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.     

The courtship and mating of the Iberian midwife toad Alytes cisternasii (Amphibia: Anura: Discoglossidae)

Sexual encounters were staged in the laboratory among hormonally-primed Iberian midwife toads, Alytes cisternasii . In this species, pairing and fertilization are terrestrial. The male cares for the developing embryos on land, carrying them twined around his hind limbs until they hatch into tadpoles which he releases into water; his investment in the offspring then ends. The courtship of A. cisternasii can be divided into a pre- and post-ovulatory phase. An encounter is initiated when the female approaches the male and is clasped by him in inguinal amplexus. Both the male and the female produce vocalizations during the period prior to the initiation of amplexus. During amplexus, only the female vocalizes, changing her call to one that is of lower intensity, longer duration and more regularly emitted than before. During inguinal amplexus, the male engages in bouts of intense pedalling and gentle rocking behaviour, each bout being initiated when the female repositions herself beneath him. Rocking and pedalling cease when the female ovulates, at which time she exhibits a posture that we call Unkenkrampf. Ovulation occurs at this time, and is followed by sperm release by the male (seen as a series of lateral compressions of his body). After sperm release, the male moves forwards to engage the female in cervical amplexus and then manoeuvres his hind limbs such that the egg string becomes tangled around his ankles. The female may exhibit additional episodes of Unkenkrampf during this period, but these are not accompanied by further egg release. Episodes of Unkenkrampf (without ovulation) also may occur after the male dismounts from the female. Similar behaviour patterns to those observed in the laboratory are seen in natural populations of A. cisternasii . We compare and contrast our observations of A. cisternasii with those of other authors for this species and also for the common midwife toad, A. obstericans .     

Reaction of compound III of myeloperoxidase with ascorbic acid

A relatively pure and stable compound III of bovine spleen myeloperoxidase was prepared from native enzyme using the aerobic oxidation of dihydroxyfumarate to generate O2-(.). Spectral scans show well defined peaks at 450 and 625 nm and an isosbestic point between compound III and native enzyme at 440 nm. Compound III decayed to native enzyme without any detectable intermediate. The rate of decay was faster at alkaline pH values and also in the presence of superoxide dismutase. Ascorbic acid reduces compound III to native enzyme with a second order rate constant of (4.0 +/- 0.1) x 10(2) M-1 s-1. The ascorbic acid reduction of compound III has potential physiological relevance since it could help maintain the catalytic cycle of myeloperoxidase to generate the bactericidal agent hypochlorous acid.     

Reaction of autoxidation products of penicillamine with myeloperoxidase

Spectral evidence is presented which shows that penicillamine is able to initiate the formation of the oxidized intermediates of myeloperoxidase in the absence of exogenous hydrogen peroxide. The autoxidation of penicillamine presumably produces superoxide which dismutates spontaneously to form hydrogen peroxide. Thus, the formation of both compounds II and III of myeloperoxidase was observed. We also report that penicillamine can directly reduce cytochrome c and therefore, it could possibly act as a one-electron donor to myeloperoxidase.     

Leishmania infantum Nicolle, 1908 from southern Spain: Characterisation of the strains from human visceral and cutaneous leishmaniasis and from sandflies; with a numerical analysis of the isoenzymatic data

This study presents the results of the characterisation of 17 strains ofLeishmania by isoenzyme electrophoresis from a focus of leishmaniasis in southern Spain: two from human visceral leishmaniasis, four from human cutaneous leishmaniasis and 11 from sandflies. The 17 strains are grouped in 6 zymodemes characterised by their variability as regards to the electrophoretic mobility of the enzymes MDH, G6PD, NP and ME. Thus, we confirm the high intraspecific variability ofLeishmania (L.) infantum in a focus of southern Spain, as already suggested by previous studies. Zymodemes GR-15 and GR-17 are also described for the first time in Spain, and they characteristically possess the same relative electrophoretic mobility in the enzyme ME (93). Sixteen zymodemes of theL. infantum complex found in southern Spain were numerically analysed on the basis of the enzymatic profiles of 122Leishmania strains characterised from this area.     

