bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase II Study of Biweekly Plitidepsin as Second-Line Therapy for Advanced or Metastatic Transitional Cell Carcinoma of the Urothelium
Authors: Dumez Herlinde , Gallardo Enrique , Culine Stephane , Galceran Joan  Carles , Schöffski Patrick , Droz Jean  P. , Extremera Sonia , Szyldergemajn Sergio , Fléchon Aude
Published: September 2009

The objective of this exploratory, open-label, single-arm, phase II clinical trial was to evaluate plitidepsin (5 mg/m2) administered as a 3-hour continuous intravenous infusion every two weeks to patients with locally advanced/metastatic transitional cell carcinoma of the urothelium who relapsed/progressed after first-line chemotherapy. Treatment cycles were repeated for up to 12 cycles or until disease progression, unacceptable toxicity, patient refusal or treatment delay for >2 weeks. The primary efficacy endpoint was objective response rate according to RECIST. Secondary endpoints were the rate of SD lasting ≥6 months and time-to-event variables. Toxicity was assessed using NCI-CTC v. 3.0. Twenty-one patients received 57 treatment cycles. No objective tumor responses occurred. SD lasting
Paramadina and its Approach to Culture and Communication : an Engagement in Civil Society
Authors: Faisal Bakti Andi
Published: September 2009

Andi Faisal Bakti

Les questions relatives à la «société civile» ont été largement débattues en Indonésie durant ces dix dernières années. Les experts musulmans utilisent deux termes différents pour exprimer ce concept : masyarakat sipil et masyarakat madani, le premier étant surtout populaire dans les cercles proches du Nahdlatul Ulama, réputé « traditionnaliste » ; le deuxième parmi les musulmans qui se veulent «modernistes» et «néo-modernistes», ces divers qualificatifs ne manquant pas d'ambiguïté. L'auteur examine le rôle de la fondation Paramadina, créée par Nurcholis Madjid, au sein des efforts consentis de part et d'autre pour l'établissement d'une «société civile», ainsi que les atouts personnels, idéologiques et stratégiques de la fondation pour atteindre ses objectifs.
Représentations de la culture matérielle des Me'en: forme et fonction des artefacts
Authors: Abbink Jon
Published: September 2009

Résumé: Cette étude présente une première analyse de la culture matérielle des Me'en (Tishana), une ethnie de l'Ethiopie méridionale. Il s'agit d'une société sans artisans ou artistes spécialisés. La question envisagée est de savoir s'il existe des critères esthétiques sous-jacents au sein d'une culture matérielle comprenant pour l'essentiel des objets d'usage quotidien, avec la perspective de dénier, dans le domaine de l'étude comparative des cultures matérielles, la distinction entre culture de "grand art" et culture d'art "rudimentaire".
History and culture of the Argobba : recent investigations
Authors: Hailu Tesfaye
Published: September 2009

Summary : The aim of this study was to investigate the history and culture of the Argobba found in the Amhara, Afar, Oromiya, and Harari National regions. It has been pointed out that the Argobba have their own traditional mode of house construction, and their own form of food preparation. Nevertheless, the study also found that there is a great deal of cultural interaction and assimilation with neighbouring ethnic groups.
La pierre et le foyer [Note sur les vers 453 à 506 de la Théogonie hésiodique]
Authors: Mezzadri Bernard
Published: September 2009

La pierre et le foyer (pp. 215-220)

Une même conception du centre et une même structure logique informent l'épisode hésiodique de la naissance des enfants de Cronos et la célèbre légende étiologique de l'omphalos. Mais l'un articule temporellemént ce que l'autre exprime spatialement: Zeus dernier et premier, Hestia première et dernière, conjoignent des opposés comme les deux aigles relient des extrêmes. La double position d'Hestia -au début et à la fin- correspond en outre à des faits indo-européens.
La prophétie de Tirésias
Authors: Ballabriga Alain
Published: September 2009

La prophétie de Tirésias (pp. 291-304)

Une analyse philologique de la prophétie de Tirésias ( Od. 1 1 , 126-37) peut établir assez facilement la faiblesse des principes aristarchéens qui en ont guidé la lecture jusqu'à nos jours: loin d'être "post-homériques" , les légendes de la Télégonie font l'objet d'une incontestable allusion dans l'Odyssée. Mais, à en juger par le résumé de Proclus, l'état final de la légende d'Ulysse dans la Télégonie se situe à son tour par rapport à l'Odyssée. D'une façon générale les relations entre poèmes épiques doivent se formuler en termes d'interactions opérant tout au long des 7e/6e siècles.
La menace du silence pour le héros de l'Iliade
Authors: Montiglio Silvia
Published: September 2009

La menace du silence pour le héros de l'Iliade (pp. 161-186)

Cette étude cherche à cerner les connotations principales du silence dans la première épopée, à partir du texte lui-même aussi bien que des gloses anciennes. Dans le cadre du "combat de paroles" auquel se livrent les héros de l'lliade, le silence s'avère être surtout une marque de défaite, d'inertie, d'impuissance. Le code homérique de la parole, en effet, présuppose la circulation rapide d'un epos constamment échangé, si bien que toute suspension silencieuse apparaît comme la rupture non souhaitable d'un tissu sonore qui se veut compact et continu. Arrêt troublant, le silence est souvent entouré de voix puissantes et toujours surmonté par une voix nouvelle, qui semble conjurer la menace qu'il représente pour le héros aussi bien que pour l'aède.
L'hybride et le mixte
Authors: Fourgous Denise
Published: September 2009

