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  • 1
    Electronic Resource
    Electronic Resource
    Growth and development of root systems: Geometrical and structural aspects (1990)
    Springer
    Acta biotheoretica 38 (1990), S. 289-302 
    Details
    ISSN: 1572-8358
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé L'agronome qui veut étudier l'absorption hydrique et minérale des racines a besoin d'un modèle dynamique tri-dimensionnel de la structure du système racinaire. Le modèle présentd est fondé sur les connaissances actuelles sur la morphogenèse racinaire. Le système racinaire y est représenté comme un ensemble d'axes caractérisés par leur ordre. En effet, les propriétés morphogénétiques des racines varient d'un ordre d l'autre. Les axes d'ordre 1 sont insérés directement sur la tige, les axes d'ordre 2 sur les axes d'ordre 1, et ainsi de suite. Les axes tendent à être de plus en plus plagiotropes et à avoir de moins en moins de faisceaux vasculaires quand l'ordre augmente. Trois processus interviennent pour faire évoluer la structure racinaire simulée au cours du temps: l'émission de nouveaux axes racinaires à partir des tiges, la croissance, et la ramification des axes
    Notes: Abstract The agronomist who wants to study the nutrient and water uptake of roots needs a quantitative three-dimensional dynamic model of the structure of root systems. The model presented takes into account current knowledge about the morphogenesis of root systems. It describes the root system as a set of root axes, characterised by their orders. The morphogenetic properties of root axes differ according to their order. The axes of order 1 are directly inserted on the stem, the axes of order 2 are inserted on axes of order 1, and so on. They tend to be more plagiotropec and to have less vascular bundles as the order increases. The evolution of the simulated structure is achieved by three processes: emission of new root axes from the shoot, growth and branching of existing root axes. The elongation of an axis depends on its order and on local growing conditions. Branches appear acropetally at a specified distance from the apex and from former branches, along ranks facing xylem poles, with a branching angle specific of their order. From the three-dimensional branched structures simulated by the model, various outputs, such as kinetics of growth and development, root profiles or cross-section maps can be computed, compared to observed data and used as inputs in uptake models. Some examples of such possible outputs are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047244
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  • 2
    Electronic Resource
    Electronic Resource
    Prenatal diagnosis of diastematomyelia (1993)
    Springer
    Pediatric radiology 23 (1993), S. 67-68 
    Details
    ISSN: 1432-1998
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fetal diastematomyelia, a malformation due to a longitudinal split of the cord, was diagnosed during the third trimester. Diagnosis was based on the visualization of a sagittal bony spur in the thoracolumbar spinal canal, associated with enlargement of the canal, hemivertebrae and spina bifida without a meningocele.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02020231
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  • 3
    Electronic Resource
    Electronic Resource
    Cell-specific density of symbiotic dinoflagellates in tropical anthozoans (1998)
    Springer
    Coral reefs 17 (1998), S. 329-337 
    Details
    ISSN: 1432-0975
    Keywords: Key words Coral ; Sea anemone ; Dinoflagellates ; Symbiosis ; Eutrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  Symbiotic dinoflagellates are abundant in the endoderm cells of tropical marine anthozoans, but the cell-specific density (CSD) of symbionts has not yet been investigated. In this study we used mechanical and enzymatic methods of maceration, and staining with substrate-specific fluorochromes, to observe a large number of individual host cells from 33 species of tropical anthozoans collected in Florida, Hawaii and Jamaica or cultured in Monaco. In the majority of species, most of the host cells contained a single algal cell (singlet). Host cells with two or more (up to six) algae were much less abundant. The average CSD for the 33 species was 1.54±0.30 (range 1.11 to 2.19). Singlets arranged in a monolayer can account for the areal density of algae observed in many anthozoans. The dinoflagellates occupy most of the interior of macerated host cells, leaving the host cytoplasm and cell membrane as a thin outer layer, often unresolvable by light microscopy. This spatial arrangement may favor diffusion and transport of CO2, bicarbonate ions, and nutrients from the environment to the algae. The effect of nutrient enrichment on CSD was determined by exposing eleven species to chronically elevated levels of ammonium-N. After four weeks all species exhibited a dramatic increase in algal mitotic index and CSD. The potential consequences of environmentally induced increases in CSD in tropical anthozoans are discussed in terms of the decreased cell-specific photosynthesis (CO2 limitation) and decreased rates of calcification observed in other studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003380050133
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  • 4
    Electronic Resource
    Electronic Resource
