[Reconstruction of complex tissue defects in temporal region: report of 3 cases]

Objective: To discuss the techniques and repairing methods of various degree of compound tissue defects in the auriculotemporal region. Methods: Retrospective analysis was conducted on three cases of different repairing methods for huge compound tissue defects in different degrees in the auriculotemporal region after the resection of the malignant tumor or sinus tract due to repeated infection in our hospital. Results: Following total removal of the tumors or sinus tract in all patients, we applied retroauricular lingual flap transfer repairing, latissimus dorsi flap free transfer repairing and vascular anastomosis, scalp tissue expansion in stage Ⅰ, then repairing the lesion with expanded scalp and filling the huge mastoid cavity with abdominal fat in stage Ⅱ, respectively, according to the characteristics of compound tissue defects in the auriculotemporal region. All free flaps survived well. Conclusions: The anatomy of the auricular-temporal area is complex and involves important vascular and neural structures of head and neck and lateral skull base. The huge composite tissue defect following auriculotemporal region surgery, which is composed of skin, muscle and bone tissue, needs to be repaired in one stage. Therefore, flexible repairing methods should be chosen based on different situations, for attaining the goal of completely removing tumor and lesions, and then, covering the operation cavity.

Genetic factors involved in delayed methotrexate elimination in children with acute lymphoblastic leukemia

BACKGROUND

Delayed excretion of methotrexate can lead to life-threatening toxicity that may result in treatment cessation, irreversible organ damage, and death. Various factors have been demonstrated to influence the pharmacokinetic process of methotrexate, including genetic and nongenetic factors.

METHODS

We investigated the genetic factors primarily related to the metabolic pathway of methotrexate in children with acute lymphoblastic leukemia with delayed elimination, defined as C_44-48h ≥ 1.0μmol/L in this study. A total of 196 patients (delayed excretion group: 98; normal excretion group: 98) who received CCCG-ALL-2015 protocol after propensity score-matched analysis were included in the study. Twenty-eight target single-nucleotide polymorphisms (SNPs) were analyzed by multiplex polymerase chain reaction and sequencing, and 25 SNPs were finally included in the study.

RESULTS

The genotype distribution of SLCO1B1 rs2306283 SNP was different between the delayed and normal excretion groups. SLCO1B1 rs2306283 AA carriers had a significantly lower methotrexate C_44-48h /D ratio than GG carriers in both groups. Furthermore, compared with the normal excretion group, SLCO1B1 rs2306283 AG and GG were risk factors for developing oral mucositis (odds ratio [OR]: 2.13; 95% confidence interval [CI]: 1.11-4.08; P < .001), hepatotoxicity (OR: 2.12; 95% CI: 1.26-3.56; P < .001), and myelosuppression (OR: 1.21; 95% CI: 1.04-1.41; P = .005) in delayed excretion group.

CONCLUSIONS

The results from this study indicate the potential role of SLCO1B1 rs2306283 as a pharmacogenomic marker to guide and optimize methotrexate treatment for delayed elimination in children with acute lymphoblastic leukemia.

[The role and mechanism of human trophoblastic cell surface antigen 2 in the invasion and metastasis of ovarian cancer]

