Exposure to emissions generated by 3-dimensional printing with polycarbonate: effects on peripheral vascular function, cardiac vascular morphology and expression of markers of oxidative stress in male rat cardiac tissue

Three-dimensional (3D) printing with polycarbonate (PC) plastic occurs in manufacturing settings, homes, and schools. Emissions generated during printing with PC stock and bisphenol-A (BPA), an endocrine disrupter in PC, may induce adverse health effects. Inhalation of 3D printer emissions, and changes in endocrine function may lead to cardiovascular dysfunction. The goal of this study was to determine whether there were any changes in markers of peripheral or cardiovascular dysfunction in animals exposed to PC-emissions. Male Sprague Dawley rats were exposed to PC-emissions generated by 3D printing for 1, 4, 8, 15 or 30 d. Exposure induced a reduction in the expression of the antioxidant catalase (Cat) and endothelial nitric oxide synthase (eNos). Endothelin and hypoxia-induced factor 1α transcripts increased after 30 d. Alterations in transcription were associated with elevations in immunostaining for estrogen and androgen receptors, nitrotyrosine, and vascular endothelial growth factor in cardiac arteries of PC-emission exposed animals. There was also a reduction eNOS immunostaining in cardiac arteries from rats exposed to PC-emissions. Histological analyses of heart sections revealed that exposure to PC-emissions resulted in vasoconstriction of cardiac arteries and thickening of the vascular smooth muscle wall, suggesting there was a prolonged vasoconstriction. These findings are consistent with studies showing that inhalation 3D-printer emissions affect cardiovascular function. Although BPA levels in animals were relatively low, exposure-induced changes in immunostaining for estrogen and androgen receptors in cardiac arteries suggest that changes in the action of steroid hormones may have contributed to the alterations in morphology and markers of cardiac function.

Biological effects of diesel exhaust inhalation. III cardiovascular function

OBJECTIVE

Inhalation of diesel exhaust (DE) has been shown to be an occupational hazard in the transportation, mining, and gas and oil industries. DE also contributes to air pollution, and therefore, is a health hazard to the general public. Because of its effects on human health, changes have been made to diesel engines to reduce both the amounts of particulate matter and volatile fumes they generate. The goal of the current study was to examine the effects of inhalation of diesel exhaust.

MATERIALS AND METHODS

The study presented here specifically examines the effects of exposure to 0.2 and 1.0 mg/m3 DE or filtered air (6h/d for 4 d) on measures of peripheral and cardio-vascular function, and biomarkers of heart and kidney dysfunction in male rats. A Tier 2 engine used in oil and gas fracking operations was used to generate the diesel exhaust.

RESULTS

Exposure to 0.2 mg/m3 DE resulted in an increase in blood pressure 1d following the last exposure, and increases in dobutamine-induced cardiac output and stroke volume 1 and 27d after exposure. Changes in peripheral vascular responses to norepinephrine and acetylcholine were minimal as were changes in transcript expression in the heart and kidney. Exposure to 1.0 mg/m3 DE did not result in major changes in blood pressure, measures of cardiac function, peripheral vascular function or transcript expression.

DISCUSSION AND CONCLUSIONS

Based on the results of this study, we suggest that exposure to DE generated by a Tier 2 compliant diesel engine generates acute effects on biomarkers indicative of cardiovascular dysfunction. Recovery occurs quickly with most measures of vascular/cardiovascular function returning to baseline levels by 7d following exposure.

Applied Force Alters Sensorineural and Peripheral Vascular Function in a Rat Model of Hand-Arm Vibration Syndrome

OBJECTIVE

This study described the effects of applied force (grip) on vascular and sensorineural function in an animal model of hand-arm vibration syndrome (HAVS).

METHODS

Rat tails were exposed to 0, 2, or 4 N of applied force 4 hr/d for 10 days. Blood flow and sensitivity to transcutaneous electrical stimulation and pressure were measured.

RESULTS

Applied force increased blood flow but reduced measures of arterial plasticity. Animals exposed to force tended to be more sensitive to 250-Hz electrical stimulation and pressure applied to the tail.

CONCLUSIONS

Effects of applied force on blood flow and sensation are different than those of vibration. Studies examining co-exposures to force and vibration will provide data that can be used to determine how these factors affect risk of workers developing vascular and sensorineural dysfunction (ie, HAVS).

Inhalation of polycarbonate emissions generated during 3D printing processes affects neuroendocrine function in male rats

Three-dimensional (3D) printing of manufactured goods has increased in the last 10 years. The increased use of this technology has resulted in questions regarding the influence of inhaling emissions generated during printing. The goal of this study was to determine if inhalation of particulate and/or toxic chemicals generated during printing with polycarbonate (PC) plastic affected the neuroendocrine system. Male rats were exposed to 3D-printer emissions (592 µg particulate/m3 air) or filtered air for 4 h/day (d), 4 days/week and total exposures lengths were 1, 4, 8, 15 or 30 days. The effects of these exposures on hormone concentrations, and markers of function and/or injury in the olfactory bulb, hypothalamus and testes were measured after 1, 8 and 30 days exposure. Thirty days of exposure to 3D printer emissions resulted in reductions in thyroid stimulating hormone, follicle stimulating hormone and prolactin. These changes were accompanied by (1) elevation in markers of cell injury; (2) reductions in active mitochondria in the olfactory bulb, diminished gonadotropin releasing hormone cells and fibers as well as less tyrosine hydroxylase immunolabeled fibers in the arcuate nucleus; and (3) decrease in spermatogonium. Polycarbonate plastics may contain bisphenol A, and the effects of exposure to these 3D printer-generated emissions on neuroendocrine function are similar to those noted following exposure to bisphenol A.

