Cloning and characterization of the cyclic guanosine monophosphate-inhibited phosphodiesterase PDE3A expressed in mouse oocyte.

In the preovulatory follicle, oocyte meiotic resumption occurs soon after the LH surge and is associated with a decrease in cAMP. Inhibition of cAMP degradation blocks germinal vesicle breakdown as well as activation of meiotic promoting factor, both hallmarks of reentry into the cell cycle. In situ and pharmacological analysis of rodent ovaries suggested the presence of a phosphodiesterase 3 (PDE3) in the germ cell but not the somatic cell compartment. Here we have investigated the structure and properties of the PDE form expressed in mouse oocytes. Polymerase chain reactions using a mouse oocyte cDNA library as a template, and primers based on the conserved sequence of rat and human PDE3As, yielded partial fragments corresponding to mouse PDE3A. Further screening of the mouse oocyte cDNA library and subsequent ligation of individual cDNA clones yielded PDE3A cDNA containing the entire coding region of mouse PDE3A. To determine the kinetic properties of this PDE, the cDNAs encoding the full-length PDE3A and NH(2)-truncation forms Delta 1 (Delta346aa) and Delta 2 (Delta608aa) were expressed in mouse Leydig tumor cells. Whereas the full-length recombinant protein was always found in the particulate fraction, the Delta 1 and Delta 2 truncated PDE3As were recovered mostly in the soluble fraction. The Michaelis constant values for hydrolysis of cAMP of PDE3A Delta 1 and PDE3A Delta 2 were similar to those of intact full-length PDE3A or oocyte PDE (0.2-0.5 microM). More importantly, there was good correlation between the rank of potency of selective and nonselective compounds in inhibiting recombinant PDE3A or PDE activity derived from cumulus-oocyte complexes and in blocking resumption of meiosis. These data provide evidence that the PDE expressed in the oocyte is a soluble form of PDE3A and that activity of this enzyme is involved in the control of resumption of meiosis.

The endogenous feeding suppressant, 2-buten-4-olide, impairs the pulsatile secretion of luteinizing hormone through endogenous opioid peptides.

OBJECTIVE: To clarify the mechanism of the suppressive effect of 2-buten-4-olide (2-B4O), an endogenous feeding suppressant, on the pulsatile secretion of luteinizing hormone (LH), by studying whether endogenous opioid peptides are involved in this suppressive effect. METHODS: Using ovariectomized (ovx) rats, blood samples were taken every 6 min for 2 h after administration of 2-B4O or saline into the third cerebroventricle (3V) and sequential i.v. injection of naloxone (0. 5 mg/kg per h) or saline. Rats were divided into three experimental groups: group 1: 3V saline + i.v. saline (control); group 2: 3V 2-B4O + i.v. saline; group 3: 3V 2-B4O + i.v. naloxone. Serum LH concentrations were determined by double-antibody RIA. To determine whether 2-B4O affected the biosynthetic activity of the opioidergic neurons within the ovx rat arcuate nucleus, we measured the concentrations of pro-opiomelanocortin (POMC) mRNA, a precursor of beta-endorphin, in the rostral arcuate nucleus using non-radioactive in situ hybridization and a computerized image-analysis system. RESULTS: 2-B4O significantly suppressed the pulse frequency of LH (group 2: 1.5+/-0.33 pulses/2 h, group 1: 2.43+/-0.2 pulses/2 h; P < 0.05), but naloxone blocked its suppressive effect and restored the pulse frequency (group 3: 3.29+/-0.36 pulses/2 h, group 2: 1.5+/-0.33 pulses/2 h: P < 0.01). There were no significant changes in the mean LH concentrations and amplitude. Furthermore, 2-B4O significantly stimulated the expression of POMC mRNA in the rostral arcuate nucleus. CONCLUSION: These results suggest that 2-B4O may impair the pulsatile secretion of LH by activating the opioid pathway within the hypothalamus.

Role of cyclic nucleotide phosphodiesterases in resumption of meiosis.

In the follicles of the mammalian and amphibian ovary, oocyte maturation is arrested at the prophase of the first meiotic division. Prior to ovulation, oocytes reenter the cell cycle, complete the meiotic division, and extrude the first polar body. Work from several laboratories including ours has provided evidence that the cAMP-mediated signal transduction pathway plays an important role in regulation of meiosis, the cyclic nucleotide acting as a negative regulator of maturation. Since cAMP can be regulated both at the level of synthesis and degradation, our laboratory is investigating the role of phosphodiesterases (PDE) in the control of cAMP levels of oocytes. Using pharmacological and molecular tools, we have determined that a PDE3 is the enzyme involved in the control of cAMP levels in the oocytes. In vitro and in vivo studies have established that inhibition of the oocyte PDE3 blocks resumption of a PDE is per se sufficient to cause resumption of meiosis in an amphibian oocyte model. The pathways regulating this PDE isoform expressed in the oocyte is under investigation, as they may uncover the physiological signals controlling meiosis.

