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Biomedical subjects

R S Robinson

Publications and source records attributed to R S Robinson.

At least 19 recordsLinked to original sources
PubMed2007

Leptin in the bovine corpus luteum: receptor expression and effects on progesterone production.

In cattle, leptin has been implicated in the control of ovarian function and has been shown to modulate steroid production by theca and granulosa cells in a number of species. However, a direct effect of leptin on bovine luteal function has not been demonstrated. This study was conducted to determine if the leptin receptor (OB-R) is expressed in the bovine corpus luteum (CL), and to examine the effects of leptin on progesterone production by dispersed luteal cells in vitro. RT-PCR was used to detect the presence of OB-R and, more specifically, the long, biologically active isoform (OB-Rb), in CL, collected on days 2-18 of the oestrous cycle (n=18). The effects of leptin on progesterone production were investigated in dispersed luteal cells prepared from CL collected on days 5 and 8 (n=14) of the cycle. The dispersed luteal cells were cultured for 24 hr with recombinant human leptin and/or LR3-IGF-1 and/or LH. OB-Rs, in particular, OB-Rb, were expressed in the CL at all stages of development. Progesterone production by luteal cells was increased (P<0.001) by treatment with LH (10 ng/ml) but treatment with leptin alone had no effect. However, in the presence of IGF-1 (100 ng/ml), leptin (10 ng/ml) caused a significant (P<0.005) increase in progesterone production. In conclusion, we have shown that the leptin receptor is expressed in the bovine CL and have demonstrated a modulatory effect of leptin on luteal progesterone production in vitro.

Animals↗
PubMed2006

Identification of elevated concentrations of estradiol in bovine uterine endometrium.

We have investigated the estradiol content of bovine endometrium and related this to circulating plasma estradiol content. In 9 heifers, mean+/-S.E.M. plasma estradiol concentration was 0.64+/-0.25 pg/ml while the mean+/-S.E.M. endometrial estradiol content was 43.0+/-14.7 pg/g tissue; there was a close relationship between plasma and tissue estradiol levels (R(2)=0.81; P<0.001). During culture of endometrial tissue there was a progressive transfer of estradiol from tissue to culture media but no change in total estradiol. Culture of endometrium from 4 heifers with 5 ng/ml testosterone for 72 h resulted in no increase in estradiol. Furthermore, immunohistochemistry revealed no aromatase protein in uterine endometrium. These results confirm high stored tissue concentrations of estradiol in bovine endometrium while providing no evidence for estradiol synthesis by this tissue. The mechanism(s) through which this sequestration of estradiol into uterine tissue occurs remains to be determined.

Animals↗
PubMed2006

Leptin infusion during the early luteal phase in ewes does not affect progesterone production.

Infusion of leptin during the ovine follicular phase has been shown to increase progesterone secretion during the subsequent luteal phase. In this study, we have assessed the effects of infusing leptin during the early luteal phase. Infusion of leptin (2.5 microg/h) into the ovarian artery of ewes with ovarian autotransplants (n=5) on day 3 of the luteal phase for 12h did not affect progesterone estradiol or LH concentrations compared to control ewes (n=5). These results suggest no direct effect of leptin on ovarian function at this stage of the estrous cycle.

Animals↗
PubMed2006

In vivo expression of interferon tau mRNA by the embryonic trophoblast and uterine concentrations of interferon tau protein during early pregnancy in the cow.

In this study, we have measured uterine concentrations of interferon tau and intensity of embryonic interferon tau mRNA expression between day 14 and 18 in cows. While interferon tau concentrations rose dramatically (P < 0.001) from day 14 to 18, there was no significant increase in the intensity of expression of interferon tau mRNA by the trophoblast. When results were analyzed on the basis of embryo size, well elongated embryos (>10 cm) produced significantly (P < 0.001) more interferon tau than smaller embryos but showed similar levels of interferon tau mRNA expression. These results demonstrate that the increase in interferon tau concentrations responsible for the maternal recognition of pregnancy results from the increase in embryo size during elongation and not from any upregulation of mRNA expression.

Animals↗
PubMed2005

Endocrine and cellular characteristics of corpora lutea from cows with a delayed post-ovulatory progesterone rise.

