盐胁迫下沙棘的渗透调节效应

分别用含有0、100、200和300mmol LNaCl的Hoagland培养液处理1年生沙棘(HippophaerhamnoidesL.)苗30d后,测定其鲜重,干重,含水量,可溶性糖、脯氨酸和无机离子(Na 、Cl-)的含量及叶片渗透势和渗透调节能力。结果表明:100mmol LNaCl处理的沙棘地上部和根的鲜重和干重最大,其含水量也最大;NaCl浓度超过100mmol L时,沙棘地上部分和根的鲜重和干重随盐浓度增加而逐步下降,其下降的趋势为地上部大于根部。随NaCl浓度不断升高,沙棘体内Na 和Cl-浓度随之升高,茎叶和根系中Cl-含量明显高于Na ,对Na 的相对吸收量多于Cl-。沙棘对盐胁迫有一定的适应能力,随NaCl浓度的升高,沙棘叶内脯氨酸含量升高,可溶性糖含量增加,渗透势降低,渗透调节能力增强。本结果可为盐碱地营造沙棘林提供依据。     

生态恢复状态下天敌对小菜蛾的自然控制作用

通过组建不同防治措施下的小菜蛾自然种群生命表,结果表明,化学防治区小菜蛾自然种群趋势指数为52.52;在生态恢复区,天敌因子对目标害虫的自然控制作用得到恢复和增强,连续4个世代的小菜蛾种群趋势指数分别为16.9、7.16、3.71和4.02,其种群数量的发展得到有效地抑制.影响小菜蛾春季第一、第二、第三及第四代种群数量的重要因子分别为绒茧蜂寄生、4龄幼虫的捕食及其它、赤眼蜂寄生和绒茧蜂寄生,其相应的排除作用控制指数分别为1.39、1.56、1.74和1.54.从天敌与小菜蛾种群相互作用的过程来看,前者对后者的控制作用表现出明显的时滞效应,其种群数量的发展需要一个累积过程.能否采取积极的田间保护、增强措施,将是充分发挥天敌控害潜能的关键因素之一.     

Casein Micelle Dispersions under Osmotic Stress

Casein micelles dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis. This technique measured an equation of state of the dispersions over a wide range of pressures and concentrations and at different ionic strengths. Three regimes were found. i), A dilute regime in which the osmotic pressure is proportional to the casein concentration. In this regime, the casein micelles are well separated and rarely interact, whereas the osmotic pressure is dominated by the contribution from small residual peptides that are dissolved in the aqueous phase. ii), A transition range that starts when the casein micelles begin to interact through their κ-casein brushes and ends when the micelles are forced to get into contact with each other. At the end of this regime, the dispersions behave as coherent solids that do not fully redisperse when osmotic stress is released. iii), A concentrated regime in which compression removes water from within the micelles, and increases the fraction of micelles that are irreversibly linked to each other. In this regime the osmotic pressure profile is a power law of the residual free volume. It is well described by a simple model that considers the micelle to be made of dense regions separated by a continuous phase. The amount of water in the dense regions matches the usual hydration of proteins.     

The effect of hypertonic saline on human corneal hydration.

Hydrophilic gel contact lenses, presoaked in various strength saline solutions, were held in intimate contact with the in vivo human cornea. A change in corneal water content was observed taking place against the induced osmotic gradient. Direct stimulation of some aspect of the mechanisms controlling corneal hydration is postulated, in a manner which may be similar to that previously reported for the in vitro rabbit cornea.     

