вход по аккаунту


The organization of the seminiferous epithelium in the mouse testis following ligation of the efferent ductules. A light microscopic study

код для вставкиСкачать
The Organization of the Seminiferous Epithelium in the
Mouse Testis Following Ligation of the Efferent
Ductules. A Light Microscopic Study
Division of Anatomical Sciences, College of Medicine, University of Florida,
Gainesville, Florida 32610
Seminiferous tubules from mouse testes were studied with the
light microscope after the efferent ductules had been ligated for 48 hours. As a
consequence of ligation, the tubules became markedly distended by the fluid
which they accumulated; the epithelium was reduced in height, and exhibited
a significantly less complex stratification than in the normal. Longitudinal sections of the distended tubules, particularly those in the early stages of the seminiferous cycle, revealed pillar-like epithelial profiles arranged in a repetitive
series. Each “pillar” consisted of Sertoli cell cytoplasm along with two generations of spermatids, the older generation embedded within the Sertoli cell, and
the younger generation aligned, one cell above the other, along its sides. Oblique
or grazing sections through tubules exhibiting the same stages of spermiogenesis
revealed band-like epithelial profiles arranged in parallel array. The two types
of epithelial configurations are interpreted as representing a series of circumferentially oriented ridges within the tubule. It is postulated that each spermatid
generation within a ridge constitutes a single clone, and that it is the cytoplasmic
bridges joining the spermatids, in combination with their attachment to the
Sertoli cells, which provide the organization, delineation, and structural stability
of the ridges.
In a n earlier study aimed at elucidating
the morphological basis of the blood-testicular barrier, seminiferous tubules from
both normal and efferent ductule ligated
testes were examined at the ukrastructural
level to determine which cellular elements
might contribute to the make-up of the
barrier (Ross, ’70). As a consequence of
ligation of the efferent ductules, the seminiferous tubules become remarkably distended, their diameters ranging up to three
to four times greater than normal. It was
clearly evident in these preparations that
the Sertoli cells were so arranged a s to
form a contiguous cytoplasmic “sheath”
within the confines of the tubule wall. The
specialized junctional complexes which
occur a t the interface of neighboring
Sertoli cells (Brokelman, ’63; Nicander,
’63, ’67; Flickinger and Fawcett, ’67) appeared to maintain the integrity, or continuity of the sheath. Whereas the genninal elements would separate, leaving gaps
ANAT. REC., 180: 565-580.
between groups of spermatocytes, the
Sertoli cells were always conjoined by the
junctional complexes no matter how distended the tubules were. Largely on the
basis of these observations, it was suggested that the Sertoli cells constitute the
permeability barrier. It was also inferred
from this study that the Sertoli cells are
responsible for the active transport of
fluid across the tubule wall.
Similar findings, with respect to delineation of the site of the barrier, were also
reported by Fawcett et al. (’70), and by
Dym and Fawcett (’71). They employed
electron opaque particulates as tracers and
found that while the contiguous peritubular myoid cells acted as a barrier for the
larger particulate substances, those of
small size (ferritin and peroxidase) penetrated more deeply into the tubule wall,
but failed to go beyond the specialized
junctions between Sertoli cells. While these
Received Feb. 1, ‘74. Accepted June 3, ‘74.
In order to assess and characterize the
authors attributed a barrier role to both the
myoid and Sertoli cells, in a more recent relationship between the developing germ
study, Dym ('73) noted that in monkeys cells and the Sertoli cell epithelium more
the peritubular cells do not impede vascu- fully, efferent ductule ligated testes were
larly introduced tracers from penetrating reexamined. The singular advantage of
into the germinal epithelium. However, the ligation for the purpose of this study lies
Sertoli cell junctions prevented entry into in the resulting effect that it has in stretchthe tubule lumen. It is known that the ing the wall of the seminiferous tubule,
architectural organization of the myoid thus reducing the degree of stratification
cells is not the same in all species studied. and complexity of the epithelium.
