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Studies of muscle fibers of the tensor tympani of the cat.

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Studies of Muscle Fibers of the Tensor
Tympani of the Cat
S. D. ERULKAR, M. L. SHELANSKI, B. L. WHITSEL AND P. OGLE
Department of Pharmacology, Schools of Medicine, University of
Pennsylvania, Philadelphia, Pennsylvania
ABSTRACT
The tensor tympani muscle of the cat has been studied using histological and electrophysiological techniques. Histological studies revealed the presence
of striated and smooth muscle fibers. The striated muscle fibers could be classified
structurally as “Fibrillenstruktur” and “Felderstruktur” fibers, suggesting that both
“fast” phasic and “slow” tonic fibers were present. Histochemical studies showed
that some of the smaIIer ( 2 5 4 0 p ) FibriIlenstruktur fibers possessed relatively large
end-plate receptor areas which stained heavily for acetylcholinesterase. The membranes and cytoplasm of even smaller diameter fibers (9-25 p ) stained for acetylcholinesterase, similar to its distribution in muscle spindles of other muscles.
Intracellular recordings showed that there were two distribution peaks of the
resting membrane potentials-one
at 40-50 mV, the other a t 70-80 mV. When the
nerve to the tensor tympani was stimulated by single square wave pulses, small
junctional potentials (40 mV) followed by a n after-hyperpolarization, were recorded
only from fibers with low resting membrane potentials - presumably slow Felderstruktur fibers. Large (70-90 mV) potentials which showed overshoot of zero potential,
and which were preceded by i n i t i d long depolarizing potentials, were recorded from
fibers with large resting membrane potentials. These fibers, which showed occasional
spontaneous activity were presumably smooth muscle fibers. Potentials similar to those
recorded from fast muscle fibers in other muscles were also occasionally recorded.
It was concluded that the cat tensor tympani possessed slow and fast striated
muscle fibers, smooth muscle fibers, and possibly some embryonic type muscle fibers.
Some striated muscle fibers respond to
stimulation of their nerves with slow, longlasting contractions or contractures, and
are incapable of conducting propagated action potentials. Peachey and Huxley (’62)
have correlated the functional properties
of these muscles with their structure, and
concluded that those fibers which respond
with slow contractions may be classified
morphologically as “Felderstruktur” fibers
(Kruger, ’49), while those which give fast
twitch responses may be classified as
“Fibrillenstruktur” fibers. Fibers with “Felderstruktur” differed from those with
“Fibrillenstruktur” by having wider, more
irregular myofibrils between which was
found a less extensive sarcoplasmic reticulum. “Slow” muscle fibers have been studied extensively in amphibia and reptiles
(Kuffler and Vaughan Williams, ’ 5 3 ) , but
in mammals have been demonstrated to be
present only in extraocular muscle (Hess,
’61) and in muscle spindles. In ’58,
Wersall, on the basis of physiological and
pharmacological studies, suggested that
mammalian middle ear muscles may posANAT. REC., 149: 279-298.
sess “slow” muscle fibers. The present
study on the tensor tympani of the cat was
undertaken to extend Wersall’s observations.
MATERIALS AND METHODS
( a ) Histochemistry. Fifteen cats were
used. The cats were anesthetized with
sodium pentobarbital (Nembutal, Abbott
Laboratories) 42 mg/kg, i.p. The bulla
was approached from the ventral side and
removed. The tensor tympani was then
exposed in the middle ear and gently removed from its insertion under 40 X magnification of a Zeiss dissection microscope.
The muscle was placed in chilled saline
solution, and frozen sections were cut at
15 u. The procedure for acetylcholinesterase staining then followed that described by Koelle and Friedenwald (’49)
and Koelle (’51, ’55). In every preparation,
selective staining for acetylcholinesterase
and butyrylcholinesterase was carried out.
(b) Light microscopy preparations. Eight
cats were used. After removal of the
tensor tympani, the muscles were fixed in
279
280
S . D. ERULKAR, M. L. SHELANSKI, B. L. WHITSEL AND P . OGLE
either formalin or Susa’s solution overnight. Transverse and longitudinal sections were cut at 10 LI thickness, and
stained with either hematoxylin and eosin
or Mayer’s hematoxylin. In two cats, the
muscles were similarly fixed and stained
with Heidenhain’s iron alum solution.
