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Biomedical subjects

M Westphal

Publications and source records attributed to M Westphal.

At least 91 records · Page 5Linked to original sources
PubMed1998

Preoperative functional magnetic resonance imaging (fMRI) of the motor system in patients with tumours in the parietal lobe.

Intracranial lesions may compromise structures critical for motor performance, and mapping of the cortex, especially of the motor hand area, is important to reduce postoperative morbidity. We investigated nine patients with parietal lobe tumours and used functional MRI sensitized to changes in blood oxygenation to define the different motor areas, especially the primary sensorimotor cortex, in relation to the localization of the tumour. Activation was determined by pixel-by-pixel correlation of the signal intensity time course with a reference waveform equivalent to the stimulus protocol. All subjects showed significant activation of the primary sensorimotor cortex while performing a finger opposition task with the affected and unaffected side. In five patients the finger opposition task additionally activated the ipsilateral sensorimotor cortex and the supplementary motor area (SMA). Extension and flexion of the foot, additionally performed in two patients, also activated the sensorimotor cortex, in one case within the perifocal oedema of the tumour. Tumour localization near the central sulcus induced displacement of the sensorimotor cortex as compared to the unaffected side in all patients with a relevant mass effect. The results of our study demonstrate that functional MRI at 1.5 T with a clinically used tomograph can reproducibly localize critical brain regions in patients with intracranial lesions.

Adult↗
PubMed1998

Tissue culture of human neurocytomas induces the expression of glial fibrilary acidic protein.

Cell cultures were established from three human neurocytoma specimens (primary and recurrent). The phenotypic evolution was analyzed by immunocytology in different culture conditions in the presence and absence of serum including the addition of epidermal growth factor, rat caudate extract, retinoic acid, and N-acetyl cystein. The cells were grown on glass cover slides or an extracellular matrix (ECM) from bovine corneal endothelial cells. Immunostainings were performed after overnight incubation and were repeated after 5 and 10 days of culture. The cultures were compared to an oligoastrocytoma also arising at the foramen of Monro and an ependymoma of the frontal lateral ventricle, two tumors supposedly originating from the same tissue matrix as the neurocytoma. After overnight incubation, 90% of the neurocytoma cells were positive for A2B5 and synaptophysin. GFAP reactivity appeared in the periphery of cell processes in less than 1% of the cells. The staining patterns and morphology were nearly identical under the different culture conditions. After 5 days, almost all cells were strongly positive for GFAP, while the number of cells remaining positive for synaptophysin and A2B5 was unchanged from the earlier time point. Again, there were no fundamental differences between the incubation conditions. At this point, cultures maintained on ECM were compared to their counterparts on untreated glass cover slides with identical staining results, although many fewer cells had attached. An identical immuno-reactive pattern was found on day 10. In contrast to the neurocytoma cultures, there was an immediate strong GFAP signal in both the mixed glioma and the ependymoma. A2B5 was also positive, but synaptophysin was absent. Because the neurocytoma specimens were synaptophysin positive but GFAP negative by immunohistochemistry, it is concluded that neurocytomas may represent a human neuronoglial precursor tumor that switches its phenotype in culture to astroglial differentiation despite very diverse culture conditions.

Adult↗
PubMed1998

Microtubule-mediated centrosome motility and the positioning of cleavage furrows in multinucleate myosin II-null cells.

To study centrosome motility and the interaction of microtubules with the cell cortex in mitotic, post-mitotic and interphase cells, (alpha)-tubulin was tagged in Dictyostelium discoideum with green fluorescent protein. Multinucleate cells formed by myosin II-null mutants proved to be especially suited for the analysis of the control of cleavage furrow formation by the microtubule system. After docking of the mitotic apparatus onto the cell cortex during anaphase, the cell surface is activated to form ruffles on top of the asters of microtubules that emanate from the centrosomes. Cleavage furrows are initiated at spaces between the asters independently of the positions of spindles. Once initiated, the furrows expand as deep folds without a continued connection to the microtubule system. Occurrence of unilateral furrows indicates that a closed contractile ring is dispensable for cytokinesis in Dictyostelium. The progression of cytokinesis in the multinucleate cells underlines the importance of proteins other than myosin II in specifying a cleavage furrow. The analysis of centrosome motility suggests a major role for a minus-end directed motor protein, probably cytoplasmic dynein, in applying traction forces on guiding microtubules that connect the centrosome with the cell cortex.

Anaphase↗
PubMed1998

Expression and synthesis of insulin-like growth factor-binding proteins in human glioma cell lines.

