Evaluation of Usefulness of Yeast-Based Biological Phantom and Preliminary Study for Verification of Hypoxic Effect of Flash Radiotherapy

PURPOSE/OBJECTIVE(S)

As a basic hypothesis for the effectiveness of flash radiation therapy, the effect of preserving normal tissue during flash radiation is due to the instantaneous chemical depletion of oxygen. A yeast-based biological phantom was created to verify the hypoxic effect of flash radiation therapy. A study to upgrade the previously developed X-Band LINAC to a flash irradiation mode is in progress, and a preceding study is conducted to evaluate the usefulness of a yeast-based biological phantom manufactured by analyzing the change in oxygen by irradiating a high dose in a general radiation therapy device.

MATERIALS/METHODS

Freeze-dried yeast sample (Saccharomyces cerevisiae, S288C) is activated and sub-cultured. For mass production of yeast samples, yeast culture medium is prepared by adding yeast colonies to the ypd medium. This study was conducted to verify the hypoxic effect among the biological mechanisms that occur during flash radiation therapy at the basic stage, and the oxygen concentration change during general radiation irradiation was measured in real time using a DO (Dissolved oxygen) meter and fiber optic sensor designed to do that. To prevent scatter, which is a concern during flash irradiation, the fiber form was used, and precise experiments are possible as a non-invasive oxygen concentration measurement method. Based on 10MV of general radiation therapy device, high-dose radiation of 500-10,000 cGy is irradiated to measure real-time oxygen concentration change.

RESULTS

As a result of irradiation with high-dose (500-10,000 cGy) radiation of general LINAC, it was confirmed that the oxygen concentration of the yeast culture medium decreased by 5.7-63.2%, and the usefulness of the biological phantom fabricated based on the yeast culture medium was evaluated.

CONCLUSION

Prior to the analysis of oxygen concentration change in yeast cells during X-Band LINAC flash irradiation, a preliminary study was conducted at a high dose in a general LINAC to obtain a significant result of oxygen concentration change and confirm the usefulness of the yeast-based biological phantom. Prior research was conducted and verified as a general irradiation experiment using a yeast-based biological phantom manufactured based on a DO meter and a fiber optic oxygen sensor. After irradiation with high-dose radiation, the oxygen concentration of the yeast culture medium was measured 5 times, and it was confirmed that there was a change in oxygen concentration of 5.7-63.2%, verifying the usefulness and stability of the biological phantom. The usefulness of the yeast-based biological phantom for high doses was confirmed, and it is expected that the usefulness of the biological phantom for flash radiation can be verified by additionally measuring the change in oxygen concentration of the biological phantom according to the high dose rate in the future.

In Situ Visualization for Control of Nano-Fibrillation Based on Spunbond Processing Using a Polypropylene/Polyethylene Terephthalate System

In situ generation of polyethylene terephthalate (PET) nanofibrils in polypropylene (PP) microfibers via fiber spinning in a spunbond process was studied in this work. The effects of polymer flow rate and air speed in the drafter on the formation of PET fibrils were investigated using a pilot scale machine. An in-situ visualization technique was applied to examine the fiber evolution events and stretch profile at die exit. A scanning electron microscope was used to analyze and investigate the morphology of the dispersed domain. The PET dispersed phase was fibrillated within the PP matrix such that a nonofibrillated composite containing fibrils with an average size around 100 nm was obtained. It was found that the final fibril size directly depends on the degree of die swell, the air speed and the polymer flow rate. It was also found that the in situ observed size of the micro-scale PP/PET fibers was well correlated to the size of the nano-scale PET fibers formed in the PP matrix. The visualization results revealed that a smaller fibril diameter was obtainable by increasing the stretching on the spin line and/or decreasing the die swell.

