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Biomedical subjects

Y Ichikawa

Publications and source records attributed to Y Ichikawa.

At least 379 records · Page 21Linked to original sources
PubMed1993

Amino acid substitutions in the floor of the putative antigen-binding site of H-2T22 affect recognition by a gamma delta T-cell receptor.

We have previously identified a self-reactive gamma delta T-cell clone (KN6) specific for the H-2T region gene product T22b. Now we have investigated by an in vitro mutagenesis analysis of the T22b gene the possibility that the interaction between the KN6 gamma delta T-cell receptor and T22b involves a peptide. The results demonstrate that mutations at the floor of the putative antigen-binding groove of T22b affect recognition by the gamma delta T-cell receptor. Furthermore, we have shown that KN6 cells react with cells that are deficient in the class I peptide transporter TAP1/TAP2. These results suggest that peptide is involved in the interaction of the KN6 T-cell receptor with T22 and that loading of T22 with the putative peptide is TAP1/TAP2-independent.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Very efficient extracellular production of cholera toxin B subunit using Bacillus brevis.

We have constructed a very efficient synthesis and secretion system for cholera toxin B subunit (CTB) of Vibrio cholerae 569B using Bacillus-brevis. The constructed expression-secretion vector has the multiple promoters and the signal peptide coding region of the mwp gene, a structural gene for one of the major cell wall proteins of B. brevis strain 47, directly followed by the gene encoding the mature CTB. A large amount of mature CTB (1.4 g per liter of culture) was secreted into the medium. It had the same amino terminal amino acid sequence as that of authentic CTB and was fully active in GM1 ganglioside binding assay.

Amino Acid Sequence↗
PubMed1993

Substrate-binding region of cytochrome P-450SCC (P-450 XIA1). Identification and primary structure of the cholesterol binding region in cytochrome P-450SCC.

Cytochrome P-450SCC (P-450 XIA1) from bovine adrenocortical mitochondria was investigated using a suicide substrate: [14C]methoxychlor. [14C]Methoxychlor irreversibly abolished the activity of the side-chain cleavage enzyme for cholesterol (P-450SCC) and the inactivation was prevented in the presence of cholesterol. The binding of [14C]methoxychlor and cytochrome P-450SCC occurred in a molar ratio of 1:1 and the cholesterol-induced difference spectrum of cytochrome P-450SCC was similar with the methoxychlor-induced difference spectrum. [14C]Methoxychlor-binding peptides were purified from tryptic-digested cytochrome P-450SCC modified with [14C]methoxychlor. Determination of the sequence of the amino-acid residues of a [14C]methoxychlor-binding peptide allowed identification of the peptide comprising the amino-terminal amino-acid residues 8 to 28.

Amino Acid Sequence↗
PubMed1993

Photoaffinity labeling of cytochrome P-45011 beta with methyltrienolone as a probe for the substrate binding region.

Methyltrienolone, a synthetic steroid, was used as a photoaffinity ligand for steroid-binding proteins. The enzymatic activity of bovine adrenocortical cytochrome P-450(11) beta was inhibited by methyltrienolone in a competitive manner without exposure to light and cytochrome P-450(11) beta was photolabeled with methyltrienolone after irradiation with UV light. The addition of 11-deoxycorticosterone during photolabeling protected cytochrome P-450(11) beta from photolabeling. Photolabeled cytochrome P-450(11) beta was digested with TPCK-treated trypsin and the peptide fragments were separated with a reverse-phase HPLC system. The labeled peptide was analyzed and its amino acid sequence was determined to be Trp428-Leu429-Asp430-Arg431. Alignment of the primary structure of cytochrome P-450(11) beta with that of cytochrome P-450cam revealed that the identified sequence corresponds to the region between the beta 3-sheet and L-helix of cytochrome P-450cam. This region of mammalian cytochromes P-450 shows poor homology with that of cytochrome P-450cam, but is well-conserved, especially at Trp-428 and preceding amino acids, as the aromatic region. The present results demonstrate that the labeled sequence contributes in part to the formation of the substrate binding pocket of cytochrome P-450(11) beta which was not expected from the results of the primary sequence alignment with cytochrome P-450cam.

