Porcine enamel matrix derivative enhances the formation of reparative dentine and dentine bridges during wound healing of amputated rat molars

We examined the biological effects of porcine enamel matrix derivative (EMD; Emdogain) on the formation of reparative dentine and dentine bridges in rat molars after pulp amputation. The pulp chambers of upper molars of Wistar rats were perforated and the amputated pulp surfaces were directly capped with either EMD or its carrier propylene glycol alginate (PGA) as control. The cavities were then restored with glass-ionomer cement. On post-amputation days 4-30, the dissected maxillae were examined by light and electron microscopy. In PGA-capped pulp, reparative dentine had been formed over the dentine walls under the prepared cavity on day 7 post-amputation and its thickness extended until day 30. On day 30, as well as reparative dentine formation, diffuse calcification had occurred beneath the amputated wound surfaces. Dentine bridge formation under the amputated coronal pulp surface was observed in 18.2% of amputated pulp on day 30. In EMD-capped pulp, reparative dentine had already been formed by odontoblast-like cells over the dentine walls, already on day 4 post-amputation, and its thickness extended until day 30. The Ca and P weight % and Ca/P ratio of reparative dentine matrix were similar to those of pre-existing dentine matrix, and these values were not different between PGA and EMD-capped pulp. Dentine bridge formation was observed in 27.3% of EMD-capped pulp on day 30. Our results suggest that EMD enhances the formation of both reparative dentine and dentine bridges during wound healing of amputated rat molar pulp.     

Antibacterial action on pathogenic bacterial spore by green tea catechins

Antibacterial effects of catechins, the major green tea polyphenols, were studied using Clostridium and Bacillus spores. Incubation with crude catechins decreased the number of C botulinum and C butyricum spores but not B cereus spores. Furthermore, the effects of six catechin derivatives on spores were investigated. (−)‐Epicatechin gallate (ECg), (−)‐epigallocatechin (EGC), (−)‐epigallocatechin gallate (EGCg) and (+)‐gallocatechin gallate (GCg) were more effective in decreasing C botulinum and C butyricum spore numbers than (+)‐catechin (C) and (−)‐epicatechin (EC). The vegetative growth of C botulinum and B cereus was inhibited by crude extracts of the catechins. Specifically, purified GCg and EGCg inhibited the vegetative growth of C botulinum and B cereus. The inhibitory effect of ECg on B cereus was similar to that of GCg. However, toxin‐production by B cereus was not inhibited by catechin. Damage to the membrane of C butyricum spores by catechin derivatives was shown using fluorescent microscopy. This study shows that low concentrations of catechins, although requiring a long exposure time, inhibited the growth of bacterial spores. However, the effects of the purified derivatives of the catechins were not the same and GCg and EGCg were found to be the most potent. Spores that are generally resistant to many disinfectants were sensitive to catechins. Copyright © 2005 Society of Chemical Industry     

The effect of small dose of topiroxostat on serum uric acid in patients receiving hemodialysis

Introduction : Topiroxostat, a recently developed xanthine oxidase inhibitor, is expected to have fewer adverse effects than allopurinol because it has different mechanism of action from alloprinol. However, its dosage, usage and safety have not been established in patients with impaired renal function or those undergoing dialysis at the development since no studies was conducted in these patients. Methods : Cross over clinical trial using 3 months of allopurinol and topiroxostat on 27 maintain Japanese HD patients were carried out. The effects on oxidative stress status of both drugs were also evaluated by measuring oxidation reduction potential. Findings : Twenty‐five of twenty‐seven patients completed study. The mean serum uric acid levels in the topiroxostat‐treated arm was significantly lower than it in the allopurinol‐treated arm time‐dependently (P < 0.0001). Corrected oxidative stress ratio defined as biological antioxidant potential/diacron reactive oxygen metabolites was significantly increased in topiroxostat‐arm (*P = 0.0035), but not in allopurinol‐arm (P = 0.1429). No significant difference was seen in diacron reactive oxygen metabolites, biological antioxidant potential, static oxidation‐reduction potential, and capacity oxidation‐reduction potential between pre and post treatment of both drugs. Discussion : It is suggested that a low dose of topiroxostat decreased serum uric acid sufficiently to maintain it below 7.0 mg/dL in patients receiving hemodialysis.     

Thermotropic and Barotropic Phase Behavior of Phosphatidylcholine Bilayers

Bilayers formed by phospholipids are frequently used as model biological membranes in various life science studies. A characteristic feature of phospholipid bilayers is to undergo a structural change called a phase transition in response to environmental changes of their surroundings. In this review, we focus our attention on phase transitions of some major phospholipids contained in biological membranes, phosphatidylcholines (PCs), depending on temperature and pressure. Bilayers of dipalmitoylphosphatidylcholine (DPPC), which is the most representative lipid in model membrane studies, will first be explained. Then, the bilayer phase behavior of various kinds of PCs with different molecular structures is revealed from the temperature–pressure phase diagrams, and the difference in phase stability among these PC bilayers is discussed in connection with the molecular structure of the PC molecules. Furthermore, the solvent effect on the phase behavior is also described briefly.     

