Effect of surface modification on hydration kinetics of carbamazepine anhydrate using isothermal microcalorimetry

The purpose of this research was to improve the stability of carbamazepine (CBZ) bulk powder under high humidity by surface modification. The surface-modified anhydrates of CBZ were obtained in a specially designed surface modification apparatus at 60°C via the adsorption of n-butanol, and powder x-ray diffraction, Fourier-Transformed Infrared spectra, and differential scanning calorimetry were used to determine the crystalline characteristics of the samples. The hydration process of intact and surface-modified CBZ anhydrate at 97% relative humidity (RH) and 40±1°C was automatically monitored by using isothermal microcalorimetry (IMC). The dissolution test for surface-modified samples (20 mg) was performed in 900 mL of distilled water at 37±0.5°C with stirring by a paddle at 100 rpm as in the Japanese Pharmacopoeia XIII. The heat flow profiles of hydration of intact and surface-modified CBZ anhydrates at 97% RH by using IMC profiles showed a maximum peak at around 10 hours and 45 hours after 0 and 10 hours of induction, respectively. The result indicated that hydration of CBZ anhydrate was completely inhibited at the initial stage by surface modification of n-butanol and thereafter transformed into dihydrate. The hydration of surface-modified samples followed a 2-dimensional phase boundary process with an induction period (IP). The IP of intact and surface-modified samples decreased with increase of the reaction temperature, and the hydration rate constant (k) increased with increase of the temperature. The crystal growth rate constants of nuclei of the intact sample were significantly larger than the surface-modified samples at each temperature. The activation energy (E) of nuclei formation and crystal growth process for hydration of surface-modified CBZ anhydrate were evaluated to be 20.1 and 32.5 kJ/mol, respectively, from Arrhenius plots, but the Es of intact anhydrate were 56.3 and 26.8 kJ/mol, respectively. The dissolution profiles showed that the surface-modified sample dissolved faster than the intact sample at the initial stage. The dissolution kinetics were analyzed based on the Hixon-Crowell equation, and the dissolution rate constants for intact and surface-modified anhydrates were found to be 0.0102±0.008 mg^1/3 min⁻¹ and 0.1442±0.0482 mg^1/3·min⁻¹. The surface-modified anhydrate powders were more stable than the nonmodified samples under high humidity and showed resistance against moisture. However, surface modification induced rapid dissolution in water compared to the control.     

A novel metal-chelating inhibitor of protein farnesyltransferase

A novel metal chelator comprising a 4-(naphthalen-1-yl)pyridine and 2-aminoethanethiol was synthesized. This showed inhibitory activity against human protein farnesyltransferase with IC(50) 1.9 microM, induced morphological change in K-ras-NRK cells at 0.5 microg/mL and showed growth inhibition of K-ras-NRK cells with IC(50) 0.32 microg/mL.     

Synthesis and hybridization property of novel 2',5'-isoDNA mimic chiral peptide nucleic acids

2',5'-isoDNA mimic chiral peptide nucleic acid (isoPNA) monomers derived from D- and L-aspartic acids were synthesized. These novel monomers were incorporated in aminoethylglycine peptide nucleic acid (aegPNA) thymine dodecamers, and the hybridization properties to RNA and DNA were demonstrated by UV thermal denaturation.     

Phlorigidosides A-C, iridoid glucosides from Phlomis rigida

From the aerial parts of Phlomis rigida, three iridoid glucosides, phlorigidoside A (2-O-acetyllamiridoside), B (8-O-acetyl-6-beta-hydroxyipolamide) and C (5-deoxysesamoside), were isolated together with the known iridoid glucosides, shanzhiside methyl ester, 8-O-acetylshanzhiside methyl ester, deoxypulcheloside I, lamiridoside, and 6-beta-hydroxyipolamide. The structures of the new compounds were elucidated based on spectral and chemical evidence.     

Micellar electrokinetic chromatography

At the present stage, many papers on MEKC, which include fundamental characteristics and applications, have been available. Because only brief discussion on some aspects of MEKC was described in this article, it is necessary to refer some of those literature when the detailed information is required. Especially, for optimization strategies of MEKC, which was not discussed in this article, theoretical discussions by Foley(85), Vindevogel and Sandra(86), and Khaledi and coworkers(87,88) should be cited, along with the review article(11).     

