ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Development  (17)
  • Springer  (17)
  • 1980-1984  (17)
  • 1980  (17)
Collection
Keywords
Publisher
  • Springer  (17)
Years
  • 1980-1984  (17)
Year
  • 1
    Electronic Resource
    Electronic Resource
    The effect of temperature onshibire ts cell clones in the compound eye ofDrosophila melanogaster (1980)
    Springer
    Development genes and evolution 188 (1980), S. 55-63 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Compound eye ; shibire ts ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have analysed the effect of temperature on both developing and adult eye cell clones homozygous forshi ST139, a temperature-sensitive mutant ofDrosophila melanogaster. The mutant gene, autonomous in its cellular expression, causes structural modifications of ommatidial cells when adult clones of cells are exposed to the restrictive temperature (29°C) for several days. However, the mutant phenotype reverses to normal within 4 days at the permissive temperature (20°C). The results of pulse, shift-up and shift-down experiments show that the temperaturesensitive period for developing compound eye cells is from the late second instar up to the early pupa. Cytodifferentiation of compound eye cells is blocked by restrictive temperature treatment during this period, whereas cell proliferation does not seem to be directly affected. These results are discussed with regard to the other known aspects of the phenotype observed in mutant individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848610
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Ganglioside changes in the chicken optic lobes and cerebrum during embryonic development (1980)
    Springer
    Development genes and evolution 188 (1980), S. 205-213 
    Details
    ISSN: 1432-041X
    Keywords: Gangliosides ; Development ; Brain ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The developmental profiles of 15 different gangliosides of the optic lobes and cerebrum of the chicken were followed from the 6 th day of incubation to hatching and correlated to morphological development. Five of these gangliosides appearing in both structures between the sixth and tenth day, have not been reported previously in higher vertebrates. Three chromatographed on TLC-plates similarly to GT3, GT2, and GT1c gangliosides, which have been demonstrated in fish brain. One fraction moved just below GQ1b and is suggested, to contain GQ1c. These “novel” gangliosides, which are possibly related to a recently proposed separate and probably phylogenetically older biosynthetic pathway, contained up to 20% of total ganglioside sialic acid. The fifth “novel” fraction, containing up to 16% of total ganglioside-sialic acid, moved below the penta-sialoganglioside GP1 and is suggested to contain hexa-sialogangliosides. There were two main changes in ganglioside synthesis, which were identical in both structures. The first occurred from the sixth to the eleventh day, parallel to decreased proliferation, maximal cell migration and neuroblast differentiation, GD3 and GD2 decreased rapidly in favour of GQ1b, GP1, and to the “novel” fractions, described above. The second occurred from the eleventh to the eighteenth day, parallel to increased growth and arborization of dendrites and axons as well as functional establishment of synaptic contacts, there was a sharp rise in the amount of GD1b, GT1b, and GD1a. Concomitantly the “novel” gangliosides decreased. At hatching GD1a was the predominant ganglioside. GM3, GM2, and GM1 were always minor fractions, each accounting for less than 4% of total ganglioside-sialic acid. GM4 was never detected, indicating neglegible myelinisation until hatching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00849050
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Studies on the regulation of the branched chain amino acyl-tRNA synthetases of the fungusNeurospora crassa (1980)
    Springer
    Development genes and evolution 189 (1980), S. 171-180 
    Details
    ISSN: 1432-041X
    Keywords: Amino acyl-tRNA synthetases ; Development ; Nuclear-mitochondrial interactions ; Neurospora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The specific activities of the branched chain amino acyl-tRNA synthetases from the cytosolic and mitochondrial fractions ofN. crassa were low in dormant conidia and increased during germination, reaching a maximum 8 h after inoculation. This stage of development is characterised by high rates of many other cellular activities. The increases in activity of synthetases of both cytosol and mitochondria are inhibited by cycloheximide indicating that they are synthesized on cytoplasmic ribosomes. The mitochondrial synthetases show a stimulation of their specific activity when mitochondrial RNA and protein synthesis are inhibited by either ethidium bromide or chloramphenicol suggesting that a mitochondrial