Determination of free follistatin levels in sera of normal subjects and patients with various diseases.

We developed an assay system for measuring free follistatin by using an anti-follistatin mouse monoclonal antibody and [125I]activin A. The sensitivity of this assay was 0.5 microgram/l and cross-reactivities with inhibin, luteinizing hormone, follicle-stimulating hormone and growth hormone were all less than 0.5%. The dose-response curves of human sera and follicular fluid were parallel to the standard curve, and the follicular fluid contained a large amount of follistatin (6.4 +/- 0.5 mg/l, mean +/- SEM; N = 13). The within- and between-assay coefficients of variation calculated from the analysis of serum samples of four different concentrations were 3.3-7.8% and 3.9-11.0%, respectively. The recovery rates of free follistatin at five different doses were 86.4 - 102.4%. When activin A was added to the same sample, free follistatin recovery rate declined dose-dependently. Gel filtration analyses of human serum and follicular fluid resulted in a single peak corresponding to authentic follistatin. Using this assay, free follistatin concentrations in sera were measured in normal, pregnant and diseased subjects. The free follistatin level in serum of normal adults was 3.5 +/- 0.2 micrograms/l (N = 60), which was significantly elevated in pregnant women (16.7 +/- 1.3 micrograms/l, N = 56), and in patients with chronic liver disease (8.1 +/- 1.1 micrograms/l, N = 20), chronic renal failure (6.7 +/- 0.9 micrograms/l, N = 42), advanced solid cancer (8.5 +/- 1.0 micrograms/l, N = 39) and hematological malignancies (6.8 +/- 1.0 micrograms/l, N = 18). These data indicated that the free follistatin concentration in serum is detectable and varies during pregnancy and in various diseased states.

Serum immunoreactive activin A levels in normal subjects and patients with various diseases.

We developed and validated a RIA for measuring serum activin A. The least detectable value of this assay was 0.1 micrograms/L, and the antibody used cross-reacted slightly with bovine inhibin (3.2%) and porcine activin AB (10.0%) but not with porcine activin B (< 0.5%). Serum activin A was extracted with acetonitrile and trifluoroacetic acid to get rid of the interaction with possible binding proteins in serum. As a result of this extraction procedure, the dose-response curve of serum extract was parallel to the standard curve and a single immunoreactive (ir-) peak was demonstrated on gel chromatographic analysis with constant recovery rates over 80%. Serum ir-activin A level in healthy adults was 1.27 +/- 0.03 micrograms/L (mean +/- SEM, n = 180); being 1.38 +/- 0.05 micrograms/L (n = 90) in male, and 1.16 +/- 0.05 micrograms/L (n = 90) in female subjects, with a tendency to increase with age. Serum ir-activin A level during pregnancy showed a marked increase with the advance of gestation; 1.65 +/- 0.41 micrograms/L (n = 7) in the early, 4.50 +/- 1.13 micrograms/L (n = 21) in the middle, and 16.32 +/- 2.25 micrograms/L (n = 26) in the late trimester, with a rapid decline after delivery. On the other hand, serum ir-activin A level was elevated in patients with hyperthyroidism (1.91 +/- 0.37 micrograms/L, n = 31), liver cirrhosis (2.03 +/- 0.71 micrograms/L, n = 10), chronic renal failure (3.41 +/- 0.34 micrograms/L, n = 41), and advanced solid cancer (2.24 +/- 0.52 micrograms/L, n = 67). These findings indicate that serum ir-activin A level varies with physiological conditions such as aging and pregnancy, and that it may reflect the altered production and metabolism of activin A in certain diseased conditions.

Immunoradiometric assay for follistatin: serum immunoreactive follistatin levels in normal adults and pregnant women.

