Cellular Membrane Stability Research Articles

Protecting the Myocardial Cell During Coronary Revascularization

Using the ischemic myocardial cell as a paradigm, competitive coronary revascularization technologies will be analyzed for their potential in causing additional myocardial cell damage during the course of therapeutic procedures. Percutaneous coronary intervention (PCI) using balloon and/or stent (bare metal or coated) approaches may be associated with myonecrosis related to atherosclerotic debris plugging the downstream coronary microcirculation as well as ischemia/reperfusion injury associated with revascularization of occluded coronary vessels. The placement of distal mechanical devices and filters during the course of PCI has not been successful in ameliorating this problem. Coronary revascularization using coronary artery bypass grafting (CABG) similarly may be associated with myocardial stunning and cell necrosis associated with ischemia/reperfusion injury. Surgically induced myocardial ischemia secondary to aortic cross clamping, results from the attenuation or cessation of coronary blood flow such that oxygen delivery to the myocardium is insufficient to meet basal myocardial requirements to preserve cellular membrane stability and viability. Recovery involves: (1) resumption of normal oxidative metabolism and the restoration of myocardial energy reserves; (2) reversal of ischemia induced cell swelling and loss of membrane ion gradients and the adenine nucleotide pool; (3) repair of damaged cell organelles such as the mitochondria and the sarcoplasmic reticulum. Despite meticulous adherence to presently known principles of surgical myocardial protection using advanced cardioplegic technologies, some patients require inotropic support and/or mechanical assist devices postoperatively, when none was required preoperatively. Which method of coronary revascularization causes the least amount of myocardial cell injury and is associated with superior long-term outcomes remains an area of increasing controversy.

Low Amounts of Sucrose Are Sufficient to Depress the Phase Transition Temperature of Dry Phosphatidylcholine, but Not for Lyoprotection of Liposomes

Disaccharides such as sucrose and trehalose play an important role in stabilizing cellular structures during dehydration. In fact, most organisms that are able to survive desiccation accumulate high concentrations of sugars in their cells. The mechanisms involved in the stabilization of cellular membranes in the dry state have been investigated using model membranes, such as phosphatidylcholine liposomes. It has been proposed that the lyoprotection of liposomes depends on the depression of the gel to liquid-crystalline phase transition temperature ( T m) of the dry membranes below ambient and on the prevention of membrane fusion by sugar glass formation, because both lead to leakage of soluble content from the liposomes. Since fusion is prevented at lower sugar/lipid mass ratios than leakage, it has been assumed that more sugar is needed to depress T m than to prevent fusion. Here, we show that this is not the case. In air-dried egg phosphatidylcholine liposomes, T m is depressed by >60°C at sucrose/lipid mass ratios 10-fold lower than those needed to depress fusion to below 20%. In fact, T m is significantly reduced at mass ratios where no bulk sugar glass phase is detectable by Fourier transform infrared spectroscopy or differential scanning calorimetry. A detailed analysis of the interactions of sucrose with the P O, C O, and choline groups of the lipid and a comparison to published data on water binding to phospholipids suggests that T m is reduced by sucrose through a “water replacement” mechanism. However, the sucrose/lipid mass ratios necessary to prevent leakage exceed those necessary to prevent both phase transitions and membrane fusion. We hypothesize that kinetic phenomena during dehydration and rehydration may be responsible for this discrepancy.

Introduction of the carrot HSP17.7 into potato (Solanum tuberosum L.) enhances cellular membrane stability and tuberization in vitro

