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Biomedical subjects

T Seki

Publications and source records attributed to T Seki.

At least 613 records · Page 34Linked to original sources
PubMed1985

Chiral discrimination of 5,6-epoxy-3-dehydroretinal by aporetinochrome and cattle opsin.

The combination of a racemic all-trans 5,6-epoxy-3-dehydroretinal (EDR) with aporetinochrome formed a mixture of two diastereomeric pigments. One of the diastereomeric pigments which contained the all-trans EDR with a negative circular dichroic (CD) band, hereafter called EDR(-)-chrome, has its visible absorption maximum around 438 nm, while the other pigment, called EDR(+)-chrome, has its maximum at 464 nm. These were substantiated by measuring the optical activities of the two EDR isomers which were extracted from a mixture of racemic all-trans EDR and a smaller amount of aporetinochrome following exposure to orange light (greater than 530 nm) that irradiates EDR(+)-chrome selectively. The extracted all-trans EDR had a negative CD band around 240 nm and the extracted 11-cis EDR had a positive band in that region with two negative bands on either side of the main band. In the case of both pigments, the effect of alkalinization on the increase of absorbance in the near-ultraviolet and the decrease of absorbance in the visible region was proportionate, qualitatively, to that on the positive CD intensities in both regions. These results suggest that the chromophore EDR in each pigment binds to the same binding site via a Schiff base. The EDR(+)-chrome exhibited properties similar to those of retinochrome, but EDR(-)-chrome showed some different properties, i.e. its formation rate was slower than that of the former one and its absorption band in the near-ultraviolet appeared even at neutral pH. Moreover, by exposing EDR(-)-chrome to yellow light (greater than 480 nm), only a part of its prosthetic all-trans EDR was isomerized and resulted in the formation of 11-cis and 13-cis isomers. This variation in photoisomerizing activity was supposed to be due to the difference in conformation of the side chain between EDR(+) and EDR(-) in aporetinochrome. Combination of 11-cis EDR with cattle opsin was also shown to result in the formation of two diastereomeric pigments. The absorption maxima of the diastereomers containing 11-cis EDR(+) and EDR(-) were at about 446 and 474 nm, respectively.

Animals↗
PubMed1985

A hydrophobic transmembrane segment at the carboxyl terminus of thy-1.

The mode of integration of the glycoprotein thy-1 within the cell membrane has been controversial due to an apparent lack of a transmembrane hydrophobic segment. Rat and mouse complementary DNA and genomic clones encoding the thy-1 molecule have been isolated and sequenced. These studies have enabled us to determine the intron-exon organization of the thy-1 gene. Furthermore, they have revealed the existence of a sequence which would encode an extra segment (31 amino acids) at the carboxyl terminus of the thy-1 molecule. These extra amino acids include a 20-amino acid hydrophobic segment which may be responsible for integration of thy-1 within the plasma membrane.

Amino Acid Sequence↗
PubMed1985

Mechanism for 6-methylcoumarin photoallergenicity.

6-Methylcoumarin (6-MC), a synthetic fragrance material, has been reported to be photoallergenic both in man and in guinea pigs. To elucidate the possible mechanism of photoallergenicity, 6-MC in ethanolic solution was exposed to 200 joules/cm2 of long-wavelength ultraviolet (UV) ranging from 320 to 400 nm for 16 hr, and was examined for its contact allergenicity by means of a modified guinea pig maximization test. Strong allergic responses were observed, indicating that UV plays a catalytic role in forming contact allergens during irradiation. The solution was fractionated to isolate and purify contact sensitizers by gel-permeation chromatography and high-performance liquid chromatography. By employing mass spectrometry and proton and carbon-13 nuclear magnetic resonance, mono- and diethyl esters of 6-MC dimer were compounds identified which showed allergic reactions in guinea pigs sensitized with UV-irradiated 6-MC.

Administration, Topical↗
PubMed1985

Isolation and characterization of mouse Thy-1 genomic clones.

The mouse Thy-1.2 gene was isolated from a C57Bl/6 cosmid library and its nucleotide sequence was determined from an 8-kilobase-long EcoRI fragment. The predicted amino acid sequence indicates that the mouse Thy-1 molecule contains a 19 amino acid leader peptide and the 112 amino acids reported previously from protein sequence analysis, plus 31 extra amino acids at the carboxyl terminus. These 31 amino acids contain a stretch of 20 amino acids, at positions 124-143, which is highly hydrophobic. RNA transfer blot analysis of RNA from mouse tissues indicates that the sequence coding for these 31 amino acids is present on poly(A)-containing RNA of brain and thymus tissues. This hydrophobic segment very likely provides the basis for integration of Thy-1 within the plasma membrane. The entire coding sequence of Thy-1 is distributed among three exons, encoding amino acid residues -19 to 8, -7 to 106, and 107 to 143, respectively. Comparison of the mouse and rat Thy-1 genes shows that both have a similar gene organization and encode a highly conserved transmembrane segment.

