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.     

Construction of linear GlcNAcβ1-6Galβ1-OR type oligosaccharides by partial cleavage of GlcNAcβ1-3(GlcNAcβ1-6)Galβ1-OR sequences with jack bean β-N-acetylhexosaminidase

Radiolabelled GlcNAc beta 1-3(GlcNAc beta 1-6)Gal (1), GlcNAc beta 1-3)GlcNAc beta 1-6)Gal beta 1-OCH3 (4), GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4Glc (7), and GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4GlcNAc (10) were cleaved partially with jack bean beta-N-acetylhexosaminidase (EC 3.2.1.30), and the digests were analysed chromatographically. All four oligosaccharides were hydrolysed faster at the (1-6) branch, than at the (1-3) branch, but a high branch specificity was observed only with the glycan 4. The saccharides 1 and 7 resembled each other in the kinetics of the enzyme-catalysed release of their two non-reducing N-acetylglucosamine units, but the glycan 10 was rather different. The partial digestions made it possible to obtain radiolabelled GlcNAc beta 1-6Gal, GlcNAc beta 1-6Gal beta 1-OCH3, GlcNAc beta 1-6Gal beta 1-4Glc, and, in particular, GlcNAc beta 1-6Gal beta 1-4GlcNAc.     

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.     

The molecular size of glycans liberated by hydrazinolysis from semliki forest virus proteins

The glycans of well characterized, [6-³H]galactose-labelled glycopeptides, GC-4 from bovine IgG₁ as well as GP-V-2 and GP-V-5 from α₁-acid glycoprotein, were liberated by hydrazinolysis. Molecular weights close to the expected values were observed by gel filtration. Desialated glycans of Semliki Forest virus proteins were likewise liberated by hydrazinolysis and subjected to gel filtration. Metabolically labelled [1-³H]galactose-oligosaccharides of the mixed viral proteins revealed an apparent molecular weight of 1800. The bi-antennary glycan liberated from the reference glycopeptide GC-4 was of 1750 daltons. A mixture of [2-³H]mannose-labelled E₁-and E₂-proteins of the virus contained L-type glycans of 1800 daltons (formerly called A-type), and M-type glycans of 1200 daltons (formerly called B-type). A fraction of the E₃-glycans isolated by affinity chromatography on Concanavalin A-Sepharose showed an average molecular weight of 2150, a value intermediate between the three- and four-antennary glycans liberated from the reference glycopeptides GP-V-5 and GP-V-2. The rest of the E₃-glycans were of 1850 daltons, a value close to the bi-antennary GC-4 glycan. We suggest that the comparatively large size of the E₃-glycans and the exposed position of E₃-proteins on the viral surface may be interrelated.     

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.     

Interactions Between Metals in Rat Liver and Kidney: Localization of Metallothionein

The interactions between two essential metals, Cu and Zn, and the localization and concentration of metallothionein have been studied in rat liver and kidney. Rats receiving daily intraperitoneal injections of Cu for 3 days, or Zn for 2 days, or Cu for 3 days followed by Zn for 2 days, were sacrificed 24, 72, 120h after the final injection. Our data indicate that Cu and Zn are both good inductors of metallothionein synthesis in rat tissues. Synergism between Cu and Zn in metallothionein synthesis was also observed as indicated by immunocytochemical experiments and chemical analysis. Moreover, in rats injected with Cu followed by Zn, the localization of metallothionein and the concentrations of both metallothionein and metal differed over time according to the organs considered. In rat kidney, a delay in the excretory process was also observed and metallothionein was present 120h after the last injection.     

Human galectin-1 recognition of poly-N-acetyllactosamine and chimeric polysaccharides

Human galectin-1 is a dimeric carbohydrate binding protein (Gal-1) (subunit 14.6 kDa) widely expressed by many cells but whose carbohydrate binding specificity is not well understood. Because of conflicting evidence regarding the ability of human Gal-1 to recognize N-acetyllactosamine (LN, Galbeta4GlcNAc) and poly-N-acetyllactosamine sequences (PL, [-3Galbeta4GlcNAcbeta1-]n), we synthesized a number of neoglycoproteins containing galactose, N-acetylgalactosamine, fucose, LN, PL, and chimeric polysaccharides conjugated to bovine serum albumin (BSA). All neoglycoproteins were characterized by MALDI-TOF. Binding was determined in ELISA-type assays with immobilized neoglycoproteins and apparent binding affinities were estimated. For comparison, we also tested the binding of these neoglycoconjugates to Ricinus communis agglutinin I, (RCA-I, a galactose-binding lectin) and Lycopersicon esculentum agglutinin (LEA, or tomato lectin), a PL-binding lectin. Gal-1 bound to immobilized Galbeta4GlcNAcbeta3Galbeta4Glc-BSA with an apparent K(d) of approximately 23 micro M but bound better to BSA conjugates with long PL and chimeric polysaccharide sequences (K(d)'s ranging from 11.9 +/- 2.9 microM to 20.9 +/- 5.1 micro M). By contrast, Gal-1 did not bind glycans lacking a terminal, nonreducing unmodified LN disaccharide and also bound very poorly to lactosyl-BSA (Galbeta4Glc-BSA). By contrast, RCA bound well to all glycans containing terminal, nonreducing Galbeta1-R, including lactosyl-BSA, and bound independently of the modification of the terminal, nonreducing LN or the presence of PL. LEA bound with increasing affinity to unmodified PL in proportion to chain length. Thus Gal-1 binds terminal beta4Gal residues, and its binding affinity is enhanced significantly by the presence of this determinant on long-chain PL or chimeric polysaccharides.