Steroid-binding proteins in follicular fluid and peripheral plasma from pigs, cows and sheep

Pork Production with Entire Males: Directions for Control of Boar Taint

Simple Summary

Castration of male piglets has traditionally been carried out to control boar taint, but animal welfare concerns about surgical castration has brought this practice under scrutiny. In addition, castration decreases growth performance and increases the environmental impact of pork production, so alternatives to castration are needed to control boar taint. In this review, we summarize the current knowledge on boar taint metabolism and outline some key areas that require further study. We also describe some opportunities for controlling the boar taint problem and propose that by defining the differences in metabolic processes and the genetic variations that can lead to boar taint in individual pigs, we can design effective custom solutions for boar taint.

Abstract

Boar taint is caused by the accumulation of androstenone and skatole and other indoles in the fat; this is regulated by the balance between synthesis and degradation of these compounds and can be affected by a number of factors, including environment and management practices, sexual maturity, nutrition, and genetics. Boar taint can be controlled by immunocastration, but this practice has not been accepted in some countries. Genetics offers a long-term solution to the boar taint problem via selective breeding or genome editing. A number of short-term strategies to control boar taint have been proposed, but these can have inconsistent effects and there is too much variability between breeds and individuals to implement a blanket solution for boar taint. Therefore, we propose a precision livestock management approach to developing solutions for controlling taint. This involves determining the differences in metabolic processes and the genetic variations that cause boar taint in specific groups of pigs and using this information to design custom treatments based on the cause of boar taint. Genetic, proteomic or metabolomic profiling can then be used to identify and implement effective solutions for boar taint for specific populations of animals.

Exposure of pregnant sows to low doses of estradiol-17β impacts on the transcriptome of the endometrium and the female preimplantation embryos†

Maternal exposure to estrogens can induce long-term adverse effects in the offspring. The epigenetic programming may start as early as the period of preimplantation development. We analyzed the effects of gestational estradiol-17β (E2) exposure with two distinct low doses, corresponding to the acceptable daily intake "ADI" and close to the no-observed-effect level "NOEL", and a high dose (0.05, 10, and 1000 μg E2/kg body weight daily, respectively). The E2 doses were orally applied to sows from insemination until sampling at day 10 of pregnancy and compared to carrier-treated controls leading to a significant increase in E2 in plasma, bile and selected somatic tissues including the endometrium in the high-dose group. Conjugated and unconjugated E2 metabolites were as well elevated in the NOEL group. Although RNA-sequencing revealed a dose-dependent effect of 14, 17, and 27 differentially expressed genes (DEG) in the endometrium, single embryos were much more affected with 982 DEG in female blastocysts of the high-dose group, while none were present in the corresponding male embryos. Moreover, the NOEL treatment caused 62 and 3 DEG in female and male embryos, respectively. Thus, we detected a perturbed sex-specific gene expression profile leading to a leveling of the transcriptome profiles of female and male embryos. The preimplantation period therefore demonstrates a vulnerable time window for estrogen exposure, potentially constituting the cause for lasting consequences. The molecular fingerprint of low-dose estrogen exposure on developing embryos warrants a careful revisit of effect level thresholds.

The characterization of androstenone transport in boar plasma

The transport of steroids by plasma proteins influences the amount of steroid available for uptake by the target tissue. In the boar, androstenone is transported to the adipose tissue where it accumulates to cause an off-odour or off-flavour in pork, known as boar taint. The mechanism of the transport of androstenone in the boar remains unclear, and the plasma protein responsible for binding androstenone has yet to be identified. Therefore, the purpose of the present study was to characterize the binding of androstenone to plasma proteins in the boar. The binding specificity of androstenone to plasma proteins was first investigated using a HPLC gel filtration method. [³H]-androstenone was incubated with plasma in the presence or absence of unlabeled competitors and the displacement of androstenone from plasma proteins was measured. In the presence of excess unlabeled competitors, [³H]-androstenone was only partially displaced from plasma proteins, indicating it binds to a low affinity high capacity plasma protein. Binding kinetics studies were also conducted to characterize the binding of androstenone and dehydroepiandrosterone (DHEA) to plasma proteins. The B_max of androstenone and DHEA was approximately the same (89.1% and 92.3%, respectively). However, the binding affinity (K) of androstenone was 6.5 fold greater than DHEA (0.39 nmol/ml and 0.06 nmol/ml, respectively). Affinity chromatography was used to remove albumin from the plasma proteins. Following incubations with androstenone and DHEA, the binding observed in the albumin free protein fraction was reduced 2.6 and 2.1 fold, respectively relative to the binding in the albumin protein fractions. These results provide direct evidence that androstenone is transported non-specifically by albumin in the plasma of the boar.

