Growth Fraction Research Articles

Effect of substrate offcut angle on BGaN epitaxial growth

Researchers expect the material BGaN to be useful in neutron detectors and ultraviolet (UV) light-emitting devices. In this study, we investigate the effect of the substrate offcut angle and polarity upon BGaN growth. In particular, BGaN is grown on top of GaN upon Al2O3 substrates with various offcut angles. In the case of Ga-polar BGaN growth, the BN mole fraction increases as the offcut angle increases. Furthermore, as the offcut angle increases, the terrace width becomes reduced, which inhibits the formation of nuclei on the terrace and promotes the incorporation of B atoms at the step edges. Such incorporation is important at the step edge (which is the stable site) during BGaN growth because B atoms are easily desorbed from the surface and easily react in the gas phase. In the case of N-polar BGaN growth, the BN mole fraction exhibits different behavior in response to the offcut angle of the substrate. For this reason, the surface of N-polar BGaN is different from that of Ga-polar BGaN as it has facets of N-polar GaN and step bunching. These results indicate that the incorporation of B atoms at step edges significantly affects the BN mole fraction in BGaN growth.

Optimized Nanoelectrode Geomerty for Enhanced Direct Extraction of Photosynthetic Electrons from Living Single Algal Cells

Plant cells highly efficiently convert solar energy into photosynthetic electrons during photosynthesis. The photosynthetic electrons (PEs) are transported via redox reactions between molecules in the thylakoid membrane of plant cells. Most of the PEs are utilized for cell growth and small fractions are stored in a form of carbohydrates within plant cells. There have been various approaches to harvest the PEs from the photosynthetic electron transfer chain during photosynthesis. These works have focused on indirect extraction of PEs from isolated photosynthetic components such as photosystem I (PSI) or fragments of thylakoid membrane that contains most of molecules involved in photosynthetic electron transfer. However, despite many advances made from those approaches, there are still challenges such as limited stability of isolated photosynthetic molecules and lowered efficiency due to use of mediators. We previously reported the feasibility of “direct” extraction of PEs from living single algal cells using AFM-compatible nanoelectrodes (NEs). Although the result demonstrated continuous extraction of PEs from living cells at high efficiency, fabrication of the customized NEs was expensive and had poor yield. More importantly, gradual leakage from algal cells occurred after NE insertion into plant cells, resulting in limited PE extraction for only up to an hour. In this study, we aimed to study NE geometry that enabled longer direct extraction of PEs from living algal cells that our previous work without using any mediator. For this, we developed horizontally-tilted cantilever NE system by which NE insertion into living cells could be optically monitored in situ and light-triggered PE extraction could be performed. A commercial AFM tip was custom-shaped into a cantilever with a nanowire (NW) at one end using focused ion beam (FIB). The NW was coated with Au and insulated with a Si3N4 passivation layer by CVD processes. For highly-localized electrochemical functions, another FIB milling was performed to expose the embedded Au only at the tip of the NW. First, we studied how the NW size affected the long-term stability of algal cells after NW insertion. Algal cells were stable for up to about 17 hours when they were inserted by NWs thinner than 500 nm, and they even proliferated after NW insertion. The electrochemical performance of the NW electrode was confirmed with the characteristics of an ultramicro electrode by running cyclic voltammetry analysis using potassium ferricyanide (K3[Fe(CN)6], 0.01M) as a redox system and potassium nitrate (KNO3, 0.1M) as an supporting electrolyte. Light-triggered electrical currents were measured after NW insertion into algal cells with light intensity of 99 μmol·m-2s-1 and potential of 0.4V (versus Ag/AgCl) applied to the NW. Potential-dependent analysis for photocurrents was performed to identify the donor of PEs. Disappearance of the light-triggered currents upon application of photosystem inhibitors also confirmed the currents originated from photosynthesis. Finally, long-term monitoring of cell stability and extraction of PEs was demonstrated for 17 hours after NW insertion into algal cells.

