Intrapleural minocycline pleurodesis for bilateral pneumothorax due to septic pulmonary embolism: a case report.

Background: Pneumothorax is a rare but serious complication of septic pulmonary embolism (SPE). SPE is a life-threatening disorder wherein infected thrombi bring infarction of the terminal and small caliber parts of the pulmonary vasculature and develop multiple nodular and cavitary lesions. Interventions other than conservative chest tube drainage for pneumothorax due to SPE have rarely been reported. Here, we present a case of bilateral pneumothorax due to SPE treated with intrapleural minocycline pleurodesis. Case Description: A 72-year-old male patient previously diagnosed as esophageal carcinoma developed metachronous bilateral pneumothorax while treated for brain metastases. Based on blood cultures and chest computed tomography images, he was diagnosed with pneumothorax secondary to SPE due to methicillin-susceptible Staphylococcus aureus bacteremia. Bilateral chest tube drainage was instituted. Continuous air leakage was found bilaterally after chest tube placement. He was treated with broad-spectrum antibiotics based on the susceptibility profile and supportive treatment for sepsis. Approximately 3 weeks later, air leakage significantly reduced. We performed intrapleural minocycline pleurodesis bilaterally to prevent the recurrence of pneumothorax; the left side was firstly treated and the right side was treated 2 weeks later. Both chest tubes were successfully removed two days after procedures. Although the patient finally died of brain metastases 1 month after pleurodesis, he never recurred pneumothorax. Conclusions: Intrapleural minocycline pleurodesis may be one of the useful and efficacious options in terms of treating intractable pneumothorax associated with SPE. Intrapleural minocycline pleurodesis could be a consideration for intractable pneumothorax related to SPE.

Two cases of airway-centered fibroelastosis treated with an antifibrotic agent and corticosteroids.

Airway-centered fibroelastosis is characterized by peribronchovascular fibroelastosis, predominantly in the upper lobes, with little-to-no pleural involvement. In this study, we describe two cases of airway-centered fibroelastosis diagnosed based on radiological and pathological findings. The first case comprised a 44-year-old man whose forced vital capacity improved over three months following treatment with nintedanib. The second case involved a 50-year-old woman who was treated with oral corticosteroids but yielded an unfavorable outcome. An effective treatment for airway-centered fibroelastosis has not yet been identified; therefore, this study may help contribute to a more thorough discussion regarding treatment strategies for this disease.

Uniportal thoracoscopic extended right apical segmentectomy with virtual-assisted lung mapping: a case report.

BACKGROUND: Pulmonary extended segmentectomy is an optional surgical treatment for early-stage non-small cell lung cancer that helps to achieve optimal surgical margins. Here, we describe a challenging instance of extended segmentectomy via uniportal video-assisted thoracic surgery with virtual-assisted lung mapping, a preoperative bronchoscopic dye marking procedure. CASE PRESENTATION: A 72-year-old woman presented with two tumors that were clinically diagnosed as early-stage lung cancer; extended right apical segmentectomy was indicated. Because the tumors had appeared unidentifiable intraoperatively, we performed virtual-assisted lung mapping for tumor localization and delineation of the optimal resection area. Surgery was conducted through a single port. All virtual-assisted lung mapping markings were visible. After dissection of the apical vessels and bronchi, a putative intersegmental line was determined using collateral ventilation. Based on the putative intersegmental plane identified by collateral ventilation and the virtual-assisted lung mapping markings, the resection line was delineated. Extended apical segmentectomy along the resection line was successfully performed via uniportal video-assisted thoracic surgery. The postoperative course was uneventful. The pathological diagnosis was minimally invasive adenocarcinoma and adenocarcinoma in situ. CONCLUSIONS: Virtual-assisted lung mapping can help to achieve optimal extended segmentectomy via uniportal video-assisted thoracic surgery.

Chromosomal Aberrations in Large Japanese Field Mice (Apodemus speciosus) Captured in Various Periods after Fukushima Daiichi Nuclear Power Plant Accident.

