Divergent immunological responses following glutaraldehyde exposure

Estimating uncertainty in LLNA EC3 data and its impact on regulatory classifications

The murine Local Lymph Node Assay (LLNA) is a test that produces numerical results (EC3 values) quantifying the sensitization potency of chemicals. These results are broadly used in toxicology and serve as a basis for various classifications, which determine subsequent regulatory decisions. The continuing interest in LLNA data and the diminished likelihood of new experimental EC3 data being generated sparked this investigation of uncertainty. Instead of using the Gaussian distribution as a default choice for assessing variability in a data set, two strictly positive distributions were proposed and their performance over the available experimental EC3 values was tested. In the application stage, how the uncertainty in EC3 values affects the possible classifications was analyzed, and the percentage of the chemicals receiving ambiguous classification was determined. It was shown that this percentage is high, which increases the risk of improper classification. Two approaches were suggested in regulatory practice to address the uncertainty in the EC3 data: the approaches based on "grey zones" and the classification distribution. If a chemical cannot be classified unambiguously, the latter appears to be an acceptable means to assess the level of sensitization potency of chemicals and helps provide better regulatory decisions.

Subacute Pulmonary Toxicity of Glutaraldehyde Aerosols in a Human In Vitro Airway Tissue Model

Glutaraldehyde (GA) has been cleared by the Center for Devices and Radiological Health (CDRH) of the Food and Drug Administration (FDA) as a high-level disinfectant for disinfecting heat-sensitive medical equipment in hospitals and healthcare facilities. Inhalation exposure to GA is known to cause respiratory irritation and sensitization in animals and humans. To reproduce some of the known in vivo effects elicited by GA, we used a liquid aerosol exposure system and evaluated the tissue responses in a human in vitro airway epithelial tissue model. The cultures were treated at the air interface with various concentrations of GA aerosols on five consecutive days and changes in tissue function and structure were evaluated at select timepoints during the treatment phase and after a 7-day recovery period. Exposure to GA aerosols caused oxidative stress, inhibition of ciliary beating frequency, aberrant mucin production, and disturbance of cytokine and matrix metalloproteinase secretion, as well as morphological transformation. Some effects, such as those on goblet cells and ciliated cells, persisted following the 7-day recovery period. Of note, the functional and structural disturbances observed in GA-treated cultures resemble those found in ortho-phthaldehyde (OPA)-treated cultures. Furthermore, our in vitro findings on GA toxicity partially and qualitatively mimicked those reported in the animal and human survey studies. Taken together, observations from this study demonstrate that the human air-liquid-interface (ALI) airway tissue model, integrated with an in vitro exposure system that simulates human inhalation exposure, could be used for in vitro-based human hazard identification and the risk characterization of aerosolized chemicals.

Diversity of Carbonyl Compounds in Biogas and Natural Gas Revealed Using High-Resolution Mass Spectrometry and Nontarget Analysis

Airborne carbonyl compounds such as formaldehyde, acrolein, and methyl ethyl ketone have long been chemicals-of-concern in the environment due to their reactivity and their potential for negative health effects. Standard methods for determining carbonyls in air, which focus on a set of 15 or fewer compounds, involve derivatization to form nonvolatile hydrazones, which can readily be analyzed via liquid chromatography (LC) with ultraviolet detectors. Here, we apply a new LC-high-resolution mass spectrometry (HRMS) method to natural gas and a variety of upgraded biofuels to better assess their total carbonyl profile using the inherent selectivity of the standard sampling methodology and the selectivity and sensitivity of HRMS. The standard method accounted for only 64% of the total carbonyl content in natural gas and between 26 and 45% of the total carbonyl content in biogas sources, with the balance detected by the new LC/HRMS method. An additional 540 compounds with molecular formulas consistent with carbonyl compounds were detected compared to only 14 target compounds using the standard method. These results demonstrate that the established method dramatically under-reports both the total carbonyl load and the diversity of carbonyl species in natural gas and biogas samples.