The timing of the post-ovulatory progesterone rise is critical to the embryonic development and survival. The aim of this study was to determine the underlying causes of delayed post-ovulatory progesterone rises. Two groups of non-lactating dairy cows with early (n = 11) or late (n = 9) post-ovulatory progesterone rises were created by inducing luteolysis in the presence of either a large (> 10 mm) or small (< 10 mm) follicle, respectively. LH pulses were measured on days 4 (all cows) and 7 (n = 7, early; n = 5, late) (day 1= ovulation). The cows were slaughtered on day 5 (n = 4 each group) or 8 (n = 7, early; n = 5, late). Immunohistochemical analysis for endothelial cells (von Willebrand Factor, VWF), steroidogenic cells (3beta-HSD) and proliferation marker (Ki67) were performed. The basal progesterone production and LH responsiveness (0.001-100 ng/ml) of dispersed luteal cells was investigated. The luteal concentrations of FGF-2 and VEGF were measured by ELISA and RIA, respectively. There were no differences in LH pulse characteristics, area of VWF staining, proliferation index, steroidogenic cell characteristics, basal or LH-stimulated progesterone production by luteal cells between cows with an early or late progesterone rise (P > 0.10). However, the area of VWF staining increased from days 5 to 8, while the proliferation index decreased (P < 0.05). Furthermore, the luteal cells were more responsive to LH on day 8 (P < 0.01). Luteal concentrations of FGF-2 were higher on day 5 (P = 0.05), while VEGF was greater on day 8 (P < 0.01). In conclusion, we have clearly shown that LH support, degree of vascularization or luteal cell steroidogenic capacity were not the major factors responsible for inadequate secretion of progesterone by the developing bovine CL.

Actins↗
PubMed2005

The induction of a delayed post-ovulatory progesterone rise in dairy cows: a novel model.

A delayed rise in post-ovulatory progesterone is associated with poor embryo development in the cow, although the underlying cause of this aberrant luteal function is poorly understood. The objective of this study was to develop a novel model, in which a delayed progesterone rise could be induced by manipulating the dynamics of the follicular phase. Luteolysis was induced in 20 dairy cows in the presence of either a larger follicle > 10 mm (LF, n = 11) or a smaller follicle < 10 mm (SF, n = 9) and transrectal ultrasonography was performed to determine follicle and CL growth and timing of ovulation. Plasma progesterone and oestradiol were analysed 3x daily. Cows were slaughtered on either day 4 (n = 4 per group) or day 7 (SF, n = 5; LF, n = 7) after ovulation. The pre-ovulatory follicle was larger in the LF group than the SF group at luteolysis (13.5 +/- 0.4 mm versus 6.7 +/- 0.7 mm, P < 0.001) and ovulation (16.7 +/- 0.3 mm versus 13.6 +/- 0.6 mm, P < 0.001). The LF group experienced a shorter follicular phase and ovulated 36 h earlier than the SF group (P < 0.001). At luteolysis, plasma oestradiol concentrations were greater in the LF group (P < 0.001), although peak concentrations were not different (P > 0.05). Moreover, higher progesterone concentrations were observed in the LF group during the early luteal phase (P < 0.05). Luteal weights were positively correlated with plasma progesterone concentrations on day 5 (P < 0.05) but not day 8. In conclusion, a model has been developed which has shown that the dynamics of follicle development during the pre-ovulatory period is an important determinant of subsequent CL development and function.

Animals↗
PubMed2004

Endocrine and paracrine control of follicular development and ovulation rate in farm species.

