bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic treatment with long-acting bromocriptine does not affect duration of the breeding season, voluntary food intake, body weight, or wool growth in the Scottish blackface ewe
Authors: Curlewis JD , Sibbald AM , Milne JA , McNeilly AS
Published: October 2005

The aim of this study was to determine whether suppression of the seasonal increase in prolactin concentrations by chronic treatment with the dopamine agonist bromocriptine would affect onset of anoestrus, voluntary food intake, body weight, and wool growth in a seasonal breed of sheep. Groups of eight Scottish Blackface ewes were injected i.m. each week with either the vehicle (Group A) or 2.0 mg (Group B), 6.0 mg (Group C), or 18.0 mg (Group D) of bromocriptine in a long-acting formulation, commencing on 18 January and terminating on 25 July (midwinter to midsummer in the northern hemisphere). Immediately before the bromocriptine injection, blood samples were taken for progesterone and prolactin determination. Voluntary food intakes were measured daily, and body weights were recorded every fortnight. Estimates of wool growth were made by weighing wool clipped from a measured area of skin once a month. Treatment had no effect on onset of anoestrus, voluntary food intake, body weight, or wool growth. Plasma prolactin concentrations increased significantly in all groups during the treatment period. From January to April, all doses of bromocriptine significantly reduced prolactin concentrations but later in the study (May and June) prolactin was significantly suppressed in Group D only, although even in this group prolactin concentrations increased between March and June. Pituitary prolactin content, measured at the end of the study in July, was also suppressed by bromocriptine. The gradual increase in prolactin concentrations in ewes receiving chronic bromocriptine was further investigated by treating a fifth group of ewes (Group E) with 18.0 mg of long-acting bromocriptine each week, commencing on 20 June.(ABSTRACT TRUNCATED AT 250 WORDS)
In vivo myometrial activity during early pregnancy and pseudopregnancy in the rat
Authors: Crane LH , Martin L
Published: October 2005

Video-laparoscopic studies in early pregnant and pseudopregnant rats showed large changes in frequency, direction of propagation and nature of myometrial contractions. Day 2 patterns of activity were essentially the same as in unmated animals at the equivalent stage of the cycle. From Days 3 to 5 there was a large increase in longitudinal and circular contractions propagating towards the oviduct, circular contractions making the greatest contribution. This circular activity may be important in retaining and spacing embryos. Circular contractions propagating towards the cervix showed smaller increases and there was a transient diminution in the frequency of longitudinal contractions in this direction on Day 5. In pregnant rats, the frequency of discrete contractions declined on Days 6-7. However, circular tone appeared to be increased and uteri showed dramatic twisting and curling, apparently due to resistance to the shortening imposed by longitudinal contractions. None of the major changes in activity appeared to be caused by embryos, because they were seen in pseudopregnant rats and, after embryo implantation, in both horns of unilaterally pregnant rats. The earliest divergence from the activity patterns of unmated rats occurred when progesterone levels first increased significantly above those of the undisturbed oestrous cycle, suggesting that progesterone has a major influence on myometrial activity. The complexity of the changes in activity raises questions about other regulatory factors, particularly in regard to coordination between the circular and longitudinal muscle layers. Anomalous results from pregnant, unilaterally pregnant, and pseudopregnant animals on Day 7 suggested that embryos exert systemic effects on myometrial activity.
Immunocytochemical localization of oestrogen receptors in the endometrium of the ewe
Authors: Cherny RA , Salamonsen LA , Findlay JK
Published: October 2005

Immunocytochemistry with monoclonal antibodies to the oestrogen receptor (ER) was used to localize ERs in sections of endometrium obtained from cycling and pregnant Corriedale ewes. Representative tissue from Days 4, 10, 14, 15, 16 and 17 of the cycle (Day 0 = onset of oestrus) and Day 15 of pregnancy was used. ER localization was also examined in tissue obtained from ovariectomized (ovex) ewes with and without subcutaneous implants containing oestrogen, progesterone, or oestrogen and progesterone. ER distribution was examined in caruncular endometrium and intercaruncular endometrium. Staining intensity varied according to cell type, stage of the cycle, steroid treatment and pregnancy. No staining was observed in endothelial cells. In all cases, ER was localized within the nuclei of positive cells. Generally, ER levels were high on Day 4 and declined to negligible values by Day 10 (corresponding to peak progesterone values) except in the deep stroma of caruncular endometrium. Positive staining reappeared in stromal cells of caruncles on Day 13 and in the luminal epithelium of intercaruncular tissue on Day 14. Peak intensity was reached on Day 15 for caruncular tissue and Day 16 for intercaruncular tissue. Ovariectomy did not cause an overall reduction in ER levels, whereas treatment with oestrogen and progesterone had variable effects depending on cell type. Progesterone did not suppress overall ER. In Day 15 pregnant tissue, ER was undetectable in all compartments except deep stroma of caruncles, indicating that factors other than progesterone, perhaps embryonic in origin, were responsible. The observation that individual cell types display differential sensitivities to oestrogen and progesterone as regards their expression of ER is consistent with the role of cell-cell interactions as modulators of cellular response to steroids through the oestrous cycle and in pregnancy.
Importance of uterine expulsion of embryos in the interceptive mechanism of postcoital oestradiol in rats
Authors: Ortiz ME , Bastias G , Darrigrande O , Croxatto HB
Published: October 2005