Unlike most rodents, the peritubular conMATERIALS AND METHODS
tractile cells in man (Ross and Long, '66)
Animals used in this study were 3as well as in ram (Ross, '70) and monkey
(Dym, '73) form a multiple layered, non- month-old CD-1 Swiss Albino mice (Charles
contiguous cellular component. In these River Laboratory), A total of 12 animals
forms, the peritubular cells thus lack the was used. While under ether anesthesia,
architectural organization to serve as 3 the left testis of each animal was exposed
by means of median suprapubic incision.
The morphological evidence obtained to A cotton ligature was tied around the efferdate clearly points to the Sertoli cell as the ent ductules at a point immediately adjafunctional barrier component of the semi- cent to the testis. Particular care was taken
niferous tubules. The means by which it to avoid impeding testicular blood flow,
serves in this capacity, and yet, at the same especially in the placement of the ligature.
time, selectively allows the developing Five of the ligated animals also underwent
germinal cells to migrate across tht Sertoli a sham operation in which the testis on
cell barrier is not known. As Dym and the right side was exposed through the
Fawcett ('71) have pointed out, the Sertoli same abdominal incision and the efferent
cells and their junctional complexes in ductules manipulated in a manner similar
effect form two compartments: ( 1 ) a basal to that performed on the left side. Howcompartment between the Sertoli junctions ever, the ductules were not ligated. Foland the basal lamina, containing the lowing the indicated treatment, the testes
spermatogonial population and early pre- were returned to their normal position and
leptotene spermatocytes, and ( 2 ) an ad- the incision was sutured closed. Forty-eight
luminal compartment above the junctions, ( 4 8 ) hours postoperatively, the testes were
containing the other germ cells.
removed from each animal while under
A seemingly complicating factor with ether anesthesia. In removing the ligated
respect to the germ cells breaching this testes, the efferent ductules and vascular
barrier to reach the adluminal compart- connections were cut distal to the ligature
ment is that they evidently pass through, in order to prevent the immediate escape of
not as single cells, but rather, as clonal fluid and consequent collapse of the semipopulations of conjoined or synplastic pri- niferous tubules.
mary spermatocytes. Furthermore, the
A marked increase in size between the
finding of cytoplasmic bridges between ligated and contralateral testis and a n
germ cells at all stages of development, in- absence of visible hemorrhage or intersticluding the spermatogonia (Gondos and tial discoloration was the basis for confirmZemjanis, '70; Dym and Fawcett, '71) ing the effectiveness of the ligature. Commeans that the number of conjoined sper- parison between the sham operated and
matids that ultimately arise from the vari- the normal (unoperated) testes revealed
ous spermatogenic divisions may be in the no apparent differences at the gross level.
hundreds. Thus, there is also the question In one of the sham operated animals, the
a s to how the spermatids, a s a large syn- ligated testis showed only a small increase
cytial population of cells, gain attachment in size. The material from this animal
and become embedded in the cytoplasm was discarded; the remainder revealed a
of the individual Sertoli cells where they marked size difference between the ligated
and contralateral testis.
undergo further maturation.
Immediately after extirpation, the ligated
and contralateral sham operated or normal
testes were dropped in toto in a 3% phosphate buffered glutaraldehyde fixative solution (pH 7.4) and allowed to remain for
three hours. Following the glutaraldehyde
fixation, several tangential slices of tissue,
approximately 1 mm in thickness, were
cut from each testis. The slices, which contained capsular tissue as well as the underlying seminiferous tubules, were then cut
1 m m cubes, rinsed, and left in
phosphate buffer (pH 7.4) overnight at
4°C. The specimens were further fixed i n
phosphate buffered 1 % osmium tetroxide
(pH 7.4) for three hours at 4’42, dehydrated in a graded series of ethanol solutions, and then embedded in Epon.
The tissues were sectioned for light microscopy at a thickness of approximately
Some were also serially sectioned to
provide up to 100 consecutive sections. Sections from the various specimens were
examined and photographed either unstained using phase-contrast optics, or
stained with toluidine blue using bright
field optics.
