Expression profiling identifies microRNA signature in pancreatic cancer

microRNAs are functional, 22 nt, noncoding RNAs that negatively regulate gene expression. Disturbance of microRNA expression may play a role in the initiation and progression of certain diseases. A microRNA expression signature has been identified that is associated with pancreatic cancer. This has been accomplished with the application of real-time PCR profiling of over 200 microRNA precursors on specimens of human pancreatic adenocarcinoma, paired benign tissue, normal pancreas, chronic pancreatitis and nine pancreatic cancer cell lines. Hierarchical clustering was able to distinguish tumor from normal pancreas, pancreatitis and cell lines. The PAM algorithm correctly classified 28 of 28 tumors, 6 of 6 normal pancreas and 11 of 15 adjacent benign tissues. One hundred microRNA precursors were aberrantly expressed in pancreatic cancer or desmoplasia (p < 0.01), including microRNAs previously reported as differentially expressed in other human cancers (miR-155, miR-21, miR-221 and miR-222) as well as those not previously reported in cancer (miR-376a and miR-301). Most of the top aberrantly expressed miRNAs displayed increased expression in the tumor. Expression of the active, mature microRNA was validated using a real-time PCR assay to quantify the mature microRNA and Northern blotting. Reverse transcription in situ PCR showed that three of the top differentially expressed miRNAs (miR-221, -376a and -301) were localized to tumor cells and not to stroma or normal acini or ducts. Aberrant microRNA expression may offer new clues to pancreatic tumorigenesis and may provide diagnostic biomarkers for pancreatic adenocarcinoma.

Signal transduction pathways of tumor necrosis factor--mediated lung injury induced by ozone in mice

RATIONALE

Increasing evidence suggests that tumor necrosis factor (TNF)-alpha plays a key role in pulmonary injury caused by environmental ozone (O(3)) in animal models and human subjects. We previously determined that mice genetically deficient in TNF response are protected from lung inflammation and epithelial injury after O(3) exposure.

OBJECTIVES

The present study was designed to determine the molecular mechanisms of TNF receptor (TNF-R)-mediated lung injury induced by O(3).

METHODS

TNF-R knockout (Tnfr(-/-)) and wild-type (Tnfr(+/+)) mice were exposed to 0.3 ppm O(3) or air (for 6, 24, or 48 h), and lung RNA and proteins were prepared. Mice deficient in p50 nuclear factor (NF)-kappaB (Nfkb1(-/-)) or c-Jun-NH(2) terminal kinase 1 (Jnk1(-/-)) and wild-type controls (Nfkb1(+/+), Jnk1(+/+)) were exposed to O(3) (48 h), and the role of NF-kappaB and mitogen-activated protein kinase (MAPK) as downstream effectors of lung injury was analyzed by bronchoalveolar lavage analyses.

RESULTS

O(3)-induced early activation of TNF-R adaptor complex formation was attenuated in Tnfr(-/-) mice compared with Tnfr(+/+) mice. O(3) significantly activated lung NF-kappaB in Tnfr(+/+) mice before the development of lung injury. Basal and O(3)-induced NF-kappaB activity was suppressed in Tnfr(-/-) mice. Compared with Tnfr(+/+) mice, MAPKs and activator protein (AP)-1 were lower in Tnfr(-/-) mice basally and after O(3). Furthermore, inflammatory cytokines, including macrophage inflammatory protein-2, were differentially expressed in Tnfr(-/-) and Tnfr(+/+) mice after O(3). O(3)-induced lung injury was significantly reduced in Nfkb1(-/-) and Jnk1(-/-) mice relative to respective control animals.

CONCLUSIONS

Results suggest that NF-kappaB and MAPK/AP-1 signaling pathways are essential in TNF-R-mediated pulmonary toxicity induced by O(3).

The shift in muscle's length-tension relation after exercise attributed to increased series compliance

Eccentric exercise can produce damage to muscle fibres. Here damage indicators are measured in the medial gastrocnemius muscle of the anaesthetised cat after eccentric contractions on the descending limb of the muscle's length-tension relation, compared with eccentric contractions on the ascending limb and concentric contractions on the descending limb. One damage indicator is a shift of the optimum length for peak active tension, in the direction of longer muscle lengths. The shift has been attributed to an increase in muscle compliance. It is a corollary of a current theory for the mechanism of the damage. With the intention of seeking further support for the theory, in these experiments we test the idea that other damage indicators, specifically the fall in twitch:tetanus ratio and in muscle force are due, in part, to such an increase in compliance. This was tested in an undamaged muscle by insertion of a compliant spring (0.19 mm N(-1)) in series with the muscle. This led to a fall in tetanic tension by 17%, a shift in optimum length of 1.7 mm in the direction of longer muscle lengths and a fall in twitch tetanus ratio by 15%. The fall in tension is postulated to be due to development of non-uniform sarcomere lengths within muscle fibres. It is concluded that after a series of eccentric contractions of a muscle, the fall in force is the result of a number of interdependent factors, not all of which are a direct consequence of the damage process.

