Inhibitory Effects of Cholesterol Derivatives on DNA Polymerase and Topoisomerase Activities, and Human Cancer Cell Growth

This paper describes the inhibitory activities of cholesterol derivatives such as cholesterol, sodium cholesteryl sulfate, cholesteryl-5α, 6α-epoxide, cholesteryl chloride, cholesteryl bromide, and cholesteryl hemisuccinate (compounds 1–6, respectively) against DNA polymerase (pol), DNA topoisomerase (topo), and human cancer cell growth. Among the compounds tested, compounds 2 and 6 revealed themselves to be potent inhibitors of animal pols, and the IC₅₀ values for pols were 0.84–11.6 and 2.9–148 μM, respectively. Compounds 2, 3 and 6 inhibited the activity of human topo II, with IC₅₀ values of 5.0, 12.5 and 120 μM, respectively. Compounds 2, 3 and 6 also suppressed human cancer cell (promyelocytic leukemia cell line, HL-60) growth, and LD₅₀ values were 8.8, 20.2 and 72.3 μM, respectively, suggesting that cell growth inhibition had the same tendency as the inhibition of topos rather than pols. Compounds 2 and 6 arrested the cells in S and G2/M phases, compound 3 arrested the cells in the G2/M phase, and these compounds also increased sub-G1 phase in the cell cycle. These results suggested that the effect of cell cycle arrest might be effective on both pols and topos activities. From these findings, the action mode of cholesterol derivatives as anti-cancer compounds is discussed.     

Diamond-like carbon thin film with controlled zeta potential for medical material application

With the purpose of applying diamond-like carbon (DLC) thin films as a biocompatible material, we experimented with introducing functional groups such as amino and carboxyl groups to the surface of DLC thin films by plasma surface treatment. From the results, it was found that the contact angle values of the DLC thin films surface were decreased with increasing in the OCO bonded network on the surface. Measurement of the zeta potential when the amounts of the functional groups were varied showed that this successfully varied the zeta potential over the wide range of − 48 mV to + 12 mV. It was found that when carboxyl groups are introduced by O₂ plasma modification of the DLC thin films surface, the zeta potential was lower than that of untreated DLC thin films sample. It was also found that amino groups can be introduced to the DLC thin films surface by NH₃ plasma treatment, the zeta potential was higher than that of untreated DLC thin films sample. This means that zeta potential of the DLC thin films can also be controlled by controlling these two functional groups. Therefore, we have succeeded in developing a multifunctional DLC thin films that does not use polymers and is suitable as a biocompatible material.     

Preparation of nanocomposites by melt compounding polylactic acid/polyamide 12/organoclay at different screw rotating speeds using a twin screw extruder

This study analyzes the effect of different screw rotating speeds on the clay dispersion and mechanical properties of nanocomposites prepared by melt compounding polylactic acid (PLA) with an organoclay in a co‐rotating twin screw extruder. Polyamide 12 (PA12) was used as an additive. Two different screw rotating speeds, 65 rpm and 150 rpm, were used in this study. According to the tensile strength data, the Young's modulus of the PLA/clay nanocomposites showed improvement at a screw rotating speed of 150 rpm. The Young's modulus improved with the addition of the organoclay to PLA matrix, but decreased when PA12 was added to the PLA matrix. The tensile strengths and elongations become small by adding organoclay to PLA matrix. The tensile strengths of the PLA/organoclay nanocomposites increased for the higher screw rotating speed (150 rpm). The d‐spacing of PLA/PA12/Clay nanocomposites was independent of the addition of PA12. The size of the clay aggregates in the PLA/PA12/Clay nanocomposites is smaller than that of PLA/Clay. Furthermore, the thermal stability of the PLA/Clay nanocomposite increases with addition of PA12, while on the whole, it had little influence on the tensile properties. POLYM. COMPOS., 29:1–8, 2008. © 2007 Society of Plastics Engineers     

Effect of Polymer Dispersant Structure on Electrosteric Interaction and Dense Alumina Suspension Behavior

The present paper reports on research on the effect of molecular structure of polymer dispersants on the relationship between the electrosteric interaction of dispersants on solid surfaces and the viscosity of suspensions. Ammonium polyacrylate with different hydrophilic to hydrophobic ratios ( m:n ) was prepared and added to dense Al₂O₃ suspensions (40 vol%). The steric interactions and adsorbed structures of dispersants on Al₂O₃ powders were examined under an atomic force microscope (AFM). An optimum hydrophilic to hydrophobic group ratio, which was obtained from the maximum repulsive force and the minimum viscosity of suspension, was determined at m :n = 3:7. The changing mechanism of the adsorbed structure and the steric interaction of dispersants and the suspension viscosity by the hydrophilic to hydrophobic molecular ratio were discussed by comparing the experimental force curve and DLVO theory.     

