[DLys(6)]-luteinizing hormone releasing hormone-curcumin conjugate inhibits pancreatic cancer cell growth in vitro and in vivo

Pancreatic ductal adenocarcinomas are invariably lethal, and developing effective treatments that have minimal side effects is a challenge. Previous studies from our laboratory have shown that conjugates of cell membrane disrupting lytic peptides and luteinizing hormone releasing hormone (LHRH) target and destroy human prostate and breast cancer cells in xenografts in the nude mouse model (Hansel et al., Mol Cell Endocrinol 2007;260-262:183-9; Hansel et al., Mol Cell Endocrinol 2007;269:26-33), which express LHRH receptors. The objectives of our study were to synthesize a bioconjugate of LHRH analog ([DLys(6)]-LHRH) and a dietary microchemical (curcumin) and test the hypothesis that [DLys(6)]-LHRH-curcumin targets and inhibits pancreatic cancer cell growth in vitro and in vivo. In in vitro studies, we determined by confocal microscopy, flow cytometry analysis and reverse transcriptase-polymerase chain reaction that MIAPaCa-2, Panc-1 and BxPC-3 pancreatic cancer cell lines express LHRH receptors. [DLys(6)]-LHRH-curcumin inhibited cell proliferation of pancreatic cancer cell lines and induced apoptotic cell death (p < 0.05). Apoptosis was induced by cleavage of polyadenosine-5'-diphosphate-ribose-polymerase and caspase-3. The activity of [DLys(6)]-LHRH-curcumin was equal to free curcumin at equimolar concentrations in vitro. Unlike curcumin itself, the [DLys(6)]-LHRH-curcumin conjugate is water soluble which allows its intravenous administration. In two in vivo studies, [DLys(6)]-LHRH-curcumin given intravenously caused a significant (p < 0.01) reduction in tumor weights and volumes, and free curcumin given by gavage at an equal dose failed to cause a significant reduction in tumor weights and volumes in the nude mouse pancreatic cancer model. [DLys(6)]-LHRH-curcumin treatment enhanced apoptosis compared to [DLys(6)]-LHRH and vehicle-treated controls in tumor tissue. In conclusion, [DLys(6)]-LHRH-curcumin may be useful in treating pancreatic cancer.

Intracytoplasmic glutathione concentration and the role of beta-mercaptoethanol in preimplantation development of bovine embryos

In vitro-matured/in vitro-fertilized bovine oocytes were cultured on cumulus cell layers in a serum-free medium (bovine embryo culture medium; BECM) supplemented with 3 mg/ml fatty acid-free BSA. The intracytoplasmic glutathione concentration of embryos was found to change significantly (P < 0.008) during the preimplantation stages, beginning to increase at the 9- to 16-cell stage (20.7 pM/embryo) and reaching the highest (P < 0.03) level at the hatched-blastocyst stage (36.7 pM/embryo). A significantly (P < 0.06) lower concentration of glutathione was obtained at the 2- to 8-cell stage (7.1 pM/embryo) than at any other stage. When inseminated oocytes were cultured in BECM supplemented with different concentrations of beta-mercaptoethanol (2-ME) to promote glutathione synthesis, higher (P < 0.05) percentages of embryos developed to the 9- to 16-cell, morula and blastocyst stages at 96, 144 and 192 h post insemination, following the addition of 6.25 and 12.5 microM than after no supplementation with 2-ME. However, when 16-cell embryos were cultured in BECM supplemented with 6.25 and 12.5 microM of 2-ME, blastocyst formation was not significantly (P > 0.9) increased. When the combined effects of 2-ME and/or cumulus cells were compared in a 2 x 2 factorial design, there was a significant (P < 0.03) effect of 2-ME on the development of oocytes to blastocysts. The presence of cumulus cells significantly (P < 0.001) affected development after the fourth cleavage (morula compaction and blastocyst formation), but there was no significant (P > 0.11) interaction between 2-ME and cumulus cells. In conclusion, intracytoplasmic glutathione concentration of bovine embryos derived from in vitro-culture increases during preimplantation development. The glutathione synthesis promoter 2-ME exerts its embryotropic role on the development before the fourth cleavage, thus yielding an improvement in blastocyst formation.

The potential for improving the growth and development of cultured farm animal oocytes

Previous predictions that the technologies for producing genetically engineered large animal embryos containing genes for faster growth rates, leaner carcasses, greater disease resistance and improved lactational performance would be available early in the twenty-first century have been, for the most part, realized. The animal industries have been slow to adopt these technological advances and it cannot be said that any of them are currently having great impact on animal agriculture worldwide. A major reason for this is the inefficiencies of the techniques for superovulation, ovum recovery, in vitro fertilization, nuclear transfer, cloning and embryo transfer. Although improvements in these techniques can be expected, the best hope for increasing the impact of embryo transfer technologies on the animal industries lies in developing ways to mature, harvest, store and fertilize in vitro the large numbers of primordial oocytes present in the ovaries of all farm animals. Although limited progress has been made in the culture of bovine primordial oocytes, it is clear that much more research is needed to achieve success in this important area.

Targeted destruction of normal and cancer cells through lutropin/choriogonadotropin receptors using Hecate-betaCG conjugate

A recent approach to cancer treatment is destruction of malignant and non-malignant tumors by hormonally targeted lytic peptides. The presence of lutropin/choriogonadotropin (LH/CG) receptors has been confirmed in several cancer cells (e.g. breast, ovarian, and prostate). In a series of experiments conducted in vitro, we have used a conjugate of the 23-amino acid lytic peptide Hecate and a 15-amino acid segment of beta-chain of CG. To test the hypothesis that Hecate-betaCG selectively destroys porcine granulosa and luteal cells, and Leydig cancer cell line (BLT-1) possessing LH/CG receptors, the conjugate was added to culture media at different concentrations of 0.5 to 10 micro M. Spleen cells and late passage of granulosa cancer cell line (KK-1) not-possessing LH/CG receptors were used as controls. The toxicity of Hecate-betaCG conjugate was concentration-dependent in all cell types but different among various cells. The toxicity of the conjugate to treated cells was closely correlated with the number of LH/CG receptors per cell. At low concentration (1 micro M), Hecate-betaCG was more cytotoxic to cells bearing LH/CG receptors than to controls (p < 0.01). In contrast to cells possessing LH/CG receptors, cancer cell line KK-1 and spleen cells were sensitive only at concentration of 5 micro M (p < 0.001). We conclude that Hecate-betaCG selectively kills cells expressing LH/CG receptors; its toxicity is dependent on the number of binding sites for LH/CG.

Targeted destruction of prostate cancer cells and xenografts by lytic peptide-betaLH conjugates

In series of experiments conducted in vitro, we have established the concept that conjugates of the lytic peptides Hecate or Phor14 with a fragment of the beta chain of LH (amino acids 80-94) selectively destroy both androgen sensitive and insensitive human prostate cancer cells. Extraction of steroids from the culture medium by charcoal reduced the ability of the conjugates to kill LNCaP, BRF41T and PC-3 cells. Addition of hormones known to up-regulate LH receptors (estradiol, testosterone or FSH) to the culture medium restored the ability of the conjugates to kill these cell lines. The toxicity of the conjugates (EC(50)) to these cell lines was closely correlated to their LH binding capacities (f mol/10(6) cells). In series of in vivo experiments we have shown that both the Hecate and Phor14-betaLH conjugates are remarkably effective in causing tumor cell necrosis and cessation of tumor growth in nude athymic mice. Treatment with Hecate-betaLH (12 mg/kg body weight) resulted in a reduction of tumor burden (mg tumor/g body weight) from 60 to 14 (P<0.0001); treatment with Phor14-betaLH (12 mg/kg body weight) reduced tumor burden to 27 mg (P<0.0001). Treatment with a high dose of Phor14-betaLH (24 mg/kg body weight) reduced the tumor burden from 60 to 12 mg/kg P<0.0001). Pretreatment of animals receiving a low dose of Phor14-betaLH (12 mg/kg) with either estradiol or follicle stimulating hormone, (FSH) resulted in reduction of tumor burden from 60 to 11 mg/kg. Administration of a second 3-week treatment after a one month recovery period caused complete regression of more than 75 percent of the tumors. No changes in body weight or histological abnormalities were found in any of the organs examined, except the testes.

