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Foetal haemopoiesis during the hepatic period. I. Relation between in vitro liver organogenesis and erythropoietic function

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THE ANATOMICAL RECORD 200:221-230 (1981)
Foetal Haemopoiesis During the Hepatic Period. 1. Relation
Between In Vitro Liver Organogenesis and Erythropoietic
Function
ANALIA C. NESSI, CARLOS E. BOZZINI, AND MORRIS V. TIDBALL
Instituto Argentino de Biologia Teorica, Calk 32 no 1824,La Plata (A.C.N.,
M.V.T.), and Catedra de Fisiologia, Facultad de Odontologia, M.T. de Aluear
2142, Buenos Aires, Argentina (C.E.B.)
ABSTRACT
Cultures of the hepatic bud, under different experimental conditions, show a direct relation between foetal age at the time of dissection and the
further organogenesis of the explant. In cultures of the septum transversum plus
hepatic bud-with or without splanchnic mesenchyme-obtained from embryos of
four to 25 somites, the capacity of endodermic cells to differentiate into hepatocytes
appears only in a small number of samples; whereas, in the hepatic bud from older
embryos (26 to 40 somites), this differentiation occurs in all cases.
The amount of time cultures were allowed to grow was important for hepatic
organogenesis, as measured by cord-like organization of hepatocytes plus their
storage capacity for glycogen. The possibility of the explants showing complete
haemopoiesis was also a condition offoetal age a t the time of explant. Haemopoiesis
was not found in cultures from embryos of less than 25 somites. On the other hand,
development of haemopoiesis did not show a direct relation to days of culture, since
the peak of this activity was observed towards the third day in vitro. Most explants
showed a generalized haemopoiesis (both interstitial and vascular) with a decay
towards the sixth day.
Endodermal cells of the hepatic bud were capable of both proliferation and
differentiation into hepatocytes, even i n those mesenchymes considered inadequate such as limb mesenchyme. In the latter case we were unable to find
haemopoiesis at any time. The septum transversum, when cultured alone, did not
contain haemopoietic cells.
Hepatic organogenesis (as a system which
depends on endomesodermal interaction for its
development) is not a typical example of highly
specific mesenchyme, induction-dependent tissue, as compared to the salivary (Lawson, '70,
'72) or pulmonary systems (Alescio and Cassini, '62; Wessells, '70; Spooner and Wessells,
'70).
Le Douarin ('64a,b, '69) considers two classes
of mesenchyme for the chick embryo hepatic
organogenesis: Those favorable (ventral in
general and septum transversum in particular)
and those unfavorable (somitic, cephalic, and
limb) for hepatic growth and differentiation.
The true origin of hepatic haemopoiesis function (HF) is probably one of the most controversial problems in modern haematology. In effect,
there is no agreement on whether this function
depends on elements formed in situ or whether
the endomesodermic component serves as a n
0003-276X/81/2002-0221$03.00 0 1981 ALAN R. LISS, INC.
adequate bed for the colonization of migrating
elements.
The purpose of this work was to study the
intrinsic haemopoietic capacity of hepatic bud
and mesenchyme, as well as the capacity of
these tissue to induce liver organogenesis
under different experimental conditions.
MATERIALS AND METHODS
Animals
CF, mouse embryos were used. In calculating
the foetal age, the morning after overnight
mating (on which the vaginal plug was observed) was considered as day 0. Pregnant
females were sacrificed by decapitation between days 9 and 10 after mating, and the
Received April 23, 1979 accepted July 31, 1980.
Carlos E. Bozzini is Career Investigator for Consejo Nacional de
Investigaciones Cientificas y Tecnicas de la Republica Argentina.
Address reprint requests to Dr. Analia C. Nessi, Instituto Argentino
de Biologia Teorica, Calle 32 no 1824, La Plata (1900),Argentina.
222
A N A L ~ Ac. NESSI, CARLOS E. BOZZINI, AND MORRIS
gravid uterus removed in sterile conditions.
