The effect of oscillating low intensity magnetic field on the Na+, K+, Ca++, and Mg++ concentrations in the maternal and fetal circulation of the dually perfused human placental cotyledon

Dual-sided perfusions of the human placental cotyledon in vitro were used to study effects of low intensity magnetic fields (MFs) of 2 mT, 50 Hz (E1, 10 perfusions) and 5 mT, 50 Hz (E2, 10 perfusions). In the control group C (10 experiments) no field was used. Perfusions lasted 180 min each. Increased release of calcium ions from the placental cotyledon was found in the fetal circulation during perfusion when the 2 mT, 50 Hz MF was used. No changes in the release of sodium and magnesium ions were observed compared to the control group. The 5 mT, 50 Hz oscillating MF intensified the release of sodium ions from the perfused cotyledon both to the fetal and maternal circulation up to the 150th min of the experiment. Increased release of magnesium ions was observed only to the fetal circulation between 120 and 180 min and of calcium ions to the fetal circulation between 60 and 180 min. No significant differences in K concentrations were found between the control and MF exposed cotyledons under conditions of these experiments.     

Induction,germination and shoot development of somatic embryos in cassava

Four Indonesian and two Latin-American cassava genotypes (Manihot esculenta Crantz), were evaluated for their ability to develop somatic embryos from young leaf lobes. All genotypes formed somatic embryos but they differed in the frequency of embryos induced. The best genotypes, M. Col 22 and Tjurug, produced germinating embryos (GE) on 81% (22.1 GE/initial leaf lobe) and 46% (4.3 GE/initial leaf lobe) of the cultured leaf lobes, respectively. Up to 57% of the germinating embryos of M. Col 22 and 12% of Tjurug produced either normal or malformed shoots. Most malformed shoots developed into shoots with normal morphology after prolonged culture. All shoots formed roots after transfer to medium without BAP. Roots of all normal and most malformed regenerants had the original ploidy level (2n=36). Regardless of whether the plants were multipliedin vitro (150 plants) or in the greenhouse (30 plants) there were no morphological differences compared to parent plants.     

Immunofluorescent analysis of fibronectin and laminin distribution in the vl mutant mouse

Summary The distribution of fibronectin and laminin was determined in the basement membrane surrounding the caudal neural tube and at the site of initial apposition of the caudal neural folds by means of indirect immunofluorescence histochemistry on 9.0- to 10.5-day mouse embryos fixed in Carnoy's solution and serially sectioned in paraffin. At early phases of development of normal (+/+) and abnormal (vl/vl) embryos the dorsolateral neural basement membrane overlying putative neural crest cells caudal to the hindlimb shows a patchy fibronectin reaction, with laminin virtually absent. In older embryos, both components are present but are discontinuous overlying the neural crest. The results suggest that since discontinuities occur in the basement membrane of abnormal as well as normal embryos, the neural crest cells are not prevented from emigrating from the abnormal neural tube; thus the faulty neural fold fusion that characterizesvl/vl embryos does not appear to be due to a suppression of emigration by the basement membrane. The results also demonstrate the advantages and reliability of embedding in paraffin for analysis of serially sectioned pathological material by means of indirect immunofluorescence, provided that normal controls and abnormals are processed simultaneously.     

Ultrastructural analysis of the midaxial extracellular matrix in spinal dysraphism

Ultrastructural aspects of the extracellular matrix (ECM) in the midaxial region of dysraphic embryos of the loop-tail (Lp) mutant mouse were analyzed by means of electron microscopy. In 17–23 somite embryos, ultrastructural differences in the ECM occurred with respect to the presence of a pair of long trailing basal laminar strands extending continuously from the ventral notochordal cells to the gut in abnormal (Lp/Lp) embryos, in contrast to short, ragged, discontinuous strands in normal (+ /+;Lpj +) embryos. The ultrastructural localization and configuration of fibronectin (FN) and laminin (L) associated with these strands, however, were similar in normals and abnormals. In addition, FN occurred over interstitial bodies, fibrils, and sporadically along the basal laminae of the neural tube (or folds), notochord, gut, and vessels, whereas L was largely confined to the basal laminae. The results indicate that although the ultrastructural pattern of FN and L reactivity are similar in normal and abnormal embryos, a disturbance in the manner whereby the notochord detaches from the gut in dysraphic embryos may be of causal significance in the etiology of dysraphism in this mutant.     

