Late enzymes of vindoline biosynthesis. Acetyl-CoA: 17-O-deacetylvindoline 17-O-acetyl-transferase

From differentiated plants of Catharanthus roseus (L.) G. Don, a specific enzyme was isolated and named acetyl-CoA : 17-O-deacetylvindoline 17-O-acetyltransferase, acting on the biosynthetic formation of the Aspidosperma type alkaloid vindoline.The enzyme shows a high selectivity towards different substrates. The acetyl-CoA-dependent transferase also catalyses the reverse reaction by hydrolysis of the 17-O-acetyl group of vindoline in the presence of free CoA. This enzyme is localized only in vindoline-containing plant parts, but was so far not detectable in cell suspension cultures of C. roseus. The enzyme allows the synthesis of labelled vindoline with high specific activity, applicable for instance as tracer for radioimmunoassays of vindoline.     

Geschlechtsspezifische Unterschiede beim Nahrungserwerb des Fichtenkreuzschnabels (Loxia curvirostra)

Summary By recording the rate of glancing (i. e. looking up), the number of seeds taken by a crossbill per unit time from a larch cone (Larix X eurolepis) was evaluated. Female crossbills took more seeds per unit time from the cones than males do. Because of similar bill (and body) sizes the sexual difference could be explained in the following ways: a) during the breeding season the females need more energy for egg production than males do for spermatogenesis; b) females are more vigilant than males.     

Filter mesh size and food particle uptake by Daphnia

Food size selection of four Daphnia, species (D. magna, D. hyalina, D. galeata, D. pulicaria) was investigated using spherical plastic beads as artificial food and with small bacteria. The size of the particles ranged from 0.1 to 35 m with special emphasis to the particle diameters between 0.1 and 1 m. In one set of experiments a mixture of differently sized particles was offered as food suspension and the selectivity of filtering was determined by comparing the size spectrum of the particles found in the gut contents with the spectrum in the food suspension. In a second series of experiments suspensions of uniformly sized particles were offered to single animals and their feeding activity was observed directly. In both types of experiments the mesh sizes of the filtering apparatus of the respective animals studied were measured after the experiments by, scanning electron microscopy. The mean sizes of the filter meshes were about 0.4–0.7 m. In all experiments the size of the particles found in the gut or those which caused high feeding activities were larger than the smallest mesh sizes of the filters. As a consequence simple mechanical sieving provides a sufficient explanation for the mechanism of particle retention of the filtering process in Daphnia. D. magna was found to feed with high efficiency on suspended freshwater bacteria, the residual species investigated showed low filtering efficiencies when bacteria were offered as food.The present study was supported by Deutscher Akademischer Austauschdients     

Peptidoglycans as promoters of slow-wave sleep. II. Somnogenic and pyrogenic activities of some naturally occurring muramyl peptides; correlations with mass spectrometric structure determination

The structures of components of the sleep-promoting material purified from human urine were established by fast atom bombardment-mass spectrometry, as reported in the accompanying paper (Martin, S. A., Karnovsky, M. L., Krueger, J. M., Pappenheimer, J. R., and Biemann, K. (1984) J. Biol. Chem. 259, 12652-12658). We report here that two substances isolated from that preparation, viz. N-acetylglucosaminyl-1,6 -anhydro-N-acetylmuramyl-Ala-gamma-Glu-diaminopimelyl-Ala) and that compound lacking the terminal alanine, are active as somnogens. Cerebro-intraventricular administration of 1 pmol of the glycotetrapeptide was sufficient to induce prolonged excess sleep in rabbits. A similar substance obtained from Brevibacterium divaricatum in which the free carboxyls of the glutamic and diaminopimelic moieties, indicated above, were amidated (N-acetylglucosaminyl-1,6-anhydro-N-anhydromura-myl-Ala-iso- Gln- epsilon-amido-diaminopimelyl -Ala-Ala) was not active as a promoter of slow-wave sleep. Deamidation of this peptide to a mixture of the free dicarboxylic forms produced a somnogenic substance. Our findings show that in addition to the muramyl form of peptidoglycan monomers, the anhydro muramyl form, with no reducing end, is compatible with somnogenic activity. Furthermore, the data obtained with a natural product amplify our earlier observations with smaller synthetic molecules of the importance of amidation/deamidation in the structure-activity relationships of muramyl peptides.     

Human Ile-Ser-bradykinin, identical with rat T-kinin, is a major permeability factor in ovarian carcinoma ascites

Ascites from patients with metastatic ovarian carcinoma contains high amounts of an activity that increases vascular permeability, as easily detected by a rat skin test. Ascites was fractionated by gel permeation and reversed-phase high-performance liquid chromatographies. The fractions were analysed for permeability-increasing activity. In this way a peptide was isolated and identified as Ile-Ser-bradykinin by sequence and amino-acid analyses. It is identical with T-kinin which has previously been detected as a product of an acute-phase protein, T-kininogen, in rats but never in human material. The so far identified human kininogens, i.e. high- and low-molecular mass kininogens, can only release Met-Lys-bradykinin or its degradations products, as Ile-Ser-bradykinin is not a part of their structure. However, the present results provide evidence that the permeability factor Ile-Ser-bradykinin under certain conditions can be produced in considerable amounts also by human tissues.