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Fine structure of the ultimobranchial body of the chick.

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Fine Structure of the Ultimobranchial Body of the Chick'
H. ISLER
Department of Biological Sciences, University of Montreal,
Montreal, Canada
ABSTRACT
The ultimobranchial bodies of the chick consisted of follicles and
cell cords. The follicles were of various sizes and shapes. Their epithelium was
simple or stratified, squamous to cuboidal, and contained two cell types. The
lumen-borderingcells had microvilli at their apex, a few long, flat ergastoplasmic
sacs, a prominent Golgi, an extensive system of smooth membrane tubules and
microvesicles, abundant free ribosomes, no granules and indented nuclei. Their
lateral membranes followed a sinuous path and their membrane at the base
showed occasional intense pinocytotic activity. Thus these cells appear well differentiated and functionally active, whatever their function may be. The second
cell type, never in contact with the lumen, also differed by its abundant granules,
the smooth path of its plasma membrane, the smooth outline of its nucleus and
the occasional presence of intranuclear vesicles. The cell cords were made essentially of these same granular cells. It was shown histoimmunologically that numerous calcitonin-containing cells were present in the cell cords; those few
present within the wall of the vesicles never bordered on the lumen. It is concluded that the granular cells are producing calcitonin, while the lumen-bordering cells contribute the holocrine secretion of the vesicle.
The ultimobranchial body of the chick,
which is responsible for the production of
calcitonin (Copp et al., '67a,b; Tauber,
'67), consists, like that of birds in general
(Watzka, '33), of cell cords and vesicles.
The fine structure of the cell cords has
been described by Stoeckel et al. ('67, '69),
Malmqvist et al. ('68), Chan et al. ('69)
and Youshak et al. ('71), but considerable
discrepancies still exist as to the number
and nature of the cell types they contain.
In addition, much less attention has been
devoted to the ultrastructure of the vesicles
(Stoeckel et al., '69; Youshak et al., '71)
than to the cell cords. The present paper
describes these structures and provides
identification of the calcitocytes by immunofluorescence.
MATERIAL AND METHODS
Male and female Leghorn chickens of
various ages (from 1 month to 2 years)
were perfused with the fixative, and the
tissues processed as described earlier (Calvert and Isler, '70), using Epon as embedding medium. The birds were anaesthetized with ether and their body cavity
opened; the ribs were cut on both sides,
ANAT. REC., 177: 441-460.
and the rib cage lifted to uncover the
heart. The needle connected to the perfusion bottle was inserted into the left ventricle and the perfusion fluid ( a buffered
mixture of 6.25% glutaraldehyde and 2%
acrolein) allowed to run for 30 minutes
with the bottle held three feet above the
bird. The electron micrographs shown in
this paper involve one-month-old-birds. All
the chickens had been fed a mixture of
powdered Purina Laboratory chow (65% )
and Purina Rabbit Checkers (35% ) from
the age of one day.
Some of the glands, together with surrounding tissues, were fixed in Bouin's
fluid, embedded in paraffin and cut serially.
Those used for immunofluorescence were
fixed in a 4% buffered formaldehyde soluor Epon, and
tion, embedded in par&
further processed according to the sandwich method of Coons ('58). Anticalcitonin antibodies were induced in the rabbit
by injecting pig calcitonina according to
Received Jan. 23, '73. Accepted May 15, '73.
1 Supported by a grant from the National Research
Council of Canada.
zThe calcitonin used in this experiment was secured through the courtesy of Eli Lilly and Company
(Canada) Limited Montreal, .and Armour Pharmaceutical Company, Kankakee, Illmois.
441
442
H. ISLER
the method of Tashjian ('70). Routine
controls of immunofluorescent reactions
were carried out by using rabbit antithyroglobulin instead of anticalcitonin antiserum. The antithyroglobulin antiserum
was obtained by the same method as for
the anticalcitonin antiserum.
RESULTS
The ultimobranchial bodies were usually
found in contact with the second (caudal)
parathyroid gland (fig. l ) , but were also
occasionally found associated with the
thymus or carotid body. Several large vesicles were often grouped into a lace-like
arrangement in one area (fig. 1 ) . The
rest of the tissue contained epithelial cell
cords, among which smaller vesicles were
present. The epithelium lining the vesicles
was often simple (figs. 2-5); it was usually cuboidal in the small ones (fig. 3 ) ,
while in the larger ones its height varied,
even within the same follicle, from extremely thin to cuboidal (fig. 3 ) . The
gland was richly vascularized (fig. 3 ) and
was supplied with a fair number of nerve
fibers (fig. 2 ) .
