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Biomedical subjects

Stephan Zierz

Publications and source records attributed to Stephan Zierz.

At least 19 recordsLinked to original sources
PubMed2004

Different sensitivities of CPT I and CPT II for inhibition by l-aminocarnitine in human skeletal muscle.

l-Aminocarnitine (l-AC) has been shown to inhibit carnitine palmitoyltransferases (CPT) in rat muscle and in rat liver. However, there are no reports on interactions of l-AC with CPT II and CPT I of human muscle. Therefore, the aim of the present work was to characterize the inhibition of human muscle CPT I and CPT II by l-AC in muscle mitochondria, skinned fibers and muscle homogenates in comparison to the established action of malonyl-CoA. Both isoenzymes were inhibited by l-AC, but sensitivity was different (CPT I, K(d)=3.8 mM l-AC; CPT II, K(d)=21.3 microM l-AC). A mixed inhibition type in respect to carnitine was detected (K(i)=3.5 microM l-AC). At 0.5 mM l-AC, CPT II was completely inhibited without affection of CPT I. In contrast, CPT I was completely inhibited by 0.4 mM malonyl-CoA (K(d)=0.5 microM), whereas CPT II was nearly not affected by this inhibitor. Using these inhibitors in muscle homogenates, activities of CPT II and CPT I were detected to be 38+/-10% and 63+/-10% of total, respectively (n=21). In intact mitochondria and different fractions of muscle homogenates after selective solubilization of CPT II by Tween 20, the extent of specific CPT inhibition changed in relation to the accessible isoenzyme pattern. Palmitoyl-carnitine-dependent respiration in skinned fibers was inhibited by high concentrations of l-AC, indicating that the inhibitor can be transported via the acyl-carnitine transporter, too. The combined use of both inhibitors (l-AC and malonyl-CoA) allows the kinetic characterization of CPT I and CPT II in human muscle homogenates. In addition, it has been shown that l-AC can be used for the study of metabolic consequences of CPT II deficiency on function of intact mitochondria.

Betaine↗
PubMed2003

Calpain inhibitor (BSF 409425) diminishes ischemia/reperfusion-induced damage of rabbit heart mitochondria.

Calpains are involved in ischemia/reperfusion-induced changes of myocard. To obtain information on the action of calpain on mitochondria, the effect of a new developed calpain inhibitor (CI) BSF 409425 on the ischemia/reperfusion-induced damage of rabbit heart mitochondria was investigated. Rabbit hearts were subjected to 45 min of global ischemia followed by 60 min of reperfusion in the presence or absence of 10nM CI. Mitochondrial properties were characterized by skinned fiber technique with pyruvate+malate as substrates. In the presence of CI, the decrease of state 3 respiration and the increase of state 4 respiration after ischemia and reperfusion were clearly smaller than without CI resulting in significantly smaller changes of respiratory control index, too. Ischemia/reperfusion-caused leaks in mitochondrial inner and outer membranes were diminished by CI. It is concluded that mitochondria are a target of calpain which reinforces the damage of oxidative phosphorylation and mitochondrial membranes during ischemia/reperfusion.

Animals↗
PubMed2003

Increased metabolic muscle fatigue is caused by some but not all mitochondrial mutations.

CONTEXT: Excessive muscle fatigue occurs in patients with a mitochondrial encephalomyopathy (MEM), but it is also a frequent problem in patients with other neuromuscular disorders (ONMD). OBJECTIVE: To determine whether, and to what extent, metabolic muscle fatigue specifically occurs in patients with an MEM. DESIGN: Metabolic muscle fatigue was assessed in a series of 21 patients with an MEM, including 13 patients with chronic progressive external ophthalmoplegia and 8 patients with various mitochondrial point mutations; 27 patients with ONMD; and 25 healthy controls. Isometric twitch force of the ankle dorsiflexors was measured after supramaximal stimulation of peroneal nerves. Six trains of stimuli (of 1 minute's duration with rates from 0.2 to 5 stimuli per second) were given to each subject. RESULTS: An abnormal decrement of the twitch amplitude that occurred during a stimulation train was found in patients with MEM and in those with ONMD. The decrement of the twitch amplitude of controls and of patients with ONMD was strongly influenced by their muscle force (P<.001). After subtraction of the influence of the muscle force, specific fatigue was notably higher in patients with chronic progressive external ophthalmoplegia than in patients with ONMD and in controls, and it correlated well with elevations of serum lactate. Specific fatigue was also abnormal in a patient with a mitochondrial G7497A mutation, but normal in patients with an A3243G or a G11778A mutation. The heteroplasmy of mitochondrial DNA in muscle correlated neither with the force measures nor with the serum lactate levels. CONCLUSIONS: Generally, metabolic muscle fatigue accompanies muscular weakness. Specifically, some but not all mitochondrial mutations cause excessive metabolic muscle fatigue.

