广西九万山藓类植物区系分析及其对划分热带,亚热带分界线的意义

九万山位于广西北部的中央(25°10’～25°25’N,108°27’E),界于泛北极植物区和古热带植物区的交汇处。其主要植被为亚热带常绿阔叶林。最高海拔为1693m,最低处仅170m。经对1850号标本的鉴定,共计有藓类植物35科、101属和189种。本文分析了九万山的藓类植物区系成分,将其划分为 10种类型。其中东亚成分最为丰富(39.33％),热带、亚热带成分次之(38.20％),而温带成分居第三位(18.54％)。本文选择了九万山临近的五个地区加以比较。其中,金佛山与九万山藓类植物的属和种的相似性系数分别为60.68％和36.87％,神农架为57.29％和33.13％。尖峰岭为48.83％和22.29％,西双版纳为57.29％和29.63％。而我国东部的武夷山则为69.86％和39.57％,其相似性系数在相比较的五个山区中为最高。九万山区有4个特有属并明显受喜马拉雅的影响。特别值得注意的是,在九万山区藓类区系中约有7％的种类是典型的热带成分。根据定量和定性的分析,笔者认为九万山的藓类区系表现出由热带向亚热带过渡的特性,其分界线可能位于九万山的南侧。     

Establishment and characterization of a new,spontaneously immortalized,pancreatic ductal cell line from the Syrian golden hamster

Spontaneously immortal pancreatic cell lines are not available. By use of a defined culture medium, such a line (TAKA-1) was established from the Syrian golden hamster. Cytological, cytogenetic, molecular biological, enzymatic and receptor patterns as well as antigenicity were studied and were compared with those of the normal hamster pancreatic ductal cells in vivo. TAKA-1 cells grew exponentially in a monolayer on collagen gel in a defined medium but did not proliferate in soft agar. Ultrastructurally, the cells closely resembled the normal hamster pancreatic ductal cells. Similarities and dissimilarities were found between the normal ductal cells and TAKA-1 cells. Similarities included the presence of cytokeratin, carbonic anhydrase and some tumor-associated antigens. However, unlike the normal ductal cells, TAKA-1 cells expressed blood group A angigen and anti-vimentin, showed affinity to selected lectins, and an abnormality of chromosome 3, which is suggested to be associated with immortality. Moreover, unlike the hamster pancreatic ductal cancer cells but like the normal hamster pancreatic ductal cells, TAKA-1 cells did not have a c-Ki-ras mutation. EGF, TGF- and secretin, but not CCK or GRP, bound to the TAKA-1 cells. TAKA-1 cells produced TGF-, and their growth was stimulated by exogenous EGF in serum-free medium. This cell line presents a suitable model for biologic and pathologic study of the hamster pancreatic ductal cells in vitro.     

Structural analysis of zinc substitutions in the active site of thermolysin.

Native thermolysin binds a single catalytically essential zinc ion that is tetrahedrally coordinated by three protein ligands and a water molecule. During catalysis the zinc ligation is thought to change from fourfold to fivefold. Substitution of the active-site zinc with Cd2+, Mn2+, Fe2+, and Co2+ alters the catalytic activity (Holmquist B, Vallee BL, 1974, J Biol Chem 249:4601-4607). Excess zinc inhibits the enzyme. To investigate the structural basis of these changes in activity, we have determined the structures of a series of metal-substituted thermolysins at 1.7-1.9 A resolution. The structure of the Co(2+)-substituted enzyme is shown to be very similar to that of wild type except that two solvent molecules are liganded to the metal at positions that are thought to be occupied by the two oxygens of the hydrated scissile peptide in the transition state. Thus, the enhanced activity toward some substrates of the cobalt-relative to the zinc-substituted enzyme may be due to enhanced stabilization of the transition state. The ability of Zn2+ and Co2+ to accept tetrahedral coordination in the Michaelis complex, as well as fivefold coordination in the transition state, may also contribute to their effectiveness in catalysis. The Cd(2+)- and Mn(2+)-substituted thermolysins display conformational changes that disrupt the active site to varying degrees and could explain the associated reduction of activity. The conformational changes involve not only the essential catalytic residue, Glu 143, but also concerted side-chain rotations in the adjacent residues Met 120 and Leu 144. Some of these side-chain movements are similar to adjustments that have been observed previously in association with the "hinge-bending" motion that is presumed to occur during catalysis by the zinc endoproteases. In the presence of excess zinc, a second zinc ion is observed to bind at His 231 within 3.2 A of the zinc bound to native thermolysin, explaining the inhibitory effect.     

