Some aspects of osmotic biology of the freshwater leech,Poecilobdella viridis (Blanchard)

Ability of the freshwater leech, Poecilobdella viridis to withstand osmotic changes was investigated by following the fluctuations of the body weight in tap-water and in different salt concentrations. The salinity tolerance limit (lethal salt concentration) of this leech was found to be 1.54% NaCl which equilibrates approximately 51.359% sea-water. There was a significant weight loss in P. viridis when kept in both, hypo- and hypertonic media. It is concluded that volume regulation (through weight changes) was slight in hypotonic media whereas in hypertonic media there was an incessant decline in body weight. Adaptive significance of these findings is discussed.     

Effects of some extrinsic factors on the respiratory metabolism of the freshwater leech,poecilobdella viridis (blanchard): desiccation and temperature

The influence of desiccation and temperature on the respiratory metabolism of P. viridis have been investigated. There was a significant (p < 0.05) downfall in the respiratory rates as the period of desiccation increased, but for after 18 hours where it was enhanced significantly. The respiration augmented significantly (p < 0.03) when the temperature of the medium increased. Q₁₀ was significantly high at 32–28°C and was low between 35 and 32°C and 20–10°C Functional significance of these changes to the leeches in combating environmental hazards is briefly discussed.     

Effect of pH on the interfacial tension of bilayer lipid membrane formed from phosphatidylcholine or phosphatidylserine

The effect of pH of an electrolyte solution on the interfacial tension of lipid membrane formed from phosphatidylcholine (PC) or phosphatidylserine (PS) was studied. The relationships were well described by an equation presented earlier based on the Gibbs isotherm but only in the proximity of the isoelectric point. Therefore, in this work models have been derived to describe the adsorption of the H⁺ and OH⁻ ions at lipid surfaces formed from PC or PS, which would reproduce changes in interfacial tension more correctly, particularly in the ranges distant from the isoelectric point. In one model, the surface is continuous with uniformly distributed functional groups constituting the centres of H⁺ and OH⁻ ion adsorption while in the other the surface is built of lipid molecules, free or with attached H⁺ and OH⁻ ions. In both models, the contributions of the individual lipid molecule forms to the interfacial tension of the bilayer were assumed to be additive.     

盐分胁迫对啤酒大麦幼苗生长、离子平衡和根际pH变化的影响

盐分胁迫不仅影响植物的生长,而且会影响植物根际微域环境。根际pH的改变对土壤养分的有效性和微生物群落组成的变化有重要影响。为了探究啤酒大麦幼苗对不同类型盐分胁迫的生理生态响应机制和根际pH变化影响的生理机制,采用水培法,通过不同类型盐分(对照、混合Na盐、混合Cl盐和NaCl)胁迫处理啤酒大麦幼苗,对其生长、离子平衡和根际pH变化进行了研究。结果表明,1)在3种不同类型盐分胁迫下,啤酒大麦幼苗地上部干重、含水量均有所降低,而根冠比增加,尤其在NaCl胁迫下啤酒大麦幼苗地上部干重较对照显著降低了17.88%,而根干重和根冠比则分别增加了19.12%和43.86%。不同类型盐分胁迫抑制了啤酒大麦幼苗根长的生长,尤其在混合Na盐胁迫下根长降低明显(P0.05),但促进了根表面积和根体积的增加,尤其在混合Cl盐胁迫下,根表面积和根体积分别增加了41.76%和84.38%。2)不同类型盐分胁迫下啤酒大麦幼苗地上部离子平衡发生改变,在混合Na盐和NaCl胁迫下啤酒大麦幼苗主要吸收Na~+,地上部K~+/Na~+、Ca~(2+)/Na~+和Mg~(2+)/Na~+显著降低;混合Cl盐和NaCl胁迫下则过量吸收Cl~-,抑制了H_2PO_4~-、NO_3~-和SO_4~(2-)的吸收。3)在混合Na盐、混合Cl盐和NaCl盐分胁迫下,啤酒大麦幼苗对阴离子的吸收总量高于对阳离子的吸收总量,离子平衡计算结果表明根际呈碱化现象,与原位显色结果一致,且在混合Cl盐胁迫下根际碱化程度最大。     

