bluuebunny/crossref_metadata_2025_split huggingface dataset:
Autophagy
Authors: Isabel Colombo María , Simon Hans‐Uwe 
Published: December 2009

Abstract

Autophagy is a conserved proteolytic mechanism that degrades cytoplasmic material including cell organelles. Although the importance of autophagy for cell homeostasis and survival has long been appreciated, our understanding of how autophagy is regulated at a molecular level just recently evolved. The importance of autophagy for the quality control of proteins is underscored by the fact that many neurodegenerative and myodegenerative diseases are characterized by an increased but still insufficient autophagic activity. Similarly, if the cellular stress, leading to
deoxyribonucleic acid
(DNA) damage, mitochondrial damage and/or damaged proteins, does not result in sufficient autophagic repair mechanisms, cells seem to be prone to transform into tumour cells. Therefore, autophagy has multiple roles to play in the causation and prevention of human diseases.

Key concepts:

Autophagy is a cellular stress response induced to ensure cell survival, but excess autophagy may lead to cell death.

The kinases TOR (target of rapamycin) and PI3K (phosphatidyl inositol 3 kinase) are two essential components of the autophagy molecular machinery.

The family of genes or proteins called Atg (for
a
u
t
opha
g
y related) comprises the core of the molecular machinery of autophagy.

Upon autophagy induction the enwrapped cytoplasmic components and organelles are recycled by degradation in the autolysosome.

Autophagy can be dysregulated and may contribute to many pathologic processes.
Microtubule Organization inDictyostelium
Authors: Gräf Ralph 
Published: December 2009

AbstractDictyosteliumamoebae contain a radial array of microtubules emanating from a single microtubule‐organizing centre called centrosome that is bound to the cytosolic face of the nucleus. Their centrosome contains no centrioles but consists of a layered core surrounded by a corona harbouring microtubule nucleation centres. It duplicates in prophase of a closed mitosis and organizes a central spindle that drives centrosome separation and chromosome segregation. ThoughDictyosteliummicrotubules are quite dynamic during mitosis, their length appears to be very stable during interphase. Microtubules are associated with a couple of conserved proteins (microtubule‐associated protein,MAPs), which are involved in centrosome biogenesis and the crosstalk of microtubule tips with the actin cell cortex. The latter becomes evident in cytokinesis, when centrosomes with their attached microtubules participate in the positioning of cleavage furrows.Key concepts:Dictyosteliumamoebae contain a nucleus‐associated centrosome that serves as the only microtubule‐organizing centre.TheDictyosteliumcentrosome contains no centrioles, but consists of a three‐layered core structure surrounded by a microtubule‐nucleating corona.If compared to the three major plaques of the yeast spindle pole body, the entire core structure of theDictyosteliumcentrosome appears equivalent to the central plaque, whereas the corona plays a similar role as the inner and outer plaques.Dictyosteliumcentrosomes duplicate at the onset of mitosis.Dictyosteliumamoebae show a closed‐type of mitosis with a persisting nuclear envelope.Dictyosteliummicrotubules are quite dynamic during mitosis but show only little growth and shrinkage during interphase.Microtubule plus ends influence actin dynamics at the cell cortex.Dictyosteliumamoebae are a useful model to study the role of the centrosome and microtubules in cell dynamics and disease.
Sex Allocation in Hermaphrodites
Authors: Kazancioğlu Erem 
Published: December 2009

