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Evolution of genome size in the Dasycladales (Chlorophyta) as determined by DAPI cytophotometry Texto completo
1998
Kapraun, Donald F. | Buratti, Jason R.
Microspectrophotometry with the DNA-localizing fluorochrome 4′,6-diamidino-2-phenylindole (DAPI) was used to estimate nuclear genome sizes in 12 species representing two families of the Dasycladales. Estimated 2C DNA contents in these taxa range from 0.7–1.4 pg in the family Dasycladaceae and from 0.9–2.4 pg in the family Acetabulariaceae. In both families, species exhibiting characteristics considered to be primitive appear to have 2C DNA contents that approximate 50% of values found in species exhibiting characteristics considered to be more advanced. Results suggest that polyploidy events have accompanied evolution in the order but apparently have been infrequent and conservatively preserved, leading to a narrow range of relatively small genome sizes. Limitations on genome size increase are discussed in terms of constraints imposed by a prolonged uninucleate stage. Interspecific comparisons of genome size and gametangium volume suggest an inverse relationship. Gametangium volume appears to have phylogentic significance, in that taxa with more advanced characteristics generally have smaller gametangia.
Mostrar más [+] Menos [-]Content of digestible energy in fish feed ingredients determined by the ingredient-substitution method
1998
Aksnes, A. (SSF, Fyllingdalen (Norway).) | Opstvedt, J.
Content of digestible energy in fish feed ingredients determined by the ingredient-substitution method
1998
Aksnes, A. | Opstvedt, J.
The content of digestible energy (DE) in various fish meals, soya protein concentrate and soya bean meal was determined in compound diets for rainbow trout (Oncorhynchus mykiss). The determinations were performed using casein with a known digestibility in trout, as a reference compound. In the determination of DE of fish feed ingredients, the test sample was exchanged with casein in the test diet. Cr2O3 was used as an inert marker, and faeces was obtained by stripping. The determination differentiated between various qualities of fish meal. Digestibility coefficients for energy in fish meals of 'high quality' (five samples), 'medium quality' (three samples) and 'fair average quality' (FAQ) (one sample) were determined to be 97.3, 94.1 and 85.3%, respectively. Corresponding values for apparent digestibility coefficient (ADC) for protein were 89.3, 86.4 and 76.7%, respectively. The directly determined values for DE were in good agreement with values obtained by calculation based on the chemical composition of the ingredient, the ADC for protein, fat and carbohydrate and the respective combustion values for these nutrients. Absolute values of soya products could be questioned due to decreased digestibility of carbohydrate with increased inclusion level and due to possible nutrient interference. An average value for DE based on five different samples of special-quality Norwegian fish meal (Norse-LT94) was determined to be 20.5 +/- 0.3 MJ kg-1 dry matter (dm). One sample of soya protein concentrate and extracted soya bean meal had values of 12.6 +/- 1.0 and 11.0 +/- 0.9 MJ kg-1 of dm. Digestibility coefficients for energy and protein were found to be higher in fish reared in freshwater compared to saltwater.
Mostrar más [+] Menos [-]The dual pumping technique (DPT) for level-determined sampling in fully screened groundwater wells
1998
Rapp, M.C. | Fulda, C. | Schafer, W. | Kinzelbach, W.
A new and inexpensive technique to obtain vertical hydrochemical profiles in aquifers is presented. The Dual Pumping Technique (DPT) is designed for use in fully-screened groundwater wells and represents an alternative to packer installations or similar sampling devices. Two pumps are placed at either end of the well screen. The ratio of their pumping rates is varied from 1 to 0. Depending on this ratio, the two pumps abstract variable portions of the influx distribution. A water divide develops in the well, separating the flow upward from the flow downward. A set of samples from the upper and lower pump are taken for different pumping rate ratios. Measured solute concentrations in these samples, together with the influx distribution determined by flow logging, are used to reconstruct vertical concentration profiles. The measured data are evaluated with a simple, robust algorithm, which is derived in the text and exemplified in the Appendix. The DPT was used to determine vertical concentration distributions of chlorinated hydrocarbon solvents (CHS) and tritium in a contaminated aquifer near Heidelberg, Germany. Comparison of the concentration profile obtained with the DPT with CHS and tritium data from a 50-m distant multilevel well showed the principal applicability of the new technique. The pattern of the vertical concentration distributions was successfully identified with the DPT, but the absolute CHS concentration values were one order of magnitude higher in the multilevel well, due to the fact that the multilevel well is probably closer to the centre of the plume than the well used for the DPT. The 3H values could be compared directly and showed an excellent agreement. Further evaluation of the DPT in a situation where a multilevel reference well is in closer vicinity to the test well is planned.
