The Experts below are selected from a list of 927 Experts worldwide ranked by ideXlab platform
Toshihiko Yada - One of the best experts on this subject based on the ideXlab platform.
-
ORIGINAL ARTICLE Lack of TRPM2 Impaired Insulin Secretion and Glucose Metabolisms in Mice
2013Co-Authors: Kunitoshi Uchida, Toshihiko Yada, Yasuhiko Minokoshi, Katsuya Dezaki, Boldbaatar Damdindorj, Hitoshi Inada, Tetsuya Shiuchi, Yasuo Mori, Makoto TominagaAbstract:OBJECTIVE—TRPM2 is a Ca 2 �-permeable nonselective cation channel activated by adenosine dinucleotides. We previously demonstrated that TRPM2 is activated by coapplication of heat and intracellular cyclic adenosine 5�-diphosphoribose, which has been suggested to be involved in intracellular Ca 2 � increase in immunocytes and pancreatic �-cells. To clarify the involvement of TRPM2 in insulin secretion, we analyzed TRPM2 knockout (TRPM2-KO) mice. RESEARCH DESIGN AND METHODS—Oral and intraperitoneal glucose tolerance tests (OGTT and IPGTT) were performed in TRPM2-KO and wild-type mice. We also measured cytosolic free Ca 2 � in single pancreatic cells using fura-2 Microfluorometry and insulin secretion from pancreatic islets. RESULTS—Basal blood glucose levels were higher in TRPM2-KO mice than in wild-type mice without any difference i
-
Lack of TRPM2 impaired insulin secretion and glucose metabolisms in mice, Diabetes 60
2011Co-Authors: Kunitoshi Uchida, Toshihiko Yada, Yasuhiko Minokoshi, Katsuya Dezaki, Boldbaatar Damdindorj, Hitoshi Inada, Tetsuya Shiuchi, Yasuo Mori, Makoto TominagaAbstract:OBJECTIVE—TRPM2 is a Ca2-permeable nonselective cation channel activated by adenosine dinucleotides. We previously demonstrated that TRPM2 is activated by coapplication of heat and intracellular cyclic adenosine 5-diphosphoribose, which has been suggested to be involved in intracellular Ca2 increase in immunocytes and pancreatic -cells. To clarify the involvement of TRPM2 in insulin secretion, we analyzed TRPM2 knockout (TRPM2-KO) mice. RESEARCH DESIGN AND METHODS—Oral and intraperito-neal glucose tolerance tests (OGTT and IPGTT) were performed in TRPM2-KO and wild-type mice. We also measured cytosolic free Ca2 in single pancreatic cells using fura-2 Microfluorometry and insulin secretion from pancreatic islets. RESULTS—Basal blood glucose levels were higher in TRPM2-KO mice than in wild-type mice without any difference i
-
ghrelin raises ca2 i via ampk in hypothalamic arcuate nucleus npy neurons
Biochemical and Biophysical Research Communications, 2008Co-Authors: Daisuke Kohno, Hideyuki Sone, Yasuhiko Minokoshi, Toshihiko YadaAbstract:Ghrelin, an orexigenic hormone, directly activates neuropeptide (NPY) neurons in the hypothalamic arcuate nucleus (ARC), and thereby stimulates food intake. The hypothalamic level of AMP-activated protein kinase (AMPK), an intracellular energy sensor, is activated by peripheral and central administration of ghrelin. We examined whether ghrelin regulates AMPK activity in NPY neurons of the ARC. Single neurons were isolated from the ARC and cytosolic Ca(2+) concentration ([Ca(2+)](i)) was measured by fura-2 Microfluorometry, followed by immunocytochemical identification of NPY, phospho-AMPK, and phospho-acetyl-CoA carboxylase (ACC). Ghrelin and AICAR, an AMPK activator, increased [Ca(2+)](i) in neurons isolated from the ARC. The ghrelin-responsive neurons highly overlapped with AICAR-responsive neurons. The neurons that responded to both ghrelin and AICAR were primarily NPY-immunoreactive neurons. Treatment with ghrelin increased phosphorylation of AMPK and ACC. An AMPK inhibitor, compound C, suppressed ghrelin-induced [Ca(2+)](i) increases. These results demonstrate that ghrelin increases [Ca(2+)](i) via AMPK-mediated signaling in the ARC NPY neurons.
