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  • Rat  (95)
  • Nicotiana
  • nitrogen
  • phosphorus
  • Springer  (232)
  • Blackwell Publishing Ltd
  • National Academy of Sciences
  • 1990-1994  (105)
  • 1980-1984  (127)
  • 1925-1929
  • 1994  (105)
  • 1984  (58)
  • 1980  (69)
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  • Springer  (232)
  • Blackwell Publishing Ltd
  • National Academy of Sciences
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  • 1990-1994  (105)
  • 1980-1984  (127)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 13 (1984), S. 335-348 
    ISSN: 1572-8927
    Schlagwort(e): Solubility ; Henry's law coefficients ; Ostwald coefficients ; aqueous solutions ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The solubility of nitrogen in pure liquid water was measured in the pressure range 45 to 115 kPa and in the temperature range 5 to 50°C. These data are used to obtain Henry coefficients H 2,1 (T,P s,1 ) at the vapor pressure P s,1 of water. The temperature dependence of H 2,1 (T,P s,1 ) is accounted for by both a Clarke-Glew (CG) type fitting equation, and a power series in T−1, as suggested by Benson and Krause (BK). The imprecision of our measurements is characterized by an average deviation of ±0.038% from a four-term CG equation, and by an average deviation of ±0.042% from a three-term BK equation. From the temperature variation of H 2,1 (T,P s,1 ) partial molar quantities referring to the solution process, such as enthalpies and heat capacities of solution, are obtained. They are given in tabular form, together with H 2,1 (T,P s,1 ) and derived Ostwald coefficients L∞, at rounded temperatures. Finally, experimental results are compared with values calculated via scaled particle theory.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 40 (1984), S. 1004-1006 
    ISSN: 1420-9071
    Schlagwort(e): Rat ; adrenocortical responsiveness ; ACTH ; plasma ; corticosterone ; plasma ; corticotropin releasing factor (CRF)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In the course of studying the plasma adrenocorticotropic hormone (ACTH) and corticosterone responses to synthetic corticotropin releasing factor (CRF), we noted some disparity in the responses. A higher dose (20 μg compared with 5 μg per rat i.a.) produced an equal plasma ACTH but greater plasma corticosterone response in adult male rats. Thus, we examined the possibility that CRF increases adrenocortical responsiveness to ACTH. CRF significantly (p〈0.0005) increased the plasma corticosterone response to ACTH in rats pretreated with dexamethasone. Thus, synthetic CRF increases corticosterone secretion in rats not only by stimulating ACTH secretion, but also by increasing the adrenocortical responsiveness to ACTH.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 40 (1984), S. 974-975 
    ISSN: 1420-9071
    Schlagwort(e): Rat ; prostaglandins ; gastric lesion ; intragastric distension model ; stress model ; indomethacin ; somatostatin preventive effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The inhibition of endogenous prostaglandin synthesis by indomethacin treatment blocks the somatostatin preventive effect on the gastric lesions induced in a stress model and has no preventive effect on an intragastric distension model.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1570-7458
    Schlagwort(e): Alsophila pometaria ; Geometridae ; Anisota senatoria ; Citheroniidae ; Quercus ; nutritional ecology ; herbivory ; nutritional indices ; consumption ; growth ; utilization efficiency ; nitrogen ; water ; tannins ; phenols ; gut pH ; digestive enzymes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé Alimentées sur feuillage jeune de chêne, les chenilles d'Alsophila pometaria avaient un taux relatif de croissance (RGR) et un taux relatif d'accumulation d'azote (RNAR) plus élevés que les chenilles d'Anisota senatoria alimentées sur feuillage mûr de chêne. Bien que le jeune feuillage soit plus efficacement digéré par A. pometaria (AD plus élevé), il n'est pas assimilé et utilisé pour la croissance avec de meilleurs rendements (les ECI ne sont pas différents). Ainsi le taux de croissance plus élevé d'A. pometaria est dû entièrement à un taux de consommation plus important (RCR et RNCR). Le feuillage jeune est significativement plus riche en azote et en eau que le feuillage mûr, mais les niveaux de phénol et de tanins sont les mêmes. A pometaria consomme les feuilles de différentes espèces de chênes au même taux, indépendamment de la teneur en azote, tandis que A. senatoria accroît sa consommation en réponse à une diminution de la teneur en azote. Il en résulte que le taux de croissance d'A. pometaria dépend directement de la teneur en azote des feuilles, tandis que celui d'A. senatoria en est indépendant. Les systèmes digestifs des deux insectes sont biochimiquement semblables et sont efficaces pour la digestion des protéines. Les tanins et les phénols n'influent pas sur les indices nutritionnels de ces deux espèces. Nous estimons que le principal intérêt de l'alimentation printanière est la disponibilité en feuillage succulent, riche en azote, et non l'absence de feuilles à haute teneur en tanin. L'alimentation printanière semble correspondre à une strategie alimentaire qui favorise la croissance aux dépens de l'efficacité tandis que l'alimentation en fin d'été est une stratégie qui favorise l'efficacité sur la rapidité.
    Notizen: Abstract The larvae of Alsophila pometaria (Harr.), feeding on the young foliage of oak, has a higher relative growth rate (RGR) and relative nitrogen accumulation rate (RNAR) than the larvae of Anisota senatoria (J. E. Smith), feeding on the mature foliage of oak. Although the young oak foliage is more efficiently digested by A. pometaria (higher AD's), it is not more efficiently assimilated and used for growth (no difference in ECI's). Thus, the higher growth rate of A. pometaria is due entirely to a higher consumption rate (RCR and RNCR). Young foliage is significantly higher in nitrogen and water than mature foliage, but phenol and tannin levels are comparable in young and old foliage. A. pometaria consumes the foliage of different oak species at the same rate, independent of nitrogen content, while A. senatoria increases its consumption rate in response to decreased nitrogen levels. As a result, the growth rate of A. pometaria is directly related to leaf nitrogen content, while the growth rate of A. senatoria is independent of leaf nitrogen. The two species of insects have digestive systems that are very similar biochemically, and that are well-designed for effective protein digestion. Tannins and phenols do not influence the nutrional indices of either species. We suggest that the major benefit of spring feeding is the availability of succulent, high-nitrogen foliage, and not the avoidance of high-tannin foliage. The spring feeder appears to have a feeding strategy that favors rapid growth at the expense of efficiency, while the late summer feeder has a strategy that favors efficiency over rate.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 36 (1984), S. 293-295 
    ISSN: 1570-7458
    Schlagwort(e): ryegrass ; Oscinella frit ; Geomyza tripunctata ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1573-0417
    Schlagwort(e): Great Basin ; climatic variations ; productivity ; organic matter ; nitrogen ; phosphorus ; hardwater lake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Sediment cores from the shallow and deep basins of Pyramid Lake, Nevada, revealed variations in composition with depth reflecting changes in lake level, river inflow, and lake productivity. Recent sediments from the period of historical record indicate: (1) CaCO3 and organic content of sediment in the shallow basin decrease at lower lake level, (2) CaCO3 content of deep basin sediments increases when lake level decreases rapidly, and (3) the inorganic P content of sediments increases with decreasing lake volume. Variations in sediment composition also indicate several periods for which productivity in Pyramid Lake may have been elevated over the past 1000 years. Our data provide strong evidence for increased productivity during the first half of the 20th Century, although the typical pattern for cultural eutrophication was not observed. The organic content of sediments also suggests periods of increased productivity in the lake prior to the discovery and development of the region by white settlers. Indeed, a broad peak in organic fractions during the 1800's originates as an increase starting around 1600. However, periods of changing organic content of sediments also correspond to periods when inflow to the lake was probably at extremes (e.g. drought or flood) indicating that fluctuations in river inflow may be an important factor affecting sediment composition in Pyramid Lake.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 1 (1980), S. 95-101 
    ISSN: 1573-0867
    Schlagwort(e): soil fertility ; phosphorus ; potassium ; green manure ; crop rotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Changes in the soil phosphorus and potassium status on three farming systems in the Northeast Polder during 25 years are related to the fertilizer regime over this period. The changes in the nutrient status of the soil are reflected in fertilizer policy. High rates of phosphate dressings markedly increased the phosphate status of the soil and built up a reserve of phosphate. In contrast, the potassium status decreased by about half, because only potatoes in the rotation were dressed with potassium. Methods of fertilization are discussed and suggestions are made with regard to possible improvements.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 37 (1994), S. 1-22 
    ISSN: 1573-0867
    Schlagwort(e): animal slurries and manures ; applications to soils ; carbon- ; nitrogen- ; phosphorus ; contamination ; crop production ; dissemination ; hazardous organics ; heavy metals ; inputs ; macro- and micronutrients ; pathogens ; sewage sludges ; survival- ; transfer- ; transport and adsorption rates in soils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The European Community is producing annually about 300 × 106 tons of sewage sludges as well as about 150, 950,160 and 200 tons of domestic, agricultural, industrial and other wastes (street litter, dead leaves etc.). About 20–25% of the German sewage sludges, which contain in average about 3.8,1.6, 0.4, 0.6, 5.3% DM−1 N, P, K, Mg and Ca, 202, 5, 131, 349, 53, 3 and 1446 mg kg−1 DM Pb, Cd, Cr, Cu, Ni, Hg, Zn as well as ca. 37 and 5 mg kg−1 Dm polychlorinated hydrocarbons and biphenyls, are recycled annually as fertilizer. In addition environmental impacts on the arable land of Germany may derive from 76,19.2, 64.7, 33.6, 7.8 and 0.1 kg ha−1 a−1 of N, P, K, Ca, Mg and Cu added as animal manures. Besides heavy metals and hazardous organics pathogens are disseminated with organic wastes. Crop production and soil fertility generally profit from the considerable amounts of plant nutrients and carbon in sewage sludges, animal slurries and manures, but the physicochemical soil properties, the composition of microbial, faunal and plant communities as well as the metabolic processes in the soil-, rhizo- and phyllosphere are changed by organic manuring. Consequences for the soil carbon-, nitrogen-and phosphorus-cycle are discussed. Impacts of heavy metals and hazardous organics on the soil biomass and its habitat as well as on transport mechanisms and surival times of disseminated pathogens in soils are reviewed with emphasis on the German situation. A proposal for future strategies (landscape recycling) is made.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 38 (1994), S. 53-59 
    ISSN: 1573-0867
    Schlagwort(e): controlled-release fertilizer ; gel ; iron ; manganese ; nitrogen ; polyacrylamide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Using diverse technological approaches, many types of delivery devices have been used to supply plant nutrients at a controlled rate in the soil. One new approach is the use of hydrophilic polymers as carriers of plant nutrients. These polymers may be generally classified as 1) natural polymers derived from polysaccharides, 2) semi-synthetic polymers (primarily cellulose derivatives), and 3) synthetic polymers. By controlling the reaction conditions when forming the polymers, various degrees of cross-linking, anionic charge, and cationic charge can be added, thereby changing their effectiveness as fertilizer carriers. When fertilizer-containing solutions are mixed with hydrophilic polymers to form a “gel” prior to application in the soil, the release of soluble nutrients can be substantially delayed compared with soluble fertilizer alone. The effectiveness of a specific controlled-release polymeric system is determined in part by its specific chemical and physical properties, its biodegradation rate, and the fertilizer source used. Addition of some polymers with nutrients has been shown to reduce N and K leaching from well-drained soils and to increase the plant recovery of added N, P, Fe, and Mn in some circumstances
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 40 (1994), S. 165-173 
    ISSN: 1573-0867
    Schlagwort(e): Animal manure ; eutrophication ; ground water ; nitrogen ; phosphorus ; surface runoff
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract With the rapid growth of the poultry industry in Oklahoma, U.S.A., more litter is applied to farm land. Thus, information is required on the impact of applications on regional soil and water resources. The effect of soil and poultry litter management on nitrogen (N) and phosphorus (P) loss in runoff and subsurface flow from four 16 m2 plots (Ruston fine sandy loam, 6 to 8% slope) was investigated under natural rainfall. Plots under Bermudagrass (Cynodon dactylon) received 11 Mg litter ha−1, which amounts to contributions of approximately 410 kg N and 140 kg P ha−1 yr−1. In spring, litter was broadcast on 3 of the plots; the upper half of one and total area of the other two. One of the total-area broadcast plots was tilled to 6 cm, the other remained as no till. The fourth plot served as a control. Relative to the control, litter application increased mean concentrations of total N and total P in runoff during the 16-week study for no-till (15.4 and 5.8 mg L−1) and tilled treatments (16.7 and 6.1 mg L−1). However, values for the half-area application (5.6 and 2.0 mg L−1) were similar to the control (5.7 and 1.3 mg L−1). Interflow (subsurface lateral flow at 70 cm depth) P was not affected by litter application; however, nitrate-N concentrations increased from 0.6 (control) to 2.9 mg L−1 (no till). In all cases, 〈 2 % litter N and P was lost in runoff and interflow, maintaining acceptable water quality concentrations. Although litter increased grass yield (8518 kg ha−1) compared to the control (3501 kg ha−1), yields were not affected by litter management. An 8-fold increase in the plant available P content of surface soil indicates long-term litter management and application rates will be critical to the environmentally sound use of this nutrient resource.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 37 (1994), S. 107-113 
    ISSN: 1573-0867
    Schlagwort(e): Ensete ventricosum ; fertilizer response ; nitrogen ; phosphorus ; potassium ; sulphur ; starch
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Ensete (Ensete ventricosum W. Cheesm.) is a root crop which stores starch in the root and in the lower part of the stem. It is grown in the southwest of Ethiopia and due to its drought resistance, it is of outstanding importance for the supply of food to the local population. Until now virtually nothing is known about the response of Ensete to fertilizer application. Field trials carried out on three representative soils in Ethiopia showed that Ensete biomass yields were increased significantly on all three soils by nitrogen and phosphorus application. Potassium had only marginal effect on biomass growth but favourably influenced starch production. Sulfate application had no major impact on growth and starch yield. The yield response was well related to the level of available nutrients in the soil, as determined by electroultrafiltration (EUF). Leaf analysis provided preliminary evidence that optimum levels of N, P, and K may be 3.8%, 0.3%, and 4.8%, respectively.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 37 (1994), S. 227-234 
