Cell Envelope Changes in Solvent-Tolerant and Solvent-Sensitive Pseudomonas putida Strains following Exposure to o-Xylene

Solvent-tolerant and -sensitive Pseudomonas putida strains were studied to determine their cell envelope changes following exposure to o-xylene. Both strains produced trans-unsaturated fatty acids. The tolerant strain showed an increase in total fatty acids, an increase in saturated fatty acids, and modified lipopolysaccharide. It is suggested that these envelope modifications aid in survival at high concentrations of organic solvents.     

Vollwertige Ernährung schützt vor Herzinfarkt: Nahrungsfette

High intake of dietary fats, especially of saturated fatty acids, is an important risk of premature coronary heart disease. LDL‐cholesterol and HDL‐cholesterol in plasma are influenced by several dietary factors and are determining by different ways the development of arteriosclerosis. n‐3 and n‐6 polyunsaturated fatty acids are essential and in a suitable ratio play a beneficial role in prevention of arteriosclerosis. The benefit of vitamins as supplements is not convincing. In view of today's knowledge it makes little sense to ingest individual nutrients in high doses, instead one should encourage consumption of a wholesome diet moderate in fat and with high dietary fibre food.     

APC mutant zebrafish uncover a changing temporal requirement for wnt signaling in liver development

Developmental signaling pathways hold the keys to unlocking the promise of adult tissue regeneration, and to inhibiting carcinogenesis. Patients with mutations in the Adenomatous Polyposis Coli (APC) gene are at increased risk of developing hepatoblastoma, an embryonal form of liver cancer, suggesting that Wnt affects hepatic progenitor cells. To elucidate the role of APC loss and enhanced Wnt activity in liver development, we examined APC mutant and wnt inducible transgenic zebrafish. APC^+/− embryos developed enlarged livers through biased induction of hepatic gene programs and increased proliferation. Conversely, APC^−/− embryos formed no livers. Blastula transplantations determined that the effects of APC loss were cell autonomous. Induction of wnt modulators confirmed biphasic consequences of wnt activation: endodermal pattern formation and gene expression required suppression of wnt signaling in early somitogenesis; later, increased wnt activity altered endodermal fate by enhancing liver growth at the expense of pancreas formation; these effects persisted into the larval stage. In adult APC^+/− zebrafish, increased wnt activity significantly accelerated liver regeneration after partial hepatectomy. Similarly, liver regeneration was significantly enhanced in APC^Min/+ mice, indicating the conserved effect of Wnt pathway activation in liver regeneration across vertebrate species. These studies reveal an important and time-dependent role for wnt signaling during liver development and regeneration.     

Description of the female and new data on the distribution of Annitella apfelbecki Klapálek, 1899 (Insecta: Trichoptera)

Annitella apfelbecki is one of three Annitella species with distribution ranges restricted to the Balkan Peninsula. In this paper, we describe the hitherto unknown female of A. apfelbecki and give the most important morphological features to enable its identification and separation from the other Annitella females. Additionally, we provide new data on distribution and discuss zoogeography, life cycle and ecology of this species.     

Experimental Sepsis Impairs Humoral Memory in Mice

Patients with sepsis are often immune suppressed, and experimental mouse models of sepsis also display this feature. However, acute sepsis in mice is also characterized by a generalized B cell activation and plasma cell differentiation, resulting in a marked increase in serum antibody concentration. Its effects on humoral memory are not clearly defined. We measured the effects of experimental sepsis on long-term immunological memory for a defined antigen: we induced colon ascendens stent peritonitis (CASP) 8 weeks after 2 rounds of immunization with ovalbumin. Four weeks later, the antigen-specific bone marrow plasma cell count had doubled in immunized non-septic animals, but remained unchanged in immunized septic animals. Sepsis also caused a decrease in antigen-specific serum antibody concentration. We conclude that sepsis weakens humoral memory by impeding the antigen-specific plasma cell pool’s development, which is not complete 8 weeks after secondary immunization.     

Resolution of d,l-menthol by interesterification with triacetin using the free and immobilized lipase of Candida cylindracea

Summary Interesterification in isooctane with triacetin as an acyl donor was found to be a new and effective method of racemic resolution of d,l-menthol, when using the free and immobilized lipase of Candida cylindracea. No water was produced by this highly stereoselective type of reaction in contrast to ester synthesis with acetic acid as an acyl donor. Even with diacetin no possible back reaction occurred and the enzyme was easily separated from the reaction solution as opposed to ester hydrolysis in aqueous systems. Inhibition of interesterification was caused by increasing concentrations of the acyl donor triacetin by more than 10 mmol·l^-1 on the one hand, and especially by diacetin on the other hand. The reaction product menthyl acetate had no influence. By adding water the interesterification activity of the lipase was reduced significantly. An alteration of the acyl donor triacetin to longerchained triglycerides caused changes in higher specific activities but poor enantioselectivities of the products, as in the case of ester synthesis starting from longer-chained organic acids.Dedicated to Prof. Dr. Fritz Wagner on the occasion of his 60th birthday     

Growth of Zea mays L. plants with their seminal roots only. Effects on plant development, xylem transport, mineral nutrition and the flow and distribution of abscisic acid (ABA) as a possible shoot to root signal

