模拟酸雨对番木瓜不同成熟度叶片膜脂过氧化作用的影响

用不同pH值(4．5、3．5、3．0、2．5)的模拟酸雨处理,研究其对番木瓜不同成熟度叶片细胞膜透性和膜 脂脂防酸组分变化的影响。结果表明,酸雨处理导致番木瓜叶片细胞膜透性、MDA含量、脂氧合酶(LOX)活 性和K+、Ca2+、Mg2+渗出量显著上升,膜脂肪酸组分中饱和脂肪酸含量增加,不饱和脂肪酸含量及不饱和指 数(IUFA)下降,嫩叶比成熟叶对酸雨的反应更敏感。运用生理指标差异达0．05显著水平评价酸雨对番木瓜 的影响阈值,嫩叶在pH3．5,成熟叶在pH3．0。     

Microwave bioeffects in the erythrocyte are temperature and pO2 dependent: Cation permeability and protein shedding occur at the membrane phase transition

Microwave exposure (2450 MHz, 60 mW/g, CW) of rabbit erythrocytes increases Na passive transport only at membrane phase transition temperatures (T_c) of 17–19°C. This permeability effect is enhanced for relative hypoxia which is characteristic of intracellular oxygen tension (pO₂ ? 5 mm Hg). Neither the permeability nor the pO₂ effects are observed in temperature-matched (± 0.05°C), sham-exposed controls. In addition, at T_c, microwave exposure is observed to induce the shedding or release of two erythrocyte proteins not seen in sham-exposed controls. Moreover, the enhanced shedding of at least seven other proteins all of molecular weight ? 28,000 D was detected in the microwave-treated samples. Using sensitive silver staining we estimate that approximately 450 fg of protein were shed per erythrocyte. These results demonstrate that temperature and pO₂ are important influences on both functional and structural responses of cell membranes to microwave radiation.     

The effects of La(III) on the peroxidation of membrane lipids in wheat seedling leaves under osmotic stress

The physiological effects of the rare earth ion La³⁺ on the peroxidation of membrane lipids in wheat (Triticum aestivum L.) seedling leaves under osmotic stress were determined. With the passage of time under osmotic stress, the inhibition ability of lanthanum ions to the relative membrane permeability and concentration of malondialdehyde, Superoxide radicals, and hydrogen peroxide caused by osmotic stress increased substantially, but no changes were noted in ferrous and relative water content. It indicated that lanthanum ions could not retain the water content because of osmotic stress. However, La³⁺ appears to decrease the production of OH by reducing the content of O₂ and H₂O₂ of Haber-Weiss and Fenton reactions, which efficiently alleviated peroxidation of membrane lipids under osmotic stress and, to some degree, protected the membrane from injury of free radicals. Thus, La³⁺ increased the tolerance ability of plant to osmotic stress, which could assure the function of membrane normal temporally after stressed.     

Fe and Fe initiated peroxidation of sonicated and non-sonicated liposomes made of retinal lipids in different aqueous media

Retina is highly susceptible to oxidative damage due to its high content of polyunsaturated fatty acids (PUFAs), mainly docosahexaenoic acid (22:6 n3). Lipid peroxidation process is thought to be involved in many physiological and pathological events. Many model membranes can be used to learn more about issues that cannot be studied in biological membranes. Sonicated liposomes (SL) and non-sonicated liposomes (NSL) prepared with lipids isolated from bovine retina and characterized by dynamic light-scattering, were submitted to lipid peroxidation, under air atmosphere at 22 °C, with Fe²⁺ or Fe³⁺ as initiator, in different aqueous media. Conjugated dienes and trienes, determined by absorption at 234 and 270 nm respectively, and thiobarbituric acid-reactive substances were measured as a function of time. Peroxidation of SL or NSL initiated with 25 μM FeSO₄ in 20 mM Tris-HCl pH 7.4 resulted in an increase in TBARS production after a lag phase of 60 min. Incubation of both types of liposomes in water resulted in shortening of the lag phase at 30 min. When lipid peroxidation was performed in 0.15 M NaCl, lag phase completely disappeared. On the other hand, FeCl₃ (25 μM) induced a limited production of TBARS only just after 30 min of incubation. When Fe²⁺- or Fe³⁺-lipid peroxidation of both types of liposomes was carried out in water or 0.15 M NaCl, formation of conjugated dienes and conjugated trienes were higher than in reactions carried out in 20 mM Tris-HCl pH 7.4.Our results established that both liposome types were susceptible to Fe²⁺- and Fe³⁺-initiated lipid peroxidation. However, Fe²⁺ showed a clearly enhanced effect on peroxidation rate and steady state concentration of oxidation products.We verified that peroxidation of liposomes made of retinal lipids is affected not only by type of initiator but also by aqueous media. This model constitutes a useful system to study formation of lipid peroxidation intermediaries and products in an aqueous environment.     