Action Potentials↗
PubMed2003

Atypical phenotypes in patients with facioscapulohumeral muscular dystrophy 4q35 deletion.

BACKGROUND: Facioscapulohumeral muscular dystrophy (FSHD) is associated with a deletion on chromosome 4q35. Recent studies have shown that this deletion is found in patients with other phenotypes in addition to those with the classic Landouzy-Dejerine FSHD phenotype. OBJECTIVE: To examine patients with atypical phenotypes and an FSHD deletion on chromosome 4q35. DESIGN: Clinical characterization and genotype-phenotype correlation. SETTING: University hospital. PATIENTS: Forty-one symptomatic subjects with deletions on chromosome 4q35. RESULTS: We found 6 patients with atypical FSHD. Three (from a single family with FSHD) had additional symptoms of chronic progressive external ophthalmoplegia (4q35 EcoRI/BlnI fragment size, 20 kilobase [kb]), and 3 patients (1 with sporadic disease and 2 from a single family) had facial-sparing scapulohumeral dystrophy (4q35 EcoRI/BlnI fragment size, 30 and 34 kb, respectively). CONCLUSIONS: The clinical presentations in patients with FSHD-associated short fragments on chromosome 4q35 are not restricted to the classic FSHD form, but constitute a variety of clinical manifestations. There seems to be no clear correlation between the atypical subtype and the DNA fragment size due to the deletion.

Adolescent↗
PubMed2003

Two novel mutations in the myophosphorylase gene in a patient with McArdle disease.

We identified two novel mutations in exon 2 of the myophosphorylase gene in a 33-year-old German women with McArdle disease. The patient was compound heterozygous for a novel nonsense mutation at codon 84 changing tyrosine to stop codon (Y84X) and for a novel missense mutation at codon 93 changing arginine to tryptophan (R93W). These mutations are the first to be described in exon 2 and expand the genetic heterogeneity in patients with McArdle disease.

Adult↗
PubMed2003

Typical facioscapulohumeral dystrophy phenotype in patients without FSHD 4q35 deletion.

There have been few reports on facioscapulohumeral dystrophy (FSHD) without 4q35 deletion. Most of them had either only mild FSHD phenotype or so called "borderline" EcoRI-fragments (35-38 kb). We analysed the clinical, electrophysiological, histological and genetic features of 46 consecutive patients from 31 families with a typical FSHD phenotype. Five patients from three families were identified with unequivocal clinical features of classical Landouzy-Dejerine FSHD, in which no typical FSHD 4q35 deletion could be seen, i. e. fragment sizes were well above 40 kb. Other possible diseases with similar phenotype were excluded. The FSHD gene itself has not been identified so far. The present study suggests that the FSHD phenotype might be caused by different molecular mechanisms.

Adult↗
PubMed2003

Babinski-Nageotte's syndrome and Hemimedullary (Reinhold's) syndrome are clinically and morphologically distinct conditions.

A hemimedullary infarction, in which medial and lateral medullary lesions occur simultaneously, is a rare cerebrovascular disease. It has been suggested that the Babinski-Nageotte's syndrome is the classical brainstem syndrome that corresponds to hemimedullary lesion. In this study we compare clinical symptoms and magnetic resonance imaging (MRI) data of two patients exhibiting classical Babinski-Nageotte's syndrome according to the original description with symptoms and MRI data of a patient with clinically complete hemimedullary lesion. Our study shows that Babinski-Nageotte's syndrome is neither clinically nor on MRI identical with hemimedullary lesion. Hypoglossal palsy, an invariable symptom of hemimedullary syndrome, is not part of the Babinski-Nageotte's syndrome according to the original description. Consistent with the original historical report, Babinski- Nageotte's syndrome is a lateral "Wallenbergian" medullary lesion with a spreading of the lesion to the more basal localised pyramidal tract. The clinical features of the hemimedullary syndrome, described in 1894 by Reinhold, and the MRI appearances in our patient with this syndrome are clearly different from other classical brainstem syndromes and should be called Reinhold's syndrome.

