Biological effects of low-frequency pulsed magnetic fields on the embryonic central nervous system development. A histological and histochemical study

Numerous experiments have yielded contradictory results on the harmful action of magnetic fields on embryonic development. Pulsed magnetic fields appear to be able to delay normal development of embryos. In the present study, fertilized Gallus domesticus eggs were exposed during incubation to pulsed magnetic fields (harmonic signals of 10 μT for 1 second with silences of 0.5 seconds) of 50 or 100 Hz frequency. Embryos extracted at 45 h of exposure to fields of 50 Hz or 100 Hz frequency had significantly (p<0.05) fewer somite pairs compared with controls of the same age. At 15 days of incubation, only embryos exposed to a 10 μT- 50 Hz field had a significantly (p<0.05) higher somatic weight. At 21 days of incubation, a significantly lower somatic weight (p<0.01) and development stage (p<0.05) was found in embryos exposed to a 10 μT-100 Hz field than in controls, while a lower development stage (p<0.05) alone was observed in those exposed to a 10 μT-50 Hz field. In addition, animals showed higher expression of the neural marker NSE (neural specific enolase) after 21 days of development as determined by immunohistochemistry, with very low expression of glycosaminoglycans identified by alcyan blue staining. These results suggest that pulsed magnetic fields may be able to hinder normal embryonic development in vivo and to alter normal neural function, at least at the intensities and frequencies analyzed in the present study.     

Thermal and metabolic responsiveness of Japanese quail embryos following periodic exposure to 2,450 MHz microwaves

Two studies were performed to determine if repeated exposure of the avian egg to microwaves can alter metabolism, temperature, and growth rate of embryos. Another aim was to supplement conventional heating with microwave heating and provide an optimal temperature for growth. Japanese quail (Coturnix coturnix japonica) eggs were exposed from day 1 through 15 of incubation (8 h/day) to sham or microwave (2,450 MHz) irradiation. Microwave exposures were at two power densities, 5 or 20 mW/cm2, and at three ambient temperatures (Tas), 30.0, 33.1, or 35.4 degrees C. Specific absorption rates for unincubated and 15-day-old incubated eggs were, respectively, 0.76 and 0.66 W kg-1 mW-1 cm-2 (i.e., 3.8 and 3.3 W/kg at 5 mW/cm2 and 15.2 and 13.2 W/kg at 20 mW/cm2). Eggs were concurrently sham exposed at each of five Tas, ranging from 27.9 to 37.5 degrees C. Tests were conducted during the 16th day of incubation (i.e., 1 day post-treatment), in the absence of microwaves, to determine metabolic rate of embryos and internal and external egg temperatures at different Tas. Repeated exposures to microwaves at 5 and 20 mW/cm2 at the same Ta (30 degrees C) increased wet-embryo mass on the 16th day by an average, respectively, of 9% and 61% when compared with predicted masses for embryos exposed at the same Ta in the absence of microwave radiation. There was no reliable indication, from post-treatment tests and comparisons with control embryos of similar mass, that repeated exposure to microwave radiation resulted in abnormal physiological development. Microwave radiation can be used to increase egg temperature and embryonic growth rate at Tas below normal incubation level without altering basic metabolic and thermal characteristics of the developing bird.     

Action of ethanol on different skull and brain parameters in the chick embryo

Fifty microliters of ethanol diluted in 50 microl of distilled water were injected into the air chamber of chick eggs immediately before their incubation, and modifications in a series of parameters were recorded. The somatic weight of the ethanol-treated embryos was lower compared with control and vehicle-administered embryos during days 13, 15, 17, and 19 of incubation, but was the same on day 21. The brain weight was lower in the ethanol-treated embryos on all the days studied (days 13, 15, 17, 19, and 21 of incubation). Skull measurements showed that the transverse anteroposterior and sagittal diameters were significantly smaller in ethanol-treated embryos compared with control and vehicle-administered embryos on days 17, 19, and 21 of incubation.     

The effect of adrenocorticotropic hormone (ACTH) on embryonic chicken gonads

Chicken embryos were exposed to a single dose of adrenocorticotropic hormone (ACTH) on the 15th day of the incubation period. Five days later, the female embryos showed a significant increase in ovarian weight, ovarian thickness and oocyte count. In contrast, the male embryos showed a significant decreased in testicle weight, seminiferous cord diameter and gonocyte number. The opposite response of testes and ovaries is discussed.     