Cross-sectional profiles of the seminiferous tubule from the normal and sham
operated testes revealed a multilayered epithelium consisting largely of germ cells at
various stages of development (fig. 1). At
the light microscope level no distinction
could be found between the normal and
sham operated groups. The thickness of
the epithelium was noted to be somewhat
reduced in those segments which contain
spermatids in very late steps of maturation, and concomitantly the tubule lumen
displayed maximal diameter. Somewhat
earlier stages of spermatid development
(also evident in fig. 1 ) revealed a smaller,
more irregular tubule lumen and a thicker
epithelial wall. The elongate spermatid
heads typically appeared in irregular clusters at these stages, Seminiferous tubules
seen in longitudinal profile exhibited essentially the same characteristics.
In contrast, the seminiferous tubules in
the ligated testes were characterized by
exceedingly large lumens which contained
numerous free spermatozoa (fig. 2 ) . While
not all of the tubules exhibited the same
degree of distension, as evidenced by differences in cross-sectional diameters, all of
the tubules were of substantially larger
diameter than the normal. Also, the tubule
epithelium was considerably reduced in
height. Despite the marked dilation of the
tubules and reduction in epithelial thickness, the features which characterize the
various stages or cellular associations of
the cycle of the epithelium were retained.
For example, in figure 2, each tubule exhibits a recognizably different stage of the
cycle. Using the classification of Leblond
and Clermont (’52) and the descriptive
account by Oakberg ( ’ 5 6 ) , the tubule in
the upper left of the figure is identified at
stage XII, the tubule to the right at stage
IX, and the tubule stretching across the
bottom of the figure at stage I.
In order to assess the character of the
epithelium and the nature of the displacement of the component cells in the ligated
testes, seminiferous tubules representative
of most of the cellular associations were
examined. Emphasis was placed on examining those tubules in which it could be
determined that the epithelium had been
cut in a plane essentially perpendicular to
the basement membrane, and at the same
time providing either a true cross-sectional
or longitudinal profile. The trueness of the
plane of section was determined largely on
the basis of uniformity of height of the
epithelium. Thus, in figure 2, it is readily
apparent that the upper right tubule has
been sectioned obliquely through part of
its wall.
Most of the tubules when viewed in
cross-section revealed a n epithelium of
relatively uniform height, though considerably reduced from that seen in the normal. Aside from the large lumens, there
were no other remarkable features. However, when viewed in longitudinal section,
many of the tubules had a markedly distinctive appearance. In these tubules the
epithelium gave the impression of being
segmented; that is, they exhibited a repetitive series of uniform, pillar-like projections extending into the tubule lumen (fig.
3 ) . Each “pillar,” when observed at higher
magnifications, was noted to consist of
Sertoli cell cytoplasm along with two generations of spermatids (fig. 4 ) . One spermatid generation was well along in devel-
opment, deeply embedded in the Sertoli
cell cytoplasm. While the nucleus of the
developing spermatid was readily apparent,
its cytoplasm was indistinguishable from
that of the Sertoli cell. The other generation was represented by very early spermatids which were usually aligned, one above
the other, along the lateral aspects of the
Sertoli cell. They appeared to be attached
to the Sertoli cell, though they probably
were not yet embedded within its cytoplasm. The spermatocytes and spermatogonia appeared at the basal region of the
“pillar,” in close proximity to the basement
Not all of the tubules observed in longitudinal section exhibited a conspicuous
pillar-like segmentation of the epithelium.
In some instances, as illustrated in figure
5, there was no noticeable segmentation.
In other instances there was only a suggestion of it. Figure 6 depicts the epithelium at stage VIII, the mature spermatid
population is in the process of being released. At this stage there is a slight semblance of segmentation as evidenced by
the grouping of the mature spermatids.
However, after the spermatids are released
(fig. 5) there is no evidence of segmentation. It is not until the next generation of
spermatids is formed at stage I that the
pillaring effect becomes evident (figs. 3 , 4).
During the course of examining the various tissue sections, a number of tubules
that had been cut in a n extremely oblique
or grazing plane were noted. In some of
these sections the angle of the cut through
the tubule wall produced a different, and
again, a rather unusual epithelial profile.
An example of such a section is seen in
figure 7. In this particular case the tubule
is not being viewed in cross-section, despite
its circular profile, but rather, it represents
a grazing section through one side of the
tubule at a point where it is making a
sharp U-turn. The general character and
stage of development of the germ cell population is the same as that seen in figure 3.