Direct linkage of thrombin to its cell surface receptors in different cell types

When ¹²⁵I-thrombin was incubated with foreskin fibroblasts, cervical carcinoma cells or fibrosarcoma cells of human origin, or with secondary chick embryo cells or Chinese hamster lung cells, it became directly linked to its cell surface receptors. The thrombin-receptor complex (TH-R) was derived exclusively from a pool of ¹²⁵I-thrombin that had become specifically bound to the cell surface. The linkage was probably covalent, since the complex was resistant to boiling in sodium dodecyl sulfate and 2-mercaptoethanol. Raising the pH to 12 disrupted TH-R, but did not affect a similar complex between epidermal growth factor and its receptor, suggesting that the linkage of these mitogens to their receptors was different. Mild trypsin treatment removed the ability of cells to form TH-R; however, after a 24-h incubation in serum-free medium, trypsin-treated cells recovered the capacity to form TH-R, suggesting that TH-R resulted from interaction of ¹²⁵I-thrombin with a cellular rather than a serum component. The mitogenic response of cells to thrombin was inversely related to the fraction of specifically bound ¹²⁵I-thrombin represented by TH-R. The role of TH-R in mitogenesis may be clarified in future studies by obtaining clones of Chinese hamster lung cells that vary in their capacities to form TH-R and to respond to the mitogenic action of thrombin.     

Influence of lipids on ice formation in cryoprotective media

Cryomicroscopic analysis demonstrated that two lipid preparations from marine vertebrates (<0.1%) and liposomes prepared from rainbow trout sperm lipids (<0.5%) efficiently hindered the growth of ice crystals during freezing of multicomponent cryoprotective media used for trout sperm cryopreservation. At higher lipid concentrations, crystals either did not form at all or had altered shape and blurred boundaries. Addition of egg yolk (10%) together with these lipids increased the size of crystal structures and markedly changed their shape.     

Effects of phytic acid on the myoglobin-t-butylhydroperoxide-catalysed oxidation of uric acid and peroxidation of erythrocyte membrane lipids

Phytic acid stimulated the myoglobin-t-butylhydroperoxide (TBHP)-catalysed oxidation of uric acid, but inhibited the peroxidation of erythrocyte membrane lipids induced by the same system. Butylated hydroxy-toluene, a free radical chain reaction-terminating antioxidant, also suppressed the myoglobin-TBHP-induced lipid peroxidation. Moreover, phytic acid inhibited the hydroxyl radical-induced degradation of deoxyribose, but the extent of inhibition in this system was reduced by increasing the ferric ion concentration, suggesting that these effects of phytic acid on the myoglobin-TBHP-mediated oxidation are more likely attributable to its metal chelating properties rather than to a free radical scavenging action. The effectiveness of phytic acid, a naturally occurring antioxidant, in the inhibition of both iron- (as previously shown) and myoglobin-dependent lipid peroxidation suggests its possible therapeutic application as a non-toxic antioxidant for ameliorating the extent of oxy-radical-mediated myocardial ischemia/reperfusion damage.Abbreviations ASC Ascorbic acid - BHT Butylated Hydroxytoluene - DMSO Dimethyl Sulfoxide - TBHP t-Butylhydroperoxide - TBA Thiobarbituric Acid - TBARS Thiobarbituric Acid-reactive Substances     

