Separability of SO2 from SO2/N2 mixture through sulfoxide-modified poly(vinyl alcohol) and cellulose membranes

Separability of SO₂ from mixtures of SO₂ and N₂ gases was studied for membranes of poly(vinyl alcohol) (PVA) and cellulose modified with methyl, ethyl, t-butyl, and phenyl vinyl sulfoxides. Of these sulfoxide-modified polymers, the phenyl vinyl sulfoxide-modified PVA membranes were found to give the best separation of SO₂. In the phenyl vinyl sulfoxide modified PVA membranes, the permeability coefficient of SO₂ increased with sulfoxide content while separability of SO₂ was maximum at a sulfoxide content of 23.5 mol %; the separation factor of SO₂ was about 170 at this sulfoxide content. © 1993 John Wiley & Sons, Inc.     

In situ measurements of aggregation and disaggregation of Cu(II) complex at liquid/liquid interface

Aggregation of Cu(II)-5-(octadecyloxy)-2-(2-thiazolylazo)phenol (TARC18) complex at the heptane/water interface was measured directly by a centrifugal liquid membrane spectrometry and a two-phase microflow API-MS method. When the pH of an aqueous phase was increased from 4 to 6, the 1:1 complex of Cu(II)-TARC18, which was formed as a positively charged complex at the interface, formed further an aggregate, accompanied by the change of spectra suggesting its aggregation. The MS spectra of the interfacial species indicated the formation of 2:3 complex for Cu(II) and TARC18 under the conditions that the aggregate was formed. This observation allowed us to analyze the interfacial aggregation stoichiometrically: the aggregate of the 2:3 complex was formed from a 1:1 complex at the interface. The addition of purine base of adenine or guanine into the system resulted in the disruption of the aggregate by the formation of a new three-element complex of 1:1:1 for Cu(II), TARC18, and the base, showing a bathochromic shift in the spectra. Thus, the disaggregation experiment showed an interfacial molecular recognition ability of the Cu(II)-TARC18 aggregate for hydrophobic bases.     

How to improve mechanical properties of polylactic acid with bamboo fibers

Bamboo fibers (BF) were mixed in polylactic acid (PLA) to improve its mechanical properties: impact strength and heat resistance. Three different types of BF were extracted from raw bamboo by either sodium hydroxide (NaOH) treatment or steam explosion in conjunction with mechanical processing. They were designated as “short fiber bundle,” “alkali-treated filament” and “steam-exploded filament,” respectively. Composite samples were fabricated by injection molding using PLA/BF pellets prepared by a twin-screw extruding machine. Among them, the highest bending strength was obtained when steam-exploded filaments were put into PLA matrix. Impact strength of PLA was not greatly improved by addition of short fiber bundles as well as both filaments. In order to improve the impact strength of PLA/BF composites, PLA composite samples were alternatively fabricated by hot pressing using medium length bamboo fiber bundles (MFB) to avoid the decrease in fiber length at fabrication. Impact strength of PLA/MFB composite significantly increased, in which long fiber bundles were pulled out from the matrix. The addition of BF improves thermal properties and heat resistance of PLA/BF composites due to the constraint of deformation of PLA in conjunction with crystallinity promoted by anneal (at 110 °C for 5 h).     

Effect of chemical fertilizer form on N2O, NO and NO2 fluxes from Andisol field

N₂O, NO and NO₂ fluxes from an Andosol soil in Japan after fertilization were measured 6 times per day for 10 months from June 1997 to April 1998 with a fully automated flux monitoring system in lysimeters. Three nitrogen chemical fertilizers were applied to the soil–calcium nitrate (NI), controlled-release urea (CU), and controlled-release calcium nitrate (CN), and also no nitrogen fertilizer (NN). The total amount of nitrogen applied was 15 g N m^–2 in the first and the second cultivation period of Chinese vegetable. In the first measuremnt period of 89 days, the total N₂O emissions from NI, CN, CU, and NN were 18.4, 16.3, 48.7, and 9.60 mgN m^–2, respectively. The total NO emissions from NI, CN, CU, and NN were 48.4, 33.7, 149, and 13.7 mgN m^–2, respectively. In the second measurement period of 53 days, the total N₂O emissions from NI, CN, and CU were 9.66, 7.23, and 20.6 mgN m^–2, respectively. The total NO emissions from NI, CN, and CU were 24.7, 2.60 and 34.2 mgN m^–2, respectively. The total N₂O emission from CU was significantly higher than CN. In the third cultivation period, all plots were applied with 10 g N m^–2 of ammonium phosphate (AP) and winter barley was cultivated. In the third measurement period of 155 days, the total N₂O and NO emissions were 9.02 mgN m^–2 and 10.2 mgN m^–2, respectively. N₂O and NO peaks were observed just after the fertilization for 30 days and 15 days, respectively. N₂O, NO and NO₂ fluxes for the year were estimated to be 38.6 81.5, 48.2 181, and –24.8 to –39.3 mgN m^–2, respectively. NO₂ was absorbed in all the plots, and a negative correlation was found between NO₂ flux and the NO₂ concentration just after the chamber closed. NO was absorbed in the winter period, and a negative correlation was found between NO flux and the NO concentration just after the chamber closed. A diurnal pattern was observed in N₂O and NO fluxes in the summer, similar to air and soil temperature. We could find a negative relationship between flux ratio of NO-N to N₂O-N and water-filled pore space (WFPS), and a positive relationship between NO-N and N₂O-N fluxes and temperature. Q₁₀ values were 3.1 for N₂O and 8.7 for NO between 530 °C.     

