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Search Results: 1 - 10 of 401298 matches for " Joji M Otaki "
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Structural analysis of eyespots: dynamics of morphogenic signals that govern elemental positions in butterfly wings
Joji M Otaki
BMC Systems Biology , 2012, DOI: 10.1186/1752-0509-6-17
Abstract: In a well-developed eyespot, the inner black core ring is much wider than the outer black ring; this is termed the inside-wide rule. It appears that signals are wider near the focus of the eyespot and become narrower as they expand. Although fundamental signal dynamics are likely to be based on a reaction-diffusion mechanism, they were described well mathematically as a type of simple uniformly decelerated motion in which signals associated with the outer and inner black rings of eyespots and PFEs are released at different time points, durations, intervals, and initial velocities into a two-dimensional field of fundamentally uniform or graded resistance; this produces eyespots and PFEs that are diverse in size and structure. The inside-wide rule, eyespot distortion, structural differences between small and large eyespots, and structural changes in eyespots and PFEs in response to physiological treatments were explained well using mathematical simulations. Natural colour patterns and previous experimental findings that are not easily explained by the conventional gradient model were also explained reasonably well by the formal mathematical simulations performed in this study.In a mode free from speculative molecular interactions, the present study clarifies fundamental structural rules related to butterfly eyespots, delineates a theoretical basis for the induction model, and proposes a mathematically simple mode of long-range signalling that may reflect developmental mechanisms associated with butterfly eyespots.Although butterfly wing patterns are highly complex, it is believed that they are produced by simple rules that determine the fate of immature scale cells fixed in a two-dimensional plane. Among the colour-pattern elements that constitute the overall wing pattern, eyespots are conspicuous symmetric elements. Partly for this reason, characterisation of eyespots via physical damage and transplantation methods has been intensively performed, with the focus on th
A frequency-based linguistic approach to protein decoding and design: Simple concepts, diverse applications, and the SCS Package
Kenta Motomura,Morikazu Nakamura,Joji M. Otaki
Computational and Structural Biotechnology Journal , 2013,
Abstract: Protein structure and function information is coded in amino acid sequences. However, the relationship between primary sequences and three-dimensional structures and functions remains enigmatic. Our approach to this fundamental biochemistry problem is based on the frequencies of short constituent sequences (SCSs) or words. A protein amino acid sequence is considered analogous to an English sentence, where SCSs are equivalent to words. Availability scores, which are defined as real SCS frequencies in the non-redundant amino acid database relative to their probabilistically expected frequencies, demonstrate the biological usage bias of SCSs. As a result, this frequency-based linguistic approach is expected to have diverse applications, such as secondary structure specifications by structure-specific SCSs and immunological adjuvants with rare or non-existent SCSs. Linguistic similarities (e.g., wide ranges of scale-free distributions) and dissimilarities (e.g., behaviors of low-rank samples) between proteins and the natural English language have been revealed in the rank-frequency relationships of SCSs or words. We have developed a web server, the SCS Package, which contains five applications for analyzing protein sequences based on the linguistic concept. These tools have the potential to assist researchers in deciphering structurally and functionally important protein sites, species-specific sequences, and functional relationships between SCSs. The SCS Package also provides researchers with a tool to construct amino acid sequences de novo based on the idiomatic usage of SCSs.
