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Biomedical subjects

N Murata

Publications and source records attributed to N Murata.

At least 145 records · Page 8Linked to original sources
PubMed1995

Unsaturation of the membrane lipids of chloroplasts stabilizes the photosynthetic machinery against low-temperature photoinhibition in transgenic tobacco plants.

Using tobacco plants that had been transformed with the cDNA for glycerol-3-phosphate acyltransferase, we have demonstrated that chilling tolerance is affected by the levels of unsaturated membrane lipids. In the present study, we examined the effects of the transformation of tobacco plants with cDNA for glycerol-3-phosphate acyltransferase from squash on the unsaturation of fatty acids in thylakoid membrane lipids and the response of photosynthesis to various temperatures. Of the four major lipid classes isolated from the thylakoid membranes, phosphatidylglycerol showed the most conspicuous decrease in the level of unsaturation in the transformed plants. The isolated thylakoid membranes from wild-type and transgenic plants did not significantly differ from each other in terms of the sensitivity of photosystem II to high and low temperatures and also to photoinhibition. However, leaves of the transformed plants were more sensitive to photoinhibition than those of wild-type plants. Moreover, the recovery of photosynthesis from photoinhibition in leaves of wild-type plants was faster than that in leaves of the transgenic tobacco plants. These results suggest that unsaturation of fatty acids of phosphatidylglycerol in thylakoid membranes stabilizes the photosynthetic machinery against low-temperature photoinhibition by accelerating the recovery of the photosystem II protein complex.

Acclimatization↗
PubMed1995

Low unsaturation level of thylakoid membrane lipids limits turnover of the D1 protein of photosystem II at high irradiance.

Turnover of the D1 protein of photosystem II (PSII) was studied in mutants of Synechocystis sp. PCC 6803 defective in the desaturation of thylakoid membrane lipids. The lack of polyunsaturated fatty acids from membranes made PSII extremely susceptible to photoinhibition and caused a significant reduction in the D1 protein content of the thylakoid membranes at high irradiances. These results may be attributed to an impaired function in the protein synthesis machinery, most probably at the translational or posttranslational level.

Chloroplasts↗
PubMed1995

Site-directed mutagenesis of histidine residues in the delta 12 acyl-lipid desaturase of Synechocystis.

In the cyanobacterium Synechocystis sp. PCC 6803, there are four acyl-lipid desaturases that are, respectively, specific to the delta 6, delta 9, delta 12 and omega 3 positions of fatty acids. The desA gene for the delta 12 acyl-lipid desaturase was modified by site-directed mutagenesis, such that four of the histidine residues that are conserved in the four desaturases and one histidine residue that is not conserved were replaced by arginine, and the mutated desA genes were overexpressed in Escherichia coli. All of these mutations eliminated the delta 12 desaturase activity. These results demonstrate that the five histidine residues are essential for the activity of the delta 12 desaturase, perhaps by providing the ligands for the catalytic Fe center.

Amino Acid Sequence↗
PubMed1995

Steroid-responsive pulmonary disorders associated with myelodysplastic syndromes with der(1q;7p) chromosomal abnormality.

We report three patients with pulmonary disorders associated with myelodysplastic syndromes (MDS). All three patients had symptoms of pyrexia and respiratory discomfort. One patient had pulmonary eosinophilia with bilateral pleural effusion, one had interstitial pneumonia, and one had bilateral pleural effusion caused by systemic vasculitis. Elevated C-reactive protein (CRP) levels, polyclonal hypergammaglobulinemia, and morphological abnormalities in peripheral blood were observed in all three patients. The bone marrow of these patients revealed trilineage dysplasia and eosinophilia. Cytogenetic analysis showed [46,XY,-7,+der(1q;7p)]. Antibiotic treatment was not effective. However, improvement was dramatic after corticosteroid treatment; CRP levels were reduced and the hypergammaglobulinemia was improved. These cases suggest that MDS with [-7,+der(1q;7p)] may be correlated with bone marrow eosinophilia and that an immunologic abnormality may be involved in the pulmonary disorders.

Adrenal Cortex Hormones↗
PubMed1995

Transformation of Synechococcus with a gene for choline oxidase enhances tolerance to salt stress.

Choline oxidase, isolated from the soil bacterium Arthrobacter globiformis, converts choline to glycinebetaine (N-trimethylglycine) without a requirement for any cofactors. The gene for this enzyme, designated codA, was cloned and introduced into the cyanobacterium Synechococcus sp. PCC 7942. The codA gene was expressed under the control of a strong constitutive promoter, and the transformed cells accumulated glycinebetaine at intracellular levels of 60-80 mM. Consequently the cells acquired tolerance to salt stress, as evaluated in terms of growth, accumulation of chlorophyll and photosynthetic activity.

