Características morfológícas y patogénicas de aislamientos de Septoria tritici Rob ex Desm

Se analizó el comportamiento cultural y patogénicos de 8 aislamientos de Septoria tritici obtenidos a partir de hojas de trigo colectadas en el campo e infectadas naturalmente. Los diversos aislamientos monospóricos pueden diferenciarse en cultivo artificial por su aspecto, la producción de esporas, la presencia o ausencia de micelio, y el color y la frecuencia de saltaciones observadas en las colonias. Las cepas varían tanto en la abundancia como en el tipo de las esporas producidas bajo condiciones similares. Además de las picnidiosporas de forma y tamaños típicos de la especie, algunas cepas produjeron sólo esporas libres muy pequeñas (microsporas), y otras, macro y mícrosporas dentro des picnidios. Los tipos culturales predominantes de los aislamientos fueron 5: - estromático (mayor frecuencia), - albino pulverulento, - levaduroide, - mixto y - miceliar. Estos tipos culturales, en algunos casos no se mantuvieron estables a través de 3 generaciones de subcultivos. Las inoculaciones efectuadas sobre plantas de trigo en invernáculo, revelaron diferencias altamente significativas en la patogenicidad de ciertas cepas. Se encontró una relacíón entre las características culturales de los aislamientos y la severidad de la enfermedad: los aislamientos de tipo albino y levaduroide fueron los menos virulentos, tanto sobre variedades resistentes como susceptibles. La presente, constitutuye la primer cita de la presencia de esta clase de microsporas de S tritici.This study analyzed the cultural and pathogenic behavior of S tritici isolates from wheat leaves infected and collected in the field. When cultured artificially, monosporic isolates were differenciated in aspect, spore production, presence or absence of mycelium, and in color and frequency of saltation observed in the colonies as shown in table I. The characteristics noted led to the classification of the cultures as mycelial (M), typical (stromatic-pycnidial) (T) (the most frequent), powdery albino (A), yeast-like (Y) and mixed (Mx) (figs 1 and 2). In some cases these cultural types, though pure, did not remain stable after three subculture generations. The variants from the parental type appeared patches or sectorings of the yeast-like and/or the mycelial type. Sometimes these appeared in the first generation, some others in the third generation, with a low frequency of appearance with respect to the parental type. In the greenhouse, inoculation in the form of wheat plants revealed highly significant differences in the pathogenicity of some strains. Correlation of the mean percentages of pycnidial coverage showed a significant difference in isolate pathogenicity levels in the same cultivar and within cultivars (table II). Thus, the existence of physiologic specialization in S tritici is again confirmed. A relationship was found between the isolates’ cultural characteristics and the disease severity: the albino and yeast-like isolates were the least virulent for both the resistant and susceptible cultivars. Under similar conditions the strains varied in spore abundance as in the spore type produced (fig 4). Besides pycnidiospores with shape and size characteristics of the species, some strains produced only very small free spores (microspores), and some others macro and microspores within pycnidia (table III). Microspores produced in vivo were much smaller than those obtained artificially. This is the first report regarding this type of microspore in S tritici

Accuracy Tests Of American Put Valuation Models For Pharmaceutical Equity Options

This study compares the performance of the Macmillan (1986), Barone-Adesi and Whaley (1987) MBAW model, Ju and Zhong (1999) MQuad model, Black-Scholes model and Put-Call Parity in pricing American put options of pharmaceutical companies. These are evaluated using actual option prices for three companies over 2000 to 2005, as opposed to the previous use of generated binomial option pricing data. We compare the forecasting accuracy by maturity, moneyness, and variance estimate. Contrary to Ju and Zhong (1999), we find that the MBAW outperforms the other models for at-the-money, and out-of-the-money options. The MQuad model performs best for in-the-money options. However, in this case both the MBAW and MQuad models estimates are very similar. Our results are consistent irrespective of option maturities and volatility estimates. These findings raise questions regarding the practice of using actual prices as the true value, compared to the previous results that use simulated prices

Life history of Megamelus scutellaris with description of immature stages (Hemiptera: Delphacidae)

