Taxonomic relations between archaebacteria including 6 novel genera examined by cross hybridization of DNAs and 16S rRNAs

DNAs from 16 species of archaebacteria including 6 novel isolates were hybridized with 16S rRNAs from 7 species representing different orders or groups of the urkingdom of archaebacteria. The yields, normalized for the number of genes per microgram of DNA, and the temperature stabilities of all hybrids were determined and related to each other. A taxonomic tree constructed from such fractional stability data reveals the same major divisions as that derived from comparative cataloging of 16S rRNA sequences. The extreme halophiles appear however as a distinct order besides the three known divisions of methanogens. The methanogens, the halophiles and Thermoplasma form one of two clearly recognizable branches of the archaebacterial urkingdom. The order represented by Sulfolobus and the related novel order Thermoproteales form the other branch. Three novel genera, Thermoproteus, Desulfurococcus and the "stiff filaments" represent three families of this order. The extremely thermophilic methanogen Methanothermus fervidus belongs to the Methanobacteriales. SN1, a methanogen from Italy, appears as another species of the genus Methanococcus. Another novel methanogen, M3, represents a genus or family of the order Methanomicrobiales.     

Human impact diminishes seedling species richness in Kakamega Forest, Kenya

Anthropogenic forest fragmentation and other kinds of human disturbance, such as selective logging, can reduce the diversity of plant and animal species. To evaluate the impact of fragmentation and small-scale disturbance on forest regeneration, we assessed species richness and total abundance of adult trees in comparison with seedlings in the heavily fragmented and disturbed Kakamega Forest, western Kenya. In nine differently disturbed 1-ha study blocks distributed across the main forest and fragments, we mapped all trees >10 cm in diameter at breast height. Additionally, we established ninety 1-m² seedling plots within these 1-ha study blocks which were monitored over 2.5 years. We recorded altogether 74 species of adult trees (30–43 per block) and 64 seedling species (24–41 per block). Neither fragmentation nor small-scale disturbance had an impact on adult tree species richness or total tree abundance. Yet, fragmentation and especially small-scale disturbance significantly reduced seedling species richness, particularly of late-successional species. While human impact did not affect diversity of adults, the impoverished species richness of seedlings suggests a reduced potential for regeneration and a loss of tree diversity in the long-term.     

Ergänzende Untersuchungen zur Ultrastruktur von Trichoplax adhaerens F.E. Schulze (Placozoa)

Zusammenfassung 1. Die Zellen des Ventralepithels bilden keine Mikrovilli, sondern ein schwammartiges Maschenwerk gefensterter Leisten und Falten, welches bei der Haftung des Tieres an der Unterlage und/oder bei der extrasomatischen Vorverdauung der Nahrung eine Rolle spielen dürfte.2. Während der Zellteilungen treten typische Centriole an den Spindelpolen auf.3. Die wachsenden Eizellen phagocytieren Fortsätze der Faserzellen, die als Trophocyten fungieren.4. Unter den gleichen Bedingungen, die zur Eibildung führen, können sogen. S-Zellen auftreten. Einige ultrastrukturelle Befunde sprechen dafür, daß es sich um Spermien handelt.

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Additional investigations on the ultrastructure of Trichoplax adhaerens F.E. Schulze (Placozoa)

Summary 1. The cells of the ventral epithelium form no microvilli but a spongy meshwork of fenestrated ledges and folds which may play a rôle in the adhesion of the animal to the substratum and/or in the extrasomatic predigestion of the food. 2. During cell division typical centrioles occur at the spindle poles. 3. The growing egg cells phagocytize projections of the fiber cells which function as trophocytes. 4. Under the same conditions leading to egg formation so-called S-cells may occur. Some ultrastructural data suggest that they are sperm cells.

     

Enzymatic ethylene formation from 1-aminocyclopropane-1-carboxylic acid by manganese,a protein fraction and a cofactor of etiolated pea shoots

The cofactor of enzymatic, 1-aminocyclopropane-1-carboxylic acid dependent ethylene formation was concentrated on cation exchange columns. When chelators of cations were added to the homogenates, cofactor activity was lost. Cofactor fractions were partly resistant to oxidation at 600° C. Mn²⁺ substituted for the cofactor in ethylene formation from 1-aminocyclopropane-1-carboxylic acid by a protein fraction isolated from etiolated pea shoots. In addition, Mn²⁺ enhanced the stimulatory effect of the concentrated cofactor. The elution volume for the cofactor on a Sephadex G-25 column was lower than that of MnCl₂. In paper electrophoresis the cofactor migrated to the cathode at pH 10.8 and 2.2. The R_F of cofactor on cellulose plates developed in butanol: acetic acid: H₂O was 0.4. After cellulose chromatography, cofactor activity had to be reconstituted by the addition of MnCl₂. Chelators, anti-oxidants, and catalase were inhibitors of Mn²⁺-cofactor-dependent ethylene formation. The protein necessary for 1-aminocyclopropane-1-carboxylic acid dependent ethylene formation in vitro was seperated from 95–98% of the total protein in homogenates by DE-52 cellulose chromatography and (NH₄)₂SO₄-fractionation.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - EDTA ethylenediaminetetraacetic acid - DDTC diethyldithiocarbamate     

Regulation of intracellular phosphatidylinositol-4-phosphate by the Sac1 lipid phosphatase

