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J Smitz

Publications and source records attributed to J Smitz.

At least 19 recordsLinked to original sources
PubMed2003

Effect of phosphodiesterase type 3 inhibitor on developmental competence of immature mouse oocytes in vitro.

In vitro use of arresters of meiosis could improve cytoplasmic maturation of immature oocytes by controlling the period of prophase I. Phosphodiesterases (PDE) are responsible for the breakdown and concomitant inactivation of the cyclic nucleotides cAMP and cGMP and are implicated in the regulation of oocyte meiotic maturation. Selective inhibitors of phosphodiesterase type 3 (PDE3) prevent meiotic resumption of mammalian oocytes. This study evaluated the impact of meiosis arrest by PDE3 inhibitor, Org 9935, on developmental competence of geminal vesicle (GV)-stage oocytes from small antral follicles. Cumulus-oocyte complexes (COC), retrieved from antral follicles 24 h after eCG exposure and cultured in the presence of PDE3 inhibitor (10 microM) for an additional 24 h, remained arrested in the meiotic prophase. The GV configuration of oocytes before and after the arrest by PDE3 inhibitor was examined. After the period of meiosis arrest, a significantly increased proportion of oocytes had acquired a nucleolus surrounded by a condensed chromatin rim at the GV, which is a morphological correlate of transcriptional repression. Removal of inhibitor resulted in 90.6% +/- 8.3% of oocytes with the first polar body extruded. Fertilization was significantly improved in oocytes that had been arrested compared with oocytes collected 24 h after eCG and undergoing in vitro maturation immediately. Embryonic preimplantation and live offspring rates of arrested oocytes were higher, although not significantly, than those of nonarrested oocytes. These results suggest that a temporal block of meiosis by PDE3 inhibitor promotes developmental competence of mice oocytes retrieved from small antral follicles.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2003

Capacity of adult and prepubertal mouse oocytes to undergo embryo development in the presence of cysteamine.

The present study was carried out to study de novo glutathione (GSH) synthesis and to evaluate the effect of stimulating GSH synthesis during in vitro maturation (IVM) of adult and prepubertal mouse oocytes on the embryo developmental rate. Adult (8 weeks old) and prepubertal mice (24-26 days old) were primed with 5 IU of PMSG and oocytes were retrieved from the ovary 48 hr later for IVM. After IVM (18 hr) Cumulus oocyte complexes (COC) were in vitro fertilized (IVF) and in vitro culture (IVC) in order to observe embryo development. The IVM medium was supplemented with: 0, 25, 50, 100, or 200 microM of cysteamine. To study the novo GSH synthesis, 5 mM BSO was added during IVM of adult or prepubertal oocyte. Developmental rates up to blastocyst were recorded for each group. Experiments also included a group of ovulated oocytes (in vivo matured) after priming with PMSG and HCG. After IVM of adult mice oocytes, an improvement was observed on embryo development in all the supplemented groups when compared with the untreated group (P < 0.05). No differences were observed in blastocyst rate among IVM oocytes with cysteamine and ovulated oocytes. Prepubertal IVM mouse oocytes had a lower cleavage rate compared with ovulated oocytes (P < 0.05). Cysteamine failed to improve prepubertal oocytes developmental rates (P > 0,05). 2-cell embryos, coming from IVM prepubertal oocytes and ovulated oocytes had the same preimplantation developmental rate up to the blastocyst stage. In prepubertal, and adult oocytes an inhibition of embryo development was observed when buthionine sulfoximide (BSO), a specific inhibitor of the gamma-glutamylcysteine synthetase, was added during oocyte maturation (P < 0.01). In conclusion, an improvement in mouse embryo development was observed when cysteamine was added to the IVM medium of adult mice oocytes. In prepubertal oocytes cysteamine addition during oocyte maturation failed to improve embryo developmental rates. The presence of BSO lowered or completely blocked blastocyst development. This proves that, de novo GSH synthesis during oocyte maturation of adult and prepubertal oocytes undoubtedly plays an important role in embryo development. The improvement on oocyte competence observed in adult mice oocytes is probably related to intracellular GSH synthesis stimulated by cysteamine. Nevertheless the reason why cysteamine failed to improve prepubertal oocytes competence remains as an open question.

Animals↗
PubMed2002

Cysteamine supplementation during in vitro maturation and embryo culture: a useful tool for increasing the efficiency of bovine in vitro embryo production.