Embryos were washed in balanced saline and
dissected under a binocular microscope in the
following way: A first incision was made between the caudal boundary of the cardiac prominence and the cephalic limit of the anterior
limb, and a second between the umbilical cord
and the caudal limit of the same limb bud (Fig.
1). Figure 2 shows the planes of section for
obtaining the septum transversum with the
hepatic bud plus coelomic mesoderm and ventral ectoderm. From the portions thus obtained,
those for the first group of study were prepared
by removal of the ventral mesoderm. The ones
for the second group were obtained in the same
way, plus a removal of the coelomic mesoderm
as shown in Figure 3.
Specimens for the third group were first prepared as for the second group, but a further
separation was made of their central portions,
which contains the hepatic bud. The epithelial
bud cannot be separated from the septum
transversum solely by mechanical methods.
For its isolation, this central part was incubated for five minutes a t 37" C in a 0.25% solution of Trypsin (Whorthington Cristalline
Trypsin) and 1%Pancreatin (Difco) in Tyrode
solution. Further separation of the endoderm
from its surrounding mesenchyme then proceeded using tungsten needles.
In embryos with more than 28 somites it is
impossible to separate all of the hepatic bud, as
a result of its peculiar organogenesis. The
hepatic primordium proliferates not by terminal buds as other endoderm-derived organs, but
by cellular migration towards the surrounding
mesenchyme. Therefore, some of these cells are
inevitably lost during digestion.
The culture techniques were done as described by Lawson ('70).
Histochemical methods
Explants were fixed a t days 0, 3, and 6 of
culture, in Carnoy solution, at 0°C for 45 min-
v. TIDBALL
utes. Embedding was done in Paraplast (Sherwood Med. Ind. Inc.). Serial sections were
mounted in three alternate groups, thus permitting different staining techniques of
analogous zones. The first group was incubated
in 0.0% amylase solution in phosphate buffer
at pH 6.8 for 30 minutes. Following that they
were stained with periodic acid, Schiff (PAS)
and Mayer Haemalum. The second group was
identically prepared except for the absence of
the enzymatic treatment. In order to test not
only proliferation, but also red blood cell differentiation, the third group was stained with
benzidine, following Pearse technique ('72),
Mayer Haemalum, and Giemsa.
EXPERIMENTAL DESIGN AND
STATISTICAL ANALYSIS
The material studied consisted of six experimental groups, divided in the following way:
Group 1: Septum transversum with hepatic
bud plus coelomic mesoderm in embryos of four
to 40 somites. In embryos of less than 15 somites, as the hepatic bud is still not formed, the
most-caudal portion of the foregut was dissected, i.e., the hepatic bud presumptive area.
Group 2: Septum transversum plus hepatic
bud from 16 to 35 somite embryos.
Group 3: Hepatic bud from embryos of 21 t o
35 somites.
Group 4: Coelomic mesoderm from 24 to 30
somite embryos.
Group 5 : Limb mesenchyme from embryos of
21 to 35 somites. This material was obtained by
removing a complete limb rudiment by a plane
of section perpendicular to the limb axis. The
ectoderm of this rudiment was then removed.
Group 6: Hepatic bud-plus-limb mesenchyme
from embryos of the same age as for group 5.
The intrinsic capability for proliferation and
differentiation of each explant and their capacity t o support development of the HF were
analysed. For this, foetal age a t dissection and
length of the in vitro period were considered.
Fig. 1. First dissection planes (-----I in a mouse embryo, after removing the whole foetal anexes. al,
Anterior limb; h, heart; mp, mandibular processes; uc, umbilical cord.
Fig. 2. A threedimensional representation of the cuneiform section from Figure 1, showing the
septum transversum (st),hepatic bud (hb),anterior limb rudiments (alr), neural tube (nt),somites ( s ) ,
and the second dissection planes.
