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Biomedical subjects

G Tews

Publications and source records attributed to G Tews.

At least 19 recordsLinked to original sources
PubMed2006

Incomplete denudation of oocytes prior to ICSI enhances embryo quality and blastocyst development.

BACKGROUND: Granulosa cells are essential mediators of oocyte maturation and fertilization. Because of the denudation of oocytes in preparation for ICSI, any potential positive effect of surplus cumulus cells (CCs) on further development would be unable to exert further effect. In order to evaluate the actual influence of adhering cumulus cells on further preimplantation development, this prospective study was carried out. METHODS: Sibling cumulus-oocyte complexes for 57 ICSI patients were split into a study group (incomplete denudation, n = 314) and a control group (complete denudation, n = 336). According to the cumulus cell pattern after partial denudation, mature gametes from the study group were further subdivided into type A oocytes, which showed several prominent CC clusters (n = 202), and type B (n = 75), which showed a more homogeneous pattern with CC covering the whole surface of the gamete. RESULTS: In immature oocytes, presence of adhered CCs led to a significant increase in resumption of meiosis (P < 0.01). Fertilization rate (P < 0.05) and ability to cleave (P < 0.01) was impaired in the study group, because of difficulties in ICSI of type B oocytes. By contrast, embryo morphology on days 2 (P < 0.01) and 3 (P < 0.05), as well as blastocyst formation, was better (P < 0.05) in the study group (55 blastocysts out of 88 zygotes) as compared to that in the control group (49/105). CONCLUSION: These data indicate that co-culture of oocytes with attached CCs may enhance preimplantation development.

Blastocyst↗
PubMed2006

Basal level of anti-Müllerian hormone is associated with oocyte quality in stimulated cycles.

BACKGROUND: Serum anti-Müllerian hormone (AMH) levels provide a powerful means for predicting ovarian response, which is reflected not only by the size of the primordial follicle pool but also by the quality of the oocytes. Considering a mutual interdependence between AMH-expressing somatic cells and gametes, this prospective morphological study was set up to evaluate whether extreme AMH levels represent diminished oocyte quality and developmental incompetence. METHODS: A total of 141 consecutive ICSI patients were subdivided into three groups using the 25th and 75th percentiles of the serum AMH levels (cycle day 3). In these three groups, morphology of all oocytes and fertilization rate, embryo quality and blastocyst formation were evaluated, and FSH, LH and estradiol (E(2)) levels were also measured. RESULTS: Cycle cancellation rate was correlated with AMH levels (P < 0.05). AMH groups 1 (<1.66 ng/ml) and 3 (>4.52 ng/ml) showed oocytes of lower quality [dark central granulation, aggregation of smooth endoplasmic reticulum (sER)] compared with the median group 2 (1.66-4.52 ng/ml). Basal serum FSH did not allow for adequate prognosis in terms of gamete appearance. Fertilization and further cleavage up to blastocyst stage was not affected by AMH levels. CONCLUSIONS: AMH seems to be superior to FSH in predicting both oocyte number and quality.

Adult↗
PubMed2005

Possible applications of a non-contact 1.48 microm wavelength diode laser in assisted reproduction technologies.

Recently, one laser system has been introduced in IVF fulfilling all safety requirements, while achieving a high standard of reproducibility in terms of ablation diameter. This 1.48 microm wavelength indium-gallium-arsenic-phosphorus (InGaAsP) semiconductor laser offers a variety of laser applications to the embryologist. On the one hand, zona pellucida of oocytes or embryos can be manipulated in order to facilitate ICSI or biopsy and assist hatching, and on the other, spermatozoa may be paralysed or immobilized prior to usage. To conclude, the 1.48 microm diode laser provides a promising tool for the microdissection of subcellular targets. The diode laser stands out due to the rapidity, the simplicity and the safety of the procedure which is supported by healthy offspring after laser application.

Animals↗
PubMed2004

Complete oocyte activation failure after ICSI can be overcome by a modified injection technique.