Affinity Labels↗
PubMed1993

Interleukin 2 induction of cytochrome P450-linked monooxygenase systems of rat liver microsomes.

The effects of interleukin 2 (IL-2), a pivotal cytokine for generating an effective immune response, on rat liver microsomal cytochrome P450-linked monooxygenase systems were investigated by measuring the contents of cytochromes b5 and P450, and the activities of various xenobiotic-metabolizing enzymes [debrisoquine and bufuralol monooxygenases (CYP2D), 7-ethoxycoumarin O-deethylase, benzphetamine N-demethylase, aniline hydroxylase and p-nitroanisole N-demethylase]. The enzymatic activities except for p-nitroanisole N-demethylase and aniline hydroxylase were increased approximately to 1.3-fold of those of untreated liver microsomes following intraperitoneal injection of IL-2 (15 U/rat). However, the amount of immunoreactive b5 protein, and the activities of aniline hydroxylase and p-nitroanisole N-demethylase were not changed by injection of IL-2. To elucidate further the mechanism of the induction of CYP2D by IL-2, quantitative analyses of immunoreactive CYP2D protein and its mRNA were conducted by western blot and slot blot hybridization analyses. The results indicated that IL-2 induced an increase in the amounts of immunoreactive CYP2D protein and its mRNA. These enzymatic activities were thus up-regulated at the mRNA level.

Animals↗
PubMed1993

Histamine and 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline are competitive inhibitors of debrisoquine 4-monooxygenase in rat liver.

The effects of histamine and 1-methyl-6,7-dihydroxy-1,2,3,4- tetrahydroisoquinoline(salsolinol) on debrisoquine 4-monooxygenation, which is catalyzed by cytochrome P-450db 1 (CYP2D1) in rat liver microsomes, were studied. Both histamine and salsolinol competitively inhibited the activity of debrisoquine 4-monooxygenase (Ki = 0.31 and 0.43 mM, respectively). These data demonstrate that histamine and salsolinol bind to the active site of CYP2D1, i.e. histamine and salsolinol have structures (molecular shape) corresponding to the active site of CYP2D1.

Animals↗
PubMed1993

Characterization of the ferredoxin gene transcripts in bovine liver and brain.

1. To study the expression of a ferredoxin gene in extra-adrenocortical tissues, the amounts and structures of the ferredoxin gene transcripts in bovine liver and brain were studied and compared to those of that in adrenocortex. 2. The sizes and amounts of the ferredoxin mRNAs were analyzed by means of Northern blotting, RNA slot blotting and RT-PCR. 3. The nucleotide sequences were determined for 39 ferredoxin cDNA clones from bovine liver. 4. The results indicated that the sizes of the ferredoxin mRNAs in liver and brain were the same as that in adrenocortex, however, their amounts were approx 1/30th and less than the latter, respectively. 5. Although the multiple forms of ferredoxin cDNA, differing in the poly(A) addition sites, were also found in liver, a minor form of ferredoxin cDNA, produced through alternative promoter usage and splicing, could not be detected in liver. 6. The nucleotide sequences of all hepato-ferredoxin cDNA clones obtained were identical to that of a major type of adreno-ferredoxin. 7. These results showed that the expression level of the ferredoxin gene in different tissues was controlled by the amount of mRNA.

Adrenal Cortex↗
PubMed1993

Interface histology of unloaded and early loaded partially stabilized zirconia endosseous implant in initial bone healing.

Clinical and histologic evaluations of partially stabilized zirconia endosseous implants under unloaded and early loaded conditions in four beagle dogs were performed to examine the possibility of osseointegration of a newly developed one-stage zirconia implant during initial bone healing. No clear difference in clinical features was observed. Direct bone apposition to the implant was generally seen in both implants. However, loss of crestal bone height was quite evident around the loaded implants. These findings suggest that the initial unloaded condition is preferable to achieve osseointegration of one-stage zirconia implants.

