Is the dog’s tendency to overimitate dependent on the relationship to the human demonstrator?

Master thesis - University of Veterinary Medicine Vienna - 2021Overimitation (the faithful copying of a perceivably unnecessary action demonstrated by a model) is a fascinating phenomenon that has so far only been investigated in children, primates and canines. While it is highly prevalent and persistent in children, primates show no evidence of overimitation. For canines the literature shows mixed evidence. While Johnston et al. (2017) and Huber et al. (2018) found half of their subjects copying an irrelevant action, Huber et al. (2020) found much lesser subjects to do so. It was concluded that dogs copy irrelevant actions if demonstrated by their caregiver or at least a familiar person, because the task is interpreted as social interaction, but not if demonstrated by a stranger. The present study followed the ones by Huber et al. (2018, 2020), but attempted to investigate dog’s underlying motivations to overimitate a human demonstrator. From the previous studies the hypothesis was derived that not only the familiarity, but the relationship quality between the dog-human dyad would facilitate the dog’s tendency to overimitate its caregiver. To test for this, two paradigms have been combined in this master thesis. First, the overimitation test developed by Huber et al. (2018) with the caregiver demonstrating an irrelevant and a relevant action. Second, a battery of tests developed by Cimarelli et al. (2019), which included exploration of an unfamiliar area, separation and reunion with the partner as well as a novel object test. The overimitation test revealed comparable results to Huber et al. (2018) but the copying accuracy was in general a little lower, probably because the high temperatures in summer negatively affected dogs’ motivation / ability to concentrate, or due to minor methodological differences. The relationship test showed results comparable to Cimarelli et al. (2019). However, due to a lack of association between the components of the relationship and the tendency to overimitate, the hypothesis could not be supported. Still, some interesting associations and grounds for further investigations were detected. Attention towards the caregiver, play, as well as joint activities including training background influenced dogs’ copying accuracies for irrelevant and relevant action. Additionally, I have argued that the perceived context and the individual goal might play a considerable role with respect to overimitation.Master thesis - University of Veterinary Medicine Vienna - 2021Overimitation (the faithful copying of a perceivably unnecessary action demonstrated by a model) is a fascinating phenomenon that has so far only been investigated in children, primates and canines. While it is highly prevalent and persistent in children, primates show no evidence of overimitation. For canines the literature shows mixed evidence. While Johnston et al. (2017) and Huber et al. (2018) found half of their subjects copying an irrelevant action, Huber et al. (2020) found much lesser subjects to do so. It was concluded that dogs copy irrelevant actions if demonstrated by their caregiver or at least a familiar person, because the task is interpreted as social interaction, but not if demonstrated by a stranger. The present study followed the ones by Huber et al. (2018, 2020), but attempted to investigate dog’s underlying motivations to overimitate a human demonstrator. From the previous studies the hypothesis was derived that not only the familiarity, but the relationship quality between the dog-human dyad would facilitate the dog’s tendency to overimitate its caregiver. To test for this, two paradigms have been combined in this master thesis. First, the overimitation test developed by Huber et al. (2018) with the caregiver demonstrating an irrelevant and a relevant action. Second, a battery of tests developed by Cimarelli