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Biomedical subjects

R Nakajima

Publications and source records attributed to R Nakajima.

At least 73 records · Page 4Linked to original sources
PubMed1990

Chromosome engineering in Saccharomyces cerevisiae by using a site-specific recombination system of a yeast plasmid.

We have developed an effective method to delete or invert a chromosomal segment and to create reciprocal recombination between two nonhomologous chromosomes in Saccharomyces cerevisiae, using the site-specific recombination system of pSR1, a circular cryptic DNA plasmid resembling 2 microns DNA of S. cerevisiae but originating from another yeast, Zygosaccharomyces rouxii. A 2.1-kilobase-pair DNA fragment bearing the specific recombination site on the inverted repeats of pSR1 was inserted at target sites on a single or two different chromosomes of S. cerevisiae by using integrative vectors. The cells were then transformed with a plasmid bearing the R gene of pSR1, which encodes the site-specific recombination enzyme and is placed downstream of the GAL1 promoter. When the transformants were cultivated in galactose medium, the recombination enzyme produced by expression of the R gene created the modified chromosome(s) by recombination between two specific recombination sites inserted on the chromosome(s).

Base Sequence↗
PubMed1990

Protective role of complement in the development of experimental pneumococcal pneumonia in mice.

To evaluate the role of complement in the lung defense against Streptococcus pneumoniae, mice decomplemented with multiple injections of cobra venom factor were challenged with type 3 pneumococci by inhalation. Without injection of cobra venom factor, the organisms were eliminated rapidly from the lungs in the majority of mice, accompanied by a significant but transient decrease in the serum C3 level. Focal pneumonia developed occasionally in some mice retaining the organisms in the lungs. By decomplementation with cobra venom factor, on the other hand, pneumococci were not eliminated completely from the lungs during the early stage of infection and afterward proliferated extensively. Consequently, the mice developed typical pneumococcal pneumonia with attendant bacteremia, while the serum C3 level has recovered compensatory during the course of infection. Thus, the complement was indicated to play an important role in the lung defense against pneumococci in mice, especially during the early stage of infection.

Animals↗
PubMed1989

Resonance Raman characterization of hog thyroid peroxidase. An SERRS study.

Resonance Raman (RR) spectra of hog thyroid peroxidase (TPO) were observed for the first time and compared with those of lactoperoxidase (LPO) and horseradish peroxidase (HRP). Since TPO purified by monoclonal antibody-assisted immunoaffinity chromatography was strongly fluorescent, the surface enhancement technique using Ag colloid adsorption was used for the oxidized form, but ordinary RR spectra could be obtained for the reduced form. The RR spectra of TPO were distinct from those of HRP in both the oxidized and reduced states and indicated the presence of six-coordinated iron-protoporphyrin.

Animals↗
PubMed1989

Pharmacologic characterization of a novel non-benzodiazepine selective anxiolytic, DN-2327.

DN-2327, 2-(7-chloro-1,8-naphthyridin-2-yl)-3-[(1,4-dioxa-8- azaspiro[4.5]dec-8-yl)carbonylmethyl]isoindolin-1-one, produced anxiolytic, taming and anti-convulsive effects when administered orally to several species of animals. DN-2327 produced few of the sedative-hypnotic and muscle-relaxant effects observed with diazepam. The durations of the anxiolytic and anti-convulsive activities of DN-2327 were much longer than those of diazepam. Tolerance to DN-2327 did not develop when it was administered daily for 14 days in an anti-conflict test (Vogel conflict test). DN-2327 showed potent displacement activity against [3H]diazepam binding. The binding affinity of DN-2327 for benzodiazepine receptors was about twenty times that of diazepam. Furthermore, the affinity of DN-2327 for benzodiazepine receptors was not enhanced by the presence of GABA. There is a wide margin between the doses of DN-2327 that cause the anxiolytic effects and its sedative-hypnotic/muscle-relaxant effects. These results suggest that DN-2327 has more marked anxioselective properties compared with the benzodiazepines.

Aggression↗
PubMed1989

Chemotherapeutic efficacy of ofloxacin against experimental pneumonia with Pseudomonas aeruginosa in guinea pigs.

The chemotherapeutic efficacy of ofloxacin against experimental pneumonia was investigated with special reference to its treatment regimen. A pneumonia model was successfully produced by inhalation of a virulent strain of Pseudomonas aeruginosa in guinea pigs immunosuppressed with cortisone acetate. One or 4 days after infection, the animals were treated orally with the fixed daily doses of ofloxacin either once a day or thrice a day for 3 consecutive days. Ofloxacin given thrice a day eliminated the organisms from the lung more efficiently than the equivalent total doses injected once a day in both series of treatment, starting 1 or 4 days after infection. The superiority of the triple dosing in chemotherapeutic efficacy of ofloxacin was found to be attributable at least to the longer retention of its pulmonary levels exceeding the antibiotic concentrations.