BACKGROUND: Complete fertilization failure after ICSI is a rare event, and it may happen repeatedly even in cases of normal sperm parameters and good ovarian response. In these cycles, alternative ICSI techniques may prove useful. METHODS: Our modified ICSI (mICSI) is characterized by aspiration close to the opposite membrane (the region of the mitochondria with a high inner mitochondrial membrane potential) which is followed by central deposition of the sperm. The method was applied prospectively to ICSI cycles of patients with a history of complete fertilization failure in previous ICSI cycles. In parallel, mICSI was compared with conventional ICSI in terms of further preimplantation development and treatment outcome. RESULTS: In patients with previous ICSI failures using conventional ICSI (no 2Pn zygotes out of 70 oocytes that had been injected) application of mICSI led to adequate fertilization (53.6%) and pregnancy rates (33.3%) (P < 0.001; P < 0.01). In patients without previous failed fertilization, no improvement in the rates of fertilization, blastocyst formation, implantation or clinical pregnancy could be seen. CONCLUSIONS: Our data indicate that the present version of ICSI is a reliable alternative to conventional ICSI. However, although it overcomes oocyte-dependent activation failure, routine application does not improve the overall results.

Adult↗
PubMed2004

Laser-assisted zona pellucida thinning prior to routine ICSI.

BACKGROUND: In MII oocytes showing difficult oolemma breakage, ICSI can cause an increase in the degeneration rate. This may be overcome by laser-assisted ICSI using a 5-10 micro m opening in the zona pellucida for injection. However, such a small opening might impair the hatching process, especially if assisted hatching is applied in addition. In order to prevent this, the present study used routine injection through an area of zona pellucida in which laser zona thinning had been applied, providing for both a reduced mechanical stress to the oocyte and assisted hatching. METHODS: This prospective study involved 100 cycles with 1016 MII oocytes. Conventional ICSI (control group) was compared with a modified laser-assisted ICSI (study group) in sibling oocytes. In the latter group oocytes were injected through an extended area of zona thinning. RESULTS: Degeneration rate was significantly lower in the study group (P < 0.004). There were no differences in fertilization, or formation and quality of blastocysts. In the study group embryo quality on day 2 was significantly better (P = 0.004) and herniation of day 5 blastocysts was increased (P = 0.005). Rates of implantation and pregnancy were not affected. However, on day 3 laser-assisted ICSI proved beneficial (P = 0.038) in terms of clinical pregnancy rate. CONCLUSIONS: The new method combines a less invasive ICSI technique with assisted hatching. Our preliminary data indicate that in addition to an improved oocyte survival, this new approach increases the hatching rate in vitro, which may explain the increase in pregnancy rate, at least in day 3 transfers.

Adult↗
PubMed2003

Developmental competence of oocytes showing increased cytoplasmic viscosity.

BACKGROUND: The objective of the study was to investigate the developmental fate of oocytes with increased cytoplasmic viscosity as assessed by the persistence of the injection funnel after withdrawal of the ICSI pipette. METHODS: For this purpose, 1008 oocytes showing a characteristic injection funnel during ICSI were subdivided into two groups according to the oocyte's ability to restore its spherical shape within 2-3 min after ICSI. Fertilization and further development was evaluated in both groups. In addition, implantation and pregnancy rates were analysed. RESULTS: In the funnel positive cohort (group 1) significantly fewer oocytes degenerated after injection (P < 0.01) compared with oocytes without persistent funnel (group 2). However, at zygote stage, presence of a halo (P < 0.05) and a optimal pronuclear pattern 0 (P < 0.01) was increased in group 2. In addition, significantly fewer poor quality embryos were found in this group (P < 0.01). The number of good quality blastocysts but not blastocyst formation was increased in group 2 (P < 0.05). This resulted in an increased clinical pregnancy rate if embryos which derived exclusively from funnel negative oocytes were transferred (P < 0.05). CONCLUSIONS: Our data suggest that cytoplasm of higher viscosity delays development up to cleavage stage and impairs optimal development. Injection funnel persistence was found to be a negative prognostic marker of preimplantation development.

Blastocyst↗
PubMed2003

Presence, but not type or degree of extension, of a cytoplasmic halo has a significant influence on preimplantation development and implantation behaviour.

