amino acid sequence of the CAB1 gene had significant homology to the recently discovered steroidogenic acute regulatory protein, StAR, which plays an essential role in cholesterol transport to mitochondria. It was established that multiple overexpressed genes are frequently present in a single amplicon.

Amino Acid Sequence↗

PubMed1997

Demonstration of the corticotectobulbar pathway from the orofacial motor cortex to the parvicellular reticular formation in the rat.

We examined a corticotectobulbar pathway from the orofacial motor cortex (OfM) to the parvicellular reticular formation (RFp), where numerous premotor neurons for the orofacial motor nuclei were known to be distributed, light and electron microscopically by using a combination of anterograde and retrograde tracing techniques. After contralateral injections of biotinylated dextranamine (BDA) into the OfM and cholera toxin B subunit (CTb) into the RFp, the overlapping distribution of ipsilateral axon terminals labeled with BDA and contralateral neurons labeled with CTb was found in the lateralmost part of the superior colliculus (SC). Furthermore, contralateral injections of BDA into the OfM and wheat germ agglutinin-horseradish peroxidase (WGA-HRP) into the RFp resulted in that ipsilateral axons labeled with BDA made asymmetrical synaptic contacts with the dendrites of contralateral SC neurons labeled with WGA-HRP.

Animals↗

PubMed1997

Molecular cloning of human GRB-7 co-amplified with CAB1 and c-ERBB-2 in primary gastric cancer.

Many amplified-chromosome regions in human cancers have been identified, while there are only a limited number of reports for amplified genes in a single amplicon. We recently isolated four cDNA clones, A39, B47, C51, and CAB1, from 500 kilobases of yeast artificial chromosome DNA containing the c-ERBB-2 gene. B47 consisted of 615 base pairs and had about 85% homology with the corresponding sequence of mouse Grb-7. We report here the structure of human GRB-7 cDNA, and we report that the amounts of mRNA for c-ERBB-2, CAB1, and GRB-7 were elevated in concordance with the amplification.

Amino Acid Sequence↗

PubMed1997

Crystallization and preliminary X-ray analysis of neuropsin, a serine protease expressed in the limbic system of mouse brain.

Neuropsin (M(r) 25032) is a serine protease expressed in the limbic system of mouse brain. It has been implicated in various neurological processes including formation of memory and may be important as a drug target in the treatment of epilepsy. The recombinant protein was produced using a baculovirus expression system and was purified. Two crystal forms were obtained by a hanging-drop vapor-diffusion method with polyethylene glycol. Preliminary X-ray crystallographic analysis revealed that crystal form I belongs to triclinic space group P1 with unit cell dimensions a = 97.16 A, b = 97.12 A, c = 46.75 A and alpha = 99.17 degrees, beta = 99.77 degrees, gamma = 117.35 degrees. Self-rotation function analysis of these data of form I indicates the position of a noncrystallographic threefold axis. There are six molecules in the crystallographic asymmetric unit. Crystal form II also belongs to triclinic space group P1 but has unit cell dimensions of a = 38.40 A, b = 55.16 A, c = 65.37 A and alpha = 95.38 degrees, beta = 89.98 degrees, gamma = 110.46 degrees with two molecules in the crystallographic asymmetric unit. Form II has a noncrystallographic twofold axis. Intensity data to 3.1 A resolution for form I and to 2.2 A resolution for form II have been collected.

Amino Acid Sequence↗

PubMed1997

Mechanism for reduction of serum folate by antiepileptic drugs during prolonged therapy.

