How Should Governments Address High Levels of Natural Radiation and Radon--Lessons from the Chernobyl Nuclear Accident and Ramsar, Iran

The authors discuss the high levels of natural background radiation in Ramsar, Iran, and offer data indicating that this has had little effect on the health of Ramsar\u27s inhabitants. The authors then examine the implications their research could have for public health policy

The need for national diagnostic reference levels: Entrance surface dose measurement in intraoral radiography

Background: Intraoral radiographies are the most frequent X-ray examinations in humans. According to International Commission on Radiation Protection (ICRP) recommendations, the selection of a diagnostic reference level (DRL) should be specific to a country or region. Critical organs such as thyroid gland are exposed to X-rays in intraoral radiography and these exposures should be kept as low as reasonably achievable. To assist the development of DRLs for intraoral radiography, a National Radiation Protection Department-sponsored pilot study was carried out. Materials and Methods: Thermoluminescent dosimetry (TLD) is widely acknowledged to be the recommended method for measuring entrance surface doses (ESD). In this study, ESD was measured using LiF thermoluminescent dosimeters (TLD-100) on the skin (either mandibular or maxillary arcs) of 40 patients. Three TLD chips were placed on the skin of each patient. The doses were averaged for each radiography and mean ESD of all patients calculated. Results: The mean ± SD entrance surface dose at the center of the beam on the patients' skin in intraoral radiography was 1.173 ± 0.606 mGy (ranged from 0.01 to 0.40 mGy). The mean ESD for male and female patients were 1.380 ± 0.823, and 1.004 ± 0.258 respectively. No statistically significant difference was found between these means. Despite its necessity, in national level, there is no published data on the diagnostic reference levels for intraoral radiography. However, the results obtained in this study are lower than those reported by investigators in other countries. Conclusion: In IR Iran, due to lack of large scale studies, no diagnostic reference levels have been set for X-ray diagnostic procedures. Due to lack of national diagnostic reference levels, it is not possible to clarify whether in intraoral radiographies any dose reduction techniques are needed. We intend to perform similar nationwide studies to set the diagnostic reference level for intraoal radio graphy

Entrance surface dose measurement on the thyroid gland in orthopantomography: The need for optimization

Background: The anatomic position and proven radiosensitivity of the thyroid make it an organ of concern in dental X-ray examinations. A National Radiation Protection Department (NRPD)-sponsored pilot study carried out in the Dental Radiology Department of RUMS., to assess if the radiation dose in panoramic radiographies could be reduced without significant impairment of the subjective image quality. Materials and Methods: Thermoluminescent dosimetry (TLD) is widely acknowledged to be the recommended method for measuring entrance surface doses (ESD). In this study, ESD was measured using LiF thermoluminescent dosimeters (TLD-100) on the thyroid of 40 patients who had referred to the School of Dentistry, Rafsanjan University of Medical Sciences. Patients were not exposed to any additional radiation and the radiographs were used for diagnostic purposes. TLDs were calibrated with radiation energies similar to those commonly used in orthopantomography. Results: The overall mean ESD on the thyroid in orthopantomography was 0.071 ± 0.012 mGy (ranged from 0.01 to 0.40 mGy). The mean ESD for radiographies performed with 66 kVp (20 patients) and 68 kVp (20 patients) were 0.072 ± 0.019, and 0.070 ± 0.016 respectively. No statistically significant difference was found between these means. Conclusions: The measured surface doses in our study are inconsistent with the only one already reported about the same experiment. However, due to lack of national diagnostic reference levels for orthopantomography, it is not clear whether in case of the PM 2002 CC unit used in this experiment, reducing the radiation dose to a level that still keeps a diagnostically acceptable image quality is necessary

Krüppel-like factor 6 is a transcriptional activator of autophagy in acute liver injury

Kruppel-like factor 6 (KLF6) is a transcription factor and tumor suppressor. We previously identified KLF6 as mediator of hepatocyte glucose and lipid homeostasis. The loss or reduction of KLF6 is linked to the progression of hepatocellular carcinoma, but its contribution to liver regeneration and repair in acute liver injury are lacking so far. Here we explore the role of KLF6 in acute liver injury models in mice, and in patients with acute liver failure (ALF). KLF6 was induced in hepatocytes in ALF, and in both acetaminophen (APAP)- and carbon tetrachloride (CCl4)- treated mice. In mice with hepatocytespecific Klf6 knockout (DeltaKlf6), cell proliferation following partial hepatectomy (PHx) was increased compared to controls. Interestingly, key autophagic markers and mediators LC3-II, Atg7 and Beclin1 were reduced in DeltaKlf6 mice livers. Using luciferase assay and ChIP, KLF6 was established as a direct transcriptional activator of ATG7 and BECLIN1, but was dependent on the presence of p53. Here we show, that KLF6 expression is induced in ALF and in the regenerating liver, where it activates autophagy by transcriptional induction of ATG7 and BECLIN1 in a p53-dependent manner. These findings couple the activity of an important growth inhibitor in liver to the induction of autophagy in hepatocytes

Strategies for blocking the fibrogenic actions of connective tissue growth factor (CCN2): From pharmacological inhibition in vitro to targeted siRNA therapy in vivo

Connective tissue growth factor (CCN2) is a major pro-fibrotic factor that frequently acts downstream of transforming growth factor beta (TGF-β)-mediated fibrogenic pathways. Much of our knowledge of CCN2 in fibrosis has come from studies in which its production or activity have been experimentally attenuated. These studies, performed both in vitro and in animal models, have demonstrated the utility of pharmacological inhibitors (e.g. tumor necrosis factor alpha (TNF-α), prostaglandins, peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonists, statins, kinase inhibitors), neutralizing antibodies, antisense oligonucleotides, or small interfering RNA (siRNA) to probe the role of CCN2 in fibrogenic pathways. These investigations have allowed the mechanisms regulating CCN2 production to be more clearly defined, have shown that CCN2 is a rational anti-fibrotic target, and have established a framework for developing effective modalities of therapeutic intervention in vivo