The
immunofluorescent
technique
showed a large number of fluorescent
calcitonin-containing cells within the cell
cords (fig. 7), as well as a smaller number
within the walls of the vesicles (fig. 6 ) ;
none of these were in contact with the
lumen. The brightest cells in the cords
were much brighter - and thus probably
contained more calcitonin - than those
within the wall of the vesicles. No evidence was found of calcitonin or thyroglobulin presence in the lumen.
Fine structure of the vesicles
The wall of the vesicle was made of two
types of cells (fig. 14) : the lumen-bordering cells and the granular cells. The
lumen-bordering cells possessed stubby or
slender microvilli at their apex (figs. 8,
13). Their lateral membranes followed a
sinuous path (figs. 8, 10, 12, 14). Where
in contact with the connective tissue, the
cells were coated with a basement membrane (fig. 12), and in several instances
the plasma membrane at the base showed
an intense pinocytotic activity (figs. 11,
15). There was frequent cell overlapping
at the base and occasionally thin strands
of cytoplasm showed a considerable number of pinocytotic vesicles, both on the side
coated with the basement membrane and
on the side in contact with the cell above
(fig. 15).
The nucleus had an irregular outline
and frequent indentations (figs. 10, 1 3 ) .
The nuclear membrane possessed numerous pores (fig. 12) and usually showed a
few small masses of attached chromatin.
One or more typical nucleoli were occasionally present, and, in some cases, a
separate small, oval, finely granular body
was also present (fig. 10).
The cytoplasm contained a few long, flat
ergastoplasmic sacs (figs. 8, 10, 12), as
well as some small ones. The smooth membrane system was well developed. The
Golgi apparatus consisted essentially of
lamellae and microvesicles, with few or
no vacuoles (fig. 14). Microvesicles about
100 mp in diameter, with pale contents
and bounded by a smooth membrane, were
present all over the cytoplasm, but were especially abundant at the apex (figs. 8, 12).
There were also a large number of tubules
with diameters usually 40 to 100 mp, or
larger, filled with a material of medium
density; they sometimes converged towards an irregularly shaped vesicle filled
with the same material and which may or
may not belong to the Golgi apparatus
(figs. 8,9). Free ribosomes were abundant
in all the cells. Filaments were present in
amounts varying from cell to cell (fig. 12).
The mitochondria were elongated, sometimes sinuous (figs. 8, 12, 14) or even
branched, and their matrix was fairly
dense; the cristae were sometimes parallel,
but were most often randomly oriented
(fig. 12); some of them were not clearly
visible; the inside peripheral membrane
was finer and also less clearly visible than
the outside one (fig. 12).
A few of the lumen-bordering cells had
an abnormally dense and vacuolated cytoplasm and poorly defined organelles (fig.
15), while their neighbours were perfectly
normal; it is probable that they were involuted cells to be eventually extruded into
the lumen. Indeed, whole or parts of cells
were frequently present in the lumen of
ultimobranchial vesicles (figs. 3, 5, 6).
The second type of cell observed in the
wall of the follicles was the granular cell
C,HICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
(figs. 14, 15). These cells were much
fewer than the bordering cells. Indeed, a
section of a particular vesicle occasionally
showed no granular cells. When present,
they were in direct contact with the lumenbordering cells but never abutted on the
lumen itself. Two types of granules were
observed in these cells. The small dark
granules (fig. 14), 100-300 mp in diameter, were round or oval, with a highly
variable density, although mostly very
dense. The large light granules (fig. 15),
200-600 mp in diameter, were oval and
had a medium to light density; the larger
ones were incompletely bound by a membrane as if it had burst and the content of
the granules was in contact with the cytoplasmic matrix (fig. 15). Some cells
showed only or mostly small granules (fig.
.14); others showed only or mostly large
granules (fig. 15); still others contained
both (fig. 14).
The plasma membrane of the granular
cells followed a smooth path, whether in
direct contact with lumen-bordering cells
(fig. 14), or with granular cells (fig. 17).
At the base, it was sometimes coated with
a basement membrane, but more often with
a thin layer of cytoplasm from another
granular or agranular cell (fig. 14). Occasionally, the agranular cytoplasmic strands
showed a high pinocytotic activity (fig. 15).