Three pairs of muscles were left in situ
and sections made of the temporal bones
through the courtesy of Dr. C. Fernandez
and Miss Cernius. The procedures included decalcification, dehydration, and
imbedding in celloidin, followed by staining with Harris’ alum hematoxylin and
eosin. Sections were cut at 20 LI and every
tenth section was stained. A further series
was also prepared which was stained with
Weil’s silver stain.
( c ) Electron microscopy preparations.
Ten cats were used. After removal of the
tensor tympani, the muscles were immediately rinsed in saline solution in which
they were left for 20 minutes. After being cut into 2-3 pieces, they were next
fixed for two hours in a 1% solution of
osmium tetroxide buffered with veronal
acetate.’,2 The specimens were then dehydrated in ethanol and embedded in
Araldite (Glauert).
The specimens were cut with glass
knives on a Porter-Blum microtome and
used in an RCA EMU 3C electron microscope. Most of the sections were stained
with the lead staining procedure recommended by Millonig (’61).
( d ) Electrophysiology. Forty cats were
used for electrophysiological recordings.
The muscle was exposed as previously
described, as much connective tissue removed as possible, and then left in situ.
Electrodes could then be inserted smoothly
into the muscle from the ventral side,
while being visualized under 40 X magnification of the Zeiss dissecting microscope.
3M KC1-filled micropipettes with tip diameters of 0.1-0.4 1-1, and from 20-100
megohms in resistance, were used for recording. A silver clip on the scalp served
as the reference electrode. In initial experiments the signal was led through a
Grass MEP-6 probe to a DC P-6 preamplifier and thence to a 502 Tektronix DC
oscilloscope. In most experiments, however, the signal was fed from the electrode
through an electrometer tube and thence
to a Bak Unity gain amplifier (Bak, ’58).
Amplification was provided by a 251-A
AEL amplifier which led to a Tektronix
502 DC oscilloscope, where the signals
were photographically recorded. Measurements were taken from the enlarged
images of the photographs.
Tonal stimulation was delivered through
a TDH-39 earphone activated by a HewlettPackard 650A oscillator. For electrical
stimulation of the nerve, two silver wire
electrodes were placed on the partially
exposed nerve, and a Grass S-4 square
wave stimulator leading to a stimulus isolation unit provided the source of stimulation. Square waves of 0.1 msec duration
were used.
RESULTS
( a ) Morphology. Transverse and longitudinal sections of the cat tensor tympani
stained with hematoxylin and eosin revealed the presence of both striated and
smooth muscle fibers (fig. 7). The striated
muscle was placed peripherally, the
smooth muscle more centrally, and both
types of muscle surrounded a central core
of connective tissue. The striated muscle
fibers could be divided into two groups. In
transverse sections, one of these groups
showed a punctate appearance (Fb in
fig. S), the fibrils being small and uniformly separated from one another. These
resembled “Fibrillenstruktur” fibers described by Kruger (’49). The second group,
on the other hand, consisted of fibers
which stained more densely with eosin
(Fe in fig. 8). The fibrils in these fibers
appeared to be irregularly spaced and
larger in diameter than those of the first
group. These were similar to “Felderstruktur” fibers also described by Kruger
(’49). Similar differences between the
two groups were seen in sections stained
with Heidenhain’s solution.
Sections of the muscle left in situ
and stained with hematoxylin and eosin
showed that there was a regional distribution of these fibers. First, smaller diameter
fibers (9-40 v) of both groups were situated on the superior and lateral edges
IPalade’s veronal acetate buffer as listed in
Pease (’60).
zThe veronal acetate buffer was adjusted to pH 8.5
with HCl before use with 0 ~ 0 4 and
,
the mixture was
then adjusted lo pH 7.5.
