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  • 1
    Electronic Resource
    Electronic Resource
    Untersuchungen an einer parasitischen Ameise (1955)
    Springer
    Insectes sociaux 2 (1955), S. 163-171 
    Details
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary 1. The male ofAnergates shows a reduction of some parts of the digestive system and the musculature of the skeleton. The volume of the brain is reduced by reduction of association centres. The anatomy of the female corresponds to a free-living species, only the stinging apparatus cannot be found. 2. During the reproductive phase a remarkable enlargement of all somatic cells takes place due to polyploidy with exception of the nervous system. To strengthen the exoskeleton the intersegmantal membranes are hardening. 3. As result of isolation ofAnergates certain analogies to regressive evolution of some cave animals are noted.
    Abstract: Résumé 1o Le mâle d'Anergates présente une réduction de la musculature squelettique et de quelques parties du tractus digestif. Le volume des ganglions cérébroïdes est diminué par suite de la réduction des centres d'association. L'anatomie de la femelle rappelle celle des femelles sauvages, à ceci près que l'aiguillon et ses annexes sont absents. 2o A part les cellules nerveuses, toutes les cellules somatiques de l'image subissent une croissance remarquable à cause de leur polyploïdie. Les membranes intersegmentales se durcissent et renforcent l'exosquelette. 3o Eu égard à l'isolement d'Anergates, on peut constater certaines analogies entre les phénomènes régressifs qu'il présente et ceux rencontrés chez des animaux cavernicoles.
    Notes: Zusammenfassung 1. Beim ♂ vonAnergates ist neben Teilen des Darmtraktes besonders die Skelettmuskulatur zurückgebildet. Das Gehirnvolumen wurde auf Kosten der assoziativen Zentren herabgesetzt. Der Bau des ♀ entspricht dem einer freilebenden Art, lediglich der Stachelapparat ist nicht mehr nachweisbar. 2. Postimaginal findet beim ♀ eine auffallende Vergrößerung aller Somazellen statt, für die — mit Ausnahme des Nervensystems — Polyploidisierungsvorgänge verantwortlich sind. Zur Festigung des Exoskeletts verhärten die Intersegmentalhäute. 3. Als Folge der Isolierung vonAnergates sind gewisse Analogien zur regressiven Evolution mancher Höhlentiere festzustellen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02224101
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  • 2
    Electronic Resource
    Electronic Resource
    Bemerkungen über den Du Bois-Reymond'schen Mittelwerthsatz (1873)
    Springer
    Mathematische Annalen 6 (1873), S. 313-318 
    Details
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01442787
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  • 3
    Electronic Resource
    Electronic Resource
    Notiz über zwei in der Wärmetheorie auftretende bestimmte Integrale (1870)
    Springer
    Mathematische Annalen 3 (1870), S. 157-160 
    Details
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01443910
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  • 4
    Electronic Resource
    Electronic Resource
    A specific chromosome element, the telomere of Drosophila polytene chromosomes (1968)
    Springer
    Chromosoma 25 (1968), S. 184-197 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The submicroscopic organization of terminal chromosome regions of Drosophila hydei polytene chromosomes is described. A compact region composed of tightly packed fibrils of 100 to 125 Å diameter embedded in an amorphous material is located at each of the chromosome ends of the 5 long chromosome arms. From this compact region, sometimes containing cavities, fibrils extend onto the nearest normal band region. The diameter of the extending fibrils is 100–125 Å, 200–250 Å or 400 Å. Pronase digestion of fixed and squashed chromosomes reduced the electron density of the amorphous matrix in the compact regions but failed to affect the diameter of the fibrils. The extending fibrils, however, showed a decrease in diameter after pronase digestion. The most frequently observed diameter values were 100–125 Å. — The volume of the terminal structures, including the compact region as well as the extending fibrils, is characteristically different for the various elements of the karyotype. Chromosome 2 displays the largest terminal structure, whereas chromosome 4 only occasionally shows the presence of compact regions. — End to end association of the long chromosome arms involves the fusion of the compact terminal structures. The non-random distribution of end to end association seems to be correlated with the volume of the terminal structures. Chromosome 2 which contains the largest compact terminal region is more frequently involved in end to end associations than any other chromosome arm. — The terminal regions show replication of DNA. They belong to the group of regions which display a discontinuous labeling pattern along the chromosomes, representing a late phase of the replication cycle. — The unique structural organization of the terminal chromosome regions, which is never observed at any other location of the genome supports the idea that they are morphological manifestations of the postulated telomeres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327177
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  • 5
    Electronic Resource
    Electronic Resource
    Differentiation of the synaptonemal complex and the kinetochore in Locusta spermatocytes studied by whole mount electron microscopy (1973)
    Springer
    Chromosoma 44 (1973), S. 231-253 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract When Locusta migratoria spermatocytes are surface-spread on various salines, the axial element of leptotene and zygotene chromosomes, and the synaptonemal complex of pachytene chromosomes are well-preserved, although, in most instances, virtually denuded of chromatin. A complex association of chromosome ends with the nuclear membrane is apparent as early as leptotene, and, as pairing is initiated, the nuclear attachment points of the partner half-bivalents fuse, apparently incorporating additional membrane material between them. The meiotic kinetochore originates in association with the axial element during early prophase, and prior to synaptonemal complex formation and chromosome condensation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00329119
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  • 6
    Electronic Resource
    Electronic Resource
    The formation of polytene chromosomes during macronuclear development of the hypotrichous ciliate Stylonychia mytilus (1981)
    Springer
