Immunohistochemical localization of Notch signaling molecules in ameloblastomas.

We examined Notch signaling molecules, Notch1 and Jagged1, in serial large cases of typical solid/multicystic ameloblastoma. In general, Notch positive staining products were frequently detected in the cytoplasms of the cells. In the same cells, Jagged positive staining were also frequently observed, while only occasionally positive in peripheral cells, especially in cuboidal cells. The results showed that these morphogenesis regulation factors are closely related to cytological differentiation in neoplastic cells of ameloblastoma. The Notch and Jagged positive-cell ratios were frequently positive, and the ratios were nearly the same between the varied histopathological, cytological patterns. However, the less-differentiated cells were fewer in number than that of well-differentiated cells.

Increase in ceramide level after application of various sizes of sphingomyelin liposomes to a cultured human skin model.

Sphingomyelin-based liposomes (SPM-L) that were sized (or not) by extrusion through a filter with pores of 100, 200, or 400 nm were applied to a three-dimensional cultured human skin model in order to evaluate which size of SPM-L was most effective at increasing its ceramide level. The diameters of the SPM-L in PBS were 102.7, 181.0, 224.0, and 380.1 nm. The diameters of the liposomes in the culture medium were 117.5, 199.2, 242.1, and 749.8 nm. The diameter of the small liposomes (<200 nm in diameter) did not change much, at least for 7 days. SPM-L in saline or culture medium were applied to the basal layer side or stratum corneum side of the cultured skin model, and ceramide II, III, V, and VI were then extracted from it. The extracted ceramide molecules were separated by HPTLC, and the concentration of each type of ceramide was quantified using a densitometer. When the small SPM-L (110 or 190 nm in diameter) were applied to the basal layer side, the levels of ceramide III and V were increased. When they were applied to the stratum corneum side, the levels of ceramide II, III, V, and VI were significantly increased compared to those of the PBS group, especially after the application of the small SPM-L (110 nm in diameter). Thus, the application of small SPM-L was useful for increasing the ceramide II, III, V, and VI levels of a cultured human skin model.

Response to myocardial ischemia/reperfusion injury involves Bnip3 and autophagy.

Ischemia and reperfusion (I/R) injury is associated with extensive loss of cardiac myocytes. Bnip3 is a mitochondrial pro-apoptotic Bcl-2 protein which is expressed in the adult myocardium. To investigate if Bnip3 plays a role in I/R injury, we generated a TAT-fusion protein encoding the carboxyl terminal transmembrane deletion mutant of Bnip3 (TAT-Bnip3DeltaTM) which has been shown to act as a dominant negative to block Bnip3-induced cell death. Perfusion with TAT-Bnip3DeltaTM conferred protection against I/R injury, improved cardiac function, and protected mitochondrial integrity. Moreover, Bnip3 induced extensive fragmentation of the mitochondrial network and increased autophagy in HL-1 myocytes. 3D rendering of confocal images revealed fragmented mitochondria inside autophagosomes. Enhancement of autophagy by ATG5 protected against Bnip3-mediated cell death, whereas inhibition of autophagy by ATG5K130R enhanced cell death. These results suggest that Bnip3 contributes to I/R injury which triggers a protective stress response with upregulation of autophagy and removal of damaged mitochondria.

Measurement of endometrial tissue blood flow: a novel way to assess uterine receptivity for implantation.

OBJECTIVE: To assess endometrial receptivity in terms of endometrial tissue blood flow (ETBF) measured hysterofiberscopically by laser blood-flowmetry, and to examine the technique's effectiveness in an in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) program. DESIGN: A prospective clinical study. SETTING(S): IVF program in a university hospital. PATIENT(S): A total of 75 infertile women with normal menstrual cycles undergoing IVF/ICSI. INTERVENTION(S): ETBF, conventional ultrasonographic, endocrinologic, and histologic parameters for receptivity and immunoreactivity for vascular endothelial growth factor (VEGF) in endometrium were assessed between days 4 and 6 of the luteal phase in a spontaneous menstrual cycle. Then all patients underwent IVF/ICSI. MAIN OUTCOME MEASURE(S): Achievement of clinical pregnancy by IVF/ICSI. RESULT(S): ETBF, VEGF expression, and the number of embryos were significantly higher in the women who became pregnant than in those who did not. By stepwise multiple logistic regression, significant predictors of pregnancy were the number of embryos and ETBF but not conventional receptivity markers. The rate of pregnancy was significantly higher in women with ETBF values of at least 29 mL/min per 100 grams of tissue than in women with lower values (42 vs. 15% in 36 and 39 women, respectively). ETBF was significantly greater in morphologically normal than abnormal uteri. In normal uteri, ETBF was greatest in the fundus. Correspondingly, in normal uteri 85% of gestational sacs were implanted in the fundus. CONCLUSION(S): ETBF is superior to conventional parameters for determining endometrial receptivity for implantation.

