Tubo-ovarian abscess caused by Clostridioides difficile after eight months of surgery: Case report and review of extraintestinal abdominal abscess cases.

We present a case of tubo-ovarian abscess (TOA) caused by Clostridioides difficile (CD) in a 43-year-old female. Despite lacking a history of sexually transmitted diseases, the patient had undergone paraovarian cystectomy nine months before admission. Transvaginal ultrasonography performed eight months post-surgery revealed left ovarian enlargement, accompanied by subsequent lower abdominal pain and fever exceeding 38 °C. As oral antibiotic treatment was ineffective, the patient was admitted to our hospital. Computed tomography upon admission revealed a massive TOA. Surgical drainage of the abscess was performed, and CD was identified in the culture from the pus. The TOA was treated with a three-month course of metronidazole and oral amoxicillin/clavulanic acid. While CD is commonly associated with colitis, extraintestinal manifestations are exceptionally rare. This case represents the inaugural report of TOA resulting from CD. A literature review on abdominal and pelvic CD abscesses found that patients undergoing surgical drainage had a favorable prognosis. Therefore, surgical intervention plays an important role in the management of CD abscesses.

A case of adenomyosis with leiomyoma that was effectively treated with relugolix and kamishoyosan add-on therapy.

BACKGROUND: Recently, relugolix, an oral gonadotropin-releasing hormone receptor antagonist, has been considered an effective therapy for leiomyoma based on a phase 3 study in Japanese women. Leiomyoma combined with severe adenomyosis occasionally occurs in perimenopausal women; however, little information on the effectiveness of relugolix against severe adenomyosis exists. CASE PRESENTATION: A 49-year-old woman was referred to our hospital with acute lower abdominal pain and abnormal uterine bleeding. Magnetic resonance imaging revealed multiple leiomyomas with diffuse adenomyosis. Left hydrosalpinx was also observed. The patient refused surgical treatment and preferred oral relugolix. Since she experienced a hot flush and headache induced by relugolix, a traditional Japanese Kampo, kamishoyosan, was added to improve the side effects of relugolix. The patient was asymptomatic at the time of this report and experienced a significant shrinkage in uterine volume. Ultimately, she avoided hysterectomy as desired. CONCLUSIONS: To our knowledge, this is the first report of co-occurring adenomyosis and leiomyoma, which was effectively treated with relugolix. Although the management of adverse side effects, including hot flush and headache by relugolix, has recently attracted attention and controversy, relugolix add-on therapy with kamishoyosan may help treat menopausal symptoms.

Detection of HPV RNA molecules in stratified mucin-producing intraepithelial lesion (SMILE) with concurrent cervical intraepithelial lesion: a case report.

BACKGROUND: Stratified mucin-producing intraepithelial lesion (SMILE) is a rare precursor lesion in the uterine cervix that is considered a variant of adenocarcinoma in situ (AIS). Although human papillomavirus (HPV) is thought to be related to the development of SMILE, there is little information available on the detection of HPV integrated into the lesion. CASE PRESENTATION: A 30-year-old female underwent a routine uterine cervical cancer screening, and her Pap smear indicated the possible existence of atypical glandular cells. A cervical biopsy with endocervical curettage was performed. The histopathological analysis showed that she had SMILE and high-grade squamous intraepithelial lesion (HSIL) on her cervix. The lesion was found to be positive for HPV genotypes 52 and 68 by multiplex PCR. In situ hybridization with HPV RNA probes revealed that these HPV types were involved in the onset of HSIL and SMILE, respectively. CONCLUSIONS: Rare, high-risk HPV genotypes may contribute to the development of SMILE, and their detection can be useful for preventing the progression to carcinoma and ensuring adequate patient management.

Expression of the glucagon-like peptide-1 receptor and its role in regulating autophagy in endometrial cancer.

