Kinetic Monte Carlo simulations of oscillatory shape evolution for electromigration-driven islands

The shape evolution of two-dimensional islands under electromigration-driven periphery diffusion is studied by kinetic Monte Carlo (KMC) simulations and continuum theory. The energetics of the KMC model is adapted to the Cu(100) surface, and the continuum model is matched to the KMC model by a suitably parametrized choice of the orientation-dependent step stiffness and step atom mobility. At 700 K shape oscillations predicted by continuum theory are quantitatively verified by the KMC simulations, while at 500 K qualitative differences between the two modeling approaches are found.Comment: 7 pages, 6 figure

The species composition of Antarctic phytoplankton interpreted in terms of Tilman's competition theory

An attempt was made, to test for the impact of resource competition on Antarctic marine phytoplankton. According to theory, species composition near competitive equilibrium should be determined by the ratios of limiting resources. Enrichment bioassays identified silicon and nitrogen as limiting nutrients for some of the most important phytoplankton species during early austral summer in the region near the Antarctic Peninsula. Together with the generally acknowledged limiting resource light, this gave three meaningful ratios of essential resources (Si:N, Si:light, N:light) and one ratio of substitutable resources (NO sub(3):NH sub(4)). Phytoplankton species assemblages were found to be well separated by the ratios of the essential resources and by mixing depth

Protocadherin 11X/Y a human-specific gene pair: an immunohistochemical survey of fetal and adult brains

Protocadherins 11X and 11Y are cell adhesion molecules of the δ1-protocadherin family. Pcdh11X is present throughout the mammalian radiation; however, 6 million years ago (MYA), a reduplicative translocation of the Xq21.3 block onto what is now human Yp11 created the Homo sapiens-specific PCDH11Y. Therefore, modern human females express PCDH11X whereas males express both PCDH11X and PCDH11Y. PCDH11X/Y has been subject to accelerated evolution resulting in human-specific changes to both proteins, most notably 2 cysteine substitutions in the PCDH11X ectodomain that may alter binding characteristics. The PCDH11X/Y gene pair is postulated to be critical to aspects of human brain evolution related to the neural correlates of language. Therefore, we raised antibodies to investigate the temporal and spatial expression of PCDH11X/Y in cortical and sub-cortical areas of the human fetal brain between 12 and 34 postconceptional weeks. We then used the antibodies to determine if this expression was consistent in a series of adult brains. PCDH11X/Y immunoreactivity was detectable at all developmental stages. Strong expression was detected in the fetal neocortex, ganglionic eminences, cerebellum, and inferior olive. In the adult brain, the cerebral cortex, hippocampal formation, and cerebellum were strongly immunoreactive, with expression also detectable in the brainstem

EXAMINING THE IMPACT OF APPROACH AND EXIT PHASE STRATEGIES ON CHANGE OF DIRECTION PERFORMANCE: A NOVEL METHODOLOGY

This study used new insole pressure technology to examine how movement strategies during approach and exit phases affect change of direction (COD) times. Participants (n=26) wore NURVV smart insoles and performed 90˚ cuts off each leg (dominant [Dom] and non-dominant [ND]). Ground contact time (GCT), cadence, centre of pressure, and return to linear sprinting metrics were analysed for four steps about the cut-step. Faster cadence and a more forefoot strike pattern predicted 58% of the variance in Dom side COD ability. ND COD ability was predicted by a faster cadence immediately post-cut and a quicker GCT two steps before the cut-step (66% of variance explained). These findings emphasize the approach phase’s crucial role in COD ability and stress the need to examine multiple steps around the cut-step for a complete understanding of COD mechanisms

Modulation of MicroRNA-194 and cell migration by HER2-targeting trastuzumab in breast cancer

Conceived and designed the experiments: XFL GAC RCB. Performed the experiments: XFL MIA WM RS MSN SZ. Analyzed the data: XFL SR. Contributed reagents/materials/analysis tools: YW GAC. Wrote the paper: XFL RCB.Trastuzumab, a humanized monoclonal antibody directed against the extracellular domain of the HER2 oncoprotein, can effectively target HER2-positive breast cancer through several mechanisms. Although the effects of trastuzumab on cancer cell proliferation, angiogenesis and apoptosis have been investigated in depth, the effect of trastuzumab on microRNA (miRNA) has not been extensively studied. We have performed miRNA microarray profiling before and after trastuzumab treatment in SKBr3 and BT474 human breast cancer cells that overexpress HER2. We found that trastuzumab treatment of SKBr3 cells significantly decreased five miRNAs and increased three others, whereas treatment of BT474 cells significantly decreased two miRNAs and increased nine. The only change in miRNA expression observed in both cell lines following trastuzumab treatment was upregulation of miRNA-194 (miR-194) that was further validated in vitro and in vivo. Forced expression of miR-194 in breast cancer cells that overexpress HER2 produced no effect on apoptosis, modest inhibition of proliferation, significant inhibition of cell migration/invasion in vitro and significant inhibition of xenograft growth in vivo. Conversely, knockdown of miR-194 promoted cell migration. Increased miR-194 expression markedly reduced levels of the cytoskeletal protein talin2 and specifically inhibited luciferase reporter activity of a talin2 wild-type 39-untranslated region, but not that of a mutant reporter, indicating that talin2 is a direct downstream target of miR-194. Trastuzumab treatment inhibited breast cancer cell migration and reduced talin2 expression in vitro and in vivo. Knockdown of talin2 inhibited cell migration/invasion. Knockdown of trastuzumab-induced miR-194 expression with a miR-194 inhibitor compromised trastuzumab-inhibited cell migration in HER2-overexpressing breast cancer cells. Consequently, trastuzumab treatment upregulates miR-194 expression and may exert its cell migration-inhibitory effect through miR-194-mediated downregulation of cytoskeleton protein talin2 in HER2-overexpressing human breast cancer cells.This work was supported by the Anne and Henry Zarrow Foundation, kind gifts from Stuart and Gaye Lynn Zarrow and from Mrs. Delores Wilkenfeld, the Laura and John Arnold Foundation, the RGK Foundation, and the MD Anderson NCI CCSG P30 CA16672. G.A.C. is supported as a Fellow at the University of Texas MD Anderson Research Trust, as a University of Texas System Regents Research Scholar and by the CLL Global Research Foundation