Objective: To explore the role and molecular mechanism of trophoblastic cell surface antigen 2 (Trop2) in the invasion and migration of ovarian cancer. Methods: Through the data mining of Cancer Cell Line Encyclopedia and TCGA database, the clinical significance of Trop2 expression was analyzed. Western blot was used to detect Trop2 protein expression in ovarian cancer cell lines including A3O, A1780 and SKOV3. SKOV3 cells were used to construct Trop2-short hairpin RNA (shRNA) cell model. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was used to detect the SKOV3 mRNA expression in SKOV3-shRNA and SKOV3-NC cells. Cell counting kit-8 (CCK8) was used to detect the proliferation of SKOV3-shRNA cells and SKOV3-NC cells. Flow cytometry was used to detect cell cycle and apoptosis in two groups of cells. Transwell array was used to detecte the invasion and migration of SKOV3-shRNA cells and SKOV3-NC cells. Western blot was used to detect the protein expressions of AKT, p-AKT, β-catenin, caspase3, bcl-2, E-cadherin and vimentin. Results: Trop2 mRNA highly expressed in ovarian cancer, and was related to the tumor stage and patient survival. Compared with A3O cells, Trop2 overexpressed in A1780 and SKOV3 cells (P<0.05). The relative expression levels of Trop2 mRNA in SKOV3-NC group and SKOV3-shRNA group were 1.18±0.24 and 0.42±0.08, with statistically significant difference (P<0.05). The results of CCK-8 array showed that the cell viability of SKOV3-NC group was significantly higher than that of SKOV3-shRNA group (P<0.05). The proportion of G(0)/G(1) cells in SKOV3-NC and SKOV3-shRNA groups were (38.67±4.22)% and (60.24±8.17)%, respectively. G(0)/G(1) arrest was observed in SKOV3-shRNA cells (P<0.05). The apoptosis rate of SKOV3-shRNA group was (26.32±1.81)%, significantly higher than (6.54±1.32)% of SKOV3-NC group (P<0.05). The number of migrating SKOV3 cells in the SKOV3-shRNA and SkOV3-NC groups were 1 255.83±108.44 and 1 679.71±213.92, while the number of invading cells were 242.49±52.09 and 473.54±73.11, respectively. Compared with the SKOV3-NC group, the number of migrating and invading SKOV3-shRNA group was significantly reduced (all P<0.05). The expressions of p-AKT2, Bcl-2, vimentin and β-catenin were down-regulated, and the expressions of caspase 3 and E-cadherin were up-regulated in SKOV3-shRNA cells. There was no significant change in the total protein level of AKT. Conclusions: Trop2 expression is related to ovarian cancer stage and postoperative survival. Trop2 can promote ovarian cancer cell proliferation and metastasis by activating the AKT/β-catenin signaling pathway and knockdown of Trop2 inhibits the progression of ovarian cancer.

Cost-Effectiveness of Dipeptidylpeptidase-4 Inhibitors Added to Metformin in Patients With Type 2 Diabetes in China

PURPOSE

Dipeptidylpeptidase-4 (DPP-4) inhibitors, including linagliptin, alogliptin, saxagliptin, sitagliptin, and vildagliptin, are used for the treatment of type 2 diabetes mellitus (T2DM) patients in China. This study assessed the economic outcomes of different DPP-4 inhibitors in patients with T2DM inadequately controlled with metformin in the Chinese context.

MATERIALS AND METHODS

In this study, the validated Chinese Outcomes Model for T2DM (COMT) was conducted to project economic outcomes from the perspective of Chinese healthcare service providers. Efficacy and safety, medical expenditure, and utility data were derived from the literature, which were assigned to model variables. The primary outputs of the model included the lifetime costs, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratio (ICER). One-way and probability sensitivity analysis was conducted to assess the potential uncertainties of parameters.

RESULTS

Of the five competing strategies, alogliptin 25 mg strategy yielded the most significant health outcome, which associated with improvements in discounted QALY of 0.007, 0.014, 0.011, and 0.022 versus linagliptin 5 mg, saxagliptin 5 mg, sitagliptin 100 mg and vildagliptin50 mg, respectively. The sitagliptin 100 mg strategy was the cheapest option. The ICER of alogliptin 25 mg against sitagliptin 100 mg strategy was $6,952 per additional QALY gained, and the rest of the strategies were dominated or extended dominated. The most influential parameters were the cost of DPP-4 inhibitors and their treatment efficacy.

CONCLUSIONS

These results suggested that alogliptin was a preferred treatment option compared with other DPP-4 inhibitors for Chinese patients whose T2DM are inadequately controlled on metformin monotherapy.

Can Population Pharmacokinetics of Antibiotics be Extrapolated? Implications of External Evaluations

BACKGROUND AND OBJECTIVE

External evaluation is an important issue in the population pharmacokinetic analysis of antibiotics. The purpose of this review was to summarize the current approaches and status of external evaluations and discuss the implications of external evaluation results for the future individualization of dosing regimens.

METHODS

We systematically searched the PubMed and EMBASE databases for external evaluation studies of population analysis and extracted the relevant information from these articles. A total of 32 studies were included in this review.

