Since author was fascinated by the important functions of calcium (Ca) for the regulation of intracellular metabolism, author has focused the studies on Ca metabolism. A parameter which evaluates bone strength is essential for the study of Ca/bone metabolism and the prevention of osteoporosis. Therefore, a machine for measurement of bone strength was developed. Dual-energy X-ray absorptiometry (DXA: bone densitometer) is used very widely in human studies, and has proved to be safer and more accurate than other techniques. Author carried out DXA to determine whether it is suitable for the measurement of low bone mineral density (BMD) in small animals. The estrogen-deficient model rat produced by ovariectomy and the estrogen- and Ca-deficient model rat produced by ovariectomy and a low Ca diet were also evaluated to clarify whether these animal models were useful as osteoporotic models. For prevention of osteoporosis, it is necessary to take enough Ca and to carry out moderate physical activity. However, Ca intake has never been sufficient in Japan. Therefore, the effects of different Ca sources, other nutrients which affect Ca metabolism and physical activity on bone metabolism were examined. It is well known that a reaching a high peak bone mass at a young age and minimizing bone loss with aging and/or the menopause are also important for prevention of osteoporosis. Therefore, the effects of diet and daily physical activity on the BMD of pre/post menopausal women were investigated using DXA from the viewpoint of osteoporosis prevention.

抄録全体を表示

Branched chain fatty acids (BCFAs) of the iso and anteiso series are synthesized from branched-chain amino acids (BCAAs) in many bacteria and in animal skin. This communication describes the biosynthesis of BCFA in Bacillus subtilis and rat skin. BCFAs of Bacillus subtilis are synthesized from the α-keto acids of BCAAs. Two distinct decarboxylases were present in the crude BCFA synthetase of Bacillus subtilis: branched chain α-keto acid (BCKA) decarbaxylase and pyruvate decarboxylase. BCFA synthetase activity was completely lost upon immunoprecipitation of BCKA decarboxylase, suggesting that this enzyme is essential for BCFA biosynthesis by Bacillus subtilis. A BCKA decarboxylase-mediated mechanism was postulated for BCFA biosynthesis. Supplementation of the diet with valine and isoleucine increased the levels of respective BCFAs in the skin surface lipids of rat. However, this was not the case for leucine. Serum levels of valine, isoleucine and their α-keto acids correlated well with the level of the respective BCFAs in the skin surface lipids. Incorporation in vivo of [14C] -BCAA and BCKA into the skin surface lipids revealed that valine and isoleucine rather than their α-keto acids were used mainly for BCFA biosynthesis by rat skin. BCFA synthesis by rat skin differed from that by bacteria in that the systems did not use leucine as a primer. Leucine was used for biosynthesis of straight-chain fatty acids rather than for BCFAs. Substrate specificity and stereoselectivity in vivo of animal BCFA synthesis was described.

抄録全体を表示

酵母に含まれるMgの生体利用性を4週齢Fischer系雄ラットを用い検討した。飼料中のMgの1/2量を酵母のMgで補った群, 飼料中のMgすべてを酵母のMgで補った群を設け2週間飼育し, Control群と比較した。血清Mgレベル, 腎臓Mgレベル, 腎臓の石灰化程度, 大腿骨重量・Ca量・P量・灰分量は, 酵母MgをMg給源とした群とControl群間に有意差がみられず, 大腿骨のMgレベルについてはControl群より有意に高い値を得た。以上の結果から, 酵母MgはMg給源として有効であると考えられた。

抄録全体を表示

体重130g前後のWistar系雄ラットに, 正常食, ミネラル欠食およびマグネシウム欠食を与えて1週間飼育した。飼育最終日の直前16時間絶食してからマグネシウムを投与して, マグネシウムの吸収分布動態を検討した。
1) マグネシウム欠食では正常食に比して体重増はいくらか小さかったが, ミネラル欠食では, 体重は著しく低下した。
2) マグネシウム欠食で低下した血漿中のマグネシウムのレベルが, マグネシウムの投与によって著しく高くなった。
3) マグネシウムの吸収動態では, 腸からの吸収速度が血液および組織への分布速度より遙かに大きく, また投与量の増加によって吸収速度が増大し, 分布速度が小さくなった。
4) 投与したマグネシウムが広範囲に分布および蓄積した。
5) ミネラルの供給不足はマグネシウムの分布容積が小さくなる重要な原因であり, 大量のマグネシウムの投与は死亡の原因となるので, マグネシウムの補充は小量ずつ一定間隔で行うのが最も適当な方法である。

抄録全体を表示