Search PubMed⌕ Search

Biomedical subjects

T Greve

Publications and source records attributed to T Greve.

At least 19 recordsLinked to original sources
PubMed2006

Investigation of respiration of individual bovine embryos produced in vivo and in vitro and correlation with viability following transfer.

BACKGROUND: Quantification of oxygen consumption by individual preimplantation embryos has the potential to improve embryo selection. This study investigated whether respiration rates of individual embryos are useful indicators of embryo viability. The effect of the Nanorespirometer on embryo viability was also evaluated. METHODS: The respiration rates of individual day 7 bovine in vivo- (n=44) and in vitro-produced (n=156) embryos were measured using the Nanorespirometer. In vivo-produced embryos were individually transferred to recipients. RESULTS: The respiration rates of in vivo-produced embryos increased with increasing morphological quality and stage of development (P < 0.05). Pregnancy rates on days 35 and 60 were 65 and 60%, respectively. The mean respiration rate did not differ significantly between embryos producing and not producing a pregnancy, but the transfer of embryos with respiration rates <0.78 nl/h, between 0.78 and 1.10 nl/h, and >1.10 nl/h resulted in 48, 100 and 25% pregnancy rate, respectively. The mean respiration rate of in vitro-produced embryos was higher than that of in vivo-produced embryos because of differences in the morphological quality and stage of development. CONCLUSION: The Nanorespirometer does not adversely influence embryo viability, but the sample size was too small to confirm the significance of the correlation observed between respiration rates and viability.

Animals↗
PubMed2006

Effect of days post-partum, breed and ovum pick-up scheme on bovine oocyte recovery and embryo development.

The objective of this study was to investigate (i) the effect of two different ovum pick-up (OPU) schemes (once vs twice weekly aspirations) on oocyte recovery rate, quality and subsequent in vitro embryo development, (ii) the influence of days post-partum on oocyte recovery and (iii) possible differences in OPU results from two different herds. In group A, OPU was performed twice weekly in two Holstein Friesian (HF) and three Danish Red and White (DRW) cows from a private herd. In the research herd, two groups of eight HF cows were investigated: group B (OPU once weekly) and group C (OPU twice weekly). The collected oocytes were subsequently submitted to in vitro embryo production. More oocytes were recovered from the private herd when compared with the research herd. In the research herd, the twice weekly scheme aspirated more oocytes than the once weekly scheme. The quality of the retrieved oocytes was significantly different between groups B and C but not between groups A and C, and HF cows yielded higher quality oocytes than DRW cows (p = 0.029). Oocytes from group C showed higher level of embryonic development than group B oocytes. No differences in blastocyst rates were observed between groups A and C. Session affected the number of retrieved oocytes and subsequent developmental rates, with these being lower in the first compared with the last sessions. Finally, there was no significant effect of days post-partum in the number and quality of the retrieved oocytes, likely because of the small group size and high variation between sessions.

Animals↗
PubMed2005

Respiration rates of individual bovine in vitro-produced embryos measured with a novel, non-invasive and highly sensitive microsensor system.

Oxygen consumption is a useful parameter for evaluating embryo quality, since it provides a valuable indication of overall metabolic activity. Over the years, several approaches have been used to measure the respiration rates of individual embryos, but a convincing method has not yet been reported. In this study, we introduce and have validated a novel high resolution microsensor technology to determine the respiration rates of individual embryos at different developmental stages. We have employed this technology to investigate the correlation between respiration rate and embryo morphology, diameter and sex. Following morphological evaluation, individual respiration rates of day 3 (n = 18) and day 7 (n = 60) bovine in vitro-produced embryos were determined. Of the measured embryos, 64 were lysed for sex diagnosis by PCR. Average respiration rates of day 7 embryos (1.30 +/- 0.064 nl/h) were 3.4-fold higher than day 3 embryos (0.38 +/- 0.011 nl/h). On day 7, the average respiration rate of quality 1 blastocysts was significantly higher than the respiration rates of the lower qualities. For both day 3 and day 7 embryos, respiration rates were directly influenced by embryo diameter but did not differ between sexes. These results have demonstrated that the novel microsensor technology can be used to accurately and rapidly (8 min) measure the respiration rates of individual embryos at different developmental stages. Respiration rates were only in partial agreement with embryo morphology, suggesting a slight discrepancy between these two methods in assessing embryo quality. It is likely that a combined assessment of embryo respiration and morphology would improve embryo classification and subsequent selection.

