Health Insurance Take-up by the Near Elderly

This study examines the effect of price on the demand for health insurance by early retirees between the ages of 55 and 64. The analysis is based on administrative data from a medium sized employer and takes advantage of a natural experiment created by the firm's health insurance contribution policy. The amount the firm contributes toward retiree health insurance coverage depends on when a person retired and her years of service at that date. As a result of this policy, there is considerable variation in out-of-pocket premiums faced by individuals in the data, but this variation is independent of the non-price attributes of the health insurance plans offered, and plausibly exogenous to individual characteristics that are likely to affect the demand for insurance. We find that price has a statistically significant but small effect on the decision to take up coverage. The implied elasticities are very similar to results found in previous studies using very different data.

Characterization of the Catalytically Active Mn(II)-loaded \u3cem\u3eargE\u3c/em\u3e-encoded \u3cem\u3eN\u3c/em\u3e-acetyl-L-ornithine Deacetylase from \u3cem\u3eEscherichia coli\u3c/em\u3e

The catalytically competent Mn(II)-loaded form of the argE-encoded N-acetyl-l-ornithine deacetylase from Escherichia coli (ArgE) was characterized by kinetic, thermodynamic, and spectroscopic methods. Maximum N-acetyl-l-ornithine (NAO) hydrolytic activity was observed in the presence of one Mn(II) ion with k cat and K m values of 550 s−1 and 0.8 mM, respectively, providing a catalytic efficiency (k cat/K m) of 6.9 × 105 M−1 s−1. The ArgE dissociation constant (K d) for Mn(II) was determined to be 0.18 μM, correlating well with a value obtained by isothermal titration calorimetry of 0.30 μM for the first metal binding event and 5.3 μM for the second. An Arrhenius plot of the NAO hydrolysis for Mn(II)-loaded ArgE was linear from 15 to 55 °C, suggesting the rate-limiting step does not change as a function of temperature over this range. The activation energy, determined from the slope of this plot, was 50.3 kJ mol−1. Other thermodynamic parameters were ΔG ‡ = 58.1 kJ mol−1, ΔH ‡ = 47.7 kJ mol−1, and ΔS ‡ = –34.5 J mol−1 K−1. Similarly, plots of lnK m versus 1/T were linear, suggesting substrate binding is controlled by a single step. The natural product, [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]leucine (bestatin), was found to be a competitive inhibitor of ArgE with a K i value of 67 μM. Electron paramagnetic resonance (EPR) data recorded for both [Mn(II)_(ArgE)] and [Mn(II)Mn(II)(ArgE)] indicate that the two Mn(II) ions form a dinuclear site. Moreover, the EPR spectrum of [Mn(II)Mn(II)(ArgE)] in the presence of bestatin indicates that bestatin binds to ArgE but does not form a µ-alkoxide bridge between the two metal ions

Co-Catalytic Metallopeptidases as Pharmaceutical Targets

Understanding the reaction mechanism of co-catalytic metallopeptidases provides a starting point for the design and synthesis of new molecules that can be screened as potential pharmaceuticals. Many of the enzymes that contain co-catalytic metallo-active sites play important roles in cellular processes such as tissue repair, protein maturation, hormone level regulation, cell-cycle control and protein degradation. Therefore, these enzymes play central roles in several disease states including cancer, HIV, stroke, diabetes, bacterial infections, neurological processes, schizophrenia, seizure disorders, and amyotrophic lateral sclerosis. The mechanism of AAP, an aminopeptidase from Aeromonas proteolytica, is one of the best-characterized examples of a metallopeptidase containing a co-catalytic metallo-active site, although this enzyme is not a specific pharmaceutical target at this time. As a large majority of co-catalytic metallopeptidases contain active sites that are nearly identical to the one observed in AAP, the major steps of their catalytic mechanisms are likely to be very similar. With this in mind, it is possible to propose a general catalytic mechanism for the hydrolysis of amino acid substrates

\u3cem\u3eargE\u3c/em\u3e-Encoded \u3cem\u3eN\u3c/em\u3e-Acetyl-l-Ornithine Deacetylase from \u3cem\u3eEscherichia coli\u3c/em\u3e Contains a Dinuclear Metalloactive Site

