Ecology of the active soil microfauna (Protozoa, Metazoa) of Wilkes Land, East Antarctica

Active ciliates, testate amoebae, nematodes, rotifers and tardigrades were examined in fresh and preserved fellfield, moss and ornithogenic soil samples of Wilkes Land. Direct counting was used to investigate abundances, community structures and protozoan diversity. Twenty-six ciliate species (nine first records for continental Antarctica, one undescribed) and five testacean species (three new records) were found. Two Colpoda species were active, further disproving Smith's hypothesis that this genus is absent in continental Antarctica. Animal frequencies varied between habitats but every group occurred in at least 74% of the samples, rotifers (95%) and testaceans (92%) being most frequent. Highest abundances were recorded in moss: 354 ciliates/g dry soil (19 species), 671 testaceans (5 species), 513 nematodes, 1,311 rotifers and 4,607 tardigrades, which thus dominated. Rotifers were most abundant in the other habitats. The microfauna was not randomly distributed because individual numbers were often strongly intercorrelated. Water and organic matter content were relevant environmental parameters; air temperature and pH probably had indirect effects. Received:28 August 1996 / Accepted:23 November 1996     

Effect of prolonged exposure to a magnetic field on the haematopoietic stem cell.

The authors studied the effect of prolonged exposure (3, 4 and 5 months) to the action of a magnetic field of 180-200 gauss formed by the poles of a rotating permanent magnet on the haematopoietic stem cells of mouse bone marrow donors. The effect of the field was evaluated from the ability of the donors' bone marrow cells to form haematopoietic colonies in the spleen of lethally irradiated mice. It was found that the number of stem cells was not reduced by the action of the above magnetic field and that proliferative capacity was likewide unimpaired.     

Thermostability of the erythrocytes of mice exposed to the action of a magnetic field.

The authors investigated the thermostability of the erythrocytes os strain CBA mice exposed to the action of a magnetic field formed by the poles of a rotating permanent magnet of 20 mT (200 GAUSS) induction. The erythrocytes of animals which spent 17 weeks in the magnetic field were significantly less heat resistance than those of the control animals. The effect on animals kept in the magnetic field during embryoyenesis and infancy and then left 3 months outside it was even more pronounced.     

A xyloglucan-specific endo-beta-1,4-glucanase from Aspergillus aculeatus: expression cloning in yeast, purification and characterization of the recombinant enzyme

A full-length c-DNA encoding a xyloglucan-specific endo -beta-1, 4- glucanase (XEG) has been isolated from the filamentous fungus Aspergillus aculeatus by expression cloning in yeast. The colonies expressing functional XEG were identified on agar plates containing azurine-dyed cross-linked xyloglucan. The cDNA encoding XEG was isolated, sequenced, cloned into an Aspergillus expression vector, and transformed into Aspergillus oryzae for heterologous expression. The recombinant enzyme was purified to apparent homogeneity by anion- exchange and gel permeation chromatography. The recombinant XEG has a molecular mass of 23,600, an isoelectric point of 3.4, and is optimally stable at a pH of 3.4 and temperature below 30 degreesC. The enzyme hydrolyzes structurally diverse xyloglucans from various sources, but hydrolyzes no other cell wall component and can therefore be considered a xyloglucan-specific endo -beta-1, 4-glucanohydrolase. XEG hydrolyzes its substrates with retention of the anomeric configuration. The Kmof the recombinant enzyme is 3.6 mg/ml, and its specific activity is 260 micromol/min per mg protein. The enzyme was tested for its ability to solubilize xyloglucan oligosaccharides from plant cell walls. It was shown that treatment of plant cell walls with XEG yields only xyloglucan oligosaccharides, indicating that this enzyme can be a powerful tool in the structural elucidation of xyloglucans.      

Preparation of soybean seed samples for FT-IR microspectroscopy

Typical preparation of seed samples for infrared (IR) microspectroscopy involves imbibition of the seed for varying time periods followed by cryosectioning. Imbibition, however, may initiate germination even at 4° C with associated changes in the chemistry of the sample. We have found that it is possible to section seeds that are sufficiently hard, such as soybeans, on a standard laboratory microtome without imbibition. The use of dry sectioning of unimbibed seeds is reported here, as well as a comparison of different mounting media and modes of analysis. Glycerol, Tissue-Tek, and ethanol were used as mounting media, and the quality of the resulting spectra was assessed. Ethanol was the preferred mountant, because it dried quickly with no residue and thus did not interfere with the spectrum of interest. Analysis in transmission mode using barium fluoride windows to hold the samples was compared with transmission-reflection analysis with sections mounted on special infrared-reflecting slides. The two modes of analysis performed well in different regions of the spectrum. The mode of analysis (transmission vs. transmission-reflection) should be based on the components of greatest interest in the sample.     

Ciliate biogeography in Antarctic and Arctic freshwater ecosystems: endemism or global distribution of species?

Ciliate diversity was investigated in situ in freshwater ecosystems of the maritime (South Shetland Islands, mainly Livingston Island, 63 degrees S) and continental Antarctic (Victoria Land, 75 degrees S), and the High Arctic (Svalbard, 79 degrees N). In total, 334 species from 117 genera were identified in both polar regions, i.e. 210 spp. (98 genera) in the Arctic, 120 spp. (73 genera) in the maritime and 59 spp. (41 genera) in the continental Antarctic. Forty-four species (13% of all species) were common to both Arctic and Antarctic freshwater bodies and 19 spp. to both Antarctic areas (12% of all species). Many taxa are cosmopolitans but some, e.g. Stentor and Metopus spp., are not, and over 20% of the taxa found in any one of the three areas are new to science. Cluster analysis revealed that species similarity between different biotopes (soil, moss) within a study area was higher than between similar biotopes in different regions. Distinct differences in the species composition of freshwater and terrestrial communities indicate that most limnetic ciliates are not ubiquitously distributed. These observations and the low congruence in species composition between both polar areas, within Antarctica and between high- and temperate-latitude water bodies, respectively, suggest that long-distance dispersal of limnetic ciliates is restricted and that some species have a limited geographical distribution.     

Analytical methods for the determination of aflatoxins in various food matrices at concentrations regarding the limits set in european regulations: development, characteristics, limits

Methods for the determination of aflatoxins in paprika, peanut butter, pistachio paste, fig paste and baby food were developed. The methods employ an immunoaffinity cleanup step and reversed-phase liquid chromatography. All steps of the analysis were tested for their suitability for all matrices with focus on method robustness, simplicity, toxicology, environment, and user friendliness. Extraction procedures, chromatographic separation and post column derivatisation techniques were elaborated for this purpose. The methods were statistically validated in collaborative trials at currently established legal limits for aflatoxins and are in the process for adoption as official methods by CEN and AOAC.