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  • Articles  (169)
  • Electron microscopy  (94)
  • nitrogen  (75)
  • Springer  (169)
  • PANGAEA
  • Biology  (124)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (45)
  • 1
    ISSN: 1573-5036
    Keywords: ammonia volatilization ; denitrification ; grazing ; model ; nitrate leaching ; nitrogen ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The model simulates the cycling of N in grassland systems grazed by beef cattle and predicts the annual amount of N in liveweight gain, and the amounts lost through ammonia volatilization, denitrification and leaching, on the basis of fertilizer application and soil and site characteristics. It aims to provide a better understanding of the way in which these various factors interact in their influence on N transformations. The model has been programmed to run on IBM-compatible personal computers and responds rapidly to changes in input parameters. The model has been constructed from the average annual amounts of N passing through various components of the N cycle in ten field systems grazed by beef cattle. The amounts were either measured directly or were calculated from empirical sub-models, assuming a balance between inputs to, and outputs from the soil inorganic N pool. The model is given wide applicability through the inclusion of a mineralization sub-model which is sensitive to soil texture, sward age, previous cropping history, and climatic zone. Another important sub-model determines the partitioning of soil inorganic N to either plant uptake or the processes of loss: the proportion partitioned to plant uptake decreases as the total amount of soil inorganic N increases. Outputs from the model indicate that fertilizer N has a strong influence on ammonia volatilization, denitrification and leaching at a given site but that, over a range of sites with a given rate of fertilizer N, total loss and the proportions lost by the three processes are greatly influenced by the amount of N mineralized by the soil. The model indicates how fertilizer N should be matched with mineralization to limit gaseous and leaching losses and to achieve optimum efficiency of N use in grazing systems.
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  • 2
    ISSN: 1432-2242
    Keywords: Mitochondrial DNA of plants ; Electron microscopy ; Suspension culture ; Vicia faba
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A comparative analysis of the Vicia faba mitochondrial genome in whole plants and in longterm suspension culture has been conducted. Restriction fragment patterns of the mtDNA isolated from these two sources were notably different. Electronmicroscopic analysis also revealed significant differences. Large circular mtDNA patterns shifted from a 37–80 kb subpopulation, which was predominant in whole plants, to 18–34 kb subpopulations although in both classes notable quantities of circular molecules of 80 to 120 kb and more were also found. Both in whole plant and suspension culture cells very large circular DNAs were observed. Some of them had lengths nearly 290 kb and could be considered as evidence of the existence of master chromosomes. The minicircular DNA population was also altered. In the suspension culture we observed a notable increase of percentage of minicircles with sizes near 1 kb. Simultaneously, the percentage of minicircles with sizes near 3.5–10 kb significantly increased in suspension culture cells. In addition, a new peak (10–12 kb) of minicircles appeared. Copy number alterations for some sequences homologous to CCC1A, CCC1B and CCC2 (Negruk et al. 1982, 1985) were shown. Southern hybridization revealed the existence of a family of minicircles having sizes 1.4–2 kb with predominance of CCC1A, CCC1B and CCC2. The copy numbers of CCC1B and some minor minicircles was changed in the suspension culture when compared with the whole plants.
