bluuebunny/crossref_metadata_2025 huggingface dataset:
Body mass index, Bishop score, and sonographic measurement of the cervical length as predictors of successful labor induction in twin gestations
Authors: Park Kyo-Hoon , Hong Joon-Seok , Kang Woong-Sun , Shin Dong-Myung , Kim Shi-Nae
Published: June 2009

Aims: To evaluate the predictive value of body mass index (BMI), Bishop score, and sonographic measurement of cervical length for predicting successful labor induction (defined as an ability to achieve the active phase of labor corresponding to a cervical dilatation of ≥4 cm within 12 h of initiating oxytocin) in near-term twin gestations.

Methods: This prospective, observational study enrolled 72 consecutive women with twin gestations at >36.0 weeks' gestation who were scheduled for induction of labor. Transvaginal ultrasound for measurement of the cervical length was performed and the Bishop score was determined by digital examination. The BMI was calculated based on the weight and height at the time of induction.

Results: Labor induction was successful in 63% (45/72) of women. The mean BMI was significantly lower in women who had successfully induced labor, but no significant differences existed with respect to the mean cervical length, median Bishop score, proportion of parous and nulliparous women, and the mean total birth weight of the twin pairs between the two patient groups. Multiple logistic regression demonstrated that only BMI provided a significant contribution in predicting successful labor induction.

Conclusions: BMI independently predicted the success of labor induction in twin gestations but the sonographic measurement of the cervical length and Bishop score had poor predictive values for successful induction.
Enhancement of Planning Ability by Transcranial Direct Current Stimulation
Authors: Dockery Colleen A. , Hueckel-Weng Ruth , Birbaumer Niels , Plewnia Christian
Published: June 2009

The functional neuroanatomy of executive function critically involves the dorsolateral prefrontal cortex. Transcranial direct current stimulation (tDCS) has been established as a noninvasive tool for transient modulation of cortical function. Here, we examined the effects of tDCS of the left dorsolateral prefrontal cortex on planning function by using the Tower of London task to evaluate performance during and after anodal, cathodal (1 mA, 15 min), and sham tDCS in 24 healthy volunteers. The key finding was a double dissociation of polarity and training phase: improved performance was found with cathodal tDCS applied during acquisition and early consolidation, when preceding anodal tDCS, but not in the later training session. In contrast, anodal tDCS enhanced performance when applied in the later sessions following cathodal tDCS. Our results indicate that both anodal and cathodal tDCS can improve planning performance as quantified by the Tower of London test. Most importantly, these data demonstrate training-phase-specific effects of tDCS. We propose that excitability decreasing cathodal tDCS mediates its early beneficial effect through noise reduction of neuronal activity, whereas a further adaptive configuration of specific neuronal connections is supported by excitability enhancing anodal tDCS in the later training phase by enhanced efficacy of active connections. This gain of function was sustained in a follow-up 6 and 12 months after training. In conclusion, the specific coupling of stimulation and training phase interventions may support the treatment of cognitive disorders involving frontal lobe functions.
Retrograde Opioid Signaling Regulates Glutamatergic Transmission in the Hypothalamus
Authors: Iremonger Karl J. , Bains Jaideep S.
Published: June 2009

Opioid signaling in the CNS is critical for controlling cellular excitability, yet the conditions under which endogenous opioid peptides are released and the precise mechanisms by which they affect synaptic transmission remain poorly understood. The opioid peptide dynorphin is present in the soma and dendrites of vasopressin neurons in the hypothalamus and dynamically controls the excitability of these cellsin vivo. Here, we show that dynorphin is released from dendritic vesicles in response to postsynaptic activity and acts in a retrograde manner to inhibit excitatory synaptic transmission. This inhibition, which requires the activation of κ-opioid receptors, results from a reduction in presynaptic release of glutamate vesicles. The opioid inhibition is downstream of Ca2+entry and is likely mediated by a direct modulation of presynaptic fusion machinery. These findings demonstrate that neurons may self-regulate their excitability through the dendritic release of opioids to inhibit excitatory synaptic transmission.
The Central Nucleus of the Amygdala and Corticotropin-Releasing Factor: Insights into Contextual Fear Memory
Authors: Pitts Matthew W. , Todorovic Cedomir , Blank Thomas , Takahashi Lorey K.
Published: June 2009

The central nucleus of the amygdala (CeA) has been traditionally viewed in fear conditioning to serve as an output neural center that transfers conditioned information formed in the basolateral amygdala to brain structures that generate emotional responses. Recent studies suggest that the CeA may also be involved in fear memory consolidation. In addition, corticotropin-releasing factor systems were shown to facilitate memory consolidation in the amygdala, which contains a high density of CRF immunoreactive cell bodies and fibers in the lateral part of the CeA (CeAl). However, the involvement of CeA CRF in contextual fear conditioning remains poorly understood. Therefore, we first conducted a series of studies using fiber-sparing lesion and reversible inactivation methods to assess the general role of the CeA in contextual fear. We then used identical training and testing procedures to compare and evaluate the specific function of CeA CRF using CRF antisense oligonucleotides (CRF ASO). Rats microinjected with ibotenic acid, muscimol, or a CRF ASO into the CeA before contextual fear conditioning showed typical levels of freezing during acquisition training but exhibited significant reductions in contextual freezing in a retention test 48 h later. Furthermore, CeA inactivation induced by either muscimol or CRF ASO administration immediately before retention testing did not impair freezing, suggesting that the previously observed retention deficits were caused by inhibition of consolidation rather than fear expression. Collectively, our results suggest CeA involvement in the consolidation of contextual fear memory and specifically implicate CeA CRF as an important mediator.
Stimulus-Specific Adaptation Occurs in the Auditory Thalamus
Authors: Anderson Lucy A. , Christianson G. Björn , Linden Jennifer F.
Published: June 2009

Neurons in the primary auditory cortex respond less strongly to a commonly occurring “standard” tone than to the same tone when it is rare or “deviant.” This phenomenon, called “stimulus-specific adaptation” (SSA), has been proposed as a possible single-neuron correlate of the mismatch negativity, a cortical evoked potential associated with stimulus novelty. Previous studies in cat did not observe SSA in single neurons in the auditory thalamus. However, these reports did not differentiate between the auditory thalamic subdivisions and did not examine the effects of changing the stimulus presentation rate. To explore the possibility of thalamic SSA more completely, we recorded extracellularly from 30 single units and 22 multiunit clusters in the ventral, medial, and dorsal subdivisions of the mouse medial geniculate body (MGB), while presenting the anesthetized animals with sequences of standard and deviant tones at interstimulus intervals of 400, 500 and 800 ms. We found SSA in the auditory thalamus at all three stimulus presentation rates, primarily in the medial subdivision but to a lesser degree also in the ventral MGB. Thalamic SSA was evident from the earliest onset of tone-evoked activity, although the latencies of responses to standard and deviant tones were not significantly different. Together with related findings of SSA in neurons of the “belt” regions of the inferior colliculus, these results demonstrate that SSA is present at subcortical levels, primarily in but not restricted to the nonlemniscal auditory pathway.
PSD-95 Is Essential for Hallucinogen and Atypical Antipsychotic Drug Actions at Serotonin Receptors
Authors: Abbas Atheir I. , Yadav Prem N. , Yao Wei-Dong , Arbuckle Margaret I. , Grant Seth G. N. , Caron Marc G. , Roth Bryan L.
Published: June 2009

Here, we report that postsynaptic density protein of 95 kDa (PSD-95), a postsynaptic density scaffolding protein, classically conceptualized as being essential for the regulation of ionotropic glutamatergic signaling at the postsynaptic membrane, plays an unanticipated and essential role in mediating the actions of hallucinogens and atypical antipsychotic drugs at 5-HT2Aand 5-HT2Cserotonergic G-protein-coupled receptors. We show that PSD-95 is crucial for normal 5-HT2Aand 5-HT2Cexpressionin vivoand that PSD-95 maintains normal receptor expression by promoting apical dendritic targeting and stabilizing receptor turnoverin vivo. Significantly, 5-HT2A- and 5-HT2C-mediated downstream signaling is impaired inPSD-95nullmice, and the 5-HT2A-mediated head-twitch response is abnormal. Furthermore, the ability of 5-HT2Ainverse agonists to normalize behavioral changes induced by glutamate receptor antagonists is abolished in the absence of PSD-95in vivo. These results demonstrate that PSD-95, in addition to the well known role it plays in scaffolding macromolecular glutamatergic signaling complexes, profoundly modulates metabotropic 5-HT2Aand 5-HT2Creceptor function.
Conditional Forebrain Inactivation of Nicastrin Causes Progressive Memory Impairment and Age-Related Neurodegeneration
Authors: Tabuchi Katsuhiko , Chen Guiquan , Südhof Thomas C. , Shen Jie
Published: June 2009

Loss of presenilin function in adult mouse brains causes memory loss and age-related neurodegeneration. Since presenilin possesses γ-secretase-dependent and -independent activities, it remains unknown which activity is required for presenilin-dependent memory formation and neuronal survival. To address this question, we generated postnatal forebrain-specificnicastrinconditional knock-out (cKO) mice, in which nicastrin, a subunit of γ-secretase, is inactivated selectively in mature excitatory neurons of the cerebral cortex.nicastrincKO mice display progressive impairment in learning and memory and exhibit age-dependent cortical neuronal loss, accompanied by astrocytosis, microgliosis, and hyperphosphorylation of the microtubule-associated protein Tau. The neurodegeneration observed innicastrincKO mice likely occurs via apoptosis, as evidenced by increased numbers of apoptotic neurons. These findings demonstrate an essential role of nicastrin in the execution of learning and memory and the maintenance of neuronal survival in the brain and suggest that presenilin functions in memory and neuronal survival via its role as a γ-secretase subunit.
Transcriptional Control of Behavior: Engrailed Knock-Out Changes Cockroach Escape Trajectories
Authors: Booth David , Marie Bruno , Domenici Paolo , Blagburn Jonathan M. , Bacon Jonathan P.
Published: June 2009

