Field experiment of a telesurgery system using a surgical robot with haptic feedback

PURPOSE

To verify the usefulness of haptic feedback in telesurgery and improve the safety of telerobotic surgery.

METHODS

The surgeon's console was installed at two sites (Fukuoka and Beppu; 140 km apart), and the patient cart was installed in Fukuoka. During the experiment, the surgeon was blinded to the haptic feedback levels and asked to grasp the intestinal tract in an animal model. The surgeon then performed the tasks at each location.

RESULTS

No marked differences in task accuracy or average grasping force were observed between the surgeon locations. However, the average task completion time was significantly longer, and the system usability scale (SUS) was significantly lower rating for remote operations than for local ones. No marked differences in task accuracy or task completion time were observed between the haptic feedback levels. However, with haptic feedback, the organ was grasped with a significantly weaker force than that without it. Furthermore, with haptic feedback, experienced surgeons in robotic surgery tended to perform an equivalent task with weaker grasping forces than inexperienced surgeons.

CONCLUSION

The haptic feedback function is a tool that allows the surgeon to perform surgery with an appropriate grasping force, both on site and remotely. Improved safety is necessary in telesurgery; haptic feedback will thus be an essential technology in robotic telesurgery going forward.

Telesurgery and telesurgical support using a double-surgeon cockpit system allowing manipulation from two locations

BACKGROUND

Although several studies on telesurgery have been reported globally, a clinically applicable technique has not yet been developed. As part of a telesurgical study series conducted by the Japan Surgical Society, this study describes the first application of a double-surgeon cockpit system to telesurgery.

METHODS

Surgeon cockpits were installed at a local site and a remote site 140 km away. Three healthy pigs weighing between 26 and 29 kg were selected for surgery. Non-specialized surgeons performed emergency hemostasis, cholecystectomy, and renal vein ligation with remote assistance using the double-surgeon cockpits and specialized surgeons performed actual telesurgery. Additionally, the impact of adding internet protocol security (IPsec) encryption to the internet protocol-virtual private network (IP-VPN) line on communication was evaluated to address clinical security concerns.

RESULTS

The average time required for remote emergency hemostasis with the double-surgeon cockpit system was 10.64 s. A non-specialized surgeon could safely perform cholecystectomy or renal vein ligation with remote assistance. Global Evaluative Assessment of Robotic Skills and System Usability Scale scores were higher for telesurgical support-assisted surgery by a non-specialized surgeon using the double-surgeon cockpits than for telesurgery performed by a specialized surgeon without the double-cockpit system. Adding IPsec encryption to the IP-VPN did not have a significant impact on communication.

CONCLUSION

Telesurgical support through our double-surgeon cockpit system is feasible as first step toward clinical telesurgery.

Artificial Intelligence-Based Prediction of Recurrence after Curative Resection for Colorectal Cancer from Digital Pathological Images

BACKGROUND

To develop an artificial intelligence-based model to predict recurrence after curative resection for stage I-III colorectal cancer from digitized pathological slides.

PATIENTS AND METHODS

In this retrospective study, 471 consecutive patients who underwent curative resection for stage I-III colorectal cancer at our institution from 2004 to 2015 were enrolled, and 512 randomly selected tiles from digitally scanned images of hematoxylin and eosin-stained tumor tissue sections were used to train a convolutional neural network. Five-fold cross-validation was used to validate the model. The association between recurrence and the model's output scores were analyzed in the test cohorts.

RESULTS

The area under the receiver operating characteristic curve of the cross-validation was 0.7245 [95% confidence interval (CI) 0.6707-0.7783; P < 0.0001]. The score successfully classified patients into those with better and worse recurrence free survival (P < 0.0001). Multivariate analysis revealed that a high score was significantly associated with worse recurrence free survival [odds ratio (OR) 1.857; 95% CI 1.248-2.805; P = 0.0021], which was independent from other predictive factors: male sex (P = 0.0238), rectal cancer (P = 0.0396), preoperative abnormal carcinoembryonic antigen (CEA) level (P = 0.0216), pathological T3/T4 stage (P = 0.0162), and pathological positive lymph node metastasis (P < 0.0001).

CONCLUSIONS

The artificial intelligence-based prediction model discriminated patients with a high risk of recurrence. This approach could help decision-makers consider the benefits of adjuvant chemotherapy.

