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Biomedical subjects

G F Walter

Publications and source records attributed to G F Walter.

At least 19 recordsLinked to original sources
PubMed2006

eLearning in education and advanced training in neuroradiology: introduction of a web-based teaching and learning application.

INTRODUCTION: New information technologies offer the possibility of major improvements in the professional education and advanced training of physicians. The web-based, multimedia teaching and learning application Schoolbook has been created and utilized for neuroradiology. METHODS: Schoolbook is technically based as a content management system and is realized in a LAMP environment. The content is generated with the help of the developed system and stored in a database. The layout is defined by a PHP application, and the webpages are generated from the system. RESULTS: Schoolbook is realized as an authoring tool so that it can be integrated into daily practice. This enables the teacher to autonomously process the content into the web-based application which is used for lectures, seminars and self-study. A multimedia case library is the central building block of Schoolbook for neuroradiology, whereby the learner is provided with original diagnostic and therapeutic data from numerous individual cases. The user can put individual emphasis on key learning points as there are various ways to work with the case histories. Besides the case-based way of teaching and learning, a systematically structured way of dealing with the content is available. CONCLUSION: eLearning offers various opportunities for teaching and learning in academic and scientific as well as in economic contexts. Web-based applications such as Schoolbook may be beneficial not only for basic university education but also for the realization of international educational programmes such as the European Master of Medical Science with a major in neuroradiology.

Computer-Assisted Instruction↗
PubMed2004

Fetal allogeneic dopaminergic cell suspension grafts in the ventricular system of the rat: characterization of transplant morphology and graft-host interactions.

Experimental transplantation trials of fetal cells in Parkinson's and Huntington's disease or multiple sclerosis still require allogeneic graft material and raise questions of graft rejection and immunosuppression. Alternatively to the striatum, the lateral ventricles have been discussed as grafting site in Parkinson's and Huntington's disease although little is known of the specific immunology of the ventricular system. To address this question, 28 adult female LEW1.W rats received intraventricular allogeneic dopaminergic cell suspension grafts from E14 DA rat fetuses. Twelve animals with syngeneic grafts served as control. Immunohistochemical examination was performed with staining for MHC expression, microglia-macrophages, various lymphocyte subsets, dopaminergic neurons and astrocytes at 4 days, and 1, 3, 6, and 12 weeks after transplantation. In all animals, intraventricular transplants were found, which showed maturation and integration in the host parenchyma at the later time points. Animals with allogeneic grafts developed a vivid immune response with strong MHC class I expression and dense lymphocyte infiltrates. Surprisingly, this immune response subsided at 12 weeks and healthy grafts remained. These results indicate (1) that, in contrast to intraparenchymal grafts, a strong immune response to allogeneic fetal cell suspension grafts can be elicited by intraventricular grafting, (2) that a peculiar immunological role of the ventricular system has to be considered in further studies, and (3) that a vivid immune response to allografts in the brain may subside without graft destruction.

Animals↗
PubMed2003

Legal pitfalls in teleneuropathology.

OBJECTIVES: This study aims to emphasize legal pitfalls, especially the often underestimated liability issues for both clients of telemedicine and "tele-doctors". The main relevance of telemedicine lies in its capability to link medical practitioners and remote hospitals to larger or specialized facilities in a very fast electronic manner. This may become even more important due to current increases in subspecialization and the demand for more precise diagnosis and consultation in difficult cases. However, every potential user or client of telemedicine should keep in mind that several questions of law are involved. METHODS: In this paper, two case studies representative of practical teleneuropathology scenarios are described. The assessment of the legal implications is focused on the personal liability of the teleneuropathologist. RESULTS: The far-reaching personal liability of the teleneuropathologist can lead to situations in which neither the insurance of the hospital nor the private professional liability insurance could be called on to refund possible damages for health impairments of a patient. CONCLUSIONS: In Germany, a contractual exclusion of liability in health matters is not admissible. With regard to the European situation, international agreements such as a European telemedicine law could be conducive to the future border-crossing development of telemedicine though, to date, the legal competencies remain with the single member countries of the European Community.

Brain Neoplasms↗
PubMed2001

Evidence of recurrent atypical meningioma with rhabdoid transformation and expression of pyrogenic cytokines in a child presenting with a marked acute-phase response: case report and review of the literature.

