Predictive marker for exposure-driven haematological toxicity of tegafur-uracil and proposed modified-dosage regimen by pharmacometric approach in rats.

Myelosuppression is a dose-limiting toxicity of uracil-tegafur (UFT), which contains uracil and the 5­fluorouracil prodrug tegafur, and inhibits the continuation of chemotherapy, causing treatment failure. A proper dosing strategy to avoid severe myelosuppression-induced discontinuation of chemotherapy is required.Plasma drug concentrations were determined in rats after single oral UFT administration of 15, 30, or 60 mg/kg. Blood cell counts were also measured after oral UFT administration for 5 days. Pharmacokinetic-toxicodynamic (PK-TD) modelling and simulation were performed to describe the time-course alterations in the blood cell counts.Severe neutropenia was observed in rats treated with 60 mg/kg UFT on day 7. A significant decrease in neutrophil counts from baseline levels prior to UFT administration was observed on day 3, whereas leukocyte and lymphocyte counts decreased on day 7. The semi-physiological PK-TD model successfully captured alterations in neutrophil counts after UFT administration, whereas the model could not well describe the platelet, leukocyte, and lymphocyte counts, possibly due to the absence of severe thrombocytopenia, leukocytopenia, and lymphocytopenia, respectively.Neutrophils are sensitive markers for estimating the grade of haematological toxicity of UFT, and a PK-TD model might be an attractive tool for quantitatively evaluating the onset and degree of myelosuppression.

Structural investigation of α-l-fucosidase from the pancreas of Patiria pectinifera, based on molecular cloning.

An α-l-fucosidase (Pap-Alf) was purified from the pancreas of a starfish Patiria pectinifera by ammonium sulfate precipitation followed by several column chromatographies. The molecular mass of the purified enzyme was estimated to be 52.6 kDa by SDS-PAGE, although gel filtration analysis of the native enzyme suggests it exists as a homodimer in solution. The purified enzyme showed maximal activity at pH 5.0 and 70 °C. The enzyme was highly specific toward a fucosyl-monosaccharide (Fuc-α-pNP), but it also showed activity toward 2-sulfo-Fuc-α-pNP and fucosyl-α-lactosides (Fuc-α-Galß1→4Glc-ß-pNP). We determined the primary structure of the α-l-fucosidase and validated its expression level in starfish tissue. Whole genome sequence analysis of P. pectinifera was also performed in the present study. Detailed primary structural analysis using bioinformatics tools revealed Pap-Alf lacks the C-terminal region that is otherwise conserved in all previously described α-l-fucosidases. Quantitative gene expression analysis of Pap-Alf in each tissue indicated that the expression of Pap-Alf gene in pancreas was 5-fold higher than in ovary.

Molecular Design and Synthesis of a Novel Substrate for Assaying Lysozyme Activity.

A novel substrate {Galß1,4GlcNAcß1,4GlcNAc-ß-pNP [Gal(GlcNAc)2-ß-pNP]} for assaying lysozyme activity has been designed using docking simulations and enzymatic synthesis via ß-1,4-galactosyltransferase-mediated transglycosylation from UDP-Gal as the donor to (GlcNAc)2-ß-pNP as the acceptor. Hydrolysis of the synthesized Gal(GlcNAc)2-ß-pNP and related compounds using hen egg-white lysozyme (HEWL) demonstrated that the substrate was specifically cleaved to Gal(GlcNAc)2 and p-nitrophenol (pNP). A combination of kinetic studies and docking simulation was further conducted to elucidate the mode of substrate binding. The results demonstrate that Gal(GlcNAc)2-ß-pNP selectively binds to a subsite of lysozyme to liberate the Gal(GlcNAc)2 and pNP products. The work therefore describes a new colorimetric method for quantifying lysozyme on the basis of the determination of pNP liberated from the substrate.

A novel analytical procedure for assaying lysozyme activity using an end-blocked chitotetraose derivative as substrate.

An end-modified ß-d-galactosyl chitotetraose derivative [44-O-ß-d-galactosyl-ß-tri-N-acetylchitotriosyl 2-acetamide-2,3-dideoxy-glucopyranose; Gal(GlcN)3D] was designed and synthesized from chitin tetrasaccharide. The derivative was chemically modified by dehydration of the reducing end GlcN and enzymatic addition of a Gal group to the non-reducing end GlcN. Hydrolysis of Gal(GlcN)3D and related compounds using hen egg-white lysozyme was then examined. Gal(GlcN)3D was specifically cleaved to Gal(GlcN)2 and GlcND. Kinetic studies and docking simulations were further conducted to elucidate its mode of binding to lysozyme. These analyses revealed the binding of Gal(GlcN)3D to lysozyme is more favorable than that of (GlcN)4D. We conclude the 4-O-substituted Gal group at the non-reducing end of Gal(GlcN)3D does not prohibit the action of lysozyme, but gives some affinity to the subsite (i.e. equivalent to GlcN). From these results, a new assay method for quantifying lysozyme was established by utilizing the Morgan-Elson reaction based on the generation of product D (2-acetamide-2,3-dideoxy-glucopyranose), which serves as a chromophore, formed from Gal(GlcN)3D by lysozyme through a conjugated reaction involving ß-N-acetylhexosaminidase. The assay system gave a linear dose-response curve in the range of 2-31 µg of lysozyme during a 15 min incubation. This novel assay method for the quantification of lysozyme is highly specific, sensitive, accurate and reproducible.