After the Fukushima Daiichi Nuclear Power Plant accident, we studied the chromosomal aberrations (dicentrics and translocations) in the splenic lymphocytes of wild mice inhabiting Fukushima prefecture. Here, we report the frequencies of chromosomal aberrations in large Japanese field mice (Apodemus speciosus) captured from 2012 to 2016 in a heavily contaminated area. The chromosomal aberrations were detected using newly developed 4-color FISH (fluorescence in situ hybridization) with A. speciosus chromosome 1-, 3-, 4- and 5-specific painting probes. The frequencies of chromosomal aberrations in mice captured in July 2012 and October 2014 were significantly higher than that in the mice inhabiting the non-contaminated control area; however, the frequency of chromosomal aberrations in mice captured in January 2016 was not. The frequency of chromosomal aberrations in individual mice tended to increase with certain dose rates and accumulated doses. Regression tree analyses suggested increasing chromosomal aberration rate in mice exposed to chronic radiation at dose rates of more than 1.1 mGy day-1 and at accumulated doses of more than 200 mGy. It is concluded that ambient dose rates in the most severely contaminated area of Fukushima prefecture and radiation doses to wild mice inhabiting this area decrease with time; consequently, chromosomal aberrations induced by radiation have not been detected 5 years after the accident.

A case of pulmonary sclerosing pneumocytoma diagnosed preoperatively using transbronchial cryobiopsy.

BACKGROUND: The preoperative diagnosis of pulmonary sclerosing pneumocytoma (PSP) is complicated since PSP has several histological structural patterns in the same neoplasm; hence, it is sometimes pathologically misdiagnosed as adenocarcinoma or carcinoid. In recent years, with the prevalence of transbronchial cryobiopsy (TBLC), we are able to obtain larger specimens than previously. However, to date, there have been no reports describing PSP diagnosed using TBLC. CASE REPORTS: A 43-year-old man was referred to our hospital for an abnormal lesion in the left lung discovered on routine health examination. A computed tomography scan of the chest revealed a 14-mm heterogeneous round nodule with surrounding ground-glass opacity in the left lower lobe. The tumor size increased to 18 mm in three weeks, and he developed bloody sputum. TBLC was performed using radial endobronchial ultrasonography and fluoroscopy. An occlusion balloon and prophylactic epinephrine were used to prevent severe bleeding. Histologically, epithelioid cells with solid proliferation, various papillary lesions, and hemosiderin-laden histiocytes were observed. Immunohistochemical staining revealed the histiocytes positive for thyroid transcription factor-1 and vimentin, and the type II pneumocyte-like-cells positive for cytokeratin 7. The tumor was preoperatively diagnosed as a PSP; the patient underwent left basal segmentectomy and consequently, a final diagnosed of PSP was formulated. CONCLUSION: We report the first case of PSP preoperatively diagnosed using TBLC. Therefore, cryobiopsy could be beneficial in the preoperative diagnosis of PSP.

Radiation effects on wild medaka around Fukushima Dai-ichi Nuclear Power Plant assessed by micronucleus assay.

Since the Fukushima Dai-ichi Nuclear Power Plant (F1-NPP) accident in 2011, radiation effects on wildlife in the contaminated areas have been a major concern. The outskirts of the F1-NPP are mainly rural areas, where many rice fields, streams and reservoirs are located. We searched for wild medaka (small aquarium fish) around the F1-NPP and found two wild medaka habitats (S1 and S2). S1 is a stream located 4 km from the F1-NPP, where the ambient dose equivalent rate was 0.4-0.9 µSv/h (2013-14), and S2 is a reservoir located 7.5 km from the F1-NPP, where the ambient dose equivalent rate was 9.8-22 µSv/h (2013-14 and 2017-18). Dosimeters were placed for one day at the locations where the medaka were captured, and the absorbed dose rates were estimated. Radiation effects on wild medaka were examined using micronucleus assay between 2013 and 2018. No significant difference in frequency of micronucleated gill cells was observed among the wild medaka from S1, S2 and our cultivated medaka that were used as a control.

