Evaluating H295R steroidogenesis assay data for robust interpretation.

The in vitro H295R steroidogenesis assay (OECD TG 456) is used to determine a chemical's potential to interfere with steroid hormone synthesis/metabolism. As positive outcomes in this assay can trigger significant higher tiered testing, we compiled a stakeholder database of reference and test item H295R data to characterize assay outcomes. Information concerning whether a Level 5 reproductive toxicity study was triggered due to a positive outcome in the H295R assay was also included. Quality control acceptance criteria were not always achieved, suggesting this assay is challenging to conduct within the guideline specifications. Analysis of test item data demonstrated that pairwise significance testing to controls allowed for overly sensitive statistically significant positive outcomes, which likely contribute to the assay's high positive hit rate. Complementary interpretation criteria (e.g., 1.5-fold change threshold) markedly reduced the rate of equivocal and positive outcomes thus improving identification of robust positive effects in the assay. Finally, a case study (positive H295R outcome and no endocrine adversity in vivo) is presented, which suggests that stricter data interpretation criteria could refine necessary in vivo follow-up testing. Overall, the described additional criteria could improve H295R data interpretation and help inform on how to best leverage this assay for regulatory purposes.

Workforce Planning Models for Oral Health Care: A Scoping Review.

BACKGROUND: For health care services to address the health care needs of populations and respond to changes in needs over time, workforces must be planned. This requires quantitative models to estimate future workforce requirements that take account of population size, oral health needs, evidence-based approaches to addressing needs, and methods of service provision that maximize productivity. The aim of this scoping review was to assess whether and how these 4 elements contribute to existing models of oral health workforce planning. METHODS: A scoping review was conducted. MEDLINE, Embase, HMIC, and EconLit were searched, all via OVID. Additionally, gray literature databases were searched and key bodies and policy makers contacted. Workforce planning models were included if they projected workforce numbers and were specific to oral health. No limits were placed on country. A single reviewer completed initial screening of abstracts; 2 independent reviewers completed secondary screening and data extraction. A narrative synthesis was conducted. RESULTS: A total of 4,009 records were screened, resulting in 42 included articles detailing 47 models. The workforce planning models varied significantly in their use of data on oral health needs, evidence-based services, and provider productivity, with most models relying on observed levels of service utilization and demand. CONCLUSIONS: This review has identified quantitative workforce planning models that aim to estimate future workforce requirements. Approaches to planning the oral health workforce are not always based on deriving workforce requirements from population oral health needs. In many cases, requirements are not linked to population needs, while in models where needs are included, they are constrained by the existence and availability of the required data. It is critical that information systems be developed to effectively capture data necessary to plan future oral health care workforces in ways that relate directly to the needs of the populations being served. KNOWLEDGE TRANSFER STATEMENT: Policy makers can use the results of this study when making decisions about the planning of oral health care workforces and about the data to routinely collect within health services. Collection of suitable data will allow for the continual improvement of workforce planning, leading to a responsive health service and likely future cost savings.

Protocol for a Randomised controlled trial to Evaluate the effectiveness and cost benefit of prescribing high dose FLuoride toothpaste in preventing and treating dEntal Caries in high-risk older adulTs (reflect trial).

BACKGROUND: Dental caries in the expanding elderly, predominantly-dentate population is an emerging public health concern. Elderly individuals with heavily restored dentitions represent a clinical challenge and significant financial burden for healthcare systems, especially when their physical and cognitive abilities are in decline. Prescription of higher concentration fluoride toothpaste to prevent caries in older populations is expanding in the UK, significantly increasing costs for the National Health Services (NHS) but the effectiveness and cost benefit of this intervention are uncertain. The Reflect trial will evaluate the effectiveness and cost benefit of General Dental Practitioner (GDP) prescribing of 5000 ppm fluoride toothpaste and usual care compared to usual care alone in individuals 50 years and over with high-risk of caries. METHODS/DESIGN: A pragmatic, open-label, randomised controlled trial involving adults aged 50 years and above attending NHS dental practices identified by their dentist as having high risk of dental caries. Participants will be randomised to prescription of 5000 ppm fluoride toothpaste (frequency, amount and duration decided by GDP) and usual care only. 1200 participants will be recruited from approximately 60 dental practices in England, Scotland and Northern Ireland and followed up for 3 years. The primary outcome will be the proportion of participants receiving any dental treatment due to caries. Secondary outcomes will include coronal and root caries increments measured by independent, blinded examiners, patient reported quality of life measures, and economic outcomes; NHS and patient perspective costs, willingness to pay, net benefit (analysed over the trial follow-up period and modelled lifetime horizon). A parallel qualitative study will investigate GDPs' practises of and beliefs about prescribing the toothpaste and patients' beliefs and experiences of the toothpaste and perceived impacts on their oral health-related behaviours. DISCUSSION: The Reflect trial will provide valuable information to patients, policy makers and clinicians on the costs and benefits of an expensive, but evidence-deficient caries prevention intervention delivered to older adults in general dental practice. TRIAL REGISTRATION: ISRCTN: 2017-002402-13 registered 02/06/2017, first participant recruited 03/05/2018. Ethics Reference No: 17/NE/0329/233335. Funding Body: Health Technology Assessment funding stream of National Institute for Health Research. Funder number: HTA project 16/23/01. Trial Sponsor: Manchester University NHS Foundation Trust, Oxford Road, Manchester, M13 9WL. The Trial was prospectively registered.

