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Biomedical subjects

T Hamamoto

Publications and source records attributed to T Hamamoto.

At least 145 records · Page 8Linked to original sources
PubMed1989

Sulfation of minoxidil in keratinocytes and hair follicles.

Minoxidil, a potent antihypertensive agent, has the unique side effect of stimulating hair growth and it has been suggested that minoxidil sulfate may be the active form of minoxidil. In this study, we investigated whether sulfation of minoxidil in various cells of the skin; hair follicle, proliferating and differentiating keratinocyte and fibroblast occurs. We provide evidence that sulfation of minoxidil occurs in the hair follicles and proliferative keratinocytes. On the other hand the activity in differentiating keratinocytes and fibroblasts was extremely low. The strong sulfation of minoxidil that occurs in hair follicle cells may be related to the hair growth stimulating effect of this drug.

Animals↗
PubMed1988

Solubilization and reconstitution of voltage-dependent calcium channel from bovine cardiac muscle. Ca2+ influx assay using the fluorescent dye Quin2.

Highly purified sarcolemmal membranes, prepared from fresh bovine heart left ventricle, were solubilized by n-octyl beta-D-glucopyranoside and reconstituted into proteoliposomes with soybean phospholipids by the detergent-dialysis method. Ca2+ flux into the proteoliposomes was determined using the fluorescent probe Quin2. A membrane potential (negative in the proteoliposome interior) that was created by K+ diffusion mediated by valinomycin accelerated the Ca2+ influx. The voltage-dependent Ca2+ influx was dependent on pretreatment of the sarcolemmal membranes with Bay K 8644 and was inhibited by various calcium antagonists including nicardipine (K0.5 = 4.5.10(-7) M), verapamil (K0.5 = 9.2.10(-9) M), diltiazem (K0.5 = 26.10(-8) M) and omega-conotoxin (K0.5 = 9.5.10(-9) M).

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1988

Incorporation of partially purified cation channels from cardiac sarcolemmal membrane into planar lipid bilayers.

Voltage-dependent calcium channels are vital to cardiac muscle contraction. Therefore it is very important to isolate physiologically active channel proteins, however there have been few reports on their solubilization and reconstitution. Highly purified sarcolemmal membranes from bovine cardiac muscle were solubilized with octylglucoside, partially purified by gel filtration, and reconstituted into planar lipid bilayer by the direct insertion method. At least, two cation channel activities were observed: one with about 4.2 pS and the other with about 28 pS in conductance. From the reversal potential, it was concluded that Ba2+ ions are the current carrier through these two channels.

Animals↗
PubMed1988

Sequence and over-expression of subunits of adenosine triphosphate synthase in thermophilic bacterium PS3.

The primary structures of all the subunits of thermophilic ATP synthase were determined, and its alpha, beta and gamma subunits could be over-expressed in Escherichia coli, because these subunits were stable and reconstitutable. DNA of 7500 base pairs in length was found to contain a cluster of nine genes for subunits of ATP synthase. The order of their reading frames (size in base pairs) was: I(381): a(630): c(216): b(489): delta(537): alpha(1507): gamma(858): beta(1419): epsilon(396), I being a gene for a small hydrophobic, basic protein expressed in vitro. All the termini of TF0F1 subunits were confirmed by peptide sequencing. Large quantities of the overexpressed thermophilic alpha, beta and gamma subunits were prepared from the extract of E. coli, by a few purification steps.

Amino Acid Sequence↗
PubMed1988

Molecular cloning and nucleotide sequence of the cyclomaltodextrin glucanotransferase gene from the alkalophilic Bacillus sp. strain no. 38-2.

The cyclomaltodextrin glucanotransferase (CGTase, EC 2.4.1.19) gene from the alkalophilic Bacillus sp. strain no. 38-2 was cloned in Escherichia coli using pBR322. A plasmid, pCS8, was isolated from a transformant producing CGTase and the cloned CGTase gene was found to be in a 5.3 kb DNA fragment. The nucleotide sequence of a 2.5 kb segment encoding the CGTase was determined. This segment showed an open reading frame which would encode a polypeptide of 712 amino acids. The pCS8 CGTase had the same enzymic properties as those of the extracellular CGTase produced by the alkalophilic Bacillus sp. strain no. 38-2. The nucleotide and amino acid sequences of this CGTase gene and gene product, respectively, have strong homology with those of the Bacillus macerans CGTase.

Amino Acid Sequence↗
PubMed1986

Direct measurement of the electrogenicity of the H+-ATPase from thermophilic bacterium PS3 reconstituted in planar phospholipid bilayers.

The proton-translocating ATPase of the thermophilic bacterium PS3 was incorporated into a planar phospholipid bilayer, and its electrogenicity was directly demonstrated. The enzyme (TF0F1) consists of a catalytic portion, F1, and a membrane-integrated portion, Fo. A short-circuit current of up to 1 nA/cm2 was generated upon the addition of ATP, and the direction of the current indicated the flow of positive charges from the TF1 side to the TF0 side. The generation of the electric current was progressively suppressed by the presence of an inhibitor of TF1 such as NaN3 or adenyl-5'-yl imidodiphosphate. An open-circuit membrane potential of 40-120 mV was also demonstrated (more negative on the TF1 side), which was inhibited by NaN3. Furthermore, an applied voltage of -180 mV (TF1 side negative) was sufficient to prevent the generation of electric current dependent on ATP hydrolysis, which indicated that the electrogenicity of TF0F1 is some 180 mV under the conditions studied. From these results it was tentatively concluded that the number of protons transported across the bilayer/mol of ATP is more than 3.

