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Biomedical subjects

T Yagi

Publications and source records attributed to T Yagi.

At least 667 records · Page 37Linked to original sources
PubMed1981

Electrocatalytic four-electron reduction of oxygen at the cytochrome c3-adsorbed electrode.

The electrocatalytic activity of cytochrome c3 for the reduction of molecular oxygen was characterized from the studies of the adsorption of cytochrome c3 and the co-adsorption of cytochrome cs with cytochrome c on the mercury electrode by the a.c. polarographic technique. The adsorption of cytochrome c3 on the mercury electrode is irreversible and is diffusion-controlled. The maximum amount of cytochrome c3 absorbed was 0.92 . 10(-11) mol . cm-2 at -0.90 V. The amount of cytochrome c3 in the mixed adsorbed layer with cytochrome c was determined from the differential capacitance measurement. It was shown that the fractional coverage of cytochrome c3 can be estimated from its bulk concentration and the diffusion coefficient (1.05 . 10(-6) cm2 . s-1). Cytochrome c3 catalyzes the electrochemical reduction of molecular oxygen from the two-electron pathways via hydrogen peroxide to the four-electron pathway at the mercury electrode in neutral phosphate buffer solution. The catalytic activity varies with the bulk concentration of cytochrome c3. The highest catalytic activity for the oxygen reduction (no hydrogen peroxide formation) is attained when one-half of the mercury electrode surface is covered by cytochrome c3. The addition of cytochrome c or bovine serum albumin to the cytochrome c3 solution inhibits the catalytic activity of cytochrome c3. The reversible polarographic behavior of cytochrome c3 through the mixed adsorbed layer of cytochrome c3 and cytochrome c was also investigated.

Adsorption↗
PubMed1981

Repair of ultraviolet radiation damage in xeroderma pigmentosum cells belonging to complementation group F.

DNA-repair characteristics of xeroderma pigmentosum belonging to complementation group F were investigated. The cells exhibited an intermediate level of repair as measured in terms of (1) disappearance of T4 endonuclease-V-susceptible sites from DNA, (2) formation of ultraviolet-induced strand breaks in DNA, and (3) ultraviolet-induced unscheduled DNA synthesis during post-irradiation incubation. The impaired ability of XP3YO to perform unscheduled DNA synthesis was restored, to half the normal level, by the concomitant treatment with T4 endonuclease V and ultraviolet-inactivated Sendai virus. It is suggested that xeroderma pigmentosum cells of group F may be defective, at least in part, in the incision step of excision repair.

Adult↗
PubMed1981

DNA repair in Bloom's syndrome fibroblasts after UV irradiation or treatment with mitomycin C.

Sensitivities to UV and mitomycin C (MC) of fibroblasts obtained from 3 Japanese patients with Bloom's syndrome (BS) were studied. One BS strain was more sensitive to UV than normal cells only in colony-forming ability. Other responses to UV, such as unscheduled DNA synthesis, host-cell reactivation and removal of UV-endonuclease-susceptible sites, were normal in all 3 strains. These BS strains were more sensitive to MC than were normal cells. However, the amounts of unscheduled DNA synthesis after treatment with MC in BS cells did not differ from those in normal cells.

Cells, Cultured↗
PubMed1981

D-lactate dehydrogenase of Desulfovibrio vulgaris.

