close

Вход

Забыли?

вход по аккаунту

?

Taste buds on the cat's circumvallate papilla after reinnervation by glossopharyngeal vagus and hypoglossal nerves.

код для вставкиСкачать
TASTE BUDS ON THE CAT'S CIRCUMVALLATE
PAPILLA AFTER REINNERVATION BY
GLOSSOPHARYNGEAL, VAGUS, AND
HYPOGLOSSAL NERVES
LLOYD GUTH
Laboratory of Xeiiroanatomical Sciences
National Institute of Nezrrological Disemes and Blindness
National Institutes of Health
U. S. Public Health Service
Department of Health, EdlkCation, and Welfare
Rethesda, illargland
TEN FIGURES
IXTRODUC'L'ION
This investigation was undertaken to determine whether
taste buds reappear f ollowiiig reinnervation by gustatory and
nongustatory nerves.
It is well-established that mammalian taste buds disappear
when denervated. For example, transection of the lingual
nerve (Olmsted, '21 ; Whiteside, '27), the chorda tympani
(Olmsted, '22), o r the glossopharyngeal nerve (Sandmeyer,
1895; &!eyer, 1897) results in loss of taste buds from the
tongur. Following denervation, the taste buds degenerate and
are sloughed from the mucosal surface (Olmsted, '21; Guth,
'57).
The formation of taste buds following reinnervation has
not been studied extensively. Reappearance of taste buds
after regeneration of the transected lingual nerve has been
reported (Olmsted and Pinger, '36; Arey and Monzingo, '42),
but relatively few animals were employed in these studies.
Several investigations have been carried out to determine
whether nongustatory nerves can also stimulate the formation
of taste buds. Roeke ('17)' Olmsted and Pinger ('36), and
25
26
LLOYD CUTH
Arey and Monzingo (’42) all obtained reinnervation of the
lingual epithelium with motor nerve fibers (by hypoglossallingual nerve anastomosis). Inasmuch as none of these studies
employed sufficient numbers of animals, appropriate controls,
or adequate quantitative methods it is not surprising that
the results of these studies differ from one another.
In the present investigation the circumvallate papillae were
studied because the compact arrangement of their taste buds
permits easy quantification. A sufficient number of animals
was employed to allow for statistical analysis of the data. I n
this way it was hoped to ascertain whether predominantly
gustatory (glossopharyngeal), motor (hppoglossal), or mixed
(vagus) nerves can stimulate the formation of taste buds.
MATERIALS B N D METHODS
Operative procedures. The following end-to-end nerve anastomoses were performed on adult cats (2.0-3.2kg) of both
sexes :
1. G-G ; proximal glossopharyngeal to distal glossopharyngeal ;
2. V-G ; proximal vagus (distal to nodose ganglion) to distal glossopharyngeal ;
3. H-G ; proximal hypoglossal to distal glossopharyngeal;
4. G-avulsion ; transcction of the glossopharyngeal nerve
and avulsion of the proximal segment from the jugular foramen.
I n the V-G and €3-G procedures the proximal portion of the
glossopharyngeal nerve was avulsed to minimize the possibility of regeneration of glossopharyngeal fibers. Sleeves of
femoral artery were used for joining the nerves. The fourth
operation, G-avulsion, was included as a control procedure.
Histologicnt procedures. After the 19th postoperative week
the animals were killed, the tongue removed, fixed for 24
hours in Heidenhain’s susa fluid, washed, dehydrated and
embedded in paraffin. Serial sections were cut a t 1 0 and
~
the slides were stained alternately by Heidenhain’s iron-hematoxylin and Bodian’s protargol methods. I n all animals the
REINNERVATION O F CLRCUMYALLATE PAPILLA
27
site of nerve anastomosis was exposed and, whenever possible,
the anastomosed nerves were removed, sectioned and stained
with protargol.
Thirteen additional animals of the H-G and G-avulsion
groups were killed at intervals from 2 to 26 weeks in order to
study the postoperative time course. Tissues from these animals were treated as above except that the sections were cut
at 7 1.1.
