Reactivation and Dedifferentiation of Differentiated Murine Erythroleukemic Cell Nuclei

A murine erythroleukemic cell line, 745 A4-TG, deficient in hypoxanthine-guanine-phosphoribosyl transferase, can be induced with 3 mM hexamethylene bisacetamide to yield at least 50% of cells undergoing irreversible erythroid differentiation and finally losing capacity for cell divisions. The effects of such induced differentiation of 745 A4-TG on its ability to form viable and proliferating hybrids when fused with 3T3 1T22 fibroblasts were investigated. We found that when the induced 745 A4-TG cells were used, more continuously proliferating hybrids were obtained than could be accounted for by the residual uninduced cells which remained in these induced preparations. This suggests that some of the induced 745 A4-TG cells, when fused with 3T3 1T22 reverted from the induced phenotype of a limited capacity for cell proliferation to an uninduced state of continuous proliferation. This observation was further confirmed with the use of fully differentiated 745 A4-TG cells, which were obtained after selection with a bromodeoxyuridine suicide treatment to eliminate the uninduced and the partially differentiated cells in the preparations. When these selected, fully differentiated cells, as characterized by their lack of proliferation capacity and thymidine kinase activity, were fused with 3T3 1T22 (also deficient in thymidine kinase), it was found that not only were viable hybrid colonies obtained in a selection medium, which precluded the proliferation of either parental cells, but these hybrids continued to proliferate for more than two months in selection medium. These data thus confirmed that some fully differentiated erythroleukemic nucleus components in the hybrids were reactivated to regain capacity for cell proliferation and to dedifferentiate to synthesize thymidine kinase for survival in the selection medium. The lack of hemoglobin synthesis by these hybrids also indicates dedifferention of these murine erythroleukemic components in the hybrids.     

Volatile components of developing tomato fruit grown under field and greenhouse conditions

Volatile components of field- and glass greenhouse-grown tomatoes(Lycopersicon esculentum MILL., variety, V. R. Moscow) of differentmaturities were studied by gas-liquid and thin-layer chromatography.The following components were separated and identified: isobutylalcohol, isopentyl alcohol, hexyl alcohol, 2-methyl-3-hexanol,isovaleraldehyde, caproaldehyde, benzaldehyde, furfural, isopentylacetate, isopentyl butyrate, isopentyl isovalerate, butyl hexanoate,hexyl hexanoate, methyl salicylate and -pinene. Chromatogramswere consistent for both field- and greenhouse-grown tomatoesat all stages of maturity. Except for isovaleraldehyde and hexylalcohol, the biosynthesis of volatile components increased alongwith the growth of fruit. Isovaleraldehyde and hexyl alcohol,presumed to give the "green leafy" aroma of tomatoes, were foundto be in their highest concentrations at the breaker and thelarge-green stages, respectively. ¹This research was supported by a research grant—UI 00449—fromthe National Center for Urban and Industrial Health, U. S. PublicHealth Service.     

本溪关门山国家森林公园游客行为特征

研究游客行为特征对于旅游资源的开发、管理以及旅游目的地的可持续发展具有重要的作用。以本溪关门山国家森林公园为研究对象,通过问卷调查的方法对游客的人口统计学特征、地域结构特征、一般行为特征、消费特征及感知特征进行了研究。结果表明:关门山国家森林公园的游客以较高学历的男性中青年为主;客源主要来自本省辽宁,并以沈阳、本溪和大连的游客为主,客源地理集中度指数为35.71;旅游的主要目的是观赏枫叶,出游时间大部分集中在每年"十一"黄金周期间,且半数以上为当日往返的短程游览者;游客偏好与家人一起出游的旅行方式,所选择的交通工具主要为自驾车和旅游专车;游客的消费结构不平衡,主要集中于景区门票和交通费,占总消费的56.7%;游客对景区的喜好度依次为龙门峡景区月台子景区小黄山景区夹砬子景区鸣翠谷景区。总的来说,游客满意度较高,有89.1%的游客愿意重游此地,游客最不满意的地方主要表现在景区卫生方面。基于调查研究结果,对关门山国家森林公园的开发建设和可持续发展提供了相关建议。     

磨盘山天然次生林凋落物数量及动态

以磨盘山5.76hm2天然次生林群落固定监测样地为平台,均匀布设144个凋落物收集器,于2006年每月末(4—11月)连续收集其凋落物,用以分析群落尺度上的凋落物产量、组成及时空变化。结果表明,天然次生林年凋落量为3039.6 kg/hm2,以凋落叶(2499.2 kg/hm2)所占的比例最大,占年凋落量的82.22%,而凋落枝仅占年凋落量的9.92%,花果皮等所占比例更小,占总量的5%以下。1a内,凋落物收集器内共收集到42种树木的凋落叶,占样地内树种总数(46种)的91.30%,其中花曲柳(Fraxinus rhynchophylla)、核桃楸(Juglans mandshurica)和蒙古栎(Quercus mongolica)3个树种的凋落叶占落叶总量的82.97%,为叶凋落量的主要来源。不同收集器之间凋落量存在较大差异,99个收集器的年凋落量在200—400 g,2个收集器超过600 g;单个收集器全年最多可收集到19种树种的凋落叶,收集到凋落叶种数12种的收集器最多(29个)。凋落量月动态呈单峰型,69.78%的凋落量产生于9—10月份,叶凋落量月动态与凋落总量变化相同。落叶以秋季为主,但树种间叶凋落节律存在差异,其中核桃楸叶的凋落高峰集中在8—9月,花曲柳和春榆(Ulmus japonica)集中在9—10月,色木槭(Acer mono)为10月,蒙古栎叶为10—11月。     

研究生高级微生物学课程教学改革与实践初探?

