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Volume 88, Issue 7
Displaying 1-5 of 5 articles from this issue
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Masaatsu Miyauchi, Hideaki Nakajima, Chizuko HiraiArticle type: Article
2014 Volume 88 Issue 7 Pages 349-357
Published: July 25, 2014
Released on J-STAGE: August 10, 2017
JOURNAL FREE ACCESSIn recent years, the importance of solar exposure for vitamin D synthesis in the human body has been pointed out. The solar exposure time necessary for the synthesis of vitamin D depends largely on geographical location, season, time of day, weather, exposed skin area, etc. Using numerical simulations we estimated that if 10 μg vitamin D were to be synthesized entirely by solar exposure to skin type III (SPT), which is considered to be the most typical skin type for Japanese people, it would necessitate 6.4 min horizontal exposure of a 600 cm^2 skin area, corresponding to the face and the back of both hands, under cloudless sky at 12:00 o'clock in July in Tsukuba. Under the same conditions, it would take 20.8 min to reach 1 MED (Minimum Erythemal Dose) which is thought to be the harmful UV exposure level for human skin. In other words, approximately 31% of the time before the skin gets red is enough for the synthesis of 10 μg vitamin D a day. On the other hand, in Sapporo which is located in the northern part of the Japanese Archipelago, the corresponding durations are 8.4 min and 27.0 min, respectively under the same conditions as in Tsukuba, whereas the necessary time in December would be 139 min and 296 min, respectively. Although the sufficient amount of vitamin D cannot be obtained by short-time exposure to solar radiation, it is thought that long-time exposure might not damage the skin. It can be concluded that for a skin area of 600 cm^2 in horizontal position, exposure time until damage would occur is generally 3 times larger than what is necessary for the synthesis of 10 μg vitamin D under strong UV radiation. It should be noted that generally, with a larger exposed skin area the solar exposure time for vitamin D synthesis could be considerably shortened.View full abstractDownload PDF (1013K) -
Shota Akai, Hiroko Ikushiro, Daiki Sawai, Hideyuki Hayashi, Nobuo Kami ...Article type: Article
2014 Volume 88 Issue 7 Pages 358-365
Published: July 25, 2014
Released on J-STAGE: August 10, 2017
JOURNAL FREE ACCESSHomoserine dehydrogenase catalyzes the conversion of L-aspartate-4-semialdehyde to L-homoserine. Homoserine dehydrogenase is required for the biosynthesis of the three essential amino acids, i.e. lysine, methionine, and isoleucine, from aspartic acid. This enzyme attracts attention also as a promising antifungal drug target. We have determined the crystal structures of homoserine dehydrogenase from Thermus thermophilus HB8 in both substrate-free form and homoserine-binding form by X-ray diffraction. Crystallization conditions were surveyed at 293 K by using a hanging-drop vapor-diffusion method. The substrate-free form was solved to 1.4 Å resolution and the homoserine-binding form was solved to 2.0 Å resolution. The homoserine dehydrogenase was a dimer with each subunit composed of three distinct domains, nucleotide-binding, dimerization, and substrate-binding domain. In the homoserine-binding forms, the amino group of homoserine made a hydrogen bond to the side chain carboxylate of Glu180. This hydrogen bond induced the conformation change of Thr165-Pro183 loop, which made the loop close to the active site. The substrate homoserine was rigidly recognized by several amino acid residues in the enzyme active site, indicating that Lys99 or Lys195 would be an essential catalytic residue to facilitate hydride transfer.View full abstractDownload PDF (5583K) -
Chie Muto, Rieko Yachi, Takahiro Ogawa, Osamu Igarashi, Chikako KiyoseArticle type: Article
2014 Volume 88 Issue 7 Pages 366-372
Published: July 25, 2014
Released on J-STAGE: August 10, 2017
JOURNAL FREE ACCESSIt has been reported that α-tocopherol (α-Toc), one of the vitamin E analogs, is effective for treatment of non-alcoholic steatohepatitis (NASH). However, the mechanisms and the effects of other vitamin E analogs have not been clarified. The present study was carried out to investigate the effects of α-Toc and γ-tocopherol (γ-Toc) on fatty liver by using a model of non-alcoholic fatty liver disease (NAFLD) induced by a methionine- and choline-deficient (MCD) diet. Thirty male Sprague-Dawley (SD) rats were divided into six groups: control (C), control+α-Toc (Cα), control+γ-Toc (Cγ), MCD(M), MCD+α-Toc (Mα), and MCD+γ-Toc (Mγ). Each diet was fed for four weeks. Although neither α-Toc nor γ-Toc affected hepatic lipids under the control diet, γ-Toc tended to reduce hepatic triacylglycerol content and lipid droplet in rats fed the MCD diet. γ-Toc also significantly increased the expression of apolipoproteinB (ApoB) mRNA, which had been suppressed by the MCD diet. Moreover, it was suggested that γ-Toc levels in the liver and plasma of the Mγ group were significantly lower than those in the Cγ group, while there were no significant differences in the liver and plasma α-Toc levels between the Cα and Mα groups. Our results suggest that γ-Toc could ameliorate hepatic steatosis induced by feeding of a MCD diet more effectively than α-Toc.View full abstractDownload PDF (4449K) -
Koji FukuiArticle type: Article
2014 Volume 88 Issue 7 Pages 373-375
Published: July 25, 2014
Released on J-STAGE: August 10, 2017
JOURNAL FREE ACCESSDownload PDF (4921K) -
Article type: Bibliography
2014 Volume 88 Issue 7 Pages 376-380
Published: July 25, 2014
Released on J-STAGE: August 10, 2017
JOURNAL FREE ACCESSDownload PDF (451K)
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