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Biomedical subjects

K Imai

Publications and source records attributed to K Imai.

At least 379 records · Page 21Linked to original sources
PubMed1999

[Therapeutic strategy for severe and fulminating ulcerative colitis].

Recent advantages of medical treatment for severe and fulminating ulcerative colitis are described. When considering therapeutic alternative for patients with severe and fulminating UC, it is the most paramount importance to assess accurately severity of disease. Next, the following is helpful guides to treat, (1)general management of patients illness, including correction of electrolytes imbalance, and sufficient fluid and alimentation therapy to avoid life-threatening complications, (2)timely surgical intervention, if disease is intractable. Two new promising approaches to severe and fulminating UC are introduced herein. One is fast-acting cyclosporine continuous intravenous administration, the other is leucocytapheresis employing new membrane filter, Cellsoba, manufactured by Asahi Medical Co. However, it remains controversial when and how physicians should abandon to surgical intervention.

Adrenocorticotropic Hormone↗
PubMed1999

[Coagulation and fibrinolytic activation in lacunar infarct patients].

Lacunar infarcts are related to occlusion of penetrating arteries. Lipohyalinosis affects the smaller arteries 40-200 microns in diameter, and atherosclerosis involves larger arteries 200-850 microns in diameter. We hypothesized that the processes of thrombus formation might be different among these two kinds of lacuner infarcts, including those caused by lipohyalinosis and atherosclerosis. We studied acute coagulation and fibrinolytic activation in lacunar infarct patients which were divided into two groups according to their size: smaller lacunar group and larger lacunar group. Then we divided lacunar infarct patients into two groups in terms of the progression of motor deficits: those who showed the progression and those did not. And coagulation and fibrinolytic activation were compared each other. One hundred and twenty four patients were enrolled in this study, including 34 control subjects, 39 patients with smaller lacune (3 mm-10 mm in diameter), 28 patients with large lacune (10 mm-20 mm), and 23 patients with atherothrombotic infarcts confirmed by angiography. The levels of TAT activity in large lacune and atherothrombotic infarcts were significantly higher than those in control subjects (p = 0.009, p < 0.0001, respectively), whereas those in small lacune were not. Also, the levels of D-dimer activity in large lacune and atherothrombotic infarcts were significantly higher than those in control subjects (p = 0.0003, p < 0.0001, respectively), whereas those in small lacune were not. The progression of motor deficits were more frequently recognized in large lacune than in small lacune: three patients out of 39 small lacune patients and 22 patients out of 28 large lacune patients (difference was significant, p = 0.001). The level of TAT activity in patients who showed progression of motor deficits was significantly higher than that in those who did not (p = 0.0002), whereas the difference of the levels of D-dimer activity in two groups did not reach significant differencial levels. The process of thrombin and fibrin formation in large lacunar infarcts which are related to microatheroma and atheroscrelosis appears to be different from that in small lacunar infarcts. Antiplatelet and anticoagulation therapy should be tailored to large lacunar infarct patients.

Aged↗
PubMed1998

Decreased DCC mRNA expression in human gastric cancers is clinicopathologically significant.

Loss of heterozygosity (LOH) or decreased expression of the deleted in colorectal cancer (DCC) gene, a candidate tumor suppressor gene, has been suggested to correlate with progression in several types of tumors. In human gastric cancers, although DCC LOH has been reported to be frequent in expanding-type tumors, the relation of decreased DCC mRNA expression with clinicopathological features, including metastatic events, remains to be investigated in detail. Therefore, expression levels of DCC mRNA were examined in 52 advanced gastric cancers by the reverse transcription-polymerase chain reaction method combined with Southern blot analysis. Overall, decreased DCC mRNA expression was observed in 27 of the tumors (52%). According to Ming's [Cancer 39, 2475-2485 (1977)] classification, the expanding type showed a significantly higher incidence (71%) than the infiltrative type (17%) (p = 0.0002). Immunohistochemical analysis demonstrated the presence of DCC expression in cancer but not non-cancerous cells in infiltrative-type lesions. An additional follow-up study of tumor recurrence in 42 patients undergoing curative resection implicated decreased DCC expression in metachronous liver metastasis. The results indicate that decreased DCC mRNA expression is closely associated not only with the expanding-type phenotype but also with liver metastasis of gastric cancers. Assessment of this parameter in primary lesions may thus find predictive application.

Adult↗
PubMed1998

The artificial alpha1beta1-contact mutant hemoglobin, Hb Phe-35beta, shows only small functional abnormalities.

