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Purpose: A radio-frequency dielectric barrier discharge (DBD) was applied as a micro-plasma device for the inactivation of bacteria, e.g., Escherichia coli.

Materials and methods: The cultured bacteria were placed on a polydimethyl siloxane (PDMS) film and placed inside the DBD cavity. The bacteria were exposed to micro-plasmas of varying oxygen/argon ratios for different exposure times. The survival of the bacteria was measured by determining bacterial growth using optical methods.

Results: The excited oxygen species increased with the increase in the oxygen to argon ratio as measured by optical emission spectroscopy (OES), but the increase of excited oxygen species in argon micro-plasma did not enhance the inactivation of bacteria. In contrast, increases in the time the bacteria were exposed to the micro-plasma were of importance. The results show that a continuous plasma flow containing energetic and reactive species may result in electro-physical interactions with bacteria exposed to the plasma leading to their inactivation.

Conclusion: For currently-employed DBD device, addition of 0.5% oxygen to the argon micro-plasma for an exposure time of 30 sec was optimum for the inactivation of E. coli.  相似文献   
3.
Purpose: The interference of electric fields (EF) with biological processes is an issue of considerable interest. No studies have as yet been reported on the combined effect of EF plus ionising radiation. Here we report studies on this combined effect using the prokaryote Microcystis panniformis, the eukaryote Candida albicans and human cells.

Materials and methods: Cultures of Microcystis panniformis (Cyanobacteria) in glass tubes were irradiated with doses in the interval 0.5–5 kGy, using a 60Co gamma source facility. Samples irradiated with 3 kGy were exposed for 2 h to a 20 V · cm?1 static electric field and viable cells were enumerated. Cultures of Candida albicans were incubated at 36°C for 20 h, gamma-irradiated with doses from 1–4 kGy, and submitted to an electric field of 180 V · cm?1. Samples were examined under a fluorescence microscope and the number of unviable (red) and viable (apple green fluorescence) cells was determined. For crossing-check purposes, MRC5 strain of lung cells were irradiated with 2 Gy, exposed to an electric field of 1250 V/cm, incubated overnight with the anti-body anti-phospho-histone H2AX and examined under a fluorescence microscope to quantify nuclei with γ-H2AX foci.

Results: In cells exposed to EF, death increased substantially compared to irradiation alone. In C. albicans we observed suppression of the DNA repair shoulder. The effect of EF in growth of M. panniformis was substantial; the number of surviving cells on day-2 after irradiation was 12 times greater than when an EF was applied. By the action of a static electric field on the irradiated MRC5 cells the number of nuclei with γ-H2AX foci increased 40%, approximately.

