Foraging ecology of Kelp Gulls in natural and anthropogenically modified environments

Humans are having a profound impact on the natural environment through a myriad of activities, such as land use change or direct exploitation of resources. Some species are able to adapt to these changes and thrive in deeply modified environments. They are often considered winners of global change. Among these are Kelp GullsLarus dominicanus in South Africa, which have a generalist foraging nature. Despite their abundance and potential role in the ecosystem, knowledge on their foraging ecology is limited, with no understanding of the role of natural and anthropogenic food resources during breeding. The aim of this thesis was to assess the foraging movements, diet and health of Kelp Gulls breeding in seven different colonies varying in proximity to landfills. GPS loggers were deployed on incubating adults to assess foraging trip patterns, effort, and habitats. Diet and trophic ecology of adults and chicks was determined during the breeding season by combining conventional diet analysis (i.e. stomach content samples and regurgitated pellets) with stable isotope analysis of blood plasma. Finally, population health was estimated using indices of body condition for adults and chicks, and blood and faecal parasites were examined. The first successful tracking data from Kelp Gulls in South Africa revealed that birds from all colonies spent more time foraging in natural environments (marine, coastal and terrestrial) than in anthropogenically modified ones, irrelevant of the distance to the nearest landfill, potentially reflecting prey profitability or availability around thebreeding colonies. Gulls also had higher foraging effort when foraging at sea (longer travelling distance), which might be balanced by foraging on high energy prey in themarine environment (e.g. fish). Diet and trophic ecology data confirmed the wide range of resources Kelp Gulls were capable of exploiting. Anthropogenic items were important food sources at some colonies, while annual differences in trophic level targeted were apparent at some other colonies, possibly reflecting varying predation levels on other seabirds. Diet and trophic ecology generally differed between adults and chicks, with chicks being fed a more marine, i.e. fish, and higher trophic level diet, potentially due to the higher energy content of fish being important for chick growth. Despite differences between colonies in foraging effort and diet, body condition of both adults and chicks was similar across colonies. Birds from one of the urban colonies, foraging at the local landfill, tended to have slightly higher body condition values, possibly due to the high fat content of anthropogenic items, although this was not significant. Blood parasites were very scarce, with only one genus identified, Haemoproteus spp. Parasite abundance was significantly lower in chicks than in adults, implicating that adults might get infected in areas outside the colony. Faecal smears revealed the presence of yeast cells (Candida spp.) in birds, coinciding with higher body condition values, possibly linked to foraging habitat choice, as birds might ingest yeast cells when feeding in urban areas contaminated with human excrement.Kelp Gulls breeding in South Africa forage on a wide variety of resources and habitats, with limited apparent impact on their parasite load and body condition. All colonies foraged to some extend on natural sources, although some colonies located in very urban areas seemed to depend more closely on anthropogenic items as food resource. Therefore, changes in e.g. landfill management might cause changes in population dynamics, with possible repercussions on neighbouring bird populations. Theirgeneralist foraging nature, among others, makes Kelp Gulls winners of global change and is partly responsible for their increased population numbers. As they are often perceived as pests, information on the foraging ecology is important to manage gull populations effectively.Thesis (PhD) -- Faculty of Sciences, School of Environmental Sciences, 202

Foraging ecology of Kelp Gulls in natural and anthropogenically modified environments

Humans are having a profound impact on the natural environment through a myriad of activities, such as land use change or direct exploitation of resources. Some species are able to adapt to these changes and thrive in deeply modified environments. They are often considered winners of global change. Among these are Kelp GullsLarus dominicanus in South Africa, which have a generalist foraging nature. Despite their abundance and potential role in the ecosystem, knowledge on their foraging ecology is limited, with no understanding of the role of natural and anthropogenic food resources during breeding. The aim of this thesis was to assess the foraging movements, diet and health of Kelp Gulls breeding in seven different colonies varying in proximity to landfills. GPS loggers were deployed on incubating adults to assess foraging trip patterns, effort, and habitats. Diet and trophic ecology of adults and chicks was determined during the breeding season by combining conventional diet analysis (i.e. stomach content samples and regurgitated pellets) with stable isotope analysis of blood plasma. Finally, population health was estimated using indices of body condition for adults and chicks, and blood and faecal parasites were examined. The first successful tracking data from Kelp Gulls in South Africa revealed that birds from all colonies spent more time foraging in natural environments (marine, coastal and terrestrial) than in anthropogenically modified ones, irrelevant of the distance to the nearest landfill, potentially reflecting prey profitability or availability around thebreeding colonies. Gulls also had higher foraging effort when foraging at sea (longer travelling distance), which might be balanced by foraging on high energy prey in themarine environment (e.g. fish). Diet and trophic ecology data confirmed the wide range of resources Kelp Gulls were capable of exploiting. Anthropogenic items were important food sources at some colonies, while annual differences in trophic level targeted were apparent at some other colonies, possibly reflecting varying predation levels on other seabirds. Diet and trophic ecology generally differed between adults and chicks, with chicks being fed a more marine, i.e. fish, and higher trophic level diet, potentially due to the higher energy content of fish being important for chick growth. Despite differences between colonies in foraging effort and diet, body condition of both adults and chicks was similar across colonies. Birds from one of the urban colonies, foraging at the local landfill, tended to have slightly higher body condition values, possibly due to the high fat content of anthropogenic items, although this was not significant. Blood parasites were very scarce, with only one genus identified, Haemoproteus spp. Parasite abundance was significantly lower in chicks than in adults, implicating that adults might get infected in areas outside the colony. Faecal smears revealed the presence of yeast cells (Candida spp.) in birds, coinciding with higher body condition values, possibly linked to foraging habitat choice, as birds might ingest yeast cells when feeding in urban areas contaminated with human excrement.Kelp Gulls breeding in South Africa forage on a wide variety of resources and habitats, with limited apparent impact on their parasite load and body condition. All colonies foraged to some extend on natural sources, although some colonies located in very urban areas seemed to depend more closely on anthropogenic items as food resource. Therefore, changes in e.g. landfill management might cause changes in population dynamics, with possible repercussions on neighbouring bird populations. Theirgeneralist foraging nature, among others, makes Kelp Gulls winners of global change and is partly responsible for their increased population numbers. As they are often perceived as pests, information on the foraging ecology is important to manage gull populations effectively.Thesis (PhD) -- Faculty of Sciences, School of Environmental Sciences, 202

