Effect of bilirubin and its photodegradation products on the respiration of mitochondria isolated from rat liver

In 0.05--0.1 mmol.l-1 concentration, bilirubin inhibits ADP-activated respiration of isolated liver mitochondria; it has no effect on respiration in the absence of ADP. Bilirubin-induced inhibition of respiration is not abolished by serum albumin, but bilirubin bound to serum albumin and the photodegradation products of bilirubin have no inhibitory effect.     

The interaction of complement components with Aeromonas species

The interaction of seven serum-sensitive Aeromonas strains with the complement system was investigated using a 2-h quantitative assay. Of the strains tested, four isolates activated both the alternative and classical pathways, two activated only the alternative pathway, and one strain was sensitive to the bactericidal action of complement through the classical pathway only. Two of the four Aeromonas caviae strains were such efficient activators of the complement system that when challenged with human sera deficient in normal concentrations of C3 and C4, they were still subject to complement-mediated bacterial lysis. This phenomenon, in conjunction with previous studies on complement activation by Aeromonas spp., may help account for the decreased incidence observed of systemic disease caused by Aeromonas caviae.     

Translation of poly(U) on ribosomes from Streptomyces aureofaciens

Slowly cooled cells of Streptomyces aureofaciens contained mainly tight-couple ribosomes. Maximum rate of polyphenylalanine synthesis on ribosomes of S. aureofaciens was observed at 40°C, while cultures grew optimally at 28°C. Ribosomes of S. aureofaciens differed from those of E. coli in the amount of poly(U) required for maximum synthetic activity. The polyphenylalanine-synthesizing activity of E. coli ribosomes was about 3-times higher than that of S. aureofaciens ribosomes. The addition of protein S1 of E. coli or the homologous protein from S. aureofaciens had no stimulatory effect on the translation of poly(U). In order to localize alteration(s) of S. aureofaciens ribosomes in the elongation step of polypeptide synthesis we developed an in vitro system derived from purified elongation factors and ribosomal subunits. The enzymatic binding of Phe-tRNA to ribosomes of S. aureofaciens was significantly lower than the binding to ribosomes of E. coli. This alteration was mainly connected with the function of S. aureofaciens 50 S subunits. These subunits were not deficient in their ability to associate with 30 S subunits or with protein SL5 which is homologous to L7/L12 of E. coli.     

Induction of human B cell differentiation by Fc region activators. II. Stimulation of IL-6 production

Fc region fragments derived from the enzymatic cleavage of human IgG have been shown to induce human peripheral blood-derived B cells to differentiate into Ig secreting cells (ISC). The synthetic peptide p23, corresponding to residues 335 to 357 in the Fc region of human IgG1, represents a region of the molecule responsible for stimulation of ISC formation. Fc region-induced ISC formation requires at least two signals; one supplied by Fc region activators and one supplied by a T cell-derived factor(s). In this report we show that the coculture of human PBMC with pFc' or p23, results in the release of factor(s) that resemble IL-6 in its pattern of biologic activity. This conclusion is based on the observations that supernatants from Fc region-stimulated PBMC cultures contained increased levels of elements that scored as positive in two assays for IL-6: the B9.9 hybridoma growth and the CESS cell differentiation assays. Moreover, RNA from Fc region-stimulation PBMC contained increased levels of IL-6 cDNA-hybridizable elements. Finally, it was observed that rabbit anti-IL-6 inhibited the ability of supernatants derived from Fc region-stimulated PBMC cultures to induce B9.9 cell proliferation as well as p23-induced ISC formation in intact PBMC cultures. Fc region fragments induce both monocytes and T cells to produce IL-6. Taken together, these results indicate that IL-6 is produced in Fc region-stimulated PBMC cultures and is involved in B cell activation by these activators.     

The Thermostable Direct Hemolysin Gene (tdh) of Vibrio hollisae Is Dissimilar in Prevalence to and Phylogenetically Distant from the tdh Genes of Other Vibrios: Implications in the Horizontal Transfer of the tdh Gene

Vibrio hollisae strains isolated recently from patients in various locations were examined for the presence of the thermostable direct hemolysin gene (tdh) using nucleic acid hybridization and polymerase chain reaction assays. The results were consistent with the previous finding that all strains of V. hollisae carry the tdh gene. In contrast, the tdh gene has been detected in a minority of strains for other Vibrio species (V. parahaemolyticus, V. cholerae non-O1, and V. mimicus). Detailed phylogenetic analysis showed that the tdh genes of the non-V. hollisae species were very closely related to each other and that the tdh gene of V. hollisae was distantly related to the tdh genes of the non-V. hollisae species. These results and the proposed insertion sequence-mediated tdh transfer mechanism suggest that the tdh gene may have been maintained stably in V. hollisae and that the tdh genes of the non-V. hollisae species may have been involved in recent horizontal transfer.     

Effect of hydrogen peroxide on sugar transport inSchizosaccharomyces pombe. Absence of membrane lipid peroxidation

Stationary unaerated cells ofS. pombe containing endogenous substrates but not energized by any exogenous ones take up 2-deoxy-d-glucose, 6-deoxy-d-glucose,d-xylose andd-arabinose actively over diffusion equilibrium. The active uptake is inhibited by 20–100 mmol/L H₂O₂ which causes an increase inK _T but has no effect onJ _max. This “competitive inhibition” indicates that H₂O₂ affects directly the sugar binding sites of the transporters. The ATP-binding site of the plasma membrane H⁺-ATPase is also affected by 100 mmol/L H₂O₂; theK _T decreases 7-fold,J _max about 2.5-fold. These effects are not likely to be mediated by membrane lipid peroxidation which appears to be lacking inS. pombe, and this lack may be one of the reasons for the high resistance of this yeast to H₂O₂. Because of thisS. pombe represents a suitable system for studying direct effects of oxidants on membrane proteins.     

Responses of epidermal diffusive conductance to simultaneous changes in two factors: Determination of interactions

Responses of the epidermal diffusive conductance (gep) to irradiance (I) during ontogeny of primary bean leaves or during their wilting were followed. Effects ofI, leaf age and leaf water potential (Ψw) as well as interactive effects (I × leaf age andI × Ψw) ongep were statistically significant.     

Removal of diacetyl from beer by adsorbants and diacetyl reductase

Removal of diacetyl from beer with adsorbants like cellulose, silica gel, activated charcoal, calcium phosphate gel, anion- and cation-exchange resins, and silicylic acid black soil bed (SABSB) was attempted in comparison with the enzyme diacetyl reductase (EC 1.1.1.5). Diacetyl could be removed from beer by the adsorbants but they had undesirable effect on the beer quality such as color, pH, and alcohol levels. These adverse effects were not observed with the use of diacetyl reductase. The results favor the enzymatic removal of diacetyl from beer as a superior approach.