Establishing isostructural metal substitution in metalloproteins using 1H NMR, circular dichroism, and Fourier transform infrared spectroscopy.

Far-UV CD, 1H-NMR, and Fourier transform infrared (FTIR) spectroscopy are three of the most commonly used methods for the determination of protein secondary structure composition. These methods are compared and evaluated as a means of establishing isostructural metal substitution in metalloproteins, using the crystallographically defined rubredoxin from Desulfovibrio gigas and its well-characterized cadmium derivative as a model system. It is concluded that analysis of the FTIR spectrum of the protein amide I resonance represents the most facile and generally applicable method of determining whether the overall structure of a metalloprotein has been altered upon metal reconstitution. This technique requires relatively little biological material (ca. 300 micrograms total protein) and, unlike either CD or 1H-NMR spectroscopy, is unaffected by the presence of different metal ions, thus allowing the direct comparison of FTIR spectra before and after metal substitution.     

Characterization of a stable,anchorage-dependent clone obtained from a spontaneously transformed mouse cell line

Summary A variant nontransformed clone, I21, was selected from the spontaneously transformed mouse fibroblast line, IT22. Selection was done by plating IT22 in methylcellulose and picking single cells after 2 d. Cultures derived from these single cells were selected again and one clone, I21, derived from the second round of selection was characterized extensively. I21 and IT22 have the same plating efficiency (PE) on plastic, but in agarose they differ by 1000-fold. In comparison to IT22, I21 has a normal morphological appearance, a lower saturation density, a higher viability in stationary phase, an increased doubling time, an increased chromosome content, and is unable to form tumors in nude mice. I21 has remained remarkably stable in culture and has not reverted to the transformed phenotype for at least 300 generations in culture. Over 100 clones of I21, expanded to 10⁶ cells, failed to show an increased PE in agarose. Even expansion of the rare colonies of I21 that grow in agarose failed to produce clones similar to IT22. The research was supported by the Medical Research Council and the National Cancer Institute of Canada. R. Godbout was supported by a 1967 Science Scholarship and by an MRC Studentship. B. L. Gallie is a Research Associate of the Ontario Cancer Treatment and Research Foundation.     

Establishment and characterization of a new human hepatocellular carcinoma cell line

Summary A human hepatocellular carcinoma cell line (FOCUS—Friendship of China and United States) was derived from a patient with primary hepatocellular carcinoma. This cell line has been in continuous culture over an 18-mo period. The morphological and ultrastructural features of FOCUS are consistent with its neoplastic hepatocellular orgin. FOCUS cells contain aspartate aminotransferase and glucose-6-phosphatase activity. In addition, α₁-antitrypsin, fibrinogen, alpha fetoprotein, and carcinoembryonic antigens were detectble in the cytoplasm of the cultured cells by immunochemical staining techniques. The karyotype of the FOCUS cell is human in origin and it contains human DNA sequences as detected by molecular hybridization analysis. The FOCUS cells do not show evidence of density-dependent inhibition of growth under confluent conditions. Repeated growth curves over an 18-mo period were identical, revealing a doubling time of 42 to 48 h. The malignant potential of FOCUS cells was further demonstrated by their ability to lead to gross tumor formation after subcutaneous infection into nude mice. From one of the solid tumors grown in nude mice, recultured cell lines have been established and found to have properties identical to the original FOCUS cell line. This FOCUS cell line represents an additional model for further investigation of tumor specific antigens and the relationship between hepatitis B virus (HBV) and hepatocellular carcinoma. Preliminary molecular characterization has indicated the existence of integrated HBV sequences within the FOCUS genome.     

