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  • 1
    Electronic Resource
    Electronic Resource
    Tunic cords, glomerulocytes, and eosinophilic bodies in a styelid ascidian, Polyandrocarpa misakiensis (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 206 (1990), S. 197-210 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Some unusual specialized structures of the tunic and epidermis in Polyandrocarpa misakiensis were studied histologically, histochemically, and electron microscopically. The tunic is leathery, containing fibers. Dorsal epidermal cells show cytoplasmic bulges at their apical ends, suggesting formation of tunic by the epidermis. Both siphons are characterized by a well-developed velum. In the dorsal mantle, especially around the siphons, numerous elongate cord-like structures of the tunic (10-30 μm in diameter) extend into the hemocoel. Each tunic cord originates from the extra-epidermal tunic, ends distally in a spade-shaped swelling, and is covered by flattened epidermal cells. The tunic cords probably act as connectors between tunic and mantle. Glomerulocytes, a kind of blood cell, are distributed throughout the hemocoel. They are disc-shaped (12-13 μm in diameter, 3 μm thick), and are characterized by a concentric fiber structure in the cytoplasm. The intracellular fibers are similar to the tunic fibers both morphologically and histochemically. The glomerulocytes appear to be derived from epidermal cells; their differentiation occurs in all regions of the epidermis. The function of glomerulocytes is unknown. Small club-shaped bodies which are intensely eosinophilic are distributed here and there in the dorsal epidermis. These eosinophilic bodies are usually located individually in epidermal pockets, and are protruded into the hemocoel. The eosinophilic body is proteinaceous and PAS-positive; it may be a secretory product of the covering epidermis. No physiological role of the eosinophilic body is yet clear. During blasto-genesis, incipient tunic cords, glomerulocytes, and eosinophilic bodies appear almost simultaneously at a stage shortly before the opening of siphons.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052060206
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  • 2
    Electronic Resource
    Electronic Resource
    Relation of nucleolar structure and position to the cytoplasmic microtubule system in Dictyostelium (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 293-303 
    Details
    ISSN: 0886-1544
    Keywords: cell movement ; microtubule-organizing center ; nucleus ; rapid-freeze substitution ; immuno-fluorescence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The cytoplasmic microtubule system seems to influence the position and structure of nucleoli in Dictyostelium discoideum amoebae in several growing and migrating states. For example, nucleoli were usually excluded from the nuclear periphery near the microtubule-organizing center (MTOC) in all cases; and in migrating adherent cells, more than half the nucleoli were located opposite the MTOC. This localization was disrupted by nocodazole treatment, after which the nucleoli were largely dispersed except near the MTOC. More extensive effects of microtubules on nucleolar structure were seen in aggregating cells. In contrast to the normal oval structure in growing cells, nucleoli took on a different morphology: they protruded from the leading edge of nuclei and elongated to form nozzle-like structures. Analysis by rapid-freeze substitution and indirect immunofluorescence showed each nozzle surrounded by more than 10 microtubules; and in the presence of nocodazole, the microtubules shortened as expected and the nozzles disappeared. Between microtubules and the outer nuclear envelope, various-sized cross-bridges were seen. The implication that microtubules were associated with the nucleoli in aggregating cells was verified in vitro: nuclei isolated from growing cells contained the MTOC but few if any detectable microtubules; but nuclei from aggregating cells were surrounded by them. These data are consistent with the notion the microtubule system may help regulate the position and conformation of nucleoli during early development of Dictyostelium.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970180406
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  • 3
    Electronic Resource
    Electronic Resource
    The position of the microtubule-organizing center relative to the nucleus is independent of the direction of cell migration in dictyostelium discoideum (1988)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 9 (1988), S. 111-116 
    Details
    ISSN: 0886-1544
    Keywords: aggregation ; cell-cell adhesion ; chemotaxis ; electron microscopy ; microcomputer analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Dictyostelium amoebae can migrate in several different modes. We tested for correlations of the direction of cell locomotion with the relative positions of the nucleus and microtubule-organizing center (MTOC). Five cases were analyzed on electron micrographs with a microcomputer. Each mode of movement showed characteristic locations of the MTOC relative to the nucleus; however, they differed in the various cases. In randomly migrating interphase amoebae, the number of cells with the MTOC located behind the nucleus was twice as great as those with the MTOC located ahead of the nucleus. During chemotactic migration toward folic acid, cells with the MTOC behind the nucleus were more numerous, with a concomitant reduction of anterior MTOCs.When amoebae aggregated on agar plates, a posterior location of the MTOC was most strikingly favored, whereas in cells aggregating under submerged conditions, the MTOC was indifferently anterior or posterior to the nucleus. (It may be significant that EDTA-resistant cell-cell adhesion was fully expressed in the former cells, but weaker in the latter.) Finally, in the case of chemotactically migrating cells from dissociated pseudoplasmodia, which adhere by means of other molecules, the MTOC was consistently ahead of the nucleus. Thus the MTOC shows no necessary preferential position anterior or posterior to the nucleus; its position, rather, correlates with the type of migration and perhaps with the nature of cell-cell adhesion.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970090203
