Distinct mechanisms triggering glial differentiation in Drosophila thoracic and abdominal neuroblasts 6-4

Neurons and glia are produced in stereotyped patterns after neuroblast cell division during development of the Drosophila central nervous system. The first cell division of thoracic neuroblast 6-4 (NB6-4T) is asymmetric, giving rise to a glial precursor cell and a neuronal precursor cell. In contrast, abdominal NB6-4 (NB6-4A) divides symmetrically to produce two glial cells. To understand the relationship between cell division and glia-neuron cell fate determination, we examined and compared the effects of known cell division mutations on the NB6-4T and NB6-4A lineages. Based on observation of expression of glial fate determination and early glial differentiation genes, the onset of glial differentiation occurred in NB6-4A but not in NB6-4T when both cell cycle progression and cytokinesis were genetically arrested. On the other hand, glial differentiation started in both lineages when cytokinesis was blocked with intact cell cycle progression. These results showed that NB6-4T, but not NB6-4A, requires cell cycle progression for acquisition of glial fate, suggesting that distinct mechanisms trigger glial differentiation in the different lineages.     

The mucin biosynthesis stimulated by epidermal growth factor occurs in surface mucus cells, but not in gland mucus cells, of rat stomach

Although epidermal growth factor (EGF) accelerates gastric mucin biosynthesis, information on whether its activation is limited to the specific mucus-producing cells is lacking. In this paper, we investigated the effects of EGF on mucin biosynthesis and the expression of its receptor in distinct layers of rat gastric mucosa, including the possible participation of nitric oxide (NO). EGF enhanced the incorporation of [3H]glucosamine and [14C]threonine into the mucin in the full-thickness tissues of the gastric mucosa. This stimulation disappeared on the removal treatment of the surface mucosal layer chiefly consisting of surface mucus cells. The EGF-induced increase in [3H]-labeled mucin in the full-thickness mucosa was not suppressed by either NG-nitro-L-arginine (10(-5) M) or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (10(-5) M). The EGF-receptor-mRNA expression was high in the surface mucosal layer but low in the deep and muscle layers of the stomach. These results suggest that EGF-induced stimulation of mucin biosynthesis is limited to the surface mucus cells of the rat gastric mucosa and is independent of the NO pathway.     

Variation of the phytoplankton community across the subtropical convergence zone in the west pacific sector of the southern ocean during early austral Summer 1995/6

Phytoplankton of the Southern Ocean, 140–148°E and 40–53°S, was sampled from early austral summer Nov. 1995 to Dec. 1995 to examine cell abundance, cell volume and biomass (cell carbon) distribution across the fronts. A total of 90 phytoplankton taxa were identified. They were 50 diatoms, 37 dinoflagellates, 2 silicoflagellates, and 1 prymnesiophyte. 73 species were observed from north of the subtropical convergence zone and 71 species from south of the subtropical convergence zone.Pseudonitzschia spp. was the most widely distributed species. Nanoplankton predominated cell number of phytoplankton throughout the stations. The abundance of diatoms was higher than that of dinofiagellates. Total biomass profiles were dependent to microphytoplankton biomass. Maximum cell number and biomass were observed from subsurface layer. Phytoplankton community changed across the subtropical convergence zone and 50–53°S (antarctic convergence zone), and physicoehemical factors seem to controll the distribution.     

Evidence for a site-specific fucosylation of N-linked oligosaccharide of immunoglobulin A1 from normal human serum

Glycopeptides containing the N-linked oligosaccharide from human serum IgA1 were analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS). Two glycopeptides, GP1 and GP2, prepared from the endoproteinase Asp-N digest of the IgA1 heavy chain, were derived from the CH2 domain (N-glycan site at Asn263) and the tailpiece portion (N-glycan site at Asn459), respectively. The structure of the attached sugar chain was deduced from the mass number of the glycopeptide and confirmed by a two-dimensional mapping technique for a pyridylaminated oligosaccharide. GP1 was composed of two major components having a fully galactosylated bianntena sugar chain with or without a bisecting N-acetylglucosamine (GlcNAc) residue. On the other hand, the GP2 fraction corresponded to the glycopeptides having a fully galactosylated and fucosylated bianntena sugar chain partly bearing a bisecting GlcNAc residue. Thus, the site-specific fucosylation of the N-linked oligosaccharide on the tailpiece of the 1 chain became evident for normal human serum IgA1.     

