TY - JOUR A1 - Grubisic, Maja A1 - Haim, Abraham A1 - Bhusal, Pramod A1 - Dominoni, Davide M. A1 - Gabriel, Katharina M. A. A1 - Jechow, Andreas A1 - Kupprat, Franziska A1 - Lerner, Amit A1 - Marchant, Paul A1 - Riley, William A1 - Stebelova, Katarina A1 - van Grunsven, Roy H. A. A1 - Zeman, Michal A1 - Zubidat, Abed E. A1 - Hölker, Franz T1 - Light Pollution, Circadian Photoreception, and Melatonin in Vertebrates JF - Sustainability N2 - Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transition to new efficient lighting technologies. However, ALAN and resulting light pollution can cause unintended physiological consequences. In vertebrates, production of melatonin—the “hormone of darkness” and a key player in circadian regulation—can be suppressed by ALAN. In this paper, we provide an overview of research on melatonin and ALAN in vertebrates. We discuss how ALAN disrupts natural photic environments, its effect on melatonin and circadian rhythms, and different photoreceptor systems across vertebrate taxa. We then present the results of a systematic review in which we identified studies on melatonin under typical light-polluted conditions in fishes, amphibians, reptiles, birds, and mammals, including humans. Melatonin is suppressed by extremely low light intensities in many vertebrates, ranging from 0.01–0.03 lx for fishes and rodents to 6 lx for sensitive humans. Even lower, wavelength-dependent intensities are implied by some studies and require rigorous testing in ecological contexts. In many studies, melatonin suppression occurs at the minimum light levels tested, and, in better-studied groups, melatonin suppression is reported to occur at lower light levels. We identify major research gaps and conclude that, for most groups, crucial information is lacking. No studies were identified for amphibians and reptiles and long-term impacts of low-level ALAN exposure are unknown. Given the high sensitivity of vertebrate melatonin production to ALAN and the paucity of available information, it is crucial to research impacts of ALAN further in order to inform effective mitigation strategies for human health and the wellbeing and fitness of vertebrates in natural ecosystems. KW - ALAN KW - artificial light at night KW - biological rhythm KW - circadian rhythm KW - melatonin Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193095 SN - 2071-1050 VL - 11 IS - 22 ER - TY - JOUR A1 - Heydarian, Motaharehsadat A1 - Yang, Tao A1 - Schweinlin, Matthias A1 - Steinke, Maria A1 - Walles, Heike A1 - Rudel, Thomas A1 - Kozjak-Pavlovic, Vera T1 - Biomimetic human tissue model for long-term study of Neisseria gonorrhoeae infection JF - Frontiers in Microbiology N2 - Gonorrhea is the second most common sexually transmitted infection in the world and is caused by Gram-negative diplococcus Neisseria gonorrhoeae. Since N. gonorrhoeae is a human-specific pathogen, animal infection models are only of limited use. Therefore, a suitable in vitro cell culture model for studying the complete infection including adhesion, transmigration and transport to deeper tissue layers is required. In the present study, we generated three independent 3D tissue models based on porcine small intestinal submucosa (SIS) scaffold by co-culturing human dermal fibroblasts with human colorectal carcinoma, endometrial epithelial, and male uroepithelial cells. Functional analyses such as transepithelial electrical resistance (TEER) and FITC-dextran assay indicated the high barrier integrity of the created monolayer. The histological, immunohistochemical, and ultra-structural analyses showed that the 3D SIS scaffold-based models closely mimic the main characteristics of the site of gonococcal infection in human host including the epithelial monolayer, the underlying connective tissue, mucus production, tight junction, and microvilli formation. We infected the established 3D tissue models with different N. gonorrhoeae strains and derivatives presenting various phenotypes regarding adhesion and invasion. The results indicated that the disruption of tight junctions and increase in interleukin production in response to the infection is strain and cell type-dependent. In addition, the models supported bacterial survival and proved to be better suitable for studying infection over the course of several days in comparison to commonly used Transwell® models. This was primarily due to increased resilience of the SIS scaffold models to infection in terms of changes in