Identification of Plasmodium malariae,a Human Malaria Parasite,in Imported Chimpanzees

It is widely believed that human malaria parasites infect only man as a natural host. However, earlier morphological observations suggest that great apes are likely to be natural reservoirs as well. To identify malaria parasites in great apes, we screened 60 chimpanzees imported into Japan. Using the sequences of small subunit rRNA and the mitochondrial genome, we identified infection of Plasmodium malariae, a human malaria parasite, in two chimpanzees that were imported about thirty years ago. The chimpanzees have been asymptomatic to the present. In Japan, indigenous malaria disappeared more than fifty years ago; and thus, it is most likely inferred that the chimpanzees were infected in Africa, and P. malariae isolates were brought into Japan from Africa with their hosts, suggesting persistence of parasites at low level for thirty years. Such a long term latent infection is a unique feature of P. malariae infection in humans. To our knowledge, this is the first to report P. malariae infection in chimpanzees and a human malaria parasite from nonhuman primates imported to a nonendemic country.     

Size-exclusion chromatography of biological samples which contain extremely alkaline proteins

An improved size-exclusion chromatography (SEC) was developed to isolate extremely basic (alkaline) proteins, such as trypsin (pI=10.5), lysozyme (pI=11), and histone (pI=10.8). Develosil 300 Diol-5 (300 x 8 mm I.D., 30 nm average pore diameter) column was used with an eluent of 0.1 M sodium phosphate, 1.5 M sodium chloride, glycerol (40%, v/v), 2-propanol (10%, v/v), and Brij-58 (1%, v/v). Under these conditions, the final apparent pH becomes to 4.0, and pH adjustment is not necessary. Column temperature and flow rate were 15 degrees C and 0.2 ml/min, respectively. This elution system is stable and reliable, and applications onto human pancreatic juice, human bile, and tissue homogenates were successfully achieved. Since this system is convenient for protein analysis, it is expected to be generally applicable to clinical and biochemical research for identifying protein components in combination with microsequencing.     

Effect of stretching on gene expression of beta1 integrin and focal adhesion kinase and on chondrogenesis through cell-extracellular matrix interactions

Differentiation of skeletal tissues, such as bone, ligament and cartilage, is regulated by complex interaction between genetic and epigenetic factors. In the present study, we attempted to elucidate the possible role of cell-extracellular matrix (ECM) adhesion on the inhibitory regulation in chondrogenesis responding to the tension force. The midpalatal suture cartilages in rats were expanded by orthopedic force. In situ hybridization for type I and II collagens, immunohistochemical analysis for fibronectin, alpha5 and beta1 integrins, paxillin, and vinculin, and cytochemical staining for actin were used to demonstrate the phenotypic change of chondrocytes. Immunohistochemical analysis for phosphorylation and nuclear translocation of extracellular signal-regulated kinase (ERK)-1/2 was performed. The role of the cell-ECM adhesion in the response of the chondroprogenitor cells to mechanical stress and the regulation of gene expression of focal adhesion kinase (FAK) and integrins were analyzed by using an in vitro system. A fibrous suture tissue replaced the midpalatal suture cartilage by the expansive force application for 14 days. The active osteoblasts that line the surface of bone matrix in the newly formed suture tissue strongly expressed the type I collagen gene, whereas they did not express the type II collagen gene. Although the numbers of precartilaginous cells expressing alpha5 and beta1 integrin increased, the immunoreactivity of alpha5 integrin in each cell was maintained at the same level throughout the experimental period. During the early response of midpalatal suture cartilage cells to expansive stimulation, formation of stress fibers, reorganization of focal adhesion contacts immunoreactive to a vinculin-specific antibody, and phosphorylation and nuclear translocation of ERK-1/2 were observed. In vitro experiments were in agreement with the results from the in vivo study, i.e. the inhibited expression of type II collagen and upregulation in integrin expression. The arginine-glycine-aspartic acid-containing peptide completely rescued chondrogenesis from tension-mediated inhibition. Thus, we conclude that stretching activates gene expression of beta1 integrin and FAK and inhibits chondrogenesis through cell-ECM interactions of chondroprogenitor cells.     

