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T Bretschneider

Publications and source records attributed to T Bretschneider.

At least 19 recordsLinked to original sources
PubMed2005

Formins and VASPs may co-operate in the formation of filopodia.

Filopodia are finger-like cell protrusions composed of parallel arrays of actin filaments, which elongate through actin polymerization at their tips. These highly dynamic structures seem to be used by many cell types as sensing organs to explore environmental cues and have been implicated in cell motility as well as in cell-substrate adhesion. Formins are highly conserved multidomain proteins that play important roles in the nucleation of actin and the formation of linear actin filaments, yet their role in filopodia formation has remained poorly defined. The Dictyostelium diaphanous-related formin dDia2 is strongly enriched in filopodia tips. Genetic and biochemical analysis revealed that this protein is important for cell migration and cell adhesion, but most importantly for the formation of filopodia. Recently, we have identified the Dictyostelium VASP (vasodilator-stimulated phosphoprotein) orthologue as a binding partner of dDia2 and provide evidence for a co-operative role of both proteins in filopodia formation.

Animals↗
PubMed2003

Diffusion-weighted echo-planar MRI of the brain with calculated ADCs: a useful tool in the differential diagnosis of tumor necrosis from abscess?

BACKGROUND AND PURPOSE: It was the aim of this study to evaluate whether brain abscesses could be distinguished reliably from necrotic brain tumors using diffusion-weighted imaging (DWI) with calculated apparent diffusion coefficients (ADCs). METHODS: The authors studied 27 lesions in 26 patients (21 tumors and metastases, 5 pyogenic brain abscesses, and 1 cerebral toxoplasmosis). DWI was obtained with a single-shot echo-planar imaging spin-echo sequence. ADCs were calculated for all images. RESULTS: ADCs (x 10(-3) mm2/s) measured in the necrotic parts of the tumors ranged from 2.94 (glioblastoma) to 1.51 (astrocytoma III). In the inflammatory lesions, ADCs ranged between 0.91 and 3.07 (cerebral toxoplasmosis and pyogenic abscess). The contrast-enhanced parts of the lesions showed ADC values from 0.77 (pyogenic abscess) up to 1.68 (glioblastoma). CONCLUSIONS: DWI with calculated ADC values does not allow the reliable differentiation of enhanced central necrotic intracranial lesions.

Astrocytoma↗
PubMed2002

Tentorial and dural calcification with tertiary hyperparathyroidism: a rare entity in chronic renal failure.

A case of rare calcification of the tentorium cerebelli, the thoracal dura mater of the spine, and the sclera in an adult male patient with tertiary hyperparathyroidism is presented. The often reported feature in the skull is that of a combination of osteopenia and osteosclerosis giving a granular bone texture. Extensive dura calcification with this condition has very rarely been reported. It is the aim of this paper to document the latter in a patient with chronic renal failure and tertiary hyperparathyroidism.

Adenoma↗
PubMed2001

Polarity, protrusion-retraction dynamics and their interplay during keratinocyte cell migration.

Keratinocyte migration on a two-dimensional substrate can be split into four distinct phases: cell extension, attachment, contraction, and detachment. It is preceded by polarization of the cell which leads to a functional asymmetry observable by the formation of a leading lamella. In this work variation of fibronectin coating concentrations and competitive inhibition with RGD peptides are used to investigate the dependency of polarization, migration, lamella dynamics, and ruffling on substrate adhesiveness. Looking at migrating human epidermal keratinocytes with a well-defined polarity we find that a fibronectin-coating concentration of 10 microg/cm(2) stimulates migration and ruffling speed twofold, whereas protrusion speed increases only by 20% (compared to 2.5 microg/cm(2) fibronectin). Nonpolar cells show a constant migration and ruffling speed independent of the amount of fibronectin. In contrast protrusion speeds of polar and nonpolar cells are equal. Treatment of cells on 10 microg/cm(2) fibronectin with 1 mg/ml GRGDS reduces the characteristic migration, protrusion, and ruffling speed of polar cells which corresponds to lowering the effective coating concentration to under 5 microg/cm(2). The probability of being polarized (quantified by a polarity index) increases with increasing fibronectin concentration. However, addition of soluble RGD on 10 microg/cm(2) fibronectin does not simply reduce the polarity index like one would expect from the corresponding changes in the other motility parameters, but it remains unchanged.

