Biomedical subjects

M Doré

Publications and source records attributed to M Doré.

At least 19 recordsLinked to original sources

PubMed2006

Cyclooxygenase-2 expression in normal and neoplastic canine mammary cell lines.

Mammary cancer is the most common cancer in female dogs. Induction of cyclooxygenase-2 (COX-2), a key enzyme in prostaglandins (PGs) biosynthesis, has been demonstrated in various cancers in humans and dogs, including mammary cancer. The objective of this study was to investigate the expression and regulation of COX-2 in canine mammary epithelial cells. Cell lines derived from normal and neoplastic canine mammary glands were cultured in the absence or presence of phorbol 12-myristate 13-acetate (PMA), and immunoblots, immunocytochemistry, radioimmunoassays, and a cell proliferation assay were used to study COX-2 expression and PGs production. Results showed that the neoplastic cell line CMT12 constitutively overexpressed COX-2 protein whereas other mammary cell lines expressed low to undetectable basal levels of COX-2 protein. Basal PGE(2) production was significantly higher (P < .05) in CMT12 compared to other cell lines. Levels of COX-2 protein in CMT12 decreased in a time-dependent manner with serum starvation, and PMA stimulation induced a strong time-dependent increase in COX-2 protein. Treatment of CMT12 cells with NS-398 (a specific COX-2 inhibitor) significantly blocked PGE(2) synthesis and reduced cell proliferation (P < .05). These results indicate that some neoplastic canine mammary cell lines constitutively overexpress COX-2, and that COX-2 inhibition decreases PGE(2) production and cell proliferation, supporting a role for COX-2 and PGs in canine mammary oncogenesis.

Animals↗

PubMed2006

Human chorionic gonadotropin-dependent induction of an equine aldo-keto reductase (AKR1C23) with 20alpha-hydroxysteroid dehydrogenase activity during follicular luteinization in vivo.

Aldo-keto reductases (AKRs) are multifunctional enzymes capable of acting on a wide variety of substrates, including sex steroids. AKRs having 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) activity can reduce progesterone to 20alpha-hydroxy-4-pregnen-3-one (20alpha-DHP), a metabolite with lower affinity for the progesterone receptor. The objective of this study was to investigate the regulation of equine AKR1C23 during human chorionic gonadotropin (hCG)-induced ovulation/luteinization. The equine AKR1C23 cDNA was cloned and shown to encode a 322 amino acid protein that is conserved (71-81% identity) when compared with mammalian orthologs. RT-PCR/Southern blotting analyses were performed to study the regulation of AKR1C23 transcripts in equine preovulatory follicles isolated between 0 and 39 h after hCG treatment (ovulation occurring 39-42 h post-hCG). Results showed the presence of low AKR1C23 expression before hCG treatment, but a marked increase was observed in follicles obtained 12 h after hCG (P<0.05). Analyses of isolated preparations of granulosa and theca interna cells identified low mRNA expression in both cell types prior to hCG treatment, with granulosa cells clearly being the predominant site of follicular AKR1C23 mRNA induction. A specific polyclonal antibody was raised against a fragment of the equine protein and immunoblotting analyses showed an increase in AKR1C23 protein in granulosa cell extracts when comparing follicles isolated at 36 h post-hCG vs those collected prior to treatment, in keeping with mRNA results. Immunohistochemical data confirmed the induction of the enzyme in follicular cells after hCG treatment. The enzyme was tested for 20alpha-HSD activity and was shown to exhibit a K(M) of 3.12 microM, and a V(max) of 0.86 pmol/min per 10 microg protein towards progesterone. The levels of 20alpha-DHP measured in follicular fluid reflected this activity. Collectively, these results demonstrate for the first time that the gonadotropin-dependent induction of follicular luteinization is accompanied by an increase in AKR1C23 expression. Considering the 20alpha-HSD activity of AKR1C23, its regulated expression in luteinizing preovulatory follicles may provide a biochemical basis for the increase in ovarian 20alpha-DHP observed during gonadotropin-induced luteinization/ovulation. (The nucleotide sequence reported in this paper has been submitted to GenBank with accession number AY955082.).

20-Hydroxysteroid Dehydrogenases↗

PubMed2005

Estrogen-dependent induction of cyclooxygenase-2 in the canine prostate in vivo.

