An algorithm for quantitatively estimating occupational endotoxin exposure in the Biomarkers of Exposure and Effect in Agriculture (BEEA) study: I. Development of task-specific exposure levels from published data

BACKGROUND/OBJECTIVE

Farmers conduct numerous tasks with potential for endotoxin exposure. As a first step to characterize endotoxin exposure for farmers in the Biomarkers of Exposure and Effect in Agriculture (BEEA) Study, we used published data to estimate task-specific endotoxin concentrations.

METHODS

We extracted published data on task-specific, personal, inhalable endotoxin concentrations for agricultural tasks queried in the study questionnaire. The data, usually abstracted as summary measures, were evaluated using meta-regression models that weighted each geometric mean (GM, natural-log transformed) by the inverse of its within-study variance to obtain task-specific predicted GMs.

RESULTS

We extracted 90 endotoxin summary statistics from 26 studies for 9 animal-related tasks, 30 summary statistics from 6 studies for 3 crop-related tasks, and 10 summary statistics from 5 studies for 4 stored grain-related tasks. Work in poultry and swine confinement facilities, grinding feed, veterinarian services, and cleaning grain bins had predicted GMs > 1000 EU/m3 . In contrast, harvesting or hauling grain and other crop-related tasks had predicted GMs below 100 EU/m3 .

SIGNIFICANCE

These task-specific endotoxin GMs demonstrated exposure variability across common agricultural tasks. These estimates will be used in conjunction with questionnaire responses on task duration to quantitatively estimate endotoxin exposure for study participants, described in a companion paper.

A Task-Specific Algorithm to Estimate Occupational (1→3)-β-D-glucan Exposure for Farmers in the Biomarkers of Exposure and Effect in Agriculture Study

OBJECTIVES

Farmers may be exposed to glucans (a cell component of molds) through a variety of tasks. The magnitude of exposure depends on each farmer's activities and their duration. We developed a task-specific algorithm to estimate glucan exposure that combines measurements of (1→3)-β-D-glucan with questionnaire responses from farmers in the Biomarkers of Exposure and Effect in Agriculture (BEEA) study.

METHODS

To develop the algorithm, we first derived task-based geometric means (GMs) of glucan exposure for farming tasks using inhalable personal air sampling data from a prior air monitoring study in a subset of 32 BEEA farmers. Next, these task-specific GMs were multiplied by subject-reported activity frequencies for three time windows (the past 30 days, past 7 days, and past 1 day) to obtain subject-, task-, and time window-specific glucan scores. These were summed together to obtain a total glucan score for each subject and time window. We examined the within- and between-task correlation in glucan scores for different time frames. Additionally, we assessed the algorithm for the 'past 1 day' time window using full-shift concentrations from the 32 farmers who participated in air monitoring the day prior to an interview using multilevel statistical models to compare the measured glucan concentration with algorithm glucan scores.

RESULTS

We focused on the five highest exposed tasks: poultry confinement (300 ng/m3), swine confinement (300 ng/m3), clean grain bins (200 ng/m3), grind feed (100 ng/m3), and stored seed or grain (50 ng/m3); the remaining tasks were <50 ng/m3 and had similar concentrations to each other. Overall, 67% of the participants reported at least one of these tasks. The most prevalent task was stored seed or grain (64%). The highest median glucan scores were observed for poultry confinement and swine confinement; these tasks were reported by 2% and 8% of the participants, respectively. The correlation between scores for the same task but different time windows was high for swine confinement and poultry confinement, but low for clean grain bins. Task-specific scores had low correlation with other tasks. Prior day glucan concentration was associated with the total glucan 'past 1 day' score and with swine confinement and clean grain bin task scores.

CONCLUSIONS

This study provides insight into the variability and key sources of glucan exposure in a US farming population. It also provides a framework for better glucan exposure assessment in epidemiologic studies and is a crucial starting point for evaluating health risks associated with glucans in future epidemiologic evaluations of this population.

