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  • Ultrastructure  (7)
  • Springer  (7)
  • American Physical Society
  • BioMed Central
  • Public Library of Science
  • Springer Nature
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  • Springer  (7)
  • American Physical Society
  • BioMed Central
  • Public Library of Science
  • Springer Nature
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Years
  • 1
    Electronic Resource
    Electronic Resource
    Early stages of synaptogenesis in the cervical spinal cord of the chick embryo (1973)
    Springer
    Cell & tissue research 138 (1973), S. 475-488 
    Details
    ISSN: 1432-0878
    Keywords: Synaptogenesis ; Spinal cord ; Chick embryo ; Coated vesicles ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Synaptogenesis was studied in 3, 4, 5 and 8 day embryos. A small number of synapses were located in the marginal zone near the motor region in 3–4 day embryos. At 5 days the number of synapses increased and synapses were also found within the motor region. At 8 days there was a large increase in the total number of synapses and most were found within the motor region. At this stage, for the first time, many knobs contained flattened synaptic vesicles. Synapses on the perikarya were rarely but occasionally observed both at the 5 and 8 day stages. A few synapses were located in the marginal zone near dorsal root entry at the 5 day stage and the number increased by the 8 day stage. Although this sequence of synaptic development resembles that found in the monkey fetus, differences in behavioral development between these two species indicate that descriptive relationships between synaptic and behavioral development must be made cautiously. Furthermore, evidence is presented which indicates that the junctional specialization is the first sign of a developing synapse and that coated vesicles, possibly derived from the Golgi apparatus, which are fused to the neural plasmalemma may be related to the initial formation of the junctional specialization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572291
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in the median eminence of the rat following deafferentation of the basal hypothalamus (1970)
    Springer
    Cell & tissue research 105 (1970), S. 1-32 
    Details
    ISSN: 1432-0878
    Keywords: Median eminence ; Rat ; Deafferentation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This report concerns a light and electron microscopic investigation of the median eminence and dorsal infundibular stem of the rat following surgical isolation (deafferentation). Using a modification of the Halász technique, the basal hypothalamus, including the arcuate nucleus and median eminence were surgically isolated from surrounding structures. Special attention was directed to the contact (external) zone of the median eminence and rostral infundibulum where tuberohypophyseal axons as well as ependymal cell processes abut upon the abluminal basement membrane of the portal perivascular space. The results of this study to date suggest that 9, 20, and 40 days following surgical isolation, there is a distinct increase in the population of tuberohypophyseal dense core vesicles. It is suggested that deafferentation abolishes inhibitory and excitatory input that serves to modify the cellular dynamics of tuberohypophyseal neurosecretory elements. Comments are also made on the presence of cistern-like structures in the lateral median eminence; the presence of vesicle-like inclusions in terminal ependymal processes is discussed in relationship to the role that ependyma may play in linking the third ventricle with the adenohypophysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340562
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructure of cell division in the marine red algaLomentaria baileyana (1986)
    Springer
    Protoplasma 131 (1986), S. 1-10 
    Details
    ISSN: 1615-6102
    Keywords: Cell division ; Lomentaria ; mitosis ; Red algae ; Rhodophyta ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitosis in the marine red algaLomentaria baileyana (Rhodymeniales, Rhodophyta) was studied with the electron microscope. Nucleus associated organelles known as polar rings (PRs) migrate to establish the division poles at prophase. At prometaphase, shallow invaginations in the nuclear envelope (NE) form on two sides of each PR and soon rupture. The gaps that are consequently formed contain several small fragments of NE. A larger region of NE remains intact between the two gaps. By metaphase several cisternae of perinuclear endoplasmic reticulum (PER) have enclosed most of the nucleus but remain absent from the polar regions. The nucleolus disperses partially and a typical metaphase plate of chromosomes is formed. Each PR has disjoined into separate proximal and distal portions. MTs converge widely on all regions of the polar area, but do not extend into the cytoplasm. Some MTs end near or at the chromosomes while others extend slightly farther past the chromosomes or diagonally to the NE. As chromosomes move to opposite poles at anaphase, they are accompanied by nucleolar material. An interzonal midpiece (IZM) is created as the pole to pole distance increases and the NE remains intact except for the polar gaps. Following detachment from the IZM, the daughter nuclei are separated by a large central vacuole as a cleavage furrow develops and eventually constricts to form two cells following pit connection formation. It is suggested that mitosis inLomentaria represents an evolutionary intermediate between that seen in the higher and lower groups of red algae. This conclusion is in agreement with conventional morphological and light microscopic criteria used to placeLomentaria in theRhodymeniales, which is considered to be the next to most advanced order in theRhodophyta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281682
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  • 4
    Electronic Resource
    Electronic Resource
    Mitosis in the freshwater red algaBatrachospermum ectocarpum (1983)
    Springer
    Protoplasma 118 (1983), S. 56-70 
    Details
    ISSN: 1615-6102