A sensitive and specific immunoradiometric assay for follistatin was developed using antifollistatin mouse monoclonal and rabbit polyclonal antibodies. The sensitivity of the assay was 0.5 micrograms/L, and cross-reactivities with recombinant human activin A and bovine inhibin were less than 0.1%. The intra- and interassay coefficients of variation were less than 10%, and the recovery rate was about 90% in human serum. The addition of activin A to the same sample resulted in a minimal influence on follistatin recovery, indicating that this assay system can measure the total level of activin-bound and unbound follistatin. Gel filtration analysis of human serum showed that the majority of immunoreactivity was eluted in a larger molecular size position than that of free follistatin, suggesting that the large part of follistatin is bound to other proteins, presumably activins, in serum. Using this assay, immunoreactive follistatin levels in various biological fluids and human sera were examined. The dose-response curves of porcine follicular and amniotic fluids were parallel to the standard curve, and porcine follicular fluid contained extremely high follistatin immunoreactivity (5.6 mg/L). The serum follistatin level in normal human volunteers was 13.3 +/- 4.7 micrograms/L (mean +/- SD; n = 60), with a tendency to increase gradually with age. On the other hand, the serum follistatin level was remarkably elevated in pregnant women (62.7 +/- 35.3 micrograms/L; n = 57), with a positive correlation with weeks of pregnancy. These data indicated that circulating immunoreactive follistatin is detectable in human serum, and the levels vary with physiological conditions such as aging and pregnancy.

[Usefulness of the combined transfusion of autologous blood as pre-deposited and preoperatively diluted in gynecological surgery].

To eliminate the risks involved in homologous blood transfusion in gynecological surgery, we studied the effect of the combined transfusion of autologous blood as predeposited and preoperatively diluted. Thirty-nine cases were operated on and studied. In 27 cases, a total of 695 ml/person of autoblood was taken during the 15 preoperative days. In 39 cases, an average of 1,038 ml/person of autoblood was collected at the beginning of surgery. In 37 out of 39 cases, we were able to avoid homologous blood transfusion. In the remaining two cases with homologous blood transfusion, although more than 3,000 ml of operative blood loss was observed, only about 700 ml of homologous blood was needed. We did not find any serious side effect with autoblood transfusion. These results demonstrate the usefulness of the combined transfusion of autologous blood as predeposited and preoperatively diluted in gynecological surgery.

Effects of 2-buten-4-olide, an endogenous feeding suppressant, on the pulsatile secretion of luteinizing hormone in ovariectomized rats.

The effects of 2-buten-4-olide (2-B40), an endogenous feeding suppressant, on the secretion of luteinizing hormone (LH) were studied in ovariectomized rats. Intraperitoneal (ip) administration of 2-B40: adult female ovariectomized Wistar rats were given daily ip injections of solution containing 2-B40 at 0, 50 or 100 mg/kg body wt for 14 days. This ip treatment with 2-B40 significantly decreased the mean LH concentration and pulse frequency of LH. Intravenous (iv) administration of 2-B40: a solution of 2-B40 (50 or 100 mg/kg body wt) was slowly injected through an intra-atrium catheter and blood samples were taken every 6 min for 2 h. This iv treatment significantly suppressed the LH pulse frequency but had no significant effect on the LH amplitude or mean LH. Injection of 2-B40 into the third cerebroventricle: the injection of 2-B40 into the third cerebroventricle of freely moving rats decreased the mean LH concentration and the frequency and amplitude of LH pulses. Third cerebroventricle injection of a corticotropin-releasing factor (CRF) receptor antagonist before third cerebroventricle injection of 2-B40: the specific CRF receptor antagonist alpha-helical-CRF (9-41) was injected into the third cerebroventricle of ovariectomized rats before injection of 2-B40. Administration of 2-B40 into the third cerebroventricle significantly decreased the mean LH, concentration and pulse frequency. Third cerebroventricle injection of the CRF antagonist at 50 micrograms/rat and then 2-B40 also resulted in significant suppression of the mean LH concentration and pulse frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of insulin-like growth factor I on gonadotropin release from the hypothalamus-pituitary axis in vitro.

The effects of insulin-like growth factor-I on gonadotropin release were studied using primary culture of rat anterior pituitary cells incubated with IGF-I (20-5000 micrograms/l) and a hypothalamus-pituitary perifusion system, in which either the mediobasal hypothalamus-pituitary unit or the pituitary were perifused with IGF-I (20-2000 micrograms/l). In primary cultures of rat anterior pituitary cells, IGF-I (2000 micrograms/l) caused a significant increase in the release of both LH (46% increase) and FSH (27% increase). It also caused a significant decrease in the cellular content of LH (9%) and FSH (19%). Its effects in stimulating gonadotropin release were suppressed by administration of anti IGF-I receptor antibody (1 mg/l). In the perifusion system, IGF-I (2000 micrograms/l) did not affect the LH release from the hypothalamus-pituitary or pituitary alone. However, it caused a significant increase in the GnRH (10(-9) mol/l) stimulated LH release from perifused pituitary. These data suggest that IGF-I enhances pituitary gonadotropin release via the IGF-I receptor, but its effect on the hypothalamus was not confirmed.

