Simple quantitative assessment of the outdoor versus indoor airborne transmission of viruses and COVID-19.

In this paper we develop a simple model of the inhaled flow rate of aerosol particles of respiratory origin i.e. that have been exhaled by other people. A connection is made between the exposure dose and the probability of developing an airborne disease. This allows a simple assessment of the outdoor versus indoor risk of contamination to be made in a variety of meteorological situations. It is shown quantitatively that for most cases, the outdoor risk is orders of magnitude less than the indoor risk and that it can become comparable only for extremely specific meteorological and topographical situations. It sheds light on various observations of COVID-19 spreading in mountain valleys with temperature inversions while at the same time other areas are much less impacted.

Computer-aided manufacturing and focused ion beam technology enable machining of complex micro- and nano-structures.

We present a novel framework for the fabrication of geometrically complex structures at the micro- and nano-scale which relies on the synergy of integrated computer-aided design and manufacturing systems (CAD/CAM) and focused ion beam (FIB) technology in a scanning electron microscope. Here we utilise industry standard G-code syntax, for the first time, to FIB machining by designing geometries with CAD, defining machining strategies and exporting G-codes with CAM and generating a coordinate list-based beam path by using a custom-built interpreter program. This allows the fabrication of complex structures from CAD models using syntax which is readily understood in the general fabrication industry. The use of G-code allows optimization of the beam path towards a reduction of beam blanking operations and tracing of contours, leading to minimized re-deposition of material. We give a detailed description of the method, use an application example to demonstrate advantages and prospects of the approach and provide the free and open-source interpreter program CAM2FIB for application of this method. We contrast and compare various existing available milling strategies and demonstrate the versatility of G-code based programming.

Modelling of ultraviolet light inactivation kinetics of methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, Clostridium difficile spores and murine norovirus on fomite surfaces.

AIMS: Quantitative data on the doses needed to inactivate micro-organisms on fomites are not available for ultraviolet applications. The goal of this study was to determine the doses of UV light needed to reduce bacteria and murine norovirus (MNV) on hard surface fomites through experimentation and to identify appropriate models for predicting targeted levels of reduction. METHODS AND RESULTS: Stainless steel and Formica laminate coupons were selected as they are common surfaces found in healthcare settings. Test organisms included methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), Clostridium difficile and MNV. The fomites were inoculated with 105 -107 bacteria or virus and exposed to a range of UV doses. The order of resistance to UV irradiation was virus, bacterial spore and vegetative cell. The best fitting inactivation curves suggested nonlinear responses to increasing doses after a 3-4 log reduction in the test organisms. The average UV doses required for a 3 log reduction in the C. difficile, MRSA and VRE were 16 000, 6164 and 11 228 (mJ-s cm-2 ) for stainless steel, respectively, and 16 000, 11 727 and 12 441 (mJ-s cm-2 ) for Formica laminate, respectively. CONCLUSIONS: Higher UV light doses are required to inactivate bacteria and viruses on hard surfaces than in suspension. Greater doses are needed to inactivate bacterial spores and MNV compared to vegetative bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Quantitative data and models on UV light doses needed to inactivate bacteria and MNV on hard surfaces are now available. The generalizable results of this study can be used to estimate required UV dosages to achieve targeted levels of inactivation based on estimated levels of contamination or to support quantitative microbial risk assessments.

Effect of Tempol on the prevention of irradiation-induced mucositis in miniature pigs.

