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S A Meyers

Publications and source records attributed to S A Meyers.

At least 19 recordsLinked to original sources
PubMed2005

Equine sperm membrane phase behavior: the effects of lipid-based cryoprotectants.

The plasma membrane of sperm can undergo lipid phase separation during freezing, resulting in irreversible damage to the cell. The objective of our study was to examine the membrane phase behavior of equine spermatozoa in the absence and presence of lipid-based cryoprotectants. Biophysical properties of sperm membranes were investigated with Fourier-transform infrared spectroscopy. Compared to fresh untreated sperm, postthaw untreated sperm showed extensive lipid phase separation and rearrangement. In contrast, postthaw sperm that were cryopreserved in egg phosphatidylcholine (egg PC)- or soy phosphatidylcholine (soy PC)-based diluents showed similar lipid phase behavior to that of fresh, untreated sperm. Studies with a deuterium-labeled PC lipid (POPCd-31) suggest that exogenous lipid from the diluents are strongly associated with the sperm membrane, and scanning electron microscopy images of treated sperm show the presence of lipid aggregates on the membrane surface. Thus, the exogenous lipid does not appear to be integrated into the sperm membrane after cryopreservation. When compared to a standard egg-yolk-based diluent (INRA 82), the soy and egg PC media preserved viability and motility equally well in postthaw sperm. A preliminary fertility study determined that sperm cryopreserved in the soy PC-based medium were capable of fertilization at the same rate as sperm frozen in the conventional INRA 82 medium. Our results show that pure lipid-based diluents can prevent membrane damage during cryopreservation and perform as well as a standard egg-yolk-based diluent in preserving sperm viability, motility, and fertility.

Animals↗
PubMed2005

Capacitation-like changes in equine spermatozoa following cryopreservation.

The primary objective of this study was to assess plasma membrane characteristics and activation of signal transduction pathways in equine spermatozoa during both in vitro capacitation and cryopreservation. Significant plasma membrane restructuring, as assessed by measurement of plasma membrane lipid disorder and phospholipid scrambling, was not observed until after cryopreservation and subsequent thawing (P < 0.05). Although in vitro capacitated cells also displayed increased plasma membrane lipid disorder and phospholipid scrambling (P < 0.05), it appeared that regulation of these events in in vitro capacitated versus cryopreserved equine spermatozoa was not identical. Addition of 5 microM staurosporine to the capacitation media reduced plasma membrane phospholipid scrambling (P < 0.05), but supplementation to the freezing extender prior to cryopreservation did not. Furthermore, progesterone was able to induce a greater degree of acrosomal exocytosis in in vitro capacitated versus frozen/thawed spermatozoa. Expression of phospholipid scramblase, a protein thought to be important in plasma membrane phospholipid scrambling, did not differ between treatments. Comparison of protein tyrosine phosphorylation patterns between in vitro capacitated and cryopreserved cells demonstrated a divergence in signal transduction. Cellular signaling in in vitro capacitated equine spermatozoa appeared to be in part dependent on activation of the cAMP/PKA pathway, whereas signaling in cryopreserved cells seemed to proceed predominantly through alternative pathways. Taken together, these data support the idea that capacitation and "cryocapacitation" are not equivalent processes.

Animals↗
PubMed2005

Spermatozoal response to osmotic stress.

The process of sperm cryopreservation imparts on sperm cells the stress of low-temperature and drastic osmotic change. Damage to the cell plasma membrane results in cell injury in a number of cellular structures and associated functions. Studies in the author's laboratory have focused upon the various mechanisms of osmotic and thermal injury including plasma membrane lipid structure, mitochondrial membrane potential, and intracellular signaling. We have determined that cryoinjury to sperm, as for somatic cells, is a multi-factorial event and some of these events are reversible while some are not.

Animals↗
PubMed2002

Immunological response of female macaques to the PH-20 sperm protein following injection of recombinant proteins or synthesized peptides.