Children presenting with acute systemic illnesses that lack specific clinical or serological defining features may be diagnosed as having a chronic infection, an atypical systemic vasculitis or a connective tissue disease, but often turn out to have occult neoplasias. Cytokines have been implicated in causing many of the systemic effects in such cases. In this study, we describe the case of a 9-year-old boy presenting at an interval of 18 months with a marked acute-phase response due to a recurrent atypical meningioma with rhabdoid transformation of the tentorium cerebelli. Resection of the recurrent tumor was curative. We evaluated in detail the local and systemic production of cytokines released by the primary and the recurrent tumor. Blood and CSF samples were taken pre-, intra-, and postoperatively, and the production of IL-6, IL-1beta, and TNF-alpha was measured by enzyme-linked immunosorbent assays (ELISA). The level of IL-6 in CSF was about 150-fold increased before tumor resection, normalizing postoperatively. On the contrary, the levels of IL-1beta and TNF-alpha in CSF and of IL-6, IL-1beta, and TNF-alpha in serum were pre-, intra-, and postoperatively within normal limits. Cytokine production was also evaluated immunohistochemically, and confirmed strong IL-6 and TNF-alpha expression in the primary and the recurrent tumor, while expression of IL-1beta was lacking. The scattered MHC class II- and leukocyte common antigen (LCA)-expressing inflammatory cells, which were infiltrating exclusively the tumoral stroma, had no detectable cytokine immunoreactivity. We conclude that chronic IL-6 and TNF-alpha production by the tumor cells in this patient was responsible for the severe systemic illness with which he presented.

Acute Disease↗
PubMed2001

Comparison of unilateral and bilateral intrastriatal 6-hydroxydopamine-induced axon terminal lesions: evidence for interhemispheric functional coupling of the two nigrostriatal pathways.

Partial lesions of the nigrostriatal dopamine system can be induced reliably by the intrastriatal injection of 6-hydroxydopamine (6-OHDA) and are considered to be analogous to the early stages of human Parkinson's disease. Previous studies have established a clear correlation between different doses and placements of the 6-OHDA toxin and the degree of neurodegenerative changes and behavioral impairments. In the present study, the influence of the interdependence between the two nigrostriatal systems in both hemispheres on the effects on sensorimotor behavioral performances after terminal 6-OHDA lesions was investigated. The behavioral effects were correlated to the extent of nigral dopamine neuron cell and striatal tyrosine-hydroxylase (TH)-positive fiber loss. Sprague-Dawley rats receiving unilateral intrastriatal 6-OHDA injections (4 x 5 microg) exhibited a 30-70% reduction in striatal TH-positive fiber density along an anterior-posterior gradient, an 80% loss of nigral dopamine neurons and a mild degree of behavioral impairments as revealed by amphetamine-induced rotational asymmetry, and a reduced performance in the stepping and postural balance tests. When the same amount of toxin was injected twice into both hemispheres (2 x 4 x 5 microg), additional behavioral deficits were observed, consisting of a significant, but temporary, weight loss, a stable reduction in general locomotor activity and explorational behavior, and a long-term deficit in skilled forelimb use. This is interesting in light of the morphological findings, in which uni- and bilaterally lesioned animals did not differ significantly in the extent of TH-immunoreactive fiber and dopamine neuron loss within the nigrostriatal system in each lesioned hemisphere. These results indicate that the interdependent regulation of the two nigrostriatal systems may provide some compensatory support for the function and behavioral performance of the lesioned side via the normal unlesioned side, which is lost in animals with bilateral lesions of the nigrostriatal system. Therefore, this model of uni- and bilateral partial lesions of the nigrostriatal system, as characterized in the present study, may foster further exploration of compensatory functional mechanisms active in the early stages of Parkinson's disease and promote development of novel neuroprotective and restorative strategies.

Adrenergic Agents↗
PubMed2001

A Schwann cell-seeded intrinsic framework and its satisfactory biocompatibility for a bioartificial nerve graft.

