Robert R. Jacobs

Sodium hydroxide-induced conformational change in schizophyllan detected by the fluorescence dye, aniline blue

Molecular conformation is considered to be an important factor in determining the biological activity of glucans; however, a simple method to detect the conformation change for glucans in solution has not been developed. We found that the fluorescence intensity of aniline blue bound to schizophyllan (SPG) can be used to estimate the relative amount of single helix converting to triple helix during different stages of a denature–renature cycle. This observation provides a method to monitor conformational change that is simpler and easier to perform than other techniques (such as solid-state 13C NMR spectroscopy). The native conformation for SPG [a branched β-(1→3) glucan] is a rigid, closed triple helix. Treatment with NaOH, followed by neutralization, produces a single helix-rich preparation. We observed that aniline blue does not stain native SPG, but will stain the renatured NaOH-treated SPG. This suggests that aniline blue binds only to single helix forms of SPG. Further supporting evidence is that the fluorescence intensity is decreased on consecutive days after neutralization, which is consistent with the report that NaOH-treated SPG gradually lost 77% of their single helix component in 1 week (N. Nagi, N. Ohno, Y. Adachi, J. Aketagawa, H. Tamura, Y. Shibata, S. Tanaka, and T. Yadomae, Biol. Pharm. Bull., 16 (1993) 822–828). The single helix is the conformation which activates the Limulus amebocyte lysate (LAL). The biological reactivity of renatured SPG, stabilized with aniline blue at different days, was evaluated using a glucan sensitive LAL. The activity of LAL toward SPG was decreased over time, suggesting that the conformation of glucan detected by fluorescence intensity correlated with the LAL activity.

Observation of a Partially Opened Triple-helix Conformation in 1→3-β-Glucan by Fluorescence Resonance Energy Transfer Spectroscopy

This study used fluorescence resonance energy transfer (FRET) spectroscopy as an indirect method to investigate the effect of NaOH treatment on the conformation of a triple-helix (1→3)-β-d-glucan and then evaluated the effect of conformation on biological activity. Previous studies have suggested that treatment of the triple-helix glucans with NaOH produces single-helix conformers. FRET spectra of the triple-helix glucan, laminarin, doubly labeled with 1-aminopyrene as donor probe and fluorescein-5-isothiocyanate as acceptor probe attached at the reducing end, showed that a partially opened triple-helix conformer was formed on treatment with NaOH. Increasing degrees of strand opening was associated with increasing concentrations of NaOH. Based on these observations we propose that a partially opened triple-helix rather than a single helix, is formed by treating the triple-helix glucans with NaOH. After neutralizing the NaOH, changes in FRET indicated that the partially opened conformer gradually reverts to the triple-helix over 8 days. Laminarian was stabilized at different degrees of partial opening and its biological activity examined using theLimulus amebocyte lysate assay and nitric oxide production by alveolar macrophage. Both Limulus amebocyte lysate activity and nitric oxide production were related to the degree of opening of the triple-helix. Partially open conformers were more biologically active than the intact triple-helix.

Airborne Endotoxins: An Association with Occupational Lung Disease

Abstract Endotoxins are a component of the cell wall of gram negative bacteria and have been implicated as the etiological agent of byssinosis as well as the cause of pulmonary responses attributed to other organic dusts. Recent studies have proposed threshold values for airborne endotoxin and suggest that consideration be given to developing an occupational standard for endotoxin. Endotoxins occur at significant levels in many work environments, and the industrial hygienist should be aware of the disease potential of this agent. The structure, biological activity, measurement, and occurrence of endotoxin in the work environment is reviewed. The feasibility of an occupational standard is discussed and recommendations made for practical evaluation of endotoxin and for additional research. Jacobs, R. R.: Airborne Endotoxins: An Association with Occupational Lung Disease. Appl. Ind. Hyg. 4:50–56; 1989.