BACKGROUND: A previous report showed that a glucagon-like peptide-1 receptor (GLP-1R) agonist (exenatide) induced apoptosis in endometrial cancer cells. However, the pathophysiological role of GLP-1R in endometrial cancer has not been fully elucidated. Here, we investigated the effects of the GLP-1R agonist liraglutide in endometrial cancer cells and examined the association between GLP-1R expression and clinicopathological characteristics in endometrial cancer patients. METHODS: Human Ishikawa endometrial cancer cells were treated with different concentrations of liraglutide. To assess the effects of liraglutide, cell viability, colony formation, flow cytometry, Western blotting, and immunofluorescence assays were performed. Autophagy induction was examined by analyzing LC3 and p62 expression and autophagosome accumulation. Moreover, using a tissue microarray, we analyzed GLP-1R expression in 154 endometrial cancer tissue samples by immunohistochemistry. RESULTS: In accordance with the previous report, liraglutide inhibited Ishikawa cell growth in a dose-dependent manner. Liraglutide significantly induced autophagy, and phosphorylated AMPK expression was elevated. Immunohistochemical analysis revealed that GLP-1R expression was associated with positive estrogen receptor and progesterone receptor status, and higher GLP-1R expression was significantly correlated with better progression-free survival. CONCLUSIONS: The use of liraglutide to target autophagy in endometrial cancer cells may be a novel potential treatment for endometrial cancer. Furthermore, higher GLP-1R expression may be associated with better prognosis in endometrial cancer patients.

Loss of the cell polarity determinant human Discs-large is a novel molecular marker of nodal involvement and poor prognosis in endometrial cancer.

BACKGROUND: Recent Drosophila studies showed that Discs-large (Dlg) is critical for regulation of cell polarity and tissue architecture. We investigated the possibility that loss of the human homologue of Drosophila Dlg (DLG1) is involved in endometrial carcinogenesis. METHODS: We analysed DLG1 expression in 160 endometrial cancers by immunohistochemical staining. Its expression was confirmed by quantitative real-time PCR (RT-PCR). We investigated the roles of DLG1 in growth and invasion by knockdown experiment in endometrial cancer cell lines. RESULTS: Human DLG1 localises at cellular membrane in normal endometrial tissues. Loss of DLG1 was observed in 37 cases (23.1%). Loss of DLG1 was observed in patients with advanced stage and high-grade histology. It was also observed in patients with nodal metastasis, deep myometrial invasion, and negative oestrogen and progesterone receptors. Patients with loss of DLG1 showed poorer overall survival (P=0.0019). Immunohistochemistry data correlated with RT-PCR data. Knockdown of Dlg1 in endometrial cancer cells resulted in accelerated tumour migration and invasion in vitro. CONCLUSIONS: Tissue polarity disturbance because of loss of DLG1 was shown to confer more aggressive characteristics to endometrial cancer cells. Our study revealed that DLG1 expression is a novel molecular biomarker of nodal metastasis, high-grade histology, and poor prognosis in endometrial cancer.

A lipid index for risk of hyperlipidemia caused by anti-retroviral drugs.

HIV-associated lipodystrophy has been reported in people taking anti-retroviral therapy (ART). Lipodystrophy can cause cardiovascular diseases, affecting the quality of life of HIV-infected individuals. In this study, we propose a pharmacological lipid index to estimate the risk of hyperlipidemia caused by anti-retroviral drugs. Lipid droplets were stained in cells treated with anti-retroviral drugs and cyclosporin A. Signal intensities of lipid droplets were plotted against the drug concentrations to obtain an isodose of 10 µM of cyclosporin A, which we call the Pharmacological Lipid Index (PLI). The PLI was then normalized by EC50. PLI/EC50 values were low in early proteinase inhibitors and the nucleoside reverse transcriptase inhibitor, d4T, indicating high risk of hyperlipidemia, which is consistent with previous findings of hyperlipidemia. In contrast, there are few reports of hyperlipidemia for drugs with high PLI/EC50 scores. Data suggests that PLI/EC50 is a useful index for estimating the risk of hyperlipidemia.

Chlamydia Peritonitis Mimicking Juvenile Carcinomatous Peritonitis Diagnosed by Exploratory Laparoscopy: A Case Report.

Chlamydia trachomatis infections may occur in multiple organs, including the lungs, lymph nodes, peritoneal cavity, and genitourinary systems. This disease results in significant ascites, the swelling of lymph nodes, and elevated tumor markers (CA125), sometimes mimicking an ovarian malignancy. At our hospital, we often perform examination laparoscopic surgery in cases of suspected gynecologic cancers before initial treatment. In this paper, we report the case of a 19-year-old woman who came to our hospital because of an ovarian tumor and ascites. There was no history of sexual intercourse (self-reported). We suspected ovarian cancer from image inspections, so we performed laparoscopic surgery for diagnosis. The final pathological diagnosis was acute-to-chronic inflammation of the bilateral fallopian tubes, and a cytologic examination of the ascites was negative for malignant cells. The C. trachomatis antigen was positive on vaginal examination after the operation. Based on this result, we diagnosed this patient with C. trachomatis infection. Chlamydia peritonitis should be a differential diagnosis for cancer peritonitis in juvenile patients with abnormal ascites. Exploratory laparoscopy should help confirm the pathological diagnosis.

