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Biomedical subjects

S Urano

Publications and source records attributed to S Urano.

At least 55 records · Page 3Linked to original sources
PubMed1988

Oxidative hemolysis of erythrocytes and its inhibition by free radical scavengers.

The oxidative hemolysis of rabbit erythrocytes induced by free radicals and its inhibition by chain-breaking antioxidants have been studied. The free radicals were generated from either a water-soluble or a lipid-soluble azo compound which, upon its thermal decomposition, gave carbon radicals that reacted with oxygen immediately to give peroxyl radicals. The radicals generated in the aqueous phase from a water-soluble azo compound induced hemolysis in air, but little hemolysis was observed in the absence of oxygen. Water-soluble chain-breaking antioxidants, such as ascorbic acid, uric acid, and water-soluble chromanol, suppressed the hemolysis dose dependently. Vitamin E in the erythrocyte membranes was also effective in suppressing the hemolysis. 2,2,5,7,8-Pentamethyl-6-chromanol, a vitamin E analogue without phytyl side chain, incorporated into dimyristoylphosphatidylcholine liposomes, suppressed the above hemolysis, but alpha-tocopherol did not suppress the hemolysis. Soybean phosphatidylcholine liposomes also induced hemolysis, and a lipid-soluble azo initiator incorporated into the soybean phosphatidylcholine liposomes accelerated the hemolysis. The chain-breaking antioxidants incorporated into the liposomes were also effective in suppressing this hemolysis.

Animals↗
PubMed1988

A comment on the evaluation of equilibrium constants for alpha-tocopherol interactions with fatty acids by absorbance in the ultraviolet region.

This paper comments on the evaluation of Erin and co-workers (Biochim. Biophys. Acta 774 (1984) 96-102) of equilibrium constants for alpha-tocopherol interactions with fatty acids on the basis of the changes of absorbance in a 200 nm ultraviolet region. It is concluded that the ultraviolet method is inadequate because it is affected by absorption in that region of the solvent, ethanol and fatty acids which they used.

Chemical Phenomena↗
PubMed1988

Influences of 7-alkyl substitution on the reversible binding of the proximate carcinogen trans-3,4-dihydroxy-3,4-dihydrobenz[a]anthracene to DNA.

The effects of 7-alkyl substitution on the reversible intercalation of the proximate carcinogen trans-3,4-dihydroxy-3,4-dihydrobenz[a]anthracene (BAD) to calf thymus DNA have been examined using time-resolved fluorescence spectroscopy. The results indicate that in 10(-3) M sodium cacodylate the binding constant of BAD is 1.8 x 10(3) M-1. 7-Ethyl substitution decreases the binding constant 1.6 times, while 7-methyl substitution increases the binding constant 1.7 times. UV Photoelectron data and results from ab initio molecular orbital calculations suggest that an increase in polarizability contributes to the increased binding accompanying methyl substitution. The decreased binding accompanying ethyl substitution arises from steric inhibition. The physical binding data correlates with the decrease in carcinogenic activity which occurs with 7-ethyl substitution of benz[a]anthracene metabolites.

Alkylation↗
PubMed1988

Reaction of tissue-type plasminogen activator with 4-methylumbelliferyl-p-guanidinobenzoate hydrochloride.

It has recently been reported that the fluorogenic serine proteolytic active site titrant, 4-methyl-umbelliferyl-p-guanidinobenzoate (MUGB), cannot be employed in this capacity for tissue-type plasminogen activator (TPA) [Geiger, M., and Binder, B.R. (1987) Biochim. Biophys. Acta 912, 34-40]. Since this observation has such important ramifications in this area of research, we have studied the reaction of MUGB with recombinant (rec)TPA under a variety of experimental conditions and find that MUGB is indeed an effective titrant of rec-two chain TPA (recTCTPA) at 4 degrees, a condition under which the deacylation rate constant is diminished to the point that acylation can be readily observed. The KS for the interaction of MUGB with recTCTPA is 43 microM-46 microM, the acylation rate constant, k2, is approximately 3.6 min-1-4.2 min-1, and the rate constant for deacylation of p-guanidinobenzoyl-recTCTPA is 0.084 min-1-0.110 min-1. This same recTCTPA, after treatment with diisopropylfluorophosphate, does not react with MUGB. Single-chain TPA (recSCTPA) has been found to acylate more slowly than its two-chain counterpart and to exhibit a higher degree of turnover of the acyl-enzyme with this reagent. These results demonstrate that the active site concentration of TCTPA can be accurately determined by titration with MUGB, a consideration which is essential to the proper kinetic evaluation of this agent and its genetic variants. On the other hand, the presteady state kinetic characteristics for MUGB toward SCTPA are not favorable for its use as a titrant with this form of the enzyme.