Adult↗
PubMed2003

A novel Twinkle gene mutation in autosomal dominant progressive external ophthalmoplegia.

Autosomal dominant progressive external ophthalmoplegia is a common neurological presentation of mitochondrial disease and is characterised by multiple deletions of mitochondrial DNA in muscle. We describe a family with autosomal dominant progressive external ophthalmoplegia caused by a novel heterozygous A to C transversion at nucleotide 956 of the Twinkle gene. The deltoid muscle biopsy of the index case revealed sparse respiratory deficient cells. Multiple mitochondrial DNA deletions were clearly evident in the index case by both long-range and real-time polymerase chain reaction assays but not by Southern blotting, highlighting the diagnostic difficulties associated with characterising patients with multiple mitochondrial DNA deletions.

Adult↗
PubMed2003

A splice junction mutation in muscle carnitine palmitoyltransferase II deficiency.

We report the first splice junction mutation to be described in the carnitine palmitoyltransferase (CPT) 2 gene in a patient with the muscle form of CPT II deficiency. The patient, a 25-year-old man, suffered from attacks of myalgia and muscle weakness in early adult life. There was biochemical evidence of CPT II deficiency. Molecular genetic analysis revealed the common S113L mutation on one allele whilst a novel mutation at the splice donor junction in intron 3 was identified on the other allele. Sequencing of reverse transcription polymerase chain reaction (RT-PCR) products clearly demonstrated that this mutation causes the skipping of exon 3, thus establishing its pathogenic role.

Adult↗
PubMed2003

Therapy of neurological disorders in systemic vasculitis.

Significant progress has been made in our understanding of the underlying cellular and molecular mechanisms associated with vasculitis. Simultaneous involvement of the nervous system and systemic organs points to shared antigenic targets or immune mechanisms operative at both sites. Although specific immunotherapy is not available, the old and new immunomodulatory therapies have been instrumental in providing effective therapy in most of these chronic autoimmune disorders. The treatment of giant cell arteritis, neurosarcoidosis, Wegener's granulomatosis, systemic lupus erythematosus, polyarteritis, Sjögren's syndrome, and Behcet disease will be reviewed.

Adjuvants, Immunologic↗
PubMed2003

Absence of known familial hemiplegic migraine (FHM) mutations in the CACNA1A gene in patients with common migraine: implications for genetic testing.

Mutations in the gene CACNA1A have been known to cause familial hemiplegic migraine (FHM); it has been suggested, based on indirect genetic studies, that this gene may also be involved in common forms of migraine. To obtain data from direct gene analysis to test this hypothesis, we investigated 143 patients with common migraine, irrespective of their family history, for the presence of mutations known to result in the FHM phenotype; the mutations V714A, R192Q, R583Q, T666M, V1457L, and 11811L were absent in our patient sample. Furthermore, exons 4, 16, 17, and 36 were completely screened by single-strand conformation polymorphism (SSCP), and no other, hitherto unknown, mutations were detected. Bearing in mind that, in particular, the T666M mutation contributes to a large proportion of FHM linked to chromosome 19, we conclude that common migraine is distinct from FHM in its molecular basis and, therefore, most likely also in its pathophysiology. The possibility, however, of the existence of allelic disorders, with mutations located in other regions of the CACNA1A gene, cannot be ruled out. Molecular testing, therefore, is at present not a feasible option for the diagnosis and classification of migraine.

Calcium Channels↗
PubMed2002

Mitochondrial respiratory rates and activities of respiratory chain complexes correlate linearly with heteroplasmy of deleted mtDNA without threshold and independently of deletion size.

