The catalytic mechanism of cyclic GMP‐AMP synthase (cGAS) and implications for innate immunity and inhibition

Cyclic GMP‐AMP synthase (cGAS) is activated by ds‐DNA binding to produce the secondary messenger 2′,3′‐cGAMP. cGAS is an important control point in the innate immune response; dysregulation of the cGAS pathway is linked to autoimmune diseases while targeted stimulation may be of benefit in immunoncology. We report here the structure of cGAS with dinucleotides and small molecule inhibitors, and kinetic studies of the cGAS mechanism. Our structural work supports the understanding of how ds‐DNA activates cGAS, suggesting a site for small molecule binders that may cause cGAS activation at physiological ATP concentrations, and an apparent hotspot for inhibitor binding. Mechanistic studies of cGAS provide the first kinetic constants for 2′,3′‐cGAMP formation, and interestingly, describe a catalytic mechanism where 2′,3′‐cGAMP may be a minor product of cGAS compared with linear nucleotides.     

Mapping the structural core of human cerebral cortex

Structurally segregated and functionally specialized regions of the human cerebral cortex are interconnected by a dense network of cortico-cortical axonal pathways. By using diffusion spectrum imaging, we noninvasively mapped these pathways within and across cortical hemispheres in individual human participants. An analysis of the resulting large-scale structural brain networks reveals a structural core within posterior medial and parietal cerebral cortex, as well as several distinct temporal and frontal modules. Brain regions within the structural core share high degree, strength, and betweenness centrality, and they constitute connector hubs that link all major structural modules. The structural core contains brain regions that form the posterior components of the human default network. Looking both within and outside of core regions, we observed a substantial correspondence between structural connectivity and resting-state functional connectivity measured in the same participants. The spatial and topological centrality of the core within cortex suggests an important role in functional integration.     

Phylogenetic analysis of the Malvadendrina clade (Malvaceae s.l.) based on plastid DNA sequences

Phylogenetic relationships within Malvaceae s.l., a clade that includes the traditional families Bombacaceae, Malvaceae s.str., Sterculiaceae, and Tiliaceae, have become greatly clarified thanks to recent molecular systematic research. In this paper, we use DNA sequences of four plastid regions (atpB, matK, ndhF, and rbcL) to study relationships within Malvadendrina, one of the two major clades of Malvaceae s.l. The four data sets were generally in agreement, but five terminal taxa manifested highly unexpected affinities in the rbcL partition, and the non-coding sequences of the trnK intron were found to provide limited phylogenetic information for resolving relationships at the base of Malvadendrina. The remaining data strongly support the existence of six major clades within Malvadendrina: Brownlowioideae, Dombeyoideae, Helicteroideae, Malvatheca (comprising Bombacoideae and Malvoideae), Sterculioideae, and Tilioideae. These data also resolve the placement of two problematic taxa: Nesogordonia (in Dombeyoideae) and Mortoniodendron (in Tilioideae). The relationships among the six clades are not definitively resolved, but the best-supported topology has Dombeyoideae as sister to the remainder of Malvadendrina (posterior probability PP=80%) and Sterculioideae as sister to Malvatheca (PP=86%). This early branching position of Dombeyoideae is supported by similarities in floral characters between members of that clade and outgroup taxa in Byttnerioideae. Similarly, the sister-group relationship of Sterculioideae and Malvatheca receives support from androecial characteristics, like subsessile or sessile anthers and an absence of staminodes, shared by these two clades.     

Effect of ambient temperature and attachment method on surface temperature measurements

Accurate measurement of skin surface temperature is essential in both thermo-physiological and clinical applications. However, a literature review of the last two decades of physiological or clinical research revealed an inconsistency or a lack of information on how temperature sensors were attached to the skin surface. The purpose of this study was to systematically compare and quantify the performance of different commercially available temperature sensors and their typical attachment methods, and, secondly, to provide a time-efficient and reliable method for testing any sensor-tape combination. In conclusion, both the sensor type and the attachment method influenced the results of temperature measurements (both its absolute and relative dimensions). The sensor shape and the contact of its sensing area to the surface, as well as the conductance of the tape were the most important parameters to minimise the influence of environmental conditions on surface temperature measurement. These results suggest that temperature sensors and attachment methods for human subject and manikin trials should be selected carefully, with a systematic evaluation of the sensor-tape system under conditions of use, and emphasise the need to report these parameters in publications.     