RESULTS

Vancomycin was investigated in 17 (53.1%) articles and was the most studied drug. Other studied drugs included gentamicin, tobramycin, amikacin, amoxicillin, ceftaroline, meropenem, fluconazole, voriconazole, and rifampicin. Nine (28.1%) studies were prospective, and the sample size varied widely between studies. Thirteen (40.6%) studies evaluated the population pharmacokinetic models by systematically searching for previous studies. Seven (21.9%) studies were multicenter studies, and 27 (84.4%) adopted the sparse sampling strategy. Almost all external evaluation studies of antibiotics (93.8%) used metrics for prediction-based diagnostics, while relatively fewer studies were based on simulations (46.9%) and Bayesian forecasting (25.0%).

CONCLUSION

The results of external evaluations in previous studies revealed the poor extrapolation performance of existing models of prediction- and simulation-based diagnostics, whereas the posterior Bayesian method could improve predictive performance. There is an urgent need for the development of standards and guidelines for external evaluation studies.

The Effect Of Food On The Pharmacokinetic Properties And Bioequivalence Of Two Formulations Of Levocetirizine Dihydrochloride In Healthy Chinese Volunteers

Purpose

The aim of this study is to assess the bioequivalence of a new generic formulation and the branded formulation of levocetirizine dihydrochloride in healthy Chinese volunteers under fasting and fed conditions, and food-intake effect on the pharmacokinetic properties is also evaluated.

Patients and methods

Volunteers were randomly allocated into two groups to receive a single oral dose of generic formulation and branded formulation under fasting or fed conditions, respectively. Blood samples were collected at designated time points. Plasma concentrations of levocetirizine were determined by UFLC-MS/MS. Safety evaluations were carried out through the study. The main pharmacokinetic parameters of the two formulations of levocetirizine were calculated using non-compartmental analysis incorporated in WinNonlin^® 7.0 software.

Results

Forty-nine volunteers were enrolled; 46 completed the studies. Under fasting and fed conditions, the 90% confidence intervals for the geometric mean of generic/branded ratios were in the range of 94.75–107.24% and 99.98–114.69% for the maximum observed concentration, and 97.13–102.50% and 98.36–103.98% for the area under the concentration–time curve. As a result of food intake before administration, the reduced rate and extent of absorption of levocetirizine were observed. Both formulations were generally well tolerated, with no serious adverse reactions reported.

Conclusion

The two formulations demonstrated essentially identical pharmacokinetic profiles and were all well within the FDA/CFDA bioequivalence standards. Meanwhile, food intake can delay the absorption rate and reduced the bioavailability of levocetirizine in healthy Chinese volunteers.

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[A comparison of the 7th and 8th edition of the AJCC TNM staging systems for predicting survival in oropharyngeal cancer]

Objective:The aim of this study is to evaluate the prognostic value of the 8th edition of AJCC TNM classification in comparison with the 7th edition for oropharyngeal cancer. Method: The clinical and pathological data of 142 patients with oropharyngeal squamous cell carcinoma were retrospectively analyzed. The p16 protein was detected by immunohistochemical staining. Survival and survival analysis were performed using the Kaplan-Meier method and the Log-rank test. Result:The 5-year disease-specific survival（DSS）,the 5-year overall survival (OS) and the median survival time for patients with oropharyngeal cancer were 55.4%,50.4% and 60.3 months, respectively. P16-immunostaining was scored positive in 39 samples (27.5%,39/142).Based on the seventh edition of AJCC staging, there were 4 patients in stage Ⅰ,17 patients in stage Ⅱ,27 patients in stage Ⅲ and 94 patients in stage Ⅳ,respectively.However, there was no significant difference in survival between the patients with stage Ⅰ-Ⅱ and those with Ⅲ-Ⅳ(5-year DSS:75.9% of stage Ⅰ-Ⅱ patients vs. 52.2% of stage Ⅲ-Ⅳ patients;P=0.109).In comparison, 22 patients were diagnosed as stage Ⅰ,24 were stage Ⅱ,27 were stage Ⅲ and 69 were stage Ⅳ using the eighth edition. The 5-year DSS for patients with stage Ⅰ,Ⅱ,Ⅲ and Ⅳ was 88.4%, 80.5%, 73.2% and 29.1%, respectively. The overall difference was statistically significant (P=0.000). Conclusion:Compared with the seventh edition staging, the eighth edition of the AJCC oropharyngeal cancer staging system considers the prognosis of patients with different causes of oropharyngeal cancer, and can more accurately predict the prognosis of patients.