The cerci of the cockroach are covered with identified sensory hairs that detect air movements. The sensory neurons that innervate these hairs synapse with giant interneurons in the terminal ganglion that in turn synapse with interneurons and leg motor neurons in thoracic ganglia. This neural circuit mediates the animal's escape behavior. The transcription factor Engrailed (En) is expressed only in the medially born sensory neurons, which suggested that it could work as a positional determinant of sensory neuron identity. Previously, we used double-stranded RNA interference to abolish En expression and found that the axonal arborization and synaptic outputs of an identified En-positive sensory neuron changed so that it came to resemble a nearby En-negative cell, which was itself unaffected. We thus demonstrated directly that En controls synaptic choice, as well as axon projections. Is escape behavior affected as a result of this miswiring? We showed recently that adult cockroaches keep each escape unpredictable by running along one of a set of preferred escape trajectories (ETs) at fixed angles from the direction of the threatening stimulus. The probability of selecting a particular ET is influenced by wind direction. In this present study, we show that early instar juvenile cockroaches also use those same ETs. En knock-out significantly perturbs the animals' perception of posterior wind, altering the choice of ETs to one more appropriate for anterior wind. This is the first time that it has been shown that knock-out of a transcription factor controlling synaptic connectivity can alter the perception of a directional stimulus.
Buprenorphine Is a Weak Partial Agonist That Inhibits Opioid Receptor Desensitization
Authors: Virk Michael S. , Arttamangkul Seksiri , Birdsong William T. , Williams John T.
Published: June 2009

Buprenorphine is a weak partial agonist at μ-opioid receptors that is used for treatment of pain and addiction. Intracellular and whole-cell recordings were made from locus ceruleus neurons in rat brain slices to characterize the actions of buprenorphine. Acute application of buprenorphine caused a hyperpolarization that was prevented by previous treatment of slices with the irreversible opioid antagonist β-chlornaltrexamine (β-CNA) but was not reversed by a saturating concentration of naloxone. As expected for a partial agonist, subsaturating concentrations of buprenorphine decreased the [Met]5enkephalin (ME)-induced hyperpolarization or outward current. When the ME-induced current was decreased below a critical value, desensitization and internalization of μ-opioid receptors was eliminated. The inhibition of desensitization by buprenorphine was not the result of previous desensitization, slow dissociation from the receptor, or elimination of receptor reserve. Treatment of slices with subsaturating concentrations of etorphine, methadone, oxymorphone, or β-CNA also reduced the current induced by ME but did not block ME-induced desensitization. Treatment of animals with buprenorphine for 1 week resulted in the inhibition of the current induced by ME and a block of desensitization that was not different from the acute application of buprenorphine to brain slices. These observations show the unique characteristics of buprenorphine and further demonstrate the range of agonist-selective actions that are possible through G-protein-coupled receptors.
Substance P Drives Endocannabinoid-Mediated Disinhibition in a Midbrain Descending Analgesic Pathway
Authors: Drew Geoffrey M. , Lau Benjamin K. , Vaughan Christopher W.
Published: June 2009

Substance P is thought to play an essential role in several forms of supraspinally mediated analgesia. The actions of substance P on synaptic transmission within descending analgesic pathways, however, are largely unknown. Here, we used whole-cell recordings from rat midbrain slices to examine the effects of substance P on GABAergic and glutamatergic transmission within the periaqueductal gray (PAG), a key component of a descending analgesic pathway that projects via the rostral ventromedial medulla (RVM) to the spinal cord dorsal horn. We found that substance P reversibly decreased the amplitude and increased the paired-pulse ratio of evoked IPSCs recorded from identified PAG-RVM projection neurons and from unidentified PAG neurons. Substance P had no effect on miniature IPSCs, implying an indirect mode of action. The effects of substance P were abolished by metabotropic glutamate type 5 and cannabinoid CB1 receptor antagonists, but unaltered by NMDA, GABAB, μ,δ-opioid, adenosine A1, and 5HT1Areceptor antagonists. Consistent with a role for endogenous glutamate in this process, substance P increased the frequency of action potential-dependent spontaneous EPSCs. Moreover, the effect of substance P on evoked IPSCs was mimicked and occluded by a glutamate transport inhibitor. Finally, these effects were dependent on postsynaptic G-protein activation and diacylglycerol lipase activity, suggesting the requirement for retrograde signaling by the endocannabinoid 2-arachidonoylglycerol. Thus, substance P may facilitate descending analgesia in part by enhancing glutamate-mediated excitation and endocannabinoid-mediated disinhibition of PAG-RVM projection neurons.
Context-Dependent Modulation of Functional Connectivity: Secondary Somatosensory Cortex to Prefrontal Cortex Connections in Two-Stimulus-Interval Discrimination Tasks
Authors: Chow Stephanie S. , Romo Ranulfo , Brody Carlos D.
Published: June 2009

In a complex world, a sensory cue may prompt different actions in different contexts. A laboratory example of context-dependent sensory processing is the two-stimulus-interval discrimination task. In each trial, a first stimulus (f1) must be stored in short-term memory and later compared with a second stimulus (f2), for the animal to come to a binary decision. Prefrontal cortex (PFC) neurons need to interpret the f1 information in one way (perhaps with a positive weight) and the f2 information in an opposite way (perhaps with a negative weight), although they come from the very same secondary somatosensory cortex (S2) neurons; therefore, a functional sign inversion is required. This task thus provides a clear example of context-dependent processing.

