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Centre de Recherche en Reproduction Animale (J.S.) and Département de Pathologie et Microbiologie (M.D.), Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada J2S 7C6
Address all correspondence and requests for reprints to: Dr. Jean Sirois, CRRA, Faculté de Médecine Vétérinaire, Université de Montréal, C.P. 5000, Saint-Hyacinthe, Quebec, Canada J2S 7C6. E-mail: siroisje{at}ere.umontreal.ca
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10 h). Therefore, the
progressively delayed expression of PGHS-2 in species with longer
ovulatory processes supports its role as a molecular determinant of the
species-specific length of the ovulatory process. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Prostaglandin G/H synthase (PGHS) is the first rate-limiting enzyme in
the biosynthesis of prostanoids from arachidonic acid (14, 15, 16). The
active enzyme is a homodimer composed of two subunits of about 70,000
daltons and one heme group. PGHS has a cyclooxygenase activity
responsible for the conversion of arachidonic acid to PGG2
and a peroxidase activity involved in the formation of PGH2
from PGG2 (14). PGH2 is the common precursor
for the synthesis of all PGs, prostacyclins, and tromboxanes. Studies
during the past 5 yr have established the presence of two distinct PGHS
isoforms, referred to as PGHS-1 and PGHS-2 (15, 16). The two isoforms
share important similarities at the protein level; they are
approximately the same size (70,000–72,000 mol weight), and all
important structural and functional domains are highly conserved (17, 18). However, PGHS-1 and -2 are clearly derived from distinct genes
located on different chromosomes and are encoded by messenger RNA of
different sizes (2.8 vs. 4.0 kilobases for PGHS-1 and -2,
respectively) (15, 16, 17, 18). Also, the two isoforms differ markedly in their
expression. PGHS-1 is present in a wide variety of tissues and is often
referred to as the constitutive form. In contrast, PGHS-2 is generally
undetectable is most tissues, but can be induced by a variety of
agonists and is referred to as the inducible form (15, 16).
In the rat ovary, the marked increase in follicular PG synthesis before
ovulation is associated with the gonadotropin-dependent induction of
PGHS enzymes in granulosa cells (19, 20). High levels of gonadotropins
were shown to selectively induce PGHS-2, but not PGHS-1, in rat
preovulatory follicles in vivo and in vitro (13, 21, 22, 23, 24). The induction in rats is very rapid, within 2–4 h after hCG
in vivo, and precedes follicular rupture by approximately
10 h (13). Recent studies in bovine preovulatory follicles suggest
that the selective induction of PGHS-2 in ovarian cells is a mechanism
that has been conserved in another species to regulate the synthesis of
PGs necessary for ovulation (12, 25). However, a striking difference
was observed in the time course of PGHS-2 induction in bovine
preovulatory follicles, with PGHS-2 expression being first detected
only 18 h after hCG treatment (12). Interestingly, the interval
from PGHS-2 induction to follicular rupture in cattle was remarkably
similar to that in rats (10 h). Therefore, the difference in the
time course of PGHS-2 induction in species with a short (rat)
vs. a long (cattle) ovulatory process incited us to propose
that the control of PGHS-2 expression could be one of the determinants
involved in dictating the species-specific length of the ovulatory
process (12).
The general objective of the present study was to use an animal model with an ovulatory process of a different length to test our hypothesis of a relationship between the time of PGHS-2 induction and ovulation. The specific objectives were to determine whether PGHS-2 is induced in equine follicles before ovulation and, if so, to characterize its time course of induction and its cellular localization.
