92 resultados para 554
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β_2肾上腺素受体(β_2AR)在哮喘患者中表现出遗传多态性。近年国外已对位点16及27进行了一些临床研究,但是所用基因分型方法不一,此外在中国人群这2个位点的多态性哮喘的关系至今仅有个别报道,我们采用所有样本测序方法,就其多态性与肺功能的关系进行初步探讨。
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鸡胚胎是一种被广泛应用于发育生物学研究的实验材料。在以鸡胚胎为动物模型的各项研究工作 中, 心率常被看作是一个很重要的反应胚胎生理活动指标。本文详细介绍了一种侵入性的心电记录新方法, 在 正常的生理条件下通过记录鸡胚胎心电的变化来监测心率。首先在蛋壳上钻孔, 将电极插人蛋内, 然后通过放 大器放大, 板转换, 将心电信号输人电脑进行分析处理, 提取与心率相关的信息。这种记录方式对胚胎损 伤较小, 不影响胚胎的正常发育具有灵敏度高, 操作简单, 容易掌握等特点。
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通过正交试验考察了成熟湿地基质在选定的影响因素及水平下的氮释放量。结果表明,25℃下氨氮的平均释放量是15℃下的2.9倍,亚硝态氮及硝态氮的释放量在两温度下无显著差异;35℃下氨氮的平均释放量是15℃下的5.6倍,亚硝态氮和硝态氮的释放量较15℃时有明显增加。由于湿地基质中COD的释放,在试验设定的进水COD浓度水平(≤40 mg/L)下,COD含量难以对氮的释放产生显著影响。湿地基质对pH有较强的缓冲能力,试验设定的进水pH基本不会影响氮的释放。
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中国科学院创新项目 (KSCX2- 1- 0 6B)资助
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淡水生态与生物技术国家重点实验室开放基金 (批准号 :2 0 0 1FB0 6)资助
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1999年 12月至 2 0 0 0年 11月 ,对华中科技大学华瑜池的原生动物群落进行了研究 ,共检出原生动物 12 5种 ,其中植鞭毛虫 19种 ,动鞭毛虫 2 8种 ,纤毛虫 6 4种 ,肉足虫 14种 .对原生动物群落结构和功能的研究表明 :1)自然条件下 ,PFU原生动物群落的种类组成数及原生动物群落的群集速度相对稳定 ;2 )自然条件下 ,PFU原生动物群落结构和功能不受季节变化的影响 ;3)当PFU原生动物群落受到外界胁迫时 ,不管这种胁迫来自物化因素或是生物因素 ,其群落结构和功能都会发生
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国家自然科学基金资助项目(39570086)
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根据1994—1998年获得的246尾标本,对中华鲟繁殖群体的性比、性腺发育成熟个体比例、年龄结构、体长和体重特征等进行了研究。并结合历史资料,对其种群资源现状进行评价,提出了相应的资源保护措施建议。
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本文报道了东湖环棱螺的种群密度、年龄结构、种群增长率和生物量、生产量、P/B系数及其在不同湖区中的季节变化;用指数生长模型计算种群增长率。以累计总增长的方法估算种群生产量。研究结果表明,水果湖区铜锈环棱螺年平均生物量为554.37克·米~(-2),累计生产量为604.99克·米~(-2)·年~(-1),P/B系数为1.09;郭郑湖区平均生物量为286.74克·米~(-2),生产量为308.99克·米~(-2)·年~(-1),P/B系数为1.08。本文还对影响铜锈环棱螺的种群变动和生产量的生态因子作了扼要的
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The present research studied the effects of age and dietary protein level on pepsin, trypsin and amylase activity and their mRNA level in Petteobagrus fulvidraco larvae from 3 to 26 days after hatch (DAH). Three DAH larvae were fed three isoenergetic diets, containing 42.8% (CP 43), 47.3% (CP 47) and 52.8% (CP 53) crude protein. Live food (newly hatched Artemia, unenriched) was included as a control. The effects of age on enzyme activity and mRNA were as follows: pepsin and trypsin activity in all treatment groups showed a significant (P < 0.05) increase at the beginning and decrease later although the timing of decrease was not the same among treatment groups and between the digestive enzymes. Pepsin and trypsin mRNA level followed the pattern of their respective enzyme changes. Age significantly affected amylase activity (P < 0.05) while age had no effect on amylase mRNA during the experimental period. The four diets significantly (P < 0.05) affected activity and mRNA level of pepsin and trypsin. Diets did not affect amylase activity or mRNA level. These results suggest that the effects of age on pepsin and trypsin gene expressions are at the transcriptional level. Dietary protein level does affect pepsin and trypsin gene expression in the early life of P. fulvidraco. There were no transcriptional effects on amylase gene expression. (c) 2005 Elsevier B.V. All rights reserved.
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Natural resistance associated macrophage protein (Nramp) controls partially innate resistance to intracellular parasites. Its function is to enhance the ability of macrophages to kill pathogens. However, little is known about the structure and function of Nramp in lower vertebrates such as teleosts. We have recently isolated a cDNA encoding Nramp from Japanese flounder (Paratichthys olivaceus). The full-length cDNA of the Nramp is 3066 bp in length, including 224 bp 5' terminal UTR, 1662 bp encoding region and 1180 bp 3' terminal UTR. The 1662-nt open reading frame was found to code for a protein with 554 amino acid residues. Comparison of amino acid sequence indicated that Japanese flounder Nramp consists of 12 transmembrane (TM) domains. A consensus transport motif (CTM) containing 20 residues was observed between transmembrane domains 8 and 9. The deduced amino acid sequence of Japanese flounder had 77.30%, 82.71%, 82.67%, 79.64%, 80.72%, 90.97%, 91.16%, 60.14%, 71.48%, 61.69%, 72.37% identity with that of rainbow trout Nramp alpha and beta, channel catfish Nramp, fathead minnow Nramp, common carp Nramp, striped sea bass Nramp, red sea bream Nramp, mouse Nramp 1 and 2, human Nramp 1 and 2, respectively. RT-PCR indicated that Nramp transcripts were highly abundant in spleen, head kidney, abundant in intestine, liver and gill, and less abundant in heart. The level of Nramp mRNA in embryos gradually increases during embryogenesis from 4 h (8 cell stage) to 80 h (hatched stage) after fertilization. (c) 2005 Elsevier Ltd. All rights reserved.