Qumtitative procedures. The narrow region about the
gustatory pore of the taste bud stains intensely with ironhematoxylin. To minimize the possibility of counting the same
taste bud in successive sections, this intensely-stained region,
rather than the entire taste bud, was counted. Furthcrmow,
taste buds were counted in alternate sections on the liematoxylin-stained slides only. Results of the taste bud counts
are expressed as the average number of taste buds per histological section of the trench wall of the circumvallate papillae.
This figure was obtained by dividing the total number of taste
buds that were counted by the total number of histological
sections of trench walls that were examined for taste buds.
Measurements also were made of the thickness of the epithelium covering the circumvallate papillae. Sections through
the center of the papillae were projected at a magnification of
165 X and traced on paper. The area of the epithelium lining
the top surface and inner trench walls of the papillae was
measured planimetrically. The length of this region was determined with a map measure. The average thickness of the
epithelium was obtained by dividing area by length.
Statistical procedures. Analysis of the taste bud counts by
Bartlett ' s test (Snedecor, '46) revealed that the variance of
taste bud counts among the 4 operative groups was not homogeneous. Consequently the data could not be subjected to a n
analysis of variance. Each of the 6 possible t-tests among the
4 groups was made by Welch's method (Bennett and Franklin, '54)-a procedure which allows for comparison between
experimental groups possessing heterogeneous variances.
28
LLOYD GUTH
RESULTS
The number of taste buds on the circumvallate papillae after
each of the 4 operative procedures is presented in table 1 and
evaluated for statistical significance in table 2. Illustrative
photomicrographs are presented in figures 2 through 5. There
is a significantly greater number of taste buds after the G-G
(fig. 2) o r V-G (fig. 3 ) procedures than after the H-G (fig. 4)
TABLE 1
Number of taste buds remaining on the circumvallate papilla o f the cat 19 weeks
after zrarious surgical procedures. See materials and methods for explanation of
abbreviations of operative procedures.
~
~~
NUMBER O F
ANIMALS
OPERATIVE
PROCEDURE
TASTE BUDS PER
TRENCH WALL
G-G
V-G
H-G
G-avulsion
1.137
0.941
0.046
0.104
STANDARD
ERROR OF
T H E MEAN
0.079
0.242
0.023
0.030
TABLE 2
Significance of the difference in mean number o f taste bzids remaining on the
circumvallate papilla after the various experimental procedures. (See table 1 for
the actual mean values). Abbreviations o f the experimental groups are explained
in the materials and methods.
EXPERIMENTAL GROUPS
COMPARED
G-G and
G-G and
G-G and
V-G and
V-G and
H-G and
V-G
H-G
G-avulsion
H-G
G-avulsion
G-avulsion
PROBABILITY O F T H E OBSERVED
OR LARGER DIIPFERENCE
0.50
0.01
0.01
0.02
0.03
0.20
CONCLUSION
Not significant
Significant
Significant
Significant
significant
Not significant
o r G-avulsion (fig. 5 ) procedures. No significance can be at-
tributed to the small differences between the G-G and V-G
procedures or between the 13-G and G-avulsion procedures.
Taste buds formed after the G-G and V-G operations are
located on the inner trench wall of the circumvallate papilla
and not on the top surface. This location of taste buds corresponds precisely to that in the normal unopcrated cat.
29
R E I N N E R V A T I O N O F CIR C UMV A LLA TE P A P I L L A
The paucity of taste buds after the H-G procedure cannot
be attributed to failure of regeneration of hypoglossal fibers.
In figure 6, regenerated hypoglossal fibers are seen coursing
through the submucosa into the mucous epithelium of the
circumvallate papilla. I n this animal, and in two others, the
anastomosed nerve fibers were traced in serial histological
‘i.
;I,,l,~~
W
OI
cn
.4
D
3
m 3
1
0
I
0
I
2
4
6
8
10
12
14
16
18
WEEKS A F T E R OPERATION
20
22
24
26
Fig. 1 Time course of taste bud disappearance a f t e r hypoglossal-glossopharyngenl nerve anastomosis (open circles) and a f t e r glossopharyngeal nerve avulsion
(closed circlcs). Each point represents one animal.
sections from their origin in the hypoglossal nerve (fig. 7)
through the operative scar (fig. 8) and into the neurilemma
sheaths of the distal segment of glossopliaryngeal nerve
(fig.. 9).
