外界高渗环境对枯草芽孢杆菌胞内自由脯氨酸含量的影响

枯草芽孢杆菌(93151)在基本培养基中培养,可耐受高达8%NaCl浓度,而在10%NaCl条件下96h内未见生长。随胞外NaCl浓度的增加,其胞内自由脯氨酸的含量相应明显增加,在8%NaCl浓度下胞内脯氨酸含量可达2.944mg·g-1干细胞重,与无NaCl条件下相比,增加了1572%,而对照菌大肠杆菌仅可耐受4%NaCl浓度,并且在不同NaCl浓度下,胞内脯氨酸含量变化不明显。     

NUCLEOLAR AND BIOCHEMICAL CHANGES DURING UNBALANCED GROWTH OF TETRAHYMENA PYRIFORMIS

Numerous nucleoli can be observed in the macronucleus of the logarithmically growing ciliated protozoan Tetrahymena pyriformis; at late log phase the nucleoli aggregate and fuse. In stationary phase this fusion process continues, leaving a very few large vacuolated nuclear fusion bodies in the nucleus. When these stationary phase cells are placed into fresh enriched proteose peptone medium, the large fusion bodies begin to disaggregate during the 2.5-hour lag phase before cell division is initiated. By 3 to 6 hours after inoculation the appearance of the nucleoli in many cells returns to what it was in logarithmic cells. In view of the possible role of nucleoli in ribosome synthesis, attempts were made to correlate the morphological changes to changes in RNA and protein metabolism. The beginning of an increased RNA synthesis was concomitant with the beginning of disaggregation of the large fusion bodies into nucleoli, which was noticed in some cells by 1 hour after the return to fresh enriched proteose peptone medium. Increased protein synthesis then followed the increased RNA synthesis by 1 hour. The supply of RNA precursors (essential pyrimidines) were removed from cultures which were grown on a chemically defined synthetic medium, in order to study the relation between nucleolar fusion and synthesis of RNA and protein. Pyrimidine deprivation drastically curtailed RNA and protein synthesis, but did not cause fusion of nucleoli. When pyrimidines were added back to this culture medium, RNA synthesis was immediately stimulated and again preceded an increased protein synthesis by 1 hour. These studies suggest the involvement of unfused nucleoli in RNA and protein synthesis and demonstrate the extreme plasticity of nucleoli with respect to changes in their environment.     

NaCl对大麦幼苗生长及姊妹染色单体交换的影响

研究了NaCl胁迫下大麦幼苗生长及根端分生细胞的姊妹染色单体交换(SCE),当NaCl浓度提高时,SCE频率明显增大而细胞分裂指数却下降,实验组主胚根及幼苗的生长速度减慢。对细胞分裂和幼苗生长的抑制强度与处理浓度间呈正相关。实验结果表明,高浓度NaCl对幼苗生长和细胞分裂是有害的,它能引起细胞内的DNA损伤,因而具有潜在的诱变或致畸作用。     

Ionic dependence of the extracellular ATP-induced permeabilization of transformed mouse fibroblasts: role of plasma membrane activities that regulate cell volume

Extracellular ATP rendered the plasma membrane of transformed mouse fibroblasts permeable to normally impermeant molecules. This permeability change was prevented by increasing the ionic strength of the isotonic medium with NaCl. Conversely, the cells exhibited increased sensitivity to ATP when the NaCl concentration was decreased below isotonicity, when the KCl concentration was increased above 5 mM while maintaining isotonicity, and when the pH of the medium was raised above 7.0. These conditions as well as the addition of ATP itself caused cell swelling. However, the effect of ATP was independent of cell volume and dependent upon the ionic strength and not the osmolarity of the medium since 1) addition of sucrose to isotonic medium did not prevent permeabilization although media made hypertonic with either sucrose or NaCl caused a decrease in cell volume; and 2) addition of sucrose or NaCl to hypotonic media caused a decrease in cell volume, but only NaCl addition decreased the response to ATP. Conditions that have been shown to inhibit plasma membrane proteins that play a reciprocal role in cell volume regulation had reciprocal effects on the permeabilization process, even though the effect of ATP was independent of cell volume. For example, inhibition of the Na+,K+-ATPase by ouabain increased sensitivity of cells to ATP while conditions which inhibit Na+,K+,Cl- -cotransporter activity, such as treatment of the cells with the diuretics furosemide or bumetanide or replacement of sodium chloride in the medium with sodium nitrate or thiocyanate, inhibited permeabilization. The furosemide concentration that inhibited permeabilization was greater than the concentration that inhibited Na+,K+,Cl- -cotransporter-mediated 86Rb+ (K+) uptake, suggesting that the effect of furosemide on the permeabilization process may not be specific for the Na+,K+,Cl- -cotransporter.     

