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Global assessment of nitrogen fertilizer: the SCOPE/IGBP nitrogen fertilizer rapid assessment project.

Nitrogen (N) availability is a key role in food and fiber production. Providing plant-available N through synthetic fertilizer in the 20th and early 21st century has been a major contributor to the increased production required to feed and clothe the growing human population. To continue to meet the global demands and to minimize environmental problems, significant improvements are needed in the efficiency with which fertilizer N is utilized within production systems. There are still major uncertainties regarding the fate of fertilizer N added to agricultural soils and the potential for reducing losses to the environment. Enhancing the technical and economic efficiency of fertilizer N is seen to promote a favorable situation for both agricultural production and the environment, and this has provided much of the impetus for a new N fertilizer project. To address this important issue, a rapid assessment project on N fertilizer (NFRAP) was conducted by SCOPE (the Scientific Committee on Problems of the Environment) during late 2003 and early 2004. This was the first formal project of the International Nitrogen Initiative (INI). As part of this assessment, a successful international workshop was held in Kampala, Uganda on 12 -16 January, 2004. This workshop brought together scientists from around the world to assess the fate of synthetic fertilizer N in the context of overall N inputs to agricultural systems, with a view to enhancing the efficiency of N use and reducing negative impacts on the environment. Regionalization of the assessment highlighted the problems of too little N for crop production to meet the nutrient requirements of sub-Saharan Africa and the oversupply of N in the major rice-growing areas of China. The results of the assessment are presented in a book (SCOPE 65) which is now available to provide a basis for further discussions on N fertilizer.

Crops, Agricultural↗

[Comparative study of the morpho-functional features of the sperm of fertile and infertile men and their relation to fertilizing ability].

The recent advances in assisted reproduction procedures have helped to the better understanding of the female reproductive physiology and pathology, however, male infertility remains as a poor explained medical problem, nevertheless it occurs in almost 50% of infertile couples. Oligoasthenozoospermia is one of the more common causes of male infertility, therefore we measured in 10 patients with this diagnosis and in 10 fertile euspermic men, besides the parameters included in the standard semen analysis, the quantitative motility (photography method), capacitation-acrosome reaction and the sperm ability to fertilize zona-free hamster oocytes, with the aim to correlate the morphofunctional characteristics of the male gametes with their fertilizing capacity. The results showed significant differences in every parameter studied, including the correlation analysis. In relation with the in vitro induction of the acrosome reaction in both groups, we found significant correlations of the sperm fertilizing ability and the progressive sperm motility with this parameter (fertile group: RS = 0.834, P less than 0.005 & RS = 0.612, P less than 0.05; infertile group: RS = 0.986, P less than 0.001 & RS = 0.536, P less than 0.05 respectively), nevertheless the sperm rate which completed this process was low in relation to the total sperm population even in the fertile men (9.4 +/- 2.0% & 4.4 +/- 2.5% acrosome reacted cells after 18 h of incubation, in the fertile and infertile males respectively). The results also showed the presence of fully capacitated spermatozoa in both groups, since they penetrated the zona-free hamster eggs and decondensed their chromatin (73.9 +/- 13.4% & 10.4 +/- 7.7% penetrated eggs in the euspermic and oligoasthenozoospermic individuals respectively), however, the spermatozoa from the oligoasthenozoospermic men showed low polyspermy indexes too (0.1 penetrated spermatozoa/inseminated oocyte). In this last group we found, in addition, that the mean sperm velocity and the abnormal sperm morphology rate showed significant correlations with the fertilizing ability of the male gametes too (RS = 0.986, P less than 0.005 & RS = -0.942, P less than 0.005. respectively). These data allow us to suggest that before an infertile man is involved in any assisted reproduction program, the presence of possible morphofunctional alterations in the spermatozoa be analyzed, with the aim to be able to make a better prognosis about the success with these patients.

Acrosome↗

The fertility-inhibiting effects of the intermediate fertility variables.

