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Ultrastructural characterization of nuage in spermatocytes of the rat testis.

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Ultrastructural Characterization of Nuage in Spermatocytes
of the Rat Testis
Department ofdnatomy, University of Miami, School of Medicine,
Miami, Florida 33152
At least six different types of nuage, as judged by morphological
appearance, were found in spermatocytes of the adult rat testis. These were characterized by form, distribution, and association with other organelles. The appearance (with time) and the dissociation of some nuage types were recorded in
conjunction with other events of the spermatogenic cycle. The data indicate that
all types of nuage behave in a dynamic way. Especially interesting were the findings concerning the chromatoid body. This structure was first observed in midpachytene spermatocytes. By late diplotene and during the first meiotic division,
it had lost its prominence such that its eventual fate could not be determined.
Large dense (0.5 pm) bodies appeared de nouo in the cytoplasm of newly formed
secondary spermatocytes. They were seen scattered throughout the cell and in
association with mitochondria. With time these bodies appeared to coalesce to
form the large definitive chromatoid of a type similar to that known to be present throughout most of the remainder of spermiogenesis.
Nuage * is the term which has been used to
describe various forms of dense material in
male and female germ cells of a wide variety
of species (Andre and Rouiller, '57; Massover,
'68; Al-Mukhtar and Webb, '71; Kalt, '73;
Eddy, '74; see Sud, '61 and Eddy, '75 for comprehensive reviews).
In recent studies (Russell, '77a,b) of the
spermatocyte population of cells in rats,
nuage was observed to be abundant within the
cytoplasm of most spermatocytes. Several different forms of nuage (as judged by morphological appearance) were seen within the same
cell type. Each type of nuage was distinctly
different in its appearance and position within the cytoplasm, and associations with other
structures. During this survey of the spermatocyte population of cells, it was casually
observed that some forms of nuage were undergoing changes which were both quantitative and qualitative in nature. Some types of
nuage would appear to arise in one particular
stage of the cycle and "vanish" in another.
The distribution and associations of the nuage
also varied considerably with time.
These preliminary observations revealed
that rat spermatocytes contained several different types of nuage and that in general this
ANAT. REG. (1978) 190: 79-98.
substance was abundant within these cells.
Therefore, it was felt that a more thorough examination of these cells would be beneficial to
further classify and characterize the morphological appearance, distribution and associations (with other structures) as well as an appearance (with time) and fate of nuage.
Five normal, adult Sherman and SpragueDawley rats were utilized in this study. Animals were anesthetized with sodium pentobarbital, and the testes fixed by vascular
perfusion through the abdominal aorta by a
retrograde method (Vitale et al., '73). First,
the testes were cleared with 0.9%saline solution followed by fixation with 5% glutaraldehyde in 0.2 M sodium cacodylate buffer (pH
7.4). The testes were removed, cut into small
pieces with a razor blade and fixed in the perfusate for a n additional hour a t room temperature. The tissue was washed in three changes
of buffer overnight, and in most cases, postfixed with a 2% OsO,: 3% potassium ferroReceived Apr. 11, '77, Accepted Aug. 5, '77.
' Present address to which all correspondence should be sent: Department of Physiology, Southern Illinois University, Carbondale,
Illinois 62901.
Fr. cloud.
cyanide mixture modified from Karnovsky
('71) and in some cases with 2% OsO, alone.3
Subsequent dehydration was performed in
ascending concentrations of ethanol and propylene oxide. The tissue was infiltrated with a
mixture of propylene oxide and Epon and
embedded in Epon. When embedded, some
seminiferous tubules of the testes were oriented in such a manner as to produce longitudinal profiles a t the time of sectioning.
One-micrometer thick sections were stained
with toluidine blue and viewed under a light
microscope. Individual tubules containing
cells at known stages of the cycle (classification of Leblond and Clermont, '52) were selected to be viewed under the electron microscope.
