Carcinogenicity of intermediate frequency magnetic field in Tg.rasH2 mice.

Although the likelihood of exposure to leaking intermediate frequency magnetic fields (MFs) from electronic devices, such as induction-heating and wireless power transfer systems, has increased, biological data assessing the health risks associated with human exposure remain insufficient. We examined the carcinogenicity of a 20 kHz MF, a typical frequency produced by induction-heating cookers, using a transgenic rasH2 mouse model. Twenty-five male and female CByB6F1-Tg(HRAS)2Jic mice were exposed to a 0.20 mT, 20 kHz MF (22 h/day) or sham-exposed for 26 weeks. As a positive control, 10 male and female rasH2 mice from the same batch were administered a single intraperitoneal injection of 75 mg/kg N-methyl-N-nitrosourea. A blinded histopathological evaluation was performed, and the same experiments were conducted twice, independently, to confirm the reproducibility of the results. Histopathological examination revealed that spontaneous neoplastic lesions, such as splenic hemangiosarcomas and gastric squamous cell papillomas, were less (1-3 per group) in the MF- and sham-exposed groups. The frequency of the neoplastic lesions was not significantly different between the groups. Eight to ten mice in each positive-control group exhibited malignant lymphoma. The outcomes were consistent between duplicated experiments, which indicates lack of carcinogenicity of 20 kHz MF in the rasH2 mouse model. Bioelectromagnetics. © 2019 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.

Acute and subchronic toxicity of 20 kHz and 60 kHz magnetic fields in rats.

Despite increasing use of intermediate frequency (IF) magnetic fields (MFs) in occupational and domestic settings, scientific evidence necessary for health risk assessments of IF MF is insufficient. Male and female Crl:CD(SD) rats (12 per sex per group) were exposed to 20 kHz, 0.20 mT(root mean square, rms) or 60 kHz, 0.10 mT(rms) sinusoidal MFs for 22 h day(-1) for 14 days (acute) or 13 weeks (subchronic). Experiments were duplicated for each frequency to ensure outcome reproducibility, and examinations were blinded for quality assurance. All rats survived without significant clinical signs until the end of experiments. Some changes in body weight between the MF-exposed and control groups were observed over the course of exposure, although the directions of the changes were inconsistent and not statistically significant after subchronic exposure. There were significant differences between MF-exposed and control groups in some organ weights and parameters in hematology and clinical chemistry, but these were minor in magnitude and not repeated in duplicate experiments. Histopathological findings reflecting toxicity were sporadic. Frequencies of other findings were similar to historic data in this rat strain, and findings had no specific relationship to changes in organ weight or parameters of hematology and clinical chemistry in each animal. The changes observed throughout this study were considered biologically isolated and were attributable to chance associations rather than to MF exposure. The results, in particular the histopathological evidence, indicate an absence of toxicity in IF MF-exposed rats and do not support the hypothesis that IF MF exposure produces significant toxicity.

Intermediate frequency magnetic field and chick embryotoxicity.

Intermediate frequency magnetic fields (MFs) have widely been used in industrial machines and home appliances, such as induction heating cookers, although toxicity studies to evaluate the potential health risks of such fields are insufficient. In induction heating cookers, the MF source (i.e. hobs), is located near the abdominal position of a person cooking. Hence, developmental effects on the fetus may be a concern in case the person is a pregnant woman. Fertile White Leghorn eggs (60/group) were either exposed to 20 kHz, 1.1 mT(rms) or 60 kHz, 0.11 mT(rms) sinusoidal MFs for 19 days during embryogenesis. The same number of eggs served as a control group. In addition, a sham-sham experiment was conducted to validate the equality between exposure and control facilities. After exposure, embryos were examined for mortality rate and stage. Live embryos were evaluated for developmental stage and gross and skeletal anomalies. Length of upper beak and leg digits was also measured. Examinations were conducted in a blinded fashion to ensure quality assurance; experiments were triplicated for each frequency to confirm the outcome reproducibility. Mortality rate and stage, incidence of malformed embryos, and developmental variables in live embryos were found to be similar between the MF-exposed and corresponding control group. Incidence of gross anomalies such as mandibular edema and skeletal anomalies such as coccyx defects were low across the experiments, and no significant group differences were noted. In conclusion, exposure to 20 kHz or 60 kHz MF did not produce any significant teratogenic developmental effects in chick embryos.

Absence of reproductive and developmental toxicity in rats following exposure to a 20-kHz or 60-kHz magnetic field.

