The placental barrier: structure, resistance, asymmetry

The concept of placental barrier has been evaluated using recent advances in ultrastructure and in transport physiology. On a structural basis, the barrier effect is grounded by the syncytiotrophoblast continuity, and by basal and plasma membrane's electrical charges and by basement membrane porosity. The aqueous phase continuity for diffusion operates through intercellular gap, fenestrations (rat, rabbit) and transcellular channels (guinea pig). However, these connections are not apparent in the human syncytiotrophobast. For the molecular size selectivity, the hemochorial placentas with a pore radius of 10 nm appear much less selective than the epitheliochorial ones. The metabolic capacity of the placental cells (trophoblast, macrophages) participates to the barrier effect by metabolizing or by converting some substrates. Similarly, trophoblast asymmetry in the location of enzymes, carriers and receptors on outer (maternal side) and on basal (fetal side) plasma membranes, and in the release of secretory products, contributes to maintain separate fetal and maternal compartments. The functional polarity of trophoblast is expressed in metabolism (corticostéroids), nutrients (amino acids) and ions (iron) transport, and most of its secretions (hPL, hCG, SP1).     

The podosome cap: past,present, perspective

Podosomes are prominent actin-based adhesion structures in a variety of cell types. They feature an extensive repertoire of functions, which requires exquisite spatiotemporal fine-tuning. Accordingly, podosomes consist of hundreds of different components, which fulfill specific structural and regulatory functions. Moreover, it has become apparent that podosome architecture is more intricate than previously believed. The classical model of an actin-rich core surrounded by a ring structure containing adhesion plaque proteins thus had to be expanded, and several additional substructures have been described, most notably the podosome cap on top of the actin-rich core. Here, we discuss the known components of the podosome cap, the history of their detection and their potential regulatory roles in podosome turnover and function. We also point out strategies for identifying further cap components and present a new model for the podosome cap as a multilayered module that fine-tunes actomyosin contractility, a central requirement for podosome architecture, dynamics and function.     

The alphaviruses: gene expression, replication, and evolution

[This corrects the article on p. 496 in vol. 58.].     

腈水解酶的来源、结构、作用机制及其应用

综合报道了腈水解酶的来源、结构、作用机制及其工业应用。     

The plant microbiota: composition,functions, and engineering

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