Silver and silver-gold appearing thin sections
(cut on a Porter-Blum MT-2 ultramicrotome),
stained with uranyl acetate and lead citrate,
were examined with a Hitachi HU-11C electron microscope.
The observations are divided into sections
- each a description of at least one morpho-
logically distinct type of nuage. Although
both glutara1dehyde:osmium and glutaraldehyde:ferrocyanide-osmium tissue treatments
were found to be adequate to demonstrate all
of the various nuage types, the latter method
was found to somewhat enhance the appearance of these structures. The first two types of
nuage considered, the 70-90-nm spherical particles and the sponge bodies, were also found
to be present in spermatogonia and will be
dealt with first. The remaining three types are
described in the order in which they appear
during the spermatogenic cycle.
70-90-nmspherical particles
Spherical particles measuring 70-90 nm
across were noted i n favorable sections
through spermatogonia and primary and secondary spermatocytes at all phases of development (figs. 1-4, 17). At high magnification
they appeared to be amorphous, but extremely
fine fibrils were sometimes seen either as part
of the densities (fig. 2) or as radiating from
their periphery. In type B spermatogonia and
preleptotene spermatocytes, these particles
were most frequently encountered in the general vicinity of the Golgi apparatus or between
i t and the nucleus (figs. 1, 4). Two to ten
spherical particles could be identified in a
typical section through this region, whereas
few were seen elsewhere in the cytoplasm (fig.
4). They stained intensely with routine methods (uranyl acetate and lead citrate), appearing of equal or greater electron density than
the heterochromatin on the inner aspect of the
nuclear envelope (figs. 1,4).I n the leptotene
phase of meiosis, these particles lost their association with the Golgi apparatus, and by the
zygotene phase, they could be seen randomly
scattered throughout the cytoplasm of the
cell. In mid and late pachytene cells, they
were observed (fig. 3) with about the same
frequency as found for zygotene and early
pachytene cells. I t was apparent a t this point,
t h a t the absolute number of such structures
had increased. Although they are seen with
about the same or greater numerical density it
is known t h a t these cells undergo a dramatic
growth phase during mid and late pachytene
(Russell and Frank, ' 7 8 ) . Spherical dense bodies were also seen in secondary spermatocytes
(fig. 17) and step 1 spermatids, but appeared
less numerous in the latter.
Sponge bodies
Large structures (0.5-1.5 p m ) which we
have termed "sponge bodies" were also found
in the cytoplasm of spermatocytes (figs. 4-6,
17) at all stages of the cycle. The general appearance of sponge bodies remained the same,
regardless of the type of cell in which they
were seen. There were, however, some differences in appearance of this structure resulting from the post-fixation procedures employed. After post-fixation with osmium
alone, these structures appeared a s a network
of fibrils overlaid by denser patches of amorphous material (fig. 5). The patches appeared
to anastomose, leaving electron translucent
areas in which only fibrils could be discerned.
In ferrocyanide:osmium treated materials,
the contrast between fibrils and dense patches
was not as obvious, thereby rendering the
structure more homogeneous in appearance.
There were still some light and dark areas
(figs. 6, 17) in evidence. In either case, this
loosely organized mass exhibited a spongy appearance and was thus referred to as a sponge
body. Although regularly seen near the nucleThe appearance of testicular tissue after glutaraldehyde-osmium
fixation has been documented by numerous investigators, however,
post treatment of tissue with ferrocyanide-osmium combination is a
newer technique and has been less widely used. For examples of tissue treated in this manner see Fawcett and Dym ("74) and Dym and
Romrell ('75). The present authors are favorably impressed by the
quality of fixation obtained using this procedure. The reader is referred to the work of Russell and Burguet ('77) for a detailed descrip
tion of tissue appearance after ferrocyanide-osmium treatment.
a r periphery of the cell, sponge bodies could be
found anywhere in the cytoplasm.
Sponge bodies were rarely observed in spermatogonia and early spermatocytes, but when
found, were small - about 0.5 p m across (fig.
