Clinical breast concerns in low-risk pediatric patients: practice review with proposed recommendations.

BACKGROUND: Fibroadenoma is overwhelmingly the most common pediatric breast lesion. Breast malignancy is quite uncommon in children, most frequently metastatic or hematological malignancy. Core biopsy has largely replaced excision for diagnosis of breast masses in adults. OBJECTIVE: The purpose of this study is two-fold: (1) compare utilization at our institution of interventional procedures vs. surgery for breast mass diagnosis in patients ≤18 years and (2) propose guidelines for breast imaging and biopsy in this population. MATERIALS AND METHODS: We extracted data for all patients ≤18 who, between 2004 and 2016, underwent either (a) imaging and/or intervention procedure, or (b) breast surgery, from the Radiology Information System and Pathology Data System, respectively. We recorded age, gender, imaging, procedure, lesion size and histopathology. RESULTS: We found 1,050 pediatric patients ≤18 years who underwent diagnostic breast ultrasound between 2004 and 2016. Of these, 168 patients underwent 199 interventional procedures. One hundred thirty patients underwent 160 core biopsies of solid lesions. Core biopsy pathology diagnosed benign lesions in 99%, of which 84.3% were fibroadenomas (n=135). One malignancy was diagnosed, B cell lymphoma. Two hundred three patients underwent surgical excision for 266 discrete lesions, and 89% were fibroadenomas. Seven benign phyllodes tumors were surgically diagnosed. No malignancies were diagnosed. CONCLUSION: Core biopsy in patients 18 years and younger is well-tolerated, has few risks, and is preferable to surgery in developing breasts, but the goal is to avoid any breast procedure whenever possible. We propose guidelines for pediatric breast imaging, follow-up, core biopsy and excisions.

GLIOMA CELL PROLIFERATION MEDIATED BY COENZYME Q10 AT SERUM DEPRIVATION IN VITRO.

Mechanisms of coenzyme Q10 effect on serum-deprived glioma cell proliferation have been studied. Our results have shown that the addition of coenzyme Q10 into serum-free culture medium leads to increase in cell viability, stimulation of cell growth, as well as restoration of mitochondrial potential and increase of quantity of energized mitochondria. It has been found out that coenzyme Q10-induced glioma cell proliferation under serum deficiency is a result of intracellular reduced glutathione concentration decrease with subsequent activation of proteinkinase C, ERK1/2 and phosphoinositol-3-kinase.

Diagnostics and treatment of insulinoma.

Insulinomas are the most common functioning pancreatic neuroendocrine neoplasms (pNENs), developed mainly from pancreatic islet cells. More than 90% of insulinomas are sporadic, benign and small sized. Autonomous production of insulin results in neuroglycopenic and adrenergic symptomatology with potential lethality. Surgery remains the only curative treatment with a high success rate. Preoperative tumor localization is challenging, but important for appropriate surgical approach. Metastatic forms represent a challenge, mainly on the field of therapy, with the need of tumor burden reduction and glycemia stabilization. The rarity of malignant forms limits reports on therapeutic strategies and outcome. Authors present in this article a summarized overview of epidemiology, clinic, diagnostics and treatment of benign and malign forms of insulinomas.

Lessons learned from an intercalibration exercise on the quantification and characterisation of microplastic particles in sediment and water samples.

An intercalibration exercise on the characterisation of microplastics in marine sediment and water samples was carried out among five laboratories involved in the implementation of the Marine Strategy Framework Directive (MSFD) in their country. The samples were prepared by mixing cleaned natural sediment and sea water with microplastics sets made of particles of various polymers, shapes and colours. Overall, the errors on total counts were under 25% in absolute value. The risk of non-detection and loss of particles is greater than the risk of contamination during sample analysis. Significant differences are observed among particle types. It appears difficult to obtain reliable and comparable data on the colour of microplastics. A comparison of the errors with regards to the protocols used led to recommend NaCl [1.2 g/cm3] density separation for sediment and one filtering step (200 µm). The operators' experience appears as a key factor for the quality of the results.

Low-Dose Image-Guided Pediatric CNS Radiation Therapy: Final Analysis From a Prospective Low-Dose Cone-Beam CT Protocol From a Multinational Pediatrics Consortium.