L'hybride et le mixte (pp. 231-246)

Quelles interprétations les auteurs anciens donnèrent-ils du qualificatif de διφυής appliqué à Cécrops, premier roi mythique d'Athènes ? Certains l'expliquèrent par son autochtonie, d'autres par son origine étrangère, d'autres encore par sa qualité d'inventeur, responsable de nombreuses et importantes découvertes pour la cité. Une thèse fort originale (Diodore de Sicile, I, 28) voit en cette double nature l'expression de la double "citoyenneté" de Cécrops, grecque et barbare. Ainsi l'hybride correspond-il exceptionnellement au mixte. On repose enfin la question du rapport entre nature hybride ou mixte et inventivité à travers l'examen rapide de quelques cas.
Cimetières et tombeaux des villages de la Syrie du Nord
Authors: Griesheimer Marc
Published: September 2009

lages of North Syria (Massif calcaire: 2nd-6th centuries AD). It provides an archaeological survey from 1991 to 1993. The analysis of the funerary areas is conducted by a spacial approach. First, the context of the tombs, second

their organisation within the built or excavated monu-

ments, finally the localisation of the funerary monuments

around the villages.
Etude de la permanence des tracés urbains et ruraux antiques à Antioche-sur-l'Oronte
Authors: Leblanc J. , Poccardi Grégoire
Published: September 2009

The systematic study of a set of ancient aerial vertical photographs of the Mandate Period belonging to the CNRS (UPR 7541) led us to establish the existence of four parcel divisions in the town of Antioch on the Orontes, its neighbourhood and the famous suburb of Daphne.

Two of them are organized according to the major directions of the reliefs. They have the same module (116 x 58 m). The third one occupies the ancient Orontes island (about 105 x 35 m). The last one is specific to Daphne.

At Antioch and Daphne, some ancient monuments have been integrated in these networks: particularly, a hippodrome and a temple in the island, maybe a theatre in Antioch, finally the Olympic stadium of Daphne, the location of which seems confirmed by its representation on a border of a late Roman mosaic called Megalopsychia found at Yakto (Daphne).
A propos de la ταυριανὴ πύλη : remarques sur la localisation présumée de la Grande Eglise d'Antioche de Syrie
Authors: Saliou Catherine
Published: September 2009

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Trois comptes ougaritiques RS 15.062, RS 18.024, RIH 78/02
Authors: Pardee Dennis
Published: September 2009

In this study, the three Ugaritic documents containing the word htbn, « account (text) », are re-edited. The goals are to settle several questions regarding the reading of the three tablets, to elucidate the structure of the texts, and, thereby, to improve our understanding of the prices indicated for the various items of merchandise exchanged. Along with the traditional philological arguments, these prices contribute in several cases to a plausible definition of the goods.
Aegyptiaca et Isiaca de la Phénicie et du Liban aux époques hellénistique et romaine
Authors: Aliquot Julien
Published: September 2009

It is an established fact that the cultural exchanges between Phoenicia and Egypt date back long before the Macedonian conquest of the Near East. Yet the study of the Phoenician and Lebanese monuments and cults also proves that the elements which were borrowed to the Egyptian religion in the area came through the Graeco-Roman culture during the Early Roman period. First, the hellenized cults of the major Egyptian deities may have been worshipped by private individuals in the Phoenician coastal cities ; then, they would have been officially admitted in the local pantheons of Byblus, Tyre, and Abila of Lysanias. The spread of the Egyptian cults in Phoenicia and in Lebanon seems to fit in with the pagan religious trends of the Roman empire during the second and the third centuries.
EVALUATING THE CHANGES IN ECONOMIC AND SOCIAL DEVELOPMENT OF LITHUANIAN COUNTIES BY MULTIPLE CRITERIA METHODS
Authors: Ginevičius Romualdas , Podvezko Valentinas
Published: September 2009

Under the conditions of the country's economy restructurization, the differences between economic and social development of various regions are becoming more prominent. To smooth these differences, a number of scientific and practical problems associated with the concepts of a region, regional policy and its aims, determination of the boundaries of a region and evaluation of its development, etc., should be thoroughly investigated. To solve such complicated problems, multicriteria evaluation methods have been recently used, which could take into consideration the major aspects of economic and social development of the regions, including the environmental problems, as well as multidimensional character of the criteria, different directions of their changing and significances. Quantitative evaluation of social and economic region's development allows us to determine the changes, taking place in this development. This, in turn, shows the effectiveness of the EU structural funds, national programmes and other facilities used in conducting the regional policy. Santrauka Šalies ūkiui iš esmės restruktūrizuojantis ir persitvarkant padidėja ekonominės ir socialinės plėtros skirtumai tarp regionų (apskričių). Juos mažinant susiduriama su daugeliu mokslui ir praktikai aktualių, spręstinų klausimų, tokių kaip regiono, regioninės politikos samprata ir tikslai, jų ribų nustatymas, plėtros supratimas, įvertinimas ir t. t. Tokiems uždaviniams spręsti pastaraisiais metais sėkmingai taikomi daugiakriterinio vertinimo būdai. Jie leidžia įvertinti visus svarbiausius regionų ekonominės ir socialinės plėtros (RESP) aspektus, taip pat ir aplinkosauginius, įvertinti rodiklių daugiadimensiškumą, nevienodą kitimo kryptį bei reikšmingumą. Galimybė kiekybiškai įvertinti RESP leidžia nustatyti šios plėtros kaitą. Būtent ji parodo, koks yra Europos struktūrinių fondų, nacionalinių programų, kitų priemonių, skirtų regioninei politikai įgyvendinti, efektyvumas.
Pattern of Arterial Calcification in Patients with Systemic Lupus Erythematosus
Authors: YIU KAI-HANG , WANG SILUN , MOK MO-YIN , OOI GAIK CHENG , KHONG PEK-LAN , MAK KA-FUNG HENRY , LAM KWOK-FAI , LAU CHAK-SING , TSE HUNG-FAT
Published: September 2009

