Showing papers by "University of Jena published in 2004"

Neuroplasticity: changes in grey matter induced by training.

Abstract: Newly honed juggling skills show up as a transient feature on a brain-imaging scan. Does the structure of an adult human brain alter in response to environmental demands1,2? Here we use whole-brain magnetic-resonance imaging to visualize learning-induced plasticity in the brains of volunteers who have learned to juggle. We find that these individuals show a transient and selective structural change in brain areas that are associated with the processing and storage of complex visual motion. This discovery of a stimulus-dependent alteration in the brain's macroscopic structure contradicts the traditionally held view that cortical plasticity is associated with functional rather than anatomical changes.

Susceptibility weighted imaging (SWI).

Abstract: Susceptibility differences between tissues can be utilized as a new type of contrast in MRI that is different from spin density, T1-, or T2-weighted imaging. Signals from substances with different magnetic susceptibilities compared to their neighboring tissue will become out of phase with these tissues at sufficiently long echo times (TEs). Thus, phase imaging offers a means of enhancing contrast in MRI. Specifically, the phase images themselves can provide excellent contrast between gray matter (GM) and white matter (WM), iron-laden tissues, venous blood vessels, and other tissues with susceptibilities that are different from the background tissue. Also, for the first time, projection phase images are shown to demonstrate tissue (vessel) continuity. In this work, the best approach for combining magnitude and phase images is discussed. The phase images are high-pass-filtered and then transformed to a special phase mask that varies in amplitude between zero and unity. This mask is multiplied a few times into the original magnitude image to create enhanced contrast between tissues with different susceptibilities. For this reason, this method is referred to as susceptibility-weighted imaging (SWI). Mathematical arguments are presented to determine the number of phase mask multiplications that should take place. Examples are given for enhancing GM/WM contrast and water/fat contrast, identifying brain iron, and visualizing veins in the brain.

Resource pulses, species interactions and diversity maintenance in arid and semi-arid environments

Abstract: Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history traits that facilitate plant survival and growth in strongly water-limited variable environments, outlining how species differences in these traits may promote diversity. Our analysis emphasizes that the variability of pulsed environments does not reduce the importance of species interactions in structuring communities, but instead provides axes of ecological differentiation between species that facilitate their coexistence. Pulses of rainfall also influence higher trophic levels and entire food webs. Better understanding of how rainfall affects the diversity, species composition, and dynamics of arid environments can contribute to solving environmental problems stemming from land use and global climate change.

Challenges in end-of-life care in the ICU

Abstract: The jurors identified numerous problems with end of life in the ICU including variability in practice, inadequate predictive models for death, elusive knowledge of patient preferences, poor communication between staff and surrogates, insufficient or absent training of health-care providers, the use of imprecise and insensitive terminology, and incomplete documentation in the medical records. The jury strongly recommends that research be conducted to improve end-of-life care. The jury advocates a “shared” approach to end-of-life decision-making involving the caregiver team and patient surrogates. Respect for patient autonomy and the intention to honour decisions to decline unwanted treatments should be conveyed to the family. The process is one of negotiation, and the outcome will be determined by the personalities and beliefs of the participants. Ultimately, it is the attending physician’s responsibility, as leader of the health-care team, to decide on the reasonableness of the planned action. In the event of conflict, the ICU team may agree to continue support for a predetermined time. Most conflicts can be resolved. If the conflict persists, however, an ethics consultation may be helpful. Nurses must be involved in the process. The patient must be assured of a pain-free death. The jury of the Consensus Conference subscribes to the moral and legal principles that prohibit administering treatments specifically designed to hasten death. The patient must be given sufficient analgesia to alleviate pain and distress; if such analgesia hastens death, this “double effect” should not detract from the primary aim to ensure comfort.

Interpreting the parameters of the diffusion model: an empirical validation.

Abstract: The diffusion model (Ratcliff, 1978) allows for the statistical separation of different components of a speeded binary decision process (decision threshold, bias, information uptake, and motor response). These components are represented by different parameters of the model. Two experiments were conducted to test the interpretational validity of the parameters. Using a color discrimination task, we investigated whether experimental manipulations of specific aspects of the decision process had specific effects on the corresponding parameters in a diffusion model data analysis (see Ratcliff, 2002; Ratcliff & Rouder, 1998; Ratcliff, Thapar, & McKoon, 2001, 2003). In support of the model, we found that (1) decision thresholds were higher when we induced accuracy motivation, (2) drift rates (i.e., information uptake) were lower when stimuli were harder to discriminate, (3) the motor components were increased when a more difficult form of response was required, and (4) the process was biased towardrewarded responses.

