C-band differentiation between the chromosomes of two subspecies of the chironomid midgeChironomus thummi

Summary The metaphase chromosomes ofChironomus th. thummi contain approximately 17% more pericentric C-band heterochromatin than the chromosomes ofChironomus th. piger with 11% heterochromatin. InCh. th. thummi, the proportion of heterochromatin appeared to be much larger in metaphase chromosomes than in polytene chromosomes. This discrepancy is interpreted as being due to the specific chromosome organization and not as the result of an underreplication of heterochromatin during polytenization.     

Alzheimer's disease: fundamental and therapeutic aspects

Alzheimer's disease is the most common type of progressive and debilitating dementia affecting aged people. In some early — as well as late-onset familial cases, a genetic linkage with chromosomes 14, 21 (early-onset) or 19 (late-onset) has been indicated. Furthermore, a direct or indirect role has been attributed to normal or structurally altered amyloid -protein (concentrated in senile plaques) and/or excessively phosphorylated tau protein (located in neurofibrillary tangles). Degeneration of cholinergic neurons and concomitant impairment of cortical and hippocampal neurotransmission lead to cognitive and memory deficits. Several compounds are being tested in attempts to prevent and/or cure Alzheimer's disease, including tacrine, which has very modest efficacy in a sub-group of patients, and new acetylcholinesterase inhibitors. Pilot experiments have also been launched using nerve growth factor (NGF) to prevent or stabilize the processes of cholinergic pathway degeneration. Alternatively, antioxidants, free radical scavengers and/or non steroidal anti-inflammatory agents may be screened as potential therapies for neurodegenerative diseases induced by multiple endogenous and/or exogenous factors. The recent use of transgenic mice, in parallel with other genetic, biochemical and neurobiological systems, in vivo and/or in vitro (cell cultures), should accelerate the discovery and development of specific drugs for the treatment of Alzheimer's disease.     

Comparison of infection frequencies in fetus by maternal ascitic cancer and leukemia cells

It was demonstrated that maternal Ehrlich cells could infect fetus in a mouse model, which is another kind of the cancer cells inducing cancer cell infection between mother and fetus besides leukemia L615 cells reported previously by the authors. Among the fetus in a pregnancy only a few of them might be infected by the maternal cancer cells. The early and medial periods of pregnancy are the dangerious periods for the cancer infection. The infection frequencies for leukemia L615 cells and Ehrlich cells are 100% and 35%, respectively; but in the late period of pregnancy they are 4.5% and zero for leukemia L615 and Ehrlich cells, respectively. This indicates that the infection frequency for leukemia L615 cells is much higher than Ehrlich cells. The infection might be caused by infiltration or invasion of the cancer cells.     

用HBSG法对多枝赖草、普那菊苣根尖染色体进行C-分带的研究

利用HBSG法对多枝赖草、普那菊苣的根尖染色体进行了C -分带研究.根据李懋学等(1991年)对C -分带的描述方法,首次确认多枝赖草染色体的C -分带为2n=28=5CT 2CTI 2CT 1CTI 1CTI 1C 1T 1TI,普那菊苣各染色体的C -分带为2n=18=2CT 4CTI 1CT 1CTI 1CT I .另外还对C -分带实验中的一些技术细节做了初步的分析.     

基于小生境遗传算法的飞行航迹规划

提出了一种基于小生境遗传算法的飞行航迹规划方法.把航迹编码为离散时间上变长度的飞行器速度和航向变化序列,并以此序列作为遗传算法种群中的个体,在这个变化序列中,每一个元素都考虑了飞行器的性能约束,因而,每个变化序列对应的航迹郝是飞行器可飞的.初始种群不是随机生成,而是根据规划起点和终点的相对关系生成的.为了防止种群收敛于局部最优解,采用基于共享函数的小生境技术增加种群的多样性.仿真结果表明,算法能快速有效地在动态环境中规划出近最优的飞行航迹.     

遗传算法在多机调度问题中的应用

本研究了总的流程时间最小的多机调度问题,建立了该问题的数学,模型并用一种改进遗传算法有效解决了该问题。这种改进遗传算法的关键是产生一组较优的初始群体,仿真实验结果表明这种改进遗传算法可以快速、高效地寻找到该问题的全局最优解。     

背角无齿蚌碱性磷酸酶的功能基团研究

在一定条件下，分别采用ＰＭＳＦ，ＤＴＴ，ＰＣＭＢ，ＮＢＳ，ＴＮＢＳ，ＳＵＡＮ，ＢｒＡｃ及ＩＡｃ等化学修饰剂，选择修饰背角无齿蚌碱性磷酸酶的多种氨基酸残基，并测定其酶活力变化。结果表明，ＰＭＳＦ，ＮＢＳ，ＴＮＢＳ，ＳＵＡＮ和ＤＴＴ的修饰能显著抑制酶的活力，而且活力的降低程度与修饰剂的浓度相关。ＢｒＡｃ，ＩＡｃ和ＰＣＭＢ的修饰不表现对酶的抑制作用。初步认为，Ｓｅｒ，Ｌｙｓ和Ｔｒｐ残基是背角无齿蚌碱性磷     

CHN大鼠乳腺癌骨髓细胞染色体的分析与研究

实验采用常规骨髓细胞染色体制片法,对CHN大鼠和正常大鼠的染色体作了镜检和核型比较。结果表明:CHN大鼠呈现染色体变异,且与正常大鼠比较有显著差异。这一结果提示,染色体变异在大鼠乳腺肿瘤发生中具有重要作用。     

冶铸轧一体化生产合同计划优化问题研究

将炼钢—连铸—热轧—精整一体化生产过程,抽象为炼钢与热轧两大加工阶段,以板坯热装比最大、交货提前/拖期率和组炉余材率最小为优化目标,综合考虑炼钢与热轧的产能,以及钢种、板坯和成品规格等约束条件,建立生产合同计划数学优化模型,并采用双层染色体遗传算法进行求解.在合同计划层次上,解决了一体化生产过程中,连铸与热轧工序之间在钢种和规格上的匹配问题.获得的合同计划,是冶铸轧一体化生产的批量计划和静态调度优化问题的合理的生产定单池.仿真实例证明了模型的合理性与算法的有效性.     

756例遗传咨询者的染色体分析

目的:探讨遗传性疾病的细胞遗传学基础.方法:对756例遗传咨询者进行外周血淋巴细胞染色体分析.结果:发现异常核型126例,异常检出率16.67%.结论:智力低下、流产、死胎、生育畸形儿、性发育不全及生殖力低下者的染色体检查,均有细胞遗传学改变.