Biomedical subjects

Friederike Neumann

Publications and source records attributed to Friederike Neumann.

7 recordsLinked to original sources

PubMed2006

[Different attitudes towards hypertension and urinary tract incontinence in elderly individuals participating in a health promotion project].

BACKGROUND: The aim of the study was to evaluate health associated attitudes of elderly individuals taking part in a community based health promotion programme. It was of interest to focus on mobility, hypertension and urinary incontinence, problems frequently observed in geriatrics. METHODS: Participants in the health promotion programme were asked to answer a standardized questionnaire about their individual risk factors and habits concerning some of the main risk factors in the elderly: social isolation, immobility, hypertension, urinary incontinence. Mobility and risk assessment for falls was assessed in a standardized way using the Chair-rising- and Timed-upand-go tests. RESULTS: The percentage of people with a healthy life style was significantly higher than in a comparable population group. Gait disturbance, mobility limitation and risk of falls were not present. 38.7 % suffered from urinary incontinence. Hypertension was, if present, diagnosed and adequately treated. The participants knew their prescribed drugs and seemed to have an excellent compliance. DISCUSSION: The participants in the health promotion programme showed an exceptionally high level of health awareness. Nevertheless, the incidence for reported urinary incontinence was significantly higher than in known epidemiological studies. The calm, reassuring atmosphere in which the questionnaire was completed and the large amount of time spent with the participants could explain this finding. The difference in dealing with hypertension and urinary incontinence is obvious. Further health promotion and disease prevention programmes for the elderly should be focused on the complex process of ageing and not only on specific single topics.

Accidental Falls↗

PubMed2005

Optimized arterial trees supplying hollow organs.

Computer models of arterial trees can be generated from optimization principles using the algorithm of constrained constructive optimization (CCO). Up to now this algorithm could handle only tissue areas of convex shape, without concavities. CCO is now generalized to cope also with non-convex organ shapes, possibly featuring external as well as internal concavities. This allows the modeling of a much larger class of interesting real arterial systems. The concept of a generalized domain-potential was developed to represent arbitrary non-convex shapes mathematically and incorporate them as boundary conditions to optimization. Domain-potentials may be derived from analytical representations as well as from finite element triangulations obtained from organ images. To demonstrate the feasibility of the concept, the optimized growth of an arterial tree model is confined to some part of an elliptical shell, representing the free wall of the left ventricle of the heart.

Algorithms↗

PubMed2005

Error estimation of geometrical data obtained by histomorphometry of oblique vessel sections: a computer model study.

The errors of radius and wall thickness of a single vessel due to oblique sectioning in histomorphometry are expressed as a function of the circular shape factor (CSF) of the section's lumen, assuming cylindrical geometry and the absence of tissue deformation. Using computer model trees generated by constrained constructive optimization, mean errors are estimated for an ensemble of vessel segments. A geometrical exclusion criterion for segments cut too obliquely is defined on the basis of a CSF-cutoff value. It is shown that CSF-values ranging from 0.95 to 0.9 are reasonable choices for a cutoff and lead to mean errors of the same order of magnitude (9.6% [9.3%] to 15.4% [14.8%] for the radius [wall thickness]) as errors due to histological tissue processing.

Animals↗

PubMed2003

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 Nterm 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 r1 of regional flows under normal physiologic conditions: model 2 gives D = 1.69 +/- 0.02 and r1 = -0.18 +/- 0.03 (n = 5), independent of Nterm 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.

Animals↗

PubMed2003

Heterogeneous perfusion is a consequence of uniform shear stress in optimized arterial tree models.

Using optimized computer models of arterial trees we demonstrate that flow heterogeneity is a necessary consequence of a uniform shear stress distribution. Model trees are generated and optimized under different modes of boundary conditions. In one mode flow is delivered to the tissue as homogeneously as possible. Although this primary goal can be achieved, resulting shear stresses between blood and the vessel walls show very large spread. In a second mode, models are optimized under the condition of uniform shear stress in all segments which in turn renders flow distribution heterogeneous. Both homogeneous perfusion and uniform shear stress are desirable goals in real arterial trees but each of these goals can only be approached at the expense of the other. While the present paper refers only to optimized models, we assume that this dual relation between the heterogeneities in flow and shear stress may represent a more general principle of vascular systems.

Arteries↗

PubMed2003

Voronoi polyhedra analysis of optimized arterial tree models.

Topological 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 alpha of the CCO models are all significantly different from the ones of random points, whereas the distributions of V, S, and alpha 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.

Algorithms↗

PubMedDate not supplied

The spatial pattern of coronary capillaries in patients with dilated, ischemic, or inflammatory cardiomyopathy.

INTRODUCTION: The goal of the present study was to compare the pattern of coronary capillaries in healthy participants and in patients with end-stage heart failure due to idiopathic dilated cardiomyopathy (DCM), ischemic cardiomyopathy (ICM), or inflammatory cardiomyopathy (InfCM). METHODS: Capillary patterns were studied in histological sections from resected hearts from patients with DCM (n=5), ICM (n=5), or InfCM (n=5) and compared with donor hearts showing no signs of cardiac disease (n=3). Patterns were characterized by the distribution of Voronoi polygon areas, A, associated with the centers of capillary profiles, nearest-neighbor distances, d, intercapillary distances (ICD), as well as by means of the pair correlation function g(r). The coefficient of variation of A, CV, was used to characterize capillary patterns as regular, random, or clustered. RESULTS: CV increased from 30.5% (control) to 33.8% (DCM), 36.6% (ICM), and to 40.3% (InfCM). d was minimal in the control group (16.5+/-4.3 microm) and increased to 18.1+/-5.2 microm in the DCM group and to 20.9+/-6.8 and 20.6+/-6.6 microm in the ICM and InfCM groups, respectively. ICD increased from 25.6+/-7.9 (control) to 28.5+/-9.2 (DCM), 34.4+/-12.2 (ICM), and 33.6+/-12.0 microm (InfCM). In all groups, g(r) was markedly different from random points; in the control and DCM group, g(r) showed a weak but distinct first maximum, characteristic for short-range order in a point pattern. CONCLUSIONS: Our data suggest that, for the patients studied, (1) the pattern of coronary capillaries is not purely random, (2) the regularity of the pattern diminishes from the control to DCM, ICM, and InfCM, and (3) ICD increases, whereas capillary density (CD) decreases, from control to DCM, ICM, and InfCM.

Adult↗