Real-Time In Vivo Imaging of Butterfly Wing Development: Revealing the Cellular Dynamics of the Pupal Wing Tissue
Masaki Iwata, Yoshikazu Ohno, Joji M. Otaki
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0089500
Abstract: Butterfly wings are covered with regularly arranged single-colored scales that are formed at the pupal stage. Understanding pupal wing development is therefore crucial to understand wing color pattern formation. Here, we successfully employed real-time in vivo imaging techniques to observe pupal hindwing development over time in the blue pansy butterfly, Junonia orithya. A transparent sheet of epithelial cells that were not yet regularly arranged was observed immediately after pupation. Bright-field imaging and autofluorescent imaging revealed free-moving hemocytes and tracheal branches of a crinoid-like structure underneath the epithelium. The wing tissue gradually became gray-white, epithelial cells were arranged regularly, and hemocytes disappeared, except in the bordering lacuna, after which scales grew. The dynamics of the epithelial cells and scale growth were also confirmed by fluorescent imaging. Fluorescent in vivo staining further revealed that these cells harbored many mitochondria at the surface of the epithelium. Organizing centers for the border symmetry system were apparent immediately after pupation, exhibiting a relatively dark optical character following treatment with fluorescent dyes, as well as in autofluorescent images. The wing tissue exhibited slow and low-frequency contraction pulses with a cycle of approximately 10 to 20 minutes, mainly occurring at 2 to 3 days postpupation. The pulses gradually became slower and weaker and eventually stopped. The wing tissue area became larger after contraction, which also coincided with an increase in the autofluorescence intensity that might have been caused by scale growth. Examination of the pattern of color development revealed that the black pigment was first deposited in patches in the central areas of an eyespot black ring and a parafocal element. These results of live in vivo imaging that covered wide wing area for a long time can serve as a foundation for studying the cellular dynamics of living wing tissues in butterflies.
Phenotypic plasticity in the range-margin population of the lycaenid butterfly Zizeeria maha
Joji M Otaki, Atsuki Hiyama, Masaki Iwata, Tadashi Kudo
BMC Evolutionary Biology , 2010, DOI: 10.1186/1471-2148-10-252
Abstract: In the recently expanded northern range margins of this species, more than 10% of the Z. maha population exhibited characteristic color-pattern modifications on the ventral wings for three years. We physiologically reproduced similar phenotypes by an artificial cold-shock treatment of a normal southern population, and furthermore, we genetically reproduced a similar phenotype after selective breeding of a normal population for ten generations, demonstrating that the cold-shock-induced phenotype was heritable and partially assimilated genetically in the breeding line. Similar genetic process might have occurred in the previous and recent range-margin populations as well. Relatively minor modifications expressed in the tenth generation of the breeding line together with other data suggest a role of founder effect in this field case.Our results support the notion that the outbreak of the modified phenotypes in the recent range-margin population was primed by the revelation of plastic phenotypes in response to temperature stress and by the subsequent genetic process in the previous range-margin population, followed by migration and temporal establishment of genetically unstable founders in the recent range margins. This case presents not only an evolutionary role of phenotypic plasticity in the field but also a novel evolutionary aspect of range expansion at the species level.Mostly due to climate warming and its associated environmental changes, recent studies have revealed the expansion of the geographical distributions of several species, including many European [1-4], American [5], and Japanese [6-8] butterflies. Although habitat associations are generally constrained at range margins, physiological adaptation was observed in British butterflies in the range expansion process [1,3,4]. In these cases, the habitat variations that certain butterfly species can colonize increased over time [1,3,4]. Such changes are well within the range of normal physiological adaptatio
Word Decoding of Protein Amino Acid Sequences with Availability Analysis: A Linguistic Approach
Kenta Motomura, Tomohiro Fujita, Motosuke Tsutsumi, Satsuki Kikuzato, Morikazu Nakamura, Joji M. Otaki
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0050039
Abstract: The amino acid sequences of proteins determine their three-dimensional structures and functions. However, how sequence information is related to structures and functions is still enigmatic. In this study, we show that at least a part of the sequence information can be extracted by treating amino acid sequences of proteins as a collection of English words, based on a working hypothesis that amino acid sequences of proteins are composed of short constituent amino acid sequences (SCSs) or “words”. We first confirmed that the English language highly likely follows Zipf's law, a special case of power law. We found that the rank-frequency plot of SCSs in proteins exhibits a similar distribution when low-rank tails are excluded. In comparison with natural English and “compressed” English without spaces between words, amino acid sequences of proteins show larger linear ranges and smaller exponents with heavier low-rank tails, demonstrating that the SCS distribution in proteins is largely scale-free. A distribution pattern of SCSs in proteins is similar among species, but species-specific features are also present. Based on the availability scores of SCSs, we found that sequence motifs are enriched in high-availability sites (i.e., “key words”) and vice versa. In fact, the highest availability peak within a given protein sequence often directly corresponds to a sequence motif. The amino acid composition of high-availability sites within motifs is different from that of entire motifs and all protein sequences, suggesting the possible functional importance of specific SCSs and their compositional amino acids within motifs. We anticipate that our availability-based word decoding approach is complementary to sequence alignment approaches in predicting functionally important sites of unknown proteins from their amino acid sequences.