The nuclei of the granular cells had a
regular outline with no identations and
few masses of chromatin attached to the
membrane. In toluidine blue-stained Epon
sections, their prominent and numerous
nucleoli made them easily distinguishable
from the bordering cells (fig. 3). Empty
membrane-bounded vesicles, 300-600 mp
in diameter, were occasionally observed
within the nucleoplasm (fig. 19).
The granular cells contained a few long
flat and some short, slightly dilated ergastoplasmic sacs (fig. 14), and, like the
bordering cells, a well developed smooth
membrane system (fig. 14) as well as
abundant free ribosomes. The mitochondria were like those in bordering cells.
The lumen of the vesicles contained
granular material in variable amounts
(fig. 13) and occasionally cells or cell
remnants (figs. 3, 5, 6).
The small vesicles were round or oval
with a regular outline (figs. 2, 3). In
443
contrast the large ones had irregular
shapes (figs. 1, 7); some were partially
divided by projections jutting into the
lumen as if a communication was being
established between two neighbouring follicles, The projecting partition was often
very thin, consisting of a collagenic core
made of parallel and seemingly rigid
arrays of microfibrils interspersed with
fine strands of fibroblastic cytoplasm, the
whole covered with a thin epithelium at
some places less than 1 thick (fig. 13).
The immediate environment of the vesicles and the rate of formation of new ones
seemed to change with age. In young birds
(i.e. 1 month old) a f,air number of small
lumina within the cell cord suggests the
beginning of new vesicles (fig. 4), while
in older birds ( 2 years old) such nascent
vesicles were rare or inexistent. Also in
young birds the vesicles were closely surrounded by cell cords (figs. 2 , 3), while in
older ones each vesicle was surrounded by
a thick layer of connective tissue (fig. 5 ) .
Fine structure of the cell cords
The cell cords were occasionally scattered between the vesicles but most of
them (with the associated capillaries)
were grouped in one large mass. They
were made essentially of granular cells in
direct contact with each other (fig. 17).
These cells were the same as those encountered in the vesicles, and contained
either small (fig. 17) or large granules
(fig. IS), or both; those with small granules were the most abundant ones. Occasionally nervous fibers partially enclosed
in Schwann cell cytoplasm abutted on
granular cells, with a 10 mp space between
the membrane of the epithelial cell and
that of the axon or Schwann cell (fig. 18).
In addition to granular cells, a few cells
of a different type were observed in the
cell cords (figs. 16, 17). They were in
direct contact with the granular cells and
shared a common basement membrane
with them. Thin strands of their cytoplasm
partly covered granular cells, separating
them from the connective tissue (figs. 16,
17) and/or separating them from each
other (fig. 17). Their nuclear membrane
was coated with a thicker layer of chromatin with clumps streaming deep into the
nucleoplasm (fig. 17). They contained
444
H. ISLER
large dilated ergastoplasmic sacs filled with
a finely granular material of medium density (figs. 16, 17) and displayed no granules. In fact they resembled fibroblasts except for their basement membrane and
their close contact with the epithelial cells.
dark cytoplasm and contain larger and
lighter granules.
In our material we find granular cells
and fibroblast-like cells. Although we fmd
two populations of granules (small dense
100-300 mp and large, lighter ones 200600 mp), we are rather inclined to ascribe
DISCUSSION
this wide range to artifactual factors. SolvThe presence of calcitonin in the ulti- ing this question requires identification of
mobranchial body of the chick was first the granules’ contents at the ultrastrucdemonstrated by Copp in 1967. The same turd level. Comparison of calcitonin granyear, it was shown that this gland con- ules in various publications is difficult betains cells similar to the calcitonin-produc- cause their appearance is affected by the
ing cells of the thyroid gland of mammals technical procedure, as the contents of the
(“light cells” or “parafollicular cells”) granule are easily washed away. It may be
(Kracht et al., ’68). They are similar in totally removed in tissue fixed with osmic
their ability to take up and decarboxylate acid only, and is better preserved in tissue
5-hydroxytryptophane (Hachmeister et al., prefixed with aldehydes. Preservation, dilu’67) and in their ultrastructural appear- tion and dissolution thus very much deance (Stoeckel et al., ’67). We believe that pend on the fixation and washing procethe present paper provides the first identi- dures, which, in turn, may account for
fication of the chick calcitocytes by the discrepancies between workers. Using the
fluorescent antibody technique.