Observed vs. self-reported agricultural activities: Evaluating 24-hr recall in a pilot study

Few studies have evaluated the validity of self-report of work activities because of challenges in obtaining objective measures. In this study, farmers' recall of the previous day's agricultural activities was compared to activities observed by field staff during air monitoring. Recall was assessed in 32 farmers from the Biomarkers of Exposure and Effect in Agriculture Study, a subset of a prospective cohort study. The farmers participated in 56 visits that comprised air monitoring the day before an interview. The answers for 14 agricultural activities were compared to activities observed by field staff during air monitoring (median duration 380 min, range 129-486). For each task, evaluated as yes/no, overall agreement, sensitivity, specificity, and kappa were calculated. Median prevalence of the 14 activities was 8% from observation and 13% from participants (range: 2-54%). Agreement was generally good to perfect, with a median overall agreement of 95% (range: 89-100%), median sensitivity of 84% (50-100%), median specificity of 95% (88-100%), and median kappa of 0.65 (0.31-1.0). Reasons for disagreement included activities occurring when the field staff was not present (i.e., milking cows), unclear timing notes that made it difficult to determine whether the activity occurred the day of and/or day before the interview, definition issues (i.e., participant included hauling in the definition of harvesting), and difficulty in observing details of an activity (i.e., whether hay was moldy). This study provides support for accurate participant recall the day after activities.

Characteristics of Registered Clinical Trials Evaluating the Role of e-Cigarettes in Cessation or Reduction of Cigarette Smoking

This observational study examines the characteristics of completed and ongoing domestic and international clinical trials registered in the World Health Organization Registry Network.

The effect of routine hoof trimming on midstance regional hoof kinetics at walk

There is a lack of objective and quality evidence-based research on the effect of trimming on hoof loading at different regions of the hoof. Our objective was to measure and compare force (F), contact area (CA), contact pressure (CP) and peak contact pressure (PCP) of the dorsal vs palmar and medial vs lateral regions of the forehooves. Nine sound equine athletes were walked across a calibrated pressure plate before and after routine hoof trimming. The F, CA, CP and PCP in medial, lateral, dorsal and palmar regions were examined pre- and post-trimming, P≤0.05 was considered significant. Dorsal CP and PCP significantly increased post-trimming (P=0.039 and P=0.019, respectively). Medial F increased about 25% after trimming, but not significantly (P=0.129). These data confirm the impact of individual hoof trimming on certain aspects of the hoof midstance biomechanics.

237.Insulin receptor expression in mouse preimplantation embryos

The insulin receptor (IR) mediates the actions of insulin and insulin-like growth factors (IGF-I and II). Two IR isoforms result from alternate splicing of exon 11, IR-A (without exon 11) and IR-B (with exon 11). Exon 11 is 36 bp and encodes 12 amino acids (717-729) in the COOH-terminus of the IR alpha-subunit. IR-A has higher binding affinity for insulin and IGF-II than IR-B. Interestingly, IR-A is predominantly expressed in fetal tissues, adult spleen, brain and tumours, where its expression has been associated with an undifferentiated state. IR-B is expressed primarily in classical insulin sensitive tissues such as adult liver and muscle. In contrast to other species, no evidence existed for IR expression prior to compaction in mice. However, both insulin and IGF-II have been shown to stimulate growth in cleaving embryos (Kaye 1997). We returned to this question using primers flanking exon 11 to detect IR-A and IR-B mRNA. Sequencing confirmed the identity of the amplified PCR products. IR-B mRNA was present in zygotes and all stages to blastocyst, IR-A mRNA was only detected in compacted morulae. Immunofluorescent confocal microsopy using a rabbit polyclonal antibody (against amino acids 128-205 of alpha-subunit) that recognizes both isoforms revealed nuclear IR localization in zygotes and cleavage stage embryos including morulae. The results demonstrate that mice like other species expresses IR throughout preimplantation development in contrast with earlier studies. Nuclear localisation of IR has been observed in hepatocytes and adipocytes and may be associated with transcriptional regulation. IR-A expression in compacted morulae may reflect the change in metabolism that occurs at this time and requires further study. (1) Kaye, P. L. (1997) Preimplantation growth factor physiology. Rev. Reprod. 2, 121–127.

A protein kinase inhibitor as an antimycobacterial agent

The protein kinase inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) was found to inhibit the growth of two different mycobacterial strains, the slow-growing Mycobacterium bovis Bacille Calmette Guerin (BCG) and the fast-growing saprophyte Mycobacterium smegmatis mc2 155, in a dose-dependent manner. While screening for the effect of kinase inhibitors on mycobacterial growth, millimolar concentrations of H7 induced a 40% decrease in the growth of M. bovis BCG when measured as a function of oxidative phosphorylation. This H7-induced decrease in growth was shown to involve a 2-log fold decrease in the viable counts of M. smegmatis within a 48-h period and a 50% reduction in the number of BCG viable counts within a 10-day period. Micromolar concentrations of H7 compound induced a significant decrease in the activity of the Mycobacterium tuberculosis protein serine/threonine kinase (PSTK) PknB. The inhibition of mycobacterial growth as well as the inhibition of a representative M. tuberculosis protein serine/threonine kinase PknB suggests that conventional PSTK inhibitors can be used to study the role that the mycobacterial PSTK family plays in controlling bacterial growth.

