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  • 1
    Electronic Resource
    Electronic Resource
    Structural changes of excitable membrane formed on the surface of protoplasmic drops isolated fromNitella (1974)
    Springer
    The journal of membrane biology 18 (1974), S. 177-186 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The protoplasmic drop isolated fromNitella became electrically excitable in an appropriate salt solution. Variations of salt composition and temperature in the external media induced discrete changes in the interfacial properties such as refractive index or surface tension, as well as in the electrical properties of the protoplasmic drop. Variation of salt composition was performed by changing the concentration of the respective component at a time from the original test solution (0.5mm NaCl, 0.5mm KNO3, 1mm Ca(NO3)2, and 2mm Mg(NO3)2) with other components being fixed. The following results were obtained: (1) An increase of concentration of univalent cation (Na+ or K+) induced a sharp rise of the refractive index from 1.42 to 1.58 at about 10mm, which was accompanied by a discrete depolarization of the membrane potential of the drop. Fluctuation of reflected light was observed at the critical concentration. (2) The refractive index remained at low values of about 1.42 in Ca2+ concentration ranging between about 0.1 and 10mm. Beyond this concentration range of Ca2+, i.e., both lower and higher, the refractive index increased discontinuously to the value of about 1.58. (3) An addition of multi-valued cations in the test solution led to an abrupt depolarization of the membrane potential at a definite concentration for each ion species. The critical salt concentration dependent strongly on thevalence of cations added, and gave the following series: Th4+〈La3+〈Ba2+, Sr2+〈Na+. (4) Lowering of the surrounding temperature induced an abrupt depolarization of the membrane potential when the Ca2+ concentration in the external solution was close to the lower critical concentration, i.e. 0.1mm. (5) A rise in temperature led to an increase of fluctuations of the membrane potential with frequent outbreaks of small spike potentials, which were followed by an abrupt depolarization. At the same time the tension at the surface decreased discontinuously from 10−1 dynes/cm to the order of 10−4 dynes/cm. All these changes were reversible. These results imply that the surface membrane of the protoplasmic drop is liable to change its structure in response to the variation of temperature, salt composition in the external media and/or electrical stimulus. Drastic variations of membrane properties such as surface tension, membrane potential and membrane resistance are discussed in connection with the structural change determined by the refractive index measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870110
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrophobicity of biosurfaces as shown by chemoreceptive Thresholds inTetrahymena, Physarum andNitella (1977)
    Springer
    The journal of membrane biology 34 (1977), S. 351-368 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Responses (chemotaxis and changes in membrane potential) ofTetrahymena, Physarum, andNitella against aqueous solution of homologous series ofn-alcohols,n-aldehydes andn-fatty acids were studied for clarifying the hydrophobic character of chemoreceptive membranes. Results were: (1) All organisms studied responded to homologous compounds examined when the concentration of these chemicals exceeded their respective threshold,C th , and the response,R, were expressed approximately asR=α log (C/C th ) forC〉C th , (2) Increase of the length of hydrocarbon chain in homologues decreasedC th . Plots of logC th against the number of carbon atoms,n, inn-alcohols,n-aldehydes andn-fatty acids showed linear relationships as represented by logC th =−An+B. A andB are positive constants for respective functional end groups of the chemicals and biological membranes used. The above empirical equation was interpreted in terms of the partition equilibrium of methylene groups between bulk solution and membrane phase. ParameterA was shown to be a measure of hydrophobicity of the membrane, andB represented the sensitivity of chemoreception of the membrane. (3) Thresholds,C th , for various hydrophobic reagents were compared with those of human olfactory reception,T. Plots of logT against logC th fell on straight lines for respective organisms with different slopes which were proportional to parameterA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870308
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of sugars on salt reception in true slime moldPhysarum polycephalum (1977)
    Springer
    The journal of membrane biology 34 (1977), S. 369-381 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Interaction between salt and sugar receptions in plasmodium ofPhysarum polycephalum was studied by using double-chamber method. Effect of sugars on salt reception was evaluated by measuring membrane potential and the motive force of tactic movement of the slime mold, where salt concentration in one compartment was increased successively with a fixed sugar concentration. Results are summarized as follows: (1) The presence ofd-glucose,d-mannose,d-maltose, or sucrose in medium led to increase of the threshold concentration,C th , for salts (chlorides and nitrates of Li, Na, K), whereasd-ribose decreased the threshold for salt reception.d-galactose showed no appreciable effect onC th of every salt species examined. No change inC th for salt reception was observed until concentration of sugars exceeded their respective thresholds. (2) Double logarithmic plots ofC th for salts against sugar concentration followed different straight lines for different cations, whose slopes being closely correlated with the effects of lyotropic number of anions in the absence of sugars. (3) Plots of logC th against the reciprocal of the absolute temperature, 1/T, gave linear relations, and the slopes of the straight line became small with increase of sugar concentration above their respective thresholds. Experimental results obtained here suggest that the structure of water at the interface of cell membrane plays an indispensable role in the interaction between salt and sugar receptions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870309
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  • 4
    Electronic Resource
    Electronic Resource
    Response ofNitella internodal cell to chemical stimulation (1975)
    Springer