Effect of ATP concentration and pH on rigor tension development and dissociation of rigor complex in glycerinated rabbit psoas muscle fiber

Isometric rigor tension development of glycerinated rabbit psoas muscle fibers in a medium, due to the formation of rigor complexes, was estimated at varying ATP concentrations from 0 to 2.5 mM and pH values from 6.75 to 8.20. The dissociation of rigor complexes was also estimated under the same conditions. When muscle fibers developed rigor tension from the relaxed and rigor states, the magnitude of rigor tension increased with increasing concentration of ATP. Transition between rigor and relaxation in single fibers occurred discontinuously at constant levels (critical levels) of ATP which were determined by pH. The critical concentrations of ATP necessary for inducing the transitions between rigor and relaxed states were also increased exponentially with increased pH. Incomplete repetition of tension development by the same fiber was also observed. This incomplete reversibility was divided into two types: one which showed a decay in rigor tension and another which showed no decay. The reason for the incomplete reversibility was discussed.     

Effect of substrate concentration,inorganic nitrogen,O2 concentration,temperature and pH on dehydrogenase activity in soil

Summary Dehydrogenase activity was measured in a sandy loam soil under a variety of incubation conditions using the reduction of 2-(p-iodophenyl-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT) to iodonitrotetrazolium formazan (INT-formazan). There was a high positive correlation between dehydrogenase activity and substrate concentration, incubation temperature, and soil pH. Dehydrogenase activity also displayed a high negative correlation with O₂ concentrations. Ammonium sulfate at concentrations from 40 to 120 g/g soil had no significant effect on dehydrogenase activity. However, at concentrations of 160 and 200 g/g, dehydrogenase activity was significantly reduced. Potassium nitrate at concentrations ranging from 40 to 200 g/g had no significant effect on soil dehydrogenase activity, whereas sodium nitrite significantly inhibited activity at concentrations of 120 and 160 g/g soil.     

Effect of NaCl and KCl on fate and growth/no growth interfaces of Listeria monocytogenes Scott A at different pH and nisin concentrations

AIMS: The fate of Listeria monocytogenes Scott A, was studied in broth, at different a(w)s (by adding NaCl or KCl from 0.0 to 1.4 mol l(-1)), pHs (from 4.0 to 7.3 by adding lactic acid), and nisin concentrations (from 0 to 100 IU ml(-1)). METHODS AND RESULTS: Increasing salt and nisin concentrations and decreasing pH resulted in lower growth rates and extended lag phases. At pH 4.5 no growth was observed while in presence of nisin and/or 1 mol l(-1) salts of both kinds, L. monocytogenes Scott A was inactivated. Equal-molar concentrations of NaCl or KCl (similar a(w)), exerted similar effects against L. monocytogenes in terms of lag phase duration, growth or death rate. The growth boundaries of L. monocytogenes Scott A at 5 degrees C were also estimated by growth/no growth turbidity data, modeled by logistic polynomial regression. The concordance of logistic models, were 99.6 and 99.8% for NaCl and KCl, respectively. CONCLUSIONS: The growth interfaces derived by both NaCl and KCl models were almost identical. Hence, NaCl can be replaced by KCl without risking the microbiological safety of the product. Increasing nisin concentrations markedly affected the interface resulting in a more inhibitory environment for L. monocytogenes Scott A. Low to medium salt concentrations (0.3-0.7 mol l(-1) of either NaCl or KCl) provided a protective effect against inhibition of L. monocytogenes Scott A by nisin. SIGNIFICANCE AND IMPACT OF THE STUDY: Modelling the growth boundaries not only contributes to the development of safer food by providing useful data, but can also be used to study interactions between factors affecting initiation of growth of pathogenic micro-organisms.     

