bluuebunny/crossref_metadata_2025 huggingface dataset:
Increasing sucrose accumulation in sugarcane by manipulating leaf extension and photosynthesis with irrigation
Authors: Inman-Bamber N. G. , Bonnett G. D. , Spillman M. F. , Hewitt M. L. , Jackson J.
Published: January 2008

High sucrose content (SC) in sugarcane stalks is a priority for all sugarcane industries world wide. Partitioning to sucrose in the cane stalk is related to the supply of photo-assimilate and the demand for assimilate by other organs. If photosynthesis could be maintained, but leaf and stalk growth constrained, by genetics or management during the stalk elongation phase, it may be possible to reduce stalk height and to increase both SC and sucrose yield. This paper reports an experiment designed to test this hypothesis and to develop a methodology to assess variation in response to source–sink manipulation in sugarcane clones. The research was conducted on a ‘low’ (Q138) and a ‘high’ (Q183) SC cultivar in two temperature controlled and airtight glasshouses (chambers) at CSIRO’s Davies Laboratory in Townsville, Australia. Potted plants of each cultivar were placed in two chambers of the Tall Plant Facility (TPF). In one chamber, plants were irrigated to minimise water stress while plants in the other chamber were irrigated to reduce plant extension rate (PER) considerably more than photosynthesis.
Water stress reduced gain in total biomass by 19% and gain in top mass by 37%, and increased sucrose mass gain by 27%. During the experiment, SC of dry matter increased 37% in the dry treatment and only 8% in the wet treatment and this effect was greater in Q183 than in Q138. Water stress reduced whole plant photosynthesis by 18%, thus largely accounting for the 19% reduction in biomass accumulation and it reduced PER by 41%, corresponding to the 37% reduction in mass of tops. Reduced PER resulted in reduced demand for photo-assimilate by fibre and tops thus allowing excess assimilate to accumulate in the form of sucrose. The techniques developed here to control PER and measure the resulting changes in carbon partitioning now allow further examination of both the control of the balance between growth and sucrose storage and the extent of genotypic variation to the response of reduced PER.
Energy transformations early in the bacteriorhodopsin photocycle revealed by DNP-enhanced solid-state NMR
Authors: Mak-Jurkauskas Melody L. , Bajaj Vikram S. , Hornstein Melissa K. , Belenky Marina , Griffin Robert G. , Herzfeld Judith
Published: January 2008

By exploiting dynamic nuclear polarization (DNP) at 90 K, we observe the first NMR spectrum of the K intermediate in the ion-motive photocycle of bacteriorhodopsin. The intermediate is identified by its reversion to the resting state of the protein in red light and by its thermal decay to the L intermediate. The
15
N chemical shift of the Schiff base in K indicates that contact has been lost with its counterion. Under these circumstances, the visible absorption of K is expected to be more red-shifted than is observed and this suggests torsion around single bonds of the retinylidene chromophore. This is in contrast to the development of a strong counterion interaction and double bond torsion in L. Thus, photon energy is stored in electrostatic modes in K and is transferred to torsional modes in L. This transfer is facilitated by the reduction in bond alternation that occurs with the initial loss of the counterion interaction, and is driven by the attraction of the Schiff base to a new counterion. Nevertheless, the process appears to be difficult, as judged by the multiple L substates, with weaker counterion interactions, that are trapped at lower temperatures. The double-bond torsion ultimately developed in the first half of the photocycle is probably responsible for enforcing vectoriality in the pump by causing a decisive switch in the connectivity of the active site once the Schiff base and its counterion are neutralized by proton transfer.
Protection against cerebral malaria by the low-molecular-weight thiol pantethine
Authors: Penet Marie-France , Abou-Hamdan Mhamad , Coltel Nicolas , Cornille Emilie , Grau Georges E. , de Reggi Max , Gharib Bouchra
Published: January 2008

We report that administration of the low-molecular-weight thiol pantethine prevented the cerebral syndrome in
Plasmodium berghei
ANKA-infected mice. The protection was associated with an impairment of the host response to the infection, with in particular a decrease of circulating microparticles and preservation of the blood–brain barrier integrity. Parasite development was unaffected. Pantethine modulated one of the early steps of the inflammation–coagulation cascade, i.e., the transbilayer translocation of phosphatidylserine at the cell surface that we demonstrated on red blood cells and platelets. In this, pantethine mimicked the inactivation of the ATP-binding-cassette transporter A1 (ABCA1), which also prevents the cerebral syndrome in this malaria model. However, pantethine acts through a different pathway, because ABCA1 activity was unaffected by the treatment. The mechanisms of pantethine action were investigated, using the intact molecule and its constituents. The disulfide group (oxidized form) is necessary to lower the platelet response to activation by thrombin and collagen. Thio-sensitive mechanisms are also involved in the impairment of microparticle release by TNF-activated endothelial cells. In isolated cells, the effects were obtained by cystamine that lacks the pantothenic moiety of the molecule; however, the complete molecule is necessary to protect against cerebral malaria. Pantethine is well tolerated, and it has already been administered in other contexts to man with limited side effects. Therefore, trials of pantethine treatment in adjunctive therapy for severe malaria are warranted.
Marketing actions can modulate neural representations of experienced pleasantness
Authors: Plassmann Hilke , O'Doherty John , Shiv Baba , Rangel Antonio
Published: January 2008

