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  • Ultrastructure  (55)
  • Prebiotic  (6)
  • Springer  (61)
  • 2020-2024
  • 2010-2014
  • 1970-1974  (61)
  • 1945-1949
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  • Springer  (61)
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  • 1
    Electronic Resource
    Electronic Resource
    Further studies of urea-catalyzed phosphorylation reactions (1973)
    Springer
    Journal of molecular evolution 2 (1973), S. 231-234 
    Details
    ISSN: 1432-1432
    Keywords: Phosphorylation ; Nucleotides ; Nucleoside Polyphosphates ; Oligonucleotides ; Urea ; Prebiotic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have analyzed the products formed when mixtures of a nucleoside and ammonium dihydrogen phosphate are heated with an excess of urea. If there is more phosphate than nucleoside in the mixture, compounds containing pyrophosphate bonds are obtained. If uridine, as nucleoside, is in excess over phosphate, di- and oligonucleotides are formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01654004
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  • 2
    Electronic Resource
    Electronic Resource
    Cytodifferentiation in the Rana pipiens oocyte (1972)
    Springer
    Cell & tissue research 126 (1972), S. 1-16 
    Details
    ISSN: 1432-0878
    Keywords: Oocyte ; Rana pipiens ; Ultrastructure ; Cytochemistry ; Enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In early diplotene frog oocytes incubated to illustrate thiamine pyrophosphatase (TPPase) activity, reaction product is uniformly distributed within the compartments of the endoplasmic reticulum and nuclear envelope as well as within the saccules and small vesicles comprising the dictyosomes. With continued oocyte development the reaction product becomes concentrated in localized regions of the dictyosome saccules. Eventually, the enzyme is no longer apparent within the endoplasmic reticulum, but is concentrated in the cisternae of the inner dictyosome saccules. The variations noted suggest that the enzyme is synthesized early in diplotene by the endoplasmic reticulum and is subsequently transported to the Golgi apparatus where it is consistently observed at later developmental stages. TPPase activity is also present in the Golgi apparatus of follicle and theca cells as well as in ovarian epithelial cells. The enzyme is also detected in micropinocytotic vesicles contained within the cells comprising the follicle envelope and in intercellular spaces of the follicle. Horseradish peroxidase injected into the coelomic cavity is transported via micropinocytotic vesicles into and through the cells comprising the follicle envelope and in intercellular spaces. The exogenous protein is not found even after a prolonged time period in early diplotene oocytes. The protein is, however, present in large spherical and “tubular” vesicles in the cortex of vitellogenic oocytes approximately 500 microns in diameter. The possible functional role of the enzyme TPPase during oogenesis is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306776
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  • 3
    Electronic Resource
    Electronic Resource
    Fine structure of tarsal sensilla in the tick Amblyomma americanum (L.) (1971)
    Springer
    Cell & tissue research 114 (1971), S. 22-37 
    Details
    ISSN: 1432-0878
    Keywords: Sensory receptors ; Arthropoda ; Acarina ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Ausgewählte Borsten am Tarsus der Zecke Amblyomma americanum (L.) (Acarina; Ixodidae; Nymphenstadium) wurden mit dem Durchstrahlungs- und Rasterelektronenmikroskop untersucht. Alle Sensillen sind mehrfach innerviert; die dicke Cuticulawandung besitzt entweder ein ausgeprägtes Porenkanalsystem oder eine schlitzförmige Öffnung nahe der Spitze. Diese Sensillen haben oft zusätzlich zwei mechanoreceptive Dendriten an der Borstenbasis angeheftet und dienen dann offenbar zwei Funktionen: Mechano- und Chemoreception. Die Feinstruktur jedes Sensillums ist ähnlich wie in anderen Arthropodensinneshaaren, mit Ausnahme der Ciliärregion des Dendriten. Statt der herkömmlichen 9 Doppeltubuli besitzen Zeckensensillen gewöhnlich 11 (“11+0”). Verglichen mit den tarsalen Borsten von Insekten und Spinnen erscheinen Zeckensensillen zwar weniger zahlreich, dafür strukturell komplexer und von größerer Vielfalt.