The use of intermediate frequency (IF) magnetic fields (MFs) in occupational equipment and domestic appliances, such as inductive heating cookers, is increasing. The WHO indicated a lack of scientific evidence needed to assess the health risk of exposure to IF MFs. Male and female rats (24/group) were exposed to a 20 kHz, 0.2 mT(rms) or 60 kHz, 0.1 mT(rms) sinusoidal MF for 22 h/day from 14 days prior to and during mating. Copulated females were exposed until gestation day 7 and sacrificed thereafter. Mated males were sacrificed to examine MF exposure effects on spermatogenesis. Reproductive examinations were blinded, and experiments were duplicated per frequency to ensure reproducibility. No statistically significant, exposure-related changes were found in the estrous cycle, copulation and fertility indices, numbers of corpora lutea and implantation sites, or pre- and postimplantation loss. No reproducible changes were observed in sperm count, motility, or morphological abnormality, or in the weights of testes and epididymides after MF exposure. No significant abnormalities were observed in gross pathology or histopathology of the uterus, ovary, testis, and epididymis in the MF- or sham-exposed groups. MF exposure during the preimplantation period was not toxic to fertility or early embryogenesis under the experimental conditions.

Lack of teratological effects in rats exposed to 20 or 60 kHz magnetic fields.

BACKGROUND: A risk assessment of magnetic field (MF) exposure conducted by the World Health Organization indicated the need for biological studies on primary hazard identification and quantitative risk evaluation of intermediate frequency (300 Hz-100 kHz) MFs. Because induction heating cookers generate such MFs for cooking, reproductive and developmental effects are a concern due to the close proximity of the fields' source to a cook's abdomen. METHODS: Pregnant Crl:CD(SD) rats (25/group) were exposed to a 20 kHz, 0.2 mT(rms) or 60 kHz, 0.1 mT(rms) sinusoidal MF or sham-exposed for 22 hr/day during organogenesis, and their fetuses were examined for malformations on gestation day 20. All teratological evaluations were conducted in a blind fashion, and experiments were duplicated for each frequency to confirm consistency of experimental outcomes. RESULTS: No exposure-related changes were found in clinical signs, gross pathology, or number of implantation losses. The number of live fetuses and low-body-weight fetuses as well as the incidence of external, visceral, and skeletal malformations in the fetuses did not indicate significant differences between MF-exposed and sham-exposed groups. Although some fetuses showed isolated changes in sex ratio and skeletal variation and ossification, such changes were neither reproduced in duplicate experiments nor were they common to specific field frequencies. CONCLUSIONS: Exposure of rats to MFs during organogenesis did not show significant reproducible teratogenicity under experimental conditions. Present findings do not support the hypothesis that intermediate frequency MF exposure after implantation carries a significant risk for developing mammalian fetuses.

Expression and localization of E-cadherin and ß-catenin in uterine carcinosarcoma.

This study was designed to analyze the subcellular localization of E-cadherin and ß-catenin both of which play a critical role in cell-cell adhesion in uterine carcinosarcoma (UCS). We performed an immunohistochemical reaction analysis of the subcellular localization of E-cadherin and ß-catenin proteins in 46 cases of UCSs consisting of 28 UCSs with heterologous sarcoma and 18 UCSs with homologous sarcoma and compared their clinicopathological features. In most UCSs, membranous expression of E-cadherin and ß-catenin was completely lost in sarcomatous components, but it was preserved in carcinomatous components. Nuclear ß-catenin expression was observed significantly more frequently in sarcomatous components (31/46, 67.4%) than in carcinomatous components (22/46, 47.8%; P = 0.0025). In sarcomatous components, nuclear ß-catenin expression was found significantly more frequently in heterologous sarcoma (23/28, 82.1%) than in homologous sarcoma (8/18, 44.4%; P = 0.0279). The stage was the only independent prognostic significant factor. These results suggest that reduced membranous expression of E-cadherin and ß-catenin may contribute to the biphasic morphology of UCS. Furthermore, although the precise mechanism is unclear, nuclear ß-catenin expression in sarcomatous components may also be associated with biphasic morphology and heterologous sarcomatous differentiation.

Cytoplasmic and stromal expression of laminin γ 2 chain correlates with infiltrative invasion in ovarian mucinous neoplasms of gastro-intestinal type.