Clinical impact of the radiological indeterminate for usual interstitial pneumonia pattern on the diagnosis of idiopathic pulmonary fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease associated with significant morbidity and mortality. The international clinical practice guidelines for the diagnosis of IPF have recently been revised. METHODS: In this single-center retrospective study conducted between June 2006 and March 2018, 27 patients with a newly classified indeterminate for usual interstitial pneumonia (UIP) pattern on high-resolution computed tomography (HRCT) who had undergone surgical lung biopsy were enrolled at the Japanese Red Cross Medical Center. Clinical and pathological characteristics and prognosis were retrospectively analyzed from patient records. RESULTS: On the basis of multidisciplinary discussion (MDD), IPF was diagnosed in six patients (22%), unclassifiable interstitial pneumonia in 5 (19%), chronic hypersensitivity pneumonitis in 10 (37%), collagen vascular disease-associated interstitial lung disease in 5 (19%), and lymphoproliferative disorder in 1 (4%) patient. Ground-glass opacity, peribronchovascular distribution, upper or middle lobe distribution, mosaic attenuation, consolidation patterns, and honeycombing were found on HRCT. Histological UIP or probable UIP was observed in seven patients. The median survival time from the initial visit was 2770 days (92.3 months). There was a significant difference in survival time in the GAP stage and honeycombing on HRCT according to the log-rank test. CONCLUSIONS: Patients with an indeterminate for UIP pattern on HRCT were more likely to have non-IPF than IPF through pathological diagnosis and MDD. GAP stage and honeycombing on HRCT may be significant risk factors for all-cause mortality.

Diagnosis and outcome of resected solitary pulmonary nodules after liver transplantation.

OBJECTIVE: Solitary pulmonary nodules after liver transplantation are challenging clinical problems. Herein, we report the causes and clinical courses of resected solitary pulmonary nodules in patients who underwent liver transplantation. METHODS: We retrospectively obtained medical records of 68 patients who underwent liver transplantation between March 2009 and June 2016. This study mainly focused on patients with solitary pulmonary nodules observed on computed tomography scans during follow-ups that were conducted until their deaths or February 2019. RESULTS: Computed tomography scans revealed solitary pulmonary nodules in 7 of the 68 patients. Definitive diagnoses were obtained using video-assisted lung resection in all seven patients. None experienced major postoperative complications. The final pathologic diagnoses were primary lung cancer in three patients, pulmonary metastases from hepatocellular carcinoma in one patient, invasive pulmonary aspergillosis in one patient, post-transplant lymphoproliferative disorder in one patient, and hemorrhagic infarction in one patient. The three patients with lung cancer were subsequently treated with standard curative resection. CONCLUSIONS: Solitary pulmonary nodules present in several serious but potentially curable diseases, such as early-stage lung cancer. Patients who present with solitary pulmonary nodules after liver transplantation should be evaluated by standard diagnostic procedures, including surgical biopsy if necessary.

Impact of preoperative pathological confirmation on surgical and postoperative outcomes of lung resection for early stage lung cancer.

INTRODUCTION: The frequency of detection of peripheral pulmonary lesion (PPL) in suspected early lung cancer has been increasing, and whether preoperative pathological diagnosis (PPD) for small PPLs should always be established before their surgical resection can become a worrisome problem for physicians. The aim of the study was to clarify the impact of obtaining PPD on surgical and postoperative outcomes of lung resection for early stage lung cancer. MATERIAL AND METHODS: This was a retrospective review of cases that underwent surgical resection for known or suspected primary lung cancer presenting pathological stage 0 or I, enrolled from June 2006 to May 2016. The patients divided into two groups according to PPD group (n = 57) and non-PPD group (n = 157) were compared. The procedure, node dissection, operation time, amount of bleeding, postoperative complications, postoperative length of stay, and postoperative recurrences were analyzed. RESULTS: Among the 214 patients, no significant differences in operation time (248.5 ± 88.6 versus 257.6 ± 89.0, min, mean ± SD, p = 0.328), amount of bleeding (195.3 ± 176.5 vs 188.1 ± 236.1, ml, p = 0.460), postoperative complication (5.2% vs 4.5%, p = 0.728), postoperative length of stay (10.6 ± 6.3 vs 10.4 ± 5.3, days, p = 0.827), or postoperative recurrences (21.0% vs 17.2%, p = 0.550) were seen between PPD and non-PPD groups. CONCLUSION: Therefore, PPD had less impact on surgical and postoperative outcomes of pathological stage 0 or I lung cancer; direct surgical resection without non-surgical biopsy would be acceptable with careful selection of cases.

