Reply
Thu 11 Mar, 2004 06:21 am
Context:
But would these spheres form hair cells? As it turns out, only some of the sphere cells were true stem cells with the capacity for self-renewal. The remainder seemed to have already progressed to the level of progenitors because Li found they expressed proteins usually found only in particular cell types. Some sphere cells, for example, tested positive for nestin, a neuronal progenitor cell marker, while others expressed bone morphogenetic proteins and Pax-2, found in the developing inner ear. Significantly, Li discovered that after maintaining the spheres for around two weeks, a subset of cells began to express specialized hair cell proteins like F-actin, espin, and myosin VIIA. All these proteins are found in the mechanosensitive bundle that protrudes from the apical surface of the hair cell. Sure enough, when Li examined the morphology of these progenitors, he found they had protruding hairlike fibers.
(1) As the writer talks about "some sphere cells, for example, tested positive for nestin...", does he mean these "some sphere cells" are the "some of the sphere cells" that are true stem cells with the capacity for self-renewal? Or does he mean "the remainder"?
(2) What does progenitor mean here, as in " Sure enough, when Li examined the morphology of these progenitors, he found they had protruding hairlike fibers "?
Oristar
When he says "some of the sphere cells ...tested positive" he means that out of the population of sphere cells not all of them tested positive. Some is a vague quantifier. The word "some" often implies a small number.
a progenitor is an ancestor in the direct line. So in this case it would be those cell that were ancestral to the sphere cells that produced protruding bundles.
Crucial here is that the cells that "have already progressed to the level of progenitors" are differentiated cells.
Of course, if you are reading this article you are probably very aware of that already...
Thanks for reply Acquiunk and Patiodog.
But sadly my understanding stood still after reading the replies.
Just because I felt what you said was all what I've known.
Reading that context, what I got is:
Nestin, a neuronal progenitor cell marker, has been tested positive in some sphere cells; that is, the cells have already progressed to the level of progenitors, which are different to true stem cells with the capacity for self-renewal.
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What do "others" mean?
Context:
while others expressed bone morphogenetic proteins and Pax-2, found in the developing inner ear.
The context here is SOME sphere cell tested positive for nestin, OTHERS expressed bone morphogenetic proteins. The author is distinguishing two types of sphere cells, those that expressed nestin, and those that expressed other kinds of proteins.
Ah, I understand the question now, I think. I'd like to modify acquiunk's answer a bit.
Some of the sphere cells were found to be stem cells and some were found to be progenitor cells. Of those that were found to be progenitor cells, some expressed nestin and some expressed bone morphogenetic proteins and Pax-2.
So, sphere cells = A + B
where A = stem cells
and B = progenitor cells.
B = B1 + B2
where B1 = cells expressing nestin
and B2 = cells expressing bone morphogenetic proteins and Pax-2
I would guess that the subset of progenitors that began to express the hairlike fibers were the cells that were expressing nestin (B1), since these are neuronal progenitors and the fibers indicate that these cells are mechanoreceptors.
Excellent reply Patiodog! Thanks!
Also thanks to Acquiunk!
I'd like to hear someone else to confirm the guess made my Patiodog.
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PS. I'm not 100% sure about "tested positive for nestin". Does it mean "we made nestin test, and found it showed positive."? Here, "nestin test" is used as a compound noun, a "term" for testing some protein that is called nestin.
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