close

Вход

Забыли?

вход по аккаунту

?

Transport and barrier function in the chorioallantoic placenta of the bat Myotis lucifugus.

код для вставкиСкачать
Transport and Barrier Function in the Chorioallantoic
Placenta of the Bat, Myofis lucifugus '
ALLEN C. ENDERS AND WILLIAM A. WIMSATT
Department of Anatomy, Washington University School of Medicine, and
Division of Biological Sciences, Cornell University, Ithaca, New York
ABSTRACT
The chorioallantoic placenta of the bat (Myotis lucifugus) is
hemodichorial and has an ectoplasmic layer and an intrasyncytial lamina interposed between the maternal blood space and the underlying endoplasmic portion
of the syncytial trophoblast. The barrier and/or transport function of the trophoblast of this species was investigated. When Thorotrast was injected into the
maternal vascular system, only small amounts appeared in the trophoblast, and
i t could not be demonstrated deep to the syncytial trophoblast.
Injected peroxidase and ferritin were both rapidly taken up by the trophoblast,
these tracers being found in coated vesicles and tubules, in multivesicular bodies,
and in dense bodies. Peroxidase was transported across the trophoblast and could
be found in macrophages in the fetal connective tissue and in vesicles in the
fetal endothelium. Since ferritin is present in the cytotrophoblast, macrophages
and fetal endothelium in uninjected as well as injected animals, the exogenous
material could not be followed beyond the syncytium. In addition to demonstrating the cytological pathway by which absorbed proteins cross the trophoblast of
the chorioallantoic placenta of the bat, the results of this study suggest that the
labyrinth in this species should be considered a possible route for passage of
endogenous proteins to the fetus.
Most recent studies concerning the cytological basis of the uptake of proteins and
other large molecules by the placenta have
been concerned with the yolk sac of rodents or rabbits. For example, Lambson
('66) showed rapid uptake of ferritin by
the rat yolk sac. Deren et al. ('66) found
that intrinsic factor stimulated vitamin B,z
uptake by the rabbit yolk sac. Carpenter
and Ferm ('69) found that Thorotrast accumulated in the hamster yolk sac. King
and Enders ('70) showed that ferritin and
peroxidase were transported by the guinea
pig yolk sac, while Thorotrast was not. Although each of these species has a hemochorial type of chorioallantoic placenta,
they all also have an inverted yolk sac, so
that this structure, especially in the later
stages of pregnancy, i s i n an excellent position to transport substances from the uterine lumen to the fetal vascular system.
Many other mammals that have hemochorial placentas do not exhibit yolk sac
inversion. In some mammals, such as man,
the yolk sac is insignificant during most of
gestation and can hardly be implicated as
ANAT. REC.,170: 381-400.
a pathway for the passage of protein. The
little brown bat (Myotis lucifugus lucifugus) has a well-developed yolk-sac placenta
(Wimsatt, '45). However, it does not invert, and it is not yet known whether proteins pass from the maternal to the fetal
organism via this structure.
Recent investigation of the chorioallantoic placenta of Myotis lucifugus has shown
that it is hemodichorial, with a syncytial
trophoblast layer overlying a cytotrophoblast layer (Enders and Wimsatt, '68).
Peculiarly there is a perforate intrasyncytial lamina derived originally from the
basement membrane of the displaced maternal endothelial cells and situated in an
intrasyncytial space which largely separates a surface layer of ectoplasm from the
rest of the underlying syncytiuum.
The experiments reported here were intended to determine whether proteins could
be transported through the trophoblast of
~~
Received Aug. 26, '70. Accepted Jan. 11, '71.
1 This study was supported in part by grants 5 R01
HD-02613 from the National Institutes of Child Health
and Human Development (A.C.E.) and GB-6435 from
the National Science Foundation (W.A.W.).
381
382
ALLEN C. ENDERS AND WILLIAM A. WIMSATT
the chorioallantoic placenta and what as- Thick sections were stained with azure B
pects of this complex arrangement of lay- for examination with the light microscope.
ers might act as temporary or permanent Thin sections were stained with lead citrate and examined using an RCA EMU 3G
barriers to the tracers employed.
electron microscope or a Philips 300 elecMATERIALS AND METHODS
tron microscope. The glutaraldehyde-fixed
Bats (Myotis lucifugus lucifugus) from blocks from peroxidase-injected animals
a wild population in the vinicity of Ithaca, were washed in buffer overnight. Both thin
New York, were brought into the laboratory free-hand slices and frozen 50 sections
where they were used within one or two were incubated for ten minutes in the
days of capture. Tracer substances were diaminobenzidine solution of Graham and
introduced into the propatagial vein of the Karnovsky (’66). The blocks were subsematernal animal at varying periods of time quently rinsed in distilled water, postfixed
before removal of the placental tissue. in osmium tetroxide and processed as
Thorotrast (Fellows-Testagar, a colloidal above.
