Search PubMed⌕ Search

Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 1,027 records · Page 57Linked to original sources
PubMed1986

Phorbol ester promotes growth of synaptic plasticity.

Iontophoretic application of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) to the intact rat hippocampus enhances potentiation produced by subsequent high frequency stimulation of the perforant path. The decay of the enhanced population spike amplitude recorded in the hilar dentate gyrus was prevented in animals receiving ejections of TPA, as compared to controls which decayed to baseline values within 2 h following high frequency stimulation. In fact, growth of the potentiated response was observed beginning at 45 min. Similar results were observed with the population excitatory postsynaptic potential slope, a measure of the synaptic response. Since tumour-promoting phorbol esters are known to translocate and activate protein kinase C (PKC) and PKC is translocated to the membrane following hippocampal potentiation, a role for membrane-associated PKC in the regulation of synaptic plasticity is suggested.

Action Potentials↗
PubMed1986

Multiple forms of ubiquitin-protein ligase. Binding of activated ubiquitin to protein substrates.

Enzyme activities that catalyzed the covalent attachment of ubiquitin to protein substrates (ubiquitin-protein ligase, UbL) were purified from the extracts of human red blood cells. These activities required the presence of ubiquitin-activating enzyme and ATP for activity. Four fractions (UbL A, B1, B2, and C) were resolved and showed different specificities toward added substrates [carboxymethylated bovine serum albumin (CM-BSA), G-actin, lysozyme, and alpha-lactalbumin]. The enzyme fractions gave different products with a given substrate. UbL A and UbL B1 were exclusively active with CM-BSA and alpha-lactalbumin, respectively. UbL B2 was most active toward CM-BSA with substantial activities to G-actin and alpha-lactalbumin and with no activity to lysozyme. UbL C showed significant activities with all four substrates, having a highest activity toward CM-BSA. There were many endogenous proteins present in the erythrocyte extract which were efficient substrates for ubiquitin conjugation. In particular, a pair of substrates were identified from erythrocyte extracts which were far more efficient substrates than the denatured proteins exogenously added.

Chromatography↗
PubMed1986

Isolation and characterization of native human renin derived from Chinese hamster ovary cells.

Transfection of Chinese hamster ovary (CHO) cells with a plasmid containing the cDNA for human preprorenin has provided cell lines that secrete 15 mg of native prorenin per liter of culture medium. Tryptic activation of the prorenin occurs by selective cleavage of the Arg66-Leu67 bond (numbering as in preprorenin). The renin product, purified in a single step and in high yield by affinity chromatography, is fully stable for as long as 8 months when stored in solution at 4 degrees C and pH 6.5. Purity of the renin was judged to be greater than 95% by gel electrophoresis, compositional and N-terminal sequence analyses, and specific enzyme activity. An important aspect of the present work is the development of a direct assay for renin which permits accurate and reproducible evaluation of enzyme units and kinetic parameters. Application of methods described herein, combined with appropriate scale-up fermentation capabilities, provides the means for generating gram quantities of human renin and its zymogen.

Animals↗
PubMed1986

Renin activation in juvenile secretory granules? Immunocytochemical experiments with an antiserum directed against the prosegment of human renin.

In immunocytochemical experiments on human kidney tissue with an antiserum directed against the prosegment of renin, only juvenile granules were clearly labeled. As the concentration of renin increases from protogranules to more mature granules, while the concentration of its prosegment decreases to subthreshold levels, it is assumed that the cleavage of the prosegment, i.e. the activation of renin, takes place in juvenile granules parallel to the condensation of the enzyme.

Cytoplasmic Granules↗
PubMed1986

alpha-Dihydrodecaprenyl phosphate as a sugar carrier in the membrane of AH 70Btc hepatoma cells.

The effect of alpha-dihydrodecaprenyl phosphate, dolichyl phosphate and solanesyl phosphate on the lipid intermediate pathway for protein glycosylation was studied with crude membrane fraction prepared from AH 70Btc hepatoma cells. alpha-Dihydrodecaprenyl phosphate increased the incorporations of [14C]mannose from GDP-[14C]mannose into CHCl3-CH3OH (2:1, v/v) extract, oligosaccharide-lipid and proteins. The above and the other data showed that alpha-dihydrodecaprenyl phosphate may function as a mannose carrier in the lipid intermediate pathway.

