Efficacy and safety of once-weekly semaglutide 1.0mg vs once-daily liraglutide 1.2mg as add-on to 1-3 oral antidiabetic drugs in subjects with type 2 diabetes (SUSTAIN 10).

AIMS: SUSTAIN 10 compared the efficacy and safety of the anticipated most frequent semaglutide dose (1.0mg) with the current most frequently prescribed liraglutide dose in Europe (1.2mg), reflecting clinical practice. METHODS: In this phase 3b, open-label trial, 577 adults with type 2 diabetes (HbA1c 7.0-11.0%) on 1-3 oral antidiabetic drugs were randomized 1:1 to subcutaneous once-weekly semaglutide 1.0mg or subcutaneous once-daily liraglutide 1.2mg. Primary and confirmatory secondary endpoints were changes in HbA1c and body weight from baseline to week 30, respectively. RESULTS: Mean HbA1c (baseline 8.2%) decreased by 1.7% with semaglutide and 1.0% with liraglutide (estimated treatment difference [ETD] -0.69%; 95% confidence interval [CI] -0.82 to -0.56, P<0.0001). Mean body weight (baseline 96.9kg) decreased by 5.8kg with semaglutide and 1.9kg with liraglutide (ETD -3.83kg; 95% CI -4.57 to -3.09, P<0.0001). The proportions of subjects achieving glycaemic targets of<7.0% and=6.5%, weight loss of=5% and=10%, and a composite endpoint of HbA1c<7.0% without severe or blood glucose-confirmed symptomatic hypoglycaemia and no weight gain were greater with semaglutide vs liraglutide (all P<0.0001). Both treatments had similar safety profiles, except for more frequent gastrointestinal disorders (the most common adverse events [AEs]) and AEs leading to premature treatment discontinuation with semaglutide vs liraglutide (43.9% vs 38.3% and 11.4% vs 6.6%, respectively). CONCLUSION: Semaglutide was superior to liraglutide in reducing HbA1c and body weight. Safety profiles were generally similar, except for higher rates of gastrointestinal AEs with semaglutide vs liraglutide.

Immunohistochemical Characterization of Sarcomas in Trp53+/- Haploinsufficient Mice.

The use of immunohistochemical (IHC) staining in determining and/or confirming the cellular origin of poorly differentiated sarcomas was evaluated in this study. Sarcomatous neoplasms were evaluated in a research study conducted in 2 strains of p53+/- haploinsufficient mice. The most common neoplasms were undifferentiated sarcomas, followed by osteosarcomas and rhabdomyosarcomas (RMSs). The RMSs were poorly differentiated and appeared similar to the pleomorphic, or adult type, RMS of humans. All sarcomas stained positive by IHC for the mesenchymal cell intermediate filament vimentin. The RMSs were identified by positive IHC staining for myogenin, a transcription factor specific to skeletal muscle. Osteosarcomas were easily identifiable on hematoxylin and eosin-stained slides; no generally accepted IHC stain specific for bone is presently available. Some of the undifferentiated sarcomas contained numerous macrophages that stained positive for F4/80, a macrophage marker; the positive-staining cells were considered to be infiltrating macrophages. One-third of the neoplasms observed in this study were associated with subcutaneous implanted electronic microchips used for animal identification. Based upon histopathologic evaluation and IHC staining, it was not possible to distinguish neoplasms associated with subcutaneous microchips from neoplasms not associated with microchips.

Lack of confidence among trainee doctors in the management of diabetes: the Trainees Own Perception of Delivery of Care (TOPDOC) Diabetes Study.

