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Different strategies of petal senescence and some important events associated with it have been discussed. On the basis of sensitivity to ethylene and associated symptoms of senescence, petal senescence has been classified into five different classes; besides changes in membrane permeability, autophagy and involvement of VPEs (Vacuolar processing enzymes), degradation of nucleic acids, protein turn over and remobilization of essential nutrients during petal senescence have been discussed. Nucleus appears to play a central role in administrating the execution of the events associated with petal senescence. Protein turn over appears to be an important factor governing petal senescence in both ethylene-sensitive and ethylene-insensitive flower systems and that the loss of membrane integrity, vacuolar autophagy and remobilization of essential nutrients being its important consequences. Autophagy seems to be a main process responsible for cell dismantling and remobilization of macromolecules besides final disintegration of nucleus. A large number of senescence-associated genes have been found to be differentially expressed during petal senescence. On the basis of the available literature, a schematic model representing some important events associated with petal senescence has been constructed. The review recommends that more elaborate work is required at cellular and organelle level to understand the ethylene-independent pathway and its execution in both ethylene-sensitive and ethylene-insensitive flower systems. It also recommends that ethylene sensitivity should not be generally assigned to plants at the family level on the basis of response of a few species in a family.  相似文献   
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It is widely accepted that oxidative stress plays a central role in alcohol-induced pathogenesis. The protective effect of binaphthyl diselenide (NapSe)2 was investigated in ethanol (Etoh)-induced brain injury. Thirty male adult Wistar rats were divided randomly into five groups of six animals each and treated as follows: (1) The control group received the vehicle (soy bean oil, 1 mL/kg, p.o.). (2) Ethanol group of animals was administered with ethanol (70% v/v, 2 mL/kg, p.o.). (3) (NapSe)2 1 mg/kg, 1 mL/kg plus ethanol 70% (v/v, 2 mL/kg, p.o. (5) (NapSe)2 10 mg/kg, 1 mL/kg) plus ethanol 70% (v/v, 2 mL/kg, p.o). After acute treatment, all rats were sacrificed by decapitation. Evidence for oxidative stress in rat brain was obtained from the observed levels of thiobarbituric acid reactive species, of non-protein thiol (NPSH) groups, and of ascorbic acid, as well as from the activities of catalase (CAT) and of superoxide dismutase (SOD). (NapSe)2 compensated the deficits in the antioxidant defense mechanisms (CAT, SOD, NPSH, and ascorbic acid), and suppressed lipid peroxidation in rat brain resulting from Etoh administration. It was concluded that ethanol exposure causes alterations in the antioxidant defense system and induces oxidative stress in rat brain. (NaPSe)2 at 5 mg/kg restored the antioxidant defenses in rat brain and mitigated the toxic effects of alcohol, suggesting that could be used as a potential therapeutic agent for alcohol-induced oxidative damage in rat brain.  相似文献   
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Trogtalite CoSe2 nanobuds encapsulated into boron and nitrogen codoped graphene (BCN) nanotubes (CoSe2@BCN‐750) are synthesized via a concurrent thermal decomposition and selenization processes. The CoSe2@BCN‐750 nanotubes deliver an excellent storage capacity of 580 mA h g?1 at current density of 100 mA g?1 at 100th cycle, as the anode of a sodium ion battery. The CoSe2@BCN‐750 nanotubes exhibit a significant rate capability (100–2000 mA g?1 current density) and high stability (almost 98% storage retention after 4000 cycles at large current density of 8000 mA g?1). The reasons for these excellent storage properties are illuminated by theoretical calculations of the relevant models, and various possible Na+ ion storage sites are identified through first‐principles calculations. These results demonstrate that the insertion of heteroatoms, B–C, N–C as well as CoSe2, into BCN tubes, enables the observed excellent adsorption energy of Na+ ions in high energy storage devices, which supports the experimental results.  相似文献   
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The release of malachite green, a commonly used triphenylmethane dye, into the environment is causing increasing concern due to its toxicity, mutagenicity, and carcinogenicity. A bacterial strain that could degrade malachite green was isolated from the water of an aquatic hatchery. It was identified as a Pseudomonas sp. based on the morphological, physiological, and biochemical characteristics, as well as the analysis of 16S rRNA gene sequence and designated as MDB-1. This strain was capable of degrading both malachite green and leucomalachite green, as well as other triphenylmethane dyes including Crystal Violet and Basic Fuchsin. The gene tmr2, encoding the triphenylmethane reductase from MDB-1, was cloned, sequenced and effectively expressed in E. coli. These results highlight the potential of this bacterium for the bioremediation of aquatic environments contaminated by malachite green.  相似文献   