Male sex hormones promote vagally mediated reflex airway responsiveness to cholinergic stimulation

A sex disparity in airway responsiveness to cholinergic stimulation has been observed in laboratory mice in that males are considerably more responsive than females, but the basis for this difference is unclear. In this report, we demonstrate that male sex hormones promote murine airway responsiveness to cholinergic stimulation via vagus nerve-mediated reflex mechanisms. In tissue bath preparations, no sex-based differences were observed in the contractile responses of isolated tracheal and bronchial ring segments to carbachol, indicating that the mechanism(s) responsible for the in vivo sex difference is (are) absent ex vivo. Bilateral cervical vagotomy was found to abolish in vivo airway responsiveness to methacholine in male mice, whereas it did not alter the responses of females, suggesting a regulatory role for male sex hormones in promoting reflex airway constriction. To test this possibility, we next studied mice with altered circulating male sex hormone levels. Castrated male mice displayed airway responsiveness equivalent to that observed in intact females, whereas administration of exogenous testosterone to castrated males restored responsiveness, albeit not to the level observed in intact males. Administration of exogenous testosterone to intact female mice similarly enhanced responsiveness. Importantly, the promotive effects of exogenous testosterone in castrated male and intact female mice were absent when bilateral vagotomy was performed. Together, these data indicate that male sex hormones promote cholinergic airway responsiveness via a vagally mediated reflex mechanism that may be important in the regulation of airway tone in the normal and diseased lung.

Inhalational Exposure to Carbonyl Sulfide Produces Altered Brainstem Auditory and Somatosensory-Evoked Potentials in Fischer 344N Rats

Carbonyl sulfide (COS), a chemical listed by the original Clean Air Act, was tested for neurotoxicity by a National Institute of Environmental Health Sciences/National Toxicology Program and U.S. Environmental Protection Agency collaborative investigation. Previous studies demonstrated that COS produced cortical and brainstem lesions and altered auditory neurophysiological responses to click stimuli. This paper reports the results of expanded neurophysiological examinations that were an integral part of the previously published experiments (Morgan et al., 2004, Toxicol. Appl. Pharmacol. 200, 131-145; Sills et al., 2004, Toxicol. Pathol. 32, 1-10). Fisher 334N rats were exposed to 0, 200, 300, or 400 ppm COS for 6 h/day, 5 days/week for 12 weeks, or to 0, 300, or 400 ppm COS for 2 weeks using whole-body inhalation chambers. After treatment, the animals were studied using neurophysiological tests to examine: peripheral nerve function, somatosensory-evoked potentials (SEPs) (tail/hindlimb and facial cortical regions), brainstem auditory-evoked responses (BAERs), and visual flash-evoked potentials (2-week study). Additionally, the animals exposed for 2 weeks were examined using a functional observational battery (FOB) and response modification audiometry (RMA). Peripheral nerve function was not altered for any exposure scenario. Likewise, amplitudes of SEPs recorded from the cerebellum were not altered by treatment with COS. In contrast, amplitudes and latencies of SEPs recorded from cortical areas were altered after 12-week exposure to 400 ppm COS. The SEP waveforms were changed to a greater extent after forelimb stimulation than tail stimulation in the 2-week study. The most consistent findings were decreased amplitudes of BAER peaks associated with brainstem regions after exposure to 400 ppm COS. Additional BAER peaks were affected after 12 weeks, compared to 2 weeks of treatment, indicating that additional regions of the brainstem were damaged with longer exposures. The changes in BAERs were observed in the absence of altered auditory responsiveness in FOB or RMA. This series of experiments demonstrates that COS produces changes in brainstem auditory and cortical somatosensory neurophysiological responses that correlate with previously described histopathological damage.

Cyclooxygenase-1 overexpression decreases Basal airway responsiveness but not allergic inflammation

Pharmacological inhibition or genetic disruption of cyclooxygenase (COX)-1 or COX-2 exacerbates the inflammatory and functional responses of the lung to environmentally relevant stimuli. To further examine the contribution of COX-derived eicosanoids to basal lung function and to allergic lung inflammation, transgenic (Tr) mice were generated in which overexpression of human COX-1 was targeted to airway epithelium. Although no differences in basal respiratory or lung mechanical parameters were observed, COX-1 Tr mice had increased bronchoalveolar lavage fluid PGE(2) content compared with wild-type littermates (23.0 +/- 3.6 vs 8.4 +/- 1.4 pg/ml; p < 0.05) and exhibited decreased airway responsiveness to inhaled methacholine. In an OVA-induced allergic airway inflammation model, comparable up-regulation of COX-2 protein was observed in the lungs of allergic wild-type and COX-1 Tr mice. Furthermore, no genotype differences were observed in allergic mice in total cell number, eosinophil content (70 vs 76% of total cells, respectively), and inflammatory cytokine content of bronchoalveolar lavage fluid, or in airway responsiveness to inhaled methacholine (p > 0.05). To eliminate the presumed confounding effects of COX-2 up-regulation, COX-1 Tr mice were bred into a COX-2 null background. In these mice, the presence of the COX-1 transgene did not alter allergen-induced inflammation but significantly attenuated allergen-induced airway hyperresponsiveness, coincident with reduced airway leukotriene levels. Collectively, these data indicate that COX-1 overexpression attenuates airway responsiveness under basal conditions but does not influence allergic airway inflammation.

Lung injury after ozone exposure is iron dependent

We tested the hypothesis that oxidative stress and biological effect after ozone (O3) exposure are dependent on changes in iron homeostasis. After O3 exposure, healthy volunteers demonstrated increased lavage concentrations of iron, transferrin, lactoferrin, and ferritin. In normal rats, alterations of iron metabolism after O3 exposure were immediate and preceded the inflammatory influx. To test for participation of this disruption in iron homeostasis in lung injury following O3 inhalation, we exposed Belgrade rats, which are functionally deficient in divalent metal transporter 1 (DMT1) as a means of iron uptake, and controls to O3. Iron homeostasis was disrupted to a greater extent and the extent of injury was greater in Belgrade rats than in control rats. Nonheme iron and ferritin concentrations were higher in human bronchial epithelial (HBE) cells exposed to O3 than in HBE cells exposed to filtered air. Aldehyde generation and IL-8 release by the HBE cells was also elevated following O3 exposure. Human embryonic kidney (HEK 293) cells with elevated expression of a DMT1 construct were exposed to filtered air and O3. With exposure to O3, elevated DMT1 expression diminished oxidative stress (i.e., aldehyde generation) and IL-8 release. We conclude that iron participates critically in the oxidative stress and biological effects after O3 exposure.