This study compares the interceptive effectiveness of 1 microgram oestradiol given as a single s.c. injection at 0900 or 1700 hours on Day 1, 2, 3, or 4 of pregnancy in rats. Increasing the interval from ovulation to treatment accelerated the oviducal transport of a larger number of embryos, the majority of which were lost from the genital tract. However, after treatment at 1700 hours on Day 3 the majority of accelerated embryos were retained in the uterus. The number of implanted embryos on Day 14 was equal to the number of eggs remaining in the tract 24 h after treatment. As a consequence, the highest interceptive effectiveness was obtained with treatment given at 1700 hours on Day 2 and at 0900 hours on Day 3 of pregnancy. Accelerated oviducal transport and uterine expulsion of embryos begin to dissociate after Day 2 of pregnancy in the rat. This explains why the most effective treatments to accelerate oviducal transport are not always the most effective to reduce the number of implantations. These data emphasize the importance of retentive and expulsive properties of the uterus for fertility and infertility.
Release of insulin-like growth factor I by the sheep placenta in vitro
Authors: Falconer J , Davies JJ , Zhang HP , Smith R
Published: October 2005

This study has utilized a tissue perifusion system to examine the release of insulin-like growth factor I (IGF I) from different regions of the sheep placenta at two stages of gestation. Placentae were obtained from ewes at either 116 +/- 7 (mean +/- s.e.) or 144 +/- 1.5 days of gestation and separated into the maternal basal plate or chorionic villous tissue. At both ages, the maternal basal plate tissue released approximately three times more IGF I than the chorionic villous tissue. No difference was found between the rate of release of IGF I from the maternal basal plate at 120 and 140 days of gestation, whereas the chorionic villous tissue released less IGF I later in gestation. Maternal basal plate tissue was less responsive to a depolarizing dose of KCl than was chorionic villous tissue at either age. After acid gel chromatography, perfusate from the basal plate had three peaks of IGF immunoreactivity (corresponding to binding protein, IGF I and a form with an intermediate molecular weight). In contrast, the chorionic villous tissue released only a form with a high molecular weight, corresponding to binding protein. These results demonstrate that the sheep placenta produced IGF I, that secretion varies between different placental zones which contain different cell types and that there are maturational changes in placental IGF I secretion. The IGFs may be involved in placental growth.
Biophysical assessment of placental and membrane dysfunction
Authors: Giles WB
Published: October 2005

During the 1960s and 1970s, the fetoplacental unit was assessed by means of biochemical studies in the form of oestriol and human placental lactogen assays. With the advent of both real-time ultrasound and fetal heart rate monitoring, the accent on fetal assessment has changed. More recently (the late 1980s) the use of Doppler ultrasound has expanded the non-invasive assessment of the fetoplacental unit. This review discusses these modalities along with reports of randomized controlled trial assessments of these modalities.
Endocrine and substrate control of fetal growth: placental and maternal influences and insulin-like growth factors
Authors: Owens JA
Published: October 2005

Fetal growth is largely controlled by the interaction of the genome with the availability of oxygen and glucose and by endocrine responses to variations in their supply. Insulin-like growth factor II (IGF-II), and probably IGF-I, modulate fetal growth. Insulin and thyroid hormones are controlled by the supply of glucose and oxygen, respectively, and they influence fetal growth, partly via IGF-I. Circulating IGF-I and -II are controlled acutely and chronically by glucose availability to the fetus. The transfer of substrates from the mother to the fetus is determined by placental transfer capacity and by placental utilization of those substrates. The fetus controls the latter via its blood concentrations of oxygen and glucose and possibly IGF-I. In the mother, placental hormones and proteins, such as progesterone, placental lactogen, placental growth hormone and proteases, increase circulating IGFs and alter the stability and concentrations of IGF binding proteins. These changes may direct the metabolic and growth adaptation of the mother to pregnancy, which ensures an adequate flow of substrates to the developing fetus.
Luteinizing hormone and follicle stimulating hormone induce premature condensation of chromatin in goat (Capra hircus) oocytes
Authors: Kumar J , Osborn JC , Cameron AW
Published: October 2005

This study tested the hypothesis that premature condensation of chromatin in goat oocytes following superovulation with 1200 i.u. pregnant mare serum gonadotrophin (PMSG) is mediated by the high luteinizing hormone (LH) activity inherent in this gonadotrophin. Goats were treated with either a standard (3.95 mL) or high (7.90 mL) dose of a highly purified follicle-stimulating hormone (FSH) preparation (Ovagen), and different doses of human chorionic gonadotrophin (hCG) were added to increase the level of LH bioactivity during superovulation. The meiotic status of oocytes obtained at sponge withdrawal was compared between different treatments and correlated with profiles of LH bioactivity in peripheral plasma. Injection of 100 i.u. hCG (which gave a plasma LH profile comparable to 1200 i.u. PMSG) or 200 i.u. hCG resulted in significantly more oocytes showing premature condensation of chromatin without germinal vesicle breakdown than with 25 i.u. hCG or treatment with FSH alone. Nevertheless, nuclear maturation was also prematurely activated in a significant number of oocytes with a high dose of FSH alone, even though LH bioactivity was not detected in plasma. It is concluded that high LH bioactivity during superovulation of goats with gonadotrophins activates the initial stages of nuclear maturation in oocytes. However, highly purified FSH preparations in high doses can also induce this apparent abnormality in the timing of oocyte maturation through mechanisms unrelated to any LH contamination.
Screening for Neisseria gonorrhoeae and Chlamydia trachomatis in a donor insemination programme
Authors: Haddad Y , Steigrad S
Published: October 2005

