Holocene dynamics of the alpine timberline in the High Sudetes

The study focuses on the High Sudetes that represent the most distinctive islands of alpine forest-free area among hercynian mid-mountains of Central Europe. Based on data from newly taken cores and previously published pollen profiles, comparison of the development of the alpine timberline position is carried out. The first of the analysed pollen profiles — the Labsky důl core in the Krkonoše Mts spans the whole period of the Holocene, the Keprník and Mezikotlí profiles in the Hruby Jeseník Mts bring information from the Subboreal/older Subatlanticum turn to the present. An exceptional position of the Krkonoše Mts in terms of permanent presence of the alpine belt throughout the Holocene was confirmed. Three oscillations of the alpine timberline during the Lower Holocene were detected in the profile from the Labsky důl site. In the Hruby Jeseník Mts a temperature dependent forest-free area existed at least since Subboreal to the present.     

Trypanosoma cruzi: Biological Characterization of Clones Derived from Chronic Chagasic Patients. II. Quantitative Analysis of the Intracellular Cycle1

The complete intracellular cycle of five cloned stocks of Trypanosoma cruzi was quantified. Marked but stable interclonal differences were found in the length of the pre-replicative lag period (18.2-34.2 h), amastigote doubling lime (8.6-21.5 h), and duration of the complete intracellular cycle (96-215 h). Strong correlations were demonstrated between these characteristics as well as to the growth rate of the epimastigote stage of the same clones grown in liquid medium. These data demonstrate that the marked heterogeneity of the natural population of T. cruzi extends to the intracellular cycle of the parasite and has important implications for our understanding of Chagas’ disease.     

Supercoil-induced Z-DNA formation within 5'-end of chicken myb proto-oncogene

We have analyzed the recently sequenced and characterized 2.9 kb fragment derived from the 5'-end of chicken myb proto-oncogene with respect to structural perturbations induced by DNA supercoiling. Within the first intron a 50 bp sequence stretch was localized, starting approximately 450 nucleotides downstream from putative ATG initiation codon, which forms a non-B-DNA structure. Fine mapping with structural probes revealed the three adjacent regions with imperfect purine-pyrimidine alternation creating together relatively long Z-forming tract, parts of which may undergo a B-Z DNA transition at different superhelical densities.     

Ribonuclease–gold Labels Chondroitin Sulphate in Guinea Pig Basophil Granules

Basophilic leucocytes are metachromatic granule-containing secretory granulocytes that contain a mixture of granular proteoglycans devoid of heparin. In guinea pigs, isolated basophilic leucocyte granules primarily contain chondroitin sulphate. We have recently demonstrated that an enzyme-affinity– gold technique to image RNA, using the reagent RNase gold, also binds specifically to heparin in human mast cell granules. Such binding is based on the known property of heparin as a competitive inhibitor of RNase. Using similar methods, we show here that RNase–gold binds to the chondroitin sulphate in the secretory granules of guinea pig basophils, thus broadening the applicability of this post-embedding affinity–gold method to studies that require imaging of chondroitin sulphate in routinely prepared electron microscopical samples.