Fig. 3. Twenty-eightrsomite stage embryo. h, heart; lm, caudal limb rudiment; mp, mandibular
process; nt, neural tube; st, septum transversum; -----,dissection planes. PAS-Haemalum staining;
magnification, x 60.
Fig. 4. Septum transversum plus hepatic bud from a 27-somite stage embryo. Large arrow-empty
wide-lumen blood vessel; small arrows-narrow-lumen sinusoids containing immature blood cells (see
discussion). The darkest area beside the hepatic bud corresponds to epithelial migrating cells from this
rudiment. PAS-Haemalum staining; magnification, x 125.
FOETAL HAEMOPOIESIS DURING THE HEPATIC PERIOD
223
224
ANALfA C. NESSI. CARLOS E. BOZZINI. AND MORRIS V. TIDBALL
of hepatocytes plus important storage of glycogen (LO-4)(Fig. 7) appears most prominently in
explants from the older embryos after six days
of culture (Table 1).
Development of pancreatic-like acini was
also found among the explants of group 1, with
a higher frequency in the younger subgroup
(43.3 ? 11.2%, compared to 8.1 ? 1.9%in the
older).
Optimal HF (HF-4) was directly related to
embryo age at the time of dissection and not to
the time explants were allowed to grow in vitro
(Figs. 9 and 11).Indeed, H F involutes to a local
and intravascular haemopoiesis (HF-2) by the
sixth day of culture. Blood cells were rarely
found in explants from embryos younger than
25 somites (Table 21, and only one case of this
age, amongst 210 explants, developed HF. This
corresponds to a frequency of 0.48% when, on
the other hand, 100.0% of explants with 26 somites or older show one of the three active
haemopoietic stages (Tables 2 and 4).
No significant difference, both from the point
of view of haemopoietic capacity or from that of
organogenesis, was observed between groups 1
and 2, as shown in Tables 1 and 3.
The third experimental group (isolated hepatic bud) was incapable of proliferation and
differentiation. Both in three and six days of
culture (in 18and 16explants, respectively) the
material was expanded in the clot and was not
viable.
The fourth experimental group (lateral
mesoderm) showed proliferation of connective
tissue cells; in nearly all of these explants a cell
loss occurred from the periphery, resulting in a
smaller size of explants a t the end of the experiment than at their plating. No blood cells were
observed at either three or six days of culture.
Limb mesenchyme explanted alone (group 5 )
or associated with hepatic bud (group6) showed
Liver organogenesis was evaluated according
to the following scale: LO-1-complete absence
of hepatic tissue; LO-2-endodermic proliferation without discernible differentation; LO3-hepatocytic differentiation, evaluated by
the presence of glycogen synthesis and storage
with the PAS-amylase histochemical method;
and LO-4-cord-like organization of hepatocytes plus important storage of glycogen.
Development of HF was evaluated according
to t h e following scale: HF-1-Absence of
haemopoiesis; HF-2-local, intravascular
haemopoiesis; HF-3-local, interstitial and intravascular haemopoiesis; and H F - P w i d e spread haemopoiesis.
Statistical analysis was based on the x2test of
the categoric variables' independence (Haber
and Runyon, '73).
RESULTS
The hepatic bud first appears at the mouse
embryo developmental stage of 15 to 17 somites. Although explants reach a chronologically equivalent age of 13 and 16 days of normal
in vivo development, both degree of differentiation and growth are retarded in vitro when
compared with normal gestation.
Experimental group 1 (septum transversum
with heptaic bud plus coelomic mesoderm)
shows development of hepatic tissue in 60.0%of
embryos with age up to 25 somites, and 83.8%
in older embryos, at the third day of culture
(Table 1).Differentiation was more extensive
in the older groups (at the time of culture) of
explants (Figs. 5 through 7, Table 1). Conversely, in the group of younger explants the
percentage of those which do not show any
hepatocyte differentiation ascends to 36.7% at
three days of culture, and to 12.5% a t six days.