Based on the application of an aggregate reproductive model, this study demonstrates that a small number of intermediate fertility variables are responsible for most of the variation in fertility levels of populations. Four variables--proportion married, contraception, induced abortion, and postpartum infecundability--are generally the most important determinants of fertility; the other intermediate factors are of less interest except in unusual circumstances. These four factors explain 96 percent of the variance in the total fertility rate in a sample of 41 populations that include developing and developed countries as well as historical populations. In the last section, the average fertility effect of the principal intermediate fertility variables is estimated for groups of contemporary populations with different total fertility rates.

Abortion, Induced↗

Ova fertilization and sperm number per fertilized ovum for selenium and vitamin E-treated charolais cattle.

Fertilization of ova, number of sperm per fertilized ovum and serum and myometrial Se concentrations were determined in Charolais cows treated with selenium and vitamin E (Se+E). Cows were considered low in Se status prior to allotment to either a control (n=20) or a Se+E-treated (n=21) group. Se+E-treated cows received 40 mg of Se as selenite and 544 IU of alpha-tocopherol acetate by IM injection at 14-day intervals throughout the study, whereas control cows received saline. Starting on day 75 of treatment, cows were checked for estrus and inseminated. Reproductive tracts were removed at slaughter with ova collected and examined for fertilization and number of adhered sperm. The proportion of recovered ova that were fertilized for control and Se+E-treated cows was 8 of 11 and 12 of 15, respectively (P > .05). For spermatozoal data, a few extreme values accounted for a non-significant trend in which a greater number of sperm were adhered to fertilized ova collected from Se+E-treated than control cows (35.6 +/- 7.2 and 24.8 +/- 7.7, respectively). When analyzing only ova with spermatozoal numbers within one S.D. of the mean number of sperm per fertilized ovum, mean (+/- S.E.M.) spermatozoal numbers for control and Se+E-treated cows were 13.5 +/- 3.1 and 36.4 +/- 5.3, respectively (P <. 005). Spermatozoal number was correlated (P <. 01) with serum and myometrial Se concentrations (r=.67 and .78, respectively) and these concentrations were greater (P <. 001) in treated animals. Low Se status was not associated with ova fertilization in this study; however, greater spermatozoal numbers for fertilized ova collected from Se+E-treated cows suggests increased sperm transport.

Journal Article↗

Completing the fertility transition in the developing world: The role of educational differences and fertility preferences.

This study summarizes patterns of educational differentials in wanted and unwanted fertility at different stages of the fertility transition. The data are from Demographic and Health Surveys in 57 less developed countries. As the transition proceeds, educational differentials in wanted fertility tend to decline and differentials in unwanted fertility tend to rise. An assessment of fertility patterns in developed and less developed countries with low fertility concludes that these differentials are likely to remain substantial when less developed countries reach the end of their transitions. This conclusion implies that the educational composition of the population remains a key predictor of overall fertility in late transitional countries and that low levels of schooling can be a cause of stalling fertility.

Birth Rate↗

Regeneration of Fertile Barley Plants from Mechanically Isolated Protoplasts of the Fertilized Egg Cell.

A simple procedure is described for the mechanical isolation of protoplasts of unfertilized and fertilized barley egg cells from dissected ovules. Viable protoplasts were isolated from ~75% of the dissected ovules. Unfertilized protoplasts did not divide, whereas almost all fertilized protoplasts developed into microcalli. These degenerated when grown in medium only. When cocultivated with barley microspores undergoing microspore embryogenesis, the protoplasts of the fertilized egg cells developed into embryo-like structures that gave rise to fully fertile plants. On average, 75% of cocultivated protoplasts of fertilized egg cells developed into embryo-like structures. Fully fertile plants were regenerated from ~50% of the embryo-like structures. The isolation-regeneration techniques may be largely genotype independent, because similar frequencies were obtained in two different barley varieties with very different performance in anther and microspore culture. Protoplasts of unfertilized and fertilized eggs of wheat were isolated by the same procedure, and a fully fertile wheat plant was regenerated by cocultivation with barley microspores.

Journal Article↗

Complete failure of fertilization in couples with mechanical infertility: implications for subsequent in vitro fertilization cycles.