    ISSN: 1573-0867
    Schlagwort(e): catch crop ; mineralization ; nitrogen ; plant species ; residual effects ; soil depletion ; winter hardiness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Ten widely different plant species were compared for their ability to reduce soil mineral nitrogen levels in the autumn and their ability to improve the nitrogen nutrition of the succeeding crop. The species included monocots and dicots, crops that survived the winter (persistent) or were winter killed (non-persistent) as well as legumes and non legumes. Their ability to reduce soil mineral nitrogen content was dependent on both root depth and persistency of the crops in the autumn. For non-persistent catch crops most of the mineralization of plant nitrogen occurred during the winter, and for some of these so early as to allow leaching of some mineralized nitrogen. For persistent crops most of the mineralization occurred shortly after incorporation in the spring. The effect of the catch crops on nitrogen uptake by the succeeding barley crop varied from 13 to 66 kg N ha−1 and the differences between the crops could not be related to any single character, but to a combination of root depth, persistency, plant nitrate accumulation, and depletion of the soil mineral nitrogen pool in spring.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 39 (1994), S. 223-228 
    ISSN: 1573-0867
    Schlagwort(e): drip-fertigation ; efficiency ; nitrogen ; sugar cane ; uptake ; yield
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Nitrogen (N) fertilizer use efficiency by sugar cane in Mauritius rarely exceeds 40%. Since drip-irrigation delivers water uniformly and directly to the root zone with little run-off, application of N via the drip-irrigation system could therefore provide a means of enhancing fertilizer N use by sugar cane. A study was initiated in Mauritius to determine what benefits would accrue from applying urea (120 kg N per ha) to sugar cane through the drip-irrigation network. The data obtained showed that the efficiency of fertilizer N when measured at harvest was nearly doubled by supplying the N daily over 10 to 20 weeks by fertigation. Increased yields of sugar or cane did not, however, accompany the improved N use efficiency. Furthermore, when N was applied through the drip-irrigation network, recovery of N at harvest did not accurately reflect N use efficiency.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 39 (1994), S. 189-197 
    ISSN: 1573-0867
    Schlagwort(e): interaction ; isotopic exchange ; phosphorus ; plant-availability ; selenium ; soil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Phosphate, applied at 5µg P cm−3, decreased selenite sorption by from 30–70% in three soils studied. Both maximum sorption (Xm) and the binding-energy of sorption as indicated by the binding-energy related constant (k) or the molar free energy (ΔG) of the sorption reaction derived from the Langmuir equation were considerably decreased. On the other hand, phosphate sorption was decreased by increasing concentration of selenite from 0.2µg Se cm−3 to 1.0µg Se cm−3 in the initial solution. The competitive sorption of phosphate with selenite was likely the main mechanism involved in the P-Se interactions. The competitively sorbed selenite exhibited much larger desorption in 0.01M CaCl2 solution, more readily extractable to 0.5M NaHCO3 and significantly higher isotopic exchangeability compared to that sorbed without the competing anion. Results from pot trial using ryegrass indicated that phosphate application increased more efficiently the plant-availability of applied fertilizer Se than that of indegeneous Se in soil.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 39 (1994), S. 199-203 
    ISSN: 1573-0867
    Schlagwort(e): farmyard manure ; floodwater ; nitrogen ; Oryza sativa L. ; partial pressure of ammonia ; urea ; Vietnam
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Farmyard manure (FYM) applied to rice-growing soils can substitute for industrial fertilizers, but little is known about the influence of FYM on the effectiveness and optimal management for industrial N fertilizers. A field experiment was conducted in northern Vietnam on a degraded soil in the spring season (February to June) and summer season (July to November) to determine the effect of FYM on optimal timing for the first application of urea. The experimental design was a randomized complete block with two rates of basal incorporated FYM (0 or 6 Mg ha−1) in factorial combination with two timings of the first application of 30 kg urea-N ha−1 (basal incorporated before transplanting or delayed until 14 to 16 d after transplanting). The FYM was formed by composting pig manure with rice straw for 3 months. Basal incorporation of FYM, containing 23 kg N ha−1, increased rice grain yield in both seasons. The yield increase cannot be attributed to reduced ammonia loss of applied urea-N, because FYM did not reduce partial pressure of ammonia (pNH3) following urea application in either season. Basal and delayed applications of urea were equally effective in the absence of FYM, but when FYM was applied rice yields in both seasons were higher for delayed (mean = 3.2 Mg ha−1) than basal (mean = 2.9 Mg ha−1) application of urea. Results suggest that recommendations for urea timing in irrigated lowland rice should consider whether farmers apply FYM.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 5 (1984), S. 371-382 
    ISSN: 1573-0867
    Schlagwort(e): nitrogen ; phosphorus ; dry areas ; apparent recovery fraction ; fertilizer management
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Agronomic efficiency (AE) is defined as the increase in economic yield of a crop per unit fertilizer applied. Components of AE are physiological efficiency and apparent recovery fraction. The latter can be further separated into uptake efficiency and availability index. Ways to increase the nitrogen fertilizer use efficiency in rainfed agriculture through fertilizer management are discussed.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Journal of biomedical science 1 (1994), S. 201-203 
    ISSN: 1423-0127
    Schlagwort(e): Hypertension ; Eicosanoid ; Rat ; Genetics ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The present paper reviews the evidence for a possible involvement of renal eicosanoids in the pathophysiology of high blood pressure in genetically hypertensive rats of the Lyon strain. Both in vivo and in vitro experiments suggest that an increased ability to synthesize the vasoconstrictor prostaglandin H2 and/or thromboxane A2 in renal vessels (1) acts as an autocrine amplifier of pressor agents and (2) may contribute to resetting the pressure natriuresis curve which is a prerequisite for the development and maintenance of hypertension.
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  • 18
    ISSN: 1420-9071
    Schlagwort(e): Rat ; cerebrospinal fluid, human ; analgesia ; naloxone ; pain indifference, congenital ; opiates, endogenous
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary CSF from a patient with congential indifference to pain was found to produce analgesia in the rat following intracerebroventricular injections. The analgesic effect was attenuated by pretreatment with naloxone suggesting the involvement of hyperactive endogenous opiate mechanisms in this patient.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 40 (1984), S. 1368-1369 
    ISSN: 1420-9071
    Schlagwort(e): Rat ; kidney ; hypertensive ; prostaglandin dehydrogenase ; hexokinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary 15-Hydroxyprostaglandin dehydrogenase (PGDH) surged in hypertensive (SHR) and normotensive (WKY) rat kidney at 8 days of age, is greatest in SHR. Hexokinase fell in SHR at 17 days of age, but thereafter was similar to WKY. This suggests multisystem enzymatic abnormalities in SHR kidney during development of hypertension.
    Materialart: Digitale Medien
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Aquatic sciences 56 (1994), S. 16-28 
    ISSN: 1420-9055
    Schlagwort(e): Chlorophyll-a ; phosphorus ; nitrogen ; lake ecosystem ; nutrient limitation ; regression analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Regression results based on data from 46 northern temperate lakes show that total phosphorus (TP) is the best predictor for phytoplankton (as chl-a) at lower trophic levels, TP 〈 200 mg · m−3. A regression including both TP and TN as regressors is the best predictor for lakes with TP 〉 200 mg · m−3. However, the good correlation is probably due to a high correlation between lake average chl-a (all years observed) and lake average TP and TN. Within single hypereutrophic lakes, TN alone is the best predictor. It was not possible to identify a medium trophic domain where TN and TP in combination was the best predictor for chl-a. The ratio TN:TP in the water decreases from about 40 to about 5 with increasing trophic level. Optimum TN:TP ratio for algal species with high abundance during late summer and autumn reflects this decreasing ratio, but within a lesser range, i.e., 20 to 5. In contrast, TN:TP ratios for species abundant during the early vernal period showed no, or an inverse, relation to the TN:TP ratio of the water.
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  • 21
    ISSN: 1432-0495
    Schlagwort(e): Nitrogen ; phosphorus ; Precipitation collector ; Nutrients rates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract The contribution of nitrogen and phosphorus due to precipitation constitutes the second most important route after superficial runoff. The sampling carried out during a two-year period by means of a precipitation collector allows us to determine the contribution of this route both qualitatively and quantitatively. Nitrogen is mainly supplied in an inorganic form, while phosphorus is principally supplied as orthophosphate. During the period of this study (March 1986–February 1988) it was found that in the Santillana Reservoir Watershed the level of nitrogen supplied by precipitation constitutes an average of 4.87% and the level of phosphorus constitutes 8.01%. The contribution of nitrogen varies in inverse ratio to precipitation and the contribution of phosphorus varies in direct ratio.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 40 (1984), S. 1008-1010 
    ISSN: 1420-9071
    Schlagwort(e): Rat ; ethanol preference ; acetaldehyde self-administration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Peripherally self-injected acetaldehyde in interaction with environmental and nutritional variables significantly enhances alcohol drinking in rats and suggests an involvement of acetaldehyde in voluntary alcohol intake.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 23
    ISSN: 1432-0827
    Schlagwort(e): Rat ; Calvarium ; Electron microscopy ; Preosteoclasts ; Osteoclasts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary This is a study of the fine structure of cells of the 20-day fetal rat calvarium. Special attention is given to identifying and characterizing preosteoclasts. These cells are relatively common and located largely, but not exclusively, at the endocranial bone surface. The preosteoclasts are characterized by abundant mitochondria, an incomplete perinuclear Golgi apparatus, and variable-shaped dense granules. The dense granules are unique in appearance in that they contain an internal dense matrix surrounded by a clear halo. Most granules are circular in shape but some are elongate or tubular in form. Granules with identical appearance are observed in osteoclasts. The preosteoclasts are mononucleate, or occasionally binucleate. It is suggested that because preosteoclasts are morphologically distinctive and relatively abundant, it should be feasible to separate these cells from a heterogeneous cell isolate.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 32 (1980), S. 63-68 
    ISSN: 1432-0827
    Schlagwort(e): Rat ; Bone formation ; Fluorochrome ; Microphotometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary A method for quantitative studies of the formation rate of bone has been developed. After vital staining with calcein, the fluorescence of a bone section was measured with a microphotometer controlled by a mini computer. After staining the bone structure with alizarin red S in a second step, the section was measured in transmitted light. The two data sets were combined and the shortest distances between the bone surface and the fluorescence lines were computed. With this information the distance distribution and the bone area between the label and the surface could be calculated in two different ways: with the single labeling and the continuous labeling techniques. The advantages and disadvantages of the two methods are discussed and compared with those of other techniques.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 32 (1980), S. 113-122 
    ISSN: 1432-0827
    Schlagwort(e): Rat ; Bone ; Metaphysis ; Quantitative ; Aging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The purpose of this work was to analyze the proximal tibial metaphysis of the 170 g rat in a quantitative histologic fashion which would allow some relation to tissue age to be established. Stained 3 µm thick tissue sections were analyzed with the aid of a Merz grid on an eyepiece reticule and a light microscope. Tissue mass and cell distribution were studied in all areas. The rate of change in tissue mass during aging of the metaphysis was calculated. Two regions of the metaphysis were identified. One, corresponding to the primary spongiosa, less than 4.45 days of age, is a region of high turnover of hard tissue and high numbers of osteoblasts and osteoprogenitor cells. The other, corresponding to the secondary spongiosa, is a region of relatively low net tissue turnover and low numbers of osteoblasts and osteoprogenitor cells. Osteoclasts were found relatively more uniformly distributed through the metaphysis than were osteoblasts and osteoprogenitor cells. The rate of bone formation in the primary spongiosa is 50 times that found in the Haversian bone of the rib of 5-year-old humans and about 500 times that found at the cortical-endosteal surface of ribs of 5-year-old humans. It is argued that both cell distribution and tissue distribution in the metaphysis support the concept that osteoblasts and osteoclasts, rather than osteocytes, are responsible for the maturation of the metaphysis. The inhomogeneous distribution of both cells and tissue in the metaphysis has definite meaning for the interpretation of findings concerning the incorporation of radionuclides into the skeleton.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 26
    ISSN: 1432-0827
    Schlagwort(e): Rat ; Hypophysectomy ; Dietary phosphorus deprivation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The demands of growth are known to exacerbate the effect of phosphorus deprivation (PD). We examined whether changes associated with PD could be prevented in young rats in which growth and growth hormone (GH) were eliminated by hypophysectomy (HPX) and whether PD in normal intact rats (INT) was associated with increased secretion of GH. INT or thyroxine- and ACTH-replaced HPX rats were fed one of the three diets: 0.31% P (NP); 0.027% P (LP), and 0.31% P, pair-fed with LP-mates (NP-PF). The results indicate that HPX did not qualitatively alter several physiologic responses to PD: (a) serum and urinary phosphorus (P) decreased and urinary calcium (Ca) increased; (b) net intestinal Ca retention fell and duodenal sac uptake of45Ca rose; and (c) external P balance was restored and duodenal sac uptake of32P-phosphate increased. Only the hypercalcemia seen in INT, LP rats was prevented by HPX. In INT rats serum immunoassayable GH levels, measured in single samples, were not different between different dietary groups while pituitary bioassayable GH was reduced in both LP and NP-PF rats when compared to the NP rats. Thus, except for hypercalcemia, the physiologic responses associated with PD are not prevented by the elimination of growth and GH, and the development of these responses in INT rats was not associated with a consistent or specific alteration in GH secretion.