MUSCLE FIBERS IN TENSOR TYMPANI
close to the attachment of the muscle to
the malleus. The fibers became progressively larger (50-90 cl) towards the medial side of the muscle. Furthermore,
towards the medial surface, the fibers with
punctate appearance (i.e. Fibrillenstruktur) became predominant, until they were
exclusively present at the medial edge.
In the region of the smaller fibers, the
“Fibrillenstruktur” fibers could be differentiated into two groups on the basis of
difference in size, and in their characteristics of staining for acetylcholinesterase.
The larger diameter fibers (25-40 w)
showed faint staining in their membranes
for acetylcholinesterase, but there was
heavy staining in the end-plate region in
all sections which were incubated from
5 to 60 minutes. The stained area was
extremely large in relation to the cross
sectional area of the muscle fiber (fig. 9),
and in those cases in which the nerve
could be seen approaching the muscle
fiber, the presynaptic terminals cupped
around the fiber in the form of a calyx,
and occupied from 30-70% of the circumference. No reliable quantitative measurements could be obtained, for it was impossible to ascertain whether the end-plate
region was at its maximum size around
the fiber. Other fibers in this region had
multiple end-plates, and these also stained
strongly for acetylcholinesterase. Figure
9 also shows that several nerve fibers may
be going to the same end-plate region of a
small muscle fiber. The end-plate region
in a fast striated muscle - the lumbrical
-is shown in figure 10, also stained for
acetylcholinesterase. The area of the endplate in relation to the circumference of
the muscle fiber is much less than that
seen in figure 9 for the muscle fibers of the
tensor tympani. Another group of fibers in
the tensor tympani, which are of smaller
diameter (9-25 M), showed heavy staining
of their membranes for acetylcholinesterase, and some staining throughout their
cytoplasm (fig. 11). Whether the heavy
staining around the fiber does in fact represent membrane staining, or whether it
represents staining of a nerve network
which surrounds the fibers is difficult to
determine. The uniformity of this staining, however, suggests that the membranes
themselves are implicated.
281
In longitudinal sections, two types of
end-plate could be distinguished. One
group (fig. 12) was similar morphologically to the “en plaque” type, which has
been described for mammalian fast striated muscle fibers, and these structures
were always seen on the larger fibers. There
was also present another type of ending
(fig. 13) similar to the “terminaisons en
grappe” or to the endings described by
Gerebtzoff (’55), which gave a much
weaker acetylcholinesterase staining reaction than the “en plaque” endings.
These endings appeared as clusters of
droplets and occupied considerable areas
of the muscle fiber. They were consistently seen on thin, small diameter fibers.
The presence of “slow” (Felderstruktur )
striated muscle fibers has also been demonstrated by electron microscopy. Figure 14
shows at 6,700 magnification a typical
fast striated muscle fiber with well defined
sarcomeres, straight Z bands, clearly defined M bands, and organized sarcoplasmic
reticulum. Adjacent to this fiber is one
with crooked, ill-defined Z bands, less
organized sarcoplasmic reticulum, and no
detectable M bands. The organization of
the myofibrils also appears to be less symmetrical, and some fibrils converge with
others, an arrangement not seen in the
fast striated muscle fibers. Higher resolution (fig. 16) of the “slow” muscle shows
that the triads are arranged at the A-I
junctions and not at the Z line as in the
“fast” muscle (fig. 15).
The calibers of the nerve fibers to the
tensor tympani are shown in the histogram of figure 1. Although there were a
few fibers of 8-10 w in diameter, the peak
of the distribution was at 3-4 cl. There
were also many small diameter unmyelinated fibers in this nerve, the values of
which have not been included in the histogram.
(b) Electrophysiology. As the electrode
penetrated the muscle there occurred
many shifts in the DC potential. In some
cases, these shifts lasted only a few seconds and the results were discarded. In
other cases, after the presumed penetration of the fiber, a steady depolarization
occurred lasting over some minutes until
zero potential was reached. Here the fibers
were assumed to be damaged, and results
282
S . D. ERULKAR, M. L. SHELANSKI, B. L. WHITSEL AND P. OGLE
%
50-
N-886
40-
30-
0
1
2
3
4
5
6
Fig. 1 Distribution of diameters of the myelinated nerve fibers to the tensor tympani
in the cat.
from these records were also discarded.
