Storage of embryonically transcribed poly(A) RNA and its utilization during metamorphosis of the hydroidHydractinia echinata

Summary The formation of tentacles and stolons during metamorphosis is severely disturbed if inhibitors of mRNA metabolism are applied during certain phases of development. The periods of sensitivity to -amanitin are late gastrulation and the disk stage of metamorphosis. A cordycepin sensitive phase exists during the first hour of metamorphosis. In all drug sensitive phases an enhanced poly(A) synthesis is found indicating increased mRNA metabolism in these stages. Pulse-chase experiments show that planula larvae store a poly(A)-rich RNA population sedimenting between 28–18s. These long living molecules are of embryonic origin, are located in RNP particles and are degraded during metamorphosis. The particles in question appear to be stored mainly in interstitial cells. In early metamorphosis no uridine is incorporated but labelled poly(A) is added to preexisting molecules.     

Der cis-trans-Positionseffekt in Heterokaryen morphologischer Mutanten von Podospora anserina

Zusammenfassung Der cis-trans-Positionseffekt in Heterokaryen der nicht gekoppelten morphologischen Mutanten z und oct-1 von Podospora anserina wird durch quantitative Kernunterschiede vorgetäuscht.Im cis-Fall führt die Wuchsverminderung von Hyphen mit überwiegendem Gehalt an Doppelmutantenkernen nach Mikrosektorenbildung im Mycel zu einer Selektion der Hyphen mit überwiegendem Wildkerngehalt. Die Doppelmutantenkerne sind nach 6 cm Wuchsstrecke aus dem Mycel verschwunden. Dieses weist daher Wildphänotyp auf.Im trans-Fall wird eine Kernentmischung durch Anastomosenbildung kompensiert, da die entestehenden Kleinsektoren gleich schnell wachsen. Das Mycel bringt daher die oct-1- und z-Merkmale in einem intermediären Phänotyp zum Ausdruck.

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The cis-trans position effect in heterocaryons of morphological mutants of Podospora anserina

Summary The cis-trans position effect of the two non-linked morphological mutants z and oct-1 in heterocaryons of Podospora anserina is caused by quantitative differences of the two types of nuclei.In the cis configuration, there is a growth diminuition of hyphae containing predominantly nuclei of the double mutant type which leads to a selection of hyphae containing mainly the wildtype nuclei. This is due to the formation of microsectors. After 6 cm of mycelial growth the double mutant nuclei are no longer distinguishable; the mycelium adopts the wild phenotype.In the trans configuration, the microsectors of both types of mutant nuclei exhibit the same growth rate; the separation of nuclei is prevented as a result of the formation of hyphal anastomoses. The mycelium shows then an intermediate phenotype with both mutant characteristics.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

81. Jahresversammlung (1968) zu Innsbruck

Ohne Zusammenfassung     

Renal handling of taurine,l-alanine,l-glutamate andd-glucose inOpsanus tau: studies on isolated brush border membrane vesicles

Summary Renal brush border membrane vesicles (bbmv) from the aglomerular toadfish (Opsanus tau), isolated by differential precipitation, were tested for their ability to actively translocate (i) taurine, known to be secreted by the kidney of several marine teleosts, and (ii)l-alanine,l-glutamic acid, andd-glucose, solutes that are normally reabsorbed in the filtering nephron. Vesicular taurine uptake displayed a Na⁺ dependence. Transport was greatest under conditions of an inward-directed Na⁺ gradient, but a significant stimulation by Na⁺ over K⁺ could also be observed in the absence of a salt gradient. At high extravesicular K⁺, the addition of valinomycin reduced taurine uptake. Na⁺-dependent³H-taurine flux was almost completely inhibited by non-labeled taurine (tracer replacement) or -alanine, but was unaffected byl-alanine. Replacement of medium chloride by SCN^– or NO ₃ ^– in the presence of Na⁺ resulted in significantly lower uptake rates under both anion gradient and anion equilibrium conditions, whereas Br^– could almost fully substitute for the stimulatory Cl^– action. These results indicate the presence of an electrogenic Na⁺-cotransport mechanism with specificity for -amino acids in the toadfish renal brush border. Whether the system under physiological conditions mediates reabsorption or secretion of taurine remains to be determined. Toadfish bbmv also translocatedl-alanine andl-glutamic acid in a Na⁺-dependent manner. Possible roles for these most likely reabsorptive transport systems in a non-filtering kidney are discussed.d-glucose uptake, however, appeared to occur via Na⁺-independent pathways, since it was not affected by phlorizin in the presence of Na⁺, or by Na⁺ replacement.Abbreviation bbmv brush border membrane vesicles     

Prostanoid formation in primary astroglial cell cultures: Ca-dependency and stimulation by A 23187, melittin and phospholipases A2 and C