    Materialart: Digitale Medien
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  • 27
    ISSN: 1432-0827
    Schlagwort(e): Loading ; Strain ; Modeling ; Rat ; Ulna
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract Adaptive changes in bone modeling in response to noninvasive, cyclic axial loading of the rat ulna were compared with those using 4-point bending of the tibia. Twenty cycles daily of 4-point bending for 10 days were applied to rat tibiae through loading points 23 and 11 mm apart. Control bones received nonbending loads through loading points 11 mm apart. As woven bone was produced in both situations, any strain-related response was confounded by the response to direct periosteal pressure. Four-point bending is not, therefore, an ideal mode of loading for the investigation of strain-related adaptive modeling. The ulna's adaptive response to daily axial loading over 9 days was investigated in 30 rats. Groups 1–3 were loaded for 1200 cycles: Group 1 at 10 Hz and 20 N, Group 2 at 10 Hz and 15 N, and Group 3 at 20 Hz and 15 N. Groups 4 and 5 received 12,000 cycles of 20 N and 15 N at 10 Hz. Groups 1 and 4 showed a similar amount of new bone formation. Group 4 showed the same pattern of response but in reduced amount. The responses in Groups 2 and 3 were either small or absent. Strains were measured with single-element, miniature strain gauges bonded around the circumference of dissected bones. The 20 N loading induced peak strains of 3500–4500 μstrain. The width of the periosteal new bone response was proportional to the longitudinal strain at each point around the bone's circumference. It appears that when a bone is loaded in a normal strain distribution, an osteogenic response occurs when peak physiological strains are exceeded. In this situation the amount of new bone formed at each location is proportional to the local surface strain. Cycle numbers between 1200 and 12,000, and cycle frequencies between 10 and 20 Hz have no effect on the bone's adaptive response.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 55 (1994), S. 33-37 
    ISSN: 1432-0827
    Schlagwort(e): Osteoporosis ; Rat ; Orchidectomy ; Exercise ; Strength
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract The effect of exercise on castration-induced osteoporosis in 3-month-old male rats weighing 264±4 g at the beginning of the experiment was studied. A testosterone deficiency was induced by orchidectomy (ORC), and the exercise group ran 10 m/minute for 1 hour a day on a treadmill at 0% grade. There were seven groups of eight rats (n=56) randomized into a control group killed at time 0, and sham, ORC and ORC and exercise groups killed at 4 and 8 weeks. ORC reduced body weight gain (with analysis of variance (ANOVA) P〈0.001), and at 4 weeks the body weight was 343±14 g in ORC group and 301±4 g in the ORC and exercise group (P〈0.01). The increase in femoral length was slower in the ORC+exercise groups. The ash weight of the tibia did not decrease significantly after ORC or ORC+ exercise. ORC did not affect 45Ca incorporation, but exercise slightly increased it in the whole tibia 8 weeks after ORC (with ANOVA P=0.057). ORC had significantly lowered the trabecular bone volume in the secondary spongiosa of the distal femur at 4 and 8 weeks, and exercise did not prevent this. This is an opposite finding to our previous study with ovariectomized female rats [12]. ORC also significantly had reduced the osteoblast-lined trabecular bone surface and the number of osteoclasts by 8 weeks after the operation. Exercise increased the osteoblast-lined surface and the number of osteoclasts. The mechanical strength of the femoral neck also was reduced after ORC and this was not prevented by exercise either. In conclusion, ORC reduces bone growth and turnover which leads to osteopenia in growing rats. Moderate treadmill exercise does not reverse the ORC-induced loss of trabecular bone and the reduced mechanical strength of the femoral neck, although it has a positive effect on the osteoblast and osteoclast indices and on calcium incorporation into bone.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 54 (1994), S. 150-154 
    ISSN: 1432-0827
    Schlagwort(e): Vitamin D analog ; KH1060 ; Kidney transplantation ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract KH1060 is a new 20-epi-vitamin D3 analog, which has exerted a considerable immunosuppressive potency in vitro. We have tested in vivo the effect of KH1060 on the suppression of renal allograft rejection in the rat. Allogenic kidney transplantation from DA donor rats to Lewis recipient rats treated intraperitoneally with KH1060 in doses from 0.2 to 6 μg/kg/day, or saline (placebo group), or CyA 10 mg/kg/day for 10 days (positive control group), was performed. Median graft survival time in KH1060-treated groups was 7–9 days, in the placebo group 6 days, whereas CyA led to long-term graft survival, 34 days in 50% of rats and 〉100 days in 50% of rats. In vivo, KH1060 failed to prolong renal allograft survival considerably, and led to development of hypercalcemia. Our results stress the existence of a large discrepancy between the in vitro and in vivo immunoregulatory effects of this vitamin D analog.
    Materialart: Digitale Medien
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  • 30
    ISSN: 1432-0827
    Schlagwort(e): Bone mechanics ; Bone composition ; Vitamin D3 ; Corticosteroid ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract The effects of 1α-vitamin D3 were studied for 6 months in 2-month-old male and female rats on a moderately low calcium diet with or without low-dose prednisolone treatment. Both cortical bone mechanical and biochemical properties were examined. Femoral bone specimens were subjected to torsional loading tests. With age, bone strength and stiffness increased in both sexes, accompanied by an increased degree of mineralization (bone ash and calcium concentrations). During growth, strength and stiffness increased more in male than in female rats. When 1α-vitamin D3 (0.5 μg/kg/day) was given alone, bone mechanical competence improved significantly whereas insulin-like growth factor-I (IGF-I) and calcium concentrations in the bone matrix were significantly reduced. Treatment with low-dose prednisolone (0.5 mg/kg/day) alone did not influence bone mechanical properties compared with intact control rats (without prednisolone) although a significant reduction in calcium concentration and an increased phosphorus concentration were measured. A combined therapy with prednisolone and 1α-vitamin D3 significantly increased bone strength, toughness, and stiffness compared with control bones. Both mineralization degree (ash and calcium concentration) and IGF-I concentration were decreased. We conclude that (1) mechanical properties of rat cortical bones improve relatively more in males compared with agematched females during growth which is related to increased bone mass and size, (2) low-dose prednisolone treatment does not change mechanical properties in males, and altered them only nonsignificantly in females despite a change in mineralization degree in both sexes; (3) treatment with 1α-vitamin D3 results in a consistent increase in mechanical competence of the bone accompanied by a significant decrease in IGF-I concentration in the bone matrix.
    Materialart: Digitale Medien
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  • 31
    ISSN: 1432-2048
    Schlagwort(e): mRNA ; Protein synthesis ; Protoplasts ; Nicotiana ; Translation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Studies of proteins synthesized in vitro by messenger RNA (mRNA) extracted from tobacco protoplasts showed that the changes in protein synthesis and especially the lack of certain proteins observed previously in isolated protoplasts did not result from a failure of translation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Planta 148 (1980), S. 462-467 
    ISSN: 1432-2048
    Schlagwort(e): Flower formation ; Leaves (in flower formation) ; Meristem (shoot) ; Nicotiana ; Roots (and flower formation)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The terminal, apical shoot meristem ofN. tabacum cv. Wisconsin 38 normally differentiates into a flower after producing 30 to 40 nodes. The influence of leaves and roots on the regulation of flowering was evaluated by counting the number of nodes produced after removal of leaves or the induction of adventitious roots. Leaf removal has no effect on the number of nodes produced before flower formation. Root induction significantly increases the number of nodes produced before flower formation. The plant behaves as if it were measuring the number of nodes between the meristem and the roots as a means of regulating meristem conversion from vegetative to floral differentiation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Planta 148 (1980), S. 491-497 
    ISSN: 1432-2048
    Schlagwort(e): Leaves (polysomes) ; Nicotiana ; Polysomes ; Poly(A)+ RNA ; Protein synthesis ; RNA (polysomal, polyA+)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The isolation of intact polysomes from leaves of tobacco (Nicotiana tabacum L.) is dependent on the age and state of development of leaves. Undegraded polysomes from young leaves in the early stages of expansion can be isolated easily by extracting the leaves in ice-cold extraction buffer (200 mM tris(hydroxymethyl)aminomethylmethane(Tris)-HCl, pH 9.0; 400 mM KCl; 200 mM sucrose; 35 mM MgCl2). Medium-size leaves give best yields of undegraded polysomes when extractions are carried out in the above buffer and in the presence of ethyleneglycol-bis-(β-amino-ethyl ether)-N,N′-tetracetic acid (EGTA) and mercaptoethanol. Isolation of polysomes from large, nearly fully expanded (mature) leaves requires all of the above plus diethyldithiocarbamate (DIECA) in the extraction medium. An extraction medium consisting of 25 mM EGTA, 0.01 M mercaptoethanol, 25 mM DIECA and 0.5% of the nonionic detergent, Nonidet-P40 (NP 40) was found to be very suitable for extraction of polysomes from all developmental stages of leaves. The polysomes extracted in the above medium showed active translation of protein in the wheat-germ in-vitro protein-synthesizing system. The translational products were similar when translations were carried out directly with polysomes or polysomal RNA, or polysomal poly(A)+ RNA from tobacco leaves. Poly(A)− polysomal RNA was a poor template in the in-vitro wheat-germ system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Planta 149 (1980), S. 7-18 
    ISSN: 1432-2048
    Schlagwort(e): Auxin metabolism ; Cell suspensions (low density) ; Medium conditioning ; Nicotiana ; Nitrogen metabolism ; Protoplasts ; Vitamin requirements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Preliminary attempts to define a completely synthetic medium able to support divisions of haploid tobacco mesophyll protoplasts at low initial densities have failed. High protoplast concentrations together with large amounts of naphtaleneacetic acid in the medium (3 mg l-1 NAA) were required for maximal induction of protoplast division. However, cell suspensions derived from haploid protoplasts after four days of preculture at high initial cell densities could be diluted to densities as low as 1–4 cells ml-1, provided the concentration of NAA in the medium was lowered to below 0.3 mg l-1. The optimal NAA supply for low cell density growth was affected by the nature of the nitrogen source. A simple minimal medium which supports the growth of these haploid cells with a plating efficiency of 30–40%, independent of the cell density in the range of 1–4 to 3·104 cells ml-1, has been established. In this medium inositol was the only vitamin stringently required for growth. Growth of cells at low densities was also possible in a medium initially containing 3 mg l-1 NAA, provided it was conditioned by the growth of protoplasts at high densities. Preliminary experiments with [14C]NAA showed that the amount of free NAA remaining in the medium after preincubation at high densities was drastically reduced. Simultaneously, NAA conjugates accumulated in the medium. The implications of these results are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Planta 149 (1980), S. 44-47 
    ISSN: 1432-2048
    Schlagwort(e): Auxin receptor ; Callus ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cultured tobacco-pith tissue contains a cytoplasmic receptor for indoleacetic acid (IAA). The concentration of binding sites is very low in comparison to that of several auxin receptors found by other investigators. A few obvious possible causes (degradation or inactivation) were investigated. From the results we conclude that the low number of binding sites is real. The receptor binds IAA optimally at pH 7.5–7.8 and at a temperature of 24–30°C, when incubated for 25–30 min. The binding is very specific, as is shown by competition experiments. The concentration of the receptor in the callus tissue changes dramatically during each culture period, which suggests a possible role in development. The receptor was partly purified by gel filtration on Sepharose 6B followed by ion-exchange chromatography on DEAE-cellulose.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Planta 149 (1980), S. 196-199 
    ISSN: 1432-2048
    Schlagwort(e): 1-Aminocyclopropane-1-carboxylic acid ; Avena ; Ethylene ; Etiolation ; Light (ethylene production) ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract White light inhibits the conversion of 1-amino-cyclopropane-1-carboxylic acid (ACC) in discs of green leaves of tobacco (Nicotiana tabacum L.) and segments of oat (Avena sativa L.) leaves by from 60 to 90%. Etiolated oat leaves do not show this effect. The general nature of the effect is shown by its presence in both a mono- and a dicotyledon. Since the leaves have been grown and pre-incubated in light, yet can produce from 2 to 9 times as much ethylene in the dark as in the light, it follows that the light inhibition is fully reversible. The inhibition by light is about equal to that exerted in the dark by CoCl2; it can be partly reversed by dithiothreitol and completely by mercaptoethanol. Thus the light is probably acting, via the photosynthetic system, on the SH group(s) of the enzyme system converting ACC to ethylene.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Planta 149 (1980), S. 205-206 
    ISSN: 1432-2048
    Schlagwort(e): Callus cultures ; Nicotiana ; Nicotine ; Tissue cultures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Callus cultures of two low-alkaloid lines of Nicotiana tabacum L. had considerably lower nicotine contents than cultures from the respective highalkaloid cultivars which were isogenic except for the two loci for alkaloid accumulation. Thus, there was a strong correlation between the nicotine content of callus cultures and the plants from which they were derived.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Planta 150 (1980), S. 9-12 
    ISSN: 1432-2048
    Schlagwort(e): Auxin binding ; Nicotiana ; Plasma membrane ; Protoplast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In vitro binding of 1-naphthaleneacetic acid (NAA) to particulate fractions from tobacco leaf protoplasts was studied. In freshly isolated protoplasts no specific binding could be detected, whereas it was present in particulate fractions from tobacco leaves. It is concluded that the NAA-binding-sites are probably located at the external face of the plasma membrane; they are destroyed during protoplast isolation by proteolytic enzymes in the cellulase and macerozyme preparations. After culturing the protoplasts for 3–4 d, the first cell divisions were observed and at the same time specific NAA-binding became detectable. The affinity constant for NAA was approx. 2·106 mol-1 and the number of binding sites increased during further culture.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Planta 150 (1980), S. 264-268 
    ISSN: 1432-2048
    Schlagwort(e): Cytokinin habituation ; Habituation, cytokinin ; Nicotiana ; Position effects (habituation) ; Size effects (habituation) ; Tissue culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Pith tissue of Nicotiana tabacum L. cv. “Havana 425” exhibits a gradient in its tendency to habituate for cytokinin on an auxin-containing medium at 35° C, about 10° C above the standard culture temperature. Explants of pith from below the 8th to 11th internode, counting from the bottom of the plant, rarely habituate for cytokinin; explants from above this threshold habituate rapidly. The explants must also be above a critical size, about 20–30 mg, to habituate. There was a pronounced interaction between size and position effects; the threshold position for cytokinin habituation shifted upward with decreasing explant size.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 40
    ISSN: 1432-2048
    Schlagwort(e): Abscisic acid ; Nicotiana ; Ribonucleic acid synthesis ; Tobacco mosaic virus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Uptake of abscisic acid from the culture medium by discs of healthy and tobacco mosaic virus-infected tobacco leaves was measured. Small (two to five-fold) increases in abscisic acid concentration in discs caused increases in rates of [3H]uridine and [3H]adenine incorporation into total nucleic acid, virus RNA and host ribosomal RNA. Net accumulation of virus RNA was also enhanced by abscisic acid. This evidence for stimulation of RNA synthesis is compared with previous reports showing inhibition of RNA synthesis in other tissues. It is suggested that the increase in endogenous abscisic acid caused by tobacco mosaic virus infection may be at least partly responsible for observed increases in rates of RNA synthesis after infection.