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Materials and Methods |
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were obtained from DuPont-New
England Nuclear Research Products (Mississauga, Canada);
PGE2 and PGF2 antibodies were purchased from
Advanced Magnetics (Cambridge, MA); nitrocellulose membranes (0.45
µm) were obtained from Schleicher and Schuell (Keene, NH);
Rainbow mol wt markers were obtained from Amersham (Arlington Heights,
IL); Kodak X-Omat AR film was purchased from Eastman Kodak (Rochester,
NY); Eagle’s Modified Essential Medium was obtained from Life
Technologies (Grand Island, NY); and Bio-Rad Protein Assay and
electrophoretic reagents were purchased from Bio-Rad Laboratories
(Richmond, CA); Vectastain ABC kit was obtained from Vector
Laboratories (Burlingame, CA); Rompun was obtained from Haver (Bayvet
Division, Shawnee, KS); Torbugesic was obtained from Fort Dodge
Laboratories (Fort Dodge, IA); Dormosedan was purchased from SmithKline
Beecham, Animal Health (West Chester, PA).
Isolation of equine preovulatory follicles and other tissues
Standardbred and Thoroughbred mares with normal estrous cycles
and weighing approximately 375–450 kg were used. Animals were teased
daily with a pony stallion for detection of estrus. Ovaries were
scanned daily by transrectal real-time ultrasonography to characterize
follicular development before surgery and to identify the ovary bearing
the presumptive ovulatory follicle.
To obtain a relatively homogeneous population of equine preovulatory follicles, hCG (2500 IU, iv) was administered during estrus when the preovulatory follicle was 35 mm in diameter. The ovary with the presumptive ovulatory follicle was removed via colpotomy 0, 12, 24, 30, 33, 36, and 39 h after hCG (n = 5 follicles/time point). Ovariectomies were performed with a chain ecraseur as previously described (26). Neuroleptanalgesia was induced during surgery with a combination of xylazine (Rompun; 0.65 mg/kg, iv), butorphanol (Torbugesic; 0.005 mg/kg, iv), and detomidine (Dormosedan; 0.02 mg/kg, iv), as previously described (27). The recovered ovary was immediately immersed in ice-cold Eagles’s MEM supplemented with penicillin (50 U/ml)-streptomycin (50 µg/ml; Life Technologies), L-glutamine (2.0 mM; Life Technologies), and nonessential amino acids (0.1 mM; Life Technologies). All preovulatory follicles collected between 0–36 h post-hCG were recovered intact. Follicles isolated 39 h post-hCG appeared to be very close to ovulation; they were very soft, and two collapsed during the procedure.
In one case, tissues were collected from a mare killed 39 h post-hCG (pentobarbital sodium, 108 mg/kg, iv). In addition to the ovary bearing the preovulatory follicle, pieces of liver, spleen, kidney, adrenal, heart, lung, and uterus were collected. Equine platelets were isolated as previously described (12) from a blood sample collected before death and used as a source of PGHS-1 (28). All animal procedures were approved by the institutional animal care and use committee of Cornell University and the Comité de Déontologie Animale of the Université de Montréal.
Isolation of follicle wall, granulosa cells, and theca interna
The preovulatory follicle was dissected from the surrounding
ovarian tissue with a scalpel, and follicular fluid was aspirated and
stored at -20 C until assayed for PGE2 and
PGF2. The follicle was cut into several pieces, and
under a dissecting microscope, the theca externa and other surrounding
tissues were dissected away from the theca interna using fine forceps,
as previously described (29, 30). The resulting theca interna with
attached granulosa cells was subsequently referred to as a follicle
wall preparation. Some pieces of follicle wall were further dissected
into preparations of granulosa cells and theca interna by gently
scraping the theca interna with a bent glass Pasteur pipette. Granulosa
cells were recovered by centrifugation. All samples were stored at -70
C until preparation of cellular extracts.
Solubilized cell extracts and immunoblot analysis
Solubilized cell extracts were prepared as previously described
(12, 21). Briefly, tissues were homogenized on ice in TED buffer (50
mM Tris, pH 8.0; 10 mM EDTA; and 1
mM DEDTC) containing 2 mM octyl glucoside and
centrifuged at 30,000 x g for 1 h at 4 C. The
crude pellets (membranes, nuclei, and mitochondria) were sonicated (8
sec/cycle, three cycles) in TED sonication buffer (20 mM
Tris, pH 8.0; 50 mM EDTA; and 0.1 mM DEDTC)
containing 32 mM octyl glucoside. The sonicates were
centrifuged at 16,000 x g for 15 min at 4 C. The
recovered supernatant (solubilized cell extract) was stored at -70 C
until electrophoretic analyses were performed. The protein
concentration was determined by the method of Bradford (Bio-Rad protein
assay).
