Heterogeneity in the ultrastructure of the mucous (goblet) cells of the rabbit palpebral conjunctiva.
OBJECTIVE
The purpose of this study was to assess objectively the ultrastructure of the secretory granules in rabbit conjunctival mucin-producing 'goblet' cells.


METHODS
The upper eyelids from five young adult dioestrous female rabbits were dissected out, stretched onto a cardboard support and prepared for transmission electron microscopy by repeated application of an isotonic two per cent glutaraldehyde fixative at room temperature. Post-fixation treatment included osmium tetroxide and staining with uranyl acetate and lead citrate. Low magnification micrographs were taken of the goblet cells of the conjunctiva, printed at a magnification of approximately 6,000 and the number, size and features of the secretory granules assessed.


RESULTS
Across the entire palpebral conjunctiva of all five rabbits, the majority of mucous cells displayed a goblet shape and the secretory granules were uniformly pale in staining. The average width of the goblet cells was 10.8 +/- 1.1 microm and the diameter of the secretory granules was 0.82 +/- 0.16 microm. However, in localised regions across the palpebral conjunctiva of two of the rabbits, some goblet cells were different in that the secretory granules had either a denser-staining core, in which some of the granules were densely staining (while others were pale) or most of the granules were densely staining. These mucous cells had an average diameter of 10.3 +/- 1.7 microm and the granule diameters averaged 0.88 +/- 0.01 microm. For these abnormal goblet cells, inflammatory cells were found in their immediate vicinity. Occasionally, goblet cells were seen to be in the process of degranulation with associated apparent cell necrosis and the mucin granule diameter was close to 1 microm.


CONCLUSIONS
The ultrastructure of the mucin-containing secretory granules of the conjunctival mucous cells is not necessarily homogeneous in character and further attention needs to be given to the effects of localised inflammation in the tissue and to possible hormonal influences.
Doughty
Michael J
MJ
Department of Vision Sciences, Glasgow-Caledonian University, Glasgow, UK.
Bergmanson
Jan P G
JP
D000818:Animals; D015550:Cell Degranulation; D048429:Cell Size; D003228:Conjunctiva / Q000648:ultrastructure*; D005143:Eyelids; D005260:Female; D020397:Goblet Cells / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009336:Necrosis; D011817:Rabbits / Q000033:anatomy & histology*; D022142:Secretory Vesicles / Q000648:ultrastructure