bluuebunny/crossref_metadata_2025 huggingface dataset:
Genome Sequence of
Thermofilum pendens
Reveals an Exceptional Loss of Biosynthetic Pathways without Genome Reduction
Authors: Anderson Iain , Rodriguez Jason , Susanti Dwi , Porat Iris , Reich Claudia , Ulrich Luke E. , Elkins James G. , Mavromatis Kostas , Lykidis Athanasios , Kim Edwin , Thompson Linda S. , Nolan Matt , Land Miriam , Copeland Alex , Lapidus Alla , Lucas Susan , Detter Chris , Zhulin Igor B. , Olsen Gary J. , Whitman William , Mukhopadhyay Biswarup , Bristow James , Kyrpides Nikos
Published: February 2008

We report the complete genome of
Thermofilum pendens
, a deeply branching, hyperthermophilic member of the order
Thermoproteales
in the archaeal kingdom
Crenarchaeota. T. pendens
is a sulfur-dependent, anaerobic heterotroph isolated from a solfatara in Iceland. It is an extracellular commensal, requiring an extract of
Thermoproteus tenax
for growth, and the genome sequence reveals that biosynthetic pathways for purines, most amino acids, and most cofactors are absent. In fact,
T. pendens
has fewer biosynthetic enzymes than obligate intracellular parasites, although it does not display other features that are common among obligate parasites and thus does not appear to be in the process of becoming a parasite. It appears that
T. pendens
has adapted to life in an environment rich in nutrients.
T. pendens
was known previously to utilize peptides as an energy source, but the genome revealed a substantial ability to grow on carbohydrates.
T. pendens
is the first crenarchaeote and only the second archaeon found to have a transporter of the phosphotransferase system. In addition to fermentation,
T. pendens
may obtain energy from sulfur reduction with hydrogen and formate as electron donors. It may also be capable of sulfur-independent growth on formate with formate hydrogen lyase. Additional novel features are the presence of a monomethylamine:corrinoid methyltransferase, the first time that this enzyme has been found outside the
Methanosarcinales
, and the presence of a presenilin-related protein. The predicted highly expressed proteins do not include proteins encoded by housekeeping genes and instead include ABC transporters for carbohydrates and peptides and clustered regularly interspaced short palindromic repeat-associated proteins.
Cofilin is a marker of myofibroblast differentiation in cells from porcine aortic cardiac valves
Authors: Pho M. , Lee W. , Watt D. R. , Laschinger C. , Simmons C. A. , McCulloch C. A.
Published: February 2008

The formation of myofibroblasts in valve interstitial cell (VIC) populations contributes to fibrotic valvular disease. We examined myofibroblast differentiation in VICs from porcine aortic valves. In normal valves, cells immunostained for α-smooth muscle actin (α-SMA, a myofibroblast marker) were rare (0.69 ± 0.48%), but in sclerotic valves of animals fed an atherogenic diet, myofibroblasts were spatially clustered and abundant (31.2 ± 6.3%). In cultured VIC populations from normal valves, SMA-positive myofibroblasts were also spatially clustered, abundant (21% positive cells after 1 passage), and stained for collagen type I and vimentin but not desmin. For an analysis of stem cells, two-color flow cytometry of isolated cells stained with Hoechst 33342 demonstrated that 0.5% of VICs were side population cells; none stained for SMA. Upon culture, sorted side population cells generated ∼85% SMA-positive cells, indicating that some myofibroblasts originate from a rare population with stem cell characteristics. Plating cells on rigid collagen substrates enabled the formation of myofibroblasts after 5 days in culture, which was completely blocked by culture of cells on compliant collagen substrates. Exogenous tensile force also significantly increased SMA expression in VICs. Isotope-coded affinity tags and mass spectrometry were used to identify differentially expressed proteins in myofibroblast differentiation of VICs. Of the nine proteins that were identified, cofilin expression and phospho-cofilin were strongly increased by conditions favoring myofibroblast differentiation. Knockdown of cofilin with small-interfering RNA inhibited collagen gel contraction and reduced myofibroblast differentiation as assessed by the SMA incorporation into stress fibers. When compared with normal valves, diseased valves showed strong immunostaining for cofilin that colocalized with SMA in clustered cells. We conclude that in VICs, cofilin is a marker for myofibroblasts in vivo and in vitro that arise from a rare population of stem cells and require a rigid matrix for formation.
Epicardial and intramural excitation during ventricular pacing: effect of myocardial structure
Authors: Taccardi Bruno , Punske Bonnie B. , Macchi Emilio , MacLeod Robert S. , Ershler Philip R.
Published: February 2008