Activity-dependent mRNA splicing controls ER export and synaptic delivery of NMDA receptors

Activity-dependent targeting of NMDA receptors (NMDARs) is a key feature of synapse formation and plasticity. Although mechanisms for rapid trafficking of glutamate receptors have been identified, the molecular events underlying chronic accumulation or loss of synaptic NMDARs have remained unclear. Here we demonstrate that activity controls NMDAR synaptic accumulation by regulating forward trafficking at the endoplasmic reticulum (ER). ER export is accelerated by the alternatively spliced C2' domain of the NR1 subunit and slowed by the C2 splice cassette. This mRNA splicing event at the C2/C2' site is activity dependent, with C2' variants predominating upon activity blockade and C2 variants abundant with increased activity. The switch to C2' accelerates NMDAR forward trafficking by enhancing recruitment of nascent NMDARs to ER exit sites via binding of a divaline motif within C2' to COPII coats. These results define a novel pathway underlying activity-dependent targeting of glutamate receptors, providing an unexpected mechanistic link between activity, mRNA splicing, and membrane trafficking during excitatory synapse modification.     

Application of chimeric glucanase comprising mutanase and dextranase for prevention of dental biofilm formation

Water‐insoluble glucan (WIG) produced by mutans streptococci, an important cariogenic pathogen, plays an important role in the formation of dental biofilm and adhesion of biofilm to tooth surfaces. Glucanohydrolases, such as mutanase (α‐1,3‐glucanase) and dextranase (α‐1,6‐glucanase), are able to hydrolyze WIG. The purposes of this study were to construct bi‐functional chimeric glucanase, composed of mutanase and dextranase, and to examine the effects of this chimeric glucanase on the formation and decomposition of biofilm. The mutanase gene from Paenibacillus humicus NA1123 and the dextranase gene from Streptococcus mutans ATCC 25175 were cloned and ligated into a pE‐SUMOstar Amp plasmid vector. The resultant his‐tagged fusion chimeric glucanase was expressed in Escherichia coli BL21 (DE3) and partially purified. The effects of chimeric glucanase on the formation and decomposition of biofilm formed on a glass surface by Streptococcus sobrinus 6715 glucosyltransferases were then examined. This biofilm was fractionated into firmly adherent, loosely adherent, and non‐adherent WIG fractions. Amounts of WIG in each fraction were determined by a phenol‐sulfuric acid method, and reducing sugars were quantified by the Somogyi–Nelson method. Chimeric glucanase reduced the formation of the total amount of WIG in a dose‐dependent manner, and significant reductions of WIG in the adherent fraction were observed. Moreover, the chimeric glucanase was able to decompose biofilm, being 4.1 times more effective at glucan inhibition of biofilm formation than a mixture of dextranase and mutanase. These results suggest that the chimeric glucanase is useful for prevention of dental biofilm formation.     

Microbial resource allocation for phosphatase synthesis reflects the availability of inorganic phosphorus across various soils

According to the resource allocation model for extracellular enzyme synthesis, microorganisms should preferentially allocate their resources to phosphorus (P)-acquiring enzyme synthesis when P availability is low in soils. However, the validity of this model across different soil types and soils differing in their microbial community composition has not been well demonstrated. Here we investigated whether the resource allocation model for phosphatase synthesis is applicable across different soil types (Andosols, Acrisols, Cambisols, and Fluvisols) and land uses (arable and forest), and we examined which soil test P and/or P fraction microorganisms responded to when investing their resources in phosphatase synthesis in the soils. The ratio of alkaline phosphatase (ALP) to β-d-glucosidase (BG) activities in the arable soils and the ratio of acid phosphatase (ACP) to BG activities in the forest soils were significantly negatively related with the available inorganic P concentration. We also observed significant effects of available inorganic P, pH, soil types, and land uses on the (ACP + ALP)/BG ratio when the data for the arable and forest soils were combined and used in a stepwise multiple regression analysis. These results suggest that microbial resource allocation for phosphatase synthesis is primarily controlled by available inorganic P concentration and soil pH, but the effects of soil types and land uses are also significant.     

Cell proliferation and abnormal nuclei induced by radiation in renal tubule epithelium as an early manifestation of late damage

The time of appearance and the dose response of radiation effects in the mouse kidney were assessed from the determination of increases in labeling index, the appearance of proximal tubule cells with abnormally large nuclei, and kidney weight loss. Increased labeling indices and abnormally large nuclei were observed in the irradiated proximal tubule cells before any other histological changes were seen. The labeling index increased with dose (from 3 to 15 Gy) but not with time (from 1 to 12 months after irradiation). Increased labeling was evident as soon as 1 month after irradiation. Cell depletion as measured by a decrease in kidney weights compared to those of age-matched controls was not significant until 6 or more months after 11-, 13-, or 15-Gy irradiation. The frequency of cells with large nuclei increased steadily during the first 9 months after 15 Gy and tended to decline between 9 and 12 months, coincident with accelerating renal weight loss. These findings are consistent with the hypothesis that the production of these cells is a result of an abortive mitotic division and their loss is an eventual result of such an aberration. The increased proliferation induced by irradiation increases the chance for an abortive mitosis and death, presumably at a subsequent mitosis, of radiation-damaged proximal tubule cells, which is a major factor in the appearance of late radiation damage in the kidney.