It was previously reported that Hb Philly with a mutation of Phe for Tyr at 35(C1)beta showed non-cooperative oxygen binding with a very high affinity and instability leading to hemolysis. Further, it lacked the 1H-NMR signal at 13.1 ppm from 2,2-dimethyl-2-silapentane-5-sulfonate in normal hemoglobin (Hb A), so that this signal was assigned to a hydrogen bond formed by Tyr-35(C1)beta. Surprisingly, our artificial mutant hemoglobin with the same mutation as Hb Philly showed slightly lowered oxygen affinity, almost normal cooperativity, the 1H-NMR signal at 13.1 ppm and no sign of instability. Our results indicate that the mutation reported for Hb Philly and the assignment of the 13.1 ppm signal need reexamination.

Amino Acid Substitution↗
PubMed1998

Cloning and characterization of the human beta4-integrin gene promoter and enhancers.

The cell-surface adhesion molecule alpha6beta4-integrin is a receptor for laminins and a component of hemidesmosomes. beta4-Integrin expression is restricted to proliferating basal keratinocytes in the epidermis and is suppressed when differentiation commences. Altered beta4-integrin expression levels correlate significantly with the aggressive behavior of cancers. In order to clarify the mechanisms that regulate transcription of the beta4-integrin gene, we cloned its 5'-flanking region. This 5'-flanking region was found to have a high G + C content and not to contain either TATA or CAAT boxes. Nested delimitation and reporter analyses mapped a basal promoter to nucleotides -106 to +105, surrounding the most proximal transcription initiation site. Gel retardation and mutational analyses revealed that cooperation between AP1 and Ets, interacting with other factors, mediated the promoter activity. In addition to the promoter element, enhancer activity was found in the first intron (+1905/+3933) and in a sequence upstream of the promoter region (-414/-107). These findings should facilitate our understanding of the regulation of beta4-integrin gene expression in processes such as cell growth and differentiation, apoptosis, and cancer development and metastasis.

Antigens, CD↗
PubMed1998

Hexagonal bilayer structuring activity of linker chains of an annelid giant hemoglobin from the polychaete Perinereis aibuhitensis.

Preferential activity of linker chains to clamp submultiples to form hexagonal bilayer (HBL) assembly of the multisubunit hemoglobin (Hb) of the polychaete Perinereis aibuhitensis (approximately 3.4 MDa) was demonstrated. To understand the HBL assembly that should rely on structuring activity of each subunit, reassociation in response to combining isolated subunits was monitored using gel filtration, SDS-PAGE, and transmission electron microscopy. The isolation of each subunit L, T, and M (L, linker chains; T, disulfide-bonded trimer A-b-B; M, monomeric chain a) of Perinereis Hb was made simply by exposing Hb to pH 10.5, where Hb was completely dissociated into its subunits L, T, and M. As a result, it was concluded that (i) subunits T and M have strong affinity to form an intermediate complex, submultiple D, which is a dodecamer of globin chains, 3[a. A-b-B], (ii) addition of subunit L to submultiple D brings about the formation of whole molecule, similarly (iii) addition of subunit M to T+L forms the whole molecule, and (iv) addition of subunit T to M+L brings about the formation of the whole molecule, too. The results obtained lead us to conclude that linkers do function to clamp 12 submultiples D up to a whole molecule at the final step of formation of Perinereis Hb. In summary, linkers appeared to have high affinity for submultiple D, a little affinity for subunit T, but no affinity for subunit M at all. Thus linker chains were demonstrated to preferentially clamp submultiples D together to form the HBL disc of the whole molecule.

Animals↗
PubMed1998

Genomic structure and sequence of a human homologue (NTHL1/NTH1) of Escherichia coli endonuclease III with those of the adjacent parts of TSC2 and SLC9A3R2 genes.

Genomic cloning and sequencing of a human homologue (the gene name, endonuclease III-like 1; gene symbol, NTHL1 or NTH1) for Escherichia coli endonuclease III, that is involved in pyrimidine base excision repair, were performed. The sequence covered the entire NTHL1 gene consisting of six exons and five introns spanning 8kb with 5' flanking (8kb) and 3' flanking (3.8kb) regions. Southern blot analysis suggested that the NTHL1 gene exists as a single copy in a haploid genome. The sequenced 5' flanking region lacks typical TATA and CAAT boxes, but contains a CpG island having putative binding sites for several transcription factors such as Ets1 and Sp1. The NTHL1 gene lies immediately adjacent to the tuberous sclerosis 2 (TSC2) gene on chromosome 16p13.3 in a 5'-to-5' orientation. Transcription initiation sites of both NTHL1 and TSC2 genes were suggested to be multiple by 5' RACE experiments. The northern hybridization experiment suggested that both genes are expressed in all tissues, but at different levels. Downstream of the NTHL1 gene, the gene for the regulatory factor 2 (SLC9A3R2/E3KARP; also called OCTS2, TKA-1 and SIP-1) of the solute carrier family 9 (sodium/hydrogen exchanger), isoform A3, lies in a 3'-to-3' orientation. This paper demonstrates for the first time the spatial relationship of these three genes (TSC2, NTHL1 and SLC9A3R2) at the nucleotide level, and the presence of multiple transcription initiation sites of the NTHL1 and TSC2 genes.

