Mapping of Unconventional Myosins in Mouse and Human

Myosins are molecular motors that move along filamentous actin. Seven classes of myosin are expressed in vertebrates: conventional myosin, or myosin-II, as well as the 6 unconventional myosin classes -I, -V, -VI, -VII, -IX, and -X. We have mapped in mouse 22 probes encompassing all known unconventional myosins and, as a result, have identified 16 potential unconventional myosin genes. These genes include 7 myosins-I, 2 myosins-V, 1 myosin-VI, 3 myosins-VII, 2 myosins-IX, and 1 myosin-X. The map location of 5 of these genes was identified in human chromosomes by fluorescencein situhybridization.     

Thrombospondin-1 suppresses wound healing and granulation tissue formation in the skin of transgenic mice

The function of the endogenous angiogenesis inhibitor thrombospondin-1 (TSP-1) in tissue repair has remained controversial. We established transgenic mice with targeted overexpression of TSP-1 in the skin, using a keratin 14 expression cassette. TSP-1 transgenic mice were healthy and fertile, and did not show any major abnormalities of normal skin vascularity, cutaneous vascular architecture, or microvascular permeability. However, healing of full-thickness skin wounds was greatly delayed in TSP-1 transgenic mice and was associated with reduced granulation tissue formation and highly diminished wound angiogenesis. Moreover, TSP-1 potently inhibited fibroblast migration in vivo and in vitro. These findings demonstrate that TSP-1 preferentially interfered with wound healing-associated angiogenesis, rather than with the angiogenesis associated with normal development and skin homeostasis, and suggest that therapeutic application of angiogenesis inhibitors might potentially be associated with impaired wound vascularization and tissue repair.     

Isolation of yeast with killer activity and its breeding with an industrial baking strain by protoplast fusion

Summary Wild strains of Saccharomyces cerevisiae were isolated from dairy products, bakery goods, fresh fruit and vegetables, and tested for killer activity. Four isolates out of 238 strains possessed killer activity. The best of these was converted to the petite form and hybridized with an industrial strain of Saccharomyces cerevisiae by protoplast fusion. Thirty-eight out of 104 isolates had killer activity, and some of these had good dough-raising activity as well.     

Floodplain ecosystem dynamics under extreme dry and wet phases in semi‐arid Australia

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Evolution of fitnesses in structured populations with correlated environments

The outcome of selection in structured populations with spatially varying selection pressures depends on the interaction of two factors: the level of gene flow and the amount of heterogeneity among the demes. Here we investigate the effect of three different levels of spatial heterogeneity on the levels of genetic polymorphisms for different levels of gene flow, using a construction approach in which a population is constantly bombarded with new mutations. We further compare the relative importance of two kinds of balancing selection (heterozygote advantage and selection arising from spatial heterogeneity), the level of adaptation and the stability of the resulting polymorphic equilibria. The different levels of environmental heterogeneity and gene flow have a large influence on the final level of polymorphism. Both factors also influence the relative importance of the two kinds of balancing selection in the maintenance of variation. In particular, selection arising from spatial heterogeneity does not appear to be an important form of balancing selection for the most homogeneous scenario. The level of adaptation is highest for low levels of gene flow and, at those levels, remarkably similar for the different levels of spatial heterogeneity, whereas for higher levels of gene flow the level of adaptation is substantially reduced.     

Maximum-likelihood estimation of site-specific mutation rates in human mitochondrial DNA from partial phylogenetic classification

The mitochondrial DNA hypervariable segment I (HVS-I) is widely used in studies of human evolutionary genetics, and therefore accurate estimates of mutation rates among nucleotide sites in this region are essential. We have developed a novel maximum-likelihood methodology for estimating site-specific mutation rates from partial phylogenetic information, such as haplogroup association. The resulting estimation problem is a generalized linear model, with a nonstandard link function. We develop inference and bias correction tools for our estimates and a hypothesis-testing approach for site independence. We demonstrate our methodology using 16,609 HVS-I samples from the Genographic Project. Our results suggest that mutation rates among nucleotide sites in HVS-I are highly variable. The 16,400–16,500 region exhibits significantly lower rates compared to other regions, suggesting potential functional constraints. Several loci identified in the literature as possible termination-associated sequences (TAS) do not yield statistically slower rates than the rest of HVS-I, casting doubt on their functional importance. Our tests do not reject the null hypothesis of independent mutation rates among nucleotide sites, supporting the use of site-independence assumption for analyzing HVS-I. Potential extensions of our methodology include its application to estimation of mutation rates in other genetic regions, like Y chromosome short tandem repeats.     

Developmental expression of a functional TASK-1 2P domain K+ channel in embryonic chick heart

Background

Background K⁺ channels are the principal determinants of the resting membrane potential (RMP) in cardiac myocytes and thus, influence the magnitude and time course of the action potential (AP).

Methods

RT-PCR and in situ hybridization are used to study the distribution of TASK-1 and whole-cell patch clamp technique is employed to determine the functional expression of TASK-1 in embryonic chick heart.

Results

Chicken TASK-1 was expressed in the early tubular heart, then substantially decreased in the ventricles by embryonic day 5 (ED5), but remained relatively high in ED5 and ED11 atria. Unlike TASK-1, TASK-3 was uniformly expressed in heart at all developmental stages. In situ hybridization studies further revealed that TASK-1 was expressed throughout myocardium at Hamilton-Hamburger stages 11 and 18 (S11 &; S18) heart. In ED11 heart, TASK-1 expression was more restricted to atria. Consistent with TASK-1 expression data, patch clamp studies indicated that there was little TASK-1 current, as measured by the difference currents between pH 8.4 and pH 7.4, in ED5 and ED11 ventricular myocytes. However, TASK-1 current was present in the early embryonic heart and ED11 atrial myocytes. TASK-1 currents were also identified as 3 μM anandamide-sensitive currents. 3 μM anandamide reduced TASK-1 currents by about 58% in ED11 atrial myocytes. Zn²⁺ (100 μM) which selectively inhibits TASK-3 channel at this concentration had no effect on TASK currents. In ED11 ventricle where TASK-1 expression was down-regulated, I_K1 was about 5 times greater than in ED11 atrial myocytes.

Conclusion

Functional TASK-1 channels are differentially expressed in the developing chick heart and TASK-1 channels contribute to background K⁺ conductance in the early tubular embryonic heart and in atria. TASK-1 channels act as a contributor to background K⁺ current to modulate the cardiac excitability in the embryonic heart that expresses little I_K1.     

Probit analysis of thermal sensation assessments

The probit technique for analysis of subjective assessments of thermal sensation is described. It enables transition temperatures from any selected thermal sensation to the adjacent thermal sensation (e.g. from neutral to warm) to be identified. A transition temperature is defined as that temperature at which the maximum number of people would change their assessment from one thermal sensation to the next. Thus if a seven-point scale of thermal sensation is used, six transition temperatures are possible. Increments between them will not necessarily be identical, as would be assumed in a linear regression analysis. The method has been applied in three studies: laboratory studies by the Kansas State University, field studies in Port Moresby, and field studies in Melbourne. In the first it is shown that men are more thermally tolerant than women, in the second it is shown that in Port Moresby the preferred temperatures of Melanesians are 2°C higher than those of Caucasians and in the third it is suggested that subjects in Melbourne have a slightly lower preferred temperature than predicted by Fanger (1972).