Energy-Dependent Endocytosis Is Responsible for Skin Penetration of Formulations Based on a Combination of Indomethacin Nanoparticles and l-Menthol in Rat and Göttingen Minipig

We previously designed a Carbopol gel formulation (N-IND/MEN) based on a combination of indomethacin solid nanoparticles (IND-NPs) and l-menthol, and we reported that the N-IND/MEN showed high transdermal penetration. However, the detailed mechanism for transdermal penetration of IND-NPs was not clearly defined. In this study, we investigated whether endocytosis in the skin tissue of rat and Göttingen minipig is related to the transdermal penetration of IND-NPs using pharmacological inhibitors of endocytosis. The pharmacological inhibitors used in this study are as follows: 54 µM nystatin, a caveolae-mediated endocytosis (CavME) inhibitor; 40 µM dynasore, a clathrin-mediated endocytosis (CME) inhibitor; and 2 µM rottlerin, a micropinocytosis (MP) inhibitor. The N-IND/MEN was prepared by a bead mill method, and the particle size of solid indomethacin was 79–216 nm. In both rat and Göttingen minipig skin, skin penetration of approximately 80% IND-NPs was limited by the stratum corneum (SC), although the penetration of SC was improved by the combination of l-menthol. On the other hand, the treatment of nystatin and dynasore decreased the transdermal penetration of indomethacin in rats and Göttingen minipigs treated with N-IND/MEN. Moreover, in addition to nystatin and dynasore, rottlerin attenuated the transdermal penetration of IND-NPs in the Göttingen minipigs’ skin. In conclusion, we found that l-menthol enhanced the SC penetration of IND-NPs. In addition, this study suggests that the SC-passed IND-NPs are absorbed into the skin tissue by energy-dependent endocytosis (CavME, CME, and/or MP pathways) on the epidermis under the SC, resulting in an enhancement in transdermal penetration of IND-NPs. These findings provide significant information for the design of nanomedicines in transdermal formulations.     

Metformin Protects against NMDA-Induced Retinal Injury through the MEK/ERK Signaling Pathway in Rats

Metformin, an anti-hyperglycemic drug of the biguanide class, exerts positive effects in several non-diabetes-related diseases. In this study, we aimed to examine the protective effects of metformin against N-methyl-D-aspartic acid (NMDA)-induced excitotoxic retinal damage in rats and determine the mechanisms of its protective effects. Male Sprague–Dawley rats (7 to 9 weeks old) were used in this study. Following intravitreal injection of NMDA (200 nmol/eye), the number of neuronal cells in the ganglion cell layer and parvalbumin-positive amacrine cells decreased, whereas the number of CD45-positive leukocytes and Iba1-positive microglia increased. Metformin attenuated these NMDA-induced responses. The neuroprotective effect of metformin was abolished by compound C, an inhibitor of AMP-activated protein kinase (AMPK). The AMPK activator, AICAR, exerted a neuroprotective effect in NMDA-induced retinal injury. The MEK1/2 inhibitor, U0126, reduced the neuroprotective effect of metformin. These results suggest that metformin protects against NMDA-induced retinal neurotoxicity through activation of the AMPK and MEK/extracellular signal-regulated kinase (ERK) signaling pathways. This neuroprotective effect could be partially attributable to the inhibitory effects on inflammatory responses.     

Preparation of microcapsules of W/O/W emulsions containing a polysaccharide in the outer aqueous phase by spray‐drying

A water‐in‐oil‐in‐water (W/O/W) multiple emulsion containing a hydrophilic substance, 1,3,6,8‐pyrenetetrasulfonic acid tetrasodium salt (PTSA), and a wall material in its inner and outer aqueous phases, respectively, was prepared by a two‐step emulsification using a rotor/stator homogenizer, and was further homogenized with a high‐pressure homogenizer. Maltodextrin or gum arabic were used as wall materials, and olive oil was used as the oily phase. The high encapsulation efficiency for PTSA (>0.9) was realized. The emulsion was spray‐dried to produce microcapsules of W/O/W type. The efficiencies of the microcapsules prepared with maltodextrin and gum arabic were 0.82 and 0.67, respectively. Stability of the microcapsules was examined at 37 °C and 12%, 33% and 75% relative humidity. Microcapsules prepared with maltodextrin were more stable than those prepared with gum arabic.