et al. (2019), which included exploration of an unfamiliar area, separation and reunion with the partner as well as a novel object test. The overimitation test revealed comparable results to Huber et al. (2018) but the copying accuracy was in general a little lower, probably because the high temperatures in summer negatively affected dogs’ motivation / ability to concentrate, or due to minor methodological differences. The relationship test showed results comparable to Cimarelli et al. (2019). However, due to a lack of association between the components of the relationship and the tendency to overimitate, the hypothesis could not be supported. Still, some interesting associations and grounds for further investigations were detected. Attention towards the caregiver, play, as well as joint activities including training background influenced dogs’ copying accuracies for irrelevant and relevant action. Additionally, I have argued that the perceived context and the individual goal might play a considerable role with respect to overimitation.Masterarbeit - Veterinärmedizinische Universität Wien - 2021Überimitation (das gewissenhafte Nachahmen einer wahrnehmbar unnötigen Handlung, die von einem Model demonstriert wird) ist ein faszinierendes Phänomen, dass bis jetzt nur bei Kindern, Primaten und Caniden untersucht wurde. Das Verhalten ist bei Kindern stark ausgeprägt, konnte bei Primaten aber noch nicht beobachtet werden. Was die Caniden betrifft, finden wir gemischte Ergebnisse in der aktuellen Literatur. Bei Johnston et al. (2017) und Huber et al. (2018) kopierte circa die Hälfte der Tiere eine unnötige Handlung, während viel weniger Individuen das gleiche Verhalten bei Huber et al. (2020) zeigten. Dies bestätigte die Hypothese von Huber et al. (2020), dass Hunde eine irrelevante Handlung vornehmlich dann kopieren, wenn sie vom Hundehalter demonstriert wird, weil sie die Aufgabe als eine soziale Interaktion verstehen, viel weniger wahrscheinlich aber, wenn sie von einem Fremden demonstriert wird. Als Folgestudie zu Huber et al. (2018, 2020) hatte diese Masterarbeit zum Ziel, die zugrundeliegende Motivation der Hunde für Überimitation weiter zu erforschen. Die Hypothese, dass die Beziehung zwischen Hund und Mensch, mehr als nur Bekanntschaft, Einfluss auf die Tendenz des Hundes zur Überimitation hat, wurde getestet. Dazu wurde eine Studie, bestehend aus zwei Tests durchgeführt. Erstens testete ich Hunde entsprechend der Überimitations-Prozedur, welche von Huber et al. (2018, 2020) entwickelt wurde. Dabei wurde der Hundehalter als Model gebeten, eine Handlungssequenz bestehend aus einer irrelevanten und einer relevanten Handlung zu demonstrieren. Zweitens führte ich den Beziehungs-Test von Cimarelli et al. (2019) durch. Dieser Test inkludiert das Erkunden eines unbekannten Areals, Trennung und Wiedervereinigung mit dem Halter sowie einen „Novel-Object-Test“. Der erste Test zeigte vergleichbare Resultate zu jenen von Huber et al. (2018). Die Genauigkeit der kopierten Aktionen war jedoch geringer, was wahrscheinlich daran lag, dass die hohen Temperaturen im Sommer die Motivation bzw. Konzentrationsfähigkeit der Hunde negativ beeinflusst haben. Der zweite Test zeigte ebenfalls gute Ergebnisse, nämlich vergleichbar mit jenen von Cimarelli et al. (2019). Allerdings konnte keine Korrelation zwischen den Komponenten der Beziehung und der Tendenz zur Überimitation gefunden werden. Daher konnte die aufgestellte Hypothese nicht unterstützt werden. Trotzdem wurden einige interessante Assoziationen und mögliche Grundlagen für die weitere Forschung entdeckt. Aufmerksamkeit dem Halter gegenüber, gemeinsames Spielen sowie gemeinsame Aktivitäten inklusive Training beeinflussten die Genauigkeit beim Kopieren der irrelevanten und der relevanten Handlung. Zusätzlich wurde argumentiert, dass der wahrgenommene Kontext und das individuelle Ziel des Hundes im Zusammenhang mit Überimitation eine wichtige Rolle spielen könnten

