Separate and Combined Effects of Chlortetracycline and Oxytetracycline on Growth and Antioxidant Enzymes in Myriophyllum Aquaticum

As two typical tetracyclines, chlortetracycline (CTC) and oxytetracycline (OTC) coexist widely in water. In the experiment, Myriophyllum aquaticum (Vell.) Verdc was exposed to the orthogonal hydroponic environment with the concentrations of CTC and OTC at 1, 10, and 50 mg/L for 7 days (7 D) and 14 days (14 D). The results showed that the plant height, relative growth rates (RGR), and photosynthetic pigment contents of M. aquaticum decreased significantly after 14 D of CTC/ OTC, which was stronger than that after 7 D, and the toxicity of CTC was stronger than OTC. The combined toxicity of the two on the RGR and total chlorophyll content was mainly synergistic or additive after 7 D. After 14 D, the interaction changed to antagonism or addition, and the response of total chlorophyll content was more obvious than that of RGR. After 7 D of combined treatments, the malondialdehyde (MDA) content decreased significantly, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities responded to different combined concentrations, respectively, and CAT was the main protective enzyme of M. aquaticum. After 14 D of combined treatments, the hydrogen peroxide (H2O2) content increased significantly, the MDA content increased first and then decreased, and POD was the main protective enzyme among the three antioxidant enzymes. Overall, this study provided the first insight into the single and combined toxicity of CTC and OTC on the growth and physiology of M. aquaticum at different time periods, revealing the reversal of the combined toxicity with time of exposure.

The physiological response of different tobacco varieties to chilling stress during the vigorous growing period

Tobacco is be sensitively affected by chilling injury in the vigorous growth period, which can easily lead to tobacco leaf browning during flue-curing and quality loss, however, the physiological response of tobacco in the prosperous period under low temperature stress is unclear. The physiological response parameters of two tobacco varieties to low temperature stress were determined. The main results were as follows: ① For tobacco in the vigorous growing period subjected to low-temperature stress at 4–16 °C, the tissue structure of chloroplast changed and photosynthetic pigments significantly decreased compared with each control with the increase of intensity of low-temperature stress. ② For tobacco in the vigorous growing period at 10–16 °C, antioxidant capacity of the protective enzyme system, osmotic adjustment capacity of the osmotic adjusting system and polyphenol metabolism in plants gradually increased due to induction of low temperature with the increase of intensity of low-temperature stress. ③ Under low-temperature stress at 4 °C, the protective enzyme system, osmotic adjusting system and polyphenol metabolism of the plants played an insignificant role in stress tolerance, which cannot be constantly enhanced based on low-temperature resistance at 10 °C. This study confirmed that under the temperature stress of 10–16 °C, the self-regulation ability of tobacco will be enhanced with the deepening of low temperature stress, but there is a critical temperature between 4 and 10 °C. The self-regulation ability of plants under low temperature stress will be inhibited.

Erythropoietin Gene Therapy Delays Retinal Degeneration Resulting from Oxidative Stress in the Retinal Pigment Epithelium

Erythropoietin (EPO) plays an important role in erythropoiesis by its action in blocking apoptosis of progenitor cells and protects both photoreceptors and retinal ganglion cells from induced or inherited degeneration. A modified form of EPO, EPO-R76E has attenuated erythropoietic activity but is effective in inhibiting apoptosis, oxidative stress, and inflammation in several models of retinal degeneration. In this study, we used recombinant Adeno Associated Virus (AAV) to provide long-term sustained delivery of EPO-R76E and demonstrated its effects in a mouse model of dry-AMD in which retinal degeneration is induced by oxidative stress in the retinal pigment epithelial (RPE) cells. Experimental vector AAV-EPO-R76E and control vector AAV-GFP were packaged into serotype-1 (AAV1) to enable RPE selective expression. RPE oxidative stress-mediated retinal degeneration was induced by exon specific deletion of the protective enzyme MnSOD (encoded by Sod2) by cre/lox mechanism. Experimental mice received subretinal injection of AAV-EPO-R76E in the right eye and AAV-GFP in the left eye. Western blotting of RPE/choroid protein samples from AAV-EPO-R76E injected eyes showed RPE specific EPO expression. Retinal function was monitored by electroretinography (ERG). EPO-R76E over-expression in RPE delayed the retinal degeneration as measured by light microscopy in RPE specific Sod2 knockout mice. Delivery of EPO-R76E vector can be used as a tool to prevent retinal degeneration induced by RPE oxidative stress, which is implicated as a potential cause of Age-Related Macular Degeneration.