Gender differences in murine airway responsiveness and lipopolysaccharide-induced inflammation

The roles of gender and sex hormones in lung function and disease are complex and not completely understood. The present study examined the influence of gender on lung function and respiratory mechanics in naive mice and on acute airway inflammation and hyperresponsiveness induced by intratracheal LPS administration. Basal lung function characteristics did not differ between naive males and females, but males demonstrated significantly greater airway responsiveness than females following aerosolized methacholine challenge as evidenced by increased respiratory system resistance and elastance (p < 0.05). Following LPS administration, males developed more severe hypothermia and greater airway hyperresponsiveness than females (p < 0.05). Inflammatory indices including bronchoalveolar lavage fluid total cells, neutrophils, and TNF-alpha content were greater in males than in females 6 h following LPS administration (p < 0.05), whereas whole-lung TLR-4 protein levels did not differ among treatment groups, suggesting that differential expression of TLR-4 before or after LPS exposure did not underlie the observed inflammatory outcomes. Gonadectomy decreased airway inflammation in males but did not alter inflammation in females, whereas administration of exogenous testosterone to intact females increased their inflammatory responses to levels observed in intact males. LPS-induced airway hyperresponsiveness was also decreased in castrated males and was increased in females administered exogenous testosterone. Collectively, these data indicate that airway responsiveness in naive mice is influenced by gender, and that male mice have exaggerated airway inflammatory and functional responses to LPS compared with females. These gender differences are mediated, at least in part, by effects of androgens.

NTP Toxicity Study Report on the atmospheric characterization, particle size, chemical composition, and workplace exposure assessment of cellulose insulation (CELLULOSEINS)

Cellulose insulation (CI) is a type of thermal insulation produced primarily from recycled newspapers. The newspapers are shredded, milled, and treated with fire-retardant chemicals. The blowing process for installing CI generates a significant quantity of airborne material that presents a potential inhalation hazard to workers. CI was selected for study based upon the high production volume, the potential for widespread human exposure, and a lack of toxicity data; insufficient information was available to determine whether inhalation studies in laboratory animals were technically feasible or necessary. Studies were conducted to characterize the chemical and physical properties of CI aerosols, to evaluate the potential acute pulmonary toxicity of CI, and to assess occupational exposure of CI installers. Workplace exposure assessments were conducted in collaboration with the National Institute for Occupational Safety and Health (NIOSH, 2001).

EVALUATION OF THE CHEMICAL COMPOSITION, PARTICLE SIZE, AND PULMONARY TOXICITY OF CELLULOSE INSULATION

Chemical analyses were performed on samples of bulk CI from four major United States manufacturers. All samples of the bulk CI were found to contain primarily amorphous cellulose (60% to 65%) with a smaller crystalline component (35% to 40%). The crystalline phase was primarily native cellulose (75% to 85%) with a minor amount of cellulose nitrate (15% to 25%). Elemental analyses of acid digests of CI materials indicated that the major components (>0.1% by weight) included aluminum, boron, calcium, sodium, and sulfur. An acid-insoluble residue present in all four materials (3% to 5% of original sample weight) was found to consist primarily of aluminum silicate hydroxide (kaolinite; approximately 85%) with minor amounts (<5% each) of magnesium silicate hydroxide (talc), potassium aluminum silicate hydroxide (muscovite), and titanium oxide (rutile). Solvent extracts of the bulk materials were analyzed for organic components by gas chromatography with flame ionization detection. Analyses revealed a mass of poorly resolved peaks. Because of the very low concentrations, further quantitative and qualitative analyses were not performed. An aerosol generation system was designed to separate CI particles based upon aerodynamic size and to simulate the process used during CI installation at work sites. Less than 0.1% of each of the CI samples was collected as the small respirable particle fraction. The mean equivalent diameter of respirable particles ranged from 0.6 to 0.7 mum. The numbers of fibers in the respirable fractions ranged from 9.7 x 103 to 1.4 x 106 fibers/g of CI. The respirable particle fractions did not contain cellulose material and consisted mainly of fire retardants and small quantities of clays. The respirable fraction from one CI sample was administered by intratracheal instillation to male Fischer 344 rats at doses of 0, 0.625, 1.25, 2.5, 5, or 10 mg/kg body weight; the bronchoalveolar lavage (BAL) fluid cellularity was evaluated 3 days later. Based upon the relatively mild severity of the inflammatory response, a dose of 5 mg/kg body weight was selected for use in a subsequent 28-day study. Rats received CI, titanium dioxide (particle controls), or sterile saline (controls). BAL fluid was evaluated 1, 3, 7, 14, and 28 days after instillation, and lung histopathology was evaluated 14 and 28 days after treatment. CI caused a greater influx of inflammatory cells than titanium dioxide and caused significant increases in BAL fluid protein and lactate dehydrogenase. These CI-induced changes in BAL fluid parameters were transient and by day 14 were not significantly different than those observed in rats treated with titanium dioxide or phosphate-buffered saline. Unlike titanium dioxide, CI treatment caused a minimal to mild nonprogressive, minimally fibrosing granulomatous pneumonitis characterized by nodular foci of macrophages and giant cells. These results indicated that few respirable particles or fibers are likely generated during the CI application and that the acute pulmonary toxicity is minimal.