Cyclooxygenase (COX)-2 is involved in several physiologic and pathologic processes. COX-2 is overexpressed in human and canine prostate cancer, but little is known about COX-2 inducers in the prostate. Our objective was to investigate the effect of sex steroid hormones on COX-2 expression in the canine prostate in vivo. COX-2 expression was evaluated by immunohistochemistry in intact and castrated dogs treated with exogenous androgen or estrogen. Results showed that no COX-2 staining was observed in prostates of untreated or androgen-treated castrated or intact dogs. However, treatment of intact and castrated dogs with estrogen resulted in squamous metaplasia with intense COX-2 expression observed in both squamous epithelial cells and in cells of acini without metaplasia. This is the first report to demonstrate the induction of COX-2 by estrogen in the prostate in vivo.

Androstane-3,17-diol↗

PubMed2003

Up-regulation of ICAM-1, CD11a/CD18 and CD11c/CD18 on human THP-1 monocytes stimulated by Streptococcus suis serotype 2.

Streptococcus suis serotype 2 is known to be a major pathogen of swine, causing mainly meningitis. It is also a zoonotic agent leading predominantly to meningitis in humans working in close contact with pigs. In this study, we investigated the ability of S. suis to up-regulate the expression of adhesion molecules involved in inflammation, using an enzyme-linked immunosorbent assay. S. suis serotype 2 stimulated the up-regulation of the expression of intercellular adhesion molecule-1 (ICAM-1, CD54), CD11a/CD18 and CD11c/CD18 on human THP-1 monocytes, but did not change that of ICAM-1, vascular cell adhesion molecule-1 (VCAM-1, CD106) and E-selectin (CD62E) on human endothelial cells. The up-regulation of adhesion molecules was time- and bacterial concentration-dependent, and cell wall components were largely responsible for such stimulation. To a lesser extent, purified haemolysin of S. suis also stimulated adhesion molecule expression. Stimulation of monocytes with strains of different origin showed that there was no clear tendency for human strains to induce a higher expression of adhesion molecules than strains from diseased pigs. Finally, monocytes stimulated with S. suis also showed an increase in adherence to endothelial cells. Hence, S. suis is capable of up-regulating important adhesion molecules involved in inflammation, which may result in an increased leucocyte recruitment into sites of infection, thus providing a possible mechanism for some of the inflammatory features of meningitis caused by this pathogen.

Antigens, CD↗

PubMed2003

Cyclooxygenase-2 expression in canine mammary tumors.

Mammary tumors are the most common neoplasms in female dogs. Induction of cyclooxygenase-2 (COX-2) has been implicated in various cancers in humans. However, expression of COX-2 has not been investigated in canine mammary tumors. Normal mammary gland (n = 4), simple or complex adenomas (n = 63), and simple or complex adenocarcinomas (n = 84) were studied by immunohistochemistry. Results showed that COX-2 was not expressed in the normal gland but was detected in 24% of adenomas and in 56% of adenocarcinomas (P < 0.001). The incidence of COX-2 expression and the intensity of the COX-2 signal were higher in adenocarcinomas than in adenomas (P < 0.001). These results demonstrate for the first time that COX-2 is induced in a proportion of canine mammary tumors and that COX-2 expression is more frequent and more intense in malignant than in benign tumors, suggesting a potential role for COX-2 in canine mammary tumorigenesis.

Adenocarcinoma↗

PubMed2001

Expression of cyclo-oxygenase-2 in naturally occurring squamous cell carcinomas in dogs.

Squamous cell carcinoma is one of the most common cancers in humans and is also a frequently diagnosed neoplasm in dogs. Induction of cyclo-oxygenase-2 (COX-2), a key rate-limiting enzyme in prostaglandin biosynthesis, has been implicated in the oncogenesis of various cancers in humans, including squamous cell carcinomas. However, expression of COX-2 has not been reported in spontaneous squamous cell carcinomas of non-human species. Canine squamous cell carcinomas share several similarities with the human disease. Therefore, the objective of this study was to determine whether COX isoenzymes were expressed in naturally occurring cases of squamous cell carcinomas in dogs. Canine normal skin (n=4) and squamous cell carcinomas (n=40) were studied by immunohistochemistry and immunoblotting analysis using polyclonal antibodies selective for COX-1 or COX-2. COX-2 was strongly expressed by neoplastic keratinocytes in all cases of squamous cell carcinomas, whereas no COX-2 was detected in normal skin and in the non-neoplastic skin and oral mucosa included in the tumor tissue samples (p<0.01). Immunoblotting analysis confirmed the restricted expression of COX-2 (72,000--74,000 molecular weight doublet) in squamous cell carcinomas only. In contrast, faint COX-1 staining was found in normal skin and in squamous cell carcinomas. This study demonstrates for the first time that COX-2 is induced in canine squamous cell carcinomas, and provides a new model to investigate the role and regulation of COX-2 gene expression in naturally occurring squamous cell carcinomas. (J Histochem Cytochem 49:867-875, 2001)