OBJECTIVE: To determine whether complete failure of fertilization of oocytes in couples with mechanical infertility during the first IVF cycle indicates a poor prognosis for subsequent IVF cycles. DESIGN: A retrospective study of 172 cycles of IVF in 50 couples with mechanical infertility and complete failure of fertilization during their first IVF trial. SETTING: In vitro fertilization unit of the Sheba Medical Center. PATIENTS: Fifty couples undergoing one to eight cycles of IVF for mechanical infertility. MAIN OUTCOME MEASURE(S): Fertilization rate of retrieved oocytes and pregnancy rate. RESULTS: Of the initial 50 couples, 44 underwent additional IVF cycles, and 43 (97.7%) achieved fertilization during the second or third cycle. Twenty-four patients conceived during the study period as a result of IVF. CONCLUSIONS: Complete failure of fertilization in couples with mechanical infertility does not necessarily persist during subsequent IVF cycles. Therefore, at least two more IVF cycles should be attempted before reverting to other therapeutic options. Complete failure of fertilization during the first cycle of IVF in couples with mechanical infertility is accompanied by a good prognosis for subsequent cycles.

Female↗

Late fertilization of unfertilized human oocytes in in vitro fertilization and intracytoplasmic sperm injection cycles: conventional insemination versus ICSI.

PURPOSE: The aim of this study was to evaluate the efficacy of intracytoplasmic sperm injection (ICSI) in comparison with conventional reinsemination using fertilization failed oocytes by conventional in vitro fertilization (IVF). METHODS: Oocytes were collected from patients of IVF or ICSI cycles. Patients were grouped by fertilization techniques: group 1: conventional IVF; group 2: reinsemination after conventional IVF failure; group 3: regular ICSI; group 4: 1-day-old ICSI after conventional IVF failure; group 5: 2-day-old ICSI after conventional IVF failure; group 6: re-ICSI after regular ICSI failure. RESULTS: In different insemination groups, normal fertilization rate was higher (P < 0.001) in 1-day-old ICSI (47.1%) and 2-day-old ICSI groups (40.0%) than in reinsemination (14.7%). Abnormal fertilization rate was higher (P < 0.05) in re-ICSI group (21.7%) than any other groups (range: 0-8%). Cleavage rate was higher in 1-day-old (36.7%) and 2-day-old ICSI groups (36.0%) than in reinsemination (5.3%, P < 0.001) or re-ICSI groups (17.4%, P < 0.05). Pregnancy rate was 27.6% and 20.0% in conventional IVF and regular ICSI groups, respectively. However, 1-day-old ICSI (group 4) and 2-day-old ICSI (group 5) were attempted once embryo transfer (ET) but failed pregnancy occurred in each group. CONCLUSIONS: In fertilization failure cycles, late ICSI increases the rate of fertilization and embryonic development and may rescue the completely failed attempt of pregnancy.

Adult↗

Evaluation of bull semen fertility by homologous in vitro fertilization tests.

In vitro fertilization assays were performed to investigate their validity in evaluating artificial insemination (AI) bull fertility. A total of 1,532 oocytes, collected from ovaries at the abattoir, were subsequently used in a 4 x 6 x 2 factorial design: 4 doses of heparin added into the capacitation and fertilization medium (0; 0.05; 0.1 and 0.2 micrograms/ml), 6 different bulls with known on-field non-return (NR) rates (range: 64.6-75.3%) and 2 different ejaculates for each bull, collected within a approximately 1-month interval. Oocytes were considered fertilized when 2 pronuclei (or more) were seen in the ooplasm. Both the heparin dose and bull exerted a highly significant effect on the in vitro fertilization (IVF) rates which ranged, per oocyte group, from 30-80%; bull x dose of heparin interaction was significant (P less than 0.001). The 0.05 micrograms/ml dose of heparin was optimal for discriminating individual bulls. At that dose, the correlation coefficients between the bulls, NR rates and the IVF rates from each ejaculate (within-bull or the mean of two ejaculates), were highly significant (r = 0.83). The rates of polyspermy were also significantly influenced by bull and heparin dose, but there was no interaction. In conclusion, capacitation and fertilization in a modified Tyrode medium containing 0.05 micrograms/ml of heparin may be a valuable tool for evaluating AI bull fertility.