Peroxidase controls consisted of plasuspension of thorium dioxide in dextrin;
0.02-0.05 ml/ animal ) was injected into centas from injected bats but with the inten animals at intervals varying from five cubation step omitted and placentas from
minutes to 60 minutes prior to removing non-injected bats in which incubation in
the placenta. Horseradish peroxidase the diaminobenzidine medium was carried
(Sigma, Type 11, 100 mg/ml saline; 0.05 out in the same manner as with the inml/animal) was injected into 15 animals jected specimens. Since it was possible that
and allowed to remain for 2, 5, 8, 15, 30, blood containing peroxidase might pass
60, 120 minutes and 11 and 18 hours. In from the maternal blood vascular system
addition, three bats were injected with into the intrasyncytial space or into areas
either 0.03 or 0.05 ml peroxidase in saline of fetal connective tissue and blood ves(40 mgiml) in the umbilical vein 8 or 15 sels, two additional controls were run. In
minutes before fixing the placenta. (Oc- one control, fixation was by vascular perclusion of the fetal vessels precluded longer fusion of the maternal system, thus flushtime intervals.) Tissue from 14 of the ing out excess blood and peroxidase prior
peroxidase-injected animals was prepared to cutting the placenta into blocks. The
for electron microscopy, and tissue from second control was an uninjected animal
all 18 was prepared for light microscopic in which the placenta was fixed, then subexamination. Ferritin (Pentex, prepared sequently diced and soaked in a peroxidase
without cadmium salts, or Mann Labora- solution, rinsed, then processed in the same
tories, “cadmium-free”; 0.05 ml/animal) way as the peroxidase-injected placentas.
was given to two animals 15 minutes, one This control served to determine whether
60 minutes, and two 12 hours before fixing peroxidase could be bound by the fixed
tissue.
the placenta.
In most instances the uteri were reDESCRIPTION
moved, opened and portions of the placenta
Thorotrast
fixed in 3% glutaraldehyde in 0.01 M phosphate buffer, pH 7.3 The placentas from
Observations on the Thorotr ast-injected
one of the injections of peroxidase into the material indicate that this tracer was dismaternal vascular system and all three of tributed throughout the maternal vascular
the animals in which peroxidase was in- space within two to five minutes (fig. 1).
jected into the fetal vascular system were In confirmaion of our preliminary studies
fixed by perfusion of the maternal vascular (Enders and Wimsatt, ’68), little Thorosystem. Blocks of placenta from Thorotrast trast could be found within the syncytial
and ferritin-injected animals were rinsed trophoblast even after one hour, and none
in 0.01 M phosphate buffer, postfixed in appeared to pass beyond this layer. Despite
2% osmium tetroxide, dehydrated in ethyl the apparent space between adjacent proalcohol and, following passage through cesses of the ectoplasmic layer at the surpropylene oxide, embedded in either Aral- face of the syncytium, Thorotrast did not
dite (Durcupan) or Epon epoxy resin. pass directly into the intrasyncytial space.
TRANSPORT BY BAT PLACENTA
Careful examination of placentas from
longer time intervals revealed Thorotrast in
a few of the multivesicular bodies and in
an occasional large vesicle. Although multivesicular bodies containing Thorotrast were
most commonly found in the ectoplasmic
layer and apical cytoplasm, in some instances they were found near the basal
region of the syncytium.
In the exceptional cases where Thorotrast was found in the intrasyncytial space,
the proximity of these particles to small
vesicles suggested that the Thorotrast had
been released from a multivesicular body
which fused with the intrasyncytial space.
Clearly the syncytial trophoblast acts as a
barrier to this colloidal particle, since little
is taken up and none can be found within
placental elements deep to the syncytium.