Objective.

To evaluate the prevalence and pattern of arterial calcification in patients with asymptomatic systemic lupus erythematosus (SLE) compared with control subjects. SLE patients are prone to adverse cardiovascular events; however, the underlying atherosclerotic process is unknown. Multidetector computed tomography (MDCT) measured arterial calcium score (CS) reflecting underlying atherosclerosis and is closely associated with cardiovascular events.

Methods.

Fifty age and sex matched SLE patients and controls were enrolled. All subjects underwent 64 slice MDCT scan to evaluate CS in coronary, carotid arteries and the aorta.

Results.

As compared with controls, SLE patients had higher mean CS and prevalence of CS > 0 across all vascular beds. After adjustment for age and sex, SLE patient odds of having CS > 0 in any vascular bed was 33.6 (95% CI: 9.5–165.2) were higher versus patients in the control group, mainly due to more prevalent coronary calcification (OR 30.0, 95% CI: 6.7–203.8). In SLE patients, the most frequent vessel with CS > 0 was coronary (42%) followed by carotid artery (24%). Further, arterial calcification occurred early involving 40% of SLE patients at age < 40 years, with increasing prevalence as age advanced.

Conclusion.

Our study confirms that patients with SLE have significantly higher prevalence and extent of systemic arterial calcification compared with age and sex matched controls.
Mimesis, en la encrucijada del exilio de Eric Auerbach
Authors: Barck Karlheinz
Published: September 2009

El presente artículo es un estudio de la obra maestra de Erich Auerbach, Mimesis, como libro del exilio. Se analiza también el modo como Auerbach confronta en él la cuestión judía y, posteriormente, se discute cuál fue la repercusión de Mimesis en las letras hispánicas, con especial atención a la valiosa labor realizada por los exiliados españoles, como Eugenio Ímaz, en su traducción y edición para FCE.
Exilios en la Bauhaus
Authors: Wittenberg Stella
Published: September 2009

La institución de la Bauhaus en la República de Weimar es uno de los acontecimientos más significativos en el Arte del siglo XX. Su importancia radica en la absoluta transformación de los planteamientos estéticos. El aspecto humano de la Bauhaus va unido a los itinerarios de vida de los maestros. Walter Gropius fue el alma de la Escuela. Tanto la ideología socialista de sus miembros como el ideario artístico vanguardista precipitaron su éxito pero también su fracaso y persecución por el nacionalsocialismo. La mayoría de sus maestros tuvieron que buscar refugio en el exilio.
Exilio y compromiso: el caso de Adolfo Sánchez Vázquez
Authors: Martínez Francisco José
Published: September 2009

Adolfo Sánchez Vázquez consideró el exilio como un destierro que cortaba las raíces de los exiliados con su tierra. Adolfo Sánchez Vázquez ha mantenido un compromiso constante con los ideales que le llevaron al destierro adaptándolos a las circunstancias cambiantes pero sin renegar de ellos de acuerdo con su interpretación del marxismo como una filosofía de la praxis y una nueva praxis de la filosofía.
Spender, la Guerra de España y los límites de la autobiografía
Authors: Insausti Gabriel
Published: September 2009

Durante los años treinta el poeta Stephen Spender fue aproximándose paulatinamente al ideario marxista, al que se adhirió a principios de 1937 con su militancia en el Partido Comunista, que abandonaría tras sus experiencias en la Guerra Civil española. Con el relato de su conversión al marxismo en los años treinta y su posterior y violenta retractación, la autobiografía de Spender World within a World plantea, entre otras cosas, una serie de cuestiones fundamentales sobre los límites de la autobiografía y sobre la naturaleza de esa escritura.
La construcción de una bóveda de crucería en la Escuela Técnica Superior de Arquitectura de Madrid
Authors: Palacios J. C. , Martín R.
Published: September 2009