Despite the importance and pervasiveness of marketing, almost nothing is known about the neural mechanisms through which it affects decisions made by individuals. We propose that marketing actions, such as changes in the price of a product, can affect neural representations of experienced pleasantness. We tested this hypothesis by scanning human subjects using functional MRI while they tasted wines that, contrary to reality, they believed to be different and sold at different prices. Our results show that increasing the price of a wine increases subjective reports of flavor pleasantness as well as blood-oxygen-level-dependent activity in medial orbitofrontal cortex, an area that is widely thought to encode for experienced pleasantness during experiential tasks. The paper provides evidence for the ability of marketing actions to modulate neural correlates of experienced pleasantness and for the mechanisms through which the effect operates.
Allosteric effects in the marginally stable von Hippel–Lindau tumor suppressor protein and allostery-based rescue mutant design
Authors: Liu Jin , Nussinov Ruth
Published: January 2008

Many multifunctional tumor suppressor proteins have low stability, a property linked to cancer development. The von Hippel–Lindau tumor suppressor protein (pVHL) is one of these proteins. pVHL forms part of the E3 ubiquitin ligase complex that regulates the degradation of the hypoxia-inducible factor (HIF). Under native conditions, free pVHL is a molten globule, but it is stabilized in the E3 complex. By using molecular dynamics simulations, we observed that the interface between the two pVHL domains is the least stable region in unbound pVHL. We designed five stable mutants: one with a mutation at the interdomain interface and the others in the α- or β-domains. Experimentally, type 2B pVHL disease mutant Y98N at the HIF binding site was shown to destabilize pVHL and decrease its binding affinity to HIF. Our simulations showed that the decrease in pVHL stability and binding affinity are allosterically regulated. The mutations designed to stabilize unbound wild-type pVHL, which are away from the elongin C and HIF binding sites, successfully stabilized the Y98N pVHL–elongin C complex and lowered the binding free energy of pVHL with HIF. Our results indicated both the enthalpic and dynamic allosteric components between the elongin C and HIF binding sites in pVHL, in the α- and β-domains, respectively, mediated by the interdomain interface and linker. Drugs mimicking the allosteric effects of these mutants may rescue pVHL function in von Hippel–Lindau disease.
Rethinking early Earth phosphorus geochemistry
Authors: Pasek Matthew A.
Published: January 2008

Phosphorus is a key biologic element, and a prebiotic pathway leading to its incorporation into biomolecules has been difficult to ascertain. Most potentially prebiotic phosphorylation reactions have relied on orthophosphate as the source of phosphorus. It is suggested here that the geochemistry of phosphorus on the early Earth was instead controlled by reduced oxidation state phosphorus compounds such as phosphite (HPO
3
2−
), which are more soluble and reactive than orthophosphates. This reduced oxidation state phosphorus originated from extraterrestrial material that fell during the heavy bombardment period or was produced during impacts, and persisted in the mildly reducing atmosphere. This alternate view of early Earth phosphorus geochemistry provides an unexplored route to the formation of pertinent prebiotic phosphorus compounds, suggests a facile reaction pathway to condensed phosphates, and is consistent with the biochemical usage of reduced oxidation state phosphorus compounds in life today. Possible studies are suggested that may detect reduced oxidation state phosphorus compounds in ancient Archean rocks.
Specificity and transmission mosaic of ant nest-wall fungi
Authors: Schlick-Steiner Birgit C. , Steiner Florian M. , Konrad Heino , Seifert Bernhard , Christian Erhard , Moder Karl , Stauffer Christian , Crozier Ross H.
Published: January 2008

Mutualism, whereby species interact to their mutual benefit, is extraordinary in a competitive world. To recognize general patterns of origin and maintenance from the plethora of mutualistic associations proves a persisting challenge. The simplest situation is believed to be that of a single mutualist specific to a single host, vertically transmitted from one host generation to the next. We characterized ascomycete fungal associates cultured for nest architecture by the ant subgeneraDendrolasiusandChthonolasius. The ants probably manage their fungal mutualists by protecting them against fungal competitors. The ant subgenera display different ant-to-fungus specificity patterns, one-to-two and many-to-one, and we infer vertical transmission, in the latter case overlaid by horizontal transmission. Possible evolutionary trajectories include a reversal from fungiculture by otherLasiussubgenera and inheritance of fungi through life cycle interactions of the ant subgenera. The mosaic indicates how specificity patterns can be shaped by an interplay between host life-cycles and transmission adaptations.
Endocytosis and recycling of AMPA receptors lacking GluR2/3
Authors: Biou Virginie , Bhattacharyya Samarjit , Malenka Robert C.
Published: January 2008

Excitatory synapses in the mammalian brain contain two types of ligand-gated ion channels: AMPA receptors (AMPARs) and NMDA receptors (NMDARs). AMPARs are responsible for generating excitatory synaptic responses, whereas NMDAR activation triggers long-lasting changes in these responses by modulating the trafficking of AMPARs toward and away from synapses. AMPARs are tetramers composed of four subunits (GluR1–GluR4), which current models suggest govern distinct AMPAR trafficking behavior during synaptic plasticity. Here, we address the roles of GluR2 and GluR3 in controlling the recycling- and activity-dependent endocytosis of AMPARs by using cultured hippocampal neurons prepared from knockout (KO) mice lacking these subunits. We find that synapses and dendritic spines form normally in cells lacking GluR2/3 and that upon NMDAR activation, GluR2/3-lacking AMPARs are endocytosed in a manner indistinguishable from GluR2-containing AMPARs in wild-type (WT) neurons. AMPARs lacking GluR2/3 also recycle to the plasma membrane identically to WT AMPARs. However, because of their permeability to calcium, GluR2-lacking but not WT AMPARs exhibited robust internalization throughout the dendritic tree in response to AMPA application. Dendritic endocytosis of AMPARs also was observed in GABAergic neurons, which express a high proportion of GluR2-lacking AMPARs. These results demonstrate that GluR2 and GluR3 are not required for activity-dependent endocytosis of AMPARs and suggest that the most important property of GluR2 in the context of AMPAR trafficking may be its influence on calcium permeability.
Membrane association and functional regulation of Sec3 by phospholipids and Cdc42
Authors: Zhang Xiaoyu , Orlando Kelly , He Bing , Xi Fengong , Zhang Jian , Zajac Allison , Guo Wei
Published: January 2008