Horseradish peroxidase
General distribution. Peroxidase activity was most widespread in tissue taken
60 minutes after injection into the maternal vascular system (fig. 2). Within the
syncytial trophoblast, peroxidase activity
was demonstrated in numerous micropinocytotic vesicles, tubular structures and multivesicular bodies (fig. 4). All three of
these structures were found in both the
ectoplasmic layer and the apical cytoplasm
underlying the intrasyncytial space. Tubules filled with reaction product were
also numerous near the basal surface of
the syncytium, but were more sparsely distributed throughout the central zone, where
they were often associated with Golgi complexes. (In individual sections many of
the profiles appear vesicular, but serial and
skip sections provided evidence of their
tubular nature. ) In multivesicular bodies
the presence of contained small vesicles
was indicated by the negative images of
these structures. Occasionally tubules were
confluent with multivesicular bodies. Contained vesicles were less frequently seen in
larger bodies near the basal portion of the
syncytium. In some regions where peroxidase reaction product was heavy at the
surface of the syncytium, activity could
also be demonstrated between adjacent
ectoplasmic processes and within the intrasyncytial space. In no instance was peroxidase activity confined to the intrasyncytial
lamina alone. Activity was either uni-
383
formly distributed or concentrated at the
edges of the intrasyncytial space rather
than within the lamina. Other areas, while
showing abundant activity in structures
within the cytoplasm, were devoid of
peroxidase activity at the surface or in the
intrasyncytial space.
Peroxidase activity delineated the space
between the syncytium and the cytotrophoblast (fig. 2). This activity was clearly
seen within the numerous desmosomes
along this border and appeared to form a
nearly continuous layer (figs. 3, 6 ) . Peroxidase was not found in the intercellular
spaces between cytotrophoblast cells (fig.
3). It was usually present in the cytotrophoblast in small vesicles, somewhat
smaller than the multivesicular bodies in
the syncytium but larger than the tubular
structures. Peroxidase activity was rare in
the basement membrane beneath the
trophoblast and was demonstrable in this
position only in a few instances where the
endothelium of a fetal vessel was closely
apposed to the cytotrophoblast (fig. 7). Occasional vesicles in the fetal endothelium
showed activity, but no activity was observed within the lumen of the fetal capillaries. Numerous vesicles and vacuoles
with peroxidase activity were found in
macrophages (Hofbauer-like cells which
are unusually abundant in the bat-Enders
and Wimsttt, '68; Enders and King, '70) in
the stroma of the placenta (fig. 2). Distribution of peroxidase activity was generalIy
similar in placentas from younger and
older stages of gestation. However, younger
placentas have numerous crystalloid-containing vacuoles. Some of these vacuoles
were heavily labeled following peroxidase
injection, while others showed no activity
(fig. 5 ) .
Time sequence of peroxidase uptake.
In placentas ranging from 2 to 30 minutes
after injection of peroxidase, the distribution of activity was irregular. Five and
eight minutes after injection peroxidase
could be found in numerous micropinocytotic vesicles, tubules and multivesicular
bodies within the syncytium (fig. 8). Only
a few tubules could be found in the deeper
cytoplasm, but some of these were in juxtaposition to the basal cell membrane (fig.
9). By 15 minutes the space between the
syncytial trophoblast and the cytotropho-
384
ALLEN C. ENDERS AND WILLIAM A. WIMSATT
blast was heavily marked by peroxidase activity, but the distribution was not as
uniform as in the later stages. Some reactive bodies were also seen in the cytotrophoblast cells by 15 minutes and were
clearly demonstrable in fetal stromal elements. The 30 minute specimens were
very similar to those described above at
60 minutes but were less heavily labeled.
Placentas taken 11 and 18 hours after
injection showed heavy and somewhat diffuse label in the macrophages of the fetal
stroma. Except for occasional patches of
tubules in the syncytial trophoblast, the
only activity still demonstrable was in
dense bodies at the base of the syncytium
and in the cytotrophoblast.
Peroxidase injection into umbilical vein.
In placentas from animals in which peroxidase had been injected into the umbilical
vein, peroxidase activity could be demonstrated not only within the fetal vessels and
endothelium but also in some of the
macrophages (fig. 11). Within the endothelium activity was heaviest in the micropinocytotic vesicles at the luminal surface
and in larger vesicles within the cytoplasm.
The label also penetrated deeply into the
intercellular spaces between endothelial
cells.
Reaction product was seen in occasional
small vesicles in the syncytial trophoblast
(fig. lo). These vesicles were often associated with Golgi regions. Peroxidase activity was also demonstrable in vesicles in the
cytotrophoblast.