    Chromosoma 82 (1981), S. 309-314 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The formation of polytene chromosomes during macronuclear development of the ciliate Stylonychia mytilus was examined in spread electron microscopical preparations. The chromatin organization of early macronuclear anlagen closely resembles the organization of micronuclear chromatin. In the course of polytenization 300 Å chromatin fibers become organized in loop-like structures laterally attached to a thinner axial fiber. It is suggested that this reorganization of chromatin during polytenization is a necessary event for the subsequent chromatin elimination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286113
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  • 7
    Electronic Resource
    Electronic Resource
    Differentiation of the Oral Field of the Sea Urchin Embryo (1964)
    [s.l.] : Nature Publishing Group
    Nature 201 (1964), S. 315-315 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1. Psammechinus miliaris, 16 h gastrula, 2 cells of the oral field. n, nucleus; m, mitochondrium; y, yolk sphere. The arrows indicate the elongated tips of the inner surface of the cells, (× c. 11,700) Examining thin sections of 16-h gastrulse of Psammech-inus miliaris in search of specific ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/201315a0
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  • 8
    Electronic Resource
    Electronic Resource
    Phasenspezifische Funktionsstrukturen in Spermatocytenkernen von Drosophila melanogaster und Ihre Abhängigkeit vom Y-Chromosom (1961)
    Springer
    Chromosoma 12 (1961), S. 676-716 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Morphological manifestations of the chromosomal metabolism have been found in the first spermatocyte nucleus of Drosophila melanogaster. These “metabolic structures” include several types of well defined components, among which the „tubuli“ and the „reticular elements“ are most conspicuous. The metabolic nature of these elements follows from their phase specifity and from cytochemical data. 2. Masses of tubuli of 300–400 Å diameter are found all over the meiotic prophase chromosomes in the spermatocyte nucleus, but not in the spermatogonial nucleus. The reticular elements appear somewhat later and usually form a single group. Both types of metabolic structures are decomposed during diakinesis when they separate from the chromosomes. 3. The tubuli are mainly composed of a basic protein. In addition they seem to contain RNA. The presence of DNA in small concentration can not yet be excluded. 4. The chromosomal origin of the tubular as well as the reticular elements follows not only from the observed contact with the chromosomes but also from the fact that spermatocyte nuclei of X/O-males of Drosophila melanogaster do not contain these components. This shows that the Y-chromosome is involved. 5. The role of the Y-chromosome in the formation of the metabolic structures has been further elucidated by studying males with partial Y-chromosomes, such as YS, YL, and Y″. Spermatocytes with the long arm of the Y (X/YLc) as a rule contain tubular and reticular elements in nearly normal quantity. X/YS and X/Y″ testes show a highly variable pattern. Some spermatocyte nuclei resemble the X/O-type while the rest represent all intermediate stages between the X/O- and the X/YL-type. 6. The lack of tubuli in X/O or in X/YS and X/YL spermatocyte nuclei is always correlated with the appearance of crystal needles in the nucleus as well as in the cytoplasm. Only very rarely in X/YS spermatocytes is an intranuclear crystal found together with a small amount of tubuli. The X/O crystal needles persist during spermatogenesis and are still found in sperm bundles. The crystal material seems to be a protein which is different from the tubular protein. 7. The possibilities of the involvement of the Y-chromosome in the formation of the metabolic chromosomal structures are discussed. It seems probable that tubuli represent a highly modified state of the Y-chromosome, or parts of this chromosome. The formation of protein crystals in X/O-spermatocytes indicates the presence of a biochemical block. The relation to fertility i.e. sperm motility is unclear. X/YL males do not produce motile sperms although tubuli are regularly present in spermatocyte nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328946
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  • 9
    Electronic Resource
    Electronic Resource
    Characterisation of male meiotic-sterile mutations in Drosophila melanogaster (1977)
    Springer
    Chromosoma 64 (1977), S. 371-392 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Male meiotic sterile mutations were selected among X-linked male—steriles by detection of micronuclei in early spermatids. Despite severe defects in the 1st or 2nd meiotic spindles in all mutants, no effect on mitosis was observed. Various features of spindle structure, chromosome segregation, and centriole movements were compared in seven meiotic steriles and in XO males. Chromosome behaviour and centriole movement were always affected concomitantly, and were both shown to be genetically independent of “centre” formation in the meiotic spindles. Precocious and delayed centromere separation was observed in the various mutants in both divisions, and similarly attributed to basic spindle lesions rather than chromosome defects. Attachment of the centriole body to the membrane of the spermatid nucleus was normal only in mutants where second division nuclei were formed. The role of the centriole body was shown to be independent of membrane attachment.—The phenomena observed in this study were discussed mainly with regard to genetic interdependence of morphogenetic processes during male meiosis. A common base for the pleiotropic defects of meiotic steriles and XO males is suggested, and the genetic control of meiosis is re-evaluated in the light of comparison with fertile meiotic mutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294944
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  • 10
    Electronic Resource
    Electronic Resource
    Accessory nuclei (nuclear membrane balloons) in the oocytes of the dipteran Phryne (1979)
    Springer
    Chromosoma 75 (1979), S. 89-99 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract True accessory nuclei with the characteristic “double” membrane structure have been observed in the oocytes of the dipterans (Nematocera) Phryne cincta and P. fenestralis. They seem to arise from proliferations of the nuclear membrane. Although they often cling to the nucleus after their formation, they differ from it in certain structural details; their inner membranes are less electron-dense, and they have a greater frequency of pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330627
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