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Biomedical subjects

M A Taverne

Publications and source records attributed to M A Taverne.

At least 19 recordsLinked to original sources
PubMed2002

Myometrial activity around estrus in sows: spontaneous activity and effects of estrogens, cloprostenol, seminal plasma and clenbuterol.

A new, nonsurgical, open-end catheter technique was used to study spontaneous uterine activity around estrus in sows, and the effects of estrogens, seminal plasma, cloprostenol, and clenbuterol on uterine activity. In the first experiment, uterine activity was studied in 14 multiparous, cyclic sows, during one or more estrous cycles, from day -4 to day 4 of the cycle (day 0: first day of standing estrus). From a few days before estrus until estrus, the percentage of sows showing any uterine contractions increased from 55 to 100%, and frequency and mean amplitude of uterine contractions for these sows increased from 15 to 22/h, and from 20 to 40 mmHg on average. After estrus, uterine activity decreased. There were large differences between sows in uterine activity, which were consistent over the days of the cycle. In the second experiment, 11.5 microg of estrogens in 100 ml saline (n = 17), 100 ml seminal plasma (n = 5), 1 mg cloprostenol in 100 ml saline (n = 10), 0.30 mg clenbuterol in 100 ml saline (n = 11), or 100 ml saline (n = 5) was infused IU, after recording spontaneous activity. Infusion with saline or seminal plasma did not affect uterine activity. Estrogens increased frequency of contractions. Cloprostenol increased both frequency and amplitude of contractions. Clenbuterol reduced both frequency and amplitude of contractions. In conclusion, this study shows that spontaneous uterine activity in sows is increased around estrus, and it supports the role of estrogens in boar seminal plasma in affecting uterine activity around mating. Further, this study has yielded possible tools to study the relation between uterine activity and sperm transport.

Adrenergic beta-Agonists↗
PubMed2001

Insulin-like growth factor-I (IGF-I) stimulates the development of cultured rat pre-antral follicles.

The aim of the present study is to investigate the effect of insulin-like growth factor (IGF-I) on the development of cultured rat pre-antral follicles. Pre-antral follicles with a diameter between 140 and 160 microm are mechanically isolated from ovaries of 10-day-old rats and cultured in groups for 6 days in FSH and insulin-containing serum-free medium in the absence or presence of IGF-I at concentrations of 1, 10, and 100 ng/ml, respectively. DNA content of the follicles before and after culture is measured to evaluate whether a possible growth is due to proliferation of follicular cells and the ultrastructure of the cultured follicles is studied with transmission electron microscopy to evaluate the quality of follicles cultured under different conditions. Furthermore, reverse transcriptase polymerase chain reaction (RT-PCR) is used to assess the gene expression of IGF-I and type I IGF receptor in pre-antral follicles. When follicles were cultured in medium containing IGF-I at a concentration of 1 and 10 ng/ml, the increase in follicle diameter after a 6-day culture differs significantly from that in the absence of IGF-I. The ultrastructure of follicles cultured in IGF-I-containing medium is better sustained when compared to that of follicles cultured in the absence of IGF-I. Especially, theca cells, which are undergoing degeneration under controlled culture condition, demonstrate normal cellular ultrastructure with some characteristics of steroid-secreting cells in the presence of IGF-I. Moreover, in oocytes of follicles cultured in the presence of IGF-I, cortical granules are observed distributed along the ooplasma membrane whereas cortical granules are hardly present in follicles cultured without IGF-I. With RT-PCR, the presence of the mRNA of IGF-I and type I IGF receptor is demonstrated in both the somatic follicular cells and the oocytes. Taken together, these results suggest that IGF-I, in the presence of follicle-stimulating hormone (FSH), enhances rat pre-antral follicle development in vitro and supports the morphology of cultured pre-antral follicles. The stimulatory effect of exogenous IGF-I on the development of pre-antral follicle together with the gene expression of both IGF-I and type I IGF receptor in pre-antral follicles suggests the involvement of IGF-I in early folliculogenesis and its actions are likely mediated by the putative type I IGF receptor, via both endocrine and paracrine/autocrine pathways.

