Multiple predator defence strategies in Daphnia pulex and their relation to native habitat

Daphnia may respond with an array of anti-predator defences(behavioural, morphological and life history) to a chemicalcue (kairomone) exuded by its predators: fish and Chaoborus.Given the wide array of potential responses, it is an interestingquestion whether anti-predator defences are coupled or independentof each other. Since anti-predator responses are costly andeven possessing the genetic information to respond to a certainpredator might involve a cost, clones may only react to predatorsthey co-occur with in nature. In this study, we provide evidencefor an uncoupling of responses by Daphnia pulex in several anti-predatordefences against Chaoborus. We were unable to detect a correlationbetween behavioural (migration), morphological (neck-spine induction)and life history [growth rate, neonate size and size at firstreproduction (SFR)] responses. Furthermore, anti-predator responsesdid not always comply with what is commonly believed. We foundthat Daphnia clones can migrate up or down when exposed to fishor Chaoborus kairomone and that population growth rate, neonatesize and SFR can increase or decrease in response to Chaoboruskairomone. We also show patterns in anti-predator defences thatseem to relate to the habitat from which clones were derived.Daphnia clones that were collected in habitats with Chaoborusas the dominant predator tended to react strongly to Chaoboruskairomone by migrating upward and producing neck-spines. Themigration behaviour against fish kairomone in these clones wasoften an unexpected upward migration. The Daphnia clone thatco-existed with fish predators showed a downward migration inthe presence of fish as well as Chaoborus kairomone. Clonesthat had occurred with either both or no predators had mixedresponses. We sometimes found an upward migration in combinationwith smaller body size as a response to Chaoborus kairomone.This may be interpreted as a behavioural defence against Chaoborusand a life-history defence against fish. Daphnia seem not toexhibit defence behaviour against predators they do not co-occurwith. It might be costly for Daphnia to maintain genetic informationto respond to these predators and protect that information fromgenetic drift.     

Tuning PAK Activity to Rescue Abnormal Myelin Permeability in HNPP

Schwann cells in the peripheral nervous systems extend their membranes to wrap axons concentrically and form the insulating sheath, called myelin. The spaces between layers of myelin are sealed by myelin junctions. This tight insulation enables rapid conduction of electric impulses (action potentials) through axons. Demyelination (stripping off the insulating sheath) has been widely regarded as one of the most important mechanisms altering the action potential propagation in many neurological diseases. However, the effective nerve conduction is also thought to require a proper myelin seal through myelin junctions such as tight junctions and adherens junctions. In the present study, we have demonstrated the disruption of myelin junctions in a mouse model (Pmp22+/-) of hereditary neuropathy with liability to pressure palsies (HNPP) with heterozygous deletion of Pmp22 gene. We observed a robust increase of F-actin in Pmp22+/- nerve regions where myelin junctions were disrupted, leading to increased myelin permeability. These abnormalities were present long before segmental demyelination at the late phase of Pmp22+/- mice. Moreover, the increase of F-actin levels correlated with an enhanced activity of p21-activated kinase (PAK1), a molecule known to regulate actin polymerization. Pharmacological inhibition of PAK normalized levels of F-actin, and completely prevented the progression of the myelin junction disruption and nerve conduction failure in Pmp22+/- mice. Our findings explain how abnormal myelin permeability is caused in HNPP, leading to impaired action potential propagation in the absence of demyelination. We call it “functional demyelination”, a novel mechanism upstream to the actual stripping of myelin that is relevant to many demyelinating diseases. This observation also provides a potential therapeutic approach for HNPP.     

