X-Ray Microscopy: Preparations for Studies of Frozen Hydrated Specimens

X-ray microscopes provide higher resolution than visible light microscopes. Wet, biological materials with a water thickness of up to about 10 μm can be imaged with good contrast using soft X-rays with wavelengths between the oxygen and carbon absorption edges (at 24 and 43 Å). The Stony Brook group has developed and operates a scanning transmission X-ray microscope (STXM) at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory. The microscope is used for imaging with a current resolution of 50 nm, and for elemental and chemical state mapping. Radiation damage imposes a significant limitation upon high resolution X-ray microscopy of room temperature wet specimens. Experience from electron microscopy suggests that cryo techniques allow vitrified specimens to be imaged repeatedly. This is due to the increased radiation stability of biological specimens in the frozen hydrated state. Better radiation stability has been shown recently with a cryo transmission X-ray microscope developed by the University of Gottingen, operating at the BESSY storage ring in Berlin, Germany. At Stony Brook, we are developing a cryo scanning transmission X-ray microscope (CryoSTXM) to carry out imaging and spectra-microscopy experiments on frozen hydrated specimens. This article will give an outlook onto the research projects that we plan to perform using the CryoSTXM

Evaluation of cortisol precursors for the diagnosis of pituitary-dependent hypercortisolism in dogs

The serum concentrations of cortisol, 17alpha-hydroxypregnenolone, 17alpha-hydroxyprogesterone, 21-deoxycortisol and 11-deoxycortisol were measured in 19 healthy dogs, 15 dogs with pituitary-dependent hypercortisolism (pdh) and eight dogs with other diseases before and one hour after an injection of synthetic adrenocorticotrophic hormone (acth). At both times the dogs with pdh had significantly higher concentrations of cortisol, 17alpha-hydroxypregnenolone, 17alpha-hydroxyprogesterone and 21-deoxycortisol than the healthy dogs. Basal 11-deoxycortisol concentrations were also significantly higher in dogs with pdh compared with healthy dogs. When compared with the dogs with other diseases, the dogs with pdh had significantly higher basal and post-acth cortisol and basal 21-deoxycortisol, and significantly lower post-acth 11-deoxycortisol concentrations. The dogs with other diseases had significantly higher post-acth cortisol, 17alpha-hydroxyprogesterone and 11-deoxycortisol concentrations than the healthy dogs. In general, the post-acth concentrations of 17alpha-hydroxypregnenolone, 17alpha-hydroxyprogesterone, 11-deoxycortisol and 21-deoxycortisol were more variable than the post-acth concentrations of cortisol, resulting in large overlaps of the concentrations of these hormones between the three groups. A two-graph receiver operating characteristic (ROC) analysis was used to maximise the sensitivity and specificity of each hormone for diagnosing hypercortisolism; it showed that the post-acth concentration of cortisol had the highest sensitivity and specificity. The overlaps between the healthy dogs, the dogs with pdh and the dogs with other diseases suggested that the individual precursor hormones would not be useful as a screening test for hypercortisolism

Peripheral Sensory Neuropathy Associates With Micro- or Macroangiopathy: Results from a population-based study of type 2 diabetic patients in Sweden

OBJECTIVE—To assess associations between peripheral sensory neuropathy (PSN) and other diabetes-related complications

Changes of the phagosomal elemental concentrations by Mycobacterium tuberculosis Mramp

