嘉兰块茎形成过程中物质变化的研究

嘉兰(Gloriosa superba L.)系百合科草本植物,其块茎含有秋水仙碱。本文研究块茎形成规律及其形成过程中物质变化。研究结果表明:块茎播后,新生的块茎在生长初期和后期生长速度都较慢,中期生长速度最快,也是嘉兰块茎产量形成的主要时期。块茎中营养物质主要是淀粉。新生块茎中淀粉含量,是随着新块茎的生长,其含量逐渐增高。叶片的光合速率和叶面积,从播后逐渐增加,开花前达到高峰,花后又逐渐降低。开花前如能增加光合叶面积,可为后期块茎生长提供较多物质。块茎中秋水仙碱含量是随着块茎的成熟与淀粉含量的渐增而增加,至收获期达到高峰。这一结果表明:收获未充分成熟的块茎,会降低秋水仙碱含量。     

白洋淀和太湖地区鸟类绦虫区系的比较研究

本文对白洋淀和太湖地区鸟类绦虫区系进行了比较研究,并对太湖鸟类绦虫区系作了初步分析。结果表明,鸟类绦虫区系分布与宿主区系分布密切相关,亲缘关系相近的宿主有许多相同的或亲缘相近的绦虫,这种现象为研究宿主与寄生虫的演化提供了可靠途径;发现鸟的越冬地绦虫种类比迁徙地种类丰富,分析其原因,除温、湿度、中间宿主等生态条件之外,与鸟的迁徙有一定关系。太湖地区的绦虫具有北方型和随遇型,亦有世界性种类和东半球广布种,提出了两地区家禽和野生鸟类所寄生的共同种类的绦虫。     

Differences in growth of transplantable ascites hepatoma among various lines of Donryu rat

A total of 48 Donryu rats from 8 colonies of 5 lines were inoculated intravenously with 10(7) cells of the ascites hepatoma strain AH 66. All the conventional rats of the lines D-1 and D-2 died between 9 and 15 days after inoculation with a good growth of implanted tumor cells. On the other hand, SPF rats of the lines A-1, B-1, C and E survived for 60 days showing complete rejection of the implanted tumor cells. A 50% of conventionalized ex-SPF rats of the lines A-2 and B-2, which had been once established as SPF colonies, and thereafter had been "re-conventionalized", rejected the tumor cells. The present observations indicate that the microbial conditions of the animal, e.g. whether the animal is SPF or not, might play an important role in the growth of the implanted ascites hepatoma.     

The disaccharide composition of heparins and heparan sulfates

Heparin and heparan sulfate can be cleaved selectively at their N-sulfated glucosamine residues by direct treatment with nitrous acid at pH 1.5. These polymers can also be cleaved selectively at their N-acetylated glucosamine residues by first N-deacetylating with hydrazine and then treating the products with nitrous acid at pH 4. These procedures have been combined and optimized for the conversion of these glycosaminoglycan chains into their disaccharide units. A modified hydrazinolysis procedure in which the glycosaminoglycans were heated with hydrazine:water (70:30) containing 1% hydrazine sulfate gave rapid rates of N-deacetylation and minimal conversion of the uronic acid residues to their hydrazide derivatives. Under these conditions, N-deacetylation was complete in 4 h and the beta-eliminative cleavage of the polymer chains that occurs during hydrazinolysis (P. N. Shaklee and H. E. Conrad (1984) Biochem. J. 217, 187-197) was eliminated. Treatment of the N-deacetylated polymer with nitrous acid at pH 3 for 15 h at 25 degrees C then gave simultaneous cleavage at the N-unsubstituted glucosamine residues and the N-sulfated glucosamine residues. These deamination conditions minimized, but did not eliminate, the side reaction in which nitrous acid-reactive glucosamine residues undergo ring contraction without glucosaminide bond cleavage. Thus, the disaccharides were obtained in a yield of 90% of those originally present in the glycosaminoglycan chains. Since the ring contraction side reaction occurs randomly at the diazotized glucosamine residues, the disaccharides formed in the pH 3 nitrous acid reaction were recovered in proportions equal to those in the original glycosaminoglycan chain.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cloning, analysis, and bacterial expression of human farnesyl pyrophosphate synthetase and its regulation in Hep G2 cells

