RBMX is a novel hepatic transcriptional regulator of SREBP-1c gene response to high-fructose diet

In rodents a high-fructose diet induces metabolic derangements similar to those in metabolic syndrome. Previously we suggested that in mouse liver an unidentified nuclear protein binding to the sterol regulatory element (SRE)-binding protein-1c (SREBP-1c) promoter region plays a key role for the response to high-fructose diet. Here, using MALDI-TOF MASS technique, we identified an X-chromosome-linked RNA binding motif protein (RBMX) as a new candidate molecule. In electrophoretic mobility shift assay, anti-RBMX antibody displaced the bands induced by fructose-feeding. Overexpression or suppression of RBMX on rat hepatoma cells regulated the SREBP-1c promoter activity. RBMX may control SREBP-1c expression in mouse liver in response to high-fructose diet.     

Plagiochilines C,D, E and F,four novel secoaromadendrane-type sesquiterpene hemiacetals from Plagiochila asplenioides and Plagiochila semidecurrens

Four novel secoaromadendrane-type sesquiterpene hemiacetals, plagiochilines C, D, E and F, together with the previously known (?)-bicyclogermacrene, have been isolated from the liverwort, Plagiochila asplenioides and their structures have been spectroscopically elucidated. From Plagiochila semidecurrens plagiochilines A and C have been obtained along with (?)-bicyclogermacrene and its related sesquiterpene hydrocarbons.     

Interaction between filamentous actin and lipid bilayer causes the increase of syringomycin E channel-forming activity

The effect of filamentous (F) actin on the channel-forming activity of syringomycin E (SRE) in negatively charged and uncharged bilayer lipid membranes (BLM) was studied. F-actin did not affect the membrane conductance in the absence of SRE. No changes in SRE-induced membrane conductance were observed when the above agents were added to the same side of BLM. However, the opposite side addition of F-actin and SRE provokes a multiple increase in membrane conductance. The similar voltage dependence of membrane conductance, equal values of single channel conductance and the effective gating charge of the channels upon F-actin action suggests that the actin-dependent increase in BLM conductance may result from an increase in the number of opened SRE-channels. BLM conductance kinetics depends on the sequence of SRE and F-actin addition, suggesting that actin-dependent rise of conductance may be induced by BLM structural changes that follow F-actin adsorption. F-actin exerted similar effect on membrane conductance of both negatively charged and uncharged bilayers, as well as on conductance of BLM with high ionic strength bathing solution, suggesting the major role for hydrophobic interactions in F-actin adsorption on lipid bilayer.     

Secular trends of sizes at birth in Japanese healthy infants born between 1962 and 1988

Body sizes at birth are important clinical indicators widely used for evaluation of prenatal growth. Japan had significant socioeconomic improvement around the 1960s, and these environmental changes may influence physiologically prenatal growth. Furthermore, in Japan, measurements of size at birth for birth certificates are weight and height. Thus, we can refer to annual data on weight and height, but not on head and chest circumference at birth. In this study we measured the weight, height, and head and chest circumference at birth among 6,563 Japanese singleton healthy infants, annually in 1962 and 1988, and examined secular trends of these anthropometric measurements. The boys consistently exceeded the girls in all four variables. Birth weight and height increased significantly from the 1960s to '70s, but did not differ between the '70s and '80s in both boys and girls. Secular trends of head and chest circumference were different from them. In both boys and girls, head and chest circumference increased significantly from the '60s to the '70s, but decreased significantly from the '70s to the '80s. No difference of head circumference during the '60s and '80s was found, but the difference of chest circumference was found. Size at birth was likely to increase from the '60s to '70s in Japan. These findings suggest that the environmental changes such as socioeconomic improvements influence the prenatal growth.     

Kinetics of opening and closure of syringomycin E channels formed in lipid bilayers

A cyclic lipodepsipeptide, syringomycin E (SME), incorporated into planar lipid membranes forms two types of channels ("small" and "large") different in their conductance by approximately a factor of six (Biophys. J. 74:2918-2925 (1998)). We analysed the dynamics of the SME-induced transmembrane current under voltage-clamp conditions to clarify the mechanisms of formation of these channels. The voltage-dependent opening/closure of SME channels in lipid bilayers are interpreted in terms of transitions between three types of clusters including 6-7 SME molecules and some lipid molecules. The initial cluster, the precursor of the other two, was in equilibrium with SME monomer molecules at the membrane surface. The other two types of clusters (State 1 and State 2) were formed from the precursor and also during their interconversions (the consecutive-parallel mechanism of transitions). State 1 was a non-conducting state in equilibrium with small channels, which partially determined the ionic conductance of lipid bilayers modified by SME. State 2 corresponded to large SME channels, major contributors to the conductance of a bilayer. The results of the theoretical analysis based on the chemical kinetics concepts were consistent with experimental observations. Such properties of the SME-induced channels as cluster organisation, voltage dependence and the existence of a non-conducting state are all features shared by many ion channels in biological membranes. This makes it possible to use SME channels as a model to study naturally occurring ion channels.     