Plasma-informed minimal residual disease (MRD) assay: A multicenter prospective study in Japanese patients with stage II colorectal cancer

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Background: ̃80% of stage II colorectal cancer (CRC) can be cured by surgery alone. However, adjuvant chemotherapy is recommended for patients with high risk features such as bowel obstruction, < 12 lymph nodes examined and T4 tumors. Traditional pathological grading and biomarkers such as carcinoembryonic antigen has limited sensitivity. Several reports indicated circulating tumor DNA (ctDNA) may represent a promising prognostic factor to assess MRD as a factor for prediction of recurrence after surgery. Here, we present a proof-of-concept study for the development of a novel plasma-based highly sensitive Next Generation Sequencing (NGS) panel using SafeSEQ technology in operable CRC Japanese patients. Methods: This multicenter prospective study recruited patients diagnosed as operable clinical stage II CRC (n = 46) with pre- and post- (4̃6 weeks) operative plasma samples collected between Nov, 2019 and Jan, 2021. ctDNA were extracted and a 14-gene NGS panel was used to analyze single nucleotide variants (SNVs) and Indels covered by gene-specific amplicons. MRD variant was defined as same variant detected in both pre- and post- operative plasma samples. Tissue NGS by a 500-gene panel was also performed in a small number of tissue samples (n = 5) to compare the concordance of plasma and tissue variants. Results: Pre- and post-operative ctDNA status of 46 patients were analyzed. ctDNA positive was observed in 69.6% (32/46, 95%CI 55.2, 81.0) pre- and 34.8% (16/46, 95%CI 22.7, 49.3) post- samples. AKT1, CTNNB1, NRAS, POLE and PPP2R1A mutation were not detected in this study. TP53 mutation was most frequently detected in both pre- (22/46) and post- (11/46) samples, whereas APC mutation was ranked 2nd in pre- (15/46) but none in post- samples. A combined 96 variants were detected in all samples, in which 76 of them were < 0.5% mutant allele frequency (MAF). MRD variants were detected in 17.4% (8/46, 95%CI 8.82, 30.99) post- samples. Evaluation of positive percentage agreement between tissue and pre- plasma samples in three patients show that a total 7 variants detected in plasma, and 3 of them were detected in tissue samples. Conclusions: This study assesses the feasibility of a plasma-informed NGS panel by evaluating pre- and post- operative plasma samples. The presence of variants with < 0.5% MAF detected in this study indicate a highly sensitive method is required for accurate MRD detection. Further observation is required to explore the relationship between MRD variant and clinical outcome such as 2-year progression-free survival.

Fibroblast growth factor receptor 2 expression, but not its genetic amplification, is associated with tumor growth and worse survival in esophagogastric junction adenocarcinoma

Background

Fibroblast growth factor receptor 2 (FGFR2) genetic alterations lead to tumor cell proliferation in various types of cancer. We hypothesized that FGFR2 amplification is associated with FGFR2 expression, resulting in tumor growth and poorer outcome in esophagogastric junction (EGJ) adenocarcinoma.

Patients and Methods

A total of 176 consecutive chemo-naive patients with EGJ adenocarcinoma were enrolled from two academic institutions. FGFR2 amplification was examined by real-time PCR (N = 140) and FGFR2 expression with immunohistochemical staining (N = 176), and compared against clinicopathological factors and patient outcomes. The effects of FGFR2 inhibition or overexpression on cell proliferation, cell cycle, and apoptosis assays were investigated in EGJ adenocarcinoma cell lines. Downstream FGFR2, AKT and ERK were also examined.

Results

Based on the correlation between FGFR2 levels and FGFR2 overexpression in vitro, FGFR2 amplification was defined as copy number > 3.0. In clinical samples, FGFR2 amplification and FGFR2 IHC expression were 15% and 61%, respectively. Although these two statuses were significantly correlated (P < 0.05), only FGFR2 IHC expression was significantly associated with tumor depth (multivariate P < 0.001) and overall survival of patients (univariate P = 0.007). Supporting these findings, FGFR2 overexpression was associated with tumor cell proliferation, cell cycle progression, and anti-apoptosis. Selective inhibition of FGFR2 sufficiently suppressed tumor cell proliferation through de-phosphorylation of AKT and ERK.

Conclusions

FGFR2 amplification was significantly associated with FGFR2 expression. FGFR2 expression (but not FGFR2 amplification) was associated with tumor growth and patient outcomes. Our findings support FGFR2 as a novel therapeutic target for EGJ adenocarcinoma.

Protein Expression of Programmed Death 1 Ligand 1 and HER2 in Gastric Carcinoma

OBJECTIVES

Programmed death 1 (PD-1) is an immunoinhibitory receptor and has been identified as a new target for immunotherapy in cancer. Here we report the expression of PD-1 ligand 1 (PD-L1) in surgically resected gastric cancer.