To clarify the importance of deleted protein and tRNA genes on the impairment of mitochondrial function, we performed a quantitative analysis of biochemical, genetic and morphological findings in skeletal muscles of 16 patients with single deletions and 5 patients with multiple deletions of mtDNA. Clinically, all patients showed chronic progressive external ophthalmoplegia (CPEO). The size of deletions varied between 2.5 and 9 kb, and heteroplasmy between 31% and 94%. In patients with single deletions, the citrate synthase (CS) activity was nearly doubled. Decreased ratios of pyruvate- and succinate-dependent respiration were detected in fibers of all patients in comparison to controls. Inverse and linear correlations without thresholds were established between heteroplasmy and (i) CS referenced activities of the complexes of respiratory chain, (ii) CS referenced maximal respiratory rates, (iii) and cytochrome-c-oxidase (COX) negative fibers. In patients with single and multiple deletions, all respiratory chain complexes as well as the respiratory rates were decreased to a similar extent. All changes detected in patients with single deletions were independent of deletion size. In one patient, only genes of ND5, ND4L as well as tRNA(Leu(CUN)), tRNA(Ser(AGY)), and tRNA(His) were deleted. The pronounced decrease in COX activity in this patient points to the high pathological impact of these missing tRNA genes. The activity of nuclear encoded SDH was also significantly decreased in patients, but to a lesser extent. This is an indication of secondary disturbances of mitochondria at CPEO. In conclusion, we have shown that different deletions cause mitochondrial impairments of the same phenotype correlating with heteroplasmy. The missing threshold at the level of mitochondrial function seems to be characteristic for large-scale deletions were tRNA and protein genes are deleted.

Citrate (si)-Synthase↗
PubMed2002

The quantitation of ADP diffusion gradients across the outer membrane of heart mitochondria in the presence of macromolecules.

We have previously provided evidence that diffusion of metabolites across the porin pores of mitochondrial outer membrane is hindered. A functional consequence of this diffusion limitation is the dynamic compartmentation of ADP in the intermembrane space. These earlier studies were done on isolated mitochondria suspended in isotonic media without macromolecules, in which intermembrane space of mitochondria is enlarged. The present study was undertaken to assess the diffusion limitation of outer membrane in the presence of 10% (w/v) dextran M20, in order to mimic the action of cytosolic macromolecules on mitochondria. Under these conditions, mitochondria have a more native, condensed configuration.Flux-dependent concentration gradients of ADP were estimated by measuring the ADP diffusion fluxes across the porin pores of isolated rat heart mitochondria incubated together with pyruvate kinase (PK), both of which compete for ADP regenerated by mitochondrial creatine kinase (mtCK) within the intermembrane space or by yeast hexokinase (HK) extramitochondrially. From diffusion fluxes and bulk phase concentrations of ADP, its concentrations in the intermembrane space were calculated using Fick's law of diffusion. Flux-dependent gradients up to 23 microM ADP (for a diffusion rate of J(Dif)=1.9 micromol ADP/min/mg mitochondrial protein) were observed. These gradients are about twice those estimated in the absence of dextran and in the same order of magnitude as the cytosolic ADP concentration (30 microM), but they are negligibly low for cytosolic ATP (5 mM). Therefore, it is concluded that the dynamic ADP compartmentation is of biological importance for intact heart cells. If mtCK generates ADP within the intermembrane space, the local ADP concentration can be clearly higher than in the cytosol resulting in higher extramitochondrial phosphorylation potentials. In this way, mtCK contributes to ensure optimal kinetic conditions for ATP-splitting reactions in the extramitochondrial compartment.

Adenosine Diphosphate↗
PubMed2002

Effect of the new matrix metalloproteinase inhibitor RO-28-2653 on mitochondrial function.

