bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of amino group pKa on the properties of stimuli‐responsive piperazine‐based polymers and hydrogels
Authors: Roshan Deen G. , Gan L. H. 
Published: October 2007

AbstractLinear homopolymers of N‐acryloyl‐N′‐alkyl piperazine (N′‐alkyl: methyl, ethyl, or propyl) and their corresponding crosslinked hydrogels were prepared. The polymers showed good responses to changes in the pH of the medium due to the presence of tertiary amine functions that could be protonated at a low pH. The nature of the N′‐alkyl group attached to the piperazine amino nitrogen greatly affected the pKa of the amino group. This in turn influenced the solution behavior of the polymers and was studied with light scattering, potentiometry, and viscosity measurements. The basicity of the polymers increased with an increase in the chain length of the N′‐alkyl substituent. The intrinsic viscosity of the polymers in a good polar organic solvent such as dimethylformamide decreased slightly with increasing temperature because of decreased thermodynamic affinity (interaction) at high temperatures. The viscosity behavior of the polymers in sodium chloride solutions was similar to that of classical polyelectrolytes. The swelling property of the hydrogels was studied with water sorption measurements, and the swelling was by anomalous (non‐Fickian) transport. The diffusion coefficient of the gels in solutions of pH 2.6 increased with increasing N′‐alkyl chain length, whereas at neutral pH, the effect was reversed. This behavior was attributed to the increase in both the basicity and hydrophobicity of the gels with an increase in the chain length of the N′‐alkyl groups. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Styrene‐assisted grafting of maleic anhydride onto polypropylene by reactive processing
Authors: Bettini S. H. P. , Ruvolo Filho A. C. 
Published: October 2007

AbstractThe grafting of maleic anhydride (MA) onto polypropylene (PP) was performed in the presence of the electron‐donating monomer styrene (ST) according to a central composite experimental design, in which the initial MA and ST concentrations were varied. The grafting of MA onto PP in the absence of ST was also performed. All reactions were carried out in the molten state in a Haake rheometer. The amount of reacted MA and the extent of degradation in PP were determined by means of Fourier transform infrared spectroscopy and melt flow index (MFI) measurements, respectively. The results showed that the presence of ST in the reactive processing caused a reduction in MFI and an increase in the level of reacted MA when the initial MA concentration equaled the initial ST concentration. An increase in the initial MA concentration presented distinct behavior that depended on the ST content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Yttria–polystyrene–polypropylene composite for fine dyeable fibers
Authors: Yu Chengbing , Jiang Chong , Chen Yanmo 
Published: October 2007

AbstractFine polypropylene fiber has many excellent properties, but it is difficult to dye because of the absence of dye sites in the molecular chain and high crystallinity. Fine polypropylene/hybrid polystyrene (yttria) fiber melt‐spun from blends of polypropylene and a small amount of nanohybrid polystyrene with modified yttria incorporated was prepared to improve the dyeing properties. The dyeability, orientation, degree of crystallinity, phase morphology, and mechanical properties of pure polypropylene and the blend fibers were investigated. It was found that the crystallinity and morphology of these phases in the blend systems were different. With the existence of nanohybrid polystyrene, the fine modified polypropylene filaments had practical mechanical properties, the amorphous region of the polypropylene/hybrid polystyrene (yttria) fiber increased, and the modified polypropylene fiber dyed easily and had good fastness to soaping because of the complexation of the disperse dye and yttrium in the blend system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Integrated Micro Flow Synthesis Based on Sequential Br–Li Exchange Reactions of p‐, m‐, and o‐Dibromobenzenes
Authors: Nagaki Aiichiro , Tomida Yutaka , Usutani Hirotsugu , Kim Heejin , Takabayashi Naofumi , Nokami Toshiki , Okamoto Hideho , Yoshida Jun‐ichi 
Published: October 2007

AbstractA micro flow system consisting of micromixers and microtube reactors provides an effective method for the introduction of two electrophiles onto p‐, m‐, and o‐dibromobenzenes. The Br–Li exchange reaction of p‐dibromobenzene with nBuLi can be conducted by using the micro flow system at 20 °C, although much lower temperatures (<−48 °C) are needed for a batch reaction. The resulting p‐bromophenyllithium was allowed to react with an electrophile in the micro flow system at 20 °C. The p‐substituted bromobenzene thus obtained was subjected to a second Br–Li exchange reaction followed by reaction with a second electrophile at 20 °C in one flow. A similar transformation can be carried out with m‐dibromobenzene by using the micro flow system. However, the Br–Li exchange reaction of o‐dibromobenzene followed by reaction with an electrophile should be conducted at −78 °C to avoid benzyne formation. The second Br–Li exchange reaction followed by reaction with an electrophile can be carried out at 0 °C. By using the present method, a variety of p‐, m‐, and o‐disubstituted benzenes were synthesized in one flow at much higher temperatures than are required for conventional batch reactions.
Why circumcision is a biomedical imperative for the 21stcentury
Authors: Morris Brian J. 
Published: October 2007