D-Lactate dehydrogenase, the starting enzyme for carbon and energy metabolism in dissimilatory sulfate-reducing bacteria, has been purified 36-fold from the soluble fraction of the sonicate of Desulfovibrio vulgaris, Miyazaki. The enzyme is specific for D-lactate (Km = 0.8 mM) and DL-2-hydroxybutyrate (probably its D-isomer) as the electron donor substrate. It reduces, in the presence of lactate, various artificial electron acceptors such as 1-methoxyphenazinium methyl sulfate, ferricyanide, tetrazolium dyes, methylene blue, and 2,6-dichlorophenol-indophenol. When 2 mol of ferricyanide was reduced, 1 mol of pyruvate was produced during the reaction. Among natural electron carriers, only cytochrome c-553 isolated from the same organism can be reduced by the enzyme. The ferric complex of pyridine-2,6-dicarboxylate can act as an electron acceptor if cytochrome c-553 is present in the reaction system. NAD+, NADP+, FAD, FMN, cytochrome c3, high-molecular-weight cytochrome, eucaryotic cytochromes c (yeast and horse) and O2 could not be reduced. The enzyme does not have any diaphorase activity. The D-lactate dehydrogenase of D. vulgaris must therefore be named D-lactate:ferricytochrome c-553 oxidoreductase [EC subclass 1.1.2]. A similar enzyme exists in the formate dehydrogenase-less mutant of D. vulgaris, Miyazaki, and in D. vulgaris, Hildenborough.

Desulfovibrio↗
PubMed1981

The structure of cytochrome c3 from Desulfovibrio vulgaris Miyazaki at 2.5 A resolution.

The structure of tetraheme cytochrome c3 isolated from Desulfovibrio vulgaris Miyazaki has been determined at 2.5 A resolution by an X-ray diffraction method. Protein phases were computed by the multiple isomorphous replacement method using the native and four heavy atom derivatives, anomalous scattering measurements of the latter being considered. The mean figure of merit was 0.77. Four heme groups are exposed on the surface of the molecule. There are some short helical segments in the polypeptide chain, and hair-pin turns are often observed at glycine and alanine residues.

Amino Acid Sequence↗
PubMed1981

On cytochrome c3 folding.

The structure of cytochrome c3 from Desulfovibrio vulgaris Miyazaki (DvM) is considered in detail by scrutinizing main chain folding together with the structure of the protein from D. desulfuricans Norway (DdN). The relative arrangement of the four heme groups in this molecule is similar to that of DdN and the disposition of alpha-carbon atoms of cysteine and histidine residues binding to heme groups is also similar. Structural differences between the two proteins occur in the shape of some specific loops of the chain on the molecular surface. As a result of a careful comparison of structures and sequences in both cytochromes c3, the reported sequence alignment of the cytochrome c3 family has been revised. Our new proposal of a sequence alignment based on the three-dimensional structures contains 24 evolutionarily conservative residues. All these conservative residues may play an important role in the folding pattern of cytochromes c3.

Amino Acid Sequence↗
PubMed1981

The intact surface layer in natural enamel caries and acid-dissolved hydroxyapatite pellets. An X-ray diffraction study.

The crystallographic features of various histological sites found in enamel carious lesions were studied by means of X-ray microbeam diffraction. The most interesting finding was the crystallinity of apatite crystals in the intact surface layer covering the demineralized lesions was higher than that of the crystals in the subsurface lesions or unaffected areas. Acid-dissolution experiments using synthetic hydroxyapatite pellets showed that a well mineralized layer was produced on the pellet surface under the condition that no Ca and PO4 ions were added to the initial acidic solution. Furthermore, X-ray diffraction analysis revealed that half-line breadth values of 004, 222, and 310 reflections of apatite pellets decreased, and their integrated peak intensities increased with dissolution time. These findings are in agreement with the results obtained in the study of enamel carious lesions, leading to the conclusion that the intact surface layer is formed by deposition of the mineral ions from dissolving subsurface lesions, and that this process is accompanied by the improvement in crystallinity of apatite crystals, possibly due to growth of the crystals.

Crystallography↗
PubMed1981

A new neurotological test for detecting cerebellar dysfunction.