Adenosine Diphosphate↗
PubMed1985

Serum collagenase-like peptidase activity in rheumatoid arthritis and systemic lupus erythematosus.

Collagenase-like (CL) peptidase activity in serum, which was measured using a newly synthesized substrate, (succinyl-Gly-Pro-Leu-Gly-Pro)-4-methylcoumaryl-7-amide, was significantly lower in patients with advanced rheumatoid arthritis or with systemic lupus erythematosus than that in normal controls. Decrease of the serum enzyme activity was more pronounced in systemic lupus erythematosus. No significant change in serum CL-peptidase activity was found in other connective tissue diseases such as mixed connective tissue disease and Sjögren's syndrome.

Arthritis, Rheumatoid↗
PubMed1985

Direct measurement of the electrogenic activity of o-type cytochrome oxidase from Escherichia coli reconstituted into planar lipid bilayers.

Turnover of o-type cytochrome oxidase purified from Escherichia coli and reconstituted into proteoliposomes leads to the generation of a transmembrane electrical potential (interior negative) by means of vectorial electron flow. In the experiments reported here, purified oxidase is reconstituted in planar lipid bilayers formed at the tip of patch pipets, and open-circuit membrane potentials generated by electron transfer are measured directly. Potentials of up to 4 mV (substrate side positive) are generated in the presence of reduced phenazine methosulfate or ubiquinol-1, and with both substrates, electrogenic activity is inhibited by cyanide. Furthermore, the membrane potential generated during oxidase turnover is inhibited progressively with applied voltages (substrate side positive), decreasing almost to zero at an applied voltage of 150 mV.

Electrochemistry↗
PubMed1985

Ouabain-resistant cells cultured in a synthetic medium.

Several strains of kidney and liver cells cultured in a synthetic medium were found to be resistant to ouabain. These cell strains were characterized because this resistance may serve as a good marker in genetic studies on somatic cells in chemically defined conditions in the absence of Na+ related growth factors and hormones. The phenotype was stable in the absence of selection for at least two years, and the original strains before adaptation to the synthetic medium were found to have ouabain sensitivity equal to the corresponding cells in the synthetic medium. The resting membrane potential, Na+,K+-ATPase activity, and growth rate of the resistant cells were similar to those of ouabain-sensitive cells. The resistance of the cells was not affected by serum or antibodies against some cytoskeletal proteins and the sensitivity of the Na+,K+-ATPase was not restored by partial purification of the membranes. Western blotting of the Na+,K+-ATPase of the ouabain-resistant cells showed that the molecular weights of its two subunits and its immunoreactivity were similar to those of the enzyme from the ouabain-sensitive strain. Thus the ouabain resistance is caused not by ouabain-like hormone produced by the cells or change in the cytoskeletal system, but by a mutation resulting in expression of an ouabain-resistant ATPase gene.

Animals↗
PubMed1985

Free alpha subunits of glycoprotein hormone with dissimilar carbohydrates produced by pathologically different carcinomas.

The two kinds of glycoprotein hormone alpha subunit ectopically produced by an undifferentiated carcinoma of the left femoral region (TM-alpha) and an adenocarcinoma of the right external genitalia (FS-alpha) were examined for amino acid composition, isoelectric focusing, molecular weight, the ability to combine with standard hCG beta and affinity with lectins (Con A, Ricin and PNA). Both TM-alpha and FS-alpha exhibited immunoantigenicity similar to standard hCG alpha. Furthermore, there were no significant differences in the amino acid compositions of TM-alpha, FS-alpha or standard hCG alpha. In isoelectric focusing, while standard hCG alpha exhibited a neutral charge, both TM-alpha and FS-alpha exhibited strong negative charges. FS-alpha was as sensitive to sialidase as standard hCG alpha, whereas most of the TM-alpha exhibited resistance to sialidase. TM-alpha contains sialidase-insensitive peripheral material with a negative charge. The affinity with Ricin-Sepharose indicated that most of the FS-alpha and some of the TM-alpha may contain terminal sialic acid and the penultimate structure, Gal beta 1----4G1cNAc; the affinity with PNA-Sepharose indicated that both may also contain terminal sialic acid and the penultimate structure, Gal beta 1----3GalNAc. These observations suggest that dissimilar glycosylation processes are present in the carcinoma ectopic biosynthesis of glycoprotein hormone alpha subunit.

Adenocarcinoma↗
PubMed1985

Leptomycins A and B, new antifungal antibiotics. III. Mode of action of leptomycin B on Schizosaccharomyces pombe.

Mode of action of leptomycin B (LMB), a new antifungal antibiotic, was studied with Schizosaccharomyces pombe. A low concentration of LMB caused inhibition of cell division, producing elongated cells with morphologically altered nuclei and several cell plates, while it inhibited nucleic acid synthesis in intact cells at 100-fold higher concentration. Addition of LMB during G2 phase in synchronous culture blocked following events in cell cycle. Analysis of the effect of LMB on cdc mutants suggested the antibiotic inhibited some specific step, possibly in M phase just prior to nuclear division.

Antifungal Agents↗