To optimize the internal environment of a collagen nerve tube, we designed a Schwann cell-seeded intrinsic framework and its biocompatibility was investigated. We fixed 6-0 polyglactin woven filaments (Vicryl) or polydioxanone monofilaments (PDS) on a silicone ring in a net fashion. It was coated with matrigel and then incubated with cultured newborn or adult Schwann cells. Furthermore, we implanted 1.5-cm-long filament-filled collagen tubes in a rat model. Using a live/dead fluorescent assay and electron microscopy, we found that adherent Schwann cells onto filaments remained viable and oriented longitudinally along filaments. The preliminary in vivo study indicated that a mild inflammatory reaction was present around the tube wall. However, nerve regeneration occurred around and between filaments. We concluded that the arrangement of Schwann cell columns onto filaments was achieved, mimicking Bünger bands. It was shown that the biomaterials did not impede nerve regeneration.

Animals↗
PubMed2001

Immunohistochemical characterization of axonal sprouting and reactive tissue changes after long-term implantation of a polyimide sieve electrode to the transected adult rat sciatic nerve.

The development of artificial microstructures suited for interfacing of peripheral nerves is not only relevant for basic neurophysiological research but also for future prosthetic approaches. Aim of the present study was to provide a detailed analysis of axonal sprouting and reactive tissue changes after implantation of a flexible sieve electrode to the proximal stump of the adult rat sciatic nerve. We report here that massive neurite growth after implantation, steadily increasing over a period of 11 months, was observed. Parallel to this increase was the expression of myelin markers like Po, whereas non-myelin-forming Schwann cells did not change. Compared to five weeks post-implantation. where both Schwann-cell phenotypes were intermingled with each other, non-myelin-forming Schwann cells occupied a peripheral position in each microfascicle after 11 months. After an initial increase, hematogenous macrophages were down-regulated in number but maintained close contact with the implant. However, at no time were signs of its degradation observed. It is concluded that the introduced flexible polyimide electrode is suitable for contacting peripheral nerves since it permits substantial neurite growth and offers excellent long-term stability.

Animals↗
PubMed2000

Cellular activity of resident macrophages during Wallerian degeneration.

The resident macrophages have been accepted as an important component of the peripheral nervous system as Schwann cells. To elucidate their role during Wallerian degeneration without interference from extrinsic hematogenous macrophages, we designed a culture system to investigate the behavior of resident macrophages in vitro. A total of 75 adult male Lewis rats were used; 2. 5-cm-length sciatic nerve explants were harvested. There were three groups. In the culture groups, the nerve explants were incubated in Dulbecco's modified Eagle's medium (DMEM) only or in DMEM supplemented with 2 microm forskolin and 10 microg/ml pituitary extract (mitogenic medium for Schwann cells). In vivo predegenerated nerves and normal nerves were used as the positive and negative controls, respectively. The observation periods extended to 3 weeks. Hematoxylin and eosin (H&E) stain was employed to estimate overall cell number in nerve explants. Macrophages were labeled with ED1; S-100 immunostaining was used to evaluate the presence of Schwann cells during Wallerian degeneration. Trichrome stain and toluidine blue stain were used to visualize the fate of myelin. In the culture groups, the number of resident macrophages increased continuously, although there were significantly fewer resident macrophages than hematogenous macrophages after 3 days of Wallerian degeneration (P < 0.01). Morphologically, resident macrophages contained densely small ED1-positive granules within their cytoplasm, even at later stages of observation, whereas hematogenous macrophages contained typical large ED1-positive foam vacuoles characteristic of their mature phagocytic ability. The cellular activity of Schwann cells was well preserved in the mitogenic medium; however, myelin removal was not significantly enhanced as compared with the DMEM groups (P > 0.05). The clearance of myelin debris was shown to be incomplete in culture groups as compared with the complete removal of myelin debris in the in vivo groups. Resident macrophages were actively involved in Wallerian degeneration, but their phagocytic and proliferation ability was limited. Schwann cells played an adjunctive role during the removal of myelin debris.

Animals↗
PubMed2000

[Oculopharyngeal muscle dystrophy. Genetic diagnosis in a family in Germany].

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant myopathy with almost benign course. Its clinical features include ptosis, dysphagia, and proximal limb muscle weakness. The OPMD gene has been localized to chromosome 14, causing expansions of GCG triplets. Scattered families with OPMD belonging to different ethnic groups have been described worldwide. We describe one from northern Germany. In genetic diagnosis, expansion of GCG triplets to 11 was observed, which proved that myopathy, which is very rare in Germany.