AbstractOrganisms in which individuals can reproduce both as males and females are called hermaphrodites. Sex allocation in hermaphrodites involves the division of reproductive resources between the male and female function, and presents an interesting contrast to species that alter sex allocation by adjusting offspring sex ratio. Theoretical and empirical research in the past four decades have largely attempted to explain when hermaphroditism is favoured, and how sex allocation in hermaphrodites is controlled. Furthermore, the application of endocrinological methods has elucidated some of the molecular processes that underlie hermaphroditic sex allocation, especially in sequential hermaphrodites. Despite significant advances in our understanding of hermaphrodites, some fundamental predictions such as the adaptiveness of changes in sex allocation have not been tested, and some basic questions on hermaphroditism have not been answered.Key concepts:In hermaphroditic organisms, individuals are capable of reproducing as both males and females.Simultaneous hermaphrodites have male and female reproductive organs that are functional at the same time, and are both involved in a mating event.Simultaneous hermaphroditism is favoured, when an increase in male and female reproduction yields diminishing fitness returns.Factors such as limited mobility, low density or self‐fertilization can result in diminishing fitness returns for males, and favour simultaneous hermaphroditism. However, local resource competition and physiological limitations could saturate fitness through female function.Simultaneous hermaphrodites can adjust sex allocation according to the social environment (e.g. mating group size), and the amount of resources available for reproduction (e.g. body size).Sequential hermaphrodites, or sex changers, reproduce as one sex for a part of their lifetime, and then switch to reproducing as the opposite sex.Sequential hermaphroditism is favoured in mating systems where individuals have consistently greater reproductive success as one sex earlier and as the other sex later in life.Sequential hermaphrodites can adjust the optimal timing of sex change according to relative size or social status in a mating group.There are also mixed hermaphroditic systems where individuals can repeatedly switch between sexes, or simultaneous hermaphrodites coexist with pure sexes.Sex change in fishes involves complex behavioural and morphological changes that are regulated by an endocrine gland system conserved across all vertebrates.
Cornification Diseases (Skin Cell Death)
Authors: Candi E , McLean WH , Didona B , Terrinoni A , Melino G 
Published: December 2009

Abstract

The outermost layer of the skin is formed by the cornified envelope (CE), which is the end product of the process of keratinization. This forms a barrier that is essential to protect the internal homeostasis of the organism from the external environment. The process of keratinization proceeds according to a complex and elaborately controlled differentiation program with the coordinated expression of genes encoding specialized components, enzymes, and regulatory molecules. The CE is a specialized structure that replaces the plasma membrane of differentiating keratinocytes and consists of proteins crosslinked by covalent bonds and lipids to form a scaffold. Understanding of the pathologies associated with defects in CE components will help clarify the molecular mechanisms and the physiological endpoints of keratinization. Here, we describe some diseases of keratinization, and give a brief overview on animal models (transgenic and knockout) with defects in the CE formation.

Key concepts:

The outermost layer of the skin is formed by the cornified envelope (CE).

The CE is a specialized structure that replaces the plasma membrane of differentiating keratinocytes. It consists of proteins crosslinked by covalent bonds and lipids to form a scaffold.

The CE is essential to provide the barrier function of the epidermis.

The transglutaminase enzymes play a major role in the formation of the CE by catalyzing the formation of crosslinks between specific proteins.

Mutations in keratin genes cause a wide variety of epidermal and other epithelial disorders.

CE lipids contribute in a significant way to the establishment of barrier function of the epidermis by impermeabilizing the cornified cell and participating in the organization of the intercellular lipid lamellae.

Defects in proteases result in barrier function abnormalities or skin diseases.

The transcription factor p63 is crucial in epidermis formation, maintaining the progenitor‐cell populations that are necessary to sustain epithelial development and morphogenesis.
Philosophy of Biological Classification
Authors: Richards Richard A 
Published: December 2009

AbstractThe Linnaean hierarchy has long served as the basis for biological classification, but there have been other systems, and there are new systems in development. There are three main philosophical questions about biological classification. The first is theoretical: what is represented? The second is about the formal structure: what are the categories and how are they related? The third is operational: what principles are used to generate the classification? Historically there have been theoretical approaches based on pragmatic interests, natural kinds and essences, Divine ideas, evolutionary history, phenetics and the phylogenetic branching of the evolutionary tree. Currently there is some consensus that classification should represent evolutionary history in terms of phylogeny, but there are competing proposals both for the formal structure of classification, and operational methods to reconstruct phylogeny.Key Concepts:The theoretical basis of a classification is what it represents. The formal structure of a classification involves the nature and organization of the categories. The operational procedures of a classification are the rules for generating the classification.
High‐Temperature Contact Formation on n‐Type Silicon: Basic Reactions and Contact Model for Seed‐Layer Contacts
Authors: Hörteis Matthias , Gutberlet Tobias , Reller Armin , Glunz Stefan W. 
Published: December 2009