Immuno Histochemical Study of Osteosarcoma Using Ki-67 as a Labeling Index in Naturally Fluoridated Community

Osteosarcoma is the most common primary malignant bone tumor which characterized microscopically by formation of osteoid or bone by the neoplastic cells (osteoblastic type) or production of fibrous tissue (fibroblastic type) and/or a cartilage (chondroblastic type). Ki-67 protein is present during all active phases of the cell cycle (G1, S, G2 and mitosis but is absent from resting cells (G0), makes it an excellent marker for determining the so called growth fraction of a given cell population. However, fluoride concentration in drinking water shows great variation between the costal-western region of Libya (mean fluoride concentration 1.38ppm) and Cairo-Egypt (0.4ppm). Therefore, the aim of this study is to evaluate and compare histopathologically the proliferative activity of Osteosarcomas in naturally fluoridated community (Libyan cases) and non-fluoridated community (Egyptian cases) as a retrospective case-control study using the labeling index Ki-67. 20 cases of Osteosarcoma from each country in a formalin-fixed embedded specimens and serial sections from the paraffin blocks for immuno histochemical examination were included in this study in which Peroxidase-antiperoxidase technique was performed. Assessment of Ki-67 proliferative activity was carried out using software image analysis and the area fraction was given by the percentage of immuno positive area to the total area of the microscope field. The result of this study showed that the mean value of area of fraction in Libyan cases was 5.33 and in Egyptian cases were 3.12. When comparing the area fraction of Ki67 immunopositivity of tumor cells in Lybian cases versus Egyptian cases, statistical analysis revealed a statistically significant difference (P value=0.023). It is concluded from this study that a high expression of Ki-67 of Osteosarcomas in fluoridated area compared to those of non-fluoridated area could explain the aggressive behavior of this tumor, in which fluoride ions may play a role as an underlying etiological factor.

A biorefinery approach to microbial oil production from glycerol by Rhodotorula glutinis

The use of biodiesel-derived glycerol as a carbon source for microbial oil production is a biorefinery engineering strategy that aims to reduce the glycerol surplus and make the microbial oil process more cost-effective. In this work, glycerol was used as the sole carbon source for the cultivation of the oleaginous yeast Rhodotorula glutinis along with only yeast extract as a nutrient supply and without pH control. Shake-flask cultivations showed that the specific growth rate and glycerol consumption of Rhodotorula glutinis were higher at lower glycerol concentrations (≤40 g L−1), while higher C/N atom ratios enhanced oil content. The present study extends the knowledge on the influence of the aeration rate and oxygen supply in cellular growth rate and microbial oil production, providing a wiser use of glycerol as an attempt to further reduce process costs. Cultivations at different air flow rates were performed in a 2 L bioreactor and showed that a low aeration rate of 0.5 L min−1 gave the best glycerol and nitrogen uptake rates, resulting in the highest growth (5.3 g L−1) and oil mass fraction (33% of the dry cell weight). A further 68% increase in cellular growth (16.8 g L−1) and a 34% oil mass fraction of the dry cell weight was achieved after applying a feeding strategy targeting combined growth and oil production.

Growth conditions of 0-group plaice Pleuronectes platessa in the western Wadden Sea as revealed by otolith microstructure analysis

Growth studies based on population-based growth estimates are limited by the fact that they do not take into account differences in age/size structure within the population. To overcome these problems, otolith microstructure analysis is often used to estimate individual growth. Here, we analyse growth of 0-group plaice in the western Wadden Sea in two years: a year preceded by a mild winter (1995) and a year preceded by a severe winter (1996). Growth was analysed by combining information on individual growth based on otolith analysis with predictions of maximum growth (= under optimal food conditions) based on a Dynamic Energy Budget model. Otolith analysis revealed that settlement occurred earlier in 1995 than in 1996. In both years, one main cohort was found, followed by a group of late settlers. No differences in mean length-at-age were found between these groups. DEB modelling suggested that growth was not maximal during the whole growing season: realized growth (the fraction of maximum growth realized by 0-group plaice) declined in the summer, although this decline was relatively small. In addition, late settling individuals exhibited lower realized growth than individuals from the main cohort. This study confirms that growth conditions for 0-group plaice are not optimal and that a growth reduction occurs in summer, as suggested in previous studies.