permeability, cell destruction and bacterial transmigration. In summary, the SIS scaffold-based 3D tissue models of human mucosal tissues represent promising tools for investigating N. gonorrhoeae infections under close-to-natural conditions. KW - 3D tissue model KW - small intestinal submucosa scaffold KW - co-culture KW - infection KW - Neisseria gonorrhoeae Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197912 SN - 1664-302X VL - 10 IS - 1740 ER - TY - JOUR A1 - Grebinyk, Anna A1 - Prylutska, Svitlana A1 - Chepurna, Oksana A1 - Grebinyk, Sergii A1 - Prylutskyy, Yuriy A1 - Ritter, Uwe A1 - Ohulchanskyy, Tymish Y. A1 - Matyshevska, Olga A1 - Dandekar, Thomas A1 - Frohme, Marcus T1 - Synergy of chemo- and photodynamic therapies with C\(_{60}\) Fullerene-Doxorubicin nanocomplex JF - Nanomaterials N2 - A nanosized drug complex was explored to improve the efficiency of cancer chemotherapy, complementing it with nanodelivery and photodynamic therapy. For this, nanomolar amounts of a non-covalent nanocomplex of Doxorubicin (Dox) with carbon nanoparticle C\(_{60}\) fullerene (C\(_{60}\)) were applied in 1:1 and 2:1 molar ratio, exploiting C\(_{60}\) both as a drug-carrier and as a photosensitizer. The fluorescence microscopy analysis of human leukemic CCRF-CEM cells, in vitro cancer model, treated with nanocomplexes showed Dox’s nuclear and C\(_{60}\)'s extranuclear localization. It gave an opportunity to realize a double hit strategy against cancer cells based on Dox's antiproliferative activity and C\(_{60}\)'s photoinduced pro-oxidant activity. When cells were treated with 2:1 C\(_{60}\)-Dox and irradiated at 405 nm the high cytotoxicity of photo-irradiated C\(_{60}\)-Dox enabled a nanomolar concentration of Dox and C\(_{60}\) to efficiently kill cancer cells in vitro. The high pro-oxidant and pro-apoptotic efficiency decreased IC\(_{50}\) 16, 9 and 7 × 10\(^3\)-fold, if compared with the action of Dox, non-irradiated nanocomplex, and C\(_{60}\)'s photodynamic effect, correspondingly. Hereafter, a strong synergy of therapy arising from the combination of C\(_{60}\)-mediated Dox delivery and C\(_{60}\) photoexcitation was revealed. Our data indicate that a combination of chemo- and photodynamic therapies with C\(_{60}\)-Dox nanoformulation provides a promising synergetic approach for cancer treatment. KW - photodynamic chemotherapy KW - synergistic effect KW - C\(_{60}\) fullerene KW - Doxorubicin KW - nanocomplex KW - leukemic cells KW - apoptosis Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193140 SN - 2079-4991 VL - 9 IS - 11 ER - TY - JOUR A1 - Villalobos, Alvaro S. A1 - Wiese, Jutta A1 - Imhoff, Johannes F. A1 - Dorador, Cristina A1 - Keller, Alexander A1 - Hentschel, Ute T1 - Systematic affiliation and genome analysis of Subtercola vilae DB165T with particular emphasis on cold adaptation of an isolate from a high-altitude cold volcano lake JF - Microorganisms N2 - Among the Microbacteriaceae the species of Subtercola and Agreia form closely associated clusters. Phylogenetic analysis demonstrated three major phylogenetic branches of these species. One of these branches contains the two psychrophilic species Subtercola frigoramans and Subtercola vilae, together with a larger number of isolates from various cold environments. Genomic evidence supports the separation of Agreia and Subtercola species. In order to gain insight into the ability of S. vilae to adapt to life in this extreme environment, we analyzed the genome with a particular focus on properties related to possible adaptation to a cold environment. General properties of the genome are presented, including carbon and energy metabolism, as well as secondary metabolite production. The repertoire of genes in the genome of S. vilae DB165\(^T\) linked to adaptations to the harsh conditions found in Llullaillaco Volcano Lake includes several mechanisms to transcribe proteins under low temperatures, such as a high number of tRNAs and cold shock proteins. In addition, S. vilae DB165\(^T\) is capable of producing a number of proteins to cope with oxidative stress, which is of particular relevance at low temperature environments, in which reactive oxygen species are more abundant. Most important, it obtains capacities to produce cryo-protectants, and to combat against ice crystal formation, it produces ice-binding proteins. Two new ice-binding proteins were identified which are unique to S. vilae DB165\(^T\). These results indicate that S. vilae has the