Ingestibility and Formulation Quality of Lansoprazole Orally Disintegrating Tablets.

Objectives. We evaluated the ingestibility and formulation quality of one branded (formulation A) and five generic (formulations B, C, D, E, and F) lansoprazole orally disintegrating (OD) tablets. Methods. Ingestibility, including the oral disintegrating time, taste, mouth feeling, and palatability, was examined by sensory testing in healthy subjects. Formulation qualities, including salivary stability, gastric acid resistance, and intestinal dissolution behavior, were examined. Results and Discussion. The oral disintegration time of formulation F (52 s) was significantly longer than that of other formulations (32-37 s). More than 90% of subjects did not experience bitterness with formulations A, E, and F, whereas 50% of subjects felt rough and powdery sensations with formulations B, C, and D. More than 80% of subjects suggested that formulations A, E, and F had good palatability. Ingestibility was different between formulations. OD tablets consist of enteric granules containing lansoprazole, which is unstable in gastric acid. Enteric granules of each formulation were stable in artificial saliva and gastric juice. No differences were observed in dissolution behaviors among the formulations, indicating that the formulation quality of the formulations was almost equivalent. Conclusions. This study provides useful information for selecting branded or generic lansoprazole OD tablets for individualized treatments.

Crucial role of the small GTPase Rac1 in insulin-stimulated translocation of glucose transporter 4 to the mouse skeletal muscle sarcolemma.

The Rho family GTPase Rac1 has been implicated in the regulation of glucose uptake in myoblast cell lines. However, no evidence for the role of Rac1 has been provided by a mouse model. The purpose of this study is to test the involvement of Rac1 in insulin action in mouse skeletal muscle. Intravenous administration of insulin indeed elicited Rac1 activation in gastrocnemius muscle, suggesting the involvement of Rac1 in this signaling pathway. We then examined whether insulin-stimulated translocation of the facilitative glucose transporter GLUT4 from its storage sites to the skeletal muscle sarcolemma depends on Rac1. We show that ectopic expression of constitutively activated Rac1, as well as intravenous administration of insulin, caused translocation of GLUT4 to the gastrocnemius muscle sarcolemma, as revealed by immunofluorescent staining of a transiently expressed exofacial epitope-tagged GLUT4 reporter. Of particular note, insulin-dependent, but not constitutively activated Rac1-induced, GLUT4 translocation was markedly suppressed in skeletal muscle-specific rac1-knockout mice compared to control mice. Immunogold electron microscopic analysis of endogenous GLUT4 gave similar results. Collectively, we propose a critical role of Rac1 in insulin-dependent GLUT4 translocation to the skeletal muscle sarcolemma, which has heretofore been predicted solely by cell culture studies.

Site-selective post-translational modification of proteins using an unnatural amino acid, 3-azidotyrosine.

An efficient method for site-selective modification of proteins using an unnatural amino acid, 3-azidotyrosine has been developed. This method utilizes the yeast amber suppressor tRNA(Tyr)/mutated tyrosyl-tRNA synthetase pair as a carrier of 3-azidotyrosine in an Escherichia coli cell-free translation system, and triarylphosphine derivatives for specific modification of the azido group. Using rat calmodulin (CaM) as a model protein, we prepared several unnatural CaM molecules, each carrying an azidotyrosine at predetermined positions 72, 78, 80 or 100, respectively. Post-translational modification of these proteins with a conjugate compound of triarylphosphine and biotin produced site-selectively biotinylated CaM molecules. Reaction efficiency was similar among these proteins irrespective of the position of introduction, and site-specificity of biotinylation was confirmed using mass spectrometry. In addition, CBP-binding activity of the biotinylated CaMs was confirmed to be similar to that of wild-type CaM. This method is intrinsically versatile in that it should be easily applicable to introducing any other desirable compounds (e.g., probes and cross-linkers) into selected sites of proteins as far as appropriate derivative compounds of triarylphosphine could be chemically synthesized. Elucidation of molecular mechanisms of protein functions and protein-to-protein networks will be greatly facilitated by making use of these site-selectively modified proteins.