Cost-effectiveness of Osimertinib as First-line Treatment and Sequential Therapy for EGFR Mutation-positive Non-small Cell Lung Cancer in China

PURPOSE

This study aimed to evaluate the cost-effectiveness of osimertinib with gefitinib or erlotinib as first-line and sequential therapy for epidermal growth factor receptor (EGFR) mutation-positive non-small cell lung cancer (NSCLC) in China.

METHODS

The Markov model was used, and the study included 3 health states over a 10-year period. Transition probabilities and safety data were collected from the FLAURA (AZD9291 versus gefitinib or erlotinib in patients with locally advanced or metastatic Non-small Cell Lung Cancer) trial. Cost and utility values were derived from local charges and literature. Sensitivity analyses were performed to observe model stability.

FINDINGS

The strategy with gefitinib or erlotinib first-line therapy and second-line gene-guided osimertinib therapy (GE-T790M) resulted in a gain of 0.31 quality-adjusted life year (QALY) at a cost of $15,200.95 per patient compared with the gefitinib or erlotinib first-line therapy and second-line chemotherapy (GE-chemotherapy). The incremental QALY and incremental cost values for first-line osimertinib therapy compared with GE-chemotherapy was 0.96 and $69,420.76, respectively. Compared with the GE-T790M strategy (0.96 QALY and $29,223.33), first-line osimertinib was estimated to be more effective (1.61 QALYs) and more costly ($83,443.14). Relative to the GE-chemotherapy strategy, the incremental cost-effectiveness ratios were $47,873.96 and $71,954.08 per QALY gained with GE-T790M and the osimertinib first-line strategy. The incremental cost-effectiveness ratio for first-line osimertinib versus GE-T790M was estimated to be $83,766.61. The results were found to be robust for univariate and multivariable sensitivity analyses.

IMPLICATIONS

Gefitinib or erlotinib first-line and chemotherapy second-line strategies were the most cost-effective first-line treatments for EGFR mutations in patients with NSCLC. Gefitinib or erlotinib first-line and gene-guided osimertinib second-line strategies were more cost-effective than osimertinib first-line treatment for patients who preferred osimertinib administration in China.

[Clinical features and prognostic factors of squamous cell carcinoma of the base of tongue：an analysis of 124 cases]

Objective:To summarize the clinicopathological characteristics and prognostic factors of squamous cell carcinoma (SCC) of the base of tongue (BOT). Method:Review the clinical data of 124 cases of patients with BOT tumors. HPV-DNA was detected using SPF10-DNA enzyme immunoassay and LiPA genotyping method. Survival rates and prognostic factors was calculated with SPSS 19.0 software using the Kaplan-Meier method and multivariate Cox model survival analysis. Result:5-year disease-specific survival (DSS), 5-year overall survival and median survival time for patients with SCC BOT were 54.5%, 48.5% and 45.2 months, respectively. HPV infection rate was 18.3%(11/60), the HPV-16 subtype in 10 cases, accounting for 90.9%(10/11). Univariate analysis results showed that smoking history (P=0.028), drinking history (P=0.001), tumor stage (P=0.009) and p16 protein expression (P=0.015) significantly affected the prognosis. The prognosis of patients with HPV positive BOT cancers was better than the HPV negative patients (5-year DSS was 80.8% compared to 54.5%), but not statistical difference (P=0.138). Multivariate analysis revealed that independent prognostic factors of BOT tumors were drinking history (P=0.006) and tumor stage (P=0.035). Conclusion:The prognosis of BOT tumor was relatively poor. Smoking history, drinking history, tumor staging and the expression of p16 protein significantly affected the prognosis. Drinking history and tumor stage were independent prognostic factors for BOT cancers.

[Clinical features of patients with head and neck malignant tumor concurrent with multiple primary carcinoma]

OBJECTIVE

To analyze the clinical characteristics of multiple primary cancers (MPC) associated with head and neck.

METHODS

A total of 71 patients with MPC associated with head and neck treated from January 2008 to November 2015 were included in the retrospective study, of them 20 patients were synchronous MPC and 51 patients were metachronous MPC; 45 (63.4%) patients were field cancerization of head neck (FCHN) and 26 (36.6%) patients were non-field cancerization of head neck (NFCHN). For the synchronous MPC patients with an interval of 0 month, the lesion sites of FCHN were treated with combined chemotherapy and radiotherapy, the site of severe lesion of NFCHN received firstly a standard treatment. Other types of MPC were treated according to international guide lines or experts consensus.