BACKGROUND: There is an increased prevalence of diabetes. Doctors in training, irrespective of specialty, will have patients with diabetes under their care. AIM: To determine levels of confidence of doctors in training in the management of diabetes and establish their training needs in this area of clinical practice. DESIGN: A national online survey of trainee doctors in the UK using a pre-validated questionnaire. METHODS: A four-point confidence rating scale was used to rate confidence in the management of diabetes and comparators. A six-point scale was used to quantify how often trainees would contribute to the management of patients with diabetes and trainees were asked about their training in managing diabetes. RESULTS: A total of 2149 doctors completed the survey. The percentage 'fully confident' in diagnosing diabetes was 27%, diagnosing and managing hypoglycaemia 55%, diagnosing and managing diabetic ketoacidosis 43%, managing intravenous (IV) insulin 27%, prescribing IV fluids for patients with diabetes 39% and altering diabetes therapy prior to surgery/other procedure 18%. In comparison, 66% and 65% were 'fully confident' in the management of angina and asthma, respectively (P < 0.05). Forty-one percent would take the initiative to optimize glycaemic control for patients under their care >80% of the time. Respectively, 19% and 35% of respondents reported that their undergraduate and postgraduate training had prepared them adequately to optimize treatment of diabetes. The majority (>70%) wanted further training in managing all aspects of diabetes care. CONCLUSIONS: Trainee doctors in the UK lack confidence in the management of diabetes, are unlikely to take the initiative to optimize glycaemic control and report a need for further training.

Inhalation toxicity studies of the alpha,beta-unsaturated ketones: ethyl vinyl ketone.

The National Toxicology Program is conducting a chemical class study to investigate the structure-activity relationships for the toxicity of alpha,beta-unsaturated ketones. Ethyl vinyl ketone (EVK) was selected for study because it is a representative straight-chain aliphatic alpha,beta-unsaturated ketone with extensive use and widespread exposure. Short-term inhalation studies of EVK were conducted to provide toxicity data for comparison with the related alpha,beta-unsaturated ketones 2-cyclohexene-1-one (CHX) and methyl vinyl ketone (MVK). These data will be used in designing chronic toxicity and carcinogenicity studies of these ketones. Male and female F344 rats and B6C3F1 mice were exposed to 0, 2, 4, or 8 ppm EVK 6 h/day, 5 days/wk for 13 wk. The nasal cavity was the major target organ of EVK in both rats and mice. Pathologic findings in both the olfactory and respiratory epithelium were observed. Lesions consisted primarily of olfactory epithelial necrosis, atrophy and regeneration, and/or hyperplasia and squamous metaplasia of the respiratory epithelium. Squamous metaplasia of the respiratory epithelium was present in all rats and mice exposed to 4 and 8 ppm EVK, and these lesions were more severe in rats than in mice. Few systemic effects were observed in rats and mice exposed to EVK. A transient decrease in total leukocytes due to decrements in lymphocyte and monocyte populations was present in male rats after exposure to 8 ppm for 3 and 21 days; however, this effect was not present after exposure for 13 wk. There were no chemical-related effects on micronucleus formation in mice, or on sperm motility and vaginal cytology in either species. EVK, like other alpha,beta-unsaturated ketones, is a reactive, direct-acting gaseous irritant with toxicity limited primarily to the upper respiratory tract.

Mercury vapor and female reproductive toxicity.