Peroxidase controls. Uninjected controls showed no reaction product when incubated for ten minutes in the diaminobenzidine substrate except for darkening
of the erythrocytes. Unincubated material
from peroxidase injected animals showed
no differences from uninjected controls. In
the peroxidase injected incubated material
both frozen sections and free-hand sliced
blocks had only a thin shell of demonstrable activity, indicating that the substrate
did not penetrate throughout the blocks
and that the peroxidase per se could not be
visualized. Sections of material fixed by
perfusion of the maternal vascular system
did not show any activity in the intrasyncytial space or lamina. Sections of material
initially fixed, then cut in a peroxidase solution showed peroxidase activity as a thin
border at the periphery of the block. The
activity was diffuse within the cytoplasm
of the damaged portions of the tissue but
also tended to extend for a short distance
along the surface of the cut maternal
blood spaces. In two blocks from one of
the animals in which peroxidase had been
injected into the fetal vessels, some activity
was present along the surface of a few of
the maternal blood spaces. This activity
can be most readily explained on the basis
of binding of the peroxidase to the partially
fixed border of the syncytium at the time
the blocks were cut, since its distribution
bore no relationship to the regions where
peroxidase was demonstrable within the
syncytial trophoblas t.
Ferritin
Sixty minutes after injection of ferritin,
molecules of this tracer could be seen in a
number of structures in the syncytial
trophoblast, cytotrophoblast and fetal
stroma. In the syncytium ferritin was
conspicuous in association with both open
and apparently closed rough surfaced micropinocytotic vesicles which fronted on
the maternal blood space and on both sides
of the intrasyncytial space (fig. 12). These
vesicles had an extracellular coat of uniform thickness between the ferritin and
the membrane proper and, in favorable
micrographs, a distinctive internal or
bristle coat. Ferritin molecules were often
found in the intrasyncytial space and
lamina but were not usually seen between
adjacent processes of the ectoplasmic layer.
Moreover the only areas of ferritin concentration were in relation to coated invaginations of the surface of the maternal blood
space and the intrasyncytial space. Ferritin was found in tubular structures in the
apical cytoplasm, in the central zone, especially near the Golgi, and in conspicuous
clusters in the basal cytoplasm of the syncytial trophoblast. The tubules had a pronounced luminal coat, enlarged or bulbous
portions and flattened regions which in
cross section showed neat lines of ferritin
molecules and in tangential section tended
to show rows of uniformly spaced ferritin
molecules in evenly spaced files (figs. 13,
1 5 ) . (The tubules and vesicles in which
the ferritin was seen are presumably of the
same type as those in which peroxidase ac-
385
TRANSPORT BY BAT PLACENTA
tivity was demonstrated. However, the
individual ferritin molecules were visualized at the surface of the coat of the tubules and vesicles, whereas the reaction
product of peroxidase activity was within
and thus obscured the coat material [See
King and Enders, '701. ) Ferritin molecules
could also be seen among the small vesicles
in multivesicular bodies and in large bodies
of irregular density.
Although ferritin was abundant in
tubules near the syncytial-cytotrophoblast
junction, only a few granules were ever
found in the space between these two
layers. In the cytotrophoblast, ferritin was
occasionally present in small vesicles, large
vesicles of irregular density and as individual molecules free in the cytoplasm (figs.
13, 15). The distribution of ferritin in
the cytotrophoblast was the same as that
seen in animals uninjected with ferritin
although more ferritin appeared to be present in injected than in uninjected animals
(fig. 14). Ferritin was also present in the
macrophages, some of which had ferritin
present in large vacuoles as well as in
smaller dense vacuoles and free in the
cytoplasm (fig. 16). As in the cytotrophoblast, some impression of increased
amounts of ferritin was given but often
macrophages in uninjected animals were
also heavily laden with ferritin. Ferritin
molecules were found free in the cytoplasm
of the fetal endothelium in small numbers
in placentas of all of the injected animals
and in uninjected animals examined at
high magnifications.
Changes with time. In animals killed
15 minutes after injection, ferritin was
abundantly present in the ectoplasm and
apical cytoplasm but was more difficult to
find deeper in the syncytium. Only an
occasional tubule containing ferritin could
be found near the syncytial-cytotrophoblast
junction. However, as in all animals including uninjected animals, free ferritin
could be seen in the cytotrophoblast.
Animals left for a long time (12 hours)
after injection still showed ferritin in some
of the tubules in the ectoplasmic layer and
apical cytoplasm, although generdly ferritin was less abundant in the syncytium
both in the apical and basal regions. However, it was abundant in larger bodies of
irregular density (dense bodies) in the
basal cytoplasm.
DISCUSSION
Ferritin, peroxidase and other proteins
have been widely used in electron microscope studies in the past decade. These
tracers have been especially useful in studying the variable permeability of blood vessels (Clementi and Palade, '69) and in
developing our understanding of the way
cells ingest and degrade proteins (Friend
and Farquhar, '67). Studies of the way in
which proteins may be transported undegraded through epithelial cells have been
made using the neonatal intestine, in
which large amounts of protein are ingested and a very small percentage passed
undegraded (Graney, '68; Deren, '68; Cornell and Padykula, '69) and the yolk sac
placenta in which the uptake is more
modest (King and Enders, '70). These
epithelia have been particularly studied
because of the passage of maternal globulins to the neonate (Morris, '68) and fetus
(Leissring and Anderson, '61) and their
possible role in passive immunity. Even in
the intestine, where the epithelial layer is
simple columnar in all species, different
pathways by which protein leaves the cell
have been postulated (Morris, '68). The
problem of passage through to the fetal
vascular system is even more complicated
in the chorioallantoic placenta because of
the divergent number and nature of layers
interposed between maternal and fetal
blood.
