Activities Of Protective Enzymes Research Articles

The Effect of Different Concentrations of Salicylic Acid on Protective Enzyme Activities of Pepper (Capsicum annuum L.) Plants

The objective of this study was to investigate the effects of different concentration (0, 0.1, 0.7, 1.5, 3, 6 and 9 mM) of SA on antioxidant enzymes in Capsicum annuum L. plants. Enzyme activities of peroxidase, polyphenol oxidase, ascorbate peroxidase, catalase and glutathione reductase were measured. The plants were grown in pots vermiculite. Before applying the salicylic acid treatments, plants filled with were irrigated with based nutrient solution (Hoagland solution) for 5 weeks. After 5 weeks, plants were sprayed with different concentrations (0, 0.1, 1.5, 3, 6 and 9 mM) of salicylic acid. Data were analyzed using SPSS software and means were compared by Duncan test. In each experiment 4 replicats were used. Concentrations of 1.5, 3, 6 and 9 mM of SA caused significant increase in polyphenol oxidase and peroxidase enzyme activities in treated leaves. Concentrations of 0.7, 1.5 ad 3 mM of SA decreased in (catalase, ascorbate peroxidase and glutathione reductase) activities, but concentrations of 6 and 9 Mm of SA increased enzyme activities. Different concentrations of salicylic acid had different effects on enzyme activities in Capsicum annuum L.

Effects of herbivore stress by Aphis medicaginis Koch on the Malondialdehyde contents and the activities of protective enzymes in different alfalfa varieties

The study focused on the dynamics of Malondialdehyde (MDA) contents and the activities of protective enzymes in the leaves of alfalfa varieties with various resistances to Aphis medicaginis Koch. The results showed that susceptible varieties always had higher MDA contents than resistant varieties, and the MDA contents tended to rise in both susceptible and resistant varieties in period of the varieties were pierced and sucked by aphids. Superoxide dismutase (SOD), peroxidase (POD) and phenylalanine ammonia-lyase (PAL) activities in susceptible varieties were lower than those in resistant varieties, and in both susceptible and resistant varieties the SOD and POD activities tended to rise at first and then decline, and the PAL activities rose to their peaks and then tended to remain stable. In the susceptible and resistant varieties the catalase (CAT) activities appeared to rise and decline alternatively; the PPO activities in resistant varieties were lower than those in susceptible varieties in early growth, but higher than those in susceptible varieties in later growth. It follows that infested by aphids, susceptible and resistant varieties had the MDA contents, variations of SOD, POD, PAL and PPO activities were closely correlated with their aphid resistances, hence these indexes could be used as physiological indexes for testing aphid resistance of alfalfa, whereas the relations of their CAT activities to their resistances needed to be further studied.

The role of antioxidant system in freezing acclimation-induced freezing resistance of Populus suaveolens cuttings

We investigated the changes in the contents of H2O2, malonaldehyde (MDA) and endogenous antioxidants, the activities of protective enzymes and some critical enzymes involved in the ascorbate-glutathione (ASA-GSH) cycle as well as freezing resistance (expressed as LT50) and correlations mentioned above, in detail using Populus suaveolens cuttings. The purpose was to explore the physiological mechanism of the enhancement of freezing resistance induced by freezing acclimation at −20°C, and to elucidate the physiological mechanisms by which trees adapt to freezing. The results showed that freezing acclimation enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), monodehydroascorbate reductase (MDAR), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR). And it increased the contents of reduced ascorbate (ASA), reduced glutathione (GSH), dehydroascorbate (DHA) and oxidized glutathione (GSSG). However, H2O2 and MDA contents and LT50 of cuttings were decreased. LT50 in cuttings was found to be closely correlated to the levels of SOD, POD, CAT, APX, DHAR, MDAR, GR, H2O2, MDA, ASA, GSH, DHA and GSSG during freezing acclimation. This suggested that the enhancement of freezing resistance of cuttings induced by freezing acclimation may relate to the distinct increase for the levels of SOD, POD, CAT, APX, DHAR, MDAR, GR, ASA, GSH, DHA, and GSSG. In addition, the observed levels of APX, DHAR, MDAR, GR, ASA, DHA, GSH and GSSG were higher than those of SOD, POD and CAT during freezing acclimation. It indicated that a higher capacity of the ASA-GSH cycle is required for H2O2 detoxification, and growth and development of cuttings. Based on the obtained results, it can be concluded that the ASA-GSH cycle plays an important role in enhancement of freezing resistance of P. suaveolens cuttings during freezing acclimation.