Locational uncertainty in georeferencing public health datasets

The assignment of locational attributes to a study subject in epidemiologic analyses is commonly referred to as georeferencing. When georeferencing study subjects to a point location using their residential street address, most researchers rely on the street centerline data model. This study assessed the potential locational bias introduced using street centerline data. It also evaluated georeferencing effects on a location-dependent, exposure assessment process. For comparison purposes, subjects were georeferenced to the center of their residential parcel of land using digitized parcel maps. A total of 10,026 study subjects residing in Jefferson County, Alabama were georeferenced using both street centerline and residential parcel methods. The mean nondirectional, linear distance between points georeferenced using both methods was 246 ft with a range of 11 to 13,260 ft. Correlation coefficients comparing differences in exposure estimates were generated for all 10,026 subjects. Coefficients increased as the geographic areas of analysis around study subjects increased, indicating the influence of nondifferential exposure misclassification.

An evaluation of the prevalence of latex sensitivity among atopic and non-atopic intensive care workers

BACKGROUND Exposure to latex is known to cause an array of symptoms, including pruritus, dermatitis, erythema, and urticaria. Workers at elevated risk for latex exposure include health care personnel whose repeated patient contact or surgical work require extensive use of latex gloves. This study evaluated the prevalence of latex allergies in atopic and non-atopic intensive care workers and sought to determine the impact of risk factors such as frequency of glove use and hand washing on latex sensitization. METHODS We evaluated the prevalence of latex sensitivity in 122 intensive care unit (ICU) workers using a questionnaire and skin prick test. Atopy and latex sensitivity were determined by skin prick test using a battery of common inhalant allergens and an extract prepared from the gloves used in the ICU. Frequency of glove use and hand washing were determined by questionnaire. RESULTS AND CONCLUSIONS Forty ICU workers (32.8%) were considered atopic by having at least one positive response to the inhalant allergens. Atopic ICU workers were more likely to have positive latex skin test than non-atopic ICU workers (atopic vs. non-atopic workers: p < 0.001, odds ratio = 14.2). Frequency of current glove use or hand washing frequency were not significant predictors of a positive response to latex; however, a positive history of atopic eczema and family history of allergies, as determined by questionnaire were significant predictors of a positive response to latex antigens.

Partially Opened Triple Helix is the Biologically Active Conformation of 1→3-β-Glucans that Induces Pulmonary Inflammation in Rats

1 M 3- g -Glucans produce pulmonary inflammation in rats and are commonly found in indoor air dust samples. Conformation is an important factor determining the biological activity of 1 M 3- g -glucans. The partially opened triple-helix conformation induced by NaOH treatment and the annealed triple-helix conformation have been identified by fluorescence resonance energy transfer spectroscopy in our previous study. The objective of this study was to examine the role of these conformations of 1 M 3- g -glucans in the induction of pulmonary inflammation in rats. A partially opened triple-helix conformation of the known inflammatory 1 M 3- g -glucan zymosan was prepared by treating zymosan with NaOH followed by neutralization and dialysis. The annealed triple-helix conformation was prepared by allowing the partially opened triple-helix conformation to anneal for 9 d at room temperature. Rats were exposed to fresh or annealed NaOH-treated zymosan via intratracheal instillation. The results show that the zymosan-induced pulmonary inflammatory responses were significantly reduced after the 9-d annealing period, which suggests that this inflammatory response was dependent on the conformation of zymosan. Freezing NaOH-treated zymosan (for 7 d) inhibited the annealing process. Exposure of rats to thawed preparations of zymosan resulted in the same inflammatory responses as the freshly prepared partially opened triple-helix zymosan. In contrast, the potency of untreated zymosan did not change significantly following a 7-d annealing period, indicating that annealing occurs only after the conformation has been modified by NaOH treatment. This study indicates that the partially opened triple helix of 1 M 3- g -glucans is more active than the closed conformation in inducing pulmonary inflammation in rats.

An in vitro comparison of the permeation of chemicals in vapor and liquid phase through pig skin.