Topical exposure to triclosan inhibits Th1 immune responses and reduces T cells responding to influenza infection in mice

Healthcare workers concurrently may be at a higher risk of developing respiratory infections and allergic disease, such as asthma, than the general public. Increased incidence of allergic diseases is thought to be caused, in part, due to occupational exposure to chemicals that induce or augment Th2 immune responses. However, whether exposure to these chemical antimicrobials can influence immune responses to respiratory pathogens is unknown. Here, we use a BALB/c murine model to test if the Th2-promoting antimicrobial chemical triclosan influences immune responses to influenza A virus. Mice were dermally exposed to 2% triclosan for 7 days prior to infection with a sub-lethal dose of mouse adapted PR8 A(H1N1) virus (50 pfu); triclosan exposure continued until 10 days post infection (dpi). Infected mice exposed to triclosan did not show an increase in morbidity or mortality, and viral titers were unchanged. Assessment of T cell responses at 10 dpi showed a decrease in the number of total and activated (CD44hi) CD4+ and CD8+ T cells at the site of infection (BAL and lung) in triclosan exposed mice compared to controls. Influenza-specific CD4+ and CD8+ T cells were assessed using MHCI and MHCII tetramers, with reduced populations, although not reaching statistical significance at these sites following triclosan exposure. Reductions in the Th1 transcription factor T-bet were seen in both activated and tetramer+ CD4+ and CD8+ T cells in the lungs of triclosan exposed infected mice, indicating reduced Th1 polarization and providing a potential mechanism for numerical reduction in T cells. Overall, these results indicate that the immune environment induced by triclosan exposure has the potential to influence the developing immune response to a respiratory viral infection and may have implications for healthcare workers who may be at an increased risk for developing infectious diseases.

Divergent hypersensitivity responses following topical application of the quaternary ammonium compound, didecyldimethylammonium bromide

Didecyldimethylammonium bromide (DDAB) is a fourth generation dialkyl-quaternary ammonium compound (QAC) that is used in numerous products for its antimicrobial properties. While many QACs have been associated with allergic disease, the toxicity and sensitization of DDAB have not been thoroughly investigated. The purpose of these studies was to evaluate the irritancy and sensitization potential of DDAB following dermal application in a murine model. DDAB induced significant irritancy (0.0625-2%), evaluated by ear swelling in female BALB/c mice. Initial evaluation of the sensitization potential was conducted using the local lymph node assay (LLNA) at concentrations ranging from 0.0625% to 2%. A concentration-dependent increase in lymphocyte proliferation was observed with a calculated EC3 value of 0.057%. Immune cell phenotyping along with local and systemic IgE levels were evaluated following 4 and 14 days of dermal application. Phenotypic analyses revealed significant and dose-responsive increases in the absolute number of B-cells, CD4⁺ T-cells, CD8⁺ T-cells, and dendritic cells in the draining lymph nodes (DLNs) following 4 and 14 days of dermal exposure with significant increases in the number of activated B-cells and dendritic cells. However, increased activation of CD4⁺ T-cell and CD8⁺ T-cells was only observed following four days of DDAB exposure. Exposure to DDAB also induced increased production of IgE as evaluated by phenotypic analysis of DLN B-cells (IgE⁺ B-cells) and measurement of total serum IgE levels following 14 days but not four days of dermal application. Significant increases in gene expression were observed in the DLN (Il-4, Il-10, and ox40l) and ear (tslp) following 4 and 14 days of DDAB exposure. These results demonstrate the potential for development of irritation and hypersensitivity responses to DDAB following dermal exposure and raise concerns about the effects of exposure duration on hypersensitivity responses.

Chemical kinetics of multiphase reactions between ozone and human skin lipids: Implications for indoor air quality and health effects

Ozone reacts with skin lipids such as squalene, generating an array of organic compounds, some of which can act as respiratory or skin irritants. Thus, it is important to quantify and predict the formation of these products under different conditions in indoor environments. We developed the kinetic multilayer model that explicitly resolves mass transport and chemical reactions at the skin and in the gas phase (KM-SUB-Skin). It can reproduce the concentrations of ozone and organic compounds in previous measurements and new experiments. This enabled the spatial and temporal concentration profiles in the skin oil and underlying skin layers to be resolved. Upon exposure to ~30 ppb ozone, the concentrations of squalene ozonolysis products in the gas phase and in the skin reach up to several ppb and on the order of ~10 mmol m^-3 . Depending on various factors including the number of people, room size, and air exchange rates, concentrations of ozone can decrease substantially due to reactions with skin lipids. Ozone and dicarbonyls quickly react away in the upper layers of the skin, preventing them from penetrating deeply into the skin and hence reaching the blood.