Published studies show that ventricular pacing in canine hearts produces three distinct patterns of epicardial excitation: elliptical isochrones near an epicardial pacing site, with asymmetric bulges; areas with high propagation velocity, up to 2 or 3 m/s and numerous breakthrough sites; and lower velocity areas (<1 m/s), where excitation moves across the epicardial projection of the septum. With increasing pacing depth, the magnitude of epicardial potential maxima becomes asymmetric. The electrophysiological mechanisms that generate the distinct patterns have not been fully elucidated. In this study, we investigated those mechanisms experimentally. Under pentobarbital anesthesia, epicardial and intramural excitation isochrone and potential maps have been recorded from 22 exposed or isolated dog hearts, by means of epicardial electrode arrays and transmural plunge electrodes. In five experiments, a ventricular cavity was perfused with diluted Lugol solution. The epicardial bulges result from electrotonic attraction from the helically shaped subepicardial portions of the wave front. The high-velocity patterns and the associated multiple breakthroughs are due to involvement of the Purkinje network. The low velocity at the septum crossing is due to the missing Purkinje involvement in that area. The asymmetric magnitude of the epicardial potential maxima and the shift of the breakthrough sites provoked by deep stimulation are a consequence of the epi-endocardial obliqueness of the intramural fibers. These results improve our understanding of intramural and epicardial propagation during premature ventricular contractions and paced beats. This can be useful for interpreting epicardial maps recorded at surgery or inversely computed from body surface ECGs.
Vascular reactivity, 5-HT uptake, and blood pressure in the serotonin transporter knockout rat
Authors: Linder A. Elizabeth , Diaz Jessica , Ni Wei , Szasz Theo , Burnett Robert , Watts Stephanie W.
Published: February 2008

The handling of serotonin [5-hydroxytryptamine (5-HT)] depends on the serotonin transporter (SERT). A SERT knockout (KO) rat is a useful model to test the hypothesis that SERT is the primary mechanism for arterial 5-HT uptake and to investigate the impact of SERT removal on blood pressure. Wild-type (WT) and KO rats were used to measure 5-HT content (plasma, raphe, aorta, carotid, and mesenteric artery), aortic isometric contraction, and blood pressure. HPLC supported the lack of circulating 5-HT in plasma (ng/ml plasma, WT, 310 ± 96; and KO, 1.0 ± 0.5; P < 0.05). Immunohistochemistry and Western blot analyses validated the presence of the SERT protein in the WT rats and a lesser expression in the KO rat. The aorta isolated from KO rats had a normal contraction to phenylephrine and norepinephrine and a normal relaxation to the endothelium-dependent agonist acetylcholine compared with the aorta from WT. In contrast, the potency of 5-HT was increased in the aorta from KO rats compared with WT rats [−log EC50 (M); WT, 5.71 ± 0.08; and KO, 6.7 ± 0.18] and maximum contraction was reduced [%phenylephrine (10 μM) contraction, WT, 113 ± 6%; and KO, 52 ± 12%]. 5-HT uptake was reduced but not abolished in arteries of the KO compared with the WT rats. Diurnal mean arterial blood pressure, heart rate, and locomotor activity level of the KO rats were similar to the WT rats. These data suggest that there are other mechanisms of 5-HT uptake in the arteries of the rat and that although the absence of circulating 5-HT and/or SERT function sensitizes arteries to 5-HT, SERT dysfunction does not impair normal blood pressure.
Interactions of nanoparticles with pulmonary structures and cellular responses
Authors: Mühlfeld Christian , Rothen-Rutishauser Barbara , Blank Fabian , Vanhecke Dimitri , Ochs Matthias , Gehr Peter
Published: February 2008

Combustion-derived and synthetic nano-sized particles (NSP) have gained considerable interest among pulmonary researchers and clinicians for two main reasons. 1) Inhalation exposure to combustion-derived NSP was associated with increased pulmonary and cardiovascular morbidity and mortality as suggested by epidemiological studies. Experimental evidence has provided a mechanistic picture of the adverse health effects associated with inhalation of combustion-derived and synthetic NSP. 2) The toxicological potential of NSP contrasts with the potential application of synthetic NSP in technological as well as medicinal settings, with the latter including the use of NSP as diagnostics or therapeutics. To shed light on this paradox, this article aims to highlight recent findings about the interaction of inhaled NSP with the structures of the respiratory tract including surfactant, alveolar macrophages, and epithelial cells. Cellular responses to NSP exposure include the generation of reactive oxygen species and the induction of an inflammatory response. Furthermore, this review places special emphasis on methodological differences between experimental studies and the caveats associated with the dose metrics and points out ways to overcome inherent methodological problems.
Role of JNK in network formation of human lung microvascular endothelial cells
Authors: Medhora Meetha , Dhanasekaran Anuradha , Pratt Phillip F. , Cook Craig R. , Dunn Laurel K. , Gruenloh Stephanie K. , Jacobs Elizabeth R.
Published: February 2008

The signaling mechanisms in vasculogenesis and/or angiogenesis remain poorly understood, limiting the ability to regulate growth of new blood vessels in vitro and in vivo. Cultured human lung microvascular endothelial cells align into tubular networks in the three-dimensional matrix, Matrigel. Overexpression of MAPK phosphatase-1 (MKP-1), an enzyme that inactivates the ERK, JNK, and p38 pathways, inhibited network formation of these cells. Adenoviral-mediated overexpression of recombinant MKP-3 (a dual specificity phosphatase that specifically inactivates the ERK pathway) and dominant negative or constitutively active MEK did not attenuate network formation in Matrigel compared with negative controls. This result suggested that the ERK pathway may not be essential for tube assembly, a conclusion which was supported by the action of specific MEK inhibitor PD 184352, which also did not alter network formation. Inhibition of the JNK pathway using SP-600125 or l-stereoisomer (l-JNKI-1) blocked network formation, whereas the p38 MAPK blocker SB-203580 slightly enhanced it. Inhibition of JNK also attenuated the number of small vessel branches in the developing chick chorioallantoic membrane. Our results demonstrate a specific role for the JNK pathway in network formation of human lung endothelial cells in vitro while confirming that it is essential for the formation of new vessels in vivo.
Digressing with Aristotle: Hieronymus Dandinus' De corpore animato (1610) and the Expansion of Late Aristotelian Philosophy
Authors: Edwards Michael
Published: February 2008

