High-density tissue-like cultivation of JAR choriocarcinoma cells for the in vitro production of human xylosyltransferase

Human xylosyltransferase is the chain-initiating enzyme involved in the biosynthesis of glycosaminoglycans. Large amounts of xylosyltransferase are required to study the biochemical properties of the native enzyme. To achieve this goal a scale-up of animal cell culture systems was inevitable due to the small amounts of the enzyme present in tissues, e.g. only 0.5 microg XT can be obtained from a chick embryo. JAR choriocarcinoma cells cultured with 10% fetal calf serum were found to secrete xylosyltransferase with relatively high activities (1.10 mU l(-1)). To reduce contaminating proteins JAR cells were adapted to serum-free conditions. Xylosyltransferase activities up to 0.22 mU l(-1) were determined in the harvested cell culture supernatant. Scaling-up of JAR cell culture in the hybrid hollow fiber bioreactor Tecnomouse resulted in the production of 15.8 mU or 270 microg XT in 0.5 l of XT-enriched cell culture supernatant using 57 l of serum-free cell culture medium. The XT activity per ml harvest solution was 200-280-fold higher in this cell culture supernatant than in cell culture flasks. In addition, the specific XT activity of the bioreactor product was 6 microU mg(-1) of total protein, which is 2-fold higher than that obtained under static culture conditions. This study clearly demonstrates the successful high-density, tissue-like cultivation of JAR choriocarcinoma cells in a hollow fiber bioreactor resulting in an effective production of native human xylosyltransferase.     

Können Tiere zählen?

The “magical” number four We know already since more than 140 years that humans have the inborn ability to recognize only up to four objects correctly if counting is strictly inhibited. Many vertebrates and the honeybee workers can remember up to four objects albeit they are unable to count. This inborn numerical competence common to humans and animals raises interesting questions concerning the purpose and the evolution of this ability. The “magical” number four is obviously a neurological, historical and mythological enigma.     

Restriction of de novo pyrimidine biosynthesis inhibits Th1 cell activation and promotes Th2 cell differentiation

Leflunomide, an inhibitor of de novo pyrimidine biosynthesis, has recently been introduced as a treatment for rheumatoid arthritis in an attempt to ameliorate inflammation by inhibiting lymphocyte activation. Although the immunosuppressive ability of leflunomide has been well described in several experimental animal models, the precise effects of a limited pyrimidine supply on T cell differentiation and effector functions have not been elucidated. We investigated the impact of restricted pyrimidine biosynthesis on the activation and differentiation of CD4 T cells in vivo and in vitro. Decreased activation of memory CD4 T cells in the presence of leflunomide resulted in impaired generation and outgrowth of Th1 effectors without an alteration of Th2 cell activation. Moreover, priming of naive T cells in the presence of leflunomide promoted Th2 differentiation from uncommitted precursors in vitro and enhanced Th2 effector functions in vivo, as indicated by an increase in Ag-specific Th2 cells and in the Th2-dependent Ag-specific Ig responses (IgG1) in immunized mice. The effects of leflunomide on T cell proliferation and differentiation could be antagonized by exogenous UTP, suggesting that they were related to a profound inhibition of de novo pyrimidine biosynthesis. These results indicate that leflunomide might exert its anti-inflammatory activities in the treatment of autoimmune diseases by preventing the generation of proinflammatory Th1 effectors and promoting Th2 cell differentiation. Moreover, the results further suggest that differentiation of CD4 T cells can be regulated at the level of nucleotide biosynthesis.     

Highly functionalized glyco-conjugated hexahydroazepindiones from saccharide imides via the Norrish type II reaction

Starting from readily available protected 6-tosylates of D-glucose and D-mannose in both their pyranoside and furanoside forms as well as 6-tosylates of alpha-D-galactopyranose, the corresponding primary succinimido derivatives were obtained in good yield by nucleophilic displacement with potassium succinimide. These imido sugars were photochemically transformed into hexahydroazepindione derivatives such as by means of a Norrish type II reaction. As expected, the intramolecular alkylation proceeded via an 1,6 H-abstraction leading to a stabilized diradical. The regiochemistry of the photoreaction was controlled by configurational, conformational and electronic features and was sometimes influenced by the protecting groups. Using this route, a facile approach to a novel class of highly functionalized sugar derived heterocycles was developed.     

