Search PubMed⌕ Search

Biomedical subjects

N Kojima

Publications and source records attributed to N Kojima.

At least 73 records · Page 4Linked to original sources
PubMed1998

Molecular cloning and functional expression of a fifth-type alpha 2,3-sialyltransferase (mST3Gal V: GM3 synthase).

The cDNA encoding a new type of alpha 2,3-sialyltransferase (mST3Gal V) was cloned from mouse brain cDNA library by PCR-based cloning approach using a pair of degenerate primers deduced from the nucleotide sequence information of mouse ST3Gal III and IV. The predicted amino acid sequence of mST3Gal V showed 27.3% and 26.4% identity to mST3Gal III and IV, respectively. The recombinant soluble mST3Gal V fused with protein-A, which expressed in the culture media of COS-7 cells, showed activity toward lactosylceramide (LacCer), and synthesized GM3. The apparent Km value for LacCer was 9.3 microM. mST3Gal V did not exhibit any activity toward other substrates we tested in this study, including glycolipids, glycoproteins and disaccharides. The mST3Gal V cDNA transfected F28-7 cells, which express large amount of lactosylceramide and very small amount of GM3 at native stage, expressed a large amount of GM3. The ST3Gal V gene was strongly expressed in mouse brain and liver, which contained a large amount of ganglioside. The gene expression seemed to be coincident with ganglioside expression in mouse. Thus, we conclude that mST3Gal V is the fifth-type alpha 2,3-sialyltransferase carrying GM3 synthetic activity.

Amino Acid Sequence↗
PubMed1998

Genomic structure and promoter activity of the mouse polysialic acid synthase (mST8Sia IV/PST) gene.

The mouse gene encoding ST8Sia IV/PST, one of two polysialic acid synthases, was isolated and characterized. The mST8Sia IV/PST gene was found to comprise over 60 kilobases and to be composed of five exons. Primer extension analysis revealed that transcription started from 333 nucleotides upstream of the translational initiation site. Transfection with nested deletion mutants of the 5'-flanking region fused to the luciferase reporter gene revealed that the promoter activity of the -107/+145 region was correlated with the gene expression of mST8Sia IV/PST in embryonal carcinoma P19 and neuroblastoma F11 cells. This proximal promoter region lacks an apparent TATA box but has putative binding sites for transcription factors Sp1 and NF-Y (CCAAT binding protein) at nucleotide positions -66/-57 and -47/-37, respectively. Individual deletions and mutations of the inverted Sp1 binding site or inverted NF-Y binding site caused significant reduction of the promoter activity, indicating that each binding site was involved in essential transcription control. Mobility shift assaying also revealed that Sp1 and NF-Y in a nuclear extract of P19 cells bind to the promoter region of the mST8Sia IV/PST gene. Deletion of the region from -60 to -40, which contains parts of both the Sp1 and NF-Y binding sites, completely abolished the promoter activity, suggesting that both Sp1 and NF-Y are synergetically involved in transcription regulation of the mST8Sia IV/PST gene in P19 and F11 cells. Although the overall structures of the two polysialic acid synthase genes (ST8Sia II/STX and IV/PST) are very similar, there is no extensive sequence homology between the 5'-flanking regions of the ST8Sia II/STX and IV/PST genes, suggesting that these two genes are expressed under different regulatory systems.

Animals↗
PubMed1998

Induction of cellular processes containing collagenase and retinoid by integrin-binding to interstitial collagen in hepatic stellate cell culture.

