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Biomedical subjects

S Daya

Publications and source records attributed to S Daya.

At least 127 records · Page 7Linked to original sources
PubMed1988

Identification of two species of suppressive factor of differing molecular weight released by in vitro fertilized human oocytes.

Preimplantation human embryos have been shown to release factors that have immunosuppressive activity and that are highly correlated with successful implantation. The present study was undertaken to determine the molecular weight of these factors using HPLC. Two peaks of suppressive activity were found associated with molecular weights of 3.7 +/- 0.3 and 1.2 +/- 0.1 kd, respectively. The potential significance of low molecular weight immunosuppressor factors in avoiding maternal inflammatory and immunologic responses is discussed.

Blastocyst↗
PubMed1988

Follicular fluid pH changes following intraperitoneal exposure of Graafian follicles to carbon dioxide: a comparative study with follicles exposed to ultrasound.

Follicular aspiration to obtain oocytes is generally performed via laparoscopy after creating a pneumoperitoneum with carbon dioxide. Such a procedure has been shown to reduce the rate of in-vitro fertilization of human oocytes and affect the rate of cleavage of rabbit embryos. These adverse effects may be caused by a reduction in follicular fluid pH due to diffusion of carbon dioxide into the follicle. In laparoscopic oocyte retrievals, a negative correlation was observed between duration of CO2 exposure and follicular fluid pH, whereas in ultrasound-guided retrievals, the pH remained unchanged. The mean pH in 78 follicles aspirated at laparoscopy was 7.22 +/- 0.03 compared with 7.62 +/- 0.01 in 35 follicles aspirated under ultrasound guidance (P = 0.0003). The results also indicate that oocytes in preovulatory follicles are surrounded by fluid that is more alkaline than plasma. Hence, the acidic environment treated by CO2 may be deleterious to subsequent reproductive function of the oocyte.

Carbon Dioxide↗
PubMed1988

Efficacy of progesterone support in the luteal phase following in-vitro fertilization and embryo transfer: meta-analysis of clinical trials.

The question of whether follicular aspiration of oocytes alters the quality of the luteal phase remains unanswered. Progesterone appears to be necessary for implantation and maintenance of an early intrauterine pregnancy and this partly has been the basis for recommending luteal phase supplementation with progesterone following oocyte retrieval. Although small increases in pregnancy rates were observed in several trials, such support with progesterone was not efficacious. However, none of the studies had sufficient statistical power to detect small improvements in pregnancy rate. Pooling the results of these trails using several methods of meta-analysis has allowed an overall effect of treatment to be calculated. This effect, as measured by the odds ratio, was not significant, indicating that there was insufficient evidence to recommend the routine use of progesterone to support the luteal phase after oocyte retrieval.

Clinical Trials as Topic↗
PubMed1988

Diagnostic test properties of serum progesterone in the evaluation of luteal phase defects.

The existence of LPD has been controversial, mainly because of inconsistencies in its diagnosis. The endometrial biopsy remains as a gold standard until newer and better tests are developed. Additional information may be provided from serum P determinations in the luteal phase by using the likelihood ratios and positive predictive values obtained in this study. Since the properties of sensitivity and specificity are inversely related, the selection of discriminatory cutoff level of serum P would optimize one at the expense of the other. There is no value that combines both sensitivity and specificity as far as correlation with endometrial biopsy is concerned.

Abortion, Spontaneous↗
PubMed1987

Separation of motile human spermatozoa by means of a glass bead column.

Fertility potential of semen depends upon the presence of viable and motile spermatozoa. A variety of techniques has been reported whereby motile spermatozoa are separated from semen for use in homologous insemination. Using a column of glass beads, we tested various sizes for spermatozoa-separating efficiency. This procedure is quick and simple and results in a significantly better recovery of motile and viable spermatozoa from poor-quality semen. Therefore it has the potential for use in intrauterine insemination for treating male factor infertility.

Cell Separation↗
PubMed1987

Fertilization and embryo development of oocytes obtained transvaginally under ultrasound guidance.

The widespread use of ultrasound for follicle development assessment and ovum pickup has raised concerns about the theoretical possibility of adverse effects on oocyte function. Studies in other species do not demonstrate any adverse effects when using sonic energies as those presently used in diagnostic ultrasound. However, no data are available concerning the effects of diagnostic ultrasound on human preovulatory oocytes. This study was conducted to determine whether there were any adverse effects on the reproductive function of oocytes using transvaginal ultrasonography. No effect on fertilization and subsequent cleavage of oocytes was demonstrated. This method can, therefore, be recommended for follicle assessment and as a better alternative to laparoscopy for oocyte retrieval.

