scholarly journals The mechanism of sunlight-mediated inactivation of Bacillus thuringiensis crystals

1991 ◽  
Vol 273 (1) ◽  
pp. 43-47 ◽  
Author(s):  
M Pusztai ◽  
P Fast ◽  
L Gringorten ◽  
H Kaplan ◽  
T Lessard ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Bacillus Thuringiensis ◽  
Time Course ◽  
Solar Spectrum ◽  
Oxygen Species ◽  
Biological Assays ◽  
Fermentation Liquor ◽  
Crystal Damage ◽  
Singlet Oxygen Species ◽  
Nm Range

Detailed photostability studies were carried out using purified delta-endotoxin crystals from Bacillus thuringiensis subspecies HD-1 and HD-73. The mechanism and time course of sunlight inactivation was investigated by: (a) monitoring the tryptophan damage in the intact crystals by Raman spectroscopy, (b) amino acid analysis and (c) biological assays using insects. The results demonstrate that, for purified HD-1 or HD-73 crystals, the 300-380 nm range of the solar spectrum is largely responsible for bringing about crystal damage and consequent loss of toxicity. Purified Bacillus thuringiensis crystals that were exposed to fermentation liquor after cell lysis were more quickly degraded by sunlight than were crystals from cells that were lysed in water. This effect is attributed to adsorption of chromophores by crystals exposed to the fermenter liquor and the subsequent ability of these chromophores to act as photosensitizers. The importance of a photosensitization mechanism in crystal degradation was further emphasized by irradiating Bacillus thuringiensis crystals in vacuo. The latter crystals were found to be less damaged (20% tryptophan loss after 24 h irradiation by the solar spectrum) compared with crystals from the same sample irradiated in air (60% (60% tryptophan loss). Other methods of decreasing exposure of the crystals to oxygen, e.g. by using glycerol as a humectant, were also found to be successful in controlling photodamage. The results concerning photodegradation support a photosensitization mechanism involving the presence of exogenous (and possibly endogenous) chromophores which create singlet oxygen species upon irradiation by light.

scholarly journals Comparative transcriptome analysis of genes involved in two peanut varieties under drought stress

2020 ◽  
Author(s):  
Chunji Jiang ◽  
Xinlin Li ◽  
Jixiang Zou ◽  
Jingyao Ren ◽  
Chunyi Jin ◽  
...  
Keyword(s):  
Drought Resistance ◽  
Time Course ◽  
Stomatal Closure ◽  
Resistance Mechanisms ◽  
Oxygen Species ◽  
Tolerance Mechanism ◽  
Physiological Characterization ◽  
Oil Crops ◽  
Differential Expressed Genes ◽  
Transcriptomic Changes

Abstract Background Peanut is one of the most important world oil crops. Peanut qualities and yields are restricted dramatically by abiotic stresses particularly by drought. Therefore, it would be beneficial to gain a comprehensive understanding on regulatory mechanisms of the peanut genomic transcriptional activities responding to drought, and hopefully extracting peanut molecular drought-resistance mechanisms. Results In this study, two peanut varieties NH5 (resistant) and FH18 (sensitive) which showed significantly differential drought-resistance were screened from twenty-three main commercial peanut cultivars and used for physiological characterization and transcriptomic analysis. NH5 leaves showed higher water and GSH contents, faster stomatal closure and lower relative conductivity (REC) than FH18. Under the time-course of 0 h (CK), 4 h (DT1), 8 h (DT2) and 24 h (DT3), drought-treatments tent to exert repressive impacts on peanut transcriptomes since the number of down-regulated differential expressed genes (DEGs) increased with the progression of treatments in both varieties. Conclusions Nevertheless, NH5 seemed to maintain stabler transcriptomic dynamics than FH18. Furthermore, annotations of identified DEGs implicated that signal transduction, elimination of reactive oxygen species, maintenance of cell osmotic potential were key drought-resistance-related pathways. Last, examination of ABA and SA components suggested that the fast stomata closure in NH5 was likely to be mediated through SA rather than ABA signaling. In all, these results have not only provided us comprehensive pictures of peanut drought transcriptomic changes, but also laid a foundation for further identification of the molecular drought tolerance mechanism in peanut and other oil crops.