Effects of a partially purified factor from chick embryos on macromolecular synthesis of embryonic pancreatic epithelia

Essentially normal development of early embryonic pancreatic epithelium occurs only in the presence of mesenchymal tissues (Golosow and Grobstein, 1962), or a particulate fraction (MF) obtained from extracts of chicken embryos (Rutter et al., 1964). We have shown that this fraction also stimulates the incorporation of thymidine-³H into DNA. This stimulatory activity was detected in particulate fractions from homogenates of several mesodermal tissues from rat and chick embryos, as well as in fibroblasts cultured from these tissues, but not in embryonic epithelial tissues. This activity may thus be related to the mesodermal tissue requirement for pancreatic development. MF was solubilized and partially purified from homogenates of chick embryos. It is stable to collagenase, hyaluronidase, and neuraminidase. Activity is lost by heating and by treatment with trypsin. It is presumed, therefore, that the factor is associated with a protein that is not collagen.The effects of the MF upon macromolecular synthesis were tested in pancreatic tissues from 12-day rat embryos. When isolated epithelia were cultured in the absence of mesoderm or MF, the rate of thymidine-³H incorporation into DNA decreased to low levels. The specific activities of DNA polymerase and deoxycytidylate deaminase in epithelial extracts also declined. In contrast, the rate of thymidine-³H incorporation into DNA increased 5- to 8-fold over the initial rates in epithelia cultured with MF. Concurrently DNA polymerase activity in tissue extracts increased by 2- to 3-fold; deoxycytidylate deaminase activity declined slightly.MF also affected RNA and protein synthesis. The rate of leucine-³H incorporation into protein and uridine-¹⁴C incorporation into RNA in isolated pancreatic epithelia was comparable to that of intact rudiments. Cultures in the presence of MF increased these rates severalfold after 20 hr. These results suggest that MF, and by implication, mesoderm, may supply a growth factor for epithelial tissue and thus serves a permissive rather than a determining role in the differentiation process in pancreatic development.     

Storability and germination of sodium alginate encapsulated somatic embryos derived from the vegetative shoot apices of mature <Emphasis Type="Italic">Pinus patula</Emphasis> trees

Storability and germination of sodium alginate encapsulated somatic embryos derived from vegetative shoot apices of mature Pinus patula trees were tested on half strength DCR basal medium without growth regulators. The germination percentage of encapsulated somatic embryos was affected significantly by the concentration of sodium alginate and the duration of exposure to calcium chloride. Somatic embryos encapsulated with 2.5 sodium alginate dissolved in DCR basal salts gave significantly higher germination (89) than other treatments. Short (5 min) incubation of the alginate encapsulated embryos in calcium chloride solution proved to be the best encapsulation procedure and the embryos subsequently gave the highest germination (89). Synthetic seeds could be stored at 2 °C for 120 days without a reduction in germination as opposed to non-encapsulated somatic embryos which showed only 9 germination after 20 days at 2 °C. Germinated synthetic seeds produced normal plantlets. This study reports for the first time the storability of encapsulated somatic embryos generated from vegetative shoot apices of mature Pinus patula trees. This has potential for application in forestry.     

Influence of 50 Hz electromagnetic fields on recurrent embryogenesis and germination of cork oak somatic embryos

Plant tissue culture techniques are carried out under environmentally controlled conditions in phytotrons. However, electric components of phytotrons generate electromagnetic fields that may act as a environmental factor influencing plant growth and morphogenesis. Isolated somatic embryos of Quercus suber, picked from embryogenic lines, were chronically exposed to a 50 Hz and 15 μT electromagnetic field generated in a Helmholtz-coil system for 8 weeks, in order to examine if the extremely low frequency (ELF) magnetic field (MF) affected the morphogenic behaviour of embryogenic cultures during recurrent embryogenesis. Germination of somatic embryos from genotype G7.1 was carried out under the same electromagnetic field, and also under conditions in which the local geomagnetic field was suppressed. The ELF MF did not influence the growth of embryogenic clumps of the assayed genotypes, but reduced the number of detachable embryos produced by genotype G3.27. The ELF MF did not modify the percentages of germination or plant formation of somatic embryos. However, somatic embryos had better germination when cultured under the suppressed geomagnetic field condition. This revised version was published online in June 2006 with corrections to the Cover Date.     