Animals↗
PubMed2005

Somatic cell amplification of early pregnancy factors in the fallopian tube.

This essay is concerned with the function of ovarian somatic cells, especially those of the cumulus oophorus, that are shed with the oocyte at the time of ovulation. Once dissociated from the surface of the oocyte(s), they remain in its close vicinity or that of the zygote(s) throughout the tubal sojourn. Most such follicular cells are not moribund or dead but continue to be synthetically active, although showing ultrastructural modification. Their secretions may include steroid hormones, prostaglandins and diverse peptides, molecules that would be presented locally to the endosalpinx. The cell suspension represents a potential route of amplification of early pregnancy signals from the embryo to influence the pattern of ovarian steroid secretion and perhaps that of folliculogenesis. Bearing in mind the relatively low concentration of hormones generated by the somatic cell suspension, vascular counter-current transfer of information is postulated from the Fallopian tube to the ipsilateral ovary. Molecular techniques are being applied as a means of examining endosalpingeal responses in four different experimental models in which the numbers and presumptive activity of suspended follicular cells are varied in pigs with spontaneous oestrous cycles. Because these animals ovulate on both ovaries, epithelial activity can be compared and contrasted between the two sides. In a final model, attempts are being made to generate early pregnancy responses in the absence of embryos by transplanting zygote-programmed cumulus cells from a mated donor into the Fallopian tube of an unmated recipient.

Animals↗
PubMed2005

Embryo technology: implications for fertility in cattle.

During the past thirty years, basic and experimental studies on classical (superovulation; non-surgical recovery and transfer of cattle embryos) and advanced embryo technologies (in vitro embryo production; cloning by somatic cell nuclear transfer) have generated structural and functional information on oocyte development and quality, fertilisation and conceptus development. This information has provided new insight, not only into these technologies per se but also into the factors contributing to fertility in cattle. It is now known that the peripheral and follicular endocrine profiles have a profound influence on the subsequent developmental competence of the embryo. It is also well established that manipulation of the oocytes or embryos may adversely affect embryonic and foetal development, leading to the so-called 'large offspring syndrome'. Information from such studies has alerted scientists to the importance of epigenetics in cattle reproduction.

Animals↗
PubMed2004

A method to reduce the invasiveness of fetal catheterization in the cow.

Surgical intervention in general anesthesia (GA) of the cow in late gestation is a stressful condition for both mother and fetus, potentially leading to premature delivery or fetal death. The present study hypothesized that fetal catheterization at days 246-253 (90% of gestation) is done with less physical and metabolic stress for the mother and fetus, when the surgery is performed on a standing cow and local anesthesia (LA) rather than on a recumbent cow in general anesthesia. Fetal and uterine maternal intra-vascular catheters were implanted during general anesthesia (GA, n=24) or local analgesia (LA, n=7). Blood gases and metabolite levels in the fetal calves and their mothers were measured during surgery and for 5 days post-operatively. During surgery, venous blood pH was higher (7.44 +/- 0.01 versus 7.39 +/- 0.01, P<0.05) and hemoglobin and oxygen contents lower in LA cows compared with GA cows (9.3 +/- 0.3 mg/dl versus 11.8 +/- 0.2 mg/dl, P<0.001 and 10.0 +/- 0.3 ml/dl versus 12.6 +/- 0.6 ml/dl, P<0.05). The differences between the two groups of fetuses reflected those of their dams in that LA fetuses showed lower arterial oxygen pressure (18.3 +/- 1.4 mmHg versus 24.8 +/- 1.4 mmHg, P<0.05) and hemoglobin (7.81 +/- 0.30 mg/dl versus 9.22 +/- 0.21 mg/dl P<0.01) and furthermore, they also showed higher blood glucose (2.4 +/- 0.2 mM versus 1.4 +/- 0.1 mM, P<0.01). During the 5 days post-surgery, 10 GA fetuses (42%) and 1 LA fetus (14%) died in utero. Bacterial contamination was implicated in six of the GA deaths and in the one LA death. In the dams with surviving calves, differences in hemoglobin (9.49 +/- 0.21 mg/dl versus 11.17 +/- 0.23 mg/dl P<0.001) and O2ct (10.9 +/- 0.3 ml/dl versus 12.5 +/- 0.5 ml/dl, P<0.05) were still present, and in addition, blood glucose was higher in LA versus GA cows (4.3 +/- 0.2 mM versus 3.8 +/- 0.1 mM, P<0.05). The choice of surgical method did not affect post-surgery blood chemistry in the surviving fetuses, except that the higher blood glucose in the LA fetuses at surgery tended to be maintained also post-operatively (2.0 +/- 0.2 mM versus 1.5 +/- 0.1 mM, P=0.07). The observed differences in blood chemistry parameters between the two methods of surgery and possibly in the fetal death may be explained by differences in catheterization method and the associated differences in physical and metabolic stress during and after surgery. Thus, surgery upon a standing cow in local anesthesia should be considered as an alternative to surgery in universal anesthesia for fetal catheterization in the cow in late gestation.

