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Biomedical subjects

T Koyama

Publications and source records attributed to T Koyama.

At least 19 recordsLinked to original sources
PubMed1992

Functional integrins from normal and glycosylation-deficient baby hamster kidney cells. Terminal processing of asparagine-linked oligosaccharides is not correlated with fibronectin-binding activity.

We have examined the properties of the alpha 5 beta 1 integrin of baby hamster kidney (BHK) cells, a ricin-resistant variant Ric14 lacking N-acetylglucosaminyl transferase I, and hence unable to complete assembly of hybrid- or complex-type N-glycans, and BHK cells treated with 1-deoxymannojirimycin (dMM), an inhibitor of Golgi mannosidases involved in the initial processing of N-glycan precursors. Comparable amounts of alpha 5 beta 1 integrin were isolated from these cells by chromatography of detergent extracts on a fibronectin cell-binding fragment affinity column and elution with EDTA. The alpha 5 beta 1 integrin obtained from normal BHK cells by fibronectin affinity chromatography contained mainly endoglycosidase H-resistant oligosaccharides, whereas in RicR14 cells or dMM-treated BHK cells these were entirely endoglycosidase H-sensitive. Analysis of lactoperoxidase labeled or long term biosynthetically 35S-labeled proteins from cultures of normal or glycosylation deficient cells showed similar steady state levels of alpha 5 beta 1 integrin and expression at the cell surface. Pulse-chase experiments in normal BHK cells showed rapid conversion of the alpha 5 subunit into a mature form containing oligosaccharides resistant to endoglycosidase H and slower maturation of a precursor beta 1 subunit, as in other cell types. In Ric14 cells the precursor beta 1 subunit was found to carry glycans larger than the fully processed Man5GlcNAc2 glycan of the mature subunit, indicating that the bulk precursor pool had not been translocated into the cis-Golgi compartment containing mannosidase I. We conclude that in BHK cells terminal oligosaccharide processing of alpha 5 beta 1 integrin subunits is not required for dimer formation, surface expression, and fibronectin binding, and that expression of the glycosylation defect of Ric14 cells on the alpha 5 beta 1 integrin does not account for the reduced adhesiveness of these cells on fibronectin compared with normal and dMM-treated BHK cells.

1-Deoxynojirimycin↗
PubMed1992

Amygdala kindling does not alter the N-methyl-D-aspartate receptor-channel complex which modulates dopamine release in the rat striatum and amygdala.

Kindling is suggested to be critically associated with enhancement of N-methyl-D-aspartate (NMDA) type excitatory amino acid synaptic transmission. The present study examined effects of kindling on NMDA-induced dopamine (DA) efflux from slices of the rat striatum and amygdala. When assayed 5-7 days after the last evoked seizure, no difference was observed between kindled and non-kindled striatum in the ability of NMDA to induce DA release, or in the effect of MK-801 or 7-chlorokynurenic acid to inhibit the amino acid-induced transmitter release. The present study revealed that NMDA receptors are also involved in the modulation of DA release in the amygdala. However, no difference was observed between kindled and non-kindled amygdala in the ability of NMDA to induce DA release. These results suggest that amygdala kindling does not alter activity of the NMDA receptor-channel complex modulating DA release in the striatum and amygdala.

Amygdala↗
PubMed1992

[Clinical evaluation of stent placement for tracheal and bronchial stenosis].

Expandable metallic stents were successfully introduced in 7 patients, including 4 with left main bronchial stenosis caused by bronchopulmonary tuberculosis, 2 with main bronchial stenosis caused by lung cancer and one with tracheal stenosis caused by adenoid cystic carcinoma. The length of stenosis was 1.5-5 cm. The stents were 1.5-2.5 cm long with barbs, and their full expanded diameter was 1.5 cm. Balloon dilatation was performed before stenting in all cases. The stents were inserted by using a 10-12 Fr catheter. In all patients except the one with tracheal stenosis, stents were introduced under local anesthesia without any difficulties. No migration of stents occurred. After stent placement, there were no respiratory difficulties, and radionuclide lung perfusion scan and chest radiographic findings such as lung atelectasis showed marked improvement in three cases. Combined therapy of stent placement and bronchial arterial infusion chemotherapy showed marked effectiveness in one case with lung cancer. Expandable metallic stents were very useful in eliminating tracheobronchial stenosis symptoms.