Absence of hepatic tissue was not observed in
older groups (Table 1).Cord-like organization
-
Fig. 5. Same explant a s in Figure 7, treated with amylase prior to the PAS-Haemalum staining;
magnification, x 500.
Fig. 6. Septum transversum plus hepatic bud, plus somatopleuric and splachnopleuric mesoderm,
from a 33-somite embryo, cultured for three days. The persistence of the coelom (c) divides the picture
into two zones: The lower part shows good liver organogenesis and optimal development of
haemopoiesis, whereas in the upper region, only a good development of epithelial cells is seen.
Bemidine-Haemalum and Giemsa staining; magnification, X 125.
Fig. 7. Septum transversum plus heaptic bud from a 30-somite stage embryo, after six days of
culture. No interstitial haemopoiesis is seen. Liver organogenesisbelongs to the fourth stage, showing
a cord-like organization of hepatocytes and important glycogen storage. PAS-Haemalum staining;
magnification, x 500.
Fig. 8. Septum transversum plus hepatic bud from a 26-somite stage embryo (six days of culture). A
big capillary lumen (cl) with numerous erythroid cells in different maturating stages, is seen. The
haemopoietic zone is only seen in close relationship to that blood vessel, showing the specific local
nature of this process, hinucleate cells (arrows). Benzidine-Haemalum and Giemsa staining; magnification, X 500.
FOETAL HAEMOPOIESIS DURING THE HEPATIC PERIOD
225
226
ANALfA C. NESSI, CARLOS E . BOZZINI. AND MORRIS V. TIDBALL
aggregate around or to form a lumen, as observed in normal development. But in day 6
cultures, in cells that show this second behavior, glycogen storage is not comparable in magnitude to the high PAS positivity of cells having
a cord-like arrangement. However, in some day
6 cultures, binucleate cells were frequently observed (Fig. 8, arrows).
The hepatic bud incapacity to proliferate and
differentiate in isolated cultures coincides with
the findings reported by Le Douarin ('64a,b,
'69). Other isolated epithelial buds, such as the
primordium of salivary glands, show similar
DISCUSSION
behavior (Lawson, '72). Nevertheless, our findGlycogen incorporation by embryo hepato- ing t h a t the hepatic bud has the capacity to
cytes is not of great importance until days 17 differentiate-even in a minor way-when in
and 18 of in vivo development (Peters et al., association with a mesenchyme considered un'63). As stated by these authors, day 18 corre- favorable, differs from t h e findings of Le
sponds to the peak of glycogen synthesis, with Douarin. The difference in experimental modvalues even higher than in normal adult cells. els could be responsible for these differences in
In the present study, day 6 explants attained a results.
Some authors (Thomas and Yoffey, '62; Yofchronologically equivalent age of 15 and 16
days of normal intrauterine development, and fey, '71) accept a n endodermal origin of
it is precisely in these explants where the opti- haemopoietic cells in the foetal liver. Neverthemal liver organogenesis (LO-4) was observed. less, the incapacity of hepatic bud-cultured
In monolayer cultures, a s there is a loss in the alone, recombined with its own mesenchyme,
original structure of the specimen, the presence or associated with limb mesenchyme-to deof glycogen is not useful for identification of velop H F shows the failure of the endodermic
hepatocytes from other endoderm-derived tis- layer for the development of haemopoiesis by
sues. Nevertheless, the presence of glycogen itself. The findings of Houssaint ('70, '72) upon
conserves its value as an hepatocyte marker in recombining mouse embryo hepatic bud with
organotypic cultures. Also, in the latter cul- lung mesenchyme obtained from chick embryos
tures, other judgement factors exist in deter- coincide with ours. On the other hand, upon
mining the degree of development; i.e., conser- associating the septum transversum with the
vation of the general architecture, especially in hepatic bud of young embryos, or utilizing the
the few days of culture. In this way, in hepatic lateral mesoderm of the same embryos, HF detissue showing good in vitro organogenesis velopment was not attained on day 3 or 6 of
with observable cord-like development, culture, even with growth and differentiation
hepatocytes will be highly PAS-positive, of the explants (Tables 2 and 4, Fig. 10). On
whereas other epithelial cells derived from the these bases, a n interesting point of discussion is
hepatic bud, i.e., pancreatic acini, epithelium of posed by t h e presence of haemopoiesis i n
bile ductules, etc., will show a tendency to explants of a given age, as opposed to the total
a good proliferation of cartilaginous tissue and
general connective tissue elements. The hepatic bud not only proliferates in these conditions, but also shows differentiation (Table 5 ,
Fig. 12). It does not reach a n optimal organogenesis, however, even in six days of culture, but some ofthe hepatocytes store glycogen
(LO-3). Original embryonic age is not critical
for the further organogenesis of the explant
(Table 5 ) but, as in groups 3 and 4, no H F was
observed. Forty-five percent of grafted
explants developed pancreatic-like acini.
