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Calcium Independent (calcium + independent)
Selected AbstractsRegulation of neuronal excitability in Drosophila by constitutively active CaMKIIDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2002Demian Park Abstract The ability of calcium/calmodulin-dependent protein kinase II (CaMKII) to become calcium independent after autophosphorylation makes this enzyme a temporal marker of neuronal activity. Here we show that the calcium-independent form of CaMKII has unique effects on larval viability, locomotion, and neuronal excitability in Drosophila. Expression of constitutively active T287D, but not calcium-dependent T287A, mutant CaMKII in Drosophila neurons resulted in decreased viability, behavioral defects, and failure of action potential propagation. The actions of T287D may be mediated, at least in part, by increased potassium conductances. Expression of T287D CaMKII also stimulated an increase in the number of boutons at the larval neuromuscular junction, but did not affect the mechanics of release. This study defines a role for autophosphorylation of CaMKII in the regulation of multiple neuronal functions including the intrinsic properties of neurons. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 24,42, 2002 [source] Synaptic stimulation of nicotinic receptors in rat sympathetic ganglia is followed by slow activation of postsynaptic potassium or chloride conductancesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2000Oscar Sacchi Abstract Two slow currents have been described in rat sympathetic neurons during and after tetanization of the whole preganglionic input. Both effects are mediated by nicotinic receptors activated by native acetylcholine (ACh). A first current, indicated as IAHPsyn, is calcium dependent and voltage independent, and is consistent with an IAHP -type potassium current sustained by calcium ions accompanying the nicotinic synaptic current. The conductance activated by a standard synaptic train was ,,3.6 nS per neuron; it was detected in isolation in 14 out of a 52-neuron sample. A novel current, IADPsyn, was described in 42/52 of the sample as a post-tetanic inward current, which increased in amplitude with increasing membrane potential negativity and exhibited a null-point close to the holding potential and the cell momentary chloride equilibrium potential. IADPsyn developed during synaptic stimulation and decayed thereafter according to a single exponential (mean ,,= 148.5 ms) in 18 neurons or according to a two-exponential time course (, = 51.8 and 364.9 ms, respectively) in 19 different neurons. The mean peak conductance activated was ,,20 nS per neuron. IADPsyn was calcium independent, it was affected by internal and external chloride concentration, but was insensitive to specific blockers (anthracene-9-carboxylic acid, 9AC) of the chloride channels open in the resting neuron. It is suggested that gADPsyn represents a specific chloride conductance activatable by intense nicotinic stimulation; in some neurons it is even associated with single excitatory postsynaptic potentials (EPSCs). Both IAHP and IADPsyn are apparently devoted to reduce neuronal excitability during and after intense synaptic stimulation. [source] The transcriptional response to alkaline pH in Saccharomyces cerevisiae: evidence for calcium-mediated signallingMOLECULAR MICROBIOLOGY, Issue 5 2002Raquel Serrano Summary The short-time transcriptional response of yeast cells to a mild increase in external pH (7.6) has been investigated using DNA microarrays. A total of 150 genes increased their mRNA level at least twofold within 45 min. Alkalinization resulted in the repression of 232 genes. The response of four upregulated genes, ENA1 (encoding a Na+ -ATPase also induced by saline stress) and PHO84, PHO89 and PHO12 (encoding genes upregulated by phosphate starvation), was characterized further. The alkaline response of ENA1 was not affected by mutation of relevant genes involved in osmotic or oxidative signalling, but was decreased in calcineurin and rim101 mutants. Mapping of the ENA1 promoter revealed two pH-responsive regions. The response of the upstream region was fully abolished by the drug FK506 or mutation of CRZ1 (a transcription factor activated by calcium/calcineurin), whereas the response of the downstream region was essentially calcium independent. PHO84 and PHO12 responses were unaffected in crz1 cells, but required the presence of Pho2 and Pho4. In contrast, part of the alkali-induced expression of PHO89 was maintained in pho4 or pho2 cells, but was fully abolished in a crz1 strain or in the presence of FK506. Heterologous promoters carrying the minimal calcineurin-dependent response elements found in ENA1 or FKS2 were able to drive alkaline pH-induced expression. These results demonstrate that the transcriptional response to alkaline pH involves different signalling mechanisms, and that calcium signalling is a relevant component of this response. [source] Purification and Characterization of Thermostable ,-Amylase from a Newly Isolated Thermophilic Bacillus stearothermophilus GRE 1ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2005S.M. Zakir Hossain A thermophilic bacterium, Bacillus stearothermophilus GRE 1, isolated from an Ethiopian hyperthermal spring produced a thermostable ,-amylase. Enzyme production in shake flask experiments while using optimum nutrient supplements and environmental conditions was 2.35 U/ml. Under optimized conditions in a bioreactor, 5-6 fold higher enzyme activity was obtained than that of a shake flask. Gel filtration chromatography yielded a purification factor of 33.62-fold and a recovery of 46.52%. The optimum temperature for activity was determined to be 60-70d,C and optimum pH was in the range of 5.5-6.0. The enzyme maintained 50% of its original activity after 45 minutes of incubation at 80d,C, and is stable at pH values of 5.0-9.0. Enzyme activity was strongly inhibited by Cu2+, Zn2+ and Fe2+. The enzyme is calcium independent and 94% and 86% relative activities were displayed with low concentrations of Co2+ and Mg2+, respectively. [source] | ||||||||||