Competing Risk Analysis in Lung Cancer Patients Over 80 Years Old Undergoing Surgery.

BACKGROUND: This study aimed to analyze cause-specific mortality in lung cancer patients over 80 years old undergoing surgery. METHODS: This retrospective, multi-institutional analysis included patients aged ≥ 80 years who underwent radical surgery for primary lung cancer from January 1998 to December 2015. Preoperative clinical data, surgical results, survival, and cause of death were evaluated. Competing risk analysis for cause-specific mortality was performed. RESULTS: Of the 337 patients (median age 82 years) enrolled and analyzed, 68.1% were male. There were 52 and 44 cancer-specific and non-cancer-specific deaths, respectively. On competing risk regression analysis, non-cancer-specific deaths were significantly associated with male sex (hazard ratio [HR]: 3.06, 95% confidence interval [CI]: 1.02-9.12, p = 0.046), coronary artery disease (HR: 2.49, 95% CI: 2.49 [1.14-5.47], p = 0.02), interstitial pneumonia (HR: 3.58, 95% CI: 1.73-7.40, p < 0.001), and pathological stage III (HR: 3.83, 95% CI: 1.44-10.13, p = 0.007). In contrast, cancer-specific deaths were significantly associated with limited resection (HR: 1.99, 95% CI: 1.02-3.89, p = 0.04) and pathological stage III (HR: 3.13, 95% CI: 1.44-6.80, p = 0.004). The 5-year cumulative incidences of lung cancer-specific and non-cancer-specific deaths were 18.0% and 15.9%, respectively. CONCLUSIONS: Prognostic factors for non-cancer-specific death were different from those of cancer-specific death, except for pathological stage. Each prognostic factor should be considered when deciding surgical indication and procedure and monitoring for pulmonary events during outpatient follow-up.

Rapid effects of benralizumab on severe asthma during surgery for residual tumor after advanced lung squamous cell carcinoma treatment with pembrolizumab.

Severe bronchial asthma is a chronic disorder of the airways that may be accompanied by comorbid diseases. Invasive treatment, including surgery, in patients with severe asthma has limitations depending on the degree of control of the asthma. A 71-year-old woman was diagnosed with squamous cell carcinoma with high programmed death-ligand 1 (PD-L1) expression and cT3N0M1a. After 13 cycles of pembrolizumab every 3 weeks, chest computed tomography (CT) revealed a dramatic decrease in the lesion size in the left upper lobe, but the size of the lesion in the right lower lobe was significantly increased. The pathological findings of the right residual tumor by CT-guided transthoracic needle biopsy (CTNB) revealed squamous cell carcinoma with no PD-L1 expression, and right lower lobectomy was recommended. However, because the patient had frequent asthma attacks and cough, surgery was considered risky. Increased blood eosinophil count was observed, and benralizumab was administered for asthma control. The symptoms disappeared 2 days after benralizumab administration, and peak flow increased. Surgery was performed 5 days after benralizumab administration. There was a marked reduction in the eosinophil count of the surgical tissue compared with the preoperative CTNB tissue. No asthma attacks were observed during and after surgery, and the control of asthma and lung cancer was stable. Benralizumab is considered promising for the treatment of eosinophilic severe uncontrolled asthma.

Nivolumab and stereotactic radiation therapy for the treatment of patients with Stage IV non-small-cell lung cancer.