Animals↗

A bridge to intracytoplasmic sperm injection--high insemination concentrations benefit patients who have a reduced chance of fertilization with standard in-vitro fertilization.

This study was carried out to determine whether high insemination concentrations (HIC) could improve fertilization and pregnancy rates in patients who had either previously demonstrated poor fertilization rates in vitro using standard protocols (Group 1) or in whom a reduced chance of fertilization was indicated at semen assessment prior to in-vitro fertilization (IVF) (Groups 2 and 3). Forty nine patients were recruited for the study. Standard IVF was carried out in 1 ml volumes using 10(5) spermatozoa/ml. HIC treatment involved co-culture of spermatozoa and oocytes in microdroplets with insemination concentrations increased 10-50 fold higher than standard IVF. Fertilization and pregnancy rates were compared between standard IVF and HIC in individual patients either in consecutive cycles (Group 1) or using sibling oocytes in the same cycle (Group 2). Group 3 patients were treated with HIC for their first treatment cycle. HIC significantly improved the fertilization rate compared with standard IVF for Groups 1 (59.7 +/- 10.7 versus 19.6 +/- 5.4% respectively) and 2 (54.9 +/- 8.5 versus 34.0 +/- 8.5% respectively). HIC increased the pregnancy rate from 0% with standard IVF to 20% per embryo transfer in Group 1 patients. A single pregnancy derived from the transfer of HIC and IVF embryos occurred in Group 2. The fertilization rate (47.2 +/- 7.6%) and pregnancy rate (31.3% per embryo transfer) for Group 3 patients was higher than predicted. There was no increase in the rate of polyploidy with HIC. Provided there are sufficient numbers of motile spermatozoa, HIC may be offered as an initial form of treatment, thus permitting referral of only the poorest responders for intracytoplasmic sperm injection (ICSI).

Adult↗

Fertility-associated antigen on bull sperm indicates fertility potential.

A 30-kDa heparin-binding protein named fertility-associated antigen (FAA) was identified in sperm membranes of beef bulls with greater fertility potential. In a survey of 2,191 beef bulls, 88% had FAA present in sperm membranes (FAA-positive), and 12% were FAA-negative. In the first study, 54 Santa Gertrudis and 51 Santa Cruz bulls were grouped (1 to 14 bulls per group) according to FAA profiles and were bred to 2,403 cows at ratios of 1 bull: 25 cows. Fertility for 14 groups of FAA-positive bulls averaged 88%, whereas three groups of FAA-negative bulls impregnated 79% of the cows. Thus, FAA-positive bulls were nine percentage points more (P < .01) fertile than FAA-negative bulls. In the second study, 2-yr-old Santa Cruz bulls (n = 26) were grouped according to FAA profiles and serving capacity. The fertility of the group of 12 high-serving-capacity, FAA-positive bulls was 87% of 270 cows. The group of six FAA-negative bulls with high serving capacity impregnated 78% of 143 cows. Among the groups of bulls with high serving capacity, FAA-positive bulls were nine percentage points more (P < .05) fertile than FAA-negative bulls. The group of eight FAA-positive bulls with low serving capacity impregnated the least (P < .01) percentage (69%) of 238 cows. Serving capacity of bulls should be considered when optimizing fertility potential. Among bulls with acceptable physical characteristics and serving capacity, determination of FAA profiles in sperm can be used as a tool to identify subfertile bulls.

Animals↗

Genetic parameters for female fertility traits and a fertility index in Spanish dairy cattle.

Genetic correlations among female fertility traits (linear and binary) were estimated using 225,085 artificial insemination records from 120,713 lactations on 63,160 Holstein cows. Fertility traits were: calving interval, days open, a linear transformation of days open, days to first insemination, interval between first and last insemination, number of inseminations per service period, pregnancy within 56 and 90 d after first insemination, and success in first insemination. A bivariate animal model was implemented using Bayesian methods in the case of binary traits. Low heritabilities (0.02 to 0.06) were estimated for these fertility traits. Strong genetic correlations (0.89 to 0.99) were found among traits, except for days to first service, where the genetic correlation with other fertility traits ranged from -0.52 to -0.18 for binary traits, and from 0.50 to 0.82 for days to first service, calving interval, and days open. Four fertility indices were proposed utilizing information from insemination records; these indices combined one indicator of the beginning of the service period and one indicator of conception rate. Two additional indices used information from the milk-recording scheme, including calving interval and a linear transformation of days open. The fertility index composed of days to first service and pregnancy within 56 d achieved the highest genetic gain for reducing fertility cost, reducing days to first service, and reducing the number of inseminations per lactation ($8.60, -1.31 d, and -0.03 AI, respectively). This index achieved at least 15% higher genetic gain than obtained from indices with information from the milk recording scheme only (calving interval and days open).

