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Comparative study of the partitioning of amphiphiles into membranes of various anhydrobiotic plants with drying
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Abstracts/Comparative Biochemist O, and Physiology. Part A 126 (2000) SI-SI63
COMPARATIVE STUDY OF THE PARTITIONING OF AMPHIPHILES MEMBRANES OF VARIOUS ANHYDROBIOTIC PLANTS WITH DRYING
INTO
Golovina E.A. and Hoekstra F.A. L a b . o f P l a n t P h y s i o l o g y , W a g e n i n g e n U n i v e r s i t y , A r b o r e t u m l a a n 4, 6 7 0 3 B D , W a g e n i n g e n , T h e Netherlands Partitioning of amphiphilic molecules from the cytoplasm into membranes with drying has been proposed as an alternative mechanism of membrane protection (Hoekstra et al., 1997). Partitioning of amphiphilic spin probe molecules into membranes during water loss has been demonstrated for cattail pollen using electron paramagnetic resonance (EPR) techniques, and the same phenomenon has been shown with respect to endogenous amphiphiles (Golovina et al., 1998). This partitioning may cause membrane disturbance, the consequences of which may range from signaling and changes in membrane permeability (Golovina et al., 1998, Hoekstra et al., 1999) to the prevention of dehydration-induced increases in the gel-to-liquid crystalline transition temperature of dry membranes (Hoekstra et al., 2000). Moreover, the insertion of amphiphilic antioxidants into membranes may help cells to survive in the dry state (Hoekstra et al., 1997). The effect of partitioned molecules could be dependent on their location in membranes. The purpose of this work was to study whether membrane properties themselves determine the location of the partitioned amphiphiles inside membranes. For such a purpose different anhydrobiotic plant systems were compared with desiccation-sensitive tissues. The location of the partitioned amphiphilic spin probe, TEMPONE, in membranes was determined by the analysis of its EPR spectra in dry samples. The properties of membranes in both the hydrated and dry state were studied by using the membrane spin probes 5-doxyl stearate (membrane surface) and 16-doxyl stearate (membrane core). We found a strong correlation between the fluidity of the membrane surface and the ability of small amphiphiles like TEMPONE to penetrate into the core of membranes. The role of membrane properties in partitioning and desiccation tolerance is discussed Golovina, E.A. et al. (1998) Plant Physiol. 118: 975-986; Hoekstra, F.A. et al. (1997) Comp. Biochem. Physiol. 117A: 335-341; Hoekstra, F.A. et al. (1999) Plant Cell Environ. 22:1121-1131; Hoekstra, F.A. and Golovina, E.A. (2000) In: Black, M., Bradford, K.J., Vasques-Ramos, J., Eds, Seed Biology: Advances and Applications. Oxon, CAB International pp 43-55
TRANSPORT OF EXOGENOUS ORGANIC SUBSTANCES BY INVERTEBRATE INTEGUMENTS: THE FIELD REVISITED G o m m e J. A u g u st K r o g h Institute, University of C o p e n h a g e n , D e n m a r k The notion that some marine or euryhaline invertebrates can use integumental uptake of organic compounds as a nutritional supplement dates back to the early part of the 20 ~hcentury. Research in this area progressed in several distinct steps, each influenced by the methodology available at the time, and by contemporary ideas in biology. This presentation will first provide a brief overview of a century's research within this area, as it relates to significant stages in the development of general animal physiology, and in particular to the role and mission of comparative physiology. Emphasis will be placed on changing paradigms, and on the interplay between this specialized, provincial area of investigation and the mainstream of physiological thought, The second part of the talk will summarize the present status of the field and - on the basis of recent data - challenge the general consensus achieved. Some questions to be asked are: To which extent does accumulative uptake of low-molecular organic solutes from natural waters reflect a specialized cellular machinery in epidermal cells and gill tissue, or are these phenomena rather an expression of general cellular properties? How can recent data pointing to an ultra-rapid turnover of some exogenous organic compounds (e.g. amino acids) be reconciled with the general concepts of secondary active transport and intracellular isosmotic regulation? What is the basis of the so-called salinity effect? Finally, a summary will be provided of recent data pointing towards an interaction between the transport of amino acids and a variety of inorganic ions and heavy metals. These data suggest that the nutritive, parental uptake of low-molecular organic compounds can be significantly influenced by metal ions in the environment, and also that the transport systems for the former compounds can act as vectors for metallic environmental contaminants.