Adaptation, Physiological↗
PubMed1995

Senescence-induced expression of a homologue of delta 9 desaturase in rose petals.

cDNAs for senescence-inducible genes were isolated by differential hybridization from a cDNA library derived from mRNAs from the petals of rose flowers. The amino acid sequence deduced from these cDNAs exhibited significant homology to those of delta 9 acyl-lipid desaturases of cyanobacteria and of delta 9 acyl-CoA desaturases of a yeast and mammals. There was no amino-terminal sequence indicative of a leader peptide for targeting to the chloroplasts or to mitochondria. Northern blot analysis indicated that the transcripts of the cDNAs were expressed specifically in petals at late developmental stages and during senescence. It is proposed that a delta 9 desaturase in the senescing petals play an important role in the degradation of saturated fatty acids of membrane lipids.

Aging↗
PubMed1995

Characterization of the murF gene of the cyanobacterium Synechocystis sp. PCC 6803.

The murF gene encodes UDP-N-acetylmuramoyl-L-alanyl-D-glutamyl-meso-2, 6-diaminopimeloyl-D-Ala-D-Ala synthetase (EC 6.3.2.15), which catalyses the final step in the synthesis of UDP-N-acetylmuramoyl-pentapeptide, the precursor of murein. An open reading frame identified as the murF gene was found in the genome of the cyanobacterium Synechocystis sp. PCC 6803. The murF gene encodes a polypeptide of 454 amino acid residues with a predicted molecular mass of 48 kDa. The murF gene is present as a single-copy gene in the genome of Synechocystis sp. PCC 6803. The amino acid sequence deduced from the murF gene is 39% identical to that of the product of the murF gene of Escherichia coli. The cyanobacterial murF gene complemented a temperature-sensitive mutation in a murF-deficient strain of E. coli, restoring the mutant's ability to synthesize a cell wall and to survive at high sublethal temperatures.

Amino Acid Sequence↗
PubMed1995

The effects of dopamine and dobutamine on liver oxygen supply-uptake relationship in the dog.

The effects of dopamine and dobutamine in various doses on liver oxygen supply-uptake relationship were studied in 12 mongrel dogs. Dopamine 3 and 7 micrograms/kg/min infusion rates and dobutamine 5 micrograms/kg/min infusion rate did not produce any changes in total liver oxygen delivery. On the contrary, total liver oxygen delivery was increased at the 15 micrograms/kg/min dopamine in fusion rate and dobutamine 10 and 15 micrograms/kg/min infusion rates. The ratio of total liver oxygen delivery to the systemic oxygen delivery was increased at the 15 micrograms/kg/min dopamine infusion rate. Liver oxygen extraction ratio was decreased at the 15 micrograms/kg/min dopamine infusion rate and at the same rate of dobutamine. These decreases were due to the increases in oxygen delivery while both oxygen uptakes were avariant from control levels. The results of this study demonstrated that high dose of dopamine (15 micrograms/kg/min) and medium and high doses of dobutamine (10 and 15 micrograms/kg/min) should be useful to increase the liver oxygen delivery. However, these increases in liver oxygen delivery during dopamine and dobutamine infusion were not associated with an improvement in liver oxygen metabolism, since liver oxygen uptake was not changed.

Animals↗
PubMed1995

The selective effects of dopamine and dobutamine on liver circulation in the dog.

The selective effects od dopamine and dobutamine in various doses on liver circulation were studied in 12 mongrel dogs. Dopamine increased portal flow but decreased hepatic arterial flow markedly as infusion rate of dopamine increased. Dopamine 3 micrograms/kg/min infusion rate produced vasodilation in mesenteric vascular bed and the portal flow ratio to cardiac output was significantly increased. Dobutamine increased both portal and hepatic arterial flows at the 5 and 10 micrograms/kg/min dobutamine infusion rates, and decreased hepatic arterial flow at the 15 micrograms/kg/min dobutamine infusion rate. Both dopamine and dobutamine increased total liver flows, however, total liver flow ratio to cardiac output was not increased. Pressure gradient of portal system was not changed during dopamine and dobutamine infusion, since both portal venous pressure and hepatic venous pressure were avariant from control values. These findings suggest that congestive hyperemia was not occurred in intrahepatic portal vascular system when portal flows were increased during dopamine and dobutamine infusion. The results of this study demonstrate that both dopamine and dobutamine did not produce selective increases in total liver blood flow. In addition, both agents should be safe to use to the normal liver patient; total liver blood flow did not decrease and intrahepatic congestive hyperemia was not occurred when portal flow was increased.

Animals↗
PubMed1995

[Post operative mediastinitis: the experience of two cases after graft replacement of the ascending aorta].

A mediastinitis after a graft replacement of the ascending aorta is serious complication and sometimes could be lethal. We have experienced two cases of such a condition, recently. In both cases, the debridement of the mediastinum and omental transposition were performed. Case 1 had a recurrent mediastinitis due to residual dead space infection, but was cured by a percutaneous drainage and a continuous irrigation. In case 2, the omentum was carefully positioned to occupy the dead space around the graft, because of the experience of the first case and gave a good result. We believe that omental transposition is an effective treatment for the postoperative mediastinitis.