Analysis of Variance↗

[Evaluation of the fertility of human sperm by interspecies (man-hamster) in vitro fertilization].

An "in vitro" fertilization test employing zona-free hamster eggs was used to analyse human spermatozoal fertilizing ability. Sperms from 28 men (group 1) whose wives were candidates for "in vitro" fertilization and embryo transfer, and from 5 men belonging to infertile couples (group 2), were evaluated for their ability to penetrate and decondense in zona-free hamster ova. All men had spermiograms in the normal range. A total of 529 eggs were inseminated with spermatozoa from group 1 and the fertilization rate was found to range from 8% to 100% with an average of 57.5%. Of the 130 ova tested with sperm from group 2 individuals, only one showed any evidence of penetration. The fertilization rate and the degree of polyspermy failed to show a significant correlation with sperm concentration in the ejaculate or motility. This cross-species system is a useful additional test to the classic spermiogram and may have a potential value as a diagnostic tool in evaluating human spermatozoal fertilizing capacity, avoiding the ethical and logistical problems associated with fertilization of human eggs "in vitro".

Animals↗

Failure of fertilization in in vitro fertilization: the "occult" male factor.

Failure of fertilization in patients undergoing in vitro fertilization (IVF) deserves extensive analysis for better prediction of the success or failure of this therapeutic modality. Consequently, we retrospectively studied the 52 couples in whom fertilization failed during Norfolk series 18 to 25, in an effort to establish the precise causes of failure. In the initial evaluation, pure oocyte abnormalities were identified in 19.2% of the cases; 32.6% showed sperm abnormalities, and a combination of oocyte and sperm anomalies was found in 7.7%. In 40.4% of the cases, failure of fertilization could not be explained. Reassessment of sperm morphology by new, strict criteria increased the identification of sperm abnormalities to 61.5% and of combined sperm and oocyte anomalies to 13.4%, for a total of 74.9% of sperm factors involved, as opposed to 40.3% in the original evaluation. The incidence of unexplained failed fertilization was substantially reduced, to 11.5%. In a control group (tubal infertility) matched by age, date, and stimulation, in whom fertilization occurred, 83.3% had normal sperm parameters as judged by the new criteria for morphology evaluation. This paper emphasizes the need for a more accurate diagnosis of sperm abnormalities to establish the true incidence of this factor in failed fertilization and to obtain information of prognostic value to patients and clinicians.

Adult↗

Failed fertilization in human in vitro fertilization analyzed with the deoxyribonucleic acid-specific fluorochrome Hoechst 33342.

The degree and normality of nuclear maturation were assessed with the fluorochrome Hoechst 33342 in two groups of inseminated human oocytes that had failed to undergo fertilization. Group 1 consisted of 67 oocytes from 27 patients, each of whom had at least two other oocytes that had been fertilized and had cleaved. Group 2 consisted of 65 oocytes from 14 patients, none of whose oocytes had been fertilized. In group 1, 52.3% of the oocytes were found to be immature (germinal vesicle stage or metaphase-telophase I), whereas in group 2 only 26% were found to be immature. Thus oocyte nuclear immaturity was the major cause of fertilization failure when companion oocytes were fertilized. When no oocytes of a patient were fertilized, most oocytes were found to be mature, so other factors, such as sperm dysfunction or zona binding abnormalities, must account for most of the fertilization failure in this group of patients.

Benzimidazoles↗

A comparison of the fertile phase as determined by the Clearplan Easy Fertility Monitor and self-assessment of cervical mucus.

