Influence of pH on the permeability of p-toluidine and aminopyrine through shed snake skin as a model membrane

The influence of pH on the permeability of p-toluidine (pKa, 5.3) and aminopyrine (pKa, 5.0) through shed snake skin as a model membrane was studied. The pH was adjusted to several values, and the solubility of the drugs in each donor was measured. Flux rates and permeability coefficients were calculated from the steady-state penetration portions. The flux rates of p-toluidine decreased as the pH value in the donor solution increased. On the other hand, the flux rates of aminopyrine were constant at any pH value. The permeability coefficients of each drug increased as the pH value in the donor solution increased. The partition coefficients (octanol/buffer) of each drug were dependent on the molecular fraction of un-ionized species. From these results, it is suggested that ionized species of p-toluidine transports through shed snake skin, but the ionized species of aminopyrine does not.     

Enhanced path smoothing based on conjugate gradient descent for firefighting robots in petrochemical complexes*

The firefighting robot system (FFRS) comprises several autonomous robots that can be deployed to fire disasters in petrochemical complexes. For autonomous navigation, the path planner should consider the robot constraints and characteristics. Specifically, three requirements should be satisfied for a path to be suitable for the FFRS. First, the path must satisfy the maximum curvature constraint. Second, it must be smooth for robots to easily execute the trajectory. Third, it must allow reaching the target location in a specific heading. We propose a path planner that provides smooth paths, satisfy the maximum curvature constraint, and allows a suitable robot heading. The path smoother is based on the conjugate gradient descent, and three approaches are proposed for this path planner to meet all the FFRS requirements. The effectiveness of these approaches is qualitatively and quantitatively evaluated by examining the generated paths. Finally, the path planner is applied to an actual robot to verify the suitability of the generated paths for the FFRS, and planning is applied to another type of robot to demonstrate the wide applicability of the proposed planner.     

Reinforcement of polypropylene by cellulose microfibers modified with polydopamine and octadecylamine

Cellulose microfibers (CMFs) having surfaces modified with polydopamine (PDPA) and octadecylamine (ODA) were prepared, and their reinforcing abilities for polypropylene (PP) were investigated. The PDPA coating was made via self-polymerization of dopamine (P-CMF), and subsequent alkylation was conducted by the reaction with ODA (OP-CMF). The modified CMFs exhibited improved dispersibility in the PP matrix due to the reduced hydrophilicity. The OP-CMF/PP composite prepared by batch mixing had a higher tensile modulus compared to that for the pure PP and composites with unmodified CMFs. However, excess alkylation lowered the tensile modulus, and the presence of an optimal degree of alkylation was demonstrated. The CMF/PP-IM composites fabricated by injection molding exhibited improved tensile properties compared to those prepared by batch mixing. Both the tensile modulus and yield stress were increased by increasing the CMF content and improved by the surface modification of the CMFs.     

Angiographic evaluation of culprit lesions in acute coronary syndrome: relation to the original site on previous coronary angiography

Recent studies suggest that release of cytokines during inflammatory states such as septic shock leads to hypocholesterolemia. To examine whether tumor necrosis factor alpha (TNF), which is the major cytokine in inflammatory disease, causes hypocholesterolemia, we measured serum levels of total (bioactive and receptor-bound) TNF, cholesterol, Apo B, and Apo A1 in seven patients with septic shock over a period of 8 days. Since elevated serum TNF levels are accompanied by the release of soluble TNF receptors, levels of TNF receptors p55 and p75 were also measured. Patients with septic shock had significantly higher serum TNF and TNF receptor levels compared with healthy controls. Increased cytokine levels were accompanied by a significant decline in total serum cholesterol apolipoprotein A1 and B. In vitro studies with cultured human skin fibroblasts, human umbilical vein endothelial cells, and HepG2 hepatoma cells showed that TNF increased the degradation of 125I-labeled low-density lipoprotein in all the cell lines tested. Recombinant soluble TNF receptors inhibited the TNF-induced stimulation of low-density lipoprotein receptor in a concentration-dependent manner. However, the calculated ratio of TNF receptors to total TNF measured in serum of these patients was not able to counteract the stimulatory effect of TNF, possibly due to the higher molar excess of TNF receptors required to achieve this effect in vitro. Our data strengthen the hypothesis that serum values of total TNF determine the extent of hypocholesterolemia during sepsis and septic shock despite the presence of a high concentration of TNF receptors. Studies with recombinant TNF also confirm the role of TNF in hypocholesterolemia in inflammation.     