A Comparison of CO2 and N2 Foaming Behaviors of PP in a Visualization System

Understanding of polypropylene (PP) foaming is critically important to reduce the weight of automotive parts. In this study, we used a batch foaming simulation system with visualization cell, to observe the foaming behaviors of PP that is blown with CO2 and N2 under various experimental conditions. We found that the nucleating agent content, initial temperature, pressure (i. e., gas content), and pressure drop rate during foaming have a significant effect on cell nucleation and cell growth. The cell density and the void fraction of PP foamed with CO2 and N2, respectively, were separately observed and compared. It was found that under the same experimental conditions, the maximum cell density of PP foamed with CO2 was higher than that of PP foamed with N2. However, the maximum cell density of PP foamed with CO2 was determined to be lower than that of PP foamed with N2, when the same gas mole numbers were employed. Based on the experimental results, optimum foaming conditions and effective processing strategies for PP-CO2 system are suggested.

High-Pressure Preform Foam Blow Molding

Recently, several companies have started to use the foaming technology in blow molding processes, primarily in extrusion blow molding. Despite the design complexity involved in the preform blow molding method, substantial advantages result when microcellular foaming and blow molding are combined. In preform and extrusion blow molding, the preform (i. e., the parison) undergoes significant biaxial stress during the inflation stage. Since either extensional or shear stress can dramatically improve cell nucleation, an externally applied stress can cause small-scale, local pressure variations throughout the sample, thus reducing the energy barrier for cell nucleation. So, unlike the current low-pressure foam blow molding technology, where cell nucleation occurs before inflating the preform/parison, we used a high-pressure system to prevent premature foaming in the shaping stage. Consequently, cell nucleation was induced after biaxial stresses were created to induce a higher cell density.

Characterization of Microcellular Foamed PVC/Cellulosic-Fibre Composites

A microcellular plastic is a foamed polymer of a cell size in the range of 0.1 to 10 μm and a cell density in the range of 109 to 1015 cells/cm3. Typically, microcellular plastics have been shown to possess superior impact strength, toughness, and fatigue life to solid polymers. Polymer/cellulosic-fibre composites make use of cellulosic-fibres as a reinforcing filler in the polymer matrix and are known to be advantageous over the neat polymers in terms of the material cost and some mechanical properties such as stiffness and specific strength. These polymer/cellulosic-fibre composites are microcellular processed to create a new class of materials with unique properties. In this paper, the feasibility of the production of microcellular PVC/cellulosic-fibre composites and the effect of the fibre content on the cell morphology are studied. Particular emphasis is given to the fibre surface treatment to investigate its effect on the microcellular morphology. Each step of microcellular PVC/cellulosic-fibre composite processing is addressed including the treatment of the cellulosic-fibre surface, the manufacture of the composite by the mixing of PVC and cellulosic-fibre, the saturation of the composite with gas, and the bubble nucleation and growth. The preliminary experimental results indicate that the surface modification of cellulosic-fibre plays a strong role in determining the interface between the polymer and fibre as well as the cellular morphology of the foamed composites.

Finite Element Analysis of Cell Coarsening in Plastic Foaming

In this study, cell coarsening in plastic foaming is investigated through numerical simulation. Cell coarsening occurring in two adjacent bubbles of different sizes in a finite volume of polymer melt is considered to be representative of the whole foaming system. A quadratic triangle-based finite element analysis with an implicit scheme for time evolution is utilized to solve the governing diffusion equation in the axisymmetric coordinate system. The effects of the bulk gas concentration, the intercellular distance, and the initial bubble sizes on cell coarsening are estimated. Efforts are made to improve a fundamental understanding of cell coarsening in plastic foaming.

Study of volume swelling and interfacial tension of the polystyrene-carbon dioxide-dimethyl ether system

We investigated the interaction of blended carbon dioxide (CO2) and dimethyl ether (DME) with polystyrene (PS) through volume swelling and interfacial tension. The experiments were carried out over a temperature range of 423-483 K, and the pressure was varied from 6.89 MPa to 20.68 MPa. With an incremental concentration of DME in the blend, the volume swelling increased while the interfacial tension between the PS/blend gas mixture and the blend gas decreased. The validity of the Simha-Somcynsky (SS) equation of state (EOS) for the ternary system was established by comparing experimentally measured volume swelling to that obtained via SS-EOS.

