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R Kaplan-Kraicer

Publications and source records attributed to R Kaplan-Kraicer.

13 recordsLinked to original sources
PubMed2005

Strontium-induced rat egg activation.

Parthenogenetic agents that evoke cytosolic calcium concentration ([Ca2+]i) oscillations similar to those evoked by sperm, mimic fertilization more faithfully than agents that trigger a single [Ca2+]i transient. Strontium chloride (SrCl2) binds to and activates the Ca2+-binding site on the inositol 1,4,5-trisphosphate receptor and evokes [Ca2+]i oscillations. Although SrCl2 has been reported to activate mouse eggs, little is known regarding the pattern of the [Ca2+]i oscillations it evokes in rat eggs and their effect on the early events of egg activation: cortical granule exocytosis (CGE) and completion of meiosis (CM). In the current study we investigated the effect of various concentrations of SrCl2 (2, 4 or 6 mM) on [Ca2+]i, by monitoring [Ca2+]i oscillations in fura-2-loaded rat eggs. Treatment with 2 mM SrCl2 was optimal for inducing the first [Ca2+]i transient, which was similar in duration to that triggered by sperm. However, the frequency and duration of the subsequent [Ca2+]i oscillations were lower and longer in SrCl2-activated than in sperm-activated eggs. The degree of CGE was identical in eggs activated by either sperm or SrCl2, as assessed by semi-quantitative immunohistochemistry combined with confocal microscopy. Evoking 1, 2 or 10 [Ca2+]i oscillations (8, 15 or 60 min in SrCl2 respectively) had no effect on the intensity of fluorescent CGE reporter dyes, while 60-min exposure to SrCl2 caused a delay in CM. Our results demonstrate that SrCl2 is an effective parthenogenetic agent that mimics rat egg activation by sperm, as judged by the generation of [Ca2+]i oscillations, CGE and CM.

Animals↗
PubMed2001

PKC in eggs and embryos.

After a spermatozoon enters the egg, rapid processes such as the cortical granules exocytosis (CGE) occur. Other, later processes are observed as well, and they include resumption of the second meiotic division, second polar body (PBII) extrusion and rearrangement of the DNA inside the pronuclei (PN). The above mentioned biochemical processes involve signal transduction pathways that are well known in other cell systems, and require mediation of second messengers like Ca2+ and diacylglycerol (DAG) which are protein kinase C (PKC) activators. The present review, based upon recently published studies, raises the possibility of PKC involvement in fertilization and in early developmental stages of the mammalian embryo.

Animals↗
PubMed2000

Molecular cloning of rat sperm galactosyl receptor, a C-type lectin with in vitro egg binding activity.

Rat sperm galactosyl receptor is a member of the C-type animal lectin family showing preferential binding to N-acetylgalactosamine compared to galactose. Binding is mediated by a Ca(2+)-dependent carbohydrate-recognition domain (CRD) identical to that of the minor variant of rat hepatic lectin receptor 2/3 (RHL-2/3). The molecular organization of the genomic DNA, cDNA, and derived amino acid sequence of rat testis galactosyl receptor have been determined and in vitro fertilization studies were conducted to ascertain its role. We have determined that the rat testis galactosyl receptor gene generates two mRNA species: one species, designated liver-type, is identical to RHL-2/3; the other, designated testis-type, contains one unspliced intron (86 nt) which alters the reading frame and changes the amino acid sequence of the carboxyl terminus. As a result, the CRD (glutamine-proline-aspartic acid/QPD) and flanked Ca(2+)-binding amino acid sequences were not present in the testis-type protein. Northern and Southern blots demonstrated presence of transcripts with unspliced intron in rat sperm but not liver. Similarly, antibody, raised against a synthetic 12-amino acid peptide (p12) encoded by the unspliced intron, recognized in immunoblots a 54 kDa receptor protein in protein extracts from testis but not from liver. Immunofluorescence and immunogold electron microscopy studies demonstrated that both protein species localized on the plasma membrane surface of the head and tail of rat sperm. Furthermore, capacitated rat sperm preincubated with polyclonal antisera to RHL-2/3 or to the CRD of the liver-type galactosyl receptor showed a statistically significant decrease in the in vitro fertilization rate. We conclude that rat sperm galactosyl receptor may play a role in egg binding and that an undetermined molecular mechanism operates to generate two proteins with identical intracellular amino terminal domain but only one of them displays a CRD and associated Ca(2+)-binding sites at the carboxyl terminal extracellular domain.

Alternative Splicing↗
PubMed2000

Anordiol produces pregnancy loss in the rat--via the embryo or via the uterus?