The five immature stages of Megamelus scutellaris Berg (Hemiptera: Delphacidae) are described and illustrated. The main characters that distinguish the various stages are body size, number of tarsomeres and tibial spines, color, and number of teeth on the metatibial spur. New biological data based on laboratory rearing and field observations show that M. scutellaris can carry out its biological cycle successfully on water hyacinth, Eichhornia crassipes (Martius) Solms Laubach (Pontederiaceae). Mating occurs close to the water level and one to four eggs per scar are laid in apical portion of petiole and pseudolaminae. Ovipositional scars are recognized by three parallel marks. In addition, the efficient rearing in captivity, the high survivorship registered, and overwintering on only water hyacinth suggest M. scutellaris as a potential biocontrol agent of this invasive aquatic weed.Facultad de Ciencias Naturales y Muse

Life history of Megamelus scutellaris with description of immature stages (Hemiptera: Delphacidae)

The five immature stages of Megamelus scutellaris Berg (Hemiptera: Delphacidae) are described and illustrated. The main characters that distinguish the various stages are body size, number of tarsomeres and tibial spines, color, and number of teeth on the metatibial spur. New biological data based on laboratory rearing and field observations show that M. scutellaris can carry out its biological cycle successfully on water hyacinth, Eichhornia crassipes (Martius) Solms Laubach (Pontederiaceae). Mating occurs close to the water level and one to four eggs per scar are laid in apical portion of petiole and pseudolaminae. Ovipositional scars are recognized by three parallel marks. In addition, the efficient rearing in captivity, the high survivorship registered, and overwintering on only water hyacinth suggest M. scutellaris as a potential biocontrol agent of this invasive aquatic weed.Facultad de Ciencias Naturales y Muse

Invasive micropapillary carcinoma of the breast overexpresses MUC4 and is associated with poor outcome to adjuvant trastuzumab in HER2-positive breast cancer

Invasive micropapillary carcinoma of the breast (IMPC) is a histological tumor variant that occurs with low frequency characterized by an inside-out formation of tumor clusters with a pseudopapillary arrangement. IMPC is an aggressive tumor with poor clinical outcome. In addition, this histological subtype usually expresses human epidermal growth factor receptor 2 (HER2) which also correlates with a more aggressive tumor. In this work we studied the clinical significance of IMPC in HER2-positive breast cancer patients treated with adjuvant trastuzumab. We also analyzed mucin 4 (MUC4) expression as a novel biomarker to identify IMPC.Fil: Mercogliano, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Inurrigarro, Gloria. Sanatorio Mater Dei Hermanas de María de Schoenstatt; ArgentinaFil: de Martino, Mara. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Venturutti, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Rivas, Martin Alfredo. Cornell University; Estados UnidosFil: Cordo Russo, Rosalia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Proietti Anastasi, Cecilia Jazmín. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Fernandez, Elmer Andres. Universidad Católica de Córdoba; ArgentinaFil: Frahm, Isabel. Sanatorio Mater Dei Hermanas de María de Schoenstatt; ArgentinaFil: Barchuk, Sabrina. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos ; ArgentinaFil: Allemand, Daniel H.. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos ; ArgentinaFil: Figurelli, Silvina. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos ; ArgentinaFil: Gil Deza, Ernesto. Instituto Oncológico Henry Moore; ArgentinaFil: Ares, Sandra. Instituto Oncológico Henry Moore; ArgentinaFil: Gercovich, Felipe G.. Instituto Oncológico Henry Moore; ArgentinaFil: Cortese, Eduardo. Ministerio de Defensa. Fuerza Aérea Argentina. Hospital Aeronáutico Central ; ArgentinaFil: Amasino, Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Guzmán, Pablo. Universidad de La Frontera; ChileFil: Roa, Juan C.. Universidad de La Frontera; ChileFil: Elizalde, Patricia Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Schillaci, Roxana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentin

Mineralización de los residuos de trigo provenientes de distintos sistemas de labranza: efecto sobre la pérdida de peso y dinámica del nitrógeno

