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Ammar H. Hawasli Della Koovakkattu Kanehiro Hayashi Anne E. Anderson Craig M. Powell Christopher M. Sinton James A. Bibb Donald C. Cooper 《PloS one》2009,4(6)
Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase that has been implicated in learning, synaptic plasticity, neurotransmission, and numerous neurological disorders. We previously showed that conditional loss of Cdk5 in adult mice enhanced hippocampal learning and plasticity via modulation of calpain-mediated N-methyl-D-aspartic acid receptor (NMDAR) degradation. In the present study, we characterize the enhanced synaptic plasticity and examine the effects of long-term Cdk5 loss on hippocampal excitability in adult mice. Field excitatory post-synaptic potentials (fEPSPs) from the Schaffer collateral CA1 subregion of the hippocampus (SC/CA1) reveal that loss of Cdk5 altered theta burst topography and enhanced post-tetanic potentiation. Since Cdk5 governs NMDAR NR2B subunit levels, we investigated the effects of long-term Cdk5 knockout on hippocampal neuronal excitability by measuring NMDAR-mediated fEPSP magnitudes and population-spike thresholds. Long-term loss of Cdk5 led to increased Mg2+-sensitive potentials and a lower threshold for epileptiform activity and seizures. Biochemical analyses were performed to better understand the role of Cdk5 in seizures. Induced-seizures in wild-type animals led to elevated amounts of p25, the Cdk5-activating cofactor. Long-term, but not acute, loss of Cdk5 led to decreased p25 levels, suggesting that Cdk5/p25 may be activated as a homeostatic mechanism to attenuate epileptiform activity. These findings indicate that Cdk5 regulates synaptic plasticity, controls neuronal and behavioral stimulus-induced excitability and may be a novel pharmacological target for cognitive and anticonvulsant therapies. 相似文献
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L. W. Sinton 《Hydrobiologia》1984,111(3):161-169
A quantitative evaluation of stream temperature alterations due to a commercial forest harvesting practice and a research
treatment is presented. Summer maximum stream temperatures averaged 1 ° C higher in the commercial clearcut and 9 °C higher
in the clearcut-herbicided watershed than in the forested control. The largest average monthly temperature increase on the
commercial clearcut (2.2 °C) occurred during April; on the clearcut-herbicided basin it occurred during June (10.5 °C). Significant
changes in stream temperature were observed on both watersheds as early as February and as late as November.
Changes in minimum stream temperatures are presented in detail along with the impact on diel temperature fluctuations. Changes
in the stream temperature regimes of the clearcut watersheds from the headwaters to the mouth of the watersheds are also given.
Potential impacts of the stream temperature alterations on aquatic ecosystems are summarized in relation to stress limits
for brook trout and other organisms.
School of Forest Resources, Pennsylvania State University, University Park, PA 16802, U.S.A.
USDA Forest Service, Northeastern Forest Experiment Station, University Park, PA 16802, U.S.A. 相似文献
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Javier F Chaparro-Riggers Bernard LW Loo Karen M Polizzi Phillip R Gibbs Xiao-Song Tang Mark J Nelson Andreas S Bommarius 《BMC biotechnology》2007,7(1):77