Active oxygen metabolism in the floral buds and leaves of the new cytoplasm male sterile (CMS) line and its maintainer line of non-heading Chinese cabbage

The cytoplasm male sterile (CMS) line and its maintainer line of the newly-bred non-heading Chinese cabbage were taken as experimental materials. The production rate of superoxide anion radical (O2 −), contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) as well as ascorbate peroxidase (APX) were determined in buds of different developmental stages and leaves during vegetative and florescence stages. As showed by the results, there were higher levels of MDA and H2O2 contents, higher O2 − production rate and higher activities of SOD, POD, and CAT in the buds of the CMS lines than that in the buds of the fertile lines, while the APX activity was different from the other three enzymes above. There were differences in activities of protective enzymes in leaves but no significant differences in MDA contents and O2 − production rate, which showed that the differences in metabolism of active oxygen between CMS and its maintainer were mainly apparent in reproductive organs.

Electron Pathways through Erythrocyte Plasma Membrane in Human Physiology and Pathology: Potential Redox Biomarker?

Erythrocytes are involved in the transport of oxygen and carbon dioxide in the body. Since pH is the influential factor in the Bohr-Haldane effect, pHi is actively maintained via secondary active transports Na+/H+exchange and HC3–/Cl–anion exchanger. Because of the redox properties of the iron, hemoglobin generates reactive oxygen species and thus, the human erythrocyte is constantly exposed to oxidative damage. Although the adult erythrocyte lacks protein synthesis and cannot restore damaged proteins, it is equipped with high activity of protective enzymes. Redox changes in the cell initiate various signalling pathways. Plasma membrane oxido-reductases (PMORs) are trans-membrane electron transport systems that have been found in the membranes of all cells and have been extensively characterized in the human erythrocyte. Erythrocyte PMORs transfer reducing equivalents from intracellular reductants to extracellular oxidants, thus their most important role seems to be to enable the cell respond to changes in intra- and extra-cellular redox environments.So far the activity of erythrocyte PMORs in disease states has not been systematically investigated. This review summarizes present knowledge on erythrocyte electron transfer activity in humans (health, type 1 diabetes, diabetic nephropathy, and chronic uremia) and hypothesizes an integrated model of the functional organization of erythrocyte plasma membrane where electron pathways work in parallel with transport metabolons to maintain redox homeostasis.

Effect of ice nucleation-active bacteria on the physiology and ultrastructure of apricot floral organs

SummaryThe effects of the ice nucleation-active (INA) bacterium Pseudomonas syringae were studied on the physiological response and ultrastructure of the floral organs of ‘Longwangmao’ apricot (Prunus armeniaca Linn.). Inoculation with INA bacteria increased the super-cooling point (SCP) of petals, stamens, and pistils by 2.1ºC, 1.6ºC, and 1.4ºC respectively. INA bacteria also enhanced the relative electrolyte leakage (REL) of membranes in the floral organs, indicating that INA bacteria increased the permeability of membranes. INA bacteria enabled apricot floral organs to maintain relatively lower superoxide dismutase (SOD) and peroxidase (POD) activities, and led to an accumulation of malonyldialdehyde (MDA) under cold stress. The ultrastructures of pollen walls, organelles in the pollen cell, ovules and egg cells in control flowers which were subjected to –3ºC changed slightly, compared with the structures at 18ºC. However, under cold stress at –3ºC, inoculation with INA bacteria resulted in disintegrated floral organs, such as a disrupted and extruded pollen exine, and even destroyed organelles in pollen cells. Plasmolysis and the formation of small vesicles and cavities in nucellar cells occurred in INA bacteria-inoculated ovules. INA bacteria also induced swelling and the eventual disappearance of the nuclear envelope of the egg cell in the ovule. These results, the decreased activities of protective enzymes, the increased SCP, REL, and MDA contents, and the disintegrated ultrastructures of floral organs inoculated with INA bacteria under cold stress, suggest that INA bacteria decreased the tolerance of floral organs to frost and aggravated the level of damage.

