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Biomedical subjects

S Nishimura

Publications and source records attributed to S Nishimura.

At least 559 records · Page 31Linked to original sources
PubMed1989

Synthesis of a gene for the protein kinase domain of the epidermal growth factor receptor and its expression in Escherichia coli.

A gene encoding the protein kinase domain of the epidermal growth factor receptor has been chemically synthesised, cloned and expressed in Escherichia coli. The 942-base-pair gene was constructed by enzymatic ligation of 56 oligonucleotides and cloned into an expression vector downstream of the E. coli trp promoter. Production of active gene product was confirmed by means of a protein kinase assay, demonstrating that the enzymatic activity of the protein kinase domain of the epidermal growth factor receptor is retained after expression in E. coli.

Amino Acid Sequence↗
PubMed1989

Conformation change of effector-region residues in antiparallel beta-sheet of human c-Ha-ras protein on GDP----GTP gamma S exchange: a two-dimensional NMR study.

The conformations of a truncated human c-Ha-ras gene product [ras(1-171) protein] in the GDP-bound form and in the GTP gamma S-bound form were compared by two-dimensional nuclear Overhauser effect spectroscopy (NOESY). As for the GDP-bound ras(1-171) protein, three NOESY cross peaks were observed in the region of 4.5-6.0 ppm, indicating a regular antiparallel beta-sheet structure. On the ligand exchange from GDP to GTP gamma S, one of the three NOESY cross peaks disappeared and the other two cross peaks were appreciably shifted. By analysis of the effects of specific deuteration of leucine residues and the homonuclear Hartmann-Hahn spectroscopy, the antiparallel beta-sheet was found to consist of residues 38-44 and residues 51-57. The conformations around Ser-39 and Leu-56 are of the regular antiparallel beta-strand type in the GDP-bound state, and largely distorted in the GTP gamma S-bound state, which is probably related to the conformational activation of the effector region of ras proteins by ligand exchange from GDP to GTP gamma S.

Amino Acid Sequence↗
PubMed1989

The effect of specific mutations at and around the gag-pol gene junction of Moloney murine leukaemia virus.

By carrying out oligonucleotide-directed mutagenesis, in vitro, on a 3.3 kb XhoI-HindIII fragment from Moloney murine leukaemia virus Mo-MuLV proviral DNA, inserted into the phagemid pTZ19R, nine separate fragments have been prepared in which mutations have been inserted at and around the gag-pol gene junction. Using these mutant fragments Mo-MuLV proviral DNA has been reassembled and cloned into pBR322. Examination of the mutant proviral DNAs in mouse culture cells indicates that a terminator codon at the gag-pol junction is essential for function, but any of the three chain terminator codons gives an active virus. Also the region of secondary structure surrounding the terminator codon must be preserved.

Amino Acid Sequence↗
PubMed1989

Primary structure and expression from complementary DNA of skeletal muscle ryanodine receptor.

The sequence of 5,037 amino acids composing the ryanodine receptor from rabbit skeletal muscle sarcoplasmic reticulum has been deduced by cloning and sequencing the complementary DNA. The predicted structure suggests that the calcium release channel activity resides in the C-terminal region of the receptor molecule, whereas the remaining portion constitutes the 'foot' structure spanning the junctional gap between the sarcoplasmic reticulum and the transverse tubule.

Amino Acid Sequence↗
PubMed1989

Homology between a region of the human retinoblastoma gene and L1 family repetitive sequences.

Five clones that hybridized weakly with the human retinoblastoma (Rb) gene were obtained by screening a human genomic library in a non-stringent condition. The DNAs of two of these clones were partially sequenced and found to contain a region with considerable homology to part of the Rb gene. These two clones were found to contain L1 family repeating sequences. This finding is discussed in relation with possible functions of the L1 family. As the L1 family is transposable, the Rb gene may be inactivated by recombination at this homologous region. Another possibility related with the DNA binding properties of Rb and L1 family proteins is also discussed.

Base Sequence↗
PubMed1989

Formation of 8-hydroxydeoxyguanosine in liver DNA of rats following long-term exposure to a peroxisome proliferator.

