Homoisoflavanones from Muscari comosum bulbs

From the bulbs of Muscari comosum 3,9-dihydropunctatin and three novel homoisoflavanones were isolated.     

Protoporphyrin‐based eggshell pigmentation predicts hatching success and offspring sex ratio in the barn swallow

Inter‐ and intraspecific variation in eggshell colouration has long fascinated evolutionary biologists. Among species, such variation may accomplish different functions, the most obvious of which is camouflage and background matching. Within species, it has been proposed that inter‐female variation in eggshell pigmentation patterns can reflect egg, maternal or paternal traits and hence may provide cues to conspecifics about egg, maternal or paternal phenotypic quality. However, the relationship between protoporphyrin‐based eggshell pigmentation and egg or maternal/paternal traits appears to be highly variable among species. We investigated patterns of intraspecific variation in Eurasian barn swallow Hirundo r. rustica protoporphyrin‐based eggshell pigmentation, and analysed its association with egg and clutch characteristics, maternal/paternal phenotypic traits and parental feeding effort. Eggshell pigmentation pattern significantly varied between breeding colonies, was significantly repeatable in first clutches laid by the same females in different years (intraclass correlation coefficient ranging between 0.56 and 0.63), but it was not significantly associated with egg traits, such as position in the laying sequence, egg mass, yolk testosterone concentration and antioxidant capacity. It was weakly or non‐significantly associated with female and male traits (sexual ornaments), but females laying darker (higher pigment intensity) first clutches had higher hatching success, suggesting that eggshell pigment intensity may predict fitness. Male nestling feeding effort was not predicted by eggshell pigmentation. In addition, females with darker breast plumage colouration (a melanin‐based trait related to fitness) laid highly protoporphyrin‐covered eggs, suggesting the presence of a previously unappreciated link between protoporphyrin biosynthesis and plumage melanisation. Moreover, the proportion of male offspring increased in clutches originating from highly protoporphyrin‐covered eggs, suggesting that parents could acquire visual cues about their future brood sex composition before egg hatching. Our results support the idea that intraspecific signalling via eggshell pigmentation is a species‐specific rather than a general feature of avian taxa.     

Design,synthesis, X-ray studies,and biological evaluation of novel BACE1 inhibitors with bicyclic isoxazoline carboxamides as the P3 ligand

We describe the design, synthesis, X-ray studies, and biological evaluation of novel BACE1 inhibitors containing bicyclic isoxazoline carboxamides as the P3 ligand in combination with methyl cysteine, methylsulfonylalanine and Boc-amino alanine as P2 ligands. Inhibitor 3a displayed a BACE1 K_i value of 10.9?nM and EC₅₀ of 343?nM. The X-ray structure of 3a bound to the active site of BACE1 was determined at 2.85?Å resolution. The structure revealed that the major molecular interactions between BACE1 and the bicyclic tetrahydrofuranyl isoxazoline heterocycle are van der Waals in nature.     

Stereoselective and species-dependent kinetics of reboxetine in mouse and rat

Reboxetine, (RS)-2-[(RS)-α-(2-ethoxyphenoxy)benzyl]morpholine methanesulphonate, is a racemic compound and consists of a mixture of the (R,R)- and (S,S)-enantiomers. In this study, brain and plasma levels of both enantiomers were determined in mice and rats after oral administration of reboxetine at doses (1.1 mg/kg, mouse; 20 mg/kg, rat) twice the respective ED₅₀ values in the antireserpine test. Plasma and brain concentrations of each enantiomer were measured up to 6 h postdosing using an HPLC method with fluorimetric detection after derivatization with a chiral agent (FLEC). In mice and rats, brain and plasma levels of the (R,R)-enantiomer were always higher than those of the (S,S)-enantiomer. After normalization for dose, the mean AUC_0-tz values of both the (R,R)- and (S,S)-enantiomers in mouse brain were about 23 and 32 times higher than in rat brain, respectively. In plasma, the corrected mean AUC_0-tz values were about 5 (R,R) and 10 (S,S) times higher in mice than in rats. These results provide evidence for the higher bioavailability and/or lower clearance of both enantiomers in mice than in rats, and for a higher penetration of both enantiomers into mouse brain compared to rat brain. © 1995 Wiley-Liss, Inc.     

