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At least 1,621 records · Page 90Linked to original sources
PubMed1987

Ovoperoxidase assembly into the sea urchin fertilization envelope and dityrosine crosslinking.

Ovoperoxidase, the enzyme implicated in hardening the extracellular coat of the fertilized sea urchin egg, is inserted into the assembling uncrosslinked (soft) fertilization membrane via specific interactions with a protein, proteoliaisin (P. Weidman, E. Kay, and B. M. Shapiro (1985). J. Cell. Biol. 100, 938-946), and the vitelline scaffold. Dityrosine crosslinks introduced by ovoperoxidase have been postulated to harden the assembled structure from such indirect data as the discovery of dityrosine in hard fertilization membranes (Foerder and B. M. Shapiro (1977). Proc. Natl. Acad. Sci. USA 74, 4214-4128; H. G. Hall (1978). Cell 15, 343-355). In this report, we show directly that soft fertilization membranes (SFM) contain no dityrosine residues but acquire these crosslinks in vitro only during hardening. In vitro hardening alters the susceptibility of the fertilization membrane to disruption in cation-depleted solutions and in detergent; the kinetics of these phenomena are all similar to those of hardening in vivo. Ovoperoxidase substrates were identified as a class of high-molecular-weight proteins of SFM by polyacrylamide gel electrophoresis after in vitro hardening or after an ovoperoxidase-catalyzed radioiodination reaction. The specificity of ovoperoxidase for particular substrates decreased once it was no longer associated with these polypeptides within the SFM. Moreover, after disruption of the SFM, ovoperoxidase had an increased capacity to iodinate an exogenous protein, myoglobin. These data suggest that assembly of ovoperoxidase into a specific locus within the soft fertilization membrane provides a regulatory mechanism to guarantee the crosslinking of only certain appropriately juxtaposed tyrosyl residues in the assembled structure.

Animals↗
PubMed1989

Identification of a major polypeptide component of the sea urchin fertilization envelope.

A monoclonal antibody (MAb No. 25-16), raised against purified cortical secretory vesicles (CVs) from the eggs of Strongylocentrotus purpuratus, has been used to identify a previously uncharacterized CV-derived polypeptide component of the sea urchin fertilization envelope (FE). MAb No. 25-16, an IgG1, bound to a group of proteins with Mr approximately 200,000 on immunoblots of CVs. This same group of proteins also was detected in fertilization product and in soft FEs prepared from early embryos, indicating that the antigen is released at fertilization by CV exocytosis and becomes incorporated into the FE. The multiple components recognized by MAb No. 25-16 apparently did not result from proteolysis during sample preparation or differential N-linked glycosylation. No simplification of the SDS-gel or immunoblot patterns was observed when samples of fertilization product or cell surface complex were prepared in the presence of a cocktail of protease inhibitors; nor was a change in mobility of any of the antigen forms detected following treatment with endoglycosidase F. Upon partial denaturation and reduction of the protein by incubation at room temperature in the presence of SDS and dithiothreitol, the antigen was shown to undergo a decrease in relative mobility on SDS-PAGE. Complete reduction and denaturation, by boiling in dithiothreitol-containing SDS sample buffer or by an on-blot reduction technique, resulted in loss of the epitope. The protein component recognized by MAb No. 25-16 underwent a striking increase in mobility on SDS-PAGE after chelation of calcium ions with EGTA. Immunogold labeling on thin sections of unfertilized eggs revealed that the antigen is located in the spiral lamellar cores of all CVs. In fertilized eggs, fixed 5 min after insemination, the antigen was detected in the FE. Based on these biochemical and immunological data, we suggest that the antigen recognized by MAb No. 25-16 is released exocytotically from the CVs into the perivitelline space at fertilization and becomes incorporated into the FE. The abundance of this antigen suggests that it may function as a structural component of the FE.

Animals↗
PubMed1990

Membrane conductance patterns during fertilization are sperm dependent in two sea urchin species.