Adult↗
PubMed1995

Antitumor activity of the new selective protein kinase C inhibitor 4'-N-benzoyl staurosporine on murine and human tumor models.

CGP 41251 (4'-N-benzoyl staurosporine, CAS 120685-11-2) has been shown to exert increased selectivity for the inhibition of protein kinase C (PKC) activity. In the present study the effect of CGP 41251 formulated in gelucire as an antitumor agent was studied in various types of murine and human tumor models. When administered at a dose of 75 mg/kg 3 times daily for 9 days, CGP 41251 prolonged the life span of the mice bearing B16 melanoma (ILS = 36%). CGP 41251, administered orally at doses of 25-225 mg/kg once daily for 9 days, however, did not show distinct efficacy in four kinds of murine tumor models (B16 melanoma, colon 26, colon 38 and M5076). In s.c.inoculated human tumor xenograft models, CGP 41251, administered orally at a dose of 200 mg/kg once daily for 4 weeks showed a broad antitumor spectrum. CGP 41251 inhibited the growth of gastric cancer (H-55), colorectal cancer (H-26), breast cancer (H-31) and lung cancer (H-74 and LC-376) with inhibition rates of 58-80%. In a histopathologic study, increase in central necrosis and condensed nuclei and vacuolar degeneration were observed, but there was no structural destruction by the treatment of CGP 41251. In addition, CGP 41251 decreased the number of PCNA (proliferating cell nuclear antigen) immunoreactive cells in human tumor cells H-55, H-26 and H-74. These results indicate that CGP 41251 shows a broad antitumor spectrum against human tumors, and it is suggested that CGP 41251 is a promising oral antitumor agent which has a novel mechanism of action.

Animals↗
PubMed1994

delta 9 Acyl-lipid desaturases of cyanobacteria. Molecular cloning and substrate specificities in terms of fatty acids, sn-positions, and polar head groups.

In cyanobacteria, the biosynthesis of unsaturated fatty acids is initiated by delta 9 acyl-lipid desaturase which introduces the first double bond at the delta 9 position of a saturated fatty acid that has been esterified to a glycerolipid. We have cloned genes, designated desC, for delta 9 acyl-lipid desaturases from two cyanobacteria, namely Anabaena variabilis and Synechocystis sp. PCC 6803. These desaturases, when expressed in Escherichia coli, desaturated stearic acid to yield oleic acid at the C-1 positions of phosphatidylethanolamine and phosphatidylglycerol, but did not desaturate palmitic acid, palmitoleic acid, and cis-vaccenic acid. These results indicate that the delta 9 acyl-lipid desaturases are specific to stearic acid esterified at the C-1 position of a glycerolipid and are nonspecific with respect to the polar head group of the glycerolipid. The deduced amino acid sequences of the delta 9 acyl-lipid desaturases are similar in part to those of stearoyl-CoA desaturases of the rat, the mouse, and Saccharomyces cerevisiae, but not to those of acyl-(acyl-carrier-protein) desaturases of higher plants.

Amino Acid Sequence↗
PubMed1994

The recovery of photosynthesis from low-temperature photoinhibition is accelerated by the unsaturation of membrane lipids: a mechanism of chilling tolerance.

In a previous study of mutants in fatty-acid desaturation of Synechocystis PCC6803, it was demonstrated that the photoinhibition of photosynthesis at low temperature in vivo is tolerated by cells as a result of the unsaturation of glycerolipids of thylakoid membranes. Since the extent of photoinhibition of photosynthesis in vivo depends on a balance between the photoinduced inactivation and the recovery from the photoinhibited state, an examination was made of the effects of the unsaturation of membrane lipids on these processes. It appears that the unsaturation of the membrane lipids does not affect the inactivation process but accelerates the recovery process and, moreover, that the apparent increase in the photoinhibition in vivo of photosynthesis at low temperature is caused by a depressed rate of recovery at low temperature.

Chloramphenicol↗
PubMed1994

Contribution of membrane lipids to the ability of the photosynthetic machinery to tolerate temperature stress.

The contribution of the unsaturation of membrane lipids to the ability of the photosynthetic machinery to tolerate temperature stress was studied in a transgenic cyanobacterium. Anacystis nidulans R2-SPc was transformed with the desA gene, which encodes the Delta12-desaturase that desaturates the fatty acids of membrane lipids in Synechocystis PCC6803. The transformant acquired the ability to introduce a second double bond into palmitoleic and oleic acids. The transformation enhanced the tolerance of the photosynthetic machinery to chilling stress but it had no detectable effect on the ability to tolerate heat stress. The transformation itself did not have any effect on photosynthetic activity. These results imply that an increase in the unsaturation of membrane lipids enhances the tolerance of the photosynthetic machinery toward chilling stress but not toward heat stress and that such an increase does not affect photosynthesis within the range of physiological temperatures.

Journal Article↗