The exocyst is an octameric protein complex implicated in tethering post-Golgi secretory vesicles at the plasma membrane in preparation for fusion. However, it is not clear how the exocyst is targeted to and physically associates with specific domains of the plasma membrane and how its functions are regulated at those regions. We demonstrate that the N terminus of the exocyst component Sec3 directly interacts with phosphatidylinositol 4,5-bisphosphate. In addition, we have identified key residues in Sec3 that are critical for its binding to the guanosine triphosphate–bound form of Cdc42. Genetic analyses indicate that the dual interactions of Sec3 with phospholipids and Cdc42 control its function in yeast cells. Disrupting these interactions not only blocks exocytosis and affects exocyst polarization but also leads to defects in cell morphogenesis. We propose that the interactions of Sec3 with phospholipids and Cdc42 play important roles in exocytosis and polarized cell growth.
Cooperation of polarized cell intercalations drives convergence and extension of presomitic mesoderm during zebrafish gastrulation
Authors: Yin Chunyue , Kiskowski Maria , Pouille Philippe-Alexandre , Farge Emmanuel , Solnica-Krezel Lilianna
Published: January 2008

During vertebrate gastrulation, convergence and extension (C&E) movements narrow and lengthen the embryonic tissues, respectively. In zebrafish, regional differences of C&E movements have been observed; however, the underlying cell behaviors are poorly understood. Using time-lapse analyses and computational modeling, we demonstrate that C&E of the medial presomitic mesoderm is achieved by cooperation of planar and radial cell intercalations. Radial intercalations preferentially separate anterior and posterior neighbors to promote extension. In knypek;trilobite noncanonical Wnt mutants, the frequencies of cell intercalations are altered and the anteroposterior bias of radial intercalations is lost. This provides evidence for noncanonical Wnt signaling polarizing cell movements between different mesodermal cell layers. We further show using fluorescent fusion proteins that during dorsal mesoderm C&E, the noncanonical Wnt component Prickle localizes at the anterior cell edge, whereas Dishevelled is enriched posteriorly. Asymmetrical localization of Prickle and Dishevelled to the opposite cell edges in zebrafish gastrula parallels their distribution in fly, and suggests that noncanonical Wnt signaling defines distinct anterior and posterior cell properties to bias cell intercalations.
Prohibitin-1 maintains the angiogenic capacity of endothelial cells by regulating mitochondrial function and senescence
Authors: Schleicher Michael , Shepherd Benjamin R. , Suarez Yajaira , Fernandez-Hernando Carlos , Yu Jun , Pan Yong , Acevedo Lisette M. , Shadel Gerald S. , Sessa William C.
Published: January 2008

Prohibitin 1 (PHB1) is a highly conserved protein that is mainly localized to the inner mitochondrial membrane and has been implicated in regulating mitochondrial function in yeast. Because mitochondria are emerging as an important regulator of vascular homeostasis, we examined PHB1 function in endothelial cells. PHB1 is highly expressed in the vascular system and knockdown of PHB1 in endothelial cells increases mitochondrial production of reactive oxygen species via inhibition of complex I, which results in cellular senescence. As a direct consequence, both Akt and Rac1 are hyperactivated, leading to cytoskeletal rearrangements and decreased endothelial cell motility, e.g., migration and tube formation. This is also reflected in an in vivo angiogenesis assay, where silencing of PHB1 blocks the formation of functional blood vessels. Collectively, our results provide evidence that PHB1 is important for mitochondrial function and prevents reactive oxygen species–induced senescence and thereby maintains the angiogenic capacity of endothelial cells.
Intraflagellar transport motors in cilia: moving along the cell's antenna
Authors: Scholey Jonathan M.
Published: January 2008

Intraflagellar transport (IFT), the motor-dependent movement of IFT particles along the axoneme, is critical for the assembly, maintenance, and function of motile and sensory cilia, and, consequently, this process underlies ciliary motility, cilium-based signaling, and ciliopathies. Here, I present my perspective on IFT as a model system for studying motor-driven cargo transport. I review evidence that kinesin-2 motors physically transport IFT particles as cargo and hypothesize that several accessory kinesins confer cilia-specific functions by augmenting the action of the two core IFT motors, kinesin-2 and dynein 1b, which assemble the cilium foundation.
Cytoskeleton assembly at endothelial cell–cell contacts is regulated by αII-spectrin–VASP complexes
Authors: Benz Peter M. , Blume Constanze , Moebius Jan , Oschatz Chris , Schuh Kai , Sickmann Albert , Walter Ulrich , Feller Stephan M. , Renné Thomas
Published: January 2008

