A phenomenological model for the photocurrent transient relaxation observed in ZnO-based photodetector devices.

We present a phenomenological model for the photocurrent transient relaxation observed in ZnO-based metal-semiconductor-metal (MSM) planar photodetector devices based on time-resolved surface band bending. Surface band bending decreases during illumination, due to migration of photogenerated holes to the surface. Immediately after turning off illumination, conduction-band electrons must overcome a relatively low energy barrier to recombine with photogenerated holes at the surface; however, with increasing time, the adsorption of oxygen at the surface or electron trapping in the depletion region increases band bending, resulting in an increased bulk/surface energy barrier that slows the transport of photogenerated electrons. We present a complex rate equation based on thermionic transition of charge carriers to and from the surface and numerically fit this model to transient photocurrent measurements of several MSM planar ZnO photodetectors at variable temperature. Fitting parameters are found to be consistent with measured values in the literature. An understanding of the mechanism for persistent photoconductivity could lead to mitigation in future device applications.

Evaluation of a Florida coastal golf complex as a local and watershed source of bioavailable contaminants.

Contaminant fate in coastal areas impacted by golf course runoff is not well understood. This report summarizes trace metal, pesticide and PCB residues for colonized periphyton, Ruppia maritima (widgeon grass), Callinectes sapidus Rathbun (blue crabs) and Crassostrea virginica Gemlin (Eastern oyster) collected from areas adjacent to a Florida golf course complex which receive runoff containing reclaimed municipal wastewater. Concentrations of 19 chlorinated pesticides and 18 PCB congeners were usually below detection in the biota. In contrast, 8 trace metals were commonly detected although concentrations were not usually significantly different for biota collected from reference and non-reference coastal areas. Residue concentrations in decreasing order were typically: zinc, arsenic, copper, chromium, lead, nickel, cadmium and mercury. Mean BCF values for the eight trace metals ranged between 160-57000 (periphyton), 79-11033 (R. maritima), 87-162625 (C. virginica) and 12-9800 (C. sapidus). Most trace metal residues in periphyton colonized adjacent to the golf complex, were either similar to or significantly less than those reported for periphyton colonized in nearby coastal areas impacted by urban stormwater runoff and treated municipal and industrial wastewater discharges. Consequently, the recreational complex does not appear to be a major source of bioavailable contaminants locally nor in the immediate watershed based on results for the selected biota.

Concomitant sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman Disease) and diffuse large B-cell lymphoma: a case report.

INTRODUCTION: Sinus histiocytosis with massive lymphadenopathy, also known as Rosai-Dorfman Disease, is a rare and benign source of lymphadenopathy first described in 1969, which mimics neoplastic processes. This disease commonly presents in children and young adults with supra-diaphragmatic lymphadenopathy or extranodal lesions consisting of tissue infiltrates composed of a polyclonal population of histiocytes. Since its description greater than 400 cases have been described, sometimes in patients with a variety of treated and untreated neoplastic diseases. However, the literature contains reports of only 19 cases of Rosai-Dorfman Disease in association with lymphomas, Hodgkin's or non-Hodgkin's. The majority of these cases have the two diagnoses, malignant lymphoma and Rosai-Dorfman Disease, separated in time. Interestingly, infradiaphragmatic lymphadenopathy was a feature in the majority of previously reported cases of Rosai-Dorfman Disease and non-Hodgkin's lymphoma. CASE PRESENTATION: This report provides details of a case with co-existing sinus histiocytosis with massive lymphadenopathy and diffuse large B cell non-Hodgkin's lymphoma. This case is the fifth described case of simultaneous Rosai-Dorfman Disease and concurrent non-Hodgkin's lymphoma. Unfortunately, the diagnosis of a clinically aggressive diffuse large B cell lymphoma was made at autopsy. The aggressive biological behavior of the diffuse large B cell lymphoma in this patient may have been related to the underlying immune dysregulation believed to be part of the pathophysiology of Rosai-Dorfman Disease. CONCLUSION: Taken together this report and the preceding reports of Rosai-Dorfman Disease and non-Hodgkin's lymphoma suggests that in cases with a diagnosis of Rosai-Dorfman Disease in the setting of prominent infradiaphragmatic lymphadenopathy, clinicians should maintain a high index of suspicion for the presence of occult non-Hodgkin's lymphoma especially if the clinical course is atypical for classic Rosai-Dorfman Disease.

Inhibition of polysome assembly enhances imatinib activity against chronic myelogenous leukemia and overcomes imatinib resistance.

Dysregulated mRNA translation is implicated in the pathogenesis of many human cancers including chronic myelogenous leukemia (CML). Because our prior work has specifically implicated translation initiation in CML, we tested compounds that could modulate translation initiation and polysomal mRNA assembly. Here, we evaluated the activity of one such compound, CGP57380, against CML cells and explored its mechanisms of action. First, using polysomal mRNA profiles, we found that imatinib and CGP57380 could independently, and cooperatively, impair polysomal mRNA loading. Imatinib and CGP57380 also synergistically inhibited the growth of Ba/F3-Bcr-Abl and K562 cells via impaired cell cycle entry and increased apoptosis. Mechanistically, CGP57380 inhibited efficient polysomal assembly via two processes. First, it enhanced imatinib-mediated inhibition of eukaryotic initiation factor 4F induction, and second, it independently impaired phosphorylation of ribosomal protein S6 on the preinitiation complex. We also identified multiple substrates of the mTOR, Rsk, and Mnk kinases as targets of CGP57380. Finally, we found a novel negative-feedback loop to the mitogen-activated protein kinase/Mnk pathway that is triggered by CGP57380 and demonstrated that an interruption of the loop further increased the activity of the combination against imatinib-sensitive and -resistant CML cells. Together, this work supports the inhibition of translation initiation as a therapeutic strategy for treating cancers fueled by dysregulated translation.