The influence of the egg and sperm on the conductance changes at fertilization in the sea urchin were investigated through cross-fertilization of two Hawaiian species, Tripneustes gratilla and Pseudoboletia indiana. The current-voltage (I-V) relation, measured in voltage-clamped eggs at intervals over the period 2-16 min following the rise to a positive membrane potential that signals sperm attachment, differs significantly in the two species. The magnitude of the conductance change depends on the species of the fertilizing sperm in both homologous and heterologous crosses. This supports the hypothesis that currents during this period arise from sperm membrane channels incorporated into the egg at sperm-egg fusion. Measurements of conductance during the first 90 sec, which includes the period of the major inward current correlated with cortical granule breakdown and elevation of the fertilization envelope, showed that the magnitude and timing of the maximum current also differed in the two species. This conductance change presumably involves an activation of egg membrane channels initiated by the sperm and would be expected to be characteristic of the egg species. However, in cross-fertilized eggs the magnitude and timing of the conductance change over this period also depends on the species of the sperm with little identifiable egg contribution, indicating that the fertilizing sperm can modulate the egg response to influence these events.

Animals↗
PubMed1991

Initiation of DNA replication cycle in fertilized eggs of the starfish, Asterina pectinifera.

Starfish oocytes or eggs were inseminated at various times between first prometaphase and pronuclear stage, and were subsequently labeled with the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) in order to detect the onset of DNA synthesis phase (S phase) during the first cell cycle using a monoclonal antibody against BrdU. The interval between fertilization and the first S phase was found to be constant (30-45 min, depending on batches) in eggs fertilized after formation of the first polar body. Eggs fertilized before first polar body formation, however, always entered the S phase 10-20 min after the second polar body formation. On the basis of these observations we conclude that (i) the chain of events triggered by fertilization, collectively called "postactivation process" for the first S phase, goes on in parallel with the process of maturation and (ii) only the final step of the postactivation process is arrested until the termination of meiosis. In eggs that had been fertilized before the first polar body formation, the female and male pronuclei exhibited uniformly distributed chromatin soon after the second polar body formation. In eggs that had been fertilized after the second polar body formation, however, the chromatin of the pronuclei remained fibrillar even during the S phase. Thus full decondensation of chromatin appears to depend on a certain advance in the postactivation process.

Animals↗
PubMed1986

Latrunculin inhibits the microfilament-mediated processes during fertilization, cleavage and early development in sea urchins and mice.

Latrunculin A, a marine toxin from a Red Sea sponge, is a potent inhibitor of the microfilament-mediated processes of fertilization and early development in sea urchins and in mice. Sperm from sea urchins, but not those from Limulus or mice, were affected by latrunculin, and fertilization in both sea urchins and in mice was arrested but at different stages. Sea urchin sperm treated with 2.6 microM latrunculin are unable to assemble acrosomal processes and their ability to fertilize eggs is impaired. The unwinding of the Limulus sperm acrosomal process occurs in the presence of latrunculin. Treated mouse sperm are able to fertilize mouse oocytes in vitro, suggesting that microfilaments may not be required in this mammalian sperm. In sea urchin eggs, sperm incorporation, microvillar elongation and cytokinesis are inhibited. Microtubule-mediated motility occurs normally. 20 nM latrunculin prevents the morphogenetic movements during gastrulation. It reduces the viscosity of actin gels from sea urchin egg homogenates. In unfertilized mouse oocytes, it prevents the colcemid-induced dispersion of the meiotic chromosomes; accumulations of cortical actin are noted adjacent to the scattered chromosomes. Sperm incorporation during mouse fertilization in vitro is unaffected suggesting that sperm entry may occur independent of microfilament activity in mammals. However, the apposition of the pronuclei at the center of the egg cytoplasm does not occur, providing evidence that cytoplasmic microfilaments may be required for the motions leading to pronuclear union during mouse fertilization. It inhibits the second polar body formation and cytokinesis. These results indicate that latrunculin is a potent inhibitor of microfilament-mediated processes in sperm, eggs and embryos, and that it may prove to be a powerful new drug for exploring the cellular behavior of microfilaments in the maintenance of cell shape and during motility.

