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PubMed2006

Fertility rates and future population trends: will Europe's birth rate recover or continue to decline?

Europe has long completed its demographic transition from high birth and death rates to low birth and death rates. But the demographic transition paradigm that has been very useful for explaining global demographic trends during the 20th century and that still has strong predictive power when it comes to projecting future trends in countries that still have high fertility, has nothing to say about the future of fertility in Europe. The currently popular notion of a 'second demographic transition' is a useful way to describe a bundle of behavioural and normative changes that recently happened in Europe, but it has no predictive power. The social sciences have not yet come up with a useful theory to predict the future fertility level of post-demographic transition societies. We even do not know whether the trend will be up or down. Given the lack of a predictive theory, this paper will try to do two things: (i) Summarize different substantive arguments that would either suggest the assumption of a recovery of fertility rates in Europe or alternatively, imply further declines. (ii) Convert this discussion of the uncertainty of future fertility trends into probabilistic population projections for Europe, thus highlighting the implications of alternative fertility levels over the coming years. We will also discuss trade-offs between fertility and immigration, and the phenomenon that Europe now has entered a period of negative momentum of population growth.

Birth Rate↗
PubMed2005

Differences between Belclare and Suffolk ewes in fertilization rate, embryo quality and accessory sperm number after cervical or laparoscopic artificial insemination.

Ewe breed has been shown to have a major effect on pregnancy rates following cervical AI using frozen-thawed semen. The main objective of this study was to examine the differences between purebred Belclare and Suffolk ewes (multiparous) in fertilization rate, number of accessory sperm and stage of embryo development on day 6 after cervical or laparoscopic AI with frozen-thawed semen. In experiment 1, Belclare and Suffolk ewes were synchronized for 12 days and were either cervically inseminated (year 1: n=28 and 31; year 2: n=16 and 15, respectively) or laparoscopically inseminated (year 2: n=13 and 14). In experiment 2, superovulated Belclare (n=4) and Suffolk (n=13) ewes were laparoscopically inseminated. All ewes were slaughtered 6 days after AI; oocytes/embryos were recovered, morphologically graded and stained to assess the number of cells and accessory spermatozoa. Data from both experiments were combined for statistical analysis. The proportion of ewes with fertilized oocytes was significantly higher following laparoscopic AI compared with cervical AI (54% versus 19%). More Belclare than Suffolk ewes yielded fertilized oocyte(s) after cervical AI (34% versus 10%, P<0.02) but there was no difference after laparoscopic AI (62% versus 60%). From the ewes that yielded at least one fertilized oocyte the proportion of Belclare ewes with embryos at the morula/blastocyst stage was significantly greater than for Suffolk ewes (94% versus 59%, P<0.02). A higher proportion of Belclare than Suffolk ewes had evidence of sperm reaching the site of fertilization following cervical AI (39% versus 15%, P<0.02) but there was no difference after laparoscopic AI (62% versus 64%, P>0.8). Amongst the ewes with evidence of sperm at the site of fertilization, laparoscopic AI resulted in a higher number of sperm per oocyte/embryo or per ewe than cervical AI (P<0.01). These results suggested that the difference in pregnancy rate between Suffolk and Belclare ewes following cervical AI was due to: (i) sperm traversing the cervix and uterus in a higher proportion of Belclare than Suffolk ewes, leading to a higher incidence of fertilization and (ii) the lower developmental competence of fertilized oocytes from Suffolk ewes.

Animals↗
PubMedDate not supplied

In vitro fertilization rate of mouse eggs with sperm after X-irradiation at various spermatogenetic stages.