Animals↗

PubMed2001

Expression of E- and P-selectin in tumor necrosis factor-induced dermatitis in dogs.

Adhesion molecules on endothelial cells play an important role in leukocyte recruitment in several inflammatory processes. Vascular selectins mediate the initial adhesion of leukocytes to the blood vessel wall during their extravasation into inflamed tissues, and in vitro studies in dogs have shown that selectin expression can be induced by cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1). The objective of this study was to determine whether vascular selectins are induced by cytokines in vivo in a cutaneous model of inflammation in dogs. Skin biopsies were collected from nine dogs at various time points after an intradermal injection of TNF-alpha (10 ng/site) or phosphate-buffered saline containing 0.1% bovine serum albumin, and immunohistochemistry was performed using anti-P-selectin (MD3) and anti-E-selectin (CL37) monoclonal antibodies. In all animals, TNF-alpha induced an inflammatory reaction that was maximal at 12 hours and then decreased by 24 and 48 hours. Control skin displayed no expression of E- and P-selectin, whereas TNF-alpha induced the expression of P-selectin and E-selectin on dermal vessels that was highest at 12 hours and 3 hours, respectively (P < 0.05). Numerous platelet aggregates recognized by the anti-P-selectin antibody were present in the lumina of vessels and in perivascular tissues. These results demonstrate that TNF-alpha can induce the expression of P- and E-selectin in vivo in dog skin and suggest that these selectins are involved in leukocyte recruitment in canine dermatitis.

Animals↗

PubMed2001

Characterization of the inflammatory infiltrate in canine chronic hepatitis.

Canine chronic hepatitis (CCH) is a progressive inflammatory disease of unknown etiology. To characterize the inflammatory infiltrate, 16 dogs with CCH were selected and classified into three groups based on the stage of fibrosis, as evaluated with Masson's trichrome stain. The inflammatory infiltrate in each liver section was immunohistochemically characterized and evaluated using CD3, lysozyme, lamba and kappa light chain, and alpha-smooth muscle actin antibodies. Numerous breeds were affected, and middle-aged females predominated in this select group. Necroinflammatory activity progressively increased and then waned as the hepatitis progressed to cirrhosis. CD3+ lymphocytes were the most numerous lymphoid cells in dogs with CCH. Degenerate hepatocytes were occasionally surrounded by CD3+ lymphocytes. Necrosis was positively correlated with the number of CD3+ lymphocytes. The lamba and kappa light chain-positive cell infiltrate was variable but generally mild. A positive correlation between the lambda and kappa light chain-positive cells and the portal alpha-smooth muscle actin was found. The number of alpha-smooth muscle actin-positive cells (myofibroblasts) in portal triads and fibrous septa was positively correlated with the stage of fibrosis. In contrast, no correlation was found between the number of lysozyme-positive cells (Kupffer cells) and the stage of fibrosis. These results further support the idea of an immune-mediated process in CCH and suggest that periductular myofibroblasts play an important role in canine liver fibrogenesis.

Actins↗

PubMed2001

Uterine angiolipoleiomyoma in a dog.

An 11-year-old crossbred Pomeranian bitch displayed a large intramural, well-delineated uterine mass in one horn, near the junction with the uterine body. The mass was composed largely of mature adipose tissue, smooth muscle cells singly and in small clusters, anomalous medium-size and large arteries, and multifocal islands of cartilaginous and osseous tissues. Smooth muscle cells stained positively for desmin, and adipocytes and chondrocytes were positive for S-100 protein. This tumor has histologic and immunohistochemical features compatible with human uterine angiolipoleiomyoma, a rare tumor that has never been reported in the veterinary literature. This benign tumor is believed to be of a choristomatous nature.

Angiomyolipoma↗

PubMed2000

Fibroleiomyomas of the tubular genitalia in female beluga whales.