Early modern scholastic and Aristotelian philosophy is now a growing area of study. However, little attention has been paid to the structure and form of late Aristotelian texts, partly because they have often been seen as baroque and excessively intricate in construction. This article examines the role of structural and stylistic issues in the De anima commentary of the Jesuit author Hieronymus Dandinus (1554-1634), focusing particularly on the techniques he used to integrate knowledge from other disciplines and expand the familiar commentary format. It argues that taking these issues seriously has important implications for our understanding of the dynamics of reading Aristotle in the early modern period.
Comparison of Multiple-Indicators, Multiple-Causes– and Item Response Theory–Based Analyses of Subgroup Differences
Authors: Willse John T. , Goodman Joshua T.
Published: February 2008

This research provides a direct comparison of effect size estimates based on structural equation modeling (SEM), item response theory (IRT), and raw scores. Differences between the SEM, IRT, and raw score approaches are examined under a variety of data conditions (IRT models underlying the data, test lengths, magnitude of group differences, and relative size of reference and focal groups). Results show that all studied methods perform similarly. All methods tend to underestimate effects as effect sizes become larger. SEM-based approaches to effect size estimation perform somewhat better at shorter test lengths, whereas approaches based on IRT and raw score perform somewhat better at longer test lengths. Although these differences between methods are detectable, they are small in magnitude.
Parent Ratings Using the Chinese Version of the Parent Gifted Rating Scales–School Form Reliability and Validity for Chinese Students
Authors: Huijun Li  , Lee Donghyuck , Pfeiffer Steve I. , Petscher Yaacov
Published: February 2008

This study examined the reliability and validity of the scores of a Chinese-translated version of the Gifted Rating Scales–School Form (GRS-S) using parents as raters and explored the effects of gender and grade on the ratings. A total of 222 parents participated in the study and rated their child independently using the Chinese version of the Parent GRS-S (CVPGRS-S). Results indicate high reliability for parent rating scores and statistically significant correlations between CVPGRS-S scale scores and students' classroom academic achievement scores. The effect sizes of the relationships were moderate. Results revealed no statistically significant grade effect on any of the six CVPGRS-S scales; small but statistically significant differences in favor of females on the six CVPGRS-S scales were found. However, the effect size was small. Research results suggest that the Chinese-translated parent version of the GRS-S holds promise for use with Chinese parents.
Cultural Relevance of Adult Attachment
Authors: Lee Young-Sun , Grossman Jennifer , Krishnan Anita
Published: February 2008

This study examined the cultural relevance of adult attachment within a Korean sample ( N = 390) using Rasch rating scale modeling. The psychometric properties of scores from the Korean version of the Revised Experiences in Close Relationships, comprised of two subscales of Anxiety (self) and Avoidance (other), were assessed. Results obtained from separate analyses on each subscale showed that (a) most items measured one common construct, either anxiety or avoidance; (b) each subscale had high estimates of both person and item separation indices; and (c) the items measuring high levels of anxiety and avoidance may not be appropriate for the sample of Korean college students.
The Changing Workplace and Its Effects
Authors: Grunberg Leon , Moore Sarah , Greenberg Edward S. , Sikora Pat
Published: February 2008

The present study explores the multiple ways employees are affected by pervasive and complex organizational change. Across a 10-year period, the authors surveyed 525 white- and blue-collar workers on four separate occasions during which time the company experienced, for example, a difficult financial period, several large downsizing events, the implementation of new technologies, and a move toward a “flatter” managerial structure. At Time 4, shortly after the organization experienced a substantial economic turnaround, the authors found that most but not all of the job and organizational attitudes returned to Time 1 levels. Many of the measures of health and various indices of the work—family relationship however showed both positive and negative lasting effects. These findings are discussed in light of current thinking regarding worker engagement and the psychological contract between workers and organizations.
Psychosocial Moderators of the Effects of Transitioning Into Filial Caregiving on Mental and Physical Health
Authors: Marks Nadine F. , Lambert James David , Jun Heyjung , Jieun Song
Published: February 2008

A life-course theoretical perspective guided this study to examine how effects on mental and physical health (depressive symptoms, hostility, global happiness, self-esteem, personal mastery, psychological wellness, self-rated physical health) of transitioning into filial caregiving for a sole surviving parent are moderated by prior relationship quality, filial obligation, race or ethnicity, education, income, employment status, marital status, and parental status. Results from models estimated using longitudinal data from 1,060 adults aged 25 to 65 years at baseline (National Survey of Families and Households, 1987 to 1994) suggested that life-course and contextual factors do contribute to patterning health risks of caregiving, often in different ways for men and women: For example, low income puts daughter caregivers at greater risk for decline in physical health, combining employment with filial caregiving is more problematic for daughters' mental health, and being an unmarried filial caregiver is more problematic for men. Heterogeneity in the experience of filial care needs further attention in future research.
Empirical Challenges in Organizational Aesthetics Research: Towards a Sensual Methodology
Authors: Warren Samantha
Published: February 2008

