Derivative chromosomal structures from a ring chromosome 4

Summary This report describes the results from cultured lymphocytes studied at metaphase, anaphase, and interphase from an individual with a ring chromosome 4. A ring was present in 90.1% of metaphases. Special attention was directed towards the occurrence of derivative chromosomal structures, such as partially duplicated and triplicated rings, tricentric rings, chains of 3 interlocked rings, rod-shaped chromosomes, pulverized rings, and others.The clinical features of the individual (small stature and impaired mental development, hypoplastic thumbs, ptosis palpebrae hypoplastic external male genitalia, abnormal dermatoglyphic pattern) did not conform to a specific phenotype.

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Zusammenfassung Die Lymphocyten eines Patienten mit Ringchromosom 4 wurden in der Meta-, Ana-und Interphase beobachtet. 90,1% der Metaphasen wiesen einen Ring auf. Besondere Aufmerksamkeit wurde abnormen, aus dem Ring entstandenen Chromosomen zugewandt. Es fanden sich u. a.: partielle Doppel-und Dreifachringe, Ringe mit 3 Zentromeren, Ringe aus 3 miteinander verketteten Ringen, stabförmige Chromosomen und pulverisierte Ringe.Die Symptome des Patienten (Minderwuchs, Schwachsinn, Hypoplasie der Daumen, Ptosis palpebrae, Hypoplasie des äußeren genitale, abnorme Dermatoglyphen) waren zum größten Teil unspezifish.

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This work was supported in part by grants from the Deutsche Forschungsgemeinschaft and is part of a thesis by R.N. for a medical doctorate.     

Ein Modell zur örtlich-zeitlichen Signalübertragung im visuellen System des Menschen auf der Basis der linearen Systemtheorie kontinuierlicher Medien

Zusammenfassung Als Modell für die Übertragung örtlich-zeitlich variabler Helligkeitsmuster durch das visuelle System des Menschen wird ein dreidimensionales, homogenes neuronales Geflecht betrachtet. Die Ausbreitung der neuronalen Erregung erfolgt anisotrop in afferenter und lateraler Richtung und wird durch eine modifizierte Wärmeleitungsgleichung beschrieben, deren Hauptmerkmal ein regenrativer Signalanteil ist. Die zeitabhängige Lösung beschreibt u.a. die zeitliche Übertragungscharakteristik für flimmernde Gitter im gesamten Frequenzbereich. Die stationäre Lösung beschreibt die örtliche Übertragungscharakteristik für Gitter, wobei auch die Struktur rezeptiver Felder mit inhibitorischem Umfeld deutlich erkennbar ist. Die Struktur der Lösung läßt verstehen, wie sich mit zunehmender Tiefe im neuronalen Geflecht der Übergang von der Ortsselektivität zur Ortsfrequenzselektivität vollzieht.

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A model for the spatial-temporal signal transmission properties of the human visual system based on the linear system theory of continuous media

In this paper, a three dimensional homogeneous neural web serves as a model for the transmission of spatial-temporal luminous pattern by the human visual system. The propagation of neuronal excitation in afferent and lateral direction is assumed to be anisotropic. It is described by a modified heat conduction equation a main feature of which is a regenerative signal component. The time-dependent solution describes f.e. the temporal transmission characteristics for flickering grids in the whole frequency range. The stationary solution contains the spatial transmission characteristics for grids as well as the structure of receptive fields with inhibitory surrounds. The structure of the solution makes it under-standable how the transition from spatial selectivity to spatial-frequency-selectivity develops with growing depth of the neuronal web.

     

Micropilot: automation of fluorescence microscopy-based imaging for systems biology

Quantitative microscopy relies on imaging of large cell numbers but is often hampered by time-consuming manual selection of specific cells. The 'Micropilot' software automatically detects cells of interest and launches complex imaging experiments including three-dimensional multicolor time-lapse or fluorescence recovery after photobleaching in live cells. In three independent experimental setups this allowed us to statistically analyze biological processes in detail and is thus a powerful tool for systems biology.     

