Necessity of 3D visualization for the removal of lower wisdom teeth: required sample size to prove non-inferiority of panoramic radiography compared to CBCT

The availability of cone beam computed tomography (CBCT) and the numbers of CBCT scans rise constantly, increasing the radiation burden to the patient. A growing discussion is noticeable if a CBCT scan prior to the surgical removal of wisdom teeth may be indicated. We aimed to confirm non-inferiority with respect to damage of the inferior alveolar nerve in patients diagnosed by panoramic radiography compared to CBCT in a prospective randomized controlled multicentre trial. Sample size (number of required third molar removals) was calculated for the study and control groups as 183,474 comparing temporary and 649,036 comparing permanent neurosensory disturbances of the inferior alveolar nerve. Modifying parameter values resulted in sample sizes ranging from 39,584 to 245,724 respectively 140,024 to 869,250. To conduct a clinical study to prove a potential benefit from CBCT scans prior to surgical removal of lower wisdom teeth with respect to the most important parameter, i.e., nerval damage, is almost impossible due to the very large sample sizes required. This fact vice versa indicates that CBCT scans should only be performed in high risk wisdom tooth removals.     

On the symmetry of siblings: automated single-cell tracking to quantify the behavior of hematopoietic stem cells in a biomimetic setup

The interplay between hematopoietic stem and progenitor cells (HSPC) and their local microenvironment is a key mechanism for the organization of hematopoiesis. To quantitatively study this process, a time-resolved analysis of cellular dynamics at the single-cell level is an essential prerequisite. One way to generate sufficient amounts of appropriate data is automatic single-cell tracking using time-lapse video microscopy. We describe and apply newly developed computational algorithms that allow for an automated generation of high-content data of single-cell characteristics at high temporal and spatial resolution, together with the reconstruction and statistical evaluation of complete genealogical histories. This methodology has been applied to the particular example of purified primary human HSPCs in bioengineered culture conditions. The combination of genealogical information and dynamic profiles of cellular properties identified a marked symmetry between sibling HSPCs regarding cell cycle time, but also migration speed and growth kinetics. Furthermore, we demonstrate that this symmetry of HSPC siblings can be altered by exogenous cues of the local biomimetic microenvironment. Using the example of HSPC growth in biomimetic culture systems, we show that our approach provides a valuable tool for the quantitative analysis of dynamic single-cell features under defined in?vitro conditions, allowing for integration of functional and genealogical data. The efficiency and accuracy of our approach pave the way for new and intriguing insights into the organizational principles of developmental patterns and the respective influence of exogenous cues not limited to the study of primary HSPCs.     

A double mobility acetabular implant for primary hip arthroplasty in patients at high risk of dislocation

IntroductionDislocation following total hip replacement continues to be a problem for which no completely satisfactory solution has been found. Several methods have been proposed to reduce the incidence of hip dislocations with varying degrees of success, including elevated rim liners, constrained liners and large diameter bearings. We present our experience with the double mobility acetabular component in patients at high risk of instability.MethodsThis was a retrospective review of 65 primary total hip arthroplasties in 55 patients (15 men, 40 women), performed between October 2005 and November 2009. The majority (80%) of patients had at least two and 26% had at least three risk factors for instability. The mean age was 76 years (range: 44–92 years). The patients were followed up for a mean duration of 60 months (range: 36–85 months).ResultsFourteen patients died and one was lost to follow-up, leaving fifty hips for final assessment. Until the final follow-up appointment, no patients had dislocation and none required revision surgery. The mean Oxford hip score improved from 45.0 to 26.5 (p<0.0001). The mean Merle d’Aubigné pain score improved from 1.4 to 4.9 (p<0.0001), the walking score from 2.3 to 3.1 (p<0.07) and the absolute hip function score from 5.4 to 10.8 (p<0.0001). There were no clinical or radiographic signs of loosening.ConclusionsThe double mobility acetabular component was successful at preventing dislocation during early to medium-term follow-up. However, as data are still lacking with regard to polyethylene wear rates at the additional bearing surface, it would be prudent to restrict the use of this implant to selected patients at high risk of instability.     

Surgical delivery of drug releasing poly(lactic-co-glycolic acid)/poly(ethylene glycol) paste with in vivo effects against glioblastoma

Introduction

The median survival of patients with glioblastoma multiforme (astrocytoma grade 4) remains less than 18 months despite radical surgery, radiotherapy and systemic chemotherapy. Surgical implantation of chemotherapy eluting wafers into the resection cavity has been shown to improve length of survival but the current licensed therapy has several drawbacks. This paper investigates in vivo efficacy of a novel drug eluting paste in glioblastoma.

Methods

Poly(lactic-co-glycolic acid)/poly(ethylene glycol) (PLGA/PEG) self-sintering paste was loaded with the chemotherapeutic agent etoposide and delivered surgically into partially resected tumours in a flank murine glioblastoma xenograft model.