    Materialart: Digitale Medien
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  • 41
    ISSN: 1432-2048
    Schlagwort(e): Nicotiana ; Protoplast ; Pyrophosphatase ; Vacuolar ATPase ; Vacuole (regeneration)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The re-formation of vacuoles in miniprotoplasts (evacuolated mesophyll protoplasts) of tobacco was investigated under different conditions. When a constant osmolarity was maintained, increasing the concentration of NaCl in the medium enhanced the regeneration of vacuoles compared to the control (0.5 M mannitol used as osmoticum). An enhanced growth rate of miniprotoplasts could also be observed under low-osmolarity conditions, by substitution of NaCl for KCl or NaNO3, or with different effectors (glycinebetaine and methyljasmonate). Using the polymerase chain reaction, one cDNA fragment of the B-subunit of the vacuolar ATPase and two fragments of the tonoplast-bound pyrophosphatase (PPase) of tobacco were cloned. Southern blot analyses indicates that for both proteins more than one gene is present in tobacco. During the regeneration of vacuoles the transcript level of the PPase increased earlier than that of the B-subunit of the vacuolar ATPase under all conditions tested (0.5 M mannitol, 0.3 M mannitol, and 0.25 M NaCl, respectively). Under salt-stress conditions (0.25 M NaCl used as osmoticum), the expression level of both proton pumps is enhanced compared to the control. This increase is not specifically due to salt stress but generally to an increased growth rate of the vacuole, since under low-osmolarity conditions the expression of the vacuolar pumps is enhanced, too.
    Materialart: Digitale Medien
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  • 42
    ISSN: 1432-2048
    Schlagwort(e): Glycosylation in vitro ; mRNA translation control ; Nicotiana ; Pollen development ; Pollen tube ; Translation in vitro
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Regulation of expression of a 69-kDa glycoprotein which occurs abundantly in tobacco (Nicotiana tabacum L.) pollen tubes but is absent in ungerminated pollen has been studied in vitro by means of a coupled translation/glycosylation system with RNA isolated from various stages of pollen development. Pollen mRNA could be translated in a rabbit reticulocyte lysate and the products glycosylated with canine pancreatic microsomal membranes. The electrophoretic pattern of translation products obtained with pollen-tube RNA showed a prominent polypeptide with an apparent molecular mass of 58 kDa. In the presence of the canine pancreatic microsomal membranes this polypeptide was glycosylated, producing the 69-kDa glycoprotein. The presence of mRNA encoding the 58-kDa precursor polypeptide was also demonstrated in ungerminated pollen and in young mid-binucleate pollen isolated from anthers. Initiation of synthesis of the 69-kDa glycoprotein at the onset of pollen germination thus occurs through unmasking of the mRNA transcribed during pollen differentiation and stored during pollen maturation and dormancy in an inactive state.
    Materialart: Digitale Medien
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  • 43
    ISSN: 1432-2048
    Schlagwort(e): Fructose 2,6-bisphosphate ; Photosynthesis ; Nicotiana ; Solanum ; Starch ; Sucrose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Here we show that fructose 2,6-bisphosphate cannot be reliably measured in mature leaves of tobacco (Nicotiana tabacum L.), potato (Solanum tuberosum L.), or stinging nettle (Urtica dioica L.) using conventional extraction techniques, since the recoveries of fructose 2,6-bisphosphate added during extraction are poor. However, fructose 2,6-bisphosphate could be extracted by boiling leaves in ethanol and aqueous buffer. Evidence for the reliability of this technique is provided by high recovery measurements of fructose 2,6-bisphosphate added to the leaves before extraction. This extraction method was used to measure changes in the level of fructose 2,6-bisphosphate throughout the photoperiod in tobacco and potato leaves. These changes are compared with the rate of accumulation of sucrose and starch in the leaf samples. Variations in the levels of fructose 2,6-bisphosphate, and the relationship between this metabolite and sucrose and starch accumulation in these leaves during the photoperiod are similar to the pattern observed in leaves of other plant species.
    Materialart: Digitale Medien
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  • 44
    ISSN: 1432-2048
    Schlagwort(e): Cell wall ; Lignification ; Nicotiana ; Oxidase ; Peroxidase ; Xylem
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A band of cells closest to the cambium in the xylem of tobacco (Nicotiana tabacum L. cv. Samsun) stems oxidized 2,2-azinobis-(3-ethylbenzo-thiazoline-6-sulphonate) (ABTS), o-dianisidine and syringaldazine in the absence of exogenously added hydrogen peroxide. The oxidation was not prevented by catalase which suggests that the oxidation is not dependent on the production and utilisation of endogenous hydrogen peroxide by cell-wall peroxidases. Cell walls, isolated from tobacco xylem, also oxidized these substrates in the absence of added hydrogen peroxide. The cell walls consumed molecular oxygen whilst oxidizing a range of compounds including coniferyl alcohol. The substrate preference and sensitivity to inhibitors suggest the presence of laccasetype polyphenol oxidases (p-diphenol:O2 oxidoreductase EC 1.14.18.1) which are covalently bound to the wall. The oxidation of coniferyl alcohol by the xylem cell walls was confirmed by assays based on the disappearance of coniferyl alcohol and was not affected by the presence of 500 units·mi-1 catalase or Superoxide dismutase. Prolonged incubation of cell walls with coniferyl alcohol led to the production of a yellow-orange water-insoluble material that precipitated with the cell walls. Although a proportion of this material was soluble in methanol, the majority was tightly associated with the cell walls. These coloured cell walls had elevated lignin contents when assayed by the acetyl-bromide method. Fourier transforminfrared spectroscopic analysis of the coloured cell walls indicated that the increased lignin content is due to the deposition of guaiacyl-type lignin. Digestion of the xylem cell walls with Driselase, a mixture of fungal glycases, produced a wall residue that had a dramatically reduced ability to oxidize ABTS in the absence of added H2O2. However, oxidase activity could not be detected in the Driselase-solubilized extract, although small amounts of oxidase activity could be recovered from the Driselaseresistant wall residue by extraction in 3 M CaCl2.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    ISSN: 1432-2048
    Schlagwort(e): Gene expression ; Nitrate ; Nitrite-reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Deletion analysis of the nitrite-reductase (NiR) promoter from spinach (Spinacia oleracea L.) fused to theβ-glucuronidase (GUS) reporter gene and introduced into tobacco (Nicotiana tabacum L., cv. Coker 176) indicates that basic elements required for light- and nitrate-dependent expression of the reporter are located within the promoter sequence -200/+131 relative to the transcription-initiation site. Detailed analysis indicates that positive regulatory elements exist between -200 and-330 as well as between -1450 and -1730, stimulating the level of GUS gene expression under all experimental conditions. Induction/reversion light-pulse experiments show that the promoter sequence -200/+131 suffices for phytochrome-mediated expression of the reporter gene. The observation that the NiR promoter from spinach exhibits full reversibility in transgenic tobacco confirms the previous conclusion that the NiR promoter from spinach fused to a GUS reporter gene and introduced into tobacco responds to nitrate and phytochrome as would be expected for tobacco (host) and not as would be expected for spinach (donor). When the plastids were damaged by photooxidation in the presence of Norflurazon, GUS activity levels were reduced to the same extent for all NiR-promoter/GUS fusions tested, indicating that the promoter region involved in the action of the ‘plastidic factor’ is between -200 and +131. The GUS gene expression under the control of the CaMV-35S promoter is not affected by light, nitrate or the ‘plastidic factor’.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 46
    ISSN: 1432-2048
    Schlagwort(e): Mutant (tobacco calli) ; Nicotiana ; Sterolbiosynthesis inhibitors ; Triazole resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Sterol overproduction is shown to be the biochemical basis of resistance to the triazole LAB 170250F (2-(4-chlorophenyl)-3-phenyl-1-(1H-1,2,4-triazol-1-yl)-2,3-oxidopropane), an inhibitor of cytochrome P450-dependent-obtusifoliol-14α-demethylase, in the tobacco (Nicotiana tabacum L. cv. Xanthi) mutant LAB 1-4. Genetic analysis at the callus level indicates that the resistance and the biochemical phenotypes co-segregate during meiotic recombination and therefore result most probably from the same mutation. Analysis of the intracellular distribution of sterols shows that in LAB 1-4 calli containing tenfold the sterol amount of the wild type, the overproduced metabolites, mainly obtusifoliol, are esterified by fatty acids and stored in hyaloplasmic lipid droplets. Thus, the mutant calli maintain a concentration of free sterols in cell membranes, mainly end-products of the sterol-biosynthesis pathway, which corresponds to physiological requirements, whereas the level of free sterols in the wild-type calli treated with the triazole is too low to ensure viability. We also show that sterol overproduction confers resistance to other phytotoxic sterolbiosynthesis inhibitors.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    ISSN: 1432-2048
    Schlagwort(e): Gene expression ; Nitrate ; Nitrite-reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Deletion analysis of the nitrite-reductase (NiR) promoter from spinach (Spinacia oleracea L.) fused to the β-glucuronidase (GUS) reporter gene and introduced into tobacco (Nicotiana tabacum L., cv. Coker 176) indicates that basic elements required for light- and nitrate-dependent expression of the reporter are located within the promoter sequence -200/+131 relative to the transcription-initiation site. Detailed analysis indicates that positive regulatory elements exist between -200 and-330 as well as between -1450 and -1730, stimulating the level of GUS gene expression under all experimental conditions. Induction/reversion light-pulse experiments show that the promoter sequence -200/+131 suffices for phytochrome-mediated expression of the reporter gene. The observation that the NiR promoter from spinach exhibits full reversibility in transgenic tobacco confirms the previous conclusion that the NiR promoter from spinach fused to a GUS reporter gene and introduced into tobacco responds to nitrate and phytochrome as would be expected for tobacco (host) and not as would be expected for spinach (donor). When the plastids were damaged by photooxidation in the presence of Norflurazon, GUS activity levels were reduced to the same extent for all NiR-promoter/GUS fusions tested, indicating that the promoter region involved in the action of the ‘plastidic factor’ is between -200 and +131. The GUS gene expression under the control of the CaMV-35S promoter is not affected by light, nitrate or the ‘plastidic factor’.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Planta 194 (1994), S. 200-214 
    ISSN: 1432-2048
    Schlagwort(e): Actin ; Cytoskeleton ; Embryo sac ; Fertilization ; Microtubule ; Nicotiana ; Synergid degeneration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The cytoskeletal organization of the embryo sac of tobacco (Nicotiana tabacum L.) was examined at maturity and during synergid degeneration, pollen-tube delivery and gamete transfer using rapid-frozen, freeze-substituted and chemically fixed material in combination with immunofluorescence and immunogold electron microscopy. Before fertilization, the synergid is a highly polarized cell with dense longitudinally aligned arrays of microtubules adjacent to the filiform apparatus at the micropylar end of the cell associated with major organelles. The cytoskeleton of the central cell is less polarized, with dense cortical microtubules in the micropylar and chalazal regions and looser, longitudinally oriented cortical microtubules in the lateral region. In the synergid and central cell, F-actin is frequently found at the surface of the organelles and co-localizes with either single microtubules or microtubule bundles. Egg cell microtubules are frequently cortical, randomly oriented and more abundant at the chalazal end of the cell; actin filaments are associated with microtubules and the cortex of the egg cell. At 48 h after pollination and before the pollen tube arrives, the onset of degeneration is evident in one of the two synergids: the electron density of cytoplasmic organelles and the ground cytoplasm increases and the nucleus becomes distorted. Although synergids otherwise remain intact, the vacuole collapses and organelles degenerate rapidly after pollen-tube entry. Abundant electron-dense material extends from the degenerated synergid into intercellular spaces at the chalazal end of the synergid and between the synergids, egg and central cell. Rhodamine-phalloidin and anti-actin immunogold labeling reveal that electron-dense aggregates in this region contain abundant actin forming two distinct bands termed “coronas”. This actin is part of a mechanism in the egg apparatus which appears to precisely position and facilitate the access of male gametes to the egg and central cell for fusion.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 49
    ISSN: 1432-2048
    Schlagwort(e): Lycopersicon ; Manduca ; Nicotiana ; Proteinase inhibitor ; Tobacco Mosaic Virus ; Wounding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Wounding of plants by insects is often mimicked in the laboratory by mechanical means such as cutting or crushing, and has not been compared directly with other forms of biotic stress such as virus infection. To compare the response of plants to these types of biotic and abiotic stress, trypsin inhibitor (TI) activity induced locally and systemically in mature tobacco (Nicotiana tabacum L.) and tomato (Lycopersicon esculentum L.) plants was followed for 12 days. In tobacco, cutting, crushing and insect feeding all induced comparable levels of TI activity of approx. 5 nmol·(mg leaf protein)−1 in wounded leaves, while tobacco mosaic virus (TMV) infection of tobacco induced 10-fold lower amounts in the infected leaves. In tomato, feeding by insects also led to the induction of a level of TI activity of 5 nmol·(mg leaf protein)−1. In contrast, both cutting and crushing of tomato leaves induced 10-fold higher amounts. These data show that biotic stress, in the form of insect feeding and TMV infection, and abiotic stress, in the form of wounding, have different effects on local levels of induced TI activity in mature tobacco and tomato plants. Irrespective of the type of wounding, in neither tobacco nor tomato could systemic induction of TI activity be observed in nearby unwounded leaves, which suggests that systemic induction of TI activity in mature tobacco and tomato plants is different from systemic TI induction in seedlings. Wounding of tobacco leaves, however, did increase the responsiveness to wounding elsewhere in the plant, as measured by an increased induction of TI activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 50
    ISSN: 1432-2048
    Schlagwort(e): Gas exchange ; Nicotiana ; Photosynthesis (C3) ; Ribulose-1,5-bisphosphate carboxylase/oxygenase kinetics ; Transgenic tobacco
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Transgenic tobacco (Nicotiana tabacum L. cv. W38) with an antisense gene directed against the mRNA of the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit was used to determine the kinetic properties of Rubisco in vivo. The leaves of these plants contained only 34% as much Rubisco as those of the wild type, but other photosynthetic components were not significantly affected. Consequently, the rate of CO2 assimilation by the antisense plants was limited by Rubisco activity over a wide range of CO2 partial pressures. Unlike in the wild-type leaves, where the rate of regeneration of ribulose bisphosphate limited CO2 assimilation at intercellular partial pressures above 400 ubar, photosynthesis in the leaves of the antisense plants responded hyperbolically to CO2, allowing the kinetic parameters of Rubisco in vivo to be inferred. We calculated a maximal catalytic turnover rate, kcat, of 3.5+0.2 mol CO2·(mol sites)−1·s−1 at 25° C in vivo. By comparison, we measured a value of 2.9 mol CO2·(mol sites)−1·−1 in vitro with leaf extracts. To estimate the Michaelis-Menten constants for CO2 and O2, the rate of CO2 assimilation was measured at 25° C at different intercellular partial pressures of CO2 and O2. These measurements were combined with carbon-isotope analysis (13C/12C) of CO2 in the air passing over the leaf to estimate the conductance for transfer of CO2 from the substomatal cavities to the sites of carboxylation (0.3 mol·m−2·s−1·bar−1) and thus the partial pressure of CO2 at the sites of carboxylation. The calculated Michaelis-Menten constants for CO2 and O2 were 259 ±57 μbar (8.6±1.9μM) and 179 mbar (226 μM), respectively, and the effective Michaelis-Menten constant for CO2 in 200 mbar O2 was 549 μbar (18.3 μM). From measurements of the photocompensation point (Γ* = 38.6 ubar) we estimated Rubisco's relative specificity for CO2, as opposed to O2 to be 97.5 in vivo. These values were dependent on the size of the estimated CO2-transfer conductance.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Planta 147 (1980), S. 467-470 