Here we develop a biologically plausible model of a context-dependent signal transformation of the stimulus encoding from S2 to PFC. To ground our model in experimental neurophysiology, we use neurophysiological data recorded by R. Romo's laboratory from both cortical area S2 and PFC in monkeys performing the task. Our main goal is to use experimentally observed context-dependent modulations of firing rates in cortical area S2 as the basis for a model that achieves a context-dependent inversion of the sign of S2 to PFC connections. This is done without requiring any changes in connectivity (Salinas, 2004b). We (1) characterize the experimentally observed context-dependent firing rate modulation in area S2, (2) construct a model that results in the sign transformation, and (3) characterize the robustness and consequent biological plausibility of the model.
Axotomy-Induced Smad1 Activation Promotes Axonal Growth in Adult Sensory Neurons
Authors: Zou Hongyan , Ho Carole , Wong Karen , Tessier-Lavigne Marc
Published: June 2009

Mature neurons have diminished intrinsic regenerative capacity. Axotomy of the peripheral branch of adult dorsal root ganglia (a “conditioning” lesion) triggers a transcription-dependent axon growth program. Here, we show that this growth program requires the function of the transcription factor Smad1. After peripheral axotomy, neuronal Smad1 is upregulated, and phosphorylated Smad1 accumulates in the nucleus. Both events precede the onset of axonal extension. Reducing Smad1 by RNA interferencein vitroimpairs axonal growth, and the continued presence of Smad1 is required to maintain the growth program. Furthermore, intraganglionic injection of BMP2 or 4, which activates Smad1, markedly enhances axonal growth capacity, mimicking the effect of a conditioning lesion. Thus, activation of Smad1 by axotomy is a key component of the transcriptional switch that promotes an enhanced growth state of adult sensory neurons.
Early Postnatal Proteolipid Promoter-Expressing Progenitors Produce Multilineage CellsIn Vivo
Authors: Guo Fuzheng , Ma Joyce , McCauley Erica , Bannerman Peter , Pleasure David
Published: June 2009

Proteolipid promoter (plp promoter) activity in the newborn mouse CNS is restricted to NG2-expressing oligodendroglial progenitor cells and oligodendrocytes. There are two populations of NG2 progenitors based on their plp promoter expression. Whereas the general population of NG2 progenitors has been shown to be multipotentin vitroand after transplantation, it is not known whether the subpopulation of plp promoter-expressing NG2 progenitors [i.e., plp promoter-expressing NG2 progenitors (PPEPs)] has the potential to generate multilineage cells during normal developmentin vivo. We addressed this issue by fate mapping Plp-Cre-ERT2/Rosa26-EYFP (PCE/R) double-transgenic mice, which carried an inducible Cre gene under the control of the plp promoter. Expression of the enhanced yellow fluorescent protein (EYFP) reporter gene in PPEPs was elicited by administering tamoxifen to postnatal day 7 PCE/R mice. We have demonstrated that early postnatal PPEPs, which had been thought to be restricted to the oligodendroglial lineage, also unexpectedly gave rise to a subset of immature, postmitotic, protoplasmic astrocytes in the gray matter of the spinal cord and ventral forebrain, but not in white matter. Furthermore, these PPEPs also gave rise to small numbers of immature, DCX (doublecortin)-negative neurons in the ventral forebrain, dorsal cerebral cortex, and hippocampus. EYFP-labeled representatives of each of these lineages survived to adulthood. These findings indicate that there are regional differences in the fates of neonatal PPEPs, which are multipotentin vivo, giving rise to oligodendrocytes, astrocytes, and neurons.
A Discrete GABAergic Relay Mediates Medial Prefrontal Cortical Inhibition of the Neuroendocrine Stress Response
Authors: Radley Jason J. , Gosselink Kristin L. , Sawchenko Paul E.
Published: June 2009

Complementing its roles in cognitive and affective information processing, the medial prefrontal cortex (mPFC) is a nodal point of a limbic forebrain circuit that modulates stress-related homeostatic mechanisms, including the hypothalamic–pituitary–adrenal (HPA) axis. mPFC influences on HPA output are predominantly inhibitory and emanate from the prelimbic and/or dorsal anterior cingulate cortical fields (PL and ACd, respectively). mPFC projections do not target HPA effector neurons in the paraventricular hypothalamic nucleus (PVH) directly, distributing instead to nearby forebrain regions, including some that house GABAergic neurons implicated in inhibitory PVH control. To identify pathway(s) subserving HPA-inhibitory mPFC influences, an initial screen for sources of GABAergic input to PVH whose sensitivity to an acute emotional (restraint) stress was diminished by PL/ACd lesions identified a discrete region of the anterior bed nucleus of the stria terminalis (aBST) as a candidate for fulfilling this role. Anatomical tracing experiments confirmed projections from PL (but not ACd) to implicated aBST cell groups, and from these to PVH. Finally, selective immunotoxin-mediated ablation of GABAergic aBST neurons recapitulated the effects of PL/ACd lesions on acute stress-induced activation of HPA output. The identification of a proximate mediator of HPA-inhibitory limbic influences provides a framework for clarifying how inhibitory neural and hormonal controls of HPA output are integrated, adaptations of the axis to chronic stress are effected, and how endocrine abnormalities may contribute to stress-related psychiatric illnesses in which mPFC dysfunction is implicated.
Rat Prefrontal Cortical Neurons Selectively Code Strategy Switches
Authors: Rich Erin L. , Shapiro Matthew
Published: June 2009

