Molecular mechanisms of hormone controlled gene expression in the breast

In a meritorious effort H. de Rothschild compiled in 1899 all publications on mammary gland development and milk – a grand total of 8375 [1]. In the preface to this publication Duclaux states: ‘Such a discrepancy between the tremendous efforts and the paltriness of the results – hundreds of scientists and thousands of research years, just to create 200 or 300 pages of truth’. The number of papers added since then must be enormous. Rather than reviewing a vast literature, I will take the liberty and focus on research which, in my opinion, shaped our understanding of hormone controlled gene expression in the developing breast. This revised version was published online in August 2006 with corrections to the Cover Date.     

Jasmonic acid spraying does not induce tuberisation in short-day-requiring potato species kept in non-inducing conditions

The potato species Solanum andigena (Juz. and Buk.) and Solanum demissum (Lindl.) that both require short days for tuberisation were kept in either long days (16 h light), or short days (8 h light) with a 30-min night break mid-way through the dark period. Tuberisation of these species was inhibited under both conditions. Repeated spraying of these plants with up to 100 μM jasmonic acid did not induce them to tuberise even though jasmonic acid was shown to be taken up and transported within the plant. This result argues against jasmonic acid itself being the transported tuber-inducing signal, although it does not exclude a role for jasmonic acid later in tuber formation and development once induction has taken place.     

Isolation and characterization of two cDNA clones encoding ATP-sulfurylases from potato by complementation of a yeast mutant

Sulfur plays an important role in plants, being used for the biosynthesis of amino acids, sulfolipids and secondary metabolites. After uptake sulfate is activated and subsequently reduced to sulfide or serves as donor for sulfurylation reactions. The first step in the activation of sulfate in all cases studied so far is catalyzed by the enzyme ATP-sulfurylase (E.C. 2.7.7.4.) which catalyzes the formation of adenosine-5′-phosphosulfate (APS). Two cDNA clones from potato encoding ATP-sulfurylases were identified following transformation of a Saccharomyces cerevisiae mutant deficient in ATP-sulfurylase activity with a cDNA library from potato source leaf poly(A)⁺ RNA cloned in a yeast expression vector. Several transformants were able to grow on a medium with sulfate as the only sulfur source, this ability being strictly linked to the presence of two classes of cDNAs. The clones StMet3-1 and StMet3-2 were further analyzed. DNA analysis revealed an open reading frame encoding a protein with a molecular mass of 48 kDa in the case of StMet3-1 and 52 kDa for StMet3-2. The deduced polypeptides are 88% identical at the amino acid level. The clone StMet3-2 has a 48 amino acid N-terminal extension which shows common features of a chloroplast transit peptide. Sequence comparison of the ATP-sulfurylase Met3 from Saccharomyces cerevisiae with the cDNA StMet3-1 (StMet3-2) reveals 31% (30%) identity at the amino acid level. Protein extracts from the yeast mutant transformed with the clone StMet3-1 displayed ATP-sulfurylase activity. RNA blot analysis demonstrated the expression of both genes in potato leaves, root and stem, but not in tubers. To the best of the authors' knowledge this is the first cloning and identification of genes involved in the reductive sulfate assimilation pathway from higher plants.     

