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Transition metal–based chromophores play a central role in a variety of light-enabled chemical processes ranging from artificial solar energy conversion to photoredox catalysis. The most commonly used compounds include elements from the second and third transition series (e.g., ruthenium and iridium), but their Earth-abundant first-row analogs fail to engage in photoinduced electron transfer chemistry despite having virtually identical absorptive properties. This disparate behavior stems from fundamental differences in the nature of 3d versus 4d and 5d orbitals, resulting in an inversion in the compounds’ excited-state electronic structure and undermining the ability of compounds with first-row elements to engage in photoinduced electron transfer. This Review will survey the key experimental observations establishing this difference in behavior, discuss the underlying reasons for this phenomenon, and briefly summarize efforts that are currently under way to alter this paradigm and open the door to new opportunities for using Earth-abundant materials for photoinduced electron transfer chemistries. [ABSTRACT FROM AUTHOR]

Large ensembles of laser-cooled atoms interacting through infinite-range photon-mediated interactions are powerful platforms for quantum simulation and sensing. Here we realize momentum-exchange interactions in which pairs of atoms exchange their momentum states by collective emission and absorption of photons from a common cavity mode, a process equivalent to a spin-exchange or XX collective Heisenberg interaction. The momentum-exchange interaction leads to an observed all-to-all Ising-like interaction in a matter-wave interferometer. A many-body energy gap also emerges, effectively binding interferometer matter-wave packets together to suppress Doppler dephasing in analogy to Mössbauer spectroscopy. The tunable momentum-exchange interaction expands the capabilities of quantum interaction-enhanced matter-wave interferometry and may enable the realization of exotic behaviors, including simulations of superconductors and dynamical gauge fields. [ABSTRACT FROM AUTHOR]

The article discusses biological mechanisms governing parental motivation in mammals. Topics include the roles of the hormones estrogen, progesterone, and prolactin in the preparation for embryo implantation, placental development, and milk production, respectively, the brain steroid receptor-rich medial preoptic area (MPOA), the impact of parenting on neural development of the infant social brain, and the link between dopamine and maternal care in rodents.

This paper discusses emerging demographic patterns and its opportunities and challenges for India. It investigates the specificities in the demographic transition in terms of various demographic parameters and the lack of homogeneity in the transition across states in the country. It presents some opportunities that can arise from having demographic changes, particularly the demographic dividend and interstate migration to overcome labor shortage in some parts. At the same time, there are serious challenges in the form of enhancing human capital development, addressing the issue of skewed sex ratio, and the possible rise in social and political unrest and conflict. [ABSTRACT FROM AUTHOR]

We generated narrowband pairs of nearly identical photons at a rate of 5 × 104 pairs per second from a laser-cooled atomic ensemble inside an optical cavity. A two-photon interference experiment demonstrated that the photons could be made 90% indistinguishable, a key requirement for quantum information-processing protocols. Used as a conditional single-photon source, the system operated near the fundamental limits on recovery efficiency (57%), Fourier transform-limited bandwidth, and pair-generation-rate-limited suppression of two-photon events (factor of 33 below the Poisson limit). Each photon had a spectral width of 1.1 megahertz, ideal for interacting with atomic ensembles that form the basis of proposed quantum memories and logic. [ABSTRACT FROM AUTHOR]

Autonomous floats profiling in high-nitrate low-silicate waters of the Southern Ocean observed carbon biomass variability and carbon exported to depths of 100 m during the 2002 Southern Ocean Iron Experiment (SOFeX) to detect the effects of iron fertilization of surface water there. Control and "in-patch" measurements documented a greater than fourfold enhancement of carbon biomass in the iron-amended waters. Carbon export through 100 m increased two- to sixfold as the patch subducted below a front. The molar ratio of iron added to carbon exported ranged between 10[sup4] and 10[sup5]. The biomass buildup and export were much higher than expected for iron-amended low-silicate waters. [ABSTRACT FROM AUTHOR]

