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91.
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Suhita Nadkarni Thomas M. Bartol Terrence J. Sejnowski Herbert Levine 《PLoS computational biology》2010,6(11)
We study local calcium dynamics leading to a vesicle fusion in a stochastic, and spatially explicit, biophysical model of the CA3-CA1 presynaptic bouton. The kinetic model for vesicle release has two calcium sensors, a sensor for fast synchronous release that lasts a few tens of milliseconds and a separate sensor for slow asynchronous release that lasts a few hundred milliseconds. A wide range of data can be accounted for consistently only when a refractory period lasting a few milliseconds between releases is included. The inclusion of a second sensor for asynchronous release with a slow unbinding site, and thereby a long memory, affects short-term plasticity by facilitating release. Our simulations also reveal a third time scale of vesicle release that is correlated with the stimulus and is distinct from the fast and the slow releases. In these detailed Monte Carlo simulations all three time scales of vesicle release are insensitive to the spatial details of the synaptic ultrastructure. Furthermore, our simulations allow us to identify features of synaptic transmission that are universal and those that are modulated by structure. 相似文献
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Peter G. Kennedy Jesse L. Schouboe Rachel H. Rogers Marjorie G. Weber Nalini M. Nadkarni 《Microbial ecology》2010,59(2):214-220
The ecological importance of microbial symbioses in terrestrial soils is widely recognized, but their role in soils that accumulate
in forest canopies is almost entirely unknown. To address this gap, this study investigated the Frankia–Alnus rubra symbiosis in canopy and forest floor roots at Olympic National Park, WA, USA. Sixteen mature A. rubra trees were surveyed and Frankia genetic diversity in canopy and forest floor nodules was assessed with sequence-based nifH analyses. A seedling bioassay experiment was conducted to determine Frankia propagule availability in canopy and forest floor soils. Total soil nitrogen from both environments was also quantified.
Nodules were present in the canopies of nine of the 16 trees sampled. Across the study area, Frankia canopy and forest floor assemblages were similar, with both habitats containing the same two genotypes. The composition of
forest floor and canopy genotypes on the same tree was not always identical, however, suggesting that dispersal was not a
strictly local phenomenon. Frankia seedling colonization was similar in canopy soils regardless of the presence of nodules as well as in forest floor soils,
indicating that dispersal was not likely to be a major limiting factor. The total soil nitrogen of canopy soils was higher
than that of forest floor soils, but the presence of Frankia nodules in canopy soils did not significantly alter soil nitrogen levels. Overall, this study indicates that the Frankia–A. rubra symbiosis is similar in canopy and forest floor environments. Because canopy roots are exposed to different environmental
conditions within very small spatial areas and because those areas can be easily manipulated (e.g., fertilizer or watering
treatments), they present microbial ecologists with a unique arena to examine root–microbe interactions. 相似文献
96.
Phosphatidylinositol-3 phosphatase myotubularin-related protein 6 negatively regulates CD4 T cells 下载免费PDF全文
Srivastava S Ko K Choudhury P Li Z Johnson AK Nadkarni V Unutmaz D Coetzee WA Skolnik EY 《Molecular and cellular biology》2006,26(15):5595-5602
Intracellular Ca2+ levels rapidly rise following cross-linking of the T-cell receptor (TCR) and function as a critical intracellular second messenger in T-cell activation. It has been relatively under appreciated that K+ channels play an important role in Ca2+ influx into T lymphocytes by helping to maintain a negative membrane potential which provides an electrochemical gradient to drive Ca2+ influx. Here we show that the Ca2+-activated K+ channel, KCa3.1, which is critical for Ca2+ influx in reactivated naive T cells and central memory T cells, requires phosphatidylinositol-3 phosphatase [PI(3)P] for activation and is inhibited by the PI(3)P phosphatase myotubularin-related protein 6 (MTMR6). Moreover, by inhibiting KCa3.1, MTMR6 functions as a negative regulator of Ca2+ influx and proliferation of reactivated human CD4 T cells. These findings point to a new and unexpected role for PI(3)P and the PI(3)P phosphatase MTMR6 in the regulation of Ca2+ influx in activated CD4 T cells and suggest that MTMR6 plays a critical role in setting a minimum threshold for a stimulus to activate a T cell. 相似文献
97.
Mukherjee MB Nadkarni AH Gorakshakar AC Ghosh K Mohanty D Colah RB 《Indian journal of human genetics》2010,16(3):154-158
BACKGROUND:
Sickle cell-β thalassemia (HbS-β thalassemia) is a sickling disorder of varying severity, which results from compound heterozygosity for sickle cell trait and β thalassemia trait. The present study was undertaken to determine the genetic factors responsible for the clinical variability of HbS-β thalassemia patients from western India.MATERIALS AND METHODS:
Twenty-one HbS-β thalassemia cases with variable clinical manifestations were investigated. The α and β globin gene clusters were studied by molecular analysis.RESULTS:
Thirteen patients showed milder clinical presentation as against eight patients who had severe clinical manifestations. Four β thalassemia mutations were identified: IVS 1-5 (G→C), codon 15 (G→A), codon 30 (G→C) and codon 8/9 (+G). α thalassemia and XmnI polymorphism in homozygous condition (+/+) were found to be common among the milder cases. The βS chromosomes were linked to the typical Arab-Indian haplotype (#31). Framework (FW) linkage studies showed that four β thalassemia mutations were associated with different β globin gene frameworks. Linkage of codon 15 (G→A) mutation to FW2 is being observed for the first time.CONCLUSION:
The phenotypic expression of HbS-β thalassemia is not uniformly mild and α thalassemia and XmnI polymorphism in homozygous condition (+/+) are additional genetic factors modulating the severity of the disease in the Indian subcontinent. 相似文献98.
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Jian-Wei Liu Shau-Fu Li Chin-Ting Wu Iván A. Valdespino Jia-Fang Ho Yeh-Hua Wu Ho-Ming Chang Te-Yu Guu Mei-Fang Kao Clive Chesson Sauren Das Hank Oppenheimer Ane Bakutis Peter Saenger Noris Salazar Allen Jean W. H. Yong Bayu Adjie Ruth Kiew Nalini Nadkarni Chun-Lin Huang Peter Chesson Chiou-Rong Sheue 《American journal of botany》2020,107(4):562-576
100.
Khushnooma Italia Farah Jijina Rashid Merchant Suchitra Swaminathan Anita Nadkarni Maya Gupta Kanjaksha Ghosh Roshan Colah 《Indian journal of human genetics》2013,19(2):251-258