BACKGROUND: Radiation therapy might modify the cancer immune environment to enhance the antitumor effect of immune checkpoint inhibitors. We performed a feasibility study of nivolumab following stereotactic radiation therapy for chemotherapy pretreated advanced non-small-cell lung cancer. PATIENTS AND METHODS: Pretreated advanced/recurrent non-small-cell lung cancer patients received stereotactic radiation therapy to one of the disease sites. Nivolumab at a dose of 3 mg/kg was given within 2 weeks after the completion of stereotactic radiation therapy and continued every 2 weeks thereafter until disease progression or unacceptable toxicities. The primary endpoint was the occurrence rate of Grade 3 pneumonitis (within 12 weeks) or other non-hematological toxicity (within 8 weeks). RESULTS: From September 2016 to September 2017, six patients were enrolled. Five received stereotactic radiation therapy to their primary lesions. All patients received nivolumab on the following day after stereotactic radiation therapy completion. Grade 3 pneumonitis occurred in one patient, but no other serious adverse events were reported for the other patients. One complete response and two partial responses were achieved. Four patients had measurable lesions outside the irradiated area, of whom three patients responded to the treatment. The initial progression sites were mainly outside the irradiated field, including one brain metastasis. CONCLUSIONS: Nivolumab therapy immediately following stereotactic radiation therapy was well tolerated. This sequential combination warrants further study.

The combination of EBUS-TBNA and the PAB antibody led to a successful treatment for lung cancer in a patient with asymptomatic sarcoidosis mimicking nodal metastasis.

Correct staging of lung cancer is important for the selection of the best therapy, but discriminating between lymphadenopathy from lung cancer and from sarcoidosis by imaging examinations is difficult. Additionally, distinguishing lymphadenopathy of sarcoidosis from sarcoid reactions which are sometimes caused by lung cancer is difficult on imaging and pathological findings. A 73-year-old woman was diagnosed as lung cancer clinical T1bN3M0 stage ШB based on false-positive 18F-fluoro-2-deoxyglucose positron emission tomography uptake. Because the effects of chemotherapy were different between the lymphadenopathy and the primary lesion, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) was performed and revealed sarcoidosis as the cause of the lymphadenopathy with using a specific monoclonal antibody against Propionibacterium acnes (PAB antibody). Accordingly, the stage was changed to clinical T1bN0M0 stage ІA, for which radical operation was performed. EBUS-TBNA should be performed aggressively when the effect of chemotherapy is different between lymphadenopathies and other lesions, and the PAB antibody can help to discriminate between sarcoidosis and sarcoid reactions caused by lung cancer. The combination of EBUS-TBNA and the PAB antibody is expected to be valuable in the definitive diagnosis of a lymphadenopathy for the staging of lung cancer.

The Significant Antitumor Activity of Nivolumab in Lung Adenocarcinoma with Choriocarcinomatous Features.

We report the case of a 60-year-old Japanese man with a metastatic brain tumor that caused ataxia. As a consequence of resection of a cerebellar tumor, the tumor was diagnosed as a poorly differentiated adenocarcinoma with choriocarcinomatous features. The patient underwent bronchoscopy, leading to a diagnosis of the same histology as the brain tumor. After the administration of first-line chemotherapy and maintenance therapy due to progressive disease, he was given nivolumab and obtained a partial response; however, 11-months later, computed tomography showed tumor progression. Our experience suggests that nivolumab has strong activity, even in patients with a rare form of lung cancer.

Risk factors for postoperative complications and long-term survival in lung cancer patients older than 80 years.

OBJECTIVES: The number of octogenarian lung cancer patients undergoing radical surgery has been increasing recently. However, knowledge regarding the risk factors for postoperative complications and reliable predictive factors for long-term survival is limited. This study aimed to investigate the risk factors of postoperative complications, and reliable prognostic factors, in lung cancer patients older than 80 years. METHODS: Lung cancer patients aged 80 years or older who underwent radical surgery were retrospectively studied; a multi-institutional analysis was conducted from January 1998 to December 2015. Preoperative and postoperative clinical data, including age, gender, smoking history, body mass index, respiratory function, Charlson Comorbidity Index, Glasgow Prognostic Score, surgical procedure, cancer histology, clinical and pathological stage, surgical result and survival time, were collected. RESULTS: A total of 337 patients, comprising 216 (64.1%) men and 121 (35.9%) women were enrolled. The median age was 82 (range 80-92) years. Of the 337 patients, 205 (60.8%) had preoperative comorbidities. Postoperative complications were observed in 119 (35.3%) patients; postoperative mortalities occurred in 6 (1.8%) patients. Univariate and multivariate analyses showed that male gender (P = 0.01) and operation time (P = 0.047) were associated with postoperative complications; in contrast, pathological Stage III (P < 0.001), male gender (P = 0.01), Charlson Comorbidity Index ≥2 (P = 0.03) and Glasgow Prognostic Score = 1/2 (P = 0.04) were independent prognostic factors for overall survival. CONCLUSIONS: The risk factors for postoperative complications (male gender and operation time) and the predictive factors affecting long-term survival (male gender, Charlson Comorbidity Index, Glasgow Prognostic Score and P-stage) should be taken into account for the effective management of patients older than 80 years with lung cancer, undergoing surgery.

