Cleaton-Jones, P

English

Wits Institutional Repository on DSPACE

S. Afr. J, D ied . Sci. (1972), 37, 101-104
SURFACE ULTRASTRUCTURE OF THE MUCOSA OF THE SOFT 
PALATE IN THE VERVET MONKEY
by
P. CLEATON-.JONES
Dental Research Unit o f  the University o f  the Witwatersrand and South African Medical Research 
Council, Jan Smuts Avenue, Johannesburg, South Africa.
[R eceived  I4t ii D ecem her , 1972]
The ullrastructurc of the surface of epithelial cells has been described by several 
workers [Wolf 1967, 1968; Bliimckc and Morgcnroth 1967; Whittaker and Adams 
1971], All of these showed some form of fine folding on the surface of the cells studied. 
So constant a finding are these line surface folds that Marowitze/ at. [1970] concluded 
that their presence is a sign of good tissue processing.
Confusion exists however in the interpretation of the appearance of the various 
types of surface folds. This paper links the two dimensional appearance of the surface 
folds seen in a transmission clectronmicrograph with the three dimensional appearance 
seen with the scanning electron microscope.
MATERIALS AND METHODS
For transmission electron microscopy (TEM), small pieces of the mucosa of the 
soft palate were removed from anaesthetised vervet monkeys (Cercopitliecus 
aethiops) and fixed in 4.5 per cent phosphate buffered glutaraldehydc solution at 
pH 7.3 for 1 hour. After washing in phosphate buffer the specimens were post-fixed 
for 30 min. in 1 per cent phosphate buffered osmium tetroxidc at pH 7.3 [Millonig, 
1961]. The tissue was again washed in buffer before dehydration in graded ethanol. 
After the specimens had been passed through propylene oxide, they were embedded 
in Araldite [Luft, 1961]. Sections were cut on a Reichert OM-U2 ultramicrotome, 
mounted on copper grids and stained with a saturated solution of uranyl acetate in 
ethyl alcohol followed by lead citrate [Reynolds, 1963]. The specimens were examined 
in a Siemens Elmiskop I electron microscope.
For scanning electron microscopy (SEM) portions of the soft palates were fixed 
in a 4.5 per cent glutaraldehydc solution buffered at pH 7.3 with phosphate buffer. 
After washing in the phosphate buffer the tissue was dehydrated using graded ethanol 
followed by ether. Alternatively, dehydration was carried out by quenching the tissue 
in isopentane cooled with liquid nitrogen followed by evaporation under vacuum 
at —40°C. All specimens were coated with gold palladium and examined in a 
Cambridge Stereoscan Mark II scanning electron microscope operated at lOkV. 
The bcam/spccimen angle was varied so as to obtain the best surface projection.
RESULTS
The cross-sectional view afforded by TEM reveals that the outermost cell surface 
displays fine projections of fairly constant height separated from each other by a 
trough also of fairly constant size (Fig. 1). On the surface at the junction between 
adjacent cells two of the fine elevations lie in close proximity thus giving the impression 
of a thicker fold on the surface (Fig. 2).
SEM displays a corrugated cell surface; two distinct forms of fine folding can be 
seen namely (a) fine folds and (b) thicker folds (Fig. 3). The fine folds or microp- 
lications are of fairly regular size but with an irregular arrangement. They run in all 
directions and can show cither a linear or a whorled pattern. Whatever the arrange­
ment, the distance between the elevations appears reasonably constant. Many of 
these fine folds arise independently but a large number are continuous with a thicker
102 The South African Journal o f  Medical Science.v
fold that seems to demarcate the boundaries of the individual surface cells. When 
one of these thicker folds is examined under high magnification a depression is 
obvious at the crest and the fold can be seen to consist of two parallel microplicalions 
(Fig. 4).
''| If desquamating epithelial cells arc also examined by SEM then the undersurface 
of these cells as well as the upper surface of the underlying cells shows the surface 
folding (Fig. 5). Similarly if successive layers of cells are examined by TEM then 
the cellular interdigitations are seen to have the same configuration as the surface 
elevations (Fig. 6).
DISCUSSION
The finding of fine folding on the surface of cells of the soft palatal epithelium 
in the vervet monkey is in agreement with that seen in other cpithclia by previous 
workers.
Wolf [1967] using a replica technique described microvilli and bulging ledge-like 
formations at intercellular borders, which showed an intercellular fissure in their 
crest. The thicker folds seen in the present study correspond to this description.
Bliimcke and Morgenroth [1967] found similar structures in corneal epithelium. 
Whittaker and Adams [1971], however, in their study of developing skin and oral 
mucosa, reported intercellular clefts occurring at sites other than on intercellular 
ridges. Isolated clefts such as they noted were seen in the present study only in a 
number of the specimens quenched in isopentane cooled with liquid nitrogen. 