Dietary exposure to acrylamide in a group of Japanese adults based on 24-hour duplicate diet samples

Acrylamide is a probable human carcinogen and known human neurotoxin that can be generated in food through heating. Using a mathematical modelling approach, our previous study estimated long-term average dietary exposure to acrylamide in the Japanese people; however, the validity of these estimates remained unknown. Here, we aimed to obtain a more accurate estimate of acrylamide exposure that would reflect the usual practice of heat processing and consumption of foods in the population. We collected duplicate diet samples and dietary records during 24 h from a group of Japanese adults. A total of 110 duplicate diet samples were analysed for acrylamide by LC-MS/MS. Data from individual dietary records were used to examine the association between dietary acrylamide exposure and consumption of selected food groups (e.g., coffee, tea, confectioneries, and vegetables prepared at high temperature [deep-frying, stir-frying, sautéing, and baking]). Of the 110 homogenised diet samples, 108 contained detectable levels of acrylamide. Dietary exposure to acrylamide ranged from 8 to 1582 ng/kg body weight (bw)/day, with the mean value of 215 ng/kg-bw/day and median value of 143 ng/kg-bw/day. This mean value was higher than the value we previously estimated for Japanese adults using a mathematical approach. Multiple linear regression analysis showed log dietary acrylamide exposure was significantly associated with consumption of coffee and vegetables prepared at high temperature during 24-hr of sampling (adj. R² = 0.250, p < 0.001). We revealed significant difference in dietary acrylamide exposure between participants who had coffee and vegetables prepared at high temperature (median, 169 ng/kg-bw/day; range, 35–1224 ng/kg-bw/day, n = 42) and those who had none of them (median, 75 ng/kg-bw/day; range, 8–311 ng/kg-bw/day, n = 15) (Steel-Dwass test, p < 0.05).     

Nicotinic acid transport mediated by pH-dependent anion antiporter and proton cotransporter in rabbit intestinal brush-border membrane

In order to determine whether the vitamin nicotinic acid is absorbed via an anion antiporter, intestinal epithelial cell membrane transport mechanisms for nicotinic acid were characterized using isolated rabbit jejunal brush-border membrane vesicles. The uptake of nicotinic acid by the membrane vesicles showed an overshoot phenomenon in the presence of an outwardly directed bicarbonate gradient or an inwardly directed proton gradient and the uptakes were two times and six times greater, respectively, than that in the absence of any ion gradient. The bicarbonate-dependent initial uptake of nicotinic acid was increased at acidic pH, showing pH-dependent transport activity. An inhibitor of anion transport, 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid, specifically reduced bicarbonate-dependent transport of nicotinic acid. The initial uptakes of nicotinic acid via the anion antiporter and the proton cotransporter were specifically inhibited by monocarboxylic acids such as acetic acid, benzoic acid, D- and L-lactic acid, pravastatin and valproic acid, but not by di- or tricarboxylic acids, bile acids or amino acids. Nicotinic acid uptake activity was, furthermore, expressed in a Xenopus laevis oocyte system after injection of messenger RNA (mRNA) derived from rabbit intestinal epithelial cells. These observations demonstrate that nicotinic acid is absorbed by two independent active transport mechanisms from small intestine, i.e. a proton cotransporter and an anion antiporter. The pH-dependence observed in the intestinal absorption of nicotinic acid might, therefore, be ascribed partly to pH-sensitive and partly to carrier-mediated transport mechanisms in the brush-border membrane.     

A variational principle for minimizing experimental measurement errors and its application to a hybrid experimental-numerical method

In general, experimentally measured fields such as moiré-interferometry fringes contain various errors associated with the measurement and subsequent data analysis. Moreover, the measured displacement field does not necessarily satisfy the equilibrium equation in solid mechanics, especially when the measurement errors are involved. First, a variational principle minimizing the experimental measurement errors is derived to overcome such difficulties. Next, on the basis of this variational principle, a new hybrid moiré-interferometry and finite-element method is developed. Concepts of restoration energy and restoration force are also presented in the context of the present hybrid method. The present hybrid method demonstrates automatic detection and elimination of the measurement errors and smooth visualization of stress contours. The present hybrid method automatically achieves the path independence of the J integral, restoring the path-dependence caused by the measurement errors.     

Characterization of plasma membrane H+-ATPase from salt-tolerant yeast Candida versatilis

Plasma membrane was isolated from the salt-tolerant yeast Candida versatilis and the ATPase in plasma membrane was characterized. The ATPase was a typical H⁺-ATPase with similar properties to the Saccharomyces cerevisiae and Zygosaccharomyces rouxii enzymes. It was reacted with antibody (IgG) raised against S. cerevisiae plasma membrane H⁺-ATPase. The ATPase activity was not changed by adding NaCl and KCl to the assay solutions, but was increased by NH, especially by ammonium sulfate. In vivo stimulation of ATPase activity was observed by the addition of NaCl into the culture medium, as observed in Z. rouxii. No in vivo activation of H⁺-ATPase by glucose metabolism was observed in C. versatilis cells and the activity was independent of the growth phase, like Z. rouxii and unlike S. cerevisiae cells.