Gene transfection of the HuLy-m2 (Leu-9) antigen into mouse L cells

Human DNA was transfected into mouse L cells and tk⁺ HuLy-m2⁺ (= CD7⁺) transfectants isolated after growth in hypoxanthine, aminopterin, thymidine medium and repeated cloning. After several cycles of transfection, > 90% of HuLy-m2⁺ L cells could be detected, by rosetting and by cytofluorography, which showed the transfectants to have a density of CD7 two to five times that found on peripheral blood lymphocytes. Despite this, the 37 kd CD7⁺ dimer could only be identified with difficulty using cell-surface radioiodination and sodium dodecyl sulfate-polyacrylamide gel electrophoresis techniques. An antiserum was produced (C3H anti-HuLy-m2⁺ L cells) which, after absorption, was shown to react with HuLy-m2 antigens present on human thymocytes and lymphocytes and on CD7⁺ transfected L cells.Abbreviations BSA bovine serum albumin - DME Dulbecco's modified Eagle's medium - EDTA ethylenediamine-tetraacetate - HAT hypoxanthine, aminopterin, thymidine - HSV herpes simplex virus - PBL peripheral blood lymphocyte - PBS phosphate-buffered saline - RFC rosette-forming cell - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - tk thymidine kinase     

Characterization of the inositol 1,4,5-trisphosphate-induced Ca2+ release in pancreatic beta-cells.

Pancreatic beta-cells isolated from obese-hyperglycaemic mice released intracellular Ca2+ in response to carbamoylcholine, an effect dependent on the presence of glucose. The effective Ca2+ concentration reached was sufficient to evoke a transient release of insulin. When the cells were deficient in Ca2+, the Ca2+ pool sensitive to carbamoylcholine stimulation was equivalent to that released by ionomycin. Unlike intact cells, cells permeabilized by high-voltage discharges failed to generate either inositol 1,4,5-triphosphate (InsP3) or to release Ca2+ after exposure to carbamoylcholine. However, the permeabilized cells released insulin sigmoidally in response to increasing concentrations of Ca2+. Also in the absence of functional mitochondria these cells exhibited a large ATP-dependent buffering of Ca2+, enabling the maintenance of an ambient Ca2+ concentration corresponding to about 150 nM even after several additional pulses of Ca2+. InsP3, maximally effective at 6 microM, promoted a rapid and pronounced release of Ca2+. The InsP3-sensitive Ca2+ pool was rapidly filled and lost its Ca2+ late after ATP depletion. The transient nature of the Ca2+ signal was not overcome by repetitive additions of InsP3. It was possible to restore the response to InsP3 after a delay of approx. 20 min, an effect which had less latency after the addition of Ca2+. These latter findings argue against degradation and/or desensitization as factors responsible for the transiency in InsP3 response. It is suggested that Ca2+ released by InsP3 is taken up by a part of the endoplasmic reticulum (ER) not sensitive to InsP3. On metabolism of InsP3, Ca2+ recycles to the InsP3-sensitive pool, implying that this pool indeed has a very high affinity for the ion. The presence of functional mitochondria did not interfere with the recycling process. The ER in pancreatic beta-cells is of major importance in buffering Ca2+, but InsP3 only modulates Ca2+ transport for a restricted period of time following immediately upon its formation. Thereafter the non-sensitive part of the ER takes over the continuous regulation of Ca2+ cycling.     

The effect of sucrose on the levels of abscisic acid, indoleacetic acid and zeatin/zeatin riboside in wheat ears growing in liquid culture

The influence of a varied sucrose supply on grain size and hormonal contents of detached wheat ears ( Triticwn aestivum L. cv. Schirokko) was investigated throughout grain development. In ears led limited amounts, or no sucrose, grain weights in both proximal and distal grain positions of the ear were reduced. Radioimmunoassay for abscisic acid, indoleacetic acid and zeatin/zeatin riboside showed that the changes in the levels of these hormones in grains and bracts were comparable to intact ears when detached ears were well supplied with sucrose. Under conditions of limited sucrose supply, higher abscisic acid levels in the distal and proximal grains of detached ears were found compared to ears supplied with adequate sucrose. Limiting sucrose supply to the ear did not alter the levels of indoleacetic acid or zeatin/zeatin riboside in either the grains or bracts of detached ears.     

Cultivar and pH effects on competition for nodule sites between isolates of Rhizobium in beans