-
leptin suppresses ghrelin induced activation of neuropeptide y neurons in the arcuate nucleus via phosphatidylinositol 3 kinase and phosphodiesterase 3 mediated pathway
Endocrinology, 2007Co-Authors: Daisuke Kohno, Masanori Nakata, Fumihiko Maekawa, Ken Fujiwara, Yuko Maejima, Motoki Kuramochi, Takuya Shimazaki, Hideyuki Okano, Tatsushi Onaka, Toshihiko YadaAbstract:Neuropeptide Y (NPY) neurons in the hypothalamic arcuate nucleus (ARC) play a central role in stimulation of feeding. They sense and integrate peripheral and central signals, including ghrelin and leptin. However, the mechanisms of interaction of these hormones in NPY neurons are largely unknown. This study explored the interaction and underlying signaling cross talk between ghrelin and leptin in NPY neurons. Cytosolic Ca2+ concentration ([Ca2+]i) in single neurons isolated from ARC of adult rats was measured by fura-2 Microfluorometry. Ghrelin increased [Ca2+]i in 31% of ARC neurons. The [Ca2+]i increases were inhibited by blockers of phospholipase C, adenylate cyclase, and protein kinase A. Ghrelin-induced [Ca2+]i increases were suppressed by subsequent administration of leptin. Fifteen of 18 ghrelin-activated, leptin-suppressed neurons (83%) contained NPY. Leptin suppression of ghrelin responses was prevented by pretreatment with inhibitors of phosphatidylinositol 3-kinase and phosphodiesterase 3 (PDE3...
-
lowering glucose concentrations increases cytosolic ca2 in orexin neurons of the rat lateral hypothalamus
Neuroscience Letters, 2001Co-Authors: Shinji Muroya, Kazuhide Uramura, Takeshi Sakurai, Morikuni Takigawa, Toshihiko YadaAbstract:Abstract Orexin neurons are specifically localized in and around the lateral hypothalamus (LH), a feeding center. Intracerebroventricular administration of orexin-A and -B stimulates feeding as well as arousal. However, little is known regarding the regulators of the orexin neuron activity. The neurons that are activated under low glucose conditions, glucose-sensitive neurons, are located in the LH and have been implicated in the control of feeding. The present study investigated the effect of glucose on the single orexin neurons isolated from the rat LH, by measuring cytosolic Ca2+ concentration ([Ca2+]i) by fura-2 Microfluorometry followed by immunocytochemical staining with anti-orexin antiserum. A shift of glucose concentration form 8.3 to 2.8 mM in the superfusion solution increased [Ca2+]i in 13 out of 32 orexin-immunoreactive LH neurons. The results demonstrate that glucose-sensitive orexin neurons are present in the LH and that these neurons may play a role in linking the metabolic state in the body to the orexigenic, and could also, awakening signaling in the brain.
Tsuneyoshi Kuroiwa - One of the best experts on this subject based on the ideXlab platform.
-
aphidicolin uncouples the chloroplast division cycle from the mitotic cycle in the unicellular red alga cyanidioschyzon merolae
European Journal of Cell Biology, 1996Co-Authors: Ryuuichi Itoh, Kyoko Toda, Hideo Takahashi, Haruko Kuroiwa, Tsuneyoshi KuroiwaAbstract:: The unicellular red alga Cyanidioschyzon merolae possesses one chloroplast, one mitochondrion, and one cell nucleus. Since the division of these organelles and cytokinesis occur in a coordinated manner, mitosis and the organelle division cycles must be tightly coupled. We report here that aphidicolin, a specific inhibitor of DNA polymerase alpha, uncouples the chloroplast division cycle from the mitotic cycle. The effects of aphidicolin on C. merolae cells were examined by both epifluorescence and electron microscopy. When cells at the S phase in synchronous culture were treated with aphidicolin, mitosis and cytokinesis did not occur, while chloroplast division did. Moreover, both of the chloroplasts in these cells continued to divide and then generated four or more chloroplasts per cell. The inhibition of cell-nuclear DNA synthesis by aphidicolin was confirmed using Microfluorometry. In addition, Microfluorometry revealed that the total size and the amount of DNA in chloroplasts in aphidicolin-treated cells remained constant during uncoupled chloroplast division. As a result, the size and amount of DNA per chloroplast decreased stepwise during chloroplast division. Electron microscopic examination of aphidicolin-treated cells showed that the second division of chloroplasts uses a chloroplast-dividing ring similar to that in cells undergoing normal chloroplast division. These results suggest that chloroplast division by the dividing ring is free from a checkpoint control that inhibits the progression of mitosis and cytokinesis in the absence of the completion of cell-nuclear DNA synthesis, and also that chloroplasts lack a checkpoint control mechanism that inhibits its division without growth or DNA synthesis of itself.
