Palatal ancient schwannoma: optical, immunohistochemical and ultrastructural study with literature review.

Schwannoma or neurilemmoma is a benign encapsulated slow-growing tumor that originates from a Schwann cell of a nerve, and is rare at intraoral locations. Different histological variants of schwannomas have been described, of these degenerative or ancient schwannoma is probably one of the least common in the oral cavity with only 16 previously reported cases, of which only one has been described in palatal location. Although ancient schwannoma shows particular characteristics, it is difficult to diagnose based on clinical and imaging appearance alone; as a result, morphological examination assisted by ancillary techniques is necessary to establish a definite diagnosis. We present a clinicopathological description of this rare variant of schwannoma, located in an unusual intraoral site, of a 26-year-old female. We illustrate the optical, immunohistochemical and ultrastructural characterization that aid diagnosis, as well as providing a review of the relevant published data of this unusual tumor.

Cervical necrotizing fasciitis of nonodontogenic origin: case report and review of literature.

Cervical necrotizing fasciitis (CNF) is a potentially fatal infection characterized by generalized necrosis of the cervical fascia that progresses rapidly. The incidence of this entity corresponds to 2.6% of all infections of the head and neck. The most frequent primary origin is dental infection, although other causes exist that should be evaluated.Delay in the diagnosis of this entity may lead to rapid progression and fatal outcome. Patients often present immunosuppression or systemic diseases that predispose them to this pathology. Cervical necrotizing fasciitis is associated with mortality rates of 7% to 20% depending on the extension of the cervical lesion. The highest rates correspond to cases that progress to mediastinitis or septic shock, which are the main and most frequent complications. Early detection and adequate emergency treatment are critical in the management of these patients and may reduce morbimortality and improve survival. The emergency services should be prepared to manage such cases efficiently, through a multidisciplinary treatment by coordinating emergency surgery with critical support and clinical stabilization of patients.We present a case of CNF of non odontogenic origin managed in our hospital.

Evolutionary dynamics of group interactions on structured populations: a review.

Interactions among living organisms, from bacteria colonies to human societies, are inherently more complex than interactions among particles and non-living matter. Group interactions are a particularly important and widespread class, representative of which is the public goods game. In addition, methods of statistical physics have proved valuable for studying pattern formation, equilibrium selection and self-organization in evolutionary games. Here, we review recent advances in the study of evolutionary dynamics of group interactions on top of structured populations, including lattices, complex networks and coevolutionary models. We also compare these results with those obtained on well-mixed populations. The review particularly highlights that the study of the dynamics of group interactions, like several other important equilibrium and non-equilibrium dynamical processes in biological, economical and social sciences, benefits from the synergy between statistical physics, network science and evolutionary game theory.

Empathy emerges spontaneously in the ultimatum game: small groups and networks.

The Ultimatum game, in which one subject proposes how to share a pot and the other has veto power on the proposal, in which case both lose everything, is a paradigmatic scenario to probe the degree of cooperation and altruism in human subjects. It has been shown that if individuals are empathic, i.e., they play the game having in mind how their opponent will react by offering an amount that they themselves would accept, then non-rational large offers well above the smallest possible ones are evolutionarily selected. We here show that empathy itself may be selected and need not be exogenously imposed provided that interactions take place only with a fraction of the total population, and that the role of proposer or responder is randomly changed from round to round. These empathic agents, that displace agents with independent (uncorrelated) offers and proposals, behave far from what is expected rationally, offering and accepting sizable fractions of the amount to be shared. Specific values for the typical offer depend on the details of the interacion network and on the existence of hubs, but they are almost always significantly larger than zero, indicating that the mechanism at work here is quite general and could explain the emergence of empathy in very many different contexts.

Complex cooperative networks from evolutionary preferential attachment.

In spite of its relevance to the origin of complex networks, the interplay between form and function and its role during network formation remains largely unexplored. While recent studies introduce dynamics by considering rewiring processes of a pre-existent network, we study network growth and formation by proposing an evolutionary preferential attachment model, its main feature being that the capacity of a node to attract new links depends on a dynamical variable governed in turn by the node interactions. As a specific example, we focus on the problem of the emergence of cooperation by analyzing the formation of a social network with interactions given by the Prisoner's Dilemma. The resulting networks show many features of real systems, such as scale-free degree distributions, cooperative behavior and hierarchical clustering. Interestingly, results such as the cooperators being located mostly on nodes of intermediate degree are very different from the observations of cooperative behavior on static networks. The evolutionary preferential attachment mechanism points to an evolutionary origin of scale-free networks and may help understand similar feedback problems in the dynamics of complex networks by appropriately choosing the game describing the interaction of nodes.

On the robustness of complex heterogeneous gene expression networks.

We analyze a continuous gene expression model on the underlying topology of a complex heterogeneous network. Numerical simulations aimed at studying the chaotic and periodic dynamics of the model are performed. The results clearly indicate that there is a region in which the dynamical and structural complexity of the system avoid chaotic attractors. However, contrary to what has been reported for Random Boolean Networks, the chaotic phase cannot be completely suppressed, which has important bearings on network robustness and gene expression modeling.