Anesthesia, General↗
PubMed2004

Combined ACTH and glucocorticoid treatment improves survival and organ maturation in premature newborn calves.

Glucocorticoids play an important role in prenatal organ maturation in many species. In humans, maternal treatment with synthetic glucocorticoids improves neonatal adaptation of prematurely born infants. In cows, pre-term calf survival is improved following a single maternal glucocorticoid administration. We hypothesized that stimulation of endogenous cortisol secretion by adrenocorticotropin (ACTH) treatment combined with maternal dexamethasone treatment, would be even more efficient in stimulating organ maturation in the prematurely delivered calf. Three groups of premature calves were delivered by caesarian section at 90% of gestation length from dams which were either untreated or injected with dexamethasone before delivery, combined with either prenatal or postnatal ACTH treatment to the calf. During the first 24h after birth, thermoregulation, blood chemistry, liver values and organ weights were recorded. In the untreated calves, survival was significantly correlated with blood oxygenation, sodium and calcium levels at the moment of birth. There were marked maturational effects of the treatments on body temperature regulation, blood acid-base status, oxygenation, glucose, insulin, IGF-1 levels, weight of the heart, liver, gastrointestinal tract and thymus weight. For many of the measured metabolic, endocrine and organ weight parameters, the intrauterine ACTH treatment was associated with improved values relative to the postnatal ACTH treatment, which appeared to have no immediate effect on calf viability. In conclusion, the premature calf delivered by caesarian section at 90% of gestation length showed blood chemistry, metabolic, endocrine and organ growth characteristics that indicated severe prematurity. However, the maturation of organ function in newborn premature calves following maternal glucocorticoid injections was further enhanced if is was preceded by intra-fetal injections of ACTH.

Adrenocorticotropic Hormone↗
PubMed2003

No peri- and postnatal effects on calves born after transfer of in vitro produced embryos vitrified by the open pulled straw (OPS) method.

The general objective of this study was to perform follow-up studies including selected peri- and postnatal characteristics on calves born after transfer of in vitro produced (IVP) embryos vitrified by the 'Open Pulled Straw' (OPS) method. An overall pregnancy rate of 16% after transfer of the OPS-vitrified IVP embryos was achieved and resulted in birth of 9 calves, with 11 AI calves serving as controls. There were no immediate or long-term effects on these calves with respect to birth weight, gestation length, perinatal mortality, growth rate, disease susceptibility and reproductive performance.

Animals↗
PubMed2003

Ovarian function and morphology in the mare after multiple follicular punctures.