Amino Acid Sequence↗
PubMed1985

The human Thy-1 gene: structure and chromosomal location.

The human Thy-1 gene has been isolated and sequenced and compared to the rat and mouse Thy-1 genes. All three genes are organized in the same way: one exon encoding the majority of the signal peptide, another encoding the transmembrane segment, and a third encoding the remainder of the protein. One major structural difference between the human and rodent Thy-1 glycoproteins is that the former contains two instead of three glycosylation sites. RNA blot analysis of a human T-cell line expressing the T3 complex showed an absence of Thy-1 mRNA, excluding the possibility that Thy-1 represents one of the component chains of T3. The structural gene for human Thy-1 was localized to the long arm of chromosome 11 by nucleic acid hybridization to genomic DNA isolated from somatic cell hybrids.

Amino Acid Sequence↗
PubMed1985

Long-term prognosis of complex partial seizures in childhood.

We studied the long-term prognosis of complex partial seizures in childhood including their electroencephalograms, behavioral problems and adaptation to school or society. In the clinical course, seizures were controlled in 25 cases out of 40 (62.5%). The rate of seizure control was significantly higher in cases with a past history of febrile convulsions, whose onset occurred before 6 years of age and in whom the CT scans were normal. Behavioral, motor and emotional problems included "clumsiness" in 25%, "poor athletes" in 22.5%, "hyperactivity" in 17.5% and "easily enraged" in 12.5% of the cases. The overall cooperation of the surroundings with the patients was thought to be as important a factor as the patients' IQ, motor or emotional problems so that they can get along in school or society.

Adolescent↗
PubMed1985

Construction of killer wine yeast strain.

A double-stranded RNA plasmid which confers the superkiller phenotype was transferred into a wine yeast (Montrachet strain 522) and its leucine-requiring derivative (strain 694) by cytoduction, using the protoplast fusion technique. The killer wine yeast constructed completely suppressed the growth of killer-sensitive strains of Saccharomyces cerevisiae in yeast extract-peptone-glucose medium at pH 4.5, whereas the killer effect was somewhat decreased at pH 3.5. The wine yeast harboring the killer factor also inhibited the growth of killer-sensitive cells satisfactorily when it was grown in grape juice.

Journal Article↗
PubMed1985

Radioimmunoassay of bleomycins.

Rabbit antisera highly specific to the bleomycinic acid moiety of bleomycins were obtained by immunizing with a conjugate of copper-complex of bleomycin A5 and bovine serum albumin. These antisera not only reacted with bleomycin A5 but also with other bleomycins such as bleomycin A2, bleomycin B2 and peplomycin. The antisera showed little cross-reactivity with deamido-, depyruvamido- and decarbamoyl-bleomycins. Thus, these antisera were found to be highly specific for the intact bleomycinic acid moiety. One of the antisera was successfully applied to radioimmunoassay of bleomycin and peplomycin in mouse and human sera. The detection limit was 1 ng/ml. This radioimmunoassay is expected to be widely used for the determination of active bleomycins in biological and clinical samples.

Animals↗
PubMed1985

Bestatin, a microbial aminopeptidase inhibitor, inhibits DNA synthesis induced by insulin or epidermal growth factor in primary cultured rat hepatocytes.

Bestatin, a microbial aminopeptidase inhibitor, inhibited insulin- or epidermal growth factor-induced DNA synthesis and cell proliferation in primary cultured hepatocytes of rats. The aminopeptidase inhibitor also affected the growth of FM3A or LOBN cells of mice, when it is included in the culture media at the concentration of 0.5 mg/ml. These results suggest the important role of the bestatin-sensitive aminopeptidase(s) in the process of DNA synthesis and proliferation of animal cells.

Aminopeptidases↗
PubMed1985

Thy-1: a hydrophobic transmembrane segment at the carboxyl terminus.

Thy-1 is a membrane glycoprotein distributed throughout mammalian species and expressed on brain tissue and various cells of the hematopoietic lineage. The nucleotide sequences of rat and mouse Thy-1 genes revealed a similar gene organization and the existence of an extra 31 amino acid segment at the carboxyl terminus not described previously. These extra amino acids, highly conserved in both species, include a 20 amino acid hydrophobic segment at the carboxyl terminus, which may be responsible for integration of Thy-1 within the plasma membrane.

Amino Acid Sequence↗
PubMed1985

Antitumor activity and toxicity of serum protein-bound platinum formed from cisplatin.