Animals↗
PubMed2001

Uterine-embryonic interaction in pig: activin, follistatin, and activin receptor II in uterus and embryo during early gestation.

The mRNA expression patterns of activin beta(A) and follistatin in the uterus and embryo, the mRNA expression of the activin receptor II in the embryo, and the localization in the uterus of the immunoreactive activin beta(A) and the receptor II proteins in the uterus were examined at gestation days 7-12 after ovulation in pig. Activin was located predominantly at the mesometrial side of the uterus during all stages of pregnancy studied. Follistatin mRNA was absent in the uterus during these stages, suggesting that activin of uterine origin is not inhibited by intra-uterine follistatin. The receptor was localized throughout the glandular and luminal epithelium of the uterus. In the embryo, activin was expressed predominantly in the epiblast before unfolding, but after unfolding of the epiblast activin expression shifted to the trophoblast. The expression pattern of follistatin mRNA was contrarily to that of activin, i.e., before unfolding predominantly in the trophoblast (days 8-9), and shifted to the epiblast at day 10. During streak stages, follistatin was detected in the node and primitive streak. Activin receptor II mRNA was first detected at day 8 in the embryoblast. At day 11, it was expressed in trophoblast cells near the epiblast, and in the first ingressing mesoderm cells. During the streak stages, it was expressed predominantly in the trophoblast. The presence of activin and its receptor in uterine epithelium and early embryonic tissues indicate that both embryonic and uterine activin are involved in intra-uterine processes, such as attachment and early embryonic development. Mol. Reprod. Dev. 59: 390-399, 2001.

Activin Receptors, Type II↗
PubMed2001

Comparison of anterior-posterior development in the porcine versus chicken embryo, using goosecoid expression as a marker.

During early embryonic development, pig and chicken embryos share striking morphological similarities. In the present study, the timing and location of expression of mRNA for goosecoid (gsc), a gene classically expressed in the nodal region of developing embryos, was examined and compared in preprimitive streak and gastrulating pig and chicken embryos. The expression of gsc appeared first in the hypoblast and second in the hypoblast of pig and chicken embryos. Because gsc expression in these tissues was not symmetrical, gsc appears to be a useful marker for the onset of embryonic polarity. During gastrulation in both species, gsc expression became confined to cells in and around the node, in the epiblast and mesoderm layers. The only significant species-related difference in the distribution of gsc expression at these stages of development was the presence of gsc expression in the gut endoderm of chicken but not pig embryos. Certainly, our results suggest that the molecular mechanisms that control anterior-posterior development in different classes of vertebrates are remarkably similar. In addition, we were able to demonstrate that the pattern of gsc expression appears to provide a more sensitive and accurate means of determining the developmental stage of early porcine embryos than the more commonly used trophoblast or embryoblast size. Using gsc expression and accompanying embryo morphometric changes, we were able to develop a four-point scale that may offer a more accurate means of quantifying early embryo development in pigs.

Animals↗
PubMed2001

Effect of activin A on in vitro development of rat preantral follicles and localization of activin A and activin receptor II.

Preantral follicles (140-160 microm) were isolated mechanically from the ovaries of 10-day-old rats and cultured in groups of four to six for 6 days in medium containing 0, 1, 10, or 100 ng/ml of activin A. Activin stimulated (P < 0.05) the growth of preantral follicles in a dose-dependent fashion and enhanced the proliferation of preantral, oocyte-free follicular cells. Furthermore, treatment with activin induced the majority of follicles to form an antrum-like structure and helped to maintain the ultrastructure of these follicles during culture. Activin A also induced further changes characteristic of follicle and oocyte maturation, such as the elongation of granulosa cells contacting the oocyte and migration of the cortical granules to the oocyte cortex. In addition, gene expression for activin and activin receptor type II (ActR II) was demonstrated in both the oocytes and the somatic cells using the reverse transcription-polymerase chain reaction, and immunohistochemical studies demonstrated the presence of activin and ActR II proteins in the somatic tissue and, especially, the oocytes of these follicles. It is concluded that, in vitro, activin A stimulates the growth of rat preantral follicles and promotes antrum formation. Furthermore, because activin A and ActR II are synthesized within preantral follicles, intrafollicular activin likely plays an important role in early follicular development.