To determine whether the induction of liver enzymes by antiepileptic drugs play a major role in folate depletion, serum concentrations of folate were measured in age-matched control subjects without anemia and in epileptic outpatients who were being treated with a single antiepileptic drug. Two of the four drugs being administered were enzyme inducers. A protein binding radioassay was used to measure folate levels. Compared with serum folate levels in controls (5.14 +/- 1.88 ng/ml: n = 74), mean serum folate levels were reduced significantly in patients treated with phenobarbitone (3.91 +/- 1.73 ng/ml, p < 0.01: n = 33) and carbamazepine (3.85 +/- 1.02 ng/ml, p < 0.01: n = 36): both of which are enzyme-inducing agents. In contrast, patients treated with the non-enzyme-inducer valproate (5.39 +/- 1.71 ng/ml: n = 41) or zonisamide (5.59 +/- 2.60 ng/ml: n = 25) exhibited serum folate levels that did not differ significantly from values in controls. Findings showed that a reduction in serum folate is associated with the induction of enzymes by antiepileptic drugs. Thus, the induction of microsomal liver enzymes may be critical to the depletion of folate by antiepileptic drugs.

Adolescent↗

PubMed1997

Cytosolic NADPH-UQ reductase-linked recycling of cellular ubiquinol: its protective effect against carbon tetrachloride hepatotoxicity in rat.

To confirm whether or not cytosolic NADPH-UQ reductase is involved in the recycling of cellular ubiquinol (UQH2) consumed during lipid peroxidation, the effect of a UQ-10 supplement on the NADPH-UQ reductase and cellular defense against oxidative damage in rat livers was investigated. Supplements of UQ-10 for 14 days enhanced the levels of UQH2-10 and NADPH-UQ reductase in rat livers without any appreciable changes in other antioxidant contents and related enzyme activities. However, the injection of carbon tetrachloride (CCl4) into the rats induced lipid peroxidation and decreased the cellular UQH2-10 contents (and increased equivalent amounts of UQ-10), as well as decreasing the ascorbic acid, reduced glutathione (GSH) and alpha-tocopherol contents of the rat livers. Administration of the UQ-10 supplement prior to the CCl4 treatment spared alpha-tocopherol (but not GSH or ascorbic acid), inhibited lipid peroxidation, and thus improved CCl4-induced hepatitis. These findings support the notion that NADPH-UQ reductase in cytosol is the enzyme responsible for the regeneration of UQH2 from UQ formed by lipid peroxidation in cells.

Animals↗

PubMed1997

Computed tomography in the diagnosis of buccal space masses.

OBJECTIVE: To evaluate the CT features of buccal space masses. PATIENTS AND METHODS: Fifty-three cases of buccal space masses were reviewed retrospectively. The diagnosis was confirmed histopathologically in all except two. CT images were assessed for the number, location, internal architecture and margin of the lesions and their relation to the surrounding structures. RESULTS: The series comprised 44 tumors (33 benign and 11 malignant) and nine non-tumorous lesions. Buccal gland tumors were all found adjacent to the outer surface of the buccinator, in contrast to epidermoid cysts and accessory parotid tumors which were completely separate from it. Hemangiomas were characterized by multiple masses or the presence of phleboliths. When ill-defined margins, violation of fascial planes and aggressive bone destruction were used as the criteria for the malignancy, only seven out of 11 malignant tumors were correctly diagnosed (sensitivity 64%). CONCLUSION: CT was useful in demonstrating the presence and location of the masses in the buccal space and sometimes in the differential diagnosis. For a mass of uncertain cause in the buccal space, a buccal gland tumor is the most likely diagnosis. The value of CT in differentiating malignant from benign buccal space lesions is limited.

Adolescent↗

PubMed1997

Exposure of fibroblasts derived from keloid patients to low-energy electromagnetic fields: preferential inhibition of cell proliferation, collagen synthesis, and transforming growth factor beta expression in keloid fibroblasts in vitro.

We studied the effects of electromagnetic fields (EMFs) on cell proliferation and collagen synthesis in both normal and keloid fibroblasts in vitro. Treatment of keloid fibroblasts with 60-Hz EMFs for 10 days resulted in the inhibition of cell proliferation, whereas no significant change in cell proliferation of normal fibroblasts was observed. EMFs inhibited collagen synthesis in keloid fibroblasts but not in normal fibroblasts without altering the ratio of type III to type I collagen, indicating that EMFs inhibit type I and type III collagen synthesis to the same extent. EMFs also decreased the expression of transforming growth factor beta (TGF-beta) in keloid fibroblasts. These results suggest that EMFs may have a useful therapeutic potential for the treatment of keloid.