AbstractCircumcision of males represents a surgical “vaccine“ against a wide variety of infections, adverse medical conditions and potentially fatal diseases over their lifetime, and also protects their sexual partners. In experienced hands, this common, inexpensive procedure is very safe, can be pain‐free and can be performed at any age. The benefits vastly outweigh risks. The enormous public health benefits include protection from urinary tract infections, sexually transmitted HIV, HPV, syphilis and chancroid, penile and prostate cancer, phimosis, thrush, and inflammatory dermatoses. In women circumcision of the male partner provides substantial protection from cervical cancer and chlamydia. Circumcision has socio‐sexual benefits and reduces sexual problems with age. It has no adverse effect on penile sensitivity, function, or sensation during sexual arousal. Most women prefer the circumcised penis for appearance, hygiene and sex. Given the convincing epidemiological evidence and biological support, routine circumcision should be highly recommended by all health professionals. BioEssays 29:1147–1158, 2007. © 2007 Wiley Periodicals, Inc.
Playing only one instrument may be not enough: Limitations and future of the antiangiogenic treatment of cancer
Authors: Quesada Ana R. , Medina Miguel Ángel , Alba Emilio 
Published: October 2007

AbstractAngiogenesis plays an essential role in tumor growth, invasion and metastasis. After initial pessimism about the usefulness of the antiangiogenic therapeutic approach for cancer, interest has increased in the development of antiangiogenic compounds after the first clinical approval of an antiangiogenic therapy. The anti‐vascular endothelial growth factor (VEGF) antibody bevacizumab has recently been approved for use in combination with chemotherapy for the treatment of metastatic colorectal and non‐small cell lung cancer patients. However, no survival benefit has been demonstrated in anti‐VEGF monotherapy trials, probably due to the high complexity of tumor angiogenesis regulation. Experimental and clinical data, including the approval of the multitargeted drugs sunitinib and sorafenib, indicate that exciting results, including tumor regression, can be expected from the combined targeting of different pathways in the tumor angiogenesis scenario. Several obstacles, including the high cost of new molecular targeted drugs make this therapeutic approach difficult. BioEssays 29:1159–1168, 2007. © 2007 Wiley Periodicals, Inc.
Bioelectricity and epimorphic regeneration
Authors: Stewart Scott , Rojas‐Muñoz Agustin , Belmonte Juan Carlos Izpisúa 
Published: October 2007

AbstractAll cells have electric potentials across their membranes, but is there really compelling evidence to think that such potentials are used as instructional cues in developmental biology? Numerous reports indicate that, in fact, steady, weak bioelectric fields are observed throughout biology and function during diverse biological processes, including development. Bioelectric fields, generated upon amputation, are also likely to play a key role during vertebrate regeneration by providing the instructive cues needed to direct migrating cells to form a wound epithelium, a structure unique to regenerating animals. However, mechanistic insight is still sorely lacking in the field. What are the genes required for bioelectric‐dependent cell migration during regeneration? The power of genetics combined with the use of zebrafish offers the best opportunity for unbiased identification of the molecular players in bioelectricity. BioEssays 29:1133–1137, 2007. © 2007 Wiley Periodicals, Inc.
Control of male germ‐cell development in flowering plants
Authors: Singh Mohan B. , Bhalla Prem L. 
Published: October 2007

AbstractPlant reproduction is vital for species survival, and is also central to the production of food for human consumption. Seeds result from the successful fertilization of male and female gametes, but our understanding of the development, differentiation of gamete lineages and fertilization processes in higher plants is limited. Germ cells in animals diverge from somatic cells early in embryo development, whereas plants have distinct vegetative and reproductive phases in which gametes are formed from somatic cells after the plant has made the transition to flowering and the formation of the reproductive organs. Recently, novel insights into the molecular mechanisms underlying male germ‐line initiation and male gamete development in plants have been obtained. Transcriptional repression of male germ‐line genes in non‐male germ‐line cells have been identified as a key mechanism for spatial and temporal control of male germ‐line development. This review focuses on molecular events controlling male germ‐line development especially, on the nature and regulation of gene expression programs operating in male gametes of flowering plants. BioEssays 29:1124–1132, 2007. © 2007 Wiley Periodicals, Inc.
A biological cosmos of parallel universes: Does protein structural plasticity facilitate evolution?
Authors: Meier Sebastian , Özbek Suat 
Published: October 2007

