Biomedical subjects
K Dietzmann
Publications and source records attributed to K Dietzmann.
Mitochondrial tRNA(Cys) mutation A5823G in a patient with motor neuron disease and temporal lobe epilepsy.
We discovered a new homoplasmic mutation in the mitochondrial cysteine tRNA of a 60-year-old Caucasian male suffering from asymmetrical pure lower motor neuron disease (MND) and temporal lobe epilepsy (TLE). Furthermore, titrations with Amytal, an inhibitor of NADH:CoQ oxidoreductase, revealed mild mitochondrial dysfunction in skeletal muscle tissue, which was described in patients with MND in an earlier report. The mutation was undetectable in 155 Caucasian controls of both sexes, in 40 MND patients and in 13 individuals suffering from TLE. It was, however, detected in a heteroplasmic state in the patient's mother, who did not suffer from a neurological disorder. Since this rare mutation affected a nonconserved base position and was not observed in MND or TLE materials, its relation to disease remains unclear.
Altered dendritic maturation and loss of GABA immunoreactivity of hippocampal neurons after prenatal exposure to chloroquine.
The aim of the study was to analyze the intrauterine and postpartal effects of Chloroquine on the dendritic maturation in the hippocampus and on the expression of GABA within hippocampal interneurons of the stratum moleculare. Fifty-nine brains of rat fetus on day 22 of gestation and 37 brains from rats from postnatal day P7 were examined. We found changes in the cytoarchitecture of hippocampal CA3 neurons on P7 day. Chloroquine treatment resulted in a significant increase of the length of the apical shafts, apical dendrites and basal dendrites of the CA3 neurons (p < 0.05) under doses comparable to serum levels reached during long-term therapy. Furthermore, an early reduction of GABA-expressing interneurons of the hippocampal striatum moleculare was observed.
Expression of matrix metalloproteinases in a series of 12 meningiomas.
The expression of metalloproteinases was evaluated in a series of 12 meningiomas of various histological subtypes including 3 meningotheliomatous, 3 fibroblastic, 4 transitional and one psammomatous meningioma (WHO grade I) as well as one anaplastic meningioma (WHO grade III). No gelatinolytic activity could be detected in all tumor samples pointing towards no or very low activity of both MMP-2 and MMP-9. At least MMP-2 mRNA could be found in 10 out of 12 tumor samples by the reverse transcription PCR method (RT-PCR) followed by electrophoresis on silver-stained polyacrylamide gels, which allows the detection even of small traces of a specific mRNA. The PCR products were identified as MMP-2 sequences without introns (mRNA-derived) by direct sequencing, thereby demonstrating a low transcriptional activity of the gene. The translation of these mRNAs, however, did not result in amounts of protein detectable by immunohistochemistry or Western blotting. Therefore, neither MMP-2 nor MMP-9 should play a major role for tumor growth within dura mater or bone structures or for brain infiltration in our tumor series. Therefore, other mechanisms must be responsible for extracellular matrix degradation at least in a fraction of meningiomas.
Short incubation with 2-methoxyestradiol kills malignant glioma cells independent of death receptor 5 upregulation.
We investigated the effects of 2-methoxyestradiol (2-ME), a promising new antitumor agent, on viable cell number and nuclear morphology of malignant glioma cells (three human and one rat glioma cell lines) and analyzed the controversial role of death recepor 5 (DR5) upregulation in 2-ME induced apoptosis. Microtiter-tetrazolium (MTT) assays showed a significant reduction of viable cells after incubation with 2 microM and 20 microM 2-ME for 48 and 72 hours in all cultures. In the 20 microM concentration, there were even significant effects in the majority of shorter incubation periods. Hoechst 33258 stains showed a substantial amount of cells with nuclear fragmentation indicating a late stage of apoptosis after 20 microM 2-ME treatments of 24 hours and more. The role of the DR5-mediated extrinsic apoptotic pathway was further studied in the three human glioma cell lines; 50 ng/ml of the DR5 ligand TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) and 2 microM 2-ME showed no synergism, as determined by MTT assays. Real-time PCR revealed no significantly increased amount of DR5 mRNA, suggesting that receptor upregulation does not play a major role for 2-ME-induced apoptosis in glioma cells, in contrast to data for a breast cancer cell line in the literature.
[Studies of the monoamine blood-brain barrier mechanism by means of the Falck-Hillarp and glyoxalate methods. Comparative studies].
Explore the source record for details and available documents.
Dendritic spines and immunoreactivity of synaptophysin in the frontal cortex of humans with infantile brain damage. A correlative study.
