Direct LC-MS/MS and indirect GC-MS/MS methods for measuring urinary bisphenol A concentrations are comparable

BACKGROUND

Bisphenol A (BPA) is typically measured in urine using an indirect method that involves enzymatic deconjugation and extraction. In contrast, the direct method measures free and conjugated BPA concurrently and sums them to estimate urinary BPA concentrations. Statistical comparison of total BPA results using the direct and indirect methods is necessary to accurately interpret biomonitoring data for risk assessments.

OBJECTIVES

To compare urinary BPA concentrations estimated from the indirect and direct methods in duplicate first trimester urine samples collected from 1879 pregnant women from the MIREC Study.

METHODS

For the indirect method, we measured urinary BPA concentrations using GC-MS/MS. For the direct method, we summed free and conjugated BPA concentrations measured using LC-MS/MS. We evaluated deviation between the two methods using the Bland-Altman analysis in the total sample and stratified (1) by specific gravity and (2) at the limit of quantification (LOQ).

RESULTS

Median urinary BPA concentrations for the direct and indirect methods were 0.89 µg BPA equivalents/L and 0.81 µg/L respectively. Concentrations from the direct method were, on average, 8.6% (95% CI: 6.7%, 10.5%) higher than the indirect method in a Bland-Altman analysis. The percent differences between the two methods was 4.0% in urines with specific gravities < 1.02 (n = 1348, 72%) and 20.3% in urine with specific gravity ≥ 1.02. In values below the LOQ (n = 663, 35%), we observed smaller average percent deviation (4.8%) between the two methods but wider limits of agreement.

DISCUSSION

Results from this study, based on the largest statistically rigorous comparison of the direct and indirect methods of BPA measurement, contrast previous findings reporting that the indirect method underestimates total BPA exposure. The difference in urinary BPA concentrations we observed with the indirect and direct methods is unlikely to alter the interpretation of health outcome data.

Surgical Approaches for Implanting Xen Gel Stent without Conjunctival Dissection

The XEN Gel Stent (Allergan Inc., an Abbvie company) is an implant that lowers intraocular pressure by creating a filtration pathway from the anterior chamber to the subconjunctival space, using the same pathway as trabeculectomy. While the primary method for implantation is via ab interno approach, it is also possible to implant the device ab externo. This technique paper details the surgical steps for closed conjunctival implantation of the Gel Stent and provides surgical pearls for enhancing outcomes.

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Effect of chemotherapy on exercise capacity in patients with advanced non-small cell lung cancer (NSCLC)

9115

Background: The 6 minute walking distance (6MW) is commonly used to evaluate cardiopulmonary exercise capacity in a variety of patient (pt) populations. Although the 6MW test improved in advanced breast cancer pts who responded to 2 cycles of chemotherapy, (Nieman et al 1995), little is known about exercise capacity of pts with inoperable lung cancer. We prospectively evaluated 6MW in advanced NSCLC pts at diagnosis and following 2 cycles of chemotherapy (CT). Methods: 6MW was performed twice pre (one practice test) and once post 2 cycles of CT. Intent to treat (ITT) analysis was performed in pts who did not complete the last walk. A score of 0 was assigned to those who died and the last observation was carried forward for those with missing data. Results: 59 pts were enrolled though 6 pts withdrew following the practice test due to clinical deterioration (2 pts), pulmonary embolism (1pt), leg pain following the practice walk (1 pt) and withdrawal of consent (2 pts). The mean age of the remaining 53 pts was 61 ±11, PS was 0–1 in 46 (87%) and 2 in 7 (13%) of pts. 8 pts (15%) were stage 3A/3B and 45 (85%) were stage 3B /4 NSCLC. 45 (85%) pts received platinum-based doublets, whereas 8 (15%) had monotherapy. 39 pts completed the study and 14 pts did not complete the second evaluation (4 died, 8 withdrew due to worsening symptoms and 2 were lost for follow-up). The practice 6MW of the 20 pts who dropped out was 361±99 m compared to 448± 93m for the 39 who completed the study (p=0.002). The 6MW decreased from 461±108 m (range 247–748) to 431±98 (range 431–630) in the 39 pts who completed the study (p=0.02) and from 444±106 to 395±107 in the 53 pts using the ITT analysis (p<0.003). There was a clinically significant (>54 m) decrease in 6MW in 11 pts (28%), an increase in 6MW in 2 pts (5%), and no change in 26 (67%) others. The 6MW was higher in men and in pts in stages 3A/B (p<0.05). Conclusions: Exercise capacity, measured by 6MW, declines significantly after two cycles of chemotherapy. This decline may have been underestimated as pts with lower 6MW were more likely to drop out of the study.

No significant financial relationships to disclose.