Alveolar Bone Loss↗
PubMed1993

A localization study of the cytochrome P-450(21)-linked monooxygenase system in adult rat brain.

Immunohistochemical studies were performed to investigate the localization of the cytochrome P-450(21)-linked monooxygenase system in rat brain using a specific antibody against bovine adrenal cytochrome P-450(21) (P-450XXIA1), which was purified electrophoretically as a single protein band and with a heme content of 18.0 nmol/mg protein from adrenocortical microsomes. The cytochrome P-450(21) was found to be mainly localized in the tractus reticulothalamicus and other ascending fibers in adult rat brains. This finding indicated that deoxycorticosterone or its derivatives could be implicated in the regulation of consciousness and the induction of an anesthetic effect.

Animals↗
PubMed1993

Effects of ionic strength and pH on the dissociation constant between NADPH-adrenoferredoxin reductase and adrenoferredoxin.

The dissociation constant between NADPH-adrenoferredoxin reductase and adrenoferredoxin was measured at various ionic strengths (0.05-0.25) and pHs (6.6-8.2) by means of a kinetic method involving pyridoxal 5'-phosphate. For each ionic strength, the maximum dissociation constant was obtained at pH 7.4. It ranged from 8.34 (ionic strength = 0.05) to 169 nM (ionic strength = 0.25) at pH = 7.4. At each pH, the dissociation constant increased along with the increase in ionic strength.

Adrenodoxin↗
PubMed1993

A novel cytochrome P-450IID6 mutant gene associated with Parkinson's disease.

Genetic polymorphism of the CYP2D6 gene [phenotypically individuals are either poor metabolizers (PM) or extensive metabolizers (EM)] has been reported to be associated with susceptibility to Parkinson's disease. We analyzed CYP2D6 genes from Japanese patients and controls, and found that EM/PM polymorphism is not a suitable marker for populations with a low PM frequency. However, a novel mutant highly associated with Parkinson's disease was discovered. The mutation was located at the HhaI site in exon 6 and changed a conserved amino acid residue, Arg296, to Cys296. The risk factor for the mutant homozygote was 5.56 (95% CI, 1.30-23.82). These results suggest that the HhaI polymorphism in the CYP2D6 gene is a part of the molecular basis of Parkinson's disease.

Arginine↗
PubMed1993

The significant effect of HLA-DRB1 matching on long-term kidney graft outcome.

Serotyping and genotyping (polymerase chain reaction with sequence-specific oligonucleotide probes method) were conducted on 520 unrelated individuals to determine the linkage disequilibrium of HLA-B and HLA-DRB1. Analyses of 511 kidney transplants (300 related and 211 cadaver recipients) were carried out at 4 transplant centers using the linkage disequilibrium of HLA-B and HLA-DRB1 established previously. All transplant recipients received CsA immunosuppression and were transplanted from June 1983 to December 1991. There were 51 significant linkages formed between HLA-B and HLA-DRB1 alleles (P < 0.05). DRB1-compatible transplants experienced a comparable 5-year graft success rate of 94% as did the HLA-identical recipients with a 100% 5-year success rate. However DRB1-incompatible recipients displayed a significantly reduced 5-year graft survival rate of 73% (73% vs. 94% P < 0.01). The 5-year graft survival rate of HLA-DR-incompatible recipients of 71% was compatible to the 73% for HLA-DRB1-incompatible recipients. No variation of rejection rate for DRB1-compatible grafts was seen in any of the 4 transplant centers. The results also indicated that HLA-DRB1 compatibility was essential for optimal success rate, regardless of HLA class I mismatches. The overall conclusion was that matching for HLA-DR was important to achieve optimal kidney graft survival on the molecular level but not on the serotyping level.

Alleles↗
PubMed1993

Lysosome labilizers potentiate the antitumor effects of tumor necrosis factor-alpha.