Characterization of plasma metabolites at late gestation and lactation in early parity sows on production and post-weaning reproductive performance

Lactation is a very energy demanding period for sows. The current study provides a better understanding of the biochemical response of first- (n = 246) or second-parity (n = 127) sows during late gestation through lactation and assesses relationships with piglet production and dam reproductive performance. Plasma samples were collected from first- or second-parity dams at late gestation (110 d gestation [d110G]), d 1 post-farrowing (d1PF), and weaning (WN) then analyzed for various stress and protein metabolism compounds, including; creatine, creatine phosphokinase (CPK) activity, creatinine, urea nitrogen, albumin, and lactate. Litter performance was measured as number of piglets nursed and piglet ADG. Post-weaning reproductive performance was assessed by measuring weaning-to-estrus interval (WEI) and subsequent ovulation rate collected at time of harvest. Plasma creatine and CPK activity increased (P < 0.05) between d110G and d1PF. Plasma creatinine decreased (P < 0.05) from d110G through WN in first-parity dams, but remained similar between d110G and d1PF before declining (P < 0.05) at WN in second-parity dams. Plasma urea nitrogen increased (P < 0.05) over the course of the study and was negatively (P < 0.05) associated with piglet ADG at d110G and d1PF and with ovulation rate at d110G (P < 0.05). Similarly, plasma albumin increased (P < 0.05) in first-parity dams over the course of the study, whereas it plateaued (P < 0.05) at d1PF and remained similar (P > 0.10) through WN in second-parity dams. First-parity dams had less (P < 0.05) plasma lactate at d110G than at d1PF or WN. However, second-parity dams had increased (P < 0.05) plasma lactate at d110G and d1PF, then decreased (P < 0.05) levels at WN. Plasma lactate at WN was positively (P < 0.05) associated with WEI in first-parity dams, but negatively (P < 0.05) related to WEI at d1PF in second-parity dams. Plasma lactate levels at all time points were positively (P < 0.05) associated with ovulation rate in second-parity dams. The biochemical profile of these dams differed by parity and merits further investigations into these differences to identify methods to improve physiological response to lactation for improved animal welfare, production, and reproductive performance.

17β-estradiol reduces Cav 1.2 channel abundance and attenuates Ca2+ -dependent contractions in coronary arteries

One mechanism by which the female sex may protect against elevated coronary vascular tone is inhibition of Ca²⁺ entry into arterial smooth muscle cells (ASMCs). In vitro findings confirm that high estrogen concentrations directly inhibit voltage‐dependent Ca_v1.2 channels in coronary ASMCs. For this study, we hypothesized that the nonacute, in vitro exposure of coronary arteries to a low concentration of 17β‐estradiol (17βE) reduces the expression of Ca_v1.2 channel proteins in coronary ASMCs. Segments of the right coronary artery obtained from sexually mature female pigs were mounted for isometric tension recording. As expected, our results indicate that high concentrations (≥10 μmol/L) of 17βE acutely attenuated Ca²⁺‐dependent contractions to depolarizing KCl stimuli. Interestingly, culturing coronary arteries for 24 h in a 10,000‐fold lower concentration (1 nmol/L) of 17βE also attenuated KCl‐induced contractions and reduced the contractile response to the Ca_v1.2 agonist, FPL64176, by 50%. Western blots revealed that 1 nmol/L 17βE decreased protein expression of the pore‐forming α_1C subunit (Ca_vα) of the Ca_v1.2 channel by 35%; this response did not depend on an intact endothelium. The 17βE‐induced loss of Ca_vα protein in coronary arteries was prevented by the estrogen ERα/ERβ antagonist, ICI 182,780, whereas the GPER antagonist, G15, did not prevent it. There was no effect of 1 nmol/L 17βE on Ca_vα transcript expression. We conclude that 17βE reduces Ca_v1.2 channel abundance in isolated coronary arteries by a posttranscriptional process. This unrecognized effect of estrogen may confer physiological protection against the development of abnormal Ca²⁺‐dependent coronary vascular tone.