Cultured hepatic stellate cells were induced to elongate long, multipolar cellular processes by interstitial collagen gel used as a substratum, as compared to flattened or round cell shapes on polystyrene surface or on Matrigel containing the basement membrane components, respectively. The process induction was inhibited by several reagents as follows: (1) anti-integrin alpha2 antibody; (2) an oligopeptide, DGEA, an integrin-binding sequence in type I collagen molecule; (3) wortmannin, a phosphatidylinositol 3-kinase inhibitor. Protein tyrosine phosphorylation was enhanced throughout cells including cellular processes by culturing on type I collagen gel. Dual fluorescence staining showed that the core of the processes contained microtubules, whereas the periphery of the processes comprised fibrillar actin. Thus, the process extension was found to depend on integrin-binding to type I collagen fibres, followed by signal transduction and cytoskeleton assembly. The cellular processes included interstitial collagenase and vitamin A-containing lipid droplets. The lipid droplets and vitamin A-autofluorescence were increased by retinyl acetate addition to the culture medium, suggesting an important role of processes in hepatic stellate cell function.

Androstadienes↗
PubMed1998

Phase-dependent electromyographic activity of the lower-limb muscles of a patient with clinically complete spinal cord injury during orthotic gait.

We examined the lower-limb electromyographic (EMG) activity from a patient with clinically complete spinal cord injury during orthotic gait. A newly developed gait orthosis was used to obtain bipedal locomotion. The surface EMG data during the gait together with the biomechanical variables were collected by way of a radio EMG system. A cyclic EMG activation pattern corresponding to the gait cycles were observed in each of the paralyzed lower-limb muscles during the orthotic gait. Although the EMG activation did not seem to contribute toward generating the gait, it showed some similarities to that of the infant stepping or immature gait. These results might be regarded as one of the indirect pieces of evidence that suggest the existence of a spinally originating motor mechanism underlying human locomotion.

Adult↗
PubMed1998

Hepatic stellate cells (vitamin A-storing cells) change their cytoskeleton structure by extracellular matrix components through a signal transduction system.

When cultured on a polystyrene surface or aminoalkylsilane-coated cover glasses, rat and human hepatic stellate cells exhibit a flattened, fibroblast-like shape with well-developed stress fibers. However, culturing the cells on type I collagen gel results in the elongation of long, multipolar cellular processes, whereas cells cultured on Matrigel maintain their round shapes. Dual fluorescence staining of microtubules and fibrillar actin indicated that the processes extend together with collagen fibers and contained microtubules as the core, whereas the periphery contained fibrillar actin. Immunofluorescence staining of vinculin showed that the focal adhesions were distributed mainly in lamellipodia when cultured on aminoalkylsilane-coated cover glasses, whereas in the cells cultured on type I collagen gel they were localized to the tips of the processes and along their bottom surface contacting collagen fibers. Wortmannin, as well as staurosporin and herbimycin A, inhibited the elongation process and induced the retraction of elongated processes. The wortmannin treatment also resulted in an alteration in focal adhesion distribution from the processes to cell bodies. These results indicate that the cell surface integrin binding to interstitial collagen fibers induces the elongation of processes through signaling events and the subsequent cytoskeleton assembly in hepatic stellate cells.

Androstadienes↗
PubMed1998

Alpha 1,6-linked fucose affects the expression and stability of polysialic acid-carrying glycoproteins in Chinese hamster ovary cells.

To determine the effect of alpha1,6-linked fucose modification of N-glycans on the expression of polysialic acids (PSAs), the expression of PSAs in a fucose-lacking mutant of Chinese hamster ovary (CHO) cells, Lec13, was compared with that in CHO K1 cells. PSA synthase activity in these cells and the antennary structures of N-glycans associated with the neural adhesion molecule (NCAM), which is a major PSA-carrying glycoprotein, did not differ between the two types of cells. Metabolic labeling of cells with [3H]glucosamine for 48 h followed by immunoprecipitation with anti-PSA monoclonal antibodies revealed that the amount of labeled PSA-carrying glycoproteins obtained from Lec13 cells was 10-times less than that from K1 cells, although the incorporation of [3H]glucosamine into total extracts and NCAM was almost the same. In contrast, when cells were pulse labeled with [35S]methionine followed by a 1 h chase, there was not such a great difference in PSA-carrying protein synthesis between K1 and Lec13 cells. However, during a prolonged chase period, PSA-carrying proteins rapidly decreased in Lec13 cells, whereas those in K1 cells did not change. The degradation of PSA-carrying glycoproteins in Lec13 cells was partly prevented when the cells were grown in fucose-containing medium. Therefore, fucose modification of core N-glycans may affect the efficient expression of PSAs through the intracellular stability of PSA-carrying glycoproteins.