EXPOSURE ASSESSMENT OF CELLULOSE INSULATION APPLICATORS

The CI exposure assessment was conducted with 10 contractors located across the United States. Air samples of total dust and respirable dust were collected for scanning electron microscopy (SEM) to characterize any fibers in the dust. Two SEM air samples for each day of CI activities were collected from the installer and hopper operator. Bulk CI samples were collected and analyzed for metal, boron, and sulfate content. Real-time and video exposure monitoring was conducted to further characterize the CI dust and workers' exposures. The exposure assessment also included a medical component. Investigators collected 175 personal breathing zone (PBZ) total dust, 106 area total dust, and 90 area respirable dust air samples during CI-related activities at the 10 contractor sites. Twenty-six employees' total dust 8-hour time-weighted averages (TWAs) exceeded the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 15 mg/m3, and 42 exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) threshold-limit value (TLV) of 10 mg/m3. Respirable dust air sampling and real-time monitoring with particle size discrimination indicated low levels of respirable dust generation. The SEM analyses revealed that fibers were an average 28 mum in length and ranged from 5 mum to 150 mum. CI installers' PBZ total dust, area total dust, and area respirable dust air samples were all significantly higher during dry attic applications than wet attic applications (P<0.01). Conversely, the hopper operators' total dust exposures were significantly higher during wet wall and ceiling applications than dry wall and ceiling applications (P=0.02). Analyses of variance tests revealed that exposure concentrations in total dust air samples collected in the PBZ of all CI workers, including installers working in attics, installers during wall applications, hopper operators during attic applications, and hopper operators during wall and ceiling applications, varied significantly during dry applications (P<0.01). The respirable dust air samples collected in attic areas, hopper areas during attic applications, and hopper areas during wall and ceiling applications also differed significantly during dry applications (P=0.03). Twenty-three workers participated in the medical phase of the investigation. The workers completed medical and work history questionnaires, performed serial peak flow tests, and completed multiple acute symptom surveys. The medical questionnaires indicated respiratory, nasal, and skin symptoms that employees attributed to CI exposure. The most common symptoms reported while working with CI included nasal symptoms (35%), eye symptoms (35%), and morning phlegm production (25%). There was a temporal association between CI exposure and eye symptoms, but there was little evidence of lower respiratory system health conditions associated with CI exposure.

CONCLUSIONS

Chemical analyses of the four bulk CI samples revealed only minor differences in additives. The major elemental components detected were aluminum, boron, calcium, sodium, and sulfur, but they were attributed to the fire retardants aluminum sulfate, boric acid, and sodium sulfate. For all four CI samples, less than 0.1% by weight was collected as the small respirable particle fraction. The fractions consisted mainly of fire retardants and smaller quantities of clays and did not contain cellulose material. Intratracheal instillation of the respirable fraction in rats produced minimal to mild inflammatory responses in the lungs with no increase in severity by 28 days after dosage. Although a significant increase in lung collagen was detected at day 28 in treated rats, microscopic evaluation revealed only a minimal to mild increase in collagen fibrils associated with granulomatous nodules. The results of these studies indicated that few respirable particles or fibers are generated during the aerosolization of CI, and that even at very high doses of respirable CI particles, acute pulmonary toxicity is minimal. These results are supported by the NIOSH workplace exposure assessment conducted on CI workers. Based on the air sample data collected from the 10 contractor site visits, there is a potential for overexposure to CI; however, respirable dust concentrations were typically low. There was increased potential for 8-hour TWAs exceeding the OSHA PEL for total and respirable dust when employees were involved in CI application activities for longer periods of time. There was evidence of work-related eye and mucous membrane irritation among some workers, which were possibly caused by the additives present in CI, such as boric acid. There was little evidence of lower respiratory system health conditions associated with CI exposure. Based upon the results of the CI chemical characterization studies, the pulmonary toxicity study, and the worksite exposure assessment, the NTP concluded that additional studies of CI in laboratory animals are not warranted at this time. However, the animal pulmonary toxicity studies and worker health surveys focused on acute CI exposures and do not preclude the possibility of toxicity resulting from chronic exposure. Although exposure concentrations of respirable CI particulate matter were low, additional information is needed on the biodurability and reactivity of CI particles and fibers in the respiratory tract. CI should continue to be regarded as a nuisance dust, and workers should continue to wear protective masks to prevent inhalation exposure to CI dusts.

Gestational mercury vapor exposure and diet contribute to mercury accumulation in neonatal rats

Exposure of pregnant Long-Evans rats to elemental mercury (Hg0) vapor resulted in a significant accumulation of Hg in tissues of neonates. Because elevated Hg in neonatal tissues may adversely affect growth and development, we were interested in how rapidly Hg was eliminated from neonatal tissues. Pregnant rats were exposed to 1, 2, or 4 mg Hg0 vapor/m3 or air (controls) for 2 hr/day from gestation day 6 (GD6) through GD15. Neonatal brain, liver, and kidney were analyzed for total Hg at various times between birth and postnatal day 90 (PND90). Milk was analyzed for Hg between birth and weaning (PND21). Before weaning, the Hg levels in neonatal tissues were proportional to maternal exposure concentrations and were highest in kidney followed by liver and then brain. There was no elimination of Hg between birth and weaning, indicating that neonates were exposed continuously to elevated levels of Hg during postpartum growth and development. Consumption of milk from exposed dams resulted in a slight increase in kidney Hg concentration during this period. Unexpectedly, neonatal Hg accumulation increased rapidly after weaning. Increased Hg was measured in both control and exposed neonates and was attributed to consumption of NIH-07 diet containing trace levels of Hg. By PND90, tissue Hg levels equilibrated at concentrations similar to those in unexposed adult Long-Evans rats fed the same diet. These data indicate that dietary exposure to trace amounts of Hg can result in a significantly greater accumulation of Hg in neonates than gestational exposure to high concentrations of Hg0 vapor.