Adolescent↗

PubMed1997

Effect of blood blow and haematocrit on the relationship between muscle venous PO2 and oxygen uptake in dog maximally contracting gastrocnemius in situ.

1. To clarify the limiting factors for peak VO2 (VO2,peak), we measured muscle venous PO2, (PVO2) and VO2,peak under various O2 delivery conditions (arterial O2 concentration x flow) via the alteration of blood flow and haematocrit (Hct) in anaesthetized dog gastrocnemius muscle (n = 11) stimulated by 1 Hz isometrically and tetanically. 2. Two levels of flow (high and moderate) were maintained by using a pump (150 and 100 mL/min per 100 g, respectively). Haematocrit was adjusted to 45 and 30% by isovolaemic haemodilution with dextran (MW 40,000). 3. The decrease in Hct induced a 31% decrease in O2 delivery (P < 0.05), a 9-12% decrease in PVO2, a 23% decrease in VO2,peak (P < 0.05) and a 12-14% increase in O2 extraction (VO2/O2 delivery) at both flow levels. The decrease in flow induced a 24-25% decrease in O2 delivery (P < 0.05), a 15-17% decrease in PVO2 (P < 0.05), a 9% decrease in VO2,peak (P < 0.05) and a 19-22% increase in O2 extraction (P < 0.05) at both Hct levels. 4. The results suggest that the limiting factor of VO/,peak, unrelated to O2 diffusion limitation (i.e. the change in the heterogeneity of VO2 to O2 delivery ratio among capillaries), due to lowering Hct may be different from that due to lowering blood flow in maximally contracting muscle.

Animals↗

PubMed1997

Alcoholic myopathy: evaluation with magnetic resonance imaging--a case study.

Magnetic resonance imaging (MRI) of thigh and leg muscles was performed in a patient with alcoholic myopathy showing myalgia, hypercreatine kinasemia, and hypermyoglobinemia. High signal intensities in both T1- and T2-weighted images were widely distributed in the affected muscle groups, which most likely reflected lipid accumulation. Although he had hypermyoglobinemia, MRI and muscle biopsy did not show findings of rhabdomyolysis, such as necrosis, regeneration, and edema. We suggest that the high signal intensities in this case may have indicated "prerhabdomyolysis" related to alcohol abuse and that muscle MRI is useful in the evaluation of alcoholic myopathy, mainly predicting the onset of rhabdomyolysis.

Alcoholism↗

PubMed1997

Oxygen uptake in maximally contracting muscle perfused at low flow with high O2 affinity erythrocytes.

To analyze the roles of blood flow and blood-tissue diffusion in determining oxygen (O2) availability to maximally exercising skeletal muscle, we investigated the influence of low flow on the O2 uptake (VO2)-venous PO2 (PVO2) relation with normal and high O2 affinity erythrocytes. We prepared normal and high O2 affinity erythrocytes by incubating human citrate-phosphate-dextrose-stored erythrocytes with and without cyanate. We perfused maximally contracting gastrocnemius muscle at 4-Hz isometric twitch with solutions containing normal and high O2 affinity erythrocytes for 3 min in anesthetized dogs. During stimulation, perfusion flow was maintained low at 50 ml.min-1.100 g-1 with a perfusion pressure of 50 mmHg. PVO2 for normal affinity erythrocytes (25.6 Torr) was significantly (p < 0.05) higher than that for high O2 affinity erythrocytes (15.9 Torr). Nevertheless, the VO2 for normal and high O2 affinity erythrocytes was approximately the same value, 6.5 ml.min-1.100 g-1 (p > 0.05). The O2 extraction rate was approximately 80% in normal and high O2 affinity erythrocytes. These results indicate that VO2 at low flow was independent of PVO2 in maximally contracting skeletal muscle, although PVO2 was reversely correlated with O2 affinity. We suggest that this PVO2-independency of VO2 at low flow is caused by long red-cell transit time in the capillary without diffusion-limitation and/or a 20% constant arterio-venous shunt of arterial O2 delivery.

