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Notes: These experiments investigate events involved in triggering sugar accumulation in the cold in tubers of Solanum tuberosum L. cv. Desirée. Sugar content, 14C-glucose metabolism, metabolite levels and activities of sucrose phosphate synthase (SPS) and starch-degrading enzymes were followed after transfer to 4°C. (i) Net sucrose accumulation began between 2 and 4 d. By 10 d, reducing sugars were also increasing. From 20 d onwards, sugar accumulation slowed. Sucrose fell, but reducing sugars continued to increase. (ii) To measure unidirectional sucrose synthesis, U-[14C]glucose was injected into tubers after various times at 4°C. The tubers were then incubated for 6 h. After 1 d at 4°C, both the absolute and the relative (expressed as a percentage of the metabolized label) rates of sucrose synthesis decreased compared to those at 20°C. Between 2 and 4 d at 4°C, labelling of sucrose increased 3-fold, to over 60% of the metabolized label. This high rate was maintained for up to 50 d in cold storage. When tissue slices were incubated with 2.5 mol m−3 U-[14C]glucose, the rate of labelling of sucrose in slices from 6 d cold-stored material was higher than in slices from warm-stored material, irrespective of whether the incubation occurred at 4°C or at 20°C. (iii) Hexose-phosphates increased during the first day after transfer to 4°C. Their levels fell during the next 3 d, as sucrose synthesis increased. They then rose (until 20 d) and fell, in parallel with the rise and decline of sucrose levels. UDPglucose remained unaltered during the first 4 d, and then increased and decreased in parallel with sucrose. (iv) SPS activity assayed in optimal conditions and the total amount of SPS protein did not change. However, when assayed in the presence of phosphate and limiting substrate concentrations, activity rose 3–5-fold between 2 and 4 d. (v) Amylases and phosphorylases were investigated using zymograms to separate isoforms. Phosphorylases did not change. Between 2 and 4 d at 4°C, a new amylolytic activity appeared. (vi) Estimates of the specific activity of the phosphorylated intermediates and the absolute rate of sucrose synthesis (calculated from the 14C-labelling data and metabolite analysis) showed that changed kinetic properties of SPS and decreased levels of hexose-phosphate are accompanied by a 6–8-fold stimulation of sucrose synthesis. They also show that the final level of sugar is partly determined by a cycle of sugar synthesis and degradation. (vii) It is concluded that the onset of sugar accumulation in cold-stored tubers is initiated by a change in the kinetic properties of SPS and the appearance of a new amylolytic activity. It is discussed how other factors, including hexose-phosphate levels and subcellular compartmentalization, could also influence the final levels of sugars by altering the balance of sugar synthesis and remobilization.

Notes: Voltage-operated Ca2+ channels are heteromultimeric proteins. Their structural diversity is caused by several genes encoding homologous subunits and by alternative splicing of single transcripts. Isoforms of α1 subunits, which contain the ion conducting pore, have been deduced from each of the six cDNA sequences cloned so far from different species. The isoforms predicted for the α1E subunit are structurally related to the primary sequence of the amino terminus, the centre of the subunit (II–III loop), and the carboxy terminus. Mouse and human α1E transcripts have been analysed by reverse transcription–polymerase chain reaction and by sequencing of amplified fragments. For the II–III loop three different α1E cDNA fragments are amplified from mouse and human brain, showing that isoforms originally predicted from sequence alignment of different species are expressed in a single one. Both predicted α1E cDNA fragments of the carboxy terminus are identified in vivo. Two different α1E constructs, referring to the major structural difference in the carboxy terminus, were stably transfected in HEK293 cells. The biophysical properties of these cells were compared in order to evaluate the importance in vitro of the carboxy terminal insertion found in vivo. The wild-type α1E subunit showed properties, typical for a high-voltage activated Ca2+ channel. The deletion of 43 amino acid residues at the carboxy terminus does not cause significant differences in the current density and the basic biophysical properties. However, a functional difference is suggested, as in embryonic stem cells, differentiated in vitro to neuronal cells, the pattern of transcripts indicative for different α1E isoforms changes during development. In human cerebellum the longer α1E isoform is expressed predominantly. Although, it has not been possible to assign functional differences to the two α1E constructs tested in vitro, the expression pattern of the structurally related isoforms may have functional importance in vivo.

Notes: The biological behaviour of meningeal haemangiopericytomas was retrospectively studied using immunohistochemical staining with MIB1, a monoclonal antibody against the Ki-67 antigen, a nuclear protein related to cell proliferation. Paraffin-embedded material from 62 tumours from 40 patients were investigated. The proliferating compartment of the tumours was estimated by evaluating the MIB1 staining index, i.e. the percentage of MIB1 positive nuclei in at least 1000 counted tumour cells in representative areas. The staining index ranged from 1.24% to 39.01%. Statistical analysis revealed no significant correlation between the staining index and recurrence-free survival (χ2 = 0.3922, P = 0.5311). Long-term observation (〉100 months), however, revealed a tendency to longer survival in the group with a staining index less than 5%. According to our results, the MIB1 staining index does not contribute to the accuracy of predicting the clinical outcome of meningeal haemangiopericytomas.

Notes: Summary The dry mass per unit area (g/µ2) for nucleus and cytoplasma was determinated by interference microscope from 1043 glioblastoma cells of 5 various glioblastomas and from 439 medulloblastoma cells of 4 various medulloblastomas. The values obtained from the glioblastoma cells are significantly higher than the values of medulloblastoma cells.

Notes: Zusammenfassung Intravenöse Injektionen von Allopregnan-3β, 16 α-diol-20-on (Sodium Excreting Factor) bewirken bei der intakten Ratte unter verschiedenen Ausgangslagen keine sichere Veränderung der renalen Wasser- und Elektrolytausscheidung. Die Bedeutung dieser Versuchsergebnisse wird besprochen.

Notes: Zusammenfassung 1. 5000 μE ADH, 0,25 mg Renin und 1 γ Hypertensin Ratten i.v. injiziert ergeben bei Wasserinfusion eine Antidiurese, bei 0,9% NaCl-Infusion wechselnde Ergebnisse und bei 1,8% NaCl-Infusion eine Diuresesteigerung. 2. Die Diuresesteigerung ist, zumindest für ADH, nicht auf eine Erhöhung der extracellulären Natriumkonzentration zu beziehen. Sie ist bei Infusion von Natriumlösungen nur dann zu beobachten, wenn die Natriumkonzentration im Harn eine gewisse Höhe erreicht hat. 3. Die Natriumausscheidung wird in jedem Falle verstärkt, prozentual am ausgeprägtesten bei Wasserdiurese. 4. Bei Injektion kleiner, nicht mehr blutdrucksteigernder Dosen weist allein ADH (100 μE) noch eine eindeutige Wirkung auf. Es wird daher angenommen, daß unter physiologischen Verhältnissen nur ADH die renale Wasser- und Natriumausscheidung der Ratte zu modifizieren vermag. 5. Durch Vorbehandlung mit Aldosteron wird die ADH-Wirkung nicht beeinflußt. 6. Die ADH-Natriurese kann nicht durch Ausdehnung des Extracellulärraumes, Bremsung der Aldosteronproduktion oder Beeinträchtigung der Aldosteronwirkung am Tubulusepithel erklärt werden. 7. Da das Glomerulumfiltrat nicht signifikant verändert wird, muß eine verminderte tubuläre Natriumrückresorption durch direkte ADH-Einwirkung angenommen werden.