Productivity in farm species is controlled by many factors, including ovulation rate. In cattle, single ovulations occur most frequently and in sheep (and goats) the number of ova released can range from one to many depending upon the breed, whilst the pig is polyovular. The processes of recruitment and selection determine the number of ovulatory follicles in all these species with FSH and subsequently LH playing major roles. GnRH-agonist models in which endogenous gonadotrophin secretion is suppressed and exogenous LH and/or FSH are administered at specific concentrations in defined patterns, are useful in all three species for elucidating the precise roles of specific hormones in stimulating follicular development. Differences in the hypothalamic-pituitary-ovarian feedback response lead to the differences in the number of ovulatory follicles, as does the pool of antral follicles from which the ovulatory ones are selected. Precocious development of follicles is also associated with more ovulations, as is the case with the Booroola due to the single gene acting through bone morphogenetic proteins (BMPs). It is well established that ovulation rate can also be influenced by exogenous hormone administration and by environmental factors such as nutrition. It has become apparent that these nuritional effects are mediated by a direct action at the level of the ovary, involving insulin, insulin-like growth factors (IGF) I and II and their binding proteins among other factors. These factors can also affect the quality of the oocyte and consequently embryo development and survival. Recently, the regulation of follicular angiogenesis has been shown to be important for the development of ovulatory follicles, particularly vascular endothelial growth factor (VEGF) which is produced primarily by the granulosa cells within the ovary and can be stimulated by gonadotrophins. Administration of VEGF has been shown to stimulate pre-antral follicular growth and increase the number of pre-ovulatory follicles. In summary both extra- and intra-ovarian factors are involved in the control of ovulation rate. Manipulation of the angiogenic process may also provide new opportunities for regulating the quality and number of follicles that ovulate.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Expression of the insulin-like growth factor (IGF) system in the bovine oviduct at oestrus and during early pregnancy.

Early mammalian embryo development in vitro can be enhanced by co-culture with oviductal cells and by the addition of insulin-like growth factors (IGFs). This study examined the expression patterns of the oviductal IGF system in cattle in relation to the number of days after oestrus and the presence or absence of embryos. Oviducts were collected from: (i) 66 nulliparous heifers on day 3, day 6 or day 16 after insemination and from (ii) ten non-pregnant, lactating cows on day 0 or day 1 of the oestrous cycle. Oviducts were coiled, frozen whole and sectioned for in situ hybridization. Expression patterns of mRNAs encoding IGF-I, IGF-II, type 1 IGF receptor (IGF-1R), and the IFG binding proteins (IGFBP)-1, -3 and -5 were determined from autoradiographs. Separate measurements were made for the mucosa and muscle layers of the infundibulum, ampulla and isthmus. None of the parameters measured differed between heifers with or without the presence of an embryo. mRNAs encoding IGF-I and IGF-1R were present in the mucosa and muscle of all three oviductal regions, and the highest value of IGF-I mRNA was measured in heifers on day 3. IGF-II mRNA was expressed predominantly in the muscle wall. IGFBP-1 mRNA was not detectable, whereas mRNAs encoding IGFBP-3 and -5 were expressed in both the muscle and mucosa. IGFBP-3 expression was higher in cows on day 0 and day 1 of the oestrous cycle than in heifers on day 3, day 6 and day 16 after insemination. A peak of IGFBP-5 expression was reached on day 6. Locally or systemically produced IGFs, regulated by IGFBPs, may act directly on the embryo or indirectly via modulation of oviductal secretions and muscular activity to influence the success of early embryo development.

Animals↗
PubMed2002

Effects of dietary polyunsaturated fatty acids on ovarian and uterine function in lactating dairy cows.

Alteration of the polyunsaturated fatty acid (PUFA) composition of milk by dietary supplementation of cows may be beneficial to human health. However, dietary PUFAs may influence synthesis of both prostaglandins and steroid hormones. This study examined the effects of dietary PUFAs on reproductive parameters in lactating cows. Cows were fed an isoenergetic control ration (n = 8) or a diet supplemented with LinPreme (n = 7) or SoyPreme (n = 8). These proprietary feeds are derived from linseed or soybeans and contain high concentrations of linolenic acid (LNA, n-3) or linoleic acid (LA, n-6) protected PUFA, respectively. Both PUFA-supplemented diets reduced plasma progesterone, particularly in the early luteal phase, and increased the number of medium-sized (5-10 mm in diameter) follicles. The diameter of the first dominant follicle, insulin-like growth factor I (IGF-I) concentrations at oestrus and cholesterol concentrations were all higher in cows fed a diet supplemented with LA (n-6) than in cows that did not receive this supplement. In cows fed a diet supplemented with LNA (n-3), there was an increase in oestradiol during the follicular phase. Diet had no effect on non-esterified fatty acid or insulin concentrations, or on the duration of the oestrous cycle. The plasma concentration of 13,14,dihydro-15 keto PGF(2alpha) after administration of 50 iu oxytocin was unaffected by diet on day 15 and day 16 of the oestrous cycle, but showed a greater response on day 17 in the LA (n-6) supplemented group. Therefore, the PUFA content of the diet can influence both ovarian and uterine function in cows. However, further studies using larger numbers of cows are required to test whether fertility is also affected by such diets.

