Fabrication of porous scaffolds by three‐dimensional plotting of a pasty calcium phosphate bone cement under mild conditions

The major advantage of hydroxyapatite (HA)‐forming calcium phosphate cements (CPCs) used as bone replacement materials is their setting under physiological conditions without the necessity for thermal treatment that allows the incorporation of biological factors. In the present study, we have combined the biocompatible consolidation of CPCs with the potential of rapid prototyping (RP) techniques to generate calcium phosphate‐based scaffolds with defined inner and outer morphology. We demonstrate the application of the RP technique three‐dimensional (3D) plotting for the fabrication of HA cement scaffolds. This was realized by utilizing a paste‐like CPC (P‐CPC) which is stable as a malleable paste and whose setting reaction is initiated only after contact with aqueous solutions. The P‐CPC showed good processability in the 3D plotting process and allowed the fabrication of stable 3D structures of different geometries with adequate mechanical stability and compressive strength. The cytocompatibility of the plotted P‐CPC scaffolds was demonstrated in a cell culture experiment with human mesenchymal stem cells. The mild conditions during 3D plotting and post‐processing and the realization of the whole procedure under sterile conditions make this approach highly attractive for fabrication of individualized implants with respect to patient‐specific requirements by simultaneous plotting of biological components. Copyright © 2012 John Wiley & Sons, Ltd.     

Impact of oral ibandronate 150 mg once monthly on bone structure and density in post-menopausal osteoporosis or osteopenia derived from in vivo μCT

The effect of ibandronate 150 mg/once monthly in the treatment of post-menopausal osteopenia and osteoporosis on bone micro-structure at the distal tibia and radius has not been considered to date. Seventy post-menopausal women with osteoporosis or osteopenia were recruited. All subjects received calcium and vitamin D supplementation and were randomized to either a group which took 150 mg ibandronate oral monthly or a placebo group over a 12-month period. μCT measures of the distal tibia and radius were conducted every three months, with DXA lumbar spine and hip measurements conducted only pre and post and serum markers of bone formation and resorption measured every 6 months. After 12-months no significant impact of ibandronate on the primary outcome measures bone-volume to tissue-volume and trabecular separation at the distal tibia (p ≥ 0.15) was found. Further multiple regression analyses of the primary end-points indicated a significant effect favoring the ibandronate intervention (p = 0.045). Analysis of secondary end-points showed greater increases in distal tibia cortical thickness, cortical density and total density (p ≤ 0.043) with ibandronate and no significant effects at the distal radius, but greater increases of hip DXA-BMD and lumbar spine DXA-BMD (p ≤ 0.017). Ibandronate use resulted in a marked reduction in bone turnover (p < 0.001). While ibandronate resulted in greater mineralization of bone, this effect differed from one body region to another. There was some impact of ibandronate on bone structure (cortical thickness) at the distal tibia, but not on bone-volume to tissue-volume or trabecular separation.     

Generation and Preclinical Characterization of a Fc-optimized GITR-Ig Fusion Protein for Induction of NK Cell Reactivity Against Leukemia

Natural killer (NK) cells are cytotoxic lymphocytes that largely contribute to the efficacy of therapeutic strategies like allogenic stem cell transplantation in acute myeloid leukemia (AML) and application of Rituximab in chronic lymphocytic leukemia (CLL). The tumor necrosis factor (TNF) family member GITR ligand (GITRL) is frequently expressed on leukemia cells in AML and CLL and impairs the reactivity of NK cells which express GITR and upregulate its expression following activation. We developed a strategy to reinforce NK anti-leukemia reactivity by combining disruption of GITR–GITRL interaction with targeting leukemia cells for NK antibody-dependent cellular cytotoxicity (ADCC) using GITR-Ig fusion proteins with modified Fc moieties. Neutralization of leukemia-expressed GITRL by the GITR domain enhanced cytotoxicity and cytokine production of NK cells depending on activation state with NK reactivity being further largely dependent on the engineered affinity of the fusion proteins to the Fc receptor. Compared with wild-type GITR-Ig, treatment of primary AML and CLL cells with mutants containing a S239D/I332E modification potently increased cytotoxicity, degranulation, and cytokine production of NK cells in a target-antigen–dependent manner with additive effects being observed with CLL cells upon parallel exposure to Rituximab. Fc-optimized GITR-Ig may thus constitute an attractive means for immunotherapy of leukemia that warrants clinical evaluation.     