Investigation of mixotrophic, heterotrophic, and autotrophic growth of Chlorella vulgaris under agricultural waste medium

ABSTRACTGrowth of Chlorella vulgaris and its lipid production were investigated under autotrophic, heterotrophic, and mixotrophic conditions. Cheap agricultural waste molasses and corn steep liquor from industries were used as carbon and nitrogen sources, respectively. Chlorella vulgaris grew remarkably under this agricultural waste medium, which resulted in a reduction in the final cost of the biodiesel production. Maximum dry weight of 2.62 g L−1 was obtained in mixotrophic growth with the highest lipid concentration of 0.86 g L−1. These biomass and lipid concentrations were, respectively, 140% and 170% higher than autotrophic growth and 300% and 1200% higher than heterotrophic growth. In mixotrophic growth, independent or simultaneous occurrence of autotrophic and heterotrophic metabolisms was investigated. The growth of the microalgae was observed to take place first heterotrophically to a minimum substrate concentration with a little fraction in growth under autotrophic metabolism, and then the cells grew more autotrophically. It was found that mixotrophic growth was not a simple combination of heterotrophic and autotrophic growth.

Expression pattern of proliferating cell nuclear antigen (PCNA) in round cell tumors of dogs from Grenada, West Indies

A retrospective study was performed on archivedtumor tissues received by the Veterinary Pathology Diagnostic Laboratory, School of Veterinary Medicine, St. George's University, Grenada over an 11 year period (2001–2011). The expression pattern of proliferating cell nuclear antigen (PCNA) was evaluated in canine round cell tumors. A total of 40 tumors comprising of transmissible venereal tumor(TVT), canine cutaneous histiocytoma(CCH)and mast cell tumor(MCT) were evaluated for PCNA expression using immunohistochemistry technique. Moderate to strong immunoreactivity was detected in most of these tumors. The percentage of immunomarked cells for PCNA was 42.1, 57.1, and 57.1 for TVT, CCH, and MCT, respectively. A statistical significance (P<0.05) between the average mitotic counts and PCNA expression for TVT and CCH was noted. PCNA expression in the TVT cases ranged from 17.4% to 56.3% which suggests the presence of variable growth fraction in this tumor. The results showed that PCNA immunohistochemistry could be an important adjunct tool in determining the biological behavior of round cell tumours.

Persistence of Bronchial Dysplasia Is Associated with Development of Invasive Squamous Cell Carcinoma.

Bronchial dysplasia (BD), a presumed precursor of pulmonary squamous cell carcinoma (SCC), rarely progresses to invasive cancer. A high-risk cohort at the University of Colorado provided an opportunity to directly sample airway epithelium at mapped sites on successive bronchoscopies. We have hypothesized that persistent dysplastic lesions showing a similar or higher level of dysplasia on follow-up biopsy, are associated with increased risk for the development of SCC. Endoscopic biopsies from 188 high-risk subjects were histologically classified according to the current WHO classification for BD using a numeric histology score ranging from 1 to 8 representing normal bronchial mucosa through invasive lung cancer. Differences in follow-up histology scores were compared between sites classified by clinical, histologic, and immunohistochemical variables. Subjects with a higher frequency of sites that persist or progress to high-grade dysplasia (≥37.5% persist/progress, N = 35 versus <37.5% persist/progress, N = 114) show a significant association with development of incident invasive SCC (adjusted HR, 7.84; 95% confidence interval, 1.56-39.39), and those with incident lung SCC have adjusted mean follow-up histology scores 1.55 U higher than in subjects without lung cancer. Current smoking, elevated Ki67 growth fraction, histologic features of angiogenic squamous dysplasia (ASD) and higher histology score in baseline biopsies are significantly associated with increased follow-up histology scores. These results show that persistent BD is associated with the development of invasive SCC. Furthermore, increased expression of Ki67, the presence of angiogenic change and degree of baseline atypia are associated with persistence of BD.

