Marine plastic litter as an artificial hard bottom fouling ground

20 fouling organisms were observed on plastic litter dredged from the Elbe estuary during July 1990; 60% of the species were typical sessile hard bottom organisms. Most individuals found on this artificial hard bottom were barnacles (Balanus crenatus, Elminius modestus), the musselMytilus edulis and the polychaeteLanice conchilega. All individuals were juveniles which had settled only recently on the plastics. The earliest settlers were not much older than 4–8 weeks.     

Cutaneous respirometry by dynamic measurement of mitochondrial oxygen tension for monitoring mitochondrial function in vivo

Progress in diagnosis and treatment of mitochondrial dysfunction in chronic and acute disease could greatly benefit from techniques for monitoring of mitochondrial function in vivo. In this study we demonstrate the feasibility of in vivo respirometry in skin. Mitochondrial oxygen measurements by means of oxygen-dependent delayed fluorescence of protoporphyrin IX are shown to provide a robust basis for measurement of local oxygen disappearance rate (ODR). The fundamental principles behind the technology are described, together with an analysis method for retrievel of respirometry data. The feasibility and reproducibility of this clinically useful approach are demonstrated in a series of rats.     

Diversity of protists and bacteria determines predation performance and stability

Predation influences prey diversity and productivity while it effectuates the flux and reallocation of organic nutrients into biomass at higher trophic levels. However, it is unknown how bacterivorous protists are influenced by the diversity of their bacterial prey. Using 456 microcosms, in which different bacterial mixtures with equal initial cell numbers were exposed to single or multiple predators (Tetrahymena sp., Poterioochromonas sp. and Acanthamoeba sp.), we showed that increasing prey richness enhanced production of single predators. The extent of the response depended, however, on predator identity. Bacterial prey richness had a stabilizing effect on predator performance in that it reduced variability in predator production. Further, prey richness tended to enhance predator evenness in the predation experiment including all three protists predators (multiple predation experiment). However, we also observed a negative relationship between prey richness and predator production in multiple predation experiments. Mathematical analysis of potential ecological mechanisms of positive predator diversity—functioning relationships revealed predator complementarity as a factor responsible for both enhanced predator production and prey reduction. We suggest that the diversity at both trophic levels interactively determines protistan performance and might have implications in microbial ecosystem processes and services.     

Cutaneous Respirometry as Novel Technique to Monitor Mitochondrial Function: A Feasibility Study in Healthy Volunteers

BackgroundThe protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) is proposed as a potential clinical non-invasive tool to monitor mitochondrial function. This technique has been evaluated in several animal studies. Mitochondrial respirometry allows measurement in vivo of mitochondrial oxygen tension (mitoPO₂) and mitochondrial oxygen consumption (mitoVO₂) in skin. This study describes the first use of a clinical prototype in skin of humans.MethodsThe clinical prototype was tested in 30 healthy volunteers. A self-adhesive patch containing 2 mg 5-aminolevulinic acid (ALA) was applied on the skin of the anterior chest wall (sternal) for induction of mitochondrial protoporphyrin IX and was protected from light for 5 h. MitoPO₂ was measured by means of oxygen-dependent delayed fluorescence of protoporphyrin IX. MitoVO₂ was determined by dynamic mitoPO₂ measurements on the primed skin, while locally blocking oxygen supply by applying local pressure with the measurement probe. MitoPO₂ was recorded before and during a 60-s period of compression of the microcirculation, at an interval of 1 Hz. Oxygen consumption (i.e. the local oxygen disappearance rate) was calculated from the decay of the mitoPO₂ slope.ResultsOxygen-dependent delayed fluorescence measurements were successfully performed in the skin of 27 volunteers. The average value (± SD) of mitoPO₂ was 44 ± 17 mmHg and mean mitoVO₂ values were 5.8 ± 2.3 and 6.1 ± 1.6 mmHg s^-1 at a skin temperature of 34°C and 40°C, respectively. No major discomfort during measurement and no long-term dermatological abnormalities were reported in a survey performed 1 month after measurements.ConclusionThese results show that the clinical prototype allows measurement of mitochondrial oxygenation and oxygen consumption in humans. The development of this clinically applicable device offers opportunities for further evaluation of the technique in humans and the start of first clinical studies.     

Habitat fragmentation, variable edge effects, and the landscape-divergence hypothesis

Edge effects are major drivers of change in many fragmented landscapes, but are often highly variable in space and time. Here we assess variability in edge effects altering Amazon forest dynamics, plant community composition, invading species, and carbon storage, in the world's largest and longest-running experimental study of habitat fragmentation. Despite detailed knowledge of local landscape conditions, spatial variability in edge effects was only partially foreseeable: relatively predictable effects were caused by the differing proximity of plots to forest edge and varying matrix vegetation, but windstorms generated much random variability. Temporal variability in edge phenomena was also only partially predictable: forest dynamics varied somewhat with fragment age, but also fluctuated markedly over time, evidently because of sporadic droughts and windstorms. Given the acute sensitivity of habitat fragments to local landscape and weather dynamics, we predict that fragments within the same landscape will tend to converge in species composition, whereas those in different landscapes will diverge in composition. This 'landscape-divergence hypothesis', if generally valid, will have key implications for biodiversity-conservation strategies and for understanding the dynamics of fragmented ecosystems.     

Using statistical analysis for setting process validation acceptance criteria for biotech products

This paper discusses the challenges of setting process validation acceptance criteria for biotech products for cases where using statistical tools is appropriate. Data are analyzed under three different scenarios that are frequently encountered in biotech applications. Scenario A represents the case when a small data set around center point conditions is available for setting acceptance criteria. Scenario B represents the case when a larger data set within normal operation conditions is available for setting acceptance criteria. Scenario C represents the case when a large characterization data set is available for setting acceptance criteria and it is possible to accurately model the impact of operation conditions on performance of the step. Statistical approaches including mean +/- 3SD, tolerance interval analysis, prediction profiler, and Monte Carlo simulation are applied to the different scenarios. Strengths and shortcomings of the different statistical tools are discussed, and the best approach for each scenario is recommended. It is shown that selection of the right statistical approach is a critical first step toward setting appropriate acceptance criteria.