Base Sequence↗
PubMed1998

Cloning and characterization of two genes encoding dihydroxyacetone kinase from Schizosaccharomyces pombe IFO 0354.

We report the cloning and characterization of two genes encoding dihydroxyacetone kinase (EC 2.7.1.29), SpDAK1 and SpDAK2, from Schizosaccharomyces pombe IFO 0354. The open reading frames of both genes encode 591 amino acids and have Mrs of 62158 and 62170, respectively. Both predicted amino acid sequences exhibited a high identity to each other (99.8%) and relatively high identities (30% to 76%) to other putative dihydroxyacetone kinase gene products. A Western blot analysis showed that these enzymes are induced by glycerol and repressed by glucose. A genomic Southern blot analysis indicated the presence of SpDAK1 and the absence of SpDAK2 in a standard laboratory strain, S. pombe 972h-.

Amino Acid Sequence↗
PubMed1998

Emergence of D-aspartic acid in the differentiating neurons of the rat central nervous system.

The rat embryonic brain was probed with anti-d-aspartic acid (d-Asp) antiserum at different stages of development. At gestational day (E) 12, weak immunoreactivity (IR) of d-Asp was apparent at the hindbrain, midbrain and caudal forebrain, whereas it became more intense and extended over the whole brain at E20. However, IR markedly decreased after parturition. In the region of the immature forebrain at an early stage of development (E12), IR was mainly a characteristic of the cytoplasm of the neuronal cells, while in the more mature hindbrain it was localized in the axonal zone. In the more differentiated forebrain at a later stage of development (E18), the IR became restricted to zones which mainly consisted of axons and processes. Consequently, in the rat central nervous system, d-Asp first emerges during embryonic development as a feature of the cytoplasm and thereafter spreads into the axonal regions of neuronal cells, before disappearing almost completely after parturition.

Animals↗
PubMed1998

Cloning and characterization of a mouse homologue (mNthl1) of Escherichia coli endonuclease III.

Endonuclease III (endoIII; nth gene product) of Escherichia coli is known to be a DNA repair enzyme having a relatively broad specificity for damaged pyrimidine bases of DNA. Here, we describe the cloning and characterization of the cDNA and the gene for a mouse homologue (mNthl1/mNth1) of endoIII. The cDNA was cloned from a mouse T-cell cDNA library with a probe prepared by PCR using the library and specific PCR primers synthesized based on the reported information of partial amino acid sequences of bovine NTHL1/NTH1 and of EST Data Bases. The cDNA is 1025 nucleotides long and encodes a protein consisting of 300 amino acids with a predicted molecular mass of 33.6 kDa. The amino acid sequence exhibits significant homologies to those of endoIII and its prokaryotic and eukaryotic homologues. The recombinant mNthl1 with a hexahistidine tag was overexpressed in a nth::cmr nei::Kmr double mutant of E. coli, and purified to apparent homogeneity. The enzyme showed thymine glycol DNA glycosylase, urea DNA glycosylase and AP lyase activities. Northern blot analysis indicated that mNthl1 mRNA is about 1 kb and is expressed ubiquitously. A 15 kb DNA fragment containing the mNthl1 gene was cloned from a mouse genomic library and sequenced. The gene consists of six exons and five introns spanning 6.09 kb. The sequenced 5' flanking region lacks a typical TATA box, but contains a CAAT box and putative binding sites for several transcription factors such as Ets, Sp1, AP-1 and AP-2. The mNthl1 gene was shown to lie immediately adjacent to the tuberous sclerosis 2 (Tsc2) gene in a 5'-to-5' orientation by sequence analysis and was assigned to chromosome 17A3 by in situ hybridization.

Amino Acid Sequence↗
PubMed1998

African elephant myoglobin with an unusual autoxidation behavior: comparison with the H64Q mutant of sperm whale myoglobin.

