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131.
广东鹤山亚热带丘陵人工林群落分析:Ⅳ 针叶林 总被引:2,自引:0,他引:2
本文研究14年林龄的马尾松人工群落和5年林龄的人工湿地松群落。通过研究这两个针叶林造林后的生境变化和现有群落的生物量、生长量、叶面积指数以及垂直生物量结构等,揭示其群落学特征,为林业实践提供理论依据。 相似文献
132.
133.
Huiling Hao Yunquan Jiang S. J. Zhang Peng Zhang Rong X. Zeng Marietta Y. W. T. Lee 《Chromosoma》1992,102(Z1):S121-S127
A continuing theme of our laboraory, has been the understanding of human DNA polymerases at the structural level. We have
purified DNA polymerases delta, epsilon and alpha from human placenta. Monoclonal antibodies to these polymerases were isolated
and used as tools to study their immunochemical relationships. These studies have shown that while DNA polymerases delta,
epsilon and alpha are discrete protiens, they must share common structural features by virtue of the ability of several of
our monoclonal antibodies to exhibit cross-reactivity. A second approach we have taken is the molecular cloning of human DNA
polymerase delta and epsilon. We have cloned the DNA polymerase delta cDNA, and this has allowed us to compare its primary
structure to those of human polymerase alpha and other members of this polymerase family. Multiple sequence alignments have
revealed that human DNA polymerase delta is also closely related to the herpes virus family of DNA polymerases. In situ hybridization
has shown that the human DNA polymerase delta gene is localized to chromosome 19 q13.3–q13.4. In order to further determine
the functional regions of the DNA polymerase δ structure we are currently expressing human pol δ inE. coli and baculovirus systems. Other work in our laboratory is directed toward examining the expression of DNA polymerase δ during
the cell cycle. 相似文献
134.
J Hartman Z Huang T A Rado S Peng T Jilling D D Muccio E J Sorscher 《The Journal of biological chemistry》1992,267(10):6455-6458
The majority of mutations which lead to clinical cystic fibrosis are located within the two predicted nucleotide binding domains of the cystic fibrosis gene product. We have used a prokaryotic expression system to synthesize and purify the first nucleotide binding domain (NBD-1, amino acids 426-588) with and without the most common mutation associated with the disease (the deletion of phenylalanine at position 508, delta F508). Both wild type and delta F508 NBD-1 bind ATP-agarose in a quantitatively comparable manner; this binding was inhibited by excess Na2ATP, trinitrophenol-ATP, or 8-azido-ATP. Irreversible NBD-1 labeling by an ATP analog was demonstrated using [32P]8-azido-ATP. This covalent labeling was inhibited by preincubation with Na2ATP, with half-maximal inhibition for Na2ATP occurring at approximately 5 mM for both the wild type and delta F508 nucleotide binding domain. These experiments are among the first to confirm the expectation that the cystic fibrosis transmembrane conductance regulator NBD-1 binds nucleotide. Since, under the conditions used in our study, NBD-1 without phenylalanine 508 displays very similar nucleotide binding characteristics to the wild type protein, our results support previous structural models which predict that the delta F508 mutation should not cause an alteration in ATP binding. 相似文献
135.
136.
Fertile rice plants have been regenerated from protoplasts of two japonica rice varieties (Radon and Baldo) using a protocol
initially developed for plant regeneration from protoplasts of an indica rice. Embryogenic calli were developed from immature
embryos of Radon and Baldo rice on a callus induction medium, and then used to establish cell suspensions. Protoplasts were
isolated from the cell suspensions, and cultured on a Millipore filter placed on a Kao/agarose medium that contained cell
clusters from suspensions of IR52 or IR45. The protoplasts grew vigorously on Kao medium and developed into embryogenic calli
within two to three weeks. Somatic embryo development occurred during a subsequent transfer of the calli to an LS medium for
two to three weeks. The calli were then transferred to MS or N6 plant regeneration medium, and within one to three weeks,
plants regenerated from 21 to 32% of the Radon calli, and 33 to 35% of the Baldo calli. Based upon these results and the previous
success in regenerating an indica variety from protoplasts, this procedure has great promise for regenerating a range of rice
varieties, and probably for regeneration of other monocotyledonous plants from protoplasts 相似文献
137.