An alkaline follicular fluid fraction induces capacitation and limited release of oviduct epithelium-bound stallion sperm

Induction of hyperactivated motility is considered essential for triggering the release of oviduct-bound mammalian spermatozoa in preparation for fertilization. In this study, oviduct-bound stallion spermatozoa were exposed for 2 h to: i) pre-ovulatory and ii) post-ovulatory oviductal fluid; iii) 100% and iv) 10% follicular fluid (FF); v) cumulus cells, vi) mature equine oocytes, vii) capacitating and viii) non-capacitating medium. None of these triggered sperm release or hyperactivated motility. Interestingly, native FF was detrimental to sperm viability, an effect that was negated by heat inactivation, charcoal treatment and 30 kDa filtration alone or in combination. Moreover, sperm suspensions exposed to treated FF at pH 7.9 but not pH 7.4 showed Ca(2+)-dependent hypermotility. Fluo-4 AM staining of sperm showed elevated cytoplasmic Ca(2+) in hyperactivated stallion spermatozoa exposed to treated FF at pH 7.9 compared to a modest response in defined capacitating conditions at pH 7.9 and no response in treated FF at pH 7.4. Moreover, 1 h incubation in alkaline, treated FF induced protein tyrosine phosphorylation in 20% of spermatozoa. None of the conditions tested induced widespread release of sperm pre-bound to oviduct epithelium. However, the hyperactivating conditions did induce release of 70-120 spermatozoa per oviduct explant, of which 48% showed protein tyrosine phosphorylation and all were acrosome-intact, but capable of acrosomal exocytosis in response to calcium ionophore. We conclude that, in the presence of elevated pH and extracellular Ca(2+), a heat-resistant, hydrophilic, <30 kDa component of FF can trigger protein tyrosine phosphorylation, elevated cytoplasmic Ca(2+) and hyperactivated motility in stallion sperm, but infrequent release of sperm pre-bound to oviduct epithelium.

Transcriptomic analysis identifies gene networks regulated by estrogen receptor α (ERα) and ERβ that control distinct effects of different botanical estrogens

The estrogen receptors (ERs) ERα and ERβ mediate the actions of endogenous estrogens as well as those of botanical estrogens (BEs) present in plants. BEs are ingested in the diet and also widely consumed by postmenopausal women as dietary supplements, often as a substitute for the loss of endogenous estrogens at menopause. However, their activities and efficacies, and similarities and differences in gene expression programs with respect to endogenous estrogens such as estradiol (E2) are not fully understood. Because gene expression patterns underlie and control the broad physiological effects of estrogens, we have investigated and compared the gene networks that are regulated by different BEs and by E2. Our aim was to determine if the soy and licorice BEs control similar or different gene expression programs and to compare their gene regulations with that of E2. Gene expression was examined by RNA-Seq in human breast cancer (MCF7) cells treated with control vehicle, BE or E2. These cells contained three different complements of ERs, ERα only, ERα+ERβ, or ERβ only, reflecting the different ratios of these two receptors in different human breast cancers and in different estrogen target cells. Using principal component, hierarchical clustering, and gene ontology and interactome analyses, we found that BEs regulated many of the same genes as did E2. The genes regulated by each BE, however, were somewhat different from one another, with some genes being regulated uniquely by each compound. The overlap with E2 in regulated genes was greatest for the soy isoflavones genistein and S-equol, while the greatest difference from E2 in gene expression pattern was observed for the licorice root BE liquiritigenin. The gene expression pattern of each ligand depended greatly on the cell background of ERs present. Despite similarities in gene expression pattern with E2, the BEs were generally less stimulatory of genes promoting proliferation and were more pro-apoptotic in their gene regulations than E2. The distinctive patterns of gene regulation by the individual BEs and E2 may underlie differences in the activities of these soy and licorice-derived BEs in estrogen target cells containing different levels of the two ERs.

