Allelic exclusion in transgenic mice that express the membrane form of immunoglobulin mu

Antibody-producing cells display a special form of regulation whereby each cell produces immunoglobulin from only one of its two sets of antibody genes. This phenomenon, called allelic exclusion, is thought to be mediated by the product of one heavy chain allele restricting the expression of the other. Heavy chains are synthesized in two molecular forms, secreted and membrane bound. In order to determine whether it is specifically the membrane-bound form of the immunoglobulin M (IgM) heavy chain (mu) that mediates this regulation, transgenic mice were created that carry a human mu chain gene altered so that it can only direct the synthesis of the membrane-bound protein. The membrane-bound form of the human mu chain was made by most of the B cells in these animals as measured by assays of messenger RNA and surface immunoglobulins. Further, the many B cells that express the human gene do not express endogenous mouse IgM, and the few B cells that express endogenous mouse mu do not express the transgene. Thus, the membrane-bound form of the mu chain is sufficient to mediate allelic exclusion. In addition, the molecular structures recognized for this purpose are conserved between human and mouse systems.     

Nuclear factors in B lymphoma enhance splicing of mouse membrane-bound mu mRNA in Xenopus oocytes

Regulation of the synthesis of membrane-bound and secreted immunoglobulin mu heavy chains at the level of RNA processing is an important element for B cell development. The precursor mu RNA is either polyadenylated at the upstream poly(A) site (for the secreted form) or spliced (for the membrane-bound form) in a mutually exclusive manner. When the mouse mu gene linked to the SV40/HSV-TK hybrid promoter was microinjected into Xenopus oocytes, the mu messenger RNA (mRNA) was altered by coinjection of nuclei of mouse surface IgM-bearing B-lymphoma cells to include the synthesis of the membrane-bound form. An increase in the membrane-bound form was not observed when nuclei of IgM-secreting hybridoma cells or fibroblast cells were coinjected. Deletion of the upstream poly(A) site did not eliminate the effect of B-lymphoma nuclei suggesting that membrane-specific splicing is stimulated. Further, splicing of other mu gene introns was not affected by coinjection of B-lymphoma nuclei. These results suggest that mature B cells contain one or more transacting nuclear factors that stimulate splicing specific for membrane-bound mu mRNA.     

Translocation and rearrangements of the c-myc oncogene locus in human undifferentiated B-cell lymphomas

The locus for the cellular myc (c-myc) oncogene in humans is located on the region of chromosome 8 that is translocated to chromosome 14 in cells from most undifferentiated B-cell lymphomas. It is shown in this study that the c-myc locus is rearranged in 5 out of 15 cell lines from patients with undifferentiated B-cell lymphomas, and that the rearrangement involves a region at the 5' side of an apparently intact c-myc gene. In at least three patients, this rearranged region appears to contain immunoglobulin heavy chain mu sequences that are located on chromosome 14. The data indicate that this region contains the crossover point between chromosomes 8 and 14. The break point can occur at different positions on both chromosomes among individual cell lines.     

J genes for heavy chain immunoglobulins of mouse

A 15,8-kilobase pair fragment of BALB/c mouse liver DNA, cloned in the Charon 4A lambda phage vector system, was shown to contain the mu heavy chain constant region (CHmu) gene for the mouse immunoglobulin M. In addition, this fragment of DNA contains at least two J genes, used to code for the carboxyl terminal portion of heavy chain variable regions. These genes are located in genomic DNA about eight kilobase pairs to the 5' side of the CHmu gene. The complete nucleotide sequence of a 1120-base pair stretch of DNA that includes the two J genes has been determined.     

Immortalization of human T lymphocytes after transfection of Epstein-Barr virus DNA

Epstein-Barr virus (EBV), a ubiquitous human herpesvirus, has the ability to transform human B lymphocytes. No other cell type has been experimentally transformed by EBV, either by intact virions or naked viral DNA and subgenomic fragments. Two immortalized human T-lymphoblastoid cell lines have now been established by transfecting cord blood lymphocytes with purified B95-8 viral DNA enclosed in fusogenic Sendai virus envelopes (RSVE) and then exposing the cells to EBV from a P3HR-1 cell subclone. One of these lines, which has been fully characterized, is termed HBD-1. This line is positive for EBV DNA and expresses surface OKT11, OKT4, and Tac receptors, but not M-1, mu immunoglobulin chains, EBV receptors, or B-1 surface markers. The cells contain fully rearranged T-cell receptor genes and germline immunoglobulin genes. The karyotype of the cells is normal, they do not require interleukin-2 for growth, and do not contain human T-lymphotropic virus type I. However, the HBD-1 cells contain incomplete EBV genomes and express several EBV-determined antigens, including the early antigen type D, membrane antigens, but not EBV-determined nuclear antigen (EBNA). This association of the EBV genome with permanently growing hematopoietic cells of non B-cell lineage should prove useful in studies on the mechanism of EBV-mediated cell transformation.     