For this reason these clefts are considered to be artefacts.
The microvilli seen by Wolf [1967] were described as fingerlike projections and 
similar projections were reported in the respiratory tract by Greenwood and Holland 
[1972]. No such structures were found with the scanning electron microscope in the 
present study. On the other hand the surface projections seen in the soft palatal 
epithelium under TEM could quite easily be labelled as microvilli without SEM. 
These microvilli in a two-dimensional transmission elcctronmicrograph become 
cross-sections of the microplications of the surface membrane when SEM findings 
are also considered.
Elias and Pauly [1966] have drawn attention to the all too common habit of con­
fusing a two-dimensional image with the three dimensional reality. One should there­
fore exercise care in the use of the term microvillus when applied to two-dimensional 
electron micrographs. To emphasise this a combination and correlation of the 
information obtained in the TEM and SEM surface studies is seen in a drawing of 
the three dimensional appearance of the surface (Fig. 7).
Finally none of the previous authors has described the origin of the microplications. 
It is felt that they arise due to the exposure of normal cell interdigitations which are 
uncovered by the exfoliation of surface cells. This is substantiated by the finding of 
microplications on the under-surface of exfoliating cells as well as the upper surface 
of the underlying cells. Also the cell interdigitations throughout the epithelial layers 
have configurations similar to those exposed on the surface.
SUMMARY
The ultrastructure of the surface of the mucosa of the soft palate of the vervet 
monkey was investigated using both transmission (TEM) and scanning electron 
microscopy (SEM). The surface of the mucosa shows fine elevations or microplica­
tions which have an irregular arrangement except at intercellular boundaries. These 
elevations are thought to be the remains of normal cell interdigitations.
CIcaton-Jones: Surface ullrastnicliirc o f  monkey soft palate 103
1 wish to thank the Poliomyelitis Research Foundation for making available the monkeys used
in this study; the Dc Beers Diamond Research Laboratories for the use of their scanning electron
microscope and Messrs. J. Eckert and R. Grcaslcy for their technical assistance. My thanks also go
to Professor D. H. Relief and Drs. W. Evans and J. Austin for their criticism.
REFERENCES
Blumcke, S. and Morgenroth, Jr. K. (1967). The stereo ultrastructurc of the external and internal 
surface of the cornea. J. Ultrastruct. Res., 18, 502-518.
Elias, H. and Pauly, J. E. (1966) Human Microanatomy 3rd ed., Philadelphia. (F. A. Davis Co., 
Philadelphia).
G reenwood, M. F. and Holland, P. (1972). The mammalian respiratory tract surface. Lab. 
Invest., 27, 296-304.
Luft, J. H. (1961). Improvements in epoxy-resin embedding methods. J. Biophys. Biochein. CytoL, 
9, 409-414.
Marowitz, W. F., Arenberg, I. K. and T halman, R. (1970). Evaluation of preparative techniques 
for the scanning electron microscope. Laryngoscope, 80, 1680-1700.
Millonig, G. (1961). Advantages of a phosphate buffer I'or0s01 solutions in fixation. J. Appl. Phrs., 
32, 1637.
Reynolds, E. S. (1963). The use of lead citrate at high pH as an electron-opaque stain in electron 
microscopy. J. Cell. Biol., 17, 208-212.
Whittaker, D. K. and Adams, D. (1971). The surface layer of human foetal skin and oral mucosa: 
A study by scanning and transmission electron microscopy. J. Anat., 108, 453-464.
Wolf, J. (1967). Structure and function of periderm. I. Superficial structure of the peridcrmal 
epithelium. Folia morph., 15, 296-305.
Wolf, J. (1968). Curve of development and disappearance of peridcrmal phase of human embryonic 
skin demonstrated by the replica method. Folia morph., 16, 36-42.
( For legends to plates see next page)
104 The South African Journal o f  Medical Sciences
LEGENDS TO ELATES
ELATE 1
Fig. 1. Transmission electron micrograph showing the fine surface projections, x 27,300.
Fig. 2. Cross section of intercellular ridge showing a cleft or depression at the summit, x 54,500 
Fig. 3. Scanning electron micrograph showing the surface microplications and the more prominent 
intercellular ridges, x 3,600.
Fig. 4. High power scanning electron micrograph showing an intercellular ridge consisting of two 
parallel microplications separated by a cleft. X 45,600.
ELATE 2
Fig. 5. Scanning electron micrograph of an exfoliating surface cell. Note the microplications on both 
the exfoliating cell above and the underlying cell surface below. X 2,700.
Fig. 6. Transmission electron micrograph of cellular inlerdigitations approximately midway through 
the epithelium, x 36,400.
Fig. 7. Diagram of the three dimensional appearance of the microplications and intercellular ridge.


Surface ultrastructure of the mucosa of the soft palate in the vervet monkey

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Surface ultrastructure of the mucosa of the soft palate in the vervet monkey

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