The Müller-Lyer Illusion in Ant Foraging

The Müller-Lyer illusion is a classical geometric illusion in which the apparent (perceived) length of a line depends on whether the line terminates in an arrow tail or arrowhead. This effect may be caused by economic compensation for the gap between the physical stimulus and visual fields. Here, we show that the Müller-Lyer illusion can also be produced by the foraging patterns of garden ants (Lasius niger) and that the pattern obtained can be explained by a simple, asynchronously updated foraging ant model. Our results suggest that the geometric illusion may be a byproduct of the foraging process, in which local interactions underlying efficient exploitation can also give rise to global exploration, and that visual information processing in human could implement similar modulation between local efficient processing and widespread computation.     

Imperfect identity of autonomous living system

We usually think that there is a clear cut between known facts and unknown facts. In category theory, this can correspond to equivalence of categories for partial map and pointed set. If this relation is satisfied, we implicitly ignore the difference of “before encoding” and “after encoding”. In this paper, we admit this discrepancy in the context of organizational endo-perspective, and make weak condition of equivalence of categories for partial map and pointed set to connect learning systems.     

Disruption of metF increased L-lysine production by Methylophilus methylotrophus from methanol

Methionine auxotrophic mutants of Methylophilus methylotrophus AS1 expressing a mutant form of dapA (dapA24) encoding a dihydrodipicolinate synthase desensitized from feedback inhibition by L-lysine, and mutated lysE (lysE24) encoding the L-lysine exporter from Corynebacterium glutamicum 2256, produced higher amounts of L-lysine from methanol as sole carbon source than did other amino acid auxotrophic mutants. Especially, the M. methylotrophus 102 strain, carrying both dapA24 and lysE24, produced L-lysine in more than 1.5 times amounts higher than the parent. A single-base substitution was identified in this auxotroph in codon-329 of the open reading frame of metF, encoding 5,10-methylene-tetra-hydrofolate reductase. We constructed a metF disruptant mutant carrying both dapA24 and lysE24, and confirmed increases in L-lysine production. This is the first report to the effect that metF deficient increased L-lysine production in methylotroph.     

Molecular dissection of the mechanisms of substrate recognition and F-actin-mediated activation of cofilin-phosphatase Slingshot-1

Slingshot-1 (SSH1), a member of a dual-specificity protein phosphatase family, regulates actin dynamics by dephosphorylating and reactivating cofilin, an actin-depolymerizing factor. SSH1 has the SSH family-specific, N-terminal, noncatalytic (SSH-N) domain, consisting of the A and B subdomains. SSH1 is activated by binding to actin filaments. In this study, we examined the mechanisms of SSH1 substrate recognition of phospho-cofilin (P-cofilin) and SSH1 activation by F-actin. We found that P-cofilin binds to a phosphatase-inactive mutant, SSH1(CS), in which the catalytic Cys-393 is replaced by Ser. Using a series of deletion mutants, we provided evidence that both the phosphatase (P) domain and the adjacent B domain are indispensable for P-cofilin binding of SSH1(CS) and cofilin-phosphatase activity of SSH1. In contrast, the A domain is required for the F-actin-mediated activation of SSH1, but not for P-cofilin binding or basal cofilin-phosphatase activity. The P domain alone is sufficient for the phosphatase activity toward p-nitrophenyl phosphate (pNPP), indicating that the SSH-N domain is not essential for the basal phosphatase activity of SSH1. Addition of F-actin increased the cofilin-phosphatase activity of SSH1 more than 1200-fold, but the pNPP-phosphatase activity only 2.2-fold, which suggests that F-actin principally affects the cofilin-specific phosphatase activity of SSH1. When expressed in cultured cells, SSH1, but not its mutant deleted of SSH-N, accumulated in the rear of the lamellipodium. Together, these findings suggest that the conserved SSH-N domain plays critical roles in P-cofilin recognition, F-actin-mediated activation, and subcellular localization of SSH1.     

