Electric fields and the nuclear membrane

Biphasic electrical currents stimulation promotes both proliferation and differentiation of fetal neural stem cells

The use of non-chemical methods to differentiate stem cells has attracted researchers from multiple disciplines, including the engineering and the biomedical fields. No doubt, growth factor based methods are still the most dominant of achieving some level of proliferation and differentiation control - however, chemical based methods are still limited by the quality, source, and amount of the utilized reagents. Well-defined non-chemical methods to differentiate stem cells allow stem cell scientists to control stem cell biology by precisely administering the pre-defined parameters, whether they are structural cues, substrate stiffness, or in the form of current flow. We have developed a culture system that allows normal stem cell growth and the option of applying continuous and defined levels of electric current to alter the cell biology of growing cells. This biphasic current stimulator chip employing ITO electrodes generates both positive and negative currents in the same culture chamber without affecting surface chemistry. We found that biphasic electrical currents (BECs) significantly increased the proliferation of fetal neural stem cells (NSCs). Furthermore, BECs also promoted the differentiation of fetal NSCs into neuronal cells, as assessed using immunocytochemistry. Our results clearly show that BECs promote both the proliferation and neuronal differentiation of fetal NSCs. It may apply to the development of strategies that employ NSCs in the treatment of various neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases.

Ion channels at the nucleus: electrophysiology meets the genome

The nuclear envelope is increasingly viewed from an electrophysiological perspective by researchers interested in signal transduction pathways that influence gene transcription and other processes in the nucleus. Here, we describe evidence for ion channels and transporters in the nuclear membranes and for possible ion gating by the nuclear pores. We argue that a systems-level understanding of cellular regulation is likely to require the assimilation of nuclear electrophysiology into molecular and biochemical signaling pathways.

Bioelectromagnetics in morphogenesis

Understanding the factors that allow biological systems to reliably self-assemble consistent, highly complex, four dimensional patterns on many scales is crucial for the biomedicine of cancer, regeneration, and birth defects. The role of chemical signaling factors in controlling embryonic morphogenesis has been a central focus in modern developmental biology. While the role of tensile forces is also beginning to be appreciated, another major aspect of physics remains largely neglected by molecular embryology: electromagnetic fields and radiations. The continued progress of molecular approaches to understanding biological form and function in the post genome era now requires the merging of genetics with functional understanding of biophysics and physiology in vivo. The literature contains much data hinting at an important role for bioelectromagnetic phenomena as a mediator of morphogenetic information in many contexts relevant to embryonic development. This review attempts to highlight briefly some of the most promising (and often underappreciated) findings that are of high relevance for understanding the biophysical factors mediating morphogenetic signals in biological systems. These data originate from contexts including embryonic development, neoplasm, and regeneration.

Electrical dimension of the nuclear envelope

Eukaryotic chromosomes are confined to the nucleus, which is separated from the rest of the cell by two concentric membranes known as the nuclear envelope (NE). The NE is punctuated by holes known as nuclear pore complexes (NPCs), which provide the main pathway for transport of cellular material across the nuclear-cytoplasmic boundary. The single NPC is a complicated octameric structure containing more than 100 proteins called nucleoporins. NPCs function as transport machineries for inorganic ions and macromolecules. The most prominent feature of an individual NPC is a large central channel, ~7 nm in width and 50 nm in length. NPCs exhibit high morphological and functional plasticity, adjusting shape to function. Macromolecules ranging from 1 to >100 kDa travel through the central channel into (and out of) the nucleoplasm. Inorganic ions have additional pathways for communication between cytosol and nucleus. NE can turn from a simple sieve that separates two compartments by a given pore size to a smart barrier that adjusts its permeabiltiy to the metabolic demands of the cell. Early microelectrode work characterizes the NE as a membrane barrier of highly variable permeability, indicating that NPCs are under regulatory control. Electrical voltage across the NE is explained as the result of electrical charge separation due to selective barrier permeability and unequal distribution of charged macromolecules across the NE. Patch-clamp work discovers NE ion channel activity associated with NPC function. From comparison of early microelectrode work with patch-clamp data and late results obtained by the nuclear hourglass technique, it is concluded that NPCs are well-controlled supramolecular structures that mediate transport of macromolecules and small ions by separate physical pathways, the large central channel and the small peripheral channels, respectively. Electrical properties of the two pathways are still unclear but could have great impact on the understanding of signal transfer across NE and gene expression.

The cytological implications of primary respiration

Observing the macroscopic complexities of evolved species, the exceptional continuity that occurs among different cells, tissues and organs to respond coherently to the proper set of stimuli as a function of self/species survival is appreciable. Accordingly, it alludes to a central rhythm that resonates throughout the cell; nominated here as primary respiration (PR), which is capable of binding and synchronizing a diversity of physiological processes into a functional biological unity. Phylogenetically, it was conserved as an indispensable element in the makeup of the subkingdom Metazoa, since these species require a high degree of coordination among the different cells that form their body. However, it does not preclude the possibility of a basal rhythm to orchestrate the intricacies of cellular dynamics of both prokaryotic and eukaryotic cells. In all probability, PR emerges within the crucial organelles, with special emphasis on the DNA (5), and propagated and transduced within the infrastructure of the cytoskeleton as wave harmonics (49). Collectively, this equivalent vibration for the subphylum Vertebrata emanates as craniosacral respiration (CSR), though its expression is more elaborate depending on the development of the CNS. Furthermore, the author suggests that the phenomenon of PR or CSR be intimately associated to the basic rest/activity cycle (BRAC), generated by concentrically localized neurons that possess auto-oscillatory properties and assembled into a vital network (39). Historically, during Protochordate-Vertebrate transition, this area circumscribes an archaic region of the brain in which many vital biological rhythms have their source, called hindbrain rhombomeres. Bass and Baker (2) propose that pattern-generating circuits of more recent innovations, such as vocal, electromotor, extensor muscle tonicity, locomotion and the extraocular system, have their origin from the same Hox gene-specified compartments of the embryonic hindbrain (rhombomeres 7 and 8) that produce rhythmically active cardiac and thoracic respiratory circuits. Here, it implies that PR could have been the first essential biological cadence that arose with the earliest form of life, and has undergone a phylogenetic ascent to produce an integrated multirhythmic organism of today. Finally, in its full manifestation, the breathing DNA (1) of the zygote could project itself throughout the cytoskeleton and modify the electromechanical properties of the plasma lamella (26), establishing the primordial axial-voltage gradients for the physiological control of development (53).