Activin Receptors, Type II↗
PubMed2001

Effects of morphine and naloxone on fetal heart rate and movement in the pig.

To test the hypothesis that an increasing opioid tonus is involved in decreases in fetal heart rate (FHR) and movement (FM) during late gestation, we studied the effects of intravenous bolus injections of morphine (1 mg) and naloxone (1 mg) on FHR and FM in the fetal pig. Twenty-one fetuses (1 per sow) were catheterized at 90-104 days of gestation (median 100 days). Recordings of FHR (electrocardiograph or Doppler-derived signals) and FM (ultrasonography) were made from 15 min before to 45 min after treatment. Morphine administration significantly decreased FHR, but it increased FHR variation and forelimb movements (LM). LM were clustered, and this stereotyped behavior has never before been observed in any mammalian fetus. Naloxone administration increased gross body movements and FHR without significant changes in FHR variation. It is concluded that FHR and motility are under opioidergic control in the pig fetus. Both morphine and naloxone induce hypermotility, suggesting that naloxone does not act as a pure opioid antagonist in the fetal pig.

Analgesics, Opioid↗
PubMed2000

In vitro culture of rat pre-antral follicles with emphasis on follicular interactions.

The present study was designed to determine whether rat pre-antral follicles can grow under in-vitro conditions. Emphasis is on whether follicular interaction is involved in in-vitro follicle culture, and furthermore its role in follicular development has been assessed. Pre-antral follicles were isolated mechanically from 10-day old rat ovaries. They were divided into small (50 microm < diameter < 100 microm) and large (120 microm < diameter < 200 microm) pre-antral follicles and cultured individually or in groups for 6 days in medium with or without fetal calf serum (FCS). Based on morphological criteria, large pre-antral follicles cultured in groups in serum-free medium had significantly higher survival rates than those cultured individually. In the presence of FCS, no significant difference was detected with respect to the survival. However, the large pre-antral follicles cultured in groups had a significantly greater increase in diameter than those cultured individually. Furthermore, follicles cultured in groups in FCS-containing medium exhibited significantly more follicular cell proliferation than those in serum-free medium, based on DNA measurement. The present culture system (with or without FCS) proved to be insufficient for small pre-antral follicles to stimulate growth comparable to that of large pre-antral follicles. The transmission electron microscopical (TEM) study revealed the ultrastructural differences between follicles cultured in FCS-containing and serum-free media. Taken together, the results suggest that interfollicular factors are involved in follicle development in vitro, which especially at the early folliculogenesis stage plays a positive role in terms of follicular growth as well as survival. The present culture model allows further investigation of factors that regulate early folliculogenesis.

Animals↗
PubMed2000

Effect of dose and day of treatment on uterine response to oxytocin in mares.

To determine the effect of dose and day of oxytocin treatment on intrauterine pressure, 6 normal mares were treated with 10 or 25 IU oxytocin 2 days before ovulation, on the day of ovulation and 2 days after ovulation. Intrauterine pressure (IUP) was measured using micro-tip-catheters (one placed intrauterine, a second and third serving as reference sensors in the vagina and external to the mare) and transmitted by telemetry for 30 min to establish a baseline before saline was administered, iv, and for an additional 30 min after saline administration. Oxytocin was then given, iv, and IUP was recorded for 60 min. No change in IUP was observed after saline injection. The administration of both 10 (n=16) and 25 (n=10) IU oxytocin induced a response (P<0.01). The intensity of response depended on the day of administration (P<0.01) and the dose of oxytocin (P<0.001). The variation of response was significantly greater after 10 IU oxytocin (CV 15.78%) compared with 25 IU oxytocin (CV 6.42%). The uterine response was greatest on Day 2 prior to ovulation and lowest on Day 2 after ovulation. The response was negatively correlated to increasing plasma progesterone (10 IU oxytocin: r = -0.435, 25 IU oxytocin: r = -0.265). There was no correlation between the uterine response and plasma estradiol-17beta concentration (P<0.01). In conclusion the results of this study show that oxytocin administration to mares before ovulation provides a greater response than after ovulation. A decline in the intensity of response after ovulation can be compensated for with a higher dose of oxytocin. Furthermore, the use of the multiple catheter technique is an effective method for assessing changes in uterine pressure.

