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  • Cell & Developmental Biology  (1,110)
  • General Chemistry  (1,050)
  • GEOPHYSICS  (823)
  • Humans  (431)
  • 1985-1989  (3,414)
  • 1988  (3,414)
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  • 1985-1989  (3,414)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 27 (1988), S. 311-320 
    ISSN: 1432-1432
    Keywords: Genome composition ; Coding sequences ; Isochores ; Humans ; Murids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The compositional distributions of coding sequences and DNA molecules (in the 50-100-kb range) are remarkably narrower in murids (rat and mouse) compared to humans (as well as to all other mammals explored so far). In murids, both distributions begin at higher and end at lower GC values. A comparison of homologous coding sequences from murids and humans revealed that their different compositional distributions are due to differences in GC levels in all three codon positions, particularly of genes located at both ends of the distribution. In turn, these differences are responsible for differences in both codon usage and amino acids. When GC levels at first+second codon positions and third codon positions, respectively, of murid genes are plotted against corresponding GC levels of homologous human genes, linear relationships (with very high correlation coefficients and slopes of about 0.78 and 0.60, respectively) are found. This indicates a conservation of the order of GC levels in homologous genes from humans and murids. (The same comparison for mouse and rat genes indicates a conservation of GC levels of homologous genes.) A similar linear relationship was observed when plotting GC levels of corresponding DNA fractions (as obtained by density gradient centrifugation in the presence of a sequence-specific ligand) from mouse and human. These findings indicate that orderly compositional changes affecting not only coding sequences but also noncoding sequences took place since the divergence of murids. Such directional fixations of mutations point to the existence of selective pressures affecting the genome as a whole.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 195 (1988), S. 45-58 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution of neutral red staining peripheral cell bodies along the nerve trunks of the thoracic median nervous system of the locust, Schistocerca gregaria, is described. Backfilling of the cells with cobalt chloride solution reveals that they are neurones with characteristic axonal processes that terminate in the neurohaemal areas of the median nerve. The neurones react with the dye acridine orange, indicating their neurosecretory nature. This is confirmed by their ultrastructural appearance at the electron microscope level. The distribution and staining properties of the cells are compared with those of peripheral neurones from other insects and the nature of their neurosecretory product is discussed.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 195 (1988), S. 83-93 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Numerous functional ergatoid replacement reproductives were found in one colony of Nasutitermes columbicus in Panama. Their morphology was mainly workerlike, although several imaginal characters such as the compound eyes and variable wing buds were more or less developed. The sex organs were fully mature and the fat body of the females, not of the males, was of the “royal” type. The development of the eyes was not accompanied by the differentiation of the optic lobes of the brain, nor was the presence of wing buds correlated with a development of the wing muscles.
    Additional Material: 8 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 195 (1988), S. 123-140 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The surface morphology of the anterior-to-posterior sequence of segment formation in embryos of a viviparous neotropical onychophoran and aspects of post-placental development seen using scanning electron microscopy are described. When all the segments have formed and the walking legs have completed their elongation, the body surface becomes covered with an embryonic cuticle that does not exhibit the hydrofuge properties seen in the adult cuticle. As soon as the walking legs have reached their full length, barbed projections are formed at their distal extremities. These projections are extensions of single cells and are covered by the embryonic cuticle. Transmission electron microscopy reveals that the cells at the distal ends of the legs and their projections have many pinocytotic vesicles at their surfaces. The cytoplasm of these cells and their projections is rich in mitochondria, rough endoplasmic reticulum, glycogen, and granules of storage material. There are minor differences in the surface morphology of the projections found at the ends of the walking legs in embryos of Peripatus acacioi and those of Peripatus biolleyi. The projections and the embryonic cuticle persist thoughout postplacental development. The role of the projections in the uptake of material by the embryo from the uterus is discussed and the possible phylogenetic significance of these projections is suggested.
