The continuous public goods game and the evolution of cooperative sex ratios

Some animals, such as Melittobia wasps and surface-living mites, have extremely female-biased sex ratios that cannot be explained by the existing local mate competition (LMC) theories. The restricted production of sons may entail cooperation among mothers, enabling the production of more daughters and avoiding severe competition among sons for insemination access. These unusual examples are characterized by the long-term cohabitation of egg-layers (foundresses) on resource patches and possible contact with oviposited eggs. By applying the logic of mutual policing, we develop a novel game theoretical model for the evolution of cooperation in sex-ratio traits. This is the first attempt to model the evolution of sex ratios based on iterated games. We assumed that foundresses have two abilities to enable mutual policing: they can monitor the sex ratio in the resource patch, and they can punish defectors that produce an overabundance of males. Numerical analysis and evolutionary simulations demonstrate that cooperative low sex ratios can evolve when the number of foundresses per patch is sufficiently small. Our model predicts a slight, but steady increase in oviposition sex ratios with an increase in the number of foundresses, which mimics the phenomenon observed in several animals with extremely female-biased sex ratios. We also discuss the relationship between our model and other models of sex-ratio evolution.     

Enzymatic properties of cellobiose 2-epimerase from <Emphasis Type="Italic">Ruminococcus albus</Emphasis> and the synthesis of rare oligosaccharides by the enzyme

The gene for cellobiose 2-epimerase (CE) from Ruminococcus albus NE1 was overexpressed in Escherichia coli cells. The recombinant CE was purified to homogeneity by a simple purification procedure with a high yield of 88%, and the molecular mass was 43.1 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis and 44.0 kDa on gel chromatography. It exhibited optimal activity around at 30 degrees C and pH 7.5, and the enzyme activity was inhibited by Al3+, Fe3+, Co2+, Cu2+, Zn2+, Pb2+, Ag+, N-bromosuccinimide, iodoacetate, and 4-chloromercuribenzoate. In addition to cello-oligosaccharides, the enzyme was found to effectively 2-epimerize lactose to yield 4-O-beta-D-galactopyranosyl-D-mannose (epilactose), which occurs in cow milk as a rare oligosaccharide. The Km and kcat/Km values toward lactose were 33 mM and 1.6 s(-1) mM(-1), and those toward cellobiose were 13.8 mM and 4.6 s(-1) mM(-1), respectively. N-Acetyl-D-glucosamine, uridine 5'-diphosphate-glucose, D-glucose 6-phosphate, maltose, sophorose, laminaribiose, and gentiobiose were inert as substrates for the recombinant CE. We demonstrated that epilactose was resistant to rat intestinal enzymes, utilized by human adult bifidobacteria, and stimulated the tight junction permeability in Caco-2 cells. These results strongly suggest that this rare disaccharide is promising for use as a prebiotic.     

Inter‐colony foraging area segregation quantified in small colonies of Adélie Penguins

Theoretical models on the movement of colonial animals predict that neighbouring colonies may segregate their foraging areas, and many seabird studies have reported the presence of such segregations. However, these studies have often lacked the appropriate null model to test the effect of neighbouring colonies on foraging areas, especially in small colonies or in short‐ranging species. Here, we examined the foraging areas of Adélie Penguins Pygoscelis adeliae from two neighbouring (2 km apart) colonies by using bird‐borne GPS loggers. The field study was conducted at Hukuro Cove colony (104 pairs) and Mizukuguri Cove colony (338 pairs) in Lützow‐Holm Bay, East Antarctica. We obtained GPS tracks for 504 foraging trips from 48 chick‐rearing Adélie Penguins and quantified the degree of overlap in the foraging areas between two colonies. We also produced simulated movement tracks by using correlated random‐walks assuming no inter‐colony competition and quantified the degree of overlap in the simulated foraging areas. Finally, we compared the results from real GPS tracks with those from simulated tracks to examine the effect of neighbouring colonies on Adélie Penguin movement. The results indicate that the degree of overlap was significantly smaller in real tracks than in simulated tracks. In real tracks, the foraging area of the smaller Hukuro Cove colony extended to the other side of the larger Mizukuguri Cove colony, unlike in simulated tracks. Consequently, we suggest that Adélie Penguins from two neighbouring colonies segregated their foraging areas and that the larger colony appeared to affect the foraging area of the smaller colony.     

