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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 991 records · Page 55Linked to original sources
PubMed1987

Complete nucleotide sequence of cDNA and deduced amino acid sequence of rat liver arginase.

Arginase (EC 3.5.3.1) catalyzes the last step of urea synthesis in the liver of ureotelic animals. The nucleotide sequence of rat liver arginase cDNA, which was isolated previously (Kawamoto, S., Amaya, Y., Oda, T., Kuzumi, T., Saheki, T., Kimura, S., and Mori, M. (1986) Biochem. Biophys. Res. Commun. 136, 955-961) was determined. An open reading frame was identified and was found to encode a polypeptide of 323 amino acid residues with a predicted molecular weight of 34,925. The cDNA included 26 base pairs of 5'-untranslated sequence and 403 base pairs of 3'-untranslated sequence, including 12 base pairs of poly(A) tract. The NH2-terminal amino acid sequence, and the sequences of two internal peptide fragments, determined by amino acid sequencing, were identical to the sequences predicted from the cDNA. Comparison of the deduced amino acid sequence of the rat liver arginase with that of the yeast enzyme revealed a 40% homology.

Amino Acid Sequence↗
PubMed1987

On experimental artifacts in the use of metal ion chelators for the determination of the cation binding constants of alpha-lactalbumin. A reply.

The binding constant of Ca2+ to the strong cation site of bovine alpha-lactalbumin has been measured directly by monitoring the free calcium concentration by Quin 2 fluorescence. A dissociation constant of 1-4 nM was calculated, which confirms the strong calcium binding properties of this protein. In order to examine whether the metal ion chelators EDTA or EGTA affect the cation binding equilbria by binding to bovine alpha-lactalbumin, calcium binding equilibria were carefully measured under highly stabilized pH and temperature conditions. Within the concentration ranges required for competitive binding by these ligands (EDTA or EGTA) (less than 1-3 mM) these chelators produced no artifacts, in contradiction to the data of Kronman and Bratcher (Kronman, M. J., and Bratcher, S. C. (1983) J. Biol. Chem. 258, 5707-5709).

Binding, Competitive↗
PubMed1987

Detection of oxidized lipid-modified erythrocyte membrane proteins by radiolabeling with tritiated borohydride.

Human erythrocyte ghosts treated with tert-butyl hydroperoxide or ADP-Fe3+ incorporated radioactivity on reduction with tritiated borohydride. The tritium incorporation closely correlated with membrane lipid oxidation as assessed by the formation of thiobarbituric acid-reactive substances and fluorescent substances. Treatment of ghosts with the inducers in the presence of butylated hydroxytoluene, thiourea, or desferrioxamine suppressed the tritium incorporation in the subsequent reduction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the tritiated ghost proteins showed that the label was incorporated into the intermolecularly cross-linked and the uncross-linked proteins of bands 1, 2, 3, 4.1, 4.2, 5 and 6, and into the noncross-linked glycophorin A (PAS-1). Glycophorin A was hardly cross-linkable but modified during membrane lipid oxidation. Possible candidates for producing borohydride-reducible functions in the proteins are various mono- and bifunctional aldehydes, as well as those for producing fluorescence and cross-links. A part of thiobarbituric acid-reactive or fluorescent substances may be involved in borohydride reduction and tritium labeling.

Aldehydes↗
PubMed1987

Identification of renin and renin messenger RNA sequence in rat ovary and uterus.

An increase in plasma prorenin during pregnancy suggests that prorenin might be synthesized in the ovary and the secretion of renin or prorenin may be stimulated by an ovarian steroid-mediated process. Recently, renin and angiotensinogen have been identified in human ovarian follicular fluid. However, there is considerable controversy over whether renin is synthesized in the ovary or derived from circulation. In the present study, we confirmed the presence of renin and renin mRNA in rat ovary and uterus by Northern blot analysis with rat renin cRNA as a hybridization probe. Our data show that ovarian or uterine renin is synthesized in the same cells. This suggests that the function of renin might be closely linked to the reproductive process.

