Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 176
MAMMALIAN OOCYTE MATURATION: MECHANISMS FOR REGULATION AND
PROSPECTS FOR PRACTICAL APPLICATION OF IN VITRO TECHNOLOGY
John J. Eppig
In 193S, Pincus and Enzmann observed that germinal vesicle (GV)
stage oocytes isolated from rabbit follicles underwent spontaneous
germinal vesicle breakdown (GVB) and emitted a polar body when
cultured in medium without the gonadotropin hormones that promote
follicular maturation and ovulation. They suggested that the ovarian
follicle exerts a meiosis-arresting influence on the oocyte until the
preowlatory surge of gonadotropins. This observation and hypothesis
began an era that has used culture systems for mammalian oocytes to
resolve the mechanisms that govern oocyte maturation. In addition to
providing clues to the molecules and pathways that regulate oocyte
maturation, the culture systems may provide the technology for
resolving problems of human infertility and for expanding populations
of rare and endangered species. This paper will review some current
concepts of the regulatory systems that govern mammalian oocyte
development, evaluate the prospects for the practical utilization of
this information, and suggest some of the future directions for
research.
The Ovarian Follicle as the Support System for Oocyte Development In
Viva
After a period of mitotic proliferation in the fetus, oogonia
enter meiosis, but the germ cells now called oocytes progress only as
far as the diplotene stage where they are arrested until shortly
before ovulation. Diplotene oocytes develop a close association with
somatic cells that are probably progenitors of granulosa cells and
form a primordial follicle. It is likely that oocytes that do not
become associated with these pregranulosa cells degenerate. Until an
oocyte is recruited into the pool of growing oocytes, the
pregranulosa cells remain in a single, often flattened, layer around
the oocyte. But when the oocyte is recruited, by unknown mechanisms,
into the pool of growing oocytes, granulosa cell proliferation occurs
concurrently with the increase in the size of the oocyte. Both
growing and nongrowing oocytes appear to be coupled to their
companion somatic cells by membrane specializations called gap
junctions, which allow the passage of low molecular weight molecules
to pass from one cell to another (Anderson and Albertini, 1976~.
Gap junctional communication between granulosa cells and the
oocyte is essential for oocyte growth, since they are a conduit for
nutritional and regulatory substances into the oocyte (Eppig, 1977,
1979; Brower and Schultz, 1982; Herlands and Schultz, 1984; Buccione,
et al,, 1987~. Although gap junctional communication can be
— 176 —
OCR for page 177
established between oocytes and other somatic cell types in vitro,
oocyte growth occurs only when oocytes communicate with granulosa
calls (Buccione et al., 1987~. Some aspects of oocyte development,
nevertheless, are independent of oocyte growth or association with
granulosa cells. Normally, as oocytes approach completion of their
growth phase, they become competent of undergoing spontaneous
maturation when liberated from their follicles and cultured (Szybec,
1972; Sorensen and Wasserman, 19761. The developmental program
governing the acquisition of meiotic competence, however, is
triggered at the onset of oocyte growth, but proceeds in the absence
of continued oocyte growth or granulosa cells (Canipari et al.,
19847. Once meiotic competence is achieved , granulosa cel is , via gap
junctional communication, help to maintain the oocyte in meiotic
arrest (Eppig and Downs, 1987~.
Because cumulus granulosa cells are coupled by gap junctions to
the oocyte and to the mural granulosa cells which make up the
follicle wall, the follicle may be a functional syncytium allowing
the movement of low molecular weight molecules throughout the
follicle by diffusion. In theory, therefore, production or
mobilization of low molecular weight regulatory substances in mural
granulosa cells in response to an agonist could result in the
diffusion of these substances to the oacyte, which may itself be
unable to produce or mobilize them. These substances could
participate in the maintenance of meiotic arrest, the induction of
maturation, or both .
Identification of Molecules and Pathways that Participate in the
Maintenance of Meiotic Arrest
Cyclic Adenosine Monophosphate (cAMP). In the ovarian follicles
of most studied mammal fan species, cAMP probably participates in the
maintenance of oocyte meiotic arrest. Support for this conclusion is
based on the following observations. Membrane permeable analogs of
cANP, such as dibutyryl cAMP (dbcAMP), and cAMP phosphodiesterase
inhibitors, such as 3-isobutyl-1-methylxanthine (IBMX), maintain
meiotic arrest in vitro (Cho et al., 1974; Wassaman et al., 1976;
Magnusson and Hillensjo, 1977~. Microinjection of an inhibitor of
cAMP-dependent protein kinase (PRI) induces GVB in oocytes cultured
in medium containing dLcAMP or IBMX (Bornslaeger et al., 1986~.