Targeted destruction of androgen-sensitive and -insensitive prostate cancer cells and xenografts through luteinizing hormone receptors

BACKGROUND

We have prepared a conjugate of a lytic peptide (hecate) and a 15-amino acid segment of the beta-chain of LH to test the concept that this conjugate will target cancer cells expressing LH receptors.

METHODS

Hecate-betaLH was added in vitro to cultures of Chinese hamster ovary (CHO) cells with and without LH receptors and to prostate cancer cells in the presence or absence of steroids, follicle-stimulating hormone (FSH), epidermal growth factor (EGF), or betaLH. PC-3 xenografts were established in male athymic nude mice and treated once a week for 3 weeks with hecate-betaLH via the lateral tail vein.

RESULTS

The conjugate showed concentration-dependent toxicity for the following prostate cancer cell lines: BRF 41 T>DU145>PC-3>LNCaP, according to their LH receptor capacities. Steroid removal reduced sensitivity to the drug in a reversible manner. Hecate-betaLH reduced the tumor burden in the nude mice from 60 to 12.5 mg/g body weight.

CONCLUSIONS

We conclude that the hecate-betaLH conjugate selectively kills androgen-dependent and-independent prostate cancer cells both in vivo and in vitro; its toxicity depends on the number of LH receptor sites present.

Design of a potent and selective inhibitor of the intermediate-conductance Ca2+-activated K+ channel, IKCa1: a potential immunosuppressant

The antimycotic clotrimazole, a potent inhibitor of the intermediate-conductance calcium-activated K(+) channel, IKCa1, is in clinical trials for the treatment of sickle cell disease and diarrhea and is effective in ameliorating the symptoms of rheumatoid arthritis. However, inhibition of cytochrome P450 enzymes by clotrimazole limits its therapeutic value. We have used a rational design strategy to develop a clotrimazole analog that selectively inhibits IKCa1 without blocking cytochrome P450 enzymes. A screen of 83 triarylmethanes revealed the pharmacophore for channel block to be different from that required for cytochrome P450 inhibition. The "IKCa1-pharmacophore" consists of a (2-halogenophenyl)diphenylmethane moiety substituted by an unsubstituted polar pi-electron-rich heterocycle (pyrazole or tetrazole) or a -CN group, whereas cytochrome P450 inhibition absolutely requires the imidazole ring. A series of pyrazoles, acetonitriles, and tetrazoles were synthesized and found to selectively block IKCa1. TRAM-34 (1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole) inhibits the cloned and the native IKCa1 channel in human T lymphocytes with a K(d) of 20-25 nM and is 200- to 1,500-fold selective over other ion channels. Using TRAM-34, we show that blocking IKCa1 in human lymphocytes, in the absence of P450-inhibition, results in suppression of mitogen-stimulated [(3)H]thymidine incorporation of preactivated lymphocytes with EC(50)-values of 100 nM-1 microM depending on the donor. Combinations of TRAM-34 and cyclosporin A are more effective in suppressing lymphocyte mitogenesis than either compound alone. Our studies suggest that TRAM-34 and related compounds may hold therapeutic promise as immunosuppressants.

Regioisomeric differentiation of 2,3- and 3,4-methylenedioxy ring-substituted phenylalkylamines by gas chromatography/tandem mass spectrometry

Numerous abused drugs of the 3,4-methylenedioxymetamphetamine (MDMA; Ecstasy; N-methyl-1-(3,4-methylenedioxyphenyl)-2-propaneamine) type and various alkyl chain- and aromatic ring-substituted isomers give very similar electron ionization (EI) mass spectra. This seriously affects the analysis of especially ring regioisomeric drug variants. Using collision-induced dissociation (CID) (argon) under EI and chemical ionization, the mass spectra of 18 2,3- and 3, 4-methylenedioxy ring-substituted phenylethylamines were recorded. These techniques permitted an unequivocal differentiation of all studied ring regioisomeric methylenedioxyphenylethylamines. CID mass spectrometry therefore appear to be a reliable tool to establish the kind of ring substitution pattern in regioisomeric methylenedioxyphenalkylamines. Copyright 2000 John Wiley & Sons, Ltd.

Intraluteal administration of a nitric oxide synthase blocker stimulates progesterone and oxytocin secretion and prolongs the life span of the bovine corpus luteum

To test the role of nitric oxide (NO) in secretory functions of bovine corpora lutea (CL), two groups of four Holstein heifers each were treated as follows: Group 1, Nomega-Nitro-L-Arginine Methyl Ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), on Day 11 or 12 of the cycle and Group 2, L-NAME on Days 17 and 18 of the cycle. All treatments were administered by an intraluteal microdialysis system (MDS). Drugs were infused for 4-hr periods on the designated days, and the treatment periods were preceded and followed by 4-hr control periods. Perfusate and jugular blood samples were collected at half-hour intervals. Perfusate samples were analyzed for progesterone (P4), oxytocin (OT), prostaglandin F2alpha (PGF2alpha), and leukotriene C4 (LTC4); jugular plasma samples were analyzed for P4, OT, and LH. Perfusion of L-NAME on Day 11 or 12 consistently increased P4 concentration in the perfusate, but had no effect on the life span of the CL. Perfusion of L-NAME on Days 17-18 also elevated P4 levels in the perfusate, and in addition, maintained P4 levels in the plasma of three of the four treated animals through Day 25 of the cycle. L-NAME perfusion also increased OT release concomitant with P4 into the perfusate at both the mid- and late-luteal phase treatments. For the most part, concentrations of LH, OT, and P4 in the jugular plasma samples collected during the perfusions were unaffected by treatments. L-NAME perfusion caused small, but significant (P < 0.05) increases in perfusate PGF2alpha and LTC4 at Days 17 and 18 and in LTC4 on Day 11 or 12. These data indicate that NO plays a direct luteolytic role in regression of the bovine CL.