Only those records have been included in
the results in which there was a sudden
clear shift of the DC potential which then
remained stable over a period of 5 to 25
minutes. Withdrawal of the electrodes
from the fiber was signaled by a sudden
shift of the DC potential to zero levels. The
distribution of resting membrane potentials (fig. 2) shows two significantly distinct peaks; one at 40-50 mV, and the
second at 70-80 mV. Penetration of fibers
in more peripheral areas resulted in rela-
tively small shifts of potential ranging
from 20-60 mV, with a peak distribution
between 40 and 50 mV. If the tensor tympani nerve was stimulated with square
wave pulses, the responses shown in figure
3 were obtained from fibers with small
resting potentials. The peak value of the
depolarizing potential is 36 mV, and that
of the hyperpolarizing potential 8 mV
(cf. Kuffler and Vaughan Williams, '53).
The time course of the total response is 64
msec. A plot of the amplitudes of the
potentials against time showed a significant deviation from the exponential. The
96
N.395
responses could be abruptly graded in
18amplitude with different strengths of stimulation (fig. 3 ) . Although no potential
16changes similar to those described above
were elicited by tonal frequencies pre14sented to either ear, often a sustained depolarization could occur. This, however,
did not return to its original level when
12the stimulation was stopped, and it was
impossible to say in these cases whether
10this depolarization was the reflection of
some damage to the membrane as a result
8of local contraction, or whether this was
a true change in the membrane proper6ties as a result of the stimulation.
When the electrode was advanced more
4deeply into the muscle, the penetration of
a fiber was signaled by a greater shift in
2the DC potential, and values of 50-90 mV
were recorded with a peak distribution
from 70-80 mV. The recordings obtained
Fig. 2 Membrane potential values recorded from some of the fibers in this-region disfrom tensor tvmuani fibers. Note two peak values,. played spontaneous activity, and the reone at 40-50-m?, the other at 70-80 mV.
corded potentials showed long initial de~~
n
283
MUSCLE FIBERS IN TENSOR TYMPANI
polarizations preceding large spikes which
overshot the zero potential by 3-17 mV
(fig. 4a). These recordings are similar to
I \
those obtained from smooth muscle fibers
(Bulbring, '55). Sometimes double spikes
were generated from a depolarizing potential and in these cases, repolarization occurred with a faster time course than that
seen for single spikes. The duration of the
spike was approximately 4 msec, and it
was followed by an after-hyperpolarization
which lasted for 10-30 msec. Often, small
depolarizing potentials which failed to
reach critical level were superimposed on
the initial depolarizing wave. Figure 4a
I
IOrnrec.
Fig. 3 Small junctional potentials recorded shows that the threshold for spike generafrom a fiber of the tensor tympani. Resting po- tion increased during the spontaneous
tential 46 mV. The top record shows responses to firing of a train of spikes even though the
two stimuli, one at an intensity just sufficient to level of the resting membrane potential
elicit a response; the second at an intensity
remained constant until no further spikes
which elicited a maximum response.
The lower record shows two responses to inten- occurred. Once spike firing stopped, howsities 60% of that needed to elicit a maximum ever, the membrane became depolarized by
response.
10 msec.
Fig. 4a Spontaneous activity of potentials, which are presumably recorded from smooth muscle
fibers. Note sustained depolarization during which no spikes are generated. Membrane potential
63mV.
4 msec.
Fig. 4b Responses from smooth muscle fibers of the tensor tympani to a sustained tonal stimulus of 1,500 cps presented to the ipsilateral ear. Arrow denotes time of onset of stimulus. Spikes
intensified. Membrane potential 70 mV. Time line denotes 4 msec peak to peak.
