Optimizing purebred selection for crossbred performance using QTL with different degrees of dominance

A method was developed to optimize simultaneous selection for a quantitative trait with a known QTL within a male and a female line to maximize crossbred performance from a two-way cross. Strategies to maximize cumulative discounted response in crossbred performance over ten generations were derived by optimizing weights in an index of a QTL and phenotype. Strategies were compared to selection on purebred phenotype. Extra responses were limited for QTL with additive and partial dominance effects, but substantial for QTL with over-dominance, for which optimal QTL selection resulted in differential selection in male and female lines to increase the frequency of heterozygotes and polygenic responses. For over-dominant QTL, maximization of crossbred performance one generation at a time resulted in similar responses as optimization across all generations and simultaneous optimal selection in a male and female line resulted in greater response than optimal selection within a single line without crossbreeding. Results show that strategic use of information on over-dominant QTL can enhance crossbred performance without crossbred testing.     

Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle

Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle.     

A new high performance liquid chromatographic technique for separation and determination of adenylic and nicotinamide nucleotides in Lactobacillus plantarum

A new technique for separation and determination of ATP, ADP, AMP, NAD⁺, NADP⁺, NADH and NADPH in Lacwbacillus plantarum has been developped. It involves acid and basic extraction of nucleotide pool, analysis by reverse-phase high performance liquid chromatography on a 5 m Spherisorb ODS-1 column and UV detection. The method offers advantages in accurate estimations of adenylic and nicotinamide nucleotides concentrations in Lactobacillus plantarum during the growth phase. Such results indicate the potential of this technique as an important research tool.     

A study on the minimum number of loci required for genetic evaluation using a finite locus model

For a finite locus model, Markov chain Monte Carlo (MCMC) methods can be used to estimate the conditional mean of genotypic values given phenotypes, which is also known as the best predictor (BP). When computationally feasible, this type of genetic prediction provides an elegant solution to the problem of genetic evaluation under non-additive inheritance, especially for crossbred data. Successful application of MCMC methods for genetic evaluation using finite locus models depends, among other factors, on the number of loci assumed in the model. The effect of the assumed number of loci on evaluations obtained by BP was investigated using data simulated with about 100 loci. For several small pedigrees, genetic evaluations obtained by best linear prediction (BLP) were compared to genetic evaluations obtained by BP. For BLP evaluation, used here as the standard of comparison, only the first and second moments of the joint distribution of the genotypic and phenotypic values must be known. These moments were calculated from the gene frequencies and genotypic effects used in the simulation model. BP evaluation requires the complete distribution to be known. For each model used for BP evaluation, the gene frequencies and genotypic effects, which completely specify the required distribution, were derived such that the genotypic mean, the additive variance, and the dominance variance were the same as in the simulation model. For lowly heritable traits, evaluations obtained by BP under models with up to three loci closely matched the evaluations obtained by BLP for both purebred and crossbred data. For highly heritable traits, models with up to six loci were needed to match the evaluations obtained by BLP.     

Purification and properties of a recombinant sulfur analog of murine selenium-glutathione peroxidase.

We previously constructed plasmids for synthesis of glutathione-peroxidase (GPx) mutants in an Escherichia coli expression system. In these recombinant proteins either cysteine ([Cys]GPx mutant) or serine ([Ser]GPx mutant) were present in place of the active-site selenocysteine (SeCys) of the natural enzyme. We have now investigated GPx activity of [Cys]GPx and [Ser]GPx mutants. Enzyme assays performed on preparations of these partially purified proteins demonstrated that the [Cys]GPx mutant exhibited a significant GPx activity, unlike the [Ser]GPx mutant. Purification of [Cys]GPx was performed in two steps of ion-exchange chromatography giving a 98% homogenous protein in 50% yield. The purified [Cys]GPx protein was shown to be a symmetrical tetramer by the means of gel-filtration HPLC and SDS/PAGE. Two isoelectric points were found (6.8 and 7.2) which may reflect two different oxidation states of the mutant protein. The GPx activity of the [Cys]GPx mutant was optimal at pH 8.5. The [Cys]GPx mutant had a specific activity approximately 1000-fold smaller than that of the natural enzyme, and was very easily inactivated by hydroperoxides. Inhibition of the activity with iodoacetate determined a pKa of 8.3, presumably that of the active-site cysteine. Unlike that of SeGPx, the GPx activity of [Cys]GPx was only slightly inhibited by mercaptosuccinate. We discuss hypothetical mechanistic constraints of either catalytic cycle, which may explain such results.     

