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Biomedical subjects

D Schmidt

Publications and source records attributed to D Schmidt.

At least 757 records · Page 42Linked to original sources
PubMedDate not supplied

Wide-spread myelinated nerve fibers of the optic disc: do they influence the development of myopia?

PURPOSE: To find correlations between the extent of myelinated nerve fibers with refraction anomalies. METHOD: Searching for myelinated nerve fibers in the slide collection of the University Eye Hospital Freiburg we found 13 patients. We distinguished between eyes with wide-spread myelinated nerve fibers located on and around the optic disc which extended to the midperiphery of the retina (6 patients; Group A) and eyes with circumscribed myelinated nerve fibers, localized merely around the optic disc (7 patients, Group B). In Group A myelinated nerve fibers spared the macula area, but were localized very close to the macula. Color fundus photographs were taken by the Zeiss Fundus camera SK50 (30 degrees and 50 degrees picture size) and by the Olympus Fundus camera GRC-W (same picture size). RESULTS: The myelinated nerve fibers were found to be unilateral in all 13 patients. In all 6 patients of Group A, a strabismus was present. The affected eye had a severe amblyopia and a unilateral myopia (-5.75 to -25.0 D). The nonaffected fellow eye showed a normal visual acuity with no or only a slight refractive error. In the 7 patients of the Group B, no strabismus was present and a normal or a slightly decreased visual acuity of the affected eye was found. No distinct refractive error was present in the affected and non-affected eyes of this group. CONCLUSIONS: Myopia only occurred in eyes with wide-spread myelinated nerve fibers but not in eyes with circumscribed myelinated nerve fibers. We assume that myelinated nerve fibers, if wide-spread, cause myopia.

Adolescent↗
PubMedDate not supplied

Myofibroblast as a major cellular constituent of villous stroma in human placenta.

The human placenta requires contractile structures to generate energy for blood propulsion. Smooth muscle cells are not present in significant numbers in the human placenta while fibroblasts lack effective contractile properties. This study provides the following evidence that the stromal cells of the placental villi, cotyledonary septa and perivascular connective tissue are myofibroblasts. (I) Stromal cells are strongly positive for dipeptidylpeptidase IV (EC 3.4.14.5) which occurs exclusively in myofibroblasts as far as connective tissue cells are concerned. (2) The isoenzyme pattern of the placental dipeptidylpeptidase IV is identical to that of myofibroblasts in palmar fibromatosis on isoelectric focusing. (3) Antibodies raised against isolated placental dipeptidylpeptidase IV cross-react with dipeptidylpeptidase IV from myofibroblasts of palmar fibromatosis as shown by immunohistochemistry. (4) On electron microscopic examination, stromal cells present all the ultrastructural features of myofibroblasts. It is concluded that, except for the vascular component and a negligible number of Hofbauer cells, myofibroblasts make up nearly all the cellular constituents of human placental villous stroma.

Dipeptidyl Peptidase 4↗
PubMedDate not supplied

Imaging and neural modelling in episodic and working memory processes.

Neuroimaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have revealed the involvement of distributed brain regions in memory processes mainly by the use of subtraction strategy based data analyses. Covariance analysis based data analysis strategies have been introduced more recently which allow functional interactions between brain regions of a neuronal network to be assessed. This contribution focuses on studies aiming to (1) establish the functional topography of episodic and working memory processes in young and old normal volunteers, (2) to assess functional interactions between modules of networks of brain regions by means of covariance based analyses and systems level modelling, (3) to characterise the temporal dynamics by the use of magnetoencephalography (MEG) and (4) to relate neuroimaging data to the underpinning neural networks. Male normal young and old volunteers without neurological or psychiatric illness participated in neuroimaging studies (PET, fMRI, MEG). Studies were approved by the ethical committee and federal authorities. Our results in young volunteers show distributed brain areas that are involved in memory processes (episodic and working memory) and show much of an overlap with respect to the network components. Systems level modelling analyses support the hypothesis of bihemispheric, asymmetric networks subserving memory processes and revealed both similarities in general and differences in the interactions between brain regions during episodic encoding and retrieval as well as working memory. Changes in memory function with ageing are evident from functional topographic studies in old volunteers activating more brain regions as compared to young volunteers. There are more and stronger influences of prefrontal regions in elderly volunteers comparing the functional models between old and young subjects. We discuss the way that the systems level models of the PET and fMRI results have implications for the underlying neural network functioning of the brain. This is done by developing simplifying assumptions, which lead from the equations describing the activities of the coupled neural modules to the systems level model equations. The resulting implications for the neural interactions are then discussed, in terms of a set of synaptically coupled neural modules. Finally, we consider how a similar analysis could be extended from the spatial to the temporal domain thus including the EEG and MEG results. The implication of preliminary MEG results presented here for the temporality arising in the interaction between the coupled neural modules in a working memory paradigm is discussed in terms of the previously developed neural network models arising from the PET and fMRI data.

