Robust Selection of the Most Discriminative Variables in the Dichotomous Problem with Application to Some Respiratory Disease Data

A robust method for selection of variables with the greatest discriminatory power is presented in the paper. The method deals with the two groups of data problem. An application of the method to some respiratory disease data and comparisons with classical procedures are given, also.     

High fidelity extrachromosomal recombination and gene targeting in plants

The precision of extrachromosomal homologous recombination and gene targeting in plant cells was investigated. Recombination was directed to introns of selectable marker genes where potential changes could persist without affecting the function and therefore the selectability of the genes. Approximately 9 kb of crossover regions was rescued and sequenced. Changes were detected at a frequency below one point mutation per 1000 bp, indicating that extrachromosomal recombination and gene targeting both appear to occur with high fidelity.     

A minichromosome-like structure in wheat embryos

A crude nuclear fraction of resting wheat embryos was used as the source of putative plant minichromosomes: unique DNA sequences the size of genes and flanked by telomere-type repeats. Preliminary separation of low-molecular-weight DNA species from chromosomal DNA (Hirt's method), velocity sedimentation, and isopycnic centrifugation were followed by PCR amplification of minichromosome-like sequences. The most abundant PCR product was cloned and sequenced. In addition to telomeric repeats (defined by a PCR primer), which were the expected sequences, the linear DNA molecule (637 pb) contained an ARS-like element, RAP1-binding site, and two relatively long ORFs. The whole sequence seems to represent a naturally occurring plant minichromosome.     

Macrophyte and macroinvertebrate patterns in unimpacted mountain rivers of two European ecoregions

Hydrobiologia - The aim of the study was to compare the patterns of development of macrophytes and macroinvertebrates in different types of reference mountain rivers. The study is based on...     

A Model for Visual Memory Encoding

Memory encoding engages multiple concurrent and sequential processes. While the individual processes involved in successful encoding have been examined in many studies, a sequence of events and the importance of modules associated with memory encoding has not been established. For this reason, we sought to perform a comprehensive examination of the network for memory encoding using data driven methods and to determine the directionality of the information flow in order to build a viable model of visual memory encoding. Forty healthy controls ages 19–59 performed a visual scene encoding task. FMRI data were preprocessed using SPM8 and then processed using independent component analysis (ICA) with the reliability of the identified components confirmed using ICASSO as implemented in GIFT. The directionality of the information flow was examined using Granger causality analyses (GCA). All participants performed the fMRI task well above the chance level (>90% correct on both active and control conditions) and the post-fMRI testing recall revealed correct memory encoding at 86.33±5.83%. ICA identified involvement of components of five different networks in the process of memory encoding, and the GCA allowed for the directionality of the information flow to be assessed, from visual cortex via ventral stream to the attention network and then to the default mode network (DMN). Two additional networks involved in this process were the cerebellar and the auditory-insular network. This study provides evidence that successful visual memory encoding is dependent on multiple modules that are part of other networks that are only indirectly related to the main process. This model may help to identify the node(s) of the network that are affected by a specific disease processes and explain the presence of memory encoding difficulties in patients in whom focal or global network dysfunction exists.     

A model study of interactions between TcAChE peripheral site segment Tyr70Val71 and loop 1 of Fasciculin 2

The continuous chain of residues (Thr7 to Ala12) of Loop1 of Fas2 (F1) and its interaction with the peripheral binding sites (Tyr70-Val71) of AChE (P1) has been studied. Our results suggest that the flexibility of Loop1 might be caused by either the partially protonated guanidine group of Arg11 under experimental conditions or by the interaction with the negatively charged center of substrates. The binding energy of F1-P1 is predicted to be -16.6 kcal/mol at the B3LYP/6-311G(d,p) level, which is assumed to originate from one isolated O7...HN10 H-bond, one possible O10...HC71 unconventional O...HC type H-bonding, and the improved pi-bonding cooperativity around the peptide group of the AChE segment Tyr70-Val71. The classical Kitaura-Morokuma energy decomposition analysis, the NPA charge analysis, and the AIM analysis consistently reveal that the peptide group in segment P1 is more polarizable, which might play the key role in the interactions between F1 and P1. The PCM solvent effect corrected results reveal decrease of the interaction energy of the considered model. The importance of Thr8 of Fas2 in the P-site binding of AChE is also concluded. Site-directed mutations on either the Fas2 residue of Thr8 or the AChE residue of Tyr70 are expected to alter the binding behavior of the Loop1 of Fas2 with AChE.     

