A distinct role of the queen in coordinated workload and soil distribution in eusocial naked mole-rats

We investigated how group members achieve collective decision-making, by considering individual intrinsic behavioural rules and behavioural mechanisms for maintaining social integration. Using a simulated burrow environment, we investigated the behavioural rules of coordinated workload for soil distribution in a eusocial mammal, the naked mole-rat (Heterocephalus glaber). We tested two predictions regarding a distinct role of the queen, a socially dominant individual in the caste system: the presence of a queen would increase the workload of other caste individuals, and the cues by a queen would affect the soil distribution. In experiment 1, we placed four individuals of various castes from the same colony into an experimental burrow. Workers exhibited the highest frequency of workload compared to other castes. The presence of a queen activated the workload by other individuals. Individuals showed a consistent workload in a particular direction so as to bias the soil distribution. These results suggest that individuals have a consensus on soil distribution and that the queen plays a distinct role. In experiment 2, we placed the odour of a queen in one of four cells and observed its effect on other individuals' workload and soil distribution. Relative to other cells, individuals frequently dug in the queen cell so the amount of soil in the queen cell decreased. These results suggest that queen odour is an important cue in coordinated workload and soil distribution in this species.     

Chaos, oscillation and the evolution of indirect reciprocity in n-person games

Evolution of cooperation among genetically unrelated individuals has been of considerable concern in various fields such as biology, economics, and psychology. The evolution of cooperation is often explained by reciprocity. Under reciprocity, cooperation can prevail in a society because a donor of cooperation receives reciprocation from the recipient of the cooperation, called direct reciprocity, or from someone else in the community, called indirect reciprocity. Nowak and Sigmund [1993. Chaos and the evolution of cooperation. Proc. Natl. Acad. Sci. USA 90, 5091-5094] have demonstrated that directly reciprocal cooperation in two-person prisoner's dilemma games with mutation of strategies can be maintained dynamically as periodic or chaotic oscillation. Furthermore, Eriksson and Lindgren [2005. Cooperation driven by mutations in multi-person Prisoner's Dilemma. J. Theor. Biol. 232, 399-409] have reported that directly reciprocal cooperation in n-person prisoner's dilemma games (n>2) can be maintained as periodic oscillation. Is dynamic cooperation observed only in direct reciprocity? Results of this study show that indirectly reciprocal cooperation in n-person prisoner's dilemma games can be maintained dynamically as periodic or chaotic oscillation. This is, to our knowledge, the first demonstration of chaos in indirect reciprocity. Furthermore, the results show that oscillatory dynamics are observed in common in the evolution of reciprocal cooperation whether for direct or indirect.     

Oscillatory membrane currents paradoxically induced via NO-activated pathways in detrusor cells

Oscillatory inward membrane currents (I(oscil-in)) reflecting intracellular Ca(2+) ([Ca(2+)](i)) activity in detrusor cells, are thought to play an important role in producing tonic bladder contractions during micturition. The present patch clamp study revealed a new activation mechanism: sodium nitroprusside (SNP), a nitric oxide (NO) donor induced I(oscil-in) in a subpopulation of detrusor cells. The inhibitory effect of niflumic acid on SNP-induced I(oscil-in) suggests that Ca(2+)-activated Cl(-) channels are responsible for this current. In addition, SNP-induced I(oscil-in) required the cooperation of Ca(2+) influx through SK&F96365-sensitive channels and intracellular Ca(2+) release channels sensitive to ryanodine but insensitive to xestospongin C (XeC). This is also true for muscarinic agonist (carbachol: CCh)-induced I(oscil-in). However, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a guanylyl cyclase inhibitor, suppressed SNP-induced I(oscil-in) but not CCh-induced I(oscil-in). The results suggest that a subpopulation of detrusor cells employ the NO/cGMP cascade to potentiate bladder contraction. Mechanisms underlying NO-induced I(oscil-in) are likely to contribute not only to the physiology but also to the pathophysiology of the lower urinary tract.     

Effects of Kupffer cell-depletion on Concanavalin A-induced hepatitis

TNF-α, IFN-γ, IL-4, and MIP-2 are known to be involved in Con A-induced hepatitis. Although Kupffer cells are reportedly involved in TNF-α production, it is largely unknown whether or not Kupffer cells also play a role in the production of other cytokines, such as IFN-γ, IL-4, and MIP-2. In this study we examined the liver injury and the levels of plasma cytokines, including above four cytokines, KC, and IL-10 in Kupffer cell-depleted mice obtained through administration of liposome-encapsulated dichloromethylene bisphosphonate. The liver injury was significantly suppressed in Kupffer cell-depleted mice, as assessed as to the plasma ALT level and histochemistry. The cytokine levels were also significantly suppressed in such mice except for those of IFN-γ, which was slightly suppressed at 12 h, and IL-10, which was not significantly suppressed at any time. Apoptosis was also significantly suppressed in such mice, as found immunohistochemically with anti-ssDNA Ab. Taken together, these results suggest that Kupffer cells are involved in the production of MIP-2, KC, IL-4, and TNF-α in Con A-induced hepatitis, thereby contributing to the liver injury either directly or indirectly.     