    ISSN: 1432-2048
    Schlagwort(e): Hydrogenperoxide ; Lignification ; Nicotiana ; Peroxidase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Three peroxidase isoenzyme-groups found in cell walls of tobacco were tested for their capacity to form H2O2. Isoenzyme-group GI, located only in cell walls (GII and GIII are also found in protoplasts) showed the highest Kapp-value for H2O2-formation. The lowest Kapp-value, i.e., maximal H2O2-formation was received for group GIII which is ionically bound to the cell wall. As shown before, GI yields maximal polymerization rates for coniferyl- and p-coumarylalcohol. These facts indicate that each of the peroxidase isoenzyme groups of the cell wall is involved with different catalytic functions within the same pathways of H2O2-formation and succeeding lignification. H2O2-formation catalyzed by all 3 groups was increased by very low concentrations of Mn2+-ions. The required amount of Mn2+ leading to maximal stimulation was in each case dependent on the basic rate of H2O2-formation. Maximal stimulation of H2O2-formation by phenolic compounds was achieved by coniferylalcohol at a concentration of 10-4M for all groups. Stimulation by p-coumaryl-and by sinapylalcohol was not as significant.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Planta 149 (1980), S. 402-407 
    ISSN: 1432-2048
    Schlagwort(e): Cytokinin ; Habituation rates ; Nicotiana ; Temperature and habituation ; Tissue culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Pith parenchyma tissue ofNicotiana tabacum L. cv. “Havana 425” becomes cytokinin habituated when incubated at 35°C on an auxin-containing medium. Under these conditions, habituated, hyperplastic nodules appear on the tissues. We used these nodules to estimate the incidence of habituation by a statistical method. The rate of habituation varied with the season. Tissue isolated from plants in the spring habituated approx. 7 times faster than did tissue isolated from plants in winter. The fact that the average rate, 〉4×10−3 per cell generation, was 100–1,000 times faster than the rate of somatic mutation inNicotiana species and depended on the physiological state of the tissue provides further evidence that habituation involves epigenetic changes rather than rare, random genetic mutations. We also found that kinetin (6-furfurylaminopurine) induced habituation and that the concentration required depended on the duration of cytokinin treatment. For long incubation times, approx. 6×10−10 M kinetin, which is about 1,000-fold lower than the concentration optimal for growth of cytokinin-requiring pith tissue, was sufficient to induce habituation. These results support the hypothesis that the habituated state is maintained by a positive feedback loop in which cytokinins either induce their own synthesis or inhibit their own degradation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 53
    ISSN: 1432-2048
    Schlagwort(e): Acetate incorporation ; Catharanthus ; Cell suspension cultures ; Fatty acids ; Glycihe ; Nicotiana ; Temperature and fatty-acid synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The fatty-acid composition of C. roseus and N. tabacum cell suspension cultures was unaffected by subculture on Wood and Braun, Murashige and Skoog, or Gamborg B5C media. However, placing the cultures — which were normally grown at 25° C — at 15° C reduced growth but resulted in enhanced formation of oleic and linolenic acids in C. roseus cultures and increased levels of linoleic and linolenic acids in cultures of G. max and N. tabacum, respectively. The incorporation of [14C]acetate into [14C]linoleic acid was more rapid in N. tabacum cells than in G. max cells, but was very poor in C. roseus where the [14C] label was distributed mainly between palmitic and oleic acids.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 54
    ISSN: 1432-2048
    Schlagwort(e): Fraction-1 protein ; Hybrid, somatic ; Nicotiana ; Protein (Fraction 1) ; Ribulose-1,5-bisphosphate carboxylase ; Somatic hybrid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In the sexual interspecific cross, Nicotiana rustica L.xN. tabacum L., N. rustica can serve as the female but not as the male parent. By fusion of protoplasts, the barrier to fertilization was overcome and somatic hybrids containing N. tabacum cytoplasm were produced as shown by isoelectric focusing of the Fraction-1 protein (F-1-protein). All somatic hybrids displayed polypeptides of the large subunit of F-1 protein (which is coded by the chloroplast genome) characteristic of only one or the other parental species. Two hybrids had large subunits of the N. tabacum type and two hybrids had those of the N. rustica type. Three hybrids contained three smallsubunit polypeptides (coded by the nuclear genome), one being characteristic of N. rustica, one characteristic of N. tabacum, and one with an isoelectric point common to both species. A fourth hybrid contained only two small-subunit polypeptides of the N. tabacum type but in a F-1 protein macromolecule whose large subunits were of the N. rustica type. One somatic hybrid was self-fertile and its F2 progeny contained large- and small-subunit polypeptides indistinguishable in their isoelectric points from those in the parent F1 hybrid. All somatic hybrids showed an aneuploid chromosome number and morphological characteristics intermediate between those of N. rustica and N. tabacum.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Planta 147 (1980), S. 389-395 
    ISSN: 1432-2048
    Schlagwort(e): Catharanthus ; Cell suspension cultures ; Glycine ; Fatty acids (synthesis, desaturation) ; Nicotiana ; Linoleic, linolenic, oleic, acids ; Temperature and fatty acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cell suspension cultures of Catharanthus roseus G. Don, Glycine max (L.) Merr. and Nicotiana tabacum L. were incubated with [14C]acetate, [14C]oleic acid and [14C]linoleic acid at five different temperatures ranging from 15 to 35° C. When the incubation temperature was increased, [14C]acetate was incorporated preferentially into [14C]palmitate, with a concomitant drop in [14C]oleate formation. Between 15 and 20° C, [14C]oleic acid accumulated in C. roseus cells. In all cultures, optimum desaturation of [14C]oleic acid to [14C]linoleic acid occurred between 20 and 25° C, and in G. max this was also the optimal range for desaturation of [14C]linoleic acid to [14C]linolenic acid. Elongation of [14C]palmitic acid was inhibited when cultures grown at 15° C for 25 h were subsequently incubated with [14C]acetate at 25° C. [14C]oleic acid accumulated in G. max and C. roseus cultures grown at 35° C for 25 h and subsequently incubated at 25° C. Desaturation of [14C]oleic acid increased up to 25° C, but then decreased or leveled off depending on the cell line and on the temperature prior to incubation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Planta 148 (1980), S. 491-497 
    ISSN: 1432-2048
    Schlagwort(e): Leaves (polysomes) ; Nicotiana ; Polysomes ; Poly(A)+ RNA ; Protein synthesis ; RNA (polysomal, polyA+)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The isolation of intact polysomes from leaves of tobacco (Nicotiana tabacum L.) is dependent on the age and state of development of leaves. Undegraded polysomes from young leaves in the early stages of expansion can be isolated easily by extracting the leaves in ice-cold extraction buffer (200 mM tris(hydroxymethyl)aminomethylmethane(Tris)-HCl, pH 9.0; 400 mM KCl; 200 mM sucrose; 35 mM MgCl2). Medium-size leaves give best yields of undegraded polysomes when extractions are carried out in the above buffer and in the presence of ethyleneglycol-bis-(β-amino-ethyl ether)-N,N′-tetracetic acid (EGTA) and mercaptoethanol. Isolation of polysomes from large, nearly fully expanded (mature) leaves requires all of the above plus diethyldithiocarbamate (DIECA) in the extraction medium. An extraction medium consisting of 25 mM EGTA, 0.01 M mercaptoethanol, 25 mM DIECA and 0.5% of the nonionic detergent, Nonidet-P40 (NP 40) was found to be very suitable for extraction of polysomes from all developmental stages of leaves. The polysomes extracted in the above medium showed active translation of protein in the wheat-germ in-vitro protein-synthesizing system. The translational products were similar when translations were carried out directly with polysomes or polysomal RNA, or polysomal poly(A)+ RNA from tobacco leaves. Poly(A)− polysomal RNA was a poor template in the in-vitro wheat-germ system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 57
    ISSN: 1432-2048
    Schlagwort(e): mRNA ; Nicotiana ; Protein synthesis ; Ribulose-1,5-bisphosphate carboxylase ; RNA (messenger) ; Translation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The products synthesized in vitro by messenger RNA (mRNA) extracted from Nicotiana sylvestris were analyzed by electrophoresis on polyacrylamide slab gels. Only three of the major polypeptides synthesized are considered here: P55, P32, and P20. P55 and P32 were translated from chloroplast mRNA. P55 corresponds to the large subunit of ribulose-1,5-bisphosphate (RuP2) carboxylase; P32 is probably a chloroplast membrane protein. P20, the polypeptide synthesized from cytoplasmic poly(A)+ RNA, is the precursor of the small subunit of RuP2 carboxylase. The balance between P20 and P32, in which their relative proportions varied inversely, was regulated by the age of the leaves and the time of illumination; we took advantage of this phenomenon to isolate the mRNA from the small subunit in relatively large amounts. This mRNA has a molecular weight of 350,000.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 58
    ISSN: 1432-2048
    Schlagwort(e): Adenosine 5′-phosphosulfate sulfotransferase ; Cell suspension culture ; Cysteine ; Enzyme regulation ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The properties and the regulation of adenosine 5′-phosphosulfate sulfotransferase extracted from cell suspension cultures ofNicotiana sylvestris was investigated. Optimal adenosine 5′-phosphosulfate sulfotransferase activity was obtained from the cells by extraction with 0.1 M tris-HCl, pH8.0, containing 2 M MgSO4 and 10 mM dithioerythritol. The K m for adenosine 5′-phosphosulfate in the sulfotransferase reaction was about 11 μM. Adenosine 5′-phosphosulfate in concentrations above 50 μM were inhibitory. The extratable adenosine 5′-phosphosulfate sulfotransferase activity decreased during cultivation with sulfate as the sole sulfur source, but after about 3 days it reached a constant level (50 to 100 nmol activated sulfate transferred h-1 mg-1 protein) which was maintained for at least 24 h. Addition of 0.5 mM cysteine to the culture medium decreased the extractable adenosine 5′-phosphosulfate sulfotransferase activity and blocked growth completely. With 0.1 mM cysteine an enzyme level of about 10% of the initial value was reached within 6 to 12 h without significant inhibition of growth. The added cysteine was absorbed rapidly and after 24 h cysteine could no longer be detected in the medium. Before the cysteine was completely depleted, the activity of adenosine 5′-phosphosulfate sulfotransferase started to increase, reaching ultimately a level which was comparable to the initial value.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Planta 147 (1980), S. 269-273 
    ISSN: 1432-2048
    Schlagwort(e): Crown gall ; Cytokinins ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cytokinins were extracted from two cultures of tobacco crown gall tumor tissue: an unorganized tissue and a teratoma which produced leafy shoots. On Sephadex LH-20 column chromatography, extracts of both types of tissue yielded two peaks of cytokinin activity with elution volumes similar to ribosylzeatin and zeatin. Ribosylzeatin and zeatin were detected and quantified by coupled gas chromatography — mass spectrometry selected ion monitoring (GC/MS SIM), comparable quantities being found in the two extracts. Full mass spectral evidence for the presence of ribosylzeatin in both tissues was obtained. No evidence was found for the presence of N6-(Δ2-isopentenyl)adenosine (i6Ade) or N6-(Δ2-isopentenyl)adenine (i6Ade) although these compounds have been reported to occur in cytokinin-habituated tobacco callus tissues.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Planta 147 (1980), S. 274-276 
    ISSN: 1432-2048
    Schlagwort(e): Cell division ; Dikegulac ; Lysis ; Nicotiana ; Plasmalemma ; Protoplasts ; Tonoplast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Dikegulac (2,3:4,6 di-o-isopropylidine-2-keto-I-gulonate) is a growth regulator used to differentially kill terminal apices, and it analogously inhibits basic metabolic functions in dividing cells, but not stationary cells, in suspension culture. This report demonstrates an analogous situation in isolated tobacco protoplasts. At the lowest concentrations, dikegulac partially suppresses division of the protoplasts. Higher concentrations are required to produce visual cytoplasmic damage to the protoplasts, which probably first occurs at the level of the plasmalemma, as the vacuoles can be released intact. Later, tonoplast disruption occurs.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Planta 148 (1980), S. 97-102 
    ISSN: 1432-2048
    Schlagwort(e): Abscisic acid ; Cell cultures ; Nicotiana ; Variants, resistant ; Water stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The goal of this work was to begin a genetic study of the molecular mode of action of abscisic acid (ABA), by isolating variant cultured cells resistant to the hormone, or to a factor which induces ABA synthesis, namely water stress. Cell cultures of Nicotiana tabacum L. cv. Wisconsin 38 and N. silvestris Speg. and Comes were chosen as the experimental materials. Studies of the effects of the two stresses on the growth of the cultures demonstrated that ABA or water stress imposed by mannitol could completely inhibit growth. These effects arose in both cases from a constant reduction of the growth rate of the cells throughout the culture period. Mannitol also induced an increase in ABA content of the cells and media of suspension cultures, although not to the concentrations required to achieve the same degree of growth inhibition when the hormone was applied exogenously.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Planta 148 (1980), S. 103-107 
    ISSN: 1432-2048
    Schlagwort(e): Abscisic acid ; Cell cultures ; Nicotiana ; Variants, resistant ; Water stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Variant clones were isolated from Nicotiana silvestris Speg. et Comes cell cultures at low frequencies following severe abscisic-acid (ABA) or mannitol-induced water-stress treatments of plated cells. N. tabacum L. variants were not recovered. Variants from the ABA selection experiments exhibited a 10-fold increase in resistance to the hormone. This trait was stable in non-selective conditions for as long as was tested (200 days), but did not alter the response of the cells to water stress. Cell lines from the waterstress selection were not more resistant to mannitol than the parent line, and had a wide range of response to ABA.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 63
    ISSN: 1432-2048
    Schlagwort(e): mRNA ; Protein synthesis ; Protoplasts ; Nicotiana ; Translation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Studies of proteins synthesized in vitro by messenger RNA (mRNA) extracted from tobacco protoplasts showed that the changes in protein synthesis and especially the lack of certain proteins observed previously in isolated protoplasts did not result from a failure of translation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Planta 148 (1980), S. 462-467 
    ISSN: 1432-2048