Acylation↗
PubMed1988

Membrane-stabilizing effect of vitamin E: effect of alpha-tocopherol and its model compounds on fluidity of lecithin liposomes.

The effects of vitamin E (alpha-tocopherol) and its model compounds on the fluidity of liposomes composed of dipalmitoylphosphatidylcholin (DPPC) and fatty acids were investigated by the measurement of the fluorescent polarization (P) using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a plobe. Although all tocopherols decreased the fluidity of liposomes which was perturbed by the inclusion of an unsaturated fatty acid having more than one double bond, alpha-tocopherol was more effective than the others. The fluidity in arachidonic acid-containing liposomes was decreased most in the presence of alpha-tocopherol and was decreased considerably by the inclusion of model compounds having a side chain at least one isoprene unit or a long straight chain instead of isoprenoid side chain. However, the chromanol with methyl group instead of the above side chain, and phytol, having no chromanol moiety, had no effect. These results show that a structural requirement for a membrane stabilization is to be either the chromanol moiety with methyl groups born on its aromatic ring or a side chain of appropriate length; an isoprenoid side chain of full length or one containing 4'a- and 8'a-methyl groups is not necessarily needed.

Arachidonic Acid↗
PubMed1988

UV photoelectron spectroscopy and ab initio characterization of valence orbital structures and conformations of neutral phosphate esters.

The HeI UV photoelectron spectrum of trimethyl phosphate (TMP) has been measured and interpreted with the aid of SCF molecular orbital calculations carried out with STO-3G, STO-3G* and 4-31G basis functions. The photoelectron spectrum of TMP is more accurately reproduced by results from 4-31G calculations than by results from STO-3G or STO-3G* calculations. However, all three basis sets yield results which predict the same assignment of the photoelectron spectrum. Results at the 4-31G level indicate that whether calculations are based on crystallographic bond angles and bond lengths or on STO-3G optimized geometries has little effect on the energetic ordering of the upper occupied orbitals. The energetic ordering of orbitals is also found to be only weakly dependent upon the torsional angle phi, describing rotation of ester groups about P-O bonds and upon the torsional angle psi, describing rotation of methyl groups about C-O bonds. For trimethyl phosphate, with C3 symmetry, the vertical ionization potentials of the upper occupied orbitals are 10.81 eV (8e), 11.4 eV (9a), 11.93 eV (7e), 12.6-12.9 eV (8a and 6e), 14.4 eV (7a) and 15.0-16.0 eV (5e and 6a). Calculations at the 4-31G level indicate that many of the highest occupied orbitals in neutral dimethyl phosphate and methyl phosphate have energies and electron distributions similar to orbitals in TMP. For TMP, a search for optimized values of phi and psi has been carried out at the STO-3G*level. In agreement with previous NMR studies and with classical potential calculations, the STO-3G* results indicate that both the gauche (phi = 53.1 degrees) and anticlinal (phi = 141.9 degrees) conformations are thermally accessible. Also in agreement with the classical potential calculations, the STO-3G* results predict that in the all gauche conformation energy is minimized when the methyl groups assume a staggered geometry (psi = 60 degrees to 80 degrees) and that an energy maximum occurs for an eclipsed geometry (phi = 0 degrees to 20 degrees). A study of the dependence of optimized values of O-P-O ester bond angles on the torsional angles, phi, was carried out at the STO-3G, STO-3G* and 4-31G levels. The results demonstrate that for C3 symmetry, the coupling of O-P-O angles to phi is influence by repulsive steric interactions.

Chemical Phenomena↗
PubMed1988

Interaction of vitamin E and its model compounds with unsaturated fatty acids in homogeneous solution.

Either alpha-tocopherol (vitamin E) or one of its model compounds having side chains of different length at the 2-position of alpha-tocopherol, forms complexes with an unsaturated fatty acid in methanol. For complex formation, the isoprenoid side chain and hydroxy group of alpha-tocopherol are unessential and, rather, the methyl groups attached to the aromatic ring of the chromanol moiety seems to be responsible. For better interaction, more than three methylene-interrupted Z double bonds of a fatty acid are necessary. These findings are incompatible with the hypothesis of Diplock and Lucy on the interaction of vitamin E with each polyunsaturated fatty acid.

