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Biomedical subjects

R Krüger

Publications and source records attributed to R Krüger.

At least 19 recordsLinked to original sources
PubMed2000

Involvement of alpha-synuclein in Parkinson's disease and other neurodegenerative disorders.

A major step in the elucidation of the pathogenesis of neurodegenerative disorders was the identification of a mutation in the alpha-synuclein gene in autosomal dominant Parkinson's disease (PD). Alpha-synuclein is the main component of Lewy bodies (LB), the neuropathological hallmark of PD. Moreover, a fragment of alpha-synuclein (NAC) is the second major component of amyloid plaques in Alzheimer's disease (AD). Recent studies of other neurodegenerative disorders such as dementia with LB (DLB), multiple system atrophy (MSA) and amyotrophic lateral sclerosis (ALS) also revealed intracellular accumulations of alpha-synuclein in affected brain regions. This may indicate that these disorders partially share common pathogenic mechanisms. Recent data provide first insights into the physiological function of alpha-synuclein and support the concept of an essential role of alpha-synuclein in neurodegeneration. Increasing knowledge on the pathogenic molecular mechanisms of neurodegeneration and of the pathophysiological function of alpha-synuclein in particular may influence future development of therapeutic strategies in neurodegenerative disorders.

Alzheimer Disease↗
PubMed2000

Dimers of pi protein bind the A+T-rich region of the R6K gamma origin near the leading-strand synthesis start sites: regulatory implications.

The replication of gamma origin, a minimal replicon derived from plasmid R6K, is controlled by the Rep protein pi. At low intracellular concentrations, pi activates the gamma origin, while it inhibits replication at elevated concentrations. Additionally, pi acts as a transcription factor (auto)repressing its own synthesis. These varied regulatory functions depend on pi binding to reiterated DNA sequences bearing a TGAGNG motif. However, pi also binds to a "non-iteron" site (i.e., not TGAGNG) that resides in the A+T-rich region adjacent to the iterons. This positioning places the non-iteron site near the start sites for leading-strand synthesis that also occur in the A+T-rich region of gamma origin. We have hypothesized that origin activation (at low pi levels) would require the binding of pi monomers to iterons, while the binding of pi dimers to the non-iteron site (at high pi levels) would be required to inhibit priming. Although monomers as well as dimers can bind to an iteron, we demonstrate that only dimers bind to the non-iteron site. Two additional pieces of data support the hypothesis of negative replication control by pi binding to the non-iteron site. First, pi binds to the non-iteron site about eight times less well than it binds to a single iteron. Second, hyperactive variants of pi protein (called copy-up) either do not bind to the non-iteron site or bind to it less well than wild-type pi. We propose a replication control mechanism whereby pi would directly inhibit primer formation.

Adenine↗
PubMed1999

Predictors of bone mineral density in patients with eating disorders.

OBJECTIVE: The objective of this study was to examine potential clinical predictors of bone density in patients with eating disorders. METHOD: We studied 137 women with anorexia nervosa, bulimia nervosa, or eating disorder not otherwise specified (NOS) after admission to the hospital. Clinical data of patients were collected by clinical interview and standardized questionnaires. Bone mineral density of the lumbar spine was measured by dual energy x-ray absorptiometry. RESULTS: Lumbar bone density was significantly correlated to present and past minimum weight even after correction for height and age. Other factors did not reach significance. CONCLUSION: Normalized present and past weight is the best predictor of lumbar bone density in patients with eating disorders. Factors like reduced caloric intake, binge eating, vomiting, menstrual status, and use of estrogen, laxatives, and nicotine seem to have no independent effect on bone density in this group of patients.

Absorptiometry, Photon↗
PubMed1999

Increased susceptibility to sporadic Parkinson's disease by a certain combined alpha-synuclein/apolipoprotein E genotype.

