Experimentelle und theoretische Untersuchungen über die Entdifferenzierung und Teilung pflanzlicher Dauerzellen

Ohne Zusammenfassung     

Doppelbrechung und Orientierungsrate der Leptonen fließenden Protoplasmas

Summary At defined speeds threads of protoplasm have been drawn out mechanically from a fusion of isolated gymnoplasts using an experimental arrangement described by Gerendás [3]. The polarization device, as well as the method of measuring the birefringence by means of a variable azimuth compensator of fixed retardation, viz. a rotating /30-mica plate, is the same as described formerly [7g-i. Then in dependence on the variable speeds of formation the protoplasmic threads show a different intensity of negative birefringence, and, what is more, it is found a distinct parallelism between birefringence, as an expression of the orientation rate of the leptones, and the speed of spinning. Always when a birefringent gel like protoplasm is put under tension, the intensity of its original birefringence or its orientation rate increases (and in the reverse order). It is to conclude that in order to analyse the leptonic structures in dependence on the effective forces, there is a great need for a quantitative approach to the anisotropy of protoplasmic constituents.     

Fusing VE-Cadherin to α-Catenin Impairs Fetal Liver Hematopoiesis and Lymph but Not Blood Vessel Formation

We have recently shown that genetic replacement of VE-cadherin by a VE-cadherin–α-catenin fusion construct strongly impairs opening of endothelial cell contacts during leukocyte extravasation and induction of vascular permeability in adult mice. Here we show that this mutation leads to lethality at midgestation on a clean C57BL/6 background. Investigating the reasons for embryonic lethality, we observed a lack of fetal liver hematopoiesis and severe lymphedema but no detectable defects in blood vessel formation and remodeling. As for the hematopoiesis defect, VE-cadherin–α-catenin affected neither the generation of hematopoietic stem and progenitor cells (HSPCs) from hemogenic endothelium nor their differentiation into multiple hematopoietic lineages. Instead, HSPCs accumulated in the fetal circulation, suggesting that their entry into the fetal liver was blocked. Edema formation was caused by disturbed lymphatic vessel development. Lymphatic progenitor cells of VE-cadherin–α-catenin-expressing embryos were able to leave the cardinal vein and migrate to the site of the first lymphatic vessel formation, yet subsequently, these cells failed to form large lumenized lymphatic vessels. Thus, stabilizing endothelial cell contacts by a covalent link between VE-cadherin and α-catenin affects recruitment of hematopoietic progenitors into the fetal liver and the development of lymph but not blood vessels.     

A diverse uncultivated microbial community is responsible for organic matter degradation in the Black Sea sulphidic zone

Organic matter degradation in marine environments is essential for the recycling of nutrients, especially under conditions of anoxia where organic matter tends to accumulate. However, little is known about the diversity of the microbial communities responsible for the mineralization of organic matter in the absence of oxygen, as well as the factors controlling their activities. Here, we determined the active heterotrophic prokaryotic community in the sulphidic water column of the Black Sea, an ideal model system, where a tight coupling between carbon, nitrogen and sulphur cycles is expected. Active microorganisms degrading both dissolved organic matter (DOM) and protein extracts were determined using quantitative DNA stable isotope probing incubation experiments. These results were compared with the metabolic potential of metagenome-assembled genomes obtained from the water column. Organic matter incubations showed that groups like Cloacimonetes and Marinimicrobia are generalists degrading DOM. Based on metagenomic profiles the degradation proceeds in a potential interaction with members of the Deltaproteobacteria and Chloroflexi Dehalococcoidia. On the other hand, microbes with small genomes like the bacterial phyla Parcubacteria, Omnitrophica and of the archaeal phylum Woesearchaeota, were the most active, especially in protein-amended incubations, revealing the potential advantage of streamlined microorganisms in highly reduced conditions.     

Synthesis of myelin glycosphingolipids (galactosylceramide and galactosyl(3-O-sulfate)ceramide (sulfatide)) by cloned cell lines derived from mouse neurotumors

Clonal cell lines derived from both spontaneous and chemically induced rat and mouse brain tumors were screened for their ability to incorporate H232SO4 into galactosyl(3-O-sulfate)ceramide (sulfatide). High levels of 35SO4 incorporation into sulfatide were found only in two of the mouse cell lines studied (G26-20 and -24). Tumors produced by subcutaneous injection of these cell lines into C57BL/6 mice were also unique in that they contained high levels of both sulfatide and galactosylceramide. The synthesis of large amounts of sulfatide and galactosylceramide by a clonal cell line of neurological origin suggests that the original tumor was of oligodendrocyte or Schwann cell origin. In common with a large number of mouse and rat astrocyte cell strains and their derived tumors, these glial cells lacked the ability to synthesize gangliosides such as monosialotetraglycosylceramide and disialotetraglycosylceramide (as judged by analytical and [3H]GlcNH2 incorporation studies). This appears to be a unique characteristic of neuroblastoma-derived cell strains such as N18, NB2a, and NB41A.     

Population structure and adaptation of a bacterial pathogen in California grapevines

Xylella fastidiosa subsp. fastidiosa causes Pierce's disease of grapevine (PD) and has been present in California for over a century. A singly introduced genotype spread across the state causing large outbreaks and damaging the grapevine industry. This study presents 122 X. fastidiosa subsp. fastidiosa genomes from symptomatic grapevines, and explores pathogen genetic diversity associated with PD in California. A total of 5218 single-nucleotide polymorphisms (SNPs) were found in the dataset. Strong population genetic structure was found; isolates split into five genetic clusters divided into two lineages. The core/soft-core genome constituted 41.2% of the total genome, emphasizing the high genetic variability of X. fastidiosa genomes. An ecological niche model was performed to estimate the environmental niche of the pathogen within California and to identify key climatic factors involved in dispersal. A landscape genomic approach was undertaken aiming to link local adaptation to climatic factors. A total of 18 non-synonymous polymorphisms found to be under selective pressures were correlated with at least one environmental variable highlighting the role of temperature, precipitation and elevation on X. fastidiosa adaptation to grapevines in California. Finally, the contribution to virulence of three of the genes under positive selective pressure and of one recombinant gene was studied by reverse genetics.     

Differential stimulation of hepatic and brain metallothioneins by ethanol

Administration of ethanol induces the synthesis of hepatic metallothionein and metallothionein mRNA in the liver but not in the brain. Furthermore, ethyl alcohol, methyl alcohol and isopropyl alcohol enhance the synthesis of metallothionein in Chang cells but not in neuroblastoma IMR-32 cells in culture. The results of this study are interpreted to suggest that the mechanisms of synthesis of metallothionein and the utilization of essential metal nutrients in the brain and peripheral tissues are not identical.     

Relationship of drinking water quality (hardness-softness) to cardiovascular mortality in Newfoundland

The profile of mortality in Newfoundland was analysed for all deaths occurring in 1969 of persons 35 to 69 years of age, of whom the total was 1036. An exceptionally high cardiovascular mortality (793 deaths/100,000) was noted for St. John''s, the capital city of Newfoundland, a city which has an extremely soft drinking-water supply. This high rate corresponds to that observed in the “high mortality belt” reported for the east coast of the United States, and in conjunction with data from mainland Canada, extends the belt across the entire eastern aspect of North America. The proportion of cardiovascular deaths of men occurring outside the hospital was less within hard drinking-water areas in Newfoundland than in the soft water areas of the province. Thus, the statistics reported here of cardiovascular mortality confirm evidence reported elsewhere on “macro-geographic” variations in this disease(s) as well as “micro-geographic” regional variations which may be dependent upon local environmental factors.