Untersuchungen zur Charakterisierung der Aufnahme, des Transports und der Reduktion von Nitrat in Blättern und Wurzeln von Brassica napus L. und Lupinus albus L. unter Einsatz der kurzlebigen Radioisotope ¹¹C und ¹³N

In dieser Arbeit wurde der Einfluss von Kalium auf die Aufnahme, den Transport und die Reduktion von Nitrat untersucht. Als Spezies mit einer bevorzugten Reduktion des Nitrats in den Blättern wurde Brassica napus L. (Sorte Liberator-00) gewählt, während Lupinus albus L. (Sorte Amiga) als Beispiel für eine Spezies mit überwiegender Nitrat-Reduktion in den Wurzeln diente. Unter Einsatz des kurzlebigen 13N wurden Aufnahmekinetiken von NO3- an Raps und Lupine erstellt, wobei zwischen Influx, Efflux und Netto-Aufnahme unterschieden wurde. Nach NH4+-Ernährung reagieren beide Spezies beim ersten Kontakt mit NO3- mit einem Anstieg der Aufnahmerate, wobei ein Efflux von NO3- erst nach einigen Stunden einsetzt. Weiterhin wurde festgestellt, dass zur Induktion der NO3--Aufnahme bereits ein kurzfristiger NO3--Puls ausreicht. Raps und Lupine zeigen bei der Nitrataufnahme das charakteristische Bild von HATS (High Affinity Transport System) bei niedrigem und LATS (Low Affinity Transport System) bei hohem Nitratangebot. Die Aufnahmerate von Raps liegt dabei deutlich über den Aufnahmeraten von häufig untersuchten Spezies wie Gerste oder Weizen, während die Lupine eine deutlich niedrigere Aufnahmerate aufweist. Werden NO3--ernährte Pflanzen unter K+-Mangel angezogen, so sind NO3--Influx und NO3--Efflux reduziert. Wird den K-Mangelpflanzen wieder K+ angeboten, so steigt der Influx stärker als der Efflux und es kommt zu einer höheren Nettoaufnahme. Der Efflux nimmt erst zeitlich verzögert zu, so dass sich hier ein ähnliches Bild wie bei der Induktion der NO3--Aufnahme bei NH4+-ernährten Pflanzen ergibt. In Lupinus albus L. NO3-, mit bevorzugter Reduktion von NO3- in der Wurzel, ist im Xylem-Exudat kein NO3- nachweisbar solange das NO3--Angebot unter 250 µM liegt. Bei Brassica napus L., mit bevorzugter NO3--Reduktion im Blatt, tritt NO3- auch bei geringem Angebot im Xylem auf. In den Blättern der Lupine ist die Nitratreduktaseaktivität (NRA) erst bei einem Nitrat-Angebot von über 1 mM festzustellen, während sich die NRA in Spross und Wurzel der Lupine und in allen Organen von Raps auch bei einen NO3--Angebot von weniger als 100 µM bestimmen lässt. Unter K+-Mangel ist die NRA in beiden Spezies reduziert. Dabei kommt es zu einer Überlagerung von einer Hemmung der NRA durch Na+, das in Nährlösungen als ausgleichendes Kation für das fehlende K+ verwendet wurde, und einer vermutlich reduzierten Synthese der Nitratreduktase. Der Einsatz radioaktiver C-Isotope (11C bzw. 14) lieferte widersprüchliche Daten. Bei einen Pulsexperiment zeigte die -K-Variante von Brassica napus L. eine höhere Verlagerung von Assimilaten in die Wurzel als die +K-Varianten. Bei einer kontinuierlichen Applikation lag der Transfer von Assimilaten jedoch deutlich niedriger als bei der +K-Variante bzw. einer Variante, die während des Versuchs auf Medium mit K+ umgestellt wurde. Der Gehalt an Malat in Blatt, Spross oder Wurzel wurde bei unterschiedlichem NO3--Angebot untersucht. Pflanzen im steady state lassen keinen großen Unterschied zwischen einem Angebot von 0,15 mM und 2,0 mM NO3- erkennen. Bei 0,15 mM NO3- ist allerdings das HATS aktiv, das einen höheren Energieeinsatz zur Aufnahme von NO3- als das bei 2 mM aktive LATS erfordert. Die höhere Malatkonzentration in der Wurzel der 150 µM NO3--Variante kann daher mit dem höheren Energiebedarf der Wurzeln zusammenhängen. Werden Raps und Lupine mit 150 µM NO3- angezogen, so ist unter K+-Mangel der Malatgehalt deutlich reduziert. Wird der K+-Mangel aufgehoben, so erfolgt ein starker Anstieg der Malatgehalte. Nach 1 d liegen die Werte deutlich über den Malatgehalten der +K-Variante, sie gehen aber in den folgenden Tagen langsam auf das Niveau der +K-Variante zurück. Die Induktion eines K+-Mangels führt zu einem langsamen Absinken der Malatgehalte in Raps oder Lupine. Wenn auch nicht unumstritten, so kann als Fazit der hier vorgestellten