We have examined the ability of a carrot (Daucus carota L.) heat shock protein gene encoding HSP17.7 (DcHSP17.7) to confer enhanced heat tolerance to potato (Solanum tuberosum L.), a cool-season crop. The DcHSP17.7 gene was fused to a 6XHistidine (His) tag to distinguish the engineered protein from endogenous potato proteins and was introduced into the potato cultivar 'Désirée' under the control of the cauliflower mosaic virus (CaMV) 35S promoter. Western analysis showed that engineered DcHSP17.7 was constitutively, but not abundantly, expressed in transgenic potato lines before heat stress. Leaves from multiple regenerated potato lines that contain the transgene exhibited significantly improved cellular membrane stability at high temperatures, compared with wild-type and vector control plants. Transgenic potato lines also exhibited enhanced tuberization in vitro: under a condition of constant heat stress, at 29 degrees C, nodal sections of the transgenic lines produced larger and heavier microtubers at higher rates, compared to the wild type and vector controls. The dry weight and percentages of microtubers that were longer than 5 mm were up to three times higher in the transgenic lines. Our results suggest that constitutive expression of carrot HSP17.7 can enhance thermotolerance in transgenic potato plants. To our knowledge, this is the first study that shows that the thermotolerance of potato can be enhanced through gene transfer.

Alleopathic voltage of salted leaves and salinity in growth and some physiological effects of wheat plants Triticum aestivum L

Experiment was conducted under glasshouse conditions to study the effect of soils containing either powder chard leaves a lone or in combination with NaCl on growth and some physiological effects'of two wheat cultivars (Veez and US 30), The results showed that the control treatment led to significant increase in plant growth concentrations of chlorophyll and carbohydrates, releative water content of leaves, cellular membrane stability as well as ionic composition improvement of the two cultivars in comparison with the plants grown in soil containing either 2% powder chard leave:; of 2% NaCl alone. However, soils containing combination of 2% powder chard leaves and 2% NaCl led to greater reduction in the plant growth and more decline in the concentrations of chlorophyll and carbohydrates, relative water content cellular membrane stability, Ca2+ and Mg2+ accumulation in the shoot and root system where there was a significant increase in and Cl" accumulation especialy in vee/ cultivar. الخلاصة

Differential destabilization of membranes by tryptophan and phenylalanine during freezing: the roles of lipid composition and membrane fusion

The stability of cellular membranes during dehydration can be strongly influenced by the partitioning of amphiphilic solutes from the aqueous phase into the membranes. The effects of partitioning on membrane stability depend in a complex manner on the structural properties of the amphiphiles and on membrane lipid composition. Here, we have investigated the effects of the amphiphilic aromatic amino acids Trp and Phe on membrane stability during freezing. Both amino acids were cryotoxic to isolated chloroplast thylakoid membranes and to large unilamellar liposomes, but Trp had a much stronger effect than Phe. In liposomes, both amino acids induced solute leakage and membrane fusion during freezing. The presence of the chloroplast galactolipids monogalactosyldiacylglycerol or digalactosyldiacylglycerol in egg phosphatidylcholine (EPC) membranes reduced leakage from liposomes during freezing in the presence of up to 5 mM Trp, as compared to membranes composed of pure EPC. The presence of the nonbilayer-forming lipid phosphatidylethanolamine increased leakage. Membrane fusion followed a similar trend, but was dramatically reduced when the anthracycline antibiotic daunomycin was incorporated into the membranes. Daunomycin has been shown to stabilize the bilayer phase of membranes in the presence of nonbilayer lipids and was therefore expected to reduce fusion. Surprisingly, this had only a small influence on leakage. Collectively, these data indicate that Trp and Phe induce solute leakage from liposomes during freezing by a mechanism that is largely independent of fusion events.

Effect of Lipid Composition on the Stability of Cellular Membranes during Freeze–Thawing of Lactobacillus acidophilus Grown at Different Temperatures