Persistent and Unusual Respiratory Findings after Prolonged Glutaraldehyde Exposure

Glutaraldehyde is commonly used in endoscopy labs to clean and disinfect instruments. It can cause direct irritation of the skin and the upper and lower airways. Health care workers are also at risk for the development of irritant-induced or sensitizer-induced occupational asthma when exposed to this chemical. Herein, we report on a patient who had frequent exposures to glutaraldehyde over one year while working in an endoscopy lab and developed chronic upper and lower respiratory tract symptoms. Multiple spirometric tests during her evaluation revealed variable results including restrictive pattern with a response to bronchodilators, obstructive pattern with a paradoxic bronchoconstrictive response to bronchodilators, and obstructive pattern with a partial response to bronchodilators. These results indicate that the distribution of inflammation and bronchial responsiveness can vary in a single patient with glutaraldehyde-induced occupational asthma. Therefore, the evaluation may be more difficult than might be expected in patients with occupational asthma, and some patients will need multiple pulmonary function tests to characterize their airway disease.

Glutaraldehyde exposure and its occupational impact in the health care environment

Despite the search for effective and less toxic substitutes, glutaraldehyde (GA) remains one of the few substances capable of high-level instrument disinfection in modern health care. Workers commonly affected include operating room nurses, radiographers, x-ray technicians and cleaners. Widespread hospital usage combined with its well-known irritant properties, has ensured an increase in occupationally-related illnesses during recent years. Operating room nurses, laboratory workers and x-ray technicians frequently contact GA in both the liquid and vapor form. Workplace exposure is usually dependent on job tasks, ventilation levels and the use of protective equipment. GA is a relatively potent irritant and sensitizer, with a well-documented history of symptoms following occupational exposure. Although mechanisms for GA toxicity have been postulated, research on the toxicological, teratogenic, and carcinogenic potential of this chemical has shown inconsistent results. Reducing workplace exposure to its lowest possible level represents the most important hazard reduction strategy. This may be achieved by keeping GA containers tightly sealed when not in use, maintaining adequate ventilation levels and the rigid adherence to appropriate personal protective equipment. Substitution with automated cold sterilization machines may be another appropriate measure, while banning unnecessary practices such as GA fogging and its use as a surface disinfectant may also be helpful in reducing occupational exposure in the health care environment.

Irritancy and allergic responses induced by exposure to the indoor air chemical 4-oxopentanal

Over the last two decades, there has been an increasing awareness regarding the potential impact of indoor air pollution on human health. People working in an indoor environment often experience symptoms such as eye, nose, and throat irritation. Investigations into these complaints have ascribed the effects, in part, to compounds emitted from building materials, cleaning/consumer products, and indoor chemistry. One suspect indoor air contaminant that has been identified is the dicarbonyl 4-oxopentanal (4-OPA). 4-OPA is generated through the ozonolysis of squalene and several high-volume production compounds that are commonly found indoors. Following preliminary workplace sampling that identified the presence of 4-OPA, these studies examined the inflammatory and allergic responses to 4-OPA following both dermal and pulmonary exposure using a murine model. 4-OPA was tested in a combined local lymph node assay and identified to be an irritant and sensitizer. A Th1-mediated hypersensitivity response was supported by a positive response in the mouse ear swelling test. Pulmonary exposure to 4-OPA caused a significant elevation in nonspecific airway hyperreactivity, increased numbers of lung-associated lymphocytes and neutrophils, and increased interferon-γ production by lung-associated lymph nodes. These results suggest that both dermal and pulmonary exposure to 4-OPA may elicit irritant and allergic responses and may help to explain some of the adverse health effects associated with poor indoor air quality.

