Serum glucose and insulin response in rats administered with sucrose or starch containing adenosine, inosine or cytosine

Blood glucose and insulin responses and gastric emptying were examined in rats intubated with sucrose or soluble starch that contained adenosine, inosine and cytosine. The increase in serum glucose and insulin levels in the rats following loading with sucrose (2.5 g/kg of body weight) or soluble starch (1.875 g/kg of body weight) was significantly reduced by the administration of adenosine, inosine and cytosine (0.0625-0.125 g/kg of body weight). The gastric emptying rates were only marginally affected by the nucleoside administration. The activities of sucrase, maltase, isomaltase and glucoamylase in a crude preparation from the small intestinal mucosa of rats were mildly inhibited by the nucleosides. The decrease in blood glucose and insulin levels may have been in response to a decrease in glucose absorption caused by the inhibiting effect of the nucleosides on the mucosal enzymes that digest sucrose, maltose, and malto- and isomalto-oligosaccharides.     

Crystallization and preliminary X-ray crystallographic analysis of extracellular giant hemoglobin from pogonophoran Oligobrachia mashikoi

An extracellular giant hemoglobin of Oligobrachia mashikoi, composed of 24 globins with the molecular mass of approximately 400 kDa was crystallized in its intact form. Two crystal forms were obtained by the vapor-diffusion method. Form I crystals obtained using sodium acetate as a precipitant belong to the space group P6(1)22 or P6(5)22, with unit-cell parameters a=112.41, c=621.25 A, and diffracted X-rays beyond 3.0 A resolution. Form II crystals obtained using PEG 10000 as a precipitant belong to the space group R32, with unit-cell parameters a=111.50, c=276.84 A, and diffracted X-rays beyond 2.9 A resolution. The crystals are suitable for X-ray crystallography to determine the supramacromolecular assembly of this giant hemoglobin.     

Surface-expressed TLR6 participates in the recognition of diacylated lipopeptide and peptidoglycan in human cells

Recognition of microbial components by TLR2 requires cooperation with other TLRs. TLR6 has been shown to be required for the recognition of diacylated lipoproteins and lipopeptides derived from mycoplasma and to activate the NF-kappaB signaling cascade in conjunction with TLR2. Human TLR2 is expressed on the cell surface in a variety of cells, including monocytes, neutrophils, and monocyte-derived, immature dendritic cells (iDCs), whereas the expression profile of TLR6 in human cells remains obscure. In this study we produced a function-blocking mAb against human TLR6 and analyzed TLR6 expression in human blood cells and cell lines and its participation in ligand recognition. TLR6 was expressed, although at a lower level than TLR2, on the cell surface in monocytes, monocyte-derived iDCs, and neutrophils, but not on B, T, or NK cells. Confocal microscopic analysis revealed that TLR6 was colocalized with TLR2 at the plasma membrane of monocytes. Importantly, TLR2/6 signaling did not require endosomal maturation, and anti-TLR6 mAb inhibited cytokine production in monocytes and iDCs stimulated with synthetic macrophage-activating lipopeptide-2 or peptidoglycan, indicating that TLR6 recognized diacylated lipopeptide and peptidoglycan at the cell surface. In addition, TLR2 mutants C30S and C36S (Cys(30) and Cys(36) in TLR2 were substituted with Ser), which were expressed intracellularly in HEK293 cells, failed to induce NF-kappaB activation upon macrophage-activating lipopeptide-2 stimulation even in the presence of TLR6. Thus, coexpression of TLR2 and TLR6 at the cell surface is crucial for recognition of diacylated lipopeptide and peptidoglycan and subsequent cellular activation in human cells.     