Lactobacillus acidophilus CRL 640 grown at the optimal temperature of 37°C (M37) appeared more sensitive to freeze-thawing than when it was grown at 25°C (M25). In the first case, 87% of the cells died, in contrast to 33% for cells grown at 25°C. All the surviving M37 cells showed sensitivity to NaCl. However, among the surviving M25 cells, only 85% were sensitive to NaCl. The rest of the cells were considered uninjured. Freeze-thawing in cells grown at 25°C showed a liberation of nucleic acids and proteins. However, the leakage was higher in M37 cells after freeze–thawing. The greater fraction of damaged cells were observed in M25 culture after freeze–thawing. A relative increase of 81% in cardiolipid (CL), with respect to total phospholipids and 72% triglycosyldiglyceride (TGDG) with respect to the total glycolipids was observed in M37. In addition, a decrease of palmitoyl (C16:0), oleoyl (C18:0) fatty acids at CL, phosphatidylglycerol (PG), and diglicosyldiglyceride (DGDG) fractions and the increase of C19 cyc and C18:0, 10-OH fatty acids in neutral lipid, and CL fractions was also apparent. In M25 cells, the concentration of DGDG and PG was higher than in M37 cells. The difference in cryotolerance between the frozen cultures emphasizes the importance of selecting appropriate conditions of growth of microorganisms for use as dietary adjuncts.

Photosystem II and cellular membrane stability evaluation in hexaploid wheat seedlings under salt stress conditions

Salinity limits crop production in large areas of the world. The application of in vitro Photosystem II (PS‐II) activity measurements to screen hexaploid wheat (Triticum aestivum, L.) genotypes for NaCl tolerance has been investigated by comparing their responses under stress and control (no added NaCl) conditions. One of the four cultivars used in the study was ‘Kharchia’ known for its high salt tolerance. Wheat seedlings were grown hydroponically in environmental chambers and treated with a range of NaCl concentrations (0.034 M, 0.17 M, 0.68 M, or 3.42 M) over a 1, 3, and 5‐day period. The salt treatments were started in the appropriate time so that they were all ten‐day‐old during harvest. Cellular membrane stability (CMS) as measured by a conductivity method and PS‐II activity values were affected adversely by NaCl concentration and duration of treatment. Both methods clearly distinguish between salt‐sensitive and salt‐tolerant genotypes. Statistical analysis showed that PS‐II activity and CMS measurements are well correlated (r=0.7589) suggesting that PS‐II activity would be used as an additional screening method besides CMS to evaluate salt tolerance of wheat.

The role of phospholipase D in signaling cascades

Phospholipases hydrolyze phospholipids, which are the backbones of biological membranes. The activities of these enzymes not only have a profound impact on the structure and stability of cellular membranes but also play a pivotal role in regulating many critical cellular functions. The activation of

Injection of vitamin A acid, vitamin E, and vitamin C for treatment of tissue necrosis.

Experimental studies concerning All-Trans Retinoic acid 0.1% with the antioxidant action of the Vitamin E (tocopherol acetate 0.20%) and Vitamin C (coated ascorbic acid 0.20%) efficacy in both the vascular neoformation induction and cellular membrane stabilization have been conducted by us to improve skin necrosis regression after routine plastic surgeries. Patients after rhytidectomy, breast reduction, and abdominoplasty with localized skin flap necrosis, were submitted to daily intradermic injections for a period of 15 days and had their skin healed by the effects of these vitamins.

Evaluation of field and laboratory predictors of drought and heat tolerance in winter cereals

In Mediterranean regions, plant breeding programs are being conducted to select genotypes having high and stable yields. Screening techniques that are able to identify desirable genotypes based on the evaluation of physiological traits related to stress tolerance could be useful, particularly if they are rapid, simple and inexpensive. The objectives of this study were: i) to evaluate the validity of four laboratory screening tests to discriminate among bread wheat (Triticum aestivum L.), durum wheat (Triticum turgidum L.) and barley (Hordeum vulgare L.) cultivars differing in adaptation to the Mediterranean climate; ii) to evaluate the repeatability of determinations performed on cultivars grown in different locations and years, and iii) to evaluate relationships among the tests and yield performance under stress. The tests were: cellular membrane stability after heat (CMS-HS) and drought stress (CMS-DS), tolerance to leaf water loss (LWL), and translocation capacity after the chemical desiccation (CD) of the photosynthetic apparatus. The CMS-HS and CMS-DS tests revealed genetic variability in all the three species. The LWL test did not differentiate genotypes at some sites. Genetic differences for grain yield, kernel weight and harvest index after chemical desiccation were evident for wheat genotypes but the test did not differentiate barley genotypes. The test performed under laboratory controlled conditions (CMS-HS, CMS-DS and LWL) was less affected by environment compared with the test based on the evaluation of the translocation capacity after chemical desiccation carried out in the field. We concluded that, when good standardization of procedures are obtained, the tests investigated can be regarded as possible tools in breeding programs for tolerance to heat and drought stress. Key words: Wheat, barley, drought screening