The frequency of in vitro fertilization of mouse eggs using sperm obtained weekly (for 1-9 weeks) from epididymis after testicular X-irradiation (200 rad) was observed. The sperm concentrations for insemination were 100, 200 and 300/mm3. The number of fertilized eggs seemed to remain constant almost at control level (90-98%) until the 4th week after X-irradiation. Thereafter, the number declined to reach a minimum level (about 30-50%) in the 6th week; they then recovered completely in the 8th week. This tendency was found at all sperm concentrations used. This result indicates that the most sensitive stage for the fertilization capacity of sperm to X-rays was the early spermatocytes or the late spermatogonia. The high radiosensitivity of the fertilization capacity of sperm irradiated during the early-spermatocyte to late-spermatogonial stage, corresponded well with the rate of induction of sperm abnormalities and spermatogenetic cell killing. The in vitro fertilization rate was not restored by an increase in sperm concentration at insemination; it is, therefore, likely that the in vitro fertilization frequency depends on the proportion of sperm with abnormal morphology and abnormal fertilization ability, and sperm number seems to have hardly any influence on the fertilization rate, as far as the in vitro fertilization experiment is concerned.

Animals↗
PubMed1988

Fertilization in vitro of bovine oocytes: analysis of some factors affecting the fertilization rates.

Ovarian follicles were aspirated from superovulated heifers at different periods from the beginning of standing heat. The follicular fluid of these follicles was analyzed for progesterone, estradiol, testosterone and androstenedione concentrations and compared to the maturation stages of the oocytes and their ability to undergo fertilization in vitro. The results obtained suggest that high concentrations of progesterone, testosterone and androstenedione compared to a lower concentration of estradiol correspond to a high proportion of M-II oocytes and a high in vitro fertilization rate.

Animals↗
PubMed1984

Effect of confinement, climatic conditions and litter parity on the seasonal variations of the fertility rate and prolificacy.

Prolificacy and fertility in sows were analysed according to the month of service, the regional locations of the herd, the type of building (confinement or open front) and the parity of the sows. Fertility varied throughout the year and was lowest in August, September and October. The regional location of the herd had little or no effect. Primiparous sows were less fertile than multiparous sows, regardless of the type of building. Results for closed buildings were better than those for semi-outdoor quarters. This difference was maximum (8%) for matings in August, September and October. Prolificacy also varied with season but was relatively unaffected by the type of housing. The largest litters were conceived in summer when the ovulation rate was highest. The extend of seasonal variation in prolificacy was higher in Brittany than in the South of France in which hot climatic conditions are more frequent in summer. The month of service and the type of housing appear to be the most important factors conditioning the annual productivity of sows.

Animals↗
PubMed1994

Superovulation in red deer (Cervus elaphus) and Père David's deer (Elaphurus davidianus), and fertilization rates following artificial insemination with Père David's deer semen.

Two comparative studies were undertaken using adult, female red and Père David's deer to examine the ovulatory response of these animals to a superovulation regimen and fertilization rates following inter- and intraspecific laparoscopic insemination. In Expt 1 six Père David's deer and 12 red deer hinds were treated during the breeding season with an intravaginal progesterone-impregnated controlled internal drug release device (CIDR) for 14 days, with 200 iu pregnant mares' serum gonadotrophin (PMSG) administered 72 h before the device was withdrawn and eight injections of ovine FSH given at 12 h intervals starting at the time of PMSG administration. Oestrous behaviour began one day after CIDR device withdrawal (Père David's deer: 24.00 +/- 2.32 h; red deer: 24.60 +/- 2.23 h). The duration of oestrus was greater in Père David's deer than in red deer (17.50 +/- 1.43 h and 8.25 +/- 3.25 h, respectively, P < 0.001). The peak LH surge of Père David's deer was 68.65 +/- 4.74 ng ml-1 occurring 29.00 +/- 2.41 h after removal of the CIDR devices. In comparison, the peak LH surge in red deer was 17.09 +/- 3.64 ng ml-1 (P < 0.001), occurring 24.00 +/- 0.00 h after CIDR device withdrawal. Pre-surge concentrations of LH were also greater (P < 0.001) in Père David's deer (1.37 +/- 0.11 ng ml-1) than in red deer hinds (0.41 +/- 0.02 ng ml-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Hormonal stimulation for in vitro fertilization: a comparison of fertilization rates and cytogenetic findings in unfertilized oocytes.