KPU-300, a Novel Benzophenone-Diketopiperazine-Type Anti-Microtubule Agent with a 2-Pyridyl Structure, Is a Potent Radiosensitizer That Synchronizes the Cell Cycle in Early M Phase.

KPU-300 is a novel colchicine-type anti-microtubule agent derived from plinabulin (NPI-2358). We characterized the effects of KPU-300 on cell cycle kinetics and radiosensitization using HeLa cells expressing the fluorescent ubiquitination-based cell cycle indicator (Fucci). Cells treated with 30 nM KPU-300 for 24 h were efficiently synchronized in M phase and contained clearly detectable abnormal Fucci fluorescence. Two-dimensional flow-cytometric analysis revealed a fraction of cells distinct from the normal Fucci fluorescence pattern. Most of these cells were positive for an M phase marker, the phosphorylated form of histone H3. Cells growing in spheroids responded similarly to the drug, and the inner quiescent fraction also responded after recruitment to the growth fraction. When such drug-treated cells were irradiated in monolayer, a remarkable radiosensitization was observed. To determine whether this radiosensitization was truly due to the synchronization in M phase, we compared the radiosensitivity of cells synchronized by KPU-300 treatment and cells in early M phase isolated by a combined method that took advantage of shake-off and the properties of the Fucci system. Following normalization against the surviving fraction of cells treated with KPU-300 alone, the surviving fractions of cells irradiated in early M phase coincided. Taken together with potential vascular disrupting function in vivo, we propose a novel radiosensitizing strategy using KPU-300.

Leaf area index mapping with optical methods and allometric models in SMEAR flux tower footprint at Järvselja, Estonia

Abstract Leaf area index (LAI) characterizes the amount of photosynthetically active tissue in plant canopies. LAI is one of the key factors determining ecosystem net primary production and gas and energy exchange between the canopy and the atmosphere. The aim of the present study was to test different methods for LAI and effective plant area index (PAIe) estimation in mixed hemiboreal forests in Järvselja SMEAR Estonia (Station for Measuring Ecosystem-Atmosphere Relations) flux tower footprint. We used digital hemispherical images from sample plots, forest management inventory data, allometric foliage mass models, airborne discrete-return recording laser scanner (ALS) data and multispectral satellite images. The free ware program HemiSpherical Project Manager (HSP) was used to calculate canopy gap fraction from digital hemispherical photographs taken in 25 sample plots. PAIe was calculated from the gap fraction for up-scaling based on ALS point cloud metrics. The all ALS pulse returns-based canopy transmission was found to be the most suitable lidar metric to estimate PAIe in Järvselja forests. The 95-percentile (H95 ) of lidar point cloud height distribution correlates very well with allometric regression models based LAI and in birch stands the relationship was fitted with 0.7 m2 m−2 residual error. However, the relationship was specific to each allometric foliage mass model and systematic discrepancies were detected at large LAI values between the models. Relationships between the spectral reflectance and allometric LAI were not good enough to be used for LAI mapping. Therefore, airborne laser scanning data-based PAIe map was created for areas near SMEAR tower. We recommend to establish a network of permanent sample plots for forest growth and gap fraction measurements into the flux footprint of SMEAR Estonia flux tower in Järvselja to provide consistent up to date data for interpretation of the flux measurements.

Comparative effects of cocaine and cocaethylene on alveolar epithelial type II cells