284
S . D. ERULKAR, M. L. SHELANSKI, B. L. WHITSEL AND P. OGLE
10-17 mV and this depolarization was
sustained. If and when spike firing resumed, the threshold levels for spike generation were considerably increased over
previous levels. Similar effects have been
observed in response to tonal stimulation
(fig. 4b), but in these cases it was rare
for spike firing to resume after an interval
of depolarization. Furthermore, with tonal
stimulation, the build-up of depolarization
to critical levels could be seen following
the onset of the stimulus. While this effect
may be a function of our tone producing
equipment, it was constantly seen in different penetrations regardless of the tonal
frequency presented. There was no quantitative relationship between the frequency
of spike firing and the tonal frequency.
When the nerve to the tensor tympani
was stimulated with different stimulus
strengths (fig. 5), the long time course of
the end-plate potential was revealed. These
epps could be graded further down by even
lower strength stimuli. The after-hyperpolarization was associated only with the
firing of the spike, and was not seen when
the spike was not generated.
A third type of potential was recorded
rarely under the conditions of these experi-
. .
2 rnsec.
Fig. 6 Intracellular recording, presumably
from a “fast” muscle fiber in the tensor tympani,
in response to electrical stimulation of the tensor
tympani nerve. Membrane potential 85 mV.
Spike truncated for ease of display. Time line
denotes 2 msec peak to peak.
ments (fig. 6). These potentials, which
were recorded from fibers with resting
membrane potentials of 70-100 mV, were
approximately 120 mV in height and 1-2
msec in duration. The spike configurations
were similar to those recorded from fast
striated muscle fibers from other preparations.
DISCUSSION
I
Fig. 5 Intracellular recordings from smooth
muscle fibers of the tensor tympani of responses
to electrical stimulation of the tensor tympani
nerve, at different stimulus strengths. Membrane
potential 50 mV.
There are present in the cat tensor
tympani both striated and smooth muscle
fibers. On the basis of the data obtained
from light and electron microscopy, it
seems clear that the striated muscle is
composed of fibers of “Felderstruktur” and
“Fibrillenstruktur” types. There is now
evidence (Peachey and Huxley, ’62) that
muscle fibers with these morphological
characteristics are functionally “slow” and
“fast” fibers respectively. Peachey and
Huxley showed these correlations to be
valid for the ilio-fibularis of the frog, but
there is some reason to question whether
the same correlations hold true in mammalian muscle. In fact, Kriiger (’49) described “Felderstruktur” fibers to be present in tonic mammalian muscles, such as
the soleus, but these muscle fibers do conduct propagated action potentials. We
must, therefore, first consider whether in
MUSCLE FIBERS IN TENSOR TYMPANI
this study the low resting potentials may
be recorded from small fibers which are
damaged by the impaling electrode, and
therefore are depolarized. This depolarization would lead to inactivation of the spike
generation mechanism. Although damage
inevitably occurred in some cells, in others
resting potentials remained stable over
many minutes and would return to zero
potential only when the microelectrode
was deliberately advanced, or the muscle
contracted due to strong stimulation of
the nerve. These facts would lead us to
believe that the low resting potentials recorded from some of these cells are not due
to damage, and that these cells are true
“slow Felderstruktur” fibers.
Small junctional potentials similar to
those recorded by Kuffler and Vaughan
Williams (’53) in the ilio-fibularis of the
frog, have been recorded in the fibers of
the tensor tympani. There is a difference
in the time course of the responses, as
those from ilio-fibularis lasted approximately 150 msec as compared to 60 msec
in the tensor tympani. The difference here
may lie in the different conditions of the
experiments. The records from the tensor
tympani were obtained with the muscle
in situ and the cat at a temperature of
approximately 37”C, whereas the records
by Kuffler and Vaughan Williams were
from the ilio-fibularis in a muscle chamber
at approximately 20 “C.
The grading of the amplitudes of the
small junctional potentials in response to
different stimulus strengths may be explained by assuming that different axom
to the end-plate region of the same fiber
are being stimulated. This has been suggested by Orkand (’63) for the gradation
of responses accompanying changes in
stimulus intensity in records from the slow
fibers of the ilio-fibularis of the frog. Figure 9 suggests that in the tensor tympani
there may be more than one nerve fiber
leading to the same end-plate region of
the muscle fiber.
