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Effect of Anesthetics on Action Potential Propagation
150a
Sunday, February 28, 2016
Neuronal function depends on exquisite local regulation of a great variety of molecules and their interactions in the interstitial spaces. The timing and magnitude of interactions in the brain must depend on the hydraulic properties governing water and solute transfer across its matrix, but quantitative information on these properties has proved notoriously difficult to obtain, and uncertainties remain. Here, we adapt osmotic stress techniques to explore pressure-volume relationships and fluid-transfer parameters in brain tissue. Within 15-30 minutes of euthanasia, sets of brain tissue samples (12/brain, ~1g each) were obtained from pigs (n =11) and immersed in baths adjusted to colloidosmotic pressures of 3-219 mmHg with polyethyleneglycol Mw 8000. The samples’ water influx/efflux was measured gravimetrically as a function of time, normalized by weight. Initial flow rates were calculated from the first derivative, at time = 0, of second-degree polynomials fitted to the progress curves. Rates were linearly proportional to the bath’s pressure (r2 > 0.9). The hydraulic conductance calculated from the slope of fitted lines was 0.029 5 0.008ml/min/g/mmHg, and the hydration potential, calculated from the pressure at initial rate = 0, was 64 5 27 mmHg (means 5 SD, n = 11).The hydraulic conductance, but not the hydration potential, decreased significantly when the bath temperature was reduced from 37 to 4 C. Compared to heart and skin, brain conductance value was higher. Further, the changes in hydraulic parameters with temperature were distinct for each organ. These results illustrate a simple, ex vivo, quantitative approach to probe specific water-transfer parameters and their changes in the brain. They indicate organ-dependent differences in flow regulation and the hydraulic properties of extracellular matrices. 751-Pos Board B531 Solitary Electromechanical Pulses in Lobster Neurons Rima Budvytyte1, Alfredo Gonzalez-Perezl1, Lars D. Mosgaard1, Edgar Villagran-Vargas2, Andrew D. Jackson3, Thomas Heimburg1. 1 Niels Bohr Institute, Copenhagen, Denmark, 2Universidad Autonoma del Estado de Mexico, Toluca, Mexico, 3Niels Bohr International Academy, Copenhagen, Denmark. Investigations of nerve activity have been focused predominantly on electrical phenomena. It is to be expected that the state of the nerve cell depend not only on electrochemical potentials and the conjugated flux of ions but also on all other thermodynamic forces including variations in lateral pressure, resulting in changes of membrane area and thickness (1-2) and temperature, resulting in heat flux (3). While both mechanical and thermal signals are very small, they are found to be in phase with voltage changes. Such findings have led to the suggestion that the action potential may be related to electromechanical solitons traveling without dissipation (4). A condition for the existence of such a soliton is the existence of an order transition in the membrane from solid to liquid lightly below physiological temperature. Here, we present ultrasensitive AFM recordings of mechanical changes on the order of 0.2 - 1.2 nm in the giant axons of the lobster. Also, when stimulated at opposite ends of the same axon of lobster, colliding action potentials pass through one another and do not annihilate, as was shown in (5). These results are submitted in Physical Review Letters X (2015) and are not consistent with expectations from the established Hodkin-Huxley model. Findings are consistent with a mechanical interpretation of the nervous impulse. 1. Iwasa, K., and I. Tasaki. 1980. Biochem. Biophys. Research Comm. 95:1328-31. 2. Tasaki, I., K. Kusano, and M. Byrne. 1989. Biophys. J. 55:1033-40. 3. Ritchie, J. M., and R. D. Keynes. 1985. Quart. Rev. Biophys. 18:451-76. 4. Heimburg, T., and A. D. Jackson. 2005. Proc. Natl. Acad. Sci. USA 102:9790-95.