BACKGROUND: Lower-dose cone-beam computed tomography protocols for image-guided radiotherapy may permit target localization while minimizing radiation exposure. We prospectively evaluated a lower-dose cone-beam protocol for central nervous system image-guided radiotherapy across a multinational pediatrics consortium. METHODS: Seven institutions prospectively employed a lower-dose cone-beam computed tomography central nervous system protocol (weighted average dose 0.7 mGy) for patients ≤21 years. Treatment table shifts between setup with surface lasers versus cone-beam computed tomography were used to approximate setup accuracy, and vector magnitudes for these shifts were calculated. Setup group mean, interpatient, interinstitution, and random error were estimated, and clinical factors were compared by mixed linear modeling. RESULTS: Among 96 patients, with 2179 pretreatment cone-beam computed tomography acquisitions, median age was 9 years (1-20). Setup parameters were 3.13, 3.02, 1.64, and 1.48 mm for vector magnitude group mean, interpatient, interinstitution, and random error, respectively. On multivariable analysis, there were no significant differences in mean vector magnitude by age, gender, performance status, target location, extent of resection, chemotherapy, or steroid or anesthesia use. Providers rated >99% of images as adequate or better for target localization. CONCLUSIONS: A lower-dose cone-beam computed tomography protocol demonstrated table shift vector magnitude that approximate clinical target volume/planning target volume expansions used in central nervous system radiotherapy. There were no significant clinical predictors of setup accuracy identified, supporting use of this lower-dose cone-beam computed tomography protocol across a diverse pediatric population with brain tumors.

Nationwide survey of CTX-M-type extended-spectrum beta-lactamases among Klebsiella pneumoniae isolates in Slovenian hospitals.

Among 177 extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolates collected from 11 Slovenian hospitals in 2005 and 2006, 60 (34%), from eight hospitals, harbored genes for CTX-M enzymes, with bla(CTX-M-15) detected by sequencing. These 60 isolates comprised 11 pulsed-field gel electrophoresis-defined strains, with several clusters of closely related isolates. Plasmids encoding CTX-M-15 enzyme were highly transmissible.

Quality of life following salvage surgery for squamous cell carcinoma of the anus.

INTRODUCTION: Squamous cell carcinoma of the anus is a rare condition. First line treatment is combined chemo-radio therapy. As many as a third of patients undergoing chemo-radiotherapy will experience recurrence. These patients often undergo salvage surgery with an extended abdominoperineal excision. The aim of this study was to examine the quality of life in disease free survivors following salvage surgery for squamous cell carcinoma of the anus. MATERIAL AND METHODS: Patients undergoing salvage surgery for SCCA at Copenhagen University Hospital Herlev between 1st of January 2011 and 31st December 2016 were identified and quality of life was assessed with EORTC QLQ-C30 and EORTC QLQ-CR29 questionnaires. RESULTS: 47 patients underwent salvage surgery for relapse or residual tumor in the period. From this cohort 25 disease-free survivors were identified. Fourteen (56%) patients returned a completed questionnaire. Overall median global health status was 75(range 20-100). Functional scores were generally high. In General, symptom scores were low, however all men reported impotence with a median symptom score of 100(range 67-100) and half the women reported dyspareunia. Urinary impairment was present in half the patients. Abdominal and buttock pain scores were low. CONCLUSION: Quality of life following salvage surgery for squamous cell carcinoma of the anus is affected but at an acceptable level. However, there are considerable side-affects in the form of impotence, dyspareunia and urinary impairment.

Measurement of superficial dose from a static tomotherapy beam.

Superficial doses were measured for static TomoTherapy Hi-Art beams for normal and oblique incidence. Dose was measured at depths < or = 2 cm along the central axis of 40 x 5 cm2 and 40 x 2.5 cm2 beams at normal incidence for source to detector distances (SDDs) of 55, 70, and 85 cm. Measurements were also made at depths normal to the phantom surface for the same beams at oblique angles of 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 83 degrees from the normal. Data were collected with a Gammex/RMI model 449 parallel-plate chamber embedded in a solid water phantom and with LiF thermoluminescent dosimeters (TLDs) in the form of powder. For comparison, measurements were made on a conventional 6 MV beam (Varian Clinac 2100C) at normal incidence and at an oblique angle of 60 degrees from the normal. TomoTherapy surface dose varied with the distance from the source and the angle of incidence. For normal incidence, surface dose increased from 0.16 to 0.43 cGy/MU as the distance from the source decreased from 85 to 55 cm for the 40 x 5 cm2 field and increased from 0.12 to 0.32 cGy/MU for the 40 x 2.5 cm2 field. As the angle of incidence increased from 0 degrees to 83 degrees, surface dose increased from 0.24 to 0.63 cGy/MU for the 40 x 5 cm2 field and from 0.18 to 0.58 cGy/MU for the 40 x 2.5 cm2 field. For normal incidence at 55 cm SDD, the surface dose relative to the dose at d(max) for the 40 x 5 cm2 TomoTherapy Hi-Art beam was 31% less than that from a conventional, flattening filter based linear accelerator. These data should prove useful in accessing the accuracy of the TomoTherapy treatment planning system to predict the dose at superficial depths for a static beam delivery.

