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Biomedical subjects

A Hamada

Publications and source records attributed to A Hamada.

At least 109 records · Page 6Linked to original sources
PubMed1985

Structural changes of rat liver microsomal membranes induced by the oral administration of carbon tetrachloride. 31P-NMR and spin-label studies.

The acute effects of carbon tetrachloride (CCl4) on the membrane structure of rat liver microsomes were studied using 31P-NMR and spin-labeling techniques. 31P-NMR spectra of rat liver microsomes were not changed appreciably after the oral administration of CCl4, indicating that the surface structures of microsomal membranes probably are not influenced by the oral administration of CCl4. Four different spin-labeled stearic acids, 5-(N-oxyl-4',4'-dimethyloxazolidine)-stearic acid (5SLS), its methyl ester (5SLSM), 12-(N-oxyl-4',4'-dimethyloxazolidine)-stearic acid (12SLS) and its methyl ester (12SLSM), were used for the estimation of membrane fluidity. The apparent rotational correlation time of 12SLS decreased from 4.0 nsec to 3.0 nsec after the oral administration of CCl4, while the order parameter of 5SLS did not change. The results suggest that CCl4 or its metabolites increase the membrane fluidity of liver microsomes primarily at hydrophobic regions rather than at the surface layer. The ESR spectrum of 5SLSM in microsomal membranes comprised two different signals; one was an anisotropic signal and the other was a rather isotropic one. The ratio of the anisotropic signal to the isotropic one decreased markedly after the oral administration of CCl4 and depended on the dose of CCl4. The suitability of this ESR technique with 5SLSM for the estimation of membrane damage is discussed.

Administration, Oral↗
PubMed1985

N-substituted imidazolines and ethylenediamines and their action on alpha- and beta-adrenergic receptors.

A series of N-substituted imidazolines and ethylenediamines were synthesized and examined for their activity in alpha- and beta-adrenergic systems. The length of the intermediate side chain between the catechol and imidazoline ring or the amine of the ethylenediamine segment was shown to affect the adrenergic activity. N-[2-(3,4-Dihydroxyphenyl)ethyl]imidazoline hydrochloride (2) and N-[2-(3,4-dihydroxyphenyl)ethyl]ethylenediamine dihydrochloride (4), both with two methylene groups between the catechol and amine segment, were found to be somewhat selective for alpha 2-adrenergic receptors while 1-(3,4-dihydroxybenzyl)imidazoline hydrochloride (1) and N-2-(3,4-dihydroxybenzyl)ethylenediamine dihydrochloride (3), both with one methylene group between the catechol and amine segment, were more selective for alpha1-adrenergic receptors in a pithed rat model. Of the four compounds examined, only compound 2 showed significant direct activity on beta1- and beta2-adrenergic receptors.

Animals↗
PubMed1984

Evidence for the occurrence of oligosaccharides from bovine glycophorin having a branching point at C-6 of N-acetylgalactosamine.

Some large acidic oligosaccharides from bovine glycophorin were purified and their structures were determined by methylation analysis, nitrous acid deamination and selective acid hydrolysis after hydrazinolysis, Smith degradation and acetolysis. One oligosaccharide was a mixture of two decasaccharides: (formula; see text) The mixture of oligosaccharides released by NaOH-NaBH4 treatment was subjected to selective acid hydrolysis after hydrazinolysis. The occurrence of N-acetylglucosamine residue attached to C-6 of the reducing terminal N-acetylgalactosaminitol was demonstrated by isolating the disaccharide, GlcNAc(1----6)GalNAcol.

Acetylgalactosamine↗
PubMed1984

Dopaminergic agonists: comparative actions of amine and sulfonium analogues of dopamine.

We have investigated the possibility that structural modifications of the sulfonium analogue of dopamine (4) would produce the same pattern of biological activity as structural modifications of dopamine. A series of methyl- tetralinyl -, and naphthalenylsulfonium analogues 5-7 were prepared and tested for their ability to inhibit the potassium-evoked release of [3H]acetylcholine from striatal slices. All compounds were tested under normal conditions and after depletion of dopamine stores with reserpine and alpha-methyl-p-tyrosine. The amine and sulfonium analogues 2-6 all showed direct agonist activity. The sulfonium analogue 7 produced, predominantly, indirect activity. In contrast to the amine analogues, chemical modifications of the sulfonium compounds produced little change in their dopamine agonist activity.

