Germ-cell transplantation has many applications in biology and animal husbandry, including investigating the complex processes of germ-cell development and differentiation, producing transgenic animals by genetically modifying germline cells, and creating broodstock systems in which a target species can be produced from a surrogate parent. The germ-cell transplantation technique was initially established in chickens using primordial germ cells (PGCs), and was subsequently extended to mice using spermatogonial stem cells. Recently, we developed the first germ-cell transplantation system in lower vertebrates using fish PGCs and spermatogonia. During mammalian germ-cell transplantation, donor spermatogonial stem cells are introduced into the seminiferous tubules of the recipient testes. By contrast, in the fish germ-cell transplantation system, donor cells are microinjected into the peritoneal cavities of newly hatched embryos; this allows the donor germ cells to migrate towards, and subsequently colonize, the recipient genital ridges. The recipient embryos have immature immune systems, so the donor germ cells can survive and even differentiate into mature gametes in their allogeneic gonads, ultimately leading to the production of normal offspring. In addition, implanted spermatogonia can successfully differentiate into sperm and eggs, respectively, in male and female recipients. The results of transplantation studies in fish are improving our understanding of the development of germ-cell systems during vertebrate evolution.

View full abstract

In the mammalian ovary, follicular development and atresia are closely regulated by cell death and survival-promoting factors, including hormones (gonadotropins) and intraovarian regulators (gonadal steroids, cytokines, and intracellular proteins). Several hundred thousand primordial follicles are present in the mammalian ovary; however, only a limited number of primordial follicles develop to the preovulatory stage and ovulate. The others, more than 99% of follicles, will be eliminated via a degenerative process known as "atresia". The endocrinological regulatory mechanisms involved in follicular development and atresia have been characterized to a large extent, but the precise temporal and molecular mechanisms involved in the regulation of these events have remained largely unknown. Recent studies suggest that the apoptosis of ovarian granulosa cells plays a major role in follicular atresia. In this review, we provide an overview of development and atresia of follicles, and apoptosis of granulosa cells in mammals.

View full abstract

Based on earlier studies with mice and pigs, the possible pleiotropic effects of the individual porcine Dominant White/KIT genotypes on the size, histological parameters, and surface features of the ovaries; on the size, histological characteristics, and volume of the testes; and on the occurrence of abnormal epididymal sperm cells were studied in two F2 generations of an intercross between Hampshire boars and Hungarian Large White sows. The KIT genotypes were determined by a PCR-RFLP method. The ovarian diameters of gilts of various KIT genotypes did not differ significantly (P=0.292), and the II pigs had the smallest diameters. The proportion of the investigated follicular types among the different KIT genotypes did not differ significantly (P=0.329-0.919), and the highest numbers of degenerated and atretic follicles were found in the ovaries of II genotype pigs, which also exhibited the highest proportion of primary follicles. The testis volume in the II homozygote white genotype boars (249.5 cm³) was significantly (P<0.01) larger than in the Ii (205.4 cm³) and ii (197.5 cm³) boars. Bodyweight and age significantly (P<0.01) affected testicular volume. KIT genotypes had no profound effect on the proportion of the various epididymal sperm abnormalities, and ii type boars showed the highest (nonsignificant) numbers of primary abnormalities. The changes in abnormal sperm cell frequency were linear to the changes in bodyweight and testis volume. We were unable to demonstrate disadvantageous effects of the KIT genotypes on the investigated ovarian, testicular, and epididymal sperm characteristics. Therefore the reproductive traits of white colored pigs examined in this study are no worse than those of pigmented breeds.

