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  • Cell & Developmental Biology  (10)
  • 1
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A fine structural analysis of the ovotestis in Aplysia was undertaken in order to analyze the site of action of the bag cell hormone. Five stages of oocyte development are described. Of particular interest is the fact that the yolk seems to be synthesized primarily by the granular endoplasmic reticulum. In addition, small muscle cells whose long, thin processes surround the follicle of the ovotestis have been pointed out. This paper suggests that bag cell extract has a direct action on these small muscle cells causing them to contract and thus expel oocytes from the ovotestis. The evidence for this suggestion is that (1) these muscle cells are the most obvious effector cells in the ovotestis, (2) there are no signs of neural innervation of these muscles, (3) the time course for the liberation of the oocytes is so short that any other method of oocyte release is unlikely, (4) there is no cytologic evidence for any other expulsion process except muscular contraction, and (5) the ripe oocytes are attached to other cells of the wall of the ovotestis only by very small, simple junctions, thus making them the most likely cells to be expelled by muscular contraction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Classical studies of the nervous system of the leech revealed that there were specific types of very large glial cells associated with various parts of the neuron. Recent microelectrode studies demonstrated that there was a low resistance to the flow charge from any one of these large glial cells to another. The present study describes a previously unreported type of glial cell, the glial cell of the fascicles. These cells, which resemble the glial cells of the connectives but are smaller, are found in the fascicles of axons that unite the connectives to the neuropil. Thus, these cells are located between the glial cells of the connectives on the one hand and the glial cells of the neuropil and packets on the other and must be taken into account in considerations of the low resistance to the transfer of charge from one glial cell to another.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Each statocyst in Apylsia californica contains 13 neurons. The statocyst nerve, which connects each statocyst to the cerebral ganglion, contains only the 13 axons of the statocyst neurons. The size of the statocyst, the number of neurons in the statocyst, and the average axonal diameter does not change even though the statocyst nerve lengthens greatly as the animal enlarges. A description of the statoconia and the supporting cells in this organ has been given. This prepazation may be useful for microelectrode studies designed to test whether the gap and cytoplasmic specializations that are used to identify active synapses, are necessary for all types of chemical synaptic transmission.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 231 (1991), S. 573-578 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The empirical and disector methods are unbiased sampling methods for determining numbers of neurons. The present study verifies and thus calibrates these methods by determining true numbers of ganglion cells in serial reconstructions and then using each method to estimate the same populations. The empirical method gives accurate counts but is laborious (inefficient). Five separate disector analyses, distinguished by height (h), were done for each ganglion. The findings are: (1) that the estimates are consistently low when h is minimal (reference and look-up sections are adjacent), but (2) the estimates are accurate when h is greater (one to four sections intervene between reference and look-up sections). We ascribe the difficulties with the first disector to “lost” or “invisible” caps. We emphasize that we would not have known of the problem unless we verified our counts. If there is suspicion that difficulties with profile recognition might occur, we recommend that serial sections of an appropriately chosen sample of tissue be prepared and 500-1,000 neurons (or, more generally, particles) be reconstructed. Then the method of choice can be used on the issue of choice to make certain of the necessary accuracy before proceeding with the main study.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 187 (1977), S. 281-289 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An electron dense material is found in the extracellular space of the nervous system of Aplysia, a marine mollusc whose ganglia are widely studied by neurobiologists. This material appears to consist of irregular electron-dense granules, with diameters of approximately 600 Å. This material is found between the glial cells that surround the neuronal perikarya. It is not found in other regions of the nervous system. Because it is found in the ganglion cell layer of the nervous system and because the neurons contain what may be the precursor of this substance, the electron-dense material is regarded as most probably being a neuronal product. The importance of this material is that it is one of the few examples of visible structure in the extracellular space of the nervous system.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 197 (1980), S. 297-303 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The present study suggests a mixture of buffered osmic acid and 1.5% potassium ferricyanide as a post-fixation to improve the fixation of neural tissue. This procedure results in an improved preservation of membranes as well as cytoplasm and cytoplasmic organelles. It is to be emphasized that the quality of the initial perfusion is the primary determinant of quality of the fixation, but the addition of 1.5% potassium ferricyanide to post-fixation fluid makes good fixation better and allows data to be gathered from otherwise unusable material.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 172 (1972), S. 489-498 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The large leech neurons known as Retzius cells contain substantial amounts of 5-hydroxytryptamine (5-HT) stored in granules. Previous studies show that these cells are able to make 5-HT from precursors. The present study, which is a combined chemical and autoradiographic analysis of these cells after the administration of radioactive 5-HT or 5-HTP, confirms that the cells make 5-HT from precursors. In addition, this study shows that the cells can acquire and store 5-HT when it is present in the environment. Thus, if 5-HT is available, these cells need not manufacture this compound from precursors. Furthermore, the newly acquired 5 HT seems to be stored in the granules that characterize these cells. Finally, this study shows that the Retzius acquire or make the 5-HT in vivo.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 194 (1979), S. 201-211 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The present study is concerned with the fine structure of the myelin sheath in rat and monkey spinal roots. Pictures are obtained that show that the intraperiod gap of the myelin sheath is continuous and opens into both the internal and external mesaxons, which in turn open into the periaxonal and endoneurial extracellular spaces. These results are compatible with the idea that the intraperiod gap is a cleft that traverses the thickness of the myelin sheath and links the periaxonal and endoneurial extracellular spaces.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 211 (1985), S. 213-217 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The present study correlates cell body and nucleolar sizes for dorsal root ganglion cells in the rat. To do this, we measured cell body areas and calculated their diameters and measured nucleolar diameters for 719 cells. These data indicate that there is a correlation in that increasing cell size is associated with increasing nucleolar size. However, there is considerable variability of cell body size for each nucleolar diameter and vice versa. Nevertheless, when nucleolar diameters are grouped, the function In D = 1.687 + 0.334 dr, where D is the diameter of the cell body and dr the rounded diameter of the nucleolus, produced an almost straight line. Thus this formula provides a good estimate of the relation of nucleolar and cell body sizes for dorsal root ganglion cells of the rat. In addition, estimates of the variances of cell body size at each nucleolar diameter are provided.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 232 (1992), S. 301-304 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The present study is a quantitative analysis of the unmyelinated fiber population in the fasciculus gracilis of the second cervical segment of cat and monkey. We find that unmyelinated fibers represent 13.7% of the total fiber population in this pathway in the cat and 18.9% in the monkey (Macaca fascicularis). The existence of such large numbers of these axons suggests that there may be a sizeable ascending fine primary afferent pathway in the fasciculus gracilis in cat and monkey whose destination is presumably the dorsal column nuclei. These findings are of interest in regard to classic ideas that the afferent fibers in the dorsal columns are large myelinated fibers that convey fine discriminative information to the dorsal column nuclei.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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