Biomedical subjects

Kristian Sandberg

Publications and source records attributed to Kristian Sandberg.

5 recordsLinked to original sources

PubMed2004

Characterization of long-term mouse brain aggregating cultures: evidence for maintenance of neural precursor cells.

An extensive characterization of fetal mouse brain cell aggregates has been performed using immunohistochemical and stereological methods. Single cell suspensions from mechanically dissociated cortex and hippocampus were cultured in serum-free, B27-supplemented medium under constant gyratory agitation for up to 56 days. Three-dimensional aggregates started to form immediately after seeding and reached a final average size of 500 microm in diameter. Among the cell types identified, neurons were the most abundant cells in the aggregates, followed by astrocytes, microglia, and oligodendrocytes. Western blotting for synaptophysin and immunostaining for neurotransmitter-related molecules indicated the presence of well-defined phenotypic characteristics of the neurons in this culture system, suggesting functionality. Proliferating cells, many with neural precursor cell properties, were seen throughout the culture period and could be isolated from the aggregates even after 2 months in culture. Neural precursor cells were isolated from the aggregates after more than 1 month in culture; these cells were successfully differentiated into neurons, astrocytes, and oligodendrocytes. The aggregate culture system may provide a versatile tool for molecular dissection of processes identified in mouse models, including transgenic animals and manipulation of neural precursor cells.

Animals↗

PubMed2003

Migration and differentiation of neural precursor cells can be directed by microglia.

Recent reports have supported the existence of neural stem cells in the adult mammalian CNS. Important features of such cells are self-renewal and multipotency, i.e., they can give rise to neurons, astrocytes, and oligodendrocytes and thus in principle replace lost cells in the CNS. Observations in several animal models of CNS diseases have shown that by unknown mechanisms endogenous as well as exogenous precursor cells preferentially migrate to damaged areas. Microglia are immunoreactive cells of nonneural lineage resident in the CNS. After injury to the CNS, microglia are rapidly activated and found concentrated at the sites of injury. In the present article we show, in two different assays, that soluble factors released from mouse microglial cells direct the migration of neural CNS precursor cells. We also provide evidence that microglia have the capacity to influence the differentiation of both adult and embryonic neural precursor cells toward a neuronal phenotype. Given that an invariant feature of pathological processes in CNS is the activation of microglia, these results indicate an important and unique role for microglia in directing the replacement of damaged or lost cells in the CNS.

Animals↗

PubMed2003

Dihydropyrimidinase related protein-2 as a biomarker for temperature and time dependent post mortem changes in the mouse brain proteome.

Proteome analysis in the central nervous system area represents a large and important challenge in drug discovery. One major problem is to obtain representative and well characterized tissues of high quality for analysis. We have used brain tissues from normal mice to study the effect of post mortem time (up to 32 h) and temperature (4 degrees C and room temperature) on protein expression patterns. A number of proteins were identified using mass spectrometry and potential markers were localized. One of the proteins identified, dihydropyrimidinase related protein-2 (DRP-2), occurs as multiple spots in two-dimensional electrophoresis gels. The ratio between the truncated form of DRP-2 (fDRP-2) and full length DRP-2 is suggested as an internal control that can be used as a biomarker of post mortem time and post mortem temperature between unrelated brain protein samples. Results of this study may be useful in future efforts to detect disease specific alterations in proteomic studies of human post mortem brain tissues.

Animals↗

PubMed2003

Generation of microglia specific reagents from phage displayed peptide libraries.

The present report concerns the generation of specific markers and the establishment of a selection procedure for microglia specific molecules from phage displayed peptide libraries. Negative selection against a mouse monocytic cell line (IC-21) and positive selection against primary mouse microglia was combined in the selection procedures using a mixture of two random peptide libraries displayed on phage. In a first set of experiments, one clone was selected that bound microglia and IC-21 cells to equal extent, and three clones that bound to unsorted primary microglia to substantially higher levels than to IC-21 cells. In the second series of experiments, microglia and IC-21 cells were mixed and CD45-positive microglia cells were collected using a FACS sorter. From the latter selection series, three clones were found that preferentially bound to microglia cells. The binding of one of the six selected microglia specific phage clones, clone V-1:19, was competed/inhibited in experiments using soluble synthetic peptides corresponding to the binding motif of the phage clone. The specific inhibition to microglia cells by this synthetic peptide was effective in the concentration range of 0.5-20 microM. The preferential binding of clone V-1:19 to microglia like cells was further demonstrated by staining a panel of cell lines and purified primary mouse microglia.

Amino Acid Sequence↗

PubMedDate not supplied

A fast reconstruction algorithm for electron microscope tomography.

We have implemented a Fast Fourier Summation algorithm for tomographic reconstruction of three-dimensional biological data sets obtained via transmission electron microscopy. We designed the fast algorithm to reproduce results obtained by the direct summation algorithm (also known as filtered or R-weighted backprojection). For two-dimensional images, the new algorithm scales as O(N(theta)M log M)+O(MN log N) operations, where N(theta) is the number of projection angles and M x N is the size of the reconstructed image. Three-dimensional reconstructions are constructed from sequences of two-dimensional reconstructions. We demonstrate the algorithm on real data sets. For typical sizes of data sets, the new algorithm is 1.5-2.5 times faster than using direct summation in the space domain. The speed advantage is even greater as the size of the data sets grows. The new algorithm allows us to use higher order spline interpolation of the data without additional computational cost. The algorithm has been incorporated into a commonly used package for tomographic reconstruction.

Algorithms↗