Epidemiological studies finding menstrual cycle abnormalities among women occupationally exposed to Hg degrees prompted us to investigate the mechanisms of reproductive toxicity of Hg degrees in the female rat. Nose-only Hg degrees vapor inhalation exposures were conducted on regularly cycling rats 80-90 days of age in dose-response and acute time-course studies, which have previously proven useful as a model to identify ovarian toxicants. Vaginal smears were evaluated daily and serum hormone levels were correlated with cycle and with ovarian morphology at necropsy. Exposure concentration-related effects of Hg degrees were evaluated by exposing rats to 0, 1, 2, or 4 mg/m3 Hg degrees vapor 2 h/day for 11 consecutive days. Tissue Hg levels correlated with exposure concentration and duration. Exposure of rats to 4 mg/m3 (but not 1 or 2 mg/m3) Hg vapor for 11 days resulted in significant decreases in body weights relative to controls. Estrous cycles were slightly prolonged in the 2 and 4 mg/m3 dose groups, and serum estradiol and progesterone levels were significantly different in the 4 mg/m3 group compared to controls. The alterations in cycle and hormones at the 4 mg/m3 exposure concentration were attributed to body weight loss and generalized toxicity. In the time-course study, rats were exposed to 2 mg/m3 Hg degrees or air beginning in metestrus and evaluated daily for 8 days. A lengthening of the cycle was detected and morphological changes were observed in the corpora lutea (CL) after exposure for 6 days. To determine if changes in the CL and cyclicity correlated with a functional defect, rats were exposed to Hg degrees vapor and evaluated for pregnancy outcome. There were no significant effects on pregnancy rate or numbers of implantation sites when rats were exposed to 1 or 2 mg/m3 Hg degrees for 8 days prior to breeding, or when exposed for 8 days after breeding. These studies indicate that exposure to Hg degrees vapor altered estrous cyclicity, but had no significant effect on ovulation, implantation, or maintenance of first pregnancy during exposure of short duration in female rats.

Inhalation toxicity studies of the alpha,beta-unsaturated ketones: 2-cyclohexene-1-one.

2-Cyclohexene-1-one (CHX) is a cyclic alpha,beta-unsaturated ketone with broad human exposure. CHX is an environmental pollutant and is present in tobacco smoke and in soft drinks sweetened with cyclamate. Interest in the toxicity of this class of compounds is due to their structural similarity to the cytotoxin acrolein. In a pilot study, rats and mice were exposed to 0, 20, 40, or 80 ppm CHX for 6 h/day. The study was terminated after 4 days due to acute toxicity in the high-dose groups. In a subsequent 14-day study, mice and rats were exposed to 0, 2.5, 5, or 10 ppm CHX for 6 h/day. All animals survived exposure until terminal sacrifice. Body weights were not significantly different from controls after 14 days of exposure. Liver/body weights were increased in male and female mice exposed to 5 and 10 ppm, and in male and female rats exposed to 10 ppm CHX. Ninety-day toxicity studies were conducted to provide data required to design chronic toxicity and carcinogenicity studies of CHX if it is determined such studies are necessary. Groups of 10 male and female F-344 rats and B6C3F1 mice were exposed to 0, 2.5, 5, or 10 ppm CHX for 6 h/day for 13 wk. All animals survived until sacrifice. Body weights were not significantly different from controls after 13 wk of exposure. Liver weights were increased in male and female mice exposed to 5 and 10 ppm and in male and female rats exposed to 10 ppm CHX. No adverse effects on bone-marrow micronuclei, sperm motility, or vaginal cytology were observed. Microscopic lesions included hyperplasia, and squamous metaplasia in the nasal cavity in rats and mice of both sexes at all doses. Nasal-cavity erosion and suppurative inflammation also occurred in high-dose mice. Larynx and lung were not affected in either sex or species. Dose-related hepatic centrilobular cytoplasmic vacuolation was seen in male rats only. These data suggest that CHX acts as an alkylating agent primarily producing toxicity at the exposure site.

Upper respiratory tract toxicity of inhaled methylvinyl ketone in F344 rats and B6C3F1 mice.