Maize (Zea mays L.) was grown in quartz sand culture eitherwith a normal root system (controls) or with seminal roots only(‘single-rooted’). Development of adventitious rootswas prevented by using plants with an etiolated mesocotyl andthe stem base was positioned 5–8 cm above the sand. Eventhough the roots of the single-rooted plants were sufficientlysupplied with water and nutrients, the leaves experienced waterdeficits and showed decreased transpiration as trans plrationalwater flow was restricted by the constant number of xylem vesselspresent in the mesocotyl. As a consequence of this restriction,transpirational water flow velocities in the metaxylem vesselsreached mean values of 270 m h^–1 and phloem transportvelocities of 5.2 m h^–1. Despite limited xylem transportmineral nutrient concentrations in leaf tissues were not decreasedin single-rooted plants, but shoot and particularly stem developmentwas somewhat inhibited. Due to the lack of adventitious rootsthe shoot:root ratio was strongly increased in the single-rootedplants, but the seminal roots showed compensatory growth comparedto those in control plants. Consistent with decreased leaf conductance,ABA concentrations in leaves of single-rooted plants were elevatedup to 10-fold, but xylem sap ABA concentrations in these plantswere lower than in controls, in good agreement with the well-wateredconditions experienced by the seminal roots. Surprisingly, however,ABA concentrations in tissues of the seminal roots of the single-rooted plants were clearly increased compared to the controls,presumably due to increased ABA import via phloem from the water-stressedleaves. The results are discussed in relation to the role ofABA as a shoot to root signal. Key words: Zea mays, seminal roots, plant development, xylem transport, mineral nutrition, ABA, shoot-to-root signal     

Detection of mitochondrial defects by laser fluorimetry

The mitochondrial function in skeletal muscle biopsies of three patients with chronic progressive external ophthalmoplegia, having deletions of the mitochondrial DNA, was studied by laser-excited fluorescence measurements of NAD(P)H and flavoproteins in saponin-skinned fibers. We detected substantially elevated steady state redox states of the mitochondrial NAD-system in the muscle fibers of these patients. Moreover, the respiratory chain-linked autofluorescence changes in the muscle fibers of these patients were larger in comparison to controls indicating substantial alterations of the mitochondrial content. These results are in line with the presence of elevated numbers of partially respiratory chain inhibited mitochondria in the skeletal muscle of chronic progressive external ophthalmoplegia patients. (Mol Cell Biochem 174: 97–100, 1997)     

Loss of recognition by cross-reactive T cells and its relation to a C-terminus-induced conformational reorientation of an HLA-B*2705-bound peptide

The human major histocompatibility complex class I antigen HLA‐B*2705 binds several sequence‐related peptides (pVIPR, RRKWRRWHL; pLPM2, RRRWRRLTV; pGR, RRRWHRWRL). Cross‐reactivity of cytotoxic T cells (CTL) against these HLA‐B*2705:peptide complexes seemed to depend on a particular peptide conformation that is facilitated by the engagement of a crucial residue within the binding groove (Asp116), associated with a noncanonical bulging‐in of the middle portion of the bound peptide. We were interested whether a conformational reorientation of the ligand might contribute to the lack of cross‐reactivity of these CTL with a peptide derived from voltage‐dependent calcium channel α1 subunit (pCAC, SRRWRRWNR), in which the C‐terminal peptide residue pArg9 could engage Asp116. Analyses of the HLA‐B*2705:pCAC complex by X‐ray crystallography at 1.94 Å resolution demonstrated that the peptide had indeed undergone a drastic reorientation, leading it to adopt a canonical binding mode accompanied by the loss of molecular mimicry between pCAC and sequence‐related peptides such as pVIPR, pLMP2, and pGR. This was clearly a consequence of interactions of pArg9 with Asp116 and other F‐pocket residues. Furthermore, we observed an unprecedented reorientation of several additional residues of the HLA‐B*2705 heavy chain near the N‐terminal region of the peptide, including also the presence of double conformations of two glutamate residues, Glu63 and Glu163, on opposing sides of the peptide binding groove. Together with the Arg‐Ser exchange at peptide position 1, there are thus multiple structural reasons that may explain the observed failure of pVIPR‐directed, HLA‐B*2705‐restricted CTL to cross‐react with HLA‐B*2705:pCAC complexes.     

Comparative analysis of the human and chicken prion protein copper binding regions at pH 6.5

Recent experimental evidence supports the hypothesis that prion proteins (PrPs) are involved in the Cu(II) metabolism. Moreover, the copper binding region has been implicated in transmissible spongiform encephalopathies, which are caused by the infectious isoform of prion proteins (PrP(Sc)). In contrast to mammalian PrP, avian prion proteins have a considerably different N-terminal copper binding region and, most interestingly, are not able to undergo the conversion process into an infectious isoform. Therefore, we applied x-ray absorption spectroscopy to analyze in detail the Cu(II) geometry of selected synthetic human PrP Cu(II) octapeptide complexes in comparison with the corresponding chicken PrP hexapeptide complexes at pH 6.5, which mimics the conditions in the endocytic compartments of neuronal cells. Our results revealed that structure and coordination of the human PrP copper binding sites are highly conserved in the pH 6.5-7.4 range, indicating that the reported pH dependence of copper binding to PrP becomes significant at lower pH values. Furthermore, the different chicken PrP hexarepeat motifs display homologous Cu(II) coordination at sub-stoichiometric copper concentrations. Regarding the fully cation-saturated prion proteins, however, a reduced copper coordination capability is supposed for the chicken prion protein based on the observation that chicken PrP is not able to form an intra-repeat Cu(II) binding site. These results provide new insights into the prion protein structure-function relationship and the conversion process of PrP.