Gastric pH Distribution and Mixing of Soft and Rigid Food Particles in the Stomach using a Dual-Marker Technique

Mixing of a particle-laden material during peristaltic flow in the stomach has not been quantified in vivo. Gastric mixing plays a key role in the digestion process; it determines the availability of acid and enzymes to individual food particles and controls the length of time particles will spend in the antral region, where they are subjected to mechanical breakdown from antral contraction waves. Solid particle mixing has been quantified using a dual-indigestible marker technique (TiO₂ and Cr₂O₃) in soft (cooked brown and white rice) and rigid (raw and roasted almonds) particle meals fed to growing pigs. All meals consisted of two portions. Each portion was separately marked by one of the two indigestible markers, and the portions were sequentially fed to the pigs. At time periods ranging from 20 to 720 min after completion of the meal, ten intragastric chyme samples were taken from each pig to determine the marker concentration and pH value. Gastric pH was not homogeneous throughout the stomach and varied over time, with differences observed between soft and rigid meals (p?<?0.0001). The total percentage of each meal that was mixed was calculated using a statistically-based mixing index (M). White rice had the greatest amount of mixing, becoming 94 % mixed after 480 min of digestion compared to 72 % mixing for brown rice. Rigid particles underwent a slower mixing process and only arrived at 65 and 71 % mixing after 720 min for raw and roasted almonds, respectively. Meal composition plays a role in the overall meal mixing during gastric digestion.     

Female preferences for single and combined traits in computer animated stickleback males

In many animal species, males have more than one secondary sexual character. Apart from theoretical considerations about the evolutionof multiple traits, there are almost no empirical studies onfemale mate choice decisions based on combinations of traitsas opposed to decisions based on single traits. Because three-spinedsticklebacks are exceptionally well suited to be tested withcomputer animation technique, which itself fills the gap of adequate test paradigms for multiple traits, we tested femalesticklebacks for their preferences for both single and combinedmale traits. We used virtual stickleback males that differedeither in red throat coloration, courtship intensity, bodysize, or in combinations of these traits. The virtual male with increased redness was found to be preferred by females,whereas the male courting more intensely was not. The testsfor combinations of traits revealed the more pronounced femalepreferences, the more traits were available to the femalesto judge male quality.     

Horizontal cells of the carp retina: Golgi impregnation and Procion-Yellow injection

Summary Application of two methods for the selective staining of neurons, Golgi impregnation and intracellular marking with Procion Yellow, has revealed the anatomical arrangements of the horizontal cells in the carp retina. There are two basic horizontal-cell types, those with axons and these without. The former can be subdivided into three groups on the basis of the pattern of branching of the dendrites. These three structural groups are also functionally distinct, as shown by the electrical recordings made during Procion-Yellow injection. The axons of these three types of cell project into the proximal part of the inner nuclear layer, where they expand to form morphologically indistinguishable terminals. Fine horizontal processes leave the surfaces of these axon terminals. The functional behavior of a terminal resembles that of the associated soma. The horizontal cells lacking axons vary in morphological appearance, but they are similar functionally.This work was supported by the Deutsche Forschungsgemeinschaft     

Molecular interactions of the intrinsic activation complex of coagulation: binding of native and activated human factors IX and X to defined phospholipid vesicles

The assembly of proteins of the intrinsic activation complex has been partially elucidated. In the present study we examine the association of gamma-carboxylated serine proteinase zymogens factors IX and X, and their proteolytically activated counterparts factors IXa and Xa to unilamellar lipid vesicles of defined composition using three types of physical measurement. Utilizing relative light scatter to estimate the dissociation constants for binding in the presence of calcium ions, it appears that factor IXa (0.93 +/- 0.37 microM) may preferentially associate with phospholipids relative to factor IX (0.35 +/- 0.08 microM). In contrast, factor X (0.34 +/- 0.14 microM), the substrate for factor IXa, appears to bind to phospholipid with a higher affinity than factor Xa (0.58 +/- 0.13 microM). These observations are compatible with the hypothesized dynamics where the forward 'traffic' is facilitated by favoring the association of factor IXa with factor X. The dissociation constants were estimated by molecular exclusion chromatography (1.1 - 2.5 microM) and do not reflect these relative and ordered differences in association with lipid vesicles. Quasi-elastic light scatter analyses indicate that each protein appears to saturate the same vesicle surface, consistent with competition for similar surface lipids, although the molecular shell formed by factor Xa (36 A) is smaller, suggesting that it has a different packing on the phospholipid surface than the other proteins (64-79 A). The pattern of preferential affinities for phospholipid is consistent with a kinetically functional forward traffic through the reaction precursors to products, and suggests that these preferential affinities may assist in the ordering of the four proteins in the intrinsic activation complex.     

Simulation of observed types of dynamics of plants and plant communities

Abstract. Observations of different plant communities over several decades reveal five types of dynamics: constant, fluctuating, growing, decaying, intermittent. With a modelling approach based on interacting particle systems (cellular automata), these distinct types of dynamics can be simulated. In addition, the proposed model shows a strong tendency towards the formation of patches when started with random initial conditions. Further, it gives evidence for dominance resulting from the interplay of plant characteristics and patterns rather than being attributable to certain plant types alone, so making questionable the existence of key species and the usefulness of a constant mapping key over extended periods. The presented model unifies the fundamental dichotomy in vegetation dynamics between determinism (predictability) and disorder (chance effects) by showing the outcome of both classical theories as special cases.