A novel method for assessing assisted female fertility: bioelectric impedance.

Early detection of declining female fertility is important for effective prevention and treatment of infertility. Age, serum concentration of FSH in the early follicular phase (basal FSH), and the clomiphene citrate (CC) challenge test correlate only with large declines in fertility. We serendipitously discovered that by a novel mechanism bioelectric impedance (BEI) sensitively reflects early fertility decrements. BEI was measured between the right and left arms by the tetrapolar method before and during ovarian stimulation for in vitro fertilization (IVF). In a stepwise multiple logistic regression analysis of five factors (BEI on luteal day 4 prior to the IVF cycle [BEI-L4], age, basal FSH, body height, and body mass index), BEI-L4 alone was a significant predictor (P<0.05) of achievement of pregnancy by IVF in 148 women (74 pregnant and 74 nonpregnant). BEI showed a nadir on the day of administration of hCG in the pregnant but not the nonpregnant group. Serum concentrations of VEGF during ovarian stimulation were significantly higher in the pregnant group, but not those of 17beta-estradiol and progesterone. The CC challenge test revealed no significant difference between 11 pregnant and 15 nonpregnant women. The clinical usefulness of BEI was evaluated in 272 consecutive IVF cycles. Rate of pregnancy was significantly higher (P<0.01) in IVF cycles with BEI-L4 > or =600 Ohms than <600 Ohms (44% and 26% in 149 and 123 cycles, respectively). When BEI-L4 was > or =600 Ohms, pregnancy rates were constantly high irrespective of age and basal FSH. In prediction of nonpregnancy, sensitivity of BEI-L4 (0.52) was significantly (P<0.05) higher than those of age and basal FSH (0.39 and 0.046, respectively). BEI, which is easy, noninvasive, and inexpensive, predicts female fertility more sensitively than age and basal FSH, probably reflecting angiogenic capacity of reproductive organs.

A therapeutic role of prolactin supplementation in ovarian stimulation for in vitro fertilization: the bromocriptine-rebound method.

In a prospective randomized study, we examined whether a novel method of ovarian stimulation, the bromocriptine-rebound method, improves in vitro fertilization (IVF) outcomes compared with the conventional long protocol using GnRH agonist and human menopausal gonadotropin (hMG). Ovulatory women with previous failed IVF-embryo transfer using the long protocol were prospectively assigned to either the bromocriptine-rebound method (group 1, 82 cycles) or the long protocol (group 2, 80 cycles). The bromocriptine-rebound method was the same as the long protocol, except that bromocriptine was administered daily from day 4 of the preceding cycle until 7 days before hMG stimulation. The numbers of follicles, fertilized oocytes, and embryos with superior morphology were higher in group 1 than in group 2. The rates of clinical pregnancy and live birth delivery per cycle were significantly higher in group 1 (38% and 33%, respectively) than in group 2 (21% and 19%, respectively). The mean concentration of serum PRL during hMG administration was significantly higher in group 1 than group 2. A significant correlation between the number of superior embryos and PRL concentrations was observed in group 1, but not in group 2. Next, we performed a retrospective study to investigate how the bromocriptine-rebound method exerts its beneficial effects. In the initial IVF with the long protocol, the mean concentration of serum PRL during hMG administration and the expression of PRL receptor (PRLr) messenger ribonucleic acid (mRNA) in granulosa cells were significantly higher in nonpregnant patients than in pregnant ones. When IVF was repeated with the bromocriptine-rebound method in the nonpregnant patients, the expression of PRLr mRNA decreased significantly. In conclusion, the bromocriptine-rebound method enhances embryonic development and the rate of live birth delivery in patients with previous failed IVF using the long protocol. We hypothesize that in the nonpregnant patients using the long protocol, the serum PRL concentration and PRLr mRNA expression are increased to compensate for poor postreceptor responsiveness of granulosa cells to PRL during oocyte maturation. The bromocriptine-rebound method may improve oocyte maturation in such patients by restoring postreceptor responsiveness of granulosa cells to PRL during the hypoprolactinemic period and increasing the PRL concentration by a rebound phenomenon after discontinuation of bromocriptine.

