Assessment of background gamma radiation levels using airborne gamma ray spectrometer data over uranium deposits, Cuddapah Basin, India - A comparative study of dose rates estimated by AGRS and PGRS

The Atomic Minerals Directorate for Exploration and Research (AMD) has conducted high-resolution airborne gamma ray spectrometer (AGRS), magnetometer and time domain electromagnetic (TDEM) surveys for uranium exploration, along the northern margins of Cuddapah Basin. The survey area includes well known uranium deposits such as Lambapur-Peddagattu, Chitrial and Koppunuru. The AGRS data collected for uranium exploration is utilised for estimating the average absorbed rates in air due to radio-elemental (potassium in %, uranium and thorium in ppm) distribution over these known deposit areas. Further, portable gamma ray spectrometer (PGRS) was used to acquire data over two nearby locations one from Lambapur deposit, and the other from known anomalous zone and subsequently average gamma dose rates were estimated. Representative in-situ rock samples were also collected from these two areas and subjected to radio-elemental concentration analysis by gamma ray spectrometer (GRS) in the laboratory and then dose rates were estimated. Analyses of these three sets of results complement one another, thereby providing a comprehensive picture of the radiation environment over these deposits. The average absorbed area wise dose rate level is estimated to be 130 ± 47 nGy h^-1 in Lambapur-Peddagattu, 186 ± 77 nGy h^-1 in Chitrial and 63 ± 22 nGy h^-1 in Koppunuru. The obtained average dose levels are found to be higher than the world average value of 54 nGy h^-1. The gamma absorbed dose rates in nGy h^-1 were converted to annual effective dose rates in mSv y^-1 as proposed by the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The annual average effective dose rates for the entire surveyed area is 0.12 mSv y^-1, which is much lower than the recommended limit of 1 mSv y^-1 by International Commission on Radiation protection (ICRP). It may be ascertained here that the present study establishes a reference data set (baseline) in these areas to assess any changes in gamma radiation levels due to mining and milling activities in future.

Human steroidogenic factor-1 (hSF-1) regulates progesterone biosynthesis and growth of ovarian surface epithelial cancer cells

The majority of cancers derived from ovarian surface epithelial (OSE) cells are lethal. Estrogens promote proliferation of OSE cells, whereas progesterone inhibits proliferation and promotes apoptosis of OSE cells. Human steroidogenic factor-1 (hSF-1) induction of the steroidogenic acute regulatory protein (StAR) gene, and the steroidogenic enzymes CYP11A1 and HSD3B2 is central to progesterone biosynthesis. Whereas hSF-1 and StAR are expressed in human ovarian surface epithelial (HOSE) cells, hSF-1 and StAR protein were not expressed in a panel of malignant ovarian cancer cell lines (SKOV-3, BG-1, and Caov-3), and in human OSE cells immortalized by SV40 large T antigen (IOSE-121). Transient expression of hSF-1 in SKOV-3 cells activated the expression of StAR, p450scc and 3betaHSD-II mRNAs, and induced progesterone biosynthesis. Additionally, hSF-1 suppressed proliferation and promoted apoptosis of SKOV-3 cells and suppressed SKOV-3 cell growth induced by ERalpha and estradiol. These findings suggest that hSF-1 is central to progesterone biosynthesis in OSE cells. Human SF-1 may decrease OSE cancer cell numbers directly by apoptosis, and indirectly by opposing estradiol-induced proliferation. These findings are consistent with the hypothesis, that down-regulation of hSF-1 contributes to progression of ovarian epithelial cancers.

Steroidogenic factor 1 messenger ribonucleic acid expression in steroidogenic and nonsteroidogenic human tissues: Northern blot and in situ hybridization studies

Steroidogenic factor-1 (SF-1), a tissue-specific orphan nuclear receptor, regulates the genes of several steroidogenic enzymes, Mullerian inhibiting substance, and the gonadotrophins. Also, this transcription factor is crucial for hypothalamic, adrenal, and gonadal organogenesis in the mouse. We recently cloned the human SF-1 (hSF-1) complementary DNA (cDNA) and now report the distribution of this factor's messenger RNA (mRNA) in human tissues. Northern blot analyses of peripheral tissues revealed high hSF-1 mRNA expression in the adrenal cortex and the gonads, but no hSF-1 mRNA was detected in the placenta. High hSF-1 mRNA expression also was seen in the spleen. In this tissue, in addition to the main transcript of 3.5-4 kb seen in the adrenal and gonads, two additional transcripts of 4.4 kb and 8 kb were noted. The additional 4.4-kb transcript also was seen in several peripheral tissues and various components of the brain. However, adult liver and heart showed only the 4.4-kb transcript. In the human brain, hSF-1 mRNA expression was widespread, including several components of the limbic system. In situ hybridization studies confirmed the strong expression of hSF-1 mRNA in adrenal cortex, ovary, testis, and the spleen, primarily within reticuloendothelial cells. Thus, in the human, the hSF1 mRNA is present in both steroidogenic and nonsteroidogenic tissues, albeit not in the placenta. In the central nervous system, the expression of hSF-1 mRNA is widespread. It is composed of several different mRNA species distributed in a tissue-specific fashion. These findings suggest that hSF-1 may play a role in reticuloendothelial/immune cell maturation and/or function, as well as nervous system development and/or neurosteroid biosynthesis.

Cloning and sequence analysis of the human gene encoding steroidogenic factor 1

The orphan nuclear receptor steroidogenic factor 1 (SF-1) plays key roles in endocrine development and function. Initially identified as a positive regulator of the cytochrome P450 steroid hydroxylases, analyses of knockout mice deficient in SF-1 revealed that SF-1 is essential for adrenal and gonadal development, pituitary gonadotropin expression and formation of the ventromedial hypothalamic nucleus. Although more limited in scope, analyses of SF-1 in humans similarly have suggested that SF-1 is important for differentiated function in adrenocortical and gonadotrope adenomas. In the hope of extending our understanding of SF-1 function by identifying possible roles of SF-1 in clinical endocrine disorders, we isolated the FTZ-F1 gene encoding human SF-1 and mapped it to chromosome 9q33. In this report, we characterize the sequence and structural organization of the human cDNA and gene encoding SF-1, providing new insights into comparative aspects of SF-1 structure that will facilitate efforts to study the role of this transcription factor in human endocrine disorders.