Fibroleiomyomas of the tubular genitalia were diagnosed in 6 of 9 adult female beluga whales from the St. Lawrence estuary, Quebec, Canada. These tumors were located in the vagina (6 of 6), the cervix (2 of 6), and the uterus (1 of 6). Endogenous hormones or xeno-estrogens may be implicated in the occurrence of these tumors.

Animals↗

PubMed1999

Induction of prostaglandin G/H synthase-2 in a canine model of spontaneous prostatic adenocarcinoma.

BACKGROUND: Prostate cancer is the most frequently occurring cancer in men in the United States, with an estimated 179 300 new cases in 1999. The induction of prostaglandin G/H synthase (PGHS), a key rate-limiting enzyme in prostaglandin biosynthesis, has been implicated in various cancers, most notably in colorectal cancers; however, the induction of PGHS expression in prostate cancer in vivo has not been reported for any species. The dog is the only nonhuman species that frequently develops spontaneous cancer of the prostate with increasing age, and the objective of this study was to determine whether PGHS isoenzymes were expressed in canine prostatic adenocarcinomas. METHODS: Four normal canine prostatic tissues and 24 canine prostatic adenocarcinomas were studied by means of immunohistochemistry and immunoblot analysis, using polyclonal antibodies specific for each of the two PGHS isoenzymes, PGHS-1 and PGHS-2. All P values were obtained by use of two-sided Fisher's exact tests. RESULTS: PGHS-1 immunostaining was localized to stromal fibroblasts and vascular endothelium in normal and cancerous prostates. PGHS-2 was not detected in normal prostates, but it was expressed by epithelial tumor cells in 18 (75%) of the 24 adenocarcinomas (P =.01). Immunoblot analysis confirmed the presence of PGHS-1 (69 000 molecular weight) in normal and cancerous tissues and the expression of PGHS-2 (72 000- to 74 000-molecular-weight doublet) only in prostatic adenocarcinomas. CONCLUSION: To our knowledge, these results demonstrate for the first time that PGHS-2 is induced in the majority of canine spontaneous prostatic adenocarcinomas and suggest that its expression may be involved in prostate cancer.

Adenocarcinoma↗

PubMed1999

Oral malignant melanoma with osteoid formation in a dog.

Melanomas are the most frequent malignant neoplasms of the oral cavity of dogs. Osteogenic melanoma is a rare variant of melanoma that has been described in humans but not in animals. We describe a case of malignant melanoma with bone production affecting the gingiva of a 12-year-old Miniature Dachshund dog. The tumor was a round, lightly pigmented mass that measured 1 cm in diameter and was hard to cut. Histologically, the tumor was composed of nests and lobules of anaplastic, round, melanin-containing cells supported by a stroma displaying abundant osteoid matrix. Many of the neoplastic melanocytic cells were in close contact with the osteoid trabeculae. Immunohistochemical tests revealed that the neoplastic cells were immunoreactive for S-100 and vimentin and showed no staining with cytokeratin. The animal had a local recurrence of the tumor 3 months after the initial excision. This is the first case of malignant melanoma with osteoid formation reported in animals.

Animals↗

PubMed1999

Characterization of cellular and vascular changes in equine follicles during hCG-induced ovulation.

In contrast to other species, the histology of the equine follicle during ovulation has not been described. Preovulatory follicles were isolated during oestrus at 0, 12, 24, 30, 33, 36 and 39 h (n = 5-6 follicles per time point) after an ovulatory dose of hCG to characterize the cellular and vascular changes associated with ovulation in mares. Pieces of follicle wall were formalin-fixed and processed for light microscopy to evaluate the general follicular morphology and quantify selected parameters. Marked changes were observed in the histology of equine follicles in the hours before ovulation. The thickness of the granulosa cell layer doubled between 0 and 39 h after hCG (77.8 +/- 4.8 versus 158.8 +/- 4.8 microns, respectively; P < 0.01). This expansion was caused primarily by a pronounced accumulation of acid mucosubstances between granulosa cells, which was first detected at 12 h after hCG and peaked at 36-39 h. In contrast, a significant thinning of the theca interna was observed after hCG treatment. Fewer cell layers were present; theca interna cells appeared smaller than before hCG; and the presence of occasional pyknotic cells was noted at 36 and 39 h after hCG. In addition, the theca layers were invaded by numerous eosinophils. No eosinophils were observed in preovulatory follicles isolated between 0 and 24 h after hCG, but the number increased to 14.0 +/- 0.8 and 5.6 +/- 0.3 eosinophils per field (x 400) in theca interna and theca externa, respectively, 39 h after hCG treatment (P < 0.01). Severe oedema, hyperaemia and haemorrhages, and significant increases in the number of blood vessels in theca interna and externa were observed at 33, 36 and 39 h after hCG. This study provides the first in-depth characterization of the sequential cellular and vascular changes that occur in equine follicles before ovulation.

