The measuring of cell features

The usefulness of various feature sets for discriminating between different cell populations cannot be assessed without considering the entire automated cytology system, from specimen preparation through scanning, cell search, cell segmentation, artifact rejection and feature extraction to object classification and multivariate data analysis methods. These different stages in the analysis procedure are discussed in this paper and illustrated by examples from the author's experience of cell analysis studies, ranging from single-cell classification experiments to a test of a complete automated system under realistic conditions on a set of 397 cell specimens.     

Growth and metabolic flexibility in groundwater bacteria

Groundwater bacteria isolated from an oligotrophic-saturated soil showed a mixed strategy of economized metabolism and migration when grown in a continuous-flow column system simulating poor or nutrient-amended growth conditions. The cells were generally <0.5m in diameter in pure groundwater, but doubled in size when the concentration of dissolved organic carbon and phosphate in groundwater was increased 10-fold. The biomass, estimated from analysis of muramic acid (MuAc) in cell wall peptidoglucans, increased at the same time by a factor of 5 when the solid support in the columns was gravel and by a factor of 10 when it was glass beads. Bacteria in pure groundwater stored 10 times more of the energy-rich polysaccharide, poly--hydroxybutyric acid (PHB), than bacteria in enriched groundwater, and those cells that were attached to the gravel stored 10 times as much as cells in the interstitial pore water. Once phosphate was added to groundwater, stored PHB was metabolized. The proportion of free-living to attached bacteria was 2 to 10 times higher in enriched compared with pure groundwater indicating a mass transport of cells as the carrying capacity of their habitat rose.     

Accumulation of a peptide toxin from the cyanobacterium Oscillatoria agardhii in the freshwater mussel Anadonta cygnea

Swan mussels (Anodonta cygnea) were exposed to a toxic strain of the cyanobacterium Oscillatoria agardhii. Mussels accumulated large amounts of the peptide Oscillatoria toxin which was present in low concentrations within the cyanobacterial cells in the test aquaria (40–60 µg Oscillatoria toxin/1). The toxin concentration in the mussels increased during the experiment and after 15 days of exposure the concentration was 70 ± 2 µg/g freeze dried tissue (mean ± range of values). The highest concentration of the toxin (130 µg/g of freeze dried tissue) was found in the hepatopancreatic tissue. The toxin did not seem to be metabolized in the mussels and they were not killed by the high toxin concentrations within them. After two months in clean water still detectable amounts of toxin were present in the mussels.     

Assignment of the gene encoding the catalytic subunit Cβ of CAMP-dependent protein kinase to the p36 band on chromosome

Summary A cDNA for the human catalytic subunit (C) of cAMP-dependent protein kinase (PKA) has been cloned from a testis cDNA library. In the present study, we have determined the chromosomal localization of this gene using a cDNA for C as a probe. Southern blot analysis of genomic DNA from human/mouse cell hybrids revealed that the presence or absence of a 20-kbXbaI fragment, which hybridized with the C probe, was concordant with the presence of human chromosome 1.In situ hybridization to metaphase chromosome confirmed the somatic cell hybrid data and regionally mapped the C gene of PKA to the p36 band on chromosome 1.     

Influence of fungi on growth and survival of Onychiurus armatus (Collembola) in a metal polluted soil

Summary The influence of food quantity and quality on growth and survival of Onychiurus armatus (Tullb.) in metal polluted environments has been investigated in laboratory experiments. The Collembola was reared on five species of fungi isolated from a metal polluted soil close to a brass mill in SE Sweden.Survival of O. armatus was improved when fungal biomass was continuously added in a polluted mor (1,300 ppm Zn and 200 ppm Cu), and when specimens were fed metal polluted fungi for 1, 3 and 7 days a week, only those that were starved had increased mortality. Allometric growth, on the other hand, was significantly reduced when Collembola was given surplus of metal polluted fungi, whereas growth losses caused by metals were offset by protein rich food. Hence, sufficient food quantities alone could overcome mortality losses but not growth retardation in a metal polluted environment.Feeding preference of O. armatus was not determined by the protein content of the fungi although this was beneficial for growth. Metals changed the relative palatability of fungal species, but one of the metal tolerant species, Paecilomyces farinosus, which was also protein rich, remained reasonably attractive for O. armatus also when it was metal polluted. The mechanisms by which growth and survival of O. armatus were promoted by a combination of protein and Zn/Cu rich fungi seemed to be crucial in understanding the fate of a population of this species in a metal polluted soil.