Figure 1 illustrates the time course of disappearance of
taste buds following €1-G and G-avulsion procedures. There
are no marked differences between the two experimental
groups. A considerable number of taste buds persists on the
30
LLOYD GUTH
circumvallate papilla at the end of the second postoperative
week, but they are undergoing desquamation from the epithelial surface (fig. 10). By the sixth postoperative week few
taste buds remain on the circumvallate papilla, and no appreciable changes occur during the ensuing 20 weeks.
The measurements of the thickness of the epithelium of the
circumvallate papillae are presented in table 3. There is no
statistically significant difference in epithelial thickness among
the 4 operative groups.
TABLE 3
Thickness of the epithelium covering the circumvallate papilla of the cat 19 weeks
after various surgical procedures. Abbreviations of the various operative procedures are explained in the section on materials and methods.
OPERATIVE
PROCEDURE
NUMBER O F
ANIMALS
AVERAGE
THICKNESS O F
EPITHELIUM
O F PAPILLAE
G-G
V-G
H-G
G-avulsion
1.595
1.560
1.526
1.479
STANDARD
ERROR O F
T H E MEAN
0.114
0.079
0.071
0.037
DISCUSSION
The glossopharyngeal nerve has not been extensively utilized in previous experiments on the nerve fiber-taste bud relationship. The lingual nerve, however, has been used in experimental investigations on the hedgehog (Boeke, '17) and
dog (Olmsted and Pinger, '36 ; Arey and Monzingo, '42). In
each study hypoglossal-lingual nerve anastomosis was performed, directing the regenerating hypoglossal fibers to the
lingual epithelium. The tongue was examined f o r the presence
of taste buds several months later. Roeke, ('17) observed
changes in the lingual mucosa that he interpreted as initial
stages in the formation of taste buds, but he presented no
quantitative data. Olmsted and Pinger ('36) described the
reappearance of taste buds in two animals sacrificed 6 months
postoperatively, whereas they found no buds in two dogs sacri-
REINNERVATION O F C I R C I J M V ~ I J L - ~ TPAPILLA
E
31
ficed 5 months postoperatively. This study, however, did not
include any animals sacrificed 6 months after lingual nerve
transection without anastomosis. Such a control group would
have ruled out the possibility that fibers other than hypoglossal ivere responsible for the reappearance of the taste
buds. Arey and Monzingo ('42) found no taste buds on the
tongue of one aiiinial sacrificed 7-5 months after hypoglossallingual anastomosis. These studies do not settle the question
of whether hypoglossal fibers a r e capable of stimulating taste
bud formation.
Thc results of the present experiment lead to the conclusion that hypoglossal fibers a r e incapable of initiating the
formation of taste buds on the circumvallate papilla. The
number of taste buds is no greater when the papilla is reinnervated by the hypoglossal nerve (H-G) than when denervated (G-avulsion). The small number of taste buds that is
fourid after either of these procedures may result from the
presence of a small number of glossopharyngeal nerve fibers
from the contralateral side.
De Castro ( '44) suggested that the vagus nerve can initiate
formation of taste buds on the circumvallate papilla. H e described taste buds on tlie circumvallate papilla of a cat 340
days after vagus-g.lossopliaryngea1 nerve anastomosis. The
results of the present experiment support De Castro's suggestion by showing quantitatively that the number of taste
buds is significantly greater after reinnervation of the papilla
by the vagus nerve (V-G) than after denervation of the papilla
(G-avulsion). Furthermore, there is no significant difference
in the number of taste buds aftw reinnervation of tlie circumvallate papilla by vagus (V-G) or glossopharyngeal (G-G)
nerves.