Genotoxic activation of benzophenone and its two metabolites by human cytochrome P450s in SOS/umu assay

The genotoxic potential of benzophenone and its metabolically related compounds, benzhydrol and p-benzoylphenol, was investigated using human cytochrome P450 (P450) enzymes. Benzophenone and its two metabolites (0.1-1mM) showed a suppression of bacterial growth without any P450 system, but no induction of umu gene expression was observed in Salmonella typhimurium TA1535/pSK1002. Human liver microsomes induced the bacterial cytotoxicity of these compounds without any umu gene expression. On the other hand, with the addition of Escherichia coli membranes expressing recombinant human P450 2A6 and NADPH-cytochrome P450 reductase (NPR), benzophenone showed umu gene expression (64 umu units/min/nmol) P450 2A6). Moderate activation of benzophenone by P450 1A1/NPR membranes, 1A2/NPR membranes, or 1B1/NPR membranes was also observed. Activation of benzhydrol and p-benzoylphenol by the P450/NPR system was similar to that of benzophenone. These results suggest that benzophenone and its metabolically related benzhydrol and p-benzoylphenol can be bioactivated by P450 2A6 and P450 family 1 enzymes. Until now, benzophenone has been investigated mainly in terms of estrogenic activity and cytotoxicity, however, the genotoxic activation of benzophenone by human cytochrome P450s should be examined in terms of the risks to humans.     

Interaction between leukemic-cell VLA-4 and stromal fibronectin is a decisive factor for minimal residual disease of acute myelogenous leukemia

Bone-marrow minimal residual disease (MRD) causes relapse after chemotherapy in patients with acute myelogenous leukemia (AML). We postulate that the drug resistance is induced by the attachment of very late antigen (VLA)-4 on leukemic cells to fibronectin on bone-marrow stromal cells. We found that VLA-4-positive cells acquired resistance to anoikis (loss of anchorage) or drug-induced apoptosis through the phosphatidylinositol-3-kinase (PI-3K)/AKT/Bcl-2 signaling pathway, which is activated by the interaction of VLA-4 and fibronectin. This resistance was negated by VLA-4-specific antibodies. In a mouse model of MRD, we achieved a 100% survival rate by combining VLA-4-specific antibodies and cytosine arabinoside (AraC), whereas AraC alone prolonged survival only slightly. In addition, overall survival at 5 years was 100% for 10 VLA-4-negative patients and 44.4% for 15 VLA-4-positive patients. Thus, the interaction between VLA-4 on leukemic cells and fibronectin on stromal cells may be crucial in bone marrow MRD and AML prognosis.     

Differential interaction of CrkII adaptor protein with platelet-derived growth factor alpha- and beta-receptors is determined by its internal tyrosine phosphorylation

CrkII is an intracellular adaptor protein involved in signal transduction by various growth factors. Activation of PDGF alpha-receptor resulted in its association with CrkII in vivo. In contrast, binding of CrkII to the PDGF beta-receptor was negligible, despite its becoming prominently phosphorylated. Bacterially expressed GST-CrkII SH2 domain specifically bound to Tyr-762 and Tyr-771 in the activated PDGF alpha- and beta- receptors, respectively. GST fusion protein of full-length CrkII also bound to the activated PDGF beta-receptor. However, tyrosine phosphorylation of GST-CrkII diminished its binding to the beta-receptor. CrkI, a truncated version of CrkII lacking the phosphorylatable tyrosine residue, could bind to both PDGF alpha- and beta-receptors in vivo. In conclusion, tyrosine phosphorylation of CrkII negatively affects its binding to the PDGF receptors. The differential binding of CrkII to the PDGF alpha- and beta- receptors may be a rationale for functional diversity between the two receptors.     

Evaluation of kinetic parameters of biochemical reaction in three-phase fluidized bed biofilm reactor for wastewater treatment

This study evaluates the kinetic parameters of biochemical reaction in three-phase fluidized bed biofilm reactor from the steady state values of the response of the system to step changes in inlet concentration. It was observed from the outlet biological oxygen demand (BOD(5)) plot of the response of the system that as the inlet BOD(5) was increased, the outlet BOD(5) also increased, reached a peak value and then decreased until it leveled to a new steady state value corresponding to the new inlet concentration level. The increase in BOD(5) was attributed to the accumulation of substrate within the reactor as well as the decrease in biofilm substrate consumption rate as the microorganisms adjusted to the new environment. Using the substrate balance at steady state and assuming Monod kinetics, an equation relating the substrate consumption rate to substrate concentration (BOD(5)) and total biofilm surface area had been established. Monod kinetic parameters were found to be K=2.20g/m(2)/day, K(m)=17.41g/m(3) and K/K(m)=0.13m/day. The ratio K/K(m) can be taken as the indicator for biofilm substrate degradation effectiveness at low substrate concentrations.     

HS1 interacts with Lyn and is critical for erythropoietin-induced differentiation of erythroid cells

Erythroid cells terminally differentiate in response to erythropoietin binding its cognate receptor. Previously we have shown that the tyrosine kinase Lyn associates with the erythropoietin receptor and is essential for hemoglobin synthesis in three erythroleukemic cell lines. To understand Lyn signaling events in erythroid cells, the yeast two-hybrid system was used to analyze interactions with other proteins. Here we show that the hemopoietic-specific protein HS1 interacted directly with the SH3 domain of Lyn, via its proline-rich region. A truncated HS1, bearing the Lyn-binding domain, was introduced into J2E erythroleukemic cells to determine the impact upon responsiveness to erythropoietin. Truncated HS1 had a striking effect on the phenotype of the J2E line-the cells were smaller, more basophilic than the parental proerythoblastoid cells and had fewer surface erythropoietin receptors. Moreover, basal and erythropoietin-induced proliferation and differentiation were markedly suppressed. The inability of cells containing the truncated HS1 to differentiate may be a consequence of markedly reduced levels of Lyn and GATA-1. In addition, erythropoietin stimulation of these cells resulted in rapid, endosome-mediated degradation of endogenous HS1. The truncated HS1 also suppressed the development of erythroid colonies from fetal liver cells. These data show that disrupting HS1 has profoundly influenced the ability of erythroid cells to terminally differentiate.