Serum vascular endothelial growth factor associated with the progression of granulosa cell tumor: a report of two cases.

BACKGROUND: Granulosa cell tumors (GCTs) account for approximately 2% of ovarian malignancies and are considered a rare type of ovarian cancer. GCTs are characterized by irregular genital bleeding after menopause due to female hormone production as well as late recurrence around 5-10 years after initial treatment. In this study, we investigated two cases of GCTs to find a biomarker that can be used to evaluate the treatment and predict recurrence. CASE PRESENTATION: Case 1 was a 56-year-old woman who presented to our hospital with abdominal pain and distention. An abdominal tumor was found, and GCTs were diagnosed. Serum vascular endothelial growth factor (VEGF) levels decreased after surgery. Case 2 involved a 51-year-old woman with refractory GCTs. Carboplatin-paclitaxel combination therapy and bevacizumab were administered after the tumor resection. After chemotherapy, a decline in VEGF levels was observed, but serum VEGF levels increased again with disease progression. CONCLUSIONS: VEGF expression may be of clinical importance in GCTs as a clinical biomarker for disease progression, which may be used to determine the efficacy of bevacizumab against GCTs.

Validation of an on-chip p16ink4a/Ki-67 dual immunostaining cervical cytology system using microfluidic device technology.

More specific screening systems for cervical cancer may become necessary as the human papillomavirus (HPV) vaccine becomes more widespread. Although p16/Ki-67 dual-staining cytology has several advantages, it requires advanced diagnostic skills. Here, we developed an automated on-chip immunostaining method using a microfluidic device. An electroactive microwell array (EMA) microfluidic device with patterned thin-film electrodes at the bottom of each microwell was used for single-cell capture by dielectrophoresis. Immunostaining and dual staining for p16/Ki-67 were performed on diagnosed liquid cytology samples using the EMA device. The numbers of p16/Ki-67 dual-stained cells captured by the EMA device were determined and compared among the cervical intraepithelial neoplasia (CIN) lesion samples. Seven normal, fifteen CIN grade 3, and seven CIN grade 2 samples were examined. The percentage of dual-positive cells was 18.6% in the CIN grade 2 samples and 23.6% in the CIN grade 3 samples. The percentages of dual-positive staining increased significantly as the severity of the cervical lesions increased. p16/Ki67 dual immunostaining using the EMA device is as sensitive as the conventional method of confirming the histopathological diagnosis of cervical samples. This system enables a quantified parallel analysis at the individual cell level.

Zinc and iron dynamics in human islet amyloid polypeptide-induced diabetes mouse model.

Metal homeostasis is tightly regulated in cells and organisms, and its disturbance is frequently observed in some diseases such as neurodegenerative diseases and metabolic disorders. Previous studies suggest that zinc and iron are necessary for the normal functions of pancreatic ß cells. However, the distribution of elements in normal conditions and the pathophysiological significance of dysregulated elements in the islet in diabetic conditions have remained unclear. In this study, to investigate the dynamics of elements in the pancreatic islets of a diabetic mouse model expressing human islet amyloid polypeptide (hIAPP): hIAPP transgenic (hIAPP-Tg) mice, we performed imaging analysis of elements using synchrotron scanning X-ray fluorescence microscopy and quantitative analysis of elements using inductively coupled plasma mass spectrometry. We found that in the islets, zinc significantly decreased in the early stage of diabetes, while iron gradually decreased concurrently with the increase in blood glucose levels of hIAPP-Tg mice. Notably, when zinc and/or iron were decreased in the islets of hIAPP-Tg mice, dysregulation of glucose-stimulated mitochondrial respiration was observed. Our findings may contribute to clarifying the roles of zinc and iron in islet functions under pathophysiological diabetic conditions.

Effect of Different Educational Interventions on Knowledge of HPV Vaccination and Cervical Cancer among Young Women: A Preliminary Report.

