In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.
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Question: Kidney donor exchanges enable recipients with immunologically incompatible donors to receive compatible living donor grafts; however, the financial management of these exchanges, especially when an organ is shipped, is complex and thus has the potential to impede the broader implementation of donor exchange programs. Representatives from transplant centers that utilize the National Kidney Registry database to facilitate donor exchange transplants developed a financial model applicable to paired donor exchanges and donor chain transplants. The first tenet of the model is to eliminate financial liability to the donor. Thereafter, it accounts for the donor evaluation, donor nephrectomy hospital costs, donor nephrectomy physician fees, organ transport, donor complications and recipient inpatient services. Billing between hospitals is based on Medicare cost report defined costs rather than charges. We believe that this model complies with current federal regulations and effectively captures costs of the donor and recipient services. It could be considered as a financial paradigm for the United Network for Organ Sharing managed donor exchange program.

Answer: Managing finances of shipping living donor kidneys for donor exchanges.

Question: Urease, a nickel-dependent metalloenzyme, is synthesized by plants, some bacteria, and fungi. It catalyzes the hydrolysis of urea into ammonia and carbon dioxide. Although the amino acid sequences of plant and bacterial ureases are closely related, some biological activities differ significantly. Plant ureases but not bacterial ureases possess insecticidal properties independent of its ureolytic activity. To date, the structural information is available only for bacterial ureases although the jack bean urease (Canavalia ensiformis; JBU), the best-studied plant urease, was the first enzyme to be crystallized in 1926. To better understand the biological properties of plant ureases including the mechanism of insecticidal activity, we initiated the structural studies on some of them. Here, we report the crystal structure of JBU, the first plant urease structure, at 2.05 A resolution. The active-site architecture of JBU is similar to that of bacterial ureases containing a bi-nickel center. JBU has a bound phosphate and covalently modified residue (Cys592) by beta-mercaptoethanol at its active site, and the concomitant binding of multiple inhibitors (phosphate and beta-mercaptoethanol) is not observed so far in bacterial ureases. By correlating the structural information of JBU with the available biophysical and biochemical data on insecticidal properties of plant ureases, we hypothesize that the amphipathic beta-hairpin located in the entomotoxic peptide region of plant ureases might form a membrane insertion beta-barrel as found in beta-pore-forming toxins.

Answer: Crystal structure of the first plant urease from jack bean: 83 years of journey from its first crystal to molecular structure.

Question: Vascular calcification is an advanced feature of atherosclerosis for which no effective therapy is available. To investigate the modulation or reversal of calcification, we identified calcifying progenitor cells and investigated their calcifying/decalcifying potentials. Cells from the aortas of mice were sorted into four groups using Sca-1 and PDGFR markers. Sca-1(+) (Sca-1(+)/PDGFR(+) and Sca-1(+)/PDGFR(-)) progenitor cells exhibited greater osteoblastic differentiation potentials than Sca-1(-) (Sca-1(-)/PDGFR(+) and Sca-1(-)/PDGFR(-)) progenitor cells. Among Sca-1(+) progenitor populations, Sca-1(+)/PDGFR(-) cells possessed bidirectional differentiation potentials towards both osteoblastic and osteoclastic lineages, whereas Sca-1(+)/PDGFR(+) cells differentiated into an osteoblastic lineage unidirectionally. When treated with a peroxisome proliferator activated receptor (PPAR) agonist, Sca-1(+)/PDGFR(-) cells preferentially differentiated into osteoclast-like cells. Sca-1(+) progenitor cells in the artery originated from the bone marrow (BM) and could be clonally expanded. Vessel-resident BM-derived Sca-1(+) calcifying progenitor cells displayed nonhematopoietic, mesenchymal characteristics. To evaluate the modulation of in vivo calcification, we established models of ectopic and atherosclerotic calcification. Computed tomography indicated that Sca-1(+) progenitor cells increased the volume and calcium scores of ectopic calcification. However, Sca-1(+)/PDGFR(-) cells treated with a PPAR agonist decreased bone formation 2-fold compared with untreated cells. Systemic infusion of Sca-1(+)/PDGFR(-) cells into Apoe(-/-) mice increased the severity of calcified atherosclerotic plaques. However, Sca-1(+)/PDGFR(-) cells in which PPAR was activated displayed markedly decreased plaque severity. Immunofluorescent staining indicated that Sca-1(+)/PDGFR(-) cells mainly expressed osteocalcin; however, activation of PPAR triggered receptor activator for nuclear factor-B (RANK) expression, indicating their bidirectional fate in vivo. These findings suggest that a subtype of BM-derived and vessel-resident progenitor cells offer a therapeutic target for the prevention of vascular calcification and that PPAR activation may be an option to reverse calcification.

Answer:
Vascular Calcifying Progenitor Cells Possess Bidirectional Differentiation Potentials