Animals↗
PubMed1986

Changes in plasma phosphate with the stimulation of anaerobic metabolism in rats during hypoxic-anoxic states.

Exposure of rats to high altitude hypoxia causes a rapid decrease in plasma Pi: this change reached the maximum value after exposure to an altitude of 6000-7000 m. Lactate increased markedly when rats were exposed to a high altitude, above 5500-6000 m, although no increase in lactate was observed on exposure to an altitude below 5500 m. Highly anoxic conditions including cyanide and carbon monoxide poisoning cause a marked increase in inorganic phosphate (Pi) and lactate in plasma. Pi entering the intracellular spaces can be utilized as the substrate of oxidative phosphorylation during exposure to an altitude below 5500-6000 m, and for glycolytic enhancement in rats exposed to an altitude above 6000 m. The increase in plasma Pi may be explained by the inhibition of mitochondrial oxidation and the degradation of high energy phosphate compounds under highly anoxic conditions.

Altitude↗
PubMed1986

Human renin gene of renin-secreting tumor.

A large amount of renin mRNA was found to be expressed in the juxtaglomerular cell (JGC) tumor, as determined by Northern analysis. We have isolated the long 5'-flanking region of the human renin gene from the tumor, and characterized the promoter region with respect to nucleotide (nt) sequence and mRNA transcription start point. Of two sets of CAAT and TATA box at 29 bp upstream from the capping site is demonstrated to be a functional promoter by the primer extension. The 1:6-kb sequence, containing the 5'-flanking region, exon 1, and part of the first intron, obtained from the tumor was in complete agreement with that of the clone from fetal liver, which does not produce renin. This indicates that abnormal expression of the human renin gene in the JGC tumor involves no major alteration in the primary structure within 1.2 kb of the 5'-flanking region. Within 1.2 kb of the 5'-flanking region, there are several nt segments exhibiting homology with the glucocorticoid, estrogen, and progesterone receptor-binding sites and enhancers. These structures may be related to the tissue-specific expression of the renin gene.

Amino Acid Sequence↗
PubMed1986

Role of the vitreous in diabetic retinopathy. I. Vitreous changes in diabetic retinopathy and in physiologic aging.

The vitreoretinal relationships in 1021 eyes of 570 patients with diabetic retinopathy and in 857 normal eyes were studied retrospectively in an attempt to identify the vitreous changes specifically related to diabetes. Complete posterior vitreous detachment (PVD) occurred in diabetic patients largely as part of the aging process, but proliferation interfered with its development. Complete PVD with nonproliferative diabetic retinopathy in the younger age groups was more prevalent in eyes treated by panretinal photocoagulation (PRP) than in untreated eyes and thus might have an association with PRP treatment. Partial PVD, seen mainly in proliferative diabetic retinopathy, had no correlation with aging. In the eyes of patients who were younger when diabetes was diagnosed, the development of partial PVD had a close correlation with the duration of diabetes. The data suggest the need for a clinical trial of early photocoagulation, before partial PVD develops, in younger-onset diabetic patients showing early proliferative changes.

Adolescent↗
PubMed1986

Temporomandibular joint arthroscopy by inferolateral approach.

A clinically successful technique for temporomandibular joint (TMJ) arthroscopy by the inferolateral approach is reported. The outline of the superior and inferior articular cavities of the TMJ except for the lower anterior pouch could be visualised; arthroscopy could be performed on most patients under local anesthesia in the out-patient operating room. Clinical usefulness and security of the TMJ arthroscopy based upon anatomical understanding is described.

Adolescent↗
PubMed1986

Gene for lysine tRNA1 may be a progenitor of the highly repetitive and transcribable sequences present in the salmon genome.