Animals↗
PubMed2000

The effect of growth hormone on rat pre-antral follicles in vitro.

The aim of the present study was to investigate whether growth hormone (GH) has any effect on the development of cultured rat pre-antral follicles. Pre-antral follicles with a diameter between 120 microm and 160 microm were mechanically isolated from 10-day-old rat ovaries and cultured in groups for 6 days in serum-free medium without GH or with GH supplemented at concentrations of 1, 10 and 100 ng/ml, respectively. DNA content of the follicles before and after culture was measured to determine whether possible growth is due to proliferation of follicular cells. To investigate the quality of follicles cultured under different conditions, the ultrastructure of the cultured follicles was studied with transmission electron microscopy. Furthermore, reverse transcriptase polymerase chain reaction (RT-PCR) was used to assess the expression of growth hormone receptor (GHR) in pre-antral follicles. GH, regardless of the concentration, stimulated the growth of pre-antral follicles. However, follicles cultured in medium supplemented with high-dose GH (100 ng/ml) showed a significantly lower survival rate compared with the other groups. Follicles cultured in GH-containing medium showed a better ultrastructure in comparison with those cultured in medium without GH. Remarkably, scattered cortical granules were observed in oocytes of follicles cultured in the presence of GH. With RT-PCR, the presence of the mRNA of GHR was demonstrated in pre-antral follicles. It can be concluded that GH promotes rat pre-antral follicle development in vitro and better supports the morphology of cultured pre-antral follicles. The gene expression of GHR suggests that the action of GH could be mediated by its receptors present in pre-antral follicles.

Animals↗
PubMed1999

Pregnancy diagnosis in sows: direct ELISA for estrone in feces and its prospects for an on-farm test, in comparison to ultrasonography.

The usefulness of fecal estrone (E1) measurement as a tool for pregnancy diagnosis was investigated. Concentrations of E1 were measured in feces from pregnant and nonpregnant sows by a direct ELISA without extraction. Highly significant differences in E1 concentrations were found in feces from nonpregnant and pregnant sows (P = 0.016 to < 0.001). Pregnancy diagnosis on Days 26 to 32 after insemination, based both on fecal E1 concentrations as measured by ELISA and ultrasonography using a 5.0 MHz linear-array transducer, was performed in a group of 496 gilts and sows. The fecal E1 test had a sensitivity (correct diagnosis of pregnancy) of 96.5% and a specificity (correct diagnosis of nonpregnancy) of 93.6%, using 3.65 ng E1/g feces as a cut-off value. For ultrasonographic pregnancy diagnosis the test sensitivity and specificity were 99.3 and 92.5%, respectively. Although an increase of fecal E1 concentrations was noticed for increasing litter sizes, the results indicated that these concentrations could not be used to predict litter size. It is concluded that the distribution of fecal E1 concentrations in both nonpregnant and pregnant sows offers a suitable basis for the development of a simple, sow-side pregnancy test.

Animal Husbandry↗
PubMed1999

PGFM response to exogenous oxytocin and determination of the half-life of oxytocin in nonpregnant mares.

We investigated the half-life of oxytocin in reproductively normal mares and the prostaglandin response after oxytocin administrations. Mares were given oxytocin, 10 or 25 iu, i.v., on the day of, or 2 days after, ovulation, and frequent jugular blood samples were collected for analysis of oxytocin and Prostaglandin F metabolite (PGFM) by RIA. Neither dose of oxytocin nor day of treatment affected the half-life of the exogenous oxytocin, which was determined to be 6.8 min. A significant increase in PGFM was observed within 6 min of oxytocin administration and peak values were observed within 10 min. PGFM response after oxytocin administration on the day of ovulation appeared elevated compared to the response 2 days after ovulation.