Despite growing scholarly interest in aesthetic dimensions of organizational life, there is a lack of literature expressly engaging with the methodological mechanics of 'doing aesthetics research'. This article addresses that gap. It begins with an overview of the conceptual idiosyncrasies of 'aesthetics' as a facet of human existence and maps out the challenges these pose for empirical research methodology. A review of methodological approaches adopted to date in empirical studies of organizational aesthetics is then presented. The remainder of the article draws on the author's experiences and suggests methods and techniques to address both conceptual and practical challenges encountered during the execution of an organizational aesthetics research project. The article calls for a firmer focus on the aesthetic experiences of organizational members in addition to those of researchers and concludes with some suggestions as to the future of such 'sensual methodologies'
Varieties of Knowledge and Their Use in Business and Management Studies: Conditions and Institutions
Authors: Whitley Richard
Published: February 2008

Many research fields combine practical goals with a search for fundamental mechanisms and make significant contributions to theoretical understanding. This is especially so in the social sciences, which are often concerned with policy issues and problems, albeit with varying degrees of directness. Business and management studies (BMS) may be more focused on practical problem solving than other social sciences, but they are equally capable of contributing major intellectual innovations. They produce a variety of kinds of knowledge that are practically useful in different conditions. At least eight types can be distinguished in terms of their horizontal and vertical isolation, and their identification of causal mechanisms. These can be expected to be more or less effective in producing desired outcomes according to three conditions: contextual independence, stability of internal causal processes, and similarity of circumstances. These conditions in turn are likely to be achieved to varying degrees in different socio-economic systems governed by different institutional arrangements, particularly those that encourage varying degrees of managerial authority sharing and inter-firm coordination of economic activities. Differences in the dominant institutions governing knowledge production and labour markets also affect the kinds of research styles and knowledge types that dominate BMS in different societies.
An Integrative Approach to Neurotoxicology
Authors: Dorman David C.
Published: February 2008

Exposure of human populations to a wide variety of chemicals has generated concern about the potential neurotoxicity of new and existing chemicals. Experimental studies conducted in laboratory animals remain critical to the study of neurotoxicity. An integrative approach using pharmacokinetic, neuropathological, neurochemical, electrophysiological, and behavioral methods is needed to determine whether a chemical is neurotoxic. There are a number of factors that can affect the outcome of a neurotoxicity study, including the choice of animal species, dose and dosage regimen, route of administration, and the intrinsic sensitivity of the nervous system to the test chemical. The neurotoxicity of a chemical can vary at different stages of brain development and maturity. Evidence of neurotoxicity may be highly subjective and species specific and can be complicated by the presence of systemic disease. The aim of this paper is to give an overview of these and other factors involved in the assessment of the neurotoxic potential for chemicals. This article discusses the neurotoxicity of several neurotoxicants (eg, acrylamide, trimethyltin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, manganese, and ivermectin), thereby highlighting a multidisciplinary approach to the assessment of chemically induced neurotoxicity in animals. These model chemicals produce a broad range of effects that includes peripheral axonopathy, selective neuronal damage within the nervous system, and impaired neuronal-glial metabolism.
Mechanisms of Injury in the Central Nervous System
Authors: Philbert Martin A. , Billingsley Melvin L. , Reuhl Kenneth R.
Published: February 2008

Neurotoxicants with similar structural features or common mechanisms of chemical action frequently produce widely divergent neuropathologic outcomes. Methylmercury (MeHg) produces marked cerebellar dysmorphogenesis during critical periods of development. The pathologic picture is characterized by complete architectural disruption of neuronal elements within the cerebellum. MeHg binds strongly to protein and soluble sulphydryl groups. Binding to microtubular -SH groups results in catastrophic depolymerization of immature tyrosinated microtubules. However, more mature acetylated microtubules are resistant to MeHg-induced depolymerization. In contrast to MeHg, the structurally similar organotin trimethyltin (TMT) elicits specific apoptotic destruction of pyramidal neurons in the CA3 region of the hippocampus and in other limbic structures. Expression of the phylogenetically conserved protein stannin is required for development of TMT-induced lesions. Inhibition of expression using antisense oligonucleotides against stannin protects neurons from the effects of TMT, suggesting that this protein is required for expression of neurotoxicity. However, expression of stannin alone is insufficient for induction of apoptotic pathways in neuronal populations. The aromatic nitrocompound 1,3-dinitrobenzene (DNB) has 2 independent nitro groups that can redox cycle in the presence of molecular oxygen. Despite its ability to deplete neural glutathione stores, DNB produces edematous gliovascular lesions in the brain stem of rats. Glial cells are susceptible despite high concentrations of reduced glutathione compared with neuronal somata in the central nervous system (CNS). The severity of lesions produced by DNB is modulated by the activity of neurons in the affected pathways. The inherent discrepancy between susceptibility of neuronal and glial cell populations is likely mediated by differential control of the mitochondrial permeability transition in astrocytes and neurons. Lessons learned in the mechanistic investigation of neurotoxicants suggest caution in the evaluation and interpretation of structure-activity relationships, eg, TMT, MeHg, and DNB all induce oxidative stress, whereas TMT and triethyltin produce neuronal damage and myelin edema, respectively. The precise CNS molecular targets of cell-specific lipophilic neurotoxicants remain to be determined.
MK-801 Neurotoxicity in Cupric Silver-Stained Sections: Lesion Reconstruction by 3-Dimensional Computer Image Analysis
Authors: Fix Andrew S. , Stitzel Susan R. , Ridder Gregg M. , Switzer Robert C.
Published: February 2008

