Distribution and some properties of NADPH and NADH oxidase in parenchymal and nonparenchymal liver cells

The activities of NADPH and NADH oxidase were determined in homogenates of isolated pure parenchymal and nonparenchymal rat liver cells at neutral (7.4) and acid (5.5) pH. The NADPH oxidase at pH 7.4 is about equally active in parenchymal and nonparenchymal cells and in both cell types is rather insensitive to KCN (1 mm) inhibition. By lowering the pH to 5.5, the NADPH oxidase of the nonparenchymal cells is stimulated (twofold) while the activity in parenchymal cells is decreased. The NADH consumption at neutral pH in parenchymal cells is 75% inhibited by KCN, while this activity in nonparenchymal cells is relatively insensitive to KCN. The NADH oxidase in both parenchymal and nonparenchymal liver cells is less active when the pH is lowered from 7.4 to 5.5. The distribution of NAD(P)H oxidases between parenchymal and nonparenchymal liver cells and the effect of pH on their activities suggest that in the nonparenchymal cells, the NADPH oxidase might play a role in the synthesis of H₂O₂ within the phagocytic vacuole. A scheme is proposed which describes the metabolic events involved in H₂O₂ formation and catabolism of endo(phago)cytosed particles in nonparenchymal liver cells.     

Influence of Diet on Experimental Swine Dysentery. 1. Effects of A Vitamin E and Selenium Deficient Diet Supplemented with 6.8 % Cod Liver Oil

Sixteen growing pigs were fed a vitamin E and selenium deficient diet; half of the animals (Group 2) were given a daily supply of vitamin E and selenium. After having been fed these diets for 53 days, the pigs were infected orally with minced colonic material from cases with typical swine dysentery. This exposure resulted in outbreaks of swine dysentery in both groups. The incubation times were, however, distinctly shorter and the clinical symptoms much more pronounced in Group 1 than in Group 2. The patho^morphological lesions in the colon also differed between the 2 groups. In the pigs of Group 1 evident pseudomembraneous lesions were observed in the spiral colon. In Group 2, the colonic alterations consisted predominantly of a catarrhal enteritis; pseudomembranes occurred in a minor part of colon in only 4 pigs. Both the clinical and the chemical observations and the pathological findings indicated a much better vitamin E and selenium balance in the pigs of Group 2. It is concluded that the treatment with vitamin E and selenium in Group 2 greatly increased resistance to swine dysentery.     

Multiple phosphorylation of rat liver 3-hydroxy 3-methylglutaryl coenzyme a reductase

Rat liver homogeneous ³²P-labeled hydroxy methylglutaryl coenzyme A reductase, was treated independently with CNBr and trypsin and the resulting [³²P]phosphopeptides were analyzed by disc gel electrophoresis. CNBr treatment produced only one ³²P-fragment of Mr 18,000. The time course of trypsin hydrolysis initially showed the appearance of some phosphopeptides, which were lately converted in two phosphopeptides of low Mr. These results provide direct support for the concept that hydroxy methyl glutaryl coenzyme A reductase kinase solubilized from microsomes phosphorylates only two sites or set of sites in the reductase molecule.     

Rapid high-performance liquid chromatographic assay for total homocysteine levels in human serum

A rapid, isocratic high-performance liquid chromatographic (HPLC) method is described for the determination of total homocysteine levels in human serum. Prior to reversed-phase HPLC analysis, the serum thiols were derivatized with SBD-F (ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate), a thiol-specific fluorogenic probe which is commercially available. Retention of SBD-homocysteine was sensitive to pH, and a mobile phase pH of 2.1 ensured baseline separation of serum thiols within 6 min. The method is simple, sensitive, reproducible (between-run coefficient of variation of 6.6%) and very suitable for routine determination of serum homocysteine levels in a clinical pathology laboratory.     