Inhalation of ortho-phthalaldehyde vapor causes respiratory sensitization in mice

Ortho-Phthalaldehyde (OPA) has been approved for high-level sterilization of heat-sensitive medical instruments and is increasingly being used as a replacement in the healthcare industry for glutaraldehyde, a known sensitizer. Numerous case reports have been published indicating workers and patients experiencing respiratory problems, anaphylaxis, skin reactivity, and systemic antibody production. Our laboratory previously demonstrated that OPA is a dermal sensitizer in mice. The goal of the present study was to determine if OPA is a respiratory sensitizer following inhalation exposure. Mice were exposed to OPA vapor and airway and lymph nodes were examined for cytokine gene expression and alterations in lymphocyte populations. Inhalation of OPA for 3 days resulted in a concentration-dependent increase in lymphocyte proliferation, mainly B lymphocytes, in the draining lymph nodes. A secondary challenge of mice with OPA resulted in a dramatic increase in the population of B lymphocytes expressing IgE. Expression of Th2 (IL-4, IL-5, and IL-13) and anti/proinflammatory (IL-10, TNFα, and IL-1β) cytokine genes was upregulated in the lymph nodes and the nasal mucosa. Mice exposed to the higher concentrations of OPA-produced OPA-specific IgG₁ antibodies indicating systemic sensitization. These findings provide evidence that OPA has the potential to cause respiratory sensitization in mice.

Fabrication of oxidized alginate-gelatin-BCP hydrogels and evaluation of the microstructure, material properties and biocompatibility for bone tissue regeneration

Composite hydrogel systems consisting of oxidized alginate, gelatin, and biphasic calcium phosphate were fabricated by the Schiff-base reaction and the effect of oxidation of alginate on the microstructure, material properties, and biocompatibility were evaluated. Alginate was modified by oxidizing the attached −OH groups to a −CHO group to facilitate interactions with the −NH2 groups of gelatin. The increased interactions between the functional groups had several effects on the materials properties, physical behaviors, and bio-compatibility. A higher degree of oxidation and thereby a higher extent of crosslinking between the −CHO and −NH2 groups resulted in an increase in water uptake and compressive strength, which was associated with a decrease in porosity, gelation time, bio-degradation rate, and to a smaller degree, biocompatibility. The hydrogel structure was highly porous and showed unique channel zed morphology with an extensive branching of the channels. The channels were not continuous and were divided into multiple segments by thin separators that were 5 µm thick and branched off of the 10–25 µm thick frame. The pores in the hydrogel system were interconnected and the porosity ranged from 44.45 to 67.89% with a pore size ranging from 100 to 300 µm. The compressive stress failure of the wet hydrogel was at 12.0 ± 1.2 MPa when the degree of alginate oxidation was 66.6%. The biocompatibility of the hydrogel system was excellent, although it was slightly lowered by oxidation. These hydrogels are promising biomaterials for bone regeneration with adjustable gelation and bio-degradation time, good mechanical strength, and excellent bio-compatibility.

The LLNA: A Brief Review of Recent Advances and Limitations

Allergic contact dermatitis is the second most commonly reported occupational illness, accounting for 10% to 15% of all occupational diseases. This highlights the importance of developing rapid and sensitive methods for hazard identification of chemical sensitizers. The murine local lymph node assay (LLNA) was developed and validated for the identification of low molecular weight sensitizing chemicals. It provides several benefits over other tests for sensitization because it provides a quantitative endpoint, dose-responsive data, and allows for prediction of potency. However, there are also several concerns with this assay including: levels of false positive responses, variability due to vehicle, and predictivity. This report serves as a concise review which briefly summarizes the progress, advances and limitations of the assay over the last decade.

Reactions of ozone with human skin lipids: sources of carbonyls, dicarbonyls, and hydroxycarbonyls in indoor air

This study has used proton transfer reaction-mass spectrometry (PTR-MS) for direct air analyses of volatile products resulting from the reactions of ozone with human skin lipids. An initial series of small-scale in vitro and in vivo experiments were followed by experiments conducted with human subjects in a simulated office. The latter were conducted using realistic ozone mixing ratios (approximately 15 ppb with occupants present). Detected products included mono- and bifunctional compounds that contain carbonyl, carboxyl, or alpha-hydroxy ketone groups. Among these, three previously unreported dicarbonyls have been identified, and two previously unreported alpha-hydroxy ketones have been tentatively identified. The compounds detected in this study (excepting acetone) have been overlooked in surveys of indoor pollutants, reflecting the limitations of the analytical methods routinely used to monitor indoor air. The results are fully consistent with the Criegee mechanism for ozone reacting with squalene, the single most abundant unsaturated constituent of skin lipids, and several unsaturated fatty acid moieties in their free or esterified forms. Quantitative product analysis confirms that squalene is the major scavenger of ozone at the interface between room air and the human envelope. Reactions between ozone and human skin lipids reduce the mixing ratio of ozone in indoor air, but concomitantly increase the mixing ratios of volatile products and, presumably, skin surface concentrations of less volatile products. Some of the volatile products, especially the dicarbonyls, may be respiratory irritants. Some of the less volatile products may be skin irritants.

