Genetics of stem volume, stem form, and branch characteristics in sapling Noble fir

Noble fir (Abies procera Rehd.), an important conifer in the Pacific Northwest, is valuable for timber, Christmas trees, and greenery products. A number of tree improvement programs emphasizing genetic improvement of bole volume growth are underway in this species. The purpose of this study was to estimate genetic control of stem volume, stem form, and branching traits and the genetic interrelationships among these traits in sapling Noble fir eleven years old. Trees from sixty families growing on three progeny test sites in southwest Washington were utilized. Large family x site interactions were evident when all 3 sites were analyzed together, consequently sites were grouped into low (two sites) and high (one site) planting environments for genetic parameter estimation. Significant amounts of family variation were present in at east one environment for ten of the thirteen traits examined. Mean estimates of individual narrow-sense heritabilities were low to moderate for all traits: volume (.22), height (.31), stem diameter (.21), taper (.09), stem sinuosity (.33), branch diameter ratio (.15), branch length ratio (.49), branch angle (.23), branch number (.10), and knot index (.13). Family heritabilities for size traits were often twice as large as individual heritabilities. Genetic correlations were strong and positive among stem growth traits (>.73), between branch length ratio and branch diameter ratio (.75), and between sinuosity and stem growth traits (.49-.54). With the exception of branch number, genetic correlations between branch traits and stem growth were weak or favorable, such that selection for stem volume should little or no negative impact on branching characteristics. Amounts of genetic and phenotypic variation present indicate moderate gains from selection and breeding programs are possible for stem growth, while lesser gains can be achieved for stem form and branching traits

Isozyme variation in Sisyrinchium sarmentosum (Iridaceae)

Sisyrinchium sarmentosum is a rare, duodecaploid plant endemic to the Mt. Adams and Mt. Hood areas of Washington and Oregon. Isozyme variation in six Washington populations was assessed to infer genetic variation in this species. Five of the six sampled populations were monomorphic for the sixteen enzymes surveyed, although at one putative locus one of these populations was monomorphic for an enzyme band pattern not seen in any other population. The sixth population had low levels of variation in two enzymes. This low level of variation has often been observed in very rare species and high polyploids. Apparently, the species has recently gone through a bottleneck, perhaps during its recent origin as a species

Acellular bi-layer silk fibroin scaffolds support functional tissue regeneration in a rat model of onlay esophagoplasty

Surgical management of long-gap esophageal defects with autologous gastrointestinal tissues is frequently associated with adverse complications including organ dysmotility, dysphagia, and donor site morbidity. In order to develop alternative graft options, bi-layer silk fibroin (SF) scaffolds were investigated for their potential to support functional tissue regeneration in a rodent model of esophageal repair. Onlay esophagoplasty was performed with SF matrices (N=40) in adult rats for up to 2 m of implantation. Parallel groups consisted of animals implanted with small intestinal submucosa (SIS) scaffolds (N=22) or sham controls receiving esophagotomy alone (N=20). Sham controls exhibited a 100% survival rate while rats implanted with SF and SIS scaffolds displayed respective survival rates of 93% and 91% prior to scheduled euthanasia. Animals in each experimental group were capable of solid food consumption following a 3 d post-op liquid diet and demonstrated similar degrees of weight gain throughout the study period. End-point μ-computed tomography at 2 m post-op revealed no evidence of contrast extravasation, fistulas, strictures, or diverticula in any of the implant groups. Ex vivo tissue bath studies demonstrated that reconstructed esophageal conduits supported by both SF and SIS scaffolds displayed contractile responses to carbachol, KCl and electrical field stimulation while isoproterenol produced tissue relaxation. Histological (Masson’s trichrome and hematoxylin and eosin) and immunohistochemical (IHC) evaluations demonstrated both implant groups produced de novo formation of skeletal and smooth muscle bundles positive for contractile protein expression [fast myosin heavy chain (MY32) and α-smooth muscle actin (α-SMA)] within the graft site. However, SF matrices promoted a significant 4-fold increase in MY32+ skeletal muscle and a 2-fold gain in α-SMA+ smooth muscle in comparison to the SIS cohort as determined by histomorphometric analyses. A stratified squamous, keratinized epithelium expressing cytokeratin 5 and involucrin proteins was also present at 2 m post-op in all experimental groups. De novo innervation and vascularization were evident in all regenerated tissues indicated by the presence of synaptophysin (SYP38)+ boutons and vessels lined with CD31 expressing endothelial cells. In respect to SIS, the SF group supported a significant 4-fold increase in the density of SYP38+ boutons within the implant region. Evaluation of host tissue responses revealed that SIS matrices elicited chronic inflammatory reactions and severe fibrosis throughout the neotissues, in contrast to SF scaffolds. The results of this study demonstrate that bi-layer SF scaffolds represent promising biomaterials for onlay esophagoplasty, capable of producing superior regenerative outcomes in comparison to conventional SIS scaffolds

Are Expansions Cost Effective for Stock Exchanges? A Global Perspective

This paper investigates the existence and extent of economies of scale and scope among stock exchanges.Evidence from 38 exchanges in 32 countries and 4 continents around the world for the years 1989-1998 indicates the existence of significant economies of scale and scope.The degree of such economies however differs by size of exchange and region.The largest stock exchanges show an increasing trend of cost effectiveness.Exchanges in North America and Europe report substantially larger economies of scale than those in the Asia-Pacific regions