MATERIALS AND METHODS

We examined formalin-fixed tumor samples from 144 gastric cancer patients with a primary diagnosis of gastric carcinoma. Immunohistochemistry was used to detect PD-L1. Human epidermal growth factor receptor 2 (HER2) expression and phosphatase and tensin homolog (PTEN) loss of heterozygosity were investigated in these patients. RNA interference was used to downregulate HER2 expression, and PD-L1 protein expression was assessed by flow cytometry using the gastric cancer cell line MKN45.

RESULTS

Overexpression of PD-L1 was significantly correlated with tumor invasion (p = 0.011) and associated with poor survival. The number of PD-L1-positive cases increased according to the HER2 score in clinical samples. siRNA-mediated downregulation of HER2 significantly decreased PD-L1 protein expression in MKN45 cells.

CONCLUSIONS

PD-L1 expression was associated with poor survival of gastric cancer, and HER2 signaling affects the expression of PD-L1 in gastric cancer. In gastric cancer, PTEN and HER2 are potential candidate biomarkers for developing human antibodies that block PD-L1.

Recurrence with pagetoid spread arising 17 years after surgery for intramucosal rectal cancer: a case report

Background

Perianal Paget’s disease (pPD) is uncommon, with only about 180 cases documented in the literature. Anorectal carcinoma with pagetoid spread is even rarer.

Case presentation

An 81-year-old woman underwent rectal cancer extirpation with a transanal approach 17 years prior. She has since undergone two reoperations for local rectal cancer recurrence. Then, warts frequently appeared on the vulva on several occasions. Warts appeared on the vulva 1 year ago, which were diagnosed as pPD by biopsy. She underwent perineal tumor resection, and the final histological diagnosis was rectal cancer recurrence with pagetoid spread. The resected stump was positive for cancer cells, and tumor progression was rapid. She underwent additional abdominoperineal resection (Miles’ operation) with lymph node dissection. However, disease progression was rapid and she died 7 months after the Miles’ operation.

Conclusions

There are some case reports describing anorectal carcinoma with pagetoid spread, however, almost of all those cases were synchronous primary anorectal cancer. Here, we report the first case of metachronous recurrence rectal cancer with pagetoid spread arising 17 years after surgery.

High ubiquitin-specific protease 44 expression induces DNA aneuploidy and provides independent prognostic information in gastric cancer

Chromosomal instability (CIN), characterized by aneuploidy, is a major molecular subtype of gastric cancer. The deubiquitinase USP44 is an important regulator of APC activation in the spindle checkpoint and leads to proper chromosome separation to prevent aneuploidy. Aberrant expression of USP44 leads CIN in cells; however, the correlation between USP44 and DNA aneuploidy in gastric cancer is largely unknown. We analyzed USP44 expression in 207 patients with gastric cancer by immunohistochemistry and found that the proportion of USP44 expression was higher in gastric cancer tumors (mean, 39.6%) than in gastric normal mucosa (mean, 14.6%) (P < 0.0001). DNA aneuploidy was observed in 124 gastric cancer cases and high USP44 expression in cancer strongly correlated with DNA aneuploidy (P = 0.0005). The overall survival was significantly poorer in the high USP44 expression group compared with the low USP44 group (P = 0.033). Notably, USP44 expression had no prognostic impact in the diploid subgroup; however, high USP44 expression was a strong poor prognostic factor for progression‐free survival (P = 0.018) and overall survival (P = 0.036) in the aneuploid subgroup. We also confirmed that stable overexpression of USP44 induced somatic copy‐number aberrations in hTERT‐RPE‐1 cells (50.6%) in comparison with controls (6.6%) (P < 0.0001). Collectively, our data show USP44 has clinical impact on the induction of DNA aneuploidy and poor prognosis in the CIN gastric cancer subtype.

Anal metastasis of rectal cancer-adenocarcinoma of squamous cells: a case report and literature review