Acrosome↗
PubMed1993

Prolonged, repetitive calcium transients in rat oocytes fertilized in vitro and in vivo.

Zona-free rat oocytes inseminated with capacitated sperm, under conditions that allow polyspermic fertilization, exhibited a rapid, transient elevation of cellular calcium (from 147 +/- 10 to 607 +/- 55 nM, n = 19, measured by Fura 2 fluorescence ratio imaging) immediately after sperm attachment. This peak was followed by a series of dramatic calcium transients of high amplitude (maximal 847 +/- 32 nM) and frequency (range 2.1 +/- 0.07 - 3.9 +/- 0.07 min), which continued for several hours. A similar pattern was seen also in zona-free oocytes fertilized with low sperm density (i.e. producing mainly monospermic attachment) and in zona-enclosed oocytes fertilized in vitro. Moreover, single or repetitive calcium transients were observed in rat oocytes fertilized in vivo. These findings indicate that in normal fertilization in vivo, sperm-oocyte interaction initiates a prolonged train of cyclical calcium changes in the oocyte. This activity may be necessary for the early events in the fertilization process.

Animals↗
PubMed1984

In vitro fertilization and embryo transfer of rabbit oocytes collected at different times after P-LH injection.

No difficulties were encountered in the collection of preovulatory oocytes from the follicles of rabbits. A mean of 11.7 ova were recovered by follicle puncture. In vitro fertilization of the preovulatory oocytes was influenced by their stage of maturation. The highest fertilization rate (83%) was obtained using oocytes collected 9 h after injection of P-LH shortly before ovulation. Only after pretreatment with FSH-P was it possible to fertilize some preovulatory oocytes without administration of P-LH. In vitro fertilized preovulatory oocytes developed in culture. After 4-5 days 47-64% reached the blastocyst stage; the corresponding rate for in vivo fertilized oocytes was 48%. After transfer of in vitro fertilized preovulatory oocytes 19-28% implantations were achieved.

Animals↗
PubMed1991

Calcium pools in sea urchin eggs: roles of endoplasmic reticulum and mitochondria in relation to fertilization.

A preparation of sea urchin eggs permeabilized with digitonin (40 microM for 2.5 min) was used to study the kinetic characteristics of the two cellular compartments suspected to play a key role in cellular calcium transfer during fertilization: an ATP-dependent Ca2+ pool (Km = 0.47 microM; Vm = 0.48 nmol/min.mg protein) probably located in the endoplasmic reticulum and a mitochondrial Ca2+ pool (Km = 1.50 microM; Vm = 0.12 nmol/min.mg protein). Fertilization triggered a decrease in the rate of ATP dependent uptake by the non-mitochondrial pool (Km = 0.59 microM; Vm = 0.15 nmol/min.mg protein) while it transiently increased the Ca2+ uptake into mitochondria (2 min post-fertilization: Km = 2.20 microM; Vm = 0.40 nmol/min.mg protein). Microanalysis studies performed on quickly frozen, freeze substituted and embedded eggs showed a transient Ca2+ enrichment of mitochondria soon after fertilization thus suggesting that mitochondria behave as a Ca2+ sink at fertilization. Results are discussed in relation to the role of endoplasmic reticulum and mitochondria in handling free calcium during the early period following sea urchin egg fertilization.

Adenosine Triphosphate↗
PubMed1982

Detection of triethylenemelamine-induced translocation heterozygotes in CD-1 mice: fertility and cytological methods.