View full abstract

The aim of the present study was to locate Ski protein, a product of cellular protooncogene c-ski, in rat ovaries in order to predict the possible involvement of Ski in follicular development and atresia. First, expression of c-ski mRNA in the ovaries of adult female rats was confirmed by RT-PCR. Then, ovaries obtained on the day of estrus were subjected to immunohistochemical analysis for Ski and proliferating cell nuclear antigen (PCNA) in combination with terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL). Ski was expressed in granulosa cells that were positive for TUNEL, but negative for PCNA, regardless of the size of follicles. Expression of Ski in TUNEL-positive granulosa cells, but not in PCNA-positive granulosa cells, was also verified in immature hypophysectomized rats having a single generation of developing and atretic follicles by treatment with equine chorionic gonadotropin. These results indicate that Ski is profoundly expressed in the granulosa cells of atretic follicles, but not in growing follicles, and suggests that Ski plays a role in apoptosis of granulosa cells during follicular atresia.

View full abstract

To reveal the mechanisms regulating the selective atresia of follicles in porcine ovaries, we examined the changes in the mRNA and protein levels of cell-death ligand, Fas/APO-1/CD95 ligand (FasL), and its receptor, Fas/APO-1/CD95 (Fas), and the localization of the proteins in granulosa cells during follicular atresia using the reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemical techniques, respectively. Trace levels of FasL mRNA and protein were detected in the granulosa cells of healthy follicles; however, weak levels were detected in those of early atretic follicles, and the levels increased during atresia. Trace/weak levels of Fas mRNA and protein were detected in the granulosa cells of healthy follicles. Fas protein was located in the cytoplasmic area, not in cell membrane area, indicating that it has no activity in regard to inducing apoptosis. When apoptosis commences in granulosa cells, Fas moves from the cytoplasmic to cell membrane area. FasL and Fas mRNAs and proteins in granulosa cells were upregulated during follicular atresia. The FasL and Fas system may play a crucial role in the regulation of apoptosis in granulosa cells during selective follicular atresia in porcine ovaries.

View full abstract

The main purpose of this study was to check whether phyto- and endogenous estrogens influence calcium ion mobilization [Ca²⁺]_i in bovine endometrial cells and whether this action is connected with biological effects i.e. prostaglandin (PG)F_2α production. In our study we used two calcium measurement methods by comparing the microscopic method with widely used quantitative - spectrofluorometric method of [Ca²⁺]_i measurement. We also wanted to confirm whether visualization of calcium ion [Ca²⁺]_i in cells using microscopic method supported by micro image analysis (Micro Image Olympus system) reflects real, qualitative changes in the ion concentration. In both methods a cell-permeable form of fluorescent [Ca²⁺]_i indicator Fura-2 was used. Cultured bovine endometrial epithelial and stromal cells influenced by phorbol-2-myristate-13-acetate (PMA; positive control), estradiol 17-β (E₂; endogenous estrogen) and active metabolites of phytoestrogens (environmental estrogens) were used as a model to study PGF_2α secretion and [Ca²⁺]_i mobilization in the cells. Equol and para-ethyl-phenol in doses of 10^-8-10^-6 M increased PGF_2α concentration both in epithelial and stromal cells (P<0.05). In both methods, equol and para-ethyl-phenol did not cause intracellular [Ca²⁺]_i mobilization in epithelial and stromal cells (P>0.05). Both methods revealed that only E₂ and PMA induced intracellular [Ca²⁺]_i mobilization in epithelial and stromal cells (P<0.05). The results of both methods were highly correlated (P<0.001; r=0.82 for epithelial cells and r=0.89 for stromal cells). In conclusion, both methods gave approximately the same results and showed that phytoestrogens, in contrast to PMA and E₂, did not cause intracellular [Ca²⁺]_i mobilization in endometrial cells. The obtained results proved that the [Ca²⁺]_i visualization method supported by micro image analysis can produce similar results to the spectrofluorometric method.