Routine histopathologic evaluation of the brain (paraffin embedding, hematoxylin and eosin staining) makes it difficult for an investigator to identify the overall location and relative extent of lesions as they relate to neural substructures. Moreover, it is very difficult to convey this information to others who are less familiar with neuroanatomy. This study combined a 3-dimensional imaging program with a cupric silver stain for neuronal degeneration in order to determine the location and extent of a focal lesion produced by MK-801 (dizocilpine maleate), a glutamate receptor antagonist that induces necrosis in a small population of neurons in the cortex of rats. A male Sprague-Dawley rat was treated with a subcutaneous dose of MK-801 (10 mg/kg) and was perfused with fixative through the left ventricle 3 days after treatment, a time point known to reveal maximal neurotoxic effects. The brain was embedded in a gelatin matrix, frozen, and serially sectioned at a thickness of 40 μm. The cupric silver method of de Olmos was used to stain frozen sections at 320-μm intervals. Using a color charged-couple device (CCD) camera and a macro lens, a series of 2-dimensional images, which encompassed the entire rostral to caudal extent of the brain, was captured. A computer program was written to define internal and external boundaries in these 2-dimensional images. Then, 3-dimensional reconstructions were generated on a Silicon Graphics workstation using IRIS "Explorer." The quality of the 3-dimensional reconstructions allowed for easy identification of various neural substructures while clearly revealing the exact location and extent of the resulting necrotic neurons that were positively identified by the cupric silver stain. This 3-dimensional lesion reconstruction method provides a powerful tool for conveying spatial information about the nature of neurotoxic lesions in the brain. In addition, it may be used to investigate further dose-response relationships and the effects of other neurotoxicants.
Fluoro-Jade: Novel Fluorochromes for Detecting Toxicant-Induced Neuronal Degeneration
Authors: Schmued Larry C. , Hopkins Keri J.
Published: February 2008

Two anionic fluorescein derivatives can be used for the simple and definitive localization of neuronal degeneration in brain tissue sections. Initial work on the first generation fluorochrome, Fluoro-Jade, demonstrated the utility of this compound for the detection of neuronal degeneration induced by a variety of well-characterized neurotoxicants, including kainic acid, 3-nitropropionic acid, isoniazid, ibogaine, domoic acid, and dizocilpine maleate (MK-801). After validation, the tracer was used to reveal previously unreported sites of neuronal degeneration associated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), methamphetamine, and d-fenfluramine. Preliminary findings with a second generation fluorescein derivative, Fluoro-Jade B, suggest that this tracer results in staining of optimal contrast and resolution in animals dosed with kainic acid. These 2 tracers can be combined with other histologic methods, including immunofluoresence and fluorescent Nissl stains. Recent preliminary findings on a number of specialized applications of Fluoro-Jade include the detection of apoptosis, amyloid plaques, astrocytes, and dead cells in tissue culture.
Virtual Neuropathology: Three-Dimensional Visualization of Lesions Due to Toxic Insult
Authors: Lester David S. , Pine P. Scott , Delnomdedieu Marielle , Johannessen Jan N. , Johnson G. Allan
Published: February 2008

A first-pass approach incorporating high-field magnetic resonance imaging (MRI) was used for rapid detection of neuropathologic lesions in fixed rat brains. This inherently 3-dimensional and nondestructive technique provides high-resolution, high-contrast images of fixed neuronal tissue in the absence of sectioning or staining. This technique, magnetic resonance microscopy (MRM), was used to identify diverse lesions in 2 well-established rat neurotoxicity models. The intrinsic contrast in the images delineated lesions that were identified using a battery of histologic stains, some of which would not be used in routine screening. Furthermore, the MRM images provided the locations of lesions, which were verified upon subsequent sectioning and staining of the same samples. The inherent contrast generated by water properties is exploited in MRM by choosing suitable pulse sequences, or proton stains. This approach provides the potential for a comprehensive initial MRM screen for neurotoxicity in preclinical models with the capability for extrapolation to clinical analyses using classical MRI.
Practical Aspects of Neuropathology: A Technical Guide for Working with the Nervous System
Authors: Fix Andrew S. , Garman Robert H.
Published: February 2008

Toxicologic pathologists are evaluating tissues from the central and peripheral nervous systems with increasing frequency. This change is being driven by recently established regulatory guidelines and intense interest in developing pharmaceutical compounds to treat various nervous system disorders. However, morphologic evaluation of the nervous system by light or electron microscopy requires special understanding and effort. Here, we review the general concepts of fixation for the nervous system, explain perfusion procedures for optimal preservation, and provide information on handling tissues to avoid artifacts. In general, fixation with aldehydes is recommended for nervous tissue (a combination of paraformaldehyde and glutaraldehyde is preferred). Electron microscopic studies require fixatives of the highest purity possible, typically paraformaldehyde prepared fresh from powder mixed with high-grade glutaraldehyde. The final osmolality of the solution should be slightly hypertonic, in the range of 400-600 mOsmol. Slight hypertonicity is very important and will facilitate maintenance of vascular distention during whole-body perfusion, which is the best method for producing high-quality tissue preparations. Special effort is necessary for handling nervous tissue in a way that minimizes artifacts because chemical fixation is not completed immediately following the perfusion. These technical details should help toxicologic pathologists in their efforts to work with the nervous system, thereby increasing their effectiveness in supporting safety characterization of new test materials undergoing toxicologic assessments.
Morphometric Analysis of the Developing Rat Brain
Authors: Duffell Stephen J. , Soames Anthony R. , Gunby Sarah
Published: February 2008