Efficacy and safety of stereotactic body radiotherapy using CyberKnife in Stage I primary lung tumor.

BACKGROUND: CyberKnife® (CK) is a new, advanced radiotherapy technique. This study aimed to evaluate its efficacy and toxicity in Japanese patients with early-stage primary lung tumor who were medically unfit and inoperable. METHODS: This retrospective study investigated patients who received CK treatment for medically inoperable Stage І primary lung tumor at the Japanese Red Cross Medical Center between June 2011 and September 2016. Each patient received a total of 36-48 Gy (median, 43 Gy) administered by CK in 4-5 fractions. RESULTS: Totally, 40 patients (T1a, n = 19; T1b, n = 15; T2a, n = 6) were included. Their median age was 86 (range, 56-95) years. Tracking required the use of fiducial markers in 28 patients and the Xsight Spine Tracking System in 12. The median follow-up was 14.5 (range, 1-51) months. Local recurrence occurred in seven (17.5%) patients. The local progression-free survival rates at 1 and 2 years were 83.9% and 74.0%, respectively. Distant recurrence occurred in regional lymph nodes (n = 5), the lung outside the radiation field (n = 3), and the bone (n = 1). Seven patients died. Overall survival rates at 1 and 2 years were 93.6% and 73.1%, respectively. Radiation pneumonitis was identified in 28 (70%) patients (Grade 1, n = 25; Grade 2, n = 2; Grade 5, n = 1). CONCLUSIONS: CK showed good local control with limited toxicity and could be an alternative treatment modality in medically inoperable patients with Stage І primary lung tumor.

Chromosomal Aberrations in Large Japanese Field Mice (Apodemus speciosus) Captured near Fukushima Dai-ichi Nuclear Power Plant.

Since the Fukushima Dai-ichi Nuclear Power Plant accident, radiation effects on nonhuman biota in the contaminated areas have been a major concern. Here, we analyzed the frequencies of chromosomal aberrations (translocations and dicentrics) in the splenic lymphocytes of large Japanese field mice (Apodemus speciosus) inhabiting Fukushima Prefecture. A. speciosus chromosomes 1, 2, and 5 were flow-sorted in order to develop A. speciosus chromosome-specific painting probes, and FISH (fluorescence in situ hybridization) was performed using these painting probes to detect the translocations and dicentrics. The average frequency of the translocations and dicentrics per cell in the heavily contaminated area was significantly higher than the frequencies in the case of the noncontaminated control area and the slightly and moderately contaminated areas, and this aberration frequency in individual mice tended to roughly increase with the estimated dose rates and accumulated doses. In all four sampling areas, the proportion of aberrations occurring in chromosome 2 was approximately >3 times higher than that in chromosomes 1 and 5, which suggests that A. speciosus chromosome 2 harbors a fragile site that is highly sensitive to chromosome breaks induced by cellular stress such as DNA replication. The elevated frequency of chromosomal aberrations in A. speciosus potentially resulting from the presence of a fragile site in chromosome 2 might make it challenging to observe the mild effect of chronic low-dose-rate irradiation on the induction of chromosomal aberrations in A. speciosus inhabiting the contaminated areas of Fukushima.

Transformation to small-cell lung cancer as a mechanism of acquired resistance to crizotinib and alectinib.