A novel rat-tail model for studying human finger vibration health effects

It has been hypothesized that the biodynamic responses of the human finger tissues to vibration are among the major stimuli that cause vibration health effects. Furthermore, the finger contact pressure can alter these effects. It is difficult to test these hypotheses using human subjects or existing animal models. The objective of this study was to develop a new rat-tail vibration model to investigate the combined effects of vibration and contact pressure and to identify their relationships with the biodynamic responses. Physically, the new exposure system was developed by adding a loading device to an existing rat-tail model. An analytical model of the rat-tail exposure system was proposed and used to formulate the methods for quantifying the biodynamic responses. A series of tests with six tails dissected from rat cadavers were conducted to test and evaluate the new model. The experimental and modeling results demonstrate that the new model behaves as predicted. Unlike the previous model, the vibration strain and stress of the rat tail does not depend primarily on the vibration response of the tail itself but on that of the loading device. This makes it possible to quantify and control the biodynamic responses conveniently and reliably by measuring the loading device response. This study also identified the basic characteristics of the tail biodynamic responses in the exposure system, which can be used to help design the experiments for studying vibration biological effects.

Effects of whole-body vibration on reproductive physiology in a rat model of whole-body vibration

Findings from epidemiological studies suggest that occupational exposure to whole-body vibration (WBV) may increase the risk of miscarriage and contribute to a reduction in fertility rates in both men and women. However, workers exposed to WBV may also be exposed to other risk factors that contribute to reproductive dysfunction. The goal of this experiment was to examine the effects of WBV on reproductive physiology in a rat model. Male and female rats were exposed to WBV at the resonant frequency of the torso (31.5 Hz, 0.3 g amplitude) for 4 hr/day for 10 days. WBV exposure resulted in a significant reduction in number of developing follicles, and decrease in circulating estradiol concentrations, ovarian luteinizing hormone receptor protein levels, and marked changes in transcript levels for several factors involved in follicular development, cell cycle, and steroidogenesis. In males, WBV resulted in a significant reduction in spermatids and circulating prolactin levels, elevation in number of males having higher circulating testosterone concentrations, and marked alterations in levels of transcripts associated with oxidative stress, inflammation, and factors involved in regulating the cell cycle. Based upon these findings data indicate that occupational exposure to WBV contributes to adverse alterations in reproductive physiology in both genders that may lead to reduction in fertility.

Biological effects of crude oil vapor. IV. Cardiovascular effects

Workers in the oil and gas extraction industry are at risk of inhaling volatile organic compounds. Epidemiological studies suggest oil vapor inhalation may affect cardiovascular health. Thus, in this hazard identification study we investigated the effects of inhalation of crude oil vapor (COV) on cardiovascular function. Male rats were exposed to air or COV (300 ppm) for 6 h (acute), or 6 h/day × 4 d/wk. × 4 wk. (sub-chronic). The effects of COV inhalation were assessed 1, 28, and 90 d post-exposure. Acute exposure to COV resulted in reductions in mean arterial and diastolic blood pressures 1 and 28 d after exposure, changes in nitrate-nitrite and H₂O₂ levels, and in the expression of transcripts and proteins that regulate inflammation, vascular remodeling, and the synthesis of nitric oxide (NO) in the heart and kidneys. The sub-chronic exposure resulted in a reduced sensitivity to α₁-adrenoreceptor-mediated vasoconstriction in vitro 28 d post-exposure, and a reduction in oxidative stress in the heart. Sub-chronic COV exposure led to alterations in the expression of NO synthases and anti-oxidant enzymes, which regulate inflammation and oxidative stress in the heart and kidneys. There seems to be a balance between changes in the expression of transcripts associated with the generation of reactive oxygen species (ROS) and antioxidant enzymes. The ability of antioxidant enzymes to reduce or inhibit the effects of ROS may allow the cardiovascular system to adapt to acute COV exposures. However, sub-chronic exposures may result in longer-lasting negative health consequences on the cardiovascular system.

Extreme oxidant amounts produced by lightning in storm clouds

Lightning increases the atmosphere's ability to cleanse itself by producing nitric oxide (NO), leading to atmospheric chemistry that forms ozone (O₃) and the atmosphere's primary oxidant, the hydroxyl radical (OH). Our analysis of a 2012 airborne study of deep convection and chemistry demonstrates that lightning also directly generates the oxidants OH and the hydroperoxyl radical (HO₂). Extreme amounts of OH and HO₂ were discovered and linked to visible flashes occurring in front of the aircraft and to subvisible discharges in electrified anvil regions. This enhanced OH and HO₂ is orders of magnitude greater than any previous atmospheric observation. Lightning-generated OH in all storms happening at the same time globally can be responsible for a highly uncertain, but substantial, 2 to 16% of global atmospheric OH oxidation.

Biological effects of inhaled hydraulic fracturing sand dust. VI. Cardiovascular effects

Hydraulic fracturing is used to access oil and natural gas reserves. This process involves the high-pressure injection of fluid to fracture shale. Fracking fluid contains approximately 95% water, chemicals and 4.5% fracking sand. Workers may be exposed to fracking sand dust (FSD) during the manipulation of the sand, and negative health consequences could occur if FSD is inhaled. In the absence of any information about its potential toxicity, a comprehensive rat animal model study (see Fedan et al., 2020) was designed to investigate the bioactivities of several FSDs in comparison to MIN-U-SIL® 5, a respirable α-quartz reference dust used in previous animal models of silicosis, in several organ systems. The goal of this study was to assess the effects of inhalation of one FSD, i.e., FSD 8, on factors and tissues that affect cardiovascular function. Male rats were exposed to 10 or 30 mg/m³ FSD (6 h/d for 4 d) by whole body inhalation, with measurements made 1, 7 or 27 d post-exposure. One day following exposure to 10 mg/m³ FSD the sensitivity to phenylephrine-induced vasoconstriction in tail arteries in vitro was increased. FSD exposure at both doses resulted in decreases in heart rate (HR), HR variability, and blood pressure in vivo. FSD induced changes in hydrogen peroxide concentrations and transcript levels for pro-inflammatory factors in heart tissues. In kidney, expression of proteins indicative of injury and remodeling was reduced after FSD exposure. When analyzed using regression analysis, changes in proteins involved in repair and remodeling were correlated. Thus, it appears that inhalation of FSD does have some prolonged effects on cardiovascular, and, possibly, renal function. The findings also provide information regarding potential mechanisms that may lead to these changes, and biomarkers that could be examined to monitor physiological changes that could be indicative of impending cardiovascular dysfunction.