The mechanism by which nongenotoxic peroxisome proliferators induce hepatocellular carcinomas in rats and mice remains intriguing. The available experimental evidence suggests that the proliferation of peroxisomes and induction of peroxisome-associated enzymes results in oxidative stress which then leads to tumorigenesis. However, so far no direct evidence for oxidative DNA damage in livers of peroxisome proliferator-treated animals has been established. In the present study we have examined the DNA obtained from the livers of rats treated with ciprofibrate, a potent peroxisome proliferator, for variable periods of time for 8-hydroxydeoxyguanosine (8-OH-dG), an adduct that results from the damage of DNA caused by hydroxyl radical. Administration of ciprofibrate in diet at a concentration of 0.025% for 16, 28, 36, or 40 weeks resulted in progressive increases in the levels of 8-OH-dG. At 16, 28, and 40 weeks of ciprofibrate treatment, the 8-OH-dG in the liver DNA was significantly increased as compared to controls. This increase in 8-OH-dG levels is attributed to persistent peroxisome proliferation resulting from chronic ciprofibrate treatment as no increase in 8-OH-dG was found in liver DNA of rats that received a single large dose of ciprofibrate. The results of this study clearly demonstrate, for the first time, that persistent proliferation of peroxisomes leads to specific oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1989

15N-labeled 5S RNA. Identification of uridine base pairs in Escherichia coli 5S RNA by 1H-15N multiple quantum NMR.

Escherichia coli 5S RNA labeled with 15N at N3 of the uridines was isolated from the S phi-187 uracil auxotroph grown on a minimal medium supplemented with [3-15N]uracil. 1H-15N multiple quantum filtered and 2D chemical shift correlated spectra gave resonances for the uridine imino 1H-15N units whose protons were exchanging slowly with solvent. Peaks with 1H/15N shifts at 11.6/154.8, 11.7/155.0, 11.8/155.5, 12.1/155.0, and 12.2/155.0 ppm were assigned to GU interactions. Two labile high-field AU resonances at 12.6/156.8 and 12.8/157.3 ppm typical of AU pairs in a shielded environment at the end of a helix were seen. Intense AU signals were also found at 13.4/158.5 and 13.6/159.2 ppm where 1H-15N units in normal Watson-Crick pairs resonate. 1H resonances at 10.6 and 13.8 ppm were too weak, presumably because of exchange with water, to give peaks in chemical shift correlated spectra. 1H chemical shifts suggest that the resonance at 13.8 ppm represents a labile AU pair, while the resonance at 10.6 ppm is typical of a tertiary interaction between U and a tightly bound water or a phosphate residue. The NMR data are consistent with proposed secondary structures for 5S RNA.

Base Composition↗
PubMed1989

Structural differences between a ras oncogene protein and the normal protein.

One of the most commonly found transforming ras oncogenes in human tumours has a valine codon replacing the glycine codon at position 12 of the normal c-Ha-ras gene. To understand the structural reasons behind cell transformation arising from this single amino acid substitution, we have determined the crystal structure of the GDP-bound form of the mutant protein, p21(Val-12), encoded by this oncogene. We report here the overall structure of p21(Val-12) at 2.2 A resolution and compare it with the structure of the normal c-Ha-ras protein. One of the major differences is that the loop of the transforming ras protein that binds the beta-phosphate of the guanine nucleotide is enlarged. Such a change in the 'catalytic site' conformation could explain the reduced GTPase activity of the mutant, which keeps the protein in the GTP bound 'signal on' state for a prolonged period time, ultimately causing cell transformation.

Crystallography↗
PubMed1989

Permanent conversion of mouse and human cells transformed by activated ras or raf genes to apparently normal cells by treatment with the antibiotic azatyrosine.

