Auxin Regulates the Initiation and Radial Position of Plant Lateral Organs

Leaves originate from the shoot apical meristem, a small mound of undifferentiated tissue at the tip of the stem. Leaf formation begins with the selection of a group of founder cells in the so-called peripheral zone at the flank of the meristem, followed by the initiation of local growth and finally morphogenesis of the resulting bulge into a differentiated leaf. Whereas the mechanisms controlling the switch between meristem propagation and leaf initiation are being identified by genetic and molecular analyses, the radial positioning of leaves, known as phyllotaxis, remains poorly understood. Hormones, especially auxin and gibberellin, are known to influence phyllotaxis, but their specific role in the determination of organ position is not clear. We show that inhibition of polar auxin transport blocks leaf formation at the vegetative tomato meristem, resulting in pinlike naked stems with an intact meristem at the tip. Microapplication of the natural auxin indole-3-acetic acid (IAA) to the apex of such pins restores leaf formation. Similarly, exogenous IAA induces flower formation on Arabidopsis pin-formed1-1 inflorescence apices, which are blocked in flower formation because of a mutation in a putative auxin transport protein. Our results show that auxin is required for and sufficient to induce organogenesis both in the vegetative tomato meristem and in the Arabidopsis inflorescence meristem. In this study, organogenesis always strictly coincided with the site of IAA application in the radial dimension, whereas in the apical–basal dimension, organ formation always occurred at a fixed distance from the summit of the meristem. We propose that auxin determines the radial position and the size of lateral organs but not the apical–basal position or the identity of the induced structures.

Implications of Longterm Diameter-Limit Harvesting: Effects on Radial Growth of Red Spruce (Picea rubens) and Genetic Diversity of White Pine (Pinus strobus)

For over 3 centuries, diameter-limit harvesting has been a predominant logging method in the northeastern United States. Silvicultural theory asserts that such intensively selective harvesting can lead to genetic degradation. A decrease in softwood productivity has recently been reported in Maine - has a long history of dysgenic selection degraded the genetic resources of Maine softwoods, contributing to a decrease in growth and productivity? This study examines two aspects of potential implications of diameter-limit harvesting: effects on residual phenotypes of red spruce and impacts on genetic diversity of white pine. Radial growth of residual red spruce trees in stands experiencing 50 years of fixed diameter-limit harvesting was measured using annual increment rings and compared with residual red spruce trees in positive selection stands. Trees remaiaing after several rounds of diameter-limit harvesting exhibited sigdicantl y smaller radial sizes throughout their lives, and displayed significantly slower growth rates for the first 80 years of measured growth. These results strongly suggest that the largest and fastest-growing genotypes and their respective gene complexes determining good radial growth have been removed from the diameter-limit stand. Dysgenic selection can be observed in fixed diarneter-limit stands, resulting in a diminished genetic resource and decreased residual stand value. To examine more direct genetic implications of long-term diameter-limit harvesting, microsatellite DNA markers were implemented to study genetic diversity of eastern white pine in Maine. Three age groups of trees were studied: mature trees older than 200 years, juvenile trees 5-30 years old, and embryos. Trees were genotyped at 10 microsatellite loci. Overall genetic diversity levels of eastern white pine in Maine were extremely high, with an average observed heterozygosity of 0.762. Genetic differentiation was minimal among and between all three age groups, although an excess of heterozygotes was shown in the mature and juvenile groups that was not reflected in the embryo group, which actually had a slight heterozygote deficiency. Allele frequencies did not differ significantly between age groups, but did reveal more rare and low frequency alleles in the embryo groups than in the mature group. Overall, low frequency alleles comprise the largest portion of alleles in the sample population, with no common alleles evident overall. These results suggest that significant genetic degradation has either not occurred for white pine, or that the results of dysgenic selection have not yet emerged. It is clear, however, that selective harvesting could result in a loss of low frequency alleles, which are a primary reserve of evolutionary potential in a species. Implications of these studies affect industrial forestry, regional economics, and ecological concerns for the northeast. Long-term diameter-limit harvesting can lead to a degradation of residual phenotypes, and an overall decrease in stand quality. Potentially, a loss of low frequency, locally adapted alleles could result in a decrease of allelic richness and degradation of the regidnal genetic resource. Decreased genetic variation can lead to seriously limited evolutionary potential of species and ecosystems, particularly in rapidly changing environments. Based on these findings, I recommend a reassessment of any harvesting prescription that includes fixed diameter-limit removals, particularly for species that have low natural genetic diversity levels or a limited natural range, such as red spruce. Maintenance of a healthy genetic reserve can avoid effects of dysgenic harvesting.