Fig. 9. Detail of Figure 6; compare this picture with Figure 11, and the lower region of Figure 8.
Benzidine-Haemalum and Giemsa staining; magnification, x 500.
Fig. 10. Septum transversum with the hepatic bud plus coelomic mesoderm from a 19-somite stage
embryo ( 3 days of culture). A rather good liver organogenesis exists. Nevertheless, no erythroid cells
are seen. c, coelom; um, undifferentiated mesenchyme. Amylase-treated section, prior to the PASHaemalum staining; magnification, X 125.
Fig. 11. Septum transversum with the hepatic bud plus coelomic mesoderm from a 33-somite stage
embryo, (six days of culture) showing a good liver organogenesis and a decay in the haemopoietic
function. Benzidine, Haemalum, and Giemsa staining; magnification, x 500.
Fig. 12. Limb mesenchyme plus hepatic bud from a 29-somite embryo, after six days of culture. In
the central area, a round epithelial formation (ep)is seen, showing their cells of cord-like organization.
In some of them a thin granulation of PAS-positive material, which disappears with the amylase
digestion, is seen. Haemopoiesis does not develop under these experimental conditions. pc, protochondral tissue; um, undifferentiated mesenchyme. PAS-Haemalum staining; magnification, x 500.
ANALIA C. NESSI, CARLOS E. BOZZINI, AND MORRIS V. TIDBALL
228
TABLE 1. Liver organogenesis in ST
+ HB + CM explants plated in block (group lJ.*
No.
of
cultures
Days
of
culture
No.
of
somites
30
3
71-25
Stages (%)
LO,
?
24
71-25
6
36.7
2.4
3
60.0
5.5
2
3.3
0.3
25.0
2.6
?
45.8
4.7
83.8
6.8
*
16.2
1.3
2
23.5
2.0
f
12.5
t 1.3
37
?
0
26-40
?
6
34
26-40
LO,
LO,
2.9
0
t 0.2
____
~~~
~
LO4
0
18.7
t 1.7
0
67.5
t 5.7
~
*Stages are gwen as the average percent of a t least four experiments (t95% confidence)
LO = liver organogenesis, ST = septum transversum, HE = hepatic bud, CM = coelomic mesoderm
TABLE 2. Haemopoietic function development in ST
plated in block (group l).*
No.
+ HB + C M explants
No.
of
cultures
Days
of
culture
of
somites
30
3
71-25
100.0
24
6
71-25
-t
95.8
4.3
i
f
2.7
0.2
t
37
34
3
6
_
_
_
HFi
26-40
26-40
~
Stages
(%)
.
HF,
0
?
HF,
HF,
0
0
0
0
0
4.2
0.2
2.8
0.2
?
70.6
6.1
f
16.2
1.3
t 6.4
78.3
20.6
1.8
?
8.8
0.6
*Stages are given as the average percent of a t least four experiments (t 95% confidence).
