On the release of fluoride from biofilm reservoirs during a cariogenic challenge: an in situ study

Abstract

Biofilm fluoride reservoirs may be a source of fluoride to the fluid phase during a sugar challenge reducing tooth mineral loss. However, the evidence for that is conflicting and has not been studied in biofilms containing different fluoride levels. In order to test fluoride release from biofilms with distinct fluoride concentrations, biofilms were grown in situ exposed to a combination of placebo, calcium and fluoride rinses forming biofilms with no (fluoride-free rinses), low (fluoride-only rinses) or high (calcium followed by fluoride rinses) fluoride concentrations, and collected before and 5?min after a sucrose challenge. Rinsing with fluoride increased fluoride concentration in the biofilm (p?<?0.05), mainly when a calcium pre-rinse was used before the fluoride (p?<?0.05). However, after a sugar challenge, no significant increase in the biofilm fluid fluoride concentration was observed, even in the fluoride-rich biofilms (p?>?0.05). Fluoride-rich biofilms do not release fluoride to the fluid phase during a sugar challenge.     

Anatomical and physiological changes of in vitro-propagated Vriesea imperialis (Bromeliaceae) in the function of sucrose and ventilated containers

Abstract

Under in vitro culture conditions, plants may present physiological and anatomical disorders, which can interfere negatively after ex vitro transfer. The aim of this investigation was to analyze the impacts of natural ventilation and sucrose supply on the anatomy and physiology of Vriesea imperialis. Plants previously grown in vitro were transferred to culture medium containing 0, 15, 30 or 45?g L^?1 sucrose. Three different culture container sealing systems were tested: lids with a green filter (81.35 gas exchanges per day), yellow filter (13.09 gas exchanges per day) or lids with a yellow filter covered with three layers of transparent polyvinylchloride (PVC) film (blocking fluent gas exchange). Sucrose concentrations influenced thickness, lignin and suberin deposition of exodermis cell wall. The modifications verified in leaves, such as higher density of stomata and trichome scales, showed that sucrose can induce osmotic stress in the plants. Photomixotrophic conditions, using containers with intermediate rate of gas exchange (yellow filter) and with 15–30?g L^?1 sucrose, produced an improvement in the growth traits and did not induce anatomical and physiological disturbances.     

The process of embryo abortion of stenospermocarpic grape and it develops into plantlet in vitro using embryo rescue

Plant Cell, Tissue and Organ Culture (PCTOC) - The fruit of ‘Dangshansuli’ pear is yellowish green in colour, while that of its mutant ‘Xiusu’ is russet in colour. A...     

呼和浩特市周边地下水CPR和DPANN类群的检测及多样性分析

【背景】候选门级辐射类群(candidate phyla radiation, CPR)和DPANN是与绝大多数已知细菌和古菌具有显著差异的独特类群,因发现较晚,人们对其认识还非常有限。已知二者类群庞大、存在广泛,但在不同生境中的多样性研究还较少,生态功能尚属未知。【目的】分析不同地下水中CPR和DPANN的多样性,探讨不同方法对CPR和DPANN检出及富集的影响。【方法】采用0.1μm滤膜收集菌体和宏基因组测序的方法分析呼和浩特市周边4个不同地下水中CPR和DPANN的多样性。比较宏基因组测序与16S rRNA基因扩增子测序对CPR和DPANN检出的影响,以及不同过滤方式和不同滤膜组合对CPR和DPANN富集的作用。【结果】4个地下水样品CPR类群检出33-64个菌门,相对丰度在0.17%-1.67%之间;DPANN检出1-7个菌门,相对丰度在0.00093%-0.07100%之间。对于CPR和DPANN,16SrRNA基因V3-V4区扩增子测序仅检出了纳古菌门(Nanoarchaeota)。1.2μm与0.1μm滤膜组合具有最好的CPR和DPANN富集效果,在及时更换滤膜的过滤方式...     