Prevalence of distal surface caries in the second molar among referrals for assessment of third molars: a systematic review and meta-analysis.

We conducted a systematic review of epidemiological studies to assess the prevalence of distal surface caries (DSC) in second molars adjacent to third molars. We searched the Cochrane Library, Lilacs, Embase, and Medline through Ovid® (Wolters Kluwer) to retrieve English and non-English papers from inception to June 2016, and supplemented this with a search of the references and by tracking citations. Three reviewers contributed: one reviewed all the papers, and the other two divided the rest between them. They extracted data, completed structured quality assessments with a validated risk of bias tool for observational studies, and categorised the summary scores. The search yielded 81 records and 11 studies were analysed. The considerable methodological diversity meant that five were not eligible for inclusion in the quantitative synthesis. A meta-analysis of six studies on the prevalence of DSC and a subgroup analysis of three on various third-molar angulations were indicated. The overall pooled prevalence estimate calculated with a random-effects model was 23% (95% CI 2% to 44%) among patients. Prevalence subtotals were 20% (95% CI 5% to 36%) for prospective, and 15% (95% CI 5% to 36%) for retrospective studies among teeth. A subgroup analysis of three studies with 1296 patients (1666 molars) yielded a prevalence of DSC of 36% (95% CI 5% to 67%) for mesial impactions and 22% (95% CI 1% to 42%) for horizontal impactions. DSC was present in 3% of distally-inclined impactions, (95% CI 1% to 5%) and in 7% (95% CI 1% to 13%) of vertical third molars. The studies varied. The risk of bias was low in one and moderate in two. European studies suggested that DSC may be present in about one in four referrals for the assessment of third molars, and that the risk is considerably higher in those with convergent third molar impactions.

Guidelines on the timing and frequency of bitewing radiography: a systematic review.

Objectives To identify guidelines on when and how frequently bitewing radiographs should be used in dentistry for the diagnosis of caries, and to provide an objective appraisal of their quality.Data sources MEDLINE (OVID), US National Guideline Clearinghouse (www.guideline.gov) and the Royal College of Surgeons of England (https://www.rcseng.ac.uk/fds/publications-clinical-guidelines/clinical_guidelines) websites were searched using a variety of relevant search terms (2 August 2016).Data selection Publications were included if they made recommendations on the issue of when and how frequently radiographs should be used in any dentally-related specialty pertaining to the diagnosis of caries; and/or if they were aimed at the individual practitioner (any health professional working within dentistry) and/or patients.Data analysis Thirteen published guidelines were included and assessed using the AGREE II instrument.Conclusions There was a significant variation amongst the guidelines in the recommendations at what age radiography should be undertaken. There was also disagreement on the frequency of repeat radiographs and how this is influenced by the age of the patient and their caries risk.

A national survey of the public's views on quality in dental care.