OBJECTIVE: The goals of this study were to (i) establish a useful miniature pig (minipig) model for irradiation-induced oral mucositis and (ii) evaluate the effect of Tempol to prevent its development. METHODS AND MATERIALS: Minipigs were irradiated with 6 Gy for five consecutive days targeting the entire oral cavity. To prevent radiation damage, minipigs were treated with 30 mg kg-1 Tempol 10 min before irradiation (n = 4), while the radiation-alone group was similarly injected with saline (n = 4). Lesions were graded using an oral mucositis score and visual inspection every 3 days, and biopsy of multiple sites was performed at day 18. Weight and chest and abdominal circumferences were measured every 3 days. RESULTS: Lesions began about 12 days after the first irradiation fraction and healed about 30 days after irradiation. Epithelial thickness was calculated on the lingual and buccal mucosa on the 18th day after the first irradiation fraction. Tempol provided modest protection from ulceration after irradiation using this treatment strategy. CONCLUSIONS: This study established a useful large animal model for irradiation-induced oral mucositis and showed modest beneficial effects of Tempol in limiting tissue damage. The latter finding may be potentially valuable in preventing oral mucositis in patients receiving irradiation for head and neck cancers.

Oxidative stress in oral diseases.

Oxidative species, including reactive oxygen species (ROS), are components of normal cellular metabolism and are required for intracellular processes as varied as proliferation, signal transduction, and apoptosis. In the situation of chronic oxidative stress, however, ROS contribute to various pathophysiologies and are involved in multiple stages of carcinogenesis. In head and neck cancers specifically, many common risk factors contribute to carcinogenesis via ROS-based mechanisms, including tobacco, areca quid, alcohol, and viruses. Given their widespread influence on the process of carcinogenesis, ROS and their related pathways are attractive targets for intervention. The effects of radiation therapy, a central component of treatment for nearly all head and neck cancers, can also be altered via interfering with oxidative pathways. These pathways are also relevant to the development of many benign oral diseases. In this review, we outline how ROS contribute to pathophysiology with a focus toward head and neck cancers and benign oral diseases, describing potential targets and pathways for intervention that exploit the role of oxidative species in these pathologic processes.

A review of methods for the calculation of solution free energies and the modelling of systems in solution.

Over the past decade, pharmaceutical companies have seen a decline in the number of drug candidates successfully passing through clinical trials, though billions are still spent on drug development. Poor aqueous solubility leads to low bio-availability, reducing pharmaceutical effectiveness. The human cost of inefficient drug candidate testing is of great medical concern, with fewer drugs making it to the production line, slowing the development of new treatments. In biochemistry and biophysics, water mediated reactions and interactions within active sites and protein pockets are an active area of research, in which methods for modelling solvated systems are continually pushed to their limits. Here, we discuss a multitude of methods aimed towards solvent modelling and solubility prediction, aiming to inform the reader of the options available, and outlining the various advantages and disadvantages of each approach.

CD44 is prognostic for overall survival in the NCI randomized trial on breast conservation with 25 year follow-up.

CD44 is a transmembrane glycoprotein involved in numerous cellular functions, including cell adhesion and extracellular matrix interactions. It is known to be functionally diverse, with alternative splice variants increasingly implicated as a marker for tumor-initiating stem cells associated with poor prognosis. Here, we evaluate CD44 as a potential marker of long-term breast cancer outcomes. Tissue specimens from patients treated on the National Cancer Institute 79-C-0111 randomized trial of breast conservation versus mastectomy between 1979 and 1987 were collected, and immunohistochemistry was performed using the standard isoform of CD44. Specimens were correlated with patient characteristics and outcomes. Survival analysis was performed using the log rank test. Fifty-one patients had evaluable tumor sections and available long-term clinical follow up data at a median follow up of 25.7 years. Significant predictors of OS were tumor size (median OFS 25.4 years for ≤2 cm vs. 7.5 years for >2 cm, p = 0.001), nodal status (median OS 17.2 years for node-negative patients vs. 6.7 years for node positive patients, p = 0.017), and CD44 expression (median OS 18.9 years for CD44 positive patients vs. 8.6 years for CD44 negative patients, p = 0.049). There was a trend toward increased PFS for patients with CD44 positive tumors (median PFS 17.9 vs. 4.3 years, p = 0.17), but this did not reach statistical significance. These findings illustrate the potential utility of CD44 as a prognostic marker for early stage breast cancer. Subgroup analysis in patients with lymph node involvement revealed CD44 positivity to be most strongly associated with increased survival, suggesting a potential role of CD44 in decision making for axillary management. As there is increasing interest in CD44 as a therapeutic target in ongoing clinical trials, the results of this study suggest additional investigation regarding the role CD44 in breast cancer is warranted.