-
aphidicolin uncouples the chloroplast division cycle from the mitotic cycle in the unicellular red alga cyanidioschyzon merolae
European Journal of Cell Biology, 1996Co-Authors: Ryuuichi Itoh, Kyoko Toda, Hideo Takahashi, Haruko Kuroiwa, Tsuneyoshi KuroiwaAbstract:: The unicellular red alga Cyanidioschyzon merolae possesses one chloroplast, one mitochondrion, and one cell nucleus. Since the division of these organelles and cytokinesis occur in a coordinated manner, mitosis and the organelle division cycles must be tightly coupled. We report here that aphidicolin, a specific inhibitor of DNA polymerase alpha, uncouples the chloroplast division cycle from the mitotic cycle. The effects of aphidicolin on C. merolae cells were examined by both epifluorescence and electron microscopy. When cells at the S phase in synchronous culture were treated with aphidicolin, mitosis and cytokinesis did not occur, while chloroplast division did. Moreover, both of the chloroplasts in these cells continued to divide and then generated four or more chloroplasts per cell. The inhibition of cell-nuclear DNA synthesis by aphidicolin was confirmed using Microfluorometry. In addition, Microfluorometry revealed that the total size and the amount of DNA in chloroplasts in aphidicolin-treated cells remained constant during uncoupled chloroplast division. As a result, the size and amount of DNA per chloroplast decreased stepwise during chloroplast division. Electron microscopic examination of aphidicolin-treated cells showed that the second division of chloroplasts uses a chloroplast-dividing ring similar to that in cells undergoing normal chloroplast division. These results suggest that chloroplast division by the dividing ring is free from a checkpoint control that inhibits the progression of mitosis and cytokinesis in the absence of the completion of cell-nuclear DNA synthesis, and also that chloroplasts lack a checkpoint control mechanism that inhibits its division without growth or DNA synthesis of itself.
Jie Liu - One of the best experts on this subject based on the ideXlab platform.
-
Alpha-latrotoxin triggers extracellular Ca2+-dependent exocytosis and sensitizes fusion machinery in endocrine cells
Acta biochimica et biophysica Sinica, 2006Co-Authors: Ping Zhao, Jie LiuAbstract:alpha-Latrotoxin from the venom of black widow spider induces and augments neurotransmitter and hormone release by way of extracellular Ca(2+) influx and cellular signal transduction pathways. By using whole cell current and capacitance recording, the photolysis of caged Ca(2+), and Ca(2+) Microfluorometry and amperometry, we investigated the stimulating effect and mechanism of alpha-latrotoxin on exocytosis in rat pancreatic beta cells, LbetaT2 cells and latrophilin plasmid-transfected INS-1 cells. Our data indicated that: (1) alpha-latrotoxin increased cytosolic Ca(2+) concentration through the formation of cation-permitting pores and subsequent Ca(2+) influx with the presence of extracellular Ca(2+); (2) alpha-latrotoxin stimulated exocytosis in normal bath solution and its stimulating effect on secretion was eradicated in Ca(2+)-free bath solution; and (3) alpha-latrotoxin sensitized the molecular machinery of fusion through activation of protein kinase C and increased the response of cells to Ca(2+) photolyzed by a flash of ultraviolet light. In summary, alpha-latrotoxin induced exocytosis by way of Ca(2+) influx and accelerated vesicle fusion by the sensitization of fusion machinery.
