Combining two-stage testing and interval mapping strategies to detect QTL for resistance to bonamiosis in the european flat oyster Ostrea edulis.

We have identified quantitative trait loci (QTL) in the flat oyster (Ostrea edulis) for resistance to Bonamia ostreae, a parasite responsible for the dramatic reduction in the aquaculture of this species. An F(2) family from a cross between a wild oyster and an individual from a family selected for resistance to bonamiosis was cultured with wild oysters injected with the parasite, leading to 20% cumulative mortality. Selective genotyping of 92 out of a total of 550 F(2) progeny (i.e., 46 heavily infected oysters that died and 46 parasite-free oysters that survived) was performed using 20 microsatellites and 34 amplification fragment length polymorphism primer pairs. Both a two-stage testing strategy and QTL interval mapping methods were used. The two-stage detection strategy had a high power with a low rate of false positives and identified nine and six probable markers linked to genes of resistance and susceptibility, respectively. Parent-specific genetic linkage maps were built for the family, spanning ten linkage groups (n = 10) with an observed genome coverage of 69-84%. Three QTL were identified by interval mapping in the first parental map and two in the second. Good concordance was observed between the results obtained after the two-stage testing strategy and QTL mapping.

Late collapse of distal radius fractures after K-wire removal: is it significant?

BACKGROUND: The aim of this study was to find out whether distal radius fractures treated by Kirschner wire (K wire) fixation loose reduction after wire removal and analyze the variables may influence this. MATERIALS AND METHODS: Patients who underwent K wire fixation for unstable fractures of distal radius over a period of 3 years were included in this retrospective study. Fractures were classified according to AO classification. Radiographs taken just prior to removal of K wires and radiographs taken at least 1 month after wire removal were analyzed to study three radiological parameters; Palmar or dorsal tilt, radial inclination and ulnar variance. Loss of these angles was analyzed statistically against variables like age, sex, AO classification and duration of fixation. RESULTS: 59 fractures were analyzed with mean age of 56 years and male to female ratio of 1:2. Average loss of radial tilt was 2.6 degrees , loss of palmar tilt was 2.6 degrees and loss of ulnar variance was 1.3 mm. CONCLUSIONS: We found that distal radius fractures treated by percutaneous K wire fixation, did not suffer significant loss of reduction of fracture position after removal of wires. This remains true regardless of age, sex, fracture type according to AO type or duration of wire fixation.

Isolation and characterization of 12 dinucleotide microsatellite loci in the anadromous fish Osmerus eperlanus (L.).

A subtractive hybridization method was used to isolate 12 dinucleotide microsatellite loci for the anadromous European smelt, Osmerus eperlanus (L.). Three to 17 (mean 8.08) alleles per locus were identified in the two populations screened, and observed heterozygosity ranged from 0.067 to 0.933. Loci in both populations showed significant deviations from Hardy-Weinberg expected frequencies. These 12 loci provide a good basis for investigation of O. eperlanus population structure.

A first-generation genetic linkage map of the European flat oyster Ostrea edulis (L.) based on AFLP and microsatellite markers.

This study presents the first genetic linkage map for the European flat oyster Ostrea edulis. Two hundred and forty-six AFLP and 20 microsatellite markers were genotyped in a three-generation pedigree comprising two grandparents, two parents and 92 progeny. Chi-square goodness-of-fit tests revealed high segregation distortion, which was significant for 32.8% of markers. Sixteen microsatellites and 235 AFLPs (170 type 1:1 AFLPs and 65 type 3:1 AFLPs) were used to build sex-specific linkage maps using crimap software. The first parental map (P(1)) consisted of 104 markers grouped in nine linkage groups, and spanned 471.2 cM with an average spacing of 4.86 cM. The second parental map (P(2)) consisted of 117 markers grouped in 10 linkage groups (which equals the haploid chromosome number), and covered 450.0 cM with an average spacing of 4.21 cM. The estimated coverage of the genome was 82.4% for the P(1) map and 84.2% for the P(2) map. Eight linkage groups that were probably homologous between the two parents contained the same microsatellites and 3:1 AFLPs (segregating through both parents). Distorted markers were not randomly distributed across the genome and tended to cluster in a few linkage groups. Sex-specific differences in recombination rates were evident. This first-generation genetic linkage map for O. edulis represents a major step towards the mapping of QTL such as resistance to bonamiasis, a parasitosis that has drastically decreased populations of flat oysters since the 1960s.

AFLP-based genetic linkage maps of the blue mussel (Mytilus edulis).