Lack of tax diversity for tropical spastic paraparesis/human T-cell lymphotropic virus type 1 (HTLV-I) associated myelopathy development in HTLV-I-infected subjects in São Paulo, Brazil

The product of human T-cell lymphotropic virus type 1 (HTLV-1) tax gene has a transactivating effect of the viral and cellular gene expression. Genetic variations in this gene have been correlated with differences in clinical outcomes. Based upon its diversity, two closely related substrains, namely tax A and tax B, have been described. The tax A substrain has been found at a higher frequency among human T-cell leukemia virus type 1 (TSP/HAM) patients than among healthy HTLV-I-infected asymptomatic subjects in Japan. In this study, we determined the distribution of tax substrains in HTLV-I-infected subjects in the city of S?o Paulo, Brazil. Using the ACCII restriction enzyme site, we detected only tax A substrain from 48 TSP/HAM patients and 28 healthy HTLV-I carriers. The sequenced tax genes from nine TSP/HAM patients and five asymptomatic HTLV-I carriers showed a similar pattern of mutation, which characterizes tax A. Our results indicate that HTLV-I tax subtypes have no significant influences on TSP/HAM disease progression. Furthermore, monophyletic introduction of HTLV-I to Brazil probably occurred during the African slave trade many years ago.     

Altered localization of amyloid precursor protein under endoplasmic reticulum stress

Recent reports have shown that the endoplasmic reticulum (ER) stress is relevant to the pathogenesis of Alzheimer disease. Following the amyloid cascade hypothesis, we therefore attempted to investigate the effects of ER stress on amyloid-beta peptide (Abeta) generation. In this study, we found that ER stress altered the localization of amyloid precursor protein (APP) from late compartments to early compartments of the secretory pathway, and decreased the level of Abeta 40 and Abeta 42 release by beta- and gamma-cutting. Transient transfection with BiP/GRP78 also caused a shift of APP and a reduction in Abeta secretion. It was revealed that the ER stress response facilitated binding of BiP/GRP78 to APP, thereby causing it to be retained in the early compartments apart from a location suitable for the cleavages of Abeta. These findings suggest that induction of BiP/GRP78 during ER stress may be one of the regulatory mechanisms of Abeta generation.     

Galectin-3 and metastasis

Galectin-3, a 31 kDa member of the β-galactoside-binding proteins, is an intracellular and extracellular lectin which interacts with intracellular glycoproteins, cell surface molecules and extracellular matrix proteins. Galectin-3 is expressed widely in epithelial and immune cells and its expression is correlated with cancer aggressiveness and metastasis. Galectin-3 is involved in various biological phenomena including cell growth, adhesion, differentiation, angiogenesis and apoptosis. Recent research revealed that galectin-3 is associated with several steps of invasion and metastasis, like angiogenesis, cell-matrix interaction, dissemination through blood flow and extravasation. Recently, we and others have shown that galectin-3 can be a reliable diagnostic marker in certain cancers and one of the target proteins of cancer treatment. In this review, we describe the involvement of galectin-3 in each steps of metastasis and clinical significance of galectin-3. Published in 2004.     

Acceleration of the oxygen reaction in CuA-deficient Nitrosomonas europaea cytochrome c oxidase as revealed by the flow-flash measurement.

The oxygen reaction of Nitrosomonas europaea cytochrome c oxidase containing either 2Cu or 1Cu per two heme a molecules was investigated by the flow-flash technique at 20 degrees C. The reaction profiles of the bacterial enzyme were essentially the same as those of bovine heart cytochrome c oxidase, although the rate of the primary oxygen compound formation was much slower. The 1Cu enzyme exhibited higher rates for both primary oxygen compound formation and intramolecular electron transfer than the 2Cu enzyme. This result clearly indicates that CuA is not essential functionally for the oxidation of ferrous heme a moieties, and suggests its structural importance in maintaining the molecular integrity of N. europaea cytochrome oxidase.     

Cytochrome oxidase of an acidophilic iron-oxidizing bacterium, Thiobacillus ferrooxidans, functions at pH 3.5

Cytochrome oxidase of Thiobacillus ferrooxidans was partially purified. The oxidase preparation had haems a and c, and oxidized ferrocytochrome c-552 of the bacterium. The optimal pH of the reaction was 3.5. The enzyme also oxidized the reduced form of rusticyanin, a copper protein of the bacterium. Our results indicate that the reduction of molecular oxygen by this enzyme may occur in the periplasm.