translation product regulates the synthesis of the mitochondrial synthetases. The activities of amino acyl-tRNA synthetases are dependent on energy production. When respiration is uncoupled from oxidative phosphorylation, synthetase specific activities decrease although the activities of other mitochondrial enzymes like NADH-dehydrogenase increase. This phenomenon suggests that more than one mechanism regulates the synthesis of mitochondrial proteins which are formed on cytoplasmic ribosomes. The synthesis of branched chain amino acyl-tRNA synthetases ofNeurospora is neither repressed by their cognate amino acids, nor is there inhibition by the precursors of these amino acids, as has been observed in other amino acyl-tRNA synthetases of various organism includingNeurospora.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00868675
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Changes of the cytoplasmic ultrastructure during development of sclerotia in Claviceps purpurea (Fr.) Tul. (1980)
    Springer
    Archives of microbiology 125 (1980), S. 251-257 
    Details
    ISSN: 1432-072X
    Keywords: Claviceps purpurea ; Ultrastructure ; Development ; Sclerotium ; Oleosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of sclerotia of Claviceps purpurea was investigated by light and electron microscopy. During the first days after infection sterigma and conidiospores are formed. The spores show a moderately developed vacuolar system, they are thick walled and contain about 20% lipid (related to the cell volume) embedded in glycogen. The sterigma are cylindrical unicellular hyphae with electron dense cytoplasm and isolated strongly contrasted lipid droplets. In maturing sclerotia the hyphae become septated with increasingly thick cell walls and a large lipid content. The lipid forms small droplets in young cells, while in the mature sclerotium it occurs in the form of very large drops, occupying the major part of the cell. Simultaneously the composition of the lipid is changed. The mature cells have several nuclei. They are partially connected by osmiophilic substances, forming a network of intercellular spaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446885
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Using ecological knowledge for development planning (1980)
    Springer
    Environmental management 4 (1980), S. 13-20 
    Details
    ISSN: 1432-1009
    Keywords: Planning ; Management ; Natural resource planning ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Since October 1977, the East-West Environment and Policy Institute in Honolulu has been conducting a multinational collaborative project to enhance the preparation and utilization of natural systems assessments in developing countries. This paper presents some of the findings to date: 1. Channels are developing rapidly for transferring ecological knowledge into political and administrative decision making. 2. The systematic approach of ecology is replacing “environmental quality” as the organizing concept for information about natural resources and the environment. 3. Benefit-cost analysis is a promising method for integrating ecological knowledge into economic development decision making. 4. The lack of baseline information, inventories, and predictive capability will not be remedied soon or easily; thus priorities for ecological research are essential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01866216
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Development of antennal sensilla during moulting inNeomysis integer (Leach) (Crustacea, Mysidacea) (1980)
    Springer
    Protoplasma 105 (1980), S. 53-67 
    Details
    ISSN: 1615-6102
    Keywords: Crustacean sensilla ; Development ; Sensilla structure ; Moulting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The sensilla are associated with 6 enveloping cells. The innermost enveloping cell (e 1) secretes the dendritic sheath (=thecogen cell). All other enveloping cells are involved in the formation of the outer cuticular apparatus in secreting the cuticle of a definite region of the new hair shaft. The development of the new sensilla begins when an exuvial space expands between old cuticle and epithelium. The newly forming hair shafts lie folded back in an invagination of the epidermal tissue. Only a distal shaft part projects into the free exuvial space. The cuticle of the distal and middle shaft region is secreted by the three middle enveloping cells (e 2–e 4) (=trichogen cells), which are arranged around the dendritic sheath. The wall of the cylinder, in which the distal shaft is situated, is formed by the cuticle of the future proximal shaft region. It is secreted by the outer enveloping cells (e 5 and e 6). Furthermore, both enveloping cells form the hair socket (=trichogen-tormogen cells). The outer dendritic segments encased within a dendritic sheath run up through the newly formed