Using Growth Factors in Human Extraction Sockets: A Histologic and Histomorphometric Evaluation of Short-Term Healing

Purpose: Ridge preservation protocols reduce crestal remodeling after tooth extraction. There is insufficient evidence on bone grafting in combination with platelet-rich plasma (PRP) or recombinant human platelet-derived growth factor (rhPDGF-BB). The aim of this study is to evaluate healing of grafted and nongrafted sockets and the effect of PRP and rhPDGF-BB on early remodeling. Materials and Methods: Forty-one patients whose treatment plan included extraction of anterior or premolar teeth were randomized into four groups. Group 1: collagen plug (control). Group 2: mineralized freeze-dried bone allograft (FDBA)/β-tricalcium phosphate (β-TCP)/collagen plug. Group 3: FDBA/β-TCP/PRP/collagen plug. Group 4: FDBA/β-TCP/rhPDGF-BB/collagen plug. At 8 weeks, a core was harvested from the center of 41 sockets. Histomorphometric analysis took place. Differences were analyzed using one-way analysis of variance (ANOVA) or chi-square tests for continuous and categorical data. Pairwise comparisons were tested using least squares means. Spearman correlation coefficients were used to evaluate the relationship of bone growth with potential confounders. A P value < .05 was considered statistically significant. Results: ANOVA did not indicate statistical significance in age, gender, smoking, ethnicity, or race distribution. Significant differences in tissue distribution were identified between groups and between different thirds of harvested core. More new bone and amorphous organic matrix was noted in the control group. In sites where bone graft was combined with growth factors, the amount of residual particles was less than in sites where bone graft was used alone. Conclusions: Inclusion of bone replacement graft suppressed new bone formation during early healing. Inclusion of PRP and rhPDGF-BB produced less residual bone graft material, indicating more rapid turnover of bone graft. All treatment modalities achieved a significant amount of new vital bone at 8 weeks postextraction

Protein phosphatase 2A affects myofilament contractility in non-failing but not in failing human myocardium

Protein phosphatase (PP) type 2A is a multifunctional serine/threonine phosphatase that is involved in cardiac excitation–contraction coupling. The PP2A core enzyme is a dimer, consisting of a catalytic C and a scaffolding A subunit, which is targeted to several cardiac proteins by a regulatory B subunit. At present, it is controversial whether PP2A and its subunits play a critical role in end-stage human heart failure. Here we report that the application of purified PP2AC significantly increased the Ca2+-sensitivity (ΔpCa50 = 0.05 ± 0.01) of the contractile apparatus in isolated skinned myocytes of non-failing (NF) hearts. A higher phosphorylation of troponin I (cTnI) was found at protein kinase A sites (Ser23/24) in NF compared to failing myocardium. The basal Ca2+-responsiveness of myofilaments was enhanced in myocytes of ischemic (ICM, ΔpCa50 = 0.10 ± 0.03) and dilated (DCM, ΔpCa50 = 0.06 ± 0.04) cardiomyopathy compared to NF. However, in contrast to NF myocytes the treatment with PP2AC did not shift force-pCa relationships in failing myocytes. The higher basal Ca2+-sensitivity in failing myocytes coincided with a reduced protein expression of PP2AC in left ventricular tissue from patients suffering from ICM and DCM (by 50 and 56% compared to NF, respectively). However, PP2A activity was unchanged in failing hearts despite an increase of both total PP and PP1 activity. The expression of PP2AB56α was also decreased by 51 and 62% in ICM and DCM compared to NF, respectively. The phosphorylation of cTnI at Ser23/24 was reduced by 66 and 49% in ICM and DCM compared to NF hearts, respectively. Our results demonstrate that PP2A increases myofilament Ca2+-sensitivity in NF human hearts, most likely via cTnI dephosphorylation. This effect is not present in failing hearts, probably due to the lower baseline cTnI phosphorylation in failing compared to non-failing hearts

Considerations for developing and implementing a safe list for alien taxa

Many species have been intentionally introduced to new regions for their benefits. Some of these alien species cause damage, others do not (or at least have not yet). There are several approaches to address this problem: prohibit taxa that will cause damage, try to limit damages while preserving benefits, or promote taxa that are safe. In the present article, we unpack the safe list approach, which we define as “a list of taxa alien to the region of interest that are considered of sufficiently low risk of invasion and impact that the taxa can be widely used without concerns of negative impacts.” We discuss the potential use of safe lists in the management of biological invasions; disentangle aspects related to the purpose, development, implementation, and impact of safe lists; and provide guidance for those considering to develop and implement such lists