A study was conducted to determine the extent to which translocation carriers can be missed in the heritable translocation test. CD-1 male mice were treated with the mutagen triethylenemelamine and bred to untreated females and male progeny were subjected to fertility and cytogenetic analyses. Fertility testing involved mating 1 male to 3 virgin females and subjecting the females to uterine analysis. The males were classified as having normal or reduced fertility according to the number of live implants produced by the females. The cytogenetic analysis involved scoring 25 primary spermatocytes per mouse for translocation multivalents. A total of 103 male progeny were analyzed. Evaluation of fertility and cytogenetic data confirmed the presence of 18 translocation heterozygotes among the male progeny. On the basis of fertility testing, 1 translocation heterozygote was classified as normal (false negative) based on the production of 11 or more live implants by at least 1 mated female. On the basis of cytogenetic analysis of 25 cells per mouse, 1 partially sterile male was classified as normal (false negative); however, analysis of additional cells showed that this mouse was a translocation heterozygote. The study demonstrates the importance of evaluating fertility and cytogenetic criteria to minimize the extent of misclassification in conducting a heritable translocation test.

Animals↗
PubMed1991

Components of stably high fertility in three areas of west Africa.

The constancy of fertility levels in Ghana, Senegal and southwest Nigeria since 1970 is separated into its nuptiality and marital fertility elements. The age-specific changes in the two components are examined and these show that the apparent stability in observed total fertility rates is essentially the outcome of the offsetting impact of increased marital fertility below age 25 and above age 40, over the effect of the increasing proportion of women remaining single up to 25 yr of age. Continuity in traditional fertility behaviour and stable nuptiality has remained operative over the broad middle segment of the reproductive lifespan of women in the three areas. The paper thus concludes that West Africa is likely to continue to display stably high fertility for many years into the next century. The social and cultural conditions behind this trend are discussed with special reference to the continued high demand for children and the low and only slowly rising contraceptive prevalence level.

Adolescent↗
PubMed1992

Contributions of the proximate determinants to fertility change in Senegal.

The 1978 World Fertility Survey (WFS) and the 1986 Demographic and Health Survey (DHS) data are used to examine the relative contributions of three proximate determinants (nuptiality or marriage, contraception and post-partum infecundability) to fertility change in Senegal. The aim is to identify the important variables that is amenable for policy towards fertility reduction. Analysis shows that there are increases in the absolute measures of all three determinants. The magnitude of change is greatest in contraceptive use, moderate in marriage but least in duration of breast-feeding. However, the index of contraceptive use exerts the least impact on fertility reduction while that of post-partum infecundability makes the strongest impact on fertility. The impact of the nuptiality index on fertility change lies in-between contraception and breast-feeding.

Abortion, Spontaneous↗
PubMed1995

Milk versus TEST-yolk--preincubated sperm; in vitro fertilization outcome.

OBJECTIVE: Preincubation of sperm in TEST-yolk medium enhances in vitro fertilization (IVF) outcome. However preincubation of sperm in milk at 5 degrees C enhances the results of sperm penetration assay and hemizona assay. This study was therefore performed to determine the influence of milk on in vitro fertilization rate of human oocytes, as compared with TEST-yolk medium. STUDY DESIGN: Forty-one consecutive couples undergoing an IVF procedure were randomized. Of these 20 couples were admitted for the milk study (group 1) and 21 couples for the TEST-yolk study (group 2). Each ejaculate was Percoll-processed and the sperm pellet was resuspended in 0.5 ml of culture medium. An equal volume of heat-inactivated homogenized cow's milk (95 degrees C, 10 min) was added to sperm suspension from group 1 and an equal volume of TEST-yolk medium was added to sperm suspension from group 2. After 2 h of incubation at 5 degrees C and washing with culture medium at 37 degrees C, oocytes were inseminated. Oocytes from group 1 couples were inseminated with milk-treated spermatozoa and those from group 2 couples with yolk-treated spermatozoa. Oocytes were evaluated for fertilization after 18 h. RESULTS: Sperm preincubated in milk fertilized 75 out of 100 mature oocytes (75%). TEST-yolk-treated sperm fertilized 45 out of 64 mature oocytes (70%). The difference was not statistically significant. CONCLUSIONS: Preincubation of spermatozoa in milk, as compared with preincubation in TEST-yolk medium yields a similar IVF outcome, so milk may be a suitable alternative medium for preincubation of spermatozoa to enhance its fertilizing potential.

