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  • 1
    Electronic Resource
    Electronic Resource
    Chloroplast DNA reassociation and grass phylogeny (1991)
    Springer
    Plant systematics and evolution 176 (1991), S. 21-31 
    Details
    ISSN: 1615-6110
    Keywords: Angiosperms ; Poaceae ; Systematics ; phylogeny ; chloroplast DNA reassociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sequence variation in chloroplast DNA (cpDNA) as measured by DNA reassociation was examined in 12 grass species to address systematic problems in thePoaceae at the subfamilial and tribal levels. Two species,Petunia (Solanaceae) andGlycine (Leguminosae), were included to determine degrees of sequence divergence in cpDNA between monocots and dicots. The data were analyzed phenetically and phylogenetically. Species were segregated into four major groups that corresponded to the subfamiliesPooideae, Oryzoideae, Chloridoideae, andPanicoideae. Representatives of thePooideae andOryzoideae grouped together as did members of theChloridoideae andPanicoideae. ThePooideae split into two major groups corresponding to the recently recognized supertribesTriticanae andPoanae. Internodes between subfamily branches were short which might indicate a burst of divergence in the family early in its evolution. Sequence similarity values between the monocot grass species and the two dicot taxa ranged from 0.15 to 0.27, representing the highly conserved sequences of the chloroplast genome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00937943
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  • 2
    Electronic Resource
    Electronic Resource
    Screening pigment granule formation in Eumesosoma roeweri (Arachnida: Opiliones) (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 203 (1990), S. 211-217 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A unique pathway that utilizes endoplasmic reticulum (ER) networks is proposed for screening pigment granule formation in the retina of adult Eumesosoma roeweri. Smooth endoplasmic reticulum (SER) functions to transport pigment particles to the formative site. Each site is composed of concentric, interconnected rings of SER that are filled with dense-cored, spherical pigment particles. Formation of the screening pigment granule begins by the release of particles from the innermost rings of carrier SER. Continued release followed by fusion and condensation of the pigment particles results in the formation of a mature pigment granule.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052030208
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Why do spermatozoa of American marsupials form pairs? A clue from the analysis of sperm-pairing in the epididymis of the grey short-tailed opossum, Monodelphis domestica (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 236 (1993), S. 465-478 
    Details
    ISSN: 0003-276X
    Keywords: Spermatozoa ; Epididymis ; Grey short-tailed opossum ; Marsupial ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In order to understand the evolutionary significance of sperm-pairing in American marsupials, an ultrastructural investigation was made of this process in the South American grey short-tailed opossum, Monodelphis domestica. One epididymis from each animal (5) was fixed for light and electron microscopy and divided into 18 segments. The contralateral tract was divided into similar segments and assessments made of the total number of spermatozoa and the proportion of sperm-pairs. The mean total sperm number was 4.20 ± 0.62 × 106/epididymis. Sperm-pairing commenced around segment 9 in the proximal corpus epididymidis and reached a maximum of 80% in the caudal sperm storage region of the duct. The sperm-pairing process was characterised by four stages. Spermatozoa exhibited parallel alignment as indicated by the positioning of identical cross-sections of sperm heads. This was followed by close apposition with acrosomal faces parallel rather than opposite. Rotation of the sperm heads around each other then apparently occurred as indicated by the morphological alignment of sections of paired sperm heads. Sperm-pairing was complete when the acrosomal faces were precisely aligned and joined. Misalignment and failure to pair was observed in about 20% of spermatozoa in the cauda epididymis. Such a complex sperm-pairing process may ensure that conjugated spermatozoa are precisely aligned so that flagella movement can be accurately coordinated for maximal progressive motility. © 1993 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092360307
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    Paper (German National Licenses)
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