The experience of pain arises from both physiological and psychological factors, including one's beliefs and expectations. Thus, placebo treatments that have no intrinsic pharmacological effects may produce analgesia by altering expectations. However, controversy exists regarding whether placebos alter sensory pain transmission, pain affect, or simply produce compliance with the suggestions of investigators. In two functional magnetic resonance imaging (fMRI) experiments, we found that placebo analgesia was related to decreased brain activity in pain-sensitive brain regions, including the thalamus, insula, and anterior cingulate cortex, and was associated with increased activity during anticipation of pain in the prefrontal cortex, providing evidence that placebos alter the experience of pain. [ABSTRACT FROM AUTHOR]

We have developed the analog of a double-pan balance for determining the masses of single molecular ions from the ratio of their two cyclotron frequencies. By confining two different ions on the same magnetron orbit in a Penning trap, we balance out many sources of noise and error (such as fluctuations of the magnetic field). To minimize the systematic error associated with the Coulomb interaction between the two ions, they are kept about 1 millimeter apart from each other, resulting in fractional uncertainty below 1 X 10[sup-11]. Such precision opens the door to numerous applications of mass spectrometry, including metrology, fundamental physics, and weighing chemical bonds. [ABSTRACT FROM AUTHOR]

The nascent field of neuroeconomics seeks to ground economic decision-making in the biological substrate of the brain. We used functional magnetic resonance imaging of Ultimatum Game players to investigate neural substrates of cognitive and emotional processes involved in economic decision-making. In this game, two players split a sum of money; one player proposes a division and the other can accept or reject this. We scanned players as they responded to fair and unfair proposals. Unfair offers elicited activity in brain areas related to both emotion (anterior insula) and cognition (dorsolateral prefrontal cortex). Further, significantly heightened activity in anterior insula for rejected unfair offers suggests an important role for emotions in decision-making. [ABSTRACT FROM AUTHOR]

Two autonomous robotic profiling floats deployed in the subarctic North Pacific on 10 April 2001 provided direct records of carbon biomass variability from surface to 1000 meters below surface at daily and diurnal time scales. Eight months of real-time data documented the marine biological response to natural events, including hydrographie changes, multiple storms, and the April 2001 dust event. High-frequency observations of upper ocean particulate organic carbon variability show a near doubling of biomass in the mixed layer over a 2-week period after the passage of a cloud of Gobi desert dust. The temporal evolution of particulate organic carbon enhancement and an increase in chlorophyll use efficiency after the dust storm suggest a biotic response to a natural iron fertilization by the dust. [ABSTRACT FROM AUTHOR]

Some of the most striking and extreme consequences of rapid, long-distance aerial dispersal involve pathogens of crop plants. Long-distance dispersal of fungal spores by the wind can spread plant diseases across and even between continents and reestablish disease in areas where host plants are seasonally absent. For such epidemics to occur, hosts that are susceptible to the same pathogen genotypes must be grown over wide areas, as is the case with many modern crops. The strongly stochastic nature of long-distance dispersal causes founder effects in pathogen populations, such that the genotypes that cause epidemics in new territories or on cultivars with previously effective resistance genes may be atypical. Similar but less extreme population dynamics may arise from long-distance aerial dispersal of other organisms, including plants, viruses, and fungal pathogens of humans. [ABSTRACT FROM AUTHOR]

The article discusses research on microbial communities designed and constructed by scientists with desirable properties to help design synthetic communities for use in biotechnology. Topics include research by Asfahl et al. regarding deferral of the tragedy of the commons through social adaptation, the pathogen Pseudomonas aeruginosa's use of diffusible signaling molecules in quorum sensing to regulate public goods, and research by He et al. on colonization resistance.

Discusses the use of scanning probe microscopies in studying individual molecules. Quantum electronics of molecular systems; Conformational and mechanical properties of the systems; Range and complexity of molecules; Interplays of mechanical and electronical behavior and chemical properties; Role of dynamics in the evolution of nanotechnology.

