水稻原生质体产生细胞团的冰冻保存和冻后再生植株形成

水稻(Oryza sativa L.)原生质体产生的细胞团加上10-20％的二甲亚枫(DMSO)和10-20％的蔗糖,置于液氮中保存。冻后细胞生存率达到对照的40-50％。存活的细胞在附加2×10~(-5)mol/l 2,4-D 的Linsmier-Skoog(Ls)固体培养基上再生长,然后将形成的愈伤组织块转到附加10~(-6)mol/l NAA,4×10~(-6)mol/l 激动素和10~(-6)mol/l 2 IP 及8％的蔗糖的 LS培养基上分化出芽并形成植株。     

Vimentin expression in oocytes, eggs and early embryos of Xenopus laevis

Immunocytochemical studies using a monoclonal anti-porcine vimentin antibody reveal a well-organized pattern of staining in Xenopus laevis oocytes, eggs and early embryos. The positions of Xenopus vimentin and desmin in two-dimensional (2D) polyacrylamide gels were first established by immunoblotting of muscle Triton extracts with anti-intermediate filament antibodies (anti-IFA), which cross-react with all intermediate filament proteins (IFPs). The anti-porcine vimentin reacts with vimentin and desmin in muscle 2D immunoblots, but only reacts with one polypeptide in oocyte blots in the position predicted for vimentin (Mr 55 x 10(3), pI 5.6). Using an anti-sense probe derived from a Xenopus vimentin genomic clone in RNase protection assays, we show that expression of vimentin begins in previtellogenic oocytes. The level of expression remains constant throughout oogenesis and in unfertilized eggs. These data suggest that vimentin is expressed in oocytes and eggs. Most interestingly, the immunocytochemical results also show that vimentin is present in the germ plasma of oocytes, eggs and early embryos. It is therefore possible that vimentin has an important role in the formation or behaviour of early germ line cells.     

Changes in lipid content and composition during the development of N-nitrosodiethylamine induced hepatocarcinoma

Alterations in lipid content and composition in the N-nitrosodiethylamine-induced hepatocarcinoma were investigated. Rats were administrated with N-nitrosodiethylamine in the drinking water for 12 weeks followed by normal tap water for another 6 weeks. The cholesterol content in the liver was increased shortly after the administration of N-nitrosodiethylamine and remained elevated after the removal of the nitrosoamine from the water. The phosphatidylethanolamine level was elevated during N-nitrosodiethylamine administration with a concomitant reduction in phosphatidylcholine level. Lysophosphatidylcholine and sphingomyelin levels were increased during the last four weeks of the study. The level of phosphatidylinositol was substantially reduced after eight weeks of N-nitrosodiethylamine treatment, and remained low during the post-treatment period. We postulate that changes in lysophosphatidylcholine and sphingomyelin may be a compensatory mechanism for maintaining the asymmetrical distribution of choline-containing lipids in the outer leaflet of the membrane. The elevated level of cholesterol may be a useful indicator for the early detection of N-nitrosodiethylamine-induced hepatocarcinoma.     

心房钠尿肽对血管紧张素II促血管平滑肌细胞增殖...

By means of technique of cell culture, 3H-thymidine incorporation and dot blot, it was demonstrated that angiotensin II (AGT II) stimulated proliferation and c-fos oncogene expression in cultured SHR vascular smooth muscle cells (VSMC) in a dose-dependent manner. This effect of AGT II was significantly inhibited by co-incubation with ANP. The results suggest that proliferation of VSMC is regulated by some interaction between AGT II and ANP.     

Generation of 19 STS markers that can be anchored at specific sites on human chromosome 21.

Sequence-tagged sites (STSs) are short stretches of DNA that can be specifically detected by the polymerase chain reaction (PCR) and can be used to construct long-range physical maps of chromosomal DNA. These STSs can be detected by PCR assays developed by reference to data obtained from the sequencing of restriction fragment length polymorphism-DNA markers for chromosome 21, which were derived from recombinant lamba-phage and plasmid clones made from DNA of a human-hamster hybrid cell line. In this report, we describe the generation of 19 new STSs that are specific for human chromosome 21.     

Effects of microsite light availability on the survival and growth of oak seedlings within a grassland

Effects of microsite light availability on the growth and survival of transplantedQuercus serrata Thunb. seedlings in aMiscanthus sinensis Anderss. grass canopy were investigated by a “plant's eye view” approach. Diffuse site factors, i.e., the fractional transmissions of diffuse photosynthetic photon flux density, were estimated at 15 cm aboveground in 108 microsites where the seedlings grew. Microsite diffuse site factors were significantly different between surviving and dead seedlings during the experiment period from April to October (F_[1,14]=10.9, P<0.01). Relative growth rate of dry weight for individual seedlings positively depended on the diffuse site factors (r²=0.482, P<0.001 in May; r²=0.312, P<0.001 in October). Only 16 seedlings produced their second stem flush within the grass canopy. The ratio of height to dry weight of the second stem flush was significantly higher for the seedlings grew in shady microsites than for those in less shady microsites (r²=0,471, P<0.01 in May). This study suggests that the microsite heterogeneity of light availability is one of the important factors affecting the establishment of tree seedlings in patchy grasslands.     