A partial length cDNA encoding farnesyl pyrophosphate synthetase (hpt807) has been isolated from a human fetal liver cDNA library in lambda gt11. DNA sequence analysis reveals hpt807 is 1115 bp in length and contains an open reading frame coding for 346 amino acids before reaching a stop codon, a polyadenylation addition sequence, and the first 14 residues of a poly(A+) tail. Considerable nucleotide and deduced amino acid sequence homology is observed between hpt807 and previously isolated rat liver cDNAs for farnesyl pyrophosphate synthetase. Comparison with rat cDNAs suggests that hpt807 is about 20 bp short of encoding the initiator methionine of farnesyl pyrophosphate synthetase. The human cDNA was cloned into a prokaryotic expression vector and Escherichia coli strain DH5 alpha F'IQ was transformed. Clones were isolated that express an active fusion protein which can be readily observed on protein gels and specifically stained on immunoblots with an antibody raised against purified chicken farnesyl pyrophosphate phosphate synthetase. These data confirm the identity of hpt807 as encoding farnesyl pyrophosphate synthetase. Slot blot analyses of RNA isolated from Hep G2 cells show that the expression of farnesyl pyrophosphate synthetase mRNA is regulated. Lovastatin increases mRNA levels for farnesyl pyrophosphate synthetase 2.5-fold while mevalonic acid, low-density lipoprotein, and 25-hydroxycholesterol decrease mRNA levels to 40-50% of control values.     

Regulation of nicotinic acetylcholine receptor function by adenine nucleotides

1. Nicotinic acetylcholine receptors (nAChR)4 from BC3H1 cells (which express a skeletal muscle-type receptor) and from Torpedo californica electric organ were expressed in Xenopus laevis oocytes and studied with a voltage-clamp technique. 2. We found that bath application of ATP in the micromolar to millimolar range increased the ACh-elicited current in both muscle and electrocyte receptors. The effect of ATP increased with successive applications. This "use-dependent" increase in potentiation was Ca2+ dependent, while the potentiation itself was not. 3. Four other nucleotides were tested on muscle nAChR: ADP, AMP, adenosine, and GTP. Of these, only ADP was a potentiator, but its effect was not use dependent. Neither ATP nor ADP affected the resting potential of the oocyte membrane. 4. ADP potentiated the response to suberyldicholine and nicotine, as well as ACh. 5. Finally, ADP reversed the phencyclidine-induced block of ACh currents in oocytes expressing muscle nAChR.     

Charge dependence of Fe(II)-catalyzed DNA cleavage.

The effect of charge of the Fe(II) reagent used to induce DNA strand cleavage reactions in the presence of a source of reducing equivalents is investigated using two oligonucleotide models. The first consists of the two strands dA20 and dT20, and an equimolar complex between them. The second is a short four-arm branched DNA complex composed of four 16-mer strands. In the former case, cleavage of the 1:1 complex by three reagents with different formal charge, Fe(II).EDTA2-, Fe(II).EDDA and Fe2+, is comparable in rate to that of the individual dT20 and the dA20 strands. While the three reagents show similar cleavage rates for the duplex and single stranded molecules, they give distinctive cutting patterns in the DNA tetramer, consistent with the presence of a site of excess negative charge at the branch point. Scission induced by Fe(II).EDTA2- shows lower reactivity at the branch site relative to duplex controls, whereas Fe(II)2+ shows enhanced reactivity. Formally neutral Fe(II).EDDA shows weak loss of cutting reactivity at the branch. The position of attack by Fe(II)2+ in the branched tetramer is shifted with respect to those of Fe(II).EDTA2- or Fe(II).EDDA; a slower migrating species is also detected in the scission of dA20.dT20 duplex by Fe(II) reaction. These results suggest that the Fe(II)2+ reaction proceeds by a different mechanism from the other agents. The difference in cutting profiles induced by the neutral and negatively charged chelated complexes is consistent with a local electrostatic repulsion of a negatively charged source of radicals, not a positively charged one.     

椭圆斜羽叶的解剖研究及斜羽叶的系统分类位置

本文根据对椭圆斜羽叶(Plagiozamites oblongifolius)钙质石化化石的研究,认为其主要特征如下:羽状复叶,叶肉无海绵组织和栅栏组织分化。羽片叶脉维管束外韧式,木质部外始式,与现代苏铁属叶脉特征相近。羽轴维管束为“U”形,外始式木质部、梯状纹孔管胞,与现代苏铁属的羽轴维管束相似。根据上述特征,目前可将斜羽叶属归入原始苏铁类植物。但是,如果斜羽叶的生殖器官同 Noeggerathia 一样,为异孢型孢子囊穗,则斜羽叶可能为一种与苏铁类起源有关的原裸子植物。