Geomagnetic activity and enhanced mortality in rats with acute (epileptic) limbic lability

Presumably unrelated behaviors (e.g. psychiatric admissions, seizures, heart failures) have been correlated with increased global geomagnetic activity. We have suggested that all of these behaviors share a common source of variance. They are evoked by transient, dopamine-mediated paroxysmal electrical patterns that are generated within the amygdala and the hippocampus of the temporal lobes. Both the probability and the propagation of these discharges to distal brain regions are facilitated when nocturnal melatonin levels are suppressed by increased geomagnetic activity. In support of this hypothesis, the present study demonstrated a significant correlation of Pearsonr=0.60 between mortality during the critical 4-day period that followed induction of libic seizures in rats and the ambient geomagnetic activity during the 3 to 4 days that preceded death; the risk increased when the 24 h geomagnetic indices exceeded 20 nT for more than 1 to 2 days.     

Thymus mast cell numbers following perinatal and adult exposures to low intensity 0.5 Hz magnetic fields

In a factorial design, 40 male 200-day-old rats that had been exposed from 2.5 days before to 2.5 days after birth to either 0.5 Hz rotating magnetic fields (RMFs) between 10^–3T to 10^–6T or to sham fields and maintained after weaning in one of two typical caging conditions were exposed as adults to either one of three 0.5 Hz RMF intensities (10^–6T, 10^–7T or 10^–8T) or to sham fields or to colony room control conditions. The numbers of mast cells (MCs/mm²) were determined for thymus tissues stained with thionin and toluidine blue. Thymuses from adult rats that had been perinatally exposed to the RMF displayed a marginally significant 20% to 35% elevation in MC numbers relative to sham-field controls. However the adult exposures did not sïgnificantlÿ affect the MC numbers. The two postweaning caging conditions, a non-magnetic field comparator variable, induced a significant 35% difference in MC numbers. The absence of sïgnificant perinatal by adult RMF exposure interactions indicated that early magnetic field exposure did not alter adult thymus responsivity to weaker but more natural intensity levels.     

Functional role of extranucleosomal DNA and the entry site of the nucleosome in chromatin remodeling by ISW2

A minimal amount of extranucleosomal DNA was required for nucleosome mobilization by ISW2 as shown by using a photochemical histone mapping approach to analyze nucleosome movement on a set of nucleosomes with varied lengths of extranucleosomal DNA. ISW2 was ineffective in repositioning or mobilizing nucleosomes with 相似文献   

Molecular mechanisms of nitrogen dioxide induced epithelial injury in the lung

The lung can be exposed to a variety of reactive nitrogen intermediates through the inhalation of environmental oxidants and those produced during inflammation. Reactive nitrogen species (RNS) include, nitrogen dioxide (.NO2) and peroxynitrite (ONOO-). Classically known as a major component of both indoor and outdoor air pollution, .NO2 is a toxic free radical gas. .NO2 can also be formed during inflammation by the decomposition of ONOO- or through peroxidase-catalyzed reactions. Due to their reactive nature, RNS may play an important role in disease pathology. Depending on the dose and the duration of administration, .NO, has been documented to cause pulmonary injury in both animal and human studies. Injury to the lung epithelial cells following exposure to .NO2 is characterized by airway denudation followed by compensatory proliferation. The persistent injury and repair process may contribute to airway remodeling, including the development of fibrosis. To better understand the signaling pathways involved in epithelial cell death by .NO2 or otherRNS, we routinely expose cells in culture to continuous gas-phase .NO2. Studies using the .NO2 exposure system revealed that lung epithelial cell death occurs in a density dependent manner. In wound healing experiments, .NO2 induced cell death is limited to cells localized in the leading edge of the wound. Importantly, .NO2-induced death does not appear to be dependent on oxidative stress per se. Potential cell signaling mechanisms will be discussed, which include the mitogen activated protein kinase, c-Jun N-terminal Kinase and the Fas/Fas ligand pathways. During periods of epithelial loss and regeneration that occur in diseases such as asthma or during lung development, epithelial cells in the lung may be uniquely susceptible to death. Understanding the molecular mechanisms of epithelial cell death associated with the exposure to .NO2 will be important in designing therapeutics aimed at protecting the lung from persistent injury and repair.     

