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41.
Summary The exact time course of phosphate consumption in a tetracycline production byStreptomyces aureofaciens has been determined. The data have been compared with model simulations according to a model proposed by Votruba et al. (1984). This led to a revision of his equation for the rate of phosphate consumption and to the proposal that phosphate is consumed proportionally to the growth rate. In contradiction to the model simulations it was found that the length of the time lag of the production is independent of the initial phosphate concentration. While the model explains the time lag through inhibition of the production by phosphate, the measured data show that there must be another or an additional reason for the lag. Simultaneously with the start of the production the organism changes from an organic substrate to ammonia as nitrogen source.All experiments have been carried out in a bubble column of 651 working volume as fed batch fermentation. An autoanalyzer and a HPLC was coupled to the reactor for automatic measurement of phosphate, ammonia, sucrose and products in short intervals. Composition of the outlet gas, pH, pO2, temperature and weight of the substrate flasks were monitored on-line. 相似文献
42.
Hasenstein, K. H. and Evans, M. L. 1988. The influence of calcium and pH on growth in primary roots of Zea mays. - Physiol. Plant. 72: 466–470.
We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 × Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 m M CaCl2 ) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 m M MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45 Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45 Ca2+ . Release of 45 Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots. 相似文献
We investigated the interaction of Ca
43.
Expression and characterization of a functional human insulin-like growth factor I receptor 总被引:20,自引:0,他引:20
G Steele-Perkins J Turner J C Edman J Hari S B Pierce C Stover W J Rutter R A Roth 《The Journal of biological chemistry》1988,263(23):11486-11492
Stable transfectants of Chinese hamster ovary (CHO) cells were developed that expressed the protein encoded by a human insulin-like growth factor I (IGF-I) receptor cDNA. The transfected cells expressed approximately 25,000 high affinity receptors for IGF-I (apparent Kd of 1.5 X 10(-9) M), whereas the parental CHO cells expressed only 5,000 receptors per cell (apparent Kd of 1.3 X 10(-9) M). A monoclonal antibody specific for the human IGF-I receptor inhibited IGF-I binding to the expressed receptor and immunoprecipitated polypeptides of apparent Mr values approximately 135,000 and 95,000 from metabolically labeled lysates of the transfected cells but not control cells. The expressed receptor was also capable of binding IGF-II with high affinity (Kd approximately 3 nM) and weakly recognized insulin (with about 1% the potency of IGF-I). The human IGF-I receptor expressed in these cells was capable of IGF-I-stimulated autophosphorylation and phosphorylation of endogenous substrates in the intact cell. This receptor also mediated IGF-I-stimulated glucose uptake, glycogen synthesis, and DNA synthesis. The extent of these responses was comparable to the stimulation by insulin of the same biological responses in CHO cells expressing the human insulin receptor. These results indicate that the isolated cDNA encodes a functional IGF-I receptor and that there are no inherent differences in the abilities of the insulin and IGF-I receptors to mediate rapid and long term biological responses when expressed in the same cell type. The high affinity of this receptor for IGF-II also suggests that it may be important in mediating biological responses to IGF-II as well as IGF-I. 相似文献
44.
Abscisic acid and water transport in sunflowers 总被引:5,自引:0,他引:5
The role of abscisic acid (ABA) in the transport of water and ions from the root to the shoot of sunflower plants (Helianthus annuus) was investigated by application of ABA either to the root medium or to the apical bud. The exudation at the hypocotyl stump of decapitated seedlings was measured with and without hydrostatic pressure (0–0.3 MPa) applied to the root. All ABA concentrations tested (10-10–10-4 mol·l-1) promoted exudation. Maximal amounts of exudate (200% of control) were obtained with ABA at 10-6·mol·l-1 and an externally applied pressure of 0.1 MPa. The effect was rapid and long-lasting, and involved promotion of ion release to the xylem (during the first hours) as well as an increase in hydraulic conductivity. Abscisic acid applied to the apical bud had effects similar to those of the rootapplied hormone. Increased rates of exudation were also obtained after osmotic stress was applied to the root; this treatment increased the endogenous level of ABA in the root as well as in the shoot. Water potentials of the hypocotyls of intact plants increased when the roots were treated with ABA at 5°C, whereas stomatal resistances were lowered. The results are consistent with the view that ABA controls the water status of the plant not only by regulating stomatal transpiration, but also by regulating the hydraulic conductivity of the root.Abbreviations and symbols ABA
abscisic acid
- Tv
volume flow
- Lp
hydraulic conductivity
- PEG
polyethyleneglycol
-
water potential
-
osmotic potential
-
osmotic value
- P
hydrostatic pressure 相似文献
45.