same technique as described in this paper,
It seems that the number and the nature we met a similar “small-and-large-granof the cell types found in the cell cords of ules” situation in the calcitocytes of the
the ultimobranchial body of the chick is rat thyroid (Calvert, ’69). For these reanot yet settled. In 1967, Stoeckel et al. sons, we do not feel that there is enough
describe five cell types: 1. granular cells evidence at this time to postulate two
with granules measuring up to 450 mp; types of calcitocyte-like cells, either in our
2. cells with the same granules but with material or in that of Stoeckel et al. (’69)
larger mitochondria; 3. cells with much or of Youshak et al. (’71).
finer granules believed to be carotid body
Carotid body cells were absent in our
cells; 4. fibroblast-like cells; 5. light gly- material. These cells are readily recognizcogen-rich cells. In 1969, the same authors able by their fine catecholamine-containdescribed only three types: 1. granular ing granules. Ultimobranchial and carotid
cells with granules measuring 150-200 bodies are often situated very close to each
mp; 2. granular cells with granules mea- other. Understandably, occasional sections
suring 250-300 my (up to 450 mp in the through the contact area may show both
young birds) ; 3. fibroblast-like cells, which calcitonin and catecholamine cells, as obthey call bordering cells. The same year served by Stoeckel et al. (’67).
Chan et al. mention two cell types: dark
We do not agree with the statement of
and light, and describe only the latter, in Stoeckel et al. (’69) that the lumen-borderwhich they find granules measuring 100- ing cells of the vesicle are of the same cell
250 mp. In a more recent paper Chan type as the fibroblast-like cells of the cell
(’71) characterizes the dark cells by their cords. In our material they are clearly difcontent in dense bodies and dilated ergas- ferent. Youshak et al. (’71) observed some
toplasmic sacs. Malmqvist et al. (’68) de- bordering cells with a denser cytoplasm,
scribe only one cell type, containing gran- which “shared many ultrastructural charules 200 mp in size. Youshak et d. (’71) acteristics with stellate cells in the parobserve two cell types in osmic acid fixed enchymatous portion of the gland.” In our
tissues: granular cells with granules mea- animals the density of the bordering cells
suring 150-300 mp and fibroblast-like varies somewhat, but in all other respects
cells, which they call stellate cells. In tis- they are identical and bear no resemblance
sues fixed with glutaraldehyde and osmic to the fibroblast-like cells. They are similar
acid some of the granular cells have a to those found in ultimobranchial vesicles
CHICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
445
of other species such as the rat (Calvert tainly does not evoke some kind of useand Isler, '70). Thus, the structural make less vestigial tissue carried over from
up of the vesicles is variable but remains embryonic life. The fact that newly-formed
essentially simple. In most cases its wall vesicles keep appearing after birth, as well
consists of one single layer of squnmous to as their increasing rather than decreasing
cuboidal bordering cells. Occasionally it number and volume with age, seems to
may possibly contain more than one layer indicate an increased dependence of the
of these cells. This point has not been adult on these structures. The contents of
ascertained by us or by others, but prob- the vesicles may be considered as a holoably not all multilayered appearances can crine secretion, since whole cells may be
be explained by oblique or tangential sec- observed in the lumen. In the adult bird
tions of the wall. In addition to the border- the lumen is often packed with acidophilic,
ing cells, and underlying them, granular spherical globules, presumably denucleated
calcitonin-containing cells may be found cells; this situation is better observed in
within the basement membrane of the non-deparaffinized sections, as much of
vesicles, away from the lumen. They are the lumen contents are lost during further
sparsely distributed in most cases, and processing. The intense pinocytotic activtheir secretory activity appears to be ity at the base of the bordering cells, as
directed toward the basement membrane. well as the abundant microvesicles at the
Whether or not the stellate-like bordering apex and throughout their cytoplasm, sugcells of Youshak et al. ('71) are to be con- gest an intense traffic between extra- and
sidered as a separate and third cell type intra-vesicular spaces. This seems to indirequires further study, in our opinion.
cate that the vesicles release a secretion of
The calcitonin granules are released their own.
from the calcitocytes in response to a rise
LITERATURE CITED
in concentration of circulating calcium
(Robertson, '68; Chan et al., '69). Trans- Calvert, R. 1969 Etude au microscope klectronique des cellules claires de la glande
plantation experiments on the frog
thymide. Thesis, University of Montreal,
(Robertson, '68) indicate that innervation
Montreal, Canada.