Plant regeneration from encapsulated somatic embryos of Carica papaya L.

Carica papaya L. (papaya) single somatic embryos (2.0 mm diameter) produced in a high-frequency liquid production system were encapsulated in two different synthetic encapsulation compounds. The frequency of regeneration from encapsulated embryos was significantly affected by (1) the concentration of sodium alginate, (2) the presence or absence of nutrient salts in the capsule, and (3) the duration of exposure to calcium chloride. A 2.5% sodium alginate concentration in a half-strength MS salts base resulted in significantly higher germination frequencies than other treatments. A relatively short (10 min) exposure to CaCl₂ provided uniform encapsulation of embryos and the highest frequencies of successful germination (77.5%). Germinated artificial seeds produced normal plantlets. Received: 12 March 1997 / Revision recieved: 24 June 1997 / Accepted: 18 July 1997     

The effect of pulsed and sinusoidal magnetic fields on the morphology of developing chick embryos

Several investigators have reported robust, statistically significant results that indicate that weak (∼ 1 μT) magnetic fields (MFs) increase the rate of morphological abnormalities in chick embryos. However, other investigators have reported that weak MFs do not appear to affect embryo morphology at all. We present the results of experiments conducted over five years in five distinct campaigns spanning several months each. In four of the campaigns, exposure was to a pulsed magnetic field (PMF); and in the final campaign, exposure was to a 60 Hz sinusoidal magnetic field (MF). A total of over 2500 White Leghorn chick embryos were examined. When the results of the campaigns were analyzed separately, a range of responses was observed. Four campaigns (three PMF campaigns and one 60 Hz campaign) exhibited statistically significant increases (P ≥ 0.01), ranging from 2-fold to 7-fold, in the abnormality rate in MF-exposed embryos. In the remaining PMF campaign, there was only a slight (roughly 50%), statistically insignificant (P = 0.2) increase in the abnormality rate due to MF exposure. When the morphological abnormality rate of all of the PMF-exposed embryos was compared to that of all of the corresponding control embryos, a statistically significant (P ≥ .001) result was obtained, indicating that PMF exposure approximately doubled the abnormality rate. Likewise, when the abnormality rate of the sinusoid-exposed embryos was compared to the corresponding control embryos, the abnormality rate was increased (approximately tripled). This robust result indicates that weak EMFs can induce morphological abnormalities in developing chick embryos. We have attempted to analyze some of the confounding factors that may have contributed to the lack of response in one of the campaigns. The genetic composition of the breeding stock was altered by the breeder before the start of the nonresponding campaign. We hypothesize that the genetic composition of the breeding stock determines the susceptibility of any given flock to EMF-induced abnormalities and therefore could represent a confounding factor in studies of EMF-induced bioeffects in chick embryos. Bioelectromagnetics 18:431–438, 1997. © 1997 Wiley-Liss, Inc.     

The ionic dependence of voltage-activated inward currents in the pharyngeal muscle of Caenorhabditis elegans

The pharynx of Caenorhabditis elegans consists of a syncytium of radially orientated muscle cells that contract synchronously and rhythmically to ingest and crush bacteria and pump them into the intestine of the animal. The action potentials that support this activity are superficially similar to vertebrate cardiac action potentials in appearance with a long, calcium-dependent plateau phase. Although the pharyngeal muscle can generate action potentials in the absence of external calcium ions, action potentials are absent when sodium is removed from the extracellullar solution (Franks et al. 2002). Here we have used whole cell patch clamp recordings from the pharynx and show low voltage-activated inward currents that are present in zero external calcium and reduced in zero external sodium ions. Whilst the lack of effect of zero calcium when sodium ions are present is not surprising in view of the known permeability of voltage-gated calcium channels to sodium ions, the reduction in current in zero sodium when calcium ions are present is harder to explain in terms of a conventional voltage-gated calcium channel. Inward currents were also recorded from egl-19 (n582) which has a loss of function mutation in the pharyngeal L-type calcium channel and these were also markedly reduced in zero external sodium. Despite this apparent dependence on external sodium ions, the current was partially blocked by the divalent cations, cadmium, barium and nickel. Using single-channel recordings we identified a cation channel for which the open-time duration was increased by depolarisation. In inside-out patches, the single-channel conductance was highest in symmetrical sodium solution. Further studies are required to determine the contribution of these channels to the pharyngeal action potential.     

