Renard L. Thomas

Analysis of stress responsive genes induced by single-walled carbon nanotubes in BJ Foreskin cells.

It is known that the mechanical properties of clay-reinforced nanocomposites are significantly affected by the dispersion of clay particles in the matrix. In this study, the effect of surface-treatment of Montmorillonite (MMT) on the fracture behavior of MMT/epoxy nanocomposite was investigated. For this purpose, fracture tests were performed using samples with three different clay concentration level. After fracture tests, SEM analysis was made on the fracture surfaces to examine the fracture mechanism. It was found that the MMT treatment using 3-aminopropyltriethoxysilane enhanced the fracture toughness increased of the MMT/epoxy nanocomposite. This is due to the improved intercalation effect and interfacial strength between MMT and epoxy matrix.

ACTIVATION OF NUCLEAR TRANSCRIPTION FACTOR–κB IN MOUSE BRAIN INDUCED BY A SIMULATED MICROGRAVITY ENVIRONMENT

SummaryMicrogravity induces inflammatory responses and modulates immune functions that may increase oxidative stress. Exposure to a microgravity environment induces adverse neurological effects; however, there is little research exploring the etiology of these effects resulting from exposure to such an environment. It is also known that spaceflight is associated with increase in oxidative stress; however, this phenomenon has not been reproduced in land-based simulated microgravity models. In this study, an attempt has been made to show the induction of reactive oxygen species (ROS) in mice brain, using ground-based microgravity simulator. Increased ROS was observed in brain stem and frontal cortex with concomitant decrease in glutathione, on exposing mice to simulated microgravity for 7 d. Oxidative stress-induced activation of nuclear factor-kappaB was observed in all the regions of the brain. Moreover, mitogen-activated protein kinase kinase was phosphorylated equally in all regions of the brain exposed to simulated microgravity. These results suggest that exposure of brain to simulated microgravity can induce expression of certain transcription factors, and these have been earlier argued to be oxidative stress dependent.

Pulmonary biocompatibility assessment of inhaled single-wall and multiwall carbon nanotubes in BALB/c mice.

With the widespread application of carbon nanotubes (CNTs) in diverse commercial processes, scientists are now concerned about the potential health risk of occupational exposures. In this study, CNT-induced pulmonary toxicity was investigated by exposing BALB/c mice to aerosolized single-wall (SW) CNT and multiwall (MW) CNT (5 μg/g of mice) for 7 consecutive days in a nose-only exposure system. Microscopic studies showed that inhaled CNTs were homogeneously distributed in the mouse lung. The total number of bronchoalveolar lavage polymorphonuclear leukocytes recovered from the mice exposed to SWCNT and MWCNT (1.2 × 106 ± 0.52 and 9.87 × 105 ± 1.45; respectively) was significantly greater than control mice (5.46 × 105 ± 0.78). Rapid development of pulmonary fibrosis in mice that inhaled CNT was also confirmed by significant increases in the collagen level. The lactate dehydrogenase levels were increased nearly 2- and 2.4-fold in mice that inhaled SWCNT and MWCNT, respectively, as compared with control mice. In addition, exposure of CNTs to mice showed a significant (p < 0.05) reduction of antioxidants (glutathione, superoxide dismutase, and catalase) and induction of oxidants (myloperoxidase, oxidative stress, and lipid peroxidation) compared with control. Apoptosis-related proteins such as caspase-3 and -8 activities were also significantly increased in mice that inhaled CNT than in control mice. Together, this study shows that inhaled CNTs induce inflammation, fibrosis, alteration of oxidant and antioxidant levels, and induction of apoptosis-related proteins in the lung tissues to trigger cell death.

Proteomic analysis of mouse hypothalamus under simulated microgravity.

Exposure to altered microgravity during space travel induces changes in the brain and these are reflected in many of the physical behavior seen in the astronauts. The vulnerability of the brain to microgravity stress has been reviewed and reported. Identifying microgravity-induced changes in the brain proteome may aid in understanding the impact of the microgravity environment on brain function. In our previous study we have reported changes in specific proteins under simulated microgravity in the hippocampus using proteomics approach. In the present study the profiling of the hypothalamus region in the brain was studied as a step towards exploring the effect of microgravity in this region of the brain. Hypothalamus is the critical region in the brain that strictly controls the pituitary gland that in turn is responsible for the secretion of important hormones. Here we report a 2-dimensional gel electrophoretic analysis of the mouse hypothalamus in response to simulated microgravity. Lowered glutathione and differences in abundance expression of seven proteins were detected in the hypothalamus of mice exposed to microgravity. These changes included decreased superoxide dismutase-2 (SOD-2) and increased malate dehydrogenase and peroxiredoxin-6, reflecting reduction of the antioxidant system in the hypothalamus. Taken together the results reported here indicate that oxidative imbalance occurred in the hypothalamus in response to simulated microgravity.

Altered cytokine expression in tissues of mice subjected to simulated microgravity.