AbstractWhile Darwin pictured organismal evolution as “descent with modification” more than 150 years ago, a detailed reconstruction of the basic evolutionary transitions at the molecular level is only emerging now. In particular, the evolution of today's protein structures and their concurrent functions has remained largely mysterious, as the destruction of these structures by mutation seems far easier than their construction. While the accumulation of genomic and structural data has indicated that proteins are related via common ancestors, naturally occurring protein structures are often considered to be evolutionarily robust, thus leaving open the question of how protein structures can be remodelled while selective pressure forces them to function. New information on the proteome, however, increasingly explains the nature of local and global conformational diversity in protein evolution, which allows the acquisition of novel functions via molecular transition forms containing ancestral and novel structures in dynamic equilibrium. Such structural plasticity may permit the evolution of new protein folds and help account for both the origins of new biological functions and the nature of molecular defects. BioEssays 29:1095–1104, 2007. © 2007 Wiley Periodicals, Inc.
The long and the short of RNA maps
Authors: Ponjavic Jasmina , Ponting Chris P. 
Published: October 2007

AbstractThe landscapes of mammalian genomes are characterized by complex patterns of intersecting and overlapping sense and antisense transcription, giving rise to large numbers of coding and non‐protein‐coding RNAs (ncRNAs). A recent report by Kapranov and colleagues1 describes three potentially novel classes of RNAs located at the very edges of protein‐coding genes. The presence of RNAs from one of these classes appears to be correlated with the expression levels of their associated genes. These results suggest that a proportion of these RNAs might have roles in the cis‐regulation of neighbouring protein‐coding genes' expression. BioEssays 29:1077–1080, 2007. © 2007 Wiley Periodicals, Inc.
Strength in numbers: High phenotypic variance in early Cambrian trilobites and its evolutionary implications
Authors: Hughes Nigel C. 
Published: October 2007

AbstractAnalysis of the degree of intraspecific morphological polymorphism during the evolutionary history of trilobites using an informatic approach1 provides striking evidence of a long‐suspected but previously unsubstantiated pattern: degrees of polymorphism are markedly higher in phylogenetically basal, stratigraphically early species. This unequivocal pattern prompts further exploration of the relationship between microevolutionary variance and macroevolutionary history. It demonstrates that the ‘traditional’ fossil record of skeletonized organisms can provide unique insight into questions of major evolutionary interest. BioEssays 29:1081–1084, 2007. © 2007 Wiley Periodicals, Inc.
Biotechnology of flavonoids and other phenylpropanoid‐derived natural products. Part II: Reconstruction of multienzyme pathways in plants and microbes
Authors: Ververidis Filippos , Trantas Emmanouil , Douglas Carl , Vollmer Guenter , Kretzschmar Georg , Panopoulos Nickolas 
Published: October 2007

AbstractPlant natural products derived from phenylalanine and the phenylpropanoid pathways are impressive in their chemical diversity and are the result of plant evolution, which has selected for the acquisition of large repertoires of pigments, structural and defensive compounds, all derived from a phenylpropanoid backboneviathe plant‐specific phenylpropanoid pathway. These compounds are important in plant growth, development and responses to environmental stresses and thus can have large impacts on agricultural productivity. While plant‐based medicines containing phenylpropanoid‐derived active components have long been used by humans, the benefits of specific flavonoids and other phenylpropanoid‐derived compounds to human health and their potential for long‐term health benefits have only been recognized more recently. In this part of the review, we discuss in detail the recent strategies and achievements used in the reconstruction of multienzyme pathways in plants and microbes in an effort to be able to attain higher amounts of the desired flavonoids and stilbenoids exploiting their beneficial properties as analyzed extensively in Part I of this review.
4‐Chloroprolines: Synthesis, conformational analysis, and effect on the collagen triple helix
Authors: Shoulders Matthew D. , Guzei Ilia A. , Raines Ronald T. 
Published: October 2007

