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A Hamada

Publications and source records attributed to A Hamada.

At least 73 records · Page 4Linked to original sources
PubMed1991

ESR measurement of radical clearance in lung of whole mouse.

Clearance of the nitroxide radicals, hydroxy-TEMPO and carboxy-PROXYL, in whole-mouse lung was directly measured by in vivo ESR. After injecting a nitroxide radical, distribution of the nitroxide radical all over the lung was confirmed by ESR imaging. The ESR signal of hydroxy-TEMPO was reduced in the lung and the clearance obeyed first-order kinetics, whereas the signal of carboxy-PROXYL remained constant. Comparison of the clearance rates of live and dead mice indicated the presence of 2 different clearance systems in the lung: loss of its paramagnetism in the lung, and transfer from alveolar to the blood circulation system.

Animals↗
PubMed1991

Structure-activity studies of new imidazolines on adrenoceptors of rat aorta and human platelets.

Potencies of new aromatic substituted fluoro or iodo analogues of catecholimidazolines on functional responses in rat aorta (alpha 1) and platelets (alpha 2) were quantified. (1) When compared either on the basis of EC50 or the dissociation constant (KA), 5-fluorocatecholimidazoline was as potent as the reference alpha 1-adrenoceptor agonist, phenylephrine in the vascular tissue. The maximum contraction of aorta produced by the fluoro analogue was, however, 17% higher than that of phenylephrine. The time required for 1/2 relaxation of the tissue after 5-fluoro hydroxy imidazoline was at least twice as long as that of the phenylephrine. The catechol moiety as well as fluorine substitution at the critical 5-position of the aromatic ring is essential for higher alpha 1 adrenoceptor-mediated potency. (2) As compared to the fluoro analogues, the adrenoceptor-mediated potencies of iodo-analogues were relatively weak on vascular tissue. Naphazoline and its analogues were partial agonists on vascular tissue with dissociation constants which ranged from 110 to 2600 nmol/l. (3) Imidazole analogues were generally less potent agonist than the imidazolines by one order of magnitude. (4) The vacular effects of all agonists were competitively blocked by prazosin with KB values which ranged from 0.04 to 0.48 nmol/l. Since the variation in KB values were within normal limits, the action of new imidazolines on rat aorta appears to be mediated mainly by the activation of the alpha 1-adrenoceptor. Prazosin 10 nmol/l abolished the vascular response of some partial agonists. This indicates a slightly different mode of interaction of agonists with the transduction process. (5) Carbon 4-substituted imidazolines produced little or no alpha 1 adrenoceptor-mediated intrinsic activity, but competitive receptor blocking potency was comparable to that of phentolamine. (6) Medetomidine was a partial agonist on the rat aorta with a KA of 260 nmol/l. When investigated as a blocker, the KB of medetomidine against phenylephrine was approximately 5600 nmol/l. The variation in the latter value was high. (7) In acetylsalicylic acid-treated human platelets, the alpha 2-adrenoceptor-mediated aggregatory effect of all fluoro analogues was weak. Iodo or naphazoline analogues did not initiate platelet aggregation but blocked the aggregation induced by epinephrine. The affinity of naphazoline for the alpha 2-adrenoceptor was 1100 nmol/l. The IC50 of medetomidine for platelet anti-aggregatory effect was 3300 nmol/l, which compares favorably with other imidazoline type of blockers of platelet aggregation. (8) Sympathomimetic vasoconstrictor actions and platelet aggregation effects of these compounds can be dissociated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Differences between freshwater and seawater killifish (Oryzias latipes) in the accumulation and elimination of pentachlorophenol.

Freshwater and seawater acclimated (FWA and SWA) killifish (Oryzias latipes) were exposed to pentachlorophenol (PCP) for 3-10 days. Uptake and clearance rates of FWA and SWA killifish were determined. The estimated bioaccumulation factors (BCF) of PCP for FWA and SWA killifish were 1680 and 370, respectively. The smaller uptake rate and faster clearance rate resulted in the lower BCF for SWA killifish. Fresh- and seawater killifish excreted the PCP metabolites, the glucuronide and sulfate conjugates of PCP; the major metabolite of freshwater killifish was PCP sulfate; for seawater acclimated fish, it was PCP glucuronide. The greater excretion of PCP glucuronide by seawater killifish may be responsible for the rapid elimination of PCP. PCP accumulation in killifish decreased with higher pH levels in both freshwater and seawater environments, but these differences were less than the effect of salinity. The results indicate that salinity can affect the accumulation and elimination of environmental pollutants in killifish.