Seasonal adaptations and the role of lipids in oceanic zooplankton

Oceanic zooplankton species exhibit quite diverse life history traits. A major driving force determining their life strategies is the seasonal variability in food supply, which is most pronounced in polar oceans where fluctuations in primary production are extreme. Seasonal adaptations are closely related to the trophic level of zooplankters, with strongest pressures occurring on herbivorous organisms. The dominant grazers, calanoid copepods and krill (Euphausiacea), have developed fascinating solutions for successful overwintering at higher latitudes. They usually exhibit a very efficient storage and utilization of energy reserves to reduce the effect of a highly seasonal primary production. The predominant larger Calanus species from the Arctic and Calanoides acutus from the Antarctic biosynthesize large amounts of high-energy wax esters with long-chain monounsaturated fatty acids and alcohols (20:1 and 22:1 isomers) as major components. They survive the dark season at depth in a stage of dormancy called diapause. In contrast, the Antarctic Calanus propinquus, a winter-active species, synthesizes primarily triacylglycerols, which are dominated by long-chain monounsaturated fatty acids with 22 carbon atoms (2 isomers) and yield even higher calorific contents. The omnivorous and carnivorous species, which are less subjected to seasonal food shortage, usually do not exhibit such an elaborate lipid biosynthesis. Herbivores usually do not utilize much of their enormous lipid reserves for overwintering, but channel this energy towards reproductive processes in late winter/early spring. Timing of reproduction is critical especially at high latitudes due to the short production period, and lipid reserves ensure early spawning independent of external resources. These energetic adaptations (dormancy, lipid storage) are supplemented by other life strategies such as extensive vertical migrations, change in the mode of life, and trophic flexibility.     

The influence of antioxidants in the thiyl radical induced lipid peroxidation and geometrical isomerization in micelles of linoleic acid

Abstract

The biomimetic model of micelles of linoleic acid containing 2-mercaptoethanol and the antioxidant was examined under gamma irradiation up to 400?Gy in aerobic or deoxygenated conditions where thiyl radicals are the main reactive species. Lipid peroxidation was retarded by ascorbic acid and α-tocopherol, whereas this process was strongly inhibited by resveratrol as effectively as the ascorbic acid/α-tocopherol mixture. Furthermore, antioxidants have a much stronger inhibitory effect on the peroxidation in the presence of 2-mercaptoethanol, and at the same time show protective properties of the double bond, decreasing the cis–trans isomerization. Under anaerobic conditions, cis–trans isomerization occurred and antioxidants efficiency increased along the series: resveratrol < α-tocopherol?<?ascorbic acid. This result is explained taking into account the double bond localization in the hydrophobic core of the micelle and the need of co-localization of the antioxidant in order to get an anti-isomerizing activity and protection of the natural lipid geometry.     

Influence of N-phthaloyl gamma-aminobutyric acid on circadian rhythms of lipid peroxidation products and antioxidants

N-Phthaloyl GABA was administrated daily (50 mg/kg body weight-i.p) to Wistar rats for 21 days and circadian rhythms of thiobarbituric acid reactive substances (TBARS) and antioxidants such as reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) were studied. N-Phthaloyl GABA was found to delay TBARS and to advance GSH, CAT and SOD acrophases. Amplitude and mesor values of these rhythms were found to be altered during N-Phthaloyl GABA treatment. Since GABA is hypothesized to be involved in conveying dark information to clock, exogenous administration of P-GABA might alter the photic information received by the clock. Our study shows that P-GABA administration alters the temporal patterns of lipid peroxidation and antioxidants in Wistar rats. But the exact mechanism remains to be explored and further research is needed.     

Influence of salt concentration on membrane lipids of halophilic bacteria

Abstract A review of salt-dependent changes in membrane lipid composition of halotolerant, moderately halophilic, and extremely halophilic bacteria is presented. The biosynthetic and regulatory mechanisms underlying the observed changes are discussed. Possible implications for the evolution of extreme halophiles and other Archaebacteria are also discussed.     

Effects of continuous-wave, pulsed, and sinusoidal-amplitude-modulated microwaves on brain energy metabolism

A comparison of the effects of continuous-wave, sinusoidal-amplitude-modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague-Dawley rats (175-225 g). Brain NADH fluorescence, adenosine triphosphate (ATP) concentration, and creatine phosphate (CP) concentration were determined as a function of modulation frequency. Brain temperatures of animals were maintained between -0.1 and -0.4 degrees C from the preexposure temperature when subjected to as much as 20 mW/cm2 (average power) CW, pulsed, or sinusoidal-amplitude modulated 591-MHz radiation for 5 min. Sinusoidal-amplitude-modulated exposures at 16-24 Hz showed a trend toward preferential modulation frequency response in inducing an increase in brain NADH fluorescence. The pulse-modulated and sinusoidal-amplitude-modulated (16 Hz) microwaves were not significantly different from CW exposures in inducing increased brain NADH fluorescence and decreased ATP and CP concentrations. When the pulse-modulation frequency was decreased from 500 to 250 pulses per second the average incident power density threshold for inducing an increase in brain NADH fluorescence increased by a factor of 4--ie, from about 0.45 to about 1.85 mW/cm2. Since brain temperature did not increase, the microwave-induced increase in brain NADH and decrease in ATP and CP concentrations was not due to hyperthermia. This suggests a direct interaction mechanism and is consistent with the hypothesis of microwave inhibition of mitochondrial electron transport chain function of ATP production.     