View full abstract

We investigated testicular and circulating levels of dimeric inhibins in Holstein bulls from the infantile to postpubertal periods (5 to 50 weeks of age) and examined the relationship between the profiles of circulating dimeric inhibins and FSH. Concentrations of total inhibin and inhibin B in the testis were highest at 4 to 5 weeks of age but decreased gradually as the bulls aged. Testicular inhibin A levels showed a gradual decline to a nadir at 15 to 26 weeks of age, but by 39 weeks, they were high again. The contents of total inhibin, inhibin A, and inhibin B per testis generally increased with age. Fractionation of testicular homogenates obtained from 15-week-old bulls by a combination of immunoaffinity chromatography and SDS-PAGE confirmed the presence of two major molecular weight forms (32 and 45 kDa) of dimeric inhibins in the testes. Circulating levels of total inhibin and inhibin A showed a significant increase in bulls at around 10 to 14 weeks of age compared to the levels between 5 and 7 weeks of age but decreased thereafter. However, immunoreactivity for inhibin B was not detected in the peripheral circulation, probably because of low sensitivity of the inhibin B assays. The concentrations of plasma FSH were high at 5 weeks of age but declined to lower levels between 11 and 40 weeks, and then increased from 41 weeks onward. There was no significant correlation between the plasma levels of FSH and inhibin A or total inhibin. The results clearly indicate that the bull testis produces inhibin A and B and secretes at least inhibin A into the circulation during postnatal development. However, the profile of circulating FSH in bulls shows no reciprocal relationship with the inhibin A or total inhibin profile during the postnatal period.

View full abstract

In order to study the effects of vertically transferred coplanar polychlorinated biphenyls on female reproductive development, female rat offspring from dams of Sprague-Dawley strain, which received daily oral administration of vehicle (corn oil) or 1 or 3 μg/kg of 3,3',4,4',5-pentachlorobiphenyl (PCB-126) from 2 weeks prior to mating with intact males until 20 days after delivery were examined from birth until puberty. Hepatic expression of the aryl hydrocarbon receptor (AhR)-inducible enzyme cytochrome P450 1A1 (CYP1A1) was detected in all offspring from PCB-126-exposed dams, indicating vertical transfer of PCB-126. Furthermore, quantification of ovarian mRNAs encoding CYP1A1, AhR and ARNT demonstrated that the ovary equipped the AhR-signaling system through which transcription of the CYP1A1 gene was enhanced in a dose-dependent manner. Exposure to PCB-126 retarded the growth of offspring in both exposed groups, while the viability of the neonates of the exposed groups was comparable to that of the oil-exposed controls. The exposure to 3 μg/kg/day reduced the ovarian weight on postnatal day (PND) 24, with atresia of most of the antral follicles and delayed vaginal opening. Exposure to 1 μg/kg/day did not produce such effects; however, both doses of PCB-126 induced external urogenital anomalies, such as vaginal thread and hypospadias, in all of the PCB-126-exposed female offspring. These results indicate that vertically transferred PCB-126 is potent enough to exert a direct effect on the ovary and adversely affect female puberty by altering the morphological and functional development of the female reproductive system.

View full abstract

The present study examined the effect of acute lipoprivation on pulsatile luteinizing hormone (LH) secretion in both normal-fat diet, ad libitum-fed and fasted female rats. To produce an acute lipoprivic condition, mercaptoacetate (MA), an inhibitor of fatty acid oxidation, was administered intraperitoneally to ad libitum-fed or 24-h fasted ovariectomized (OVX) rats with or without an estradiol (E2) implant, that produces a negative feedback effect on LH pulses. The steroid treatment was performed to determine the effect of estrogen on lipoprivic changes in LH release, because estrogen enhances fasting- or glucoprivation-induced suppression of LH pulses. Pulsatile LH secretion was suppressed by MA administration in a dose-dependent manner in the ad libitum-fed OVX and OVX+E2 rats. LH pulses were more severely suppressed in the 24-h-fasted OVX and OVX+E2 rats compared to the ad libitum-fed rats. Estrogen slightly enhanced lipoprivic suppression but the effect was not significant. In the present study, increased plasma glucose and free-fatty acid concentrations may indicate a blockade of fatty acid metabolism by the MA treatment, but food intake was not affected by any of the MA doses. Acute vagotomy did not block lipoprivic suppression of LH pulses. Thus, the present study indicates that lipid metabolism is important for maintenance of normal reproductive function even in rats fed a normal-fat diet and lipoprivation may be more critical in fasted animals that probably rely more heavily on fatty acid oxidation to maintain appropriate metabolic fuel levels. In addition, failure of blockade of lipoprivic LH inhibition by vagotomy suggests that lipoprivic information resulting in LH suppression is not transmitted to the brain via the vagus nerve.

