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Biomedical subjects

T Klockgether

Publications and source records attributed to T Klockgether.

At least 73 records · Page 4Linked to original sources
PubMed2000

Neurologic complications in immune-mediated heparin-induced thrombocytopenia.

OBJECTIVE: To evaluate neurologic complications in patients with immune-mediated heparin-induced thrombocytopenia (HIT) with respect to incidence, clinical characteristics, outcome, and therapy. METHODS: One hundred and twenty consecutive patients with immune-mediated HIT were recruited over a period of 11 years and studied retrospectively for the occurrence of neurologic complications. Diagnosis of HIT was based on established clinical criteria and confirmed by detection of heparin-induced antibodies using functional and immunologic tests. RESULTS: Eleven of the 120 patients (9.2%) presented with neurologic complications; 7 suffered from ischemic cerebrovascular events, 3 from cerebral venous thrombosis, and 1 had a transient confusional state during high-dose heparin administration. Primary intracerebral hemorrhage was not observed. The relative mortality was much higher (Chi-square test, p < 0.01) in HIT patients with neurologic complications (55%) as compared to patients without neurologic complications (11%). The mean platelet count nadir in neurologic patients was 38 +/- 25 x 10(9)/l on average, and was lower in patients with fatal outcome compared to those who survived (21 +/- 13 x 10(9)/l versus 58 +/- 21 x 10(9)/l; p < 0.05, Wilcoxon test). In three patients neurologic complications preceded thrombocytopenia. There was a high coincidence of HIT-associated neurologic complications with other HIT-associated arterial or venous thrombotic manifestations. CONCLUSION: Neurologic complications in HIT are relatively rare, but associated with a high comorbidity and mortality. HIT-associated neurologic complications include cerebrovascular ischemia and cerebral venous thrombosis. They may occur at a normal platelet count.

Adult↗
PubMed2000

Altered expression of calcium- and apoptosis-regulating proteins in multiple system atrophy Purkinje cells.

The expression patterns of the calcium binding proteins calbindin and parvalbumin and of the apoptosis modulating proteins Bcl-2, Bax, and Bcl-x were studied in the cerebellum of patients with multiple system atrophy (MSA). Calbindin and parvalbumin immunoreactivity was markedly decreased in MSA Purkinje cells whereas Bax and Bcl-x protein expression was increased. Bcl-2 expression was restricted to a subpopulation of granule neurons, but no decrease of Bcl-2 was evident in MSA. Additional DNA end-labeling (ISEL) studies revealed only one possible apoptotic Purkinje cell nucleus, but nuclei in the cerebellar white matter, probably oligodendrocytes, in the cerebellum of patients with MSA. The present results suggest that a diminished calcium binding capacity of MSA Purkinje cells might lead to a change in the regulation of proteins of the bcl-2 family that could favor the pathologic initiation of apoptosis.

Apoptosis↗
PubMed2000

The molecular biology of the autosomal-dominant cerebellar ataxias.

Autosomal-dominant cerebellar ataxias (ADCA) may present as progressive or paroxysmal disorders. While the progressive ataxias have been named spinocerebellar ataxias (SCA), the paroxysmal disorders are designated episodic ataxias (EA). Until now, three different mutational mechanisms resulting in distinctive pathogenesis have been identified. The first type of mutation present in SCA1, SCA2, SCA3, and SCA7 is an expanded CAG repeat in genes of unknown function that are translated into proteins with expanded polyglutamine tracts. A common ultrastructural feature of these disorders is the formation of neuronal intranuclear inclusions (NII) harboring the expanded disease proteins and a variety of other proteins. The pathogenic role of these inclusions has yet to be clarified. A second group of disorders is the result of mutations in genes that code for ion channels. In EA-1, a disorder characterized by episodes of ataxia provoked by movement and startle, missense mutations in a potassium channel gene, KCNA1, have been found. Patients with EA-2, another form of paroxysmal ataxia, carry nonsense mutations of the gene encoding the alpha1A voltage-dependent calcium channel subunit, CACNA1A, that are predicted to result in truncated channel proteins. In SCA6, a progressive ataxia, an expanded CAG repeat in the 3' translated region of the CACNA1A gene, has been found. The third type of mutation is an untranslated CTG expansion resembling the mutation found in myotonic dystrophy. It is associated with a progressive ataxia, SCA8.

