bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epigenetic programming of differential gene expression in development and evolution
Authors: Monk Marilyn 
Published: May 2005

AbstractThis review covers data on changing patterns of DNA methylation and the regulation of gene expression in mouse embryonic development. Global demethylation occurs from the eight‐cell stage to the blastocyst stage in pre‐implantation embryos, and global de novo methylation begins at implantation. We have used X‐chromosome inactivation in female embryos as a model system to study specific CpG sites in the X‐linked Pgk‐1 and Gópd housekeeping genes and in the imprinted regulatory Xist gene to elucidate the role of methylation in the initiation and maintenance of differential gene activity. Methyl‐ation of the X‐linked housekeeping genes occurs very close in time to their inactivation, thus raising the question as to whether methylation could be causal to inactivation, as well as being involved in its maintenance. A methylation difference between sperm and eggs in the promoter region of the Xist gene, located at the X‐chromosome inactivation centre, is correlated with imprinted preferential inactivation of the paternal X chromosome in extra‐embryonic tissues. Based on our data, a picture of the inheritance of methylation imprints and speculation on the significance of the Xist imprint in development is presented. On a more general level, an hypothesis of evolution by “adaptive epige‐netic/genetic inheritance” is considered. This proposes modification of germ line DNA in response to a change in environment and mutation at the site of modification (e.g., of methylated cytosine to thymine). Epigenetic inheritance could function to shift patterns of gene expression to buffer the evolving system against changes in environment. If the altered patterns of gene activity and inactivity persist, the modifications may become “fixed” as mutations; alternatively, previously silenced gene networks might be recruited into function, thus appearing as if they are “acquired characteristics.” An extension of this hypothesis is “foreign gene acquisition and sorting” (selection or silencing of gene function according to use). “Kidnapping” and sorting of foreign genes in this way could explain the observation that increased complexity in evolution is associated with more “junk” DNA. Adaptive epigenetic/genetic inheritance challenges the “central dogma” that information is unidirectional from the DNA to protein and the idea that Darwinian random mutation and selection are the sole mechanisms of evolution. © 1995 Wiley‐Liss, Inc.
Genetic conflict and evolution of mammalian X‐chromosome inactivation
Authors: Moore Tom , Hurst Laurence D. , Reik Wolf 
Published: May 2005

AbstractThe existence of parentally imprinted gene expression in the somatic tissues of mammals and plants can be explained by a theory of intragenomic genetic conflict, which is a logical extension of classical parent‐offspring conflict theory. This theory unites conceptually the phenomena of autosomal imprinting and X‐chromosome inactivation. We argue that recent experimental studies of X‐chromosome inactivation and andro‐genetic development address previously published predictions of the conflict theory, and we discuss possible explanations for the occurrence of random X‐inactivation in the somatic tissues of eutherians. © 1995 Wiley‐Liss, Inc.
Parent‐of‐origin specific effects on the methylation of a transgene in the zebrafish, Danio rerio
Authors: Martin C. Cristofre , McGowan Ross 
Published: May 2005

AbstractWe have examined the inheritance of a transgene locus in the zebrafish, Daniorerio and demonstrated that its methylation is af fected by the sex of the parent contributing the allele. This parent‐of‐origin effect on the zebrafish transgene appears to be identical to imprinting as seen in mammals except that in zebrafish, passage of the locus through a female tended to decreased its methylation, whereas passage through a male increased it. Methylation of the transgene in gametic tissues differed from somatic tissue with the locus being hypomethylated in sperm and hypermethylated in the unfertilized egg. The potential identification of imprinting in the zebrafish has important ramifications with respect to the evolution of the process as well as for understanding the role of imprinting in mammals. © 1995 Wiley‐Liss, Inc.
Chromatin structure and imprinting: Developmental control of DNase‐I sensitivity in the mouse insulin‐like growth factor 2 gene
Authors: Feil Robert , Handel Mary Ann , Allen Nicholas D. , Reik Wolf 
Published: May 2005

