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901.
Slow cortical potential biofeedback and the startle reflex 总被引:4,自引:0,他引:4
Stuart Brody Harald Rau Fabiola Köhler Harald Schupp Werner Lutzenberger Niels Birbaumer 《Applied psychophysiology and biofeedback》1994,19(1):1-11
The negativity of slow cortical potentials (SCP) of the surface EEG is a measure of brain excitability, correlating with motor and cognitive preparation. Selfcontrol of SCP positivity has been shown to reduce seizure activity. Following SCP biofeedback from a central EEG electrode position, subjects gained bidirectional control over their SCP. The current study used a modified feedback methodology, and found a positive relationship between negativity and magnitude of EMG startle response (a measure of cortical and subcortical arousal, particularly aversive response disposition). Greater success in SCP differentiation was associated with self-report of less relaxation during negativity training.This research was supported by the Deutsche Forschungsgemeinschaft under grant No. SFB 307. 相似文献
902.
Heinz Löffler 《Hydrobiologia》1993,264(3):169-174
The northwestern area of the Pannonian Lowland extends into Austria. The climatic and hydrologic attributes of this biographic region promote the existence of extremely astatic bodies water lacking any fish and hence the occurrence of Anostraca, Notostraca, Laevicaudata and Spinicaudata. Zoogeographical and ecological features as well as the extinction of species due to anthropogenic influence are described.Dedicated to Prof. Dr F. Berger, Lunz, Austria, on the occasion of his 90th birthdayDedicated to Prof. Dr F. Berger, Lunz, Austria, on the occasion of his 90th birthday 相似文献
903.
Jaromir Konecny Michael Eckert Michael Schöniger G. Ludwig Hofacker 《Journal of molecular evolution》1993,36(5):407-416
Summary We lay new foundations to the hypothesis that the genetic code is adapted to evolutionary retention of information in the
antisense strands of natural DNA/RNA sequences. In particular, we show that the genetic code exhibits, beyond the neutral
replacement patterns of amino acid substitutions, optimal properties by favoring simultaneous evolution of proteins encoded
in DNA/RNA sense-antisense strands. This is borne out in the sense-antisense transformations of the codons of every amino
acid which target amino acids physicochemically similar to each other. Moreover, silent mutations in the sense strand generate
conservative ones in its antisense counterpart and vice versa. Coevolution of proteins coded by complementary strands is shown
to be a definite possibility, a result which does not depend on any physical interaction between the coevolving proteins.
Likewise, the degree to which the present genetic code is dedicated to evolutionary sense-antisense tolerance is demonstrated
by comparison with many randomized codes. Double-strand coding is quantified from an information-theoretical point of view. 相似文献
904.
Rheinberger HJ 《Journal of the history of biology》1993,26(3):443-471
The living world is one of complexity, the result of innumerable interactions among organisms, cells, molecules. In analyzing a problem, the biologist is constrained to focus on a fragment of reality, on a piece of the universe which he arbitrarily isolates to define certain of its parameters.In biology, any study thus begins with the choice of a system. On this choice depend the experimenter's freedom to maneuver, the nature of the questions he is free to ask, and even, often, the type of answer he can obtain. 相似文献
905.
Studies on the batch extraction of lactic acid using an emulsion liquid membrane system are reported. The membrane phase consists of the tertiary amine carrier Alamine 336 and the surfactant Span 80 dissolved in n-heptane/paraffin and aqueous solutions of sodium carbonate in the internal phase. The effects of internal phase reagent, extraction temperature, and initial external phase pH on the extraction efficiency and the emulsion swelling are examined. A statistical factorial experiment on extraction from clarified lactic acid fermentation broth was carried out to obtain knowledge of the performance of the extraction system from a broth. The extraction efficiency from the fermentation broth is found to be lower as compared to aqueous solutions of pure lactic acid. The effect of pH and the presence of other ionic species on selectivity are discussed. (c) 1993 John Wiley & Sons, Inc. 相似文献
906.
