Psychostimulant use and clinical outcome of repetitive transcranial magnetic stimulation treatment of major depressive disorder.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) is an effective treatment for major depressive disorder (MDD). Psychostimulant medication use may be associated with improved rTMS outcomes, but a detailed understanding of these relationships is lacking. METHODS: We compared MDD subjects taking psychostimulants (n = 37) with those not taking one of these medications (n = 53) during a course of 30 rTMS treatments. Changes in the 30-item Inventory of Depressive Symptomatology Self Report (IDS-SR30) subscale scores were examined at treatment 30. We also subdivided subjects into three categories based on drug mechanism and looked at IDS-SR30 total score after treatments 10, 20, and 30. RESULTS: Subjects taking psychostimulants had a significantly greater overall clinical improvement than those not taking these medications at treatment 30. The psychostimulant group also improved significantly more than the control group in "sleep" and "mood/cognition," but not "anxiety/arousal" IDS-SR30 subscales. No differences were detected among individual drug categories, which may reflect the limited sample size for individual medications. There was a negative dose-response relationship for the lisdexamfetamine/dextroamphetamine group, in which lower doses were associated with better clinical outcome. CONCLUSIONS: Psychostimulant medications may enhance clinical efficacy of rTMS for MDD by preferentially impacting specific symptom domains. For some psychostimulants, these effects may be dose-dependent. Prospective clinical trials are needed to guide psychostimulant augmentation of brain stimulation therapies.

Qualitative and Quantitative Neuropathology Approaches Using Magnetic Resonance Microscopy (Diffusion Tensor Imaging) and Stereology in a Hexachlorophene Model of Myelinopathy in Sprague-Dawley Rats.

It is well established that hexachlorophene, which is used as an antibacterial agent, causes intramyelinic edema in humans and animal models. The hexachlorophene myelinopathy model, in which male Sprague-Dawley rats received 25 to 30 mg/kg hexachlorophene by gavage for up to 5 days, provided an opportunity to compare traditional neuropathology evaluations with magnetic resonance microscopy (MRM) findings. In addition, stereology assessments of 3 neuroanatomical sites were compared to quantitative measurements of similar structures by MRM. There were positive correlations between hematoxylin and eosin and luxol fast blue stains and MRM for identifying intramyelinic edema in the cingulum of corpus callosum, optic chiasm, anterior commissure (aca), lateral olfactory tracts, pyramidal tracts (py), and white matter tracts in the cerebellum. Stereology assessments were focused on the aca, longitudinal fasciculus of the pons, and py and demonstrated differences between control and treated rats, as was observed using MRM. The added value of MRM assessments was the ability to acquire qualitative 3-dimensional (3-D) images and obtain quantitative measurements of intramyelinic edema in 26 neuroanatomical sites in the intact brain. Also, diffusion tensor imaging (fractional anisotropy [FA]) indicated that there were changes in the cytoarchitecture of the white matter as detected by decreases in the FA in the treated compared to the control rats. This study demonstrates creative strategies that are possible using qualitative and quantitative assessments of potential white matter neurotoxicants in nonclinical toxicity studies. Our results lead us to the conclusion that volumetric analysis by MRM and stereology adds significant value to the standard 2-D microscopic evaluations.

The Assessment of Longitudinal Sections of Rat Female Reproductive Tissues for NTP 2-Year Toxicity and Carcinogenicity Studies.

The National Toxicology Program (NTP) now uses an extended longitudinal sectioning protocol for the uterus to better evaluate female rodent reproductive tract toxicity for all developmental and reproductive toxicology and 2-year toxicity and carcinogenicity bioassays. The previous protocol for toxicity/carcinogenicity studies involved 1 cross section midway through each uterine horn and collection of uterine cervix and vagina only if gross lesions were present. Here we compare the histological findings of the original cross sections with the additional longitudinal sections of residual uterine tissues of 7 chronic NTP rat bioassays. The goal of this study was to determine whether there might be any advantages to examining additional uterine tissue. The longitudinal protocol allowed for 10 to 20 times more uterine tissue for evaluation. Results indicate that the potential advantages of a more complete evaluation of female reproductive tract tissue include increased detection of reproductive targets, increased detection of neoplastic and nonneoplastic lesions, improved detection of tissue origin of neoplasms, less reliance on gross identification of lesions, improved accuracy in the application of severity grades, and increased detection of preneoplastic or subtle lesions.