Stimulation of virus-induced fusion of Ehrlich ascites tumor cells by 3',5'-cyclic AMP.

HVJ(Sendai virus)-induced fusion of Ehrlich ascites tumor cells was found to be stimulated by treatments which increase the intracellular level of cyclic AMP. This stimulation was optimal at an external concentration of Ca⁺⁺ of about 0.5 mM. During the process of cell fusion, the intracellular concentration of cyclic AMP was increased with a maximum at 2 min after the initiation of the fusion reaction.Evidence is also presented which suggests that the increase of the cyclic nucleotide is a part of control mechanism of HVJ-induced fusion of eukariotic cells. Thus, this cyclic AMP-stimulated process could be one of the step(s) requiring ATP and Ca⁺⁺, both of which are necessary for the overall fusion process of the tumor cells.     

Effect of hypertonicity on survival of unprotected human cultured cells following freezing and thawing

An investigation was carried out on the post-thaw survival of unprotected human heteroploid EUE cells, either maintained in isotonic medium (0.137 M NaCl) or adapted to hypertonicity (0.356 M NaCl) and frozen in medium with an increased concentration of NaCl. A fivefold increase in the survival fraction of the adapted cells in comparison with the unadapted ones was observed when cells were frozen in isotonic medium. When cells were frozen in hypertonic medium (0.356 M NaCl), the two cell types exhibit comparable survival values. The results are discussed, with special attention to cell defense mechanisms against freezing injury.     

Changes in DNA polymerase activity associated with cell fusion in cultures of embryonic muscle

In cultures of differentiating chicken embryo muscle cells there is a steep decline in DNA polymerase activity which closely parallels the time of rapid cell fusion and the formation of multinucleated myotubes. The DNA polymerase activity remaining in the cultures is almost completely associated with single unfused cells. Cell fusion does not require a confluent culture and fusion capability appears to be severely reduced in the remaining single cells following an approximately ten hour time period during which the majority of fusion takes place. A model is presented to explain the observed kinetics of cell growth and cell fusion in vitro.     

High-pressure adaptation by salt stress in a moderately halophilic bacterium obtained from open seawater

High-pressure adaptation was examined using a moderately halophilic bacterium (Micrococcus roseus), which was isolated from open seawater and capable of growing in 15% w/v NaCl (optimum NaCl concentration: 3% w/v). After treatment at 207 MPa, colony-forming units (CFUs) significantly decreased; however, the loss of integral cells after pressure was only 30% when direct cell count was performed microscopically. In order to investigate the piezotolerance of M. roseus under high pressure without morphological change, the survival of cells was examined under pressure at 138 MPa for 2 h. M. roseus in 3% NaCl was still sensitive to pressure at 138 MPa. However, the cells in the third generations showed remarkably increased pressure resistance, and no significant loss of viability was confirmed. Furthermore, when M. roseus was cultured in 1, 3, 5, 10 and 15% NaCl, the survival ratio proportionally increased at increased NaCl concentration. M. roseus cultured in 15% NaCl was remarkably resistant (94.7% viability) to pressure at 138 MPa, even when suspended in lower concentration of NaCl. This suggests that NaCl concentrations in growth culture affect the piezotolerance of M. roseus and that this species has an ability to adapt to high pressure.     

葡萄糖浓度对细胞融合效果的影响

目的:细胞融合是细胞生物学领域近30年来得到迅速发展的一项新兴技术手段,因其操作简便、人工可控等优点在研究核质互作、肿瘤发生、疫苗研发和培育新型生物品种等方面均有广泛应用。其中,利用聚乙二醇(PEG)进行化学融合是细胞融合中最为常用且简便的技术手段。PEG化学融合效果受到多种因素影响,如PEG浓度、Ca2+、Mg2+、pH值等,然而对于糖类物质在细胞融合中的影响未见报道。本文旨在为了更全面了解PEG法诱导的化学细胞融合,通过优化融合条件以提高化学细胞融合效率。方法:选取鸡血血细胞为材料,通过改变原Hanks缓冲液中葡萄糖浓度,观察比较各组细胞融合率,探究葡萄糖浓度在化学细胞融合中的影响,并通过对比结果获得了对于鸡血血细胞应采用的最适葡萄糖浓度区间。结果:对于鸡血血细胞融合实验,葡萄糖浓度在10-14 mmol/L范围内细胞融合效率较原Hanks液配方高2倍左右。结论:葡萄糖对细胞融合效果具有一定的影响,可以通过调节葡萄糖浓度提高细胞融合率,从而为PEG化学细胞融合提供一种更为优化的方案。     

