Evaluation of quantitative trait loci affecting intramuscular fat and reproductive traits in pigs using marker-assisted introgression.

We investigated the effects of previously identified quantitative trait loci (QTL) in an experimental backcross (BC) between Chinese Meishan pigs and commercial Duroc pigs. We performed marker-assisted introgression of two QTL for intramuscular fat (IMF) content (IMF population) and three QTL for reproductive traits (reproduction population) from a donor Meishan pig into a recipient Duroc pig. At the fourth BC generation of the IMF population and third BC generation of the reproduction population, carrier animals were selected for the production of animals homozygous for the QTL. Our previous studies have shown that the presence of a Meishan allele on the IMF QTL is associated with low IMF values, and the Meishan allele on the reproductive QTL is associated with large litters. In this study, the presence of a Duroc allele at the IMF QTL on SSC9 resulted in a 0.27% increase in IMF (additive effect = 0.27 ± 0.08), whereas the presence of a Meishan allele at the IMF QTL on SSC7 resulted in a 0.34% increase in IMF (additive effect = -0.34 ± 0.09). The presence of the Meishan allele at the IMF QTL on SSC7 thus had the opposite effect to our previous studies, that is, increased IMF. In the reproduction population, we observed no differences between the genotypes of the three QTL in regard to number of corpora lutea or litter size. Marker-assisted introgression at these QTL is thus unlikely to result in an associated increase in litter size. These results show that it is possible to introgress alleles from other breeds into a selection population using molecular markers; any unexpected results might be associated with the genetic background.

The effects of single and epistatic quantitative trait loci for fatty acid composition in a Meishan x Duroc crossbred population.

We performed a whole genome QTL analysis to confirm the existence of QTL affecting fatty acid composition and to investigate the effects of additive, dominance, imprinting, and epistatic interactions between QTL in an F(2) resource population. The F(2) population, comprising 166 pigs, was obtained by crossing a Duroc boar and a Meishan sow. The F(2) population was measured for fatty acid composition and was used for whole genome QTL analysis, using a total of 180 microsatellite markers. The suggestive and significant thresholds were equivalent to likelihood ratio test statistics (LRT) of 13.7 and 20.5, respectively. For single QTL analysis, 2 suggestive QTL and 1 significant QTL were detected. Suggestive QTL for C14:0 and C16:1 were identified on chromosomes 12 and 7, respectively, and a significant QTL for C18:2 was detected on chromosome 5 with the greatest LRT of 22.9. For C14:0, a significant QTL with paternal imprinting effect was also detected on chromosome 12, where the locus was in the same region as an additive QTL effect, with a large LRT of 24.2. The suggestive QTL on chromosome 7 was not significant when correction for backfat thickness was included. For epistatic QTL analysis, a total of 5 epistatic pairs were located on chromosomes 4, 5, 9, and 16. The same epistatic pairs were significant when correction for backfat thickness was included. The individual QTL identified in the single QTL analysis and in the epistatic QTL analysis were not the same loci, except for C18:2. For C14:0, an epistatic QTL pair was detected on chromosome 16, with the least P-value of 4.9 x 10(-12). The present study constitutes one of the first reports on the mapping of imprinted QTL and epistatic pairs of QTL affecting fatty acid composition in a swine population.

Effect of valproic acid on pharmacokinetics of active metabolites of cyclophosphamide in mice.

The effects of valproic acid (VPA) on pharmacokinetics of cyclophosphamide (CPM) alkylating metabolites were investigated in male BALB/c mice. The pharmacokinetics of CPM alkylating metabolites was found to be dose-dependent representing the decrease of formation and elimination rates of the metabolites. A nonlinear increase of area under blood concentration of CPM alkylating metabolites-time curve (AUC) occurred with increasing CPM dose of 100, 200, and 300 mg/kg body weight. The effects of VPA (100 mg/kg dose) coadministered with CPM were similar to those of the increase of the CPM dose in preventing the activation of CPM and the elimination of its alkylating metabolites. The delayed disposition of CPM alkylating metabolites resulted in a 1.5-fold increase (p less than 0.02) of AUC which was considered the most important pharmacokinetic parameter in the CPM therapy. VPA which was injected i.p. at a dose of 100, 200, or 300 mg/kg increased the pentobarbital induced-sleep time by 81, 138, or 192%, respectively. In order to assess the effect of VPA on drug metabolizing enzyme(s) activity in humans, the ratio of daily urinary 6-hydroxycortisol to 17-hydroxycorticosteroids, which can reflect cytochrome P-450 activity, was determined in 5 healthy volunteers. The ratio was rapidly and significantly decreased (p less than 0.05) and this reduction continued during VPA administration. These findings and those reported in the literature concerning CPM metabolism suggest that the delay of CPM alkylating metabolites elimination resulted in part from microsomal enzyme(s) inhibition by VPA.

Intermedilysin, a novel cytotoxin specific for human cells secreted by Streptococcus intermedius UNS46 isolated from a human liver abscess.

A novel cytotoxin (intermedilysin) specific for human cells was identified as a cytolytic factor of Streptococcus intermedius UNS46 isolated from a human liver abscess. Intermedilysin caused human cell death with membrane blebs. Intermedilysin was purified from UNS46 culture medium by means of gel filtration and hydrophobic chromatography. The purified toxin was resolved into major and minor bands of 54 and 53 kDa, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These proteins reacted with an antibody against intermedilysin. Five internal peptide fragments of intermedilysin were sequenced and found to have 42 to 71% homology with the thiol-activated cytotoxin pneumolysin. However, the action of intermedilysin differed from that of thiol-activated cytotoxins, especially in terms of a lack of activation by dithiothreitol and resistance to treatments with N-ethylmaleimide and 5,5'-dithio-bis-(2-nitrobenzoic acid), although cholesterol inhibited the toxin activity. Intermedilysin was potently hemolytic on human erythrocytes but was 100-fold less effective on chimpanzee and cynomolgus monkey erythrocytes. Intermedilysin was not hemolytic in nine other animal species tested. Since human erythrocytes treated with trypsin were far less sensitive to intermedilysin than were the intact cells, a cell membrane protein(s) may participate in the intermedilysin action. These data demonstrated that intermedilysin is distinguishable from all known bacterial cytolysins.