The significant feature here is that instead
of the pillar-like epithelial profiles, several,
almost linear bands of epithelium are
seen. Furthermore, the bands are oriented
in the same direction, forming a n essentially parallel array. In assessing the relationship of epithelial profiles of this type
with those of the segmented pillar-type
configuration, it becomes evident that they
both represent the same component; the
distinction between the two being only the
plane of section. In effect, a three dimensional perspective would reveal the epithelium in the form of a series of ridges rather
than true pillar or cylindrical units. The
ridges are not only arranged in parallel
array, but they are also oriented at right
angles to the direction of the tubule. This
becomes quite evident when observing the
longitudinally sectioned tubule, in which
case the “pillar” profile is always present
(fig. 3 ) . While it is not possible to demonstrate a configuration of actual ridges in a
two dimensional section, such structures
would appear as a consecutive series of
epithelial projections when viewed on end,
as is the case in figure 3, or as linear bands
when viewed in a section that passes along
the length of the ridge, as is the case in
figure 7.
Occasionally, both the “band” and pillar” type epithelial profiles were noted in
the same tubule. In these instances, there
was actually a transition from the one epithelial configuration to the other (figs. 8,
9 ) . This is attributed to a turn or change
in direction of the tubule. The presence of
the two profiles in a single tubule, cut in
varying planes because of its curvature, is
consistent with the concept that they represent the same unit structure - the difference between the two profiles being
only the perspective from which they are
Perhaps the most pertinent question
that remains with respect to the geometry
of these segmental ridges is the relationship that each has to its neighbor. For example, are they continuous spirals; do they
form complete circles; or, do they consist
of even shorter segments? Also, there is
some possibility that they may have a
branching configuration. Frequently one
ridge appears to abut or join its neighbor
(fig. 7). Serial sections tend to indicate
that there is no true branching or union
between one ridge and another. Where
there may be a suggestion of branching in
one section, it is frequently absent several
sections removed.
While it was found to be exceedingly
difficult to determine the length of any
given ridge, discontinuities or gaps were
noted along the length of some ridges
(fig. 7). In most cases, it seems likely that
this can be attributed to irregularities in
the height of the ridge, causing the knife
to miss short, depressed segments rather
than being representative of true discontinuities.
It has been recognized for some time
that ligation of the efferent ducts of the
mammalian testes causes a marked distension of the seminiferous tubules (van
Wagenen, '26; Oslund, '26; Smith, '62).
The effect is produced by the secretion and
accumulation of fluid within the tubules, a
process attributed to a n active transport
mechanism involving the Sertoli cells
(Ross, '70; Setchell, '70) combined with
the inability for reabsorption to occur in
the excurrent ducts. While ligation will i n
time result in cessation of spermatogenesis,
and eventually atrophy of the tubule (van
Wagenen, '24, '26; Oslund, '26; Smith,
'62), the short term effect offers certain
advantages in elucidating the organization
and relationship of the cells that constitute
the tubule wall. In effect, the induced distension of the tubules provides a means of
visualizing the seminiferous epithelium in
a relatively simplified configuration. Thus,
instead of the multiple layered and rather
complex cell patterns seen in the normal
tubule at certain stages of spermatogenesis, ligation reveals defined aggregates of
germ cells grouped in specific association
with the Sertoli cell elements. The most
striking feature noted in relation to these
cell aggregates, when viewed in appropriately oriented sections, is their dimensional
organization. Rather than simple clusters
of cells, the epithelium assumes the form
of a series of parallel ridges oriented a t
right angles to the tubule.
These ridges are particularly prominent
in the early stages of the epithelial cycle.
Interestingly, it is at these same stages in
the normal, longitudinally sectioned tubules that the more mature spermatids appear in regular tight clusters (Perey et al.,
'61; Parvinen and Vanha-Perttula, '72).
They are not evident in the cross-sectioned
tubule. Thus, there is clearly an asymmetric organizational pattern of the spermatid population.
In attempting to explain the epithelial
ridges, i t might be first assumed that they
occur simply as a result of the tubule being
stretched, the ridges representing a preferential parting or separation of the epithelium as the tubules elongate. I n part, this
is undoubtedly true. However, the tubules
are also subject to extensive radial distension, yet this seems to have no effect in
causing a segmental separation of the
epithelium as evidenced by the cross-sectional profiles.