Adult↗
PubMedDate not supplied

Transformation of NIH 3T3 cells by a human c-sis cDNA clone.

The mechanism of leukaemogenic transformation by human T-cell leukaemia/lymphoma virus (HTLV), a retrovirus implicated in the aetiology of certain adult T-cell leukaemias and lymphomas, is unknown but is conceivably associated with the expression of the cellular analogues of retroviral oncogenes. The HUT-102 cell line, derived from a cutaneous T-cell lymphoma and infected with HTLV, expresses several cellular oncogenes. It is unusual among haemopoietic cell lines in that one of these is c-sis, the gene from which the oncogene v-sis of the simian sarcoma virus was derived, and perhaps the gene for platelet-derived growth factor (PDGF). To explore the possible role of c-sis expression in HTLV-induced disease, we have obtained cDNA clones of c-sis from HUT-102 cells. Here we describe two such clones and report that one of them transforms NIH-3T3 cells. This is the first example of transformation of NIH-3T3 cells by a human onc gene other than c-ras or Blym, as well as the first demonstration of transformation by a human cDNA clone.

Animals↗
PubMedDate not supplied

[Diagnostic value of imaging procedures in nephroblastoma before preoperative chemotherapy: initial results].

According to the international SIOP 9 study preoperative chemotherapy for patients between 6 months and 16 years old is a major component of the therapeutic management of Wilms' tumour. Prior to treatment, the diagnosis is established by diagnostic imaging alone, without biopsy. This study was therefore undertaken to verify the accuracy of diagnostic imaging in the German GPO study group. Between July 1988 and November 1990, 156 patients with known histology were registered in the study centre. Of these patients, 67% (105/156) received preoperative chemotherapy. The diagnosis was initially established by US, TVP and CT, and in some cases MRT without prior biopsy. Of these preoperatively treated patients, 92.4% (97/105) had Wilms' tumour or one of its variants. Five patients had a different malignant tumour. Three cases, i.e. 2.8% of the preoperatively treated patients or 1.9% of all registered patients with known histology, had benign tumours of the kidney. Morphologically, the Wilms' tumour was revealed by a characteristic inhomogeneity in sonography and the CT scan. The inhomogeneity in the CT scan increased following injection of contrast medium. Intratumoral bleeding and cystic areas were observed frequently in the native scan. Calcifications were seen in 5% of the cases. The predictive value of pretherapeutic diagnostic imaging was good enough to justify instituting chemotherapy without diagnostic biopsy. It is still difficult in diagnostic imaging to differentiate the very rare benign cystic nephroma from malignant nephroblastoma. Intravenous pyelography proved to be the best method for distinguishing extrarenal from renal tumours.

Child↗
PubMedDate not supplied

The applicability of immunohistochemistry in the diagnosis and differential diagnosis of malignant soft tissue tumors. A reevaluation based on the material of the Kiel Pediatric Tumor Registry.

The diagnosis and differential diagnosis of malignant soft tissue tumors not infrequently poses great difficulties, especially in those cases which lack any feature of differentiation by conventional light microscopy. These difficulties have been partially resolved through the application of ultrastructural investigations. Recently considerable progress has been achieved using immunohistochemistry. At the Kiel Pediatric Tumor Registry we were able to reduce the percentage of unclassified soft tissue sarcomas from 17.6% in 1982 to 4.5% in 1989. Particularly useful were antibodies against the different types of intermediate filaments, muscle-specific actin, myoglobin, and the neural markers neuron-specific enolase and protein S-100. In contrast to the expected immunophenotype rhabdomyosarcomas, malignant peripheral neuroectodermal tumors and malignant schwannomas showed expression of cytokeratins. Moreover, in many cases rhabdomyosarcomas and synovial sarcomas expressed neural markers. Ewing's sarcoma and malignant peripheral neuroectodermal tumor are histogenetically related, but differ in grade of neural differentiation. In all soft tissue sarcomas immunohistochemistry is very useful to obtain information on the cellular heterogeneity. Despite the great achievements not every soft tissue sarcoma can be diagnosed with certainty. There will always be a baseline of unclassified cases due to problems which are not caused by the tumor itself but rather by diagnostic circumstances.