Directed cortical actin assembly is the driving force for intercellular adhesion. Regulated by phosphorylation, vasodilator-stimulated phosphoprotein (VASP) participates in actin fiber formation. We screened for endothelial proteins, which bind to VASP, dependent on its phosphorylation status. Differential proteomics identified αII-spectrin as such a VASP-interacting protein. αII-Spectrin binds to the VASP triple GP5-motif via its SH3 domain. cAMP-dependent protein kinase–mediated VASP phosphorylation at Ser157 inhibits αII-spectrin–VASP binding. VASP is dephosphorylated upon formation of cell–cell contacts and in confluent, but not in sparse cells, αII-spectrin colocalizes with nonphosphorylated VASP at cell–cell junctions. Ectopic expression of the αII-spectrin SH3 domain at cell–cell contacts translocates VASP, initiates cortical actin cytoskeleton formation, stabilizes cell–cell contacts, and decreases endothelial permeability. Conversely, the permeability of VASP-deficient endothelial cells (ECs) and microvessels of VASP-null mice increases. Reconstitution of VASP-deficient ECs rescues barrier function, whereas αII-spectrin binding-deficient VASP mutants fail to restore elevated permeability. We propose that αII-spectrin–VASP complexes regulate cortical actin cytoskeleton assembly with implications for vascular permeability.
Being there: cellular targeting of voltage-gated sodium channels in the heart
Authors: Bennett Vann , Healy Jane
Published: January 2008

Voltage-gated sodium (Nav) channels in cardiomyocytes are localized in specialized membrane domains that optimize their functions in propagating action potentials across cell junctions and in stimulating voltage-gated calcium channels located in T tubules. Mutation of the ankyrin-binding site of Nav1.5, the principal Nav channel in the heart, was previously known to cause cardiac arrhythmia and the retention of Nav1.5 in an intracellular compartment in cardiomyocytes. Conclusive evidence is now provided that direct interaction between Nav1.5 and ankyrin-G is necessary for the expression of Nav1.5 at the cardiomyocyte cell surface.
Ca2+-activated K+ Channels in Murine Endothelial Cells: Block by Intracellular Calcium and Magnesium
Authors: Ledoux Jonathan , Bonev Adrian D. , Nelson Mark T.
Published: January 2008

The intermediate (IKCa) and small (SKCa) conductance Ca2+-sensitive K+ channels in endothelial cells (ECs) modulate vascular diameter through regulation of EC membrane potential. However, contribution of IKCa and SKCa channels to membrane current and potential in native endothelial cells remains unclear. In freshly isolated endothelial cells from mouse aorta dialyzed with 3 μM free [Ca2+]i and 1 mM free [Mg2+]i, membrane currents reversed at the potassium equilibrium potential and exhibited an inward rectification at positive membrane potentials. Blockers of large-conductance, Ca2+-sensitive potassium (BKCa) and strong inward rectifier potassium (Kir) channels did not affect the membrane current. However, blockers of IKCa channels, charybdotoxin (ChTX), and of SKCa channels, apamin (Ap), significantly reduced the whole-cell current. Although IKCa and SKCa channels are intrinsically voltage independent, ChTX- and Ap-sensitive currents decreased steeply with membrane potential depolarization. Removal of intracellular Mg2+ significantly increased these currents. Moreover, concomitant reduction of the [Ca2+]i to 1 μM caused an additional increase in ChTX- and Ap-sensitive currents so that the currents exhibited theoretical outward rectification. Block of IKCa and SKCa channels caused a significant endothelial membrane potential depolarization (≈11 mV) and decrease in [Ca2+]i in mesenteric arteries in the absence of an agonist. These results indicate that [Ca2+]i can both activate and block IKCa and SKCa channels in endothelial cells, and that these channels regulate the resting membrane potential and intracellular calcium in native endothelium.
A portable fibre-probe ultraviolet light emitting diode (LED)-induced fluorescence detection system
Authors: Buah-Bassuah Paul K , von Bergmann Hubertus M , Tatchie Ebenezer T , Steenkamp Christine M
Published: January 2008

A portable fibre-probe fluorescence detection system comprising a continuous-wave high-power ultraviolet light emitting diode (UV LED) emitting at 365 nm as excitation source, a bifurcated fibre probe with a six-around-one fibre configuration to illuminate and read from a large target area (∼3.6 mm2) and an integrated PC-coupled spectrometer has been developed. The construction, calibration and operation of the fluorescence detection system are described. Demonstrative test measurements with the system for possible inspection of different ripening stages on some batches of horticultural and agricultural products (lemon, mandarin, banana leaf and ivy leaf) have been performed and results presented. The system is portable, comparatively low cost, easily operated and relative immune to ambient light, thus being suitable for field measurements.
Visible work: the role of students in the creation of Liebig's Giessen research school
Authors: Jackson Catherine M
Published: January 2008

Historians have generally confined Liebig's students and assistants to a peripheral role in the development of his Giessen laboratory. This paper argues that these young chemists were essential to Liebig's early success, fulfilling his need for experimental work and producing the apparently independent publications which established the credibility of his new method of organic analysis. Liebig's students and assistants embodied a particular solution to the provision of technician labour and they show us that the technician's role vastly transcends the merely manipulative. The technician, just as much as the scientist, has a history—albeit one that remains largely untold.
Nanotribology and nanomechanics in nano/biotechnology
Authors: Bhushan Bharat
Published: January 2008