Proteins (15–65 µg) present in cell extracts were resolved by
one-dimensional SDS-PAGE and electrophoretically transferred to
nitrocellulose filters as previously described (12, 21). Filters were
incubated with one of two affinity-purified polyclonal antibodies
raised in rabbits against ovine PGHS-1 (12, 21) and diluted 1:25 in TBS
(10 mM Tris-buffered saline, pH 7.5) containing 2% nonfat
dry milk. The specificity of each antibody has previously been
characterized in rat, ovine, and bovine tissues; antibody 9181 has been
shown to recognize both PGHS isoforms (PGHS-1 and PGHS-2), whereas
antibody 8223 has been shown to react only with PGHS-1 in all species
tested (12, 21, 31). [125I]Protein A (1 x
106 cpm/ml TBS-2% milk) was used to visualize
immunopositive proteins. Filters were washed three times (20 min/wash)
in TBS-0.05% Tween and exposed to film at -70 C. For quantification
purposes, bands from the nitrocellulose filters were excised and
counted in a 
-counter.
Immunohistochemistry
Immunohistochemical staining for PGHS was performed using the
Vectastain avidin:biotin complex (ABC kit, Vector Laboratories,
Burlingame, CA), as previously described (32). Briefly, pieces of
follicles were formalin fixed and paraffin embedded, and 3 µm-thick
sections were deparaffinized through graded alcohol series. Endogenous
peroxidase was quenched by incubating the slides in 0.3% hydrogen
peroxide in methanol for 30 min. After rinsing in PBS for 15 min,
sections were incubated with diluted normal goat serum for 20 min at
room temperature. Primary anti-PGHS antibody 9181 (diluted 1:100) was
applied, and sections were incubated overnight at 4 C. Control sections
were incubated with PBS only or with anti-PGHS antibody 8223 that is
selective for PGHS-1. After rinsing in PBS for 10 min, a biotinylated
goat antirabbit antibody (1:222 dilution) was applied, and sections
were incubated for 45 min at room temperature. Sections were washed in
PBS for 10 min and incubated with the avidin DH-biotinylated
horseradish peroxidase H reagents for 45 min at room temperature. After
a 10-min PBS wash, the reaction was revealed using diaminobenzidine
tetrahydrochloride as the peroxidase substrate. Sections were
counterstained with Gill’s hematoxylin stain and mounted.
PGE2 and
PGF2 RIAs
Samples were assayed for PG content by specific RIAs as
previously described (12). The PGE2 antibody cross-reacts
50% with PGE1, 6% with PGA2, 3% with
PGA1, and less than 1.4% with all other eicosanoids
tested. The PGF2 antibody cross-reacts 100% with
PGF1, 1.1% with PGE1 and
6-keto-PGF1, and less than 0.6% with all eicosanoids
tested. Because the PGF2 antibody cross-reacts 100%
with PGF1, PGs measured with the assay were referred to
as total PGF. For each PG, all samples were analyzed in a single assay.
Intraassay coefficients of variation for PGE2 and
PGF2 were 11.7% and 8.7%, respectively.
Statistical analysis
One-way ANOVA was used to test the effect of time after hCG on
PG concentrations in follicular fluid and on relative amounts of
immunoreactive PGHS-2 protein in follicle wall extracts. When ANOVAs
indicated significant differences, Fisher’s least significant
differences test was used to compare individual means.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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). The signal
appeared as a 72,000 Mr band and a smaller 60,000
Mr band believed to correspond to a proteolytic fragment of
the intact protein, as described in other species (12, 21, 31). When a
duplicate blot was probed with antibody 8223 (selective for PGHS-1), no
immunoreactive PGHS was detected in follicles 36 h post-hCG, but
PGHS-1 was detected in positive controls [ovine PGHS-1 and equine
platelets, which are known to contain PGHS-1 (28); Fig. 1B].
