Action ofN-methyl-N′-nitro-N-nitrosoguanidine inRhizobium trifolii

Rhizobium trifolii was highly resistant to the lethal effect ofN-methyl-N-nitro-N-nitrosoguanidine (MNNG), but it was sensitive to the mutagenic action of this chemical. A concentration of 500g/ml yields a survival of between 1% and 10%, which allows us to obtain a higher number of mutants than lower concentrations that yield higher survival rates. Lethal damage produced by nitrosoguanidine was repaired, and repair is inhibited by acriflavine.     

Detection of salmonellas by DNA hybridization with a fluorescent alkaline phosphatase substrate.

This study evaluates a DNA hybridization assay for salmonella with AttoPhos (JBL Scientific, San Luis Obispo, CA), a fluorescent substrate for alkaline phosphatase. The probe used (50 ng/ml) was a biotinylated 600 bp fragment consisting of a tandem repeat of an insertion sequence (IS200) found in most Salmonella spp. evaluated. The hybridization was carried out at 65 degrees C for 2 h without prior prehybridization and hybrids were detected by the addition of a streptavidin-alkaline phosphatase conjugate. Circles (5 mm) were cut from the membrane and placed in a cuvette containing 1 ml of 1 mmol/l AttoPhos. The reaction was evaluated after 30 min at 37 degrees C with a fluorometer with an excitation wavelength of 440 nm and an emission wavelength of 550 nm. The sensitivity of the probe was estimated to be 10,000 copies of target DNA or 5 x 10(-20) mol of DNA. All 74 salmonella strains tested reacted with the probe but none of the 98 heterologous species tested gave positive results. The results of this study indicate that our assay method, which employs a biotinylated tandem repeat of IS200 and AttoPhos, is a specific and highly sensitive quantitative method for the detection of salmonellas.     

Note on the diet of the jaguar in central Brazil

Diet of the jaguar Panthera onca in the Cerrado, central Brazil, was investigated based on a sample of genetically identified jaguar scats. At least nine prey species were observed in 35 scat samples. Giant anteaters Myrmecophaga tridactyla contributed more than 75 % of biomass to the observed diet. Tapirs Tapirus terrestris and peccaries Tayassu pecari and Pecari tajacu contributed approximately 6 % to jaguar diet each, and small mammals contributed least to the jaguar diet. At 0.121, dietary niche breadth was narrower than reported in most other studies. Due to their physical characteristics and abundance, giant anteaters are likely the most profitable prey for jaguars in Emas National Park, and as an important prey, they should be included in jaguar conservation efforts.     

Extensive gaps and biases in our knowledge of a well‐known fauna: implications for integrating biological traits into macroecology

Aim Ecologists seeking to describe patterns at ever larger scales require compilations of data on the global abundance and distribution of species. Comparable compilations of biological data are needed to elucidate the mechanisms behind these patterns, but have received far less attention. We assess the availability of biological data across an entire assemblage: the well‐documented demersal marine fauna of the United Kingdom. We also test whether data availability for a species depends on its taxonomic group, maximum body size, the number of times it has been recorded in a global biogeographic database, or its commercial and conservation importance. Location Seas of the United Kingdom. Methods We defined a demersal marine fauna of 973 species from 15 phyla and 40 classes using five extensive surveys around the British Isles. We then quantified the availability of data on eight key biological traits (termed biological knowledge) for each species from online databases. Relationships between biological knowledge and our predictors were tested with generalized linear models. Results Full data on eight fundamental biological traits exist for only 9% (n= 88) of the UK demersal marine fauna, and 20% of species completely lack data. Clear trends in our knowledge exist: fish (median biological knowledge score = six traits) are much better known than invertebrates (one trait). Biological knowledge increases with biogeographic knowledge and (to a lesser extent) with body size, and is greater in species that are commercially exploited or of conservation concern. Main conclusions Our analysis reveals deep ignorance of the basic biology of a well‐studied fauna, highlighting the need for far greater efforts to compile biological trait data. Clear biases in our knowledge, relating to how well sampled or ‘important’ species are suggests that caution is required in extrapolating small subsets of biologically well‐known species to ecosystem‐level studies.     

Unusual growth pattern in the Frasnian alveolitids (Tabulata) from the Holy Cross Mountains (Poland)

Abstract: Growth periodicity is a phenomenon occurring in fossil and modern corals. The most apparent feature is growth banding, and environmental changes are broadly accepted as controls on this phenomenon. If environment controls the growth, then all corallites within a colony should repeat the same growth pattern, as individuals are clones and must have shared the same environment. A study on several species of Alveolitidae (Anthozoa, Tabulata) from the Late Devonian (Early Frasnian) of the Holy Cross Mountains (Poland) shows that the growth pattern varies between neighbouring individuals within the same corallum. This contradicts observations of closely related Favositida as demonstrated on Pachyfavosites sp. from the Givetian of Avesnois, France, where neighbouring individuals repeat the same pattern. Therefore, environmental control on growth rhythm in Alveolitidae can be excluded; the causes of differences between individuals remain unknown.     