Respiration modulates oscillatory neural network activity at rest

Despite recent advances in understanding how respiration affects neural signalling to influence perception, cognition, and behaviour, it is yet unclear to what extent breathing modulates brain oscillations at rest. We acquired respiration and resting state magnetoencephalography (MEG) data from human participants to investigate if, where, and how respiration cyclically modulates oscillatory amplitudes (2 to 150 Hz). Using measures of phase–amplitude coupling, we show respiration-modulated brain oscillations (RMBOs) across all major frequency bands. Sources of these modulations spanned a widespread network of cortical and subcortical brain areas with distinct spectrotemporal modulation profiles. Globally, delta and gamma band modulations varied with distance to the head centre, with stronger modulations at distal (versus central) cortical sites. Overall, we provide the first comprehensive mapping of RMBOs across the entire brain, highlighting respiration–brain coupling as a fundamental mechanism to shape neural processing within canonical resting state and respiratory control networks (RCNs).

Despite recent advances, it remains unclear to what extent breathing modulates brain oscillations at rest. This magnetoencephalography study in human participants identifies a widespread brain network of neural oscillations that are coupled to the respiratory rhythm.     

The relationship between inflammation and new bone formation in patients with ankylosing spondylitis

Introduction  

Spinal inflammation as detected by magnetic resonance imaging and new bone formation as identified by conventional radiographs are characteristic of ankylosing spondylitis. Whether and how spondylitis and syndesmophyte formation are linked are unclear. Our objective was to investigate whether and how spinal inflammation are associated with new bone formation in ankylosing spondylitis.     

Faunal impact on vegetation structure and ecosystem function in mangrove forests: A review

The last 20 years witnessed a real paradigm shift concerning the impact of biotic factors on ecosystem functions as well as on vegetation structure of mangrove forests. Before this small scientific revolution took place, structural aspects of mangrove forests were viewed to be the result of abiotic processes acting from the bottom-up, while, at ecosystem level, the outwelling hypothesis stated that mangroves primary production was removed via tidal action and carried to adjacent nearshore ecosystems where it fuelled detrital based food-webs. The sesarmid crabs were the first macrofaunal taxon to be considered a main actor in mangrove structuring processes, thanks to a number of studies carried out in the Indo-Pacific forests in the late 1970s and early 1980s. Following these classical papers, a number of studies on Sesarmidae feeding and burrowing ecology were carried out, which leave no doubts about the great importance of these herbivorous crabs in structuring and functioning Old world ecosystems. Although Sesarmidae are still considered very important in shaping mangrove structure and functioning, recent literature emphasizes the significance of other invertebrates. The Ocypodidae have now been shown to have the same role as Sesarmidae in terms of retention of forest products and organic matter processing in New world mangroves. In both New and Old world mangroves, crabs process large amounts of algal primary production, contribute consistently to retention of mangrove production and as ecosystem engineers, change particle size distribution and enhance soil aeration. Our understanding of the strong impact of gastropods, by means of high intake rates of mangrove products and differential consumption of propagules, has changed only recently. The role of insects must also be stressed. It is now clear that older techniques used to assess herbivory rates by insects strongly underestimate their impact, both in case of leaf eating and wood boring species and that herbivorous insects can potentially play a strong role in many aspects of mangrove ecology. Moreover, researchers only recently realized that ant–plant interactions may form an important contribution to our understanding of insect–plant dynamics in these habitats. Ants seem to be able to relieve mangroves from important herbivores such as many insects and sesarmid crabs. It thus seems likely that ants have positive effects on mangrove performance.     

Oxidative stress and lipid mediators induced in alveolar macrophages by ultrafine particles

In ambient aerosols, ultrafine particles (UFP) and their agglomerates are considered to be major factors contributing to adverse health effects. Reactivity of agglomerated UFP of elemental carbon (EC), Printex 90, Printex G, and diesel exhaust particles (DEP) was evaluated by the capacity of particles to oxidize methionine in a cell-free in vitro system for determination of their innate oxidative potential and by alveolar macrophages (AMs) to determine production of arachidonic acid (AA), including formation of prostaglandin E2 (PGE2), leukotriene B4 (LTB4), reactive oxygen species (ROS), and oxidative stress marker 8-isoprostane. EC exhibiting high oxidative potential induced generation of AA, PGE2, LTB4, and 8-isoprostane in canine and human AMs. Printex 90, Printex G, and DEP, showing low oxidative capacity, still induced formation of AA and PGE2, but not that of LTB4 or 8-isoprostane. Aging of EC lowered oxidative potential while still inducing production of AA and PGE2 but not that of LTB4 and 8-isoprostane. Cellular ROS production was stimulated by all particles independent of oxidative potential. Particle-induced formation of AA metabolites and ROS was dependent on mitogen-activated protein kinase kinase 1 activation of cytosolic phospholipase A2 (cPLA2) as shown by inhibitor studies. In conclusion, cPLA2, PGE2, and ROS formation was activated by all particle types, whereas LTB4 production and 8-isoprostane were strongly dependent on particles' oxidative potential. Physical and chemical parameters of particle surface correlated with oxidative potential and stimulation of AM PGE2 and 8-isoprostane production.