Estradiol, progesterone, testosterone profiles in human follicular fluid and cultured granulosa cells from luteinized pre-ovulatory follicles

BACKGROUND

The production of sex steroids by follicular cells is proposed to be influenced by the maturity of the incumbent oocyte. Thus steroid levels may reflect suitability of an oocyte for IVF. We examined follicular fluids and granulosa cell production of steroid from IVF patients in order to test the relationship between steroid levels and fertilization.

METHODS

Follicular fluid and granulosa cells were extracted from 206 follicles of 35 women undergoing controlled ovarian stimulation. Follicular fluid was assayed for estradiol, progesterone and testosterone. Granulosa cells were cultured from individual follicles and their culture media assayed for production of these hormones after 24 hrs in vitro. Levels of steroids were correlated with follicular diameter, oocyte recovery and subsequent fertilization.

RESULTS

Follicular fluid levels of progesterone were 6100 times higher than that of estradiol, and 16,900 times higher that of testosterone. Despite the size of follicle triggered after controlled luteinization, the levels of progesterone and testosterone were maintained at relatively constant levels (median 98.1 micromoles/L for progesterone, and 5.8 nanomoles/L for testosterone). However, estradiol levels were slightly lower in the larger follicles (follicular diameter 10-15 mm, median 25.3 nanomoles/L; follicles > = 15 mm, median 15.1 nanomoles/L; linear correlation r = -0.47, p < 0.0001). With respect to oocyte recovery, no steroid showed a significant association in follicular fluid levels. Similarly no difference in follicular fluid steroid levels was found for those oocytes that did or did not fertilize. Significant quantities of progesterone were produced by the granulosa cells but production was constant regardless of the size of follicle from which the cells originated. Estradiol levels were only detectable in 10 of 121 cultures examined, and testosterone in none. Interestingly, when an oocyte was present follicular estradiol levels correlated with progesterone levels. However, when absent, follicular estradiol levels correlated with testosterone levels but not with progesterone.

CONCLUSIONS

The principle steroid product of luteinized pre-ovulatory granulosa is progesterone, a differentiation triggered by the gonadotropin surge. However, absolute steroid levels are associated with follicular size, not oocyte maturation/ability to fertilize.

Studies on 5alpha-androst-16-en-3-one binding to porcine serum, plasma and testicular cytosolic fraction and to human serum

The present study evaluated whether a specific androstenone-binding protein is present in porcine and human serum, and in the cytosolic fraction of porcine testis. The binding of [(3)H]-androstenone to serum and testicular cytosol was measured in the absence (total binding) and presence (non-specific binding) of unlabelled androstenone. The optimization of the assay is described. As a part of the assay validation, the binding of [(3)H]-dihydrotestosterone ([(3)H]-DHT) to porcine and human serum was also examined. As expected, specific binding of [(3)H]-DHT was detected in human serum, but not in porcine serum. No specific androstenone-binding protein was detected, either in porcine or human serum, or in the cytosolic fraction of porcine testis. The amount of non-specific binding of [(3)H]-androstenone was slightly lower in porcine serum compared to human serum. Between-animal variations in [(3)H]-androstenone binding were studied in plasma samples from 15 animals with androstenone concentrations ranging from 1.1 to 23.1 ng/mL. Mean values+/-standard deviations of binding in these samples were 15.2+/-0.9% for total binding and 15.9+/-0.8% for non-specific bindings. Low between-animal variations indicate that androstenone binding does not affect androstenone accumulation in fat.

