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Search Results: 1 - 10 of 372 matches for " Sumitomo Yasuhiko "
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Identification of a novel enhancer that binds Sp1 and contributes to induction of cold-inducible RNA-binding protein (cirp) expression in mammalian cells
Sumitomo Yasuhiko,Higashitsuji Hiroaki,Higashitsuji Hisako,Liu Yu
BMC Biotechnology , 2012, DOI: 10.1186/1472-6750-12-72
Abstract: Background There are a growing number of reports on the sub-physiological temperature culturing of mammalian cells for increased recombinant protein yields. However, the effect varies and the reasons for the enhancement are not fully elucidated. Expression of cold-inducible RNA-binding protein (cirp, also called cirbp or hnRNP A18) is known to be induced in response to mild, but not severe, hypothermia in mammalian cells. To clarify the molecular mechanism underlying the induction and to exploit this to improve the productivity of recombinant proteins, we tried to identify the regulatory sequence(s) in the 5′ flanking region of the mouse cirp gene. Results By transiently transfecting HEK293 cells with plasmids expressing chloramphenicol acetyltransferase as a reporter, we found that the cirp 5′ flanking region octanucleotide 5′-TCCCCGCC-3′ is a mild-cold responsive element (MCRE). When 3 copies of MCRE were placed upstream of the CMV promoter and used in transient transfection, reporter gene expression was increased 3- to 7-fold at 32°C relative to 37°C in various cell lines including HEK293, U-2 OS, NIH/3T3, BALB/3T3 and CHO-K1 cells. In stable transfectants, MCRE also enhanced the reporter gene expression at 32°C, although more copy numbers of MCRE were necessary. Sp1 transcription factor bound to MCRE in vitro. Immunohistochemistry and chromatin immunoprecipitation assays demonstrated that more Sp1, but not Sp3, was localized in the nucleus to bind to the cirp regulatory region containing MCRE at 32°C than 37°C. Overexpression of Sp1 protein increased the expression of endogenous Cirp as well as a reporter gene driven by the 5′ flanking region of the cirp gene, and down-regulation of Sp1 had the opposite effect. Mutations within the MCRE sequence in the 5′ flanking region abolished the effects of Sp1 on the reporter gene expression both at 37°C and 32°C. Conclusions Cold-induced, as well as constitutive, expression of cirp is dependent, at least partly, on MCRE and Sp1. The present novel enhancer permits conditional high-level gene expression at moderately low culture temperatures and could be utilized to increase the yield of recombinant proteins in mammalian cells.
Irrelevance of Conjectural Variation in a Private Duopoly with Consistent Conjectures: The Relative Performance Approach and Network Effects  [PDF]
Yasuhiko Nakamura
Modern Economy (ME) , 2013, DOI: 10.4236/me.2013.49A002
Abstract:

This paper explores the equilibrium market outcomes in the contexts of both quantity-setting and price-setting private duopolies with the consistent conjectures of two private firms, wherein they maximize the weighted sum of their own profits and their respective opponent firm’s profit. Similar to the private duopoly without network effects wherein the two private firms maximize their genuine relative profits, in the private duopoly with network effects such that both firms maximize the weighted sum of their own profits and their respective opponent firm’s profit, we show that the equilibrium outcomes in the quantity-setting competition with the consistent conjectures of both firms are equivalent to those in the price-setting competition with the consistent conjectures of both firms.

Capacity Choice in a Private Duopoly: A Unilateral Externality Case  [PDF]
Yasuhiko Nakamura
Theoretical Economics Letters (TEL) , 2013, DOI: 10.4236/tel.2013.34034
Abstract:

This paper studies capacity choice in a quantity-setting and price-setting private duopoly with differentiated goods wherein either of two firms has a price-raising effect on the price level of the product of the opponent firm. In both quantity-setting and price-setting competition, whether the price-raising effect of the product of one firm on the price level of the other firm’s product is strong or weak strictly depends on the differences between the quantities and capacity levels of both firms. More precisely, in the quantity-setting competition, when the price-raising effect is sufficiently strong, both firms choose under-capacity, whereas when such an effect is sufficiently weak, both firms choose overcapacity. Furthermore, in the price-setting competition, when the price-raising effect is sufficiently strong, both firms choose over-capacity, whereas when such an effect is sufficiently weak, both firms choose under-capacity. Therefore, the presence of the price-raising effect as the unilateral externality strikingly changes the difference between each firm’s quantity and capacity level in the contexts of both the quantity-setting competition and the price competition in a private duopoly with differentiated goods.

Social Welfare under Quantity Competition and Price Competition in a Mixed Duopoly with Network Effects: An Analysis  [PDF]
Yasuhiko Nakamura
Theoretical Economics Letters (TEL) , 2013, DOI: 10.4236/tel.2013.34035
Abstract:

In their recent work, Matsumura and Ogawa (2012) showed that in the context of a mixed duopoly, equilibrium social welfare is higher in price-setting competition than in quantity-setting competition. We found that when the strength of network effects is sufficiently high, the above result is totally reversed; thus, in a mixed duopoly, the presence of network effects weakens the superiority of price-setting competition with respect to equilibrium social welfare.