Cultures of all 4450 specimens of semen from 193 semen donors were negative for N. gonorrhoeae. A MicroTrak direct fluorescence microscopy test for the detection of Ch. trachomatis was used to screen 448 specimens from all 268 recipients of semen on an insemination programme for 3 1/2 years; all pre-insemination endocervical samples and all subsequent endocervical samples were negative. It is considered that the incidence of gonorrhoeae or chlamydia in our recipients or donors is very low. Fluorescence microscopy is a specific and cost-effective screening technique for Ch. trachomatis.
Gonadotrophin-induced oestrus and ovulation in the polyovulatory marsupial Sminthopsis crassicaudata
Authors: Rodger JC , Breed WG , Bennett JH
Published: October 2005

Sminthopsis crassicaudata is a small (approximately 16 g) polyovulatory dasyurid marsupial which has the potential to become an important model species. This study examined the use of exogenous hormone treatment to manipulate the breeding of S. crassicaudata and as a means to obtain timed developmental stages for further study. Two thirds (21/32) of the females treated with 1.0 or 5.0 I.U. of pregnant mare serum gonadotrophin (PMSG) had ovulated when the contents of their reproductive tracts were examined 5 or 6 days later. Only one of eight females treated with 0.2 I.U. PMSG had ovulated in the same period. Although a similar proportion of animals treated with 1.0 I.U. and 5.0 I.U. ovulated, the ovulation rate was significantly lower when the higher dose was administered (mean of 10.5 ovulations per female v. 3.8 ovulations per female). In addition, the ovaries of 6/8 of the animals treated with 5.0 I.U. PMSG had luteinized follicles with degenerating oocytes, evidence of over-stimulation. Follicular luteinization also occurred in 4/8 animals treated with 1 I.U. PMSG. Oocyte maturation and ovulation occurred following PMSG stimulation without injection of synthetic gonadotrophin releasing hormone (GnRH). Treatment with a 10-micrograms dose of GnRH following PMSG seemed to have no effect on the outcome. Of the females that had ovulated by Day 6, three quarters had mated and some had fertilized eggs and two-cell embryos in the oviducts and uteri. In a further series of experiments the subsequent development of embryos conceived after PMSG treatment was assessed. Two thirds of treated females mated within 7 days of treatment and 60% of these matings yielded embryos when examined 11 days after PMSG. However, full-term development was only achieved in one animal. Gonadotrophin treatment of S. crassicaudata thus may have application as a means to obtain mature or maturing oocytes, cleavage stage embryos and blastocysts, but at this stage it appears not to offer promise as a method to achieve full-term development.
Comparison of the SpermMar test with currently accepted procedures for detecting human sperm antibodies
Authors: Kay DJ , Boettcher B
Published: October 2005

To eliminate the possibility of immunological infertility in spontaneously infertile and re-anastomosed men, a screening test that can be applied directly to semen is desirable. The SpermMar test is one such possibility. In this study, indirect tests for sperm antibodies using the commercial SpermMar test have been applied to a panel of sera whose reactions in the tube slide agglutination test (TSAT), gelatin agglutination test (GAT) and sperm immobilization test (SIT) for sperm antibodies are well characterized. The results from the SpermMar tests are compared directly with those obtained from Immunobead tests carried out at the same time. Results from screening tests performed on 30 sera confirmed complete correspondence between the GAT, SpermMar and Immunobead tests. When sera were titrated, the Immunobead test proved slightly more sensitive than the GAT and the SpermMar test was slightly more sensitive than the Immunobead test. The SpermMar test proved easier to use and to assess than the Immunobead test and it is recommended for consideration as a screening procedure for sperm antibodies despite the fact that at this stage only IgG antibodies can be detected.
Effect of oxytocin on the pattern of electromyographic activity in the oviduct and uterus of the ewe around oestrus
Authors: Gilbert CL , Cripps PJ , Wathes DC
Published: October 2005

This study tested the hypothesis that the administration of oxytocin in doses equivalent to endogenous concentrations at and around oestrus could affect uterine and oviductal muscular activity at the time of gamete transport. Four ewes were fitted with recording electrodes in the left ampulla, ampullary-isthmic junction, utero-tubal junction and uterine horn. After surgical recovery, recordings from conscious free-standing animals were made for up to 10 h per day from Day -3 to Day +3 relative to oestrus in each ewe. Daily blood samples were taken for progesterone radioimmunoassay, and a vasectomized ram used to assess oestrus. A range of physiological doses of oxytocin (10-100 mU), or control saline injections were given intravenously. Electromyographic (EMG) activity was measured before and after injections. Spontaneous activity throughout the reproductive tract was low on Day -3 but increased to peak at oestrus (P < 0.05), when the pattern of activity consisted of short (2-10 s) co-ordinated high amplitude bursts (2-5 min-1). After oestrus, as overall activity declined, longer episodes of activity appeared but these occurred with a much slower frequency (1-4 h-1). Responsiveness to oxytocin was greatest on the day of oestrus at all electrode sites. Elevated responsiveness (relative to Day -3, the late luteal phase) was seen from Day -1 to Day +2 at the ampullary-isthmic junction and uterus, but on the day of oestrus only at the ampulla and utero-tubal junction. Duration of increased EMG activity after oxytocin injection ranged from 5 to 20 min. These results show for the first time that the uterine and oviductal musculatures of the ewe in vivo reached a peak in sensitivity to physiological concentrations of oxytocin at oestrus. When combined with information on oxytocin receptor populations and endogenous circulating concentrations, this suggest that endogenous oxytocin could influence oviduct and myometrial activity at this time.
Differential pituitary response to GnRH in pregnant Booroola-Assaf and Assaf ewes
Authors: Gootwine E , Bor A , Shalhevet D , Zenou A , Braw-Tal R
Published: October 2005