    The journal of membrane biology 25 (1975), S. 271-284 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Electrical response of excitable internodal cell ofNitella was studied by applying various kinds of odorants to the cell. Changes in membrane potential and resistance during responses induced by odorants were measured intracellularly under a variety of ionic environments in the media. Results were: 1) Some odorants (coumarin, isoamylacetate, methylacetate, 1-octanol, 1-butanol, 1-propanol) produced an all-or-nothing type action potential when the concentration of odorant exceeded a certain threshold. The action depended on the odorant concentration,C. Other odorants (heptanoic acid, β-ionon) induced gradual depolarization of the membrane potential without evoking an action potential. 2) Membrane resistanceR m changed in various ways during depolarization: some odorants led to a temporal or gradual decrease inR m, and others caused an increase inR m when the membrane potential was depolarized by the application of odorants. 3) Magnitude of response to odorantsOR was found to be represented by the following equation: $$OR = (\alpha + \beta \sqrt 1 )\log (C/C_{th} ) for C \geqq C_{th} $$ where α and β are constants for a given odorant,I the ionic strength in the medium, andC th the threshold concentration of the odorant. 4) Plots of olfactory threshold of human and of internodal cell ofNitella gave a straight line having slope unity. 5) Local application of odorants on the internodal cell induced impulses which transmitted from the part treated by odorants to the other portion. Physico-chemical and physiological implications of the results obtained were discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868579
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  • 5
    Electronic Resource
    Electronic Resource
    Effective fixed charge density governing membrane phenomena. VI. Activity coefficients and mobilities of small ions in aqueous solutions of poly(styrenesulfonic acid) (1973)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 77 (1973), S. 2995-2998 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100643a013
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  • 6
    Electronic Resource
    Electronic Resource
    Olfactory response in excitable protoplasmic droplet and internodal cell of Nitella (1975)
    [s.l.] : Nature Publishing Group
    Nature 253 (1975), S. 629-631 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] An internodal cell of Nitella flexilis, immersed in a solution containing 0.5 mM CaCl2 and 300 mM mannitol with no univalent cation species, has a resting potential of about - lOOmV and an action potential of 50-60 mV (about 30s long) after electrical stimulation. The excitable protoplasmic droplet ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/253629a0
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  • 7
    Electronic Resource
    Electronic Resource
    Two steady states in membrane potential deflection in relation to chemoreception and chemotaxis byPhysarum polycephalum (1985)
    Springer
    Protoplasma 124 (1985), S. 219-223 
    Details
    ISSN: 1615-6102
    Keywords: Chemoreception ; Chemotaxis ; Physarum polycephalum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the plasmodium ofPhysarum polycephalum application of various monovalent cation salts elicited either a depolarization or a hyperpolarization of the membrane potential. The hyperpolarization was restricted to phosphates and bicarbonates of large cations (Na+, Li+, NMe4 +, NEt4 +). More than 50 other combinations of cations (K+, Rb+, Cs+, NH4 +) and anions (Cl−, NO3 −, SO4 2−, acetate, lactate, citrate, etc.) induced the depolarization. In both cases the magnitude of the deflection in membrane potential (Δϕ) varied linearly with logarithm of concentration above the threshold Cth (∼10−4 M for all monovalent cation salts examined) according to the following equation: Δϕ=± R log (C/Cth). The value of R was 10–15 mV, and plus and minus signs correspond to depolarization and hyperpolarization, respectively. Depolarizing and hyperpolarizing agents competed with each other and exhibited a sharp transition between the two states of the membrane which were characterized by — R and R in the above equation or displayed a strong hysteresis, depending on which agents had first been applied to the plasmodial membrane. This transition in the membrane potential corresponded to the transition between positive and negative taxis at the behavioral level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290773
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  • 8
    Electronic Resource
    Electronic Resource
    Fragmentation of the plasmodium into equally sized pieces by low temperatures in the true slime moldPhysarum polycephalum: A new morphogenesis (1999)
    Springer
    Protoplasma 206 (1999), S. 131-136 
    Details
    ISSN: 1615-6102
    Keywords: Morphogenesis ; Cell size ; Thermal transition ; Plasmodium ; Physarum polycephalum ; Temperature compensation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We found a new type of morphogenesis in the plasmodia of the true slime moldPhysarum polycephalum: The plasmodium broke temporarily into pieces with uniform size at low temperatures. This fragmentation took place sharply around 5 h after the organism was transferred to low temperatures, and, unlike dormant spherulation, the fragments coalesced to recover the large plasmodium in about 15 h. Each fragment contained about 8 nuclei. The volume of the fragments remained constant under slight compression, but was halved under strong compression. The fragmentation showed a sharp temperature transition. The transition temperature was constant at 16 °C when plasmodia had been cultured above 16 °C, and decreased gradually as the culture temperature decreased below 16 °C. Both cycloheximide and actinomycin D inhibited the fragmentation in a dose-dependent manner, indicating that the transcription and protein synthesis took a part in the fragmentation. The tested strains with a high chemoreception sensitivity exhibited fragmentation similar to that of the strain with low sensitivity, but the transition temperature was lower. The biological significance of the fragmentation and its relationship with the other morphogenetic processes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279259
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  • 9
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    Design of an Injectable in Situ Gelation Biomaterials for Vitreous Substitute (2011)
    American Chemical Society
    Details
    Publication Date: 2011-11-14
    Print ISSN: 1525-7797
    Electronic ISSN: 1526-4602
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 10
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    Effective fixed charge density governing membrane phenomena. VI. Activity coefficients and mobilities of small ions in aqueous solutions of poly(styrenesulfonic acid) (1973)
    American Chemical Society
    Details
    Publication Date: 1973-12-01
    Print ISSN: 0022-3654
    Electronic ISSN: 1541-5740
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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