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961.
962.
963.
L Missiaen J B Parys A F Weidema H Sipma S Vanlingen P De Smet G Callewaert H De Smedt 《The Journal of biological chemistry》1999,274(20):13748-13751
Calmodulin inhibits inositol 1,4,5-trisphosphate (IP3) binding to the IP3 receptor in both a Ca2+-dependent and a Ca2+-independent way. Because there are no functional data on the modulation of the IP3-induced Ca2+ release by calmodulin at various Ca2+ concentrations, we have studied how cytosolic Ca2+ and Sr2+ interfere with the effects of calmodulin on the IP3-induced Ca2+ release in permeabilized A7r5 cells. We now report that calmodulin inhibited Ca2+ release through the IP3 receptor with an IC50 of 4.6 microM if the cytosolic Ca2+ concentration was 0.3 microM or higher. This inhibition was particularly pronounced at low IP3 concentrations. In contrast, calmodulin did not affect IP3-induced Ca2+ release if the cytosolic Ca2+ concentration was below 0.3 microM. Calmodulin also inhibited Ca2+ release through the IP3 receptor in the presence of at least 10 microM Sr2+. We conclude that cytosolic Ca2+ or Sr2+ are absolutely required for the calmodulin-induced inhibition of the IP3-induced Ca2+ release and that this dependence represents the formation of the Ca2+/calmodulin or Sr2+/calmodulin complex. 相似文献
964.
Fire regimes have three inter-related components that can affect population dynamics: frequency, intensity and season. However,
there has been little effort to study the effects of any of these components on arbuscular mycorrhizas (AM). In order to examine
the long-term effects of fire frequency on AM colonization, the roots of Dillwynia retorta were examined at 32 sites supporting Hawkesbury Sandstone vegetation in the Sydney region of southeastern Australia. These
sites were representative of the broad-scale variability in fire frequencies with respect to the length and timing of inter-fire
intervals found in the Sydney region during the previous 30 years. The length of the shortest inter-fire interval was significantly
correlated with total AM colonization, and the length of the longest inter-fire interval was related to the arbuscular colonization.
The length of the most-recent inter-fire interval and the time since the shortest inter-fire interval were not related to
AM colonization in D. retorta. Furthermore, AM colonization was directly related to the local abundance of the host plant, indicating that the effects
of fire frequency on AM colonization are likely to occur indirectly via direct effects on the host plant. Canonical correspondence
analysis demonstrated that the presence and abundance of alternate potential hosts had no influence on mycotrophy in D. retorta. Thus, the impact of fire on D. retorta was probably the main factor influencing its mycorrhizal status in relation to fire history.
Accepted: 16 October 1998 相似文献
965.
Jean L. Santos Paulo R. Yamasaki Chung Man Chin Célio H. Takashi Fernando R. Pavan Clarice Q.F. Leite 《Bioorganic & medicinal chemistry》2009,17(11):3795-3799
New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3a–l) were evaluated against Mycobacterium tuberculosis H37Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis. 相似文献
966.
967.
968.
A frameshift mutation (2869insG) in the second transmembrane domain of the CFTR gene: identification, regional distribution, and clinical presentation. 下载免费PDF全文
969.
970.
It is widely believed that environmental variability is the main cause for fluctuations in commercially exploited small pelagic
fish populations around the world. Nevertheless, density-dependent factors also can drive population dynamics. In this paper,
we analyzed thirteen years of a relative abundance index of two clupeoids fish populations coexisting in the central-south
area off Chile, namely the common sardine, Strangomera bentincki, and anchovy, Engraulis ringens. We applied the classical diagnostic tools of time series analysis to the observed time-series. Also, the realized per capita
population growth rate was studied with the aim of detecting the feedback structure that is characterizing the population
dynamics of the two species. The analysis suggests that population fluctuations of the two species have an important density-dependent
component, displaying first-order (direct density-dependent) and second-order (delayed density-dependent) simultaneously.
The density-dependent component explained 70.5 and 55.6 % of the realized per capita population growth rate of common sardine
and anchovy, respectively. The deterministic skeleton model showed an asymptotic convergence to equilibrium density. In presence
of a stochastic environment, fluctuations were reproduced for the species showing a component of fluctuation with a period
of 4 year. The intrinsic dynamics of each species is typical of interacting species resulting from trophic interactions. It
is postulated that the second-order dynamics of S. bentincki and E. ringens in central-south Chile, may be the result from interactions with a specialist predator (the fishing fleet), interacting with
exogenous environmental factors. 相似文献