Adult↗
PubMed1987

Human chorionic gonadotropin increase in normal early pregnancy.

Serial determinations of human chorionic gonadotropin have been used in evaluating early pregnancies. This has been based on linear regression of logarithm-transformed hCG levels. However, these levels are changing in a curvilinear fashion as pregnancy advances. Consequently the simple linear model does not provide a good fit to the data. To define more precisely the normal values for hCG increase, serial determinations were performed on serum samples obtained from 29 patients who were carrying normally advancing pregnancies. Gestational age was established with basal body temperature records. Three gestational age periods were identified each with a linear increase in hCG. This was translated into hCG doubling times and percentage increase over time. These tables may be used to determine if an early pregnancy is advancing normally.

Adult↗
PubMed1987

Immunosuppressor factor(s) produced by decidua-associated suppressor cells: a proposed mechanism for fetal allograft survival.

Mechanisms that explain failure of rejection of the antigenic fetus by the mother appear to lie at the fetomaternal interface. Successful pregnancies have been correlated with the presence of decidua-associated suppressor cells. Supernatants from these cells were tested for their ability to suppress the proliferation of interleukin 2-dependent cells and were also subjected to high-performance liquid chromatography. Decidual supernatant was found to have peak suppressive activity at two molecular weights (43,000 and 21,000 daltons). The activity of decidual supernatant was directed specifically at interleukin 2-dependent cells and interfered with interleukin 2 action. The importance of this mechanism in graft rejection is well known. Decidual supernatant may thus prevent fetal allograft rejection by preventing the maternal cytotoxic effectors from receiving the interleukin 2-dependent help that they need to proliferate and remain actively cytolytic.

Animals↗
PubMed1987

Effect on fertilization of intra-peritoneal exposure of oocytes to carbon dioxide.

Follicular aspiration is generally performed via laparoscopy after creating a pneumoperitoneum with carbon dioxide (CO2). Adverse effects on embryo development may occur following exposure to CO2, which is known to cause a decrease in follicular fluid pH. Such a reduction in pH may affect fertilization and early embryonic development and this study was carried out to study these effects. Oocytes obtained by laparoscopy were compared with those obtained under ultrasonic guidance to determine whether CO2 exposure had any adverse effect. The results suggest that CO2 may affect fertilization, but once this has occurred, there is no effect of CO2 on the rate of cleavage of the embryos.

Carbon Dioxide↗
PubMed1987

Improvement in semen quality using glass bead column.

Fertilizing ability of semen requires the presence of viable and motile spermatozoa whose surface-membrane integrity is maintained. Male infertility is often the result of these variables being suboptimal. Various in vitro methods have been reported that separate good-quality spermatozoa from such ejaculates. In this study we describe a simple procedure that uses a column of glass beads to separate spermatozoa from poor quality semen. The filtered spermatozoa have significantly better progressive motility and viability and also have enhanced fertilizing capacity. Such a method may have clinical use for semen preparation prior to intrauterine insemination and in vitro fertilization. It may also have a role in the assessment of semen to determine fertilization potential and hence provide prognostic information to infertile couples.

Cell Separation↗
PubMed1986

An in vitro fertilization and embryo transfer pilot study: treatment-dependent and treatment-independent pregnancies.

A pilot program of in vitro fertilization and embryo transfer at McMaster University is described. Fourteen couples with a clinical diagnosis of infertility due to apparent tubal dysfunction, with evidence of ovulation, and with normal semen analysis underwent induction of superovulation with human menopausal gonadotropin. At laparoscopy, 82 follicles were aspirated and 19 oocytes were recovered. Eleven oocytes demonstrated cleavage and all inseminated oocytes were transferred 49 to 65 1/2 hours after insemination. In vitro fertilization therapy resulted in two pregnancies, one leading to a spontaneous abortion and the other to the birth of a healthy female infant. At 10 to 12 months after in vitro fertilization therapy in the remaining 12 patients, there were three additional pregnancies (treatment-independent), one ectopic and two intrauterine. One patient was delivered of a healthy female infant. In vitro fertilization therapy should be evaluated by a randomized controlled clinical trial.

Adult↗
PubMed1986

Production of immunosuppressor factor(s) by preimplantation human embryos.

