对林檎分类学地位的研究

林檎与花红在新梢、花、果方面均有较大的差别,其树干及大枝上有寄生瘤状突起。中国绵苹果的酶谱差异较大,林檎与花红的酶谱最接近,主酶带均为三条,其中有两条Rf值分别为0.53、0.56的主酶带相同;林檎比花红多出一条Rf值为0.80的弱酶带。结果表明,林檎为花红的一个变种。     

利用秆维管束进行中国散生竹类的聚类分析

本文是应用模糊聚类分析方法研究中国散生竹类分类的一次尝试。分类特征采用了竹秆上、中、下三段各类型维管束数,方法上使用了模糊(Fuzzy)直接聚类分析进行综合分析。经电子计算机运算后,不仅取得了与传统分类基本一致的分类结果,同时也表明这种方法较之其它一些植物数量分类方法简便易行,此外还讨论了一些中国散生竹类分类上的问题。     

杉木的混农林业

杉木是中国南方的重要用材树种,栽培十分广泛,人工造林历史在一千年以上,目前杉木人工林达1.0×10~7ha。杉木林地混种农作物是杉木产区的传统习惯,并形成一种独特的栽培制度,通过林粮间作,以耕代抚,既有农业收益,又抚育了杉木,促进了幼林的生长。这项经验在杉木产区长期世代相传,且因地制宜,在问作方式、作物种类等方面不断发展,如间种方式上有先农后林、林农同时或先林后农等,间种作物种类还有油料作物、经济作物     

茶园冬季乔木落叶的分解和矿质元素释放

在我国南方存在着一种传统植茶方式——茶林复合生态系统,近年来人们已逐步认识到它在维持土壤肥力,抗御自然灾害和保证茶叶内质特性等方面的作用,然而对冬季乔木落叶分解和矿质元素释放的作用尚无报道。本文是对安徽省黄山市休宁县茶树-乌桕复合园和茶树-板栗复合园的冬季乔木落叶分解的研究,为全面认识茶林复合生态系统的性质提供依据。     

松茶间作茶树叶片的解剖构造和气孔活动

本文利用光镜技术和MK-3型自动气孔计对松茶间作和单作茶园茶树叶片的解剖构造和气孔传导力进行了比较研究。研究表明,间作茶园茶树叶片的上表皮、栅拦组织和全叶均比单作茶树薄,分别为单作茶树的82.7％,78.2％和67.2％,叶质柔嫩。叶片气孔传导力比单作茶园低。嫩叶传导力>老叶;1芽5叶新梢按叶序3叶>2、4叶>1、5叶;按树冠垂直分布,冠上叶(0—5cm)>冠中叶(10—15cm)>冠下叶(30cm左右)。说明气孔传导力不仅受生态条件影响,与自身的叶龄、叶位等生理机能也有密切关系。     

Effects of glucose on the production of recombinant protein C in mammalian cell culture

Effects of glucose on a cultured Chinese hamster ovary cell line producing recombinant human protein C were investigated. After the recombinant cells reached confluency, they were maintained in the medium containing 10% serum and different levels of glucose in either batch or daily-exchange mode. High concentrations of glucose to the cultures yielded higher cell densities. Daily exchanges of media produced higher cell densities than the corresponding batch culture. Total protein C production per cell decreased with time in batch culture, in accordance with the declined glucose metabolism. Supplementation of the media with high levels of glucose diminished both the expression and gamma-carboxylation activities of the recombinant cells. Production of protein C persisted in daily-exchange culture, resulting in a constant production rate of protein C. In this case again, glucose reduced the specific productivity of recombinant protein C. An apparent glucose inhibition constant was determined to be 0.11 mg/mL by Dixon plots. The ability to gamma-carboxylate recombinant protein C was also impaired at the highest level of glucose. From these results, a strategy to maximize recombinant protein C productivity is discussed.     