Chromosome Aberrations↗
PubMed2000

Significantly increased prevalence of factor V Leiden in patients with dural arteriovenous fistulas.

Resistance to activated protein C (APCR) is the most common genetic risk factor for venous thrombosis and is generally caused by a mutation in the factor V (FV) gene leading to FV Leiden. The recent finding of FV Leiden in three of seven patients with dural arteriovenous fistulas (DAVFs) prompted us to evaluate systematically the role of APCR due to FV Leiden in the pathogenesis of DAVFs in 22 patients and age- and sex-matched controls. We found a significantly higher frequency of APCR and FV Leiden in the patient group than among controls (5/22 vs. 0/22, P=0.048, Fisher's exact test). We conclude that APCR due to FV Leiden is of pathogenetic significance in a subgroup of DAVFs.

Activated Protein C Resistance↗
PubMed2000

Cell death in polyglutamine diseases.

An increasing number of inherited neurodegenerative diseases are known to be caused by trinucleotide repeat expansions in the respective genes. At least nine disorders result from a CAG trinucleotide repeat expansion which is translated into a polyglutamine stretch in the respective proteins: Huntington's disease (HD), dentatorubral pallidolysian atrophy (DRPLA), spinal bulbar muscular atrophy (SBMA), and several of the spinocerebellar ataxias (SCA1, 2, 3, 6, 7 and 12). Although the molecular steps leading to the specific neuropathology of each disease are unknown and are still under intensive investigation, there is increasing evidence that some CAG repeat disorders involve the induction of apoptotic mechanisms. This review summarizes the clinical and genetic features of each CAG repeat disorder and focuses on the common mechanistic steps involved in the disease progression of these so-called polyglutamine diseases. Among the common molecular features the formation of intranuclear inclusions, the recruitment of interacting polyglutamine-containing proteins, the involvement of the proteasome and molecular chaperones, and the activation of caspases are discussed with regard to their potential implication for the induction of cell death.

Animals↗
PubMed2000

Effect of 1-methyl-4-phenylpyridinium on glutathione in rat pheochromocytoma PC 12 cells.

We investigated the effect of the selective dopaminergic neurotoxin 1-methyl-4-phenylpyridinium (MPP+) on glutathione redox status and the generation of reactive oxygen intermediates (ROI) in rat pheochromocytoma PC 12 cells in vitro. Treatment with MPP+ (250 microM) led to a 63% increase of reduced glutathione (GSH) after 24 h, while a 10-fold higher concentration of MPP+ (2.5 mM) depleted cellular GSH to 12.5% of control levels within that time. Similarly, the complex I-inhibitor rotenone induced a time-dependent loss of GSH at 1 and 10 microM, whereas treatment with lower concentrations of rotenone (0.1, 0.01 microM) increased cellular GSH. Both MPP+ and rotenone increased cellular levels of oxidised glutathione (GSSG) and the higher concentrations of both compounds led to an elevated ratio of oxidised glutathione (GSSG) vs total glutathione (GSH + GSSG) indicating a shift in cellular redox balance. MPP+ or rotenone did not induce the generation of ROI or significant elevation of intracellular levels of thiobabituric acid reactive substances (TBARS) for up to 48 h. Our data suggest that MPP+ has differential effects on glutathione homeostasis depending on the degree of complex I-inhibition and that inhibition of complex I is not sufficient to generate ROI in this paradigm.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

Temporal, regional, and cell-specific changes of iNOS expression after intrastriatal microinjection of interferon gamma and bacterial lipopolysaccharide.