Development of an image pre‐processor for operational hyperspectral laryngeal cancer detection

Hyperspectral imaging (HSI) is a technology with high potential in the field of non‐invasive detection of cancer. However, in complex imaging situations like HSI of the larynx with a rigid endoscope, various image interferences can disable a proper classification of cancerous tissue. We identified three main problems: i) misregistration of single images in a HS cube due to patient heartbeat ii) image noise and iii) specular reflections (SR). Consequently, an image pre‐processor is developed in the current paper to overcome these image interferences. It encompasses i) image registration ii) noise removal by minimum noise fraction (MNF) transformation and iii) a novel SR detection method. The results reveal that the pre‐processor improves classification performance, while the newly developed SR detection method outperforms global thresholding technique hitherto used by 46%. The novel pre‐processor will be used for future studies towards the development of an operational scheme for HS‐based larynx cancer detection.

RGB image of the larynx derived from the hyperspectral cube and corresponding specular reflections ( a ) manually segmented and ( b ) detected by a novel specular reflection detection method.     

IL-33 facilitates rapid expulsion of the parasitic nematode Strongyloides ratti from the intestine via ILC2- and IL-9-driven mast cell activation

Parasitic helminths are sensed by the immune system via tissue-derived alarmins that promote the initiation of the appropriate type 2 immune responses. Here we establish the nuclear alarmin cytokine IL-33 as a non-redundant trigger of specifically IL-9-driven and mast cell-mediated immunity to the intestinal parasite Strongyloides ratti. Blockade of endogenous IL-33 using a helminth-derived IL-33 inhibitor elevated intestinal parasite burdens in the context of reduced mast cell activation while stabilization of endogenous IL-33 or application of recombinant IL-33 reciprocally reduced intestinal parasite burdens and increased mast cell activation. Using gene-deficient mice, we show that application of IL-33 triggered rapid mast cell-mediated expulsion of parasites directly in the intestine, independent of the adaptive immune system, basophils, eosinophils or Gr-1⁺ cells but dependent on functional IL-9 receptor and innate lymphoid cells (ILC). Thereby we connect the described axis of IL-33-mediated ILC2 expansion to the rapid initiation of IL-9-mediated and mast cell-driven intestinal anti-helminth immunity.     

Evaluation of Different Biomarkers to Predict Individual Radiosensitivity in an Inter-Laboratory Comparison–Lessons for Future Studies

Radiotherapy is a powerful cure for several types of solid tumours, but its application is often limited because of severe side effects in individual patients. With the aim to find biomarkers capable of predicting normal tissue side reactions we analysed the radiation responses of cells from individual head and neck tumour and breast cancer patients of different clinical radiosensitivity in a multicentric study. Multiple parameters of cellular radiosensitivity were analysed in coded samples of peripheral blood lymphocytes (PBLs) and derived lymphoblastoid cell lines (LCLs) from 15 clinical radio-hypersensitive tumour patients and compared to age- and sex-matched non-radiosensitive patient controls and 15 lymphoblastoid cell lines from age- and sex- matched healthy controls of the KORA study. Experimental parameters included ionizing radiation (IR)-induced cell death (AnnexinV), induction and repair of DNA strand breaks (Comet assay), induction of yH2AX foci (as a result of DNA double strand breaks), and whole genome expression analyses. Considerable inter-individual differences in IR-induced DNA strand breaks and their repair and/or cell death could be detected in primary and immortalised cells with the applied assays. The group of clinically radiosensitive patients was not unequivocally distinguishable from normal responding patients nor were individual overreacting patients in the test system unambiguously identified by two different laboratories. Thus, the in vitro test systems investigated here seem not to be appropriate for a general prediction of clinical reactions during or after radiotherapy due to the experimental variability compared to the small effect of radiation sensitivity. Genome-wide expression analysis however revealed a set of 67 marker genes which were differentially induced 6 h after in vitro-irradiation in lymphocytes from radio-hypersensitive and non-radiosensitive patients. These results warrant future validation in larger cohorts in order to determine parameters potentially predictive for clinical radiosensitivity.     