Animals↗
PubMed2001

Effect of dietary polyunsaturated fatty acids on uterine prostaglandin synthesis in the cow.

Dietary polyunsaturated fatty acid (PUFA) intake in humans can affect the incidence of a variety of diseases including coronary heart disease. Feeding high PUFA diets to cows can alter the PUFA content of milk for human consumption. PUFAs supply the precursors for prostaglandin (PG) synthesis and PGs in turn influence many aspects of reproduction. This study examined the effects of a control (CONT), a high n-6 PUFA diet (derived from protected soya) and a high n-3 diet (derived from protected linseed) on uterine PG synthesis in the lactating dairy cow. Endometrial explants obtained on days 15-17 of the oestrous cycle were cultured for an initial 42 h in vitro in fully defined medium (basal production) and then challenged with control medium, oxytocin (OT; 20 or 200 nM) or calcium ionophore A23187 (CaI; 10 microM). PGF(2 alpha), PGE(2) and 6-keto-PGF(1 alpha) were measured in the spent medium. The experiments were repeated using tissue from two groups of cows, nine in Experiment 1 (three cows per diet) and seven in Experiment 2 (four CONT and three n-6). Results of the two experiments were consistent. The basal concentrations of all three PGs were significantly lower (>50% reduction) in the n-6-fed group in comparison with CONT and n-3 groups. The n-3 diet did not alter basal PGF(2 alpha) and PGE(2) but increased 6-keto-PGF(1 alpha). The n-6 diet also inhibited the ability of the tissue to respond to both OT and CaI, with significant reductions in the stimulated levels of all three PGs. In contrast, the n-3 diet only had minor effects; it did not alter the response to OT but did reduce the long-term response to CaI at 24 h post treatment. In conclusion, dietary PUFA intake can inhibit PG production in bovine endometrial explants, with a more pronounced effect following n-6 rather than n-3 supplementation. These data suggest that a high n-6 diet reduces the endometrial capacity to produce PGs and may therefore have implications for the control of luteolysis and other PG-mediated events such as ovulation.

6-Ketoprostaglandin F1 alpha↗
PubMed2001

Expression of oxytocin, oestrogen and progesterone receptors in uterine biopsy samples throughout the oestrous cycle and early pregnancy in cows.

This study examined the expression patterns of oxytocin and steroid receptors in the bovine endometrium during the oestrous cycle and early pregnancy to elucidate their respective roles in the regulation of luteolysis and the maternal recognition of pregnancy. In Expt 1, uterine biopsies were collected from four cows throughout three oestrous cycles each, to provide daily samples. In Expt 2, uterine tissue was collected on days 12, 14, 16 and 18 of the oestrous cycle (n = 20) or early pregnancy (n = 16). Oxytocin receptor, oestrogen receptor alpha and progesterone receptor mRNAs were localized by in situ hybridization, and localization of oestrogen receptor and progesterone receptor was confirmed by immunocytochemistry. All three receptors showed time- and cell-specific expression patterns. Oestrogen receptor alpha increased in all regions at oestrus but high concentrations were also found in the luminal epithelium during the mid-luteal phase and in the deep glands throughout the oestrous cycle. Progesterone receptor expression was higher in the stroma than it was in the types of epithelial cell, and increased expression was observed at oestrus and during the early luteal phase. The cyclical upregulation of oxytocin receptors in the luminal epithelium on about day 16 was not related to preceding changes in the endometrial expression of either oestradiol alpha or progesterone receptors. During early pregnancy, oxytocin receptor expression was suppressed. Oestrogen receptor a concentrations increased in the non-pregnant cows and decreased in the pregnant cows between days 16 and 18, but these changes followed rather than preceded the upregulation of oxytocin receptors in the non-pregnant cows. It is concluded that the initial upregulation of oxytocin receptors in the luminal epithelium, which triggers luteolysis, is not associated directly with changes in expression of oestrogen receptor alpha.

Animals↗
PubMed2000

The expression of the IGF system in the bovine uterus throughout the oestrous cycle and early pregnancy.