Results

Surgical delivery of the paste was successful and practical, with no toxicity or surgical morbidity to the animals. The paste was retained in the tumour cavity, and preliminary results suggest a useful antitumour and antiangiogenic effect, particularly at higher doses. Bioluminescent imaging was not affected significantly by the presence of the paste in the tumour.

Conclusions

Chemotherapy loaded PLGA/PEG paste seems to be a promising technology capable of delivering active drugs into partially resected tumours. The preliminary results of this study suggest efficacy with no toxicity and will lead to larger scale efficacy studies in orthotopic glioblastoma models.     

Competitive clonal hematopoiesis in mouse chimeras explained by a stochastic model of stem cell organization

Many current experimental results show the necessity of new conceptual approaches to understand hematopoietic stem cell organization. Recently, we proposed a novel theoretical concept and a corresponding quantitative model based on microenvironment-dependent stem cell plasticity. The objective of our present work is to subject this model to an experimental test for the situation of chimeric hematopoiesis. Investigating clonal competition processes in DBA/2-C57BL/6 mouse chimeras, we observed biphasic chimerism development with initially increasing but long-term declining DBA/2 contribution. These experimental results were used to select the parameters of the mathematical model. To validate the model beyond this specific situation, we fixed the obtained parameter configuration to simulate further experimental settings comprising variations of transplanted DBA/2-C57BL/6 proportions, secondary transplantations, and perturbation of stabilized chimeras by cytokine and cytotoxic treatment. We show that the proposed model is able to consistently describe the situation of chimeric hematopoiesis. Our results strongly support the view that the relative growth advantage of strain-specific stem cells is not a fixed cellular property but is sensitively dependent on the actual state of the entire system. We conclude that hematopoietic stem cell organization should be understood as a flexible, self-organized rather than a fixed, preprogrammed process.     

Ultrastructural localization of human platelet thrombospondin, fibrinogen, fibronectin, and von Willebrand factor in frozen thin section

We have investigated the localization of thrombospondin (TSP), fibrinogen, fibronectin, and von Willebrand factor in human platelets by transmission electron microscopy of antibody-stained ultrathin frozen sections. In negatively stained thin sections, alpha granules were identified on the basis of their smooth, roughly spherical shape, size, single limiting electron-lucent 100 A membrane, and frequent presence of electron-dense nucleoid. In contrast, mitochondria exhibited characteristic double membranes and cristae. Sections were separately stained with affinity-purified polyclonal antibodies to these proteins as well as with three monoclonal anti-TSP antibodies. Antibody specificity was documented in radioimmunoassays, by immunofluorescent cross-blocking, and by staining of bands of appropriate mobility in Western blots of whole platelets. Bound antibody was visualized using a 5-nm colloidal gold-avidin conjugate. In resting cells, staining of virtually all alpha granules was observed for all four proteins. In contrast, consistent staining was absent from other organelles, including plasma membranes, mitochondria, and vacuolar structures that may represent the open canalicular system.     

A multipurpose transposon system for analyzing protein production, localization, and function in Saccharomyces cerevisiae

Analysis of the function of a particular gene product typically involves determining the expression profile of the gene, the subcellular location of the protein, and the phenotype of a null strain lacking the protein. Conditional alleles of the gene are often created as an additional tool. We have developed a multifunctional, transposon-based system that simultaneously generates constructs for all the above analyses and is suitable for mutagenesis of any given Saccharomyces cerevisiae gene. Depending on the transposon used, the yeast gene is fused to a coding region for β-galactosidase or green fluorescent protein. Gene expression can therefore be monitored by chemical or fluorescence assays. The transposons create insertion mutations in the target gene, allowing phenotypic analysis. The transposon can be reduced by cre–lox site-specific recombination to a smaller element that leaves an epitope tag inserted in the encoded protein. In addition to its utility for a variety of immunodetection purposes, the epitope tag element also has the potential to create conditional alleles of the target gene. We demonstrate these features of the transposons by mutagenesis of the SPA2, ARP100, SER1, and BDF1 genes.     

Expression of platelet-derived growth factor and its receptors by two pre-B acute lymphocytic leukemia cell lines

Platelet-derived growth factors (PDGF) are potent regulators of cell proliferation. The three isoforms of PDGF AA, AB, and BB are encoded by two genes: PDGF A and PDGF B. The v-sis oncogene is homologous to the PDGF-B gene. v-sis can transform cells that express the appropriate PDGF receptors. Two different types of receptors, PDGF-alpha and PDGF- beta, also encoded by two genes, have been identified. We show that two cell lines. SMS-SB and NALM-6, both derived from pre-B-cell acute lymphocytic leukemias, express the PDGF-A chain gene, and one of them, SMS-SB, releases PDGF-A chains into the media. The SMS-SB cells also express the PDGF-beta receptor, whereas NALM-6 cells express the PDGF- alpha receptor and bind PDGF. This extends the possible targets for PDGF to the B-cell lineage lymphocytes.