Elephant myoglobins both from Asian and African species have a glutamine in place of the usual distal (E7) histidine at position 64. We have isolated native oxymyoglobin directly from the skeletal muscle of African elephant (Loxodonta africana), and examined the autoxidation rate of oxymyoglobin (MbO2) to metmyoglobin (metMb) as a function of pH in 0.1 M buffer at 25 degreesC. As a result, African elephant MbO2 was found to be equally resistant to autoxidation as sperm whale myoglobin. However, the elephant myoglobin exhibited a distinct rate saturation below pH 6. Kinetic analysis of the pH profiles for the autoxidation rate has disclosed that African elephant MbO2 does not show any proton-catalyzed process, such as the one that can play a dominant role in the autoxidation reaction of sperm whale myoglobin by involving the distal histidine as its catalytic residue. Such a greater stability of African elephant MbO2 at low pH could be explained almost completely by the single H64Q mutation of sperm whale myoglobin. In African elephant aqua-metmyoglobin the Soret band was considerably broadened so as to produce another peak in the pentacoordinate 395 nm region. This unique spectral feature was therefore analyzed to show that the myoglobin is in equilibrium between two species, depending upon the presence or absence of a water molecule at the sixth coordinate position.

Africa↗
PubMed1998

Biosynthesis of D-aspartate in mammalian cells.

In this communication, we demonstrate that D-aspartate (D-Asp) is synthesized in pheochromocytoma cells (PC12). To our knowledge this is the first report of biosynthesis of D-Asp in mammalian cells. Synthesis of D-Asp was demonstrated by its time-dependent accumulation in the cell culture, and by the fact that this accumulation was proportional to the number of inoculated cells. D-Asp in PC12 cells was identified by (i) co-elution with authentic D-Asp on two different HPLC columns, an octadesyl silica column and a Pirkle-type chiral column, (ii) reversed elution order of D-Asp and L-Asp on another Pirkle-type chiral column with an opposite configuration, and (iii) sensitivity to D-Asp oxidase. In the cells the amount of D-Asp was approx. 12-14% of total Asp and no other investigated D-amino acid was detected. The amount of D-Asp did not increase during the culture of mouse 3T3 fibroblasts and human neuroblastoma NB-1 cells. Immunocytochemical staining with anti-D-Asp antiserum demonstrated that D-Asp synthesized is present in the cytoplasm of the cells.

3T3 Cells↗
PubMed1998

N-(4-nitro-2,1,3-benzoxadiazoyl-7-yl)-N-methyl-2-aminoacetohydrazide (NBD-CO-Hz) as a precolumn fluorescent derivatization reagent for carboxylic acids in high-performance liquid chromatography.

A new fluorescent reagent for carboxylic acids, N-(4-nitro-2,1,3-benzoxadiazoyl-7-yl)-N-methyl-2-aminoacetohydr azide (NBD-CO-Hz) was synthesized and its applicability as a precolumn derivatization reagent in high-performance liquid chromatography was examined. NBD-CO-Hz reacted with 2-arylpropionic acids (2-APAs), a group of non-steroidal antiinflammatory drugs (NSAIDs) in the presence of a condensing agent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and pyridine at room temperature for 2 h to give fluorescent adducts. The reaction solution was subjected to a reversed phase or a chiral stationary phase HPLC and the derivatives were detected fluorometrically at a wavelength of 530 nm with an excitation of 475 nm. The detection limits were in the fmol range on column.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

D-aspartate uptake into cultured rat pinealocytes and the concomitant effect on L-aspartate levels and melatonin secretion.

Significant amounts of D-aspartate (Asp) are found in mammalian tissues and D-Asp is presumed to play some significant, but as yet undefined physiological role. However, it is not known whether D-Asp is synthesized in mammals. In this study, we addressed this issue in cultured rat pinealocytes, parenchymal cells of the pineal gland, which contain significant amounts of D-Asp. Biosynthesis of D-Asp was found to be minimal to non-existent in cultured rat pinealocytes. We then investigated the mechanism of uptake of D-Asp into these cells and its consequent effect on cell function. D-Asp was efficiently taken up into cells, in a time- and dose-dependent manner. Interestingly, the L-Asp levels in the cells and media decreased concomitantly with the uptake of D-Asp. This decrease was not due to D-Asp cytotoxicity, since the cellular levels of othernted. D-Serine and D-alanine were not taken up efficiently into the cells and the cellular levels of L-serine and L-alanine were unchanged. Also, immunocytochemical staining with anti-D-Asp antibody showed that D-Asp, which had been taken up into the cells, was dispersed throughout the cytoplasm. In response to norepinephrine stimulation, pinealocytes, which had been pretreated with D-Asp released D-Asp as well as L-Asp. In these cells, norepinephrine-induced secretion of melatonin, a pineal hormone, was suppressed. The mechanism of this suppression is discussed here.

Animals↗