RESULTS

With the mean follow-up of 63.4 months, the 3-year and 5-year overall survival (OS) were 84.6% and 75.7% respectively. The 3-year and 5-year OS were 56.4% and 37.6% respectively in patients with synchronous MPC, and were 92.2% and 84.2% respectively in patients with metachronous MPC. There was significant difference in the OS between patients with metachronous MPC and patients with synchronous MPC (P=0.0002). The 3-year and 5-year OS were 85.7% and 77.9% respectively in patients with FCHN, and were 82.9% and 72.8% respectively in patients with NFCHN, with no significant difference between the two groups (P=0.297).

CONCLUSION

With correct diagnosis and effective curative treatment, some of patients with MPC can get long-term survival, showing the better prognosis in metachronous MPC compared to synchronous MPC.

Establishment of an animal model of spontaneous cervical lymph node metastasis of laryngeal squamous cell carcinoma and obtaining laryngocarcinoma cells with high metastatic potential

To establish an animal model of spontaneous cervical lymph node metastasis of laryngeal squamous cell carcinoma and obtain laryngocarcinoma cells with high metastatic potential, laryngeal squamous cell carcinoma cell line HEP-2 in logarithmic phase were inoculated under the lingual margin mucosa of nude mice. HEP-2 cells metastasized to the cervical lymph nodes were isolated, cultured, and re-inoculated under the lingual margin mucosa of nude mice twice. The tumor formation in the tongue and in the cervical lymph nodes was confirmed by pathological examination. Carcinoma cells' ability of invasion and migration was detected by transwell assay. Human specific Alu sequences were detected by PCR, which indicated that the tumor cells originated from human laryngeal squamous cell carcinoma cell line HEP-2. Finally, an animal model of spontaneous lymph node metastasis of laryngeal squamous cell carcinoma was successfully established. Laryngeal squamous cell carcinoma cells with high metastatic potential to lymph nodes were obtained through repeated inoculations. .

[The state of cytoskeleton and its links "oxygen-peroxide" effects in some pathologies and apoptosis]

The cytoskeleton elements, especially the system of the microtubules, are responsible for production of cell backbone system, creation the global spatial ordered organization for efficient transport processes. Microtubules are involved into transportation of mitochondria, peroxisomes, microsomes, lyzosomes, Golgi apparatus, vesicular structures, some enzymes, adhesion molecules and, possibly, O2-depoting compounds. During disorganization of microtubules, mitochondria (principal consumers of intracellular O2), lose uninterrupted "address" delivery oxidizing substrates and O2. This may be one of important factors underlying mitochondrial dysfunctions accompanied by a rise and/or intensification of cells hyperoxia and oxidative stress. These impairments are obviously responsible for oxygen-peroxide effects in aging, age-related pathologies, carcinogenesis and apoptosis. The agents, both stabilizing and disorganizating microtubules appear to be apoptogenic for the tumors cells.

Autoantibody against beta1-adrenergic receptor and left ventricular remodeling changes in response to metoprolol treatment

