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791.
Niels Tommerup Else Mortensen Morten H. Nielsen Rolf -D. Wegner Detlev Schindler Margareta Mikkelsen 《Human genetics》1993,92(4):339-346
A high frequency of spontaneous chromosomal breakage, endomitosis, endoreduplication and hypersensitivity toward both the alkylating agent Trenimon and the radiomimetric drug bleomycin was observed in phytohemagglutinin-stimulated peripheral lymphocytes from a girl with craniosynostosis, microcephaly, ptosis, bird-like facies, and moderate mental retardation. We also observed abnormal chromosomal spiralization and some aspects of abnormal cellular division. Several fruitless attempts were made to establish a cell line. The parents were consanguineous, supporting the existence of a new, rare, autosomal, recessive condition in man. The mutation might involve a gene involved in DNA repair and/or regulation of the mitotic cycle. 相似文献
792.
The new concept of a nonequilibrium parameter P is applied to a reduced Brusselator, considered as a kinetic model for cellular processes. The reduction corresponds to omitting a monomolecular reaction. The deviation from equilibrium is due to a fixed nonequilibrium value of an extracellular concentration B, responsible for energizing and determining the steady-state value of the overall chemical affinity ?. The value of ? is insensitive to different steady states possible for a given set of rate constants. In contrast, the parameter P is state dependent. In particular, it may jump together with state variables. Two limiting cases of high ? are investigated, B→ 0 and B→ 1. In the first case P grows monotonically with ?. In the second case there is always a steady state solution with P→ 0. The physical interpretation of this effect of “equilibrium far from equilibrium” reveals the real predictive power of the parameter P. Relaxation regimes are investigated for a doubly reduced Brusselator. Both P and ? are in general time dependent and have jumps in their time derivatives. The canonical form of P is compared with the noncanonical one in the context of robustness of the new concept with respect to incomplete information about the system studied. These forms of P are different in relaxation to a nonequilibrium state and coincide in relaxation to an equilibrium state. 相似文献
793.
V P Pastushenko H Schindler 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1997,352(1349):39
A parameter-free method is presented for the level detection in ion channel records via recovery of step wise current changes. No assumptions about ion channel mechanism are made. The primary detection of the transitions is made by statistical filtering the data using the Student''s t-test. The event currents are calculated as the average value of the current between two adjacent transitions. An optimal ideal trace is found by maximization of a likelihood function. The distribution of event currents recovered from the raw data is then analysed, again by using the Student''s t-test, for their grouping into separate statistical ensembles, defining current levels. The method is subjected to rigorous test using simulated data, and is compared with several other methods. It produces the levels of channel current, their noise amplitudes and distributions of dwell times, the desired information for constructing the channel mechanism. 相似文献
794.
795.
The Effects of Stocking and Removal of a Nonnative Salmonid on the Plankton of an Alpine Lake 总被引:2,自引:1,他引:1
Bighorn Lake, a fishless alpine lake, was stocked with nonnative brook trout, Salvelinus fontinalis, in 1965 and 1966. The newly introduced trout rapidly eliminated the large crustaceans Hesperodiaptomus arcticus and Daphnia middendorffiana from the plankton. In July 1997, we began to remove the fish using gill nets. The population comprised 261 fish that averaged
214 g in wet weight and 273 mm in fork length. Thereafter, zooplankton abundance increased within weeks. Early increases were
caused by the maturation of Diacyclops bicuspidatus, few of which reached copepodid stages before the removal of the fish because of fish predation. Daphnia middendorffiana, absent when fish were present, reappeared in 1998. Hesperodiaptomus arcticus, which had been eliminated by the stocked fish, did not return. The proportion of large zooplankton increased after fish
removal, but their overall biomass did not change. Algal biomass was low and variable throughout the 1990s and correlated
with water temperature but not with nutrient concentrations or grazer densities. Diatoms were the most abundant algal taxon
in the lake, followed by Dinophyceae. Chrysophyceans and cryptophyceans were eliminated after the fish were removed. Chlorophyll
a concentrations were unaffected. Gill netting is a viable fish eradication technique for smaller (less than 10 ha), shallow
(less than 10 m deep) lakes that lack habitable inflows and outflows or other sensitive species. Further work is required
to define appropriate removal methods for larger lakes and watersheds.