AbstractContact formation on n‐type silicon, especially using a high‐temperature process, has been the subject of research for more than 40 years. After its application in microelectronics, n‐type silicon is widely used in silicon solar cells as the emitter layer. The formation of a low ohmic contact grid using an industrially feasible process step is one of the key features required to improve the solar‐cell efficiency. The contact materials, typically deposited in a printing step, have to fulfil several functions: opening the dielectric antireflection layer and forming an intimate metal‐semiconductor contact with good mechanical adhesion and low specific contact resistance. As the used contact inks typically contain several functional materials, such as silver and a glass frit, the detailed contact formation is still not entirely understood. Therefore, the chemical reactions during the contact firing process have been studied in detail by thermogravimetric differential thermal analysis in combination with mass spectroscopy. Based on these studies, a contact ink has been developed, optimized and tested on silicon solar cells. In this paper, the mechanism of the etching process, the opening of a dielectric layer, the influence of different atmospheres and the impact of the glass‐frit content are investigated. The observed microscopic contact structure, the resulting electrical solar‐cell parameters and the studied reactions are combined to clarify the physics behind the high‐temperature contact formation.
Effects of self‐reported health conditions and pesticide exposures on probability of follow‐up in a prospective cohort study
Authors: Montgomery Martha P. , Kamel Freya , Hoppin Jane A. , Freeman Laura E. Beane , Alavanja Michael C.R. , Sandler Dale P. 
Published: December 2009

AbstractBackgroundWe investigated the potential for selection bias due to non‐participation in the follow‐up of a large prospective cohort study.MethodsLicensed pesticide applicators (52,395 private; 4,916 commercial) in the Agricultural Health Study provided demographic, health, and pesticide exposure information at enrollment (1993–1997) and in a 5‐year follow‐up telephone interview. Factors associated with non‐participation in the follow‐up were identified using multiple logistic regression. Potential for selection bias was evaluated by comparing exposure–disease associations between the entire cohort and the follow‐up subset.ResultsSixty‐six percent of private and 60% of commercial applicators completed the follow‐up interview. Private and commercial applicators who did not complete the follow‐up reported at enrollment younger age, less education, lower body mass index, poorer health behaviors but fewer health conditions, and lower pesticide use. Estimates of exposure–disease associations calculated with and without non‐participants did not indicate strong selection bias.ConclusionsDifferences between non‐participants and participants in the follow‐up interview were generally small, and we did not find significant evidence of selection bias. However, the extent of bias may depend on the specific exposure and outcome under study. Am. J. Ind. Med. 53:486–496, 2010. © 2009 Wiley‐Liss, Inc.
Efficient synthesis of conjugated alkynyl cycloalkenones: Pd(PPh3)4–AgOAc‐ catalyzed direct coupling of 1‐alkynes with 3‐oxocycloalkenyl triflates
Authors: Jiang Chenggang , Zhang Zonglei , Xu Hangxian , Sun Liang , Liu Lanhai , Wang Cunde 
Published: December 2009

AbstractPalladium—silver acetate‐catalyzed cross coupling of vinyl triflates and 1‐alkynes was investigated. This strategy offered a very straightforward and efficient method for access to conjugated alkynyl cycloalkenones from the conjugated vinyl triflates and 1‐alkynes. Moreover, the triflates derived from 1,3‐cycloalkadione needed no further purification and could be reacted immediately with 1‐alkynes to provide the conjugated alkynyl cycloalkenones in excellent overall yields. Copyright © 2009 John Wiley & Sons, Ltd.
Organocatalytic synthesis of cyanohydrin trimethylsilyl ethers by potassium 4‐benzylpiperidinedithiocarbamate under solvent‐free conditions
Authors: Dekamin Mohammad G. , Alizadeh Roghieh , Reza Naimi‐Jamal M. 
Published: December 2009