Animals↗
PubMed1998

Portal vein anomaly associated with deviation of the ligamentum teres to the right and malposition of the gallbladder.

PURPOSE: To develop a complete clinical picture of a portal vein anomaly associated with a rightward-deviated ligamentum teres. MATERIALS AND METHODS: Three hundred twenty-seven consecutive living donor candidates for partial liver transplantation were evaluated for hepatic vascular abnormalities with computed tomography supplemented with intraoperative examinations. Special attention was given to the branching pattern of the portal system and the relative positions of the umbilical portion of the portal vein, the ligamentum teres, and the gallbladder. RESULTS: Four donor candidates (1.2%) had a portal vein anomaly associated with a rightward-deviated ligamentum teres. In all four, the umbilical portion of the portal vein (and hence the ligamentum teres) was abnormal, lying above the gallbladder bed and giving off major branches to the right anterior segment. If unrecognized, these might have been ligated, leading to major complications in the donors. CONCLUSION: A portal vein anomaly associated with a rightward-deviated ligamentum teres is an important clinical entity that is not as rare as indicated in the literature. This anomaly should be kept in mind during preoperative examination of the liver.

Adult↗
PubMed1998

Effects of oxygen and carbon dioxide on mean cell volume.

Changes in mean cell volume (MCV) following addition of CO2, O2 or both to venous blood treated with ethylenediaminetetraacetic acid were studied in an attempt to evaluate the effects of saturation with these gases. The MCV before the addition was taken to be 100%. When CO2 was mixed with each of 353 samples, the mean increase (+/- SD) was 6.10 +/- 1.72%. When O2 was added to 335 specimens, the mean decrease was 1.42 +/- 0.96%. When first CO2 and then O2 was added to 266 samples, the mean change (the sum for each sample of the absolute value of the increase plus that of the decrease) was 7.39 +/- 1.90%. Results of samples of venous and arterial blood from 15 subjects were compared to check these observations in vivo. The MCV of venous blood was always larger than that of arterial blood.

Adolescent↗
PubMed1998

Binding specificities of lectins to immobilized glycoproteins and oligosaccharides differ from those of immobilized lectins to oligosaccharides.

The carbohydrate-binding specificities of lectins in solution to glycoproteins and neoglycolipids immobilized on a solid phase were analyzed in order to establish a simple, rapid method for structural analysis of the carbohydrate moieties of small amounts of individual glycoproteins blotted on membrane. Eight glycoproteins containing typical O-linked tetrasaccharides or a series of typical N-linked oligosaccharides of the high-man-nose type, hybrid type, and complex type and 6 neoglycoproteins containing mono- or di-saccharides were dot blotted on membranes and the membranes were then reacted with 8 kinds of horseradish peroxidase-conjugated lectins before and after heat treatment. Neoglycolipids containing the glycoprotein-derived oligosaccharides immobilized on a thin layer chromatography plate were also reacted with lectins. The heat treatment of the membrane increased lectin reactivity toward the glycoproteins. The carbohydrate-binding behavior of lectins, Phaseolus vulgaris erythroagglutinin, wheat germ agglutinin, and concanavalin A in solution toward glycoproteins and neoglycolipids immobilized on a solid phase differed from that of immobilized lectins toward oligosaccharides in solution. This difference should be noted in lectin detection of specific carbohydrates of individual glycoproteins on membrane.

Glycoproteins↗
PubMed1998

CJ-12,373, a novel topoisomerase II inhibitor: fermentation, isolation, structure elucidation and biological activities.