From the cytological observations reported here, some aspects of the function
of the chorioallantoic placenta as a barrier
and as a pathway for the passage of large
molecules between the maternal and fetal
organisms in Myotis can be derived.
The finding of peroxidase in the space
between the syncytial and cytotrophoblast
by 8 to 15 minutes after injection indicates
very rapid transport through the syncytial
trophoblast, but its visualization is made
possible by the relatively slow passage out
of this space. However, the appearance of
peroxidase in macrophages 15 to 30 minutes after injection probably indicates both
rapid passage of some of the peroxidase
through the cytotrophoblast and the remarkable ability of macrophages to seques-
386
ALLEN C. ENDERS AND WILLIAM A. WIMSATT
ter small amounts of protein from the
surrounding medium.
The widespread distribution of peroxidase activity 60 minutes after injection is
an indication of the time necessary to mark
or saturate the structures involved in transport at the particular level of tracer injected rather than directly indicating the
rate of transport. Although peroxidase can
be visualized both in the connective tissue
and occasionally in fetal endothelium after
injection into the maternal vascular system, it is less certain whether it passes
undegraded into the fetal vascular system.
That this endothelium may be permeable
to peroxidase is shown by the passage of
peroxidase out of the fetal capillaries into
the trophoblast after injection into the
umbilical vessels. Consequently it is probable that this material can get across to
the fetus after injection into the maternal
vascular system, but we still lack direct
evidence of this passage.
The observation that peroxidase passes
from the fetal vessels into the surrounding
connective tissue is not necessarily an indication of a general vascular permeability to
proteins in the bat placenta, since it is not
known whether peroxidase can induce patency of the junctional complexes or, by
bringing about serotonin and histamine release, produce increased vascular permeability. Such increases in permeability have
been demonstrated in somatic capillaries
of some other species (Karnovsky, ’67). It
is significant, however, that peroxidase that
leaked from these vessels was taken up by
the syncytium, indicating that proteins
which leave the fetal vascular system can
penetrate towards the maternal vascular
system at least as far as the syncytial
trophoblast.
The generalized morphological pathway
for both tracer proteins into and through
the syncytium is apparently similar.
Briefly, it consists of uptake by coated vesicles, and passage into tubules from which
it passes either to the basal cytoplasm of
the syncytium by way of the Golgi or to
multivesicular bodies and eventually to
dense bodies. Some specific aspects of this
passage and transport to the fetal vessels
are more problematic. The ectoplasmic
layer of the syncytial trophoblast appears
to be very active in uptake of exogenous
proteins. The number of coated tubules in
the stalks connecting the ectoplasm with
the endoplasm of the syncytial trophoblast
indicates that some passage of protein may
be directly through these connections. The
large numbers of coated vesicles opening
on both surfaces of the intrasyncytial space
suggest that material might also pass into
the endoplasm by release from the ectoplasm into the intrasyncytial space, with
subsequent uptake on the endoplasmic
side. Although ferritin was relatively uniformly distributed within the intrasyncytial
space and lamina, peroxidase activity was
usually spotty or absent. The most likely explanation of this observation is that the
peroxidase or its reaction product was
washed from the intrasyncytial space during preparative procedures. (The deeper
regions of the blocks that would be less accessible to leaching were not penetrated by
the substrate.) Despite the possibility that
some contained materials might be artifactually removed, it appears unlikely that
these spaces act as a “sink for accumulation of large amounts of exogenous protein.
It is possible, however, that some extracellular digestion could occur in this space.
Wimsatt (’58, ’62) demonstrated alkaline
phosphatase activity in the intrasyncytial
lamina but no studies have been made of
hydrolytic enzymes operating at an acid
pH in the bat. Studies of hydrolytic enzymes would be useful not only in studying
the role of multivesicular bodies with regard to the intrasyncytial space, but also
are necessary to elucidate the role of these
structures and of dense bodies in degradation of ingested protein. The role played by
these structures in degradation of protein
has been clearly delineated in the kidney
(Miller and Palade, ’64; Maunsbach, ’66)
and the vas deferens (Friend and Farquhar, ’67). Comparable studies have yet to
be made concerning the placenta.