hair shaft and continue to the old cuticular apparatus. The connection between sensory cells and old hair shaft is maintained until ecdysis. On ecdysis the old cuticle is shed and the newly formed shaft of the sensillum is everted like the invaginated finger of a glove. The dendritic sheath and the outer dendritic segments break off at the tip of the new hair shaft. Morphologically this moulting process ensures that the sensitivity of the receptors is maintained until ecdysis. The internal organization of the sensory cells shows no striking changes during the moulting cycle. An increased number of vesicles is accumulated distally within the inner dendritic segments and distributed throughout the outer segments of the dendrites. The cytoplasmic feature of the enveloping cells indicates that synthesis and release of substances for the cuticular apparatus of the new sensillum take place.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279849
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The ultrastructural development of the macrogamete ofEimeria stiedai (1980)
    Springer
    Protoplasma 104 (1980), S. 33-41 
    Details
    ISSN: 1615-6102
    Keywords: Development ; Eimeria stiedai ; Macrogamete ; Ultrastructural changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of the macrogamete ofEimeria. stiedai in the epithelial cells of the bile ducts of rabbits was studied by electron microscopy. A macrogamete was first identified by the presence of a large central nucleus with prominent nucleolus, and subsequently by the appearance of wall forming bodies. The macrogamete was limited by an outer single membrane under which there were remnants of a second membrane. The parasitophorous vacuole, in which the macrogamete was located, was often narrow and it contained no intravacuolar-tubules or -folds. As macrogametogony proceeded wall forming bodies of Type I and II, canaliculi, electron pale spaces (lipid) and polysaccharide granules increased in number. Granular endoplasmic reticulum, mitochondria and Golgi bodies were present throughout.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279366
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The susceptibility of terrestrial gastropods to experimental infection withElaphostrongylus rangiferi Mitskevich (Nematoda: Metastrongyloidea) (1980)
    Springer
    Parasitology research 62 (1980), S. 7-14 
    Details
    ISSN: 1432-1955
    Keywords: Elaphostrongylus rangiferi ; Rangifer tarandus ; Gastropods ; Susceptibility ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Sixteen species of terrestrial gastropods, collected at Tromsöya, northern Norway, were experimentally brought into contact with first stage larvae ofElaphostrongylus rangiferi, a parasite causing neurological disorders in reindeer,Rangifer tarandus (L.). All species were susceptible to infection but there were considerable variations in incidence and intensity of infections and in the development of the nematode in the different gastropod species. InDiscus ruderatus, Arion silvaticus, Deroceras laeve, Euconulus fulvus, andTrichia hispida, development to infective third stage larvae took about 20 days at 20°C. InSuccinea pfeifferi, Deroceras reticulatum andArianta arbustorum development was somewhat slower. InCochlicopa lubrica, Arion subfuscus, A. hortensis, Vitrina pellucida, Nesovitrea spp., andClausilia bidentata, only small numbers of larvae developed and at a very slow rate. InVertigo lilljeborgi andPunctum pygmaeum, the larvae did not develop. Growth in length ofE. rangiferi inD. ruderatus was rapid and continuous up to the second molt (about 15 days postinfection). Thereafter there was a slower growth rate. Tissue reactions against the infection were observed in eleven of the gastropod species. No obvious relationship between the degree of tissue reactions and susceptibility to infection was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00925362
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Microtubules, dendritic spines and spine apparatuses (1980)
    Springer
    Cell & tissue research 208 (1980), S. 171-181 
    Details
    ISSN: 1432-0878
    Keywords: Microtubules ; Dendritic spine apparatus ; Synapse ; Development ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using techniques for enhanced microtubular preservation, including albumin pretreatment (Gray, 1975), occipital cortex of rats was studied electron microscopically at various ages of development. A close structural relationship was seen between microtubules, sacs of SER and the postsynaptic “thickening” in primordial spines and with the dense “plate” material of spine apparatuses. Stereoscopic preparations in addition show a more complicated substructure than previously described for the “plate”. Microtubules may contribute to the formation of the “plate” of the spine apparatus which in turn is associated with the postsynaptic “thickening” of the mature spine. Possible functional correlates are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234868