Multiple joint effusions associated with high-dose imatinib therapy in a patient with chronic myelogenous leukaemia.

Imatinib mesylate is a small molecule tyrosine kinase inhibitor that has significant efficacy in the treatment of chronic myelogenous leukaemia (CML). However, it is likely that patients with CML will require prolonged and perhaps life-long therapy. In general, the side-effects of imatinib therapy have been mild to moderate, with the large majority of patients tolerating prolonged periods of therapy. However, a minority of patients are completely intolerant of therapy, while others are able to remain on therapy despite significant side-effects. Here, we describe a novel form of fluid retention presenting as multiple joint effusions in a patient with advanced phase CML on high-dose imatinib, as well as successful measures that were undertaken to control this adverse event. Although fluid retention, including periorbital oedema, pleural and pericardial effusions, as well as life-threatening cerebral oedema have been previously described and attributed to imatinib, this is the first case of imatinib-associated polyarticular effusions that we are aware of. Further work will be required to confirm a casual relationship between imatinib therapy and this novel side-effect, as well as to determine the underlying pathophysiologic mechanisms.

Sediment toxicity and community composition of benthos and colonized periphyton in the Everglades-Florida Bay transitional zone.

This survey provides information on sediment toxicity and structural characteristics of the macrobenthic and periphytic algal communities at 10 locations in northeast Florida Bay. Whole sediments were not acutely toxic to Mysidopsis bahia (marine invertebrate) and Hyalella azteca (freshwater invertebrate) relative to reference sediment. Survival was between 80% and 100%. Community structure of the macrobenthos and algal-periphyton varied spatially. A total of 116 benthic species were identified at the 10 locations; mean density was greater in Shell Creek (10,017 organisms/m2) and least in Canal C-103 (441 organisms/m2). Tubificids and the crustacean Halmyrapseudes bahamensis (Family: Apseudidae) dominated the benthos at 4 of 10 locations. One hundred and six species of periphytic algae representing 52 genera were identified on substrates colonized for 21 days. Mean algal density was greater in Florida Bay (19,440 cells/cm2) and least in Long Sound (10 cells/cm2). Diatoms and blue green algae dominated the algal-periphyton. Major diatom genera were Navicula, Brachysira and Nitzschia. The more abundant and widely occurring blue-green taxa were species of Oscillatoria, Polycystis and Lyngbya. Ash free dry weight and chlorophyll a were significantly greater for periphyton colonized in Canal C-111 and Florida Bay and the least in Long Sound. Spatial variation and the availability of reference areas are important issues that need consideration in future biomonitoring efforts conducted in this region to ensure relevancy of results.

Potential genotoxicity of wastewater-contaminated pore waters with comparison to sediment toxicity and macrobenthic community composition.

The objectives of this survey were to determine the genotoxic potential of sediment pore waters above and below 10 wastewater outfalls and to compare the results to sediment chemical quality guidelines, acute toxicity, and macrobenthic community composition. The focus of the study was on genotoxicity since its occurrence in environmental media below wastewater discharges in the Gulf of Mexico region has not been reported in the scientific literature. Pore waters from 43 sediment samples were assayed using a microbial mutagenicity assay before and after activation with a rat liver microsome mix (S-9). A combination of either direct or activated responses was observed for 40% of the pore waters. Direct, activated, and both direct and activated responses were observed in 5, 26, and 9% of the total samples, respectively. Mutagenic effects were observed below 7 of the 10 outfall areas and in 4 of 6 control areas associated with 6 outfalls. The lowest pore water concentrations causing an activated mutagenic response were statistically similar above and below the outfalls. Mutagenicity occurred more frequently than acute toxicity to estuarine and freshwater invertebrates and there was no consistent relationship between its occurrence and the exceedance of sediment chemical quality guidelines. In contrast, there was some indication that mutagenic activity paralleled low benthic community diversity.

Effects of a coastal golf complex on water quality, periphyton, and seagrass.

The objective of this study was to provide baseline information on the effects of a golf course complex on water quality, colonized periphyton, and seagrass meadows in adjacent freshwater, near-coastal, and wetland areas. The chemical and biological impacts of the recreational facility, which uses reclaimed municipal wastewater for irrigation, were limited usually to near-field areas and decreased seaward during the 2-year study. Concentrations of chromium, copper, and organochlorine pesticides were below detection in surface water, whereas mercury, lead, arsenic, and atrazine commonly occurred at all locations. Only mercury and lead exceeded water quality criteria. Concentrations of nutrients and chlorophyll a were greater in fairway ponds and some adjacent coastal areas relative to reference locations and Florida estuaries. Periphyton ash free dry weight and pigment concentrations statistically differed but not between reference and non-reference coastal areas. Biomass of Thalassia testudinum (turtle grass) was approximately 43% less in a meadow located adjacent to the golf complex (P < 0.05). The results of the study suggest that the effects of coastal golf courses on water quality may be primarily localized and limited to peripheral near-coastal areas. However, this preliminary conclusion needs additional supporting data.