Mostrar más [+] Menos [-]Dissolved iron at subnanomolar levels in the Southern Ocean as determined by ship-board analysis Texto completo
1998
Jong, J. T. M. de | Das, J. den | Bathmann, Ulrich | Stoll, M. H. C. | Kattner, Gerhard | Nolting, R. F. | Baar, H. J. W. de
Spatial variation in hydraulic conductivity determined by slug tests in the Canadian River alluvium near the Norman Landfill, Norman, Oklahoma
1998
Scholl, M. A. (Martha A) | Christenson, Scott C.
Genetic variation of the resin top fungus in Finland as determined by random amplified microsatellites (RAMS) Texto completo
1998
Hantula, J. | Niemi, E.M. | Kaitera, J. | Jalkanen, R. | Kurkela, T. | Metsäntutkimuslaitos
Genetic variation of the resin top fungus in Finland as determined by random amplified microsatellites (RAMS)
1998
Hantula, J. | Maarit Niemi, E. | Kaitera, J. | Jalkanen, R. | Kurkela, T.
Die Untersuchung von Aecidien von Peridermium pini (Endocronartium pini), dem Erreger des Kienzopfes an Pinus sylvestris, mit Hilfe von molekularen Markern (zufaellig amplifizierte Mikrosatelliten, RAMS) zeigte eine geringe genetische Variation zwischen den Populationen dieses Rostpilzes in Finnland. Die Methode erlaubte die Identifizierung heterozygoter Aecidien anhand von zwei Genloci, es wurde jedoch nur ein geringer Heterozygotiegrad nachgewiesen. Die RAMS-Muster von Aecidiosporen aus Finnland, Thetford (UK) und von Cronartium flaccidum aus Italien waren sehr aehnlich. Dies laesst auf eine nahe genetische Verwandtschaft zwischen den autoezischen und den heteroezischen Formen dieser Rostpilze schliessen.
Mostrar más [+] Menos [-]Setting in motion the immune mechanisms underlying genetically determined resistance and susceptibility to infection with Leishmania major
1998
Launois, P. | Conceicao-Silva, F. | Himmerlich, H. | Parra-Lopez, C. | Tacchini-Cottier, F. | Louis, J.A. (WHO Immunology Research and Training Centre, Institute of Biochemistry, University of Lausanne, 1066 Epalinges (Switzerland))
Genetically determined resistance to flavivirus infection in wild Mus musculus domesticus and other taxonomic groups in the genus Mus Texto completo
1998
Sangster, M. Y. | Mackenzie, J. S. | Shellam, G. R.
Inherited resistance to flaviviruses in laboratory mice is a rare trait conferred by an autosomal dominant gene (Flv ʳ ). To provide information on genetic resistance to flaviviruses in wild mice, we analysed (i) wild M. m. domesticus trapped in Australia, and (ii) mice representing other species and subspecies in the genus Mus. Mice were screened for resistance relative to C3H/HeJ mice by intracerebral challenge with Murray Valley encephalitis virus or yellow fever virus, and breeding studies were undertaken to identify inherited resistance factors. Widespread flavivirus resistance was demonstrated in Australian M. m. domesticus. A single, autosomal dominant Flv ʳ -like gene appeared to be primarily responsible, but there was some evidence for additional inherited resistance factors. Flavivirus resistance was also identified in other taxonomic groups, and a genetic basis for this resistance was demonstrated in M. m. musculus (Skive), M. spretus, and M. spicilegus. Interestingly, M. m. musculus (CZI-O) were more susceptible than C3H/HeJ mice. Our findings show that genetic resistance to flaviviruses is common in divergent taxonomic groups in the genus Mus, suggesting that the trait has an ancient evolutionary origin, but whether flavivirus resistance genes have an anti-viral role or serve some other function is unknown.
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