Biomedical subjects

A Giese

Publications and source records attributed to A Giese.

78 records · Page 5Linked to original sources

PubMedDate not supplied

Dissecting glioma invasion: interrelation of adhesion, migration and intercellular contacts determine the invasive phenotype.

The invasive cellular behavior of malignant gliomas is determined by receptor mediated cell-substratum contacts and cell-cell interaction as well as cellular locomotion. This study attempts to break down the complex phenomena of the invasive process into their components of attachment to neighboring cells, aggregate formation, adhesion to matrix substratum, migration and invasion into three-dimensional cellular aggregates separately analyzed in different in vitro assay systems. Using a panel of 13 glioma cell lines, adhesion to non-specifically or merosin coated surfaces was correlated to monolayer cell migration and dissemination of tumor cells from aggregates plated on these substrates. The formation kinetics of aggregates were determined and compared to the ability of these cells to rapidly attach and form mechanically stable cell-cell contacts. The motility rates in the different assay systems as well as cell-cell attachment was correlated to invasion of re-aggregated tumor cells into fetal rat brain. A tight positive correlation was found for substrate adhesion and monolayer migration. In contrast, cell-substratum contacts had little influence on dissemination of cells out of three-dimensional aggregates and no association between monolayer migration and migration of cells out of aggregates was detected. The ability of glioma cells to rapidly form aggregates was associated with enhanced migration out of aggregates. The capacity to invade fetal rat brain aggregates was correlated with the capacity to form stable intercellular adhesion as measured in a cell-cell adhesion assay. Invasion in this system was not found to be associated with migration in monolayer or with migration out of tumor aggregates. This study highlights that current in vitro assays for invasion only represent isolated aspects of the multi-cascade process which is involved in tumor cell invasion.

Animals↗

PubMedDate not supplied

The cellular prion protein binds copper in vivo.

The normal cellular form of prion protein (PrPC) is a precursor to the pathogenic protease-resistant forms (PrPSc) believed to cause scrapie, bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease. Its amino terminus contains the octapeptide PHGGGWGQ, which is repeated four times and is among the best-preserved regions of mammalian PrPC. Here we show that the amino-terminal domain of PrPC exhibits five to six sites that bind copper (Cu(II)) presented as a glycine chelate. At neutral pH, binding occurs with positive cooperativity, with binding affinity compatible with estimates for extracellular, labile copper. Two lines of independently derived PrPC gene-ablated (Prnp0/0) mice exhibit severe reductions in the copper content of membrane-enriched brain extracts and similar reductions in synaptosomal and endosome-enriched subcellular fractions. Prnp0/0 mice also have altered cellular phenotypes, including a reduction in the activity of copper/zinc superoxide dismutase and altered electrophysiological responses in the presence of excess copper. These findings indicate that PrPC can exist in a Cu-metalloprotein form in vivo.

Animals↗

PubMedDate not supplied

Comparative assessment of the functional p53 status in glioma cells.

BACKGROUND: p53 is the most frequently mutated gene in human cancers and its functional integrity is an important predictor of treatment response and clinical outcome. The majority of mutations found in different types of cancer cluster within the DNA binding domain encoded by exons 5-8. In clinical specimens the functional status of p53 is, therefore, often evaluated by direct mutation analysis of exons 5-8 or indirectly by immunostaining and evaluation of the subcellular localization pattern or protein accumulation. MATERIALS AND METHODS: In a panel of glioma cell lines, the status of the P53 gene was analyzed by temperature gradient gel electrophoresis (TGGE) of exons 5-8 and direct sequencing of all p53 exons. The nuclear accumulation of p53 in unstressed cells was assessed by immunostaining. These data were correlated with stress induction of the p53 protein, nuclear translocation and a direct determination of the transcriptional activity of endogenous p53 protein and induction of p53 target genes. RESULTS: Our analysis demonstrated that a p53 gene mutation analysis limited to exons 5-8 and analysis of immunostaining patterns can not serve as reliable predictors of functional p53 in tumor cells. Conversely, in some presumably rare cases, the transcriptional activity of p53 may be retained in tumor cells in the presence of a mutation and a pathological immunostaining pattern. In our analysis, the constitutive dephosphorylation at Ser 376 correlated with the nuclear accumulation of p53, but not with the transcriptional activity of the protein. This suggests that constitutive dephosphorylation at Ser376 may be one of the factors determining stabilization of mutant and wild-type p53, which is frequently observed in glial tumors. CONCLUSION: The incidence of a dysfunctional p53 protein in gliomas may be higher than expected, based on a single parameter evaluation by mutation analysis of exons 5-8 or assessment of p53 accumulation and subcellular localization by immunostaining.

