The Effects of Rapid Temperature Changes on HK,PK and HSP70 of Litopenaeus vannamei in Different Seasons

Activities of hexokinase(HK),pyruvate kinase(PK) and levels of HSP70 were measured to evaluate the response of Litopenaeus vannamei to rapid temperature changes under controlled laboratory conditions.Shrimps were subjected to a quick temperature change from 27℃ to 17℃ for the summer case(Cold temperature treatment),or from 17℃ to 27℃ for the winter case(Warm temperature treatment).After 0.5,1,3,6,12,24,48,and 72 h of exposure time,shrimps were sampled and prepared for further analysis.The results showed that the effect of acute temperature changes on activities of HK was significant.Patterns of variations of the two glycolytic enzymes suggested that enzymes in the glycolysis cycle could adjust their activities to meet the acute temperature change.The HSP70 level increased in both cold and warm temperature treatments,suggesting that the rapid temperature changes activated the process of body's self-protection.But the difference in expression peak of HSP70 might be related to the different body size and the higher thermal sensitivity to temperature increase than to temperature decrease of L.vannamei.

日本糖业在中国市场上的开拓及竞争(1903—1937)

1895年日本占领中国产糖重镇台湾,在台湾糖业基础上,日本大力发展本国制糖业,并着力拓展东亚市场。1903年日糖正式进入中国市场,到1937年中日全面战争爆发,日糖在中国市场上的开拓及竞争活动,既改变了传统的中日糖品贸易格局,即由中国向日本输入糖品及技术的格局转变为由日本向中国输入糖品及技术的局面;也改变了近代中国乃至整个东亚市场上的糖品竞争格局,即由爪哇糖及香港糖两糖统治的格局转变为日糖、香港糖两糖独大的局面。从这些活动中,不难看出,这一时期中外糖品之间的竞争形势,依旧为进口机制洋糖同国内土法制糖之间的竞争,外糖商仍通过商品输出手段来控制中国的糖品销售市场,而并未完全过渡到资本与商品输出手段并用的阶段;同时,日糖在中国市场上的成功是由政府扶植、糖商积极进取及侵略活动等多方因素共同促成的,而国糖三十多年的发展停滞及倒退,虽然是由局势动荡、政府无力、糖商无识及外糖入侵等一系列因素造成的,不过,日糖的成功是这一系列因素中较为关键的一种。因此,可以肯定,对日糖在中国市场上开拓及竞争活动的分析是解读国糖衰退及东亚糖品竞争格局演变的关键所在。