On the turnover of exogenous ferritin in the cephalopod optic gland. A microprobe study

Summary X-ray energy emission spectra of iron show that horse spleen ferritin, after injection into the blood of the octopus, is taken up, accumulated and disposed of again by lysosomes of the optic gland.Part of this work is supported by the Swiss National Foundation.     

The cyclic nucleotide-gated ion channel CNGA3 contributes to coolness-induced responses of Grueneberg ganglion neurons

Localized to the vestibule of the nasal cavity, neurons of the Grueneberg ganglion (GG) respond to cool ambient temperatures. The molecular mechanisms underlying this thermal response are still elusive. Recently, it has been suggested that cool temperatures may activate a cyclic guanosine monophosphate (cGMP) pathway in the GG, which would be reminiscent of thermosensory neurons in Caenorhabditis elegans. In search for other elements of such a cascade, we have found that the cyclic nucleotide-gated ion channel CNGA3 was strongly expressed in the GG and that expression of CNGA3 was confined to those cells that are responsive to coolness. Further experiments revealed that the response of GG neurons to cool temperatures was significantly reduced in CNGA3-deficient mice compared to wild-type conspecifics. The observation that a cGMP-activated non-selective cation channel significantly contributes to the coolness-evoked response in GG neurons strongly suggests that a cGMP cascade is part of the transduction process.     

Selective inhibition of cotranslational translocation of vascular cell adhesion molecule 1

Increased expression of vascular cell adhesion molecule 1 (VCAM1) is associated with a variety of chronic inflammatory conditions, making its expression and function a target for therapeutic intervention. We have recently identified CAM741, a derivative of a fungus-derived cyclopeptolide that acts as a selective inhibitor of VCAM1 synthesis in endothelial cells. Here we show that the compound represses the biosynthesis of VCAM1 in cells by blocking the process of cotranslational translocation, which is dependent on the signal peptide of VCAM1. CAM741 does not inhibit targeting of the VCAM1 nascent chains to the translocon channel but prevents translocation to the luminal side of the endoplasmic reticulum (ER), through a process that involves the translocon component Sec61beta. Consequently, the VCAM1 precursor protein is synthesized towards the cytosolic compartment of the cells, where it is degraded. Our results indicate that the inhibition of cotranslational translocation with low-molecular-mass compounds, using specificity conferred by signal peptides, can modulate the biosynthesis of certain secreted and/or membrane proteins. In addition, they highlight cotranslational translocation at the ER membrane as a potential target for drug discovery.     

Crystal structure of the FimD usher bound to its cognate FimC-FimH substrate

Type 1 pili are the archetypal representative of a widespread class of adhesive multisubunit fibres in Gram-negative bacteria. During pilus assembly, subunits dock as chaperone-bound complexes to an usher, which catalyses their polymerization and mediates pilus translocation across the outer membrane. Here we report the crystal structure of the full-length FimD usher bound to the FimC-FimH chaperone-adhesin complex and that of the unbound form of the FimD translocation domain. The FimD-FimC-FimH structure shows FimH inserted inside the FimD 24-stranded β-barrel translocation channel. FimC-FimH is held in place through interactions with the two carboxy-terminal periplasmic domains of FimD, a binding mode confirmed in solution by electron paramagnetic resonance spectroscopy. To accommodate FimH, the usher plug domain is displaced from the barrel lumen to the periplasm, concomitant with a marked conformational change in the β-barrel. The amino-terminal domain of FimD is observed in an ideal position to catalyse incorporation of a newly recruited chaperone-subunit complex. The FimD-FimC-FimH structure provides unique insights into the pilus subunit incorporation cycle, and captures the first view of a protein transporter in the act of secreting its cognate substrate.     

Collaboration encourages equal sharing in children but not in chimpanzees

Humans actively share resources with one another to a much greater degree than do other great apes, and much human sharing is governed by social norms of fairness and equity. When in receipt of a windfall of resources, human children begin showing tendencies towards equitable distribution with others at five to seven years of age. Arguably, however, the primordial situation for human sharing of resources is that which follows cooperative activities such as collaborative foraging, when several individuals must share the spoils of their joint efforts. Here we show that children of around three years of age share with others much more equitably in collaborative activities than they do in either windfall or parallel-work situations. By contrast, one of humans' two nearest primate relatives, chimpanzees (Pan troglodytes), 'share' (make food available to another individual) just as often whether they have collaborated with them or not. This species difference raises the possibility that humans' tendency to distribute resources equitably may have its evolutionary roots in the sharing of spoils after collaborative efforts.     

An Algorithm for Computing Cutpoints in Finite Metric Spaces

The theory of the tight span, a cell complex that can be associated to every metric D, offers a unifying view on existing approaches for analyzing distance data, in particular for decomposing a metric D into a sum of simpler metrics as well as for representing it by certain specific edge-weighted graphs, often referred to as realizations of D. Many of these approaches involve the explicit or implicit computation of the so-called cutpoints of (the tight span of) D, such as the algorithm for computing the “building blocks” of optimal realizations of D recently presented by A. Hertz and S. Varone. The main result of this paper is an algorithm for computing the set of these cutpoints for a metric D on a finite set with n elements in O(n3) time. As a direct consequence, this improves the run time of the aforementioned O(n6)-algorithm by Hertz and Varone by “three orders of magnitude”.     

多功能土地利用 应对未来景观福利和服务需要

该书是2005年在爱沙尼亚塔图市（Tartu）举行的未来景观网络国际研讨会的论文集，大会主题是“多功能土地利用：应对未来景观福利和服务需要”。传统的土地利用重视土地的生产能力，这种生产能力是同产品产量密切相关的，在对土地的改造中，为了方便运输和管理，大面积种植一种粮食，往往将不同景观特征同质化，