Effects of(NH_4)_(2)SO_(4) on chilling tolerance in guar seedlings under different lighting conditions

Guar seedlings were grown in greenhouse,and effects of leaf spray(NH_4)_2SO_4 on changes of superoxide dismutase(SOD),peroxidase(POD) activities and malondialdehyde(MDA) content in leaves and death rate of seedlings were studied in different photon flux densities(PDF) after chilling 12 hours at 2±0.5℃.The results showed,SOD and POD activities were lower,MDA content was higher,and death rate of seedlings was higher in the treatment recovered under normal sunlight in greenhouse than those of the control.When the seedlings wre recovered under 90mu-mol·m~(-2)·s~(-1) weak light for 2--4 days, SOD and POD activities were higher than those of the control, MDA content kept at a low level, and seedlings were survived normally. Application of (NH_4)_(2)SO_(4) increased protective enzyme activities, reduced MDA content in leaves during recovery time after chilling 12 hours, improved seedling resistance to low temperature, and significantly decreased the death rate of guar seedlings. The effect is the best for seedlings sprayed with 0.2% (NH_4)_(2)SO_(4), followed by 0.4% (NH_4)_(2)SO_(4). If weak light is given to seedlings after a short-term chilling, active oxygen species would be reduced and chilling injury could be alleviated or even eliminated.

Effects of Water Stress on the Protective Enzyme Activities and Lipid Peroxidation in Roots and Leaves of Summer Maize

A systematic study was conducted to determine the effects of water stress on the activities of protective enzymes and lipid peroxidation in maize. The results showed that, under water stress, the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in leaves and roots increased sharply at prophase and metaphase growth stages, such as, male tetrad stage, but then declined towards the physiological maturity. The protective enzyme activities in roots were lower than those in leaves. The content of malondialdehyde (MDA) increased according to the severity of water stress. The content of MDA in roots was lower than that in leaves. The activities of protective enzymes and lipid peroxidation in roots were positively related to that in leaves with most of the correlation coefficients being significant. The content of soluble proteins in roots and leaves decreased with increasing drought stress. The ear characteristics deteriorated and the economic yields of maize decreased significantly under water stress. The main factors that caused reduction of yields were the decrease in the number of ear kernels and 100-kernel weight.

Leaf development and photosynthetic properties of three tropical tree species with delayed greening

Leaf developmental patterns were characterized for three tropical tree species with delayed greening. Changes in the pigment contents, photosynthetic capacity, stomata development, photosystem 2 efficiency, rate of energy dissipation, and the activity of partial protective enzymes were followed in developing leaves in an attempt to elucidate the relative importance of various photoprotective mechanisms during leaf ontogeny. Big leaves of Anthocephalus chinensis, a fast-growing light demanding species, expanded following an exponential pattern, while relatively small leaves of two shade-tolerant species Litsea pierrei and Litsea dilleniifolia followed a sigmoidal pattern. The juvenile leaves of A. chinensis and L. pierrei contained anthocyanin located below the upper epidermis, while L. dilleniifolia did not contain anthocyanin. Leaves of A. chinensis required about 12 d for full leaf expansion (FLE) and photosynthetic development was delayed 4 d, while L. pierrei and L. dilleniifolia required 18 or 25 d for FLE and photosynthetic development was delayed 10 or 15 d, respectively. During the leaf development the increase in maximum net photosynthetic rate was significantly related to changes in stomatal conductance and the leaf maturation period was positively related to the steady-state leaf dry mass per area for the three studied species. Dark respiration rate of leaves at developing stages was greater, and pre-dawn initial photochemical efficiency was lower than that of mature leaves. Young leaves displayed greater energy dissipation than mature leaves, but nevertheless, the diurnal photoinhibition of young L. dilleniifolia leaves was higher than that of mature leaves. The young red leaves of A. chinensis and L. pierrei with high anthocyanin contents and similar diurnal photoinhibition contained more protective enzymes (superoxide dismutase, ascorbate peroxidase) than mature leaves. Consequently, red leaves may have higher antioxidant ability.

