Feasibility of Gold Fiducial Markers as a Surrogate for Gross Tumor Volume Position in Image-Guided Radiation Therapy of Rectal Cancer

Imaging- and therapeutic targets in neoplastic and musculoskeletal inflammatory diseas

Has the Rate of CD4 Cell Count Decline before Initiation of Antiretroviral Therapy Changed over the Course of the Dutch HIV Epidemic among MSM?

Introduction:Studies suggest that the HIV-1 epidemic in the Netherlands may have become more virulent, leading to faster disease progression if untreated. Analysis of CD4 cell count decline before antiretroviral therapy (ART) initiation, a surrogate marker for disease progression, may be hampered by informative censoring as ART initiation is more likely with a steeper CD4 cell count decline.Methods:Development of CD4 cell count from 9 to 48 months after seroconversion was analyzed using a mixed-effects model and 2 models that jointly modeled CD4 cell counts and time to censoring event (start ART

Non-AIDS defining cancers in the D:A:D Study-time trends and predictors of survival : a cohort study

BACKGROUND:Non-AIDS defining cancers (NADC) are an important cause of morbidity and mortality in HIV-positive individuals. Using data from a large international cohort of HIV-positive individuals, we described the incidence of NADC from 2004-2010, and described subsequent mortality and predictors of these.METHODS:Individuals were followed from 1st January 2004/enrolment in study, until the earliest of a new NADC, 1st February 2010, death or six months after the patient's last visit. Incidence rates were estimated for each year of follow-up, overall and stratified by gender, age and mode of HIV acquisition. Cumulative risk of mortality following NADC diagnosis was summarised using Kaplan-Meier methods, with follow-up for these analyses from the date of NADC diagnosis until the patient's death, 1st February 2010 or 6 months after the patient's last visit. Factors associated with mortality following NADC diagnosis were identified using multivariable Cox proportional hazards regression.RESULTS:Over 176,775 person-years (PY), 880 (2.1%) patients developed a new NADC (incidence: 4.98/1000PY [95% confidence interval 4.65, 5.31]). Over a third of these patients (327, 37.2%) had died by 1st February 2010. Time trends for lung cancer, anal cancer and Hodgkin's lymphoma were broadly consistent. Kaplan-Meier cumulative mortality estimates at 1, 3 and 5 years after NADC diagnosis were 28.2% [95% CI 25.1-31.2], 42.0% [38.2-45.8] and 47.3% [42.4-52.2], respectively. Significant predictors of poorer survival after diagnosis of NADC were lung cancer (compared to other cancer types), male gender, non-white ethnicity, and smoking status. Later year of diagnosis and higher CD4 count at NADC diagnosis were associated with improved survival. The incidence of NADC remained stable over the period 2004-2010 in this large observational cohort.CONCLUSIONS:The prognosis after diagnosis of NADC, in particular lung cancer and disseminated cancer, is poor but has improved somewhat over time. Modifiable risk factors, such as smoking and low CD4 counts, were associated with mortality following a diagnosis of NADC

Coexistence of aerobic chemotrophic and anaerobic phototrophic sulfur bacteria under oxygen limitation

The aerobic chemotrophic sulfur bacterium Thiobacillus thioparus T5 and the anaerobic phototrophic sulfur bacterium Thiocapsa roseopersicina M1 were co-cultured in continuously illuminated chemostats at a dilution rate of 0.05 h(-1). Sulfide was the only externally supplied electron donor, and oxygen and carbon dioxide served as electron acceptor and carbon source, respectively. Steady states were obtained with oxygen supplies ranging from non-limiting amounts (1.6 mol O-2 per mol sulfide, resulting in sulfide limitation) to severe limitation (0.65 mol O-2 per mol sulfide). Under sulfide limitation Thiocapsa was competitively excluded by Thiobacillus and washed out. Oxygen/sulfide ratios between 0.65 and 1.6 resulted in stable coexistence. It could be deduced that virtually all sulfide was oxidized by Thiobacillus. The present experiments showed that Thiocapsa is able to grow phototrophically on the partially oxidized products of Thiobacillus. In pure Thiobacillus cultures in steady state extracellular zerovalent sulfur accumulated. in contrast to mixed cultures. This suggests that a soluble form of sulfur at the oxidation state of elemental sulfur is formed by Thiobacillus as intermediate. As a result, under oxygen limitation colorless sulfur bacteria and purple sulfur bacteria do not competitively exclude each other but can coexist. It was shown that its ability to use partially oxidized sulfur compounds, formed under oxygen limiting conditions by Thiobacillus, helps explain the bloom formation of Thiocapsa in marine microbial mats.</p