AbstractThe insulin‐like growth factor 2 (Igf2) gene on distal mouse chromosome 7 is expressed predominantly from the paternal allele. In previous studies we identified two regions of paternal allele‐specific methylation; one at ˜ 3 kb upstream of promoter 1, and a second in the 3′, coding portion of the gene. The 3′ region is methylated in an expressing tissue (fetal liver), whereas in a non‐expressing tissue (fetal brain), it is not methylated. By contrast, in the 5′ region, the paternal allele is highly methylated in all tissues. Here, we have studied another characteristic of chromatin, namely, sensitivity to DNase‐1 and have focused our developmental analysis on the two differentially methylated regions of Igf2. In the upstream region, four clustered DNase‐I hypersensitive sites (HSS) were detected in embryonic stem (ES) cells and in midgestation embryos, but not in neonatal liver or brain. In promoter 1 (P1), at β 0.3 kb upstream of exon 1, we detected a tissue‐specific HSS that was present in neonatal liver, in which P1 is active, but was absent in ES cells, the embryo, and in neonatal brain. No DNase‐I HSS were detected in the 3′ differentially methylated region of Igf2. In all these regions, we did not detect differences in DNase‐I sensitivity between the parental chromosomes. These results establish major developmental and tissue‐specific control of chromatin in the Igf2 locus. The presence of the HSS upstream of Igf2 precedes transcriptional activation of the Igf2 gene and may be indicative of a promoter for another transcript that is transcribed in the opposite direction. The HSS in P1 is largely liver‐specific; this promoter therefore is differently regulated than the more general fetal promoters P2 and P3. Whereas methylation can be allele‐specific, presumably reflecting the gene imprint, the nuclease sensitivity, as detected by our assay, is not. These results, taken together with previous observations, reveal developmental and tissue‐specific complexity in the expression of the parental imprint at the level of chromatin and transcription. We propose that epigenetic features of tissue‐specific control and of the control of allelic expression are intricately linked. © 1995 Wiley‐Liss, Inc.
Differential amplification of pheromone genes of the ciliate Euplotes raikovi
Authors: La Terza Antonietta , Miceli Cristina , Luporini Pierangelo 
Published: May 2005

AbstractIn hypotrich ciliates, the entire silent chromosomal genome of the germinal nucleus (micronucleus) undergoes extensive DNA rearrangements that, during the development of the somatic nucleus (macronucleus) at the beginning a new cell life cycle, eventually result in the production of linear DNA molecules. These molecules represent functional genes, each one consisting of a central coding region flanked by two shorter regions, which apparently lack canonical elements for regulation of replication and transcription. These are amplified to thousands of copies in the “adult” macronucleus of the vegetative cell. We defined the extent of this amplification for allelic codominant genes which, in the macronucleus of Euplotes raikovi, encode polypeptide cell recognition factors (pheromones). This amplification was shown to be allele‐specific. The copy numbers of genes coding for pheromones Er‐1, Er‐2, and Er‐10 were determined to be 2.5 ‐ 2.9 × 104, 0.9 ‐ 1.2 × 104, 1.6 ‐ 1.85 × 104 respectively, and these numbers did not appreciably vary during the vegetative cell proliferation. This differential amplification of pheromone genes was (i) independent of whether two genes coexisted in the same heterozy‐gous cell or were separated in the corresponding homozygotes, and (ii) directly correlated with quantitative variations in mRNA synthesis and pheromone secretion. On the basis of these results, it is suggested that a mechanism of gene‐specific amplification may be used by hypotrich ciliates to modulate gene expression. © 1995 Wiley‐Liss, Inc.
Two isoforms of xenopus retinoic acid receptor γ2 (B) exhibit differential expression and sensitivity to retinoic acid during embryogenesis
Authors: Crawford Michael J. , Liversage Richard A. , Varmuza Susannah L. 
Published: May 2005

AbstractWe report the isolation of two retinoic acid receptor isoforms (RARγ), which differ only in the 5′ untranslated and putative N‐terminus A regions. The two isoforms appear to serve as early markers for the presumptive neural axis; however, their expression patterns differ. RARγ2, 1 is first expressed at gastrulation at the dorsal lip and subsequently along the presumptive neural axis. RARγ2.2 represents the full‐length sequence of a receptor cDNA already partially characterized and present as a maternal transcript [Ellinger‐Ziegelbauer and Dreyer (1991); Genes Dev 5:94‐104, (1993): Mech Dev 41:31‐46; Pfeffer and DeRobertis, (1994) Mech Dev: 45:147‐153]. Unlike RARγ2.2, the 2.1 variant is not expressed either in pre‐somitic mesoderm or notochord. RARγ2.1 is strongly expressed in branchial arches and to a lesser extent in the neural floor plate. The two isoforms also exhibit differential sensitivity to retinoic acid. Constitutive expression of RARγ2.2 following neurulation appears to be depressed by treatment with retinoic acid, but domains of highest expression, namely, the head and tail, remain relatively unaffected, as do patterns of expression prior to late neurulation. By contrast, RARγ2.1 is not transcribed in retinoid‐inhibited structures. Using microinjection techniques, we show that changes of RARγ2.1 expression in presumptive head structures occur as an early and local consequence of retinoic acid administration. Since RARγ2.1 expression is inhibited by retinoic acid, we tested to see if other treatments that perturb axis formation had any effect. Surprisingly, UV irradiation did not suppress expression of the RARγ2.1 transcript, suggesting that its inhibition by retinoic acid is not due solely to inhibition of anterior neural development. These experiments demonstrate a new subdivision of isoforms that undergo differential expression during development and that exhibit differential sensitivity to retinoic acid and to UV. This sensitivity and the presence of this isoform variant in regions that are known to exhibit polarizing activity strengthen the hypothesis that these receptors play a primary role during morphogenesis.
Comparative biochemical and stress analysis of genetically selected drosophila strains with different longevities
Authors: Force Allan G. , Staples Tiffany , Soliman Sherif , Arking Robert 
Published: May 2005