A novel method of ovarian stimulation for in vitro fertilization: bromocriptine-rebound method.

OBJECTIVE: To examine whether a new method of ovarian stimulation, bromocriptine-rebound method, improves IVF outcomes compared with the conventional long protocol of GnRH agonist and hMG regimen. DESIGN: A prospective clinical trial. SETTING: In vitro fertilization program at a university hospital. PATIENTS: Endocrine-normal ovulatory women less than 40 years of age, with normal male partners and previous failed IVF-ET using long protocol. INTERVENTIONS: Patients were assigned to either bromocriptine-rebound method (group 1) or long protocol (group 2). The bromocriptine-rebound method was the same as the long protocol, except that bromocriptine was administered daily from day 4 of the preceding cycle until 7 days before hMG stimulation. MAIN OUTCOME MEASURES: The number of cleaved and morphologically superior embryos, pregnancy rate per oocyte pick-up, and serum PRL concentrations during administrations of hMG. RESULTS: Significantly more embryos were cleaved and had superior morphology in group 1 than group 2. Clinical and ongoing pregnancy rates per oocyte pick-up were significantly higher in group 1 (42% and 38%, respectively) than group 2 (24% and 21%, respectively). The mean PRL concentration was significantly higher in the group 1 than group 2. A significant correlation between the number of superior embryos and PRL concentrations was observed in group 1, but not in group 2. CONCLUSION: The bromocriptine-rebound method enhanced embryonic development, resulting in an increased pregnancy rate compared with the long protocol.

An improvement in the embryo quality and pregnancy rate by the pulsatile administration of human menopausal gonadotropin in patients with previous unsuccessful in vitro fertilization attempts.

OBJECTIVE: To examine whether the pulsatile administration of hMG improves IVF outcomes in patients with previous unsuccessful attempts using IM injections of hMG. DESIGN: A prospective randomized study. SETTING: In vitro fertilization program at a university hospital. PATIENTS: Eighty-eight endocrine-normal ovulatory women under 40 years of age, with normal male partners and a history of unsuccessful IVF treatment by the IM administration of hMG. INTERVENTIONS: Patients were assigned randomly to receive either IM (bolus group) or pulsatile administration of hMG (pulsatile group) after pituitary desensitization by a GnRH agonist. MAIN OUTCOME MEASURES: The proportion of retrieved oocytes with a polar body, the number of fertilized oocytes and embryos, the proportion of morphologically superior embryos, and the rate of pregnancy per initiated cycle were compared. RESULTS: The proportion of retrieved oocytes with a polar body and the number of fertilized oocytes and embryos were similar in both groups. Significantly more embryos had superior morphology in the pulsatile group (77%) than the bolus group (52%). The rates of overall and clinical pregnancy per initiated cycle were significantly higher in the pulsatile group (39% and 30%, respectively, n = 44) than in the bolus group (18% and 11%, respectively, n = 44). CONCLUSION: In women with failed IVF attempts using IM administration of hMG, the pulsatile administration of hMG produces superior embryos and, hence, a higher pregnancy rate.

[A novel method of ovarian stimulation for in vitro fertilization (bromocriptine-rebound method) increases developmental potential of oocytes and pregnancy rate].

A novel method of ovarian stimulation for IVF is reported. Endocrine-normal ovulatory women with a history of unsuccessful IVF attempts by means of a long protocol of a GnRH agonist/hMG regimen (L regimen) were studied. Ovaries were stimulated by the three regimens described below. The bromocriptine-rebound (BR) regimen consisted of bromocriptine (B) 2.5mg/day administered daily beginning on day 4 of the preceding cycle and buserelin acetate administered beginning in early high phase. Administration of B was discontinued in the low phase of the IVF cycle and daily administration of hMG was begun 7 days later. HCG was administered when dominant follicles reached 16-18 mm in diameter. The bromocriptine-continuous (BC) regimen was the same as the BR regimen, except that B was administered until the administration of hCG. The L regimen was the same as the BR regimen, except that no B was administered. The pregnancy rate per oocyte retrieval was significantly higher on the BR regimen (56% in 70 cycles) than the L regimen (33% in 46 cycles), and lowest on the BC regimen (29% in 7 cycles). The rate of fertilization and cleavage per oocyte and the proportion of morphologically-good embryos were significantly higher on the BR regimen (59.1% and 57.3%, respectively) than the L regimen (46.3% and 48.0%, respectively), and lowest on the BC regimen (49.0% and 41.7%, respectively). Serum PRL concentrations (ng/ml) at the time hMG was started were 14.9 +/- 1.5, 7.9 +/- 1.7 and 2.5 +/- 0.7 on the BR, L and BC regimens, respectively. The results of this study show that the BR regimen increases the developmental potential of oocytes and the pregnancy rate, probably because of increasing serum PRL levels to within the normal range.