Capacity Choice in a Price-Setting Mixed Duopoly with Network Effects  [PDF]
Yasuhiko Nakamura
Modern Economy (ME) , 2013, DOI: 10.4236/me.2013.45044
Abstract:

This paper explores the capacity choice for a public firm that is a welfare-maximizer and for a private firm that is a pure-profit-maximizer in the context of a price-setting mixed duopoly with a simple mechanism of network effects where the surplus that a firms client gets increases with the number of other clients of that firm. In this paper, we show that the public firm chooses over-capacity irrespective of the strength of network effects and the demand parameter, and that the difference between the output level and capacity level of the private firm strictly depends on the values of both the strength of network effects and the demand parameter. More precisely, the private firm chooses over-capacity when the strength of network effects is high relative to the demand parameter, while it chooses under-capacity otherwise.

Quantity Competition and Price Competition with a Duopoly in a Consumer-Friendly Firm: A Welfare Analysis  [PDF]
Yasuhiko Nakamura
Modern Economy (ME) , 2013, DOI: 10.4236/me.2013.411082
Abstract:


This paper conducts a welfare analysis in a duopoly with differentiated and substitutable goods composed of one consumer-friendly firm and one absolute profit maximizing firm. We suppose that the consumer-friendly firm maximizes the weighted sum of its absolute profit and consumer surplus. In such a duopoly, when the degree of product differentiation is sufficiently high and the weight that the consumer-friendly firm puts on consumer surplus in its objective function is sufficiently high, the equilibrium social welfare is larger in the quantity competition than in the price competition, which implies that the result is reverse of that obtained in the standard duopoly with substitutable goods composed of absolute profit maximizing firms.


Irrelevance of Conjectural Variation in a Mixed Duopoly: The Case of Relative Performance and Consistent Conjectures  [PDF]
Yasuhiko Nakamura
Theoretical Economics Letters (TEL) , 2013, DOI: 10.4236/tel.2013.35A2002
Abstract:

This study explores the equilibrium outcomes in the contexts of quantity-setting and price-setting mixed duopolies with consistent conjectures of both the social welfare maximizing public firm and the relative profit maximizing private firm. Similar to the private duopoly composed of only relative profit maximizing firms, we show that in the mixed duopoly, the equilibrium outcomes in the quantity-setting competition with the consistent conjectures of both firms are equivalent to those in the price-setting competition with the consistent conjectures of both firms.

Capacity Choice in a Quantity-Setting Mixed Duopoly with Network Effects  [PDF]
Yasuhiko Nakamura
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.41007
Abstract:

This paper explores the capacity choice for a public firm that is a social welfare-maximizer and a private firm that is an absolute profit-maximizer in the context of a quantity-setting mixed duopoly with a simple mechanism of network effects where the surplus that a firm’s client gets increases with the number of other clients of the firm. In this paper, we show that the social welfare-maximizing public firm chooses under-capacity irrespective of both the degree of product differentiation and strength of network effects, whereas the absolute profit-maximizing private firm chooses over-capacity irrespective of both the degree of product differentiation and strength of network effects, which is strikingly different from the results on the capacity choice problems for public and private firms obtained in price-setting mixed duopolistic markets in the existing literature.

Biased Managers as Strategic Commitment in a Mixed Duopoly  [PDF]
Yasuhiko Nakamura
Theoretical Economics Letters (TEL) , 2014, DOI: 10.4236/tel.2014.49112
Abstract: This paper analyzes a model in which both the owner of a social welfare-maximizing public firm and the owner of an absolute profit-maximizing private firm can hire biased managers for strategic reasons in a mixed duopoly in the contexts of both a price competition and a quantity competition. In this paper, in a mixed duopoly, we show that in the contexts of both a price competition and a quantity competition, the owners of both firms employ more aggressive managers. In particular, in the result obtained in the price competition, the attitude of the manager employed by the owner of the private firm reverses to that obtained in the case of classical strategic delegation works.
Development of Simultaneous HPLC-Fluorescence Assay of Phenol and Chlorophenols in Tap Water after Pre-Column Derivatization with 3-Chlorocarbonyl-6,7-dimethoxy-1- methyl-2(1H)-quinoxalinone  [PDF]
Yasuhiko Higashi
Detection (Detection) , 2016, DOI: 10.4236/detection.2016.41003
Abstract: Chlorophenols (2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol and 2,4, 6-trichlorophenol) may be presented in natural waters or drinking water as a result of disinfection processes involving chlorination, or as contaminants derived from domestic products, industrial operations and agricultural chemicals. A previous HPLC-UV method for determination of phenol and five chlorophenols in tap water using 4-fluoro-7-nitro-2,1,3-benzoxadiaole as a UV labeling reagent shows limited sensitivity. Here, we present an improved HPLC-fluorescence detection method for simultaneous determination of phenol and the above chlorophenols in tap water after pre-column derivatization with 3-chlorocarbonyl-6,7-dimethoxy-1-methyl-2(1H)-quino- xalinone (DMEQ-COCl), using a short, narrow column (50 × 2.1 mm i.d., packed with 5 μm particles of C18 material) to improve the sensitivity. Standard samples containing the compounds are derivatized with DMEQ-COCl in borate buffer (pH 9.0) at room temperature for 3 mins. The response is linear in the concentration range of 0.01 - 0.05 to 0.5 mg/L with r2 values ≥0.9967 for all compounds. The lower limits of detection are 0.001 to 0.008 mg/L, and the coefficients of variation are less than 8.8%. The recovery values from tap water spiked with standard samples are satisfactory. The present method is suitable for examining whether or not tap water samples are contaminated with phenol and chlorophenols in excess of regulatory values.
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