We report the construction of the first genetic linkage map in the blue mussel, Mytilus edulis. AFLP markers were used in 86 full-sib progeny from a controlled pair mating, applying a double pseudo-test cross strategy. Thirty-six primer pairs generated 2354 peaks, of which 791 (33.6%) were polymorphic in the mapping family. Among those, 341 segregated through the female parent, 296 through the male parent (type 1:1) and 154 through both parents (type 3:1). Chi-square goodness-of-fit tests revealed that 71% and 73% of type 1:1 and 3:1 markers respectively segregated according to Mendelian inheritance. Sex-specific linkage maps were built with mapmaker 3.0 software. The female framework map consisted of 121 markers ordered into 14 linkage groups, spanning 862.8 cM, with an average marker spacing of 8.0 cM. The male framework map consisted of 116 markers ordered into 14 linkage groups, spanning 825.2 cM, with an average marker spacing of 8.09 cM. Genome coverage was estimated to be 76.7% and 75.9% for the female and male framework maps respectively, rising to 85.8% (female) and 86.2% (male) when associated markers were included. Twelve probable homologous linkage group pairs were identified and a consensus map was built for nine of these homologous pairs based on multiple and parallel linkages of 3:1 markers, spanning 816 cM, with joinmap 4.0 software.

Disruption of doubly uniparental inheritance of mitochondrial DNA in hybrid mussels (Mytilus edulis x M. galloprovincialis).

Blue mussels of the genus Mytilus have an unusual mode of mitochondrial DNA inheritance termed doubly uniparental inheritance (DUI). Females are homoplasmic for the F mitotype which is inherited maternally, whereas males are heteroplasmic for this and the paternally inherited M mitotype. In areas where species distributions overlap a varying degree of hybridization occurs; yet genetic differences between allopatric populations are maintained. Observations from natural populations and previous laboratory experiments suggest that DUI may be disrupted by hybridization, giving rise to heteroplasmic females and homoplasmic males. We carried out controlled laboratory crosses between Mytilus edulis and M. galloprovincialis to produce pure species and hybrid larvae of known parentage. DNA markers were used to follow the fate of the F and M mitotypes through larval development. Disruption of the mechanism which determines whether the M mitotype is retained or eliminated occurred in an estimated 38% of M. edulis x M. galloprovincialis hybrid larvae, a level double that previously observed in adult mussels from a natural M. edulis x M. galloprovincialis hybrid population. Furthermore, reciprocal hybrid crosses exhibited contrasting types of DUI disruption. The results indicate that disruption of DUI in hybrid mussels may be associated with increased mortality and hence could be a factor in the maintenance of genetic integrity for each species.

Mitochondrial DNA variation in the scallop Pecten maximus (L.) assessed by a PCR-RFLP method.

Two PCR-RFLP mitochondrial DNA (mtDNA) markers were developed through the cloning and sequencing of mtDNA from the scallop Pecten maximus, and were used to study genetic differentiation off UK and Atlantic coast populations of this species. Although no distinct pattern of mtDNA haplotype frequencies was apparent and no diagnostic haplotypes were identified for any population, sequence divergence data provided convincing evidence that a P. maximus sample taken from Mulroy Bay, Eire, a semi-enclosed sea lough, was genetically differentiated form all other samples. However, this could not be unequivocally attributed to a restriction in gene flow, as the sample consisted of an ongrown single spatfall, which may not have been representative of the wild population. Despite the inability to separate populations on the basis of haplotype frequency, it was noteworthy that the frequency pattern of the commonest haplotype varied between sampling sites in a manner similar to that of allozyme allele frequencies in Aequipecten opercularis, a scallop species with a similar distribution and life history, for which there is evidence of population subdivision. Pecten maximus from St. Brieuc Bay, reasoned to be a self-recruiting population from reproductive and physiological evidence, could not be separated from other populations using mtDNA markers. Further investigation of this population with alternative markers is warranted.

Urinary retention after total hip replacement. A prospective study.

We report a prospective study of the factors associated with acute urinary retention after total hip replacement in 103 consecutive male patients. Eleven patients (10.7%) developed retention after operation. Of the factors investigated before operation three had predictive value: inability to pass urine into a bottle whilst lying in bed, urinary peak-flow rates indicative of obstruction, and a history of previous bladder outflow problems. This study suggests that patients showing one or more of these factors should be assessed and if necessary treated by a urologist before arthroplasty, so as to avoid the need for catheterisation, and the consequent risk of deep infection.