Ovarian mucinous neoplasms of gastro-intestinal type (GI-type) are known to be a heterogeneous tumor composed of benign, borderline and non-invasive and invasive malignant lesions. The presence of infiltrative invasion is also known to be an important prognostic factor of this neoplasm. Laminin γ 2 chain, known to stimulate tumor cell invasion and migration, has not been sufficiently investigated in ovarian mucinous neoplasms. The purpose of this study was thus to clarify the role of laminin γ 2 in ovarian mucinous neoplasms of GI-type. We selected each morphological phase of tumor development from 61 cases of mucinous neoplasms of the GI-type: 55 adenoma lesions, 60 borderline lesions, 20 microinvasive lesions, 17 intraepithelial carcinoma lesions, 38 expansile invasive carcinoma lesions, 19 infiltrative invasive carcinoma lesions and 5 mural nodules lesions; and evaluated the localization of laminin γ 2 in the lesions using immunohistochemical method. The staining pattern was classified into i) basement membranous (BM), ii) cytoplasmic (CYT) and iii) stromal (S) pattern. The BM pattern was characteristic in adenoma, borderline, and interaepithelial and expansile invasive carcinoma lesions. The CYT and S patterns were characteristic in infiltrative invasive lesions. The staining pattern of mural nodules was similar to that of infiltrative invasion. The infiltrative invasion of GI-type ovarian mucinous neoplasms may be promoted by cytoplasmic and/or stromal expression of laminin γ 2 chain.

Lack of chick embryotoxicity after 20 kHz, 1.1 mT magnetic field exposure.

This investigation was undertaken because biological studies to evaluate the effects of intermediate frequency magnetic fields are insufficient. White Leghorn fertile eggs (60/group) were either exposed to a 20 kHz, 1.1 mT(rms) sinusoidal magnetic field or sham-exposed during the first 2, 7, or 11 days of embryogenesis. Lower dose exposures at 0.011 and 0.11 mT(rms) for 2 days were also conducted to elucidate possible dose-response relationships. Additional eggs given all-trans-retinoic acid, a teratogen, were exposed to the 1.1 mT(rms) magnetic field for the same periods to investigate the modification of embryotoxicity. After exposure, embryos were examined for mortality and developmental abnormalities. Developmental stage, number of somite pairs, and other developmental endpoints were also evaluated. Experiments were triplicated and conducted in a blind fashion. No exposure-related changes were found in any of the endpoints in intact embryos exposed to 1.1 mT(rms) or to the lower doses of 0.11 and 0.011 mT(rms) magnetic fields. Retinoic acid administration produced embryotoxic responses, which were embryonic death and developmental abnormalities, in 40-60% of embryos in the sham-exposed groups. The magnitude of these responses was not changed significantly by the magnetic field exposures. Under the present experimental conditions, exposure to 20 kHz magnetic field up to 1.1 mT(rms) was not embryotoxic in the chick and did not potentiate the embryotoxic action of retinoic acid.

Hobnail-like cells in serous borderline tumor do not represent concomitant incipient clear cell neoplasms.

Hobnail-like cells, which suggest a diagnosis of clear cell carcinoma, are also focally observed in serous borderline tumor of the ovary, causing diagnostic confusion. However, the precise nature of hobnail-like cells in serous borderline tumor has not been well characterized. The purpose of this study was to clarify whether or not hobnail-like cells in serous borderline tumor represent concomitant incipient clear cell neoplasms. First, we carefully reviewed hematoxylin and eosin slides taken from 115 ovarian tumors diagnosed as clear cell carcinoma (73 cases), mixed adenocarcinoma containing clear cell carcinoma (5 cases), and serous borderline tumor (37 cases) to clarify the frequency of coexistence of typical clear cell carcinoma and serous borderline tumor. Through the hematoxylin and eosin review, we paid special attention to the cytologic features of hobnail-like cells in serous borderline tumor and serous borderline tumor-like papillary areas in clear cell carcinoma. Second, we selected 19 serous borderline tumors and 16 clear cell carcinomas, in which hobnail-like cells were easily recognizable, and investigated the immunohistochemical expression of estrogen receptor and Wilms tumor gene protein. No coexistence of clear cell carcinoma and serous borderline tumor was evident in any of the above 115 ovarian tumors. Hobnail-like cells were focally positive for estrogen receptor and Wilms tumor gene protein in nearly all serous borderline tumors. Hobnail-like cells in all clear cell carcinomas were completely negative for estrogen receptor and Wilms tumor gene protein, although estrogen receptor expression was very focally observed (less than 5% area) in non-hobnail cells of only one clear cell carcinoma. In conclusion, hobnail-like cells in serous borderline tumor do not represent concomitant incipient clear cell neoplasms because (1) clear cell carcinoma and serous borderline tumor do not coexist and (2) hobnail-like cells in clear cell carcinoma and serous borderline tumor are immunophenotypically distinct. Recognition of our conclusion may protect a patient with "conspicuous hobnail-like cells in serous borderline tumor" from an erroneous overdiagnosis of "concomitant clear cell carcinoma admixed with serous borderline tumor."