Normal prenatal growth of the golden hamster (author's transl)]

In the golden hamster (Mesocricetus auratus) the gestation period and the loculus size of the gravid uterus from day 6 to day 15.5 (parturition) of gestation as well as the weight, width (umbilcus-black) and lenght (crown-rump) of the embryos from day 9 to the parturition were measured. The results obtained were as follows: 1. The gestation period of the golden hamster was 15 days and 15 +/- 3 hours post coitum. 2. The average values of the length (in the direction of uterine long axis) and width (mesome-trial-antimesometrial axis) in the loculus of the gravid uterus were 0.39 cm and 0.56 cm at 6 days, and 2.42 cm and 1.74 cm at 15.5 days (partiurition), respectively. 3. The average values of the crown-rump measurements, width (umblicus-back) and weight in the hamster embryos were 0.42 cm, 0.24 cm and 0.026 g at 9 days, and 2.40 cm, 1.39 cm and 2.272 g at 15.5 days (parturition), respectively. 4. The loculus size of the gravid uterus, the crown-rump measurements and width (umblicus-back) of the embryos in the period from day 13 to day 14 of gestation were markedly increased in comparison with any other period, and the weight increase of the embryos occurred rapidly from day 13 of gestation. 5. The shape of the loculus during the gestation was ovoid (mesometrial-antimesometrial axis) until the end of 10 days converged to the spherical form and thereafter changed gradually to the ovoid from in the direction of uterine long axis contraly to the previous days.     

Restriction of proliferation of primordial germ cells by the irradiation of Japanese quail embryos with soft X-rays.

Primordial germ cells (PGCs) are the progenitor cells for the gametes. Avian PGCs are located in the central region of the area pellucida at the blastoderm stage. Shortly after further incubation, they migrate to the extra-embryonic germinal crescent, and then as soon as the blood vessels form, they enter the circulation and finally settle in the gonadal primordium. We have developed a simple method using soft X-ray irradiation (18 kV power, 20 cm distance) to reduce the number of PGCs in Japanese quail embryos, which should be useful in preparing recipient embryos for PGC-transfer studies. When embryos were exposed to the soft X-rays for 40 s before incubation, the concentration of circulating PGCs was less than one-fifth that in controls after 2 days of incubation. Embryos at day 6 of incubation contained approximately half the number of PGCs compared to controls when they were exposed before or at day 2 of incubation. Irradiation for 40 s is recommended taking into consideration the restriction of proliferation of PGCs, and viability and hatchability.     

Embryonic developmental plasticity of the chick: increased CO(2) during early stages of incubation changes the developmental trajectories during prenatal and postnatal growth

This study investigated the effect of non-ventilation of the incubator during the first 10 days of incubation on carbon dioxide (CO(2)) concentrations in the incubator and its effects on the embryonic and post-hatch development of the chicken (Gallus gallus). Two different incubation conditions were created, one incubator was kept at standard conditions, with adequate ventilation (V) and a second incubator was non-ventilated (NV) during the first ten days of incubation, allowing the CO(2) to rise. After the first 10 days, both incubations were continued under standard conditions. The experiment was repeated twice with different ages of the breeders (45 and 60 wks) which resulted in different CO(2) levels at ED10 (1.5 and 1%). The CO(2) concentration in the V incubators remained below 0.1% in these first 10 days. The eggs of the NV incubation showed higher pCO(2) levels in the air cell from ED10 until ED14 compared to the eggs of the V group. The NV embryos had significantly higher absolute and relative (to egg weight) body weights from ED10 until ED18, pointing to an accelerated embryonic growth. At internal pipping, the NV chick embryos had higher plasma corticosterone and T(3) levels and higher pCO(2) in the air cell. Chicks incubated under NV conditions hatched 10 h earlier in the first and 15 h earlier in the second experiment and the spread of hatch was narrower. During the post-hatch period, the NV chickens had a higher body weight compared to the V chickens. From these results, it is clear that higher levels of CO(2) during the first ten days of incubation have persistent (epigenetic) effects during the incubation and early post-hatch period.     

