Evaluating Fire Temperatures During a Prescribed Burn of a Restored Tallgrass Prairie

Wildfire is recognized to have shaped the great prairies of the central US. While the vast majority of these grasslands have been lost there remain significant remnants as well as sites under active restoration. Prescribed fire is often used in these systems in order to maximize the success of the native grasses. Beginning in 1999 Cedarville University established a prairie restoration site and have used disturbances, such as fire, to maintain the system. Without this regular burn, the prairie would likely show decreased grass growth and increased growth of forb species. The Cedarville Prairie Restoration site has a variable topography, with several small hills and valleys. Such variations can affect the way that fire travels and burns. Therefore, our objective is to evaluate the relationships between prairie topography and fire temperature. We will use a 25 x 25 meter grid within the prairie, placing stakes attached to tags painted with thermo-sensitive paint at regular intervals along the grid. Following the prescribed fire in early April we will we analyze the tags to determine the temperature of the fire at each location on the grid. From this we will generate a heat intensity map in order to investigate patterns. In particular, we anticipate that the fire will burn at higher temperatures on slopes upward from its point of origin. We also anticipate that the fire will burn at lower temperatures in valley areas, due to moisture accumulation

Potential Prostate Cancer Drug Target: Bioactivation of Androstanediol by Conversion to Dihydrotestosterone: Figure 1.

High affinity binding of dihydrotestosterone (DHT) to the androgen receptor (AR) initiates androgen-dependent gene activation required for normal male sex development in utero, and contributes to prostate cancer development and progression in men. Under normal physiological conditions, DHT is synthesized predominantly by 5α-reduction of testosterone, the major circulating androgen produced by the testis. During androgen deprivation therapy, intratumoral androgen production is sufficient for AR activation and prostate cancer growth even though circulating testicular androgen levels are low. Recent studies indicate that the metabolism of 5α-androstane-3α,17β-diol by 17β-hydroxysteroid dehydrogenase 6 in benign prostate and prostate cancer cells is a major biosynthetic pathway for intratumoral synthesis of DHT that binds AR and initiates transactivation to promote prostate cancer growth during androgen deprivation therapy. Drugs that target the so-called backdoor pathway of DHT synthesis provide an opportunity to enhance clinical response to LHRH agonists or antagonists, AR antagonists, inhibitors of 5α-reductase enzymes, finasteride or dutasteride, and steroid metabolism enzyme inhibitors, ketoconazole or the recently available abiraterone acetate

Atmospheric Pressure Photoionization Tandem Mass Spectrometry of Androgens in Prostate Cancer

Androgen deprivation therapy is the most common treatment option for advanced prostate cancer. Almost all prostate cancers recur during androgen deprivation therapy, and new evidence suggests that androgen receptor activation persists despite castrate levels of circulating androgens. Quantitation of tissue levels of androgens is critical to understanding the mechanism of recurrence of prostate cancer during androgen deprivation therapy. A liquid chromatography atmospheric pressure photoionization tandem mass spectrometric method was developed for quantitation of tissue levels of androgens. Quantitation of the saturated keto-steroids dihydrotestosterone and 5-α-androstanedione required detection of a novel parent ion, [M + 15]+. The nature of this parent ion was explored and the method applied to prostate tissue and cell culture with comparison to results achieved using electrospray ionization

The Fading Optical Counterpart of GRB~970228, Six Months and One Year Later

We report on observations of the fading optical counterpart of the gamma-ray burst GRB 970228, made with the Hubble Space Telescope STIS CCD approximately six months after outburst and with the HST/NICMOS and Keck/NIRC approximately one year after outburst. The unresolved counterpart is detected by STIS at V=28.0 +/- 0.25, consistent with a continued power-law decline with exponent -1.14 +/- 0.05. The counterpart is located within, but near the edge of, a faint extended source with diameter ~0."8 and integrated magnitude V=25.8 +/- 0.25. A reanalysis of HST and NTT observations performed shortly after the burst shows no evidence of proper motion of the point source or fading of the extended emission. Only the extended source is visible in the NICMOS images with a magnitude of H=23.3 +/- 0.1. The Keck observations find K = 22.8 +/- 0.3. Several distinct and independent means of deriving the foreground extinction in the direction of GRB 970228 all agree with A_V = 0.75 +/- 0.2. After adjusting for Galactic extinction, we find that the size of the observed extended emission is consistent with that of galaxies of comparable magnitude found in the Hubble Deep Field (HDF) and other deep HST images. Only 2% of the sky is covered by galaxies of similar or greater surface brightness; therefore the extended source is almost certainly the host galaxy. Additionally, we find that the extinction-corrected V - H and V - K colors of the host are as blue as any galaxy of comparable or brighter magnitude in the HDF. Taken in concert with recent observations of GRB 970508, GRB 971214, and GRB 980703 our work suggests that all four GRBs with spectroscopic identification or deep multicolor broad-band imaging of the host lie in rapidly star-forming galaxies.Comment: 24 pages, Latex, 4 PostScript figures, to appear in the May 10 issue of The Astrophysical Journal (Note: displayed abstract is abridged