Quality of life and survival in patients receiving chemotherapy for advanced non-small cell lung cancer (NSCLC)

19649

Background: Quality of life (QoL) is an important endpoint measure in clinical cancer trials. We evaluated prospectively the effects of two cycles of chemotherapy (CT) on QoL and the relationship between QoL and survival in advanced NSCLC patients (pts). Methods: The short-form of the SF36 was completed prior to and after 2 cycles of chemotherapy. An ITT analysis was used; a score of 0 was assigned to those who died and the last observation was carried forward for those with missing data. Results: Fifty-nine pts consented to participate and pre-chemo evaluation was available for 58 pts. Of these 58, only 40 pts completed the study (4 died, 14 did not complete the post evaluation). There were 26M: 32F with a median age of 61±11 years. Fifty pts (86%) were stage 3B (pl. eff)/4 and 50pts (86%) were PS 0–1. Overall QoL decreased significantly from 100±19 to 91±36 after two cycles of chemotherapy (p=0.03). This decline was attributed to a significant decrease in the physical health subscale (p=0.001), with 36% of pts reporting a clinically significant decline of =2. No change in the mental health subscale was observed. The symptoms that had the most profound negative impact on the physical health subscale were: ‘easily get sick’ (54%), ‘increased pain’ (30%) and ‘decreased activities’ (27%). SD+PR occurred in 36 (62%) pts, whereas 22 (38%) pts had PD after two cycles of chemotherapy. No correlation was found between response to chemo and change in QoL. The median survival (15±6.8mo), of pts whose QoL score remained stable or improved (n=36) was significantly better than those (n=22) whose QoL decreased (9±3.2 mo) (p=0.01). Conclusions: QoL decreased following chemotherapy due to a decrease in the physical health subscale. Further studies are required to determine if training can improve physical health and thus QoL and survival.

No significant financial relationships to disclose.

Quantitative determination of hexamethylene diisocyanate (HDI), 2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate (2,6-TDI) monomers at ppt levels in air by alkaline adduct coordination ionspray tandem mass spectrometry

Occupational exposures to isocyanates can lead to occupational asthma. Once sensitized, some workers could react to isocyanate monomers at concentrations below 1% of the Permissible Exposure Limit of 5 ppb in air. Currently available methods are not sufficiently sensitive to adequately evaluate isocyanates present at these levels in workplace air. This article describes a novel method for isocyanate determination allowing the ultratrace quantification in workplace air of hexamethylene diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate monomers. Sampling is performed during a complete workshift at a flow rate of 1 L min(-1) with a cassette containing a 1-(2-methoxyphenyl)piperazine-impregnated 25 mm filter. Analysis is performed using liquid chromatography hyphenated with coordination ionspray tandem mass spectrometry. The analytical method's linearity was measured for a concentration range varying from the limit of detection of 0.04-0.13 ng mL(-1), depending on the monomer, up to approximately 32 ng mL(-1) for every isocyanate monomer, all with correlation coefficients (R(2)) greater than 0.999. The analytical method's lower limit of quantification combined with an adapted sampling strategy allow the quantification of isocyanate monomers down to 0.04 ppt for an 8 h work shift when a lithium adduct is used, which is more than 300 times lower than the most sensitive method currently available. This novel method can be used to confirm the very low level of isocyanate monomers for the safe reassignment of sensitized workers and it is also useful for charting the isocyanate dispersion tail in workplace environments.

Clonal deletion of some V beta+ T cells in peripheral lymphocytes from C57BL/6 mice infected with MHV3

Mouse hepatitis virus type 3 infection is generally accompanied by a severe immune dysfunction involving thymic or splenic T cell subpopulations. We postulate that the peripheral lymphoid cell depletions were caused by a selective deletion of some V beta subsets of mature T cells, as observed with superantigens. We have examined the expression of V beta 6, V beta 8 and V beta 14 in T cell subpopulations from the spleen and lymph nodes of pathogenic L2-MHV3-infected C57BL/6 mice. Cytofluorometric study showed decreases in splenic V beta 8+, V beta 6+, and V beta 14+ T cell subpopulations at 72 hrs post-infection. Single positive CD4+ T cells were diminushed but not the CD8+ cells. In contrast, the various V beta splenic cell populations were not modified in mice infected with a non- pathogenic YAC-MHV3 variant. However, the V beta 8/CD4 ratio increased in splenic cells but decreased in lymphocytes from lymph nodes. The V beta 14/CD4 ratio decreased only in splenic cells while V beta 6/CD4 ratios were not modified. These results suggest that alterations in V beta cell populations may play a role in the L2-MHV3-induced immunodeficiency.

Effect of compost on rhizosphere microflora of the tomato and on the incidence of plant growth-promoting rhizobacteria

Four commercial composts were added to soil to study their effect on plant growth, total rhizosphere microflora, and incidence of plant growth-promoting rhizobacteria (PGPR) in the rhizosphere of tomato plants. Three of the compost treatments significantly improved plant growth, while one compost treatment significantly depressed it. Compost amendments caused only small variations in the total numbers of bacteria, actinomycetes, and fungi in the rhizosphere of tomato plants. A total of 709 bacteria were isolated from the four compost treatments and the soil control to determine the percentage of PGPR in each treatment. The PGPR tests measured antagonism to soilborne root pathogens, production of indoleacetic acid, cyanide, and siderophores, phosphate solubilization, and intrinsic resistance to antibiotics. Our results show that the addition of some composts to soil increased the incidence in the tomato rhizosphere of bacteria exhibiting antagonism towards Fusarium oxysporum f. sp. radicis-lycopersici, Pyrenochaeta lycopersici, Pythium ultimum, and Rhizoctonia solani. The antagonistic effects observed were associated with marked increases in the percentage of siderophore producers. No significant differences were observed in the percentage of cyanogens, whereas the percentages of phosphate solubilizers and indoleacetic acid producers were affected, respectively, by one and two compost treatments. Intrinsic resistance to antibiotics was only marginally different among the rhizobacterial populations. Our results suggest that compost may stimulate the proliferation of antagonists in the rhizosphere and confirm previous reports indicating that the use of composts in container media has the potential to protect plants from soilborne root pathogens.