This study used pig skin to compare vapor and liquid permeation of benzene, n-butanol, and toluene in vitro. Vapors of radio-labeled chemicals were generated by passing purified air through two saturators in series containing the labeled chemical. The generated vapor was directed into the donor compartment of a modified liquid permeation cell. For liquid permeation experiments, neat chemicals were dosed directly on the surface of the skin. The variability of the generated concentrations for the vapor phase of each chemical ranged from 3-7%. The mean flux of the liquid chemicals was significantly higher than those of the vapor phase. There was no significant difference in the flux of the individual chemicals in the liquid phase. In the vapor phase test, the flux of toluene and benzene were not significantly different; however, for n-butanol the flux was significantly lower than the for either benzene or toluene.

Characterization of an Aerosol Chamber for Human Exposures to Endotoxin

The objective of this study was to develop and characterize an exposure chamber in which human subjects could be exposed to low dust concentrations carrying an endotoxin coating. An exposure chamber, dust dispersion method, and endotoxin characterization technique were developed for inhalation exposures. A 6.27 m3 exposure chamber was designed and constructed from cinder block, glass windows, and Plexiglas. Using an acetone adhesion process, Enterobacter agglomerans were adsorbed onto respirable cellulose particles to create the endotoxin aerosol. The size distribution of the endotoxin-treated particles was verified using light microscopy and cascade impactors. A dry powder dust generator was refined to consistently disperse small quantities of the aerosol into the chamber to maintain dust concentrations at approximately 250 micrograms/m3. Dust levels during the chamber exposures were monitored using a portable continuous aerosol monitor (PCAM). During initial exposure runs, PCAM monitoring stations were positioned at different locations within a 0.5-meter matrix to document mixing patterns. Total dust and cascade impactor samples were collected throughout each exposure period to characterize the chamber operating system and insure the mean airborne dust concentration fulfilled target levels. A one-factor analysis of variance at the 95 percent confidence interval illustrated that there was not a statistically significant difference in the mean dust concentration throughout the exposure runs compared to the individual runs. Together the consistency of the total dust filters, endotoxin concentrations, and aerosol-monitoring instrument were adequate to allow use of the chamber for experimental studies involving human volunteers.

Varicella-Zoster Virus Susceptibility in Day-Care Workers

Abstract The susceptibility of day-care workers to varicella-zoster virus (VZV) was evaluated by determining antibody to VZV in 545 day-care workers using a commercial enzyme-linked immunosorbent assay (ELISA). Historical information about primary infection with VZV and demographic data were obtained from questionnaires completed by 494 workers. The proportion of daycare workers susceptible to VZV was 4.8 percent, and the seronegativity among workers with a negative history of VZV infection was 13.6 percent. These data indicate that a small proportion of the day-care workers are susceptible to varicella infection. The following recommendations are made to enhance the well-being of day-care workers. All day-care workers susceptible to VZV should be made aware of the adverse health affects associated with VZV if contracted. Susceptible workers identified by the serological screen should be sent home for 8-21 days after exposure if VZV infection occurs in the day-care setting. All day-care workers who are of...

Analysis of potential mercury policies: The impact of stream basin characteristics on susceptible populations

Human exposure to Hg through fish consumption from local waterways is an ongoing concern to regulatory decision makers. Previously described population exposure and bioaccumulation models were combined to analyze the impact of potential policies on susceptible populations. The combined model simulated the problem of Hg exposure by examining the system from the point of Hg in the water column to its concentration in population biomarkers. Evaluated policy scenarios included the protectiveness of fish consumption advisories, total maximum daily load changes, and watershed management strategies. Simulations indicated that the characteristics of a basin combined with the unique pattern of intake rates of susceptible populations determine the risk associated with fish consumption from a given waterway. Each population had a unique pattern of biomarker response to changes in fish tissue Hg. Management strategies that lowered bioaccumulation rates also reduced ecosystem services. Reducing fish tissue contamination through reductions in Hg loading to watersheds is a long-term solution. For the short-term, fish consumption advisories should be used to protect populations from adverse exposures. The combination of characteristics of the basin and the populations that fish from the waterway should be the determinant for setting advisories.