Embryonic loss prior to implantation appears to be a significantly frequent phenomenon and this is further reinforced by the very low pregnancy rates reported by in vitro fertilization and embryo transfer programs. Implantation failure may possibly be the result of rejection of the antigenic embryo by the hostile maternal immune system. The mechanism by which embryos in successful pregnancies escape these rejection responses may depend upon their ability to produce factor(s) that suppress in vitro mitogen-induced lymphocyte proliferation. Only 43% of cleaved embryos demonstrated this ability. We postulate that successful pregnancies are dependent upon the production by embryos of immunosuppressor factor(s) that has a direct suppressive effect on the maternal immune response.

Blastocyst↗
PubMed1986

Immunoregulatory molecules of trophoblast and decidual suppressor cell origin at the maternofetal interface.

The mammalian fetus expresses a variety of paternal histocompatible, oncofetal, and trophoblast antigens against which the mother can mount an immune response. Survival of the "fetal graft" appears to depend upon local immunosuppressive mechanisms in lymph nodes draining the uterus and at the intrauterine implanation site itself. Nonspecific not-T-Fc-receptor-bearing small lymphocytes containing cytoplasmic granules present in successfully allopregnant mice can suppress both the generation of maternal-antipaternal killer T cells and the infiltration of cytotoxic T lymphocytes into sponge-matrix allografts during the effector phase of the immune response. These suppressor cells are deficient at the implantation sites of xenogeneic and allogeneic mouse embryos that are susceptible to maternal immunity and are destined to resorb. A soluble suppressor factor of approximately 100,000 daltons in size can be obtained from the suppressor cells and acts to block the response of T cells to interleukin-2 by interfering with IL-2 receptors. The development of the suppressor cells in the decidua requires certain hormonal signals as well as signals provided by trophoblast cells. Freshly explanted or cultured murine trophoblast cell lines elaborate soluble factor(s) that are active in recruitment or activation of suppressor cells. Since suppressor cells may be isolated from decidua of successfully allopregnant humans, the suppressor cell mechanism and its regulation may represent a key factor in the protection of the "fetal allograft" from rejection by maternal immunity.

Abortion, Spontaneous↗
PubMed1986

The interaction between nifedipine and isoprenaline in isolated guinea-pig tracheal muscle precontracted with methacholine.

Our previous studies on the bronchodilator potential of the calcium channel blockers showed that nifedipine antagonised the relaxant effect of isoprenaline in isolated preparations of guinea-pig tracheal muscle which were contracted with cumulative doses of methacholine. For the present study we decided to investigate firstly, whether this interaction would persist in tissue precontracted with methacoline in the presence of isoprenaline and secondly, to investigate the effect of cumulative nifedipine concentrations on any such interaction. Our results show that nifedipine is capable of reversing methacholine-induced contractions with an ID50 value of 3.5 X 10(-8) M. However, in tissues precontracted with methacholine in the presence of isoprenaline, nifedipine induces further contraction followed by relaxation, resulting in a biphasic curve. This interaction appears to be a potentially dangerous one and should be investigated further in in vivo models.

Animals↗
PubMed1985

Suppressor cells in human decidua.

Decidual suppressor cells have been found in the murine system. These cells are absent at the implantation sites of interspecies mouse embryos which become infiltrated by maternal cytotoxic cells. Suppression is also deficient at the sites of the spontaneous resorption of fetuses in allomated intraspecies pregnancies. This study was carried out to determine whether similar suppressor cells were present in the decidua during successful human allopregnancies. Decidua was obtained from gestations of 13 to 15 weeks and from term gestations, and the lymphocytes were tested for their ability to suppress the response of their peripheral blood lymphocytes to concanavalin A. Eight of eight 13- to 15-week decidual lymphocytes proved to be suppressive. At term seven of twelve lymphocyte preparations at a lower concentration of cells and six of seven at a higher concentration showed suppression. Suppressor cells appear to be present in human decidua and may play a role in preventing maternal immunologic attack on the allogenic embryo, thereby preventing spontaneous abortion.

Cells, Cultured↗
PubMed1985

Preliminary characterization of two types of suppressor cells in the human uterus.

Survival of the mammalian fetus in an immunologically hostile host has been shown to be determined by the properties of the tissue at the maternal-fetal interface. Suppressor cells have been found in the decidua in both murine and human systems. This study was carried out to further characterize these cells and to determine whether they were present in abnormal early pregnancies and in the endometrium at the time of implantation. Suppressor cells appear in the endometrium after ovulation, and their activity is present in the decidua of successful pregnancies but is absent in missed abortions. Two types of cells have been identified. An early phase large cell appears to be hormone dependent, and later phase small cell appears to be trophoblast dependent. This would suggest that suppressor cells may play a role in protecting the fetal allograft, from the time of implantation, against maternal immunity, thereby allowing a pregnancy to succeed.

Abortion, Missed↗