46.
Yuji Okawara David Ko Steven D. Morley Dietmar Richter Karl P. Lederis 《Cell and tissue research》1992,267(3):545-549
Summary In situ hybridization procedure with a 32P-labelled synthetic oligonucleotide probe was used to detect corticotropin-releasing factor-encoding messenger RNA (CRF mRNA) in the hypothalamus of the white sucker, Catostomus commersoni. Adjacent sections were immunostained by a sucker CRF-specific antiserum. CRF mRNA-containing neurons were identified by autoradiography in the magnocellular and parvocellular subdivisions of the preoptic nucleus (PON). Many of these neurons were also immunostained by sucker antiserum, showing the same distribution patterns. These results confirm the presence of CRF mRNA and CRF peptide in the white sucker hypothalamus and support the view that the magnocellular and parvocellular neurons of the PON may be involved in the control of adrenocorticotropic hormone secretion from the pituitary in the white sucker. 相似文献
47.
Of the five human alcohol dehydrogenase (ADH) genes located in the region q21–25 of chromosome 4, genetic markers have been reported previously only for class I enzymes, ADH1-3. Here, new restriction fragment length polymorphisms (RFLPs) are described for the genes of two other classes, ADH4 () and ADH5 ( or formaldehyde dehydrogenase, FDH). The frequencies and modes of inheritance of these RFLPs were determined with DNA both from unrelated individuals and from families. A polymorphic PstI site is assigned to the fourth intron of the ADH4 gene. Pairwise linkage disequilibrium calculations for these new RFLPs and already known RFLPs at the ADH2 and ADH3 loci establish strong linkage disequilibria between polymorphic MspI and BstXI sites in the ADH5 gene as well as between XbaI and MspI sites in the ADH3 gene. Furthermore, linkage disequilibria were detected between RFLPs of the ADH2 and ADH3 genes as well as between those of the ADH4 and ADH5 genes. The latter disequilibrium implies a hitherto unknown physical proximity of two genes belonging to different ADH classes. The RFLPs were used to construct chromosomal haplotypes that include three ADH classes. Of the 16 possible haplotypes for four RFLP markers used here, 10 were experimentally detected. The potential application of the ADH RFLPs and haplotypes in linkage or association studies of inherited diseases such as familial alcoholism is discussed. 相似文献
48.
49.
Rhida M'Rad Marek Sanak Georges Deschenes Jing Zhou Catherine Bonaiti-Pellie Laurent Holvoet-Vermaut Solange Heuertz Marie-Claire Gubler Michel Broyer Jean-Pierre Grunfeld Karl Tryggvason Marie-Claude Hors-Cayla 《Human genetics》1992,90(4):420-426
Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age. 相似文献
50.
Karl J. Siegert 《Archives of insect biochemistry and physiology》1992,21(2):129-143
Activation and inactivation of fat body glycogen phosphorylase was investigated in ligated abdomens of larval Manduca sexta and in vitro. After maximal activation through Manduca adipokinetic hormone (AKH) or chilling, inactivation of glycogen phosphorylase commenced as soon as the stimulus for the activation was removed indicating that the enzyme system in the fat body is fine-tuned to low phosphorylase activities which is necessary to allow glycogen synthesis. In intact ligated abdomens phosphorylase can be activated repeatedly by either stimulus showing that the fat body system does not lose its responsiveness. It was impossible to achieve complete conversion of the inactive form of phosphorylase into the active form even after administration of AKH and simultaneous chilling. © 1992 Wiley-Liss, Inc. 相似文献