Novelty detection and context dependent processing of sky-compass cues in the brain of the desert locust Schistocerca gregaria

NERVOUS SYSTEMS facilitate purposeful interactions between animals and their environment, based on the perceptual powers, cognition and higher motor control. Through goal-directed behavior, the animal aims to increase its advantage and minimize risk. For instance, the migratory desert locust should profit from being fast in finding a fresh habitat, thus minimizing the investment of bodily resources in locomotion as well as the risk of starvation or capture by a predator en route. Efficient solutions to this and similar tasks – be it finding your way to work, the daily foraging of worker bees or the seasonal long-range migration of monarch butterflies - strongly depend on spatial orientation in local or global frames of reference. Local settings may include visual landmarks at stable positions that can be mapped onto egocentric space and learned for orientation, e.g. to remember a short route to a source of benefit (e.g. food) that is distant or visually less salient than the landmarks. Compass signals can mediate orientation to a global reference-frame (allothetic orienation), e.g. for locomotion in a particular compass direction or to merely ensure motion along a straight line. Whilst spatial orientation is a prerequisite of doing the planned in such tasks, animal survival in general depends on the ability to adequately respond to the unexpected, i.e. to unpredicted events such as the approach of a predator or mate. The process of identifying relevant events in the outside world that are not predictable from preceding events is termed novelty detection. Yet, the definition of ‘novelty’ is highly contextual: depending on the current situation and goal, some changes may be irrelevant and remain ´undetected´. The present thesis describes neuronal representations of a compass stimulus, correlates of novelty detection and interactions between the two in the minute brain of an insect, the migratory desert locust Schistocerca gregaria. Experiments were carried out in tethered locusts with legs and wings removed. More precisely, adult male subjects in the gregarious phase (see phase theory, Uvarov 1966) that migrates in swarms across territories in North Africa and the Middle East were used. The author performed electrophysiological recordings from single neurons in the locust brain, while either the compass stimulus (Chapter I) or events in the visual scenery (Chapter II) or combinations of both (Chapter III) were being presented to the animal. Injections of a tracer through the recording electrode, visualized by means of fluorescent-dye coupling, allowed the allocation of cellular morphologies to previously described types of neuron or the characterization of novel cell types, respectively. Recordings were focused on cells of the central complex, a higher integration area in the insect brain that was shown to be involved in the visually mediated control of goal-directed locomotion. Experiments delivered insights into how representations of the compass cue are modulated in a manner suited for their integration in the control of goal-directed locomotion. In particular, an interaction between compass-signaling and novelty detection was found, corresponding to a process in which input in one sensory domain (object vision) modulates the processing of concurrent input to a different exteroceptive sensory system (compass sense). In addition to deepening the understanding of the compass network in the locust brain, the results reveal fundamental parallels to higher context-dependent processing of sensory information by the vertebrate cortex, both with respect to spatial cues and novelty detection

Der negative Einfluss disseminierter Tumorzellen auf das Überleben von Patienten nach Resektion kolorektaler Lebermetastasen

An einem Patientengut von 108 Patienten wurde der Einfluss disseminierter Tumorzellen im peripheren Blut und im Knochenmark nach Resektion kolorektaler Lebermetastasen untersucht. Als Nachweismethode wurde die RT-PCR verwendet

Brain fiber tract plasticity in experimental spinal cord injury: diffusion tensor imaging.

Diffusion tensor imaging (DTI) and immunohistochemistry were performed in spinal cord injured rats to understand the basis for activation of multiple regions in the brain observed in functional magnetic resonance imaging (fMRI) studies. The measured fractional anisotropy (FA), a scalar measure of diffusion anisotropy, along the region encompassing corticospinal tracts (CST) indicates significant differences between control and injured groups in the 3 to 4 mm area posterior to bregma that correspond to internal capsule and cerebral peduncle. Additionally, DTI-based tractography in injured animals showed increased number of fibers that extend towards the cortex terminating in the regions that were activated in fMRI. Both the internal capsule and cerebral peduncle demonstrated an increase in GFAP-immunoreactivity compared to control animals. GAP-43 expression also indicates plasticity in the internal capsule. These studies suggest that the previously observed multiple regions of activation in spinal cord injury are, at least in part, due to the formation of new fibers

Automatic quantification of lobular inflammation and hepatocyte ballooning in NAFLD liver biopsies

Automatic quantification of cardinal histologic features of nonalcoholic fatty liver disease (NAFLD) may reduce human variability and allow continuous rather than semiquantitative assessment of injury. We recently developed an automated classifier that can detect and quantify macrosteatosis with greater than or equal to 95% precision and recall (sensitivity). Here, we report our early results on the classifier's performance in detecting lobular inflammation and hepatocellular ballooning. Automatic quantification of lobular inflammation and ballooning was performed on digital images of hematoxylin and eosin–stained slides of liver biopsy samples from 59 individuals with normal liver histology and varying severity of NAFLD. Two expert hepatopathologists scored liver biopsies according the nonalcoholic steatohepatitis clinical research network scoring system and provided annotations of lobular inflammation and hepatocyte ballooning on the digital images. The classifier had precision and recall of 70% and 49% for lobular inflammation, and 91% and 54% for hepatocyte ballooning. In addition, the classifier had an area under the curve of 95% for lobular inflammation and 98% for hepatocyte ballooning. The Spearman rank correlation coefficient for comparison with pathologist grades was 45.2% for lobular inflammation and 46% for hepatocyte ballooning. Our novel observations demonstrate that automatic quantification of cardinal NAFLD histologic lesions is feasible and offer promise for further development of automatic quantification as a potential aid to pathologists evaluating NAFLD biopsies in clinical practice and clinical trials

