Effects of ethylene and NO on AsA-GSH in lotus under cadmium stress.

Under the background of Cd (50 µmol·L-1) stress, we added ethylene precursor ACC (100 µmol·L-1), ACC + nitric oxide synthase (NOS) inhibitor L-NNA (200 µmol·L-1), ACC + nitrate reductase (NR) inhibitor Tu (1 mmol·L-1), ACC + nitric oxide (NO) scavenger PTIO (200 µmol·L-1), NO donor SNP (500 µmol·L-1), SNP + ethylene signal inhibitor STS (100 µmol·L-1) to examine their effects on the damage degree of leaves and response mechanisms of AsA-GSH cycle in lotus 'Weishanhuhonglian'. Results showed toxic symptom of lotus leaves under Cd stress. The relative conductivity, malondialdehyde (MDA), as well as ascorbic acid (AsA) and glutathione (GSH) contents were significantly increased, but the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) were obviously decreased. Compared with Cd stress, adding ACC significantly increased the damage area of lotus leaves, decreased activities of the above-mentioned four antioxidant enzymes and increased AsA and GSH contents. SNP aggravated the toxic symptom of lotus leaves and decreased GR and MDHAR activities. PTIO significantly relieved the toxic symptom of leaves, increased activities of APX, GR, MDHAR and DHAR, but decreased AsA and GSH contents compared with Cd and ACC treatment. However, the effects of L-NNA and Tu were not as obvious as PTIO's. In comparison with Cd and SNP treatment, STS relieved the toxic symptom of leaves, increased APX, GR, MDHAR and DHAR activities, and decreased AsA and GSH contents. Taken together, these results showed the synergistic effects of ethylene and NO in regulating lotus responses to Cd stress through AsA-GSH cycle.

Isolation and characterization of a heme oxygenase-1 gene from Chinese cabbage.

Heme oxygenase-1 (HO1) is a heme-catabolizing enzyme induced by a variety of stress conditions. This article described the cloning and characterization of BrHO1 gene which codes for a putative HO1 from Chinese cabbage (Brassica rapa subsp. pekinensis). BrHO1 consists of three exons and encodes a protein precursor of 32.3 kD with a putative N-terminal plastid transit peptide. The amino acid sequence of BrHO1 was 84% similar to Arabidopsis counterpart HY1. The three-dimensional structure of BrHO1 showed a high degree of structural conservation compared with the known HO1 crystal structures. Phylogenetic analysis revealed that BrHO1 clearly grouped with the HO1-like sequences. The recombinant BrHO1 protein expressed in Escherichia coli was active in the conversion of heme to biliverdin IXα (BV). Furthermore, the results of subcellular localization of BrHO1 demonstrated that BrHO1 gene product was most likely localized in the chloroplasts. BrHO1 was differently expressed in all tested tissues and could be induced upon osmotic and salinity stresses, cadmium (Cd) exposure, hydrogen peroxide (H(2)O(2)), and hemin treatments. Together, the results suggested that BrHO1 plays an important role in abiotic stress responses.

Characterization of a wheat heme oxygenase-1 gene and its responses to different abiotic stresses.

In animals and recently in plants, heme oxygenase-1 (HO1) has been found to confer protection against a variety of oxidant-induced cell and tissue injuries. In this study, a wheat (Triticum aestivum) HO1 gene TaHO1 was cloned and sequenced. It encodes a polypeptide of 31.7 kD with a putative N-terminal plastid transit peptide. The amino acid sequence of TaHO1 was found to be 78% similar to that of maize HO1. Phylogenetic analysis revealed that TaHO1 clusters together with the HO1-like sequences in plants. The purified recombinant TaHO1 protein expressed in Escherichia coli was active in the conversion of heme to biliverdin IXa (BV), and showed that the V(max) was 8.8 U·mg(-1) protein with an apparent K(m) value for hemin of 3.04 µM. The optimum Tm and pH were 35 °C and 7.4, respectively. The result of subcellular localization of TaHO1 showed that the putative transit peptide was sufficient for green fluorescent protein (GFP) to localize in chloroplast and implied that TaHO1 gene product is at least localized in the chloroplast. Moreover, we found that TaHO1 mRNA could be differentially induced by the well-known nitric oxide (NO) donor sodium nitroprusside (SNP), gibberellin acid (GA), abscisic acid (ABA), hydrogen peroxide (H(2)O(2)) and NaCl treatments. Therefore, the results suggested that TaHO1 might play an important role in abiotic stress responses.