Electron impact induced fragmentation of N2H⁺ and N2D⁺.

Electron impact dissociation of protonated and deuterated nitrogen ions has been studied using a crossed beams apparatus. Absolute cross sections for dissociation channels producing N(+) and NH(+), respectively, are presented. The observations of subthreshold signals in these measurements indicate the presence of ro-vibrationally and possibly electronically excited states in the parent ions. Comparisons with other measurements are given.

Resistance exercise and lipoproteins in postmenopausal women.

The specific aims of this study were to quantify the effects of 12 weeks of resistance training, as well as a single session of resistance exercise on lipids and lipoproteins in obese, postmenopausal women. 21 obese, postmenopausal women, not on hormone replacement therapy (age=65.9 ± 0.5 yr; BMI=32.7 ± 0.8 kg/m(2)), were randomly assigned to control (n=12) and exercise (n=9) groups matched for age and BMI. For 12 weeks, 3 days/week, the exercise group performed 10 whole body resistance exercises (3 sets at 8-RM). Fasting (10 h) blood samples were collected immediately prior to and 24 h after the first and last exercise and control session. Serum was assayed for concentrations of total cholesterol, triglycerides, LDL-C, HDL-C, HDL 2-C, HDL 3-C, non-HDL-C and TC:HDL and LDL:HDL ratios. The exercise group exhibited a significant (P<0.01) improvement in muscular strength, but no change in BMI, body mass or body composition post-training. Total cholesterol, LDL-C and non-HDL-C were significantly (P<0.05) lower in the exercise compared to the control group following the 12 weeks of resistance training. Whole body resistance training provides obese, postmenopausal women a non-pharmacological approach for the reduction of lipid and lipoprotein-cholesterol concentrations.

Determining the water content of nominally anhydrous minerals at the nanometre scale.

The amount and distribution of water in nominally anhydrous minerals (NAMs) are usually determined by Fourier-transform infrared spectroscopy. This method is limited by the spot size of the beam to the study of samples with dimensions greater than a few micrometers. Here, we demonstrate the potential of using photoinduced force microscopy for the measurement of water in NAMs with samples sizes down to the nanometer scale with a study of water concentration across grain boundaries in forsterite. This development will enable the study of water speciation and diffusion in small-grained rock matrixes and allow a determination of the influence of nanoscale heterogeneity on the incorporation of water to NAMs.

Nitric oxide potentiates hydrogen peroxide-induced killing of Escherichia coli.

Previously, we reported that nitric oxide (NO) provides significant protection to mammalian cells from the cytotoxic effects of hydrogen peroxide (H2O2). Murine neutrophils and activated macrophages, however, produce NO, H2O2, and other reactive oxygen species to kill microorganisms, which suggests a paradox. In this study, we treated bacteria (Escherichia coli) with NO and H2O2 for 30 min and found that exposure to NO resulted in minimal toxicity, but greatly potentiated (up to 1,000-fold) H2O2-mediated killing, as evaluated by a clonogenic assay. The combination of NO/H2O2 induced DNA double strand breaks in the bacterial genome, as shown by field-inverted gel electrophoresis, and this increased DNA damage may correlate with cell killing. NO was also shown to alter cellular respiration and decrease the concentration of the antioxidant glutathione to a residual level of 15-20% in bacterial cells. The iron chelator desferrioxamine did not stop the action of NO on respiration and glutathione decrease, yet it prevented the NO/H2O2 synergistic cytotoxicity, implicating metal ions as critical participants in the NO/H2O2 cytocidal mechanism. Our results suggest a possible mechanism of modulation of H2O2-mediated toxicity, and we propose a new key role in the antimicrobial macrophagic response for NO.