    Notes: Summary Selected tarsal bristles of the tick Amblyomma americanum (L.) (Acarina: Ixodidae; nymphal stage) were studied by means of scanning and transmission electron microscopy. All sensilla are multi-innervated and have thick cuticular walls containing either an elaborate pore canal system or a single slit opening at the tip. These sensilla, often equipped with two mechanoreceptive dendrites attached to the bristle base, apparently serve a dual function: mechano- and chemoreception. The fine structure of each sensillum is similar to that of other arthropod setae except for the ciliary region of the dendrite. Instead of the common 9 double-tubules, the tick sensilla usually have 11 (“11+0”). Compared to insect or spider tarsal bristles, tick setae are less abundant but more complex in structure and of greater variety.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00339463
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrastructure of Haller's organ in the tick Amblyomma americanum (L.) (1972)
    Springer
    Cell & tissue research 124 (1972), S. 275-292 
    Details
    ISSN: 1432-0878
    Keywords: Sensory receptors ; Acarina ; Amblyomma americanum ; Haller's organ ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Das Hallersche Organ auf dem Tarsus der Zecke Amblyomma americanum (L.) (Acarina: Ixodidae; Nymphenstadium) wurde mit dem Durchstrahlungs- und Rasterelektronenmikroskop untersucht. Es besteht aus einer distalen Sensillengruppe, die in einer flachen „Wanne“ gelegen ist, und einer proximalen „Kapsel“, welche mehrere Sensillen einschließt. Alle sieben Sensillen der „Wanne“ (A1–A7) sind dickwandig und mehrfach innerviert (2–9 Neurone), jedoch können mindestens 3 verschiedene Typen unterschieden werden: A1 und A2 besitzen große Poren (〉1000 Å), die mit Pfropfen versehen sind, und sie sind zudem die einzigen Sensillen mit sich verzweigenden Dendriten; A3 und A5 sind durch eine radspeichenartige Anordnung der Cuticulawandung charakterisiert, ferner durch feine Poren (100–200 Å), welche die Speichen zentral durchziehen; A4, A6, und A7 zeigen kein Porensystem, doch wird eine einzelne Öffnung an der Spitze vermutet. Die „Kapsel“ enthält 7 dünnwandige, stumpf endigende Sensillen und mehrere nichtsensorische Cuticulavorsprünge. Alle Sensillen besitzen große „Pfropfporen“ in der Cuticulawandung und zahlreiche dendritische Verzweigungen mehrerer Neuronen (3–5) im Lumen. Drüsenmündungen wurden in der „Kapsel“ festgestellt, ihre Bedeutung wird diskutiert. Die Feinstruktur des Hallerschen Organs entspricht dem Postulat von Lees (1948), wonach die „Kapsel“ der Geruchsrezeption, die „Wanne“ der Feuchtigkeitsrezeption dienen soll.
    Notes: Summary Haller's organ on the tarsus of the tick Amblyomma americanum (L.) (Acarina: Ixodidae; nymphal stage) was studied by scanning and transmission electron microscopy. It consists of a distal bristle group, (the “anterior pit”), and a proximal “capsule” which encloses several sensilla. The seven sensilla of the anterior pit (A1–A7) are all thick-walled and multi-innervated (2–9 neurons), but at least three different types can be differentiated. Sensilla A1 and A2 possess large, plugged pores (〉1000 Å) and are the only sensilla with branching dendrites. A3 and A5 are characterized by a spoke-wheel arrangement of the cuticle wall and very fine pores (100–200 Å) penetrating the “spokes” centrally; A4, A6, and A7 do not exhibit any pore system but a single opening at the bristle tip is assumed. The capsule contains seven thin-walled, blunt-tipped sensilla, and several non-sensory cuticular projections (pleomorphs). All of these sensilla possess large “plugged” pores in the cuticle wall and numerous dendritic branches of several neurons (3–5) in the lumen. Glandular openings were found inside the capsule; their significance is discussed. The fine structure of Haller's organ supports the functions postulated by Lees (1948), namely olfaction for the capsule and humidity reception (among others) for the anterior pit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00355031
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  • 5
    Electronic Resource
    Electronic Resource
    The ultrastructure of the skin of Tilapia mossambica (Peters) (1974)
    Springer
    Cell & tissue research 154 (1974), S. 251-264 
    Details
    ISSN: 1432-0878
    Keywords: Skin ; Tilapia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the skin of Tilapia mossambica (Peters) is described. In certain areas the epidermal surface forms so-called Epidermal Surface Patterns. Two types of epidermal cells are distinguished and their differences noted. The epidermal surface is covered by a layer of acid mucopolysaccharide, yet the contents of the mucus cells did not react with ruthenium red. The dermis consists mainly of bundles of collagen fibres and associated fibroblasts, but melanophores, iridophores and complex melano-iridophores are also present. Aspects of the development and structure of the guanine platelets and the melanosomes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223167
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  • 6
    Electronic Resource
    Electronic Resource
    The structure of some bivalve shell carbonates prepared by ion-beam thinning (1972)
    Springer
    Calcified tissue international 10 (1972), S. 38-48 
    Details
    ISSN: 1432-0827
    Keywords: Bivalve ; Molluse ; Shell ; Carbonates ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La technique du bombardement à l'aide d'ion d'argon est utilisée pour réduire l'épaisseur de la coquille de carbonate de calcium des bivalvesMytilus etMercenaria pour examen au microscope électronique par transmission et en diffraction électronique; une comparaison est réalisée à l'aide de répliques simples, servant de témoins. Les résultats obtenus confirment les études antérieures de répliques et de microscopie par balayage. De plus, une structure “aérée” est mise en évidence dans la coquille des aragonites, et surtout dans le nacre deMytilus. Cette structure est interprêtée comme un artefact induit par la chaleur, formé par l'inclusion d'eau et de matériel organique, interprétation qui concorde avec les études chimiques et de microscopie électronique.