Effect of 2-buten-4-olide, an endogenous suppressant of feeding, on reproductive function in rats.

The effects of 2-buten-4-olide, an endogenous feeding suppressant, on the estrous cycle and LH secretion were studied to determine the influence of this compound on reproductive function. Estrous cycling female Wistar rats were treated ip with 2-buten-4-olide (0, 30 or 100 mg.kg-1.day-1) for 2 weeks. Treatment with 100 mg.kg-1.day-1 delayed the estrous cycle. 2-Buten-4-olide increased the pituitary content of LH (1651.3 +/- 164.4 vs 927.7 +/- 65.1 ng/pituitary; p less than 0.01), and decreased the serum LH level compared with the control level in diestrus (0.16 +/- 0.01 vs 0.26 +/- 0.03 microgram/l; p less than 0.05). However, it did not affect the GnRH content of the mediobasal hypothalamus. The direct effects of 2-buten-4-olide on the pituitary response to GnRH was examined by perifusing the pituitary. Medium containing 2-buten-4-olide (10(-4) mol/l) suppressed the pituitary response to GnRH (2 micrograms/l) (percent increase at 50 min after start of GnRH stimulation: 180 +/- 47 vs 406 +/- 66%; p less than 0.05). These findings suggest that 2-buten-4-olide is involved in the regulation of pituitary gonadotropin secretion directly by suppressing the pituitary responsiveness to GnRH, and that 2-buten-4-olide may play an important role in starvation-induced anestrus.

[Clinical implication of serum antibody to Thomsen-Friedenreich antigen in patients with gynecological malignancies].

Thomsen-Friedenreich antigen (T-antigen) is a carbohydrate antigen that is expressed in a variety of cancer tissues. T-antigen is thought to have an antigenicity because circulating T antibodies can be detected as natural antibodies in humans. In this study, we examined the serum T antibody titers in patients with gynecological cancer using the hemagglutination test, and studied the relationship between the expression of T-antigen in cancer tissues and serum TA-4 levels and serum T antibody titers. Serum T antibody titers in patients with gynecological cancer were lower than those in normal controls, especially in endometrial and ovarian cancer (p less than 0.05) in which T-antigen was strongly expressed. Furthermore, the low antibody titers correlated with the expression of T-antigen in cancer tissues. T antibody titers significantly increased (p less than 0.01) after operation and the inverse relationship was found with the levels of circulating TA-4 in cervical cancer patients. These findings suggests that patients with gynecological cancer immunologically responded to T-antigen and the measurement of circulating T antibodies may be useful as an indicator of the progression of cancer in tissues.

[Expression of Thomsen-Friedenreich antigen (T-Ag) in gynecologic cancer tissues].

The expression of Thomsen-Friedenreich antigen (T-Ag), the precursor of MN blood group antigen, was studied by the ABC method with Arachys Hypogaea lectin (PNA) and the relationship of the results to the histology and clinical behavior of primary gynecologic cancers were examined. The results were as follows: 1. In cervical squamous cell tumors, the incidence of the expression of T-Ag in invasive cancers (52.9%, 37/70) was significantly higher (p less than 0.05) than that in intraepithelial tumors (28.6%, 8/28). No cryptic T-Ag(-) tissue was found in intraepithelial tumors or microinvasive cancers. 2. In squamous cell carcinomas of the cervix, the incidence of cryptic T-Ag(-) tissue was high (36.4%, 4/11) in tissue of the small cell non-keratinizing type, the most undifferentiated type, whereas it was not found in 5 cases of well-differentiated keratinizing carcinoma examined. 3. In stage Ib and II cervical cancers, no relationship was recognized between the expression of T-Ag in primary lesion and extension to the parametrium or the pelvic lymph nodes. 4. The incidence of T-Ag(+) tissue in adenocarcinomas of the uterine cervix (62.5%, 5/8), the endometrium (91.7%, 11/12), and the ovarian (80%, 8/10) was higher than that in squamous cell carcinoma of the uterine cervix (52.5%, 32/61). 5. In endometrial cancers, no relationship was recognized between the expression of T-Ag and hormone receptor status.