Long-Term Exposure of Female Sheep to Physiologic Concentrations of Estradiol: Effects on the Onset and Maintenance of Reproductive Function, Pregnancy, and Social Development in Female Offspring1

As steroids and steroid-like compounds accumulate in the environment, it has become important to understand how low-dose exposure affects reproductive function. Ovary-intact sheep were used in a multigenerational study, to determine whether chronic exposure to low levels of estrogen disrupts reproductive function and behavior. We assessed parameters of reproductive performance in control and postnatally estradiol-treated females (Generation 1, G1), and their offspring (Generation 2, G2). In the G1 animals, 17beta-estradiol (E) was administered continuously from 4 wk of age at two doses via subcutaneous implants (ultralow E [<1 pg/ml in circulation, n = 8] or low E [1-3 pg/ml, n = 8]). Both doses delayed puberty; low E also produced pronounced prepubertal and seasonal anestrus hypogonadotropism, and delayed the onset of the second breeding season. All G1 animals conceived and produced offspring (G2), the treatment of which resulted from continuous maternal exposure during pregnancy and lactation. Behavioral observations of G2 females revealed that low prenatal E modestly masculinized play behavior and increased the frequency of attempts to displace competitors relative to ultralow E and control animals. The timing and magnitude of the LH surge also differed in prepubertal low prenatal E females relative to the controls, although these differences were not evident when retested at one year of age. These findings support the hypothesis that chronic exposure to physiologic amounts of exogenous estrogens has multigenerational effects on behavior and neuroendocrine function. Despite these disruptive steroid actions, ovarian cyclicity and fertility are not invariably compromised, pointing to an impressive resiliency of the reproductive axis to insult by exogenous estrogenic compounds.

Steroid concentrations in follicular fluid aspirated repeatedly from transitional and cyclic mares

The objectives of the present study were to determine follicular progesterone (P4) and estradiol-17beta (E2) in transitional mares and to compare follicular steroid concentrations between transitional and cyclic mares. Follicles > 8 mm were aspirated under transvaginal ultrasound-guidance 4 times at 3 to 4 day intervals (T1-T4) in Norwegian pony mares during vernal transition. During the breeding season, follicular aspirations were conducted in each mare on Day 6, Day 14 and Day 18 after ovulation of 3 separate estrous cycles (Day of ovulation = Day 0). Plasma and follicular fluids were analyzed for P4 and E2 with ELISA and RIA, respectively. Plasma P4 concentrations remained below 1 ng/mL throughout T1-T4, while the follicular P4 concentrations increased significantly to cyclic levels after the first transitional aspiration. Plasma E2 concentrations similarly remained at low levels during the course of the transitional aspirations, while the follicular E2 concentrations increased gradually over the 4 aspirations to cyclic concentrations. The mares ovulated on average 9.8 +/- 1.6 (mean +/- SEM) days after the last transitional aspiration, and 16.6 +/- 0.2, 11.3 +/- 1.5 and 23.2 +/- 4.4 days after aspirations conducted on Day 6, 14 and 18, respectively. The present study demonstrates that in the transitional mare newly developing follicles exhibit biosynthesis of P4 and E2. Furthermore, an increase in follicular steroid concentrations is not necessarily reflected in the peripheral steroid concentrations.

The plasma sex steroid binding protein (SBP or SHBG). A critical review of recent developments on the structure, molecular biology and function

Significant developments have taken place within the past five years on the characterization, molecular biology and function of the plasma sex steroid-binding protein, SBP (or sex hormone binding globulin, SHBG). During the span of that time, amino acid sequences of two SBPs have been established, amino acid residues in the steroid-binding site have been identified, the structure of the human SBP gene has been deduced and evidence for the possible existence of a SBP membrane receptor has been presented. This review covers the salient aspects of these and other developments including a critical analysis of the various proposed models and interpretations with regards to the structure, evolution, molecular biology and function of SBP.

Sex steroid changes in porcine cystic ovarian disease

Ten sex steroids were measured in the peripheral serum and ovarian follicular fluid of female pigs with or without cystic ovarian disease. In general, progestin, especially progesterone, accumulated excessively in the fluid contained in cystic compared with normal follicles. Nonluteinized cystic follicles contained up to four times the progesterone concentration found in large normal preovulatory follicles. Levels of this steroid increased with luteinization of cystic follicles to as much as 10 times those found in large preovulatory follicles. In contrast, the concentration of follicular fluid androgens and estrogens in cystic follicles were, at best, barely detectable (5 to 10 pg/ml). These results are indicative of a steroidogenic blockade in the conversion of C21 progestin to C19 androgens and C18 estrogens in the cystic follicles. In spite of an enormous accumulation of follicular progestin and subnormal concentration of androgens and estrogens, circulating levels of these hormones in pigs bearing cystic ovaries were in the normal range for cycling sows. Clearly, the hormonal abnormalities in the cystic follicles are not reflected in the serum profiles of these steroids.