Evaluation of sub-microsecond recovery resonators for in vivo electron paramagnetic resonance imaging.

Time-domain (TD) electron paramagnetic resonance (EPR) imaging at 300MHz for in vivo applications requires resonators with recovery times less than 1 micros after pulsed excitation to reliably capture the rapidly decaying free induction decay (FID). In this study, we tested the suitability of the Litz foil coil resonator (LCR), commonly used in MRI, for in vivo EPR/EPRI applications in the TD mode and compared with parallel coil resonator (PCR). In TD mode, the sensitivity of LCR was lower than that of the PCR. However, in continuous wave (CW) mode, the LCR showed better sensitivity. The RF homogeneity was similar in both the resonators. The axis of the RF magnetic field is transverse to the cylindrical axis of the LCR, making the resonator and the magnet co-axial. Therefore, the loading of animals, and placing of the anesthesia nose cone and temperature monitors was more convenient in the LCR compared to the PCR whose axis is perpendicular to the magnet axis.

Transcriptional responses to ionizing radiation reveal that p53R2 protects against radiation-induced mutagenesis in human lymphoblastoid cells.

The p53 protein has been implicated in multiple cellular responses related to DNA damage. Alterations in any of these cellular responses could be related to increased genomic instability. Our previous study has shown that mutations in p53 lead to hypermutability to ionizing radiation. To investigate further how p53 is involved in regulating mutational processes, we used 8K cDNA microarrays to compare the patterns of gene expression among three closely related human cell lines with different p53 status including TK6 (wild-type p53), NH32 (p53-null), and WTK1 (mutant p53). Total RNA samples were collected at 1, 3, 6, 9, and 24 h after 10 Gy gamma-irradiation. Template-based clustering analysis of the gene expression over the time course showed that 464 genes are either up or downregulated by at least twofold following radiation treatment. In addition, cluster analyses of gene expression profiles among these three cell lines revealed distinct patterns. In TK6, 165 genes were upregulated, while 36 genes were downregulated. In contrast, in WTK1 75 genes were upregulated and 12 genes were downregulated. In NH32, only 54 genes were upregulated. Furthermore, we found several genes associated with DNA repair namely p53R2, DDB2, XPC, PCNA, BTG2, and MSH2 that were highly induced in TK6 compared to WTK1 and NH32. p53R2, which is regulated by the tumor suppressor p53, is a small subunit of ribonucleotide reductase. To determine whether it is involved in radiation-induced mutagenesis, p53R2 protein was inhibited by siRNA in TK6 cells and followed by 2 Gy radiation. The background mutation frequencies at the TK locus of siRNA-transfected TK6 cells were about three times higher than those seen in TK6 cells. The mutation frequencies of siRNA-transfected TK6 cells after 2 Gy radiation were significantly higher than the irradiated TK6 cells without p53R2 knock down. These results indicate that p53R2 was induced by p53 protein and is involved in protecting against radiation-induced mutagenesis.

Nitroxide stable radicals protect beating cardiomyocytes against oxidative damage.

The protective effect of stable nitroxide radicals against oxidative damage was studied using cardiomyocyte cultures obtained from newborn rats. Monolayered cardiomyocytes were exposed to H2O2 and the effect on spontaneous beating and leakage of LDH was determined. Hydrogen peroxide irreversibly blocked rhythmic beating and resulted in a significant membrane injury as shown by release of LDH. The injury was prevented by catalase which removes H2O2 and by cell-permeable, metal-chelating agents such as desferrioxamine or bipyridine. In contrast, reagents which are excluded from the cell such as superoxide dismutase or DTPA did not protect the cells against H2O2. Five- and six-membered ring, stable nitroxide radicals which have previously been shown to chemically act as low-molecular weight, membrane-permeable, SOD-mimetic compounds provided full protection. The nitroxides prevented leakage of LDH and preserved normal cardiomyocyte contractility, presumably by intercepting intracellular O2-radicals. Alternatively, protection may result through nitroxides reacting with reduced transition metal ions or by detoxifying secondary organic radicals.