Thin slices of behavior as cues of personality and intelligence.

Abstract: Self-reports, peer reports, intelligence tests, and ratings of personality and intelligence from 15 video-taped episodes were collected for 600 participants. The average cross-situational consistency of trait impressions across the 15 episodes was .43. Shared stereotypes related to gender and age were mostly accurate and contributed little to agreement among judges. Agreement was limited mainly by nonshared meaning systems and by nonoverlapping information. Personality inferences from thin slices of behavior were significantly associated with reports by knowledgeable informants. This association became stronger when more episodes were included, but gains in prediction were low beyond 6 episodes. Inferences of intelligence from thin slices of behavior strongly predicted intelligence test scores. A particularly strong single predictor was how persons read short sentences.

Underlying Processes in the Implicit Association Test: Dissociating Salience From Associations

Abstract: The authors investigated whether effects of the Implicit Association Test (IAT) are influenced by salience asymmetries, independent of associations. Two series of experiments analyzed unique effects of salience by using nonassociated, neutral categories that differed in salience. In a 3rd series, salience asymmetries were manipulated experimentally while holding associations between categories constant. In a 4th series, valent associations of the target categories were manipulated experimentally while holding salience asymmetries constant. Throughout, IAT effects were found to depend on salience asymmetries. Additionally, salience asymmetries between categories were assessed directly with a visual search task to provide an independent criterion of salience asymmetries. Salience asymmetries corresponded to IAT effects and also accounted for common variance in IAT effects and explicit measures of attitudes or the self-concept.

Procalcitonin and C-reactive protein during systemic inflammatory response syndrome, sepsis and organ dysfunction.

Abstract: Both C-reactive protein (CRP) and procalcitonin (PCT) are accepted sepsis markers. However, there is still some debate concerning the correlation between their serum concentrations and sepsis severity. We hypothesised that PCT and CRP concentrations are different in patients with infection or with no infection at a similar severity of organ dysfunction or of systemic inflammatory response. One hundred and fifty adult intensive care unit patients were observed consecutively over a period of 10 days. PCT, CRP and infection parameters were compared among the following groups: no systemic inflammatory response syndrome (SIRS) (n = 15), SIRS (n = 15), sepsis/SS (n = 71) (including sepsis, severe sepsis and septic shock [n = 34, n = 22 and n = 15]), and trauma patients (n = 49, no infection). PCT and CRP concentrations were higher in patients in whom infection was diagnosed at comparable levels of organ dysfunction (infected patients, regression of median [ng/ml] PCT = -0.848 + 1.526 sequential organ failure assessment [SOFA] score, median [mg/l] CRP = 105.58 + 0.72 SOFA score; non-infected patients, PCT = 0.27 + 0.02 SOFA score, P 12). PCT and CRP concentrations were 1.58 ng/ml and 150 mg/l in patients with sepsis, 0.38 ng/ml and 51 mg/l in the SIRS patients (P < 0.05, Mann–Whitney U-test), and 0.14 ng/ml and 72 mg/l in the patients with no SIRS (P < 0.05). The kinetics of both parameters were also different, and PCT concentrations reacted more quickly than CRP. PCT and CRP levels are related to the severity of organ dysfunction, but concentrations are still higher during infection. Different sensitivities and kinetics indicate a different clinical use for both parameters.