Evaluation of dicarbonyls generated in a simulated indoor air environment using an in vitro exposure system

Over the last two decades, there has been increasing awareness regarding the potential impact of indoor air pollution on health. Exposure to volatile organic compounds (VOCs) or oxygenated organic compounds formed from indoor chemistry has been suggested to contribute to adverse health effects. These studies use an in vitro monitoring system called VitroCell, to assess chemicals found in the indoor air environment. The structurally similar dicarbonyls diacetyl, 4-oxopentanal (4-OPA), glyoxal, glutaraldehyde, and methyl glyoxal were selected for use in this system. The VitroCell module was used to determine whether these dicarbonyls were capable of inducing inflammatory cytokine expression by exposed pulmonary epithelial cells (A549). Increases in the relative fold change in messenger RNA expression of the inflammatory mediators, interleukin (IL)-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF-alpha) were identified following exposure to diacetyl, 4-OPA, glyoxal, glutaraldehyde, and methyl glyoxal when compared to a clean air control. Consistent results were observed when the protein levels of these cytokines were analyzed. Exposure to 4-OPA significantly elevated IL-8, IL-6, GM-CSF, and TNF-alpha while glutaraldehyde caused significant elevations in IL-6, IL-8, and TNF-alpha. IL-6 and IL-8 were also significantly elevated after exposure to diacetyl, glyoxal, and methyl glyoxal. These studies suggest that exposure to structurally similar oxygenated reaction products may be contributing to some of the health effects associated with indoor environments and may provide an in vitro method for identification and characterization of these potential hazards.

Irritancy and allergic responses induced by topical application of ortho-phthalaldehyde

Although ortho-phthalaldehyde (OPA) has been suggested as an alternative to glutaraldehyde for the sterilization and disinfection of hospital equipment, the toxicity has not been thoroughly investigated. The purpose of these studies was to evaluate the irritancy and sensitization potential of OPA. The EpiDerm Skin Irritation Test was used to evaluate in vitro irritancy potential of OPA and glutaraldehyde. Treatment with 0.4125 and 0.55% OPA induced irritation, while glutaraldehyde exposure at these concentrations did not. Consistent with the in vitro results, OPA induced irritancy, evaluated by ear swelling, when mice were treated with 0.75%. Initial evaluation of the sensitization potential was conducted using the local lymph node assay at concentrations ranging from 0.005 to 0.75%. A concentration-dependent increase in lymphocyte proliferation was observed with a calculated EC3 value of 0.051% compared to that of 0.089%, previously determined for glutaraldehyde. Immunoglobulin (Ig) E-inducing potential was evaluated by phenotypic analysis of draining lymph node (DLN) cells and measurement of total and specific serum IgE levels. The 0.1 and 0.75% exposed groups yielded significant increases in the IgE+B220+ cell population in the lymph nodes while the 0.75% treated group demonstrated significant increases in total IgE, OPA-specific IgE, and OPA-specific IgG(1). In addition, significant increases in interleukin-4 messenger RNA and protein expression in the DLNs were observed in OPA-treated groups. The results demonstrate the dermal irritancy and allergic potential of OPA and raise concern about the proposed/intended use of OPA as a safe alternative to glutaraldehyde.