Immunohistochemical characterization of mullerian mucinous borderline tumors: possible histogenetic link with serous borderline tumors and low-grade endometrioid tumors.

Mullerian mucinous borderline tumor and gastrointestinal mucinous borderline tumor are considered mucinous tumor subtypes. However, it has been reported that mullerian mucinous borderline tumor shares many clinicopathologic features with serous borderline tumor. Furthermore, some investigators have explained the histogenesis of mullerian mucinous borderline tumor by metaplastic and hyperplastic transformation of endometriosis (Fukunaga M, Ushigome S. Epithelial metaplastic changes in ovarian endometriosis. Mod Pathol. 1998;11:784-788). The purpose of this study is to substantiate the concept that mullerian mucinous borderline tumor is histogenetically closer to serous borderline tumor or low-grade endometrioid tumor than to gastrointestinal mucinous borderline tumor by directly comparing their immunophenotype. A total of 80 cases of low-grade ovarian tumors composed of 20 mullerian mucinous borderline tumors, 20 gastrointestinal mucinous borderline tumors, 20 serous borderline tumors, and 20 low-grade endometrioid tumors were immunohistochemically evaluated for the expression of estrogen receptor, progesterone receptor, vimentin, WT-1, beta-catenin, and PTEN. Almost all cases of mullerian mucinous borderline tumor, serous borderline tumor, and low-grade endometrioid tumor showed diffuse and strong nuclear expression of estrogen receptor and progesterone receptor. In addition, about half of the mullerian mucinous borderline tumor, serous borderline tumor, and low-grade endometrioid tumor cases showed focal but strong vimentin cytoplasmic expression. In contrast, gastrointestinal mucinous borderline tumor showed no expression of estrogen receptor, progesterone receptor, or vimentin, except for 1 case in which estrogen receptor expression was very focally and weakly observed. WT-1 nuclear expression was observed in most serous borderline tumors and only 15% of low-grade endometrioid tumor, but mullerian and gastrointestinal mucinous borderline tumor cases were completely negative. beta-Catenin nuclear expression was significantly more frequent in low-grade endometrioid tumor than in mullerian mucinous borderline tumor, gastrointestinal mucinous borderline tumor, or serous borderline tumor. PTEN expression was significantly lower in low-grade endometrioid tumor than in mullerian mucinous borderline tumor, gastrointestinal mucinous borderline tumor, and serous borderline tumor. Multiple comparisons of quantitative immunoreactivities of estrogen receptor, progesterone receptor, and vimentin revealed that the gastrointestinal mucinous borderline tumor expression profiles were significantly different from those of mullerian mucinous borderline tumors, serous borderline tumors, and low-grade endometrioid tumors. The immunohistochemical expression profiles of estrogen receptor, progesterone receptor, and vimentin substantiate the concept that the histogenesis of mullerian mucinous borderline tumor is closer to those of serous borderline tumor and low-grade endometrioid tumor than to that of gastrointestinal mucinous borderline tumor. However, aberrant beta-catenin and PTEN protein expression, both of which are known to contribute to the tumorigenesis of low-grade endometrioid tumor, appeared to be less important for the tumorigenesis of mullerian mucinous borderline tumor.

Malignant transformation of mature cystic teratoma to squamous cell carcinoma involves altered expression of p53- and p16/Rb-dependent cell cycle regulator proteins.

Ovarian mature cystic teratomas (MCT) uncommonly undergo malignant transformation to squamous cell carcinoma (SCC). While alterations in the p53 tumor suppressor gene and protein have been shown, few studies have analyzed other molecular changes leading to this malignant conversion. The purpose of the present study was to investigate 21 samples of SCC arising in MCT for altered expression in known p53- and p16/Rb-dependent cell cycle regulatory proteins, and the association between their expression and cellular proliferation and histological features. Overexpression of the p53 protein was observed in 14 SCC (67%), while four (19%) had point mutations in the p53 gene. Reduced expression of the p16 protein was observed in 18 SCC (86%), while p16 gene alterations (hypermethylation (29%) and point mutation (33%)) were found in 11 (52%). Furthermore, a statistically significant correlation was observed between p53 and Rb overexpression (P=0.0010), and the overexpression of both p53 and Rb was respectively significantly correlated with increased cellular proliferation. The results indicate that alterations in both the p53 and p16-Rb pathways are associated with SCC arising in MCT.

Ovarian undifferentiated carcinoma resembling giant cell carcinoma of the lung.