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Postnatal development of somatotrophs and mammotrophs in the pars distalis of the C57BL mouse (1980)
    Springer
    Cell & tissue research 211 (1980), S. 441-448 
    Details
    ISSN: 1432-0878
    Keywords: Somatotroph ; Mammotroph ; Development ; Mouse ; Pituitary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pars distalis of the pituitary gland of the C57BL mouse was studied by means of electron microscopy during postnatal stages of males ranging in age from newborn through 24 days, with particular emphasis on the somatotrophs and mammotrophs. During this period, growth curves were plotted in order to correlate postnatal growth patterns with the state of differentiation of the somatotrophs in the pars distalis. In the newborn, the somatotrophs show well developed organelles, including rough endoplasmic reticulum and Golgi complexes. These cells are not as densely packed with granules as the adult somatotrophs; however, from days 5 through 24, they show a progressive accumulation of granules. Although mammotrophs are scarce in the newborn, they are readily distinguishable in the pars distalis at 5 days. Male mice in small litters show a progressive increase in body weight between birth and 11–12 days, at which time the rate slackens until 18–19 days when the rate again increases. Growth curves for mice from large litters are similar to those from smaller litters, except that the transitory decrease in rate is more prominent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234398
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    Role of innervation on the embryonic development of skeletal muscle (1980)
    Springer
    Cell & tissue research 210 (1980), S. 383-393 
    Details
    ISSN: 1432-0878
    Keywords: Avian skeletal muscle ; Development ; Normal, aneural, paralyzed muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The extent to which the motor innervation regulates the embryonic development of skeletal muscle was investigated by comparing changes in normal, aneural, and paralyzed superior oblique muscle of the duck embryo. The muscle was made aneural by permanently destroying the trochlear motor neurons with electrocautery on day 7 i.e., three days prior to innervation. Embryos were paralyzed by daily application of α-bungarotoxin onto the chorioallantoic membrane from day 10 onwards. The differentiation of myoblasts and myotubes in the aneural muscle was severely affected and did not progress to the myofiber stage. A mass of dead cells in the aneural muscle was replaced by connective tissue. Although the differentiation of myoblasts and myotubes was also retarded in the paralyzed muscle, numerous muscle cells progressed to the myofiber stage. Neuromuscular junctions of normal ultrastructure were seen in all paralyzed muscles. Degeneration of some cells in the paralyzed muscle occurred but there was no evidence of a massive wave of cell death similar to that observed in the aneural muscle. These observations suggest that both the trophic factors from the nerve and the nerve-evoked muscle activity are essential for the execution of the developmental program of the muscle. Trophic factors may play a larger role in differentiation, and maintenance of the muscle than muscle activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220196
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    The programming of silk-gland development in Bombyx mori (1980)
    Springer
    Cell & tissue research 213 (1980), S. 311-324 
    Details
    ISSN: 1432-0878
    Keywords: Bombyx ; Silk-gland ; Starvation ; Development ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cytological development of the silk gland has been studied by light and electron microscopy in silkworms experimentally starved at different periods of the natural feeding stage during the fifth instar. When newly molted animals are not provided with food, no sign of growth is observed. Starvation initiated early during the obligatory feeding period, stops cell growth and development of the organelles involved in protein synthesis and secretion, whereas it induces the appearance of organelles concerned with autolysis. These effects are reversible if starvation is not prolonged beyond two days. Starvation during the facultative feeding period, at the time of massive fibroin production, results in quantitative and qualitative modifications of organelles related to the decrease of fibroin production and the onset of autolysis. Rough endoplasmic reticulum, responsible for fibroin synthesis, forms transitory whorls. Fibroin transport via the Golgi apparatus and secretion of the protein into the gland lumen decrease parallel to fibroin synthesis, so that no fibroin storage can be detected in any organelle. After food deprivation, autophagosomes and secondary lysosomes rapidly develop in the cytoplasm, and if starvation continues portions of the cytoplasm are sequestered and completely destroyed. If animals are refed, fibroin production is resumed and autolysis declines. These ultrastructural alterations of the silk gland during experimental starvation are very similar to those observed during the periods of physiological starvation (molt and cocoon spinning) and generally considered to be under hormonal control. Our results raise the question of the nature of interactions between alimentary and hormonal factors which control silk-gland development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234790