Effect of Prolonged Repeated Exposure to Formaldehyde Donors with Doses Below the EC3 Value on Draining Lymph Node Responses

In the Local Lymph Node Assay (LLNA), a stimulation index of 3 (SI = 3) is established as a threshold value for hazard identification of sensitization. The corresponding EC3 value, the effective concentration inducing a threefold increase compared to controls, can possibly predict threshold levels for sensitization in humans. Exposure to a dose below the threshold dose would not result in an induction of an immune response. Each repeated contact would be considered and viewed as a new contact and as long as the dose is below the threshold there will be no response, even after repeated exposures. However, repeated exposure may result in local accumulation eventually resulting in a dose that induces a response above the threshold for immunization. We investigated lymph node responses after short and prolonged exposure to formaldehyde donors, chemicals that are highly reactive with proteins and may thus persist in the skin. The studies were performed with formaldehyde and formaldehyde releasers (formaldehyde, paraformaldehyde, Quaternium-15, 2-Chloro-N-(hydroxymethyl)acetamide, and hexamethylenetetramine), at concentrations that induce a SI = 2, i.e., below the threshold for hazard identification. For all test chemicals investigated enhanced lymph node responses were obtained when comparing long-term prolonged exposure to short-term exposure, while three of five chemicals induced responses above SI = 3. Our results show that repeated and prolonged exposure to doses below the EC3 value can induce reactions above the SI = 3, the hazard identification threshold for sensitization in mice. So, when discussing the possible use of the EC3 as benchmark for risk assessment, one should consider duration of exposure and the possibility of local accumulation of the chemical under investigation.

Evaluation of irritancy and sensitization potential of metalworking fluid mixtures and components

There are approximately 1.2 million workers exposed to metalworking fluids (MWF), which are used to reduce the heat and friction associated with industrial machining and grinding operations. Irritancy and sensitization potential of 9 National Toxicology Program (NTP) nominated MWFs (TRIM 229, TRIM VX, TRIM SC210, CIMTECH 310, CIMPERIAL 1070, CIMSTAR 3800, SYNTILO 1023, SUPEREDGE 6768, and CLEAREDGE 6584) were examined in a combined local lymph node assay (LLNA). BALB/c mice were dermally exposed to each MWF at concentrations up to 50%. Significant irritation was observed after dermal exposure to all MWFs except CIMTECH 310 and SYNTILO 1023. Of the 9 MWFs, 6 induced greater than a 3-fold increase in lymphocyte proliferation and 7 tested positive in the irritancy assay. TRIM VX yielded the lowest EC3 value (6.9%) with respect to lymphocyte proliferation. Chemical components of TRIM VX identified using HPLC were screened for sensitization potential using structural activity relationship (SAR) modeling and the LLNA. TOPKAT predicted triethanolamine (TEA) as a sensitizer while Derek for Windows predicted only 4-chloro-3-methylphenol (CMP) to be positive for sensitization. When tested in the LLNA only CMP (EC3 = 11.6%) and oleic acid (OA) (EC3 = 29.7%) were identified as sensitizers. Exposure to all tested TRIM VX components resulted in statistically significant irritation. An additive proliferative response was observed when mixtures of the two identified sensitizing TRIM VX components, OA and CMP, were tested in the LLNA. This is one explanation of why the EC3 value of TRIM VX, with respect to lymphocyte proliferation, is lower than those assigned to its sensitizing components.

Comparative studies of lymph node cell subpopulations and cytokine expression in murine model for testing the potentials of chemicals to induce respiratory sensitization

OBJECTIVES

To investigate immunological changes in lymph nodes based on expression of cell-specific receptors and cytokine expression profile and accompanying inflammatory reactions in lungs of mice treated with chemicals of known potentials to induce respiratory sensitization and those in which activity in this regard is unclear.

MATERIALS AND METHODS

On day 1 and 7, Balb/c mice received toluene-2,4-diisocyanate (TDI), trimellitic anhydride (TMA), 1-chloro-2,4-dinitrobenzene (DNCB), glutaraldehyde (GA), formaldehyde (FA), benzalkonium chloride (ChB) or vehicle. On day 14, they received a single intranasal instillation with the same chemical or vehicle. On day 15, auricular lymph nodes (LN) were excised and used for analyzes of T-, B-cells, expression of CD44 and for the estimation of IL-4 and IFN-gamma production after in vitro stimulation with concanavalin A (ConA) and also for IL-4 and IFN-gamma mRNA expression analyses using Real-Time PCR. Inflammatory changes in lungs were observed by estimation of TNF-alpha and MIP-2 concentrations and cell numbers and their type in BAL.