Chemical Reactivity and Respiratory Toxicity of the α-Diketone Flavoring Agents: 2,3-Butanedione, 2,3-Pentanedione, and 2,3-Hexanedione.

Occupational exposure to 2,3-butanedione (BD) vapors has been associated with severe respiratory disease leading to the use of potentially toxic substitutes. We compared the reactivity and respiratory toxicity of BD with that of two structurally related substitutes, 2,3-pentanedione (PD) and 2,3-hexanedione (HD). Chemical reactivity of the diketones with an arginine substrate decreased with increasing chain length (BD > PD > HD). Animals were evaluated the morning after a 2-week exposure to 0, 100, 150, or 200 ppm BD, PD, or HD (postexposure) or 2 weeks later (recovery). Bronchial fibrosis was observed in 5/5 BD and 5/5 PD rats at 200 ppm and in 4/6 BD and 6/6 PD rats at 150 ppm in the postexposure groups. Following recovery, bronchial fibrosis was observed in all surviving rats exposed to 200 ppm BD (5/5) or PD (3/3) and in 2/10 BD and 7/9 PD rats exposed to 150 ppm. Bronchial fibrosis was observed only in 2/12 HD-exposed rats in the 200 ppm postexposure group. Patchy interstitial fibrosis affected lungs of recovery groups exposed to 200 ppm PD (3/3) or BD (1/5) and to 150 ppm PD (4/9) or BD (7/10) and correlated with pulmonary function deficits. BD and PD were more reactive and produced more bronchial fibrosis than HD.

Comparison of Renal Amyloid and Hyaline Glomerulopathy in B6C3F1 Mice: An NTP Retrospective Study.

Due to potential misdiagnosis of hyaline glomerulopathy (HG) for amyloidosis, a retrospective study of B6C3F1 mice from the National Toxicology Program (NTP) archives was undertaken to determine whether HG had occurred in prior NTP studies and, if so, whether these 2 glomerular lesions could be routinely discriminated. Kidney slides from 7 amyloid-positive control mice, 2 HG-positive control mice, 3 normal or negative control mice, and 41 potential HG mice (with renal-only deposits previously diagnosed as amyloid) were evaluated using hematoxylin and eosin (H&E), periodic acid Schiff (PAS), Congo red (CR), and Masson's trichrome (MT) stains. Utilizing these techniques, HG was reliably distinguished from amyloidosis. All 41 potential HG mice had glomerular deposits histochemically inconsistent with amyloid; the deposits were PAS positive and CR negative. Four of the 41 mice were selected for transmission electron microscopy of the glomerular deposits; ultrastructurally, the deposits in these animals were consistent with HG and not amyloid. Our findings indicate that HG is a spontaneous lesion in B6C3F1 mice of low occurrence, is commonly misdiagnosed as amyloidosis, and is more likely than amyloid to cause glomerular deposits in mice without evidence of deposits in other tissues. Also, HG can be distinguished from amyloid on H&E evaluation; however, the distinction is improved with use of PAS or CR staining and/or ultraviolet evaluation.

Inhaled diesel emissions generated with cerium oxide nanoparticle fuel additive induce adverse pulmonary and systemic effects.

Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here, we evaluated whether DECe results in greater adverse pulmonary effects compared with DE. Male Sprague Dawley rats were exposed to filtered air, DE, or DECe for 5 h/day for 2 days. N-acetyl glucosaminidase activity was increased in bronchial alveolar lavage fluid (BALF) of rats exposed to DECe but not DE. There were also marginal but insignificant increases in several other lung injury biomarkers in both exposure groups (DECe > DE for all). To further characterize DECe toxicity, rats in a second study were exposed to filtered air or DECe for 5 h/day for 2 days or 4 weeks. Tissue analysis indicated a concentration- and time-dependent accumulation of lung and liver cerium followed by a delayed clearance. The gas-phase and high concentration of DECe increased lung inflammation at the 2-day time point, indicating that gas-phase components, in addition to particles, contribute to pulmonary toxicity. This effect was reduced at 4 weeks except for a sustained increase in BALF γ-glutamyl transferase activity. Histopathology and transmission electron microscopy revealed increased alveolar septa thickness due to edema and increased numbers of pigmented macrophages after DECe exposure. Collectively, these findings indicate that DECe induces more adverse pulmonary effects on a mass basis than DE. In addition, lung accumulation of cerium, systemic translocation to the liver, and delayed clearance are added concerns to existing health effects of DECe.

Comparative time course profiles of phthalate stereoisomers in mice.

More efficient models are needed to assess potential carcinogenicity hazard of environmental chemicals based on early events in tumorigenesis. Here, we investigated time course profiles for key events in an established cancer mode of action. Using a case study approach, we evaluated two reference phthalates, di(2-ethylhexyl) phthalate (DEHP) and its stereoisomer di-n-octyl phthalate (DNOP), across the span of a two-year carcinogenicity bioassay. Male B6C3F1 mice received diets with no phthalate added (control), DEHP at 0.12, 0.60, or 1.20%, or DNOP at 0.10, 0.50, or 1.00% (n = 80-83/group) for up to 104 weeks with six interim evaluations starting at week 4. Mean phthalate doses were 139, 845, and 3147 mg/kg/day for DEHP and 113, 755, and 1281 mg/kg/day for DNOP groups, respectively. Incidence and number of hepatocellular tumors (adenoma and/or carcinoma) were greater at ≥ 60 weeks for all DEHP groups with time and dose trends, whereas DNOP had no significant effects. Key events supported a peroxisome proliferator-activated receptor alpha (PPARα) mode of action for DEHP, with secondary cytotoxicity at the high dose, whereas DNOP induced modest increases in PPARα activity without proliferative or cytotoxic effects. Threshold estimates for later tumorigenic effects were identified at week 4 for relative liver weight (+24%) and PPARα activity (+79%) relative to the control group. Benchmark doses (BMDs) for these measures at week 4 clearly distinguished DEHP and DNOP and showed strong concordance with values at later time points and tumorigenic BMDs. Other target sites included testis and kidney, which showed degenerative changes at higher doses of DEHP but not DNOP. Our results highlight marked differences in the chronic toxicity profiles of structurally similar phthalates and demonstrate quantitative relationships between early bioindicators and later tumor outcomes.

Proceedings of the 2013 National Toxicology Program Satellite Symposium.

The 2013 annual National Toxicology Program (NTP) Satellite Symposium, entitled "Pathology Potpourri," was held in Portland, Oregon, in advance of the Society of Toxicologic Pathology's 32nd annual meeting. The goal of the NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers' presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included a caudal tail vertebra duplication in mice; nephroblastematosis in rats; ectopic C cell tumor in a hamster; granular cell aggregates/tumor in the uterus of a hamster; Pneumocystis carinii in the lung of a rat; iatrogenic chronic inflammation in the lungs of control rats; hepatoblastoma arising within an adenoma in a mouse; humoral hypercalcemia of benignancy in a transgenic mouse; acetaminophen-induced hepatotoxicity in rats; electron microscopy images of iatrogenic intraerythrocytic inclusions in transgenic mice; questionable hepatocellular degeneration/cell death/artifact in rats; atypical endometrial hyperplasia in rats; malignant mixed Müllerian tumors/carcinosarcomas in rats; differential diagnoses of proliferative lesions of the intestine of rodents; and finally obstructive nephropathy caused by melamine poisoning in a rat.

Morphologic aspects of rodent cardiotoxicity in a retrospective evaluation of National Toxicology Program studies.