BACKGROUND: There is a lack of evidence and poor understanding of quality measurement and improvement in dentistry. The aim of this study was to undertake a nationally representative survey of the public in England to explore their views on the meaning of quality in dentistry. METHODS: A cross sectional survey of the adult population (18 years and over) of England was undertaken. A sample size of 500 was set to provide a precision to plus or minus 5% after allowing for item non-response. A quota sampling approach was used, with predetermined quotas set for sex, age, working status and tenure to ensure the sample was nationally representative. Question selection and design were informed by the literature and a series of interviews with the public. Simple content analysis was used to identify themes in the responses to open questions. Dental service use, gender, age, ethnicity and social class were recorded. Frequency distributions were computed and outputs were cross-tabulated with various population sub-group categories. RESULTS: Five hundred and thirteen people were interviewed. Approximately 20% of patients reported that their care was suboptimal; a third thought it was poor value for money and 20% did not trust their dentist. Good interpersonal communication, politeness and being put at ease were the most important factors that elicited positive responses. Negative factors were cost of care and waiting times. In making an assessment of quality, access (40% of all responses), technical quality of care (35%), professionalism (30%), hygiene/cleanliness (30%), staff attitude (27%), pain-free treatment (23%), value for money (22%), and staff putting patients at ease (21%) all emerged as important factors. CONCLUSIONS: Quality in dentistry is multi-dimensional in nature, and includes different elements and emphases to other areas of healthcare. The results will inform the development of a measure of quality in dentistry.

Guidelines for clinical use of CBCT: a review.

OBJECTIVES: To identify guidelines on the clinical use of CBCT in dental and maxillofacial radiology, in particular selection criteria, to consider how they were produced, to appraise their quality objectively and to compare their recommendations. METHODS: A literature search using MEDLINE (Ovid(®)) was undertaken prospectively from 1 January 2000 to identify published material classifiable as "guidelines" pertaining to the use of CBCT in dentistry. This was supplemented by searches on websites, an internet search engine, hand searching of theses and by information from personal contacts. Quality assessment of publications was performed using the AGREE II instrument. Publications were examined for areas of agreement and disagreement. RESULTS: 26 publications were identified, 11 of which were specifically written to give guidelines on the clinical use of CBCT and contained sections on selection criteria. The remainder were a heterogeneous mixture of publications that included guidelines relating to CBCT. Two had used a formal evidence-based approach for guideline development and two used consensus methods. The quality of publications was frequently low as assessed using AGREE II, with many lacking evidence of adequate methodology. There was broad agreement between publications on clinical use, apart from treatment planning, in implant dentistry. CONCLUSIONS: Reporting of guideline development is often poorly presented. Guideline development panels should aim to perform and report their work using the AGREE II instrument as a template to raise standards and avoid the risk of suspicions of bias.

The development and piloting of a leadership questionnaire for general dental practitioners: preliminary results from the North West of England and Tokyo.

OBJECTIVES: Key reforms in England and Japan have called for greater clinical leadership from general dental practitioners to deliver improvements in the quality of care for patients. In England, the reorganisation of the National Health Service has led to the development of Local Professional Networks to ensure services are clinically led, patient and outcome focused. In Japan, the rapidly changing demographics have led to calls for general dental practitioners to become more active in meeting the emerging population health challenges. Both require engagement at a strategic and a local level. However, little is known about what is meant by clinical leadership in dentistry or what training needs exist. The aim of this study was to develop and pilot a questionnaire to understand what general dental practitioners feel is important about clinical leadership and how they rate themselves. METHODS: A 61-item questionnaire was developed from the literature, an earlier qualitative study and refined through cognitive interviews. Questionnaires were distributed to general dental practitioners across the North West of England and Tokyo, using random sequence generation. For each item, the participant had to record whether they thought the statement was an important component of clinical leadership and how they rated themselves. Both were rated using a seven-point Likert scale. Data reduction was undertaken using principal component analysis to examine for factor loadings within the questionnaire. Differences in mean scores were also used to highlight substantive differences in how general dental practitioners rated the different components of leadership and how they rated themselves. RESULTS: The response rate for the pilot was low (22.9% and 7.5% for North West and Tokyo respectively). The items that were considered to be important in leadership reduced to two components in the North West (accounting for 62.1% of the total variance): 'How to lead' and 'How not to lead'. In Tokyo, 56.4% of the total variance was explained by three components: 'Demonstrating personal qualities', 'Working with others' and 'How not to lead'. When the self-rated items were reduced, three factors were found to be important in the North West: 'Working with others', 'Setting direction' and 'Managing services' (55.1% of the variance). 'Working with others', 'Demonstrating personal qualities', 'Pragmatism', 'Setting direction' and 'Improving services' were found to be important in Tokyo (52.8% of the variance). The questionnaire items relating to integrity, team-working and having a positive attitude during difficult times were rated highly by both groups. Items relating to providing vision for team, being assertive and having a positive attitude had the greatest mean difference, suggesting possible areas of training need. CONCLUSION: The nature of the pilot study and the poor response rate makes any conclusion difficult to infer. Among those that participated, leadership was understood to be more important at a practice level rather than at a strategic level. The questionnaire should be refined further based on the results of the pilot and the data reduction.