Stress and mortality in the red-tailed phascogale, Phascogale calura (Marsupialia: Dasyuridae)

An investigation was made of endocrine changes occurring during the life history of Phascogale calura, a small, arboreal, squirrel-like insectivorous marsupial. Following a 3-week mating period in July each year, all males disappear from the population and it is presumed that they die. During the mating period the plasma cortisol concentration in males increased to a greater extent than did the plasma corticosterone. During this period the plasma concentration of CBG decreased in the males but not in the females, which resulted in competition between the two glucocorticoids for binding sites and a 25-fold sex difference in free cortisol concentration. The plasma testosterone concentration in males reached its maximum value about the time of disappearance of the males and the plasma lacked high-affinity binding for androgens. The depression in CBG concentration was androgen dependent since castration of captive males caused a marked increase in plasma CBG concentration which could be reversed with androgen administration. Postmorten examination of moribund males revealed evidence of hemorrhage from gastric ulcers and some evidence of immune suppression and disease. It is considered that a state of stress in males triggered by aggressive interactions following an elevation in plasma testosterone concentration during mating and antagonized by an androgen-dependent decrease in CBG concentration results in suppression of both immune and inflammatory reactions. This is the first detailed description of endocrine changes which accompany a stress-related total male mortality in a dasyurid marsupial species which does not belong to genus Antechinus.

Progesterone-binding protein in the corpus luteum, blood and lymph of sheep

A protein which binds progesterone but not cortisol was found in luteal cytosol, utero-ovarian venous plasma, ovarian lymph and jugular venous plasma of sheep. The protein was isolated from other steroid-binding activities present in luteal cytosol and plasma by de-adsorption from hydroxyapatite with 40 mM phosphate. In all cases, it bound progesterone at 4 degrees C with an equilibrium affinity constant of the order of 10(6) l/mol, but did not bind cortisol. After chromatography on hydroxyapatite and Sephadex G-200, the protein obtained from utero-ovarian venous plasma had lost much of its steroid-binding activity, but migrated as a monomer of molecular weight 64 000 in polyacrylamide gel. Bovine luteal cytosol is reported to contain two proteins which bind progesterone similarly. In ruminants, these proteins may participate in the biosynthesis and secretion of progesterone from luteal cells and its transport in blood.

A study of ovarian activity in the ewe using chronic catheterization of the utero-ovarian vein

Eighty-six adult, cyclic, anestrous and postpartum Ile-de-France ewes were placed under general anaesthesia. A catheter was inserted in the utero-ovarian vein (u.o.v.) of one or both ovaries in each ewe. The animals were kept unrestrained in pens and allowed to experience normal maternal behaviour, including suckling. Oestrus was detected with rams. Out of 167 catheters inserted, 70.7% allowed repetitive blood collection, 24.0% were obstructed for short periods and 5.4% remained completly blocked. Oestradiol- 17beta was assayed without extraction from the u.o.v. plasma samples. From these results, we conclude that this technique is suitable for investigating the mechanisms involved in the recovery of cyclical ovarian activity after parturition, particularly because the follicular response to endogenous gonadotropins can be assessed. This is not possible when plasma samples are obtained from a jugular vein.

Biogenic amine levels in the mid-term human fetus

Spectrophotofluorometric assays were used to measure concentrations of DA, NA, 5-HT and 5-HIAA present in extracts of brain tissue and CSF taken from midterm gestational fetuses of both sexes. The presence of biogenic amines was demonstrated in fetuses as early as 10.5 weeks gestation. In the hypothalamus, the concentrations (expressed in ng/100 mg tissue) ranged from 10.2 to 62.2 for NA, 11.6 to 258.8 for DA, 7.6 to 38.6 for 5-HT and 56.6 to 114.1 for 5-HIAA. Concentrations of DA and 5-HT were found to be significantly (P less than 0.05) higher in the hypothalamus than in the cortex, but those of NA and 5-HIAA were similar in both areas. No sex difference was observed. The concentrations of biogenic amines in the CSF (expressed in ng/ml) were 63.1-286.7 for NA, 43.2-108.1 for DA, 30.9-87.5 for 5-HT and 8.0-42.8 for 5-HIAA.