    Schlagwort(e): Flower formation ; Leaves (in flower formation) ; Meristem (shoot) ; Nicotiana ; Roots (and flower formation)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The terminal, apical shoot meristem ofN. tabacum cv. Wisconsin 38 normally differentiates into a flower after producing 30 to 40 nodes. The influence of leaves and roots on the regulation of flowering was evaluated by counting the number of nodes produced after removal of leaves or the induction of adventitious roots. Leaf removal has no effect on the number of nodes produced before flower formation. Root induction significantly increases the number of nodes produced before flower formation. The plant behaves as if it were measuring the number of nodes between the meristem and the roots as a means of regulating meristem conversion from vegetative to floral differentiation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 7 (1994), S. 250-258 
    ISSN: 1432-2145
    Schlagwort(e): Reproductive barrier ; Interspecific hybridization ; Nicotiana ; Unilateral incongruity Pollen tube
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nicotiana tabacum was used as a pistillate parent and crossed with three self-compatible species, N. rustica, N. repanda and N. trigonophylla, which were previously reported to have pollen tubes unilaterally inhibited by N. tabacum pistil. Temporal and morphological observations revealed distinct differences of pollen tube behavior among these incongruous crosses. Pollen tubes of N. repanda were arrested in stigma and those of N. rustica in the middle of the style. On the other hand, pollen tubes of N. trigonophylla continued growing at a slow rate. Tubes of N. repanda and N. rustica showed morphological abnormalities such as swelling, thick wall, and irregular callose deposition. In addition, tubes of N. rustica often elongated in reverse direction and wound about in the middle of the style. Although the tubes of N. trigonophylla were apparently normal in morphology, they were distributed throughout the transmitting tissue, differing from the self-pollination of N. tabacum in which they were confined to the peripheral region of it. The diversity of pollen tube behavior indicates that physiological causes of incongruity are different among the three crosses. Bud pollination enabled pollen tubes to reach the ovary in all crosses, indicating that the N. tabacum pistil acquired its ability to inhibit foreign pollen tube elongation with its development. When interspecific hybrids between N. tabacum and the other three species were pollinated by parental species, tubes reached the ovary in all crosses, but the elongation rate of tubes slowed down and morphology was abnormal.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 14 (1994), S. 451-490 
    ISSN: 1572-8986
    Schlagwort(e): Transport coefficients ; transport properties ; viscosity ; thermal conductivity ; electrical conductivity ; diffusion coefficient ; Chapman Enskog method ; argon ; nitrogen ; oxygen ; plasma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Calculated values of the viscosity, thermal conductivity, and electrical conductivity of argon, nitrogen, and oxygen plasmas, and mixtures of argon anti nitrogen and of argon anti oxygen, are presented. In addition, combined ordinary, pressure, and thermal diffusion coefficients are given for the gas mixtures. These three combined diffusion coefficients fully describe di fusion of the two gases, irrespective of their degree of dissociation or ionizati on. The calculations, which assume local thermodynamic equilibrium, are performed! for atmospheric-pressure plasmas in the temperature range /torn 300 to 30,000 K. A number of the collision integrals used in calculating the transport coefficients are significantly more accurate than values used in previous theoretical studies, resulting in more reliable values of the transport coefficients. The results are compared with those of published theoretical and experimental studies.
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  • 67
    ISSN: 1573-5028
    Schlagwort(e): genome organization ; in vitro transcription ; in vitro processing ; Nicotiana ; pseudogenes ; serine tRNA genes ; serine tRNAs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The existence of six serine codons results in a complex pattern of tRNASer isoacceptors in organisms and organelles. According to the original wobble hypothesis, a minimum of three isoacceptors should be sufficient to read the six serine codons. We have isolated five cytoplasmic tRNAsSer from leaves of Nicotiana rustica. Their nucleotide sequences identify them as four different isoacceptors with the anticodons cm5UGA, CGA, IGA and GCU. For tRNASer with IGA anticodon, two species have been detected which vary only by one nucleotide in the long extra arm. The first three isoacceptors recognize codons of the type UCN whereas the fourth isoacceptor reads the two serine codons AGC and AGU. The tRNASer sequences were used to design appropriate primers for the amplification of Nicotiana nuclear tRNASer genes by the polymerase chain reaction (PCR). A total number of eight tRNASer genes differing in the coding region were thus identified. Selected PCR DNA fragments were then employed as probes for the isolation of the corresponding genes from a nuclear DNA library of N. rustica. Sequence analyses revealed that five of the isolated seven clones contained tRNASer genes which are identical in sequence with the five cytoplasmic tRNAsSer mentioned above. None of them contains an intervening sequence. This is the first time that all putative cellular tRNASer isoacceptors and their corresponding genes have been characterized in an eukaryotic organism. Most of the tRNASer genes are functional as deduced from in vitro transcription and processing studies. Two of the genes yield pre-tRNAsSer which are not or poorly converted to mature tRNA in a plant extract. The approximate tRNASer gene number was estimated by hybridization of specific DNA probes to Eco RI-cleaved Nicotiana nuclear DNA. The overall hybridization pattern indicates that members of each particular tRNASer gene family do not appear to be clustered but distributed randomly throughout the Nicotiana genome.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 26 (1994), S. 1747-1757 
    ISSN: 1573-5028
    Schlagwort(e): cDNA gene family ; NeIF-4A ; RNA helicase ; translation initiation factor ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Characterization of cDNAs encoding eukaryotic translation initiation factor 4A (eIF-4A) indicates the expression of a minimum of ten related genes in tobacco leaf cells. The ten groups fall into two gene families, NeIF-4A2 and NeIF-4A3. The majority of the cDNAs exhibit significant sequence similarity to the NeIF-4A2 family at both the DNA and deduced amino acid levels. Northern analysis using specific probes indicates variable expression of four family members in various tobacco organs. Western analysis, using an anti-tobacco eIF-4A polyclonal antibody, reveals a complex pattern of immunologically related polypeptides of approximately 46 kDa. Subcellular fractionation suggests that at least one eIF-4A-related polypeptide is located in the chloroplast where it is ribosome-associated.
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  • 69
    ISSN: 1432-2048
    Schlagwort(e): Abscisic acid ; Brassica ; Glycine ; Gossypium ; Lea mRNAs ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cloned mRNAs identify three programs of gene expression in cotton (Gossypium hirsutum L.) embryos that are associated with the maturation (reserve accumulation) stage, the postabscission stage, which is marked by expression of Late-embryogenesis-abundant (Lea) mRNAs, and germination (broadly defined as including all events through early postgerminative growth). In order to test if the regulation of these programs is the same in other dicotyledonous species, their expression was studied in normal and cultured maturation-stage, postabscission-stage, and mature embryo-stage embryos or seed of oilseed rape (Brassica napus L.), soybean (Glycine max [L.] Merr.), and tobacco (Nicotiana tabacum L.) using cotton and other cDNA probes. During postabscission, Lea mRNAs accumulated in all test species and were induced in earlier maturation-stage embryos by excision and culture on basal medium. Abscisic acid often enhanced this induction in the test species. Germinationspecific mRNAs were induced in cultured maturationstage and postabscission-stage embryos of all test species. These results indicate that the regulation of embryonic and germination programs is similar in all dicotyledons tested. Because excised embryos simultaneously induced postabscission and germination programs, the effects of exogenous growth regulators and other factors on such embryos probably reflect stress responses of germinating mature embryos rather than the identity of endogenous regulators of embryogenesis.
    Materialart: Digitale Medien
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  • 70
    ISSN: 1432-2048
    Schlagwort(e): Amino acid ; Hexose uptake ; Nicotiana ; Photosynthesis ; Sucrose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The subcellular distribution of hexoses, sucrose and amino acids among the stromal, cytosolic and vacuolar compartments was analysed by a nonaqueous fractionation technique in leaves of tobacco (Nicotiana tabaccum L.) wild-type and transgenic plants expressing a yeast-derived invertase in the cytosolic, vacuolar or apoplasmic compartment. In the wild-type plants the amino acids were found to be located in the stroma and in the cytosol, sucrose mainly in the cytosol and up to 98% of the hexoses in the vacuole. In the leaves of the various transformants, where the contents of hexoses were greater than in wild-type plants, again 97–98% of these hexoses were found in the vacuoles. It is concluded that leaf vacuoles contain transporters for the active uptake of glucose and fructose against a high concentration gradient. A comparison of estimated metabolite concentrations in the subcellular compartments of wild-type and transformant plants indicated that the decreased photosynthetic capacity of the transformants is not due to an osmotic effect on photosynthesis, as was shown earlier to be the case in transformed potato leaves, but is the result of a long-term dedifferentiation of tobacco leaf cells to heterotrophic cells.
    Materialart: Digitale Medien
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Planta 194 (1994), S. 200-214 
    ISSN: 1432-2048
    Schlagwort(e): Actin ; Cytoskeleton ; Embryo sac ; Fertilization ; Microtubule ; Nicotiana ; Synergid degeneration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The cytoskeletal organization of the embryo sac of tobacco (Nicotiana tabacum L.) was examined at maturity and during synergid degeneration, pollen-tube delivery and gamete transfer using rapid-frozen, freeze-substituted and chemically fixed material in combination with immunofluorescence and immunogold electron microscopy. Before fertilization, the synergid is a highly polarized cell with dense longitudinally aligned arrays of microtubules adjacent to the filiform apparatus at the micropylar end of the cell associated with major organelles. The cytoskeleton of the central cell is less polarized, with dense cortical microtubules in the micropylar and chalazal regions and looser, longitudinally oriented cortical microtubules in the lateral region. In the synergid and central cell, F-actin is frequently found at the surface of the organelles and co-localizes with either single microtubules or microtubule bundles. Egg cell microtubules are frequently cortical, randomly oriented and more abundant at the chalazal end of the cell; actin filaments are associated with microtubules and the cortex of the egg cell. At 48 h after pollination and before the pollen tube arrives, the onset of degeneration is evident in one of the two synergids: the electron density of cytoplasmic organelles and the ground cytoplasm increases and the nucleus becomes distorted. Although synergids otherwise remain intact, the vacuole collapses and organelles degenerate rapidly after pollen-tube entry. Abundant electron-dense material extends from the degenerated synergid into intercellular spaces at the chalazal end of the synergid and between the synergids, egg and central cell. Rhodamine-phalloidin and anti-actin immunogold labeling reveal that electron-dense aggregates in this region contain abundant actin forming two distinct bands termed “coronas”. This actin is part of a mechanism in the egg apparatus which appears to precisely position and facilitate the access of male gametes to the egg and central cell for fusion.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 72
    ISSN: 1432-2048
    Schlagwort(e): Arabinogalactan protein ; Cell wall ; Lignin ; Nicotiana ; Polysaccharide ; Style
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The cell walls of styles of Nicotiana alata Link et Otto (ornamental tobacco; Solanaceae) were analysed chemically and examined histochemically. Cell-wall preparations were obtained from whole styles and from isolated transmitting-tissue cells. The style epidermal cells were shown histochemically to have thick, lignified secondary walls. These walls probably constituted a large proportion of the cell-wall preparation from whole styles as analysis of whole-style walls indicated that the major polysaccharides were xylans and cellulose, which are typical of lignified secondary walls of Magnoliopsida (dicotyledons). Lignification of the style epidermal walls was also demonstrated histochemically in 10 other species (5 genera including Nicotiana) of the sub-family Cestroideae of the Solanaceae, but not in 15 species (9 genera) of the sub-family Solanoideae of the Solanaceae, nor in 3 other species of dicotyledons and 2 species of Liliopsida (monocotyledons). Analysis of the cell-wall preparation from isolated transmitting-tissue cells of N. alata indicated that these contained cellulose, xyloglucans, and pectic polysaccharides, which is typical of primary cell walls of dicotyledons. However, the analysis indicated that the walls also contained an unusually high proportion of Type II arabinogalactans. Staining of the transmitting-tissue cell-wall preparation with β-glucosyl Yariv reagent, a histochemical reagent specific for arabinogalactan proteins, confirmed their presence, which may be related to the role of these cells in secreting the stylar extracellular matrix.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 73
    ISSN: 1432-2048
    Schlagwort(e): Auxin (accumulation, metabolism) ; Nicotiana ; Protoplast (leaf)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Uptake and metabolism of exogenous naphthalene-1-acetic acid (NAA) and indole-3-acetic acid (IAA) have been studied in tobacco (Nicotiana tabacum L. cv. Xanthi) mesophyll protoplasts. Both auxins entered protoplasts by diffusion under the action of the transmembrane pH gradient without any detectable participation of an influx carrier. Molecules were accumulated by an anion-trapping mechanism and most of them were metabolized within hours, essentially as glucose-ester and amino-acid conjugates. Protoplasts were equipped with a functional auxin-efflux carrier as evidenced by the inhibitory effect of naphthylphtalamic acid on IAA efflux. Basically, similar mechanisms of NAA and IAA uptake occurred in protoplasts. However, the two auxins differed in their levels of accumulation, due to different membrane-transport characteristics, and the nature of the metabolites produced. This shows the need to estimate the accumulation and the metabolism of auxins when analyzing their effects in a given cell system. The internal auxin concentration could be modulated by changing the transmembrane pH gradient, giving an interesting perspective for discriminating between the effects of intra- and extracellular auxin on physiological processes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 74
    ISSN: 1432-2048
    Schlagwort(e): Nicotiana ; Photosynthesis ; Proton pumping ; Pyrophosphatase ; Transgenic tobacco ; Vacuole
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic characteristics of transgenic tobacco (Nicotiana tabacum L.) plants with a soluble pyrophosphatase in the cytosol of their leaf cells were compared to those of wild-type plants. Although the development of the transgenic plants was somewhat retarded compared to the wild type, as shown by stunted growth and delayed flowering, photosynthetic responses were comparable in transgenic and wild-type leaves of similar physiological age. In particular, light-dependent proton transport into the vacuoles of leaf mesophyll cells was not decreased in leaves of the transgenic plants, which did not contain pyrophosphate in the cytosol owing to the presence of a soluble pyrophosphase. This shows that light-stimulated proton pumping did not require the pumping activity of the tonoplast pyrophosphatase. Apparently, light-stimulated proton pumping can be based solely on the activity of the tonoplast ATPase.