-
Alpha-latrotoxin Triggers Extracellular Ca2+-dependent Exocytosis and Sensitizes Fusion Machinery in Endocrine Cells
2005Co-Authors: Ping Zhao, Jie LiuAbstract:Abstract α from the venom of black widow spider induces and augments neurotransmitter and hormone release by way of extracellular Ca2+ influx and cellular signal transduction pathways. By using whole cell current and capacitance recording, the photolysis of caged Ca2+, and Ca2+ Microfluorometry and amperometry, we investigated the stimulating effect and mechanism of α-latrotoxin on exocytosis in rat pancreatic β cells, LβT2 cells and latrophilin plasmid-transfected I α latrotoxin increased cytosolic Ca2+ concentration through the formation of cation-permitting pores and sub-sequent Ca2+ influx with the presence of extracellular Ca2+ α latrotoxin stimulated exocytosis in normal bath solution and its stimulating effect on secretion was eradicated in Ca2+-free bath solution; and α latrotoxin sensitized the molecular machinery of fusion through activation of protein kinase C and increased the response of cells to Ca2+ photolysed by a flash of ultraviolet α latrotoxin induced exocytosis by way of Ca2+ influx and accelerated vesicle fusion by the sensitization of fusion machinery. Key words α-latrotoxin; exocytosis; calcium; Ca2+-sensitivity of fusion; protein kinase C (PKC); capacitance measurement; amperometr
Ryuuichi Itoh - One of the best experts on this subject based on the ideXlab platform.
-
aphidicolin uncouples the chloroplast division cycle from the mitotic cycle in the unicellular red alga cyanidioschyzon merolae
European Journal of Cell Biology, 1996Co-Authors: Ryuuichi Itoh, Kyoko Toda, Hideo Takahashi, Haruko Kuroiwa, Tsuneyoshi KuroiwaAbstract:: The unicellular red alga Cyanidioschyzon merolae possesses one chloroplast, one mitochondrion, and one cell nucleus. Since the division of these organelles and cytokinesis occur in a coordinated manner, mitosis and the organelle division cycles must be tightly coupled. We report here that aphidicolin, a specific inhibitor of DNA polymerase alpha, uncouples the chloroplast division cycle from the mitotic cycle. The effects of aphidicolin on C. merolae cells were examined by both epifluorescence and electron microscopy. When cells at the S phase in synchronous culture were treated with aphidicolin, mitosis and cytokinesis did not occur, while chloroplast division did. Moreover, both of the chloroplasts in these cells continued to divide and then generated four or more chloroplasts per cell. The inhibition of cell-nuclear DNA synthesis by aphidicolin was confirmed using Microfluorometry. In addition, Microfluorometry revealed that the total size and the amount of DNA in chloroplasts in aphidicolin-treated cells remained constant during uncoupled chloroplast division. As a result, the size and amount of DNA per chloroplast decreased stepwise during chloroplast division. Electron microscopic examination of aphidicolin-treated cells showed that the second division of chloroplasts uses a chloroplast-dividing ring similar to that in cells undergoing normal chloroplast division. These results suggest that chloroplast division by the dividing ring is free from a checkpoint control that inhibits the progression of mitosis and cytokinesis in the absence of the completion of cell-nuclear DNA synthesis, and also that chloroplasts lack a checkpoint control mechanism that inhibits its division without growth or DNA synthesis of itself.