The adaptation of the vestibulo-ocular reflex (VOR) was studied in 26 normal subjects and 26 patients with cerebellar lesions, using horizontal vision-reversal prisms. In normal subjects, the adaptation of gain after wearing prisms for one hour was approximately 50% of the VOR value in the dark. In contrast to this, patients with cerebellar lesions showed less adaptation--approximately 20% after a one-hour forced adaptation task. These were type A, higher gain in the initial level and abnormal adaptation (10 cases); type B, higher gain in the initial level and normal adaptation (5 cases); and type C, normal initial level and abnormal adaptation (11 cases). The cases showing the typical type-A responses tended to have severe widespread or midline lesions of the cerebellum. Typical type-B cases had mild cerebellar lesions, and typical type-C cases tended to have lesions restricted to one side of the cerebellum. From these results, it can be speculated that reduction of VOR adaptation occurs when one side of the cerebellum has severe lesions, but it is sufficient to produce a normal vestibulo-ocular reflex if at least half of the cerebellum is intact.

Adult↗
PubMed1981

The effect of rectal administration of insulin on the short-term treatment of alloxan-diabetic dogs.

Six alloxan-diabetic dogs with fasting plasma glucose levels above 200 mg/100 mL were treated with rectal administration of insulin suppositories twice a day for 6--9 days. The effectiveness was compared with that of subcutaneous insulin injections. In three diabetic dogs with fasting plasma glucose levels below 300 mg/100 mL, both insulin suppository at a dose of 20 U (2.3 U/kg) and subcutaneous insulin at a dose of 0.2 U/kg showed a similar effect in reducing fasting glucose levels and daily urinary glucose amounts. In dogs with higher fasting glucose levels, 0.5 U of subcutaneous insulin/kg is less effective in reducing fasting glucose than 50 U (5.2 U/kg) suppositories, in spite of the same effects on daily urinary glucose output. Postprandial glucose responses were significantly lessened with rectal administration of insulin suppositories. The integrated area of increase in peripheral insulin concentration after subcutaneous infection of 0.2 or 0.5 U insulin/kg was significantly greater than that after rectal administration of an insulin suppository (2.3 or 5.2 U/kg, respectively). These results indicate that diabetes could be controlled by the daily rectal administration of an insulin suppository instead of the conventional subcutaneous injection.

Animals↗
PubMed1981

High-voltage electron microscopy of radiation damages in octacalcium phosphate.

The present high-voltage electron microscopic study showed two types of radiation damages in OCP. The first type commenced with the formation of voids, which later grew and coalesced along the c-axis. The second type was characterized by the appearance of paired and concentric strain fields and the subsequent formation of dislocations. The origin of the strain fields is attributed tentatively to a precipitation of a second phase in the crystal.

Calcium Phosphates↗
PubMed1981

In vivo distribution of 14C-labeled N4-behenoyl-1-beta-D-arabinofuranosylcytosine in mice.

In order to clarify the pharmacological characteristics of N4-behenoyl-1-beta-d-arabinofuranosylcytosine (BHAC) and 1-beta-D-arabinofuranosylcytosine (AraC) with regard to their distribution in vivo, 14C-labeled BHAC and 13C-labeled AraC were injected intravenously into mice. Their in vivo distribution was determined by whole-body macroautoradiography and by an oxidation method. The disappearance rates of BHAC[cytosine-2-14C] and BHAC[behenoyl-l-14C] from the blood were slower than that of AraC[cytosine-2-14C], and the elimination rates of BHAC[cytosine-2-14C] and BHAC[behenoyl-14C] into the urine and feces were also slower than that of AraC[cytosine-2-14C]. The total amounts of BHAC[cytosine-2-14C] and BHAC[behenoyl-1-14C] eliminated within 48 hr after the injection were small. AraC[cytosine-2-14C] was equally distributed in each organ, while large amounts of BHAC[cytosine-2-14C] were found in and the placentae. The BHAC[behenoyl-1-14C]level in the thymus was lower than that of BHAC[cytosine-2-14C]. A very low level of radioactivity was found in most of the organs 6 hr after the injection of Arac[cytosine-2-14C], but BHAC[cytosine-2-14C] was observed even 24 hr after the injection. Radioactivity was still found in the liver, spleen, kidneys and adrenal glands of mice injected with BHAC[behenoyl-1-14C] even after 72 hr. In pregnant mice, AraC]cytosine-2-14C] was transmitted to the fetuses, but only a very small amount of 14C-BHAC was transmitted to the fetuses.

