The DNA damage spectrum produced by simulated sunlight

The mutagenic effects of ultraviolet and solar irradiation are thought to be due to the formation of DNA photoproducts, most notably cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)PPs). Experimental systems for determining the levels and sequence dependence of photoproduct formation in DNA have often used high doses of short-wave (UVC) irradiation. We have re-assessed this issue by using DNA sequencing technologies and different doses of UVC as well as more physiologically relevant doses of solar irradiation emitted from a solar UV simulator. It has been questioned whether hot alkali treatment can detect (6-4)PPs at all sequence positions. With high UVC doses, the sequence distribution of (6-4)PPs was virtually identical when hot alkali or UV damage endonuclease (UVDE) were used for detection, which appears to validate both methods. The (6-4)PPs form at 5'-TpC and 5'CpC sequences but very low levels are seen at all other dipyrimidines including 5'-TpT. Contrary to expectation, we find that (6-4) photoproducts form at almost undetectable levels under conditions of irradiation for up to five hours with the solar UV simulator. The same treatment produces high levels of CPDs. In addition, DNA glycosylases, which recognize oxidized and ring-opened bases, did not produce significant cleavage of sunlight-irradiated DNA. From these data, we conclude that cyclobutane pyrimidine dimers are at least 20 to 40 times more frequent than any other DNA photoproduct when DNA or cells are irradiated with simulated sunlight.     

The role of vacuolar malate-transport capacity in crassulacean acid metabolism and nitrate nutrition. Higher malate-transport capacity in ice plant after crassulacean acid metabolism-induction and in tobacco under nitrate nutrition

Anion uptake by isolated tonoplast vesicles was recorded indirectly via increased H(+)-transport by H(+)-pumping of the V-ATPase due to dissipation of the electrical component of the electrochemical proton gradient, Deltamu(H+), across the membrane. ATP hydrolysis by the V-ATPase was measured simultaneously after the Palmgren test. Normalizing for ATP-hydrolysis and effects of chloride, which was added to the assays as a stimulating effector of the V-ATPase, a parameter, J(mal)(rel), of apparent ATP-dependent malate-stimulated H(+)-transport was worked out as an indirect measure of malate transport capacity. This allowed comparison of various species and physiological conditions. J(mal)(rel) was high in the obligate crassulacean acid metabolism (CAM) species Kalancho? daigremontiana Hamet et Perrier, it increased substantially after CAM induction in ice plant (Mesembryanthemum crystallinum), and it was positively correlated with NO(3)(-) nutrition in tobacco (Nicotiana tabacum). For tobacco this was confirmed by measurements of malate transport energized via the V-PPase. In ice plant a new polypeptide of 32-kD apparent molecular mass appeared, and a 33-kD polypeptide showed higher levels after CAM induction under conditions of higher J(mal)(rel). It is concluded that tonoplast malate transport capacity plays an important role in physiological regulation in CAM and NO(3)(-) nutrition and that a putative malate transporter must be within the 32- to 33-kD polypeptide fraction of tonoplast proteins.     

Low pH-induced formation of ion channels by clostridium difficile toxin B in target cells

Clostridium difficile toxin B (269 kDa), which is one of the causative agents of antibiotic-associated diarrhea and pseudomembranous colitis, inactivates Rho GTPases by glucosylation. Here we studied the uptake and membrane interaction of the toxin with eukaryotic target cells. Bafilomycin A1, which prevents acidification of endosomal compartments, blocked the cellular uptake of toxin B in Chinese hamster ovary cells cells. Extracellular acidification (pH 相似文献   

Biofilm formation by haloarchaea

A fluorescence‐based live‐cell adhesion assay was used to examine biofilm formation by 20 different haloarchaea, including species of Halobacterium, Haloferax and Halorubrum, as well as novel natural isolates from an Antarctic salt lake. Thirteen of the 20 tested strains significantly adhered (P‐value < 0.05) to a plastic surface. Examination of adherent cell layers on glass surfaces by differential interference contrast, fluorescence and confocal microscopy showed two types of biofilm structures. Carpet‐like, multi‐layered biofilms containing micro‐ and macrocolonies (up to 50 μm in height) were formed by strains of Halobacterium salinarum and the Antarctic isolate t‐ADL strain DL24. The second type of biofilm, characterized by large aggregates of cells adhering to surfaces, was formed by Haloferax volcanii DSM 3757^T and Halorubrum lacusprofundi DL28. Staining of the biofilms formed by the strongly adhesive haloarchaeal strains revealed the presence of extracellular polymers, such as eDNA and glycoconjugates, substances previously shown to stabilize bacterial biofilms. For Hbt. salinarum DSM 3754^T and Hfx. volcanii DSM 3757^T, cells adhered within 1 day of culture and remained viable for at least 2 months in mature biofilms. Adherent cells of Hbt. salinarum DSM 3754^T showed several types of cellular appendages that could be involved in the initial attachment. Our results show that biofilm formation occurs in a surprisingly wide variety of haloarchaeal species.     