Biochemical Genetics of Short‐Season Cotton Cultivars that Express Early Maturity Without Senescence

Abstract: The present study is aimed to investigate the mechanism of the biochemical genetic in short‐seasoned cotton (Gossypium hirsutum L.) (SSC). Ten cultivars from two types of SSC were selected, five SSC with no premature senescence crossed with five SSC with premature senescence. The parents, F1, and F2 from the reciprocal crosses were field tested in replication in 2001 and 2002. The results indicated that the activities of protective enzymes of the antioxidant system, such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), were higher in the early maturing SSC with premature senescence compared with activities in the SSC parental cultivars that showed premature senescence, whereas the malondialdehyde (MD A) content in former group was lower than that in latter group. Various genetic variances and heritabilities for these biochemical traits and auxin (IAA), abscisic acid (ABA), and chlorophyll (Chl a+b) contents were also estimated. Significant additive variance for CAT, POD, ABA, and IAA existed, whereas CAT specific activity and SOD activity were largely controlled by dominant effects. Both maternal and dominant variances played equally predominant roles in the specific activity of POD and SOD, MDA, and soluble portents. The relative contribution of the various genetic components to the phenotypic variation varied in the boll‐setting period.(Managing editor: Li‐Hui ZHAO)

Effects of temperature on oxidative stress defense systems, lipid peroxidation and lipoxygenase activity in Phalaenopsis

Higher plants growing in natural environments experience various abiotic stresses. The aim of this study was to determine whether exposure to temperature-stress would lead to oxidative stress and whether this effect varied with different exposure periods. The thermal dependencies of the activities of protective enzymes, photosynthetic efficiency (Fv/Fm), protein, non-protein thiol (NP-SH), cysteine content, lipoxygenase (LOX) activity (EC 1.13.11.12) and malondialdehyde (MDA) content at 25–40 °C were determined for 4, 24 and 48 h in leaf and root segments of Phalaenopsis. The increase in MDA level and LOX activity may be due to temperature-associated oxidative damage to leaf and root segments. Temperature-stress induced not only activities of active oxygen species (AOS) scavenging enzymes but also protein, NP-SH and cysteine content in both leaf and root segments at 30 °C for 4 and 24 h (except for 48 h in some cases) compared to 25 °C—and greenhouse-grown leaf and root segments indicating that antioxidants enzymes played an important role in protecting plant from temperature-stress. However, activities of dehydroascorbate reductase (DHAR, EC 1.8.5.1), glutathione peroxidase (GPX, EC 1.11.1.9) and glutathione- S-transferase (GST, EC 2.5.1.18) in leaf and root, glutathione reductase (GR, EC 1.6.4.2) in leaf and guaiacol peroxidase (G-POD, 1.11.1.7) in root segments were induced significantly at 40 °C compared to 25 °C and greenhouse-grown plants suggesting that these enzymes play protective roles at high temperature. In contrast, activities of superoxide dismutase (SOD, EC 1.15.1.1) and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) in leaf and root, catalase (CAT, EC 1.11.1.6) in root, GR in root, and protein, cysteine, NP-SH content in both root and leaf and Fv/Fm ratio were diminished significantly at 40 °C compared to 25 °C—and greenhouse-grown plants. These indicate that these enzymes were apparently not involved in detoxification process and sensitive at higher temperature. Also, the close relation between activities of enzymes with their metabolites at 30 °C than 40 °C indicated that the antioxidants enzymes and metabolites both may play an important role in protecting cells against the temperature-stress.