Family relationships as an explanatory variable in childhood dental caries: a systematic review of measures.

It is widely acknowledged that parental beliefs (self-efficacy) about oral health and parental oral health-related behaviours play a fundamental role in the establishment of preventative behaviours that will mitigate against the development of childhood dental caries. However, little attention has been given to the wider perspective of family functioning and family relationships on child oral health. For oral health researchers, exploration of this association requires the use of reliable, valid and appropriate assessment tools to measure family relationships. In order to promote methodologically sound research in oral health, this systematic review aims to provide a guide on self-report psychometric measures of family functioning that may be suitable to utilize when exploring childhood dental caries. This systematic review has identified 29 self-report measures of family functioning and evaluated them in terms of their psychometric support, constructs measured and potential utility for oral health research. The majority of the measures reported adequate levels of reliability and construct validity. Construct evaluation of the measures identified five core domains of family functioning, namely 'communication', 'cohesion/engagement', 'control', 'involvement' and 'authoritative/rigid parenting style'. The constructs were subsequently evaluated with respect to their potential relevance to child oral health. Herewith this review provides a framework to guide future research to explore family functioning in furthering our understanding of the development of childhood dental caries.

CLN5 mutations are frequent in juvenile and late-onset non-Finnish patients with NCL.

OBJECTIVES: To explore a potential expansion of the phenotypic and genotypic characteristics of Finnish variant late-infantile neuronal ceroid lipofuscinosis (NCL), we screened a collection of 47 patients with clinically diagnosed NCL in whom no molecular diagnosis had been made. METHODS: We used PCR amplification of genomic DNA, followed by fluorescent-labeled dideoxy-nucleotide chain termination sequencing and multiplex ligation-dependent probe amplification, to screen our cohort of patients for mutations in CLN5. We collected ethnic background, clinical, and pathologic information, as available, to clarify the breadth of CLN5 disease expression and to explore possible genotype-phenotype correlations. RESULTS: We identified 10 patients with pathogenic CLN5 mutations, including 11 mutations not previously described: 4 missense, 5 out-of-frame insertion/deletion mutations, and 2 large intragenic deletions. We also documented 3 previously reported CLN5 mutations. The age at disease onset in this cohort is predominantly juvenile rather than late infantile. Importantly, we have identified 2 adult-onset patients who share a common pathogenic allele. The majority of patients presented with motor and visual impairments and not seizures. In those patients with available longitudinal data, most had progressed to global neurodevelopmental and visual failure with seizures within 1 to 4 years. CONCLUSIONS: Our study suggests that CLN5 mutations 1) are more common in patients with neuronal ceroid lipofuscinosis (NCL) than previously reported, 2) are found in non-Finnish NCL patients of broad ethnic diversity, and 3) can be identified in NCL patients with disease onset in adult and juvenile epochs. CLN5 genetic testing is warranted in a wider population with clinical and pathologic features suggestive of an NCL disorder.

Microbial degradation of the biocide polyhexamethylene biguanide: isolation and characterization of enrichment consortia and determination of degradation by measurement of stable isotope incorporation into DNA.

AIMS: To isolate micro-organisms capable of utilizing polyhexamethylene biguanide (PHMB) as a sole source of nitrogen, and to demonstrate biodegradation of the biocide. METHODS AND RESULTS: Two consortia of bacteria were successfully enriched at the expense of PHMB, using sand from PHMB-treated swimming pools as inoculum. Both consortia were shown to contain bacteria belonging to the genera Sphingomonas, Azospirillum and Mesorhizobium. It was shown that the presence of both Sphingomonas and Azospirillum spp. was required for extensive growth of the consortia. In addition, the Sphingomonads were the only isolates capable of growth in axenic cultures dosed with PHMB. Using a stable isotope (15N)-labelled PHMB, metabolism of the biocide by both consortia was demonstrated. By comparing the level of 15N atom incorporation into bacterial DNA after growth on either 15N-PHMB or 15N-labelled NH4Cl, it was possible to estimate the percentage of PHMB biodegradation. CONCLUSIONS: The microbial metabolism of nitrogen from the biguanide moiety of PHMB has been demonstrated. It was revealed that Sphingomonas and Azospirillum spp. are the principal organisms responsible for growth at the expense of PHMB. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate the microbial metabolism of PHMB.