Adult↗
PubMed1992

[Experimental study of water jet angioplasty].

A newly invented angioplasty by using water jet energy was investigated for evaluating its safety and effectiveness in 3 dogs. The water jet was produced from a small tip nozzle (0.2 mm in diameter) of catheter by injecting 20 ml of diluted contrast medium. By using this method recanalization of femoral arterial occlusion produced by fresh thrombi was achieved in all 3 dogs. Post recanalization angiography showed no apparent small vessel occlusions. Injection apart more than 5 mm from the inner surface of human aorta provoked no apparent changes histopathologically. Water jet angioplasty may be useful in treating vascular occlusive disease.

Animals↗
PubMed1992

Immobilization of protein ligands with methyl vinyl ether-maleic anhydride copolymer.

Methyl vinyl ether-maleic anhydride copolymer (MMAC) is a water-insoluble polymer with an acid anhydride group which reacts with amino groups of ligands to form stable amide bonds. MMAC was used to immobilize protein ligands on two kinds of supports, the wells of plastic microtitre plates for enzyme-linked immunosorbent assay and related methods, and gels for affinity adsorbents. The wells were first coated with MMAC and then allowed to react with proteins. The immobilization of proteins by this method was efficient and occurred in a dose-dependent manner. Shodex Et123, a gel having amino groups, was incubated with MMAC, and then the activated Shodex was used to immobilize high concentrations of proteins. Concanavalin A-Shodex thus obtained had high affinities and was successfully used for the high-performance liquid affinity chromatography of sugar derivatives on a short column.

Chromatography, High Pressure Liquid↗
PubMed1992

MK-801, a non-competitive antagonist of NMDA receptor, prevents methamphetamine-induced decrease of striatal dopamine uptake sites in the rat striatum.

We investigated the effects of MK-801, a non-competitive antagonist of NMDA receptor, on methamphetamine-induced decrease in dopamine (DA) uptake sites in the rat striatum. Repeated administrations of an escalating dose of methamphetamine (2.5, 5, 7.5, 10 mg/kg s.c. x2, every other day for a week) produced decreased DA uptake sites assayed by binding with [3H]GBR 12935 in the striatum. Co-administration of MK-801 and methamphetamine significantly prevented the methamphetamine-induced decrease in striatal [3H]GBR 12935 binding. Administration of MK-801 alone did not affect [3H]GBR 12935 binding. These results suggest that some neurochemical effects of methamphetamine may be mediated via mechanism involving excitatory amino acids.

Animals↗
PubMed1992

[Usefulness of dopamine administration after transcatheter hepatic arterial embolization based upon portal hemodynamics].

We evaluated usefulness of dopamine administration after transcatheter hepatic arterial embolization (TAE) for the prevention of hepatic failure in experimental and clinical study. In experimental study we measured portal blood flow in dogs with doppler catheter before and after TAE. Administration of dopamine after TAE increased portal blood flow significantly. In a clinical study the usefulness of dopamine was investigated in a clinical laboratory test. It revealed that serum GOT and GPT improved earlier with dopamine administration after TAE. In conclusion dopamine increased portal blood flow and decreased hepatic parenchymal damage after TAE.

Animals↗
PubMed1992

Estimation of the oxygen gradient across phospholipid bilayers of mitochondria from reperfused rabbit hearts after ischemia.

Mitochondria isolated from myocardium exposed to 30 minute ischemia followed by 30 minute reperfusion showed an increase in membrane viscosity and a decrease in wobbling angle of phospholipids, compared with those from the normally perfused myocardium in anesthetized open-chest rabbits. The values for the membrane viscosity were used to estimate the oxygen gradient across the lipid bilayers of mitochondrial membranes with a model of cylindrical diffusion. The effective diffusion coefficient for oxygen, DO2, was approximated to be 6.5 and 6.3 x 10(-5) cm2/sec in the control and ischemic-reperfused area, respectively, by comparing reported DO2 values with values for membrane viscosity. For the surface area of the inner mitochondrial membrane including cristae and for the oxygen consumption rate of the myocardium, reported values for rats and cats, respectively, were employed. Using these values, oxygen gradients across the lipid bilayers of mitochondrial lipid membranes were estimated to be only 0.055 and 0.057 nM in the control and 30 minute ischemic-reperfused myocardium, respectively. If the mitochondrial membranes are hydrated because of the ischemia-reperfusion, the absorption coefficient of the membrane to oxygen will decrease and the oxygen gradient will be increased. In the present study, however, the fluorescence life time of DPH, the hydrophobic fluorophore, showed no shortening despite the ischemia-reperfusion. Hence, no indication of membrane hydration was obtained.