Animals↗
PubMed1998

Comparison of ultrasonography, bovine pregnancy-specific protein B, and bovine pregnancy-associated glycoprotein 1 tests for pregnancy detection in dairy cows.

At Days 26 to 58 after AI, 138 Holstein-Friesian dairy cows were repeatedly examined by ultrasonography, using a 7.5 MHz linear-array rectal transducer. The total calving rate was 37.6% (52/138), and late embryonic mortality occurred 8.6% of the cows (12/138). On the days of ultrasound scanning, blood samples were drawn from the jugular vein for measuring the concentration of bovine pregnancy-specific protein B (bPSPB) and bovine pregnancy-associated glycoprotein 1 (bPAG 1). When compared with calving results, there were no significant differences in accurate diagnosis of pregnant cows were found between the 3 methods. However, when recognition of an embryo proper with a beating heart was used as the criterion for positive ultrasonographic diagnosis significantly fewer (P < 0.001) pregnant cows were correctly identified than by the other 2 tests. When compared with the noncalving cows, significantly fewer (P < 0.001) false positive diagnoses were made by the 2 ultrasonographic tests than by the PSPB and bPAG 1 tests, while significantly fewer (P < 0.001) false positive diagnoses were made by the bPSPB test than by the bPAG 1 test. The accuracy of detecting nonpregnant animals by both protein tests was limited by the relatively long half-life of these proteins after calving and by early embryonic mortality.

Animals↗
PubMed1998

Evaluation of false ultrasonographic diagnoses in cows by measuring plasma levels of bovine pregnancy-associated glycoprotein 1.

Between days 27 and 59 after artificial insemination (AI), 189 ultrasonographic pregnancy diagnoses were made in 56 dairy cows using a 7.5 MHz linear-array rectal transducer. Blood samples were withdrawn from a jugular vein on the day of AI, on day 21, and after each ultrasonographic examination between days 27 and 31, days 34 and 38, days 41 and 45 and days 55 and 59 after AI. Plasma concentrations of bovine pregnancy-associated glycoprotein 1 (bPAG-1) were measured by radioimmunoassay. The results showed that before day 31, ultrasonographic scanning was not very sensitive because six of the 30 calving cows were incorrectly diagnosed as non-pregnant. In five of these animals, the uterus was located far cranial to the pelvic inlet. Five of the cows examined between days 27 and 31 were pregnant on the basis of plasma bPAG-1 levels on the same day, using 0.5 ng/ml as the cut-off point. Plasma levels of bPAG-1 and progesterone proved that four of the cows which had early positive ultrasonographic diagnoses but did not produce a calf, were pregnant when they were examined.

Animals↗
PubMed1998

Influence of linoleic/linolenic acid ratio in the diet of periparturient cattle on plasma concentrations of PGF2 alpha metabolite and placental expulsion rate.

Forty-eight cows Holstein Friesian x Dutch Friesian (HF x DF) were randomly assigned to 2 groups fed 1 of 2 diets (isocaloric and isonitrogenous but different in linoleic/linolenic acid ratio) from 4 wk before expected parturition until 7 d after calving. Effects of the diet on plasma linoleic/linolenic acid ratio, plasma PGFM levels and placental explusion rate were studied. Dietary treatment resulted in significant differences in linoleic/linolenic acid ratio in blood plasma (1.00 +/- .22 vs 4.41 +/- .53). The placental expulsion rate was not significantly different between the 2 treatment groups. Plasma PGFM levels, as analyzed for 28 cows from 30 d before parturition until 1.5 d after parturition, were similar for the diets. Cows with a longer placental expulsion rate had lower PGFM levels at parturition (for instance, placental expulsion rate shorter (n = 11) and longer (n = 17) than 6 h, 1248 vs 2965 pg/ml, residual standard deviation 1185 pg/ml, P < 0.01). The results show that the dietary linoleic/linolenic acid ratio can influence the plasma linoleic/linolenic acid ratio without affecting the placental expulsion rate or plasma PGFM levels around parturition.