Exogeneous substances affecting development of in vitro-derived bovine embryos before and after embryonic genome activation

Three experiments were conducted to evaluate how exogenous substances [fetal bovine serum (FBS), arachidonic acid (AA), glutathione (GSH), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF), fibroblast growth factor (FGF), insulin, transferrin and selenium (ITS)] affect preimplantation bovine embryo development. Cumulus-oocyte complexes (COC) were matured and fertilized in vitro, and their development was monitored up to 192 h post insemination in a two-step culture system. In Experiment 1, inseminated oocytes were cultured in modified bovine embryo culture medium (mBECM) supplemented with FBS or BSA for up to 60 h post insemination, and the resultant 8-cell embryos were then cultured singly in mBECM supplemented with AA+GSH+PDGF+TGF. More (P<0.005) blastocysts were derived from 8-cell embryos produced in media containing FBS than BSA. In Experiment 2, the 8-cell embryos produced in mBECM supplemented with FBS were cultured singly in mBECM as follows: 1) no supplementation; 2) AA and GSH or 3) AA, GSH, PDGF and TGF. Compared with no supplementation, a significant (P<0.05) increase in the proportion of 16-cell embryos and morulae was obtained after the addition of either AA+GSH or AA+GSH+PDGF+TGF. In Experiment 3, oocytes were cultured singly in mBECM as follows: 1) no supplementation; 2) AA+GSH+PDGF+TGF; 3) AA+GSH+PDGF+TGF and FGF; 4) AA+GSH+PDGF+TGF and ITS; 5) AA+GSH+PDGF+TGF, FGF and ITS or 6) FBS. Eight-cell embryos grown in each system were subsequently cultured singly in mBECM with AA+GSH+PDGF+TGF. More (P<0.05) 16-cell embryos were obtained in medium supplemented with either AA+GSH+PDGF+TGF and ITS or FBS than in unsupplemented medium. Fewer (P<0.05) oocytes developed to the 8-cell stage with the addition of AA+GSH+PDGF+TGF and FGF than without. In conclusion, embryo development to the blastocyst stage is regulated by exogenous AA, GSH, PDGF, FGF and ITS in a stage-specific manner.

Development of bovine IVF oocytes cultured in medium supplemented with a nitric oxide scavenger or inhibitor in a co-culture system

Bovine IVF oocytes were cultured in modified bovine embryo culture medium (mBECM) supplemented with either a nitric oxide (NO) scavenger, hemoglobin (Hb, 1 microg/mL) and/or a NO synthesis inhibitor, L(omega)-nitro-L-arginine methyl ester (L-NAME, 1 or 1000 nM) in a cumulus-granulosa cell co-culture system. In Experiment 1, a total of 1,675 cumulus-oocytes complexes was collected for 7 mo and cultured to the blastocyst stage in mBECM with or without Hb after IVM and IVF. There were significant (P<0.0024) model effects of Hb addition and month of oocyte collection on embryo development. A significant (P<0.0023) monthly variation was detected in all developmental stages. However, addition of Hb to mBECM consistently enhanced embryo development to the blastocyst stage over all months. No statistical differences were found in the interaction between Hb addition and month except for the cleavage rate. Overall, a greater percentage of oocytes developed to the 8-cell (P<0.0459), 16-cell (P<0.001), morula (P<0.0013) and blastocyst (P<0.0024) stages after the addition of Hb. In Experiment 2, addition of L-NAME to mBECM supplemented with Hb did not further stimulate prehatched development. In conclusion, the promoting effect of Hb on in vitro development of embryos is highly repeatable over an extended period of time.

Development of in-vitro-derived bovine embryos cultured in 5% CO2 in air or in 5% O2, 5% CO2 and 90% N2

To evaluate the effects of a three gas mixture of 5% O2, 5% CO2 and 90% N2 (OCN) on preimplantation embryo development, bovine in-vitro fertilization (IVF) oocytes were cultured in a defined medium (mBECM) with various supplements either under 5% CO2 in air or under OCN. When cultured in mBECM alone, embryo development was significantly stimulated in OCN compared to 5% CO2 in air (experiment 1). In the OCN atmosphere, blastocyst formation was further increased after addition of fetal bovine serum (FBS; 10%) or FBS + cumulus granulosa cells (CGC) to mBECM. The ratio of blastocysts to 8-cell embryos, number of hatched blastocysts and embryo diameter were markedly increased, and zona thickness was decreased after FBS addition. However, development up to the morula stage was fully supported by mBECM alone. There was no significant effect of beta-mercaptoethanol (ME; 10 microM) in OCN. In the 5% CO2 atmosphere, embryo development was significantly (P < 0.05) enhanced after addition of FBS + CGC + ME. In experiment 2, in OCN, FBS added at 60 h post-insemination was effective in stimulating blastocyst formation, but changes in medium volume per oocyte from 13.6 to 1.36 microliters had only a marginal effect. In conclusion, OCN gas mixture provides a suitable atmosphere for early embryo growth in vitro and mBECM + FBS in the optimal culture medium under this atmosphere.

Improved development of in vitro-derived bovine embryos by use of a nitric oxide scavenger in a cumulus-granulosa cell coculture system

This study was conducted to examine the hypothesis that nitric oxide (NO) affects prehatching development of bovine oocytes fertilized in vitro. In experiment 1, inseminated oocytes were cultured in a cumulus-granulosa cell (CG) coculture system to which 0.008 or 0.04 mM of sodium nitroprusside (SNP), a spontaneous NO releaser, was added at 18 or 60 hr postinsemination. Embryo development was greatly (P < 0.001) inhibited by the addition of SNP, regardless of time of addition or SNP concentration. In experiment 2, eight-cell embryos were cultured singly in a defined medium, to which 0.0016, 0.008, or 0.04 mM of SNP was added. Development to the blastocyst stage was greatly (P < 0.001) decreased after addition of SNP compared with no addition. Higher (P < 0.02) concentration of NO metabolites was found in developmentally arrested embryos than in developing embryos at 144 hr postinsemination (experiment 3). In experiment 4, blastocyst formation of oocytes cocultured with CGs was significantly (P < 0.02) increased after addition of hemoglobin (Hb, 1 microgram/ml), an NO scavenger. Prehatching development of oocytes was significantly (P < 0.05) increased after addition of Hb at different time intervals (18, 60, or 144 hr postinsemination) in experiment 5. Embryo development was not enhanced by Hb addition to the culture medium in the absence of CGs (experiment 6). Prehatching development of eight-cell embryos derived from a Hb-containing culture system was not promoted by the further addition of Hb after transfer of the embryos to a defined and CG-free single-embryo culture system (experiment 7). In conclusion, NO, which may be secreted from CGs, has an inhibitory role in prehatching development of bovine oocytes fertilized in vitro, and use of an NO scavenger, Hb, in a coculture system enhances blastocyst formation.

High environmental temperature and humidity decrease oocyte quality in Bos taurus but not in Bos indicus cows

Two experiments were conducted to assess the effects of environmental temperature and humidity on the quality and developmental capabilities of bovine oocytes. In Experiment 1, Bos taurus (Holstein and crossbred Angus) cows were subjected to 5 weekly sessions of ultrasound-guided follicle aspiration from February 16 through March 23 (cool season) and 5 sessions from May 22 through June 20 (hot season). In Experiment 2, Bos taurus (Holstein) and Bos indicus (Brahman) cows were superstimulated (Super-Ov) during the months of August (hot season) or January (cool season), and each cow was subjected to a single oocyte aspiration session. In each experiment, oocytes were classified as normal or abnormal based on ooplasm morphology and cumulus cell layers. In Experiment 1, oocytes classified as normal were in vitro matured and fertilized (IVM/IVF), and the resulting embryos cultured for 8 d. All oocytes recovered from superstimulated cows in Experiment 2 were matured and fertilized in vitro and the subsequent embryos cultured for 8 d, regardless of their morphological appearance. In Experiment 1, Bos taurus cows produced a higher (P = 0.02) percentage of normal oocytes during the cool season (75.9 +/- 8.0) than during the hot season (41.0 +/- 9.5). The percentage of fertilized oocytes developing to the 2-cell (82.4), 8-cell (65.4) and morula (46.6) stages were also greater (P < or = 0.06) during the cool season than the hot season (45.0, 21.2, 6.0 for 2-cell, 8-cell and morula stages, respectively). In Experiment 2, Bos taurus cows (Holstein) had a lower (P = 0.01) percentage of normal oocytes in the hot season (24.5 vs 80.0) and a lower (P < or = 0.003) percentage of fertilized oocytes developing to the 8-cell, morula and blastocyst stages. No difference (P > or = 0.57) in the percentage of normal oocytes or in embryo development was detected between seasons in Bos indicus (Brahman) cows. In conclusion, high environmental temperature and humidity resulted in a marked decline in the quality of oocytes retrieved from Bos taurus cows and markedly decreased their in vitro developmental capabilities. In contrast, a high percentage of oocytes retrieved from Bos indicus cows exhibited normal morphology and yielded a high proportion of blastocysts, regardless of season.