Evaluation of an Innovative Transitional Care Clinic in an Interprofessional Teaching Practice

During transitions of care, great opportunity exists for miscommunication, poor care coordination, adverse events, medication errors and unnecessary healthcare utilization costing billions of dollars annually. An Interprofessional Transitions of Care (IPTC) clinic was developed utilizing a Family Medicine team that included physicians, nurses, a clinical social worker, and a clinical pharmacist. The purpose of this study was to determine if utilization of an IPTC clinic prevented hospital readmission, and to identify factors that predict most benefit from an interprofessional approach to transitions of care. A retrospective chart review of 1,001 patients was completed. A treatment group (TG) of 501 patients were offered IPTC clinic appointments following hospital discharge. A control group (CG) of 500 patients were hospitalized and received traditional follow-up prior to development of the IPTC clinic. Traditional follow-up typically consisted of an automated appointment reminder and a physician office visit. Outcomes assessed included 30-day hospital readmission of TG versus CG, and whether patient characteristics predisposed specific patient groups to attend IPTC appointments or benefit more from IPTC participation. Compared with CG, patients who completed an IPTC appointment were 48% less likely to be readmitted to the hospital within 30 days. Patients with congestive heart failure and cellulitis particularly benefited from IPTC. Telephone contact within two business days of discharge was the greatest predictor of patients attending an IPTC appointment. These results demonstrate that an interprofessional approach to transitions in care effectively addresses this high risk for error and high cost time in the continuum of care

High Resolution Vascular Imaging of the Rat Spine using Liposomal Blood Pool MR Agent

High resolution, vascular magnetic resonance imaging of the spine region in small animals poses several challenges. The small anatomical features, extravascular diffusion, and the low signal-to-noise ratio limit the use of conventional contrast agents. We hypothesize that a long circulating, intravascular liposomal-encapsulated MR contrast agent (liposomal-Gd) would facilitate visualization of small anatomical features of the perispinal vasculature not visible with conventional contrast agent (Gd-DTPA)

Opsin expression, physiological characterization and identification of photoreceptor cells in the dorsal rim area and main retina of the desert locust, Schistocerca gregaria.

For compass orientation many insects rely on the pattern of sky polarization, but some species also exploit the sky chromatic contrast. Desert locusts, Schistocerca gregaria, detect polarized light through a specialized dorsal rim area (DRA) in their compound eye. To better understand retinal mechanisms underlying visual navigation, we compared opsin expression, spectral and polarization sensitivities and response-stimulus intensity functions in the DRA and main retina of the locust. In addition to previously characterized opsins of long-wavelength-absorbing (Lo1) and blue-absorbing visual pigments (Lo2), we identified an opsin of an ultraviolet-absorbing visual pigment (LoUV). DRA photoreceptors exclusively expressed Lo2, had peak spectral sensitivities at 441 nm and showed high polarization sensitivity (PS 1.3-31.7). In contrast, ommatidia in the main eye co-expressed Lo1 and Lo2 in five photoreceptors, expressed Lo1 in two proximal photoreceptors, and Lo2 or LoUV in one distal photoreceptor. Correspondingly, we found broadband blue- and green-peaking spectral sensitivities in the main eye and one narrowly tuned UV peaking receptor. Polarization sensitivity in the main retina was low (PS 1.3-3.8). V-log I functions in the DRA were steeper than in the main retina, supporting a role in polarization vision. Desert locusts occur as two morphs, a day-active gregarious and a night-active solitarious form. In solitarious locusts, sensitivities in the main retina were generally shifted to longer wavelengths, particularly in ventral eye regions, supporting a nocturnal lifestyle at low light levels. The data support the role of the DRA in polarization vision and suggest trichromatic colour vision in the desert locust

Role of the K1K_1 meson in K0K^0 photoproduction off the deuteron

Neutral kaon photoproduction off the nucleon and deuteron has been reinvestigated by utilizing the new experimental data on both targets. An isobar model for elementary operator and impulse approximation for the reaction on the deuteron have been used. The available free parameters in the elementary model have been extracted from both elementary and deuteron data. In contrast to the elementary reaction, fitting the deuteron data requires an inclusion of weighting factor. The result indicates that the angular distribution of the elementary $K^0\Lambda$ process does not show backward peaking behavior.Comment: 4 pages, 4 figures, prepared for the Fifth Asia-Pacific Conference on Few-Body Problems in Physics 2011 (APFB2011), Seoul, Korea, August 22-26, 201