AbstractCollagen is an abundant, triple‐helical protein comprising three strands of the repeating sequence: Xaa–Yaa–Gly. (2S)‐Proline and (2S,4R)‐4‐hydroxyproline (Hyp) are common in the primary structure of collagen. Here, we use nonnatural proline derivatives to reveal determinants of collagen stability. Specifically, we report high‐yielding syntheses of (2S,4S)‐4‐chloroproline (clp) and (2S,4R)‐4‐chloroproline (Clp). We find that the molecular structure of Ac‐Clp‐OMe in the solid state is virtually identical to that of Ac‐Hyp‐OMe. In contrast, the conformational properties of Ac‐clp‐OMe are similar to those of Ac‐Pro‐OMe. Ac‐Clp‐OMe has a stronger preference for a trans amide bond than does Ac‐Pro‐OMe, whereas Ac‐clp‐OMe has a weaker preference. (Pro–Clp–Gly)10 forms triple helices that are significantly more stable than those of (Pro–Pro–Gly)10. Triple helices of (clp–Pro–Gly)10 have stability similar to those of (Pro–Pro–Gly)10. Unlike (Pro–Clp–Gly)10 and (clp–Pro–Gly)10, (clp–Clp–Gly)10 does not form a stable triple helix, presumably due to a deleterious steric interaction between proximal chlorines on different strands. These data, which are consistent with previous work on 4‐fluoroprolines and 4‐methylprolines, support the importance of stereoelectronic and steric effects in the stability of the collagen triple helix and provide another means to modulate that stability. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 443–454, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Biomembranen – Wächter des zellulären Grenzverkehrs. Von Pumpen, Carriern und Kanälen
Authors: Bernhardt Ingolf 
Published: October 2007

AbstractFür das Verständnis der Funktion einer biologischen Membran ist die Kenntnis der Struktur sowie der Dynamik der Membranbestandteile (Lipide, Proteine) eine essenzielle Voraussetzung. Der Transport von biologisch relevanten Substanzen und Ionen über die Barriere einer biologischen Membran erfolgt durch spezifische Transportmechanismen, die man in verschiedene Kategorien einteilen kann (Pumpen, Carrier, Kanäle). Werden alle spezifischen Transporter blockiert oder gehemmt, kann man einen Rest‐(“Leak”)‐Transport messen, für den es verschiedene Gründe gibt.
Kalt, kälter, am kältesten
Authors: Hille‐Rehfeld Annette 
Published: October 2007

AbstractUm schädlichen Umwelteinflüssen zu entgehen, enthält unsere Haut eine Vielfalt von Schmerzsinneszellen, deren Erregung unter anderem motorische Funktionen steuert und so Ausweichreaktionen auslöst. Dazu gehören thermosensitive Zellen, durch die wir beispielsweise unangenehm kühle Temperaturen von schädlicher Kälte unterscheiden können. Dass einige Thermosensoren gleichzeitig auch Chemosensoren darstellen, ist die Grundlage für bekannte Sinnestäuschungen.
Assoziation zwischen Herzerkrankungen und Depressionen
Authors: Baghai Thomas C. , Binder Elisabeth , Schüle Cornelius , Lucae Susanne , Eser Daniela , Müller‐Myhsok Bertram , Möller Hans‐Jürgen , Holsboer Florian , Rupprecht Rainer , Bondy Brigitta 
Published: October 2007

AbstractVeränderungen im ACE‐Gen erhöhen möglicherweise das Risiko für Depressionen und kardiovaskuläre Erkrankungen. Forschungen der vergangenen Jahre zeigten bereits, dass zwischen diesen Krankheiten eine unheilvolle Allianz besteht: Koronare Herzerkrankungen steigern das Risiko für Depressionen, diese wiederum verschlechtern die Prognose bei koronaren Herzerkrankungen. Eine Schlüsselrolle spielt dabei offensichtlich das Gen für das Angiotensin‐Converting‐Enzym (ACE‐Gen), das die Entstehung von koronaren Herzerkrankungen beeinflusst.
Die Rolle des fetalen Kälberserums in Zellkulturmedien
Authors: Schrödel Andrea 
Published: October 2007

AbstractZellkulturexperimente können die Anzahl von Tierversuchen in der Grundlagenforschung drastisch reduzieren und finden daher eine breite Anwendung. Um Zellen in Kultur zu halten, muss eine Umgebung geschaffen werden, die das Wachstum und die Teilung der Zellen erlaubt. Hierzu sind seit Beginn des 20. Jahrhunderts diverse Medien entwickelt worden. Üblicherweise wird auch heute noch ein gewisser Anteil an Fetalem Kälberserum dem Kulturmedium zugemengt.
Nonlinear calibrations on the assay of dilitiazem and two of its metabolites from plasma samples by means of liquid chromatography and ESI/MS2 detection: application to a bioequivalence study
Authors: Georgita Cristina , Albu Florin , David Victor , Medvedovici Andrei 
Published: October 2007