The incidence and mortality rates of cervical cancer are rising among young women in Japan. In November 2021, the Japanese Ministry of Health, Labour, and Welfare reinstated the active recommendation for the human papillomavirus (HPV) vaccine, which was discontinued in June 2013 due to reports of adverse reactions, including chronic pain and motor dysfunction, following vaccination. However, vaccine hesitancy among the younger generation remains, and it is essential to identify the barriers in vaccination uptake. Therefore, we aimed to conduct a randomized study using different methods of providing educational contents to improve health literacy regarding cervical cancer and HPV vaccination among female students in Japan. Here, we present the results of our preliminary report and discuss current topics related to HPV vaccination in Japan. Data were collected from 27 female students-divided into three groups: no intervention, print-based intervention, and social networking service-based intervention-using the health literacy scale and communicative and critical health literacy scale. Our primary results indicate that participants' knowledge and health literacy improved post-intervention. Therefore, medical professionals must provide accurate scientific knowledge regarding routine HPV vaccination and the risk of cervical cancer to young women to improve their health literacy and subsequently increase the HPV vaccination rates.

Case report: Posterior reversible encephalopathy syndrome, an adverse effect of lenvatinib and pembrolizumab combination therapy, in a patient with advanced endometrial cancer.

Background: Lenvatinib-pembrolizumab combination (LEAP) is an approved therapy in Japan for advanced endometrial cancer, based on the data from the KEYNOTE-775 clinical trial. We report a case of posterior reversible encephalopathy syndrome (PRES) in a patient who received LEAP therapy for advanced endometrial cancer. Case presentation: A 53-year-old patient with stage IVB endometrial cancer having rectal metastases, after four cycles of paclitaxel-carboplatin therapy, was found to have increased rectal invasion, peritoneal dissemination, and multiple paraaortic lymph node metastases. She was treated with LEAP therapy and discharged on day 12 without adverse events, except for mild anemia on day 11 of treatment. She was carefully managed in the outpatient department, but on day 18, she was admitted to the emergency department with severely impaired consciousness and generalized seizures. Computed tomography of the head and lumbar tap showed no abnormal findings, and the seizures resolved with anticonvulsant medication alone. Based on a thorough physical examination and findings on magnetic resonance imaging (MRI), which showed high signal intensity in the left occipital lobe, encephalopathy, rather than encephalitis, was the likely diagnosis. Symptomatic improvement was observed, and pembrolizumab monotherapy was resumed. Conclusions: If consciousness is impaired during LEAP treatment, it is necessary to differentiate between immunogenic encephalitis caused by pembrolizumab or encephalopathy caused by lenvatinib. MRI and lumbar tap can help in distinguishing between the two and diagnosing the responsible drug.

Occupational exposure of platinum-based anti-cancer drugs: five-year monitoring of hair and environmental samples in a single hospital.

BACKGROUND: Occupational exposure to chemotherapeutic agents in hospitals is a critical issue. Here, we focused on occupational exposure to platinum-based anti-cancer drugs (PDs) by evaluating platinum concentrations in hair and environmental workplace samples to monitor the risk among workers. METHODS: Hospital workers who dealt with or without PDs, patients treated with PDs, and non-medical office workers outside the hospital donated hair samples and completed a questionnaire regarding their history of handling PDs, including any incidents. Hair samples were collected and surface wipe sampling was performed in July 2010 and April 2015, before and after moving to a new building and introducing a revised safety program in August 2010. Samples were analyzed by inductively coupled plasma-mass spectrometry. RESULTS: Platinum concentrations in hair from PDs-handling workers was significantly higher than in non-PDs-handling workers (P = 0.045), although 50 times lower than that from PDs-treated patients. Platinum concentrations in the hospital environment had decreased at the second survey 5 years later but had not changed significantly in the hair samples from hospital workers. CONCLUSION: Platinum concentrations in hair are likely dependent on the frequency of handling PDs. Reduced environmental contamination from PDs did not influence platinum levels in hospital workers' hair. Continuous monitoring by measuring platinum concentrations in the environment and in hair would provide information regarding these issues.

Cu and Zn isotope ratio variations in plasma for survival prediction in hematological malignancy cases.