The fine structure of the neural lobe of the mouse after transplantation under the kidney capsule

Summary The neurohypophysis of donor mice was implanted under the renal capsule of the recipients. The pituicytes survived while the neurosecretory axons disappeared. The ultrastructure of the glial cells was observed seven and nine weeks after transplantation. There were no signs of phagocytotic activity although remnants of axons were still present at seven weeks. The numerous processes of the pituicytes form a network with intercellular spaces wide in younger and narrower in older implants. The cells are connected by desmosomes and gap junctions. Pituicytes as well as blood vessels preserve their organotypic appearance. The transplant thus represents an experimental model for investigations on pituicytes in vivo in the absence of neurosecretory axons.Fellow of the Alexander von Humboldt-Stiftung. On leave from Department of Histology and Embryology, Institute of Biostructure, Academy of Medicine, Pozna, Poland     

His164 regulates accessibility to the active site in fungal 17beta-hydroxysteroid dehydrogenase

17beta-Hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17beta-HSDcl) is an NADPH-dependent member of the short-chain dehydrogenase/ reductase superfamily. To study the catalytic properties of this enzyme, we prepared several specific mutations of 17beta-HSDcl (Tyr167Phe, His164Trp/Gly, Tyr212Ala). Wild-type 17beta-HSDcl and the 17beta-HSDcl mutants were evaluated by chromatographic, kinetic and thermodynamic means. The Tyr167Phe mutation resulted in a complete loss of enzyme activity, while substitution of His164 with Trp and Gly both resulted in higher specificity number (V/K) for the steroid substrates, which are mainly a consequence of easier accessibility of steroid substrates to the active-site hollow under optimized conditions. The Tyr212Ala mutant showed increased activity in the oxidative direction, which appears to be a consequence of increased NADPH dissociation. The kinetic characterizations and thermodynamic analyses also suggest that His164 and Tyr212 in 17beta-HSDcl have a role in the opening and closing of the active site of this enzyme and in the discrimination between oxidized and reduced coenzyme.     

Acetylcholinesterase inhibitory activity of lycopodane-type alkaloids from the Icelandic Lycopodium annotinum ssp. alpestre

The aim of this study was to investigate structures and acetylcholinesterase inhibitory activities of lycopodane-type alkaloids isolated from an Icelandic collection of Lycopodium annotinum ssp. alpestre. Ten alkaloids were isolated, including annotinine, annotine, lycodoline, lycoposerramine M, anhydrolycodoline, gnidioidine, lycofoline, lannotinidine D, and acrifoline, as well as a previously unknown N-oxide of annotine. ¹H and ¹³C NMR data of several of the alkaloids were provided for the first time. Solvent-dependent equilibrium constants between ketone and hemiketal form of acrifoline were determined. Conformation of acrifoline was characterized using NOESY spectroscopy and molecular modelling. The isolated alkaloids were evaluated for their in vitro inhibitory activity against acetylcholinesterase and butyrylcholinesterase. Ligand docking studies based on mutated 3D structure of Torpedo californica acetylcholinesterase provided rationale for low inhibitory activity of the isolated alkaloids as compared to huperzine A or B, which are potent acetylcholinesterase inhibitors belonging to the lycodine class. Based on the modelling studies the lycopodane-type alkaloids seem to fit well into the active site gorge of the enzyme but the position of their functional groups is not compatible with establishing strong hydrogen bonding interactions with the amino acid residues that line the binding site. The docking studies indicate possibilities of additional functionalization of the lycopodane skeleton to render potentially more active analogues.