外源一氧化氮供体硝普钠浸种对盐胁迫下小麦幼苗碳氮代谢及抗氧化系统的影响

预先用0.1mmol/L的SNP(硝普钠,NO供体)浸种,研究NO预处理对120mmol/L NaCl胁迫下两小麦品种(扬麦12和淮麦17)幼苗叶片抗氧化系统、碳氮代谢及蛋白酶活性的影响。结果表明,NO预处理能有效地抑制NaCl胁迫下小麦幼苗叶片超氧阴离子释放(O.2-)和过氧化氢(H2O2)积累,提高超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性,降低丙二醛(MDA)含量,提高叶绿素、类胡萝卜素和可溶性总糖含量。另外,NO预处理显著提高叶片可溶性蛋白质含量,以及内肽酶和羧肽酶活性。分析表明,NO有利于维持盐胁迫下小麦碳氮代谢正常运转,从而促进植株生长,提高小麦幼苗株高、鲜重和干重。试验条件下,NO对淮麦17的促进作用大于扬麦12。     

Osmoregulation in Dunaliella tertiolecta: effects of salt stress,and the external pH on the internal pH

The intracellular pH of the halotolerant green algae Dunaliella tertiolecta, was determined by the distribution of 5,5-dimethyl-2(¹⁴C)-oxalolidine-2,5-dione (DMO) between the cell and the surrounding medium. 5,5-dimethyl-2(¹⁴C)oxalolidine-2,4-dione was not metabolized by the algal cells. The intracellular pH of Dunaliella tertiolecta was 6.8 in the dark and 7.4 in the light. During a salt stress, after two hours, the intracellular pH was increased by 0.2 pH units in both light and dark. The salt stressed cells maintained a constant pH of about 7.5 over the pH range of 6.5 to 8.5. Because of the relatively low permeability coefficient of the plasma membrane for DMO, this technique does not permit rapid pH determinations during the induction period after a salt stress. The magnitude of the salt induced pH changes measured 2 h after the salt stress implies a minor importance of this alkalization in this time range, but does not exclude a larger importance of pH changes for osmoregulation during the induction period.Abbreviations Chl chlorophyll - DMO 5,5-dimethyl-2(¹⁴C)oxalolidine-2,4-dione - PCV packed cell volume - SDS sodium dodecyl sulfate     

盐胁迫对4树种叶片中K^＋和Na^＋的影响及其耐盐能力的评价

通过盆栽试验,对我国南方银杏（Ginkgo biloba L.)、侧柏[Patycladus orentalis(L.)Franco]、火炬松（Pinus taeda L.)和剌槐(Robinia Pseudoacacia L.)4造林树种苗木叶片中K^ 、N^ 浓度浓度和N^ ／K^ 比进行测定,盐处理水平为0.0％（CK）、0.1%、0.3%和0.5％。随着盐浓度的提高,各树种叶片中Na^ 浓度和N^ ／K^ 有逐渐升高的趋势,但K^ 浓度变化较小;随着盐胁迫时间的推移,各树种叶片中Na^ 、K^ 浓度和Na^ /K^ 比都没有明显的变化规律。方差分析和多层比较表明,侧柏、火炬松和剌槐叶片中Na^ 、K^ 浓度和N^ ／K^ 比在4组处理间的差异均达显著或极显著水平。4树种中剌槐和侧柏的耐盐能力最强,银杏次之,火炬松最弱。     

Characterization of hybridoma cell responses to elevated pCO(2) and osmolality: intracellular pH, cell size, apoptosis, and metabolism.

