Metabolic products of microorganisms. 192. The anthraquinones of the Aspergillus glaucus group. II. Biological activity

From the mycelia of Aspergillus cristatus the following anthraquionic pigments were isolated: catenarin, emodin, erythroglaucin, rubrocristin, physcion, physcion-9-anthrone, questin, viocristin, and isoviocristin. The latter two do not belong to the 9, 10-anthraquinone series but to the 1,4-anthraquinones, and so far they have not been reported among naturally occurring quinones.Emodin, catenarin, viocristin, and isoviocristin snowed antibacterial activity with minimal inhibitory concentrations ranging from 1–10 g/ml. In Bacillus brevis catenarin and emodin inhibited the incorporation of uracil and leucine preferentially. At higher concentrations the incorporation of thymidine into the trichloroacetic acid-precipitable fraction of cells was also affected. In the presence of viocristin or isoviocristin all three macromolecular syntheses came to a halt. Rubrocristin, erythroglaucin, and physcion showed no significant inhibitory effects.In Ehrlich ascites carcinoma cells catenarin, emodin, and viocristin inhibited the incorporation of uridine and thymidine. The incorporation of leucine was hardly affected.In vitro, inhibition of DNA-dependent RNA polymerase from Escherichia coli by catenarin and to a lesser extent by emodin was observed, whereas rubrocristin (catenarin-8-methyl ether), physcion, and erythroglaucin were not active.Abbreviations MIC minimal inhibitory concentration - TCA trichloroacetic acid - ECA Ehrlich ascites carcinoma Metabolic Products of Microorganisms. 191. W. Keller-Schierlein und B. Joos; Über das 4-Oxohomotyrosin, ein Abbauprodukt des Echinocandins. Helv. Chim. Acta (in press)     

Vertical distribution and cyst production of Peridiniella catenata (Dinophyceae) during a spring bloom in the Baltic Sea

Vertical distribution and cyst production of the chain-forming,spring dinoflagellate Peridiniella catenata were studied throughoutthe spring season of 2000 in the coastal Gulf of Finland. Numbersof cells were monitored in the water column, and cyst sedimentationwas recorded using multiple sediment traps moored at three discretedepths. At the onset of the spring bloom, most of the populationwas situated in the euphotic zone. When the bloom progressed,the population was more evenly dispersed throughout the watercolumn. Coinciding with the decline of the spring bloom, afternitrogen depletion, a general reduction of cell size of P. catenataand a break-up of chains were observed. Resting cysts startedto appear shortly after the peak of the bloom, in sedimentationtraps moored at 30 and 40 m depth. Cysts were only retrievedfrom the uppermost sediment trap on three of the six samplingoccasions, constituting only a small proportion of all cystsproduced by P. catenata during spring. Our results suggest thatcyst production of this vertically migrating organism takesplace to a large extent in deep water layers and emphasizesthe necessity of whole water column monitoring in studies aimingto understand in situ life-cycle transformations of verticallymigrating dinoflagellates.     

Morphology of the prothoracic discs and associated sensilla of Acanthocnemus nigricans (Coleoptera, Acanthocnemidae)

The Australian ‘little ash beetle’ Acanthocnemus nigricans (Coleoptera, Cleroidea, Acanthocnemidae) is attracted by forest fires. A. nigricans has one pair of unique prothoracic sensory organs and it has been speculated that these organs may play a role in fire detection. Each organ consists of a cuticular disc, which is fixed over an air-filled cavity. On the outer surface of the disc, about 90 tiny cuticular sensilla are situated. The poreless outer peg of a sensillum is 3–5 μm long and is surrounded by a cuticular wall. One ciliary sensory cell innervates the peg. As a special feature, the outer dendritic segment is very short already terminating below the cuticle. A massive electron-dense cylindrical rod, which most probably represents the hypertrophied dendritic sheath, extends through the cuticular canal connecting the tip of the outer dendritic segment to the peg. The dendritic inner segment and the soma are fused indistinguishably. Thin, leaflike extensions of glial cells deeply extend into that conjoint and considerably enlarged compartment which also contains large numbers of mitochondria. In summary, the sensilla of the sensory disc of A. nigricans represent a new type of insect sensillum of hitherto unknown function. The possible role of the prothoracic sensory organ in fire detection is discussed.     

The Golgi-Localized γ-Ear-Containing ARF-Binding (GGA) Proteins Alter Amyloid-β Precursor Protein (APP) Processing through Interaction of Their GAE Domain with the Beta-Site APP Cleaving Enzyme 1 (BACE1)

Proteolytic processing of amyloid-β precursor protein (APP) by beta-site APP cleaving enzyme 1 (BACE1) is the initial step in the production of amyloid beta (Aβ), which accumulates in senile plaques in Alzheimer’s disease (AD). Essential for this cleavage is the transport and sorting of both proteins through endosomal/Golgi compartments. Golgi-localized γ-ear-containing ARF-binding (GGA) proteins have striking cargo-sorting functions in these pathways. Recently, GGA1 and GGA3 were shown to interact with BACE1, to be expressed in neurons, and to be decreased in AD brain, whereas little is known about GGA2. Since GGA1 impacts Aβ generation by confining APP to the Golgi and perinuclear compartments, we tested whether all GGAs modulate BACE1 and APP transport and processing. We observed decreased levels of secreted APP alpha (sAPPα), sAPPβ, and Aβ upon GGA overexpression, which could be reverted by knockdown. GGA-BACE1 co-immunoprecipitation was impaired upon GGA-GAE but not VHS domain deletion. Autoinhibition of the GGA1-VHS domain was irrelevant for BACE1 interaction. Our data suggest that all three GGAs affect APP processing via the GGA-GAE domain.     

Cathepsins B, K, and L are regulated by a defined collagen type II peptide via activation of classical protein kinase C and p38 MAP kinase in articular chondrocytes

Degradation of the extracellular matrix (ECM) is a prominent feature in osteoarthritis (OA), which is mainly because of the imbalance between anabolic and catabolic processes in chondrocytes resulting in cartilage and bone destruction. Various proteases act in concert to degrade matrix components, e.g. type II collagen, MMPs, ADAMTS, and cathepsins. Protease-generated collagen fragments may foster the destructive process. However, the signaling pathways associated with the action of collagen fragments on chondrocytes have not been clearly defined. The present data demonstrate that the N-terminal telopeptide of collagen type II enhances expression of cathepsins B, K, and L in articular chondrocytes at mRNA, protein, and activity levels, mediated at least in part through extracellular calcium. We also demonstrate that the induction is associated with the activation of protein kinase C and p38 MAP kinase.