Histochemical and molecular overview of the thymus as site for T-cells development

The thymus represents the primary site for T cell lymphopoiesis, providing a coordinated set for critical factors to induce and support lineage commitment, differentiation and survival of thymus-seeding cells. One irrefutable fact is that the presence of non-lymphoid cells through the thymic parenchyma serves to provide coordinated migration and differentiation of T lymphocytes. Moreover, the link between foetal development and normal anatomy has been stressed in this review. Regarding thymic embryology, its epithelium is derived from the embryonic endodermal layer, with possible contributions from the ectoderm. A series of differentiating steps is essential, each of which must be completed in order to provide the optimum environment for thymic development and function. The second part of this article is focused on thymic T-cell development and differentiation, which is a stepwise process, mediated by a variety of stromal cells in different regions of the organ. It depends strongly on the thymic microenvironment, a cellular network formed by epithelial cells, macrophages, dendritic cells and fibroblasts, that provide the combination of cellular interactions, cytokines and chemokines to induce thymocyte precursors for the generation of functional T cells. The mediators of this process are not well defined but it has been demonstrated that some interactions are under neuroendocrine control. Moreover, some studies pointed out that reciprocal signals from developing T cells also are essential for establishment and maintenance of the thymic microenvironment. Finally, we have also highlighted the heterogeneity of the lymphoid, non-lymphoid components and the multi-phasic steps of thymic differentiation. In conclusion, this review contributes to an understanding of the complex mechanisms in which the foetal and postnatal thymus is involved. This could be a prerequisite for developing new therapies specifically aimed to overcome immunological defects, linked or not-linked to aging.     

Adaptation of endoplasmic reticulum exit sites to acute and chronic increases in cargo load

The biogenesis of endoplasmic reticulum (ER) exit sites (ERES) involves the formation of phosphatidylinositol-4 phosphate (PI4) and Sec16, but it is entirely unknown how ERES adapt to variations in cargo load. Here, we studied acute and chronic adaptive responses of ERES to an increase in cargo load for ER export. The acute response (within minutes) to increased cargo load stimulated ERES fusion events, leading to larger but less ERES. Silencing either PI4-kinase IIIα (PI4K-IIIα) or Sec16 inhibited the acute response. Overexpression of secretory cargo for 24 h induced the unfolded protein response (UPR), upregulated COPII, and the cells formed more ERES. This chronic response was insensitive to silencing PI4K-IIIα, but was abrogated by silencing Sec16. The UPR was required as the chronic response was absent in cells lacking inositol-requiring protein 1. Mathematical model simulations further support the notion that increasing ERES number together with COPII levels is an efficient way to enhance the secretory flux. These results indicate that chronic and acute increases in cargo load are handled differentially by ERES and are regulated by different factors.     

Discovering implicit protein–protein interactions in the <Emphasis Type="Italic">Cell Cycle</Emphasis> using bioinformatics approaches

The cell division control protein (Cdc2) kinase is a catalytic subunit of a protein kinase complex, called the M phase promoting factor, which induces entry into mitosis and is universal among eukaryotes. This protein is believed to play a major role in cell division and control. The lives of biological cells are controlled by proteins interacting in metabolic and signaling pathways, in complexes that replicate genes and regulate gene activity, and in the assembly of the cytoskeletal infrastructure. Our knowledge of protein–protein (P–P) interactions has been accumulated from biochemical and genetic experiments, including the widely used yeast two-hybrid test. In this paper we examine if P–P interactions in regenerating tissues and cells of the anuran Xenopus laevis can be discovered from biomedical literature using computational and literature mining techniques. Using literature mining techniques, we have identified a set of implicitly interacting proteins in regenerating tissues and cells of Xenopus laevis that may interact with Cdc2 to control cell division. Genome sequence based bioinformatics tools were then applied to validate a set of proteins that appear to interact with the Cdc2 protein. Pathway analysis of these proteins suggests that Myc proteins function as the regulator of M phase initiation by controlling expression of the Akt1 molecule that ultimately inhibits the Cdc2-cyclin B complex in cells. P–P interactions that are implicitly appearing in literature can be effectively discovered using literature mining techniques. By applying evolutionary principles on the P–P interacting pairs, it is possible to quantitatively analyze the significance of the associations with biological relevance. The developed BioMap system allows discovering implicit P–P interactions from large quantity of biomedical literature data. The unique similarities and differences observed within the interacting proteins can lead to the development of the new hypotheses that can be used to design further laboratory experiments.     

Angiopoietin-like protein 3 modulates barrier properties of human glomerular endothelial cells through a possible signaling pathway involving phosphatidylinositol-3 kinase/protein kinase B and integrin alphaVbeta3

Podocytes can influence glomerular endothelial cell (GEnC) barrier properties and take part in the development of proteinuria by some molecules. Angiopoietin-like protein 3 (Angptl3), secreted by podocytes, is a member of the angiopoietin-like protein family that has important biological functions in endothelial cells. In our previous studies, we showed that mRNA expression of Angptl3 increased significantly in kidneys of children with minimal change nephrotic syndrome. And the mRNA level of Angptl3 was increased in the glomerulus of adriamycin rats with the development of proteinuria. It was also found that Angptl3 was expressed in the cytoplasm of cultured podocytes. Thus, Angptl3 might influence the biological functions of GEnCs in a paracrine manner. In this study, we found that Angptl3 could increase the permeability of GEnCs and increase the level of protein kinase B phosphorylation in cultured GEnCs in vitro. LY294002, a phosphatidylinositol-3 kinase inhibitor, could prevent the increase of permeability of GEnCs induced by Angptl3. Our results also indicated that the integrin αVβ3 antibody (LM609) could block the Angptl3-induced protein kinase B phosphorylation.     

