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JLUpub ist das institutionelle Repositorium der Justus-Liebig-Universität.
JLUpub bietet Mitgliedern und Angehörigen der Universität die Möglichkeit neben wissenschaftlichen Dokumenten auch Forschungsdaten elektronisch zu veröffentlichen und dauerhaft zugänglich zu machen. Alle Veröffentlichungen erhalten einen Digital Object Identifier (DOI) und werden über nationale und internationale Bibliothekskataloge sowie Suchmaschinen nachgewiesen und auffindbar.
Neue Veröffentlichungen:
New aspects of coccidia-triggered modulation of the host cellular cell cycle
(2025) Rojas Barón, Lisbeth Cecilia
Apicomplexan parasites are a large group of protists with an obligate intracellular lifestyle, impacting human and veterinary health worldwide. The Sarcocystidae family contains notable species like Toxoplasma gondii, a critical zoonotic pathogen, and Neospora caninum, cause of abortion in cattle and of neurological disorders in canid hosts. Although both parasites differ in their host specificity and in distinct aspects of their life cycle, they also share common characteristics in their sophisticated ability to modulate host cell functions. Here, we focused on molecular and cellular mechanisms involved in parasite infection-driven host cell cycle dysregulation.
T. gondii is well recognized to significantly affect host cell cycle progression, regardless of MOI, infection times and, importantly, the cellular model used in experimentation. While many former studies used immortalized or tumour cells, potentially exhibiting dysregulated cell cycling, current analyses addressed T. gondii infections in primary cells by analyzing different cell types (fibroblasts, endothelial and epithelial cells) and donor species (human, bovine). Here, we revealed a T. gondii-driven cell type- and origin-independent S-phase arrest. Notably, cyclin B1, a critical regulator of mitosis entry, remained unchanged across all cell types, indicating that mitosis checkpoint modulation is not involved in host cellular S-phase stasis. Beyond interphase effects, T. gondii infection led to aberrant mitosis in all mitotic subphases, characterized by chromosome miscondensation and supernumerary centrosome formation. Moreover, all cell types showed an increased proportion of binucleated phenotypes, indicating impaired cytokinesis, which also occurred independently of cell origin or type.
Given that different T. gondii genotypes show varying pathogenicity in the field, host cell cycle regulation may also be influenced by haplotypes. To explore this, different strain infections (Me49, NED) were comparatively analysed in primary host cells. In line with RH, Me49 and NED strains also induced host S-phase arrest. Further analyses on key regulatory proteins of S-phase control and M-phase enter revealed a cyclin B1 downregulation only for NED infections. Additionally, the mitotic rate was reduced by NED infections, concomitant with altered chromosome arrangement and irregular chromosome bridges within the mitotic spindle. Moreover, T. gondii Me49 and NED strains also led to an enhanced proportion of binucleated host cells, indicative of cytokinesis failure. Thereby, this cellular phenotype was here described for the first time for all haplotype infections, demonstrating cytokinesis impairment as intrinsic, haplotype-independent mechanism of T. gondii.
Chromosome missegregation and cytokinesis impairment are key features of chromosome instability being associated with DNA damage in cells. As determined in the current work, RH, Me49 and NED strains indeed all induced DNA double-strand breaks with the RH strain driving - by far - the most pronounced effects. Moreover, referring to cytokinesis failure, a significant proportion of both RH- and NED-infected binucleated host cells showed DNA damage foci. Interestingly, NED-infected cells exhibited an increased proportion of micronuclei, thereby highlighting parasite strain-specific insults on host cellular genomic stability.
Under genotoxic stress, cells activate the DNA damage response to maintain genome integrity. Repair mechanisms for this type of damage include the homologous recombination (HR) and non-homologous end joining (NHEJ) pathways, which were here profiled for RH strain infections. As expected, the HR pathway was activated by an upregulation of ATM pathway-related proteins, which classically are induced by DNA double-strand breaks.