Abuse of cocaine (COC) and alcohol have been among the leading causes of non-prescription drug-related deaths in the USA and are known to cause acute and chronic lung diseases. The co-abuse of COC and alcohol results in the production of an active metabolite, cocaethylene (CE). The effects of COC and its metabolites on the respiratory system have been scarcely studied. This study was aimed at comparing the toxic effects of eqimolar concentration (1 mM) of COC and CE on alveolar epithelial type II cells. This was performed by measuring cell growth, viability, clonogenic activity, cell cycle and reactive oxygen species (ROS) generation. The treatment of CE and COC resulted in a significant inhibition of cell proliferation with the formation of an average of three colonies which measured about 1.74 × 10−15 m each and 25 colonies each of about 5.73 × 10−15 m, respectively, while untreated cells yielded 31 colonies of 8.75 × 10−15 m (p < 0.05). The treatments of CE and COC resulted in the reduction of the growth fraction of alveolar epithelial type II cells without significant decrease in viability. In addition, there was an approximately twofold increase in ROS generation as compared to the controls (p < 0.05). Therefore, CE-induced inhibition of cellular proliferation may contribute to the pathogenesis of diffuse alveolar damage in co-abusers of COC and alcohol.

Sulphuric acid and aerosol particle production in the vicinity of an oil refinery

In this paper we introduce in-situ observations of trace gases, aerosol particles and their precursors in the vicinity of an oil refinery and industrial area in Kilpilahti, Southern Finland. We conducted a one-month measurement campaign near the oil refinery during summertime when the sulphur dioxide concentrations at the site are typically the highest. The source areas around the measurement location were divided into three sectors: oil refinery area, industrial area and non-industrial area. The atmospheric concentrations of aerosols and trace gases showed a large temporal variability, when exposed to the different source areas. The median sulphur dioxide concentrations for the oil refinery, industrial and non-industrial area were 1.88 ppbv, 0.75 ppbv and 0.38 ppbv, respectively, and the corresponding sulphuric acid concentrations were 11.5 × 106 molecules/cm3, 4.4 × 106 molecules/cm3 and 1.3 × 106 molecules/cm3. The observed concentrations were similar to what have been measured in urban or industrial sites. The ratio between sulphuric acid and sulphur dioxide was the highest when the air mass was coming from the oil refinery. The correlation between the sulphuric acid and 1–2 nm particle concentrations was significant, but the composition of the particles remained unknown as no neutral sulphuric acid clusters were detected with the mass spectrometer. Only a few new particle formation events were observed during the measurement period, and during these events a large fraction of the particle growth could be explained by sulphuric acid condensation.

Abstract 3550: Expression of Oct-2, OCA-B, BCL6, PU.1 and IRF8 predicts prognosis in Diffuse Large B Cell Lymphoma patients

Abstract Diffuse Large B Cell Lymphoma (DLBCL) is the most common B cell Non Hodgkin lymphoma in adults. While 50% of patients are cured with standard therapy, a large fraction either relapse or have primary refractory disease. Relapse is the major cause of treatment failure and death in these patients. Remains imperative the availability of markers that could predict response to therapy. DLBCL is a heterogeneous group of diseases that arise from germinal center (GC) B cells. Gene expression profiling has classified DLBCL into two subgroups Activated B Cell Like (ABC) and Germinal Center B Cell Like (GCB). Multiple mutations associated with its biology have been identified by next generation sequencing but little is known about their prognostic role. The transit of B cells through the GC is controlled by sequential activation and repression of transcription factors. BCL6 role in GC development and derived B cell lymphomas is well known. Oct2 and its cofactor OCAB control BCL6 expression being responsible for its up regulation in centroblasts (Blood 144; 22). Oct2/OCAB recognize a non canonical binding site in BCL6 promoter. Oct2 is recruited to its target gene by PU1/IRF8. Co-IPs assays in BJAB and HBL1 showed the interactions among these factors. The downregulation of PU1 or IRF8 expression using shRNAs significantly decreased Oct2/OCAB binding enrichment on BCL6 promoter. Based on these observations we decided to analyze the expression of the GC highly expressed Oct2, OCAB, BCL6, PU1 and IRF8 transcription factors by immunohistochemistry, in paraffin embedded biopsies of DLBCL patients obtained at diagnosis. We included 73 patients [38 male Md age and range 59.07 (25-85); 35 female 59.4 (17-82)]. The univariate analysis showed no correlation between the percentage of positive tumor cells and the clinical-pathological parameters indicative of prognosis. Similarly there was a lack of correlation both with the immune-phenotype markers routinely evaluated and the growth fraction marker Ki67. The Kaplan-Meier study showed that tumors with Oct2, BCL6 and IRF8 expression higher than 70% [(Log Rank Test X2 = 3,7) p = 0.05; 4,0 p = 0.04 and 4,0 p = 0.04 respectively] correlated with poor prognosis and reduced OS. This correlation remained independent of the tumor stage in the multivariate analysis. Meanwhile 88%, 54% and 60% of patients showed more than 70% of positive tumor cells for Oct2, BCL6 and IRF8, only 17.8% and 5.5% reached that percentage for OCAB and PU1. Furthermore, OCAB and PU1 expression was completely lost in 42.5% and 63% of the patients. The OCAB and PU1 expression loss correlated with poor prognosis and reduced OS. We believe that the evaluation of these molecules would be useful to assess prognosis in DLBCL patients at the time of diagnosis. All together these findings imply potential therapeutic considerations since we might need to attack simultaneously diverse interactions among multiple proteins in this B cell lymphoma. Citation Format: Erica A. Rojas Bilbao, Elisa D. Bal de Kier Joffe, Marta E. Zerga, Lydia I. Puricelli, Stella Maris N. Ranuncolo. Expression of Oct-2, OCA-B, BCL6, PU.1 and IRF8 predicts prognosis in Diffuse Large B Cell Lymphoma patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3550. doi:10.1158/1538-7445.AM2015-3550