Conversely , microinj ection of the active catalytic subunit of
cAMP-dependent protein kinase maintains meiotic arrest (Bornslaeger
et al., 1986~. Finally, a decrease in the cAMP content of mouse
(Schultz et al ., 1983 ); and rat (Racowsky, 1984 ~ oocytes appears to
precede GVB, but such a decrease is not observed in the oocytes of
hamsters (Racowsky, 1985a; Hubbard, 1986), sheep (Moor and Heslop,
1981), or pigs (Racowsky, 1985b). Oocytes of several mammalian
species appear able to produce their own cAMP because they possess an
adenylate cyclase system (Urner et al., 1983; Ekholm et al., 1984;
Bornslaeger and Schultz, 1985a; Racowsky, 1985ab; Ruyt et al.,
1988~. It is not clear, however, that the oocytes of all of these
species can produce levels of cAMP adequate for the maintenance of
Idiotic arrest. If not, the cAMP molecule is small enough to
177 -
OCR for page 178
traverse gap junctions and, theoretically therefore, should be able to
enter the oocyte from the cumulus/mural granulosa cell syncytium. Thus
far, however' attempts to demonstrate such movement (Racowsky, 1984,
1985b; Bornsleager and Schultz, 1985b) have resulted in ambiguous
conclusions because it is not known whether increases in the
concentrations of cAMP in oocytes after elevating levels of cAMP in
cumulus cells are the result of the transfer of cAMP from the cumulus
cells, or the generation of substances in the cumulus cells that increase
production of cAMP, or decrease loss of cAMP, in the oocyte.
Oocyte Maturation Inhibitor (OMI) Preparations of follicular fluid
from several species prolong the maintenance of the GV stage in cultured
oocytes (Tsafriri et a1., 1982~. Evidence has been presented that the
active meiosis-arresting fraction of porcine follicular fluid is a low
molecular weight peptide and has been referred to as OMI (Tsafriri et al.,
19827. Confirmation of the existence of OMI awaits purification to
homogeneity. Crude preparations of OMI, however, apparently act via
cumulus cells, and the meiosis-arresting action is reversed by treatment
with luteinizing hormone (LH) (Tsafriri et al., 1982~.
Mullerian Inhibiting Substance (MIS) MIS, also known as
anti-Mullerian hormone (AMH), has been identified in bovine follicular
fluid and evidence from one group suggests that partially purified MIS has
transient meiosis-arresting activity in rat, but not mouse oocytes
(Takahashi et al., 1986~. Recently, however, it has been demonstrated
that immunopurified, biologically active MIS does not maintain meiotic
arrest in rat oocytes (Tsafriri et al., 1988~. It was suggested,
therefore, that the meiosis-arresting action of he partially purified
preparation of MIS could be that of a contaminant (Tsafriri et al.,
19887. These studies emphasize the importance of a complete purification
of biological preparations before clear identification and
characterization of active factors can be possible.
Purines Hypoxanthine was found in preparations of porcine follicular
fluid (Downs et al ., 1985 ~ . This purine accounted for most of the
meiosis-arresting activity of porcine follicular fluid on mouse oocytes.
Concentrations of hypoxanthine in biological fluids can be increased
substantially by a variety of pathological conditions, including anoxia.
Since the porcine foil icular fluid used for analysis was not collected
under conditions that would prevent the artifactual generation of
hypoxanthine, the concentration of purines in mouse follicular fluid was
assessed when collection was made under more controlled conditions (Eppig
et al., 1985~. For example, the conversion of adenosine to hypoxanthine
was prevented by treatment with an inhibitor of adenosine deaminase;
nonetheless, millimalar concentrations of hypaxanthine were found. In
addition, murine follicular fluid was found to contain substantial amounts
of adenosine. Although it is still possible that the concentration of
hypaxanthine in mouse follicular fluid is not as high as reported because
of rapid intrafollicular changes, it should be kept in mind that the
ovarian follicle is not vascularized central to the thecal layers and a
low oxygen concentration may be a natural condition in situ. In addition,
- 178 -
OCR for page 179
hypoxanthine is the predominant purine found in rapidly frozen intact
ovaries (Eppig, unpublished results).
When assessed at concentrations estimated to be present in murine
follicular fluid, hypoxanthine maintained most mouse oocytes in meiotic
arrest. Adenosine had only a transient meiosis-arresting action, but
augmented the stable inhibitory effect of hypoxanthine (Eppig et al.,
1985~. The meiosis-arresting action of hypoxanthine andadenosine was
fully reversible. Moveover, oocytes that were maintained in the GV stage
by these purines for 24 hours and then matured in medium without purines
could be fertilized and underwent embryonic development (Downs et al.,
1986a).
Inhibitors of inosine monophosphate (IMP) dehydrogenase induced GVB
in oocytes that had been maintained in meiotic arrest by hypoxanthine in
vitro. The IMP-dehydrogenase inhibitors, however, did not induce GVB in
oocytes arrested in the GO stage by guanosine, the most potent of the
purines tested for meiosis-arresting activity (Downs et al., 1986b).
These results indicate that the meiosis-arresting action of hypoxanthine
in vitro may be mediated through the production of guanyl compounds.