Terrestrial ecosystems from space: a review of earth observation products for macroecology applications

Aim Earth observation (EO) products are a valuable alternative to spectral vegetation indices. We discuss the availability of EO products for analysing patterns in macroecology, particularly related to vegetation, on a range of spatial and temporal scales. Location Global. Methods We discuss four groups of EO products: land cover/cover change, vegetation structure and ecosystem productivity, fire detection, and digital elevation models. We address important practical issues arising from their use, such as assumptions underlying product generation, product accuracy and product transferability between spatial scales. We investigate the potential of EO products for analysing terrestrial ecosystems. Results Land cover, productivity and fire products are generated from long‐term data using standardized algorithms to improve reliability in detecting change of land surfaces. Their global coverage renders them useful for macroecology. Their spatial resolution (e.g. GLOBCOVER vegetation, 300 m; MODIS vegetation and fire, ≥ 500 m; ASTER digital elevation, 30 m) can be a limiting factor. Canopy structure and productivity products are based on physical approaches and thus are independent of biome‐specific calibrations. Active fire locations are provided in near‐real time, while burnt area products show actual area burnt by fire. EO products can be assimilated into ecosystem models, and their validation information can be employed to calculate uncertainties during subsequent modelling. Main conclusions Owing to their global coverage and long‐term continuity, EO end products can significantly advance the field of macroecology. EO products allow analyses of spatial biodiversity, seasonal dynamics of biomass and productivity, and consequences of disturbances on regional to global scales. Remaining drawbacks include inter‐operability between products from different sensors and accuracy issues due to differences between assumptions and models underlying the generation of different EO products. Our review explains the nature of EO products and how they relate to particular ecological variables across scales to encourage their wider use in ecological applications.     

Low back pain during pregnancy caused by a sacral stress fracture: a case report

Introduction

Sublingual hematoma secondary to excessive anticoagulation is a rare but potentially fatal condition, and few cases have been documented in the literature.

Case presentation

We report the case of a 73-year-old Caucasian woman who attended our Accident and Emergency department with massive sublingual hematoma causing superior displacement of the tongue. The condition was found to be the result of an elevated international normalized ratio, further complicated by a traumatic mandibular denture.

Conclusions

In summary, we recommend the immediate reversal of anticoagulation therapy on admission of patients with severe sublingual hematoma. We further advise surgical decompression/drainage if required and to continue meticulous monitoring. In all cases of early recognition of sublingual hematoma, prompt medical treatment and continuous clinical monitoring is essential, and may prevent the need for a surgical airway procedure.     

Development of a Small D-Enantiomeric Alzheimer's Amyloid-β Binding Peptide Ligand for Future In Vivo Imaging Applications

Alzheimer's disease (AD) is a devastating disease affecting predominantly the aging population. One of the characteristic pathological hallmarks of AD are neuritic plaques, consisting of amyloid-β peptide (Aβ). While there has been some advancement in diagnostic classification of AD patients according to their clinical severity, no fully reliable method for pre-symptomatic diagnosis of AD is available. To enable such early diagnosis, which will allow the initiation of treatments early in the disease progress, neuroimaging tools are under development, making use of Aβ-binding ligands that can visualize amyloid plaques in the living brain. Here we investigate the properties of a newly designed series of D-enantiomeric peptides which are derivatives of ACI-80, formerly called D1, which was developed to specifically bind aggregated Aβ1-42. We describe ACI-80 derivatives with increased stability and Aβ binding properties, which were characterized using surface plasmon resonance and enzyme-linked immunosorbent assays. The specific interactions of the lead compounds with amyloid plaques were validated by ex vivo immunochemistry in transgenic mouse models of AD. The novel compounds showed increased binding affinity and are promising candidates for further development into in vivo imaging compounds.