In vitro propagation of loblolly pine via direct somatic organogenesis from mature cotyledons and hypocotyls

A high-efficiency two-step culture procedure for direct somaticorganogenesis in loblolly pine (Pinus taeda L.) resulting inthe formation of multiple shoot structures induced on cotyledons andhypocotyls of mature zygotic embryos is described. Mature zygoticembryos of eight genotypes of loblolly pine were used as explants toinduce direct somatic organogenesis with this two-step culture method,involving the induction and the differentiation of direct adventitiousshoots. After mature zygotic embryos of eight genotypes of loblolly pinewere cultured on induction medium containing 2,4-dichlorophenoxyaceticacid (2,4-D) or -naphthaleneacetic acid (NAA), 6-benzyladenine(BA), and kinetin for 2–3 weeks, embryos were transferred todifferentiation medium. Adventitious shoot regeneration via directsomatic organogenesis with the frequency of 8.7–27.8% wasobtained from mature zygotic embryo cultures of the genotypes tested.The highest mean number of 32.6 adventitious shoots per mature zygoticembryo was produced from genotype La. The tissue culture protocol of invitro shoot regeneration via direct somatic embryogenesis was optimizedafter examining the periods of the induction culture, chillingtreatment, glutamine concentration, and basic medium levels. Rooting wasachieved on TE medium supplemented with 0.5 mg/l indole-3-butyric acid(IBA), 0.5 mg/l gibberellic acid (GA₃), and 1 mg/l6-benzyladenine (BA), and regenerated plantlets were established insoil. These results suggested that adventitious shoot regeneration viadirect somatic organogenesis could be useful for clonal micropropagationof some genotypes of loblolly pine and for establishing a transformationsystem of this coniferous species.     

The anti-tumour effect of Klebsiella pneumoniae capsular polysaccharides

K24 capsular polysaccharide (K24-CPS), with a known structure of a repeating unit, was isolated from the capsule of Klebsiella pneumoniae serotype K24. The polysaccharide was found to suppress the proliferation of Ehrlich ascites tumour (EAT) cells in vitro, but did not alter the cell cycle distribution of cells. K24-CPS treatment reduced the tyrosine phosphorylation of some proteins in EAT cells. Furthermore, the treatment also decreased the expression of c-JUN, but had no effect on the levels of c-FOS and c-MYC. It is speculated that the growth suppression effect of K24-CPS may be related to its effect in down-regulating c-JUN expression.     

Influence of Environmental Salinity on Messenger RNA Levels of Growth Hormone, Prolactin, and Somatolactin in Pituitary of the Channel Catfish (Ictalurus punctatus)

Pituitary growth hormone (GH), prolactin (PRL), and somatolactin (SL) messenger RNA levels in channel catfish (Ictalurus punctatus) were examined under various environmental and physiological conditions. Catfish were sampled following salinity challenge, during the winter (December) and spring or summer (April or July), and at different sizes (15–18 g, 620–664 g, and 956–1134 g). When catfish (956–1134 g) were transferred from freshwater to saline water containing 8 ppt NaCl, their plasma [Na⁺] increased significantly above values in the freshwater control group until they were transferred back to freshwater. Pituitary GH mRNA levels were low for the first 24 hours following transfer to saline water, but thereafter were significantly elevated above control values until the fish were transferred back to freshwater. Pituitary GH mRNA levels were highest in July and lowest in December. Growth hormone mRNA levels were also elevated in the size groups 15–18 g and 956–1134 g in July when compared with December values. Pituitary PRL mRNA levels increased for the first 24 hours following transfer to saline water (956–1134 g), but thereafter were significantly lower than control values until the fish were transferred back to freshwater. Pituitary PRL mRNA levels were highest in April and July and lowest in December, and were also elevated in the size groups 620–664 g and 956–1134 g. Pituitary SL mRNA levels were unaffected in catfish transferred to saline water; however, levels were significantly elevated in catfish of the 956–1134-g size group sampled in April when compared with December. These results suggest the involvement of GH in adaptation to brackish water and of PRL in adaptation to freshwater in the catfish, and seasonal and size-related differences in pituitary GH, PRL, and SL mRNA levels. Received May 17, 2000; accepted October 30, 2000     

CD43 potentiates CD3-induced proliferation of murine intestinal intraepithelial lymphocytes

