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排序方式: 共有730条查询结果,搜索用时 15 毫秒
81.
Nikrodhanond AA Ortiga-Carvalho TM Shibusawa N Hashimoto K Liao XH Refetoff S Yamada M Mori M Wondisford FE 《The Journal of biological chemistry》2006,281(8):5000-5007
Hypothalamic thyrotropin-releasing hormone (TRH) stimulates thyroid-stimulating hormone (TSH) secretion from the anterior pituitary. TSH then initiates thyroid hormone (TH) synthesis and release from the thyroid gland. Although opposing TRH and TH inputs regulate the hypothalamic-pituitary-thyroid axis, TH negative feedback is thought to be the primary regulator. This hypothesis, however, has yet to be proven in vivo. To elucidate the relative importance of TRH and TH in regulating the hypothalamic-pituitary-thyroid axis, we have generated mice that lack either TRH, the beta isoforms of TH receptors (TRbeta KO), or both (double KO). TRbeta knock-out (KO) mice have significantly higher TH and TSH levels compared with wild-type mice, in contrast to double KO mice, which have reduced TH and TSH levels. Unexpectedly, hypothyroid double KO mice also failed to mount a significant rise in serum TSH levels, and pituitary TSH immunostaining was markedly reduced compared with all other hypothyroid mouse genotypes. This impaired TSH response, however, was not due to a reduced number of pituitary thyrotrophs because thyrotroph cell number, as assessed by counting TSH immunopositive cells, was restored after chronic TRH treatment. Thus, TRH is absolutely required for both TSH and TH synthesis but is not necessary for thyrotroph cell development. 相似文献
82.
Miyanaga A Koseki T Miwa Y Mese Y Nakamura S Kuno A Hirabayashi J Matsuzawa H Wakagi T Shoun H Fushinobu S 《The Biochemical journal》2006,399(3):503-511
Alpha-L-arabinofuranosidase catalyses the hydrolysis of the alpha-1,2-, alpha-1,3-, and alpha-1,5-L-arabinofuranosidic bonds in L-arabinose-containing hemicelluloses such as arabinoxylan. AkAbf54 (the glycoside hydrolase family 54 alpha-L-arabinofuranosidase from Aspergillus kawachii) consists of two domains, a catalytic and an arabinose-binding domain. The latter has been named AkCBM42 [family 42 CBM (carbohydrate-binding module) of AkAbf54] because homologous domains are classified into CBM family 42. In the complex between AkAbf54 and arabinofuranosyl-alpha-1,2-xylobiose, the arabinose moiety occupies the binding pocket of AkCBM42, whereas the xylobiose moiety is exposed to the solvent. AkCBM42 was found to facilitate the hydrolysis of insoluble arabinoxylan, because mutants at the arabinose binding site exhibited markedly decreased activity. The results of binding assays and affinity gel electrophoresis showed that AkCBM42 interacts with arabinose-substituted, but not with unsubstituted, hemicelluloses. Isothermal titration calorimetry and frontal affinity chromatography analyses showed that the association constant of AkCBM42 with the arabinose moiety is approximately 10(3) M(-1). These results indicate that AkCBM42 binds the non-reducing-end arabinofuranosidic moiety of hemicellulose. To our knowledge, this is the first example of a CBM that can specifically recognize the side-chain monosaccharides of branched hemicelluloses. 相似文献
83.
Sakata M Kawasaki T Shibue T Takada A Yoshimura H Namiki H 《Biochemical and biophysical research communications》2006,351(2):566-570
This study characterized the magnetic materials found within Daphnia resting eggs by measuring static magnetization with a superconducting quantum interference device (SQUID) magnetometer, after forming two types of conditions, each of which consists of zero-field cooling (ZFC) and field cooling (FC). Magnetic ions, such as Fe(3+), contained in Daphnia resting eggs existed as (1) paramagnetic and superparamagnetic particles, demonstrated by a magnetization and temperature dependence of the magnetic moments under an applied magnetic field after ZFC and FC, and (2) ferromagnetic particles with definite magnetic moments, the content of which was estimated to be very low, demonstrated by the Moskowitz test. Conventionally, biomagnets have been directly detected by transmission electron microscopes (TEM). As demonstrated in this study, it is possible to nondestructively detect small biomagnets by magnetization measurement, especially after two types of ZFC and FC. This nondestructive method can be applied in detecting biomagnets in complex biological organisms. 相似文献
84.