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  • 4
    Electronic Resource
    Electronic Resource
    Minute protrusions of the cuticle: Fine surface structures of the tunic in ascidians (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 204 (1990), S. 67-73 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fine structure of the cuticular surface of the tunic was studied by scanning and transmission electron microscopy in 25 species belonging to 9 families of ascidians. The cuticular surface is ornamented with numerous minute protrusions in some species, but not in others. The minute protrusions are usually papillate in shape, and less than ∼0.05 μm high (in some species of the families Polyclinidae and Polycitoridae), or ∼0.1 μm high (in all species of Botryllidae, all colonial species of Styelidae and one solitary species of Pyuridae). In Clavelina miniata (Polycitoridae), the tunic is provided with parallel ridges on the surface of which papillate protrusions are distributed. The minute protrusions of Halocynthia roretzi (Pyuridae) are irregularly shaped, giving an appearance of paving stones. No protrusions are found in the families Didemnidae, Cionidae, Perophoridae, and Ascidiidae, and in one solitary species of Styelidae. At least in some colonial species, the density of the minute protrusions is lower at the edge of the colony than elsewhere. It is very probable that minute protrusions are found shortly after the secretion of tunic, growing larger both in size and in number as the tunic becomes older.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052040108
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  • 5
    Electronic Resource
    Electronic Resource
    In vitro effect of a thymic epithelial culture supernate or thymosin fraction 5 on rabbit platelet aggregation and intracellular cyclic AMP levels (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 133 (1987), S. 499-506 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Supernates of thymic epithelial cell culture (STEC) strongly inhibit aggregation induced by addition of adenosine diphosphate (ADP: 1 μM) or thrombin (0.5 unit per ml) to washed platelet suspensions and accelerated the restoration from ADP-triggered aggregation. At the same time, STEC increased the level of platelet adenosine 3′,5′-cyclic monophosphate (cyclic AMP) in a dose-dependent manner. Depending on the concentration used, thymosin fraction 5 increased the level of intracellular cyclic AMP ranging between 5 and 100 μg per ml, as well as inhibiting ADP-induced platelet aggregation. The activities of both STEC and thymosin fraction 5 were found to act exclusively on cyclic AMP phosphodiesterase activity in platelets. In contrast the supernates from Chang, HeLa, or HCC-M cells did not affect platelet aggregation induced by ADP, but slightly increased the cyclic AMP level (Chang, HeLa). Within 2 min after the treatment with STEC, more than 50% of the maximum inhibitory activity on platelet aggregation and increases in intracellular cyclic AMP were observed. These activities disappeared following STEC treatment with pronase E. STEC activity was found predominantly in the 1,000-50,000-dalton fractions. These activities were not altered when STEC was treated by adenosine deaminase. The level of prostaglandin E (PGE) derivaties in STEC was about two times that found in the control culture medium. These data suggest that the biological activity of STEC in the platelets might be attributed to thymosinlike polypeptides and PGE1.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041330310
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  • 6
    Electronic Resource
    Electronic Resource
    An examination of the method of sizing the spermatozoa of the domestic fowl and duck with an electronic counter (1986)
    New York, NY : Wiley-Blackwell
    Gamete Research 13 (1986), S. 125-134 
    Details
    ISSN: 0148-7280
    Keywords: avian spermatozoa ; cell volume ; electronic counter ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Although many estimations have been made electronically of mammalian sperm volume, detailed investigations have not been reported for avian spermatozoa with an electronic counter. In the present study, sizing of spermatozoa of fowls and Muscovy and Pekin drakes was examined using a Coulter counter (model ZB). In our preliminary work on fowl sperm volumes, we found mono- or di-morphic distribution displays that were modified depending on the combination of amplification (AMP) and aperture current (APC). Therefore, methodology to estimate the fowl and drake sperm volume was examined. Dilution of semen had no effect on the dimorphic distribution pattern of the sperm volume. Density-gradient centrifugation did not separate two kind of particles in the semen in either continuous or discontinuous Percoll gradients; therefore, we varied settings of AMP and APC, and found that the most suitable settings for measuring sperm volumes of these birds are 1 for AMP and 8 for APC. With these settings, mean volumes of spermatozoa were 5.1 μm3 for fowls, 5.7 μm3 for Muscovy drakes, and 5.6 μm3 for Pekin drakes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120130205