Acetylcholine↗
PubMed1984

Synthesis and evaluation of substituted 2-phenylcyclobutylamines as analogues of hallucinogenic phenethylamines: lack of LSD-like biological activity.

cis- and trans-2-(2,4,5-trimethoxyphenyl)cyclobutylamine and trans-2-(2,5-dimethoxy-4-methylphenyl)cyclobutylamine were synthesized as conformationally restricted analogues of hallucinogenic phenylisopropylamines. In rats trained to discriminate saline from LSD (0.08 mg/kg, ip) in a two-lever drug discrimination paradigm, no generalization of the LSD stimulus to the cis trimethoxy compound occurred at doses up to 20 mg/kg. For both of the trans compounds, partial generalization of the LSD cue occurred at doses of 5 mg/kg or greater. In contrast, complete generalization occurred with trans-2-(2,5-dimethoxy-4-methylphenyl)cyclopropylamine. The ED50 for this compound and the doses of the trans cyclobutyl homologues at which significant drug-appropriate responding occurred indicate that the latter are on the order of 50-75 times less potent than the cyclopropylamine analogue. The lack of generalization to the cyclobutylamines indicates either that their discriminative stimulus properties differ from LSD or that they lack discriminative effects.

Animals↗
PubMed1983

Amino acid sequence and oligosaccharide attachment sites of the glycosylated domain of dog erythrocyte glycophorin.

Glycophorin was prepared from dog erythrocyte membranes by extraction with lithium diiodosalicylate and partition in aqueous phenol. Tryptic and chymotryptic treatments of the glycophorin produced two major glycopeptides labeled T1 and CH1, respectively. The glycopeptides were isolated by gel chromatography followed by ion-exchange chromatography, and subjected to amino acid sequence analysis. Both glycopeptides represented the amino-terminal domain of the major dog glycophorin; T1 of 52 residues and CH1 of 43 residues. The amino-terminal sequence of dog glycophorin does not have significant homology with those of human, horse or porcine glycophorins. This result is in good agreement with our previous proposal that there is no homology in the sequence of the amino-terminal glycosylated domain of glycophorin.

Amino Acid Sequence↗
PubMed1983

Differences in the applicability of the easson-stedman hypothesis to the alpha 1- and alpha 2-adrenergic effects of phenethylamines and imidazolines.

The enantiomers of 2-(3,4, alpha-trihydroxybenzyl)imidazoline and the corresponding desoxy derivative, 2-(3,4-dihydroxybenzyl)imidazoline, were evaluated at alpha 1- and alpha 2-adrenergic receptors to test the applicability of the Easson-Stedman hypothesis to the imidazoline class of alpha-adrenergic agonists. A series of closely related phenethylamines was included for comparison. The Easson-Stedman hypothesis states that optically active adrenergic agonists possessing an asymmetric hydroxyl-substituted benzylic carbon atom will have the following relative potencies: R(-) greater than S(+) = desoxy. While the phenethylamines were found to adhere to the Easson-Stedman hypothesis at both alpha 1- and alpha 2-adrenergic receptors, the optically active imidazolines did not. These findings further support our previous observations that the phenethylamines and imidazolines may interact differently with alpha-adrenergic receptors.

Animals↗
PubMed1983

Optically active catecholimidazolines: a study of steric interactions at alpha-adrenoreceptors.

The optical isomers and deoxy form of 2-(3,4, alpha-trihydroxybenzyl)imidazoline hydrochloride were examined for their alpha-adrenergic activity on rat aorta. The rank order of stimulant activity was deoxy (2) congruent to (R)-(-)-1 greater than (S)-(+)-1. This is in contrast to catecholamines in which the order of activity is (R)-(-)-epinephrine greater than (S)-(+)-epinephrine = epinine (deoxyepinephrine). The relative order of potency for the isomers of 2-(3,4, alpha-trihydroxybenzyl)imidazoline is different than that predicted by the Easson--Stedman theory for stereoisomers of catecholamines. Also, substitution of the deoxy compound 2 with substituents, methyl or benzyl, in the 4-position lowers the alpha-adrenergic agonist activity, and differences observed between optical isomers were small.

Animals↗
PubMed1982

Structural studies of the acidic oligosaccharide units from bovine glycophorin.