Untersuchungen das von Ben Zioni et al. (1971) vorgestellte Modell eines K+-Shuttles zwischen Xylem und Phloem zur Erklärung vieler der beschriebenen Effekte beitragen.Studies to charaterize uptake, transport and reduction of nitrate in leaves and roots of Brassica napus L. and Lupinus albus L. using short-lived radio isotopes 11C and 13N This study examines the effect of potassium on nitrate uptake, nitrate transport and nitrate reduction in plants. Brassica napus L (species Liberator-00) was selected as a species with predominant nitrate reduction in the leaves, while Lupinus albus L. (species Amiga) was representing plants with a predominant reduction in the roots. Usage of the short-lived radioisotope 13N permitted to generate NO3---uptake kinetics of oilseed rape and white lupin with distinction between influx, efflux and net uptake. Upon first contact with NO3-following NH4+-nutrition both species show an increasing uptake rate of nitrate. Initially nitrate efflux is missing but it starts after several hours. Further on it was stated that a short term pulse of NO3- is sufficient for induction of NO3--uptake. Oilseed rape and white lupin show the typical picture of nitrate uptake kinetics at low supply (HATS=high affinity transport system) or high supply (LATS=low affinity transport system). Nitrate uptake rate of oilseed rape is much higher than the one of commonly studied species like wheat or barley, while nitrate uptake rate of white lupin is much lower. Plants grown under K+-deficiency show lower NO3--influx and lower efflux. As soon as K+ is applied NO3--influx increases stronger than efflux, causing a higher net uptake of NO3-. Nitrate efflux increases after a lag period, showing a similar reaction like the induction of NO3--uptake after previous NH4+-nutrition. In Lupinus albus L. where the roots are the main site for nitrate reduction it is not possible to detect NO3-- in xyleme exudate as long as NO3- supply is below 250 µM. For Brassica napus L., with preferred reduction of NO3- in the leaves, NO3- can be detected in xyleme exudate even at low supply. Nitrate reductase activity (NRA) in leaves of white lupin is not present at nitrate supply below 1 mM. However NRA can be determined in roots and shoot of white lupin as well as in all plant parts of oilseed rape even at NO3--supply lower than 100 µM. NRA in both species is reduced under K+-deficiency. For the deficient plants an interaction of inhibition of nitrate reductase (NR) by Na+, which is used to replace K+ as a cation in nutrient solutions, and a probably reduced synthesis of NR seems to take place. Using radiolabelled carbon-isotopes showed mismatching data. In a pulse experiment the K+-deficient plants of Brassica napus L. showed higher export of assimilates to the roots than the K++-supplied control. At continuous application the transfer of assimilates to the root was much less in the -K-plants compared to +K plants or plants that have been switched from -K to +K medium during the experiment. The concentration of malate in leaves, stem or roots was checked at different levels of nitrate supply. Plants at steady state showed little difference between nitrate supply of 0.15 mM or 2.0 mM. Nevertheless at 0.15 mM the HATS is responsible for NO3- uptake, demanding an increased energy input for NO3- uptake than the LATS which is active at 2 mM. Increased malate concentration in the roots of the 150 µM-plants could be associated with the increased energy demand of the roots. Oilseed rape and white lupin, grown with 150 µM NO3-, showed reduced malate content under K+-deficiency. As soon as K+ is resupplied a strong increase of malate can be determined. One day after supply with K+ malate reaches a level above the one of continously K+-supplied plants, but during the next days the concentration declines. Induction of K+-deficiency slowly leads to a reduction of malate contents in oilseed rape and white lupin. Also not undisputed, the model of a K+-shuttle between xyleme and phloeme presented by Ben Zioni et al. (1971) can contribute to the explanation of the described effects