is not a requirement for this response; Cdvert, R., and H. Isla 1970 Fine struoture
rather, they suggest an inhibitory role of
of a third epithelial component of the t h p i d
gland of the rat. Anat. Rec., 168: 2 3 4 2 .
the nerve fibers on the mechanism triggerChan, A. S. 1971 Fine stmature of the ultimoing the release of the granules.
h m c h i a l gland in bhe chick. Proc. E ~ ~ J I O X I
Like most endocrine glands, the ultimoMicrosc. Soc. of America, 29: 510-511.
branchial gland is richly vascularized. Chan, A. S., J. D. Cipera and L. F. Wlmger
1969 The ultimobnanchial g l a d of the chick
Figure 3 shows numerous capillaries
and its response to a high calcium diet. Rev.
among the cell cords. A similar observaCan. Biol., 28: 19-31.
tion was made by Stoeckel et al., '69.
Coons, A. H. 1958 Fluorescent antibody m&hCysts or vesicular duct-like structures
ods. In: Gemnal Cytochemid M&hods. J. F.
are a common feature of all ultimobranDanielli, ed. Vol. 1. Academic Press, New York,
pp. 3 9 9 4 2 2 .
chial glands (Watzka, '33), and except for
the calcitocytes which they may contain, Copp, D. H., D. W. Cockcroft arnd Y. Kueh 1967a
Cakitonin from ultimmbranchiai glands of dogtheir role is still thoroughly unknown.
fish and chickens. Science, 158: 924-925.
What appeared to be degenerative border1967b Ultimobnanchial migin of oalciing cells were occasionally found, but no
tcmin. Hypooalwmic efiect of extraats from
chicken glamds. C m . J. Physiol. Pbaraacol.,
degenerative vesicles were present. No
45: 1095-1099.
interruption in the epithelium was ever
U., J. Kracht, H. Kruse and
observed, even when i t was only a fraction Hacheisttx,
M. Lede 1967 Localisation von C-Zelkn im
of 1 p thick. The structure of the borderdtimobranchidkijrpex des Haushuhm. Natuzing cells, with microvilli, prominent
wisseruschaften, 54: 619.
Golgi's and fairly well developed ergasto- Kracht, J., U. Hachmeister, H.-J. Bcreustedt,
J. Biinicke and M. Lenke 1968 Histopathoplasmic sacs indicates a well differentiated
logical investigation a C cellis. In: Oalcitonin.
and functionally active cell. Thus, the
Proc. sympos. on thyrocdcibnin and the C
morphology of many of the vesicles cercells, 1967. Springer-Verlag. pp. 143-151.
446
H. ISLER
Malmqvist, E., L. E. Ericson, S. Almqvist and
R. Ekholm 1968 Granulated cells, uptake of
mine precursors, and calcium lowering mtivity in the ultimobranchid body of the domestic fowl. J. Ultnastruct. Res., 23: 457461.
Robert-,
D.R. 1968 The ultimobranchial body
in Rana pipias. VrI. Cellular responses in
denervatied glands in autoplastic transplants. Z.
zewmxh., 90: 273-288.
Stoeckel, M. E., and A. Porte 1967 Sur l'ultrastructure des c o r p s ultiunobmmchiaux du poussin. C. R. Aoad. Sc. (Paris), S r i e D, 265:
2051-2053.
1969 Etude ultrastructmale des c o r p s
ulthobranchiaux du poubt. I. Aspeot normal
et &veloppememt embryomaire. 2. Zellforsch.,
94: 495-512.
Tashjian, A. H. Jr., P. H. Bell and L. Leyine
1970 1mmunochemish-y of thyracakitmhs:
Species differences and studies of the r e w o n ship betwxm structure and irmn~n010gbdactivity. In: Calcitonin 1969. Proc. second internat. sympos. Springer-Verlag, pp. 359-375.
Tantber, S. D. 1967 The ultimobranchial origin
of thyrwalcitonin. P m . Namtl. h a d . Sci., 58:
1684-1687.
Watzka. M.
1933 Vergleichede Untersuchungen uber den ultimobranchialen Korpw.
Ztsuhft. f. mikr. mat. Forsch., 34: 485-533.
Youshak, M. S., and C. C. Capen 1971 Ultrastructural evaluation of ultimobranchtal glands
from normal and os6eopetrotic chickens. Gen.
and Comp. Endomin., 16: 430-442.