Nakayama H Miyazaki T Kitamura K Hashimoto K Yanagawa Y Obata K Sakimura K Watanabe M Kano M 《Neuron》2012,74(2):384-396
Functional neural circuit formation during development involves massive elimination of redundant synapses. In the cerebellum, one-to-one connection from excitatory climbing fiber (CF) to Purkinje cell (PC) is established by elimination of early-formed surplus CFs. This process depends on glutamatergic excitatory inputs, but contribution of GABAergic transmission remains unclear. Here, we demonstrate impaired CF synapse elimination in mouse models with diminished GABAergic transmission by mutation of a single allele for the GABA synthesizing enzyme GAD67, by conditional deletion of GAD67 from PCs and GABAergic interneurons or by pharmacological inhibition of cerebellar GAD activity. The impaired CF synapse elimination was rescued by enhancing GABA(A) receptor sensitivity in the cerebellum by locally applied diazepam. Our electrophysiological and Ca2+ imaging data suggest that GABA(A) receptor-mediated inhibition onto the PC soma from molecular layer interneurons influences CF-induced Ca2+ transients in the soma and regulates CF synapse elimination from postnatal day 10 (P10) to around P16. 相似文献
85.
Takahiro Wakahama Aitor Laza‐Martínez Ahmad Iskandar Bin Haji Mohd Taha Hidetoshi Okuyama Kiyohito Yoshida Kazuhiro Kogame Koichiro Awai Masanobu Kawachi Takashi Maoka Shinichi Takaichi 《Journal of phycology》2012,48(6):1392-1402
The molecular structure of the carotenoid lactoside P457, (3S,5R,6R,3′S,5′R,6′S)‐13′‐cis‐5,6‐epoxy‐3′,5′‐dihydroxy‐3‐(β‐d ‐galactosyl‐(1→4)‐β‐d ‐glucosyl)oxy‐6′,7′‐didehydro‐5,6,7,8,5′,6′‐hexahydro‐β,β‐caroten‐20‐al, was confirmed by spectroscopic methods using Symbiodinium sp. strain NBRC 104787 cells isolated from a sea anemone. Among various algae, cyanobacteria, land plants, and marine invertebrates, the distribution of this unique diglycosyl carotenoid was restricted to free‐living peridinin‐containing dinoflagellates and marine invertebrates that harbor peridinin‐containing zooxanthellae. Neoxanthin appeared to be a common precursor for biosynthesis of peridinin and P457, although neoxanthin was not found in peridinin‐containing dinoflagellates. Fucoxanthin‐containing dinoflagellates did not possess peridinin or P457; green dinoflagellates, which contain chlorophyll a and b, did not contain peridinin, fucoxanthin, or P457; and no unicellular algae containing both peridinin and P457, other than peridinin‐containing dinoflagellates, have been observed. Therefore, the biosynthetic pathways for peridinin and P457 may have been coestablished during the evolution of dinoflagellates after the host heterotrophic eukaryotic microorganism formed a symbiotic association with red alga that does not contain peridinin or P457. 相似文献
86.
Tajima K Han X Satoh Y Ishii A Araki Y Munekata M Taguchi S 《Applied microbiology and biotechnology》2012,94(2):365-376
Recently, we succeeded in isolating a thermotolerant bacterium, Pseudomonas sp. SG4502, which is capable of accumulating polyhydroxyalkanoate (PHA) even at 55 °C, as a source of thermostable enzymes.
In this study, we cloned a pha locus from the bacterium and identified two genes encoding PHA synthases (PhaC1SG and PhaC2SG). Two mutations, Ser324Thr and Gln480Lys, corresponding to those of a lactate (LA)-polymerizing enzyme (LPE) from mesophilic
Pseudomonas sp. 61-3 were introduced into PhaC1SG to evaluate the potential of the resulting protein as a “thermostable LPE”. The mutated PhaC1SG [PhaC1SG(STQK)] showed high thermal stability in synthesizing P(LA-co-3HB) in an in vitro reaction system under a range of high temperatures. Requirement of 3HBCoA as a priming unit for LA polymerization
by the LPE has been suggested in both of the in vitro and in vivo experiments. Based on the finding, the PhaC1SG(STQK)-mediated synthesis of a LA-based copolymer with a block sequence was achieved in the in vitro system by sequential
feeding of the corresponding two substrates. This in vitro reaction system using the thermostable LPE provides us with a versatile
way to synthesize the various types of LA-based copolymers with desired sequence patterns, random or block, depending on the
way of supplying hydroxyalkanoates (mixed or sequential feeding). 相似文献
87.