capacity to employ different mechanisms to live under the extreme and cold conditions prevalent in Llullaillaco Volcano Lake. KW - cold adaptation KW - Subtercola vilae KW - genome analysis KW - systematic affiliation KW - Llullaillaco Volcano Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197394 SN - 2076-2607 VL - 7 IS - 4 ER - TY - JOUR A1 - Liu, Ruiqi A1 - Kinoshita, Masato A1 - Adolfi, Mateus C. A1 - Schartl, Manfred T1 - Analysis of the role of the Mc4r system in development, growth, and puberty of medaka JF - Frontiers in Endocrinology N2 - In mammals the melanocortin 4 receptor (Mc4r) signaling system has been mainly associated with the regulation of appetite and energy homeostasis. In fish of the genus Xiphophorus (platyfish and swordtails) puberty onset is genetically determined by a single locus, which encodes the mc4r. Wild populations of Xiphophorus are polymorphic for early and late-maturing individuals. Copy number variation of different mc4r alleles is responsible for the difference in puberty onset. To answer whether this is a special adaptation of the Mc4r signaling system in the lineage of Xiphophorus or a more widely conserved mechanism in teleosts, we studied the role of Mc4r in reproductive biology of medaka (Oryzias latipes), a close relative to Xiphophorus and a well-established model to study gonadal development. To understand the potential role of Mc4r in medaka, we characterized the major features of the Mc4r signaling system (mc4r, mrap2, pomc, agrp1). In medaka, all these genes are expressed before hatching. In adults, they are mainly expressed in the brain. The transcript of the receptor accessory protein mrap2 co-localizes with mc4r in the hypothalamus in adult brains indicating a conserved function of modulating Mc4r signaling. Comparing growth and puberty between wild-type and mc4r knockout medaka revealed that absence of Mc4r does not change puberty timing but significantly delays hatching. Embryonic development of knockout animals is retarded compared to wild-types. In conclusion, the Mc4r system in medaka is involved in regulation of growth rather than puberty. KW - medaka KW - Mc4r KW - knockout KW - puberty KW - growth Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201472 VL - 10 ER - TY - JOUR A1 - Krebs, Markus A1 - Behrmann, Christoph A1 - Kalogirou, Charis A1 - Sokolakis, Ioannis A1 - Kneitz, Susanne A1 - Kruithof-de Julio, Marianna A1 - Zoni, Eugenio A1 - Rech, Anne A1 - Schilling, Bastian A1 - Kübler, Hubert A1 - Spahn, Martin A1 - Kneitz, Burkhard T1 - miR-221 Augments TRAIL-mediated apoptosis in prostate cancer cells by inducing endogenous TRAIL expression and targeting the functional repressors SOCS3 and PIK3R1 JF - BioMed Research International N2 - miR-221 is regarded as an oncogene in many malignancies, and miR-221-mediated resistance towards TRAIL was one of the first oncogenic roles shown for this small noncoding RNA. In contrast, miR-221 is downregulated in prostate cancer (PCa), thereby implying a tumour suppressive function. By using proliferation and apoptosis assays, we show a novel feature of miR-221 in PCa cells: instead of inducing TRAIL resistance, miR-221 sensitized cells towards TRAIL-induced proliferation inhibition and apoptosis induction. Partially responsible for this effect was the interferon-mediated gene signature, which among other things contained an endogenous overexpression of the TRAIL encoding gene TNFSF10. This TRAIL-friendly environment was provoked by downregulation of the established miR-221 target gene SOCS3. Moreover, we introduced PIK3R1 as a target gene of miR-221 in PCa cells. Proliferation assays showed that siRNA-mediated downregulation of SOCS3 and PIK3R1 mimicked the effect of miR-221 on TRAIL sensitivity. Finally, Western blotting experiments confirmed lower amounts of phospho-Akt after siRNA-mediated downregulation of PIK3R1 in PC3 cells. Our results further support the tumour suppressing role of miR-221 in PCa, since it sensitises PCa cells towards TRAIL by regulating the expression of the oncogenes SOCS3 and PIK3R1. Given the TRAIL-inhibiting effect of miR-221 in various cancer entities, our results suggest that the influence of miR-221 on TRAIL-mediated apoptosis is highly context- and entity-dependent. KW - Cancer Cell Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-202480 VL - 2019 ER - TY - JOUR A1 - Molinas-González, Carlos R. A1 - Castro, Jorge A1 - González-Megías, Adela A1 - Leverkus, Alexandro B. T1 - Effects of post-fire deadwood management on soil macroarthropod communities JF - Forests N2 - Dead wood comprises a vast amount of biological legacies that set the scene for ecological regeneration after wildfires, yet its removal is the most frequent management strategy worldwide. Soil-dwelling organisms are conspicuous, and they provide essential ecosystem functions, but their possible affection by different post-fire management strategies has so far been neglected. We analyzed the abundance, richness, and composition of belowground macroarthropod communities under two contrasting dead-wood management regimes after a large wildfire in the Sierra Nevada Natural and National Park (Southeast Spain). Two plots at different elevation were established, each containing three replicates of two experimental treatments: partial cut, where trees were cut and their branches lopped off and left over the ground, and salvage logging, where all the trees were cut, logs were piled, branches were mechanically masticated, and slash was spread on the ground. Ten years after the application of the treatments, soil cores were extracted from two types of microhabitat created by these treatments: bare-soil (in both treatments) and under-logs (in the partial cut treatment only). Soil macroarthropod assemblages were dominated by Hemiptera and Hymenoptera (mostly ants) and were more abundant and richer in the lowest plot. The differences between dead-wood treatments were most evident at the scale of management interventions: abundance and richness were lowest after salvage logging, even under similar microhabitats (bare-soil). However, there were no significant differences between microhabitat types on abundance and richness within the partial cut treatment. Higher abundance and richness in the partial cut treatment likely resulted from higher resource availability and higher plant diversity after natural regeneration. Our results suggest that belowground macroarthropod communities are sensitive to the manipulation of dead-wood legacies and that management through salvage logging could reduce soil macroarthropod recuperation compared to other treatments with less intense management even a decade after application. KW - forest fire KW - burnt-wood KW - species richness KW - soil fauna KW - post-fire management Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193079 SN - 1999-4907 VL - 10 IS - 11 ER - TY - JOUR A1 - Latifi, Hooman A1 - Valbuena, Ruben T1 - Current trends in forest ecological applications of three-dimensional remote sensing: Transition from experimental to operational solutions? JF - Forests N2 - The alarming increase in the magnitude and spatiotemporal patterns of changes in composition, structure and function of forest ecosystems during recent years calls for enhanced cross-border mitigation and adaption measures, which strongly entail intensified research to understand the underlying processes in the ecosystems as well as their dynamics. Remote sensing data and methods are nowadays the main complementary sources of synoptic, up-to-date and objective information to support field observations in forest ecology. In particular, analysis of three-dimensional (3D) remote sensing data is regarded as an appropriate complement, since they are hypothesized to resemble the 3D character of most forest attributes. Following their use in various small-scale forest structural analyses over the past two decades, these sources of data are now on their way to be integrated in novel applications in fields like citizen science, environmental impact assessment, forest fire analysis, and biodiversity assessment in remote areas. These and a number of other novel applications provide valuable material for the Forests special issue “3D Remote Sensing Applications in Forest Ecology: Composition, Structure and Function”, which shows the promising future of these technologies and improves our understanding of the potentials and challenges of 3D remote sensing in practical forest ecology worldwide. KW - 3D remote sensing KW - composition KW - forest ecology KW - function KW - structure Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193282 SN - 1999-4907 VL - 10 IS - 10 ER - TY - THES A1 - Derakhshani, Shaghayegh T1 - Measles virus infection enhances dendritic cell migration in a 3D environment T1 - Die Masernvirusinfektion verstärkt die Migration dendritischer Zellen in einer 3D-Umgebung N2 - The respiratory system is amongst the most