Potential Role of Flavonoids in the Prevention of Intestinal Neoplasia: A Review of Their Mode of Action and Their Clinical Perspectives

Intestinal neoplasia (adenomas and carcinomas) can possibly be prevented by a diet rich in vegetables and fruits, treatment with aspirin and other nonsteroidal antiinflammatory drugs, and early colonoscopic removal of adenomas. Ballast, fiber, and secondary plant products could play a major role in colon cancer prevention. Recently there has been much experimental work in vitro and in vivo about flavonoids as inducers of bioprevention. Flavonoids are secondary plant products with a wide variety of beneficial biological properties, and they possess anticarcinogenic, antimutagenic, and antioxidative modes of actions. Flavonoids are the main components of a healthy diet containing fruits and vegetables and are concentrated especially in tea, apples, and onions. We will focus this review on flavonoids which are derived from tea products such as proanthocyanidins (green tea) and flavons (camomille tea). Oral supplementation with bioflavonoids derived from tea could be used in humans to prevent growth of intestinal neoplasia such as adenomatous polyps of the colon. Flavonoids are a large group of natural compounds of which only a few have been used in animal models, cell cultures, and enzyme studies to inhibit mutagenic and carcinogenic events. Their clinical mode of action was evaluated by epidemiological studies, but no intervention studies in humans have been performed so far. In vitro flavonoids can bind electrophils, inactivate oxygen radicals, prevent lipid peroxidation, and inhibit DNA oxidation. In cell cultures they increase the rate of apoptosis, inhibit cell proliferation, and angiogenesis. In vivo they can induce the activities of protective enzymes (conjugating enzymes such as glutathione transferases and glucuronosyl transferases) of the intestine and the liver. In models of intestinal polyposis, flavonoids suppress polyp formation. Some epidemiological studies show a protective effect of flavonoids contained in fruits, vegetables, and tea. Flavonoid mixtures of tea origin supplied as nutritional supplements could be studied as a new way of bioprevention of intestinal neoplasia (colon adenomas and cancer). Therefore, a controlled, randomized clinical study should be performed to evaluate the efficacy of flavonoids.

Study of the tolerance ofHippochaete ramosissimum to Cu stress

We investigated the tolerance of Hippochaete ramosissimum and the changes in physiological metabolism following exposure to copper using pot experiments and analyzing plant physiology and biochemistry. The results showed that Cu tolerance in Hippochaete ramosissimum varied significantly between different populations; the tolerance of plants living in Cu polluted areas for extended periods of time exceeded that of plants living in unpolluted areas. SOD and POD activities in highly Cu tolerant plants increased noticeably following exposure to Cu. This indicates that maintaining and increasing the two kinds of protective enzyme activities are the primary foundations of plant tolerance. However, no change in CAT activity was demonstrated following Cu exposure. In summary, there existed considerable differences in physiological metabolism between different populationsof Hippochaete ramosissimum following exposure to Cu.

Osmophobic Effect of Glycerol on Irreversible Thermal Denaturation of Rabbit Creatine Kinase

Protein stability plays an extremely important role not only in its biological function but also in medical science and protein engineering. Osmolytes provide a general method to protect proteins from the unfolding and aggregation induced by extreme environmental stress. In this study, the effect of glycerol on protection of the model enzyme creatine kinase (CK) against heat stress was investigated by a combination of spectroscopic method and thermodynamic analysis. Glycerol could prevent CK from thermal inactivation and aggregation in a concentration-dependent manner. The spectroscopic measurements suggested that the protective effect of glycerol was a result of enhancing the structural stability of native CK. A further thermodynamic analysis using the activated-complex theory suggested that the effect of glycerol on preventing CK against aggregation was consistent with those previously established mechanisms in reversible systems. The osmophobic effect of glycerol, which preferentially raised the free energy of the activated complex, shifted the equilibrium between the native state and the activated complex in favor of the native state. A comparison of the inactivation rate and the denaturation rate suggested that the protection of enzyme activity by glycerol should be attributed to the enhancement of the structural stability of the whole protein rather than the flexible active site.

