Friederike Neumann

Minimal local anaesthetic volumes for sciatic nerve block: evaluation of ED99 in volunteers

BACKGROUND This randomized, double-blinded volunteer study was designed to evaluate the ED(99) volume of local anaesthetic for sciatic nerve blocks using a step-up/step-down methodology. METHODS A maximum of 20 volunteers were included to receive an ultrasound-guided sciatic nerve block with mepivacaine 1.5% and a starting volume of 0.2 ml mm(-2) cross-sectional nerve area. In cases of a complete sensory block, the volume was reduced by 0.02 ml mm(-2) cross-sectional nerve area until the first block failed. Thereafter, the volume of local anaesthetic was increased by 0.02 ml mm(-2) cross-sectional nerve area. After three cycles of successful/failed blocks, the ED(99) volume of local anaesthetic could be calculated by a probability function. The influence of the volumes of local anaesthetics on sensory onset times and duration of sensory block was evaluated by linear regression. RESULTS The ED(99) volume of local anaesthetic for sciatic nerve block was calculated with 0.10 ml mm(-2) cross-sectional nerve area. The correlation between the volume of local anaesthetic and the sensory onset time was weak (r=0.14), whereas the correlation between the volume of local anaesthetic and the duration of sensory block was moderate (r=0.65). CONCLUSIONS This is the first study where an ED(99) volume of local anaesthetic for sciatic nerve block has been evaluated. The resulting local anaesthetic volume of 0.10 ml mm(-2) cross-sectional nerve area seems to have no impact on sensory onset time, whereas the duration of sensory block is shorter.

Staged Growth of Optimized Arterial Model Trees

AbstractThere is a marked difference in the structure of the arterial tree between epi- and endocardial layers of the human heart. To model these structural variations, we developed an extension to the computational method of constrained constructive optimization (CCO). Within the framework of CCO, a model tree is represented as a dichotomously branching network of straight cylindrical tubes, with flow conditions governed by Poiseuilles law. The tree is grown by successively adding new terminal segments from randomly selected points within the perfusion volume while optimizing the geometric location and topological site of each new connection with respect to minimum intravascular volume. The proposed method of “staged growth” guides the generation of new terminal sites by means of an additional time-dependent boundary condition, thereby inducing a sequence of domains of vascular growth within the given perfusion volume. Model trees generated in this way are very similar to reality in their visual appearance and predict diameter ratios of parent and daughter segments, the distribution of symmetry, the transmural distribution of flow, the volume of large arteries, as well as the ratio of small arterial volume in subendocardial and subepicardial layers in good agreement with experimental data. From this study we conclude that the method of CCO combined with staged growth reproduces many characteristics of the different arterial branching patterns in the subendocardium and the subepicardium, which could not be obtained by applying the principle of minimum volume alone.

High-affinity Rb binding, p53 inhibition, subcellular localization, and transformation by wild-type or tumor-derived shortened Merkel cell polyomavirus large T antigens.

ABSTRACT Interference with tumor suppressor pathways by polyomavirus-encoded tumor antigens (T-Ags) can result in transformation. Consequently, it is thought that T-Ags encoded by Merkel cell polyomavirus (MCPyV), a virus integrated in ∼90% of all Merkel cell carcinoma (MCC) cases, are major contributors to tumorigenesis. The MCPyV large T-Ag (LT-Ag) has preserved the key functional domains present in all family members but has also acquired unique regions that flank the LxCxE motif. As these regions may mediate unique functions, or may modulate those shared with T-Ags of other polyomaviruses, functional studies of MCPyV T-Ags are required. Here, we have performed a comparative study of full-length or MCC-derived truncated LT-Ags with regard to their biochemical characteristics, their ability to bind to retinoblastoma (Rb) and p53 proteins, and their transforming potential. We provide evidence that full-length MCPyV LT-Ag may not directly bind to p53 but nevertheless can significantly reduce p53-dependent transcription in reporter assays. Although early region expression constructs harboring either full-length or MCC-derived truncated LT-Ag genes can transform primary baby rat kidney cells, truncated LT-Ags do not bind to p53 or reduce p53-dependent transcription. Interestingly, shortened LT-Ags exhibit a very high binding affinity for Rb, as shown by coimmunoprecipitation and in vitro binding studies. Additionally, we show that truncated MCPyV LT-Ag proteins are expressed at higher levels than those for the wild-type protein and are able to partially relocalize Rb to the cytoplasm, indicating that truncated LT proteins may have gained additional features that distinguish them from the full-length protein. IMPORTANCE MCPyV is one of the 12 known polyomaviruses that naturally infect humans. Among these, it is of particular interest since it is the only human polyomavirus known to be involved in tumorigenesis. MCPyV is thought to be causally linked to MCC, a rare skin tumor. In these tumors, viral DNA is monoclonally integrated into the genome of the tumor cells in up to 90% of all MCC cases, and the integrated MCV genomes, furthermore, harbor signature mutations in the so-called early region that selectively abrogate viral replication while preserving cell cycle deregulating functions of the virus. This study describes comparative studies of early region T-Ag protein characteristics, their ability to bind to Rb and p53, and their transforming potential.