The concentration of cryoprotective lectins in mistletoe ( Viscum album L.) leaves is correlated with leaf frost hardiness

The leaves of mistletoe (Viscum album L.) contain three galactose- and N-acetylgalactosamine-specific isolectin groups (ML I, II, III). The groups ML I and ML III showed strong cryoprotective activity during freezing and thawing of isolated spinach (Spinacia oleracea L.) thylakoid membranes, while ML II showed no such activity. The cryoprotective efficiency of the proteins was correlated with their relative hydrophobicity, as determined by a fluorescence titration assay. We found that the frost hardiness of mistletoe leaves was seasonally regulated under natural conditions. While leaves harvested in winter were not damaged by freezing to −20 °C, leaves harvested in July had already suffered 70% electrolyte leakage after freezing to −5 °C. Likewise, the amount of ML I and ML III varied during the year, with the highest amounts of these cryoprotective lectins in winter and early spring and the lowest amounts during the summer months. There was no comparable change in the amount of ML II. These data suggest that some lectins may play a role in the stabilization of cellular membranes under environmental stress conditions.

Sporophytic and Gametophytic Components of Thermotolerance Affected by Pollen Selection

This study was undertaken to assess the effect of in vivo male gametophytic selection on components of thermotolerance in maize. The F1 between a tolerant (Pa33) and a susceptible (B37) genotype was used as pollen source. Male gametophytic selection was carried out by applying a two-h treatment of 50°C to immature tassels in the field. The resulting F2 and backcross generations were evaluated for sporophytic and gametophytic components of thermotolerance, including cellular membrane stability, heat shock protein synthesis, pollen germination, and tube growth rate. Both expression of heat shock proteins 102, 84, and 17 kDa and pollen germination ability under a high-temperature regime were significantly higher in the selected than in the nonselected progenies. No response to selection was detected for cellular membrane stability and pollen tube growth rate. These results suggest that pollen selection can serve to improve at least some gametophytic and sporophytic components of thermotolerance.

Acetyl-L-carnitine and Alzheimer's disease: pharmacological considerations beyond the cholinergic sphere.

Since ALCAR and L-carnitine are "shuttles" of long chain fatty acids between the cytosol and the mitochondria to undergo beta-oxidation, they play an essential role in energy production and in clearing toxic accumulations of fatty acids in the mitochondria. ALCAR has been considered of potential use in senile dementia of the Alzheimer type (SDAT) because of its ability to serve as a precursor for acetylcholine. However, pharmacological studies with ALCAR in animals have demonstrated its facility to maximize energy production and promote cellular membrane stability, particularly its ability to restore membranal changes that are age-related. Since recent investigations have implicated abnormal energy processing leading to cell death, and severity-dependent membrane disruption in the pathology of Alzheimer's disease, we speculate that the beneficial effects associated with ALCAR administration in Alzheimer patients are due not only to its cholinergic properties, but also to its ability to support physiological cellular functioning at the mitochondrial level. This hypothetical mechanism of action is discussed with respect to compelling supportive animal studies and recent observations of significant decrease of carnitine acetyltransferase (the catalyst of L-carnitine acylation to acetyl-L-carnitine) in autopsied Alzheimer brains.