F r o m these data it is impossible to ascertain the degree of
nerve fiher specificity required for the formation of taste
buds. The hypoglossal nerve, which is almost exclusively
motor, is incapable of initiating taste bud formation. The
vagus nerve is of mixed constitution but predominantly sensory (Foley and Dubois, '37). Inasmuch a s the sensory com-
32
LLOT-D C U T H
poiiciiit may colitaill gustatory (iberh, it cari~iotbe dctei*iiiiiictl
whclthcr fibers of g:.clnei*aIsclnsatioii a r e capal)lc of stimulating
taste bud formation. Tlie variahility of the ~ i u m h e rof taste
h t l s (stantlard ( ~ r o of
r thc nieaii) is greater aftcr the V-(i
t h a n aftcr the G-G procedures (table 1). This diffciwlce rrlap
be a reflection of thc greater proportion of motor fibers in the
vagus 11eiw. Howevei* 110 definitive statement call be niadc
liecauscl tlic statistical proha1)ility of the diffcrcvicc l)et\vccn
tlic two variances is at the 8% level of confidence.
AIarkcd tliiiiniiig of tlic cpithclinni lining the ci rcuiiiv;illatcb
papilla occui’s within oiic week after 1)ilateral trailsect ioii of
tlic glossopliaryngeal ncrvc in tlic r a t (Guth, ’57). ?\To coniparable atrophy was observed in tlie present study. However,
these studies difftli. in rcgard to specics investigated, postoperative survival time, and operativc proceclurc (bilateral
vs. unilateral). Tliese differences in experimental design niap
also be used to explain why many taste huds were found oil
tlic tongue of the cat 2.5 n ~ e k spostoperativcl-y whcrcas viiatually all taste butis had clisappcared from the rat’s tongue
by the end of the first postoperative ivcck.
H U m f A 412 Y
Tlic follokving ciicl-to-cnd ricrvc aiiitstoinoses were performccl in 13 adult cats : proximal glossopliaryngeal to distal
glossopliaryngeal (G-G) ; proxirn;tl vagus to distal glossop1i;tryngenl (V-G) ; pi-osirnal hypoglossnl to distal glossopliaiyngcal (H-G). In a control group of 4 cats tlic glossopharyiigeal nervc was transcctcd and the proximal scgnirnt
avulsed (G-avulsion). Cats were killed after 19 week5 and the
circuirivallate papillae examined histologically for tastt. ljutls.
A significantly greater numbcr of taste 1mds \vas found
after the G-G and V-G proccdurcs than after tlic H-G o r Gavulsion operations. There was 110 significant difference in
n G-Q and V-G gi*oups 1101’
number of taste l~utlsb e t ~ \ ~ c etlic
between the H-G and G-avulsion groups.
T\vo further groups of H-G and G-avulsion animals 1vc.r.e
studied at 2, 6, 12, 16, a n d 26 weeks postoperatively. Tlic time
REINNEBVATION O F CIRCUMVALLATE PAPILLA
33
course of disappearance of taste buds was similar in the two
groups.
It is concluded that all but a small number of taste buds on
the ipsiIatera1 circumvallate papillae of the cat disappear
after unilateral transection of the glossopharyngcal nerve.
Reappearance of taste buds occurs upon reinnervation of the
papilla by either glossopharyngeal nerve o r vagus nerve.
However, reinnervation by the hypoglossal nerve does not
induce formation of taste buds.
ACKNOWLEDGMEXT
The author gratefully acknowledges the assistance of Mr.
Samuel TIT. Greenhouse of the Biometries Branch, National
Institute of Mental Health, in the statistical analysis of the
data.
IJTTERATURE CITED
AREY, L. R.,AND F. 1,. MONZINGO3942 Can hypoglossal nerve fibers indure the
formation of taste buds3 Q. Bull. ATorthwest. Univ. M. School, 2 6 :
170-178.
BENNETT,
C., AND N. FRANKLIN
19.54 “8tntistical analysis in rhcmistry and
the chemical industry.” R’rw York, Wiley, pp. 176-177.
BOEKE,J. 1917 Rtudien zur Nervcnregrneration 11. Verh. K. Akad. Wetcnsch.
Amst., 1 9 : 1-71.