Owing to larger surface area in micro/nanoelectromechanical systems (MEMS/NEMS), surface forces such as adhesion, friction, and meniscus and viscous drag forces become large when compared with inertial and electromagnetic forces. There is a need to develop lubricants and identify lubrication methods that are suitable for MEMS/NEMS. For BioMEMS/BioNEMS, adhesion between biological molecular layers and the substrate, and friction and wear of biological layers may be important, and methods to enhance adhesion between biomolecules and the device surface need to be developed. There is a need for development of a fundamental understanding of adhesion, friction/stiction, wear, the role of surface contamination and environment, and lubrication. MEMS/NEMS materials need to exhibit good mechanical and tribological properties on the micro/nanoscale. Most mechanical properties are known to be scale dependent. Therefore, the properties of nanoscale structures need to be measured. Component-level studies are required to provide a better understanding of the tribological phenomena occurring in MEMS/NEMS. The emergence of micro/nanotribology and atomic force microscopy-based techniques has provided researchers with a viable approach to address these problems. This paper presents an overview of micro/nanoscale adhesion, friction, and wear studies of materials and lubrication studies for MEMS/NEMS and BioMEMS/BioNEMS. It also presents a review of scale-dependent mechanical properties, and stress and deformation analysis of nanostructures.
Biological attachment devices: exploring nature's diversity for biomimetics
Authors: Gorb Stanislav N
Published: January 2008

Many species of animals and plants are supplied with diverse attachment devices, in which morphology depends on the species biology and the particular function in which the attachment device is involved. Many functional solutions have evolved independently in different lineages of animals and plants. Since the diversity of such biological structures is huge, there is a need for their classification. This paper, based on the original and literature data, proposes ordering of biological attachment systems according to several principles: (i) fundamental physical mechanism, according to which the system operates, (ii) biological function of the attachment device, and (iii) duration of the contact. Finally, we show a biomimetic potential of studies on biological attachment devices.
The Ediacaran emergence of bilaterians: congruence between the genetic and the geological fossil records
Authors: Peterson Kevin J , Cotton James A , Gehling James G , Pisani Davide
Published: January 2008

Unravelling the timing of the metazoan radiation is crucial for elucidating the macroevolutionary processes associated with the Cambrian explosion. Because estimates of metazoan divergence times derived from molecular clocks range from quite shallow (Ediacaran) to very deep (Mesoproterozoic), it has been difficult to ascertain whether there is concordance or quite dramatic discordance between the genetic and geological fossil records. Here, we show using a range of molecular clock methods that the major pulse of metazoan divergence times was during the Ediacaran, which is consistent with a synoptic reading of the Ediacaran macrobiota. These estimates are robust to changes in priors, and are returned with or without the inclusion of a palaeontologically derived maximal calibration point. Therefore, the two historical records of life both suggest that although the cradle of Metazoa lies in the Cryogenian, and despite the explosion of ecology that occurs in the Cambrian, it is the emergence of bilaterian taxa in the Ediacaran that sets the tempo and mode of macroevolution for the remainder of geological time.
Back in time: a new systematic proposal for the Bilateria
Authors: Baguñà Jaume , Martinez Pere , Paps Jordi , Riutort Marta
Published: January 2008

Conventional wisdom suggests that bilateral organisms arose from ancestors that were radially, rather than bilaterally, symmetrical and, therefore, had a single body axis and no mesoderm. The two main hypotheses on how this transformation took place consider either a simple organism akin to the planula larva of extant cnidarians or the acoel Platyhelminthes (planuloid–acoeloid theory), or a rather complex organism bearing several or most features of advanced coelomate bilaterians (archicoelomate theory). We report phylogenetic analyses of bilaterian metazoans using quantitative (ribosomal, nuclear and expressed sequence tag sequences) and qualitative (HOX cluster genes and microRNA sets) markers. The phylogenetic trees obtained corroborate the position of acoel and nemertodermatid flatworms as the earliest branching extant members of the Bilateria. Moreover, some acoelomate and pseudocoelomate clades appear as early branching lophotrochozoans and deuterostomes. These results strengthen the view that stem bilaterians were small, acoelomate/pseudocoelomate, benthic organisms derived from planuloid-like organisms. Because morphological and recent gene expression data suggest that cnidarians are actually bilateral, the origin of the last common bilaterian ancestor has to be put back in time earlier than the cnidarian–bilaterian split in the form of a planuloid animal. A new systematic scheme for the Bilateria that includes the Cnidaria is suggested and its main implications discussed.
The evolution of nervous system centralization
Authors: Arendt Detlev , Denes Alexandru S , Jékely Gáspár , Tessmar-Raible Kristin
Published: January 2008

It is yet unknown when and in what form the central nervous system in Bilateria first came into place and how it further evolved in the different bilaterian phyla. To find out, a series of recent molecular studies have compared neurodevelopment in slow-evolving deuterostome and protostome invertebrates, such as the enteropneust hemichordateSaccoglossusand the polychaete annelidPlatynereis. These studies focus on the spatially different activation and, when accessible, function of genes that set up the molecular anatomy of the neuroectoderm and specify neuron types that emerge from distinct molecular coordinates. Complex similarities are detected, which reveal aspects of neurodevelopment that most likely occurred already in a similar manner in the last common ancestor of the bilaterians, Urbilateria. This way, different aspects of the molecular architecture of the urbilaterian nervous system are reconstructed and yield insight into the degree of centralization that was in place in the bilaterian ancestors.
The evolution of the Ecdysozoa
Authors: Telford Maximilian J , Bourlat Sarah J , Economou Andrew , Papillon Daniel , Rota-Stabelli Omar
Published: January 2008