[1,2-13C2]-D-glucose profiles of the serum, liver, pancreas, and DMBA-induced pancreatic tumors of rats

OBJECTIVES

In vitro stable isotope glucose tracer studies indicate that undifferentiated cells of the pancreas use glucose primarily through the nonoxidative reactions of the pentose cycle for nucleic acid ribose synthesis, whereas normal or less transformed cells primarily use the oxidative branch of the cycle.

METHODS

The pancreatic heads of 4 groups (5/group) of male rats were implanted with time-release pellets designed to deliver placebo or 7,12-dimethylbenzanthracene (DMBA) at 11, 33, or 56 mg/d. Four weeks after pancreatic exposure to DMBA, [1,2-C2]-D-glucose tracer (1 g/kg) was injected intraperitoneally followed by sera collection at 1 and 2 hours and harvest of tumors, adjacent pancreatic tissue, and sera at 3 hours.

RESULTS

Tumors (2-9 mm) were found across DMBA groups, with the largest in the high-dose group (> or =5 mm). Selective monitoring by gas chromatography-mass spectrometry of the doubly-labeled [1,2-C2]-D-ribose of RNA, which requires nonoxidative synthesis in the pentose cycle, showed a 2.8-, 2.9-, and 5.7-fold increase in pancreatic tumors. Liver and adjacent pancreas preferentially produced [1-C1]-D-ribose through the oxidative reactions of the cycle. Tumor-bearing animals also cleared and recycled tracer glucose at a faster rate.

CONCLUSIONS

Simultaneous selective positional ion monitoring of C-labeled metabolites and their mass isotopomers in tissues and blood opens new avenues for the early detection and response to therapy testing of pancreatic cancer using GC-MS and/or magnetic resonance imaging-based methods. This study emphasizes the benefits of stable isotope-based dynamic metabolic profiling, when applied in vivo, and the several advantages it offers to positron emission tomography.

Interdisciplinary neurotoxicity inhalation studies: Carbon disulfide and carbonyl sulfide research in F344 rats

Inhalation studies were conducted on the hazardous air pollutants, carbon disulfide, which targets the central nervous system (spinal cord) and peripheral nervous system (distal portions of long myelinated axons), and carbonyl sulfide, which targets the central nervous system (brain). The objectives were to investigate the neurotoxicity of these compounds by a comprehensive evaluation of function, structure, and mechanisms of disease. Through interdisciplinary research, the major finding in the carbon disulfide inhalation studies was that carbon disulfide produced intra- and intermolecular protein cross-linking in vivo. The observation of dose-dependent covalent cross-linking in neurofilament proteins prior to the onset of lesions is consistent with this process contributing to the development of the neurofilamentous axonal swellings characteristic of carbon disulfide neurotoxicity. Of significance is that valine-lysine thiourea cross-linking on rat globin and lysine-lysine thiourea cross-linking on erythrocyte spectrin reflect cross-linking events occurring within the axon and could potentially serve as biomarkers of carbon disulfide exposure and effect. In the carbonyl sulfide studies, using magnetic resonance microscopy (MRM), we determined that carbonyl sulfide targets the auditory pathway in the brain. MRM allowed the examination of 200 brain slices and made it possible to identify the most vulnerable sites of neurotoxicity, which would have been missed in our traditional neuropathology evaluations. Electrophysiological studies were focused on the auditory system and demonstrated decreases in auditory brain stem evoked responses. Similarly, mechanistic studies focused on evaluating cytochrome oxidase activity in the posterior colliculus and parietal cortex. A decrease in cytochrome oxidase activity was considered to be a contributing factor to the pathogenesis of carbonyl sulfide neurotoxicity.

A comparison of the Ranson, Glasgow, and APACHE II scoring systems to a multiple organ system score in predicting patient outcome in pancreatitis

BACKGROUND

Systems for evaluating acute pancreatitis are useful in hospitalized patients. Traditional systems of evaluation are well established but might be outdated. We propose a Multiple Organ System Score (MOSS) containing data that are more consistently collected and which are accurate in predicting patient outcome.

METHODS

A retrospective chart review of 49 patients was completed. We determined if the physician obtained all of the variables necessary to calculate Ranson, Glasgow, or APACHE II scores, if these scores were predictive of patient outcome in the form of length of hospital stay (LOS), and if new, more frequently evaluated variables could be used.

RESULTS

None of the patients could be assigned complete scores. According to Spearman rank correlation, both Glasgow and MOSS showed correlation with patient outcome when APACHE II and Ranson did not.

CONCLUSIONS

Although larger studies should be performed, the MOSS is useful in predicting outcomes of patients with acute pancreatitis.