The National Toxicology Program is conducting a chemical class study to investigate the structure-activity relationships for the toxicity of alpha,beta-unsaturated ketones. Methylvinyl ketone (MVK) was selected for study because it is a representative straight-chain aliphatic alpha,beta-unsaturated ketone and because of its extensive use and widespread exposure. Short-term inhalation studies of MVK were conducted to provide toxicity data for comparison with other alpha,beta-unsaturated ketones and for use in designing chronic toxicity and carcinogenicity studies. In 2-week studies, rats and mice were exposed to 0, 0.25, 0.5, 1, 2, 4, or 8 ppm MVK 6 h/day, 5 days/week for 12 exposures. Morbidity and early deaths occurred in all male and female rats after 1 exposure and in 2 male mice after 10 exposures to 8 ppm. Rats exhibited nasal cavity toxicity and lung necrosis at 4 ppm. No toxicity was observed in animals exposed to less than 2 ppm. Based on these results a 13-week study was conducted at 0, 0.5, 1, and 2 ppm MVK. As observed in the 2-week study, the nasal cavity was the main target organ and rats were more sensitive than mice. Respiratory and olfactory epithelial necrosis were prominent by day 21 in the rat. At study termination these lesions were still evident but not as severe as noted earlier. Additionally, changes such as olfactory epithelial regeneration and metaplasia (respiratory) as well as respiratory epithelial hyperplasia and metaplasia (squamous) were clearly evident. Nasal lesions in mice were limited to a subtle squamous metaplasia of transitional and/or respiratory epithelium covering predominantly the tips of naso- and maxilloturbinates in Levels I and II. A transient, leukopenia was observed in rats exposed to 2 ppm, however, this effect was not present after 13 weeks of exposure. In mice, leukocyte counts were significantly decreased at all exposure concentrations after 13 weeks of exposure. Absolute testicular and epididymal weights and sperm counts were decreased at the high dose only. MVK can be characterized as a reactive, direct-acting gaseous irritant. MVK exposure causes the same nasal cavity lesions as the cyclic alpha,beta-unsaturated ketone, 2-cyclohexen-1-one, although at lower exposure concentrations.

Characterization of hepatocellular resistance and susceptibility to styrene toxicity in B6C3F1 mice.

Short-term inhalation exposure of B6C3F1 mice to styrene causes necrosis of centrilobular (CL) hepatocytes. However, in spite of continued exposure, the necrotic parenchyma is rapidly regenerated, indicating resistance by regenerated cells to styrene toxicity. These studies were conducted to test the hypothesis that resistance to repeated styrene exposure is due to sustained cell proliferation, with production of hepatocytes that have reduced metabolic capacity. Male mice were exposed to air or 500 ppm styrene (6 h/day); hepatotoxicity was evaluated by microscopic examination, serum liver enzyme levels, and bromodeoxyuridine (BrdU)-labeling index (LI). Metabolism was assessed by measurement of blood styrene and styrene oxide. Both single and repeated exposures to styrene resulted in mortality by Day 2; in mice that survived, there was CL necrosis with elevated BrdU LI at Day 6, and complete restoration of the necrotic parenchyma by Day 15. The BrdU LI in mice given a single exposure had returned to control levels by Day 15. Re-exposure of these mice on Day 15 resulted in additional mortality and hepatocellular necrosis, indicating that regenerated CL cells were again susceptible to the cytolethal effect of styrene following a 14-day recovery. However, in mice repeatedly exposed to styrene for 14 days, the BrdU LI remained significantly increased on Day 15, with preferential labeling of CL hepatocytes with enlarged nuclei (karyomegaly). If repeated exposures were followed by a 10-day recovery period, CL karyomegaly persisted, but the BrdU LI returned to control level and CL hepatocytes became susceptible again to styrene toxicity as demonstrated by additional mortality and acute necrosis after a challenge exposure. These findings indicated a requirement for continued styrene exposure and DNA synthesis in order to maintain this resistant phenotype. Analyses of proliferating-cell nuclear-antigen (PCNA) labeling were conducted to further characterize the cell cycle kinetics of these hepatocytes. The proportion of cells in S-phase was increased by repeated exposure. However, PCNA analysis also revealed an even larger increase in the G1 cell compartment with repeated exposures, without a concurrent increase in G2 phase or in mitotic cell numbers. These data indicate that resistance to styrene-induced necrosis under conditions of repeated exposure is not due to sustained cell turnover and production of new, metabolically inactive cells, but rather is due to some other, as yet unknown, protective phenotype of the regenerated cells.