Likewise, IMP dehydrogenase inhibitors induced GVB upon injection into
mice primed for 24 hours with PMSG. One of these inhibitors, bredinin,
induced the maturation of almost all the meiotically competent ovarian
oocytes within 6 hours of injection (Downs and Eppig, 1987). It is not
likely that the G1lB-inducing action of IMP dehydrogenase inhibitors was
mediated by gonadotropins since other manifestations of gonadotropin
action such as cumulus expansion, thinning of the apical wall of the
follicle, or cessation of DNA synthesis in the granulosa cells were not
observed after injection of the inhibitors (Downs and Eppig, 1987). These
results support the idea that, in mice, the formation of guanyl compounds
via the IMP dehydrogenase pathway is essential for the maintenance of
meiotic arrest in vivo.
Because of the evidence indicating the importance of cAMP in
maintaininq meiotic arrest in mouse oocytes, the hypothesis that purines,
particularly hypoxanthine and adenosine, may maintain meiotic arrest by
promoting meiosis-blocking levels of cAMP in oocytes was tested. The
maintenance of meiotic arrest was correlated with elevated cAMP levels in
cumulus cell-enclosed oocytes cultured in medium containing hypoxanthine
or hypoxanthine plus adenosine . In addition, microinj ection of oocytes
with an inhibitor of cAMP-dependent protein kinase induced GVB in oocytes
cultured in medium containing hypaxanthine ~ Downs et al ., 19 8 9 ~ . These
results show that hypaxanthine arrests mouse oocytes in the GV stage, at
least in part, by maintaining meiosis-blocking levels of cAMP in the
oocytes. Hypaxanthine, and also guanosine and adenosine, inhibited cAMP
phosphodiesterase activity in ly~ates of mouse oocytes and augmented the
cAMP-elevating action of follicle-stimulating hormone (FSH) in intact
oocyte-cumulus cell complexes. These result. suggest that one way that
hypaxanthine may maintain meiosis-blocking levels of cAMP is by preventing
hydrolysis of cAMP. It is likely, though, that purines promote the
elevation of cAMP by other mechanisms as well.
- 179 —
OCR for page 180
Future research on the maintenance of meiotic arrest must focus on
the identif ication of specif ic molecules in the cAMP-dependent pathway in
oocytes. Moreover, ~ greater understanding is needed regarding the role
of purines, such as hypoxanthine, adenosine, and GHP in meiotic arrest,
and how the metabolism of these purines is regulated. It is likely that
several different interconnecting pathways participate in the maintenance
of meiotic arrest and that the relative contribution of these pathways may
vary from species to species. The interactions of various factors such as
gonadotropins, steroid hormones, and growth factors in the regulation of
these pathways will be dif f icult to study, but their resolution is
essential for a basic understanding of the mechanisms that maintain
meiotic arrest.
Induction of Oocyte Maturation
Oocyte maturation in viva is induced in ovulatory follicles by the
preovulatory surge of LH. The mechanism by which LH promotes maturation,
however, is not well understood. LH could stimulate the granulosa cells
to some action that would deprive the oocyte of maturation-arresting
substances. For example, LH could terminate the production of
meiosis-arresting substances or promote the catabolism of these
substances, or it could disrupt the gap junctional system that delivers
the meiosis arresting substances to the oocyte. The concentration of cAMP
in the intact follicle does not decrease after stimulation with hCG
(Schultz et al., 1983~. Nor is there a decrease in the concentration of
hypoxanthine or adenosine in murine follicular fluid before GVB (Eppig et
al., 1985~. It is clear, therefore, that a decrease in the concentration
of these substances in the whole follicle is not the mechanism of
hCG-induced oocyte maturation. Moreover, the gap junctional communication
between the oocyte and its companion cumulus cells does not decrease
before G~B in vivo (Moor et al., 1981; Eppig, 1982; Salustri and Siracusa,
1983~. It is possible that there are differences between the movement of
the molecular markers used to measure gap junctional communication and the
movement of meiosis-arresting substances, but if they are analogous, then
it can be concluded that a disruption in the communication between cumulus
cells and the oocyte is not the mechanism of LH-induced oocyte
maturation. It has been suggested that LH induces a reduction in the
communication between the mural granulosa cells and cumulus cells and
tbereby reduces the movement of meiosis-arresting substances to the
oocyte-cumulus cell complex (Larsen et al., 19873. If cAMP is the
meiosis-arresting substance that moves from the follicle wall to the
oocyte-cumulus cell complex to maintain meiotic arrest, then a decrease in
the cAMP content of the intact complex should precede GVB, or commitment
to undergo GVB. Such a decrease in the cAMP content of the intact
oocyte-cumulus cell complex was not detected after injecting mice with
human chorionic gonadotropin (hCG) (Shultz et al., 1983; Eppig and Downs,
19883. These results, however, do not eliminate the possibility that the
passage of other meiosis-arresting substances from the follicle wall to
the oocyte-cumulus cell complex could be reduced.