Anordiol, the dihydroxylated metabolite of anordrin, is an antiestrogen with estrogenic activity that is known to inhibit fertility. The following study was conducted to determine the mechanism of this antifertility effect. Anordiol was administered orally to rats, prior to implantation, on Day 2 of pregnancy. Control animals were treated with the vehicle only. The effectiveness of the agent in terminating pregnancy was determined on Day 14 of pregnancy. Anordiol was 100% effective in abolishing pregnancy at a dose of 0.6 mg/Kg. Administration of smaller doses resulted in a decreased number of implanting embryos, in a dose-dependent manner. An additional dose of anordiol on Day 3 of pregnancy yielded similar results. To determine whether pregnancy impairment by anordiol is exerted via the embryo or via the uterus, reciprocal embryo transfers were performed. Day 5 blastocysts were transferred into the uteri of pseudopregnant rats. In one set of experiments, the donor rats were treated with anordiol, and in the second set the recipient rats were treated. The results indicate that the effects of anordiol administration are exerted via the embryo as well as the uterus.

Abortion, Induced↗
PubMed1996

Viscosity and refractive index of follicular fluid in relation to in vitro fertilization.

PURPOSE: To set the standard values of follicular fluid viscosity and refractive index, and to investigate a possible relationship between these physiological parameters and the outcome of in vitro fertilization treatment. DESIGN AND RESULTS: 128 samples of follicular fluid were collected from 40 in vitro fertilization patients. Viscosity determinations (centipoise; mean +/- SD) for shear rates of 23, 46, 115, and 230 were 2.04 +/- 0.86, 1.84 +/- 0.49, 1.48 +/- 0.27, and 1.38 +/- 0.22, respectively. The average (+/- SD) refractive index was 1.030 +/- 0.002. There was no significant difference between the values of thawed frozen fluids and fresh samples of the same specimens. The data showed no correlation between follicular fluid viscosity or refractive index and the presence of oocytes, their maturation grade or their fertilizing capacity. CONCLUSIONS: For the first time, values of the viscosity and refractive index of follicular fluid obtained during in vitro fertilization have been determined. However, these preliminary results did not reveal any relationship between the physiological parameters examined and the outcome of in vitro fertilization treatment.

Female↗
PubMed1996

Tamoxifen and RU39411 synergize with mifepristone to produce preimplantation pregnancy loss by increasing embryo transport (rat).

Tamoxifen is a non-steroidal antiestrogen that possesses antagonistic as well a agonistic properties, while RU39411 is an antiestrogen that is known to possess only antagonistic properties. These steroid antagonists were administered orally to rats, with or without mifepristone, an antiprogestational agent, prior to implantation on Day 2 of pregnancy. The status of pregnancy was assessed on Day 14. Low doses of tamoxifen reduced litter size and weight and inducing embryonic absorption in some animals; a dose of 0.25 mg/Kg prevented pregnancy in all animals. RU39411 also had a dose-dependent effect on pregnancy, but a higher dose (0.5 mg/Kg) was required to achieve the same degree of pregnancy prevention. Addition of mifepristone to both antiestrogens had a synergistic effect on reducing litter size and weight. To determine the mechanism by which antiestrogens terminate pregnancy in rats, oviducts and uteri of treated rats were examined for the presence of embryos on Day 3 and 4 of pregnancy, times when most embryos would be expected to be in the oviducts. Most of the embryos of the treated animals were found in the oviducts on Day 3 of pregnancy. By Day 4, only a few embryos were still present in oviducts. These observations suggest acceleration of embryo transport by Day 4 of pregnancy. There was no accumulation of embryos in the uterus. Since acceleration of embryo transport through the reproductive tract in rat is induced by low doses of estrogens, it is likely that the agonistic action of tamoxifen is responsible for pregnancy prevention in these experiments. The fact that RU39411 also prevents pregnancy by a similar mechanism suggests that this estrogen antagonist also has some estrogen agonist effects on the oviduct. The fact that both antiestrogens also affected embryo weight could suggest the action of the antihormones on other mechanisms controlling embryo development.

Abortifacient Agents, Steroidal↗
PubMed1995

Anordiol and RU486 synergize to produce preimplantation pregnancy loss by increasing embryo transport (rat).

RU486, an antiprogestational agent, and anordiol (dihydroxylated metabolite of anordrin) which has an estrogenic and antiestrogenic activity, are known to inhibit fertility. These agents were administered orally, alone or together, to rats prior to implantation, on Day 2 of pregnancy. Control animals were fed with the vehicle only. The effectiveness of the agents in terminating pregnancy in female rats was determined on Day 14 of pregnancy. Anordiol presented a dose-dependent effect on abolishing pregnancy, being 100% effective at 2.5 mg/Kg and non-effective at 0.6 mg/Kg. RU486 did not prevent pregnancy even at a dose of 4 mg/Kg. Doses of RU486 and anordiol that were ineffective when administered alone, prevented pregnancy in 70% of the rats when these agents were given together. To determine the mechanism by which these drugs prevent pregnancy, oviducts and uteri of rats were examined for presence of embryos on Day 3 of pregnancy. Only 29% of embryos were recovered from the oviducts of rats treated with 2.5 mg/Kg anordiol (compared to 89% in control group) plus an additional 9% from the uteri. In combination, anordiol and RU486 had a synergistic effect on embryo transport in the rats' reproductive tract, without any apparent accumulation in the uterus. These results led us to conclude that the pregnancy preventing action of anordiol plus RU486 is mostly due to accelerated transport of the embryos in the reproductive tract prior to implantation.