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Prenatal and early postnatal development of the glial cells in the median eminence of the rat (1980)
    Springer
    Cell & tissue research 211 (1980), S. 117-137 
    Details
    ISSN: 1432-0878
    Keywords: Eminentia mediana ; Neurohypophysis ; Development ; Pituicytes ; Tanycytes ; Astrocytic tanycytes ; Oligodendrocytes ; Astrocytes ; Microglia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of the glial cells of the rat median eminence (ME), including the supraependymal cells, was investigated from embryonic day (ED) 14 through postnatal day (PD) 7, and pituicyte development from ED 12 through ED 17. The anlage of the ME and neurohypophysis shows a neuroepithelial-like structure at ED 12. From ED 13 to 15, the cells of both regions start to differentiate. At the ultrastructural level, only one cell type appears. At the beginning of ED 16, glioblasts of the oligodendrocyte and astrocyte series migrate laterally (from the region of the arcuate nucleus) into the ME. Also at this time the first distinctive structural features appear in the neurohypophysial anlage, the cells of which later develop into pituicytes. Starting at ED 18, tanycytes and astrocytic tanycytes arise in the ME from local glial cells, and somewhat later oligodendroblasts and astroblasts are formed from immigrant glioblasts. Due to their common features, the pituicytes, tanycytes and astrocytic tanycytes apparently represent different forms of the same parent cell type. Microglial and supraependymal cells are first seen at ED 12. Initially, they resemble the prenatal phagocytic connective tissue cells and mature in the fetus into typical electron-dense microglia and macrophage-like supraependymal cells. Both cell types are apparently of mesodermal origin. The microglial elements of the ME probably migrate from the mesenchyma through the basement into the nervous tissue. The intraventricular macrophages of the infundibular region may originate from microglia, epiplexal cells and subarachnoid macrophages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233728
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    The parcellation theory and its relation to interspecific variability in brain organization, evolutionary and ontogenetic development, and neuronal plasticity (1980)
    Springer
    Cell & tissue research 213 (1980), S. 179-212 
    Details
    ISSN: 1432-0878
    Keywords: Neocortex ; Evolution ; Development ; Plasticity ; Visual system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Recently discovered neocortical equivalents in anamniotes and certain patterns of interspecific variability in brain organization provide new insights into evolutionary and ontogenetic mechanisms of development. The new data suggest that nervous systems become more complex, not by one system invading another, but by a process of parcellation that involves the selective loss of connections of the newly formed daughter aggregates and subsystems. The parcellation process is reflected in the normal ontogenetic development of the CNS in a given species and can be manipulated, to a certain extent, by deprivation or surgically induced sprouting. The parcellation theory allows certain predictions about the range of variation of a given system at all levels of analysis including the cellular and aggregate levels. For example, the interspecific variability in organization of cortical columns, thalamic nuclei, cortical areas and tectal layers can be explained. The findings, summarized here, suggest that diffuse, undifferentiated systems existed in the beginning of vertebrate evolution and that during the evolution of complex behaviors, and analytical capacities related to these behaviors, a range of patterns of neural systems evolved that relate to these functions. One principle underlying the growth, differentiation and multiplication of neural systems appears to be the process of parcellation as defined by the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234781
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Studies on formation and resorption of fish scales (1980)
    Springer
