Etude ultrastructurale de la transformation du corps élémentaire en corps initial chez lesRickettsiella

Summary An intermediate stage between the elementary and the initial bodies of theRickettsiella genus is defined as the beginning of an intracellular cycle. It is characterized by several structural changes in the dense elementary body: the cytoplasm becomes less electron-dense; thus, the nucleoid and the ribosomes are visible. The inner layer of the cell-wall becomes progressively clearer and the trilamellar structure of the inner and outer membranes appears distinctly. Preinitial body is proposed as name of this stage of development.     

A20 (TNFAIP3) deficiency in myeloid cells triggers erosive polyarthritis resembling rheumatoid arthritis

A20 (TNFAIP3) is a protein that is involved in the negative feedback regulation of NF-κB signaling in response to specific proinflammatory stimuli in different cell types and has been suggested as a susceptibility gene for rheumatoid arthritis. To define the contribution of A20 to rheumatoid arthritis pathology, we generated myeloid-specific A20-deficient mice and show that specific ablation of Tnfaip3 in myeloid cells results in spontaneous development of a severe destructive polyarthritis with many features of rheumatoid arthritis. Myeloid-A20-deficient mice have high levels of inflammatory cytokines in their serum, consistent with a sustained NF-κB activation and higher TNF production by macrophages. Destructive polyarthritis in myeloid A20 knockout mice was TLR4-MyD88 and IL-6 dependent but was TNF independent. Myeloid A20 deficiency also promoted osteoclastogenesis in mice. Together, these observations indicate a critical and cell-specific function for A20 in the etiology of rheumatoid arthritis, supporting the idea of developing A20 modulatory drugs as cell-targeted therapies.     

From Philosophy to Engineering

In the years since I first thought of the possibility of producing artificial black holes, my focus on it has shifted from the role of life in the universe to a practical suggestion for the middle-term future, which I think of as on the order of a few centuries.     

A Maturing of Systems Thinking? Evidence from Three Perspectives

This paper reviews trends in systems theory/thinking from the 1970s to the early 2000s. It proposes a maturation of the field based on certain conceptual and methodological advances that have sought to liberate systems thinking from earlier strictures. An edited dialogue among three prominent systems thinkers from different systems schools—Merrelyn Emery, Bob Flood, and Eric Wolstenholme—provides evidence. Similarities and differences are identified, complementarities among the schools are derived and analyzed, and trajectories for future research are indicated.     

Excitatory glycine receptors containing the NR3 family of NMDA receptor subunits

The N-methyl-D-aspartate subtype of glutamate receptor (NMDAR) serves critical functions in physiological and pathological processes in the central nervous system, including neuronal development, plasticity and neurodegeneration. Conventional heteromeric NMDARs composed of NR1 and NR2A-D subunits require dual agonists, glutamate and glycine, for activation. They are also highly permeable to Ca2+, and exhibit voltage-dependent inhibition by Mg2+. Coexpression of NR3A with NR1 and NR2 subunits modulates NMDAR activity. Here we report the cloning and characterization of the final member of the NMDAR family, NR3B, which shares high sequence homology with NR3A. From in situ and immunocytochemical analyses, NR3B is expressed predominantly in motor neurons, whereas NR3A is more widely distributed. Remarkably, when co-expressed in Xenopus oocytes, NR3A or NR3B co-assembles with NR1 to form excitatory glycine receptors that are unaffected by glutamate or NMDA, and inhibited by D-serine, a co-activator of conventional NMDARs. Moreover, NR1/NR3A or -3B receptors form relatively Ca2+-impermeable cation channels that are resistant to Mg2+, MK-801, memantine and competitive antagonists. In cerebrocortical neurons containing NR3 family members, glycine triggers a burst of firing, and membrane patches manifest glycine-responsive single channels that are suppressible by D-serine. By itself, glycine is normally thought of as an inhibitory neurotransmitter. In contrast, these NR1/NR3A or -3B 'NMDARs' constitute a type of excitatory glycine receptor.     

Contributions of microbial biofilms to ecosystem processes in stream mesocosms

In many aquatic ecosystems, most microbes live in matrix-enclosed biofilms and contribute substantially to energy flow and nutrient cycling. Little is known, however, about the coupling of structure and dynamics of these biofilms to ecosystem function. Here we show that microbial biofilms changed the physical and chemical microhabitat and contributed to ecosystem processes in 30-m-long stream mesocosms. Biofilm growth increased hydrodynamic transient storage-streamwater detained in quiescent zones, which is a major physical template for ecological processes in streams-by 300% and the retention of suspended particles by 120%. In addition, by enhancing the relative uptake of organic molecules of lower bioavailability, the interplay of biofilm microarchitecture and mass transfer changed their downstream linkage. As living zones of transient storage, biofilms bring hydrodynamic retention and biochemical processing into close spatial proximity and influence biogeochemical processes and patterns in streams. Thus, biofilms are highly efficient and successful ecological communities that may also contribute to the influence that headwater streams have on rivers, estuaries and even oceans through longitudinal linkages of local biogeochemical and hydrodynamic processes.     

“一氧化氮养生法”让你远离心脑血管病

一氧化氮是生物学中最简单的分子之一。尽管它的结构及其简单,但目前一氧化氮被认为是体内最重要的信号分子,对机体健康至关重要。一氧化氮是一种很强的信号分子,存在于心血管系统、神经系统乃至全身。在一氧化氮的诸多作用中,以血管舒张作用最为重要。一氧化氮可舒张和扩张血管以确保心脏的足够血供。一氧化氮的另一个重要作用就是减慢动脉粥样硬化斑块在血管壁的沉积。我的研究强烈提示利用一氧化氮可以拮抗动脉粥样硬化斑块的形成。     

Editorial

Systemic Practice and Action Research -     

Editorial

Systemic Practice and Action Research -