The O-glycosidically-linked carbohydrate units of glycophorin from bovine erythrocyte membrane were released by alkaline borohydride treatment. These oligosaccharides were separated into the neutral fractions and the acidic fractions by ion-exchange chromatography followed by gel filtration. The two acidic fractions (fractions 10 and 13) which have the smallest molecular weight in acidic oligosaccharides, were further purified by gel filtration on Bio-Gel P-4 column. Two acidic oligosaccharides (fractions 10-I and 10-II), heptasaccharides, were separated by gel filtration on a Bio-Gel P-4 column from fraction 10. These structures were determined by methylation analyses, nitrous acid deamination after hydrazinolysis and Smith degradation after desialylation. In addition, the structures were also analyzed by direct-probe mass spectrometry of the permethylated derivatives before and after desialylation. These studies indicated that one of them (fraction 10-I) was NeuNGc alpha(2 leads to 3)Gal beta(1 leads to 4)GlcNac beta(1 leads to 3)Gal beta(1 leads to 4)GlcNAc beta (1 leads to 3)Gal beta(1 leads to 3)GalNAcol and another heptasaccharide (fraction 10-II) was Gal beta (1 leads to 4)GlcNAc beta (1 leads to 3)Gal beta (1 leads to 3)[NeuNGc alpha(2 leads to 3)Gal beta(1 leads to 4)GLcNAc beta(1 leads to 6)]GalNAcol. Although another acidic fraction (fraction 13, was obtained as a single peak on a Bio-Gel P-4 column, it appeared to be the mixture of a heptasaccharide, NeuNGc alpha(2 leads to 3)Gal beta(1 leads to 4)GlcNAc beta(1 leads to 3 or 6)[Gal beta (1 leads to 4)GLcNAc beta (1 leads to 6 or 3)]Gal beta (1 leads to 3)GalNAcol and an oligosaccharide similar to fraction 10-II, by analysis of two products obtained by Smith degradation after desialylation.

Animals↗
PubMed1982

Primary structure of horse erythrocyte glycophorin HA. Its amino acid sequence has a unique homology with those of human and porcine erythrocyte glycophorins.

The complete amino acid sequence of the major sialoglycoproteins of horse erythrocyte membranes, glycophorin HA, was determined by manual sequencing methods, using tryptic, chymotryptic, and cyanogen bromide fragments. Glycophorin HA is a polypeptide chain of 120 amino acid residues and contains 10 oligosaccharide units attached to the amino-terminal side of the molecule. Its amino terminus is pyroglutamic acid. All of the oligosaccharides are linked O-glycosidically to threonine or serine residues. The amino acid sequence is consistent with the transmembrane orientation of glycophorins. There is no significant homology between the glycosylated domains of horse, human, and porcine glycophorins, but there is a considerable homology between the hydrophobic domains of the three glycophorins, which interact with the lipid bilayer of the erythrocyte membrane.

Amino Acid Sequence↗
PubMed1982

Isolation and characterization of alkali-labile oligosaccharide units from porcine erythrocyte glycophorin.

The oligosaccharide units of glycophorin isolated from porcine erythrocyte membranes were released by alkaline borohydride treatment and purified by gel filtration and ion-exchange chromatography. Structures of the O-glycosidic oligosaccharides were determined by methylation analysis, the methylated sugar being identified by gas-liquid chromatography-mass spectrometry and nitrous acid deamination after hydrazinolysis. The major oligosaccharide was a trisaccharide, Gal(1 leads to 3)[Neu-NGly(2 leads to 6)]GalNAc. The other oligosaccharides were larger and contained Glc-NAc. One was a pentasaccharide, Gal(1 leads to 3)Gal(1 leads to 4)GlcNAc(1 leads to 3)Gal(1 leads to 3)GalNAc. The structure of the trisaccharide was also analyzed by direct-probe mass spectrometry of the permethylated derivative, and the result obtained was consistent with the proposed structure.

Animals↗
PubMed1982

Glycophorins of bovine erythrocyte membranes. Isolation and preliminary characterization of the major component.

Crude glycophorin fraction was prepared from bovine erythrocyte membranes by extraction with lithium diiodosalicylate and partition in aqueous phenol. The crude fraction was further separated into three fractions by gel chromatography and ion-exchange chromatography. The major fraction, designated glycophorin BA, accounts for 80% of the crude fraction. Its carbohydrate content was 79% by weight including galactose, N-acetylgalactosamine, N-acetylglucosamine and N-glycolylneuraminic acid. Iodosobenzoate treatment of glycophorin BA produced two fragments; one is a highly glycosylated segment and the other a hydrophobic peptide. The amino-terminal sequence of the hydrophobic peptide representing the carboxyl-terminal half of glycophorin BA was determined. The other two fractions, IIIa and IIIb, were still heterogeneous when analyzed by gel electrophoresis. Fraction IIIa contained two glycophorins having apparent molecular weights of 46,000 and 42,000, while fraction IIIb contained a glycoprotein having a marked tendency to aggregate.

Amino Acids↗