Anaerobic degradation of papermill sludge in a two-phase digester containing rumen microorganisms and colonized polyurethane foam

Summary The use of reticulated polyurethane foam as a support material for the immobilization of methanogenic associations and its application to the anaerobic treatment of fine particulate solid wastes was investigated. The colonization of polyurethane support particles in a continuous upflow reactor fed on a mixture of acetate, propionate and butyrate, was both rapid and dense. The combination of rumen microorganisms and colonized support particles in a two-phase digester resulted in an efficient anaerobic decomposition of papermill sludge.     

Phytoplankton monitoring by flow cytometry

The application of flow cytometry to the monitoring of phytoplanktonis demonstrated. A comparison is made with conventional approachesto phytoplankton monitoring: light microscopy for the determinationof species abundance, and chlorophyll a determination and insitu chlorophyll a measurement by fluorescence for the determinationof the biomass. Flow cytometric measurements correlate wellwith these conventional types of measurements, as has been shownby comparing a full year of monitoring data obtained at a fixedmonitoring location 10 km off the Dutch coast. Flow cytometrybridges the gap between labour-intensive, but highly informative,microscopic observations and simple biomass measurements withless information content: via flow cytometry optical data areobtained at high speed for individual particles, which can betranslated into biomass information. On the basis of the flowcytometric measurements, rough discrimination of phytoplanktonspecies groups is possible, particularly for the abundant species.Of crucial importance is careful calibration of the flow cytometer,to ensure quantitative and comparable measurements over a longperiod of time. Calibration and quality assurance aspects arecovered in detail. ³Present address: Akzo Nobel Central Research Laboratories Arnhem,Department CRL, PO Box 9300, NL-6800 SB Arnhem, The Netherlands     

Antigen-specific helper activity in serum of mice primed with sheep red cells. I. Definition of the test system and comparison with other systems

An adoptive transfer system is described to measure serum helper activity in the primary antibody response to sheep red blood cells (SRBC). Mice injected with a high dose of cyclophosphamide and reconstituted with rabbit anti-thymocyte serum-treated spleen cells were used as recipients. Serum obtained 9 hr after ip injection of normal mice with 2 × 10⁸ SRBC (S(SRBC)) injected i.v. in the recipients caused a significant enhancement of the antibody response to 2 × 10⁷ SRBC. The serum helper activity was not generated in thymectomized animals and could be absorbed from S(SRBC) by normal and formalinized SRBC. The SRBC-specific serum helper activity (SSHA) is heat labile (30 min 56 °C) and shows allogeneic restriction. Another test system described in literature for measuring T-cell help in vivo was less suited to measure SSHA in the response to 2 × 10⁷ SRBC. A system using normal mice injected with 10⁵ SRBC for determining specific immune response-enhancing factor (SIREF), demonstrated SIREF activity in S(SRBC). It did, however, not measure SSHA, as absorption of S(SRBC) with formalinized SRBC did not abolish the activity in that system.     

EPR studies of the photodissociation reactions of cytochrome c oxidase-nitric oxide complexes

Three complexes of NO with cytochrome c oxidase are described which are all photodissociable at low temperatures as measured by EPR. The EPR parameters of the cytochrome a²⁺₃-NO complex are the same both in the fully reduced enzyme and in the mixed-valence enzyme. The kinetics of photodissociation of cytochrome a²⁺₃-NO and recombination of NO with cytochrome a²⁺₃ (in the 30–70 K region) revealed no differences in structure between cytochrome a²⁺₃ in the fully reduced and the mixed-valence states. The action spectrum of the photodissociation of cytochrome a²⁺₃-NO as measured by EPR has maxima at 595, 560 and 430 nm, and corresponds to the absorbance spectrum of cytochrome a²⁺₃-NO. Photodissociation of cytochrome a²⁺₃-NO in the mixed-valence enzyme changes the EPR intensity at g 3.03, due to electron transfer from cytochrome a²⁺₃ to cytochrome a³⁺. The extent of electron transfer was found to be temperature dependent. This suggests that a conformational change is coupled to this electron transfer. The complex of NO with oxidized cytochrome c oxidase shows a photodissociation reaction and recombination of NO (in the 20–40 K region) which differ completely from those observed in cytochrome a²⁺₃-NO. The observed recombination occurs at a temperature 15 K lower than that found for the cytochrome a²⁺₃-NO complex. The action spectrum of the oxidized complex shows a novel spectrum with maxima at 640 and below 400 nm; it is assigned to a Cu²⁺_B-NO compound. The triplet species with Δm_s = 2 EPR signals at g 4 and Δm_s = 1 signals at g 2.69 and 1.67, that is observed in partially reduced cytochrome c oxidase treated with azide and NO, can also be photodissociated.     