Suppression of the degradation of recombinant human apolipoprotein E by a protease inhibitor obtained from fetal bovine serum in serum-free culture

The recombinant human apolipoprotein E (Apo-E) produced by Chinese hamster ovary cells (CHO-322 cells) in serum free culture was degraded to 24K and 23K fragments that contained N-terminal amino acid. The degradation site of Apo-E to 24K fragment was between Arg180 and Leu181 and the C-terminal amino acid of 23K fragment was Gly169. In fetal bovine serum (FBS)-containing culture, the degradation was inhibited. However, in calf serum (CS) the inhibitory activity was not detected. Thus, we attempted the purification of the factor with this inhibitory activity from FBS. A protease inhibitor was purified to give a single peak from FBS by ammonium sulfate precipitation and combination of several column chromatographies. When this FBS-derived protease inhibitor (FBS-d-PI) was added to serum-free culture of CHO-322 cells, degradation of recombinant Apo-E to the 24K and 23K fragments was dose-dependently suppressed and accumulation of intact Apo-E in culture supernatant was observed. FBS-d-PI was found to be a glycoprotein with relative molecular size of 75K daltons under reducing condition, and 85K daltons under nonreducing condition by SDS-PAGE. A complex of FBS-d-PI and a cellular protease was also detected in culture supernatant by western blot analysis using mouse monoclonal antibodies against FBS-d-PI.     

Factors affecting recurrent shoot multiplication in in vitro cultures of 17- to 20-year-old douglas fir trees

Summary The effects of sucrose concentration, addition of ammonium nitrate, and exposure to N⁶-benzyl-adenine (BA) on multiplication potential with shoots derived from shoot cultures of 17- to 20-yr-old Douglas fir trees [Pseudotsuga menziesii (Mirb.) Franco] were compared. Each of these conditions, when compared independently, affected recurrent shoot multiplication and influenced shoot development, as measured by the abundance of shoot apices. Sucrose concentration was influential, the use of 25 g · liter⁻¹ providing twice the multiplication obtained with 20 g · liter⁻¹, and 14 × that obtained with the 30 g · liter⁻¹ concentration routinely used (tree 11). Ammonium nitrate usage also improved multiplication, a 2.5 times improvement being obtained after incorporation of 100 mg · liter⁻¹ NH₄NO₃ into the medium (tree 33). Shoot cultures were responsive but relatively sensitive to addition of BA, the best improvement in multiplication (5 times) being obtained with brief exposures to 3 mg · liter⁻¹ BA (tree 11). Although shoot cultures were responsive to the conditions investigated, differences in shoot multiplication and development were not displayed for several weeks. It was not possible therefore to repeat all the treatments with more than one genotype; however, when this was possible a genotype-dependent variation in response was evident.     

Toxoplasma gondii: Purine synthesis and salvage in mutant host cells and parasites

Toxoplasma gondii, growing exponentially in heavily infected mutant Chinese hamster ovary cells that had a defined defect in purine biosynthesis, did not incorporate [U-¹⁴C]glucose or [¹⁴C]formate into the guanine or adenine of nucleic acids. Intracellular parasites therefore must be incapable of synthesizing purines and depend on their host cells for them. Extracellular parasites, which are capable of limited DNA and RNA synthesis, efficiently incorporated adenosine nucleotides, adenosine, inosine, and hypoxanthine into their nucleic acids; adenosine 5′-monophosphate was the best utilized precursor. Extracellular parasites incubated with ATP labeled with ³H in the purine base and ³²P in the α-phosphate incorporated the purine ring 50-fold more efficiently than they did the α-phosphate. Thus, ATP is largely degraded to adenosine before it can be used by T. gondii for nucleic acid synthesis. Two pathways for the conversion of adenosine to nucleotides appear to exist, one involving adenosine kinase, the other hypoxanthine—guanine phosphoribosyl transferase. In adenosine kinase-less mutant parasites, the efficiency of incorporation of ATP or adenosine was reduced by 75%, which indicates the adenosine kinase pathway was predominant. Extracellular parasites incorporated ATP into both the adenine and the guanine of their nucleic acids, so ATP from the host cell could supply the entire purine requirement of T. gondii. However, ATP generated by oxidative phosphorylation in the host cell is not essential for parasites because they grew normally in a cell mutant that was deficient in aerobic respiration and almost completely dependent upon glycolysis.