The catalytic and structural properties of the argE-encoded N-acetyl-l-ornithine deacetylase (ArgE) from Escherichia coli were investigated. On the basis of kinetic and ITC (isothermal titration calorimetry) data, Zn(II) binds to ArgE with Kd values that differ by ∼20 times. Moreover, ArgE exhibits ∼90% of its full catalytic activity upon addition of one metal ion. Therefore, ArgE behaves similarly to the aminopeptidase from Aeromonas proteolytica (AAP) in that one metal ion is the catalytic metal ion while the second likely plays a structural role. The N-acetyl-l-ornithine (NAO) deacetylase activity of ArgE showed a linear temperature dependence from 20 to 45 °C, indicating that the rate-limiting step does not change over this temperature range. The activation energy for NAO hydrolysis by ArgE was 25.6 kJ/mol when loaded with Zn(II) and 34.3 kJ/mol when loaded with Co(II). Electronic absorption and EPR (electron paramagnetic resonance) spectra of [Co·(ArgE)] and [CoCo(ArgE)] indicate that both divalent metal binding sites are five coordinate. In addition, EPR data show clear evidence of spin−spin coupling between the Co(II) ions in the active site but only after addition of a second equivalent of Co(II). Combination of these data provides the first physical evidence that the ArgE from E. coli contains a dinuclear Zn(II) active site, similar to AAP and the carboxypeptidase G2 from Pseudomonas sp. strain RS-16 (CPG2)

Identification of a Histidine Metal Ligand in the \u3cem\u3eargE\u3c/em\u3e-Encoded \u3cem\u3eN\u3c/em\u3e-Acetyl-L-Ornithine Deacetylase from \u3cem\u3eEscherichia coli\u3c/em\u3e

The H355A, H355K, H80A, and H80K mutant enzymes of the argE-encoded N-acetyl-L-ornithine deacetylase (ArgE) from Escherichia coli were prepared, however, only the H355A enzyme was found to be soluble. Kinetic analysis of the Co(II)-loaded H355A exhibited activity levels that were 380-fold less than Co(II)-loaded WT ArgE. Electronic absorption spectra of Co(II)-loaded H355A-ArgE indicate that the bound Co(II) ion resides in a distorted, five-coordinate environment and Isothermal Titration Calorimetry (ITC) data for Zn(II) binding to the H355A enzyme provided a dissociation constant (Kd) of 39 μM. A three-dimensional homology model of ArgE was generated using the X-ray crystal structure of the dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae confirming the assignment of H355 as well as H80 as active site ligands

Thyroid Hormone Deiodinases and Cancer

Deiodinases constitute a group of thioredoxin fold-containing selenoenzymes that play an important function in thyroid hormone homeostasis and control of thyroid hormone action. There are three known deiodinases: D1 and D2 activate the pro-hormone thyroxine (T4) to T3, the most active form of thyroid hormone, while D3 inactivates thyroid hormone and terminates T3 action. A number of studies indicate that deiodinase expression is altered in several types of cancers, suggesting that (i) they may represent a useful cancer marker and/or (ii) could play a role in modulating cell proliferation – in different settings thyroid hormone modulates cell proliferation. For example, although D2 is minimally expressed in human and rodent skeletal muscle, its expression level in rhabdomyosarcoma (RMS)-13 cells is threefold to fourfold higher. In basal cell carcinoma (BCC) cells, sonic hedgehog (Shh)-induced cell proliferation is accompanied by induction of D3 and inactivation of D2. Interestingly a fivefold reduction in the growth of BCC in nude mice was observed if D3 expression was knocked down. A decrease in D1 activity has been described in renal clear cell carcinoma, primary liver cancer, lung cancer, and some pituitary tumors, while in breast cancer cells and tissue there is an increase in D1 activity. Furthermore D1 mRNA and activity were found to be decreased in papillary thyroid cancer while D1 and D2 activities were significantly higher in follicular thyroid cancer tissue, in follicular adenoma, and in anaplastic thyroid cancer. It is conceivable that understanding how deiodinase dysregulation in tumor cells affect thyroid hormone signaling and possibly interfere with tumor progression could lead to new antineoplastic approaches

Breaking the Cycle of Homelessness

With funding from Department of Health and Human Services secured by United Power for Action and Justice, CURL partnered with United Power for  Chicago Health Outreach, Deborah's Place and Lakefront SRO to evaluate their systems integration demonstration project. The overall goal of the demonstration project was to break the cycle of homelessness by providing services in a coordinated fashion.