Effect of salinity of medium on cellular fatty acid composition of marine algaPorphyridium cruentum (Rhodophyceae)

Porphyridium cruentum Näg. (clone 161) was found to grow best in medium containing between 0.45 M and 0.8 M NaCl. From studies done on growing cultures, the palmitic acid content of the cells decreased with increasing NaCl concentration of the medium. Conversely, when the culture was transferred from a 0.8 M NaCl medium to 0.2 M NaCl, the amount of palmitic acid in thePorphyridium cells increased with time of incubation and it contributed up to 64.5% of the total fatty acid content. There appears to be a negative correlation between the cellular content of palmitic acid and the growth lag. The oleic acid content varied only marginally with increasing NaCl concentration. The poly-unsaturated acid content (linolenic and arachidonic acids) decreased initially and then increased with NaCl concentration up to and beyond ca. 0.8 M NaCl respectively. At 1.5 M NaCl, the poly-unsaturated fatty acids amounted to 78.2% of the total fatty acids in the cell. For stationary phaseP. cruentum cultures, a similar relationship existed between fatty acids and NaCl concentration. However, palmitic acid was accumulated up to three-fold more when compared to the exponential culture grown in low salinity. In addition stearic acid was also found in significant quantities.     

Photosynthetic Activity during the Life Cycle of Synchronous Skeletonema Cells

A culture of Skeletonema costatum grown at a light intensity of 3 klux and at 20°C was synchronized in diurnally intermittent illumination of 12 hour light and 12 hour dark. The culture was hardly fully synchronous as the cell division period lasted about 9 hours. The cell division started in the middle of the light period. The concentration of the pigments: chlorophyll a, chlorophyll 6 and fucoxanthin and the rate of light-saturated photosynthesis were followed every hour during the 24 hour period. Both the concentration of pigments and the photosynthetic activity showed a rhythmical variation. The concentration per cell of all three pigments examined increased during the development of the cells and decreased automatically during the period of cell division. An increase in the pigment concentration was found only in the light period. The rate of light-saturated photosynthesis calculated per unit of cell number increased during the cell development and decreased during the division period. The increase in the photosynthetic activity at light-saturation started about 4 hours after the end of cell division, which was 4 hours before the light was turned on while the increase in the concentration of chlorophyll a first started 1–2 hours after this moment. The variation in photosynthetic activity was compared with that found by other workers. The results found with Chlorella ellipsoidea by Japanese scientists (Nihci et al.) was explained as an inhibition phenomenon because the cells were not adapted to the experimental conditions.     

Differential behavior of liposome-introduced specific RNAs in living Drosophila cells

We have developed a protocol for efficiently introducing macromolecules into Drosophila tissue culture cells using liposomes. By carefully adjusting the fusion parameters, conditions have been established to routinely encapsulate 15–30% of the starting material into liposomes and to introduce 20–30% of the liposome-encapsulated material into the cells during a 30-minute fusion period. Essentially, all of the cells receive material from the liposomes and 10⁹ cells can be fused at once. The fusion does not have any measureable effect on cell viability as assayed by trypan blue exclusion, growth rate, and cell morphology. We have utilized this technique to introduce radioactive RNAs into nonradioactive cells, thus enabling the behavior of the introduced RNAs to be followed unambiguously. Liposome-introduced small nuclear RNAs (snRNAs) are stable in the cell for at least 25 hours (approximately two cell generations), with 80% of the radioactivity remaining trichloroacetic acid (TCA) precipitable and the gel electrophoresis pattern remaining essentially unchanged. This is in contrast to liposome-introduced cytoplasmic RNAs, which are only 20% TCA precipitable after the first hour. In the cell, the introduced snRNAs attain a 10–35-fold higher concentration in the nucleus than the cytoplasm. Nuclear accumulation is not seen with Drosophila tRNA or 5s RNA, both of which attain the same nuclear as cytoplasmic RNA concentration.     