Animals↗

PubMed1997

Fracture analysis of cast pure Ti and Ti-6Al-4V alloy for dental use.

The fracture behavior of cast two types of pure Ti and Ti-6Al-4V alloy was understood by acoustic emission (AE) analysis during a fracture toughness test. Specimens for test were cast by the lost wax method using a specially designed Ti casting machine of pressure-different method for dental use. A fatigue crack was inserted from the machined notch tip into the body of a specimen in the range of 0.45-0.55 a/W. Acoustic emission signals released during the fracture toughness test were detected by two sensors attached to both ends of the specimen. Then the signals were recorded and analysed by the PAC 3000/3104 system. From the early stage of the fracture toughness test, AE signals started to be released in all types of specimens tested. A reaction layer with the investment materials of about 50-100 microns was thought to be the result of the AE release from an early stage of the fracture toughness test. A microfracture behavior of the cast pure Ti and Ti alloys was proposed based on the results obtained from the AE releasing pattern and fracture surface findings.

Acoustics↗

PubMed1996

Characterization of NADPH-dependent ubiquinone reductase activity in rat liver cytosol: effect of various factors on ubiquinone-reducing activity and discrimination from other quinone reductases.

Cytosolic NADPH-dependent ubiquinone reductase (NADPH-UQ reductase) accounted for about 68% of the total ubiquinone (UQ) reductase activity in rat liver homogenate [Takahashi, T. et al. (1995) Biochem. J. 309, 883-890]. We investigated the effects of various factors on this enzyme activity in rat liver cytosol with the aim of elucidating its physiological roles. The NADPH-UQ reductase in rat liver cytosol catalyzed the reduction of UQ to UQH2 with concomitant oxidation of equimolar NADPH. The optimal pH was around 7.4, and the optimal temperatures were about 28 degrees C for NADH and about 37 degrees C for NADPH. NADH, deamino NADH, and deamino NADPH were much less active hydrogen donors than NADPH, whereas reduced nicotinamide mononucleotide, ascorbate, erythorbate, reduced glutathione, and cysteine were inactive. As the hydrogen acceptor, UQ-9 had the highest Vmax/Km among the long-chain UQ homologues tested. FAD and FMN stimulated the activity. Anionic detergents, Mg2+ and Sr2+ also enhanced the activity. Rotenone, malonic acid, antimycin A, and KCN, which inhibit mitochondrial and microsomal electron transfer enzymes, superoxide dismutase, and acetylated cytochrome c had no effect on the NADPH-UQ reductase activity. These results indicated that the NADPH-UQ reductase in rat liver cytosol is a flavoprotein that reduces UQ-10 by a two-electron reduction mechanism and is distinguishable from known microsomal and mitochondrial enzymes, as well as DT-diaphorase [EC 1.6.99.2].

Adenine Nucleotides↗

PubMed1996

Cellular antioxidant defense by a ubiquinol-regenerating system coupled with cytosolic NADPH-dependent ubiquinone reductase: protective effect against carbon tetrachloride-induced hepatotoxicity in the rat.