En la Escuela Superior de Arquitectura de Madrid, el Departamento de Construcción ha puesto en marcha una experiencia pedagógica de extraordinario interés. En el marco de una nueva asignatura llamada Taller de Construcción Gótica, los alumnos han podido llevar a cabo la construcción de una bóveda de crucería. Las bóvedas “góticas” son objeto de estudio desde distintos puntos de vista, sin embargo, los conocimientos adquiridos en estas áreas jamás se confrontan con la práctica real. Esta experiencia pedagógica propone invertir los términos, es decir, redescubrir y dar un sentido a la teoría a través de la experiencia física de la construcción. Durante su construcción se fueron poniendo de relieve todos los problemas inherentes a este tipo de construcciones; en primer lugar el conocimiento histórico del objeto y su autor, su concepción geométrica y el descubrimiento de su forma esférica. A continuación dio comienzo la talla de las diferentes piezas que componen la bóveda, y seguidamente la construcción de las cimbras que, una vez acabadas permitieron llevar a cabo el montaje de la bóveda. Finalmente se llevó a cabo el descimbrado de la misma. Sobre todo este proceso, trata el artículo que a continuación se presenta. Cualquier conocimiento teórico queda rebasado por la riqueza de la experiencia de su puesta en práctica real.
El análisis de visibilidad en la evaluación de impacto ambiental de nuevas construcciones
Authors: Otero I. , Varela E. , Mancebo S. , Ezquerra A.
Published: September 2009

Hoy en día es necesario reconciliar el desarrollo urbano con el equilibrio ecológico y adoptar un urbanismo con base territorial amplia, para controlar la localización y regulación de los usos y actividades. Dentro de este contexto, el trabajo que se expone en el presente artículo, se planteó como objetivo último la localización de nuevas áreas urbanas de baja densidad en el entorno del Corredor del Henares de Guadalajara (España). Los modelos de capacidad e impacto diseñados al efecto consideran como uno de sus componentes más importantes la calidad visual del paisaje, que se basa, a su vez, en un estudio exhaustivo de la visibilidad del territorio. El objeto de los análisis de visibilidad es determinar las áreas visibles desde cada punto o conjunto de puntos, bien simultáneamente o en secuencia, con vistas a la posterior evaluación de la medida en que cada área contribuye a la percepción del paisaje y a la obtención de ciertos parámetros globales que permitan caracterizar un territorio en términos visuales. Siguiendo la línea enunciada, el trabajo trata de realizar una aportación en el campo de los estudios de visibilidad, mediante el diseño de un modelo de visibilidad, posteriormente programado e implementado en SIG (Sistemas de Información Geográfica); se describe el proceso seguido para realizar esta tarea, centrándose en las dificultadas que se presentaron y su resolución. El análisis de visibilidad desarrollado constituyó un punto importante tanto en el modelo de capacidad de acogida de la actividad como en el modelo del impacto que ésta puede producir en el medio. La construcción de un modelo de visibilidad permite valorar de forma objetiva la visibilidad del territorio desde todos los puntos de interés.
La planificación en la construcción de los poblados del Instituto Nacional de Colonización
Authors: Rabasco P.
Published: September 2009

El Instituto Nacional de Colonización fue el brazo ejecutor de uno de los proyectos más importantes en el ideario social y económico del franquismo. La construcción de más de doscientos poblados dentro de un amplio proceso de creación de nuevos regadíos, posibilitó todo un campo de experimentación en el ámbito del urbanismo y de la arquitectura. En este estudio nos centraremos en la evolución de los aspectos constructivos, haciendo especial hincapié en la planificación a la hora de elaborar las propuestas de viviendas, y de construir las nuevas poblaciones. En estos procesos veremos cómo se evidencian carencias técnicas y cómo, del mismo modo, surgen nuevos recursos basados en la realidad de la España del franquismo. Nos centraremos especialmente en los informes de evolución de obra de los poblados de Setefilla (Fernando de Terán, 1965) y de El Priorato (Antonio Fernández Alba, 1964), dos de los proyectos más destacados de los llevados a cabo por el Instituto, por dos arquitectos que llevaron la experimentación en el campo del urbanismo hasta sus máxima expresión teórica. Comprobaremos cómo se siguió una planificación zonal, y cómo existieron igualmente otros procesos de abandono y desocupación en los poblados que forzaron una política de rehabilitación que modificó notablemente las estructuras originarias de algunos de los poblados.
InitiatortRNAsin Bacteria and Eukaryotes
Authors: Rasmussen Louise CV , Laursen Brian S , Mortensen Kim K , Sperling‐Petersen Hans U
Published: September 2009

A special type of transferribonucleic acid(tRNA) is employed in the initiation step of protein synthesis. The differences between the tRNAs involved in initiation and elongation establish the specificity and recognition of the tRNAs by the factors and enzymes involved in the initiation and elongation steps of protein synthesis. The important determinants of the initiator tRNA in bacteria are the absence of a Watson–Crick base pair between positions 1 and 72 in the acceptor stem and the presence of three conserved consecutive G:C base pairs in the anticodon stem. Formylation of the methionine attached to this initiator tRNA is an important feature. Conversely, the eukaryotic initiator tRNA is mainly determined by the presence of a particular A1:U72 Watson–Crick base pair in the acceptor stem as well as the nature of the base pairs 50:64 and 51:63 in the TΨC (T) stem.

Key concepts

Initiator tRNA brings methionine to the initiation complex for initiation of protein synthesis.

Structural features of initiator tRNAs ensure that they are recognized by translation initiation factors and discriminated against by translation elongation factors.

The important determinants of initiator tRNA in bacteria are the absence of a Watson–Crick base pair between positions 1 and 72 in the acceptor stem and the presence of three conserved consecutive G:C base pairs in the anticodon stem.

The important determinants of initiator tRNA in eukaryotes are the presence of a particular A1:U72 Watson–Crick base pair in the acceptor stem as well as the nature of the base pairs 50:64 and 51:63 in the T stem.

