Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution

Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic. It has been suggested that sea-salt-induced chemical cycling of Hg (through 'atmospheric mercury depletion events', or AMDEs) and wet deposition via precipitation are sources of Hg to the Arctic in its oxidized form (Hg(ii)). However, there is little evidence for the occurrence of AMDEs outside of coastal regions, and their importance to net Hg deposition has been questioned. Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide, raising questions as to the sources of high Arctic Hg loading. Here we present a comprehensive Hg-deposition mass-balance study, and show that most of the Hg (about 70%) in the interior Arctic tundra is derived from gaseous elemental Hg (Hg(0)) deposition, with only minor contributions from the deposition of Hg(ii) via precipitation or AMDEs. We find that deposition of Hg(0)-the form ubiquitously present in the global atmosphere-occurs throughout the year, and that it is enhanced in summer through the uptake of Hg(0) by vegetation. Tundra uptake of gaseous Hg(0) leads to high soil Hg concentrations, with Hg masses greatly exceeding the levels found in temperate soils. Our concurrent Hg stable isotope measurements in the atmosphere, snowpack, vegetation and soils support our finding that Hg(0) dominates as a source to the tundra. Hg concentration and stable isotope data from an inland-to-coastal transect show high soil Hg concentrations consistently derived from Hg(0), suggesting that the Arctic tundra might be a globally important Hg sink. We suggest that the high tundra soil Hg concentrations might also explain why Arctic rivers annually transport large amounts of Hg to the Arctic Ocean

Structural relaxation of polystyrene in nanolayer confinement

a b s t r a c t The physical aging of polystyrene (PS) confined in a multilayered film arrangement was explored using differential scanning calorimetry (DSC). The multilayered films were produced via multilayer coextrusion and consisted of alternating layers of PS and polycarbonate (PC), with PS layer thicknesses ranging from 50 nm to 500 nm. A 125 mm bulk control film of pure PS was also extruded and studied for comparison. The glass transition temperatures (T g ) of the PS in multilayered films did not appear to be systematically dependent on layer thickness, and T g values in all PS/PC films were similar to the bulk value of 104 C. Two approaches were used to investigate the structural relaxation of PS in the layered films. In the first method, PS layers were aged isothermally at 80 C after annealing above the T g of PS (135 C for 15 min) to reset the thermal history and provide a well-defined starting point for aging experiments. Recovered enthalpy data for aged films (calculated from DSC thermograms) showed that the aging rate in the PS layers decreased with decreasing layer thickness. Calculated aging rates were also compared with the fraction of interphase material (which increases significantly with decreasing layer thickness), and the decrease in aging rate for films with thinner layers was found to correlate with an increase in interphase fraction. The elevated T g of the interphase material (compared to pure PS) was suggested as a possible reason for reduced aging rates in the thin PS layers. In the second method, PS layers were cooled from above their T g at different rates under confinement by PC layers. After this cooling step was performed, subsequent heating thermograms revealed that the enthalpy recovered upon reheating through the T g of PS was similar for bulk and nanolayered films

Nonmelanoma Skin Cancer in Nonwhite Organ Transplant Recipients

Importance: Organ transplant recipients have a higher incidence of skin cancer. This risk is magnified over time and with continued exposure to immunosuppression. Skin cancer in nonwhite patients is associated with greater morbidity and mortality owing to diagnosis at a more advanced stage, which suggests that nonwhite organ transplant recipients are at even higher risk. Objective: To describe demographic and clinical factors and the incidence of skin cancer in nonwhite organ transplant recipients. Design, Setting, and Participants: We performed a retrospective medical record review of patients who were organ transplant recipients (154 were white and 259 nonwhite [black, Asian, Hispanic, Pacific Islander]) seen from November 1, 2011, to April 18, 2016 at an academic referral center. Main Outcomes and Measures: Variables were analyzed and compared between racial groups, including sex, age, race/ethnicity, Fitzpatrick type, type and location of skin cancer, type of organ transplanted, time to diagnosis of skin cancer after transplantation, and history of condyloma acuminata and/or verruca vulgaris. Results: Most of the 413 patients (62.7%) evaluated were nonwhite organ transplant recipients; 264 were men, and 149 were women. Their mean (SD) age was 60.09 (13.59) years. Nineteen skin cancers were identified in 15 patients (5.8%) representing 3 racial/ethnic groups: black (6 patients), Asian (5), and Hispanic (4). All squamous cell carcinomas in blacks were diagnosed in the in situ stage, located on sun-protected sites, and occurred in patients whose lesions tested positive for human papilloma virus (HPV) and/or who endorsed a history of condyloma acuminata or verruca vulgaris. Most skin cancers in Asians were located on sun-exposed areas and occurred in individuals who emigrated from equatorial locations. Conclusions and Relevance: Nonwhite organ transplant recipients are at risk for developing skin cancer posttransplantation. Follow-up in a specialized transplant dermatology center and baseline total-body skin examination should be part of posttransplantation care in all organ transplant recipients, including nonwhite patients. A thorough inspection of the groin and genitalia is imperative in black organ transplant recipients. History of HPV infection, particularly in black organ transplant recipients, and sun exposure/emigration history in Asian organ transplant recipients should be documented. Vigilant photoprotection may be of lesser importance in the prevention of skin cancer in black organ transplant recipients. Risk factors for nonwhite organ transplant recipients differ between races/ethnicities and warrant further study in efforts to better counsel and prevent skin cancer in these patients