Stimulus Discrimination in Cerebellar Purkinje Neurons

Cerebellar Purkinje neurons fire spontaneously in the absence of synaptic input. Overlaid on this intrinsic activity, excitatory input from parallel fibres can add simple spikes to the output train, whereas inhibitory input from interneurons can introduce pauses. These and other influences lead to an irregular spike train output in Purkinje neurons in vitro and in vivo, supplying a variable inhibitory drive to deep cerebellar nuclear neurons. From a computational perspective, this variability raises some questions, as individual spikes induced by excitatory inputs are indistinguishable from intrinsic firing activity. Although bursts of high-frequency excitatory input could be discriminated unambiguously from background activity, granule neurons are known to fire in vivo over a wide range of frequencies. This would mean that much of the sensory information relayed through the cerebellar cortex would be lost within the random variation in background activity. We speculated that alternative mechanisms for signal discrimination may exist, and sought to identify characteristic motifs within the sequence of spikes that followed stimulation events. We found that under certain conditions, parallel fibre stimulation could reliably add a “couplet” of spikes with an unusually short interspike interval to the output train. Therefore, despite representing a small fraction of the total number of spikes, these signals can be reliably discriminated from background firing on a moment-to-moment basis, and could result in a differential downstream response

Follow-up of Bernese Mountain dogs and other dogs with serologically diagnosed Borrelia burgdorferi infection: What happens to seropositive animals?

<p>Abstract</p> <p>Background</p> <p>Data on the long-term outcome of <it>B. burgdorferi </it>infections in adult dogs are sparse. The aim of the present study was to investigate whether Bernese Mountain dogs with serological evidence of natural <it>B. burgdorferi </it>infection more often develop signs such as lameness, azotemia or proteinuria during a follow-up period of 2.5 to 3.0 years. Seropositive Bernese Mountain dogs were compared to seronegative Bernese Mountain dogs and to seropositive and seronegative control dogs of other breeds.</p> <p>Dogs included in a previous study on the prevalence of antibodies against <it>B. burgdorferi </it>in Bernese Mountain dogs were re-evaluated. Antibodies against <it>B. burgdorferi </it>were determined using an ELISA with a whole-cell sonicate as antigen and results were confirmed using a Western blot assay.</p> <p>Results</p> <p>Fifty-three Bernese Mountain dogs and 30 control dogs were re-evaluated. Re-evaluation was performed between 2.5 and 3.0 years (median 2.7 years) after the first assessment.</p> <p>The age of the dogs at the second evaluation ranged from 3 to 11 years (median 6 years). There were no significant differences with regard to poor general condition or lameness between the first and the second evaluation.</p> <p>At the first evaluation 22 (42%) of the Bernese Mountain dogs and 11 (37%) of the control dogs were considered positive for antibodies against <it>B. burgdorferi</it>. At the second evaluation 25 (47%) of the Bernese Mountain dogs and 12 (40%) of the control dogs were considered positive; 69% of the dogs showed the same serological result at both examinations and 31% were seroconverted or seroreverted. During the first examination, azotemia was diagnosed in 6 Bernese Mountain dogs and during the second examination in 11 Bernese Mountain dogs. No control dogs had azotemia in this study. In seropositive dogs there was no increase in lameness or signs of renal disease over time.</p> <p>Conclusion</p> <p>It may be concluded that antibodies against <it>B. burgdorferi </it>determined by whole cell ELISA and confirmed by Western blot were neither associated with the development of lameness nor with signs of renal disease like azotemia or proteinuria in dogs observed over a period of 2.5 to 3.0 years.</p