Exposure to graphene nanoparticles induces changes in measures of vascular/renal function in a load and form-dependent manner in mice

Graphenes isolated from crystalline graphite are used in several industries. Employees working in the production of graphenes may be at risk of developing respiratory problems attributed to inhalation or contact with particulate matter (PM). However, graphene nanoparticles might also enter the circulation and accumulate in other organs. The aim of this study was to examine how different forms of graphene affect peripheral vascular functions, generation of reactive oxygen species (ROS) and changes in gene expression that may be indicative of cardiovascular and/or renal dysfunction. In the first investigation, different doses of graphene nanoplatelets were administered to mice via oropharyngeal aspiration. These effects were compared to those of dispersion medium (DM) and carbon black (CB). Gene expression alterations were observed in the heart for CB and graphene; however, only CB produced changes in peripheral vascular function. In the second study, oxidized forms of graphene were administered. Both oxidized forms increased the sensitivity of peripheral blood vessels to adrenoreceptor-mediated vasoconstriction and induced changes in ROS levels in the heart. Based upon the results of these investigations, exposure to graphene nanoparticles produced physiological and alterations in ROS and gene expression that may lead to cardiovascular dysfunction. Evidence indicates that the effects of these particles may be dependent upon dose and graphene form to which an individual may be exposed to.

Acute Vibration Induces Peripheral Nerve Sensitization in a Rat Tail Model: Possible Role of Oxidative Stress and Inflammation

Prolonged occupational exposure to hand-held vibrating tools leads to pain and reductions in tactile sensitivity, grip strength and manual dexterity. The goal of the current study was to use a rat-tail vibration model to determine how vibration frequency influences factors related to nerve injury and dysfunction. Rats were exposed to restraint, or restraint plus tail vibration at 62.5 Hz or 250 Hz. Nerve function was assessed using the current perception threshold (CPT) test. Exposure to vibration at 62.5 and 250 Hz, resulted in a reduction in the CPT at 2000 and 250-Hz electrical stimulation (i.e. increased Aβ and Aδ, nerve fiber sensitivity). Vibration exposure at 250 Hz also resulted in an increased sensitivity of C-fibers to electrical stimulation and thermal nociception. These changes in nerve fiber sensitivity were associated with increased expression of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in ventral tail nerves, and increases in circulating concentrations of IL-1 β in rats exposed to 250-Hz vibration. There was an increase in glutathione, but no changes in other measures of oxidative activity in the peripheral nerve. However, measures of oxidative stress were increased in the dorsal root ganglia (DRG). These changes in pro-inflammatory factors and markers of oxidative stress in the peripheral nerve and DRG were associated with inflammation, and reductions in myelin basic protein and post-synaptic density protein (PSD)-95 gene expression, suggesting that vibration-induced changes in sensory function may be the result of changes at the exposed nerve, the DRG and/or the spinal cord.

Contact area affects frequency-dependent responses to vibration in the peripheral vascular and sensorineural systems

Repetitive exposure to hand-transmitted vibration is associated with development of peripheral vascular and sensorineural dysfunctions. These disorders and symptoms associated with it are referred to as hand-arm vibration syndrome (HAVS). Although the symptoms of the disorder have been well characterized, the etiology and contribution of various exposure factors to development of the dysfunctions are not well understood. Previous studies performed using a rat-tail model of vibration demonstrated that vascular and peripheral nervous system adverse effects of vibration are frequency-dependent, with vibration frequencies at or near the resonant frequency producing the most severe injury. However, in these investigations, the amplitude of the exposed tissue was greater than amplitude typically noted in human fingers. To determine how contact with vibrating source and amplitude of the biodynamic response of the tissue affects the risk of injury occurring, this study compared the influence of frequency using different levels of restraint to assess how maintaining contact of the tail with vibrating source affects the transmission of vibration. Data demonstrated that for the most part, increasing the contact of the tail with the platform by restraining it with additional straps resulted in an enhancement in transmission of vibration signal and elevation in factors associated with vascular and peripheral nerve injury. In addition, there were also frequency-dependent effects, with exposure at 250 Hz generating greater effects than vibration at 62.5 Hz. These observations are consistent with studies in humans demonstrating that greater contact and exposure to frequencies near the resonant frequency pose the highest risk for generating peripheral vascular and sensorineural dysfunction.

Transcriptional Pathways Altered in Response to Vibration in a Model of Hand-Arm Vibration Syndrome

OBJECTIVE

The aim of this study was to use an established model of vibration-induced injury to assess frequency-dependent changes in transcript expression in skin, artery, and nerve tissues.

METHODS

Transcript expression in tissues from control and vibration-exposed rats (4 h/day for 10 days at 62.5, 125, or 250 Hz; 49 m/s, rms) was measured. Transcripts affected by vibration were used in bioinformatics analyses to identify molecular- and disease-related pathways associated with exposure to vibration.

RESULTS

Analyses revealed that cancer-related pathways showed frequency-dependent changes in activation or inhibition. Most notably, the breast-related cancer-1 pathway was affected. Other pathways associated with breast cancer type 1 susceptibility protein related signaling, or associated with cancer and cell cycle/cell survivability were also affected.