Quantitative calcium measurements in subcellular compartments of Plasmodium falciparum-infected erythrocytes

The acidic food vacuole exerts several important functions during intraerythrocytic development of the human malarial parasite Plasmodium falciparum. Hemoglobin taken up from the host erythrocyte is degraded in the food vacuole, and the heme liberated during this process is crystallized to inert hemozoin. Several anti-malarial drugs target food vacuolar pathways, such as hemoglobin degradation and heme crystallization. Resistance and sensitization to some antimalarials is associated with mutations in food vacuolar membrane proteins. Other studies suggest a role of the food vacuole in ion homeostasis, and release of Ca2+ from the food vacuole may mediate adopted physiological responses. To investigate whether the food vacuole is an intracellular Ca2+ store, which in turn may affect other physiological functions in which this organelle partakes, we have investigated total and exchangeable Ca2+ within the parasite's food vacuole using x-ray microanalysis and quantitative confocal live cell Ca2+ imaging. Apparent free Ca2+ concentrations of approximately 90, approximately 350, and approximately 400 nM were found in the host erythrocyte cytosol, the parasite cytoplasm, and the food vacuole, respectively. In our efforts to determine free intracellular Ca2+ concentrations, we evaluated several Ca2+-sensitive fluorochromes in a live cell confocal setting. We found that the ratiometric Ca2+ indicator Fura-Red provides reliable determinations, whereas measurements using the frequently used Fluo-4 are compromised due to problems arising from phototoxicity, photobleaching, and the strong pH dependence of the dye. Our data suggest that the food vacuole contains only moderate amounts of Ca2+, disfavoring a role as a major intracellular Ca2+ store.     

Oxidation of glycerol,lactate, and propionate by Propionibacterium freudenreichii in a poised-potential amperometric culture system

Growth of Propionibacterium freudenreichii was studied with glycerol, lactate, and propionate as energy sources and a three-electrode poised-potential amperometric electrode system with hexacyanoferrate (III) as mediator. In batch culture experiments with glycerol and lactate as substrates, hexacyanoferrate (III) was completely reduced. Growth yields increased and the fermentation patterns were shifted towards higher acetate formation with increasing hexacyanoferrate (III) concentrations (0.25–8.0 mM). In experiments with regulated electrodes, glycerol, lactate, and propionate were oxidized to acetate and CO₂, and the electrons were quantitatively transferred to the working electrode. Growth yields of 29.0, 13.4 and 14.2 g cell material per mol were calculated, respectively. The high cell yield obtained during propionate oxidation cannot be explained solely by substrate level phosphorylation indicating that additional energy was conserved via electron transport phosphorylation. Furthermore, this result indicated complete reversibility of the methyl-malonyl-CoA pathway in propionic acid bacteria.     

Graph-based iterative Group Analysis enhances microarray interpretation

Background  

One of the most time-consuming tasks after performing a gene expression experiment is the biological interpretation of the results by identifying physiologically important associations between the differentially expressed genes. A large part of the relevant functional evidence can be represented in the form of graphs, e.g. metabolic and signaling pathways, protein interaction maps, shared GeneOntology annotations, or literature co-citation relations. Such graphs are easily constructed from available genome annotation data. The problem of biological interpretation can then be described as identifying the subgraphs showing the most significant patterns of gene expression. We applied a graph-based extension of our iterative Group Analysis (iGA) approach to obtain a statistically rigorous identification of the subgraphs of interest in any evidence graph.     

Isolation and partial characterization of basic proteinases from stem bromelain

Crude bromelain extracts from pineapple stems (Ananas comosus) were fractionated by two-step FPLC-cation-exchange chromatography. At least eight basic proteolytically active components were detected. The two main components F4 and F5 together with the most active proteinase fraction F9 were characterized by SDS-PAGE, mass spectroscopy, multizonal cathodal electrophoresis, partial amino acid sequence, and monosaccharide composition analysis. F9 amounts to about 2% of the total protein and has a 15 times higher specific activity against the substratel-pyroglutamyl-l-phenylanalyl-l-leucine-p-nitroanilide (PFLNA) than the main component F4. The molecular masses of F4, F5, and F9 were determined to 24,397, 24,472, and 23,427, respectively, by mass spectroscopy. Partial N-terminal amino acid sequence analysis (20 amino acids) revealed that F9 differs from the determined sequence of F4 and F5 by an exchange at position 10 (tyrosineserine) and position 20 (asparagine glycine). F4 and F5 contained fucose, N-acetylglucosamine, xylose, and mannose in ratio of 1.02.01.02.0, but only 50% of the proteins seem to be glycosylated, whereas F9 was found to be unglycosylated. Polyclonal antibodies (IgG) against F9 detected F4 and F5 with tenfold reduced reactivity. ThepH optimum of F4 and F5 was betweenpH4.0 and 4.5 and for F9 close to neutralpH. The kinetic parameters for PFLNA hydrolysis were similar for F4 (K _m 2.30 mM,k _cat 0.87 sec^–1 and F5 (K _m 2.42 mM,k _cat 0.68 sec^–1), and differed greatly from F9 (K _m 0.40 mM,k _cat 3.94 sec^–1).Dedicated to H. Tschesche, Bielefeld, Germany, on behalf of his 60th anniversary.