Anal metastasis of colorectal cancer is very rare and is usually associated with a history of anal disease, including anal fistula, fissure, hemorrhoidectomy, and anastomotic injury. We report a case of rectal cancer with a synchronous anal metastasis consisting of adenocarcinoma of squamous cells without a history of anal disease. A 60-year-old woman had a chief complaint of melena. She had a 1.5-cm anal tumor on the perianal skin, and a Bollman type 2 rectal tumor on the Ra portion was found on colonoscopy. Biopsy of both tumors revealed a similar histology of well- to moderately differentiated adenocarcinoma. There was no sign of metastases in lymph nodes or other organs. For the purpose of diagnosis and treatment, transperineal local resection of the anal tumor was performed, and it was histologically identified as adenocarcinoma of squamous cells with no invasion to muscles, lymph ducts, or microvessels. The pathological margin was free. Then, to achieve radical cure, laparoscopic low anterior resection (LAR) with D3 lymphadenectomy was performed. The histological diagnosis of the anal tumor was adenocarcinoma of squamous cells without invasion to muscles, lymph ducts, or vessels. The surgical margin was completely free. Immunohistochemical analysis of both tumors revealed similar staining patterns, and the final diagnosis was rectal cancer with metastasis to the anal skin. The patient received no postoperative therapy, and no recurrences have been observed 12 months after surgery. We expect that our sphincter-preserving surgical strategy provided a good prognosis for the synchronous rectal cancer and anal metastasis. This is a rare report of a case with an anal metastasis of colorectal cancer on perianal squamous cells without a history of anal disease that was resected while preserving anal function.

Successful surgical intervention for rectal perforation due to polyarteritis nodosa: report of a case

Background

Polyarteritis nodosa (PAN) is a primary systemic necrotizing vasculitis with diffuse organ involvements, resulting in a high mortality rate due to multiple organ failure. Although the small bowel is the frequently targeted organ of PAN-associated vasculitis, rectal involvement is very rare, and only one case of rectal bleeding has been previously reported. The mortality rate of PAN with gastrointestinal (GI) perforation is reportedly much higher than that of without severe GI involvement. We herein report the first case of rectal perforation due to PAN, successfully managed with an adequate surgical intervention.

Case presentation

A 66-year-old woman with PAN had abdominal pain and melena with guarding. Computed tomography scan showed abdominal free air and bubbles in the rectal hematoma. We diagnosed it acute peritonitis, and emergency surgery was performed. After removing rectal hematoma and necrotic tissue, a huge lack of rectal wall spreading to the pelvirectal space was observed. In order to totally remove the necrotic tissue, abdominoperineal resection was needed. Together with histopathological examinations which showed neutrophils and fibrinous necrosis, we finally diagnosed rectal perforation due to PAN. At 19-month follow-up after surgery, she was still healthy with a stable disease of PAN.

Conclusions

We herein reported the first case of successfully managed rectal perforation due to PAN. Early adequate surgical resection may be important for the case with rectal perforation.

Prognostic Significance of Sarcopenia in Patients with Esophagogastric Junction Cancer or Upper Gastric Cancer

BACKGROUND

The association between sarcopenia and postoperative outcomes for patients with gastrointestinal malignancies remains controversial. This study aimed to assess the impact of sarcopenia on short- and long-term outcomes after surgery for esophagogastric junction cancer (EGJC) or upper gastric cancer (UGC).

METHODS

The study reviewed 148 patients with EGJC or UGC who underwent surgical resection. The patients were categorized into the sarcopenia group or the non-sarcopenia group according to their skeletal muscle index calculated using abdominal computed tomography images. The study compared clinicopathologic factors, postoperative complications, and prognosis between the two groups.

RESULTS

Sarcopenia was present in 19 patients (32.2%) with EGJC and 23 patients (25.8%) with UGC. The 5-year overall survival (OS) and recurrence-free survival (RFS) rates were significantly poorer in the sarcopenia group than in the non-sarcopenia group (OS 85.5 vs 54.8%, P = 0.0010; RFS 78.7 vs 51.7%, P = 0.0054). The development of postoperative complications did not differ significantly between the two groups. Both the uni- and multivariate analyses showed that N stage (P < 0.0001) and sarcopenia (P = 0.0024 and 0.0293, respectively) were independent poor prognostic factors for OS.

CONCLUSIONS

Sarcopenia was strongly associated with a poor long-term prognosis for patients with EGJC or UGC who underwent surgery. The results suggest that special attention might be needed during the development of treatment strategies for patients with sarcopenia who intend to undergo operations for EGJC and UGC.

High expression of the Notch ligand Jagged-1 is associated with poor prognosis after surgery for colorectal cancer