Animals↗
PubMed1987

The fate of prorenin during granulopoiesis in epithelioid cells. Immunocytochemical experiments with antisera against renin and different portions of the renin prosegment.

Comparative immunocytochemical experiments with antisera directed against renin and three synthetical peptides (Pro 1, Pro 2A and Pro 3) covering almost the entire span of human renin prosegment were performed on human kidney tissue. With anti-Pro 1, i.e. the antiserum which recognizes the NH2 terminus of human prorenin, no clear immunolabeling of juxtaglomerular epithelioid cell secretory granules could be obtained. It is therefore concluded that the corresponding portion of human prorenin may be cleaved off in the Golgi complex. After application of anti-Pro 3, the antiserum which recognizes the COOH terminus of the prosegment, only the juvenile secretory granules of epithelioid cells were consistently labeled, whereas, in contrast, some of the intermediate and most of the mature secretory granules were anti-Pro 3-negative. As the immunoreactivity of mature renin increased remarkably from protogranules to mature secretory granules, it is suggested that the cleavage of the COOH terminus of the prosegment, i.e. the activation of renin, takes place in juvenile and intermediate granules during condensation of the enzyme. The immunoreactivity of Pro 2A, corresponding to the middle portion of the prosegment, disappeared in a somewhat earlier stage of granulopoiesis than that of Pro 3. It is therefore concluded that the corresponding segmental cleavage, the result of which is a truncated version of intact prorenin, occurs in the protogranules of epithelioid cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytoplasmic Granules↗
PubMed1987

Quantitative structure activity relationship studies on the activation of yeast AMP deaminase by polyamines.

Quantitative structure activity relationship studies on the activation of AMP deaminase by polyamines were carried out. Polyamine enhanced the maximal velocity of AMP deaminase without changing the affinity for the substrate AMP. Activation by polyamines of AMP deaminase can be accounted for by the simple Michaelis-Menten mechanism in the presence of ATP. A close correlation between the structure and activation constants for polyamines suggests that the binding of polyamine to AMP deaminase involves primarily polar interactions.

AMP Deaminase↗
PubMed1987

Relationship between renin mRNA and renin secretion in adrenalectomized, salt-depleted, or converting enzyme inhibitor-treated rats.

Renin secretion was stimulated in rats by adrenalectomy (ADX), by treatment with the converting enzyme inhibitor enalapril (MK 421), or by feeding a low salt diet plus furosemide treatment (FUR). Relative amounts of renin mRNA were measured by densitometric Northern blot analysis using a 32P-labeled 700 bp mouse submaxillary gland cDNA fragment as hybridization probe. Renin secretion was measured in isolated kidneys taken from pretreated rats. Treatment resulted in a 4.4-, 7- and 12.7-fold increase in total renin mRNA in kidneys of ADX, MK 421 and FUR rats, respectively. Plasma renin levels increased 5-, 9- and 12-fold in ADX, MK 421 and FUR rats, whereas ex vivo secretion rates from the isolated kidney were 4.7-, 0.5- and 4.2-fold, respectively, that of controls. Thus, a close relationship between increases in renin secretion in vivo (reflected by plasma renin concentration) and renin mRNA exists, whereas secretion rates in the isolated perfused kidney ex vivo change in a non-proportional fashion.

Adrenalectomy↗
PubMed1987

Stimulation of anaerobic metabolism in rats at high altitude hypoxia--adrenergic effects dependent on dietary states.

1. Plasma lactate and pyruvate were increased more markedly in fed rats than in fasted rats exposed to an 8000 m altitude. 2. The increase in plasma lactate and pyruvate was enhanced and inhibited by the alpha 1-adrenergic antagonist prazosin and the beta-blocker propranolol, respectively, in fasted rats exposed to an 8000 m altitude. Blood glucose was not changed by adrenergic blockades under the same conditions. 3. Prazosin and propranolol showed no effect on glycolytic metabolites in plasma in fed rats submitted to an 8000 m altitude. Blood glucose of fed rats was increased by alpha 1-blockade during severe hypoxia. 4. In fasted rats whose energy metabolism depends on oxidation mainly, alpha 1- and beta-adrenergic receptors can participate in the stimulation of respiration and the glycogen degradation, respectively, during an exposure to severe hypoxia. In fed rats energy metabolism depends on glycolysis, which utilizes blood glucose as the substrate preferentially during hypoxia.