Pituitary response to exogenous gonadotrophin-releasing hormone (GnRH) was examined at a late stage of pregnancy in 10 Booroola-Assaf ewes heterozygous at the FecB locus (FecBFec+) and in 11 Assaf ewes that were non-carriers (Fec+Fec+). Basal plasma luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations were similar in the two genotypes. Administration of 100 micrograms of GnRH resulted in a significant increase (P < 0.05) in plasma LH and FSH concentrations in most of the ewes treated. Maximal responses were observed 105-135 min after GnRH treatment. Pituitary responses to GnRH were significantly lower (P < 0.05) in Booroola-Assaf than in Assaf ewes. The decreased pituitary responsiveness observed in FecB gene carriers compared with Fec+Fec+ ewes might be due to differences in the concentrations of ovarian or uterine hormones modulating the release of gonadotrophin. The results suggest that FecB-specific differences can be observed at the pituitary level.
Actions of platelet activating factor (PAF) on gametes and embryos: clinical aspects
Authors: Pike IL , Ammit AJ , O'Neill C
Published: October 2005

Platelet activating factor (PAF) is a phospholipid widespread in body tissues. Previous reviews have discussed its production by preimplantation embryos and the evidence implicating it as an autocrine mediator in aspects of gamete and embryo physiology. Human spermatozoa contain variable amounts of PAF, the amount contained depending on the source and method of preparation of the sperm. Incubation of human sperm with PAF tends to increase their forward velocity, especially in samples with slow motility. PAF treatment causes an increase in the proportion of acrosome-reacted sperm and in their ability to penetrate both zona-free hamster ova and cervical mucus. PAF has been found in human follicular fluid at ovulation. A role for PAF in ovulation has been suggested, because PAF antagonists reduce the rate of ovulation in rats. In some studies, modest improvements to mouse in vitro fertilization (IVF) rates have been achieved with PAF supplementation of media under specific conditions. Furthermore, in the rabbit and mouse, PAF antagonists have been reported to inhibit fertilization in vivo and in vitro respectively. However, addition of PAF to human IVF medium, but only at the time of insemination and fertilization, had no effect on either fertilization or pregnancy rates. Sensitive bio- and immuno-assays have shown that PAF is secreted by human embryos into their fluid milieu. PAF secretion by these zygotes during culture, although markedly variable, has been correlated with the achievement of pregnancy and pregnancy outcome. Although the secretion of PAF by the mouse embryo decreases during culture in vitro, exogenous PAF enhances embryo viability during culture. Similarly, culture of human zygotes in PAF-supplemented medium prior to embryo transfer significantly increases the chance of achieving pregnancy. Both the implantation and live-birth rates are increased in human IVF by addition of PAF to the medium.
Early pregnancy factor has immunosuppressive and growth factor properties
Authors: Morton H , Cavanagh AC , Athanasas-Platsis S , Quinn KA , Rolfe BE
Published: October 2005

Early pregnancy factor (EPF) was first described as a pregnancy-associated substance, although recent studies suggest a more general link with cell development. It is a product of actively dividing cells and its apparent functional importance to them suggests its potential as a regulator of cell proliferation. The recent discovery of EPF in platelets has provided a comparatively rich and readily available source of EPF. The purification procedures employed to isolate EPF from this source have also been applied to pregnancy serum and urine, medium conditioned by oestrous mouse ovaries (stimulated with prolactin and embryo-conditioned medium), medium conditioned by tumour cells, and serum from rats 24 h after partial hepatectomy (PH). In all instances, biological activity followed the same pattern throughout. Furthermore, the final active reversed-phase high-performance liquid chromatography fraction from all sources was bound specifically by immobilized anti-EPF monoclonal antibodies (MAbs), indicating that the active fractions produced from these diverse sources are very closely related, if not identical. Some differences have been observed in the behaviour of EPF in various conditions. EPF is produced by proliferating tumour cells and by liver cells post-PH, and passive immunization studies with anti-EPF MAbs have shown that these cells need EPF for survival. In contrast, EPF has not been detected as a product of the pre-embryo, and addition of anti-EPF MAbs to embryo cultures does not adversely affect development from the 2-cell to the blastocyst stage. Although the pre-embryo is not dependent on EPF for its development in vitro, neutralization of EPF in vivo by anti-EPF MAbs retards its development. Thus, EPF appears to play an indirect role in maintaining the pre-embryo. By virtue of its ability to suppress the delayed-type hypersensitivity reaction, it has been suggested that EPF might act as an immunological response modifier of the maternal immune system. Alternatively, the effect of EPF on lymphocytes may be to reduce the expression of all or some cytokines and this could inhibit development. Whether or not EPF acts more directly as an autocrine growth factor from around the time of implantation, when the embryo first begins synthesis of EPF, is not known and remains to be investigated.
Identification of molecules and mechanisms involved in the 'early pregnancy factor' system
Authors: Clarke FM
Published: October 2005