In 2 studies, a method of linear morphometry was applied to regulatory developmental neurotoxicity studies in the rat. The first study involved the development of the brain during postnatal days (PNDs) 7-63, and the second involved the effects of 8 mg/kg IP trimethyltin chloride (TMT) to rats at PND 8, with morphometry performed at PNDs 12 and 24. The results of the TMT linear morphometry were compared with those from stereologic counting of neurons in the cerebral cortex, piriform cortex, and hippocampus. Stereology produces more meaningful data than simple linear morphometry for use in the regulatory assessment of the developmental neurotoxicity potential of compounds.
Phenotype vs Genotype in the Evolution of Astrocytic Brain Tumors
Authors: Kleihues Paul , Ohgaki Hiroko
Published: February 2008

Astrocytic brain tumors are the most frequent human gliomas and they include a wide range of neoplasms with distinct clinical, histopathologic, and genetic features. Diffuse astrocytomas are predominantly located in the cerebral hemispheres of adults and have an inherent tendency to progress to anaplastic astrocytoma and (secondary) glioblastoma. The majority of glioblastomas develop de novo (primary glioblastomas), without an identifiable less-malignant precursor lesion. These subtypes of glioblastoma evolve through different genetic pathways, affect patients at different ages, and are likely to differ in their responses to therapy. Primary glioblastomas occur in older patients and typically show epidermal growth factor receptor ( EGFR) overexpression, PTEN mutations, p16 deletions, and, less frequently, MDM2 amplification. Secondary glioblastomas develop in younger patients and often contain TP53 mutations as their earliest detectable alteration. Morphologic variants of glioblastoma were shown to have intermediate clinical and genetic profiles. The giant cell glioblastoma clinically and genetically occupies a hybrid position between primary (de novo) and secondary glioblastomas. Gliosarcomas show identical gene mutations in the gliomatous and sarcomatous tumor components, which strongly supports the concept that there is a monoclonal origin for gliosarcomas and an evolution of the sarcomatous component due to aberrant mesenchymal differentiation in a highly malignant astrocytic neoplasm.
Tumors of the Nervous System in Carcinogenic Hazard Identification
Authors: Rice Jerry M. , Wilbourn Julian D.
Published: February 2008

In the absence of adequate data on humans, it is biologically plausible and prudent to regard agents and mixtures for which there is sufficient evidence of carcinogenicity in experimental animals, usually rats and mice, as if they presented a carcinogenic risk to humans. Prediction of cancer sites in humans from bioassay data in rodents is much less certain, however, regardless of organ or tissue. For tumors of the nervous system, there is practically no basis for judging the validity of such predictions, as only ionizing radiation is known to cause tumors of the central nervous system (CNS) in humans. Brain tumors are relatively uncommon findings in bioassays and are rare in untreated rodents, even in rats, which appear to be the most susceptible species. However, CNS tumors have been readily induced in rodents by systemic exposures to some chemicals, notably N-nitrosoalkylureas and other alkylating agents and certain alkyl hydrazine derivatives. CNS tumors in rodents have played a significant role in carcinogenic hazard evaluations of several other chemicals, including acrylonitrile, ethylene oxide, and acrylamide, and have been implicated as part of the tumor spectrum induced by vinyl chloride and certain inorganic lead compounds. In some of these evaluations, it is not certain that all tumors diagnosed as primary brain tumors were correctly identified. Diagnostic difficulties have been presented by undifferentiated small-cell tumors that may invade the brain, including carcinomas of the nasal cavity and undifferentiated schwannomas arising in cranial nerve ganglia, and by the difficulty of reliably distinguishing between focal reactive gliosis and early glial neoplasms. The most striking experimental finding regarding the induction by chemicals of tumors of the nervous system is the dramatically greater susceptibility of the fetal and neonatal nervous system to some carcinogens, as compared with the susceptibility of the nervous system in adults of the same species.
Review Article: Paradoxical Effects of Phenobarbital on Mouse Hepatocarcinogenesis
Authors: Lee Gang-Hong
Published: February 2008

Phenobarbital was the first tumor promoter for rodent liver to be associated with the 2-stage or initiation-promotion concept of carcinogenesis. In rats and mice preinitiated with genotoxic carcinogens, phenobarbital administration increases the number of hepatocellular tumors by approximately 5-fold despite its nongenotoxicity. However, in mice phenobarbital occasionally exhibits strong inhibitory effects on hepatocarcinogenesis initiated with the potent carcinogen diethylnitrosamine. Both positive and negative effects of phenobarbital on hepatocytic proliferation and apoptosis, which are mechanistically involved in the promotion stage of hepatocarcinogenesis, have been described. These complex outcomes of phenobarbital treatment and their effects on hepatocarcinogenesis in mice raise serious issues regarding extrapolation of experimental data from laboratory animals to human risk assessment. Recent work suggests that the paradoxical actions of phenobarbital on hepatocarcinogenesis can be understood by consideration of qualitative diversity in initiated lesions and differential responses to promotion stimulus.
Origin and Distribution of Potassium Bromate-Induced Testicular and Peritoneal Mesotheliomas in Rats
Authors: Crosby Lynn M. , Morgan Kevin T. , Gaskill Betty , Wolf D.C. , Deangelo A.B.
Published: February 2008