Abstracts/Comparative Biochemist O, and Physiology. Part A 126 (2000) SI-SI63
COMPARATIVE STUDY OF THE PARTITIONING OF AMPHIPHILES MEMBRANES OF VARIOUS ANHYDROBIOTIC PLANTS WITH DRYING
INTO
Golovina E.A. and Hoekstra F.A. L a b . o f P l a n t P h y s i o l o g y , W a g e n i n g e n U n i v e r s i t y , A r b o r e t u m l a a n 4, 6 7 0 3 B D , W a g e n i n g e n , T h e Netherlands Partitioning of amphiphilic molecules from the cytoplasm into membranes with drying has been proposed as an alternative mechanism of membrane protection (Hoekstra et al., 1997). Partitioning of amphiphilic spin probe molecules into membranes during water loss has been demonstrated for cattail pollen using electron paramagnetic resonance (EPR) techniques, and the same phenomenon has been shown with respect to endogenous amphiphiles (Golovina et al., 1998). This partitioning may cause membrane disturbance, the consequences of which may range from signaling and changes in membrane permeability (Golovina et al., 1998, Hoekstra et al., 1999) to the prevention of dehydration-induced increases in the gel-to-liquid crystalline transition temperature of dry membranes (Hoekstra et al., 2000). Moreover, the insertion of amphiphilic antioxidants into membranes may help cells to survive in the dry state (Hoekstra et al., 1997). The effect of partitioned molecules could be dependent on their location in membranes. The purpose of this work was to study whether membrane properties themselves determine the location of the partitioned amphiphiles inside membranes. For such a purpose different anhydrobiotic plant systems were compared with desiccation-sensitive tissues. The location of the partitioned amphiphilic spin probe, TEMPONE, in membranes was determined by the analysis of its EPR spectra in dry samples. The properties of membranes in both the hydrated and dry state were studied by using the membrane spin probes 5-doxyl stearate (membrane surface) and 16-doxyl stearate (membrane core). We found a strong correlation between the fluidity of the membrane surface and the ability of small amphiphiles like TEMPONE to penetrate into the core of membranes. The role of membrane properties in partitioning and desiccation tolerance is discussed Golovina, E.A. et al. (1998) Plant Physiol. 118: 975-986; Hoekstra, F.A. et al. (1997) Comp. Biochem. Physiol. 117A: 335-341; Hoekstra, F.A. et al. (1999) Plant Cell Environ. 22:1121-1131; Hoekstra, F.A. and Golovina, E.A. (2000) In: Black, M., Bradford, K.J., Vasques-Ramos, J., Eds, Seed Biology: Advances and Applications. Oxon, CAB International pp 43-55
TRANSPORT OF EXOGENOUS ORGANIC SUBSTANCES BY INVERTEBRATE INTEGUMENTS: THE FIELD REVISITED G o m m e J. A u g u st K r o g h Institute, University of C o p e n h a g e n , D e n m a r k The notion that some marine or euryhaline invertebrates can use integumental uptake of organic compounds as a nutritional supplement dates back to the early part of the 20 ~hcentury. Research in this area progressed in several distinct steps, each influenced by the methodology available at the time, and by contemporary ideas in biology. This presentation will first provide a brief overview of a century's research within this area, as it relates to significant stages in the development of general animal physiology, and in particular to the role and mission of comparative physiology. Emphasis will be placed on changing paradigms, and on the interplay between this specialized, provincial area of investigation and the mainstream of physiological thought, The second part of the talk will summarize the present status of the field and - on the basis of recent data - challenge the general consensus achieved. Some questions to be asked are: To which extent does accumulative uptake of low-molecular organic solutes from natural waters reflect a specialized cellular machinery in epidermal cells and gill tissue, or are these phenomena rather an expression of general cellular properties? How can recent data pointing to an ultra-rapid turnover of some exogenous organic compounds (e.g. amino acids) be reconciled with the general concepts of secondary active transport and intracellular isosmotic regulation? What is the basis of the so-called salinity effect? Finally, a summary will be provided of recent data pointing towards an interaction between the transport of amino acids and a variety of inorganic ions and heavy metals. These data suggest that the nutritive, parental uptake of low-molecular organic compounds can be significantly influenced by metal ions in the environment, and also that the transport systems for the former compounds can act as vectors for metallic environmental contaminants.