Fine mapping a locus controlling leg morphology in the domestic dog.

The domestic dog offers a remarkable opportunity to disentangle the genetics of complex phenotypes. Here, we explore a locus, previously identified in the Portuguese water dog (PWD), associated with PC2, a morphological principal component characterized as leg width versus leg length. The locus was initially mapped to a region of 26 Mb on canine chromosome 12 (CFA12) following a genome-wide scan. Subsequent and extensive genotyping of single-nucleotide polymorphisms (SNPs) and haplotype analysis in both the PWD and selected breeds representing phenotypic extremes of PC2 reduced the region from 26 Mb to 500 kb. The proximity of the critical interval to two collagen genes suggests that the phenotype may be controlled by cis-acting mechanisms.

SNPs in ecological and conservation studies: a test in the Scandinavian wolf population.

Single nucleotide polymorphisms (SNPs) have the potential to become the genetic marker of choice in studies of the ecology and conservation of natural populations because of their capacity to access variability across the genome. In this study, we provide one of the first demonstrations of SNP discovery in a wild population in order to address typical issues of importance in ecology and conservation in the recolonized Scandinavian and neighbouring Finnish wolf Canis lupus populations. Using end sequence from BAC (bacterial artificial chromosome) clones specific for dogs, we designed assays for 24 SNP loci, 20 sites of which had previously been shown to be polymorphic in domestic dogs and four sites were newly identified as polymorphic in wolves. Of the 24 assayed loci, 22 SNPs were found to be variable within the Scandinavian population and, importantly, these were able to distinguish individual wolves from one another (unbiased probability of identity of 4.33 x 10(-8)), providing equivalent results to that derived from 12 variable microsatellites genotyped in the same population. An assignment test shows differentiation between the Scandinavian and neighbouring Finnish wolf populations, although not all known immigrants are accurately identified. An exploration of the misclassification rates in the identification of relationships shows that neither 22 SNP nor 20 microsatellite loci are able to discriminate across single order relationships. Despite the remaining obstacle of SNP discovery in nonmodel organisms, the use of SNPs in ecological and conservation studies is encouraged by the advent of large scale screening methods. Furthermore, the ability to amplify extremely small fragments makes SNPs of particular use for population monitoring, where faecal and other noninvasive samples are routinely used.

Comparison of MultiMap and TSP/CONCORDE for constructing radiation hybrid maps.

Radiation hybrid (RH) map construction allows investigators to locate both type I and type II markers on a given genome map. The process is composed of two steps. The first consists of determining the pattern distribution of a set of markers within the different cell lines of an RH panel. This is mainly done by polymerase chain reaction (PCR) amplification and gel electrophoresis, and results in a series of numbers indicating the presence or the absence of each marker in each cell line. The second step consists of a comparison of these numbers, using various algorithms, to group and then order markers. Because different algorithms may provide (slightly) different orders, we have compared the merits of the MultiMap and TSP/CONCORDE packages using a data set of information currently under analysis for construction of the canine genome RH map.

Meiotic linkage mapping of 52 genes onto the canine map does not identify significant levels of microrearrangement.

In an effort to extend our understanding of the evolutionary relationship between the canine and human genomes, we have developed and positioned 52 new gene-associated polymorphic markers on the canine meiotic linkage map. Canine-specific PCR primers were developed from the consensus of published sequences of several mammalian genomes and were designed to span intronic regions, thus optimizing the probability that a polymorphic site was included. The resulting markers were analyzed on a panel of three-generation canine reference families and the data were incorporated into the current meiotic linkage map. The data were compared with those generated by three chromosome paint studies in an effort to understand the distribution and frequency of microrearrangements within the canine genome. Forty-eight of 52 genes map to a chromosomal region predicted to contain genes from the corresponding region of the human genome according to all published reciprocal chromosome paint studies. Meiotic linkage mapping data for three genes can be used to resolve discrepancies between the published reciprocal chromosome paint studies, and for an additional two genes, meiotic mapping data allow evolutionary breakpoints to be more precisely defined. We conclude that microrearrangements of evolutionarily conserved segments between the canine and human genomes are rare, occurring for less than 0.5% of gene data reported to date. In addition, we have found that the placement of genes on the meiotic linkage map is a useful mechanism for resolving discrepancies between existing data sets.

Estimation of total systemic arterial compliance in humans.

