Interactions between plasma proteins and pulmonary surfactant: pulsating bubble studies

The influence of human albumin, alpha-globulin, and fibrinogen on the actions of porcine pulmonary surfactant in a pulsating bubble surfactometer has been investigated. All three proteins detracted from the ability of the surfactant to adsorb to the air-water interface. The proteins also reduced the ability of surfactant to lower the opening pressures of bubbles cycling between different sizes in suspensions of surfactant. This was equivalent to restricting the ability of the surfactant to achieve low surface tension during compression of the surface. Of the three proteins, globulin competed most effectively with surfactant during the adsorption process, and albumin competed the least effectively. The proteins also may have interfered with the processes of surface refinement, which usually yields a monolayer enriched enough in dipalmitoyl phosphatidylcholine to achieve very low surface tension (very low opening pressures in the bubbles). Of the three proteins tested, albumin was least deleterious to surface refining whereas globulin and fibrinogen appeared to be about equally detrimental to the process.     

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains. The enzyme in strain BK5 is shown to be both functionally and structurally related to the nitrate reductase of Paracoccus denitrificans and Escherichia coli.Abbreviation TMAO trimethylamine-N-oxide     

Specificity of binding to four-way junctions in DNA by bacteriophage T7 endonuclease I.

T7 endonuclease I binds specifically to four-way junctions in duplex DNA and promotes their resolution into linear duplexes. Under conditions in which the nuclease activity is blocked by the absence of divalent cations, the enzyme forms a distinct protein-DNA complex with the junction, as detected by gel retardation and filter binding assays. The formation of this complex is structure-specific and contrasts with the short-lived binding complexes formed on linear duplex DNA. The binding complex between T7 endonuclease I and a synthetic Holliday junction analog has been probed with hydroxyl radicals. The results indicate that the nuclease binds all four strands about the junction point.     

Resistance to human serum of gonococci in urethral exudates is reduced by neuraminidase

Gonococci examined directly from urethral exudates are resistant to killing by human serum, but most strains become susceptible on subculture. Previous work with gonococci grown in vitro indicates that resistance in vivo is due to sialylation of gonococcal lipopolysaccharide (LPS) by a host factor, cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA) or a related compound present in urogenital secretions and blood cells including phagocytes, which exude during inflammation. This sialylation inhibits the reaction between bactericidal IgM in serum and its target LPS sites. Here, we confirm the indication by using gonococci grown in vivo. Crucial to the above conclusions was the marked reduction of CMP-NANA-conferred serum resistance when gonococci were treated with neuraminidase to remove sialyl groups from their LPS. We now show that the serum resistance of gonococci in urethral exudates was reduced by treatment with neuraminidase from more than 95% (calculated in relation to controls incubated with heated serum) to 2-11% according to sample and incubation time. Subculture of the gonococci also reduced resistance to 9-11% but resistance was restored to more than 95% by incubation with CMP-NANA. This work is the culmination of an investigation that underlines the need to identify specific host factors and the virulence determinants they induce in vivo in future studies of pathogenicity.     

Growth and production of Euphausia lucens in the southern Benguela Current

The growth rate of a population of Euphausia lucens from thewest coast of South Africa was estimated from laboratory studiesand from monthly size-frequency distributions of samples collectedover a 1-year period. Laboratory studies indicated that growthrates ranged from 0.131 (larvae) to 0.047 mm day^–1 (juveniles),while size-frequency distributions suggested a growth rate of{small tilde}0.026 mm day^–1 for the adults. The mean annualbiomass from the inshore, intermediate and offshore regionsranged from 9.75 to 47.29 mg dry wt m^–3 with the highestbiomass being found in the inshore region. Calyptopis larvaewere present for most months of the year, indicating continuousrecrwtment. The relative contribution of flesh, moults and eggsto the total annual production was estimated separately forall three regions. Production due to growth (P_g) was estimatedto be 92.71–185.60 mg dry wt m^–3 year^–1, whileexuviai production (P_e) varied between 60.01 and 281.38 mg drywt m year Production of eggs (P_r) was estimated to range from5.07 to 12.39 mg dry wt m year the lowest value being obtainedin the inshore region. Moult production represented {small tilde}6times the mean biomass in each region, while the P/B ratio forflesh production varied from 3.92 to 8.91, the highest ratiobeing obtained in the offshore region. Total P/B ratios rangedfrom 10.14 to 16.01.