4). In mid and late pachytene spermatocytes,
they increased in size to reach a diameter of 1
p m or greater (figs. 5, 6). More than one
sponge body may be present in these cells, and
when more than one was present, they were
usually seen to be several micrometers apart.
Sponge bodies could be found in secondary
spermatocytes (fig. 17) and young spermatids,
although they were only occasionally encountered. Therefore, i t was thought that not every
secondary spermatocyte or spermatid contained a sponge body.
Zntermitochondrial substance
Intermitochondrial substance was characteristically seen among mitochondrial clusters (figs. 3, 7). Appearing as loosely organized
strands, this material completely filled the
gap between mitochondria, stretching from
the outer membrane of one mitochondrion to
make contact with that of another. The space
between mitochondria in these regions was
measured to be on the order of 0.1 p m or narrower. This substance did not appear to be as
tightly packed as t h a t of the 70-90-nm particles, nor did i t appear as electron opaque. I t
more closely resembled the sponge body in
density and appearance.
Cells from the earlier phases of spermatocyte development (e.g., spermatogonia, preleptotene, leptotene, and zygotene spermatocytes) and also spermatogonia showed
little or no mitochondrial clustering (figs. 1,
4). When two or more mitochondria were seen
near each other in these cells, this substance
was usually absent (fig. 1). It first became
prominent in pachytene cells a t Stage I1 of the
cycle, where mitochondria were noticeably
clustered. Thereafter (until Stage XIV), it
became increasingly more abundant. During
and after the first meiotic metaphase, the mitochondria were dispersed leaving no visible
evidence of intermitochondrial substance
(figs. 12, 16, 17).
30-nm particles
Clusters of dense particles were observed in
the cytoplasm of dividing Meiosis I cells
(metaphase- telophase) and in secondary
spermatocytes. These measured about 20-30
nm across (figs. 16, 17). I t was our concern at
first that these particles might be clustered
ribosomes or glycogen particles. Upon close
examination of ferrocyanide:osmium treated
tissues, it was found that ribosomes were poorly preserved (figs. 3, 6-13) under these conditions, yet the 30 nm particles were easily
visualized. In addition, in tissues secondarily
fixed with osmium alone, the ribosomes stood
out in sharp contrast to the cytoplasmic matrix (figs. 1, 4-5), where they appeared considerably smaller than the 30 nm particles.
These observations indicated that the slightly
larger 30-nm particles were not ribosomes.
Russell and Burguet ('77) have shown that
glycogen particles display a homogeneous texture with well circumscribed boundaries and
thus differed considerably in appearance from
the 30-nm particles seen in the present study.
Several hundred of these particles appeared
to be present in a single cluster (in section),
and there may be one or more clusters within
each cell. At high magnification a filamentous
texture could be discerned in some particles
(fig. 16 inset). Particles of similar size and appearance were occasionally seen in much
smaller groups scattered throughout the cytoplasm. Few 30-nm particles appeared in aggregates in Meiosis I1 cells, and almost none in
young spermatids. In many cases particles of
the same size and appearance were seen within the nucleus of pachytene cells, diplotene
cells (figs. 3,9), and the nuclear zone of dividing Meiosis I cells (fig. 16).
Chromatoid body
The descriptions provided below are of two
structures which appeared in succession; one
in mid and late pachytene, and the other in
secondary spermatocytes and spermatids. For
the reason that the latter persists throughout
the remainder of spermiogenesis and has also
been considered to be chromatoid by most investigators, it will be termed the definitive
chromatoid in this report. The structure appearing in earlier pachytene and diplotene
phases will simply be referred to a s the chromatoid body.
Thechromatoid body was first seen in Stage
VIII in a region close to the nuclear envelope
of pachytene spermatocytes (fig. 9). It was
invariably associated with small (60-90 nm
across) round vesicles which, unlike t h e
neighboring smooth endoplasmic reticulum,
contained dense material on their internal
aspect. In any one section through a late
pachytene cell, several patches of this mate-
rial were usually seen near the nucleus. By
diplotene most of the patches had formed one
or two large aggregates near the nucleus (fig.