AbstractPotassium 4‐benzylpiperidinedithiocarbamate was found to be an efficient organocatalyst for facile addition of trimethylsilyl cyanide to a wide variety of aldehydes and ketones to afford corresponding cyanohydrin trimethylsilyl ethers in high to quantitative yields. The reaction proceeded smoothly by employing 2.0 mol% PBPDC loading under mild conditions at room temperature within a very short reaction time. Copyright © 2009 John Wiley & Sons, Ltd.
Sulfonated poly(ether ether ketone)‐induced porous poly(ether sulfone) blend membranes for the separation of proteins and metal ions
Authors: Arthanareeswaran G. , Thanikaivelan P. , Raajenthiren M. 
Published: December 2009

AbstractAsymmetric ultrafiltration (UF) membranes were prepared by the blending of poly(ether sulfone) (PES) and sulfonated poly(ether ether ketone) (SPEEK) polymers with N,N′‐dimethylformamide solvent by the phase‐inversion method. SPEEK was selected as the hydrophilic polymer in a blend with different composition of PES and SPEEK. The solution‐cast PES/SPEEK blend membranes were homogeneous for all of the studied compositions from 100/0 to 60/40 wt % in a total of 17.5 wt % polymer and 82.5 wt % solvent. The presence of SPEEK beyond 40 wt % in the casting solution did not form membranes. The prepared membranes were characterized for their UF performances, such as pure water flux, water content, porosity, and membrane hydraulic resistance, and morphology and melting temperature. We estimated that the pure water flux of the PES/SPEEK blend membranes increased from 17.3 to 85.6 L m−2 h−1 when the concentration of SPEEK increased from 0 to 40 wt % in the casting solution. The membranes were also characterized their separation performance with proteins and metal‐ion solutions. The results indicate significant improvement in the performance characteristics of the blend membranes with the addition of SPEEK. In particular, the rejection of proteins and metal ions was marginally decreased, whereas the permeate flux was radically improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Short‐term and long‐term performance of thermosets exposed to water at elevated temperatures
Authors: Römhild S. , Bergman G. , Hedenqvist M. S. 
Published: December 2009

AbstractThe water‐transport, mechanical, and chemical‐structure changes in various vinyl ester, novolac, and urethane‐modified vinyl ester thermosets exposed to water at 50 to 95°C for times up to 1000 days have been studied within the framework of a larger study of osmotic blistering in fiber reinforced plastics (FRP) process components. The water sorption saturation concentration did not reach a steady‐state value but gradually increased in many cases upon long‐term exposure. The diffusion coefficient was not significantly affected. Infrared spectroscopy and gas chromatography‐mass spectrometry indicated that the net mass loss from the thermosets on immersion in water was due to the leaching of non‐reacted styrene, monomer, and additives. It is suggested that this, together with polymer relaxation processes (as measured on specimens under tension in water at 80°C), is the primary reason for the time‐dependent increase in the water saturation concentration. Infrared spectroscopy indicated that, even at the highest temperatures, hydrolysis of the polymer ester groups was small. Correlations were found between the styrene content in the uncured thermosets, the estimated solubility parameters, and the sorption and diffusion coefficients. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Effect of poly(acrylic acid) end‐group functionality on inhibition of calcium oxalate crystal growth
Authors: Wallace Andrew D. , Al‐Hamzah Ali , East Christopher P. , Doherty William O. S. , Fellows Christopher M. 
Published: December 2009