RESULTS

There were no significant changes in cell subpopulations of T helper cells in LN. The percent of B cells was significantly increased after treatment with DNCB, TDI, and GA. Increased expression of CD44 on T cells was also observed. Both IL-4 and IFN-gamma were found increased in TDI- and FA-treated mice, while only IL-4 was increased in TMA-treated mice. Real-Time PCR analyses, however, showed increased IL-4 mRNA expression for TDI- and TMA-, and IFN-gamma mRNA expression for DNCB-treated mice. We haven't observed significant changes in inflammatory reactions in the lungs of exposed animals.

CONCLUSIONS

Studying immunological changes with first determining the activation status of T cells followed by analyzes of expression of mRNA for Th1 and Th2 cytokines in murine model could be a useful method for assessment of the potentials of chemicals to induce respiratory sensitization but is not sufficient. Addition of ventilatory measurements, but not necessarily inflammatory reactions, could complete the model.

Impact of aldehyde content on amphotericin B-dextran imine conjugate toxicity

The biocompatibility of oxidized dextran (40 kDa) was investigated in vitro. The contribution of aldehyde groups to the toxicity of polymer-drug conjugates, such as dextran-amphotericin B (AmB) was evaluated. Oxidized dextran was proved to be toxic against the RAW 264.7 cell line with an IC50 of 3 micromol/mL aldehydes. Modification of aldehyde groups and their reaction with ethanolamine reduced the toxicity at least 15-fold. Accordingly, the antifungal and antileishmanial dextran-AmB imine conjugate, which contains unreacted aldehyde groups, was modified with ethanolamine and compared to dextran-AmB amine and imine conjugates. Modification of the imine conjugate with ethanolamine reduced its toxicity toward the RAW cell line by 100%. The effect on Leishmania major parasites was 5 times higher than that of the dextran-AmB amine conjugate. The dextran-AmB-ethanolamine conjugate was at least 15 times less hemolytic than free AmB. Stability and drug release profiles in buffer solution were investigated. The imine conjugates released free AmB while the amine conjugate did not. It is concluded that aldehyde groups may contribute to cell toxicity. This toxicity is reduced by converting the aldehyde groups into imine conjugates with ethanolamine. The results have direct implications toward the safety of AmB-polysaccharide conjugates used against fungal and leishmanial infections.

UNRESOLVED ISSUES IN DIALYSIS: Dialyzer Best Practice: Single Use or Reuse?

Outcome studies have shown either no additional risk or a small additional risk for hospitalization and mortality associated with reprocessing dialyzers. Although the risks from reprocessing dialyzers have yet to be fully elucidated, reuse can be done safely if it is performed in full compliance with the standards of Association for the Advancement of Medical Instrumentation (AAMI). Like most industrial processes, however, complete control of the reuse process in a clinical environment and full compliance with regulations at all times is difficult. Potential errors and breakdowns in the reuse process are continuing concerns. The quality controls for reprocessing of dialyzers are not equal to the rigor of the manufacturing process under the purview of the U.S. Food and Drug Administration (FDA). Therefore, if one were to determine "best practice," single use is preferable to reuse of dialyzers based on medical criteria and risk assessment. The long-term and cumulative effects of exposure to reuse reagents are unknown and there is no compelling medical indication for reprocessing of dialyzers. The major impediment when deciding to convert from reuse to single use of dialyzers is economic. The experience in Fresenius Medical Care-North America (FMCNA) facilities demonstrates that converting from a practice of reuse to single use is achievable. However, the overall economic impact of conversion to single use is provider specific. The dominance of reuse has been negated of late by a major shift in practice toward single use. Physicians and patients should be well informed in making decisions regarding the practice of single use versus reuse of dialyzers.

Occupational allergens in dentistry

PURPOSE OF REVIEW

Dental professionals and their physicians frequently do not recognize, accurately diagnose or appropriately manage occupational allergies. Dental allergen identification, diagnostics and practical avoidance strategies are summarized in this review.

RECENT FINDINGS

Methacrylates, natural rubber latex proteins, rubber glove allergens, and glutaraldehyde are the predominant allergens in dentistry. Reactions range from cell-mediated contact allergy to urticaria and occupational asthma.

SUMMARY

Despite recent advances in allergen characterization and increased awareness of selected allergens, treatment of occupational allergies can be improved. Better information and improved cooperation between dental workers and their clinicians is needed.