5. Gonzalez-Perez, A., R. Budvytyte, L. D. Mosgaard, S. Nissen, and T. Heimburg. 2014. Phys. Rev. X 4:031047. 752-Pos Board B532 Effect of Anesthetics on Action Potential Propagation Tian Wang, Henrike Sasse-Middelhoff, Lars Mosgaard, Thomas Heimburg. Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark. Local anesthesia has been attributed to the specific interaction of local anesthetics with (sodium) channel proteins, while the action of general anesthetics still remains unclear. However, already at the beginning of 20th century Meyer and Overton independently found that the critical anesthetic dose of anesthetics, regardless of their types, is linearly proportional to their solubility in olive oil. Based on this finding, in 2005 Heimburg and Jackson proposed that the action potential is a density pulse (soliton) propagating in biological membranes, which explains anesthesia by freezing point depression law that originates from van’t Hoff’s law. In this work, we conduct experiments on nerves from lobsters and earthworms to study the effect of anesthetics on compound action potential and action potential from a single neuron. The experimental data are then compared with the simulation results by solving the soliton equations in 1D cylindrical membrane with anesthetics inside the system. Anesthetics move the chain melting transition temperature of membranes far away from the physiological temperature, which requires a higher free energy to induce the phase transition, resulting in a higher stimulation voltage to reach the maximum amplitude of the action potential. 753-Pos Board B533 The Value of Encrypting Biophysical Data Peter S. Pennefather1, West Suhanic2. 1 Pharmaceutical Science, University of Toronto, Toronto, ON, Canada, 2 gDial Inc, Toronto, ON, Canada. We have shown how data quanta can be recorded as a value and recordingrecord pair. That recording-record can be made sufficiently detailed so that reproducibility and meaning of each value is evident. Only then does a value become data. Our open source BioTIFF platform, now allows each value generated by an instrument to be stored together with its recordingrecord as a data quanta in a dedicated archive. This atomizes the data and allows each value to be subsequently re-used and re-interpreted in ways that may not have been anticipated when first recorded. The procedure also makes it possible to encrypt all data quanta (value plus recordingrecord) as they are generated. Here we discuss the potential value of using modern public-private key encryption technology to fully protect the data quanta. At the same time enough unencrypted information can be indexed and registered to allow data identity and integrity also to be made evident and data quanta to be rediscovered. Scenarios illustrating the value and implications of routinely using such data encryption are presented. Data is most valued when accompanied by thoughtful and comprehensive analysis, synthesis and conclusions regarding what the data means and implies. The data’s authors can share private keys when and with whom they wish to reveal the data with their interpretation. Consider the case of biophysical interpretation of data related to cellular and macromolecular system dynamics in human brain tissue. Identities of the people involved, including those whose brain tissue was examined need to be recorded within the value associated recording-record but may not be relevant for biophysical interpretation. After confidential peer review each data quanta used can be published in a partially encrypted manner where only relevant value qualifying information is made public while uniquely identifying each data quanta used.
Sunday, February 28, 2016
Neuronal function depends on exquisite local regulation of a great variety of molecules and their interactions in the interstitial spaces. The timing and magnitude of interactions in the brain must depend on the hydraulic properties governing water and solute transfer across its matrix, but quantitative information on these properties has proved notoriously difficult to obtain, and uncertainties remain. Here, we adapt osmotic stress techniques to explore pressure-volume relationships and fluid-transfer parameters in brain tissue. Within 15-30 minutes of euthanasia, sets of brain tissue samples (12/brain, ~1g each) were obtained from pigs (n =11) and immersed in baths adjusted to colloidosmotic pressures of 3-219 mmHg with polyethyleneglycol Mw 8000. The samples’ water influx/efflux was measured gravimetrically as a function of time, normalized by weight. Initial flow rates were calculated from the first derivative, at time = 0, of second-degree polynomials fitted to the progress curves. Rates were linearly proportional to the bath’s pressure (r2 > 0.9). The hydraulic conductance calculated from the slope of fitted lines was 0.029 5 0.008ml/min/g/mmHg, and the hydration potential, calculated from the pressure at initial rate = 0, was 64 5 27 mmHg (means 5 SD, n = 11).The hydraulic conductance, but not the hydration potential, decreased significantly when the bath temperature was reduced from 37 to 4 C. Compared to heart and skin, brain conductance value was higher. Further, the changes in hydraulic parameters with temperature were distinct for each organ. These results illustrate a simple, ex vivo, quantitative approach to probe specific water-transfer parameters and their changes in the brain. They indicate organ-dependent differences in flow regulation and the hydraulic properties of extracellular matrices. 