A Pure Theory of Aggregate Price Determination  [PDF]
Masayuki Otaki
Theoretical Economics Letters (TEL) , 2011, DOI: 10.4236/tel.2011.13026
Abstract: This article considers aggregate price determination related to the neutrality of money. When the true cost of living can be defined as a function of prices in an overlapping generations (OLG) model, the marginal cost of a firm depends solely on the current and future prices. Thus, the sequence of equilibrium price becomes independent of the quantity of money. Hence, money becomes non-neutral. However, when people hold the extraneous belief that prices increases proportionately with money, this belief becomes self-fulfilling as long as the increment of money and true cost of living are low enough to guarantee full employment.
The Role of Money: Credible Asset or Numeraire?  [PDF]
Masayuki Otaki
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.22031
Abstract: It is well known that money is neutral if 1) people hold the extraneous belief that it is an only numeraire and does not possess intrinstic value, and 2) new money is injected into an economy as its own interest in the OLG model under perfect information (Lucas [1] Theorem (2)). We find that whenever 1) is not satisfied and money is rationally held to have substance value, money becomes non-neutral even if we use the same model as Lucas [1].
A Keynesian Model of a Small Open Economy under a Flexible Exchange Rate  [PDF]
Masayuki Otaki
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23051
Abstract: This article considers the international diffusion of business cycles on the basis of a rigorous dynamic microeconomic foundation. The seminal work of Laursen and Metzler [1] suggests that the employment-isolation effect under the flexible exchange rate system is imperfect even if international capital mobility is completely prohibited. Assuming a small country model rather than the two-country model of Laursen and Metzler [1], we obtain the following results. (i) The business fluctuation of the world economy diffuses to the small country through a change in the inflation rate caused by the change in the real exchange rate. In this sense, the employment isolation is imperfect. (ii) Domestic monetary expansion has only an effect weaker than that of Mundell [2]-Fleming [3]. This is because a monetary expansion, which always accompanies a fiscal expansion, raises the current domestic price and lowers the inflation rate as long as the purchasing power of money (the inverse of future price) is kept intact. Such disinflation reduces the consumption demand in addition reducing the expansionary multiplier effect.
A Macroeconomic Consequence of Foreign Direct Investment: The Welfare Economics of Industrial Hollowing  [PDF]
Masayuki Otaki
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.24076
Abstract: This article considers macro and welfare economic implications concerning foreign direct investment under a flexible exchange rate system. There are serious conflicts between foreign-invested firms and their home country as a whole. Although lower wages incentivize firms to obtain foreign direct investment, such a movement harms the welfare of the home-country’s economy in the following ways. First, an increase in unemployment in the home country worsens the economy’s welfare as proved by Otaki [1]. Second, an appreciation in the real exchange rate, which is induced by the transfer of earned profits in foreign countries to the home country, reduces the value of profits in terms of domestic goods. We prove that such an appreciation entirely cancels the benefit from the cost reduction that originates from the foreign direct investment in lower-wage countries. In the end, only the downturn in employment circumstance remains. In this sense, the glut of foreign direct investment is harmful and, some coordination is required between firms and the government of the home country.
A Microeconomic Foundation for Optimum Currency Areas: The Case for Perfect Capital Mobility and Immobile Labor Forces  [PDF]
Masayuki Otaki
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.24073
Abstract: This article provides a microeconomic foundation for Mundell’s optimum currency area theory. We consider twin countries where labor forces are fixed to each country although the real capital moves internationally. When the central bank in each country behaves non-cooperatively, it will raise the domestic interest rate to attract more real capital and increase the rent of her residences. However, the fierce competition between the central banks ultimately exacerbates the disparity in income distribution. Moreover, when the real capital or the financial intermediary as its agent does not have a nationality, the worsened income distribution also results in the inefficient resource allocation. Thus, such twin countries should unify their central banks and coordinate their monetary and interest policies. In other words, these countries constitute an optimum currency area.
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