Multiple memory systems are distinguished by different sets of neuronal circuits and operating principles optimized to solve different problems across mammalian species (Tulving and Schacter, 1994). When a rat selects an arm in a plus maze, for example, the choice can be guided by distinct neural systems (White and Wise, 1999) that encode different relationships among perceived stimuli, actions, and reward. Thus, egocentric or stimulus–response associations require striatal circuits, whereas spatial or episodic learning requires hippocampal circuits (Packard et al., 1989). Although these memory systems function in parallel (Packard and McGaugh, 1996), they can also interact competitively or synergistically (Kim and Ragozzino, 2005). The neuronal mechanisms that coordinate these multiple memory systems are not fully known, but converging evidence suggests that the prefrontal cortex (PFC) is central.

The PFC is crucial for abstract, rule-guided behavior in primates and for switching rapidly between memory strategies in rats. We now report that rat medial PFC neuronal activity predicts switching between hippocampus- and caudate-dependent memory strategies. Prelimbic (PL) and infralimbic (IL) neuronal activity changed as rats switched memory strategies even as the rats performed identical behaviors but did not change when rats learned new contingencies using the same strategy. PL dynamics anticipated learning performance whereas IL lagged, suggesting that the two regions help initiate and establish new strategies, respectively. These neuronal dynamics suggest that the PFC contributes to the coordination of memory strategies by integrating the predictive relationships among stimuli, actions, and reward.
Nitric Oxide as an Endogenous Peripheral Modulator of Visceral Sensory Neuronal Function
Authors: Page Amanda J. , O'Donnell Tracey A. , Cooper Nicole J. , Young Richard L. , Blackshaw L. Ashley
Published: June 2009

Nitric oxide (NO) plays important roles in CNS and smooth muscle function. Here we reveal an additional function in peripheral sensory transmission. We hypothesized that endogenous NO modulates the function of gastrointestinal vagal afferent endings. The nonselective NO synthase (NOS) inhibitorNG-nitro-l-arginine methyl ester hydrochloride increased responses to tactile mechanical stimuli of mucosal afferent endings in two species, in some cases severalfold. This was mimicked by a neuronal NOS inhibitor but not an endothelial NOS inhibitor. NOS inhibitors did not affect the responsiveness of smooth muscle afferent endings, suggesting that the endogenous source of NO is exclusively accessible to mucosal receptors. The role of the NO-soluble guanylyl cyclase (sGC)–cGMP pathway was confirmed using the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one and the cGMP phosphodiesterase 5′ inhibitor sildenafil. The first enhanced and the second inhibited mechanosensory function. Exogenous NO, from the donorS-nitroso-N-acetylpenicillamine, significantly reduced mechanosensitivity of both types of ending. Up to one-third of stomach-projecting afferent neurons in the nodose ganglia expressed neuronal NOS (nNOS). However, anterograde-traced vagal endings were nNOS negative, indicating NOS is not transported peripherally and there are alternative sources of NO for afferent modulation. A subpopulation of enteroendocrine cells in the gut mucosa were nNOS positive, which were found anatomically in close apposition with mucosal vagal afferent endings. These results indicate an inhibitory neuromodulatory role of epithelial NO, which targets a select population of vagal afferents. This interaction is likely to play a role in generation of symptoms and behaviors from the upper gastrointestinal system.
Kontinuierliche Selbstkalibrierung von StereokamerasContinuous Self-Calibration of Stereo Cameras
Authors: Dang Thao , Stiller Christoph
Published: June 2009

Dieser Artikel beschreibt ein Verfahren zur kontinuierlichen Selbstkalibrierung von Stereokameras und gibt in [1] gewonnene Ergebnisse in verkürzter Form wieder. Die Bedeutung der einzelnen Kameraparameter für die Tiefenrekonstruktion wird untersucht und eine theoretisch fundierte Beschreibung der gesamten Verarbeitungskette einer stereoskopischen Selbstkalibrierung geliefert. Unterschiedliche geometrische Bedingungsgleichungen – die Epipolarbedingung zwischen korrespondierenden Punkten in zwei Bildern, die trilinearen Bedingungen zwischen Bildtripeln und der Bündelausgleich bei längeren Bildverbänden – werden einheitlich in einem Gauß–Helmert-Modell formuliert, welches eine Kalibrierung mit hoher Genauigkeit erlaubt. Die Bestimmung der Kameraparameter erfolgt mit einem robusten, rekursiven Schätzverfahren für Gauß–Helmert-Modelle, basierend auf einem Iterativen Erweiterten Kalman-Filter. Es konnte gezeigt werden, dass eine Kombination verschiedener Bedingungsgleichungen die Zuverlässigkeit der Parameterschätzung erhöht. Die Leistungsfähigkeit der kontinuierlichen Selbstkalibrierung wird anhand realer Bilddaten eines aktiven Stereosystems demonstriert.
Einsatz neuartiger Doppler-Signalverarbeitungstechniken zur Untersuchung von turbulenten ScherschichtströmungenApplication of Novel Doppler-Signal Evaluation Techniques for the Investigation of Turbulent Shear Flows
Authors: Neumann Mathias , Shirai Katsuaki , Czarske Jürgen
Published: June 2009

