On Thu, 8 Apr 1999, Geoff McAuliffe wrote:

> > capsules of most organs. Look around small blood vessels. There are
> > none in the CNS.
> 
>     I beg to differ. Try Silver et al., 1996, Trends in
> Neuroscience19:25-31; "Mast cells in the brain: evidence and functional
> significance".

 That's true Geoff, though Silver et al were writing about a bird's
 brain. In rats there are mast cells around some cerebral blood
 vessels (e.g. Devel. Neurosci. 4:220-224, 1981; Acta Anat. 124:149-158,
 1985), but perhaps these are not quite truly "in" the brain. 
 You do get truly intraparenchymal mast cells in parts of the 
 brains of some mammals, in the habenular nuclei (as in the pigeon) and 
 also in nearby dorsal and medial parts of the thalamus (e.g. 
 Nature 210:756-757, 1966; J. Anat. 121:303-311, 1976; Acta Anat.
 75:443-452, 1970). The only mammals (to my knowledge) that have
 these truly in-the-brain mast cells, in contact with neurons and
 glia, are the hedgehog, the tree-shrew and the slow loris.

> Also, there are mast cells in the meninges. Dimlich et al. 1991, J.
> Neurocytology 485-503,  "Linear arrays of homogenous mast cells in the
> dura mater of the rat".

  The dura mater of the rat has been much used for experiments
  with mast cells. See big book, "The Mast Cells" by Hans Selye
  (Butterworths, 1963). This would be a good +ve control tissue;
  so would rat or mouse external ear or tongue, which also
  contain lots of connective tissue-type mast cells. Rodent
  mast cell granules survive pretty well any fixation. For other
  species an alcoholic fixative will give the best results
  (Carnoy and alcoholic Bouin are both OK).

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1