Animals↗
PubMed1990

In vivo ESR measurement of free radicals in whole mice.

The in vivo measurement of nitroxide radicals in whole mouse was carried out by L-band ESR spectroscopy. Spectra were successively observed in hepatic and bladder domains of female mice after intravenous administration of spin-labeled compounds (CPROXYL or TEMPOL). The signal intensities from both domains decreased gradually. The kinetic constants of clearance in the hepatic domain were 0.09/min for CPROXYL and 0.71/min for TEMPOL. The clearance constants in the bladder domain coincided with those in the hepatic domain within experimental error, whereas the constants in collected blood were 1/7-1/10 of those in the hepatic or bladder domains. The mechanism of clearance of nitroxide radicals in whole mice is discussed.

Animals↗
PubMed1990

Synthesis and alpha 2-adrenoceptor effects of substituted catecholimidazoline and catecholimidazole analogues in human platelets.

It is known that the steric requirements for the interactions of catecholamines and catecholimidazolines with alpha 1- and alpha 2-adrenoceptors are different. New analogues of desoxycatecholimidazoline (1), desoxycatecholimidazole (3), benzylic hydroxyl substituted imidazole (4), and the aromatic fluorine substitution analogues of 1 at the 2 (5), 5 (6), and 6 (7) positions, and a set of asymmetric 4-substituted catecholimidazolines, S-8 and R-8, were prepared and tested for interaction with alpha 2-adrenoceptors in human platelets. With the exception of 3, all compounds were selective for alpha-adrenoceptor-mediated responses in human platelets. Introduction of a double bond in imidazoline 1 to give an imidazole 3 or the introduction of a benzylic hydroxyl group to 3, as in 4, reduced the inhibition of platelet aggregation with a rank order potency of 1 greater than 3 greater than 4. Fluorine atom substitution at the 2-, 5-, or 6-positions only slightly modified the inhibitory activity of 1. Each analogue (1, 3-7) produced alpha 2-mediated inhibition of platelet adenylate cyclase and can be classified as a partial agonist. The inhibition potency of S-8 and R-8 against epinephrine-induced aggregatory responses were greatly different, and only R-8 and 4 were alpha 2-agonists on human platelet function. Our studies provide further evidence for the differential interaction of catecholamines and catecholimidazolines in alpha 1- and alpha 2-adrenoceptor systems.

Blood Platelets↗
PubMed1990

Effects of oxygen on the membrane structure and the metabolism of lipophilic nitroxide in rat liver microsomes.

The effects of oxygen on the metabolism of lipophilic nitroxide and the membrane structure of microsomes were investigated with an ESR spectrometer equipped with a hand-made gas-permeable sampling tube. The half life of gas change in the membrane was confirmed to be 48 s by the line-width of the ESR signal. The signal intensity of lipophilic nitroxide in microsomal membranes decreased with NADPH under N2 and increased under O2. The change of signal intensity was reversible, suggesting that lipophilic nitroxide can be used as an indicator of the redox state in membranes for in vivo ESR imaging.

Animals↗
PubMed1990

Enhancing effect of C1q on IgG monoclonal antibody binding to hapten.

We have previously demonstrated that IgG antibody binding to microfilariae of Dirofilaria immitis increased in the presence of purified C1q. The present study was designed to examine the mechanism of the C1q effect using a system with an antihapten monoclonal antibody (MoAb) and a hapten as an antigen. Microtiter plates were coated with 4-hydroxy-3-nitrophenyl-acetyl (NP)-bovine serum albumin (BSA), and mouse anti-NP MoAb (IgG) was added in the presence of C1q. The amount of IgG which bound to NP-BSA increased with the addition of C1q (p less than 0.01) when the antibody had both specificity to the antigen and ability to fix C1q. The C1q effect, examined using two anti-NP MoAbs with different affinities, was more apparent with the low-affinity antibody (LAMoAb) than with the high-affinity (HAMoAb; percent enhancement of IgG binding was 19 vs. 12%). The C1q effect on LAMoAb binding was doubled when a small amount of HAMoAb was incubated with LAMoAb. The C1q effect on IgG binding might be operative in the early phase of infection, where a small amount of high-affinity antibody and a relatively large amount of low-affinity antibody are produced in the host.

Adjuvants, Immunologic↗
PubMed1990

Alpha-tocopherol-induced hexagonal HII phase formation in egg yolk phosphatidylcholine membranes.