Identifying athletes at risk of hamstring strains and how to protect them

1. One common soft-tissue injury in sports involving sprinting and kicking a ball is the hamstring strain. Strain injuries often occur while the contracting muscle is lengthened, an eccentric contraction. We have proposed that the microscopic damage to muscle fibres that routinely occurs after a period of unaccustomed eccentric exercise can lead to a more severe strain injury. 2. An indicator of susceptibility for the damage from eccentric exercise is the optimum angle for torque. When this is at a short muscle length, the muscle is more prone to eccentric damage. It is known that subjects most at risk of a hamstring strain have a previous history of hamstring strains. By means of isokinetic dynamometry, we have measured the optimum angle for torque for nine athletes with a history of unilateral hamstring strains. We also measured optimum angles for 18 athletes with no previous history of strain injuries. It was found that mean optimum angle in the previously injured muscles was at a significantly shorter length than for the uninjured muscles of the other leg and for muscles of both legs in the uninjured group. This result suggests that previously injured muscles are more prone to eccentric damage and, therefore, according to our hypothesis, more prone to strain injuries than uninjured muscles. 3. After a period of unaccustomed eccentric exercise, if the exercise is repeated 1 week later, there is much less evidence of damage because the muscle has undergone an adaptation process that protects it against further damage. We propose that for athletes considered at risk of a hamstring strain, as indicated by the optimum angle for torque, a regular programme of mild eccentric exercise should be undertaken. This approach seems to work because evidence from a group of athletes who have implemented such a programme shows a significant reduction in the incidence of hamstring strains.

Contribution of magnetic resonance microscopy in the 12-week neurotoxicity evaluation of carbonyl sulfide in Fischer 344 rats

In this carbonyl sulfide (COS) study, magnetic resonance microscopy (MRM) and detailed light microscopic evaluation effectively functioned in parallel to assure that the distribution and degree of pathology in the brain was accurately represented. MRM is a powerful imaging modality that allows for excellent identification of neuroanatomical structures coupled with the ability to acquire 200 or more cross-sectional images of the brain, and the ability to display them in multiple planes. F344 rats were exposed to 200-600 ppm COS for up to 12 weeks. Prior to MRM, rats were anesthetized and cardiac perfused with McDowell Trump's fixative containing a gadolinium MR contrast medium. Fixed specimens were scanned at the Duke Center for In Vivo Microscopy on a 9.4 Tesla magnetic resonance system adapted explicitly for microscopic imaging. An advantage of MRM in this study was the ability to identify lesions in rats that appeared clinically normal prior to sacrifice and the opportunity to identify lesions in areas of the brain which would not be included in conventional studies. Other advantages include the ability to examine the brain in multiple planes (transverse, dorsal, sagittal) and obtain and save the MRM images in a digital format that allows for postexperimental data processing and manipulation. MRM images were correlated with neuroanatomical and neuropathological findings. All suspected MRM images were compared to corresponding H&E slides. An important aspect of this study was that MRM was critical in defining our strategy for sectioning the brain, and for designing mechanistic studies (cytochrome oxidase evaluations) and functional assessments (electrophysiology studies) on specifically targeted anatomical sites following COS exposure.

Chemical and physical characteristics of cellulose insulation particulates, and evaluation of potential acute pulmonary toxicity

BACKGROUND

During installation of cellulose insulation (CI) in new and older houses, significant quantities of airborne material are generated. This study characterized the chemical and physical properties, and potential acute pulmonary toxicity of CI.

METHODS

CI from four manufacturers was analyzed for inorganic additives and trace element impurities. Aerosols were generated and size fractionated. The number and size of fibrous and nonfibrous particles in the respirable fractions were determined. Respirable CI particulates were intratracheally instilled in rats (5 mg/kg) to evaluate potential pulmonary toxicity.

RESULTS

CI samples were similar in composition with small differences due primarily to fire retardants. Less than 0.1% of CI was respirable and contained few fibers. Acute exposure to CI caused transient inflammation in the lungs and increased 4-hydroxyproline. Microscopic evaluation revealed a minimal to mild, non-progressing granulomatous pneumonitis.

CONCLUSIONS

Low concentrations of respirable particles were found in CI aerosols. Particles consisted primarily of fire retardants with few fibers, and caused mild pulmonary toxicity in rats.

Damage to the human quadriceps muscle from eccentric exercise and the training effect

Nine participants performed two bouts of a step exercise, during which the quadriceps muscle of one leg acted eccentrically. Before and after the exercise, isokinetic torque was measured over a range of knee angles to determine the optimum angle for torque. Immediately after the first bout of exercise, the quadriceps showed a significant (P < 0.05) shift of 15.6 +/- 1.4 degrees (mean +/-sx) of its optimum angle in the direction of longer lengths, suggesting the presence of damage. A drop in peak torque, together with delayed soreness and swelling, confirmed that damage to muscle fibres had occurred. After the second bout of exercise, 8 days later, the shift in optimum angle was 10.4 +/- 1.0 degrees, which was significantly less than after the first bout (P < 0.05). Other indicators of damage were also reduced. In addition, the muscle exhibited a sustained shift in optimum angle (3.4 +/- 0.9 degrees), suggesting that some adaptation had taken place after the first bout of exercise. We conclude that muscles like the quadriceps can show evidence of damage after a specific programme of eccentric exercise, followed by an adaptation response. This is despite the fact that the quadriceps routinely undergoes eccentric contractions in everyday activities.