Perifusion culture system for bovine embryos: improvement of embryo development by use of bovine oviduct epithelial cells, an antioxidant and polyvinyl alcohol

Three experiments were conducted in an attempt to improve a continuous flow-perifusion system capable of maintaining embryo development for long periods of time. Bovine embryos (8-16 cells) obtained from static co-culture with cumulus cells in a serum-free medium were perifused in an ACUSYST-S cell culture incubator. Culture chambers of the incubator consisted of a 0.2-mL unit (Chamber 1) connected to a 1.5-mL unit (Chamber 2), with the outflow from Chamber 1 routed to the inlet to Chamber 2. A bovine embryo culture medium supplemented with 3 mg mL-1 bovine serum albumin (BSA) and 25 mM HEPES was used as a perifusion culture medium (PCM). Embryos were perifused in Chamber 2 for 24, 48 and 72 h and further co-cultured in a static system up to 216 h after insemination. In Experiment 1, conditioning PCM with frozen-thawed bovine oviduct epithelial cells (BOEC) placed in Chamber 1 enhanced (P < 0.05) blastocyst formation of embryos in Chamber 2, after 24, 48 and 72 h of perifusion culture. The proportion of blastocysts was not further increased by placing BOEC in Chamber 2 along with the embryos. In Experiment 2, embryos were perifused with PCM conditioned with BOEC in Chamber 1 for 48 h or 72 h. A higher proportion of perifused embryos developed to the blastocyst stage after addition of 25 U mL-1 or 50 U mL-1 of superoxide dismutase (SOD) to PCM than in its absence. However, blastocyst formation of embryos perifused for 72 h was not increased after addition of 50 U mL-1 SOD compared with its absence. In Experiment 3, the proportions of morulae and blastocysts were not decreased by replacement of 3 mg mL-1 BSA with 1 mg mL-1 polyvinyl alcohol (PVA) in a BOEC-conditioned medium containing 50 U mL-1 SOD after perifusion for 48 h. In conclusion, PCM conditioning with BOEC and addition of an antioxidant to the perifusion medium improved the developmental capacity of perifused embryos. PVA is an adequate replacement for BSA in the perifusion medium.

Roles of leukotrienes in bovine corpus luteum regression: an in vivo microdialysis study

A microdialysis system (MDS) was surgically implanted into the corpora lutea (CL) of 12 normally cycling Holstein heifers. Heifers were either allowed to undergo spontaneous luteolysis (Spontaneous, n = 6) or received an intramuscular injection of prostaglandin F2 alpha (PGF2 alpha) on Day 12 of the estrous cycle (Induced, n = 6). The MDS was implanted on Day 11 in the induced heifers and on Day 17 in Spontaneous heifers. CL were perfused with Ringer's solution at a flow rate of 3 ml/hr beginning immediately after surgery. Dialysate samples were collected hourly for 3-4 days. Samples were assayed for progesterone (P4), oxytocin (OT), PGF, and leukotrienes B (LTB) and C (LTC). Dialysate OT was undetected in all but one Spontaneous and one induced heifer. Lipoxygenase products of arachidonic acid (AA) metabolism (LTB and LTC) in the dialysate were found to be closely associated with luteal regression. In Spontaneous heifers, the mean interval from the first hormone peak to the onset of P4 decline was similar for PGF, LTB, and LTC, with the first peak occurring at 12.8 +/- 8.1, 22.0 +/- 6.1, and 11.0 +/- 8.9 hr before the onset of P4 decline, respectively. The peak LTC value was greater (P < 0.05) than peak LTB or PGF. The 12-hr sampling interval with the highest LTC peak frequency was highly correlated (r = 1.0; P < 0.01) with the onset of P4 decline, but the highest LTB and PGF peak frequencies were not associated with the onset of P4 decline. Indeed, the mean numbers of PGF and LTB hormone peaks were higher (P < 0.05) after the onset of P4 decline than before. Administration of PGF2 alpha on Day 12 of the estrous cycle stimulated a decline in P4 secretion and an increase in the secretion of PGF, LTB, and LTC from the CL. In induced animals, the peak level of PGF was greater (P < 0.05) than peak LTB. These results suggest that the AA metabolites LTB and, especially, LTC play important roles during normal regression of the bovine CL.

Effects of dexamethasone administration to diestrus cows on systemic progesterone, estrogen and uterine cyclooxygenase production

Parenteral administration of dexamethasone to diestrus cattle can extend the length of the natural estrous cycle. In mice, dexamethasone has been shown to inhibit production of the second isozyme of the cyclooxygenase (COX) enzyme (a rate limiting enzyme in prostaglandin formation). Therefore, the purpose of this study was to determine the effect of dexamethasone on estrous cycle length and COX-1 and -2 production by the uterine endometrium of cyclic cattle. Nine crossbred beef cows that exhibited two previous normal estrous cycles were randomly assigned to two treatments; a control group administered intramuscular injections of vehicle, and a dexamethasone group administered 8 mg of dexamethasone (Azium, Schering Corp., Kenilworth, NJ). Both groups received twice daily injections on day 13-22 of the treatment cycle. Uterine endometrial biopsies were collected on days 16, 19 and 22 of the treatment cycle. Blood samples were collected daily on day 13-22 of the treatment cycle for plasma progesterone and estradiol concentrations.

Effect of unilateral ovariectomy, gonadotropin stimulation and immunization against a synthetic peptide of the inhibin α-subunit on follicular development and oocyte recovery in cattle

Nulliparous Holstein cows were randomly distributed among 4 treatment groups to test the effects of treatments, including unilateral ovariectomy, anti-inhibin immunization and gonadotropin stimulation on ovarian follicle population and oocyte recovery. The Control treatment consisted of intact cows (I-Control). Unilaterally ovariectomized cows were included in the 3 remaining treatments consisting of ovariectomy alone (U-Control), cows immunized against a synthetic peptide of the alpha(c)-subunit of bovine inhibin (alpha(c)I; U-IH), and cows stimulated with FSH (Super-Ov; 75 units/female/week) and also immunized with alpha(c)I as in the previous treatment (U-IH/FSH). Oocytes were collected by transvaginal ultrasound-guided aspiration on a weekly basis from cows in each treatment for 5 consecutive weeks. Intact Control cows had a greater (P<0.05) number of follicles > or = 3 mm per female (4.7) than the U-Control and U-IH cows (2.6 and 2.9, respectively), and had a similar number of follicles as the U-IH/FSH treatment group (3.5). The numbers of follicles aspirated (2.7 to 3.6) and oocytes recovered/cow (1.6 to 2.6) were similar for cows in the I-Control, U-IH and U-IH/FSH treatment groups. Cows in the U-Control treatment group had a lower (P<0.05) number of aspirated follicles (2.0) and recovered oocytes (1.1) than the I-Control cows. Cows in the U-IH/FSH and U-IH treatments had follicles with larger (P<0.01) diameters (8.7 and 8.2 mm, respectively) than cows in the I-Control (6.6 mm) and U-Control (5.7 mm) treatments. In conclusion, unilateral ovariectomy did not result in compensatory increase of follicle number or size in the intact ovary; cows in the U-IH/FSH treatment group had a greater number of follicles aspirated than the U-Control cows. In addition, the anti-alpha(c)I immunization may have played a role in increasing the number and diameter of the follicles. None of the treatments evaluated in this study improved oocyte retrieval over that of the intact, nontreated cows.