Indoleamine and catecholamine concentrations in the mid-term human fetal brain

Because of the likelihood that androgen-induced sex specific brain differentiation is mediated by various neurotransmitters, their concentrations were measured in the mid-term human fetal hypothalamus, cortex and cerebrospinal fluid (CSF). Tissue was collected from 32 hysterotomy specimens aged from 10 to 23 weeks, immediately frozen in liquid nitrogen, and stored at -20 degrees C. 5-Hydroxytryptamine (5-HT), 5-hydroxy indole acetic acid (5-HIAA), norepinephrine (NE) and dopamine (DA) levels were measured by a fluorometric assay. Cord serum testosterone levels were measured by radioimmunoassay. In the male fetuses, hypothalamic concentrations of 5-HT, 5-HIAA and NE were all significantly increased in comparison to those in the cortex. Because the number of female fetuses was small, only the 5-HIAA levels were seen to be significantly higher in the hypothalamus than in the cortex. In the CSF from fetuses of both sexes, the DA levels were greatly raised. Concentrations of NE were significantly higher in male fetuses aged from 14-16 weeks, a time when plasma testosterone levels are also elevated. It is hypothesized that the raised plasma testosterone and hypothalamic NE concentrations are inter-related.

Regulation of oviduct function in pigs by local transfer of ovarian steroids and prostaglandins: a mechanism to influence sperm transport

Blood was collected from a prominent ear vein and from the arterioles supplying the caudal portion of each oviduct in 5 estrous animals. Sampling was arranged at 4 preovulatory intervals, and just after ovulation in the fifth animal. Steroid hormones and prostaglandins were determined by radioimmunoassay of plasma. Whereas the concentration of cortisol did not differ between peripheral and oviduct blood samples, the overall values for progesterone, androstenedione and estradiol were significantly higher in oviduct samples (P less than 0.001) - frequently by 5- to 10-fold or more. The concentration of these three hormones in oviduct blood corresponded, in most instances, with the number of preovulatory follicles or recent ovulations in the adjacent ovary but suitable statistical correlations could not be performed. Prostaglandin F2 alpha was also present in higher concentrations in oviduct compared with peripheral plasma (P less than 0.005), although pulmonary clearance of prostaglandins would have influenced the peripheral values. Differences in the concentration of prostaglandin E2 were not significant. A local transfer of follicular hormones from the ovarian vein to the ovarian and utero-tubal arteries is proposed as a means of regulating oviduct function. Elevated concentrations of steroids and prostaglandins transferred in this way would permit incisive changes in the patency and contractile activity of the isthmus, thereby facilitating the periovulatory phase of sperm transport from the caudal portion of the oviduct to the site of fertilization.

In the absence of protein, estradiol suppresses meiosis of porcine oocytes in vitro

The effect of estradiol on the spontaneous maturation of porcine oocytes was investigated. Cumulus-enclosed (intact) and cumulus-free (denuded) oocytes were cultured in the presence of estradiol-17 beta (0 to 10 microgram/ml) in a chemically defined bicarbonate-buffered medium that contained either dextran or BSA, or in a complex Hepes-buffered medium that was supplemented with serum. After 24 hr, chromatin spreads were prepared and meiotic maturation was scored. The biochemical integrities of the cumulus cells were assessed by determination of the estradiol and progesterone content of spent media after culture of intact oocytes in the presence of 0.5 X 10(-6) M testosterone and 10 microgram/ml follicle-stimulating hormone. Estradiol did not significantly affect the onset of maturation of either intact or denuded oocytes that were cultured in medium containing either BSA or serum. In serum-supplemented medium, however, the progression of maturation beyond metaphase I was significantly affected by the steroid in a dose-dependent manner. The steroid significantly inhibited the release from meiotic arrest of both types of oocyte cultured in medium supplemented with dextran. Supplementation of all media with testosterone and FSH significantly stimulated the synthesis of estradiol by the cumulus cells, compared with that of control groups. The synthesis of progesterone, however, was significantly stimulated by testosterone and FSH only in the BSA and serum-supplemented media. It is concluded that exogenous estradiol has the capacity to arrest meiosis in vitro but that this capacity can only be expressed if no exogenous protein(s) is present. In the absence of exogenous protein, progesterone synthesis by the adherent cumulus cells is minimal.