Because of its location on the sperm surface and its multiple functions during fertilization, the PH-20 protein is a potential target for contraceptive vaccines. Cynomolgus macaques were immunized using four different adjuvants together with synthesized peptides or recombinant proteins representing selected regions of macaque PH-20. The synthesized peptide (amino acids 387-412, designated Peptide 4) was used as a linear molecule in a 1:1 ratio with a peptide sequence of tetanus toxoid, as well as a multiple antigenic peptide (MAP) matrix held together by scaffolding lysine residues. In the MAP construct, the ratio of Peptide 4 to tetanus peptide was 4:1. To circumvent the poor production of recombinant PH-20 in bacterial cells, two truncated forms of the molecule were expressed in Escherichia coli, G18 (encoding amino acids 143-510) and E10 (encoding amino acids 291-510). The adjuvants were Montanide ISA 51, Titermax Gold, Syntex adjuvant formulation (SAF), and QS-21. All of the antigen/adjuvant combinations produced significant immune responses as measured by ELISA. The circulating antibodies from immunized animals recognized macaque sperm surface PH-20 on Western blots and were shown by indirect immunofluorescence to bind to the surface of macaque sperm. Montanide and Titermax were associated with higher titers of anti-PH-20 antibodies than QS-21 and SAF adjuvants. Immunization with Titermax, however, resulted in sterile abscesses in 4 of 8 animals injected. We conclude that antigens derived from synthesized peptides and recombinant proteins representing selected regions of the PH-20 molecule can be used as vaccine components in combination with the adjuvant Montanide to elicit a significant sperm-directed antibody response in immunized macaques.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed2001

Equine sperm-oocyte interaction: the role of sperm surface hyaluronidase.

The plasma membrane over the sperm head of several mammalian species has been shown to express a glycerolphosphatidylinositol-linked hyaluronidase known as PH-20. This protein has been associated with the sperm's interaction with the oocyte cumulus matrix and zona pellucida. The characteristics of PH-20 in equine sperm have not been clearly defined. In this study, ejaculated gel-free semen from five stallions and epididymal sperm from isolated epididymis from 10 stallions was used to characterize the PH-20 activity in equine sperm. Affinity purified anti-equine PH-20 polyclonal antibody was used to immunodetect sperm surface-associated PH-20 and immunolabel whole sperm. The intracellular calcium indicator, Fluo-3, was used to assess sperm intracellular calcium. Stallion sperm express a surface-associated hyaluronidase localized to the posterior sperm head region in ejaculated sperm. Following in vitro capacitation and acrosomal exocytosis, the inner acrosomal membrane (IAM) displays intense hyaluronidase fluorescence suggesting that the IAM and hyaluronidase plays a significant role in zona penetration by sperm. Sperm incubated in hyaluronan (HA)-containing capacitation medium display an elevated intracellular calcium concentration (P<0.01) that is associated with translocation of PH-20 antigenic sites on the sperm surface in addition to increases in protein tyrosine phosphorylation. Caput- and cauda-derived sperm display developmentally unique PH-20 immunofluorescence expression patterns. These data suggest that the differential expression of PH-20 in ejaculated and epididymal sperm could be involved in cumulus penetration, sperm-egg recognition, and oolemmal fusion in this species.

Acrosome Reaction↗
PubMed2001

Posttranslational processing of PH-20 during epididymal sperm maturation in the horse.