REASONS FOR PERFORMING STUDY: In the mare, ultrasound-guided transvaginal oocyte recovery and transfer might offer a way to circumvent the demanding procedures of in vitro embryo production. Before clinical application, the possible consequences for subsequent fertility have to be considered. OBJECTIVES: To examine ovarian function and morphology in mares after repeated follicular punctures. METHODS: A total of 14-26 follicular puncture sessions were conducted on each of 4 Norwegian pony mares over a period of 8 years. The ovaries of these mares were recovered by bilateral ovariectomy or at post mortem and subjected to macroscopic inspection and histology. For comparison, ovaries were collected from 7 nonaspirated control mares and processed for histology. RESULTS: In all experimental mares, ovarian function, defined as the ability regularly to ovulate preovulatory follicles and develop corpora lutea, remained normal during their last breeding season. Gross examination and histology showed that normal follicular and corpus luteum development was accompanied by the formation of condensed reparative fibrosis and normal local haemosiderosis of the ovarian stroma in all experimental mares. In one mare, an ovary contained several foci of chronic apostematous oophoritis, while a cystic structure lined with a single layer of epithelial-like cells and surrounded by a cartilaginous capsule was present in the other ovary. CONCLUSIONS AND POTENTIAL RELEVANCE: Repeated follicular aspirations do not hamper future folliculogenesis, ovulation and corpus luteum formation. However, ovarian puncture induces reparative fibrosis in the ovarian stroma and involves a risk of inducing abscess formation within the ovarian tissue which may impair fertility.

Animals↗
PubMed2002

Pure preovulatory follicular fluid promotes in vitro maturation of in vivo aspirated equine oocytes.

In the mare, rates of fertilization and development are low in oocytes matured in vitro, and a closer imitation of in vivo conditions during oocyte maturation might be beneficial. The aims of the present study were, therefore, to investigate whether (1) equine oocytes can be matured in vitro in pure equine preovulatory follicular fluid, (2) priming of the follicular fluid donor with crude equine gonadotrophins (CEG) before aspiration of preovulatory follicular fluid promotes the in vitro maturation rate, (3) the in vitro maturation rate differs between oocytes aspirated during estrus and those aspirated again 8 days after the initial follicular aspiration, and (4) high follicular concentrations of meiosis activating sterols (MAS) are beneficial for in vitro maturation of equine oocytes. During estrus, 19 pony mares were treated with 25 mg CEG. After 24 h (Al) and again after 8 days (A2), all follicles >4mm were aspirated and incubated individually for 30 h in the following culture media: standard culture medium (SM), preovulatory follicular fluid collected before CEG containing low MAS concentrations (FF1), preovulatory follicular fluid collected before CEG containing high MAS concentrations (FF2) or preovulatory follicular fluid collected 35 h after administration of CEG containing low MAS concentrations (FF3). Cumulus expansion rate was significantly affected by culture medium. The overall nuclear maturation rate was significantly higher for oocytes collected at A1 (67%) than for oocytes collected at A2 (30%). For oocytes collected at A1, the maturation rates were 71% (FF1), 61% (FF2), 79% (FF3) and 56% (SM). An electrophoretic protein analysis of the culture media revealed the presence of a 200-kDa protein in FF3. The results demonstrate that (1) equine oocytes can be matured during culture in pure equine preovulatory follicular fluid, (2) preovulatory follicular fluid collected after gonadotrophin-priming seems superior in supporting in vitro maturation than standard culture medium, (3) oocytes aspirated 8 days after a previous aspiration are less competent for in vitro maturation than oocytes recovered during the initial aspiration, and (4) the regulation of meiotic resumption during in vitro culture of equine oocytes might be related to the presence of a 200-kDa protein.

Animals↗
PubMed2002

Macromolecule absorption and cortisol secretion in newborn calves derived from in vitro produced embryos.