Animals↗
PubMed1992

Does ethnicity influence the prevalence of adrenal hyperandrogenism and insulin resistance in polycystic ovary syndrome?

OBJECTIVE: Our purpose was to determine the prevalence of adrenal hyperandrogenism and insulin resistance in patients with hyperandrogenic chronic anovulation, also called polycystic ovary syndrome, living in the United States, Italy, and Japan. STUDY DESIGN: Seventy-five women with polycystic ovary syndrome, 25 each from the United States, Italy, and Japan, and 10 ovulatory controls were studied. Hirsutism, obesity, and the presence of cystic ovaries were assessed, as were blood levels for estrogen, luteinizing hormone, testosterone, adrenal androgens, and insulin. All patients received an insulin tolerance test to assess insulin resistance. RESULTS: Women from Japan were less obese (p < 0.05) and did not have hirsutism, although the percentage of cystic ovaries (68% to 80%) was comparable. Serum luteinizing hormone, testosterone, and estradiol were similar, but levels of 3 alpha-androstanediol glucuronide, which was elevated in women from the United States and Italy, was normal in women from Japan. The adrenal androgens, dehydroepiandrosterone sulfate and 11 beta-hydroxyandrostenedione were elevated in 48% to 64% of the patients and by a similar percentage in the three groups. Fasting insulin was elevated in all groups, but was significantly higher in women from the United States and Italy compared with women from Japan (p < 0.05). However, insulin resistance as assessed by dissociation constant of insulin tolerance test values was significantly elevated but similar in the three groups and occurred in 68% to 76% of patients. CONCLUSION: In polycystic ovary syndrome, although obesity and hirsutism vary according to dietary, genetic, and environmental factors, the prevalence of adrenal androgen excess and insulin resistance appear to be fairly uniform. These results suggest that these factors may be involved in the pathophysiologic features of the disorder.

Adrenal Gland Diseases↗
PubMed1992

Suppressive effect of coenzyme Q10 on phospholipase A2 activation in cardiac cells after prolonged swimming.

Phospholipase A2 (PLA2) activity is elevated in cardiac microsomal fractions and phospholipids (PL) are much reduced in both the cardiac mitochondria and microsomal fractions from rats subjected to prolonged swimming. Preadministration of coenzyme Q10 (CoQ10 i.v. 30 mg/kg) significantly suppressed these changes. Two groups of 8-week-old male Wistar rats were trained to swim, receiving 30 min of training for 4 days. On the fifth day they were given an intravenous injection of either 30 mg/kg CoQ10 in saline or 1 ml saline. Thirty minutes later they began to swim for 3 hours carrying a weight representing 3% of body weight. On completion of the swim they were sacrified by instantaneous decapitation, and cardiac mitochondria were isolated. Mitochondria were also prepared from saline injected, unexercised control rats. Phosphatidylethanolamine (PE) and phosphatidylcholine (PC) concentrations were measured with HPLC and PLA2 activity was assayed fluorometrically. The mitochondrial concentrations (means +/- SEM, n = 6) of PE and PC were respectively 126 +/- 22 and 140 +/- 22 nmol/mg protein in the exercise-CoQ10 group against 66 +/- 4 and 50 +/- 10 nmol/mg protein in the exercise-saline group. The specific PLA2 activities (expressed as nmol degraded dipyrene phosphorylethanolamine substrate/hr/mg protein) in the microsomes was 0.20 +/- 0.02 in the exercise-CoQ10 group against 0.30 +/- 0.02 in the exercise-saline group. These results suggest CoQ10 has a protective effect against an excessive reduction in mitochondrial membrane phospholipids during prolonged exercise.

Animals↗
PubMed1992

Quantitative determination of pertussis toxin-sensitive G proteins using [32P]ADP-ribosylation in human platelet membranes: negative correlation with ages.

