When erythrocytes are exposed to hypoxia, hemoglobin (Hb) stabilizes in the T-state by capturing 2,3-bisphosphoglycerate. This process could reduce the intracellular pool of glycolytic substrates, jeopardizing cellular energetics. Recent observations suggest that hypoxia-induced activation of glycolytic enzymes is correlated with their release from Band III (BIII) on the cell membrane. Based on these data, we developed a mathematical model of erythrocyte metabolism and compared hypoxia-induced differences in predicted activities of the enzymes, their products, and cellular energetics between models with and without the interaction of Hb with BIII. The models predicted that the allostery-dependent Hb interaction with BIII accelerates consumption of upstream glycolytic substrates such as glucose 6-phosphate and increases downstream products such as phosphoenolpyruvate. This prediction was consistent with metabolomic data from capillary electrophoresis mass spectrometry. The hypoxia-induced alterations in the metabolites resulted from acceleration of glycolysis, as judged by increased conversion of [

The planthopper Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) is a serious insect pest of rice, Oryza sativa L., and has developed resistance to fipronil in Japan. Sequence analysis of L. striatellus RDL gamma-aminobutyric acid (GABA) receptor subunit (LS-RDL) genes from a fipronil-resistant population and a fipronil-susceptible strain identified the A2'N mutation (index number for M2 membrane-spanning region), that was previously implicated in fipronil resistance in the planthopper Sogatella furcifera (Horváth) (Hemiptera: Delphacidae). Nineteen of 21 fipronil-resistant L. striatellus individuals were genotyped as heterozygous for the A2'N mutation, suggesting that this mutation is associated with fipronil resistance and that most fipronil-resistant L. striatellus express wild-type and A2'N mutant LS-RDL simultaneously. To confirm the role of the A2'N mutation of LS-RDL, Drosophila Mel-2 cells were transfected with wild-type and A2'N mutant LS-RDL genes, either individually or together. A membrane potential assay showed that fipronil had no inhibitory effect at 10 microM on cells transfected with the A2'N mutant LS-RDL gene with or without the wild-type LS-RDL gene. By contrast, the IC50 value of fipronil for wild-type LS-RDL homomers was 14 nM. These results suggest that the A2'N mutation of the RDL GABA receptor subunit confers fipronil resistance in L. striatellus as well as S. furcifera.

Common warts (verruca vulgaris) are the most commonly seen benign cutaneous tumors. However, warts in the hands and feet regions often respond poorly to treatment, some are resistant to more than 6 months of treatment with currently available modalities, including cryotherapy, being defined as refractory warts. We investigated the usefulness of long-pulsed neodymium:yttrium-aluminum-garnet (LP-Nd:YAG) treatment for refractory warts. The clinical trial was conducted on 20 subjects (11 male, nine female) with a total of 34 lesions (periungual/subungual areas, plantar areas, fingers and/or toes). All the subjects suffered from refractory warts despite conventional treatments for more than 6 months. The patients were administrated up to six sessions of treatment, at intervals of 4 weeks between sessions, with an LP-Nd:YAG at a spot size of 5 mm, pulse duration of 15 msec and fluence of 150-185 J/cm 2 . Evaluation of the treatment results at 24 weeks after the initial treatment showed complete clearance of the refractory warts in 56% of the patients. Histological evaluation showed separation of the dermis and epidermis at the basement membrane with coagulated necrosis of the wart tissue in the lower epidermis, as well as coagulation and destruction of the blood vessels in the papillary dermis following the laser irradiation. No scarring, post-hyperpigmentary changes or serious adverse events were documented. Our preliminary results show that LP-Nd:YAG treatments are safe and effective for refractory warts of hands and feet, causing minimal discomfort, and is a viable treatment alternative.

In an integrative approach to gaining a better understanding of cell-wide molecular networks at the systems level (systems biology), many attempts at computer simulations of metabolic networks have been made. Because of the simplicity of its structure and components, and the availability of kinetic information, erythrocyte metabolism has been the focus of mathematical modeling for over three decades [1], and is a leading example of the use of mathematical modeling not only for understanding biochemical regulation, but also as the basis for the construction of other mathematical frameworks [2][3][4][5]. For example, models of erythrocyte metabolism were able to predict the importance of the de novo synthesis of glutathione and its mechanism of action in glucose-6-phosphate dehydrogenase (G6PDH)-deficient cells [6], and to analyze Methemoglobin (metHb), an oxidized form of hemoglobin, is unable to bind and carry oxygen. Erythrocytes are continuously subjected to oxidative stress and nitrite exposure, which results in the spontaneous formation of metHb. To avoid the accumulation of metHb, reductive pathways mediated by cytochrome b5 or flavin, coupled with NADH-dependent or NADPH-dependent metHb reductases, respectively, keep the level of metHb in erythrocytes at less than 1% of the total hemoglobin under normal conditions. In this work, a mathematical model has been developed to quantitatively assess the relative contributions of the two major metHbreducing pathways, taking into consideration the supply of NADH and NADPH from central energy metabolism. The results of the simulation experiments suggest that these pathways have different roles in the reduction of metHb; one has a high response rate to hemoglobin oxidation with a limited reducing flux, and the other has a low response rate with a high capacity flux. On the basis of the results of our model, under normal oxidative conditions, the NADPH-dependent system, the physiological role of which to date has been unclear, is predicted to be responsible for most of the reduction of metHb. In contrast, the cytochrome b5-NADH pathway becomes dominant under conditions of excess metHb accumulation, only after the capacity of the flavin-NADPH pathway has reached its limit. We discuss the potential implications of a system designed with two metHbreducing pathways in human erythrocytes.Abbreviations cytb5, cytochrome b5; cytb5R, (NADH-dependent) cytochrome b5 reductase; FR, (NADPH-dependent) flavin reductase; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; G6PDH, glucose-6-phosphate dehydrogenase; GSSG, oxidized glutathione; GSH, glutathione (reduced form); LDH, lactate dehydrogenase; metHb, methemoglobin.

The results of the simulation were consistent with the estimated situation of real G6PD-deficient cells. These results suggest that the de novo glutathione synthesis pathway and the GSSG export system play an important role in alleviating the consequences of G6PD deficiency.