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1.
F. Kato T. Hino A. Nakaji M. Tanaka Y. Koyama 《Molecular & general genetics : MGG》1995,247(3):387-390
In many species of actinomycetes, carotenogenesis can be photoinduced. The capacity to respond to photoinduction is, however unstable and, in various strains of Streptomyces, is lost at a relatively high frequency. In Streptomyces setonii ISP5395, which normally produces no carotenoids, carotenoid-producing mutants can be obtained following protoplast regeneration. We report here the characterization of a gene, crtS, which was isolated from one such mutant and can confer on wild-type S. setonii ISP5395 cells the capacity to synthesize carotenoids. Sequence analysis of crtS reveals an open reading frame, which shows homology to genes that encode alternative sigma factors in Bacillus subtilis. We propose that crtS encodes a sigma factor which is necessary for the expression of a cryptic gene(s) for carotenoid biosynthesis in S. setonii ISP5395. 相似文献
2.
Julie A. Harris Akihiko Koyama Sumihiro Maeda Kaitlyn Ho Nino Devidze Dena B. Dubal Gui-Qiu Yu Eliezer Masliah Lennart Mucke 《PloS one》2012,7(9)
Accumulation of hyperphosphorylated tau in the entorhinal cortex (EC) is one of the earliest pathological hallmarks in patients with Alzheimer’s disease (AD). It can occur before significant Aβ deposition and appears to “spread” into anatomically connected brain regions. To determine whether this early-stage pathology is sufficient to cause disease progression and cognitive decline in experimental models, we overexpressed mutant human tau (hTauP301L) predominantly in layer II/III neurons of the mouse EC. Cognitive functions remained normal in mice at 4, 8, 12 and 16 months of age, despite early and extensive tau accumulation in the EC. Perforant path (PP) axon terminals within the dentate gyrus (DG) contained abnormal conformations of tau even in young EC-hTau mice, and phosphorylated tau increased with age in both the EC and PP. In old mice, ultrastructural alterations in presynaptic terminals were observed at PP-to-granule cell synapses. Phosphorylated tau was more abundant in presynaptic than postsynaptic elements. Human and pathological tau was also detected within hippocampal neurons of this mouse model. Thus, hTauP301L accumulation predominantly in the EC and related presynaptic pathology in hippocampal circuits was not sufficient to cause robust cognitive deficits within the age range analyzed here. 相似文献
3.
4.
Deoxyribonucleoside triphosphate imbalance. 5-Fluorodeoxyuridine-induced DNA double strand breaks in mouse FM3A cells and the mechanism of cell death 总被引:10,自引:0,他引:10
A Yoshioka S Tanaka O Hiraoka Y Koyama Y Hirota D Ayusawa T Seno C Garrett Y Wataya 《The Journal of biological chemistry》1987,262(17):8235-8241
The mechanism of cytotoxic action of 5-fluorodeoxyuridine (FdUrd) in mouse FM3A cells was investigated. We observed the FdUrd-induced imbalance of intracellular deoxyribonucleoside triphosphate (dNTP) pools and subsequent double strand breaks in mature DNA, accompanied by cell death. The imbalance of dNTP pools was maximal at 8 h after 1 microM FdUrd treatment; a depletion of dTTP and dGTP pools and an increase in the dATP pool were observed. The addition of FdUrd in culture medium induced strand breaks in DNA, giving rise to a 90 S peak by alkaline sucrose gradient sedimentation. The loss of cell viability and colony-forming ability occurred at about 10 h. DNA double strand breaks as measured by the neutral elution method were also observed in FdUrd-treated cells about 10 h after the addition. These results lead us to propose that DNA double strand breaks play an important role in the mechanism of FdUrd-mediated cell death. A comparison of the ratio of single and double strand breaks induced by FdUrd to that observed following radiation suggested that FdUrd produced double strand breaks exclusively. Cycloheximide inhibited both the production of DNA double strand breaks and the FdUrd-induced cell death. An activity that can induce DNA double strand breaks was detected in the lysate of FdUrd-treated FM3A cells but not in the untreated cells. This suggests that FdUrd induces the cellular DNA double strand breaking activity. The FdUrd-induced DNA strand breaks and cell death appear to occur in the S phase. Our results indicate that imbalance of the dNTP pools is a trigger for double strand DNA break and cell death. 相似文献
5.
The mode of entry of herpes simplex virus type 1 into Vero cells 总被引:3,自引:0,他引:3
The mode of entry of herpes simplex virus type 1 (HSV-1) into Vero cells was investigated quantitatively with biological techniques. The entry of virus occurred rapidly when the virus-adsorbed cells were incubated at 37 C. The kinetics of virus entry was found to be similar to that of the process of uncoating, indicating that the uncoating of HSV-1 occurs simultaneously with the entry of virus into the cell. Experiments with ammonium chloride revealed that acidity in endosomes is not necessary for the entry or uncoating of HSV-1, in contrast with the cases of enveloped RNA viruses. In addition, endocytosis of the virus seems to be one of the processes of entry for HSV-1. However, the kinetics of endocytosis showed that the cell-bound virus is endocytosed gradually and suggested that the endocytosis of HSV-1 does not lead the virus to an uncoating process. These results are most consistent with a mechanism of entry for HSV-1 involving fusion of the viral envelope with the plasma membrane of the host cell. 相似文献
6.
