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  • Life and Medical Sciences  (4)
  • 1970-1974  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    The fine structure of the tegument of Tylocephalum metacestodes: With emphasis on a new type of microvilliThis research was supported in part by a grant (Contract 14-17-007-662G) from the Bureau of Commercial Fisheries, U.S. Department of the Interior, and in part by a grant from the NIH Institutional Biomedical Research Fund, University of Hawaii. (1970)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 130 (1970), S. 11-23 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Electron microscope studies on Tylocephalum metacestodes embedded in the tissues of the oyster, Crassostrea virginica, have revealed that the tegument of the larval tapeworm is comprised of an external and an internal level which are partially separated by a basal lamina and two layers of muscles. The outer tegumentary level is comprised of an anucleate, cytoplasmic syncytium in which are embedded large and small vesicles and mitochondria. Surfacial hooks are also embedded therein. The internal level is comprised of relatively large discrete cells including mitochondria, rough endoplasmic reticulum, and large and small vesicles. These cells are intermittently connected with the external level by cytoplasmic bridges.Arising from the external level are unusual microvilli each of which terminates as a spherical vesicle. The stem of each microvillus is covered by a unit membrane which is continuous with that overlaying the body surface. In addition, each microvillus includes an external layer of medium electron density, a medial layer of intense electron density, and a core of heterogenous, medium electron density. These structures may be intertwined and bundles can be observed at the light microscope level as fibril-like projections from the parasite's body surface. One of their possible functions may be to prevent intimate contact between the encapsulating fibers of host origin and the parasite's body surface. In addition, the contraction and distention of the circular muscles result in microvillar movement which may keep the surrounding host fluids, including those of nutritional importance to the parasite, in a state of flux thus hypothetically permitting more uniform uptake.The abundance of vesicles in the syncytial external level of the tegument appears to be characteristic of the more primitive marine cestodes belonging to the orders Trypanorhyncha and Lecanicephala.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051300104
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  • 2
    Electronic Resource
    Electronic Resource
    Lanthanum-induced alterations of cellular electrolytes in Ehrlich ascites tumor cells: A new view (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 80 (1972), S. 149-153 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have shown previously that Ehrlich ascites tumor cells maintained at room temperature under an oxygen atmosphere lose Na+, K+ and Cl- isosmotically when exposed to La+++ (0.1 to 1.0 mM). Concomitant with these changes there is an increase in the recorded membrane potential (increasing intracellular negativity). The present studies further characterize the effect of La+++ on electrolyte distribution. Ehrlich ascites tumor cells were maintained at 0.5° C to permit Na+ gain and K+ loss. The addition of 1 mM La+++ to low temperature cells induces rapid loss of Na+, K+ and Cl-. This net loss of cellular electrolytes occurs even in cells depleted of ATP content using 2-deoxyglucose (5 mM) and rotenone (10-6 M). Analysis of the appearance of tracer 22Na in the environment of cells preloaded with the radioisotope shows that La+++-induced changes in membrane permeability or in active ion transport mechanisms are not responsible for the dramatic loss of electrolytes from experimental cells. The electrolyte loss occurs only when the cells are resuspended mechanically during the washing procedure used to prepare the cells for electrolyte determination.We conclude that the results of La+++ interaction with Ehrlich ascites tumor cells are twofold. As we have previously reported, La+++ stabilizes and causes a hyperpolarization of the membrane potential. Secondly, La+++ predisposes the cell membrane to become highly permeable when subjected to mechanical stress.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040800116
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  • 3
    Electronic Resource
    Electronic Resource
    Lanthanum-Induced alterations in cellular electrolytes and membrane potential in ehrlich ascites tumor cells (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 79 (1972), S. 299-308 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have investigated the effect of varying La+3 concentrations (0.01 mM to 2.0 mM) on membrane potential and electrolyte composition of Ehrlich ascites tumor cells. La+3 concentrations less than 0.02 mM had no effect. Above 0.02 mM, La+3 induced concentration-dependent loss of electrolytes and water from the cells. At 1.0 mM the effect was maximal and resulted in an 87% reduction in cellular K+, 79% in Cl- and 21% in Na+ within 4.8 minutes. The Na+ loss occurred even in the face of an electrochemical potential gradient favoring Na+ entry. La+3 increased the recorded values of membrane potential; the magnitude of the effect was related to the external La+3 concentration, and was maximal at 1.0 mM. Studies using 140La showed that La+3 binds rapidly to the cell surface and does not enter the cells. The amount of La+3 bound to the cells was related to the external La+3 concentration by a sigmoidal curve and was maximal at about 1.0 mM. The bound La+3 could not be displaced by either added La+3 or Ca+2. Agents known to effect the integrity of the cell membrane, such as phospholipase C, neuraminidase, pronase and Hg+2 were tested for their ability to displace bound La+3. Only pronase displaced bound La+3, indicating that La+3 associates with cell protein. It is hypothesized that La+3 rapidly interacts with membrane protein causing alterations in membrane permeability and capacity to actively transport ions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040790215
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of multivalent cations on the membrane potential of the ehrlich ascites tumor cell (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 79 (1972), S. 117-125 
    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 di- and trivalent cations on the membrane potential of the Ehrlich ascites tumor cell has been investigated using micro-electrode techniques. In solutions free of multivalent cations the average membrane potential for 46 cells was 8.3 ± 0.5 mv (SE). However, the potentials were not stable and decayed with a half-time of about six seconds. Addition of Ca++ decreased the rate of decay and concomitantly increased the membrane potential. The magnitude of these effects was a function of the Ca++ concentration. At the optimum concentration (2 mM), the half-time of decay was increased to 12 seconds and the membrane potential was raised to 17.8 ± 1.7 mv (SE). The related alkaline-earth cations, Sr++, Ba++ and Mg++ had similar effects on both the stability and magnitude of the membrane potential. The effect of La+++, which was qualitatively similar to that of the divalent cations, was also concentration dependent. However, 100-fold lower concentrations were adequate to achieve comparable effects. Moreover, membrane potentials were stable for up to ten minutes in La+++-containing solutions. Variations in intracellular Cl- content induced by temperature changes were paralleled by changes in membrane potentials. However, the potentials were not those expected for a simple Cl- electrode.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040790114
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