The biochemical basis of antimicrobial responses in Manduca sexta

Innate immunity is essential for the wellbeing of vertebrates and invertebrates. Key components of this defense system include pattern recognition receptors that bind to infectious agents, extra-and intra-cellular proteins that relay signals, as well as molecules and cells that eliminate pathogens. We have been studying the defense mechanisms in a biochemical model insect, Manduca sexta. In this insect, hemolin, peptidoglycan recognition proteins, β-1,3-glucan recognition proteins and C-type lectins detect microbial surface molecules and induce immune responses such as phagocytosis, nodulation, encapsulation, melanization and production of antimicrobial peptides. Some of these responses are mediated by extracellular serine proteinase pathways. The proteolytic activation of prophenoloxidase （proPO） yields active phenoloxidase （PO） which catalyzes the formation of quinones and melanin for wound healing and microbe killing. M. sexta hemolymph proteinase 14 （HP 14） precursor interacts with peptidoglycan or β-1,3-glucan, autoactivates, and leads to the activation of other HPs including HP21 and proPO-activating proteinases （PAPs）. PAP-1, -2 and -3 cut proPO to generate active PO in the presence of two serine proteinase homologs. Inhibition of the proteinases by serpins and association of the proteinase homologs with bacteria ensure a localized defense reaction. M. sexta HP1, HP6, HP8, HP17 and other proteinases may also participate in proPO activation or processing of spatzle and plasmatocyte spreading peptide.     

Breeding of wastewater treatment yeasts that accumulate high concentrations of phosphorus

Inorganic phosphate is an essential nutrient. In general, microorganisms take up phosphorus when the extracellular phosphorus concentration is low, but not when it is high. In Saccharomyces cerevisiae, the major phosphate transporters, such as Pho84p, and acid phosphatases (APases), such as Pho5p, are regulated in parallel by the phosphate signal transduction pathway (PHO pathway). We found that PHO mutants expressing PHO84 and PHO5, even under high-P conditions, could take up phosphorus at twice the rate of the wild-type strain. The regulatory pathway for phosphorus accumulation in two wastewater treatment yeasts, Hansenula fabianii J640 and Hansenula anomala J224-1, was found to be similar to that in S. cerevisiae. We screened for mutants of these yeasts that constitutively expressed APase. Such mutants formed blue colonies on high phosphorus concentration agar plates containing 5-bromo-4-chloro-3-indolylphosphate (X-phosphate). We found four mutants of H. fabianii J640 and one mutant of H. anomala J224-1 that accumulated from 2.2 to 3.5 times more phosphorus than the parent strains. The growth rates and abilities to remove dissolved total nitrogen and dissolved organic carbon of the mutants were similar to those of the parent strains. In addition, the mutants removed 95% of dissolved total phosphorus from shochu wastewater, while the parent strain removed only 50%.     

Cellulase elicitor induced accumulation of capsidiol in Capsicum annumm L. suspension cultures

When growth-phase cell suspension cultures of Capsicum annuum were treated with cellulase-elicitor preparation at 3 μg/ml, the level of capsidiol was transiently increased in the culture media rather than in the cells reaching its maximum approx 24 h after treatment. With methyl jasmonate it took 18 h. Elicitor treatment doubled phospholiphase A₂ (PLA₂) activity but simultaneous treatment with aristolochic acid, a PLA₂ inhibitor, inhibited sesquiterpenoid accumulation as well as PLA₂ activity. Mastoparan, a G protein activator, treatment also increased PLA₂ activity and capsidiol production. Taken together, the present study shows that induction of capsidiol production in the C. annuum is mediated by PLA₂ activation.     

WHY DO PARASITIC CUCKOOS HAVE SMALL BRAINS? INSIGHTS FROM EVOLUTIONARY SEQUENCE ANALYSES

Brain size is under many opposing selection pressures. Estimating their relative influence and reconstructing the brain's evolutionary history have, however, proved difficult. Here, we confirm the suggestion that the brain of brood parasitic cuckoos is smaller in relation to their body weight than that of nonparasitic cuckoo species. Two hypotheses explaining reductions in brain size are tested, using phylogenetically controlled correlations and evolutionary pathway analyses. In a novel approach, the pathway models are combined to build the most likely evolutionary sequence of trait changes correlating with changes in brain size. Brain size changed before brood parasitism, followed by a shift toward less-productive habitats and an increase in migration. This sequence shows that brain size was not reduced as a consequence of a loss of cognitive skills related to chick provisioning, and it offers no support for the hypothesis that an increase in energetic demands or a reduction in energy availability selected for a reduction of brain size. Instead, the sequence suggests that the reduction in energetic demands due to the smaller brain size and parasitic breeding strategy may have enabled parasitic cuckoos to colonize new niches.