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A field experiment was conducted to determine the influence of follicular profiles over 4 d prior to superovulation on superovulatory responses in terms of the number of large follicles (F; ≥ 7mm) at oestrus and in the number of the corpus luteum (CL) 7 d later. Ultrasonography was performed once daily over 4 d prior to gonadotropin treatment (day 0) and on the day of oestrus during superstimulation. Animals conventionally superovulated (400 mg Folltropin-V) between day 8 to 12 of the oestrous cycles and 88 superovulation cycles were considered in the present experiment. Data were analysed by means of the GLM procedure of the SAS. Each type of superovulatory responses was divided into three classes - low, medium, and high. The profiles of changes in the mean diameter of the largest follicle (F1) and in the mean differences between the diameters of F1 and the second largest (F2) follicle (F1-F2) during the 4 d prior to superovulation did not differ (P>0.1) among the three classes of follicular and ovulatory responses. The proportions of superovulation cycles with high follicular and ovulatory responses were 69% and 52%, respectively. The results of the present experiment suggest that high follicular or ovulatory responses are not associated with follicular profiles prior to the initiation of superovulation.
Leaving on ovaries a morphologically dominant follicle on the day of start of superovulation significantly lowered its effectiveness in heifers. Mechanical removal of the dominant follicle increased the effectiveness of superovulation. Influence of elimination of a dominant follicle was especially visible in these cases, in which the follicle remained on the ovary during 4 d before the programme started. Significant differences were ascertained in the numbers of corpora lutea found on ovaries on the day of embryo collection and in the numbers of nonfertilized ova.
Twenty five Holstein-Friesian heifers, clinically normal and with regular oestrous cycles, were used for induction of superovulation (PMSG-PGF2alphalpha-Neutralpha-PMSG). Animals were divided into 5 groups receiving: I - detomidine (40 µg/kg b.w.), II - doxazosin (0.2 mg/kg b.w.), III - yohimbine HCL 1% (1 ml/50 kg b.w.), IV - carazolol (0.01 mg/ kg b.w., i.v.), and V – physiological saline (1 ml/50 kg b.w.). The heifers with PGF2alphalpha-induced cycles were treated with the substances 88 hrs after being given a single i.m. injection of 2500 IU PMSG. All animals were examined by ultrasonography, and by the number and size of ovarian follicles > 3 mm in diameter. The follicles were divided into 3 groups according to the diameter. Blood plasma was stored at -20°C until LH, P4, E2 and PGFM analyses. In the control (V) group, two waves of follicle growth were observed. Yohimbine produced a significant blockage of ovulation. The mean number of corpora lutea in the group III was significantly lower than that in the control group (p< 0.02). No significant differences in the number of corpora lutea were observed between the groups I, II and III. The increase in E2 concentrations could be the response to the PMSG treatment with two waves of growth of large follicles before and after ovulation. Pulsatile LH release was altered by yohimbinum injection, however, the greater amplitude of pulses immediately following yohimbinum administration are suggestive of a positive influence of the alpha-2 adrenergic receptors antagonist. Yohimbinum administration did not affect plasma concentration of examined hormones. There was a difference between the plasma levels of LH after the doxazosin injection. Single injection of the stimulators and blockers of adrenergic receptors did not affect superovulatory response in terms of the numbers of CL, unruptured follicles and embryos recovered. The affectivity of artificial insemination was not significantly different between the control group and the detomidinum groups, while in the yohimbinum group it was significantly lower.
The aim of this study was to investigate superovulatory responses of cows according to the status of various follicular classes on day 0 (day of initiation of the superovulatory treatment). One hundred and two superovulation cycles were selected. The animals were superstimulated between days 8 and 12 of oestrous cycle with 400 mg of Folltropin-v given in decreasing doses over a 4 d period and luteolysis was induced with two intramuscular injections of cloprostenol. The ovaries of all cows were examined by ultrasonography on day 0, at oestrus, and on day 7 after oestrus. The results showed that the follicular and ovulatory responses were higher (P<0.0l ) in cows that were superovulated in the presence of a high (≥6) number of follicles than in the presence of a low (≤5) number of follicles 4 to 6 mm in diameter. Follicular and ovulatory responses did not differ according to the status of the three other follicular classes studied. Additionally, the mean numbers of fertilised structures and unfertilised ova were not influenced by the status of any of the follicular classes studied. In conclusion, the follicular and ovulatory responses were influenced by the status at initiation day of the superovulatorv treatment.
The aim of this study was to determine the influence of alpha- and ß-stimulators (alpha-stimulator: detomidinum HCl) as well as blockers (alpha1-blocker: doxazosin, alpha2- blocker: yohimbinum HCL, ß-blocker: carazolol) on bovine granulosa cells culture from preovulatory follicles. The cell culture was passed in TCM 199 medium with 10% FCS and antibiotics. Tested substances were added to the culture medium in different concentrations. The experiment began when at least 80% of the wells were covered (in four well culture dish of NUNCK-DK). The culture medium was collected every 24 h for hormone analysis. Hormone levels of T, E2, and P4 were determined. The culture was used up to 120 hours. Our results showed a decrease in P-4 secretion after detomidinum addition for all tested concentrations. A slight testosterone level increase was seen in the first 24 hours and then its concentration remained at a constant low level. A slight increase in 17-ß estradiol secretion was also observed. After yohimbinum addition, a statistically significant decrease of progesterone was observed for all concentrations tested. No significant changes were observed at other hormones levels when compared with the control. Doxazosin, when added into the culture medium, did not cause any statistically significant changes in hormone secretions. The addition of carazolol caused a significant decrease in progesterone secretion after culturing for 48 hours. Changes observed in other hormones levels did not differ statistically from the control. These results seem to support the hypothesis that drugs stimulating and blocking adrenergic receptors may play some role in ovarian steroidogenesis in cows.
The aim of the present study was to evaluate the stimulating effect of synthetic GnRH analogues without the use of prostaglandins on ovarian follicular growth dynamic and oestrus. The study was made on 30, 3 to 9-year-old Lithuanian Black and White (LBW) and German Black and White (GBW) breed cows. The study was conducted in the Lithuanian Veterinary Academy practical training and research farm. Oestrus in 23 cows was stimulated using synthetic GnRH analogues Dalmarelin (Lecirelin) (Fatro S. p. A., Italy) and in 14 cows with the use of Depherelin® (Gonavet® 50, Veyx-Pharma GmbH, Germany). Dalmarelin (Lecirelin) induced oestrus in 100% of the stimulated cows, and Depherelin® (Gonavet® 50) induced oestrus in 92.9 % of stimulated cows. Following an injection of synthetic GnRH analogues, preparations Depherelin® and Dalmarelin, plasma progesterone concentration decreased, due to the ovulation of dominant follicle or onset of the new follicular wave. Cows stimulated with Dalmarelin had a faster follicular growth rate and bigger size of follicles at ovulation compared to Depherelin® and control group cows (p = 0.05). In the pregnancy trial that followed 45 days after artificial insemination, the highest percentage (43.5 %) of pregnant cows was determined in the group of cows stimulated with Dalmarelin.
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