The questions that then arise are : What
accounts for this perferential epithelial
segmentation, and what significance, if
any, does it have? I n considering the
Sertoli cells, there appears to be little reason to assume that they alone can account
for this phenomenon. While the basal portion of the Sertoli cell possesses lateral
processes which join with those of neighboring cells by means of the special junctional complexes (Flickinger and Fawcett,
'67; Ross, '70; Dym and Fawcett, '70), the
apical cytoplasm stands essentially as a
free column. Indeed, the only attachment
that exists at the level of the supranuclear
portion of the cell is that of the developing
spermatids which become firmly embedded
within recesses of the apical Sertoli cell
cytoplasm. At these sites junctional complexes, identical to those seen in the basal
portion of the cell, are present (Flickinger
and Fawcett, '67). While these specialized
structures are limited to the Sertoli cell,
with no comparable facing component in
the developing spermatid, they apparently
function, a t least in part, in maintaining
firm adhesion between spermatid and
Sertoli cell.
In further examining the relationship
between the developing spermatids and the
Sertoli cells a n important consideration involves the clonal and syncytial nature of
the germinal cells. The existence of cytoplasmic bridges joining germ cells in the
mammalian testis is well documented
(Burgos and Fawcett, '55; Fawcett and
Burgos, '56; Fawcett et al., '59; Gondos and
Zemjanis, '70; Dym and Fawcett, '71;
Rowley et al., '71). It is now clearly evident that these intercellular bridges are
present not only in the spermatocyte and
spermatid generations, but that they also
join even the type A spermatogonia (Dym
and Fawcett, '71). The cytoplasmic continuity, which apparently persists from the
very early spermatogonial divisions, would
thus result in clones consisting of large
numbers of spermatids joined by cytoplasmic bridges.
Since the spermatids are conjoined by
these bridges, they are not free to move
about independent of one another. It is
assumed that as the tubules are distended
the cytoplasmic bridges maintain their
integrity. At least there is no evidence at
the light microscopic level to suggest that
the bridges might become disrupted allowing the spermatids to separate from one
another. Since the spermatids become
embedded within the apical Sertoli cell
cytoplasm, they are not only retained in
a syncytial mass, but they must also gain
attachment to only those Sertoli cells that
are within the immediate spatial limits of
the clone. This would then imply that each
of the circumferentially oriented epithelial
ridges would contain spermatids from no
more than two clones, one representing a n
early generation, the second, a later or
older generation; and that all of the spermatids that make up a clone within a
ridge would have been derived from a pair
of type A spermatogonia. Unless the ridges
are spirally arranged, adjacent ridges
would contain unrelated or separate clonal populations which arose from different
pairs of type A spermatogonia.
If the interpretations given here are correct, it raises the interesting question as to
why each spermatid clone becomes oriented essentially in a linear array. Dym
and Fawcett ('71) point out that successive mitoses of spermatogonia are not consistent in their orientation, but probably
alternate at right angles. They conclude
that the resulting cells are not aligned in
a row, but form a network of interconnected cells around and between the bases
of the columnar Sertoli cells. It would seem
that as a result of the divisions that follow
from each pair of type A spermatogonia,
thereby producing the spermatids and
spermatocytes, some directional orientation must occur. Without this it is difficult
to conceive how the linear epithelial ridges
are produced.
A final point which warrants consideration is the relationship between the epithe-
lial ridges and the various segments or
cellular associations that occur along the
length of the seminiferous tubules. In a n
extremely detailed analysis of the organization of the seminiferous epithelium, Perey
et al. ('61) noted that the different cellular associations each of which defines a
specific segment along the length of the
seminiferous tubule, has sharply demarcated limits. They found an abrupt change
between one segment and the next with no
transition in between. Also, the boundaries,
though rather irregular, tended to be perpendicular to the axis of the tubule. Both
of these aspects are markedly consistent
with the organization of the epithelial
ridges as observed in this study. Indeed, it
appears quite reasonable to think of each
cellular association as consisting of a series
of epithelial ridges.