Comparison of Posttransplant Dermatologic Diseases by Race

Importance: The risk for skin cancer has been well characterized in white organ transplant recipients (OTRs); however, most patients on the waiting list for organ transplant in the United States are nonwhite. Little is known about cutaneous disease and skin cancer risk in this OTR population. Objective: To compare the incidence of cutaneous disease between white and nonwhite OTRs. Design, Setting, and Participants: This retrospective review of medical records included 412 OTRs treated from November 1, 2011, through April 22, 2016, at an academic referral center. Prevalence and characteristics of cutaneous disease were compared in 154 white and 258 nonwhite (ie, Asian, Hispanic, and black) OTRs. Clinical factors of cutaneous disease and other common diagnoses assessed in OTRs included demographic characteristics, frequency and type of cancer, anatomical location, time course, sun exposure, risk awareness, and preventive behavior. Main Outcomes and Measures: Primary diagnosis of malignant or premalignant, infectious, and inflammatory disease. Results: The 412 patients undergoing analysis included 264 men (64.1%) and 148 women (35.9%), with a mean age of 60.1 years (range, 32.1-94.3 years). White OTRs more commonly had malignant disease at their first visit (82 [67.8%]), whereas nonwhite OTRs presented more commonly with infectious (63 [37.5%]) and inflammatory (82 [48.8%]) conditions. Skin cancer was diagnosed in 64 (41.6%) white OTRs and 15 (5.8%) nonwhite OTRs. Most lesions in white (294 of 370 [79.5%]) and Asian (5 of 6 [83.3%]) OTRs occurred in sun-exposed areas. Among black OTRs, 6 of 9 lesions (66.7%) occurred in sun-protected areas, specifically the genitals. Fewer nonwhite than white OTRs reported having regular dermatologic examinations (5 [11.4%] vs 8 [36.4%]) and knowing the signs of skin cancer (11 [25.0%] vs 10 [45.4%]). Conclusions and Relevance: Early treatment of nonwhite OTRs should focus on inflammatory and infectious diseases. Sun protection should continue to be emphasized in white, Asian, and Hispanic OTRs. Black OTRs should be counseled to recognize the signs of genital human papillomavirus infection. Optimal posttransplant dermatologic care may be determined based on the race or ethnicity of the patients, but a baseline full-skin assessment should be performed in all patients. All nonwhite OTRs should be counseled more effectively on the signs of skin cancer, with focused discussion points contingent on skin type and race or ethnicity

Cancer Cell-Associated MT1-MMP Promotes Blood Vessel Invasion and Distant Metastasis in Triple-Negative Mammary Tumors.

Functional roles for the cancer cell-associated membrane type I matrix metalloproteinase (MT1-MMP) during early steps of the metastatic cascade in primary tumors remain unresolved. In an effort to determine its significance, we determined the in vivo effects of RNAi-mediated downregulation in mammary cancer cells on the migration, blood and lymphatic vessel invasion (LVI), and lymph node and lung metastasis. We also correlated the expression of cancer cell MT1-MMP with blood vessel invasion (BVI) in 102 breast cancer biopsies. MT1-MMP downregulation in cancer cells decreased lung metastasis without affecting primary tumor growth. The inhibition of lung metastasis correlated with reduced cancer cell migration and BVI. Furthermore, cancer cell-expressed MT1-MMP upregulated the expression of MT1-MMP in vascular endothelial cells, but did not affect MT1-MMP expression in lymphatic endothelial cells, LVI, or lymph node metastasis. Of clinical importance, we observed that elevated MT1-MMP expression correlated with BVI in biopsies from triple-negative breast cancers (TNBC), which have a poor prognosis and high incidence of distant metastasis, relative to other breast cancer subtypes. Together, our findings established that MT1-MMP activity in breast tumors is essential for BVI, but not LVI, and that MT1-MMP should be further explored as a predictor and therapeutic target of hematogenous metastasis in TNBC patients. Cancer Res; 71(13); 4527-38. ©2011 AACR