A serum-free medium for use in a cumulus cell co-culture system for bovine embryos derived from in vitro maturation and in vitro fertilization

The objective of this study was to develop a serum-free medium for the co-culture of bovine embryos that would yield a percentage of blastocysts equal to that obtained with fetal bovine serum (FBS)-supplemented medium. Cumulus cell-enclosed oocytes (CEO) matured and inseminated in vitro were cultured in a tissue culture medium (TCM)-199 or in a serum-free medium (bovine embryo culture medium; BECM) until 240 h post insemination. Replacement of 10% (v/v) FBS with either 3 mg crystallized bovine serum albumin (BSA)/ml or 3 mg fatty acid-free BSA/ml in TCM-199 had no effect (P > 0.14) on embryo development to the >or= 2-cell (51 to 60%), >or= 8-cell (24 to 33%), blastocyst (16 to 19%) and hatched-blastocyst (7 to 10%) stages at 48, 96, 192 and 240 h post insemination, respectively. Oocyte-enclosing cumulus cells in BSA-supplemented medium grew in clusters rather than in layers, as was noted in FBS-supplemented medium. When CEO were cultured in fatty acid-free BSA-supplemented media (TCM-199 and BECM), a significantly (P < 0.001) higher percentage of oocytes developed to blastocysts after culture with (22%) or without (18%) a cumulus cell monolayer than after denuding the oocytes (7%). Glucose in concentrations of 0 to 5.56 mM added for periods of 18 and 120 h post-insemination had neither a stimulatory nor a deleterious effect on preimplantation development. In conclusion, a serum-free medium supplemented with BSA can be successfully used in a cumulus cell co-culture system for bovine embryos.

Roles of growth factors in the development of bovine embryos fertilized in vitro and cultured singly in a defined medium

Bovine embryos at the 8- or 16-cell stage were cultured singly, or in groups (10-12 embryos), in the presence or absence of bovine oviduct epithelial cells (BOEC) in a defined medium which was used as a basic culture medium. A higher (P < 0.05) proportion of 8-cell embryos (48.3-50.8%) cultured singly developed beyond the 8-cell stage after the addition of platelet-derived growth factor (PDGF)-AB (1 ng mL-1) only, or with PDGF-AB + basic fibroblast growth factor (bFGF; 1 ng ml-1) + transforming growth factor (TGF)-beta 1 beta 2 (1 ng mL-1) than in basic medium alone (30.3%). In contrast, a significantly (P < 0.02) higher percentage (62.6-65.8%) of 16-cell embryos developed to the morula stage after the addition of TGF-beta 1 beta 2 only, or the addition of TGF-beta 1 beta 2 + bFGF + PDGF-AB than in basic medium alone (30.2%). These proportions were not significantly (P > 0.05) different from the proportions obtained when embryos were cultured in groups, but were significantly (P < 0.005) lower than the proportions obtained when embryos were cultured in groups on BOEC monolayers. Arachidonic acid (50 ng mL-1), beta-mercaptoethanol (10 microM) and glutathione (10-1000 microM) stimulated the development of 8-cell embryos in the presence of PDGF and TGF-beta 1 beta 2; blastocyst formation was observed for the first time in 8-cell embryos cultured singly in the presence of these embryotrophic substances (2.2-6.2%).

Effect of media substitutes on bovine granulosa cell function and proliferation during in vitro culture

The development of a serum-free culture system for bovine granulosa cells that would allow for cellular proliferation without induction of steroidogenesis would provide researchers with an important in vitro tool for determining differentiation mechanisms during folliculogenesis. The objective of the present study was to determine the effect of a commercially prepared serum substitute and a medium supplement on proliferation and progesterone production by bovine granulosa cells. Granulosa cells were obtained by aspirating the follicular fluid of follicles 2 to 8 mm in diameter. For each experiment, growth curves to determine the proliferative and steroidogenic response of granulosa cells to several different medium additions were constructed. Cells were counted on d 1, 2, 4, 6, and 8 of culture to determine cell concentration and the media harvested to determine progesterone content. In Exp. 1, granulosa cells were seeded at an initial rate of 5.0 x 10(5) for 48 h in serum-supplemented medium then allotted to one of five treatments including medium alone or medium containing fetal bovine serum (FBS; 1%), Gibco BRL media supplement-x (GMS-X; 1%), fatty acid-free bovine serum albumin (FAF-BSA; 4 mg/mL), or SerXtend (5%). For Exp. 2 and 3, granulosa cells were plated in serum-supplemented medium for either 48 or 24 h and seeded at either 5.0 x 10(5) or 2.5 x 10(5) cells/flask, respectively, and cultured in different concentrations of SerXtend. All treatment media supported granulosa cell proliferation to some extent; the SerXtend treatment provided the highest proliferation rate at all concentrations above .3125%. Also, during the proliferative stage of the growth curve, cells in the SerXtend treatment produced lower amounts of progesterone compared with cells in the other treatments. In summary, granulosa cells may be propagated in vitro in a serum-free environment without inducing progesterone production.

Contact-associated interactions between large and small bovine luteal cells during the estrous cycle

This experiment was designed to study the effects of cell-to-cell contact, arachidonic acid (10 microM; AA), oxytocin (10 microM), and luteinizing hormone (5 ng; LH) on bovine luteal cell function. Corpora lutea collected from Holstein cows between Days 10 and 12 (n = 4; midluteal stage) or 17 and 18 (n = 4; late-luteal stage) of the estrous cycle (Day 0 = estrus) were dispersed, and small and large cells were separated by unit gravity sedimentation and flow cytometry. Large and small luteal cells were either incubated together, allowing intercellular contact, or separately, without intercellular contact, with culture well inserts. Cells were incubated in a modified Ham's F-12-N-hydroxyethylpiperazine-N'-2-ethanesulfonic acid medium. After an 18-hr preincubation period, treatments were introduced and cells were incubated for 240 hr. Media samples were collected and treatments were replaced at 48-hr intervals. Incubations were maintained at 37 degrees C in 5% CO2 in humidified air. Overall, progesterone secretion decreased with increased incubation time (P < 0.0001), regardless of treatment, stage of the cycle, or cell arrangement. During the 18-hr pretreatment period, large and small luteal cells with contact secreted more progesterone than did luteal cells without contact during both the mid- (P < 0.0001) and late-luteal stages (P < 0.06) of the estrous cycle. After treatments were initiated, both mid- and late-stage luteal cells treated with LH secreted more (P < 0.0001) progesterone than occurred with any other treatment; oxytocin, AA, and control treatments were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Interactions between large and small luteal cells collected during the mid- or late-luteal stages of the bovine oestrous cycle