8). At low magnification these aggregates appeared as anastomosing strands of dense material, and numerous small vesicles were positioned at the side of each strand. At higher
magnification the strands were found to be
composed of fine filaments (about 5 nm
across) which appeared conspicuous only if
sectioned longitudinally (fig. 8).
In late diplotene spermatocytes and in
dividing Meiosis I cells, the chromatoid body
was only rarely seen, but when observed i t was
evident that its appearance had changed considerably. The dense material that was seen in
pachytene was present, but it was poorly represented (fig. 10). The size of the aggregation
had decreased considerably and the packing of
the dense material was looser. A few small
vesicles were present in the vicinity of the
dense material. They were irregularly shaped
and contained uniformly granular material on
their internal aspect. Due to the decreased
prominence of the chromatoid, it was rarely
observed and was thus difficult to follow in
cells past diplotene. As a consequence, the
eventual fate of the chromatoid of pachytene
and diplotene cells was therefore not determined in this study.
Longitudinal sections of tubules displaying
Stages XIII, XIV and I were useful in visualizing the formation of the definitive chromatoid
body. As in previous studies in which longitudinal sections were utilized to follow a specific
process that occurs with time (Russell, '77a),
it was found that a logical step-by-step sequence of events occurred in these respective
stages, which could be visualized sequentially
under the electron microscope.
In newly formed secondary spermatocytes,
large (0.5 pm), spherical dense bodies were
seen scattered throughout the cell (figs. 12,
17). In virtually all cases, they were found in
close association with one or more mitochondria. At first glance they appeared to be composed of fine particles: however, upon closer
examination, a fine filamentous texture could
be detected (fig. 11). Secondary spermatocytes
which were slightly more advanced in development occasionally displayed interconnected
dense bodies which appeared to lack associations with mitochondria. They were joined to
one another by a bridge of material of the
same type and also demonstrated associated
small vesicles, similar to those seen around
the chromatoid of pachytene cells (fig. 12).
With time, more dense bodies were seen to be
interconnected and fewer were seen in association with mitochondria. The interconnected
dense bodies lost their rounded form and were
transformed into a network of anastomosing
irregularly-shaped strands (fig. 13). Many
small vesicles were seen around the anastomotic structure, some of which appeared to be
connected to it by fine filaments. Also associated with the forming definitive chromatoid
were a few membrane bound structures which
were quite variable in appearance (fig. 13).
In secondary spermatocytes which adjoined
dividing Meiosis I1 cells, the definitive chromatoid was generally seen (in sections) as
two separate components which were somewhat different in appearance (fig. 13). One
was large and round, and displayed numerous
internal foci which were electron translucent.
The other appeared to be formed by a loose
network of irregularly shaped dense strands.
Close examination revealed that these strands
were not of a consistent density (fig. 14). At
high magnification, the dense material of the
definitive chromatoid appeared as small fibrils; each about 4-6 nm in diameter (fig.
14). The chromatoid in dividing Meiosis I1
cells was prominent (fig. 15), and it appeared
identical to that just described for mature secondary spermatocytes.
