131
Static, Low-Frequency, and Pulsed Magnetic Fields
3.3.1.4 Reproduction and Development
There is a series of reports concerning the effects of many different kinds of magnetic
fields on reproduction and development. In particular, in the last 10 years the effects
of strong SMFs, including MRI fields (uniform SMFs, gradient magnetic fields, and
radiofrequency [RF] pulse fields), on fertility, the developing embryo, and the fetus have
been investigated in great detail (Ueno and Shigemitsu 2007). In contrast, more recently,
reports on the effects of extremely weak magnetic fields or removal of the geomagnetic
field have been increasing.
The Persinger research group (Whissell and Persinger 2007) investigated the interaction between NO modulation and perinatal weak magnetic fields. Dams were exposed
from 2 days before to 14 days after birth to one of six magnetic field conditions (7 Hz;
1 nT, 5 nT, 10 nT, 50 nT, 500 nT, and sham) and given one among water, NO precursor
L-arginine, or the NOS inhibitor N-methylarginine (NMA). At weaning (day 22), their
offsprings were placed in the open field for observation. Rats given 50- or 500-nT field +
water were hyperactive and showed increased rearing and bodyweight. These effects
were attenuated or absent in groups given 50- or 500-nT field + NMA. The behavior of
groups given sham field + L-arginine was similar to that of animals given 50- or 500-nT
field + water. Results suggested a critical developmental role for NO and the involvement
of NO in magnetic field effects. The same research group further examined the effects
of extremely weak magnetic fields (0.5 Hz, 5–10 nT, for 8 days; McDonald and Persinger
2009). Adult rats were perinatally exposed to magnetic field or sham conditions while
their mothers drank tap water containing the NOS inhibitor L-arginine methyl ester
(L-NAME) or tap water alone. One week after birth the rats were rendered hypoxic for
1 minute or they served as controls. Exposure to either the magnetic field or the NOS
inhibitor reduced the numbers of neurons within the bed nucleus of the stria terminalis
by about 25%, whereas exposure to either the hypoxia or the magnetic field resulted in
comparable decreases in cell numbers within the ventromedial nucleus (dorsomedial
part). Males had 15% fewer neurons in these nuclei compared with females. The results
of for the interactions involving perinatal exposure to the magnetic field were comparable to the magnitudes of those associated with one minute of hypoxia for one week
postnatally. These results showed the sensitivity of specific structures of the developing
brain to interactions between subtle environmental variables.
The same research group investigated the effects of weak magnetic fields (7 Hz,
≤1.2 μT) on blood chemistry, cerebral sizes, and hippocampal cytomorphology in adult
male and female albino Wistar rats (St-Pierre, Mazzuchin, and Persinger 2008). Rats
had been exposed during their entire prenatal development period to any of the following magnetic fields: very low (5–20 nT), low (30–50 nT), medium (90–580 nT), or high
(590 nT to 1.2 μT). Adult rats that had been exposed prenatally to the physiologically
patterned magnetic fields at low and medium intensities exhibited peak elevations of
aminotransaminase, glucose, and uric acid. Numbers of cytometric anomalies were also
found to be significantly elevated within regions of the hippocampus known for neuronal neogenesis in adults. The results suggested that a common factor in cellular adhesion
or plasticity might be permanently altered by prenatal exposure to a narrow intensity of
a series of physiologically patterned magnetic fields.
Static, Low-Frequency, and Pulsed Magnetic Fields
3.3.1.4 Reproduction and Development
There is a series of reports concerning the effects of many different kinds of magnetic
fields on reproduction and development. In particular, in the last 10 years the effects
of strong SMFs, including MRI fields (uniform SMFs, gradient magnetic fields, and
radiofrequency [RF] pulse fields), on fertility, the developing embryo, and the fetus have
been investigated in great detail (Ueno and Shigemitsu 2007). In contrast, more recently,
reports on the effects of extremely weak magnetic fields or removal of the geomagnetic
field have been increasing.
The Persinger research group (Whissell and Persinger 2007) investigated the interaction between NO modulation and perinatal weak magnetic fields. Dams were exposed
from 2 days before to 14 days after birth to one of six magnetic field conditions (7 Hz;
1 nT, 5 nT, 10 nT, 50 nT, 500 nT, and sham) and given one among water, NO precursor
L-arginine, or the NOS inhibitor N-methylarginine (NMA). At weaning (day 22), their
offsprings were placed in the open field for observation. Rats given 50- or 500-nT field +
water were hyperactive and showed increased rearing and bodyweight. These effects
were attenuated or absent in groups given 50- or 500-nT field + NMA. The behavior of
groups given sham field + L-arginine was similar to that of animals given 50- or 500-nT
field + water. Results suggested a critical developmental role for NO and the involvement
of NO in magnetic field effects. The same research group further examined the effects
of extremely weak magnetic fields (0.5 Hz, 5–10 nT, for 8 days; McDonald and Persinger
2009). Adult rats were perinatally exposed to magnetic field or sham conditions while
their mothers drank tap water containing the NOS inhibitor L-arginine methyl ester
(L-NAME) or tap water alone. One week after birth the rats were rendered hypoxic for
1 minute or they served as controls. Exposure to either the magnetic field or the NOS
inhibitor reduced the numbers of neurons within the bed nucleus of the stria terminalis
by about 25%, whereas exposure to either the hypoxia or the magnetic field resulted in
comparable decreases in cell numbers within the ventromedial nucleus (dorsomedial
part). Males had 15% fewer neurons in these nuclei compared with females. The results
of for the interactions involving perinatal exposure to the magnetic field were comparable to the magnitudes of those associated with one minute of hypoxia for one week
postnatally. These results showed the sensitivity of specific structures of the developing
brain to interactions between subtle environmental variables.
The same research group investigated the effects of weak magnetic fields (7 Hz,
≤1.2 μT) on blood chemistry, cerebral sizes, and hippocampal cytomorphology in adult
male and female albino Wistar rats (St-Pierre, Mazzuchin, and Persinger 2008). Rats
had been exposed during their entire prenatal development period to any of the following magnetic fields: very low (5–20 nT), low (30–50 nT), medium (90–580 nT), or high
(590 nT to 1.2 μT). Adult rats that had been exposed prenatally to the physiologically
patterned magnetic fields at low and medium intensities exhibited peak elevations of
aminotransaminase, glucose, and uric acid. Numbers of cytometric anomalies were also
found to be significantly elevated within regions of the hippocampus known for neuronal neogenesis in adults. The results suggested that a common factor in cellular adhesion
or plasticity might be permanently altered by prenatal exposure to a narrow intensity of
a series of physiologically patterned magnetic fields.