The heart is increasingly recognized as a target for toxicity. As studies in laboratory rodents are commonly used to investigate the potential toxicity of various agents, the identification and characterization of lesions of cardiotoxicity is of utmost importance. Although morphologic criteria have been established for degenerative myocardial lesions in rats and mice, differentiation of spontaneously occurring lesions from toxin-induced or toxin-related lesions remains difficult. A retrospective light microscopic evaluation was performed on the hearts of F344 rats and B6C3F(1) mice from National Toxicology Program (NTP) studies of six chemicals identified in the NTP database in which treatment-induced myocardial toxicity was present. Two previously defined myocardial lesions were observed: "cardiomyopathy" that occurred spontaneously or as a treatment-related effect and "myocardial degeneration" that occurred as a treatment-related effect. Both lesions consisted of the same basic elements, beginning with myofiber degeneration and necrosis, with varying amounts of inflammation, interstitial cell proliferation, and eventual fibrosis. This observation is indicative of the heart's limited repertoire of responses to myocardial injury, regardless of the nature of the inciting agent. A prominent differentiating factor between spontaneous and treatment-induced lesions was distribution and lesion onset. Once the respective lesions had undergone fibrosis, however, they generally appeared morphologically indistinguishable.

Photodynamic therapy of vertebral metastases: evaluating tumor-to-neural tissue uptake of BPD-MA and ALA-PpIX in a murine model of metastatic human breast carcinoma.

Photodynamic therapy has been successfully applied to numerous cancers. Its potential to treat cancer metastases in the spine has been demonstrated previously in a preclinical animal model. The aim of this study was to test two photosensitizers, benzoporphyrin-derivative monoacid ring A (BPD-MA) and by 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX), for their potential use to treat bony metastases. The difference in photosensitizer concentration in the spinal cord and the surrounding tumor-bearing vertebrae was of particular interest to assess the risk of potential collateral damage to the spinal cord. Vertebral metastases in a rat model were generated by intracardiac injection of human breast cancer cells. When tumor growth was confirmed, photosensitizers were injected systemically and the animals were euthanized at different time points. The following tissues were harvested: liver, kidney, ovaries, appendicular bone, spinal cord and lumbar vertebrae. Photosensitizer tissue concentration of BPD-MA or PpIX was determined by fluorescence spectrophotometry. In contrast to BPD-MA, ALA-PpIX did not demonstrate an appreciable difference in the uptake ratio in tumor-bearing vertebrae compared to spinal cord. The highest ratio for BPD-MA concentration was found 15 min after injection, which can be recommended for therapy in this model.

Characterization of spontaneous and chemically induced cardiac lesions in rodent model systems: the national toxicology program experience.

Induction of heart disease can be related to exposure to a number of agents, including environmental chemicals. Studies with laboratory rodents are commonly used to identify cardiotoxic agents and to investigate mechanisms of toxicity. This study was conducted to characterize spontaneous and chemically-induced rodent heart lesions. A retrospective light-microscopic evaluation was performed on the hearts of F344 rats and B6C3F1 mice from National Toxicology Program studies of six chemicals in which chemically-induced myocardial toxicity was present: oxymetholone, monochloroacetic acid, 3,3'-4,4'- tetrachoroazoxybenzene, diethanolamine, urethane, and methyl bromide. Two myocardial lesions were observed: cardiomyopathy (multifocal myofiber degeneration that could occur spontaneously or as a treatment effect) and degeneration (diffuse myofiber degeneration that was clearly related to treatment). Oxymetholone produced cardiotoxicity that was apparent as an increase in the incidence and average severity of cardiomyopathy. The remaining five chemicals produced degeneration, which appeared morphologically similar with each of the chemicals. Based on available information concerning possible mechanisms by which each of these chemicals may induce cardiotoxicity, this evaluation indicated it may be possible to place the chemicals into two main categories: (1) those that primarily affected the coronary vasculature with secondary effects on the myocardium (oxymetholone), and (2) those that had a direct toxic effect on the myocardial cells (the remaining five chemicals). Beyond this, however, light-microscopic findings did not indicate any specific mechanisms. Additional morphologic evaluations, such as electron microscopy or special histochemical or immunostains, may help identify specific subcellular sites of toxic damage, which in turn can indicate appropriate types of molecular mechanistic studies.