In order to elucidate the evolution of C4 syndrome, the taxonomic relationships, leaf anatomy, and ecological and global distribution of C3 and C4 species in the genusRhynchospora were investigated. The anatomical observation for 181 species revealed that 26 C4 species occurred within theCapitatae group of the subgenusHaplostyleae, a natural group showing highly advanced morphological characteristics, together with several C3 species. In spite of there being rather few C4 species, they possessed two kinds of Kranz anatomical structure differing from each other in the location of Kranz cells. Some C3 species ofCapitatae showed radial arrangement in mesophyll cells surrounding vascular bundles, which is distinguished from typical non-Kranz anatomy. The C4 species extended their ecological ranges from wet habitats to dry savanna grasslands, while the C3 species showed the best development in wet habitats. The C3 species were widespread from tropical to temperate regions with partial range extension into subarctic regions of both hemispheres, showing conspicuously high concentration of species in the New World, but being absent from arid climatic regions. The C4 species were distributed mostly in tropics and subtropics, showing two separate distributional centers in South and Central America and in Tropical Asia and Australia. The range of C4 species was nearly completely included in the C3 range. In conclusion, it seems that inRhynchospora the C4 syndrome evolved relatively recently, and arose in at least two separate phylogenetic trends in the tropics and the subtropics, more probably in the Neotropics. 相似文献
7.
Porcine polymorphonuclear leukocyte NADPH-cytochrome c reductase generates superoxide in the presence of cytochrome b559 and phospholipid 总被引:1,自引:0,他引:1
F Sakane H Kojima K Takahashi J Koyama 《Biochemical and biophysical research communications》1987,147(1):71-77
NADPH-cytochrome c reductase and cytochrome b559 were purified from the membrane fraction of phorbol myristate acetate-stimulated porcine polymorphonuclear leukocytes. The highly purified reductase oxidized NADPH and generated superoxide when combined with partially purified cytochrome b559 in the presence of phosphatidylcholine. In the same system, but under the anaerobic condition, the reductase was found to reduce cytochrome b559. 相似文献
8.
Y Koyama M Imoto M Tanaka Y Fukuda Y Miyazawa I Nakano T Ozawa 《Biochemistry international》1989,18(2):399-403
In order to elucidate the role of histamine in the liver, we studied the effect of a histamine H1-receptor antagonist on the carbohydrate and lipid metabolism in the rat liver. The administration of the H1-receptor antagonist decreased significantly the contents of glycogen and malonyl-CoA in the liver. However, it did not affect the levels of serum glucose and free fatty acid. These results suggest that histamine may play a part in the regulation of metabolism of carbohydrates and lipids in the liver. 相似文献
9.
Cytosolic adenylate kinase catalyzes the synthesis of thiamin triphosphate from thiamin diphosphate 总被引:2,自引:0,他引:2
An attempt was made to purify a porcine skeletal muscle enzyme catalyzing the formation of thiamin triphosphate (TTP) from thiamin diphosphate (TDP), requiring ATP, Mg2+ and a cofactor (creatine). As the purification proceeded, the reaction requirements for ATP and creatine were lost and then a requirement for ADP was manifested. The activity responsible for TTP synthesis from TDP, ADP, and Mg2+ was found to be copurified with adenylate kinase [EC 2.7.4.3] activity, and was finally purified to a single band on SDS-PAGE. Antiserum obtained against the purified enzyme preparation inhibited both adenylate kinase activity and the TTP-synthesizing activity to exactly the same extent. These results indicate that adenylate kinase catalyzes TTP formation from TDP in vitro. 相似文献
10.
The membrane viscosity of peripheral blood lymphocytes (PBLs) of equine, bovine and canine was measured by the use of time-resolved fluorescence depolarization technique with 1, 6-diphenyl-1,3,5-hexatriene (DPH). The viscosity values were 0.55, 0.59 and 0.50 poise for equine, bovine and canine PBLs, respectively. These values were compared with steady-state anisotropies and order parameters measured from electron spin resonance (ESR) of 5-doxyl stearic acid. Both values were increased with increase of viscosity. The fluid property of the membranes stimulated with phytohemagglutinin-P (PHA) was measured with steady-state fluorescence anisotropy and ESR. Little change of membrane fluidity was recognized with both methods during the stimulation with PHA. It appears that PHA activation process for these lymphocytes does not included large increase of the membrane fluidity which significantly accelerate the diffusion velocity of receptors in the plasma membrane. 相似文献