Expression of natural killer receptor alleles at different Ly49 loci occurs independently and is regulated by major histocompatibility complex class I molecules.

Ly49 receptor genes are expressed by subsets of natural killer (NK) cells in an overlapping fashion, accounting for the capacity of NK subsets to attack host cells that have selectively downregulated self-major histocompatibility complex (MHC) class I molecules. It was shown previously that most NK cells express only one or the other allele of a given Ly49 gene, while a smaller population expresses both alleles. However, the methods used to detect monoallelic and biallelic cells were nonquantitative. Here, new allele-specific antibodies were used to provide the first quantitative examination of biallelic and monoallelic expression of Ly49A and Ly49G2. The results demonstrate conclusively that most Ly49A(+) and Ly49G2(+) NK cells express the corresponding gene in a monoallelic fashion, with a smaller subset expressing both alleles. Unexpectedly, biallelic Ly49A(+) NK cells were more numerous than predicted by completely independent allelic expression, suggesting some heterogeneity among NK progenitors in the potential to express a given Ly49 gene. The data also show that cells expressing one allele of Ly49G2 may express Ly49A from the same or opposite chromosome with equal likelihood, indicating that the expressed allele is chosen independently for different Ly49 genes. Finally, the data demonstrate that biallelic expression of Ly49A or Ly49G2 occurs least frequently in mice that express ligands for these receptors (H-2(d) mice), and most frequently in class I-deficient mice. Thus, biallelic expression of Ly49 genes is regulated by interactions of NK cell progenitors with MHC class I molecules

A putative proline-rich protein of B. napus

Proline-rich proteins are among the major protein components of plant cell walls. So far, two different proline-rich cell wall proteins have been described in Brassica napus. This paper reports a study on expression and sequence analysis of a novel class of a proline-rich putative protein, tentatively designated Ae4. The largest ORF of Ae4 encodes 166 amino acid residues without the start and stop codons. Ae4 is a partial length cDNA. The Ae4 gene expression was investigated and the results demonstrate that it accumulates in all vegetative tissues tested as well as in the embryogenic culture of Brassica napus. However, expression of Ae4 was undetectable in the non-embryogenic and cytokinin-treated embryogenic tissues. These results indicate that the Ae4 gene might play a role in somatic embryo formation

Molecular characterization of Dg3, a cDNA that encodes a novel lipid transfer protein in Brassica napus

In this study, we have analysed the sequence of Dg3 clone using bioinformatic tools, determined copy number of this transcript in the genome of B. napus and expression levels at various tissues/organ. The cDNA contained 307-base pair open reading frame encoding 102 amino acid residues, 60-base pair 5`-untranslated region and 127-base pair 3`-untranslated region. The predicted mature protein has a molecular weight of 9.2 kDa and is acidic, with a predicted isoelectric point (pI) of 6.2. The Dg3 sequence has all the conserved structural characteristics of plant LTPs and showed highest homology to LTPs from other plant species. The transcripts of Dg3 were detected in all tested tissues but highest expression was in siliques and in vitro embryogenic cultures. Possible roles of Dg3 during somatic embryogenesis and normal plant development are discussed

Distribution of arabinogalactan protein (AGP) epitopes on the anther derived embryoid cultures of Brassica napus

The anther-derived embryoid cultures of Brassica napus is stably embryogenic and has an extracellular matrix (ECM) layer covering the surface of the developing embryoids. In this study, the distribution of arabinogalactan protein (AGP) epitopes in the ECM layer and the embryogenic tissue of winter oilseed rape were investigated by immuno-labelling with anti-AGP monoclonal antibodies (mAb JIM4, JIM8, and JIM 13). There was no labelling by the JIM4 and JIM8 mAbs in the ECM layer, unlike what was reported in other plant species. JIM 13 epitope is developmentally regulated because it was only present in the ECM layer of the mature embryogenic tissue. These observations indicate a possible variability in the AGP epitopes present in the ECM layer among the different plant species. JIM8 and JIM 13 epitopes were found in some epidermal cells of embryogenic tissue, but not in the non-embryogenic tissue, implying that AGPs might have a specific role in embryogenic competency or determining the cell fate of the B. napus embryogenic cell