When salmon total DNA was transcribed in a HeLa cell extract, a discrete 6S RNA was found to be synthesized by RNA polymerase III. We isolated several phage clones containing the 6S RNA gene from a salmon genomic library and determined the sequences of two representative clones. The 5' part of the gene showed remarkable sequence homology with the lysine tRNA1 molecule. This homology extended to secondary structures, and the numbers of nucleotides in the stem and loop structures in the 6S RNA were the same as those in lysine tRNA1. Further, the pseudouridylic acid residues synthesized by HeLa pseudouridylate synthase(s) were determined to be at uridine-27 and uridine-55, which are the positions of these modified nucleosides in lysine tRNA1. These results strongly suggest that the lysine tRNA1 gene is a progenitor of the highly repetitive and transcribable sequences in the salmon genome.

Animals↗
PubMed1986

Endogenous inhibitor of nonlysosomal high molecular weight protease and calcium-dependent protease.

An endogenous inhibitor of high molecular weight protease was purified from human erythrocytes and partially characterized. The inhibitor was isolated by DEAE-Sephacel ion-exchange chromatography followed by separation on a Bio-Gel A-0.5m column. The inhibitor displayed a native Mr of 240,000 and contained a single subunit of Mr 40,000 after NaDodSO4/polyacrylamide gel electrophoresis. The Mr 240,000 hexamer inhibited high molecular weight protease noncompetitively (Ki = 8.3 X 10(-8) M) and showed marked susceptibility to proteolytic digestion and heat treatment. The purified factor was also a potent inhibitor of calcium-dependent protease (Ki = 2.8 X 10(-8) M), whereas it had no effect on trypsin, chymotrypsin, or papain. Heat treatment (50-70 degrees C X 10 min) caused loss of inhibition against high molecular weight protease; however, inhibition of calcium-dependent protease was stable under the same conditions. This result is consistent with different domains on the inhibitor that interact with high molecular weight protease and calcium-dependent protease. Together with earlier studies in which repression of inhibitor by an ATP-ubiquitin-dependent process was proposed, the present results suggest a general mechanism for regulation of multiple nonlysosomal proteases that are complexed with endogenous inhibitors.

Adenosine Triphosphate↗
PubMed1986

Synthesis and characterization of human prorenin in Escherichia coli.

DNA sequences encoding Ile-Glu-Gly-Arg and human prorenin were joined and placed under the transcriptional control of the Escherichia coli trp promoter-operator in the expression vector pTR501. E. coli cells transformed with pTR501 expressed high levels (30% of total cell protein) of prorenin as part of a hybrid protein with the trp E gene product. The chimeric protein, accumulated in a sedimentable form, was dissolved in 6 M guanidine X HCl, purified to near homogeneity, and renatured by dialysis. The complete prorenin sequence was then excised from the renatured hybrid protein using blood coagulation factor Xa, a proteinase which is highly specific for the tetrapeptide insert Ile-Glu-Gly-Arg introduced between the 9 amino-terminal residues of the trp E gene product and the first amino acid (Thr 1) of prorenin. Human prorenin thus obtained was readily activatable with trypsin and showed close similarities to naturally occurring prorenin in its biochemical and immunochemical properties.

Base Sequence↗
PubMed1986

Thyrotropin releasing hormone levels in human cerebrospinal fluid in various neurologic diseases.

Thyrotropin releasing hormone (TRH) in the human cerebrospinal fluid (CSF) of 102 patients with non-neurologic and neurologic diseases was measured by a specific TRH radioimmunoassay. TRH levels in CSF were 17.6 +/- 3.4 pg/ml (mean +/- SE) in non-neurologic diseases. TRH levels in CSF were significantly elevated in cases of spinal cord tumor and multiple sclerosis (acute phase). Elevated TRH levels in CSF were decreased in these diseases by operation or prednisolone treatment, respectively. From these data, it is suggested that TRH is present in the human CSF and that measurement of TRH levels in CSF may be a useful indicator of the activity of certain neurologic diseases.

Adolescent↗
PubMed1986

Isolation of postsynaptic densities from day-old chicken brain.

