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Biomedical subjects

M Alikani

Publications and source records attributed to M Alikani.

46 records · Page 3Linked to original sources
PubMed1992

Implantation enhancement by selective assisted hatching using zona drilling of human embryos with poor prognosis.

Assisted hatching by zona drilling using acidic Tyrode's solution was performed during three randomized trials in 330 in-vitro fertilization patients. The trials were designed in order to study the overall effect of the procedure and whether characteristic patient [i.e. maternal age and basal levels of follicle stimulating hormone (FSH)] and embryonic features (i.e. zona pellucida thickness) are important for the decision to perform assisted hatching routinely. Couples (n = 137; Trial 1) in whom the female partner had normal basal FSH levels were randomized in a control group (without micromanipulation) and a zona drilling group (all embryos micromanipulated). The incidence of implantation (67/239; 28%) of zona-drilled embryos compared favourably with that of control embryos (49/229; 21%), but the difference was not significant. Retrospective analysis revealed that those embryos whose zonae were thicker than 15 microns were rescued. In order to test the validity of this finding, selective assisted hatching was performed on embryos with a poor prognosis in 163 other patients (Trial 2). The couples were randomized into a control group and a group in which embryos were selectively zona-drilled, based on zona thickness and other embryonic features. The rate of embryonic implantation in the selectively zona-drilled group was 25% (70/278), significantly (P less than 0.05) higher than that of control embryos (51/285; 18%). Although it was demonstrated retrospectively and prospectively that assisted hatching by zona drilling is effective in embryos with thick zonae (greater than or equal to 15 microns), patients whose embryos have thin (less than 13 microns) zonae may be jeopardized by the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Embryo Implantation↗
PubMed1992

Is the human oocyte plasma membrane polarized?

Using scanning electron microscopy, we have shown that the plasma membrane of the human metaphase II oocyte is organized in evenly spaced, short microvilli of 1-3 microns in length. In contrast to other mammals studied to date, there is no microvillus-free area overlying the metaphase spindle and there were no other indications of polarization at this level of organization. Functional polarity of the plasma membrane, studied using localized microsurgery of the zona pellucida followed by insemination, suggests that sperm fusion and entry in the human may occur anywhere over the oocyte surface. Aged oocytes and those exposed to acidic Tyrode's solution had surfaces which were not homogeneously covered by microvilli. Oocytes exposed to a sucrose solution and subzonally injected with spermatozoa showed evidence of partial cortical granule exocytosis.

Cell Membrane↗
PubMed1992

Selective assisted hatching of human embryos.

Overall results of assisted hatching by zona drilling using acidic Tyrode's solution performed during three randomised trials in 330 in vitro fertilisation (IVF) patients are presented. It was demonstrated retrospectively and prospectively that assisted hatching by zona drilling was effective in embryos with thick zonae (> 15 microns). This procedure is called selective assisted hatching. In order to investigate whether the success rate of embryos with thin zonae (< 13 microns) can be improved further, a fourth trial was executed in 40 consenting patients. Embryos with thin zonae were left intact in one group (control), while the outside of zonae of similar embryos were thinned with acidic Tyrode's solution. Results thus far indicate that embryos with thin zonae do not benefit from this technique. Embryonic implantation (fetal heartbeat per embryo) was high (26%-27%) in both arms of the trial, probably as a result of selective zona drilling of low prognosis embryos with thick zonae. A method is presented for quantifying zona hardening in human embryos. The exposure to acidic Tyrode's solution of each embryo was expressed as a function of the duration to pierce the zona and the diameter of the needle. Preliminary findings suggested that embryonic viability is correlated with zona hardening. In order to test the hypothesis that extracellular fragments may affect embryonic viability, small amounts of fragments were removed from embryos during assisted hatching. The pregnancy rate in 36 patients with extracted fragments was relatively high (41%) considering the poor morphology of the embryos involved.

Adult↗
PubMed1992

Advances in clinical micromanipulation of gametes and embryos. Assisted fertilization and hatching.

Several methods for micromanipulation of human gametes have been proposed to enhance fertilization in cases of male infertility. Of these methods, two have been successful in producing pregnancies and live births worldwide; these include partial zona dissection and subzonal sperm insertion. During the period between October 1989 and July 1991, 251 patients with male infertility due to impaired sperm function were treated with in vitro fertilization in conjunction with gamete micromanipulation at our center. Sixty pregnancies (24% per cycle, 42% per replacement) resulted in 144 patients. The details of these treatments are discussed. In another study, in an attempt to increase the incidence of implantation, we have conducted three clinical trials of assisted hatching and selected assisted hatching. The combined results of the trials indicate a clinical pregnancy rate of 51% in the control group and 60% in the micromanipulated group (P less than .05). Moreover, while 20% of the embryos replaced in the control group implanted the implantation rate was increased to 28% in the experimental group (P less than .05). Methodologies and possible implications of these treatments are discussed.