    Materialart: Digitale Medien
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  • 75
    ISSN: 1432-1890
    Schlagwort(e): Nicotiana ; Glomus species ; arbuscular mycorrhiza ; gene expression ; specific polypeptides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Changes in gene expression were studied during the establishment of arbuscular mycorrhizal symbiosis in tobacco roots from an amphidiploid hybrid Nicotiana glutinosa x N. debneyi. Polypeptide patterns from control roots and from roots infected by Glomus mosseae or G. intraradices were resolved by two-dimensional polyacrylamide gel electrophoresis and followed in a time-course analysis. Arbuscular mycorrhizal infection led to significant modifications in polypeptide patterns with: (a) decreased amounts of some polypeptides, (b) increased accumulation of others, and (c) appearance of newly-induced polypeptides. Comparisons made during infection development by the two Glomus species demonstrated that protein modifications changed in relation to the mycorrhizal state of the tobacco roots.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 69 (1984), S. 1-14 
    ISSN: 1432-2242
    Schlagwort(e): Nicotiana ; Evolution of plastid DNA ; Comparative restriction site mapping ; Insertions and deletions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Plastid DNA of seven American and four Australian species of the genus Nicotiana was examined by restriction endonuclease analysis using the enzymes Sal I, Bgl I, Pst I, Kpn I, Xho I, Pvu II and Eco RI. These endonucleases collectively distinguish more than 120 sites on N. tabacum plastid DNA. The DNAs of all ten species exhibited restriction patterns distinguishable from those of N. tabacum for at least one of the enzymes used. All distinctive sites were physically mapped taking advantage of the restriction cleavage site map available for plastid DNA from Nicotiana tabacum (Seyer et al. 1981). This map was extended for the restriction endonucleases Pst I and Kpn I. In spite of variation in detail, the overall fragment order was found to be the same for plastid DNA from the eleven Nicotiana species. Most of the DNA changes resulted from small insertions/deletions and, possibly, inversions. They are located within seven regions scattered along the plastid chromosome. The divergence pattern of the Nicotiana plastid chromosomes was strikingly similar to that found in the genus Oenothera subsection Euoenothera (Gordon et al. 1982). The possible role of replication as a factor in the evolution of divergence patterns is discussed. The restriction patterns of plastid DNA from species within a continent resembled each other with one exception in each instance. The American species N. repanda showed patterns similar to those of most Australian species, and those of the Australian species N. debneyi resembled those of most American species.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 67 (1984), S. 491-497 
    ISSN: 1432-2242
    Schlagwort(e): Tobacco ; Chloroplast DNA ; Cybrids ; Male sterility ; Tentoxin resistance ; Plastid recombinants ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Protoplasts of a mutant line of Nicotiana tabacum having a maternally-transmitted chlorophyll deficiency were fused with protoplasts of two alloplasmic-male-sterile Nicotiana lines by the “donor-recipient” technique. In both fusion experiments variegated plantlets were regenerated which were shown to contain cytoplasms of mixed chloroplast nature. This confirms that with the “donor-recipient” method one can obtain mixed cytoplasms of genetically different chloroplasts. We present a convenient system to assay for genetic recombination between chloroplasts by combining use of several cytoplasmic markers: vis. chlorophyll pigmentation, chloroplast DNA restriction patterns, tentoxin resistance and male sterility. Within the limits of the experiment no recombinant types were recovered.
    Materialart: Digitale Medien
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 69 (1984), S. 121-128 
    ISSN: 1432-2242
    Schlagwort(e): Somatic cell ; Fusion ; Inheritance ; Nuclear genes ; Nicotiana
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Callus protoplasts of a Nicotiana tabacum chlorophyll-deficient mutant were fused with mesophyll protoplasts from one of following five sources: 4 cmsanalogs of tobacco bearing the cytoplasms of N. plumbaginifolia, N. suaveolens, N. repanda, and N. undulata, respectively, as well as wild species N. glauca. In another series of experiments, callus protoplasts from the chlorophyll-deficient genome Su/Su mutant of tobacco were fused with mesophyll protoplasts of the wild species N. glauca and those of a plastome chlorophyll-deficient tobacco mutant. The screening of hybrids consisted of visual identification followed by mechanical isolation and cloning of heteroplasmic fusion products in microdroplets of nutrient medium. Studies of regenerated plants included the analyses of gross morphology of plants, leaf and flower morphology, analysis of chromosome size and morphology and chromosome numbers, studies of multiple molecular forms of esterase and amylase, analysis of chloroplast DNA restriction patterns and analyses of chlorophyll-deficiency controlled by Su and P − genes. The study of progeny of 41 clones representing all species' combinations demonstrated that regenarants of most (63%) clones from intraspecific (for nuclear genes) combinations were cybrid forms, whereas in the case of the fusion N. tabacum + N. glauca, the true nuclear hybrids prevailed and the proportion of cybrids did not exceed 26%. Clones regenerating both hybrid and cybrid plants from the same fusion product were also found.
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 67 (1984), S. 185-193 
    ISSN: 1432-2242
    Schlagwort(e): Nicotiana ; Chloroplast DNA ; Deletion ; Restriction ; Hot spot ; Inverted repeats
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A physical map containing six restriction sites of the Nicotiana tabacum chloroplast genome, together with the BamHI maps of N. tabacum, N. otophora and N. knightiana, and the SmaI maps of N. acuminata, N. plumbaginifolia, N. langsdorffii, N. otophora, N. tabacum, N. tomentosiformis and N. knightiana was constructed. In Nicotiana chloroplast genomes, the most frequently observed variations are point mutations. Deletions are also detected. Most of the observed changes are confined to one area of the large single copy region, which is designated as the “hot spot”. Based on the evidence obtained from Nicotiana chloroplast genomes, an origin of the inverted repeats in this genus is proposed. We suggest that the inverted repeats represent a vestige of what were once two identical, complete chloroplast genomes joined together in a head-to-head and tail-to-tail fashion, and that deletions generated the current chloroplast genome organization.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 67 (1984), S. 333-336 
    ISSN: 1432-2242
    Schlagwort(e): Nicotiana ; Chlamydomonas ; Chloroplast DNA ; RuBPCase ; E. coli ; B. subtilis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary RuBPCase, the enzyme responsible for carboxylation and oxidation of RuBP in a wide variety of photosynthetic organisms, is the major protein found in the chloroplast. Here we present the first evidence for direct expression in E. coli and B. subtilis of tobacco and Chlamydomonas ct-DNA sequences coding for the LS of RuBPCase as demonstrated by a simple in situ immunoassay.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 58 (1980), S. 121-127 
    ISSN: 1432-2242
    Schlagwort(e): Nicotiana ; Cytoplasmic-male-sterility ; Somatic hybridization ; Plastid segregation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Restoration of male fertility was achieved by fusing protoplasts from male sterile (CMS) Nicotiana sylvestris plants with X-irradiated protoplasts derived from fertile N. tabacum plants. The CMS N. sylvestris plants were derived from a previous somatic hybridization experiment and contained alien (Line 92) cytoplasm. About one quarter of the regenerated plants were found to be cybrids. i.e. they consisted of N. sylvestris nuclei combined with all or some components of N. tabacum cytoplasm. In one half of these cybrids male fertility was restored to different levels. The chloroplasts of the two parental donors differ in respect to tentoxin sensitivity: chloroplasts of CMS N. sylvestris are sensitive while those of N. tabacum are insensitive. It could therefore be demonstrated that there was an independent segregation of chloroplast type and male fertility/sterility: several somatic cybrids were male fertile but tentoxin sensitive and others were tentoxin insensitive yet they were male sterile. Only in about one half of the somatic cybrids was male fertility restored together with restoration to tentoxin insensitivity.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 236 (1984), S. 373-381 
    ISSN: 1432-0878
    Schlagwort(e): Merkel cell surface ; Quinacrine fluorescence ; Lectins ; Vibrissae ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Surface carbohydrates on the Merkel cell of the outer root sheath (ORS) were investigated in 1to 4-day-old rat vibrissae by use of rhodamine isothiocyanate (RITC)-conjugated lectins. The red fluorescence of RITC provided a convenient assay for lectin binding to the Merkel cell, which is itself identified by its green fluorescence following selective uptake of the dye quinacrine. In monolayers or suspensions of freshly dissociated ORS cells, the Merkel cell showed high affinity for the α-fucose-specific lectin, Ulex europeus agglutinin I (UEA-I), thus revealing a novel feature for a basally located cell. Other high-affinity lectins included concanavalin A (Con A), wheat germ agglutinin (WGA), soybean agglutinin (SBA), and Ricinus communis agglutinin I (RCA-I). In contrast, Dolichos biflorus (DBA), Bandeiraea simplicifolia I and II (BS-I and BS-II), and peanut agglutinin (PNA) virtually excluded the Merkel cell, though PNA-binding sites were unmasked after neuraminidase treatment. Other dispersed ORS cells had varying lectin affinities, and generally binding was inhibited by a competing haptenic sugar. The pattern of lectin binding seen in cryostat and paraffin sections of the vibrissa suggested that the Merkel cells share surface properties with their neighboring basal and/or spinous cells; however, unshared properties are likely to exist since ingrowing mechanosensory nerves recognize the Merkel cells, and not other epidermal cells, as their targets.