Blepharoptosis↗
PubMed2000

Comparison of clinical performance, histology and single-fiber contractility in free neurovascular muscle flaps.

The aim of this study was to obtain further insights about muscle regeneration processes in free neurovascular flaps. In cases of insufficient functional return of muscle strength, several factors, such as diminished axonal ingrowth, fatty degeneration, or connective tissue proliferation are discussed. In the study, free neurovascular latissimus dorsi (LD) flaps were examined after a regeneration period of 2 to 6 years. Clinical function (M1 to M4) and histopathologic characteristics of the muscle grafts were correlated. The rare instances of secondary procedures, such as tenolysis or scar correction, were used for biopsies of the muscle graft. Free neurovascular LD flaps were examined after a regeneration period between 2 and 6 years. The grafted LD was compared to normal, healthy LD muscle. Normal LD muscle showed a typical homogeneous pattern of types 1 and 2 fibers in a ratio of almost 1:1. No significant differences concerning fiber distribution and fiber diameters in three anatomic areas of the LD (proximal, medial, caudal) could be detected. After regeneration, the authors found the following: type grouping of muscle fiber types, fiber splitting, and groups of hypertrophic and atrophic fibers. Most of the muscle fibers were not reinnervated by axons and were atrophic or degenerated. The essential proliferation of connective and fatty tissue was absent. Normal and hypertrophic fibers were found mainly in the muscle grafts with good clinical results. In muscle grafts with good contraction force (M4), 46 percent of reinnervated muscle fibers were found; M3 contractility was correlated with 31 percent of reinnervated muscle fibers; M2 with 24 percent; and M1 with 21 percent of reinnervated fibers. The force of a free muscle graft seems to depend mainly on the quality of nerve regeneration. Characteristics of the muscle fiber itself were not examined extensively, because the single-fiber contractility of the regenerated fibers was similar to the contractility of normal, healthy fibers.

Adult↗
PubMed2000

Disruption of intracerebral progression of C6 rat glioblastoma by in vivo treatment with anti-CD44 monoclonal antibody.

OBJECT: Glioblastoma multiforme (GBM) invasiveness is a complex process that involves recognition and attachment of GBM cells to particular extracellular matrix (ECM) molecules before migrating into proteolytically modified matrix and inducing angiogenesis. The CD44 molecule, which is a transmembrane adhesion molecule found on a wide variety of cells including GBM, has been suggested as the principal mediator of migration and invasion. The aim of the present study was to demonstrate whether an antibody specific to the standard form of CD44 (CD44s, 85-90 kD) might prevent invasion and thus disrupt progression of C6 GBM in vivo. METHODS: Immunostaining demonstrated homogeneous expression of CD44s on the surface of C6 GBM cells and tumors. Flow cytometric analysis demonstrated binding saturation of anti-CD44s monoclonal antibody (mAb) to the receptor at 1 microg/5 x 10(5) cells. Blocking of CD44s in vitro resulted in a dose-dependent progressive (up to 94+/-2.7%; mean +/- standard deviation [SD]) detachment of C6 cells from ECM-coated culture. Blocking of CD44s in vivo resulted in significantly reduced C6 brain tumors (3.6+/-0.4% [SD])--measured as the quotient: tumor surface (mm2)/brain surface (mm2) x 100--compared with untreated (19.9+/-0.9%) or sham-treated (19.2+/-1.1 to 19.3+/-2.5% [SD]) rats. Disruption of C6 GBM progression correlated with an improved food intake; treated rats were significantly less cachectic (166.6+/-16.4 g [SD]) than those that were untreated (83+/-2.7 g [SD]) or sham-treated (83.4+/-1.1 to 83+/-2.2 g [SD]) rats. CONCLUSIONS: The authors conclude that CD44s-targeted treatment with specific mAb may represent an effective means for preventing progression of highly invasive GBMs.

Animals↗
PubMed2000

Telemedicine of the future: teleneuropathology.

