Purple membrane vesicles: Morphology and proton translocation

Summary Purple membrane vesicles prepared by different techniques differ widely in their morphology and ability to establish a proton gradient in the light. The procedures used to prepare active vesicles do not completely dissociate the purple membrane and thus preserve a preferential orientation of the protein, while most of the lipid is exchanged for added lipid. Responses to illumination are largely determined by the size of the vesicles and the degree to which bacteriorhodopsin is preferentially oriented. Any attempt to compare the interaction of different lipids with bacteriorhodopsin by measuring the pH response must take these factors into account.With an improved technique we have obtained vesicles of rather uniform size and bacteriorhodopsin orientation, which accumulate protons with an initial rate of 160 ng H⁺ sec^–1 mg^–1 protein at light intensities of 10⁶ erg cm^–2 sec^–1. The kinetics of the process are complex and at present insufficiently understood.     

Erhöhung der Zelltemperatur auf etwa 35° vermindert die Farbstoffbildung in den verschiedensten Klassen der Lebewesen und zerstört farbstoffbildendes Ferment

Schlußbemerkung Die meisten wilden Spezies werden in ihrem genetisch bedingten Fermentbestand so eingerichtet sein, daß sie unter normalen Bedingungen in ihren lebenswichtigen Farbkleide nicht leiden. Daher wird man starken Ferment- und damit Farbstoffschwund meist erst in der oberen Grenze erträglicher Zelltemperaturen und nur in Ausnahmefällen, am ehesten noch bei domestizierten Mutationen vorfinden.Nochmals betone ich, daß der Mechanismus der Fermentinaktivierung weiter durchforscht werden muß.Am Schluß meiner letzten Arbeit sagte ich: Wenn nachDanneel der erste Teil der Kälteschwärzung des Russenkaninchens ohne Sauer stoffaufnahme und der zweite nach meiner Beobachtung noch in 45° verlaufen kann, so spielt sich die ganze Reaktion außerhalb des eigent lichen Lebensprozesses ab. Meine Beobachtung, daß es an der ausge preßten, kaum lebende Zellen enthaltenden Hämolymphe der Weißlings puppe eine ganz ähnliche Kälteschwärzung gibt, spricht in gleichem Sinne.Diese Gruppe von Kälteschwärzungen wird sich schon aus diesem Grunde nicht vererben, und so vererbte sich ja auch die Kälteschwärzung der Russenkaninchen nicht.     

Gleichzeitig reifender Hanf

Ohne Zusammenfassung     

Eine neue Methode zur Feststellung des Ploidiegrades beiBeta-Rüben

Ohne ZusammenfassungMit 2 Abbildungen     

Elaborate ornaments are costly to maintain: evidence for high maintenance handicaps

Elaborate secondary sexual traits, such as the ornamental plumageof birds, may be favored by female choice because they serveas honest indicators of male quality. Elaborate traits are thoughtto be honest signals because they are expensive to produce andincrease predation risk. Here we investigate another potentialcost of elaborate traits, i.e., the time and energy requiredto maintain them in good condition. We tested the hypothesisthat species of birds with ornamental plumage invest more timein maintenance behavior than do related species without suchplumage. To test the hypothesis we quantified the maintenancebehavior of nine ornamental and nine non-ornamental speciesin aviaries and zoos. To test the validity of using captivebirds, we first collected data on 12 captive species for whichdata from wild individuals were also available. The maintenancetimes of captive and wild individuals were highly correlatedacross species. Maintenance time was also correlated with plumagelength, independent of body size. Ornamental species had longerplumage than non-ornamental species, and they devoted significantlymore time to maintenance. Time spent on maintenance cannot bedevoted to other activities. This temporal trade-off reinforcesthe honesty of ornamental plumage. We suggest that high maintenancehandicaps are present in a variety of animals.     

A-seco-oleane-type triterpenes from Phomopsis sp. (strain HKI0458) isolated from the mangrove plant Hibiscus tiliaceus

From the fermentation broth of an unidentified Phomopsis sp. (strain HKI0458) isolated from the mangrove plant Hibiscus tiliaceus, four A-seco-oleane-type triterpenes, namely 3,4-seco-olean-11,13-dien-4,15alpha, 22beta,24-tetraol-3-oic acid (1), 3,4-seco-olean-11,13-dien-4,7beta,22beta,24-tetraol-3-oic acid (2), 3,4-seco- olean-13-en-4,7,15,22,24-pentaol-3-oic acid (3), and 3,4-seco-olean-13-en-4,15,22,24-tetraol-3-oic acid (4) were obtained. Their structures were elucidated by extensive spectroscopic (UV, IR, FABMS, and 2D NMR) data analyses.     

DM-GRASP/ALCAM/CD166 is required for cardiac morphogenesis and maintenance of cardiac identity in first heart field derived cells

Vertebrate heart development requires specification of cardiac precursor cells, migration of cardiac progenitors as well as coordinated cell movements during looping and septation. DM-GRASP/ALCAM/CD166 is a member of the neuronal immunoglobulin domain superfamily of cell adhesion molecules and was recently suggested to be a target gene of non-canonical Wnt signalling. Loss of DM-GRASP function did not affect specification of cardiac progenitor cells. Later during development, expression of cardiac marker genes in the first heart field of Xenopus laevis such as Tbx20 and TnIc was reduced, whereas expression of the second heart field marker genes Isl-1 and BMP-4 was unaffected. Furthermore, loss of DM-GRASP function resulted in defective cell adhesion and cardiac morphogenesis. Additionally, expression of DM-GRASP can rescue the phenotype that results from the loss of non-canonical Wnt11-R signalling suggesting that DM-GRASP and non-canonical Wnt signalling are functionally coupled during cardiac development.     

<Emphasis Type="Italic">Ignicoccus hospitalis</Emphasis> and <Emphasis Type="Italic">Nanoarchaeum equitans</Emphasis>: ultrastructure,cell–cell interaction,and 3D reconstruction from serial sections of freeze-substituted cells and by electron cryotomography

Ultrastructure and intercellular interaction of Ignicoccus hospitalis and Nanoarchaeum equitans were investigated using two different electron microscopy approaches, by three-dimensional reconstructions from serial sections, and by electron cryotomography. Serial sections were assembled into 3D reconstructions, for visualizing the unusual complexity of I. hospitalis, its huge periplasmic space, the vesiculating cytoplasmic membrane, and the outer membrane. The cytoplasm contains fibres which are reminiscent to a cytoskeleton. Cell division in I. hospitalis is complex, and different to that in Euryarchaeota or Bacteria. An irregular invagination of the cytoplasmic membrane is followed by separation of the two cytoplasms. Simultaneous constriction of cytoplasmic plus outer membrane is not observed. Cells of N. equitans show a classical mode of cell division, by constriction in the mid-plane. Their cytoplasm exhibits two types of fibres, elongated and ring-shaped. Electron micrographs of contact sites between I. hospitalis and N. equitans exhibit two modes of interaction. One is indirect and mediated by thin fibres; in other cells the two cell surfaces are in direct contact. The two membranes of I. hospitalis cells are frequently seen in direct contact, possibly a prerequisite for transporting metabolites or substrates from the cytoplasm of one cell to the other. Rarely, a transport based on cargo vesicles is observed between I. hospitalis and N. equitans.