For a long time the 'early pregnancy factor' has defied molecular definition. First described in 1976, this phenomenon is revealed in vitro by the rosette inhibition assay, in which a lymphocyte-modifying activity in maternal serum is detected within hours of fertilization; it is present for at least the first two-thirds of pregnancy, with continued detection dependent upon the presence of a viable embryo or fetus. It has potential applications in early pregnancy testing, for monitoring fetal well-being and in the study of fertility control. Although the activity detected is one of a complex biological fluid (pregnancy serum) in a complex biological assay, this ability of pregnancy sera to cause increased rosette inhibition titres (RIT) has generally been ascribed to the presence of an 'early pregnancy factor' (EPF). The common usage of the term EPF has implied the existence in pregnancy sera of a unique factor, which has often been assumed to be a novel, pregnancy-specific protein with the unique capacity to induce increased RITs. Recent results render this concept untenable. These studies have begun to identify the molecules and mechanisms which cause the expression of increased RITs. In particular, thioredoxin or thioredoxin-like molecules have been identified as involved in the mechanisms by which pregnancy sera induced increased RITs. As a result, a new paradigm for the EPF phenomenon is presented which helps to resolve many of the enigmatic properties previously ascribed to the so-called 'early pregnancy factor' and which may assist in the further understanding of the molecular mechanisms of communication between embryo and mother prior to implantation.
Timing of the window of uterine sensitivity to decidual stimuli in mice
Authors: Finn CA , Pope MD , Milligan SR
Published: October 2005

The refractory period that follows the period of sensitivity to a decidual stimulus in ovariectomized hormone treated mice was investigated. Medroxyprogesterone acetate provided constant progestin concentrations and silastic implants containing oestradiol maintained constant nidatory oestrogen concentrations. The nidatory stimulus was provided by crushing the uterus with a haemostat or by the intrauterine instillation of arachis oil. The decidual response was assessed by measuring changes in uterine weight or by examining the stroma for the presence of alkaline phosphatase. Sensitivity to the oil was first observed approximately 14 h after the insertion of the oestradiol implant but this sensitivity had waned by 32 h and was absent at 40 h. Crushing the uterus initiated a decidual response in mice treated with progestin alone but if the oestradiol implant was inserted then the uterus was responsive to crushing 24 h after insertion but not at 45 h. The traumatic decidual cell reaction (crushing), although not requiring nidatory oestradiol for its successful initiation, was nevertheless subject to the refractoriness that followed oestradiol sensitivity.
Fertility of superovulated ewes after intrauterine or oviducal insemination with low numbers of fresh or frozen-thawed spermatozoa
Authors: Maxwell WM , Evans G , Rhodes SL , Hillard MA , Bindon BM
Published: October 2005

Two experiments investigated the effects of number of spermatozoa inseminated and time and site of insemination of fresh and frozen-thawed semen on fertility in Merino ewes treated with intravaginal progestagen pessaries and a combination of pregnant mare serum gonadotrophin and follicle stimulating hormone. In Experiment 1, ewes were inseminated in the uterus or oviducts with totals of 10(4), 10(5), 10(6) or 10(7) fresh spermatozoa 44 or 68 h after pessary removal. Ova recovered 48 h later were classified as fertilized if they had cleaved. Proportion of fertile ewes (ewes with fertilized ova per ewes inseminated) and fertilization rate of ova (ova fertilized per ova recovered) were higher for inseminations 44 h (63% and 45%) than 68 h (38% and 19%) after pessary removal (P < 0.001). More ewes were fertile after oviducal (61%) than after intrauterine insemination (39%; P < 0.05), and with high (10(6) and 10(7)) than with low (10(4) and 10(5)) doses of spermatozoa for intrauterine (54% v. 24%; P < 0.05) but not for oviducal inseminations (63% v. 59%). Fertilization of ova was better after oviducal than after intrauterine inseminations (44% v. 22%; P < 0.001), and with high than with low doses of spermatozoa (45% v. 21%; P < 0.001). In Experiment 2, ewes were inseminated with 10(5), 5 x 10(5) or 10(6) total fresh or frozen-thawed spermatozoa in the uterus or oviducts, 44 h after pessary removal.
Effect of prepubertal gonadectomy and sex steroid treatment on the growth and lymphocyte populations of the rat thymus
Authors: Windmill KF , Meade BJ , Lee VW
Published: October 2005

The age at which rats are most sensitive to prepubertal gonadectomy, in terms of thymic growth, was investigated. Gonadectomy enhanced thymic growth at each age; the greatest difference in thymic weight between gonadectomized and intact animals occurred in male rats gonadectomized at 5 weeks of age (64%) and in female rats gonadectomized at 4-5 weeks of age (43-46%). The effect of various synthetic sex steroids on growth and lymphocyte populations of the thymus in gonadectomized rats was examined. Diethylstilboestrol, 1 mg per animal, inhibited thymic growth by more than 35% in both males and females. Ethinyloestradiol, 40 micrograms per animal, inhibited thymic growth by 26% in males but by only 4% in females. Fluoxymesterone, 10 mg per animal, inhibited thymic growth by more than 46% in both sexes. Norgestrel, 12 micrograms per animal, had no effect on thymic growth. The synthetic steroids that significantly inhibited thymic growth decreased the intensity and altered the localization of staining for total T cells (antibody clone MRC OX 19), T helper cells and macrophages (W 3/5), T cytotoxic/suppressor cells (MRC OX 8) and B cells (MRC OX 12).
Secretion of transferrin in ovine seminiferous tubule cell cultures in response to FSH: influence of breed, season of birth and age of lambs
Authors: Monet-Kuntz C , Fontaine I
Published: October 2005