Animals↗
PubMed1998

Release of proinflammatory cytokines related to luteolysis and the periparturient acute phase response in prostaglandin-induced parturition in cows.

An acute phase response was previously found in cows at parturition, which might be associated with uterine cytokine release. Five late pregnant cows were implanted with vascular catheters in both the maternal aorta and uterine vein. Blood samples were taken to study temporal relationships between changing plasma levels of proinflammatory cytokines and the periparturient acute phase response following prostaglandin (PG)-induced luteolysis at Day 275 of gestation. The plasma levels of three proinflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and interleukin-6 (IL-6), as well as progesterone (P4), PGFM and serum amyloid A (SAA) were measured every 4 h between PG induction and expulsion of the calf. In the arterial plasma, progesterone levels dropped to baseline levels within 10 h following PG treatment, indicative of complete luteolysis. Contrary to expectations, the uterine vein samples showed lower proinflammatory cytokine levels compared with the maternal aorta values. A classical acute phase response, as assessed by SAA, was observed during the expulsive stage, but not during luteolysis.

Animals↗
PubMed1997

Plasma prolactin, growth hormone and progesterone concentrations in pseudopregnant, hysterectomized and pregnant goats.

Jugular plasma prolactin (PRL), growth hormone (GH) and progesterone (P4) levels were estimated in goats under three different conditions with prolonged luteal function (P4 > or = 1 ng/ml): pseudopregnant animals (n = 4), goats hysterectomized during early pregnancy (n = 4) and does with normal pregnancy (n = 4). Mean duration (+/- S.E.M.) of luteal phases were 189 +/- 20, 171 +/- 10, and 147 +/- 2 days in the three groups, respectively. Until day 120, mean PRL levels were below 150 ng/ml in each group. After day 120 of the luteal phase, PRL concentrations were significantly higher than before, but continued to increase up to 800 ng/ml only in pregnant animals around parturition. Mean GH levels varied between 2 and 3 ng/ml in animals of each group during the luteal phase. Only after parturition, a significant elevation occurred. P4 levels in pseudopregnant animals were significantly lower than in the other two groups between days 10 and 55, and showed a gradual but continuous decline towards the end of the luteal phase. After hysterectomy of early pregnant animals, P4 concentrations decreased to levels measured in pseudopregnant animals but were significantly higher again as compared to pseudopregnant animals between days 121 and 150. It is concluded that a pseudopregnant condition, characterized by intrauterine fluid accumulation, is not related to increased plasma PRL and GH concentrations. The low and gradually decreasing plasma progesterone levels in the pseudopregnant animals probably reflect the absence of a luteotrophic stimulus by the conceptus. The progesterone profile in the animals that were hysterectomized during early pregnancy suggests that the corpora lutea of these does have been permanently changed by the presence of the conceptus during the first weeks of the luteal phase.

Animals↗
PubMed1997

Evaluation of false ultrasonographic pregnancy diagnoses in sows by measuring the concentration of unconjugated estrogens in feces.

On Days 26, 28, and 30 after AI, ultrasonographic pregnancy diagnoses were performed on 207 gilts and sows by using a 3.5 MHz linear-array transducer. Fecal samples were taken from the rectum after each ultrasonographic examination, and the concentrations of unconjugated estrogens in selected samples (n = 73) were measured by RIA. Fecal unconjugated estrogen concentration of 11.7 ng/g feces or higher was indicative of pregnancy. The overall sensitivity and specificity of the ultrasonographic test was 99% for farrowing sows and 73.1% for nonfarrowing sows. With one exception, sows with a false negative diagnosis by ultrasonography on Day 26 were correctly diagnosed pregnant by elevated fecal unconjugated estrogens or repeated ultrasonographic examinations on Days 28 or 30. Return to estrus around the sampling period may cause false positive results in the unconjugated estrogen assay, while early embryonic mortality can result in false positive diagnoses in both the ultrasonographic test and estrogen assay. Although there was a positive correlation between the concentrations of unconjugated estrogens in the feces and litter size at farrowing in the selected sows, it seems very unlikely that fecal estrogens can provide an accurate tool for predicting litter size.

Journal Article↗