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As an extension of our previous work we not only evaluated the relationship between acidosis and lipid peroxidation in rat's kidney homogenate, but also determined for the first time the potential anti-oxidant activity of diphenyl diselenide, diphenyl ditelluride and ebselen at a range of pH values (7.4–5.4). Because of the pH dependency of iron redox cycling, pH and iron need to be well controlled and for the reason we tested a number of pH values (from 7.4 to 5.4) to get a closer idea about the role of iron under various pathological conditions. Acidosis increased rate of lipid peroxidation in the absence Fe (II) in kidney homogenates especially at pH 5.4. This higher extent of lipid peroxidation can be explained by; the mobilized iron which may come from reserves where it is weakly bound. Addition of iron (Fe) chelator desferoxamine (DFO) to reaction medium completely inhibited the peroxidation processes at all studied pH values including acidic values (5.8–5.4). In the presence of Fe (II) acidosis also enhanced detrimental effect of Fe (II) especially at pH (6.4–5.4). Diphenyl diselenide significantly protected lipid peroxidation at all studied pH values, while ebselen offered only a small statistically non-significant protection. The highest anti-oxidant potency was observed for diphenyl ditelluride. These differences in potencies were explained by the mode of action of these compounds using their catalytic anti-oxidant cycles. However, changing the pH of the reaction medium did not alter the anti-oxidant activity of the tested compounds. This study provides evidence for acidosis catalyzed oxidative stress in kidney homogenate and for the first time anti-oxidant potential of diphenyl diselenide and diphenyl ditelluride not only at physiological pH but also at a range of acidic values.  相似文献   
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The purpose of this study was to investigate the physical stability of a coating system consisting of a blend of two sustained release acrylic polymers and its influence on the drug release rate of theophylline from coated pellets. The properties of both free films and theophylline pellets coated with the polymer blend were investigated, and the miscibility was determined via differential scanning calorimetry. Eudragit® RS 30 D was plasticized by the addition of Eudragit® NE 30 D, and the predicted glass transition temperature (T g) of the blend was similar to the experimental values. Sprayed films composed of a blend of Eudragit® NE 30 D/Eudragit® RS 30 D (1:1) showed a water vapor permeability six times greater than films containing only Eudragit® NE 30 D. The presence of quaternary ammonium functional groups from the RS 30 D polymer increased the swellability of the films. The films prepared from the blend exhibited stable permeability values when stored for 1 month at both 25°C and 40°C, while the films which were composed of only Eudragit® NE 30 D showed a statistically significant decrease in this parameter when stored under the same conditions. Eudragit® NE 30 D/Eudragit® RS 30 D (1:1)-sprayed films decreased in elongation from 180% to 40% after storage at 40°C for 1 month, while those stored at 25°C showed no change in elongation. In coated pellets, the addition of Eudragit® RS 30 D to the Eudragit® NE 30 D increased the theophylline release rate, and the pellets were stable when stored at 25°C for a period of up to 3 months due to maintenance of the physico-mechanical properties of the film. Pellets stored at 40°C exhibited a decrease in drug release rate over time as a result of changes in film physico-mechanical properties which were attributed to further coalescence and densification of the polymer. When the storage temperature was above the T g of the composite, instabilities in both drug release rate and physical properties were evident. Stabilization in drug release rate from coated pellets could be correlated with the physico-mechanical stability of the film formulation when stored at temperatures below the T g of the polymer.  相似文献   
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N H Waseem  K Labib  P Nurse    D P Lane 《The EMBO journal》1992,11(13):5111-5120
Five monoclonal antibodies raised against rat PCNA cross-reacted with a similar protein in the fission yeast Schizosaccharomyces pombe. One of these was used to screen an S.pombe cDNA expression library. An incomplete cDNA was isolated and used to screen a genomic library, identifying a single gene, designated pcn1+ (proliferating cell nuclear antigen). The gene encodes a protein of 260 amino acids, with a deduced sequence 52% identical to human and rat PCNAs, which are 98.5% identical to each other. The budding yeast PCNA homologue POL30 is only 35% identical to the human and rat proteins. Pcn1 has a region near the C-terminus of particularly high homology to higher eukaryotic PCNA proteins. pcn1+ is essential for viability and delta pcn1 cells undergo aberrant DNA replication before cell cycle arrest. Overproduction of the protein leads to cell cycle delay in G2. Disruption of pcn1+ is complemented by the human PCNA gene, demonstrating that these genes are functional homologues.  相似文献   
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