Characterization of inhaled alpha-methylstyrene vapor toxicity for B6C3F1 mice and F344 rats.

alpha-Methylstyrene (AMS) is a chemical intermediate used in the synthesis of specialty polymers and copolymers. Inhalation studies of AMS were conducted because of the lack of toxicity data and the structural similarity of AMS to styrene, a toxic and potentially carcinogenic chemical. Male and female B6C3F1 mice were exposed to 0, 600, 800, or 1000 ppm AMS 6 h/day, 5 days/week, for 12 days. After 1 exposure, 21% (5/24) of female mice were found dead in the 1000-ppm group, 56% (10/18) in the 800-ppm group, and 6% (1/18) in the 600-ppm concentration group. After 12 exposures, relative liver weights were significantly increased and relative spleen weights were significantly decreased in both male and female mice at all concentrations. No microscopic treatment-related lesions were observed. A decrease in hepatic glutathione (GSH) was associated with AMS exposure for 1 and 5 days. Male and female F344 rats were exposed to 0, 600 or 1000 ppm AMS for 12 days. No mortality or sedation occurred in AMS-exposed rats. Relative liver weights were significantly increased in both males and females after 12 exposures to 600 or 1000 ppm. An increased hyaline droplet accumulation was detected in male rats in both concentration groups; no significant microscopic lesions were observed in other tissues examined. Exposure of male and female F344 rats and male NBR rats to 0, 125, 250 or 500 ppm AMS, 6 h/day for 9 days resulted in increased accumulation of hyaline droplets in the renal tubules of male F344 rats in the 250 and 500 ppm concentration groups. Although AMS and styrene are structurally very similar, AMS was considerably less toxic for mice and more toxic for male rats than styrene.

Toxicity of divinylbenzene-55 for B6C3F1 mice in a two-week inhalation study.

Divinylbenzene (DVB) is a crosslinking monomer used primarily for copolymerization with styrene to produce ion-exchange resins. The toxicity of inhaled DVB was investigated because of the potential for worker exposure and the structural similarity of DVB to styrene, a potential carcinogen. Male and female B6C3F1 mice were exposed to 0, 25, 50, or 75 ppm DVB for 6 hr/day, 5 days/week for up to 2 weeks. Six mice/sex/dose group were killed after 3, 5, and 10 exposures and six mice/sex in the 75 ppm group were killed 7 days after 10 exposures. The most severe effects occurred in the nasal cavity and liver, with less severe effects occurring in the kidneys. In the nasal cavity olfactory epithelium acute necrosis and inflammation were present at early time points followed by regeneration, architectural reorganization, and focal respiratory metaplasia by 7 days after the last exposure. Olfactory epithelial changes were concentration-dependent with extensive involvement at 75 ppm and peripheral sparing at 25 ppm. There was also necrosis and regeneration of olfactory-associated Bowman's glands as well as the lateral nasal (Steno's) glands. Hepatocellular centrilobular (CL) necrosis was observed only in the 75 ppm dose group and was similar to that caused by styrene. A time-dependent progression was observed, characterized by CL degeneration after 1 exposure, necrosis after 3 and 5 exposures, and chronic inflammation with CL karyomegaly after 10 exposures and 7 days after the 10th exposure. Hepatic GSH levels were decreased in a dose-dependent manner. In the kidneys, transient tubular damage was observed in some male mice exposed to 75 ppm, and appeared to be a response to DVB-induced tubular epithelial injury.

Effects of various pretreatments on the hepatotoxicity of inhaled styrene in the B6C3F1 mouse.