Identifies both the binding orientation and the contact and noncontact residues of a peptide derived from the nucleotide exchange factor Sos. Negative regulation of Src tyrosine kinase activity; SH3-ligand interactions; Binding of peptide ligands in two opposite orientations.

Describes the construction of directionally oriented peptide layers 1000 angstroms thick by polymerization on gold and indium-tin-oxide glass. Use of a functionalized surface on which the initiation sits for polymerization are spaced at a distances consistent with the helical diameter of the peptide; Retention of helicity of polyalanine layer after heating at 180 degrees for seven days.

Second- and third-row transition metal complexes are widely employed in photocatalysis, whereas earth-abundant first-row transition metals have found only limited use because of the prohibitively fast decay of their excited states. We report an unforeseen reactivity mode for productive photocatalysis that uses cobalt polypyridyl complexes as photocatalysts by exploiting Marcus inverted region behavior that couples increases in excited-state energies with increased excited-state lifetimes. These cobalt (III) complexes can engage in bimolecular reactivity by virtue of their strong redox potentials and sufficiently long excited-state lifetimes, catalyzing oxidative C(sp2)-N coupling of aryl amides with challenging sterically hindered aryl boronic acids. More generally, the results imply that chromophores can be designed to increase excited-state lifetimes while simultaneously increasing excited-state energies, providing a pathway for the use of relatively abundant metals as photoredox catalysts. [ABSTRACT FROM AUTHOR]

Presents research which identified correlations between minimum temperatures (Tmin) and vegetation variables on the shortgrass steppe. Ecological consequences of increases in global Tmin; Sensitivity of this ecosystem to Tmin increases; Effects of increased Tmin in spring; Impact of reductions of Bouteloua gracilis on the ecosystem.

Investigates the phylogeny of the attine ant fungi. Analysis of subunit ribosomal RNA gene sequences; Comparison of the topology of the attine fungal symbiont phylogenetic tree with a tree based on attine ant morphology; Coevolution of attine ants and their fungal symbionts.

For decades, social psychological theories have posited that the automatic processes captured by implicit measures have implications for social outcomes. Yet few studies have demonstrated any long-term implications of automatic processes, and some scholars have begun to question the relevance and even the validity of these theories. At baseline of our longitudinal study, 135 newlywed couples (270 individuals) completed an explicit measure of their conscious attitudes toward their relationship and an implicit measure of their automatic attitudes toward their partner. They then reported their marital satisfaction every 6 months for the next 4 years. We found no correlation between spouses' automatic and conscious attitudes, which suggests that spouses were unaware of their automatic attitudes. Further, spouses' automatic attitudes, not their conscious ones, predicted changes in their marital satisfaction, such that spouses with more positive automatic attitudes were less likely to experience declines in marital satisfaction over time. [ABSTRACT FROM AUTHOR]

Colloidal nanocrystals of metals, semiconductors, and other functional materials can self-assemble into long-range ordered crystalline and quasicrystalline phases, but insulating organic surface ligands prevent the development of collective electronic states in ordered nanocrystal assemblies. We reversibly self-assembled colloidal nanocrystals of gold, platinum, nickel, lead sulfide, and lead selenide with conductive inorganic ligands into supercrystals exhibiting optical and electronic properties consistent with strong electronic coupling between the constituent nanocrystals. The phase behavior of chargestabilized nanocrystals can be rationalized and navigated with phase diagrams computed for particles interacting through short-range attractive potentials. By finely tuning interparticle interactions, the assembly was directed either through one-step nucleation or nonclassical two-step nucleation pathways. In the latter case, the nucleation was preceded by the formation of two metastable colloidal fluids. [ABSTRACT FROM AUTHOR]

The article offers perspective on research reported by Yin et al. elsewhere in the issue on the development of a water oxidation catalyst (WOC) that participates in a photochemical reaction to render carbonaceous fuels from solar energy. The fuel-generation technology enabled by the WOC is viewed to be essential to exploiting solar energy on a competitive basis. It allows solar energy to be used at times that sunlight is not available. Important characteristics for WOCs are said to include long life or the ability to be regenerated.