1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales

Sagittarius A*, the ~4 x 10^6 solar mass black hole candidate at the Galactic Center, can be studied on Schwarzschild radius scales with (sub)millimeter wavelength Very Long Baseline Interferometry (VLBI). We report on 1.3 mm wavelength observations of Sgr A* using a VLBI array consisting of the JCMT on Mauna Kea, the ARO/SMT on Mt. Graham in Arizona, and two telescopes of the CARMA array at Cedar Flat in California. Both Sgr A* and the quasar calibrator 1924-292 were observed over three consecutive nights, and both sources were clearly detected on all baselines. For the first time, we are able to extract 1.3 mm VLBI interferometer phase information on Sgr A* through measurement of closure phase on the triangle of baselines. On the third night of observing, the correlated flux density of Sgr A* on all VLBI baselines increased relative to the first two nights, providing strong evidence for time-variable change on scales of a few Schwarzschild radii. These results suggest that future VLBI observations with greater sensitivity and additional baselines will play a valuable role in determining the structure of emission near the event horizon of Sgr A*.Comment: 8 pages, submitted to ApJ

5α-reductase type 3 expression in human benign and malignant tissues: A comparative analysis during prostate cancer progression

A third isozyme of human 5α-steroid reductase, 5α-reductase-3, was identified in prostate tissue at the mRNA level. However, the levels of 5α-reductase-3 protein expression and its cellular localization in human tissues remain unknown

5α-ReductaseType 3 Enzyme in Benign and Malignant Prostate

Currently available 5α-reductase inhibitors are not completely effective for treatment of benign prostate enlargement, prevention of prostate cancer (CaP), or treatment of advanced castration-recurrent (CR) CaP. We tested the hypothesis that a novel 5α-reductase, 5α-reductase-3, contributes to residual androgen metabolism, especially in CR-CaP

Activation of the Androgen Receptor by Intratumoral Bioconversion of Androstanediol to Dihydrotestosterone in Prostate Cancer

The androgen receptor (AR) mediates the growth of benign and malignant prostate in response to dihydrotestosterone (DHT). In patients undergoing androgen deprivation therapy for prostate cancer, AR drives prostate cancer growth despite low circulating levels of testicular androgen and normal levels of adrenal androgen. In this report we demonstrate the extent of AR transactivation in the presence of 5α-androstane-3α,17β-diol (androstanediol) in prostate-derived cell lines parallels the bioconversion of androstanediol to DHT. AR transactivation in the presence of androstanediol in prostate cancer cell lines correlated mainly with mRNA and protein levels of 17β-hydroxysteroid dehydrogenase 6 (17β-HSD6), one of several enzymes required for the interconversion of androstanediol to DHT and the inactive metabolite, androsterone. Levels of retinol dehydrogenase 5, and dehydrogenase/reductase short-chain dehydrogenase/reductase family member 9, which also convert androstanediol to DHT, were lower than 17β-HSD6 in prostate-derived cell lines, and higher in the castration-recurrent human prostate cancer xenograft. Measurements of tissue androstanediol using mass spectrometry demonstrated androstanediol metabolism to DHT and androsterone. Administration of androstanediol dipropionate to castration-recurrent CWR22R tumor bearing athymic castrated male mice produced a 28-fold increase in intratumoral DHT levels. AR transactivation in prostate cancer cells in the presence of androstanediol resulted from the cell-specific conversion of androstanediol to DHT, and androstanediol increased LAPC-4 cell growth. The ability to convert androstanediol to DHT provides a mechanism for optimal utilization of androgen precursors and catabolites for DHT synthesis