Parkinson's disease (PD) is one of the most common neurodegenerative disorders affecting about 1% of Western populations older than age 50. The pathological hallmark of PD are Lewy bodies, that is, intracytoplasmic inclusion bodies in affected neurons of the substantia nigra. Recently, alpha-synuclein (alpha-SYN) has been identified as the main component of Lewy bodies in sporadic PD, suggesting involvement in neurodegeneration via protein accumulation. The partially overlapping pathology of PD and Alzheimer's disease, as well as striking structural similarities of alpha-SYN and apolipoprotein E, which is a major risk factor for late-onset Alzheimer's disease, prompted us to investigate the influence of different alpha-SYN and apolipoprotein E alleles for developing sporadic PD. We performed association studies in 193 German PD patients and 200 healthy control subjects matched for age, sex, and origin. A polymorphism in the promoter region of the alpha-SYN gene (NACP-Rep1) as well as of the closely linked DNA markers D4S1647 and D4S1628 revealed significant differences in the allelic distributions between PD patients and the control group. Furthermore, the Apo epsilon4 allele but not the Th1/E47 promoter polymorphism of the apolipoprotein E gene was significantly more frequent among early-onset PD patients (age at onset, <50 years) than in late-onset PD. Regarding the combination of the Apo epsilon4 allele and allele 1 of the alpha-SYN promoter polymorphism, a highly significant difference between the group of PD patients and control individuals has been found, suggesting interactions or combined actions of these proteins in the pathogenesis of sporadic PD. PD patients harboring this genotype have a 12.8-fold increased relative risk for developing PD during their lives.

Aged↗
PubMed1999

Parkinson's disease--a multifactorial neurodegenerative disorder.

The pathogenesis of idiopathic Parkinson's disease (PD) is not known, but is thought to be multifactorial, deriving from environmental factors acting on genetically predisposed individuals with aging. Association studies of DNA polymorphisms are able to detect a genetic background predisposing to PD. Mechanisms as oxidative stress, xenobiotica toxicity and altered dopamine metabolism might lead to a selective cell death of most vulnerable nerve cells and represent the primary subject to be studied by DNA analysis. Furthermore, protein aggregation is likely to be a major cause for the disease. Recently it has been shown that alpha-synuclein is accumulated in Lewy bodies of sporadic PD and mutated in some rare families with an autosomal dominant trait of the disease (ADPD). The identification of further genes responsible for PD will subsequently lead to first insights into the pathogenesis of one of the most common neurodegenerative disorders in humans.

Humans↗
PubMed1999

[Structure of a cell bank for transplantation of HLA-typed, cryopreserved human adult retinal pigment epithelial cells].

BACKGROUND: The transplantation of retinal pigment epithelial cells (RPE) in patients with age-related macular degeneration is discussed as a future therapy. A cornea bank can serve as a source for cells that can be isolated, cultivated, HLA-typed and cryopreserved for subsequent tissue-compatible transplantation. METHODS: RPE cells are isolated enzymatically from donor eyes and are cultured in a specially designed growth medium. After multiplication, one part of the culture is cryopreserved; the other part is subcultured for HLA-typing. Completely typed and morphologically sufficiently well-differentiated cell cultures are registered on a donor list (RPE cell bank) and can be provided for cell transplantations with matching HLA type in patients suffering from RPE degenerative diseases. RESULTS: A total of 461 cell cultures have been prepared since 1996; 116 fully typed and well-differentiated cell cultures are stored in our cell bank. Since January 1998 patients who agreed to have an RPE transplantation have been registered on a waiting list. Seven transplantations have already been performed. CONCLUSION: RPE cells can be stored cryopreserved in a cell bank and can be kept available for transplantation for a prolonged period of time.

Adolescent↗
PubMed1999

Physiological features of primary cultures and subcultures of human retinal pigment epithelial cells before and after cryopreservation for cell transplantation.