Bacterial initiator tRNA is aminoacylated by methionyl tRNA synthetase, which mainly interacts with the anticodon.

The methionine of bacterial initiator tRNA is formylated by methionyl tRNA transformylase, which mainly recognizes the absence of the 1:72 base pair.

Initiation factor IF2 ensures recognition and correct binding of bacterial initiator tRNA to the ribosomal P‐site by interacting primarily with the formyl group and the 3′ end of the acceptor arm.

Initiation factor IF3 performs proofreading of the 30S initiation complex by verifying base pairing between 5′C of bacterial initiator tRNA anticodon and 3′G of mRNA initiation codon.

Bacterial initiator tRNA undergoes several conformational changes during translation initiation to ensure correct positioning in the P‐site of the ribosome.

Bacterial initiator tRNA is not a substrate for peptidyl tRNA hydrolase.
DNADamage
Authors: Moore Bryn S , Morris Lydia P , Doetsch Paul W
Published: September 2009

Various biochemical and physical events alter the structure and properties ofdeoxyribonucleic acid(DNA), such as damage to the bases as well as single‐ and double‐strand break (DSB) induction. The sources for cellular DNA damage include exposures to environmental chemicals and radiation as well as endogenous processes resulting from normal cellular metabolism. Conversion of DNA into these forms can have deleterious biological consequences for cells, including development of cancer and other detrimental outcomes. The basis for these biological endpoints is largely dependent on the interactions between the DNA damage and the cell's DNA replication and gene expression machinery. Technologies exist for the detection and measurement of DNA damage in cells. Each of these methods functions in different contexts and with varying degrees of sensitivity.

Key concepts

The rates of induction of variousdeoxyribonucleic acid(DNA) lesions, including spontaneous hydrolysis and oxidative DNA damage, have been estimated.

DNA damage has been associated with various physiological conditions including cancer, neurodegenerative diseases, heart disease and the process of ageing.

Damage from a variety of exogenous and endogenous sources induces DNA base lesions and strand breaks, which can be detected by various molecular and biochemical methods.

Damaged deoxyribonucleotides can be incorporated into DNA during synthesis due to errors by the polymerase and/or disruptions of nucleotide pool balance.

Many of the features of DNA in chromatin, including DNA–protein interactions and sequence context, greatly impact the manner in which damage is distributed within the genome.

Chemotherapeutic agents, used to treat cancers, often target DNA resulting in tumour cell death.
Polysaccharides
Authors: BeMiller James N
Published: September 2009

Polysaccharides are carbohydrate polymers containing from approximately 35 (usually more than 100) to as many as 60 000 monosaccharide units. Polysaccharides have a range of general structures (from linear to various branched structures) and shapes. They are structural components of cell walls of bacteria, fungi, algae and higher plants and of the exoskeletons of insects and crustaceans, are energy‐ and carbon‐storage substances, and serve various other functions as extracellular materials of plants, animals and microorganisms. They are the most abundant (by mass) of all organic substances in living organisms, comprising about two‐thirds of the dry weight of the total biomass. Some have commercial value as isolated substances.

Key concepts

Polysaccharides are polymers of sugar (carbohydrate) units.

Polysaccharides are ubiquitous in nature. They are present in all plant tissues.

Polysaccharides comprise about three‐fourths of the total biomass on Earth.

Polysaccharides serve as structural materials, as reserve food materials and in other functions.

Polysaccharides occur in a wide range of shapes and sizes.

Polysaccharides are hydrophilic and either dissolve in or absorb water.

Polysaccharides are produced and used commercially in large volumes.
Lipids
Authors: Yeagle Philip L
Published: September 2009

Lipids are molecular building blocks for the most fundamental structures in biology, including the serum lipoproteins, the membranes of cells and cellular organelles and the membranes of enveloped viruses. Lipids provide a form of energy storage, like an electrical battery for an organism. Lipids are the metabolic precursors of hormones and signalling molecules in cells. Lipids regulate, often in specific ways, the functionality of biological membranes. A nearly uncountable catalogue of lipid molecules is found in nature, their individual structures imparting a wide variety of properties essential to the structures and functions of lipids in life.

Key concepts:

The hydrophobic effect, which governs the behaviour of hydrocarbons in water, controls the structures formed by lipids.

Phospholipids, as well as many other lipids, spontaneously form bilayer structures when confronted with water, in accordance with the hydrophobic effect.

Lipid bilayers provide the fundamental architecture of biological membranes.

Lipid bilayers determine many of the properties of biological membranes including their limited permeability.

Thousands of different lipid species are found in biological membranes, but a classification system emphasizes the similarities in specific classes.

Unsaturation in the hydrocarbon chains of lipid bilayers supports the liquid crystal state of bilayers in biology, essential to the proper functioning of membrane enzymes.

Membrane bilayers are highly anisotropic and their dynamics determine further the properties of the membranes.

Although bilayers are inherently stable, defects in bilayer structure are required to initiate critical membrane fusion events.

Membrane lipids play biological roles in membrane biology as well as structural roles.

In biological membranes, lipids are generally asymmetrically distributed across the bilayer.