OBJECTIVE: The purpose of this study was to compare fertilization and aneuploidy rates after two stimulation protocols in an IVF program. DESIGN: This was a retrospective study. SETTING: The study took place in the IVF laboratory of an Infertility Department. METHODS: In 349 treatment cycles, clomiphene citrate (CC) and human menopausal gonadotropin (hMG) were used in one group (N = 233) and hMG after treatment with a gonadotropin-releasing hormone agonist (GnRHa) in two other groups (long protocol): goserelin (N = 73) and buserelin (N = 43). Cytogenetic analysis was performed on all unfertilized oocytes in both groups. RESULTS: Fertilization rates were significantly higher in the GnRHa/hMG group than in the CC/hMG group, but cleavage rates and embryo quality were not different. Of 736 oocytes prepared for cytogenetic analysis, 256 were karyotyped: 172 were found to be euploid and 84 aneuploid. More oocytes were aneuploid in the GnRHa/hMG group than in the CC/hMG group and this difference was statistically different after analysis of the data using a specially designed mathematical model. CONCLUSION: If no selection against chromosomally abnormal oocytes takes place at the time of fertilization, more abnormal oocytes are harvested with GnRHa/hMG protocols than with CC/hMG. If, on the other hand, there is a selection against oocytes with some chromosomal imbalance, there is no intrinsic effect of GnRH agonists on the chromosomal complement of the oocyte, and the real aneuploidy frequency in all oocytes, fertilized and unfertilized, is the same in the GnRHa/hMG and in the CC/hMG group.

Aneuploidy↗
PubMed2005

[Correlation of intersubspecific hybrid rice spikelet fertilization rate with temperature and related statistic model].

Using four types of rice, i. e., indica-japonica hybrid, intermediate hybrid, indica and japonica cultivars as test materials, this paper studied the sensitivity of intersubspecific hybrid rice to climatic factors, and the correlations between spikelet fertilization rate (SFR) and daily meteorological factors during 2000 and 2001. The results showed that the SFR of intersubspecific hybrids was lower than that of indica and japonica cultivars. Among eleven meteorological factors, temperature was the key factor, and the mean temperature within five or seven days around panicle flower blooming affected the SFR significantly. A comprehensive model of SFR-temperature was established, with which, the fittest temperature and safe temperature for fertilization of intersubspecific hybrids was estimated to be 28.2 - 29.3 degrees C and 23.4 - 24.3 degrees C, 2.2 degrees C and 1.5 degrees C higher than those of indica and japonica cultivars, respectively. It was suggested that the safe heading date for planting intersubspecific hybrid should be moved up to the last ten-day of September to the first ten-day of October in southern China, the first ten-day of September in middle and lower reaches of Yangtze River Valley, and the last ten-day of August to the first ten-day of September in rice planting area between Yangtze and Huai River.

Chromosomes, Plant↗
PubMed2005

Relationship between nuclear chromatin decondensation (NCD) in vitro and other sperm parameters and their predictive value on fertilization rate in IVF program.

PURPOSE: The purpose of this study was to determine the in-vitro induced nuclear chromatin decondensation (NCD) of human spermatozoa and its value in combination with routine semen analysis in predicting the outcome of in-vitro fertilization (IVF). METHODS: The ejaculate of 52 couples, undergoing IVF, was incubated with lithium diidosalicylic acid (LIS) and dithiothreitol (DTT) (G.1) or with heparin and sodium dodecyl sulphate (SDS) (G.2) to induce chromatin decondensation (NCD). Smears were made at 30, 60, and 120 min after incubation. RESULTS: NCD was evaluated by morphometrical detection of the surface area of the spermatozoa using a semiautomatic image analysis system (IBAS). In both groups, the sperm heads showed a significant enlargement after 30, 60, and 120 min incubation in comparison to the initial size. However, no correlation was found between NCD at various periods of time and the fertilization rates. The mean area of the sperm heads in the native sample in the G.1 was 9.45+/- 1.33 microm(2) and 9.02+/- 1.15 microm(2) in the G.2. This area increased after incubation for 30, 60, and 120 min to 10.92 +/- 1.48, 12.26+/- 2.16, 13.54+/- 3.14, and 15.35+/- 7.78 microm(2) in the first group (G.1) and to 10.29 +/- 1.15, 11.23 +/- 1.85, 11.46 +/- 1.97, and 11.27 +/- 2.82 microm(2) in the second group, respectively. CONCLUSIONS: NCD in vitro after incubation with LIS + DTT or heparin + SDS could not be recommended as a predictive parameter for IVF outcome.