A comparison of the frequency and type of chromosomal abnormalities in human sperm after different sperm capacitation conditions.

Human sperm karyotypes can be prepared after fusion of human sperm with Golden hamster oocytes. Most laboratories use one of two methods of sperm capacitation: incubation of freshly-ejaculated sperm in Biggers, Whitten, and Whittingham (BWW) medium for 5-7 h at 37 degrees C or sperm storage in (N-tris [hydroxymethyl]methyl-2-aminoethanesulfonic acid; 2-([2-hydroxy-1,1-bis(hydroxymethyl)ethyl]amino)ethanesulfonic acid) (TES)-Tris yolk buffer (TYB) for 1-3 days at 4 degrees C. Since there have been conflicting reports as to whether there is a difference in the frequency of structural chromosomal abnormalities between BWW capacitation and storage in TYB for 2 days, we analyzed a larger number of karyotypes (8974) from 136 donors to determine if there was any difference in the frequency or type of chromosomal abnormalities in sperm treated by fresh BWW capacitation, storage in TYB for 1 day (TYB-1), or storage in TYB for 2 days (TYB-2). There was no difference in the frequency of numerical chromosomal abnormalities or sex ratio in any of the three treatment groups. However, there was a significantly increased frequency of structural chromosomal abnormalities after storage in TYB-1 and TYB-2. There was no difference in the frequency or type of structural chromosomal abnormalities after sperm storage in TYB-1 compared to TYB-2.     

Chlorophyll a fluorescence as a monitor of nanosecond reduction of the photooxidized primary donor P-680 Of photosystem II

1. Changes in the fluorescence yield of aerobic Chlorella vulgaris have been measured in laser flashes of 15 ns, 30 ns and 350 ns half time. The kinetics after the first flash given after a 3 min dark period could be simulated on a computer using the hypothesis that the oxidized acceptor Q and primary donor P+ are fluorescence quenchers, and Q- is a weak quencher, and that the reduction time for P+ is 20-35 ns. 2. The P+ reduction time for at least an appreciable part of the reaction centers was found to be longer after the second and subsequent flashes. In the first 5 flashes an oscillation was observed. Under steady state conditions, with a pulse separation of 3 s, a reduction time for P+ of about 400 ns for all reaction centers gave the best correspondence between computed and experimental fluorescence kinetics.     

The effect of genomic information on optimal contribution selection in livestock breeding programs

Background

Long-term benefits in animal breeding programs require that increases in genetic merit be balanced with the need to maintain diversity (lost due to inbreeding). This can be achieved by using optimal contribution selection. The availability of high-density DNA marker information enables the incorporation of genomic data into optimal contribution selection but this raises the question about how this information affects the balance between genetic merit and diversity.

Methods

The effect of using genomic information in optimal contribution selection was examined based on simulated and real data on dairy bulls. We compared the genetic merit of selected animals at various levels of co-ancestry restrictions when using estimated breeding values based on parent average, genomic or progeny test information. Furthermore, we estimated the proportion of variation in estimated breeding values that is due to within-family differences.

Results

Optimal selection on genomic estimated breeding values increased genetic gain. Genetic merit was further increased using genomic rather than pedigree-based measures of co-ancestry under an inbreeding restriction policy. Using genomic instead of pedigree relationships to restrict inbreeding had a significant effect only when the population consisted of many large full-sib families; with a half-sib family structure, no difference was observed. In real data from dairy bulls, optimal contribution selection based on genomic estimated breeding values allowed for additional improvements in genetic merit at low to moderate inbreeding levels. Genomic estimated breeding values were more accurate and showed more within-family variation than parent average breeding values; for genomic estimated breeding values, 30 to 40% of the variation was due to within-family differences. Finally, there was no difference between constraining inbreeding via pedigree or genomic relationships in the real data.

Conclusions

The use of genomic estimated breeding values increased genetic gain in optimal contribution selection. Genomic estimated breeding values were more accurate and showed more within-family variation, which led to higher genetic gains for the same restriction on inbreeding. Using genomic relationships to restrict inbreeding provided no additional gain, except in the case of very large full-sib families.