We previously demonstrated the presence of insulin-like growth factors (IGFs) and IGF-receptors in human glioma cell lines derived from primary glioblastomas. The biological action of IGFs is modulated by specific IGF-binding proteins (IGFBP)-1 to -7. By means of polymerase chain reaction (PCR), we detected mRNA transcripts for IGFBP-1 in 42%, IGFBP-2 in 65%, IGFBP-3 in 97%, IGFBP-4 in 3%, IGFBP-5 in 74%, IGFBP-6 in 94% and IGFBP-7 in 87% of the glioma cell lines. The specificity of the PCR reaction was verified by direct sequencing of the PCR product. In addition, the content of the most prevalent IGFBP-3 was measured in conditioned medium from glioma cells by specific radioimmunoassay with levels ranging from < 1 to 620 ng/ml. Moreover, the presence of membrane-bound IGFBPs (44, 50 and 60 kDa) as well as IGF-II receptors was demonstrated by using 125I-labelled IGF-II as a ligand. In conclusion, IGFBPs may modulate the IGF-mediated effects in these cell lines.

Aged↗
PubMed1998

Absence of polyomavirus JC in glial brain tumors and glioma-derived cell lines.

The human neurotropic papovavirus JC, a close relative of simian virus 40, has been associated with the formation of brain tumors in humans because of its ability to induce such tumors in other primates under experimental conditions. Here we have analyzed 30 brain tumors classified as either oligodendroglioma or astrocytoma and 22 cell lines derived from human gliomas for the presence of JC viral sequences using polymerase chain reaction with two different sets of primers. None of the tumors or cell lines contained JC viral sequences. Similarly, we failed to detect expression of JC T antigen in any of 26 human glioma lines analyzed in this study. We conclude that JC virus is not a major cause of human brain tumors.

Brain Neoplasms↗
PubMed1997

Microfilament dynamics during cell movement and chemotaxis monitored using a GFP-actin fusion protein.

BACKGROUND: The microfilament system in the cortex of highly motile cells, such as neutrophils and cells of the eukaryotic microorganism Dictyostelium discoideum, is subject to rapid re-organization, both spontaneously and in response to external signals. In particular, actin polymerization induced by a gradient of chemoattractant leads to local accumulation of filamentous actin and protrusion of a 'leading edge' of the cell in the direction of the gradient. In order to study the dynamics of actin in these processes, actin was tagged at its amino terminus with green fluorescent protein (GFP) and observed with fluorescence microscopy in living cells of D. discoideum. RESULTS: Purified GFP-actin was capable of copolymerizing with actin. In the transfected cells of D. discoideum studied, GFP-actin made up 10-20% of the total actin. Microfilaments containing GFP-actin were capable of generating force with myosin in an in vitro assay. Observations of single living cells using fluorescence microscopy showed that the fusion protein was enriched in cell projections, including filopodia and leading edges, and that the fusion protein reflected the dynamics of the microfilament system in cells that were freely moving, being chemotactically stimulated, or aggregated. When confocal sections of fixed cells containing GFP-actin were labeled with fluorescent phalloidin, which binds only to filamentous actin, there was a correlation between the areas of GFP-actin and phalloidin fluorescence, but there were distinct sites in which GFP-actin was more prominent. CONCLUSIONS: Double labeling with GFP-actin and other probes provides an indication of the various states of actin in motile cells. A major portion of the actin assemblies visualized using GFP-actin are networks or bundles of filamentous actin. Other clusters of GFP-actin might represent stores of monomeric actin in the form of complexes with actin-sequestering proteins.

Actin Cytoskeleton↗
PubMed1997

The road less travelled: c-kit and stem cell factor.

Autocrine stimulation of growth factor receptors by autonomously produced ligands regulates different aspects of cellular transformation and progression. In several tumors, including gliomas, multiple autocrine systems are activated and may exert different functions in the malignant transformation process. The c-kit proto-oncogene is widely expressed in human gliomas, and it may be activated by its co-expressed ligand, stem cell factor (SCF). Studies in glioma cell lines as well as different tumor types suggest the possibility of intracellular interactions of c-kit with SCF. Although c-kit and SCF may not play a primary and causal role in the initiation and progression of glial tumors they may still be contributing factors in glioma biology. It can be hypothesized that the parallel activation of several autocrine systems including some of which have found less attention in gliomas, such as c-kit/SCF, could compromise the efficacy of therapies targeting different autocrine loops. A better understanding of the multiplicity and mechanisms of autocrine stimulation has implications for the development of new therapies interfering with autocrine tumor cell growth.