The chief relevance of telemedicine lies in its capability to link medical practitioners and remote hospitals to larger or specialized facilities in a very fast electronic manner. This may become even more important due to current increase in subspecialization and demand for more precise diagnosis and consultation in difficult cases. A network attaching small clinics or laboratories to larger and more specialized units, and to highly specialized referral centers may improve the professional standard of health care services and education. For a wider use, a technological standardization will be required, since the existence of several types of computer and numerous image manipulation programs, have resulted in a proliferation of file formats. However, every potential user or client of telemedicine should keep in mind, that standardization also includes legal and ethical issues such as patient confidentiality and malpractice avoidance. The adoption of workable guidelines and protocols is required. Telepathology in general and teleneuropathology in particular is the practice of pathology at a distance, viewing digitized images of histological slides on a video monitor rather than directly through a light microscope. For the transmission of the digitized images from a telemicroscope to the remote diagnostic video monitor, different technologies such as ordinary telephone lines, broadband telecommunications channels, and the Internet can be used. The transmitted images may serve for primary neuropathological diagnosis, teleconsultation, quality assurance, proficiency testing, and distance learning. Static-imaging and dynamic-imaging are the two major competing technologies of telemicroscopy. Static-imaging systems appear to have levels of diagnostic accuracy which are not satisfactory for diagnostic neuropathology. On the contrary, high levels of diagnostic accuracy can be achieved using dynamic-imaging systems with the transmission of live video images in real time and by using a robotized telemicroscope with the possibility to examine the entire histological specimen under control of the remote teleneuropathologist.

Diagnostic Techniques, Neurological↗
PubMed2000

Multimedia-based courseware in the Virtual Learning Center at the Hannover Medical School.

The commercial use of the World Wide Web causes an extensive change in information technology. Web browser are becoming the universal front-end for all kinds of client-server applications. The possibilities of telematics offer a base for multimedia applications, for instance telelearning. Learning is not limited by geography and does not cause pressure of time by the user. The development of such multimedia information and communication systems demands cooperative working teams of authors, who are able to master several areas of medical knowledge as well as the presentation of these using different multimedia facilities. A very important part of graphic design in the context of multimedia applications is the creation and interactive use of images (still, moving). The growth and the complexity of medical knowledge as well as the need for continuous, fast, and economically feasible maintenance impose requirements on the media used for medical education and training. Web-based courseware in the Virtual Learning Center at the Hannover Medical School is an innovative education resource for medical students and professionals.

Computer-Assisted Instruction↗
PubMed1999

Expression of granulocyte colony-stimulating factor in recurrent glial tumors is inversely correlated with tumor progression.

We have previously reported that in vivo-expression of granulocyte colony-stimulating factor (G-CSF) is a characteristic feature of reactive and neoplastic astrocytes. The aim of the present study was to analyze the expression of G-CSF protein in primary and recurrent astroglial, oligodendroglial and mixed glial-differentiated tumors. G-CSF expression was present in all GFAP-positive tumors excepting glioblastomas. G-CSF expression was significantly reduced in recurrent tumors more dedifferentiated than their primary counterparts. G-CSF expression was absent in all GFAP-negative tumors such as oligodendrogliomas. Our results demonstrate that G-CSF is a highly sensitive differentiation marker of neoplastic astrocytes, which is lost during tumor progression.

Adolescent↗
PubMed1999

Viability of cultured nerve grafts: An assessment of proliferation of Schwann cells and fibroblasts.

Previous studies demonstrated that the viability of nerve grafts had a positive effect on nerve regeneration, while the cold storage of nerve grafts obtained few viable cells at the later stage. The purpose of this study was to examine the cellular activities of Schwann cells and fibroblasts in cultured nerve grafts prior to transplantation. 2.5-cm long sciatic nerve grafts were harvested from 75 male Lewis rats. Two different media were utilized to culture the nerve grafts up to 3 weeks: Dulbecco's modified eagle medium (DMEM) only or DMEM supplemented with 2 microM forskolin and 10 microg/ml pituitary exact (mitogen medium for Schwann cells). In vivo predegenerated and normal nerve grafts were used as positive and negative controls, respectively. We employed a 5-bromo-2'-deoxyuridine (BrdU) incorporation method to evaluate the proliferating cells in the cultured nerve grafts. S-100 and vimentin immunostaining were used to estimate the presence of Schwann cells and fibroblasts in all nerve grafts at different intervals. The results showed that the proliferating cells increased progressively under culture conditions. The proliferating cells distributed evenly in small fascicles (average diameter 251 +/- 71.5 microm), whereas they appeared mainly in the margin of large fascicles (average diameter 624 +/- 87.3 microm). The mitogen medium stimulated Schwann cell multiplication more significantly in comparison with DMEM after 3 days of culture (P < 0.01), however, there were fewer fibroblasts present in the mitogen medium than in DMEM after 2 days of culture (P < 0.01). It is suggested that the viability of nerve grafts can be preserved under culture conditions. Furthermore, the cellular activity of the Schwann cells and fibroblasts in nerve grafts can be manipulated in in vitro Wallerian degeneration.