BACKGROUND: One striking disadvantage of in vitro culturing of human retinal pigment epithelial (RPE) cells is the loss of epithelial differentiation and specific cell function during culture. This may be one of the main reasons for the failure of RPE cell transplantation. The aim of this study was to evaluate cell culture conditions ensuring the maintenance of differentiation and function of RPE cells after subcultivation and storage in liquid nitrogen. METHODS: Enzymatically isolated cells were seeded onto coated culture dishes, cultured with a specially formulated improved growth medium until confluence and then cryopreserved in liquid nitrogen for 16-66 months. HLA class I and II typing was performed before cryopreservation and after thawing. Expression of Ca2+ channels in primary, first-passage and cryopreserved RPE cells was studied using the patch-clamp technique. RESULTS: After cryopreservation no loss of any HLA antigen was detectable in 12 of 14 cell strains studied. Patch-clamp experiments demonstrated that high-threshold L-type Ca2+ channels, which are typical for freshly isolated cells, could be detected in first-passage and cryopreserved RPE cells only when improved culture conditions were employed, not in conventionally cultured cells. The characteristics of these channels showed little change in subcultured cells compared to primary cultures. CONCLUSION: This is the first study showing the maintenance of adult human RPE-specific cell differentiation and characteristics in vitro after primary culture and after cryopreservation using improved cell culture methods. The optimization and quality control of cell culture is an important prerequisite for successful cell transplantation.

Adolescent↗
PubMed1999

Analysis of the parkin deletion in sporadic and familial Parkinson's disease. Short communication.

Recently a mutation in the parking gene has been identified as the cause for an autosomal-recessively inherited form of early onset Parkinson's disease (EOPD). The disease causing minimal deletion has been defined as a homozygous exon 4 loss in the parkin gene among Japanese patients. We investigated 140 sporadic and familial EOPD patients of German ancestry for the exon 4 deletion in the parkin gene. None of our patients exhibited a homozygous deletion of exon 4, suggesting a minor role of this mutation for EOPD in Caucasians. Nevertheless a detailed mutation analysis is warranted to explore the overall significance of mutations in the parkin gene in EOPD.

Adult↗
PubMed1998

Replication of R6K gamma origin in vitro: discrete start sites for DNA synthesis dependent on pi and its copy-up variants.

The regulation of the plasmid R6K gamma origin (gamma ori) is accomplished through the ability of the pi protein to act as an initiator and inhibitor of replication. Hyperactive variants of this protein, called copy-up pi, allow four to tenfold increases of gamma ori plasmid DNA in vivo. The higher activity of copy-up pi variants could be explained by an increase in the initiator function, a decrease in the inhibitor activity, or a derepression of a more efficient mechanism of replication that can be used by wt pi (pi35. 0) only under certain conditions. We have compared the replication activities of wt pi35.0 and copy-up pi mutants in vitro, and analyzed the replication products. It is shown that copy-up variants are several-fold more active than wt pi35.0 in replication. This appears to be due to enhanced specific replication activity of copy-up mutants rather than elevated fractions of protein proficient in DNA binding. Furthermore, biochemical complementation revealed that pi200 (copy-up) is dominant over wt pi35.0. The elevated activity of copy-up pi is not caused by an increased rate of replisome assembly as inferred from in vitro replication assays in which the lag periods observed were similar to that of wt pi35.0. Moreover, only one round of semiconservative, unidirectional replication occurred in all the samples analyzed indicating that copy-up pi proteins do not initiate multiple rounds of DNA synthesis. Rather, a larger fraction of DNA template replicates in the presence of copy-up pi as determined by electron microscopy. Two clusters of discrete DNA synthesis start sites are mapped by primer extension near the stability (stb) locus of the gamma ori. We show that the start sites are the same in the presence of wt pi35.0 or copy-up proteins. This comparative analysis suggests that wt pi35.0 and copy-up variants utilize fundamentally similar mechanism(s) of replication priming.

Amino Acid Substitution↗
PubMed1998

Selegiline as immunostimulant--a novel mechanism of action?