Probabilistic encoding of stimulus strength in astrocyte global calcium signals

Astrocyte calcium signals can range in size from subcellular microdomains to waves that spread through the whole cell (and into connected cells). The differential roles of such local or global calcium signaling are under intense investigation, but the mechanisms by which local signals evolve into global signals in astrocytes are not well understood, nor are the computational rules by which physiological stimuli are transduced into a global signal. To investigate these questions, we transiently applied receptor agonists linked to calcium signaling to primary cultures of cerebellar astrocytes. Astrocytes repetitively tested with the same stimulus responded with global signals intermittently, indicating that each stimulus had a defined probability for triggering a response. The response probability varied between agonists, increased with agonist concentration, and could be positively and negatively modulated by crosstalk with other signaling pathways. To better understand the processes determining the evolution of a global signal, we recorded subcellular calcium “puffs” throughout the whole cell during stimulation. The key requirement for puffs to trigger a global calcium wave following receptor activation appeared to be the synchronous release of calcium from three or more sites, rather than an increasing calcium load accumulating in the cytosol due to increased puff size, amplitude, or frequency. These results suggest that the concentration of transient stimuli will be encoded into a probability of generating a global calcium response, determined by the likelihood of synchronous release from multiple subcellular sites

TIRANA. Architecture as Political Actor

This book on the architecture of Tirana contains findings of the interdisciplinary seminar “TIRANA. Architecture as Political Actor” at Bauhaus-Universität Weimar. In photographs, texts and diagrams it shows the approach to an unknown city that was explored following the ideas of the Actor Network Theory (ANT). Thus, the book gives an insight into scientific as well as artistic works, both mirroring the attempt to grasp the role of architecture within political processes in the 20th century and today. In this compilation of the architectural-political networks, an image of the city of Tirana emerges that gives an idea of specific built structures as well as of the architecture as political actor on a meta-level. In doing so, the book itself becomes an actor in the discussion of the relationship of architecture and politics in Albania and an example for the use of ANT as scientific-artistic tool for the research on architectural “things” in the context of a city

Characterization of high-molecular weight by-products in the production of a trivalent bispecific 2+1 heterodimeric antibody

The development of increasingly complex antibody formats, such as bispecifics, can lead to the formation of increasingly complex high- and low-molecular-weight by-products. Here, we focus on the characterization of high molecular weight species (HMWs) representing the highest complexity of size variants. Standard methods used for product release, such as size exclusion chromatography (SEC), can separate HMW by-products from the main product, but cannot distinguish smaller changes in mass. Here, for the identification of the diverse and complex HMW variants of a trivalent bispecific CrossMAb antibody, offline fractionation, as well as production of HMW by-products combined with comprehensive analytical testing, was applied. Furthermore, HMW variants were analyzed regarding their chemical binding nature and tested in functional assays regarding changes in potency of the variants. Changes in potency were explained by detailed characterization using mass photometry, SDS-PAGE analysis, native mass spectrometry (MS) coupled to SEC and bottom-up proteomics. We identified a major portion of the HMW by-products to be non-covalently linked, leading to dissociation and changes in activity. We also identified and localized high heterogeneity of a by-product of concern and applied a CD3 affinity column coupled to native MS to annotate unexpected by-products. We present here a multi-method approach for the characterization of complex HMW by-products. A better understanding of these by-products is beneficial to guide analytical method development and proper specification setting for therapeutic bispecific antibodies to ensure constant efficacy and patient safety of the product through the assessment of by-products

New evidence for habitat specific selection in Wadden Sea Zostera marina populations revealed by genome scanning using SNP and microsatellite markers

Eelgrass Zostera marina is an ecosystem-engineering species of outstanding importance for coastal soft sediment habitats that lives in widely diverging habitats. Our first goal was to detect divergent selection and habitat adaptation at the molecular genetic level; hence, we compared three pairs of permanently submerged versus intertidal populations using genome scans, a genetic marker-based approach. Three different statistical approaches for outlier identification revealed divergent selection at 6 loci among 46 markers (6 SNPs, 29 EST microsatellites and 11 anonymous microsatellites). These outlier loci were repeatedly detected in parallel habitat comparisons, suggesting the influence of habitat-specific selection. A second goal was to test the consistency of the general genome scan approach by doubling the number of gene-linked microsatellites and adding single nucleotide polymorphism (SNP) loci, a novel marker type for seagrasses, compared to a previous study. Reassuringly, results with respect to selection were consistent among most marker loci. Functionally interesting marker loci were linked to genes involved in osmoregulation and water balance, suggesting different osmotic stress, and reproductive processes (seed maturation), pointing to different life history strategies. The identified outlier loci are valuable candidates for further investigation into the genetic basis of natural selection

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field