Flow Visualization and Performance Measurements of a Flagellar Propeller

A new type of propeller that is optimized for low Reynolds numbers is required to propel a small object in a medium where the flow is dominated by viscous rather than inertial forces.A propeller in the shape of a bacterial flagellum seems an appropriate choice for driving a small object.Accordingly,in this study,we visualized the velocity field induced by a spring-like propeller inspired by the Escherichia coli flagellum,using a macroscopic model and applying stereoscopic particle image velocimetry.We also experimentally evaluated the effect of pitch and rotational speed on the performance of this flagellar propeller.Silicone oil,which has a kinematic viscosity 100,000 times that of water,was used as the working fluid to generate a low Reynolds number for the macroscopic model.Thrust,torque,and velocity were measured as functions of pitch and rotational speed,and the efficiency of the propeller was calculated from the measured results.We found that the flagellar propeller reached a maximum efficiency when the pitch angle was approximately 53°.Compared to pitch,rotational speed had a relatively small effect on the efficiency,and the pitch altered the flow pattern behind the rotating propeller.     

Brain catecholamine alterations accompanying development of anorexia in rats bearing the Walker 256 carcinoma

In the present study, the relationship between central catecholamine levels and the anorexia induced by Walker 256 carcinoma was investigated. Results indicate that the anorexia is not due to depletion of central catecholamines. Tumor bearing rats sacrificed at night, when spontaneous food intake is selectively depressed, showed increased norepinephrine levels in the hypothalamus, cortex and hippocampus and increased dopamine levels in the striatum, midbrain, and cortex. Increased nighttime hypothalamic norepinephrine levels were positively correlated with the magnitude of spontaneous food intake in tumor rats.     

Developmental changes of sepiapterin synthase activity associated with a variegated purple gene in Drosophila melanogaster

A variegated position effect on the autonomous gene, purple, has been studied enzymologically in Drosophila melanogaster. Sepiapterin synthase, the enzyme system associated with pr ⁺, was examined for activity in different developmental stages of the fly. The results indicate that T(Y:2) pr ^c5, cn/pr^c4 cn flies (flies in which pr ⁺ has been translocated and which exhibit variegation) have a reduced amount of enzyme activity as compared with both Oregon-R and pr ¹ flies. This reduction in activity was not found in larval stages, which suggests that the inactivation process probably occurs in late larval or early pupal stages. The phenotype of the variegated adult has white eyes with red-colored spots and patches where drosopterins occur. The phenotype of the fly carrying the translocation is modified by the presence of additional Y chromosomes. This extends the observation from other systems that extra heterochromatin acts to suppress the variegated position effect. The advantages of studying the variegation by measuring enzyme activity, as well as the phenotypic expression, are several; for example, the developmental time at which variegation occurs may be estimated even though drosopterin synthesis is not occurring.The Oak Ridge National Laboratory is operated by Union Carbide Corporation for the Department of Energy under Contract No. W-7405-eng-26.     

Association between the −159C/T CD14 gene polymorphism and tuberculosis in a Korean population

The aim of the present study was to confirm the association between the CD14 −159C/T polymorphism and tuberculosis in the Korean population and to elucidate the functional basis for this putative association. CD14 −159C/T genotypes were determined by PCR – restriction fragment length polymorphism analysis in 274 tuberculosis patients and 422 healthy controls. Recombinant CD14 promoter–luciferase reporter constructs, including the −159T or −159C allele, were transfected into K562 and BEAS-2B cells, and luciferase activities were measured and compared. Levels of serum sCD14 and interferon-γ secreted by peripheral blood mononuclear cells (PBMCs) were measured using enzyme-linked immunosorbent assay.The frequency of −159TT genotypes was higher in tuberculosis patients than in healthy controls. The promoter activity of the −159T allele was higher than that of the −159C allele. Serum sCD14 levels were higher among tuberculosis patients with −159TT genotypes than among those with −159CC genotypes and interferon-γ release by PBMCs was decreased in subjects with −159TT genotypes. In conclusion, the −159TT CD14 genotypes were associated with tuberculosis development in Koreans. This association might be a result of the higher promoter activity of the −159T allele, the higher level of sCD14, and the decreased interferon-γ secretion in subjects with −159TT genotypes.