DE CASTRO,F. 1944 Sobrr cl inccnnisino de encitxion de 10s quirnioceptores y
baroceptores del glosofaringeo, utilizanilo un arco reflejo formado
entre 10s sistomas vngo-afrrcnte y simpatico. Trab. Lab. Invest. Biol.
Univ. Mad., 36: 345-395.
FOLEY,
J. o., AND P. 8. DUBOIS 1937 Quantitative studies of the vagus ncrvc
in the cat. I. The ratio of scnsorp t o motor fibers. J . Comp. Nrur., 6 7 :
49-68.
GUTIT, L. 1957 The effects of glossophnrpngeal nerve transection on the circnnivallate papilla of the rat. Anat. Rcc., 128: 715-732.
HAYES,E. R., AND R. ELLIOTT 1942 Distribution of the taste buds on the
tongue of the kitten, with particuIar reference t o those innervated by
the chorda tympani branch of the facial nerve. J. Comp. Neur., 7 6 :
227-238.
MEYER, R. 1897 Durrhschneidungsversuche am Nervus glossopharyngeus. Arch.
mikr. Anat., 48: 143-145.
OL~ISTED,J. M. D. 1921 Effect of cutting the lingual nerve of the dog. J.
Comp. Neur., 33: 149-154.
1922 Taste fibers and the chorda tympani nerve. J. Comp. Neur.,
3 4 : 337-341.
OLifSTKD,
of tnstc: buds after
J. If. I)., ASD W. I<. I’IMQY,B 1936 ~<cgeuerittio~i
sut.urc of tlic liitgr~iilit.iiil Iiypoglossrtl nerves. Am. J. Physiol., 1 ZG:
225-227.
HASDSIHYER, w. 1895 U e h r diw vc?rli:tltiw der (~e s~lt~iia ~k~kiiospe
iiiich ii
hrrliArch. A1i:i.t.. Ily4ol., I’liysiol.
wliitcitluiig iles K. g1oss0~1biir~1tgc.11~.
AM., Jg. 1895: 8. 264-”?(i.
SnmEt:otL, G . W. 1946 “St.:itistic:il hlctltotls.’ ’ Auics, Iowa., low1 Htatn College
Press, Chap. 30, pp. 214458.
WIIITEHIDE,
B. 1927 New(! overlttp iii tlic gustatory apparatus of tlw rat. J .
Comp. Xeur., 44: 3(3-377.
PLATE 1
ISSI’IASATIOX OF F1CIUHF.R
35
6
Circuii1v:ill:Ltc p:i.pill:L of s cat 19 \i,ecks after aiiast~oiiiosisof proximal liypoglossal niitl distal glosaopharyngeal iicrvc segiiiciits (H-G) . Protsrgol staiii,
390 X . Itcgciicrating Iiypoglossal fibers aIe coursing through submucosa into
epi tlieliuiii.
7
Fibers of proxiiiixl scgiiiwt of liypogloss:1.1 iiervc. Protargol staiii, 190
8
Rcgciier:itCd fibers t h a t fi:tvo eliicrgcd froni the proximal segment of liypoglossal I I ~ I ’ V C a11d arc coursing tlirougli tlic scar bctwecii tlic anastoiiiosed iiervc
ends. Prot.argo1 stain, 600 x .
9
Itcgciierateil 1iypogloss:xl fibers 1c:iring tlie scar aiid eiiteriiig the distal
glossopfiaryngenl n t w e segiiiciit. Protargol stain, 190 x .
10
x.
Circ.univallnte papilla of a. cat, 2.5 weeks after trailsection of tlic glossopli:~ry~~g~:11
iicrvc. Two taste buds are uncleryoing desquaination from thc surface
of t,lic iiiiier trench wall. Hcideiiliaiii’s iron liematoxylin stain, 340 x.
36
PLATE 2
37
Документ
Категория
Без категории
Просмотров
8
Размер файла
752 Кб
Теги
taste, papilla, cat, buds, nerve, reinnervation, circumvallate, hypoglossal, vagus, glossopharyngeal
1/--страниц
Пожаловаться на содержимое документа