Some lipids are second messengers in intracellular signalling systems.
Glycerophospholipids
Authors: Farooqui Akhlaq A
Published: September 2009

Glycerophospholipids are derivatives of
sn
‐glycero‐3‐phosphoric acid. They contain an
O
‐acyl or
O
‐alkyl or
O
‐alk‐1′‐enyl residue at the
sn
‐1 position and an
O
‐acyl residue at the
sn
‐2 position of the glycerol moiety and are defined on the basis of the substituents on the phosphoric acid at the
sn
‐3 position. Glycerophospholipids are asymmetrically distributed between the two bilayers. They not only constitute the backbone of cellular membranes but also provide the membrane with a suitable environment, fluidity and ion permeability. They are synthesized at the endoplasmic reticulum and are transported to other membranous structures by phospholipid exchange and transfer proteins. Once glycerophospholipids are laid down in a biomembrane, they undergo interconversion reactions (base exchange, methylation and decarboxylation). These reactions and activities of phospholipases may be responsible for the turnover, compositional maintenance and rearrangements of glycerophospholipids in membranes. This process results in the modulation of membrane function. Glycerophospholipids are multifunctional molecules. They are precursors for second messengers. In addition, they may be involved in membrane fusion, apoptosis and regulation of the activities of membrane‐bound enzymes and ion channels.
Arabidopsis
: Flower Development and Patterning
Authors: Krizek Beth A
Published: September 2009

The development of flowers and floral organs is directed by intricate genetic programmes, many aspects of which appear to be shared among all angiosperms. Early acting genes establish floral meristem identity in lateral organ primordia initiated at the periphery of the shoot apical meristem. Later, floral organ primordia arise at precise positions within these floral meristems and take on one of the four distinct identities (sepals, petals, stamens and carpels). A simple model (ABCE model), supported by both molecular and genetic experiments in

Arabidopsis

, explains how a small number of regulatory genes act in different combinations to specify these different organ types. These regulatory genes encode transcription factors that control the expression of many target genes responsible for organogenesis.

Key concepts

Lateral organs produced by the shoot apical meristem during reproductive development acquire their identity as flowers through the action of floral meristem identity genes such as
LEAFY
and
APETALA1
.

The identities of each of the four organ types of a flower (sepal, petal, stamen and carpel) is conferred by a unique combination of floral organ identity gene activities, referred to as class A, B, C and E in the ABCE model.

The activities of the class A, B, C and E genes are restricted to particular regions within a developing flower primarily, but not exclusively, through transcriptional regulation.

The proteins encoded by the class A, B, C and E genes encode transcription factors that form multimeric transcriptional regulatory complexes that control the expression of distinct sets of genes.

Many aspects of the genetic programmes conferring floral meristem identity and floral organ identity are conserved among all angiosperms.
Cleavage and Gastrulation in Mouse Embryos
Authors: Papenbrock Tom , Wild Arthur E , Fleming Tom P
Published: September 2009

After fertilization of the mammalian oocyte, the developmental programme leading to the conceptus begins with the early cleavage divisions. Lineage differentation begins after the early and mammal‐specific event of compaction and continues throughout development of the blastocyst. This structure, unique to mammals, after implantation will give rise to the various embryonic and extraembryonic tissues of the developing conceptus. Soon after implantation, the orientation of the main body axis becomes apparent with the primitive streak, and the node at its anterior end. Gastrulation through the primitive streak results in the formation and segregation of the three germ layers and the establishment of the basic body plan of the developing fetus. Finally, we compare mammalian early development to other vertebrates.

Key concepts:

Being higher animals, the early development of mammals prepares for and culminates in the generation of three tissue layers by gastrulation.

Many aspects of early mammalian development are shared with fellow amniote animals (reptiles and birds) and even with anamniote vertebrates (e.g. amphibians).

Mammals have however evolved specific adaptations to development in the mother's womb, in particular with regard to early stages of development and the role of the extraembyronic tissues.
Immunological Tolerance: Therapeutic Induction
Authors: Anderton Stephen M
Published: September 2009

When the natural mechanisms of immune tolerance breakdown, autoimmune or allergic disease can result. There is considerable experimental evidence that the ultimate response to antigen, full immunity or tolerance, is dependent on the activation status of the antigen presenting dendritic cells, with those in steady state inducing tolerance. Current therapeutic options either deplete immune cell populations, interfere with immune cell trafficking to the tissues or inhibit inflammatory cytokine function or lymphocyte signalling. Although these treatments can be effective for certain diseases, they carry with them significant adverse effects and it is unlikely that they induce true, long‐lived immune tolerance. Cellular therapies using either tolerogenic dendritic cells, or regulatory T cells may be able to achieve this. Alternatively, administration of antigen in tolerogenic form can provide the most specific therapy, with the least risk of adversely affecting normal immune function against infection or neoplasia.

Key concepts

Peripheral tolerance mechanisms consist of lymphocyte apoptosis, anergy and regulation.

Current therapeutic options for the clinic can be effective, but in general are nonspecific and may not provide long‐term tolerance.

Dendritic cell (DC) activation status determines the type of immune response. Activated DC provokes immunity whereas steady state DC promotes tolerance.

‘Tolerogenic’ DC can be administered to give protection from rodent models of autoimmune disease, allergy and graft rejection.

Administration of antigen in tolerogenic form (without adjuvant) also provides protection from disease models.

Transfer of antigen‐specific regulatory T cells can also protect against disease, and can be curative in some models.