En siembra directa y monocultivo los patógenos necrótrofos son más severos, porque aumentan el período de supervivencia sobre los rastrojos retenidos en el suelo. La descomposición de los residuos de cosecha depende de factores edáficos (temperatura, humedad y disponibilidad de nutrientes), químicos del rastrojo (concentración de N o la relación C/N, contenidos de lignina y carbohidratos solubles) y factores de manejo, (cantidad de rastrojo, tamaño de sus partículas (descomposición dentro o sobre el suelo) El objetivo fue investigar la pérdida de peso del rastrojo según los contenidos iniciales de nitrógeno en el suelo, trazando su dinámica

Presence of the Aphid, Chaetosiphon fragaefolii, on Strawberry in Argentina

Seasonal abundance of the strawberry aphid complex under different agronomic practices in the outskirts of La Plata, Argentina was studied on strawberry, Fragaria x ananassa Duchesne (Rosales: Rosaceae). Aphid densities were low in strawberry fields in which insecticides and fungicides were used. In addition to Aphis gossypii, Aphis fabae, Mysus persicae and Macrosiphum euphorbiae, the aphid, Chaetosiphon fragaefolii (Cockerell) (Homoptera: Aphididae), was recorded for the first time in this horticultural area. Life history and some demographic parameters were calculated for C. fragaefolii. The mean duration of nymphal stages was 10.44 days, the oviposition period was 11.8 days, and the mean number of nymph/female/day was 2.4 ± 0.3. Demographic parameters analyzed included the net reproductive rate Ro = 14.55 ± 0.096 nymph/female, generation time T=16.91 ± 0.035 days, and the intrinsic rate of increase rm = 0.158 ± (0.004). No parasites were found associated with C. fragaefolli. The pathogenic fungus, Entomophthora planchoniana Cornu (Zygomycetes: Entomophthorales) was the main mortality factor. Although aphids are not the main pests in strawberry fields, C. fragaefolii can be a serious problem because it can transmit several virus diseases of strawberry. Greater knowledge of life history traits and mortality factors of this species is needed in order to design appropriate control strategies

Markov analysis of stochastic resonance in a periodically driven integrate-fire neuron

We model the dynamics of the leaky integrate-fire neuron under periodic stimulation as a Markov process with respect to the stimulus phase. This avoids the unrealistic assumption of a stimulus reset after each spike made in earlier work and thus solves the long-standing reset problem. The neuron exhibits stochastic resonance, both with respect to input noise intensity and stimulus frequency. The latter resonance arises by matching the stimulus frequency to the refractory time of the neuron. The Markov approach can be generalized to other periodically driven stochastic processes containing a reset mechanism.Comment: 23 pages, 10 figure

A Fokker-Planck formalism for diffusion with finite increments and absorbing boundaries

Gaussian white noise is frequently used to model fluctuations in physical systems. In Fokker-Planck theory, this leads to a vanishing probability density near the absorbing boundary of threshold models. Here we derive the boundary condition for the stationary density of a first-order stochastic differential equation for additive finite-grained Poisson noise and show that the response properties of threshold units are qualitatively altered. Applied to the integrate-and-fire neuron model, the response turns out to be instantaneous rather than exhibiting low-pass characteristics, highly non-linear, and asymmetric for excitation and inhibition. The novel mechanism is exhibited on the network level and is a generic property of pulse-coupled systems of threshold units.Comment: Consists of two parts: main article (3 figures) plus supplementary text (3 extra figures

Development of Upper Body Coordination During Sitting in Typically Developing Infants

Our goal was to determine how the actions of the thorax and the pelvis are organized and coordinated to achieve independent sitting posture in typically developing infants. The participants were 10 typically developing infants who were evaluated longitudinally from first onset of sitting until sitting independence. Each infant underwent nine testing sessions. The first session included motor evaluation with the Peabody test. The other eight sessions occurred over a period of 4 mo where sitting behavior was evaluated by angular kinematics of the thorax and the pelvis. A physical therapist evaluated sitting behavior in each session and categorized it according to five stages. The phasing relationship of the thorax and the pelvis was calculated and evaluated longitudinally using a one-way analysis of variance. With development, the infants progressed from an in-phase (moving in the same direction) to an out-of-phase (moving in an opposite direction) coordinative relationship between the thorax and the pelvis segments. This change was significant for both sagittal and frontal planes of motion. Clinically, this relationship is important because it provides a method to quantify infant sitting postural development, and can be used to assess efficacy of early interventions for pediatric populations with developmental motor delays