The importance of Notch signaling in colorectal cancer (CRC) carcinogenesis and progression has previously been presented. Increased expression of Jagged‐1 (JAG1), a Notch ligand, in CRC has been revealed, but the detailed prognostic significance of JAG1 in CRC has not been determined. Protein expression of JAG1 was examined using immunohistochemistry in 158 CRC specimens. Expression of JAG1 and E‐cadherin and their associations with clinicopathologic characteristics, overall survival (OS) and relapse‐free survival (RFS) were evaluated. In vitro studies using compounds to regulate intracellular signaling and small interfering RNA to silence JAG1 were performed in a colon cancer cell line. JAG1 expression in cancerous tissues was weak, moderate or strong in 32%, 36% and 32% of specimens, respectively, and correlated with histologic type and T stage. In multivariate analysis, JAG1 expression, histologic type and lymphatic invasion independently correlated with OS and RFS. The combination of high JAG1 expression and low E‐cadherin expression had an additive effect toward poorer OS and RFS compared with the low JAG1/high E‐cadherin expression subtype. A significant correlation between JAG1 expression and KRAS status was detected in groups stratified as high E‐cadherin expression. In vitro studies suggested that RAS‐MEK‐MAP kinase and the Wnt pathways positively regulated JAG1 expression. Gene silencing with siJAG1 indicated that JAG1 promotes the transition from epithelial to mesenchymal characteristics and cell growth. High expression of JAG1 is regulated by various pathways and is associated with poor prognosis through promoting the epithelial to mesenchymal transition and cell proliferation or maintaining cell survival in CRC.

Distant lymph node metastases caused by esophageal cancer invasion to the lamina propria: a case report

Background

Pathological examination after endoscopic submucosal dissection revealed that a 62-year-old male had esophageal squamous cell carcinoma with lamina propria mucosal invasion and lymphatic permeation.

Case presentation

The patient underwent subtotal esophagectomy and reconstruction as an additional therapy. At 3 years and 4 months after esophagectomy, enlargement of abdominal para-aortic lymph nodes metastases was detected by computed tomography scanning. A total of 50.4 Gy of radiation and two cycles of 5-fluorouracil plus cisplatin were administered. The lymph node metastases were markedly reduced by chemoradiotherapy; however, at 1 year and 1 month later (4 years and 5 months after esophagectomy), left adrenal gland recurrence was found. Although resection was performed, the patient died from cancer progression at 5 years and 4 months after esophagectomy.

Conclusions

This case demonstrates that esophageal squamous cell carcinoma with invasion to the lamina propria and lymphatic permeation has the potential to cause distant metastases.

Development of fistula between esophagogastric anastomotic site and cartilage portion of trachea after subtotal esophagectomy for cervical esophageal cancer: a case report

A 65-year-old man with cT3N2M0 stage III cervical esophageal cancer underwent subtotal esophagectomy and gastric tube reconstruction through the retrosternal route after neoadjuvant chemoradiotherapy. The anastomosis was located adjacent to the left side of the trachea, and a circular stapler was used for anastomosis. Postoperative anastomotic leakage occurred, and an esophagotracheal fistula between the esophagogastric anastomotic site and cartilage portion of the trachea was observed on postoperative day 44. The patient underwent division of the fistula, direct suturing of the anastomotic leakage site, left pectoralis major muscle flap placement, and tracheotomy. He was discharged home on postoperative day 120 on an oral diet. All previous reports of tracheobronchial fistula describe the occurrence of the fistula at the membranous portion of the trachea. The formation of a fistula between the esophagogastric anastomotic site and cartilage portion of the trachea is considered a possible complication when a high esophagogastric anastomosis is created.

Cardiac tamponade due to bleeding as a potential lethal complication after surgery for esophageal cancer

BACKGROUND

Cardiac tamponade, due to bleeding in the pericardial space after esophagectomy for esophageal cancer, is an extremely rare complication and may be associated with sudden hemodynamic instability that can lead to death unless there is prompt diagnosis and appropriate treatment.

CASE REPORT

A 76-year-old man underwent sub-total esophagectomy via a cervico-right thoracoabdominal approach and reconstruction with a gastric tube through the retrosternal route. On postoperative day 4, the patient developed hypotension due to cardiac tamponade caused by bleeding into the pericardial space and he had a decreased level of consciousness. Pericardial resection and open drainage via a minimal left anterior thoracotomy was performed that resulted in hemodynamic improvement followed by an uneventful recovery.

CONCLUSION

Cardiac tamponade due to postoperative bleeding, which is a rare but life-threatening complication, should be considered as a cause of hemodynamic instability in the early postoperative period after esophagectomy.

Surgical treatment of stage IV non-small cell lung cancer

Most stage IV non-small-cell lung cancer (NSCLC) patients are not amenable to curative treatment. The purpose of this study was to analyse our initial experience with an aggressive surgical strategy for stage IV NSCLC, and to define which patients can benefit from this treatment. Forty-six stage IV NSCLC patients who underwent surgical resection of both primary lung cancer and metastatic sites from April 1989 to December 2010 were included in this study. The record of each patient was reviewed for age, gender, pN status, sites of metastasis, histology, surgical procedure and duration of survival. There were 13 females and 33 males. Their median age was 62.0 years (range, 44-82 years). The overall 5-year survival rate was 23.3% (median, 20.0 months), and the disease-free survival rate was 15.8% at 5 years (median, 16.1 months). Patients with the pN2 status had a significantly worse survival than patients with a pN0 or pN1 status (8.6 versus 33.1%, P = 0.0497). According to a multivariate Cox proportional hazards analysis, no independent predictor of survival was identified. The results of our study suggest that surgical treatment can extend the survival in stage IV NSCLC patients if the patients can tolerate surgery.