Bromodeoxyuridine in tumors and chromosomes detected with a monoclonal antibody.

Using a monoclonal antibody to bromodeoxyuridine (BUdR) and immunohistochemistry, we measured the incorporation of this thymidine analogue into the DNA of human normal and malignant cells exposed in vivo. BUdR given as a constant intravenous infusion for 12 or 24 h daily for up to 13 d resulted in a steady-state plasma level of 10(-6) M during the infusion. We demonstrated extensive incorporation of BUdR into both normal skin, normal bone marrow, and malignant melanoma cells. In addition, this infusion of BUdR was adequate to identify sister chromatid exchanges from human marrow chromosomes exposed in vivo. Using this constant infusion, significant but reversible (acute) toxicity was observed with myelosuppression and skin photosensitivity. These techniques, which are considerably less cumbersome and time-consuming than the use of radioactive isotopes of thymidine, can be used for further human studies of cell kinetics and chromosomal replication in both normal and malignant cells.

Transmission Kikuchi diffraction versus electron back-scattering diffraction: A case study on an electron transparent cross-section of TWIP steel.

The present case study compares transmission Kikuchi diffraction (TKD) with electron back-scattering diffraction (EBSD) on the same area of an electron transparent cross-section of a twinning induced plasticity steel. While TKD expectedly provides better clarity of internal defect substructures in the band contrast map, EBSD returns orientation data that approaches the quality of the TKD map. This was rationalised by Monte Carlo simulations of the electron energy spreads, which showed that due to the geometry-based compromises associated with adapting a conventional EBSD detector (which is off-axis with respect to the incident electron beam) to TKD, a broadening in the electron energy distribution of the forward-scattered electrons collected on the detector phosphor screen, is unavoidable. In this circumstance, the values of the full-widths at half-maximum of the energy distributions for TKD and EBSD are of the same order. It follows that EBSD on electron transparent cross-sections may be a viable alternative to TKD when: (i) conventional EBSD detectors are adapted to TKD and, (ii) sample microstructures comprise features whose sizes do not mandate the application of TKD.

Protein folds and functions.

BACKGROUND: The recent rapid increase in the number of available three-dimensional protein structures has further highlighted the necessity to understand the relationship between biological function and structure. Using structural classification schemes such as SCOP, CATH and DALI, it is now possible to explore global relationships between protein fold and function, something which was previously impractical. RESULTS: Using a relational database of CATH data we have generated fold distributions for arbitrary selections of proteins automatically. These distributions have been examined in the light of protein function and bound ligand. Different enzyme classes are not clearly reflected in distributions of protein class and architecture, whereas the type of bound ligand has a much more dramatic effect. CONCLUSIONS: The availability of structural classification data has enabled this novel overview analysis. We conclude that function at the top level of the EC number enzyme classification is not related to fold, as only a very few specific residues are actually responsible for enzyme activity. Conversely, the fold is much more closely related to ligand type.

In vitro studies of Taxol as a radiation sensitizer in human tumor cells.