Animals↗
PubMed1997

Heregulins and the ErbB-2/3/4 receptors in gliomas.

The activation of autocrine loops involving proto-oncogene related receptor tyrosine kinases has led to the analysis of a large number of growth factor systems in human glioma specimens and cell lines. The ErbB-2 system, also called HER-2 or neu, is analogous to the epidermal growth factor receptor system (EGF-R, ErbB-1). Neuregulins consist of a large family of proteins arising from alternative mRNA splicing of a single gene located at 8p22-p11. Activation of ErbB-2 by neuregulins occurs in heterodimeric complexes with ErbB-3 and ErbB-4. A panel of human glioma cell lines, which had previously been analyzed for ErbB-2 expression, was examined for ErbB-3 and ErbB-4 expression. Coordinate expression of ErbB-2, -3 or -4 was not observed in these cell lines. Despite the presence of a complete system capable of signaling in about half the cell lines, no constitutive activation of ErbB-2, -3 or -4 was observed, and autophosphorylation of ErbB-2 in response to heregulin was observed only in one cell line from the panel, NCE-G84. Moreover, the addition of recombinant heregulin or antibodies capable of disrupting ErbB-2/ErbB-3 complexes had no effect on cell proliferation. We conclude that the role of neuregulins and its receptors in the control of glioma cell proliferation may be limited or may be context dependent on in situ conditions which are lost in vitro. Alternatively, neuregulins may be involved in cell differentiation or survival in the central nervous system. Data supporting these conclusions are described in more detail herein.

Brain Neoplasms↗
PubMed1997

Somatostatin and somatostatin receptors in the diagnosis and treatment of gliomas.

Somatostatin analogues are in clinical use for the diagnosis and treatment of several oncological indications, namely pituitary adenomas and endocrine gastrointestinal tumors. In addition for a variety of malignancies their potential value is being studied. It has been speculated that somatostatin plays a role in the homeostasis of gliomas, and that gliomas could be susceptible to antiproliferative effects of somatostatin analogues. These assumptions were tested in 20 human cell lines derived from malignant gliomas and 4 glioblastoma tissue specimens, which were analyzed for their expression of the five known somatostatin receptor genes (SSTR1-5) and for the receptor function. Using semiquantitative PCR techniques, SSTR2 transcripts were found in all 20 cell lines and 4 glioblastomas, SSTR1 transcripts were detected in 9 cell lines and 4 glioblastomas, and SSTR3 transcripts were noted in 7 cell lines and 1 glioblastoma. SSTR4 and SSTR5 transcripts were only rarely detected. Gene expression profiles in glioblastoma tissue specimens resembled those of the cell lines in quality as well as quantity, with average transcript levels being highest for the SSTR2, followed by SSTR1 and SSTR3. However, when compared to GH3 anterior pituitary tumor cells, the relative amounts of PCR amplified DNA fragments were found to be at least 120 fold lower in glioblastoma cell lines and tumor specimens. Binding studies indicated that glioblastoma derived cells contained only minute amounts of SSTRs. No inhibition of proliferation was observed when 10 selected cell lines were incubated with somatostatin-14 (SST-14) or octreotide (SMS 201-995) at concentrations ranging from 10(-9) M to 10(-6) M, however, the proliferation of two cell lines was weakly stimulated after 6 days of incubation with 10(-6) M octreotide. The activity of adenylate cyclase, stimulated by forskolin, was inhibited by maximally 25% at 10(-6) M SST-14 or octreotide in one of 5 selected glioblastoma cell lines. Somatostatin peptides do not seem to exert anti-proliferative effects on glioblastoma cells and therefore appear to be of no obvious value for glioblastoma therapy. Most likely the amount of cell surface SSTRs is not sufficient to mediate antiproliferative effects. Since it has been described that SSTRs are detectable on most differentiated gliomas as well as astrocytes, it may be speculated that SSTRs may be relevant only in the context of well differentiated cellular programs but lose their significance with progressive dedifferentiation.

Animals↗
PubMed1997

[Asymptomatic cerebral aneurysms--surgical and endovascular therapy options].