The involvement of CD43 in cell proliferation of murine intestinal intraepithelial lymphocytes (IEL) has been studied in in vitro CD3-stimulated cell cultures. In the presence of either IL-2 or IL-15, CD3 stimulation of IEL resulted in low levels of proliferation as measured by thymidine incorporation, whereas no proliferation occurred upon CD3 stimulation in the absence of cytokines. The combination of both cytokines to IEL cultures synergistically enhanced CD3-induced proliferation by approximately threefold that of cultures supplemented with either cytokine alone. Most importantly, however, proliferation of IEL was significantly greater when CD3 stimulation occurred in conjunction with CD43 triggering, indicating that CD43 functions as a coactivational signal for murine IEL. These findings indicate that a spectrum of potential proliferative responses exist among murine IEL depending on the types and combinations of signals received, and that because under normal conditions murine IEL are largely devoid of CD28 expression, a classical T-cell coactivational molecule, the capacity for high-level IEL proliferation may reside with CD43.     

自发性高血压大鼠心肌和血管组织牛磺酸的转运障碍

在自发性高血压大鼠（SHR）的心肌和主动脉血管组织上观察牛磺酸（taurine)转运和牛磺酸转运体（taurine transporter,TAUT) mRNA 的改变,结果显示,与对照组WKY大鼠相比,SHR组血浆牛磺酸水平和牛磺酸释放量增加,而心肌和血管组织牛磺酸水平和TAUT mRNA含量均降低,牛磺酸最大转运速率（Vmax)分别低24％和35％（P＜0．05）,米氏常数（Km)值分别高16％和39％（P＜0．05）,这些结果提示,SHR的心肌和血管组织牛磺酸转运障碍可能与TAUT活性和亲和力降低及TAUT基因水平的下调有关。     

高同型半胱氨酸血症致动脉粥样硬化的细胞分子机制

同型半胱氨酸（homocysteine,Hcy)是蛋氨酸代谢途径产生的含硫氨基酸,其代谢紊乱可以诱导高同型半胱氨酸血症的发生,已被临床及流行病学资料证实为动脉粥样硬化发病的独立危险因子。Hcy通过激活二酰甘油－蛋白激酶C－（DAG－PKC）及丝裂素活化蛋白激酶（MAPK）途径,诱导相关基因的表达,促进细胞钙化,启动脂质过氧化应激,从而损伤心血管系统。金属硫蛋白,牛磺酸,L－精氨酸作为内源性小分子物质,成为继维生素B6,B12之后控制和治疗高同型半胱氨酸血症的新途径。     

SNPCEQer: detecting SNPs in sequences generated by the Beckman CEQ2000 DNA Analysis System

SNPCEQer identifies and reports SNPs in sequences obtained from the Beckman CEQ2000 DNA Analysis System. SNPCEQer aligns sequences obtained using CEQ2000 heterozygote detection analysis and reports discrepancies between individual sequences and the consensus sequence it generates from this set as SNPs when the individual base calls have high-quality values. SNPCEQer reported comparable numbers of SNPs to the UNIX-based PolyPhred (148 vs. 165, respectively) in regions amplified from eight genes. A total of 21 different SNPs was discovered. Each gene region was analyzed in 96-306 samples. SNPCEQer was designed to operate from Windows NT, making SNP detection more accessible to users without UNIX systems. SNPCEQer is available free of charge at http://innovation.swmed.edu.     

Two genetic circuits repress the Caenorhabditis elegans heterochronic gene lin-28 after translation initiation

The heterochronic gene lin-28 of the nematode Caenorhabditis elegans controls the relative timing of diverse developmental events during the animal's larval stages. lin-28 is stage-specifically regulated by two genetic circuits: negatively by the 22-nt RNA lin-4 and positively by the heterochronic gene lin-14. Here, we show that lin-28 is repressed during normal development by a mechanism that acts on its mRNA after translation initiation. We provide evidence that lin-14 inhibits a negative regulation that is independent of the lin-4 RNA and involves the gene daf-12, which encodes a nuclear hormone receptor. The lin-4-independent repression does not affect the initiation of translation on the lin-28 mRNA, and like the lin-4-mediated repression, acts through the gene's 3'-untranslated region. In addition, we find that lin-4 is not sufficient to cause repression of lin-28 if the lin-4-independent circuit is inhibited. Therefore, the lin-4-independent circuit likely contributes substantially to the down-regulation of lin-28 that occurs during normal development. The role of lin-4 may be to initiate or potentiate the lin-4-independent circuit. We speculate that a parallel lin-4-independent regulatory mechanism regulates the expression of lin-14.