Frequent c-fms activation by proviral insertion in mouse myeloblastic leukaemias

Retroviruses lacking oncogenes can induce tumours in animals, and the tumour cells are frequently found to contain proviral DNA inserted next to a proto-oncogene, which is thus placed under the regulatory control of the retroviral long terminal repeat (LTR). This altered regulation leads to overexpression of the proto-oncogene, which presumably contributes to the growth properties of the tumour cells. fim-2 has been described as a retroviral integration site frequently and specifically involved in murine myeloblastic leukaemias induced in vivo or in vitro by the replication-competent Friend murine leukaemia virus (F-MuLV). Here we report that fim-2 spans the 5'-end of the murine proto-oncogene c-fms, known to code for a transmembrane glycoprotein with tyrosine kinase activity probably identical to the receptor of the haemopoietic growth factor, monocyte-macrophage colony-stimulating factor (M-CSF or CSF-1). Proviral integration in the fim-2 region results in a high expression of a normal sized c-fms messenger RNA. We also observe that some tumours have lost the fim-2/c-fms germ line allele. These results provide the first evidence for the presumed involvement of c-fms in myelomonocytic leukaemias.     

A gradient of sex linkage in the pseudoautosomal region of the human sex chromosomes

Three independent pseudoautosomal loci are linked to sex determination at frequencies which define a gradient of linkage. The segregation patterns of these loci indicate that X/Y recombination results from a single obligatory meiotic crossing-over in the pseudoautosomal region. Recombination in male germ cells in the terminal regions of the short arms of the X and Y chromosomes in 10-fold greater than between the same regions of the X chromosomes in female germ cells.     

粗细端不等长阶梯形变幅杆谐振频率的实验研究

研究了粗细端不等长阶梯形变幅杆的谐振频率,分析了谐振频率的降低系数β随面积比的对数lnN2变化的规律,发现粗细端不等长变幅杆与等长变幅杆谐振频率系数随面积比对数的变化关系相似,并且在lnN2>2.40时与局部共振现象吻合.这为阶梯形变幅杆的研究和设计提供了一定依据.     

An inherited limb deformity created by insertional mutagenesis in a transgenic mouse

We have created an insertional mutation that leads to a severe defect in the pattern of limb formation in the developing mouse. The novel recessive mutation is phenotypically identical and non-complementary to two previously encountered limb deformity mutations, and is closely linked to a dominant mutation that gives rise to a related limb dysmorphism. The inserted element thus provides a molecular genetic link with the control of pattern formation in the mammalian embryo.     

Very high frequency of lymphoma induction by a chemical carcinogen in pim-1 transgenic mice

Infection of mice with Moloney murine leukaemia virus (MuLV) induces T-cell lymphomas after an average latency period of 150 days. In these lymphomas the MuLV DNA is frequently integrated into the mouse chromosomal DNA in the vicinity of the pim-1 oncogene. Transgenic mice overexpressing the pim-1 oncogene are predisposed to develop T-cell lymphomas, but only to the extent that approximately 10% of the mice develop a lymphoma within 240 days. When these mice are infected with MuLV, lymphomas develop in all mice in only 50-60 days. In these lymphomas MuLV DNA is integrated near either the c-myc or N-myc gene, suggesting that pim-1 and myc synergize in lymphomagenesis. To determine whether this system has a more general application, we have now tested the susceptibility of pim-1 transgenic mice to N-ethyl-N-nitrosourea (ENU), a chemical carcinogen. With a single low dose of ENU, nearly all pim-1 transgenic mice, but only 15% of non-transgenic mice, develop T-cell lymphomas within 200 days. All ENU-induced lymphomas in both pim-1 transgenic and non-transgenic mice express high levels of c-myc messenger RNA, supporting the notion that pim-1 and c-myc synergize in lymphoma induction. We propose that pim-1 transgenic mice could be used to test the oncogenic potential of other chemical compounds.     

Production of a mutation in mouse En-2 gene by homologous recombination in embryonic stem cells

A full understanding of the function of genes that control developmental events can be obtained only by a combination of molecular and mutational analysis. One putative developmental gene is the mouse engrailed-like gene En-2, which was isolated by virtue of its extensive homology to Drosophila engrailed, which contributes to the control of segmentation in the developing insect. Our hybridization analysis in situ has revealed that expression of En-2 is restricted to a specific domain of the developing central nervous system from 8 days of development on, indicating a role for the gene in establishing spatial domains in the brain. Unfortunately no En-2 mutations are available to elucidate further its function in development. To this end, we report here the isolation of three pluripotent embryonic stem cell lines in which one copy of the homoeobox-containing gene, En-2, has been altered by homologous recombination.     

