Table Of ContentTHE STUDY OP THE PRIMORDIAL GERM
CELLS IN EMBRYONIC CHICK BLOOD
A Thesis
Presented to
the Faculty of the Department of Zoology
The U niversity of Southern C alifornia
In P artial Fulfillm ent
of the Requirements for the Degree
Master of Science
by
John Beno
June 1951
UMI Number: EP67187
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This thesis, written by
John Beno
under the guidance of h ^ .. Faculty Committee,
and approved by all its members, has been
presented to and accepted by the Council on
Graduate Study and Research in partial fulfill
ment of the requirements for the degree of
Master of Science
Faculty Committee
Chairman
'J -~ n C k M /
TABLE OF CONTENTS
Introduction
Introduction..........................................................................1
H istorical Review .............................................................. 1
M aterial and Methods
M aterials ................................................................................ 9
M ethods...........................................................................................10
Observations. ...........................................................................................16
D iscussion................................................... 21
Summary................................................................................................... 25
L iterature c ite d .................................................................. 27
LIST OF PLATES
PLATES PAGE
Plate 1.............................................................................................. 29
P late 2 ..............................................................................................30
Plate 3 ..............................................................................................31
LIST OF TABLES
TABLES PASS
Table I ..................................................................................... 32
Table I I ...................................................................... 33
Introduction
Extensive studies on the prim ordial ge?mn cells have '
I
: been made on d ifferen t ch.-i.cfc strain s with conflicting re- i
l i
.su its. Since none of these studies have dealt w ith the
I i
i
technique of blood smears from embryonic chick blood, this~ '
j ' - I
iproc.edure was used to determine (1) at exactly what hours ofj
! i
incubation the prim ordial germ ce lls are found at a maximum
In the blood, (2) to observe and record the rela tiv e sizes
1
i l
|of the prim ordial germ ce lls in .the two thoroughbred |
; _ I
jvarieties used in the experiment, (3) to observe any signs j
i
of a possible division of these cells while they are d is tr i-1
buted in the blood,. (4) to observe and record any signs of
possible degeneration of these c e lls, (5) to observe the :
l
structure of the m itochondria, a ttra c tio n sphere and i
f |
nucleus, (6) to study the possible m igration of intravenous!^
In jected and v ita lly stained prim ordial germ cells in. young j
jpullets and cockerels. ;
i i
: H isto rical Review
Perhaps the most extensive .work.done on the study
;Of the prim ordial germ cells in the chick was by Swift
■(1.914) who described these cells.. In structure they are ;
i
i
Immense, in. comparison w ith neighboring, c e lls . Their shape
I
jis always round or oval w ith an average diam eter of 14 to
IB m icra. The nucleus is large, vesicular, spherical, and
usually eccen trically placed* It is surrounded by a d efi- j
> ■ i
1 n ite nuclear membrane while the chromatin w ithin the nucleus
-v i
, is eith er in granular or thread form* D efinite arrangement j
i,
.
'of chromatin appears only a fte r fixation* . The a ttra c tio n
sphere is most ch aracteristic of the"prim ordial germ c e lls, ;
being present in a ll stages from the origin of the germ c e ll
| to its entrance into the in d ifferen t gonads.* A ttraction j
i spheres serve as the best c rite rio n for the id e n tifica tio n *
; of these ce lls in the chick* Yolk spheres appear Just j
'a f te r the origin of the young germ c e lls. Swift found th at I
• II
embryos of 20-26 somites contained the greatest number of j
' yolk spheres. The mitochondria retained th e ir character- |
is tio rod-shape in a ll the embryos examined in the primitive!
I
i streak stage and the 4-1/2 day embryo. They measured from j
i . [
: 1 to 3 mi era in length and"-were not homogeneous in structuie:
j The m ajority of the prim ordial germ cells measured from 14
, to 16 micra and a few as much as 22 miera. The a ttra c tio n
! spherermeasured from 3 to' 4 micra in diam eter. The p ri- |
mondial germ ce lls in the chick arise an terio rly and j
'a n te ro la te ra lly in the embryo in a specialized region of the
; endoderm w all ju st at the margin of the area pellucida.
i
These germ c e lls are at f ir s t in the space between the endo-
i ' j
1 derm and ectoderm due to the la te appearance of the mesoderm
i
■ " * 1
in th is region. L ater, due to th e ir amoeboid powers, they
enter the mesoderm. Swift fu rth er found th at they are at j
ifirs t carried by th e ir own movement and la te r by the blood ;
to a ll p arts of the embryo and vascular area where they re
main, generally d istrib u ted u n til the 20 somite stage. In
embryos of 20 to 22 som ites, the prim ordial germ ce lls
become more numerous in the splanchnic mesoderm. At th is
(period the majority^ are found in the vessels but a few are
found in the tissu e s. In embryos of 23 to 25 som ites, the
<m ajority of the prim ordial germ ce lls are found in the
i
i splanchnic mesoderm, w ith a few s t i l l present in the blood
vessels. In embryos of 26 to 29 som ites, the prim ordial
: germ ce lls are in the radix m esenteries and coelomic epi-
i
thelium . They remain in. th is position u n til.th e formation
! of the gonads begins., when they gradually pass into the
i gonadal region. The relativ e number and location of the
p rim o rd ial germ ce lls are as follow s:
6,9 somite stage.............most of the germ
ce lls are isolated
in groups of two or
three and lie in the
space between the
endoderm and meso
derm.
10,12,16,19 som ites.. . .there is one germ
c e ll in the heart
region of the 12
somite embryo. I
21 somite sta g e ...............has seventy-three j
i prim ordial germ cells
; 'v in a ll in. which
six ty are contained in ;
the vessels throughout ;
the embryo and vascular
area while th irte e n are'
'Outside of the blood
vessels. Of these j
six ty , th irty are in
the vessels of the j
splanchnic mesodermo f ,
the head region. j
25 somite stage .is the tra n sitio n stage
in embryos. The germ j
' ce lls are present in
the blood and in the (
splanchnic mesoderm
near the coelpmic j
angle• ;
26 to 29 som ites one hundred and ten ;
prim ordial germ cells j
were counted w ith
ninety-eight in the ;
region of the splanch-j
nic mesoderm and 1
twelve in the somato-
|)leuric side of the
coelomic area. - Germ :
c e lls were found in ;
groups of two to four !
and singly. |
1
3 1 to 3 3 som ites.. . .the prim ordial germ j
cells are no longer in
the blood.
Swift (1915) noted th at there are more prim ordial germ
sells, in the germinal epithelium of the le ft female gonad
than in the germinal epithelium of the le ft male, gonad.
The oogonia or descendants of the prim ordial germ ce lls
are round or oval in a ll cases, having a large nucleus
containing coarse chromatin granules. Swift (1916)