Decreased mortality of Norman murine sarcoma in mice treated with the immunomodulator, Acemannan 总被引:6,自引:0,他引:6
An extract from the parenchyma of Aloe barbadensis Miller shown to contain long chain polydispersed beta (1,4)-linked mannan polymers with random O-acetyl groups (acemannan, Carrisyn) was found to initiate the phagocyte production of monokines that supported antibody dependent cellular cytotoxicity and stimulated blastogenesis in thymocytes. Acemannan, in both enriched and highly purified forms, was administered intraperitoneally to female CFW mice into which murine sarcoma cells had been subcutaneously implanted. The rapidly growing, highly malignant and invasive sarcoma grew in 100% of implanted control animals, resulting in mortality in 20 to 46 days, dependent on the number of cells implanted. Approximately 40% of animals treated with acemannan at the time of tumor cell implantation (1.5 x 10(6) cells) survived. Tumors in acemannan-treated animals exhibited vascular congestion, edema, polymorphonuclear leukocyte infiltration, and central necrosing foci with hemorrhage and peripheral fibrosis. The data indicate that in vivo treatment of peritoneal macrophages stimulates the macrophage production of monokines, including interleukin-1 and tumor necrosis factor. The data further indicate that sarcomas in animals treated i.p. with acemannan at the time of tumor cell implantation were infiltrated by immune system cells, became necrotic, and regressed. The combined data suggest that acemannan-stimulated synthesis of monokines resulted in the initiation of immune attack, necrosis, and regression of implanted sarcomas in mice. 相似文献
138.
本文报道低温胁迫下风眼莲叶片脱落酸(ABA)、可溶性蛋白质和水势的测定结果。低温胁迫时脱落酸和可溶性蛋白质含量远高于对照,(前者含量最高可达对照的4倍,后者可达到对照的2.75倍),而且脱落酸和蛋白质含量随温度降低而升高。蛋白质的生物合成抑制剂亚胺环己酮证明,可溶性蛋白质含量升高,原因是有部分是新合成的。在各种低温处理下获得了几乎相同于对照的叶片水势。我们推测:低温胁迫下,脱落酸水平的相应变化不是由于低温诱导水分胁迫所致,而是低温胁迫本身诱导。 相似文献
139.
Lie-Min Hu Stephen F. Kemp Chun-Fu Peng M.Joycelyn Elders W.Grady Smith 《FEBS letters》1990,270(1-2):100-104
1,9-Dideoxyforskolin inhibits proteoglycan synthesis and xyloside-initiated glycosaminoglycan (GAG) synthesis in chick embryo chondrocytes. Dideoxyforskolin does not affect the length of xyloside-initiated GAG chains secreted into the medium but chains from the dense proteoglycan secreted into the medium appear slightly longer. Incorporation of labeled serine into the dense proteoglycan and subsequent digestion with Pronase revealed a dramatic decrease in percent of total radioactivity associated with GAG chains in the proteoglyean from cultures treated with forskolin or dideoxyforskolin. These observations suggest that these diterpenes have a specific inhibitory effect on chain initiation reactions and thus may be useful tools in the study of proteoglycan synthesis and processing. 相似文献
140.
A common sequence in the inverted terminal repetitions of human and avian adenoviruses 总被引:8,自引:0,他引:8
The termini of the avian chick embryo lethal orphan (CELO) virus DNA have been sequenced. The results revealed a 63-bp-long inverted terminal repetition (ITR) which shared the sequence ATAATA with all adenovirus termini, thus far analyzed. The CELO virus ITR differed from those of the mammalian adenoviruses in two major aspects: (i) it is not a perfect duplication; (ii) it begins with a 5'-guanylic acid residue instead of the cytidylic acid normally observed in adenoviruses. 相似文献