Animals↗
PubMed1988

Beneficial effect of muroctasin on experimental leukopenia induced by cyclophosphamide or irradiation in mice.

Subcutaneous injection of N2-[N-acetylmuramoyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine (MDP-Lys(L18), muroctasin), a synthetic muramyl dipeptide derivative, favoured recovery of mice from experimental leukopenia induced by cyclophosphamide or by irradiation with X-rays. These effects were observed only when MDP-Lys(L18) treatment occurred after cyclophosphamide injection or X-ray irradiation. Prophylactic treatment resulted in neither preventive nor restorative efficacy on leukopenia. In contrast, glutathione was hardly effective on leukopenia in both models, irrespective of treatment timing. The restorative efficacy of muroctasin was found to be dose-dependent and to be attributable at least to its augmenting effect on colony-stimulating factor production, followed by the marked proliferation and differentiation of myeloblasts towards mature granulocytes in the bone marrow. These beneficial effects of MDP-Lys(L18) warrant further evaluation of its clinical usefulness.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1987

The mechanism of oxyperoxidase formation from ferryl peroxidase and hydrogen peroxide.

Formation of oxyperoxidase from the reaction of ferryl horseradish peroxidase with H2O2 is inhibited by a small amount of tetranitromethane (TNM), a powerful scavenger of superoxide anion radical. The inhibition by TNM, however, does not exceed 35% as the TNM concentration is increased above 5 microM. The stoichiometry of the reaction in the presence of TNM suggests the following equation for TNM-sensitive formation of oxyperoxidase. Ferryl peroxidase + H2O2----(ferric peroxidase + O2- + H+)----oxyperoxidase The kinetic study on the TNM-resistant formation of oxyperoxidase suggests that the displacement of the oxygen with H2O2 takes place at the sixth coordination position at maximal rates of 0.048 and 0.054 s-1 for peroxidases A and C, respectively, at 5 degrees C. The TNM-sensitive and -resistant reactions are concluded to occur in parallel, and both yield oxyperoxidase. In either mechanism, the protonated form of ferryl peroxidase is active and the pK alpha value is 7.1 for peroxidase A and 8.6 for peroxidase C. Oxyperoxidase decomposes spontaneously with a large activation energy (23.0 kcal/mol), and the reaction of ferryl peroxidase with H2O2 reaches a steady level of oxyperoxidase, which depends on pH and the concentration of H2O2.

Ferric Compounds↗
PubMed1987

The effect of polymerization of horseradish peroxidase on the peroxidase activity in the presence of excess H2O2: a background for a homogeneous enzyme immunoassay.

The phenol oxidation catalyzed by horseradish peroxidase (HRP) is slowed down by the presence of excess H2O2. This inhibition is due to accumulation of Compound III, which is a catalytically sluggish form of HRP. When HRP is polymerized through covalent bonds, Compound III becomes unstable and the peroxidase activity is less sensitive to excess H2O2. Under suitable experimental conditions, the phenol oxidation is increased by about 20-fold upon polymerization of the enzyme. This fact represents the principle of a homogeneous enzyme immunoassay reported by Hoshino et al. (J. Biochem. 97, 113-118 (1985)). The ratio of the peroxidase activities of monomeric and polymerized HRPs is 1 : 4 when phenol is replaced by resorcinol, and the difference is no larger when guaiacol and catechol are used as electron donors.

Horseradish Peroxidase↗
PubMed1987

Lack of effectiveness of ofloxacin against experimental syphilis in rabbits.

Ofloxacin, a new pyridone-carboxylic acid derivative, was evaluated in experimental syphilis in rabbits in comparison with penicillin G. Experimental syphilis was established by intradermal injection of Treponema pallidum subsp. pallidum Nichols. Ten days after infection, the dermal lesions were characterized by syphilitic papula accompanied with central necrosis. These animals were subsequently treated either with ofloxacin twice a day at an oral dose of 10 mg/kg or with penicillin G once a day at an intramuscular dose of 10,000 U/kg for 21 consecutive days. In penicillin G-treated animals, the dermal lesions became smaller as early as day 3 of treatment and almost disappeared during the therapy. In marked contrast to remarkable efficacy of penicillin G was further development of the lesions in ofloxacin-treated animals, showing no difference in pathological manifestations as compared to untreated animals. The results of nontreponemal serologic test correlated well with the response of animals to treatment.

