Interlaboratory performance and quantitative PCR data acceptance metrics for NIST SRM® 2917

Surface water quality quantitative polymerase chain reaction (qPCR) technologies are expanding from a subject of research to routine environmental and public health laboratory testing. Readily available, reliable reference material is needed to interpret qPCR measurements, particularly across laboratories. Standard Reference Material® 2917 (NIST SRM® 2917) is a DNA plasmid construct that functions with multiple water quality qPCR assays allowing for estimation of total fecal pollution and identification of key fecal sources. This study investigates SRM 2917 interlaboratory performance based on repeated measures of 12 qPCR assays by 14 laboratories (n = 1008 instrument runs). Using a Bayesian approach, single-instrument run data are combined to generate assay-specific global calibration models allowing for characterization of within- and between-lab variability. Comparable data sets generated by two additional laboratories are used to assess new SRM 2917 data acceptance metrics. SRM 2917 allows for reproducible single-instrument run calibration models across laboratories, regardless of qPCR assay. In addition, global models offer multiple data acceptance metric options that future users can employ to minimize variability, improve comparability of data across laboratories, and increase confidence in qPCR measurements.

Use of diamond sensors for a high-flux, high-rate X-ray pass-through diagnostic

X-ray free-electron lasers (XFELs) deliver pulses of coherent X-rays on the femtosecond time scale, with potentially high repetition rates. While XFELs provide high peak intensities, both the intensity and the centroid of the beam fluctuate strongly on a pulse-to-pulse basis, motivating high-rate beam diagnostics that operate over a large dynamic range. The fast drift velocity, low X-ray absorption and high radiation tolerance properties of chemical vapour deposition diamonds make these crystals a promising candidate material for developing a fast (multi-GHz) pass-through diagnostic for the next generation of XFELs. A new approach to the design of a diamond sensor signal path is presented, along with associated characterization studies performed in the XPP endstation of the LINAC Coherent Light Source (LCLS) at SLAC. Qualitative charge collection profiles (collected charge versus time) are presented and compared with those from a commercially available detector. Quantitative results on the charge collection efficiency and signal collection times are presented over a range of approximately four orders of magnitude in the generated electron-hole plasma density.

Integrative Survey of 68 Non-overlapping Upstate New York Watersheds Reveals Stream Features Associated With Aquatic Fecal Contamination

Aquatic fecal contamination poses human health risks by introducing pathogens in water that may be used for recreation, consumption, or agriculture. Identifying fecal contaminant sources, as well as the factors that affect their transport, storage, and decay, is essential for protecting human health. However, identifying these factors is often difficult when using fecal indicator bacteria (FIB) because FIB levels in surface water are often the product of multiple contaminant sources. In contrast, microbial source-tracking (MST) techniques allow not only the identification of predominant contaminant sources but also the quantification of factors affecting the transport, storage, and decay of fecal contaminants from specific hosts. We visited 68 streams in the Finger Lakes region of Upstate New York, United States, between April and October 2018 and collected water quality data (i.e., Escherichia coli, MST markers, and physical–chemical parameters) and weather and land-use data, as well as data on other stream features (e.g., stream bed composition), to identify factors that were associated with fecal contamination at a regional scale. We then applied both generalized linear mixed models and conditional inference trees to identify factors and combinations of factors that were significantly associated with human and ruminant fecal contamination. We found that human contaminants were more likely to be identified when the developed area within the 60 m stream buffer exceeded 3.4%, the total developed area in the watershed exceeded 41%, or if stormwater outfalls were present immediately upstream of the sampling site. When these features were not present, human MST markers were more likely to be found when rainfall during the preceding day exceeded 1.5 cm. The presence of upstream campgrounds was also significantly associated with human MST marker detection. In addition to rainfall and water quality parameters associated with rainfall (e.g., turbidity), the minimum distance to upstream cattle operations, the proportion of the 60 m buffer used for cropland, and the presence of submerged aquatic vegetation at the sampling site were all associated based on univariable regression with elevated levels of ruminant markers. The identification of specific features associated with host-specific fecal contaminants may support the development of broader recommendations or policies aimed at reducing levels of aquatic fecal contamination.

Inhibin is present in the corpus luteum of pseudopregnant rats and can interact with progesterone to inhibit resumption of estrous cycles

The corpora lutea (CL) of ovaries of adult pseudopregnant (PSP) rats were stained by immunohistochemistry for inhibin alpha subunit using sheep alpha-chain1-27 antibody as a measure of inhibin content. Staining was light in estrous cycle CL (stage III), increased in Day 2 and Day 4 PSP CL and reached maximal density on day 6 PSP when both large cells and many small cells stained. Staining was decreased in CL from 8 and 10 day PSP. Granulosa cells of growing follicles showed light stain on days 8 and 10 of PSP. Adult female rats were treated for 5 days beginning at estrous cycle Stage III (cornified masses). In Experiment 1, three groups of rats were used: 1. implanted with 30mm progesterone capsules and injected with saline, 2. implanted with 30mm progesterone capsules and injected with 10 ng rh inhibin A daily, 3. implanted with empty capsules and injected with 10 ng rh inhibin A daily. Both groups of rats with progesterone implants had significantly slower return of cycling after removal of the capsules than did the rats injected with 10ng rh inhibin A alone. In Experiment 2, the same treatments were given except that 20ng of rh inhibin A (10ng 2x/day) was given to both inhibin treatment groups. Rats treated with progesterone and 20ng inhibin had a significantly slower return of cyclic activity (4.4 days) over that found in the other two treatment groups. We conclude that the absence of cyclic activity in PSP rats is possibly due to the secretion of both inhibin and progesterone by the CL.

Effects of irradiation on the interaction of fluorescent probes with lymphocytes

Low doses of radiation reduce the rate and magnitude of fluorescent probe interaction with spleen cells. The uptake of 8-anilino-naphthalene sulfonic acid (ANS), but not diphenyl-hexatriene (DPH), is reduced in a dose-dependent fashion in cells that receive 25-100 rads. The effects of irradiation are most evident in a "medium" fluorescent subpopulation with no effect observed for a "dim" subpopulation. Splenic lymphocytes enriched for T cells show lower uptake of ANS, compared with a B-cell-enriched population. In addition, the normal decrease in ANS fluorescence polarization that occurs during the initial 10 minutes of probe interaction is attenuated in irradiated cells. These findings are consistent with the notion that low doses of radiation limit the penetration of ANS, but not DPH, into a less restrictive microenvironment within the plasma membranes of T, but not B, cells.

The role of the macrophages in Marek's disease: in vitro and in vivo studies

Macrophages form S- and K-strain Leghorn chickens, susceptible and restant to Marek's disease (MD) respectively, were studied to determine the macrophage contribution to the dynamics of MD infection, tumorigenesis and genetic resistance to this disease. In vitro studies demonstrated that macrophages from bothstrains were similar in their responses toward JM strain of Marek's disease virus (MDV) and JM-1 tumor cells. Macrophages were observed to phagocytize JM virus, but the interiorized virus was not seen to replicate within the macrophage or induce antigenic changes of the cell membrane. Clearance of JM-1 tumor cells was by both cytolytic and phagocytic mechanism. In vivo selective suppression of macrophage functions by antimacrophage serum or trypan blue inoculations resulted in significantly elevated viral titers and increased tumorigenesis, as compared to infected, non-suppressed or non-infected control groups. Results from this study indicate that genetic susceptibility or resistance to MD, as exhibited by S- and K-strain chickens, respectively, is not controlled at the macrophage level. The role of the macrophage in MD infection appears to be specifically surveillance.