Quantitative expression of maize HSPs: genetic dissection and association with thermotolerance

In higher plants, within-species qualitative polymorphism for heat shock proteins (HSPs) is extremely rare, even between genotypes showing different heritable levels of thermotolerance. Here we have explored the amount of quantitative variability in HSP synthesis in maize. We have analyzed the quantitative expression of the typical HSPs in a set of recombinant inbreds (RIs) derived from the f1 hybrid between a thermotolerant (T232)- and a thermosensitive (CM37)-genotype, characterized for about 200 mapped RFLP loci. Significant differences were detected in the level of expression of five HSPs, and their frequency distribution in the RI population is that of a quantitative trait. Subsequent mapping of loci controlling the characters, based on RFLP analysis, confirmed the multigenic control of HSP expression: the regression analysis of the band intensities of each variant HSP on RFLPs revealed, for the different HSPs, a minimum number of three to eight quantitative trait loci (QTLs) accounting for a high proportion (0.35-0.60) of the genetic variability of these bands. An analysis of the correlation between the variability of HSPs and that of cellular membrane stability, a cellular component of thermotolerance, did not reveal any significant association of the two parameters.

Alpha-Cyclodextrin Sulphate, an anti-HIV Agent, Retains its Antiviral Effect in the Presence of Hydrocortisol Phosphate

Cyclodextrin sulphates alpha (a) and beta (b) were found to be inhibitors of replication of human immunodeficiency virus (HIV-1) in phytohaemagglutinin (PHA)-stimulated human peripheral blood mononuclear cells (PBMC); the same cells were also stimulated to proliferate (Anand et al., 1990). B-Cyclodextrin sulphate was also found to stimulate another, more complex, cell proliferation-neovascularization process in rabbit cornea (Folkman et al., 1989). Since the process of neovascularization is generally associated with progression of tumour growth and other pathologies, it is obvious that its stimulation by an antiviral compound may be a serious side effect. Nevertheless endotoxin-induced neovascularization can be suppressed by simultaneous treatment with b-cyclodextrin sulphate and glucocorticoids (Folkman et al., 1989). The same co-treatment may possibly be used to improve antiviral action of cyclodextrin sulphates, but such a combination therapy may not be free of complications. Glucocorticoids also affect the stability of various cellular membranes. Treatment of cells in vitro by glucocorticoids is known to stabilize their lysozymes. Glucocorticoids affect both the proliferative capacity of the cells (Cristofalo, 1972) and cytopathic effects of rabies viral infection. Furthermore, it has been reported that the cytopathic effects of rabies and of yellow fever viruses were inhibited while those of the polio virus were only mildly affected (Hannoun et al., 1965). Consequently, in this work we evaluated effects of a glucocorticoid and of glucocorticoid-a-cyclodextrin sulphate combination on HIV-1 replication.

Effect of pH shifts induced by oxygenating crystalloid cardioplegic solutions

Oxygenation of a bicarbonate-containing crystalloid cardioplegic solution alters the partial pressure of both oxygen (O 2) and carbon dioxide (CO 2). Therefore, oxygenating St. Thomas' Hospital II plus glucose (11 mmol/L) cardioplegic solution with 95% O 2 + 5% CO 2 induces a pH shift to 7.0 (10 °C) as opposed to pH 9.3 with 100% O 2. In an isolated working rat heart model, we show that pH 7.0 (10 °C) improves mechanical postischemic recovery in the absence or presence of O 2. However, in the absence of O 2, pH 7.0 appears to inhibit glycolysis and diminish the stability of cellular membranes. The provision of O 2 independently improved mechanical recovery and at pH 7.0, improved the preservation of the sarcolemma. Increasing the O 2 content by including a perfluorocarbon (FC-43) in the oxygenated St. Thomas' plus glucose cardioplegia is not additionally beneficial. St. Thomas' Hospital plus glucose cardioplegic solution should be oxygenated, but with 95% O 2 + 5% CO 2 and not 100% O 2.