Overimitation in Dogs: Is There a Link to the Quality of the Relationship with the Caregiver?

Overimitation, the copying of causally irrelevant or non-functional actions, is well-known from humans but completely absent in other primates. Recent studies from our lab have provided evidence for overimitation in canines. Previously, we found that half of tested pet dogs copied their human caregiver’s irrelevant action, while only few did so when the action was demonstrated by an unfamiliar experimenter. Therefore, we hypothesized that dogs show overimitation as a result of socio-motivational grounds. To test this more specifically, here we investigated how the relationship with the caregiver influenced the eagerness to overimitate. Given the high variability in the tendency to overimitate their caregiver, we hypothesized that not only familiarity but also relationship quality influences whether dogs faithfully copy their caregiver. For this purpose, on the one hand we measured the overimitation tendency (with the same test as in the two studies before) and on the other hand the relationship quality between the dogs and their caregivers. Although we found no significant correlation between the two test results, our data might suggest that, on average, dogs who overimitated seemed to show more referential and affiliative behaviours towards the owner than dogs who showed less or no copying of the irrelevant action. Notably, as a group, those dogs that showed the highest level of copying accuracy of the irrelevant action showed the highest level of gazing and synchronization towards the owner

Red blood cells serve as intravascular carriers of myeloperoxidase

Myeloperoxidase (MPO) is a heme enzyme abundantly expressed in polymorphonuclear neutrophils. MPO is enzymatically capable of catalyzing the generation of reactive oxygen species (ROS) and the consumption of nitric oxide (NO). Thus MPO has both potent microbicidal and, upon binding to the vessel wall, pro-inflammatory properties. Interestingly, MPO - a highly cationic protein - has been shown to bind to both endothelial cells and leukocyte membranes. Given the anionic surface charge of red blood cells, we investigated binding of MPO to erythrocytes. Red blood cells (RBCs) derived from patients with elevated MPO plasma levels showed significantly higher amounts of MPO by flow cytometry and ELISA than healthy controls. Heparin-induced MPO-release from patient-derived RBCs was significantly increased compared to controls. Ex vivo experiments revealed dose and time dependency for MPO-RBC binding, and immunofluorescence staining as well as confocal microscopy localized MPO-RBC interaction to the erythrocyte plasma membrane. NO-consumption by RBC-membrane fragments (erythrocyte ghosts) increased with incrementally greater concentrations of MPO during incubation, indicating preserved catalytic MPO activity. In vivo infusion of MPO-loaded RBCs into C57BL/6J mice increased local MPO tissue concentrations in liver, spleen, lung, and heart tissue as well as within the cardiac vasculature. Further, NO-dependent relaxation of aortic rings was altered by RBC bound-MPO and systemic vascular resistance significantly increased after infusion of MPO-loaded RBCs into mice. In summary, we find that MPO binds to RBC membranes in vitro and in vivo, is transported by RBCs to remote sites in mice, and affects endothelial function as well as systemic vascular resistance. RBCs may avidly bind circulating MPO, and act as carriers of this leukocyte-derived enzyme. (C) 2014 Elsevier Ltd. All rights reserved

Myeloperoxidase attracts neutrophils by physical forces

Recruitment of polymorphonuclear neutrophils (PMNs) remains a paramount prerequisite in innate immune defense and a critical cofounder in inflammatory vascular disease. Neutrophil recruitment comprises a cascade of concerted events allowing for capture, adhesion and extravasation of the leukocyte. Whereas PMN rolling, binding, and diapedesis are well characterized, receptor-mediated processes, mechanisms attenuating the electrostatic repulsion between the negatively charged glycocalyx of leukocyte and endothelium remain poorly understood. We provide evidence for myeloperoxidase (MPO), an abundant PMN-derived heme protein, facilitating PMN recruitment by its positive surface charge. In vitro, MPO evoked highly directed PMN motility, which was solely dependent on electrostatic interactions with the leukocyte's surface. In vivo, PMN recruitment was shown to be MPO-dependent in a model of hepatic ischemia and reperfusion, upon intraportal delivery of MPO and in the cremaster muscle exposed to local inflammation or to intraarterial MPO application. Given MPO's affinity to both the endothelial and the leukocyte's surface, MPO evolves as a mediator of PMN recruitment because of its positive surface charge. This electrostatic MPO effect not only displays a so far unrecognized, catalysis-independent function of the enzyme, but also highlights a principal mechanism of PMN attraction driven by physical forces. (Blood. 2011; 117(4):1350-1358