1. The roles of cytochrome P450 monooxygenases (P450) and glutathione (GSH) in styrene hepatotoxicity were investigated in mice by pretreating with either phenobarbital (PB; P450 inducer), SKF 525A (P450 inhibitor), N-acetylcysteine (NAC; GSH precursor), or saline (vehicle control) prior to a 6-h exposure to either 500 ppm styrene on air. 2. Styrene caused hepatocellular degeneration or necrosis in all groups; these changes were more extensive and severe in mice pretreated with PB. Styrene significantly increased relative liver weights and serum ALT and SDH levels only in mice pretreated with PB. NAC did not prevent GSH depletion or hepatotoxicity. 3. In the fat of SKF 525A-pretreated mice a slight but statistically significant increase in styrene levels was observed, suggesting that metabolism was decreased; the SO/styrene ratio in the fat of PB-pretreated mice showed a slight, but statistically significant, increase indicating a slight increase in styrene metabolism. Neither SKF 525A nor PB caused changes in microsomal enzyme activity in vitro. 4. These results suggest that styrene may be activated by a pathway not totally dependent upon P450 enzyme activity, or more likely that PB and SKF 525A are not specific for the P450 enzymes involved in activation and detoxification of styrene.

Comparative pulmonary absorption, distribution, and toxicity of copper gallium diselenide, copper indium diselenide, and cadmium telluride in Sprague-Dawley rats.

Copper gallium diselenide (CGS), copper indium diselenide (CIS), and cadmium telluride (CdTe) are novel compounds used in the photovoltaic and semiconductor industries. This study was conducted to characterize the relative toxicities of these compounds and to evaluate the pulmonary absorption and distribution after intratracheal instillation. Female Sprague-Dawley rats were administered a single equimolar dose (70 mM) of CGS (21 mg/kg), CIS (24 mg/kg), CdTe (17 mg/kg), or saline by intratracheal instillation. Bronchoalveolar lavage fluid (BALF) protein, fibronectin, inflammatory cells, lung hydroxyproline, and tissue distribution were measured 1, 3, 7, 14, and 28 days after instillation. Relative lung weights were significantly increased in CIS- and CdTe-treated rats at most time points. Inflammatory lesions in the lungs consisting of an influx of macrophages, lymphocytes, and PMNs were most severe in CdTe-treated rats, intermediate in CIS-treated rats, and minimal in rats receiving CGS. Hyperplasia of alveolar type 2 cells was present in CIS- and CdTe-treated rats and was greatest in CdTe-treated rats. Pulmonary interstitial fibrosis was observed in CdTe-treated rats at all time points. All three compounds caused marked increases in total BALF cell numbers, with the greatest increase observed in CIS-treated rats. BALF protein, fibronectin, and lung hydroxyproline were significantly increased in all treated animals and were highest in CdTe-treated animals. There was no apparent pulmonary absorption or tissue distribution of CGS. Indium levels increased in extrapulmonary tissues of CIS-treated rats, although Cu and Se levels remained unchanged. CdTe was absorbed from the lung to a greater extent than CGS and CIS. Cd and Te levels decreased in the lung and increased in extrapulmonary tissues. Of these compounds CdTe presents the greatest potential health risk because it causes severe pulmonary inflammation and fibrosis and because it is readily absorbed from the lung may potentially cause extrapulmonary toxicity.

Acute pulmonary toxicity of copper gallium diselenide, copper indium diselenide, and cadmium telluride intratracheally instilled into rats.

Acute toxicity studies were conducted on copper gallium diselenide (CGS), copper indium diselenide (CIS), and cadmium telluride (CT), three novel compounds used in the photovoltaic and semiconductor industries. Female Sprague-Dawley rats (six rats/dose) were administered 0, 12, 25, 50, or 100 mg/kg body wt of CGS, CIS, or CT by intratracheal instillation. At 72 hr after treatment, body weight gain was significantly decreased in the 100 mg/kg CIS group and in all CT dose groups. Lung weights were increased in most chemical-treated rats, with CT causing the greatest increase. Total numbers of cells in bronchoalveolar lavage fluid (BALF) were significantly increased in treated rats and were greatest in the 100 mg/kg CIS group. Differential cell counts of BALF demonstrated a marked decrease in the percentage of alveolar macrophages and an increase in the percentage of polymorphonuclear leukocytes in all dose groups of all three chemicals. Slight to moderate increases in lactate dehydrogenase activity were observed in BALF from CGS- and CIS-treated rats; marked increases were observed in CT-treated rats. BALF protein was significantly increased in rats treated with CIS and CT. Microscopic examination revealed lymphoid hyperplasia in lungs of rats treated with all three chemicals. CT caused necrosis of the terminal bronchiolar epithelium and epithelium of the alveolar duct region with inflammation, prominent fibrin exudates, and type II cell hyperplasia. CGS and CIS also caused intraalveolar inflammation and type II cell hyperplasia, but did not cause the necrosis and fibrin exudate observed in lungs of CT-treated rats. Based on changes in lung weight, BALF indices, and histopathology, CT was the most toxic for the lung; CIS had intermediate toxicity and CGS was the least toxic. The solubilities of CGS and CIS were relatively low and similar at both pH levels and do not readily explain the observed differences in pulmonary toxicity. The solubility of CdTe was considerably greater than that of CGS and CIS and likely contributed to the greater toxicity of this compound.