    Principal modifications of the Duhamel procedure in the treatment of Hirschsprung's disease Analysis based on results of an international retrospective study of 2,430 patients (1998)
    Springer
    Pediatric surgery international 13 (1998), S. 125-132 
    Details
    ISSN: 1437-9813
    Keywords: Key words Hirschsprung's disease ; Duhamel's procedure ; Modifications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the literature, many articles refer to the DUHAMEL technique or some of its modifications in the treatment of Hirschsprung's disease, however, no complete review of all of them has been published to date. The authors present an analysis of the principal modifications of this technique based on the results of an international retrospective survey that evaluated a series of 2,430 patients as well as data from the literature. The important role of the internal anal sphincter in the physiology of continence is emphasized; understanding its function is an imperative prerequisite for a successful Duhamel procedure. The original technique, which used two crushing Kocher clamps as proposed by Duhamel in 1956, as well as a majority of the modifications with various spur-crushing instruments are no longer in use. At present, surgeons generally use staplers for the colorectal anastomosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003830050265
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  • 5
    Electronic Resource
    Electronic Resource
    Benthic diatoms as the major food source in the sub-Antarctic marine hydroidSilicularia rosea (1996)
    Springer
    Polar biology 16 (1996), S. 507-512 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analysis of the gut contents and scanning electron microscopy examination of the benthic hydroidSilicularia rosea from intertidal communities of Potter Cove (King George Island, South Shetlands) suggest that diatoms are the principal source of food for this species. The great number of items captured daily by each polyp (a mean of 287 in January and 162 in December) and the benthic origin of these prey items suggest an adaptation to daily resuspension processes caused by tidal currents. This is an unusual trophic strategy for a benthic hydroid, which would result in an important degree of independence from the highly fluctuating planktonic food conditions in Antarctic waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02329070
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  • 6
    Electronic Resource
    Electronic Resource
    Microextraction of Nuclear Proteins from Single Maize Embryos (1997)
    Springer
    Plant molecular biology reporter 15 (1997), S. 371-376 
    Details
    ISSN: 1572-9818
    Keywords: band shift assay ; DNA binding protein ; maize ; nuclear protein extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The analysis of DNA binding proteins can be difficult when only small quantities of tissue expressing the desired protein are available. We present a protocol for the preparation of nuclear extracts from as little as 100 mg of tissue. This protocol is well suited for extraction of DNA binding proteins from tissues that are difficult to obtain in large quantities such as maize embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007428802474
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  • 7
    Electronic Resource
    Electronic Resource
    Contributions of p53 and PMA to g-irradiation induced apoptosis in Jurkat cells (1999)
    Springer
    Hematology and cell therapy 41 (1999), S. 153-161 
    Details
    ISSN: 1279-8509
    Keywords: p53 ; Apoptosis ; PKC ; g-irradiation ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Several mutations prevent the expression of p53 in the human lymphoblastoid T cell line Jurkat. Restoration of p53 in Jurkat cells had no effect on the cell growth but markedly increased the amount of apoptosis induced by g-irradiation. Inhibition of RNA synthesis using 5,6-dichlorobenimidizole riboside had little effect on apoptosis induced by irradiation in the presence of p53 and did not affect the p53-independent apoptotic pathway. Expression of p53 also had no effect on the expression levels of proteins such as Fas, GADD45, Bax, Bcl-2, Bcl-xL or p53 induced proteins (PIGS) in resting cells or after irradiation. Activation of protein kinase C by phorbol 12-myristate 13-acetate produced an almost complete inhibition of p53-independent apoptosis following irradiation, whereas no significant effect was observed on the rate of p53-induced apoptosis. Although phorbol 12-myristate 13-acetate strongly induced p21 and stabilised p53 in the resting transfected Jurkat cells, neither apoptosis nor cell arrest was observed. In summary, this work shows that p53 enhances the radiosensitivity of Jurkat cells through an apoptotic process that is triggered by irradiation and is largely independent of RNA synthesis and protein kinase C activation. Apoptosis in p53- negative Jurkat cells is strongly inhibited by PMA indicating that the pathway triggered by p53 may be distinct from apoptotic pathways used in its absence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00282-999-0153-0
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  • 8
    Electronic Resource
    Electronic Resource
    Evidence of the co-activation of α-motoneurones and static γ-motoneurones of the sartorius medialis muscle during locomotion in the thalamic cat (1990)
    Springer
    Experimental brain research 82 (1990), S. 191-198 