Several types of nuage found in male germ
cells have been described a t the electron microscopic level. These include among others:
"Type A bodies" in rat gonocytes (Franchi and
Mandl, '64; Novi and Saba, '68); intermitochondria1 dense material in spermatogonia of the rat (Eddy, '741, rabbit (Nicander
and Ploen, '691, and human (Burgos et al., '70;
Wartenberg et al., ' 7 0 , in spermatocytes of
the r a t (Andre, '62; Fawcett et al., '70; Eddy,
'741, mouse (Fawcett et al., '70), rabbit (Nicander and Ploen, '69), chinchilla (Fawcett e t
al., '70) and monkey (Fawcett et al., '701, in
primordial germ cells of the rat (Eddy, '74)
and in gonocytes of the r a t (Eddy, '74);accumulations of fibrous material in primordial
germ cell of the rat (Eddy, '74); "chromatoid
body" in spermatogonia of a Cyprinid fish
(Schjeide et al., '721, in spermatocytes of the
rat (Fawcett e t al., '70; Susi and Clermont,
'70; Comings and Okada, '72; Eddy, '741, rabbit (Nicander and Ploen, '69) and monkey
(Fawcett et al., '701, and in spermatids of the
r a t (Watson, '52, Brokelmann, '63; Swift, '56;
Eddy, '70; Fawcett et al., '70; Susi and
Clermont, '70; Parvinen and Jokelainen, '74;
Soderstrom and Parvinen, '761, mouse (Fawcett e t al., '70; Comings and Okada, '721, guinea pig (Fawcett and Ito, '58; Burgos e t al.,
'70; Fawcett e t al., '701, Chinese hamster
(Fawcett et al., '701, cat (Burgos and Fawcett,
'551, ram (Courot and Loir, '681, monkey (Fawcett et al., '70) and the human (Burgos et al.,
'70); satellite chromatoid in chinchilla spermatocytes (Fawcett e t al., '70), in guinea pig
spermatids (Fawcett e t al., '701, and 40-60 nm
spherical bodies (Fawcett et al., '70). In view
of the multiplicity of species and cell types,
there was obvious need to document and classify all of the types of nuage in one species and
preferably in one cell type of this species. This
task has not been undertaken in the past.
The present study has demonstrated that
rat spermatocytes contain several distinct
types of nuage (at least 6) when judged by
morphological appearance and associations
with other organelles. Although the morphological heterogeneity of nuage within a single
species has been recognized in the past (Kalt,
'73; Eddy, '75), it has not been shown that up
to six varieties may be present in a single cell
type. One of the forms of nuage, the chromatoid body, has been studied extensively;
another, the intermitochondrial material, has
been previously characterized. I t was difficult
to determine (due to species and tissue preparation differences) whether the 70-90-nm
spherical particles or the sponge body has
been described. A structure showing slight
similarities to the sponge body has been described and illustrated for rabbit spermatocytes (Nicander and Ploen, '69). In guinea pig
spermatids, and in chinchilla spermatocytes
Fawcett e t al., ('70) have described a similar
appearing structure which was found in close
relation to the chromatoid body. A relationship of this type was not demonstrated in the
present study. Dense spherical particles (of
40-60-nmacross), similar in appearance to the
70-90-nm particles seen in the present study,
have been observed in spermatocytes (species
not indicated; Fawcett e t al., '70). The smaller
(30 nm) dense particles have, to our knowledge, not been reported.
The present study was not intended to shed
light on the functional significance of nuage
in spermatogenesis. However, i t has shown
from a morphological standpoint that nuage
behaves in a dynamic way during the sper-
matogenic cycle, a way which a t some time in
the future may be functionally correlated
with other events of spermatogenic process. It
(intermitochondrial material, chromatoid, definitive chromatoid, and 30-nm spherical particles) becomes visible a t specific stages of the
cycle, increases in size or amount (sponge
body, 70-90-nm particles) or changes position
(70-90-nm particles, definitive chromatoid)
and form (30-nm particles, definitive chromatoid).
The present study raises a question about
the timing of the initial appearance of the definitive chromatoid body in spermatogenesis.
Especially interesting was the finding that
material which is present in rat pachytene
and diplotene spermatocytes, previously referred to as chromatoid by several investigators (Sud, '61; Nicander and Ploen, '69; Susi
and Clermont, '70; Comings and Okada, '72;
Eddy, '74; Soderstrom and Parvinen, '76;
Russell, '77b) appears to dissociate just prior
to and during the meiotic divisions. Shortly
thereafter (in secondary spermatocytes),a different form of nuage was observed scattered
throughout the cytoplasm. I t appeared to coalesce and form the definitive chromatoid.