Physiologically patterned weak magnetic fields applied over left frontal lobe increase acceptance of false statements as true.

Fifty men and women were exposed to only one of four experimentally generated magnetic fields over the left prefrontal region (above the eyebrow) or to a sham field immediately after the words "true" or "false" were presented following statements of definitions of words for a "foreign language". Three of the patterns (25 Hz, 50 Hz, or burst-firing) with intensities between 1 and 10 microT were presented for 1 s during the refutation process (immediately after the offset of "true" or "false") for specific statements from a total of 28 statements. The fourth pattern was a variable approximately 7-10 Hz (10 nT) field generated from the circuitry that was present continuously during the entire experiment. When the statements were presented again, the groups who had received the burst-firing ("limbic") or 25 Hz pulsed magnetic fields during the refutation process accepted about twice the number of false statements as true compared to those exposed to the 50 Hz field or sham-field conditions. The treatments did not significantly affect the numbers of true statements accepted as false. These results suggest that the appropriately pulsed magnetic field during the refutation process of what one has been told or has heard can increase the probability a person will accept a false statement as true.

Increased theta activity in quantitative electroencephalographic (QEEG) measurements during exposure to complex weak magnetic fields.

Previous research has shown that exposure to circumcerebral weak magnetic fields with different rates of acceleration applied in a counterclockwise rotation around the head was associated with increased estimations of subjective time and as much as a 30% increase in power within the theta range within quantitative electroencephalographic (QEEG) recordings. The largest effect was associated with magnetic fields applied with 20 ms rates of change through each of the successively stimulated, equally spaced, 8 circumcerebral solenoids. The purpose of the present study was to compare the intracerebral power spectra associated with the rotation of the same patterns in either the clockwise or counterclockwise direction. The results generally replicated previous reports and showed enhanced power over regions of the left hemisphere during clockwise rotations and over the right hemisphere during counterclockwise rotations. These results were considered congruent with the creation of "interference patterns" between the rostral-caudal generation of endogenous cerebral magnetic fields putatively associated with consciousness and the spatial direction of the applied rotating magnetic fields.

Antimicrobial disinfection effect of a laundering procedure for hospital textiles against various indicator bacteria and fungi using different substrates for simulating human excrements.

Recent studies confirm the increase of nosocomial infections and microbial resistance. One of the possible causes is infected textiles due to inappropriate laundering procedures. Most Slovenian laundries use thermal laundering procedures with high energy and water consumption to disinfect hospital textiles. In addition to this fact, there is an increasing number of hospital textiles composed of cotton/polyester blends that cannot endure high temperatures of thermal disinfection. On the other hand, decreasing the temperature of laundering procedures enhances the possibility of pathogenic microorganisms to survive the laundering procedure. In our research, we determined the antimicrobic laundering effect by simulating a common laundering procedure for hospital textiles in the laboratory washing machine at different temperatures by the use of bioindicators. Enterococcus faecium, Staphylococcus aureus, Mycobacterium terrae, Enterobacter aerogenes, and Pseudomonas aeruginosa were used for determining the antibacterial laundering effect. Candida albicans was used for determining the antifungal laundering effect. Swine blood, artificial sweat, and swine fat were used as substrates for simulating human excrements and were inoculated together with the chosen microorganisms onto cotton pieces to simulate real laundering conditions. It was found that E. faecium, S. aureus, E. aerogenes, and P. aeruginosa survived at 60 degrees C, but no microorganisms were found at 75 degrees C.

Circadian dependence of interferon antitumor activity in mice.

