Competitive reversals and environment-dependent resource partitioning in Erodium

Summary Effects of drought and varying plant density on the competitive coexistence of two winter annual Erodium species were studied using multiple regression analysis. Significant indications of resource partitioning were detected for interspecific mixtures under spring drought. Competitive superiority also was environment-dependent with E. botrys dominating with drought in autumn, while E. brachycarpum dominated with drought in spring. The results suggest that competitive coexistence in Erodium is promoted by processes both equilibrial (e.g., resource partitioning) and nonequilibrial (e.g. competitive reversals).     

Wound-healing defect of CD18(-/-) mice due to a decrease in TGF-beta1 and myofibroblast differentiation

We studied the mechanisms underlying the severely impaired wound healing associated with human leukocyte-adhesion deficiency syndrome-1 (LAD1) using a murine disease model. In CD18(-/-) mice, healing of full-thickness wounds was severely delayed during granulation-tissue contraction, a phase where myofibroblasts play a major role. Interestingly, expression levels of myofibroblast markers alpha-smooth muscle actin and ED-A fibronectin were substantially reduced in wounds of CD18(-/-) mice, suggesting an impaired myofibroblast differentiation. TGF-beta signalling was clearly involved since TGF-beta1 and TGF-beta receptor type-II protein levels were decreased, while TGF-beta(1) injections into wound margins fully re-established wound closure. Since, in CD18(-/-) mice, defective migration leads to a severe reduction of neutrophils in wounds, infiltrating macrophages might not phagocytose apoptotic CD18(-/-) neutrophils. Macrophages would thus be lacking their main stimulus to secrete TGF-beta1. Indeed, in neutrophil-macrophage cocultures, lack of CD18 on either cell type leads to dramatically reduced TGF-beta1 release by macrophages due to defective adhesion to, and subsequent impaired phagocytic clearance of, neutrophils. Our data demonstrates that the paracrine secretion of growth factors is essential for cellular differentiation in wound healing.     

Phosphatidylserine membrane domain clustering induced by annexin A2/S100A10 heterotetramer

By means of scanning force and fluorescence microscopy of artificial membranes immobilized on mica surfaces, the lateral organization of the annexin A2/S100A10 heterotetramer (annexin A2t) and its influence on the lateral organization of the lipids within the membrane have been elucidated. Planar lipid bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS) were prepared on atomically flat mica surfaces by the spreading of unilamellar vesicles. Fluorescence images of fluorescently labeled annexin A2t and scanning force microscopy images of nonlabeled protein bound to POPC/POPS bilayers show the formation of micrometer-sized lateral protein domains in the presence of 1 mM CaCl2. By means of scanning force microscopy, not only protein domains became discernible but also small membrane domains, which were attributed to POPS-enriched areas. A depletion of these POPS domains was observed in the vicinity of annexin A2t protein domains. These results indicate that annexin A2t is a peripheral membrane-binding complex capable of inducing lipid segregation.     

Plasma levels of coenzyme Q10 in children with hyperthyroidism

OBJECTIVES: In hyperthyroidism, increased oxygen consumption and free radical production in the stimulated respiratory chain leads to oxidative stress. Apart from its antioxidative function, coenzyme Q10 (CoQ10) is involved in electron transport in the respiratory chain. The aim of this study was to determine whether there is a correlation between an increased respiratory chain activity and the state of CoQ10 in children with hyperthyroidism. METHODS: The CoQ10 plasma concentration was measured by high-performance liquid chromatography in 12 children with hyperthyroidism before and after treatment. RESULTS: In the hyperthyroid state, the plasma level of CoQ10 was significantly decreased in comparison with the level in the euthyroid state. The correction of the hyperthyroid state resulted in a normalization of the CoQ10 level. CONCLUSION: Plasma CoQ10 deficiency appears to be related to the stimulated respiratory chain activity in children with hyperthyroidism.     