Whether or not the material of the pachytene
and diplotene chromatoid assumed a different
form or appearance in secondary spermatocytes is unknown. An answer to this question
will likely await biochemical, cytochemical
andlor autoradiographic studies. In a recent
report, Soderstrom and Parvinen ('76) indicated that the chromatoid body of rat spermatids is capable of incorporating (3H) uridine. No mention was made whether grains
were observed over the chromatoid of pachytene cells; however, occasional labeling was
demonstrated over mitochondria1 clusters of
the latter cells. Further work along this line is
needed to show whether both the pachytene
chromatoid and the definitive chromatoid are
actually the same or whether they differ in
composition. Indeed i t has yet to be shown
whether any of the nuage types have similar
chemical compositions.
I t was noted that the definitive chromatoid
first appeared in newly formed secondary
spermatocytes. By late Stage XIV it resembled the chromatoid seen throughout the remainder of spermiogenesis. Knowledge of this
sequence of events allowed us to make previously difficult distinctions, between certain
cell types, a t the ultrastructural level. For
example, dividing Meiosis I cells may be dis-
tinguished from dividing Meiosis I1 cells by
the presence of the definitive chromatoid in
the latter. Likewise, many secondary spermatocytes (newly formed) may be identified,
and thereby distinguished from step 1 spermatids, by the presence of the large (0.5 pm)
spherical dense bodies (the precursors of the
definitive chromatoid) in the former.
Monesi (’65) has shown that uridine (3H) is
incorporated into the nucleus of pachytene
cells (around chromosomes) and is seen in this
position for a considerable period of time.
However, as the cells enter metaphase, this
radioactive substance is found in the cytoplasm. He interpreted these results to indicate
that most of the RNA synthesized during meiotic prophase is suddenly released into the cytoplasm when the cell enters metaphase. If
this were occurring it might be expected that
this RNA be present in some visible form. In
the present study two new types of nuage were
observed within the cytoplasm during and immediately after division of primary spermatocytes; the small, 30-nm particles, and the
larger, 0.5-pm spherical particles. One or
more of these particles might be long-lived
RNA which is transferred from the nucleus to
the cytoplasm. Such RNAs might be involved
with protein synthesis a t a later time in the
spermatogenic process.
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Watson, M. L., 1952 Spermatogenesis in the albino rat as
revealed by electron microscopy. J. Biophys. Biochem. Cytol, 4: 475-478.
1 Section through the nucleus (n) and Golgi apparatus (GI of a preleptotene spermatocyte. Several dense particles (arrowheads) measuring 70-90 nm are seen in the
vicinity of the nucleus. Although in this case some mitochondria (m) are adjoining
each other, they do not display intermitochondrial material. In this tissue secondarily
fixed with osmium alone, the ribosomes (encircled) a r e clearly visualized. X 21,200.
2 High magnification micrograph showing several 70-90 -nm dense particles (arrows).
In some regions fine fibrils are seen composing this form of nuage (arrowheads) or are
seen radiating from its periphery. X 77,700.
3 Section through a late pachytene spermatocyte showing both nuclear (n) and cytoplasmic areas. Particles 70-90 nm across (arrowheads) are scattered throughout the
cytoplasm Intermitochondrial material (small arrows) is seen in regions where mitochondria (m) are in clusters. The nucleolus is complex; one component displays dense
particles measuring about 20-30nm across (large arrow). Ribosomes (encircled) are
poorly visualized in this ferrocyanide:osmium treated tissue. x 17,000.
Lonnie Russell and Beryn Frank
4 A low magnification micrograph showing a type B spermatogonium. Particles (70-90
nm: arrowheads) are seen near the Golgi (G) and also near the nuclear periphery. In
this cell, mitochondria1 clustering is not apparent. A sponge body (arrow) is observed
near a n intercellular bridge (b). x 9,800.
Figs. 5 , 6 High magnification of late pachytene spermatocytes showing the sponge body.