Time course of structure, function, and metabolic changes due to an exogenous source of oxygen metabolites in rat heart

1989 ◽  
Vol 67 (12) ◽  
pp. 1549-1559 ◽  
Author(s):  
Madhu Gupta ◽  
Pawan K. Singal
Keyword(s):  
Time Course ◽  
Active Oxygen Species ◽  
Lipid Peroxide ◽  
High Energy ◽  
Active Oxygen ◽  
High Energy Phosphates ◽  
Oxygen Species ◽  
Peroxide Content ◽  
Resting Tension ◽  
Contractile Failure

Effects of xanthine (2 mM) and xanthine oxidase (10 U/L) perfusion on myocardial function, lipid peroxide content, high-energy phosphates and their metabolites, and ultrastructure were examined in isolated perfused rat hearts to define the time course of myocardial injury due to exogenous supply of active oxygen species. Peak-developed force and dF/dt showed a decline within 5 min and complete contractile failure was seen at 20 min. Resting tension was higher at 10 min and reached a maximum value of 400% at 40 min. These changes in contractile parameters were reduced by superoxide dismutase (1.2 × 105 U/L), catalase (2 and 4 × 104 U/L), and mannitol (10 and 20 mM). Lipid peroxide content was significantly higher at 5 min and rose continuously with xanthine – xanthine oxidase (X–XO) perfusion. A close correlation was noted (r = 0.935) between increased lipid peroxide content and a decrease in peak-developed force. Creatine phosphate and adensoine triphosphate (ATP) showed a time-dependent decrease due to X–XO perfusion. Loss of ATP also correlated (r = 0.819) with the contractile failure. Adenosine diphosphate showed an increase at 5 min followed by a decrease at 20 and 40 min. Adenosine monophosphate, adenosine, and creatine content increased with X–XO perfusion. In a semiquantitative morphometric study, significant myocardial and vascular changes became apparent only after 10 min of X–XO perfusion. When a 5-min perfusion with X–XO was followed by a control perfusion, a recovery of developed force and normal structure was noted at 40 min. These data show that X–XO induced contractile failure involves partially reduced forms of oxygen such as superoxide, hydroxyl radicals, and hydrogen peroxide. The negative inotropic effect of a vascular supply of these active oxygen species may be related to increased lipid peroxidation as well as the loss of high-energy phosphates. Structural damage to myocytes and blood vessels and a rise in resting tension were delayed events requiring a continuous and longer exposure to radical species.Key words: myocardial failure, oxygen radicals, lipid peroxidation, myocardial high-energy phosphates, myocardial cell damage, antioxidant protection.

Structural and Physical Characterization of Li2O:P2O5:MO3 (M = Cr2, Mo, W) Ion Conducting Glasses

1992 ◽  
Vol 293 ◽  
Author(s):  
B.V.R. Chowdari ◽  
K.L. Tan ◽  
W.T. Chia
Keyword(s):  
Raman Spectroscopy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Photoelectron Spectroscopy ◽  
Oxygen Species ◽  
X Ray ◽  
Ion Conducting ◽  
Phosphate Groups ◽  
Glass Compositions

AbstractThe conductivity of the Li2O:P2O5:MO3 (M = Cr2, Mo, W) glasses increases as P2O5 is progressively substituted by MO3 and as the Li2O content increases. Amongst the glass compositions studied, the 0.50Li2O:0.20P2O5:0.30WO3 glass has the highest conductivity at 25°C of 2. 1×10−6 ×−1 cm−1. The glass transition temperature of the glasses increases initially with network former substitution, reaches a maximum at around MO3/P2O5 = 1, and decreases with further substitution. X-ray photoelectron spectroscopy reveals the presence of M ions in more than one oxidation state and oxygen species such as P=O, P-O-P, P-O, M-O-M, M-O and P-O-M. Raman spectroscopy shows that the Li2O:P2O5:MoO3 and Li2O:P2O5:WO3 glasses consist of PO4, MoO4 (WO4) and MoO6 (WO6) polyhedra while the Li2O:P2O5:Cr2O3 glasses consist of the PO4 and CrO6 polyhedra only. The phosphate groups are preferentially modified by Li2O in comparison with the tungstate, molybdate and chromate groups. The increasing number of non-bridging oxygen atoms per phosphate group may be related to the increasing conductivity with the progressive substitution of MO3 for P2O5.

