Some synchorological aspects of basiphilous pine forests in Fennoscandia

Basiphilous pine forests and related birch forests are herb-and grass-rich forests on calcareous substrate. These forests are complex communities with floristic/ecological elements from different vegetation types occurring in a subtle micromosaic. These elements are e.g. species from acidophilous conifer forests, thermophilous forest-rim communities, calcareous shallow-soil and steppe communities, eutrophic wet meadows and fens, and in northern Fennoscandia also species from alpine Dryas heaths. Four associations are recognized in Fennoscandia: Convallario-Pinetum, Melico-Piceetum pinetosum, Peucedano-Pinetum and Epipacto atrorubentis-Betuletum. The main association is the Convallario-Pinetum, a widespread community in Fennoscandia and Estonia with a considerable floristic variation between the different regions. Examples of the floristic variation along west-east profiles and south-north profiles in Fennoscandia are presented. The basiphilous pine forest complex can be divided into a number of ecological types along the moisture and nutritional gradients. A further subdivision into geographical types (races) is presented.Nomenclature follows Lid (1974) for vascular plants, Nyholm (1954–1969) for musci and Dahl & Krog (1973) for lichens.     

Differences in reactivity of confluent and nonconfluent cultures of human endothelial cells toward thrombin-stimulated platelets or heparinized salt solution

Summary This study examined whether nonconfluent endothelial cell cultures reacted differently than confluent ones toward thrombin-stimulated platelets or a heparinized salt solution. The adherence to the endothelial cell cultures of⁵¹Cr-labeled human platelets stimulated at different thrombin concentrations was studied. There was significantly higher adherence of stimulated platelets to nonconfluent cultures compared with confluent ones. This was confirmed by scanning electron microscopy, which also revealed a tendency for the platelets to adhere at the cell periphery. Electron microscopy also showed that thrombin-stimulated platelets induced endothelial cell contraction. Part of the peripheral endothelial cell surface toward the bottom of the culture dish was inverted, facing the lumen of the dish. This phenomenon was particularly seen in nonconfluent cultures. When⁵¹Cr-labeled endothelial cultures were incubated with a mildly injurious fluid as heparinized sodium acetate and 20% serum, at 20° C for 30 min, the nonconfluent cultures showed significantly more cell detachment and release of⁵¹Cr than the confluent ones. We conclude that under the conditions of the present experiments there are differences in the reactivity of confluent and nonconfluent endothelial cell cultures. These differences probably reflect biological dissimilarities. In experiments where properties of cultured endothelium are studied, care should be taken that the degree of confluency is standardized.     

Properties of action potentials carried by divalent cations in identified leech neurons

Properties of divalent cation potentials carried by either Sr2+ or Ca2+ ions in Na+-free, TEA-Ringer solution were characterized in identified neurons of two species of leeches (Macrobdella and Haementeria). In Macrobdella, the overshoot of the potentials varied logarithmically with [Sr2+]0 (28.5 mV per 10-fold change). The overshoot, Vmax, and duration of the potentials increased with increasing divalent cation concentration and saturated at about 20 to 30 mM [Sr2+]0. The Vmax, amplitude, and duration of the potentials were reversibly blocked by Co2+ and Mn2+. The block by Mn2+ could be well-fitted by a reverse Langmuir-curve with an apparent KI of 100 micromolar. The local anesthetic procaine also reversibly inhibited the Vmax and duration of the potentials. The inhibition was greater at alkaline pH suggesting that procaine blocks the calcium channel from inside the membrane. The identified leech neurons examined in Macrobdella varied considerably in their ability to sustain somatic divalent cation potentials. Stimulation of T cells and most motoneurons produced no or only weak potentials, whereas stimulation of Retzius, N, Nut, and AP cells evoked overshooting potentials of several seconds' duration. Stimulation of the ALG cell of Haementeria in normal Ringer solution evoked a slowly-rising, purely Ca2+-dependent potential of approximately 100 ms duration. This response was TTX-resistant, unaffected by complete removal of Na+ from the Ringer solution, and abolished by 1 mM Mn2+. The overshoot varied logarithmically with a slope of 28 mV/decade change in [Ca2+]0.     

