Search results for "Isolation"

Genetic population structure of two cryptic Gammarus fossarum types across a contact zone

1998

Previous studies have revealed inconsistent results about the taxonomic status of European Gammarus fossarum forms. The variability in morphology and hybridization ability has not shown clear geographic patterns, whereas on a genetical basis two Central European G. fossarum forms have been proposed. In the present study the genetic structure of G. fossarum populations was investigated across a natural contact zone. For the first time direct comparisons of allotopic versus syntopic populations were feasible. 24 Populations of G. fossarum plus 4 populations of G. pulex (as outgroup) were sampled along 2 transects across the contact zone. The genotypes of about 60 individuals per population we…

Leaf shape variation and taxonomic boundaries in two sympatric rupicolous species of Helichrysum (Asteraceae: Gnaphalieae), assessed by linear measur…

2012

Quantifying and understanding the causes of population differentiation in plants are critical for assessing the taxonomic structure of species, as the level of differentiation among populations may correspond to incipient speciation. Using linear and geometric morphometric approaches, phenotypic variation and associations between leaf traits and geographic and environmental characteristics were investigated in Helichrysum crassifolium and the widespread and sympatric Helichrysum pendulum: two species exhibiting conspicuous leaf variation in size and shape. The morphometric results show that both species have distinct patterns of leaf shape variation. However, overlapping values link the ran…

Population genetic structure of the butterflyMelitaea didyma(Nymphalidae) along a northern distribution range border

1996

The population genetic structure of the butterfly Melitaea didyma was studied along the northern distribution range border in Central Germany by means of allozyme electrophoresis. Individuals were sampled from a total of 21 habitat patches from four regions, and two provinces. Sampling was designed to estimate local vs. regional differentiation. High levels of variability were found, He= 0.14-0.21. The mean expected sample heterozygosity from one region, Mosel, was significantly lower than from the Hammelburg region, He= 0.17 and 0.19, respectively. Two hierarchical levels of genetic differentiation were found. Within regions individuals sampled from different patches behaved as belonging t…

Comparative population genetic structures of the fruit flyUrophora carduiand its primary parasitoidEurytoma robusta

2003

The interaction between two species may depend on geographic scale and this in turn can affect co-evolution among them. The present study comparatively examines population genetic structures of the tephritid gall fly Urophora cardui and its primary ectoparasitoid Eurytoma robusta for inference of relative dispersal patterns and host parasitoid specificity. Genetic differentiation patterns indicated two levels of hierarchical structure in both species: locally similar distance-dependencies but globally differences. Locally, both species showed isolation by distance and a high correlation between host anti parasitoid F ST for the same population-pairs was found. At the local level, E. robusta…

Micromanipulation Techniques for the Isolation of Single Microorganisms

2005

A prerequisite for the biochemical and physiological investigation of microorganisms is the isolation and management of pure cultures. The only absolute criterion of purity for a bacterial culture is that it has been derived from the progeny of a single cell. Failure to apply this criterion may lead to much effort in proving the purity of a culture. All strains upon which research is to be based should therefore be rigorously purified before starting to investigate the properties of individual organisms (Johnstone 1969). Ecologically oriented microbiologists are faced especially with the problem of how to obtain a pure culture of certain microbial strains from their densely populated natura…

Standardization of islet isolation outcome- A new automatic system to determine pancreatic islet viability

2011

Pancreatic islet transplantation is emerging as a therapeutic approach for patients affected by diabetes. This approach consists of a minimally invasive procedure replacing insulin-producing cells (pancreatic islets). The technique has been proven successful, but limitations have been identified. One of the major challenges of the procedure is the counting of the isolated pancreatic islets, which is currently jeopardized by subjectivity and inaccuracy. Determination of the accurate islet number is a crucial factor in determining the correlation between the isolation product and clinical outcome. In the proposed study, we have developed software capable of objectively evaluating islet number…

Genetic diversity in the wild : cyclic population dynamics and population isolation

2013

Comparative analysis of physical-chemical precipitation methods of circulating exosome isolation from human biofluids.

2015

Evaluation of CandiSelect4, a new chromogenic medium for isolation and presumptive identification of Candida species from clinical specimens

2008

Abstract In clinical laboratories, isolation of Candida species is generally based on the culture of specimens on Sabouraud dextrose agar. This strategy does not allow species identification on primary culture and makes it difficult to detect mixed cultures. Chromogenic media contain substrates that react specifically with different Candida species, and partly overcome these difficulties. Objectives The aim of this study was to compare two chromogenic media: (i) CandiSelect4 (C4), a new medium developed for direct identification of C. albicans and presumptive identification of C. krusei , C. tropicalis and C. glabrata (ii) CHROMagar Candida (CH), a medium licensed for direct identification …

Bearing fault detection based on time-frequency representations of vibration signals

2015

To prevent failures of a rolling bearing in the gearbox drive system, acceleration sensors are used to detect fault-related signals of the bearing. It is a big challenge to observe and identify signals caused by bearing defects in the time domain or the frequency spectrum by a conventional Fourier analysis. The time-frequency representation of the fault-related signals implemented by the windowed Fourier transform is studied in this work. It is shown that the fault characteristic frequencies can be clearly identified in the time-frequency spectrum if a fault occurs in the bearing of the gearbox at different speeds. Otherwise, the shaft frequency and its multiples are the main harmonics in t…