Reports the development of molecular hydrogen, H[sub 2] into fuel. Generation of a resource to help solve energy problems from the sun; Revelation of a stationary generator based on a hydrogen fuel cell by General Motors; Discussion on the process of fuel production.

Explores the factors that led to the deterioration of lowland forests of the Sunda Shelf in Indonesia. Possible destruction of the forests by 2005 on Sumatra and 2010 on Kalimantan; Allocation of use rights over timber-rich rainforest to powerful conglomerates and politico-business families; Legislation on regional autonomy that were vague about the extent of regional autonomy for resource planning and management.

Conservation of angular momentum is a familiar tenet in science but has seldom been invoked to understand (or predict) chemical processes. We have developed a general formalism based on Wigner's original ideas concerning angular momentum conservation to interpret the photo-induced reactivity of two molecular donor-acceptor assemblies with physical properties synthetically tailored to facilitate intramolecular energy transfer. Steady-state and time-resolved spectroscopic data establishing excited-state energy transfer from a rhenium(I)-based charge-transfer state to a chromium(III) acceptor can be fully accounted for by Förster theory, whereas the corresponding cobalt(III) adduct does not undergo an analogous reaction despite having a larger cross-section for dipolar coupling. Because this pronounced difference in reactivity is easily explained within the context of the angular momentum conservation model, this relatively simple construct may provide a means for systematizing a broad range of chemical reactions. [ABSTRACT FROM AUTHOR]

Investigated the molecular dynamics occurring in the earliest stages following photo-induced charge transfer. Role of solvent dynamics in the kinetics and mechanism of excited-state evolution; Description of the principal axis of symmetry; Carrying out of the transient absorption measurements.

Ribosome profiling has revealed pervasive but largely uncharacterized translation outside of canonical coding sequences (CDSs). In this work, we exploit a systematic CRISPR-based screening strategy to identify hundreds of noncanonical CDSs that are essential for cellular growth and whose disruption elicits specific, robust transcriptomic and phenotypic changes in human cells. Functional characterization of the encoded microproteins reveals distinct cellular localizations, specific protein binding partners, and hundreds of microproteins that are presented by the human leukocyte antigen system. We find multiple microproteins encoded in upstream open reading frames, which form stable complexes with the main, canonical protein encoded on the same messenger RNA, thereby revealing the use of functional bicistronic operons in mammals. Together, our results point to a family of functional human microproteins that play critical and diverse cellular roles. [ABSTRACT FROM AUTHOR]

Discusses the International Decade for Natural Disaster Reduction, sponsored by the United Nations in the 1990s. Observation of the declaration in the United States; Role of the Federal Emergency Management Agency (FEMA); Emphases for the future; Natural disaster losses; Emergence of mitigation; International progress.

Laser-cooled and quantum degenerate atoms are being pursued as quantum simulators and form the basis of today’s most precise sensors. A key challenge toward these goals is to understand and control coherent interactions between the atoms. We observe long-range exchange interactions mediated by an optical cavity, which manifest as tunable spin-spin interactions on the pseudo spin- ½ system composed of the millihertz linewidth clock transition in strontium. This leads to one-axis twisting dynamics, the emergence of a many-body energy gap, and gap protection of the optical coherence against certain sources of decoherence. Our observations will aid in the future design of versatile quantum simulators and the next generation of atomic clocks that use quantum correlations for enhanced metrology. [ABSTRACT FROM AUTHOR]

Transition metal catalysis has traditionally relied on organometallic complexes that can cycle through a series of ground-state oxidation levels to achieve a series of discrete yet fundamental fragment-coupling steps. The viability of excited-state organometallic catalysis via direct photoexcitation has been demonstrated. Although the utility of triplet sensitization by energy transfer has long been known as a powerful activation mode in organic photochemistry, it is surprising to recognize that photosensitization mechanisms to access excited-state organometallic catalysts have lagged far behind. Here, we demonstrate excited-state organometallic catalysis via such an activation pathway: Energy transfer from an iridium sensitizer produces an excited-state nickel complex that couples aryl halides with carboxylic acids. Detailed mechanistic studies confirm the role of photosensitization via energy transfer. [ABSTRACT FROM AUTHOR]