Azatyrosine [L-beta-(5-hydroxy-2-pyridyl)-alanine], an antibiotic isolated from Streptomyces chibanensis, inhibited the growth of NIH 3T3 cells transformed by the activated human c-Ha-ras gene but did not significantly inhibit the growth of normal NIH 3T3 cells. Surprisingly, upon treatment with azatyrosine most of the transformed cells apparently became normal. These apparently normal cells, named revertant cells, grew in the presence of azatyrosine and stopped growing when they reached confluency, and their normal phenotype persisted during prolonged culture in the absence of azatyrosine. The revertant cells did not grow in soft agar and scarcely proliferated in nude mice. The human c-Ha-ras gene present in transformed NIH 3T3 cells was still present in the revertant cells and was expressed to the same extent as in the original transformed cells, producing the same amount of activated p21. Treatment with azatyrosine caused similar conversion of NIH 3T3 cells transformed by activated c-Ki-ras, N-ras, or c-raf to apparently normal cells, but NIH 3T3 cells transformed by hst or ret were not exclusively converted by azatyrosine. Human pancreatic adenocarcinoma cells, which are known to contain an amplified activated c-Ki-ras gene and an amplified c-myc gene, were also converted to flat and giant revertant cells by treatment with azatyrosine.

Alanine↗
PubMed1989

Organization of ribosomal RNA genes in Alternaria alternata Japanese pear pathotype, a host-selective AK-toxin-producing fungus.

DNA encoding ribosomal RNA (rRNA) of Alternaria alternata Japanese pear pathotype has been cloned in lambda replacement vector, lambda Fix. Restriction endonuclease mapping and Southern hybridization with the 18S and 28S rRNAs of Saccharomyces cerevisiae revealed the A. alternata rDNA to be tandemly repeating 8.15-kilobase pair unit. The restriction fragments of the unit were then subcloned in the plasmid vector Bluescribe M13- and partially sequenced. The determined sequences were compared with previously reported sequences of S. cerevisiae rRNAs and their genes. The locations of DNA sequences encoding the 5.8S, 18S, and 28S rRNAs were determined by homology search using reported sequences. The complete DNA sequence for 5.8S rRNA of the fungus was found to be highly conserved at more than 90% homology in the fungi analyzed. However, sequence diversities were observed in limited regions involved in a helix structure, the helix (e), found at position 116-137.

Alternaria↗
PubMed1989

A clinical analysis of 32 brainstem haemorrhages; with special reference to surviving but severely disabled cases.

Thirty-two patients with CT-documented primary brainstem haemorrhage were reviewed retrospectively to obtain a clearer overall clinical picture, especially of the severely disabled survivors. They were divided into 3 groups according to outcome: eleven cases (Group 1) died within 1 month following haemorrhage, 11 cases (Group 2) survived but became bedridden, necessitating full living support, and 10 cases (Group 3) showed minimal neurological deficits and resumed normal activities. Owing to CT and improved critical care, the survival rate was 66% for the whole series. Group 2 comprised 34% of all cases. These patients were mostly alert, quadruplegic, and communicated only with great difficulty. The most common initial symptoms and CT finding in each group were as follows; Group 1: unconsciousness, respiratory disturbance, negative light reflex, tachycardia, and haematoma greater than 3.0 cm; Group 2: disturbance of consciousness, respiratory disturbance, positive light reflex, normal heart rate, and 2.0 greater than haematoma less than 3.5 cm; and Group 3: alertness or only slight disturbance of consciousness, normal respiration, positive light reflex, normal heart rate, haematoma less than 2.5 cm. Although there is an overlap among them, these findings will be useful to distinguish the three groups from each other. Patients with disturbance of consciousness, respiratory disturbance, positive light reflex, normal heart rate, and 2.0 greater than haematoma less than 3.5 cm, have a chance to survive, but in severely disabled condition, if they were treated with vigorous intensive care in the acute stage.

Adult↗
PubMed1989

Prolonged exposure to a K-rich medium makes the rat mast cell membrane permeable to external calcium ions.