Finally, current cell cycle-related analyses were extended to N. caninum infections in the same host cell type to elucidate eventual species-specific strategies. N. caninum caused late S-phase arrest concomitant with cyclin A2 and cyclin B1 upregulation at 24 h p. i. (followed by cyclin A2 decrease at 32 h), confirming irregularities from S- to G2/M transition-phase. Interestingly, irregular nuclear morphologies were observed in N. caninum-infected cells, illustrated as invaginations and stretches of nuclear membrane disintegration and quantified as smaller nuclear areas, indicating that the host cellular nuclear structure was affected by N. caninum. Further analyses on the nuclear protein lamin B1 revealed an increased proportion of cells with inhomogeneous lamin B1 patterns, several nuclear folding and invaginations, phenomena reported for the first time for coccidian infections. Moreover, the perinuclear area was altered since actin filaments normally being anchored to the nuclear periphery and transversing the nucleus (actin cap) were absent in infected cells alongside with a decreased total cellular actin abundance, highlighting that N. caninum infection indeed interferes with the host actin cytoskeleton leading to nuclear membrane destabilization and abnormal shaping. Overall, these findings contrast with alterations induced by different T. gondii strains, emphasizing species-specific events in host cell modulation.
Nicht-invasive Biomarker als Indikatoren einer rechtskardialen Dysfunktion bei Patienten mit einer inoperablen chronisch thromboembolischen pulmonalen Hypertonie vor und nach einer pulmonalen Ballonangioplastie
(2024) Barde, Marta
In der vorliegenden Arbeit konnte gezeigt werden, dass die kardialen Biomarker N-terminales pro-B-Typ natriuretisches Peptid (NT-proBNP), mid-regionales pro-atriales natriuretisches Peptid (MR-proANP), soluble suppression of tumorigenicity (sST2) und pregnancy associated plasma protein-A (PAPP-A) vielversprechende Biomarker für die Risikostratifizierung sowie das Therapiemonitoring von Patienten mit einer chronisch thromboembolischen pulmonalen Hypertonie (CTEPH) sein können.
In der Studie wurden 22 inoperable CTEPH-Patienten eingeschlossen, die im Zeitraum zwischen 2014 und 2016 mittels interventioneller pulmonaler Ballonangioplastie (BPA) therapiert wurden. Im Studienkollektiv zeigte sich eine Verbesserung der hämodynamischen sowie der morphologischen und funktionellen kardialen Parameter nach einer BPA-Therapie. Die Expression der nicht-invasiven Biomarker assoziierte mit den morphologischen und funktionellen kardialen Parametern vor der BPA-Therapie. Anhand der Biomarkerspiegel von NT-proBNP, MR-proANP, sST2 und PAPP-A konnten Patienten mit einer schwergradigen Rechtsherzdysfunktion (RVEF <35 %) vor Therapiebeginn identifiziert werden. Eine Multimarkerstrategie erscheint in diesem Kontext vielversprechend.
Nach der Therapie korrelierte die relative Veränderung der kardialen Biomarker, insbesondere des NT-proBNP und MR-proANP mit den relativen Veränderungen der morphologischen und funktionellen kardialen Parameter der MRT. Anhand der relativen Veränderung der Biomarkerspiegel von NT-proBNP (<53 %) und MR-proANP (<24 %) konnten Patienten mit nicht ausreichendem Therapieansprechen im Sinne einer ungenügenden Erholung der RVEF nach der Therapie identifiziert werden.
Einflüsse einer pansengeschützten Methionin- und Lysin-Supplementation der Futterration auf die Entwicklungskompetenz boviner Kumulus-Oozyten-Komplexe
(2025) Ritz, Markus
Als Bausteine von Proteinen sind Aminosäuren wichtige Nahrungsbestandteile und von großer Bedeutung für die Reproduktionsleistung von Milchkühen. Ziel der Arbeit war es, darzustellen, inwieweit sich die Supplementation pansengeschützten Methionins und Lysins auf die Entwicklungskompetenz boviner Kumulus-Oozyten-Komplexe (KOK) auswirkt, da sie als die am stärksten limitierenden Aminosäuren für Milchkühe gelten.
Für den Versuch wurden 30 pluripare Holstein-Kühe in zwei Gruppen unterteilt, wobei 14 von ihnen post partum eine Supplementation der Futterration mit pansengeschütztem Methionin und Lysin erhielten. Ab dem 40. Tag post partum erfolgte die KOK-Gewinnung mittels Ovum Pick-Up (OPU) achtmal im wöchentlichen Abstand. Vor dem OPU wurden Blutproben zur Bestimmung der Plasma-Aminosäurekonzentration genommen. Begleitende Milchuntersuchungen dienten der Leistungskontrolle der Kühe.