Recovery of a top predator mediates negative eutrophic effects on seagrass

A fundamental goal of the study of ecology is to determine the drivers of habitat-forming vegetation, with much emphasis given to the relative importance to vegetation of “bottom-up” forces such as the role of nutrients and “top-down” forces such as the influence of herbivores and their predators. For coastal vegetation (e.g., kelp, seagrass, marsh, and mangroves) it has been well demonstrated that alterations to bottom-up forcing can cause major disturbances leading to loss of dominant vegetation. One such process is anthropogenic nutrient loading, which can lead to major changes in the abundance and species composition of primary producers, ultimately affecting important ecosystem services. In contrast, much less is known about the relative importance of apex predators on coastal vegetated ecosystems because most top predator populations have been depleted or lost completely. Here we provide evidence that an unusual four-level trophic cascade applies in one such system, whereby a top predator mitigates the bottom-up influences of nutrient loading. In a study of seagrass beds in an estuarine ecosystem exposed to extreme nutrient loading, we use a combination of a 50-y time series analysis, spatial comparisons, and mesocosm and field experiments to demonstrate that sea otters (Enhydra lutris) promote the growth and expansion of eelgrass (Zostera marina) through a trophic cascade, counteracting the negative effects of agriculturally induced nutrient loading. Our results add to a small but growing body of literature illustrating that significant interactions between bottom-up and top-down forces occur, in this case with consequences for the conservation of valued ecosystem services provided by seagrass.Understanding the relative influence of “bottom-up” vs. “top-down” forces on vegetated assemblages has long been an important conceptual goal of the study of ecology (1–4). As many vegetated habitats have declined globally in past decades (5–8), with concurrent losses of valued ecosystem services, investigations of drivers of vegetation sustainability have also taken on applied significance and urgency in conservation science (9, 10). Human activities have altered bottom-up forces, for instance by increasing nutrient availability (11, 12), and top-down forces, by hunting and fishing of top predators (5, 13). Detecting the relative role of such alterations and interactions between them is critical for supporting key vegetated habitats and their ecosystem services.Investigations of bottom-up and top-down forces in a single system can be challenging. Changes at the top of food webs have been demonstrated to affect vegetation in a diversity of ecosystems (5, 13–15). However, apex predators have been depleted or lost entirely across most of the natural world (5, 13), including many near-shore marine systems (5, 16). It is difficult to understand ecosystem-level effects of an apex predator if it is extremely rare or absent (17). Nearshore systems lacking apex predators have often undergone conspicuous changes in bottom-up forces resulting from human activities, so attention has focused on these latter changes, rather than on a potential role for apex predators or for interactions between top-down and bottom-up changes to the ecosystems. The few studies that have successfully investigated the relative importance of bottom-up and top-down factors on dominant vegetation over ecosystem scales have determined that strong interactions can occur (3, 18, 19).Seagrasses are a globally distributed group of marine angiosperms that provide valued ecosystem services, such as fueling secondary production, creation of habitat for many other species (9), shoreline protection, and carbon sequestration from the surrounding seawater and overlying atmosphere (8, 10). Seagrass beds have declined in many regions of the world, often because of the smothering effects of algal epiphytes that are enhanced by nutrient loading (8, 20, 21). Furthermore, top-down consumer control, via mesograzers and small predators, has also been established as an important factor in regulating the interaction between seagrass and their algal competitors, especially in elevated nutrient loading and eutrophic conditions (16, 22–27). Mediation of competitive interactions between primary producers is directly controlled by herbivores, which have consistently demonstrated preferential consumption of algal epiphytes vs. seagrasses (27–30), thus benefitting rather than harming the dominant primary producer. Additionally, there is strong evidence from cage experiments that intermediate predators (such as fish and crabs) are capable of regulating grazer assemblages in seagrass beds (22, 23, 25, 26), leading to a trophic cascade that mediates the competition between seagrass and their epiphytes. Seagrass ecosystems thus provide an opportunity to examine bottom-up and top-down forces, and the interaction between them.Recovery of top predator populations has the potential to restore trophic structure and ecosystem function to degraded ecosystems. We found an ideal study system to examine the potential role of recovering apex predators in mediating bottom-up effects, a nutrient-loaded and eutrophic estuarine ecosystem supporting eelgrass (Zostera marina) and recovering sea otters (Enhydra lutris). Sea otters are keystone species capable of structuring nearshore communities (kelp forests and soft-bottom) through their high predation pressure (31–33). We used a 50-y time series tracking ecosystem degradation and recolonization by sea otters, spatial comparisons between sites with varying sea otter predation and nutrient loading, and manipulative mesocosm and field experiments to investigate the interaction between bottom-up forces and a recovering top predator population.     

Involvement of general practitioners in palliative cancer care: a qualitative study

Purpose

General practitioners play an important role in palliative care for cancer patients. The intensity of care and its medical complexity make palliative care a demanding task for general practitioners. This study explored general practitioners' perceptions of their involvement in palliative cancer care and the constraints they confront.

Methods

We conducted semi-structured interviews with 13 German general practitioners. Recruitment occurred by means of purposeful sampling to secure maximum heterogeneity. The interviews were electronically recorded, transcribed, and then analyzed using qualitative content analysis according to Mayring.

Results

A number of themes were identified. General practitioners describe being intensely involved in the final phase of their patients' lives. When providing home-based end-of-life care to cancer patients, general practitioners become aware of the limitations in their medical skills and knowledge and their ability to provide round-the-clock care. They find it helpful and satisfying to collaborate with trusted care providers and seek to cooperate with specialized palliative care services for outpatients.

Conclusions

The substantial involvement of general practitioners in end-of-life care for cancer patients pushes them to their limits because of the major time commitment required, and the need for special skills for which they have received no training. It will be a challenge to provide general practitioners with the structural and personal support they need to provide home-based palliative care for their cancer patients at end of life.