Lamina-specific localization of silicon accumulation in two broadleaf tree species

Journal of Plant Research - Silicon (Si) accumulation differs greatly among plant species, as revealed by an increasing number of studies reporting whole-leaf Si concentration for a wide range of...     

Efficient production of IGG human monoclonal antibodies by lymphocytes stimulated by lipopolysaccharide,pokeweed mitogen,and interleukin 4

Summary Extensive screening of the mitogens lipopolysaccharide (LPS), pokeweed mitogen (PWM), andStaphylococcus aureus Cowan I (SAC I), alone and in combination and with and without interleukin (IL) was performed forin vitro activation of regional lymph node lymphocytes from lung cancer patients for the production of human IgG, IgM, and IgA. As assessed by electrofusion of the lymphocytes following their exposure to these agents with mouse myeloma cells and incubation of the fused hybridoma, a remarkable stimulatory effect was shown by LPS and particularly by LPS plus IL-4, which was substantially greater than that of either SAC I or PWM with or without various IL. Optimization studies indicated that the addition of PWM to LPS and IL-4 in the culture medium further stimulated the human antibody (Ab) production, and that the optimal formulation for stimulations of human IgG production was a culture medium containing 20 μg/ml of LPS, 1/500 of PWM, and 100 u/ml of IL-4.     

Formation of bioorganic compounds in aqueous solution induced by flames

Flames of flammable gases, when blown against a surface of an aqueous solution of organic compounds, were found to induce oxidation as well as other reactions in the solution. This reaction would be regarded as a new model for formation of bioorganic molecules in the primitive hydrosphere exposed to some radical-containing atmosphere.     

The RNA-binding protein Puf5 and the HMGB protein Ixr1 contribute to cell cycle progression through the regulation of cell cycle-specific expression of CLB1 in Saccharomyces cerevisiae

Puf5, a Puf-family RNA-binding protein, binds to 3´ untranslated region of target mRNAs and negatively regulates their expression in Saccharomyces cerevisiae. The puf5Δ mutant shows pleiotropic phenotypes including a weakened cell wall, a temperature-sensitive growth, and a shorter lifespan. To further analyze a role of Puf5 in cell growth, we searched for a multicopy suppressor of the temperature-sensitive growth of the puf5Δ mutant in this study. We found that overexpression of CLB2 encoding B-type cyclin suppressed the temperature-sensitive growth of the puf5Δ mutant. The puf5Δ clb2Δ double mutant displayed a severe growth defect, suggesting that Puf5 positively regulates the expression of a redundant factor with Clb2 in cell cycle progression. We found that expression of CLB1 encoding a redundant B-type cyclin was decreased in the puf5Δ mutant, and that this decrease of the CLB1 expression contributed to the growth defect of the puf5Δ clb2Δ double mutant. Since Puf5 is a negative regulator of the gene expression, we hypothesized that Puf5 negatively regulates the expression of a factor that represses CLB1 expression. We found such a repressor, Ixr1, which is an HMGB (High Mobility Group box B) protein. Deletion of IXR1 restored the decreased expression of CLB1 caused by the puf5Δ mutation and suppressed the growth defect of the puf5Δ clb2Δ double mutant. The expression of IXR1 was negatively regulated by Puf5 in an IXR1 3´ UTR-dependent manner. Our results suggest that IXR1 mRNA is a physiologically important target of Puf5, and that Puf5 and Ixr1 contribute to the cell cycle progression through the regulation of the cell cycle-specific expression of CLB1.     

Image-based parameter inference for epithelial mechanics

Measuring mechanical parameters in tissues, such as the elastic modulus of cell-cell junctions, is essential to decipher the mechanical control of morphogenesis. However, their in vivo measurement is technically challenging. Here, we formulated an image-based statistical approach to estimate the mechanical parameters of epithelial cells. Candidate mechanical models are constructed based on force-cell shape correlations obtained from image data. Substitution of the model functions into force-balance equations at the cell vertex leads to an equation with respect to the parameters of the model, by which one can estimate the parameter values using a least-squares method. A test using synthetic data confirmed the accuracy of parameter estimation and model selection. By applying this method to Drosophila epithelial tissues, we found that the magnitude and orientation of feedback between the junction tension and shrinkage, which are determined by the spring constant of the junction, were correlated with the elevation of tension and myosin-II on shrinking junctions during cell rearrangement. Further, this method clarified how alterations in tissue polarity and stretching affect the anisotropy in tension parameters. Thus, our method provides a novel approach to uncovering the mechanisms governing epithelial morphogenesis.     