Evaluation of surfactant-aided degumming of vegetable oils by membrane technology

The first step in the process of vegetable oil refining is degumming, in which phospholipids and mucilaginous gums are removed that otherwise result in a low-grade oil. A membrane process is remarkably simple yet potentially offers many advantages in degumming. Studies were conducted on surfactant-aided membrane degumming with soybean and rapeseed oils in a magnetically stirred flat membrane batch cell with different types of microfiltration membranes. The reduction of phospholipids in soybean oil was in the range of 85.8–92.8% during the membrane process. The phosphorus content of membrane permeates of soybean oil was in the range of 20–58 mg/kg. Crude rapeseed oil contained higher amount of nonhydratable phospholipids and hence resulted in lower reduction in phospholipids, in the range of 66.4–83.2%. Addition of hydratable phospholipids could improve the efficiency of degumming in the membrane process without using any electrolyte, resulting in improvement of quality as well as quantity of the phospholipids.     

Superhydrophobic/superhydrophilic micropatterning on a carbon nanotube film using a laser plasma-type hyperthermal atom beam facility

Superhydrophobic/superhydrophilic micropatterning on a carbon nanotube (CNT) film has been achieved using a laser plasma-type hyperthermal atom beam facility, which produces a small amount of damage and generates a highly anisotropic beam. Fluorination and oxidation on CNT films by exposure to fluorine-atom and oxygen-atom beams caused superhydrophobic and superhydrophilic surfaces, respectively, while maintaining the as-grown fibrous forms of the CNT films. Micropatterned oxidation on CNT films without using photoresists created superhydrophilic microdots and microchannels.     

Decreasing resistances of membrane-electrode assemblies containing hydrocarbon-based ionomers for improving their anodic performances

To improve methanol-oxidation performances of membrane-electrode assemblies composed of a hydrocarbon-based ionomers, the resistances involved in the reaction were decreased. Electrochemical impedance spectroscopy revealed that the proton-conductive resistance (R_i) in the anode was decreased from 0.54 to 0.40 Ω cm² by increasing a loading ratio of platinum-ruthenium to carbon support of anode catalyst from 54 to 73 wt.%. In addition, R_i was decreased to be 0.25 Ω cm² by increasing ion-exchange capacity (IEC) of the ionomer from 1.4 to 2.9 mequiv. g⁻¹. Consequently, the polarization resistance of the anode was significantly decreased, in turn, increasing current density of methanol oxidation at the potential of 0.45 V from 0.110 to 0.244 A cm⁻².     

E7766, a Macrocycle-Bridged Stimulator of Interferon Genes (STING) Agonist with Potent Pan-Genotypic Activity

A strategy for creating potent and pan-genotypic stimulator of interferon genes (STING) agonists is described. Locking a bioactive U-shaped conformation of cyclic dinucleotides by introducing a transannular macrocyclic bridge between the nucleic acid bases leads to a topologically novel macrocycle-bridged STING agonist (MBSA). In addition to substantially enhanced potency, the newly designed MBSAs, exemplified by clinical candidate E7766 , exhibit broad pan-genotypic activity in all major human STING variants. E7766 is shown to have potent antitumor activity with long lasting immune memory response in a mouse liver metastatic tumor model. Two complementary stereoselective synthetic routes to E7766 are also described.     

Possibility of Japanese Cedar Pollen Causing False Positives in the Deep Mycosis Test

Because Japanese cedar pollen (JCP) contains beta-1,3-d-glucan (BG), there is concern that its lingering presence in the atmosphere, especially during its scattering period, may cause false positives in the factor-G-based Limulus amebocyte lysate (LAL) assay used to test for deep mycosis (i.e., G-test). Hence, we examined whether the LAL assay would react positively with substances contained in JCP by using the G-test to measure JCP particles and extracts. BG was purified from the JCP extract on a BG-specific affinity column, and the percentage extractability was measured using three different BG-specific quantitative methods. The G-test detected 0.4 pg BG in a single JCP particle and 10 fg from a single particle in the extract. The percentage extractability of JCP-derived BG was not significantly different among the three quantitative methods. As the JCP particles should technically have been removed during serum separation, they should be less likely to be a direct false-positive factor. However, given that the LAL-assay-positive substances in the JCP extract were not distinguishable by the three BG-specific quantitative methods, we conclude that they may cause the background to rise. Therefore, in Japan false positives arising from JCP contamination should be considered when testing patients for deep mycosis.     

Evaluating building fire safety through egress prediction: A standard application in Japan

Egress calculation, or predicting human flow during egress, is widely applied in Japan using a standardized method for evaluating the fire safety of building plans. This paper illustrates the methods involved in egress calculation using concrete examples and a sample plan. The egress calculation plays an important role in evaluating building plans and in complementing existing fire regulations. However, further investigation needs to be done into human behavior and how it factors into egress.