AbstractWe have performed a comparative analysis of the effects of age of reproduction on the biochemical (protein, lipid, and glycogen content) and stress resistance (ability to survive starvation, desiccation, and exogenous paraquat) parameters on 10 sister lines of five different Drosophila strains. Four pairs of these sister lines were selected under different regimens for either early or delayed reproduction; the fifth pair was maintained in a nonselected state and served as the baseline strain to which all others were compared. It is generally accepted that the early regimens give rise to short‐lived phenotypes, whereas the delayed regimens give rise to long‐lived phenotypes. Our results suggest that a mechanism involving lipid and starvation resistance is not operative in our long‐lived strains. In addition, a mechanism involving glycogen content and desiccation resistance is only weakly supported. Finally, there is strong support for a mechanism that gives rise to enhanced paraquat resistance and therefore may involve regulatory changes in the pattern of ADS gene expression. In addition, the 15‐day early age at reproduction regimen (M type) shows qualitatively similar responses to that of the late age at reproduction regimen (L type). These results suggest that correlations between biochemical traits and longevity must be interpreted with caution. We discuss possible reasons for these results, including the possibility of multiple mechanisms, each leading to a different extended longevity phenotype.
Paraquat resistance and starvation conditions in the selection for longevity extremes in drosophila melanogaster populations previously selected for long and short developmental period
Authors: Cunha Gilson Luis Da , Mânica Da Cruz Ivana Beatrice , Fiorino Patrícia , De Oliveira Alice Kalisz 
Published: May 2005

AbstractThis paper analyzes the interaction between resistance to free radicals, development under starvation conditions, sex, and its consequences to the lifespan of Drosophila mela‐nogaster populations selected for developmental time and longevity. Our data suggest that the interaction between these physiological and environmental parameters is modulated largely by the pre‐imaginal developmental time, since the response to selection for longevity extremes depends strongly on the previous selection for developmental time extremes.
Calixarene‐Based Picolinamide Extractants for Selective An/Ln Separation from Radioactive Waste
Authors: Casnati Alessandro , Della Ca' Nicola , Fontanella Marco , Sansone Francesco , Ugozzoli Franco , Ungaro Rocco , Liger Karine , Dozol Jean‐Francois 
Published: May 2005

AbstractEleven novel ligands having picolinamide or thiopicolinamide binding groups at the upper or lower rim of calix[4]‐, calix[6]‐ and calix[8]arenes have been synthesised. The conformational properties of some of these ligands were studied in solution by means of NMR spectroscopy and in the solid state by X‐ray diffraction. Their ability to extract AmIII or EuIII from water to NPHE (o‐nitrophenyl hexyl ether) was tested at different concentrations of LiNO3, HNO3 and of a lipophilic dicarbollide anion (BrCosan). The data show a high cooperation between binding sites of the calixarene ligands in comparison to data obtained with the model ligand N‐butyl picolinamide (19). Some of these ligands show very high distribution coefficients for Am3+ (DAm > 300) and good Am/Eu selectivity at pH ≥ 3, which open up interesting perspectives for their application in the treatment of low acidity radioactive waste. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
From Amino Acids to Enantiopure Bicyclic Isoxazolidinylpyridin‐4(1H)‐ones through Intramolecular Nitrone Cycloadditions
Authors: Romeo Roberto , Iannazzo Daniela , Piperno Anna , Chiacchio Maria A. , Corsaro Antonino , Rescifina Antonio 
Published: May 2005