The effects of contact between large and small bovine luteal cells together with those of luteinizing hormone (LH) or arachidonic acid (AA) on progesterone production during the oestrous cycle were investigated. Corpora lutea were collected during the mid-luteal stage (Days 10-12; n = 4) and late-luteal stage (Days 17-18; n = 4) of the oestrous cycle. Large and small luteal cells were dispersed and separated and then incubated together or separately. Mid-luteal stage cells were treated with LH (0 or 5 ng) whereas late-luteal stage cells were treated with LH (0 or 5 ng) or AA (0 or 10 microM). Culture medium was collected and replaced 1, 3 and 6 h after starting treatments. Progesterone production decreased (P < 0.0001) with increased incubation time irrespective of cell arrangement, the stage of the oestrous cycle or treatment. During the 18 h before treatment, cells in the contact arrangement produced more progesterone (P < 0.003) than cells without contact in both mid- and late-luteal stages of the oestrous cycle; progesterone production within cell arrangements between prospective treatment groups was similar. After initiating treatments, mid-luteal stage cells in the control group without contact produced more progesterone (P < 0.01) than cells with contact. Mid-luteal stage cells treated with LH produced more (P < 0.0001) than control cells; progesterone production between cell arrangements within the LH treatment group was similar. In the late-luteal stage cells, both LH and AA increased (P < 0.01) progesterone production by comparison with control cells; LH and AA treatment groups produced similar results.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of progesterone production in bovine luteal cells by co-incubation with bovine blastocyst-stage embryos or trophoblastic vesicles

A study was conducted to determine whether bovine blastocyst-stage embryos and trophoblastic vesicles stimulate the production of progesterone in bovine luteal cells during incubation in vitro. The effects of co-incubation of these embryos and vesicles with uterine endometrial tissue on progesterone production was also investigated. Bovine small and large luteal cells were obtained on day 12 of the oestrous cycle, dispersed by unit gravity sedimentation and recombined to provide preparations free of accessory cells. Blastocyst-stage embryos were obtained on day 7 and trophoblastic vesicles were obtained from bovine embryos on day 12. A uterine endometrial tissue sample was obtained from the same cow from which the corpus luteum was taken. Treatment groups were arranged in 24-well plates as follows: luteal cells alone; luteal cells and one trophoblastic vesicle; luteal cells and one blastocyst embryo; luteal cells and a 10 mg uterine endometrial sample; luteal cells, one trophoblastic vesicle and a uterine endometrial sample; and luteal cells, one blastocyst embryo and a uterine endometrial sample. All treatment groups were incubated (at 37 degrees C under 5% CO2) in Ham's F-12 medium supplemented with antibiotics (100 micrograms penicillin ml-1 and 100 U streptomycin ml-1, L-glutamine (0.29 mg ml-1), insulin (5 micrograms ml-1), transferrin (5 micrograms ml-1) and selenium (5 ng ml-1) for 12 h. Samples of the medium were harvested 10 min (basal concentration) and 2, 6 and 12 h after incubation to determine the concentrations of progesterone and prostaglandin.(ABSTRACT TRUNCATED AT 250 WORDS)

Interactions between large and small bovine luteal cells in a sequential perifusion co-culture system

The objectives of this experiment were to study large and small luteal cell interactions and examine the effect of arachidonic acid (AA) on progesterone production by separated bovine luteal cells. Corpora lutea collected from Holstein cows (n = 5) on d 12 of the estrous cycle were dispersed, and small (SLC) and large (LLC) luteal cells were separated by unit gravity sedimentation and flow cytometry. Cells were incubated at 37 degrees C in separate perifusion chambers with a modified Ham's F-12-HEPES medium and aerated with 95% O2:5% CO2. The flow rate of medium was 100 microL/min, and fractions were collected at 30-min intervals for 4 h. Luteal cells were arranged in tandem so that medium from the first cell type would pass through the chamber containing the second cell type. Luteal cells were arranged so that medium flowed from 1) SLC to SLC, 2) LLC to LLC, 3) SLC to LLC, 4) LLC to SLC, 5) SLC to LLC, 6) LLC to SLC; medium for arrangements 5 and 6 contained 10 microM AA. Cells in arrangements 5 and 6 were perifused for 30 min before AA was added. Progesterone was measured with an enzymeimmunoassay. The LLC to LLC arrangement had a greater (P < .05) average progesterone secretion rate than all other cell arrangements, and the SLC to SLC arrangement had the least progesterone secretion rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of development of in vitro-matured and in vitro-fertilized bovine embryos by platelets

In vitro-fertilized bovine embryos were incubated in Menezo's B2 medium (MB2) supplemented with 2 mg/mL of BSA. In Exp. 1, eight-cell stage embryos were allotted to one of the following groups: control medium (MB2), MB2 with 20 ng/mL of platelet-activating factor (PAF), 1 x 10(7) bovine blood platelets (Platelets), oviductal cells (BOEC), BOEC and 20 ng/mL of PAF (BOEC+PAF), or BOEC and 1 x 10(7) platelets (BOEC+Platelets). In Exp. 2, eight-cell embryos were allotted to one of the following groups: control medium (MB2), MB2 with 1 x 10(7) platelets (Platelets), 1 x 10(7) platelets and 10 micrograms/mL of platelet-derived growth factor antibody (Platelets+anti-PDGF), 1 x 10(7) platelets and 1 microgram/mL of indomethacin (Platelets+Indomethacin), or 1 x 10(7) platelets and 3 micrograms/mL of mianserin (Platelets+Mianserin). Embryos were incubated at 39 degrees C in 5% CO2 in groups of five until 8 d after in vitro fertilization (IVF). In Exp. 1, Platelets stimulated embryo development to the morula, blastocyst, and expanded blastocyst stages. Embryo development was greatest in the BOEC+Platelets group on d 7 and 8 after IVF. Only embryos incubated in the BOEC+Platelets treatment group reached the hatched blastocyst stage on d 8. In Exp. 2, embryos incubated in the Platelets treatment group had the greatest (P < .05) proportion develop beyond the eight-cell stage. Embryos incubated in the Platelets + anti-PDGF group had less (P < .05) development beyond the eight-cell stage and to the morula stage. These results indicate that the stimulatory effects of PDGF on bovine embryo development may be derived from both the oviductal epithelium and platelets.