Earlier reports indicate that calves derived from in vitro produced (IVP) embryos are more susceptible to neonatal disease than calves produced after artificial insemination (AI) or natural mating. The aims of the present study were to investigate whether calves born after IVP embryos show an altered macromolecule absorption (immunoglobulin G (IgG) and porcine serum albumin (PSA)) compared with AI calves and whether the macromolecule absorption could be related to the degree of acidosis or to the cortisol secretion around birth. Hence, IgG and PSA absorption in control AI calves (n=7) was compared with that in two groups of IVP calves (IVP-defined: SOFaa embryo culture with polyvinyl alcohol, n=6; IVP-serum: SOFaa embryo culture with serum and co-culture, n=8). The calves were fed colostrum (40ml/kg) at 2, 6 and 12h after birth. At 24h after birth, both AI and IVP calves had achieved a level of plasma IgG sufficient to provide passive immunization (>15mg/ml). When the values were adjusted for the varying colostral IgG contents and the degree of acidosis, the IVP-defined calves had significantly lower peak plasma IgG concentrations than the AI calves at 18-24h after birth (P<0.04). However, when the macromolecule marker (PSA), was fed to all calves at 2 and 12h after birth the resulting plasma PSA levels were significantly lower in the AI calves compared with the IVP calves during the whole observation period (P<0.0001). Calves with a moderate neonatal acidosis (mean pH<7.2 during the first 30min after birth) had reduced peak plasma IgG concentration at 18-24h after birth (P<0.02) compared to calves without acidosis. The basal and ACTH-stimulated cortisol levels were lower in the newborn IVP-defined calves than in the AI calves (P<0.05) and the IVP-serum calves (P<0.002). Cortisol levels shortly after birth correlated positively with birth weight (r=0.60, P<0.0001) and with gestation length (r=0.34, P<0.04). Since, the IVP calves absorbed sufficient amounts of IgG from colostrum to acquire sufficient passive immunity, we conclude that the lower viability described in IVP offspring probably is not caused by an impaired passive immunization. IVP-defined calves had significantly lower absorption efficiency of IgG compared with AI calves, whereas absorption of a non-Ig macromolecule (PSA) was higher for IVP than AI calves. This might indicate a more selective absorption in AI calves in favor of IgG. Acidosis around birth affected immunoglobulin absorption negatively. IVP-defined calves had significantly lower cortisol levels the first 3h after birth and during an ACTH-challenge and a lower IgG absorption efficiency, which might indicate a mild degree of organ dysmaturity in these calves.

Absorption↗
PubMed2001

Transcriptional activity in in vivo developed early cleavage stage bovine embryos.

Bovine embryos developed in vivo from the first to the fourth post-fertilization cell cycles were processed for ultrastructural autoradiography after incubation with 3H-uridine for 10 h. We wished to detect and localize transcriptional activity. During the first (1-cell stage) and second (2-cell stage) cell cycles we observed electron-dense fibrillar spheres (nucleolus precursor bodies) and fibrillo-granular complexes in the nuclei. During these cell cycles, autoradiographic labeling was observed in heterochromatic areas and at the periphery of the fibrillo-granular complexes. During the third cell cycle (4-cell stage) the electron dense fibrillar spheres exhibited vacuolization. Autoradiographic labeling was found in heterochromatic areas and in the vacuoles of the fibrillar spheres. During the fourth cell cycle (8-cell stage), the electron dense fibrillar spheres exhibited both a large eccentric vacuole and peripheral smaller vacuoles. Autoradiographic labeling was found in heterochromatic areas throughout the nucleus and over the substance of the vacuolated fibrillar spheres, especially where chromatin penetrated into them and where presumptive fibrillar centers were formed. In conclusion, a low level of transcription can be detected in in vivo developed bovine embryos as early as the one-cell stage. Moreover, nuclear entities that probably prepare for nucleolus formation during the fourth cell cycle, display a progressive autoradiographic labeling that signals a possible initiation of transcription of the ribosomal RNA genes during the third cell cycle.

Animals↗
PubMed2001

Testicular concentration of meiosis-activating sterol is associated with normal testicular descent.