Animals↗
PubMed1999

CD44s-targeted treatment with monoclonal antibody blocks intracerebral invasion and growth of 9L gliosarcoma.

Glioma invasiveness is a complex process involving recognition and attachment of tumor cells to particular extracellular matrix (ECM) molecules prior to migrating into proteolytically modified matrix and inducing angiogenesis. CD44 is a group of transmembrane adhesion molecules found on a wide variety of cells including gliomas that has been suggested as the principal mediator of migration/invasion. The aim of the present study was to demonstrate whether antibody specific for the standard form of CD44 (CD44s, 85-90 kDa) might prevent invasion, thus blocking growth of the 9L gliosarcoma in vivo. High expression of CD44s on the surface of 9L cells and brain tumors was demonstrated by immunochemistry. Fluorescence-activated cell sorting (FACS) demonstrated binding saturation of anti-CD44s monoclonal antibody (mAb) to the receptor at 1 microg/5 x 10(5) cells. Blocking of CD44s in vitro resulted in a dose-dependent progressive, up to 95%+/-2.5% detachment of 9L cells from ECM-coated culture surfaces. Blocking of CD44s in vivo resulted in significantly reduced 9L brain tumors (2.5%+/-0.4%)--measured as the quotient: tumor surface (mm2)/brain surface (mm2) x 100--as compared to untreated (16.1%+/-2.2%) or sham-treated rats (16%+/-3.7% to 16.1%+/-3%). We conclude that CD44s-targeted treatment with specific mAb may be an effective means for preventing glioma progression.

Animals↗
PubMed1999

Induction of heat shock protein 70 in the rat brain following intracisternal infusion of autologous blood: evaluation of acute neuronal damage.

OBJECT: Investigation into a potential treatment for the acute period following onset of spontaneous subarachnoid hemorrhage (SAH) is hampered by the lack of a standardized experimental model. For that purpose the authors elaborated on a small-animal model in which computer-controlled intracisternal blood infusion is used and investigated whether this model can reliably reproduce acute neuronal injury after SAH. METHODS: Whole autologous blood (blood-infused group) or isotonic saline (control group) was infused into the cisterna magna or olfactory cistern of rats. The infusions decreased exponentially during a 5-minute period. Throughout the infusion period, intracranial pressure (ICP) was monitored. Neuronal injury was quantified by observing tissue immunoreactivity to a 70-kD heat shock protein (HSP70) and comparing this with the tissue's reaction to hematoxylin and eosin staining. On Days 1, 3, and 5, the CA1, CA3, and dentate gyrus regions of the hippocampus were analyzed, respectively. During saline infusion ICP increased within seconds beyond 80 mm Hg and afterward decreased in accordance with the infusion rate. During the infusion of blood, the same initial pressure peak was found, but the ICP remained increased beyond this pressure level throughout the 5-minute infusion period. The HSP70 immunoreactivity in the saline-infused group was found only on Day 1 in the CA1 region and the dentate gyrus, but not in the CA3. After injection of whole blood, there was HSP70-positive staining in the CA1, CA3, and dentate gyrus regions throughout the observation period. CONCLUSIONS: The controlled cisternal infusion of blood caused neuronal injury that resembled that of previous experimental models that produce SAH by rupture of intracranial vessels with endovascular techniques. Unlike those experiments, the intracisternal infusion technique presented by the authors provides more standardized bleeding with regard to ICP, the volume of subarachnoid blood, and the extent of acute cellular injury.

Animals↗