Zur Technik und Methode der Bienenversuche mit Farbpapieren und Glasfiltern

Zusammenfassung Die Tatsache, daß reflektiertes Tageslicht für die Biene dann neutral oder farblos ist, wenn es in seiner spektralen Zusammensetzung nicht wesentlich von der Zusammensetzung des Sonnenlichtes — soweit dieses den Bienen sichtbar ist — abweicht, bzw. die Tatsache, daß bei mehr oder weniger vollständigem Fehlen von Ultraviolett weißes Licht für die Biene farbig wird, macht bestimmte Vorsichtsmaßregeln im Gebrauch von Farbpapieren, Graupapieren, Glasplatten und Filtergläsern im Bienenversuch notwendig. Solche Vorsichtsmaßregeln sind bisher nicht oder nicht ausreichend beachtet worden. Für die wichtigeren Ergebnisse bleibt das ohne nachteilige Folgen, einige weitere Ergebnisse erscheinen nun zweifelhaft und sollten nachgeprüft werden.     

Wahrnehmungspsychologische Untersuchungen am Eichelhäher. I.

Ohne Zusammenfassung     

Partial Resistance of Carrot to Alternaria dauci Correlates with In Vitro Cultured Carrot Cell Resistance to Fungal Exudates

Although different mechanisms have been proposed in the recent years, plant pathogen partial resistance is still poorly understood. Components of the chemical warfare, including the production of plant defense compounds and plant resistance to pathogen-produced toxins, are likely to play a role. Toxins are indeed recognized as important determinants of pathogenicity in necrotrophic fungi. Partial resistance based on quantitative resistance loci and linked to a pathogen-produced toxin has never been fully described. We tested this hypothesis using the Alternaria dauci – carrot pathosystem. Alternaria dauci, causing carrot leaf blight, is a necrotrophic fungus known to produce zinniol, a compound described as a non-host selective toxin. Embryogenic cellular cultures from carrot genotypes varying in resistance against A. dauci were confronted with zinniol at different concentrations or to fungal exudates (raw, organic or aqueous extracts). The plant response was analyzed through the measurement of cytoplasmic esterase activity, as a marker of cell viability, and the differentiation of somatic embryos in cellular cultures. A differential response to toxicity was demonstrated between susceptible and partially resistant genotypes, with a good correlation noted between the resistance to the fungus at the whole plant level and resistance at the cellular level to fungal exudates from raw and organic extracts. No toxic reaction of embryogenic cultures was observed after treatment with the aqueous extract or zinniol used at physiological concentration. Moreover, we did not detect zinniol in toxic fungal extracts by UHPLC analysis. These results suggest that strong phytotoxic compounds are present in the organic extract and remain to be characterized. Our results clearly show that carrot tolerance to A. dauci toxins is one component of its partial resistance.     

Inhibition of the Differentiation of Monocyte-Derived Dendritic Cells by Human Gingival Fibroblasts

We investigated whether gingival fibroblasts (GFs) can modulate the differentiation and/or maturation of monocyte-derived dendritic cells (DCs) and analyzed soluble factors that may be involved in this immune modulation. Experiments were performed using human monocytes in co-culture with human GFs in Transwell® chambers or using monocyte cultures treated with conditioned media (CM) from GFs of four donors. The four CM and supernatants from cell culture were assayed by ELISA for cytokines involved in the differentiation of dendritic cells, such as IL-6, VEGF, TGFβ1, IL-13 and IL-10. The maturation of monocyte-derived DCs induced by LPS in presence of CM was also studied. Cell surface phenotype markers were analyzed by flow cytometry. In co-cultures, GFs inhibited the differentiation of monocyte-derived DCs and the strength of this blockade correlated with the GF/monocyte ratio. Conditioned media from GFs showed similar effects, suggesting the involvement of soluble factors produced by GFs. This inhibition was associated with a lower stimulatory activity in MLR of DCs generated with GFs or its CM. Neutralizing antibodies against IL-6 and VEGF significantly (P<0.05) inhibited the inhibitory effect of CM on the differentiation of monocytes-derived DCs and in a dose dependent manner. Our data suggest that IL-6 is the main factor responsible for the inhibition of DCs differentiation mediated by GFs but that VEGF is also involved and constitutes an additional mechanism.     

Transfer RNA maturation in Chlamydomonas mitochondria,chloroplast and the nucleus by a single RNase P protein

The maturation of tRNA precursors involves the 5′ cleavage of leader sequences by an essential endonuclease called RNase P. Beyond the ancestral ribonucleoprotein (RNP) RNase P, a second type of RNase P called PRORP (protein‐only RNase P) evolved in eukaryotes. The current view on the distribution of RNase P in cells is that multiple RNPs, multiple PRORPs or a combination of both, perform specialised RNase P activities in the different compartments where gene expression occurs. Here, we identify a single gene encoding PRORP in the green alga Chlamydomonas reinhardtii while no RNP is found. We show that its product, CrPRORP, is triple‐localised to mitochondria, the chloroplast and the nucleus. Its downregulation results in impaired tRNA biogenesis in both organelles and the nucleus. CrPRORP, as a single‐subunit RNase P for an entire organism, makes up the most compact and versatile RNase P machinery described in either prokaryotes or eukaryotes.