Modeling the patrol behavior of the Diacamma’s gamergate

The gamergate (generally called the “queen”) of the Diacamma sp. walks around in the nest and comes into contact with the workers. The gamergate informs the workers of its presence by physical contact. This behavior is called a “patrol.” In previous work, it was reported that the gamergate controls its patrolling time depending on the colony size. How does the gamergate know the colony size, and how does it control the patrolling time? In this article, we propose a simple dynamics to explain this behavior. We assume that the gamergate and the workers have internal states which interact by physical contacts. By numerical simulations, we confirm that the patrol time of the proposed model depends on the size of the colony.     

The unification problem for confluent right-ground term rewriting systems

The unification problem for term rewriting systems (TRSs) is the problem of deciding, for a given TRS R and two terms M and N, whether there exists a substitution θ such that Mθ and Nθ are congruent modulo R (i.e., Mθ↔_R^*Nθ). In this paper, the unification problem for confluent right-ground TRSs is shown to be decidable. To show this, the notion of minimal terms is introduced and a new unification algorithm for obtaining a substitution whose range consists of minimal terms is proposed. Our result extends the decidability of unification for canonical (i.e., terminating and confluent) right-ground TRSs given by Hullot [Proceedings of the 5th Conference on Automated Deduction, LNCS, vol. 87, 1980, p. 318] in the sense that the termination condition can be omitted.     

Rhythmic behavior of social insects from single to multibody

Revealing the evolution of well-organized social behavior requires understanding a mechanism by which collective behavior is produced. A well-organized group may be produced by two possible mechanisms, namely, a central control and a distributed control. In the second case, local interactions between interchangeable components function at the bottom of the collective behavior. We focused on a simple behavior of an individual ant and analyzed the interactions between a pair of ants. In an experimental set-up, we placed the workers in a hemisphere without a nest, food, and a queen, and recorded their trajectories. The temporal pattern of velocity of each ant was obtained. From this bottom-up approach, we found the characteristic behavior of a single worker and a pair of workers as follows: (1) Activity of each individual has a rhythmic component. (2) Interactions between a pair of individuals result in two types of coupling, namely the anti-phase and the in-phase coupling. The direct physical contacts between the pair of workers might cause a phase shift of the rhythmic components in individual ants. We also build up a simple model based on the coupled oscillators toward the understanding of the whole colony behavior.     

Roll of the rhythmic component in the proactive control of a human hand

In terms of evolution, the strategy of catching prey would have been an important part of survival in a constantly changing environment. A prediction mechanism would have developed to compensate for any delay in the sensory-motor system. In a previous study, “proactive control” was found, in which the motion of the hands preceded the virtual moving target. These results implied that the positive phase shift of the hand motion represents the proactive nature of the visual-motor control system, which attempts to minimize the brief error in the hand motion when the target changes position unexpectedly. In our study, a visual target moves in circle (13 cm diameter) on a computer screen, and each subject is asked to keep track of the target’s motion by the motion of a cursor. As the frequency of the target increases, a rhythmic component was found in the velocity of the cursor in spite of the fact that the velocity of the target was constant. The generation of a rhythmic component cannot be explained simply as a feedback mechanism for the phase shifts of the target and cursor in a sensory-motor system. Therefore, it implies that the rhythmic component was generated to predict the velocity of the target, which is a feed-forward mechanism in the sensory-motor system. Here, we discuss the generation of the rhythmic component and its roll in the feed-forward mechanism.     

Prophylactic effect of Lactobacillus oral vaccine expressing a Japanese cedar pollen allergen

Lactic acid bacteria (LAB) represent an attractive delivery vehicle for oral allergy vaccine because of their safety as a food microorganism as well as their potent adjuvant activity triggering anti-allergic immune response. Here, we report the generation of recombinant LAB expressing a major Japanese cedar pollen allergen Cry j 1 (Cry j 1-LAB), and their prophylactic effect in vivo. To facilitate heterologous expression, the codon usage in the Cry j 1 gene was optimized for the host LAB strain Lactobacillus plantarum by the recursive PCR-based exhaustive site-directed mutagenesis. Use of the codon-optimized Cry j 1 cDNA and a lactate dehydrogenase gene fusion system led to a successful production of recombinant Cry j 1 in L. plantarum NCL21. We also found that oral vaccination with the Cry j 1-LAB suppressed allergen-specific IgE response and nasal symptoms in a murine model of cedar pollinosis.     

Genomic reorganization between two sibling yeast species,Saccharomyces bayanus and Saccharomyces cerevisiae

Genomic comparison of two sibling yeast species, Saccharomyces bayanus and Saccharomyces cerevisiae, was performed by Southern blot analysis with various S. cerevisiae gene probes following electrophoretic karyotyping. Fifteen genes on chromosome IV of S. cerevisiae were examined and classified into two groups. Gene probes of CEN4 and TRP1, as well as six other genes located on the left arm of the chromosome hybridized to a 1100-kb chromosome of S. bayanus that is smaller than chromosome IV of S. cerevisiae. On the other hand, probes of seven genes located on the right arm of chromosome IV hybridized to a 1350-kb chromosome that is homeologous to chromosome IV, judging from its size. Two genes located on the left arm of chromosome II hybridized to the 1350-kb chromosome, while four genes on the right arm hybridized to the 1100-kb chromosome. These pieces of evidence indicate that chromosomes II and IV of S. cerevisiae are rearranged into 1350-kb and 1100-kb chromosomes in S. bayanus. Furthermore, it is suggested that chromosome XV is rearranged into two chromosomes (800 and 850 kb in size) in S. bayanus. The translocation points of chromosomes II and IV were delimited using S. cerevisiae prime clone membranes. The results indicated that the translocation points are located close to the FUR4 locus on chromosome II and close to the RAD57 locus on chromosome IV.