It is generally accepted that spermatozoa become functionally mature during epididymal transit. The objective of this study was to determine whether the cellular location of equine PH-20 is modified during epididymal transit and, if so, the mechanism for such modification. Sperm were isolated from caput and cauda epididymal regions from stallions undergoing castration (n = 7) and used as whole sperm cell or subjected to nitrogen cavitation for isolation of plasma membrane proteins. Both caput and cauda sperm and sperm protein extracts were subjected to N-deglycosylation, O-deglycosylation, or trypsinization. The SDS-PAGE and Western blot analysis using a polyclonal anti-equine PH-20 IgG were performed in sperm extracts, and indirect immunofluorescence on whole sperm was also performed to determine the cellular distribution of plasma membrane PH-20 following similar treatments (deglycosylation or trypsinization). Hyaluronan substrate gel electrophoresis was performed to detect hyaluronidase activity in SDS-PAGE proteins. Western blots revealed significant differences in electrophoretic migration of PH-20 proteins from caput and cauda epididymal sperm. No effect was seen from deglycosylation treatments on the Western blot pattern; caput protein extracts exposed to trypsin showed the same band pattern as extracts from the cauda epididymis. N-deglycosylation resulted in the loss of hyaluronidase activity of sperm from both epididymal regions, whereas O-deglycosylation or trypsinization did not affect hyaluronidase activity. In caput epididymal sperm, the PH-20 protein is distributed over the entire sperm head; in cauda epididymal sperm, it is restricted to the postacrosomal region. No effect from deglycosylation on the cellular distribution of PH-20 was observed; however, treatment with trypsin changed the cellular distribution of PH-20 in caput sperm similar to that of the distribution of cauda sperm. These results suggest that PH-20 distribution during epididymal maturation is dependent on proteolytic trypsin-like mechanisms and, possibly, on complementary membrane-associated factors.

Animals↗
PubMed2001

Effects of vitamin D (calcitriol) on transitional cell carcinoma of the bladder in vitro and in vivo.

PURPOSE: Vitamin D (calcitriol) has significant antiproliferative effects on various tumor cells in vitro and in vivo. In the clinical situation a major impediment to systemic administration of calcitriol is the side effect of hypercalcemia. To test the potential usefulness of calcitriol for bladder cancer treatment, we studied the antiproliferative effect of vitamin D on 2 human bladder cancer cell lines, 253j and T-24, in vitro. We also examined the in vivo effects of calcitriol in an animal model of bladder cancer using intravesical administration to avoid the toxicity of systemic calcitriol therapy. MATERIALS AND METHODS: The presence of vitamin D receptors in normal and neoplastic human bladder tissue, and tumor cells T-24 and 253j was determined by immunoblot analysis. Tumor cell proliferation in the presence or absence of calcitriol was determined using a crystal violet assay. Calcitriol induced apoptosis was determined by morphology, polyadenosine diphosphate ribose polymerase cleavage and annexin V binding. In vivo studies were performed by weekly intravesical instillation of calcitriol in female Fischer 344 rats after induction of tumors by N-methyl nitrosourea. Calcitriol administration was started 3 weeks after tumor induction for 7 doses at weekly intervals. RESULTS: Normal and neoplastic human bladder tissue, and the cell lines expressed vitamin D receptors. In the 253j and T-24 cell lines proliferation was significantly inhibited by calcitriol. Progressive cleavage of full length polyadenosine diphosphate ribose polymerase was observed in calcitriol treated cells starting as early as 4 hours after exposure. Similar changes were not observed in the control cells treated with vehicle (ethanol) alone. After 24 hours of treatment with calcitriol 45.8% of 253j cells bound annexin compared to 16.5% of control cells (chi-square p <0.001). Of the control animals 66% developed bladder tumors and 55% of the animals treated with calcitriol early (3 weeks) after tumor induction developed bladder tumors. Almost all of the tumors that developed in the calcitriol group were unifocal, and only 20% were invasive compared to 50% of those in the control animals. CONCLUSIONS: These results demonstrate that calcitriol inhibits proliferation and induces apoptosis in human bladder tumor cells in vitro, and may have therapeutic potential in bladder cancer. In vivo studies using an N-methylnitrosourea induced model of bladder cancer demonstrate that early institution of intravesical calcitriol therapy after carcinogen exposure results in fewer tumors, which are also less likely to be multifocal, high grade or invasive. With our protocol a short course of intravesical calcitriol administration did not result in any significant toxicity.

Administration, Intravesical↗
PubMed2000

Urothelial pathophysiological changes in feline interstitial cystitis: a human model.