Survival of amphibian embryos after continuous ultrasound treatment

The influence of continuous ultrasound on the embryonic development of grass frog Rana temporaria has been investigated. Intact embryos at the blastula stage were treated by ultrasound of different frequency (0.88 and 2.64 MHz), intensity (0.05-1.0 W/cm2), and duration (1-15 min). The treatment with ultrasound of frequency 0.88 MHz and intensity 0.05 W/cm2 for 1-5 min tended to increase the proportion of normally developing embryos up to hatch (10-25% of control). Increasing the intensity of ultrasound (0.88 MHz) to 0.7-1.0 W/cm2 and the duration of its action to 5-15 min induced the death of almost all of treated embryos. No significant differences were found between the development of control embryos and embryos treated with ultrasound of middle intensity (0.2-0.7 W/cm2) for 1-5 min. The exposure of amphibian embryos to ultrasound of frequency 2.64 MHz and intensity 0.05-0.7 W/cm2 for 1-5 min did not change their survival. Increasing the intensity of ultrasound (2.64 MHz) to 1.0 W/cm2 and the duration of its action to 5 min decreased the number of normal developing embryos (by 35%).     

Neural crest origin of cardiac ganglion cells in the chick embryo: Identification and extirpation

Using interspecific grafting of neural crest between quail and chick embryos, it was determined that the cardiac ganglia originate from the cranial region (somites 1–2) of the vagal neural crest (somites 1–7). Neuronal uptake of [³H]choline was used as an index of neuronal development in the chick atrium. Normal uptake was found to be quite high between Days 8 and 14 of incubation. Following extirpation of neural crest over somites 1 to 3 at stages 8 to 10, neuronal uptake in 8-day chick atrium was decreased by 25–60% depending on the stage at which the lesion was performed. It is thought that the residual uptake represents preganglionic terminals from the dorsal motor nucleus of the vagus. Embryos with extirpations of neural crest over somites 1–3 performed at stage 9 showed the greatest decrease of neuronal choline uptake and did not live beyond 11 days of incubation. However, hearts from embryos with partial lesions (performed at stage 10) were treated on incubation Days 12 and 15 for demonstration of acetylcholinesterase in the subepicardial plexus. These hearts showed much less extensive neural plexus with sparse, small cardiac ganglia.     

Studies of the teratogenic potential of exposure of rats to 6000-MHz microwave radiation. II. Postnatal psychophysiologic evaluations

Wistar rats (36) were exposed daily throughout pregnancy to a power density level of 35 mW/cm2 of 6000-MHz microwave radiation (11), sham irradiated (10), or used as control animals (15). Litters were culled to a maximum of eight F1a offspring/litter (total = 124) on Postnatal Day 1 and subjected to a series of reflex tests beginning Day 3. Mothers were rebred 10 days after weaning. Teratologic evaluations were completed on 263 F1b offspring. Weekly weights were recorded for 298 F1a offspring. At 60 days, behavioral testing was initiated on 121 offspring. At 90 days, offspring were bred within/across groups. Teratologic evaluations were completed on 659 F2 term fetuses. Organ weight analyses were completed on 17 mothers and 181 F1a adult offspring, and blood analyses on 21 mothers and 131 offspring. Sex differences within groups were observed in four behavioral tests and in blood data. Significant differences between groups were observed for: F1b term fetal weight; F1a eye opening, postnatal growth to the fifth week, water T-maze and open field test results; and several organ/body weight ratios. These results indicate that exposure to 6000-MHz radiation at this power density level may result in subtle long-term neurophysiologic alterations not detectable at term using conventional morphologic teratologic procedures.     

Development of chicken embryos exposed to an intermittent horizontal sinusoidal 50 Hz magnetic field

The effects of intermittent exposure (2 h on/22 h off) to a 200 μT horizontal, sinusoidally oscillating (50 Hz) magnetic field were studied in 210 fertilized chicken eggs. Two hundred ten control eggs (sham-exposed) were incubated in the same chamber as the experimental eggs. Chick embryos were examined for developmental anomalies and maturity stage after 48 h of incubation. Immunohistochemical analysis of extracellular membrane components (laminin, fibronectin, and type IV collagen) were conducted on day 7 and histological examinations for malformations of brain, liver, and heart, on days 7, 12, and 18 of incubation. Furthermore, egg fertility and egg weights were evaluated on days 2, 7, 12, and 18. The investigation also measured the body weight of chickens for 90 days from hatching and included histological analysis of body organs. Each variable was investigated blind. Statistical comparison between exposed and sham-exposed values did not show significant differences in any of the variables investigated. Thus, it appears that the exposure of embryos to an intermittent 200 μT magnetic field at 50 Hz does not cause developmental anomalies, changes in maturity stage, alterations in distribution of extracellular membrane components, or malformations in the brain, liver, or heart. Moreover, there were no differences in body weight, morphology, or histology of central nervous system, liver, heart, or testis in 90-day-old chickens hatched from exposed in comparison to sham-exposed eggs. © 1996 Wiley-Liss, Inc.     