Here we study expression of the inducible isoform of nitric oxide synthases after intrastriatal microinjection of interferon-gamma and bacterial lipopolysaccharide in the rat at different time points to detect time- and localisation-dependent changes of iNOS expression. Three different areas in the striatum and the corpus callosum were evaluated. Antibodies against the glial fibrillary acidic protein and the microglia/brain macrophage epitope ED1 were used to detect colocalization of inducible nitric oxide synthase with astrocytes or activated microglia/brain macrophages, respectively. Inducible nitric oxide synthase-positive cells occurred first in intravascular and perivascular cells at 4 h. Perivascular and parenchymal inducible nitric oxide synthase expression increased up to 24 h in the striatum, whereas in the corpus callosum inducible nitric oxide synthase expression was maximal after 16 h. Inducible nitric oxide synthase was still present in perivascular cells 7 days after immunostimulation. At all time points, inducible nitric oxide synthase was predominantly detected in ED1-positive microglia/brain. Nitrotyrosine immunohistochemistry was performed to detect NO-mediated nitration of proteins at all time points. Nitrotyrosine-positive neurons and microglial cells were detected from 24 h until 7 days after immunostimulation and were absent in controls. Detailed knowledge of the changes in the time course and cellular source of inducible nitric oxide synthase expression following brain immunostimulation provide a basis for establishing treatment strategies and windows of therapeutic intervention during neuroinflammation.

Animals↗
PubMed2000

Molecular analysis of the PTEN, TP53 and CDKN2A tumor suppressor genes in long-term survivors of glioblastoma multiforme.

Despite multimodal therapy, glioblastoma multiforme (GBM) is associated with a poor prognosis with a median survival of less than 1 year. However, a small number of patients with GBM shows survival times of several years. Although clinical features like age and performance status at diagnosis are well known prognostic parameters, molecular markers for prognosis of overall survival are still lacking. Therefore, we compared 2 age- and gender-matched groups of GBM patients with different post-operative time to tumor progression (TTP), defined as 'short-term' for TTP of less than 6 months (n = 21), and 'long-term' for TTP of more than 24 months (n = 21) for genetic alterations of the PTEN, CDKN2A and TP53 genes as well as overexpression of the EGFR, p53 and Mdm2 proteins. For the GBMs with 'short-term' TTP vs. 'long-term' TTP, the studies revealed PTEN mutations in 4/21 vs. 2/21, TP53 mutations in 5/21 vs. 8/21, homozygous deletion of the CDKN2A gene in 5/21 vs. 6/21, overexpression of EGFR in 7/20 vs. 10/20, accumulation of p53 protein in 9/20 vs. 7/20 and of Mdm2 protein in 0/20 vs. 1/20 cases studied. Taken together, our data indicate that mutations of the PTEN and TP53 tumor suppressor genes, homozygous deletion of the CDKN2A gene as well as overexpression of the EGFR, p53 and Mdm2 proteins lack prognostic significance for overall survival time in patients with GBMs.

Adult↗
PubMed2000

Evoked potentials in multiple system atrophy (MSA).

OBJECTIVES: To study the involvement of pyramidal tracts and sensory pathways in multiple system atrophy (MSA). MATERIALS AND METHODS: Evoked potential studies were performed in 45 MSA patients suffering from either MSA of cerebellar type (MSA-C) or MSA of parkinsonian type (MSA-P). RESULTS: Motor evoked potentials were normal in all MSA patients, whereas visual and somatosensory evoked potential abnormalities were found in about 40% of the MSA patients with no significant difference between the cerebellar (MSA-C) and parkinsonian (MSA-P) subgroup. Abnormal latencies of wave III in brainstem auditory evoked potentials were significantly more frequent in MSA-C. CONCLUSIONS: Abnormalities of somatosensory, visual and auditory evoked potentials are frequent findings in MSA, whereas abnormal motor evoked potentials are not a characteristic feature of the disease.

Adult↗
PubMed2000

New insights into the metabolic consequences of large-scale mtDNA deletions: a quantitative analysis of biochemical, morphological, and genetic findings in human skeletal muscle.

In order to study putative genotype phenotype correlations in mitochondrial disorders due to large-scale mtDNA deletions we performed a quantitative analysis of biochemical, morphological, and genetic findings in 20 patients. The size of the mtDNA deletions varied from 2 to 7.5 kb with a degree of heteroplasmy ranging from 16% to 78%. Applying improved methods for measuring respiratory chain enzyme activities, we found highly significant inverse correlations between the percentage of cytochrome c oxidase (COX)- negative fibers and citrate synthase (CS) normalized COX ratios. Significant correlations were also established between CS normalized complex I and complex IV ratios as well as between the degree of heteroplasmy of mtDNA deletions and the percentage of ragged red fibers, COX-negative fibers, and CS normalized complex I and complex IV ratios. Our results indicate that the degree of heteroplasmy of mtDNA deletions is mirrored on the histological as well as the biochemical level. Furthermore, our findings suggest that single large-scale deletions equally influence the activities of all mitochondrially encoded respiratory chain enzymes. Even low degrees of heteroplasmy of mtDNA deletions were found to result in biochemical abnormalities indicating the absence of any well-defined mtDNA deletion threshold in skeletal muscle.

