Sexual difference in the requirement for sulfur-containing amino acids in the silkworm, <i>Bombyx mori</i>

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  • 家蚕の含硫アミノ酸要求にみられる雌雄間差異
  • カサン ノ ガンリュウ アミノサン ヨウキュウ ニ ミラレル シユウカン サイ

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Abstract

Sexual difference of sparing effect of dietary cystine on methionine requirement in the silkworm was investigated using synthetic diets in which graded doses of methionine and cystine were added. Newly ecdysed 5th-instar larvae were reared for 5 days on these diets, and after measurement of body weight the larval haemolymph was collected by cutting the abdominal legs. The concentration of protein and amino acids of larval haemolymph were determined by the method of LOWRY et al. and method of YEMM and COCKING, respectively.<br>The rate of in vivo conversion of DL-cystine-1-14C to 14CO2 by the larvae was determined. Larvae reared on the diet containing methionine 3mg/g and cystine of 0mg/g, 1mg/g, or 3mg/g were injected with 0.2μCi of DL-cystine-1-14C (35mCi/mM) and the radioactivity of respired 14CO2 was measured in a liquid scintilation counter 6 and 12 hours after injection.<br>1. In the presence of 3mg methionine/g of the dry diet, the growth of the male larvae was not improved by the addition of cystine, whereas in the female larvae the growth-promoting effect of cystine was observed. These facts show that the female larvae require more sulfur-containing amino acid than the male larvae.<br>2. The concentration of protein in larval haemolymph was correlated to some degree with the larval growth. There was sexual difference in the effect of the dietary sulfur-containing amino acid on the concentration of haemolpmph protein.<br>3. It was shown that the concentration of free amino acids in haemolymph was higher in poorly grown larvae than in the normally grown larvae.<br>4. The recoveries of 14CO2 from larvae injected with DL-cystine-1-14C increased according to the increase of the level of dietary cystine. In the same level of dietary cystine, the recovery of 14CO2 from the female larvae was significantly less than that from the male larvae.

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