脊髓灰质炎病毒感染赤麂细胞株的实验研究

脊髓灰质炎病毒的敏感细胞范围一直局限于灵长类动物细胞。用该病毒感染处理非灵长类的赤麂肺二倍体细胞(KIZ-7901),可诱导9.0—14.7%的细胞出现染色体畸变,除见有染色体或单体断裂外,还见有断片、双着丝粒、环、互换、易位和缺失等。也可引致姐妹染色单体交换率(SCE)的显著提高。脊髓灰质炎病毒感染赤麂细胞后,不产生特异的CPE,不明显影响细胞群体的增殖。应用病毒滴定、包涵体检查,间接免疫荧光试验和电镜检查,都可查见细胞内有病毒或其抗原物质存在。这提示脊髓灰质炎病毒在非灵长类的赤麂细胞内呈现非杀细胞性感染。     

Suppression of lymphocyte proliferation by a nonspecific factor produced by the burkitt lymphoma-derived lymphoblast cell line

Summary The DAUDI lymphoblast cell line derived from a patient with Burkitt lymphoma was obtained from two different sources. One of these (DAUDI-I) produced a factor that inhibited lymphocyte proliferation in both human and mouse regardless of the stimulator, i.e. allogeneic lymphocytes or mitogens. Glutaraldehyde treatment eliminated production of the factor and demonstrated that DAUDI-I was capable of stimulating normal lymphocytes in MLR. A second DAUDI cell line (DAUDI-S) did not produce the inhibitory factor and was capable of MLR stimulation. Supported by the Children's Leukemia Foundation of Michigan, NIH Grants AI 11013 and AI 11335, and the Kidney Foundation of Michigan.     

Effects of Na readmission on cellular45Ca fluxes in Na-Depleted guinea pig taenia coli

Summary The removal of Na from the medium causes a cellular Ca uptake in the smooth muscle of the guinea pig taenia coli which is rapidly reversed if medium Na is readmitted. This net extrusion was characterized in tissues which were first Na-depleted in a zero-Na (sucrose) solution. Li was able to substitute for Na in mediating this effect. K was also able to mimic Na in this respect if the depolarization-mediated Ca influx caused by the isotonic K solution was blocked with 10^–5 m D-600. The net Ca extrusion upon Na readmission was due to a small decrease in Ca influx, as well as a marked increase in the transmembrane Ca efflux rate, as revealed by⁴⁵Ca washout experiments. The increased⁴⁵Ca efflux upon Na readmission could be mimicked by Li, K, choline and tris. We conclude that the Na/Ca-exchange hypothesis is insufficient to explain these data, in that both Ca extrusion and⁴⁵Ca efflux can be stimulated in the absence of a Na gradient, or in the absence of any monovalent cationic gradient. These observations are discussed in terms of a possible intracellular competition of Ca and monovalent cations for anionic binding sites, as well as with regard to a possible direct stimulation of a plasmalemmal CaATPase by monovalent cations.     

Caffeine inhibition of postreplication repair of UV-damaged DNA in mouse epidermal cells

The effect of caffeine (0.25–1.5 mM) on UV-irradiated (5 and 10 J/m²) primary cultures of mouse epidermal cells (EPD) and an in vitro transformed cell line (PDV) was studied at the cellular and molecular levels. A synergistic reduction in cell survival induced by caffeine with UV-irradiation was found in the PDV cells at 10 J/m² but not at 5 J/m². When conversion of low molecular weight newly-synthesized DNA to high molecular weight DNA was studied in both cell types, caffeine at 1.5 mM had no effect on this conversion in unirradiated cultures. At 5 J/m², caffeine had a transitory inhibitory effect on this conversion. However, at 10 J/m² caffeine had a strong permanent inhibitory effect on this conversion at doses higher than 0.5 mM in PDV cells and higher than 0.25 mM in EPD cells. This apparent inhibition of elongation by caffeine in irradiated cells could not be accounted for by an effect on the rate of DNA synthesis. In PDV cells there was a direct correlation in terms of effective caffeine dose level between synergistic reduction in cell survival after UV and the effect on DNA elongation. Irradiated EPD cells were more sensitive to the inhibitory effect of caffeine on DNA elongation.