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Biomedical subjects

T Yagi

Publications and source records attributed to T Yagi.

At least 631 records · Page 35Linked to original sources
PubMed1983

Amino acid sequence of cytochrome c-553 from Desulfovibrio vulgaris Miyazaki.

The complete amino acid sequence of cytochrome c-553 from Desulfovibrio vulgaris Miyazaki has been determined. The protein has a single polypeptide chain containing 79 amino acid residues and has the typical characteristics of small mitochondrial cytochromes. Contrary to the expectation that the amino acid sequence of cytochrome c-553 from D. vulgaris Miyazaki is closely related to that from D. vulgaris Hildenborough, the two are not alike, except for the 20 NH2-terminal residues and the 4 carboxyl-terminal residues; however, the tryptic peptides obtained from the two cytochromes are similar to each other. The sequence of cytochrome c-553 from D. vulgaris Miyazaki resembles that of Pseudomonas cytochrome c-551. The phylogenetic situation of Desulfovibrio cytochrome c-553 in the phylogenetic tree of the cytochrome c super-family is discussed.

Amino Acid Sequence↗
PubMed1983

The bacterial oxidation of vitamin B6. 4-Pyridoxic acid dehydrogenase: a membrane-bound enzyme from Pseudomonas MA-1.

A highly specific inducible membrane-bound 4-pyridoxic acid dehydrogenase has been solubilized and purified to apparent homogeneity from Pseudomonas MA-1 grown with pyridoxine as a sole source of carbon and nitrogen. The undenatured enzyme migrates as a single band on gel electrophoresis; denatured preparations show two barely resolved bands (Mr = 63,000 and 61,000). Undenatured preparations aggregate readily, as evidenced by Mr values of 148,000, 470,000, and greater than 670,000 obtained by density gradient centrifugation or by gel filtration under various conditions. The enzyme contains FAD but no Fe or acid-labile S; an average minimum molecular weight of 131,000 was calculated from the FAD content. In the presence of 2,6-dichloroindophenol, the enzyme dehydrogenates 4-pyridoxic acid to the corresponding aldehyde; this reaction is not inhibited by CN-. At the pH optimum of 8.0, a Vm of approximately 7.0 mumol min-1 mg-1 and a Km of 9 microM were obtained. 2,6-Dichloroindophenol, phenazine methosulfate, and menadione are effective electron acceptors; ubiquinones are less active, while NAD, FAD, and O2 are inactive. However, in membrane fractions, oxygen supports 4-pyridoxic acid oxidation via a CN--sensitive electron transport chain, indicating that the dehydrogenase probably is coupled to ATP generation in such preparations.

Alcohol Oxidoreductases↗
PubMed1983

Evaluation of the brain-stem function by the auditory brain-stem response and the caloric vestibular reaction in comatose patient.

The auditory brain-stem response (ABR) and the caloric vestibular reaction (CVR) were investigated in 100 patients in deep coma to evaluate the brain-stem function of these patients precisely and to predict their prognosis accurately. In the first ABR examination, 54 patients showed normal and 46 abnormal ABRs. Among the latter, five showed partial wave disappearance and 21 exhibited no ABRs. Twenty-six of the 30 patients who recovered (87%) showed normal ABRs and 21 of the 57 who died (37%) also exhibited normal latency at that time. On the other hand, all the patients who showed wave disappearance (the absence of or only wave I response) died. Forty of 86 patients who underwent the CVR test showed some reaction. However, 46 patients showed no CVRs even in the first examination. Twenty-two of 26 patients who recovered exhibited some eye movements, while the remaining four showed no reaction at that time. From these results the following statements can be made. If total or partial (wave I) disappearance of the ABR in comatose patients is observed, one can predict a poor prognosis or death. If no reaction is observed in the CVR, however, one cannot always expect a poor prognosis.

Auditory Perception↗
PubMed1983

Crystallization and properties of aromatic amine dehydrogenase from Pseudomonas sp.