A novel isochroman carboxylic acid CJ-12,373 was isolated from Penicillium sp. CL22557. CJ-12,373 inhibits both DNA gyrase-mediated supercoiling and relaxation without the formation of a cleavage intermediate, suggesting that CJ-12,373 inhibits DNA gyrase at a stage distinct from the religation step. CJ-12,373 is not selective for procaryotic DNA gyrase as it also inhibits relaxation mediated by eukaryotic topoisomerase II. The antimicrobial potency of CJ-12,373, however, is largely attributed to its inhibition of DNA gyrase.

Anti-Bacterial Agents↗
PubMed1998

Novel lactone compounds from Mortierella verticillata that induce the human low density lipoprotein receptor gene: fermentation, isolation, structural elucidation and biological activities.

Among methods of controlling hypercholesterolemia and hyperlipidemia is the direct stimulation of hepatic low density lipoprotein (LDL) receptors. Two novel lactone compounds, CJ-12,950 and CJ-13,357, containing and unusual oxime moiety, were isolated from a zygomycete Mortierella verticillata. These lactones are potent inducers of the LDL receptor gene in vitro, that enhanced LDL receptor expression in human hepatocytes 2-fold at 100 nM.

Cell Culture Techniques↗
PubMed1998

New quinolone compounds from Pseudonocardia sp. with selective and potent anti-Helicobacter pylori activity: taxonomy of producing strain, fermentation, isolation, structural elucidation and biological activities.

Eight novel quinolones with anti-Helicobacter pylori activity were isolated from the actinomycete Pseudonocardia sp. CL38489. The quinolones were very potent against H. pylori with MICs up to 0.1 ng/ml. The quinolones appear to be specific for H. pylori, since they did not show antimicrobial activity when tested against a panel of other microorganisms.

4-Quinolones↗
PubMed1998

Erinacine E as a kappa opioid receptor agonist and its new analogs from a basidiomycete, Hericium ramosum.

A kappa opioid receptor binding inhibitor was isolated from the fermentation broth of a basidiomycete, Hericium ramosum CL24240 and identified as erinacine E (1). Three analogs of 1 were produced by fermentation in other media and by microbial biotransformation. Of these compounds, 1 was shown to be the most potent binding inhibitor. Preliminary SAR studies of these compounds indicated that all functional groups and side chains were required for the activity. Compound 1 was a highly-selective binding inhibitor for the kappa opioid receptor: 0.8 microM (IC50) for kappa, >200 microM for mu, and >200 microM for delta opioid receptor. Compound 1 suppressed electrically-stimulated twitch responses of rabbit vas deferens with an ED50 of 14 microM. The suppression was recovered by adding a selective kappa opioid receptor antagonist nor-binaltorphimine, indicating that 1 is a kappa opioid receptor agonist.

Animals↗
PubMed1998

[Functional difference between the left supplementary motor area and the left premotor area in a task of confrontation naming and word fluency].

We assessed the faculty of confrontation naming and word fluency of the 11 patients afflicted with frontal lobe infarction or hemorrhage. All the patients were right-handed and manifested transcortical motor aphasia due to cerebrovascular diseases. We carried out the Western Aphasia Battery, and we adopted V-A; the naming task involved confrontation naming of 20 objects, and V-B; the word fluency task involved the naming as many animals as possible in a one minute period. Six patients who have lesions in the left medial frontal lobe performed excellency in the confrontation naming task but exhibited poor word fluency, and 5 patients who have lesions in the left dorso-lateral frontal lobe performed poorly in both tasks. This results suggests that the left dorso-lateral frontal lobe is important in confrontation naming, while the left medial frontal lobe is important in word fluency. Mushiake et al. (1991) showed that the premotor area was involved in visually guided sequential movements, and the supplementary motor area was involved internally determined sequential movements in primates. Regarding language function as analogous to movement, confrontation naming is analogous to visually guided movements and word fluency is analogous to internally determined movements. Thus, our results suggest that the functional difference between the left medial frontal lobe, which includes the supplementary motor area, and the left dorso-lateral frontal lobe, which includes the premotor area, which was demonstrated in primates for movement is also true of language function in humans.