HF = haemopoietic function; ST = septum transversum; HB = hepatic bud; CM = coelornic mesoderm.
TABLE 3 . Liver organogenesis in ST
No.
of
cultures
Days
of
culture
No.
of
somites
57
3
16-25
45
6
16-25
+ HB explants plated in block (group 2).*
36
3
6
26-35
26-35
.
LO,
LO,
LO,
LO,
0
43.0
f 2.8
57.0
? 3.8
?
20.0
2.5
t 2.5
2
27.0
2.0
?
15.0
0.9
t
85.0
5.6
t
27.0
2.0
63.9
2.8
*
14.0
1.1
f
13.0
i 0.9
27
Stages
- _____ -.
0
0
?
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ~
*Stages are mven as the average percent of a t least five experiments ( 2 95% confidence)
LO = liver organogeneis, ST = septum transversum, HB = hepatic bud
0
33.1
86.0
0.1
229
FOETAL HAEMOPOIESIS DURING THE HEPATIC PERIOD
+ H B explants
TA B L E 4 . Haemopoietic function deuelopment in S T
plated in block (group 21.*
No.
Days
of
culture
No.
of
cultures
Stages (%)
~~
of
somites
H FI
HF,
~
HF:,
HF,
~~
57
3
16-25
100.0
0
0
0
45
6
16-25
100.0
0
0
0
27
3
26-35
0
0
?
36
6
26-35
0
?
63.9
2.8
7.4
0.3
2
14.0
92.6
4.2
11.1
0.1
-c 1.1
f
*Stages are given as the average percent of a t least five experiments ( ? 95% confidence),
HF haemopoietic function: ST = septum transversum; HI3 = hepatic bud.
~
TABLE 5. Lruer organogenesrs rn HB explants grafted on limb mesenchyme (group 6).*
Stages (%I
No.
of
cultures
Days
of
culture
No.
of
somites
LO,
LO1
LO,
58
6
21-25
0
37.5
i
z 2.5
62.5
t 4.1
0
42
6
26-35
0
66.7
3.2
0
LO4
~~~
&
*Stages are given as the average percent of at least seven experiments
I,O = liver organogenesis; HB = hepatic bud.
(?
33.3
1.8
_f
95% confidence)
TABLE 6. Haemopoietic functron deuelopment in H B explants grafted on lrmb
mesenchyme (group 61."
~~
Stages (%)
No.
of
cultures
Days
of
culture
No.
of
somites
HFr
HFI
HF,
58
6
21-25
100.0
0
0
0
42
6
26-35
100.0
0
0
0
~
~
~
~
~
*Stages are given as the average percent of a t least seven experiments
HF = haemopoietic function; HB = hepatic bud.
incapacity for such function in specimens obtained from younger embryos. Johnson and
Jones ('73) obtained similar results, but these
authors suggested that 28 somites is the critical
stage for division between explants with or
without the capacity to develop haemopoiesis.
They suppose the embryonic layers to be too
immature before that period to bring about the
interactive phenomena that result in active
HF. It must be pointed out that the septum
(?
HF,
~
95% confidence).
transversum is traversed by t h e omphalomesenteric veins in periods prior to the
critical age for t h e development of haemopoiesis i n vitro. Why is i t then, if the
migrational theory is valid, that HF does not
develop earlier? We propose t h a t purely
mechanical factors may play a role in these
experiments. In effect, in embryos up to 24 somites of development, the omphalomesenteric
vein lumens are very wide in relation to the
230
ANALtA C. NESSI, CARLOS E. BOZZINI, AND MORRIS V. TIDBALL
septum size, and it is possible that on handling
during dissection and successive washings, circulating haemopoietic cells are separated from
the explants. Note the empty lumen of a wide
capillary in Figure 4 (large arrow). On the contrary, omphalomesenteric veins after giving
rise to thinner branches (Fig. 4,small arrows)
could facilitate the retention of haemopoietic
cells found amid the septum transversum, thus
making their loss during processing improbable.