Chromatin remodeling by ISW2 and SWI/SNF requires DNA translocation inside the nucleosome

Chromatin-remodeling complexes regulate access to nucleosomal DNA by mobilizing nucleosomes in an ATP-dependent manner. In this study, we find that chromatin remodeling by SWI/SNF and ISW2 involves DNA translocation inside nucleosomes two helical turns from the dyad axis at superhelical location-2. DNA translocation at this internal position does not require the propagation of a DNA twist from the site of translocation to the entry/exit sites for nucleosome movement. Nucleosomes are moved in 9- to 11- or approximately 50-base-pair increments by ISW2 or SWI/SNF, respectively, presumably through the formation of DNA loops on the nucleosome surface. Remodeling by ISW2 but not SWI/SNF requires DNA torsional strain near the site of translocation, which may work in conjunction with conformational changes of ISW2 to promote nucleosome movement on DNA. The difference in step size of nucleosome movement by SWI/SNF and ISW2 demonstrates how SWI/SNF may be more disruptive to nucleosome structure than ISW2.     

Day time wheel running activity in laboratory rats following geomagnetic event of 5–6 July 1974

Albino laboratory rats that were given free access to running wheels while maintained on a 12:12 h L:D schedule were observed to display marked increases in day cycle activity following an unusually intense geomagnetic storm. The activity changes were not immediate but peaked one day to several days after the storm. Two less intense geomagnetic storm conditions during the 51 day observation period were associated with less marked activity increases. Ambient room temperature fluctuations were not significantly correlated with either geomagnetic activity or day cycle activity measures.     

Combined effects of complex magnetic fields and agmatine for contextual fear learning deficits in rats

Acute post-training exposures to weak intensity theta-burst stimulation (TBS) patterned complex magnetic fields attenuated the magnitude of conditioned fear learning for contextual stimuli. A similar learning impairment was evoked in a linear and dose-dependent manner by pre-conditioning injections of the polyamine agmatine. The present study examined the hypothesis that whole-body applications of the TBS complex magnetic field pattern when co-administered with systemic agmatine treatment may combine to evoke impairments in contextual fear learning. Within minutes of 4 mg/kg agmatine injections, male Wistar rats were fear conditioned to contextual stimuli and immediately exposed for 30 min to the TBS patterned complex magnetic field or to sham conditions. TBS patterned complex magnetic field treatment was found to linearly summate with the contextual fear learning impairment evoked by agmatine treatment alone. Furthermore, we report for sham-treated rats, but not rats exposed to the synthetic magnetic field pattern, that the magnitude of learned fear decreased and the amount of variability in learning increased, as the K-index (a measure of change in intensity of the time-varying ambient geomagnetic field) increased during the 3-hr intervals over which conditioning and testing sessions were conducted.     

Possible cardiac driving by an external rotating magnetic field

The possible role of a rotating magnetic field as a potential "driver" for experimentally drug-induced failing heart systems was investigated. In two experiments, rats that had been exposed during successive doses of pentobarbital for approximately four hours to a rotating magnetic field of 0.5 Hz, 1–20 gauss, showed contraction rates within the field frequency range significantly longer than either control field or sham-field rats before cessation of QRS. However no significant differences were found between the groups in SGOT, serumiron or oxyhemoglobin levels. Implications of the results are discussed in relation to natural ELF cardiofrequency signals and failing cardiac systems.

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Zusammenfassung In zwei Experimenten mit Ratten wurde untersucht ob rotierende magnetische Felder als Steuerfaktor bei barbituratinduziertem Nachlassen der Herzfunktion eine Rolle spielen. Tiere, die in 30 Min Abständen Na-Pentobarbiturat erhielten und während 4 Stunden einem rotierenden magnetischen Feld der Stärke von 0,5 Hz 10–20 Gauss ausgesetzt waren, zeigten signifikant längere Herzkontraktionsraten innerhalb des Feldfrequenzbereiches vor dem Stillstand des QRS als Kontrollgruppen. Im Serumtransaminase- (GOT), Serumeisen- und Oxyhämoglobinspiegel waren am Versuchsende keine signifikanten Unterschiede zwischen den Gruppen feststellbar. Die Bedeutung der Befunde wird unter Bezug auf natürliche niederfrequente elektromagnetische Herzfrequenzimpulse und geschwächte Herzfunktion besprochen.

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Resume L'auteur a étudié les possibilités d'effets d'un champ magnétique tournant agissant comme "stimulateur" possible des systèmes cardiaques défaillants par suite de l'influence de drogues administrées expérimentalement. Lors de deux expériences, des rats, sous l'influence de doses successives de pentobarbital, ont été exposés pendant approximativement quatre heures à un champ tournant de 0.5 Hz et 1–20 gauss. Ils ont alors montré des rythmes de contractions comprises dans les limites de l'échelle de fréquence du champ, de durée significativement plus longue avant la cessation du QRS, que ceux de rats exposés à un champ de contrôle ou à un champ simulé. Cependant, les groupes n'ont pas montré de différences marquantes en ce qui concerne les niveaux de la transaminase du sérum, du taux de fer ou de l'oxyhémoglobine. Les implications des résultats sont étudiées dans la relation existant entre les signaux naturels de fréquence cardiaque IF et les systèmes cardiaques défaillants.