From owner-biophysics@net.bio.net Thu Nov 26 22:00:00 1998 Path: biosci!news.stanford.edu!newsfeed.berkeley.edu!newsfeed.enteract.com!ix.netcom.com!news From: flefever@ix.netcom.com(F. Frank LeFever) Newsgroups: bionet.biophysics,bionet.microbiology,bionet.neuroscience Subject: Re: The truth is out there Date: 27 Nov 1998 03:17:38 GMT Organization: ICGNetcom Lines: 158 Message-ID: <73l5ki$735@dfw-ixnews8.ix.netcom.com> References: <721spg$cr7$1@nnrp1.dejanews.com> <36449D67.378533CC@pop3.concentric.net> <36449FE2.313F8F3@pop3.concentric.net> <36477CA4.D2FED10@pop3.concentric.net> <3647B373.953F0A70@pop3.concentric.net> <3649B0AF.E720E242@psci.net> <364AAB63.C5056FB9@pop3.concentric.net> <364B5C6D.75E14B08@indiana.edu> <72s9eb$2fe@apple.telalink.net> <36523785.484B17DE@pop3.concentric.net> <912019876.8168.0.nnrp-08.d4e44203@news.demon.co.uk> <73im3f$ogr@dfw-ixnews3.ix.netcom.com> <912075256.24982.0.nnrp-03.d4e44203@news.demon.co.uk> NNTP-Posting-Host: nyc-ny74-41.ix.netcom.com X-NETCOM-Date: Thu Nov 26 9:17:38 PM CST 1998 Xref: biosci bionet.biophysics:4575 bionet.microbiology:15172 bionet.neuroscience:26037 My comments are interdigitated below: In <912075256.24982.0.nnrp-03.d4e44203@news.demon.co.uk> "Andrew K Fletcher" writes: > >Hi Frank, Hi Ken, > >The flow of water in plants and trees is relevant to this discussion, it was >my interest in this that led directly to my working with spinal cord injury, >ms and other neurological conditions. I'd be surprised if the processes were the same (i.e. water transport in trees, CSF formation and transport and absorption). What is your thesis re relevance of CSF circulation to MS? to spinal cord injury? >" >Frank, could you please summarise the content of 'this wonderful process' >referred to in your posting and its relationship with how water reaches the >leaves of trees. No, sorry, I could not. Anyway, I thought you had listed the basic components of the processe(s) yet could not accept an explanation in these terms. re your summary from the textbook account: what's the publication date of that textbook? If a later edition, was this section revised in the light of work done between earlier and later editions? I am no expert in this area, but it was clear to me from the presentations by the panel of very very expert neuroscientists at this NSF (National Science Foundation) satellite meeting (preceding the Society for Neuroscience annual meeting) that there were still questions to be answered regarding CSF sources, contents, circulation, and absorption and/or other clearance mechanisms. Much of what your summary says may be true, but much may be yet open to correction. My own interest was not in mechanisms of circulation per se, but in the central focus of the conference, which was the extent to which neuroactive substances in the CSF could enter the CSF and reach targets via the CSF in sufficient amounts to be physiologically significant, and the kinds of long-term neural integration which might be subserved by this mechanism. F. Frank LeFever, Ph.D. New York Neuropsychology Group > >The flow of cerebrospinal fluid as described in Principles of Anatomy and >Physiology is as follows. > >The entire central nervous system contains between 80 and 150 ml (3 to 5oz) >of cerebrospinal fluid, colourless fluid of watery consistency. Chemically >it contains, proteins, glucose, urea and salts. It also contains some >lymphocytes. > >With regard to its circulatory function, cerebrospinal fluid delivers >nutritive substances filtered from the blood to the brain and spinal cord >and removes wastes and toxic substances produced by brain and spinal cord >cells. > >It then goes on to illustrate the path of the circulation of CSF. > >The flow of cerebrospinal fluid as described in Advanced Human Biology: J. >Simpkins, J.I.Williams, is as follows. > >Pressure compensation >CSF is produced from and returns to the blood passively in response to >pressure differences between the blood and CSF. The effects of increases in >blood pressure distending intercranial vessels can thus be reduced as more >CSF is produced. > >Page 125 The beating of the cilia cells sets up currents in the >cerebrospinal fluid, thus helping the circulation of metabolites. Astrocytes >are connected to the bases of ependymal cells which may assist exchange of >metabolites between CSF and neurons in the central nervous system. > >Fig 14.43, page 285 shows a simple drawing which illustrates the circulation >of fluids by arrows from the choroid plexus down one side of the spine and >up another side, it also shows a flow over the the surface of the brain, >indicated by an arrow on both sides. > >I did read an article, which was a reprint of text from another physiology >book, which I can't find, that stated something along these lines. >Circulation in the CSF occurs due to respiration, postural, and circulatory >influences. > >Ken Collins wrote: > >I've not studied it, but I expect the cerebrospinal fluid flows through >active >dynamics... when it's produced, it goes into the ventricles, more is >produced... >what was produced earlier flows to "get out of the way" of what's just been >produced. I don't know where the "drain" is... expect it's a distributed >thing, >too. ken Collins > >Original post. > >>>Could someone therefore sum up the accepted mechanism for circulation >>in the >>>cerebrospinal fluid, so that we have an independent benchmark for >>further >>>discussions? Only then will we see if this road leads us to any >>conclusions. >> >> >>- - - - - -(snip) - - - - - - - >>F. Frank LeFever, Ph.D. wrote. > >>I won't comment on his itemizing the forces by which water could be >>lifted up into trees and then demanding to know how this happens. >>(Incidentally, I found treatment of this wonderful process in Murchie's >>"The Seven Mysteries of Life" fascinating; too bad he got spooky on the >>last 2-3 mysteries...) > >>However, I too am interested in CSF, and attended a satellite >>conference (sponsored by NSF, prior to the Society for Neuroscience >>meeting early this month) on CSF as a communications system. Among >>other things, problems of its circulation were considered. >> >>F. Frank LeFever, Ph.D. >>New York Neuropsychology Group > > > .