Fractal analysis of extra‐embryonic vascularization in Japanese quail embryos exposed to extremely low frequency magnetic fields

Magnetic fields (MF) can alter the dynamic behavior of vascular tissue and may have a stimulatory or inhibitory effect on blood vessel growth. Fractal geometry has been used in several studies as a tool to describe the development of blood vascular networks. Due to its self‐similarity, irregularity, fractional dimension, and dependence on the scale of vessel dimensions, vascular networks can be taken as fractal objects. In this work, we calculated the fractal dimension by the methods of box counting (D_bc) and information dimension (D_inf) to evaluate the development of blood vessels of the yolk sac membrane (YSM) from quail embryos exposed to MF with a magnetic flux density of 1 mT and a frequency of 60 Hz. The obtained results showed that when the MF was applied to embryos aged between 48 and 72 h, in sessions of 2 h (6 h/day) and 3 h (9 h/day) with exposure intervals between 6 and 5 h, respectively, blood vascular formation was inhibited. Exposure sessions shorter than 2 h or longer than 3 h had no observable change on the vascular process. In contrast, the magnetic field had no observable change on the YSM vascular network for embryos aged between 72 and 96 h, irrespective of the exposure time. In conclusion, these results show a “window effect” regarding exposure time. Bioelectromagnetics 34:114–121, 2013. © 2012 Wiley Periodicals, Inc.     

The embryonic development of Xenopus laevis under a low frequency electric field

The aim of this study was to determine the effects of a low frequency electric field on the early embryonic development of frogs. The embryos of African clawed toads, Xenopus laevis, were exposed to a 20-μA electric current during the cleavage stages. The developmental processes of embryos during and after electric field exposure were monitored for teratogenic effects. All the embryos continuously exposed to the electric field died without undergoing any developmental processes. However, when the embryos were exposed to the electric field for 20-min periods (four times/over 2 d), the embryos developed into both normal tadpoles (70 %) and malformed tadpoles with light edema, reduced pigmentation, or axial anomalies, such as crooked tails. After exposure, the control embryos were at development stage 35.5 (2 d 2 h), while the normal embryos of the assay group were at developmental stage 41(3 d 4 h). There was a 1 d 2 h difference between the two developmental stages, revealing the importance of that time period for embryogenesis. In conclusion, the effects of electric current on Xenopus embryos are dependent on the initial developmental stage and the duration of exposure.     

Histochemical analysis of the neural basal lamina in the hindbrain region of exencephalic mutant mice

The neural basal lamina in hindbrain regions of exencephalic loop-tail (Lp/Lp) mice and of their normal (+/+; Lp/+) littermates was analyzed histochemically at the electron microscopic level by means of enzyme digestion and alcian blue staining with critical electrolyte concentrations (CEC) of MgCl2. At 9 days of gestation, the normal and abnormal embryos showed a similar pattern of alcian blue staining with a CEC of 0.00 M or 0.05 M MgCl2. However, with a CEC of 0.30 M MgCl2, the basal lamina in the abnormals stained more prominently, particularly the lamina rara externa, suggesting the presence of more sulfated glycosaminoglycans (GAG) in the abnormals. Moreover, predigestion of the tissues with Streptomyces hyaluronidase, which removes hyaluronic acid (HA), indicated that the abnormal basal lamina contained relatively less HA than in the normal embryos. By 10 days of gestation the normal basal lamina contained relatively more sulfated GAG and less HA and was thus more similar in appearance to that in the abnormal embryos. This apparently premature shift from HA predominance to sulfated GAG predominance in the abnormal basal lamina may be of significance in the etiology of dysraphism in this mutant.     