The effect of alpha-tocopherol and its acetate on the membrane structure of egg yolk phosphatidylcholine (egg PC) dispersions was investigated using phosphate-31 nuclear magnetic resonance (31P-NMR) and small-angle X-ray diffraction. The incorporation of alpha-tocopherol into egg PC dispersions induced a change in the 31P-NMR spectrum from a multilamellar bilayer line shape to a hexagonal HII one. The phase transition by alpha-tocopherol was also confirmed by small-angle X-ray diffraction analysis. The amount of hexagonal HII phase increased with increase in concentration of alpha-tocopherol. Egg PC dispersions containing a molar ratio of 0.8 of alpha-tocopherol gave a 31P-NMR spectrum of an approximately hexagonal HII type at 37 degrees C. The amount of hexagonal HII phase increased with increasing temperature, indicating that the alpha-tocopherol-induced phase transition is thermotropic and that the transition temperature of egg PC membranes from the lamellar to the hexagonal HII phase is lowered by alpha-tocopherol. The incorporation of alpha-tocopherol acetate did not induce any phase transition. This fact indicates that the hydroxyl group of alpha-tocopherol may play an important role in the hexagonal HII phase formation of egg PC dispersions.

Egg Yolk↗
PubMed1989

Amino acid sequence of monkey erythrocyte glycophorin MK. Its amino acid sequence has a striking homology with that of human glycophorin A.

A major sialoglycoprotein, glycophorin MK, was isolated from monkey erythrocyte membranes by extraction with lithium diiodosalicylate and partition in aqueous phenol. Chemical analysis of glycophorin MK revealed that the glycophorin consists of 51% protein and 49% carbohydrate by weight, and contains no N-glycosidic oligosaccharide units. Only N-glycolylneuraminic acid (Neu5Gc) was detected as sialic acid. The amino acid sequence of glycophorin MK was determined, which demonstrated that the glycophorin consists of 144 amino acid residues and 18 oligosaccharide units linked O-glycosidically to the peptide backbone through serine or threonine residues. The molecular weight was estimated to be about 35,000 based on the amino acid residues and carbohydrate content. By comparison of the amino acid sequence with those of human, equine and porcine glycophorins, a striking sequence homology was observed between monkey and human glycophorin. Glycophorin MK demonstrated both M and N blood group activities.

Amino Acid Sequence↗
PubMed1989

ESR study on synthetic glyceroglycolipid liposomal membranes.

We previously reported that glyceroglycolipid liposomes without cholesterol activated mouse peritoneal macrophages in vivo and in vitro, whereas glyceroglycolipid liposomes containing equimolar cholesterol did not. In order to characterize the properties of the glyceroglycolipid membranes, ESR spectroscopic studies were carried out with an acyl spin-labeled galactosyl ceramide (SL-GC) or a headgroup spin-labeled phospholipid (SL-6-DPPA) in 1,2-dipalmitoyl[beta-cellobiosyl-(1'---3)]glycerol (Cel-DAG) liposomal membranes. The ESR spectrum of the SL-GC in the Cel-DAG liposomes at 37 degrees C was a single broad line, indicating that the SL-GC molecules were excluded almost completely from Cel-DAG domains and formed clusters in the membranes. The spectrum of SL-6-DPPA in the Cel-DAG liposomes at 37 degrees C showed broad resonance lines with the central peak being the highest, while that at 60 degrees gave narrow lines with the low-field peak being the highest. This observation and rotational correlation time analysis showed that the molecular motions of spin-label moiety of the SL-6-DPPA were extremely restricted at 37 degrees C but not above Tc. These results suggest that below Tc the Cel-DAG molecules are packed tightly and restricted in motion in the membrane. Incorporation of cholesterol into the Cel-DAG liposomal membranes gave (1) the spectra of the SL-GC triplet, and (2) the spectra of the SL-6-DPPA narrow resonance with the low-field peak being the highest. These results suggest that cholesterol disturbs the rigid-packed structure of the Cel-DAG membrane and increases the molecular motions of the Cel-DAG. The DSC analysis of Cel-DAG with and without cholesterol agreed well to the results of the ESR technique. Thus we assume that peritoneal macrophages recognize the rigid-packed carbohydrate residues which are restricted in motion on the Cel-DAG membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

Structure of the major O-glycosidic oligosaccharide of monkey erythrocyte glycophorin.