CONCLUSION

Occupational exposure to vibration may result in DNA damage and alterations in cell signaling pathways that have significant effects on cellular division.

Changes in the expression of calcitonin gene-related peptide after exposure to injurious stretch-shortening contractions

One of the factors that can result in musculoskeletal injuries, and time off work, is exposure to repetitive motion. The goal of this study was to determine if skeletal muscle injury induced by exposure to injurious stretch-shortening cycles (iSSCs), resulted in hyperalgesia in the hind limb and changes in calcitonin-gene related peptide (CGRP) immunolabeling in the dorsal root ganglia (DRG) in young and old male rats.

METHODS

Young (3months) and old (30months) male Fisher 344×BN F1 rats were anesthetized with isoflurane and the left hind limbs were exposed to 15 sets of 10 SSCs. Control animals were exposed to a single bout of SSCs of equal intensity. Sensitivity to mechanical stimulation was assessed using von Frey filaments prior to beginning the experiment, and on days 2 and 9 following exposure to iSSCs. Rats were euthanized one, 3 or 10days after the exposure. The ipsilateral DRG were dissected from the L4-5 region of the spine, along with the left tibialis anterior (LTA) muscle.

RESULTS

Rats exposed to iSSCs were more sensitive to mechanical stimulation than control rats 2days after the exposure, and showed a reduction in peak force 3days after exposure. Changes in sensitivity to pressure were not associated with increases in CGRP labeling in the DRG at 3days. However, 9days after exposure to iSSCs, old rats still displayed an increased sensitivity to mechanical stimulation, and this hyperalgesia was associated with an increase in CGRP immunolabeling in the DRG. Young rats exposed to iSSC did not display a change in CGRP immunolabeling and sensitivity to mechanical stimulation returned to control levels at 10days.

CONCLUSIONS

These findings suggest that hyperalgesia seen shortly after exposure to iSSC is not influenced by CGRP levels. However, in cases where recovery from injury may be slower, as it is in older rats, CGRP may contribute to the maintenance of hyperalgesia.

Long-term daily vibration exposure alters current perception threshold (CPT) sensitivity and myelinated axons in a rat-tail model of vibration-induced injury

Repeated exposure to hand-transmitted vibration through the use of powered hand tools may result in pain and progressive reductions in tactile sensitivity. The goal of the present study was to use an established animal model of vibration-induced injury to characterize changes in sensory nerve function and cellular mechanisms associated with these alterations. Sensory nerve function was assessed weekly using the current perception threshold test and tail-flick analgesia test in male Sprague-Dawley rats exposed to 28 d of tail vibration. After 28 d of exposure, Aβ fiber sensitivity was reduced. This reduction in sensitivity was partly attributed to structural disruption of myelin. In addition, the decrease in sensitivity was also associated with a reduction in myelin basic protein and 2',3'- cyclic nucleotide phosphodiasterase (CNPase) staining in tail nerves, and an increase in circulating calcitonin gene-related peptide (CGRP) concentrations. Changes in Aβ fiber sensitivity and CGRP concentrations may serve as early markers of vibration-induced injury in peripheral nerves. It is conceivable that these markers may be utilized to monitor sensorineural alterations in workers exposed to vibration to potentially prevent additional injury.

The effects of repetitive vibration on sensorineural function: biomarkers of sensorineural injury in an animal model of metabolic syndrome

Exposure to hand-transmitted vibration in the work-place can result in the loss of sensation and pain in workers. These effects may be exacerbated by pre-existing conditions such as diabetes or the presence of primary Raynaud's phenomena. The goal of these studies was to use an established model of vibration-induced injury in Zucker rats. Lean Zucker rats have a normal metabolic profile, while obese Zucker rats display symptoms of metabolic disorder or Type II diabetes. This study examined the effects of vibration in obese and lean rats. Zucker rats were exposed to 4h of vibration for 10 consecutive days at a frequency of 125 Hz and acceleration of 49 m/s(2) for 10 consecutive days. Sensory function was checked using transcutaneous electrical stimulation on days 1, 5 and 9 of the exposure. Once the study was complete the ventral tail nerves, dorsal root ganglia and spinal cord were dissected, and levels of various transcripts involved in sensorineural dysfunction were measured. Sensorineural dysfunction was assessed using transcutaneous electrical stimulation. Obese Zucker rats displayed very few changes in sensorineural function. However they did display significant changes in transcript levels for factors involved in synapse formation, peripheral nerve remodeling, and inflammation. The changes in transcript levels suggested that obese Zucker rats had some level of sensory nerve injury prior to exposure, and that exposure to vibration activated pathways involved in injury and re-innervation.

Effect of serum nicotine level on posterior spinal fusion in an in vivo rabbit model

BACKGROUND CONTEXT

Cigarette smoking has a deleterious effect on spinal fusion. Although some studies have implied that nicotine is primarily responsible for poor fusion outcomes, other studies suggest that nicotine may actually stimulate bone growth. Hence, there may be a dose-dependent effect of nicotine on posterior spinal fusion outcomes.

PURPOSE

The purpose of this study was to determine if such a relationship could be shown in an in vivo rabbit model.

STUDY DESIGN/SETTING

This is a prospective in vivo animal study.

METHODS

Twenty-four adult male New Zealand white rabbits were randomly divided into four groups. All groups received a single-level posterolateral, intertransverse process fusion at L5-L6 with autologous iliac crest bone. One group served as controls and only underwent the spine fusion surgery. Three groups received 5.25-, 10.5-, and 21-mg nicotine patches, respectively, for 5 weeks. Serum nicotine levels were recorded for each group. All animals were euthanized 5 weeks postoperatively, and spinal fusions were evaluated radiographically, by manual palpation, and biomechanically. Statistical analysis evaluated the dose response effect of outcomes variables and nicotine dosage. This study was supported by a portion of a $100,000 grant from the Orthopaedic Research and Education Foundation. Author financial disclosures were completed in accordance with the journal's guidelines; there were no conflicts of interests disclosed that would have led to bias in this work.