Defense Response of Pumpkin Rootstock To Cadmium

Cadmium pollution is severe in cucumber, although grafting is an effective method to improve its stress tolerance. Pumpkin is the commonly-used grafting rootstock for cucumber, and the breeding of rootstock with cadmium tolerance plays a vital role in the safe production of cucumber. However, there are no reports on rootstocks specific for cadmium tolerance. In this study, the rootstock of a pumpkin cross combination and its parents were used for the study of cadmium stress. The results indicated that under the 24mg·L− 1cadmium stress, the relative conductivity of cross combination decreased by 35.86%~36.31% compared with the parents. When the concentrations of cadmium stress were 8 mg·L− 1and 16 mg·L− 1, respectively, the peroxidase (POD) activity of cross combination was higher than those of the parents. The subcellular distribution of cadmium in the root systems of the cross and the 041 − 1 parent was in the cell wall first, followed by the cytoplasm and organelle, while that in the root system of 360-3 parent was in the cell wall first, followed by the organelle and cytoplasm. Under cadmium stress with the 24mg·L− 1concentration, the transfer coefficient of cross was significantly lower than that of the parents. The cross initiated the activity of membrane protective enzyme POD under cadmium stress, relieved the damage to membrane, and reduced the toxicity of cadmium through the accumulation of cadmium in the cell wall that blocked its entrance to the cytoplasm. This study provides a theoretical foundation to breed cadmium-tolerant rootstocks for melon vegetables.

Antioxidant and Cytoprotective Potential of Erythropoietin in Mitigating Oxidative Stress-Induced Changes in the Retinal Pigment Epithelium

Erythropoietin (EPO) protects cells by inhibiting apoptosis, oxidative stress and inflammation in several models of retinal degeneration. In this study, we demonstrate the effects of recombinant Adeno Associated Virus (AAV) vector-mediated delivery of a modified form of erythropoietin (EPO-R76E) in an established mouse model of dry-AMD in which retinal degeneration is induced by RPE oxidative stress. Experimental vector AAV-EPO-R76E and control vector AAV-GFP were packaged into serotype-1 (AAV1) to enable RPE selective expression. RPE oxidative stress-mediated retinal degeneration was induced by exon specific deletion of the protective enzyme MnSOD (encoded by Sod2) by cre/lox mechanism. Experimental mice received subretinal injection of AAV-EPO-R76E in the right eye and AAV-GFP in the left eye. Western blotting of RPE/Choroid protein samples from AAV-EPO-R76E injected eyes showed RPE specific exogenous protein expression. Retinal degeneration was monitored by electroretinography (ERG). EPO-R76E over-expression in RPE delayed the progressive retinal degeneration as measured by light microscopy in RPE specific Sod2 knockout mice. Delivery of EPO-R76E vector can be used as a tool to prevent retinal degeneration induced by RPE oxidative stress as seen in this mouse model.