[Effects of the maturity of human oocytes on fertilization and embryonic development: application of oocyte maturation in medium containing follicle-stimulating hormone].

A total of 2,145 oocytes from 355 IVF cycles were classified as overmature (O), mature (M), transitional (T), immature (I) and abnormal (A) according to the morphology of the corona radiata. The rates of fertilization (%F) and embryonic development (%D) per oocyte were the highest in the M group, and decreased significantly with the decreasing maturity of the oocytes (T and I) and were the lowest in the A group. Decreases in %F and %D were also observed in the O group. %F and %D were significantly higher in oocytes with a polar body (PB) than without a PB. Mature oocytes classified according to the morphology of the corona radiata had significantly higher %F and %D than those classified according to the morphology of the cumulus oophorus. %F and %D were increased when T-oocytes without a PB and I-oocytes were matured in vitro for 18-24 hours in medium supplemented with FSH. A normal female baby was delivered, following IVF-ET of two T-oocytes matured in vitro with FSH.

Administration of human chorionic gonadotropin for in vitro fertilization-embryo transfer based on the serum luteinizing hormone (LH) concentration: the importance of synchronization with endogenous LH rises.

OBJECTIVE: To examine whether synchronized administration of hCG at the onset of the endogenous LH rise promotes successful IVF. DESIGN: A prospective randomized study. SETTING: In vitro fertilization program at a university hospital. PATIENTS: A total of 208 IVF cycles in 148 patients. INTERVENTIONS: Serum LH concentrations were measured daily and hMG was administered daily. Independent of follicle size and E2 concentration, hCG was administered as soon as the LH concentration exceeded the J level, defined as the minimum value + (the day 3 value-the minimum value) x 1/3(J group). Alternatively, hCG was administered when the serum LH concentration turned to increase but was still less than the J level, or 1 day after the serum LH concentration exceeded the J level (non-J group). RESULTS: The rates of total and ongoing pregnancy per cycle were significantly higher in the J group (35.6% and 26.0%, respectively, n = 104) than in the non-J group (21.2% and 12.5%, respectively, n = 104). Pregnancies in the J group were achieved over a wide range of dominant follicle diameters (13 to 25 mm), E2 levels (198 to 1,700 pg/mL; conversion factor to SI units, 3.671), and E2 level per follicle > or = 12 mm (24 to 225 pg/mL per follicle) recorded on the day of hCG administration. CONCLUSION: Synchronized administration of hCG in accordance with endogenous LH rises produces a high rate of pregnancy in IVF.

Hydatidiform mole with a surviving coexistent fetus following in-vitro fertilization.

A case of a hydatidiform mole with a surviving coexistent fetus following in-vitro fertilization and embryo transfer is reported. The diagnosis was established at 12 weeks gestation and pregnancy was maintained until 31 weeks, during which time transient hyperthyroidism and lung metastasis developed. No difference was observed in pronucleus formation and early embryonic development between the two embryos, which resulted in a complete mole and a normal fetus. DNA finger-print analysis, karyotype analysis and histopathological examination confirmed that the pregnancy was a twin of a complete mole and a normal conception. DNA fingerprint analysis was performed with a single-locus probe cocktail. All DNA bands from the tumour were of paternal origin, and the bands from the placenta were of paternal and maternal origin.

Prolactin inhibits ovulation by reducing ovarian plasmin generation.