Increasing carbon dioxide from five percent to ten percent improves rabbit blastocyst development from cultured zygotes.

One-cell rabbit zygotes were cultured at 39 degrees C in basal synthetic medium II (BSM-II) with 5%, 10%, or 15% CO2 and humidified air to determine the effect of CO2 concentration on development in vitro. After 4 days in culture, 37% of the embryos grown in 10% or 15% CO2 had reached the hatching blastocyst stage, but only 10% of the embryos were hatching when cultured under 5% CO2 (P = 0.01). Over all blastocysts, cell numbers were 207, 246, and 205 for the 5%, 10%, and 15% CO2 treatments, respectively. In a second experiment to determine if there was a beneficial effect, particularly at the blastocyst stage, of a higher concentration of CO2, embryos were cultured 4 days in either 5% or 10% CO2 or for 2 days in 5% CO2 followed by 2 days in 10% CO2. The numbers of blastomeres per embryo and embryo diameter were greater (P < 0.05) in embryos cultured continuously in 10% CO2 or in 10% CO2 only during days 3 and 4 of culture than in embryos cultured continuously in 5% CO2. In a third experiment, one-cell rabbit zygotes were cultured with 5% or 10% CO2 in a defined, protein-free medium consisting of 1:1 RPMI 1640 and Dulbecco's modified Eagle's medium. The proportion of embryos hatching and cell counts were significantly greater (P < 0.01) when cultured in the presence of 10% CO2. These data indicate that a 10% CO2 atmosphere exerts a beneficial effect on the development of zygotes into expanding and hatching rabbit blastocysts in vitro.     

Rht10基因对‘鲁麦15’农艺性状和光合生理特性的影响

利用鲁麦15、Rht10鲁麦15、Ms2鲁麦15及Ms2+Rht10鲁麦15近等基因系为试验材料,研究了Rht10基因对小麦农艺性状、净光合速率(Pn)、蒸腾速率(Tr)等光合生理特性的影响.结果表明,Rht10使小麦的挑旗、抽穗、开花期均推迟了4～5 d;Rht10对鲁麦15和Ms2鲁麦15的降秆强度分别为53.77%和53.00%,穗长显著缩短(P<0.05),千粒重显著减少,但对有效穂数无显著影响(P>0.05).含有Rht10基因的材料与不含此基因的材料之间的光合生理参数普遍存在显著差异,但在不同时期不同参数差异正负不同;在灌浆后期,Rht10对Pn有显著正效应(P<0.05);从开花期到灌浆后期,Pn与气孔导度(Gs)、胞间二氧化碳浓度(Ci)总体变化趋势相同,且相关性显著,表明Pn在一定程度上受气孔因素的限制;在灌浆中后期,Rht10对Gs有明显的正效应;在抽穗和开花期,Rht10对Tr有明显的正效应;Rht10对叶片水分利用效率(WUE)在4个生育期有明显的负效应.由此可见,Rht10基因对小麦的生育期、株高、穗长都有明显的不利影响,对各项光合生理参数也有普遍正向或负向的影响,在利用Rht10进行杂交育种时应充分考虑此基因带来的不利效应.     

Effect of different cryoprotectants and vitrificant solutions on the hatching rate of turbot embryos (Scophthalmus maximus)