ARHGAP18, a GTPase-activating protein for RhoA, controls cell shape, spreading, and motility

Rho GTPases are molecular switches that transmit biochemical signals in response to extracellular stimuli to elicit changes in the actin cytoskeleton. Rho GTPases cycle between an active, GTP-bound state and an inactive, GDP-bound state. These states are regulated by two distinct families of proteins-guanine nucleotide exchange factors and GTPase-activating proteins (GAPs). We studied the role of a previously uncharacterized GAP, ARHGAP18 (MacGAP). Overexpression of ARHGAP18 suppressed the activity of RhoA and disrupted stress fiber formation. Conversely, silencing of ARHGAP18 by small interfering RNA transfection-enhanced stress fiber formation and induced rounding of cells. We examined the role of ARHGAP18 in cell spreading and migration. Immunofluorescence analysis revealed that ARHGAP18 was localized to the leading edge during cell spreading and migration. ARHGAP18-knockdown cells showed impaired spreading, premature formation of stress fibers, and sustained activation of RhoA upon cell attachment. In addition, knockdown and overexpression of ARHGAP18 resulted in the inhibition and promotion of cell migration, respectively. Furthermore, ARHGAP18 was required for the polarization of cells for migration. Our results define ARHGAP18 as one of the crucial factors for the regulation of RhoA for the control of cell shape, spreading, and migration.     

Functional conservation between fission yeast moc1/sds23 and its two orthologs, budding yeast SDS23 and SDS24, and phenotypic differences in their disruptants

The moc1/sds23 gene was isolated to induce sexual development of a sterile strain due to overexpression of adenylate cyclase in Schizosaccharomyces pombe. Here, we studied the functional conservation between moc1/sds23 and its two orthologs SDS23 and SDS24 in Saccharomyces cerevisiae. We observed that the temperature sensitivity, salt tolerance, cell morphology, and sterility of the Deltamoc1 mutant in S. pombe were recovered by expressing either S. cerevisiae SDS23 or SDS24. We found that deletion of both SDS23 and SDS24 resulted in the production of a large vacuole that was reversed by the expression of S. pombe moc1/sds23. In these ways we found that S. pombe Moc1/Sds23 and S. cerevisiae SDS23p or SDS24p are functional homologs. In addition we found that the Deltasds23 Deltasds24 diploid strain reduces cell separation in forming pseudohyphal-like growth in S. cerevisiae. Thus S. pombe moc1/sds23 and S. cerevisiae SDS23 or SDS24 are interchangeable with each other, but their disruptants are phenotypically dissimilar.     

Functionality of the TOL plasmid under varying environmental conditions following conjugal transfer

Conjugation of catabolic plasmids in contaminated environments is a naturally occurring horizontal gene transfer phenomenon, which could be utilized in genetic bioaugmentation. The potentially important parameters for genetic bioaugmentation include gene regulation of transferred catabolic plasmids that may be controlled by the genetic characteristics of transconjugants as well as environmental conditions that may alter the expression of the contaminant-degrading phenotype. This study showed that both genomic guanine–cytosine contents and phylogenetic characteristics of transconjugants were important in controlling the phenotype functionality of the TOL plasmid. These genetic characteristics had no apparent impact on the stability of the TOL plasmid, which was observed to be highly variable among strains. Within the environmental conditions tested, the addition of glucose resulted in the largest enhancement of the activities of enzymes encoded by the TOL plasmid in all transconjugant strains. Glucose (1 g/L) enhanced the phenotype functionality by up to 16.4 (±2.22), 30.8 (±7.03), and 90.8 (±4.56)-fold in toluene degradation rates, catechol 2,3-dioxygenase enzymatic activities, and xylE gene expression, respectively. These results suggest that genetic limitations of the expression of horizontally acquired genes may be overcome by the presence of alternate carbon substrates. Such observations may be utilized in improving the effectiveness of genetic bioaugmentation.     

Microglial cell origin and phenotypes in health and disease

Microglia - resident myeloid-lineage cells in the brain and the spinal cord parenchyma - function in the maintenance of normal tissue homeostasis. Microglia also act as sentinels of infection and injury, and participate in both innate and adaptive immune responses in the central nervous system. Microglia can become activated and/or dysregulated in the context of neurodegenerative disease and cancer, and thereby contribute to disease severity. Here, we discuss recent studies that provide new insights into the origin and phenotypes of microglia in health and disease.