Sialic acids and the major O-glycosidic oligosaccharide of glycophorin MK from monkey (Japanese monkey, Macaca fuscata) erythrocyte membranes were characterized. N-Glycolylneuraminic acid (Neu5Gc) was found as the major sialic acid, which was confirmed by gas-liquid chromatography-mass spectrometry as the trimethylsilyl methyl ester. Three O-glycosidic oligosaccharide units were obtained from a tryptic glycopeptide that contained all of the carbohydrate units in glycophorin MK by mild alkaline borohydride/borotritide treatment. Carbohydrate analyses of the oligosaccharides revealed that they were composed of Neu5Gc, galactose and N-acetylgalactosaminitol in the molar ratios of 1:1:1 (trisaccharide), 2:1:1 (tetrasaccharide) and 3:1:1 (pentasaccharide). The content of oligosaccharide units was estimated to be 1:12:5 for penta-, tetra- and trisaccharide, respectively, based on the yields, the molecular weight, and the number of oligosaccharide attachment sites in the amino-acid sequence. The tetrasaccharide was the major oligosaccharide and its structure was proposed to be Neu5Gc alpha 2-3Gal beta 1-3[Neu5Gc alpha 2-6]GalNAcol.

Animals↗
PubMed1989

Localization of the active center of nitroxide radical reduction in rat liver microsomes: its relation to cytochrome P-450 and membrane fluidity.

The properties and localization of the active center of NADPH-dependent nitroxide radical reduction in rat liver microsomes were investigated with the following five spin-probes as substrates; tetramethylpiperidinol-N-oxyl (TEMPOL) and four spin-labeled stearic acid derivatives with a nitroxide radical at the 5th, 7th, 12th, or 16th position of the hydrocarbon chain (abbreviated as 5SLS, 7SLS, 12SLS, and 16SLS, respectively). The ESR signals of these spin-probes in microsomes decreased on the addition of NADPH, and the decay was inhibited by pretreatment with SKF-525A. Experiments with various microsomal preparations induced by phenobarbital (PB), polychlorinated biphenyls (PCB), or 3-methylcholanthrene (3-MC) revealed that the reduction rate was correlated to the concentration of cytochrome P-450 but not to that of NADPH reductase. Thus, the nitroxide radicals of the SLSs and TEMPOL seem to be reduced by the combined action of NADPH-cytochrome P-450 reductase and cytochrome P-450. The decay showed a lag time, but no distinct correlation was observed between the lag time and the spin-probe species. On the other hand, the initial velocity of the nitroxide reduction depended strongly on the spin-probe species. Among the five spin-probes, 7SLS was reduced most quickly, followed by 5SLS, 12SLS, TEMPOL, and 16SLS in that order. The reduction rate varied from 0.18/min for 7SLS to 0.08/min for 16SLS. There was a linear relation between the cytochrome P-450 content and the reduction rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The immunopotentiating property of lipophilic muramyl dipeptide and its molecular state in liposomal membranes: plaque-forming cell responses and ESR studies.

The immunopotentiating property of spin-labeled lipophilic muramyl dipeptide (SL-MDP) in liposomes was studied as to the plaque-forming cell (PFC) response to glycophorin, as an antigen, in membranes. The effect of SL-MDP depended on the densities of both SL-MDP itself and the antigen. The addition of the optimal amount of SL-MDP to liposomes containing a low density (0.016 mol%) of the antigen increased the PFC response by three times, whereas the presence of SL-MDP in optimal antigen density (0.032 0.127 mol%) membranes was rather inhibitory. In these liposomes, the amounts and molecular states of SL-MDP were determined from ESR spectra and are discussed in connection with its immunopotentiating property.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1989

Paradoxical effects of isothiocyanate analog of tolazoline on rat aorta and human platelets.

The isothiocyanate analog (IBI) of tolazoline produced contraction of the rat aortic strip, with an ED50 value of 1.63 x 10(-5) M. The maximum contraction of the analog was nearly equal to that of tolazoline or phenylephrine. At 27 degrees C the tissue reactivity of phenylephrine and IBI was similar. When compared at equiactive concentrations, the total duration of contraction of IBI was three times longer than that of tolazoline. Thus, the longer duration of action of IBI may be attributed to the S=C=N group substitution of the molecule. IBI at 10(-6) M shifted the dose-response curve of phenylephrine to the right with reduction in maxima. Phentolamine and other alpha 1 or alpha 2 adrenoceptor blockers failed to block the responses of IBI in aorta, whereas verapamil or nifedipine blocked the response significantly. It appears that IBI is acting through calcium-channel-sensitive or calcium-receptor-related mechanism(s). In aspirin-treated platelets from human plasma, a distinct phase of aggregation induced by epinephrine can be blocked by IBI with KB of 2 x 10(-5) M. This indicates a small but selective alpha 2 related action of IBI. The aggregation induced by ADP or second component of aggregation induced by epinephrine were also blocked by IBI at concentrations comparable to that of the alpha 2-adrenoceptor-mediated response. This indicates a lack of specificity of IBI in differentiating various phases of aggregation. Therefore, as compared to tolazoline, IBI presents an interesting paradox in its interaction with various receptors or mechanisms in the vascular tissue and platelets.