Prediction of the prognosis and surgical indications for pulmonary metastectomy from colorectal carcinoma in patients with combined hepatic metastases

BACKGROUND

The value of surgical treatment for patients with pulmonary and hepatic metastases from colorectal carcinoma is controversial. The purpose of this study was to analyze our initial experience with this aggressive strategy, and to define the prognosis and the surgical indications.

METHODS

The records of 35 patients who underwent surgical treatments for both hepatic and pulmonary metastases from colorectal carcinoma, from January 1997 to December 2008, were retrospectively analyzed.

RESULTS

There were 18 females and 17 males with a median age was 62.0 years. The primary colorectal neoplasm was located at the colon in 23 patients (65.7%) and in the rectum in 12 patients (34.3%). The overall 5-year and 10-year survival rates were 65.3% and 31.5% from the date of primary colorectal resection, respectively. For patients who underwent metachronous hepatic and pulmonary surgical treatment, the 10-year survival rate was 40.9%, which was significantly better than that of those undergoing synchronous hepatic and pulmonary surgical treatment (p=0.0265). Patients who have pulmonary less than ten of metastasis thus seemed to have a better prognosis than those with more than ten, but the difference was quite significant (p=0.0719). In a multivariate Cox proportional hazards model, synchronous hepatic and pulmonary metastases was identified as an independent predictor of adverse survival (p=0.0073).

CONCLUSIONS

The results of our study suggest that hepatic and pulmonary surgical treatment can provide a better prognosis for patients with metachronous hepatic and pulmonary metastases from colorectal carcinoma. We believe that aggressive metastasectomy can be an option for selected patients, even if a patient has been previously treated for hepatic and pulmonary metastases from colorectal carcinoma.

A method for identifying causative chemicals of allergic contact dermatitis using a combination of chemical analysis and patch testing in patients and animal groups: application to a case of rubber boot dermatitis

A 63-year-old woman developed allergic contact dermatitis from rubber boots. Initial investigation, by patch testing in the patient and chemical analysis of the causative rubber boots, revealed that mercaptobenzothiazole (MBT) and dibenzothiazyl disulfide (MBTS) were the causative chemicals. Subsequent investigations were performed by patch testing in animal groups. An extract of the causative rubber boots, MBT and MBTS were used for sensitization of guinea pigs by the guinea pig maximization test (GPMT). 3 animal groups, A (with the boot extract), B (with MBT) and C (with MBTS) were successfully prepared. The boot extract was fractionated by column chromatography and thin-layer chromatography (TLC). Each fraction was subjected to patch testing in the animal groups. Positive reactions in all groups would show that the active fractions contained MBT-type compounds, whereas a positive reaction in group A but negative ones in group B and C would show that the active fractions did not contain any MBT-type compounds. Each fraction was then analyzed by gas chromatography (GC), GC-mass spectrometry (GC-MS), direct inlet-MS (DI-MS) and high-performance liquid chromatography (HPLC). By this investigation, we found not only known allergens (MBT, MBTS), but also unknown allergens: S-substituted MBT-type compounds and styrenated phenol (SP). Thus, SP was shown to be a candidate as a human sensitizer even though the patient did not react to it.

[A study on the usefulness of the OECD Combined Repeat Dose and Reproductive/Developmental Toxicity Screening Test (ReproTox)]

We studied the usefulness of the OECD combined Repeat Dose and Reproductive/Developmental Toxicity Screening Test (ReproTox) using cyclophosphamide (CP), which is well known for its toxicological properties. CP was given daily by gavage to groups of 12 male and 12 female 8-week-old Sprague-Dawley rats at doses of 0, 2, 3, 4.5 or 6.7 mg/kg. Significant decreases in body weight and food consumption were observed in males given 6.7 mg/kg and in all treated females. One, 3 and 12 females died during pregnancy in the groups given 3, 4.5 and 6.7 mg/kg, respectively. In males 2 died in the 6.7 mg/kg group. Leukopenia and anemia were evident in treated males. The thymus and spleen weights were significantly decreased in treated rats. Histopathologically, atrophy of the thymus, spleen and bone marrow was observed. With respect to the reproductive/developmental toxicity, dose-dependent increases in postimplantation loss and postnatal death of pups were found in treated dams. The body weight of pups from treated dams was significantly lowered. Thus, most of the known toxicological properties of CP regarding systemic toxicity and reproductive/developmental toxicity were clearly demonstrated in this study. Therefore ReproTox can be considered a useful screening test for assessing repeat dose and reproductive/developmental toxicity of existing chemicals of high production volume, although teratogenic potential and adverse effects on spermatogenesis and fertility were not detected under the present experimental conditions.

