Stimulation of Growth and Nucleic Acid Biosynthesis at Low Concentration of Abscisic Acid in Tissue Culture of Spinacia oleracea

The effect of abscisic acid on growth, ultrastructure and nucleic acid biosynthesis was studied in tissue culture of spinach (Spinacia oleracea L.). Low concentration (0.01 mg l^?1) of abscisic acid increased fresh and dry weight of calluses, whereas 1.0 mg l^?1 was inhibitory. The stimulating effect was observed only in the presence of a relatively high concentration of kinetin (1 mg l^?1). The inhibitory effect was partly overcome by the same kinetin concentration. The low concentration of abscisic acid probably accelerated the induction of callus growth after subculture and stimulated cell division in the exponential phase of growth. Electron microscopy showed the presence of numerous polysomes and rough endoplasmic reticulum in callus cells grown at the stimulating abscisic acid concentration. Control cells and cells at the inhibitory concentration had slightly hyaline cytoplasm and were more vacuolated. Incubation of callus tissue with ³²P in the presence of stimulating concentration of abscisic acid showed a significant increase in the rate of biosynthesis of all nucleic acid classes after 8 h, whereas inhibitory concentration produced a decrease in ³²P incorporation. However, when the tissue was grown in the presence of abscisic acid for 20 days, both concentrations decreased the rate of nucleic acid biosynthesis, as compared to the controls.     

Intracellular calcium buffering capacity in isolated squid axons

Changes in ionized calcium were studied in axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy. Absorption changes measured in situ were calibrated in vitro with media of ionic composition similar to axoplasm containing CaEGTA buffers. Calcium loads of 50-2,500 μmol/kg axoplasm were induced by microinjection, by stimulation in 112 mM Ca seawater, or by soaking in choline saline with 1-10 mM Ca. Over this range of calcium loading of intact axoplasm, the ionized calcium in the axoplasm rose about 0.6 nM/μM load. Similar loading in axons preteated with carbonyl cyanide 4- trifluoromethoxyphenylhydrazone (FCCP) to inhibit the mitochondrial proton gradient increased ionized calcium by 5-7 percent of the imposed load, i.e. 93-95 percent of the calcium load was buffered by a process insensitive to FCCP. This FCCP- insensitive buffer system was not saturated by the largest calcium loads imposed, indicating a capacity of at least several millimolar. Treatment of previously loaded axons with FCCP or apyrase plus cyanide produced rises in ionized calcium which could be correlated with the extent of the load. Analysis of results indicated that, whereas only 6 percent of the endogenous calcium in fresh axons is stored in the FCCP-sensitive (presumably mitochondrial) buffer system, about 30 percent of an imposed exogenous load in the range of 50-2,500 μM is taken up by this system.     

安徽庐江鸭乙型肝炎病毒LJ-76转染细胞系的建立

为建立鸭乙型肝炎病毒ＬＪ－７６的转染细胞系,将ＬＪ－７６病毒ＤＮＡ插入到ｐＵＣ１９的ＥｃｏＲⅠ位点上,分离得到含有双拷贝ＬＪ－７６ＤＮＡ的重组质粒．通过磷酸钙沉淀方法,将经ＣｓＣｌ等密度离心纯化的ＬＪ－７６ＤＮＡ双体导入到人肝癌细胞ＢＥＬ７４０２中．收集转染细胞的培养液进行蔗糖密度梯度离心,所得沉淀经检测发现含有ＬＪ－７６ＤＮＡ并具有特异性ＤＨＢＶ内源性ＤＮＡ多聚酶活性;对上述样品通过ＤｏｔＥＩＡ检测ＤＨＢＶ核心抗原及表面抗原结果为阳性．Ｓｏｕｔｈｅｒｎｂｌｏｔ分析表明转染细胞内存在病毒ＤＮＡ复制中间体ｃｃｃＤＮＡ、ｓｓＤＮＡ和ｒｃＤＮＡ,而ｃｃｃＤＮＡ被认为是复制活动较为活跃的标志．电镜观察转染细胞的上清发现有病毒颗粒的存在．     

Identification of methylation markers for the prediction of nodal metastasis in oral and oropharyngeal squamous cell carcinoma

Hypermethylation is an important mechanism for the dynamic regulation of gene expression, necessary for metastasizing tumour cells. Our aim is to identify methylation tumour markers that have a predictive value for the presence of regional lymph node metastases in patients with oral and oropharyngeal squamous cell carcinoma (OOSCC). Significantly differentially expressed genes were retrieved from four reported microarray expression profiles comparing pN0 and pN+ head-neck tumours, and one expression array identifying functionally hypermethylated genes. Additional metastasis-associated genes were included from the literature. Thus genes were selected that influence the development of nodal metastases and might be regulated by methylation. Methylation-specific PCR (MSP) primers were designed and tested on 8 head-neck squamous cell carcinoma cell lines and technically validated on 10 formalin-fixed paraffin-embedded (FFPE) OOSCC cases. Predictive value was assessed in a clinical series of 70 FFPE OOSCC with pathologically determined nodal status. Five out of 28 methylation markers (OCLN, CDKN2A, MGMT, MLH1 and DAPK1) were frequently differentially methylated in OOSCC. Of these, MGMT methylation was associated with pN0 status (P = 0.02) and with lower immunoexpression (P = 0.02). DAPK1 methylation was associated with pN+ status (P = 0.008) but did not associate with protein expression. In conclusion, out of 28 candidate genes, two (7%) showed a predictive value for the pN status. Both genes, DAPK1 and MGMT, have predictive value for nodal metastasis in a clinical group of OOSCC. Therefore DNA methylation markers are capable of contributing to diagnosis and treatment selection in OOSCC. To efficiently identify additional new methylation markers, genome-wide methods are needed.     

Confirmation of quantitative trait loci affecting fatness in chickens

In this report we describe the analysis of an advanced intercross line (AIL) to confirm the quantitative trait locus (QTL) regions found for fatness traits in a previous study. QTL analysis was performed on chromosomes 1, 3, 4, 15, 18, and 27. The AIL was created by random intercrossing in each generation from generation 2 (G₂) onwards until generation 9 (G₉) was reached. QTL for abdominal fat weight (AFW) and/or percentage abdominal fat (AF%) on chromosomes 1, 3 and 27 were confirmed in the G₉ population. In addition, evidence for QTL for body weight at the age of 5 (BW5) and 7 (BW7) weeks and for the percentage of intramuscular fat (IF%) were found on chromosomes 1, 3, 15, and 27. Significant evidence for QTL was detected on chromosome 1 for BW5 and BW7. Suggestive evidence was found on chromosome 1 for AFW, AF% and IF%, on chromosome 15 for BW5, and on chromosome 27 for AF% and IF%. Furthermore, evidence on the chromosome-wise level was found on chromosome 3 for AFW, AF%, and BW7 and on chromosome 27 for BW5. For chromosomes 4 and 18, test statistics did not exceed the significance threshold.     

广义隐Markov模型在基因识别中的应用

广义隐Markov模型(GHMM)是基因识别的一种重要模型,但是其计算量比传统的隐Markov模型大得多,以至于不能直 接在基因识别中使用。根据原核生物基因的结构特点,提出了一种高效的简化算法,其计算量是序列长度的线性函数。在此 基础上,构建了针对原核生物基因的识别程序GeneMiner,对实际数据的测试表明,此算法是有效的。