Matrix metalloproteinases (MMPs) have recently become interesting as potential anticancer drugs. RO-28-2653 is a promising compound because of its antimetastatic and antiangiogenic activities. Due to the structural similarity of RO-28-2653 to mitochondriotoxic agents, speculation has arisen that this substance might impair mitochondrial function. We, therefore, investigated the effects of RO-28-2653 on mitochondrial enzymes and on the functional properties of isolated mitochondria and skinned muscle fibers from rat hearts. Results were compared to the action of amytal and 2,4-dinitrophenol (2,4-DNP), both of which are well documented mitochondriotoxic compounds. In contrast to 2,4-DNP, RO-28-2653 did not uncouple oxidative phosphorylation, although higher concentrations of the compound did impair mitochondrial function. Using malate/pyruvate as substrate, 50 microM of RO-28-2653 inhibited mitochondrial respiration in isolated mitochondria and skinned fibers by 23 and 11%, respectively while 2mM of amytal elicited almost complete inhibition of the mitochondrial respiration. RO-28-2653 (50 micro) inhibited succinate-dependent respiration in both systems by 43 and 24%, respectively while 2mM of amytal caused 41 and 23% inhibition, respectively. There was no change in the ADP/O ratios. RO-28-2653 (50 microM) did not significantly alter the activity of the respiratory chain complexes or succinate dehydrogenase, although citrate synthase (CS) was inhibited by upto 71%. This inhibition was non-competitive at a K(i) of 25+/-5 microM. Inhibitory effects in the presence of hydrophobic substances, such as BSA and Triton X-100, were significantly lower in both test systems. In conclusion, high concentrations of RO-28-2653 impair mitochondrial function, although compared to amytal and 2,4-DNP, this is rather low. The resultant impairment is less pronounced in the more complex skinned muscle fiber system, and is dependent on hydrophobic interactions.

Animals↗
PubMed2002

A novel nonsense mutation (515del4) in muscle carnitine palmitoyltransferase II deficiency.

We identified a novel nonsense mutation in the carnitine palmitoyltransferase (CPT; EC 2.3.1.21) II gene in a patient with biochemical evidence of CPT II deficiency. The 39-year-old man suffered from the muscle form of CPT II deficiency. Attacks of myalgia and muscle weakness started in childhood and led to renal failure five times. A mild proximal weakness of the lower limbs was left as a residue. Molecular genetic analysis revealed the common S113L mutation on one allele. On the other allele a novel 4-bp deletion starting at codon 515 (515del4) was found leading to frameshift that results in a stop codon 15 codons upstream. Our data further expand the genetic heterogeneity in patients with CPT II deficiency.

Adult↗
PubMed2002

Frequent low penetrance mutations in the Lamin A/C gene, causing Emery Dreifuss muscular dystrophy.

Emery Dreifuss muscular dystrophy is a genetically heterogeneous disorder characterized by the clinical triad of early onset contractures, progressive muscular wasting and weakness with humeroperoneal distribution and cardiac conduction defects. Mutations in the Lamin A/C (LMNA) gene are responsible for the autosomal dominant and the autosomal recessive forms. Familiar and sporadic patients carrying mutations in the LMNA gene show high variability in the clinical symptomatology and age of onset. In this report, we describe four families harboring missense mutations in the LMNA gene and we show that the effect of mutations ranges from silent to fully penetrant. We suggest that incomplete penetrance of dominant mutations in the LMNA gene is a common feature and we emphasize the significance of mutational analysis in relatives of sporadic cases of laminopathies, as asymptomatic carriers face high risk of sudden cardiac death.

Adolescent↗
PubMed2002

Mitochondrial dysfunction in sepsis: evidence from bacteraemic baboons and endotoxaemic rabbits.

Mitochondria, that provide most of the ATP needed for cell work, and that play numerous specific functions in biosyntheses and degradations, as well as contributing to Ca2+ signaling, also play a key role in the pathway to cell death. Impairment of mitochondrial functions caused by mutations of mt-genome, and by acute processes, are responsible for numerous diseases. The involvement of impaired mitochondria in the pathogenesis of sepsis is discussed. By means of the skinned fiber technique and high resolution respirometry, we have detected significantly reduced rates of mitochondrial respiration in heart and skeletal muscle of endotoxaemic rabbits. Mitochondria from heart were more affected than those from skeletal muscle. Decreased respiration rates were accompanied by reduced activities of complex I + III of the respiratory chain. Endotoxin-caused impairment was also detectable at the level of the Langendorff perfused heart, where the coronary vascular resistance was significantly increased. For an investigation of the influence of bacteraemia on the mitochondrial respiratory chain, baboons were made septic by infusion of high and low amounts of E. coli. For complex I + III and II + III, a clear dose-dependent decrease was detectable and in animals which died in septic shock, a further decrease of enzyme activities in comparison to the controls were found. These results are discussed in the light of current knowledge on the role of mitochondria in cell pathology in respect to sepsis. In conclusion, we present evidence that mitochondrial function is disturbed during sepsis. Besides ischaemic and poison-induced disturbances of mitochondrial function, sepsis is a further example of an acute disease where impaired mitochondria have to be taken into account.

Animals↗