A model for effects of adaptive immunity on tumor response to chemotherapy and chemoimmunotherapy

Complete clinical regressions of solid tumors in response to chemotherapy are difficult to explain by direct cytotoxicity alone, because of low growth fractions and obstacles to drug delivery. A plausible indirect mechanism that might reconcile this is the action of the immune system. A model for interaction between tumors and the adaptive immune system is presented here, and used to examine controllability of tumors through the interplay of cytotoxic, cytostatic and immunogenic effects of chemotherapy and the adaptive immune response. The model includes cytotoxic and helper T cells, T regulatory cells (Tregs), dendritic cells, memory cells, and several key cytokines. Nearly all parameter estimates are derived from experimental and clinical data. Individual tumors are characterized by two parameters: growth rate and antigenicity, and regions of tumor control are identified in this parameter space. The model predicts that inclusion of the immune response significantly expands the region of tumor control for both cytostatic and cytotoxic chemotherapies. Moreover, outside the control zone, tumor growth is delayed significantly. An optimal fractionation schedule is predicted, for a fixed cumulative dose. The model further predicts expanded regions of tumor control when several forms of immunotherapy (adoptive T cell transfer, Treg depletion, and dendritic cell vaccination) are combined with chemotherapy. Outcomes depend greatly on tumor characteristics, the schedule of administration, and the type of immunotherapy chosen, suggesting promising opportunities for personalized medicine. Overall, the model provides insight into the role of the adaptive immune system in chemotherapy, and how scheduling and immunotherapeutic interventions might improve efficacy.

Metallothionein Expression in Dogs With Chronic Hepatitis and Its Correlation With Hepatic Fibrosis, Inflammation, and Ki-67 Expression.

The chronic form of primary hepatitis occurs commonly in dogs, and the etiology is rarely found. Metallothionein (MT) is a heavy metal-binding protein found in many organs, including the liver. MT was recently shown to enhance liver regeneration and decrease hepatic fibrosis in human beings. This study examined the expression of MT in 24 cases of chronic hepatitis in dogs using immunohistochemistry. To understand the role of MT as a determinant of hepatic inflammation, fibrosis, bile duct proliferation, and regeneration, we correlated its expression with histologic lesions of chronic hepatitis, such as hepatic inflammation, fibrosis, and bile duct proliferation, as well as hepatocellular growth fraction as measured by Ki67 immunolabeling. Hepatocellular growth fraction was used as a measure of hepatic regeneration. Regression analysis revealed a significant positive correlation between MT labeling intensity and growth fraction (r(2) = 0.29, P < .05). The percentage of MT-positive cells and the overall MT expression were both positively correlated with growth fraction (r(2) = 0.25 and 0.26, respectively; P < .05). A negative correlation was found between the overall MT labeling and fibrosis (r(2) = 0.18, P < .05). A similar trend of negative correlation was also found between the percentage of MT-positive cells and fibrosis, but the P value was not statistically significant (r(2) = 0.14, P = .0684). These findings suggest a protective role of MT in dogs affected by chronic hepatitis, similar to its role in human beings. These dogs may respond to treatment modules focusing on enhancing the expression of MT.