Osmotic injury of PC-3 cells by hypertonic NaCl solutions at temperatures above 0 degrees C

Cell injury due to osmotic dehydration, which is regarded as a major cause of injury during freeze-thaw processes, was examined closely using a perfusion microscope. Human prostatic adenocarcinoma cells (PC-3), which were put in a chamber, were subjected to hyperosmotic stresses by perfusing NaCl solutions of varying concentrations into the chamber. Cells were exposed to 2.5 and 4.5M NaCl solutions for 1-60 min by changing the concentrations at 0.2, 1, and 10 M/min. Decrease in cell viability was biphasic: the viability decreased first after the increase in NaCl concentration due to dehydration and then after return to isotonic conditions due to rehydration. Rehydration was substantially more responsible for cell injury than dehydration, which was marked at lower NaCl concentrations and lower temperatures. Injury resulting from contraction was negligible at the 2.5 M NaCl solution. While the hypertonic cell survival, which was determined without a return to isotonic conditions, was almost independent of time of exposure to hyperosmotic concentrations, the post-hypertonic survival after returning to isotonic conditions decreased with increasing exposure time, suggesting that the rehydration-induced injury was a consequence of time-dependent alteration of the plasma membrane. The post-hypertonic survival was lower for higher NaCl concentrations and higher temperatures, which was qualitatively consistent with previous studies. Effects of the rate of concentration change on the post-hypertonic cell survival were observed at 4.5 M; the highest rate of survival was obtained by slower increase and faster decrease in the NaCl concentration. However, the effect was negligible at 2.5 M.     

Osmotic threshold and sensitivity for vasopressin release and fos expression by hypertonic NaCl in ovine fetus

In adults, hyperosmolality stimulates central osmoreceptors, resulting in arginine vasopressin (AVP) secretion. Near-term fetal sheep have also developed mechanisms to respond to intravascular hypertonicity with stimulation of in utero AVP release. However, prior studies demonstrating fetal AVP secretion have utilized plasma tonicity changes greater than those required for adult osmotically induced AVP stimulation. We sought to examine near-term fetal plasma osmolality threshold and sensitivity for stimulation of AVP secretion and to correlate plasma hormone levels with central neuronal responsiveness. Chronically instrumented ovine fetuses (130 +/- 2 days) and maternal ewes simultaneously received either isotonic or hypertonic intravascular NaCl infusions. Maternal and fetal plasma AVP and angiotensin II (ANG II) levels were examined at progressively increasing levels of plasma hypertonicity. Intravenous hypertonic NaCl gradually elevated plasma osmolality and sodium levels. Both maternal and fetal plasma AVP increased during hypertonicity, whereas ANG II levels were not changed. Maternal AVP levels significantly increased with a 3% increase in plasma osmolality, whereas fetal plasma AVP significantly increased only at higher plasma osmolality levels (over 6%). Thus the slope of the regression of AVP vs. osmolality was greater for ewes than for fetuses (0.232 vs. 0.064), despite similar maternal and fetal plasma osmolality thresholds for AVP secretion (302 vs. 304 mosmol/kg). Hyperosmolality induced Fos immunoreactivity (FOS-ir) in the circumventricular organs of the fetal brain. FOS-ir was also demonstrated in the fetal supraoptic and paraventricular nuclei (SON and PVN), and double labeling demonstrated that AVP-containing neurons in the SON and PVN expressed Fos in response to intravenous NaCl. These results demonstrate that, in the ovine fetus at 130 days of gestation, neuroendocrine responses to cellular dehydration are functional, although they evidence a relatively reduced sensitivity for AVP secretion compared with the adult.     

Tolerance-like condition developing in mice under the effect of antigen of erythrocyte lysate]

Lysate of sheep red blood cells obtained by the treatment of these cells with distilled water and purified by ultracentrifugation in cold possessed a weak immunogenicity. Its administration to mice caused the state of hyporeactivity to sheep red blood cells (a reduction of the immune response level to 10-25% of control. The capacity of the mise spleen cells to respond by immune reaction to the red blood cells following adoptive transfer was not disturbed. At the early periods after the lysate administrations the mouse spleen cells possessed a weak supressive activity in case of their transfer to the intact animals. The blood serum of mice treated with the lysate possessed a blocking activity which disappeared after the serum absorption with sheep red blood cells. A conclusion was drawn that hyporeactivity originating in mice after the lysate administration was caused by the presence in the serum of antibodies inhibiting the immune response.     

