Dormancy in peach (Prunus persica L.) flower buds

Morphological studies were carried out with peach flower buds collected monthly in 1989 and 1990, from two months before leaf fall (7 March) until two to three weeks before bloom (7/8 August). Chilled (2–4°C for 30 days) and unchilled buds were exposed to 20 to 25°C, 100% RH and continuous light. Gibberellin A₃ (3 ng or 30 ng) was applied to some of the non-chilled cuttings at three days intervals. Then, 12, 19, and 26 days after they were planted, the buds were sampled and processed for histological studies. Cultured flower buds (chilled or unchilled) had accelerated anther and gynoecium morphogenesis after 12 days under controlled conditions, compared to buds processed immediately after collection from the field. Chilling treatment augmented the bud culture effect, while Gibberellin A₃ applications to the excised buds retarded bud morphogenesis to a stage comparable to that of buds collected directly from the field. This, suggests that the comparatively high levels of Gibberellin A_1/3 we previously found in mid winter [15, 18] could be at least one of the factors that controls floral bud dormancy by retarding anther and gynoecium development.     

Development of a one-step enzyme immunoassay for the quantitation of gibberellin A3 in barley seeds

The development of a sensitive and specific enzyme immunoassay for GA₃ is reported. This method was based on the use of peroxidase labelled GA₃ and immobilized antibodies. In order to obtain a rapid immunoassay, several steps of purification were analyzed to show their necessity. Barley seed extracts were assayed at different steps of purification to exhibit the effect of extract components on the assay. It was demonstrated that HPLC had to be performed when a selective quantitation of GA₃ was required. This assay allowed GA₃ to be measured with reproducibility as its unmethylated form and the quantitation of GA₃ in barley seeds with this enzyme immunoassay was correlated to a GC-MS method.Abbreviations GA₃ gibberellin A₃ - EIA enzyme immunoassay - DMF dimethylformamide - TEA tri(n)ethylamine - BSA bovine serum albumin - OVA ovalbumine - ECF ethylchloroformate - PB phosphate buffer     

Phospholipid dependence of the anion transport system of the human erythrocyte membrane. Studies on reconstituted band 3/lipid vesicles

Band 3 protein extracted from human erythrocyte membranes by Triton X-100 was recombined with the major classes of phospholipid occurring in the erythrocyte membrane. The resulting vesicle systems were characterized with respect to recoveries, phospholipid composition, protein content and vesicle size as well as capacity and activation energy of sulfate transport. Transport was classified into band-3-specific fluxes and unspecific permeability by inhibitors. Transport numbers (sulfate ions per band 3 per minute) served as a measure of functional recovery after reconstitution. The transport properties of band 3 proved to be insensitive to replacement of phosphatidylcholine by phosphatidylethanolamine, while sphingomyelin and phosphatidylserine gradually inactivated band-3-specific anion transport when present at mole fractions exceeding 30 mol%. The activation energy of transport remained unaltered in spite of the decrease in transport numbers. The results, which are discussed in terms of requirements of band 3 protein function with respect to the fluidity and surface charge of its lipid environment, provide a new piece of evidence that the transport function of band 3 protein depends on the properties of its lipid environment just as the catalytic properties of some other membrane enzymes. The well-established species differences in anion transport (Gruber, W. and Deuticke, B. (1973) J. Membrane Biol. 13, 19–36) may to some extent reflect this lipid dependence.     

Enhanced Noradrenergic Neuronal Activity Increases Homovanillic Acid Levels in Cerebrospinal Fluid

Idazoxan, a highly specific and selective alpha 2-adrenoceptor antagonist, caused a dose-dependent increase in the concentration of homovanillic acid (HVA) a metabolite of 3,4-dihydroxyphenylethylamine, in cisternal CSF of freely moving rats. This increase in HVA level could be antagonized by the alpha 2-adrenoceptor agonist medetomidine. The increase was directly proportional to the concurrent elevation in level of 3-methoxy-4-hydroxyphenylglycol, a metabolite of noradrenaline, in the CSF of individual rats and followed a similar time course. It is suggested that the HVA level in CSF may be increased under conditions of enhanced noradrenergic activity and that, in such situations, it reflects noradrenergic rather than dopaminergic neuronal activity. Care should be taken, therefore, when changes in central dopaminergic activity are assessed by measurements of HVA level in CSF.     

Identity of common phosphoprotein substrates stimulated by interleukin 2 and diacylglycerol suggests a role of protein kinase C for IL 2 signal transduction

Interleukin 2 (IL 2) is a polypeptide growth factor essential for the proliferation and differentiation of T lymphocytes, large granulocytic lymphocytes, and, potentially, cells of the antibody-producing lineage, B lymphocytes. Many of the biological properties of IL 2 may be mimicked or potentiated by a potent class of tumor promoters, phorbol esters. Phorbol esters have recently been shown to associate with and activate a unique phospholipid/Ca2+-dependent phosphotransferase, protein kinase C (PK-C). Utilizing two-dimensional gel electrophoresis, we have compared the IL 2 and diacylglycerol-induced protein phosphorylation patterns of several IL 2-dependent murine cell lines. Both IL 2 and synthetic diacylglycerol, 1-oleyl-2-acetylglycerol (OAG), stimulated phosphorylation of a number of protein substrates in intact cells compared to unstimulated controls. Three groups of substrates were identified; the first showed increased phosphorylation following stimulation with either IL 2 or OAG, while the second and third groups showed increased phosphorylation following stimulation with IL 2 but not OAG, and with OAG but not IL 2, respectively. Here, we characterize the kinetics of phosphorylation of one cellular substrate, p68, which appears to be phosphorylated in response to direct activators of PK-C or lymphoid or myeloid growth factors in their respective lineage cell lines. The observation that IL 2 also stimulates a unique series of phosphoproteins in addition to those induced by direct PK-C activators suggests that IL 2 may initiate additional protein kinase activities, unrelated to PK-C, which may also be critical for the ligand-receptor signal transduction process regulating growth and gene expression.