The slow “Felderstruktur” fibers of the
tensor tympani are discretely localized in
the supero-lateral edge of the muscle. In
this region are also localized ”Fibrillenstruktur” fibers, which are of small diameter (approximately 25-40 LI)and small
length (approximately 45-100 P); it has
285
been shown by cholinesterase staining that
in these fibers the area of the end-plate is
large in relation to the area of the fiber
itself. Indeed, it appears that the presynaptic terminal forms a calyx around
the muscle fiber, and we must consider the
functional consequences of this arrangement. It is known that an increase in the
receptor area does give rise to tonic contractions. WersU (’58) suggested that
in the middle ear muscles, the small muscle fibers may play a part in tonic contraction in view of the disproportionately great
influence of the large end-plate region.
In slow muscle fibers of amphibia, however, the increase in receptor area is in the
form of mutiple end-plates on the individual fibers; there would thus be a difference
in relation to the activation of many small
areas of the membrane, perhaps at different times, in these fibers as compared to
the activation of a large area of the membrane simultaneously in the tensor tympani fibers. Burke and Ginsborg (’56a, b )
concluded, however, that the spatial uniformity of the slow junctional potentials
in slow fibers would suggest at a first approximation that the junctional regions
are sufficiently close together to be regarded as a continuous strip of membrane.
It may in fact be possible that, in spite
of all possible precautions, diffusion by the
acetylcholinesterase stain in our preparations is obscuring multiple end-plates
which are located close together on the
fiber. Such multiple end-plates have been
seen in a few fibers in these experiments,
and in figure 9 it does appear that there
are multiple nerve fibers being distributed
to the same end-plate region of the small
muscle fiber. Whether the increase in receptor area, therefore, is in the form of
multiple end-plates or as a continuous strip
on the membrane, both types of muscle
would show long-lasting contractions. The
structures which appear to be responsible
for tonic contraction are localized to one
region of the tensor tympani, and it seems
likely that these fibers with large end-plate
areas may be muscle fibers comparable
with those in an embryological stage of
development (Kupfer and Koelle, ’51 ;
Diamond and Miledi, ’59). The smaller
(9-25 p) muscle fibers whose membranes
were stained for acetylcholinesterase may
286
S. D. ERULKAR, M.
L. SHELANSKI, B. L. WHITSEL AND P. OGLE
reflect a primitive stage of development.
Similar staining characteristics from membranes have been seen in the tail of the
golash, (Lundin, '59), but not in mammalian muscle except in muscle spindles.
In this context, it is interesting to note
the observation of Edgeworth ('14) that
in the rabbit the proximal portion of the
tensor tympani atrophies prior to adult
development. While these fibers may be
similar to muscle spindles in their staining characteristics, no proprioceptive endings were found. Carmel ('63) has shown,
that in the cat the other middle ear muscle
- the stapedius - is smiliar in structure
and physiological characteristics to other
mammalian "fast" muscles. The different
site of development of the stapedius to that
of the tensor tympani may account for
their morphological and functional diff erences.
The presence of smooth muscle fibers
in the cat tensor tympani has been confirmed in this study (Byrne, '38). The
potentials recorded from these fibers are
similar in configuration to, although somewhat larger than, those recorded from
other smooth muscle sites (Bulbring, '55;
Burnstock and Holman, '61). In fact, in
response to tonal stimulation there occurs
a step-like build up of the potential to
critical levels similar to that seen with
repetitive stimulation of the nerve to the
vas deferens Burnstock and Holman, '61 ).
The interesting observation in this study
is the sustained depolarization which is
recorded from these fibers following a
train of spikes. During such a train there
was a progressive increase in the threshold
for spike generation until spike firing
stopped. Although no tension records were
obtained, it would appear likely that the
muscle was in a contracture during the
sustained depolarization. Some preliminary experiments on the effects of depolarizing agents (KCl, Clo, succinylcholine) on this muscle have in fact shown
a depolarization with no spike firing, which
accompanies a long lasting contraction
(see Wersiill, '58). The question here,
however, is whether the sustained depolarization is a result of some intrinsic property of the muscle or whether it is caused
by the stretching of the smooth muscle by
the surrounding tonic striated muscle. In
records from taenia coli, Bulbring ('62)
has shown that stretching of the muscle
gives rise to an overall increase in membrane depolarization accompanied by an
increased rate of spike firing. This pattern
is not evident in our records. No increase
in spike firing occurs, and the overall
resting membrane potential remains essentially the same until spike firing stops
when the membrane becomes depolarized.