Fisher waves and front roughening in a two-species invasion model with preemptive competition.

We study front propagation when an invading species competes with a resident; we assume nearest-neighbor preemptive competition for resources in an individual-based, two-dimensional lattice model. The asymptotic front velocity exhibits an effective power-law dependence on the difference between the two species' clonal propagation rates (key ecological parameters). The mean-field approximation behaves similarly, but the power law's exponent slightly differs from the individual-based model's result. We also study roughening of the front, using the framework of nonequilibrium interface growth. Our analysis indicates that initially flat, linear invading fronts exhibit Kardar-Parisi-Zhang (KPZ) roughening in one transverse dimension. Further, this finding implies, and is also confirmed by simulations, that the temporal correction to the asymptotic front velocity is of O(t(-2/3)).

Oral toxicity study of 2-pentenenitrile in rats with reproductive toxicity screening test.

A combined repeated-dose toxicity study with reproduction was conducted with 2-pentenenitrile (2-PN). Rats (10/sex per dose level) were dosed with 2-PN once daily by gavage at dose levels of either 0, 1, 3, or 10 mg kg(-1) day(-1) for 28 days, prior to and during cohabitation, and through day 3 of lactation. General clinical observations were recorded daily; body weights were recorded weekly. A neurobehavioral evaluation consisting of a functional observational battery and motor activity was conducted in all parental rats (10/sex per group). Clinical pathology parameters (hematology, clinical chemistry, coagulation) were measured in parental rats. Pup weights and clinical signs were recorded at birth and on lactation day 4. Parental rats were given a gross pathological examination, organ weights were obtained, and histological examination was conducted for the control and 10 mg kg(-1) day(-1) groups. No effects were seen with regard to mortality, clinical signs, functional observational battery and motor activity, hematology, or organ weights. Females receiving 10 mg/kg and males from all dose groups showed lower body weight gains and feed efficiency. Increased albumin concentrations were seen in both sexes given 10 mg/kg. Females in the 10 mg/kg group showed degeneration of the olfactory mucosa. No effects on the numbers of pups born, number surviving to lactation day 4, pup weight, and no gross anatomical development changes were observed. Under the conditions of this study, the no-observed-effect level (NOEL) for systemic toxicity in rats was 3 mg kg(-1) day(-1), based on degeneration of olfactory mucosa in females at 10 mg kg(-1) day(-1). The NOEL for reproductive and neurobehavioral toxicity in rats and for toxicity to offspring was 10 mg kg(-1) day(-1), the highest dose level tested.

Reproductive and developmental toxicity of inhaled 2,3-dichloro-1,3-butadiene in rats.

Inhalation developmental and reproductive toxicity studies were conducted with 2,3-dichloro-1,3-butadiene (DCBD), a monomer used in the production of synthetic rubber. In the reproductive toxicity study, Crl:CD(SD)IGS BR rats (24/sex/group) were exposed whole body by inhalation to 0, 1, 5, or 50 ppm DCBD (6 h/day) for approximately 10-11 weeks total, through premating (8 weeks; 5 days/week), cohabitation of mating pairs (up to 2 weeks, 7 days/week), post-cohabitation for males (approximately 7 days) and from conception to implantation (gestation days 0-7 [GD 0-7]), followed by a recovery period (GD 8-21) for presumed pregnant females. Estrous cyclicity was evaluated during premating (last 3 weeks) and cohabitation. Reproductive organs and potential target organs, sperm parameters, and GD 21 fetuses (viability, weight, external alterations) were evaluated. In the developmental study, pregnant Crl:CD(SD)IGS BR rats (22/group) were exposed whole body by inhalation to 0, 1, 10, or 50 ppm DCBD (6 h/day) on GD 6-20; dams were necropsied on GD 21 (gross post-mortem only) and fetuses were evaluated (viability, weight, and external, visceral and skeletal exams). During the in-life portion of the studies, body weight, food consumption, and clinical observation data were collected. At 50 ppm, gasping and labored breathing occurred in both studies during the first few exposures; body weight and food consumption parameters were affected in parental animals from both studies, but were more severely affected in the developmental study. Fetal weight was decreased in the developmental study at 50 ppm. Degeneration of the nasal olfactory epithelium was observed in the reproduction study at 50 ppm. There were no effects on reproductive function, embryo-fetal viability, or increases in fetal structural alterations in either study. The no-observed-adverse-effect level (NOAEL) for reproductive toxicity was 50 ppm. The NOAEL for systemic toxicity in the reproduction study was 5 ppm based on adverse effects on body weight and food consumption parameters and nasal olfactory epithelial toxicity at 50 ppm in parental rats. The NOAEL for maternal and developmental toxicity was 10 ppm based on reduced maternal weight gain and food consumption and reduced fetal weight at 50 ppm in the developmental toxicity study.