A small protein in model membranes: a time-resolved fluorescence and ESR study on the interaction of M13 coat protein with lipid bilayers

Model membranes with unsaturated lipid chains containing various amounts of M13 coat protein in the -helical form were studied using time-resolved fluorescence and ESR spectroscopy. The lipid-to-protein (L/P) ratios used were > 12 to avoid protein-protein contacts and irreversible aggregation leading to -polymeric coat protein. In the ESR spectra of the 12-SASL probe in dioleoyl phosphatidylcholine (DOPC) bilayers no second protein induced component is observed upon incorporation of M13 coat protein. However, strong effects are detected on the ESR lineshapes upon changing the protein concentration. The ESR lineshapes are simulated by assuming a fixed ratio between the parallel (D) and perpendicular (D) diffusion coefficients of 4, and an order parameter equal to zero. It is found that increasing the protein concentration from L/P to L/P 15 results in a decrease of the rotational diffusion coefficient D from 3.4 × 10⁷ to 1.9 × 10⁷ s^–1. In the time-resolved fluorescence experiments with DPH-propionic acid as a probe, it is observed that increasing the M13 coat protein concentration causes an increase of the two fluorescent lifetimes, indicating an increase in bilayer order. Analysis of the time-resolved fluorescence anisotropy decay allows one to quantitatively determine the order parameters P₂ and P₄, and the rotational diffusion coefficient D of the fluorescent probe. The order parameters P₂ and P₄ increase from 0.34 to 0.55 and from 0.59 to 0.77, respectively, upon adding M13 coat protein to DOPC bilayers with an L/P ratio of 35. The rotational diffusion coefficient D of the DPH-propionic acid probe decreases on incorporating M13 coat protein, in accordance with the ESR results. It is concluded that M13 coat protein in the -monomeric state is not able to produce a long living lipid boundary shell and consequently an immobilization of the lipids. An overall effect on the lipids is induced, resulting in a reduction in the dynamics and an increase in average lipid order. The hydrophobic region of M13 coat protein is proposed to perfectly match the lipid bilayer, resulting in a relatively small distortion of the bilayer structure of the lipid system.     

On predatory tendencies in the feeding ecology of the fairy shrimp Streptocephalus proboscideus (Frauenfeld, 1873) (Crustacea: Anostraca)

The feeding habits of the filter-feeding fairy shrimp Streptocephalus proboscideus are documented experimentally by offering them ciliates, Volvox, rotifers, nematodes and small crustaceans as prey. Escape capabilities (e.g. swimming speed) rather than size or shape were found to determine these animals' vulnerability to predation by the fairy shrimp. Ingestion rates for Volvox increased hyperbolically with size and, at the high temperatures in which they live, fairy shrimps may daily remove the equivalent of their body weight from the environment.     

The accuracy of population density estimates of a horizontally distributed zooplankton community in Dutch fish ponds

To elucidate the effect of the horizontal distribution of different zooplankton populations on the accuracy of population density estimates in a fish pond, 40 samples were taken according to a rectangular grid which divided the pond into 5 longitudinal rows and 10 transversal columns. The zooplankton consisted of 55% copepods (mainly Acanthocyclops viridis), 43% cladocerans (mainly Daphnia longispina and Bosmina longirostris) and 2% Rotatoria. The index of patchiness was mostly higher than 1, revealing a strongly clumped distribution. B. longirostris and D. longispina aggregated in the centre of the pond, exhibiting a shore avoiding behaviour. Chydoridae and Ceriodaphnia quadrangula were concentrated in the littoral zone. Besides this habitat related dispersion, a more passive wind induced distribution was detected for most taxonomic groups. Copepod nauplii were concentrated at the leeward side of the pond while elder copepod stages of A. viridis were found in higher densities at the windward end. Based on the calculated coefficients of variation, a table of the accuracies of the density estimates in relation to the number of samples was presented. For more detailed studies on a particular species population, about 25 samples (column samples of 10 L each) are needed to obtain an accuracy varying between 10 an 20%, depending upon the taxonomic group. A slightly higher precision can be obtained, however at a strongly increasing effort. For the practice of fish farming, two to five sample stations should suffice to estimate the total zooplankton abundance with a 30 to 10% accuracy respectively.