The accumulation of reaction product in
the space between the syncytium and cytotrophoblast of peroxidase-injected animals
is dramatic, and is in marked contrast to
the sparsity of ferritin particles in this location. Direct comparison of abundance is
not possible because of the amplification of
peroxidase by enzymatic incubation. Nevertheless, the accumulation of ferritin in
the basal tubules of the syncytium and the
TRANSPORT BY BAT PLACENTA
absence of these molecules from the space
between syncytium and cytotrophoblast
probably indicate either that ferritin is released from the syncytium less rapidly than
peroxidase or that the cytotrophoblast picks
up this molecule more rapidly than it does
peroxidase. Accumulation of peroxidase in
the space between the syncytium and cytotrophoblast and the absence of this material in the intercellular space between cytotrophoblast cells suggest that the apical
junctional complexes between cytotrophoblast cells are at least a partial barrier to diffusion of peroxidase, and could
be expected to be an even greater barrier to
the passage of the larger ferritin molecule.
Because of the large amount of endogenous ferritin in the cytotrophoblast, macrophages and fetal endothelium, it is not possible to say that the exogenous ferritin was
transported. However, both the normal
presence of ferritin in the inner layers of
the placenta in uninjected animals and the
lack of accumulation of these molecules
despite the rapid uptake by the syncytium
of injected animals are indications that ferritin is transported.
Jollie ('64) studied ferritin injected into
the maternal vascular system of the rat and
suggested that its transport was blocked by
the middle layer of trophoblast of the
chorioallantoic placenta. However, Tillack
('66) showed ferritin in the basement
membrane and endothelium beneath all
three layers of trophoblast 45 minutes after
injection into the maternal vascular system. King and Enders ('71) found both
peroxidase and ferritin in the fetal vessels
of the chorioallantoic placenta of the
guinea pig after injection of these tracers
into the maternal vascular system, despite
the fact that the yolk sac has been implicated as the major pathway for passage of
endogenous proteins in this species (Leissring and Anderson, '61).
Although the data from this study of the
placenta of the little brown bat are qualitative, the rapid fashion in which exogenous protein was transported across the
syncytium indicates that in this vespertilionid the chorioallantoic placenta has to be
considered a probable pathway in the passage of proteins from the maternal to the
fetal organism.
387
LITERATURE CITED
Carpenter, S. J., and V. H. Ferm 1969 Uptake
and storage of Thorotrast by the rodent yolk sac
placenta: An electron microscope study, Am.
J. Anat., 125: 429-456.
Clementi, F., and G. E. Palade 1969 Intestinal
capillaries. I. Permeability to peroxidase and
ferritin. J. Cell Biol., 41: 33-58.
Cornell, R., and H. A. Padykula 1969 A cytological study of intestinal absorption in the
suckling rat. Am. J. Anat., 125: 291-316.
Deren, J. J. 1968 Development of intestinal
structure and function. In: Handbook of
Physiol., Alimentary Canal, 111. Williams and
Wilkins Co., Baltimore, Maryland, pp. 10991123.
Deren, J. J., H. A. Padykula and T. H. Wilson
1966 Development of structure and function
in the mammalian yolk sac. 11. Vitamin BIZuptake by rabbit yolk sacs. Devel., Biol., 13: 349369.
Enders, A. C., and B. F. King 1970 The cytology
of Hofbauer cells. Anat. Rec., 167: 231-252.
Enders, A. C., and W. A. Wimsatt 1968 Formation and structure of the hemodichorial chorioallantoic placenta of the bat (Myotis Zucifugus
h c i f u g u s ) . Am. J. Anat., 122: 453-490.
Friend, D. S., and M. G. Farquhar 1967 Functions of coated vesicles during protein absorption in the rat was deferens. J. Cell Biol., 35:
357-376.
Graham, R. C., and M. J. Karnovsky 1966 The
early stage of absorption of injected horseradish
peroxidase i n the proximal tubule of the mouse
kidney: Ultrastructural cytochemistry by a
new technique. J. Histochem. Cytochem., 14:
291-302.
Graney, D. 0. 1968 The uptake of ferritin by
ileal absorptive cells in suckling rats. An electron microscope study. Am. J. Anat., 123: 227253.
Jollie, W. P. 1965 Visualization of a block to
placental transport of protein and dextrin in
the rat. Bull. Tulane Univ. Med. Faculty, 24:
213-224.
Karnovsky, M. J. 1967 The ultrastructural basis
of capillary permeability studied with peroxidase as a tracer. J. Cell Biol., 35: 213-236.