The optimum condition to quantitate the [32P]ADP-ribosylation catalyzed by pertussis toxin (islet-activating protein, IAP) in human platelet membranes was investigated. Autoradiography indicated the incorporation of 32P into the band corresponding to the molecular weight of 40-41 kDa, which was augmented by the addition of GTP in the presence of 10 mM MgCl2. On the other hand, non-hydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) enhanced the IAP-catalyzed [32P]ADP-ribosylation only in the absence of MgCl2. The amounts of IAP-catalyzed [32P]ADP-ribosylation in the presence of 100 microM GTP and 10 mM MgCl2 were linear in proportion to the protein concentrations within the limited range of protein concentrations, indicating that this simple quantitative method could be adequately used to evaluate the IAP-sensitive G proteins. Data from fifteen healthy volunteers (7 males and 8 females ranging 24 to 60 years old) indicate that the amounts of IAP-sensitive G proteins in platelet membranes are significantly negatively correlated with ages.

Adenosine Diphosphate↗
PubMed1992

Effect of phencyclidine on spontaneous and N-methyl-D-aspartate (NMDA)-induced efflux of dopamine from superfused slices of rat striatum.

Phencyclidine (PCP) acts as an indirect dopamine (DA) agonist by inhibiting the neuronal reuptake of DA, while it also works as a N-methyl-D-aspartate (NMDA) antagonist. Aiming to investigate characteristics of these two properties of PCP in the same experimental system, the effects of PCP on spontaneous and NMDA-induced efflux of DA from superfused slices of the striatum of the rat were examined. Dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) in the samples of superfusate were extracted by alumina extraction and measured by high-performance liquid chromatography with electrochemical detection (HPLC-EC). Phencyclidine at concentrations greater than 1 microM, produced a concentration-dependent increase of the spontaneous efflux of DA. The efflux of DOPAC was also concentration-dependently increased by PCP. However, PCP inhibited the efflux of DA induced by NMDA, even at a small concentration (0.1 microM), which did not alter the spontaneous efflux of the transmitter. The mode of the inhibition by PCP was shown to be noncompetitive, with an estimated IC50 value of 280 nM. These results suggest that PCP, at small concentrations, reduces the synaptic levels of DA by blocking the facilitating effect of endogenous glutamate on the release of DA and, at slightly greater concentrations, the drug also works as an indirect DA agonist, to increase the levels of the transmitter in the synaptic clefts. The clinical significance of the dual effects of PCP is discussed in relation with the unique schizophrenomimetic property of PCP.

Animals↗
PubMed1992

The preclinical safety evaluation of human monoclonal antibody against cytomegalovirus.

The human monoclonal antibody against cytomegalovirus (Mab C23) was examined pharmacokinetically and toxicologically as part of the preclinical studies prior to approval for human use. Rats given repeated intravenous administrations of Mab C23 produced no antibodies against Mab C23 and maintained a blood Mab C23 level in a dose-dependent manner. However, pregnant rabbits produced antibodies against Mab C23. The half-life of Mab C23 in plasma was 15.9 days in rats, which was similar to that of normal human serum gamma-globulin (NHSG). Neither behavioral effects nor circulatory disturbance was found in mice, rats, and dogs even after a single intravenous injection of 100 or 200 mg/kg, which corresponds to 50 or 100 times the intended clinical dosage. The repeated doses of 2, 10, or 20 mg/kg of Mab C23 on six occasions with 1- or 2-week intervals elicited a transient decrease in leukocyte counts in rats given 10 or 20 mg/kg, but no adverse effects in cynomolgus monkeys. Mab C23 did not cause any reproductive or developmental toxicity when administered to rats and rabbits at dose levels of 20 mg/kg or less. However, pregnant animals showed lower plasma levels of Mab C23 than non-pregnant animals. The chromosomal aberration test disclosed no clastogenicity in human lymphocytes. An immunostaining for Mab C23 revealed no localizations in several tissues of cynomolgus monkeys given intravenous doses of Mab C23.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Biological markers of depression: WHO multi-center studies and future perspective.

Dexamethasone suppression test (DST), imipramine platelet binding and sleep EEG in depressed patients were studied by the network of WHO Collaborating Centers. DST and sleep EEG indicated abnormalities characteristic to depression, but imipramine platelet binding failed to show difference between depressed and normal subjects. 20 papers related to markers of depression were presented at the 17th Congress of CINP, Kyoto, 1990. They were introduced under 5 headings: 1) DST and its modifications, 2) serotonergic functions, 3) platelet studies, 4) ocular potentials and melatonin, and 5) brain imaging. There are reviewed here.

Biomarkers↗