The Early Neural Plate Rules over the Mesoderm

AbstractIn this issue of Developmental Cell, Richard Harland and colleagues describe evidence that an inductive interaction between the neural plate and the paraxial mesoderm regulates somite development and somite size

Nearly Finitary Matroids

In this thesis, we study nearly finitary matroids by introducing new definitions and prove various properties of nearly finitary matroids. In 2010, an axiom system for infinite matroids was proposed by Bruhn et al. We use this axiom system for this thesis. In Chapter 2, we summarize our main results after reviewing historical background and motivation. In Chapter 3, we define a notion of spectrum for matroids. Moreover, we show that the spectrum of a nearly finitary matroid can be larger than any fixed finite size. We also give an example of a matroid with infinitely large spectrum that is not nearly finitary. Assuming the existence of a single matroid that is nearly finitary but not $k$-nearly finitary, we construct classes of matroids that are nearly finitary but not $k$-nearly finitary. We also show that finite rank matroids are unionable. In Chapter 4, we will introduce a notion of near finitarization. We also give an example of a nearly finitary independence system that is not $k$-nearly finitary. This independence system is not a matroid. In Chapter 5, we will talk about Psi-matroids and introduce a possible generalization. Moreover, we study these new matroids to search for an example of a nearly finitary matroid that is not $k$-nearly finitary. We have not yet found such an example. In Chapter 6, we will discuss thin sums matroids and consider our problem restricted to this class of matroids. Our results are motivated by the open problem concerning whether every nearly finitary matroid is $k$-nearly finitary for some $k$.Comment: PhD Thesis, UC Davis (2018

Inheritance and Characterization of Strong Resistance to Phosphine in Sitophilus oryzae (L.)

Sitophilus oryzae (Linnaeus) is a major pest of stored grain across Southeast Asia and is of increasing concern in other regions due to the advent of strong resistance to phosphine, the fumigant used to protect stored grain from pest insects. We investigated the inheritance of genes controlling resistance to phosphine in a strongly resistant S. oryzae strain (NNSO7525) collected in Australia and find that the trait is autosomally inherited and incompletely recessive with a degree of dominance of -0.66. The strongly resistant strain has an LC50 52 times greater than a susceptible reference strain (LS2) and 9 times greater than a weakly resistant strain (QSO335). Analysis of F2 and backcross progeny indicates that two or more genes are responsible for strong resistance, and that one of these genes, designated So-rph1 , not only contributes to strong resistance, but is also responsible for the weak resistance phenotype of strain QSO335. These results demonstrate that the genetic mechanism of phosphine resistance in S. oryzae is similar to that of other stored product insect pests. A unique observation is that a subset of the progeny of an F1 backcross generation are more strongly resistant to phosphine than the parental strongly resistant strain, which may be caused by multiple alleles of one of the resistance genes

Retarded Postimplantation Development of X0 Mouse Embryos: Impact of the Parental Origin of the Monosomic X Chromosome

AbstractAbout 12–17% of the embryos obtained by mating mice carrying the In(X)1H orPafmutations are of the 39,X (X0) genotype. Depending on the mutant mice used for mating, the monosomic X chromosome can be inherited from the paternal (XP) or the maternal (XM) parent. The XP0 embryos display developmental retardation at gastrulation and early organogenesis. XP0 embryos also display poor development of the ectoplacental cone, which is significantly smaller in size and contains fewer trophoblasts than XX siblings. In contrast, XM0 embryos develop normally and are indistinguishable from XX littermates. In both types of X0 embryos, an X-linkedlacZtransgene is expressed in nearly all cells in both the embryonic and the extraembryonic tissues, suggesting that X inactivation does not occur when only one X is present. Of particular significance is the maintenance of an active XPchromosome in the extraembryonic tissues where normally the paternal X chromosome is preferentially inactivated in XX embryos. The differential impact of the inheritance of X chromosomes from different parents on the development of the X0 embryos raises the possibility that the XPis less capable than the XMin providing the appropriate dosage of X-linked activity that is necessary to support normal development of the embryo and the ectoplacental cone. Alternatively, the development of the XP0 embryo may be compromised by the lack of activity of one or several X-linked genes which are expressed only from the maternal X chromosome. Without the activity of these genes, embryonic development may be curtailed even though all other loci on the XPchromosome are actively transcribed

The U.S. versus international ethics codes for accountants: A computerized content analysis

Abstract. This study applies computerized content analysis techniques, including term frequency analysis, readability index, and cosine similarity, to compare the U.S. versus international ethics codes for professional accountants. It reveals and compares new characteristics of these ethics codes. The U.S. ethics code is found to be less readable but more reflective of moral values concerning social order. The international ethics code emphasizes the independence and confidentiality principles, while the U.S. ethics code emphasizes independence and responsibilities. There are more similarities within the U.S. ethics code and within the international ethics code than between these ethics code