Investigating the Diversity of Radial Glia Fates in the Rat Neocortex

Radial Glia (RG) are a mitotically active population of cells which reside within the ventricular zone at the lateral ventricle and give rise to the pyramidal neurons and astrocytes of the neocortex. Through cellular divisions, RG produce two daughter cells, one which resides in the ventricular zone and becomes another RG while the other is an immature progenitor which migrates away from the ventricle and populates the growing cortex. RG have been found to be a heterogeneous population of cells which express different surface antigens and genetic promoters which may influence the cellular fate of their progeny. In this study we have investigated the progenitor profiles of two promoters, nestin (a neural intermediate filament) and GLAST (astrocyte specific glutamate transporter) within the RG. In-utero electroporation was used to transfect reporter plasmids under the control of promoter driven Cre-Recombinase into the RG lining the lateral ventricle during mid-neurogensesis (E14). It was found that there was a large amount of overlap between the nestin and GLAST expressing populations of RG, however, there was still a small subset of cells which exclusively expressed GLAST. This prompted us to investigate the lineage of these two promoters using the PiggyBac transposon system which uses promoter driven episomal plasmids to incorporate a reporter gene into the genome of the transfected cells, allowing use to trace their full progeny. Our data shows that nestin expressing RG generate mostly neurons and few astrocytes while the GLAST expressing RG generate a greater proportion of astrocytes to neurons.

The multiple location time weighted index: Using patient activity spaces to calculate primary care service areas

Geographic health planning analyses, such as service area calculations, are hampered by a lack of patient-specific geographic data. Using the limited patient address information in patient management systems, planners analyze patient origin based on home address. But activity space research done sparingly in public health and extensively in non-health related arenas uses multiple addresses per person when analyzing accessibility. Also, health care access research has shown that there are many non-geographic factors that influence choice of provider. Most planning methods, however, overlook non-geographic factors influencing choice of provider, and the limited data mean the analyses can only be related to home address. This research attempted to determine to what extent geography plays a part in patient choice of provider and to determine if activity space data can be used to calculate service areas for primary care providers. ^ During Spring 2008, a convenience sample of 384 patients of a locally-funded Community Health Center in Houston, Texas, completed a survey that asked about what factors are important when he or she selects a health care provider. A subset of this group (336) also completed an activity space log that captured location and time data on the places where the patient regularly goes. ^ Survey results indicate that for this patient population, geography plays a role in their choice of health care provider, but it is not the most important reason for choosing a provider. Other factors for choosing a health care provider such as the provider offering "free or low cost visits", meeting "all of the patient's health care needs", and seeing "the patient quickly" were all ranked higher than geographic reasons. ^ Analysis of the patient activity locations shows that activity spaces can be used to create service areas for a single primary care provider. Weighted activity-space-based service areas have the potential to include more patients in the service area since more than one location per patient is used. Further analysis of the logs shows that a reduced set of locations by time and type could be used for this methodology, facilitating ongoing data collection for activity-space-based planning efforts. ^

NRAS and BRAF mutations in primary cutaneous melanoma: A comparison of mutation rates between radial and vertical growth phases in individual tumors