important compartments in the human body. Due to its connection to the external environment, it is one of the most common portals of pathogen entry. Airborne pathogens like measles virus (MV) carried in liquid droplets exhaled from the infected individuals via a cough or sneeze enter the body from the upper respiratory tract and travel down to the lower respiratory tract and reach the alveoli. There, pathogens are captured by the resident dendritic cells (DCs) or macrophages and brought to the lymph node where immune responses or, as in case of MV, dissemination via the hematopoietic cell compartment are initiated. Basic mechanisms governing MV exit from the respiratory tract, especially virus transmission from infected immune cells to the epithelial cells have not been fully addressed before. Considering the importance of these factors in the viral spread, a complex close-to-in-vivo 3D human respiratory tract model was generated. This model was established using de-cellularized porcine intestine tissue as a biological scaffold and H358 cells as targets for infection. The scaffold was embedded with fibroblast cells, and later on, an endothelial cell layer seeded at the basolateral side. This provided an environment resembling the respiratory tract where MV infected DCs had to transmigrate through the collagen scaffold and transmit the virus to epithelial cells in a Nectin-4 dependent manner. For viral transmission, the access of infected DCs to the recipient epithelial cells is an essential prerequisite and therefore, this important factor which is reflected by cell migration was analyzed in this 3D system. The enhanced motility of specifically MV-infected DCs in the 3D models was observed, which occurred independently of factors released from the other cell types in the models. Enhanced motility of infected DCs in 3D collagen matrices suggested infection-induced cytoskeletal remodeling, as also verified by detection of cytoskeletal polarization, uropod formation. This enforced migration was sensitive to ROCK inhibition revealing that MV infection induces an amoeboid migration mode in DCs. In support of this, the formation of podosome structures and filopodia, as well as their activity, were reduced in infected DCs and retained in their uninfected siblings. Differential migration modes of uninfected and infected DCs did not cause differential maturation, which was found to be identical for both populations. As an underlying mechanism driving this enforced migration, the role of sphingosine kinase (SphK) and sphingosine-1-phosphate (S1P) was studied in MV-exposed cultures. It was shown in this thesis that MV-infection increased S1P production, and this was identified as a contributing factor as inhibition sphingosine kinase activity abolished enforced migration of MV-infected DCs. These findings revealed that MV infection induces a fast push-and-squeeze amoeboid mode of migration, which is supported by SphK/S1P axis. However, this push-and-squeeze amoeboid migration mode did not prevent the transendothelial migration of MV-infected DCs. Altogether, this 3D system has been proven to be a suitable model to study specific parameters of mechanisms involved in infections in an in vivo-like conditions. N2 - Die respiratorische System ist ein wesentlicher physiologischer Bestandteil. Durch die direkte und konstante Verbindung der Atemwege mit der äußeren Umgebung sind sie einer der häufigsten Pfade für den Eintritt von Krankheitserregern in den Körper. Luftübertragene Krankheitserreger wie das Masern-Virus (MV), das in Flüssigkeitströpfchen mitgeführt und von Patienten durch Husten oder Niesen ausgeatmet wird, können über die oberen Atemwege in den Körper gelangen und sich bis in die unteren Atemwege und bis zu den Alveolen ausbreiten. Dort werden diese Krankheitserreger von den dort residenten dendritischen Zellen (DC) oder Makrophagen erworben und zu sekundären lymphatischen Organen transportiert, in denen sowohl virus-spezifische Immunantworten, aber auch – wie im Falle von MV – die hämatogene Dissemination initiiert wird. Der Austrittsmechanismus des MV aus den Atemwegen, insbesondere dessen Übertragung von infizierten Immunzellen auf die Epithelzellen und die Faktoren, die diesen Ablauf bestimmen, wurden jedoch bisher unzureichend untersucht. In Anbetracht der Bedeutung dieser Faktoren für die Virusausbreitung wurde ein komplexes, realitätsnahes in-vivo 3D-Modell der menschlichen Atemwege erstellt. Dieses Modell wurde