Unique barrier properties of the urothelial surface membrane permit urine storage. Interstitial cystitis causes disabling dysuria, and frequency. Similarly, feline interstitial cystitis (FIC) occurs in cats. These studies define the permeability and structural properties of normal and FIC urothelium. To determine the effects of bladder filling, groups were studied before and after hydrodistention. Normal urothelium with or without hydrodistention exhibited high transepithelial resistances (TER) and low water and urea permeabilities, resembling other species. Fluorescence confocal microscopy revealed localization of the marker AE-31 to the apical surface of all umbrella cells in normal urothelium, with the tight junction protein ZO-1 localized to tight junctions. Scanning and transmission electron microscopy revealed uniform distribution of luminal cells with characteristic apical membrane and tight junction morphology. Urothelium in FIC animals displayed reduced TER and increased water and urea permeability following hydrodistention. Structural studies in FIC revealed denuded urothelium, with appearance of AE-31 in underlying epithelial cells. The results demonstrate severe epithelial damage and dysfunction in FIC and suggest novel approaches toward examining the etiology and therapy of IC.

Animals↗
PubMed1999

A plasma membrane-associated hyaluronidase is localized to the posterior acrosomal region of stallion sperm and is associated with spermatozoal function.

Sperm hyaluronidase has been implicated in sperm penetration of the extracellular matrix of the cumulus oophorus and may play a crucial role in gamete interaction and fertility in mammals. The objectives of this study were to characterize the enzyme activity of equine sperm hyaluronidase and to investigate its cellular distribution. Zymography of stallion sperm plasma membrane extracts was used to identify hyaluronidase activity in protein bands. Affinity-purified polyclonal IgG raised against equine sperm hyaluronidase was used to label fresh and capacitated stallion sperm, followed by indirect immunofluorescence. Equine sperm plasma membrane extracts displayed 3 major protein bands with potent hyaluronidase activity of approximately 54, 59, and 83 kDa. Under reducing conditions, a single protein band was observed at 62 kDa, although the reduced sample exhibited no enzyme activity. The polyclonal IgG labeled the postacrosomal region of stallion sperm and was redistributed over the acrosomal region during in vitro capacitation in a significant percentage of sperm cells. These studies suggest that a specific protein localized to the equine sperm head displays hyaluronidase activity, gets redistributed over the acrosomal region during capacitation, and may be important in fertility in this species.

Acrosome↗
PubMed1998

Medical management of urinary calculi in a stallion with breeding dysfunction.

A 9-year-old Thoroughbred stallion was examined because of breeding dysfunction and possible urethritis. The stallion had good libido and readily obtained an erection, mounted, and intromitted but did not thrust and ejaculate. After mounting the mare, the stallion would squeal and dismount. Endoscopic examination of the urethra and bladder revealed irregular, spiculate yellow crystals (< 1 cm in size) and sabulous deposits; numerous calculi were embedded in the mucosa of the bladder. Because the horse was at the start of a breeding season, the owner would not give permission for general anesthesia. Medical management was attempted, because postoperative convalescence after surgical removal of calculi might have curtailed breeding activities, and the calculi were small. Every 1 to 3 days, the bladder was lavaged with saline solution containing acetic acid, and anti-inflammatory and antimicrobial drugs were administered. The stallion was able to return to breeding mares, and sperm numbers and semen quality were good. However, urine contamination of the ejaculate was detected, suggesting that the stallion may have had a primary neurologic deficit affecting bladder control and function that was causing calculi to form secondarily because of delay in movement of urine through the urinary tract.

Animals↗
PubMed1998

Disruption of guinea pig urinary bladder permeability barrier in noninfectious cystitis.