In the cryptorchid stallion, spermatogenesis is arrested at various levels before the completion of meiosis. In men, infantile cryptorchidism is also often associated with oligo- and azoospermia during adulthood. An impairment of spermatogenesis might be reflected in the level of locally produced factors. Formerly, a meiosis-activating sterol (T-MAS) has been isolated in murine and bovine testes. This sterol possesses the potential to trigger resumption of meiosis in cultured mouse oocytes, indicating that it might play an important role in the regulation of the meiotic process in the female gamete. The function of T-MAS in the testis is still unclear, but T-MAS may be associated with spermatogenesis. The objectives of this study were 1) to demonstrate the presence of T-MAS in equine testes, 2) to compare the contents of T-MAS in testicular tissue of stallions with complete and incomplete testicular descent and 3) to compare testicular T-MAS concentration before and after puberty Testes were collected from 16 normal and cryptorchid stallions submitted for castration and stored at -80 degrees C until the content of T-MAS was measured quantitatively with an HPLC-assay. In stallions > or = 2 years of age, the content of T-MAS was higher (P < 0.001) in normal testes (19.3+/-1.1 microg T-MAS/g, n=7) than in inguinally (4.1+/-2.4 microg T-MAS/g, n=4) or abdominally located testes (1.6+/-0.2 microg T-MAS/g, n=2). The contents of T-MAS in normal testes from stallions < 2 years of age (2.8+/-1.5 microg T-MAS/g, n=4) was lower than in normal testes from stallions > or =2 years of age (P < 0.001) From the present study it can be concluded that T-MAS is present in equine testicular tissue. Furthermore, the present study demonstrates that the production of T-MAS in testicular tissue is, concurrently with spermatogenesis, associated with normal testicular descent and is temporarily related to the onset of puberty.

Aging↗
PubMed2001

Endocrine disrupting compounds: effect of octylphenol on reproduction over three generations.

With the growing concern that environmental chemicals might impair human and animal fertility, it is important to investigate the possible influence of these substances on sexual differentiation and genital development of mammals. Many of these substances are suspected to interfere with endocrine processes, and exposure during critical periods of prenatal development might affect reproductive performance over several generations. Alkylphenols and their metabolites are lipophilic substances exerting apparent estrogenic action in in vitro and in vivo testing systems. With the widespread industrial use of alkylphenols, these are disseminated in the environment with sewage sludge, and domestic animals and humans are likely to be exposed via the food chain. Using the pig as an in vivo model, we studied the effect of intrauterine exposure to tertiary octylphenol (OP) on essential reproductive parameters over 3 generations. Sows were treated daily from D 23 to 85 of pregnancy with either 0, 10 or 1000 micrograms OP/kg body weight. Treatment with OP extended pregnancy length and induced basal cell proliferation in the cervical epithelium of the parental generation. In F1 offspring of sows treated with the low dosage of OP, onset of puberty was accelerated. Furthermore, when F1 gilts and F1 boars originating from sows treated with high dosages of OP were bred, the litter size was reduced. The results of the present study are compared with previous reports on estrogenicity of OP, and the usefulness of in vivo animal or embryo models for the evaluation of possible consequences of human exposure to endocrine disrupting compounds is discussed. Furthermore, possible consequences of exposure to endocrine disrupting compounds for the embryo transfer industry are addressed.

Animals↗
PubMed2001

Effect of two activation treatments and age of blastomere karyoplasts on in vitro development of bovine nuclear transfer embryos.

The yield and quality of (a) parthenogenetic blastocysts produced by two activation treatments (cycloheximide [CHX] or 6-dimethylaminopurine [DMAP]) and (b) nuclear transfer blastocysts generated using these two activation treatments and three different ages of karyoplast derived from day 3, 4, or 5 in vitro produced donor embryos, were examined in order to define an optimal nuclear transfer protocol. The two activation protocols comprised calcium ionophore followed by either CHX or DMAP. Parthenogenetic blastocyst yields were greater (P < 0.001) following activation with DMAP than CHX (59.7 +/- 5.1 vs. 31.4 +/- 4.5 [mean +/- SEM]). In contrast, nuclear transfer blastocyst rates per fused embryo were lower (P < 0.0001) using cytoplasts activated with DMAP. The individual rates using day 3, 4, and 5 donors and using CHX and DMAP activation treatments were 31.9 +/- 5.0, 31.7 +/- 6.2, 20.4 +/- 7.3 and 27.8 +/- 4.7, 20.1 +/- 7.5, 12.7 +/- 8.3, respectively. Blastocyst rate per fused embryo was negatively correlated (P = 0.0091) with the total number of blastomeres per donor embryo. Despite this inverse relationship, the calculated potential blastocyst yield per donor embryo was positively correlated (P < 0.0048) to karyoplast age. The individual potential yields on days 3, 4, and 5 and for the two activation protocols (CHX and DMAP) were 4.7 +/- 0.8, 7.2 +/- 1.2, 10.1 +/- 2.1 and 3.8 +/- 0.8, 5.5 +/- 2.1, 7.3 +/- 4.1, respectively. One possible explanation for the observed inverse relationship is that differentiation events during early cleavage are able to reduce the ability of the cytoplast to reprogram the transferred karyoplast and hence reduce blastocyst yields. The mechanism that mediates the differential effect of the CHX and DMAP on blastocysts yields between parthenogenetic and nuclear transfer embryos remains to be elucidated. In conclusion, the results indicate that although activation of oocytes with DMAP can produce a higher percentage of blastocysts, CHX activation is superior for use in nuclear transfer.