Appearance, “state,” and behavior in male zebra finches, Taeniopygia guttata

Secondary sexual traits are often costly to produce and therefore an individual’s appearance can signal its quality. As the quality of an individual influences the payoffs associated with the actions it can perform, its appearance should also influence its behavior. Here we investigate whether male zebra finches, Taeniopygia guttata, change their behavior (and their energetic states) after artificial manipulations of their appearance, using different colored leg bands, and if such effects carry over after the end of the manipulation, as might be expected if appearance-mediated social dynamics “lock” individuals into different states. During three experimental phases, in which all males in a group wore neutral colored leg bands at the beginning (phase I), then wore attractive, unattractive, and neutral colored bands, respectively (phase II), before wearing the neutral color again (phase III), we found no evidence of an effect of the appearance manipulation on state, weight or any behavioral traits we measured. Nevertheless, we found that individuals that stored more fat were more likely to initiate and win aggressive interactions but were less likely to be recipients of aggression. This association between energetic state and aggressive behavior is discussed from both strategic body mass regulation and sexual selection perspectives.     

Differential effects of intranasal oxytocin on sexual experiences and partner interactions in couples

Knowledge about the effects of the neuropeptide oxytocin (OXT) on human sexual behaviors and partner interactions remains limited. Based on our previous studies, we hypothesize that OXT should be able to positively influence parameters of sexual function and couple interactions.     

The Genetic Reprogramming of Polyamine Homeostasis During the Functional Assembly,Maturation, and Senescence-Specific Decline of the Photosynthetic Apparatus in Hordeum vulgare

Polyamines (PAs) are ubiquitous aliphatic amines important and, in many cases, essential for plant growth, abiotic stress response, and tolerance. Here we provide evidence for genetic reprogramming of PA homeostasis that occurs during the de-etiolation, maturation, and senescence of the primary leaf in Hordeum vulgare (barley). We analyzed expression levels of key genes in the anabolic and catabolic branches of PA metabolism throughout the life cycle of etioplasts, at all steps of the functional assembly of the photosynthetic apparatus, and during leaf senescence. The changes in the total PAs titer of the leaf were followed throughout the different developmental stages. Furthermore, we align all three stages of the photosynthetic performance (rapid light-dependent de-etiolation, phase of optimal efficiency, and senescence-induced deterioration) with the changes in PA homeostasis. Finally, we focus on two phases during aging (early and late senescence) and we present their bioenergetic (for example, PSII maximal efficiency, ATPase conductivity) and genetic profiles, with emphasis on sensitive parameters that describe this process for the photosynthetic apparatus and PA metabolism, respectively. In conclusion, the fine tuning of PA homeostasis is regulated by the simultaneous genetic reprogramming of the anabolic and catabolic branches of PA metabolism and adjusts all the developmental changes from de-etiolation to maturation and senescence.     

Still a one species genus? Strong genetic diversification in the world’s largest living odonate,the Neotropical damselfly Megaloprepus caerulatus

Mesoamerican biodiversity is increasingly threatened by anthropogenic destruction of natural land cover. Habitat degradation and climate change are primary threats to specialized forest odonate species that are important model organisms for forest health and defining conservation units. The extreme niche specialization of Megaloprepus caerulatus, the world’s largest extant odonate, makes it well suited as an indicator for changing environmental conditions. Megaloprepus, which is considered to be a monospecific genus, is highly dependent on old growth forests whose water filled tree holes are limiting reproductive resources for this species. Here, we focus on the question how historical and recent fragmentation events, strong niche conservatism and ecological conditions have affected population dynamics, viability and the species status in this evolutionarily old genus. Two mitochondrial sequence markers (ND1 and 16S rRNA) and a set of microsatellites were used to analyze population structure and genetic diversity of M. caerulatus in the northern part of its distributional range. Results suggested an absence of gene flow and no shared haplotypes among the study populations. Statistical parsimony indicated high sub-structuring among populations with sequence diversity similar to levels found at the species level compared to other odonates. In sum, the genetic data suggest that Megaloprepus may actually consist of more than one species. The taxonomic status of the group should be revised in light of the three distinct genetic clusters found in different forest regions. The results may also allow insights into the impact of recent and historical habitat fragmentation on a strong Neotropical forest restricted insect species.