907.
Cell-free supernatant of pelleted zoospores was found to be more suitable for maintaining viable zoospores and developed cysts
than the supernatant of mature cysts. Conductivity and pH measurements indicated quantitative changes in the ionic composition
of a suspension ofP. infestans zoospores during their conversion into cysts. An increase in conductivity in the incipient cyst suspension was followed by
a decrease of conductivity in the maturing cyst suspension. The conductivity changes correlated closely with K+ fluxes which, in turn, coincided with the reverse, but stoichiometrically smaller, H+ fluxes. Zoospores treated with 1.5 μmol/L DCCD (an inhibitor of plasma membrane H+-ATPase) or 100 mmol/L Li+ (an inhibitor of cell motility) released predominantly K+ and other cations and their O2 consumption decreased. The H+/K+ exchange is therefore very probably associated with an operation of the plasma membrane H+-ATPase. The differential decrease in respiration caused by DCCD and Li+ was used to estimate the energy demand for cell motility and spore development. 相似文献
908.
Stationary unaerated cells ofS. pombe containing endogenous substrates but not energized by any exogenous ones take up 2-deoxy-d-glucose, 6-deoxy-d-glucose,d-xylose andd-arabinose actively over diffusion equilibrium. The active uptake is inhibited by 20–100 mmol/L H2O2 which causes an increase inK
T but has no effect onJ
max. This “competitive inhibition” indicates that H2O2 affects directly the sugar binding sites of the transporters. The ATP-binding site of the plasma membrane H+-ATPase is also affected by 100 mmol/L H2O2; theK
T decreases 7-fold,J
max about 2.5-fold. These effects are not likely to be mediated by membrane lipid peroxidation which appears to be lacking inS. pombe, and this lack may be one of the reasons for the high resistance of this yeast to H2O2. Because of thisS. pombe represents a suitable system for studying direct effects of oxidants on membrane proteins. 相似文献
909.
The impact of organic nutrients and massive addition of bacteria was followed in lake water mesocosms in a eutrophic lake. Increased DOM initiated a sequence of trophic responses indicated by rapid increases in bacterioplankton, protozoa, and algal biomass. The populations of Keratella cochlearis and Keratella quadrata showed a distinct response by rapid increase in birth rate followed by maxima of production and abundance. This succession clearly reflected the trophic position of these rotifer populations in the food chain. A reverse response was observed in Conochilus unicornis. 相似文献
910.
Immunoaffinity co-purification of cytokinins and analysis by high-performance liquid chromatography with ultraviolet-spectrum detection 总被引:1,自引:0,他引:1
A rapid methodology for the simultaneous analysis of a large number of cytokinins is presented. The cross-reactivity of a mixture of polyclonal antibodies against zeatin riboside and isopentenyladenosine was exploited in a protocol that can be used for immunoaffinity purification of 23 additional cytokinins. Ligands include the cytokinin bases zeatin, dihydrozeatin, isopentenyladenine, benzyl-adenine and kinetin, and their corresponding nucleoside, nucleoside-5′-monophosphate, and 9-glucoside derivatives, as well as cis-zeatin, cis-zeatin riboside, the 2-methylthiol derivatives of isopentenyladenosine and zeatin riboside, and benzyl-adenine-3-glucoside. Mixtures of cytokinins could be retained with high recoveries of all the components. Immunoaffinity purification of extracts of Arabidopsis thaliana (L.) Heynh. and Solarium tuberosum L. gave fractions clean enough, as verified by gas chromatographymass spectrometry (GC-MS), to allow analysis of endogenous cytokinins using a single high-performance liquid chromatography (HPLC) step with on-line UV-spectrum detection. The detection limit was 4–6 pmol. The procedure described forms a routine assaying technique that is faster and simpler, yet yields better qualitative and quantitative information than the commonly used procedure of immunoassaying of HPLC fractions. 相似文献