    Abstract: Zusammenfassung Die Beschießung mit Argonionen wurde angewendet, um die Dicke von Calciumcarbonat-Schalen der zweischaligen MuschelnMytilus undMercenaria zu reduzieren. Diese Technik erlaubte die Ausführung von Transmissions-Elektronenmikroskopie und Elektronendiffraktion, wobei gleiche Proben nach einer bereits bestehenden Methode vorbereitet und als Kontrollen herangezogen wurden. Es wurden zusätzliche Resultate zu den Muschelstruktur-studien erhalten, welche früher publizierte Arbeiten unterstützen, die mit der Abklatschmethode und der Raster-Elektronenmikroskopie ausgeführt worden waren. Zusätzlich wurde eine „schaumartige” Struktur der Muschelaragoniten, besonders im Perlmutter vonMytilus, beobachtet. Da es sich um ein durch Hitze verursachtes Artefakt handelt, wird diese Struktur als Einschlüsse von Wasser und organischem Material interpretiert, was den Befunden von verschiedenen veröffentlichten chemischen und elektronenmikroskopischen Arbeiten entspricht.
    Notes: Abstract Use is made of the argon ion-bombardment technique to reduce the thickness of calcium carbonate shells of the bivalvesMytilus andMercenaria for transmission electron microscopy and electron diffraction, with comparison of single-stage replicas of similar specimens serving as controls. As an additional approach to shell structure studies, it gives results which support earlier published work with both replicas and scanning microscopy. In addition, a “frothy” structure is detected in the shell aragonites, especially inMytilus nacre. As a heat-induced artifact, it is interpreted as representing trapped water and organic material inclusions, an interpretation consistent with several published chemical and electron microscope studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012534
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  • 7
    Electronic Resource
    Electronic Resource
    Studies in prebiotic synthesis. VII (1972)
    Springer
    Journal of molecular evolution 1 (1972), S. 249-257 
    Details
    ISSN: 1432-1432
    Keywords: Prebiotic ; Nucleosides ; Dry-phase ; Seawater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The purine nucleosides (adenosine, guanosine, inosine, xanthosine) are formed when the corresponding purine bases and D-ribose are heated together in the presence of certain salts and minerals. The salts remaining after the evaporation of seawater are particularly effective in these syntheses. The relevance of these reactions for prebiological evolution is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01660244
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  • 8
    Electronic Resource
    Electronic Resource
    On the possible role of crystals in the origins of life (1974)
    Springer
    Journal of molecular evolution 3 (1974), S. 141-150 
    Details
    ISSN: 1432-1432
    Keywords: Adsorption ; Clay ; Montmorillonite ; Phosphoramidates ; Polymerization ; Prebiotic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nucleoside phosphoramidates derived from polyamines containing at least three amine groups are strongly adsorbed by sodium and magnesium montmorillonite clays even from very dilute solutions. Heating the dried clay-phosphoramidate mixture results in the production of small amounts of the dinucleotides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01796559
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  • 9
    Electronic Resource
    Electronic Resource
    Catalysts for the self-polymerization of adenosine cyclic 2′,3′-phosphate (1973)
    Springer
    Journal of molecular evolution 2 (1973), S. 303-316 
    Details
    ISSN: 1432-1432
    Keywords: Polymerization ; Phosphorylation ; Adenosine Cyclic 2′,3′-phosphate ; Oligonucleotides ; Amines ; 2-Aminoethanol ; Amino Acids ; Prebiotic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When adenosine cyclic 2′,3′-phosphate is evaporated from solution in the presence of simple catalysts such as aliphatic diamines at alkaline pH, and maintained in a dry state at moderate temperatures (25-85°C), self-polymerization to give oligonucleotides of chainlength up to at least 6 is observed. The products contain an excess of [3′→5′]-linkages over [2′→5′]-linkages. The effects of different catalysts and reaction conditions on the efficiency of the reaction are described. The prebiological relevance of these reactions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01654098
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  • 10
    Electronic Resource
    Electronic Resource
    The possible role of inorganic thiophosphate as a prebiotic phosphorylating agent (1974)
    Springer
    Journal of molecular evolution 3 (1974), S. 317-321 
    Details
    ISSN: 1432-1432
    Keywords: Thiophosphate ; Thymidine ; Phosphorylation of Nucleosides ; Prebiotic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It is proposed that inorganic thiophosphate was a versatile and highly reactive constituent of the primitive earth. Some of the ramifications of this assumption with regard to prebiotic chemistry stem from the dual nature of thiophosphate as the most superior nucleophilic agent and an energy rich phosphate. The Michael addition of thiophosphate to acrylonitrile yieldsS-cyanoethylphosphorothioate in high yield. This compound in turn can be used to phosphorylate 2′-deoxythymidine in organic solvents and in the solid state. A mixture of 5′ and 3′-dTMP were identified via chromatography, elementary analysis and NMR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01796047
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