Adrenergic alpha-Antagonists↗
PubMed1987

Osteoma in mandibular condyle.

A case of peripheral osteoma occurring in the mandibular ramus in a 26-year-old man is reported. Radiographic examination revealed a pedunculated, protruding globular, bone-like opaque mass around the notch of the right mandibular ramus. Histopathological examination showed a lamellar bone structure with irregular arrangement. Wide trabeculae, narrow interstitial areas, and many fibrovascular channels were detected by scanning electron microscopy. Thus, characteristic findings of a compact osteoma were obtained clinically and histopathologically.

Adult↗
PubMed1987

The role of angiotensin II in the regulation of ACTH secretion.

1. In rats and in at least some other species, IV and IVT AII stimulate ACTH secretion. 2. Although AII increases ACTH secretion by a direct action on pituitary cells in vitro, it appears to act instead by stimulating CRH secretion in vivo. 3. The CRH stimulating effect of circulating AII is mediated by an action of the AII on one or more of the circumventricular organs of the brain. 4. AII administered into the cerebral ventricles and, presumably, centrally generated AII, increase CRH secretion by acting on AII receptors inside the blood-brain barrier as well as in the circumventricular organs. 5. A possible role for the renin-angiotensin system in mediating the increase in ACTH secretion produced by stress has been suggested, and the degree of involvement may vary from one stress to another. However, as yet we have been unable to obtain any evidence that either circulating AII or centrally generated AII plays a role in the increase in ACTH secretion produced by ether stress in rats and surgical stress in dogs.

Adrenocorticotropic Hormone↗
PubMed1987

Production of low-affinity penicillin-binding protein by low- and high-resistance groups of methicillin-resistant Staphylococcus aureus.

Methicillin- and cephem-resistant Staphylococcus aureus (137 strains) for which the cefazolin MICs are at least 25 micrograms/ml could be classified into low-resistance (83% of strains) and high-resistance (the remaining 17%) groups by the MIC of flomoxef (6315-S), a 1-oxacephalosporin. The MICs were less than 6.3 micrograms/ml and more than 12.5 micrograms/ml in the low- and high-resistance groups, respectively. All strains produced penicillin-binding protein 2' (PBP 2'), which has been associated with methicillin resistance and which has very low affinity for beta-lactam antibiotics. Production of PBP 2' was regulated differently in low- and high-resistance strains. With penicillinase-producing strains of the low-resistance group, cefazolin, cefamandole, and cefmetazole induced PBP 2' production about 5-fold, while flomoxef induced production 2.4-fold or less. In contrast, penicillinase-negative variants of low-resistance strains produced PBP 2' constitutively in large amounts and induction did not occur. With high-resistance strains, flomoxef induced PBP 2' to an extent similar to that of cefazolin in both penicillinase-producing and -negative strains, except for one strain in which the induction did not occur. The amount of PBP 2' induced by beta-lactam antibiotics in penicillinase-producing strains of the low-resistance group correlated well with resistance to each antibiotic. Large amounts of PBP 2' in penicillinase-negative variants of the low-resistance group did not raise the MICs of beta-lactam compounds, although these strains were more resistant when challenged with flomoxef for 2 h. Different regulation of PBP 2' production was demonstrated in the high- and low-resistance groups, and factor(s) other than PBP 2' were suggested to be involved in the methicillin resistance of high-resistance strains.

Anti-Bacterial Agents↗
PubMed1987

Increased susceptibility to cephamycin-type antibiotics of methicillin-resistant Staphylococcus aureus defective in penicillin-binding protein 2.

A methicillin-resistant strain of Staphylococcus aureus which produced low-affinity penicillin-binding protein 2' (PBP 2') spontaneously lost PBP 2 when the strain was cultivated at 43 degrees C overnight. At 37 degrees C, the mutant had increased susceptibility to cephamycin-type beta-lactams, which showed high affinity for PBP 4. This result suggests that inhibition of PBP 4, in addition to that of PBP 2, is necessary to kill methicillin-resistant strains.