Vitrification could provide a promising tool for the cryopreservation of fish embryos. However, in order to achieve a vitrifiable medium, a high concentration of permeable cryoprotectants must be employed, and the incorporation of high molecular weight compounds should also be considered. The toxicity of these permeable and non-permeable agents has to be assessed, particularly when high concentrations are required. In the present study, permeable and non-permeable cryoprotectant toxicity was determined in turbot embryos at two development stages (F stage-tail bud and G stage-tail bud free). Embryos treated with pronase (2mg/ml, 10 min at 22 degrees C) were incubated in dimethyl sulfoxide (Me2SO), methanol (Meth.) or ethylene glycol (EG) in concentrations ranging from 0.5 to 6M for periods of 10 or 30 min, and in 5, 10, and 15% polyvinylpyrrolidone (PVP), 10, 15, and 20% sucrose or 0.1, 1, and 2% X-1000 for 2 min. The embryos were then washed well and incubated in seawater until hatching. The toxicity of permeable cryoprotectants increased with concentration and exposure time. There were no significant differences between permeable cryoprotectants. However, embryos tolerated higher concentrations of Me2SO than other cryoprotectants. Exposure to permeable cryoprotectants did not affect the hatching rate except at G stage with X-1000 treatment and 20% sucrose. Taking into account the cryoprotectant toxicity and the vitrification ability of cryoprotectant mixtures, three vitrification solutions (V1, V2, and V3), and one protocol for stepwise incorporation were designed. The tested solutions contained 5M Me2SO+2M Meth+1M EG plus 5% PVP, 10% sucrose or 2% X-1000. The hatching rate of embryos that had been exposed to the the vitrification solutions was analyzed and no significant differences were noticed compared with the controls. Our results demonstrate that turbot embryos can be subject to this cryoprotectant protocol without deleterious effect on the hatching rate.     

Expression of mRNA for 3HADH in manipulated embryos to produce germline chimeric chickens

Germline chimeric chickens were produced by the transfer of primordial germ cells (PGCs) or blastoderm cells. The hatchability of eggs produced by transfer of exogenous PGCs is usually low. The purpose of the present study was investigated to express (3-hydroxyacyl CoA dehydrogenase) 3HADH which is a limiting enzyme in the beta-oxidation of fatty acids for hatching energy. Manipulations of both donor and recipient eggshells were as follows. A window approximately 10 mm in diameter was opened at the pointed end of the eggs at stage 12–15 days incubation. Donor PGCs, taken from the blood vessels of donor embryos from fertilized eggs at the same stage of development, were injected into the blood vessels of recipient embryos. The muscles of chicks in the eggs with transferred PGCs were removed after 20 days of incubation. A cDNA was prepared from the total RNA. The expression of 3HADH in the manipulated embryos was investigated using real-time PCR analysis. Real-time PCR analysis showed that expression of 3HADH was reduced in the muscles of manipulated embryos.     

The effects of short- and long-term exposure of chick embryos to neutral red on the frequency of sister-chromatid exchange

The chick embryo was used to study the effects of neutral red (NR) on the frequency of sister-chromatid exchange (SCE) in specific tissues exposed to this mutagen for short and long periods as development proceeded. In short-term trials, aqueous NR at doses of 10, 25 and 100 μg was injected in 3-day and 6-day embryos. In each case, embryos were also treated with 5-bromodeoxyuridine (BrdU) for a 24-h period (two cell cycles) and harvested at 4 days and 7 days, resp. A long-term exposure (about 8 cell cycles) was achieved by exposing embryos to NR from day 3 to day 7 of incubation. At a NR dose of 25 μg, the chronic exposure resulted in a doubling of the rate of SCE (11.4/cell) over that observed in embryos exposed for only 24 h at either days 3–4 (6.0/cell) or days 6–7 (6.0/cell). At 100 μg of NR, the same relationship held with SCE rates of 14.2/cell for the chronic exposure versus rates of 8.0/cell (3–4 days) and 6.9/cell (6–7 days). At 10 μg of NR, no such accumulation of SCE occurred upon long-term treatment.These results show an enhanced SCE response upon growth of embryonic cells in the presence of NR for several days. This may be the result of the persistence of past lesions with the addition of more lesions upon continued exposure to NR.     

MNNG-induced mutations in the adult gill and hepatopancreas and in embryos of rpsL transgenic zebrafish

To evaluate the feasibility of a mutagenicity assay using adult rpsL transgenic zebrafish, 4- to 8-month-old females were exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (0, 15 or 30 mg/L in a water bath for 2 h). At 2 weeks after exposure, MNNG showed a concentration-dependent significant increase in mutant frequency (MF) of 8 x 10(-5), 18 x 10(-5), and 51 x 10(-5), respectively, in the gill. DNA sequencing revealed that 60-74% of the induced mutations were G:C to A:T transitions, consistent with the known mutagenic effects of MNNG. A marginal but significant increase in MF was observed in the hepatopancreas only in the group exposed to 30 mg/L, with the induction of some G:C to A:T transitions. A time-course of the appearance of mutations was determined in fish treated with 15 mg/L MNNG. In both, the gill and hepatopancreas, a higher MF was observed at 3 weeks than at 2 weeks, suggesting that an expression time of at least 3 weeks is preferable for the assay. When embryos (29 h post-fertilization) were exposed to MNNG (0, 50, and 150 mg/L) for 1 h, MFs increased significantly with an increase in the concentration of MNNG (5 x 10(-5), 40 x 10(-5), and 144 x 10(-5), respectively) at 3 days after exposure. G:C to A:T transitions were the predominant mutations, and these occurred at the same sites in the rpsL gene as in adult tissues. Thus, MNNG induces typical mutations in the gill and hepatopancreas of adult fish, and in embryos, suggesting that the rpsL zebrafish is a useful tool for monitoring genotoxicity caused by water-borne mutagens.     