Space flight is known to induce microgravity-associated immune dysfunction in humans, non-human primates and rodents. To understand the mechanism underlying these defects, several studies in rodents have been conducted in a ground-based antiorthostatic suspension (AOS) model that would mimic the effects of microgravity. In all these in vivo studies that showed the effects on cytokine profiles actually investigated the ex vivo production from culturing the cells isolated from whole organism that was exposed to space flight and/or microgravity. So, the purpose of the study was to examine the in vivo expression of cytokines in mice in immunologically important tissue environments of mice that were subjected to AOS. Cytokines such as Interleukin-1β (IL-1β), IL-2, IL-3, IL-6, Interferon-γ (IFN-γ) and Tumor Necrosis Factor-α (TNF-α) were measured by Enzyme Linked Immunosorbent Assay (ELISA) in the homogenates of spleen tissue, lymph nodes and also in serum of AOS mice and compared with that of control mice. AOS induced no change in the IL-3 levels, but IL-1β was increased significantly whereas IL-2 levels decreased in spleen, lymph nodes and serum. IL-6 levels did not differ in spleen but were significantly increased in lymph nodes and serum of AOS mice. IFN-γ levels in spleen did not change but showed nonsignificant reduction in lymph nodes and significant reduction in serum in response to AOS. TNF-α levels in spleen and serum were unchanged and increased in lymph nodes. This in vivo cytokine study confirms the earlier findings that microgravity-simulated conditions induce tissue-specific immune response (Mol Cell Biochem 266: 79–85, 2004)

Simulated microgravity activates apoptosis and NF-κB in mice testis

Microgravity is known to have significant effect on all aspects of reproductive function in animal models. Recent studies have also shown that microgravity induces changes at the cellular level, including apoptosis. Our effort here was to study the effect of simulated microgravity on caspase-8 and the caspase-3 activities, the effectors of the apoptotic pathway and on the transcription factor NF-κB a signaling molecule in mouse testis. Morey-Holton hind limb suspension model was used to simulate microgravity. Caspase-8 and 3 fluorometric assays were carried out and HLS mice testis exhibited a 51% increase in caspase-8 and caspase-3 compared to the controls. A sandwich ELISA-based immunoassay was carried out for detection of NF-κB which again significantly increased in the test mice. Testosterone levels were measured using an ELISA kit and in HLS mice the decrease was significant. There was also a significant decrease in testis weight in the test mice. Simulated microgravity activates caspase 8, 3 and NF-κB necessary to stimulate the apoptotic pathway in mice testis. This may account for the drop in testis weight and testosterone level further affecting testicular physiology and function.

Measurement of Volatile Organic Compounds in the Urban Atmosphere of Harris County, Texas

Volatile organic compounds (VOCs) are a major component of urban air pollution. It is well documented that exposure to certain types of VOCs can cause adverse health effects such as cancer, immune and neurological damage, and reproductive and endocrine disorders. Urban air samples were collected at five locations in Harris County, Texas to determine the measurement of VOCs in the ambient air of residential areas in close proximity to industrial facilities that emit toxic air pollutants into the air. Three locations used in this study were located along the Houston Ship Channel (HSC), in the heart of one of the largest petrochemical complexes in the nation. Two other sampling locations were located many miles away from the ship channel and any industrial facilities that are required to report toxic air emissions. Air samples were collected daily over an 8-h period from December 2002 to March 2003. The samples were collected in 6-L stainless steel Silonite-coated canisters and analyzed using a modified version of EPA Method TO-15. A total of 53 compounds was quantitated using a gas chromatograph mass spectrometer system coupled to a cryogenic preconcentrator. Eighteen alkanes and oxygenated compounds were identified, along with 7 alkenes and 5 aromatic compounds. Several alkanes such as butane, isobutane, 2-methyl butane, and pentane were detected at all five sites. The total VOC concentrations determined were highest at two of the industrial sites and lowest at the site farthest away from the ship channel and any industrial facilities. This study concluded that the atmosphere near Harris Countys industrial complex had higher concentrations of VOCs than the atmosphere in areas farther away from the HSC. The atmosphere of areas downwind from emission sources were found to be directly affected by toxic air emissions from industrial process but not at the levels seen in areas closer to the HSC.

Activation of activator protein-1 in mouse brain regions exposed to simulated microgravity

SummaryMicrogravity induces stress, and the brain is one of the targets that is more influenced in this environment. Alteration in transcription factors can have enormous effect because of discrepancy in the signaling process of the cells. Activator protein-1 (AP-1) is a stress-regulated transcription factor and is involved in the regulation of physiological and pathological stimuli that include cytokines, growth factors, and stress signals. In the present study, an attempt has been made to observe the effect of a microgravity environment on the activation of AP-1 in the mouse brain. Our results show tha0105 AP-1 transcription factor is activated in simulated microgravity conditions in different regions of the brain. The activation of the AP-1 is dependent upon the increased kinase activity of c-Jun NH-terminal2 kinase-1. These results suggest tha0105 microgravity stress in the brain can elicit AP-1 activity.