Substantial open-ocean phytoplankton blooms to the north of South Georgia, South Atlantic, during summer

Substantial open-ocean phytoplankton blooms in the Antarctic Zone to the northwest of South Georgia, South Atlantic are described. Chlorophyll a, nutrient and physical oceanography data, collected between 2 and 5 January 1994 and again 1 mo later between 2 and 4 February along a 450 km transect comprising 14 stations, are presented. The transect crossed the Subantarctic and the Polar Front. During the January transect survey, in 2 locations to the south of the Polar Front, average surface mixed-layer chlorophyll a concentrations were >8 and >13 mg m-3, and were associated with silicate, nitrate and phosphate depletions (0.3 and >1.4 mmol m-3 respectively). One of the phytoplankton blooms was associated with the nearby Polar Front, but the origin of a bloom further south, well within the Antarctic Zone, was not clear. Phytoplankton production predicted by nutrient drawdown was far greater than the observed biomass on both surveys. If a common Antarctic Zone origin is accepted for the southern bloom, a decline in biomass of ~2.7 mol C m-2 occurred in the upper 50 m of the water column between the 2 surveys, which cannot be accounted for by zooplankton grazing. If the bloom had originated in Subantarctic water advected to the south of the Polar Front, initial nutrient concentrations would have been lower and consequently predicted production was closer to the observed biomass values. Nevertheless, the area may be one of intense but local carbon export

Human embryonic stem cells passaged using enzymatic methods retain a normal karyotype and express CD30

Human embryonic stem cells (hESCs) are thought to be susceptible to chromosomal rearrangements as a consequence of single cell dissociation. Compared in this study are two methods of dissociation that do not generate single cell suspensions (collagenase and EDTA) with an enzymatic procedure using trypsin combined with the calcium-specific chelator EGTA (TEG), that does generate a single cell suspension, over 10 passages. Cells passaged by single cell dissociation using TEG retained a normal karyotype. However, cells passaged using EDTA, without trypsin, acquired an isochromosome p7 in three replicates of one experiment. In all of the TEG, collagenase and EDTA-treated cultures, cells retained consistent telomere length and potentiality, demonstrating that single cell dissociation can be used to maintain karyotypically and phenotypically normal hESCs. However, competitive genomic hybridization revealed that subkaryotypic deletions and amplifications could accumulate over time, reinforcing that present culture regimes remain suboptimal. In all cultures the cell surface marker CD30, reportedly expressed on embryonal carcinoma but not karyoptically normal ESCs, was expressed on hESCs with both normal and abnormal karyotype, but was upregulated on the latter. © 2008 Mary Ann Liebert, Inc

Bioluminescence imaging of human embryonic stem cells transplanted in vivo in murine and chick models

Research into the behavior, efficacy, and biosafety of stem cells with a view to clinical transplantation requires the development of noninvasive methods for in vivo imaging of cells transplanted into animal models. This is particularly relevant for human embryonic stem cells (hESCs), because transplantation of undifferentiated hESCs leads to tumor formation. The present study aimed to monitor hESCs in real time when injected in vivo. hESCs were stably transfected to express luciferase, and luciferase expression was clearly detected in the undifferentiated and differentiated state. When transfected hESCs were injected into chick embryos, bioluminescence could be detected both ex and in ovo. In the SCID mouse model, undifferentiated hESCs were detectable after injection either into the muscle layer of the peritoneum or the kidney capsule. Tumors became detectable between days 10-30, with approximately a 3 log increase in the luminescence signal by day 75. The growth phase occurred earlier in the kidney capsule and then reached a plateau, whilst tumors in the peritoneal wall grew steadily throughout the period analysed. These results show the widespread utility of bioluminescent for in vivo imaging of hESCs in a variety of model systems for preclinical research into regenerative medicine and cancer biology. © Copyright 2009, Mary Ann Liebert, Inc