BACKGROUND: Chronobiological studies with anticancer drugs have shown that their effectiveness and/or toxicity is significantly influenced by the time of their administration in the circadian cycle. Previous studies also have shown that the myelotoxicity of interferons is similarly influenced. PURPOSE: This study was undertaken to evaluate the antitumor activity of interferons as a function of their administration to animals at defined points in the circadian cycle with equal light and dark periods. METHODS: A murine tumor model was employed. Following adaptation to alternating cycles of 12 hours of light and 12 hours of dark for a period of 2-3 weeks, C57BL/6 mice were inoculated with B16 melanoma cells intraperitoneally at different hours after light onset. Exactly 24 hours after inoculation, each group received intraperitoneal injections of either recombinant human interferon alpha (rHuIFN-alpha A/D), recombinant murine IFN-gamma (rMuIFN-gamma), or interferon-carrier solution as control (once a day for 5 days) and were monitored for the length of their survival. RESULTS: The antitumor activity (calculated as percent increased life span) of both rHuIFN-alpha A/D and rMuIFN-gamma varied with the points at which they were administered in the circadian cycle. However, the points showing minimum and maximum activity for rHuIFN-alpha A/D (12-16 and 0-4 hours after light onset, respectively) did not correspond with the points for the rMuIFN-gamma (0-8 and 16 hours after light onset, respectively). To generate maximum antitumor activity, approximately fivefold higher amounts of rHuIFN-alpha A/D were required at 12 than at 4 hours after light onset (dose range, 3333-90,000 IU/d) (P < .0001). Similarly, for rMuIFN-gamma at least 8.5-fold greater amounts were required at 8 than at 16 hours after light onset (dose range, 667-6000 IU/d) (P < .01). CONCLUSIONS: In the murine tumor model, administration of rHuIFN-alpha A/D at 4 hours after light onset and rMuIFN-gamma at 16 hours after light onset may produce maximum antitumor activity.

Impact of the New Jersey Breast Density Law on Imaging and Intervention Volumes and Breast Cancer Diagnosis.

PURPOSE: Increased breast density is acknowledged as an independent risk factor for breast cancer and may obscure malignancy on mammography. Approximately half of all mammograms depict dense breasts. Legislation related to mandatory breast density notification was first enacted in Connecticut in 2009. On May 1, 2014, New Jersey joined other states with similar legislation. The New Jersey breast density law (NJBDL) mandates that mammography reports acknowledge the relevance and masking effect of mammographic breast density. The aim of this study was to assess the impact of the NJBDL at one of the state's largest ACR-accredited breast centers. METHODS: A retrospective chart review was performed to determine changes in imaging and intervention utilization and modality of cancer diagnosis after enactment of the legislation. Data for the present study were extracted from a review of all patients with core biopsy-proven malignancy at a large outpatient breast center between November 1, 2012, and October 31, 2015. Data were divided into the 18-month period before the implementation of the NJBDL (November 1, 2012 to April 30, 2014) and the 18-month period after passage of the law (May 1, 2014 to October 31, 2015). RESULTS: Screening ultrasound increased significantly after the implementation of the NJBDL, by 651% (1,530 vs 11,486). MRI utilization increased by 59.3% (2,595 vs 4,134). A total of 1,213 cancers were included in the final analysis, 592 in the first time period and 621 after law implementation. Breast cancer was most commonly detected on screening mammography, followed by diagnostic mammography with ultrasound for palpable concern, in both time periods. Of the 621 cancers analyzed, 26.1% (n = 162) were found in patients 50 years of age or younger. Results demonstrated that with respect to how malignancies were detected, age and average mammographic density were both statistically significant (P = .002). CONCLUSIONS: The NJBDL succeeded in publicizing the masking effect of dense breasts. The number of supplemental screening ultrasound and MRI examinations increased after the implementation of this legislation. An efficacy analysis affirmed the high sensitivity of screening MRI compared with other modalities. The use of MRI increased core biopsy efficiency and reduced the number of biopsies needed per cancer diagnosed.

Circadian variations in myelosuppressive activity of interferon-alpha in mice: identification of an optimal treatment time associated with reduced myelosuppressive activity.