    Materialart: Digitale Medien
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 236 (1984), S. 711-715 
    ISSN: 1432-0878
    Schlagwort(e): Gastric antral mucosa ; Caerulein ; Gastrointestinal hormones ; Cholecystokinin ; Trophic effect ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The growth-promoting effect of caerulein on antral gastric mucosa was explored using Wistar rats. Implanted osmotic minipumps were used to administer submaximal doses of either caerulein or saline to normal rats for up to 4 days. In one group, reflux of bile and pancreatic juice into the stomach was avoided by previous surgical diversion of the distal common bile duct to the jejunum. DNA synthetic and mitotic activity in the antrum epithelium were estimated by 3H-thymidine pulse labelling and autoradiography during the administration of the peptide. The rate of cell migration was determined in animals killed 1, 2 and 3 days after the 3H-thymidine pulse. Administration of caerulein to normal rats provoked significant increases in both labelling and mitotic indices, and a significant acceleration of the upward cell migration in the glandular tubes. In the animals with distal diversion of bile and pancreatic secretions both labelling and mitotic indices were also increased over control values under the effect of the peptide. These data indicate that administration of caerulein stimulates cell proliferation in the antral gastric mucosa. This effect cannot be explained through increased reflux of pancreaticobiliary secretions in the stomach.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 236 (1984), S. 699-709 
    ISSN: 1432-0878
    Schlagwort(e): Testis ; Spermatogenic cycle ; Sertoli cell ; Lipid ; Morphometry ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The volume and surface area of lipid inclusions often present in the cytoplasm of rat Sertoli cells was measured directly from semi-thin sections of perfusion-fixed testicular tissues using an image analyser linked to a light microscope. Sertoli cell nuclei were used as a reference for comparing any variations in the measured parameters of lipid inclusions during the rat spermatogenic cycle. Volume density of Sertoli cell lipid inclusions was assessed by morphometric analysis of Sertoli cells photographically reconstructed from electron micrographs. Maximum lipid content in Sertoli cells occurred during stages IX–XIV of the spermatogenic cycle, then declined at stages I–III and remained low from stages IV–VIII. The persistence and increase in number of many large Sertoli cell lipid inclusions beyond the stage where spermatid residual bodies are phagocytosed within the Sertoli cells (stage IX) suggests that the synthesis and lipolysis of Sertoli cell lipid inclusions represents an intrinsic functional cycle of the Sertoli cells. Stage-dependent variations in the lipid content of rat Sertoli cells offers morphological evidence that the metabolic duties of the Sertoli cells are synchronised with the spermatogenic cycle to provide local coordination of the proliferation and maturation of the germ cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 236 (1984), S. 717-724 
    ISSN: 1432-0878
    Schlagwort(e): Ovary ; Ovarian follicle ; Atresia ; Immunoregulation ; Immune tolerance ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Thy-1+ cells, producing Thy-1+ material, have been demonstrated by the indirect immunoperoxidase technique in the theca of growing ovarian follicles of the rat. OX-2 antigen, known as the minor glycoprotein of rat thymocytes, was detected in granulosa cells of non-growing follicles. Ia+ cells of dendritic type and/or activated macrophages were identified in the granulosa of advanced degenerating follicles, and remnants of the zona pellucida exhibited immunoglobulins. In some ovaries immunoglobulins were also bound to the zona pellucida of oocytes of early degenerating antral follicles. Medium-sized antral follicles with degenerating granulosa were occasionally invaded by cells carrying antigens of cytotoxic T lymphocytes or other T lymphocyte subsets, while degenerating large antral follicles were sometimes invaded by cells exhibiting antigen of cells with natural killer function (but not antigens of T lymphocytes). Granulosa cells of some degenerating antral follicles exhibited class-I antigens derived from the major histocompatibility complex. We suggest that cell-mediated control mechanisms of antigen expression and metabolism of tissue cells during their differentiation and degeneration should be considered in addition to the well-documented hormonal dependence of some tissues.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 237 (1984), S. 245-252 
    ISSN: 1432-0878
    Schlagwort(e): Pineal organ ; Interstitial cells ; Astrocytes ; Immunocytochemistry ; Rat ; Mouse
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Antigenic markers characteristic of astrocytes and their differentiative states (i.e., glial fibrillary acidic protein (GFAP), vimentin, and M1 and C1 antigens) were investigated in the pineal gland of mouse and rat using double immunolabeling techniques. In both species the socalled interstitial cells as characterized by TEM were shown to be astrocytes, since they expressed vimentin, but neither fibronectin (a marker for fibroblasts and endothelial cells) nor the neuron-specific L1 antigen or tetanus toxin receptors. Subpopulations of vimentin-positive pineal astrocytes were also GFAP- and C1- antigen-positive. M1- antigenpositive cells were not detected. It is concluded that a considerable proportion of interstitial cells in the pineal gland of rat and mouse are immature astrocytes which, in contrast to other parts of the central nervous system, persist into adulthood.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 87
    ISSN: 1432-0878
    Schlagwort(e): Thyroid gland, fetal ; Cytoskeleton ; Cytocha lasin B ; Vinblastine ; Colchicine ; Follicular development (thyroid) ; Tissue culture ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Thyrotropic hormone (TSH) or cAMP accelerate the formation of follicular cavities in the explanted thyroid gland of the 15-day-old rat fetus. Cytochalasin B or vinblastine and nocodazole or colchicine, which disorganize microfilamental and microtubular structures respectively, inhibit or completely block in vitro-induced folliculogenesis. Exposure of the thyroid tissue to lumicolchicine, a structural isomer of colchicine deprived of antimicrotubular activity, does not inhibit the activation of folliculogenesis induced by TSH. These results are strong evidence for the supposition that microfilaments and microtubules are involved in the TSH-stimulated mechanisms resulting in thyroid folliculogenesis. Folliculogenesis requires the integrity of both microfilaments and microtubules.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 88
    ISSN: 1432-0878
    Schlagwort(e): CRF-neurons ; Hypothalamus ; Development, ontogenetic ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Appearance of immunoreactive corticotropin-releasing factor (CRF)-containing neurons was studied in developing hypothalamus of the rat by use of antisera against rat- and ovine CRF. These neurons were first recognized in the lateral and paraventricular nuclei on days 15.5 and 16.5 of gestation, respectively, when antiserum against rat CRF was employed. Antiserum against ovine CRF revealed the cells two days later exclusively in the latter nucleus. In both nuclei, the neurons increased in number with development. The neurons in the paraventricular nucleus appeared to project their immunoreactive processes to the median eminence via the periventricular and lateral pathways. In the median eminence, the immunoreaction with antiserum to rat CRF was first recognized in its anterior portion in the form of dots on day 16.5 of gestation but as beaded fibers in the external layer on day 17.5; these structures increased in amount with development in rostro-caudal direction. Although antiserum to ovine CRF was less potent in immunostainability than antiserum to rat CRF, it also revealed the beaded fibers in the median eminence on day 17.5 of gestation. Since evidence is available that the paraventricular nucleus is involved in corticotropin release, it is concluded that, in rats, the hypothalamic regulatory mechanism controlling the release of corticotropin initially appears on days 16.5–17.5 of gestation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 89
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 205 (1980), S. 11-17 
    ISSN: 1432-0878
    Schlagwort(e): Pineal organ ; Subcommissural organ ; Vasopressin ; Oxytocin ; Vasotocin ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Vasopressin and oxytocin were specifically demonstrated in the rat brain using the unlabelled antibody-enzyme method and purification of the first antiserum. Vasopressin and oxytocin fibres extend via the subcommissural organ or habenular commissure into the pineal stalk and terminate in the anterior part of the pineal organ. In addition, immediately adjacent to the subsommissural organ many vasopressin-containing fibres run caudally toward the central grey. These results are discussed in relation to the proposed presence of vasotocin in the pineal gland.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 210 (1980), S. 167-170 
    ISSN: 1432-0878
    Schlagwort(e): Neuropeptides ; VIP-immunoreactive neurons ; Retina ; Amacrine cells ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Immunoreactive vasoactive intestinal polypeptide (VIP) was detected in a population of amacrine cells in the retina of the rat. Processes of these cells reach both the inner and outer half of the inner plexiform layer where they form sublayers. The VIP neurons are different from previously known amacrine cell types.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 210 (1980), S. 181-189 
    ISSN: 1432-0878
    Schlagwort(e): Catecholamines ; Neurophysin ; Simultaneous demonstration ; Functional interaction ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary A method was developed that allows the analysis of neuropeptides and monoamines in a single tissue section by the application of the unlabeled antibody method for peptide staining to tissue sections freeze-dried for formaldehyde-induced monoamine histofluorescence. The hypothalamic magnocellular system of male albino rats served as a model for this study; neurons were stained with anti-neurophysin sera, which mark the vasopressin- and oxytocin-associated proteins. Neurophysin-containing perikarya appeared to be surrounded by catecholamine-containing varicosities. This phenomenon was seen to varying degrees within the supraoptic and paraventricular nuclei. The juxtaposition of varicosities and peptidergic neurons suggests an afferent fiber-target neuron relationship that might favor a functional interaction between monoamines and neuropeptides.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 211 (1980), S. 105-115 
    ISSN: 1432-0878
    Schlagwort(e): Rat ; Preovulatory follicle ; Ultrastructure ; Degeneration ; Atresia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary To identify and describe ovarian follicles committed to undergo follicular degeneration (atresia), immature rats were primed with pregnant mare serum gonadotropin (PMSG). After PMSG treatment, preovulatory follicles develop but subsequently degenerate. Prior to the appearance of pyknotic nuclei (Stage I of atresia), degenerative changes were observed in focal areas of the granulosa cell layer. These changes include “blebbing” of the cytoplasm and alterations in the shape of the granulosa cells. The appearance of these degenerative changes coincides with a decrease in ovarian concentrations of estradiol and testosterone. Since estrogens and androgens maintain the follicle, the decline in estradiol and testosterone could be responsible for the further degenerative alterations that lead to complete deterioration of the preovulatory follicle. In Stage I atretic follicles, lysosome-derived autophagic vacuoles develop and macrophages invade both the thecal and granulosa cell layers. The combined actions of the autophagic vacuoles and macrophages could destroy both the granulosa-cell and thecal layers and thereby transform the preovulatory follicle into an ovarian cyst.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 93
    ISSN: 1432-0878
    Schlagwort(e): Lymph node ; Macrophages ; Postcapillary high endothelial venules ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The afferent lymphatic vessels of rat popliteal lymph nodes were interrupted, and the histological alterations in the lymph nodes occurring 1 to 14 weeks after operation were studied. One week after operation the number of macrophages was considerably reduced and continued to decrease during the subsequent time periods studied. A 6 weeks most macrophages had disappeared. Simultaneously the immunological activity diminished and had completely disappeared 8 weeks after operation. Three weeks after operation the endothelial cells of the postcapillary high endothelial venules had flattened, and the number of immigrating lymphocytes was greatly reduced. Subsequently the lymph nodes became depleted of both macrophages and lymphocytes, leaving only the reticuloendothelial framework.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    ISSN: 1432-0878
    Schlagwort(e): Key words: Pituitary ; Pars tuberalis ; α-Subunit ; Immunocytochemistry ; In situ hybridization ; Rat ; Mouse ; Guinea-pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone α-subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the α-subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light- and electron-microscopic immunocytochemistry demonstrated α-subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the β-subunit of luteinizing hormone, an antibody that labelled scattered gonadotrophs. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    ISSN: 1432-0878
    Schlagwort(e): Caldesmon ; Actin ; Immunocytochemistry ; Small intestine ; Smooth muscle ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The distribution of caldesmon (a calmodulin-binding, F-actin-interacting protein) (Sobue et al. 1982) and of actin was studied in the rat's small intestine by means of light-microscopic immunocytochemistry. Positive immunostaining for caldesmon was seen in smooth muscle cells of the intestinal wall, and of blood vessels, and in the apical portion of the absorptive epithelial cells. The immunoreactivity in goblet cells was difficult to recognize. The positive reaction to immunostaining for actin showed almost the same pattern as that for caldesmon. These results suggest that this calmodulin-binding protein may play an important role in the control of actin-myosin interaction in smooth muscle cells and in non-muscle cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 235 (1984), S. 433-438 
    ISSN: 1432-0878
    Schlagwort(e): Mammary gland ; Ferritin-concanavalin A ; Concanavalin A ; Endocytosis ; Membrane reuse ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Ferritin-concanavalin A (Fer-Con A) was used to label the apical plasma membrane of the lactating cell to determine whether membrane internalization takes place. Rat glands were infused in vivo via the teat with 0.2 mg of Fer-Con A in 0.2 ml tris buffer (pH 7.0) containing 0.1% trypan blue, the latter acting as a marker of the infusate. Tissues were obtained from separate animals 5, 10 and 60 min postinfusion. Fer-Con A was seen in alveolar lumina bound to the outer surfaces of apical plasma membrane, microvilli and milk fat globules. It was observed within lactating cells on the inner membrane surfaces of endocytotic vesicles, Golgi cisternae, and secretory vesicles containing casein micelles, and in multivesicular bodies and lysosomes. Internalization of the ferritin-lectin conjugate into casein-containing secretory vesicles was detectable in the 5-min postinfusion tissue. Lysosomes were the only structures in control tissue that contained particles bearing some resemblance to Fer-Con A. The data provide evidence that apical plasma membrane is internalized and distributed to a number of intracellular compartments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 235 (1984), S. 449-452 
    ISSN: 1432-0878
    Schlagwort(e): Suprachiasmatic nucleus ; Morphometry ; Synapses ; Sexual dimorphism ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The suprachiasmatic nucleus (SCN) of male rats was estimated to contain 16×106 synaptic appositions (unilaterally) or 250×106 appositions in 1 mm3 tissue of the nucleus with an average of 1404 appositions per neuron. There are significantly fewer synaptic appositions in the suprachiasmatic nucleus of female rats (15×106 per SCN or 236×106 in 1 mm3 tissue of SCN with 1264 appositions per neuron on an average). Additionally, numbers of various types of synapses (axo-somatic, invaginated, dendrodendritic and optic) are estimated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    ISSN: 1432-0878
    Schlagwort(e): Monosodium-1-glutamate ; Neuropathology ; Rat ; Superior colliculus ; Toxicology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Systemic administration of monosodium-1-gluta-mate by single injections of 4 mg/g body weight in infant rats (2–10 days of age) results in acute swelling of cytoplasm and nuclear pyknosis of neurons in the stratum zonale and stratum griseum superficiale of the superior colliculus. Multiple daily doses of 4 mg/g body weight monosodium-1-glutamate result in an almost complete loss of neurons in these two superficial layers. The deeper layers appear not to be affected. No pathological effects were observed in the lateral geniculate body or pretectal complex. Light-and electron-microscopic studies reveal that the optic nerves are remarkably shrunken and many myelinated as well as unmyelinated axons are lost. Injection of 3Hproline into the vitreous body of one eye results in limited transport to the suprachiasmatic nucleus, lateral geniculate body and to lateral portions of the superior colliculus. The small percentage of intact axons in the optic nerve, as well as the limited proline transport from the eye, suggest that administration of monosodium-1-glutamate leaves intact some optic fibers, a portion of which belongs to the retinohypothalamic tract.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    ISSN: 1432-0878
    Schlagwort(e): Exocrine pancreas ; Calcium pool ; Calcium release ; Electron microscopy ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In an attempt to identify a cellular Ca2+-pool, from which calcium is released when secretagogues are applied, tissue fragments of the rat exocrine pancreas were incubated and fixed with glutaraldehyde in the presence of calcium. By means of this procedure electron-dense deposits were found on plasma membranes. X-ray microanalysis showed that these deposits contain calcium. Stimulation of tissue fragments with the use of the secretagogues carbachol or cholecystokinin reduced the number of deposits by about 80%. When the antagonist atropine was applied after carbachol stimulation, deposits reappeared on cell membranes, which then disappeared again after a second stimulation with cholecystokinin. In the presence of procaine, carbachol was inhibited and only slightly reduced the Ca2+-deposits on the plasma membranes. These results suggest that a calcium pool, from which calcium is released to induce enzyme secretion on stimulation, is located in the cell membrane
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    ISSN: 1432-0878
    Schlagwort(e): Somatostatin ; Ontogenesis ; Electron-microscopic immunohistochemistry ; Median eminence ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The development of immunoreactive (ir) somatostatin-containing nerve terminals in the rat median eminence (ME) has been examined electron-microscopically. Nerve fibers containing ir particles scattered throughout the axoplasm are first seen in the external layer of the ME on day 18.5 of gestation, and, on day 21.5 appear to terminate on the basement membrane of the perivascular space of the portal vessels. After birth, the fiber terminals contain several membrane-limited granules, which are labeled with ir PAP particles. Ultrathin, Epon-embedded sections of ME, treated by the protein A gold-labeling method for somatostatin, demonstrate positively labeled granules in the nerve fibers in the postnatal ME, but in the prenatal tissue, no specific gold-labeling is found. These findings show that, in the external layer of the ME, somatostatin storing occurs in the granules in the axonal terminals after birth.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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