A Neural Mass Model to Simulate Different Rhythms in a Cortical Region

An original neural mass model of a cortical region has been used to investigate the origin of EEG rhythms. The model consists of four interconnected neural populations: pyramidal cells, excitatory interneurons and inhibitory interneurons with slow and fast synaptic kinetics, GABAA, slow and GABAA,fast respectively. A new aspect, not present in previous versions, consists in the inclusion of a self-loop among GABAA,fast interneurons. The connectivity parameters among neural populations have been changed in order to reproduce different EEG rhythms. Moreover, two cortical regions have been connected by using different typologies of long range connections. Results show that the model of a single cortical region is able to simulate the occurrence of multiple power spectral density (PSD) peaks; in particular the new inhibitory loop seems to have a critical role in the activation in gamma (γ) band, in agreement with experimental studies. Moreover the effect of different kinds of connections between two regions has been investigated, suggesting that long range connections toward GABAA,fast interneurons have a major impact than connections toward pyramidal cells. The model can be of value to gain a deeper insight into mechanisms involved in the generation of γ rhythms and to provide better understanding of cortical EEG spectra

Quantum Monte Carlo investigation of small He-4 clusters with a He-3 impurity

Small helium (He-4) clusters containing the lighter isotope He-3 are studied by means of quantum Monte Carlo methods. Accurate ground state energies and structural properties are obtained using accurate trial wave functions and the Tang-Tonnies-Yiu (TTY) helium-helium pair potential. The dimer He-4-He-3 is not bound; as well as the trimer (HeHe2)-He-4-He-3. The smallest cluster containing He-3 is He-4(2) He-3 with a nonrigid structure having a marked linear contribution. Interestingly, this weakly bound system, with an energy one order of magnitude less than the He-4(3) trimer, is able to bind another He-3 atom, forming the tetramer He-4(2) He-3(2), which shows the odd feature of having five out of six unbound pairs. In general, the substitution of a single He-4 atom in a pure cluster with a He-3 atom leads to an energetic destabilization, as the pair He-4-He-3 is not bound. The isotopic impurity is found to perturb only weakly the distributions of the remaining He-4 atoms, which retain the high floppiness already found in the pure clusters. As the number of atoms increases the isotopic impurity has the marked tendency to stay on the surface of the cluster. This behavior is consistent with the formation of the so-called "Andreev states" of a single He-3 in liquid He-4 helium and droplets, where the impurity tends to form single-particle states on the surface of the pure He-4

Causality estimates among brain cortical areas by Partial Directed Coherence: simulations and application to real data

The problem of the definition and evaluation of brain connectivity has become a central one in neuroscience during the latest years, as a way to understand the organization and interaction of cortical areas during the execution of cognitive or motor tasks. Among various methods established during the years, the Partial Directed Coherence (PDC) is a frequency-domain approach to this problem, based on a multivariate autoregressive modeling of time series and on the concept of Granger causality. In this paper we propose the use of the PDC method on cortical signals estimated from high resolution EEG recordings, a non invasive method which exhibits a higher spatial resolution than conventional cerebral electromagnetic measures. The principle contributions of this work are the results of a simulation study, testing the performances of PDC, and a statistical analysis (via the ANOVA, analysis of variance) of the influence of different levels of Signal to Noise Ratio and temporal length, as they have been systematically imposed on simulated signals. An application to high resolution EEG recordings during a foot movement is also presented

Biomechanical And Histological Evaluation Of Hydrogel Implants In Articular Cartilage.

We evaluated the mechanical behavior of the repaired surfaces of defective articular cartilage in the intercondylar region of the rat femur after a hydrogel graft implant. The results were compared to those for the adjacent normal articular cartilage and for control surfaces where the defects remained empty. Hydrogel synthesized by blending poly(2-hydroxyethyl methacrylate) and poly(methyl methacrylate-co-acrylic acid) was implanted in male Wistar rats. The animals were divided into five groups with postoperative follow-up periods of 3, 5, 8, 12 and 16 weeks. Indentation tests were performed on the neoformed surfaces in the knee joint (with or without a hydrogel implant) and on adjacent articular cartilage in order to assess the mechanical properties of the newly formed surface. Kruskal-Wallis analysis indicated that the mechanical behavior of the neoformed surfaces was significantly different from that of normal cartilage. Histological analysis of the repaired defects showed that the hydrogel implant filled the defect with no signs of inflammation as it was well anchored to the surrounding tissues, resulting in a newly formed articular surface. In the case of empty control defects, osseous tissue grew inside the defects and fibrous tissue formed on the articular surface of the defects. The repaired surface of the hydrogel implant was more compliant than normal articular cartilage throughout the 16 weeks following the operation, whereas the fibrous tissue that formed postoperatively over the empty defect was stiffer than normal articular cartilage after 5 weeks. This stiffness started to decrease 16 weeks after the operation, probably due to tissue degeneration. Thus, from the biomechanical and histological point of view, the hydrogel implant improved the articular surface repair.33307-1