Cell Adhesion↗
PubMed2001

Spinal metastases from renal cell carcinoma: effect of preoperative particle embolization on intraoperative blood loss.

BACKGROUND AND PURPOSE: Surgical repair of spinal metastases from renal origin is often complicated by excessive bleeding. The purpose of this study was to assess the effect of preoperative particulate embolization on intraoperative blood loss. METHODS: Twenty spinal metastases from renal origin (17 patients) treated by preoperative embolization with polyvinyl alcohol particles were analyzed retrospectively. Surgical decompression was performed within 2 days after embolization. A control group of 10 patients with 11 spinal metastases of renal origin underwent surgery without embolization. The effect of preoperative embolization, of completeness of embolization, and of particle size on the estimated intraoperative blood loss was analyzed using nonparametric statistical tests. RESULTS: Complete embolization was achieved in 10 cases and partial embolization in the other 10. The estimated blood loss of 19 embolized and 11 control cases was available from the surgical report. Median intraoperative blood loss in 19 embolized lesions was 1500 mL (range, 300-8000 mL), compared with 5000 mL (range, 1440-15000 mL) in the control group. Even after partial embolization, blood loss (median, 2000 mL) was significantly lower than in the control group. No significant differences in estimated blood loss were noted between the use of particles smaller than 250 microm and those larger than 250 microm. No embolization-related permanent neurologic deficit or skin or muscle necrosis occurred. CONCLUSION: Preoperative embolization of spinal metastases of renal origin with polyvinyl alcohol particles is safe and might reduce intraoperative blood loss significantly. Even partial embolization seems to be effective.

Aged↗
PubMed1999

A model for dictyostelium slug movement

Dictyostelium slug movement results from the coordinated movement of its 10(5)constituent cells. We have shown experimentally that cells in the tip of the slug show a rotational cell movement while the cells in the back of the slug move periodically forward (Siegert & Weijer, 1992). We have put forward the hypothesis that cell movement in slugs is controlled by chemotaxis to scroll waves generated in the tip which convert to twisted scroll or planar waves in the back of the slug (Bretschneider et al., 1995). The coordinated movement of all individual cells in response to these waves could then result in forward movement of the slug. We now test this hypothesis by extending our model for mound formation (Bretschneider et al., 1997) to include two cell types with different signalling and movement properties. All cells are able to relay cAMP and move chemotactically in response to cAMP gradients. Cells interact by adhesion, pressure and friction with neighbouring cells and the extracellular matrix. The model can generate stable scroll waves propagating from the tip to the back of a slug which coordinate forward cell movement and result in slug migration. We use the model to investigate the influence of cell type specific differences in excitability, adhesion and cell interactions on slug motion. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Squamous cell carcinoma arising in an intradiploic epidermoid cyst.

A 71-year-old woman presented with the symptoms of a posterior cranial fossa mass. CT and MRI revealed a lytic lesion in the occipital bone and a tumour infiltrating the dura mater, venous sinuses and cerebellum. Histopathology demonstrated a moderately differentiated squamous cell carcinoma arising from a primarily intradiploic epidermoid cyst. Despite surgery and radiotherapy, the tumour progressed and the patient died 1 year later.

Aged↗
PubMed1997

A Model for Cell Movement During Dictyostelium Mound Formation

Dictyostelium development is based on cell-cell communication by propagating cAMP signals and cell movement in response to these signals. In this paper we present a model describing wave propagation and cell movement during the early stages of Dictyostelium development, i.e. aggregation and mound formation. We model cells as distinct units whose cAMP relay system is described by the Martiel-Goldbeter model. To describe cell movement we single out three components: chemotactic motion, random motion and motion due to pressure between cells. This pressure result in cells crawling on top of each other and therefore to the extension of the aggregate into the third dimension. Using this model we are able to describe aggregation up to the mound stage. The cells in the mound move in a rotational fashion and their movement is directed by the counter-rotating spiral of the chemo-attractant cAMP. Furthermore, we show that the presence of two subpopulations with different inherent chemotactic velocities can lead to cell sorting in the mound. The fast moving cells collect into the centre while the slow cells occupy the rest of the mound. This model allows the direct comparison of the properties of the cAMP waves properties and movement behavior of individual cells with experimental data. Thereby it allows a critical test of our understanding of the basic cellular principles involved in the morphogenesis of a simple eukaryote.Copyright 1997 Academic Press Limited Copyright 1997 Academic Press Limited