In clinical studies the MAO-B inhibitor selegiline appears to slow the progression of neurological deficits in Parkinson's disease (PD) and the cognitive decline in Alzheimer's disease (AD). The mechanisms of action remain unclear. Several lines of evidence indicate an immune-mediated pathophysiology of PD and AD. According to animal trials, selegiline increases the survival rate of immune suppressed mice. Stimulation of the immune response to bacterial or viral infection or in chronic inflammatory processes in managed by an increased synthesis of the cytokines interleukin-1 beta (IL-1 beta) and subsequent interleukin-6 (IL-6). Outcome of viral or bacterial infections in the brain highly correlates with levels of the cytotoxic cytokine tumor-necrosis-factor-alpha (TNF). The aim of our study was to characterize the influence of selegiline on the biosynthesis of IL-1 beta, IL-6 and TNF in human peripheral blood mononuclear cells (PBMC) from healthy blood donors. After isolation and washing PBMC were cultured without and with selegiline in three different concentrations (0.01 mumol/l, 0.001 mumol/l, 0.0001 mumol/l) in a humidified atmosphere (7% CO2). Then cultures were centrifuged and supernatants were collected for IL-1 beta, IL-6 and TNF ELISA-assays. Treatment of cultured PBMC with various concentrations induced an increased synthesis of IL-1 beta (ANOVA F = 9.703, p = 0.0007), IL-6 (ANOVA F = 20.648, p = 0.0001) and a reduced production of TNF (ANOVA F = 3.770, p = 0.040). These results indicate, that the influence of selegiline on the cytokine biosynthesis may also contribute to its putative neuroprotective properties.

Adjuvants, Immunologic↗
PubMed1998

Genetic dissection of familial Parkinson's disease.

In the past few years, the genetic contribution to Parkinson's disease (PD) has gained major attention and has resulted in the identification of the first mutant gene, called alpha-synuclein, involved in the pathogenesis of autosomal-dominant PD. alpha-Synuclein is a major component of Lewy bodies, which are a neuropathological feature of PD. Furthermore, deletions in the parkin gene have been identified as the primary cause in rare forms of autosomal-recessive juvenile PD. The elucidation of polygenic changes in the dopamine pathway, mitochondrial dysfunction, and metabolism of xenobiotics is now technically possible by means of association and genotype studies. The increasing knowledge of the pathogenesis of PD at a molecular level will have important implications for the development of individual therapeutic strategies to prevent disease progression.

Amino Acid Sequence↗
PubMed1998

Spinocerebellar ataxia type 6: genotype and phenotype in German kindreds.

OBJECTIVE: Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant cerebellar ataxia (ADCA) of which the mutation causing the disease has recently been characterised as an expanded CAG trinucleotide repeat in the gene coding for the alpha1A-subunit of the voltage dependent calcium channel. The aim was to further characterise the SCA6 phenotype METHODS: The SCA6 mutation was investigated in 69 German families with ADCA and 61 patients with idiopathic sporadic cerebellar ataxia and the CAG repeat length of the expanded allele was correlated with the disease phenotype. RESULTS: Expanded alleles were found in nine of 69 families as well as in four patients with sporadic disease. Disease onset ranged from 30 to 71 years of age and was significantly later than in other forms of ADCA. Age at onset correlated inversely with repeat length. The SCA6 phenotype comprises predominantly cerebellar signs in concordance with isolated cerebellar atrophy on MRI. Non-cerebellar systems were only mildly affected with external ophthalmoplegia, spasticity, peripheral neuropathy, and parkinsonism. Neither these clinical signs nor progression rate correlated with CAG repeat length. CONCLUSIONS: This study provides the first detailed characterisation of the SCA6 phenotype. Clinical features apart from cerebellar signs were highly variable in patients with SCA6. By comparison with SCA1, SCA2, and SCA3 no clinical or electrophysiological finding was specific for SCA6. Therefore, the molecular defect cannot be predicted from clinical investigations. In Germany, SCA6 accounts for about 13% of families with ADCA. However, up to 30% of SCA6 kindreds may be misdiagnosed clinically as sporadic disease due to late manifestation in apparently healthy parents. Genetic testing is therefore recommended for the SCA6 mutation also in patients with putative sporadic ataxia.

Adult↗
PubMed1997

Effects of fluvoxamine on depression, anxiety, and other areas of general psychopathology in bulimia nervosa.