Different pig phenotypes affect adherence of Escherichia coli to jejunal brush borders by K88ab, K88ac, or K88ad antigen

At least five different porcine phenotypes were distinguished with the three serological variants of the K88 antigen in the brush border adhesion test. Pigs of one phenotype (A) are susceptible to adherence of all three variants, pigs of three phenotypes are susceptible to only two (B and C) or one (D) of the K88 variants, and pigs of one phenotype (E) are entirely resistant to adhesion of K88 antigen did not interfere with the adhesion of K88ab- or K88ac-positive Escherichia coli, whereas in most cases K88ab and K88ac antigen completely blocked the adhesion of K88ad-positive E. coli. Likewise, K88ab antigen blocked the adhesion of K88ac-producing E. coli to both type A and type B brush borders, and vice versa.

Radioimmunoassay of estradiol-17 beta in unextracted ewe plasma

A radioimmunoassay for estradiol-17 beta (E 2 beta) without solvent extraction is described. It can be used for plasma samples with concentrations higher than 10 pg/ml. Tritiated E 2 beta, and a specific antiserum in phosphate buffer were added to plasma samples, the total incubation volume being 0,5 ml. An identical volume of steroid free plasma to that assayed in unknowns (0.050 -0.2 ml) was added to the standard curve. Immunoprecipitation was used to separate bound and free E2 beta and the bound radioactivity counted in the polyproplene assay tube. The calculated regression of E2 beta measured on plasma loaded with excess E2 beta (y = 0.987x / 3.8; R = 0.99) and that of E2 beta measured in the same sample by the direct assay on that of E2 beta found by a reference extraction method (y = 0.998x / 14.9; R = 0.98) as well as the presence of parallelism between the standard curve and different volumes of plasma and acceptable inter and intra assay coefficients of variation show that this method is suitable for the measurement of E2 beta in uteroovarian venous plasma. However, this method cannot be used for peripheral plasma of pregnant animals because it is not specific. The method was found useful in a study on the effect of gonadotrophin pulses on the ovary when many samples had to be analysed. Furthermore, there is a potential for automatization which would facilitate more detailed analyses of ovarian-hypophyseal relationships.

Specificity of inhibition by steroids of porcine oocyte maturation in vitro

In order to examine the influence of several steroids on the process of oocyte maturation, denuded (adherent cumulus granulosa cells mechanically removed) and intact (cumulus granulosa cells left attached) porcine oocytes were cultured in the presence or absence of estradiol-17 beta, estradiol-17 alpha, testosterone, cortisol, progesterone, or the nonsteroidal estrogen diethyl stilbestrol (all at 10 microgram/ml) in defined medium that contained either BSA or dextran. Estradiol-17 beta was the only steroid to exert a significant inhibitory effect on the maturation of denuded oocytes, and did so only in BSA supplemented medium. The inhibition was reversible in that oocytes, cultured in steroid-free medium after initial culture in estradiol-17 beta medium, resumed meiotic maturation. Oocytes took up 3H-estradiol-17 beta in both media, although less radiolabel entered oocytes in BSA supplemented medium. The majority of label in the oocytes, when cultured with either medium, was not displaced by excess radioinert estradiol-17 beta or progesterone, nor were the oocytes saturated even when cultured in 10(-6) M estradiol-17 beta. Autoradiography of sectioned oocytes after culture in 3H-estradiol-17 beta has shown that there was no selective accumulation of silver grains over the germinal vesicle as was the case with granulosa cell nuclei. This observation suggests that estradiol-17 beta may not act at the level of the oocyte nucleus.