AbstractHomochiral bicyclic isoxazolidinylpyridin‐4(1H)‐ones have been synthesised by an intramolecular nitrone cycloaddition process, starting from homochiral β‐amino acids. Stereoselection at C2 or C3 of the acyclic substrate appears to give the best results in the control of the stereochemistry of the new formed chiral centres. The synthetic approach has been further directed towards functionalised piperidones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Palladium‐Mediated 11C‐Carbonylative Cross‐Coupling of Alkyl/Aryl Iodides with Organostannanes: An Efficient Synthesis of Unsymmetrical Alkyl/Aryl [11C‐carbonyl]Ketones
Authors: Karimi Farhad , Barletta Julien , Långström Bengt 
Published: May 2005

Abstract[11C]Carbon monoxide in low concentration, palladium complexes, alkyl/aryl iodides, and organostannanes are utilized in the synthesis of twenty alkyl [carbonyl‐11C]ketones. The activated palladium(0) species [Pd{P(o‐Tol)3}2] was generated in situ from tris(dibenzylideneacetone)palladium(0) [Pd2(dba)3] and a large excess of tri‐o‐tolylphosphane [P(o‐Tol)3]. The Stille coupling reactions were performed in a micro‐autoclave system. Radiochemical yields of 11C‐labelled alkyl/aryl ketones were in the range of 37–98 % with specific radioactivity up to 300 GBq μmol–1. Using this method, 4'‐aminoacetophen[13C‐arbonyl)one 6 was synthesised in order to confirm the position of labelling (δ = 196.7 ppm, CDCl3). The presented approach is an efficient way for synthesising 11C‐labelled alkyl/aryl ketones with acceptable radiochemical yield and is generally applicable in 13C‐labelling syntheses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Efficient Synthesis of the Azabicyclo[3.3.1]nonane Ring System in the Alkaloid Methyllycaconitine Using Bis(alkoxymethyl)alkylamines as Aminoalkylating Agents in a Double Mannich Reaction
Authors: Brimble Margaret A. , Brocke Constanze 
Published: May 2005

AbstractThe double Mannich reaction of cyclic β‐keto esters with bis(alkoxymethyl)alkylamines provides an efficient and versatile method for the construction of azabicyclo[3.3.1]nonanes and azabicyclo[3.2.1]octanes. The optimum conditions for efficient reaction involve use of the activator trichloromethylsilane in acetonitrile as solvent at ambient temperature. The utility of this synthetic method is further demonstrated by the facile synthesis of several AE ring analogues 39, 42 of the alkaloid methyllycaconitine by appendage of the key N‐(methylsuccininimido)anthranilate pharmacophore to the N‐(3‐phenylpropyl)‐substituted double Mannich adducts 18, 27. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Highly Diasteroselective and Remarkably π‐Facially Selective Lewis Acid‐Catalysed Diels–Alder Cycloaddition Reactions: Access to Novel 1,3,4‐Trisubstituted 2‐Azetidinones
Authors: Bhargava Gaurav , Mahajan Mohinder P. , Saito Takao , Otani Takashi , Kurashima Mai , Sakai Ken 
Published: May 2005

AbstractDiastereoselective and π‐facially selective Lewis acid‐catalysed intermolecular Diels–Alder reactions of 3‐butadienylazetidin‐2‐ones with a variety of symmetrical dienophiles (maleic anhydride, N‐phenylmaleimide, N‐p‐tolylmaleimide, benzoquinone and naphthoquinone) resulting in the synthesis of diastereomerically pure 1,3,4‐trisubstituted 2‐azetidinones are reported. The effects of different Lewis acids on the yields of the selectively formed diastereoisomers under different reaction conditions are also examined. Preferential chelation between the Lewis acid complexes of the different dienophiles and the carbonyl oxygens in the dienylazetidin‐2‐ones has been invoked to explain the observed π‐facial selectivity. The Lewis acid complexes of the dienophiles have been shown to approach preferentially from the si‐faces of the dienes, resulting in the formation of π‐facially selective “endo” adducts. The structures of these “endo” adducts have even been supported by X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
XNA (xylo Nucleic Acid): A Summary and New Derivatives
Authors: Ravindra Babu B. , Raunak  , Poopeiko Nicolai E. , Juhl Martin , Bond Andrew D. , Parmar Virinder S. , Wengel Jesper 
Published: May 2005