Systemic arterial compliance, a major component of aortic input impedance, was determined in 10 patients with congestive heart failure secondary to idiopathic dilated cardiomyopathy and 11 age-matched control subjects found free of detectable cardiovascular disease. Total arterial compliance was determined from high-fidelity ascending aortic pressure and velocity recordings using 1) the traditional monoexponential aortic diastolic pressure decay and 2) the direct solution of the equation, which describes the three-element windkessel model of the arterial system. Resting values for total arterial compliance (x10(-3) cm5/dyn) derived from method 1 were significantly correlated with compliance derived from method 2 (r = 0.89, P less than 0.01). However, method 1 values (control mean 1.15 +/- 0.27, heart failure mean 1.18 +/- 0.54) were consistently and significantly lower (P less than 0.001) than method 2 values (control mean 1.59 +/- 0.50, heart failure mean 1.38 +/- 0.60). Resting total arterial compliance in heart-failure patients was not significantly different from control subjects. Total arterial compliance did not significantly change with exercise in either group despite increases in arterial pressure. However, nitroprusside administration in the heart-failure group increased total arterial compliance both at rest and on exercise compared with the unmedicated state. These different methodological approaches to the estimation of total arterial compliance in humans resulted in significantly different absolute values for compliance, although both methods provided concordant results with respect to the response of arterial compliance to physiological and pharmacological interventions.(ABSTRACT TRUNCATED AT 250 WORDS)

Tomograpy in radionuclide brain imaging and cisternography.

A new radionuclide tomographic scanner produces 12 tomographic brain images instead of a single conventional brain scan. This scanner has important advantages over conventional radionuclide scanning. The size, shape, and extent of a lesion and its relationship to surrounding structures are better defined. Tomography often permits a firm diagnostic impression in studies that would be equivocal with the use of routine scanning. Tomography may also be used in conjunction with radionuclide cisternography to provide a clear visualization of the CSF pathways and ventricles and to distinguish overlying structures.

Chronic anteromedial instability of the knee.

This is a review of 26 patients with 2 or more years of knee pain or giving way or both in whom the most striking clinical finding was moderate or marked anteromedial instability. Of 27 knees, more than 15 responded favorably to a thigh-muscle-strengthening program. The Lenox Hill brace proved to be a useful adjunct in 9 patients.

Technique for multi-view radionuclide angiography.

A new method utilizing computer subtraction allows 2 separate radionuclide angiograms to be performed during a single laboratory visit. Two separate intravenous injections of the radionuclide are given so that the patient's head can be imaged in 2 different projections. Background activity from the first injection is subtracted by the computer to allow good resolution of blood flow following the second injection. A static brain scan is performed after the second injection. Although single-view radionuclide angiography is widely used in the diagnostic evaluation of the brain, the addition of a second projection provides additonal important diagnostic information. The views obtained, however, must be determined individually for each patient on the basis of the clinical history and neurologic signs. The selection of appropriate views, the diagnostic quality of the studies, and the practical clinical application of this technique are illustrated by 2 case reports.

Comparison of preoperative, intraoperative and early postoperative total hip replacement with and without trochanteric osteotomy.

A series of 100 consecutive patients with total hip replacements in whom trochanteric osteotomy was performed was compared with 100 patients in whom the greater trochanter was left in place. The groups were comparable with respect to age and incidence of osteoarthritis and connective tissue disorders. Although no statistically significant difference was noted among trochanterectomy groups or disease subgroups in terms of preoperative impairment as indicated by preoperative Harris score, 16 patients presented exposure problems necessitating trochanteric osteotomy despite preoperative plans to leave the trochanter in place. Salvage operations after unsuccessful previous operations were performed in 18 patients in the osteotomy group and 11 in the nonosteotomy group. Mean operating time was 3 hours for patients in the osteotomy group and 2 hours for those in the nonosteotomy group. Considerably more intraoperative and postoperative blood replacement was required in the patients having osteotomy. Patients sat, stood, walked, and left the hospital sooner in the nonosteotomy group than in the osteotomy group. Trochanteric bursitis requiring treatment 3 or more months after operation occurred in 17 patients having osteotomy and in 3 patients not having osteotomy. Hematomas developed in 15 patients in the osteotomy group and in 4 in the nonosteotomy group. Ectopic bone formation was observed in 12 of the osteotomy group, 8 with limitation of function, and 5 of the nonosteotomy group; non had symptoms. Six osteotomized patients had troublesome abductor weakness secondary to wire breakage and proximal migration of the trochanter. The rates of infection and thrombophlebitis were low in both groups. When exposure was not difficult, leaving the trochanter intact had many advantages.