Abortion, Induced↗
PubMed1995

Experimental extension of the time interval between oocyte maturation and ovulation: effect on fertilization and first cleavage.

OBJECTIVE: To test the hypothesis that impaired fertility in human patients with high LH concentrations throughout the follicular phase of the menstrual cycle reflects premature maturation of their oocytes. DESIGN: Previous information that resumption of meiosis is induced by lower hCG concentrations than that required for stimulation of follicular rupture was confirmed and used for establishment of a rat animal model in which oocyte maturation and ovulation can be separated experimentally. In further experiments hypophysectomized, pregnant mare serum gonadotropin (PMSG)-primed, immature female rats injected with 1.1 IU of hCG, a dose found to induce maturation in 72.9% +/- 6% of the rats with no effect on ovulation, were administered with a second injection of an ovulatory dose (4 IU) of hCG, 24 hours later. The ovulated eggs were subjected to IVF. RESULTS: Fertilization and first cleavage in oocytes recovered from our experimental animal model were similar to that observed in control PMSG-primed, either hypophysectomized or intact rats, treated by a single injection of 4 IU of hCG. CONCLUSIONS: The extension of the time interval between oocyte maturation and ovulation in the rat does not result in a lower rate of fertilization or a reduced incidence of cleavage. However, an inferior developmental capacity of these embryos cannot be ruled out.

Animals↗
PubMed1990

The relationship between sperm parameters and fertilizing capacity in vitro: a predictive role for swim-up migration.

The relationship between sperm parameters and fertilizing capacity in vitro was examined retrospectively, with the aim of finding predictive criteria for successful in vitro fertilization. Three hundred thirty semen samples were used to inseminate 1462 oocytes. Conventional parameters of sperm concentration and percentage motility in the ejaculate as well as swim-up migration were analyzed in relation to fertilization rate. It was shown that the probability of fertilizing human oocytes in vitro decreases significantly when (a) the sperm concentration is below 20 x 10(6) spermatozoa/ml ejaculate (P = 0.006), (b) motility is lower than 80% (P = 0.002), or (c) less than 4 x 10(6) motile spermatozoa/ml are concentrated in the swim-up fraction (P less than 0.0001). It was also demonstrated that nonfertilizing sperm could not be distinguished from fertilizing sperm by the conventional criteria but rather by the average concentration of motile spermatozoa in the swim-up fraction [12.5 +/- 1.5 and 22.3 +/- 2.3 x 10(6)/ml for the 0 and the 100% fertilization groups, respectively (mean +/- SE; P less than 0.01)]. Thus, the swim-up migration technique can serve as a predictive test for the in vitro fertilizing capacity of sperm.

Fertilization in Vitro↗
PubMed1989

The effect of preinsemination interval upon fertilization of human oocytes in vitro.

A correlation between oocyte maturity, duration of preinsemination interval (PII) and fertilization rate in vitro has been suggested. Therefore, delayed insemination is being widely practised in many IVF centres. The purpose of this study was to investigate prospectively the effect of PII upon the fertilization rate in vitro. A total of 1474 oocytes were inseminated following incubation for between 30 and 540 min. The duration of the PII was determined randomly. It was found that neither fertilization rate (on average 46.9%) nor pregnancy rate (20.4%, calculated per embryo transfer) were affected by PII for any given degree of oocyte-cumulus maturity. The ability to inseminate oocytes at any time (within 9 h following egg collection) to the convenience of the biologist further simplifies the technology of IVF.

Adult↗
PubMedDate not supplied

Comparison of different follicle-stimulating hormone and luteinizing hormone ratios for ovulation induction during in vitro fertilization.

Five normally menstruating women were treated in an attempt to induce development of multiple follicles. They were randomly divided into two groups. The first group, consisting of three women, was treated with a combination of follicle stimulating hormone (FSH) and human menopausal gonadotropin (hMG) (combination FSH/hMG). The second group, two women, was treated with hMG only. Following a nonconceptual cycle, the treatments were exchanged. The increment patterns of serum estradiol during the follicular phase and progesterone levels in both groups were identical. Ultrasonographic scanning revealed similar number and size of the growing follicles, which subsequently terminated in the same oocyte recovery rate in both groups (7.6 +/- 3.4 oocytes/procedure in the combination FSH/hMG and 8.0 +/- 2.5 in the hMG-only group). Fertilization and cleavage rates were also similar. These data indicate that high FSH/LH levels in different ratios do not alter ovarian response and oocyte fertilization potential.

Adult↗