5.3 S RNA is a discrete cleavage product from the 5′-terminus of 18 S RNA of rat liver ribosomes

A 5.3 S RNA species observed in urea-gel electrophoretic analysis of the RNA of the small ribosomal subunit of rat liver has been identified from its sequence as the 5′-terminal 133–134 base fragment of 18 S RNA. Presumably it is cleaved by an endogenous endonuclease when the ribosomal subunits are dissociated, because it usually is not observed in 18 S RNA obtained by direct extraction of cells or tissues.     

Flux boundary measurements for the study of tree stability

The shear strength of soil is an important parameter that affects tree stability and can vary depending on the magnitude of the soil’s negative pore-water pressure (matric suction). The surface flux boundary condition affects the matric suction of soil, and therefore is important for tree stability. Field measurements were performed around a roadside tree for 2 years. The instrumentation results show that the matric suction in the soil fluctuated between 0 and 35 kPa. Matric suction changes in the soil could lead to a decrease in the tree resistive moment of up to 80 %.     

Biochemical Characterization of the Chlamydomonas reinhardtii α-1,4 Glucanotransferase Supports a Direct Function in Amylopectin Biosynthesis

Plant α-1,4 glucanotransferases (disproportionating enzymes, or D-enzymes) transfer glucan chains among oligosaccharides with the concomitant release of glucose (Glc). Analysis of Chlamydomonas reinhardtii sta11-1 mutants revealed a correlation between a D-enzyme deficiency and specific alterations in amylopectin structure and starch biosynthesis, thereby suggesting previously unknown biosynthetic functions. This study characterized the biochemical activities of the α-1,4 glucanotransferase that is deficient in sta11-1 mutants. The enzyme exhibited the glucan transfer and Glc production activities that define D-enzymes. D-enzyme also transferred glucans among the outer chains of amylopectin (using the polysaccharide chains as both donor and acceptor) and from malto-oligosaccharides into the outer chains of either amylopectin or glycogen. In contrast to transfer among oligosaccharides, which occurs readily with maltotriose, transfer into polysaccharide required longer donor molecules. All three enzymatic activities, evolution of Glc from oligosaccharides, glucan transfer from oligosaccharides into polysaccharides, and transfer among polysaccharide outer chains, were evident in a single 62-kD band. Absence of all three activities co-segregated with the sta11-1 mutation, which is known to cause abnormal accumulation of oligosaccharides at the expense of starch. To explain these data we propose that D-enzymes function directly in building the amylopectin structure.     

Biochemical studies of membrane bound Plasmodium falciparum mitochondrial L-malate:quinone oxidoreductase,a potential drug target

Plasmodium falciparum is an apicomplexan parasite that causes the most severe malaria in humans. Due to a lack of effective vaccines and emerging of drug resistance parasites, development of drugs with novel mechanisms of action and few side effects are imperative. To this end, ideal drug targets are those essential to parasite viability as well as absent in their mammalian hosts. The mitochondrial electron transport chain (ETC) of P. falciparum is one source of such potential targets because enzymes, such as L-malate:quinone oxidoreductase (PfMQO), in this pathway are absent humans. PfMQO catalyzes the oxidation of L-malate to oxaloacetate and the simultaneous reduction of ubiquinone to ubiquinol. It is a membrane protein, involved in three pathways (ETC, the tricarboxylic acid cycle and the fumarate cycle) and has been shown to be essential for parasite survival, at least, in the intra-erythrocytic asexual stage. These findings indicate that PfMQO would be a valuable drug target for development of antimalarial with novel mechanism of action. Up to this point in time, difficulty in producing active recombinant mitochondrial MQO has hampered biochemical characterization and targeted drug discovery with MQO. Here we report for the first time recombinant PfMQO overexpressed in bacterial membrane and the first biochemical study. Furthermore, about 113 compounds, consisting of ubiquinone binding site inhibitors and antiparasitic agents, were screened resulting in the discovery of ferulenol as a potent PfMQO inhibitor. Finally, ferulenol was shown to inhibit parasite growth and showed strong synergism in combination with atovaquone, a well-described anti-malarial and bc₁ complex inhibitor.     

Role of endothelin-1-dependent up-regulation of leptin in oral mucosal repair.

Leptin, a multifunctional hormone that regulates food intake and energy expenditure, has emerged recently as an important modulator of inflammatory cascades associated with wound healing. In this study, we applied the animal model of buccal mucosal ulcer to investigate the role of endothelin-1 (ET-1) and leptin in soft oral tissue repair. Using groups of rats with experimentally induced buccal mucosal ulcers we show that ulcer onset was characterized by a marked increase in the mucosal level of ET-1 and leptin. However, while the ET-1 level gradually declined with healing, the mucosal level of leptin increased reaching maximum expression on the 4th day of healing. Therapeutic administration of phosphoramidon, an inhibitor of ECE-1 activity, not only led to a 53.2% drop in the ET-1, but also produced a dose-dependent reduction (up to 50.9%) in the mucosal level of leptin and up to 42.3% decline in the rate of ulcer healing. A marked drop (54.2%) in the mucosal level of leptin and the reduction (46.8%) in the rate of ulcer healing was also attained in the presence of ETA receptor antagonist BQ610 administration, but not the ETB receptor antagonist BQ788. Moreover, administration of ERK inhibitor, PD98059 in the presence of ETB receptor antagonist, but not the ETA receptor antagonist, caused the reduction the mucosal leptin level as well as a decline in the rate of ulcer healing. Our findings are the first to implicate the requirement for both ET-1 and leptin in orderly progression of the events of soft oral tissue repair. We also show that ET-1 is a key factor in up-regulation of leptin production associated with oral mucosal ulcer healing , and that the effect of ET-1 on leptin production is a consequence of ETA receptor activation and subsequent signaling through MAPK/ERK.     

Cobalt toxicity in anaerobic granular sludge: influence of chemical speciation

The influence of cobalt speciation on the toxicity of cobalt to methylotrophic methanogenesis in anaerobic granular sludge was investigated. The cobalt speciation was studied with three different media that contained varying concentrations of complexing ligands [carbonates, phosphates and ethylenediaminetetraacetic acid (EDTA)]. Three fractions (nominal added, dissolved and free) of cobalt were determined in the liquid media and were correlated with data from batch toxicity experiments. The average concentration of cobalt that was required for 50% inhibition of methanogenic activity (IC₅₀) for free Co²⁺ in the three sets of measurements was 13 μmol/L with a standard deviation of 22% and a similarity of 72% between the data obtained in the three different media for the range of cobalt concentrations investigated. The standard deviation of the IC₅₀ for the other two fractions was much higher, i.e. 85 and 144% for the added cobalt and dissolved cobalt, respectively, and the similarity was almost 0% for both fractions. Complexation (and precipitation) with EDTA, phosphates and carbonates was shown to decrease the toxicity of cobalt on methylotrophic methanogenesis. The free cobalt concentration is proposed to be the key parameter to correlate with cobalt toxicity. Thus, the toxicity of cobalt to granular sludge can be estimated based on the equilibrium-free cobalt concentration.