— 180 -
OCR for page 181
After mice are injected with hCG, the cAMP content of the intact
oocyte-cumulus cell complexes increases (Shultz et al., 1983) even though
the gap junctional communication between the oocyte and the cumulus cells,
which should allow the transfer of cAMP, is not reduced (Eppig and Downs,
1988~. One explanation for this observation is that the oocytes become
stimulated to secrete or hydrolyze their cAMP by a signal produced by the
granulosa/cumulus cells in response to LH/hCG. Alternatively,-the cumulus
cells may have been stimulated to selectively reduce the transfer of cAMP,
and not markers of gap junctional communication, to the oocytes.
There is evidence for a positive, maturation-inducing signal produced
by granulosa cells in response to gonadotropin or epidermal growth factor
(EGF) (Eppig and Downs, 1987; Downs et al., 1988~. This signal overcomes
the ef feet of meiosis-arresting substances. GOB is induced in cumulus
cell-enclosed oocytes by either FSH or EGF even in the continual presence
of hypoxanthine, dbcAMP, or IBMX. The frequency at which these agonists
induced GVB is greater than the frequency of GVB promoted by simply
denuding the oocytes in medium containing the meiosis-arresting substance,
thus indicating that the agonists do not function merely by promoting the.
uncoupling of the cumulus cells from-the oocyte. The identification of
maturation-inducing signals is a major area for future research.
Moreover, the possible physiological role, if any, of growth factors such
as EGF in the regulation of oocyte maturation needs to be resolved.
Similarities Between Mechanisms that Govern Meiotic and Mitotic Cel 1
· · ~
Division ~
There are several lines of evidence suggesting that mechanisms that
govern the induction of oocyte maturation are similar to the mechanisms
involved in the induction of mitotic cell division. First, an
autocatalytic maturation-promoting factor (MPF) is produced in frog
oocytes in response to progesterone (Reynhout and Smith, 1974), in
starfish oocytes in response to 1-methyladenine (Kishimoto and Kanatani,
1976), and in maturing mammalian oocytes (Sorenson et.al., 1974~. A
similar factor is also present in somatic cells as they enter M phase of
the cell cycle (Kishimoto et al., 1982~. Moreover, it has recently been
shown that MPF purified from frog oocytes contains the product of a
homolog of a mitosis control gene, cdc2+, of yeast (Dunphy et al., 1988;
Gautier et al., 1988~. Second, mRNA- coding for the clam protein cyclin A,
a protein whose level rises and falls during both meiotic divisions of the
oocyte and during the cell cycle of early embryogenesis, induces meiotic-
maturation upon injection into frog oocytes (Swenson et al., 1986~.
Third, an increase in free intracellular calium appears to be an essential
part of the mechanisms that promote somatic cell division (Poenie et al.,
1985; Hafner and Petzelt, 1987 ; Iwigg et al., 1988) . Likewise, calcium
ionophores, which increase free intracellular calcium by uptake, induce
the maturation of mammalian oocytes maintained in meiotic arrest with
dUcAMP or IBMX (Powers and Paleos, 1982; Racowsky, 19861. Moreover,
inhibitors of calmodulin prevent the spontaneous maturation of murine
oocytes, but do not prevent a decline in oocyte cAMP (Bornslaeger et al.,
1984~. This observation supports the idea that intracellular calcium
plays an important role in the initiation of GVB and functions in a
- 181
OCR for page 182
pathway distinct from, but perhaps parallel to, the pathway activated by a
decline in cAMP levels. Increases in the concentration of free calcium in
oocytes could result from either the mobilization of calcium from
intracellular stores or the uptake of external calcium. One could
speculate that the maturation-inducing signal communicated from granulosa
cells to the oocyte could be a factor(~) that promotes an increase in free
calcium in the oocyte, by internal mobilization or uptake, or the signal
could be calcium itself. It will be important to investigate these
parallels between the control mechanism of mitotic and meiotic cell
division further.
Murine Oocyte Growth and Development in Culture
Murine oocytes grow and acquire competence to undergo GVB in culture
(Eppig, 19771. Oocyte growth is dependent upon metabolic coupling to
granulosa cells, but the acquisition of competence to undergo GVB is not
(Canipari et al. , 1984~ . Therefore, the developmental program governing
the acquisition of GVB competence is independent of oocyte growth.
Moreover, the acquisition of GVB competence does not appear to require
gonadotropins or steroid hormones (Eppig, 19771. In the rat, however, ESH
and estradiol increase the frequency at which GVB competence is acquired
(Bar-Am) et al., 19837.
For many years it was thought that oocytes that had matured in vitro
were defective because they could not be fertilized and undergo embryonic
development. The main reason for failure was thought to be the inability
of ova matured in vitro to promote the development of the male pronucleus,
but the failure was probably due to inadeguate culture systems because it
was later demonstrated that cumulus cell-enclosed murine oocytes that
mature spontaneously in vitro are competent of fertilization and embryonic
development at frequencies equivalent to oocytes that mature in response
to superovulatory regimen in viva (Schroeder and Eppig, 1984~.