Kinetics and activation energy of recrystallization of intracellular ice in mouse oocytes subjected to interrupted rapid cooling

Intracellular ice formation (IIF) is almost invariably lethal. In most cases, it results from the too rapid cooling of cells to below −40 °C, but in some cases it is manifested, not during cooling, but during warming when cell water that vitrified during cooling first devitrifies and then recrystallizes during warming. Recently, Mazur et al. [P. Mazur, I.L. Pinn, F.W. Kleinhans, Intracellular ice formation in mouse oocytes subjected to interrupted rapid cooling, Cryobiology 55 (2007) 158–166] dealt with one such case in mouse oocytes. It involved rapidly cooling the oocytes to −25 °C, holding them 10 min, rapidly cooling them to −70 °C, and warming them slowly until thawed. No IIF occurred during cooling but intracellular freezing, as evidenced by blackening of the cells, became detectable at −56 °C during warming and was complete by −46 °C. The present study differs in that the oocytes were warmed rapidly from −70 °C to temperatures between −65 and −50 °C and held for 3–60 min. This permitted us to determine the rate of blackening as function of temperature. That in turn allowed us to calculate the activation energy (E_a) for the blackening process; namely, 27.5 kcal/mol. This translates to about a quadrupling of the blackening rate for every 5 °C rise in temperature. These data then allowed us to compute the degree of blackening as a function of temperature for oocytes warmed at rates ranging from 10 to 10,000 °C/min. A 10-fold increase in warming rate increased the temperature at which a given degree of blackening occurred by 8 °C. These findings have significant implications both for cryobiology and cryo-electron microscopy.     

A strategy for screening an inhibitor of viral silencing suppressors, which attenuates symptom development of plant viruses

To find out whether we can control plant virus diseases by blocking viral RNA silencing suppressors (RSSs), we developed a strategy to screen inhibitors that block the association of RSSs with siRNAs using a surface plasmon resonance assay. The screened chemicals were tested in competition with RSSs for binding to siRNAs using a mobility shift assay. We then confirmed that tested chemicals actually inhibited the RSS activity in vivo using a protoplast assay which was developed for this purpose. This entire system can be adapted to screening inhibitors of not only plant viruses but also some animal viruses possessing RSSs.     

A lysophosphatidic acid receptor lacking the PDZ-binding domain is constitutively active and stimulates cell proliferation

Lysophosphatidic acid (LPA) is an extracellular signaling lipid that regulates cell proliferation, survival, and motility of normal and cancer cells. These effects are produced through G protein-coupled LPA receptors, LPA(1) to LPA(5). We generated an LPA(1) mutant lacking the SerValVal sequence of the C-terminal PDZ-binding domain to examine the role of this domain in intracellular signaling and other cellular functions. B103 neuroblastoma cells expressing the mutant LPA(1) showed rapid cell proliferation and tended to form colonies under serum-free conditions. The enhanced cell proliferation of the mutant cells was inhibited by exogenous expression of the plasmids inhibiting G proteins including G(betagamma), G(alphai) and G(alphaq) or G(alpha12/13), or treatment with pertussis toxin, phosphoinositide 3-kinase (PI3K) inhibitors or a Rho inhibitor. We confirmed that the PI3K-Akt and Rho pathways were intrinsically activated in mutant cells by detecting increases in phosphorylated Akt in western blot analyses or by directly measuring Rho activity. Interestingly, expression of the mutant LPA(1) in non-tumor mouse fibroblasts induced colony formation in a clonogenic soft agar assay, indicating that oncogenic pathways were activated. Taken together, these observations suggest that the mutant LPA(1) constitutively activates the G protein signaling leading to PI3K-Akt and Rho pathways, resulting in enhanced cell proliferation.     

Identification of novel non-peptide CXCR4 antagonists by ligand-based design approach

The design and synthesis of novel non-peptide CXCR4 antagonists is described. The peptide backbone of highly potent cyclic peptide-based CXCR4 antagonists was entirely replaced by an indole framework, which was expected to reproduce the disposition of the key pharmacophores consistent with those of potential bioactive conformations of the original peptides. A structure–activity relationship study on a series of modified indoles identified novel small-molecule antagonists having three pharmacophore functional groups through the appropriate linkers.     

Development of high-throughput screening system for osteogenic drugs using a cell-based sensor

To effectively treat osteoporosis and other bone-loss disorders, small compounds that potently induce bone formation are needed. The present study initially attempted to establish a monitoring system that could detect osteogenic differentiation easily, precisely, and noninvasively. For this purpose, we established pre-osteoblastic MC3T3E1 cells stably transfected with the GFP reporter gene driven by a 2.3 kb fragment of rat type I collagen promoter (Col1a1GFP-MC3T3E1). Among these cells, we selected a clone that fluoresced upon osteogenic stimulation by BMP2. The GFP fluorescence intensity corresponded well to the intensity of alkaline phosphatase (ALP) staining and to the level of osteocalcin (Oc) mRNA. Using this system, we screened natural and synthetic compound libraries and thus identified an isoflavone derivative, glabrisoflavone (GI). GI induced ALP staining and Oc mRNA in a dose-dependent manner. The Col1a1GFP-MC3T3E1 system may be useful for identifying novel osteogenic drugs.