Autoantibodies specific for the beta(1)-adrenoceptor (beta(1)-AR) have been implicated in the pathology of congestive heart failure (CHF). We hypothesized that the presence of autoantibodies against beta(1)-AR (anti-beta(1)-AR) is associated with left ventricular (LV) remodelling in response to metoprolol. Synthetic beta(1)-AR peptides served as the target antigen in an ELISA (enzyme-linked immunosorbent assay) were used to screen the sera of 106 CHF patients. Patients were separated into positive (+) anti-beta(1)-AR or negative (-) anti-beta(1)-AR groups according to their anti-beta(1)-AR reactivity. Echocardiography (ECG) was performed at baseline and after one year of metoprolol therapy in combination with standard treatment regime for CHF, that is, digoxin, diuretics and an ACEI (angiotensin-converting enzyme inhibitor). The dose of metoprolol was doubled on a biweekly basis up to 50 mg x 2 daily (b.i.d./day) or attainment of maximum tolerated dose. Ninety-six patients completed final data analysis. Fifty-four patients with (+) anti-beta(1)-AR had greater improvements than 42 patients with (-) anti-beta(1)-AR in LVEDD (left ventricular end-diastolic dimension) (P < 0.01, from 69 +/- 0.8 to 58.0 +/- 0.5 mm vs. 69.0 +/- 0.8-63.6 +/- 0.9 mm) and LVESD (left ventricular end-systolic dimension) (P < 0.01, from 57.1 +/- 1.4 to 43.9 +/- 0.8 mm vs. 56.2 +/- 0.9-48.6 +/- 1.0 mm), and LVEF (left ventricular ejection fraction) (P < 0.01, from 35.4 +/- 1.3 to 49.8 +/- 0.6% vs. 34.4 +/- 1.0-44.3 +/- 1.1%) by metoprolol therapy in combination with standard treatment regime for one year. Of the CHF patients with (+) anti-beta(1)-AR, 65.4% responded to target metoprolol dose as compared to 21.4% of CHF patients without anti-beta(1)-AR (P < 0.01). Response to target metoprolol dose occurred more rapidly in (+) anti-beta(1)-AR than (-) anti-beta(1)-AR of CHF patients (67.5 +/- 2.4 vs. 100.8 +/- 3.0 days, P < 0.01). These results demonstrated that CHF patients with (+) anti-beta(1)-AR had greater improvements in LV remodelling and heart function by metoprolol as compared to (-) anti-beta(1)-AR patients. Moreover, patients with (+) anti-beta(1)-AR have better tolerance to metoprolol therapy than patients without anti-beta(1)-AR.

Renal abnormalities in schoolchildren

To establish prevalence of some renal abnormalities in schoolchildren, an epidemiologic study of 132,686 schoolchildren, including 69,903 boys and 62,783 girls, was conducted from March 1987 to May 1988 in the city of Taipei. At the health station of each school, the students were screened quickly by a physician with portable real-time ultrasound equipment. When a renal abnormality was detected or suspected, the examinee was referred to Taipei Municipal Women and Children's Hospital for further investigation. Radiologic and urologic procedures were then selectively performed to establish the correct diagnosis. Renal abnormalities were detected in 645 students (approximately 0.5% of total population screened). There were 256 cases of hydronephrosis, 103 cases of unilateral renal agenesis, 128 cases of unilateral small kidney, 90 cases of renal cystic disorders, 30 cases of ectopic kidney, and 38 cases of other abnormalities. Surgically correctable lesions were demonstrated in 50 of these students. Rapid renal ultrasonography was found to effectively detect some renal abnormalities initially, and prevalence could then be established after further investigations.

A rapid method to produce anti-gentamicin antibody

The aminoglycoside antibiotic, gentamicin, was conjugated to erythrocytes or bovine serum albumin (BSA) by a simple procedure in which ECDI was employed as the coupling reagent. When rabbits were immunized by injecting gentamicin-goat erythrocyte conjugates, three kinds of antibody were produced: 1. anti-gentamicin antibody, 2. anti-ECDI antibody, 3. goat erythrocyte agglutinins. The interfering anti-ECDI antibody was easily neutralized by adding acidified ECDI solution to the immune serum. Goat agglutinins were avoided by employing rabbit erythrocytes as the carrier cell in the hemagglutination titration. Highly specific anti-gentamicin antiserum was produced in rabbits by first injecting an initial dose of gentamicin-BSA conjugate as an emulsion in incomplete Freund's adjuvant via the foot pad, followed by multiple intravenous injections of gentamicin-erythrocyte conjugates. The immunization took approximately 21 days. High titered anti-gentamicin antibody was also produced by foot pad inoculation of gentamicin-BSA conjugates; however, the time necessary to achieve comparable titers was considerably longer (55 days). The antibodies produced by both immunization procedures were mainly of the IgG class.

Mutagenicity of benzidine and related compounds employed in the detection of hemoglobin

Seven compounds commonly used as chromagens for the detection of hemoglobin and its derivatives have been assayed for mutagenicity employing the Salmonella/mammalian microsome test. Three of these compounds, benzidine, o-dianisidine, and o-tolidine, were shown to be mutagenic. Since benzidine and o-tolidine are already known to be carcinogens, there is a high probability that o-dianisidine will also prove to be a carcinogen. Four compounds tested with this system, o-anisidine, diphenylamine, guaicol, and o-toluidine, were not mutagenic.