A number of antitumor drugs have been shown to vary in their toxicity and in their antitumor potency according to the time in the circadian cycle at which they are administered. It was of interest to determine whether other agents, such as a biological response modifier, would also exhibit differential potency during the circadian cycle. Interferons (IFNs) are biological response modifiers which have antitumor and antiviral activity and which also have toxic side effects. A mouse model was used to study one of these toxic side effects, peripheral white blood cell (WBC) suppression. Interferon-induced peripheral WBC suppression was evaluated as a function of the time of recombinant human (rh) IFN-alpha A/D administration. Mice were maintained on cycles of 12 hours of light and 12 hours of darkness. The rhIFN-alpha A/D was administered at various hours after light onset (HALO). The rhIFN-alpha A/D-induced peripheral WBC suppressive effect varied in its intensity in a cyclical manner. Administration of rhIFN-alpha A/D at 0 HALO caused the greatest suppressive effect, while administration of rhIFN-alpha A/D at 8 HALO caused the least suppressive effect. Mice treated at 8 HALO were found to be about 10-fold less sensitive to the peripheral WBC suppressive effects of rhIFN-alpha A/D than mice treated at 0 HALO. This differential sensitivity to the peripheral WBC suppressive effects of rhIFN-alpha A/D was examined for 6 different times in the circadian cycle and was found to be a general effect, occurring throughout the circadian cycle. Using a granulocyte/macrophage colony-forming unit (GM-CFU) assay, bone marrow function was also shown to be differentially affected by treatment with rhIFN-alpha A/D at 0 HALO and 8 HALO in a manner parallel to that seen with peripheral WBC. Thus, rhIFN-alpha A/D exerts a differential effect on peripheral WBC counts and on bone marrow function according to the time in the circadian cycle at which it is administered to the mouse. Such temporal variation in the myelosuppressive activity of interferons could be important in designing future clinical trials with these antiviral and antitumor agents. Administration of interferons at empirically determined times in the circadian cycle could be used to reduce the myelotoxic side effects of interferons in humans.

Systemic effects of orally administered interferons and interleukin-2.

Orally administered interferons (IFN-alpha, IFN-beta, and IFN-gamma) have been shown to exert a number of systemic effects. Orally administered IFNs exert dose-dependent suppressive effects on the peripheral white blood cell (WBC) count. The suppression of the peripheral WBC count is mediated by a suppression of the function of the bone marrow, as measured in an in vitro bone marrow colony-forming assay. The peripheral WBC and bone marrow suppressive effects of orally administered IFNs are at least as potent as those occurring with parenterally administered IFNs. However, the mechanism by which orally administered IFNs exert these peripheral WBC suppressive and bone marrow suppressive effects differs significantly from that of parenterally administered IFNs: orally administered IFN is not detectable in the serum, the effect of orally administered IFN is not blocked by circulating antibody, the effect of orally administered IFN can be adoptively transferred by injection with peripheral white blood cells from donor mice, and the effect of orally administered IFN develops more slowly than that of parenterally administered interferon. Orally administered IFN-alpha employed alone and in synergistic combination with intraperitoneally administered IFN-gamma can exert an antitumor effect. Finally, orally administered interleukin-2 can exert a suppressive effect on both the peripheral white blood cell count and on the bone marrow. These observations suggest that the oral route may be an effective and novel mechanism for the efficacious administration of IFNs and other lymphokines/cytokines.

Trophoblastic interferons: do they modulate uterine cellular markers at the time of conceptus attachment in the pig?

Between days 12 and 20 of pregnancy, the trophectoderm of the porcine conceptus secretes two species of interferons (IFN): IFN-gamma (Type II), which is produced in substantial amounts, and IFN-delta (type I), for which secretion peaks at days 15-16 of gestation. The role of these embryonic IFNs is not known. We made the assumption that, in the pig, one possible role of these IFNs may be the remodelling and/or depolarization of the uterine endometrial epithelium, as a prerequisite for implantation and establishment of a functional placenta. A comparative analysis by immunohistochemistry of several cell membrane markers and ECM components of the cyclic and pregnant uterus was performed at day 15 post-oestrus. The markers were those likely to differ between a pregnant and cyclic uterus, or between different stages of pregnancy. A highly specific marker of IFN-gamma activity, namely MHC class II antigens in the uterine mucosa, was also examined. This study provides so far unreported data: in the endometrial epithelium of the pregnant uterus, we observed a partial relocalization of ZO-1, a marker of epithelial tight junctions, thus suggesting significant changes to the endometrial polarity. Heparan-Sulphate Proteoglycan (HSPG) expression did not differ significantly between cyclic and pregnant uteri. In contrast with the accepted rodent model of trophoblast-uterus adhesion, the porcine trophoblast and luminal epithelium were negative for HSPG. Finally, MHC class II antigens were absent from the cyclic uterus, but markedly induced in the day 15 pregnant uterus, particularly in endothelial cells, suggesting that IFN-gamma may indeed cross the maternal epithelium. This hypothesis was supported by the observation of IFN-gamma immunoreactivity associated with clusters of endometrial cells in the pregnant uterus.