Riesenkerne im Endosperm vonAllium ursinum

Zusammenfassung In der chalazalen Region des Endosperms vonAllium ursinum entstehen Riesenkerne, die eine besondere permanent-prophasische Struktur besitzen und während ihres Wachstums polyploid, und zwar zunächst offenbar hexaploid und 12-ploid werden. Sie entwickeln sich völlig kontinuierlich, also ohne zwischengeschaltete Mitosen oder Interphasen, aus triploiden Kernen des jungen Endosperms, die selbst stark vergrößert sind. In alten Embryosäcken treten auch Riesenkerne auf, die mit größter Wahrscheinlichkeit als 24-ploid anzusprechen sind.Die Polyploidisierung der Riesenkerne entspricht nicht dem für Angiospermen typischen endomitotischen Formwechsel. Sie ist wohl als besonders extreme Hemmung und Umbildung von Mitosen aufzufassen, die eine Eigentümlichkeit des Endosperms darstellt.Die 12-ploiden Riesenkerne besitzen gegenüber diploiden Kernen des äußeren Integuments ungefähr das 100fache Volumen, gegenüber den vermutlich oktoploiden Kernen des Wassergewebes der Samenanlagen ungefähr das 20–30fache, gegenüber den triploiden Kernen des jungen Endosperms das 4–7fache Volumen. Die bedeutende Größe der triploiden Kerne des jungen Endosperms —später werden die Kerne sukzessive kleiner —beruht auf gesteigerter Chromosomengröße (die Chromosomen sind etwa 3 1/2 mal voluminöser als in anderen Mitosen) und auf Vermehrung extrachromosomaler Substanz.Die Kerne des Wassergewebes und des gewöhnlichen Endosperms besitzen gewebespezifische Struktur; die Riesenkerne des physiologisch hoch aktiven Basalapparates sind besonders auffallend gewebespezifisch organisiert: sie enthalten in prophasischer Ausbildung Diplo-, bzw. Quadruplound vermutlich Oktuplochromosomen.Als gelegentliche Beobachtungen an nichtchalazalen Regionen des Endosperms seien erwähnt: das Auftreten von Spindeln, die an einem Pol einen, am anderen Pol zwei Tochterzellen ergeben; das Vorkommen häufiger Mitosestörungen in späteren Stadien und wohl damit im Zusammenhang die Bildung hexaploider und wohl 12-ploider Endosperm-kerne, die weitere Mitosen einzugehen vermögen.     

Lebendbeobachtung der Chromatophorenteilung der DiatomeeNitzschia

Continuous intra vitam observations inNitzschia palea and supplementary ones in two otherN.-species show that the division of the platelike chromatophore is intimately connected with mitosis and cytokinesis. It starts and goes on in a strictly regular course. When the ingrowing plasmatic zone of cytokinetic separation reaches the distal edge of each chromatophore, a narrow split originates and deepens until it has reached the middle of the chromatophore or a little more. Only then a second split arises at the proximal edge of the chromatophore; from there it grows in inverse direction, until it meets the first formed split in a distance of about one third from the proximal end of the chromatophore. Under normal circumstances the position of the meeting point is nearly invariable, the speed of the two progressing splits is the same, and the splitting of the two chromatophores of one cell is nearly exactly synchronized. There is only little variation in the beginning, as the split can form in somewhat different ways. Thereby a striking plasticity of the chromatophore is apparent. The cytokinesis including chromatophore division lasts about 4 1/2–5 minutes. Until now the mode of chromatophore division inNitzschia remains without analogy.     

Das Sediment des Kummerower Sees. Untersuchungen des Chemismus und der Diatomeenflora

The Sediment of Lake Kummerow. Investigations on the Chemism and the Diatom Flora The paper deals with the distribution of chemical parameters and of diatoms in the deposits of the eutrophic Lake Kummerow (GDR), produced during about the last 3500 years. The sediment consists of a calcareous gyttja with a very low content of sand and clay. The results indicate a relatively constant trophic state of the lake in former times and an increased production within the last five centuries. Stephanodiscus astraea and its variety minutula is by far the most constant diatom species; in the uppermost parts of the sediment small sized planctonic taxa are increasing, in the main Stephanodiscus hantzschii var. pusillus, Melosira granulata var. angustissima, Asterionella formosa and Synedra acus var. angustissima and var. radians.     

New Colors for Histology: Optimized Bivariate Color Maps Increase Perceptual Contrast in Histological Images

Background

Accurate evaluation of immunostained histological images is required for reproducible research in many different areas and forms the basis of many clinical decisions. The quality and efficiency of histopathological evaluation is limited by the information content of a histological image, which is primarily encoded as perceivable contrast differences between objects in the image. However, the colors of chromogen and counterstain used for histological samples are not always optimally distinguishable, even under optimal conditions.

Methods and Results

In this study, we present a method to extract the bivariate color map inherent in a given histological image and to retrospectively optimize this color map. We use a novel, unsupervised approach based on color deconvolution and principal component analysis to show that the commonly used blue and brown color hues in Hematoxylin—3,3’-Diaminobenzidine (DAB) images are poorly suited for human observers. We then demonstrate that it is possible to construct improved color maps according to objective criteria and that these color maps can be used to digitally re-stain histological images.