Replication, Gene Expression and Particle Production by a Consensus Merkel Cell Polyomavirus (MCPyV) Genome

Merkel Cell Polyomavirus (MCPyV) genomes are clonally integrated in tumor tissues of approximately 85% of all Merkel cell carcinoma (MCC) cases, a highly aggressive tumor of the skin which predominantly afflicts elderly and immunosuppressed patients. All integrated viral genomes recovered from MCC tissue or MCC cell lines harbor signature mutations in the early gene transcript encoding for the large T-Antigen (LT-Ag). These mutations selectively abrogate the ability of LT-Ag to support viral replication while still maintaining its Rb-binding activity, suggesting a continuous requirement for LT-Ag mediated cell cycle deregulation during MCC pathogenesis. To gain a better understanding of MCPyV biology, in vitro MCPyV replication systems are required. We have generated a synthetic MCPyV genomic clone (MCVSyn) based on the consensus sequence of MCC-derived sequences deposited in the NCBI database. Here, we demonstrate that transfection of recircularized MCVSyn DNA into some human cell lines recapitulates efficient replication of the viral genome, early and late gene expression together with virus particle formation. However, serial transmission of infectious virus was not observed. This in vitro culturing system allows the study of viral replication and will facilitate the molecular dissection of important aspects of the MCPyV lifecycle.

Clinical Evaluation of Pressure-Controlled Intermittent Coronary Sinus Occlusion: Randomized Trial During Coronary Artery Surgery

Pressure-controlled intermittent coronary sinus occlusion (PICSO) was evaluated in a randomized trial in 30 patients undergoing bypass surgery. PICSO was applied for one hour during early reperfusion. Myocardial function was determined from short-axis cross-sectional views of intraoperative two-dimensional echocardiography. Changes of sectional and segmental wall motion during extracorporeal circulation were analyzed. Although sectional wall motion did not change significantly, hypokinetic segments were preserved better in PICSO-treated patients than in controls (-1.3 +/- 2.4 versus -9.1 +/- 2.6 delta% fractional area change; p less than 0.04). Although not significant, the same trend was found for normal and severely hypokinetic segments. Cumulative enzyme release was related to coronary sinus occluded pressure (r = 0.94; p less than 0.006), indicating washout of metabolites during PICSO. Three months after operation, functional classification was similarly favorable in both groups. Long-term effects of PICSO cannot be predicted because PICSO was applied only during early reperfusion. We conclude that PICSO is a safe procedure and that its short-term beneficial effects on myocardial function suggest a preservation of myocardial viability.

Predictors of falls in elderly people during rehabilitation after hip fracture--who is at risk of a second one?

Summary.Background: A fall in old age is known as a common consequence of frailty and decline as well as a risk factor for further falls. Studies identifying hip fracture patients who are at risk of a further fall are lacking. Therefore it was of interest to evaluate the risk factors for falling in a high-risk population, i.e., patients during rehabilitation after recent proximal femur fracture. Methods: 935 consecutive patients who had surgical intervention after acute fracture of the proximal femur underwent a multidimensional assessment within the first two days after admission to the rehabilitation ward. Falls during the stay on the rehabilitation ward were registered. The baseline data were compared between fallers and non-fallers. Findings: 11.8% of the patients fell during rehabilitation. Risk factors associated with a fall were increasing age, male gender, type of surgery, the use of a rollator and nocturnal urinary incontinence. The risk of falling increased in the middle of the second week of rehabilitation, when frailer patients gained mobility and ability to walk by themselves, while they were not yet safe enough. Interpretation: It was possible to compose a risk profile for future falls. Those identified as ’at risk of a further fall‘ should be selectively offered protective devices and special training programs in order to prevent future fractures. As for the surgical intervention, the type of surgery in relation to age and long-term outcome is of particular interest since the use of the more expensive total hip arthroplasty procedure may be more cost effective in the long term.Zusammenfassung.Hintergrund: Stürze sind bekannte Folgen von allgemeiner Schwäche und Gebrechlichkeit älterer Menschen, gleichzeitig aber auch der wichtigste Risikofaktor für einen weiteren Sturz. Es fehlen Studien, die das Sturzrisiko von Patienten nach Schenkelhalsfraktur evaluieren. Deshalb wurden Patienten im Rahmen der Rehabilitation nach hüftgelenksnaher Femurfraktur bezüglich ihres weiteren Sturzrisikos evaluiert. Patienten und Methode: Es wurden 935 Patienten nach chirurgischer Sanierung einer hüftgelenksnahen Femurfraktur im Rahmen der Aufnahmeuntersuchung zur Rehabilitation im Sinne eines multidimensionalen Geriatrischen Assessment untersucht. Die Stürze während der Rehabilitation wurden exakt dokumentiert und die Basisdaten des Assessments zwischen „Stürzern“ und „Nicht-Stürzern“ verglichen. Ergebnisse: 11,8% der Patienten stürzten während der Rehabilitation. Als spezielle Risikofaktoren konnten das Alter per se, das männliche Geschlecht, der Bedarf eines Rollators und nächtliche Inkontinenz identifiziert werden. Das Sturzrisiko nahm während der zweiten Woche signifikant zu. Bei zunehmender Mobilität, ohne gleichzeitige Sicherheit, stieg das Sturzrisiko insbesondere für die gebrechlichen Patienten. Diskussion: Im Rahmen der Studie konnte ein besonderes Risikoprofil in dieser Hochrisikogruppe identifiziert werden. Jenen Patienten sollte während der Rehabilitation spezielle Trainingsprogramme und protektive Maßnahmen angeboten werden, um eine weitere Fraktur zu verhindern. Gleichzeitig bedarf es weiterer Studien, um den Einfluss der verwendeten Osteosynthese auf das Sturzrisiko zu überprüfen.

