Does Exertion Affect N2 Absorption?

[Puffer Fish]

Bubble, am dating myself with the cell wall comment...I understand the correct term today is membrane...in doing a quick review of names, I'm surprised just how many names have changed... although I should not be, as you use the term "ex vivo", which I had never heard of (I know it as "in vitro".)

Note: Not sure what one today calls the outside of cells that have rigid walls.. as "wall" seems to be used only for plant cells.

In any case, the issue as to membrane and stiff structures surrounding cells versus the everything else is a valid concern. As is the issue of measurement protocal. Without methology of the measurement, one is left to guess how it was done.

Even using the term "spinal cord" sort of implies it was not very detailed information, as what part of the spinal cord are we talking about?

I doubt seriously that all those structures have the indentical gas absorption characteristics.

My experience with research papers that do not provide test protocals is that they usually also are not very accurate.

 

[Bubbletrubble]

@Puffer Fish: Yup, the names of structures can change over time. I specifically used the term "ex vivo" rather than "in vitro" because some people interpret "in vitro" to mean in a cell-free system. "Ex vivo" refers to growing the cells/tissue outside the living body. I'm equally careful when I talk or write about cell culture experiments. Some people will refer to cell culture work as an "in vitro" study, which can lead to some confusion. Another term you might see bandied about is "explant" which is what an "ex vivo" preparation of tissue might also be called.

I completely agree on needing clarification of the term "spinal cord." It can mean one thing to a neurobiologist and quite another to a mathematician who's trying to model biological processes.

Well, to be fair, I haven't had the time to consult the reference that DCBC cited yet...so it's possible that the protocols are described in the text. More likely, the authors probably cited a primary research article. So that would be another paper we'd have to look up to get a better handle on how those numbers were derived.

One more point of clarification is that the numbers cited by DCBC were likely "aggregate" numbers meaning that the values would apply to the entire tissue. I don't think the authors meant to say that all cell types within a tissue have "identical gas absorption characteristics."

Thanks for including that diagram of the spinal cord. Looking at it reminds us of how complex the CNS is. It's pretty amazing to learn about where those lower motor neurons reside (ventral horns), where they send their nerve fibers (posterior pyramidal tracts), and how lesions at various levels in the spinal cord correlate with specific clinical findings. Pretty neat stuff...

 

[Puffer Fish]

@Puffer Fish: Yup, the names of structures can change over time. I specifically used the term "ex vivo" rather than "in vitro" because some people interpret "in vitro" to mean in a cell-free system. "Ex vivo" refers to growing the cells/tissue outside the living body. I'm equally careful when I talk or write about cell culture experiments. Some people will refer to cell culture work as an "in vitro" study, which can lead to some confusion. Another term you might see bandied about is "explant" which is what an "ex vivo" preparation of tissue might also be called.

I completely agree on needing clarification of the term "spinal cord." It can mean one thing to a neurobiologist and quite another to a mathematician who's trying to model biological processes.

Well, to be fair, I haven't had the time to consult the reference that DCBC cited yet...so it's possible that the protocols are described in the text. More likely, the authors probably cited a primary research article. So that would be another paper we'd have to look up to get a better handle on how those numbers were derived.

One more point of clarification is that the numbers cited by DCBC were likely "aggregate" numbers meaning that the values would apply to the entire tissue. I don't think the authors meant to say that all cell types within a tissue have "identical gas absorption characteristics."

Thanks for including that diagram of the spinal cord. Looking at it reminds us of how complex the CNS is. It's pretty amazing to learn about where those lower motor neurons reside (ventral horns), where they send their nerve fibers (posterior pyramidal tracts), and how lesions at various levels in the spinal cord correlate with specific clinical findings. Pretty neat stuff...

Thanks for understanding... I took comparative anatomy some 35 years ago, and it is not something I use. Gas laws, RO and a lot of other relevant aspects of this issue I do, but only in single dimensional aspects, and this is so not a single dimensional issue.

I have not found (and have tried) much information as to what exactly is happening in spinal DCS... the little that is know is that it causes swelling.. the swelling blocks blocks any circulation, and the area dies. What does not seem to be known is, well the detail.

Is the expanding gas, by itself, the issue? Does the gas block circulation, which then causes the swelling? Is it just one area of the spinal cord? The importance of this is somewhat critical, as this is not a case of just gas absorption and release...

It is a great example of why just studying a single aspect may not show the real issues. It could very well be the absorption rate is very low, but the critical tolerence level is also really low.

Wish the research was a bit more detailed and focused..

 

[TSandM]

Is the expanding gas, by itself, the issue? Does the gas block circulation, which then causes the swelling? Is it just one area of the spinal cord? The importance of this is somewhat critical, as this is not a case of just gas absorption and release...

This is one of the areas of DCS where there is little known for certain. It is fairly clear that bubble formation is some part of the issue, but not all. Bubble kinetics and the time course of DCS fairly clearly show that there has to be more to it than that, as does the fact that some people have high grade bubbling on Dopper examination but no symptoms at all. Activation of some type of immune response by the bubbles is suspected, but studies which have looked at, for example, complement activation, have had inconsistent results.