Cysteamine when added during in vitro maturation (IVM) or in vitro embryo culture (IVC) stimulates glutathione (GSH) synthesis and improves embryo developmental rates. This suggests that GSH synthesis is decreased in the in vitro produced embryo. The present study was carried out to evaluate if addition of cysteamine to culture medium at the same time, during IVM and IVC of bovine oocytes, may promote an overall improvement on the developmental rate and embryo quality. Oocytes were matured in TCM 199 supplemented with 10% (v/v) fetal calf serum, hormones, and 0 or 100 microM of cysteamine for 24 hr. After IVM, the oocytes were fertilized (day 0). Day 2 embryos (2-8 cell) were washed and transferred to fresh IVC medium supplemented with 0, 25, 50, or 100 microM of cysteamine and cultured for 48 hr. After this, embryos were cultured in IVC medium without cysteamine until day 8 of IVC. In the present study, we confirmed our previous results by demonstrating that the percentage of embryos that developed to the blastocyst stage was significantly higher (P < 0.05) when 100 microM of cysteamine was added during IVM, and this was further improved when 100 and 50 microM of cysteamine where present during IVM and IVC, respectively (P < 0.05). After cryopreservation, no differences were observed on embryo development, but a significant increase on embryo hatching was found between unsupplemented and supplemented oocytes with 100 and 50 microM of cysteamine during IVM and IVC, respectively (P < 0.05). We can conclude that GSH synthesis stimulation during bovine IVM with cysteamine, concomitant with GSH stimulation during IVC, will be a useful and simple tool for increasing the efficiency of in vitro bovine embryo production.

Animals↗
PubMed2002

Effects of aromatase inhibition on in vitro follicle and oocyte development analyzed by early preantral mouse follicle culture.

In vivo studies on folliculogenesis have documented a relation among intrafollicular steroid content, follicle growth, and oocyte development. This study examined how profound changes in androgen/estrogen ratio would affect mouse in vitro follicular development. Arimidex, a potent follicular aromatase inhibitor was used for this purpose. Early preantral follicles were cultured for 12 days up to the preovulatory stage. Oocyte's meiotic maturation, spindle and chromosome configurations, in vitro fertilization and preimplantation embryo development were evaluated. Compared to controls, Arimidex reduced E2 concentration in follicle culture medium by a factor 1000, and an expected simultaneous accumulation of testosterone was measured in the conditioned medium. Arimidex treatment provoked a dose-dependent earlier differentiation of the granulosa cells as judged by an earlier antrallike cavity formation and slightly elevated basal progesterone secretion. Follicle survival exceeded 98% in all groups and all follicles responded normally to HCG/EGF addition on day 12 by cumulus mucification. By the HCG ovulatory challenge, progesterone output was reduced in Arimidex supplemented groups suggesting preovulatory luteinization. These results indicate that in vitro mouse follicles can develop normally under very low levels of estrogens and that a local androgen increase by a factor 3 is not atretogenic. Oocyte growth did not differ among culture conditions. Arimidex treatment induced a dose dependent enhancement of GVBD and polar body formation rate in response to HCG at the end of culture. Spindle and chromosome analyses demonstrated that in all groups, 90% of the oocytes which extruded a polar body had also reached the MII stage. While most of the cultured MII oocytes had a normal spindle and well aligned chromosomes, significantly less oocytes were fertilized in the groups cultured in the presence of Arimidex. Once fertilized, however, there was found to be no difference for preimplantation embryo development between controls and Arimidex treatment. These data suggest that in mice a pronounced estrogenic environment is not essential for in vitro folliculogenesis. Drastic changes in the intrafollicular steroid concentrations do not disrupt meiotic maturation nor compromise early preimplantation development, but adversely affect fertilization of in vitro grown oocytes.

Anastrozole↗
PubMed2002

Plasma and follicular fluid concentrations of LHRH antagonist cetrorelix (Cetrotide) in controlled ovarian stimulation for IVF.