Inhalation toxicity of methylglutaronitrile in rats.

Methylglutaronitrile (MGN) is a high-boiling (263 degrees C) solvent/intermediate used in the fiber industry. Twenty male rats per group were exposed nose-only to condensation aerosol/vapor concentrations of approximately either 5, 25, or 200 mg/m3 of MGN for 6 h/day, 5 days/week over a 4-week period. Ten rats/group were sacrificed one day after the final exposure and the remaining rats after a four-week recovery period. No effects were observed in clinical observations during the exposure period, but body-weight depression was observed in the 200 mg/m3 group. The 200 mg/m3 group showed minimal decreases in red blood cell count, hemoglobin, and hematocrit values accompanied by increases in reticulocytes. There were no other effects observed in clinical or pathologic evaluations in the study. A neurobehavioral battery of tests (including grip strength, functional observational battery, and motor activity tests) given at the end of the exposure and recovery periods showed no MGN effects. During the 4-week recovery, body weights in the 200 mg/m3 group returned to normal and the hematologic findings in all groups were normal. Based on the above findings of body weight depression at 200 mg/m3, the no-observed-adverse-effect level (NOAEL) for this study was considered to be 25 mg/m3.

Inhalation toxicity of dimethyl piperidinone.

A mixture of 1,3-dimethyl-2-piperidinone and 1,5-dimethyl-2-piperidinone (DMPD) (approximately 63-37 parts by weight) was tested for its inhalation toxicity in rats following 90-day repeated exposures. Male and female rats were exposed whole-body to either 0, 51, 230, or 310 mg/m(3) DMPD for 6 h/day, 5 days/weak for 90 days. Clinical signs, growth, clinical pathology, tissue pathology, neurobehavior, neuropathology, and semen quality were evaluated. No compound-related adverse effects were noted in clinical signs, body weights, food consumption, clinical laboratory evaluations, neurobehavioral evaluations, neuropathology, or sperm counts. Laryngeal changes consisting of minimal squamous epithelial hyperplasia and degeneration/necrosis of the cartilage were present in male and female rats exposed to 310 mg/m(3) both immediately following exposure and after the 1-month recovery period Male rats exposed to DMPD had increased relative kidney weights, increased formation of hyaline droplets and granular casts, and increased incidence of chronic progressive nephropathy. These kidney effects are consistent with increased accumulation of the urinary protein alpha(2 mu)-globulin, which has been well essential for several xenobiotics. The subsequent increased incidence of progressive nephropathy was specific to male rats with the alpha(2 mu) syndrome. Male and female rats exposed to 230 or 310 mg/m(3) had centrilobular hepatocellular hypertrophy, and male rats exposed to 310 mg/m(3) had increased relative liver weights. These liver changes were reversible following the recovery period and were considered not to represent adverse toxicological effects of treatment. Since the male rat-specific renal findings do not connote adversity for man and are net considered relevant to human hazard assessment, the no-observed-effect level in male and female rats was 230 mg/m(3), based on the microscopic changes in the larynx exposed to 310 mg/m(3).

Chronic toxicity and oncogenicity of N-methylpyrrolidone (NMP) in rats and mice by dietary administration.