Animals↗
PubMed2001

Immunohistochemical localization of estrogen receptor-alpha in sex ducts and gonads of newborn piglets.

Estrogen receptor-alpha (ER-alpha) expression in piglet uteri has previously been reported from day 15 after birth. Nevertheless, uterine tissue has been reported to be estrogen sensitive from the day of birth. Since estrogen action in the uterine tissue is suggested to be mediated principally by ER-alpha, the present study aimed to evaluate the presence of ER-alpha in uteri of 1- to 2-day-old piglets by means of immunohistochemistry. In addition, sex ducts and gonads of both sexes were examined. The results clearly demonstrate the presence of ER-alpha immunopositive cells in uterine tissue, which explains its estrogen responsiveness. Immunostaining was most intense in the glandular epithelial cells and is suggested to indicate participation of ER-alpha in adenogenesis. In oviducts, almost all epithelial cells were immunostained moderately positive, while the stroma cells were stained comparably more positive. The functional significance of this intensity difference is uncertain but could indicate that part of the estrogen action on the epithelium is mediated through the stroma cells, as is known for the uterus. In ovaries, the surface epithelium and stroma cells were immunostained, whereas germ and granulosa cells were immunonegative. It is speculated that ER-alpha might be involved in yet unknown intraovarian mechanisms. In male sex ducts, immunostaining was virtually confined to the epithelium of efferent ducts. All cells in the epididymis as well as in vas deferens were immunonegative. The unique presence of ER-alpha in efferent ducts corresponds with localization in other species, where it has been shown to be involved in fluid reabsorption. The obtained data on localization of ER-alpha correspond with the present knowledge, obtained in ER-alpha knockout mice, of the biological function of ER-alpha within male and female gonads and sex ducts.

Animals↗
PubMed2001

Chromosomal abnormalities and developmental kinetics in in vivo-developed cattle embryos at days 2 to 5 after ovulation.

The frequency of chromosome abnormalities was investigated in cattle embryos (n = 256) derived from superovulated heifers (n = 35) on Days 2, 3, 4, and 5 postovulation (PO). Interphase nuclei (n = 4358) were analyzed for chromosome abnormalities using fluorescent in situ hybridization with chromosome 6- and chromosome 7-specific probes and the developmental rate was described by scoring cell numbers. We found that 93%, 85%, 84%, and 69% of the embryos from Days 2, 3, 4, and 5 PO, respectively, displayed a normal diploid chromosome number in all cells. Of the embryos containing abnormal cells, mixoploidy was significantly more frequent than polyploidy. The percentage of mixoploidy at Days 2, 3, 4, and 5 PO was 5%, 13%, 16%, and 31%, respectively, whereas the percentages of polyploidy were 2%, 2%, 0%, and 0%, respectively. The mean number of cells per embryo was 4.7, 8, 11.5, and 48.3, respectively, at Days 2, 3, 4, and 5 PO. Thus, in vivo-developed embryos were significantly more advanced than the in vitro-produced (IVP) embryos except for Day 2. In conclusion, a significantly lower frequency of chromosomally abnormal embryos, in particular displaying polyploidy early after fertilization, was seen in in vivo versus IVP embryos, and these chromosomal abnormalities may be inherent to the process of IVP in cattle.

Animals↗