Cetrorelix was administered in differing daily dosages for controlled ovarian stimulation. The dosage levels were 3 mg (9 cycles), 1 mg (19 cycles), 0.5 mg (43 cycles), 0.25 mg (46 cycles) and 0.1 mg (7 cycles). In the 3 mg, 1 mg and 0.5 mg group the respective median plasma concentrations of cetrorelix on the day of oocyte pick-up (OPU) were 2.10 ng/ml, 1.42 ng/ml and 0.88 ng/ml and 1.03 ng/ml, 0.46 ng/ml and 0.49 ng/ml on the day of embryo transfer (ET). In the 0.25 mg and 0.1 mg groups plasma cetrorelix levels were below the limit of quantification. The cetrorelix concentrations in follicular fluid (FF) in the 0.25 mg group were detectable in only 14 out of 44 samples, while in the 0.1 mg group no detectable concentrations could be obtained. We also examined 80 cycles after single doses of 5 mg (7 cycles), 3 mg (42 cycles), and 2 mg (31 cycles) cetrorelix. On the day of OPU the respective median plasma concentrations of cetrorelix were 0.57 ng/ml, 0.62 ng/ml, and 0.56 ng/ml, and 0.61 ng/ml and 0.28 ng/ml on the day of ET in the 5 mg and 3 mg groups. In the 2 mg group, the plasma concentrations fell to below limits of quantification in 8/9 samples on the day of ET. In 26 out of 27 FF samples cetrorelix was detectable in the 3 mg single dose group (median level: 0.69 ng/ml).

Adult↗
PubMed2002

The prevalence of autoantibodies in an elderly sub-Saharan African population.

In the present prospective, census-based study we have investigated the prevalence of organ-specific and non-organ-specific autoantibodies (AAb) in 152 unselected Cameroonians aged 60 years and older living in the community. AAb were detected in 49% of the participants. Non-organ-specific AAb (47%) predominated over organ-specific AAb (7%). Anti-TPO, anti-Tm, anti-Tg and anti-PC AAb were completely absent. RF was the most frequent AAb, being found in 57 (38%) cases. The prevalences of anti-SMA and RF were significantly higher in women than in men (respectively, P=0.023 and P=0.016). Higher serum concentrations of gammaglobulins were accompanied by a higher prevalence of RF (P < 0.0001) and a lower prevalence of ANA (P=0.036). The overall prevalence of AAb was higher in the filaria-infected (60%) compared to the non-infected (42%) participants (P=0.046). There was no significant influence of the vitamin D status, number of pregnancies, physical activity or medication use on the prevalence of AAb. In this study a heterogeneous pattern for the presence of the various AAb was found. Some AAb, which are commonly encountered in other studies on elderly subjects, were completely absent in this population. This diversified pattern of AAb prevalence therefore argues in favour of exogenous influences in the occurrence of AAb in elderly populations.

Aged↗
PubMed2001

Avoidance of multiple pregnancies after ovulation induction by supernumerary preovulatory follicular reduction.

OBJECTIVE: To evaluate the effect of supernumerary preovulatory follicular reduction as an approach to avoid multiple pregnancies in ovulation induction or superovulation cycles. DESIGN: Retrospective study. SETTING: Tertiary referral center. PATIENT(S): In 26 cycles, 24 patients underwent ovulation induction or superovulation with either clomiphene citrate or hMG. INTERVENTION(S): Selective follicle aspiration was performed before hCG administration. MAIN OUTCOME MEASURE(S): Clinical pregnancy rate and numbers of multiple pregnancies. RESULT(S): A mean number of 4.5 follicles with a diameter > or =15 mm and a mean number of 4.5 follicles with a diameter < or =14 mm were observed before hCG administration. A mean number of 2.3 follicles with a diameter > or =15 mm and a mean number of 1.8 follicles with a diameter < or =14 mm were aspirated before the hCG administration. Seven singleton pregnancies (26.9% per cycle) ensued from the treatment. CONCLUSION(S): Aspiration of supernumerary follicles after ovulation induction or superovulation seems to be a valid approach to avoid multiple pregnancies without affecting pregnancy rate.

Adult↗
PubMed2001

In vitro follicle growth: achievements in mammalian species.

The exact mechanisms regulating in vivo folliculogenesis in mammalians have only been partly unravelled. Some processes, such as the initiation of growth of primordial follicles are still poorly understood. This increases the difficulty to culture follicles in vitro as the primordial follicles will be the ultimate starting material for culture. There are important species differences in regulation and timing of maturation, which makes it difficult to transpose techniques. Only in the mouse model, live pups were born when primordial or early preantral follicles were cultured entirely in vitro. Although no systems are as yet permitting complete in vitro culture of early follicle stages in large animals or humans, parts of folliculogenesis have been successfully reproduced in vitro. This review summarizes achievements of the last years in follicle culturing starting off at several stages of development. Future applications of in vitro follicle culture include fertility preservation for humans, preservation of rare animal species and creation of oocyte banks for research.