RESULTS

The average serum levels of nicotine from the different patches were 7.8±1.9 ng/mL for the 5.25-mg patch group; 99.7±17.7 ng/mL for the 10.5-mg patch group; and 149.1±24.6 ng/mL for the 21-mg patch group. The doses positively correlated with serum concentrations of nicotine (correlation coefficient=0.8410, p<.001). The 5.25-mg group provided the best fusion rate, trabeculation, and stiffness. On the basis of the palpation tests, the fusion rates were control (50%), 5.25 mg (80%), 10.5 mg (50%), and 21 mg (42.8%). Radiographic assessment of trabeculation and bone incorporation and biomechanical analysis of bending stiffness ratio were also greatest in the 5.25-mg group. Radiographic evaluation showed a significant (p=.0446) quadratic effect of nicotine dose on spinal fusion.

CONCLUSIONS

The effects of nicotine on spinal fusion are complex, may be dose dependent, and may not always be detrimental. The uniformly negative effects of smoking reported in patients undergoing spinal fusion may possibly be attributed to the other components of cigarette smoke.

Antivibration gloves: effects on vascular and sensorineural function, an animal model

Anti-vibration gloves have been used to block the transmission of vibration from powered hand tools to the user, and to protect users from the negative health consequences associated with exposure to vibration. However, there are conflicting reports as to the efficacy of gloves in protecting workers. The goal of this study was to use a characterized animal model of vibration-induced peripheral vascular and nerve injury to determine whether antivibration materials reduced or inhibited the effects of vibration on these physiological symptoms. Rats were exposed to 4 h of tail vibration at 125 Hz with an acceleration 49 m/s(2). The platform was either bare or covered with antivibrating glove material. Rats were tested for tactile sensitivity to applied pressure before and after vibration exposure. One day following the exposure, ventral tail arteries were assessed for sensitivity to vasodilating and vasoconstricting factors and nerves were examined histologically for early indicators of edema and inflammation. Ventral tail artery responses to an α2C-adrenoreceptor agonist were enhanced in arteries from vibration-exposed rats compared to controls, regardless of whether antivibration materials were used or not. Rats exposed to vibration were also less sensitive to pressure after exposure. These findings are consistent with experimental findings in humans suggesting that antivibration gloves may not provide protection against the adverse health consequences of vibration exposure in all conditions. Additional studies need to be done examining newer antivibration materials.

Effects of acute inhalation of aerosols generated during resistance spot welding with mild-steel on pulmonary, vascular and immune responses in rats

Spot welding is used in the automotive and aircraft industries, where high-speed, repetitive welding is needed to join thin sections of metal. Epoxy adhesives are applied as sealers to the metal seams. Pulmonary function abnormalities and airway irritation have been reported in spot welders, but no animal toxicology studies exist. Therefore, the goal of this study was to investigate vascular, immune and lung toxicity measures after exposure to these metal fumes in an animal model. Male Sprague-Dawley rats were exposed by inhalation to 25 mg/m³ to either mild-steel spot welding aerosols with sparking (high metal, HM) or without sparking (low metal, LM) for 4 h/d for 3, 8 and 13 d. Shams were exposed to filtered air. Bronchoalveolar lavage (BAL), lung gene expression and ex vivo BAL cell challenge were performed to assess lung toxicity. Lung resistance (R(L)) was evaluated before and after challenge with inhaled methacholine (MCh). Functional assessment of the vascular endothelium in isolated rat tail arteries and leukocyte differentiation in the spleen and lymph nodes via flow cytometry was also done. Immediately after exposure, baseline R(L) was significantly elevated in the LM spot welding aerosols, but returned to control level by 24 h postexposure. Airway reactivity to MCh was unaffected. Lung inflammation and cytotoxicity were mild and transient. Lung epithelial permeability was significantly increased after 3 and 8 d, but not after 13 d of exposure to the HM aerosol. HM aerosols also caused vascular endothelial dysfunction and increased CD4+, CD8+ and B cells in the spleen. Only LM aerosols caused increased IL-6 and MCP-1 levels compared with sham after ex vivo LPS stimulation in BAL macrophages. Acute inhalation of mild-steel spot welding fumes at occupationally relevant concentrations may act as an irritant as evidenced by the increased R(L) and result in endothelial dysfunction, but otherwise had minor effects on the lung.

Recovery of vascular function after exposure to a single bout of segmental vibration

Work rotation schedules may be used to reduce the negative effects of vibration on vascular function. This study determined how long it takes vascular function to recover after a single exposure to vibration in rats (125 Hz, acceleration 5 g). The responsiveness of rat-tail arteries to the vasoconstricting factor UK14304, an α2C-adrenoreceptor agonist, and the vasodilating factor acetylcholine (ACh) were measured ex vivo 1, 2, 7, or 9 d after exposure to a single bout of vibration. Vasoconstriction induced by UK14304 returned to control levels after 1 d of recovery. However, re-dilation induced by ACh did not return to baseline until after 9 d of recovery. Exposure to vibration exerted prolonged effects on peripheral vascular function, and altered vascular responses to a subsequent exposure. To optimize the positive results of work rotation schedules, it is suggested that studies assessing recovery of vascular function after exposure to a single bout of vibration be performed in humans.