Primary cutaneous melanoma is a cancer arising from melanocytes in the skin. In recent decades the incidence of this malignancy has increased significantly. Mortality rates are high for patients with tumors measuring over a few millimeters in thickness. Response rates to conventional radiation and chemotherapy are very low in patients with metastatic melanoma. New therapies targeting melanoma’s aberrant cell signaling pathways such as the MAP Kinase pathway are being developed. Mutations of NRAS and BRAF genes are quite common in cutaneous melanoma and lead to constitutive activation of the MAP Kinase pathway. This study tests the hypothesis that NRAS and BRAF mutations increase as a tumor progresses from the noninvasive radial growth phase (RGP) to the invasive vertical growth phase (VGP). Laser capture microdissection was used to obtain separate, pure tumor DNA samples from the RGP and VGP of thirty primary cutaneous melanomas. PCR was used to amplify NRAS exon 2 and BRAF exon 15 tumor DNA. The amplified DNA was sequenced and analyzed for mutations. An overall mutation rate of 74% was obtained for the twenty-three melanomas in which there were complete sequence results. With the exception of one melanoma NRAS and BRAF mutations were mutually exclusive. All seven NRAS exon 2 mutations involved codon 61. Three of these melanomas had mutations in both the RGP and VGP. The remaining four tumors were wild type for NRAS exon 2 in the RGP but mutated in the VGP. Of the fifteen BRAF exon 15 mutated melanomas all but one involved codon 600. Twelve of the fifteen BRAF exon 15 mutations were the T1799A type. Nine of the fifteen BRAF mutated tumors had the same mutation in both the RGP and VGP. Five of fifteen melanomas had wild type RGP DNA and BRAF exon 15 mutated VGP DNA. A single melanoma had BRAF exon 15 mutated DNA in the RGP and wild type DNA in the VGP. Overall, these results suggest a trend toward the acquisition of NRAS and BRAF mutations as cutaneous melanomas change from a noninvasive to an invasive, potentially deadly cancer.^

STUDIES ON CHOLINERGIC FUNCTION AND MEMORY IN MICE (CHOLINOTOXINS, WORKING, REFERENCE MEMORY, RADIAL ARM MAZE)

Considerable evidence suggests that central cholinergic neurons participate in either acquisition, storage or retrieval of information. Experiments were designed to evaluate information processing in mice following either reversible or irreversible impairment in central cholinergic activity. The cholinergic receptor antagonists, atropine and methylatropine were used to reversibly inhibit cholinergic transmission. Irreversible impairment in central cholinergic function was achieved by central administration of the cholinergic-specific neurotoxins, N-ethyl-choline aziridinium (ECA) and N-ethyl-acetylcholine aziridinium (EACA).^ ECA and EACA appear to act by irreversible inhibition of high affinity choline uptake (proposed rate-limiting step in acetylcholine synthesis). Intraventricular administration of ECA or EACA produced persistent reduction in hippocampal choline acetyltransferase activity. Other neuronal systems and brain regions showed no evidence of toxicity.^ Mice treated with either ECA or EACA showed behavioral deficits associated with cholinergic dysfunction. Passive avoidance behavior was significantly impaired by cholinotoxin treatment. Radial arm maze performance was also significantly impaired in cholinotoxin-treated animals. Deficits in radial arm maze performance were transient, however, such that rapid and apparent complete behavioral recovery was seen during retention testing. The centrally active cholinergic receptor antagonist atropine also caused significant impairment in radial arm maze behavior, while equivalent doses of methylatropine were without effect.^ The relative effects of cholinotoxin and receptor antagonist treatment on short-term (working) memory and long-term (reference) memory in radial arm maze behavior were examined. Maze rotation studies indicated that there were at least two different response strategies which could result in accurate maze performance. One strategy involved the use of response algorithms and was considered to be a function of reference memory. Another strategy appeared to be primarily dependent on spatial working memory. However, all behavioral paradigms with multiple trails have reference memory requirements (i.e. information useful over all trials). Performance was similarly affected following either cholinotoxin or anticholinergic treatment, regardless of the response strategy utilized. In addition, rates of behavioral recovery following cholinotoxin treatment were similar between response groups. It was concluded that both cholinotoxin and anticholinergic treatment primarily resulted in impaired reference memory processes. ^

Lo masivo ante lo diferente : Rituales de interacción y energía emocional en el segmento radial "Da para darse"