Animals↗
PubMed2001

Improving in vitro maturation of oocytes in the human taking lessons from experiences in animal species.

One to three per cent of infertile women develop severe ovarian hyperstimulation syndrome after superovulation for assisted reproduction treatment (ART). This severe complication can be avoided when oocytes are obtained at an immature stage (germinal vesicle stage) out of small or medium-sized follicles. This hypothesis has been tested in several infertile women, but clinical pregnancies are disappointlingly low. This new approach in ART is still at an experimental phase and this treatment has still to be improved before routine clinical application. Experimental work in animals and humans suggest a beneficial effect in providing a short preliminary pretreatment with follicle-stimulating hormone to select for a developing cohort of follicles. The aspiration of oocyte cumulus complexes is carried out with a short needle applying reduced aspiration pressure. A crucial point is to provide the appropriate culture environment for the immature oocytes. An optimal cumulus-enclosed human oocyte culture system needs to be defined. The composition of the culture medium could be suggested by in vitro work carried out in animal models. As developmental competence is established during the latest phases of oocyte growth and is dependent on the storage of RNA, a prolonged in vitro maturation period (before inducing nuclear maturation) could provide the necessary transcriptional and translational changes. The conditions to achieve this improved cytoplasmic maturation by prolonging the in vitro culture remain to be defined. More objective noninvasive parameters for oocyte maturity are also needed to pursue research in this field.

Animals↗
PubMed2001

Protein synthesis during maturation of bovine oocytes, effect of epidermal growth factor.

The objective of this study was to determine whether epidermal growth factor (EGF) affected protein synthesis in oocytes during maturation. Initially, the effect of EGF on oocyte maturation was examined to ensure that there was a beneficial effect of EGF in the protein-free maturation medium used in these studies. Results showed that the presence of EGF during maturation significantly enhanced cleavage rate and development to the blastocyst stage. Development after maturation in the presence of EGF was similar to that seen in medium containing serum, luteinizing hormone, follicle-stimulating hormone and estradiol. Protein synthesis was examined in immature oocytes and after 16 or 24 h maturation. Oocytes from each group were labelled by incubation for 4 h with 35S-methionine, the proteins were then separated by two-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Between 400 and 500 proteins could be separated using this method and marked changes in protein synthesis was observed during maturation. Changes in eight different proteins were observed when protein patterns from oocytes matured for 16 h with and without EGF were compared. These results suggest that EGF plays a physiological role in oocyte maturation and identification of the proteins induced by EGF could be important for improving our understanding of oocyte maturation in vitro.

Animals↗
PubMed2001

Comparison of LH concentrations in the early and mid-luteal phase in IVF cycles after treatment with HMG alone or in association with the GnRH antagonist Cetrorelix.

Luteinizing hormone (LH) is mandatory for the maintenance of the corpus luteum. Ovarian stimulation for IVF has been associated with a defective luteal phase. The luteal phases of two groups of patients with normal menstrual cycles and no endocrinological cause of infertility were retrospectively analysed in IVF cycles. Thirty-one infertile patients stimulated with human menopausal gonadotrophins (HMG) for IVF to whom the gonadotrophin-releasing hormone (GnRH) antagonist Cetrorelix 0.25 mg was also administered to prevent the LH surge (group I) were compared with 31 infertile patients stimulated with HMG alone (group II). Despite differences in the stimulation outcome, luteal LH serum concentrations were similar in the two groups. LH values dropped from 2.3 +/- 1 IU/l on the day of human chorionic gonadotrophin (HCG) administration to 1.1 +/- 0.7 IU/l on day HCG +2 in group I (P < 0.0001) and from 5.1 +/- 3 to 1.2 +/- 1.7 IU/l (P < 0.0001) in group II. In the mid-luteal phase, LH concentrations were low in both groups. Our results suggest that suppressed LH concentrations in the early and mid-luteal phase may not be attributed solely to the GnRH-antagonist administration. Pituitary LH secretion may be inhibited by supraphysiological steroid serum concentrations via long-loop feedback and/or by the central action of the exogenously administered HCG via a short-loop mechanism.