An amine dehydrogenase was purified to homogeneity from an extract of a bacterium of the genus Pseudomonas grown in a medium containing beta-phenylethylamine as a sole carbon source and obtained in a crystalline form with about 100-fold purification. The purified enzyme catalyzed the oxidative deamination of various aromatic amines as well as some aliphatic amines to a lesser extent. An artificial electron acceptor such as phenazine methosulfate was required for the catalysis. The molecular weight determined by sedimentation equilibrium was 103,000 and the molecule seemed to be composed of two pairs of two nonidentical subunits (Mr 46,000 and 8000). The enzyme had a dull yellow-green color with an absorption maximum at 445 nm and this chromophore appeared to be involved in the catalytic action of the enzyme.

Amino Acids↗
PubMed1983

Kinetic study on the successive four-step reduction of Cyt c3.

A detailed kinetic study on the successive four-step reduction of cyt c3, which has four heme units in a single protein, III4 leads to III3II leads to III2II2 leads to III II3 leads to II4, was carried out by stopped-flow electronic spectroscopy (SF-UV) and stopped-flow circular dichroism spectroscopy (SF-CD). Based on the absorbance change vs. time and the ellipticity change vs. time at the characteristic CD, together with the electronic absorption of the enzyme, rate constants for the successive four electron transfer steps, k1-k4, were successfully estimated by computer simulation. The rate constants of the four steps (k1 = 19.8 s-1, k2 = 11.9 s-1, k3 = 8.9 s-1, and k4 = 1.6 s-1; 8.0 10(-4) M Na2S2O4) are quite different from the statistical values (4: 3: 2: 1), thus excluding the possibility of random reduction of hemes of equal reactivities. Instead, each heme has its own reactivity, probably dependent on its local environment. The value of k3 is somewhat higher than the statistical value, indicating the existence of an autoacceleration effect, although small. This autoacceleration is most probably due to a unique heme-heme and/or heme-environment interaction since unusual CD and electronic absorptions were observed at 350-400 nm at about the time corresponding.

Animals↗
PubMed1983

Measurement of the blood flow of the nasal mucosa by the hydrogen clearance method.

The tissue blood flow of the nasal mucosa in normal subjects and patients with nasal allergy was studied by the hydrogen clearance method. The flow in the inferior turbinate in normal subjects and patients with nasal allergy did not differ. The test results were highly reproducible and were almost the same in different anterior parts of the inferior turbinate. The effects of nasal spray with vasoconstrictor and nasal provocation by an allergen-containing paper disc on the blood flow of the inferior turbinate were examined in normal subjects and patients with nasal allergy. The flow decreased remarkably after spray with vasoconstrictor. The flow also decreased remarkably in the mucosal membrane close to the area of contact of the allergen disc, whereas it increased at the area 10 mm away from the disc. The hydrogen clearance method is useful for clinical studies of nasal circulation.

Adolescent↗
PubMed1983

Characteristics of human soft tissue sarcomas in xenografts and in vitro.

Two permanent, transplantable strains of rhabdomyosarcoma (SAS) and synovial sarcoma (KUSHI) were established by transplanting them serially into nude mice. The original SAS tumor and its transplant were histologically identical and gave an appearance of so-called embryonal rhabdomyosarcoma. The KUSHI tumor changed after the second passage, showing the biphasic pattern of synovial sarcoma, while undifferentiated myoblast-like cells were observed throughout the original tumor. Three in vitro cell lines from the SAS and one from the KUSHI tumor were successfully established. The human origin of the SAS and KUSHI transplanted tumors could be verified by the presence of human chromosomes. The cells cultured from the SAS tumor were more sensitive to anticancer drugs than those of the KUSHI tumor. However, as the number of serial passages on nude mice increased, the sensitivities of the SAS cells decreased, while those of the KUSHI cells increased. The modal chromosome number of the SAS tumor changed from 51 to 49 to 46 during serial passages on nude mice. These observations suggest that the sensitivities to anticancer drugs not only differ among soft tissue sarcomas of different histologic types, but also change continuously during the growth of the tumor itself.