The IGF system is expressed in the uterus during the oestrous cycle and early pregnancy and is likely to play an important role in regulating the development of the embryo and uterus. The IGF peptides (IGF-I and -II) mediate their effects through the type 1 IGF receptor (IGF-1R), while the IGF-binding proteins (IGFBP-1 to -6) modulate their interaction with the receptor. In this study, the expression of the IGF system in the bovine uterus was determined throughout the oestrous cycle and on day 16 of pregnancy. Endometrial biopsy samples were collected from four cows over three cycles such that there were samples for every 2 days from day 0 (oestrus) to day 14 and then every day until day 21. To assess the effect of pregnancy, uterine horn cross-sections were collected on day 16 from 15 pregnant (PREG), five inseminated non-pregnant (INP) and nine uninseminated cyclic controls (CONT). The expression of mRNA for the IGFs, IGF-1R and IGFBP-1 to -5 was determined by in situ hybridisation and the results were quantified by measuring the optical density units from autoradiographs. The main region of IGF-I mRNA expression was the sub-epithelial stroma underlying the luminal epithelium. The expression of IGF-I mRNA was highest at oestrus and lowest during the early and late luteal phases. On day 16, IGF-I mRNA levels were low in all groups, with pregnancy having no effect on the IGF-I mRNA concentrations. The strongest expression of IGF-II mRNA was in the caruncular stroma, with pregnancy having no significant effect in this region. IGF-1R mRNA was also present in the caruncles and was strongly expressed in all epithelial cells both throughout the oestrous cycle and during early pregnancy. The expression of IGFBP-1 mRNA was confined to the luminal epithelium, with the strongest expression seen on day 14 of the cycle. On day 16 the expression of IGFBP-1 mRNA was higher in the PREG group compared with the CONT group. The expression of IGFBP-2 mRNA was localised to the sub-epithelial stroma with more INP than PREG cows showing detectable levels of IGFBP-2. The strongest expression of IGFBP-3 mRNA was in the caruncular stroma; expression in the endometrial stroma was similarly decreased during early pregnancy. IGFBP-5 mRNA was mainly expressed in the inner ring of myometrium and was not affected by pregnancy on day 16. In conclusion, these results show that many components of the uterine IGF system are differentially regulated during the oestrous cycle and early pregnancy and suggest that modulation of the IGF system may influence uterine activity during this period.

Analysis of Variance↗
PubMed1999

The effect of pregnancy on the expression of uterine oxytocin, oestrogen and progesterone receptors during early pregnancy in the cow.

The expression of oxytocin receptor (OTR) in the uterine endometrium plays an important role in the initiation of luteolysis. During early pregnancy, the conceptus secretes interferon tau (IFN|gt) which inhibits OTR up-regulation and luteolysis. In this study, uterine horn cross sections were collected on day 16 from 15 pregnant cows (PREG), 9 uninseminated controls and 5 inseminated cows with no embryo present. The latter two groups had similar results and were combined to form a single non-pregnant (NP) group. The animals were given an oxytocin challenge shortly before tissue collection to assess prostaglandin F2alpha (PGF2alpha) release through the measurement of the metabolite 13,14-dihydro-15-keto PGF2alpha (PGFM). The mRNAs for OTR, oestrogen receptor (ER) and progesterone receptor (PR) were localised by in situ hybridisation. The results were quantified by optical density (OD) measurements from autoradiographs using image analysis. OTR protein was measured by autoradiography with iodinated oxytocin antagonist and ER and PR protein was detected by immunocytochemistry. The release of PGFM after the oxytocin challenge was significantly higher in the 14 NP cows (187%+/-15%) compared with the PREG group (131%+/-11%) (P<0.01). Low concentrations of OTR mRNA were localised to the luminal epithelium (LE) in 6 out of the 14 NP cows, of which 2 also expressed OTR protein, while OTR mRNA and protein were undetectable in all the pregnant animals. These results indicated that the sampling time coincided with the onset of the luteolytic mechanism in the NP cows. On day 16 ER mRNA was detectable in both the LE and glands of both PREG and NP animals. There were no differences in either ER mRNA or protein between NP and PREG samples. PR mRNA was moderately expressed in the caruncular stroma, with lower levels in the dense caruncular-like stroma and glands. There were no differences between PREG and NP animals. The expression of PR mRNA and protein in the deep glands was variable between animals. These results suggested that, in cows, the presence of an embryo suppressed the expression of OTR, but had no effect on the expression of the transcriptionally regulated ER on day 16.