Although most cell membranes permit rapid flux of water, small nonelectrolytes, and ammonia, the apical membranes of bladder epithelial umbrella cells, which form the bladder permeability barrier, exhibit strikingly low permeabilities to these substances. In cystitis, disruption of the bladder permeability barrier may irritate the bladder wall layers underlying the epithelium, causing or exacerbating inflammation, and increasing urinary frequency, urgency, and bladder pain. To determine the effects of inflammation on the integrity of the permeability barrier, guinea pigs were sensitized with ovalbumin, and the bladders were exposed subsequently to antigen by instillation on the urinary side. Inflammation of the bladder wall markedly reduced transepithelial resistance of dissected epithelium mounted in Ussing chambers and increased water and urea permeabilities modestly at 2 h and more strikingly at 24 h after induction of the inflammation. Transmission and scanning electron microscopy of bladders at 30 min and 24 h after antigen exposure revealed disruption of tight junctions, denuding of patches of epithelium, and occasional loss of apical membrane architecture. These permeability and structural effects did not occur in nonsensitized animals in which the bladders were exposed to antigen and in sensitized animals exposed to saline vehicle rather than antigen. These results demonstrate that inflammation of the underlying muscle and lamina propria can disrupt the bladder permeability barrier by damaging tight junctions and apical membranes and causing sloughing of epithelial cells. Leakage of urinary constituents through the damaged epithelium may then exacerbate the inflammation in the underlying muscle layers.

Animals↗
PubMed1997

Hyaluronidase activity of macaque sperm assessed by an in vitro cumulus penetration assay.

A model system consisting of cynomolgus macaque sperm and ovulated hamster ova-cumulus complexes (OCCs) was utilized to study the role of the sperm protein PH-20 in cumulus penetration. The hyaluronidase activity of solubilized macaque sperm PH-20 was evaluated using an ELISA-like microplate assay prior to and following the addition of the hyaluronidase inhibitors heparin (0-100 microg/ml) and apigenin (250 microM), as well as the Ig fraction of a polyclonal antibody raised against purified recombinant macaque PH-20 (R10; 10-400 microg/ml). Sperm motility following exposure to enzyme inhibitors was evaluated using computer-aided sperm motility analysis. Macaque sperm were labeled with the permeant fluorescent nuclear dye, Hoechst 33342, and were coincubated with ovulated hamster OCCs for 30 min at 37 degrees C. The addition of heparin, apigenin, or R10 antibody to solubilized sperm extracts resulted in a linear dose-dependent decrease in hyaluronidase activity (P < .01). In the heterologous cumulus penetration assay, fluorescently labeled macaque sperm that were pretreated with heparin (1-100 microg/ml), apigenin (250 microM), or R10 antibody (Ig fraction, 10-400 microg/ml) demonstrated a dose-dependent decrease in the ability to penetrate hamster OCCs (P < 0.01), in the absence of effects on sperm motility. In the homologous assay, experiments using macaque OCCs and fluorescently labeled macaque sperm confirmed that the same concentrations of heparin and R10 antibody similarly suppressed spermatozoal cumulus penetration (P < .01). These results suggest that macaque sperm PH-20-derived hyaluronidase participates in cumulus penetration in this species, and that this model system is useful for further studies into primate gamete interaction.

Animals↗
PubMed1996

Zona pellucida binding and zona-induced acrosome reactions in horse spermatozoa: comparisons between fertile and subfertile stallions.

Diagnostic tests that probe sperm function are needed to determine the potential etiologies of subfertility and to explore treatments of subfertility in stallions. Using epifluorescence and phase contrast microscopy, a comparison was made between ejaculates from 3 fertile and 3 subfertile stallions in which sperm-zona pellucida binding and acrosomal status were measured. Motile spermatozoa were selected by Percoll gradient centrifugation and were capacitated in vitro using TEST:TALP capacitation medium at 39 degrees C under humidified air containing 5% CO2. Concentration of motile spermatozoa was held constant during co-incubation with oocytes for fertile and subfertile ejaculates. The total number of zona pellucida-bound spermatozoa was higher for fertile stallions than for subfertile stallions (P < 0.05). Similarly, the percentage of acrosome reactions in zona pellucida-bound spermatozoa was higher for the 3 fertile stallions than for the 3 subfertile stallions (P < 0.05). These results indicate that spermatozoa from fertile stallions may interact with female gametes differently from that of subfertile stallions and suggest that sperm functions are measurable and may vary with fertility.