AbstractThe assay of diltiazem (DLTZ) and its active metabolites desacetyldiltiazem (DAcD) and desmethyldiltiazem (DMeD) in plasma samples was achieved by means of an HPLC/(ESI)MS2 method. The diastereoisomer of diltiazem, namely {(2R,3S)‐5‐[2‐(dimethylamino)ethyl]‐2‐(4‐methoxyphenyl)‐4‐oxo‐2,3,4,5‐tetrahydro‐1,5‐benzothiazepin‐3‐yl acetate} was used as internal standard (IS). Sample preparation was based on protein precipitation by means of organic solvent addition (acetonitrile). The isocratic elution based on a reversed‐phase mechanism allows good separation of the analytes within 15 min. Atmospheric pressure electrospray ionization was used. All analytes were monitored in the MS2‐MRM mode. A fragmentation schema is proposed for the target compounds. As the method was designed for bioequivalence purposes, a full validation procedure was considered. On validation, nonlinear calibrations were observed. Consequently, concentration intervals requiring nonlinear calibrations are discussed. Low limits of quantification in the 0.6–1 ng/mL concentration range were obtained. The analytical method was successfully applied to a single dose (120 mg), open‐label, randomized, two‐period, two‐sequence, crossover bioequivalence study of two commercially available solid oral dosage pharmaceutical formulations (tablets). Copyright © 2007 John Wiley & Sons, Ltd.
Clenbuterol marketed as dietary supplement
Authors: Parr Maria K. , Koehler Karsten , Geyer Hans , Guddat Sven , Schänzer Wilhelm 
Published: October 2007

AbstractIn several studies it has been demonstrated that products containing pharmaceutically active ingredients are marketed as dietary supplements. Most of these products contain anabolic steroids. Recently products for weight loss containing active drugs have also appeared on the market. In the present case a healthy male ordered the product ‘Anabolic burner’ via the Internet. The product was received from a German dispatcher and paid by bank transfer to a German bank account. After ingesting one tablet he reported tremor and delivered a urine sample. This urine was found to contain 2 ng/mL of clenbuterol utilizing LC‐MS/MS analysis. Additionally the product itself was analyzed with GC‐MS for clenbuterol, yielding a content of about 30 µg per tablet. The beta‐2 agonist clenbuterol is only legally available on prescription and is classified as prohibited doping substance in sports. The present case for the first time confirms the presence of clenbuterol in a dietary supplement. It again demonstrates the common problem with products on the supplement market, where non‐licensed pharmaceuticals and doping substances are easily available. The ingestion of these products containing additions of therapeutic drugs can lead to side effects and/or interactions with conventional medicines. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of huperzine A in human plasma by liquid chromatography–electrospray tandem mass spectrometry: application to a bioequivalence study on Chinese volunteers
Authors: Li Wei , Li Jianhua , Hu Qin 
Published: October 2007

AbstractA simple, sensitive and selective LC‐MS‐MS method has been developed for the quantification of huperzine A in human plasma. Huperzine A and pseudoephedrine hydrochloride (internal standard) were isolated from human plasma by extraction with ethyl acetate, chromatographed on a C18 column with a mobile phase consisting of 0.2% formic acid–methanol (15:85, v/v) and detected using a tandem mass spectrometer with an electrospray ionization interface. The lower limit of quantification was 0.0508 ng/mL, and the assay exhibited a linear range of 0.0508–5.08 ng/mL (r = 0.9998). The method was successfully applied to investigate the bioequivalence between two kinds of tablets (test vs reference product) in 18 healthy male Chinese volunteers. After a single 0.2 mg dose for the test and reference product, the resulting means of major pharmacokinetic parameters such as AUC0−24, AUC0−∞, Cmax, Tmax and t1/2 of huperzine A were 16.35 ± 3.42 vs 16.38 ± 3.61 ng h/mL, 17.53 ± 3.80 vs 17.70 ± 3.97 ng h/mL, 2.47 ± 0.49 vs 2.51 ± 0.51 ng/mL, 1.3 ± 0.4 vs 1.2 ± 0.3 h and 5.92 ± 0.75 vs 6.18 ± 0.66 h, respectively, indicating that these two kinds of tablets were bioequivalent. Copyright © 2007 John Wiley & Sons, Ltd.