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LTD induction suppresses LTP-induced hippocampal adult neurogenesis
Chun, Sung Kun,Sun, Woong,Jung, Min Whan Lippincott Williams Wilkins, Inc. 2009 NEUROREPORT - Vol.20 No.14
Neurogenesis persists in certain adult brain regions including the dentate gyrus. Recent studies have shown that long-term potentiation (LTP) induction in the afferent pathway enhances adult neurogenesis in the dentate gyrus. Here, we investigated whether long-term depression (LTD) induction also affects adult neurogenesis. We induced LTD in the dentate gyrus in one hemisphere and compared the amount of progenitor proliferation with that in the other hemisphere. Unlike LTP induction, LTD induction per se did not affect progenitor cell proliferation in the dentate gyrus. However, when LTD was induced a day before LTP induction, neuronal progenitor cell proliferation facilitated by LTP induction was markedly blunted. These results show that two forms of synaptic plasticity, LTP and LTD, differentially influence hippocampal adult neurogenesis.
Chun, Chi-Sung,Kim, Ji-Hyun,Lim, Hyun-Ae,Sohn, Ho-Yong,Son, Kun-Ho,Kim, Young-Kyoon,Kim, Jong-Sang,Kwon, Chong-Suk The Korean Society of Food Science and Nutrition 2004 Preventive Nutrition and Food Science Vol.9 No.2
The free radical scavenging activities and the protective effects of Rhus javanica extracts against oxidative damage induced by reactive oxygen species (ROS) were investigated. n-Hexane, ethyl acetate and water fractions were prepared from a methanol extract. DPPH radical, superoxide anion and hydroxyl radical scavenging activities were estimated. Intracellular ROS formation was quantified using fluorescent probes, 2', 7'-dichlorofluorescin diacetate (DCFH-DA) for hydroxyl radical and dihydroethidium (DHE) for superoxide anion. The oxidative DNA damage was investigated by the comet assay in HepG$_2$ cells exposed either to $H_2O$$_2$ or to menadione. The highest $IC_{50}$/ values for DPPH radical scavenging activity was found in the ethyl acetate fraction with a value of 5.38 $\mu\textrm{g}$/mL. Cells pretreated with $\geq$ 1 $\mu\textrm{g}$/mL of the ethyl acetate extract had significantly increased cell viability compared to control cells, which were not pretreated with the extract. Intracellular ROS formation and DNA damage in HepG$_2$ cells, which were pretreated with the various concentrations of Rhus javanica ethyl acetate extract and then incubated either with $H_2O$$_2$ or with menadione, reduced in a dose-dependent manner. These findings suggest that Rhus javanica might have biologically active components which have strong protective effects against ROS induced oxidative damages to the biomolecules, such as cell membranes and DNA.
Role of Ca<SUP>2</SUP> in the Stimulation of Glucose Transport by Insulin in Adipocytes
Sung-Hoe Chang,Yeon Jin Jang,Kun-Koo Park,Ghi Su Kim,Hee Jeong Ryu,Chun Sik Park 대한생리학회-대한약리학회 1999 The Korean Journal of Physiology & Pharmacology Vol.3 No.3
<P> We investigated the role of Ca<SUP>2</SUP> and protein kinases/phosphatases in the stimulatory effect of insulin on glucose transport. In isolated rat adipocytes, the simple omission of CaCl<SUB>2</SUB> from the incubation medium significantly reduced, but did not abolish, insulin-stimulated 2-deoxy glucose (2-DG) uptake. Pre-loading adipocytes with intracellular Ca<SUP>2</SUP> chelator, 5,5 -dimethyl bis (<I>o</I>-aminophenoxy)ethane-N,N,N N tetraacetic acetoxymethyl ester (5,5 -dimethyl BAPTA/AM) completely blocked the stimulation. Insulin raised intracellular Ca<SUP>2</SUP> concentration ([Ca<SUP>2</SUP>]<I><SUB>i</SUB></I>) about 1.7 times the basal level of 72⁑5 nM, and 5,5 -dimethyl BAPTA/AM kept it constant at the basal level. This correlation between insulin-induced increases in 2-DG uptake and [Ca<SUP>2</SUP>]<I><SUB>i</SUB></I> indicates that the elevation of [Ca<SUP>2</SUP>]<I><SUB>i</SUB></I> may be prerequisite for the stimulation of glucose transport. Studies with inhibitors (ML-9, KN-62, cyclosporin A) of Ca<SUP>2</SUP>-calmodulin dependent protein kinases/phosphatases also indicate an involvement of intracellular Ca<SUP>2</SUP>. Additional studies with okadaic acid and calyculin A, protein phosphatase-1 (PP-1) and 2A (PP-2A) inhibitors, indicate an involvement of PP-1 in insulin action on 2-DG uptake. These results indicate an involvement of Ca<SUP>2</SUP>-dependent signaling pathway in insulin action on glucose transport.