Collectively, these results indicate that PGHS-2, but not PGHS-1, is
induced in equine follicles before ovulation.
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).
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). The band detected in nonovarian
tissues was of the same size as PGHS-1 (70,000 Mr) present
in platelets. Immunoreactive PGHS-2 (72,000 Mr) present in
follicle wall was slightly larger in size than PGHS-1, a characteristic
shared with PGHS isoforms in other species (12, 21, 31). To verify the
identity of the PGHS signal in nonovarian tissues, a duplicate blot was
probed with the PGHS-1-selective antibody (8223; Fig. 3B). The results
confirmed that PGHS-1 was present in all nonovarian tissues, and as
expected, the PGHS-2 signal present in follicle wall could not be
detected by the isoform-1-specific antibody (Fig. 3, A and B).
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). No PGHS-2 was detected in isolated
preparations of theca interna (Fig. 4, A and C). The lower PGHS-2 band
(60,000 Mr) appeared more intense in granulosa cells than
in follicle wall and probably resulted from degradation of the intact
protein during the isolation of each cell type.
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). In contrast, an
intense PGHS-2 staining was detected in granulosa cells, but not in
theca interna, when follicles were isolated 36 h post-hCG
treatment (Fig. 5, B and C). The staining in some cells was
particularly strong in the perinuclear region (Fig. 5C). No staining
was observed when adjacent sections of follicles isolated 36 h
post-hCG treatment were first incubated with PBS alone (data not shown)
or with a PGHS-1-selective antibody (Fig. 5D).
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). However, a
marked and significant increase in follicular fluid concentrations of
PGE2 and PGF was observed in follicles isolated 36 and
39 h after hCG treatment (Fig. 6). Levels of PGE2 and
PGF increased from 0.66 ± 0.13 and 0.05 ± 0.01 ng/ml to
39.6 ± 15.3 and 9.9 ± 2.7 ng/ml between 0 and 36 h
post-hCG treatment, respectively (P < 0.01).
Follicular fluid concentrations of PGE2 and PGF at 39
h were not significantly different from those 36 h post-hCG
treatment (P > 0.05; Fig. 6).
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shows the relationship among the time
of PGHS-2 induction, the time of ovulation, and the length of the
ovulatory process in all three species. The results clearly indicate a
direct relationship between the time course of PGHS-2 induction and the
length of the ovulatory process. A species with a short ovulatory
process, such as the rat, shows a very rapid induction of PGHS-2 after
hCG treatment (4 h post-hCG) (13). In contrast, there is a marked delay
in PGHS-2 induction in species with a long ovulatory process, such as
cows (18 h post-hCG) (12) and mares (30 h post-hCG) (this study).
Interestingly, despite these marked differences in the time course of
PGHS-2 induction in species with a short vs. a long
ovulatory process, the interval from PGHS-2 induction to ovulation is
remarkably conserved across species (10 h; Fig. 7).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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This study is also the first to report the presence and regulation of PGHS enzymes in the equine species. The characteristics of equine PGHS-1 and PGHS-2 were similar to those of other species (13, 17, 18, 31, 34, 35, 36, 37). PGHS-1 was constitutively expressed, although at different levels, in a variety of tissues in the normal animal. In contrast, PGHS-2 expression was more restricted and detected only in preovulatory follicles after hCG treatment. A small difference in Mr was observed between the two isoforms, with PGHS-2 (72,000 Mr) being slightly larger than PGHS-1 (70,000 Mr) as observed in other species (12, 22, 31). The smaller 60,000 Mr band detected in association with the intact PGHS-2 band (72,000 Mr) probably corresponds to a breakdown fragment of the protein, as observed in rat and bovine follicles (12, 21). In this study, the increased intensity of the 60,000 Mr band in extracts of granulosa cells vs. follicle wall suggests that the intact protein was adversely affected by the additional manipulations needed for the isolation of granulosa cells. The immunohistochemical localization of PGHS-2 identified an intense staining in the perinuclear region of some granulosa cells. This subcellular localization of PGHS-2 has been reported in mouse 3T3 fibroblasts (38).