Synaptic plasma membranes from chicken brain were used to isolate a postsynaptic density (PSD) fraction using an aqueous two-phase polymer system and the detergent n-octyl glucoside. The protein and glycoprotein composition and the morphology of the day-old chicken brain PSD fraction were compared with a PSD fraction isolated from 12-week-old chicken brain. The PSD fraction from day-old chicken brain contained predominantly PSDs although, like the fraction from 12-week-old chicken, there was some membrane contamination. The major polypeptides in the day-old chicken fraction resolved by polyacrylamide gel electrophoresis comigrated with alpha- and beta-tubulin (Mr 57,000 and 55,000) and actin (Mr 45,000). The major PSD polypeptide (mPSDp) of 12-week-old chicken forebrain, which has a molecular weight of 52,000 was not a major component in day-old chicken. A polypeptide of molecular weight 63,000 was also far more prominent in the 12-week-old chicken PSD fraction whereas the reverse was true for a polypeptide of 31,000. Day-old chicken brain PSDs contained at least 14 concanavalin A-binding glycoproteins of high (greater than 85,000) molecular weight, the two most prominent having molecular weights of 170,000 and 180,000. In contrast to the polypeptide composition, the glycoprotein pattern of day-old chicken PSDs was very similar to that of the 12-week-old bird. Intraperitoneally injected [3H]fucose was incorporated into the glycoproteins of synaptic plasma membranes and PSDs from day-old chickens.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1986

7 alpha-formylamino substituent confers beta-lactamase-inactivating potency on 1-oxacephalosporins.

7 alpha-Formylamino-1-oxacephalosporins 7 alpha-formylamino-7 beta-[2- (methylaminocarbonyl)amino-2-(2-thienyl)acetamido]-3-[(1-methyl-1H -tetra zol-5-yl)thiomethyl]-1-oxa-3-cephem-4-carboxylic acid (F1) and 7 alpha-formylamino-7 beta-(2-[(4-ethyl-2,3-dioxopiperazine-1- yl)carbonylamino]-2-phenylacetamido)-3-[(1-methyl-1H-tetr azol-5-yl) thiomethyl]-1-oxa-3-cephem-4-carboxylic acid (F2) were stable against penicillinases and, moreover, inactivated cephalosporinases of Pseudomonas aeruginosa, Citrobacter freundii, and Enterobacter cloacae. Extensive studies of the inactivation of cephalosporinase of P. aeruginosa showed that it resulted from the formation of a transiently stable enzyme-compound complex. The 7 alpha-formylamino substituent was involved in the enzyme inactivation, because 7 alpha-methoxy congeners did not inactivate the enzyme. The number of compound molecules required for inhibition of an enzyme molecule was found to be 36 for F1 and 5.5 for F2, which suggests that the pathway to the complex formation branched off the hydrolysis pathway. Half-lives of the complexes were 400 min for F1 and 260 min for F2. 7 alpha-Formylamino compounds F1 and F2 had antibacterial activities similar to those of 7 alpha-methoxy congeners against beta-lactamase-producing gram-negative bacteria, whereas they were less active against non-beta-lactamase-producing strains of Escherichia coli and Staphylococcus aureus. The conclusion was that the 7 alpha-formylamino substituent conferred the ability to inactivate cephalosporinase on the 1-oxacephalosporins tested, without much impairment of their antibacterial activity.

Anti-Bacterial Agents↗
PubMed1986

Aryl hydrocarbon hydroxylase activity in rat submandibular glands.

The activities of aryl hydrocarbon hydroxylase and 7-ethoxycoumarin O-de-ethylase in the rat submandibular gland, both of which are normally very low, were increased about 10- and 25-fold, respectively, by administration of 3-methylcholanthrene. The increased activity of aryl hydrocarbon hydroxylase was inhibited by 7,8-benzoflavone but little if any by metyrapone and SKF-525A. The submandibular gland aryl hydrocarbon hydroxylase was also inhibited by antibodies elicited against rat liver cytochrome P-448 and NADPH-cytochrome P-450 reductase, respectively, and slightly by anti-cytochrome b 5 antibody, suggesting that submandibular gland aryl hydrocarbon hydroxylase resembles that of the liver, not only in the immunochemical properties of cytochrome P-450 involved, but also in the entire enzyme complex, including the electron transferring system. Cofactor(s) required by aryl hydrocarbon hydroxylase in submandibular gland was NADPH, whereas NADH sustained the reaction at a much slower rate (about 20%). NADH showed some additive action when added with NADPH.

7-Alkoxycoumarin O-Dealkylase↗