The prevalence of mitral valve prolapse in children with anxiety disorders.

Studies in adults have suggested a comorbidity of mitral valve prolapse and anxiety disorders, especially panic disorder. The nature of the association between these disorders is yet unclear. In the last years, case studies have appeared, reporting on the comorbidity of anxiety disorders and mitral valve prolapse in children. The present study evaluated the prevalence of mitral valve prolapse in children with anxiety disorders as compared to normal controls. The study group consisted of 52 children, 6-18 years old, with a diagnosis of panic disorder (9.6%), separation anxiety disorder (65.4%) and/or overanxious disorder (61.5%). Fifty-one normal age- and gender-matched healthy children served as controls. All participants were evaluated for the presence of mitral valve prolapse by cardiac auscultation and echocardiography. None of the 52 children with anxiety disorder and one of the 51 control children (1.96%) had mitral valve prolapse. There appears to be no association between childhood anxiety disorders and mitral valve prolapse. Whether children with panic disorder proper show a greater prevalence of mitral valve prolapse remains an open question. Implications to the association of mitral valve prolapse and panic disorder are discussed.

Thyroid function in attention deficit and hyperactivity disorder.

In view of the recent conflicting findings regarding the causative role of thyroid abnormalities in attention deficit hyperactivity disorder (ADHD), we performed a replication study to clarify the issue and establish clinical guidelines. Thyroid tests were performed in 43 ADHD children and 28 age- and gender-matched controls. Sixteen ADHD children showed total triiodothyronine (TT3) levels which were slightly above the upper limit of normal, but no significant difference in TT3 values was noted between the ADHD and the control groups. Moreover, none of the ADHD subjects had abnormal levels of total thyroxine, free thyroxine, thyroid stimulating hormone or total triiodothyronine reuptake. The present study supplies additional evidence for the lack of an association between thyroid function and ADHD, and counters the suggestion that thyroid function be routinely screened for in ADHD children.

Case series: brief parent-child group therapy for childhood anxiety disorders using a manual-based cognitive-behavioral technique.

OBJECTIVE: To report on a brief parent-child group therapy program for children with anxiety disorders. METHOD: Twenty-four children with an anxiety disorder and their parents participated in a 10-session treatment. Children were evaluated at pretreatment (T1), posttreatment (T2), 12-month follow-up (T3), and 36-month follow-up (T4). Ten children were also assessed on entering a waiting period (T0). RESULTS: There were no significant symptomatic changes between T0 and T1. Anxiety symptoms decreased significantly during the treatment and follow-up periods. Depressive symptoms changed only during the follow-up period. The percentage of children with no current anxiety disorder was 71% at T2 and 91% at T4. Children of mothers with an anxiety disorder improved more than children of nonanxious mothers, whereas the anxiety level of anxious mothers remained stable. CONCLUSIONS: Brief parent-child group psychotherapy may serve as a time-limited, cost-effective, and efficient intervention.

Exposure to a theta-burst patterned magnetic field impairs memory acquisition and consolidation for contextual but not discrete conditioned fear in rats.

Preceding or immediately following fear-conditioning rats were exposed for 30 min to either a sham field, one of two symmetrical (sine-wave 7, 20 Hz) magnetic fields or to one of two complex magnetic fields whose waveforms were modeled after salient electrophysiological patterns within either the hippocampal formation (theta-burst) or the amygdaloid complex (burst-firing). The magnetic fields were presented in successive 2s intervals through each of the three spatial planes and then simultaneously within all three planes. Field strengths ranged between 0.5 and 1 microTesla. Only the group exposed after the conditioning to the theta-burst (hippocampal) magnetic fields displayed evidence of forgetting, as inferred by their marked attenuation of freezing behavior, during contextual extinction 24h later. This powerful treatment explained 75% of the variance in the extinction scores. Behavioral responses to the discrete conditioned stimulus were not affected. These findings are consistent with the involvement of the hippocampus in learned fear to contextual stimuli but not to discrete auditory stimuli and suggest that physiologically relevant stimuli may be delivered to the brain by weak, complex magnetic fields whose intensities are ubiquitous within modern environments.