Construction of recombinant industrial Saccharomyces cerevisiae strain with bglS gene insertion into PEP4 locus by homologous recombination

The bglS gene encoding endo-1,3-1,4-β-glucanase from Bacillus subtil＆ was cloned and sequenced in this study. The bglS expression cassette, including PGK1 promoter, bglS gene fused to the signal sequence of the yeast mating pheromone a-factor （MFals）, and ADH1 terminator with G418-resistance as the selected marker, was constructed. Then one of the PEP4 allele of Saccharomyces cerevisiae WZ65 strain was replaced by bglS expression cassette using chromosomal integration of polymerase chain reaction （PCR）-mediated homologous recombination, and the bglS gene was expressed simultaneously. The recombinant strain S. cerevisiae （SC-βG） was preliminarily screened by the clearing hydrolysis zone formed after the barley β-glucan was hydrolyzed in the plate and no proteinase A （PrA） activity was measured in fermenting liquor. The results of PCR analysis of genome DNA showed that one of the PEP4 allele had been replaced and bglS gene had been inserted into the locus of PEP4 gene in recombinant strains. Different endo-1,3-1,4-β-glucanase assay methods showed that the recombinant strain SC-βG had high endo-1,3-1,4-β-glucanase expression level with the maximum of 69.3 U/（h·ml） after 60 h of incubation. Meanwhile, the Congo Red method was suitable for the determination of endo-1,3-1,4-β-glucanase activity during the actual brewing process. The current research implies that the constructed yeast strain could be utilized to improve the industrial brewing property of beer.     

双臂质量不同音叉振动周期与频率的研究

在分析音叉受迫振动的基础上,利用周期测定仪测定周期快捷方便的优点,将负载分别加在音叉某一臂上的不同位置,研究音叉的振动周期和频率与所加负载在音叉不同位置的关系,得到了随着位置的不同,音叉的频率与周期为非线性变化。当在音叉某一位置不变而逐渐增加负载质量,发现周期与质量为线性关系,并为正相关,而频率与质量为线性关系,但为负相关,而且正相关与负相关的线性相关系数很高。其结果揭示了振动周期和频率与音叉双臂质量不同时的关系。     

High variability of the gvpA-gvpC region in Microcystis

Gas vesicles provide buoyancy to Microcystis and other common cyanobacterial bloom-forming species. gvpA and gvpC are structural genes encoding gas vesicle proteins. Phylogenetic analyses of 10 Microcystis strains/uncultured samples showed that gvpC and each intergenic segment of the gvpA-gvpC region can be divided into two types. The combination of different types of gvpC and intergenic segments is an important factor that diversifies this genomic region. Some Microcystis strains isolated in China possess a 172 to 176 bp sequence tag in the intergenic segment between gvpA and gvpC. The gvpA-gvpC region in Microcystis can be divided into at least 4 classes and more numbers of subclasses. Compared to rbcLX and other regions, the high variability of the gvpA-gvpC region should be more useful in identifying geographical isolates or ecotypes of Microcystis.     

High variability of the gvpA-gvpC region in Microcystis

Gas vesicles provide buoyancy to Microcystis and other common cyanobacterial bloom-forming species. gvpA and gvpC are structural genes encoding gas vesicle proteins. Phylogenetic analyses of 10 Microcystis strains/uncultured samples showed that gvpC and each intergenic segment of the gvpA-gvpC region can be divided into two types. The combination of different types of gvpC and intergenic segments is an important factor that diversifies this genomic region. Some Microcystis strains isolated in China possess a 172 to 176 bp sequence tag in the intergenic segment between gvpA and gvpC. The gvpA-gvpC region in Microcystis can be divided into at least 4 classes and more numbers of subclasses. Compared to rbcLX and other regions, the high variability of the gvpA-gvpC region should be more useful in identifying geographical isolates or ecotypes of Microcystis.     

高压自屏蔽方法对高压高频信号的测量

在对用高压高频电源驱动的介质阻挡放电时空动力学研究的过程中,针对高压高频信号难以测量的问题,采用高压自屏蔽的方法,解决了高压漏电流引起的分压电阻过热的问题,实现了高压高频信号的精密测量.     

Presynaptic enhancement shown by whole-cell recordings of long-term potentiation in hippocampal slices

Long-term potentiation (LTP) of synaptic transmission in the hippocampus is a widely studied model system for understanding the cellular mechanisms of memory. In region CA1, LTP is triggered postsynaptically by Ca2(+)-dependent activation of protein kinases, but the locus of persistent modification remains controversial. Statistical analysis of synaptic variability has been proposed as a means of settling this debate, although a major obstacle has been the poor signal-to-noise ratio of conventional intracellular recordings. We have applied the whole-cell voltage clamp technique to study synaptic transmission in conventional hippocampal slices (compare refs 28-30). Here we report that robust LTP can be recorded with much improved signal resolution and biochemical access to the postsynaptic cell. Prolonged dialysis of the postsynaptic cell blocks the triggering of LTP, with no effect on expression of LTP. The improved signal resolution unmasks a large trial-to-trial variability, reflecting the probabilistic nature of transmitter release. Changes in the synaptic variability, and a decrease in the proportion of synaptic failures during LTP, suggest that transmitter release is significantly enhanced.