Conclusions: Application of an EF following irradiation greatly increases cell death. The observation that the DNA repair shoulder in the survival curve of C. albicans is suppressed when cells are exposed to irradiation + EF suggests that EF likely inactivate cellular recovering processes. The result for the number of nuclei with γ-H2AX foci in MRC5 cells indicates that an EF interferes mostly in the DNA repair mechanisms. A molecular ad-hoc model is proposed.  相似文献   
4.
Mitochondria and chloroplasts are major sources of free radical generation in living organisms. Because of this, these organelles require strong protection from free radicals and associated oxidative stress. Melatonin is a potent free radical scavenger and antioxidant. It meets the criteria as a mitochondrial and chloroplast antioxidant. Evidence has emerged to show that both mitochondria and chloroplasts may have the capacity to synthesize and metabolize melatonin. The activity of arylalkylamine N‐acetyltransferase (AANAT), the reported rate‐limiting enzyme in melatonin synthesis, has been identified in mitochondria, and high levels of melatonin have also been found in this organelle. From an evolutionary point of view, the precursor of mitochondria probably is the purple nonsulfur bacterium, particularly, Rhodospirillum rubrum, and chloroplasts are probably the descendents of cyanobacteria. These bacterial species were endosymbionts of host proto‐eukaryotes and gradually transformed into cellular organelles, that is, mitochondria and chloroplasts, respectively, thereby giving rise to eukaryotic cells. Of special importance, both purple nonsulfur bacteria (R. rubrum) and cyanobacteria synthesize melatonin. The enzyme activities required for melatonin synthesis have also been detected in these primitive species. It is our hypothesis that mitochondria and chloroplasts are the original sites of melatonin synthesis in the early stage of endosymbiotic organisms; this synthetic capacity was carried into host eukaryotes by the above‐mentioned bacteria. Moreover, their melatonin biosynthetic capacities have been preserved during evolution. In most, if not in all cells, mitochondria and chloroplasts may continue to be the primary sites of melatonin generation. Melatonin production in other cellular compartments may have derived from mitochondria and chloroplasts. On the basis of this hypothesis, it is also possible to explain why plants typically have higher melatonin levels than do animals. In plants, both chloroplasts and mitochondria likely synthesize melatonin, while animal cells contain only mitochondria. The high levels of melatonin produced by mitochondria and chloroplasts are used to protect these important cellular organelles against oxidative stress and preserve their physiological functions. The superior beneficial effects of melatonin in both mitochondria and chloroplasts have been frequently reported.  相似文献   
5.
目的 探讨妊娠合并糖尿病对产妇剖宫产后产褥期感染病原菌特点及耐药性的影响。方法 回顾性分析2018年5月—2021年7月贵阳市妇幼保健院79例剖宫产后产褥期感染患者的临床资料,根据妊娠期是否合并糖尿病分为研究组47例(妊娠合并糖尿病)和对照组32例(妊娠未合并糖尿病)。比较两组患者的一般资料、不同感染部位病原菌特点、产褥期感染病原菌分布情况、产褥期感染的主要革兰阳性菌(金黄色葡萄球菌、表皮葡萄糖菌)和主要革兰阴性菌(大肠埃希菌、铜绿假单胞菌)对常见抗菌药物的耐药性。结果 两组孕周、喂养方式、感染部位、年龄、产程比较,差异无统计学意义(P >0.05);79例剖宫产后产褥期感染患者中共分离检出94株菌株(对照组41株、研究组53株),两组病原菌感染部位比较,差异无统计学意义(P >0.05);94株菌株中革兰阳性菌50株(53.19%),革兰阴性菌32株(34.04%),真菌12株(12.77%),两组产褥期感染的革兰阳性菌、真菌数比较,差异无统计学意义(P >0.05),研究组产褥期感染的革兰阴性菌多于对照组(P <0.05);研究组产褥期感染的革兰阴性菌中大肠埃希菌多于对照组(P <0.05);两组产褥期感染的金黄色葡萄球菌对氨苄青霉素、氧氟沙星、头孢拉定、环丙沙星的耐药性均>50%,研究组产褥期感染的金黄色葡萄球菌对头孢噻肟的耐药性高于对照组(P <0.05);两组产褥期感染的大肠埃希菌对氨苄青霉素、头孢他啶、庆大霉素的耐药性均>50%,研究组产褥期感染的铜绿假单胞菌对哌拉西林/他唑巴坦、亚胺培南的耐药性高于对照组(P <0.05)。结论 妊娠合并糖尿病对产妇剖宫产后产褥期感染病原菌特点及耐药性具有一定的影响,其可增加革兰阴性感染率,也可提高金黄色葡萄球菌与铜绿假单胞菌的耐药性。  相似文献   
6.
《Dental materials》2022,38(2):384-396
ObjectivesOral bacterial adhesion on dental implant materials has been extensively studied using in vitro systems but has yielded results restricted to in vitro growth patterns due to limitations in species selection, sustained fastidious anaerobe growth, and mixed culture longevity. The aim of this study was to develop an oral bacterial biofilm model consisting of colonizers representative of the oral microbiome exhibiting temporal shifts characteristic of plaque development and maturation in vivo.MethodsStreptococcus oralis, Actinomyces naeslundii, Aggregatibacter actinomycetemcomitans, Veillonella parvula, Fusobacterium nucleatum, and Porphyromonas gingivalis were grown in monoculture prior to combination in mixed culture. Commercially pure titanium (cpTi) and yttria-stabilized zirconia (ZrO2) disks with polished, acid-etched, or sandblasted surfaces were prepared to evaluate oral bacterial adhesion. After 6 h, 1, 3, 7, 14 and 21 days, genomic DNA from planktonic and adherent bacteria was isolated. Quantitative polymerase chain reaction (qPCR) was used to enumerate the amount and proportion of each species.ResultsEarly-colonizing S. oralis and A. actinomycetemcomitans, dominated after 6 h prior to secondary colonization by F. nucleatum and V. parvula in planktonic (1 day) and sessile (3 days) form. A. naeslundii maintained relatively low but stable bacterial counts throughout testing. After 14 days, late-colonizing P. gingivalis became established in mixed culture and persisted, becoming the dominant species after 21 days. The composition of adherent bacteria across all substrates was statistically similar at all timepoints with notable exceptions including lower S. oralis bacterial counts on polished cpTi (3 days).SignificanceWithin the present model’s limitations, multispecies oral bacterial attachment is similar on surface-treated cpTi and ZrO2.  相似文献   