Animals↗
PubMed1999

The regulation of interferon-tau production and uterine hormone receptors during early pregnancy.

During early pregnancy the bovine embryo must produce a protein called interferon tau which inhibits the development of the luteolytic mechanism. Failure to inhibit luteolysis is the major cause of pregnancy loss in cows. The embryo must produce sufficient quantities of interferon tau by about day 16 to prevent luteolysis. Its ability to achieve this is largely dependent on the pattern of maternal progesterone production. A late rise in progesterone after ovulation or poor progesterone secretion during the luteal phase results in the development of poor embryos capable of producing little or no interferon tau at the critical time. The embryo inhibits luteolysis by preventing development of oxytocin receptors on the luminal epithelium of the uterine endometrium and thus oxytocin-induced secretion of PGF2 alpha and by the induction of a prostaglandin synthesis inhibitor within the endometrium. In sheep it has been hypothesised that interferon tau acts to inhibit endometrial oestrogen receptors and thus oestrogen-induced up-regulation of oxytocin receptors. In cows, the embryo inhibits the development of oxytocin receptors and the initiation of luteolysis without causing any change in uterine oestrogen receptors. Thus in the cow, the mechanism by which interferon tau inhibits oxytocin receptor development remains to be determined.

Animals↗
PubMed1998

Role of the insulin-like growth factor system in uterine function and placental development in ruminants.

Maternal nutrition during pregnancy influences fetal and placental weights. The insulin-like growth factors (IGF) are also important determinants of fetal size. Furthermore, the expression of several components of the IGF system is regulated by nutrition. Effects of nutrition on fetal growth could therefore be mediated by the IGF system in the uterus and placenta. The oviductal mucosa produces IGF-I, which may influence oviductal secretions or act directly on embryonic type 1 IGF receptors. In the uterus, IGF-I mRNA is localized to the stroma surrounding the endometrial glands, which contain high concentrations of IGF type 1 receptors. Uterine IGF-I concentrations fall during pregnancy; therefore, glandular activity is more likely influenced by systemic than local IGF-I production. The IGF-II mRNA is present in both caruncles and fetal placental mesoderm, but concentrations are much higher in the latter. The actions of IGF-I and IGF-II on the endometrium and placenta are influenced by IGF-binding proteins. In the ewe, mRNAs for IGF binding protein-1 and -5 are located in the luminal and glandular epithelia, IGF binding proteins-2 and -4 are produced in the subepithelial stroma, and IGF binding protein-4 is also in the placentome capsule; IGF binding protein-3 is more widely expressed in both maternal and fetal tissues. The IGF binding proteins, therefore, form a major barrier to the passage of IGF between the fetal and maternal circulatory systems.

Animals↗
PubMed1990

Effect of a mouthrinse containing triclosan and a copolymer on plaque formation in a normal oral hygiene regimen.

A 6-day, double-blind parallel clinical study was conducted to determine the effect on plaque formation of a mouthrinse containing 0.03% [corrected] triclosan (Irgacare MP) and 0.25% of a copolymer of methoxyethylene and maleic acid (Gantrez), as compared to a flavored/colored water placebo mouthrinse. A total of 47 subjects were stratified into two balanced groups using their pre-prophylaxis plaque score. All subjects received a thorough oral prophylaxis at the start of the study. Each group was randomly assigned to the use of either the water placebo mouthrinse or the mouthrinse containing triclosan/copolymer. Subjects rinsed their mouths twice daily (mornings and evenings) for 1 minute with 15 cc of their assigned mouthrinse. Immediately after rinsing, the subjects brushed their teeth for 30 seconds with a commercially available dentifrice containing 0.76% sodium monofluorophosphate in a silica base and a soft-bristled toothbrush. The morning rinsing/brushing procedure was conducted under supervision at the clinical facility. The evening rinsing/brushing procedure was performed at home. After 5 days' use of their assigned mouthrinse, subjects were evaluated by the dental examiner for plaque formation using the modified Quigley-Hein scoring procedure. The results indicated that the triclosan/copolymer mouthrinse provided a 31.03% reduction in plaque formation as compared to the water placebo mouthrinse. This reduction was statistically significant at the 99% level of confidence.

Adult↗