The present study was undertaken to investigate the effects of prolactin (PRL) on gonadotropin-induced ovulation and the biosynthesis of prostaglandin (PG), leukotriene (LT), and plasmin in in vitro perfused rabbit ovaries. The addition of PRL to the perfusate inhibited hCG-induced ovulation in vitro in a dose-dependent manner. Although exposure to hCG significantly increased PGF2 alpha, PGE2, and LTB4 production by perfused rabbit ovaries, PRL did not affect the secretion rates of PGs and LTB4 stimulated by hCG administration. The ovarian plasmin generation was determined by measuring the amount of plasmin bound to its major inhibitor, alpha 2-plasmin inhibitor (alpha 2PI-Plm). Exposure to hCG enhanced biphasically the ovarian secretion rate of alpha 2 PI-Plm, while PRL at a dose of 10(3) ng/ml significantly inhibited the hCG-stimulated generation of alpha 2 PI-Plm in ovaries throughout the entire perfusion period. A significant correlation was observed between ovulatory efficiency and ovarian plasmin generation in the PRL-treated ovaries. Additionally, PRL inhibited intrafollicular concentrations of alpha 2 PI-Plm in hCG-treated ovaries in a dose-dependent manner. These observations substantiate an essential role for a plasma-generating system in the cascade of events leading to ovulation. In conclusion, PRL may act directly on the ovary and block ovulation, at least in part, via the inhibition of ovarian plasmin generation.

Direct ovarian effect of growth hormone in the rabbit.

PROBLEM: This study was undertaken to assess whether growth hormone (GH) can stimulate follicle growth and ovarian steroidogenesis via putative GH receptors. METHOD: In vitro perfused rabbit ovary. RESULTS: Ovulation occurred in neither the control ovaries nor experimental ovaries treated with 100 ng/ml of GH, whereas all ovaries exposed to 50 IU of human chorionic gonadotropin (hCG) ovulated. The addition of GH to the perfusate significantly stimulated the follicle growth in the absence of gonadotropin. The percent change in follicle diameter in GH-treated ovaries did not differ significantly from that in hCG-treated ovaries. Exposure to GH significantly stimulated the meiotic maturation in the follicular oocytes, as compared with the contralateral control ovaries. Although the concentration of progesterone in the perfusate did not differ significantly between GH-treated and control ovaries, GH stimulated estradiol production by the perfused rabbit ovaries. Rabbit ovary membranes exhibited high affinity binding sites of hGH (Kd = 6.1 x 10(-9) M). CONCLUSION: GH acts on the rabbit ovary to stimulate the follicle growth, oocyte maturation, and ovarian estradiol production by interacting with the specific receptors located in ovarian plasma membranes.

Gonadotropin stimulates ovarian renin-angiotensin system in the rabbit.

The present study was undertaken to assess the role of ovarian renin-angiotensin system (RAS) in the preovulatory cascade induced by gonadotropin exposure. In the in vitro perfused rabbit ovaries, exposure to human chorionic gonadotropin (hCG) enhanced the secretion rate of angiotensin II (Ang II) within 1 h. The secretion rate reached maximal levels at 6 h and then declined thereafter. The intrafollicular Ang II content and renin-like activity were also significantly increased at 2 and 4 h after exposure to hCG, compared with control ovaries perfused with medium alone. The level of intrafollicular Ang II after hCG exposure significantly exceeded the concentration of Ang II in an equivalent volume of plasma. The addition of 1 microM captopril to the perfusate significantly inhibited the secretion rate of Ang II stimulated by hCG; however, captopril affected neither the ovulatory efficiency nor prostaglandin production in ovaries treated with hCG. Captopril significantly inhibited the resumption of meiosis in the ovulated ova and follicular oocytes stimulated by hCG. The administration of 100 micrograms Ang II at 2-h intervals to the perfusate reversed the inhibitory effects of captopril on hCG-induced oocyte maturation. In conclusion, these data indicate that gonadotropin stimulates renin-like activity and Ang II production in the rabbit ovary. Ovarian renin-angiotensin system may play an important role in the process of oocyte maturation after exposure to gonadotropin.

A simple and efficacious criterion based on serum LH levels to time hCG administration for human in vitro fertilization.