Subsequently, normal development after maturation in vitro has also been
reported for oocytes form some other species such as the sheep
{Staigmiller and Moor, 1984 ~ . Much remains to be done, however, to
resolve the optimal conditions for oocyte maturation for each species that
will promote maximal developmental potential.
Murine oocytes indicate that oocytes sequentially develop competence
for maturation, then fertilization and cleavage to the two-cel1 stage, and
then development to blastocyst (Eppig and Schroeder, 1989~. The
competence for each of these developmental capacities is acquired in vitro
and does not require the presence of gonadotropins. Oocytes isolated in
mid-growth phase from 12 day old mice, have been grown , matured ,
fertil ized, and cultured to the 2-cell stage in vitro, and developed to
term after transfer to the oviducts of pseudopregnant foster mothers.
Continued progress in the development of the technology for oogenesis in
182 -
OCR for page 183
vitro is dependent upon basic studies on oocyte nutrition and metabolism,
and on the action of hormones, growth factors, and other factors that
control the differentiation and function of the functionally integrated
oocyte-granulosa cell complex in viva.
Prospects for the Practical Utilization of Oocyte Culture Systems
Expansion of Populations of Rare or Agriculturally Important Mammals
Very few primary oocytes that are present in the ovary are ovulated
and made available for fertilization in mammals. For example, it has been
estimated that there are more than 150,000 primordial follicles in the
bovine ovary at birth, but not more than 3 DO of these will ever be
ovulated normally (Erickson, 19663. Techniques of superovulation could
increase the reproductive capacity of ~ cow only about tenfold even i f it
could be superovulated yearly during its reproductive lifespan (Seidel,
1981). This general rule probably holds true for most mammals. There is,
therefore, a tremendous pool of oocytes having the potential for
development and, therefore, expanding populations if the oocytes could be
rescued from their normal fate of degeneration. One approach to such a
rescue is to isolate the oocytes from their natural environment and grow
them in vitro and, as described above, significant progress has been made
to achieving this using mice as a model system. This technology would be
applicable to the expansion of populations of agriculturally important
animals such as those that have been genetically engineered for desirable
characteristics, of important genetically engineered experimental animals,
or of endangered species.
Our culture system for murine oocyte maturation in vitro rescues
degenerating oocytes from deceased mice. Significant necrotic changes are
readily apparent in the oocytes of mice dead for six hours at ambient
temperatures but these changes are reversed during oocyte maturation in
vitro. The eggs derived from the rescued oocytes can be fertilized and
undergo normal development. Thus, it may be possible to salvage the
oocytes of rare or agriculturally important animals even after unforeseen
death. Eggs derived from murine ova that mature in vitro can also be
frozen and show almost normal capacity for fertilization and development
after thawing. Thus valuable ova can be presented after development in
vitro if appropriate sperm are not immediately available.
Genetic Engineering. Jenkins and Copeland (1985) have reported that
the germ line of SWR/J-RF/J hybrid mice become infected with ecotropic
retroviru~es during oogenesis. Moreover, Panthier et. al (1988) have
produced tranagenic mice by inoculation of newborn SWR/J females with an
ecotropic murine leukemia virus. These findings, along with the
development of oocyte culture systems, could present a unique opportunity
for the introduction of genes into the germline. Protocols could be
- 183
OCR for page 184
developed to infect oocytes with retroviruses carrying specific genes that
would become integrated into the germ line, introducing a significant
advancement in the technology for producing transgenic mice. Preliminary
studies have produced one mouse with integrated retrovirus after infecting
Skytel during maturation in vitro. Perhaps greater success will be
achieved in experiments wherein oocytes are infected during more prolonged
development or maintenance in culture.
Clinical Applications In vitro fertilization ~ I~F) has become a
~list, c clinical resolution to a variety of infertility problems in both
women and men. Nevertheless, the success rate could be increased by a
radical change in this protocol to util ize oocyte maturation in vitro
rather than the protocols of hormonal stimulation currently in use. The
stipulatory protocols which promote follicular development and maturation
of oocytes in multiple follicles in humans probably produces eggs with a
reduced developmental capacity. Moreover, these protocols probably do not
promote optimal development of the uterine epithelium for the implantation
of the embryo. An alternative to the hyperstimulatory techniques is
oocyte maturation in vitro. Our studies with mice indicate that ova with
full developmental capacity can be recovered even from degenerating
follicles. Thus, it may be possible to recover immature oocytes form
several antral follicles, excluding the dominant preovulatory follicle,
and mature them in culture while the preovulatory follicle prepares the
uterus normally for implantation. Current ultrasonic techniques for
follicular visualization and oocyte aspiration do not allow sufficient
resolution of the follicles for this procedure, but this is an engineering
problem with the ultrasound equipment and could be resolved with
appropriate incentive.