BACKGROUND: Since there is considerable disagreement in grading cytoplasmic haloes, this prospective study was set up to evaluate if certain subtypes of haloes are related to further development. METHODS: Out of a total of 152 patients, 713 zygotes could be checked for the formation of a halo. Where present, haloes were subdivided into concentric (symmetric) and polar (asymmetric) types. In addition, each halo was measured accurately to see if the extension of the halo might influence further development. In parallel, pronuclear patterns were checked. RESULTS: Halo-positive zygotes did not differ from halo-negative ones in terms of embryo quality and blastocyst formation rate. However, quality of blastocysts (assessed by their inner cell mass consistency) was significantly increased (P < 0.001) if a halo appeared at zygote stage. This phenomenon was not related to type of halo or degree of halo. In terms of pronuclear pattern, pattern 0 (0A, 0B) led to significantly more blastocysts (P < 0.001) of better quality (P = 0.002) compared with patterns 1-5. A stepwise logistic regression showed no relationship between different halo types and pronuclear pattern 0. CONCLUSIONS: The present study indicates that any halo has a positive prognostic value on blastocyst quality, irrespective of the fact that it is light or extreme, polar or concentric. In addition, the developmental advantage of pattern 0 is confirmed.

Adult↗
PubMed2002

Reproducibility of three-dimensional ultrasound endometrial volume measurements in patients with postmenopausal bleeding.

OBJECTIVE: To evaluate the reproducibility of transvaginal three-dimensional (3D) endometrial volume measurement in patients with postmenopausal bleeding and to compare the reproducibility of this technique to that of two-dimensional (2D) endometrial thickness measurement. METHODS: In a prospective, blinded study, transvaginal ultrasound examinations were performed in 51 consecutive patients with postmenopausal bleeding. Three-dimensional volume and 2D thickness measurements were made and intraobserver and interobserver reproducibility of each technique were assessed. RESULTS: The intraobserver correlation of 3D endometrial volume measurement of the first observer was 0.97 and that of the second observer was 0.99. Thus, mean intraobserver correlation was 0.98. The mean interobserver correlation was 0.95 (0.95 vs. 0.96). There was no significant difference in reproducibility at different volume cut-offs. The mean intra- and interobserver correlation of endometrium volume measurements for five patients with endometrial carcinoma did not differ significantly from that for patients without carcinoma (0.98, 0.98 vs. 0.98, 0.95). The intraobserver correlation of 2D endometrial thickness measurements from the first observer was 0.71 and that from second observer 0.87. Thus, mean intraobserver correlation of the endometrial thickness measurements was 0.79. The mean interobserver correlation was 0.76 (0.84 vs. 0.70). CONCLUSIONS: Endometrial volume and thickness measurements by 3D and 2D ultrasound, respectively, show good reproducibility but the reproducibility of 3D ultrasound is better.

Double-Blind Method↗
PubMed2002

[Sonographic measurement of endometrium thickness as a predictive value for pregnancy through IVF].

AIM: This prospective study was performed to evaluate the predictive value of endometrium thickness in patients undergoing IVF-ET. METHOD: Measurements of endometrium thickness as well as pattern assessments were performed in 936 cycles (722 patients) on the day of administering human chronic gonadotropin (HCG). RESULTS: The overall pregnancy rate was 31.1 % (291/936). The age of non pregnant patient was significantly higher (p < 0.029). There was a significant influence of oestradiol (p < 0.029), number of transferred embryos (p < 0.004), and embryo quality (p < 0.002) on the pregnancy rate. Overall, the mean (+/- SD) endometrium thickness was 11.16 mm (+/- 2.13). The mean (+/- SD) endometrium thickness of pregnant patients was 11.25 mm (+/- 2.19). The mean (+/- SD) endometrium thickness of non-pregnant patients was 11.12 mm (+/- 2.10). A stepwise logistic regression analysis showed no statistically significant correlation between endometrium thickness and pregnancy rate (p < 0.23). CONCLUSION: Sonographic measurement of endometrium thickness on the day of human chorionic treatment with gonadotropin is not useful in predicting IVF outcome.

