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  • 1
    ISSN: 1432-0983
    Keywords: Hansenula polymorpha ; Peroxisomes ; Organelle biogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the methylotrophic yeast Hansenula polymorpha, approximately 25% of all methanol-utilization-defective (Mut-) mutants are affected in genes required for peroxisome biogenesis (PER genes). Previously, we reported that one group of per mutants, termed Pim-, are characterized by the presence of a few small peroxisomes with the bulk of peroxisomal enzymes located in the cytosol. Here, we describe a second major group of per mutants that were observed to be devoid of any peroxisome-like structure (Per-). In each Per- mutant, the peroxisomal methanol-pathway enzymes alcohol oxidase, catalase and dihydroxyacetone synthase were present and active but located in the cytosol. Together, the Pim- and Per- mutant collections involved mutations in 14 different PER genes. Two of the genes, PER5 and PER7, were represented by both dominant-negative and recessive alleles. Diploids resulting from crosses of dominant per strains and wild-type H. polymorpha were Mut- and harbored peroxisomes with abnormal morphology. This is the first report of dominant-negative mutations affecting peroxisome biogenesis.
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  • 2
    ISSN: 1432-0983
    Keywords: Key words Peroxisome biogenesis ; Methanol metabolism ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Hansenula polymorpha per6-210 mutant is impaired in respect of growth on methanol (Mut–) and is characterized by aberrant peroxisome formation. The functionally complementing DNA fragment contains two open reading frames. The first encodes dihydroxyacetone kinase (DAK), a cytosolic enzyme essential for formaldehyde assimilation; the second ORF codes for a novel protein (Pak1p). We have demonstrated that per6-210 cells lack DAK activity, causing the Mut– phenotype, and have strongly reduced levels of Pak1p, resulting in peroxisomal defects. Sequence analysis revealed that per6-210 contains a mutation in the 3′ end of the DAK coding region, which overlaps with the promoter region of PAK1. Possibly this mutation also negatively affects PAK1 expression.
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  • 3
    ISSN: 1432-0983
    Keywords: Key wordsPichia pastoris ; Peroxisome degradation ; Autophagy ; VPS15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methylotrophic yeasts contain large peroxisomes during growth on methanol. Upon exposure to excess glucose or ethanol these organelles are selectively degraded by autophagy. Here we describe the cloning of a Pichia pastoris gene (PpVPS15) involved in peroxisome degradation, which is homologous to Saccharomyces cerevisiae VPS15. In methanol-grown cells of a P. pastoris VPS15 deletion strain, the levels of peroxisomal marker enzymes remained high after addition of excess glucose or ethanol. Electron microscopic studies revealed that the organelles were not taken up by vacuoles, suggesting that PpVPS15 is required at an early stage in peroxisome degradation.
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  • 4
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Tachyarrhythmie ; Kardioverter Defibrillator ; Psychogene Triggerung ; Emotional-kognitive Faktoren ; Key words Tachyarrhythmia ; Implantable cardioverter defibrillator ; Emotional stress ; Psychic arousal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Tachyarrhytmias often occur during increased emotional arousal or mental excitation. The implantable cardioverter defibrillator (ICD) allows the exact documentation of arrhythmic episodes and their time of onset. Therefore, the type of arrhythmia can be differentiated as well as the circumstances surrounding the event. These features allow the assessment of possible psychic arrhythmogenic factors in the natural environment. We analyzed the ICD-protocols of three male patients (in ages between 60 and 68), whose devices had successfully terminated a ventricular tachycardia and compared the onset of the episodes with the patients' detailed descriptions of the corresponding life situations. The analysis of the circumstances at the time of arrhythmia-onset revealed a relationship between the occurrence of life-threatening arrhythmias in natural environment and emotional stress. The stressors could be defined as situations of increased vulnerability leading to sympathetic excitation. The induction of tachyarrhythmia was promoted in case 1 by acute psychic distress (public speaking), by the increasing panic-attack-like vicious circle of the cognitive anticipation of an unfavorable outcome (case 2), and an adverse anger reaction superimposed on persistent feelings of help- and hopelessness (case 3). These findings are in line with several experimental and epidemiological studies providing evidence for a relationship between psychic arousal and the induction of tachyarrhythmias. The knowledge of emotional and mental factors that function as a trigger for arrhythmias may lead to new therapeutic approaches in the prevention of sudden cardiac death.
    Notes: Zusammenfassung Tachyarrhythmien treten häufig während erhöhter psychischer Erregung auf. Bei Patienten, bei denen ein Kardioverter Defibrillator (ICD) implantiert wurde, lassen sich arrhythmische Episoden und deren Onset-Zeitpunkt exakt aufzeichnen und erlauben so einerseits die Differenzierung der aufgetretenen Rhythmusstörung und andererseits eine detailliertere Analyse der situativen Umstände und möglicher an der Auslösung beteiligter psychischer Komponenten. In der vorliegenden einzelfallbezogenen Studie wurden bei 3 männlichen Patienten im Alter zwischen 60 und 68 Jahren, bei denen der ICD erfolgreich eine ventrikuläre Tachykardie terminiert hatte, die ICD-Protokolle und die damit korrespondierenden Patientenaussagen analysiert. Die Analyse der akuten Onset-Bedingungen konnte ausgeprägte Zusammenhänge zwischen lebensbedrohlichen Herzrhythmusstörungen in natürlicher Umgebung und emotionalen Stressoren aufdecken. Als Stressoren wurden unterschieden eine vulnerable Situation, die eine psychogene Triggerung maligner Arrhythmien bewirkte (Fall 1); eine Panikepisoden-ähnliche Erwartungsspannung (Fall 2) sowie eine aversive Ärgerreaktion, die auf dem Boden eines andauernden Zustandes von Hilf- und Ausweglosigkeit (Fall 3) einen besonders potenten sympathiko-exzitatorischen Stimulus darstellt. Dieses Ergebnis deckt sich mit einer Reihe von laborexperimentellen und epidemiologischen Studien, die einen Zusammenhang zwischen psychischer Erregung und der Entstehung von Tachyarrhythmien belegen. Die Berücksichtigung emotional-kognitiver Faktoren bei der Arrhythmogenese könnte ein Beitrag bei der Therapie zur Prävention des plötzlichen Herztodes werden.