    Additional Material: 46 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 195 (1988) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 195 (1988), S. 257-303 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The vertebral centra of Hiodon, Elops, and Albula are direct perichordal ossifications (autocentra) which enclose the arcocentra as in Amia. An inner ring of ovoid cells forms in late ontogeny from the intervertebral space inside the autocentrum. The chordacentrum is reduced or completely absent in centra of adult Elops, whereas it forms an important portion of the centra in adult Hiodon. The posterior portion of the compound ural centrum 3+4+5 is partially (Hiodon) or fully formed by the chordacentrum (Elops, Albula). The haemal arches and hypurals are fused medially by cartilage or bone trabecles of the arcocentrum with the centra, even though they appear autogenous in lateral view in Elops and Albula. The composition of the caudal skeleton of fossil teleosts and the ontogeny of that of Hiodon, Elops, and Albula corroborate a one-to-one relationship of ural centra with these dorsal and ventral elements. The first epural (epural 1) of Elops relates to ural centrum 1, whereas the first epural (epural 2) of Hiodon and Albula relates to ural centrum 2. In Albula, the first ural centrum is formed by ural centrum 2 only. With 4 uroneurals Hiodon has the highest number within recent teleosts. Juvenile specimens of Hiodon have eight, the highest number of hypurals within recent teleosts; this is the primitive condition by comparison with other teleosts and pholidophorids. Reduction of elements in the caudal skeleton is an advanced feature as seen within elopomorphs from Elops to Albula. Such reductions and fusions occur in osteoglossomorphs also, but the lack of epurals and uroneurals separates most osteoglossomorphs (except Hiodon) from all other teleosts.
    Additional Material: 28 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 195 (1988), S. 327-344 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fertilized egg and the two-cell stage and four-cell stage of the marsupial Antechinus stuartii were studied by transmission electron microscopy. The features that make the fertilized egg of Antechinus stuartii different from those of any eutherian mammal are (1) the presence of a shell and (2) the relatively large quantity and polarized distribution of cytoplasmic inclusions, including lipid, protein yolk bodies, and protein fibers. Mitochondria and vesicles of smooth endoplasmic reticulum are also polarized in distribution. Early cleavage differs from that of eutherians in several ways: (1) it occurs in the uterus; (2) there is extrusion of a large, single, membrane-bound yolk mass at first cleavage; and (3) blastomeres become separated after the second cleavage division and thus do not adhere by cell-to-cell contacts. Prior to the second division, blastomeres are connected to each other by remnants of the midbody and to the yolk mass by remnants of a cytoplasmic bridge. The yolk mass after extrusion is surrounded by plasma membrane and contains inclusions of lipid, protein yolk bodies, and fibers, as well as mitochondria and smooth endoplasmic reticulum. The blastomeres of the two-cell and four-cell stages also show intracellular polarization in the distribution of retained inclusions and organelles. Vesicles developing at the periphery of blastomeres and discharging their contents extracellularly increase in size and number from the fertilized egg to the four-cell stage. The discharged contents may be implicated in early development of the blastula cavity.
    Additional Material: 13 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 196 (1988), S. 15-22 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Morphology of branchial chloride cells in the freshwater teleosts Plecoglossus altivelis, Cyprinus carpio, and Oreochromis mossambicus was studied by light and transmission electron microscopy. The chloride cell has an apical membrane directly in contact with the outer medium. Generally, two or more neighboring chloride cells share an apical pit, forming a multicellular complex. The chloride cells form a multicellular complex in which cells differ in cytoplasmic electron density, development of tubular system, and in cell size. Chloride cells are linked by junctions which are shallower than the tight junctions that occur between neighboring pavement cells or between pavement and chloride cells. Multicellular complexes of chloride cells create additional paracellular pathways marked apically by the shallower junctions. Since junctional structure affects transepithelial permeability, development of multicellular complexes of chloride cells in freshwater fishes may be related to the transport of some substances as in the gills of marine fishes.
    Additional Material: 11 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 196 (1988), S. 23-31 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The nerve pathways in the praesoma are described for the first time for a member of the genus Octospinifer. Eleven nerves, five paired, and one single, are traced from the cerebral ganglion to their associations with the musculature of the body wall, neck sense organs, and the musculature of the proboscis wall and the invertor muscles of the proboscis. The structure and location of the Stützzelle (support cell) and its association with the neck sense organs are described. A comparison with the nervous system in the praesoma of Noechinorhynchus and Paulisentis is discussed.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 196 (1988) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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