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The Social Security earnings test reform in 2000 eliminated the earnings test for all individuals between the normal retirement age (NRA) and age sixty-nine. The earnings test has long been accused of imposing a disincentive on the labor supply among older workers. In this article, we argue that the policy change may also have affected the labor supply among people who were just below the NRA around 2000. We utilize approaches embedded with a difference-in-differences design to estimate the anticipation effect on the labor supply of the slightly younger group (aged sixty-two to sixty-four) using an even younger cohort as the control group. Our preferred estimates indicate that the cohort aged sixty-two to sixty-four had worked 5.4 percent more weeks per year and 5.1 percent more hours per week after the earnings test reform in 2000. [ABSTRACT FROM AUTHOR]

Antibodies are the most important reagents for the development of highly sensitive and specific immunoassays to quantify analytes of interest in food and environmental samples. While immunoglobulin G (IgG)-derived antibodies from rabbit and mouse are traditionally employed in immunoassays, recent findings suggest that chicken egg yolk antibody (immunoglobulin Y (IgY)) provides several advantages over mammalian IgG. However, limited studies to date have examined the possibility of replacing IgG with IgY in immunoassays. In the current investigation, the performance of chicken IgY and IgG derived from rabbit and mouse was systematically compared in terms of sensitivity, specificity, and matrix effect under parallel conditions with three typical assay formats, specifically, indirect competitive enzyme-linked immunosorbent assay (icELISA), fluorescence polarization immunoassay (FPIA), and colloidal gold immunochromatographic assay (GICA), for detection of sulfamethazine (SMZ) as the reference molecule. We evaluated and discussed the influence of different coating antigens, tracers, and physicochemical factors on the performance of IgY and IgG in the immunoassays. Under optimized conditions, the sensitivities of icELISA (IC50 values of 6.70, 4.76, and 1.66 ng mL−1 with recoveries of 86.1-131.8% and precision of < 12%) and FPIA (IC50 values of 24.79, 20.87, and 10.83 ng mL−1 with recoveries of 81.8-120.2% and precision of < 17.3%) based on both IgY and IgG were sufficient to detect SMZ in milk while only GICA based on mouse IgG provided acceptable sensitivity. Our collective data indicate that IgY could be an acceptable alternative to mammalian antibodies in some situations (in icELISA and FPIA) for use in the development of effective immunoassays for screening and detection of veterinary drug residues in food samples. [ABSTRACT FROM AUTHOR]

Immunoglobulin Y (IgY) is derived from egg yolk and has been identified as a cheap and high-yield immunoreagent. The application of IgY in immunoassays for the detection of chemical contaminants in food samples has rarely been reported. In this work, we describe a rapid and sensitive fluorescence polarization immunoassay (FPIA) for valnemulin (VAL) using IgY which was produced using a previously prepared immunogen. Three fluorophore-labeled VAL tracers were synthesized and the sensitivity of the best tracer (VAL-DTAF) in the optimized FPIA with antibody IgY demonstrated an IC value of 12 ng mL in buffer. After evaluation of several extraction procedures, acidified acetonitrile was selected to extract VAL from swine tissue. The recoveries of VAL in spiked swine tissue at three levels (50, 100, and 200 μg kg) were higher than 79 % with coefficients of variation (CVs) lower than 12 %. The limit of detection (LOD) of the FPIA in swine tissue was 26 μg kg and was lower than the maximum residue limit (MRL) of VAL set by the European Union. The study showed that IgY could be a good substitute for IgG when developing a high-throughput assay for chemical residues. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Immunoassays based on the current available antibodies for large multi-sulfonamide screening programs have suffered from high selectivity for individual sulfonamides and a wide range of selectivities for different sulfonamides. In this study, five synthesized haptens, HS, BS, CS, SA10, and TS and two sulfonamides, SG and SMX were used as haptens, which may or may not contain a ring structure at the N1 position of the sulfonamides, were selected to evaluate the effectiveness for producing group-specific monoclonal antibodies (MAbs). Mice immunized with three different two-ring haptens were used for hybridoma production, which resulted in three unique MAbs recognizing 10, 13, and 15 sulfonamides showing 50 % inhibition (IC) at concentrations below 100 ng mL. MAb 4D11 derived from one novel immunizing hapten could recognize 12 sulfonamides with IC values ranging from 1.2 to 12.4 ng mL, almost within 1 order of magnitude. These produced MAbs show lower IC values in addition to significantly improved group specificity compared with previously generated MAbs. This study clearly indicates that the careful selection of the immunizing hapten has an important effect on the specificity of the generated antibodies. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Polyclonal and monoclonal antibodies against valnemulin, a new semi-synthetic antibiotic derivative of pleuromutilin administered to treat swine dysentery and pneumonia, were generated. To achieve high enzyme-linked immunosorbent assay sensitivity for valnemulin, several heterologous coating antigens were prepared and evaluated, differing in the length of the spacer arm and the conjugation site between valnemulin and carrier protein. After the optimisation of immuno-reagents dilution, the enzyme-linked immunosorbent assay, based on polyclonal antibody number 2 and one heterologous coating antigen, showed the highest sensitivity with an IC50value for valnemulin of 0.96 ng/mL in buffer. For spiked porcine liver, an extraction procedure with a mixture of acetonitrile and 0.01 M hydrochloric acid (40:60 v/v) was proposed and no further sample pre-treatment other than 10 times dilution of the extract was necessary prior to analysis, which gave recovery values ranging from 75.7% to 89.4%. The dynamic assay range and the limit of detection of the assay were 2.4−49.9 and 1.67 µg/kg for porcine liver, respectively. The assay was compared with a confirmation method based on LC-MS/MS by using valnemulin-treated samples, and a satisfactory correlation between both methods was observed. [ABSTRACT FROM PUBLISHER]