The γ -Tubulin Complex Protein GCP4 Is Required for Organizing Functional Microtubule Arrays in Arabidopsis thaliana

Microtubule (MT) nucleation and organization depend on the evolutionarily conserved protein γ -tubulin, which forms a complex with GCP2-GCP6 (GCP for γ -Tubulin Complex Protein). To date, it is still unclear how GCP4-GCP6 (the non-core GCPs) may be involved in acentrosomal MT nucleation in plant cells. We found that GCP4 was associated with γ -tubulin in vivo in Arabidopsis thaliana. When GCP4 expression was repressed by an artificial microRNA, transgenic plants exhibited phenotypes of dwarfism and reduced organ size. In mitotic cells, it was observed that the γ -tubulin signal associated with the mitotic spindle, and the phragmoplast was depleted when GCP4 was downregulated. Consequently, MTs failed to converge at unified spindle poles, and the bipolar phragmoplast MT array frequently had discrete bundles with extended minus ends, resulting in failed cytokinesis as reflected by cell wall stubs in leaf epidermal cells. In addition, cortical MTs in swollen guard cells and pavement cells of the leaf epidermis became hyperparallel and bundled, which was likely caused by frequent MT nucleation with shallow angles on the wall of extant MTs. Therefore, our results support the notion that GCP4 is an indispensable component for the function of γ -tubulin in MT nucleation and organization in plant cells.     

Parents' Knowledge about Enterobiasis Might Be One of the Most Important Risk Factors for Enterobiasis in Children

To know the prevalence of Enterobius vermicularis infection and what are the most important risk factors, we evaluated the incidence and risk factors of enterobiasis among children attended in kindergartens in Busan metropolitan city, Republic of Korea. A total of 1,674 children from 21 kindergartens in 11 of 16 autonomous districts of Busan were evaluated for E. vermicularis infection by the cellotape anal swab technique. The overall egg-positive rate for E. vermicularis was 10.7% (179/1,674), and the prevalence of enterobiasis in each kindergarten ranged between 0% and 32.4%. There was an increasing tendency of the egg positive rate according to the population density; the higher the population density communities had, the higher egg-positive rate for E. vermicularis was detected (P = 0.001). Among personal hygiene factors involving children, thumb-sucking (P = 0.036) and fingernail-trimming (P = 0.024) were highly associated with enterobiasis. In addition, taking anthelmintic medications against E. vermicularis infection was strongly associated with enterobiasis (P = 0.014). Moreover, parents'' knowledge of enterobiasis was correlated significantly with the incidence of enterobiasis of their children (P = 0.006). In conclusion, we need to consider not only personal hygiene but also parents'' knowledge about enterobiasis as a factor in order to develop new strategies for elimination or to complete reduction of enterobiasis in Korea.     

MODIFIED VACUOLE PHENOTYPE1 Is an Arabidopsis Myrosinase-Associated Protein Involved in Endomembrane Protein Trafficking