The length of the ovulatory process varies remarkably across species,
lasting about 14 h in rats (39), 28–30 h in cattle (40), 36
h in humans (41), and 36–48 h in horses (10). Yet, the molecular basis
for this difference remains completely unresolved. One striking result
of this study is the distinct time course of PGHS-2 induction observed
in equine follicles compared with those reported in other species.
Using the hCG-induced ovulation model, expression of PGHS-2 in equine
follicles (30 h post-hCG) occurred 12 and 26 h later than that in
bovine (18 h post-hCG) or rat (4 h post-hCG) follicles, respectively
(12, 13). Collectively, these studies clearly indicate that the control
of PGHS-2 expression is related to the species-specific length of the
ovulatory process, with PGHS-2 induction being progressively delayed in
species with longer ovulatory processes. Interestingly, the interval
from PGHS-2 induction to follicular rupture is remarkably similar
across species (10 h), which suggests that the cascade of events
triggered by the induction of PG synthesis and leading to follicular
rupture is highly conserved across species. Therefore, these results
identify the induction of PGHS-2 as a determining point in the
progression of the ovulatory process, with variations in the length of
the ovulatory process among species being attributed to events
occurring before, and not after, PGHS-2 induction.
The molecular basis for the marked differences in the time course of
PGHS-2 induction in species with a short vs. a long
ovulatory process has not been determined. It is puzzling to consider
that it takes only 4 h to induce PGHS-2 in rat preovulatory
follicles (12), while the same agonist requires 30 h to have the
same effect in equine follicles. Differences in the activation of
second messenger systems and/or in the regulation of gene transcription
are probably involved. Studies in rats have identified some of the
molecular mechanisms involved in the rapid regulation of PGHS-2 in
granulosa cells (24, 42, 43, 44, 45, 46). Multiple signaling pathways are involved,
including primarily the protein kinase A pathway, but also protein
kinase C and tyrosine kinases (24, 42, 43, 44, 45, 46). The rapid induction is
dependent on transcriptional (-amanitin-sensitive) and
translational/posttranslational (cycloheximide-sensitive) controls
(43). The promoter of the rat PGHS-2 gene has been isolated (44), and
its characterization has identified consensus CAAT box and E box
cis-acting elements as putative modulators of PGHS-2 gene
expression by gonadotropins in granulosa cells (45, 46). Comparative
studies in monoovulatory species with a long ovulatory process have not
been reported, but will be needed to unravel the basis for
species-specific control of PGHS-2 induction in granulosa cells.
In summary, this study showed that the marked increase in PG synthesis
in equine follicles before ovulation was associated with a
time-dependent and granulosa cell-specific induction of PGHS-2 by
gonadotropins. The induction occurred 30 h after hCG treatment,
which is clearly distinct from that observed in rat (4 h post-hCG) and
bovine (18 h post-hCG) preovulatory follicles. However, the interval
from PGHS-2 induction to follicular rupture (10 h) was similar to
that observed in species with shorter ovulatory processes. Therefore,
the relatively late induction of PGHS-2 in mares supports its role
as a molecular determinant of the species-specific length of the
ovulatory process.
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Acknowledgments |
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Footnotes |
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Received June 3, 1997.