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  • 7
    Electronic Resource
    Electronic Resource
    Metabolic basis for differential glutamine requirements of human leukemia cell lines (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 143 (1990), S. 150-153 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We compared the ability of human leukemia cell lines of various origins to grow in glutamine-deficient media. The growth of B lymphoblastoid cell lines, including promyelocytic HL-60, is highly dependent on glutamine, whereas T-cell lines are able to proliferate in glutamine-free media. Such glutamine dependency has a good inverse correlation with the activity of glutamine synthetase. Moreover, glutamine synthetase can be induced in glutamine-deficient media, especially in glutamine-independent cells. In HL-60 cells, glutamine deprivation results in the decrease of both ATP and dATP levels. The addition of adenine to the culture medium abolishes these changes without restoring cell growth, indicating that the effects of glutamine deprivation on cell growth cannot be fully explained by the perturbation of adenine nucleotide pools.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041430120
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  • 8
    Electronic Resource
    Electronic Resource
    Modulation of growth and differentiation in normal human keratinocytes by transforming growth factor-β (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 145 (1990), S. 95-101 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of transforming growth factor-type β 1(TGF-β) on the growth and differentiation of normal human skin keratinocytes cultured in serum-free medium was investigated. TGF-β markedly inhibited the growth of keratinocytes at the concentrations 〉2 ng/ml under low Ca2+ conditions (0.1 mM). Growth inhibition was accompanied by changes in cell functions related to proliferation. Remarkable inhibition of DNA synthesis was demonstrated by the decrease of [3H]thymidine incorporation. The decrease of [3H]thymidine incorporation was observed as early as 3 hr after addition of TGF-β. TGF-β also decreased c-myc messenger RNA (mRNA) expression 30 min after addition of TGF-β. This rapid reduction of c-myc mRNA expression by TGF-β treatment is possibly one of the main factors in the process of TGF-β-induced growth inhibition of human keratinocytes. Since growth inhibition and induction of differentiation are closely related in human keratinocytes, the growth-inhibitory effect of TGF-β under high Ca2+ conditions (1.8 mM Ca2+ differentiation-promoting culture environment) was examined. TGF-β inhibited the growth of keratinocytes under high Ca2+ conditions in the same manner as under low Ca2+ conditions, suggesting that it is a strong growth inhibitor in both low and high Ca2+ environments. The induction of keratinocyte differentiation was evaluated by measuring involucrin expression and cornified envelope formation: TGF-β at 20 ng/ml increased in-volucrin expression from 9.3% to 18.8% under high Ca2+ conditions, while it decreased involucrin expression from 7.0% to 3.3% under low Ca2+ conditions. Cornified envelope formation was modulated in a similar way by addition of TGF-β: TGF-β at 20 ng/ml decreased cornified envelope formation by 53% under low Ca2+ conditions, while it enhanced cornified envelope formation by 30.7% under high Ca2+ conditions. Thus, the effect of TGF-β on keratinocyte differentiation is Ca2+ dependent. It enhances differentiation of human keratinocytes under high Ca2+ conditions, but inhibits differentiation under low Ca2+ conditions. Taken together, there is a clear discrepancy between TGF-β effects on growth inhibition and induction of differentiation in human keratinocytes. These data indicate that growth inhibition of human keratinocytes by TGF-β is direct and not induced by differentiation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041450114
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  • 9
    Electronic Resource
    Electronic Resource
    Preface (1989)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 12 (1989), S. 179-179 
    Details
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060120302
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  • 10
    Electronic Resource
    Electronic Resource
    Detection of small displacement of atoms in crystals by atom resolution electron microscopy (1989)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 12 (1989), S. 180-200 
    Details
    ISSN: 0741-0581
    Keywords: Image processing ; Aberration-free focus ; Radiation damage ; In situ observation of atomic column ; Atoms around lattice imperfections ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Four kinds of works on the detection of displacement of atoms in crystals are shown. The irregular small displacement of atoms has been detected, with an accuracy of about 0.1 Å around dislocations and stacking faults in Au crystals as shown by their electron microscope images. The displacement of the atomic images is recorded by aberration-free focus (AFF). Even when the periodic displacement of atoms in SiC and TaS2 crystals is around 0.1% of the lattice constant, this displacement has been revealed as the weak-contrast anomaly in the images. Using in situ observations by a TV system attached to an electron microscope, the rapid movements of atoms that have taken place within 1/30 sec have been recorded. Using the technique of successive subtraction of the images by TV system and image sigma, only the images of moving atoms in Au crystal have been recorded each 1/10 sec.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060120303
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