Journal Article↗
PubMed1996

The PH-20 protein in cynomolgus macaque spermatozoa: identification of two different forms exhibiting hyaluronidase activity.

In these experiments, we have characterized the bifunctional sperm protein PH-20 in macaque sperm and studied its hyaluronidase activity. Intact sperm were evaluated before the acrosome reaction (AR), and a soluble form of PH-20 released during acrosomal exocytosis was also investigated. Western blots of SDS-PAGE of acrosome-intact sperm extracts revealed a 64-kDa form of PH-20 was recognized by a polyclonal antibody (R-10) raised in rabbits against purified, recombinant cynomolgus macaque sperm PH-20. The soluble components released during the AR which were recognized by the R-10 antibody included both the 64-kDa form and a 53-kDa form of PH-20. An ELISA-like procedure for determining PH-20 hyaluronidase activity indicated that acrosome-intact sperm exhibited two peaks of hyaluronidase activity near pH 4 and > or = pH 7. The majority of enzyme activity in acrosome-intact sperm extracts occurred at neutral pH, while the soluble hyaluronidase activity released at the AR was predominantly acid-active. Hyaluronidase activity of PH-20 at different pH optima was investigated using hyaluronic acid substrate gel electrophoresis, and results indicated that the 64-kDa polypeptide had a broad range, with the majority of activity at neutral pH (pH 7). The 53-kDa polypeptide in sperm extracts only exhibited activity at acid pH (pH 4). The hyaluronidase activities of both enzymes could be inhibited by apigenin. The soluble PH-20 hyaluronidase activity released during the AR was primarily of the acid-active 53-kDa form. Fine structural localization of PH-20 using Fab fragments of R-10 IgG demonstrated that PH-20 was associated not only with sperm membranes, but also with the dispersing acrosomal contents. These data suggest that the more neutral-active form of PH-20 (64 kDa) is present on the plasma and inner acrosomal membranes and gives rise to the soluble acid-active form at the time of the AR. The generation of the soluble form of PH-20 may result from the action of acrosomal enzymes, which could include proteases, glycosidases, and phospholipases.

Acrosome↗
PubMed1995

Location of the PH-20 protein on acrosome-intact and acrosome-reacted spermatozoa of cynomolgus macaques.

Fluorescence microscopy and transmission electron microscopy (TEM) were used to determine the location of the membrane protein PH-20 on spermatozoa of cynomolgus macaques. Rabbit antiserum raised against recombinant cynomolgus macaque sperm PH-20 was used as the primary antibody, and the second antibody was goat anti-rabbit IgG conjugated with either fluorescein isothiocyanate or 15 nm gold particles. Spermatozoa were evaluated before capacitation and after capacitation and induction of acrosome reactions with calcium ionophore A23187. In sperm suspensions with a high percentage of intact acrosomes, fluorescence labeling was observed uniformly over most of the sperm head. The sperm midpiece and tail were not labeled. In sperm suspensions with a high percentage of acrosome reactions, most spermatozoa labeled intensely over the anterior sperm head, but labeling of the posterior sperm head was greatly reduced. TEM of acrosome-intact spermatozoa revealed gold particles distributed uniformly on the plasma membrane overlying the acrosome, the equatorial segment, and most of the post-acrosomal region. After the acrosome reaction, gold label was present on the inner acrosomal membrane and on the plasma membrane overlying the equatorial segment. Very little label was present on the plasma membrane in the post-acrosomal region of acrosome-reacted spermatozoa. The location of PH-20 on the surface of macaque spermatozoa suggests a function for this protein in primary and/or secondary binding to the zona pellucida. The apparent decrease in amount of PH-20 on the posterior head of macaque spermatozoa following the acrosome reaction is consistent with the migration of this protein to the inner acrosomal membrane, as demonstrated previously for the homologous PH-20 protein of guinea pig spermatozoa.