Pulmonary and cardiovascular responses of rats to inhalation of silver nanoparticles

Exposure to wet aerosols generated during use of spray products containing silver (Ag) has not been evaluated. The goal was to assess the potential for cardiopulmonary toxicity following an acute inhalation of wet silver colloid. Rats were exposed by inhalation to a low concentration (100 μg/m(3) ) using an undiluted commercial antimicrobial product (20 mg/L total silver; approximately 33 nm mean aerodynamic diameter [MAD]) or to a higher concentration (1000 μg/m(3)) using a suspension (200 mg/L total silver; approximately 39 nm MAD) synthesized to possess a similar size distribution of Ag nanoparticles for 5 h. Estimated lung burdens from deposition models were 0, 1.4, or 14 μg Ag/rat after exposure to control aerosol, low, and high doses, respectively. At 1 and 7 d postexposure, the following parameters were monitored: pulmonary inflammation, lung cell toxicity, alveolar air/blood barrier damage, alveolar macrophage activity, blood cell differentials, responsiveness of tail artery to vasoconstrictor or vasodilatory agents, and heart rate and blood pressure in response to isoproterenol or norepinephrine, respectively. Changes in pulmonary or cardiovascular parameters were absent or nonsignificant at 1 or 7 d postexposure with the exceptions of increased blood monocytes 1 d after high-dose Ag exposure and decreased dilation of tail artery after stimulation, as well as elevated heart rate in response to isoproterenol 1 d after low-dose Ag exposure, possibly due to bioavailable ionic Ag in the commercial product. In summary, short-term inhalation of nano-Ag did not produce apparent marked acute toxicity in this animal model.

Pulmonary and cardiovascular responses of rats to inhalation of a commercial antimicrobial spray containing titanium dioxide nanoparticles

Our laboratory has previously demonstrated that application of an antimicrobial spray product containing titanium dioxide (TiO(2)) generates an aerosol of titanium dioxide in the breathing zone of the applicator. The present report describes the design of an automated spray system and the characterization of the aerosol delivered to a whole body inhalation chamber. This system produced stable airborne levels of TiO(2) particles with a median count size diameter of 110 nm. Rats were exposed to 314 mg/m(3) min (low dose), 826 mg/m(3) min (medium dose), and 3638 mg/m(3) min (high dose) of TiO(2) under the following conditions: 2.62 mg/m(3) for 2 h, 1.72 mg/m(3) 4 h/day for 2 days, and 3.79 mg/m(3) 4 h/day for 4 days, respectively. Pulmonary (breathing rate, specific airway resistance, inflammation, and lung damage) and cardiovascular (the responsiveness of the tail artery to constrictor or dilatory agents) endpoints were monitored 24 h post-exposure. No significant pulmonary or cardiovascular changes were noted at low and middle dose levels. However, the high dose caused significant increases in breathing rate, pulmonary inflammation, and lung cell injury. Results suggest that occasional consumer use of this antimicrobial spray product should not be a hazard. However, extended exposure of workers routinely applying this product to surfaces should be avoided. During application, care should be taken to minimize exposure by working under well ventilated conditions and by employing respiratory protection as needed. It would be prudent to avoid exposure to children or those with pre-existing respiratory disease.

Nicotine Increases Osteoblast Activity of Induced Bone Marrow Stromal Cells in a Dose-Dependent Manner: An in vitro Cell Culture Experiment

Previous studies by our group showed that nicotine delivered via a transdermal nicotine patch significantly enhanced posterior spinal fusion rates in rabbits. Nicotine transdermal patches provide a steady serum level; there may be a dose-dependent effect of nicotine on posterior spinal fusion. In an in vitro cell culture model of rabbit bone marrow-derived osteoblast-like cells, cells were exposed to different concentrations of nicotine (0, 20, 40, 80 ng/mL and 10, 100, 250 μg/mL). Wells were stained with an alkaline phosphatase (ALP) staining kit to determine ALP enzyme activity. Cells were stained with Von Kossa for mineralization. A two-way analysis of variance (ANOVA) using dose and time as variables showed significant differences among groups; post hoc analysis showed that the 100-μg/mL dose of nicotine significantly enhanced ALP activity over controls. A one-way ANOVA using dose as the variable showed that the 100- and 250-μg/mL doses had significantly greater mineralization than controls. Dose-response analysis revealed a statistically significant effect of nicotine dose on ALP activity and Von Kossa activity. The effects of nicotine on spinal fusion may be dose-dependent and due to stimulation of osteoblastic activity. Nicotine may not be responsible for the inhibited bone healing observed in smokers.

Acute effects of COREXIT EC9500A on cardiovascular functions in rats

These studies characterized cardiovascular responses after an acute inhalation exposure to COREXIT EC9500A, the oil dispersant used in the Deepwater Horizon oil spill. Male Sprague-Dawley rats underwent a single 5-h inhalation exposure to COREXIT EC9500A (average exposure level 27.12 mg/m(3)) or air. On d 1 and 7 following the exposure, rats were implanted with indwelling catheters and changes in heart rate and blood pressure were assessed in response to increasing levels of adrenoreceptor agonists. A separate group of rats was euthanized at the same time points, ventral tail arteries were dissected, and vascular tone along with dose-dependent responses to vasoconstricting and dilating factors were assessed in vitro. Agonist-induced dose-dependent increases in heart rate and blood pressure were greater in COREXIT EC9500A-exposed than in air-exposed rats at 1 d but not 7 d after the exposure. COREXIT EC9500A exposure also induced a rise in basal tone and reduced responsiveness of tail arteries to acetylcholine-induced vasodilation at 1 d but not 7 d following the exposure. These findings demonstrate that an acute exposure to COREXIT EC9500A exerts transient effects on cardiovascular and peripheral vascular functions.