[Acute and subacute toxicity studies of Bis(2,3-dibromopropyl) phosphate magnesium in rat]

Acute and subacute oral toxicity tests of Bis(2,3-dibromopropyl) phosphate magnesium (Bis-BP.Mg) were carried out in Wistar rats. In the acute toxicity test, Bis-BP.Mg suspended in arabic gum was administered orally to a group consisting of 10 male and 10 female rats, and they were observed for 14 days. LD50 values of male and female rats were 283 (253 approximately 314) mg/kg and 261 (219 approximately 310) mg/kg, respectively. As toxic symptoms, eyelid closure, crouching, shivering and staggering gait were observed in the treated groups of both sexes. In gross findings, hypertrophy, discoloration and necrotic change of the liver, and hypertrophy and discoloration of the kidney were observed in the treated groups. In histopathological examination, necrosis, desquamation, large nuclei formation of the tubular epithelium, and tubular dilatation of the kidney and necrosis of the liver cells were observed in the treated groups. In the subacute toxicity test, groups of rats consisting of 5 males and 5 females were fed a commercial diet containing 0, 30, 100, 300 and 1000 ppm Bis-BP.Mg for 45 days. In body weight and food consumption, there were no significant difference between the control and treated groups. Significant increases were observed in the liver and kidney weights of male rats fed 1000 ppm Bis-BP.Mg. Histopathologically, desquamation, swelling, and large nuclei formation of the tubular epithelium and tubular dilatation of the kidney were observed, but they were much less frequent than those in the acute toxicity test. It was concluded that Bis-BP.Mg has apparent renal toxicity.

[Comparative studies on acute toxicity of glutaraldehyde using young and old rats]

Acute oral toxicity test of glutaraldehyde (GA) was carried out in young (5-6W) and old (57-60W) Wistar/ST rats. Experiment 1: Various doses of GA were administered by gavage. After 30 minutes, the rats showed abnormal gait, then took an abdominal or lateral position after 4 hours. Gross erosion, discoloration and thickening of the glandular stomach mucosa and hyperemia of the liver, intestine and lung were observed in the dead rats. The LD50 values were 283 mg/kg for young rats and 141 mg/kg for old rats. Experiment 2: One half of the LD50 doses (140 mg/kg and 70 mg/kg of GA) were administered to young and old rats by gavage, respectively. Both groups showed a similar toxicity. Organ weights were not changed. In gross findings, erosion, discoloration and thickening of the glandular stomach mucosa were observed on day 1-7, but these damages were recovered by day 14. Histopathologically, atrophy, degeneration, necrosis, hemorrhage, edema and cell infiltration of the glandular stomach mucosa were found on day 1. Recovery from these changes was observed from day 3. Changes in several serum enzyme activities were observed on day 1-3. Therefore, susceptibility to the acute toxic effect of GA was higher in old rats than in young rats. However, no apparent differences were observed in the toxic profiles by GA between young and old rats.

Phosgene (chlorophenyl)hydrazones, strong sensitizers found in yellow sweaters bleached with sodium hypochlorite, defined as causative allergens for contact dermatitis by an experimental screening method in animals

12 young men developed allergic contact dermatitis from wearing yellow cotton sweaters. We attempted to identify the causative agents by an experimental screening method in animals. Guinea pigs were sensitized with an acetone extract of the sweater material, by means of the guinea pig maximization test (GPMT). Active ingredients were then separated from the extract, by step-by-step patch test screening of chromatographic fractions in the guinea pigs, and finally analyzed by gas chromatography-mass spectrometry (GC-MS). Although there were 2 allergens with important activity (1 in the fraction eluted from the silica gel column with hexane, and 1 in the methanol fraction), the present study is focussed on the fat-soluble allergens in the hexane fraction. GC-MS analysis revealed that 4 kinds of phosgene (chlorophenyl)hydrazones (PCPHs) were present in the hexane fraction. PCPHs prepared in our laboratory showed strong eliciting activities, not only in the guinea pigs sensitized with the extract, but also in a male volunteer sensitized by exposure to a yellow sweater during irritancy testing. Phosgene (2,5-dichlorophenyl)hydrazone, which was the main component among the PCPHs found in the sweater, sensitized guinea pigs even at the 1 ppm level. From these results, we conclude that PCPHs were one of the allergens responsible for the cases.