Adult↗
PubMed2002

Prospective hatching of embryos developed from oocytes exhibiting difficult oolemma penetration during ICSI.

BACKGROUND: The hormonal milieu during ovarian stimulation is known to affect oolemma behaviour as well as zona pellucida thickness and structure. This led us to investigate whether a special subgroup of patients with oocytes where penetration of the oolemma is difficult during ICSI may benefit from assisted hatching. METHODS: A total of 77 couples (mean age: 32.9 +/- 4.6 years; range: 22-38) had oocytes that could hardly be penetrated by the ICSI pipette. Nineteen patients underwent two ICSI cycles, giving a total number of 96 cycles, which were randomly split into either the study group (n = 52) or the non-hatching group (n = 44). Hatching was done using a non-contact 1.48 mm wavelength diode laser. Implantation and pregnancy rates were recorded. RESULTS: The pregnancy rate was 36.6% (19/52) in the study group and 13.6% (6/44) in the non-hatching group (P < 0.05). In addition, a higher number (P < 0.05) of embryos implanted in the study group (23/106; 21.7%) than in the non-hatching group (9/92; 9.8%). CONCLUSIONS: Once oolema penetration during ICSI has proven difficult, prospective hatching of embryos considered for transfer may increase their implantation behaviour.

Adult↗
PubMed2002

First polar body morphology and blastocyst formation rate in ICSI patients.

BACKGROUND: It may be beneficial to identify, at a very early stage of development, concepti that will result in viable blastocysts by using a non-invasive technique. METHODS: Homogeneous groups in terms of first polar body (PB) morphology were analysed with regard to fertilization, embryo quality and blastocyst formation. The strategy was to transfer a maximum of two blastocysts with an adequate inner cell mass deriving from oocytes with identical first PBs in order to obtain information about the actual implantation potential. RESULTS: A significant relationship between first PB morphology and embryo quality was found. Fragmentation after 2 days was increased in embryos derived from oocytes with fragmented first PBs (P < 0.05) in comparison with those derived from oocytes with intact PBs. No similar correlation could be demonstrated for fertilization rate. Embryos in the intact first PB group showed an increased rate of blastocyst formation as compared with the fragmented first PB group (P < 0.05). In addition, a significant difference in implantation rate (48.6 versus 22.0%; P < 0.025) and ongoing pregnancy rate (68.4 versus 34.8%; P < 0.05) was observed for the intact versus fragmented groups respectively. CONCLUSION: In conclusion, the current study provides further evidence that preselection at a very early stage may be helpful in identifying a subgroup of preimplantation embryos with a good prognosis to form blastocysts and, consequently, to implant.

Adult↗
PubMed2001

Embryo fragmentation in vitro and its impact on treatment and pregnancy outcome.

OBJECTIVE: To determine the impact of embryo fragmentation on pregnancy, obstetric, and perinatal outcome. DESIGN: Retrospective analysis of embryo transfers that were homogeneous in regard to the degree of fragmentation. SETTING: Fertility center. PATIENT(S): A cohort of 460 fresh embryo transfers. INTERVENTION(S): A total of 164 pregnancies were analyzed for the incidence of antepartum complications during gestation, obstetric (multiple pregnancy, preterm delivery, cesarean section), and perinatal outcome (sex, birth weight, admission to neonatal intensive care unit, malformations). MAIN OUTCOME MEASURE(S): Implantation and clinical pregnancy rate, obstetric and perinatal outcome. RESULT(S): Embryo fragmentation and number of embryos per transfer showed a significant influence on clinical pregnancy and implantation rate. No such relation was found concerning complications, multiple pregnancy rate, incidence of cesarean section, gestation week, birth weight, and average time at the neonatology. On the other hand, pregnancies derived from bad-quality embryos had a significantly higher rate of malformations. CONCLUSION(S): The higher percentage of malformations found in bad-quality embryos may be due to a higher percentage of apoptotic features and chromosomal disorders. For ethical reasons, the transfer of embryos with >50% fragmentation should be considered only after consultation with the patient.

Adult↗