Animals↗
PubMed1980

A novel purification procedure of L-lysine 6-aminotransferase from Flavobacterium lutescence.

A new method for the purification of L-lysine 6-aminotransferase (L-lysine: 2-oxoglutarate 6-aminotransferase, EC 2.6.1.36) was devised, in which affinity chromatography with L-lysylacetamidododecyl-Sepharose 6B, the most effective affinity adsorbent, was substituted for the heat treatment. The yield of the enzyme with the present procedure was approx. twice as high as that with the previous procedure (Soda, K. and Misono, H. (1968) Biochemistry 7, 4110-4119). The enzyme purified by this method was activated 2-fold by heat treatment (65 degrees C for 5 min). The enzyme has absorption maxima at 340 and 415 nm, derived from the bound pyridoxal 5'-phosphate, which are identical with those of the enzyme obtained with the procedure including heat treatment. These results rule out the possibility that the formation of the 340-nm pyridoxal 5'-phosphate of the enzyme is an artifact of heat treatment.

Chromatography, Affinity↗
PubMed1980

Use of 1-methoxy-5-methylphenazinium methyl sulfate (1-methoxyPMS) in the assay of some enzymes of diagnostic importance.

1-Methoxy-5-methylphenazinium methyl sulfate (1-methoxyPMS) is a photochemically stable electron mediator between NAD(P)H and tetrazolium dyes. We have examined the efficiency of 1-methoxyPMS as an electron mediator in the assay of human lactate dehydrogenase (LDH, EC 1.1.1.27) and the activity staining of LDH isozymes after electrophoresis. The turnover number of 1-methoxyPMS as an electron mediator between NADH and nitrotetrazolium blue was 10--12 s-1, which is a value equal to that of PMS. Correlation coefficient between the estimated LDH activities of human sera obtained with 1-methoxyPMS and those obtained with diaphorase was 0.998. 1-MethoxyPMS successfully substituted for the unstable PMS in the activity staining of LDH isozymes of human serum, giving less background staining. We conclude that 1-methoxyPMS will be useful for routine methods of activity assay and activity staining of enzymes of diagnostic importance.

Clinical Enzyme Tests↗
PubMed1980

A study of cases with partial disappearance of the waves in the auditory brain stem response.

Twenty cases which showed partial loss of ABR waves were reported. Only wave I was recorded in 18 ears tested. Wave I and II; I-III; and I-IV responses were observed in four, eight, and five ears tested, respectively. Cases included pontine glioma (8), acoustic tumor (4), West syndrome (2), leukodystrophy (2), facial neurinoma (1), epidermoid tumor (1), pontine bleeding (1), and unknown cause (1). Fourteen of 20 were tumor cases. This fact indicates that if the ABR shows partial loss of waves, the examiner should first suspect the space-occupying lesions of the brain stem.

Brain Neoplasms↗
PubMed1980

Cytotoxic effects of protease inhibitors on human cells. 2. Effect of elastatinal.

Effects of elastatinal, a protease inhibitor, on DNA repair and its cytotoxicity were investigated in normal human, xeroderma pigmentosum and Chinese hamster V79 cells. There were no effects of elastatinal on DNA repair and UV-induced sister chromatid exchanges, and all 3 cell lines demonstrated essentially the same sensitivity to the cytotoxic effect of elastatinal. These results were quite different from those by antipain, another protease inhibitor, and caffeine.

Animals↗
PubMed1980

Cytotoxic effects of protease inhibitors on human cells. 1. High sensitivity of xeroderma pigmentosum cells to antipain.

Antipain had little effect on UV-survival and UV-induced sister chromatid exchanges in normal and xeroderma pigmentosum (XP) cells, suggesting that it may not affect DNA repair. Antipain itself produced a small, but significant, amount of sister chromatid exchanges. XP cells showed very high sensitivity to the cytotoxic effect of antipain, but an SV40-transformed XP cell strain did not demonstrate high sensitivity.

Adolescent↗