Animals↗
PubMed1986

Oxygen exchange between the Fe(IV) = O heme and bulk water for the A2 isozyme of horseradish peroxidase.

Resonance Raman spectra were observed for compound II of horseradish peroxidase A2, and the Fe(IV) = O stretching Raman line was identified at 775 cm-1. This Raman line shifted to 741 cm-1 upon a change of solvent from H2(16)O to H2(18)O, indicating occurrence of the oxygen exchange between the Fe(IV) = O heme and bulk water. The oxygen exchange took place only at the acidic side of the heme-linked ionization with pKa = 6.9.

Catalysis↗
PubMed1986

In vitro activity of DQ-2556, a new cephalosporin.

The in vitro antibacterial activity of DQ-2556, a new semisynthetic cephalosporin, was compared with that of ceftazidime and cefotaxime. The activity of DQ-2556 against members of the family Enterobacteriaceae was roughly comparable to that of cefotaxime. Against Pseudomonas aeruginosa, DQ-2556 was slightly less active than ceftazidime. DQ-2556 was more active than the reference cephalosporins against staphylococci. Haemophilus influenzae and Neisseria gonorrhoeae were also highly susceptible to DQ-2556.

Bacteria↗
PubMed1985

Spectra of chloroperoxidase compounds II and III.

Chloroperoxidase was present as Compound II during the peroxidatic oxidation of ascorbic acid. Compound III (oxy-form) was formed when excess hydrogen peroxide was added to Compound II. By decreasing the temperature it was possible to measure the spectra of Compounds II and III in the Soret and visible regions. Each spectrum was found to resemble that of the corresponding form of lactoperoxidase. Under the experimental conditions, chloroperoxidase Compound III was apparently converted to Compound II in parallel with the decomposition of hydrogen peroxide and finally to the ferric enzyme.

Ascorbic Acid↗
PubMed1985

Nucleotide sequence of the Bacillus stearothermophilus alpha-amylase gene.

The nucleotide sequence of the Bacillus stearothermophilus alpha-amylase gene and its flanking regions was determined. An open reading frame was found, comprising a total of 1,647 base pairs (549 amino acids) and starting from a GUG codon as methionine. It was shown by NH2-terminal amino acid sequence analysis that the extracellular amylase consisted of 515 amino acid residues, which corresponded to a molecular weight of 58,779. Thus the NH2-terminal portion of the gene encodes 34 amino acid residues as a signal peptide. The amino acid sequence deduced from the alpha-amylase gene was fairly homologous (61%) with that of another thermostable amylase from Bacillus amyloliquefaciens.

Amino Acid Sequence↗
PubMed1985

Physiological aspects of free-radical reactions.

Enzymes which catalyze the formation of free radicals in vitro will catalyze similar reactions in vivo. We believe that the formation of some kinds of free radicals has definite physiological meanings in metabolism. In this sense, the enzymes forming such free radicals are concluded to be in evolutionally advanced states. Elaborated structure and function of enzymes such as horseradish peroxidase and microsomal flavoproteins support the idea. Deleterious and side reactions caused by free radicals are assumed to be minimized in vivo by localizing the reactions, but this assumption should be verified by future studies.

Animals↗
PubMed1981

Horseradish peroxidase C.

Horseradish peroxidase C (HRP; ferric) reacts with H2O2 to form Compound I, with an equilibrium constant of about 10(14) M-1. Two-step reduction of Compound I to Compound II and further to the ferric enzyme occurs reversibly at Eo' values of 0.90 and 0.93 V (pH 7.0), respectively. The pH dependence of Eo' values for each one-electron step, ferrous leads to ferric leads to Compound II leads to Compound I indicates that presence of redox-linked ionization at pKa values of 7.3 in the ferrous state, 11.0 in the ferric and 8.6 in Compound II. Zinc-substituted HRP C is oxidized to its free-radical form at an Eo' value of 0.74 (pH 6.0) Comparison of oxidized zinc HRP C with Compound I shows that Compound I contains a porphyrin pi-cation radical. The flash photolysis study on the NO-ferric HRP C complex clearly indicates that the iron is pentacoordinated in HRP C while it is hexacoordinated in metmyoglobin. From the kinetic analysis of the acid-alkaline conversion of HRP C, the second-order rate constants of the reactions with H+ and HO- are estimated to be 1.5 X 10(10) and 6.7 X 10(4) M-1s-1, respectively. The latter rate constant greatly varies with the kind of hemoproteins. In the presence of HRP C and O2, indole-3-acetate is oxidized to its hydroperoxide form, which reacts effectively with HRP C to form Compound I and further converts Compound I to a verdohemoprotein.

Electron Transport↗