Sesquiterpene lactones from Achillea collina J. Becker ex Reichenb

The flower heads of Achillea collina afforded 31 individual sesquiterpene lactones, among which nine guaianolides (1, 16, 20, 21, 23, 27-30), a germacranolide (18) and a dimeric guaianolide (31) were found to be new natural products. The lactones 2-4, 12, 14, 15, 17, 19 and 25 were isolated for the first time from the investigated species. Their structures were established by spectral methods.     

Glutamine Synthetase in Muscle Is Required for Glutamine Production during Fasting and Extrahepatic Ammonia Detoxification

The main endogenous source of glutamine is de novo synthesis in striated muscle via the enzyme glutamine synthetase (GS). The mice in which GS is selectively but completely eliminated from striated muscle with the Cre-loxP strategy (GS-KO/M mice) are, nevertheless, healthy and fertile. Compared with controls, the circulating concentration and net production of glutamine across the hindquarter were not different in fed GS-KO/M mice. Only a ∼3-fold higher escape of ammonia revealed the absence of GS in muscle. However, after 20 h of fasting, GS-KO/M mice were not able to mount the ∼4-fold increase in glutamine production across the hindquarter that was observed in control mice. Instead, muscle ammonia production was ∼5-fold higher than in control mice. The fasting-induced metabolic changes were transient and had returned to fed levels at 36 h of fasting. Glucose consumption and lactate and ketone-body production were similar in GS-KO/M and control mice. Challenging GS-KO/M and control mice with intravenous ammonia in stepwise increments revealed that normal muscle can detoxify ∼2.5 μmol ammonia/g muscle·h in a muscle GS-dependent manner, with simultaneous accumulation of urea, whereas GS-KO/M mice responded with accumulation of glutamine and other amino acids but not urea. These findings demonstrate that GS in muscle is dispensable in fed mice but plays a key role in mounting the adaptive response to fasting by transiently facilitating the production of glutamine. Furthermore, muscle GS contributes to ammonia detoxification and urea synthesis. These functions are apparently not vital as long as other organs function normally.     

Population variability of nonacosan-10-ol and n-alkanes in needle cuticular waxes of Macedonian pine (Pinus peuce GRISEB.)

This is the first report on population variability of nonacosan-10-ol and n-alkanes in needle epicuticular waxes of Macedonian pine (Pinus peuce GRISEB.) Hexane extracts of needle samples, originating from two natural populations in Montenegro (Zeletin and Sjekirica) and from one population in Serbia (Mokra Gora) were analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The amount of nonacosan-10-ol varied individually from 41.3 to 72.31% (average 55.9%), with the Sjekirica population being statistically divergent (64.4% on average). The results showed n-alkanes in epicuticular waxes ranging from C?? to C??. The most abundant alkanes were C??, C??, C??, and C?? (15.5, 11.1, 10.6, and 10.5% on average, resp.). The carbon preference index of Pinus peuce ranged from 1.0 to 4.3 (1.9 on average). Average chain length ranged from 18.4 to 27.7 (average 25.7). A high level of inidividual quantitative variation in all of these hydrocarbon parameters was also detected. These results were compared with published data on other species from the Pinus genus.     

Comparison of chicken erythroid cell nuclear isolation methods using morphological,immunochemical and biochemical criteria

Chicken erythroid nuclei were prepared using four published methods. Our findings indicate that nuclei prepared by nitrogen cavitation are less likely to be contaminated with plasma membrane fragments than those made by procedures involving cell disruption by hypotonic lysis. However, globin gene sequences were much less sensitive to DNase I digestion in nuclei prepared by nitrogen cavitation. This suggests that the conformation of chromatin was altered by the cavitation procedure. Analysis of the proteins solubilized during limited DNase I digestion of nuclei prepared by both hypotonic lysis and cavitation revealed no appreciable differences in HMG proteins but a notable difference in the RNP-associated proteins and core histones.Abbreviations HMG high mobility group nonhistone chromosomal protein - RNP ribonucleoprotein - SSC 14 mM sodium citrate buffered saline pH 7.0 - PMSF phenylmethanesulfonyl fluoride - EDTA ethylenediaminetetraacetic acid - DTT dithiothreitol - PBS 10 mM sodium phosphate buffered saline pH 7.2 - NP-40 Nonidet P-40 (octylphenoxypolyethoxyethanol) - SS-DNA single-stranded DNA - RSB reticulocyte standard buffer, 0.01 M NaCl, 0.003 M MgCl₂, 0.01 M Tris-HCI, pH 7.4.     

Silphiperfolane sesquiterpene acids from Artemisia chamaemelifolia Vill

The aerial parts of Artemisia chamaemelifolia Vill. afforded, in addition to five known sesquiterpene acids, a new 5-epi-cantabrenolic acid (6).     

Immobilization of alliinase on porous aluminum oxide

Membrane filters prepared from porous aluminum oxide (Anopore) were investigated for their potential use as a durable support for enzymes. Alliinase (EC 4.4.1.4) was chosen as a model enzyme for immobilization experiments. To allow for smooth fixation, the enzyme was immobilized indirectly by sugar-lectin binding. Monomolecular layers of the lectin concanavalin A and alliinase were applied by self-assembling processes. As an anchor for these layers, the sugar, mannan, was covalently coupled to the membrane surface. This procedure exhibits several advantages: (i) enzyme immobilization can be carried out under smooth conditions; (ii) immobilization needs little time; and (iii) protein layers may be renewed.