MTSS1 is a metastasis driver in a subset of human melanomas

In cancers with a highly altered genome, distinct genetic alterations drive subsets rather than the majority of individual tumours. Here we use a sequential search across human tumour samples for transcript outlier data points with associated gene copy number variations that correlate with patients survival to identify genes with pro-invasive functionality. Employing loss and gain of function approaches in vitro and in vivo, we show that one such gene, MTSS1, promotes the ability of melanocytic cells to metastasize and engages actin dynamics via Rho-GTPases and cofilin in this process. Indeed, high MTSS1 expression defines a subgroup of primary melanomas with unfavourable prognosis. These data underscore the biological, clinical and potential therapeutic implications of molecular subsets within genetically complex cancers.

Morphometry of human coronary arterial trees

Some groups, including ours, have been generating arterial tree models using constrained constructive optimization (CCO). Arterial trees have been grown to arbitrary resolution without input of anatomical data. We performed this study to learn about the shortcomings that might have resulted from neglecting the anatomical data in CCO models.

Fractal properties of perfusion heterogeneity in optimized arterial trees: a model study.

Regional blood flows in the heart muscle are remarkably heterogeneous. It is very likely that the most important factor for this heterogeneity is the metabolic need of the tissue rather than flow dispersion by the branching network of the coronary vasculature. To model the contribution of tissue needs to the observed flow heterogeneities we use arterial trees generated on the computer by constrained constructive optimization. This method allows to prescribe terminal flows as independent boundary conditions, rather than obtaining these flows by the dispersive effects of the tree structure. We study two specific cases: equal terminal flows (model 1) and terminal flows set proportional to the volumes of Voronoi polyhedra used as a model for blood supply regions of terminal segments (model 2). Model 1 predicts, depending on the number N term of end-points, fractal dimensions D of perfusion heterogeneities in the range 1.20 to 1.40 and positively correlated nearest-neighbor regional flows, in good agreement with experimental data of the normal heart. Although model 2 yields reasonable terminal flows well approximated by a lognormal distribution, it fails to predict D and nearest-neighbor correlation coefficients r 1 of regional flows under normal physiologic conditions: model 2 gives D = 1.69 ± 0.02 and r 1 = −0.18 ± 0.03 (n = 5), independent of N term and consistent with experimental data observed under coronary stenosis and under the reduction of coronary perfusion pressure. In conclusion, flow heterogeneity can be modeled by terminal positions compatible with an existing tree structure without resorting to the flow-dispersive effects of a specific branching tree model to assign terminal flows.

Voronoi Polyhedra Analysis of Optimized Arterial Tree Models

AbstractTopological and metric properties of Voronoi polyhedra (VP) generated by the distal end points of terminal segments in arterial tree models grown by the method of constrained constructive optimization (CCO) are analyzed with the aim to characterize the spatial distribution of their supply sites relative to randomly distributed points as a reference model. The distributions of the number Nf of Voronoi cell faces, cell volume V, surface area S, area A of individual cell faces, and asphericity parameter α of the CCO models are all significantly different from the ones of random points, whereas the distributions of V, S, and α are also significantly different among CCO models optimized for minimum intravascular volume and minimum segment length (p < 0.0001). The distributions of Nf, V, and S of the CCO models are reasonably well approximated by two-parameter gamma distributions. We study scaling of intravascular blood volume and arterial cross-sectional area with the volume of supplied tissue, the latter being represented by the VP of the respective terminal segments. We observe scaling exponents from 1.20 ± 0.007 to 1.08 ± 0.005 for intravascular blood volume and 0.77 ± 0.01 for arterial cross-sectional area. Setting terminal flows proportional to the associated VP volumes during tree construction yields a relative dispersion of terminal flows of 37% and a coefficient of skewness of 1.12.