PLATES
Abbreviations
av, wical vesicle
B, lumen-bordering cell
bm, basement membnane
C, cellcord
oa, ciapillazy
ch, nuclear chmm~atin
co, collagen
ct, connective tissue
cy, basal cytoplasmic process
er, exgmbopiasm
F, fibroblast
f, filament
m, fihrobhst-like d l
G, granular cell
g,
aPPmatw
gr, granule
L, lumen
m, liateral membrane
mi, mirochomkion
mv, microvillus
N, m e f i b e r
nb, nuclear body
nv, nuclem vesicle
P, parathymid gland
p, nucleaz pore
pv, pinocybtic
R, c d r e m n m t s
s, Schwaam Cell
m, s m t h m e m h a m
U, ultimobranchid body
V, dtimobzanchiail vesicle
ve, intracytophsmic vesicle
PLATE 1
EXPLANATION OF FIGURES
1 Paraffin section of a 76-day-old male chick ultimobranchid body
( U ) attached bo parathyroidal tissue (P). The gland consists of a
mass of cell cords ( C ) oontaininig vasicles ( V ) of various size a d
shape, which me either isolated in the mass (Vl) or grouped in a
lace-lilce lmangement (V,). Nobe the pamtd pamtkionbg of some of
the vesicles and the variable and inhomogeneous content of their
lu-a.
Hematoxylin and eosin s t a g . x 50.
2
Paraffin seetion of a 76-day-oLd a& chick uihobramhial body,
showing four vesicles ( V ) among cell cords (C). Note the variruhon
in the height of the vesicular epithelium and fhe cell protruding
(probably being extruded) into the lumen of the uppr night vesicle.
Very libde connective tissue is present around vesicles and beibwen
ell conds in the young birds. Nobe the bundle of nerve fibers ( N ) .
Hemaboxylin and eosin staining. x 500.
3
Epon section 'of a 32-day-old &male chick ultimobranchid body,
showing a small vesicle (upper V ) Ibed with cuboidail cells, and
part of a large vesicle (lower V ) lined with cells of vaious heights
m d oonta-g
cell remnants in its lumen. The rest of the tissue
consisbs essentially of cell oords ( C ) and oappillaries (ca) with libtle
connective tissue elements. Note the large number of nucleoli in
the oord cells as companzd to the l u m m i h r d e r h g cells of the vesicles. Tohidineblue staining. x 500.
4
Same gland as in figure 3, showing three tiny vesicles ( V ) , two of
which, presumably newly-formed (upper left), appear in the midst
of a cell cord and contain nuclei with blm smooth OUand c m spicaous nuchmli chanacteristuc of a cord's cell. In oontrast, the well
differentiated vesicle in the lower right oorner shows the paucinuclwlabed and indented nuclei chairactexistac of lumen-bordering d l s .
Hmahoxylin-stained epon seotion. x 500.
5
Paraffin setion of a 28-month-old chick. The connective tissue (ct)
is much more abundant, both uound the vesicles ( V ) and be-m
the cell cords (upper Left o m e r ) . than in young birds (fig. 2 ) . Note
the lasge a?llKI1LIutof cell mmmants in the lumen of the lower vesicle.
HemetoxyLin and -sin staining. x 300.
&7
448
Immunofluorescmt staining of odcibonh-containhg cells in a 28month-old chick, using anticalcitonin antiserum. Numerous flusorescent cdcibocytes (arrows) m e present in the ell cords (fig. 7) and
only a few in the walls of vesicles (fig. 6). Sane of these a m very
close tm,but do not border on the lumen. The lumen-bord-g
cells
(B) and the cell remnants ( R ) in the vesicular lumina often show
a moderabe white, unspeifw fluorescence. x 300.
CHICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
H. Tsler
PLATE 1
449
PLATE 2
EXPLANATION O F FIGURES
8-1 1
450
Lumen-bordering cells of chick ultimobranchid vesicles. The nuclei of these cells have indentations, little chromatin attached to
the nuclear membrane and a n ocoasbnal oval, finely granulated
body (nb, fig. 10). The apical membrane shows mkrovilli (mv) of
various sizes and shapes jutting into the lumen (L, fig. 8 ) . The
lateral membranes ( m ) , when i n contact with a neighbour bordering cell, follow a sinuous path (figs. 8, 9, 10). The plasma membrane at the base is coated with a basemient membrane (bm, fig. 11)
and occasiondly shows intenisle pinmytotic activity (pv, fig. 11).