scholarly journals Mechanical Wounding Induces Catalase Gene (VsCat) in Leaves of Common Vetch

2021 ◽  
Author(s):  
Saeid Abu-Romman ◽  
Tarek G. Ammari
Keyword(s):  
Time Course ◽  
Oxygen Species ◽  
Biotic Factors ◽  
Quantitative Real Time Pcr ◽  
Mechanical Wounding ◽  
Common Vetch ◽  
Catalase Gene ◽  
Defense Systems ◽  
Time Course Study ◽  
Scavenging Enzymes

Background: In plants, wounding can result from mechanical injuries or from biotic factors induced by herbivores infestation and pathogen infection. Wounding enhances the production of reactive oxygen species (ROS). Enzymatic and nonenzymatic defense systems have been reported in plants to immediately combat increased levels of ROS. Plant catalases are encoded by a multigene family and are the major scavenging enzymes catalyzing the dismutation of toxic hydrogen peroxide to water and dioxygen. Methods: In the preasent work, a quantitative real-time PCR was used to quantify the expression level of a catalase gene from common vetch (Vicia sativa; VsCat) in response to mechanical wounding. Result: The results of the time course study showed that the transcript levels of VsCat were significantly increased in wounded leaves at all-time points examined with a peak expression of 7.6 folds at 2 h post wounding. The increased expression of VsCat might represent a direct defense against elevated H2O2 generated during wounding.

scholarly journals Action of activated 27,000 Mr toxin from Bacillus thuringiensis var. israelensis on Malpighian tubules of the insect, Rhodnius prolixus

1989 ◽  
Vol 94 (3) ◽  
pp. 601-608
Author(s):  
S.H. Maddrell ◽  
J.A. Overton ◽  
D.J. Ellar ◽  
B.H. Knowles
Keyword(s):  
Bacillus Thuringiensis ◽  
Cell Membrane ◽  
Basal Cell ◽  
Time Course ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Bathing Solution ◽  
Concentrated Solutions ◽  
Intracellular Milieu

The action of activated 27,000 Mr toxin from Bacillus thuringiensis var. israelensis (Bti toxin) on Malpighian tubules of Rhodnius prolixus has been investigated. Its binding to the tubules is slowed by low temperature but is not prevented even at 0 degree C. The binding is less effective at pH 10 than at pH7. Pretreatment of the tubules with 0.1 mmol l-1 ouabain or bumetanide or 1 mumol l-1 5-hydroxytryptamine did not affect the toxicity of the toxin. The toxin causes very large changes in the trans-epithelial potential difference; it changes from 40 mV, lumen negative, often to more than 100 mV, lumen positive. This reflects an initial collapse of the potential of the basal cell membrane, followed by a large positive-going potential change at the luminal cell membrane. Just prior to the effects of the toxin on rapid fluid secretion, the basal cell membrane becomes permeable to sucrose molecules. Raffinose at 170 mmol l-1 in the bathing solution does not protect the tubules from Bti toxin action but dextran, Mr5000, at 60 mmol l-1 significantly delayed failure of fluid secretion and, even more, the onset of staining of the tubule cells with Trypan Blue. Exposing tubules to saline that is calcium-free and/or magnesium-free, or has a composition adjusted to be similar to that of the intracellular milieu, does not affect the time course of failure of fluid secretion induced by the toxin. There is no evidence that effective aggregates of Bti toxin molecules are formed in concentrated solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

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