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  • 5
    ISSN: 1432-5241
    Keywords: Facelift ; SMAS ; Trifurcated SMAS flap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract While SMAS surgery revolutionized facelift procedures, the single flap created by conventional dissections suffers the drawback that it can only be advanced in one direction and sutured in place under uniform tension. Division of the flap into three segments overcomes this problem and allows independent pull to be applied in different directions to the upper midface, cheek, and neck.
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  • 6
    ISSN: 1432-0517
    Keywords: Key words Sampling ; Quality assessment ; Statistical modelling ; Uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  The methodology of evaluating the performance of sampling, sample preparation, and subsampling is reviewed. The requirements to be set for a successful experiment are revisited. The central role of the reference method is explained, and so is the choice of the parameters and the measurement methods. Based on the principles of the "Guide to the expression of uncertainty in measurement" (GUM), a statistical model is developed that demonstrates the influence of the experimental design on the outcome of the assessment experiment. This relationship is often overlooked in practice, as it is hardly mentioned in written standards dealing with this kind of quality assessments. The statistical framework thus developed covers the statistical procedures commonly appearing in written standards. Finally, the issue of testing the significance of the bias obtained from the experiment is discussed.
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  • 7
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Three fermentable substances, glucose, 1,2-ethanediol and 1,2-propanediol were checked as cosubstrates for the fermentation of glycerol by Clostridium butyricum and Citrobacter freundii with the aim of achieving a complete conversion of glycerol to 1,3-propanediol. Glucose was fermented by C. butyricum mainly to acetate, CO2 and reducing equivalents in the presence of glycerol and contributed markedly to the 1,3-propanediol yield. However, because of relatively slow growth on glucose, complete conversion was not achieved. If the two glycols were used as cosubstrates for glycerol fermentation, the 1,3-propanediol yield did not increase but dimished considerably, as they were converted to more reduced products, i.e. alcohols instead of acids. From 1,2-propanediol 2-propanol was formed in addition to 1-propanol. The ratio of the propanols was dependent on the culture conditions.
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  • 8
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Three fermentable substances, glucose, 1,2-ethanediol and 1,2-propanediol were checked as cosubstrates for the fermentation of glycerol by Clostridium butyricum and Citrobacter freundii with the aim of achieving a complete conversion of glycerol to 1,3-propanediol. Glucose was fermented by C. butyricum mainly to acetate, CO2 and reducing equivalents in the presence of glycerol and contributed markedly to the 1,3-propanediol yield. However, because of relatively slow growth on glucose, complete conversion was not achieved. If the two glycols were used as cosubstrates for glycerol fermentaton, the 1,3-propanediol yield did not increase but dimished considerably, as they were converted to more reduced products, i.e. alcohols instead of acids. From 1,2-propanediol 2-propanol was formed in addition to 1-propanol. The ratio of the propanols was dependent on the culture conditions.
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  • 9
    ISSN: 1432-072X
    Keywords: Key wordsAspergillus nidulans ; Peroxisomes ; Peroxisome biogenesis ; PTS1 ; PTS2 ; Glyoxylate ; cycle ; Microbodies ; Isocitrate lyase ; Malate synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In previous work, we have demonstrated that oleate induces a massive proliferation of microbodies (peroxisomes) in Aspergillus nidulans. Although at a lower level, proliferation of peroxisomes also occurrs in cells growing under conditions that induce penicillin biosynthesis. Here, microbodies in oleate-grown A. nidulans cells were characterized by using several antibodies that recognize peroxisomal enzymes and peroxins in a broad spectrum of eukaryotic organisms such as yeast, and plant, and mammalian cells. Peroxisomes were immunolabeled by anti-SKL and anti-thiolase antibodies, which suggests that A. nidulans conserves both PTS1 and PTS2 import mechanisms. Isocitrate lyase and malate synthase, the two key enzymes of the glyoxylate cycle, were also localized in these organelles. In contrast to reports of Neurospora crassa, our results demonstrate that A. nidulans contains only one type of microbody (peroxisomes) that carry out the glyoxylate cycle and contain 3-ketoacyl-CoA thiolase and proteins with the C-terminal SKL tripeptide.
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  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Observations of impact sites were conducted at the Institut de Radio Astronomic Millimetrique (IRAM) 30-m telescope at Pico Veleta, Spain, on 17-28 July 1994. We searched for rotational lines of several molecular and ionic species that could plausibly be injected into, or generated in, ...
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