Continuous central venous and pulmonary artery oxygen saturation monitoring in the critically ill

Abstract: To compare the course of continuously measured mixed and central venous O2 saturations in high-risk patients and to evaluate the impact of various factors that might interfere with reflection spectrophotometry. Prospective, descriptive study in the interdisciplinary ICU of a university hospital. 32 critically ill patients with triple-lumen central vein catheters, including 29 patients requiring pulmonary artery catheterization. The accuracy of fiberoptic measurements was assessed by comparison to reference co-oximeter results at regular intervals. We examined the effect on measurement accuracy of physiological variables including hematocrit, hemoglobin, pH, temperature, and the administration of various solutions via central venous catheter. Continuous parallel measurements of SvO2 and ScvO2 were performed in patients with each type of catheters over a total observation time of 1097 h. ScvO2 values were more accurate and stable than in vitro oximeter measurements (r=0.96 from 150 samples, mean difference 0.15%, average drift 0.10%/day) and was not significantly affected by synchronous infusion therapy or by changes in hematocrit, hemoglobin, pH, or temperature. ScvO2 values closely paralleled SvO2, whether measured in vitro (r=0.88 from 150 samples) or in vivo (r=0.81 from 395,128 samples) but averaged about 7±4 saturation percentage higher. ScvO2 changed in parallel in 90% of the 1,498 instances in which SvO2 changed more than 5% (over an average of 43 min). Continuous fiberoptic measurement of central vein O2 saturation has potential to be a reliable and convenient tool which could rapidly warn of acute change in the oxygen supply/demand ratio of critically ill patients.

Low-nonlinearity single-transverse-mode ytterbium-doped photonic crystal fiber amplifier.

Abstract: We report on an air-clad large-core single-transverse-mode ytterbium-doped photonic crystal fiber with a mode-field-diameter of 35 µm, corresponding to a mode-field-area of ~1000 µm2. In a first experiment this fiber is used to amplify 10-ps pulses to a peak power of 60 kW without significant spectral broadening due to self-phase modulation allowing for the frequency up-conversion of these pulses using narrow-bandwidth phase-matched nonlinear crystals.

The 5-lipoxygenase pathway promotes pathogenesis of hyperlipidemia-dependent aortic aneurysm

Abstract: Activation of the 5-lipoxygenase (5-LO) pathway leads to the biosynthesis of proinflammatory leukotriene lipid mediators. Genetic studies have associated 5-LO and its accessory protein, 5-LO-activating protein, with cardiovascular disease, myocardial infarction and stroke. Here we show that 5-LO-positive macrophages localize to the adventitia of diseased mouse and human arteries in areas of neoangiogenesis and that these cells constitute a main component of aortic aneurysms induced by an atherogenic diet containing cholate in mice deficient in apolipoprotein E. 5-LO deficiency markedly attenuates the formation of these aneurysms and is associated with reduced matrix metalloproteinase-2 activity and diminished plasma macrophage inflammatory protein-1alpha (MIP-1alpha; also called CCL3), but only minimally affects the formation of lipid-rich lesions. The leukotriene LTD(4) strongly stimulates expression of MIP-1alpha in macrophages and MIP-2 (also called CXCL2) in endothelial cells. These data link the 5-LO pathway to hyperlipidemia-dependent inflammation of the arterial wall and to pathogenesis of aortic aneurysms through a potential chemokine intermediary route.

Functional Conversion Between A-Type and Delayed Rectifier K+ Channels by Membrane Lipids

Abstract: Voltage-gated potassium (Kv) channels control action potential repolarization, interspike membrane potential, and action potential frequency in excitable cells. It is thought that the combinatorial association between distinct alpha and beta subunits determines whether Kv channels function as non-inactivating delayed rectifiers or as rapidly inactivating A-type channels. We show that membrane lipids can convert A-type channels into delayed rectifiers and vice versa. Phosphoinositides remove N-type inactivation from A-type channels by immobilizing the inactivation domains. Conversely, arachidonic acid and its amide anandamide endow delayed rectifiers with rapid voltage-dependent inactivation. The bidirectional control of Kv channel gating by lipids may provide a mechanism for the dynamic regulation of electrical signaling in the nervous system.

EMG activity as a function of the performer's focus of attention.

Abstract: In previous studies of attentional focus effects, investigators have measured performance outcome. Here, however, the authors used electromyography (EMG) to determine whether differences between external and internal foci would also be manifested at the neuromuscular level. In 2 experiments, participants (N = 11, Experiment 1; N = 12, Experiment 2) performed biceps curls while focusing on the movements of the curl bar (external focus) or on their arms (internal focus). In Experiment 1, movements were performed faster under external than under internal focus conditions. Also, integrated EMG (iEMG) activity was reduced when performers adopted an external focus. In Experiment 2, movement time was controlled through the use of a metronome, and iEMG activity was again reduced under external focus conditions. Those findings are in line with the constrained action hypothesis (G. Wulf, N. McNevin, & C. H. Shea, 2001), according to which an external focus promotes the use of more automatic control processes.