Characterization of terminal NeuNAcalpha2-3Galbeta1-4GlcNAc sequence in lipooligosaccharides of Neisseria meningitidis

Group B and C Neisseria meningitidis are the major cause of meningococcal disease in the United States and in Europe. N . meningitidis lipooligosaccharide (LOS), a major surface antigen, can be divided into 12 immunotypes of which L1 through L8 were found among Group B and C organisms. Groups B and C but not Group A may sialylate their LOSs with N-acetylneuraminic acid (NeuNAc) at the nonreducing end because they synthesize CMP-NeuNAc. Using sialic acid-galactose binding lectins as probes in an ELISA format, six of the eight LOS immunotypes (L2, L3, L4, L5, L7, and L8) in Groups B and C bound specifically to Maackia amurensis leukoagglutinin (MAL), which recognizes NeuNAcalpha2- 3Galbeta1-4GlcNAc/Glc sequence, but not to Sambucus nigra agglutinin, which binds NeuNAcalpha2-6Gal sequence. The combination of SDS-PAGE and MAL-blot analyses revealed that these six LOSs contained only the NeuNAcalpha2-3Galbeta1-4GlcNAc trisaccharide sequence in their 4.1 kDa LOS components, which have a common terminal lacto-N-neotetraose (LNnT, Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc) structure when nonsialylated as shown by previous studies. The LOS-lectin binding was abolished when the LOSs were treated with Newcastle disease viral neuraminidase which cleaves alpha2-->3 linked sialic acid. Methylation analysis of a representative LOS (L2) confirmed that NeuNAc is 2-->3 linked to Gal. Thus, these LOSs structurally mimic certain glycolipids, i.e., paragloboside (LNnT-ceramide) and sialylparagloboside and some glycoproteins in having LNnT and N-acetyllactosamine sequences, respectively, with or without alpha2-->3 linked NeuNAc. The molecular mimicry of the LOSs may play a role in the pathogenesis of N.meningitidis by assisting the organism to evade host immune defenses in man.      

Spectroscopic and kinetic properties of the oxidized intermediates of lignin peroxidase from Phanerochaete chrysosporium

Stopped-flow rapid scan techniques were used to obtain a spectrum of nearly homogeneous lignin peroxidase compound I (LiPI) under pseudo-first order conditions at the unusually low pH optimum (3.0) for the enzyme. The LiPI spectrum had a Soret band at 407 nm with approximately 60% reduced intensity and a visible maximum at 650 nm. Under steady-state conditions a Soret spectrum for lignin peroxidase compound II (LiPII) was also obtained. The Soret maximum of LiPII at 420 nm was only approximately 15% reduced in intensity compared to native LiP. Transient state kinetic results confirmed the pH independence of LiPI formation over the pH range 3.06-7.39. The rate constant was (6.5 +/- 0.2) x 10(5) M-1 S-1. Addition of excess veratryl alcohol to LiPI resulted in its reduction to LiPII with subsequent reduction of LiPII to the native enzyme. Reactions of LiPI and LiPII with veratryl alcohol exhibited marked pH dependencies. For the LiPI reaction the rate constants ranged from 2.5 x 10(6) M-1 S-1 at pH 3.06 to 4.1 x 10(3) M-1 S-1 at pH 7.39; for the LiPII reaction, 1.6 x 10(5) M-1 S-1 (pH 3.06) to 2.3 x 10(3) M-1 S-1 (pH 5.16). These single turnover experiments demonstrate directly that the pH dependence of these reactions dictates the overall pH dependence of this novel enzyme. These results are consistent with the one-electron oxidation of veratryl alcohol to an aryl cation radical by LiPI and by LiPII.     

Simultaneous Detection of Aeromonas salmonicida, Flavobacterium psychrophilum, and Yersinia ruckeri, Three Major Fish Pathogens, by Multiplex PCR

A multiplex PCR assay based on the 16S rRNA genes was developed for the simultaneous detection of three major fish pathogens, Aeromonas salmonicida, Flavobacterium psychrophilum, and Yersinia ruckeri. The assay proved to be specific and as sensitive as each single PCR assay, with detection limits in the range of 6, 0.6, and 27 CFU for A. salmonicida, F. psychrophilum, and Y. ruckeri, respectively. The assay was useful for the detection of the bacteria in artificially infected fish as well as in fish farm outbreaks. Results revealed that this multiplex PCR system permits a specific, sensitive, reproducible, and rapid method for the routine laboratory diagnosis of infections produced by these three bacteria.