Coexistence of aerobic chemotrophic and anaerobic phototrophic sulfur bacteria under oxygen limitation

The aerobic chemotrophic sulfur bacterium Thiobacillus thioparus T5 and the anaerobic phototrophic sulfur bacterium Thiocapsa roseopersicina M1 were co-cultured in continuously illuminated chemostats at a dilution rate of 0.05 h(-1). Sulfide was the only externally supplied electron donor, and oxygen and carbon dioxide served as electron acceptor and carbon source, respectively. Steady states were obtained with oxygen supplies ranging from non-limiting amounts (1.6 mol O-2 per mol sulfide, resulting in sulfide limitation) to severe limitation (0.65 mol O-2 per mol sulfide). Under sulfide limitation Thiocapsa was competitively excluded by Thiobacillus and washed out. Oxygen/sulfide ratios between 0.65 and 1.6 resulted in stable coexistence. It could be deduced that virtually all sulfide was oxidized by Thiobacillus. The present experiments showed that Thiocapsa is able to grow phototrophically on the partially oxidized products of Thiobacillus. In pure Thiobacillus cultures in steady state extracellular zerovalent sulfur accumulated. in contrast to mixed cultures. This suggests that a soluble form of sulfur at the oxidation state of elemental sulfur is formed by Thiobacillus as intermediate. As a result, under oxygen limitation colorless sulfur bacteria and purple sulfur bacteria do not competitively exclude each other but can coexist. It was shown that its ability to use partially oxidized sulfur compounds, formed under oxygen limiting conditions by Thiobacillus, helps explain the bloom formation of Thiocapsa in marine microbial mats.</p

The role of microbial mats during primary succession in calcareous dune slacks: an experimental approach

Laminated microbial mats from a sandy beach plain were grown in water-saturated pots in a glass house for six months and then used to assess their effect on the establishment of juveniles of three plant species representing different successional stages in dune slack development. The selected species were Samolus valerandi, characteristic of pioneer stages, Calamagrostis epigejos, characteristic of more productive, late successional stages, and Juncus alpinoarticulatus, which occurs in a wide range of successional stages. Juveniles of all three species that were placed on top of intact living microbial mats established themselves in the mat. C. epigejos and J. alpinoarticulatus survived for several weeks but later on their numbers decreased and the total biomass production of the species after six months was poor. S. valerandi, in contrast, grew profusely in intact microbial and algal mats. Heating of the microbial mat by heat sterilization, prior to the experiment, did not improve the performance of the species. When the juveniles were planted in the microbial mats after breaking the surface of the mat, the survival of juveniles of C. epigejos and J. alpinoarticulatus was much higher and so was the biomass of surviving plants after six months. Planting of Samolus in the mats had some positive effect on the survival percentage of the juveniles, but not on the total biomass at the end of the experiment. Slightly lower water tables had a negative effect on the performance of all species. Measurements of the pH in the pots revealed that there were no significant differences in the top layer. Sulphide concentrations were very low in all the pots where juveniles had been planted and also in the pots with S. valerandi. Relatively high concentrations (30 - 50 µmol/l) were found in pots with poor growth of Juncus and Calamagrostis plants. These values may exceed toxic levels for these species. Although oxygen concentrations in the pots were generally low, no relation existed between plant biomass and oxygen content, indicating that plant growth was not primarily limited by oxygen stress. These experiments support the idea that microbial mats may assist in extending the life span of early pioneer stages during dune slack succession by inhibiting the growth of species of later successional stages.