Role of platelet-derived growth factor in development of in vitro matured and in vitro fertilized bovine embryos

This experiment was designed to determine whether the stimulatory effects of bovine oviductal epithelial cells (BOEC) on development of early bovine embryos are due to platelet-derived growth factor (PDGF). Four hundred and twenty five 8-cell bovine embryos derived from in vitro maturation and in vitro fertilization procedures were equally and randomly allotted to one of the following culture treatment groups: control medium alone (Menezo's B2 medium; MB2), MB2 with 1 ng PDGF ml-1 (PDGF), 1 ng PDGF ml-1 and 10 micrograms anti-PDGF antibody ml-1 (PDGF + Ab), BOEC or BOEC and 10 micrograms anti-PDGF antibody ml-1 (BOEC + Ab). All embryos were cultured in 100 microliters of serum-free MB2 medium supplemented with 2 mg fatty-acid-free bovine serum albumin ml-1. Embryos for all treatment groups were incubated at 39 degrees C and 5% CO2 in humidified air in groups of five embryos per well in 96-well culture plates until 7 days after in vitro insemination. A higher proportion of embryos developed to > 8-cell and to the morula stage following culture with PDGF, BOEC or BOEC+Ab than with MB2 alone. Incubation of PDGF and BOEC-treated embryos with anti-PDGF reduced development to the morula and blastocyst stages. However, anti-PDGF did not completely inhibit blastocyst development when added to BOEC. In addition, embryos incubated with BOEC and anti-PDGF contained a reduced number of inner cell mass cells compared with embryos incubated with BOEC alone. These results indicate that PDGF provides a developmental stimulus similar to BOEC for bovine embryos at the fourth cell cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Assay of embryo-derived platelet activating factor (EDPAF) by an equine platelet aggregation assay: Preliminary data concerning its presence in bovine embryo culture media

This study was designed to establish a sensitive bioassay for bovine platelet-activating factor (PAF), to determine if the bovine embryo secretes PAF in vitro and if PAF release is correlated with the embryo's potential to establish a pregnancy. Using an equine platelet aggregation assay, lipid extracted culture media from 33 Day-7 embryos (individually cultured for 18 hours in 1 ml of Ham's F10 containing 0.4% BSA at 37 degrees C in an air: CO2 mixture of 95:5 prior to their transfer to recipient heifers) and from control media (n=15, Ham's F10+0.4% BSA incubated simultaneously without embryos) were investigated. In addition, culture media from Day-6 (n=6) and Day-1 (2-cell, n=12) bovine embryos that were cultured for 4 hours but not transferred were examined. The aggregation assay proved to be sensitive to 5 pg of PAF. The assay proved to be specific, since the PAF receptor antagonist SRI 63-441 inhibited platelet aggregation induced by culture media in dosages comparable to aggregation induced by synthetic PAF18. From the 15 Day-7 embryos that established a pregnancy 2 contained measurable amounts of PAF in their culture media. No PAF was detected in the culture media from 13 embryos that succeeded, in the 18 embryos that failed to establish a pregnancy, or in the control media. One of 6 Day-6 embryos and 3 of 12 Day-1 (2-cell) embryos secreted detectable amounts of PAF into the culture media. Although the results indicate that some bovine embryos release PAF or a PAF-like substance in vitro, PAF measurements in the culture medium seem not to be a suitable method for the evaluation of bovine embryos prior to transfer.

Role of arachidonic acid and its metabolites in the regulation of progesterone and oxytocin release from the bovine corpus luteum

We have examined the effects of arachidonic acid (AA) and some of its metabolites on progesterone (P4) and oxytocin (OT) release by corpora lutea obtained from Holstein heifers at day 8 of the estrous cycle (Day 0 = estrus). The luteal cells were dispersed with collagenase and small and large cells were separated by unit gravity sedimentation and flow cytometry. After an 18-hr preincubation period, the cells were incubated in the presence of various treatments for 1 hr, followed by a 23-hr incubation period with no treatment. OT was secreted by the large, but not by the small, luteal cells into the incubation medium. AA elicited a significant (P less than 0.05) release of OT from the large cells and P4 from both the large and small cells within 1 hr of incubation, having a specific effect at a concentration of 10 microM. Larger doses (25 and 100 microM) of AA adversely affected the cell viability. Phospholipases A2 (0.5 unit/ml) and C (0.05 unit/ml) and calcium ionophore A23187 (0.1 microM) stimulated OT release from the large cells to the same extent as AA (10 microM). Inhibition of the AA cyclooxygenase metabolic pathway by indomethacin did not affect AA-induced release of OT and P4, although exogenous prostaglandins F2 alpha and I2 (5-25 ng/ml) stimulated the release of OT. Lipoxygenase products of AA (hydroxyeicosatetraenoic acid and leukotrienes; 25 ng/ml) also stimulated OT release. Inhibition of the lipoxygenase metabolic pathway by nordihydroguaiaretic acid abolished AA-induced release of both OT and P4. These results suggest that intracellular accumulation of free AA may modulate secretory functions in the bovine corpora lutea, including OT and P4 release.

Coculture of in vitro fertilized bovine embryos with oviductal epithelial cells originating from different stages of the estrous cycle

Bovine embryos derived from in vitro fertilization procedures were cocultured in vitro with oviductal cells obtained from heifers between d 4 and 6 or d 14 and 16 of the estrous cycle. In addition, proteins secreted by oviductal cells isolated between d 4 and 6 or d 14 and 16 of the cycle were monitored. Embryos (2- to 4-cell) were incubated in Tissue Culture Medium-199 with 10% fetal bovine serum with or without oviductal cells at 39 degrees C for 10 d following in vitro insemination. There were more morulae, blastocysts, and hatched blastocysts following coculture with oviductal cells than with culture in medium alone. However, no differences were noted in embryo development following coculture with oviductal cells obtained between d 4 and 6 or d 14 and 16 of the estrous cycle. Also, no differences were detected in the amount of [35S]methionine-labeled proteins secreted by oviductal cells isolated from different days of the estrous cycle. These results indicate that oviductal epithelial cells isolated from early and late luteal phases of the estrous cycle will effectively support early embryonic development following prolonged in vitro culture.

Cellular distribution and cycle phase dependency of gonadotropin and eicosanoid binding sites in bovine corpora lutea

Bovine luteal functions are regulated by gonadotropins and eicosanoids. The specific binding sites that presumably mediate the actions of these regulatory agents have previously been characterized in bovine luteal tissue. However, the cellular distribution and/or the cycle phase dependency of these binding sites have never been investigated. In the present study, we investigated these parameters by using quantitative light microscope autoradiography. The results showed that both small and large luteal cells contained binding sites for LH/hCG, prostaglandin (PG)E2, PGF2 alpha, PGI2, and leukotriene (LT)C4. In addition, luteal blood vessels contained LH/hCG and LTC4 binding sites and luteal fibroblasts contained PGE2 binding sites. On a per cell basis, there were more binding sites for all ligands in large luteal cells as compared to small or nonluteal cells. After correction for the cellular area differences, small luteal cells contained more LH/hCG, PGE2, PGI2, and LTC4 binding sites, while large luteal cells contained more PGF2 alpha binding sites. The small and large luteal cell binding of hCG, PGE2, PGI2, and LTC4 increased from early to mid luteal phase, followed by a decline in the late luteal phase. PGF2 alpha binding, on the other hand, increased from early to late luteal phase. In contrast to luteal cells, binding of hCG and LTC4 to luteal blood vessels and binding of PGE2 to luteal fibroblasts did not change during the cycle. These results suggest that LH/hCG and eicosanoid regulation of luteal function is more complex than previously envisioned and it involves both small and large luteal cells and, in some cases, also nonluteal cells.

Prolonged gestation in a Holstein cow: adenohypophyseal aplasia and skeletal pathology in the offspring

A Holstein fetus was delivered by Caesarean section at a gestational age of 441 days. The pituitary pars distalis was aplastic and the adrenal and thyroid glands were severely hypoplastic. Arrested or retarded cartilage cell maturation resulted in absence or minimal development of epiphyseal ossification centers, delayed ossification of carpal bones, and arrest of longitudinal growth of bones. The pathophysiology of prolonged gestation and of skeletal pathology is discussed.