Vibration disrupts vascular function in a model of metabolic syndrome

Vibration-induced white finger (VWF) is a disorder seen in workers exposed to hand-transmitted vibration, and is characterized by cold-induced vasospasms and finger blanching. Because overweight people with metabolic syndrome are pre-disposed to developing peripheral vascular disorders, it has been suggested that they also may be at greater risk of developing VWF if exposed to occupational vibration. We used an animal model of metabolic syndrome, the obese Zucker rat, to determine if metabolic syndrome alters vascular responses to vibration. Tails of lean and obese Zucker rats were exposed to vibration (125 Hz, 49 m/s(2) r.m.s.) or control conditions for 4 h/d for 10 d. Ventral tail arteries were collected and assessed for changes in gene expression, levels of reactive oxygen species (ROS) and for responsiveness to vasomodulating factors. Vibration exposure generally reduced the sensitivity of arteries to acetylcholine (ACh)-induced vasodilation. This decrease in sensitivity was most apparent in obese rats. Vibration also induced reductions in vascular nitric oxide concentrations and increases in vascular concentrations of ROS in obese rats. These results indicate that vibration interferes with endothelial-mediated vasodilation, and that metabolic syndrome exacerbates these effects. These findings are consistent with idea that workers with metabolic syndrome have an increased risk of developing VWF.

SEM and raman spectroscopy of multiwalled carbon nanotubes grown by novel technique of ash supported catalysts

Multiwalled carbon nanotubes (MWCNTs) were grown on a novel ASC catalyst and on catalyst deposited by SCC method on silicon wafer, by thermal CVD of acetylene. Fe and Ni were used as catalyst for ASC. Samples were analyzed by SEM and Raman spectroscopy. SEM analysis shows that CNTs grown on ASC have narrower diameter distribution (64+/-6 nm) compared to CNTs grown on SCC (67+/-10.5 nm). However, SEM and Raman spectroscopy studies show CNTs grown on SCC are of better quality. The same samples were studied after standard purification procedure of oxidation after annealing at high temperatures. SEM and Raman spectroscopy show that overall quality of ensemble of CNTs has improved. After annealing, diameter decreases for larger diameter approximately 200 nm nanotubes while it increases for CNTs of smaller diameter approximately 70 nm. To explain the increase in diameter of approximately 70 nm CNT's, a phenomenological model has been proposed. The results of Raman spectroscopy and SEM corroborate the proposed model.

Parental reports of emotional and behavioural difficulties on the SDQ for school-age children with vertically acquired HIV infection living in London

This study uses a screening questionnaire (the Strengths and Difficulties Questionnaire, SDQ) to indicate levels of parental or carer concern about behavioural or emotional difficulties in a representative group of school-age children with vertically acquired HIV attending London clinics. Fourteen per cent of the total 107 children screened were reported to have behavioural and emotional difficulties scoring in the "abnormal" range. Older children tended to have higher scores. Overall, levels of reported difficulties were found to be similar to those reported for other chronic childhood illnesses and slightly higher than in the general child population.

Proapoptotic factor Bax is increased in satellite cells in the tibialis anterior muscles of old rats

Aging impairs the ability of muscle to adapt to exercise or injury. The goal of this study was to determine whether age-related changes in muscle adaptability could be the result of satellite cell apoptosis. Ten days after exposure to an injury protocol, estimates of edema in the exposed tibialis anterior muscles were higher in old (30 months) than young (3 months) rats, and isometric force levels were lower in old rats. Both young and old rats displayed an increase in MyoD labeling in the exposed muscle, indicating that injury induced satellite-cell activation. However, there were more MyoD-labeled cells that coexpressed the proapoptotic factor, Bax, in old than in young rats, suggesting that decrements in muscle recovery may be associated with an increase in satellite-cell apoptosis. Based on these findings we conclude that reducing satellite-cell apoptosis in aged animals may improve muscle recovery after injury.

Acute vibration reduces Aβ nerve fiber sensitivity and alters gene expression in the ventral tail nerves of rats

Long-term occupational exposure to hand-arm vibration can result in a permanent reduction in tactile sensitivity in exposed fingers and hands. Little is known about how vibration causes this reduction in sensitivity, and currently no testing procedures have been developed to monitor changes in sensory perception during ongoing exposures. We used a rat-tail model of hand-arm vibration syndrome (HAVS) to determine whether changes in sensory nerve function could be detected after acute exposure to vibration. Nerve function was assessed using the current perception threshold (CPT) method. We also determined whether changes in nerve function were associated with changes in gene transcription. Our results demonstrate that the CPT method can be used to assess sensory nerve function repeatedly in rats and can detect transient decreases in the sensitivity of Abeta nerve fibers caused by acute exposure to vibration. This decrease in Abeta fiber sensitivity was associated with a reduction in expression of nitric oxide synthase-1, and a modest increase in calcitonin gene-related peptide transcript levels in tail nerves 24 h after vibration exposure. These transient changes in sensory perception and transcript levels induced by acute vibration exposure may be indicators of more prolonged changes in peripheral nerve physiology.

Parental views on disclosure of diagnosis to their HIV-positive children

Parents of HIV-positive children are known to delay disclosure of diagnosis. This study examines the concerns parents attending a South London family clinic had about disclosure of diagnosis to school-aged children with HIV, to establish the stages they were at in terms of the disclosure process and to find out what plans they had regarding further disclosure. Thirteen families with vertically-infected children who did not know their HIV diagnosis were included in the study. Findings showed that parents generally partially disclose information about the illness without naming it and delay full disclosure. The most frequently given reason for delay in talking to their child about HIV was fear that the child may accidentally reveal their diagnosis, thereby simultaneously revealing maternal HIV status and exposing the family to potential stigmatization, discrimination and prejudice.

