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101.
Inadequate suppression of plasma cortisol after 1-2 mg dexamethasone is frequently observed in depressive patients. To further investigate the pathophysiology underlying cortisol nonsuppression after dexamethasone we compared cortisol and corticotropin (ACTH) response to human corticotropin-releasing factor (h-CRF), lysine vasopressin (LVP), and a concurrent administration of both peptides after pretreatment with 1.5 mg dexamethasone in six male controls. Neither h-CRF nor LVP were able to produce a marked elevation of dexamethasone suppressed plasma cortisol and ACTH. If both peptides were administered in combination, a substantial escape of plasma cortisol from dexamethasone suppression was observed. ACTH responses changed in concordance with those of cortisol indicating that the LVP-CRF interaction takes place at the pituitary level. Our finding is consistent with a multihormonal control of pituitary-adrenal activity and bears several implications for interpretation of dexamethasone suppression test results in depressive illness. 相似文献
102.
Conditioned culture media taken from fibroblast cell lines derived from skin biopsies of control or of patients with Cystic Fibrosis (CF) were incubated with membranes of rat submandibular glands. The Na/K - ATPase activity of these membranes was inhibited when treated with CF-media, including both ouabain sensitive and insensitive activities. However, the membrane associated Mg-ATPase, Ca-ATPase, and both basal and hormone-stimulated adenylate cyclase activities were relatively unaffected. Thus, a factor or factors produced by CF-fibroblasts was shown to be active in a cell-free system derived from an exocrine gland. 相似文献
103.
Adventitious buds on embryos of Picea abies (L.) Karst. developed after a pulse treatment with 250 μ M benzyladenine (BA) of pH 5.5 for 2 h. Light and temperature regimes were not critical during the initial stages. Adventitious buds developed faster after a pulse treatment and the variation among different experiments was lower compared to when the embryos were cultured on media supplemented with BA. Various stages of the differentiation of adventitious buds were identified: stage 1 - appearance of meristematic centres (approximately the first two weeks); stage 2 - development of adventitious bud primordia (approximately the third week); stage 3 - adventitious bud development (from approximately the 4th to the 8th week). This system may be used for further studies on bud differentiation. 相似文献
104.
The rooting of hypocotyl cuttings from 20-day-old seedlings of Pinus sylvestris L. cultured in vitro is discussed. About 40% of the cuttings cultured on medium lacking activated charcoal produced roots during the first two months. When activated charcoal was added to the medium, either root formation (75% formed roots) or wound tissue growth (95% formed large wound tissues) was stimulated in different experiments. These large wound tissues did not develop any roots. The anatomical changes in the basal part of the cuttings were similar during the first two weeks in all the cuttings studied. A vascular cylinder composed of short tracheids with many pores developed. Thereafter the differentiation process became varied. The amount of wound tissue produced and the time for rooting differed among the cuttings. Tracheid nests which were in contact with the vascular system in the hypocotyl via short tracheids were observed after three weeks. Subsequently, roots developed from the tracheid nests. The longer root formation was delayed, the larger the wound tissue became.
Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed. 相似文献
Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed. 相似文献
105.
Features of Crassulacean acid metabolism (CAM) were studied in a variety of different succulents in response to climatic conditions between March 1977 and October 1983 in the southern Namib desert (Richtersveld). A screening in 1977 and 1978 revealed that nearly all investigated succulents performed a CAM, but overnight accumulation of malate declined gradually with decreasing soil water potential, tissue osmotic potential, and leaf water content. This was further substantiated by an extended period of insufficient rainfall in 1979 and 1980 which damaged the evergreen CAM succulents between 80 and 100%. In most of the species still living, neither CO2-gas exchange nor diurnal acid fluctuation, indicative of CAM, could be detected unless an abundant rainfall restored both CAM features. Plants persisted in a stage of latent life.Water supply is one necessary prerequisite for CAM in the Richtersveld. But even well-watered plants with CAM were sensitive to short-term water stress caused by high water-vapour partialpressure deficit (VPD) in the night, which reduced or prevented CO2 uptake and resulted in a linear relation between overnight accumulated malate and VPD. The results do not support the opinion that, for the Namib succulents, CAM is an adaptive mechanism to water stress since long-term and short-term water stress stopped nocturnal malate synthesis, but instead lead to the conclusion that nocuturnal CO2 fixation is only performed when the water status of the plant can be improved simultaneously.Abbreviations CAM
Crassulacean acid metabolism
- VPD
water vapour pressure deficit
Dedicated to Professor H. Ziegler on the occasion of his 60th birthday 相似文献
106.