Role of p38 MAPK in lupeol-induced B16 2F2 mouse melanoma cell differentiation

We examined the signaling mechanisms involved in the differentiation-inducing activity of lupeol toward B16 2F2 melanoma cells. alpha-Melanocyte stimulating hormone (alpha-MSH), forskolin and dibutyryl cAMP, which are believed to be cAMP-elevating agents and analogues, enhanced lupeol-induced B16 2F2 cell differentiation. However, H89, an inhibitor of protein kinase A, completely abolished B16-2F2 cell differentiation induced by lupeol. Furthermore, we studied the role of mitogen-activated protein kinases (MAPKs) in lupeol-induced B16 2F2 cell differentiation. U0126, an inhibitor of MAPK kinases, induced B16 2F2 cell differentiation and enhanced the cell differentiation induced by lupeol. However, SB203580, a selective inhibitor of p38 MAPK, completely blocked lupeol-induced B16 2F2 cell differentiation. Western blot analysis revealed that 10 microM lupeol transiently elevated the level of phosphorylation of p38 MAPK. The phosphorylation of p38 MAPK was detected on the addition of 1 microM lupeone, another lupane triterpene, but was not induced by 1 microM lupeol. These results suggested that lupeol induced B16 2F2 cell differentiation through activation of p38 MAPK, and that the structural differences at C-3 of lupane triterpenes played an important role in the activation of p38 MAPK.     

RALyase; a terminator of elongation function of depurinated ribosomes

Plant ribosomal RNA apurinic site specific lyase (RALyase) cleaves the phosphodiester bond at the depurinated site produced by ribosome-inactivating protein, while the biological role of this enzyme is not clear. As the depurinated ribosomes retain weak translation elongation activities, it was suggested that RALyase completes the ribosome inactivation. To confirm this point, we measured the effects of the phosphodiester cleavage using a fusion of wheat RALyase produced with a cell-free protein synthesis system from wheat germ. The results indicated that RALyase diminishes the residual elongation activities of the depurinated ribosomes.     

Role of high mobility group protein-1 (HMG1) in amyloid-beta homeostasis

In Alzheimer's disease (AD), fibrillar amyloid-beta (Abeta) peptides form senile plaques associated with activated microglia. Recent studies have indicated that microglial Abeta clearance is facilitated by several activators such as transforming growth factor-beta1 (TGF-beta1). The relationship between microglia and Abeta formation and deposition is still unclear. In the present study, high mobility group protein-1 (HMG1) inhibited the microglial uptake of Abeta (1-42) in the presence and absence of TGF-beta1. In addition, HMG1 bound to Abeta (1-42) and stabilized the oligomerization. In AD brains, protein levels of HMG1 were significantly increased in both the cytosolic and particulate fractions, and HMG1 and Abeta were colocalized in senile plaques associated with microglia. These results suggest that HMG1 may regulate the homeostasis of extracellular Abeta (1-42) and Abeta oligomerization.     

Analysis of Escherichia coli anaplerotic metabolism and its regulation mechanisms from the metabolic responses to altered dilution rates and phosphoenolpyruvate carboxykinase knockout

The gluconeogenic phosphoenolpyruvate (PEP) carboxykinase is active in Escherichia coli during its growth on glucose. The present study investigated the influence of growth rates and PEP carboxykinase knockout on the anaplerotic fluxes in E. coli. The intracellular fluxes were determined using the complementary methods of flux ratio analysis and metabolic flux analysis based on [U-(13)C(6)]glucose labeling experiments and 2D nuclear magnetic resonance (NMR) spectroscopy of cellular amino acids and glycerol. Significant activity of PEP carboxykinase was identified in wild-type E. coli, and the ATP dissipation for the futile cycling via this reaction accounted for up to 8.2% of the total energy flux. Flux analysis of pck deletion mutant revealed that abolishment of PEP carboxykinase activity resulted in a remarkably reduced flux through the anaplerotic PEP carboxylase and the activation of the glyoxylate shunt, with 23% of isocitrate found being channeled in the glyoxylate shunt. The changes in intracellular metabolite concentrations and specific enzyme activities associated with different growth rates and pck deletion, were also determined. Combining the measurement data of in vivo fluxes, metabolite concentrations and enzyme activities, the in vivo regulations of PEP carboxykinase flux, PEP carboxylation, and glyoxylate shunt in E. coli are discussed.