Terpenoids from Euphorbia helioscopia and Their Cytotoxic Activities against H1975 Cells

Three previously undescribed diterpenoids, helioscopnoids A–C, and eight known compounds were isolated from the whole plants of Euphorbia helioscopia. Their structures were established by extensive analysis of spectra and data comparison with previous literatures. Among them, compound 4 was identified as 24,24-dimethoxy-25,26,27-trinoreuphan-3β-ol with revised configurations of C-13, C-14, and C-17 (13R*, 14R*, 17R*). Cytotoxicity assays revealed that all compounds exhibited varying levels of cytotoxicity against H1975 cells, with compound 9 displaying the most potent activity, as indicated by cell viability rates of 18.13 % and 20.76 % at concentrations of 20 μM and 5 μM, respectively. This study expands the understanding of E. helioscopia terpenoids’ structural diversity and biological activities, contributing to the exploration of potential therapeutic applications.     

INTRAPOPULATION DIFFERENTIATION IN ANNUAL PLANTS. III. THE CONTRASTING EFFECTS OF INTRA- AND INTERSPECIFIC COMPETITION

The roles of intraspecific and interspecific competition in producing differentiation within populations of Veronica peregrina were studied in two populations under controlled, greenhouse conditions. In nature, each population spans an environmental gradient across the center and sides of a temporary, vernal pool in California. Individuals at the center are subjected to intense intraspecific competition produced by high densities (to 30 seedlings/cm²) generated by quasi-simultaneous germination (90% of seeds germinate in one week). Individuals at the periphery are subjected to interspecific competition with grasses, which shade out the Veronica 4–6 weeks after the onset of winter growth. I predicted that 1) when grown under immediate intraspecific competition in the greenhouse, offspring of plants from the central subpopulation (C) would perform better (i.e., grow larger and produce more seeds) than those from the periphery (P) and that 2) when grown under delayed interspecific competition provided by Agrostis tenuis and Lollium multiflorum, offspring of plants from the periphery would perform better than those from the center. Both predictions were confirmed. The center-periphery differences were pronounced and statistically significant in an undisturbed population (V-2), while in a population disturbed by yearly plowing (V-3), the differences tended to be consistent with those in V-2 but seldom significant. Distribution of variability tended to be positively skewed and/or leptokurtic in subpopulations grown under “foreign” competition (i.e., intraspecific for P plants and interspecific for C plants) but was normally distributed following exposure to “familiar” competition. Timing of competition affected many results. There were four additional significant differences between the central and peripheral subpopulations. 1) Germination rate: the faster rate in central plants can be advantageous under immediate intraspecific competition. The slower rate in peripheral plants can be advantageous under conditions of erratic and unpredictable soil moisture. 2) Response to nutrient competition: central plants were more sensitive to N-deficiency and peripheral plants were more sensitive to P-deficiency. 3) Allocation of biomass: central plants allocated a greater proportion of biomass to seeds, while peripheral plants allocated a greater proportion of biomass to leaves under all growing conditions. 4) Root elongation: at the seedling stage, central plants have longer roots, while at the adult stage, peripheral plants have longer roots (but not more root mass). Most components of this complex pattern of differentiation are interpretable in an adaptive context. Other results defy simple explanations and underline the importance of phenotypic plasticity, which was pronounced in the competition experiments.     

Dynamic changes of mechanically activated channels and K+ channels at injury site of peripheral nerve in rat

Ectopic ion channels developed locally at the injury site after nerve damage by light ligation around common sciatic nerve of the rats. Different channel types have different processes of formation, accumulation and degeneration. During the first three days after injury, mechanically activated channels that are modulated by Ca++ channel activities first appeared. As the nerve fibers begin to be excited by TEA, a blocker of K+ channels, suggesting that the accumulation of K+ channels, the responsibility of mechanically activated channels was declining. Onset of K+ channels was from the 3rd postoperative day and lasted up to the fiftieth day. This time course of K+ channel development was closely related to allodynia and hyperalgesia of neuropathic animal behaviour. The results suggest that chronic contraction injury induces a dynamic change in the ectopic mechanically activated channels and K+ channels at the injury site of nerve and there is an interchange in the development time courses of the mechanic     

1α,25-dihydroxy-24-oxo-16-ene vitamin D3, a metabolite of a synthetic vitamin D3 analog, 1α,25-dihydroxy-16-ene vitamin D3, is equipotent to its parent in modulating growth and differentiation of human leukemic cells

