Biomonitoring of arylamines: haemoglobin adducts of aniline derivatives

Aromatic amines are important intermediates in industrial manufacturing. They are used in a large number of products, such as pesticides, dyes, plastics and pharmaceuticals. The parent arylamines can be metabolically released from these arylamine-based compounds and form DNA and protein adducts after N-oxidation to N-hydroxy arylamines. Aromatic amine derivatives, including the industrial intermediates acetoacetanilide, acetoacet-m-xylidide and N-ethylaniline, were examined for their ability to form Hb adducts in rats as potential biomarkers of exposure. The haemoglobin binding indices (HBI=binding [mmol mol^-1 Hb]/dose [mmol kg^-1 body weight]) of the arylamines were determined 24 h after oral administration to female Wistar rats. The precipitated haemoglobin was dissolved in 0.1 M sodium hydroxide in the presence of internal standards. After hexane extraction the released arylamines were analysed by gas chromatography-mass spectrometry (GC-MS). For aniline released from acetoacetanilide an HBI of 15 and for 2,4-dimethylaniline released from acetoacet-m-xylidide an HBI of 0.129 were determined. The HBIof aniline released from N-ethylaniline was 45.     

Conopy architecture of Larrea tridentata (DC.) Cov., a desert shrub: foliage orientation and direct beam radiation interception

Summary At sites in the United States, creosote bushes (Larrea tridentata (DC.) Cov.) orient foliage clusters predominantly toward the southeast. Foliage of bushes at the southernmost distribution extreme in Mexico shows no predominant orientation. Clusters at all sites are inclined between 33° and 71° from the horizontal. Inclinations are steeper in the drier and hotter Mojave Desert than in the Chihuahuan Desert. Individual leaflets, though not measured, appear more randomly oriented than foliage clusters. In several populations studied, branches were shorter in the southeastern sectors of the crown, reducing self-shading early in the morning. Measurements of direct beam radiation interception by detached branches, using digital image processing, indicated that foliage clusters oriented toward the southeast exhibited less self-shading during spring mornings than clusters oriented northeast. This effect was not apparent at the summer solstice. This type of canopy architecture may tend to minimize self-shading during the morning hours when conditions are more favorable for photosynthesis, resulting in an improved daily water use efficiency.     

The membrane dialysis bioreactor with integrated radial-flow fixed bed —a new approach for continuous cultivation of animal cells

A hybridoma cell was cultivated continuously in a membrane dialysis bioreactor with an integrated radial-flow fixed bed consisting of porous Siran^® carriers over a period of 6 weeks. Antibodies accumulated to an average of 100 mg l^?1, approx. 10 times more than in fixed bed cultures without dialysis membrane. Serum costs could be reduced about 85% due to an appropriate feeding strategy. Siran^® carriers with 3–5 mm diameter showed an advantage compared to those with 1–2 mm diameter. For the 3–5 mm carrier the specific glucose uptake rate and the MAb production rate were constant, if the velocity was between 0.09 mm s^?1 and 0.75 mm s^?1. At higher velocities cells are washed out of the bed. Furthermore antibody consistency and cell stability were verified in long-term cultivations over a period of 96 days. From an estimation of the antibody concentration reachable with the reactor concept under optimal conditions a concentration 45 times higher compared to axial-flow fixed bed reactors and 11 times higher compared to stirred tank reactors can be expected.     