Oligomeric assembly regulating mitochondrial HtrA2 function as examined by methyl-TROSY NMR

Human High temperature requirement A2 (HtrA2) is a mitochondrial protease chaperone that plays an important role in cellular proteostasis and in regulating cell-signaling events, with aberrant HtrA2 function leading to neurodegeneration and parkinsonian phenotypes. Structural studies of the enzyme have established a trimeric architecture, comprising three identical protomers in which the active sites of each protease domain are sequestered to form a catalytically inactive complex. The mechanism by which enzyme function is regulated is not well understood. Using methyl transverse relaxation optimized spectroscopy (TROSY)-based solution NMR in concert with biochemical assays, a functional HtrA2 oligomerization/binding cycle has been established. In the absence of substrates, HtrA2 exchanges between a heretofore unobserved hexameric conformation and the canonical trimeric structure, with the hexamer showing much weaker affinity toward substrates. Both structures are substrate inaccessible, explaining their low basal activity in the absence of the binding of activator peptide. The binding of the activator peptide to each of the protomers of the trimer occurs with positive cooperativity and induces intrasubunit domain reorientations to expose the catalytic center, leading to increased proteolytic activity. Our data paint a picture of HtrA2 as a finely tuned, stress-protective enzyme whose activity can be modulated both by oligomerization and domain reorientation, with basal levels of catalysis kept low to avoid proteolysis of nontarget proteins.

Growth and Physiological Characteristics of Sassafras tzumu Hemsl. Seedlings Under Cadmium (Cd) Stress

The effects of cadmium stress on the growth and physiological characteristics of Sassafras tzumu Hemsl. were studied in pot experiments. Five Cd levels were tested (CT: 0 mg/kg, Cd5: 5 mg/kg, Cd20: 20 mg/kg, Cd50: 50 mg/kg, and Cd100: 100 mg/kg). The growth and physiological characteristics of the sassafras seedlings in each level were measured. The results showed that soil Cd had negative influences on sassafras growth and reduced the net growth of plant height and the biomass of leaf, branch and root. The contents of hydrogen peroxide and malondialdehyde increased with increasing cadmium concentration; this indicated that cadmium stress had a certain effect on the peroxidation of the inner cell membranes in the seedlings that resulted in damage to the cell membrane structure. Superoxide dismutase activity increased in treatments Cd50 and Cd100 compared to that in the other treatments, while peroxidase activity increased steadily with increasing cadmium concentration; these results suggest that peroxidase is likely the main protective enzyme involved in the reactive oxygen removal system in sassafras seedlings. The increase in proline content with increasing cadmium concentration indicated that cadmium stress induced proline synthesis to resist osmotic stress in the seedlings. Compared to that in CT, the soluble sugar content declined under the different treatments. The soluble protein content first increased and then decreased with increasing cadmium stress. At different levels of cadmium stress, the chlorophyll content in the seedlings first increased and then decreased, and it was higher in the Cd5 and Cd20 treatments than that in the CT treatment. These results reflect that cadmium has photosynthesis-promoting effects at low concentrations and photosynthesis-suppressing effects at high concentrations. The photosynthetic gas exchange parameters and photosynthetic light-response parameters showed downward trends with increasing cadmium concentration compared with those in CT; these results reflect the negative effects of cadmium stress on photosynthesis in sassafras seedlings.

Evaluation of Anticonvulsant and Anti-oxidant Potentials of Basella Alba by Influencing the Brain Enzyme Levels in Laboratory Animals

Epilepsy and convulsions constitute a significant class of symptoms that are commonly seen in many neurological diseases. It is understood that there is an apparent alteration in the levels of the enzymes which present brain during epilepsy. Anti-oxidant drugs are known to elevate the protective enzyme levels in the body and restore them to ensure the proper functioning is done. But when the enzyme levels are not managed properly, they can cause further damage and deterioration of the tissue. Basella alba is one of such drugs, which is rich in anti-oxidant chemical constituents. Many researchers concluded that many components like vitamin A, C and flavonoids, polyphenols are being reported. In the study, Basella alba was investigated for effect on an anti-oxidant enzyme in the brain. The extracts showed a better activity and prevented the brain tissue damage from any oxidative free radical generation. The enzyme levels were healthy at the dose of 400mg/kg of extract.