Desde el estudio clásico de Bajtin se considera que el sexo es un tópico fuerte de las culturas populares. Este trabajo presenta avances de una investigación en curso sobre el segmento radial "Da para darse" del programa Perros de la calle en FM Metro de Buenos Aires. En él, una persona llama a la radio porque quiere tener sexo ("darse") con otra persona, la cual es llamada en vivo sin saber que está saliendo al aire, y tras conversar con el oyente puede acceder o no. Los datos fueron grabados digitalmente de 17 programas (alrededor de 60 "casos") entre junio y diciembre de 2009, totalizando más de 9 horas de audio, desgrabados y codificados íntegramente. Siguiendo la "teoría de los rituales de interacción" de Randall Collins, esta ponencia se centra en dos categorías emergentes del análisis: las respuestas de lo masivo, encarnado en los conductores, primero, ante "casos" homosexuales o bisexuales; y segundo, ante participantes-"otros" en términos de clase (un joven de clases populares) y procedencia (un cordobés muy excéntrico). La teoría de los rituales de interacción, aunque parecería orientarse a encuentros cara-a-cara, prueba ser útil para analizar este tipo de usos sociales de los medios masivos de comunicación

Lo masivo ante lo diferente : Rituales de interacción y energía emocional en el segmento radial "Da para darse"

Desde el estudio clásico de Bajtin se considera que el sexo es un tópico fuerte de las culturas populares. Este trabajo presenta avances de una investigación en curso sobre el segmento radial "Da para darse" del programa Perros de la calle en FM Metro de Buenos Aires. En él, una persona llama a la radio porque quiere tener sexo ("darse") con otra persona, la cual es llamada en vivo sin saber que está saliendo al aire, y tras conversar con el oyente puede acceder o no. Los datos fueron grabados digitalmente de 17 programas (alrededor de 60 "casos") entre junio y diciembre de 2009, totalizando más de 9 horas de audio, desgrabados y codificados íntegramente. Siguiendo la "teoría de los rituales de interacción" de Randall Collins, esta ponencia se centra en dos categorías emergentes del análisis: las respuestas de lo masivo, encarnado en los conductores, primero, ante "casos" homosexuales o bisexuales; y segundo, ante participantes-"otros" en términos de clase (un joven de clases populares) y procedencia (un cordobés muy excéntrico). La teoría de los rituales de interacción, aunque parecería orientarse a encuentros cara-a-cara, prueba ser útil para analizar este tipo de usos sociales de los medios masivos de comunicación

Estructura discursiva de la entrevista radial

Tabla de contenidos: La noticia como forma de comunicación. La entrevista como género discursivo. Descripción del corpus. Enfoques y temas clave en el análisis de la interacción verbal. La estructura del intercambio. Aproximación al análisis.

Analytic Kramer kernels, Lagrange-type interpolation series and de Branges spaces

The classical Kramer sampling theorem provides a method for obtaining orthogonal sampling formulas. In particular, when the involved kernel is analytic in the sampling parameter it can be stated in an abstract setting of reproducing kernel Hilbert spaces of entire functions which includes as a particular case the classical Shannon sampling theory. This abstract setting allows us to obtain a sort of converse result and to characterize when the sampling formula associated with an analytic Kramer kernel can be expressed as a Lagrange-type interpolation series. On the other hand, the de Branges spaces of entire functions satisfy orthogonal sampling formulas which can be written as Lagrange-type interpolation series. In this work some links between all these ideas are established.

Neuromorphic Detection of Vowel Representation Spaces

In this paper a layered architecture to spot and characterize vowel segments in running speech is presented. The detection process is based on neuromorphic principles, as is the use of Hebbian units in layers to implement lateral inhibition, band probability estimation and mutual exclusion. Results are presented showing how the association between the acoustic set of patterns and the phonologic set of symbols may be created. Possible applications of this methodology are to be found in speech event spotting, in the study of pathological voice and in speaker biometric characterization, among others.

Spaces of the Past, Histories of the Present: An Interview with Stuart Elden and Derek Gregory

The ontologies of space and territory, our experience of them and the techniques we use to govern them, the very conception of the socio-spatial formations that we inhabit, are all historically specific: they depend on a genealogy of practices, knowledges, discourses, regulations, performances and representations articulated in a way that is extremely complex yet nevertheless legible over time. In this interview we look at the logic and the patterns that intertwine space and time — both as objects and tools of inquiry — though a cross-disciplinary dialogue. The discussion with Stuart Elden and Derek Gregory covers the place of history in socio-spatial theory and in their own work, old and new ways of thinking about the intersection between history and territory, space and time, the implications of geography and history for thinking about contemporary politics, and the challenges now faced by critical thought and academic work in the current neo-liberal attack on public universities and the welfare state