The xylem sap of maple (Acer platanoides) trees--sap obtained by a novel method shows changes with season and height

Xylem sap of log pieces of maple trees was collected by a novelpressure/decompression method developed recently for the mechanicaldrying of timber. Seasonal changes and spatial distributionsof the osmotic potential, the pH and the concentrations of majorsolutes and of the plant stress-hormone abscisic acid (ABA)were investigated. Sucrose and quebrachitol were the main components of the xylemsap. The sucrose concentration varied between 10 mM and 25 mMduring the winter months and declined to a minimum during theperiod of bud burst. Quebrachitol was found in concentrationsof up to 7 mM with a high variability throughout the year. Highconcentrations of ABA were measured during the summer seasonand in mid-winter. Rainfall caused an increase of ABA in somesamples. The osmotic potential of the xylem sap increased with the heightof the collection site. The pH of the sap decreased by approximatelyone unit between the base of the trunk and the crown. The increaseof the osmotic potential was mainly due to sucrose, quebrachitoland potassium. Malate contributed to the decrease of the pH.ABA of the xylem sap increased with decreasing moisture contentof the wood. Key words: Pressure/decompression method, xylem sap, abscisic acid, sucrose, quebrachitol, Acer platanoides     

Electrical responses of the marine ciliate Euplotes vannus (Hypotrichia) to mechanical stimulation at the posterior cell end

Electrical responses upon mechanostimulation at the posterior cell end were investigated in the marine hypotrichous ciliate Euplotes vannus. A new mechanostimulator was developed to mimic stimuli that are identical with those involved in cell-cell collisions. The receptor potential hyperpolarized by 18–35 mV within 12–25 msec, reached a peak value of -62 mV with a delay of 4–9 msec after membrane deformation, and was deactivated after 50–70 msec. Cirri were stimulated to beat accelerated backward. The corresponding receptor current exerted a similar time course with a peak of 2.4 nA. The shift of the reversal potential by 57.6 mV at a tenfold increase of [K⁺] ₀ identifies potassium ions as current carriers within the development of the receptor potential. An intracellular K concentration of 355 mmol/liter was calculated for cells in a medium that was composed similar to sea-water. The mechanically activated potassium current was totally inhibited by extracellular TEA and intracellular Cs⁺, and partially inhibited by extracellular 4-AP. The total inhibition of the current by injected EGTA points to a Ca dependence of the posterior mechanosensitivity. It was confirmed by the increase of the peak current amplitude with rising [Ca²⁺] ₀ . Sodium presumably repolarizes the receptor potential because the repolarization was delayed and after-depolarizations were eliminated in media without sodium. Since deciliation did not affect mechano-sensitivity, the corresponding ion channels reside within the soma membrane.The authors wish to thank Mr. Norbert Spreckelmeier from the electronics workshop and Mr. Herbert Lutter from the fine-mechanical workshop of the department for their excellent work, Mrs. G. Key and Mr. H. Mikoleit for skillful technical assistance and for preparing the figures. This work was supported by Deutsche Forschungsgemeinschaft, SFB 171, C7.     

Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.     

Selective Staining of Eosinophils and Their Immature Precursors in Tissue Sections and Autoradiographs with Congo Red

The use of Congo red as an elective stain for eosinophilic granulocytes and their precursors in tissue sections and autoradiographs is demonstrated and discussed. The 0.5% alcoholic Congo red solution of Highman, normally used for the detection of amyloid, may also be used with only minor changes. This simple method may aid in the diagnosis of special hematological problems and facilitates the recognition of eosinophil granulocytes as well as proliferating and nonproliferating myelocytes in autoradiographs from paraffin sections.     

Enriched populations of rat retinal ganglion cells: Studies using a cell-type specific surface marker

Cells dissociated from adult and neonatal rat retinas were separated by density gradient centrifugation. Previous work had shown that rat retinal cells labelled by an immunofluorescence assay for the Thy-1 antigen were chiefly or exclusively ganglion cells, and so the proportion of Thy-1 positive cells in the density gradient fractions was used as an index of the enrichment of ganglion cells. The proportion of Thy-1 positive neonatal cells was increased from about 0.4% in the initial dissociate to about 8% in the most enriched fraction of a Percoll step gradient. Amongst adult cells the initial 0.7% Thy-1 positive cells were increased to roughly 2% in the best fraction of a metrizamide step gradient.

The presence of relatively large numbers of Thy-1 positive cells in other fractions suggested that it would be difficult to further increase the proportion of rat ganglion cells by methods based on their sedimentation properties. These results demonstrate the importance of cell-type specific markers in attempts to purify cells from the central nervous system.     

Ubiquitous soluble Mg(2+)-ATPase complex. A structural study.

We have performed a detailed structural analysis of the soluble Mg(2+)-ATPase complex purified from Xenopus laevis ovary, which is an abundant and ubiquitous homo-oligomeric protein complex located in the nucleus and in the cytoplasm, belonging to a novel multigene-family of putative Mg(2+)-ATPases. Enzyme activity staining after non-denaturing polyacrylamide gel electrophoresis revealed that Mg(2+)-ATPase activity of the native protein is dependent on oligomerization and could not be detected in dissociated subunits. For the native protein a sedimentation coefficient of 15.3 S and a corresponding relative molecular mass of 612,000 was determined by analytical ultracentrifugation and a relative molecular mass of 590,000 was estimated from scanning transmission electron microscopy, supporting our previous conclusion that the oligomer comprises six 97,000 Mr subunits. Conventional electron microscopy of negatively stained specimens revealed the Mg(2+)-ATPase complex to be a hexagonal molecule in its favoured "end-on" projection and a double-banded molecule in its "side-on" projection (approx. 12 nm diameter; approx. 9 nm height). In addition, dimerized complexes could be observed in negatively stained specimens, yielding pronounced hexameric images and four-banded images in their end-on and side-on orientations, respectively (approx. 12 nm diameter; approx. 18.5 nm height). Two-dimensional (2D = mono-molecular) crystals have been produced from the dimerized complexes by the negative staining carbon film technique. Hexagonal crystals with a p6 plane group symmetry were obtained from molecules in their end-on orientation and longitudinal arrays with a p2 symmetry from complexes in their side-on orientation. A low-resolution molecular model of the native protein, derived from averages of these two 2D crystals, is presented. From our results we propose oligomerization as an inherent structural principle of organization for this whole newly defined Mg(2+)-ATPase multigene-family, that includes such seemingly diverse functionally defined proteins as mammalian and yeast "vesicle fusion" and "peroxisome assembly" proteins and the product of the yeast cell cycle gene CDC48.