Phosphatidylinositol 4-phosphate (PtdIns(4)P) regulates diverse cellular processes, such as actin cytoskeletal organization, Golgi trafficking and vacuolar biogenesis. Synthesis and turnover of PtdIns(4)P is mediated by a set of specific lipid kinases and phosphatases. Here we show that the polyphosphoinositide phosphatase Sac1p has a central role in compartment-specific regulation of PtdIns(4)P. We have found that sac1Delta mutants show pleiotropic, synthetically lethal interactions with mutations in genes required for vacuolar protein sorting (Vps). Disruption of the SAC1 gene also caused a defect in the late endocytic pathway. These trafficking phenotypes correlated with a dramatic accumulation of PtdIns(4)P at vacuolar membranes. In addition, sac1 mutants displayed elevated endoplasmic reticulum PtdIns(4)P. The accumulation of PtdIns(4)P at the endoplasmic reticulum and vacuole and the endocytic defect could be compensated by mutations in the PtdIns 4-kinase Stt4p. Our results indicate that elimination of Sac1p causes accumulation of a Stt4p-specific PtdIns(4)P pool at internal membranes which impairs late endocytic and vacuolar trafficking. We conclude that Sac1p functions in confining PtdIns(4)P-dependent processes to specific intracellular membranes.     

Lack of orthogonal particle assemblies and presence of tight junctions in astrocytes of the goldfish (Carassius auratus)

Summary Specific antibodies raised against a human 28 000 dalton cerebellar calcium-binding protein (CaBP) were used in an immunocytochemical study during development of the rat cerebellum. Both light and electron microscopy showed (1) that labelling was entirely restricted to the Purkinje cells, (2) that it appeared very early in Purkinje cell development, (3) that the entire cell was labelled from the tip of the smallest dendrites to the axonal terminals, and (4) that with increasing age, the immunoreaction appeared to be progressively restricted to the cell and organelle membranes.     

Die Muskulatur des Eileiters von Carausius morosus

Zusammenfassung An lebenden Muskelfasern aus dem Eileiter von Carausius morosus wurden die Veränderungen der A- und I-Zonen im Verlauf spontaner Kontraktionen beobachtet. Die A-Zone verkürzt sich in den Fasern, deren Sarkomerenlänge bei voiler Kontraktion gleich groß oder kürzer als die ruhende A-Zone wird. In kontrahierten A-Zonen treten keine Kontraktionsbanden auf. Auch extrem kontrahierte Sarkomeren zeigen noch eine schmale I-Zone. In manchen Fasern verkürzt sich während einer Kontraktionswelle die A-Zone nicht, sondern nur die I-Zone.

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Summary The appearance of living muscle fibres from the oviduct of Carausius morosus was observed with the polarizing microscope as it changes during spontaneous contractions. In many fibres the A-bands shorten. In these cases, the contracted sarcomeres are found to be as long as, or shorter than the length of resting A-bands. The A-bands look always homogeneous, no contraction bands are observed when they shorten. In fully contracted sarcomeres, the I-bands become narrow but they do not disappear. In many fibres, the A-bands remain constant, and only the I-bands shorten during contractions.

     

Über die Wirkung von Digitalis und anderen Glykosiden auf die Keimung und das Wachstum von Pflanzen

Zusammenfassung Entgegen der Behauptung vonFahrenkamp ergibt eine fehlerstatistisch gesicherte Untersuchung bei keiner Konzentration herzwirksamer Glykoside eine Förderung der Samenquellung, der Keimung, der Katalaseaktivität, des Keimwurzelwachstums und des Ernteertrags von Kulturpflanzen. Das gilt sowohl für die nachFahrenkamp in den Handel gebrachten Viviflor-Präparate, wie fürDigitalis-, Adonis-, Scilla- undConvallaria-Tinkturen,Digitalis-Preßsaft und wäßrige Lösungen von Digitalin und Digitonin. Die bei höheren Konzentrationen auftretenden Hemmungswirkungen gehen auf den Alkoholgehalt der Viviflorpräparate und Tinkturen zurück. Diese Schädigung nimmt mit steigender Temperatur ab; sie beruht nicht auf einer entquellenden Wirkung und auch nicht auf einer Hemmung der Katalaseaktivität, da diese Erscheinungen erst bei viel höheren Konzentrationen auftreten als die Wachstumsschädigungen. Die Schädigung durch wäßrige Digitoninlösung höherer Konzentration nimmt entgegengesetzt der Alkoholschädigung mit steigender Temperatur zu. Auch diese Wirkung geht nicht über die Quellung oder Katalaseaktivität. Abschließend ergibt sich, daß keinerlei Aussicht besteht, auf dem vonFahrenkamp vorgeschlagenen Weg einer Glykosidbehandlung eine Erntesteigerung zu erzielen.Mit 9 Abbildungen.Auszug aus meiner Dissertation: Kritische Untersuchungen über die vonFahrenkamp angegebene Methode einer Wachstumsbeschleunigung und Ernteerhöhung durchDigitalis und verwandte Glykoside, Darmstadt 1945. Den Herrn Professoren Dr.O. Stocker und Dr.L. Schmitt, welche die Arbeit angeregt und in ihren Instituten Betreut haben, bin ich zu großem Dank verpflichtet.