AbstractA number of series of poly(acrylic acids) (PAA) of differing end‐groups and molecular weights prepared using atom transfer radical polymerization were used as inhibitors for the crystallization of calcium oxalate at 23 and 80°C. As measured by turbidimetry and conductivity and as expected from previous reports, all PAA series were most effective for inhibition of crystallization at molecular weights of 1500–4000. However, the extent of inhibition was in general strongly dependent on the hydrophobicity and molecular weight of the end‐group. These results may be explicable in terms of adsorption/desorption of PAA to growth sites on crystallites. The overall effectiveness of the series didn't follow a simple trend with end‐group hydrophobicity, suggesting self‐assembly behavior or a balance between adsorption and desorption rates to crystallite surfaces may be critical in the mechanism of inhibition of calcium oxalate crystallization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
The effect of propylene–ethylene copolymers with different comonomer content on melting and crystallization behavior of polypropylene
Authors: Chen Jinyao , Cao Ya , Li Huilin 
Published: December 2009

AbstractThe effect of propylene–ethylene copolymers (PEc) with different ethylene‐unit contents on melting and crystallization behaviors of isotactic‐polypropylene (iPP) were investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The results show that the addition of PEc decreases significantly crystallization temperature (Tc) of iPP, but slightly affects melting temperature (Tm). With increasing the ethylene‐unit content of the propylene–ethylene copolymers, the decrease in crystallization temperature of iPP is smaller. The PLM results show that the spherulite growth rate decreases with increasing crystallization temperature for iPP and iPP/PEc blends. The higher the ethylene‐unit content of the copolymers is, the lower the spherulite growth rate (G) of iPP/PEc blends is. The influence of the PEc on nucleation rate constant (Kg) and fold surface energy (σe) of iPP was examined by nucleation theory of Hoffman and Lauritzen. The results show that both Kg and σe of iPP/PE20(80/20) and iPP/PE23(80/20) blends are higher than those of iPP, demonstrating that the overall crystallization rate of iPP/PEc blends decreased as compared to that of iPP, resulting from the decrease of the nucleation rate and the spherulite growth rate of iPP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
DNA supercoiling helps to unlink sister duplexes after replication
Authors: Vologodskii Alexander 
Published: December 2009

AbstractDNA supercoiling is one of the mechanisms that can help unlinking of newly replicated DNA molecules. Although DNA topoisomerases, which catalyze the strand passing of DNA segments through one another, make the unlinking problem solvable in principle, it remains difficult to complete the process that enables the separation of the sister duplexes. A few different mechanisms were developed by nature to solve the problem. Some of the mechanisms are very intuitive while the others, like topology simplification by type II DNA topoisomerases and DNA supercoiling, are not so evident. A computer simulation and analysis of linked sister plasmids formed inEscherichia colicells with suppressed topoisomerase IV suggests an insight into the latter mechanism.
Boron‐Containing Protoporphyrin IX Derivatives and Their Modification for Boron Neutron Capture Therapy: Synthesis, Characterization, and Comparative In Vitro Toxicity Evaluation
Authors: El‐Zaria Mohamed E. , Ban Hyun Seung , Nakamura Hiroyuki 
Published: December 2009

AbstractA novel series of boronated porphyrins for potential use in boron neutron capture therapy (BNCT) and photodynamic therapy (PDT) for tumor suppression is described. Protoporphyrin IX {i.e., bis(α‐methyl‐β‐pentylethylether)protoporphyrin IX, and bis(α‐methyl‐β‐dodecanylethylether)protoporphyrin IX} bearing polyhedral borane anions (B12H11SH2−, B12H11NH3−, or B12H11OH2−) were synthesized with reasonable yields. Modification of the protoporphyrin IX structure was achieved by variation of the lengths of the alkyl chains (pentyl and dodecanyl) attached through ether linkages to the former vinyl groups. The goal of this modification was to develop boronated porphyrins with chemical and physical properties that differed from those of protoporphyrin IX. Performance of an MTT assay with each derivative revealed that the synthesized boronated porphyrins showed low cytotoxicities in a variety of cancer cells. Of these compounds, B12H11NH22−‐conjugated porphyrin induced a significant increase in the level of boron accumulation and PDT efficacy against HeLa cells.