Acute toxicity tests on 113 environmental chemicals

Acute toxicity tests on 113 environmental chemicals were conducted by the order of the Japanese government agencies. the LD50s or LC50s for 23 household chemicals, 11 medical drugs, 10 drug additives, 20 food additives, 13 industrial chemicals, 14 environmental pollutants, 12 agricultural chemicals and 5 organic solvents are presented together with the major toxic signs and symptoms and macroscopic changes in tissues. These toxicity data will be useful as an information source for regulatory purposes and also for prediction of the potential for acute toxicity of a wide variety of new chemicals.

Comparison of the toxicity of p-dichlorobenzene (p-DCB) administered to male F344 rats orally or by the inhalation route

The organ distribution and toxicity of p-DCB were compared in rats after either inhalation or oral administration. Male F344 rats were exposed to 500 or 125 ppm for 24 hr in a whole body inhalation chamber (H and L groups) or received a single dose of 300 mg/kg by gavage (PO group). The concentrations of p-DCB in the serum, liver, kidney and fatty tissues were measured by gas chromatography at intervals during and up to 24 hr after the treatment. Peak serum values for the L and H groups were lower than in the PO animals, but the organ/serum distribution ratios of p-DCB tended to be higher, in some cases markedly, in rats receiving the inhalation treatment. Significant increases in the levels of blood urea nitrogen, hepatic glutamic oxaloacetic transaminase and glutamic pyruvate transaminase and significant decreases in the levels of serum total cholesterol were observed only in the inhalation groups. Microscopically, the appearance of numerous eosinophilic droplets, together with swelling and desquamation of the proximal tubular epithelium of the kidney was especially noteworthy in H and L p-DCB treated groups. Thus, both biochemical and histopathological abnormalities induced by p-DCB were more pronounced in rats administered the compound by the inhalation route.

Nephrotoxic effect of tris(2,3-dibromopropyl)phosphate on rat urinary metabolites: assessment from 13C-NMR spectra of urines and biochemical and histopathological examinations

Rats received either single oral doses of 0, 25, 50, 100 and 200 mg/kg tris(2,3-dibromopropyl)phosphate (Tris-BP) or repeated doses of 50, 100 and 200 mg/kg/day Tris-BP for 7 days. Urine was collected over a 24-hr period and subjected to 13C-NMR and biochemical examinations. Tris-BP produced significant increases of urinary glucose and lactate. Urinary gamma-glutamyltransferase, lactate dehydrogenase and alkaline phosphatase levels were significantly elevated on the first 2 days of post-treatment. Histopathologically, the kidney exhibited proximal tubular damage at a dose of 200 mg/kg. There was a good correlation among the histopathological, biochemical results, and the 13C-NMR urinary metabolite fingerprints in the assessment of Tris-BP-induced renal damage. The abnormal patterns of metabolite excretion suggested that the lesions produced by Tris-BP were caused by changes in the metabolic function of tubular epithelial cells. The urinary excretion of lactate, enzymes and inhibition of glucose reabsorption from the tubular lumina may be attributed to necrosis and desquamation of the tubular cell.

Short-term toxicity study of 4-dimethylaminoazobenzene in marmosets

The marmoset, a small non-human primate, has rarely been used in toxicological studies. A short-term toxicity study was performed on common marmosets (BW = 330 +/- 32 g). Fifteen male marmosets received oral administration of DAB at a dose level of 56 mg/kg/day and 4 control animals received corn oil alone for a period of 15 days. Hematological, biochemical, histopathological and bone marrow examinations were carried out on the 5th, 10th and 15th day of treatment. Body weight decreased continuously and two animals died on day 10. Decreases in RBC, Hb and Ht and increases in MCV and WBC were observed. Uric acid and glucose were increased and AlP and LAP were decreased. Aldolase, GOT and GPT were increased by day 10, and thereafter recovery of aldolase to the control level and decreases of GOT and GPT were observed. Relative organ weights of the liver, kidney, spleen and adrenal were increased. Histologically, C-cell hyperplasia of the thyroid and slight changes of the liver were noted. Marrow total cell counts were not changed, but the G/E ratio was reduced. Thus, macrocytic anemia, an increase of marrow erythroblasts due to anemia and changes of biochemical parameters indicating liver injury were observed in marmosets; these findings were similar to those in rats in the previous experiments.