Journal Article↗
PubMed1997

Cerebral CT angiography in the diagnosis of acute subarachnoid hemorrhage.

PURPOSE: To evaluate the usefulness of CT angiography (CTA) in the detection of intracranial aneurysms in patients with acute subarachnoid hemorrhage (SAH). MATERIAL AND METHODS: In 53 patients with nontraumatic SAH a helical contrast-enhanced CTA was performed. CTA data were reconstructed with maximum intensity projection (MIP). Each patient underwent selective arteriography of the cerebral vessels (as the gold standard). CTA (axial images and MIP reconstructions) and arteriography were evaluated separately and their diagnostic information was compared. RESULTS: In 14 of the 53 patients neither CTA nor angiography showed a vascular malformation. In the remaining 39 patients, angiography demonstrated a total of 51 aneurysms ranging in size from 3 mm to 16 mm. CTA missed one of these aneurysms, which was located at the internal carotid artery. 3-D CT reconstruction was slightly superior to arteriography in the demonstration of the neck, shape and direction of the aneurysms. Partial thrombosis of 3 aneurysms was demonstrated only by CTA. CONCLUSION: Although CTA cannot replace cerebral arteriography in the diagnostic work-up of acute SAH, it proved to be helpful in demonstrating the topographic anatomy of cerebral aneurysms and surrounding structures.

Acute Disease↗
PubMed1995

Three-dimensional scroll waves of cAMP could direct cell movement and gene expression in Dictyostelium slugs.

Complex three-dimensional waves of excitation can explain the observed cell movement pattern in Dictyostelium slugs. Here we show that these three-dimensional waves can be produced by a realistic model for the cAMP relay system [Martiel, J. L. & Goldbeter, A. (1987) Biophys J. 52, 807-828]. The conversion of scroll waves in the prestalk zone of the slug into planar wave fronts in the prespore zone can result from a smaller fraction of relaying cells in the prespore zone. Further, we show that the cAMP concentrations to which cells in a slug are exposed over time display a simple pattern, despite the complex spatial geometry of the waves. This cAMP distribution agrees well with observed patterns of cAMP-regulated cell type-specific gene expression. The core of the spiral, which is a region of low cAMP concentration, might direct expression of stalk-specific genes during culmination.

Adenosine Triphosphate↗
PubMed1984

[Results of radiculomyelography with dimer-X following lumbar intervertebral disk operations].

In radiculomyelogram after operation of lumbar intervertebral disk has been investigated an adhesive arachnopathy in 24 out of 86 patients. It appears increased in patients with two operations of the intervertebral disk, revision of several intervertebral spaces and after massed prolapses. The etiological importance of hyperosmolar X-ray contrast media is comparatively slight. Characteristical clinical findings were not evident in patients with arachnopathy. In some patients the protein content in cerebrospinal fluid was raised, it could be observed as an unspecific reaction and a relative monocytosis in the cytogram. Two third of the patients with recurrent nucleus pulposus prolapse were diagnosed rightly by radiculomyelography, though there are difficulties in the differentiation of adhesive-fibrotic changes.

Adult↗
PubMed1979

[Comparative experimental animal studies of the effects of various nuclear pharmaceuticals on the EEG].

Some of the radiopharmaceuticals presently recommended for cisternoscintigraphy were compared, in experiments on animals, for their effects upon bioelectric activity. On relaxed cats, electroencephalography did not show any effects upon bioelectric activity for 198 Au and 169 Yb Ca DTPA. One test animal each of seven and six cats examined using 169 Yb DTPA and 131 J HSA showed changes in the electroencephalogram subsequent to suboccipital application.

Animals↗