Brief cognitive training interventions in young adulthood promote long-term resilience to drug-seeking behavior

Environmental stress and deprivation increase vulnerability to substance use disorders in humans and promote drug-seeking behavior in animal models. In contrast, experiences of mastery and stability may shape neural circuitry in ways that build resilience to future challenges. Cognitive training offers a potential intervention for reducing vulnerability in the face of environmental stress or deprivation. Here, we test the hypothesis that brief cognitive training can promote long-term resilience to one measure of drug-seeking behavior, cocaine conditioned place preference (CPP), in mice. In young adulthood, mice underwent cognitive training, received rewards while exploring a training arena (i.e. yoked control), or remained in their home cages. Beginning 4 weeks after cessation of training, we conditioned mice in a CPP paradigm and then tested them weekly for CPP maintenance or daily for CPP extinction. We found that a brief 9-day cognitive training protocol reduced maintenance of cocaine CPP when compared to standard housed and yoked conditions. This beneficial effect persisted long after cessation of the training, as mice remained in their home cages for 4 weeks between training and cocaine exposure. When mice were tested for CPP on a daily extinction schedule, we found that all trained and yoked groups that left their home cages to receive rewards in a training arena showed significant extinction of CPP, while mice kept in standard housing for the same period did not extinguish CPP. These data suggest that in early adulthood, deprivation may confer vulnerability to drug-seeking behavior and that brief interventions may promote long-term resilience

Myeloperoxidase aggravates pulmonary arterial hypertension by activation of vascular Rho-kinase

Pulmonary arterial hypertension (PAH) remains a disease with limited therapeutic options and dismal prognosis. Despite its etiologic heterogeneity, the underlying unifying pathophysiology is characterized by increased vascular tone and adverse remodeling of the pulmonary circulation. Myeloperoxidase (MPO), an enzyme abundantly expressed in neutrophils, has potent vasoconstrictive and profibrotic properties, thus qualifying as a potential contributor to this disease. Here, we sought to investigate whether MPO is causally linked to the pathophysiology of PAH. Investigation of 2 independent clinical cohorts revealed that MPO plasma levels were elevated in subjects with PAH and predicted adverse outcome. Experimental analyses showed that, upon hypoxia, right ventricular pressure was less increased in Mpo(-/-) than in WT mice. The hypoxia-induced activation of the Rho-kinase pathway, a critical subcellular signaling pathway yielding vasoconstriction and structural vascular remodeling, was blunted in Mpo(-/-) mice. Mice subjected to i.v. infusion of MPO revealed activation of Rho-kinase and increased right ventricular pressure, which was prevented by coinfusion of the Rho-kinase inhibitor Y-27632. In the Sugen5416/hypoxia rat model, PAH was attenuated by the MPO inhibitor AZM198. The current data demonstrate a tight mechanistic link between MPO, the activation of Rho-kinase, and adverse pulmonary vascular function, thus pointing toward a potentially novel avenue of treatment