Prostaglandin (PG) and thromboxane B₂ (TXB₂) biosynthesis was studied in cultured astrocytes from neonatal rat brain hemispheres. After two weeks of cultivation, prostanoids were formed with the spectrum: PGD₂ > TXB₂ > PGF₂ > PGE₂, as measured by specific radioimmunoassays. Under basal conditions PGD₂ biosynthesis (9.55 ng/mg protein/15 min) was in the same order of magnitude as the sum of the other prostanoids. The formation of prostanoids was stimulated in a concentration dependent manner (up to 6–10 fold) by the calcium ionophore A 23187 (0.01–10 μM) as well as by melittin (0.01–5 μg/ml), phospholipase A₂ (10–40 U/ml) and phospholipase C (0.01–1 U/ml). Basal and evoked PG and TXB₂ biosynthesis depended on the availability of Ca²⁺, as demonstrated in Ca²⁺ free incubation medium containing Na₂EDTA (1 μM), or with verapamil (100 μM) and 3,4,5-trimethoxybenzoic acid-8-(diethylamino)-octylester-HCl (TMB-8, 1–100 μM). Indomethacin (10 μM), mepacrine (100 μM) and p-bromophenacylbromide (50 μ M) inhibited basal and evoked PG formation. Thin-layer chromatography (TLC) detection after incubation of the cells with [³H]arachidonic acid (1 μCi/ml, for 60 min) confirmed the results obtained by radioimmunoassay. Incubation of [³H]arachidonic acid labelled cells with inonophore or phospholipases, followed by lipid extraction and TLC, showed that A 23187 liberated [³H]arachidonic acid predominantly from phosphatidylethanolamine, whereas phospholipase A₂ and C reduced mainly the labelling of the phosphatidyl-inositol/-choline fraction. Potassium depolarization of the cells did not enhance prostanoid formation. Similarly, drugs with affinity to - or β-adrenoceptors, or to dopamine-, 5-hydroxytryptamine-, muscarine-, histamine-, glutamate-, aspartate-, GABA, adenosine- and opioid-receptors failed to stimulate prostanoid biosynthesis. Also compounds like angiotensin, bradykinin and thrombin were ineffective in this respect.

In conclusion, our results confirm that cultured astrocytes possess the complete pattern of enzymes necessary for prostanoid formation and hence might play a crucial role in brain prostanoid biosynthesis. Stimulation of prostanoid biosynthesis involves Ca²⁺-dependent activation of phospholipase A₂, cyclooxygenase reaction and further PG metabolism. However, the endogenous stimulus for enhanced prostanoid synthesis in the brain still has to be established.     

Spinach ferredoxin is a calcium-binding protein

Spinach-leaf ferredoxin was identified as a calcium-binding protein by ⁴⁵Ca autoradiography on nitrocellulose membranes and with the cationic carbocyanine dye 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naphtho[1,2-d]thiazolium bromide (stains-all). Binding of ⁴⁵Ca was observed at pH 6.8 and pH 7.8 and in the presence of 5 mM and 20 mM MgCl₂. At the higher MgCl₂ concentration the Ca²⁺-binding capacity is reduced. Only micromolar concentrations of LaCl₃, however, are required to achieve a similar effect. Both the oxidized and reduced forms of ferredoxin bind calcium.Abbreviations PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate - stains-all 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naptho[1,2-d]thiazolium bromide     

Lineage-specific expression of c-fos and c-fms in human hematopoietic cells: Discrepancies with the in vitro differentiation of leukemia cells

In vitro differentiation studies using the bipotential human leukemia cell line, HL60, have indicated that high levels of expression of two proto-oncogenes, c-fos and c-fms, are restricted to the myelomonocytic lineage. No such expression has been detected in induced granulocytic cells. In striking contrast to these observations, we found that c-fos mRNA levels are very high in purified human granulocytes, but barely detectable in blood monocytes and tissue macrophages. Human granulocytes contain, however, relatively low levels of c-fos protein, indicating that c-fos mRNA is inefficiently translated or that the protein is rapidly degraded in these cells. In closer agreement with the in vitro results, the level of the expression of c-fms is high in purified blood monocytes and undetectable in granulocytes. We found, however, that the evolution of monocytes into tissue macrophages is accompanied by a significant decrease in c-fms expression, suggesting that the function of c-fms is restricted to specific stages of monocytic differentiation. Our observations also show that results obtained using in vitro differentiation systems have to be regarded with caution, since they may not reflect the in vivo situation.     

Litter decomposing and ectomycorrhizalBasidiomycetes in an igapó forest

An igapó forest near the confluence of Rio Tarumã Mirim (Tarumãzinho) and Rio Negro has been studied. It is a typical ectotroph forest with a raw humus layer and suppressed litter decomposing activity by Higher (i.e., carpophore-producing) Fungi. The number of the latter is about one-fifth of that observed in the (anectotrophic) terra firme forest. All ectotrophically mycorrhizal fungi observed belonged in three families:Amanitaceae, Boletaceae, Russulaceae. Leguminosae are dominant, and of theseAldina latifolia andSwartzia cf.polyphylla were demonstrably ectomycorrhizal. The scarcity of mineral nutrients in the soils of igapó, campinarana and campina is overcome by direct cycling through ectomycorrhizae. This is in contrast to other black- and white-water inundated forest communities in Amazonia.Litter Decomposition and Ectomycorrhiza in Amazonian Forests3. Previous contributions seeSinger & Araujo (1979) andSinger & al. (1983).