Giant cell carcinoma (GCC) is a highly aggressive variant of sarcomatoid carcinoma of the lung. To date, however, there have been no reported cases of ovarian carcinoma mainly composed of GCC. Herein is reported the case of a 54-year-old Japanese woman with an undifferentiated ovarian carcinoma producing granulocyte colony-stimulating factor (G-CSF) and an inflammatory cytokine. Histologically, the tumor was composed of cohesive nests or discohesive pleomorphic mononucleated or multinucleated tumor giant cells, accompanied by inflammatory cell infiltration and emperipolesis. Immunohistochemically, the tumor cells were focally positive for epithelial membrane antigen and cytokeratin 7. Clinically, after the initial surgery, the tumor had rapid regrowth along with the production of G-CSF and an inflammatory cytokine. Adjuvant chemotherapy was administered but induced severe heart failure and severe neutropenia, probably due to the presence of hypercytokinemia and excess G-CSF. Upon the appearance of these fatal side-effects the chemotherapy was immediately discontinued and replaced with radiotherapy. The recognition of this type of ovarian tumor is important for clinical management, because adjuvant chemotherapy is the standard treatment for clinical management of epithelial ovarian cancer.

Lack of promotion effects of 50 Hz magnetic fields on 7,12-dimethylbenz(a)anthracene-induced malignant lymphoma/lymphatic leukemia in mice.

New-born CD-1 mice were initiated with a single subcutaneous injection of 60 microg 7,12-dimethylbenz(a)anthracene (DMBA) within 24 h after birth. After weaning, the mice were randomly divided into five groups of 100, 50 males and 50 females each. One group served as a cage control. The other four groups of mice were exposed to either 0 (sham-exposed), 7, 70, or 350 microT(rms) circularly polarized 50 Hz magnetic fields (MFs) for 22 h/day, 7 days/week for 30 weeks. Animals were observed daily and the development of malignant lymphoma/lymphatic leukemia was examined histopathologically. The experiment was conducted twice. There was no observed sexual difference in the cumulative proportions of mice with malignant lymphoma/lymphatic leukemia and a 3-way analysis of deviance using the Cox regression model revealed no interactions between experiment, sex, or group. The cumulative proportions of mice with malignant lymphoma/lymphatic leukemia in the MF-exposed groups were not significantly higher than those in the sham-exposed group of each sex in individual experiments and in males and females combined in each experiment, and in all the animals from the two experiments combined. These data provide no evidence to support the hypothesis that power frequency MFs is a significant risk factor for hematopoietic neoplasia.

Studies of 50 Hz circularly polarized magnetic fields of up to 350 microT on reproduction and embryo-fetal development in rats: exposure during organogenesis or during preimplantation.

Groups of mated female Sprague-Dawley rats were simultaneously exposed to 0 (sham exposed), 7, 70, or 350 microT (rms) circularly polarized 50 Hz magnetic fields (MF) for 22 h/day on gestational day 8-15, the period of rat fetal organogenesis (organogenesis study) or from day 0 to day 7 of gestation, the rat preimplantation period (preimplantation study). Developmental toxicity was assessed on gestational day 20. Identical experiments were repeated to confirm reproducibility of both studies. In both studies, statistically significant differences between exposed and sham exposed animals were observed in several measured parameters; however, these differences only appeared in one, but not both replicate experiments and generally at only an isolated exposure level. Because these differences were not reproducible and did not show a dose response relationship, they were not considered related to MF exposure. In the organogenesis study, lower kidney weights of dams were seen at 70 and 350 microT in Experiment 1. Lower dam liver weights and lower mean body weights of viable female and male fetuses were seen at 70 microT in Experiment 2. Otherwise, there were no differences in these parameters or in group means for fetal loss after implantation, number of viable fetuses, fetal body weight and sex ratio, incidences of external, visceral, and skeletal abnormalities or variations, or tissue abnormalities after histopathological examination. In the preimplantation study, dam health and indices for reproduction and embryo-fetal development, including pre or postimplantation loss, number and body weight of live fetuses, and sex ratio, external, skeletal abnormalities and variations, and skeletal ossification did not differ. Dam inorganic phosphorous concentration at 350 microT was elevated in one experiment and depressed in another. In one experiment, visceral abnormalities, primarily thymic remnant in neck and accessory liver lobe, were increased in the 7 microT group. Based on these results from two studies, we conclude that circularly polarized 50 Hz MF exposure of up to 350 microT during the fetal organogenesis or during the preimplantation period does not affect reproduction and embryo-fetal development in Sprague-Dawley rats.