Some neurodegenerative disorders of adults involving mental retardation are associated with reduction of dendritic spines and number of synapses. A study was performed to prove the changes in the density of dendritic spines and synaptophysin-immunoreactive granules in the frontal cortex of cases with infantile brain damage and a possible correlation between them. Specimen from cortex of children and adolescents with severe mental retardation, aged 3 to 24 years and a group of non-psychiatric age-matched controls were processed according to the Golgi-Kopsch method. Density of dendritic spines on the apical dendrites of layer V pyramidal neurons (Brodman area 10) was analysed in correlation to the density of synaptophysin-reactive granules (counts/microns 2) in the same region. Both density of spines and number of immunoreactive granules were reduced in brains with infantile damages, but there was no correlation between spine density and the number of immunoreactive granules against synaptophysin.
Mdr1 mRNA expression differs between grade III astrocytomas and glioblastomas.
104 N2-frozen samples from 33 astrocytic tumors previously untreated with cytotoxic drugs have been analyzed for the expression of p-glycoprotein transcripts (mdrl) by RT-PCR using beta2-microglobulin as an internal control. A remarkable variation was observed even within a single tumor in 50% of the cases. Nevertheless, a difference became visible between the groups of anaplastic astrocytomas and glioblastomas. While 78% of the grade 3 astrocytomas contained at least a minimum of 1 sample with a very low mdr1 expression, this was the case only in 23% of the glioblastomas. This supports an earlier observation revealing a positive correlation between tumor grading and the tumor cell fraction stained with the monoclonal antibody JSB1. On the other hand, no major differences were found between the histological groups when the samples with the highest mdr1 expression were selected to represent the individual tumors. Those samples are less informative. They might be derived from tumor regions in which capillaries deliver a larger fraction of the total mRNA pool. No induction of mdr1 was observed in some early astrocytoma or glioblastoma cell cultures even after administration of high concentrations of the drugs ACNU and VM26, often used in glioma therapy.
Stiff-man syndrome: possible autoimmune etiology targeted against GABA-ergic cells.
We report the case of a female patient, who died at the age of 66 years. Besides an insulin-dependent diabetes mellitus (IDDM) she had developed the clinical symptoms of stiff-man-syndrome (SMS) and harbored autoantibodies against glutamate-decarboxylase (GAD) in blood and liquor. GAD catalyzes the biosynthesis of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). The autopsy revealed typical alterations observed in diabetes mellitus including an incomplete fibrosis of pancreatic Langerhans islets. A decrease of GABA-ergic cells in the cerebellar cortex was observed, and a size reduction of Renshaw cells in the spinal cord. Furthermore, a dilution series of a polyclonal GABA antibody delivered a reduced immunofluorescence in the cerebellum. In skeletal muscle a neurogenic atrophy was observed. As described in literature, the clinical symptoms decayed following clonazepam administration. We suggest that this case including GAD autoantibodies, dramatic loss of GAD-expressing pancreatic cells, and loss or atrophy of GABA secretory neurons, supports the hypothesis that SMS may be an autoimmune disease directed against GABA-ergic cells. Furthermore, we suggest a neuronal hypersensitivity at the spinal cord level caused by the atrophic Renshaw cells.
MGMT- and P450 3A-inhibitors do not sensitize glioblastoma cell cultures against nitrosoureas.
UNLABELLED: AIM, MATERIAL AND METHODS: Using RT-PCR and immunohistochemistry the expression of cytochrome P450 was evaluated in a series of 22 glioblastomas and 4 anaplastic astrocytomas (WHO grade III). Since rat liver P450 can catalyze the denitrosation of the nitrosourea compound BCNU in vitro, cell culture experiments were performed to test a possible sensitizing effect of P450 3A inhibitors (tiamulin and ketoconazole) in BCNU treatment of glial tumor cells. O6-benzylguanine (BG), an inhibitor of the DNA repair enzyme O6-methylguanine-DNA-methyltransferase (MGMT), was used in parallel experiments, since MGMT is discussed as a main mechanism in nitrosourea resistance. RESULTS: RT-PCR reactions with primers designed according to the sequences for CYP1A1 and CYP2E1 were always positive, while those for CYP1A2 and CYP2D6 were negative. The strongest PCR products were detected with CYP3A primers, but CYP3A expression was heterogeneous within the tumor samples. Antibodies to human liver CYP3A4 stained a subfraction of tumor cells (18% of the cells in glioblastomas and 14% in grade III astrocytomas) and to some extend neurons in normal brain areas, while astrocytes were negative. For cell culture experiments with P450 3A and MGMT inhibitors, early passages of 3 glioblastomas, a late passage of an immortalized cell line derived from a reoccurring glioblastoma, and the human glioblastoma line LN405 were used. The sensitivity of the tumor cells for both nitrosourea compounds was very low, when low concentrations were applied (comparable to the achievable blood concentrations in glioma patients). Strong effects did only occur when the concentrations were raised 9-fold or 27-fold. CONCLUSION: In no case could a significant sensitizing effect of P450 3A- and MGMT inhibitors be demonstrated.