The relationship of damage to and death of ascitic tumor cells during starvation to the ATP and free calcium content in the cells

Ascite tumor cells EL-4 were incubated in conditions of energy starvation (Hanks salt solution with rothenone and without glucose) at 37 degrees C for 3 hours. Under these conditions, some structural cell damages appeared within the first hours: enlarging and flattening of the cells, blebbing, vacuolization of the cytoplasm, nuclear chromatin condensation. Later on, a share of cells with obvious damage decreased, whereas that of the cells stained with trypan blue (dead cells) much increased (up to 90% after a 3 hour incubation). The cellular ATP decreased abruptly (up to 10% of the control) during the first 10 minutes of starvation. Free Ca2+ concentration increased within 1 hour of incubation more than two-fold. The conditions promoting Ca2+ influx (ionophore A23187 + Ca2+ in medium) accelerated the damage and cell death. However, the increase in free Ca2+ concentration did not trigger any damage in the energy-starved cells, since in the Ca2(+)-depleted medium (no increase in free Ca2(+)-concentration) the development of damages was not prevented. The damage initiation was irreversible: the addition of glucose to cell suspensions after 0.5-1 hour of their incubation in energy-starved condition did not prevent the development of damage, while ATP content in these cells was much increased.     

Mg^2＋浓度对细胞融合效果的影响

目的：细胞融合是细胞生物学中一种常用的技术,有着广泛的应用,如单克隆抗体制备,核质研究,疫苗研发等。其中,聚乙二醇（PEG）化学融合是最为常用的一种细胞融合技术,影响PEG化学细胞融合效果的因素有很多,但是对一些具体因素的研究的不是很全面。本文旨在为了更全面的了解PEG诱导的化学细胞融合的影响因素,优化融合条件,以此扩大PEG化学融合应用范围。方法：以鸡血血红细胞为材料,通过调节已有的Hanks融合液中镁离子浓度,比较各实验组以及对照组的细胞融合率,探究了Mg^2＋浓度对细胞融合效果的影响,确定了为提高细胞融合效率应使用的Mg^2＋浓度区间。结果：可以在原有的Hanks配方的基础上,调节Mg^2＋浓度至10 mmol/L-20 mmol/L这个范围,细胞融合率较大。结论：Mg^2＋对细胞融合有一定影响,通过调节Mg^2＋浓度至上述合适区间可以达到较高的细胞融合率,从而为PEG化学融合提供了一种优化方案。     

真盐生植物盐地碱蓬根系边缘细胞在耐盐中的作用初探

以黄河三角洲潮间带盐地碱蓬种子生成的幼苗为材料,研究了NaCl胁迫对盐地碱蓬生长与根系边缘细胞的影响。盐地碱蓬的第一个边缘细胞几乎与根尖同步产生,当根长达到13mm时,边缘细胞数目达到最大值。NaCl胁迫抑制边缘细胞的活性,但低浓度的NaCl处理增加边缘细胞的数目。低浓度NaCl处理时果胶甲基酯酶（PME）的活性比对照有明显增加,超氧化物歧化酶（SOD）活性随着NaCl浓度的增加呈现先上升后下降的趋势,低浓度NaCl可以增加盐地碱蓬根内过氧化氢酶（CAT）的活性,NaCl处理时间和处理浓度都对过氧化物酶（POD）活性的影响不明显。这些结果表明,盐地碱蓬至少部分通过增加调控活性氧（ROS）水平增加PME活性及根系边缘细胞数目来抵抗NaCl胁迫。     

Effects of osmotic stress on Methanococcus thermolithotrophicus: 13C-edited 1H-NMR studies of osmolyte turnover

In vivo NMR studies of the thermophilic archaeon Methanococcus thermolithotrophicus, with sodium formate as the substrate for methanogenesis, were used to monitor formate utilization, methane production, and osmolyte pool synthesis and turnover under different conditions. The rate of formate conversion to CO2 and H2 decreased for cells adapted to higher external NaCl, consistent with the slower doubling times for cells adapted to high external NaCl. However, when cells grown at one NaCl concentration were resuspended at a different NaCl, formate utilization rates increased. Production of methane from 13C pools varied little with external NaCl in nonstressed culture, but showed larger changes when cells were osmotically shocked. In the absence of osmotic stress, all three solutes used for osmotic balance in these cells, l-alpha-glutamate, beta-glutamate, and Nepsilon-acetyl-beta-lysine, had 13C turnover rates that increased with external NaCl concentration. Upon hyperosmotic stress, there was a net synthesis of alpha-glutamate (over a 30-min time-scale) with smaller amounts of beta-glutamate and little if any of the zwitterion Nepsilon-acetyl-beta-lysine. This is a marked contrast to adapted growth in high NaCl where Nepsilon-acetyl-beta-lysine is the dominant osmolyte. Hypoosmotic shock selectively enhanced beta-glutamate and Nepsilon-acetyl-beta-lysine turnover. These results are discussed in terms of the osmoadaptation strategies of M. thermolithotrophicus.     