CO(2) partial pressure (pCO(2)) in industrial cell culture reactors may reach 150-200 mm Hg, which can significantly inhibit cell growth and recombinant protein production. The inhibitory effects of elevated pCO(2) at constant pH are due to a combination of the increases in pCO(2) and [HCO(-) (3)], per se, and the associated increase in osmolality. To decouple the effects of pCO(2) and osmolality, low-salt basal media have been used to compensate for this associated increase in osmolality. Under control conditions (40 mm Hg-320 mOsm/kg), hybridoma cell growth and metabolism was similar in DMEM:F12 with 2% fetal bovine serum and serum-free HB GRO. In both media, pCO(2) and osmolality made dose-dependent contributions to the inhibition of hybridoma cell growth and synergized to more extensively inhibit growth when combined. Elevated osmolality was associated with increased apoptosis. In contrast, elevated pCO(2) did not increase apoptotic cell death. Specific antibody production also increased with osmolality although not with pCO(2). In an effort to understand the mechanisms through which elevated pCO(2) and osmolality affect hybridoma cells, glucose metabolism, glutamine metabolism, intracellular pH (pHi), and cell size were monitored in batch cultures. Elevated pCO(2) (with or without osmolality compensation) inhibited glycolysis in a dose-dependent fashion in both media. Osmolality had little effect on glycolysis. On the other hand, elevated pCO(2) alone had no effect on glutamine metabolism, whereas elevated osmolality increased glutamine uptake. Hybridoma mean pHi was approximately 0.2 pH units lower than control at 140 mm Hg pCO(2) (with or without osmolality compensation) but further increases in pCO(2) did not further decrease pHi. Osmolality had little effect on pHi. Cell size was smaller than control at elevated pCO(2) at 320 mOsm/kg, and greater than control in hyperosmotic conditions at 40 mm Hg.     

Dependence of the intracellular concentrations of univalent ions and hydrogenase activity on the salt composition and pH of the medium in the haloalkaliphilic sulfate-reducing bacterium <Emphasis Type="Italic">Desulfonatronum thiodismutans</Emphasis>

It has been shown that the intracellular concentrations of Na⁺, K⁺, and Cl^? ions in Desulfonatronum thiodismutans depend on the extracellular concentration of Na⁺ ions. An increase in the extracellular concentration of Na⁺ results in the accumulation of K⁺ ions in cells, which points to the possibility that these ions perform an osmoprotective function. When the concentration of the NaCl added to the medium was increased to 4%, the concentration gradient of Cl^? ions changed insignificantly. It was found that D. thiodismutans contains two forms of hydrogenase—periplasmic and cytoplasmic. Both enzymes are capable of functioning in solutions with high ionic force; however they exhibit different sensitivities to Na⁺, K⁺, and Li⁺ salts and pH. The enzymes were found to be resistant to high concentrations of Na⁺ and K⁺ chlorides and Na⁺ bicarbonate. The cytoplasmic hydrogenase differed significantly from the periplasmic one in having much higher salt tolerance and lower pH optimum. The activity of these enzymes depended on the nature of both the cationic and anionic components of the salts. For instance, the inhibitory effect of NaCl was less pronounced than that of LiCl, whereas Na⁺ and Li⁺ sulfates inhibited the activity of both hydrogenase types to an equal degree. The highest activity of these enzymes was observed at low Na⁺ concentrations, close to those typical of cells growing at optimal salt concentrations.     

Effect of acute pH depression on the survival of the freshwater amphipod Hyalella azteca at variable temperatures: field and laboratory studies

Field observations on temperature and pH of a small pond showed that a amphipod population of Hyalella azteca was exposed to variable seasonal pH between 5.10–5.85, and water temperatures between 2–21 °C. Laboratory experiments were designed to simulate seasonal temperatures and field pHs of a small pond habitat. Laboratory bioassay experiments were conducted to determine the survival of Hyalella azteca at pHs 4, 5, 6 and 7, and varying temperatures of 5°, 10°, 15°, 20° and 25 °C.The LT₁₀₀ at pH 4 and 25 °C was 5.7 ± 0.47 days, compared to 47.3 ± 2.49 days at 5 °C. An Analysis of Variance (ANOVA) showed temperature was a significant (p > 0.0001) source of variation in the acute lethality of pH to H. azteca. A Duncans Multiple Range Test (DMRT) further showed that in laboratory experiments at pH 4, there was a significant difference ( = 0.01) between the LT_100s at 5°, 10°, 15° and 20 °C, but not between temperatures 20° and 25 °C.     