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  • 3
    ISSN: 1432-0878
    Keywords: Tetrabenazine ; Noradrenaline ; Constricted nerves ; Noradrenaline depletion in vitro ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The accumulation of noradrenaline proximal to a constriction applied to cat hypogastric nerves in vitro has been studied in preparations treated with tetrabenazine. The accumulation of amine was almost completely abolished by the drug. Evidence is presented which suggests that tetrabenazine exerts a direct noradrenaline-depleting effect on the intraneuronal storage vesicles. Recovery of noradrenaline levels after the removal of the drug was rapid and was effected by the biosynthesis of new noradrenaline within the axon.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 187 (1978), S. 457-472 
    ISSN: 1432-0878
    Keywords: Ovarian follicles (sheep) ; Theca interna ; Oestrogen ; Androgen ; Capillaries ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The theca interna of non-atretic ovarian follicles from 2.0 mm in diameter up to the stage shortly following ovulation was studied by light and electron microscopy. In follicles 〈3.0mm in diameter, the theca interna consisted of about 8–12 layers of flattened cells, together with many capillaries and small bundles of collagen. Two main forms of cellular differentiation were seen. These were towards either fibroblast-like cells or presumed steroidogenic cells whose cytoplasm contained large amounts of predominantly smooth tubular endoplasmic reticulum, to which some ribosomes were attached. The majority of cells were of relatively undifferentiated or intermediate structure. In larger follicles up to the early stages of oestrus the theca interna cells became larger and less flattened, and cells rich in tubular endoplasmic reticulum became proportionately more numerous. By 18 h after the onset of oestrus the theca interna was oedematous, and many cells possessed pseudopodia. Many cells also contained numerous lipid droplets, but there were no signs of thecal cell degeneration or death. Shortly after ovulation the basal lamina of the membrana granulosa was incomplete, and it became more difficult to distinguish between theca and granulosa layers. Structural heterogeneity, with two major cell types and cells of intermediate structure, was present at all stages. It was concluded that: (1) the theca interna of 2.0–2.9 mm follicles contained many cells whose structure was compatible with a steroidogenic capacity; (2) changes in the differentiated thecal cells up to the early stages of oestrus were quantitative rather than qualitative, and suggestive of an increased steroidogenic capacity; (3) the accumulation of lipid in many cells of the theca interna by 18 h after the onset of oestrus probably reflected a reduction in steroidogenic activity; and (4) there was no evidence of any structural specialization to facilitate the transport of steroids from the theca interna to the membrana granulosa.
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  • 5
    ISSN: 1432-0878
    Keywords: Key words: Scorpion venom ; Exocrine pancreas ; Secretagogue ; Electron microscopy ; Pancreatitis ; cis-Golgi aggregates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We studied in vivo and in vitro morphological aspects of pancreatic acinar cells after treatment with Tityus serrulatus venom (TSV). After three hours in an in vitro system, positive secretagogue effects of the venom were identifiable both at the light-microscopic (LM) and the electron-microscopic (EM) levels. At 1 μg/ml TSV, maximal secretion (as measured in a concomitant radiolabeling dose-response experiment) of exocrine proteins at 58% was manifest as a discharge of most zymogen granules (ZG) and consequent appearance of secretory material in acinar lumina. At the supramaximal dose of 10 μg/ml TSV, exocytotic images were often observed also with secretory contents previously discharged. The lowest dose of venom at 0.01 μg/ml caused no stimulation of zymogen discharge above resting secretion levels; however, morphological changes were observed. At high doses of TSV, both in vivo and in vitro, large aggregates associated with the cis-Golgi develop between this region and the endoplasmic reticulum (ER). Since Tityus venoms have been associated with causation of pancreatitis, we were interested in comparisons of our experimental tissue with parameters attributed to development of the disease. Our studies have demonstrated considerable evidence that large intracellular vacuoles, discharged ZG, effaced acinar lumina with disappearance of microvilli and other manifestations of possible early events in pancreatitis are indeed frequently observed both in pancreatic lobules in vitro and in whole pancreas in vivo when exposed to TSV.
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  • 6
    ISSN: 1432-0878
    Keywords: Scorpion venom ; Exocrine pancreas ; Secretagogue ; Electron microscopy ; Pancreatitis ; cis-Golgi aggregates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We studied in vivo and in vitro morphological aspects of pancreatic acinar cells after treatment with Tityus serrulatus venom (TSV). After three hours in an in vitro system, positive secretagogue effects of the venom were identifiable both at the light-microscopic (LM) and the electron-microscopic (EM) levels. At 1 μg/ml TSV, maximal secretion (as measured in a concomitant radiolabeling dose-response experiment) of exocrine proteins at 58% was manifest as a discharge of most zymogen granules (ZG) and consequent appearance of secretory material in acinar lumina. At the supramaximal dose of 10 μg/ml TSV, exocytotic images were often observed also with secretory contents previously discharged. The lowest dose of venom at 0.01 μg/ml caused no stimulation of zymogen discharge above resting secretion levels; however, morphological changes were observed. At high doses of TSV, both in vivo and in vitro, large aggregates associated with the cis-Golgi develop between this region and the endoplasmic reticulum (ER). Since Tityus venoms have been associated with causation of pancreatitis, we were interested in comparisons of our experimental tissue with parameters attributed to development of the disease. Our studies have demonstrated considerable evidence that large intracellular vacuoles, discharged ZG, effaced acinar lumina with disappearance of microvilli and other manifestations of possible early events in pancreatitis are indeed frequently observed both in pancreatic lobules in vitro and in whole pancreas in vivo when exposed to TSV.