Process characterization for metal-affinity chromatography of an Fc fusion protein: a design-of-experiments approach

The utility of a design-of-experiments approach was investigated for process characterization of a metal-affinity chromatographic purification process for an Fc fusion protein. This approach gave a better understanding of some of the key process variables as well as robustness for this step in the purification process. Single-variable experiments were employed to screen some of the potentially important variables in this step. Ranges for these variables were set based on prior experience in clinical manufacturing with similar processes. Following these experiments, a fractional factorial study was employed to further investigate the most important variables and their interactions. Key operational variables that had an impact on step yield and eluate purity were identified. In addition, the study helped identify a worst-case scenario for the step purity and helped assure that the rest of the process would successfully purify the product. This paper demonstrates the utility of a design-of-experiments approach for the characterization and validation of process chromatography steps in downstream processing. In addition, this study emphasizes the utility of robustness studies early in process development and establishes a strategy for future robustness studies.

2'-Fluoropyrimidine RNA-based aptamers to the 165-amino acid form of vascular endothelial growth factor (VEGF165). Inhibition of receptor binding and VEGF-induced vascular permeability through interactions requiring the exon 7-encoded domain

Vascular endothelial growth factor (VEGF) has been implicated in the pathological induction of new blood vessel growth in a variety of proliferative disorders. Using the SELEX process (systematic evolution of ligands by exponential enrichment), we have isolated 2'-F-pyrimidine RNA oligonucleotide ligands (aptamers) to human VEGF165. Representative aptamers from three distinct sequence families were truncated to the minimal sequence capable of high affinity binding to VEGF (23-29 nucleotides) and were further modified by replacement of 2'-O-methyl for 2'-OH at all ribopurine positions where the substitution was tolerated. Equilibrium dissociation constants for the interaction of VEGF with the truncated, 2'-O-methyl-modified aptamers range between 49 and 130 pM. These aptamers bind equally well to murine VEGF164, do not bind to VEGF121 or the smaller isoform of placenta growth factor (PlGF129), and show reduced, but significant affinity for the VEGF165/PlGF129 heterodimer. Cysteine 137 in the exon 7-encoded domain of VEGF165 forms a photo-inducible cross-link to a single uridine residue in each of the three aptamers. The aptamers potently inhibit the binding of VEGF to the human VEGF receptors, KDR and Flt-1, expressed by transfected porcine aortic endothelial cells. Furthermore, one of the aptamers is able to significantly reduce intradermal VEGF-induced vascular permeability in vivo.

Economic outcomes associated with the use of risperidone in a naturalistic group practice setting

The purpose of this cohort pilot study was to compare the resource utilization and economic outcomes associated with the use of risperidone versus haloperidol in a naturalistic setting. Patient charts from a large psychiatric group practice were reviewed, and hospital billing data were obtained. Patients meeting the inclusion criteria were placed into one of two cohorts depending on their medication history. Thirty patients treated with risperidone met the selection criteria, and a random quota sampling technique was used to allow for a matched control cohort of 30 patients treated with haloperidol. In the haloperidol and risperidone cohorts, 24 and 28 patients, respectively, were evaluated statistically. Mean utilization rates and costs per patient per month for each service were estimated by using regression analysis. Patients in the risperidone cohort had significantly fewer hospitalizations than did those in the haloperidol cohort (P = 0.004). Likewise, risperidone patients had significantly lower hospitalization costs than haloperidol patients (P = 0.005). Conversely, patients treated with risperidone visited the physician more frequently than did those treated with haloperidol (P = 0.0005). Estimated mean total monthly costs were $123.34 lower (95% confidence interval = $464, $217) per patient in the risperidone cohort than in the haloperidol cohort ($1,636.11 vs $1759.45; P = 0.4693). Significant reductions in hospital costs in the risperidone cohort offset higher medication and physician costs. Overall, total monthly costs were similar for the two cohorts.

In vitro selection of RNAs that bind to the human immunodeficiency virus type-1 gag polyprotein

RNA ligands that bind to the human immunodeficiency virus type-1 (HIV-1) gag polyprotein with 10(-9) M affinity were isolated from a complex pool of RNAs using an in vitro selection method. The ligands bind to two different regions within gag, either to the matrix protein or to the nucleocapsid protein. Binding of a matrix ligand to gag did not interfere with the binding of a nucleocapsid ligand, and binding of a nucleocapsid ligand to gag did not interfere with the binding of a matrix ligand. However, binding of a nucleocapsid ligand to gag did interfere with binding of an RNA containing the HIV-1 RNA packaging element (psi), even though the sequence of the nucleocapsid ligand is not similar topsi. The minimal sequences required for the ligands to bind to matrix or nucleocapsid were determined. Minimal nucleocapsid ligands are predicted to form a stem-loop structure that has a self-complementary sequence at one end. Minimal matrix ligands are predicted to form a different stem-loop structure that has a CAARU loop sequence. The properties of these RNA ligands may provide tools for studying RNA interactions with matrix and nucleocapsid, and a novel method for inhibiting HIV replication.

Comprehensive chemical modification interference and nucleotide substitution analysis of an RNA pseudoknot inhibitor to HIV-1 reverse transcriptase

We had previously used in vitro RNA selection techniques to describe a consensus RNA pseudoknot that binds and inhibits HIV-1 reverse transcriptase (HIV-RT). In this work we constructed variants of this consensus pseudoknot in order to evaluate the contributions of individual nucleotide identities and secondary structure to affinity for HIV-RT. We have also used chemical modification of ligand RNAs to corroborate the predicted structure of the pseudoknot, to discover which modifiable groups are protected from chemical attack when bound to HIV-RT, and to find which modifications interfere with binding to HIV-RT. A novel interference study is presented which involves selection of ligands from a pool created by mixed reagent oligonucleotide synthesis in order to rapidly determine allowed substitutions of 2'-OCH3 groups for the usual 2'-OH group in such RNA ligands.