When cisplatin was incubated with mouse serum, its cytotoxicity towards P388 leukemia cells decreased with the formation of non-ultrafiltrable or protein-bound platinum. The cytotoxicity of prepared mouse serum protein-bound platinum at 100 microgram/ml (as the cisplatin-equivalent concentration) was less than that of cisplatin at 0.125 microgram/ml. The prepared protein-bound platinum exhibited antitumor activity against colon adenocarcinoma 26 in mice, when administered iv daily for 9 consecutive days at 32 and 64 mg/kg (as the cisplatin-equivalent dose). Cisplatin similarly administered exhibited antitumor activity at daily doses of only 1 and 2 mg/kg. Administration of the protein-bound platinum at such high doses as 32 and 64 mg/kg (as the cisplatin-equivalent dose) caused elevation of serum BUN and reduction of bone marrow cells in mice. After iv administration of cisplatin to mice at 6 mg/kg, ultrafiltrable platinum was detected in the plasma for the first 30 min. Thereafter platinum was found only in protein-bound form. When mice were iv inoculated with colon adenocarcinoma 26 more than 30 min after cisplatin administration, no prolongation of the life span was observed. From these results, it is concluded that mouse serum protein-bound platinum does not contribute significantly to cisplatin antitumor activity and toxicity in mice.

Animals↗
PubMed1985

Amplification of c-yes-1 proto-oncogene in a primary human gastric cancer.

Abnormalities of cellular oncogenes in 22 cases of human primary gastric cancer were screened by Southern blot analysis using 16 onc probes. Human cellular sequences related to the v-yes oncogene of Y73 avian sarcoma virus (human c-yes-1 gene) were found to be amplified in a primary gastric cancer. The degree of amplification was about 4- to 5-fold. Another v-yes-related cellular gene (human c-yes-2, a pseudogene) was not amplified in this tumor. The normal stomach tissue adjacent to the tumor tissue in the same patient showed no amplification of c-yes-1 gene, suggesting that the amplified c-yes-1 is involved in the onset or the progress of this carcinoma.

Electrophoresis, Agar Gel↗
PubMed1985

[The antitumor activity of intraperitoneally- or orally-administered etoposide in animals and its administration-schedule dependency].

The antitumor activity of etoposide against a wide variety of transplantable tumors in mice and rats was examined. Etoposide exhibited antitumor activity by both i.p. and p.o. administrations but a much larger effect was obtained in the former case. In addition, the effective dose of etoposide was much less in i.p. administration. In order to further investigate this large difference of etoposide effect the level of etoposide in the blood was followed after administration of 3H-etoposide via i.p. and p.o. routes. Although the maximum levels for both were seen 10 to 20 min after administration, the level in i.p. administration was much higher than that in p.o. administration. For instance, the level seen for i.p. administration at 8 mg/kg was comparable to that for p.o. administration at a much higher dose of 128 mg/kg. The administration schedule dependency of etoposide antitumor activity was examined using L1210 leukemia as the target tumor. When etoposide was administered alone on day, 1, the effect was the smallest obtained in i.p. as well as in p.o. administrations among the schedules examined in this study. Under other schedules where etoposide was administered i.p. and p.o. once a day for 3, 5 and 9 consecutive days from day 1 and on every other day, that is, days 1, 3 and 5, higher antitumor effects were seen.

Adenocarcinoma↗
PubMed1984

Selective determination of alpha 2-plasmin inhibitor activity in plasma using chromogenic substrate.

In determination of antiplasmin activity of alpha 2-plasmin inhibitor (alpha 2 PI) using an amidolytic method, alpha 2-macroglobulin (alpha 2 M) in concentrations present in normal plasma inhibits the cleavage of chromogenic substrates by plasmin even if the reaction time between alpha 2M and plasmin is shortened as much as possible. The purpose of this study was to develop a new method to assay alpha 2 PI selectively with the chromogenic substrate S-2251 using an end-point method. The antiplasmin activity of alpha 2 M was destroyed by the addition of methylamine hydrochloride. In a case of congenital alpha 2 PI deficiency, antiplasmin activity determined with the previous method without the addition of methylamine was 20% of normal plasma, whereas the results obtained using this newly developed method was 5%. A statistically significant correlation between alpha 2 PI levels determined with this method and with a single radial immunodiffusion method was observed in plasma samples collected from 40 healthy subjects and 11 patients with disseminated intravascular coagulation (DIC). In two cases of DIC, in which markedly depleted levels of alpha 2 PI and normal concentrations of alpha 2 M were observed, antiplasmin activities measured without the addition of methylamine were higher than the ones measured immunologically, whereas the results obtained with the method described here were in accordance with the antigenicities of alpha 2 PI.

Aged↗