unter Verwendung von de-zellularisiertem Schweinedarmgewebe als biologischem Gerüst und H358 Epithelzellen als Empfänger etabliert. Dieses Grundgerüst wurde mit Fibroblastenzellen eingebettet. Später wurde auf der basolateralen Seite der Modelle eine Endothelzellschicht eingebracht, um eine Umgebung zu schaffen, die der der Atemwege ähnelt. Somit mussten die Virus-Donoren, MV-infizierte DC durch das Kollagengerüst wandern und das Virus auf Epithelzellen in einer Nektin-4 abhängigen Weise übertragen. Für die Virusübertragung ist der Zugang infizierter DC zu den Empfänger-Epithelzellen eine wesentliche Voraussetzung, weshalb dieser wichtige Faktor, der sich in der Zellmigration widerspiegelt, in diesem 3D-System analysiert wurde. Eine erhöhte Beweglichkeit spezifisch MV-infizierter DCs wurde in den 3D-Modellen beobachtet. Dies erwies sich als unabhängig von löslichen Faktoren der anderen Zelltypen in den Modellen. Erhöhte Beweglichkeit infizierten DCs wurde auch in 3D-Kollagenmatrizes gesehen, was auf einen infektionsvermittelten zytoskelettalen Umbau hindeutete, der auch anhand von Zytoskelettpolarisation und Uropodbildung bestätigt wurde. Die MV-Infektion induzierte einen schnellen amöboiden Migrationsmodus in den DCs, der sich als sensitiv gegenüber ROCK-Hemmung erwies. Im Gegensatz zu uninfizierten DCs gleichen Reifungsstadiums waren in infizierten DCs Podosomenstrukturen und Filopodien sowie deren Aktivität stark reduziert. Als potentiell zur verstärkten Motilität infizierter DCs beitragender Faktor wurde die Rolle der Sphingosinkinase (SphK) und des Sphingosin-1-phosphats (S1P) in MV-exponierten Kulturen untersucht. In dieser Arbeit wurde gezeigt, dass die S1P-Produktion durch eine MV-Infektion erhöht wurde, und in der Tat zur für infizierte DCs beobachteten erhöhten Geschwindigkeit beitrug, da diese sensitiv gegenüber Hemmung der Sphingosinkinase-Aktivität war. Diese Ergebnisse zeigen, dass die MV-Infektion einen schnellen amöboid-artigen Migrationsmodus induziert, der von der SphK/S1P-Achse unterstützt wird. Dieser Push-and-Squeeze-Amoeboid-Migrationsmodus verhinderte jedoch nicht die transendotheliale Migration von MV-infizierten DCs. Insgesamt hat sich dieses 3D-System als geeignetes Modell erwiesen, um die spezifische Parameter von Mechanismen von Infektionen in einem in-vivo-ähnlichen Zustand zu untersuchen. KW - Dendritische Zelle KW - Zell Migration KW - Masern-Virus KW - 3D-Modell KW - Sphingosine-1-phosphats KW - Dendritic cell KW - Cell migration KW - Measles virus KW - 3D tissue model KW - Tissue engineering KW - Sphingosine-1-phosphate Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-189182 ER - TY - JOUR A1 - Hovestadt, Thomas A1 - Thomas, Jeremy A. A1 - Mitesser, Oliver A1 - Schönrogge, Karsten T1 - Multiple host use and the dynamics of host-switching in host-parasite systems JF - Insect Conservation and Diversity N2 - The link between multi‐host use and host switching in host–parasite interactions is a continuing area of debate. Lycaenid butterflies in the genus Maculinea, for example, exploit societies of different Myrmica ant species across their ranges, but there is only rare evidence that they simultaneously utilise multiple hosts at a local site, even where alternative hosts are present. We present a simple population‐genetic model accounting for the proportion of two alternative hosts and the fitness of parasite genotypes on each host. In agreement with standard models, we conclude that simultaneous host use is possible whenever fitness of heterozygotes on alternative hosts is not too low. We specifically focus on host‐shifting dynamics when the frequency of hosts changes. We find that (i) host shifting may proceed so rapidly that multiple host use is unlikely to be observed, (ii) back and forth transition in host use can exhibit a hysteresis loop, (iii) the parasites' host use may not be proportional to local host frequencies and be restricted to the rarer host under some conditions, and (iv) that a substantial decline in parasite abundance may typically precede a shift in host use. We conclude that focusing not just on possible equilibrium conditions but also considering the dynamics of host shifting in non‐equilibrium situations may provide added insights into host–parasite systems. KW - Host-parasite interaction KW - Maculinea butterfly KW - Myrmica ant non-equilibrium dynamics KW - population genetics Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204747 VL - 12 IS - 6 ER -