King, B. F., and A. C. Enders 1970 Protein
absorption and transport by the guinea pig visceral yolk sac placenta. Am. J. Anat., 129:
261-288.
1971 Protein absorption by the guinea
pig chorioallantoic placenta. Am. J. Anat., 130:
409-430.
Lambson, R. 0. 1966 A n electron microscopic
visualization of transport across rat visceral
yolk sac. Am. J. Anat., 118: 21-52.
Leissring, J. C., and J. W. Anderson 1961 The
transfer of serum proteins from mother to
young in the guinea pig. I. Prenatal rates and
routes. Am. J. Anat., 109: 149-155.
Maunsbach, A. B. 1966 Absorption of ferritin
by rat kidney proximal tubule cells. J. Ultrastruct. Res., 16: 1-12.
Miller, F., and G. E. Palade 1964 Lytic activities
urotein absomtion droulets. An
._
.
- in
_.
-renal
_
.
.
388
ALLEN C. ENDERS AND WILLIAM A. WIMSATT
electron microscopical cytochemical study. J.
Cell Biol., 23: 519-552.
Morris, I. G. 1968 Gamma globulin absorption
in the newborn. Handbook of Physiol., Alimentary Canal, 111. Williams and Wilkins Co., Baltimore, Maryland, pp. 1491-1512.
Tillack, T. W. l'966 The transport of ferritin
across the placenta of the rat. Lab. Invest., 15:
896-909.
Wimsatt, W. A. 1945 The placentation of a
vespertilionid bat (Myotis Zucifugus Zucifugus ).
Am. J. Anat. 77: 1-51.
1958 The d a n t o i c placental barrier in
Chiroptera: a new concept of its organization
and histochemistry. Acta anat., 32: 141-186.
1962 Some aspects of the comparative
anatomy of the mammalian placenta. Am. J.
Ob. Gyn., 84: 1568-1594.
PLATE 1
EXPLANATION OF FIGURE
1
This micrograph shows the general arrangement of the trophoblast of
the labyrinth of the little brown bat placenta. The maternal blood
space (MBS) contains numerous particles of Thorotrast. A n ectoplasmic layer (EL) separates the maternal blood space from the intrasyncytial space (IS), below which is the endoplasmic portion of the
syncytial trophoblast. The intrasyncytial lamina appears as a slightly
darker material in the center of the intrasyncytial space. The cytotrophoblast shares numerous desmosomal junctions with the overlying
syncytium. Note that the Golgi membranes tend to be basally situated
in the syncytium. Note also that there is no tendency for the Thorotrast to accumulate at the surface of the syncytium, and none of it is
contained within the syncytium. Five minutes after Thorotrast injection, 12 mm CRL. x 26,200.
TRANSPORT BY BAT PLACENTA
Allen C. Enders and William A. Wimsatt
PLATE 1
389
PLATE 2
EXPLANATION OF FIGURES
2
Micrograph showing the general distribution of peroxidase activity 60
minutes after injection into the maternal vascular system. Activity is
present in small vesicles and tubules and in multivesicular bodies in
the apical cytoplasm. It also rims the intrasyncytial space (arrows).
Heavy accumulation of activity is seen between the cytotrophoblast
and the syncytium. The Golgi zones ( G ) also constitute an area where
numerous structures containing reaction product can be found. At the
extreme bottom is a portion of a fetal macrophage ( M ) , also showing
peroxidase activity. 19 mm CRL x 15,600.
3 In this micrograph of the junction between the syncytial trophoblast
and cytotrophoblast, it c a n be seen that the intercellular space between
the two contains reaction product, including the region of a desmosome (D). However, the reaction product does not extend beyond the
junctional complex (arrow) betwen two cytotrophoblast cells and is
not seen in the intercellular space (ICS) between these cells. Two vesicles in the cytotrophoblast contain reaction product. Numerous small
vesicles and tubules in the syncytium also have reaction product. Sixty
minutes after injection. 19 mm CRL x 23,900.
390
TRANSPORT BY BAT PLACENTA
Allen C. Enders and William A. Wimsatt
PLATE 2
391
PLATE 3
EXPLANATION OF FIGURES
4
In this micrograph of the apical region of the syncytial trophoblast,
there are numerous small vesicles and tubules (T) and several multivesicular bodies (MVB) in which the vesicles appear as a negative
image. Sixty minutes, 19 mm CRL x 21,300.
5
At the junction between the syncytium and cytotrophoblast seen in
this micrograph 60 minutes after injection, peroxidase activity has
accumulated in small tubules and vesicles but an unusually small
amount appears in the intercellular space. Of particular interest is that
peroxidase has accumulated in some of the vacuoles containing crystalloids (large arrows) but not others (small arrow). 4 mm CRL.