    Details
    ISSN: 1432-1106
    Keywords: Fusimotor neurones ; Muscle spindles ; Muscular afferences ; Locomotion ; Thalamic cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity in α and γ efferent axon populations and in group I and group II afferent fibre populations innervating a flexor muscle, the sartorius medialis, was observed during spontaneous locomotor movements in the thalamic cat. Multi-unit discharges of each kind of fibre were obtained by electronic sorting of the action potentials from the overall activity of a thin, intact branch of the sartorius medialis nerve. The following results were obtained: (1) The γ-motoneurones have a phasic behaviour characterized by a single discharge period during the hip flexion (swing phase of the step-cycle). (2) The γ-motoneurones are co-activated with the homonymous α-motoneurones. (3) Between rhythmic α and γ discharges, i.e. during the hip extension (stance phase of the step cycle), both α- and γ-motoneurones were normally silent. However, in 5 out of 17 experiments, a few units of the γ population fired at very low frequency. (4) Two observations indicate that the γ-motoneurones that are co-activated with the α-motoneurones by central locomotor commands are predominantly of the static type. In actual locomotion, the rhythmic fusimotor discharges over-compensate the depressor effect on the firing rate of the group II afferents of the unloading of muscle spindles by the active shortening of the parent muscle. In fictive locomotion, when the transmission of the excitation is blocked by selective curarization in alpha skeleto-motor junctions alone, the rhythmic fusimotor discharges elicit in-phase modulations not only of the group I but also of the group II fibres. The group II afferent population consists almost entirely of fibres arising from spindle secondary endings which are located primarily on intrafusal muscle fibres whose contraction is exclusively controlled by static fusimotor motoneurones. In the two experimental circumstances, the analysis of the group I fibre discharge does not allow to decide whether dynamic γ motoneurones are firing or silent during rhythmic γ discharge. (5) The group I and group II afferent discharges during the step-cycle showed two frequency peaks, one static-fusimotor dependent while the contracting muscle shortened during the hip flexion (swing) phase, the other length-change dependent while the relaxed muscle was rapidly stretched during the first part of the hip extension (stance) phase. Then, during the second part of hip extension when the muscle was slowly stretched in the absence of fusimotor drive, the firing rate of the spindle afférents decreased to a low level. The spindle sensory endings during the extension phase showed low dynamic and static responsiveness like deefferented spindles. (6) The results obtained in sartorius medialis (flexor) muscle are discussed in comparison with the results previously obtained in gastrocnemii (extensor) muscles (Bessou et al. 1986). The consequences of the predominant activation of the static or dynamic fusimotor system in functionally different muscles are considered with respect to the proprioceptive or motor role of musclespindles during muscle contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230851
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  • 9
    Electronic Resource
    Electronic Resource
    Structural organization and polymorphism of the alpha satellite DNA sequences of chromosomes 13 and 21 as revealed by pulse field gel electrophoresis (1991)
    Springer
    Human genetics 〈Berlin〉 86 (1991), S. 311-316 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary More than 30 unrelated individuals were analysed by pulse field gel electrophoresis for the alphoid centromeric sequences of chromosomes 13 and 21. These individuals had DNA patterns all different from each other and were most probably heterozygous at both loci. When several nuclear families were analysed in this manner, segregation was shown to be Mendelian, and no recombination event was detected over the 150 meioses scored in this study. Alphoid DNA sequences, therefore, constitute highly polymorphic centromeric markers, which can be used in linkage analysis for loci close to the centromeres of chromosomes 13 and 21.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202418
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  • 10
    Electronic Resource
    Electronic Resource
    Crystallization Kinetics of Polypropylene-polyethylene-based Copolymers (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 57-65 
    Details
    ISSN: 1572-8943
    Keywords: artificial ageing ; DSC ; dynamic crystallization ; isoconversional method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A crystallization kinetics analysis of several polypropylene-polyethylene (PP-PE), PP-rich copolymers was made by means of differential scanning calorimetry. The crystallization was studied via calorimetric measurements at different cooling rates. Several additives were added to the base material. Some test samples were subjected to artificial ageing processes. A modified isoconversional method was used to describe the crystallization process under non-isothermal conditions. The value of the Avrami parameter was determined for primary and secondary crystallization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010123819994
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