Vertical decoupling of nitrate assimilation and nitrification in the Sargasso Sea

The fraction of phytoplankton growth that leads to the rain of organic carbon out of the sunlit surface ocean (“export production”) is central to the ocean׳s sequestration of atmospheric carbon dioxide. Nitrate assimilation has long been taken as a measure of export production; however, this has recently been questioned by suggestions that much of the nitrate in the sunlit layer (the “euphotic zone”) originates from biological nitrogen (N) already in surface waters. This view has been supported by recent observations of euphotic zone nitrate elevated in δ18O relative to its δ15N, taken as indicative of nitrification (the oxidation of recycled ammonium to nitrite and then nitrate). To evaluate the potential importance of nitrification in the Sargasso Sea euphotic zone, we measured the δ15N and δ18O of seawater nitrate for samples with ≥0.2µM nitrate collected on 18 cruises in the Sargasso Sea, and here we present the first large data set to correct for the low but often measurable concentrations of nitrite. Regardless of season, nitrate (i.e., nitrate-only rather than nitrate+nitrite as is commonly reported) δ15N and δ18O increase in unison from below the base of the euphotic zone toward the surface. This pattern derives from nitrate assimilation by phytoplankton, implying that nitrification is much slower than the upward transport of nitrate into the lower Sargasso Sea euphotic zone. In the twilight zone below the euphotic zone, we observe a rise in nitrate δ18O (relative to deeper waters) that is not accompanied by a rise in δ15N, suggesting nitrification co-occurring with nitrate assimilation. Nitrification, therefore, does not appear to occur in euphotic zone waters overlapping with nitrate assimilation only in the ~150m-thick twilight zone layer below it. In net, the data argue for a simpler N cycle for the Sargasso Sea euphotic zone than has recently been suggested, with the rate of euphotic zone nitrate assimilation approximating that of organic carbon export to the deep ocean.

Development of a squamous cell carcinoma mouse model for immunotoxicity testing

An important component of safety assessment of new pharmaceuticals is evaluation of their potential to increase the risk of developing cancer in humans. The traditional 2-year rodent bioassay often is not feasible or scientifically applicable for evaluation of biotherapeutics. Additionally, it has poor predictive value for non-genotoxic immunosuppressive compounds. Thus, there is a need for alternative testing strategies. A novel 3-stage tumor model in syngeneic C3H/HeN mice was evaluated here to study the effects of immunosuppressive drugs on tumor promotion and progression in vivo. The model employed a skin squamous cell carcinoma cell line (SCC VII) due to the increased prevalence of squamous cell carcinoma (SCC) in humans associated with immunosuppression after transplants. Local invasion, colonization and tumor progression were evaluated. The validation set of immunosuppressive drugs included: Cyclosporin (CSA), cyclophosphamide (CTX), azathioprine, etanercept, abatacept and prednisone. Local invasion was evaluated by histological assessment as well as fluorescence trafficking from Qdot®-labeled tumor cells from the site of inoculation to the draining lymph node. Colonization was evaluated by lung colony counts following intravenous inoculation. Tumor progression was assessed by morphometric analysis of lesion area, angiogenesis and growth fraction of established metastatic neoplasia. Immunosuppressive drugs in the validation set yielded mixed results, including decreased progression. The methods and results described herein using an in vivo syngeneic mouse tumor model can provide insight about the assessment of immunosuppressive drugs in carcinogenicity risk assessment.