Rat mast cells, pretreated with a Ca-free, high KCl medium for more than 30 min, released histamine when subsequently exposed to a medium containing 0.1-2 mM Ca, despite the absence of voltage-dependent Ca channels. Morphological studies showed that high KCl-treated cells became swollen and that the addition of Ca caused degranulation (exocytosis). Ca-stimulated histamine release was inhibited when the high KCl treatment medium contained dinitrophenol and 2-deoxyglucose. The response to Ca was also observed when KCl in the treatment medium was replaced by RbCl, CsCl, KBr or KNO3. When the high K-treated cells were incubated with 0.5 mM 45Ca at 0-1 degree C, 45Ca uptake by these cells was much larger than that by untreated cells, suggesting that the membrane permeability to Ca of these cells is increased. Although prolonged (90 min) incubation of the cells with an isotonic KCl medium increased the rate of leakage of lactate dehydrogenase possibly reflecting extensive cell swelling, most cells recovered the ability of responding to stimulation with compound 48/80 or with simultaneous removal of Na and Ca when subsequently incubated with a Na-based medium containing Ca. Raising the KCl concentration above normal osmolarity in the treatment medium reduced the extents of cell swelling, without reducing the response to Ca addition. Under various other experimental conditions, a poor correlation was also found between the extents of swelling and the magnitude of the response to Ca. These results raised the possibility that intracellular accumulation of a particular species of anions increased membrane permeability to Ca.

Animals↗
PubMed1989

A case of aortic intimal sarcoma manifested with acutely occurring hypertension and aortic occlusion.

Primary tumor of the aorta is extremely rare. An instance of aortic intimal sarcoma, namely fibromyxosarcoma, which extended from the beginning of the descending aorta to 7 cm above the abdominal bifurcation, with clinical evidence of acutely occurring hypertension, arterial embolism of the lower extremities, renal infarction, and aortic occlusion in a 50-year-old male is reported. The tumor was limited to the intima and composed of spindle-shaped tumor cells with abundant myxoid extracellular matrices. The tumor cells were negative for Factor VIII, Desmin, or Myoglobin, but were positive for Vimentin or Factor XIIIa in immunoperoxidase studies. An electron microscopic examination revealed a large amount of rough endoplasmic reticulum in the cytoplasm. Parenchymal metastases were observed in both the lungs and thoracic vertebrae. A review of literature on the clinical and pathological aspects of the tumor was made.

Aorta, Abdominal↗
PubMed1989

Methylreductic acid and hydroxymethylreductic acid: oxygen radical-forming agents in heated starch.

Two compounds forming oxygen radicals were isolated from heated starch by monitoring the potency to form 8-hydroxydeoxyguanosine from deoxyguanosine during purification procedures. These compounds were identified as hydroxymethylreductic acid and methylreductic acid. The former compound was mutagenic to Salmonella strains TA100, TA102 and TA104 and the latter compound induced sister-chromatid exchanges in human NL3 cells. Hydroxymethylreductic acid was found to be a novel compound. Considerable amounts of these compounds were detected in various heat-processed foods.

Animals↗
PubMed1989

Mesangiolytic glomerulonephritis associated with Takatsuki's syndrome: an analysis of five renal biopsy specimens.

Renal biopsy specimens from five patients with Takatsuki's syndrome were studied. Proteinuria and hematuria were modestly positive in four cases and three cases, respectively. One case demonstrated early azotemia, while four cases revealed normal serum creatinine levels. All cases displayed glomerular enlargement and lobulation, mesangial cell proliferation, and double contour structure, simulating membranoproliferative glomerulonephritis. It is noteworthy that mesangial loosening was also detected in the renal biopsy specimens of this study. This change was present diffuse-globally in the well-developed cases and focal-globally or segmentally in the developing cases. In addition, various morphologic expressions were observed, ie, microaneurysms congested with RBCs, tentatively termed mesangial hyaline thrombi, nodule-like lesions, and tiny to small-sized mesangiolytic lesions. Since all these features could be explained by low-grade mesangiolysis, the renal alteration associated with this syndrome was termed mesangiolytic glomerulonephritis. Humoral factor(s) also toxic to the mesangium were implicated.

Adult↗
PubMed1989

Surgical treatment and radiological consideration of supergiant cerebral aneurysms.

We have collected four cases of supergiant cerebral aneurysm, each greater than 6.0 cm in diameter. Two of these cases were saccular aneurysms of the anterior communicating artery and middle cerebral artery, of which the necks were clipped with resection of the aneurysms. Another patient had a fusiform aneurysm of the middle cerebral artery, which was resected accompanied by a reconstructive procedure of cerebral blood flow. The last patient had a fusiform aneurysm of the internal carotid artery. Following internal carotid artery occlusion surgery with superficial temporal artery-middle cerebral artery anastomosis, the aneurysm completely disappeared radiologically within several months.

Adolescent↗