1α,25(OH)₂-16-ene-D₃, a synthetic analog of the steroid hormone, 1α,25(OH)₂D₃, has great potential to become a drug in the treatment of leukemia and other proliferative disorders, because of its minimal in vivo calcemic activity associated with a potent inhibitory effect on cell growth. However, at present, the mechanisms through which 1α,25(OH)₂-16-ene-D₃ expresses its biological activities are still not completely understood. Our previous in vitro study in a perfused rat kidney indicated for the first time that 1α,25(OH)₂-16-ene-D₃ and 1α,25(OH)₂D₃ are metabolized differently. 1α,25(OH)₂-24-oxo-16-ene-D₃, an intermediary metabolite of 1α,25(OH)₂-16-ene-D₃ formed through the C-24 oxidation pathway, accumulated significantly in the perfusate when compared to 1α,25(OH)₂-24-oxo-D₃, the corresponding intermediary metabolite of 1α,25(OH)₂D₃. In a subsequent in vivo study, we also reported that 1α,25(OH)₂-24-oxo-16-ene-D₃ exerted immunosuppressive activity equal to its parent, without causing significant hypercalcemia. In order to establish further the critical role of 1α,25(OH)₂-24-oxo-16-ene-D₃, in generating some of the key biological activities ascribed to its parent, we performed the present in vitro study using a human myeloid leukemic cell line (RWLeu-4) as a model. Comparative target tissue metabolism studies indicated that 1α,25(OH)₂-16-ene-D₃ and 1α,25(OH)₂D₃ are metabolized differently in RWLeu-4 cells, and the differences were similar to the ones we previously observed in the rat kidney. The significant finding was the accumulation of 1α,25(OH)₂-24-oxo-16-ene-D₃ in RWLeu-4 cells because of its resistance to further metabolism. Biological activity studies indicated that both 1α,25(OH)₂-16-ene-D₃ and its 24-oxo metabolite produced growth inhibition and promoted differentiation of RWLeu-4 cells to the same extent, and these activities were several fold higher than those exerted by 1α,25(OH)₂D₃. In addition, the genomic action of each vitamin D compound was assessed in a rat osteosarcoma cell line (ROS 17/2.8) by measuring its ability to transactivate a gene construct containing the vitamin D response element of the osteocalcin gene linked to the growth hormone reporter gene. In these studies, both 1α,25(OH)₂-16-ene-D₃ and its 24-oxo metabolite exerted similar but potent transactivation activity which was several fold greater than that exerted by 1α,25(OH)₂D₃ itself. In summary, our results indicate that the production and slow clearance of the bioactive intermediary metabolite, 1α,25(OH)₂-24-oxo-16-ene-D₃, in RWLeu-4 cells contributes significantly to the final expression of the enhanced biological activities ascribed to its parent analog, 1α,25(OH)₂-16-ene-D₃.     

一类竞争扩散方程组在Neumann边条件下解的渐近行为

本文主要采用比较方法讨论了一类竞争扩散方程组在Neumann边条件下解的渐近行为,得到了解的稳定性区域．     

RT－cDNA克隆－PCR法获取犬瘟热病毒融合蛋白基因（F）

纯化鸡胚成纤维细胞培养的犬瘟热病毒（ＣａｎｉｎｅＤｉｓｔｅｍｐｅｒＶｉｒｕｓ,ＣＤＶ）,获得病毒基因组ＲＮＡ后,反转录合成双链病毒Ｆ基因ｃＤＮＡ。将此双链ｃＤＮＡ平端插入ＰＵＣ１９质粒ＳａｍⅠ位点构建重组质粒,进行ｃＤＮＡ克隆。以重组克隆质粒为模板ＰＣＲ扩增,获得ＣＤＶ全长Ｆ基因。将此Ｆ基因插入表达载体ＰＢＶ２２０,在大肠杆菌中表达,通过对表达产物的最终鉴定,可确认所获片段为ＣＤＶ全长Ｆ基因．     

林带中阻力分布的理论与实验研究

推导了风向垂直于林带走向时林带内的阻力分布的解析式,比较了３种所面形状林带的阻力分布特点,并用风洞实验资料进行了验证,简析了在实际生产中的应用．     

GM_3对小鼠腹腔巨噬细胞磷脂代谢转换率的影响

神经节苷脂ＧＭ_３对小鼠腹腔常驻巨噬细胞（Ｒ－Ｍ）和Ｇｅ－１３２体内激活的巨噬细胞（Ｇｅ－１３２－Ｍ）的磷脂代谢转换有显著的影响,当这两种Ｍ在体外用ＧＭ_３处理时,表现出［￣（３２）Ｐ］Ｐｉ和［￣３Ｈ］肌醇参入ＰＩ降低,参入ＰＩＰ、ＰＩＰ_２增加;但在［￣（３２）Ｐ］Ｐｉ和［￣３Ｈ］胆碱参入ＰＣ上,Ｒ－Ｍ与Ｇｅ－１３２－Ｍ不同,即ＧＭ_３促进同位素前体参入Ｒ－Ｍ的ＰＣ,抑制它们参入Ｇｅ－１３２－Ｍ的ＰＣ．以上结果表明ＧＭ３可能提高了ＰＩ或ＰＩＰ的磷酸激酶的活性,致使［￣（３２）Ｐ］ＰＩＰ和［￣（３２）Ｐ］ＰＩＰ_２增多,［￣（３２）Ｐ］ＰＩ减少．激活的Ｍ（Ｇｅ－１３２－Ｍ）本身ＰＣ代谢转换率较Ｒ－Ｍ高,当Ｇｅ－１３２－Ｍ再受ＧＭ_３刺激,ＰＣ代谢转换率降低,这提示ＧＭ_３对激活的Ｍ的ＰＣ代谢转换有调节作用．     

RFLP tagging of a salt tolerance gene in rice

A salt tolerant rice mutant (M-20) was obtained through selection in vitro. Its tolerance was stably inherited over eight generations and most traints between M-20 and its sensitive original 77–170 (Oryza sativa) were very similar. By deriving an F₂ population of M-20 × 77–170 and splitting every F₂ individual into two parts, with one part planted in normal conditions and another part in saline conditions, the inheritance of salt tolerance in rice was studied. Under normal conditions, there was no apparent segregation among F₂ individuals. Under saline conditions, however, the segregation of traits was obvious. According to our standards, the ratio of salt sensitive:moderately-tolerant:tolerant plants was 25:42:18, in accordance with a 1:2:1 ratio. It suggested that the improvement of salt tolerance in our materials was induced by the mutation of a major tolerant gene which showed incomplete dominance. By use of 130 RFLP probes distributed throughout the rice genome, the gene was tagged by a single copy DNA probe, RG4, which was located on chromosome 7. The genetic distance between the salt tolerant gene and RG4 was 7.0 ± 2.9 cM. Based on the split method, a method which could be currently used to evaluate the damage of salt stress in rice was proposed.