Some explants, even those considered in the
best conditions of development for both HF and
organogenesis, show peripheral areas where
haemopoiesis is absent. Similar changes may be
observed in the marginal zones of the normally
in-vivo-developedhepatic lobes (Nessi and Bozzini, ’79). The presence of these areas (Fig. 6,
upper part) in an explant that shows some
zones very densely populated by blood cells and
some other zones free of these elements, opposes the idea of the embryonic layers being too
immature to interact, resulting in an active de
novo haemopoiesis. On the contrary, the
present findings favor the migrational theory.
REFERENCES
AIescio, T., and A. Cassini (1962) Induction in vitro of
tracheal buds by pulmonary mesenchyme grafted on
tracheal epithelium. J. Exp. Zool., 150:83-94.
Haber, A., and R.P. Runyon (1973) Estadistica General.
Bogota, Caracas, Mexico, etc. Fondo Educativo Interamericano, p. 266.
Houssaint, E., N. Le Douarin, and A. Weaver (1970) Mise en
evidence de glycogzne dans le foie de l’embryon de poulet
des le stade de 4 jours d’incubation. C.R. Acad. Sci. (Paris),
271: 1315-1318.
Houssaint, E. (1972) Etude des capacites de differentiation
de l’endoderme hepatique de l’embryon de Souris. C.R.
Acad. Sci. (Paris), 275t461-464.
Johnson, G.R., and R.O. Jones (1973) Differentiation of the
m a m m a l i a n hepatic primordium i n vitro. I. Morphogenesis and the onset of haemopoiesis. J. Embryol.
Exp. Morphol., 30t83-96.
Lawson, K.A. (1970) Morphogenesis and functional differentiation of the rat parotid gland in vivo and in vitro. J.
Embryol. Exp. Morphol., 24t411-424.
Lawson, K.A. (1972) The role of mesenchyme in the morphogenesis and functional differentiation of rat salivary
epithelium. J. Embryol. Exp. Morphol., 27t497-513.
Le Douarin, N. (1964a) Isolement experimental du mesenchyme propre du foie et r6le morphogene de la composante
mesodermique dans l’organogenese hepatique. J. Embryol. Exp. Morphol., 12.141-160.
Le Douarin, N. (1964b) Induction de l’endoderme prehepatique par le mesoderme de l’aire cardiaque chez
I’embryon de poulet. J. Embryol. Exp. Morphol., 12t651664.
Le Douarin, N. (1971)Les apports recents des cultures et des
greffes en biologie animale. Masson, Paris, p. 95.
Nessi, A.C., and C.E. Bozzini (1979) Foetal haernopoiesis
during the hepatic period. 11. Topographic histology. J.
Embryol. Exp. Morphol., 52t13-21.
Pearse, A.G.E. (1972) Histochemistry, 3rd Ed. Churchill
Livingstone, Edinburgh and London, p. 1387.
Peters, V., G. Kelly, and H. Dembitzer (1963) Cytologic
changes in fetal and neonatal hepatic cells of the mouse.
Ann. N.Y. Acad Sci., 111.87-103.
Thomas, D.B., and J.M. Yoffey (19621 Human foetal
haemopoiesis. I. The cellular composition of foetal blood.
Br. J. Haematol., 8.290-301.
Spooner, B.S., and N.K. Wessells (1970) Mammalian lung
development: Interactions in primordium formation and
bronchial morphogenesis. J. Exp. Zool., 175:445-454.
Wessells, N.K. (1970) Mammalian lung development: Interactions in formation and morphogenesis of tracheal
buds. J. Exp. Zool., 175.455-466.
Yoffey,J.M. (1971)The stem cell problem in the fetus. Isr. J.
Med. Sci., 7t825-833.
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relations, period, organogenesis, haemopoiesis, hepatica, live, foetal, function, erythropoietin, vitro
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