Pathogenic mycobacteria survive within phagosomes which are thought to represent a nutrient-restricted environment. Divalent cation transporters of the Nramp family in phagosomes and mycobacteria (Mramp) may compete for metals that are crucial for bacterial survival. The elemental concentrations in phagosomes of macrophages infected with wild-type Mycobacterium tuberculosis (M. tuberculosis strain H37Rv) and a M. tuberculosis Mramp knockout mutant (Mramp-KO), derived from a clinical isolate isogenic to the strain MT103, were compared. Time points of 1 and 24 h after infection of mouse peritoneal macrophages (bcgS) were compared in both cases. Increased concentrations of P, Ni and Zn and reduced Cl concentration in Mramp-KO after 1 h of infection were observed, compared to M. tuberculosis vacuoles. After 24 h of infection, significant differences in the P, Cl and Zn concentrations were still present. The Mramp-KO phagosome showed a significant increase of P, Ca, Mn, Fe and Zn concentrations between 1 and 24 h after infection, while the concentrations of K and Ni decreased. In the M. tuberculosis vacuole, the Fe concentration showed a similar increase, while the Cl concentration decreased. The fact that the concentration of several divalent cations increased in the Mramp-KO strain suggests that Mramp may have no impact on the import of these divalent cations into the mycobacterium, but may function as a cation efflux pump. The concordant increase of Fe concentrations within M. tuberculosis, as well as within the Mramp-KO vacuoles, implies that Mramp, in contrast to siderophores, might not be important for the attraction of Fe and its retention in phagosomes of unstimulated macrophages

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Nanostructured TiO2 and graphene-based materials constitute components of actual interest in devices related to solar energy conversion and storage. In this work, we show that a thin layer of electrochemically reduced graphene oxide (ECrGO), covering nanostructured TiO2 photoelectrodes, can significantly improve the photoactivity. In order to understand the working principle, ECrGO/TiO2 photoelectrodes with different ECrGO thicknesses were prepared and studied by a set of photoelectrochemical measurements. Methanol in alkaline conditions was employed as effective hole acceptor probe to elucidate the electronic phenomena in the electrode layers and interfaces. These studies underline the hole accepting properties of ECrGO and reveal the formation of a p-n junction at the interface between ECrGO and TiO2. It is shown for the first time that the resulting space charge region of about 10 nm defines the operational functionality of the ECrGO layer. Films thinner than the space charge region act as hole transport layer (HTL), which efficiently transfers holes to the liquid interface thus leading to enhanced photoactivity. Thicker films however act as hole blocking layer (HBL), resulting in a systematic decrease of the photoactivity. The finding of a thickness dependent threshold value for the operation of ECrGO as HTL and HBL is of general interest for the fabrication of optoelectronic devices with improved performance

Warship wrecks and their munition cargos as a threat to the marine environment and humans: The V 1302 “JOHN MAHN” from World War II

In addition to endangering sea traffic, cable routes, and wind farms, sunken warship wrecks with dangerous cargo, fuel, or munitions on board may emerge as point sources for environmental damage. Energetic compounds such as TNT (which could leak from these munitions) are known for their toxicity, mutagenicity, and carcinogenicity. These compounds may cause potential adverse effects on marine life via contamination of the marine ecosystem, and their entry into the marine and human food chain could directly affect human health. To ascertain the impending danger of an environmental catastrophe posed by sunken warships, the North Sea Wrecks (NSW) project (funded by the Interreg North Sea Region Program) was launched in 2018. Based on historical data (derived from military archives) including the calculated amount of munitions still on board, its known location and accessibility, the German World War II ship “Vorpostenboot 1302” (former civilian name - “JOHN MAHN”) was selected as a case study to investigate the leakage and distribution of toxic explosives in the marine environment. The wreck site and surrounding areas were mapped in great detail by scientific divers and a multibeam echosounder. Water and sediment samples were taken in a cross-shaped pattern around the wreck. To assess a possible entry into the marine food chain, aged mussels were exposed at the wreck, and wild fish (pouting), a sedentary species that stays locally at the wreck, were caught. All samples were analyzed for the presence of TNT and derivatives thereof by GC–MS/MS analysis. As a result, we could provide evidence that sunken warship wrecks emerge as a point source of contamination with nitroaromatic energetic compounds leaking from corroding munitions cargo still on board. Not only did we find these explosive substances in bottom water and sediment samples around the wreck, but also in the caged mussels as well as in wild fish living at the wreck. Fortunately so far, the concentrations found in mussel meat and fish filet were only in the one-digit ng per gram range thus indicating no current concern for the human seafood consumer. However, in the future the situation mayworsen as the corrosion continues. Fromour study, it is proposed that wrecks should not only be ranked according to critical infrastructure and human activities at sea, but also to the threats they pose to the environment and the human seafood consumer