Embryo Implantation↗
PubMed1991

Partial zona dissection or subzonal sperm insertion: microsurgical fertilization alternatives based on evaluation of sperm and embryo morphology.

OBJECTIVE: To establish guidelines for application of partial zona dissection, subzonal sperm insertion, and regular in vitro fertilization (IVF) in severe male factor patients. DESIGN: Two studies were performed: partial zona dissection and IVF was applied in 57 couples during the first period, and subzonal sperm insertion was also applied in a second group of 47 couples. SETTING: Procedures were performed in an academic research environment. PATIENTS, PARTICIPANTS: Couples who failed fertilization previously, others not acceptable for IVF, and a third group in whom IVF was expected to fail. INTERVENTIONS: Oocytes were micromanipulated with either partial zona dissection or subzonal sperm insertion, or the zona pellucida was left intact. Embryos were replaced in patients prophylactically treated with methylprednisolone and antibiotics. MAIN OUTCOME MEASURES: Because several microsurgical fertilization techniques are now available, this study was performed to compare sperm parameters, embryo morphology, fertilization, and implantation rates after application of two successful micromanipulation procedures. RESULTS: Twenty-one pregnancies were established in 104 patients, 5 definitely from subzonal sperm insertion and 4 from partial zona dissection. Patients who failed IVF before had a similar chance of pregnancy after the use of micromanipulation, as first time patients (9/53 versus 12/51). In a subgroup of 15 patients who failed IVF with insufficient numbers of motile sperm, fertilization was significantly higher after subzonal sperm insertion. Partially zona-dissected embryos from couples with severe teratozoospermia (less than or equal to 5% normal forms; strict criteria) had significantly more morphological abnormalities than those from patients with moderate teratozoospermia (6% to 10% normal forms). In severely teratozoospermic patients, significantly fewer partially zona-dissected than subzonally inserted embryos implanted. CONCLUSIONS: The decision of which micromanipulation method to perform can possibly be based on careful analysis of sperm morphology.

Embryo Implantation↗
PubMed1991

Microsurgical fertilization and teratozoospermia.

Semen parameters were correlated with the outcome of partial zona dissection (PZD) in 42 couples with male factor infertility. Although fertilization rates were reduced, 12% of the embryos implanted following replacement. Spermatozoa from teratozoospermic sperm populations were able to fuse with oocytes following zona penetration through the artificial gaps. PZD followed by insemination with less than 5% normal spermatozoa led to 20 embryos which, upon replacement, did not implant. Motility and sperm count were not clearly correlated with the outcome of PZD and are therefore less useful indicators for patient selection. Teratozoospermic patients who previously failed to fertilize were compared to a group of similar patients who had not attempted IVF before. Although fertilization was significantly improved in first-time patients, 41% of the patients whose spermatozoa were initially unable to fertilize had at least one embryo when PZD was performed. Several pregnancies were established in this group. Subzonal sperm insertion (SZI) and PZD were compared in 19 patients using sibling oocytes. A significant fraction of spermatozoa from infertile men were able to fuse with the oolemma when directly inserted into the perivitelline area. Using a sucrose solution to shrink the ooplasm, only 1% of the oocytes were damaged during SZI. Monospermic fertilization rates following PZD and SZI were 15 and 16%, respectively. Both micromanipulation methods were successful in most patients. However, in two small groups of patients, only one technique resulted in fertilization.

Female↗
PubMed1990

Laboratory techniques for handling gametes and embryos.

This review describes some basic and novel principles pertaining to the science of in vitro fertilization and embryo culture. Several systems for cell-free culture of gametes and embryos are described. The advantages of a coculture or helper cell system was investigated in several clinical trials using bovine cells from the reproductive tract. Improved embryonic morphology and implantation indicate that standard IVF culture provides suboptimal conditions. Microsurgical methods for assisting in vitro fertilization in cases of severe male factor infertility are also discussed. Thus far, it has been demonstrated that mechanical opening of the zona pellucida by methods such as partial zona dissection enhances fertilization. In addition, the introduction of a limited gap in the zona seems to facilitate hatching of the blastocyst, which may benefit all patients undergoing in vitro fertilization.

Cell-Free System↗