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We have identified a naturally occurring, dominant mutation that causes dwarfism in domestic pigs (Sus scrofa). With a positional candidate gene approach, the dwarf phenotype was shown to be a result of a single amino acid change, G590R, in the alpha1 (X) chain of type X collagen. Type X collagen is a homotrimer of alpha1(X) chains encoded by the COL10A1 gene, which is expressed in hypertrophic chondrocytes during the process of endochondral ossification. An amino acid substitution at the equivalent position in human type X collagen, G595E, has previously been shown to cause Schmid metaphyseal chondrodysplasia (SMCD), which is a relatively mild skeletal disorder associated with dwarfism and growth plate abnormality. Consistent with the clinical phenotype of SMCD patients, radiological and histological examination of the dwarf pigs revealed metaphyseal chondrodysplasia in the long bones. Yeast-based, two-hybrid protein interaction studies and in vitro assembly experiments demonstrated that the amino acid substitution interfered with the ability of the mutated collagen molecules to engage in trimerization. This work establishes that the chondrodysplastic dwarf pigs by genetic, biochemical, radiological and histological criteria provide a valid animal model of SMCD.

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A recessive autosomal mutation has been found in the CXBI/ByEss recombinant-inbred line but in neither of the parental strains, C57BL/6ByEss and BALB/cByEss. Its presence in the CXBI/ByJax and CXBI/ByLac sublines suggests an origin early in inbreeding. The locus, seminal vesicle shape (svs), appears to be linked to the albino locus on chromosome 7. The homozygote has seminal vesicles with a smooth tubular external appearance. In segregating crosses homozygotes had slightly lighter seminal vesicles but the weights of other androgen target organs were not reduced. Exogenous testosterone increased the size of the seminal vesicles but did not alter their shape. The mutation did not affect the pattern of proteins on SDS-acrylamide gel electrophoresis, which did differ between the parental strains. The locus affecting a 27000 Da protein has provisionally been assigned the symbol svp-4.

The occurrence of metronidazole resistance was investigated among Campylobacter jejuni in raw poultry meat collected from supermarkets. MICs were determined by the agar dilution procedure in the testing range of 3 to 60 microg/ml metronidazole. The MICs showed a bimodal distribution with a significant proportion of metronidazole-resistant isolates among C. jejuni from raw broiler and turkey meat. Metronidazole resistance occurred most frequently among turkey meat isolates (P < 0.005). This is the first report of foodborne bacteria carrying metronidazole resistance.