Competition and phylogeny determine community structure in Müllerian co-mimics

Until recently, the study of negative and antagonistic interactions (for example, competition and predation) has dominated our understanding of community structure, maintenance and assembly. Nevertheless, a recent theoretical model suggests that positive interactions (for example, mutualisms) may counterbalance competition, facilitating long-term coexistence even among ecologically undifferentiated species. Müllerian mimics are mutualists that share the costs of predator education and are therefore ideally suited for the investigation of positive and negative interactions in community dynamics. The sole empirical test of this model in a Müllerian mimetic community supports the prediction that positive interactions outweigh the negative effects of spatial overlap (without quantifying resource acquisition). Understanding the role of trophic niche partitioning in facilitating the evolution and stability of Müllerian mimetic communities is now of critical importance, but has yet to be formally investigated. Here we show that resource partitioning and phylogeny determine community structure and outweigh the positive effects of Müllerian mimicry in a species-rich group of neotropical catfishes. From multiple, independent reproductively isolated allopatric communities displaying convergently evolved colour patterns, 92% consist of species that do not compete for resources. Significant differences in phylogenetically conserved traits (snout morphology and body size) were consistently linked to trait-specific resource acquisition. Thus, we report the first evidence, to our knowledge, that competition for trophic resources and phylogeny are pivotal factors in the stable evolution of Müllerian mimicry rings. More generally, our work demonstrates that competition for resources is likely to have a dominant role in the structuring of communities that are simultaneously subject to the effects of both positive and negative interactions.     

Cryopyrin activates the inflammasome in response to toxins and ATP

A crucial part of the innate immune response is the assembly of the inflammasome, a cytosolic complex of proteins that activates caspase-1 to process the proinflammatory cytokines interleukin (IL)-1beta and IL-18. The adaptor protein ASC is essential for inflammasome function, binding directly to caspase-1 (refs 3, 4), but the triggers of this interaction are less clear. ASC also interacts with the adaptor cryopyrin (also known as NALP3 or CIAS1). Activating mutations in cryopyrin are associated with familial cold autoinflammatory syndrome, Muckle-Wells syndrome and neonatal onset multisystem inflammatory disease, diseases that are characterized by excessive production of IL-1beta. Here we show that cryopyrin-deficient macrophages cannot activate caspase-1 in response to Toll-like receptor agonists plus ATP, the latter activating the P2X7 receptor to decrease intracellular K+ levels. The release of IL-1beta in response to nigericin, a potassium ionophore, and maitotoxin, a potent marine toxin, was also found to be dependent on cryopyrin. In contrast to Asc-/- macrophages, cells deficient in the gene encoding cryopyrin (Cias1-/-) activated caspase-1 and secreted normal levels of IL-1beta and IL-18 when infected with Gram-negative Salmonella typhimurium or Francisella tularensis. Macrophages exposed to Gram-positive Staphylococcus aureus or Listeria monocytogenes, however, required both ASC and cryopyrin to activate caspase-1 and secrete IL-1beta. Therefore, cryopyrin is essential for inflammasome activation in response to signalling pathways triggered specifically by ATP, nigericin, maitotoxin, S. aureus or L. monocytogenes.     

VARIATION OF WOVEN FABRIC GEOMETRY——Non-uniform Flattening of Yarns

In previous research much effort has been devoted to the geometry of woven fabrics and relat-ed problems under the assumption of constant yarn configuration in fabric.This paper will first re-port that image crimp (yarn crimp measured by an image analysis method) seems larger than actualvalue.From the explanation of this result,the variation of yarn configuration in woven fabric dueto the non-uniform flattening is revealed.The significance of this actual structure of woven fabricsis discussed.It is believed that the variation of yarn configuration is very important for fabric per-formance,and may be an advantage for fabric quality.     

Isolation of coenzyme B12 from liver of germ-free mice

Zusammenfassung Die enzymatische Synthese von Cobamid-Coenzymen ist aus Extrakten, die von Mikroorganismen gewonnen wurden, gut bekannt, nicht aber von Säugetiergeweben. Unsere Befunde mit Cobamid-Coenzymen in der Leber von keimfreien Mäusen scheint anzuzeigen, dass die Verwandlung von Vitamin B₁₂ in Coenzymform von Enzymen der Säugetiergewebe katalysiert werden kann.     

Characterization of an expressed CD3-associated Ti gamma-chain reveals C gamma domain polymorphism

The majority of human T cells express an antigen receptor consisting of a disulphide-linked heterodimer (Ti) of relative molecular mass 80,000-90,000 (Mr 80-90K) which is noncovalently associated with a set of at least three proteins of Mr 20-28K termed CD3 (Leu4, T3). Whereas both chains of Ti, an acidic alpha-chain of Mr 48-54K and a more basic beta-chain of Mr 40-44K, contain variable and constant region domains, the component peptides of CD3 are invariant. Several laboratories have more recently reported the expression of CD3 in association with a novel protein. On the surface of long-term T-cell lines and one thymocyte clone this novel structure consists of a 40K protein noncovalently linked to a 55 or 62K protein identified as the protein product of the Ti gamma-chain gene, a T-cell specific gene which like the Ti alpha- and Ti beta-chain genes undergoes rearrangement of variable (V) and joining (J) region gene segments. On the human T-cell leukaemic line PEER we have detected only a single 55K glycoprotein associated with CD3. We here demonstrate that an anti-Ti gamma-peptide antiserum reacts with the 55K CD3-associated protein on PEER. Most previously described human Ti gamma-chain complementary DNA clones encode the products of non-functional rearrangements. One of the Ti gamma cDNAs isolated from PEER, however, represents a functional rearrangement reported for the first time in a cell which expresses a Ti gamma-chain protein product on the cell surface. Interestingly, a 48-base-pair (bp) sequence in the constant (C) region domain of this functional Ti gamma-chain cDNA is triplicated in PEER and duplicated in other cDNAs isolated from PEER and other cell lines.     

Mutations in RAI1 associated with Smith-Magenis syndrome

Smith-Magenis syndrome (SMS) is a mental retardation syndrome associated with deletions involving chromosome 17p11.2. Persons with SMS have characteristic behavioral abnormalities, including self-injurious behaviors and sleep disturbance, and distinct craniofacial and skeletal anomalies. We identified dominant frameshift mutations leading to protein truncation in RAI1 in three individuals who have phenotypic features consistent with SMS but do not have 17p11.2 deletions detectable by standard fluorescence in situ hybridization techniques.