Association of Piriformospora indica with Arabidopsis thaliana roots represents a novel system to study beneficial plant–microbe interactions and involves early plant protein modifications in the endoplasmic reticulum and at the plasma membrane

Abstract: Piriformospora indica, an endophytic fungus of the Sebacinaceae family, colonizes the roots of a wide variety of plant species and promotes their growth, in a manner similar to arbuscular mycorrhizal fungi. The results of the present study demonstrate that the fungus interacts also with the non-mycorrhizal host Arabidopsis thaliana and promotes its growth. The interaction is detectable by the appearance of a strong autofluorescence in the roots, followed by the colonization of root cells by fungal hyphae and the generation of chlamydospores. Promotion of root growth was detectable even before noticeable root colonization. Membrane-associated proteins from control roots and roots after cultivation with P. indica were separated by two-dimensional gel-electrophoresis and identified by electrospray ionization mass spectrometry and tandem mass spectrometry. Differences were found in the expression of glucosidase II, beta-glucosidase PYK10, two glutathione-S-transferases and several so-far uncharacterized proteins. Based on conserved domains present in the latter proteins their possible roles in plant-microbe interaction are predicted. Taken together, the present results suggest that the interaction of Arabidopsis thaliana with P. indica is a powerful model system to study beneficial plant-microbe interaction at the molecular level. Furthermore, the successful accommodation of the fungus in the root cells is preceded by protein modifications in the endoplasmatic reticulum as well as at the plasma membrane of the host.

Novel Haloperoxidase from the Agaric Basidiomycete Agrocybe aegerita Oxidizes Aryl Alcohols and Aldehydes

Abstract: Agrocybe aegerita, a bark mulch- and wood-colonizing basidiomycete, was found to produce a peroxidase (AaP) that oxidizes aryl alcohols, such as veratryl and benzyl alcohols, into the corresponding aldehydes and then into benzoic acids. The enzyme also catalyzed the oxidation of typical peroxidase substrates, such as 2,6-dimethoxyphenol (DMP) or 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS). A. aegerita peroxidase production depended on the concentration of organic nitrogen in the medium, and highest enzyme levels were detected in the presence of soybean meal. Two fractions of the enzyme, AaP I and AaP II, which had identical molecular masses (46 kDa) and isoelectric points of 4.6 to 5.4 and 4.9 to 5.6, respectively (corresponding to six different isoforms), were identified after several steps of purification, including anion- and cation-exchange chromatography. The optimum pH for the oxidation of aryl alcohols was found to be around 7, and the enzyme required relatively high concentrations of H2O2 (2 mM) for optimum activity. The apparent Km values for ABTS, DMP, benzyl alcohol, veratryl alcohol, and H2O2 were 37, 298, 1,001, 2,367 and 1,313 μM, respectively. The N-terminal amino acid sequences of the main AaP II spots blotted after two-dimensional gel electrophoresis were almost identical and exhibited almost no homology to the sequences of other peroxidases from basidiomycetes, but they shared the first three amino acids, as well as two additional amino acids, with the heme chloroperoxidase (CPO) from the ascomycete Caldariomyces fumago. This finding is consistent with the fact that AaP halogenates monochlorodimedone, the specific substrate of CPO. The existence of haloperoxidases in basidiomycetous fungi may be of general significance for the natural formation of chlorinated organic compounds in forest soils.

Associations of caregiver stressors and uplifts with subjective well-being and depressive mood: a meta-analytic comparison.

Abstract: The present meta-analytic study gives a systematic review of research on depression and the subjective well-being of caregivers. We integrate results from 60 studies on informal caregivers' subjective well-being (e.g., positive affect, life-satisfaction) and contrast them with the result of studies on caregiver depression. Analyses were based on a two-factor model of subjective well-being that distinguishes between positive and negative dimensions of well-being (e.g., happiness and depression). The strongest effects were domain-specific: uplifts of caregiving were associated with subjective well-being and caregiving stressors were associated with depression. In addition, weaker effects that crossed domains were present: uplifts were weakly associated with depressive symptoms. In addition, lower levels of caregivers' subjective well-being were weakly related to care receivers' physical and cognitive impairments, as well as behaviour problems, but not to the amount of caregiving. Type of care recipients' illness and the measure of well-being moderated, in part, the association between stressors/uplifts and subjective well-being.