AbstractFully modified homopyrimidine 2'‐deoxy‐xylo nucleic acid (dXNA) form triple helixes with complementary DNA/RNA with thermal stabilities comparable to those of the corresponding DNA:DNA and DNA:RNA duplexes. However, a single or few insertions of dXNA monomers in a DNA strand significantly lower duplex stabilities. The dXNA monomers are known to adopt predominantly an N‐type furanose conformation in solution. With a desire to increase the binding affinity, seven sugar‐modified XNA monomers (H, F, N, M, K, P and Q) have been synthesised and their effect on hybridization towards DNA and RNA complements studied. The introduction of 2'‐fluoro and 2'‐hydroxy substituents was expected to induce conformational restriction towards C3'‐endo‐type furanose conformation of monomer F derived from 1‐(2'‐deoxy‐2'‐fluoro‐β‐D‐xylofuranosyl)thymine and monomer H derived from 1‐(β‐D‐xylofuranosyl)thymine. The presence of functionalites facing the minor groove as in 1‐(2'‐amino‐2'‐deoxy‐2'‐N,4'‐C‐methylene‐β‐D‐xylofuranosyl)thymine (monomer N), 1‐[4‐C‐(N‐methylpiperazinyl)methyl‐β‐D‐xylofuranosyl]thymine (monomer P), 1‐(4‐C‐piperazinylmethyl‐β‐D‐xylofuranosyl)thymine (monomer Q), 1‐(4‐C‐hydroxymethyl‐β‐D‐xylofuranosyl)thymine (monomer M) and 9‐(4‐C‐hydroxymethyl‐β‐D‐xylofuranosyl)adenine (monomer K) was studied, with monomer N being locked in an N‐type furanose conformation. Besides, an efficient synthesis of known xylo‐LNA phosphoramidite 19, required for the incorporation of 1‐(2'‐O,4'‐C‐methylene‐β‐D‐xylofuranosyl)thymine (monomer L) is described. For comparison, hydridization data of various XNAs reported in the literature are included in the discussion section. The thermal denaturation studies show that XNAs containing conformationally locked monomers (N and L) display improved binding affinity, and that partially modified DNA/XNA chimera, or fully modified XNA display preferential hybridization towards RNA complements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Domino Heck–Diels–Alder Reactions of Differently Substituted Cyclopropylallenes
Authors: Knoke Mario , de Meijere Armin 
Published: May 2005

AbstractSeveral substituted cyclopropylallenes were coupled under Heck conditions with aryl iodides and aryl bromides, respectively, and the 1,3,5‐hexatrienes resulting with ring‐opening of the cyclopropyl group, were captured in situ by a number of reactive dienophiles to yield oligosubstituted cyclohexene derivatives (8–86 %, 33 examples) with diastereomeric ratios ranging from 1.4:1 to 4.9:1. The influences of the number, the nature and the pattern of substituents have been elaborated. The [4+2] cycloaddition most probably proceeds in two steps through a mesomerically well stabilized 1,6‐zwitterionic intermediate. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Studies on the Synthesis of Macrocyclic Allenes by Ring Closing Metathesis and Doering–Moore–Skattebøl Reaction
Authors: Janßen Christian E. , Krause Norbert 
Published: May 2005

AbstractSeveral efficient synthetic approaches to allenic cyclophanes of the general structure 2/3, which are of interest as chiral ligands or host molecules, are described. The combination of the ruthenium‐catalyzed ring‐closing metathesis and the Doering–Moore–Skattebøl (DMS) reaction using the Seyferth reagent PhHgCBr3 provided a straightforward access to the allenic cyclophane 8. The macrocycles 13 and 17 with the allenic bridge between the aromatic units were also obtained efficiently by copper‐promoted SN2'‐substitution of propargylic acetates and ring‐closing metathesis. Alternatively, macrocyclic allenes can be synthesized by ring‐closing metathesis of α,ω‐bisallenes, as was demonstrated by the formation of the products 20, 21, and 23. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Cover Picture: A New Glucose: Towards Conformationally Locked Hexoses through Annulation (Eur. J. Org. Chem. 11/2005)
Authors: Mehta Goverdhan , Ramesh Senaiar S. 
Published: May 2005

AbstractThe cover picture shows the concept of carbocyclic annulation (trans‐ring fusion) to lock hexoses, such as β‐glucose, in their unnatural axial‐rich conformation, while retaining their natural configuration. The bipolarofacial nature of these novel cyclohexane ring annulated sugar entities is reflected in their channel‐like supramolecular assembly in the solid state, consisting of a hydrophilic interior and a hydrophobic exterior. Details are discussed in the article by G. Mehta and S. S. Ramesh on p. 2225 ff.