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101.
Michiya Itoh Hiroko Mizukoshi Kiyokazu Fuke Shigeru Matsukawa Kazuhiro Mawatari Yoshimasa Yoneyama Minoru Sumitani Keitaro Yoshihara 《Biochemical and biophysical research communications》1981,100(3):1259-1265
The fluorescence spectra and fluorescence lifetimes due to tryptophan residues in HbA, Hb Chesapeake, NES-des-Arg Hb and Hb Kempsey were determined at room temperature. The fluorescence intensity and apparent fluorescence lifetimes decrease when the deoxy or T structure in HbA changes to the oxy or R structure, while no significant difference was observed in Hb Kempsey. The difference of fluorescence behavior was ascribed to the quaternary conformational transition of T- and R-states. 相似文献
102.
Characterization and categorization of fluorescence activated cell sorted planarian stem cells by ultrastructural analysis 总被引:1,自引:0,他引:1
Higuchi S Hayashi T Hori I Shibata N Sakamoto H Agata K 《Development, growth & differentiation》2007,49(7):571-581
Planarians have regenerative ability made possible by pluripotent stem cells referred to as neoblasts. Classical ultrastructural studies have indicated that stem cells can be distinguished by a unique cytoplasmic structure known as the chromatoid body and their undifferentiated features, and they are specifically eliminated by X-ray irradiation. Recently, by using fluorescence activated cell sorting (FACS), planarian cells were separated into two X-ray-sensitive fractions (X1 and X2) and an X-ray-insensitive fraction (XIS) according to DNA content and cytoplasmic size. Here we analyzed the fractionated cells by transmission electron microscopy (TEM). First, we found that both undifferentiated cells (stem cells) and regenerative cells (differentiating cells) were concentrated in the X1 fraction containing the S/G2/M phase cells. The regenerative cells were considered to be committed stem cells or progenitor cells, suggesting that some stem cells may maintain proliferative ability even after cell fate-commitment. Second, we succeeded in identifying a new type of stem cells, which were small in size with few chromatoid bodies and a heterochromatin-rich nucleus. Interestingly, they were concentrated in the X2 fraction, containing G0/G1 phase cells. These results suggest that planarian stem cells are not homogeneous, but may consist of heterogeneous populations, like mammalian stem cells. 相似文献
103.
Wnt signaling functions in axis formation and morphogenesis in various animals and organs. Here we report that Wnt signaling is required for proper brain patterning during planarian brain regeneration. We showed here that one of the Wnt homologues in the planarian Dugesia japonica, DjwntA, was expressed in the posterior region of the brain. When DjwntA-knockdown planarians were produced by RNAi, they could regenerate their heads at the anterior ends of the fragments, but formed ectopic eyes with irregular posterior lateral branches and brain expansion. This suggests that the Wnt signal may be involved in antero-posterior (A-P) patterning of the planarian brain, as in vertebrates. We also investigated the relationship between the DjwntA and nou-darake/FGFR signal systems, as knockdown planarians of these genes showed similar phenotypes. Double-knockdown planarians of these genes did not show any synergistic effects, suggesting that the two signal systems function independently in the process of brain regeneration, which accords with the fact that nou-darake was expressed earlier than DjwntA during brain regeneration. These observations suggest that the nou-darake/FGFR signal may be involved in brain rudiment formation during the early stage of head regeneration, and subsequently the DjwntA signal may function in A-P patterning of the brain rudiment. 相似文献
104.
Onishi Yuki Yamamura Yusuke Hosogi Misa Higashi Hiroshi Ogita Kiyokazu Kinjo Toshihiko Uno Kyosuke Yoneda Yukio Kuramoto Nobuyuki 《Neurochemical research》2022,47(9):2780-2792
Neurochemical Research - Trimethyltin (TMT) has been used as a cytotoxin to neurons rather than glial cells in the mammalian hippocampus. The systemic administration of TMT led to declined... 相似文献
105.
106.