Ecdysozoa is a clade composed of eight phyla: the arthropods, tardigrades and onychophorans that share segmentation and appendages and the nematodes, nematomorphs, priapulids, kinorhynchs and loriciferans, which are worms with an anterior proboscis or introvert. Ecdysozoa contains the vast majority of animal species and there is a great diversity of body plans among both living and fossil members. The monophyly of the clade has been called into question by some workers based on analyses of whole genome datasets. We review the evidence that now conclusively supports the unique origin of these phyla. Relationships within Ecdysozoa are also controversial and we discuss the molecular and morphological evidence for a number of monophyletic groups within this superphylum.
N-myc coordinates retinal growth with eye size during mouse development
Authors: Martins Rodrigo A.P. , Zindy Frederique , Donovan Stacy , Zhang Jiakun , Pounds Stanley , Wey Alice , Knoepfler Paul S. , Eisenman Robert N. , Roussel Martine F. , Dyer Michael A.
Published: January 2008

Myc family members play crucial roles in regulating cell proliferation, size, differentiation, and survival during development. We found that N-myc is expressed in retinal progenitor cells, where it regulates proliferation in a cell-autonomous manner. In addition, N-myc coordinates the growth of the retina and eye. Specifically, the retinas of N-myc-deficient mice are hypocellular but are precisely proportioned to the size of the eye. N-myc represses the expression of the cyclin-dependent kinase inhibitor p27Kip1 but acts independently of cyclin D1, the major D-type cyclin in the developing mouse retina. Acute inactivation of N-myc leads to increased expression of p27Kip1, and simultaneous inactivation of p27Kip1 and N-myc rescues the hypocellular phenotype in N-myc-deficient retinas. N-myc is not required for retinal cell fate specification, differentiation, or survival. These data represent the first example of a role for a Myc family member in retinal development and the first characterization of a mouse model in which the hypocellular retina is properly proportioned to the other ocular structures. We propose that N-myc lies upstream of the cell cycle machinery in the developing mouse retina and thus coordinates the growth of both the retina and eye through extrinsic cues.
Human ES cell-derived neural rosettes reveal a functionally distinct early neural stem cell stage
Authors: Elkabetz Yechiel , Panagiotakos Georgia , Al Shamy George , Socci Nicholas D. , Tabar Viviane , Studer Lorenz
Published: January 2008

Neural stem cells (NSCs) yield both neuronal and glial progeny, but their differentiation potential toward multiple region-specific neuron types remains remarkably poor. In contrast, embryonic stem cell (ESC) progeny readily yield region-specific neuronal fates in response to appropriate developmental signals. Here we demonstrate prospective and clonal isolation of neural rosette cells (termed R-NSCs), a novel NSC type with broad differentiation potential toward CNS and PNS fates and capable of in vivo engraftment. R-NSCs can be derived from human and mouse ESCs or from neural plate stage embryos. While R-NSCs express markers classically associated with NSC fate, we identified a set of genes that specifically mark the R-NSC state. Maintenance of R-NSCs is promoted by activation of SHH and Notch pathways. In the absence of these signals, R-NSCs rapidly lose rosette organization and progress to a more restricted NSC stage. We propose that R-NSCs represent the first characterized NSC stage capable of responding to patterning cues that direct differentiation toward region-specific neuronal fates. In addition, the R-NSC-specific genetic markers presented here offer new tools for harnessing the differentiation potential of human ESCs.
A nonclassical bHLH–Rbpj transcription factor complex is required for specification of GABAergic neurons independent of Notch signaling
Authors: Hori Kei , Cholewa-Waclaw Justyna , Nakada Yuji , Glasgow Stacey M. , Masui Toshihiko , Henke R. Michael , Wildner Hendrik , Martarelli Benedetta , Beres Thomas M. , Epstein Jonathan A. , Magnuson Mark A. , MacDonald Raymond J. , Birchmeier Carmen , Johnson Jane E.
Published: January 2008

Neural networks are balanced by inhibitory and excitatory neuronal activity. The formation of these networks is initially generated through neuronal subtype specification controlled by transcription factors. The basic helix–loop–helix (bHLH) transcription factor Ptf1a is essential for the generation of GABAergic inhibitory neurons in the dorsal spinal cord, cerebellum, and retina. The transcription factor Rbpj is a transducer of the Notch signaling pathway that functions to maintain neural progenitor cells. Here we demonstrate Ptf1a and Rbpj interact in a complex that is required in vivo for specification of the GABAergic neurons, a function that cannot be substituted by the classical form of the bHLH heterodimer with E-protein or Notch signaling through Rbpj. We show that a mutant form of Ptf1a without the ability to bind Rbpj, while retaining its ability to interact with E-protein, is incapable of inducing GABAergic (Pax2)- and suppressing glutamatergic (Tlx3)-expressing cells in the chick and mouse neural tube. Moreover, we use an Rbpj conditional mutation to demonstrate that Rbpj function is essential for GABAergic specification, and that this function is independent of the Notch signaling pathway. Together, these findings demonstrate the requirement for a Ptf1a–Rbpj complex in controlling the balanced formation of inhibitory and excitatory neurons in the developing spinal cord, and point to a novel Notch-independent function for Rbpj in nervous system development.
Control of stem nematode (Ditylenchus dipsaci) in narcissus and tulip by organophosphate and organocarbamate pesticides
Authors: DAMADZADEH M. , HAGUE N. G. M.
Published: January 2008

Carbofuran, phoxim and thiofanox dips and aldicarb, carbofuran, phenamiphos and thiofanox granular applications were compared with a thionazin dip in pot experiments in a glasshouse to control stem nematode (Ditylenchus dipsaci (Kühn) Filipjev) in narcissus and tulip bulbs. Carbofuran and phoxim controlled stem nematode as effectively as thionazin. Treatment of bulbs with thionazin, carbofuran or phoxim prevented stem nematodes laying eggs in the bulbs. Phoxim has the advantage of low mammalian toxicity.
TIME‐RESOLVED PHOTOACOUSTIC CALORIMETRY OF TRYPTOPHAN IN WATER AND ORGANIC SOLVENTS
Authors: Brancaleon L. , Crippa P. R. , Minari C.
Published: January 2008