Tissue sections were examined from a 2-year bioassay of male Fischer 344 rats treated with potassium bromate administered in drinking water. All animals exhibiting peritoneal mesotheliomas also had mesotheliomas of the tunica vaginalis testis mesorchium (the reverse was not true), and the correlation of these 2 types of mesotheliomas was highly significant (r2 = 0.98). Mapping of the tunica vaginalis tumors at all time points and at all bromate concentrations revealed a pattern of increasing incidence of tumor formation on the mesothelium of the tunica vaginalis testis as a function of proximity to the mesorchial ligament. Thus, the mesorchium appears to be the major mesothelial target site for potassium bromate-mediated carcinogenesis. The frequency of occurrence of mesotheliomas by location was tunica vaginalis testis (25%), mesosplenium (20%), mesentery (10%), mesojejunum/mesocolon (8%), bladder (6.5%), mesogastrium (13%), liver serosa (5%), and kidney, small intestine, and rectum (1% each). A complete cross-section of the rat testis was prepared and used to construct a complete map of the mesothelium. Any attempt to determine the role of local dose and tissue susceptibility for the purpose of interspecies risk extrapolation must take into account the complex anatomy and physiology of this region of the visceral and testicular suspensory apparatus. Improved histologic approaches are needed for adequate assessment of this delicate suspensory system.
Acute Injury to Differentiating Clara Cells in Neonatal Rabbits Results in Age-Related Failure of Bronchiolar Epithelial Repair
Authors: Smiley-Jewell Suzette M. , Liu Frank J. , Weir Alison J. , Plopper Charles G.
Published: February 2008

Nonciliated bronchiolar (Clara) cells are progenitor cells during lung development. During differentiation, they have a heightened injury susceptibility to environmental toxicants bioactivated by cytochrome P450 monooxygenase. When neonatal rabbits are treated with the P450-mediated cytotoxicant 4-ipomeanol (IPO), abnormal bronchiolar epithelium results. This study establishes the impact of IPO cytotoxicity on 3 stages of rabbit Clara cell differentiation, early (2.5 and 5 days postnatal [DPN]), intermediate (7 and 9 DPN), and late (15 and 21 DPN), and relates the cytotoxicity to the extent of bronchiolar repair. Neonates received a single dose of IPO (5 mg/kg) and were assessed by qualitative pathology 48 hours later for injury or at 4 weeks for repair. IPO injured the 3 stages of Clara cell differentiation to the same degree; epithelium was swollen, exfoliated, and squamated. Epithelial repair differed among the 3 stages. Bronchioles of animals treated during early and intermediate stages had simple squamous and irregularly shaped cuboidal cells. Animals treated during late stages were similar to controls. Thus, differentiating Clara cells are susceptible to injury by the P450-mediated cytotoxicant IPO, but the extent of repair varies based on when the initial injury occurs.
Expression of Cytokines and Proteases in Mast Cells in the Lesion of Subcapsular Cell Hyperplasia in Mouse Adrenal Glands
Authors: Kim Jong-Soo , Kubota Hisayo , Nam Sang-Yoon , Doi Kunio , Saegusa Junzo
Published: February 2008

To examine the possible roles of mast cells in the pathogenesis of subcapsular cell hyperplasia (SCH) in the adrenal glands of mice, we investigated the expression of certain cytokines, including stem cell factor (SCF), tumor necrosis factor-alpha (TNF-α), nerve growth factor (NGF), and basic fibroblast growth factor (bFGF), and mast cell-specific proteases, such as mouse mast cell protease (mMCP)-2 and mMCP-7. The mRNAs of c- kit (SCF receptor), bFGF, TNF-α, mMCP-2, and mMCP-7 were expressed in both the adrenal glands and the mouse bone marrow-derived mast cells (mBMMCs). Immunoreactivities for cytokines (SCF, NGF, TNF-α) and proteases (mMCP-2, mMCP-7) were exclusively located in the mast cells in SCH lesions. The immature mBMMCs did not express the mRNAs of SCF and NGF, whereas the mast cells in the SCH lesions showed the expression of SCF and NGF. These findings suggest that SCH may provide a favorable microenvironment for functional maturation of mast cells to produce SCF and NGF, and the mast cells in SCH lesions synthesize SCF and NGF and may, in part, use them in autocrine fashion for their survival and differentiation. Therefore, mast cells may contribute to SCH pathogenesis by producing a range of multifunctional cytokines and proteases.
Platelet Kinetics in Dogs Treated with a Glycoprotein IIb/IIIa Peptide Antagonist
Authors: Weiss Douglas J. , Mirsky Michael L. , Evanson Oral A. , Fagliari Jose , Mcclenahan David , Mccullough Bruce
Published: February 2008

Platelet glycoprotein IIb/IIIa (GPIIb/IIIa) receptor antagonists have been highly effective inhibitors of platelet aggregation in preclinical studies and in clinical trials. However, decreased platelet counts have been documented in preclinical studies and in some patients receiving GPIIb/IIIa antagonists. We evaluated changes in platelet kinetics and fate in dogs receiving the GPIIb/IIIa receptor antagonist RPR 109891 orally for 4 days. Dogs receiving RPR 109891 had a 22-52% decrease in platelet count with the nadirs at 3-5 days after initiation of treatment. Platelet survival time was reduced by 19%, and platelet half-life was reduced by 63%. Indium-111-labeled platelets were rapidly cleared from the blood within 1 hour after administration of RPR 109891 on treatment days 1 and 2. This clearing was associated with a sharp increase in radioactivity in spleen but not in liver or lung. Platelet clearance was markedly attenuated on treatment days 3 and 4. Platelet counts returned to baseline within 1 week after discontinuation of treatment. These data indicate that RPR 109891 causes rapid and selective sequestration of platelets in the spleen.
Nedocromil Sodium Inhibits Canine Adenovirus Bronchiolitis in Beagle Puppies
Authors: Anderson Kurt A. , Lemen Richard J. , Weger Natalie S. , Huizhong Chen  , Bowers Mark C. , Witten Mark L. , Lantz R. Clark , Bice David E. , Muggenburg Bruce A.
Published: February 2008

