High population density promotes the evolution of ownership

Previous studies have discussed the evolution of ownership using the Hawk–Dove–Bourgeois game. Decisive parameters are resource values (V) and contest costs (C). However, ownership may also evolve as a result of the effects of population density. To compare the effects of population density with those of resource values, I created a learning-based model of a revised Hawk–Dove–Bourgeois game. The game simulates the dynamics of agents that struggle for regions (“territories”) along a line. With appropriate sets of r (resource value) and l (reciprocal of the population density), the model showed that ownership is more likely to evolve when the resource value is small and population density is high. An area containing high-value resources is likely to accompany high population density. However, simulations showed that population density has stronger effects than resource value on the evolution of ownership.     

Alternating Dependency of Cytokinin Activity on the Number of Methylene Units in ω-Phenylalkyl Derivatives of Some Purine Cytokinins and 4-Substituted Pyrido[3,4-d]pyrimidine

ω-Phenylalkyl derivatives of N⁶-substituted adenine, N⁶-substituted adenosine and 6-alkoxy-purine with odd numbers of methylenes had relatively high activity, while the corresponding 2-methyl-4-substituted-aminopyrido[3,4-d]pyrimidines with even numbers of methylenes had high activity in an Amaranthus betacyanin test and lettuce seed germination test. These results suggest that the ω-phenyl groups of the cytokinins play a specific role for cytokinin-receptor binding and that the pyrido[3,4-d]pyrimidines interact with a receptor in a different binding mode.     

Calcium waves in mammalian heart: quantification of origin, magnitude, waveform, and velocity

A dual, digital, indo-1 fluorescence imaging system was used to obtain high-speed ratiometric images of [Ca2+]i waves in single voltage-clamped mammalian cardiac cells. The spatiotemporal origin of [Ca2+]i waves in depolarized cells was detected as the spontaneous appearance, over 100-300 ms, of domelike regions of elevated [Ca2+]i, approximately 20 microns in diameter and 300 nM at the center. Images of [Ca2+]i taken at 67-ms intervals during propagation of [Ca2+]i waves revealed that the [Ca2+]i wave front was 1) constant in shape, 2) spatially steep, typically rising from 500 to 1200 nM in about 10 microns, and 3) propagating at constant velocity, typically 100 microns/s at 22 degrees C. The observed spatial and temporal patterns of origin and propagation of [Ca2+]i waves are consistent with the hypothesis that [Ca2+]i waves arise from propagating Ca2(+)-induced release of Ca2+ mediated by diffusion of cytosolic Ca2+. The [Ca2+]i waves are smaller in peak magnitude and can occupy a larger fraction of the cell than thought previously on the basis of indirect observations.     

Synthesis of four stereoisomers of 4-amino-2-(hydroxymethyl)tetrahydrofuran-4-carboxylic acid

The 5-benzyl ether, 15, of a 1,2,4,5-pentanetetrol of known 2S configuration was made by a multistep synthesis from d-ribose. Ring-closure of the 1-O-tosyl derivative, 17, with retention of configuration, followed by oxidation, gave the 2S enantiomer, 22, of 2-benzyloxymethyl-4-oxotetrahydrofuran. The latter was converted by a hydantion synthesis into the 4-amino-4-carboxylic acid (mixture of 2S,4R and 2S,4S isomers, 28 and 29). Spontaneous lactonization of the 2S,4R diastereomer proved it to have the “cis” configuration. The remaining, 2S,4S diastereomer then must be “trans” it is identical with a natural compound recently isolated from an acid hydrolyzate of diabetic urine. In a parallel synthesis, the 4-O-mesyl derivative (de-O-isopropylidenated 19) was cyclized, with inversion at ring-position 2, leading after oxidation to the 2R enantiomer, 25, of the 4-oxotetrahydrofuran. The hydantoin synthesis this time yielded a mixture of the 2R,4R and 2R,4S amino-acids. Spontaneous lactonization of the latter showed it to have the “cis” configuration. Absolute configurations were assigned to the four optically active products, based on the known absolute configuration of d-ribose and the known mechanisms of the synthetic reactions.     