Kimura KR Nakata M Sumitomo T Kreikemeyer B Podbielski A Terao Y Kawabata S 《Journal of bacteriology》2012,194(4):804-812
The group A streptococcus (GAS) Streptococcus pyogenes is known to cause self-limiting purulent infections in humans. The role of GAS pili in host cell adhesion and biofilm formation is likely fundamental in early colonization. Pilus genes are found in the FCT (fibronectin-binding protein, collagen-binding protein, and trypsin-resistant antigen) genomic region, which has been classified into nine subtypes based on the diversity of gene content and nucleotide sequence. Several epidemiological studies have indicated that FCT type 1 strains, including serotype M6, produce large amounts of monospecies biofilm in vitro. We examined the direct involvement of pili in biofilm formation by serotype M6 clinical isolates. In the majority of tested strains, deletion of the tee6 gene encoding pilus shaft protein T6 compromised the ability to form biofilm on an abiotic surface. Deletion of the fctX and srtB genes, which encode pilus ancillary protein and class C pilus-associated sortase, respectively, also decreased biofilm formation by a representative strain. Unexpectedly, these mutant strains showed increased bacterial aggregation compared with that of the wild-type strain. When the entire FCT type 1 pilus region was ectopically expressed in serotype M1 strain SF370, biofilm formation was promoted and autoaggregation was inhibited. These findings indicate that assembled FCT type 1 pili contribute to biofilm formation and also function as attenuators of bacterial aggregation. Taken together, our results show the potential role of FCT type 1 pili in the pathogenesis of GAS infections. 相似文献
88.
Takuya Matsumoto Masanobu Kawachi Hideaki Miyashita Yuji Inagaki 《Journal of plant research》2012,125(6):705-711
Green-colored plastids in the dinoflagellates Lepidodinium chlorophorum and L. viride have been widely believed as the remnant of an endosymbiotic prasinophyte. This hypothesis for the origin of the Lepidodinium plastids is solely based on an unpublished result quoted in Elbr?chter and Schnepf (Phycologia 35:381–393, 1996) hinting at the presence of a characteristic carotenoid in prasinophytes, prasinoxanthin, in the L. chlorophorum cells. On the other hand, a recent work failed to detect prasinoxanthin in a culture of L. chlorophorum. Unfortunately, we cannot conduct any additional experiments to examine whether the two strains considered in the previous studies are truly of L. chlorophorum, as neither of the two strains is publicly available. We here investigated the pigment composition of L. chlorophorum strain NIES-1868 maintained as a mono-algal culture under laboratory conditions, and detected no sign of prasinoxanthin. The pigment composition of strain NIES-1868 is consistent with previous phylogenetic analyses based on plastid-encoded genes of the same strain, which successfully excluded prasinoxanthin-containing algae from the origin of the L. chlorophorum plastid. We also determined nucleus-encoded 18S ribosomal RNA (rRNA) genes from four Lepidodinium strains (including strain NIES-1868). Analyses of 18S rRNA sequences showed an extremely close relationship among strain NIES-1868 and other Lepidodinium cells/strains originating from different geological locations, suggesting that the cells/strains corresponding to these rRNA sequences lack prasinoxanthin. 相似文献
89.
Tagaya Y Osaki A Miura A Okada S Ohshima K Hashimoto K Yamada M Satoh T Shimizu H Mori M 《Protein and peptide letters》2012,19(9):997-1004
Nucleobindin-2 is a 420 amino acid EF-hand Ca2+ binding protein that can be further processed to generate an 82 amino terminal peptide termed Nesfatin-1. To examine the function of secreted Nucleobindin-2 in adipocyte differentiation, cultured 3T3-L1 cells were incubated with either 0 or 100 nM of GST, GST-Nucleobindin-2, prior to and during the initiation of adipocyte differentiation. Nucleobindin-2 treatment decreased neutral lipid accumulation (Oil-Red O staining) and expression of several marker genes for adipocyte differentiation (PPARγ, aP2, and adipsin). When Nucleobindin- 2 was constitutively secreted into cultured medium, cAMP content and insulin stimulated CREB phosphorylation were significantly reduced. On the other hand, intracellularly overexpressed Nucleobindin-2 failed to affect cAMP content and CREB phosphorylation. Taken together, these data indicate that secreted Nucleobindin-2 is a suppressor of adipocyte differentiation through inhibition of cAMP production and insulin signal. 相似文献
90.
Ohi K Hashimoto R Nakazawa T Okada T Yasuda Y Yamamori H Fukumoto M Umeda-Yano S Iwase M Kazui H Yamamoto T Kano M Takeda M 《PloS one》2012,7(4):e35696