View full abstract

Relaxin is a peptide hormone found in seminal plasma that has a physiological influence on sperm motility in some species. There are no reports on the effect of relaxin on acrosome reaction and utilization of glucose in boar spermatozoa. In this study, to investigate the effects of relaxin on sperm motility, acrosome reaction, and incorporation and oxidation of labeled glucose, boar spermatozoa were washed and preincubated for swim-up and then incubated (0-6 h) with 0, 20, or 40 ng/ml relaxin in mTALP medium. The results indicated that the addition of relaxin stimulated sperm motility significantly (P<0.05) during 1-4 h of incubation. The percentage of acrosome-reacted live spermatozoa was higher (P<0.05) when the spermatozoa were treated with 20 or 40 ng/ml relaxin. The rate of incorporation, and oxidation of glucose were also greater (P<0.05) in the spermatozoa incubated with relaxin compared to the control spermatozoa. The rate of incorporation and oxidation of ¹⁴C-glucose were increased in correlation with acrosome reaction up to 4 h of incubation and then decreased in line with the increasing incubation period. In conclusion, the present study demonstrates that relaxin accelerates not only motility but also the acrosome reaction and utilization of glucose in boar spermatozoa.

View full abstract

In mammals, embryo implantation is an essential step in reproduction. Implantation is a phenomenon that involves crosstalk between the blastocyst and the maternal endometrium. However, the molecular basis of the connections between the blastocyst and endometrium is not yet fully understood. Amphiregulin is a member of the epidermal growth factor family and is known to be expressed in the luminal epithelium of the mouse uterus on 3.5 days post coitum (dpc). Thus, to clarify the mechanism of amphiregulin at fetomaternal interface, we analyzed the expression pattern of amphiregulin mRNA in the oviducts and uteri of pregnant and psuedopregnant mice by means of real-time PCR. Amphiregulin expression in the pregnant uterus dramatically increased on 2.5 dpc, peaked on 3.5 dpc, and declined by 5.5 dpc. Furthermore, to analyze the effect of the presence of an embryo on amphiregulin expression, we determined the expression pattern of amphiregulin mRNA in the uterus after embryo transfer on 0.5 and 1.5 dpc. A previous study showed that the expression of amphiregulin mRNA depends on the concentration of progesterone. However, our present results indicate that amphiregulin mRNA is upregulated by the presence of fertilized eggs in the lumen of the oviduct on 0.5 dpc.

View full abstract

Nonylphenol (NP), a kind of environmental chemical, is thought to imitate endogenous hormones, inhibit the actions of hormones, and induce reproductive abnormalities. A number of experimental animals, usually rats, have been used to evaluate the potential reproductive toxicity of NP. However, the findings of previous studies were contradictory in some cases. Therefore, we used ICR mice as a biomodel for in utero study of NP. After mating, 8- to 12-week-old females were assigned to four groups (n=8) for subcutaneous injections from day 5 to 20 of gestation. Group I animals received corn oil alone as a control, while the mice of groups II, III and IV received NP at concentrations of 1/1000, 1/100 and 1/10 of the LD₅₀, respectively. A dose-dependent decrease was observed in terminal body weights of males of the F1 generation; however, a very small negative effect was only found in the females of the NP1/10 group. No significant effect was found on the liver weights of both sexes. The weights of the testis and epididymis were slightly decreased in the NP1/10 group. The NP1/100 treatment increased ovary weight considerably. The uterus weight tended to be increased in the NP treatment groups; however, there were large variations. The gestational exposure of the groups had no significant effect on the rate of pregnancy (94.4-100%) and the number of fetuses per litter (13.6-14.3 males, 12.3-13.7 females) compared with the control group. However, the overall mortality of fetuses/embryos was increased considerably in the NP1/100 (male: 13.9%) and NP1/10 (female: 9.8%) groups. These results suggest that exposure to NP in utero possibly affects the body weight and some reproductive organ weights, but does not influence the potential fertility of the F1 generation.