Translation of cellular therapies (using DC or regulatory T cells) or tolerogenic antigen will require a fuller understanding of the critical autoantigens/epitopes that drive autoimmune pathology.
Phloem Structure and Function
Authors: Schulz Alexander , Thompson Gary A
Published: September 2009

The phloem collects photoassimilates in green leaves, distributes them in the plant and supplies the heterotrophic plant organs (e.g. fruits, buds and roots). Phloem structure is specialized for loading, long‐distance transport and unloading of assimilates. The conducting cells, called sieve elements, are highly modified to create a low‐resistance pathway composed of contiguous living cells, whose long‐term viability is maintained through an intimate association with companion (or Strasburger) cells. The difference in turgor pressure that is generated by osmotically active assimilates within this living conduit is the physical force that drives long‐distance transport through sieve elements. Plant species have evolved a variety of strategies to generate and maintain turgor pressure between source tissues, where assimilates are synthesized or released, and sink tissues, where assimilates are utilized or stored. Signalling molecules accessing the phloem are swept along with assimilates and trigger important growth processes such as flowering.

Key concepts

Long‐distance transport of assimilates occurs from source to sink, that is, from the green leaves, which produce a surplus of assimilates to the plant organs which consume assimilates.

The conducting cells are the sieve elements in the phloem which offer a low‐resistance pathway, characterized by a reduced cytoplasm and sieve pores in the connecting cell walls.

Reduction of the sieve‐element cytoplasm is accompanied by a dependency of sieve elements on neighbouring cells, called companion cells in angiosperms, and Strasburger cells in gymnosperms, that hold the sieve elements alive.

The mechanism of phloem transport is based on a high sugar concentration in the sieve element‐companion cell complexes of source leaves, which osmotically builds up a high turgor pressure.

Accumulation of sugars in the source phloem is called phloem loading and depends either on sucrose transporters in the plasma membrane of sieve‐element companion cell complexes, or enzyme activity in the companion cells of the source phloem.

Phloem transport is utilized for signal transport, including rapid electropotential waves, mobile noncodingribonucleic acids(RNAs) and mobile transcription factors that are responsible for wound responses and developmental switches in the target tissue.
Ion Motive
ATPases
:
P
‐type
ATPases
Authors: Shin Jai Moo , Sachs George
Published: September 2009

Regulation of ions such as calcium, sodium and potassium ions is very important for cell life. One of ion‐regulating enzymes is classified as ion motive
adenosine triphosphatase
(
ATPase
). Ion motive
ATPases
exchange two different ions across the membrane at the expense of ATP energy. The Ca
2+
‐
ATPase
transports Ca ion in exchange for H ion; the Na
+
/K
+
or H
+
/K
+
ATPase
transports Na ion or hydronium ion from the cytoplasmic region to the exocytoplasmic region with the exchange of K ion from the exoplasmic domain to the cytoplasmic domain. The Ca
2+
‐
ATPase
has single catalytic subunit. The Na
+
/K
+
and H
+
/K
+
ATPases
consist of two subunits α and β. The α subunit is the catalytic subunit, having 10 transmembrane domains. The β subunit is a glycosylated protein.

Key concepts

Ion motive ATPases

P‐type ATPase transport ions across the membrane

Regulating ion concentrations.
Plasmodesmata
Authors: Faulkner Christine R , Oparka Karl J
Published: September 2009

Plasmodesmata are plasma membrane‐lined pores that span the adjoining walls of plant cells. They permit the intercellular passage of molecules and signals and play a central role in plant physiology and development. Plasmodesmata are also conduits through which viral genomes spread during infection, and many viruses encode movement proteins that modify plasmodesmata, facilitating the intercellular trafficking of macromolecules. Recent evidence suggests that many endogenous plant proteins and systemicribonucleic acid(RNA)‐based signals also utilize plasmodesmata for cell‐to‐cell and long‐distance movement. It appears that the substructural morphology of plasmodesmata is central to their role in cell‐to‐cell communication, allowing them to function as controllable ‘valves’ that regulate the intercellular passage of molecules.

Key Concepts

Plant cells are connected to each other by cytoplasmic bridges called plasmodesmata. The continuous interconnected cytoplasm in plants is referred to as the symplasm.

A tube of endoplasmic reticulum passes though plasmodesmata and connects the endoplasmic reticulum of neighbouring cells, thus providing endomembrane continuity between cells.

Primary plasmodesmata are formed at cytokinesis when strands of endoplasmic reticulum are trapped between fusing vesicles in the developing cell wall.

Secondary plasmodesmata are formed across existing cell walls, including those at graft unions, and usually arise immediately adjacent to existing plasmodesmata.

Molecules smaller than the size exclusion limit (SEL) of plasmodesmata are able to move freely through the cytolplasmic channel of plasmodesmata by simple diffusion.

The SEL of plasmodesmata may increase or decrease to allow changes in plasmodesmatal conductance. This may occur under different conditions, for example, in response to intracellular factors such as cytoplasmic calcium levels or in response to changes in turgor pressure between cells.

Some endogenous proteins and some movement proteins encoded by plant viruses are able to increase the SEL of plasmodesmata to facilitate their own passage into neighbouring cells. This enables these proteins to function in cells in which they are not normally expressed.

Regions of cells may be connected by plasmodesmata that share an SEL different to the SEL of neighbouring cells. These regions of cells are called symplasmic domains.