Animals↗
PubMed1982

Kinetics of cytochrome b oxidation in antimycin-treated submitochondrial particles.

It has been shown that in bovine heart submitochondrial particles, antimycin and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) inhibit the oxidation of NADH, succinate, and reduced ubiquinone incompletely, the uninhibited rate being about 20-40 nmol of substrate oxidized min-1 (mg of protein)-1. By contrast, rotenone, cyanide, BAL (2,3-dimercaptopropanol), and 5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole [Trumpower, B. L., & Haggerty, J. G. (1980) J. Bioenerg. Biomembr. 12, 151-164] caused essentially complete inhibition when added alone or after maximal inhibition by antimycin or HQNO. Having thus ascertained that the electron leak through the antimycin block appeared to follow the normal path through complex III (ubiquinol: cytochrome c oxidoreductase) and cytochrome oxidase, the reduction of the b cytochromes by substrates and their oxidation through the leak in the antimycin block by molecular oxygen were studied. It was shown that at normal electron flux from NADH and succinate, both cytochromes b562 and b566 were reduced in antimycin-treated submitochondrial particles. Their oxidation after substrate exhaustion was biphasic, however. At 565 minus 575 nm, 56% of the total reduced cytochrome b was oxidized through the leak in the antimycin block at a more rapid rate, while the remaining 44% was oxidized about 10 times slower. When electron flux from substrates to complex III was slowed down by the use of inhibitors or substrates at less than or equal to 0.1 Km concentration, then only reduced b562 accumulated in antimycin-treated particles. The oxidation of b562 after substrate exhaustion or inhibition of substrate oxidation by an appropriate inhibitor occurred at a rate comparable to that of the slower reoxidation phase described above. These results indicated, therefore, that cytochromes b566 and b562 are oxidized through the leak in the antimycin block at two different rates, the reoxidation rate of b566 being about 10 times faster than that of b562. The implications of these findings on the kinetic relationship of these two cytochromes in the respiratory chain have been discussed.

Animals↗
PubMed1982

Reversible inhibition of the mitochondrial ubiquinol-cytochrome c oxidoreductase complex (complex III) by ethoxyformic anhydride.

The mitochondrial ubiquinol-cytochrome c oxidoreductase (complex III) is inhibited by ethoxyformic anhydride (EFA). The inhibition is readily reversed by hydroxylamine, suggesting the involvement of essential histidyl or possibly tyrosyl residues. The spectrum of ethoxyformylated complex III in the UV region showed a peak at 238 nm, indicative of N-(ethoxyformyl)histidine. Addition of hydroxylamine caused a large decrease of the 238-nm peak, which amounted to 16 mol of (ethoxyformyl)histidine/mol of cytochrome c1. Hydroxylamine addition to ethoxyformylated complex III also caused a small change at about 280 nm, which could be due to reversal of 1.6 O-ethoxyformylated tyrosyl residues/mol of cytochrome c1. Among many inhibitors of the cytochrome bc1 region of the respiratory chain, EFA is the only reagent known to cause reversible inhibition by covalent modification of amino acid residues. The inhibition site of EFA was determined to be between cytochromes b-562 and c1. However, unlike antimycin, which also inhibits in the same region, EFA did not promote the reduction of cytochrome b-566 in particles treated with substrates. In addition, it was found that EFA inhibits proton translocation in the cytochrome bc1 region and is a more effective electron transport inhibitor when added to reduced particles as compared to oxidized particles. These results together with the strong possibility that the EFA target is a histidyl or possibly a tyrosyl residue have been discussed in relation to the mechanism of proton translocation by complex III.

Anaerobiosis↗