In fact, the progressive increase in the
durations of the initial depolarization preceding the spikes, until these spikes are
no longer triggered, suggests that changes
are taking place in the membrane properties of the fiber.
The relative rarity of action potentials
similar to those obtained from fast striated
muscle fibers does not, we feel, reflect the
absence of this type of muscle in the
tensor tympani as a whole. Rather, it suggests that our electrodes did not penetrate
that part of the muscle containing many
of these fibers. Occasionally, such potentials were obtained, and another approach
by the electrode would probably have recorded these potentials more frequently.
It would appear therefore that the cat
tensor tympani consists of several different
types of muscle fiber, some of which may
have more primitive characteristics than
the others.
ACKNOWLEDGMENTS
I wish to thank Drs. G. B. Koelle and
C. P. Bianchi for continued guidance and
help throughout this study. I am also
grateful to Miss Cornelia Geesey for technical assistance. Grants NB-02941 and
NB-00282 are also acknowledged.
LITERATURE CITED
Bak, A. F. 1958 A unity gain cathode follower.
Electroencephalog. and Clin. Neurophysiol., 10:
745.
Bulbring, E. 1955 Correlation between membrane potential, spike discharge and tension in
smooth muscle. J. Physiol., 128: 200-221.
1962 Electrical activity in intestinal
smooth muscle. Phys. Rev., 42, S u p p l . 5:
160-174.
Burke, W., and B. L. Ginsborg 1956a The electrical properties of the slow muscle fibre membrane. J. Physiol., 132: 586-598.
1956b The action of the neuromuscular
transmitter on the slow fibre membrane. J.
Physiol., 132: 599-610.
MUSCLE FIBERS I N TENSOR TYMPANI
Burnstock, G., and M. E. Holman 1961 The
transmission of excitation from autonomic
nerve to smooth muscle. J. Physiol., 155:
115-133.
Byrne, I. G. 1938 Studies on the physiology of
the ear. London: Lewis and Co.
Carmel, P. 1963 Personal communication.
Diamond, J., and R. Miledi 1959 The sensitivity of foetal and new-born rat muscle to acetylcholine. J. Physiol., 149: 50P.
Edgeworth, F. H. 1914 On the development
and morphology of the mandibular and hyoid
muscles of mammals. Quart. J. Micr. Sci., 59:
573-643.
Gerebtzoff, M. A. 1955 Les quatre localisations
de l'acetylcholinesterase dans les muscles stries
des mammifkres et des oiseaux. C. R. SOC.Biol.,
(Paris) 149: 823-826.
Hess, A. 1961 The structure of slow and fast
extrafusal muscle fibers in the extraocular muscles and their nerve endings in guinea pigs.
J. Cell. and Comp. Physiol., 58: 63-79.
Koelle, G. B. 1951 The elimination of enzymatic diffusion artifacts in the histochemical
localization of cholinesterases and a survey of
their cellular distributions. J. Pharmacol. Exp.
Ther., 103: 153-171.
1955 The histochemical identifkation
of acetylcholinesterase in cholinergic, adrenergic and sensory neurons. J. Pharmacol. Exp.
Ther., 114: 167-184.
Koelle, G. B., and J. S. Friedenwald 1949 A
histochemical method for localizing cholines-
287
terase activity. Proc. SOC.Exper. Biol., N. Y.,
70: 617-622.
Kruger, P. 1949 Die Innervation der tetanischen und tonischen Fasern der quergestreiften
Skeletmuskulatur des Wirbeltiere. Anat. A m . ,
97: 169-175.