The purpose of this study was to compare the fertile phase of the menstrual cycle as determined by the Clearplan Easy Fertility Monitor (CPEFM) with self-monitoring of cervical mucus. One-hundred women (mean age = 29.4 years) observed their cervical mucus and monitored their urine for estrogen and luteinizing hormone metabolites with the CPEFM on a daily basis for 2-6 cycles and generated 378 cycles of data; of these, 347 (92%) had a CPEFM peak. The beginning of the fertile window was, on average, day 11.8 (SD = 3.4) by the monitor and day 9.9 (SD = 3.0) by cervical mucus (r = 0.43, p < 0.001). The average first day of peak fertility by the monitor was 16.5 (SD = 3.6) and by cervical mucus 16.3 (SD = 3.7) (r = 0.85, p < 0.001). The mean length of the fertile phase by the monitor was 7.7 days (SD = 3.1) and by cervical mucus 10.9 days (SD = 3.7) (t = 12.7, p < 0.001). The peak in fertility as determined by the monitor and by self-assessment of cervical mucus is similar but the monitor tends to underestimate and self-assessment of cervical mucus tends to overestimate the actual fertile phase.

Adolescent↗

Successful fertilization and pregnancy after intracytoplasmic sperm injection and oocyte activation with calcium ionophore in a normozoospermic patient with extremely low fertilization rates in intracytoplasmic sperm injection cycles.

OBJECTIVE: To investigate the effect of calcium ionophore on the fertilization rate of a patient with normozoospermia who nonetheless exhibited a low fertilization rate in intracytoplasmic sperm injection (ICSI). DESIGN: Case report. SETTING: In vitro fertilization center. PATIENT(S): A male patient whose sperm, though diagnosed as normal by semen analysis, exhibited a severely low fertilization rate in ICSI cycles. INTERVENTION(S): Oocytes were activated by calcium ionophore after ICSI. MAIN OUTCOME MEASURE(S): Fertilization rate after oocyte activation; ultrastructure and protein expression of the patient's sperm. RESULT(S): The fertilization rate of oocytes activated with calcium ionophore (12 of 15, 80.0%) was higher than that of the nonactivated oocytes (4 of 16, 25.0%). Four embryos derived from the activated oocytes were transferred, resulting in a twin pregnancy. Further investigation revealed abnormalities in the patient's sperm: many nuclear vacuoles were observed and the expression of some proteins was absent. CONCLUSION(S): Oocyte activation with calcium ionophore was effective at increasing the fertilization rate of dysfunctional sperm characterized by ultrastructural and protein expression anomalies.

Adult↗

Sperm protamine 1/protamine 2 ratios are related to in vitro fertilization pregnancy rates and predictive of fertilization ability.

OBJECTIVE: To evaluate whether aberrant sperm P1/P2 ratios are predictive of abnormal fertilizing ability and are related to in vitro fertilization (IVF) outcome. DESIGN: Prospective case-control study. SETTING: University-based infertility and IVF clinic. PATIENT(S): Forty-three male infertility patients with an abnormally reduced P1/P2 ratio, 251 patients with a normal P1/P2 ratio, and 121 patients with an abnormally elevated P1/P2 ratio. INTERVENTION(S): Human IVF, the sperm penetration assay (SPA), and sperm protamine quantification via nuclear protein extraction, gel electrophoresis, and densitometry analysis. MAIN OUTCOME MEASURE(S): Sperm P1/P2 ratios; P1 and P2 quantities; SPA scores; and IVF-fertilization, embryo-quality, pregnancy, delivery, and spontaneous-abortion rates. RESULT(S): Standard IVF fertilization rates and SPA scores were significantly reduced in patients with abnormally low and high P1/P2 ratios. In vitro fertilization embryo quality was comparable between these groups, but pregnancy rates were significantly reduced in patients with abnormally reduced P1/P2 ratios. CONCLUSION(S): The P1/P2 ratio has a significant relationship to sperm fertilization ability. The relationship between protamines and fertilization ability is not understood but may be either a reflection of generalized abnormalities during spermiogenesis or an indication of protamine deficiency acting as a regulator or checkpoint of spermatogenesis.

Biomarkers↗