Comparison of styrene hepatotoxicity in B6C3F1 and Swiss mice.

Inhalation exposure to styrene at concentrations that cause metabolic saturation results in significantly greater hepatotoxicity in B6C3F1 mice than in Swiss mice; females of both strains are more susceptible than males. These studies were conducted to investigate the mouse strain and gender differences in susceptibility to hepatotoxicity caused by repeated exposure to styrene at concentrations that do not cause metabolic saturation. Male and female B6C3F1 and Swiss mice (8 weeks old) were exposed to 0, 150, or 200 ppm styrene for 6 hr/day, 5 days/week, for up to 2 weeks. Changes in body and liver weights, serum alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) levels, liver histopathology, and total liver glutathione (GSH) were evaluated after 2, 3, 5, and 10 exposures (six mice/sex/strain/time point/concentration). Blood levels of styrene and styrene-7,8-oxide (SO) were measured in mice exposed to 200 ppm styrene for 2,3, or 5 days (six mice/sex/strain/time point/concentration). Serum ALT and SDH levels were significantly elevated only in female B6C3F1 mice after 3 exposures to 200 ppm styrene; enzyme levels had returned to control levels when measured after 5 and 10 exposures. Degeneration and coagulative necrosis of centrilobular hepatocytes were observed in female B6C3F1 mice exposed 2, 3, and 5 days to 150 or 200 ppm styrene; incidences of these lesions were greater in the 200 ppm than in the 150 ppm dose group. After 10 days of exposure to 150 or 200 ppm styrene, hepatocellular lesions had resolved, although a residual chronic inflammation was present in livers of most female B6C3F1 mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytogenetic and germ cell effects of phosphine inhalation by rodents: II. Subacute exposures to rats and mice.

Phosphine (PH3) is a highly toxic grain fumigant to which there is significant human workplace exposure. To determine the in vivo cytogenetic effects of inhalation of PH3, male F344/N rats and B6C3F1 mice were exposed to target concentrations of 0, 1.25, 2.5, or 5 ppm PH3 for 6 hr/day for 9 days over an 11-day period. Approximately 20 hr after the termination of exposures, blood was removed from the mice and rats by cardiac puncture and the lymphocytes cultured for analyses of sister chromatid exchanges and chromosome aberrations in rats and mice, and micronuclei (MN) in cytochalasin B-induced binucleated lymphocytes from mice. In addition, bone marrow (rats) and peripheral blood (mice) smears were made for the analysis of MN in polychromatic and normochromatic erythrocytes. No significant increase in any of the cytogenetic endpoints was found at any of the concentrations examined. These results indicate that concentrations of PH3 up to 5 ppm are not genotoxic to rodents when administered by inhalation for 9 days during an 11-day period as measured by several cytogenetic assays. To evaluate the effects of PH3 on male germ cells, a dominant lethal test was conducted in male mice exposed to 5 ppm PH3 for 10 days over a 12-day period and mated to groups of untreated females (2 females/male) on each of 6 consecutive 4-day mating intervals. None of the 6 groups of females exhibited a significant increase in percent resorptions. These results indicate that exposure to 5 ppm PH3 by inhalation does not induce dominant lethality in male mouse germ cells at steps in spermatogenesis ranging from late differentiating spermatogonia/early primary spermatocytes through mature sperm.

