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排序方式: 共有673条查询结果,搜索用时 15 毫秒
71.
Hojo F Sato D Matsuo J Miyake M Nakamura S Kunichika M Hayashi Y Yoshida M Takahashi K Takemura H Kamiya S Yamaguchi H 《Applied and environmental microbiology》2012,78(15):5247-5257
When Tetrahymena ciliates are cultured with Legionella pneumophila, the ciliates expel bacteria packaged in free spherical pellets. Why the ciliates expel these pellets remains unclear. Hence, we determined the optimal conditions for pellet expulsion and assessed whether pellet expulsion contributes to the maintenance of growth and the survival of ciliates. When incubated with environmental L. pneumophila, the ciliates expelled the pellets maximally at 2 days after infection. Heat-killed bacteria failed to produce pellets from ciliates, and there was no obvious difference in pellet production among the ciliates or bacterial strains. Morphological studies assessing lipid accumulation showed that pellets contained tightly packed bacteria with rapid lipid accumulation and were composed of the layers of membranes; bacterial culturability in the pellets rapidly decreased, in contrast to what was seen in ciliate-free culture, although the bacteria maintained membrane integrity in the pellets. Furthermore, ciliates newly cultured with pellets were maintained and grew vigorously compared with those without pellets. In contrast, a human L. pneumophila isolate killed ciliates 7 days postinfection in a Dot/Icm-dependent manner, and pellets harboring this strain did not support ciliate growth. Also, pellets harboring the human isolate were resuscitated by coculturing with amoebae, depending on Dot/Icm expression. Thus, while ciliates expel pellet-packaged environmental L. pneumophila for stockpiling food, the pellets packaging the human isolate are harmful to ciliate survival, which may be of clinical significance. 相似文献
72.
The phosphoarginine shuttle system effectively regenerates ATP in the cilia of Paramecium caudatum. To estimate the effective concentration of ATP‐regenerating enzymes, we attempted to reconstitute certain ATP‐regenerating systems within the cilia of intact cortical sheets using exogenous enzymes and high‐energy substances. The addition of phosphoenolpyruvate, which is one of the substrates in glycolysis, did not increase the ciliary beat frequency, whereas phosphocreatine together with exogenous creatine kinase, effectively increased the ciliary beat frequency. In the presence of 0.6 mg/ml creatine kinase and 0.4 mM phosphocreatine, the ciliary beat frequency was comparable to that produced by the addition of phosphoarginine. This result indicates that the reconstituted phosphocreatine shuttle system can work as an artificial ATP‐regenerating system for ciliary movements. The effective concentration of creatine kinase in the reconstituted phosphocreatine shuttle system was estimated to be about 7.4 μM based on the molecular mass of creatine kinase (MW 81,000). Therefore, the effective concentration of arginine kinase in the cilia of live Paramecium is approximately 10 μM. This estimated concentration of intraciliary arginine kinase is sufficient to maintain a high ATP concentration throughout the cilia of P. caudatum. 相似文献
73.
74.
Yokoyama U Minamisawa S Quan H Akaike T Suzuki S Jin M Jiao Q Watanabe M Otsu K Iwasaki S Nishimaki S Sato M Ishikawa Y 《The Journal of biological chemistry》2008,283(42):28702-28709
We have demonstrated that chronic stimulation of the prostaglandin E2-cAMP-dependent protein kinase A (PKA) signal pathway plays a critical role in intimal cushion formation in perinatal ductus arteriosus (DA) through promoting synthesis of hyaluronan. We hypothesized that Epac, a newly identified effector of cAMP, may play a role in intimal cushion formation (ICF) in the DA distinct from that of PKA. In the present study, we found that the levels of Epac1 and Epac2 mRNAs were significantly up-regulated in the rat DA during the perinatal period. A specific EP4 agonist, ONO-AE1-329, increased Rap1 activity in the presence of a PKA inhibitor, PKI-(14-22)-amide, in DA smooth muscle cells. 8-pCPT-2'-O-Me-cAMP (O-Me-cAMP), a cAMP analog selective to Epac activator, promoted migration of DA smooth muscle cells (SMC) in a dose-dependent manner. Adenovirus-mediated Epac1 or Epac2 gene transfer further enhanced O-Me-cAMP-induced cell migration, although the effect of Epac1 overexpression on cell migration was stronger than that of Epac2. In addition, transfection of small interfering RNAs for Epac1, but not Epac2, significantly inhibited serum-mediated migration of DA SMCs. In the presence of O-Me-cAMP, actin stress fibers were well organized with enhanced focal adhesion, and cell shape was widely expanded. Adenovirus-mediated Epac1, but not Epac2 gene transfer, induced prominent ICF in the rat DA explants when compared with those with green fluorescent protein gene transfer. The thickness of intimal cushion became significantly greater (1.98-fold) in Epac1-overexpressed DA. O-Me-cAMP did not change hyaluronan production, although it decreased proliferation of DA SMCs. The present study demonstrated that Epac, especially Epac1, plays an important role in promoting SMC migration and thereby ICF in the rat DA. 相似文献
75.