View full abstract

The objective of this study was to describe the responses of the plasma progesterone and cortisol concentrations in ovariectomized lactating cows to low doses of adrenocorticotropic hormone (ACTH). The estrous cycles in 3 lactating cows were synchronized, and the cows were ovariectomized in the luteal phase. ACTH challenge tests were conducted at doses of 3, 6, 12 and 25 IU. Blood samples were collected at 30 min intervals, and the plasma progesterone and cortisol concentrations were analyzed by EIA. A concomitant rise in plasma progesterone and plasma cortisol was observed in cows treated with 12 IU or higher doses of ACTH. Significant increments in the plasma cortisol concentrations were observed at all doses of ACTH. The means (± SE) of the peak plasma progesterone concentrations after the 3, 6, 12 and 25 IU ACTH challenge tests were 0.6 ± 0.1, 1.3 ± 0.4, 1.5 ± 0.3 and 2.4 ± 0.3 ng/ml, respectively. The means of the peak plasma cortisol concentrations in the 3 cows after the ACTH challenge were 14.0 ± 1.5, 17.0 ± 2.5, 23.3 ± 3.0, and 33.3 ± 7.0 ng/ml, respectively. The effects of the doses, time after treatment, and their interaction on the plasma progesterone concentrations after the ACTH challenge were significant (P<0.01). Likewise, the effects of the doses, time after treatment, and their interaction on the plasma cortisol concentrations after the ACTH challenge were significant (P<0.01). The mean AUC values for the plasma progesterone and cortisol concentrations after the ACTH treatments were also significantly affected by the dose of ACTH (P<0.01 and P<0.05, respectively). A significantly positive correlation was obtained between the peak plasma progesterone and cortisol concentrations after different doses of ACTH (r=0.7, P<0.05). The results suggest that lactating dairy cows are capable of secreting a significant amount of adrenal progesterone, reaching up to the minimal concentration necessary to cause suppression of estrus in response to 12 IU ACTH (P<0.01). The concomitant plasma cortisol concentration was 23.3 ng/ml.

View full abstract

The present study was performed to examine seasonal changes in the fructose concentrations of seminal plasma and glucose and testosterone concentrations of blood plasma over the course of a year (from November 2004 to November 2005) using 5 Suffolk rams. Osmolality of the seminal plasma was also measured. The fructose concentrations in the seminal plasma increased as the breeding season approached, with the maximum in October (179.8 mg/dl) and the minimum in May (6.9 mg/dl), although there were no significant differences during the year. Osmolality of the seminal plasma in February (304 mOsm) was significantly (P<0.05) lower than in January (325 mOsm), July (327 mOsm), and August (325 mOsm). It was also significantly (P<0.05) lower in November (308 mOsm) than in January and August. The blood plasma glucose concentration in October (79.3 mg/dl) was significantly (P<0.05) higher than in January and February (43.2 and 43.7 mg/dl, respectively). The blood plasma testosterone (T) concentrations were significantly (P<0.05) higher in September (8.5 ng/ml) and October (10.2 ng/ml) than in other months. The fructose concentrations in the seminal plasma appeared to be related to the glucose and T concentrations in the blood plasma. These results show that fructose concentrations in the seminal plasma and blood plasma glucose and T concentrations tended to increase during the breeding season, with the highest concentrations in October.

View full abstract