The response of lamb Sertoli cells to follicle stimulating hormone (FSH) was investigated by measuring transferrin secretion in seminiferous tubule cell cultures throughout the non-pubertal and the prepubertal periods. Cells could be cultured from birth until they attained a testicular weight of 19 g. The characteristics of individual dose-response curves were compared according to the breed, season of birth and testicular weight of the lambs. At the same season of birth and within a given testis weight range, dose-response curves of Romanov and Ile-de-France lambs were similar. Within a given testis weight range, spring-born animals exhibited a higher maximal transferrin secretion than autumn-born lambs, but the ED50 was similar. The main factor of variation of the dose-response curve parameters was the testicular weight of the lambs: the amplitude of FSH response increased 3-fold from a testicular weight of 6 g onwards, i.e. from the appearance of spermatogonia in seminiferous tubules. The ED50 increased 5-fold from 11 g onwards, i.e. from the beginning of the prepubertal period. Thus, Sertoli cells become less sensitive to FSH as spermatogenesis develops in seminiferous tubules. This phenomenon is largely the result of higher phosphodiesterase activity and is greatly reduced by 1-methyl-3-isobutyl-xanthine (MIX).
Porcine granulosa cell conditioned media as autocrine regulator of progesterone secretion
Authors: Denkova RT , Ivanov IG , Kanchev LN
Published: October 2005

The ability of porcine granulosa cells to release a progesterone inhibiting substance(s) was examined in vitro. Granulosa cells (SGCs, MGCs and LGCs) were harvested from small, medium or large antral follicles respectively. The effect of granulosa cell conditioned media obtained from small follicles (SGCCM) was studied in the culture of LGCs by estimation of progesterone secretion; the conditioned media evoked the inhibition of progesterone secretion by the LGCs. SGCCM produced by various numbers of cultured granulosa cells showed a dose-related inhibition of progesterone production. A maximum inhibitory effect was noted when a 5-fold concentration of SGCCM was used. The addition of SGCCM had no effect on the growth of the cultured cells. The factor(s) inhibiting progesterone secretion appeared to be a nonsteroidal substance of molecular mass greater than 10 kDa and was heat-stable and trypsin-sensitive. The data presented support the suggestion that the conditioned media generated by primary cultures of SGCs contain nonsteroidal regulators capable of inhibiting progesterone secretion by cultured LGCs; this inhibitory activity can play an important autocrine regulatory role in the process of follicular differentiation.
Oxidative utilization of glucose, acetate and lactate by early preimplantation sheep, mouse and cattle embryos
Authors: Waugh EE , Wales RG
Published: October 2005

The production of radiolabelled CO2 from [U-14C]glucose, [1-14C]lactate, and [U-14C]acetate was used to study the oxidative metabolism of embryos recovered from sheep, mice and cattle. Sheep embryos showed an increasing capacity to oxidize glucose after the 4- to 8-cell stage and oxidative turnover of this substrate at the blastocyst stage was four times that at the early stages. Decarboxylation of carbon-1 of lactate followed a pattern similar to that seen for glucose oxidation, but acetate oxidation was low and did not follow the trends with development seen for the other substrates. Furthermore, estimates of incorporation of acetate into the macromolecules of sheep embryos were low compared with similar estimates for glucose and, unlike glucose, did not increase with development. Oxidation of all three substrates by mouse embryos increased with development but the rate of CO2 production from acetate was low compared with that from the other substrates. A combination of lactate or glucose with acetate had no influence on the utilization of acetate by mouse morulae/early blastocysts, nor did acetate influence utilization of the other substrates. Cattle morulae/early blastocysts also produced more CO2 from glucose and lactate than from acetate and the incorporation of carbon from acetate into the macromolecules of these embryos was less than from glucose. Overall, cattle embryos showed the greatest ability to metabolize acetate but were not as effective in using the other substrates as either sheep or mouse embryos at the same stage.
Oxidation of
Authors: Wales RG , Waugh EE
Published: October 2005

Acetate metabolism by the sheep conceptus was assessed by measuring CO2 production during a 2.5-h incubation of embryos and samples of the extraembryonic membranes in HEPES-buffered media containing 1.12 mM [U-14C]acetate. The rate of oxidation of acetate by embryonic tissue showed little change between Days 13 and 15 of pregnancy but greatly decreased by Days 17 and 19. By contrast, oxidation of the substrate by the trophoblast increased substantially with development and was five times the early rate by Day 19. Oxidation of acetate by the yolk sac also increased 4-fold between Days 17 and 19. The addition of glucose to incubations of extraembryonic membranes resulted in some reduction in the oxidation of acetate by the yolk sac and allantois but had little effect on the trophoblast. At Days 13 and 15, the rate of oxidation of acetate by the embryonic disc was 6-7 times that by the trophoblast. As development progressed, this situation was reversed and by Day 19 the trophoblast metabolized more than five times the amount of acetate per microgram than did the Day-19 embryo. Although acetate metabolism by yolk sac and allantois on Day 17 was low, its metabolism by the yolk sac increased to values similar to those for the trophoblast at Day 19 but its utilization by the allantoic membrane remained low. Comparison of the estimates of ATP generated from acetate by these tissue with those published for glucose demonstrates that acetate is much less effective than glucose for the provision of metabolic energy.
Platelet activating factor (PAF) enhances mitosis in preimplantation mouse embryos
Authors: Roberts C , O'Neill C , Wright L
Published: October 2005