The influence of fatigue on damage from eccentric contractions in the gastrocnemius muscle of the cat

Eccentric exercise is unique in that it can lead to muscle damage and soreness. Concentric exercise is not accompanied by evidence of damage. There are reports in the literature that muscle fatigue is a factor determining the amount of damage from eccentric exercise. Our theory for the damage process predicts that susceptibility for damage is independent of fatigue. Experiments were carried out to test this prediction as well as to seek other evidence in support of our theory. Comparisons were made between the effects of eccentric and concentric contractions. The nerve supply to the medial gastrocnemius muscle of the anaesthetized cat was divided into three equal portions in terms of the tension they generated. In the first experiment a muscle portion was fatigued by giving it 200 shortening contractions over 12 mm at a shortening speed of 50 mm s(-1). This led to a mean fall in isometric tension (37 +/- 4%) without a significant shift in the optimum length for peak active tension. Giving the fatigued muscle 10 eccentric contractions, active stretches over 6 mm at 50 mm s(-1), beginning from the muscle's optimum length led to a further fall in tension (11% +/- 7%) and a significant shift in optimum length (3.7 mm +/- 0.6 mm) in the direction of longer muscle lengths. The shift in optimum was taken as an indicator of muscle damage. This shift was not significantly different from that seen after eccentric contractions carried out on an unfatigued muscle. After a series of eccentric or concentric contractions, tension at the end of a ramp shortening of 6 mm at 10 mm s(-1) fell more than isometric tension, and by near equal amounts for the two kinds of contractions. In an unfatigued muscle, if tension was altered by changing the rate of stimulation, the fall in shortening tension was greater than after either concentric or eccentric contractions. These observations were seen to be consistent with predictions of the proposed mechanism for the damage process.

Neurotoxicity of carbonyl sulfide in F344 rats following inhalation exposure for up to 12 weeks

Carbonyl sulfide (COS), a high-priority Clean Air Act chemical, was evaluated for neurotoxicity in short-term studies. F344 rats were exposed to 75-600 ppm COS 6 h per day, 5 days per week for up to 12 weeks. In rats exposed to 500 or 600 ppm for up to 4 days, malacia and microgliosis were detected in numerous neuroanatomical regions of the brain by conventional optical microscopy and magnetic resonance microscopy (MRM). After a 2-week exposure to 400 ppm, rats were evaluated using a functional observational battery. Slight gait abnormality was detected in 50% of the rats and hypotonia was present in all rats exposed to COS. Decreases in motor activity, and forelimb and hindlimb grip strength were also detected. In rats exposed to 400 ppm for 12 weeks, predominant lesions were in the parietal cortex area 1 (necrosis) and posterior colliculus (neuronal loss, microgliosis, hemorrhage), and occasional necrosis was present in the putamen, thalamus, and anterior olivary nucleus. Carbonyl sulfide specifically targeted the auditory system including the olivary nucleus, nucleus of the lateral lemniscus, and posterior colliculus. Consistent with these findings were alterations in the amplitude of the brainstem auditory evoked responses (BAER) for peaks N3, P4, N4, and N5 that represented changes in auditory transmission between the anterior olivary nucleus to the medial geniculate nucleus in animals after exposure for 2 weeks to 400 ppm COS. A concentration-related decrease in cytochrome oxidase activity was detected in the posterior colliculus and parietal cortex of exposed rats as early as 3 weeks. Cytochrome oxidase activity was significantly decreased at COS concentrations that did not cause detectable lesions, suggesting that disruption of the mitochondrial respiratory chain may precede these brain lesions. Our studies demonstrate that this environmental air contaminant has the potential to cause a wide spectrum of brain lesions that are dependent on the degree and duration of exposure.

Force matching errors following eccentric exercise

During eccentric exercise contracting muscles are forcibly lengthened, to act as a brake to control motion of the body. A consequence of eccentric exercise is damage to muscle fibres. It has been reported that following the damage there is disturbance to proprioception, in particular, the senses of force and limb position. Force sense was tested in an isometric force-matching task using the elbow flexor muscles of both arms before and after the muscles in one arm had performed 50 eccentric contractions at a strength of 30% of a maximum voluntary contraction (MVC). The exercise led to an immediate reduction of about 40%, in the force generated during an MVC followed by a slow recovery over the next four days, and to the development of delayed onset muscle soreness (DOMS) lasting about the same time. After the exercise, even though participants believed they were making an accurate match, they made large matching errors, in a direction where the exercised arm developed less force than the unexercised arm. This was true whichever arm was used to generate the reference forces, which were in a range of 5-30% of the reference arm's MVC, with visual feedback of the reference arm's force levels provided to the participant. The errors were correlated with the fall in MVC following the exercise, suggesting that participants were not matching force, but the subjective effort needed to generate the force: the same effort producing less force in a muscle weakened by eccentric exercise. The errors were, however, larger than predicted from the measured reduction in MVC, suggesting that factors other than effort might also be contributing. One factor may be DOMS. To test this idea, force matches were done in the presence of pain, induced in unexercised muscles by injection of hypertonic (5%) saline or by the application of noxious heat to the skin over the muscle. Both procedures led to errors in the same direction as those seen after eccentric exercise.