渗透胁迫下小麦根系渗透调节与根冠淀粉水解的研究

用不同浓度的PEG—600对抗旱性不同的小麦幼苗进行渗透胁迫处理,研究了小麦幼苗根系的淀粉酶活性、可溶性糖含量、渗透势、渗透调节能力和根冠淀粉的水解状况。结果表明,随着渗透胁迫程度的加重,抗旱性强的小麦品种昌乐5号和北农2号根系渗透势和饱和渗透势的降低程度大于抗旱性弱的小麦品种鲁麦5号和921842,并且抗旱性强的小麦品种根系的渗透调节能力大于抗旱性弱的小麦品种。随着渗透胁迫程度的加重．各品种小麦根冠淀粉粒均有不同程度的减少。而抗旱性强的品种根冠淀粉粒的减少程度小于抗旱性弱的品种;抗旱性强的小麦品种根系淀粉酶活性显著高于抗旱性弱的小麦品种,但是,随着渗透胁迫程度的加重,抗旱性弱的品种淀粉酶活性增加的幅度远高于抗旱性强的品种。可溶性糖含量的变化趋势与淀粉酶活性的变化趋势一致．即渗透胁迫下根冠淀粉水解程度大的小麦品种,可溶性糖的含量高。但根冠淀粉水解在根系的渗透调节以及在小麦适应水分胁迫中的作用还有待于进一步探讨。     

Osmotic stress as a factor in the detrimental effect of glycerol on human platelets

The aim of this work was to determine the importance of osmotic stress as a damaging factor in the detrimental effect of glycerol on human platelets. The severity of osmotic stress was mitigated by reducing the rate of change of glycerol concentration in the suspending medium. The classical permeability equations were used to predict cell volume changes in response to step changes in extracellular glycerol concentration. Protocols were devised that limited cellular shrinkage during glycerol addition and cellular swelling during glycerol dilution. When glycerol was added and diluted rapidly, the recovery of the hypotonic stress response with respect to untreated controls was unaffected by 0.25 mol/liter glycerol, but was reduced to ca. 65% after exposure to 0.5 mol/liter glycerol and to ca. 25% after exposure to 1 mol/liter glycerol. When 1 mol/liter glycerol was added and removed slowly such that cell volume remained within the range of 60-130% of normal volume, recovery of the hypotonic stress response was improved to ca. 50%, and the aggregation response was undiminished. Osmotic stress was therefore at least partly responsible for the damage caused by glycerol. However, platelets were damaged more after slow dilution from 1 mol/liter glycerol, when cellular swelling was limited to 116% of normal volume, than after rapid dilution from 0.25 or 0.5 mol/liter glycerol, which resulted in cellular swelling to 123% and 146% of normal volume, respectively. Thus, a possible toxic effect of glycerol cannot as yet be discounted.     

Osmotic adaptation in Ulva lactuca under fluctuating salinity regimes

A study has been made of the osmotic responses of the green intertidal alga, Ulva lactuca, under two fluctuating salinity regimes; sinusoidal and square-wave fluctuations between 30 and 100% sea water in a 12 h cycle. These regimes closely resemble the tidal fluctuation of salinity encountered by the alga in its natural estuarine habitat. Data on changes in the inorganic ions, potassium, sodium, chloride and sulphate; in the organic solute, dimethylsulphoniopropionate; in the total sugar levels and estimated osmotic and turgor pressures under the two salinity regimes are reported. Significant differences in the solute responses under these different conditions were detected. In general, better control of ion fluxes appeared to be exercised under the sinusoidal conditions which also buffered changes in dimethylsulphoniopropionate levels. Influxes of potassium were highly light-dependent. Chloride levels conspicuously failed to reach the steady-state levels in the 6-h-hyper-osmotic part of either the abrupt or gradual cycle. The possible significance of these data, which may better reflect osmotic changes in the natural environment, and some of the problems encountered, particularly in accounting for charge balance under some conditions, are discussed.Abbreviations DSMP 3-(dimethylsulphonio)propionate - FW fresh weight