Some proteins and RNA molecules pass into the plant's translocation stream and move over long distances. These macromolecules traffic through the plasmodesmata that join sieve elements (SE) and companion cells within the phloem. These macromolecules may have a site of action distant to their site of expression and synthesis.
Plant Microtubules: Their Role in Growth and Development
Authors: Lloyd Clive W
Published: September 2009

The close association of cortical microtubules with cell walls is a characteristic of immobile plant cells. In interphase, the cortical array helps organize the cell wall and before division is replaced by a narrower preprophase band that forecasts where the new cross‐wall will be attached after mitosis. The mitotic spindle is essentially similar to the general eukaryotic model but the lack of centrosomes at the poles means that the plant spindle looks different, having broader poles and reduced astral microtubules. During cytokinesis, the rigid cellulose‐rich wall does not contract inwards to separate the divided chromosomes; instead, a new cross‐wall is laid down by a ring of phragmoplast microtubules that expands outwards until it fuses with the parent wall at the site predicted by the preprophase band. In plants, microtubules therefore have a particularly direct connection with morphogenesis.

Key concepts:

Plant cells are immobile – their shape held by a cellulose‐rich cell wall.

The passive entry of water into the vacuole generates the turgor pressure that drives cell expansion.

The direction of cell expansion is regulated according to the way that inelastic cellulose microfibrils are oriented in the cell wall.

Cortical microtubules attached to the cytoplasmic face of the plasma membrane channel the movement of the enzyme complexes as they extrude cellulose microfibrils into the wall.

Plant microtubules are highly dynamic, moving by a modified form of treadmilling in which new tubulin subunits are added at one end, as other subunits are lost from the opposite end.

The cortical array of microtubules arises out of the self‐organization of microtubules that emerge from multiple, scattered nucleation sites.

The plane of cell division is forecast by the preprophase band. This transient, cortical structure contains microtubules, actin, endoplasmic reticulum and Golgi vesicles.

In higher plants, which have no centrioles, the mitotic spindle has broad poles and few astral microtubules.

The cytokinetic apparatus, the phragmoplast, is comprised of two interdigitating circlets of microtubules and actin filaments. Golgi vesicles are directed to the line of overlap to deposit the cell plate.

The new cross‐wall grows out centrifugally, like a ripple in a pond, until it contacts the parental wall previously marked by the preprophase band.
Bone Homeostasis: Extracellular Calcium Levels and Their Control
Authors: McDonald Fraser
Published: September 2009

Calcium (Ca2+) is an essential ion within the human body. It is an extraordinary ion whose homeostasis is controlled and managed by many organs (bone, intestine, kidney, skin and thyroid). For a student, Ca2+is a clear example of the complexities of biological control and understanding these basic principles is a very sound foundation for understanding other biological control mechanisms. The ion is responsible for the correct coordination of many functions and constitutes a large part of the inorganic component of the skeleton in the form of hydroxyapatite crystals. Calcium levels are kept within a specific range, regulated principally by three hormones – parathyroid hormone, calcitonin and cholecalciferol (vitamin D3) – although other paracrine substances can have a major effect. Excessive variations can lead to abnormalities of nerve function and porous bones (hypocalcaemia) or pathological calcification (hypercalcaemia).

Key concepts

Ca2+is a unique ion maintaining both the independent functional capacity of the organism being part of the rigid endoskeleton and having unique qualities controlling, very precisely, cell function.

Its characteristic role at cellular level can not only control ‘immediate’ cellular events such as exocytosis and contraction but it can also influence genetic effects in the longer term.

As an ion whose serum levels are controlled closely it demonstrates clearly basic principles of homeostasis that can serve as a foundation for understanding control of other ions/metabolites.

The control of serum Ca2+demonstrates very clearly the interaction of several systems that are required to function correctly.
Plant Interactions with Herbivores
Authors: Blumenthal Dana , Augustine David
Published: September 2009

Plants are eaten by a tremendous array of herbivores, including almost half of known insect species. Although herbivores consume most plants to some degree, many plants are also relatively well defended, and herbivore populations are often limited by predators. The net result of these processes is that the extent of herbivory, and the strength of its effects on plant populations and ecosystem processes, are highly variable. Herbivores strongly influence plants in aquatic environments, productive environments and environments with nutritious, poorly defended plants or few predators. Effects of herbivores can also be accentuated through positive feedbacks between herbivory and soil resources, in which herbivore‐mediated changes in plant community composition accelerate or decelerate nutrient cycling. Although research on herbivory has focused primarily on natural systems, few of these systems are free of human influence. Humans dramatically change plant–herbivore relationships by removing predators, increasing plant resource availability and moving both plants and herbivores around the globe.

Key concepts

Plants defend themselves effectively, using a combination of chemical defences and physical defences and tolerance.

Plant defence theory aims to explain variation among species and ecosystems in the types and amounts of plant defence.

In addition to plant defences, the extent of herbivory is limited by predation, which can greatly reduce herbivore abundance.

Despite plant defences and predation, herbivores often have strong effects on plants.

Positive feedbacks between plant resources, plant traits and herbivores can increase the influence of herbivores on plants and ecosystems.

Humans dramatically alter plant–herbivore dynamics by moving plants and herbivores, reducing the abundance of predators, increasing nutrient availability and changing the spatial distribution of plant communities.