Current protocols for human I~F and embryo culture are not based on
exhaustive experimentation to define optimal culture conditions for human
ova or embryos. Ethical problems have hindered progress in this area.
One of these problems involves the source of ova for the studies.
However, if immature oocytes could be recovered from ovaries removed for
various clinical reasons and matured in culture with full developmental
potential, the ethical problems associated with the source of ova for
embryo research would be reduced.
Clinical realization of maturation in vitro as an antecedent to IVF
will require basic studies to resolve likely differences in conditions for
oocyte maturation that impart full developmental capacity between human
and mouse oocytes. It would probably be advantageous and appropriate to
carry out initial studies using non-human primate oocytes. Moreover,
continued basic studies on oocyte metabolism and its regulation by
companion somatic cells, hormones, meiotic regulatory substances and
growth factors using rodent systems is essential. Mouse ova were used in
the pioneering studies on IVF that have produced the clinical successes we
now see every day. Certainly, experiments with mouse oocytes will
continue to be indicators of what is possible with other species.
- 184
OCR for page 185
Acknowledgments
Research in my laboratory is supported by grants HD20575, HD21970 and
ED23839 from the National Institutes of Health. The contents of this
paper do not necessarily represent the official views of that agency. My
most sincere-thanks to Roberto Buccione, Allan Schroeder and Barbara
V~nderhyden for their helpful suggestions for this paper.
- 185
OCR for page 186
References
Anderson, A., D. F. Albertini . 1976 Gap Junctions between the oocyte and
companion follicle cells in the mammalian ovary. J. Cell Biol.
71: 680-686.
Bar-Ami, S.A. Nimrod, A.M.H. Brodie, and A Tsafriri. 1983. Role of PSH
and oestradiol-17B in the development of meiotic competence in rat
oocytes. J. Steroid. Biochem. 19: 965-971
Bornslaeger, E.A., M.W. Wilde, and R.M. Schultz. 1984. Regulation of
mouse oocyte maturation: involvement of cyclic AMP phosphodiesterase
and calmodulin. Dev. Biol. 105:488-499.
Bornslaeger, E . A., and R. M. Schultz . 19 8 5a . Adenylate cyclase activity
in zone-free mouse oocytes. Exp. Cell Res. 156: 277-281.
. 19858. Regulation of mouse oocyte maturation: effect of ele-
vating cumulus cell cAMP levels. Biol. Reprod. 33: 689-704 .
Bornslaeger, E.A., P. Hattie, and R.M. Schultz. 1986. Involvement
of cAMP-dependent protein kinase and protein phosphorylation in
regulation of mouse oocyte maturation. Dev. Biol. 114:453-462.
grower, P.T., and R.M. Schultz. 1982. Intercellular communication
between granulosa cells and mouse oocytes: existence and possible
nutritional role during oocyte growth. Dev. Biol . 90: 144-153 .
Buccione, R., S. Cecconi , C. Tatone, F. Mangia, and R. Colonna. 1987 .
Follicle cell regulation of mammmalian oocyte groth. J. Exp. Zool.
242: 351-354.
Canipari, R., F1 Palombi, M. Riminucci, and F. Mangia. 1984. Early
programming of maturation competence in mouse oogenesis. Dev. Biol.
102: 519-524.
Cho, W.R. ,- S. Stern, and J.D. Biggers. 1974. Inhibitory effect of
dibutyryl cAMP on mouse oocyte maturation in vitro. J. Exp.Zool.
187: 383-386.
Downs , S . M ., D. L. Coleman , P . F . Ward-Bailey , and J . J . Eppig . 19 8 5 .
Bypaxanthine is the principal inhibitor of murine oocyte maturation
in a low molecular weight fraction of porcine follicular fluid.
Proc. Nat. Acad. Sci. USA 82: 454-458.
Downs , S . M., A. C. Schroeder, and J. J . Eppig. 198 6a . The developmental
capacity of mouse oocytes following maintenance of meiotic arrest in
~ritro. Gamete Res . 15: 3 05-316 .
Downs, S.M., D.L. Coleman, and J.J. Eppig. 1986b. Maintenance of murine
meiotic arrest: uptake and metabolism of hypoxanthine and adenosine
by cumulus cell-enclosed and denuded oocytes. Dev. Biol.
117:174-183.
— 186 —
OCR for page 187
Downs, S.M., and J.J. Eppig. 1987. Induction of mouse oocyte maturation
in vivo by perturbants of purine metabolism. Biol. Reprod.
36:431-437.
Downs, S.H., S.A.J. Daniel, and J.J. Eppig. 1988. Induction: of matur-
ation in cumulus cell-enclosed mouse oocytes by follicle-stimulating
hormone and epidemical growth factor: evidence for a positive stimulus
of somatic cell origin. J. Exp. Zool. 245:86-96.; ~
Downs, S.~., Daniel, S.A.J., Bornslaeger, E.A., Hoppe, P.C., and J.J.