Molecular markers (RFLPs and HSPs) for the genetic dissection of thermotolerance in maize

Cellular membrane stability (CMS) is a physiological index widely used to evaluate thermostability in plants. The genetic basis of the character has been studied following two different approaches: restriction fragment length polymorphism (RFLP) analysis, and the effects of segregating heat shock protein (HSP) loci. RFLP analysis was based on a set of recombinant inbreds derived from the T32 × CM37 F1 hybrid and characterized for about 200 RFLP loci. Heritability of CMS estimated by standard quantitative analysis was 0.73. Regression analysis of CMS on RFLPs detected a minimum number of six quantitative trait loci (QTL) accounting for 53% of the genetic variability. The analysis of the matrices of correlation between RFLP loci, either within or between chromosomes, indicates that no false assignment was produced by this analysis. The effect of HSPs on the variability of the CMS was tested for a low-molecular-weight peptide (HSP-17) showing presence-absence of segregation in the B73 × Pa33 F2 population. Although the genetic variability of the character was very high (h (2)=0.58) the effect of HSP-17 was not significant, indicating either that the polypeptide is not involved in the determination of the character or that its effect is not statistically detectable.

The histidine-containing dipeptides, carnosine and anserine: Distribution, properties and biological significance

The biological significance of histidine-containing dipeptides discovered within the composition of nitrogenous extracts of skeletal muscles at the beginning of this century is still open to question. The present investigation is concerned with the analysis of distribution and metabolism of these compounds with special reference to their effects on functional activity of membrane-linked enzymatic systems, stability of cellular membranes, muscle contractability, etc. The proposed hypothesis on stabilizing properties of carnosine and related substances on biological membranes is based on the ability of the dipeptides to interact with lipid peroxidation products and active oxygen species and to prevent membrane damage. This remarkable antioxidative effect of carnosine reflects the high therapeutic value of this compound as an anti-inflammatory drug and a prominent tool in wound healing.

Breeding for heat and drought tolerance in bread wheat by means of field and laboratory screening procedures

SummaryAbout 200 varieties have been cultivated during the period 1985–1989 in quite different environmental conditions: in Italy near Milano in the Po Valley, in Sicily (Catania) and in two locations in Morocco. Optimal growing conditions, with supplementary irrigation when necessary, and both heat and drought stressing conditions have been created by either delaying the sowing date or drying up the green apparatus with chemical desiccants. Drought susceptibility indices (DSI) were therefore calculated.All the cultivars have been screened with the following laboratory tests: Cellular membrane stability in heat stress and drought stress conditions (CMShs and CMSds respectively), germination in osmotic solution (GOS), seedlings heat shock (SHS) and excised leaf water loss (LW).The relationships among the different evaluation indices for tolerance to stress conditions, their reliability and repeatability are discussed in relation to the possibility of application in plant breeding. It has been concluded tha...

Effect of L-carnitine and acetyl-L-carnitibe on the human erythrocyte membrane stability and deformability

In this study we examined the effect of carnitine and acetylcarnitine on the human erythrocyte membrane stability and membrane deformability. Since erythrocyte membranes are impermeable to these compounds, we resealed erythrocyte ghosts in the presence of different concentations of carnitine or acetylcarnitine. Resealed ghosts can be adequately studied in their cellular deformability and membrane stability properties by means of ektacytometry. Both carnitine and acetylcarnitine alter the membrane stability but not membrane deformability of the red cell membrane. Resealed ghosts containing 20, 50, 150, and 300 μM carnitine had 1.1, 1.6, 0.9, and 0.7 times the normal stability. While resealed ghosts containing 20, 50, 150, and 300 μM acetylcarnitine had 1.1, 1.5, 1.3, and 1.2 times the normal stability. Such changes were found to be reversible. We also conducted SDS PAGE of cytoskeletal membrane proteins from membrane fragments and residual membranes produced during membrane stability analysis, and unsheared resealed membranes in those samples where we observed an increase or a decrease of membrane stability. No changes in the cytoskeletal membrane proteins were noticed, even when the samples, prior SDS PAGE analysis, were treated with or without dithiothreitol. In addition, fluorescence steady state anisotrpy of DPH in the erythrocyte membrane treated with carnitine or acetylcarnitine shows no modification of the lipid order parameter. Our results would suggest that both carnitine and its acetyl-ester, at physiological concentrations, may increase membrane stability in mature erythrocytes, most likely via a specific interaction with one or more cytoskeletal proteins, and that this effect would manifest when the erythrocytes are subjected to high shear stress.