title: Supravital microwave experiments support that the formation of "dark" neurons is propelled by phase transition in an intracellular gel system.
abstract: BACKGROUND
  Based on circumstantial evidences, we (Gallyas, F., Farkas, O., Mázló, M., 2004. Gel-to-gel phase transition may occur in mammalian cells: Mechanism of formation of "dark" (compacted) neurons. Biol. Cell 96, 313-324.) proposed that the formation of "dark" neurons (striking compaction of visibly normal ultrastructural elements accompanied with large-scale fluid excretion), which occur in many neurological diseases such as ischemia, proceeds with a non-enzymatic mechanism.
  
  
  OBJECTIVE
  To support this proposition, the present paper deals with the results of supravital experiments using microwave irradiation.
  
  
  METHODS
  After transcardial glutaraldehyde fixation followed by decapitation, a pin was stuck into rat brains just before and just after they were warmed up to 80 degrees C and maintained at this temperature for various periods of time by controlled microwave irradiation.
  
  
  RESULTS
  Independently of the duration of irradiation, the pre-irradiation pin sticking produced numerous "dark" neurons in an approximating 500-microm-wide zone around its track whereas the post-irradiation pin sticking did the same only when the irradiation was shorter than 55 s. The excreted fluid was present in neighbouring astrocytic processes but not in the extracellular space.
  
  
  CONCLUSIONS
  The formation of "dark" neurons is completed in less than 55 s under the circumstances of the experiment. As neurons are poor in readily consumable chemical energy in the absence of blood circulation, this rapid and massive fluid excretion cannot be explained by any enzyme-mediated membrane-related pump mechanism. An osmotic mechanism can also be discounted. In contrast, it is in conformity with the above mentioned non-enzymatic (physicochemical) phenomenon, the phase transition of a supra-cytoskeletal gel network storing free energy in the form of non-covalent interactions.
authors.affiliation: Department of Neurosurgery, University of Pécs, H-7623 Pécs, Rét utca 2, Hungary. ferenc.gallyas.sen@aok.pte.hu
authors.forename: Ferenc
authors.initials: F
authors.lastname: Gallyas
authors.forename: József
authors.initials: J
authors.lastname: Pál
authors.forename: Péter
authors.initials: P
authors.lastname: Bukovics