Adolescent↗
PubMedDate not supplied

[Immunopathology of brain tumors].

The various classifications of brain tumors are characterized by a rather disturbing diversity of tumor designations. This diversity results from the heterogeneity of human brain tumors, but also from the lack of knowledge about the histogenesis of many of these tumors. The histogenesis of some of the different types of tumor could be resolved by the application of electron microscopical studies. New aspects are gained from immunohistochemical investigations using mono- and polyclonal antibodies against intermediate filaments (GFAP, vimentin, cytokeratins), neuron-specific enolase (NSE), protein S-100, carcinoembryonic antigen (CEA), myelin-associated glycoprotein (Leu 7), synaptophysin and nuclear proliferating antigen (Ki-67). The present paper gives a survey on how immunohistochemistry can be advantageously used in the diagnosis of brain tumors.

Antigens, Differentiation, T-Lymphocyte↗
PubMedDate not supplied

[Soft tissue neoplasms--progress and limits of pathologico-anatomic diagnosis].

Current classifications of soft tissue tumors are based principally on the histogenetic type of the tumor thereby abandoning descriptive terms such as spindle cell sarcoma, round cell sarcoma etc. Insight into the histogenesis of a number of soft tissue tumor types has been gained from electron microscopical studies. In addition, these studies provided valuable data to establish certain neoplasms as tumor entities. Thus, the histogenesis of clear cell sarcoma of tendons and aponeuroses has been traced to melanocytes, and it is now universally accepted that biphasic synovial sarcoma consists of epithelial and fibroblastic components. Despite these advances, about 10% of all soft tissue sarcomas remain unclassified when light- and electron microscopy are used in combination. Further improvement in the classification of soft tissue malignancies has been achieved applying immuno-histological techniques. As in other types of malignant tumors mono- and polyclonal antibodies against intermediate filament proteins are especially useful. Other "markers" include protein S-100, neuronspecific enolase (NSE), epithelial membrane antigen (EMA) and panleucocyte antigen (LCA). Regular use of all these markers enabled us to reduce the percentage of unclassified soft tissue sarcomas from 17.6% in the "pre-immune era" to 6.1%.

Antibodies, Monoclonal↗
PubMedDate not supplied

[Rhabdomyosarcoma: morphology and cellular differentiation].

544 malignant soft tissue tumors have been collected at the Pediatric Tumor Registry in Kiel including 300 cases of rhabdomyosarcoma (55%). In 237 of the 300 cases the diagnosis is certain. Liposarcoma and malignant fibrous histiocytoma which are typical tumors of adult age are rare in our material. Among rhabdomyosarcomas embryonal rhabdomyosarcoma (eRMS) clearly predominates accounting for almost 72% of all rhabdomyosarcomas. Differentiation of tumor cells in eRMS may vary considerably. Therefore, three groups of eRMS were distinguished and analyzed for clinico-pathologic features: 1. Primitive eRMS with less than 10 rhabdomyoblasts. 2. Intermediate eRMS with 10-50% rhabdomyoblasts. 3. Well differentiated eRMS with greater than 50% rhabdomyoblasts. By immunohistochemistry, vimentin positive cells were found in all three groups. The number of desmin positive cells depended upon the grade of differentiation. Thus, there were more desmin positive cells in well differentiated eRMS. Primitive and well differentiated eRMS were predominantly located in the head and neck area, intermediate eRMS in the abdomen. Primitive eRMS were noted in higher stages than tumors of the other two groups. Response to chemotherapy as evaluated in the 7th week of treatment was better in well differentiated eRMS. Moreover, patients of this group achieved more often complete remission. It is concluded from the present study that differentiation in eRMS may have an influence on the clinical presentation and clinical course of the disease. Therefore, this question should be investigated in more detail in a larger prospective study.

Abdominal Neoplasms↗