Biomedical subjects

Anders Rosengren

Publications and source records attributed to Anders Rosengren.

4 recordsLinked to original sources

PubMed2006

Failure of transplanted bone marrow cells to adopt a pancreatic beta-cell fate.

Recent studies in normal mice have suggested that transplanted bone marrow cells can transdifferentiate into pancreatic beta-cells at relatively high efficiency. Herein, adopting the same and alternative approaches to deliver and fate map-transplanted bone marrow cells in the pancreas of normal as well as diabetic mice, we further investigated the potential of bone marrow transplantation as an alternative approach for beta-cell replacement. In contrast to previous studies, transplanted bone marrow cells expressing green fluorescence protein (GFP) under the control of the mouse insulin promoter failed to express GFP in the pancreas of normal as well as diabetic mice. Although bone marrow cells expressing GFP under the ubiquitously expressed beta-actin promoter efficiently engrafted the pancreas of normal and hyperglycemic mice, virtually all expressed CD45 and Mac-1/Gr-1, demonstrating that they adopt a hematopoietic rather than beta-cell fate, a finding further substantiated by the complete absence of GFP(+) cells expressing insulin and the beta-cell transcription factors pancreatic duodenal homeobox factor-1 and homeodomain protein. Thus, transplanted bone marrow cells demonstrated little, if any, capacity to adopt a beta-cell fate.

Animals↗

PubMed2005

Center of volume and total heart volume variation in healthy subjects and patients before and after coronary bypass surgery.

BACKGROUND: Total heart volume variation (THVV) and center of volume variation (COVV) likely affects the efficiency of cardiac pumping, but no study has determined COVV of the heart throughout the cardiac cycle or the effect of surgery on THVV in adults. Therefore, the purposes of this study were to determine COVV in healthy adults and patients with cardiac failure due to ischemic heart disease (IHD), identify any difference in THVV between these two groups, and determine how these parameters are affected by coronary bypass surgery. METHODS: Six healthy volunteers and eight patients before and after surgery were investigated with cardiovascular magnetic resonance imaging. The atrioventricular plane movement (AVPM), THVV and time resolved three-dimensional coordinates of the center of the cardiac volume (COVV) were measured. RESULTS: COVV followed a loop in 3D space that between the end-points was approximately 2 mm with no difference between healthy subjects and patients before surgery (P = 0.093), although AVPM was significantly lower in patients (P = 0.002). However, after surgery the COVV during the cardiac cycle doubled (P = 0.012) and the increase in THVV was significant (P = 0.050), although of very small magnitude, and the AVPM remained unchanged (P = 0.401). CONCLUSION: COVV and THVV were similar in patients and healthy subjects even though AVPM was lower in the patient population. After surgery, however, COVV doubled despite a very small change in THVV and no change in AVPM. Taken together, the results of this study may provide new insights into the energy expenditure and efficiency of cardiac pumping.

Adult↗

PubMed2004

Computation of the Ising partition function for two-dimensional square grids.

An improved method for obtaining the Ising partition function of n x n square grids with periodic boundary is presented. Our method applies results from Galois theory in order to split the computation into smaller parts and at the same time avoid the use of numerics. Using this method we have computed the exact partition function for the (320 x 320) grid, the ( 256 x 256 ) grid, and the ( 160 x 160 ) grid, as well as for a number of smaller grids. We obtain scaling parameters and compare with what theory prescribes.

Journal Article↗

PubMed2003

Reduction of the sign problem using the meron-cluster approach.

The sign problem in quantum Monte Carlo calculations is analyzed using the meron-cluster solution. A meron is a loop that alters the sign of the configuration, and the concept of merons can be used to solve the sign problem for a limited class of models. Here we show that the method can be used to reduce the sign problem in a wider class of models. We investigate how the meron solution evolves between a point in parameter space where it eliminates the sign problem and a point where it does not affect the sign problem at all. In this intermediate regime, the merons can be used to reduce the sign problem. The average sign still decreases exponentially with system size and inverse temperature, but with a different prefactor. The sign exhibits the slowest decrease in the vicinity of points where the meron-cluster solution eliminates the sign problem. We have used stochastic series expansion quantum Monte Carlo combined with the concept of directed loops.

Journal Article↗