Bei dem durchgeführten OPU ergaben sich Wiederfindungsraten von 61,3 ± 29,4 % für die Versuchsgruppe (RPAA) und 62,6 ± 33,5 % für die Kontrollgruppe (CON). Die gewonnenen Oozyten von RPAA (n=240) und CON (n=299) wurden zu einem großen Teil der In-vitro Produktion zugeführt. Hierbei erwiesen sich die Teilungsraten (RPAA: 84,1 ± 5,9 %; CON: 81,9 ± 8,6 %) und die Entwicklungsraten (Tag 7: 18,3 ± 4,4 % vs.15,4 ± 8,9 %) beider Gruppen als ähnlich.
Der Milchproteingehalt (RPAA 3,15 ± 0,25 %; CON 3,05 ±0,22 %; p = 3,3 x 10-5) und der Milchfettgehalt (RPAA 4,18 ± 0,5 %; CON 4,01 ±0,5 %; p = 0,001) von Kühen der RPAA-Gruppe zeigten eine geringfügige Erhöhung im Vergleich zu den Kühen der CON-Gruppe. Bezüglich der Milchmenge und des Milchharnstoffgehaltes wurden keine Unterschiede zwischen den Gruppen festgestellt.
Insgesamt sanken die Aminosäurekonzentrationen im Plasma durch die Supplementation pansengeschützten Methionins und Lysins (p = 0,005). Dieser Effekt spiegelte sich vor allem bei den essenziellen Aminosäuren wider (p = 0,04), wobei auch die nicht-essenziellen Aminosäuren eine Tendenz dazu zeigten. Zudem war der Gehalt von Threonin, Glutamin und Valin bei RPAA signifikant niedriger.
Bei der RT-qPCR konnte eine signifikant geringere Expression von HSPA1A, DNMT1 und MAT2B bei expandierten Blastozysten der RPAA-Gruppe von Tag 7 im Vergleich zu denen der CON-Gruppe nachgewiesen werden.
Die Lipidanalyse ergab vor allem bei unreifen Oozyten Unterschiede, die sich als Veränderungen des Fettsäuremusters der eingelagerten Triacylglyceride (TAGs) darstellten. Insbesondere ließ sich ein erhöhter Gehalt an Ölsäure (18:1) in unreifen Oozyten von Kühen, die die Kontrollration erhielten, nachweisen. In reifen Oozyten zeigten sich diese Unterschiede lediglich bei einer Komponente (TAG (60:4) FA 18:1), es fanden sich allerdings größere Mengen an Etherlipiden in den reifen Oozyten der CON-Gruppe. Expandierte Blastozyten wiesen einen höheren Gehalt der Phosphatidylcholine (34:1) und (34:2) in der RPAA-Gruppe auf. O-Behenoylcarnitin kam hingegen vermehrt in Embryonen der CON-Gruppe vor.
Die Metabolomanalyse deckte lediglich Unterschiede bei den unreifen Oozyten auf. Diese stellten sich als erhöhte Gehalte an Laurinsäure, Thymidin, Erythrosephosphat und Acetylcarnitin in Oozyten der RPAA-Gruppe dar.
Abschließend kann festgehalten werden, dass die Supplementation pansengeschützten Methionins und Lysins keinen signifikanten Einfluss auf die Entwicklungsraten von Oozyten in der In-vitro Produktion hat, jedoch vermutlich zu einer Reduktion der DNA-Methylierung und des oxidativen Stresses von Oozyten und Embryonen führt und die Qualität verbessert.
Seeing Resonance: On Students’ Perception-Based Reasoning in Organic Chemistry
(2025) Braun, Irina
Representations are central to conceptual understanding and problem-solving in Organic Chemistry. Resonance, in particular, is a concept that is closely linked to the construction and interpretation of resonance structures. However, understanding these structures as dynamic electron distribution imposes a high cognitive load on learners. While research has emphasized manifold conceptual barriers learners encounter with this concept, little is known about how students perceive resonance structures and use these representations in problem-solving.
To address this gap, a quantitative study with Organic Chemistry (OC) I students investigated how the variation of structural features influences students’ consideration of resonance stabilization across different molecular structures. A k-means cluster analysis revealed different profiles regarding students’ proficiency in recognizing resonance stabilization. It became evident that students’ decision-making on resonance was markedly influenced by the visual affordances of the structural features. Students’ consideration of resonance was often guided by the visual similarity of features to familiar structural patterns. Yet, students’ flexibility in perceiving resonance increased with higher prior conceptual knowledge.
Quantitative analysis further revealed that students’ recognition of resonance significantly depends on the display of electron lone pairs, as students showed an affirmation bias towards resonance stabilization when electron lone pairs were present.