We found that NADPH-dependent ubiquinone reductase (NADPH-UQ reductase) in rat liver cytosol reduces ubiquinone (UQ) to ubiquinol (UQH2) in lipid membranes and consequently inhibits lipid peroxidation [Takahashi T., et al., Biochem. J., 309, 883-890 (1995)]. Here we examined whether or not this UQH2-regenerating system functions as a cellular antioxidant defense in animals. Rats were given UQ-10 for 2 weeks, and were then exposed to carbon tetrachloride (CCl4). The UQ-10 supplement increased only in the NADPH-UQ reductase and the UQH2-10 pool of rat liver without any appreciable change in the levels of other antioxidant factors. On the other hand, CCl4 markedly increased plasma aspartate aminotransferase and alanine aminotransferase, liver weight and thiobarbituric acid reacting substances formation, which are indicators of CCl4-hepatitis, and it decreased the liver levels of L-ascorbic acid, reduced form of glutathione (GSH), alpha-tocopherol, NADPH-UQ reductase and glutathione S-transferase. However, all the above indicators of CCl4-induced hepatitis were significantly improved in rats given UQ-10. Furthermore, alpha-tocopherol, but neither L-ascorbic acid nor GSH, was significantly saved. UQ-10 supplement also was recovered glutathione S-transferase and NADPH-UQ reductase activities slightly. These results indicated that UQ-10 given to rats increased the cellular UQH2-10 pool and cytosolic NADPH-UQ reductase activity in their livers, resulting in the inhibition of lipid peroxidation in the biomembranes, and consequently protected the rats from the CCl4-hepatotoxicity.

Animals↗

PubMed1995

Protective effect of coenzyme Q10 on cultured skeletal muscle cell injury induced by continuous electric field stimulation.

The protective effect of coenzyme Q10 (CoQ10) on continuous electric field stimulation-induced muscular injury was investigated in cultured cells established from neonatal rat femoral muscles. After cultivation for 9 days, skeletal muscle cells contracted and relaxed rhythmically for 4 hr in response to continuous electric field stimulation (power, 5 V; duration, 5 msec; amplitude, 3 Hz). After the onset of the stimulation, lactate and lactate dehydrogenase (LDH) release and intracellular Ca2+ contents ([Ca2+]i) at relaxation increased gradually. In contrast, the intracellular ATP contents decreased. The addition of 5 microM CoQ10, but not alpha-tocopherol and radical scavengers, to the culture medium protected the cells against these biochemical changes after the stimulation. Verapamil, an inhibitor of Ca2+ channels, also attenuated the increase in [Ca2+]i at relaxation and LDH. These results suggested that one of the causal mechanisms of muscular injury is an increase in [Ca2+]i due to the excess entry of extracellular Ca2+, and that CoQ10 can protect skeletal muscle cells against such undesirable biochemical changes.

Adenosine Triphosphate↗

PubMed1995

Reduction of ubiquinone in membrane lipids by rat liver cytosol and its involvement in the cellular defence system against lipid peroxidation.

Rat liver homogenates reduced ubiquinone (UQ)-10 to ubiquinol (UQH2)-10 in the presence of NADPH rather than NADH. This NADPH-dependent UQ reductase (NADPH-UQ reductase) activity that was not inhibited by antimycin A and rotenone, was located mainly in the cytosol fraction and its activity accounted for 68% of that of the homogenates. Furthermore, the NADPH-UQ reductase from rat liver cytosol efficiently reduced both UQ-10 incorporated into egg yolk lecithin liposomes, and native UQ-9 residing in rat microsomes, to the respective UQH2 form in the presence of NADPH. The gross redox ratios of UQH2-9/(UQ-9 + UQH2-9) in individual tissues of rat correlated positively with the log of their respective cytosolic NADPH-UQ reductase activities, while the redox ratios in every intracellular fraction from liver were at about the same level, irrespective of NADPH-UQ reductase activities in the respective fractions. The combined addition of rat liver cytosol and NADPH inhibited to a great extent 2,2'-azobis(2,4-dimethyl-valeronitrile)-induced lipid peroxidation of UQ-10-fortified lecithin liposomes and completely inhibited such peroxidation in the liposomes in which UQH2-10 replaced UQ-10. The NADPH-UQ reductase activity was clearly separated from DT-diaphorase (EC 1.6.99.2) activity by means of Cibacron Blue-immobilized Bio-Gel A-5m chromatography. In conclusion, the NADPH-UQ reductase in cytosol, which is a novel enzyme to our knowledge, was presumed to be responsible for maintaining the steady-state redox levels of intracellular UQ and thereby to act as an endogenous antioxidant in protecting intracellular membranes from lipid peroxidation that is inevitably induced in aerobic metabolism.

Animals↗