Several CD4 domains can play a role in human immunodeficiency virus infection in cells.

The human immunodefiency virus (HIV) uses the human CD4 glycoprotein as a receptor for infection of susceptible cells. Cells expressing a series of mutated forms of the CD4 gene have shown a variability in their ability to support replication of three HIV type 1 (HIV-1) and three HIV-2 strains. Moreover, when different stages of virus production were examined by a variety of assays, a consistent delay was observed in all cell lines containing CD4 mutants compared with those with intact full-length CD4. Cells expressing the CD4.415 mutant (modified at the serine 415 corresponding to a phosphorylation site of the cytoplasmic domain) showed only a minimal effect on virus replication. Cells expressing CD4.403 and CD4.401 mutants (lacking the whole cytoplasmic domain) manifested a moderate delay in production of virus progeny. The most substantial effect on HIV replication was observed in cells expressing a chimeric hybrid containing sequences corresponding to the first 177 residues of the N-terminal CD4 fused to CD8 sequences encoding the hinge, transmembrane, and cytoplasmic domains of the human CD8. Furthermore, in a cell-to-cell contact assay, fusion was absent when the CD4 proximal membrane domain was replaced by the CD8 counterpart. In addition, a strong correlation between the down-modulation of the surface CD4 and HIV expression was observed. These observations suggest that in addition to the known binding region, other domains of CD4 could play an important role in regulating HIV entry of cells.     

Biologic markers in ethylene oxide-exposed workers and controls

Ethylene oxide (EtO) is an alkylating agent and a model direct-acting mutagen and carcinogen. This study has evaluated a panel of biologic markers including EtO-hemoglobin adducts (EtO-Hb), sister-chromatid exchanges (SCEs), micronuclei, chromosomal aberrations (CAs), DNA single-strand breaks (SSB) and an index of DNA repair (ratio of UDS to NA-AAF-DNA binding) in the peripheral blood cells of 34 workers at a sterilization unit of a large university hospital and 23 controls working in the university library. Comprehensive environmental histories were obtained on each subject including detailed occupational and smoking histories. Industrial hygiene data obtained prior to the study and personal monitoring during the 8 years preceding the study showed that workers were subject to low-level exposure near or below the current Occupational Safety and Health Administration (OSHA) standard of 1 ppm (TWA). Personal monitoring data obtained during 2 weeks prior to blood sampling were uniformly less than 0.3 ppm (TWA). After adjusting for smoking, EtO workplace exposure was significantly (p less than 0.001) associated with EtO-Hb (a carcinogen-protein adduct) and 2 measures of SCEs [the average number of SCEs/cell (SCE50) and the number of high frequency cells (SCEHFC)]. There was an apparent suppression of DNA repair capacity in EtO-exposed individuals as measured by the DNA repair index; i.e., the ratio of unscheduled DNA synthesis (UDS) and NA-AAF-DNA binding (p less than 0.01). No association of DNA repair index with smoking was found. Another important finding of this study is the highly significant correlation between EtO-Hb adduct levels and SCEHFC (p less than 0.01) and SCEs (p less than 0.02) which provides evidence of a direct link between a marker of biologically effective dose and markers of genotoxic response. In contrast, micronuclei, CAs and SSBs were not significantly elevated in the workers. The activity of the u-isoenzyme of glutathione-S-transferase (GT) was measured as a possible genetic marker of susceptibility and a modulator of biomarker formation. However, possibly because of confounding by age, no significant relationships were found between GT and any of the exposure-related markers by ANOVA or among other independent variables by regression. This study demonstrates significant effects of low-level EtO exposure, independent of smoking history, near or below 1 ppm on multiple biomarkers and suggests that the current OSHA standard may not be adequately protective. Previously described effects of smoking on EtO-Hb adducts, SCEs and SCEHFC were also seen in this study.(ABSTRACT TRUNCATED AT 400 WORDS)     

The cellular and molecular regulation of 1,25(OH)2D3 production

The synthesis of 1,25(OH)₂D₃ is a critical control point in the regulation of calcium metabolism, and possibly in the growth and differentiation of a number of cell types. This paper reviews our current understanding of the regulation of this process at the cellular and molecular levels, with the emphasis on the mechanisms of feedback control 1,25(OH)₂D₃ itself, control of parathyroid hormone, the roles of cyclic AMP dependent protein kinase and protein kinase C, and the interaction between the various intracellular regulators of 1,25(OH)₂D₃ production.