External electric fields stimulate the electrogenic calcium/sodium exchange in plant protoplasts

External electric fields of low intensity stimulated calcium influx in protoplasts isolated from carrot cell suspension cultures in field intensity dependent and frequency-dependent ways. The field-induced calcium uptake involved a temperature-dependent system that was saturable by external calcium. The induction process appeared mainly cumulative as long as the morphology of the protoplasts did not change (up to 10 min). The stimulation elicited by the electric fields was effective even after switching the field off; the influx increased for 5 min and then slowed down to its initial value 15 min later. During electrostimulation, an additional amount of ATP was accumulated; on removal of the stimulatory field, the extra amount of ATP was consumed, whereas the plasma membrane was hyperpolarized and sodium ions were expelled from the protoplasts. Inhibition of either ATP accumulation or consumption results in the inhibition of both calcium influx and sodium efflux, demonstrating that these processes are coupled. From the data obtained in this work, it may be concluded that the electric field stimulates an ATP synthase like activity; the consumption of the ATP thus formed elicits an electric potential (probably due to the efflux of cations and more specifically sodium) that drives the influx of calcium.     

Extremely low-frequency magnetic field exposure and protection against UV-induced death in chicken embryos

We report on a study where 4-day old chicken embryos from different flocks were pre-treated with 50 Hz magnetic fields (MF) prior to a 60-min UV-C exposure (1.7 mW/cm(2)) to investigate the possible protective effect of MF exposure on UV-induced embryo death. Different flux densities (0.010, 0.025, 0.050, 0.10, and 0.20 mT), field directions (vertical and horizontal), as well as MF exposure times (10, 20, and 60 min) were employed. We did not find any significant effects by MF exposure, irrespective of exposure time, flux density, or field direction on the survival of embryos. Neither could we find any flock dependency on sensitivity to MF exposure.     

Prenatal death and malformations after irradiation of mouse zygotes with neutrons or X-rays

Female mice (strain: "Heiligenberger Stamm") were irradiated with neutrons (7 MeV) or X-rays when embryos were at the early zygote stage; uterine contents were examined on gestation day 19 for prenatal mortality and malformed fetuses. For both radiation qualities, the dose-dependent survival curve fitted well to a simple exponential equation; the neutron relative biological efficiency (RBE) value was 2.3. The major fraction of deaths induced by exposure to neutrons or X-rays occurred before implantation. Aside from dead embryos, malformed fetuses were observed 19 days p.c. (postconception). The number of malformed fetuses increased with a linear-quadratic function of neutron or X-ray dose. Malformations were mainly gastroschisis, although omphaloceles and anencephalies were also observed. The neutron RBE value for the induction of malformations varied from 2.0 to 2.8 in the dose range tested. Except after 75-cGy neutrons, no significant increase in the proportion of stunted or skeletally malformed fetuses was noted. Our results indicated that the reaction of preimplantation embryos to irradiation could be more complex than the simple "all-or-none" response considered so far.     

Hyperglycemia, hypoxia and their combination exert oxidative stress and changes in antioxidant gene expression: studies on cultured rat embryos

INTRODUCTION: Hyperglycemia and hypoxia are well‐known teratogens that may affect many animal species, including man. We hypothesize that a combination of hypoxia and hyperglycemia will increase embryonic damage produced by either factor individually. We investigated the interrelationship between hyperglycemia and hypoxia and their effects on genes involved in the balance of embryonic redox status. METHODS: Rat embryos (10.5‐day‐old) were cultured for 28 hr in culture medium with about 6 mg/ml of glucose and 20% oxygen (hyperglycemia), with 10% oxygen (hypoxia) and 2.4 g/ml glucose (normal) or a combination of both 6 mg/ml glucose and 10% oxygen. Antioxidant capacity was determined by activity and gene expression of antioxidant enzymes: Cu/Zn SOD, Mn‐SOD, CAT, and GSH‐px using real time PCR. RESULTS: Hyperglycemia, hypoxia, or their combination, decreased embryonic growth and induced a high rate (62–78%) of anomalies mainly of the nervous system, heart, and limbs. CAT mRNA and GSH‐px mRNA were decreased in the malformed embryos exposed to hyperglycemia, to hypoxia or their combination. CAT mRNA was also decreased in the nonmalformed embryos subjected to hyperglycemia and hypoxia. Cu/Zn SOD mRNA was increased in all experimental embryos whether malformed or not, whereas Mn‐SOD was drastically decreased. Total SOD and CAT like activity were changed very little in the experimental embryos compared to controls. CONCLUSIONS: Both hyperglycemia, hypoxia, and their combination reduce embryonic growth and development, induce embryonic anomalies, and modify the expression of the principle antioxidant genes. However, hypoxia does not seem to enhance the damaging effects of hyperglycemia except its effects of embryonic growth. Birth Defects Res (Part B) 92:231–239, 2011. © 2011 Wiley‐Liss, Inc.     

