HPLC separation of the enantiomers of nicotine and nicotine-like compounds

A sensitive and reproducible HPLC method utilizing a commercially available chiral α₁-acid glycoprotein (AGP) phase has been developed to separate and quantify the enantiomers of nicotine. The method is suitable for routine use as indicated by column life. The quantification of (R/S:0.05/99.95)-nicotine or (R/S:99/1)-nicotine was possible. In addition, the separation or at least partial separation of the enantiomers of nornicotine and nornicotine-derived compounds was achieved. © 1993 Wiley-Liss, Inc.     

Conservative resource utilization in the common blue butterfly–evidence for low costs of accepting absent host plants?

We studied host plant preference of the common blue butterfly, Polyommatus icarus , and larval performance on two different host plants, Oxytropis campestris and Lotus corniculatus . The study species is a small lycaenid butterfly believed to be relatively sedentary. The study populations originated from two different and widely separated geographical areas. In one area both hosts are naturally occurring, with O. campestris being most abundant at the study sites, in the other area only one of the host plants, L. corniculatus , is present. There was no difference in oviposition preference or larval performance between populations from the two different areas. Hence, P. icarus from sites dominated by O. campestris has not evolved a higher preference for or better performance on this host plant. More surprisingly, P. icarus from the area were O. campestris is completely absent has retained not only good larval performance on this host plant but also high female preference for it. This conservatism at a large geographical scale is seen even though there seems to be genetic variation present in both populations, at least for preference but perhaps also for performance. We suggest that such lack of variation in resource utilization between populations may be evidence for weak selection against "preferences" for plants that are rare or absent. A combination of other constraining factors may also contribute to some degree, especially stepping-stone gene flow between populations.     

Continuous representations of time-series gene expression data.

We present algorithms for time-series gene expression analysis that permit the principled estimation of unobserved time points, clustering, and dataset alignment. Each expression profile is modeled as a cubic spline (piecewise polynomial) that is estimated from the observed data and every time point influences the overall smooth expression curve. We constrain the spline coefficients of genes in the same class to have similar expression patterns, while also allowing for gene specific parameters. We show that unobserved time points can be reconstructed using our method with 10-15% less error when compared to previous best methods. Our clustering algorithm operates directly on the continuous representations of gene expression profiles, and we demonstrate that this is particularly effective when applied to nonuniformly sampled data. Our continuous alignment algorithm also avoids difficulties encountered by discrete approaches. In particular, our method allows for control of the number of degrees of freedom of the warp through the specification of parameterized functions, which helps to avoid overfitting. We demonstrate that our algorithm produces stable low-error alignments on real expression data and further show a specific application to yeast knock-out data that produces biologically meaningful results.     

Reinstatement of Chiastocaulon Carl (Plagiochilaceae), Based on Evidence from Nuclear Ribosomal ITS and Chloroplast Gene rps4 Sequences

Abstract: Morphological approaches have led to controversial opinions regarding the systematic position of the Asian Jungermannia dendroides Nees within the family Plagiochilaceae. In recent times, the taxon was treated both as genus Chiastocaulon Carl, as a member of Plagiochila sect. Dendroideae Gottsche, Lindenb. and Nees, and as a representative of Plagiochila subgen. Chiastocaulon (Carl) Inoue. Sequences of the chloroplast‐encoded rps4 gene and the internal transcribed spacers of nuclear ribosomal DNA of 28 representatives of the Plagiochilaceae and Herbertus subdentatus (Herbertaceae, outgroup) were obtained to test the different hypotheses. Maximum likelihood analyses were performed, both on the separate and combined data sets, and in all cases resulted in a single optimal topology. The different phylogenies were congruent, but the analyses of the combined data set led to an overall more significant bootstrap support. Jungermannia dendroides was placed in a moderately supported clade with Pedinophyllum interruptum and Plagiochilion mayebarae, sister to the well supported Plagiochila clade. The topology justifies the recognition of Jungermannia dendroides as genus Chiastocaulon. Plagiochila frondescens (Nees) Lindenb., P. fruticosa Mitt. and P. pulcherrima Horik., placed alongside Chiastocaulon/Plagiochila dendroides by some authors, form a robust clade within Plagiochila (Dumort.) Dumort., assignable to P. sect. Fruticosae Inoue. The three species share the dendroid habit and alternating foliation with Chiastocaulon dendroides but lack well developed ventral intercalary branches. 11 sectional clades with robust bootstrap support were identified within the Plagiochila lineage. Many morphological characters of monophyletic lineages within the Plagiochilaceae appeared homoplastic, indicating that a natural subdivision of the family is only possible by the integration of molecular data. The molecular topologies justify a hierarchical subdivision of Plagiochila at some point in the future; however, well supported sectional groups of the molecular trees will presumably lack morphological autapomorphisms.     

In vitro and in vivo action of antisense RNA

The transient or permanent expression of antisense RNA represents one option to apply antisense techniques in biotechnology and medical research. Despite the increasing importance and use of antisense nucleic acids as well as their significant antisense-specific phenotypic effects in vivo, there is an obvious lack of explanation for the mechanism of their action. By studying naturally occurring antisense RNA and analyzing their mechanism of action we attempt to learn more about the design, the use, and the critical parameters of artificial antisense RNA. Attempts to derive models from biochemical and structural studies for the interactions between antisense RNAs and their targets will be discussed.     

Presynaptic Nicotinic Receptors Stimulate Increases in Intraterminal Calcium of Chick Sympathetic Neurons in Culture

Abstract: Stimulation of chick sympathetic neurons in culture by the cholinergic agonists acetylcholine, nicotine, and 1,1-dimethyl-4-phenylpiperazinium (all at 10–1,000 µmol/L) induced concentration-dependent increases of free calcium levels measured by fura 2 fluorescence in neuronal processes. The response evoked by acetylcholine had both nicotinic and muscarinic components, whereas that induced by 1,1-dimethyl-4-phenylpiperazinium was purely nicotinic. Tetrodotoxin (0.3 µmol/L) blocked completely the increase of intraterminal free calcium level evoked by electrical stimulation. On the other hand, stimulation with 1,1-dimethyl-4-phenylpiperazinium still evoked 20–25% of the control response in the presence of tetrodotoxin. The concentration-response relationship of 1,1-dimethyl-4-phenylpiperazinium stimulation did not differ in the absence and in the presence of tetrodotoxin. The nicotinic antagonists d -tubocurarine (10 µmol/L) and mecamylamine (10 µmol/L), but not α-bungarotoxin (125 nmol/L), prevented the increase of intraterminal free calcium level evoked by 1,1-dimethyl-4-phenylpiperazinium (100 µmol/L) in the presence of tetrodotoxin. These observations indicate the presence of nicotinic receptors on neuronal processes that increase the intraterminal concentration of free calcium and probably modulate transmitter release. Their pharmacological properties are similar to those of nicotinic receptors located on neuronal cell bodies.