An integrated practical implementation of continuous aqueous two‐phase systems for the recovery of human IgG: From the microdevice to a multistage bench‐scale mixer‐settler device

Aqueous two‐phase systems (ATPS) are a liquid‐liquid extraction technology with clear process benefits; however, its lack of industrial embracement is still a challenge to overcome. Antibodies are a potential product to be recovered by ATPS in a commercial context. The objective of this work is to present a more integral approach of the different isolated strategies that have arisen in order to enable a practical, generic implementation of ATPS, using human immunoglobulin G (IgG) as experimental model. A microfluidic device is used for ATPS parameters preselection for product recovery. ATPS were continuously operated in a mixer‐settler device in one stage, multistage and multistage with recirculation configuration. Single‐stage pure IgG extraction with a polyethylene glycol (PEG) 3350‐phophates ATPS within continuous operation allowed a 65% recovery. Further implementation of a multistage platform promoted a higher particle partitioning reaching a 90% recovery. The processing of IgG from a cell supernatant culture harvest in a multistage system with top phase recirculation resulted in 78% IgG recovery in bottom phase. This work conjugates three not widely spread methodologies for ATPS: microfluidics, continuous and multistage operation.     

Multivariate analysis applied to tomato hybrid production

Summary Twenty characters were measured on 60 tomato varieties cultivated in the open-air and in polyethylene plastic-house. Data were analyzed by means of principal components, factorial discriminant methods, Mahalanobis D² distances and principal coordinate techniques. Factorial discriminant and Mahalanobis D² distances methods, both of which require collecting data plant by plant, lead to similar conclusions as the principal components method that only requires taking data by plots. Characters that make up the principal components in both environments studied are the same, although the relative importance of each one of them varies within the principal components. By combining information supplied by multivariate analysis with the inheritance mode of characters, crossings among cultivars can be experimented with that will produce heterotic hybrids showing characters within previously established limits.     

Dying like rabbits: general determinants of spatio-temporal variability in survival

1. Identifying general patterns of how and why survival rates vary across space and time is necessary to truly understand population dynamics of a species. However, this is not an easy task given the complexity and interactions of processes involved, and the interpopulation differences in main survival determinants. 2. Here, using European rabbits (Oryctolagus cuniculus) as a model and information from local studies, we investigated whether we could make inferences about trends and drivers of survival of a species that are generalizable to large spatio-temporal scales. To do this, we first focused on overall survival and then examined cause-specific mortalities, mainly predation and diseases, which may lead to those patterns. 3. Our results show that within the large-scale variability in rabbit survival, there exist general patterns that are explained by the integration of factors previously known to be important at the local level (i.e. age, climate, diseases, predation or density dependence). We found that both inter- and intrastudy survival rates increased in magnitude and decreased in variability as rabbits grow old, although this tendency was less pronounced in populations with epidemic diseases. Some causes leading to these higher mortalities in young rabbits could be the stronger effect of rainfall at those ages, as well as, other death sources like malnutrition or infanticide. 4. Predation is also greater for newborns and juveniles, especially in population without diseases. Apart from the effect of diseases, predation patterns also depended on factors, such as, density, season, and type and density of predators. Finally, we observed that infectious diseases also showed general relationships with climate, breeding (i.e. new susceptible rabbits) and age, although the association type varied between myxomatosis and rabbit haemorrhagic disease. 5. In conclusion, large-scale patterns of spatio-temporal variability in rabbit survival emerge from the combination of different factors that interrelate both directly and through density dependence. This highlights the importance of performing more comprehensive studies to reveal combined effects and complex relationships that help us to better understand the mechanisms underlying population dynamics.     

Removal of N-glycans from cell surface proteins induces apoptosis by reducing intracellular glutathione levels in the rhabdomyosarcoma cell line S4MH

Expression of determined Asn-bound glycans (N-glycans) in cell surface glycoproteins regulates different processes in tumour cell biology. Specific patterns of N-glycosylation are displayed by highly metastatic cells and it has been shown that inhibition of N-glycan processing restrains cell proliferation and induces cell death via apoptosis. However, the mechanisms by which different N-glycosylation states may regulate cell viability and growth are not understood. Since malignant cells express high levels of intracellular glutathione (GSH) and a reduction of intracellular GSH induces cell death via apoptosis, we investigated whether GSH was involved in the induction of apoptosis by removal of cell surface N-glycans. We found that removal of N-glycans from cell surface proteins by treating the rhabdomyosarcoma cell line S4MH with tunicamycin or N-glycosidase resulted in a reduction in intracellular GSH content and cell death via apoptosis. Moreover, GSH depletion caused by the specific inhibitor of GSH synthesis BSO induced apoptosis in S4MH cells. This data indicates that adequate N-glycosylation of cell surface glycoproteins is required for maintenance of intracellular GSH levels that are necessary for cell survival and proliferation.