Animals↗
PubMed1987

Smoking, alpha 1-antitrypsin and decreased fertility in women.

There is epidemiologic evidence that smoking by women is associated with decreased fertility. Little is known about the biological mechanism(s) that might underlie a direct association. The effect of smoking on genital secretions, including levels of alpha 1-antitrypsin (AlAT), has not been studied. Low midcycle levels of AlAT appear to favour fertility by facilitating sperm migration and/or penetration. Smoking increases serum levels of functional AlAT. Since AlAT is produced only in the liver, levels in other tissues may reflect serum levels. It is postulated that smoking-induced increases in serum AlAT result in higher levels of AlAT in genital secretions, including those at midcycle, thereby impeding fertility. Support of an effect of serum AlAT levels on fertility is provided by studies of AlAT deficient persons, in whom fertility seems to be enhanced. An adverse effect of smoking on fertility through an increase in genital tract AlAT levels would be reversible.

Cervix Uteri↗
PubMed2005

Perinatal outcomes of in vitro fertilization twins: a systematic review and meta-analyses.

OBJECTIVE: Uncontrolled studies suggest that in vitro fertilization twins have increased rates of preterm birth and low birth weight and would warrant increased antenatal monitoring. The objective of this meta-analysis was to determine whether the incidence of poor obstetric outcomes is higher for in vitro fertilization twins than for spontaneously conceived twins who were matched for maternal age. STUDY DESIGN: Medline and EMBASE were searched with comprehensive search strategies. Case-control and cohort studies of twins who were conceived by in vitro fertilization or in vitro fertilization/intracytoplasmic sperm injection, with the transfer of fresh embryos or cryopreserved (frozen) in women with infertility, and/or whose partners were subfertile or infertile, compared with naturally (spontaneously) conceived twins who were matched for maternal age (case-control studies) or which were controlled for it (cohort studies). Two reviewers independently assessed titles, abstracts, and study quality and extracted the data. Statistical analysis was performed with commercial statistical software. Dichotomous data were meta-analyzed with odds ratios as measures of effect size, and continuous data was meta-analyzed with mean differences. Interstudy variation was incorporated with the assumption of a random effects model for the treatment effect. RESULTS: Compared with spontaneously conceived twins who were matched for maternal age, in vitro fertilization twins have an increased risk of preterm birth between 32 and 36 weeks of gestation (odds ratio, 1.48; 95% CI, 1.05-2.10), and an elevated risk of preterm birth at <37 weeks of gestation when parity is also matched for an odds ratio of 1.57 (95% CI, 1.01-2.44). There was an increased rate of cesarean delivery among in vitro fertilization twins (odds ratio, 1.33; 95% CI, 1.06-1.67). There were no significant differences in incidences of perinatal death, low birth weight infants, or congenital malformations. CONCLUSION: In vitro fertilization twins have increased rates of preterm birth compared with spontaneously conceived twins who were matched for maternal age, despite the fact that their outcomes would be expected to be better because of the decreased proportion of monochorionic twins.

Case-Control Studies↗
PubMed2005

A novel method for constructing murine cDNA library enriched with maternal mRNAs exhibiting de novo independent post-fertilization polyadenylation.

Recently, mouse maternal mRNAs such as SSEC-D, Spin, beta-catenin, Ptp4a1, and Maid have been found to exhibit de novo independent polyadenylation after fertilization. To obtain an overall picture of post-fertilization polyadenylation events, we developed a novel method for constructing murine fertilized egg cDNA library enriched with cDNAs exhibiting de novo independent polyadenylation. As a pilot study, we isolated at least four new maternal mRNAs exhibiting extension of poly(A) tail in fertilized 1-cell eggs. Moreover, various types of polyadenylation of maternal RNAs were observed at this stage, suggesting the presence of novel mechanisms for regulating the length of poly(A) tails of maternal mRNA. This is the first report of successful construction of a cDNA library enriched with newly polyadenylated maternal mRNAs derived from post-fertilized mouse eggs. This cDNA library will be useful for molecular analysis of the mechanisms underlying post-fertilization polyadenylation of mammalian maternal RNAs.