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  • 7
    ISSN: 1573-5036
    Keywords: grassland ; leaching ; leaf litter ; macro-organic matter ; mineralization ; nitrogen ; ploughing ; roots ; stubble
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The amounts of organic matter in the stubble, litter, root and soil macro-organic matter fractions of two swards of perennial ryegrass that had received normal applications of either fertilizer or cattle urine were, on average for the four fractions, about 3000, 500, 11,500 and 8,800 kg ha−1. The swards had been established 8 or 15 years previously and each was sampled at intervals over a period of about one year. The amounts of N contained in the four fractions were, on average, 68, 12, 249 and 240 kg ha−1, a total of 569 kg N ha−1. With other swards, increasing rates of application of fertilizer N were found to have little effect on the amounts of organic matter in stubble and roots. Concentrations of N in the organic matter of the stubble and roots, however, increased significantly with increasing rate of fertilizer application, though, with stubble, moderate rates of application had little effect. Assessments based on these data, together with other published information, indicate that the amount of N mineralized from the combined stubble, litter, root and macro-organic matter fractions during the first year after ploughing may range from about 40 kg to at least 360 kg N ha−1 depending on the age of the sward and its recent management. The amount mineralized is likely to increase with age of sward, with increasing rate of fertilizer N and with utilisation by grazing rather than cutting.
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  • 8
    ISSN: 1573-5095
    Keywords: actinorhizae ; fertilization ; Frankia ; nitrogen ; nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To determine if inoculation increases nodulation and yield of bare-root red alder (Alnus rubra Bong.), fumigated nursery plots were treated with inoculum and ammonium sulfate (28 kg N ha−1) in a factorial experiment. Inoculum was alder soil with 100 infective units of Frankia g−1. Seedlings were evaluated for nodulation at age 10 wk and when lifted, at age 9 mo. Inoculation produced earlier and more extensive nodulation and increased seedling root collar diameter, height, and dry weight. Fertilization decreased seedling height, but did not decrease nodulation. No interaction of fertilization with inoculation was found. Inoculated unfertilized plots had the highest yield of packable seedlings (257 m−2), and uninoculated fertilized seedlings had the lowest yield (126 m−2).
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  • 9
    ISSN: 1573-5036
    Keywords: bacteria ; legume growth ; nitrogen ; nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Several Indonesian and some imported Rhizobium strains were assessed for their effectiveness in nodulating four legume species in four soil types of Java. Naturally occurring Rhizobia formed effective symbioses onVigna unguiculata, Macroptilium atropurpureum andDesmodium heterocarpon in all four soils and the applied strains, with some exceptions, did not infect a majority of nodules of these legumes.Centrosema pubescens was more specific in its Rhizobia requirements and applied strains formed effective symbioses in two clay soils, but not in two sandy loam soils.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 197 (1979), S. 281-294 
    ISSN: 1432-0878
    Keywords: Electron microscopy ; Light microscopy ; Gastric mucosa ; Reptilia ; Cytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The gastric mucosa of a reptile, the lizard Tiliqua scincoides, has been examined by light and electron microscopy. The gastric pits lead into glands that are extensively coiled in the proximal stomach but become progressively shorter and straighter in the distal stomach. The following epithelial cell types have been identified: (i) Surface mucous cells (SMC) line the entire lumenal surface as well as the pits. They contain mucus granules that stain with periodic acid-Schiff and, like the granules of mammalian SMC, commonly contain an electron dense core that appears not to be mucus (periodic acid-chromic acid-silver methenamine nonreactive). (ii) Glandular mucous cells are present in glands throughout the mucosa. They are probably homologous with the mucous neck and antral gland cells of mammals; like SMC their mucus granules contain nonglycoprotein cores. (iii) Oxynticopeptic cells (OPC) are the predominant cell type in the proximal glands but become infrequent distally. Their fine structure resembles that of OPC in other nonmammalian vertebrates, with features like those of both parietal cells and zymogen cells of mammals, (iv) Endocrine cells of three different types have been identified. Two of these show close similarities to the EC and ECL cells of mammals.
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