Extracellular localization of napin in the embryogenic tissues of Brassica napus spp. oleifera

Napin, a storage protein, has been reported to be transcribed abundantly during the pre-embryogenic stage and associated with the induction of Brassica napus secondary embryogenesis. In this study, we studied the distribution pattern of napin in the winter oilseed rape embryogenic tissue in comparison to that of the non-embryogenic tissue using the indirect immunofluorescence localisation coupled with the ultrastructural immunogold labelling techniques. Immunolocalisation studies revealed that the extracellular matrix layer outside the outer epidermal cell wall of B. napus embryogenic tissues contained napin. This is the first study to report the extracellular localisation of napin. In addition, we have also further characterised the expression pattern of Eg1 that encodes for napin in the B. napus embryogenic tissue

Documentary Linguistics and Computational Linguistics: A response to Brooks

National Foreign Language Resource Cente

About the role of 2D screening in High Temperature Superconductivity

The 2D screening is investigated in a simple single band square tight-binding model which qualitatively resembles the known electronic structure in high temperature superconductors. The Coulomb kernel for the two particle Bethe-Salpeter equation in the single loop (RPA) approximation for the polarization can be evaluated in a strong tight binding limit. The results indicate an intense screening of the Coulomb repulsion between the particles, which becomes stronger and anisotropic when the Fermi level approach half filling (or equivalently, when the Fermi surface approach the Van Hove singularities) and rapidly decreases away it. The effect is also more pronounced for quasi-momenta regions near the corners of the Brillouin cell, which correspond to dual spatial distances of the order few unit cells. Therefore, a possible mechanism is identified which could explain the existence of extremely small Cooper pairs in these materials, as bounded anisotropic composites joined by residual super-exchange or phonon interactions.Comment: 16 pages, 4 figures, presented in the " Conference on Strongly Interacting Systems at the Nanoscale", ICTP, Trieste, Italy (8-12 August 2005

Gender and cultural differences in school motivation

The purpose of this research was to explore gender differences and cultural differences in school motivation among students from eight culturally diverse groups from Western and non-Western societies. The selected groups come from Hong Kong, the Philippines, Singapore, Australia, the Netherlands, and Qatar. More than 10,000 secondary school students reported their mastery, performance, social, and extrinsic motivation. Results showed (very) small to moderately large gender differences, which were largely in line with prior research in Western societies. Moreover, significant differences in school motivation across the eight cultural groups were found, however, only the Qatari sample strongly deviated from the other samples. In all cultural groups, females had slightly higher scores on mastery motivation and social motivation (except for Qatari students), and in several Western and non-Western samples, males had slightly higher scores on performance motivation. Gender differences in extrinsic motivation were less straightforward

Surface acoustic wave stimulated Brillouin scattering in thin-film lithium niobate waveguides

We report the first-ever experimental observation of backward stimulated Brillouin scattering (SBS) in thin-film lithium niobate (TFLN) waveguides. The peak Brillouin gain coefficient of the z-cut LN waveguide with a crystal rotation angle of 20$^{\circ}$ is as high as 84.9m$^{-1}$W$^{-1}$, facilitated by surface acoustic waves (SAW) at 8.06GHz

Flip Graphs of Degree-Bounded (Pseudo-)Triangulations

We study flip graphs of triangulations whose maximum vertex degree is bounded by a constant $k$. In particular, we consider triangulations of sets of $n$ points in convex position in the plane and prove that their flip graph is connected if and only if $k > 6$; the diameter of the flip graph is $O(n^2)$. We also show that, for general point sets, flip graphs of pointed pseudo-triangulations can be disconnected for $k \leq 9$, and flip graphs of triangulations can be disconnected for any $k$. Additionally, we consider a relaxed version of the original problem. We allow the violation of the degree bound $k$ by a small constant. Any two triangulations with maximum degree at most $k$ of a convex point set are connected in the flip graph by a path of length $O(n \log n)$, where every intermediate triangulation has maximum degree at most $k+4$.Comment: 13 pages, 12 figures, acknowledgments update