温度、pH及CO2对白藜芦醇与过氧亚硝基相互作用的影响

白藜芦醇(Resveratrol,Res)是植物在遇到紫外线照射、真菌感染等不利条件下自然产生的抗毒素,存在于多种植物中,具有明显的消炎、抗癌、抗血栓等作用。本文利用紫外-可见光谱法研究了Res与过氧亚硝基阴离子(Peroxynitrite anion,ONOO-)的相互作用,提出了反应机理。研究了温度、pH及CO2对Res与ONOO-反应的影响,结果表明低温、偏碱性pH有利于反应的进行;CO2存在时Res仍能与ONOO-反应,但反应机理与前面不同。     

Effect of changes in the pH and carbon dioxide evolution rate on the measured respiratory quotient of fermentations

The total concentration of dissolved carbon dioxide in fermentation broths is one to two orders of magnitude greater than that of oxygen for pH > 6.5. The rate of change in this total concentration can be sufficiently large to produce a discrepancy between the carbon dioxide transfer rate (CTR) across the gas-liquid interface, available from gas analyses, and the carbon dioxide evolution rate (CER) of biomass in the fermentor. The CER is the variable of most interest to fermentation technologists but cannot be measured directly. The CTR is commonly used to yield the measured respiratory quotient (called here the TQ, or transfer quotient). Evaluation of the real underlying respiratory quotient (RQ), however, requiures the unmeasureable CER. Equations defining the problem are presented and are found to accurately predict the discrepancy between the TQ and the RQ in fed-batch fermentations of Escherichia coli. During the exponential growth phase, the TQ is less than the RQ. A changing pH can cause the TQ to be bigger or smaller than the RQ, while pH fluctuations associated with on-off pH controller action make the CTR and hence the TQ noisy. The RQ is estimated on-line during an E. coli fermentation and is shown to be constant during the fermentation, even though the TQ varies greatly. (c) 1992 John Wiley & Sons, Inc.     

乳酸菌胆盐水解酶和共轭脂肪酸产生及对宿主脂代谢影响的研究进展

乳酸菌是一类影响宿主脂代谢的人体肠道益生菌。乳酸菌对脂代谢的影响作用与其产生胆盐水解酶(bile salt hydrolase,EC3.5.1.24,BSH)及共轭转化多不饱和脂肪酸(polyunsaturated fatty acids,PUFAs)关系密切。菌株差异、菌群分布和饮食差异是影响BSH及共轭脂肪酸产生的重要因素。本文重点阐述了两类物质对宿主脂代谢的影响机制,以期为后续研究提供借鉴。BSH能够降解肝脏分泌的胆汁酸(bile acids,BAs),降低脂类物质的吸收。BAs的降解产物胆汁酸脱氧胆酸(deoxycholic acid,DCA)和石胆酸(lithocholic acid,LCA)能够通过机体信号通路法尼类X受体(farnesoid X receptor,FXR)、小异二聚体伴侣(small heterodimer partner,SHP)及肝脏X受体(liver X receptor,LXR)等信号通路进行调控,促进胆固醇转运及向BAs转化。此外,BSH还能够通过下调固醇调节元件结合蛋白1c (sterol regulatory element binding protein 1c,SREBP-1c)、上调5ʹ-腺苷单磷酸激活蛋白激酶α(5ʹ-AMP activated protein kinase,AMPKα)和过氧化物酶体增殖物激活受体α (peroxisome proliferator-activated receptor α,PPARα)抑制脂质合成,促进脂质的分解。PUFAs可被乳酸菌转化产生共轭脂肪酸,如共轭亚油酸(conjugated linoleic acid,CLA)和共轭亚麻酸(conjugated linolenic acid,CLNA),CLA/CLNA能够促进机体产生瘦素(leptin,LP),抑制食欲、促进能量消耗;CLA/CLNA还可以通过激活PPARα进行调控,促进人体脂质的氧化分解。乳酸菌通过以上多种途径共同作用调节宿主的脂代谢,对深入理解乳酸菌调控脂代谢机制及临床应用有着重要意义。     