Inhibition by tributyltin of herring skeletal muscle lactate dehydrogenase activity

The activity of herring ( Clupea harengus) skeletal muscle lactate dehydrogenase (EC 1.1.1.27) LDH-A 4 isoenzyme was examined in the presence of tributyltin chloride (TBT). This paper reports the in vitro inhibition of LDH activity with increasing concentration of TBT. Bovine serum albumin (BSA) added to the LDH-A 4 isoenzyme prior to the addition of TBT was able to protect enzyme activity against inhibition by this toxicant. The observed protection of LDH-A 4 activity increased with increasing BSA concentration in the incubation medium. The results suggest that the presence of BSA could protect LDH activity from direct binding of TBT to LDH.

Does zinc produce reactive oxygen species in Ruditapes decussatus?

Zinc is an essential trace element with many enzymatic functions that include antioxidant properties. To investigate whether an excess of Zn in the cells produces cytotoxicity or tissue damage or an imbalance in the antioxidant systems, marine clams ( Ruditapes decussatus) were exposed to two sublethal Zn concentrations (100 and 1000 μg L −1) for 28 days. The effects of Zn on the activities of protective antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase, both total and selenium-dependent), lipid peroxidation, and metallothionein induction were followed in the gills and digestive gland of these clams. The results indicate that the effect of Zn exposure in this clam species depends not only on the tissue but also on the Zn concentration present. In the gills, catalase activity was enhanced by Zn exposure, whereas total glutathione peroxidase activity was inhibited. Lipid peroxidation occurred only in the clams exposed to the highest Zn concentration. In the digestive gland, the impact of Zn exposure on metabolic activity was less evident than in the gills. The most evident effect in both tissues was the enhancement of catalase activity by Zn exposure. Catalase and total glutathione peroxidase activities as well as lipid peroxidation are promising biomarkers to assess the effects of Zn in the gills of R. decussatus.

Oxidative inactivation of purified plasma membrane Ca2+-ATPase by hydrogen peroxide and protection by calmodulin.

Calmodulin (CaM)-regulated plasma membrane Ca(2+)-ATPase (PMCA) is critical for the regulation of free intracellular Ca(2+) levels. PMCA activity and levels in neuronal membranes are decreased with aging, possibly due to oxidation-induced inactivation. In the present studies, inhibition of PMCA by H(2)O(2) was characterized in enzyme purified from human erythrocyte membranes. Basal and CaM-stimulated PMCA activities were inhibited by exposure to H(2)O(2) (25-100 microM). However, neither the concentration-dependent enhancement of PMCA activity by CaM nor the binding of CaM to H(2)O(2)-exposed PMCA was disrupted by treatment with H(2)O(2). Rates of inactivation by H(2)O(2) of basal and CaM-stimulated PMCA were nearly identical. The addition of CaM after exposure to H(2)O(2) did not protect enzyme activity, although the binding of CaM to PMCA before exposure to H(2)O(2) protected the enzyme completely, indicating a CaM-induced conformational state resistant to oxidation. H(2)O(2) quenched Trp fluorescence in PMCA, an index of conformational changes, with a rate similar to that observed for enzyme inactivation. H(2)O(2) enhanced the solvent accessibility of Trp residues in PMCA, whereas accessibility of the only Trp residue in the CaM-binding domain peptide was unaltered. Exposure of PMCA to H(2)O(2) led to aggregate formation partially reversible by dithiothreitol (DTT) but not to recovery of activity. Amino acid analysis indicated Cys modification following H(2)O(2) exposure but no Cys oxyacids. Because DTT did not reverse inactivation by H(2)O(2), it appears that the disulfide bond formation led to conformational changes that were not fully reversed when the bonds were reduced. Preincubation of PMCA with CaM protected the enzyme from undergoing this conformational change.