A 56-year-old woman, a never-smoker, had postoperative recurrence of anaplastic lymphoma kinase rearranged lung cancer. She achieved a partial response to treatment with an anaplastic lymphoma kinase tyrosine kinase inhibitor, crizotinib. After the tumor regrowth, crizotinib was switched to alectinib; once again a partial response was observed. At the second recurrence, transbronchial needle aspiration of the right paratracheal node was performed, which revealed cytological findings of small-cell carcinoma. While treatment with cisplatin-irinotecan chemotherapy made reduction of some tumor shadows, including the biopsied mediastinal lymph nodes, new, small, nodular shadows, highly suggestive of pulmonary metastases, were detected in both lung fields. This case may show proof of the transformation to small-cell lung cancer as a mechanism of resistance to anaplastic lymphoma kinase tyrosine kinase inhibitors in anaplastic lymphoma kinase rearranged tumor. However, this transformation may also be only one part of the resistance mechanism of the heterogeneous tumor.

Chromosomal Aberrations in Wild Mice Captured in Areas Differentially Contaminated by the Fukushima Dai-Ichi Nuclear Power Plant Accident.

Following the Fukushima Dai-ichi Nuclear Power Plant accident, radiation effects on nonhuman biota in the contaminated areas have been a great concern. The induction of chromosomal aberrations in splenic lymphocytes of small Japanese field mice (Apodemus argenteus) and house mice (Mus musculus) inhabiting Fukushima Prefecture was investigated. In mice inhabiting the slightly contaminated area, the average frequency of dicentric chromosomes was similar to that seen in mice inhabiting a noncontaminated control area. In contrast, mice inhabiting the moderately and heavily contaminated areas showed a significant increase in the average frequencies of dicentric chromosomes. Total absorbed dose rate was estimated to be approximately 1 mGy d(-1) and 3 mGy d(-1) in the moderately and heavily contaminated areas, respectively. Chromosomal aberrations tended to roughly increase with dose rate. Although theoretically, the frequency of chromosomal aberrations was considered proportional to the absorbed dose, chromosomal aberrations in old mice (estimated median age 300 days) did not increase with radiation dose at the same rate as that observed in young mice (estimated median age 105 days).

Estimation of absorbed radiation dose rates in wild rodents inhabiting a site severely contaminated by the Fukushima Dai-ichi nuclear power plant accident.

The dose rates of radiation absorbed by wild rodents inhabiting a site severely contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident were estimated. The large Japanese field mouse (Apodemus speciosus), also called the wood mouse, was the major rodent species captured in the sampling area, although other species of rodents, such as small field mice (Apodemus argenteus) and Japanese grass voles (Microtus montebelli), were also collected. The external exposure of rodents calculated from the activity concentrations of radiocesium ((134)Cs and (137)Cs) in litter and soil samples using the ERICA (Environmental Risk from Ionizing Contaminants: Assessment and Management) tool under the assumption that radionuclides existed as the infinite plane isotropic source was almost the same as those measured directly with glass dosimeters embedded in rodent abdomens. Our findings suggest that the ERICA tool is useful for estimating external dose rates to small animals inhabiting forest floors; however, the estimated dose rates showed large standard deviations. This could be an indication of the inhomogeneous distribution of radionuclides in the sampled litter and soil. There was a 50-fold difference between minimum and maximum whole-body activity concentrations measured in rodents at the time of capture. The radionuclides retained in rodents after capture decreased exponentially over time. Regression equations indicated that the biological half-life of radiocesium after capture was 3.31 d. At the time of capture, the lowest activity concentration was measured in the lung and was approximately half of the highest concentration measured in the mixture of muscle and bone. The average internal absorbed dose rate was markedly smaller than the average external dose rate (<10% of the total absorbed dose rate). The average total absorbed dose rate to wild rodents inhabiting the sampling area was estimated to be approximately 52 µGy h(-1) (1.2 mGy d(-1)), even 3 years after the accident. This dose rate exceeds 0.1-1 mGy d(-1) derived consideration reference level for Reference rat proposed by the International Commission on Radiological Protection (ICRP).