Chromatin↗
PubMed1994

Long-run migration incentives and migration effects: the case of different fertility rates.

"In this paper the direction of the long-run migration incentive in the presence of closed borders and the long-run welfare effects of a regime change from 'autarky' to 'free permanent migration' are studied. A difference in birth-country specific fertility rates is treated as the final cause for the creation of migration incentives in a two-country model where the standard overlapping-generations framework is used.... Opening the borders for permanent migration can always lead to the equalization of labour force growth rates. A continuum of such equilibria with migration does exist, but the application of the concept of migration-stability, introduced in this paper, gives reason to the suspicion that free migration can also lead to a collapse of the emigration country's economy." (SUMMARY IN GER)

Demography↗
PubMed2001

Fertilization rate and preimplantation development after intracytoplasmic sperm injection.

Intracytoplasmic sperm injection (ICSI) is the treatment of choice in cases of male factor infertility. In the present review, all data from the literature regarding early fertlilization and preimplantation embryo development are analysed. ICSI seems to offer better fertilization rates than conventional IVF, even in the absence of a male factor and in prospective, randomized studies on sibling oocytes. Blastocyst formation is lower in ICSI than in IVF. This may be due to sublethal disturbances in oocyte architecture and function. Implantation and pregnancy rates, however, are similiar in ICSI and conventional IVF. Therefore, it can be concluded that ICSI offers a safe approach, as far as is known to date, for the treatment of male factor infertility. Embryo selection in cases of sublethal damage to oocytes seems to take place in the early preimplantation stages. Nor does the risk of monozygotic twinning, which was also proposed to be higher in ICSI compared with conventional IVF, seem to increase with this procedure.

Journal Article↗
PubMedDate not supplied

Immunization with spermatozoal peptide antigens resulting in immuno-suppression of fertility rates in female rats.

Low molecular weight peptides have been isolated from the rat epididyml sperm surface using gel chromatography and preparative thin-layer chromatography. After coupling the partially purified peptides to rat albumin these were injected into female Wistar rats. Immunization with these spermatozoal peptides resulted in significantly reduced fertility rates as determined by the frequency of pregnancies and the number of fetuses per rat. The purification steps revealed that these rat spermatozoal peptides were comparable with peptides isolated form human ejaculated spermatozoa. It is therefore assumed that immunization with these antigens might induce sterility in humans.

Animals↗
PubMed1987

Capacitation-related changes in antigen distribution on mouse sperm heads and its relation to fertilization rate in vitro.

The anti-mouse sperm monoclonal antibody OBF13 did not react with fresh epididymal sperm. However, when sperm were incubated in a culture medium capable of inducing capacitation, the entire head of the sperm began to react with this antibody. This change of reactivity was not observed when sperm were incubated in a Ca2+-free medium. The change of the reactivity to the antibody was studied in relation to the fertilizing ability of sperm as measured in an in vitro fertilization system; a significant correlation was observed between the appearance of head-stained sperm and fertilization rate.

Acrosome↗
PubMed2000

Correlation of oocyte morphology with fertilization rate and embryo quality after intracytoplasmic sperm injection.

To determine whether the morphology of the oocyte assessed under light microscopy is related to the results of intracytoplasmic sperm injection (ICSI). 135 ICSI oocytes from 15 patients were analyzed. Transvaginal ultrasound-guided oocytes retrieval with oocyte morphology evaluation based on shape of the first polar body and perivitelline space followed by ICSI. After 48 hours, embryo quality was evaluated and compared to each pre-injected oocyte morphology. Normal fertilization was achieved in 81.5 per cent of the oocytes (110/135). Abnormal fertilization (3 pronuclei) was 1.5 per cent (2/135). Fertilization rate of oocytes with good morphology was higher than those with poor morphology, but there was no statistical significance (82.4% vs 79.5%; p > 0.05). Oocytes with good morphology were significantly fertilized to be embryos with good quality (p < 0.001). This study suggests that oocyte morphology correlates with embryo quality after ICSI.

Adult↗