751-Pos Board B531 Solitary Electromechanical Pulses in Lobster Neurons Rima Budvytyte1, Alfredo Gonzalez-Perezl1, Lars D. Mosgaard1, Edgar Villagran-Vargas2, Andrew D. Jackson3, Thomas Heimburg1. 1 Niels Bohr Institute, Copenhagen, Denmark, 2Universidad Autonoma del Estado de Mexico, Toluca, Mexico, 3Niels Bohr International Academy, Copenhagen, Denmark. Investigations of nerve activity have been focused predominantly on electrical phenomena. It is to be expected that the state of the nerve cell depend not only on electrochemical potentials and the conjugated flux of ions but also on all other thermodynamic forces including variations in lateral pressure, resulting in changes of membrane area and thickness (1-2) and temperature, resulting in heat flux (3). While both mechanical and thermal signals are very small, they are found to be in phase with voltage changes. Such findings have led to the suggestion that the action potential may be related to electromechanical solitons traveling without dissipation (4). A condition for the existence of such a soliton is the existence of an order transition in the membrane from solid to liquid lightly below physiological temperature. Here, we present ultrasensitive AFM recordings of mechanical changes on the order of 0.2 - 1.2 nm in the giant axons of the lobster. Also, when stimulated at opposite ends of the same axon of lobster, colliding action potentials pass through one another and do not annihilate, as was shown in (5). These results are submitted in Physical Review Letters X (2015) and are not consistent with expectations from the established Hodkin-Huxley model. Findings are consistent with a mechanical interpretation of the nervous impulse. 1. Iwasa, K., and I. Tasaki. 1980. Biochem. Biophys. Research Comm. 95:1328-31. 2. Tasaki, I., K. Kusano, and M. Byrne. 1989. Biophys. J. 55:1033-40. 3. Ritchie, J. M., and R. D. Keynes. 1985. Quart. Rev. Biophys. 18:451-76. 4. Heimburg, T., and A. D. Jackson. 2005. Proc. Natl. Acad. Sci. USA 102:9790-95.
5. Gonzalez-Perez, A., R. Budvytyte, L. D. Mosgaard, S. Nissen, and T. Heimburg. 2014. Phys. Rev. X 4:031047. 752-Pos Board B532 Effect of Anesthetics on Action Potential Propagation Tian Wang, Henrike Sasse-Middelhoff, Lars Mosgaard, Thomas Heimburg. Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark. Local anesthesia has been attributed to the specific interaction of local anesthetics with (sodium) channel proteins, while the action of general anesthetics still remains unclear. However, already at the beginning of 20th century Meyer and Overton independently found that the critical anesthetic dose of anesthetics, regardless of their types, is linearly proportional to their solubility in olive oil. Based on this finding, in 2005 Heimburg and Jackson proposed that the action potential is a density pulse (soliton) propagating in biological membranes, which explains anesthesia by freezing point depression law that originates from van’t Hoff’s law. In this work, we conduct experiments on nerves from lobsters and earthworms to study the effect of anesthetics on compound action potential and action potential from a single neuron. The experimental data are then compared with the simulation results by solving the soliton equations in 1D cylindrical membrane with anesthetics inside the system. Anesthetics move the chain melting transition temperature of membranes far away from the physiological temperature, which requires a higher free energy to induce the phase transition, resulting in a higher stimulation voltage to reach the maximum amplitude of the action potential. 753-Pos Board B533 The Value of Encrypting Biophysical Data Peter S. Pennefather1, West Suhanic2. 1 Pharmaceutical Science, University of Toronto, Toronto, ON, Canada, 2 gDial Inc, Toronto, ON, Canada. We have shown how data quanta can be recorded as a value and recordingrecord pair. That recording-record can be made sufficiently detailed so that reproducibility and meaning of each value is evident. Only then does a value become data. Our open source BioTIFF platform, now allows each value generated by an instrument to be stored together with its recordingrecord as a data quanta in a dedicated archive. This atomizes the data and allows each value to be subsequently re-used and re-interpreted in ways that may not have been anticipated when first recorded. The procedure also makes it possible to encrypt all data quanta (value plus recordingrecord) as they are generated. Here we discuss the potential value of using modern public-private key encryption technology to fully protect the data quanta. At the same time enough unencrypted information can be indexed and registered to allow data identity and integrity also to be made evident and data quanta to be rediscovered. Scenarios illustrating the value and implications of routinely using such data encryption are presented. Data is most valued when accompanied by thoughtful and comprehensive analysis, synthesis and conclusions regarding what the data means and implies. The data’s authors can share private keys when and with whom they wish to reveal the data with their interpretation. Consider the case of biophysical interpretation of data related to cellular and macromolecular system dynamics in human brain tissue. Identities of the people involved, including those whose brain tissue was examined need to be recorded within the value associated recording-record but may not be relevant for biophysical interpretation. After confidential peer review each data quanta used can be published in a partially encrypted manner where only relevant value qualifying information is made public while uniquely identifying each data quanta used.