Metabolic stress induces a Wnt-dependent cancer stem cell-like state transition

Reciprocal interactions between cancer cells and the tumor microenvironment drive multiple clinically significant behaviors including dormancy, invasion, and metastasis as well as therapy resistance. These microenvironment-dependent phenotypes share typical characteristics with cancer stem cells (CSC). However, it is poorly understood how metabolic stress in the confined tumor microenvironment contributes to the emergence and maintenance of CSC-like phenotypes. Here, we demonstrate that chronic metabolic stress (CMS) in a long-term nutrient deprivation induces a Wnt-dependent phenoconversion of non-stem cancer cells toward stem-like state and this is reflected in the transcriptome analysis. Addition of Wnt3a as well as transfection of dominant-negative Tcf4 establishes an obligatory role for the Wnt pathway in the acquisition of CSC-like characteristics in response to metabolic stress. Furthermore, systematic characterization for multiple single cell-derived clones and negative enrichment of CD44+/ESA+ stem-like cancer cells, all of which recapitulate stem-like cancer characteristics, suggest stochastic adaptation rather than selection of pre-existing subclones. Finally, CMS in the tumor microenvironment can drive a CSC-like phenoconversion of non-stem cancer cells through stochastic state transition dependent on the Wnt pathway. These findings contribute to an understanding of the metabolic stress-driven dynamic transition of non-stem cancer cells to a stem-like state in the tumor metabolic microenvironment.

Adsorption of Surface-Modified Silica Nanoparticles to the Interface of Melt Poly(lactic acid) and Supercritical Carbon Dioxide

With the purpose of fabricating polymer nanocomposite foams and preventing coalescence in foaming processes, the interfacial tension of poly(lactic acid) (PLA)-silica composites is investigated in this work. Synthesized silica nanoparticles (SNs) with a CO2-philic surface modification are used as the dispersed nanoparticles. Interfacial tension is a key parameter in processing of polymer foams since it directly affects the final foam properties, such as cell size and cell density. Interfacial tension of silica-containing PLA and supercritical carbon dioxide (CO2) is measured using axisymmetric drop shape analysis profile (ADSA-P) pendant drop method at high pressures and high temperatures. The interfacial tension between PLA and supercritical CO2 is observed to decrease as a result of the nanoparticles' adsorption to the interface. These results indicate that the reduction in interfacial tension with increasing silica content significantly deviates from a linear trend; there is a minimum at 2 wt % loading of the SNs and then the interfacial tension curve reaches a plateau. Contact angle measurements show an affinity of the SNs for the polymer-supercritical CO2 interface, and these obtained results are used to calculate the binding energy of the nanoparticles to the PLA/CO2 interface. In addition to interfacial properties, the adsorption of silica nanoparticles at the interface is also studied in detail with scanning electron microscopy.

Simha-Somcynsky Equation of State Modeling of the PVT Behavior of PP/Clay-Nanocomposite/CO2 Mixtures

The Pressure-Volume-Temperature (PVT) property of polymer nanocomposite (PNC)/gas solutions is an important fundamental property in the foaming of PNC. However, accurate data have not yet been reported. We examined the PVT behaviors of polypropylene (PP) and PP/organoclay polymer nanocomposite (PP-PNC) by monitoring the swelling changes of the polymer melt in supercritical carbon dioxide (scCO2). A model was adopted that describes the PVT behaviors of PP-PNC with and without dissolved gas. Based on the model, a PNC consists of two sections: a hard section (a nanoparticle surrounded by solidified polymer) and a soft section (neat polymer). It was observed that an infusion of nanoparticles decreased the swelling. It seems that the hard section had a minimal free volume in which to dissolve the blowing agents, and that the number of hard sections increased with the infusion of nanoparticles. As a result, the total gas absorption capacity of the system decreased, and consequently, the swelling also decreased.