Der einfluss des anomeren effektes auf furanosekonformationen. Röntgenstrukturanalyse fünf isomerer methyl-3,6-anhydrohexofuranoside

X-Ray crystallographic analysis of five isomeric methyl 3,6-anhydrohexofuranosides, methyl 3,6-anhydro-β-d-glucofuranoside (1), methyl 3,6-anhydro-α-l-idofuranoside (2), methyl 3,6-anhydro-β-d-mannofuranoside (3), methyl 3,6-anhydro-α-d-glucofuranoside (5), and methyl 3,6-anhydro-α-d-mannofuranoside (7), showed that the anomeric effect determines the conformation of the furanoid ring, which resulted in the quasi-axial orientation of the aglycon in all cases. Thus, 2 adopts an almost ideal E₂ conformation, whereas 1 and 3 having the same R configuration at the anomeric center showed conformations of the furanoid ring intermediate between E₂ and ¹T₂. Of the anomers 5 and 7 having an S configuration at C-1, 7 showed a related but opposite geometry, intermediate between ²E and ²T₁, and 5 had a ^oT₁ conformation, slightly distorted into ^oE. The anhydroring of all compounds showed a C-6 endo orientation, with the exception of 7, in which C-6 is exo oriented. These results from compounds in the solid state were compared with the conformations of the same compounds in solution, as deduced by ¹H-n.m.r. spectroscopy.     

In vitro studies on the subcellular location of glucosidase I and glucosidase II in dog pancreas

When programmed with yeast prepro--factor mRNA, the heterologous reticulocyte/dog pancreas translation system synthesizes two pheromone related polypeptides, a cytosolically located primary translation product (pp--F_cyt, 21 kDa) and a membrane-specific and multiply glycosylated e-factor precursor (pp--F₃, 27.5 kDa). Glycosylation of the membrane specific pp--F₃ species is competitively inhibited by synthetic peptides containing the consensus sequence Asn-Xaa-Thr as indicated by a shift of its molecular mass from 27.5 kDa to about 19.5 kDa (pp--F₀) , whereas the primary translation product pp--Fcyt is not affected. Likewise, only the glycosylated pp--F₃ structure is digested by Endo H yielding a polypeptide with a molecular mass between PP--F₀ and pp--Fcyt. These observations strongly suggest that the primary translation product is proteolytically processed during/on its translocation into the lumen of the microsomal vesicles. We believe that this proteolytic processing is due to the cleavage of a signal sequence from the pp--Fcyt species, although this interpretation contradicts previous data from other groups. The distinct effect exerted by various glycosidase inhibitors (e.g. 1-deoxynojirimycin, N-methyl-dNM, 1-deoxymannojirimycin) on the electrophoretic mobility of the pp--F₃ polypeptide indicates that its oligosaccharide chains are processed to presumbly Man₉-GlcNAc₂ structures under thein vitro conditions of translation. This oligosaccharide processing is most likely to involve the action of glucosidase I and glucosidase II as follows from the specificity of the glycosidase inhibitors applied and the differences of the molecular mass observed in their presence. In addition, several arguments suggest that both trimming enzymes are located in the lumen of the microsomal vesicles derived from endoplasmic reticulum membranes.Abbreviations dNM 1-deoxynojirimycin - N-Me-dNM N-methyl-dNM - dMM 1-deoxymannojirimycin - CCCP carbonylcyanide m-chlorophenyl hydrazone     

Facile synthesis of 2′-substituted lactoses

Isopropylidenation of lactose with 2,2-dimethoxypropane in the presence ofp-toluenesulfonic acid gave two products, which were identified by¹H- and¹³C-NMR as 2,35,63,4-tri-O-isopropylidenelactose dimethyl acetal (1) and its 6-O-(2-methoxy)-isopropyl derivative (2). These products were used for the synthesis of 2-O-methyllactose (7), 2,6-di-O-methyllactose (9) and 2-O-benzyllactose (13).     