History, synthesis, properties, applications and regulatory issues of prebiotic oligosaccharides

In this chapter, the health promoting effects of carbohydrate prebiotics are addressed. A brief description of their synthesis, thermo-physical properties, mechanisms of action, technological applications and current regulatory issues are presented

Unsaturated polyester resins: influence of the styrene concentration on the miscibility and mechanical properties

Abstract Styrene is frequently used as comonomer for unsaturated polyester (UP) resins. Variations in the styrene content in the polyester affect the resulting properties. Dynamic mechanical tests show the phase separation in the cured resin with an increase of styrene concentration. The dependence of the glass transition temperature of the UP resin on the styrene content is complex and reflects a balance of elastic forces of the network and the immiscibility of polystyrene and UP. The thermal stability and the mechanical properties are governed by the phase behaviour of the mixture and therefore can be controlled by the styrene content.

A mouse mammary tumor virus env-like exogenous sequence is strictly related to progression of human sporadic breast carcinoma

A viral etiology of human breast cancer (HBC) has been postulated for decades since the identification of mouse mammary tumor virus (MMTV). The detection of MMTV env-like exogenous sequences (MMTVels) in 30% to 40% of invasive HBCs increased attention to this hypothesis. Looking for MMTVels during cancer progression may contribute to a better understanding of their role in HBC. Herein, we analyzed HBC preinvasive lesions for the presence of MMTVels. Samples were obtained by laser microdissection of FFPE tissues: 20 usual-type ductal hyperplasias, 22 atypical ductal hyperplasias (ADHs), 49 ductal carcinomas in situ (DCISs), 20 infiltrating ductal carcinomas (IDCs), and 26 normal epithelial cells collateral to a DCIS or an IDC. Controls included reductive mammoplastic tissue, thyroid and colon carcinoma, and blood samples from healthy donors. MMTVels were detected by fluorescence-nested PCR. DNA samples from the tissues of nine patients were analyzed by real-time quantitative PCR, revealing a different viral load correlated with stage of progression. Furthermore, as never previously described, the presence of MMTVels was investigated by chromogenic in situ hybridization. MMTVels were found in 19% of normal epithelial cells collateral to a DCIS or an IDC, 27% of ADHs, 82% of DCISs, and 35% of IDCs. No MMTVels were found in the control samples. Quantitative PCR and chromogenic in situ hybridization confirmed these results. These data could contribute to our understanding of the role of MMTVels in HBC. (Am J Pathol 2011, 179:2083-2090; DOI: 10.1016/j.ajpath.2011.06.046

Melanoma-restricted genes

Human metastatic cutaneous melanoma has gained a well deserved reputation for its immune responsiveness. The reason(s) remain(s) unknown. We attempted previously to characterize several variables that may affect the relationship between tumor and host immune cells but, taken one at the time, none yielded a convincing explanation. With explorative purposes, high-throughput technology was applied here to portray transcriptional characteristics unique to metastatic cutaneous melanoma that may or may not be relevant to its immunogenic potential. Several functional signatures could be identified descriptive of immune or other biological functions. In addition, the transcriptional profile of metastatic melanoma was compared with that of primary renal cell cancers (RCC) identifying several genes co-coordinately expressed by the two tumor types. Since RCC is another immune responsive tumor, commonalities between RCC and melanoma may help untangle the enigma of their potential immune responsiveness. This purely descriptive study provides, therefore, a map for the investigation of metastatic melanoma in future clinical trials and at the same time may invite consideration of novel therapeutic targets

Development and characterization of iron-pectin beads as a novel system for iron delivery to intestinal cells

Iron deficiency is the most common nutritional deficit worldwide. The goal of this work was to obtain iron-pectin beads by ionic gelation and evaluate their physiological behavior to support their potential application in the food industry. The beads were firstly analyzed by scanning electronic microscopy, and then physical-chemically characterized by performing swelling, thermogravimetric, porosimetry, Mössbauer spectroscopy and X-ray fluorescence analyses, as well as by determining the particle size. Then, physiological assays were carried out by exposing the beads to simulated gastric and intestinal environments, and determining the iron absorption and transepithelial transport into Caco-2/TC7 cells. Iron-pectin beads were spherical (diameter 1-2 mm), with high density (1.29 g/mL) and porosity (93.28%) at low pressure, indicating their high permeability even when exposed to low pressure. Swelling in simulated intestinal medium (pH 8) was higher than in simulated gastric medium. The source of iron [FeSO4 (control) or iron-pectin beads] did not have any significant effect on the mineral absorption. Regarding transport, the iron added to the apical pole of Caco-2/TC7 monolayers was recovered in the basal compartment, and this was proportional with the exposure time. After 4 h of incubation, the transport of iron arising from the beads was significantly higher than that of the iron from the control (FeSO4). For this reason, iron-pectin beads appear as an interesting system to overcome the low efficiency of iron transport, being a potential strategy to enrich food products with iron, without altering the sensory properties.Centro de Investigación y Desarrollo en Criotecnología de Alimento