The Puf family of RNA-binding proteins in plants: phylogeny, structural modeling, activity and subcellular localization

<p>Abstract</p> <p>Background</p> <p>Puf proteins have important roles in controlling gene expression at the post-transcriptional level by promoting RNA decay and repressing translation. The Pumilio homology domain (PUM-HD) is a conserved region within Puf proteins that binds to RNA with sequence specificity. Although Puf proteins have been well characterized in animal and fungal systems, little is known about the structural and functional characteristics of Puf-like proteins in plants.</p> <p>Results</p> <p>The Arabidopsis and rice genomes code for 26 and 19 Puf-like proteins, respectively, each possessing eight or fewer Puf repeats in their PUM-HD. Key amino acids in the PUM-HD of several of these proteins are conserved with those of animal and fungal homologs, whereas other plant Puf proteins demonstrate extensive variability in these amino acids. Three-dimensional modeling revealed that the predicted structure of this domain in plant Puf proteins provides a suitable surface for binding RNA. Electrophoretic gel mobility shift experiments showed that the Arabidopsis AtPum2 PUM-HD binds with high affinity to BoxB of the Drosophila Nanos Response Element I (NRE1) RNA, whereas a point mutation in the core of the NRE1 resulted in a significant reduction in binding affinity. Transient expression of several of the Arabidopsis Puf proteins as fluorescent protein fusions revealed a dynamic, punctate cytoplasmic pattern of localization for most of these proteins. The presence of predicted nuclear export signals and accumulation of AtPuf proteins in the nucleus after treatment of cells with leptomycin B demonstrated that shuttling of these proteins between the cytosol and nucleus is common among these proteins. In addition to the cytoplasmically enriched AtPum proteins, two AtPum proteins showed nuclear targeting with enrichment in the nucleolus.</p> <p>Conclusions</p> <p>The Puf family of RNA-binding proteins in plants consists of a greater number of members than any other model species studied to date. This, along with the amino acid variability observed within their PUM-HDs, suggests that these proteins may be involved in a wide range of post-transcriptional regulatory events that are important in providing plants with the ability to respond rapidly to changes in environmental conditions and throughout development.</p

Investigating physician acceptance of telemedicine technology: A survey study in Hong Kong

Fast-growing interest in telemedicine and increased investment in its enabling technology have made physician technology acceptance a growing concern for development and management of telemedicine. In this study, we used Theory of Planned Behavior to investigate technology acceptance by physicians who practiced in public tertiary hospitals in Hong Kong. Our data supported the investigated theory, whose explanatory power of physicians' technology acceptance was moderate, however. Overall, physicians showed positive attitudes towards use of telemedicine technology and exhibited moderate intention to use it, particularly for clinical tasks. Furthermore, several implications for development and management of telemedicine can also be drawn from the findings.published_or_final_versio

The Effect of Regulatory Sequence Elements upon the Initiation of DNA Replication of the Minute Virus of Mice

AbstractThe minute virus of mice (MVM) genome is a linear single-stranded length of approximately 5000 nucleotides of DNA with unique terminal palindromic sequences at both ends. The left (3′) hairpin is used to prime the initiation of DNA synthesis on parental single-strand DNA while the right (5′) hairpin or stem-plus-arms structure can also prime the initiation of DNA synthesis during synthesis of dimer and higher oligomers as well as synthesis of progeny single strands. Previous studies have shown that if viral duplex DNA was input into anin vitroDNA replication system using extracts from uninfected HeLa cells, the 5′ end of the molecule was able to form a hairpin and initiate DNA synthesis by DNA polymerase δ (Cossonset al.(1996),Virology216, 258–264). In this study, the effect of the deletion of knowncis-acting genetic elements upon the initiation of DNA replication was studied using a series of MVM mutants with deletions within the 5′ terminal region. Mutants containing deletions of elements A (nucleotides 4489–4636), B (nucleotides 4636–4695), and either one or both of the 65-bp repeats (nucleotides 4720–4785 and 4785–4849) were used as template in thein vitroDNA replication system. When element A was deleted, the efficiency of initiation decreased significantly. Subsequent removal of element B, leaving just the two 65-bp repeats, restored levels of initiation back to those seen in the wild-type genome. In the absence of either A or B both 65-bp repeats were necessary for efficient initiation, and removal of one of these repeats caused a decrease in efficiency. Thus, element B appeared to have a negative regulatory effect (in the absence of element A), and element A appeared to have a positive regulatory effect, at least in the presence of element B. These data demonstrate, for the first time, a complex interaction between thesecis-acting regulatory elements which can function as both positive or negative regulators in the initiation of MVM DNA replication