OBJECTIVE: To test the efficacy of a simple criterion--LH level--for administration of hCG in an IVF program. DESIGN: Prospective, with retrospective analysis of other criteria for hCG administration. SETTING: University hospital IVF program. PATIENTS AND INTERVENTIONS: Eighty-four patients, in 110 cycles, were given 150-300 IU at 10-11 A.M. daily beginning on day 3 of the cycle. Serum LH measured daily 8:30-9:30 A.M., hCG administered on night of day LH level first exceeded J, defined as minimum value + (day 3 value-minimum) x 1/3. OUTCOME MEASURES: Pregnancy (after IVF + ET); serum concentrations of estradiol and LH. RESULTS: Total and ongoing pregnancy per cycle: 35% and 27% respectively. If hCG is administered one day early or late by the J criterion, the pregnancy rate is reduced. CONCLUSIONS: Pregnancies occurred over wide follicle diameter (14-21 mm) and estradiol level (229-2,050 pg/mL) ranges. LH is recommended for timing hCG administration.

Pump-induced frequency shifting of switched pulses in an interferometric all-optical switch.

The induced frequency chirping of switched pulses in an interferometric all-optical switch that uses pump-induced nonlinear phase shifts is investigated. Using a nonlinear fiber Sagnac interferometer switch, it is shown that switched pulses suffer from frequency shift and broadening and can be compressed by using an anomalous group-velocity-dispersion fiber. It is also demonstrated that picosecond probe pulses can be switched while retaining their temporal and spectral profiles if pump-probe walk-off is employed.

Possible involvement of leukotrienes in human luteal function.

The present study was undertaken to assess the ability of human corpora lutea to produce leukotriene B4 (LTB4). The maximum capacity of luteal cells to secrete progesterone was attained on day 4, and both the basal production and the responsiveness to hCG decreased thereafter. In contrast, the production of LTB4 by cultured luteal cells was significantly reduced on day 4, but increased thereafter. The basal concentration of LTB4 produced by luteal cells varied from 75 to 590 pg/10(5) cells/2 days. LTB4 production appeared to decrease concomitantly with increased-progesterone production in cultured luteal cells. Exposure to hCG decreased significantly LTB4 production by cultured luteal cells on day 4. An inhibitor of the lipoxygenase pathway, nordihydroguaiaretic acid (NDGA), inhibited LTB4 production in a dose-dependent manner. However, NDGA did not affect basal progesterone production by the cultured luteal cells. A significant inverse relationship existed between the accumulation rates of progesterone and LTB4 in the luteal cells. Furthermore, the addition of LTB4 inhibited progesterone production in a dose-dependent manner in both the presence and absence of hCG. In conclusion, LTB4 could be synthesized by human corpora lutea in vitro, and correlated inversely with the secretion rates of progesterone. These data suggest that LTB4 produced locally in the corpus luteum may be an important regulator in human luteal regression.

Stimulatory role of cyclic adenosine monophosphate as a mediator of meiotic resumption in rabbit oocytes.

The present study was undertaken to assess the role of alterations of intraoocyte cAMP concentrations in the meiotic maturation of isolated and follicle-enclosed oocytes. In isolated oocyte culture, the intracellular cAMP content of denuded oocytes declined within 15 min of incubation, whereas the cAMP content of cumulus-enclosed oocytes did not change substantially for 1.5 h of incubation, and then declined abruptly. Commitment to meiotic maturation was preceded by reduced concentrations of intraoocyte cAMP. Forskolin inhibited the spontaneous maturation of cumulus-enclosed oocytes in a dose-dependent manner. However, this inhibition was attenuated as the duration of incubation increased. Forskolin significantly stimulated the intracellular cAMP content of denuded and cumulus-enclosed oocytes, but intraoocyte cAMP returned to pretreatment values within 4 h. The decline in intraoocyte cAMP was followed by the meiotic maturation of isolated oocytes. In in vitro perfused rabbit ovaries, exposure to forskolin at 10(-4) M, as well as to 50 IU human CG, accelerated the meiotic maturation of follicle-enclosed oocytes. The intraoocyte cAMP content increased significantly within 30 min and reached its maximum 2 h following exposure to forskolin. Thereafter, cAMP decreased abruptly and returned to pretreatment levels by 6 h. These alterations of intraoocyte cAMP contents following exposure to forskolin paralleled those observed in human CG-treated ovaries. The decline in cAMP content of follicle-enclosed oocytes was followed by their meiotic maturation. In conclusion, the sustained elevation of intraoocyte cAMP levels inhibits the initiation of meiotic maturation in isolated and follicle-enclosed oocytes. Within the follicle, resumption of meiosis is triggered via a transient increase in intraoocyte cAMP, but commitment to meiosis must await the decline of intraoocyte cAMP.