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.     

Epidermal capillariasis in South African clawed frogs (Xenopus laevis)

Significant morbidity and mortality of South African clawed frogs, Xenopus laevis, can be caused by parasitism of the epidermis by a capillarid nematode. These worms produce an erosive dermatitis that is complicated by infection with gram-negative microorganisms. The nematode apparently has a direct life cycle that can be completed within the epidermis of the frog. These characteristics are suggested by the lack of an intermediate host and failure to detect visceral migration. Another unique feature of the parasite was the presence of larvated eggs, in utero. Some have named the parasite Capillaria xenopodis, whereas others called it Pseudocapillaroides xenopi to distinguish it form the typical members of the genus Capillaria.     

Definition of the surface antigens of Mycobacterium malmoense and use in studying the etiology of a form of mycobacteriosis

Mycobacterium malmoense is the latest of a roster of atypical mycobacteria implicated in pulmonary infections. Yet it lacks recognizable phenotypic features to allow its ready identification. Some 23 clinical isolates of M. malmoense were examined for homologous seroagglutination reactions and characteristic surface antigens. One group showed concordant agglutination interreactions and an identical spectrum of glycolipids and are regarded as M. malmoense sensu stricto. The glycolipids are of the newly found, trehalose-containing lipooligosaccharide class. De-O-acylation followed by high-pressure liquid chromatography revealed one major and several minor oligosaccharides. Partial acidic cleavage to release glycosidically linked trehalose, alpha-mannosidase digestion to demonstrate the presence of a non-reducing-end mannobiose, perdeuteriomethylation, partial acid hydrolysis, reduction, and O ethylation, combined with 1H nuclear magnetic resonance and electron impact and fast-atom bombardment mass spectrometry revealed the structure of the major oligosaccharide as alpha-D-Manp-(1----3) -alpha-D-Manp-(1----[2-alpha-L-Rhap-(1--]4--3)-alpha-L-Rh ap- (1----3)-alpha-D-Glcp-(1----1)-alpha-D-Glcp, in which two of the 2-alpha-L-Rhap residues are O methylated at C-3. (Man, mannose; Rha, rhamnose; Glc, glucose; p, pyranosyl). The structures of the minor oligosaccharides were also determined; they differ at the distal nonreducing end. The dominant oligosaccharide was acylated by octanoate, 2-methyleicosanoate, and 2,4-dimethylpentacosanoate to yield the major species-specific surface antigen of M. malmoense, which we regard as the most characteristic feature of the pathogen.     

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.     

Further novel amido sugars within the glycopeptidolipid antigens of Mycobacterium avium

The individual serovars of the Mycobacterium avium complex, a source of serious and persistent infections in individuals with underlying immune deficiencies, also present an extraordinary set of novel sugar epitopes as part of their type-specific glycopeptidolipid surface antigens. Californium desorption-mass spectrometry has been successfully applied to the holistic glycopeptidolipid antigen of M. avium serovar 12 and its per-O-acetyl derivative, to arrive at the following structure, of molecular mass 1876: (Sequence: see text). The pentasaccharide hapten, released as the tetraglycosyl alditol, was subjected to methylation analysis, absolute configurational analysis, 1H NMR and fast atom bombardment-mass spectrometry to arrive at the structure: 4-(2'-Hydroxy) propionamido-4,6-dideoxy-3-O-Me-Glcp (beta 1----3)-4-O-Me-L-Rhap (alpha 1----3)-L-Rhap (alpha 1----3)-L-Rhap (alpha 1----2)-6-deoxytalitol. Two-dimensional proton correlation spectroscopy was also applied to determine the configuration of the unique distal segment of the oligosaccharide unit. The significance of this structure in the context of the fully elucidated structures of the antigens from 12 of the 31-member M. avium complex is discussed.     

A new peptide in the FMRFamide family isolated from the CNS of the hawkmoth, Manduca sexta

We have purified a FMRFamide-like peptide from extracts of brain-subesophageal ganglion of the moth, Manduca sexta. The purification was monitored with a new, competitive ELISA, and accomplished with ion exchange and reverse-phase HPLC. The peptide structure was determined by a combination of tandem mass spectrometry and automated Edman degradation. The amino acid sequence of the peptide is less than Glu-Asp-Val-Val-His-Ser-Phe-Leu-Arg-Phe-amide (pEDVVHSFLRF-NH2). In a separate purification, an identical peptide was isolated from extracts of brain-associated neurohemal structures. We have named this peptide ManducaFLRFamide, to indicate its homology with other members of the "FMRFamide" family. In bioassays, chemically synthesized peptide increased the force of neurally evoked contractions in the major power-producing flight muscles, the dorsal longitudinal muscles. This observation suggests that hormonally released ManducaFLRFamide may play a role in sustaining or promoting the flight behavior necessary for mate-seeking (in males) or oviposition (in females) in sphingid moths.     

Neutron RBE for primate spinal cord treated with clinical regimens.

The RBEs of high-energy neutrons given in 9 or 12 fractions for cervical spinal cord injury in rhesus monkeys was determined using photons at 2.2 Gy per fraction as the reference radiation. Because the dose-response functions were not parallel, the RBE was not constant but rather increased with dose or, equivalently, with the probability of myelopathy. This required the development of a novel method of determining the RBE versus level of response. The RBE is presented as a function of probability of myelopathy from 0.1 to 99%. At a 50% incidence of myelopathy, the RBE (+/- 1 SE) was 5.22 +/- 0.15. A difference in the histopathology of lesions induced by photon and neutron treatments was observed.     

A mathematical model of life-threatening hyperthermia during infancy.

A mathematical model was created to test the hypothesis that a partially covered febrile infant may develop potentially lethal temperature elevation. Infants may be at special risk to develop hyperthermia because, unlike older children, infants may not be able to remove blankets in response to temperature elevation. The model compared heat production (MTsk) with heat loss (Qtot). The difference between these terms is the excess energy (E): MTsk - Qtot = E. In most situations the simulated infant transfers heat to the environment as rapidly as it is produced (E less than 0), so hyperthermia does not result. In some situations, heat production exceeds heat loss (E greater than 0), causing progressive warming. The time was calculated for the simulated infant to progress from 41 to 43.4 degrees C (defined as a lethal end point). In certain circumstances, this may occur in less than 90 min. An infant at high risk of hyperthermia may not appear to be covered by a conspicuous excess of insulation (less than or equal to 3.5 cm may be sufficient). In many situations, heat loss is more closely determined by exposed body surface area than by blanket thickness. These findings have important implications for understanding the antecedents of hyperthermia in infants and may help in understanding the role of hyperthermia in certain pediatric illnesses.     

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.