Validation

To validate whether this procedure improves distinguishability of objects and background in histological images, we re-stain phantom images and N = 596 large histological images of immunostained samples of human solid tumors. We show that perceptual contrast is improved by a factor of 2.56 in phantom images and up to a factor of 2.17 in sets of histological tumor images.

Context

Thus, we provide an objective and reliable approach to measure object distinguishability in a given histological image and to maximize visual information available to a human observer. This method could easily be incorporated in digital pathology image viewing systems to improve accuracy and efficiency in research and diagnostics.     

Zur Kenntnis der OscillatoriaceePseudanabaena galeata (Cyanophyta)

If exsiccated trichomes ofPseudanabaena galeata are immersed in water, striking changes occur as a consequence of lysis and maceration. The locomotion of living trichomes differs from that inOscillatoriaceae. This and other differences make it doubtful, whetherPs. galeata belongs to theOscillatoriaceae; at any rate it occupies an aberrant position.

     

Analysis of the proteome of Pseudomonas putida KT2440 grown on different sources of carbon and energy

Using 2D electrophoresis the protein expression pattern during growth on carbon sources with different impact on carbon catabolite repression of phenol degradation was analysed in a derivative of Pseudomonas putida KT2440. The cytosolic protein pattern of cells growing on phenol or the non-repressive substrate pyruvate was almost identical, but showed significant differences to that of cells growing with the repressive substrates succinate or glucose. Proteins, which were mainly expressed in the presence of phenol or pyruvate, could be assigned to the functional groups of transport, detoxification, stress response, amino acid, energy, carbohydrate and nucleotide metabolism. The addition of succinate to cells growing with phenol ('shift-up') resulted in the inhibition of the synthesis of these proteins. Proteins with enhanced expression at growth with succinate or glucose were proteins for de novo synthesis of nucleotides, amino acids and enzymes of the TCA cycle. The synthesis of proteins, necessary for phenol catabolism was regulated in different manners following the addition of succinate. Whereas the synthesis of Phl-proteins (subunits of the phenolhydroxylase) only decreased slowly, was the translation of the Cat-proteins (catechol 1,2-dioxygenase, cis,cis-muconate cycloisomerase and muconolactone isomerase) repressed immediately and the synthesis of the Pca-proteins (beta-ketoadipate enolactone hydrolase, beta-ketoadipate succinyl-CoA transferase and beta-ketoadipyl CoA thiolase) remained unaffected.     

The C-terminal domain of the Arabinosyltransferase Mycobacterium tuberculosis EmbC is a lectin-like carbohydrate binding module

The D-arabinan-containing polymers arabinogalactan (AG) and lipoarabinomannan (LAM) are essential components of the unique cell envelope of the pathogen Mycobacterium tuberculosis. Biosynthesis of AG and LAM involves a series of membrane-embedded arabinofuranosyl (Araf) transferases whose structures are largely uncharacterised, despite the fact that several of them are pharmacological targets of ethambutol, a frontline drug in tuberculosis therapy. Herein, we present the crystal structure of the C-terminal hydrophilic domain of the ethambutol-sensitive Araf transferase M. tuberculosis EmbC, which is essential for LAM synthesis. The structure of the C-terminal domain of EmbC (EmbC(CT)) encompasses two sub-domains of different folds, of which subdomain II shows distinct similarity to lectin-like carbohydrate-binding modules (CBM). Co-crystallisation with a cell wall-derived di-arabinoside acceptor analogue and structural comparison with ligand-bound CBMs suggest that EmbC(CT) contains two separate carbohydrate binding sites, associated with subdomains I and II, respectively. Single-residue substitution of conserved tryptophan residues (Trp868, Trp985) at these respective sites inhibited EmbC-catalysed extension of LAM. The same substitutions differentially abrogated binding of di- and penta-arabinofuranoside acceptor analogues to EmbC(CT), linking the loss of activity to compromised acceptor substrate binding, indicating the presence of two separate carbohydrate binding sites, and demonstrating that subdomain II indeed functions as a carbohydrate-binding module. This work provides the first step towards unravelling the structure and function of a GT-C-type glycosyltransferase that is essential in M. tuberculosis.