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Insertion of bone substitution materials accelerates healing of osteoporotic fractures. Biodegradable materials are preferred for application in osteoporotic patients to avoid a second surgery for implant replacement. Degraded implant fragments are often absorbed by macrophages that are removed from the fracture side via passage through veins or lymphatic vessels. We investigated if lymphatic vessels occur in osteoporotic bone defects and whether they are regulated by the use of different materials. To address this issue osteoporosis was induced in rats using the classical method of bilateral ovariectomy and additional calcium and vitamin deficient diet. In addition, wedge-shaped defects of 3, 4, or 5 mm were generated in the distal metaphyseal area of femur via osteotomy. The 4 mm defects were subsequently used for implantation studies where bone substitution materials of calcium phosphate cement, composites of collagen and silica, and iron foams with interconnecting pores were inserted. Different materials were partly additionally functionalized by strontium or bisphosphonate whose positive effects in osteoporosis treatment are well known. The lymphatic vessels were identified by immunohistochemistry using an antibody against podoplanin. Podoplanin immunopositive lymphatic vessels were detected in the granulation tissue filling the fracture gap, surrounding the implant and growing into the iron foam through its interconnected pores. Significant more lymphatic capillaries were counted at the implant interface of composite, strontium and bisphosphonate functionalized iron foam. A significant increase was also observed in the number of lymphatics situated in the pores of strontium coated iron foam. In conclusion, our results indicate the occurrence of lymphatic vessels in osteoporotic bone. Our results show that lymphatic vessels are localized at the implant interface and in the fracture gap where they might be involved in the removal of lymphocytes, macrophages, debris and the implants degradation products. Therefore the lymphatic vessels are involved in implant integration and fracture healing.
Signaling cooperation
(2015)
We examine what an applicant’s vita signals to potential employers about her willingness to cooperate in teams. Intensive social engagement may credibly reveal that an applicant cares about the well-being of others and therefore is less likely to free-ride in teamwork situations. We find that contributions in a public goods game strongly increase in a subject’s degree of social engagement as indicated on her résumé (and rated by an independent third party). Engagement in other domains, such as student or sports associations, is not positively correlated with contributions. In a prediction experiment with human resource managers from various industries, we find that managers use résumé content effectively to predict relative differences in subjects’ willingness to cooperate. Thus, young professionals signal important behavioral characteristics to potential employers through the choice of their extracurricular activities.
We examine trust and trustworthiness of individuals with varying professional preferences and experiences. Our subjects study business and economics in Frankfurt, the financial center of Germany and continental Europe. In the trust game, subjects with a high interest in working in the financial industry return 25 percent less than subjects with a low interest. We find no evidence that the extent of professional experience in the financial industry has a negative impact on trustworthiness. We also do not find any evidence that the financial industry screens out less trustworthy individuals in the hiring process. In a prediction game that is strategically equivalent to the trust game, the amount sent by first-movers was significantly smaller when the second-mover indicated a high interest in working in finance. These results suggest that the financial industry attracts less trustworthy individuals, which may contribute to the current lack of trust in its employees.
MAPK6/ERK3 is an atypical member of the MAPKs. An essential role has been suggested by the perinatal lethal phenotype of ERK3 knockout mice carrying a lacZ insertion in exon 2 due to pulmonary disfunction and by defects in function, activation and positive selection of T cells. To study the role of ERK3 in vivo, we generated mice carrying a conditional Erk3 allele with exon3 flanked by LoxP sites. Loss of ERK3 protein was validated after deletion of Erk3 in the female germ line using zona pellucida 3 (Zp3)-cre and a clear reduction of the protein kinase MK5 is detected, providing first evidence for the existence of the ERK3/MK5 signaling complex in vivo. In contrast to the previously reported Erk3 knockout phenotype, these mice are viable and fertile, do not display pulmonary hypoplasia, acute respiratory failure, abnormal T cell development, reduction of thymocyte numbers or altered T cells selection. Hence, ERK3 is dispensable for pulmonary and T-cell functions. The perinatal lethality, lung and T-cell defects of the previous ERK3 knockout mice are likely due to ERK3-unrelated effects of the inserted lacZ-neomycin-resistance-cassette. The knockout mouse of the closely related atypical MAPK ERK4/MAPK4 is also normal suggesting redundant functions of both protein kinases.