Aneurysmal subarachnoid hemorrhage carries a risk of 50% mortality. Therefore it is recommended to also treat asymptomatic, previously unruptured aneurysms. Deciding whether to treat or to observe depends on the consideration of risk of hemorrhage and the surgical risk. Such decision could be facilitated if predisposing factors affecting the outcome were known. 15 Patients with 19 unruptured aneurysms managed in a period when both, surgical and endovascular treatment options were available, were selected from a group of 47 asymptomatic patients documented since 1984. The patients were either operated (n = 9) or were treated by endovascular occlusion with GDC coils (n = 6). In most cases, a long history of headaches eventually lead to a CT-scan or MRI in which a suspicious abnormality was found. Upon subsequent angiography, 8 middle cerebral, 6 carotid, 3 basilar and 1 pericallosal, and ophthalmic artery aneurysm(s), respectively, were found. The aneurysms varied from 4 to 30 mm in diameter. The patients were followed between 9 months and 2.5 years. Treatment results in this small series were independent from size, location, age or sex of the patient. The initial, mostly unrelated symptoms persisted after treatment in most cases. The morbidity according to GOS in this small series (3 out of 19 patients deteriorated) is not representative of the complete series where morbidity and mortality was 5.4% and 1.2% respectively). In agreement with the literature reviewed herein, we recommend surgical treatment of previously unruptured aneurysms, especially when the patients are below 60 years of age. In patients with posterior circulation aneurysms, endovascular coil occlusion is a valid alternative, especially in older patients with concurrent medical problems.

Adult↗
PubMed1997

[Differential therapy of cerebral angiomas].

Patients with cerebral arteriovenous malformations (cAVMs) are usually young at the time of diagnosis with a mean age of 32 years. These patients are in a crucial phase of their lives, starting a family and establishing a professional position. Facing a relative annual risk of 2 to 3% for a severe hemorrhage which cumulates to a 50% risk of hemorrhage over the next four decades of their lives, these patients have to make the decision about possible treatment of their cAVM. Advice can only be given to the patients on an individual basis because there are almost no two identical lesions. Nevertheless, based on a grading system and within established treatment regimens, risk estimations are possible and particularly with close neuroradiological/neurosurgical cooperation these risks can be defined and minimized. In this context we report a series of 184 patients with cAVMs which were taken care of at the Departments of Neurosurgery and Neuroradiology at the University of Hamburg between February 1988 and July 1996 and who were treated according to a standardized joint protocol with interventional and microsurgical options.

Adult↗
PubMed1996

Adenovirus-mediated p53 gene transfer suppresses growth of human glioblastoma cells in vitro and in vivo.

Alterations in the p53 tumor-suppressor gene occur in 35-60% of human glioblastomas, and re-introduction of p53 can suppress neoplastic growth. To evaluate the potential for p53 gene therapy of glioblastoma, we have analyzed the response of human glioblastoma cell lines in vitro and in vivo to experimental therapy with replication-deficient recombinant adenoviruses encoding wild-type p53 (rAd-p53). Western blot analyses showed high-level expression of p53 protein after treatment with rAd-p53, and transgene expression was dependent on promoter strength. A p53-specific dose-dependent inhibition of in vitro cellular proliferation was observed in 5 of 6 cell lines, and growth inhibition corresponded to adenovirus-mediated gene transfer and expression. p53-specific cell death was quantitated by release of the lactate dehydrogenase enzyme. Fragmentation of DNA into nucleosomal oligomers and the occurrence of a hypodiploid cell population detected by flow cytometry provided evidence for apoptosis. Studies in nude mice demonstrated that ex vivo infection with rAd-p53 suppressed the tumorigenic potential of human glioblastoma cells. Furthermore, direct injection of rAd-p53 into established s.c. xenografts inhibited tumor growth. Our observations suggest that re-introduction of wild-type p53 may have potential clinical utility for gene therapy of glioblastoma.

Adenoviridae↗
PubMed1996

Migration of human glioma cells in response to tumour cyst fluids.

Glial tumours often show high degrees of local invasion that lead to local recurrence of the disease. Extracellular matrix components as well as soluble factors may play a critical role in this poorly understood process. Cyst fluid from human brain tumours may accumulate such autocrine produced factors and may represent a source were those factors may be easily obtained and studied. We have studied the effect of cyst fluids harvested from 17 glial tumours, 3 meningiomas, and three metastases on the motility of established human glioma cell lines. Both cyst fluids of high grade and low grade gliomas contained varying degrees of motility enhancing activity. No such activity was identified in cyst fluids obtained from meningiomas. The relation of mitogenic and motogenic activity in three selected cyst fluids was analysed using a quantitative monolayer migration assay. Quantitative analysis of cyst fluid effects on both proliferation and migration indicate that tumour cyst fluids contain factors that strongly stimulate cell migration and that maximum stimulation of migration did not occur at concentrations optimal for cell proliferation. Our findings indicate that glial tumours in fact produce and secrete soluble factors that may contribute to their dissemination in brain tissue.

Adult↗