Adult↗
PubMed2001

Effects of low O2 and ageing on spindles and chromosomes in mouse oocytes from pre-antral follicle culture.

To assess their quality, spindles were analysed in mouse oocytes from pre-antral follicle culture. High or low oxygen tension was present during the last 16 or 20 h post human chorionic gonadotrophin (HCG)/epidermal growth factor (EGF) addition. Most oocytes from pre-antral follicle culture possessed typical anastral spindles with flat poles resembling those of ovulated, in-vivo-matured oocytes of sexually mature mice, while denuded oocytes in-vitro matured to metaphase II (MII) formed significantly longer, slender spindles with pointed, narrow poles. Spindles in oocytes from follicle culture were only slightly shorter and less compact at the equator as compared with those of oocytes matured in vivo. Chromosomes were well aligned at the equator in MII oocytes obtained from follicle culture with high oxygen. Maturation rate was significantly reduced by lowering oxygen tension to 5% O2. Prolonged culture and the presence of only 5% O2 dramatically increased the percentage of MII oocytes with unaligned chromosomes. These observations indicate that sufficient oxygen supply and time of retrieval after initiation of resumption of maturation by HCG as well as the microenvironment and cell-cell interactions between oocytes and their somatic compartment are critical in affecting the oocyte's capacity to mature to MII, to form a functional spindle, and to align chromosomes correctly.

Animals↗
PubMed2001

Ovulation induction disrupts luteal phase function.

Abnormalities in the luteal phase have been detected in virtually all the stimulation protocols used in in vitro fertilization, on both the hormonal and endometrial levels. Supraphysiological follicular or luteal sex steroid serum concentrations, altered estradiol: progesterone (E2/P) ratio, and disturbed luteinizing hormone pituitary secretion leading to corpus luteum insufficiency or a direct drug effect have been postulated as the main etiologic factors. Luteinizing hormone supports corpus luteum function, and low LH levels have been described after human menopausal gonadotropin treatment, after gonadotropin-releasing hormone (GnRH)-agonist treatment, or after GnRH-antagonist treatment. These low luteal LH levels may lead to an insufficient corpus luteum function and consequently to a shortened luteal phase or to the low luteal progesterone concentrations frequently described after ovulation induction. A direct effect of the GnRH agonist or GnRH antagonist on human corpus luteum or on human endometrium and thus on endometrial receptivity cannot be excluded, as GnRH receptors have been described in both compartments. Endometrial histology has revealed a wide range of abnormalities during the various stimulation protocols. In GnRH-agonist cycles, mid-luteal biopsies have revealed increased glandulo-stromal dyssynchrony and delay in endometrial development, strong positivity of endometrial glands for progesterone receptors, decreased alphavbeta3-integrin subunit expression, and earlier appearance of surface epithelium pinopodes. These factors suggest a shift forwards of the implantation window. Progesterone supplementation improves endometrial histology, and its necessity has been well established, at least in cycles using GnRH agonists.

Endometrium↗
PubMed2001

Rapid detection of macroprolactin in the form of prolactin-immunoglobulin G complexes by immunoprecipitation with anti-human IgG-agarose.

Immunoprecipitation with anti-human immunoglobulin G-agarose was evaluated for the detection of prolactin-immunoglobulin G (PRL-IgG) complexes in macroprolactinemic samples from hyperprolactinemic patients (prolactin measured using the automated Elecsys PRL assay; Roche Diagnostics, Mannheim, Germany). Using the polyethylene glycol (PEG) precipitation test on serum samples with PRL above 1000 mIU/l, we detected macroprolactin in 38 out of 175 samples with a recovery below 50%. Gel filtration chromatography on a subset of hyperprolactinemic samples confirmed that macroprolactin was the predominant immunoreactive form of PRL in samples which showed a recovery < or = 50%. In 37 out of 38 samples containing macroprolactin, immunoprecipitation with anti-human IgG (anti-hIgG)-agarose revealed a higher PRL-binding (19.1-91.3%) than in the sera containing monomeric PRL (< 10%). In conclusion, we found that PEG precipitation detected macroprolactin in 21.7% of samples with elevated PRL levels as measured by the Elecsys PRL assay, and that in the vast majority of these samples the presence of PRL-IgG complexes could be demonstrated by immunoprecipitation with anti-hIgG-agarose. In view of the high prevalence of PRL-IgG complexes in hyperprolactinemic patients and the simplicity of the test, immunoprecipitation with anti-hIgG-agarose might play a role in the routine laboratory handling of hyperprolactinemic samples, especially with regards to PRL assays where PEG causes interference.