Evaluation of Sensory Evoked Potentials in Long Evans Rats Gestationally Exposed to Mercury (Hg0) Vapor

Mercury is known to alter neuronal function and has been shown to cross the placental barrier. These experiments were undertaken to examine if gestational exposure to mercury vapor (Hg(0)) would result in alterations in sensory neuronal function in adult offspring. Dams were exposed to 0 or 4 mg/m(3) Hg(0) for 2 h/day from gestational days 6-15. This exposure paradigm has been shown to approximate a maximal tolerated dose of Hg(0) for the dams. Between postnatal days 140-168, male and female offspring (one of each gender/dam) were examined using a battery of sensory evoked potentials. Peripheral nerve action potentials, nerve conduction velocity, somatosensory evoked responses (cortical and cerebellar), brainstem auditory evoked responses, pattern evoked potentials, and flash evoked potentials were quantified. Gestational exposure to 4 mg/m(3) Hg(0) did not significantly alter any of the evoked responses, although there was a suggestion of a decrease in compound nerve action potential (CNAP) amplitudes in male animals for the 3 mA stimulus condition. However, this possible change in CNAP amplitudes was not replicated in a second experiment. All evoked potentials exhibited predictable changes as the stimulus was modified. This shows conclusively that the evoked responses were under stimulus control, and that the study had sufficient statistical power to detect changes of these magnitudes. These results indicate that gestational exposure to 4 mg/m(3) Hg(0) did not result in changes in responses evoked from peripheral nerves, or the somatosensory, auditory, or visual modalities.

Human forearm position sense after fatigue of elbow flexor muscles

After a period of eccentric exercise of elbow flexor muscles of one arm in young, adult human subjects, muscles became fatigued and damaged. Damage indicators were a fall in force, change in resting elbow angle and delayed onset of soreness. After the exercise, subjects were asked to match the forearm angle of one arm, whose position was set by the experimenter, with their other arm. Subjects matched the position of the unsupported reference arm, when this was unexercised, with a significantly more flexed position in their exercised indicator arm. Errors were in the opposite direction when the reference arm was exercised. The size of the errors correlated with the drop in force. Less consistent errors were observed when the reference arm was supported. A similar pattern of errors was seen after concentric exercise, which does not produce muscle damage. The data suggested that subjects were using as a position cue the perceived effort required to maintain a given forearm angle against the force of gravity. The fall in force from fatigue after exercise meant more effort was required to maintain a given position. That led to matching errors between the exercised and unexercised arms. It was concluded that while a role for muscle spindles in kinaesthesia cannot be excluded, detailed information about static limb position can be derived from the effort required to support the limb against the force of gravity.

Low-frequency depression of tension in the cat gastrocnemius muscle after eccentric exercise

Subjecting a muscle to a series of eccentric contractions in which the contracting muscle is lengthened results in a number of changes in its mechanical properties. These include a fall in isometric tension that is particularly pronounced during low-frequency stimulation, a phenomenon known as low-frequency depression (LFD). Reports of LFD have not taken into account the shift in optimum length for active tension generation to longer muscle lengths that takes place after eccentric contractions. Given the length dependence of the stimulation frequency-tension curve, we tested the hypothesis that the change in this relationship after eccentric exercise is due to the shift in optimum length. We measured LFD by recording tension in response to a linearly increasing rate of stimulation of the nerve to medial gastrocnemius of anesthetized cats, over the range 0-100 pulses per second. Tension responses were measured before and after 50 eccentric contractions consisting of 6-mm stretches starting at 3 mm below optimum length and finishing at 3 mm above it. An index of LFD was derived from the tension responses to ramp stimulation. It was found that LFD after the eccentric contractions was partly, but not entirely, due to changes in the muscle's optimum length. An additional factor was the effect of fatigue. These observations led to the conclusion that the muscle length dependence of LFD was reduced by eccentric contractions. All of this means that after eccentric exercise the tension deficit at low rates of muscle activation is likely to be less severe than first thought.

Fluoxetine exposures: are they safe for children?

Although it is generally believed that unintentional ingestions of fluoxetine by children are relatively safe, there are no large published studies supporting this concept. The goal of this retrospective study is to determine the signs and symptoms of these children. Inclusion criteria included fluoxetine exposures from six certified regional poison centers: <6 years old, known amount, single substance, 20 mg or more ingested, and follow up done to determine outcome. One hundred twenty cases met all inclusion criteria. Average age was 25 months +/- 12 months. Median amount ingested was 20 mg. Mild signs and symptoms were noted in 3.3%, and no major signs or symptoms were reported. In 48 cases, a milligram per kilogram dose was calculated, and the median dose ingested was 2.26 mg/kg. In 92% of the cases, the amount ingested was 60 mg or below. These children will have no adverse effects or only minimal effects and require no emergency treatment or gastric decontamination.

The role of Toll-like receptor 4 in environmental airway injury in mice

Inhalation of toxins commonly found in air pollution contributes to the development and progression of asthma and environmental airway injury. In this study, we investigated the requirement of toll-like receptor 4 (TLR4) in mice for pulmonary responses to three environmental toxins: aerosolized lipopolysaccharide, particulate matter (residual oil fly ash), and ozone. The physiologic and biologic responses to these toxins were evaluated by the extent of airway responsiveness, neutrophil recruitment to the lower respiratory tract, changes in inflammatory cytokines, and the concentration of protein in the lavage fluid. Genetically engineered, TLR4-deficient mice (C57BL/6(TLR4-/-)) were unresponsive to inhaled lipopolysaccharide, except for minimal increases in some inflammatory cytokines. In contrast, C57BL/6(TLR4-/-) mice did not differ from wild-type mice in their airway response to instilled residual oil fly ash or acute ozone exposure; however, we found that, despite a robust inflammatory response, C57BL/6(TLR4-/-) mice are protected against the development of airway hyperresponsiveness after subchronic ozone exposure. These data demonstrate in the mouse that the requirement of TLR4 for pulmonary inflammation depends on the nature of the toxin and appears specific to toxin and exposure conditions.