Extending these findings, a qualitative interview study investigated students’ perceptual processes when drawing (un-)productive resonance structures in context. Using eye-tracking, students’ connection of visual information and attention distribution to structural features were examined. Analyzing students’ verbal drawing rationales further served to triangulate eye-tracking data. While the productivity of resulting resonance structures did not depend on the total amount of integrated and connected visual information, productive drawings were characterized by a more straightforward drawing process transitioning from previous to target drawing. Moreover, the results showcased that flexibility in perceiving interrelated structural features is crucial for constructing valid resonance structures.
The interview study also served to investigate students’ use of resonance across different task contexts in OC I. Coordination Class Theory was used as an analytical lens to analyze students’ problem-solving. Results showed that students’ concept use was diverse and shaped by the complex interplay of task affordances and individual factors. However, a more detailed comparison of students’ concept use revealed that a more reflective and flexible use of their structural drawings enhanced productive concept use, both in terms of students’ task approaches and the activation of task-relevant resources.
Thus, this thesis demonstrates that flexibility in perceiving and engaging with representations is crucial for the successful use of resonance in Organic Chemistry. By highlighting the close link between conceptual and perceptual processes in students’ reasoning about resonance, it yields new, process-oriented insights into how students perceive, construct, and use resonance structures in problem-solving.
Cultural engagement during the digital age - Prerequisites, processes and outcomes of digital cultural engagement
(2024-04-24) Gotthardt, Karina Aylin
Due to the shift of cultural engagement opportunities into the digital space, it is essential to analyze prerequisites, processes and outcomes of this relative new form of cultural engagement. Two types of opportunities for (digital) cultural engagement were examined, first exploring the amount of participation in cultural activities during the COVID-19 pandemic. Subsequently, an opportunity to engage directly with digital culture via a virtual reality art-gallery was developed. In this VR-environment, the textual information accompanying the paintings was altered to study its role as a potential factor influencing this digital cultural engagement opportunity. Individual characteristics such as valuing of culture, openness to experience, positive affect and expertise were understood as prerequisites for utilization. Current motivational and emotional processes were understood as part of utilization and as mediating the relationship between prerequisites and possible positive outcomes of digital cultural engagement.
Article 1 focused on the beneficial effects of cultural engagement during the COVID-19 pandemic, exploring what was being used and by whom, by examining the amount of participation in self-initiated as well as digital cultural activities. It was analyzed to what extend motivational (basic need fulfillment) and emotional (aesthetic experiences) processes might mediate the relationship between (digital) cultural engagement and its impact on optimism.
Article 2 focused on the influence of expertise, openness to experience and positive affect prior to the VR-visit on positive affect after the VR-visit, expecting aesthetic experiences to mediate this relationship. Here, three types of aesthetic experiences were assessed, deepening the focus on emotional processes of paper one, and broadening the attention to include the psychophysiological measurements heart rate and heart rate variability. Moreover, the influence of these psychophysiological signals on self-assessed aesthetic experiences was investigated in a separate analysis.
Article 3 pinned down on the importance of the path between expertise and positive affect after the VR-experience. It was investigated whether positive affect might mediate the relationship between expertise and aesthetic judgement. Moreover, the type of textual information, either stylistic or affective, that accompanied the paintings was expected to moderate the relationship between expertise and positive affect after the VR-experience.
Results showed that during the COVID-19 pandemic, both cultural activities were able to increase aesthetic experience and perceived autonomy, but only digital cultural offerings were connected to an increase in perceived relatedness, which in turn was able to increase optimism. Visiting the VR-art-gallery resulted in a decrease in negative affect compared to before the visit. Individual prerequisites were able to impact positive affect after the VR experience. Especially openness to experience and high positive affect before the visit led to an increase in positive affect after the visit when self-assessed aesthetic experience during the visit were high. Women with high expertise reported high positive affect after the VR-visit when they experienced a higher heart rate during the visit, highlighting the potential impact of gender on subjective interpretations of physiological responses in the VR environment. In the VR-gallery, textual information did not moderate the relationship between expertise and positive affect; Rather, the impact of the affective textual information indicate that the VR context might increase the valence of emotionally charged content, indicating that this type of content might enhance digital cultural engagement.
Taken together, digital cultural engagement opportunities can have an impact on positive outcomes, but predispositions and processes during utilization, as well as factors shaping the opportunities are vital to understanding the full scope of their impact.