Kinetic and Spectroscopic Characterization of the H178A Methionyl Aminopeptidase from \u3cem\u3eEscherichia coli\u3c/em\u3e

To gain insight into the role of the strictly conserved histidine residue, H178, in the reaction mechanism of the methionyl aminopeptidase from Escherichia coli (EcMetAP-I), the H178A mutant enzyme was prepared. Metal-reconstituted H178A binds only one equivalent of Co(II) or Fe(II) tightly with affinities that are identical to the WT enzyme based on kinetic and isothermal titration calorimetry (ITC) data. Electronic absorption spectra of Co(II)-loaded H178A EcMetAP-I indicate that the active site divalent metal ion is pentacoordinate, identical to the WT enzyme. These data indicate that the metal binding site has not been affected by altering H178. The effect of altering H178 on activity is, in general, due to a decrease in kcat. The kcat value for Co(II)-loaded H178A decreased 70-fold toward MGMM and 290-fold toward MP-p-NA compared to the WT enzyme, while kcat decreased 50-fold toward MGMM for the Fe(II)-loaded H178A enzyme and 140-fold toward MP-p-NA. The Km values for MGMM remained unaffected, while those for MP-p-NA increased approximately 2-fold for Co(II)- and Fe(II)-loaded H178A. The kcat/Km values for both Co(II)- and Fe(II)-loaded H178A toward both substrates ranged from ∼50- to 580-fold reduction. The pH dependence of log Km, log kcat, and log(kcat/Km) of both WT and H178A EcMetAP-I were also obtained and are identical, within error, for H178A and WT EcMetAP-I. Therefore, H178A is catalytically important but is not required for catalysis. Assignment of one of the observed pKa values at 8.1 for WT EcMetAP-I was obtained from plots of molar absorptivity at λmax(640) vs pH for both WT and H178A EcMetAP-I. Apparent pKa values of 8.1 and 7.6 were obtained for WT and H178A EcMetAP-I, respectively, and were assigned to the deprotonation of a metal-bound water molecule. The data reported herein provide support for the key elements of the previously proposed mechanism and suggest that a similar mechanism can apply to the enzyme with a single metal in the active site

Loss of TRAIL-receptors is a recurrent feature in pancreatic cancer and determines the prognosis of patients with no nodal metastasis after surgery.

Agonistic antibodies targeting TRAIL-receptors 1 and 2 (TRAIL-R1 and TRAIL-R2) are being developed as a novel therapeutic approach in cancer therapy including pancreatic cancer. However, the cellular distribution of these receptors in primary pancreatic cancer samples has not been sufficiently investigated and no study has yet addressed the issue of their prognostic significance in this tumor entity. Applying tissue microarray (TMA) analysis, we performed an immunohistochemical assessment of TRAIL-receptors in surgical samples from 84 consecutive patients affected by pancreatic adenocarcinoma and in 26 additional selected specimens from patients with no lymph nodes metastasis at the time of surgery. The prognostic significance of membrane staining and staining intensity for TRAIL-receptors was evaluated. The fraction of pancreatic cancer samples with positive membrane staining for TRAIL-R1 and TRAIL-R2 was lower than that of cells from surrounding non-tumor tissues (TRAIL-R1: p<0.001, TRAIL-R2: p = 0.006). In addition, subgroup analyses showed that loss of membrane staining for TRAIL-R2 was associated with poorer prognosis in patients without nodal metastases (multivariate Cox regression analysis, Hazard Ratio: 0.44 [95% confidence interval: 0.22-0.87]; p = 0.019). In contrast, analysis of decoy receptors TRAIL-R3 and -R4 in tumor samples showed an exclusively cytoplasmatic staining pattern and no prognostic relevance. This is a first report on the prognostic significance of TRAIL-receptors expression in pancreatic cancer showing that TRAIL-R2 might represent a prognostic marker for patients with early stage disease. In addition, our data suggest that loss of membrane-bound TRAIL-receptors could represent a molecular mechanism for therapeutic failure upon administration of TRAIL-receptors-targeting antibodies in pancreatic cancer. This hypothesis should be evaluated in future clinical trials

Culture, Health, and Science: A Multidisciplinary Liberal Arts Alternative to the Public Health Major

Since the 2003 call by the Institute of Medicine to educate undergraduates in public health, various models have emerged for incorporating public health into the liberal arts and sciences. One model is a professionalized public health major that uses core public health competencies to prepare a workforce of health professionals. A second model offers a broad-based public health major rooted in liberal arts principles, resisting the utilitarian trend toward human capital formation. A third model resists even the label of “public health,” preferring instead to introduce undergraduates to many ways of analyzing human health and healing. The multidisciplinary Culture, Health, and Science Program, based on six key commitments for preparing liberal arts students to analyze health and respond to global health challenges, is offered as an alternative to the public health major