Adolescent↗
PubMed2000

The heat shock response inhibits NF-kappaB activation, nitric oxide synthase type 2 expression, and macrophage/microglial activation in brain.

The heat shock response (HSR) provides protection against stress-induced damage, and also prevents initiation of inflammatory gene expression via inhibition of NFkappaB activation. This article describes experiments demonstrating that the HSR prevents induction of nitric oxide synthase type 2 (NOS2) in rat brain. Twenty four hours after intrastriatal injection of lipopolysaccharide (LPS), IL-1beta, and IFN-gamma, NOS2 immunoreactive cells were detected in striatum, corpus callosum, and to a lesser extent in cortex. Induction of a HSR by whole body warming to 41 degrees C for 20 minutes, done 1 day before LPS plus cytokine injection, reduced the number of NOS2-positive staining cells to background levels. Staining for EDI antigen revealed that the HSR also suppressed microglial/brain macrophage activation in the same areas. Striatal injection of LPS and cytokines induced the rapid activation of NFkappaB, and this activation was prevented by prior HS, which also increased brain IkappaB-alpha expression. These results suggest that establishment of a HSR can reduce inflammatory gene expression in brain, mediated by inhibition of NFkappaB activation, and may therefore offer a novel approach to treatment and prevention of neurological disease and trauma.

Animals↗
PubMed2000

Recent advances in degenerative ataxias.

Since the discovery of the first mutations that cause hereditary ataxias in the early 1990s, there has been continuous progress in deciphering the molecular pathogenesis of degenerative ataxias. Recent research in Friedreich's ataxia, the most frequent recessive ataxia, has provided further evidence that the clinical phenotype of this disorder is caused by abnormal oxidative phosphorylation due to mitochondrial dysfunction. The dominantly inherited spinocerebellar ataxias (SCAs) are genetically heterogeneous. Up to now, 11 distinct loci have been identified. The mutations that cause SCA1, SCA2, SCA3, SCA6 and SCA7 share the common feature of an expanded CAG sequence, encoding an abnormally long polyglutamine tract within the respective gene products. Recent pathogenetic research points to the importance of abnormal protein-protein interaction and altered gene transcription. The aetiology of many sporadic ataxias remains obscure. In some patients, association of ataxia with specific serum antibodies (antigliadin, antiglutamic acid decarboxylase) suggests an immune pathogenesis.

Ataxia↗
PubMed2000

Nerve conduction studies in multiple system atrophy.

To study the frequency and severity of peripheral neuropathy in multiple system atrophy (MSA), we performed nerve conduction studies in 42 MSA patients suffering from either cerebellar MSA (MSA-C) or parkinsonian MSA (MSA-P). Abnormal nerve conduction was present in 24% of the patients. Abnormalities were significantly more frequent in MSA-P (43%) compared to MSA-C (14%). Motor nerve conduction velocities were reduced in 4% of the MSA-C and in 7% of the MSA-P patients. Abnormal compound muscle action potentials were more frequent in MSA-P (29% versus 7% in MSA-C) pointing to a more pronounced loss of motor axons in this subgroup. Sensory nerve conduction velocities were abnormal in 4% of the MSA-C and 14% of the MSA-P patients, and mean sensory nerve action potentials were normal in all MSA-C and reduced in 7% of the MSA-P patients. The data provide evidence that the peripheral nervous system is differentially affected in MSA-C and MSA-P.

Action Potentials↗
PubMed1999

MPP+ inhibits proliferation of PC12 cells by a p21(WAF1/Cip1)-dependent pathway and induces cell death in cells lacking p21(WAF1/Cip1).