Two experiments were carried out to evaluate the effect of acidity on bean-Rhizobium competition for nodule sites. SevenPhaseolus vulgaris host cultivars differing in acid-pH tolerance were grown in sand culture, and irrigated using a sub-irrigation system and nutrient solutions of pH 4.5, 5.0, 5.5, and 6.0. A mixed inoculant of two antibiotically markedRhizobium leguminosarum bvphaseoli strains CIAT899 (acid-tolerant) and CIAT632 (acid-sensitive) was used. The acid-tolerant CIAT899 dominated CIAT632 in nodule occupancy across all cultivars and pH treatments. Although several of the varieties had previously been identified as PH-tolerant, and these cultivars performed better than those reported to be acid sensitive, all showed a marked increase in nodulation and plant development when the pH was raised from 4.5 to 6.0. The second experiment using a modified Leonard jar system varied the inoculation ratio between CIAT899 and UMR1116 (acid-sensitive, inefficient in N₂-fixation) and contrasted nodulation response for the bean varieties Preto 143 (pH-tolerant) and Negro Argel (pH-sensitive) at 3 pH treatments (4.5, 5.5, 6.5). There was a significant effect of host cultivar, ratio of inoculation, and pH on the percentage of nodule occupancy by each strain. At low pH CIAT899 had higher nodule occupancy than UM1116 in the variety Negro Argel but had the same percentage of nodulation when the variety was Preto 143. Increasing the cell concentration of UMR1116 produced more inefficient nodules at all treatment combinations and reduced plant growth for both cultivars used.     

Effects of nucleotides and divalent cations on phospholipase activity in Saccharomyces cerevisiae

Divalent cations activate the lysophospholipase and transacylase reactions catalyzed by the same enzymes in the yeast Saccharomyces cerevisiae. The activation was observed at neutral pH, but not at the pH optimum of lysophospholipase/transacylase, near 3.5. Adenine nucleotides, especially AMP and ADP, are strong inhibitors of the same group of enzymes. Half maximal inhibition by AMP was found at a concentration of about 20 M. The inhibition by nucleotides in low concentrations is enhanced by divalent cations.     

Production of sterigmatocystin by Aspergillus versicolor isolated from roughage

A total of 69 samples of hay and straw collected during the winter period of 1984/85 were surveyed for their contamination by Aspergillus versicolor. The percentage of A. versicolor-positive samples was 14.5%. Nineteen A. versicolor strains mainly isolated from roughage were tested for the production of sterigmatocystin. All of the isolates examined were capable of producing different levels of sterigmatocystin on a cracked corn substrate. The majority of these strains were highly toxigenic; 53% of the isolates produced more than 500 mg/kg of sterigmatocystin. These findings suggest that corn is a very suitable substrate for sterigmatocystin production and that particularly in the surface layers of feed stocks and corn silos such toxigenic strains of A. versicolor can produce considerable growth and possibly sterigmatocystin, too.     

Evolutionary conservation of the human homologue of the yeast cell cycle control gene cdc2 and assignment of Cd2 to chromosome 10

Summary The human homologue of the fission yeast Schizosaccharomyces pombe cell cycle control gene cdc2 has been assigned to chromosome 10. DNA hybridization reveals that this gene is highly conserved in vertebrates. The human CDC2 gene probe detects a simple two-allele polymorphism in Taq1-digested DNA.     

Aestival dormancy in the cabbage moth Mamestra brassicae L. (Lepidoptera: Noctuidae)

Summary In a geographically wide distribution the life cycles of different populations of the cabbage moth Mamestra brossicae are adapted to a remarkable diversity of climatic conditions. This is undoubtedly a proof of its success in adaptation. Some populations living in regions characterized by a drought period interrupting the growth season are capable of distinguishing between one critical day length signalling the onset of the drought period and another signalling the end of the growth season. This study, therefore, is primarily concerned with the geographical patterns in the variability of the adaptional responses of populations exposed to environmental conditions requiring different strategies and tactics in, synchronizing individual, life cycles. It is also a contribution to our understanding of evolutionary mechanisms maintaining median responses to photoperiodically inductive day lengths in geographically different populations. The populations investigated originated from regions differing in predictability of the incidence, onset and duration of a drought period: Freiburg (48.0°N, Southern Germany), Avignon (44.0°N, Southern France), and Argelès (42.5°N, Southern France). Geographical variation with respect to both onset and duration of a drought period consequently results in clinal variation of the variability of innate day length thresholds triggering aestival dormancy and of innate duration of aestivation. In this paper we considered the influence of geographically changing temperatures on aestival dormancy induction. Even in southern populations of M. brassicae a temperature dependent switch off-mechanism exists which prevents aestival dormancy under certain environmental conditions. The effective temperatures vary geographically, too. What the geographical patterns in adaptive responses really are, is discussed.This research was supported by the Deutsche Forschungsgemeinschaft (Sa 259/3-1)     

Methode zum Nachweis der Dauersporen des Kohlhernieerregers Plasmodiophora brassicae in gärtnerischen Kultursubstraten

Populations of pathogenic Pseudomonas syringae pv. syringae were monitored on apparently healthy leaves, blossoms, and fruit from two apple orchards with known histories of blister bark and a pear orchard with a known history of blossom blast. Populations on blossoms and fruits were higher on pears than on apples. Yellow-pigmented, non-pathogenic bacteria might have suppressed or masked the presence of P. syringae pv. syringae on apple trees. Populations of P. syringae pv. syringae on apple and pear leaves fluctuated sharply but higher levels generally occurred during the 1984/85 growing season than during the drier 1983/84 season. This investigation indicates that the resident phase of P. syringae pv. syringae is probably a major source of inoculum for apple blister bark and pear blossom blast in South Africa.