Preimplantation mouse embryos were used to determine whether the reported significant increase in embryo metabolism and viability achieved through supplementation of the culture medium with the ether phospholipid 1-o-alkyl-2-acetyl-sn-glycero-3-phosphocoline (platelet activating factor, PAF) is attributable to an enhanced rate of mitosis. Blastocyst-stage embryos cultured in the presence of 0.186 to 18.6 microM exogenous PAF had a significantly (P < 0.01) higher mitotic index (the proportion of cells arrested in metaphase following incubation in colchicine) than those cultured without PAF. At the 8-cell stage, 29% more blastomeres were in metaphase in the PAF-treated group (P < 0.01) 8 h after the addition of colchicine, but by 16 h there was no difference between groups; thus, PAF increased the rate at which cells entered metaphase but did not increase the total number. The mitotic index showed a negative correlation with the number of cells within blastocysts. PAF had a significantly (P < 0.01) greater impact on the mitotic index of blastocysts with fewer cells. The action of PAF was specific, being completely blocked by the PAF-receptor antagonist WEB 2086 (33 microM). In the absence of exogenous PAF the mitotic index was lower with WEB 2086 than without, suggesting inhibition of the action of endogenous embryo-derived PAF. These results show that PAF stimulates the rates at which cells within the preimplantation mouse embryo enter metaphase in vitro and suggest that it would decrease their doubling time, perhaps accounting for the embryotrophic actions of PAF.
Microencapsulation of bovine spermatozoa for use in artificial insemination: a review
Authors: Nebel RL , Vishwanath R , McMillan WH , Saacke RG
Published: October 2005

A technique for microencapsulation of bovine spermatozoa has been developed with minimal spermatozoal injury and thus of potential use in artificial insemination. The polymers poly-l-lysine, polyvinylamine and protamine sulfate have proven best for membranes. Encapsulation has been successful with capsules ranging in size from 0.75 to 1.5 mm, and with sperm concentrations from 45 to 180 x 10(6) cells mL-1. Successful extenders include CUE, CAPROGEN, and egg yolk-citrate-glycerol (maximum 10% v/v egg yolk for normal capsular shape). Capsule fragility (ability to rupture under ageing and physical stress) is negatively related to membrane thickness which ranges from 1.92 to 5.32 microns (depending on the concentration of polymer used) and positively related to concentration of sperm encapsulated. Heterospermic studies have shown that encapsulated sperm are capable of fertilization in vivo, but are at a disadvantage to unencapsulated sperm when cows are inseminated at conventional times. Uterine retention of inseminates is favoured by capsules having a 'sticky' membrane. Using current procedures, preliminary homospermic fertility studies indicate that sperm encapsulated with poly-l-lysine or protamine sulfate may achieve normal fertility.
Biological factors affecting subzonal sperm microinjection results
Authors: Gianaroli L , Magli MC , Ferraretti AP , Fortini D , Feliciani E , Fiorentino A
Published: October 2005

One hundred and sixteen couples with severe male factor infertility underwent 139 subzonal sperm microinjection cycles. In total, 1343 oocytes were microinjected, resulting in a fertilization rate of 24%, followed by a cleavage rate of 65%. In 26% of the zygotes, fertilization was delayed and embryos derived from these zygotes demonstrated a poor capacity for further growth and implantation. In 102 of 139 cycles (73%) embryo transfer was performed, resulting in 9 pregnancies. This study followed the fate of injected oocytes and early embryo development to investigate biological factors that influence the results of subzonal injection.
Transgenic strategies to increase disease resistance in livestock
Authors: Muller M , Brem G
Published: October 2005

Approaches to modify disease resistance or susceptibility by transgenic means will be a major asset to animal welfare as well as to the economics of animal production. Candidates for gene transfer experiments include all genes known to influence non-specific and specific host defence mechanisms against infectious pathogens. Additional strategies such as 'intracellular immunization', 'genetic and congenital immunization', antisense RNA approaches and targeted disruption of disease susceptibility genes promise to gain importance in conferring increased disease resistance. The cytokine network regulates cellular viability, growth and differentiation in physiological and pathophysiological states. Detailed understanding of cytokine signal transduction pathways and transcriptional activators will provide not only new target molecules for modulating the immune response but will also facilitate the elucidation of host-pathogen interactions.
Ovulatory activity, hormonal induction of ovulation and fertility of young Cashmere and Angora female goats in a temperate environment
Authors: Ritar AJ , Robertson JA , Evans G
Published: October 2005