Changes in fisheries discard rates and seabird communities

Abstract: It is clear that discards from commercial fisheries are a key food resource for many seabird species around the world(1-8). But predicting the response of seabird communities to changes in discard rates is problematic and requires historical data to elucidate the confounding effects of other, more 'natural' ecological processes. In the North Sea, declining stocks, changes in technical measures, changes in population structure(9) and the establishment of a recovery programme for cod (Gadus morhua(10)) will alter the amount of fish discarded. This region also supports internationally important populations of seabirds(11), some of which feed extensively, but facultatively, on discards, in particular on undersized haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus)(1-3). Here we use long-term data sets from the northern North Sea to show that there is a direct link between discard availability and discard use by a generalist predator and scavenger-the great skua (Stercorarius skua). Reduced rates of discarding, particularly when coupled with reduced availability of small shoaling pelagic fish such as sandeel (Ammodytes marinus), result in an increase in predation by great skuas on other birds. This switching of prey by a facultative scavenger presents a potentially serious threat to some seabird communities.

Kilometer-range nonlinear propagation of femtosecond laser pulses.

Abstract: Ultrashort, high-power laser pulses propagating vertically in the atmosphere have been observed over more than 20 km using an imaging 2-m astronomical telescope. This direct observation in several wavelength bands shows indications for filament formation at distances as far as 2 km in the atmosphere. Moreover, the beam divergence at 5 km altitude is smaller than expected, bearing evidence for whole-beam parallelization about the nonlinear focus. We discuss implications for white-light Lidar applications.

The Acquisition of Complex Sentences

Abstract: This book presents a comprehensive study of how children acquire complex sentences. Drawing on observational data from English-speaking children aged 2 to 5, Holger Diessel investigates the acquisition of infinitival and participial complement clauses, finite complement clauses, finite and nonfinite relative clauses, adverbial clauses, and coordinate clauses. His investigation shows that the development of complex sentences originates from simple non-embedded sentences and that two different developmental pathways can be distinguished: complex sentences including complement and relative clauses evolve from simple sentences that are gradually expanded to multiple-clause constructions, and complex sentences including adverbial and coordinate clauses develop from simple sentences that are integrated in a specific biclausal unit. He argues that the acquisition process is determined by a variety of factors: the frequency of the various complex sentences in the ambient language, the semantic and syntactic complexity of the emerging constructions, the communicative functions of complex sentences, and the social-cognitive development of the child.

'Special geometry of Euclidean supersymmetry I: Vector multiplets'

Abstract: We construct the general action for abelian vector multiplets in rigid 4-dimensional euclidean (instead of minkowskian) = 2 supersymmetry, i.e., over space-times with a positive definite instead of a lorentzian metric. The target manifolds for the scalar fields turn out to be para-complex manifolds endowed with a particular kind of special geometry, which we call affine special para-K?hler geometry. We give a precise definition and develop the mathematical theory of such manifolds. The relation to the affine special K?hler manifolds appearing in minkowskian = 2 supersymmetry is discussed. Starting from the general five-dimensional vector multiplet action we consider dimensional reduction over time and space in parallel, providing a dictionary between the resulting euclidean and minkowskian theories. Then we reanalyze supersymmetry in four dimensions and find that any (para-)holomorphic prepotential defines a supersymmetric lagrangian, provided that we add a specific four-fermion term, which cannot be obtained by dimensional reduction. We show that the euclidean action and supersymmetry transformations, when written in terms of para-holomorphic coordinates, take exactly the same form as their minkowskian counterparts. The appearance of a para-complex and complex structure in the euclidean and minkowskian theory, respectively, is traced back to properties of the underlying R-symmetry groups. Finally, we indicate how our work will be extended to other types of multiplets and to supergravity in the future and explain the relevance of this project for the study of instantons, solitons and cosmological solutions in supergravity and M-theory.