从研究生"高级微生物学"课程的定位、研究生学习该课程的目的、知识背景差异及教学过程中的问题等方面分析了目前研究生"高级微生物学"教学中存在的问题。通过教学内容的优化、教材建设、教学方法改革、师资队伍建设以及建立师生交流平台等方面进行教学改革实践,取得了较好的教学效果。     

强壮前沟藻化感物质分析

微藻化感作用是一种极其复杂的生理、生态学现象。选取强壮前沟藻指数生长初期Ⅰ和平台生长初期Ⅱ两个阶段的滤液对中肋骨条藻、海洋原甲藻、锥状斯氏藻及球等鞭金藻生长的影响进行了研究,并萃取了阶段Ⅱ的粗提物,抑藻检测表明其具有"杀藻"效应,通过GC/MS分析该粗提物中具有潜在化感作用的物质种类。研究发现强壮前沟藻两个生长阶段的滤液对中肋骨条藻均产生强烈致死效应(phaseⅠ:F=15.18475,P=0.00298<0.05;phaseⅡ:F=6.24559,P=0.03149<0.05);锥状斯氏藻在强壮前沟藻滤液中生长,实验结束时两个阶段中的细胞密度分别是对照组的79.3%和68.9%;海洋原甲藻在强壮前沟藻生长阶段Ⅱ滤液实验的最后3d,其生长受到显著抑制(F=4.84438,P=0.04925<0.05);而等鞭金藻在强壮前沟藻两个生长阶段滤液中被抑制现象不明显(P>0.05)。强壮前沟藻滤液实验表明,强壮前沟藻能够向微环境中分泌代谢产物来抑制中肋骨条藻和海洋原甲藻的生长,并且这种抑制效应具有种类特殊对应性。上述实验结果还表明,强壮前沟藻生长阶段Ⅱ的滤液具有的生长抑制作用较为明显。采用乙酸乙酯萃取强壮前沟藻生长阶段Ⅱ滤液中的代谢产物,检测发现其代谢粗提物具有溶藻效应,GC/MS分析结果表明粗提物中存在4种可能产生化感抑制作用的物质,其中二丁基羟基甲苯(Butylated Hydroxytoluene BHT)被认为具有抗滤过性病原体和抗微生物活性。     

植物核DNA含量在全球尺度上的纬度变异式样及其气候适应意义——以菊科植物为例

核DNA含量是重要的生物学概念,涉及DNA C-值和基因组大小。前人有关植物核DNA含量在纬度梯度上的变异规律存在着矛盾的报道,而且多数将核DNA含量与纬度、海拔、气候等因素之间的关系描述成线性关系。核DNA含量是否具有环境适应上的意义,也还存在争议。先前有关核DNA含量与环境因素间关系的矛盾性报道可能与取样过小、地理范围过窄、研究对象遗传背景差异过大有关。如果对一个遗传背景相近的类群在全球范围内进行取样,核DNA含量会呈现有规律的纬度梯度变化,可能与大的气候因素之间存在非线性关系。菊科(Asteraceae)是被子植物的最大科,是一个广泛认可的自然分类群。为揭示全球空间尺度上植物核DNA含量在纬度梯度上的变异规律,以及这种变异是否具有环境适应意义,以菊科为对象开展了核DNA含量与纬度、生物气候因素关系的统计分析。从"植物DNA C-值数据库"检索到822种菊科植物的核DNA含量数据;在全球范围内,沿经度方向上设立10条样带,每条样带横跨15个经度,每条样带又均分成22个样块,每个样块纵跨7.5个纬度;其次,从"世界气候数据网站"下载1950—2000年时间段14个生物气候因子数据,应用Arc GIS 9.3获得每个样块14个生物气候因子的平均值;根据"全球生物多样性信息网站"记录,计算每个样块菊科植物平均的核DNA含量数据。为避免气候变量之间的多重共线性对数据分析的影响,应用主成分分析对数据进行了降维,发现最冷季度平均温度、最干季度雨量分别是第一、二主成分上荷载最大的因子,去除与它们相关性在-0.7至+0.7之间的其他气候因子后获得了最冷季度平均温度、最干季度雨量和最湿月份雨量三个变量用于进一步数据分析。结果发现,菊科植物在全球10个样带上的核DNA含量与纬度关系密切,与最冷季度平均温度、最干季度雨量和最湿月份雨量呈现极显著的单峰型的非线性关系,可以用二项式进行拟合。因此,全球空间尺度上植物核DNA含量沿着纬度梯度有规律性的非线性变化,这种变化具有很强的气候适应意义。