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References |
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receptor in bovine preovulatory follicles. Endocrinology 137:3348–3355[Abstract]
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S. M. Quirk, R. G. Cowan, and R. M. Harman Progesterone Receptor and the Cell Cycle Modulate Apoptosis in Granulosa Cells Endocrinology, November 1, 2004; 145(11): 5033 - 5043. [Abstract] [Full Text] [PDF]
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 J. Sirois, K. Sayasith, K. A. Brown, A. E. Stock, N. Bouchard, and M. Dore Cyclooxygenase-2 and its role in ovulation: a 2004 account Hum. Reprod. Update, September 1, 2004; 10(5): 373 - 385. [Abstract] [Full Text] [PDF]
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 M. W. Peters, J. R. Pursley, and G. W. Smith Inhibition of intrafollicular PGE2 synthesis and ovulation following ultrasound-mediated intrafollicular injection of the selective cyclooxygenase-2 inhibitor NS-398 in cattle J Anim Sci, June 1, 2004; 82(6): 1656 - 1662. [Abstract] [Full Text] [PDF]
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K. A. Brown, D. Boerboom, N. Bouchard, M. Dore, J. G. Lussier, and J. Sirois Human Chorionic Gonadotropin-Dependent Regulation of 17{beta}-Hydroxysteroid Dehydrogenase Type 4 in Preovulatory Follicles and Its Potential Role in Follicular Luteinization Endocrinology, April 1, 2004; 145(4): 1906 - 1915. [Abstract] [Full Text] [PDF]
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D. Boerboom, K. A. Brown, D. Vaillancourt, P. Poitras, A. K. Goff, K. Watanabe, M. Dore, and J. Sirois Expression of Key Prostaglandin Synthases in Equine Endometrium During Late Diestrus and Early Pregnancy Biol Reprod, February 1, 2004; 70(2): 391 - 399. [Abstract] [Full Text] [PDF]
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E. Segi, K. Haraguchi, Y. Sugimoto, M. Tsuji, H. Tsunekawa, S. Tamba, K. Tsuboi, S. Tanaka, and A. Ichikawa Expression of Messenger RNA for Prostaglandin E Receptor Subtypes EP4/EP2 and Cyclooxygenase Isozymes in Mouse Periovulatory Follicles and Oviducts During Superovulation Biol Reprod, March 1, 2003; 68(3): 804 - 811. [Abstract] [Full Text] [PDF]
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A. E. Stock, N. Bouchard, K. Brown, A. P. Spicer, C. B. Underhill, M. Dore, and J. Sirois Induction of Hyaluronan Synthase 2 by Human Chorionic Gonadotropin in Mural Granulosa Cells of Equine Preovulatory Follicles Endocrinology, November 1, 2002; 143(11): 4375 - 4384. [Abstract] [Full Text] [PDF]
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 D. M. Duffy and R. L. Stouffer Follicular administration of a cyclooxygenase inhibitor can prevent oocyte release without alteration of normal luteal function in rhesus monkeys Hum. Reprod., November 1, 2002; 17(11): 2825 - 2831. [Abstract] [Full Text] [PDF]
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 S. Lajoie, J. Sirois, and M. Dore Induction of Cyclo-oxygenase-2 Expression in Naturally Occurring Gastric Ulcers J. Histochem. Cytochem., July 1, 2002; 50(7): 923 - 934. [Abstract] [Full Text] [PDF]
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C. M. Komar, O. Braissant, W. Wahli, and T. E. Curry Jr. Expression and Localization of PPARs in the Rat Ovary During Follicular Development and the Periovulatory Period Endocrinology, November 1, 2001; 142(11): 4831 - 4838. [Abstract] [Full Text] [PDF]
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D. M. Duffy and R. L. Stouffer The ovulatory gonadotrophin surge stimulates cyclooxygenase expression and prostaglandin production by the monkey follicle Mol. Hum. Reprod., August 1, 2001; 7(8): 731 - 739. [Abstract] [Full Text] [PDF]
