Design of artificial extracellular matrices for tissue engineering

The design of artificial extracellular matrix (ECM) is important in tissue engineering because artificial ECM regulates cellular behaviors, including proliferation, survival, migration, and differentiation. Artificial ECMs have several functions in tissue engineering, including provision of cell-adhesive substrate, control of three-dimensional tissue structure, and presentation of growth factors, cell-adhesion signals, and mechanical signals. Design criteria for artificial ECMs vary considerably depending on the type of the engineered tissue. This article reviews the materials and methods that have been used in fabrication of artificial ECMs for engineering of specific tissues, including liver, cartilage, bone, and skin. This article also reviews artificial ECMs used for modulation of stem cell behaviors for tissue engineering applications.     

High Performance Control of Matrix Converter Fed Induction Motor Drive System

I Introduction Matrix converter(MC)is a modern energyconversion device that has been developed over the lastthree decades[1~5].Matrix converter fed motor drive issuperiorto pulse width modulation(PWM)inverter drivessince it provides bi-directional power f…     

Systematic DC/small-signal/large-signal analysis of heterojunctionbipolar transistors using a new consistent nonlinear model

In this paper, a new systematic approach to heterojunction bipolar transistors (HBT's) characterization and modeling is presented. The proposed approach is based on a new compact HBT nonlinear circuit model which accounts for both self-heating and the temperature dependence effects. The model's parameters are extracted from measured dc-IV characteristics and S-parameters. The power characteristics of the device are then predicted using the extracted model without any further optimizations. The same model is also used for intermodulation distortion analysis. The model has been implemented in a number of commercial nonlinear simulators and in an in-house computer code. Results are presented for two different size devices showing good agreement with measurements     

Biopharmaceutics classification by high throughput solubility assay and PAMPA

The purpose of the present study was to examine the relevancy of the high throughput solubility assay and permeability assay to the biopharmaceutics classification system (BCS). Solubility and permeability were measured by high throughput solubility assay (HTSA) and parallel artificial membrane permeation assay (PAMPA), respectively. High throughput solubility assay was performed using simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid without bile acid (SIF, pH 6.8). We categorize 18 drugs based on the BCS using HTSA and PAMPA. Fourteen out of 18 drugs were correctly classified (78% success rate). The result of the present study showed that HTSA could predict BCS class with a high success rate, and PAMPA could also be useful to predict the permeation of drugs.     

Calcium channels in the GABAergic presynaptic nerve terminals projecting to meynert neurons of the rat

Effects of selective Ca2+ channel blockers on GABAergic inhibitory postsynaptic currents (IPSCs) were studied in the acutely dissociated rat nucleus basalis of Meynert (nBM) neurons attached with nerve endings, namely, the "synaptic bouton" preparation, and in the thin slices of nBM, using nystatin perforated and conventional whole-cell patch recording modes, respectively. In the synaptic bouton preparation, nicardipine (3 x 10(-6) M) and omega-conotoxin-MVIIC (3 x 10(-6) M) reduced the frequency of spontaneous postsynaptic currents by 37 and 22%, respectively, whereas omega-conotoxin-GVIA had no effect. After blockade of L- and P/Q-type Ca2+ channels, successive removal of Ca2+ from external solution had no significant effect on the residual spontaneous activities, indicating that N-, R-, and T-type Ca2+ channels are not involved in the spontaneous GABA release. Thapsigargin, but not ryanodine, increased the frequency of spontaneous IPSCs in both the synaptic bouton and slice preparations, suggesting the partial contribution of the intracellular Ca2+ storage site to the spontaneous GABA release. In contrast, omega-conotoxin-GVIA (3 x 10(-6) M) and omega-conotoxin-MVIIC (3 x 10(-6) M) suppressed the evoked IPSCs by 31 and 37%, respectively, but nicardipine produced no significant effect. The residual evoked currents were abolished in Ca2+-free external solution but not in the external solution containing 10(-5) M Ni2+, suggesting the involvement of N-, P/Q-, and R-type Ca2+ channels but not L- and T-type ones in the evoked IPSCs. Neither thapsigargin nor ryanodine had any significant effects on the evoked IPSCs. It was concluded that Ca2+ channel subtypes responsible for spontaneous transmitter release are different from those mediating the transmitter release evoked by nerve stimulation.