5 In this tissue post-treated with osmium alone, the sponge body appears as a meshwork
of the fine fibrils (arrowheads) overlaid by denser material (arrow). Ribosomes
(encircled) are conspicuous. X 41,000.
6 In this ferrocyanide:osmium post-fixed tissue the sponge body appears more homogeneous than that seen in figure 5, although some denser areas may be discerned.
Arrowheads indicate fibrils. Ribosomes (encircled) a r e poorly visualized. x 41,000.
Lonnie Russell and Beryn Frank
7 Late pachytene spermatocyte showing two mitochondrial clusters and the intermitochondrial substance (asterisk). X 55,000.
8 Late pachytene spermatocyte showing both nuclear (n) and cytoplasmic areas. The
chromatoid appears as irregularly shaped, anastornosing strands of electron dense
material. Arrowheads indicate the small fibrils which form these strands. Numerous
small vesicles (v) are spaced along the strands. X 40,400.
Lonnie Russell and Beryn Frank
9 Stage VII pachytene spermatocyte showing the forming chromatoid body in a position near the nucleus (n).
Interconnected dense material (arrowheads) is seen near several small round vesicles (v). In contrast to
nearby smooth endoplasmic reticulum (large arrow), these vesicles contain electron dense material. A
spherical particle (70-90nm: small arrow) is shown a t some distance from the forming chromatoid. Smaller
20-30-nm particles (p) are seen within the nucleus. X 32,000.
10. This chromatoid body within a diplotene spermatocyte is small. The dense material (arrow) appears loosely
packed and is barely distinguishable from the cytoplasmic matrix. Accompanying vesicles (v) are
irregularly shaped and scattered among the dense material. X 45,300.
Figs. 11-13 Secondary spermatocytes showing the dense material forming the definitive chromatoid.
11 A 0.5-pm dense body is associated with a n obliquely sectioned mitochondrion (m) of a young secondary
spermatocyte. Arrowheads indicate the filamentous components within this structure. X 75,000.
12 Several 0.5-pm dense bodies are observed in close association with mitochondria (m) in two adjoining
young secondary spermatocytes. In one cell, a pair of these dense bodies is interconnected (arrow) and
shows a n association with several small vesicles (arrowheads). X 22,500.
13 The definitive chromatoid is seen near the nucleus (n) of a mature secondary spermatocyte. Two components can be distinguished. One (large arrow) appears as a large rounded structure with numerous internal
electron-translucent areas. The other (small arrow) appears as irregularly-shaped anastomosing strands
which are associated with many small vesicles (v). Membrane bounded structures (arrowheads) are often
seen in the vicinity of this complex. X 10,800.
Lonnie Russell and Beryn Frank
14 Definitive chromatoid of secondary spermatocyte a t high magnification showing
t h a t i t is composed of strands of dense material and numerous vesicles (v). The vesicles are round and, unlike nearby smooth endoplasmic reticulum h e r ) , contain an
electron opaque matrix. The fibrillar nature of the dense material is evident in some
regions (small arrowheads). Large arrowheads indicate areas in which the dense material appears especially electron opaque. x 45,000.
15 Secondary spermatocytes in prophase of the second meiotic division. The definitive
chromatoid (arrow) is seen outside the nuclear region (n). x 7,500.
Lonnie Russell and Beryn Frank
16 First meiotic metaphase showing both nuclear (n) and cytoplasmic regions. Clusters
of 30-nm particles (small arrows) are seen in both regions. A large cluster is shown
a t higher magnification in the inset. Some particles display a fibrillar texture
(arrowheads). x 22,100.
17 Young secondary spermatocyte showing several types of nuage. These include the
sponge body (s), dense bodies of the definitive chromatoid (c),70-90-nmparticles (isolated arrows) and 30-nm particles (arrowheads). X 15,400.
Lonnie Russell and Beryn Frank
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ultrastructure, testis, characterization, spermatocytes, nuage, rat
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