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E. M. P. de Almeida, C. Piche, J. Sirois, and M. Dore Expression of Cyclo-oxygenase-2 in Naturally Occurring Squamous Cell Carcinomas in Dogs J. Histochem. Cytochem., July 1, 2001; 49(7): 867 - 876. [Abstract] [Full Text] [PDF]
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H. Matsumoto, W.-g. Ma, W. Smalley, J. Trzaskos, R. M. Breyer, and S. K. Dey Diversification of Cyclooxygenase-2-Derived Prostaglandins in Ovulation and Implantation Biol Reprod, May 1, 2001; 64(5): 1557 - 1565. [Abstract] [Full Text]
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J. Liu, M. Antaya, D. Boerboom, J. G. Lussier, D. W. Silversides, and J. Sirois The Delayed Activation of the Prostaglandin G/H Synthase-2 Promoter in Bovine Granulosa Cells Is Associated with Down-regulation of Truncated Upstream Stimulatory Factor-2 J. Biol. Chem., December 3, 1999; 274(49): 35037 - 35045. [Abstract] [Full Text] [PDF]
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 C. Tremblay, M. Dore, P. N. Bochsler, and J. Sirois Induction of Prostaglandin G/H Synthase-2 in a Canine Model of Spontaneous Prostatic Adenocarcinoma J Natl Cancer Inst, August 18, 1999; 91(16): 1398 - 1403. [Abstract] [Full Text] [PDF]
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B. J. Davis, D. E. Lennard, C. A. Lee, H. F. Tiano, S. G. Morham, W. C. Wetsel, and R. Langenbach Anovulation in Cyclooxygenase-2-Deficient Mice Is Restored by Prostaglandin E2 and Interleukin-1{beta} Endocrinology, June 1, 1999; 140(6): 2685 - 2695. [Abstract] [Full Text]
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 A. F. de Arriba, F. Cavalcanti, A. Miralles, Y. Bayón, A. Alonso, M. Merlos, J. García-Rafanell, and J. Forn Inhibition of Cyclooxygenase-2 Expression by 4-Trifluoromethyl Derivatives of Salicylate, Triflusal, and Its Deacetylated Metabolite, 2-Hydroxy-4-trifluoromethylbenzoic Acid Mol. Pharmacol., April 1, 1999; 55(4): 753 - 760. [Abstract] [Full Text]
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A. Kerban, D. Boerboom, and J. Sirois Human Chorionic Gonadotropin Induces an Inverse Regulation of Steroidogenic Acute Regulatory Protein Messenger Ribonucleic Acid in Theca Interna and Granulosa Cells of Equine Preovulatory Follicles Endocrinology, February 1, 1999; 140(2): 667 - 674. [Abstract] [Full Text]
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M. Mikuni, M. Pall, C.M. Peterson, C.A. Peterson, P. Hellberg, M. Brännström, J.S. Richards, and L. Hedin The Selective Prostaglandin Endoperoxide Synthase-2 Inhibitor, NS-398, Reduces Prostaglandin Production and Ovulation In Vivo and In Vitro in the Rat Biol Reprod, November 1, 1998; 59(5): 1077 - 1083. [Abstract] [Full Text]
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D. Boerboom and J. Sirois Molecular Characterization of Equine Prostaglandin G/H Synthase-2 and Regulation of Its Messenger Ribonucleic Acid in Preovulatory Follicles Endocrinology, April 1, 1998; 139(4): 1662 - 1670. [Abstract] [Full Text] [PDF]
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J. S. Richards Editorial: Sounding the Alarm--Does Induction of Prostaglandin Endoperoxide Synthase-2 Control the Mammalian Ovulatory Clock? Endocrinology, October 1, 1997; 138(10): 4047 - 4048. [Full Text] [PDF]
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F. Filion, N. Bouchard, A. K. Goff, J. G. Lussier, and J. Sirois Molecular Cloning and Induction of Bovine Prostaglandin E Synthase by Gonadotropins in Ovarian Follicles Prior to Ovulation in Vivo J. Biol. Chem., August 31, 2001; 276(36): 34323 - 34330. [Abstract] [Full Text] [PDF]
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