Turbulenz ist eines der letzten Rätsel der klassischen Physik, das noch nicht vollständig geklärt ist. In diesem Beitrag wird eine neue Messtechnik vorgestellt, die zeitlich und örtlich hochaufgelöste Untersuchungen von Geschwindigkeiten turbulenter Scherströmungen ermöglicht.
Immunization with thyroglobulin induces Graves'-like disease in mice
Authors: Endo Toyoshi , Kobayashi Tetsuro
Published: June 2009

We immunized AKR/N mice with bovine thyroglobulin (Tg) once every 2 weeks and monitored their time-dependent changes in 125I uptake activity in the thyroid glands. After 3 months, anti-Tg antibody was positive in all sera from the immunized mice. Serum free tri-iodothyronine (T3) and free thyroxine (T4) levels in the immunized mice (n=6) were significantly higher than those in the saline injected (control) mice (n=6). Neck counts as well as scintigraphy of the thyroid glands revealed that iodide uptake activity of the immunized mice was not suppressed, but was instead higher than that of the control mice. Two of the six immunized mice showed extremely high iodide uptake activity. The thyroid glands of these two mice were diffusely enlarged and the height of the epithelial cells was also increased. In addition, two mice with high iodide uptake activity produced a high titer of thyroid-stimulating antibody. Additional experiments showed that 4 out of 11 AKR/N mice and 3 out of 10 C57BL6 mice immunized with Tg had high serum free T3/free T4 levels, high 125I uptake activity of the thyroid, and positive thyroid-stimulating antibody activity. Diffuse goiter, thyrotoxicosis, high iodide uptake activity, and positive thyroid-stimulating antibody are the characteristics of Graves' disease. Thus, these mice exhibit the symptoms of Graves' disease. These results suggest that immunization with Tg induces Graves'-like disease in mice and that our methods will provide a new animal model of Graves' disease.
Skewed attacks, stability, and host suppression
Authors: Singh Abhyudai , Murdoch William W. , Nisbet Roger M.
Published: June 2009

It is well known that the model equilibrium in the Nicholson‐Bailey framework for parasitoid–host interactions can be stabilized if there is variation in the risk of parasitism among individual hosts. We show that the shape of the distribution of risk among hosts is crucial in determining stability. Stability for all values of the reproduction rate R of the host requires the distribution to be skewed, with a modal risk of zero. As a consequence, a distribution of risk with nonzero mode but otherwise sufficiently high variability will not stabilize the host–parasitoid equilibrium for certain values of R.

We also develop a new, simple, and general criterion for stability, according to which the host–parasitoid equilibrium is stable if and only if the adult host equilibrium density increases as host reproductive rate R increases. This reinforces previous results that skewed risk of the type needed for stability reduces parasitoid efficiency and hence the parasitoid's ability to suppress the host. Finally, we identify appropriate measures that can be made in the field to relate skew in risk of parasitism to stability.
The numerical and functional responses of a granivorous rodent and the fate of Neotropical tree seeds
Authors: Klinger Rob , Rejmánek Marcel
Published: June 2009

Despite their potential to provide mechanistic explanations of rates of seed dispersal and seed fate, the functional and numerical responses of seed predators have never been explicitly examined within this context. Therefore, we investigated the numerical response of a small‐mammal seed predator,Heteromys desmarestianus, to disturbance‐induced changes in food availability and evaluated the degree to which removal and fate of seeds of eight tree species in a lowland tropical forest in Belize were related to the functional response ofH. desmarestianusto varying seed densities. Mark–recapture trapping was used to estimate abundance ofH. desmarestianusin six 0.5‐ha grids from July 2000 to September 2002. Fruit availability and seed fate were estimated in each grid, and two experiments nested within the grids were used to determine (1) the form of the functional response for nine levels of fruit density (2–32 fruits/m2), (2) the removal rate and handling times, and (3) the total proportion of fruits removed. The total proportion of fruits removed was determined primarily by the numerical response ofH. desmarestianusto fruit availability, while removal rates and the proportion of seeds eaten or cached were related primarily to the form of the functional response. However, the numerical and functional responses interacted;H. desmarestianusshowed strong spatial and temporal numerical responses to total fruit availability, and their density relative to fruit availability resulted in variation in the form of the functional response. Types I, II, and III functional responses were observed, as were density‐independent responses, and these responses varied both among and within fruit species. The highest proportions of fruits were eaten when the Type III functional response was detected, which was when fruit availability was high relative toH. desmarestianuspopulation density. Numerous idiosyncratic influences on seed fate have been documented, but our results indicate that shifts in the numerical and functional responses of seed predators to seasonal and interannual variation in seed availability potentially provide a general mechanistic explanation for patterns of removal and fate for vertebrate‐dispersed seeds.
The intertwined population biology of two Amazonian myrmecophytes and their symbiotic ants
Authors: Frederickson Megan E. , Gordon Deborah M.
Published: June 2009