The molecular and biochemical mode of cell death of dopaminergic neurons in Parkinson's disease (PD) is uncertain. In an attempt at further clarification we studied the effects of 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), on dopaminergic PC12 cells. In humans and nonhuman primates MPTP/MPP+ causes a syndrome closely resembling PD. MPP+ toxicity is thought to be mediated by the block of complex I of the mitochondrial electron transport chain. Treatment of undifferentiated PC12 cells with MPP+ primarily inhibited proliferation of PC12 cells and secondarily led to cell death after the depletion of all energy substrates by glycolysis. This cell death showed no morphological characteristics of apoptosis and was not blocked by treatment with caspase inhibitors. The inhibition of cell growth was not dependent on an inhibition of complex I activity since MPP+ also inhibited cell proliferation in SH-SY5Y cells lacking mitochondrial DNA and complex I activity (p0 cells). As shown by flow cytometric analysis, MPP+ induced a block in the G0/G1 to S phase transition that correlated with increased expression of the cyclin-dependent kinase inhibitor p21(WAF1/Cip1) and growth arrest. Since treatment with 1 microM MPP+ caused apoptotic cell death in p21(WAF1/Cip1)-deficient (p21(-/-)) but not in parental (p21(+/+)) mouse embryo fibroblasts, our data suggest that in an early phase MPP+-induced p21(WAF1/Cip1) expression leads to growth arrest and prevents apoptosis until energy depletion finally leads to a nonapoptotic cell death.

1-Methyl-4-phenylpyridinium↗
PubMed1999

Glutathione depletion and neuronal cell death: the role of reactive oxygen intermediates and mitochondrial function.

Glutathione (GSH) levels are supposed to determine the vulnerability of many cells towards a wide array of insults. We investigated the effects of chronic inhibition of GSH synthesis and acute depletion of GSH on cerebellar granule neurons in vitro and determined cytoplasmic and mitochondrial GSH with relation to mitochondrial function and generation of reactive oxygen intermediates (ROI). l-buthionine sulfoximine (BSO), which irreversibly blocks gamma-glutamyl-cysteine synthase, led to a time- and concentration-dependent loss of cytoplasmic GSH, while mitochondrial GSH was relatively preserved. No increased generation of ROI was detected over 48 h and the mitochondrial membrane potential was largely maintained. Neuronal degeneration occurred when mitochondrial GSH levels had fallen below 50% of control after 24-36 h. In contrast, direct conjugation of mitochondrial and cytoplasmic GSH with etacrynic acid (EA), resulted in immediate loss of mitochondrial GSH, a large increase of ROI within 2 h, subsequent collapse of the mitochondrial membrane potential and complete cell death within 4-8 h. Electron microscopy studies revealed an as yet unknown change of the chromatin structure to a homogeneous granular pattern after BSO, while EA resulted in typical necrotic changes. No typical features of apoptosis, i.e., no chromatin condensation or DNA fragmentation were detected after GSH depletion after BSO or EA treatment.

Animals↗
PubMed1999

Differential effects of L-buthionine sulfoximine and ethacrynic acid on glutathione levels and mitochondrial function in PC12 cells.

We investigated the effect of glutathione (GSH) depletion on mitochondrial function and generation of reactive oxygen intermediates (ROI) in PC12 cells in vitro. Direct depletion of cellular GSH using ethacrynic acid (EA, 500 mM) resulted in a concentration-dependent generation of ROI and cell death within 24 h. Treatment with 500 microM L-buthionine sulfoximine (BSO), which inhibits GSH synthesis, reduced cellular GSH but did not lead to generation of ROI. Furthermore, cells remained viable up to 72 h. Analysis of subcellular fractions revealed complete loss of cytosolic and mitochondrial GSH within 4 h of EA treatment. In contrast, BSO-treated cells still maintained 100% GSH in the mitochondrial fraction for 4 h and 6% for 48 h. Mitochondrial complex II/IIi and IV activities were not significantly decreased up to 48 h of BSO treatment while EA treatment resulted in a complete loss of complex II/III activity and a 70% reduction of complex IV activity within 4 h. These findings suggest that mitochondrial GSH is critical for the maintenance of mitochondrial function and cellular viability.

Animals↗