Anti-Bacterial Agents↗
PubMed1987

Differentiation of mechanisms for mobilization of calcium in smooth muscle.

Techniques to dissociate different sites or stores important for Ca2+ entry or release in smooth muscle include washouts of 45Ca in cold La3+ -substituted solutions. Scatchard-coordinate plots of Ca2+ uptake, substitution of Sr2+ for Ca2+, and both desaturation and rate coefficient plots. Rabbit aortic smooth muscle is particularly useful because Ca2+ mobilization components can be clearly separated. Other vascular preparations investigated (e.g., renal vessels, coronary arteries) appear to have similar components, but their relative importance varies. Respiratory smooth muscle also has similar Ca2+ mobilization components, but they are less readily dissociated by techniques employed in vascular smooth muscles. In guinea pig trachea, cold La3+ washouts do not retain cellular Ca2+ as well as in other preparations: use of other experimental approaches including the Ca2+ channel entry stimulator, CGP 28392, can demonstrate different Ca2+ uptake mechanisms for K+ -stimulated and agonist-induced Ca2+ uptake. In rabbit aorta, CGP 28392 potentiates tension increases elicited with lower concentrations of added K+ but has no effect on norepinephrine-induced contraction. A general model illustrating different Ca2+ entry mechanisms present in three types of smooth muscle provides examples drawn from a spectrum of possible variations in smooth muscle specificity for Ca2+ mobilization.

Animals↗
PubMed1987

Role of brain serotonergic pathways and hypothalamus in regulation of renin secretion.

To investigate the role of brain serotonergic neurons in the regulation of renin secretion, we measured changes in plasma renin activity (PRA), and, in some instances, plasma renin concentration (PRC), plasma angiotensinogen, and plasma adrenocorticotropic hormone (ACTH) in rats with lesions of the dorsal raphe nucleus and lesions of the paraventricular nuclei, dorsomedial nuclei, and ventromedial nuclei of the hypothalamus. We also investigated the effects of p-chloroamphetamine (PCA), immobilization, head-up tilt, and a low-sodium diet in the rats with dorsal raphe, paraventricular, and dorsomedial lesions. Lesions of the dorsal raphe nucleus abolished the increase in PRA produced by PCA but had no effect on the increase produced by immobilization, head-up tilt, and a low-sodium diet. Paraventricular lesions, which abolish the increase in plasma ACTH produced by PCA, immobilization, and head-up tilt, decreased plasma angiotensinogen. The paraventricular lesions abolished the PRA and the PRC responses to PCA and the PRA but not PRC response to immobilization, head-up tilt, and a low-sodium diet. The ventromedial lesions abolished the PRA and PRC responses to PCA and did not reduce plasma angiotensinogen. The data suggest that paraventricular lesions depress angiotensinogen production by the liver and that the paraventricular and ventromedial nuclei are part of the pathway by which serotonergic discharges increase renin secretion. They also suggest that the serotonergic pathway does mediate the increases in renin secretion produced by immobilization, head-up tilt, and a low-sodium diet.

Animals↗
PubMed1987

Site at which angiotensin II acts to stimulate ACTH secretion in vivo.

To investigate the site at which angiotensin II (AII) acts to increase adrenocorticotrophic hormone (ACTH) secretion, the effects of intraventricular (IVT) or intravenous (IV) injection of the AII antagonist saralasin on the ACTH responses to IVT or IV injection of AII were examined in conscious male rats. AII does not cross the blood-brain barrier, but IVT as well as IV saralasin are known to prevent the binding of circulating AII to circumventricular organs. IV AII (0.2-200 ng) induced dose-related increases in ACTH secretion and a transient increase in the corticotrophin-releasing hormone (CRH) content of the median eminence. IVT injection of saralasin (10 micrograms) blocked the ACTH responses to IV AII. The same dose of saralasin given intravenously did not produce a comparable decrease in the ACTH response to IV AII. IVT injection of 1 and 10 ng AII increased plasma ACTH in a dose-related manner. The increase in plasma ACTH induced by IVT administration of angiotensin was not inhibited by IV infusion of saralasin (12 micrograms/kg/min). On the other hand IV infusion of this dose of saralasin abolished or reduced the ACTH response to IV injection of larger doses of AII. These data support the conclusion that circulating AII stimulates ACTH secretion by acting on the circumventricular organs to increase CRH secretion. They also suggest that AII receptors inside the blood-brain barrier as well as AII receptors in the circumventricular organs trigger increases in ACTH secretion.