Eppig. 1989. Maintenance of meiotic arrest in mouse oocytes by
purines: modulation of cAMP levels and cAMP phosphodiesterase
activity.~{Gamete Res. (in press).
Dunphy, W.G., L. Brizuela, D. Beach, and J. Newport. 1988. The Xenopus
cdc2 protein is a component of MPE, a cytoplasmic regulator of
mitosis. Cell 54:423-431.
Ekholm, C., T. Hillensjo, C. Magnusson, and S. Rosberg. 1984. Stimula-
tion and inhibition of rat oocyte meiosis by forskolin. Biol.
Reprod. 30:537-543.
Eppig, J.J., 1977. Mouse oocyte development in vitro with various culture
systems. Dev. Biol. 60:371-388
. , ,
. 1979. A comparison between oocyte growth in coculture with
granulosa cells and oocytes with granulosa cell-oocyte junctional
contact maintained in vitro. J. Exp. Zool. 209:345-353.
. 1982. The relationship between cumulus cell-oocyte coupling,
oocyte meiotic maturation, and cumulus expansion. Dev. Biol.
89:268-272.
Eppig, J.J., Ward-Bailey, snd D.L. Coleman. 1985. Hypoxanthine and
adenosine in murine ovarian follicular fluid: concentrations and
activity-in maintaining oocyte meio~ic arrest. Biol. Reprod.
33:1041-1049.
Eppig, J.J., and S.M. Downs. 1987. The effect of hypoxanthine on mouse
oocyte growth and development in vitro: maintenance of meiotic arrest
and gonadotropin-1nduced oocyte maturation. Dev. Biol. 119:313-321.
. 1988. Gonadotropin-induced murine oocyte maturation in vivo is
not associated with decreased cyclic adenosine monophosphate in the
oocyte-cumulus cel1 complex. Gamete Res. 20:125-131.
Eppig, J.J., and A.C. Schroeder. 1989. Capacity of mouse oocytes from
preantral follicles to undergo embryogenesis and development to live
young after growth, maturation and fertilization in vitro. Biol.
Reprod. (in press).
- 187 -
OCR for page 188
Erickson, B. H . 1966 . Development and senescence of the postnatal
bovine oval. J. An. Sci. 25. 800-805.
Gautier, J., C. Norbury, M. Lohka, P. Nurse, and J. Caller. 1988. Purified
maturation-promoting factor contains the product of a Xenopus homol og
of the fission yeast cell cycle control gene cdc2~. Cell 54-433-439.
Ilafner, M., and C. Petzelt. 1987. Inhibition of mitosis by an antibody to
the mitotic calcium transport system. Nature 330: 264-266 .
Berlands, R.L., and R.M. Schultz. 1984. Regulation of mouse oocyte growth:
probable nutritional role for intercellular communication between
follicle cells and oocytes in oocyte growth. J. Exp. Zool.
229:317-325.
Hubbard, C.J. 1986. Cyclic AMP changes in the component cells of Greafian
follicles: possible influences on maturation in the follicle-enclosed
oocytes of hamsters. Dev. Biol. 118:343-351.
Jenkins, N.A., and N.G. Copeland. 1985. High frequency germline
acquisition of ecotropic MuLV proviruses in SWR/J-RF/J hybrid mice.
Cell. 43:811-819.
Rishimoto, T., and H. Xanatani. 1976. Cytoplasmic factor responsible for
germinal vesicle breakdown and meiotic maturation in starfish oocyte.
Nature 260:321-322.
Rishimoto, T., R. Ruriyama, H. Kondo, and H. Kanatani. 1982. Generality of
the action of various maturation-promoting factors. Exp. Cell Res.
137: 121-126.
Xuyt, J.R.M., T.A.M. Xruip, and M. DeJong-8rink. 1988. Cytochemical local-
ization of adenylate cyclase in bovine cumulus-oocyte complexes. Exp.
Cell Res. 174:139-145. ~
Larsen, W.J., S.E. Wert, and G.D. Brunner. 1987. Differential modulation
of rat follicle gap junction populations at ovulation. Dev. Biol.
112: 61-71.
liagnusson, C., and T. Hillensj o. 1977 . Inhibition of maturation and
metabolism of rat oocytes by cyclic AMP. J. Exp. Zool . 201 :138-147 .
floor, R.M., and J.P. Heslop. 1981. Cyclic AMP in mammalian follicle cells
and oocytes during maturation. J. Exp. Zool. 216:205-209.
- 188
OCR for page 189
Moor, R.M., J.C. Osborn, D.G. Cran, and D.E. Walters. 1981. Selective
effect of gonadotrophins on cell coupling, nuclear maturation and
protein synthesis in mammalian oocytes. J. Embryol. Exp. Morphol.
61:347-365.