Bovine corpus luteum function after removal of granulosa cells from the preovulatory follicle

Experiments were conducted to determine the effects of removing granulosa cells from bovine preovulatory follicles on subsequent corpus luteum (CL) function. Holstein heifers were assigned to three groups: untreated controls (n = 6), removal of granulosa cells (n = 9) and removal and return of granulosa cells (n = 7). Surgery was performed 18-24 hr after the onset of estrus and in all cases after the preovulatory luteinizing hormone (LH) surge. Jugular venous blood was collected and estrous activity monitored twice daily. Corpora lutea were formed in six heifers in each group. Concentrations of plasma progesterone were reduced (P less than 0.05) on Days 7-17 in heifers from which granulosa cells were removed when compared to the other two groups. There were no differences in the lengths of the estrous cycles nor concentrations of LH in the three groups. In summary, these experiments support the concept that granulosa cells make a substantial contribution to the output of progesterone by the cyclic CL but may have a limited role in determining the functional lifespan of the CL. These experiments also establish the fact that granulosa cells develop into functional luteal cells after their removal and return to the preovulatory follicle.

Differential effects of calcium on progesterone production in small and large bovine luteal cells

We studied the effects of calcium (Ca2+) ions in progesterone (P) production by separated small and large luteal cells. Corpora lutea were collected from 31 heifers between days 10 and 12 of the estrous cycle. Purified small and large cells were obtained by unit gravity sedimentation and flow cytometry. P accumulation in cells plus media was determined after incubating 1 x 10(5) small and 5 x 10(3) large cells for 2 and 4 h respectively. Removal of Ca2+ from the medium did not influence basal P production in the small cells (P greater than 0.05). However, stimulation of P by luteinizing hormone (LH), prostaglandin E2 (PGE2), 8-bromo-cyclic 3',5' adenosine monophosphate (8-Br-cAMP) and prostaglandin F2 alpha (PGF2 alpha) was impaired (P less than 0.05) by low Ca2+ concentrations. LH and PGE2-stimulated cAMP production was not altered by low extracellular Ca2+ concentrations, and PGF2 alpha had no effect on cAMP. In contrast, basal as well as LH and forskolin-stimulated P production were attenuated (P less than 0.05) in Ca2(+)-deficient medium in the large cells. However, P production stimulated by 8-Br-cAMP was not altered in Ca2(+)-deficient medium. Steroidogenesis in large cells was also dependent on intracellular Ca2+, since 8-N, N-diethylamineocytyl-3,4,5-trimethoxybenzoate (TMB-8), an inhibitor of intracellular Ca2+ release and/or action, suppressed (P less than 0.05) basal, LH and 8-Br-cAMP stimulated P. In contrast, basal P in small cells was not altered by TMB-8; whereas LH-stimulated P was reduced 2-fold (P less than 0.05). The calcium ionophore, A23187, inhibited LH-stimulated P in small cells and both basal and agonist-stimulated P in large cells. These studies show that basal P production in small cells does not require Ca2+ ions, while hormone-stimulated P production in small cells and both basal and hormone-stimulated P in large cells do require Ca2+. The inhibitory effect of Ca2+ ion removal was exerted prior to the generation of cAMP in the large cells, but distal to cAMP generation in hormone-stimulated small cells. The calmodulin/protein kinase C antagonist, W-7, also inhibited both basal and hormone-stimulated P production in both small and large luteal cells, indicating that P production in luteal cells also involves Ca2(+)-calmodulin/protein kinase C-dependent mechanisms.

Oxytocin-specific RNA, oxytocin and progesterone concentrations in corpora lutea of heifers treated with oxytocin

Sixteen virgin Holstein heifers were used to study the role of oxytocin in luteal function. Oxytocin (100 i.u.) was administered on Days 2-5 (Exp. 1) or Days 2-6 (Exp. 2), and the corpora lutea were collected and weighed on Day 6 or Day 8, respectively. Plasma progesterone values and tissue concentrations of progesterone and oxytocin were determined by radioimmunoassay. In addition, the tissue level of the oxytocin-specific transcript was measured by dot-blot hybridization. Expression of the oxytocin-specific transcript was not affected by oxytocin treatment in either experiment. In contrast, plasma progesterone values and tissue progesterone and oxytocin concentrations were all decreased after 5 days of oxytocin treatment (Exp. 2), but not after 4 days (Exp. 1). Since oxytocin concentrations were reduced while the level of its transcript remained unaffected, oxytocin injections might be influencing either peptide processing or release.

Arachidonic acid and its metabolites increase cytosolic free calcium in bovine luteal cells

We studied the effects of arachidonic acid and its metabolites on intracellular free calcium concentrations ([Ca2+]i) in highly purified bovine luteal cell preparations. Corpora lutea were collected from Holstein heifers between days 10 and 12 of the estrous cycle. The cells were dispersed and small and large cells were separated by unit gravity sedimentation and flow cytometry. The [Ca2+]i was determined by spectrofluorometry in luteal cells loaded with the fluorescent Ca2+ probe, Fura-2. Arachidonic acid elicited a dose-dependent increase in [Ca2+]i in both small and large luteal cells, having an effect at concentrations as low as 5 microM; and was maximally effective at 50 microM. Several other fatty acids failed to exert a similar response. Addition of nordihydroguaiaretic acid (NDGA) or indomethacin failed to suppress the effects of arachidonic acid. In fact, the presence of both inhibitors resulted in increases of [Ca2+]i, with NDGA exerting a greater stimulation of [Ca2+]i than indomethacin. Prostaglandin F2 alpha (PGF2 alpha) as well as prostaglandin E2 (PGE2) increased [Ca2+]i in the small luteal cells. These results support the idea that arachidonic acid exerts a direct action in mobilizing [Ca2+]i, in the luteal cells. Furthermore, they demonstrate that the cyclooxygenase (PGF2 alpha and PGE2) and lipoxygenase products of arachidonic acid metabolism also play a role in increasing [Ca2+]i in bovine luteal cells. Since the bovine corpus luteum contains large quantities of arachidonic acid, these findings suggest that this compound may regulate calcium-dependent functions of the corpus luteum, including steroid and peptide hormone production and secretion.

Phorbol ester receptors in bovine luteal cells: relationship to protein kinase C

We investigated the binding kinetics of the tumor-promoting phorbol ester, phorbol-12,13-dibutyrate (PBt2) to dispersed total bovine luteal cells, purified small luteal cells, and purified luteal protein kinase C (PKC). Saturation analysis and competitive displacement techniques were used. Binding of [3H]PBt2 to total luteal cell preparations resulted in two distinct affinities. The high affinity component was characterized by a Kd of 4.5 +/- 1.5 nM. Analysis of [3H]PBt2 binding to total cells using competitive displacement demonstrated that the low affinity binding was specific and displaceable but dependent on concentrations of [3H]PBt2 far above the Kd for the high affinity binding. In contrast to the total cell preparations, only high affinity binding was observed in intact purified small luteal cells (Kd = 0.96 +/- 0.04 nM). Partial purification of luteal cytosolic PKC by DEAE-Sephadex chromatography resulted in co-elution of PKC enzyme activity and the [3H]PBt2 binding activity. Under conditions of saturating calcium (0.1 mM) and phosphatidylserine (PS) (100 micrograms/tube) concentrations, binding to the partially purified PKC preparation was found to be of a single high affinity and exhibited a Kd (1.3 +/- 0.2 nM) similar to the high affinity binding observed in intact cells. These results suggest that the primary phorbol ester receptor in luteal cells is PKC. However, a low affinity, high capacity [3H]PBt2 binding site also exists within the corpus luteum, either in the large cells or in the accessory cell fraction which consists mainly of endothelial cells.