Cumulate causes for the low contents of sulfide-loving elements in the continental crust

Despite the economic importance of chalcophile (sulfide-loving) and siderophile (metal-loving) elements (CSEs), it is unclear how they become enriched or depleted in the continental crust, compared with the oceanic crust. This is due in part to our limited understanding of the partitioning behaviour of the CSEs. Here I compile compositional data for mid-ocean ridge basalts and subduction-related volcanic rocks. I show that the mantle-derived melts that contribute to oceanic and continental crust formation rarely avoid sulfide saturation during cooling in the crust and, on average, subduction-zone magmas fractionate sulfide at the base of the continental crust prior to ascent. Differentiation of mantle-derived melts enriches lower crustal sulfide- and silicate-bearing cumulates in some CSEs compared with the upper crust. This storage predisposes the cumulate-hosted compatible CSEs (such as Cu and Au) to be recycled back into the mantle during subduction and delamination, resulting in their low contents in the bulk continental crust and potentially contributing to the scarcity of ore deposits in the upper continental crust. By contrast, differentiation causes the upper oceanic and continental crust to become enriched in incompatible CSEs (such as W) compared with the lower oceanic and continental crust. Consequently, incompatible CSEs are predisposed to become enriched in subduction-zone magmas that contribute to continental crust formation and are less susceptible to removal from the continental crust via delamination compared with the compatible CSEs

DRE-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers

Nonlinear parabolized stability equations and secondary instability analyses are used to provide a computational assessment of the potential use of the discrete roughness elements (DRE) technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural laminar flow airfoil with a leading-edge sweep angle of 34.6deg, free-stream Mach number of 0.75 and chord Reynolds numbers of 17 x 10(exp 6), 24 x 10(exp 6) and 30 x 10(exp 6) suggest that DRE could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small wavelength stationary crossflow disturbances (i.e., DRE) also suppresses the growth of most amplified traveling crossflow disturbances

Effect of different rhBMP-2 and TG-VEGF ratios on the formation of heterotopic bone and neovessels

Bioengineered bone substitutes might represent alternatives to autologous bone grafts in medically compromised patients due to reduced operation time and comorbidity. Due to the lack of an inherent vascular system their dimension is limited to the size of critical bone size defect. To overcome this shortcoming, the experiment tried to create heterotopic bone around vessels. In vivo, a two-component fibrin and thrombin gel containing recombinant bone morphogenic protein (rhBMP-2) and transglutamate vascular endothelial growth factor (TG-VEGF) in different ratios, respectively, was injected into a dimensionally stable membrane tube, wrapped around the femoral vessel bundle in twelve New Zealand white rabbits. Sacrifice occurred eight weeks postoperatively. Microcomputed tomography of the specimens showed significantly increased bone volume in the rhBMP-2 to TG-VEGF ratio of 10 to 1 group. Histology showed new bone formation in close proximity to the vessel bundle. Immunohistochemistry detected increased angiogenesis within the newly formed bone in the rhBMP-2 to TG-VEGF ratios of 3 to 1 and 5 to 1. Heterotopic bone was engineered in vivo around vessels using different rhBMP-2 and TG-VEGF ratios in a fibrin matrix injected into a dimensionally stable membrane tube which prevented direct contact with skeletal muscles.published_or_final_versio

QTL analysis of production traits on SSC3 in a Large White×Meishan pig resource family

In order to locate the genetic regions that are responsible for economically important traits, a resource population was established by crossing Large White boars and Meishan sows. Phenotypic data of a total of 287 F2 offspring were collected from 1998 to 2000 and QTL analysis conducted using nine microsatellites on Sus scrofa chromosome 3 (SSC3). Least square regression interval mapping revealed two significant QTL effects on dressing percentage and moisture in m. longissimus dorsi, respectively. They were located at 136 cM and 22 cM in the genetic linkage map, near the marker Sw349 and Swr1637, respectively. QTL for dressing percentage had an additive effect of -1.035 ± 0.296% and a dominance effect of 1.056 ± 0.481%, and the explained phenotypic variance was 15.9%. The additive and dominance effects of QTL for moisture in m. longissimus dorsi were -0.025 ± 0.076% and 0.365 ± 0.101%, respectively, indicating that this QTL seemed to be significantly dominant in action. The present study confirms previously identified QTL and provides an important step in the search for the actual major genes involved in the traits of economic interest. South African Journal of Animal Science Vol. 36(2) 2006: 122-12

Polymorphism of the pig-implantation protein 3 (preis3) gene and its association with litter size traits

The pre-implantation protein 3 (prei3), which might play a role in pre-implantation embryogenesis, is one of the promising candidate genes for litter size traits in pigs. In this study, a single nucleotide polymorphism (SNP: T802G) in intron 6 of the pig prei3 gene was detected and a genotyping assay for this SNP was developed. An association study for this SNP with litter size was performed in two independent populations. One population consisted of crossbred sows derived from Landrace, Large White, Chinese Tongcheng and/or Chinese Meishan (Line DIV). The other population constituted of crossbred animals derived from Chinese Qingping and Duroc (QD). Statistical analysis demonstrated that, in first parity, 2.65 more piglets were born and 3.82 more piglets were born alive in sows in Line DIV with genotype TT than with genotype GG. For second and subsequent litters, in both the DIV and QD lines there were significant differences in the number of piglets born alive between TG and GG sows, with the TG sows producing more piglets born alive than the GG sows. These results suggest that the prei3 SNP is significantly associated with litter size in the two populations studied, and could be useful in selection for increasing litter size in pigs. Further investigations on more pig populations with large sample sizes are needed to confirm this. South African Journal of Animal Science Vol. 36(3) 2006: 209-21

RNA interference of argininosuccinate synthetase restores sensitivity to recombinant arginine deiminase (rADI) in resistant cancer cells

Background Sensitivity of cancer cells to recombinant arginine deiminase (rADI) depends on expression of argininosuccinate synthetase (AS), a rate- limiting enzyme in synthesis of arginine from citrulline. To understand the efficiency of RNA interfering of AS in sensitizing the resistant cancer cells to rADI, the down regulation of AS transiently and permanently were performed in vitro, respectively. Methods We studied the use of down-regulation of this enzyme by RNA interference in three human cancer cell lines (A375, HeLa, and MCF-7) as a way to restore sensitivity to rADI in resistant cells. The expression of AS at levels of mRNA and protein was determined to understand the effect of RNA interference. Cell viability, cell cycle, and possible mechanism of the restore sensitivity of AS RNA interference in rADI treated cancer cells were evaluated. Results AS DNA was present in all cancer cell lines studied, however, the expression of this enzyme at the mRNA and protein level was different. In two rADI-resistant cell lines, one with endogenous AS expression (MCF-7 cells) and one with induced AS expression (HeLa cells), AS small interference RNA (siRNA) inhibited 37-46% of the expression of AS in MCF- 7 cells. ASsiRNA did not affect cell viability in MCF-7 which may be due to the certain amount of residual AS protein. In contrast, ASsiRNA down- regulated almost all AS expression in HeLa cells and caused cell death after rADI treatment. Permanently down-regulated AS expression by short hairpin RNA (shRNA) made MCF-7 cells become sensitive to rADI via the inhibition of 4E-BP1-regulated mTOR signaling pathway. Conclusions Our results demonstrate that rADI-resistance can be altered via AS RNA interference. Although transient enzyme down- regulation (siRNA) did not affect cell viability in MCF-7 cells, permanent down- regulation (shRNA) overcame the problem of rADI-resistance due to the more efficiency in AS silencing