Sex determination in the mosquito Aedes aegypti is governed by a dominant male-determining factor (M factor) located within a Y chromosome-like region called the M locus. Here, we show that an M-locus gene, Nix, functions as an M factor in A. aegypti. Nix exhibits persisten M linkage and early embryonic expression, two characteristics required of an M factor. Nix knockout with clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 resulted in largely feminized genetic males and the production of female isoforms of two key regulators of sexual differentiation: doublesex and fruitless. Ectopic expression of Nix resulted in genetic females with nearly complete male genitalia. Thus, Nix is both required and sufficient to initiate male development. This study provides a foundation for mosquito contro strategies that convert female mosquitoes into harmless males. [ABSTRACT FROM AUTHOR]

Despite their diversity, vertebrate retinae are specialized to maximize either photon catch or visual acuity. Here, we describe a functional type that is optimized for neither purpose. In the retina of the elephantnose fish (Gnathonemus petersii), cone photoreceptors are grouped together within reflecting, photonic crystal--lined cups acting as macroreceptors, but rod photoreceptors are positioned behind these reflectors. This unusual arrangement matches rod and cone sensitivity for detecting color-mixed stimuli, whereas the photoreceptor grouping renders the fish insensitive to spatial noise; together, this enables more reliable flight reactions in the fish's dim and turbid habitat as compared with fish lacking this retinal specialization. [ABSTRACT FROM AUTHOR]

Powdery mildews are phytopathogens whose growth and reproduction are entirely dependent on living plant cells. The molecular basis of this life-style, obligate biotrophy, remains unknown. We present the genome analysis of barley powdery mildew, Blumeria graminis f.sp. hordei (Blumeria), as well as a comparison with the analysis of two powdery mildews pathogenic on dicotyledonous plants. These genomes display massive retrotransposon proliferation, genome-size expansion, and gene losses. The missing genes encode enzymes of primary and secondary metabolism, carbohydrate-active enzymes, and transporters, probably reflecting their redundancy in an exclusively biotrophic life-style. Among the 248 candidate effectors of pathogenesis identified in the Blumeria genome, very few (less than 10) define a core set conserved in all three mildews, suggesting that most effectors represent species-specific adaptations. [ABSTRACT FROM AUTHOR]

Tumor progression is driven by genetic mutations, but little is known about the environmental conditions that select for these mutations. Studying the transcriptomes of paired colorectal cancer cell lines that differed only in the mutational status of their KRAS or BRAF genes, we found that GLUT1, encoding glucose transporter-1, was one of three genes consistently up-regulated in cells with KRAS or BRAF mutations. The mutant cells exhibited enhanced glucose uptake and glycolysis and survived in low-glucose conditions, phenotypes that all required GLUT1 expression. In contrast, when cells with wild-type KRAS alleles were subjected to a low-glucose environment, very few cells survived. Most surviving cells expressed high levels of GLUT1, and 4% of these survivors had acquired KRAS mutations not present in their parents. The glycolysis inhibitor 3-bromopyruvate preferentially suppressed the growth of cells with KRAS or BRAF mutations. Together, these data suggest that glucose deprivation can drive the acquisition of KRAS pathway mutations in human tumors. [ABSTRACT FROM AUTHOR]

The oceanic biological pump drives sequestration of carbon dioxide in the deep sea via sinking particles. Rapid biological consumption and remineralization of carbon in the "twilight zone" (depths between the euphotic zone and 1000 meters) reduce the efficiency of sequestration. By using neutrally buoyant sediment traps to sample this chronically understudied realm, we measured a transfer efficiency of sinking particulate organic carbon between 150 and 500 meters of 20 and 50% at two contrasting sites. This large variability in transfer efficiency is poorly represented in biogeochemical models. If applied globally, this is equivalent to a difference in carbon sequestration of more than 3 petagrams of carbon per year. [ABSTRACT FROM AUTHOR]

