Implications of Neuroplasticity to the Philosophical Debate of Free Will and Determinism

Neuroplasticity, the capacity of the brain to induce changes in response to environmental stimuli, entails a continuous rearrangement of the neural network through a complex interaction between genetics and environment. Within this process, the plastic brain uses its internal representations to predict future conditions and proactively proceed to actions. It can be said that plasticity demands a rethinking of the concept of determinism as the process of coming-to-be is directly related to modifications produced by experience. Pure determinism and complete randomness are the two ends of a spectrum of positions relevant to the debate of the existence of free will. However, none conceptually supports free decision-making. How brain activity and the conscious experience of volition are related to one another has been a matter of significant research, with a plethora of findings indicating that early brain signals precede the self-reported time of the decision to act. The meaning of these findings, however, has been debated at both a theoretical and empirical level and the controversy is still ongoing. Consciousness is intertwined with free will along the dimension of time as it would otherwise be purposeless, taking place right at the next moment. Electrical activity of the brain is a measure of neurophysiological function and contributes to the understanding of processes that underlie high-order cognitive functions. A multidisciplinary approach in the study of free will could be designed in a way that philosophical concepts are connected to neural correlates by psychologically functionalizing them in terms of cognitive abilities. Such abilities are at the margins of conscious and nonconscious sensory information and are closely linked to brain processes of executive functions like attentional control and working memory

Personhood

The motives for bringing about the Hellenic-Serbian Dialogue Series originate from the sentiment that mutual relations between Greeks and Sebs far surpass the cultural exchange between Greece and Serbia. Knowing that cooperation does not simply fall into one’s lap, but must be initiated by human will and energy, a group of philosophers from Athens and Novi Sad, the proverbial “Athens of Serbia,” committed themselves to improving this state of affairs, at least within the confines of their area of expertise, philosophy. It is our firm intent to carry out the promise of the title of this series in the following years. Apart from mere cooperation between our two institutions, our aim is also to facilitate an international dialogue that would involve a wide range of thinkers, regardless of their place of employment. The topic of this second volume is personhood, which was spurred on by the need to investigate the condition of humanity in the twenty-first century. With this second volume of the Hellenic-Serbian Philosophical Dialogue Series we have done our best to produce a rich, multi-faceted, broadly scoped, and inspiring book; we wish it becomes for the reader the ideal vehicle for an intellectually stimulating journey.Publishe

Modernity and Contemporaneity

Modernity and Contemporaneity is the 3rd volume in the Hellenic-Serbian Philosophical Dialogue Series, a project that was initiated as an emphatic token of the will and commitment to establish permanent and fruitful collaboration between two strongly bonded Departments of Philosophy, this of the National and Kapodistrian University of Athens, and that of the University of Novi Sad respectively. This collaboration was founded from the very beginning upon friendship, mutual respect and strong engagement, as well us upon our firm resolution to establish a solid continuity in the editing project. The publication of this volume allows us to entertain feelings of contentment and confidence that this objective of the project has been accomplished.Publishe

Investigation of the mechanical behavior of osteoblasts during attachment on substrates of natural biomaterials