Reproductive parameters of young Cashmere and Angora goats born between 1988 and 1990 and grazed on temperate pastures in southern Australia were examined with a view to reducing the age of first breeding. Females born in August or October of 1989 and 1990 were examined each month by laparoscopy to determine natural ovulatory activity when 6-19-months old. Cashmeres commenced ovulating as young as 7 months of age or as light as 12 kg. Almost all Cashmeres were ovulating by 8-10 months of age at a liveweight of at least 18 kg, and their breeding season extended from April to October. By comparison with Cashmeres, Angoras grew more slowly, fewer ovulated, they commenced ovulation later, their ovulation rates were lower and their breeding season was shorter. A stratified sample of these females was injected with 200 I.U. or 400 I.U. of pregnant mare serum gonadotrophin (PMSG) after treatment with controlled internal drug release (CIDR) devices for 16-18 days to induce ovulation at 6, 9, 12, 15 and 19 months of age. Ovulation rates after CIDR-PMSG treatment were higher for Cashmeres than for Angoras and tended to be higher for females injected with 400 I.U. PMSG than 200 I.U. PMSG. The proportion of females remaining anovulatory after exogenous hormonal treatment was higher for Angoras than for Cashmeres (38% and 10% respectively) but it was not affected by the dose of PMSG or age. For kids born in 1989, the kidding rates to insemination (with follow-up mating) after CIDR-PMSG treatment for 8-month-old and 20-month-old Cashmeres (in the breeding season) were similar (75.0% and 83.8% respectively) but the rate for 14-month-old Cashmeres was only 10.0% (in the non-breeding period). The kidding rates for Angoras bred at 8, 14 and 20 months of age were 8.4%, 20.0% and 30.0% respectively. Ovulatory activity and fertility in the non-breeding period, with or without CIDR-PMSG treatment, did not improve with melatonin treatment.
The proopiomelanocortin gene is expressed as both full-length and 5'truncated transcripts in rodent Leydig cells
Authors: Ivell R
Published: October 2005

A reverse transcription polymerase chain reaction (RT-PCR) assay was developed to distinguish between full-length transcripts and functionally aberrant, truncated transcripts of the proopiomelanocortin (POMC) gene. This assay was applied to RNA obtained from the testes of rats and mice, to Percoll-purified primary mouse Leydig cells, and to various Leydig-derived cell lines. The results indicate a very low level of expression for the full-length transcripts in whole rodent testis, in mouse Leydig cells and in the MA10 cell line. In Leydig cells, the major transcripts of the POMC gene were the shorter, truncated transcripts where the regions corresponding to exons 1 and 2 are missing.
Effects of tumour necrosis factor alpha (TNF alpha) on ovulation in the rat ovary
Authors: Brannstrom M , Bonello N , Wang LJ , Norman RJ
Published: October 2005

The effects of tumour necrosis factor alpha (TNF alpha) on ovulation rate, ovarian secretion of steroids, and on tissue concentrations of the ovulatory mediators plasminogen activator (PA) and prostaglandins were examined in rat ovaries perfused in vitro for 20 h. Unstimulated control ovaries did not ovulate whereas luteinizing hormone (LH; 100 ng mL-1) induced ovulations in all ovaries (2.6 +/- 0.7). TNF alpha (40 ng mL-1) induced ovulations in 3 of 5 ovaries (0.8 +/- 0.4). When TNF alpha was added concomitantly with LH, the LH-induced ovulation rate was increased four-fold (10.6 +/- 1.3). This effect was not seen when TNF alpha was added 5 h after LH (3.2 +/- 0.6). More progesterone was released when TNF alpha was combined with LH by comparison with LH alone. Tissue concentrations of prostaglandin F2 alpha (PGF2 alpha) and PGE were increased by the addition of TNF alpha when compared with the control group, but did not exceed those observed in the LH group, when TNF alpha was combined with LH. PA activity in the tissue was unaffected by TNF alpha and the LH-induced increase in PA activity was inhibited when TNF alpha was combined with LH. The results demonstrate that the proinflammatory cytokine TNF alpha promotes ovulations in the rat ovary.
Sperm preparation for intracytoplasmic injection: methods and relationship to fertilization results
Authors: Bourne H , Richings N , Liu DY , Clarke GN , Harari O , Baker HW
Published: October 2005

Sperm preparation for intracytoplasmic sperm injection (ICSI) is described and the effect of high speed centrifugation during preparation on fertilization rate is evaluated. No significant differences were found in the 2-pronuclear or abnormal fertilization rates between sibling oocytes injected with sperm prepared by swim-up or mini-Percoll combined with high speed centrifugation. The high fertilization rate obtained with both methods indicates that high speed centrifugation is not necessary to prepare sperm for ICSI. Fertilization rates were also compared for sperm obtained from ejaculates, fresh and frozen epididymal aspirates, and testicular biopsies. High fertilization rates were obtained from all groups but they were significantly higher in those oocytes injected with epididymal sperm (78% per oocyte surviving injection). The high fertilization rate with epididymal sperm may reflect sperm quality or may result from the method of sperm preparation for injection. Fertilization after the injection of sperm from which the tail was dislodged during immobilization was compared with that obtained using intact sperm. A significantly lower rate of 2-pronuclear fertilization was found in those oocytes injected with sperm heads only (55%) compared with intact sperm (68%), although cleavage rates between the two groups were similar. The use of hypo-osmotic medium to select potentially live sperm from an immotile sample is also described and fertilization was obtained after the injection of sperm with a structural defect which were selected using this technique. These results indicate that high fertilization rates can be obtained with ejaculated, epididymal and testicular sperm without special treatment.(ABSTRACT TRUNCATED AT 250 WORDS)