Design, synthesis, and structure-activity relationship of podocarpic acid amides as liver X receptor agonists for potential treatment of atherosclerosis

A series of podocarpic acid amides were identified as potent agonists for Liver X receptor alpha and beta subtypes, which are members of a nuclear hormone receptor superfamily that are involved in the regulation of a variety of metabolic pathways including cholesterol metabolism. We recently reported podocarpic acid anhydride and imide dimers as potent LXR agonists. Through parallel organic synthesis, we rapidly identified a series of new podocarpate leads with stable structures exemplified by adamantyl- and phenylcyclohexylmethyl-podocarpic acid amides (14 and 18). Compound 18 exhibited LXRalpha/beta 50/20 nM (binding affinity) and 33.7/35.3-fold receptor inductions. Synthesis, SAR, and biological activities of new podocarpate analogs are discussed.     

Dichroismus und Doppelbrechung Vergoldeter Chloroplasten

Zusammenfassung Es wird versucht, die von pflanzlichen Objekten mit Erfolg bisher nur an der Zellwand durchgeführten dichroitischen Edelmetallfärbungen für die Erforschung des Feinbaues der Chloroplasten zu verwerten. Die Analyse von Dichroismus und Doppelbrechung goldgefärbter Chloroplasten macht eine zweidimensional periodische Anordnung der submikroskopischen Goldkristalle wahrscheinlich, und aus dieser kann weiterhin ein lamellarer Bau der Chloroplasten gefolgert werden, der auch auf Grund anderer Befunde naheliegt. Diebisher vorliegenden Beobachtungen an lebenden Chloroplasten lassen sich mit der Annahme eines optisch aktiven, dichroitischen, negativ einachsig doppelbrechenden Systems mit Austritt der optischen Achse normal zur Frontalansicht physikalisch erklären, womit die hier entwickelten Vorstellungen gut vereinbar sind.Herrn Professor Dr. Kurt Noack danken wir für die Förderung dieser Untersuchungen und dafür, daß er Instrumente aus den Mitteln der Deutschen Forschungsgemeinschaft zur Verfügung stellte.     

Loss of phylogenetic information in chorion gene families of Bombyx mori gene conversion

The silkmoth chorion has provided a stimulating model for the study of evolution and developmental regulation of gene families. Previous attempts at inferring relationships among chorion sequences have been based on pairwise comparisons of overall similarity, a potentially problematic approach. To remedy this, we identified the alignable regions of low sequence variability and then analyzed this restricted database by parsimony and neighbor-joining methods. At the deepest level, the chorion sequence tree is split into two branches, called "alpha" and "beta." Within each branch, early- and late-expressing genes each constitute monophyletic groups, while the situation with middle-expressing genes remains uncertain. The HcB gene family appears to be the most basal beta-branch group, but this conclusion is qualified because the effect of gene conversion on branching order is unknown. Previous studies by Eickbush and colleagues have strongly suggested that ErA, HcA, and HcB families undergo gene conversion within a gene family, whereas the ErB family does not. The occurrence of conversion correlates with a particular tree structure; namely, branch lengths are much greater at the base of the family than at higher internodes and terminal branches. These observations raise the possibility that chorion gene families are defined by gene conversion events (reticulate evolution) rather than by descent with modification (synapomorphy).      