Brain Neoplasms↗

PubMedDate not supplied

Polymorphism at codon 129 of the prion protein gene determines cerebellar pathology in Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD) is a transmissible neurodegenerative disorder characterized by the accumulation of proteinase-resistant prion protein (PrP) in the brain. Pathological changes in the cerebellum are common and include atrophy of the granular layer, spongiform change in the molecular layer, and astrocytic gliosis of the cerebellar cortex and white matter. In most cases of sporadic CJD immunohistochemistry for PrP shows widespread granular deposits of the scrapie isoform of the prion protein (PrPSc) in the cerebellar cortex. In a minority of cases plaque-like deposits of PrPSc are detectable. The genetic background of this phenomenon was investigated in 47 cases of sporadic CJD. Immunohistochemistry using antibodies against PrP was performed in brain autopsy specimens. A genetic analysis of the prion protein gene (PRNP) showed overrepresentation of homozygosity for either methionine (M/M) or valine (V/V) at the polymorphic codon 129 in CJD patients as compared to 74 controls. No significant difference in allele frequency between the 2 groups was found. Plaques or plaque-like PrPSc deposits were found in 9 cases of CJD and were associated with the presence of valine at codon 129 on at least 1 allele of PRNP. CJD patients homozygous for valine (V/V) were on an average more than 5 years younger than patients with M/M or M/V at codon 129.

Adult↗

PubMedDate not supplied

Postmortem delay and temperature conditions affect the in situ end-labeling (ISEL) assay in brain tissue of mice.

Apoptotic cell changes occurring under certain developmental, physiological, and pathological conditions have been of increasing interest during recent years. Due to occasional difficulties in detecting apoptosis in routinely stained sections, various methods have been developed to facilitate tissue examination. Fragmentation of DNA during the process of apoptosis is a prerequisite for detection in the in situ end-labeling (ISEL) procedure. It is yet unclear whether other mechanisms of cell change that induce DNA fragmentation such as necrosis and postmortem autolysis also show positive staining with the ISEL technique. To investigate whether the ISEL assay visualizes autolytic DNA changes along with apoptotic DNA fragmentation, we tested the technique on brain tissue of mice after different time intervals (0, 6, 12, 24, 48, 72 h) of postmortem delay (PMD) and at 2 different temperatures of postmortem storage (4 degrees C and room temperature (RT)). Our semiquantitative results show that up to 24 h of PMD no prominent difference in labeling is observable at both temperatures. After 48 and 72 h of PMD at RT clusters of labeled cells begin to appear. Clusters of stained cells should therefore not be considered as apoptosis when using the ISEL assay.

Animals↗

PubMedDate not supplied

Glioma cell adhesion and migration on human brain sections.

Within the brain, dissemination of glioma cells follows myelinated fiber tracts and extracellular matrix containing structures such as the basement membranes of blood vessels. These patterns represent the two major routes of invasion frequently observed in clinical disease. Previously, we have characterized the substrates for preferential glioma adhesion and migration on purified ECM protein. In this study sections of human brain from different anatomical regions were used as adhesive substrates and also characterized for the presence and distribution of matrix proteins. Adhesion of marker gene transfected glioma cell suspensions to different regions and anatomical structures of human brain was quantified using a computer assisted image analysis system. Monoclonal antibodies against different adhesion molecules were used to inhibit glioma cell attachment ot specific anatomical structures. In addition, glioma cell aggregates were allowed to adhere to brain sections and single cells were observed to migrate out of these aggregates. Scanning electron microscopy was used to morphologically study the preferred routes of glioma dissemination on brain sections. In brain sections different kinetics of cell adhesion to distinct structures were observed. Within 15 minutes cells adhered and spread on blood vessels and arachnoid tissue containing sections. Choroid plexus and the ventricular wall were also adhesive structures. Adhesion to cortex required 1 hour, while adhesion and spreading on myelinated fiber tracts was retarded and required several hours of incubation. The predominant matrix proteins in small vessels were found to be laminin, collagen type IV, and fibronectin. Choroid plexus and the ependyma showed a similar composition of matrix proteins. Arachnoid fibers contained different types of collagens, predominately type I and III, whereas the only matrix protein identified in the subependyma was fibronectin. Antibodies to the alpha 2, alpha 3, and beta 1 integrin subunits completely blocked adhesion to arachnoid tissue, anti-NCAM inhibited attachment to cortex. Adhesion to blood vessels in brain sections could only be inhibited to 50% by anti-integrin beta 1. Antibodies to the av containing integrin av beta 3 also blocked 50% of adhesion to vessels. Our findings indicate that adhesion of glioma cells to brain sections most rapidly takes place on ECM protein containing regions, especially blood vessels which may serve as guiding structures for glioma dissemination.

Brain↗