Aphasia, Broca↗
PubMed1997

Rescuing impairment of long-term potentiation in fyn-deficient mice by introducing Fyn transgene.

To examine the physiological role of the Fyn tyrosine kinase in neurons, we generated transgenic mice that expressed a fyn cDNA under the control of the calcium/calmodulin-dependent protein kinase IIalpha promoter. With this promoter, we detected only low expression of Fyn in the neonatal brain. In contrast, there was strong expression of the fyn-transgene in neurons of the adult forebrain. To determine whether the impairment of long-term potentiation (LTP) observed in adult fyn-deficient mice was caused directly by the lack of Fyn in adult hippocampal neurons or indirectly by an impairment in neuronal development, we generated fyn-rescue mice by introducing the wild-type fyn-transgene into mice carrying a targeted deletion in the endogenous fyn gene. In fyn-rescue mice, Schaffer collateral LTP was restored, even though the morphological abnormalities characteristic of fyn-deficient mice were still present. These results suggest that Fyn contributes, at least in part, to the molecular mechanisms of LTP induction.

Age Factors↗
PubMed1997

The Aspergillus nidulans genes chsA and chsD encode chitin synthases which have redundant functions in conidia formation [corrected and republished article originally appeared in Mol Gen Genet 1996 Jun; 251(4):442-50].

We previously isolated three chitin synthase genes (chsA, chsB, and chsC) from Aspergillus nidulans. In the present work, we describe the isolation and characterization of another chitin synthase gene, named chsD, from A. nidulans. Its deduced amino acid sequence shows 56.7% and 55.9% amino acid identity, respectively, with Cal1 of Saccharomyces cerevisiae and Chs3 of Candida albicans. Disruption of chsD caused no defect in cell growth or morphology during the asexual cycle and caused no decrease in chitin content in hyphae. However, double disruption of chsA and chsD caused a remarkable decrease in the efficiency of conidia formation, while double disruption of chsC and chsD caused no defect. Thus it appears that chsA and chsD serve redundant functions in conidia formation.

Amino Acid Sequence↗
PubMed1997

Differential expression of S-adenosylmethionine synthetase isozymes in different cell types of rat liver.

Mammalian S-adenosylmethionine (AdoMet) synthetase exists as two isozymes, liver-type and nonhepatic-type enzymes, which are the products of two different genes. It is known that the liver-type isozyme is only expressed in adult liver. Whereas, the nonhepatic-type isozyme is widely distributed in various tissues. In addition to the liver-type isozyme, a minor amount of the nonhepatic-type isozyme is also detected in adult liver. To investigate the distribution of these two isozymes in the liver in detail, the localization of these two isozymes was examined in each cell type of liver using a combination of cell fractionation technique and Western blot analysis. In the parenchymal cells, the liver-type isozyme protein was predominantly expressed, and a small amount of the nonhepatic-type isozyme protein was also detected. On the other hand, in the stellate cells the nonhepatic-type isozyme protein was exclusively or only expressed. Interestingly, a large amount of both isozymes were present in endothelial and Kupffer cell fraction. Using both antibodies to anti-rat nonhepatic-type and liver-type isozymes, respectively, immunohistochemical analysis clearly confirmed these results. In addition, in cultured hepatocellular carcinoma cells (FAA-HTC1), the nonhepatic-type isozyme protein only was detected, and the liver-type isozyme protein completely disappeared. This result indicates that the changes in the isozyme expression is regulated within the parenchymal cells. Administration of hepatotoxic drug carbon tetrachloride (CCl4) to rats resulted in about 40% to 50% reduction of enzyme activity in parenchymal cells and stellate cells compared with those of control rats. However, enzyme activity in endothelial and Kupffer cell fraction was not changed.

Animals↗