A two-year feeding study in rats and an 18-month feeding study in mice were conducted to evaluate the potential chronic toxicity and oncogenicity of NMP in Crl:CD (SD)BR rats and B6C3F1/CrlBR mice. Groups of 62 male and female rats were administered diets containing 0, 1600, 5000, or 15,000 ppm of NMP for approximately 2 years. Groups of 50 male and female mice were administered diets containing 0, 600, 1200, or 7200 ppm NMP for approximately 18 months. In vivo parameters were evaluated weekly during the first 3 months of the study, and every other week or monthly during the remainder of the study. For rats, an ophthalmoscopic examination was conducted prior to study start and near the end of the study. Periodically, blood samples were collected from rats and mice for determination of leukocyte differential counts, and from mice for red blood cell morphology. After approximately 2 years of dietary administration in rats and 18 months in mice, all surviving animals were sacrificed. Selected tissues were processed for morphological evaluation. Over the course of the two-year study in rats, test substance-related decrements in body weight and weight gain occurred in 15,000 ppm males and females, which correlated with decreased food consumption and food efficiency. A toxicologically significant, test substance-related increase in the incidence of severe chronic progressive nephropathy occurred in 15,000 ppm males. Several morphological changes noted grossly and/or microscopically were secondary to the increased severity of chronic progressive nephropathy. NMP was not oncogenic in male or female rats at dietary concentrations of 15,000 ppm and below. A test substance-related decrease in the percentage of 15,000 ppm males surviving to the end of the two-year study compared to the control group resulted from the higher incidence of severe chronic progressive nephropathy. However, a sufficient population of 15,000 ppm rats were at risk for potential oncogenicity, so the lower survival did not impair the ability to detect an oncogenic response in this study. There were no adverse, test substance-related effects on the incidences of clinical observations, ophthalmic observations, or differential leukocyte counts in males or females, or on survival of females at any dietary concentration. Male and female mice administered dietary concentrations of 7200 ppm had significantly increased liver weight, significantly increased incidence of hepatocellular adenoma, and significantly increased foci of cellular alteration in the liver. At 7200 ppm, male mice also had an increased incidence of hepatocellular carcinoma while the increased incidence of hepatocellular carcinoma in female mice fell within the historical control range. In addition, the incidence of hepatocellular hypertrophy was increased in 7200 ppm males. Liver weight and hepatocellular hypertrophy were also increased in 1200 ppm males. There were no adverse, test substance-related effects on the incidences of clinical observations, food consumption, body weight, differential leukocyte counts, red blood cell morphology, or survival in either males or females at any dietary concentration. Under the conditions of the study, the no-observed-effect level for NMP was 5000 ppm for male and female rats, 600 ppm for male mice, and 1200 ppm for female mice.

Acute and subchronic neurotoxicological evaluation of tetrahydrofuran by inhalation in rats.

Groups of adult male and female rats received exposure to tetrahydrofuran (THF) vapor by inhalation in acute or subchronic exposure scenarios. Acute exposure concentrations were 0, 500, 2500, or 5000 ppm for 6 hr. Evaluations conducted immediately after exposure included clinical observations, motor activity assessments (MA), and a battery of functional tests (FOB) designed to reveal nervous system dysfunction. During exposure to 2500 and 5000 ppm, rats had a diminished or absent startle response to a punctate auditory alerting stimulus. Following exposure to 5000 ppm, male and female rats were lethargic, exhibited abnormal gait or mobility, and splayed rear feet. Lethargy and splayed rear feet were also observed in females exposed to 2500 ppm. During the subsequent FOB, males exposed to 5000 ppm had a lower incidence of palpebral closure, higher incidences of slow or absent righting reflex, and a biphasic pattern of reduced motor activity followed by increased motor activity. Females exposed to 5000 ppm had increased incidences of palpebral closure in the open field, increased incidences of slow or absent righting reflex, and decreased motor activity. During the 14-week subchronic exposure series, daily THF exposure concentrations were 0, 500, 1500, or 3000 ppm, and neurobehavioral evaluations occurred on non-exposure days at approximately monthly intervals. Diminished startle responses to an auditory alerting stimulus were observed during exposure to 1500 or 3000 ppm; however, repeated exposures did not cause additional neurobehavioral or pathological effects. This pattern of effects is suggestive of transient sedation. Despite daily reinstatement of acute sedative effects during repeated exposure with up to 3000 ppm, THF did not produce any persistent or cumulative effects on nervous system structure or function. The demonstrated no-observed-effect level of THF for both acute and subchronic exposure was 500 ppm.

Absorption of dimethylacetamide (DMAC) following application of a polymer film to the skin of rabbits.