Melatonin stimulates the activity of protective antioxidative enzymes in myocardial cells of rats in the course of doxorubicin intoxication.

The study aimed at determining the effect of melatonin on the activity of protective antioxidative enzymes in the heart and of lipid peroxidation products in the course of intoxication with doxorubicin (DOX). The rats were categorized into four groups, receiving: 0.9% NaCl i.p. (NaCl control); melatonin [20 mg/kg body weight (b.w.)] s.c. (control Mel); DOX (2.5 mg/kg b.w.) i.p.; melatonin plus DOX in doses as above. All the substances were administered once in a week for four consecutive weeks. Homogenates of heart tissue were examined for activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), levels of reduced glutathione (GSH) and of lipid peroxidation indices (MDA + 4-HDA). Administration of melatonin alone did not induce alterations in levels of MDA + 4-HDA, GSH, or in activity of GPx, SOD or CAT, as compared to the group receiving 0.9% NaCl. GSH levels decreased following DOX but remained at normal levels following DOX and melatonin. The level of MDA + 4-HDA increased following DOX, as compared with the control, a change prevented by the combination of DOX + melatonin. Activities of GPx, SOD and CAT were higher in groups receiving DOX and/or DOX plus melatonin than in control groups. Activity of CAT and the level of GSH in the group receiving DOX plus melatonin were significantly higher than in the group intoxicated with DOX alone. The obtained results demonstrate that, when given in parallel with DOX, melatonin protects cardiomyocytes from damaging effects of the cytostatic drug (reflected by the levels of MDA + 4-HDA). The protective effect resulted, in part from the augmented levels of GSH and from stimulation of CAT activity by melatonin in cardiomyocytes subjected to the action of DOX.

Salicylic acid changes activities of H 2O 2-metabolizing enzymes and increases the chilling tolerance of banana seedlings

Pretreatment in the chilling-sensitive banana seedlings by spraying 0.5 mM salicylic acid (SA) hydroponic solution onto leaves and irrigating to roots at 30/22 °C for 1 day induced an increase of chilling tolerance during subsequent 5 °C chilling stress. Pretreatment of 0.5 mM SA treatment at 30/22 °C for 1 day did not result in a remarkable change in superoxide dismutases (SOD) activity, but reduced catalases (CAT) and ascorbate peroxidase (APX) activities, and increased peroxidases (POX) activity. During a 5 °C chilling stress period, however, SA pretreatment caused an activation of SOD, CAT and APX activities, while it did not change POX activity. Different effects of SA on protective enzyme activities could be associated with hydrogen peroxide (H 2O 2) metabolism. Measurement of H 2O 2 levels and staining with diaminobenzidine (DAB) indicated that SA pretreatment at 30/22 °C resulted in H 2O 2 accumulation; however, during subsequent 5 °C chilling stress, SA pretreatment reduced H 2O 2 overproduction. The results suggested that H 2O 2 metabolism could participate in enhanced chilling tolerance of SA in banana plants.

Effects of sound stimulation on protective enzyme activities and peroxidase isoenzymes of chrysanthemum

One of the important fields in cell biology is physical stimulus on the growth of plant cells and organs. The effects of strong sound wave on thermodynamic properties, cell cycles and calcium ion signaling transduction of plants have been studied. In this work, chrysanthemum seedlings are treated by sound wave with a certain intensity (100 db) and frequency (1000 Hz) for 3, 6, 9, 12 and 15 days, respectively, and each day for 60 min. The research results show that the activities of protective enzymes and the peroxidase isoenzymes increase at varying degrees. Compared with the control group, there is no new enzyme band in POD electrophoretogram for experimental groups. Our experimental data imply that better promotion for chrysanthemum is obtained under sound wave for 9 days.