Received 30 May 2000; Accepted 14 November 2000. 相似文献
796.
797.
798.
Schindler D Grebhan K Albrecht A Schönborn J Kohnle U 《International journal of biometeorology》2012,56(1):57-69
Data on storm damage attributed to the two high-impact winter storms ‘Wiebke’ (28 February 1990) and ‘Lothar’ (26 December
1999) were used for GIS-based estimation and mapping (in a 50 × 50 m resolution grid) of the winter storm damage probability
(PDAM) for the forests of the German federal state of Baden-Wuerttemberg (Southwest Germany). The PDAM-calculation was based on weights of evidence (WofE) methodology. A combination of information on forest type, geology, soil
type, soil moisture regime, and topographic exposure, as well as maximum gust wind speed field was used to compute PDAM across the entire study area. Given the condition that maximum gust wind speed during the two storm events exceeded 35 m s-1, the highest PDAM values computed were primarily where coniferous forest grows in severely exposed areas on temporarily moist soils on bunter
sandstone formations. Such areas are found mainly in the mountainous ranges of the northern Black Forest, the eastern Forest
of Odes, in the Virngrund area, and in the southwestern Alpine Foothills. 相似文献
799.
The potential involvement of D1 and D2 dopamine receptors in the effects of cocaine on cardiovascular function in squirrel monkeys was evaluated. A low dose of cocaine (0.1 mg/kg i.v.) produced increases in both blood pressure and heart rate. At the higher doses of cocaine (1.0-3.0 mg/kg) the heart rate response was biphasic, consisting of an early decrease followed by an increase in heart rate 10-20 min following injection. The dopamine D2 antagonist haloperidol (0.1 mg/kg i.m.) attenuated the heart rate increasing effect of cocaine, but doses as high as 0.03 mg/kg did not alter the blood pressure increase. The D1 antagonist SCH 23390 (0.01-0.03 mg/kg i.m.) did not attenuate either the blood pressure or heart rate increasing effects of cocaine. The D2 agonist quinpirole (1.0 mg/kg i.v.) produced increases in heart rate similar to cocaine, with little effect on blood pressure. Although effective against the heart rate increasing effect of cocaine, haloperidol (0.01 mg/kg) did not antagonize the heart rate increasing effects of quinpirole. The D1 agonist SKF 38393 (3.0 mg/kg i.v.) decreased heart rate and increased blood pressure. The blood pressure increasing effect of SKF 38393 was antagonized by 0.01 mg/kg SCH 23390. Haloperidol's ability to partially antagonize the tachycardiac response to cocaine suggests the involvement of D2 receptors in that response. However, the failure of haloperidol to antagonize quinpirole's tachycardiac effect suggests that non-dopaminergic mechanisms may also be involved in haloperidol's antagonism of cocaine's tachycardiac effect. The pressor effects of cocaine do not appear to be controlled by selective dopamine receptors. 相似文献
800.
Lateral diffusion in biological membranes. A normal-mode analysis of diffusion on a spherical surface. 总被引:9,自引:2,他引:7 下载免费PDF全文
A new approach is described for the analysis of lateral diffusion in biological membranes. It is shown that a suitably defined first moment of the concentration distribution on a spherical surface decays as a single exponential with a relaxation rate proportional to the diffusion coefficient and inversely proportional to the square of the radius of the sphere. The approach is illustrated with an example of fluorescence redistribution after photobleaching of membrane proteins in a spectrin-deficient spherocytic mouse erythrocyte membrane. 相似文献