    Keywords: Carposporophyte ; Cell division ; Mitosis ; Rhodophyta ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitotic ultrastructure was observed in meristematic cells of carposporophyte generations of the freshwater red algaBatrachospermum ectocarpum. Prior to nuclear division, cell elongation occurs resulting in the nucleus being located at the proximal end of the cell and separated by a large central vacuole from a distal “empty region” which the daughter nucleus eventually occupies. In late prophase, nuclear envelope-attached polar rings are situated adjacent to shallow nuclear invaginations. At prometaphase the nuclear invaginations extend deeply into the nucleus forming continuous cytoplasmic channels containing microtubules. Perinuclear ER and a typical equatorial chromosomal plate are formed by metaphase at which time the nuclear envelope lining the cytoplasmic channels has dispersed. Chromosomal and non-chromosomal microtubules converge at the poles where a single, large gap is seen in the otherwise intact nuclear envelope. Polar rings were not detected in the few mitotic cells observed beyond prometaphase but are thought to be present. During anaphase an interzonal midpiece is formed and the distal-most incipient daughter nucleus moves laterally past the central vacuole into the apical “empty region”. Features of mitosis inBatrachospermum are believed to be intermediate between those exhibited by the lower and higher orders of red algae, this being consistent with the taxonomic placement of the genus in theNemaliales, the least advanced order of the classFlorideophyceae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284747
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of cell division and reproductive differentiation of male plants in theFlorideophyceae (Rhodophyta). Mitosis inDasya baillouviana (1981)
    Springer
    Protoplasma 106 (1981), S. 329-341 
    Details
    ISSN: 1615-6102
    Keywords: Dasya ; Mitosis ; Rhodophyta ; Spermatangia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitosis in the marine red algaDasya baillouviana (Ceramiales, Florideophyceae) was observed with the electron microscope. Most details of the process are quite similar to those observed in the other macroscopic red algae studied to date. However, some minor variations were noted. At late prophase a very small nuclear envelope protrusion (NEP) is formed at each division pole subjacent to the “nucleus associated organelle” known as the polar ring (PR) and 2–3 cisternae of perinuclear endoplasmic reticulum (PER) are commonly present during metaphase-anaphase. In contrast, in the other florideophycean algae where mitosis has been reported, a prominent NEP is present at late prophase (McDonald personal communication,Scott et al. 1980) and only a single cisterna of PER is observed. Additionally, during mid-late interphase and in mitotically-quiescent cells ofDasya, a single cisterna of smooth-surfaced ER is always juxtaposed with each PR. The possible significance of PER in theFlorideophyceae and other multinucleate organisms is discussed as well as the likely functions of spindle-associated smooth ER. It is suggested that ultrastructural features of mitosis should be useful as criteria to aid in the interpretation of the phylogeny of red algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275563
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  • 6
    Electronic Resource
    Electronic Resource
    The occurrence of calyx nodules inPsychotria spp. (Rubiaceae) (1984)
    Springer
    Protoplasma 121 (1984), S. 199-208 
    Details
    ISSN: 1615-6102
    Keywords: Psychotria ; Leaf nodules ; Calyx nodules ; Symbiosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence and structure of calyx nodules in the flowers of two leaf nodulated rubiaceous speciesPsychotria punctata Vatke andPsychotria kirkii Hiern. has been described for the first time at the ultrastructural level. Bacteria, resident in colleter-secreted mucilage in the space between calyx and corolla, invade stomatal pores which develop on the calyx protoderm. The bacteria proliferate in the substomatal cavity and then invade the calyx mesophyll. This invasion is most pronounced inP. punctata where the bacteria even penetrate and enter the cells of the vascular tissue. Although no sheath forms around the calyx nodules, the calyx mesophyll cells surrounded by the bacteria become identical in shape, size and secretory function to the invasive mesophyll cells of leaf nodules. The functional and evolutionary significance of calyx nodulation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282313
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  • 7
    Electronic Resource
    Electronic Resource
    Mycorrhizal improvement in non-leguminous nitrogen fixing associations with particular reference toHippophaë rhamnoides L. (1984)
    Springer
    Plant and soil 78 (1984), S. 189-199 
    Details
    ISSN: 1573-5036
    Keywords: Alnus Hippophaë ; Mycorrhiza ; Myrica ; Nitrogenase ; Phosphate ; Triple symbiosis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The roots ofHippophaë rhamnoides which regularly bear actinomycete induced nodules when growing on Scottish sand dunes have also been found to support an endomycorrhizal association withGlomus fasciculatus. Ultrastructural and cytochemical studies carried out on the indigenous infections of establishedHippophaë mycorrhizal roots would support the postulate that transport is indeed occurring between the fungal symbiont and the host plant and vice versa in respect of phosphate and carbohydrate. Experiments using various inoculation regimes, demonstrated the significant improvement in the mycorrhizal/nodulated plants compared to the nodulated-only and the mycorrhizal-only plants with respect to plant growth, uptake of phosphate and nitrogenase activity, when grown in a medium poor in combined nitrogen and soluble phosphate. Preliminary work onAlnus andMyrica species growing in Central Scotland indicates that the mycorrhizae associated with these nodulated root systems exhibit a different interaction pattern which may be dependent on habitat type and associated angiosperm species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277850
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