Myeloperoxidase Mediates Postischemic Arrhythmogenic Ventricular Remodeling

Rationale: Ventricular arrhythmias remain the leading cause of death in patients suffering myocardial ischemia. Myeloperoxidase, a heme enzyme released by polymorphonuclear neutrophils, accumulates within ischemic myocardium and has been linked to adverse left ventricular remodeling. Objective: To reveal the role of myeloperoxidase for the development of ventricular arrhythmias. Methods and Results: In different murine models of myocardial ischemia, myeloperoxidase deficiency profoundly decreased vulnerability for ventricular tachycardia on programmed right ventricular and burst stimulation and spontaneously as assessed by ECG telemetry after isoproterenol injection. Experiments using CD11b/CD18 integrin-deficient (CD11b(-/-)) mice and intravenous myeloperoxidase infusion revealed that neutrophil infiltration is a prerequisite for myocardial myeloperoxidase accumulation. Ventricles from myeloperoxidase-deficient (Mpo(-/-)) mice showed less pronounced slowing and decreased heterogeneity of electric conduction in the peri-infarct zone than wildtype mice. Expression of the redox-sensitive gap junctional protein Cx43 (Connexin 43) was reduced in the peri-infarct area of wild-type compared with Mpo(-/-) mice. In isolated wild-type cardiomyocytes, Cx43 protein content decreased on myeloperoxidase/H2O2 incubation. Mapping of induced pluripotent stem cell-derived cardiomyocyte networks and in vivo investigations linked Cx43 breakdown to myeloperoxidase-dependent activation of matrix metalloproteinase 7. Moreover, Mpo(-/-) mice showed decreased ventricular postischemic fibrosis reflecting reduced accumulation of myofibroblasts. Ex vivo, myeloperoxidase was demonstrated to induce fibroblast-to-myofibroblast transdifferentiation by activation of p38 mitogen-activated protein kinases resulting in upregulated collagen generation. In support of our experimental findings, baseline myeloperoxidase plasma levels were independently associated with a history of ventricular arrhythmias, sudden cardiac death, or implantable cardioverter-defibrillator implantation in a cohort of 2622 stable patients with an ejection fraction >35% undergoing elective diagnostic cardiac evaluation. Conclusions: Myeloperoxidase emerges as a crucial mediator of postischemic myocardial remodeling and may evolve as a novel pharmacological target for secondary disease prevention after myocardial ischemia

Myeloperoxidase Mediates Postischemic Arrhythmogenic Ventricular Remodeling

Rationale: Ventricular arrhythmias remain the leading cause of death in patients suffering myocardial ischemia. Myeloperoxidase, a heme enzyme released by polymorphonuclear neutrophils, accumulates within ischemic myocardium and has been linked to adverse left ventricular remodeling. Objective: To reveal the role of myeloperoxidase for the development of ventricular arrhythmias. Methods and Results: In different murine models of myocardial ischemia, myeloperoxidase deficiency profoundly decreased vulnerability for ventricular tachycardia on programmed right ventricular and burst stimulation and spontaneously as assessed by ECG telemetry after isoproterenol injection. Experiments using CD11b/CD18 integrin–deficient (CD11b−/−) mice and intravenous myeloperoxidase infusion revealed that neutrophil infiltration is a prerequisite for myocardial myeloperoxidase accumulation. Ventricles from myeloperoxidase-deficient (Mpo−/−) mice showed less pronounced slowing and decreased heterogeneity of electric conduction in the peri-infarct zone than wild-type mice. Expression of the redox-sensitive gap junctional protein Cx43 (Connexin 43) was reduced in the peri-infarct area of wild-type compared with Mpo−/− mice. In isolated wild-type cardiomyocytes, Cx43 protein content decreased on myeloperoxidase/H2O2 incubation. Mapping of induced pluripotent stem cell–derived cardiomyocyte networks and in vivo investigations linked Cx43 breakdown to myeloperoxidase-dependent activation of matrix metalloproteinase 7. Moreover, Mpo−/− mice showed decreased ventricular postischemic fibrosis reflecting reduced accumulation of myofibroblasts. Ex vivo, myeloperoxidase was demonstrated to induce fibroblast-to-myofibroblast transdifferentiation by activation of p38 mitogen-activated protein kinases resulting in upregulated collagen generation. In support of our experimental findings, baseline myeloperoxidase plasma levels were independently associated with a history of ventricular arrhythmias, sudden cardiac death, or implantable cardioverter–defibrillator implantation in a cohort of 2622 stable patients with an ejection fraction \u3e35% undergoing elective diagnostic cardiac evaluation. Conclusions: Myeloperoxidase emerges as a crucial mediator of postischemic myocardial remodeling and may evolve as a novel pharmacological target for secondary disease prevention after myocardial ischemia