Esaki M Takemura G Kosai K Takahashi T Miyata S Li L Goto K Maruyama R Okada H Kanamori H Ogino A Ushikoshi H Minatoguchi S Fujiwara T Fujiwara H 《American journal of physiology. Heart and circulatory physiology》2008,294(2):H1048-H1057
Hepatocyte growth factor (HGF) reportedly exerts beneficial effects on the heart following myocardial infarction and during nonischemic cardiomyopathy, but the precise mechanisms underlying the latter have not been well elucidated. We generated nonischemic cardiomyopathy in mice by injecting them with doxorubicin (15 mg/kg ip). Two weeks later, when cardiac dysfunction was apparent, an adenoviral vector encoding human HGF gene (Ad.CAG-HGF, 1x10(11) particles/mouse) was injected into the hindlimb muscles; LacZ gene served as the control. Left ventricular dilatation and dysfunction normally seen 4 wk after doxorubicin administration were significantly mitigated in HGF-treated mice, as were the associated cardiomyocyte atrophy/degeneration and myocardial fibrosis. Myocardial expression of GATA-4 and a sarcomeric protein, myosin heavy chain, was downregulated by doxorubicin, but the expression of both was restored by HGF treatment. The protective effect of HGF against doxorubicin-induced cardiomyocyte atrophy was confirmed in an in vitro experiment, which also showed that neither cardiomyocyte apoptosis nor proliferation plays significant roles in the present model. Upregulation of c-Met/HGF receptor was noted in HGF-treated hearts. Among the mediators downstream of c-Met, the activation of extracellular signal-regulated kinase (ERK) was reduced by doxorubicin, but the activity was restored by HGF. Levels of transforming growth factor-beta1 and cyclooxygenase-2 did not differ between the groups. Our findings suggest the HGF gene delivery exerts therapeutic antiatrophic/degenerative and antifibrotic effects on myocardium in cases of established cardiac dysfunction caused by doxorubicin. These beneficial effects appear to be related to HGF-induced ERK activation and upregulation of c-Met, GATA-4, and sarcomeric proteins. 相似文献
76.
Rashel M Uchiyama J Ujihara T Takemura I Hoshiba H Matsuzaki S 《Biochemical and biophysical research communications》2008,368(2):192-198
We report identification of a novel site-specific DNA recombination system that functions in both in vivo and in vitro, derived from lysogenic Staphylococcus aureus phage phiMR11. In silico analysis of the phiMR11 genome indicated orf1 as a putative integrase gene. Phage and bacterial attachment sites (attP and attB, respectively) and attachment junctions were determined and their nucleotide sequences decoded. Sequences of attP and attB were mostly different to each other except for a two bp common core that was the crossover point. We found several inverted repeats adjacent to the core sequence of attP as potential protein binding sites. The precise and efficient integration properties of phiMR11 integrase were shown on attP and attB in Escherichia coli and the minimum size of attP was found to be 34bp. In in vitro assays using crude or purified integrase, only buffer and substrate DNAs were required for the recombination reaction, indicating that other bacterially encoded factors are not essential for activity. 相似文献
77.
Masaharu Takemura 《Journal of molecular evolution》2001,52(5):419-425
A number of molecular forms of DNA polymerases have been reported to be involved in eukaryotic nuclear DNA replication, with
contributions from α-, δ-, and ε-polymerases. It has been reported that δ-polymerase possessed a central role in DNA replication
in archaea, whose ancestry are thought to be closely related to the ancestor of eukaryotes. Indeed, in vitro experiment shown
here suggests that δ-polymerase has the potential ability to start DNA synthesis immediately after RNA primer synthesis. Therefore,
the question arises, where did the α-polymerase come from? Phylogenetic analysis based on the nucleotide sequence of several
conserved regions reveals that two poxviruses, vaccinia and variola viruses, have polymerases similar to eukaryotic α-polymerase
rather than δ-polymerase, while adenovirus, herpes family viruses, and archaeotes have eukaryotic δ-like polymerases, suggesting
that the eukaryotic α-polymerase gene is derived from a poxvirus-like organism, which had some eukaryote-like characteristics.