Novel High‐Temperature Antiferroelectric‐Based Dielectric NaNbO3–NaTaO3 Solid Solutions Processed in Low Oxygen Partial Pressures

The (1?x)NaNbO₃–(x)NaTaO₃ solid solution was investigated for x ≤ 0.4 in terms of new high‐temperature and high‐permittivity dielectric system that is suitable for base metal inner electrode capacitor applications. The addition of Ta significantly enhanced the resistivity of the dielectric, resulting in superior resistivity than the dielectrics‐formulated BaTiO₃ systems that dominate the multilayer ceramic capacitor dielectric devices. The voltage dependence of the permittivity was also superior to BaTiO₃‐based materials, providing higher capacitance at higher temperatures. A transmission electron microscopy study illustrated that the grains had so‐called core‐shell structure. According to the electron diffraction analysis, the core region had an inhomogeneous structure between antiferroelectric and ferroelectric phases, and shell region had an incommensurate ferroelectric‐like structure. The core and shell region had Nb‐ and Ta‐rich composition, respectively, and their interface was compositionally sharp, implying that shell region was formed via a liquid phase during the sintering process with an incongruent Ta dissolution reprecipitation. We anticipate that these or similar materials based on the alkali‐niobate perovskites can be further enhanced to provide capacitor solutions from 150°C to 250°C, which is an important range for a number of new AC–DC invertor and engine control units.     

Use of the inferior epigastric artery for coronary artery bypass grafting: preoperative digital subtraction angiography

Between September 1994 and January 1995, the inferior epigastric artery (IEA) was used as a free graft for direct coronary artery bypass grafting in 4 patients. The IEA is excised from its origin from the external iliac artery as a pedicle with an "oval cuff" of 3 mm in diameter to facilitate the direct anastomosis with the aorta. The 4-week postoperative angiographic study showed that the IEA grafts were patent in all patients. We found that the IEA varies in length, diameter, and the pattern of branching between patients and between the right and left sides in the same patient. The preoperative digital subtraction angiography was useful for evaluating the suitability of IEA.     

Insights into multistep phosphorelay from the crystal structure of the C-terminal HPt domain of ArcB

The histidine-containing phosphotransfer (HPt) domain is a novel protein module with an active histidine residue that mediates phosphotransfer reactions in the two-component signaling systems. A multistep phosphorelay involving the HPt domain has been suggested for these signaling pathways. The crystal structure of the HPt domain of the anaerobic sensor kinase ArcB has been determined at 2.06 A resolution. The domain consists of six alpha helices containing a four-helix bundle-folding. The pattern of sequence similarity of the HPt domains of ArcB and components in other signaling systems can be interpreted in light of the three-dimensional structure and supports the conclusion that the HPt domains have a common structural motif both in prokaryotes and eukaryotes.     

Nonthermal plasma approach in direct methanol synthesis fromCH4

Direct methanol synthesis from CH₄ and O₂ has been experimentally studied using pulsed discharge plasma in concentric-cylinder-type reactors. The methanol production becomes efficient with an increase in the average electric field strength of the reactor. A combination of the pulsed discharge and catalysts was tested and was proved to be effective in increasing both the production and selectivity of methanol. In the present stage, about 2% of CH₄ can be converted into other hydrocarbons, and a methanol yield of around 0.5% and selectivity of 38% can be obtained when a catalyst of V₂O₅+SiO₂ is combined with the pulsed discharge plasma     

Crystallization of porcine insulin with carbon dioxide as acidifying agent

Recent studies on the use of volatile electrolytes such as CO₂ in protein precipitation showed that these agents are a promising alternative to the conventional acids. This use of volatile electrolytes prevents protein denaturation due to local pH extremes, and saline effluent generation is greatly reduced, as the volatile electrolyte may be separated and recovered from solution just by pressure release. In this work, insulin was successfully crystallized in the presence of zinc using CO₂ as acidifying agent. The crystals obtained were rhombohedral, a common shape for porcine insulin crystals that contain zinc in their structure, and their average size varied with the mixing applied.     

Neuroprotection,Growth Factors and BDNF-TrkB Signalling in Retinal Degeneration

Neurotrophic factors play key roles in the development and survival of neurons. The potent neuroprotective effects of neurotrophic factors, including brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), glial cell-line derived neurotrophic factor (GDNF) and nerve growth factor (NGF), suggest that they are good therapeutic candidates for neurodegenerative diseases. Glaucoma is a neurodegenerative disease of the eye that causes irreversible blindness. It is characterized by damage to the optic nerve, usually due to high intraocular pressure (IOP), and progressive degeneration of retinal neurons called retinal ganglion cells (RGCs). Current therapy for glaucoma focuses on reduction of IOP, but neuroprotection may also be beneficial. BDNF is a powerful neuroprotective agent especially for RGCs. Exogenous application of BDNF to the retina and increased BDNF expression in retinal neurons using viral vector systems are both effective in protecting RGCs from damage. Furthermore, induction of BDNF expression by agents such as valproic acid has also been beneficial in promoting RGC survival. In this review, we discuss the therapeutic potential of neurotrophic factors in retinal diseases and focus on the differential roles of glial and neuronal TrkB in neuroprotection. We also discuss the role of neurotrophic factors in neuroregeneration.