中国植物采集先行者钟观光的采集考证

基于文献与标本的研究, 本文重新梳理和考证了中国植物采集先行者钟观光先生的采集历史。钟观光是我国第一个进行大规模植物标本采集的学者, 已知其最早的标本采自1912年(采集于北京), 最晚的是1933年(采集于浙江)。目前能够确定的钟观光采集的馆藏标本计10,228份, 其中大部分保存于北京大学生物系植物标本室(PEY, 4,584份)、中国科学院植物研究所植物标本馆(PE, 2,966份)和北京师范大学生命科学学院植物标本室(BNU, 2,032份), 共计9,582份, 约占钟观光馆藏标本总数的93.7%。英国皇家植物园邱园植物标本馆、爱丁堡植物园标本馆、美国哈佛大学植物标本馆等亦存有少量钟观光采集的标本(16份)。     

Protective Effects of Anthocyanins from Coreopsis tinctoria against Oxidative Stress Induced by Hydrogen Peroxide in MIN6 Cells

Anthocyanins (AC) from Coreopsis tinctoria possesses strong antioxidant properties, while the effects of AC on cells damage induced by reactive oxygen species (ROS) in diabetes mellitus diseases progression have not been reported. The present study was carried out to evaluate the protective property of AC against cellular oxidative stress with an experimental model, H₂O₂‐exposed MIN6 cells. AC could reverse the decrease of cell viability induced by H₂O₂ and efficiently suppressed cellular ROS production and cell apoptosis. In addition, Real‐time PCR and Western blot analyses indicated that AC could protect MIN6 cells against oxidative injury through increasing the translocation of Nrf2 into nuclear, decreasing the phosphorylation level of p38 and up‐regulating the protein expression of antioxidant enzyme (SOD1, SOD2 and CAT). Thus, this study provides evidence to support the beneficial effect of AC in inhibiting MIN6 cells from H₂O₂‐induced oxidative injury.     

Hydrolysis of filter-paper cellulose to glucose by two recombinant endogenous glycosyl hydrolases of Coptotermes formosanus

Abstract Genes encoding for glycosyl hydrolases (GH) in multiple families were recovered from an expression sequence tag library of Coptotermes formosanus, a xylophagous lower termite species. Functional analyses of these genes not only shed light on the mechanisms the insect employs to successfully use cellulosic materials as energy sources, which may serve as strategic targets for designing molecular-based bio-pesticides, but also enrich discoveries of new cellulolytic enzymes for conversion of biomass into biofuel. Our study demonstrated that cellulose could be converted to glucose by two recombinant endogenous glycosyl hydrolases (endo-β-1,4 glucanase in GH9 and β-glucosidase in GH1). While the former cleaved cellulose to cellobiose and cellotriose, the resulting simple cellodextrins were digested to glucose. Both of the Escherichia coli-expressed recombinant proteins showed properties that could be incorporated in a glucose-based ethanol production program.     

Susceptibility to cell death induced by blockade of MAPK pathway in human colorectal cancer cells carrying Ras mutations is dependent on p53 status

Constitutive activation of mitogen-activated protein kinase (MAPK) pathway is implicated in a variety of human malignancies especially those that carry Ras mutations and is currently exploited as a cancer therapeutic target. The variability of response by cancer cells to the inhibition of the Ras/MAPK pathway both in vivo and in vitro, however, suggests that the genetic background of the tumor cell may modulate the effectiveness of this directed therapeutic. In a panel of colorectal cancer cell lines that carry Ras mutations and have constitutively active MEK/MAPK, we found that inhibition of the MAPK upstream kinase MEK by the small molecular MEK inhibitor U0126 induced cell death only in p53 wild-type cells. By contrast, p53-deficient cells were not affected by blocking the MEK/MAPK pathway. Using isogenic colon cancer cell lines and RNA interference, we show that loss of p53 significantly reduces MAPK phosphorylation and renders cells resistant to U0126 treatment. These findings reveal a critical role for p53 in MAPK-driven cell survival and place p53 upstream in the control cascade of MAPK activity. The therapeutic implication of these observations is that MAPK inhibitors will be most beneficial as a therapeutic agent in p53 normal colon cancers where constitutively active MAPK resulting from a Ras mutation is required for cell survival.