Abstract: Very little has been done in the direct study of nonradiative decays of Trp, indole and derivatives, in spite of their relatively low fluorescence quantum yields. Time‐resolved photoacoustic calorimetry is an ideal technique for this kind of study: it is very sensitive in the detection of small amounts of heat released and, in principle, allows a broad band of temporal resolution. The photoacoustic apparatus used for our measurements offers a temporal window between 10 ns and 10 μs. The analysis of the waveforms, based on a particular deconvolution method, simultaneously gives the fraction of energy released and the associated lifetime. In a broad sense, time‐resolved photoacoustic spectroscopy can be seen as a complementary method to traditional radiative techniques such as static, time‐resolved fluorescence and flash photolysis. The present work presents studies of Trp in different solvents in order to acquire new information about the interaction of this chromophore with solvents. From our measurements the high sensitivity of Trp to solvents is confirmed. The formation of complexes is evident at the excited state (exciplexes), between the chromophore and one or more molecules of solvent. These exciplexes are characterized by having an energy different from that of the singlet and triplet of Trp. Moreover, photoacoustic measurements detect, in water, the presence of another electronic state, which seems to have characteristics similar to a triplet‐like state reported in other work.
THE INTERACTION OF MELANIN WITH 8‐METHOXYPSORALEN: EFFECT ON RADIATIVE AND NONRADIATTVE TRANSITIONS. A FLUORESCENCE AND PULSED PHOTOACOUSTIC STUDY
Authors: Losi Aba , Viappiani Cristiano , Crippa Pier Raimondo
Published: January 2008

Abstract: The interaction of 8‐methoxypsoralen (8‐MOP) with synthetic eumelanin was investigated using static and time‐resolved fluorescence and pulsed photoacoustic calorimetry. Due to the strong overlap of the absorption bands of melanin and 8‐MOP, a method is presented to account for the systematic errors introduced by the optical filter effect exerted by each absorbing species in the fluorescence and the photoacoustic measurements. As a preliminary step to the understanding of the nonradiative behavior of the psoralen‐melanin complexes, the photoacoustic parameters of 8‐MOP in various solvents were determined. Spectroscopic data indicate the absence of interaction at the ground‐state level, whereas the singlet excited state of 8‐MOP is quenched by the pigment; the average fluorescence lifetimes are independent of the melanin concentration, thus indicating a static quenching mechanism. The photoacoustic data show that the quenching process involves an increased intersystem crossing probability, which is almost unaffected by the presence of oxygen, as expected for a molecule essentially acting as a type I photosensitizing agent.
RESOLUTION OF THE INDIVIDUAL TRYPTOPHANYL CONTRIBUTIONS TO THE NEAR‐ULTRAVIOLET DICHROIC ACTIVITY OF APOMYOGLOBIN
Authors: SIRANGELO IVANA , IRACE GAETANO , BISMUTO ETTORE
Published: January 2008

Abstract: The individual tryptophanyl contributions to the near‐ultraviolet dichroic activity of apomyoglobin in its native conformation have been resolved. This was accomplished by comparing the spectra of two classes of apomyoglobin with different aromatic residue contents and observing the effect of a specific modification of indole residues. The circular dichroism (CD) spectra of apomyoglobins containing two tryptophanyl residues, i.e. Trp A‐5 and A‐12, show the presence of a positive peak centered at 292 nm, attributable to indolic chromophore, which is missing in the CD spectrum of tuna apomyoglobin possessing only Trp A‐12. Moreover, the specific modification of Trp A‐5 by 2‐hydroxy‐5‐nitrobenzyl bromide is shown by the lack of the 292 nm peak and the appearance of a positive band at longer wavelength. The pH dependence of the position of this band suggests that it arises from the 2‐hydroxy‐5‐nitrobenzyl moiety. The results suggest that Trp A‐12 does not substantially contribute to the optical activity in the near ultraviolet.
THE USE OF TETRAZOLIUM SALTS TO DETERMINE SITES OF DAMAGE TO THE MITOCHONDRIAL ELECTRON TRANSPORT CHAIN IN INTACT CELLS FOLLOWING in vitro: PHOTODYNAMIC THERAPY WITH PHOTOFRIN II
Authors: Musser David A. , Oseroff Allan R.
Published: January 2008

Abstract: A method is described utilizing the tetrazolium salts neotetrazolium chloride (NTC), triphenyltetrazolium chloride (TTC), C,N‐diphenyl‐N′‐4,5‐dimethylthiazol‐2‐yrtetrazolium bromide (MTT) and various substrates to elucidate damage to the mitochondrial electron transport chain of intact cells following in vitro photodynamic therapy (PDT). Using this methodology, a portion of the dark toxicity manifested by Photofrin II (PII) was found to occur prior to entry of electrons into the transport chain through Complex I, as evidenced by the fact that the inhibition of MTT reduction was reversible by the addition of malic acid to the culture media. A second site of dark toxicity was found to be Complex IV (cytochrome oxidase). After photoirradiation of the cells, Complex I was found to be affected since malic acid could no longer reverse the inhibition of MTT reduction but it could be reversed by the addition of succinic acid, whose electrons enter the transport chain at Complex II. A second and more sensitive site of photoirradiation damage was found to be Complex IV. A region near cytochrome C was also affected by photoirradiation but appreciably less so than noted for Complexes I and IV. A kinetic analysis of MTT and TTC reduction following photoirradiation indicated that MTT reduction was sustained at a normal rate for 1 h after which it slowed down and eventually plateaued. In contrast, TTC reduction was found to be inhibited almost immediately indicating Complex IV is extremely susceptible to photoirradiation damage. Compared to other assays of mitochondrial function requiring subcellular fractionation, the use of tetrazolium salts is simpler to perform and can be done using physiologically relevant conditions.
PHOTOSENSITIZED INHIBITION OF PHOTOSYNTHETIC 14CO2 FIXATION BY α‐TERTHIENYL AND ULTRAVIOLET‐A*
Authors: Brennan Thomas M.
Published: January 2008