    Cell & tissue research 211 (1980), S. 303-316 
    Details
    ISSN: 1432-0878
    Keywords: Fish scale ; Fine structure ; Development ; Calcification ; Cyprinodon variegatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scale formation in Cyprinodon variegatus was found to be initiated at about 26 to 30 days after hatching. Ultrastructural investigation revealed that within 4 to 6 h in the first-formed scales the marginal cells begin to flatten and differentiate into osteogenic cells, which later change to osteoblasts and fibroblasts. These cells are separated from the surrounding epithelial cells by a basal lamina. The osteoid is formed by the marginal and osteogenic cells; the osseous layer by the osteoblasts; and the fibrillary plate by the fibroblasts. The osteoid is formed within 2 to 3 h after the initiation of the scale, and within 20 to 24 h the osseous layer is formed. Hydroxyapatite crystals are deposited in the matrix of the osseous layer without apparent association with collagen fibers. No matrix vesicles or dense bodies are evident at the sites of calcification. The fibrillary plate arises 18 to 20 h after the initiation of the scale. It is also partially calcified, but not before the third week of scale formation. The crystals develop almost exclusively between the collagen fibers at the extreme edge of the calcifying front, but solid calcification of the fibers results with further growth of the crystals. The fibroblasts appear to participate in calcification of the fibrillary plate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236451
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Description of understory development in a tree plantation with a new method of data structuring (1980)
    Springer
    Plant ecology 40 (1980), S. 185-191 
    Details
    ISSN: 1573-5052
    Keywords: Clustering ; Data-processing ; Michigan ; Numerical method ; Phytosociology ; Stratum ; Understory ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During May and June, 1974, relevés were obtained from 30 plantation stands in the Saginaw Forest in southeastern Michigan. The canopy trees in these plantations were planted between 1904 and 1938. The understory has developed naturally over the years. The forest plantations offer opportunities for study of the effects of the canopy on the structure and species composition of the understory. A new numerical method of data structuring was used, which is based on the detection patterns of associated species within the table of 30 relevés from Saginaw Forest plantations. The method employs two difference measures. DIF 1 uses presence/absence data and DIF 2 the cover/abundance values obtained from the relevés. Both difference measures supply distance values for every pair of relevés. The least dissimilar relevés are then grouped together by the farthest neighbor agglomerative algorithm of Lance & Williams (1967). The DIF 1 analysis was inconclusive, but the DIF 2 analysis gave coherent results. It has shown that relevés with similar canopies have similar understories. The differences in understories among the relevés are due less to species composition than to the relative abundances of the species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228485
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Vegetation development in a former orchard under different treatments: A preliminary report (1980)
    Springer
    Plant ecology 43 (1980), S. 95-102 
    Details
    ISSN: 1573-5052
    Keywords: Aegopodion podagrariae ; Arrhenatherion elatioris ; Development ; Dynamics ; Experiment ; Fertilization ; Mowing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Vegetation development in a former orchard on loamy moist soil after removal of the fruit trees under different treatment is described with the help of multivariate methods. Data on 20 plots over 9 years are treated with a simple classification program and a PCA ordination. Two main groups of plots are involved: one in a relatively moist part of the area where the trees were removed in 1970, one in a slightly drier area where the trees had been removed earlier. The first group is characterized by forbs such as Urtica dioica and Lamium maculatum, the second by grasses, mainly Arrhenatherum elatius. Under a mowing regime the plots of the first group change in the direction of the second group. Under continued fertilization the Urtica vegetation can be maintained. Establishment and/or rapid spread of Urtica can be brought about in Arrhenatherum dominated sites by (re-) introduction of nitrogen fertiliser. Not mowing leads to a dense Urtica-Lamium stand in which Lamium maculatum finds an optimum some years after mowing is stopped. The methods of summarizing the site-time data are discussed and some new ones announced for further research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121022
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...