Adrenocorticotropic Hormone↗
PubMed1987

Role of hydroxyl radicals derived from granulocytes in lung injury induced by phorbol myristate acetate.

Lung injury induced by phorbol myristate acetate (PMA) is closely associated with toxic oxidants released from activated granulocytes. But the major toxic oxidant causing lung damage is not really known. We have, therefore, conducted investigations using various oxygen radical scavengers. The intravenous administration of dimethylthiourea (DMTU), a potent hydroxyl radical scavenger, or of superoxide dismutase (SOD), a superoxide anion scavenger, plus catalase, a hydrogen peroxide scavenger, to rabbits intravenously injected with PMA prevented biochemical data and cellularity indicative of lung damage in lung lavages. Morphologically, the lungs of PMA-injected rabbits revealed mild interstitial edema, aggregates of granulocytes within the interstitial capillaries, and the increase of granulocytes in alveolar spaces. Furthermore, there was direct morphologic evidence of pulmonary endothelial cell disruption. In rabbits treated with DMTU or SOD plus catalase, there was no evidence of destructive changes in the lungs. SOD-treated rabbits did not show evidence of protection from PMA-induced lung injury. Only a little protection was provided by catalase treatment. Moreover, in the ultracytochemical study for examination of hydrogen peroxide (H2O2) generation, the number of H2O2-generated granulocytes remarkably decreased in lung lavages of catalase-treated rabbits, but destructive changes were observed in the lungs. In contrast, though the number of H2O2-generated granulocyte was not decreased in lung lavages of DMTU-treated rabbits, treatment with DMTU could afford protection from lung injury. These data indicate that the hydroxyl radical, a toxic oxidant derived from stimulated granulocytes, is deeply involved in the pathogenesis of PMA-induced lung injury.

Animals↗
PubMed1987

Effects of adrenergic drugs on isolated and perfused hearts of streptozotocin-induced diabetic rats.

To examine the myocardial contractile response of the diabetic heart, effects of isoproterenol (ISO) and norepinephrine (NE) on perfused hearts isolated from streptozotocin (STZ)-induced diabetic rats and insulin-treated diabetic rats were evaluated. Male Sprague-Dawley rats, weighing 200-260 g, were divided into the control (C)-group, diabetes mellitus (DM)-group and diabetes mellitus treated with insulin (DMI)-group. The C group was injected with buffered vehicle. DM and DMI groups were injected intravenously with 60 mg/kg STZ on the first day. Three days after STZ injection, the DMI group was subsequently treated with 4 U of Lente insulin subcutaneously every day. At 45 days after injection of STZ, experiments were performed using a Langendorff perfused heart preparation. The heart was paced at 300 beats/min, and myocardial developed tension (T) was measured isometrically. Plasma glucose values (mg/dl) were 142.4 +/- 8.7 in C, 499.3 +/- 15.6 in DM and 370.6 +/- 27.6 in DMI group. The order of percent increase in T induced by ISO (3 X 10(-9) - 3 X 10(-8) g) was C = DMI much greater than DM, and that by NE (10(-7) - 10(-6) g) was C greater than DMI greater than DM. On the other hand, the percent increase in T induced by CaCl2 (1.1 X 10(-4) - 2.2 X 10(-3) g) and aminophylline (AMI, 0.31 X 10(-3) - 5.00 X 10(-3) g) was not significantly different among three groups. These results indicate that adrenergic receptor-mediated contractile response was significantly depressed in the diabetic heart.

Aminophylline↗