Free and kerogen‐bound biomarkers from late Tonian sedimentary rocks record abundant eukaryotes in mid‐Neoproterozoic marine communities

Lipid biomarker assemblages preserved within the bitumen and kerogen phases of sedimentary rocks from the ca. 780–729 Ma Chuar and Visingsö Groups facilitate paleoenvironmental reconstructions and reveal fundamental aspects of emerging mid‐Neoproterozoic marine communities. The Chuar and Visingsö Groups were deposited offshore of two distinct paleocontinents (Laurentia and Baltica, respectively) during the Tonian Period, and the rock samples used had not undergone excessive metamorphism. The major polycyclic alkane biomarkers detected in the rock bitumens and kerogen hydropyrolysates consist of tricyclic terpanes, hopanes, methylhopanes, and steranes. Major features of the biomarker assemblages include detectable and significant contribution from eukaryotes, encompassing the first robust occurrences of kerogen‐bound regular steranes from Tonian rocks, including 21‐norcholestane, 27‐norcholestane, cholestane, ergostane, and cryostane, along with a novel unidentified C₃₀ sterane series from our least thermally mature Chuar Group samples. Appreciable values for the sterane/hopane (S/H) ratio are found for both the free and kerogen‐bound biomarker pools for both the Chuar Group rocks (S/H between 0.09 and 1.26) and the Visingsö Group samples (S/H between 0.03 and 0.37). The more organic‐rich rock samples generally yield higher S/H ratios than for organic‐lean substrates, which suggests a marine nutrient control on eukaryotic abundance relative to bacteria. A C₂₇ sterane (cholestane) predominance among total C₂₆–C₃₀ steranes is a common feature found for all samples investigated, with lower amounts of C₂₈ steranes (ergostane and crysotane) also present. No traces of known ancient C₃₀ sterane compounds; including 24‐isopropylcholestanes, 24‐n‐propylcholestanes, or 26‐methylstigmastanes, are detectable in any of these pre‐Sturtian rocks. These biomarker characteristics support the view that the Tonian Period was a key interval in the history of life on our planet since it marked the transition from a bacterially dominated marine biosphere to an ocean system which became progressively enriched with eukaryotes. The eukaryotic source organisms likely encompassed photosynthetic primary producers, marking a rise in red algae, and consumers in a revamped trophic structure predating the Sturtian glaciation.     

A focus on fixation

Three fixation issues related to immunostaining are discussed here: 1) Generally, a tissue block is fixed, then embedded and sectioned (pre-fixation). The type of fixative applied, crosslinking or coagulating, has an impact on selecting an epitope retrieval method. Individual antigens have a fixation–retrieval characteristic. 2) A long fixation time, especially with crosslinking fixatives, may compromise the result of immunostaining. This negative effect varies among different antigens and can be partially restored by applying a more sensitive/efficient detection system such as tyramide amplification. 3) Sections cut from a fresh frozen tissue block usually are acetone fixed (post-fixation). This was accepted as the “gold standard” for a long time. Post-fixation, however, may have serious consequences for preservation of small peptides leaking from the cut open cells, whereas this is not the case with pre-fixed intact cells. Consequently, the concept of an acetone post-fixed cryostat tissue section as “gold standard” no longer exists and a more appropriate use of the terms immunohistochemistry and immunocytochemistry therefore seems justified. For many antibodies, it is not known whether a formalin fixed, paraffin embedded tissue specimen is appropriate. Suggestions are made for creating a positive control cell block for testing such antibodies.     

Association between pygmy right whales (Caperea marginata) and areas of high marine productivity off Australia and New Zealand

Abstract

Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata.