Electromagnetic Field (EMF) Radiation Alters Estrogen Release from the Pig Myometrium during the Peri-Implantation Period.

An electromagnetic field (EMF) may affect the functions of uterine tissues. This study hypothesized that EMF changes the estrogenic activity of pig myometrium during the peri-implantation period. Tissue was collected on days 15-16 of the gestation and incubated in the presence of EMF (50 and 120 Hz, 2 and 4 h). The cytochrome P450 aromatase type 3 (CYP19A3) and hydroxysteroid 17ß dehydrogenase type 4 (HSD17B4) mRNA transcript abundance, cytochrome P450arom (aromatase), and 17ß hydroxysteroid dehydrogenase 17ßHSD) protein abundance and estrone (E1) and estradiol-17ß (E2) release were examined using Real-Time PCR, Western blot and radioimmunoassay. Selected myometrial slices were treated with progesterone (P4) to determine whether it functions as a protector against EMF. CYP19A3 mRNA transcript abundance in slices treated with EMF was less at 50 Hz (2 h) and greater at 120 Hz (2 and 4 h). HSD17B4 mRNA transcript was greater in slices treated with EMF at 120 Hz (2 h). Progesterone diminished EMF-related effects on CYP19A3 and HSD17B4. When P4 was added, EMF had suppressive (50 and 120 Hz, 2 h) or enhancing (50 Hz, 4 h) effects on aromatase abundance. The E1 release was lower after 4 h of EMF treatment at 50 Hz and P4 did not protect myometrial E1 release. In conclusion, EMF alters the synthesis and release of E1 and did not affect E2 release in the myometrium during the peri-implantation period.

Effects of electromagnetic field (EMF) radiation on androgen synthesis and release from the pig endometrium during the fetal peri-implantation period.

An electromagnetic field (EMF) may have effects on female reproduction. This study was conducted to determine whether EMF [50 and 120 Hz, 2 and 4 h of incubation in the presence or absence of progesterone (P4, 10-5 M)] affects androgen synthesis and release from the pig endometrium. Endometrial slices were collected from pigs (n = 5) during the fetal peri-implantation period (i.e., days 15-16 of gestation) and treated in vitro with EMF. The selected endometrial slices were treated with P4 to determine whether this hormone has effects on protection of the tissue from EMF radiation. The CYP17A1 and HSD3B1 mRNA transcript abundance, steroid 17αhydroxylase/17, 20-lyase (cytochrome P450c17) and hydroxyΔ5steroid dehydrogenase/3ß and steroidΔisomerase (3ßHSD) protein abundance were examined using Real-Time PCR and Western Blot procedures, respectively. In media collected after incubation, the concentrations of androstenedione (A4) and testosterone (T) were quantified used a RIA. When P4 was added to the culture medium, EMF radiation had suppressive effects on endometrial T release after 2 and 4 h of incubation when the EMF treatment was occurring and increased A4 release after 4 h of incubation with EMF at 120 Hz. When there was no inclusion of P4, release of A4 was decreased after 2 h of EMF treatment at 120 Hz and after 4 h of EMF treatment at 50 and 120 Hz. Progesterone did not have functions that protected the pig endometrium against EMF radiation during the fetal peri-implantation period.

Controlled hatching at the prescribed site using femtosecond laser for zona pellucida drilling at the early blastocyst stage.

PURPOSE: To study whether the application of femtosecond laser pulses for zona pellucida (ZP) drilling of blastocysts at the embryonic or abembryonic poles can promote hatching to start immediately through the hole formed and ensure high hatching rates and embryo viability. METHODS: Mouse blastocyst (E3.5) ZP were microdissected with femtosecond laser pulses (514-nm wavelength, 280-fs pulse duration, 2.5-kHz repetition rate) close to the trophoblast or inner cell mass (ICM). The sizes of the holes formed were in the range of 4.5-8.5 µm. Additional longitudinal incisions (5-7-µm long) on either side of the hole were created to determine whether hatching had started at the correct position. Embryos post-laser-assisted ZP drilling and intact embryos were cultured under standard conditions for 2 days; embryo quality was assessed twice daily. The hatching rates and in vitro and in vivo implantation rates (only for embryos with ZP dissected close to the ICM) were estimated. RESULTS: Femtosecond laser-assisted ZP drilling at the early blastocyst stage facilitated embryo hatching to start at the artificial opening with probability approaching 100%. Despite the artificial opening's small size, no embryo trapping during hatching was observed. Both experimental groups had higher hatching rates than the control groups (93.3-94.7% vs. 83.3-85.7%, respectively). The in vitro implantation rate was comparable with that of the control group (92.3% vs. 95.4%). No statistically significant differences were obtained in the in vivo implantation rates between the experimental and control groups. CONCLUSIONS: Blastocyst-stage femtosecond laser microsurgery of ZP is fast and delicate and enables the hatching process to be initiated in a controlled manner through a relatively small opening, with no embryo trapping.

Laser irradiation pretreatment improves endometrial preparation of frozen-thawed embryo transfer in recurrent implantation failure patients.

Recurrent implantation failure (RIF) remains a clinical dilemma. Helium-Neon (He-Ne) laser irradiation has recently become more popular under certain clinical conditions. Given the unique therapeutic effects, we were interested in determining whether pretreatment with He-Ne laser irradiation prior to frozen-thawed embryo transfer (FET) would improve the microcirculation and cause the release of growth factors and cytokines, thus improving endometrial receptivity and the clinical pregnancy rates. Patients chose for themselves whether to proceed with (n = 29) or without (n = 31) pretreatment with He-Ne laser irradiation prior to FET. The clinical pregnancy rate (37.9%) and implantation rate (20.3%) were higher in the laser-treatment group than in the control group (35.5% and 15.9%, respectively, p = .844 and .518, respectively). The live birth rate was higher in the laser-treatment group (27.6% vs. 25.8%, respectively, p = .876) and the miscarriage rate was lower in the laser-treatment group (18.2% and 27.3%, respectively, p = .611). No side effects or complications from laser irradiation were encountered in patients who received the laser treatment. We concluded that pretreatment with He-Ne laser prior to FET may be an alternative choice for RIF-affected women; however, additional well-designed prospective studies are necessary to determine the precise clinical value of this treatment.

Microgravity inhibits decidualization via decreasing Akt activity and FOXO3a expression in human endometrial stromal cells.

Decidualization is characterized by the differentiation of endometrial stromal cells (eSCs), which is critical for embryo implantation and maintenance of pregnancy. In the present study, we investigated the possible effect of simulated microgravity (SM) on the process of proliferation and in vitro decidualization using primary human eSCs. Exposure to SM for 36 h decreased the proliferation and migration of eSCs significantly, without inducing cell death and changes in cell cycle progression. The phosphorylation of Akt decreased under SM conditions in human eSCs, accompanied by a simultaneous decrease in the level of matrix metalloproteinase (MMP)-2 and FOXO3a. Treatment with Akti, an Akt inhibitor, decreased MMP-2 expression, but not FOXO3a expression. The decreased level of FOXO3a under SM conditions impeded autophagic flux by reducing the levels of autophagy-related genes. In addition, pre-exposure of eSCs to SM significantly inhibited 8-Br-cAMP induced decidualization, whereas restoration of the growth status under SM conditions by removing 8-Br-cAMP remained unchanged. Treatment of human eSCs with SC-79, an Akt activator, restored the reduced migration of eSCs and decidualization under SM conditions. In conclusion, exposure to SM inhibited decidualization in eSCs by decreasing proliferation and migration through Akt/MMP and FOXO3a/autophagic flux.

The effect of light exposure on the cleavage rate and implantation capacity of preimplantation murine embryos.

During assisted reproduction the embryos are subjected to light. We investigated the relationship between light exposure and the developmental- and implantation capacity of mouse embryos. In vitro cultured embryos were exposed to white or red filtered light, then transferred to the uteri of pseudo-pregnant females. The mice were sacrificed on day 8.5 and implantation sites were counted. The number of nucleic acid containing (PI+) extracellular vesicles (EVs) in culture media of light-exposed and control embryos, as well as, the effect of the EVs on IL-10 production of CD8+ spleen cells was determined by flow cytometry. DNA fragmentation in control and light exposed embryos was detected in a TUNEL assay. The effect of light on the expression of apoptosis-related molecules was assessed in an apoptosis array. Light exposure significantly reduced the implantation capacity of the embryos. The harmful effect was related to the wavelength, rather than to the brightness of the light. Culture media of light exposed groups contained significantly higher number of PI + EVs than those of the control embryos, and failed to induce IL-10 production of spleen cells. The number of nuclei with fragmented DNA, was significantly higher in embryos treated with white light, than in the other two groups. In conclusion exposure to white light impairs the implantation potential of in vitro cultured mouse embryos. These effects are partly corrected by using a red filter. Since there is no information on the light sensitivity of human embryos, embryo manipulation during IVF and ICSI should be performed with caution.

The effect of laser-assisted hatching on pregnancy outcomes of cryopreserved-thawed embryo transfer: a meta-analysis of randomized controlled trials.

It is well known that laser-assisted hatching (LAH) is the most popular and ideal embryo hatching technology, but the relevance to pregnancy outcomes of cryopreserved-thawed embryo transfer (ET) is controversial. The purpose of this meta-analysis was to evaluate the effects of LAH on pregnancy outcomes of cryopreserved-thawed ET. We searched for relevant studies published in the PubMed, EMBASE, and Cochrane Central databases up to March 2017. This meta-analysis was primarily used to evaluate the effect of laser-assisted hatching on assisted reproductive outcomes: clinical pregnancy, embryo implantation, multiple pregnancy, miscarriage, and live birth. Using the Mantel-Haenszel fixed effects model and random effects model, we determined the summary odds ratios (OR) with 95% confidence intervals (CIs). There were 12 randomized controlled trials (more than 2574 participants) included in our analysis. The rates of clinical pregnancy (OR = 1.65, 95% CI = 1.24-2.19, I 2 = 49), implantation (OR = 1.59, 95% CI = 1.06-2.38, I 2 = 82%), multiple pregnancy (OR = 2.30, 95% CI = 1.30-4.07, I 2 = 33%), miscarriage (OR = 0.86, 95% CI = 0.50-1.48, I 2 = 0%), and live birth (OR = 1.09, 95% CI = 0.77-1.54, I 2 = 0%) revealed comparable results for both groups. In summary, this meta-analysis demonstrates that LAH is related to a higher clinical pregnancy rate, embryo implantation rate, and multiple pregnancy rate in women with cryopreserved-thawed embryos. However, LAH is unlikely to increase live birth rates and miscarriage rates. Due to the small sample evaluated in the pool of included studies, large-scale, prospective, randomized, controlled trials are required to determine if these small effects are clinically relevant.

Effects of melatonin administration on embryo implantation and offspring growth in mice under different schedules of photoperiodic exposure.

BACKGROUND: Embryo implantation is crucial for animal reproduction. Unsuccessful embryo implantation leads to pregnancy failure, especially in human-assisted conception. Environmental factors have a profound impact on embryo implantation. Because people are being exposed to more light at night, the influence of long-term light exposure on embryo implantation should be explored. METHODS: The effects of long photoperiodic exposure and melatonin on embryo implantation and offspring growth were examined. Long photoperiodic exposure (18:6 h light:dark) was selected to resemble light pollution. Melatonin (10-2, 10-3, 10-4, 10-5 M) was added to the drinking water of mice starting at Day 1 (vaginal plugs) until delivery. RESULTS: Melatonin treatment (10-4,10-5 M) significantly increased litter sizes compared to untreated controls (12.9 ± 0.40 and 12.2 ± 1.01 vs. 11.5 ± 0.43; P < 0.05). The most effective concentration of melatonin (10-4 M) was selected for further investigation. No remarkable differences were found between melatonin-treated mice and controls in terms of the pups' birth weights, weaning survival rates, and weaning weights. Long photoperiodic exposure significantly reduced the number of implantation sites in treated mice compared to controls (light/dark, 12/12 h), and melatonin rescued this negative effect. Mechanistic studies revealed that melatonin enhanced the serum 17ß-estradiol (E2) levels in the pregnant mice and upregulated the expression of the receptors MT1 and MT2 and p53 in uterine tissue. All of these factors may contribute to the beneficial effects of melatonin on embryo implantation in mice. CONCLUSION: Melatonin treatment was associated with beneficial effects in pregnant mice, especially those subjected to long photoperiodic exposure. This was achieved by enhanced embryo implantation. At the molecular level, melatonin administration probably increases the E2 level during pregnancy and upregulates p53 expression by activating MT1/2 in the uterus. All of the changes may improve the microenvironment of the uterus and, thus, the outcomes of pregnancy.

The Protective Effect of N-Acetylcysteine on Ionizing Radiation Induced Ovarian Failure and Loss of Ovarian Reserve in Female Mouse.

Ionizing radiation may cause irreversible ovarian failure, which, therefore, calls for an effective radioprotective reagent. The aim of the present study was to evaluate the potential radioprotective effect of N-acetylcysteine (NAC) on ionizing radiation induced ovarian failure and loss of ovarian reserve in mice. Kun-Ming mice were either exposed to X-irradiation (4 Gy), once, and/or treated with NAC (300 mg/kg), once daily for 7 days before X-irradiation. We examined the serum circulating hormone levels and the development of ovarian follicles as well as apoptosis, cell proliferation, and oxidative stress 24 hours after X-irradiation. In addition, morphological observations on the endometrial luminal epithelium and the fertility assessment were performed. We found that NAC successfully restored the ovarian and uterine function, enhanced the embryo implantation, improved the follicle development, and altered the abnormal hormone levels through reducing the oxidative stress and apoptosis level in granulosa cells while promoting the proliferation of granulosa cells. In conclusion, the radioprotective effect of NAC on mice ovary from X-irradiation was assessed, and our results suggested that NAC can be a potential radioprotector which is capable of preventing the ovarian failure occurrence and restoring the ovarian reserve.

2.45 GHz microwave irradiation-induced oxidative stress affects implantation or pregnancy in mice, Mus musculus.

The present experiment was designed to study the 2.45 GHz low-level microwave (MW) irradiation-induced stress response and its effect on implantation or pregnancy in female mice. Twelve-week-old mice were exposed to MW radiation (continuous wave for 2 h/day for 45 days, frequency 2.45 GHz, power density=0.033549 mW/cm(2), and specific absorption rate=0.023023 W/kg). At the end of a total of 45 days of exposure, mice were sacrificed, implantation sites were monitored, blood was processed to study stress parameters (hemoglobin, RBC and WBC count, and neutrophil/lymphocyte (N/L) ratio), the brain was processed for comet assay, and plasma was used for nitric oxide (NO), progesterone and estradiol estimation. Reactive oxygen species (ROS) and the activities of ROS-scavenging enzymes- superoxide dismutase, catalase, and glutathione peroxidase-were determined in the liver, kidney and ovary. We observed that implantation sites were affected significantly in MW-irradiated mice as compared to control. Further, in addition to a significant increase in ROS, hemoglobin (p<0.001), RBC and WBC counts (p<0.001), N/L ratio (p<0.01), DNA damage (p<0.001) in brain cells, and plasma estradiol concentration (p<0.05), a significant decrease was observed in NO level (p<0.05) and antioxidant enzyme activities of MW-exposed mice. Our findings led us to conclude that a low level of MW irradiation-induced oxidative stress not only suppresses implantation, but it may also lead to deformity of the embryo in case pregnancy continues. We also suggest that MW radiation-induced oxidative stress by increasing ROS production in the body may lead to DNA strand breakage in the brain cells and implantation failure/resorption or abnormal pregnancy in mice.

Rat fertility and embryo fetal development: influence of exposure to the Wi-Fi signal.

In recent decades, concern has been growing about decreasing fecundity and fertility in the human population. Exposure to non-ionizing electromagnetic fields (EMF), especially radiofrequency (RF) fields used in wireless communications has been suggested as a potential risk factor. For the first time, we evaluated the effects of exposure to the 2450MHz Wi-Fi signal (1h/day, 6days/week) on the reproductive system of male and female Wistar rats, pre-exposed to Wi-Fi during sexual maturation. Exposure lasted 3 weeks (males) or 2 weeks (females), then animals were mated and couples exposed for 3 more weeks. On the day before delivery, the fetuses were observed for lethality, abnormalities, and clinical signs. In our experiment, no deleterious effects of Wi-Fi exposure on rat male and female reproductive organs and fertility were observed for 1h per days. No macroscopic abnormalities in fetuses were noted, even at the critical level of 4W/kg.

Selection against spermatozoa with fragmented DNA after postovulatory mating depends on the type of damage.

BACKGROUND: Before ovulation, sperm-oviduct interaction mechanisms may act as checkpoint for the selection of fertilizing spermatozoa in mammals. Postovulatory mating does not allow the sperm to attach to the oviduct, and spermatozoa may only undergo some selection processes during the transport through the female reproductive tract and/or during the zona pellucida (ZP) binding/penetration. METHODS: We have induced DNA damage in spermatozoa by two treatments, (a) a scrotal heat treatment (42 degrees C, 30 min) and (b) irradiation with 137Cs gamma-rays (4 Gy, 1.25 Gy/min). The effects of the treatments were analyzed 21-25 days post heat stress or gamma-radiation. Postovulatory females mated either with treated or control males were sacrificed at Day 14 of pregnancy, and numbers of fetuses and resorptions were recorded. RESULTS: Both treatments decreased significantly implantation rates however, the proportion of fetuses/resorptions was only reduced in those females mated to males exposed to radiation, indicating a selection favoring fertilization of sperm with unfragmented DNA on the heat treatment group. To determine if DNA integrity is one of the keys of spermatozoa selection after postovulatory mating, we analyzed sperm DNA fragmentation by COMET assay in: a) sperm recovered from mouse epididymides; b) sperm recovered from three different regions of female uterine horns after mating; and c) sperm attached to the ZP after in vitro fertilization (IVF). Similar results were found for control and both treatments, COMET values decreased significantly during the transit from the uterine section close to the uterotubal junction to the oviduct, and in the spermatozoa attached to ZP. However, fertilization by IVF and intracytoplasmatic sperm injection (ICSI) showed that during sperm ZP-penetration, a stringent selection against fragmented-DNA sperm is carried out when the damage was induced by heat stress, but not when DNA fragmentation was induced by radiation. CONCLUSION: Our results indicate that in postovulatory mating there is a preliminary general selection mechanism against spermatozoa with low motility and fragmented-DNA during the transport through the female reproductive tract and in the ZP binding, but the ability of the ZP to prevent fertilization by fragmented-DNA spermatozoa is achieved during sperm-ZP penetration, and depends on the source of damage.

Laser-assisted hatching increases pregnancy and implantation rates in cryopreserved embryos that were allowed to cleave in vitro after thawing: a prospective randomized study.

BACKGROUND: Cryopreservation of embryos may lead to zona hardening that may compromise in vivo hatching and implantation following thawing and transfer. Assisted hatching (AH) has been advocated as a means of assisting the natural hatching process and enhancing implantation. METHODS: The aim of this study was to assess in a prospective randomized manner the effect of laser-assisted hatching (LAH) on implantation as well as clinical and multiple pregnancy rates (the primary outcome) after the transfer of frozen-thawed embryos. All embryos were thawed the day before transfer, and LAH was performed the next day on embryos that cleaved. Control group consisted of embryos that were transferred without AH. RESULTS: The performance of LAH significantly increased implantation (9.9 versus 20.1%, P < 0.01), clinical pregnancy (27.3 versus 40.9, P < 0.05) and multiple pregnancy rates (16 versus 40.3%, P < 0.07). In the LAH group, significantly more excess embryos that were left in culture hatched in vitro. CONCLUSIONS: LAH improves the outcome of frozen-thawed embryo transfer when performed before transfer on embryos that were allowed to cleave.

Effects of low-frequency magnetic fields on implantation in rats.

Effects of 50-Hz sinusoidal magnetic fields (MFs) on embryo implantation, serum 17beta-estradiol, progesterone, testosterone, and melatonin levels, and on estrogen receptor (ER) and progesterone receptor (PgR) densities in the uterus were studied during the preimplantation and implantation periods in rats. Pregnant Wistar rats were exposed to magnetic r.m.s. field strengths of 10 or 100 A/m (13 or 130 microT) or sham-exposed (controls) from day 0 of pregnancy for 24 h/day and killed during light and dark periods between 70 h and 176 h after ovulation. MFs did not influence the mean total number of implantations. The nocturnal mean serum melatonin concentration decreased by 34 and 38% at 10 and 100 A/m, respectively. At the same time, the first embryos, at an early developmental stage, arrived in the uterus in the MF-exposed groups. Serum estradiol and progesterone levels did not significantly change. Nuclear PgR and ER densities in the uterus decreased before implantation and there was an increased incidence of early stage embryos and fewer hatched embryos were found in the uterus at 100 A/m. During the early implantation period, the uterine cytosolic ER/PgR-ratio was increased at 100 A/m and no implants were concomitantly found in uterus. The nuclear ER/PgR-ratio decreased during implantation in both MF-groups due to decreased nuclear ER density. At the same time, 19% and 15% of the embryos (calculated from the corpora luteae) at 10 and 100 A/m, respectively, were yet morulae and not implanted. In summary, the results show that MFs do not impair implantation in rats although there may be some borderline changes in the transport and development of embryos and associated endocrinologic parameters.

Lethal and teratogenic effects in two successive generations of the HLG mouse strain after radiation exposure of zygotes -- association with genomic instability?

We analysed the transmission of lethal and teratogenic events to the subsequent generation in HLG/Zte mice after exposure of the zygote stage to 1 Gy X-rays. As observed in previous studies, our results on teratogenic events occurring in the same generation, which was exposed during the zygote stage, reveal a significantly higher risk for the induction of gastroschisis. Interesting new insights came from the study of lethal and teratogenic effects in the generation obtained after mating female mice, which were exposed during their zygote stage, to unexposed males. An approximately 2-fold higher level of damage was manifest in this generation compared with controls, expressed mainly as a significant increase of prenatal mortality (P<0.01). Although there was an increase in the number of malformed fetuses on day 19 of gestation (6.5% cases of gastroschisis compared to 3.5% in the controls), the frequency of gastroschisis in the exposed group was just not statistically significant (P>0.05). These results are in line with the hypothesis that genomic instability is involved in the damage seen after radiation exposure of the zygote stage of HLG mice.

Factors of importance for implantation and problems after treatment for childhood cancer.

The uterus is of fundamental importance to reproduction; it nourishes the early embryo and accommodates growth and differentiation of the developing fetus. It is thus possible that the modalities employed to treat childhood cancer, that is; chemotherapeutic agents, and particularly irradiation, may result in damage to the uterine structure (musculature and local vasculature), with potential impairment of normal uterine function and thus increased risk of subsequent defective implantation. This may result in an impaired reproductive outcome (increased risk of spontaneous abortion, preterm labour, and low-birth-weight infants). Thus the reproductive problems foreseen following treatment of childhood cancer will be 1) ovarian failure or impaired ovarian activity and 2) uterine/endometrial structural and functional damage. The mode of treatment and age at its administration will be the major determinants of residual ovarian and uterine function. To understand the mechanisms that may be responsible for potential problems in reproductive function after treatment, it is essential to consider the mechanisms governing normal early pregnancy. Ovarian estradiol (E) and progesterone (P) secreted in a cyclical manner orchestrate the spatial and temporal morphological and functional changes in the endometrium required for implantation. In the absence of sex steroids, the endometrium is inactive. Implantation takes place in the midsecretory phase, that is, 5-9 days postovulation. E and P act sequentially to regulate cellular concentrations of their respective receptors and in turn gene transcription events are initiated to prepare the endometrium for implantation. A complex interaction exists between the network of uterine cells (epithelial, stroma, vascular, haemopoietic) and the endocrine system. Several key factors implicated in the implantation process will be addressed. There is published evidence that reports the risk of pubertal failure and early menopause after treatment for childhood cancer and, in those women who continue with ovarian activity and achieve pregnancy, a risk of poor reproductive outcome. It is likely that radiation damage to the uterus will adversely effect pregnancy potential. Our own group has reported impaired uterine characteristics in women after abdominal irradiation. More recently, we have shown that lower doses of radiotherapy (as with total-body irradiation) may be associated with a potential for improved uterine characteristics in response to physiological sex steroid replacement. The outlook after chemotherapy alone may be more optimistic; our early data support a normal uterine morphological response. Reproductive outcome in these patients remains unpredictable, so simple noninvasive assessment of uterine characteristics may provide data of predictive value with respect to future fertility potential.

Effects on female fertility and germinal cells in prepubertal and adult rats (Rattus norvegicus) after X-ray irradiation.

In this work we analyse the effects of ionizing radiation in prepubertal and adult female rats, using as parameters, implantation sites, embryonic loss, and synaptonemal complex (SC) analysis of the female F1 of the pregnant rats. Our preliminary results show a decrease statistically significant in fertility of irradiated groups, but cytogenetic analysis did not shown any inherited damage attributed to radiation. At the same time, our results seem to indicate a higher resistance of oocytes from prepubertal rats and support the possible use of GnRH agonists as oestrus cycle suppressors to turn adult rats into gonadal quiescence.

Increased resorptions in CBA mice exposed to low-frequency magnetic fields: an attempt to replicate earlier observations.

This paper has two aims. First, it reports the findings of a study on the effects of low-frequency magnetic fields on reproduction. Second, it serves as an example of an attempt to replicate the results of an experimental study in an independent laboratory and discusses some of the problems of replication studies. To try to replicate the findings of a study reporting increased resorptions (fetal loss) in mice exposed to 20 kHz magnetic fields with sawtooth waveform and to study the possible effects of 50 Hz sinusoidal fields, pregnant mice were exposed to magnetic fields from day 0 to 18 of pregnancy, 24 h per day. The flux densities of the vertical magnetic fields were 15 microT (peak-to-peak) at 20 kHz and 13 or 130 microT (root mean square) at 50 Hz. Two strains of animals were used: CBA/S mice imported from the laboratory reporting the original observations, and a closely related strain CBA/Ca. The CBA/S mice were cleaned of pathogenic microbes and parasites before they were imported into our laboratory. The magnetic field exposures did not affect resorption rate in CBA/Ca mice. In CBA/S, the frequency of resorptions was higher in the exposed mice than in the control group. However, the increase was not significantly different from either the no-effect hypothesis or the results of the original study we were attempting to replicate. Differences between the two studies and difficulties in interpreting the results are discussed. It is concluded that the results tend more to support than argue against increased resorptions in CBA/S mice exposed to the 20 kHz magnetic field. The results demonstrate that animal strain is an important variable in bioelectromagnetics research: even closely related strains may show different responses to magnetic field exposure.

Nutritional stress-induced implantation failure in laboratory mice: inhibition by continuous illumination.

The implantation failure in newly inseminated mice induced by food deprivation for 48 hr, beginning at 0900 hrs on day 4 post coitum, was prevented by simultaneous exposure to light continuously for 48 or 36 hr. Food-deprived females that were exposed to continuous light for 36 hr showed a significant increase in fetal resorption as compared with food-deprived females exposed to continuous light for 48 hr. Since failure of hypophysial prolactin release appears to be the primary endocrine cause of the inanition-induced implantation failure, the results suggest that exposure to continuous light protects implantation in food-deprived females by stimulating luteotrophic activity.

Fetal loss in mice exposed to magnetic fields during early pregnancy.

The effects of low-frequency magnetic fields (MFs) on early pregnancy were studied in CBA/S mice. The magnetic field was a 20 kHz, 15 microT sawtooth. Pregnant females were divided into four groups, two control groups and two exposed groups. One group was exposed to MFs continuously from day 1 postconception (pc) until day 5.5 pc, and the other group was exposed continuously until day 7 pc. All animals were sacrificed on day 19 pc, the day before partus, and their uterine contents were analyzed. No significant increase in the resorption (early fetal death) rate was found in the exposed animals compared to the sham controls. In the group exposed during days 1.0-5.5 pc, the body weight and length of the living fetuses were significantly decreased. Except on day 3 pc (progesterone) and day 13 pc (calcium) in the treated groups, there were no significant differences in progesterone and calcium levels in peripheral blood. Implantation occurred on the same day in MF-treated and control animals.