Antigen-Antibody Complex↗
PubMed2001

Alterations in ovarian function of mice with reduced amounts of KIT receptor.

The KIT receptor, present on oocyte and theca cells in ovarian follicles, and its ligand, KIT LIGAND, produced by granulosa cells, are encoded at the Kit gene and the Mgf gene, respectively. Both Kit and Mgf mutations affect oogenesis and folliculogenesis. In this study, the ovarian function of heterozygous mice with a mutation Kit(W-lacZ) was examined. Firstly, the amounts of KIT and KIT LIGAND proteins in the ovaries of mice at different ages were determined. Secondly, in vivo and in vitro folliculogenesis of wild type and heterozygous mice were compared. Western blotting showed that the amounts of both KIT and KIT LIGAND proteins were decreased in mutant mice. Ovarian follicle populations were counted and more type 5a follicles and fewer type 5b (preantral follicles) were present in ovaries from Kit(W-lacZ/+) ovaries. Furthermore, the relationships between oocyte size and follicle size differed between wild type and heterozygous mice. This finding may be a consequence of altered proliferation of granulosa cells or of altered oocyte growth in mutant mice. Other features of folliculogenesis, such as initiation of follicular growth, total follicle population and follicular atresia, were not affected by the mutation. Analysis of in vitro folliculogenesis did not reveal other differences between wild type and mutant mice. It is concluded that the Kit(W-lacZ) mutation affects the expression of KIT and KIT LIGAND proteins, resulting in alterations in granulosa cell proliferation and/or oocyte growth in preantral follicles.

Animals↗
PubMed2001

Differences in follicular function of 3-month-old calves and mature cows.

After in vitro maturation, fertilization and development, the percentage of fertilized eggs developing to the blastocyst stage is usually lower in calves compared with cows. It is unknown whether this low ability to develop in vitro is inherent to calf oocytes or is caused by altered follicular maturation. The latter possibility was explored in the present study using two markers of follicle function: in vitro steroidogenesis by intact follicles and aromatase activity of follicular walls. Calf follicles > 9 mm in diameter had a low ability to produce oestradiol (ten times reduction compared with cows) despite a testosterone output by theca cells which was similar to that observed in cows. This finding is in agreement with the low aromatase activity of granulosa cells of calf follicles measured by tritiated water release assay. Qualitative and quantitative differences between calf and cow follicular fluids were assessed using western blotting (inhibin and activin, heat shock protein 90, Müllerian inhibiting substance) and assays (inhibin and activin) to determine whether this defective aromatase could be produced by alterations in the amounts of follicular proteins modulating aromatase (inhibin and activin, heat shock protein 90, Müllerian inhibiting substance). Western blotting of follicular fluid proteins demonstrated three main bands (59, 57 and < 30 kDa) and one minor band (34 kDa) with the anti-alpha inhibin antibody, whereas a single 18 kDa band was detected when an anti-beta inhibin antibody was used. Calf follicular fluid contained similar amounts of all main inhibin forms (alpha and beta) but a 34 kDa alpha inhibin form was missing. The amounts of dimeric inhibin were similar between cows and calves but small follicles from calves contained more activin. Single bands at 70 kDa (Müllerian inhibiting substance) and 90 kDa (heat shock protein 90) were detected by western blotting. Müllerian inhibiting substance was missing from calf follicular fluid and heat shock protein 90 was present in smaller amounts in calf versus cow follicular fluid. None of the above differences could explain the defective aromatase of calf follicles. Two-dimensional separation of the [35S]-labelled proteins secreted by follicular walls originating from calf or cow follicles matched for size and follicle health was performed and 151 spots were observed on the master gel, which summarized all the spots present at least once. Fifteen spots were present in calves and not in cows. Quantitative differences were also detected with three spots containing more proteins in cows than in calves. Whether some of these proteins can alter maturation of follicles or oocytes requires further investigation.

Activins↗