Styrene inhalation toxicity studies in mice. II. Sex differences in susceptibility of B6C3F1 mice.

Styrene is a commercially important chemical used in the production of plastics and resins. In initial short-term styrene inhalation studies, toxicity was significantly greater in male B6C3F1 mice than in females, suggesting that males may metabolize styrene more extensively and/or may be less able to detoxify reactive metabolites. In addition, a nonlinear dose-response was observed where toxicity and mortality were greater in mice exposed to 250 ppm than in those exposed to 500 ppm. These studies were conducted to investigate potential mechanism(s) for sex differences and the nonlinear dose-response in styrene toxicity by evaluating the effects of repeated styrene exposure on styrene oxide production, hepatic GSH availability, and hepatotoxicity in male and female B6C3F1 mice. Mice (36/sex/dose) were exposed to 0, 125, 250, or 500 ppm styrene 6 hr/day for up to 3 days. Styrene exposure caused increased mortality and hepatotoxicity (centrilobular necrosis, increased serum liver enzymes) in males and females after one or two exposures to 250 and 500 ppm. Hepatic GSH levels were decreased in a dose-dependent manner in males and females. After one exposure, GSH levels in males rebounded above controls in all dose groups. After three exposures to 125 or 250 ppm males appeared to maintain GSH levels; GSH was still decreased in the 500 ppm group. GSH levels in females were decreased after each exposure in all dose groups to lower levels than in males, and did not rebound above controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Styrene inhalation toxicity studies in mice. III. Strain differences in susceptibility.

Inhalation toxicity studies were conducted to evaluate mouse strain differences in the susceptibility to styrene vapors. Male and female B6C3F1, C57BL/6, Swiss, and DBA/2 mice (8 weeks old) were exposed to 0, 125, 250, or 500 ppm styrene 6 hr/day, for 4 days (20/sex/dose). Histopathological changes and changes in liver weights were evaluated as a measure of hepatotoxicity. Styrene uptake and styrene-7,8-oxide (SO) formation were estimated by measuring levels of styrene and SO in blood. An estimate of SO detoxification by conjugation with GSH was obtained by measuring hepatic GSH depletion. In general, mortality, increased liver weights, and hepatocellular necrosis were observed in the 250 and 500 ppm dose groups for all strains and both sexes. Considerable sex and strain differences were observed. Mortality, increased liver weights, and hepatocellular necrosis were greatest in B6C3F1 and C57BL/6 mice in the 250 ppm dose group and in males; hepatotoxicity was similar in both strains. Swiss mice exhibited dose-dependent increases in mortality, liver weights, and in hepatocellular necrosis, with only slight sex differences at early time points. Hepatotoxicity in DBA/2, B6C3F1, and C57BL/6 strains was greater at 250 than 500 ppm; however, toxicity was less severe in DBA/2 than in other strains based on absence of mortality in either sex and less extensive liver necrosis at both 250 and 500 ppm. Blood styrene and SO levels did not correlate well with strain differences in toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary tumors of the facial nerve: diagnosis and management.

Benign primary tumors of the facial nerve are frequently misdiagnosed because of variable and subtle clinical manifestations. Three such cases of facial nerve neuroma seen in the past 3 years will be presented. Difficulties in patient assessment including the lack of specificity for topographic testing, as well as the capricious behavior of the facial nerve in these patients will be discussed. The efficacy of diagnostic techniques presently available and in use including computerized tomography and electrodiagnostic studies will be discussed. Diagnosis of these tumors might generally be thought to be straightforward and easier with the advent of new diagnostic techniques, but this has, in fact, not been the case. Techniques for removal and repair will be presented. The combined approach utilizing the mastoid and middle fossa will be presented.