Analysis of Variance↗

PubMed1998

Platelet-leukocyte interactions.

Platelet-leukocyte interactions may contribute to the development of several pathological conditions, including myocardial ischemic disorders. Using an in vitro system that simulates vascular flow conditions, we investigated platelet-neutrophil adhesion. Collagen-adherent platelets were shown to express P-selectin and were able to mediate the binding of flowing neutrophils. Some of the adherent neutrophils displayed signs of cellular activation. Flow cytometric analyses revealed that activation induced a rapid and marked reduction of the P-selectin ligand, with levels decreased by 71% after 15 minutes of stimulation. Using a visual assay of platelet-neutrophil rosetting, we showed that the P-selectin ligand was translocated and clustered at the uropod of neutrophils after the shape changes and polarization induced by stimulation. Activated neutrophils that were bound to surface-adherent platelets also displayed the clustering of P-selectin ligand at the uropod, and these neutrophils detached from the platelets when a shear stress was applied through the adhesion chamber. These results indicate that stimulation of neutrophils induces changes in the surface expression and distribution of the ligand for P-selectin, and that these changes might influence the adhesive interactions occurring between neutrophils and activated platelets.

Animals↗

PubMed1998

Expression of prostaglandin G/H synthase type 1, but not type 2, in human ovarian adenocarcinomas.

Prostaglandin endoperoxide synthase (PGHS) is a key rate-limiting enzyme in prostaglandin biosynthesis. PGHS has recently been shown to be expressed in human colorectal cancers and in experimental cutaneous papillomas and carcinomas. However, PGHS expression has not been investigated in ovarian cancers. The objectives of this study were to determine whether PGHS isoenzymes are expressed in human ovarian cancer and, if so, to identify which isoform is involved (PGHS-1 and/or PGHS-2) and to characterize its cellular localization. Sixteen human ovarian adenocarcinomas were studied by immunohistochemistry using specific antibodies recognizing PGHS-1 or PGHS-2. Results showed that all adenocarcinomas demonstrated the presence of tumor cells expressing PGHS-1 but not PGHS-2. Patterns of staining of tumor cells varied among different types of adenocarcinomas, with cells presenting either a mostly diffuse cytoplasmic immunoreactivity or, alternatively, a staining mainly concentrated around the nucleus. No correlation between the intensity of the immunostaining and the degree of malignancy of tumors could be established (r 5 20.03; p>0.05). Immunoblot analysis with PGHS-1-selective antibodies of cell extracts from adenocarcinomas revealed the presence of a characteristic 72,000 Mr immunoreactive band. Therefore, these results show for the first time that PGHS-1 is expressed in human ovarian adenocarcinomas. (J Histochem Cytochem 46:77-84, 1998)

Adenocarcinoma, Mucinous↗

PubMed1998

P-selectin expression in canine cutaneous inflammatory diseases and mast cell tumors.

P-selectin, a member of the selectin family of adhesion molecules, mediates the initial adhesion of leukocytes to the blood vessel wall during their emigration from the circulation. Adhesion molecules play an important role in the pathogenesis of several diseases, including various skin conditions. The objectives of the present study were to characterize the expression of vascular P-selectin in the skin of dogs suffering from inflammatory diseases or from common cutaneous neoplasms, and to determine if a correlation exists between P-selectin expression and inflammatory cell infiltration in these conditions. Immunohistochemistry was performed on formalin-fixed canine skin using a specific anti-canine P-selectin monoclonal antibody (MD3). Results showed that P-selectin was minimally expressed in normal canine skin. However, the number of P-selectin-expressing blood vessels was significantly increased (P < 0.05) in cases of allergic dermatitis, autoimmune dermatitis, pyogranulomatous dermatitis, dermatophytosis, and panniculitis. Highest P-selectin expression (percentage of MD3-positive vessels and intensity of the reaction) was observed in cases of autoimmune and pyogranulomatous dermatitis (55.3+/-7.4 and 44.0+/-9.9% P-selectin-positive vessels, respectively). In all conditions studied, a positive correlation existed between the number of P-selectin-positive blood vessels and the number of infiltrating leukocytes (r=0.556, P < 0.01). A significant number of blood vessels in mast cell tumors also expressed P-selectin, whereas no staining was observed in any of the histiocytomas examined. These results reveal that P-selectin expression is increased in different types of canine inflammatory skin diseases and suggest that P-selectin could participate in the local recruitment of leukocytes in canine cutaneous diseases.