Solution structure and backbone dynamics of the second PDZ domain of postsynaptic density-95

The second PDZ domain of postsynaptic density-95 (PSD-95 PDZ2) plays a critical role in coupling N-methyl-D-aspartate receptors to neuronal nitric oxide synthase (nNOS). In this work, the solution structure of PSD-95 PDZ2 was determined to high resolution by NMR spectroscopy. The structure of PSD-95 PDZ2 was compared in detail with that of alpha1-syntrophin PDZ domain, as the PDZ domains share similar target interaction properties. The interaction of the PSD-95 PDZ2 with a carboxyl-terminal peptide derived from a cytoplasmic protein CAPON was studied by NMR titration experiments. Complex formation between PSD-95 PDZ2 and the nNOS PDZ was modelled on the basis of the crystal structure of the alpha1-syntrophin PDZ/nNOS PDZ dimer. We found that the prolonged loop connecting the betaB and betaC strands of PSD-95 PDZ2 is likely to play a role in both the binding of the carboxyl-terminal peptide and the nNOS beta-finger. Finally, the backbone dynamics of the PSD-95 PDZ2 in the absence of bound peptide were studied using a model-free approach. The "GLGF"-loop and the loop connecting alphaB and betaF of the protein display some degree of flexibility in solution. The rest of the protein is rigid and lacks detectable slow time-scale (microseconds to milliseconds) motions. In particular, the loop connecting betaB and betaC loop adopts a well-defined, rigid structure in solution. It appears that the loop adopts a pre-aligned conformation for the PDZ domain to interact with its targets.

Characterization of topoisomerase II-DNA interaction and identification of a DNA-binding domain by ultraviolet laser crosslinking

We have used ultraviolet laser crosslinking to characterize the DNA-binding properties of highly purified yeast topoisomerase II in the absence of ATP. A single 5 ns, 20 mJ pulse of 266 nm light produced optimal crosslinking to a short DNA duplex, with an efficiency of 0.25%. An equilibrium binding constant (Keq) of 1.2 +/- 0.5 x 10(8) M(-1) was determined from kinetic analysis. Topoisomerase II showed highest affinity for supercoiled DNA. Limited proteolysis of crosslinked topoisomerase II-DNA complexes showed a site of crosslinking to be within a 29-kDa fragment with Leu-681 at its amino-terminal end. This region contains the active Tyr-783 and is homologous to the amino-terminal region of the DNA-binding bacterial gyrase GyrA subunit, suggesting a conserved DNA-binding mechanism.

The effect of long-term chlorpromazine and desipramine treatment on adrenal corticosterone, cyclic AMP, and cholesterol distribution in rats

1. Male rats were injected intraperitoneally with chlorpromazine (10 mg/kg) and desipramine (10 mg/kg), respectively, twice daily for 2 weeks. 2. The adrenal corticosterone concentrations were significantly lowered in chlorpromazine- and desipramine-treated rats. 3. Large dose of corticotrophin would increase the adrenal corticosterone level in chlorpromazine-treated but the adrenal response was significantly less than in the untreated controls. 4. The adrenal cyclic AMP level was similar in treated and control rats and the adrenal response to corticotrophin was not decreased at the cyclic AMP level. 5. The cholesteryl ester concentrations in the adrenals were significantly increased by drug treatment, although the free cholesterol concentrations were unchanged in the cytosol and mitochondrial cell fractions. 6. The possible site of action of chlorpromazine in suppressing corticosterone production is discussed.

House dust mite and house dust allergy

Skin testing and the radioallergosorbent test (RAST) with extracts of house dust and mite (D. farinae) were performed on 100 patients. Correlation between positive prick tests with the two antigens was low, many more reactions being obtained with the house dust antigen in patients clinically positive to house dust. Also, for both antigens, the degree of reactivity was higher with the prick test than with RAST. It is concluded that, in this geographic area, house dust extract is more suitable than mite extract for skin testing and, by inference, for hyposensitization therapy of house dust-sensitive patients.