The elucidation of the human genome sequence has made it possible to identify genetic alterations in cancers in unprecedented detail. To begin a systematic analysis of such alterations, we determined the sequence of well-annotated human protein-coding genes in two common tumor types. Analysis of 13,023 genes in 11 breast and 11 colorectal cancers revealed that individual tumors accumulate an average of ∼90 mutant genes but that only a subset of these contribute to the neoplastic process. Using stringent criteria to delineate this subset, we identified 189 genes (average of 11 per tumor) that were mutated at significant frequency. The vast majority of these genes were not known to be genetically altered in tumors and are predicted to affect a wide range of cellular functions, including transcription, adhesion, and invasion. These data define the genetic landscape of two human cancer types, provide new targets for diagnostic and therapeutic intervention, and open fertile avenues for basic research in tumor biology. [ABSTRACT FROM AUTHOR]

Binding of Sonic Hedgehog (Shh) to Patched (Ptc) relieves thelatter's tonic inhibition of Smoothened (Smo), a receptor that spans thecell membrane seven times. This initiates signaling which, by unknownmechanisms, regulates vertebrate developmental processes. We find thattwo molecules interact with mammalian Smo in an activation-dependentmanner: C proteincoupled receptor kinase 2 (GRK2) leads tophosphorylation of Smo, and β-arrestin 2 fused to green fluorescentprotein interacts with Smo. These two processes promote endocytosis ofSmo in clathrin-coated pits. Ptc inhibits association of β-arrestin2 with Smo, and this inhibition is relieved in cells treated with Shh. ASmo agonist stimulated and a Smo antagonist (cyclopamine) inhibited bothphosphorylation of Smo by GRK2 and interaction of β-arrestin 2 withSmo. β-Arrestin 2 and GRK2 are thus potential mediators ofsignaling by activated Smo. [ABSTRACT FROM AUTHOR]

We demonstrate that the cell wall of living Saccharomyces cerevisiae (baker's yeast) exhibits local temperature-dependent nanomechanical motion at characteristic frequencies. The periodic motions in the range of 0.8 to 1.6 kHz with amplitudes of ∼3 nm were measured using the cantilever of an atomic force microscope (AFM). Exposure of the cells to a metabolic inhibitor causes the periodic motion to cease. From the strong frequency dependence on temperature, we derive an activation energy of 58 kJ/mol, which is consistent with the cell's metabolism involving molecular motors such as kinesin, dynein, and myosin. The magnitude of the forces observed (∼10 nN) suggests conceited nanomechanical activity is operative in the cell. [ABSTRACT FROM AUTHOR]

Ecosystem responses to increased variability in rainfall, a prediction of general circutation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and ptant species diversity. However, carbon cycling processes such as soil CO[SUB2] flux, CO[SUB2] uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidty alter key carbon cycling processes and plant community composition, independent of changes in total precipitation. [ABSTRACT FROM AUTHOR]

Deals with a study which explored the interplay between the properties of a protein active site and a chemical event using a ligand that had photochemical reactivity as an optical sensor. Initial observations; Determination and dissociation of constant values for the trans-stilbene; Result of the X-ray crystallography; Nature of exciplex.

Presents research on the anti-inflammatory properties of cytochrome P450 epoxygenase-derived eicosanoids. The epoxyeicosatrienoic acids (EETs); Cytochrome P450 isoform CYP2J2 as a potential source of EETs in human endothelial cells; Inhibitory effects of EETs on cytokine-induced endothelial cell adhesion molecule expression and leukocyte adhesion to the vascular walls; Role of EETs in vascular inflammation.