Enhancement of in vitro cytotoxic activity of tumor necrosis factor-alpha (TNF-alpha) was observed in combination with lysosome labilizers, particularly with urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and lipoprotein lipase (LPL). The concentration of TNF-alpha resulting in 50% cytotoxicity to L929 cells was only 20-30% of the value for TNF-alpha alone, when used in combination with a nontoxic dose of u-PA, t-PA or LPL. Furthermore, combined intravenous (i.v.) administration of TNF-alpha (3.5 x 10(5) U/mouse) and u-PA (300 IU/mouse) markedly increased the in vivo antitumor activity of TNF-alpha to Meth A tumors transplanted into BALB/c mice; the tumor weight in co-administered mice was about 40% of that in mice given TNF-alpha alone on day 6. The combination therapy of TNF-alpha (7.0 x 10(4) U/mouse, i.v.) and u-PA (300 IU/mouse, i.v.) was also effective for L929 tumors in Crj:CD-1(1CR)-nu nude mice compared with the conventional therapy with TNF-alpha alone. These results suggest that the combination of TNF-alpha and lysosome labilizers is a promising antitumor therapeutic regimen with clinical potential.

Animals↗
PubMed1993

Progressive renal failure in patients with lupus nephritis.

OBJECTIVE: To investigate the mode of progression to renal failure in patients with lupus nephritis in relation to disease activity and responsiveness to corticosteroid therapy. DESIGN: Retrospective clinical study. SETTING: University hospital. SUBJECTS: Twenty-eight patients with progressive lupus nephritis (Cr > or = 1.4 mg dl-1). INTERVENTIONS: Rapidity of progression was defined as the slope of the reciprocal of serum creatinine values. Lupus activity was scored using the systemic lupus erythematosus disease activity index system. MAIN OUTCOME MEASURES: Improvement of serum creatinine values after 6 months of therapy. RESULTS: Rapidity of progression, which was calculated during the deterioration in kidney function, reflected systemic and serological disease activity, and moreover closely correlated with response to corticosteroid therapy.

Creatinine↗
PubMed1993

[Detection of Chlamydia pneumoniae by polymerase chain reaction].

We aimed at developing a method for early detection of Chlamydia pneumoniae (C. pneumoniae) from clinical specimens. For this purpose, we amplified C. pneumoniae-specific DNA fragments by polymerase chain reaction. A pair of 24 mer of oligonucleotides which were complementary to the sequences within the region encoding the major outer membrane were synthesized and used as primers. As the results, all three standard strains of C. pneumoniae (AR-39, TW-183 and AR-388) were identified by the detection of the amplified products of 174 base pairs, while each strain of Chlamydia trachomatis and Chlamydia psittaci and a total of 11 strains of bacteria and a strain of Mycoplasma pneumoniae were not. Thus, the present method was found to provide a very high specificity and also a high sensitivity of a detectable level of 10 x 10(-9) inclusion-forming units.

Base Sequence↗
PubMed1993

[A case of encephalopathy accompanying Mycoplasma pneumoniae pneumonia in an adult].

We experienced a 39-year-old male who developed neurological complication during a course of Mycoplasma pneumoniae pneumonia. The diagnosis of M. pneumoniae pneumonia was made on the basis of elevation of specific antibody (CF) titer in convalescent serum. Electroencephalogram showed diffuse damage in the brain, but no other abnormalities were not found on brain CT-scan and MRI. In the cerebrospinal fluid, the number of cells did not increase and the M. pneumoniae CF titer was not elevated. From these results, we concluded that encephalopathy in this patient was raised by an allergic reaction of the brain tissue to M. pneumoniae antigen. Until now, encephalitis or meningoencephalitis accompanied with M. pneumoniae infection has been reported by many investigators, but reports on encephalopathy due to M. pneumoniae are few. Therefore, we reported herein a case of encephalopathy following Mycoplasma pneumoniae pneumonia with several references.

Adult↗