BACKGROUND: Cells exposed to paclitaxel (Taxol) develop a cell cycle arrest in G2/M. It has long been recognized that late G2 and M are the most radiosensitive phases of the cell cycle. PURPOSE: These studies were performed to assess the in vitro radiosensitization properties of paclitaxel in human tumor cell lines. METHODS: The effect of paclitaxel at concentrations ranging from 0 to 10,000 nM on the radiation sensitivity (from 0 to as much as 10 Gy in certain experiments) of human breast (MCF-7), lung (A549), ovary (OVG-1), and pancreas (PC-Sh) adenocarcinoma cells was determined using clonogenic assays. DNA flow cytometry studies were performed to define the cell cycle characteristics of populations of cells that had been treated for 6-72 hours with 0, 100, 1000, or 10,000 nM paclitaxel. RESULTS: All cell lines developed a G2/M block after exposure to 100-10,000 nM paclitaxel for 24 hours. However, the degree of radiosensitization produced by paclitaxel varied among the cell lines. The sensitizer enhancement ratio (SER) of paclitaxel at 10% survival was 1.8 in MCF-7 cells and 1.6 in OVG-1 cells. However, paclitaxel at any concentration was unable to enhance the radiation sensitivity of A549 cells. PC-Sh cells demonstrated a complex and inconsistent radiosensitization response to paclitaxel. At 10% survival, an SER of 1.5 was observed in PC-Sh cells. However, at 1% survival, no radiosensitization was observed in PC-Sh cells. Maneuvers that prevented paclitaxel from producing a G2/M block, including coincident treatment with cycloheximide or treatment of cells in plateau phase of growth, completely abrogated the radiosensitization afforded by paclitaxel in MCF-7 cells. CONCLUSIONS: Paclitaxel is a modest radiosensitizer in some, but not all, human tumor cells. The degree of radiosensitization that we have observed with paclitaxel is similar to what has been found with other chemotherapeutic agents. The absence of radiosensitization by paclitaxel in MCF-7 cells grown to plateau phase or treated with cycloheximide implies that the development of a G2/M block is a necessary condition for paclitaxel radiosensitization. However, the inability of paclitaxel to radiosensitize A549 cells despite the presence of a G2/M block in those cells demonstrates that a G2/M block is not a sufficient condition for paclitaxel radiosensitization. IMPLICATIONS: Paclitaxel can radiosensitize to a modest degree some, but not all, human cell lines by a mechanism that requires the production of a G2/M cell cycle block. Additional studies are needed to define more clearly the mechanism by which paclitaxel radiosensitizes cells.

Heterogeneity in the radiation survival curves and biochemical properties of human lung cancer cell lines.

Human lung cancers of distinct histology exhibit different responses to radiation therapy in vivo. For examination of the basis of this phenomenon, the radiation survival curves and levels of relevant enzymes were determined in 16 lung cancer cell lines derived from tumors of different histology. These included lines from 5 adenocarcinomas, 7 small cell tumors, 3 variant small cell tumors, and 1 large cell tumor. These findings were compared to those obtained with the use of a normal skin fibroblast cell line. Whether cloned in liquid culture or soft agarose, cell lines had similar radiation survival curves. These curves were consistent with the apparent in vivo radiation responsiveness of the tumors. Although considerable heterogeneity in radiation survival curves was observed among the cell lines, cells from large cell lines and small variant lines had pronounced shoulders and extrapolation numbers (n) from 5.6 to 14. In contrast, cells from small cell lines and adenocarcinoma cell lines were more "sensitive" (-n values of 1-3.3). In these cell lines, levels of DNA polymerase beta, glutathione (GSH), GSH transferase, GSH reductase (NAD(P)H), gamma-glutamyltransferase did not correlate with radiation parameters of sensitivity. DNA polymerase beta and GSH levels were, however, higher than those in a line of normal skin fibroblasts. These cell lines may be useful in identifying the basis of the variable responsiveness of human lung cancer cells to ionizing radiation.

212Bismuth linked to an antipancreatic carcinoma antibody: model for alpha-particle-emitter radioimmunotherapy.

For comparison of cytotoxicity from alpha-particle irradiation with that from conventional x-irradiation, 212Bi, an alpha-emitting radionuclide, was attached to a monoclonal antibody that recognizes a cell surface antigen on human pancreatic carcinoma cells. For a given level of survival, the 212Bi-antibody complex was found to be approximately 20 times more efficient in cell killing than x-irradiation and 5 times more cytotoxic when compared with the cytotoxicity of an antigen-negative cell line or an isotype-matched control antibody. High linear energy transfer radioimmunotherapy using alpha emitters linked to monoclonal antibodies may be useful in vivo and in vitro for selectively killing target cell populations, especially those resistant to other forms of treatment.