We have examined potential changes in the isotopic compositions of Fe, Cu and Zn (using multi-collector inductively coupled plasma-mass spectrometry) and the corresponding concentrations (using inductively coupled plasma-atomic emission spectrometry) in plasma from hematological malignancy (HM) patients and assessed their prognostic capability. Together with clinical laboratory test values, data were examined in view of a 5-years survival prediction. Plasma Cu and Zn isotope ratios and their concentrations were significantly different in HM patients compared to matched controls (P < 0.05). Both δ65Cu and δ66Zn values showed significant mortality hazard ratios (HRs) in HM. The group of patients with decreased δ65Cu and increased δ66Zn values showed significantly poorer survival from the early phase (HR 3.9; P = 0.001), forming a unique cohort not identified based on laboratory test values. Well-known prognostic factors for HM, such as the creatinine level, and anemia-related values were highly correlated with the δ66Zn value (P < 0.05). Time-dependent ROC curves based on the δ65Cu or δ66Zn value were similar to that based on the creatinine concentration (a well-known prognostic factor in HM), indicating that δ65Cu or δ66Zn values are useful for prognosis of HM. Variations in stable isotope ratios of essential mineral elements have thus been shown to reflect alterations in their homeostasis due to physiological changes in malignancies with higher sensitivity than concentrations do.

Evaluating the Angiogenetic Properties of Ovarian Cancer Stem-like Cells using the Three-dimensional Co-culture System, NICO-1.

Cancer stem cells (CSCs) reside in a supportive niche, constituting a microenvironment comprised of adjacent stromal cells, vessels, and extracellular matrix. The ability of CSCs to participate in the development of endothelium constitutes an important characteristic that directly contributes to the general understanding of the mechanisms of tumorigenesis and tumor metastasis. The purpose of this work is to establish a reproducible methodology to investigate the tumor-initiation capability of ovarian cancer stem cells (OCSCs). Herein, we examined the neovascularization mechanism between endothelial cells and OCSCs along with the morphological changes of endothelial cells using the in vitro co-culture model NICO-1. This protocol allows visualization of the neovascularization step surrounding the OCSCs in a time course manner. The technique can provide insight regarding the angiogenetic properties of OCSCs in tumor metastasis.

The proteasome deubiquitinase inhibitor bAP15 downregulates TGF-ß/Smad signaling and induces apoptosis via UCHL5 inhibition in ovarian cancer.

The ubiquitin-proteasome pathway plays an important role in the regulation of cellular proteins. As an alternative to the proteasome itself, recent research has focused on methods to modulate the regulation of deubiquitinating enzymes (DUBs) upstream of the proteasome, identifying DUBs as novel therapeutic targets in breast, endometrial, and prostate cancers, along with multiple myeloma. bAP15, an inhibitor of the 19S proteasome DUBs UCHL5 and USP14, results in cell growth inhibition in several human cancers; however, the mechanism remains poorly understood in ovarian cancer. Here, we found that aberrant UCHL5 expression predicted shorter progression-free survival (PFS) in a cohort of 1435 patients with ovarian cancer described in the Gene Expression Omnibus and The Cancer Genome Atlas databases. The subgroup of patients with TP53 mutations was significantly more likely to exhibit poor PFS (p <0.001). Moreover, we found bAP15 could suppress TP53-mutant ovarian cancer cell survival by regulating TGF-ß signaling through inhibiting UCHL5 expression and dephosphorylating Smad2, consequently inducing apoptosis. bAP15 (2.5 and 5.0 mg/kg) also exerted significant anti-tumor effect on nude mice bearing subcutaneous SKOV3 xenografts. As activated TGF-ß signaling is involved in ovarian cancer progression, these findings suggest that UCHL5 inhibition offers potential opportunities for a novel targeted therapy against TGF-ß-activated ovarian cancer.

Pulmonary clearance kinetics and extrapulmonary translocation of seven titanium dioxide nano- and submicron materials following intratracheal administration in rats.

We evaluated and compared the pulmonary clearance kinetics and extrapulmonary translocations of seven titanium dioxide (TiO2) nano- and submicron particles with different characteristics, including size, shape and surface coating. Varying doses of TiO2 nano- and submicron particles dispersed in 0.2% disodium phosphate solution were intratracheally administered to male F344 rats. The rats were euthanized under anesthesia for 3, 28 and 91 days after administration. Ti levels in pulmonary and various extrapulmonary organs were determined using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The lungs, including bronchoalveolar lavage fluid (BALF), contained 55-89% of the administered TiO2 dose at 3 days after administration. The pulmonary clearance rate constants, estimated using a one-compartment model, were higher after administration of 0.375-2.0 mg/kg body weight (bw) (0.016-0.020/day) than after administration of 3.0-6.0 mg/kg bw (0.0073-0.013/day) for six uncoated TiO2. In contrast, the clearance rate constant was 0.011, 0.0046 and 0.00018/day following administration of 0.67, 2.0 and 6.0 mg/kg bw TiO2 nanoparticle with Al(OH)3 coating, respectively. Translocation of TiO2 from the lungs to the thoracic lymph nodes increased in a time- and dose-dependent manner. Furthermore, the translocation of TiO2 from the lungs to the thoracic lymph nodes after 91 days was higher when Al(OH)3 coated TiO2 was administered (0.93-6.4%), as compared to uncoated TiO2 (0.016-1.8%). Slight liver translocation was observed (<0.11%), although there was no clear trend related to dose or elapsed time. No significant translocation was observed in other organs including the kidney, spleen and brain.