Abstract: A variety of naturally occurring photosensitizers of plant origin were tested for their ability to cause ultraviolet‐A (UVA)‐dependent inhibition of photosynthetic 14CO2 fixation in leaf disks of Pisum sativum L. At 0.1 mM concentrations and 60 min UVA irradiation, α‐terthienyl was strongly inhibitory, harmine and sanguinarine inhibited to a lesser degree, and curcumin, 8‐methoxypsoralen and nordihydroguaiaretic acid had no effect under the conditions tested. Alpha‐terthienyl + UVA treatments that fully inhibited 14CO2 fixation had no effect on fresh weight, chlorophyll or protein content of the tissue. Chloroplast malate dehydrogenase and glyceraldehyde‐3‐phosphate dehydrogenase were inhibited 45% and 29%, respectively, by α‐terthienyl + UVA treatment. Electron transport from H2O to the reducing side of photosystem I was inhibited to a similar extent, suggesting interference with the reductive activation of chloroplast enzymes. Alpha‐terthienyl + UVA‐treated tissue exhibited a seven‐fold increase in leakage of labeled photosynthate into the external medium. Treated leaf disks showed no ability to recover 14CO2 fixing ability over a 24 h period. These results indicate photosensitized damage at the level of the thylakoid membranes resulting in partial loss of electron transport capability and more general damage to chloroplast and cell membranes.
ERYTHEMAL UV‐B IRRADIANCE (ROBERTSON‐BERGER SUNBURN METER DATA) UNDER OZONE DEFICIENCIES IN WINTER/SPRING 1993
Authors: Blumthaler Mario , Ambach Walter , Silbernagl Roland , Staehelin Johannes
Published: January 2008

Abstract: Robertson‐Berger sunburn meter data recorded from August 1992 to May 1993 (Innsbruck, 577 m above sea level, Austria) were compared with measurements taken in previous years. In February and March 1993 instantaneous values on clear days were found to be higher by up to 37% than those registered in previous years (1986–1988). However, in winter/spring 1993 daily totals for all days, averaged over 7 days, were within the range of standard deviation of the previous years (1981–1988). Therefore the cumulative UV‐B exposure of the ecosystem is within the general range of variability even under the record low ozone values in winter/spring 1993, while single peak doses were enhanced significantly.
UVB Monochromatic Action Spectrum for the Inhibition of Photosynthetic Oxygen Production in the Green Alga Dunaliella salina
Authors: Ghetti Francesco , Fuoco Silvana , Checcucci Giovanni
Published: January 2008

The effect of monochromatic UVB (280–315 nm) irradiation on the photosynthetic activity of the marine green alga Dunaliella salina was investigated by monitoring the rate of oxygen exchange. Samples were irradiated with narrow bands centered at different UV wavelengths (281, 290, 300, 310 and 322 nm). In a first set of experiments the samples were preirradiated keeping constant the irradiance and varying exposure time. By increasing UVB fluence, a wavelength‐dependent decrease in the rate of oxygen production was observed. In a second set of experiments oxygen exchange was monitored simultaneously to UVB irradiation. The decline in the rate of oxygen production was sharper at short wavelengths and faster with increasing UVB photon flux density. The photon fluence action spectra derived from the two sets of experiments are in good agreement and indicate a decrease in the UVB‐inhibiting effectiveness of two orders of magnitude from about 0.2 (mmol m‐2)‐1 at 281 nm to about 0.003 (mmol m‐2)‐1 at 322 nm. The photon flux density action spectrum derived from the second set of experiments indicates a smoother decrease from about 0.2 (pmol s‐l m‐2)‐1 at 281 nm to about 0.05 (pmol s‐l m‐z)‐l at 310 nm.
Ultraviolet‐A‐Dependent Inhibition of Cytoplasmic Aconitase Activity of Iron Regulatory Protein‐1 in NCTC 2544 Keratinocytes
Authors: Giordani Anne , Morlière Patrice , Djavaheri‐Mergny Mojgan , Santus René
Published: January 2008

The aconitase activity of the cytoplasmic iron regulatory protein‐1 of NCTC 2544 keratinocytes is effectively inhibited by physiological doses of UVA. The time course of the photoinactivation is biphasic. A fast step is first observed corresponding to about 50% inactivation after exposure to 5 J/cm2of UVA followed by a much slower photoinactivation at higher doses. The water‐soluble antioxidant N‐acetylcysteine only partially inhibits the pho‐toinduced inactivation of the cytoplasmic aconitase function, whereas the lipophilic vitamin E, the iron chelator, desferrioxamine and the superoxide dismutase inhibitor, diethyldithiocarbamate do not protect at all. As a consequence, reactive oxygen species such as O2‐, H2O2 and lipid peroxides and hydroperoxides seem to play a rather minor role in the inactivation induced by the UVA pho‐tooxidative stress although an oxidative stress produced by O2‐ H2O2 is known to inhibit reversibly and effectively cytoplasmic aconitase activity in mammalian cells.