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Interspecies hybrids between distinct species of the genus Xiphophorus are often used in varied research investigations to identify genomic regions associated with the inheritance of complex traits. There are 24 described Xiphophorus species and a greater number of pedigreed strains; thus, the number of potential interspecies hybrid cross combinations is quite large. Previously, select Xiphophorus experimental crosses have been shown to exhibit differing characteristics between parental species and among the hybrid fishes derived from crossing them, such as widely differing susceptibilities to chemical or physical agents. For instance, genomic regions harboring tumor suppressor and oncogenes have been identified via linkage association of these loci with a small set of established genetic markers. The power of this experimental strategy' is related to the number of genetic markers available in the Xiphophorus interspecies cross of interest. Thus, we have undertaken the task of expanding the suite of easily scored markers by characterization of Xiphophorus microsatellite sequences. Using a cross between Xiphophorus maculatus and X. andersi, we report a linkage map predominantly composed of microsatellite markers. All 24 acrocentric chromosome sets of Xiphophorus are represented in the assembled linkage map with an average intergenomic distance of 7.5 cM. Since both male and female [F.sub.1] hybrids were used to produce backcross progeny, these recombination rates were compared between 'male' and 'female' maps. Although several genomic regions exhibit differences in map length, male- and female-derived maps are similar. Thus Xiphophorus, in contrast to zebrafish, Danio rerio, and several other vertebrate species, does not show sex-specific differences in recombination. The microsatellite markers we report can be easily adapted to any Xiphophorus interspecies and some intraspecies crosses, and thus provide a means to directly compare results derived from independent experiments.

Arrhythmogenic right ventricular dysplasia (ARVD) is a complex arrhythmogenic cardiomyopathy, characterized by a partial or total replacement of the right ventricular myocytes by fatty and fibrous tissue. In this study, we present a case of ARVD in 17 year old girl, who was admitted to the hospital after syncope with ventricular arrhythmia. The echocardiography did not demonstrate structural cardiac abnormalities but the magnetic resonance recently showed thinning of the right ventricular wall. The girl was treated with the lidocaine, amiodarone and next, after radiofrequency catheter ablation she was receiving metoprolol. The girl has remained asymptomatic for four years of follow-up. [ABSTRACT FROM AUTHOR]

In the faint star KIC 9700322 observed by the Kepler satellite, 76 frequencies with amplitudes from 14 to 29 000 ppm were detected. The two dominant frequencies at 9.79 and 12.57 d (113.3 and 145.5 μHz), interpreted to be radial modes, are accompanied by a large number of combination frequencies. A small additional modulation with a 0.16 d frequency is also seen; this is interpreted to be the rotation frequency of the star. The corresponding prediction of slow rotation is confirmed by a spectrum from which km s is obtained. The analysis of the spectrum shows that the star is one of the coolest δ Sct variables. We also determine T = 6700 ± 100 K and = 3.7 ± 0.1, compatible with the observed frequencies of the radial modes. Normal solar abundances are found. An frequency quintuplet is also detected with a frequency separation consistent with predictions from the measured rotation rate. A remarkable result is the absence of additional independent frequencies down to an amplitude limit near 14 ppm, suggesting that the star is stable against most forms of non-radial pulsation. A low-frequency peak at 2.7763 d in KIC 9700322 is the frequency difference between the two dominant modes and is repeated over and over in various frequency combinations involving the two dominant modes. The relative phases of the combination frequencies show a strong correlation with frequency, but the physical significance of this result is not clear. [ABSTRACT FROM AUTHOR]

Lithium has long been known to be a good tracer of non-standard mixing processes occurring in stellar interiors. Here we present the results of a large survey aimed at determining the surface Li abundance in a sample of about 800 giant (RGB and AGB) stars with accurate Hipparcos parallaxes. We compare the observed Li behaviour with that predicted by stellar models including rotation and thermohaline mixing. [ABSTRACT FROM PUBLISHER]