The superposition of a temporally incoherent magnetic field inhibits 60 Hz-induced changes in the ODC activity of developing chick embryos

Previously, we have shown that the application of a weak (4 μT) 60 Hz magnetic field (MF) can alter the magnitudes of the ornithine decarboxylase (ODC) activity peaks which occur during gastrulation and neurulation of chick embryos. We report here the ODC activity of chick embryos which were exposed to the superposition of a weak noise MF over a 60 Hz MF of equal (rms strength). In contrast to the results we obtain with a 60 Hz field alone, the activity of ODC in embryos exposed to the superposition of the incoherent and 60 Hz fields was indistinguishable from the control activity during both gastrulation and neurulation. This result adds to the body of experimental evidence which demonstrates that the superposition of an incoherent field inhibits the response of biological systems to a coherent MF. The observation that a noise field inhibits ODC activity changes is consistent with our speculation that MF-induced ODC activity changes during early development may be related to MF-induced neural tube defects at slightly later stages (which are also inhibited by the superposition of a noise field). Bioelectromagnetics 19:53–56, 1998. © 1998 Wiley-Liss, Inc.     

The propagation speeds of calcium action potentials are remarkably invariant

This paper critically compiles all published cases of established or putative calcium action potentials (or ultrafast calcium waves) where their speeds are known and are not limited by intercellular delays. The 127 cases include data from neurons or nerve nets within systems that range from cnidaria, ctenophores, molluscs, crustaceans, worms, echinoderms and tunicates up to mammalian brains; from muscle cells within organisms that range from Beröe, Cestum, moths, a crab, molluscs, a tunicate, frogs, chick embryos and turtles up to mammalian hearts; from epithelia in cnidaria and tunicates; even from a dinoflagellate and an insectivorous plant as well as reconstituted heart strands. They reveal a restriction to values of about 10–40 cm/sec at 20 degrees C and comparable restrictions at other temperatures. Moreover — unlike the speeds of sodium action potentials — the speeds of calcium ones are unrelated to cell diameter, at least over the available range of about 0.1 to 30 microns. Why do calcium action potentials have such fixed propagation speeds? Perhaps evolution has driven them to be the fastest waves of calcium influx which avoid subsurface poisoning.     

Changes in the Membrane Permeability of Frog's Sartorius Muscle Fibers in Ca-Free EDTA Solution

The changes in the membrane permeability to sodium, potassium, and chloride ions as well as the changes in the intracellular concentration of these ions were studied on frog sartorius muscles in Ca-free EDTA solution. It was found that the rate constants for potassium and chloride efflux became almost constant within 10 minutes in the absence of external calcium ions, that for potassium increasing to 1.5 to 2 times normal and that for chloride decreasing about one-half. The sodium influx in Ca-free EDTA solution, between 30 and 40 minutes, was about 4 times that in Ringer's solution. The intracellular sodium and potassium contents did not change appreciably but the intracellular chloride content had increased to about 4 times normal after 40 minutes. By applying the constant field theory to these results, it was concluded that (a) P_Cl did not change appreciably whereas P_K decreased to a level that, in the interval between 10 and 40 minutes, was about one-half normal, (b) P_Na increased until between 30 and 40 minutes it was about 8 times normal. The low value of the membrane potential between 30 and 40 minutes was explained in terms of the changes in the membrane permeability and the intracellular ion concentrations. The mechanism for membrane depolarization in this solution was briefly discussed.