-
aphidicolin uncouples the chloroplast division cycle from the mitotic cycle in the unicellular red alga cyanidioschyzon merolae
European Journal of Cell Biology, 1996Co-Authors: Ryuuichi Itoh, Kyoko Toda, Hideo Takahashi, Haruko Kuroiwa, Tsuneyoshi KuroiwaAbstract:: The unicellular red alga Cyanidioschyzon merolae possesses one chloroplast, one mitochondrion, and one cell nucleus. Since the division of these organelles and cytokinesis occur in a coordinated manner, mitosis and the organelle division cycles must be tightly coupled. We report here that aphidicolin, a specific inhibitor of DNA polymerase alpha, uncouples the chloroplast division cycle from the mitotic cycle. The effects of aphidicolin on C. merolae cells were examined by both epifluorescence and electron microscopy. When cells at the S phase in synchronous culture were treated with aphidicolin, mitosis and cytokinesis did not occur, while chloroplast division did. Moreover, both of the chloroplasts in these cells continued to divide and then generated four or more chloroplasts per cell. The inhibition of cell-nuclear DNA synthesis by aphidicolin was confirmed using Microfluorometry. In addition, Microfluorometry revealed that the total size and the amount of DNA in chloroplasts in aphidicolin-treated cells remained constant during uncoupled chloroplast division. As a result, the size and amount of DNA per chloroplast decreased stepwise during chloroplast division. Electron microscopic examination of aphidicolin-treated cells showed that the second division of chloroplasts uses a chloroplast-dividing ring similar to that in cells undergoing normal chloroplast division. These results suggest that chloroplast division by the dividing ring is free from a checkpoint control that inhibits the progression of mitosis and cytokinesis in the absence of the completion of cell-nuclear DNA synthesis, and also that chloroplasts lack a checkpoint control mechanism that inhibits its division without growth or DNA synthesis of itself.
Ping Zhao - One of the best experts on this subject based on the ideXlab platform.
-
Alpha-latrotoxin triggers extracellular Ca2+-dependent exocytosis and sensitizes fusion machinery in endocrine cells
Acta biochimica et biophysica Sinica, 2006Co-Authors: Ping Zhao, Jie LiuAbstract:alpha-Latrotoxin from the venom of black widow spider induces and augments neurotransmitter and hormone release by way of extracellular Ca(2+) influx and cellular signal transduction pathways. By using whole cell current and capacitance recording, the photolysis of caged Ca(2+), and Ca(2+) Microfluorometry and amperometry, we investigated the stimulating effect and mechanism of alpha-latrotoxin on exocytosis in rat pancreatic beta cells, LbetaT2 cells and latrophilin plasmid-transfected INS-1 cells. Our data indicated that: (1) alpha-latrotoxin increased cytosolic Ca(2+) concentration through the formation of cation-permitting pores and subsequent Ca(2+) influx with the presence of extracellular Ca(2+); (2) alpha-latrotoxin stimulated exocytosis in normal bath solution and its stimulating effect on secretion was eradicated in Ca(2+)-free bath solution; and (3) alpha-latrotoxin sensitized the molecular machinery of fusion through activation of protein kinase C and increased the response of cells to Ca(2+) photolyzed by a flash of ultraviolet light. In summary, alpha-latrotoxin induced exocytosis by way of Ca(2+) influx and accelerated vesicle fusion by the sensitization of fusion machinery.
-
Alpha-latrotoxin Triggers Extracellular Ca2+-dependent Exocytosis and Sensitizes Fusion Machinery in Endocrine Cells
2005Co-Authors: Ping Zhao, Jie LiuAbstract:Abstract α from the venom of black widow spider induces and augments neurotransmitter and hormone release by way of extracellular Ca2+ influx and cellular signal transduction pathways. By using whole cell current and capacitance recording, the photolysis of caged Ca2+, and Ca2+ Microfluorometry and amperometry, we investigated the stimulating effect and mechanism of α-latrotoxin on exocytosis in rat pancreatic β cells, LβT2 cells and latrophilin plasmid-transfected I α latrotoxin increased cytosolic Ca2+ concentration through the formation of cation-permitting pores and sub-sequent Ca2+ influx with the presence of extracellular Ca2+ α latrotoxin stimulated exocytosis in normal bath solution and its stimulating effect on secretion was eradicated in Ca2+-free bath solution; and α latrotoxin sensitized the molecular machinery of fusion through activation of protein kinase C and increased the response of cells to Ca2+ photolysed by a flash of ultraviolet α latrotoxin induced exocytosis by way of Ca2+ influx and accelerated vesicle fusion by the sensitization of fusion machinery. Key words α-latrotoxin; exocytosis; calcium; Ca2+-sensitivity of fusion; protein kinase C (PKC); capacitance measurement; amperometr