The existence of small unit-segments
consisting of a pair of type A spennatogonia and their progeny has also been
postulated (Perey et al., '6 1). Within each
of these unit segments, the cells were
noted to develop with precise synchrony,
but cells of neighboring unit-segments
could be at a slightly more or less advanced
step of development. In view of the organization of the epithelial ridges, as demonstrated in this paper, and the character of
the unit-segment, as postulated by Perey
and co-workers ('61), it is extremely likely
that the two reflect the same fundamental
entity, namely, a family of cells having
common derivation, which mature in a
circumscribed and identifiable site in the
tubule wall.
Brokelmann, J. 1963 Fine structure of germ
cells and Sertoli cells during the cycle of the
seminiferous epithelium in the rat. Z. Zellforsch., 59: 820-850.
Burgos, M. H., and D. W. Fawcett 1955 Studies
on the fine structure of the mammalian testis.
I. Differentiation of the spermatids in the cat
(Felis Domestica). J. Biophys. Biochem. Cytol.,
1: 287-300.
Dym, M. 1973 The fine structure of the monkey (Macaca) Sertoli cell and its role in maintaining the blood-testis barrier. Anat. Rec., 175:
Dym, M., and D. W. Fawcett 1970 The bloodtestis barrier in the rat and the physiological
compartmentation of the seminiferous epithelium. Biol. Reprod., 3: 308-326.
1971 Further observations on the numbers of spermatogonia, spermatocytes, and
spermatids connected by intercellular bridges
in the mammalian testis. Biol. Reprod., 4:
Fawcett, D. W., and M. H. Burgos 1956 Observations on the cytomorphosis of the germinal and interstitial cells of the human testis.
In: Ageing of Transient Tissues. Vol. 2. G. E. W.
Wostenholme and E. C. P. Millar, eds. Churchill,
London, pp. 86-96.
Fawcett, D. W., S. Ito and D. Slautierback 1959
The occurrence of intercellular bridges in
groups of cells exhibiting synchronous differentiation. J. Biophys. Biochem. Cytol., 5: 453460.
Fawcett, D. W., L. V. Leak and P. M. Heidger
1970 Electron microscopic observations on the
structural components of the blood-testis barrier. J. Reprod. Fert., Suppl. 10, pp. 105-122.
Flickinger, C., and D. W. Fawcett 1967 The
junctional specializations of Sertoli cells in the
seminiferous epithelium. Anat. Rec., 158: 207221.
Gondos, B., and R. Zemjanis 1970 Fine structure of spermatogonia and intercellular bridges
in Macaca nemestrina. J. Morph., 131: 431-446.
Leblond, C . P., and Y. Clermont 1952 Definition of the stages of the cycle o f the seminiferous epithelium in the rat. Ann. N. Y. Acad.
Sci., 55: 548-573.
Nicander, L. 1963 Some ultrastructural features of mammalian Sertoli cells. J. Ultrastruct.
Res., 8: 190-191.
1967 An electron microscopic study of
cell contacts in the seminiferous tubules of
some mammals. Z. Zellforsch. Microsk. Anat.,
83: 375-397.
Oakberg, E. F. 1956 A description of spermiogenesis in the mouse and its use in analysis of
the cycle of the seminiferous epithelium and
germ cell renewal. Am. J. Anat., 99: 391-414.
Oslund, R. M. 1926 Ligation of vasa efferentia
in rats. Am. J. Physiol., 77: 83-90.
Parvinen, M., and T. Vanha-Perttula 1972
Identification and enzyme quantitation of the
states of the seminiferous epithelial wave in
the rat. Anat. Rec., 174: 435-450.
Perey, B., Y. Clermont and C. P. Leblond 1961
The wave of the seminiferous epithelium in the
rat. Am. J. Anat., 108: 47-77.
Ross, M. H. 1970 The Sertoli cell and the bloodtesticular barrier: A n electronmicroscopic
study. Fortschritte der Andrologie, Morphological Aspects of Andrology. A. F. Holstein and
E. Horstmann, eds., Grosse Verlag GmbH, Berlin, 1 : 83-86.
Ross, M. H., and I. R. Long 1966 Contractile
cells in human seminiferous tubules. Science,
153: 1271-1273.