Regulatory capacities of a broiler and layer strain exposed to high CO2 levels during the second half of incubation

It has been shown that during embryonic chicken (Gallus gallus) development, the metabolism of broiler embryos differs from that of layers in terms of embryonic growth, pCO2/pO2 blood levels, heat production, and heart rate. Therefore, these strains might adapt differently on extreme environmental factors such as exposure to high CO2. The aim of this study was to compare broiler and layer embryos in their adaptation to 4% CO2 from embryonic days (ED) 12 to 18. Due to hypercapnia, blood pCO2 increased in both strains. Blood bicarbonate concentration was ~10 mmol/L higher in embryos exposed to high CO2 of both strains, while the bicarbonates of broilers had ~5 mmol/L higher values than layer embryos. In addition, the pH increased when embryos of both strains were exposed to CO2. Moreover, under CO2 conditions, the blood potassium concentration increased in both strains significantly, reaching a plateau at ED14. At ED12, the layer strain had a higher increase in CAII protein in red blood cells due to incubation under high CO2 compared to the broiler strain, whereas at ED14, the broiler strain had the highest increase. In conclusion, the most striking observation was the similar mechanism of broiler and layer embryos to cope with high CO2 levels.     

Development of the differential effect of oxazepam on spontaneous and activated motility in chick embryos

Development of the acute depressant effect of oxazepam (in a dose of 10 mg/kg egg weight) on spontaneous and activated motor activity was studied in chick embryos (incubation age 11-19 days). The depressant effect of oxazepam was demonstrated for the first time in 13-day-old embryos. From the 15th day of incubation it led to prolonged depression of embryonic motility. From the 15th day the depressant effect of oxazepam depended on the connections of the central motor output with the prosencephalon. In mesencephalic, rhombencephalic and spinal preparations the effect of oxazepam was insignificant. In 13- and 15-day-old embryos oxazepam blocked the activating effect of strychnine and pentylenetetrazol, but not the picrotoxin-induced activation. The picrotoxin activation of embryonic motility was incompletely blocked for the first time in 17-day-old and completely only in 19-day-old embryos. The results are discussed with reference to heterochronia of development of the various components in the complex GABA receptor.     

Teratogenic effects of sinusoidal extremely low frequency electromagnetic fields on morphology of 24 hr chick embryos

To examine the potential teratogenicity of electromagnetic fields (EMF; sinusoidal and rectangular) on development of chick embryos (white leghorn), 221 freshly fertilized chicken eggs (55-65 g) were exposed during first 24 hr of postlaying incubation (38 degrees +/- 0.5 degree C) to 24 different EMFs, with 50Hz repetition rate and 8.007-10.143 mT flux density. Following exposure, the exposed fertilized chicken eggs (n = 8-10) and sham-exposed fertilized chicken eggs (n = 15) were incubated simultaneously for 8 more days and unexposed control fertilized chicken eggs (n = 20) for 9 days in absence of EMFs. The embryos were removed from egg shells and studied blind. All 24 EMF exposed-groups (inside the coil with exposure) showed an increase in the percentage of developmental anomalies compared to sham-exposed (inside the coil with no exposure) and control groups (outside the coil). Further, egg's weight was evaluated on day 9. This variable did not show significant difference between control and exposed-groups. The investigation also covered the measurement of body weight, length of crown to rump, length of tip of the beak to occipital bone, heart and liver weight. Statistical comparison between sham-exposed and control values did not show significant differences, but comparison between 8.007, 8.453 and 8.713 mT exposed-groups and control groups showed significant differences; in other exposed-groups, the changes were not significant. These results revealed that 50 Hz electromagnetic fields can induce irreversible developmental alterations in 24 hr chick embryos and confirm that its strength could be a determinant factor for the embryonic response to extremely low frequency electromagnetic fields (window effects).