Animals↗
PubMed2005

Revisiting the agronomic benefits of manure: a correct assessment and exploitation of its fertilizer value spares the environment.

The ongoing disintegration of agriculture into specialized farms, specialized regions and even specialized countries, has disrupted local nutrient cycles. This process is promoted and sustained by the use of mineral fertilizers. Ample availability of mineral fertilizers has changed farmers' perception and appreciation of manure. By now, manure is looked upon as 'waste' in some regions. It is a contradiction in terms, however, to regard biological by-products as 'waste'. Apart from this cultural aspect, economical and environmental considerations per se, justify a rehabilitation of manure. First of all a correct assessment of the fertilizer value is required. The present paper explains how to determine the nitrogen fertilizer value (NFV) of manures in a unbiased manner. Subsequently, recommendations are made on how to exploit the potential NFV as good as possible. Undeniably, it is easier to manage mineral fertilizers than manure. However, when proper attention is given to the composition of manure and decisions on rates, timing and placement are made correspondingly, the NFV can be enhanced. This should lead to a drastic reduction of mineral fertilizer use, nutrient surpluses and environmental pollution. Under such conditions, 'manure', 'precision farming' and 'environment' can become reconciled again.

Agriculture↗
PubMed2004

NAADP triggers the fertilization potential in starfish oocytes.

In invertebrates oocytes or eggs, the fertilization or activation potential establishes the fast electrical block to polyspermy and, in some species, provides the Ca2+ influx which contributes to the following intracellular Ca2+ wave. In echinoderms, the molecule triggering the activation potential is still unknown. The aim of this study was to assess whether nicotinic acid-adenine dinucleotide phosphate (NAADP) elicited the fertilization potential in starfish oocytes. The changes in membrane potential induced by the sperm were measured in oocytes held at a low resting potential, so that the Ca2+-action potential was inactivated and only the initial slower depolarization caused by the sperm could be studied. Decreasing extracellular Na+ concentration did not prevent the onset of the fertilization potential, while removal of external Ca2+ abolished it. The pre-incubation with SK&F 96365 and verapamil and the pre-injection of BAPTA inhibited the fertilization potential, while the injection of heparin only reduced its duration. The biophysical and pharmacological properties of the sperm-elicited depolarization were similar to those displayed by the NAADP-activated Ca2+-mediated current recently described in starfish oocytes. Indeed, the desensitization of NAADP-receptors prevented the onset of the fertilization potential. Taken together, these data suggest that NAADP could trigger the fertilization potential in starfish oocytes.

Action Potentials↗
PubMed2006

Fertility preservation in female cancer patients: current developments and future directions.

OBJECTIVE: To review the current advances in fertility preservation strategies and to discuss future directions with an emphasis on ovarian tissue cryobanking. DESIGN: The publications related to fertility preservation in cancer patients were identified through Medline and other bibliographic databases, focusing on the most recent developments. CONCLUSION(S): There are several options for fertility preservation in cancer patients. Even though most of them are still experimental and their efficacy and reliability have not been determined, the future of fertility preservation in women with cancer is promising. In particular, the recent report of a live birth after transplantation of human ovarian tissue has reinforced the clinical potential of ovarian tissue banking for fertility preservation. Many exciting studies are underway to improve the efficacy and solve the problems with current fertility preservation strategies. It is inevitable that we will see the emergence of more complex ethical problems with the application of new technologies to humans. However, continuous efforts to improve current strategies and to develop new strategies will benefit many women and children who are facing premature ovarian failure and sterility.

Female↗