The effects of hyperthermia and hyperthermia plus microwaves on rat brain energy metabolism

The effects of hyperthermia, alone and in conjunction with microwave exposure, on brain energetics were studied in anesthetized male Sprague-Dawley rats. The effect of temperature on adenosine triphosphate concentration [ATP] and creatine phosphate concentration [CP] was determined in the brains of rats that were maintained at 35.6, 37.0, 39.0, and 41.0 degrees C. At 37, 39, and 41 degrees C brain [ATP] and [CP] were down 6.0, 10.8, and 29.2%, and 19.6, 28.7, and 44%, respectively, from the 35.6 degrees C control concentrations. Exposure of the brain to 591-MHz radiation at 13.8 mW/cm2 for 0.5, 1.0, 3.0, and 5.0 min caused further decreases (below those observed for 30 degrees C hyperthermia only) of 16.0, 29.8, 22.5, and 12.3% in brain [ATP], and of 15.6, 25.1, 21.4, and 25.9% in brain [CP] after 0.5, 1.0, 3.0, and 5.0 min, respectively. Recording of brain reduced nicotinamide adenine dinucleotide (NADH) fluorescence before, during, and after microwave exposure showed an increase in NADH fluorescence during microwave exposure that returned to preexposure levels within 1 min postexposure. Continuous recording of brain temperatures during microwave exposures showed that brain temperature varied between -0.1 and +0.05 degrees C. Since the microwave exposures did not induce tissue hyperthermia, it is concluded that direct microwave interaction at the subcellular level is responsible for the observed decrease in [ATP] and [CP].     

Thermal action of 2.45 GHz microwaves on the cytoplasm of Chinese hamster cells

In order to demonstrate possible specific effects of microwaves at the cellular level V-79 Chinese hamster cells were exposed to 2.45-GHz radiation at power levels of 20–200 mW/cm² and at specific absorption rates of 10–100 mW/g. Intracellular cytoplasmic changes were observed by fluorescence polarization using a method based on the intracellular enzymatic hydrolysis of nonfluorescent fluorescein diacetate (FDA). At levels of absorbed energy below 90 J/g, modifications of microviscosity and mitochondrial state were absent, but a slight stimulation of enzymatic hydrolysis of FDA was observed which may be explained by microwave-induced alterations of cellular membranes possibly due to differences in heating pattern of microwaves compared to water-bath heating. At levels of absorbed energy above 90 J/g, the decrease of enzymatic hydrolysis of FDA, increase in degree of polarization, and increase of permeation of the fluorescent marker correlated well with the decrease in cell viability as measured by the exclusion of trypan blue. At equal absorbed energy, microwaves were found to exert effects comparable to classical heating except that permeation was slightly more affected by microwave than by classical heating. This suggests that membrane alteration produced by microwaves might differ from those induced by classical heating or that microwaves may have heated the membrane to higher temperatures than did classical heating.     

Effect of selenium on lipids, lipid peroxidation, and sulfhydryl group in neuroendocrine centers of rats

