Comparative evaluation of morphology and osteogenic behavior of human Wharton's jelly mesenchymal stem cells on 2D culture plate and 3D biomimetic scaffold

Expansion of seeded human Wharton's jelly mesenchymal stem cells (hWJ-MSCs) on 2D culture plates and 3D nano-hydroxyapatite/chitosan/gelatin scaffolds, from morphology and osteoactivity points of view, were investigated. Cell attachment and spreading, temporal expression profiles of selected osteogenic gene and protein markers, intracellular alkaline phosphatase enzyme activity (ALP activity), and matrix mineralization were assayed over the course of the experiments. Morphological results demonstrated hWJ-MSCs had greater affinity to adhere onto the 3D scaffold surface, as the number and thickness of the filopodia were higher in the 3D compared with 2D culture system. Functionally, the intracellular ALP activity and extracellular mineralization in 3D scaffolds were significantly greater, in parallel with elevation of osteogenic markers at the mRNA and protein levels at all-time point. It is concluded that 3D scaffolds, more so than 2D culture plate, promote morphology and osteogenic behavior of WJ-MSCs in vitro, a promising system for MSCs expansion without compromising their stemness before clinical transplantation.     

Remediation of a Diesel-Contaminated Soil Using a Fenton-Like Advanced Oxidation Process: Optimization by Response Surface Methodology

Magnetite, a naturally occurring mineral of iron oxide, and zero-valent iron (ZVI) were used to catalyze hydrogen peroxide and initiate a dark Fenton-like reaction of diesel-contaminated loamy sand in a batch system at circumneutral pH. The effects of hydrogen peroxide concentration and catalyst content on the removal efficiency of total petroleum hydrocarbons (TPHs) were studied. A central composite rotatable design was applied and the derived equation for magnetite and ZVI were linear and quadratic, respectively. In both equations, the factor of hydrogen peroxide concentration was more significant than catalyst content. At optimum conditions (4.27 wt% of catalyst content and 2.17 mol/L of hydrogen peroxide), 57% and 67% of TPH removal were achieved by magnetite and ZVI, respectively. The obtained results suggest the potential of ZVI and magnetite to catalyze a heterogeneous Fenton-like reaction at circumneutral pH. It seems that using ZVI, rather than magnetite, as a catalyst may result in slightly more TPH mineralization; however, since magnetite is a naturally occurring mineral, it may be able to compete economically with ZVI.     

Learning Pitch with STDP: A Computational Model of Place and Temporal Pitch Perception Using Spiking Neural Networks

Pitch perception is important for understanding speech prosody, music perception, recognizing tones in tonal languages, and perceiving speech in noisy environments. The two principal pitch perception theories consider the place of maximum neural excitation along the auditory nerve and the temporal pattern of the auditory neurons’ action potentials (spikes) as pitch cues. This paper describes a biophysical mechanism by which fine-structure temporal information can be extracted from the spikes generated at the auditory periphery. Deriving meaningful pitch-related information from spike times requires neural structures specialized in capturing synchronous or correlated activity from amongst neural events. The emergence of such pitch-processing neural mechanisms is described through a computational model of auditory processing. Simulation results show that a correlation-based, unsupervised, spike-based form of Hebbian learning can explain the development of neural structures required for recognizing the pitch of simple and complex tones, with or without the fundamental frequency. The temporal code is robust to variations in the spectral shape of the signal and thus can explain the phenomenon of pitch constancy.