Effects of pH, salt, and macromolecular crowding on the stability of FK506-binding protein: an integrated experimental and theoretical study

Environmental variables can exert significant influences on the folding stability of a protein, and elucidating these influences provides insight on the determinants of protein stability. Here, experimental data on the stability of FKBP12 are reported for the effects of three environmental variables: pH, salt, and macromolecular crowding. In the pH range of 5-9, contribution to the pH dependence of the unfolding free energy from residual charge-charge interactions in the unfolded state was found to be negligible. The negligible contribution was attributed to the lack of sequentially nearest neighboring charged residues around groups that titrate in the pH range. KCl lowered the stability of FKBP12 and the E31Q/D32N double mutant at small salt concentrations but raised stability after approximately 0.5 M salt. Such a turnover behavior was accounted for by the balance of two opposing types of protein-salt interactions: the Debye-Hückel type, modeling the response of the ions to protein charges, favors the unfolded state while the Kirkwood type, accounting for the disadvantage of the ions moving toward the low-dielectric protein cavity from the bulk solvent, disfavors the unfolded state. Ficoll 70 as a crowding agent was found to have a modest effect on protein stability, in qualitative agreement with a simple model suggesting that the folded and unfolded states are nearly equally adversely affected by macromolecular crowding. For any environmental variable, it is the balance of its effects on the folded and unfolded states that determines the outcome on the folding stability.     

Interaction of carbon nanotubes with curcumin: Effect of temperature and pH on simultaneous static and dynamic fluorescence quenching of curcumin using carbon nanotubes

Curcumin (Cur) has medicinal properties, undergoes hydrolysis, and has low water solubility that limits its bioavailability and industrial usage. Different host molecules such as carbon nanotubes (CNT) can be useful in improving solubility and stabilizing Cur, therefore understanding the interaction of Cur with host molecules such as CNT is crucial. In this study, UV–visible light absorption and fluorescence spectroscopic techniques have been applied to reveal the interaction of Cur with CNT. Visible light absorption of Cur increases with CNT concentration, whereas fluorescence intensity of Cur is quenched in the presence of CNT. The obtained results confirm that fluorescence reduction is due to both static and dynamic quenching and is a result of the ground state and excited‐state complex formation. The pH environment influences the quenching rate due to deprotonation of Cur at higher pH; excess OH‐ ion concentration in the solution further discourages electrostatic interaction between the deprotonated form of Cur with CNT. It is found that at lower temperatures (<35°C) dynamic quenching is much more dominant and at higher temperatures (45°C) static quenching is more dominant. The interaction is further supported using X‐ray diffraction patterns and Fourier transform infrared spectra in the solid state, and suggests encapsulation of curcumin within the CNT. It is further evident that fluorescence quenching of Cur using CNT is further enhanced in the presence of several salts, as increase in ionic strength of the solution pushes the hydrophobic Cur molecule towards the CNT core by increasing the proximity between them.     

环境因子对沟金针虫呼吸代谢的影响

为了探讨沟金针虫Pleonomus canaliculatus对不同环境条件的适应性, 应用多通道昆虫呼吸仪测定了不同温度、O₂浓度、光照强度和湿度条件下沟金针虫的呼吸率。结果显示: 沟金针虫的呼吸模式为不规则波动型。温度和光照强度对沟金针虫的CO₂释放率影响突出, 不同处理间差异显著; 不同温度条件下, CO₂释放率最小和最大值分别为5℃时的7.22 μL/h和35℃时的180.74 μL/h, 两者间存在极显著差异（P<0.01）; 强光条件下的沟金针虫呼吸代谢强度大约是无光条件下的2倍（P<0.05）。不同的O₂浓度和空气相对湿度对沟金针虫的CO₂释放率无明显影响。同时确定了沟金针虫呼吸速率对温度的敏感性——Q₁₀值。结果表明沟金针虫在呼吸代谢过程中对温度和光照反应敏感, 对低氧和湿度环境的适应性较强。