Arachidonic Acid↗
PubMed1988

Action of vitamin E as antioxidant in phospholipid liposomal membranes as studied by spin label technique.

The action of alpha-tocopherol in the phosphatidylcholine liposomal membranes was studied by spin label technique in order to elucidate the role of vitamin E in the membranes. The fluidity of the liposomal membranes decreased with increasing concentrations of saturated phosphatidylcholine, cholesterol, and alpha-tocopherol. However, the physical effect of alpha-tocopherol was quite small at its physiological concentrations. The effects of structure of various kinds of chromanols on the membrane fluidity were studied. The fluidity of the liposomal membranes decreased with increasing length of the side chain at 2-position of 6-chromanols. This effect was smaller when the side chain at the 2-position did not possess branched methyl group. The effect of tocopherols on the membrane fluidity was larger in the inner part of the membranes. Ascorbic acid residing in the aqueous phase interacted with the nitroxide spin probe incorporated into the membranes and the rate was smaller as the nitroxide group was buried deeper in the phospholipid bilayer. The spin probes incorporated into liposomal membranes were consumed as the oxidation proceeded. alpha-Tocopherol suppressed both the oxidation of membranes and the decrease of spin probe, but when alpha-tocopherol was depleted, the spin probe decreased and the membranes became more rigid as the oxidation proceeded.

Antioxidants↗
PubMed1987

Membrane stabilization of vitamin E; interactions of alpha-tocopherol with phospholipids in bilayer liposomes.

13C Spin-lattice relaxation times (T1) of 13C-labeled alpha-tocopherol in three kinds of liposomes varying in their contents of arachidoyl residues have been measured by 13C-NMR spectroscopy. On the basis of T1 values, it is proved that the segmental motion of isoprenoid side chain of alpha-tocopherol tends to increase with an increase in the distance from the chromanol moiety, and that three methyl groups attached on the aromatic ring, have some affinity to unsaturated fatty acid residues rather than those of the isoprenoid side chain. These results are incompatible with the hypothesis of Diplock et al. (1) which 4'a- and 8'a-methyl groups of isoprenoid side chain are fitted in the Z-pockets of arachidoyl chain of polyunsaturated lipids in membrane.

Animals↗
PubMed1986

Aphidicolin-resistant mutants of bacteriophage phi 29: genetic evidence for altered DNA polymerase.

Aphidicolin-resistant mutants (Aphr) of Bacillus subtilis bacteriophage phi 29 were isolated after mutagenesis with hydroxylamine. Efficiency of plating (e.o.p.) of the resistant mutants was not reduced at 500 microM aphidicolin, although e.o.p. of wild type phi 29 was less than 10(-5) at the same concentration of aphidicolin. By recombination and complementation analyses, both sites of the mutations, aph-71 and aph-101, of Aphr71 and Aphr101, respectively, were mapped in gene 2 which encodes phi 29 DNA polymerase. The activity of wild type phi 29 DNA polymerase, in a partially purified fraction, was inhibited by aphidicolin. DNA polymerases from Aphr71 and Aphr101, prepared in the same manner as that of wild type, were resistant to the drug. These results indicate that the acquisition of the aphidicolin resistance of Aphr71 and Aphr101 of bacteriophage phi 29 results from a structural alteration of phi 29 DNA polymerase which reduces sensitivity to aphidicolin.

Aphidicolin↗
PubMed1983

[Quantitative evaluation of thallium-201 exercise myocardial scintigraphy and its display on the two-dimensional view of the left ventricular wall as the functional image].

We developed a new method for the quantitative evaluation of 201T1 exercise myocardial scintigraphy. Final diagnostic images obtained by this method were displayed on the two-dimensional views of the left ventricular wall. Five projection images obtained 10 min and 3 hrs after exercise were recorded respectively in the magnetic disk. Each image was divided into seven fan-shaped segments utilizing the apical image as the reference which was placed in the middle. The corrected uptake indices were examined in 20 normal controls and served as the normal data. Each segment was then judged to be intact or ischemic or infarcted by matching the segmental uptakes of the images given 10 min and 3 hrs after exercise. The results were displayed on the computer-assisted color monitor as the two-dimensional view of the left ventricular wall. In order to evaluate its diagnostic usefulness in coronary artery disease, comparative coronary angiography was performed in 25 patients. The present technique proved to have high sensitivity and specificity both in left anterior descending artery and right coronary artery diseases (88 and 78%, respectively in the former and 83 and 89%, respectively in the latter).