Clathrin-mediated endocytic signals are required for the regeneration of, as well as homeostasis in, the planarian CNS 总被引:1,自引:0,他引:1
Planarians have a well-organized central nervous system (CNS), including a brain, and can regenerate the CNS from almost any portion of the body using pluripotent stem cells. In this study, to identify genes required for CNS regeneration, genes expressed in the regenerating CNS were systematically cloned and subjected to functional analysis. RNA interference (RNAi) of the planarian clathrin heavy chain (DjCHC) gene prevented CNS regeneration in the intermediate stage of regeneration prior to neural circuit formation. To analyze DjCHC gene function at the cellular level, we developed a functional analysis method using primary cultures of planarian neurons purified by fluorescence-activated cell sorting (FACS) after RNAi treatment. Using this method, we showed that the DjCHC gene was not essential for neural differentiation, but was required for neurite extension and maintenance, and that DjCHC-RNAi-treated neurons entered a TUNEL-positive apoptotic state. DjCHC-RNAi-treated uncut planarians showed brain atrophy, and the DjCHC-RNAi planarian phenotype was mimicked by RNAi-treated planarians of the mu-2 (micro2) gene, which is involved in endocytosis, but not the mu-1 (micro1) gene, which is involved in exocytosis. Thus, clathrin-mediated endocytic signals may be required for not only maintenance of neurons after synaptic formation, but also axonal extension at the early stage of neural differentiation. 相似文献
107.
Nishimura K Inoue T Yoshimoto K Taniguchi T Kitamura Y Agata K 《Journal of neurochemistry》2011,119(6):1217-1231
Planarians have robust regenerative ability dependent on X-ray-sensitive pluripotent stem cells, called neoblasts. Here, we report that planarians can regenerate dopaminergic neurons after selective degeneration of these neurons caused by treatment with a dopaminergic neurotoxin (6-hydroxydopamine; 6-OHDA). This suggests that planarians have a system to sense the degeneration of dopaminergic neurons and to recruit stem cells to produce dopaminergic neurons to recover brain morphology and function. We confirmed that X-ray-irradiated planarians do not regenerate brain dopaminergic neurons after 6-OHDA-induced lesioning, suggesting that newly generated dopaminergic neurons are indeed derived from pluripotent stem cells. However, we found that the majority of regenerated dopaminergic neurons were 5-bromo-2'-deoxyuridine-negative cells. Therefore, we carefully analyzed when proliferating stem cells became committed to become dopaminergic neurons during regeneration by a combination of 5-bromo-2'-deoxyuridine pulse-chase experiments, immunostaining/in situ hybridization, and 5-fluorouracil treatment. The results strongly suggested that G(2) -phase stem cells become committed to dopaminergic neurons in the mesenchymal space around the brain, after migration from the trunk region following S-phase. These new findings obtained from planarian regeneration provide hints about how to conduct cell-transplantation therapy for future regenerative medicine. 相似文献
108.
109.
Protein components of post‐synaptic density lattice,a backbone structure for type I excitatory synapses 下载免费PDF全文
Tatsuo Suzuki Kiyokazu Kametani Weiheng Guo Weidong Li 《Journal of neurochemistry》2018,144(4):390-407
110.
Binding activity of a putative central neurotransmitter, L-glutamic acid, was examined in the supernatant preparations solubilized from rat retinal membranes by Nonidet P-40. [3H]Glutamate binding activity increased linearly with increasing concentrations of the solubilized proteins up to 15 micrograms. The binding activity reached an equilibrium within 10 min at 2 degrees C, while increasing with incubation time up to 60 min at 30 degrees C. Addition of an excess of nonradioactive glutamate rapidly decreased the activity at 30 degrees C. Scatchard analysis revealed that the solubilized retinal binding activity consisted of a single component with a KD of 0.25 microM and a Bmax of 57.4 pmol/mg protein. The solubilized binding activity exhibited a stereospecificity and a structure selectivity to L-glutamate, and was abolished by quisqualate, L-glutamate diethyl ester, and DL-2-amino-3-phosphonopropionate. None of the other agonists and antagonists for the central excitatory amino acid receptors affected the binding activity. Reduction of incubation temperature from 30 degrees C to 2 degrees C resulted in a drastic attenuation of the binding activity due to decrement of the number of the apparent binding sites. Cation-exchange column chromatography revealed that unidentified radioactive material was in fact formed during the incubation of [3H]glutamate with the retinal preparations at 30 degrees C. These results suggest that retinal [3H]glutamate binding activity may be derived at least in part from the quisqualate-sensitive membranous enzyme with a stereospecific and structure-selective high affinity for the central neurotransmitter. 相似文献