Isolation and fractionation of CHO chromosomes in aqueous two phase systems using charged polymers and base specific macroligands

Summary Chromosomes were isolated in a preparative scale by synchronisation of CHO cells with a double Thymidine block followed by an arrest in the metaphase by addition of Colcemid. Under proper cultivation conditions a mitotic index of 77% total cells could be routinely achieved. Bulk chromosome preparations free of nuclei and other subcellular particles have been obtained by low speed centrifugation followed by a 60 transfer countercurrent distribution using aqueous two phase systems composed of polyethylenglycol and dextran. The partition of CHO chromosomes previously purified in aqueous two phase systems were studied further to develop a protocol for the separation and isolation of individual chromosomes. Partition experiments with chromosomes changing the electrostatic phase potential by addition of charged PEG-derivatives suggest the existence of relatively highly charged chromosome groups. Most promising results with regard to separation were obtained using two PEG-derivatives, which interact specifically with the bases in DNA. For this affinity partitioning a GC- and AT-specific macroligand were employed. Comparing CCD's using each of these ligands information on the GC and AT content of exposed DNA in the chromosomes groups could be derived, demonstrating that specific sequences of DNA are accessible at the surface of metaphase chromosomes.     

Close linkage between X-linked ectodermal dysplasia and a cloned DNA sequence detecting a two allele restriction fragment length polymorphism in the region Xp11-q12

Summary EDA (ectodermal dysplasia, anhidrotic) is an X-linked recessive disorder characterized by hypohidrosis, hypoor anodontia, and hypotrichosis. A possible linkage between the gene for EDA and a number of restriction fragment length polymorphisms (RFLPs) spread over the X chromosome was investigated in two Danish families segregating EDA. No recombination between the gene for EDA and our probe pTAK8, which detects a two allele polymorphism in the region Xp11-q12, was found in nine informative meiotic events (seven of which are phase known), giving a maximal lod score of 2.41 at a recombination fraction of 0.00. This juxtacentromeric location of the gene for EDA agrees well with the linkage data obtained with the other markers used in this study.     

The detection of phantom targets in noise by serotine bats; negative evidence for the coherent receiver

Summary Using a target simulator three serotine bats,Eptesicus serotinus, were trained to judge whether a phantom target was present or absent. The echolocation sounds emitted by the bats during the detection were intercepted by a microphone, amplified and returned by a loudspeaker as an artificial echo, with a delay of 3.2 ms and a sound level determined by the overall gain and cry amplitude. The cry level of each pulse was measured and the echo level received by the bat was calculated. The target was presented in 50% of the trials and the gain adjusted using conventional up/down procedures. Under these conditions between 40 and 48 dB peSPL were required for 50% detection (Figs. 2, 3).In a subsequent experiment the phantom target was masked with white noise (N_o) with a spectrum level of –113 dB re. 1 Pa·Hz^–1/2. The thresholds were increased by 7–14 dB. Energy density (S) of a single pulse was measured and used to estimate S/N_o, which ranged from 36–49 dB at threshold. Theoretically the coherent receiver model predicts the ratio between hits and false alarms observed for the bats at a S/N_o of ca. 1–2 dB. Since the bats require 40–50 dB higher S/N_o (Fig. 3), this is taken as negative evidence for coherent reception (cross correlation).Furthermore, a strong sensitivity to clutter was found since there seemed to exist a fixed relationship between thresholds and clutter level.Abbreviations C clutter - Nbw noise in a specified bandwidth - No noise in i Hz bandwidth - peSPL peak equivalent sound pressure level - S signal energy - SD standard deviation - Y/N Yes/No psychometry - 2AFC two alternative forced choice psychometry