Characterization of the binding sites for nimodipine and (-)-desmethoxyverapamil in bovine cardiac sarcolemma 总被引:5,自引:0,他引:5
P Ruth V Flockerzi E von Nettelbladt J Oeken F Hofmann 《European journal of biochemistry》1985,150(2):313-322
The bovine cardiac sarcolemmal binding sites for the dihydropyridine nimodipine and the phenylalkylamine (-)-desmethoxyverapamil were studied. The density of the nimodipine and (-)-desmethoxyverapamil binding sites increased 8.3-fold and 3.4-fold with the sarcolemma. The binding sites for both compounds were destroyed by trypsin. Nimodipine bound in the presence of 1 mM free calcium to a high-affinity and a low-affinity site with apparent Kd values of 0.35 +/- 0.09 nM (n = 9) and 33 +/- 6.0 nM (n = 9) and with apparent densities of 0.3 +/- 0.05 pmol/mg (n = 9) and 8.2 +/- 1.0 pmol/mg (n = 9). The binding to the high-affinity site was abolished by 1 mM EGTA. The binding sites were specific for dihydropyridines. The (-)-isomers of several phenylalkylamines inhibited nimodipine binding by an apparent allosteric mechanism. (-)-Desmethoxyverapamil bound in the presence of 5 mM EGTA to a high-affinity and a low-affinity site with apparent Kd values of 1.4 +/- 0.3 nM (n = 6) and 171 +/- 26 nM (n = 6) and with apparent densities of 0.16 +/- 0.02 pmol/mg (n = 6) and 13.6 +/- 2.7 pmol/mg (n = 6). The binding to both sites was inhibited by calcium with a half-maximal concentration of 4.3 mM. The binding sites were specific for the other phenylalkylamines and had a higher affinity for the (-)-isomers than for the (+)-isomers. Nimodipine inhibited the binding of (-)-desmethoxyverapamil by an apparent allosteric mechanism. d-cis-Diltiazem inhibited non-competitively the binding of (-)-[3H]desmethoxyverapamil with a Ki of 3.7 microM. Diltiazem up to concentrations of 10 microM did not affect the amount of nimodipine bound at equilibrium at 20 degrees C. However, but in agreement with this result, diltiazem decreased threefold at 20 degrees C the dissociation and association rates for the high-affinity nimodipine receptor. These rates were only marginally affected at 4 degrees C and 37 degrees C. d-cis-Diltiazem reversed in a competitive manner the inhibition of nimodipine binding elicited by the addition of (-)-desmethoxyverapamil with a Ka value of 1.6 microM. The amount of nimodipine bound was inhibited by 50% by the adenosine uptake inhibitors nitrobenzylthioinosine and hexobendine with apparent median inhibitory concentrations of 1 nM and 3 nM, respectively. Nitrobenzylthioinosine completely abolished binding of nimodipine to the low-affinity site, but did not affect binding to the high-affinity site.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
107.
Synthesis and stability of arylsulfatase A and B in fibroblasts from multiple sulfatase deficiency 总被引:3,自引:0,他引:3
Fibroblasts from patients with multiple sulfatase deficiency were analyzed for activities of arylsulfatase A and B, iduronate 2-sulfatase and sulfamatase. A group of patients (group I) severely deficient in all sulfatases (residual activities less than or equal to 10% of control) were differentiated from patients (group II) with residual sulfatase activities of up to 90% of control. The synthesis and stability of arylsulfatase A and B were determined in pulse-chase labelling experiments. The apparent rate of synthesis of arylsulfatase A and B varied from 30% to normal in both fibroblasts from group I and II multiple sulfatase deficiency. In group I the molecular activity of the arylsulfatase A and B was more than 10-fold lower than in control fibroblasts. In group II the molecular activity of the arylsulfatase A was twofold to threefold lower and that of arylsulfatase B half of normal. In fibroblasts of both groups the stability of arylsulfatase A polypeptides was significantly diminished. For arylsulfatase B the instability was restricted to the mature 47000-Mr polypeptide and was variable within both groups. These results demonstrate that multiple sulfatase deficiency is a heterogeneous disorder, in which the primary defects can impair both the catalytic properties and the stability of sulfatases. 相似文献
108.
M I Al-Sheikhly H P Schuchmann C von Sonntag 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1985,47(4):457-462
In the radiolysis of aqueous formate-containing solutions a chain reaction (i, ii) proceeds in the presence of N2O. CO2-. + N2O + H2O----CO2 + N2 + .OH + OH- (i) .OH + HCO2-.----CO2-. + H2O (ii) The chain length depends on the dose rate and the N2O concentration but not on the formate concentration. Typically, G(CO2) approximately 140 molecules (100 eV)-1 is found, with an equivalent amount of N2, at a dose rate of 3 X 10(-3) Gy s-1. The rate constant for the rate-determining step in this chain reaction has been calculated at k(i) = 1600 dm3 mol-1 s-1. The possible relevance of this chain reaction in radiation biological studies is briefly discussed. 相似文献
109.
Summary Three cyanobacterial isolates (two LPP-B forms and one Anabaena or Nostoc species) from different environments could mobilize uranium from low-grade ores. After 80 days, up to 18% uranium had been extracted from coal and 51% from carbonate rock by the filamentous cyanobacterium OL3, a LPP-B form. Low growth requirements with regard to light and temperature optima make this strain a possible candidate for leaching neutral and alkaline low-grade uranium ores. 相似文献
110.
Peter von Feiten Hans Zürrer Reinhard Bachofen 《Applied microbiology and biotechnology》1985,23(1):15-20
Summary Cells ofRhodospirillum rubrum have been immobilized in various gels and tested for photobiological hydrogen production. Agar proved to be the best immobilizing
agent with respect to production rates as well as stability. Agar immobilized cells were also superior compared to liquid
suspension cultures. Growth conditions of the cells prior to immobilization, e.g. cell age, light intensity or nutrient composition,
were of primary importance for the activity in the later immobilized state. A reactor with agar immobilized cells has been
operated successfully over 3000 h with a loss of the activity of about 60%. Mean rates for hydrogen production for immobilized
cells in this work during the first 60 to 70 hours after immobilization were in the range of 18 to 34 μl H2 mg−1 d.w. h−1 and thus by a factor of up to 2 higher than liquid cultures under the same conditions. Maximal rates of hydrogen production
(57 μl H2 ml−1 immobilized cell suspension) were reached in agar gel beads with cells immobilized after 70 h growth in liquid culture in
the light and a cell density of 1.0 mg ml−1, 70 h after immobilization. 相似文献