The efficacy of fluvoxamine in maintaining improvement of general psychopathology (depression, obsessive-compulsive symptoms, anxieties, interpersonal trust, and body perception) was tested in a double-blind placebo-controlled study of 72 patients with bulimia nervosa who were being treated successfully with inpatient behavioral psychotherapy. Over a period of about 15 weeks (2-3 weeks inpatient titration phase, 12 weeks outpatient relapse-prevention phase), fluvoxamine or placebo were given. The relapse-prevention design was used to avoid potential confounding effects of other concomitant treatments. Assessments concerning general psychopathology were made on the basis of expert ratings (CGI, HDRS) and self ratings (HSCL, Eating Disorders Inventory (EDI)-subscales "ineffectiveness," "perfectionism," "maturity fears," "interpersonal distrust," and "interoceptive awareness"). Fluvoxamine had significant effects in preventing relapse as measured on the basis of the Clinical Global Impression (CGI) scale "severity of illness", and a positive trend for relapse preventing effects was observed for the HSCL "general symptomatic index". Further, a relapse preventing effect was observed for the HSCL subscale "obsessive-compulsive symptoms", but not for the EDI subscale "perfectionism". Various dependent variables measuring depression showed no significant relapse-preventing effects of fluvoxamine, but only positive trends. Fluvoxamine had no relapse preventing effects according to our results for dependent variables assessing anxieties, interpersonal trust, and body perception. During a final short (4-week) off-medication phase, no statistically significant effects of discontinuation of medication, but some trends in the expected directions, were observed.

Adult↗
PubMed1996

Selegiline stimulates biosynthesis of cytokines interleukin-1 beta and interleukin-6.

Several lines of evidence indicate an immune-mediated pathophysiology of Parkinson's disease (PD) and Alzheimer's disease (AD). In clinical studies the monoamine oxidase-B inhibitor Selegiline appears to slow the progression of neurological deficits in PD and the cognitive decline in AD. The immune response to bacterial or viral infection and in chronic inflammatory processes is stimulated by an increased synthesis of the cytokines interleukin-1 beta (IL-1 beta) and subsequently interleukin-6 (IL-6). We investigated the influence of Selegiline on the synthesis of IL-1 beta and IL-6 in peripheral blood mononuclear cells (PBMC) from healthy blood donors cultured with or without Selegiline (10(-8)M, 10(-9)M or 10(-10)M) in a humidified atmosphere (7% CO2). Treatment of cultured PBMC with Selegiline significantly increased synthesis of both cytokines. The effect of Selegiline on cytokine biosynthesis may contribute to its putative neuroprotective properties.

Humans↗
PubMed1996

Fluvoxamine in prevention of relapse in bulimia nervosa: effects on eating-specific psychopathology.

In a double-blind, placebo-controlled study of 72 patients with bulimia nervosa treated successfully with inpatient psychotherapy, the efficacy of fluvoxamine in maintaining improvement was tested. Fluvoxamine and placebo, respectively, were given over a period of about 15 weeks (2-3 weeks inpatient titration phase, 12 weeks outpatient relapse-prevention [maintenance] phase). The variables assessed concerned bulimic behavior and other aspects of eating disorders, global status, depression, anxieties, obsessive-compulsive behavior, and other aspects of psychopathology. Because the dropout rate was relatively high (N = 27 [33%]) and because it was considerably higher in the fluvoxamine group (19 out of 37 subjects), analyses were performed on the intent-to-treat sample (ideally including all 72 subjects). Results of the completer sample analyses (including only those subjects who finished the study) are briefly presented for comparison. In both the intent-to-treat and the completer analyses, the following scales showed fluvoxamine to have a significant effect in reducing the return of bulimic behavior: (1) self-ratings: Eating Disorder Inventory (EDI)-bulimia, urges to binge in previous week and the number of actual binges in the previous week; (2) expert ratings: Psychiatric Status Rating Scales for Bulimia nervosa, Structured Interview for Anorexia and Bulimia nervosa (SIAB)-"total score," SIAB-subscale "fasting," and SIAB-subscale "vomiting." Two further variables (EDI-total score and SIAB-subscale "bulimia") showed the superior relapse prevention effects of fluvoxamine compared with placebo for the completer sample, while they did not reach significance for group-by-time interactions in the intent-to-treat sample. During a final, short (4-week) off-medication phase, no effect of the discontinuation of medication was observed.

Adolescent↗
PubMed1995

[Viewpoints].

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Eligibility Determination↗