The understanding of the phenomena that take place during cell-biomaterial interactionand the correlation of cell mechanical parameters with complicated processes at theextracellular environment (ECM) is driving the future of biomaterial design.The aim of the present study was the investigation of attachment and of alterations ofmechanical properties of osteoblasts during the initial phase of attachment on chitosanbiopolymer substrate.The preparation of the chitosan substrates was done with covalent immobilization of thebiopolymer on glass surface (control substrate). X-Ray photolelectron spectroscopyconfirmed the alteration of the surface chemical composition. Mean surface roughness, asmeasured by Atomic Force Microscopy, was increased 4-fold compared to glass, while themean contact angle was found 3 times higher on chitosan substrate.The mean number and spreading area of the attached cells, were determined by ScanningElectron Microscopy images and the use of image processing program. Up to 30 minutes,the number of attached cells was higher on chitosan, while after 45 minutes, it was on glass. At all time points, the mean spreading area was greater on chitosan.To quantify attachment, the micropipette aspiration technique was used at experiments ofdetachment of individual osteoblasts. The ‘’detachment impulse’’, I, was calculated, as theintegral of the applied force at time required (I=SFdt) for complete detachment of onecell, and it was found statistically higher on chitosan at all attachment times. With thequantified Polymerase Chain Reaction, the αν, α4, β1 and β3 gene integrin expression wasfound significantly increased from 30 to 120 minutes of attachment on chitosan. Usingconfocal scanning microscopy, higher expression of focal adhesion kinase was observedon chitosan at 30 and 120 minutes of attachment.Additionally, the micropipette aspiration technique was used at stretching and creepexperiments so as to calculate the alterations of cell’s Young modulus, E, and apparentviscosity, η. Mean values were increased at the course of spreading for both surfaces,demonstrating greater values on chitosan. The present study is a complete phenomenological approach of the mechanical behaviorof osteoblasts during attachment. Attachment on chitosan is accompanied by alterationsof the mechanical behavior and is associated with critical biochemical processes.Η κατανόηση των φαινομένων που λαμβάνουν χώρα κατά την αλληλεπίδρασηκυττάρου βιοϋλικού και η συσχέτιση μηχανικών παραμέτρων του κυττάρου μεπολύπλοκες διεργασίες στο εξωκυττάριο (ECM) περιβάλλον οδηγεί το μέλλον στοσχεδιασμό των βιοϋλικών.Σκοπός της διατριβής ήταν η διερεύνηση της προσκόλλησης και των μεταβολών τωνμηχανικών ιδιοτήτων οστεοβλαστών στους αρχικούς χρόνους προσκόλλησης σευπόστρωμα του βιοπολυμερούς χιτοζάνης.Η προετοιμασία υποστρωμάτων χιτοζάνης έγινε με ομοιοπολική πρόσδεση τουβιοπολυμερούς σε επιφάνεια γυαλιού (επιφάνεια ελέγχου). Με φασματοσκοπίαφωτοηλεκτρονίων από ακτίνες Χ επιβεβαιώθηκε η μεταβολή της επιφανειακήςχημικής σύστασης. Η μέση επιφανειακή τραχύτητα, με χρήση ΜικροσκοπίαςΑτομικής Δύναμης, βρέθηκε 4 φορές μεγαλύτερη στη χιτοζάνη σε σύγκριση με τογυαλί, ενώ η μέση γωνία διαβροχής ήταν περίπου 3 φορές μεγαλύτερη στη χιτοζάνη. Ο αριθμός και η μέση επιφάνεια εξάπλωσης των προσκολλημένων κυττάρων,προσδιορίστηκαν από φωτογραφίες ηλεκτρονιακού μικροσκοπίου σάρωσης καιχρήση λογισμικού ανάλυσης εικόνας. Μέχρι τα 30 λεπτά, ο αριθμός ήτανμεγαλύτερος στη χιτοζάνη, ενώ μετά τα 45 λεπτά, στο γυαλί. Σε όλους τουςχρόνους, η μέση επιφάνεια εξάπλωσης ήταν μεγαλύτερη στη χιτοζάνη.Για την ποσοτικοποίηση της προσκόλλησης, χρησιμοποιήθηκε η τεχνική τηςμικροπιπέττας σε πειράματα αποκόλλησης μεμονωμένων οστεοβλαστών.Υπολογίστηκε η “ώθηση αποκόλλησης”, I, ως το ολοκλήρωμα της εφαρμοζόμενηςδύναμης στο χρόνο (I=SFdt) για την πλήρη αποκόλληση ενός κυττάρου και βρέθηκεστατιστικά μεγαλύτερη στη χιτοζάνη σε όλους τους χρόνους. Με την τεχνικήΠοσοτικής Αλυσιδωτής Αντίδρασης Πολυμεράσης, η έκφραση των γονιδίωνιντεγκρινών αν, α4, β1 και β3 βρέθηκε σημαντικά αυξημένη στη χιτοζάνη από τα 30στα 120 λεπτά. Με συνεστιακό μικροσκόπιο σάρωσης, παρατηρήθηκε αυξημένη έκφραση της κινάσης εστιακής προσκόλλησης στη χιτοζάνη στα 30 και στα 120λεπτά.Τέλος, χρησιμοποιήθηκε η τεχνική της μικροπιπέττας σε πειράματα εφελκυσμού καιερπυσμού των οστεοβλαστών και υπολογίστηκαν οι μεταβολές του μέτρου Young, Ε,και του φαινόμενου ιξώδους, η. Οι μέσες τιμές βρέθηκαν αυξημένες στην πορεία τηςπροσκόλλησης στις δύο επιφάνειες, παρουσιάζοντας υψηλότερες τιμές στηχιτοζάνη.Η παρούσα διατριβή είναι μια ολοκληρωμένη φαινομενολογική προσέγγιση τηςμηχανικής συμπεριφοράς της οστεοβλάστης κατά την προσκόλληση. Η προσκόλλησηστη χιτοζάνη συνοδεύεται από μεταβολές στη μηχανική συμπεριφορά και συνδέεταιμε κρίσιμες βιοχημικές διεργασίες

Insights into the Alteration of Osteoblast Mechanical Properties upon Adhesion on Chitosan

Cell adhesion on substrates is accompanied by significant changes in shape and cytoskeleton organization, which affect subsequent cellular and tissue responses, determining the long-term success of an implant. Alterations in osteoblast stiffness upon adhesion on orthopaedic implants with different surface chemical composition and topography are, thus, of central interest in the field of bone implant research. This work aimed to study the mechanical response of osteoblasts upon adhesion on chitosan-coated glass surfaces and to investigate possible correlations with the level of adhesion, spreading, and cytoskeleton reorganization. Using the micropipette aspiration technique, the osteoblast elastic modulus was found higher on chitosan-coated than on uncoated control substrates, and it was found to increase in the course of spreading for both substrates. The cell-surface contact area was measured throughout several time points of adhesion to quantify cell spreading kinetics. Significant differences were found between chitosan and control surfaces regarding the response of cell spreading, while both groups displayed a sigmoidal kinetical behavior with an initially elevated spreading rate which stabilizes in the second hour of attachment. Actin filament structural changes were confirmed after observation with confocal microscope. Biomaterial surface modification can enhance osteoblast mechanical response and induce favorable structural organization for the implant integration