Robust and emergent Physarum logical-computing

There have been many attempts for realization of emergent computing, but the notion of emergent computing is still ambiguous. In an open system, emergence and an error cannot be specified distinctly, because they are dependent on the dis-equilibration process between local and global behaviors. To manifest such an aspect, we implement a Boolean gate as a biological device made of slime mold Physarum polycephalum. A Physarum (slime mold) Boolean gate could be an internally instable machine, while it has the potential for emergent computing. First, we examined whether Physarum Boolean gate works properly, and then examined its behaviors when the gate is collapsed in terms of hardware. The behavior of Physarum changes and self-repairing computing is achieved as a result. The self-repairing against internal failure is one of attributes of emergent and robust computing.     

Learning process by goldfish and its use of a local site as a map

The issue we address is whether an animal knows or understands the significance of learning. We constructed an animal's own conceptualization via resolving a paradox underlying the process of learning. We found a kind of self-similar pattern in the behavior of goldfish resolving a paradoxical experimental problem. The pattern can be considered as a solution to the paradox in the experiment. An animal's own learning should be revised through solving paradoxes. The dualism of mechanistic thinking and vitalism can thus be avoided.     

The effects of 20 days bed rest on serum lipids and lipoprotein concentrations in healthy young subjects

The effects of 20 days bed rest (BR) on serum lipids and lipoprotein concentrations were investigated in 23 healthy young subjects (13 males and 10 females, aged 19 to 25 yr.). After 20 days BR, VO2max was reduced in both genders, but body composition did not change. The ratio of glucose area to insulin area during an oral glucose tolerance test decreased gradually throughout BR, which suggested a decrease in insulin sensitivity. Estimated changes in plasma volume from the beginning of BR were largest at day 3 of BR (-9.1% in females and -3.4% in males) and seemed to return the initial level at the end of BR in both genders. The increase in serum triglycerides and the decrease in high density lipoprotein (HDL) cholesterol, and apolipoprotein AI were observed in both genders during BR. In a smaller study of 4 males and 5 females, 20 days BR was associated with a decrease in HDL, cholesterol, a decrease in apolipoprotein AI and apolipoprotein AII, decrease in a plasma postheparin lipoprotein lipase activity and an increase in very low density lipoprotein triglyceride. Overall, the data suggested that the decrease in lipoprotein lipase activity and insulin sensitivity may contribute to the impairment in HDL metabolism.     

Short review of human prolonged horizontal bed rest studies in Japan

As many as 700,000-1,000,000 Japanese are spending a substantial part of their life in bed not being able to resume standing position due to disease and/or accident. Our objectives were urgently derived from that fact. The research project group at Faculty of Medicine, University of Tokyo, in Japan have studied effects of prolonged horizontal bed rest on humans since 1990. Financial supports from the Japanese Ministry of Education (Grant-in aide for scientific research), National Aero Space Development Agency of Japan and Japan Federation for Health Sciences have enabled us to perform five prolonged bed rest experiments for 5 years from 1990 to 1994. Many scientists in Europe, America and Russia have already made a heap of studies on this subject since the latter half of 1940s (eg. 39). However, our studies mainly focused upon the effects of inactivity on human health to determine how to bring a human from inactivity back to an unrestricted active life. This short review is going to summarize our results obtained from 1990 to 1993.     

L-Arabinose induces synthesis of secreted beta-galactosidase in the filamentous fungus penicillium canescens

The mechanism of induction of secreted beta-galactosidase was studied in the filamentous fungus Penicillium canescens. L-Arabinose and its metabolite L-arabitol induce the synthesis of the enzyme. Apart from beta-galactosidase, L-arabinose induces the synthesis of other extracellular carbohydrolases including alpha-L-arabinofuranosidase. Increasing L-arabinose concentration above 1 mM or addition of other carbon sources results in carbon catabolite repression of the synthesis of the secreted enzymes. The data suggest that arabinofuranosidase can regulate the synthesis of secreted enzymes in P. canescens, thus controlling the level of free L-arabinose.     

Activated renin-angiotensin-aldosterone system and its effects on cardiovascular system during 20-days horizontal bed rest

Change in circulating blood volume by bed rest has been suggested to effect on many cardiovascular responses after bed rest including orthostatic intolerance and exercise performance. However, there is a lack of consensus on effect of renin-angiotensin-aldosterone system (RAAS) on baseline heart rate and blood pressure during bed rest, although RAAS is the most potent fluid regulating system. The purpose of this study was to clarify the effect of RAAS on changes in baseline cardiovascular system and urine excretion.