Optimization of Dispersion of Nanosilica Particles in a PP Matrix and Their Effect on Foaming

Nanocomposites based on isotactic polypropylene (PP) and nanosilica (SiO2) were prepared using a co-rotating twin-screw extruder (TSE). The effect of operating variables, such as screw speed and screw configuration on the dispersion of nanosilica in the polymer matrix has been studied, using TEM imaging. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good nanosilica dispersion. Furthermore, the effects of filler loading and amount of a maleated polypropylene (PP-g-MA) compatibilizer on the degree of SiO2 dispersion were investigated. The foaming performance of the composites was evaluated using a batch foaming simulation system, and an extrusion foaming setup that employed respectively N2 and CO2 blowing agents. Well-dispersed surface-modified hydrophobic SiO2 particles acted as effective nucleating agents for foaming, when used at loadings below 1 phr.

Challenges to the Formation of Nano-cells in Foaming Processes

This paper uses a finite element analysis to investigate the morphological changes of nano-cells in a polystyrene (PS) – CO2 foaming system. The system was composed of a finite polymer melt with a central cell and eight surrounding cells. The computational domain was discretized using linear triangular elements. The growth and shrinkage of nano-sized cells were tracked using the moving mesh method. The effects of the initial bulk gas concentration, cell size, intercellular distance, and system temperature on cell ripening were examined. The results show that smaller nano-sized cell(s) are doomed to collapse very quickly once they have interacted with larger cell(s), making it difficult to survive. Efforts were made to improve the general understanding of the challenges posed to the formation of nano-cells in foaming processes.

Anti-inflammatory effect of sinomenine by inhibition of pro-inflammatory mediators in PMA plus A23187-stimulated HMC-1 Cells

BACKGROUND AND OBJECTIVES

Sinomenine is an alkaloid compound and a prominent anti-inflammatory agent found in the root of the climbing plant Sinomenium acutum. However, its effects on the mechanism of human mast cell line (HMC)-1-mediated inflammation remained unknown.

MATERIALS AND METHODS

To provide insight into the biological effects of sinomenine, we examined its influence on the pro-inflammatory cytokine production in HMC-1 cells stimulated by phorbol 12-myristate-13-acetate (PMA) plus A23187 by evaluating the stimulated cells in the presence or absence of sinomenine. In the present study, the pro-inflammatory cytokine production was measured using ELISA, Reverse Transcription-polymerase chain reaction (RT-PCR) and nuclear factor (NF)-kappaB, mitogen-activated protein kinases (MAPKs) pathway activation, as determined by Western blot analysis. Also, cyclooxygenase (COX)-2 expression was measured through Western blot and RT-PCR analysis.

RESULTS

Sinomenine inhibited the pro-inflammatory cytokine production induced by PMA plus A23187 in a dose-dependent manner. Furthermore, sinomenine inhibited the phosphorylations of extracellular signal-regulated kinase (ERK) and p38 MAPKs as well as the translocation of NF-kappaB p65 through reduced IkappaBalpha degradation. In addition, sinomenine suppressed COX-2 protein and mRNA expression dose-dependently.

CONCLUSIONS

Taken together, the results of this study indicate that the anti-inflammatory effects of sinomenine may occur via the inhibition of pro-inflammatory cytokine and COX-2 production through the inhibition of MAPKs and NF-kappaB pathway activation by PMA plus A23187 stimulation in HMC-1 cells.

Elsevier Trophoblast Research Award lecture: The multifaceted role of Nodal signaling during mammalian reproduction

Nodal, a secreted signaling protein in the transforming growth factor-beta (TGF-β) superfamily, has established roles in vertebrate development. However, components of the Nodal signaling pathway are also expressed at the maternal-fetal interface and have been implicated in many processes of mammalian reproduction. Emerging evidence indicates that Nodal and its extracellular inhibitor Lefty are expressed in the uterus and complex interactions between the two proteins mediate menstruation, decidualization and embryo implantation. Furthermore, several studies have shown that Nodal from both fetal and maternal sources may regulate trophoblast cell fate and facilitate placentation as both embryonic and uterine-specific Nodal knockout mouse strains exhibit disrupted placenta morphology. Here we review the established and prospective roles of Nodal signaling in facilitating successful pregnancy, including recent evidence supporting a potential link to parturition and preterm birth.