A major question in ecology is: how do mutualisms between species affect population dynamics? For four years, we monitored populations of two Amazonian myrmecophytes,Cordia nodosaandDuroia hirsuta,and their symbiotic ants. In this system, we investigated how positive feedback between mutualistic plants and ant colonies influenced population processes at two scales: (1) how modular organisms such as plants and ant colonies grew, or η‐demography, and (2) how populations grew, orN‐demography. We found evidence of positive feedback between ant colony and plant growth rates. Plants with mutualistic ants (Aztecaspp. andMyrmelachista schumanni) grew in a geometric or autocatalytic manner, such that the largest plants grew the most. By contrast, the growth of plants with parasitic ants (Allomerus octoarticulatus) saturated. Ant colonies occupied new domatia as fast as plants produced them, suggesting that mutualistic ant colonies also grew geometrically or autocatalytically to match plant growth. Plants became smaller when they lost ants. While unoccupied, plants continued to become smaller until they had lost all or nearly all their domatia. Hence, the loss of mutualistic ants limited plant growth.C. nodosaandD. hirsutalive longer than their ant symbionts and were sometimes recolonized after losing ants, which again promoted plant growth. Plant growth had fitness consequences for ants and plants; mortality and fecundity depended on plant size. Positive feedback between ants and plants allowed a few plants and ant colonies to become very large; these probably produced the majority of offspring in the next generation.
What time is it? Choice of time origin and scale in extended proportional hazards models
Authors: Fieberg John , DelGiudice Glenn D.
Published: June 2009

The analysis of telemetry data offers many unique challenges due to both the observation process and the complexity of the underlying system (e.g., risk of mortality may be influenced by both age and a wide range of environmental variables). Although semi‐parametric proportional hazards (SPPH) models have been proposed for analyzing ecological data, recent applications have failed to address the importance of choosing an appropriate time origin and scale for analysis. We compared models fit to a long‐term deer (Odocoileusspp.) survival data set using three alternative survival timescales: age, time since start of study, and time since 6 June (with a seasonally recurrent timescale). Temporal variability in risk resulted from multiple sources (e.g., changes in hunting pressure, winter severity), and the risk of mortality varied nonlinearly with age (highest risk for young and older individuals). Age‐varying hazards were represented well using regression splines, but temporal variability was more difficult to model using parametric assumptions. Annual survival estimates using the three timescales differed considerably. The model using a study‐based timescale most closely tracked temporal patterns in risk. Given the difficulties in modeling temporal variability using parametric assumptions, we recommend this approach over an age‐based or recurrent timescale when using SPPH models to evaluate the impact of large (naturally occurring or experimental) disturbances or to estimate annual age‐specific survival rates. Lastly, we discuss the strengths and limitations of SPPH models relative to fully parametric approaches.
Plant rhizospheric N processes: what we don't know and why we should care
Authors: Frank Douglas A. , Groffman Peter M.
Published: June 2009

An improved understanding of the rapid nitrogen fluxes that occur in plant rhizospheres has not been adequately incorporated into the study of how soil N availability and plant N uptake control a number of important ecological processes. One reason for this is that current methods that measure N availability do not account for the rapid exchange of resources between roots and their closely associated microbial communities. In this paper, we review the tight interactions between roots and microbes and discuss why ignoring the significance of these interactions has led to unrepresentative estimates of N availability in intact plant communities and an incomplete understanding of the environmental factors that control plant‐available N. We also explain why current standard methods to measure soil N availability do not account for important rhizospheric processes. Finally, we issue a challenge to develop new methods that will estimate soil N transformations in intact plant communities and offer some potential approaches that may help catalyze this effort.
Rapid evolution, seasonality, and the termination of parasite epidemics
Authors: Duffy Meghan A. , Hall Spencer R. , Cáceres Carla E. , Ives Anthony R.
Published: June 2009

Why do epidemics end? This simple question has puzzled ecologists and epidemiologists for decades. Early explanations focused on drops in host density arising from highly virulent parasites and, later, on the effects of acquired immunity. More recently, however, two additional epidemic‐ending mechanisms have surfaced: environmental change (including seasonality) and rapid evolution of increased resistance of hosts to infection. Both mechanisms, via either decreasing seasonal temperatures or evolution of resistance, act by altering transmission rates. To explore these possibilities, we tracked five epidemics of a virulent yeast parasite in lake populations ofDaphnia dentiferafrom late summer through autumn. We then fit and compared performance of time‐series models that included temperature‐dependent and/or evolutionary changes in transmission rates. The analyses show evolution to be the better explanation of epidemic dynamics. Thus, by integrating data and models, this study highlights the potential role of evolution in driving the termination of epidemics in natural populations.
Long‐term monitoring and experimental manipulation of a Chihuahuan Desert ecosystem near Portal, Arizona, USA
Authors: Ernest S. K. Morgan , Valone Thomas J. , Brown James H.
Published: June 2009

Desert ecosystems have long served as model systems in the study of ecological concepts (e.g., competition, resource pulses, top‐down/bottom‐up dynamics). However, the inherent variability of resource availability in deserts, and hence consumer dynamics, can also make them challenging ecosystems to understand. Study of a Chihuahuan desert ecosystem near Portal, Arizona, USA, began in 1977. At this site, 24 experimental plots were established in 1977 and divided among controls and experimental manipulations. Experimental manipulations over the years include removal of all or some rodent species, all or some ants, seed additions, and various alterations of the annual plant community. While some of these manipulations were discontinued early on, others (i.e., ant and rodent manipulations) have been maintained throughout the study. Monitoring of the composition and abundances of ants, plants, and rodents has occurred continuously on all 24 plots. From 1977 to 2002, individual‐level data on rodents (i.e., species, sex, size, reproductive condition) were collected monthly for each plot. From 1983 to 2002, the species‐level abundances of plants were sampled on permanent quadrats. From 1977 to 2002, the species‐level abundance of ant colonies was recorded for each plot, and from 1988 to 2002 additional information on ant abundances were recorded. Finally, from 1980 to 2002 we recorded precipitation at the study site.