Tissue distribution and clearance of intravenously administered titanium dioxide (TiO2) nanoparticles.

The organ-tissue distribution and clearance of Degussa P25 TiO2 nanoparticles were determined after intravenous administration to rats (0.95 mg/kg bodyweight) using an inductively coupled plasma sector field mass spectrometer. The detection limits of Ti analysis, 0.54 and 1.4 ng/mL for blood and urine and 0.35-2.0 ng/g tissue for several organ tissues, enabled determination of tissue distribution and clearance for organs in which Ti content could not be previously determined due to low concentrations. Blood concentrations of TiO2 were 420 and 19 ng/mL at 5 and 15 min after administration, which were equivalent of only 2.8% and 0.13% of the administration dose, respectively. At 6 h, 94%, 2.0%, 0.17%, 0.023%, 0.014% and 0.026% of administered TiO2 was found in the liver, spleen, lung, kidney, heart and blood, respectively. Liver and spleen TiO2 burden was significantly higher in the administration than control group (p < 0.01) and did not decrease up to 30 days after administration, while TiO2 burden in the lung, kidney, heart and blood decreased over time. A two-step decay model was more suitable than a one-step decay model for the decay curves of pulmonary TiO2 burden but did not improve fitting to the decay curves of kidney TiO2 burden. No translocation to the brain was confirmed at a lower detection limit than was applied in previous studies. Ti content in faeces and urine in the TiO2 administration group did not differ from that in the control group.

Dose-dependent clearance kinetics of intratracheally administered titanium dioxide nanoparticles in rat lung.

AEROSIL(®) P25 titanium dioxide (TiO2) nanoparticles dispersed in 0.2% disodium phosphate solution were intratracheally administered to male F344 rats at doses of 0 (control), 0.375, 0.75, 1.5, 3.0, and 6.0 mg/kg. The rats were sacrificed under anesthesia at 1 day, 3 days, 7 days, 4 weeks, 13 weeks, and 26 weeks after administration. Ti levels in various pulmonary and extrapulmonary organs were determined using sensitive inductively coupled plasma sector field mass spectrometry. One day after administration, the lungs contained 62-83% of TiO2 administered dose. Twenty-six weeks after administration, the lungs retained 6.6-8.9% of the TiO2 administered at the 0.375, 0.75, and 1.5 mg/kg doses, and 13% and 31% of the TiO2 administered at the 3.0 and 6.0 mg/kg doses, respectively. The pulmonary clearance rate constants from compartment 1, k1, were estimated using a 2-compartment model and were found to be higher for the 0.375 and 0.75 mg/kg doses of TiO2 (0.030/day for both) than for TiO2 doses of 1.5-6.0 mg/kg (0.014-0.022/day). The translocation rate constants from compartment 1 to 2, k12, were estimated to be 0.015 and 0.018/day for the 0.375 and 0.75 mg/kg doses, and 0.0025-0.0092/day for doses of 1.5-6.0mg/kg. The pulmonary clearance rate constants from compartment 2, k2, were estimated to be 0.0086 and 0.0093/day for doses of 0.375 and 0.75 mg/kg, and 0-0.00082/day for 1.5-6.0 mg/kg doses. Translocation of TiO2 from the lungs to the thoracic lymph nodes increased in a time- and dose-dependent manner, accounting for 0.10-3.4% of the administered dose at 26 weeks. The measured thoracic lymph node burdens were a much better fit to the thoracic lymph node burdens estimated assuming translocation from compartment 1 to the thoracic lymph nodes, rather than those estimated assuming translocation from compartment 2 to the thoracic lymph nodes. The translocation rate constants from the lungs to the thoracic lymph nodes, kLung→Lym, were 0.000037-0.00081/day, and these also increased with increasing doses of TiO2. Although a small amount of TiO2 had translocated to the liver by 3 days after the administration (0.0023-0.012% of the highest dose administered, 6.0 mg/kg), translocation to the other extrapulmonary organs was not detected.