马铃薯黑痣病发生与不同种植密度关系研究报告

本试验研究不同种植密度对马铃薯产量、性状及黑痣病影响,试验结果表明在播种密度3500(株/亩)至4000(株/亩)时,马铃薯平均亩产最高,病害发生情况最轻及商品率高。     

食用菌废培养料对小麦和大豆产量的影响

采菇之后的废培养料条施种小麦,麦收后种大豆,从两茬作物的产量看,废培养料250公斤/亩深施加少量化肥(N3.5公斤/亩,P_2O_51.75公斤/亩)与单施化肥(N7公斤/亩,P_2OP_53.5公斤/亩)相比,差异不显著;较之250公斤/亩废培养料深施不加化肥,大豆增产显著(α=0.05);较之浅施废培养料250公斤/亩和125公斤/亩两处理,小麦分别增产9.1％和11.6％,均达显著(α=0.01)水平。废培养料125公斤/亩与不施肥相比,小麦、大豆产量均未出现显著差异。     

FMC公司系列药剂防除移栽水稻田莎草的试验

针对莎草科杂草基数较大的田块受害重 ,防除难度大 ,与之相应的安全有效除草药剂还较少 ,我们采用了FMC公司系列药剂进行了试验。结果显示 :Harrier 70 .5 %DF剂量每 6 6 7m2 在30～ 5 0g ,均能有效防除三棱草 ,但安全性较差 ;用Harrier 70 5 %DF每 6 6 7m2 剂量 2 5g与 6 .7g威农 30 %WP配合施用 ,F 796 72 5 %WG 6 7g与MCPA 5 6 % 4 7 6g或威农 30 %WP 8 9g配合施用 ,快灭灵 4 0 %DF 4 2g与威农 6 7g配合施用也能有效防除 ,部分有轻微药害 ,但后期基本能够恢复     

不同处理时长对棉隆土壤处理防治芹菜根腐病防治效果的研究

本次试验针对棉隆30kg/亩土壤处理方法，设置了两个处理时长，旨在研究通过棉隆相同浓 度条件下土壤处理不同处理时长对芹菜根腐病的防治效果。结果表明:经过124 天覆膜土壤处理的芹 菜地生长82 天后，芹菜死亡率为8.9%，产量为6954.5kg/亩；经过10 天覆膜处理的芹菜地经过相同生 长期后芹菜的死亡率为18.1%，产量为6219.4kg/亩；对照经过相同生长期后的死亡率为54.5%，产量为 2927.7kg/亩。因此，说明棉隆覆膜对芹菜根腐病的防治效果与土壤处理时间长短存在直接关系。系 统性研究棉隆     

夏播小麦品种比较与育种方向探讨

夏播小麦在海拔较高的山区丘陵旱地种植,可以充分利用七、八、九月雨水多、温度高、光照足的自然条件,扬长避短,发挥天时地利的优势;为改变我省旱地小麦产量长期低而不稳的局面,探索了一条新的增产途径。目前可利用适合夏播的小麦品种不多,主要的是夏麦1号(青春13×墨巴66)与晋春3号即忻春矮2号(咸农39×墨巴66),播种面积逐年扩大,1981年在平遥夏播小麦684,4亩,平均亩产153斤;最高亩产521斤。1982年在榆次县扩大面积1389亩,平均亩产190斤;最高亩产达到531,5斤。 1981年在榆次县选用13个品种(系),1982年选用12个品种,进行品种比较与区域试验。结果产量较高超过对照的有:伊尼亚×44,3696,80-1和7064等,主要增产原因是每亩穗数较多超过23万;每穗有20粒左右,千粒重达到40克以上。因为亩穗数增加,叶面积系数也相应大幅度增加,这样,从时间上和空间上充分利用太阳光能,同化积累更多的干物质;为获得高产奠定物质基础。多穗形品种的穗数增多,与产量提高密切相关。保苗增穗的主要途径有三:(1)窄行匀播,合理密植,增加基本苗。(2)种子处理,增强抗性;确保总茎数。(3)提高分蘖力,促进增加成穗数。单靠增加穗粒数与千粒重来提高夏播小麦产量,还有一定的局限性;而培育多穗型品种可能是主要方向。在多穗型的基础上,再选择大粒品种也是夏播小麦育种的一个重要目标。产量结构的设计是:每亩20——25万穗,每穗20粒,千粒重40——45克;亩产就可达到300斤左右。     

氮磷化肥施用量对烟草产量与品质影响的研究

试验表明在豫西丘陵地区,对烟草合理施用氮磷化肥具有明显的增产作用。每亩施纯氮3kg其产值高于2kg,N:P_2O_5=1:1～1.5为宜。     

泾源县玉米全膜双垄覆盖沟播密度试验

试验结果表明,在全膜双垄覆盖条件下,种植密度为4500株/667m2产量表现最好,为685.9kg/667m2;其次,种植密度为4000株/667m2产量为597.5kg/667m2;种植密度为2500株/667m2和3000株/667m2表现欠佳。     

残膜对土壤水分运移的影响

采用室内模拟的方法对残膜影响土壤水分运移进行了研究。结果表明,残膜会阻碍土壤水分向上移动,而且残留量和残膜面积越大,阻碍作用越明显。此外,残膜对土壤水分下渗有一定的促进作用。     

茄子“3414”肥料效应田间试验

从“3414”回归最优设计原理设置的茄子肥效试验数据,获得三元肥料效应函数方程,由此数学模型得出理论氮磷钾最佳施肥量配方为N24．23kg／667m^2,P2O54．70kg／667m^2和K2O17．12kg／667m^2,可获得最佳产量3626．77kg／667m^2。综合分析本试验结果,结合当地农业生产实际,氮磷钾建议推荐施用量分别为25kg／667m^2、6kg／667m^2和20kg／667m^2。     

春小麦新品种“甘春86—5001”丰产栽培技术研究

在黄羊镇农怍物试验站对新品种“甘春86—5001”进行了密度和化肥用量的2因素5水平正交回归旋转设计的模式化栽培技术研究。结果表明,在中等地力条件下,甘春86～5001以亩施纯氮9～13公斤,纯磷6～9公斤,每亩基本苗40～45万较好。密度与施化肥的最佳组合为密度41.8万苗,亩施纯氮11.75公斤,纯磷8.2公斤,每亩籽粒产量可达650.8公斤,其相应的产量结构为成穗数44.45万,穗粒数39.5粒,千粒重43.13克。本文还分析了生物产量,主要经济性状和倒伏率与密度及施肥量的关系,指出超高产品种的选育和栽培管理必须重视倒伏问题。