X 23,800.
6 Enlarged portion of the syncytial-cytotrophoblast junction demonstrating that peroxidase readily penetrates the desmosome (lower right).
Sixty minutes, 19 mm CRL x 46,300.
7
This micrograph shows peroxidase activity in the basement membrane
underlying the cytotrophoblast and in a vesicle ( V ) in the fetal endothelium. As usual the activity is heavy in the intercellular space between the syncytium and cytotrophoblast. Sixty minutes, 19 mm CRL
X
392
17,500.
TRANSPORT BY BAT PLACENTA
Allen C. Enders and William A. Wimsatt
PLATE 3
393
PLATE 4
EXPLANATION OF FIGURES
8
Trophoblast eight minutes after injection of proxidase into the maternal vascular system. Peroxidase is already in some of the multivesicular bodies and a few tubules or vesicles (arrows) deeper in the cytoplasm, but none has appeared as yet at the junction between syncytium and cytotrophoblast. Note also the absence of reaction product
in the intrasyncytial space in this specimen fbied by perfusion of the
maternal vascular system. 21 mm CRL x 25,400.
9 Although this animal was killed only five minutes after injection of
peroxidase into the maternal vascular system, some tubules clearly
show activity (T) and small amounts of reaction product are beginning to appear in the intercellular space between the syncytium and
cytotrophoblast (arrows). Such regions are relatively rare at this short
time interval. 1.5 mm CRL x 24,200.
10 In this micrograph of tissue fixed eight minutes after injection of peroxidase into the umbilical vessels, peroxidase activity is seen not only
in the fetal capillary (FC) but also in a vesicle in the cytotrophoblast
( V ) and in tubules and vesicles near the Golgi regions of the syncytium (arrows). 18 mm CRL X 24,200.
394
TRANSPORT BY BAT PLACENTA
PLATE 4
Allen C. Enders and William A. Wimsatt
395
PLATE 5
EXPLANATION O F FIGURES
11
Eight minutes after injection of peroxidase into the fetal vascular
system, activity was seen not only in the fetal capillary but also in
the micropinocytotic vesicles (mv) and vacuoles (Va) of a macrophage in the connective tissue of the labyrinth. 18 mm CRL x 22,600.
12 The general distribution of ferritin in the syncytium is seen in this
micrograph from a placenta taken 60 minutes after injection of the
maternal vascular system. Ferritin is present in coated micropinocytotic vesicles (arrows), in a multivesicular body (MVB), within
the intrasyncytial space, in tubules near the basal surface of the
syncytium (T),and in numerous tangentially sectioned tubules and
vesicles in the apical cytoplasm. 11 mm CRL x 54,800.
396
TRANSPORT BY BAT PLACENTA
Allen C. Enders and William A. Wimsatt
PLATE 5
397
PLATE 6
EXPLANATION OF FIGURES
13 In this micrograph of the syncytial-cytotroFhoblastborder ferritin is
seen in flattened tubular structures (T), where it is clearly displaced
from the limiting membrane by the surface coat, and in numerous
other vesicles and tubules. Ferritin is also seen free in the cytoplasm
in the cytotrophoblast in the lower left corner (squares). Sixty
minutes, 11 mm CRL
58,500.
x
14
In this micrograph of placenta from an uninjected animal, ferritin
molecules ( squares ) are nevertheless common in the cytotrophoblast.
12 mm CRL x 47,600.
15 Micrograph of the junction between the syncytial trophoblast (left)
and cytotrophoblast (right). When the tubules in the syncytium are
sectioned tangentially, the ferritin appears in a highly ordered arrangement (lines). Ferritin is free in the cytoplasm of the cytotrophoblast (square). Sixty minutes, 11 mm CRL x 70,600.
16 This micrograph of a macrophage in the connective tissue of the
labyrinth shows abundant ferritin in the dense bodies (DB), a vacuole
(Va) and free in the cytoplasm. Although ferritin is unusually
abundant in macrophages taken 12 hours after injection of ferritin
into the maternal vascular system, it is also found in the cytoplasm
and dense bodies of macrophages in uninjected animals. 14 mm CRL
x
398
49,500.
TRANSPORT BY BAT PLACENTA
Allen C. Enders and William A. Wimsatt
PLATE 6
399
Документ
Категория
Без категории
Просмотров
2
Размер файла
1 936 Кб
Теги
lucifugus, bat, transport, barriers, placental, function, chorioallantoic, myotis
1/--страниц
Пожаловаться на содержимое документа