Nedocromil sodium is a nonsteroidal anti-inflammatory drug used to control asthmatic attacks. Our hypothesis is that nedocromil sodium inhibits virus-induced airway inflammation, a common trigger of asthma. We nebulized nedocromil sodium into beagle dogs (n = 10, mean ± SEM ages: 149 ± 13 days) before and after inoculation with canine adenovirus type 2 (CAV2). Control dogs (n = 10) received saline aerosols and were either infected with CAV2 (Sa1/CAV2, n = 7, mean ± SEM ages: 140 ± 11 days) or were not infected (Sal/Sal, n = 3, ages: 143 ± 0 days). All dogs were anesthetized with choralose (80 mg/kg IV), intubated, and mechanically ventilated. Pulmonary function tests and bronchoalveolar lavage (BAL) were performed using standard techniques. Pulmonary function tests revealed no significant change between the nedocromil sodium and non-nedocromil-treated groups. The percentage of infected bronchioles was quantitated as the number of inflamed airways of 40 bronchioles examined times 100 for each dog. Nedocromil-treated dogs had significantly (p < 0.05) less mucosal inflammation (mean ± SEM, 39% ± 5%), epithelial denudation (36% ± 5%), and BAL neutrophilia (11 ± 3) than did Sal/CAV2 dogs (51% ± 6%, 57% ± 4%, and 33% ± 8%, respectively). We concluded that pretreatment with nedocromil sodium aerosols attenuated CAV2-induced airway inflammation in these beagle puppies.
Olfactory Neuron Loss in Adult Male CD Rats Following Subchronic Inhalation Exposure to Hydrogen Sulfide
Authors: Brenneman Karrie A. , Arden James R. , Gross Elizabeth A. , Dorman David C.
Published: February 2008

Dysosmia and anosmia are reported to occur following human exposure to hydrogen sulfide (H2S) gas. The clinical association between H2S exposure and olfactory dysfunction in humans necessitates evaluation of the nasal cavity and olfactory system in experimental animals used to study H2S toxicity. The purpose of this study was to subchronically expose 10-week-old male CD rats to relatively low concentrations of H2S and to histologically evaluate the nasal cavity for exposure-related lesions. Rats (n = 12/ group) were exposed via inhalation to 0, 10, 30, or 80 ppm H2S 6 h/d and 7 d/wk for 10 weeks. Following exposure to 30 and 80 ppm H2S, a significant increase in nasal lesions limited to the olfactory mucosa was observed. The lesions, which consisted of olfactory neuron loss and basal cell hyperplasia, were multifocal, bilaterally symmetrical, and had a characteristic rostrocaudal distribution pattern. Regions of the nasal cavity affected included the dorsal medial meatus and the dorsal and medial portions of the ethmoid recess. The no observed adverse effect level for olfactory lesions in this study was 10 ppm. For perspective, the American Conference of Governmental Industrial Hygienists threshold limit value (TLV) recommendation for H 2S is currently 10 ppm (proposed revision: 5 ppm), so the concentrations employed in the present study were 3 and 8 times the TLV. These findings suggest that subchronic inhalation exposure to a relatively low level of H2 S (30 ppm) can result in olfactory toxicity in rats. However, because of differences in the breathing style and nasal anatomy of rats and humans, additional research is required to determine the significance of these results for human health risk assessment.
Effects of 2,4,6-Trinitrotoluene in a Holistic Environmental Exposure Regime on a Terrestrial Salamander, Ambystoma tigrinum
Authors: Johnson Mark S. , Holladay Steven D. , Lippenholz Kelly S. , Tenkins Jennifer L. , Mccain Wilfred C.
Published: February 2008

2,4,6-Trinitrotoluene (TNT) is a defense-related environmental contaminant present at high concentrations in soil at some military installations. Tiger salamanders (Ambystoma tigrinum, family Ambystomatidae) were exposed to TNT in a soil matrix and fed earthworms that had also been exposed to TNT via contaminated soil. Such exposure was previously shown to result in significant accumulation of both TNT and TNT metabolites by salamanders. Following 14 days of combined oral and dermal exposures, salamanders were evaluated for signs of toxicity. Control and TNT-exposed salamanders gained weight (p < 0.025). In addition, organ to body weight ratios (kidney, liver, and spleen) were not affected by treatment. The function of splenic phagocytic cells was evaluated because these cells are sensitive to certain environmental chemical exposures. Neither the chemiluminescence response (H2O2 production) nor the phagocytic capacity of such cells were different between controls and treatment groups. In like manner, no changes were seen in the peripheral hematologic parameters investigated. Histopathologic evaluations were inconclusive, yet the liver revealed the presence of heavily pigmented iron-rich phagocytes (melanomacrophages). This investigation presents a realistic approach and preliminary data for investigating the effects of xenobiotic exposure in a soil matrix on a terrestrial vertebrate.