Current progress in DNA barcoding and future implications for entomology

DNA barcoding is a technique for identifying organisms based on a short, standardized fragment of genomic DNA. The standardized sequence region is called a DNA barcode because it is like a barcode tag for each taxon. Since the proposition of this concept and the launch of a large project named the Barcode of Life, this simple technique has attracted attention from taxonomists, ecologists, conservation biologists, agriculturists, plant‐quarantine officers and others, and the number of studies using the DNA barcode has rapidly increased. The extreme diversity of insects and their economical, epidemiological and agricultural importance have made this group a major target of DNA barcoding. However, there is some controversy about the utility of DNA barcoding. In this review, we present an overview of DNA barcoding and its application to entomology. We also introduce current advances and future implications of this promising technique.     

Nitric oxide (NO) serves as a retrograde messenger to activate neuronal NO synthase in the spinal cord via NMDA receptors.

We have recently demonstrated that nitric oxide (NO) produced by neuronal NO synthase (nNOS) in the spinal cord is involved in the maintenance of neuropathic pain. To clarify whether NO itself affected nNOS activity in the spinal cord as a retrograde messenger, we examined the involvement of the NO/cGMP signaling pathway in the regulation of nNOS activity by NADPH-diaphorase histochemistry. NO-generating agents NOR3 (t(1/2)=30min) and SNAP (t(1/2)=5h), but not NOR1 (t(1/2)=1.8min), significantly enhanced NADPH-diaphorase staining in the spinal cord. 8-Br-cGMP also enhanced it similar to that by NOR3, and 8-Br-cAMP and forskolin, an activator of adenylate cyclase, enhanced it moderately. NOR1 and NOR3 markedly increased the cGMP level in the spinal cord. The enhancement of NADPH-diaphorase staining by NOR3 was significantly inhibited by CPTIO, an NO scavenger, ODQ, a soluble guanylate cyclase inhibitor, and KT5823, an inhibitor of cGMP-dependent protein kinase. Additionally, the NOR3-enhanced nNOS activity was completely inhibited by NMDA antagonists MK-801 and d-AP5, partially by the GluRepsilon2-selective antagonist CP-101,606, and was attenuated in GluRepsilon1(-/-) and GluRepsilon1(-/-)/epsilon4(-/-) mice. These results suggest that NO may regulate nNOS activity as a retrograde messenger in the spinal cord via activation of NMDA receptor containing GluRepsilon1 and GluRepsilon2 subunits.     

A multiscale computational fluid dynamics approach to simulate the micro-fluidic environment within a tissue engineering scaffold with highly irregular pore geometry

Mechanical stimulation can regulate cellular behavior, e.g., differentiation, proliferation, matrix production and mineralization. To apply fluid-induced wall shear stress (WSS) on cells, perfusion bioreactors have been commonly used in tissue engineering experiments. The WSS on cells depends on the nature of the micro-fluidic environment within scaffolds under medium perfusion. Simulating the fluidic environment within scaffolds will be important for gaining a better insight into the actual mechanical stimulation on cells in a tissue engineering experiment. However, biomaterial scaffolds used in tissue engineering experiments typically have highly irregular pore geometries. This complexity in scaffold geometry implies high computational costs for simulating the precise fluidic environment within the scaffolds. In this study, we propose a low-computational cost and feasible technique for quantifying the micro-fluidic environment within the scaffolds, which have highly irregular pore geometries. This technique is based on a multiscale computational fluid dynamics approach. It is demonstrated that this approach can capture the WSS distribution in most regions within the scaffold. Importantly, the central process unit time needed to run the model is considerably low.

     

Nuclear matrix association regions of rat alpha 2-macroglobulin gene

We have identified DNA fragments which bind specifically to the nuclear matrix in vitro, termed matrix association regions (MARs), in the first and fourth introns of rat alpha 2-macroglobulin gene. The MAR in the first intron is enriched with sequences closely related to the cleavage consensus of topoisomerase II, and contains the binding site of nuclear factor-alpha, a sequence-specific DNA binding protein reported previously.     

Stereoselective total synthesis of ceramide Di-, Tri- and tetrahexosides of wheat flour

The first total synthesis of glycosphingolipids isolated from wheat flour has been achieved in a regio- and stereo-controlled manner.Abbreviations THF tetrahydrofuran - DMF dimethylformamide Part 53 in the series Synthetic Studies on Cell Surface Glycans