Small cell lung cancer: will recent progress lead to improved outcomes?

Small cell lung cancer (SCLC) is an aggressive neuroendocrine malignancy with a unique natural history characterized by a short doubling time, high growth fraction, and early development of widespread metastases. Although a chemotherapy- and radiation-sensitive disease, SCLC typically recurs rapidly after primary treatment, with only 6% of patients surviving 5 years from diagnosis. This disease has been notable for the absence of major improvements in its treatment: Nearly four decades after the introduction of a platinum-etoposide doublet, therapeutic options have remained virtually unchanged, with correspondingly little improvement in survival rates. Here, we summarize specific barriers and challenges inherent to SCLC research and care that have limited progress in novel therapeutic development to date. We discuss recent progress in basic and translational research, especially in the development of mouse models, which will provide insights into the patterns of metastasis and resistance in SCLC. Opportunities in clinical research aimed at exploiting SCLC biology are reviewed, with an emphasis on ongoing trials. SCLC has been described as a recalcitrant cancer, for which there is an urgent need for accelerated progress. The NCI convened a panel of laboratory and clinical investigators interested in SCLC with a goal of defining consensus recommendations to accelerate progress in the treatment of SCLC, which we summarize here.

The dynamic interaction between combustible renewables and waste consumption and international tourism: the case of Tunisia.

This paper employs the autoregressive distributed lag (ARDL) bounds methodological approach to investigate the relationship between economic growth, combustible renewables and waste consumption, carbon dioxide (CO2) emissions, and international tourism for the case of Tunisia spanning the period 1990-2010. The results from the Fisher statistic of both the Wald test and the Johansen test confirm the presence of a long-run relationship among the variables under investigation. The stability of estimated parameters has been tested, while Granger causality tests recommend a short-run unidirectional causality running from economic growth and combustible renewables and waste consumption to CO2 emissions, a bidirectional causality between economic growth and combustible renewables and waste consumption and unidirectional causality running from economic growth and combustible renewables and waste consumption to international tourism. In the long-run, the error correction terms confirm the presence of bidirectional causality relationships between economic growth, CO2 emissions, combustible renewables and waste consumption, and international tourism. Our long-run estimates show that combustible renewables and waste consumption increases international tourism, and both renewables and waste consumption and international tourism increase CO2 emissions and output. We recommend that (i) Tunisia should use more combustible renewables and waste energy as this eliminates wastes from touristic zones and increases the number of tourist arrivals, leading to economic growth, and (ii) a fraction of this economic growth generated by the increase in combustible renewables and waste consumption should be invested in clean renewable energy production (i.e., solar, wind, geothermal) and energy efficiency projects.

The density of microvessels positive for Wilms' tumour-1 protein (WT-1) is an independent predictor of recurrence risk in meningiomas.

Wilms' tumour-1 (WT-1) protein m-RNA was recently demonstrated in meningiomas, suggesting the potential application of WT-1 immunotherapy in these tumours. The aim of the present study was to analyze the immunohistochemical expression of WT-1 protein, its correlation with the clinico-pathological variables and association with vascular endothelial growth factor (VEGF) expression, in a series of 60 meningiomas of different histotype and histological grade. None of the cases expressed WT-1 in the neoplastic cells, while endothelial expression was evidenced in a variable number of tumour vessels in all the meningiomas. The density of microvessels positive for WT-1 (WT-1 MVD) was significantly higher in meningiomas showing higher histological grade (P = 0.0191), growth fraction (P = 0.0201), expression of VEGF (P = 0.0288) and recurrence risk (P = 0.022). In addition, high WT-1 MVD was a significant independent predictive factor for a shorter recurrence-free survival (RFS) in patients with completely resected meningiomas (P = 0.0028). In conclusion, this study shows that WT-1 MVD is correlated with the biological aggressiveness of meningiomas. Although no staining for WT-1 was evidenced in the neoplastic cells of these tumours, WT-1 endothelial expression in the tumour vessels might represent a target for WT-1 immunotherapy in the aim of reducing their blood supply and growth.