7.
《Dental materials》2022,38(5):848-857
ObjectiveDental plaque is a complex structure (called a biofilm) that is produced by a community of oral bacteria. As microorganisms accumulate in the oral cavity, bacteria can assemble into biofilms that protect them from antibiotics and disinfectants, which contribute to dental cavities and oral infections that acts as the seed for further infections throughout the body. Therefore, there is great interest in developing dental sealants that can effectively eliminate biofilms formed from an assortment of oral bacteria species.MethodsIn previous papers, it was shown that both in vivo and in vitro use of organo-selenium dental sealants have the potential to be an effective method for preventing dental caries and plaque formation. However, our previous in vitro study only examined the effect of the organo-selenium sealants on Streptococcus mutans and salivarius. Since that time, this organo-selenium sealant has been changed to improve its curing time.ResultsWe showed a selenium containing sealant (SeLECT-DefenseTM) can completely eliminate biofilm formation on the sealant at selenium concentrations of 0.25% and higher, by S. salivarius, S. sanguinis, or S. mutans, individually or in combination. This selenium containing sealant can also completely inhibit the same bacteria from growing under the sealant, while control sealant cannot. The selenium containing sealant was tested for stability and it was found to still kill these same bacteria after soaking for the equivalent of one year in PBS (pH 7.4). It was also found that the combination of the three bacteria were also killed by the selenium sealant, thus ruling out potential synergism of the bacteria in forming resistance.SignificanceThe following study showed that this modified selenium dental sealant effectively eliminates species of bacteria both on and under the dental sealant.  相似文献   
8.
9.
Objective: The study aimed to determine if multiple displacement amplification could be used to provide abundant target DNA and DNA probes for checkerboard DNA–DNA hybridization. Methods: Multiple displacement amplification was used to amplify 1 and 10 ng DNA from 16 individual bacterial species, DNA from single colonies, from a mixture of 20 bacterial species and oral biofilm samples, such as supragingival plaque, subgingival plaque, buccal swab and root canal samples. Samples in reaction buffer were heat‐denatured at 95°C for 3 min and cooled to 4°C. Φ29 DNA polymerase was added and the mixture was incubated at 30°C for 16–18 h. The quantity of the product was evaluated by the Picogreen assay. The amplified material was labeled with digoxigenin. The probes were compared with probes obtained from unamplified DNA using checkerboard DNA–DNA hybridization. Both amplified DNA and unamplified DNA were used as targets on the membrane. Amplified oral biofilm samples were compared to unamplified samples using checkerboard DNA–DNA hybridization. Results: The DNA yield ranged from 4 to 11 μg. DNA–DNA hybridization showed that the amplified genome of each species used either as target or as probe provided signals equivalent to controls and that amplification of a mixture of species provided signals comparable to those provided by the unamplified source mixture. Amplified oral biofilm samples exhibited comparable proportions of bacterial DNA when compared to the original unamplified samples. Conclusions: The multiple displacement amplification technique is a simple and reliable method to uniformly amplify DNA for use in checkerboard DNA–DNA hybridization. It is also a useful tool in the amplification of clinical samples.  相似文献   
10.
BackgroundSulfated polysaccharides from red marine algae have presented a variety of potentially therapeutic biological effects, however, their antinocicpetive and anti-inflammatory properties are not well understood.MethodsMale Swiss mice were pretreated with a sulfated polysaccharidic fraction obtained from the marine alga Acanthophora muscoides (AmII) (1, 3 or 9 mg/kg, iv) 30 min prior to either receiving an injection of 0.8% acetic acid or 1% formalin or prior to a thermal stimulus. AmII (1, 3 or 9 mg/kg, sc) was evaluated on carrageenan-, dextran- bradykinin-, histamine- and serotonin-induced rat paw edema models. AmII (500 jig, sc) was also injected into the paw. Additionally, mice were treated with the total sulfated polysaccharides from A. muscoides (Am-TSP) (20 mg/kg, ip) for 14 days.ResultsAmII reduced the number of acetic acid-induced writhes and licking time in the second phase of the formalin test, but it did not alter the response latency in the hot plate test, suggesting that its antinociceptive action occurs through a peripheral mechanism. AmII did not reduce carrageenan-induced paw edema and MPO activity. However, it reduced dextran-, histamine- and serotonin- induced paw edemas, but not bradykinin-induced edema, suggesting that histamine is the major target of AmII anti-edematogenic activity. AmII inj ected into the paw did not evoke local edema. Furthermore, Am-TSP induced no consistent signs of systemic damage, as revealed by body mass, organs wet weight and by biochemical, hematological and histopathological analyses.ConclusionAmII has important antinociceptive and anti-inflammatory properties and represents an important therapeutic agent warranting future studies.  相似文献   
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