Acrosome↗
PubMed1994

Effect of dose of GnRH analog on ovulation in mares.

Proper timing of insemination for optimal conception is accomplished by frequent palpations per rectum, by ultrasonography of the preovulatory follicle and/or by treatment with hCG or GnRH. Sustained release of GnRH from implants has been shown to hasten ovulation. Therefore, 2 studies were conducted to evaluate the efficacy of a GnRH analog, deslorelin, for hastening ovulation in nonlactating cyclic mares. The GnRH implant was 2.3x3.7 mm and released deslorelin for 2 to 3 days. In Experiment 1, 60 nonlactating, cycling mares were assigned to 1 of 5 doses: 0, 1.2, 1.7, 2.2 and 2.7 mg per implant. Mares were assigned sequentially on the first day of estrus (Day 1). Ovaries were examined per rectum and with ultrasonography every 12 h until ovulation. Once the mares obtained a follicle>30 mm, they were injected subcutaneously with a GnRH implant. The mares were inseminated every other day during estrus with semen from 1 of 3 stallions. Pregnancy was determined with ultrasonography. Experiment 2, 40 nonlactating, cyclic mares were assigned to 1 of 5 treatments (same treatments as in Experiment 1). Data were obtained on interval to ovulation, duration of estrus and pregnancy rates at 12, 18 and 35 d after ovulation. Time to ovulation was shorter (P<0.05) in GnRH-treated mares than in control mares in the Experiment 1. Mean time to ovulation was 68, 49, 48, 47, 44 h in Experiment 1, and 91, 66, 58, 46, 58 h in Experiment 2 for mares given 0, 1.2, 1.7, 2.2 and 2.7 mg/mare in the 2 trials. Averaged for both experiments, the proportion of mares ovulating within 48 h of treatment was 40, 75, 85, 90 and 90% for 0, 1.2, 1.7, 2.2 and 2.7 mg/mare. For both experiments, there was no effect of GnRH on pregnancy rate. In summary, a subcutaneous implant containing GnRH analog induced ovulation in most mares by 48 h of injection, and there was no advantage of doses higher than 2.2 mg/mare.

Journal Article↗
PubMed1992

Synchronization of estrus in dairy goats given norgestomet and estradiol valerate at various stages of the estrous cycle.

Dairy goats were given subcutaneous implants with 3 mg of norgestomet (NOR) and IM injections of 0.625 mg of estradiol valerate and 0.375 mg of norgestomet on day 0 of the estrous cycle (estrus; NOR 0, n = 18), on postestrus day 4 (NOR 4, n = 18), or on postestrus day 11 (NOR 11, n = 15). Ear implants were removed after 9 days. Mean (+/- SE) hours from removal of ear implants to onset of estrus and proportion of goats responding were 36 +/- 3.8 and 83%, 33 +/- 4.0 and 61%, and 36 +/- 2.7 and 93% for groups NOR 0, NOR 4, and NOR 11, respectively. There were no significant differences between treatment groups in time to onset of estrus. The percentage of goats in group NOR 11 that had signs of estrus was significantly greater than the percentage of goats in group NOR 4. Of the goats in groups NOR 0, NOR 4, and NOR 11 that had signs of estrus, 53, 55, and 86%, respectively, had onset of behavioral estrus between 24 and 48 hours after implant removal. All goats that had signs of estrus had onset of behavioral estrus between 12 and 72 hours after implant removal. Mean (+/- SE) hours from removal of ear implants to time of peak concentrations of luteinizing hormone (LH) were 49 +/- 4.1, 49 +/- 3.8, and 49 +/- 4.0 for groups NOR 0, NOR 4, NOR 11, respectively (not different). The percentage of goats in group NOR 11 that had LH peaks was significantly greater than the percentage of goats in group NOR 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