A first linkage map of Cichorium intybus L. using a one-way pseudo-testcross and PCR-derived markers

We have used a one-way pseudo-testcross mapping strategy in combination with different types of PCR-based markers (RAPD, AFLP, SAMPL) to construct a first linkage map for variegated chicory (Cichorium intybus L. var. silvestre Biskoff, n=9), a self-incompatible vegetable species. The success of such a strategy depends on the presence of sufficiently high levels of heterozygosity in the individual plant which is being mapped and on the informativeness of the marker system that is used. A total of 371 markers, comprising 16 RAPDs, 72 SAMPLs and 283 AFLPs, were scored in 46 F₁ individuals obtained from an interspecific cross between a C. intybus outbred individual and a C. endivia inbred line. Grouping of the markers at a LOD score of 4.0 resulted in 13 linkage groups covering 1330 cM. A framework map covering 1201.4 cM was assembled by using all markers that could be ordered with a LOD greater than 2.0. We estimate the total genome size of chicory to be ca. 1405 cM, thus considerably smaller than that estimated for lettuce (1950 cM). The usefulness of the different marker systems that were applied is analysed in terms of level of heterozygosity and marker index, i.e. number of different genetic loci that may be simultaneously analysed per experiment. Out of the 371 markers, 50 of them showed segregation distortion which is discussed in terms of the hybrid origin of the variegated chicory.     

Advancing cell wall inhibitors towards clinical applications

Natural products represent a major source of approved drugs and still play an important role in supplying chemical diversity. Consistently, 2014 has seen new, natural product-derived antibiotics approved for human use by the US Food and Drug Administration. One of the recently approved second-generation glycopeptides is dalbavancin, a semi-synthetic derivative of the natural product A40,926. This compound inhibits bacterial growth by binding to lipid intermediate II (Lipid II), a key intermediate in peptidoglycan biosynthesis. Like other recently approved antibiotics, dalbavancin has a complex history of preclinical and clinical development, with several companies contributing to different steps in different years. While our work on dalbavancin development stopped at the previous company, intriguingly our current pipeline includes two more Lipid II-binding natural products or derivatives thereof. In particular, we will focus on the properties of NAI-107 and related lantibiotics, which originated from recent screening and characterization efforts.     

Histone-lysine methyltransferase activity from sea-urchin embryo nuclei. Changes in substrate specificity upon purification

The S-adenosylmethionine:histone-lysine methyltransferase (EC 2.1.1.43) enzyme activity, present in the chromatin of sea-urchin embryo nuclei, has been purified about 300-fold with 30% overall yield. The initial activity in the nucleus transfers methyl groups to the epsilon-amino group of lysines and acceptor proteins are chromatin-bound H3 and H4 histones. In contrast, the purified enzyme activity transfers methyl groups to the arginines and acceptor proteins are soluble H3 and H4 histones. The two changes in substrate specificity do not occur at the same time. The variation of acceptor protein from chromatin-bound to soluble histones occurs at the first step, upon nuclei sonication, when no protein fractionation has yet been performed. At that step, lysine is still the only methylated side-chain. The variation of the methylated amino acid from lysine to arginine occurs gradually with increasing enzyme purification. The enzyme activity has a molecular mass of about 200 kDa. Saturation curves for H3 and H4 histones, used as substrate either individually or in total histones, and for AdoMet show no substantial dependence on enzyme purification. Maximal activity for the enzyme, at all purification levels, occurs at about pH 8 for all substrate histones. An increase in the relative concentrations of di- and trimethyllysine derivatives is observed with the more purified enzyme preparations, while the ratio of mono- and dimethylarginine derivatives remains constant. The data are taken as evidence that the same protein molecule is responsible for the two activities.     

THE REGULATION OF RNA SYNTHESIS AND PROCESSING IN THE NUCLEOLUS DURING INHIBITION OF PROTEIN SYNTHESIS

The effect of protein synthesis inhibition by cycloheximide on nucleolar RNA synthesis and processing has been studied in HeLa cells. Synthesis of 45S RNA precursor falls rapidly after administration of the drug. However, the nucleolar content of 45S RNA remains relatively constant for at least 1 hr because the time required for cleavage of the precursor molecule into its products is lengthened after treatment with cycloheximide. The efficiency of transformation of 45S RNA to 32S RNA remains constant with approximately one molecule of the 32S RNA produced for each cleavage of a molecule of 45S RNA. However, shortly after the cessation of protein synthesis the formation of 18S RNA becomes abortive. The amount of 32S RNA present in the nucleolus remains relatively constant. After long periods of protein synthesis inhibition the 28S RNA continues to be synthesized and exported to the cytoplasm but at a greatly reduced rate. When the protein synthesis inhibitor is removed, a prompt, although partial, recovery in the synthesis rate of 45S RNA occurs. The various aspects of RNA synthesis regulation and processing are discussed.