Zaragozic acids production from discomycetes

In search for new zaragozic acids and their derivatives that are potent inhibitors of squalene synthase, discomycetes of the order Leotiales were cultured and their fermentation broth was assayed. Three strains in 2 unidentified species ofMollisia were found to produce zaragozic acid D3 and three new analogs (F-10863s). Fermentative production, productivity of F-10863s and mycological characteristics of the producers are described. Discomycetes are expected to be a biological resource providing novel bioactive compounds.     

Effects of concentrated carbon dioxide on the fruiting of several cultivated basidiomycetes (II)

Edible basidiomycetesFlammulia velutipes andPleurotus ostreatus were cultivated in the usual manner on media based on sawdust and rice bran, and the cultures were exposed to slowly flowing CO₂-enriched air (550 (control), 3,000, 6,000, and 9,000µl/l) for seven days at different stages of cultivation. When the cultures were exposed at the primordium stage (less than 10 mm in length), length and yield of fruit-bodies increased and pileus expansion was slightly inhibited inF. velutipes, while inP. ostreatus length increased, yield decreased, and pileus expansion was greatly inhibited. When the cultures with fruit-bodies larger than 10 mm were exposed, length and yield were insensitive and pileus expansion was greatly inhibited inF. velutipes, while inP. ostreatus length was insensitive, but pileus expansion was heavily damaged by trumpet-like deformation and yield decreased. The different action of CO₂ on the two species appeared to be due to the different anatomical structures of their fruit-bodies.     

Ionomycin-induced calcium influx induces neurite degeneration in mouse neuroblastoma cells: analysis of a time-lapse live cell imaging system

Reactive oxygen species induce neuronal cell death. However, the detailed mechanisms of cell death have not yet been elucidated. Previously, we reported neurite degeneration before the induction of cell death. Here, we attempted to elucidate the mechanisms of neurite degeneration before the induction of cell death using the neuroblastoma N1E-115 cell line and a time-lapse live cell imaging system. Treatment with the calcium ionophore ionomycin induced cell death and neurite degeneration in a concentration- and time-dependent manner. Treatment with a low concentration of ionomycin immediately produced a significant calcium influx into the intracellular region in N1E-115 cells. After 1-h incubation with ionomycin, the fluorescence emission of MitoSOX^TM increased significantly compared to the control. Finally, analysis using a new mitochondrial specific fluorescence dye, MitoPeDPP, indicated that treatment with ionomycin significantly increased the mitochondrial lipid hydroperoxide production in N1E-115 cells. The fluorescence emissions of Fluo-4 AM and MitoPeDPP were detected in the cell soma and neurite regions in ionomycin-treated N1E-115 cells. However, the emissions of neurites were much lower than those of the cell soma. TBARS values of ionomycin-treated cells significantly increased compared to the control. These results indicate that ionomycin induces calcium influx into the intracellular region and reactive oxygen species production in N1E-115 cells. Lipid hydroperoxide production was induced in ionomycin-treated N1E-115 cells. Calcium influx into the intracellular region is a possible activator of neurite degeneration.     

Structure-activity relationship of polyphenols on inhibition of chemical mediator release from rat peritoneal exudate cells

Summary The effect of phenolic compounds in foodstuffs on histamine and leukotriene B₄ (LTB₄) release from rat peritoneal exudate cells and their antioxidative activity were examined to assess their antiallergenic activities. Among them, triphenols such as pyrogallol and gallic acid inhibited histamine release from the cells, but diphenols did not. On the other hand, o- and p-diphenols such as catechol and hydroquinone with strong antioxidative activity inhibited LTB₄ release as strongly as pyrogallol, but an m-derivative resorcinol with weak antioxidative activity did not. Though carboxylated compounds and their noncarboxylated counterparts were antioxidative, the former exerted a much weaker inhibitory effect on the LTB₄ release than the latter. In flavonols, only myricetin with a triphenolic B ring strongly inhibited histamine release, but all flavonols strongly suppressed LTB₄ release irrespective of the number of OH groups in the B ring. Among flavonoids with an o-diphenolic B ring, flavonol and flavone with a C₄-carbonyl group strongly inhibited LTB₄ release, whereas the activity of anthocyan without C₄-carbonyl was much weaker than the above compounds. These results suggest that triphenolic structure is essential for the inhibition of histamine release. On the other hand, antioxidative activity and membrane permeability of phenolic compounds seemed to be essential for the inhibition of LTB₄ release. In addition, the C₄-carbonyl group seemed to be important for strongly inhibiting LTB₄ release.