José C. B. da Silva

The Osteogenic Priming of Mesenchymal Stem Cells is Impaired in Experimental Diabetes

Diabetes mellitus encompasses a group of metabolic conditions embracing the dysfunction and failure of various tissues and organs, including bone. Sustained bone alterations seem to result from anabolic, rather than catabolic processes, and suggest a decreased osteoblastic recruitment and activity. Current knowledge on the cellular and molecular mechanisms were provided by studies performed with osteogenic populations cultured in diabetic‐simulated conditions, and osteogenic‐induced precursor populations harvested from diabetic animals, sustaining an impaired cellular behavior in terms of osteogenic responsiveness and function. However, the reasons leaning to this impairment remain essentially unknown, as the priming capability and functionality of undifferentiated precursors, developed within the diabetic environment, have not been addressed. Accordingly, this work aims to evaluate the functionality and osteogenic priming capability of bone marrow‐derived mesenchymal stem cells (MSCs), harvested from animals with experimental diabetes, and grown in the absence of any given differentiation factor. MSCs developed within a diabetic microenvironment displayed an impaired behavior, with diminished cell viability and proliferation, altered cytoskeleton organization, impaired osteogenic priming, and increased adipogenic activation. Further, the osteogenic induction of diabetic MSCs resulted in an impaired osteogenic commitment. The modified cell phenotype may be related, at least in part, with altered activity of ERK WNT and p38 signaling pathways in diabetic‐derived cultures. Specific strategies, aiming the modulation of the verified hindrances, may be of therapeutic value to enhance the functionality of diabetic MSCs and sustain an improved outcome in the metabolism and regeneration of the bone tissue in diabetic conditions. J. Cell. Biochem. 116: 1658–1667, 2015.

A minocycline-releasing PMMA system as a space maintainer for staged bone reconstructions?in vitro antibacterial, cytocompatibility and anti-inflammatory characterization

In the present work, we study the development and biological characterization of a polymethyl methacrylate (PMMA)-based minocycline delivery system, to be used as a space maintainer within craniofacial staged regenerative interventions. The developed delivery systems were characterized regarding solid state characteristics and assayed in vitro for antibacterial and anti-inflammatory activity, and cytocompatibility with human bone cells. A drug release profile allowed for an initial burst release and a more sustained and controlled release over time, with minimum inhibitory concentrations for the assayed and relevant pathogenic bacteria (i.e., Staphylococcus aureus, slime-producer Staphylococcus epidermidis and Escherichia coli) being easily attained in the early time points, and sustained up to 72 h. Furthermore, an improved osteoblastic cell response-with enhancement of cell adhesion and cell proliferation-and increased anti-inflammatory activity were verified in developed systems, compared to a control (non minocycline-loaded PMMA cement). The obtained results converge to support the possible efficacy of the developed PMMA-based minocycline delivery systems for the clinical management of complex craniofacial trauma. Here, biomaterials with space maintenance properties are necessary for the management of staged reconstructive approaches, thus minimizing the risk of peri-operative infections and enhancing the local tissue healing and early stages of regeneration.

In vivo tissue response and antibacterial efficacy of minocycline delivery system based on polymethylmethacrylate bone cement

This study aims the in vivo biological characterization of an innovative minocycline delivery system, based on polymethylmethacrylate bone cement. Bone cements containing 1% or 2.5% (w/w) minocycline were formulated and evaluated through solid-state characterization. Biological evaluation was conducted in vivo, within a rat model, following the subcutaneous and bone tissue implantation, and tissue implantation associated with Staphylococcus aureus is challenging. The assessment of the tissue/biomaterial interaction was conducted by histologic, histomorphometric and microtomographic techniques. Minocycline addition to the composition of the polymethylmethacrylate bone cement did not modify significantly the cement properties. Drug release profile was marked by an initial burst release followed by a low-dosage sustained release. Following the subcutaneous tissue implantation, a reduced immune-inflammatory reaction was verified, with diminished cell recruitment and a thinner fibro-connective capsule formation. Minocycline-releasing cements were found to enhance the bone-to-implant contact and bone tissue formation, following the tibial implantation. Lastly, an effective antibacterial activity was mediated by the implanted cement following the tissue challenging with S. aureus. Kinetic minocycline release profile, attained with the developed polymethylmethacrylate system, modulated adequately the in vivo biological response, lessening the immune-inflammatory activation and enhancing bone tissue formation. Also, an effective in vivo antibacterial activity was established. These findings highlight the adequacy and putative application of the developed system for orthopedic applications.

A Comparison of Classification Techniques for Detection of VoIP Traffic

A new breed of applications for Voice over IP (VoIP) communications has emerged in recent years, providing a viable service for voice communications on the Internet. Mostly provided as over-the-top services, both standards-based Session Initiation Protocol (SIP) VoIP services and proprietary alternatives such as Skype, Google Talk and Yahoo! Voice have earned considerable popularity, mostly because of their low cost and ease of use. However, for various reasons, such as usage policy enforcement, quality assurance, security or specific business interests, there is a need to detect and monitor the presence of VoIP traffic on data networks. The main objective of this paper is to present a survey of techniques for detection and classification of VoIP protocol traffic, with an emphasis on two major categories (profiling of network traffic patterns and modeling of communication flows for anomaly detection) also discussing the several algorithms and techniques within these two groups. Legacy techniques are also briefly described, albeit for the sake of completeness.

Internal Solitary Waves System in the Mozambique Channel

Satellite images of the Mozambique Channel (MC), collected by Synthetic Aperture Radars (SARs) from the Envisat and European Remote Sensing (ERS) satellites, reveal sea surface signatures of oceanic Internal Solitary Waves (ISWs). The MC has been expected to be a major hotspot for the generation of Internal Tides (ITs) in the ocean. New results now show that the Sofala bank (or shelf, located near 20°S, 36°E) is indeed a strong and previously unknown source for the generation of ITs and ISWs. The hotspot region is located between 20 and 21°S, where the barotropic tidal forcing and tidal transports are highest in the area, due to the particular nature of the bathymetry there. Two distinct types of ISWs are observed to travel offshore, away from the shelf-break, and their possible generation mechanisms are discussed. Mode 2 ISWs propagating in MC are also observed in SAR imagery. It is discussed that they may be generated by a tidal beam impinging the thermocline from below, in a similar process to some of the Mode 1 ISWs generated off the Sofala bank. ISW refraction patterns, often observed in SAR imagery in MC are presented, and a particular example is shown where ISWs and eddy-like features are seen to interact. The influence of these rotating features in the refraction patterns is briefly discussed. Finally, it is shown that large-scale atmospheric gravity waves of solitary-like form are also frequently observed in the region, and thus care must be taken when discriminating oceanic and atmospheric ISW signatures in SAR images, if a correct interpretation is to be made.