Cloning and characterization of a heme oxygenase-2 gene from alfalfa (Medicago sativa L.).

Heme oxygenase (HO, EC 1.14.99.3) catalyzes the oxidation of heme and performs vital roles in plant development and stress responses. Two HO isozymes exist in plants. Between these, HO-1 is an oxidative stress-response protein, and HO-2 usually exhibited constitutive expression. Although alfalfa HO-1 gene (MsHO1) has been investigated previously, HO2 is still poorly understood. In this study, we report the cloning and characterization of HO2 gene, MsHO2, from alfalfa (Medica sativa L.). The full-length cDNA of MsHO2 contains an ORF of 870 bp and encodes for 290 amino acid residues with a predicted molecular mass of 33.3 kDa. Similar to MsHO1, MsHO2 also appears to have an N-terminal transit peptide sequence for chloroplast import. Many conserved residues in plant HO were also conserved in MsHO2. However, unlike HO-1, the conserved histidine (His) required for heme-iron binding and HO activity was replaced by tyrosine (Tyr) in MsHO2. Further biochemical activity analysis of purified mature MsHO2 showed no HO activity, suggesting that MsHO2 may not be a true HO in nature. Semi-quantitative RT-PCR confirmed its maximum expression in the germinating seeds. Importantly, the expression levels of MsHO2 were up-regulated under sodium nitroprusside (SNP) and H(2)O(2) (especially) treatment, respectively.

Dipyridamole 201Tl myocardial SPECT imaging in patients with dilated cardiomyopathy / 中华核医学杂志

Objective To explore the characteristics of dipyridamole 201 Tl myocardial perfusion imaging (MPI) SPECT in patients with dilated cardiomyopathy. Methods Thirty patients with dilated cardiomyopathy underwent pharmacological stress 201Tl MPI SPECT after intravenous infusion of dipyridamole (0. 56 mg/kg) for 4 min. The early and delayed SPECT images were acquired respectively at 10 and 240 min after 201Tl injection. The images were analyzed and reported by two or three experienced nuclear medicine physicians. Results All patients were found to have abnormal perfusion patterns at delay imaging, however 90.00% (27/30) were also abnormal at early images. Six patients had reverse redistribution. Conclusion Dipyridamole 201Tl MPI SPECT imaging may be of some value for the assessment of patients with dilated cardiomyopathy.

The diagnostic value of dipyridamole (201)Tl-SPECT myocardial imaging and exercise myocardial (99)Tc(m)-MIBI-SPECT imaging on detecting cardiac syndrome X / 中华心血管病杂志

<p><b>OBJECTIVE</b>To compare the value of dipyridamole (201)Tl Single photon emission computed tomography (SPECT) myocardial imaging and exercise myocardial (99)Tc(m)-MIBI SPECT imaging on diagnosing cardiac syndrome X.</p><p><b>METHODS</b>Sixty-three patients with known cardiac syndrome X were divided into dipyridamole (201)Tl SPECT myocardial imaging group (group 1, n = 35) and exercise myocardial (99)Tc(m)-MIBI-SPECT imaging group (group 2, n = 28) and the diagnostic accuracy rates were compared.</p><p><b>RESULTS</b>Thirty-one out of 35 cardiac syndrome X patients showed reverse redistribution in group 1 and the diagnostic accuracy rate was 89%. Positive test results were evidenced 24 out of 28 cardiac syndrome X patients in group 2 and the diagnostic accuracy rate was 87% (P > 0.05 vs. group 1).</p><p><b>CONCLUSION</b>The diagnostic accuracy rates of these two myocardial imaging methods were satisfactory and comparable on detecting cardiac syndrome X.</p>