These data have been used in a variety of publications documenting the effects of the experimental manipulations as well as the response of populations and communities to long‐term changes in climate and habitat. Sampling is ongoing and this database will be periodically updated.

The complete data sets corresponding to abstracts published in the Data Papers section of the journal are published electronically in Ecological Archives at 〈http://esapubs.org/archive〉. (The accession number for each Data Paper is given directly beneath the title.)
Functional leaf traits and biodiversity effects on litter decomposition in a stream
Authors: Schindler Markus H. , Gessner Mark O.
Published: June 2009

Rapid loss of biodiversity worldwide has raised concerns about the consequences to ecosystem functioning, including processes such as litter decomposition. Consequent experiments with litter mixtures to assess effects of changing tree composition and diversity on decomposition have given mixed results, but the causes are not clear. Reasoning that such conflicting accounts reported in the literature may be reconciled by considering differences in functional litter traits, we conducted a field experiment in a stream with leaf litter from nine deciduous tree species mixed in a total of 40 combinations. Fine‐mesh and coarse‐mesh litter bags were used to distinguish between potential effects mediated by microbial decomposers and detritivores. We hypothesized that diversity effects would emerge in species mixtures containing functionally dissimilar leaves but be absent in mixtures of functionally similar litter as assessed by determining proximate lignin, nitrogen, and phosphorus contents of the litter. Mean decomposition rates of litter mixtures did not lend support to our hypothesis for either microbial decomposition (as inferred from mass loss in fine‐mesh litter bags) or decomposition caused by both microbes and detritivores (mass loss from coarse‐mesh bags). Decomposition rates were largely controlled by litter lignin content, whereas P and especially N were not important. In line with our hypothesis, the most recalcitrant (slowly decomposing) and most labile (rapidly decomposing) species decomposed slower and faster, respectively, in litter mixtures comprising different decay categories than in homogenous mixtures composed of a single decay category or in single‐species litter bags. However, across decay categories, evidence was weak in support of the idea that functional litter dissimilarity matters, in spite of plausible mechanisms that could cause such effects.
Water availability directly determines per capita consumption at two trophic levels
Authors: McCluney Kevin E. , Sabo John L.
Published: June 2009

Community ecology has long focused on energy and nutrients as currencies of species interactions. Evidence from physiological ecology and recent studies suggest that in terrestrial systems, water may influence animal behavior and global patterns of species richness. Despite these observations, water has received little attention as a currency directly influencing animal species interactions. Here, we show that the per capita interaction strength between predatory wolf spiders and their primary prey, field crickets, is strong (−0.266) when predators and prey are maintained in ambient dry conditions, but is near zero (0.001) when water is provided ad libitum. Moreover, crickets consume 31‐fold more moist leaf material in ambient dry conditions, switching from old litter to moist green leaves when free water is scarce. Under dry conditions, animals may make foraging decisions based first on water needs, not energy or nutrients, suggesting strong and predictable effects of alterations in aridity on species interactions.
Prioritized phenotypic responses to combined predators in a marine snail
Authors: Bourdeau Paul E.
Published: June 2009

Although many species face numerous predators in nature, the combined impact of multiple predators on the inducible defenses of prey has rarely been studied. Prey may respond with an intermediate phenotype that balances the risk from several sources or may simply respond to the most dangerous predator. I examined the separate and combined effects of the presence of shell‐breaking (crabs,Cancer productus) and shell‐entry (seastars,Pisaster ochraceus) predators fed conspecific snails on the defensive shell morphology and antipredator behavior of a marine snail (Nucella lamellosa). When exposed to each feeding predator separately, snails responded with a combination of morphological defenses that reflect the attack mode of the predator and a generalized behavioral response. Snails responded to feeding crabs by increasing refuge use and producing a thick, rotund shell. Snails responded to feeding seastars with increased refuge use but produced elongate shells with high spires that allowed for greater retraction of the soft tissue. Seastar‐induced phenotypes reduced susceptibility to seastars relative to crab‐induced phenotypes, but crab‐induced phenotypes did not significantly reduce susceptibility to crabs, indicating an asymmetrical functional trade‐off. When feeding predators were combined, snails produced a morphological phenotype similar to that expressed in the presence of the predator that imposed the highest mortality at the population level, suggesting that predator‐induced morphology was prioritized according to predation risk. These results suggest that prioritizing conflicting defenses according to predator danger may be a common strategy for prey responding to combined predators, particularly in conjunction with generalized behavioral responses that reduce overall risk in multiple‐predator environments.