Coronary Disease↗
PubMed1982

[Effects of methyl o-(4-hydroxy-3-methoxycinnamoyl) reserpate (CD-3400) on erection and ejaculation in dogs].

Effects of methyl o-(4-hydroxy-3-methoxycinnamoyl)reserpate (CD-3400), a new antihypertensive agent belonging to the class of rauwolfia alkaloids, on erection and ejaculation in dogs were investigated and compared with such effects of reserpine and rescinnamine in dogs. A single dose of CD-3400 (0.125 mg/kg) administered orally to normal dogs produced no effects on erection and ejaculation, although the same dose of reserpine and rescinnamine resulted in a marked suppression of only ejaculation at 24 and 48 hr after administration. CD-3400 (0.5 mg/kg) administered orally, as well as reserpine (0.125 mg/kg) and rescinnamine (0.125 mg/kg) suppressed ejaculation at 24 hr after administration; however, the suppressive effect of CD-3400 on ejaculation was weaker and shorter than that of reserpine or rescinnamine and recovered 96 hr after administration. The order of the suppressive effect of the agents was as follows: reserpine greater than rescinnamine greater than CD-3400. Repeated administration of reserpine (0.01 mg/kg/day p.o.) for 20 days, produced a marked suppressive effect on ejaculation, whereas the effect of CD-3400 (0.06 mg/kg/day p.o.) was also weaker than that of reserpine. 24 hr after oral administration in a single dose of CD-3400 (0.5 mg/kg), reserpine (0.125 mg/kg) or rescinnamine (0.125 mg/kg), the ratios of dopamine (DA) to serotonin (5-HT) in the anterior hypothalamus and hippocampus were decreased significantly as compared with the control. These results indicate that CD-3400 results in a weaker suppressive effect on ejaculation as compared to reserpine and rescinnamine, and CD-3400-induced suppression may be due to a decrease in the ratio of DA to 5-HT in the anterior hypothalamus and hippocampus.

Administration, Oral↗
PubMed1980

Effect of trapidil on prostacyclin generation of arterial wall.

Prostacyclin (PGI2) has been reported to be a labile but potent inhibitor of platelet aggregation and a powerful vasodilator. This paper reports the effect of trapidil on PGI2 generation in rat aorta by means of bioassay system. The aortic ring was incubated in 0.05 M Tris HCl buffer (pH 7.5) for 10 min. This incubation medium was added into human PRP, and then incubated at 37 degrees C for 2 min., and ADP was added. PGI2 activity was assayed by the inhibitory percentage of ADP induced platelet aggregation. When the aortic ring was incubated in a medium containing trapidil, PGI2 generation was accelerated. This acceleration was inhibited by pretreatment with indomethacin. Moreover, the aortas of rats intravenously injected with 30 mg/kg of trapidil were incubated in the same way, and PGI2 activity in the medium was estimated. More potent PGI2 activity was observed in the aortas of rat treated with trapidil compared with the controls. These results indicate that acceleration of PGI2 generation from aorta by trapidil is involved in the mode of action of this drug of thrombus formation.

Animals↗
PubMed1977

Radical scavenging reactions of alpha-tocopherol. II. The reaction with some alkyl radicals.

alpha-Tocopherol was reacted with some alkyl radicals (ethyl, n-propyl, iso-propyl, n-butyl, and sec-butyl radical) to study its radical scavenging reactivity. The two types of products (alkyl ethers of alpha-tocopherol and cyclohexadienones) were obtained on treatment of each radial. These structures were determined by the spectral analysis. It was observed that alpha-tocopherol is very sensitive to the alkyl racidals and that the yields of the cyclohexadienones are decreased and that of the alkyl ethers are not much varied with an increase of carbon numbers of the alkyl radicals.

Chemical Phenomena↗
PubMed1976

A radical scavenging reaction of alpha-tocopherol with methyl radical.

To study a radical scavenging reaction of alpha-tocopherol, it was reacted with methyl radical in dimethyl sulfoxide. Two main products, a geminal dimethyl cyclohexadienone and methyl ether of alpha-tocopherol, were obtained and these structures were determined by 13C nuclear magnetic resonance spectroscopy. The radical methylation data of alpha-tocopherol suggested that a delocalize radical species would be an intermediate.

Chemical Phenomena↗