Tyrosine phosphorylation, regulated by protein tyrosine phosphatases (PTPs) and kinases (PTKs), is important in signaling pathways underlying tumorigenesis. A mutational analysis of the tyrosine phosphatase gene superfamily in human cancers identified 83 somatic mutations in six PTPs (PTPRF, PTPRC, PTPRT, PTPN3, PTPNT3, PTPN14), affecting 26% of colorectal cancers and a smaller fraction of lung, breast, and gastric cancers. Fifteen mutations were nonsense, frameshift, or splice-site alterations predicted to result in truncated proteins lacking phosphatase activity. Five missense mutations in the most commonly altered PTP (PTPRT) were biochemically examined and found to reduce phosphatase activity. Expression of wild-type but not a mutant PTPRT in human cancer cells inhibited cell growth. These observations suggest that the mutated tyrosine phosphatases are tumor suppressor genes, regulating cellular pathways that may be amenable to therapeutic intervention. [ABSTRACT FROM AUTHOR]

Constitutive Hedgehog (Hh) pathway activity is associated with initiation of neoplasia, but its role in the continued growth of established tumors is unclear. Here, we investigate the therapeutic efficacy of the Hh pathway antagonist cyclopamine in preclinical models of meduUobtastoma, the most common malignant brain tumor in children. Cyciopamine treatment of murine medultoblastoma cells blocked proliferation in vitro and induced changes in gene expression consistent with initiation of neuronal differentiation and loss of neuronal stem cell-like character. This compound also caused regression of murine tumor allografts in vivo and induced rapid death of cells from freshly resected human medullobtastomas, but not from other brain tumors, thus establishing a specific role for Hh pathway activity in medulloblastoma growth. [ABSTRACT FROM AUTHOR]

The article discusses the physiology of conifer plants. Efficient water transport in plants allows for increased photosynthetic uptake of carbon dioxide for a given vascular investment and should improve fitness through enhanced growth and reproduction. The evolution of long, multicellular xylem vessels from short, unicellular tracheids reduces the number of times water must flow through high-resistance pits that link conduits end-to-end. Accordingly, the tracheid-based wood of conifers should have much higher flow resistance per length than the vesseled wood of angiosperms. It was found that conifers had lower sapwood-area resistivity than did angiosperms for the same average conduit diameter. Even on the basis of an individual conduit, conifer tracheids averaged only 1.2 times the resistivity of vessels for the same diameter. The reduction in resistivity achieved by the torus-margo pit membrane is equivalent to a 7.7-fold increase in conduit length. Thus, the evolution of the torus-margo membrane within the gymnosperm lineage from homogenous pits was equivalent to the evolution of vessels within the angiosperms.

Phosphatidylinositol 3-kinases (PI3Ks) are lipid kinases that regulate signaling pathways important for neoplasia, including cell proliferation, adhesion, survival, and motility. To determine if PI3Ks are genetically altered in tumorigenesis, researchers sequenced PI3K genes in human cancers and corresponding normal tissue. They initially examined the sequences of 117 exons that encode the predicted kinase domains of these genes in 35 colorectal cancers. Mutations in PIK3CA were also identified in 4 of 15 glioblastomas, 3 of 12 gastric cancers, 1 of 12 breast cancers and 1 of 24 lung cancers.

Tyrosine kinase (TK) are central regulators of signaling pathways that control differentiation, transcription, cell cycle progression, apoptosis, motility, and invasion. Although a few TK genes have been shown to be mutationally altered in specific human cancers, it is not known how many or how often members of the TK gene family are altered in any particular cancer type. To evaluate whether these genes were genetically altered in colorectal cancer, initially all exons encoding their predicted kinase domains were analyzed. Two independent observations support the hypothesis that the mutations found in the seven genes mutated in more than one tumor were functional rather than coincidental. First, the ratio of nonsynonymous to synonymous mutations is a reliable indicator of selection, as synonymous alterations are unlikely to exert a selective growth advantage. Second, the prevalence of nonsynonymous alterations in the kinase domains. Though the effect of the mutations on kinase function has not yet been experimentally tested, their positions within each protein suggest that many of them may be activating in nature.