Über die Struktur der Thylakoide von Rhodopseudomonas spheroides

Zusammenfassung Die Thylakoidmembranen von Rhodopseudomonas spheroides erscheinen nach Negativkontrastierung in Profilstellung etwa 40 Å dick. Die aus der Schattenlänge ermittelte Dicke von angetrockneten unfixierten Thylakoiden betrug 81±1 Å, woraus sich ebenfalls eine Dicke der Thylakoidmembran von 40 Å ergibt. Die Proteinschicht besitzt anscheinend eine locker gebaute Mittelzone, in die sich Kontrastierungsmittel einlagern kann. Da diese Strukturen sich bei Behandlung mit Chloroform nicht merklich verändern und da Thylakoide 53% Proteine enthalten, besteht die fragliche Schicht ganz oder vorwiegend aus Proteinen. Die Proteinschicht besteht, wie die Elektrophorese in Polyacrylamidgel zeigt, aus verschiedenen Proteinen. Die Bestimmung der Gestalt und Größe der Proteinmoleküle in Lösung stößt wegen ihrer Neigung zu Aggregation auf Schwierigkeiten. Die Proteinmoleküle sollten wegen der gleichmäßigen Dicke der Proteinschicht wenigstens in einer Dimension eine Größe von 40 Å haben.Die Lipide lassen sich in den Thylakoiden nur abbilden, wenn gewisse Präparations-und Aufnahmebedingungen eingehalten werden. In negativ-kontrastierten Präparaten treten sie nach Fixierung mit Osmiumtetroxid- oder Glutardialdehydlösung gelegentlich in Form von Myelinfiguren in Erscheinung. Aufnahmen von gefriergetrockneten Thylakoiden zeigen nach Behandlung mit Osmiumtetroxiddämpfen eine schwächer kontrastierte Außenschicht und eine stärker kontrastierte Zone im Inneren. Da die Lipide etwa doppelt so viel Kontrastierungsmittel binden wie die Proteine, enthält die stärker kontrastierte Zone die Lipide. Die Dicke von angetrockneten Thylakoiden, die aus fixierten Zellen isoliert worden waren, betrug 158±2 Å. Aus diesen Befunden läßt sich ableiten, daß die Thylakoidmembran aus einer etwa 40 Å dicken monomolekularen Proteinschicht und einer etwa gleich dicken Lipidschicht besteht, die im Innern des Thylakoids lokalisiert ist. Nur in seltenen Fällen gelang es, diese Anordnung von Proteinen und Lipiden in Thylakoiden abzubilden, die fixiert, negativkontrastiert und zusätzlich schräg bedampft worden waren.Zur Erklärung der Labilität der Lipide in der wasserfreien Thylakoidmembran wird angenommen, daß an der Stabilisierung des Lipoproteinsystems hydrophobe Wechselwirkungen zwischen den hydrophoben Teilen der Lipidmoleküle und den apolaren Aminosäureresten der Proteine beteiligt sind.

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The structure of thylakoids of Rhodopseudomonas spheroides

Summary After negative staining, the thylakoid membranes of Rhodopseudomonas spheroides appear to be approximately 40 Å thick. The medium thickness of dired, unfixed thylakoids in obliquely shadow cast specimens is 81±1 Å which was calculated from the length of the shadow. This also indicates a thickness of 40 Å for the thylakoid membrane. Since there is no structural alteration following treatment with chloroform and since thylakoids contain 53% protein, it is concluded that the layer seen in unfixed and negatively stained preparations principally consists of protein. It would appear that the protein layer has a middle zone of less dense material in which the staining substances can be incorporated. Electrophoretic studies in polyacrylamide gel indicates that the protein layer consists of different proteins. Because the protein molecules tend to aggregate, it is difficult to determine their shape and size. At least one dimension of these protein molecules cannot exceed 40 Å, since the protein membrane has a uniform thickness.In thylakoids, lipids can only be seen when certain preparation and electron microscopic conditions are observed. In negatively stained specimens, the lipids sometimes appear as myelin figures after fixation with osmium tetroxide solution or glutaraldehyde. Lyophilized thylakoids, fixed with osmium tetroxide vapor, show an outer layer of less contrast and a stronger contrasted middle zone. The latter one contains the lipids since the lipids bind approximately twice as much staining material as proteins. When thylakoids were isolated from prefixed cells and shadowed, a thickness of 158±2 Å was determined. It is concluded, therefore, that the thylakoid membrane of Rhodopseudomonas spheroides consists of a monomolecular protein layer of about 40 Å and a lipid layer of approximately the same thickness which is located inside the thylakoid. Only when thylakoids were fixed, negatively stained and — in addition — obliquely shadow cast, the proposed arrangement of proteins and lipids could occasionally be seen simultaneously.It would appear that hydrophobic interactions between hydrophobic parts of the lipid molecule and the apolar amino acid residues of the proteins are important to stabilize the lipoprotein system of the thylakoid. This could account for the extreme lability of the lipids in water-free preparations and the difficulty to locate them properly within the thylakoid membrane.