The cells contain long, flat ergastoplasmic sacs (er, figs. 8, l o ) ,
a well-developed Golgi apparatus with lamellae and microvesicles
(g, fig. lo), a n elaborate system of s m t h membcane tubules occasionally converging mto a complex sac-like structure (sm, figs.
8, 9), long sinuous mitochondria ( m i ) and apical vesicles (av,
figs. 8, 9 ) . Figures 8 and 10: x 4,500; figures 9 aad 11: x 30,000.
CHICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
PLATE 2
H. Isler
45 1
PLATE 3
EXPLANATION OF FIGURE
12 Lumen-bordiering celBs of a n ultimobramhial vesicle. Note the nuclear
pores ( p ) , the sinuous lateral membranes (m), the long, flat ergastoplasmic sacs (err), the apical microvesicles (av), the filaments ( f ) ,
the density of the mitochondria1 matrix (mi), the abundance of free
ribosomes and the basement membrane (bin). x 20,000.
452
CHICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
H. Isler
PLATE 3
453
PLATE 4
EXPLANATION O F FIGURES
13 Partition protruding into the lumen of a n ultimobranchid vesicle
and partially separating it into two compartnients, the lower onie containing a denser material than the upper one. The partition is made
of a oore of oollagen f i b d s (00) and fibroblastic cytoplasm ( F ) ,
coveaed with a thin layer of cytoplasm of bordering cells ( B ) which
show the characberisltic microvilli ( m v ) , and nuclear indentation
(IoweT right). x 3,500.
14 Wall of a n ultimobranchial vesicle containing both bordering (B)
and granular ( G ) cells. Note ( m ) the smooth outline of the granular
cells as compared to the sinuous path followed by the membrane of
two neighbour bordering cells. The granular cells show granules ( g r )
of various sizes and densities, long, flat ergastoplasmic sacs (er), a n
array of smooth membrane tubules and microvesicles (ve) and free
ribosomefs. Their base is often ooated with a fine stnanid of cytoplasm
(cy) which is itself oovered with a basement membnane (bm). Most
of the granules in the cell on the right are of the small variety,
while the cell on the lower left contains both small and large granules. L, vesicular lumen; g , Golgi; mi, mitochondrion. x 6,500.
454
CHICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
H. Isler
PLATE 4
455
PLATE 5
EXPLANATION OF FIGURES
15 Wall of a n ultimobranchial vesicle containing a granular cell ( G )
filled with large granules ( g r ) whose membranes are disrupted. This
cell lies between two bordering cells ( B ) displaying intense pinocytotic activity ( p v ) . The cell in contact with the lumen ( L ) of the
vesicle is vacuolated and in the process of being shed into the lumen.
bm, basement membrane. x 29,000.
16
456
Fibroblast-like cell (FL) extending cytoplasmic processes (cy ) around
a granular cell ( G ) i n a n ultimobranchial cell cord. Note its large,
dilated ergastoplasmic sac ( e r ) and its basement membrane ( b m ) .
X 14,000.
CHICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
H. Isler
PLATE 5
457
PLATE 6
EXPLANATION OF FIGURES
17 Part of a cell cord in a n ulthobranchiatl body. The cords consist
essentially of g r m u h r cells (G), and a few fibroblast-like cells (FL)
very h h e q u e n t l y observed. These granular oells ane similar to the
gmanulax cells of the vesicles; nate the nucleoli, the small, dense
granules (gr), the Golgi appazatus (g), the scant chromatin on the
nuclear membrane, and the cytoplasmic processes (cy) at the sides
facing the connective tissue. These processes partly belong (lower
which is characlberized
right corner) bo the fibroblast-like cell (n)
by the diis'tribution, of its chromatin along tlie nuclear membrane
(ch), and by the presence of dilated ergastoplasmic sacs (er). But
unlike true fibroblasts (F), this cell is coated with a basement membrane (bm). x 6,000.
18 Granular cell ( G ) of a cell cord, with large granules (gr), in contact
with a Schwann cell ( S ) and with some af its nerve fibers (N).
ct, connective tissue. x 14,000.
19 Two granular cells of a cell cord with intranuclear, membraneboundeid vesicles (nv). ct, connective tissue. x 16,000.
458
CHICK ULTIMOBRANCHIAL BODY FINE STRUCTURE
H. Isler
PLATE 6
459
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