Ionic homeostasis disturbance is involved in tomato cell death induced by NaCl and salicylic acid

The ability of salicylic acid and NaCl to induce programmed cell death by disturbing ionic homeostasis was investigated using tomato suspension culture cells. NaCl (300?mM) and salicylic acid (1?mM) inhibited cell growth and caused cell death within 1?wk of exposure. Treatment with NaCl increased the production of reactive oxygen species and the permeability of plasma membrane, but it also led to a reduction in the pH of the culture medium and resulted in a disturbance in ionic homeostasis of the cells. Salicylic acid-induced cell death in tomato suspension culture was also accompanied by production of reactive oxygen species and increases in both electrolyte leakage and pH of the culture media. However, reactive oxygen species production was not significantly different in cultures treated with a lethal salicylic acid concentration and 100?mM NaCl, in which most of the cells survived. A decrease in the K⁺/Na⁺ ratio was observed only in those cell cultures in which the salicylic acid treatment induced the death of cells. These results suggest that the decrease of the intracellular K⁺ concentration and K⁺/Na⁺ ratio is a common phenomenon in triggering programmed cell death by lethal concentrations of salicylic acid and NaCl.     

Immunofluorescent Detection of Enterotoxin B in Food and a Culture Medium

Both Staphylococcus aureus strains 243 and S-6 cells producing enterotoxin B and free enterotoxin in food and culture medium were rapidly demonstrated by using the fluorescent-antibody technique. Comparison of cell fluorescence and enterotoxin B production determined by double gel diffusion showed that an estimation of enterotoxin production could be made by observing the degree of cell fluorescence. The fluorescent-antibody technique was used to determine whether cells were producing enterotoxin under varying nutritional and environmental conditions: NaCl concentration, culture aeration, and time and temperature of incubation in Brain Heart Infusion broth and shrimp slurries. At the various NaCl concentrations, the fluorescence of cells was found positively associated with enterotoxin B production only during the first 12 hr of growth. As the NaCl concentration was increased from 0 to 10%, the fluorescence of cells and toxin production decreased. Maximum for cell fluorescence and enterotoxin production was observed at 37 C. Little or no difference in cell fluorescence and enterotoxin production with both strains was found between Brain Heart Infusion broth and shrimp slurry cultures. All results obtained with the fluorescent-antibody technique were verified with double gel diffusion for enterotoxin detection and quantitation.     

Effect of salt solutions on the radiosensitivity of mammalian cells. IV. Treatment with NaCl solutions containing ouabain, NEM, PNAP, cysteamine or DMSO.

The effects of a wide concentration range of NaCl solutions containing either ouabain, ethanol, para-nitroacetophenone (PNAP), N-ethylmaleimide (NEM), cysteamine or dimethyl sulphoxide (DMSO) on cellular radiosensitivity have been examined. Ouabain and NEM treatment increased the radiosensitivity of V79 Chinese hamster cells, but the action of these chemicals did not depend on the concentration of NaCl. PNAP increased cellular radiosensitivity with increasing NaCl concentration reaching a maximum effect at 0.6 to 0.7 M NaCl. The radioprotective properties of cysteamine, DMSO and ethanol were all strongly dependent on the NaCl concentration in a complex but qualitatively similar manner. DMSO (2.0 M) increased radiation survival of cells after a 1380 rad dose by a factor of about 10(4) when present in 0.075 M NaCl and by a factor of 8.7 when present in 1.2 M NaCl.     

Effect of intracellular ATP on La(3+)-induced aggregation and fusion of human erythrocytes

The influence of intracellular ATP level on the aggregation and fusion of human erythrocytes, induced by La3+ in the concentration range 20-330 microM was studied. The aggregation of intact red blood cells differs from that of cells with increased and decreased contents of ATP. Incubation of erythrocyte aggregates at 37 degrees C did not lead to cell fusion. At the same time, incubation of erythrocyte aggregates with decreased and increased ATP contents in the presence of La3+ induced a pronounced cell fusion.