Animals↗

PubMed1997

Prostaglandin G/H synthase-2 is expressed in bovine preovulatory follicles after the endogenous surge of luteinizing hormone.

To determine whether prostaglandin G/H synthase-2 (PGHS-2) induction occurs under physiological conditions, heifers were ovariectomized and preovulatory follicles were isolated 0 (n = 4), 18 (n = 4), and 24 h (n = 4) after the onset of estrus. The time of the LH surge was determined in blood samples collected every 4 h pre- and postestrus. Preparations of follicle wall and isolated theca interna and granulosa cells were analyzed for PGHS-2 protein and mRNA by immunoblot and Northern blot, respectively. Immunohistochemistry was used to document the in situ localization of PGHS-2 protein, and follicular fluid concentrations of prostaglandin (PG) E2 and PGF2alpha were determined to monitor changes in PG synthetic activities. Results showed that PGHS-2 mRNA (4.0 kilobases) and protein (74000 Mr) were absent in preovulatory follicles isolated at the onset of estrus, low in follicles obtained 18 h after estrus (16.0 +/- 1.2 h post-LH surge), and markedly induced 24 h postestrus (20 +/- 0 h post-LH surge). Immunoblot and immunohistochemical analyses revealed that PGHS-2 protein was selectively induced in granulosa cells. Follicular fluid concentrations of PGE2 and PGF2alpha increased significantly (p < 0.01) between 0 and 24 h after estrus (from 2.8 +/- 0.2 to 87.9 +/- 30.9 ng/ml for PGE2; from 0.05 +/- 0.02 to 68.9 +/- 23.6 ng/ml for PGF2alpha). Collectively, these results clearly demonstrate that the induction of PGHS-2 in bovine preovulatory follicles is a physiological event that occurs after the endogenous LH surge.

Animals↗

PubMed1997

The late induction of prostaglandin G/H synthase-2 in equine preovulatory follicles supports its role as a determinant of the ovulatory process.

PGs are important mediators of the ovulatory process and prostaglandin G/H synthase-2 (PGHS-2) is a key rate-limiting enzyme in the PG biosynthetic pathway. To determine whether PGHS-2 is regulated in equine follicles before ovulation and, if so, to characterize its time course of induction, preovulatory follicles were isolated during estrus, 0, 12, 24, 30, 33, 36, and 39 h after an ovulatory dose of hCG (n = 5 follicles/time point). Cellular extracts were obtained from preparations of follicle wall (theca interna with attached granulosa cells), isolated granulosa cells, and theca interna and were analyzed by Western blot using specific anti-PGHS antibodies. Immunohistochemistry was used to characterize the in situ localization of PGHS-2 protein in preovulatory follicles, and follicular fluid concentrations of PGE2 and PGF were determined. The results showed the induction of PGHS-2, but not PGHS-1, in equine follicles before ovulation. The PGHS-2 protein (72,000 mol wt) was undetectable 0, 12, and 24 h post-hCG, first became apparent at 30 h, and reached maximal levels 39 h after hCG treatment. The induction of follicular PGHS-2 was localized exclusively in granulosa cells, and a pronounced staining was observed in the perinuclear region. Follicular fluid concentrations of PGE2 and PGF were low and not different between 0-33 h, but levels were increased at 36 and 39 h post-hCG (P < 0.01). Thus, the time course of PGHS-2 induction in equine follicles (30 h post-hCG) is clearly distinct from those previously observed in rat (4 h post-hCG) and bovine (18 h post-hCG) preovulatory follicles. Interestingly, in all three species, the interval from PGHS-2 induction to follicular rupture is highly conserved (approximately 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.

Analysis of Variance↗