The effects of various doses of sodium selenite (0.05, 0.1, and 0.2 mg/kg body weight, ip) were studied on the content of phospholipids, cholesterol, esterified fatty acids (EFA), gangliosides, thiobarbituric acid reactive substance (TBARS), and sulfhydryl group in neuroendocrine centers of male Wistar rats for 7 d. The lowest dose of Se (0.05 mg/kg) did not alter the above parameters significantly in neuroendocrine centers. The content of phospholipids was depleted significantly in the pituitary and depletion in the pineal was 80.22% with a 0.1-mg/kg dose of Se, but this dose elevated its level significantly in the hypothalamus. Conversely, a 0.2-mg/kg dose of selenium elevated the level of phospholipids significantly in the pituitary and hypothalamus, the elevation in the pineal was 70%. Selenium, 0.1 mg/kg, elevated the level of cholesterol in the pituitary but depleted its level in the pineal (56.8%) and hypothalamus (13.60%). Selenium, 0.2 mg/kg, elevated the level of cholesterol significantly in the hypothalamus but its level was not significant in the pituitary and pineal. The depletion of esterified fatty acid in the pituitary and pineal with doses of 0.1 and 0.2 mg/kg was significant in the pituitary, whereas its depletion in the pineal was 85.4% and 69.26%, respectively. Selenium, 0.1 and 0.2 mg/kg, depleted the level of gangliosides significantly and dose dependently in the pituitary but has elevated its level significantly and dose dependently in the hypothalamus. Its depletion in the pineal was 87.1% and 67.8% with the 0.1- and 0.2-mg/kg dose of selenium, respectively. Selenium, 0.1 mg/kg, increased the content of TBARS significantly in neuroendocrine centers and its elevation in the pineal was 703.8%. Selenium, 0.2 mg/kg, elevated its level in the pituitary and it was 126.9% in the pineal, but this dose depleted its level significantly in the hypothalamus. The content of the sulfhydryl group with a 0.1-mg/kg dose of selenite was depleted significantly in neuroendocrine centers and it was 55.9% in the pineal. Selenium, 0.2 mg/kg, depleted the level of the sulfhydryl group more significantly in the pituitary and pineal, but its elevation in hypothalamus was significant.     

Comparative effects of pulsed and continuous-wave 2.8-GHz microwaves on temporally defined behavior

The effects of pulsed-(PW) and continuous-wave (CW) 2.8-GHz microwaves were compared on the performance of rodents maintained by a temporally defined schedule of positive reinforcement. The schedule involved food-pellet reinforcement of behavior according to a differential-reinforcement-of-low-rate (DRL) contingency. The rats were independently exposed to PW and to CW fields at power densities ranging from 1 to 15 mW/cm². Alterations of normal performance were more pronounced after a 30-minute exposure to the PW field than to the CW field. The rate of emission of appropriately timed responses declined after exposure to PW at 10 and 15 mW/cm², whereas exposure at the same power levels to the CW field did not consistently affect the rate of responding. Change in performance associated with microwave exposure was not necessarily related to a general decline in responding: in some instances, increases in overall rates of responding were observed.     

Protective role of ascorbic acid against lipid peroxidation and myocardial injury

Ascorbic acid (AH₂) is a potential scavenger of superoxide radical and singlet oxygen. In the guinea pig, marginal AH₂ deficiency results in intracellular oxidative damage in the cardiac tissue as evidenced by lipid peroxidation, formation of fluorescent pigment and loss of structural integrity of the microsomal membranes. The oxidative damage does not occur due to lack of enzymatic scavengers of reactive oxygen species such as superoxide dismutase, catalase and glutathione peroxidase. Also, glutathione transferase activity is not decreased in AH₂ deficiency. Lipid peroxidation, fluorescent pigment formation and protein modification disappear after AH₂ therapy. These results, if extra-polated to human beings, would indicate that chronic subclinical AH₂ deficiency may result in progressive oxidative damage which in the long run may lead to permanent degenerative diseases in the heart.     

Antioxidant status and lipid peroxidation in the blood of breast cancer patients of different ages

Oxidative stress is considered to be implicated in the pathophysiology of breast cancers. In this study we investigated the level of oxidative stress and antioxidant (AO) status in the blood of breast cancer patients of different ages. The level of lipid hydroperoxides (LP) was measured in blood plasma and the activities of copper, zinc superoxide dismutase (CuZnSOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) enzymes, as well as the level of total glutathione (GSH) and CuZnSOD protein were measured in blood cells of breast cancer patients and age-matched healthy subjects. Our results showed that breast carcinoma is related to increase of lipid peroxidation in plasma with concomitant decrease of AO defense capacity in blood cells, which becomes more pronounced during aging of the patients. Suppression of CuZnSOD activity related to breast cancer is most likely caused by decreased de novo synthesis of this enzyme. Similar patterns of suppression in CuZnSOD and CAT activities related to aging were recorded both in controls and patients. Age-related decrease in CuZnSOD activity seems not to be caused by altered protein levels of this enzyme. Suppression of AO enzymes associated with breast cancer and aging is most likely the cause of increased levels of reactive oxygen species (ROS). Our results indicate significant role of oxidative-induced injury in the breast carcinogenesis, particularly during the later stages of aging. Overall, our data support the importance of endogenous AOs in the etiology of breast cancer across all levels of predicted risk.