Collective behavior in relation with changing environments: Dynamics,modularity, and agency

Collective behavior operates without central control, using local interactions among participants to adjust to changing conditions. Many natural systems operate collectively, and by specifying what objectives are met by the system, the idea of agency helps to describe how collective behavior is embedded in the conditions it deals with. Ant colonies function collectively, and the enormous diversity of more than 15K species of ants, in different habitats, provides opportunities to look for general ecological patterns in how collective behavior operates. The foraging behavior of harvester ants in the desert regulates activity to manage water loss, while the trail networks of turtle ants in the canopy tropical forest respond to rapidly changing resources and vegetation. These examples illustrate some broad correspondences in natural systems between the dynamics of collective behavior and the dynamics of the surroundings. To outline how interactions among participants, acting in relation with changing surroundings, achieve collective outcomes, I focus on three aspects of collective behavior: the rate at which interactions adjust to conditions, the feedback regime that stimulates and inhibits activity, and the modularity of the network of interactions. To characterize the dynamics of the surroundings, I consider gradients in stability, energy flow, and the distribution of resources and demands. I then propose some hypotheses that link how collective behavior operates with changing environments.     

Novel thieno[2,3-b]- and [3,4-b]pyrans as potassium channel openers. Thiophene systems—XVII

The syntheses and antihypertensive activity of the thieno[3,4-b]pyran and thieno[2,3-b]pyran isosteres of the potassium channel opener (PCO) RWJ 26629 (± 2a) are reported. While the unsubstituted thiophene derivatives were active at 20 mg/kg, introduction of a strong electron withdrawing group in the 2-position of the thieno[3,2-b] series increased potency. Similar substitution on the thieno[3,4-b] series significantly lowered potency. Compounds 26 and 30 are approximately 5-fold more potent than the prototypic PCO cromakalim (± 1).     

Modeling an immune response to influenza A virus infection in alveolar epithelial cells

Influenza A viruses (IAV) have been the cause of several influenza pandemics in history and are a significant threat for the next global pandemic. Hospitalized influenza patients often have excess interferon production and a dysregulated immune response to the IAV infection. Obtaining a better understanding of the mechanisms of IAV infection that induce these harmful effects would help drug developers and health professionals create more effective treatments for IAV infection and improve patient outcomes. IAV stimulates viral sensors and receptors expressed by alveolar epithelial cells, like RIG-I and toll-like receptor 3 (TLR3). These two pathways coordinate with one another to induce expression of type III interferons to combat the infection. Presented here is a queuing theory-based model of these pathways that was designed to analyze the timing and amount of interferons produced in response to IAV single stranded RNA and double-stranded RNA detection. The model accurately represents biological data showing the necessary coordination of the RIG-I and TLR3 pathways for effective interferon production. This model can serve as the framework for future studies of IAV infection and identify new targets for potential treatments.     

GENETIC EVIDENCE FOR MULTIPLE ORIGINS OF DIOECY IN THE HAWAIIAN SHRUB WIKSTROEMIA (THYMELAEACEAE)

Dioecy is unusually common in the Hawaiian Islands, yet little is known about the evolutionary biology of this breeding system. A native shrub, Wikstroemia, has an unusually diverse array of breeding systems: two forms of dioecy, cryptic and morphological dioecy, as well as hermaphroditism (perfect flowers). The existence of two forms of dioecy is significant for three reasons: 1) the presence of cryptic unisexuals that are functionally unisexual, but retain the appearance of hermaphroditism in both sexes, is strong evidence for the ancestral status of hermaphroditism; 2) the production of nonfunctional pollen, by female cryptic unisexuals, is a new instance of a phenomenon which has previously been reported for a few other species; 3) the two forms of dioecy are morphological markers which are useful in hybridization studies for tracing the genetic basis of their inheritance. Crosses were made between cryptically unisexual individuals (C), between morphologically unisexual individuals (M), and between the two types of unisexuality. The offspring of crosses between individuals with the same sex type usually resulted in offspring with that sex type, but most of the progeny of between-sex type crosses were, unexpectedly, perfect-flowered hermaphrodites. These results show that genetic control of sex determination is not homologous in all populations, suggesting that dioecy has evolved at least twice in Hawaiian Wikstroemia. The genetic data further suggest that males are the heterozygous sex.     

FORMATION OF NUCLEOSIDE DIPHOSPHATE MONOSACCHARIDES (NDP-SUGARS) BY THE AGAROPHYTE PTEROCLADIA CAPILLACEA (RHODOPHYCEAE)1

The following nucleoside diphosphate monosaccharides (sugar nucleotides) were identified by HPLC from Pterocladia capillacea Born and Thur.: ADP-glucose, UDP-glucose, UDP-d -galactose, and GDP-glucose + mannose. GDP-l -galactose was not identified due to the lack of a standard. Several extraction methods were evaluated for their efficacy. A freeze/ thaw (liquid N₂) step fallowed by formic acid (1 M) extraction, reduced pressure evaporation, and solubilization in water was the preferred method. Differences in media nitrate that resulted in different tissue-N levels (1.8, 2.3, and 3.5% dry wt) and agar yields (34, 31, and 28% dry wt, respectively) also resulted in a marked difference in UDP-d -galactose and ADP-glucose tissue levels (decrease with increasing tissue-N) while the levels of the other sugar nucleotide agar precursors remained unchanged. Activities of UDP-glucose, GDP-glucose, and GDP-mannose pyrophosphorylases, and UDP-D-glucose-4-epimerase were detected in cell-free extracts using unlabeled and ¹⁴C-labeled substrates. This study-strongly supports the proposition that the d -galactose component of agar is synthesized via G-1-P → UDP-glucose→ UDP-d -galactose and that, the l -galactoae component is produced via mannose-1-P → GDP-mannose → GDP-l -galactose.     

1H, 15N and 13C resonance assignments and secondary structure determination of the RNA-binding domain of E. coli rho protein

Summary Protein fragments containing the RNA-binding domain of Escherichia coli rho protein have been over-expressed in E. coli. NMR spectra of the fragment containing residues 1–116 of rho protein (Rho116) show that a region of this protein is unfolded in solution. Addition of (dC)₁₀ to this fragment stabilizes the folded form of the protein. The fragment comprising residues 1–130 of rho protein (Rho130) is found to be stably folded, both in the absence and presence of nucleic acid. NMR studies of the complex of Rho 130 with RNA and DNA oligonucleotides indicate that the binding-site size, affinity, and specificity of Rho 130 are similar to those of intact rho protein; therefore, Rho 130 is a suitable model of the RNA-binding domain of rho protein. NMR line widths as well as titration experiments of Rho130 complexed with oligonucleotides of various lengths suggest that Rho130 forms oligomers in the presence of longer oligonucleotides. ¹H, ¹⁵N and ¹³C resonance assignments were facilitated by the utilization of two pulse sequences, CN-NOESY and CCH-TOCSY. The secondary structure of unliganded Rho130 has been determined by NMR techniques, and it is clear that the RNA-binding domain of rho is more structurally similar to the cold shock domain than to the RNA recognition motif.Abbreviations Rho116, Rho130 protein containing the first 116 (130) residues of rho - CSD cold shock domain - RRM RNA recognition motif - RBD RNA-binding domain - IPTG isopropyl -D-thiogalactopyranoside - EDTA ethylenediaminetetraacetic acid - NOE nuclear Overhauser enhancement