Kapton Film is a polymer with high strength and thermal resistance finding use in a wide variety of applications. In the preparation of this film, the uncured material could contain up to 30% dimethylacetamide (DMAC). Note that the final product Kapton Film has been thermally cured with the DMAC removed. During processing, dermal contact with the film is anticipated, and the possibility exists of DMAC transfer from the uncured film, to and through the skin. In this study, 2 x 2-inch pieces of film were applied to the skin of a group of rabbits and secured in place for a single 4-hour contact time. An amount of liquid DMAC corresponding to the amount contained in the 2-inch square was applied to the skin of a separate group of rabbits for 4 hours. Urine samples were collected over the intervals of application to 4 hours post application (8 hours total) or 4 to 20 hours post application (16 hours). The amount of the urinary metabolite monomethylacetamide (MMAC) was determined analytically in these samples. Urine from 2 untreated rabbits was collected at the same time to serve as controls. The amount of urinary MMAC found in the rabbit rine from animals exposed to uncured Kapton Film at both ollection intervals was similar to the amount seen in the controls (background). Rabbits treated with DMAC liquid had measurable urinary MMAC levels that were approximately 100 times background. It is concluded that, under the conditions of this study, very little, if any, DMAC from the uncured Kapton Film was absorbed through the skin (and excreted in the urine as MMAC).

Subchronic toxicity of cyclohexane in rats and mice by inhalation exposure.

Inhalation studies were conducted to determine the potential toxicity and/or potential neurotoxicity of cyclohexane. Groups of rats and mice were exposed to 0, 500, 2000, or 7000 ppm concentrations of cyclohexane vapor 6 hr/day, 5 days/week for 14 weeks. Subgroups of rats and mice were further observed during a 1-month recovery period. Functional observational battery (FOB) and motor activity (MA) behavioral tests were conducted on rats. These tests were conducted prior to the exposure series and during weeks 4, 8, and 13 on non-exposure days. Clinical pathology evaluations were conducted after approximately 7, 13, and 18 weeks. Approximately 14 and 18 weeks after study initiation, tissues from rats and mice were histologically processed and evaluated by light microscopy. During exposure to 2000 or 7000 ppm, rats and mice had a diminished response or an absent response to delivery of a punctate auditory alerting stimulus. Immediately following removal of rats from the inhalation chambers, 7000 ppm males and females and 2000 ppm females displayed a compound-related increase in the incidence of wet and/or stained fur (which occurred in the areas of the mouth, chin, and/or perineum). These signs were transient, were not observed during exposure or prior to exposure the following day, and were not associated with any behavioral or morphological changes. During exposure sessions, mice exposed to 7000 ppm exhibited clinical signs of toxicity which included hyperactivity, circling, jumping/hopping, excessive grooming, kicking of rear legs, standing on front legs, and occasional flipping behavior. Clinical signs of toxicity observed in 7000 ppm mice immediately after exposure included hyperactivity, hyperreactivity, ruffled fur (females only), gait abnormalities, spasms in both rear legs, and excessive grooming (males only). The clinical signs observed in mice during and immediately after exposure were transient, and were not present prior to the subsequent exposure. A few mice exposed to 2000 ppm appeared hyperactive during exposure in the latter portion of the study. There were no compound-related changes in mean body weights, body weight gains, food consumption, food efficiency, or mortality; and there were no ophthalmological abnormalities in rats or mice. In addition, there were no compound-related effects on 37 different behavioral parameters assessed during the FOB or during motor activity tests in rats. Male and female mice exposed to 7000 ppm had slight increases in measures of circulating erythrocyte mass (red blood cells, hemoglobin, hematocrit) and plasma protein concentration (males only). Male rats and male and female mice exposed to 7000 ppm had significantly increased relative liver weights, and 7000 ppm male mice also had significantly increased absolute liver weights at the end of the exposure period. At the end of the 1-month recovery period, absolute and relative liver weights of male and female mice were similar to control. However, relative liver weights of 7000 ppm male rats continued to be significantly higher at the end of the recovery period. Male and female rats exposed to 7000 ppm had a significantly increased incidence of hepatic centrilobular hypertrophy at the end of the exposure period, which was not observed at the conclusion of the 1-month recovery period. No microscopic changes were observed in mice. In rats, the no-observed-effect level (NOEL) for acute, transient effects was 500 ppm based on a diminished/absent response to an auditory alerting stimulus at 2000 ppm and above. The NOEL for subchronic toxicity in rats was 7000 ppm based on the lack of adverse effects on body weight, clinical chemistry, tissue morphology, and neurobehavioral parameters. In mice, the NOEL for acute, transient effects was 500 ppm based on behavioral changes during exposure at 2000 ppm and above. The NOEL for subchronic toxicity in mice is 2000 ppm based on hematological changes at 7000 ppm.