Receptor occupancy by a bovine sialoglycopeptide inhibitor correlates with inhibition of protein synthesis

We have isolated from bovine cerebral cortex cells and purified to homogeneity an 18,000 dalton, pl 3.0 sialoglycopeptide that inhibits protein synthesis and DNA synthesis of nontransformed but not transformed cells without affecting uptake of radiolabeled precursors. In this paper, we examine the relationship between the binding of the sialoglycopeptide inhibitor to 3T3 cells and inhibition of protein synthesis. Binding of the sialoglycopeptide to 3T3 cells was rapid at 37 degrees C and reached a maximum at 30 min; the binding at 37 degrees C was shown to be saturable and specific. Scatchard analysis of the binding indicated that 3T3 cells contained about 2 X 10(4) receptors/cell with a dissociation constant of 1.0-1.5 nM. Several lines of evidence indicated that receptor occupancy on 3T3 cells correlated with the protein synthesis inhibitory activity of the sialoglycopeptide. A comparison of the kinetics of inhibitor binding with the kinetics of protein synthesis inhibition demonstrated that binding directly correlated with the inhibition of protein synthesis, concentration-dependent inhibition of protein synthesis directly correlated with concentration-dependent receptor occupancy, and a direct correlation was also observed between the kinetics of inhibitor dissociation from its specific cell surface receptor and the kinetics of recovery from protein synthesis inhibition.     

Elektronenmikroskopische Untersuchungen zur Lipid-Speicherung in den Nierentubuli von Drosophila melanogaster

Zusammenfassung In den Zellen der Nierentubuli (Malpighische Gefäße) von Drosophila melanogaster werden Lipide in der gleichen Weise wie das 3-Hydroxykynurenin gespeichert. Diese Substanzen werden in Erweiterungen des endoplasmatischen Retikulums akkumuliert. Bei älteren Larven verschwinden diese Lipidtropfen. Dabei legen sich entweder Mitochondrien um die Depots oder sie werden von Membranstapeln des endoplasmatischen Retikulums umgeben und abgebaut. Die funktionelle Bedeutung dieser Befunde wird diskutiert.

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Electronmicroscopic studies on the lipid storage in the renal tubules of Drosophila melanogaster

Summary In the cells of the renal tubules (Malpighian tubules) of Drosophila melanogaster lipids are stored in the same way as 3-hydroxykynurenin. These substances are found in dilatations of the endoplasmic reticulum. In later larval stages the lipid droplets gradually disappear. In theses stages the lipid droplets are either closely associated with the mitochondria or they are removed by concentric membrane arrays of the endoplasmic reticulum. The functional significance of these findings is discussed.

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Diese Untersuchung wurde mit Unterstützung der Deutschen Forschungsgemeinschaft durchgeführt.     

Changes in carbohydrate composition and trehalase-activity during the budding cycle of Saccharomyces cerevisiae

Summary The carbohydrate composition and the specific activity of the trehalase of cyclic partially synchronised yeast populations have been investigated. Under glucose limitation and appropriate cultural conditions synchronous growth in a chemostat was achieved. The cells accumulated the reserve carbohydrates during the single cell phase between two buddings. The rapid degradation of part of these reserves began shortly before the swelling of the bud. The importance of the mobilisation of endogenous reserves for the development of the cell is discussed.The specific activity of the trehalase changed during the budding cycle. The result gives rise to the assumption that the synthesis of this enzyme is linked to the growth cycle.     

Semisynthesis of Arg15, Glu15, Met15, and Nle15-aprotinin involving enzymatic peptide bond resynthesis

The semisynthesis of homologues of aprotinin, the bovine pancreatic trypsin inhibitor, is described. The P₁ lysine¹⁵ residue was replaced by two methods. The first procedure, which consisted of two enzymatic steps for the incorporation of other amino acids has previously been described. The second approach consisted of six steps of both enzymatic and chemical nature. The modified inhibitor, in which the lysine¹⁵-alanine¹⁶ peptide bond is hydrolyzed, was used as the starting material. All carboxyl groups of the modified inhibitor were esterified with methanol; the lysine¹⁵ methylester group was then selectively hydrolyzed. Afterward, lysine¹⁵ itself was split off. Arginine, glutamic acid, methionine, andl-2-aminohexanoic acid (norleucine, Nle) were incorporated using water-soluble carbodiimide combined with an acylation catalyst. The methylester group was used to prevent polymerization. The reactive-site peptide bonds were resynthesized using either chymotrypsin or trypsin.