Adrenergic alpha-Antagonists↗
PubMed1989

Fc-epsilon-receptor-bearing lymphocytes in patients with clonorchiasis.

Expression of Fc-epsilon-receptors (Fc epsilon R) on peripheral blood lymphocytes was examined in patients with clonorchiasis. Mean serum IgE levels in these patients was 2,518 IU/ml. Fc epsilon R was detected by flow cytometry analysis with monoclonal antibody. The frequency of Fc epsilon R+ lymphocytes and the density of Fc epsilon R on the cells in the patients were similar to those in normal subjects. Most of the Fc epsilon R+ lymphocytes were B cells. The number of Fc epsilon R+ cells decreased after incubation in serum-free medium at 37 degrees C for 3 h. The amount of regulatory molecules of IgE production, IgE binding factor, was not significantly different between the patients and normal subjects. The number of Fc gamma R bearing T or B cells in the patients was also similar to that of normal subjects. These results indicate that the mechanisms of elevated serum IgE in patients with clonorchiasis might be different from other diseases with hyperglobulinemia E.

Adolescent↗
PubMed1989

Effect of host lattice on antigenicity of glycophorin in membranes.

The influence of the host lattice on the antigenicity of glycophorin in membranes was confirmed by complement-dependent immune lysis of liposomes with two rabbit antisera, which were prepared by immunization with either human red blood cells or isolated glycophorin A. The immune lysis by either antiserum depended on the kind of phospholipid in the liposomes. Anti-glycophorin antiserum more strongly recognized glycophorin in egg-lecithin membranes than in dipalmitoyl-lecithin membranes, as did anti-red blood cell antiserum. Cholesterol in the liposomal membranes influenced the antigenicity of glycophorin. The relationship between the state of glycophorin in membranes and recognition by antibody is discussed.

Antigen-Antibody Reactions↗
PubMed1989

Effect of aromatic fluorine substitution on the alpha and beta adrenoceptor-mediated effects of 3,4-dihydroxytolazoline in the pithed rat.

The alpha and beta adrenoceptor-mediated effects of the catecholimidazoline, 3,4-dihydroxytolazoline, and its 2-, 5- and 6-aromatic fluorine-substituted derivatives have been studied in the cardiovascular system of the pithed rat. All four compounds produced vasopressor responses in beta adrenoceptor blocked (propranolol, 3 mg/kg i.v.) animals. The pressor responses produced by all four compounds were antagonized by the selective alpha-1 adrenoceptor antagonist, prazosin (0.1 mg/kg i.v.), and were relatively unaffected by the selective alpha-2 adrenoceptor antagonist, rauwolscine (0.5 mg/kg i.v.), indicating that vasoconstriction produced by the fluorinated imidazolines was mediated exclusively by postjunctional vascular alpha-1 adrenoceptors. The rank order of potency at the alpha-1 adrenoceptor was: 5-fluoro greater than 2-fluoro greater than desfluoro greater than 6-fluoro. At higher doses, 3,4-dihydroxytolazoline and its fluorinated derivatives produced an alpha-2 adrenoceptor-mediated inhibition of neurogenic tachycardia in animals pretreated with prazosin, with all four compounds being equipotent. In rats with complete alpha adrenoceptor blockade [phenoxybenzamine (3 mg/kg i.v.), prazosin (0.1 mg/kg i.v.) and rauwolscine (1 mg/kg i.v.)] whose blood pressure was elevated by constant infusion of angiotensin II (150 ng/kg/min i.v.), high doses of the 2-fluoro-, but not the 5-, 6- or desfluoro catecholimidazoline derivatives, produced a beta-2 adrenoceptor-mediated vasodepressor response. All four compounds produced a beta-1 adrenoceptor-mediated positive chronotropic response in pithed rats with the rank order of potency being: 2-fluoro = 5-fluoro greater than desfluoro greater than 6-fluoro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