We identified an Arabidopsis (Arabidopsis thaliana) ethyl methanesulfonate mutant, modified vacuole phenotype1-1 (mvp1-1), in a fluorescent confocal microscopy screen for plants with mislocalization of a green fluorescent protein-δ tonoplast intrinsic protein fusion. The mvp1-1 mutant displayed static perinuclear aggregates of the reporter protein. mvp1 mutants also exhibited a number of vacuole-related phenotypes, as demonstrated by defects in growth, utilization of stored carbon, gravitropic response, salt sensitivity, and specific susceptibility to the fungal necrotroph Alternaria brassicicola. Similarly, crosses with other endomembrane marker fusions identified mislocalization to aggregate structures, indicating a general defect in protein trafficking. Map-based cloning showed that the mvp1-1 mutation altered a gene encoding a putative myrosinase-associated protein, and glutathione S-transferase pull-down assays demonstrated that MVP1 interacted specifically with the Arabidopsis myrosinase protein, THIOGLUCOSIDE GLUCOHYDROLASE2 (TGG2), but not TGG1. Moreover, the mvp1-1 mutant showed increased nitrile production during glucosinolate hydrolysis, suggesting that MVP1 may play a role in modulation of myrosinase activity. We propose that MVP1 is a myrosinase-associated protein that functions, in part, to correctly localize the myrosinase TGG2 and prevent inappropriate glucosinolate hydrolysis that could generate cytotoxic molecules.The plant endomembrane system is a complex network of subcellular compartments that includes the endoplasmic reticulum (ER), Golgi apparatus, vacuole, plasma membrane, secretory vesicles, and numerous intermediary compartments. Protein trafficking through the endomembrane system requires specific cargo recognition and delivery mechanisms that are mediated by a series of highly specific targeting signals (Surpin and Raikhel, 2004), whose proper recognition is critical for the function of numerous downstream processes, such as floral development (Sohn et al., 2007), gravitropism (Kato et al., 2002; Surpin et al., 2003; Yano et al., 2003), abiotic stress tolerance (Zhu et al., 2002), autophagy (Surpin et al., 2003; Bassham., 2007), pathogen defense (Robatzek, 2007), and turgor pressure and growth (De, 2000).The importance of protein trafficking for plant survival was demonstrated by the identification of the essential Arabidopsis (Arabidopsis thaliana) gene VACUOLELESS1 (VCL1; Rojo et al., 2001). VCL1 was identified as a homolog of Saccharomyces cerevisiae VPS16, which is critical for yeast vacuole biogenesis. Knockouts of yeast VPS16 lack discernible vacuoles but survive despite their severe phenotype. The absence of vacuoles in Arabidopsis vcl1-1 mutants results in embryo lethality (Rojo et al., 2001). The essential nature of trafficking in plants was also demonstrated by insertional mutagenesis of syntaxin genes, where lethality was observed after disruption of single genes in families with highly homologous members (Lukowitz et al., 1996; Sanderfoot et al., 2001). Thus, despite large families of endomembrane components with many homologous genes, many are not redundant in Arabidopsis.Although embryo-lethal mutations provide critical data, it is difficult to obtain additional information. Less severe mutations have proven successful for functional genetics studies of endomembrane trafficking proteins. For example, point mutations in the KATAMARI1/MURUS3 (KAM1/MUR3; Tamura et al., 2005) and KATAMARI2/GRAVITROPISM DEFECTIVE2 (KAM2/GRV2; Tamura et al., 2007; Silady et al., 2008) genes lead to disruption of endomembranes, resulting in the formation of perinuclear aggregates containing organelles. Nonlethal trafficking disruptions have also been generated using chemical genomics, where small molecules were used to perturb trafficking of a soluble cargo protein (Zouhar et al., 2004) and localization of endomembrane markers (Surpin et al., 2005; Robert et al., 2008). Such studies have provided valuable clues about these essential cellular processes.In order to obtain less severe, viable mutants with defects in endomembrane protein trafficking, we previously identified point mutants with defects in localization of a tonoplast reporter protein, GFP:δ-TIP (Avila et al., 2003). Two hundred one putative mutants were grouped into four categories based on the nature of their defects. One unique mutant, cell shape phenotype1, was recently characterized as a trehalose-6-phosphate synthase with roles in regulation of plant architecture, epidermal pavement cell shape, and trichome branching (Chary et al., 2008).Here, we describe an endomembrane trafficking mutant categorized by perinuclear aggregates of GFP:δ-TIP fluorescence (Avila et al., 2003). We refer to this mutant as modified vacuole phenotype1-1 (mvp1-1). At least five endomembrane fusion proteins are partially relocalized to these structures. Positional cloning identified MVP1 as a myrosinase-associated protein (MyAP) localized previously to the tonoplast by proteomics (Carter et al., 2004). mvp1-1 mutants showed reduced endomembrane system functionality, as demonstrated by defects in growth, utilization of stored carbon, gravitropic responsiveness, salt sensitivity, and increased susceptibility to a fungal necrotroph. MVP1 interacted specifically with THIOGLUCOSIDE GLUCOHYDROLASE2 (TGG2), a known myrosinase protein in Arabidopsis, and the mvp1-1 mutation had a significant effect on nitrile production during glucosinolate hydrolysis, suggesting a role in myrosinase function. Furthermore, MVP1 may function in quality control of glucosinolate hydrolysis by contributing to the proper tonoplast localization of TGG2.     

Classification of genus Pseudomonas by MALDI-TOF MS based on ribosomal protein coding in S10-spc-alpha operon at strain level

We have proposed a rapid phylogenetic classification at the strain level by MALDI-TOF MS using ribosomal protein matching profiling. In this study, the S10-spc-alpha operon, encoding half of the ribosomal subunit proteins and highly conserved in eubacterial genomes, was selected for construction of the ribosomal protein database as biomarkers for bacterial identification by MALDI-TOF MS analysis to establish a more reliable phylogenetic classification. Our method revealed that the 14 reliable and reproducible ribosomal subunit proteins with less than m/z 15,000, except for L14, coded in the S10-spc-alpha operon were significantly useful biomarkers for bacterial classification at species and strain levels by MALDI-TOF MS analysis of genus Pseudomonas strains. The obtained phylogenetic tree was consisted with that based on genetic sequence (gyrB). Since S10-spc-alpha operons of genus Pseudomonas strains were sequenced using specific primers designed based on nucleotide sequences of genome-sequenced strains, the ribosomal subunit proteins encoded in S10-spc-alpha operon were suitable biomarkers for construction and correction of the database. MALDI-TOF MS analysis using these 14 selected ribosomal proteins is a rapid, efficient, and versatile bacterial identification method with the validation procedure for the obtained results.