Panthier, J.J., Condamine, H., and Jacob, F. 1988. Inoculation of newborn
SWR/J females with an ecotropic murine leukemia virus can produce
transgenic mice. Proc Nat Acad Sci (USA) 85:1156-1160.
Pincus, G., and E.V. Enzmann. 1935. The comparative behavior of mammalian
eggs in vivo and in vitro. I. The activation of ovarian eggs. J. Exp.
Hed. 62:655-675.
Poenie, M.J. Alderton, R. Steinhardt, and R. Tsien. 1986. Calcium rises
abruptly and briefly throughout the cell st the onset anaphase.
Science 233:996-889.
Powers, R.D., and G.A. Paleos. 1982. Combined effects of calcium and
dibutyryl cyclic AMP on germinal vesicle breakdown in the mouse
oocyte. J. Reprod. Fert. 66:~-8.
Racowsky, C. 1984. Effect of forskolin on the spontaneous maturation and
cyclic AMP content of rat oocyte-cumulus complex. J. Reprod. Fert.
72: 107-116.
. 1985a. Effect of forskolin on the spontaneous maturation and
cyclic AMP content of hamster oocyte-cumulus complexes. J. Exp. Zool.
234: 87-96.
. 1985b. Effect of forskolin on maintenance of meiotic arrest and
stimulation of cumulus expansion, progesterone and cyclic AMP
production by pig oocyte-cumulus complexes. J. Reprod. Fert. 74:9-21.
. 1986. The releasing action of calicum upon cyclic AMP-dependent
meiotic arrest in hamster oocytes. J. Exp. Zool. 239:263-275.
Reynhout,. J.X., and r.D. Smith. 1974. Studies on the appearance and nature
of a maturation-inducing factor in the cytoplasm of amphibian oocytes
exposed to progesterone. Dev. Biol. 38:394-400.
Salustri, A., and G. Siracusa. 1983. Metabolic coupling, cumulus expansion
and meiotic resumption in mouse cumuli oophori cultured in vitro in
the presence of FSH or dbcAMP, or stimulated in vivo by hCG. J.
Reprod. Fert. 68:335-341.
Schroeder,:A.C., and J.J. Eppig. 1984. The developmental capacity of mouse
oocytes that matured spontaneously in vitro is normal. Dev. Biol.
102:493-497.
- 189 -
OCR for page 190
Schultz, R.M., R. Montgomery, and J. Belanoff. 1983. Regulation of mouse
oocyte maturation: implication of a decrease in oocyte cAMP and
protein dephosphorylation in commitment to resume meiosis. Dev. Biol.
97:264-273.
Seidel, G.E., 1981. Superovulation and embryo transfer in cattle. Science
211:351-358.
Sorensen, R.A., M.S. Cyert., and R.A. Pedersen. 1985. Active maturation-
promoting factor is present in mature mouse oocytes. J. Cell Biol.
100:1637-1604.
Sorensen, R.A., and P.M. Wasserman. 1976. Relationship between growth
oocytes meiotic maturtion of the mouse oocyte. Dev. Biol. 50:531-536.
Staigmiller, R. B., and R.M. Moor. 1984 . Effect of follicle cells on the
maturation and development competence of ovine oocytes matured
outside the follicle. Gamete Res. 9: 221-229.
Swenson, K. I ., K.M. Farrell , and J.V. Ruderman. 1986 . The clam embryo
protein cycl in A induces entry into M phase and the resumption of
meiosis in Xenopus oocytes. Cell 47: 861-870.
Szybek, X. 1972. In vitro maturation of oocytes from sexually immature
mice. J. Endocrinol. 54:527-528.
Takahashi, M., S.S. Koide, and P.K. Donahoe. 1986. Mullerian inhibiting
substance as oocyte meiosis inhibitor. Mol. Cell. Endocrin.
47:225-234.
Tsafriri, A., N. Dekel, and S. Bar-Ami. 1982. The role of oocyte matur-
ation inhibitor in follicular regulation of oocyte maturation. J.
Reprod. Fert. 64:541-551.
Tsafriri, A., J. Picard, and N. Josso. 1988. Immunopurified anti-
Mullerian hormone does not inhibit spontaneous resumption of meiosis
in vitro of rat oocytes. Biol. Reprod. 38:481-485.
Twigg, J., B. Patel, and M. Whitaker. 1988. Translational control of
InsP3-induced chromatin condensation during the early cell cycles of
sea urchin embryos. Nature 332:366-369.
Orner, F., W.L. Herrmann, E.E. Baulieu, and S. Schorderet-Slatkine. 1983.
Inhibition of denuded mouse oocyte meiotic maturation by forskolin,
an activator of adenylate cyclase. Endocrinology 113:1170-1172.
Wassarman, P.M., W.J. Josefowicz, and G.E. Letourneau. 1976. Meiotic
maturation of mouse oocytes in vitro: inhibition of maturation at
specific stages of nuclear progression. J. Cell Sci. 22:531-545.
- l9C
Representative terms from entire chapter:
oocyte maturation