Furthermore, the poxvirus's proliferation independent from the host-cell nucleus suggests the possibility that this virus
could infect non-nucleated cells, such as ancestral eukaryotes. I wish to propose here a new hypothesis for the origin of
the eukaryotic nucleus, posing symbiotic contact of an orthopoxvirus ancestor with an archaebacterium, whose genome already
had a δ-like polymerase gene.
Received: 26 October 2000 / Accepted: 16 January 2001 相似文献
78.
Taichiro Takemura Masahiro Yamashita Makoto K. Shimada Sadayuki Ohkura Takayoshi Shotake Mikio Ikeda Tomoyuki Miura Masanori Hayami 《Journal of virology》2002,76(4):1642-1648
Simian T-cell leukemia viruses (STLVs) are the simian counterparts of human T-cell leukemia viruses (HTLVs). A novel, divergent type of STLV (STLV-L) from captive baboons was reported in 1994, but its natural prevalence remained unclear. We investigated the prevalence of STLV-L in 519 blood samples from wild-living nonhuman primates in Ethiopia. Seropositive monkeys having cross-reactive antibodies against HTLV were found among 22 out of 40 hamadryas baboons, 8 of 96 anubis baboons, 24 of 50 baboons that are hybrids between hamadryas and anubis baboons, and 41 of 177 grivet monkeys, but not in 156 gelada baboons. A Western blotting assay showed that sera obtained from seropositive hamadryas and hybrid baboons exhibited STLV-L-like reactivity. A PCR assay successfully amplified STLV sequences, which were subsequently sequenced and confirmed as being closely related to STLV-L. Surprisingly, further PCR showed that nearly half of the hamadryas (20 out of 40) and hybrid (19 out of 50) baboons had STLV-L DNA sequences. In contrast, most of the seropositive anubis baboons and grivet monkeys carried typical STLV-1 but not STLV-L. These observations demonstrate that STLV-L naturally prevails among hamadryas and hybrid baboons at significantly high rates. STLV-1 and -2, the close relative of STLV-L, are believed to have jumped across simian-human barriers, which resulted in widespread infection of HTLV-1 and -2. Further studies are required to know if STLV-L is spreading into human populations. 相似文献
79.
Mutated SEA-D227A-conjugated antibodies greatly enhance antitumor activity against MUC1-expressing bile duct carcinoma 总被引:8,自引:0,他引:8
Hideaki Kodama Masanori Suzuki Yu Katayose Masao Shinoda Naoki Sakurai Shin-ichi Takemura Hiroshi Yoshida Hisaaki Saeki Masahiko Ichiyama Kohei Tsumoto Ryutaro Asano Izumi Kumagai Kohzoh Imai Yuji Hinoda Seiki Matsuno Toshio Kudo 《Cancer immunology, immunotherapy : CII》2001,50(10):539-548
For the purpose of establishing a new adoptive immunotherapy for bile duct carcinoma (BDC), we have directed our attention to superantigens (SAgs), the most potent known activators of T lymphocytes. In our previous study, staphylococcal enterotoxin A (SEA) was conjugated chemically with MUSE11 mAb, which recognizes the MUC1 cancer-associated antigen, and shown to enhance the specific cytotoxic activity of T-LAK cells against MUC1-expressing BDC cells (TFK-1) in vitro and in vivo. However, it is probable that SEA might cause side-effects because of nonspecific binding to class II positive cells. In order to overcome these, we generated mutated SEA (mSEA) by changing Asp at position 227 of native SEA to Ala, which has reduced affinity to MHC class II molecules, but retains the potential for T cell activation. When mSEA-D227A was administered to rabbits to examine effects on blood pressure, 500 times more mSEA-D227A was tolerated than native SEA. This prompted us to construct a mSEA-D227A-conjugated mAb, reactive with MUC1. It augmented the antitumor activity of T-LAK cells significantly, and furthermore, mSEA-D227A could be conjugated to two bispecific antibodies, BsAb (anti-MUC1 x anti-CD3) and BsAb (anti-MUC1 x anti-CD28), which in combination had greater enhancing effects than mSEA-D227A-conjugated anti-MUC1 mAb, and combination of unconjugated BsAbs. These findings indicate a utility of mSEA-D227A-conjugated antibodies for targeted cancer immunotherapy. 相似文献
80.