Kuffler, S. W.,and E. M. Vaughan Williams,
1953 Small nerve junctional potentials. The
distribution of small motor nerves to frog skeletal muscle, and the membrane characteristics
of the fibres they innervate. J. Physiol., 121:
289-317.
Kupfer, C., and G. B. Koelle 1951 A histochemical study of cholinesterase during the
formation of the motor end-plate of the albino
rat. J. Exp. Zool., 116: 399-414.
Lundin, S. J. 1959 Acetylcholinesterase in goldfish muscles. Biochem. J., 72: 210-214.
Millonig, G. 1961 A modified procedure for
lead staining of thin sections. J.B.B.C., 11:
736-739.
Orkand, R. K. 1963 A further study of electrical responses in slow and twitch muscle fibres
of the frog. J. Physiol., 167: 181-191.
Peachey, L. D., and A. F. Huxley 1962 Structural identification of twitch and slow striated
muscle fibers of the frog. J. Cell. Biol., 13:
177-180.
Pease, D. C. 1960 Histological Technique for
Electron Microscopy. Academic Press, New
York.
Wersall, R. 1958 The tympanic muscles and
their reflexes. Acta Oto-Laryng. Suppl. 139.
PLATE 1
EXPLANATION OF FIGURES
7 Tensor tympani; longitudinal section (10 p ) , fixed in formalin, and
and stained with hematoxylin and eosin. X 140. Sm, smooth muscle
fibers; St, striated muscle fibers.
8
288
Tensor tympani; cross section (15 p ) , fixed in formalin, and stained
with Harris’ alum hematoxylin and eosin. X 520. Fe, Felderstruktur
fibers; Fb, Fibrillenstruktur fibers.
MUSCLE FIBERS I N TENSOR TYMPANI
PLATE 1
S. D. Erulkar, M. L. Shelanski, B. L. Whitsel and P. Ogle
289
PLATE 2
EXPLANATION
OF
FIGURES
9 Localization of AChE at end-plates of small muscle fibers of the tensor
tympani. Frozen section (15 p ) . Note the large area of AChE activity
relative to the circumference of the muscle fiber. X 600.
10 Cross section of the first lumbrical muscle of the cat’s paw, showing
end-plate region stained for AChE. Compare relative portion of muscle fiber stained to that in above figure. X 600.
290
MUSCLE FIBERS IN TENSOR TYMPANI
S. D. Erulkar, M. L. Shelanski, B. L. Whitsel and P. Ogle
PLATE 2
291
PLATE 3
EXPLANATION
292
OF
FIGURES
11
Heavy pericellular staining for AChE of small muscle fibers i n tensor
tympani. Counterstained with hematoxylin and eosin. Frozen section (15 p ) . x 720.
12
Longitudinal section (15 p ) of tensor tympani showing “en plaque”
type end-plates. Gold Chloride stain. X460.
13
Longitudinal section of thin small diameter fiber, stained for AChE.
witk clusters of endings similar to those described by Gerebtzoff:
X 720.
MUSCLE FIBERS IN TENSOR TYMPANI
S. D. Erulkar, M. L. Shelanski, B. L. Whitsel and P. Ogle
PLATE 3
293
PLATE 4
EXPLANATION
294
OF
FIGURES
14
Electron micrograph of tensor tympani showing single “slow” striated
muscle fiber adjacent to “fast” striated fiber. Arrow shows point of
convergence of myofibrils in slow fiber.
15
Electron micrograph a t higher resolution than above showing “fast”
muscle fiber with M bands present, and triads (arrow) located at
the Z line. Z, 2 lines; M, M-bands.
MUSCLE FIBERS I N TENSOR TYMPANI
S . D. Erulkar, M. L. Shelanski, B. L. Whitsel and P. Ogle
PLATE 4
295
16 Higher resolution of “slow” muscle fiber, showing triads (arrows) placed at the A-I junctions. Muscle contracted. Glycogen
granules are abundantly present. Z, Z lines.
EXPLANATION OF FIGURE
PLATE 5
MUSCLE FIBERS I N TENSOR TYMPANI
S. D. Erulkar, M. L. Shelanski, B. L. Whitsel and P. Ogle
PLATE 5
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