Meletemata quaedam de lectis : dissertatio inauguralis medica

http://tartu.ester.ee/record=b1922301~S1*es

Optimal Design of a Medium-Voltage Grid Analyzer

Much research has been done for medium-voltage applications, where multilevel inverters are challenging classical low-voltage inverters, connected by transformers. Although the decision is very crucial for system costs and performance, comparisons of both approaches are missing, being now introduced for the application of a medium-voltage grid analyzer

Glutamic Acid Residues in HIV-1 p6 Regulate Virus Budding and Membrane Association of Gag

The HIV-1 Gag p6 protein regulates the final abscission step of nascent virions from the cell membrane by the action of its two late (l-) domains, which recruit Tsg101 and ALIX, components of the ESCRT system. Even though p6 consists of only 52 amino acids, it is encoded by one of the most polymorphic regions of the HIV-1 gag gene and undergoes various posttranslational modifications including sumoylation, ubiquitination, and phosphorylation. In addition, it mediates the incorporation of the HIV-1 accessory protein Vpr into budding virions. Despite its small size, p6 exhibits an unusually high charge density. In this study, we show that mutation of the conserved glutamic acids within p6 increases the membrane association of Pr55 Gag followed by enhanced polyubiquitination and MHC-I antigen presentation of Gag-derived epitopes, possibly due to prolonged exposure to membrane bound E3 ligases. The replication capacity of the total glutamic acid mutant E0A was almost completely impaired, which was accompanied by defective virus release that could not be rescued by ALIX overexpression. Altogether, our data indicate that the glutamic acids within p6 contribute to the late steps of viral replication and may contribute to the interaction of Gag with the plasma membrane

Oral HRAS Mutation in Orofacial Nevus Sebaceous Syndrome (Schimmelpenning-Feuerstein-Mims-Syndrome): A Case Report With a Literature Survey

Background/Aim: The aim of this study was to present the long-term course of a patient with nevus sebaceous syndrome (NSS). Recent genetic studies place the syndrome in the emerging group of so-called RASopathies. The focus of the report is on surgical treatment and morphological and genetic findings of the face and oral cavity. Case Report: A female patient was treated for congenital alterations of facial skin and oral mucosa. The oral lesions were removed repeatedly. Eruption of teeth on the lesion sites was made easier by the measures taken. However, after repeated ablation of the affected gingiva, the periodontal papillomatous epithelium re-differentiated into the same reddish, conspicuous, hyperplastic epithelium. The teeth in the affected region showed noticeable changes in position, surface, and shape. A HRAS mutation was detected only in the regions of altered oral epithelia and not in adjacent soft tissues. Conclusion: Reports on NSS rarely address oral manifestations. The recorded alterations of oral soft and hard tissues in NSS indicate a topographical relationship between the development of oral mucosa and teeth as well as the long-lasting impact of a sporadic mutation on organ development at this site

Highly conserved serine residue 40 in HIV-1 p6 regulates capsid processing and virus core assembly

Background: The HIV-1 p6 Gag protein regulates the final abscission step of nascent virions from the cell membrane by the action of two late assembly (L-) domains. Although p6 is located within one of the most polymorphic regions of the HIV-1 gag gene, the 52 amino acid peptide binds at least to two cellular budding factors (Tsg101 and ALIX), is a substrate for phosphorylation, ubiquitination, and sumoylation, and mediates the incorporation of the HIV-1 accessory protein Vpr into viral particles. As expected, known functional domains mostly overlap with several conserved residues in p6. In this study, we investigated the importance of the highly conserved serine residue at position 40, which until now has not been assigned to any known function of p6. Results: Consistently with previous data, we found that mutation of Ser-40 has no effect on ALIX mediated rescue of HIV-1 L-domain mutants. However, the only feasible S40F mutation that preserves the overlapping pol open reading frame (ORF) reduces virus replication in T-cell lines and in human lymphocyte tissue cultivated ex vivo. Most intriguingly, L-domain mediated virus release is not dependent on the integrity of Ser-40. However, the S40F mutation significantly reduces the specific infectivity of released virions. Further, it was observed that mutation of Ser-40 selectively interferes with the cleavage between capsid (CA) and the spacer peptide SP1 in Gag, without affecting cleavage of other Gag products. This deficiency in processing of CA, in consequence, led to an irregular morphology of the virus core and the formation of an electron dense extra core structure. Moreover, the defects induced by the S40F mutation in p6 can be rescued by the A1V mutation in SP1 that generally enhances processing of the CA-SP1 cleavage site. Conclusions: Overall, these data support a so far unrecognized function of p6 mediated by Ser-40 that occurs independently of the L-domain function, but selectively affects CA maturation and virus core formation, and consequently the infectivity of released virions

Immunophenotyping and Transcriptomic Outcomes in PDX-Derived TNBC Tissue

Cancer tissue functions as an ecosystem of a diverse set of cells that interact in a complex tumor microenvironment (TME). Genomic tools applied to biopsies in bulk fail to account for this tumor heterogeneity while single cell imaging methods limit the number of cells which can be assessed or are very resource intensive. The current study presents methods based on flow cytometric analysis and cell sorting using known cell surface markers (eg, CD184, CD24, CD90) to identify and interrogate distinct groups of cells in triple-negative breast cancer (TNBC) clinical biopsy specimens from patient-derived xenograft (PDX) models. The results demonstrate that flow cytometric analysis allows a relevant subgrouping of cancer tissue and that sorting of these subgroups provides insights on cancer cell populations with unique, reproducible and functionally divergent gene expression profiles. The discovery of a drug resistance signature implies that uncovering the functional interaction between these populations will lead to deeper understanding of cancer progression and drug response. Implications: PDX-derived human breast cancer tissue was investigated at the single cell level and cell subpopulations defined by surface markers were identified which suggest specific roles for distinct cellular compartments within a solid tumor