Rowley, M. J., J. D. Berlin and C. G. Heller 1971
The ultrastructure of four types of human
spermatogonia. Z. Zellforsch. Microsk. Anat.,
112: 139-157.
Setchell, B. P. 1970 Testicular blood supply,
lymphatic drainage, and secretion of fluid. In
The Testis. A. D. Johnson, W. R. Gomes and
N. L. Vandemark, eds. Academic Press, Inc.,
New York, I , pp. 101-239.
Smith, G. 1962 The effects of ligation of the
vasa efferentia and vasectomy o n testicular
function in the adult rat. J. Endocrin., 23: 385399.
Van Wagenen, G. 1924 Degeneration of germinal epithelium in the testis of the rat as a
result of efferent duct ligation. Anat. Rec., 27:
1926 Degeneration and regeneration of
the seminiferous tubules after ligation of the
ductuli efferentes in the rat. Anat. Rec., 32: 225.
A cross-section of portions of four seminiferous tubules from a normal
testis. Tubules at certain stages of the cycle exhibit small differences
in epithelial thickness and luminal diameters. Note that the tubule in
the upper left which contains spermatids that are about to be released
exhibits a larger lumen and somewhat thinner epithelial wall than
the tubule below it. Phase contrast. x 250.
A section through portions of three distended tubules from a ligated
testis. The lumens are exceedingly large and the thickness of the epithelium is very much reduced as compared to the normal. The features which characterize the various stages of the epithelial cycle
are still evident in these highly distended tubules. Phase contrast.
X 250.
Michael H . Ross
5 73
A longitudinal section of a distended tubule at stage 1. The seminiferous epithelium is segmented and appears as a series of pillar-like
projections. This is particularly evident in the lower portion of the
micrographs where the tissue has been cut in a plane normal to the
epithelial wall and parallel to the axis of the tubule. Numerous free
spermatids are present in the lumen of the tubule. Toluidine blue.
A higher power of the epithelium shown in figure 3. The more mature
spermatid population (Sp') is embedded in the Sertoli cell cytoplasm
( S C ) . The younger spermatids (Sp2) are aligned, one above the other,
along the lateral surfaces of the Sertoli cells. Toluidine blue. x 400.
x 200.
Michael H . Ross
The epithelium from the adjoining walls of two longitudinally sectioned, distended tubules is shown in this micrograph. The upper
tubule is at stage IX. The epithelium in this tubule exhibits no discernible segmentation. The epithelium of the lower tubule is segmented and reveals the pillar-like profiles. Toluidine blue. x 225.
Portions of two longitudinally sectioned tubules similar to that shown
in figure 5 . The upper tubule is at stage VIII. Here there is only a
semblance of segmentation as evidenced by the grouping of the
mature spermatids at the tubule lumen. The lower tubule exhibits
the epithelial “pillars,” though their form is somewhat vague due to
the angle of section. Toluidine blue. x 225.
A grazing sections along the wall of a distended tubule is shown at
the site where it is making a sharp U-turn. Despite its circular profile, it does not represent a cross-sectioned tubule. The most significant
feature seen in this micrograph is the presence of several discrete
linear bands of epithelium. The dotted lines represent the projected
course of additional epithelial bands not included within the section
because of the curvature of the tubule wall. The epithelial bands seen
in this micrograph represent the same unit structure as the pillarlike forms observed i n the longitudinally sectioned tubules. The three
dimensional configuration of the epithelium is therefore a series of
parallel ridges. Toluidine blue. x 200.
Michael H. Ross
Longitudinally sectioned, distended tubules are shown in these two
micrographs. In each the tubule is undergoing a sharp turn as seen
on the left side of the illustration. The portion of the tubule which
has been longitudinally sectioned exhibits the pillar-like epithelial
configuration. Where the tubule turns, its wall is obliquely sectioned
and the epithelium is seen in transition to the band-like configuration, similar to that shown in figure 7. Toluidine blue. X 200.
Michael H.Ross
Без категории
Размер файла
1 314 Кб
epithelium, ligation, seminiferous, stud, microscopy, following, testis, ductule, mouse, light, efferent, organization
Пожаловаться на содержимое документа