Interactions between uptake of amino acids and inorganic nitrogen in wheat plants

Soil-borne amino acids may constitute a source of nitrogen (N) for plants in various terrestrial ecosystems but their importance for total N nutrition is unclear, particularly in nutrient-rich arable soils. One reason for this uncertainty is lack of information on how the absorption of amino acids by plant roots is affected by the simultaneous presence of inorganic N forms. The objective of the present study was to study absorption of glycine (Gly) and glutamine (Gln) by wheat roots and their interactions with nitrate (NO<sub>3</sub><sup>−</sup>) and ammonium (NH<sub>4</sub><sup>+</sup>) during uptake. The underlying hypothesis was that amino acids, when present in nutrient solution together with inorganic N, may lead to down-regulation of the inorganic N uptake, thereby resulting in similar total N uptake rates. Amino acids were enriched with double-labelled <sup>15</sup>N and <sup>13</sup>C, while NO<sub>3</sub><sup>−</sup> and NH<sub>4</sub><sup>+</sup> acquisition was determined by their rate of removal from the nutrient solution surrounding the roots. The uptake rates of NO<sub>3</sub><sup>−</sup> and NH<sub>4</sub><sup>+</sup> did not differ from each other and were generally about twice as high as the uptake rate of organic N when the different N forms were supplied separately in concentrations of 2 mM. Nevertheless, replacement of 50% of the inorganic N with organic N was able to restore the N uptake to the same level as that in the presence of only inorganic N. Co-provision of NO<sub>3</sub><sup>−</sup> did not affect glycine uptake, while the presence of glycine down-regulated NO<sub>3</sub><sup>−</sup> uptake. The ratio between <sup>13</sup>C and <sup>15</sup>N were lower in shoots than in roots and also lower than the theoretical values, reflecting higher C losses via respiratory processes compared to N losses. It is concluded that organic N can constitute a significant N-source for wheat plants and that there is an interaction between the uptake of inorganic and organic N

Estudio de solicitaciones en seccionadores de una estacion mixta aire-GIS ante la transferencia de carga entre barras

En este trabajo se presenta un caso real de funcionamiento que demuestra las exigencias a las que se ven sometidos los seccionadores que realizan transferencia de carga entre barras en una estación mixta aire-GIS en 132 kV. El objetivo del trabajo fue evaluar la hipótesis presentada por el fabricante, a fin de corroborar o desestimar las causales señaladas para la falla. Para ello, además del análisis de la respectiva normativa internacional, se realizaron simulaciones para determinar el nivel de solicitaciones que se originan, ante la operación de seccionadores en el paralelo de barras y traspaso de carga, para las condiciones de funcionamiento que posee la estación. Se implementaron modelos circuitales y cálculos que explican los fenómenos que suceden ante estas maniobras. En este caso se registran deterioros en los aparatos de seccionamiento que tienen su origen en un funcionamiento anómalo, atribuible a solicitaciones no contempladas en la estación donde estuvieron instalados.Comité de Estudio B3 - SubestacionesInstituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE

Estudio de solicitaciones en seccionadores de una estacion mixta aire-GIS ante la transferencia de carga entre barras

En este trabajo se presenta un caso real de funcionamiento que demuestra las exigencias a las que se ven sometidos los seccionadores que realizan transferencia de carga entre barras en una estación mixta aire-GIS en 132 kV. El objetivo del trabajo fue evaluar la hipótesis presentada por el fabricante, a fin de corroborar o desestimar las causales señaladas para la falla. Para ello, además del análisis de la respectiva normativa internacional, se realizaron simulaciones para determinar el nivel de solicitaciones que se originan, ante la operación de seccionadores en el paralelo de barras y traspaso de carga, para las condiciones de funcionamiento que posee la estación. Se implementaron modelos circuitales y cálculos que explican los fenómenos que suceden ante estas maniobras. En este caso se registran deterioros en los aparatos de seccionamiento que tienen su origen en un funcionamiento anómalo, atribuible a solicitaciones no contempladas en la estación donde estuvieron instalados.Comité de Estudio B3 - SubestacionesInstituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE

Estudio de solicitaciones en seccionadores de una estacion mixta aire-GIS ante la transferencia de carga entre barras

En este trabajo se presenta un caso real de funcionamiento que demuestra las exigencias a las que se ven sometidos los seccionadores que realizan transferencia de carga entre barras en una estación mixta aire-GIS en 132 kV. El objetivo del trabajo fue evaluar la hipótesis presentada por el fabricante, a fin de corroborar o desestimar las causales señaladas para la falla. Para ello, además del análisis de la respectiva normativa internacional, se realizaron simulaciones para determinar el nivel de solicitaciones que se originan, ante la operación de seccionadores en el paralelo de barras y traspaso de carga, para las condiciones de funcionamiento que posee la estación. Se implementaron modelos circuitales y cálculos que explican los fenómenos que suceden ante estas maniobras. En este caso se registran deterioros en los aparatos de seccionamiento que tienen su origen en un funcionamiento anómalo, atribuible a solicitaciones no contempladas en la estación donde estuvieron instalados.Comité de Estudio B3 - SubestacionesInstituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE

Tumor size as prognostic factor in osteosarcomas

9061 Background: Multidisciplinary treatment of osteosarcoma has achieved overall survival greater than 70%. Several prognostic factors have been described. In our country it is frequent to diagnose voluminous tumors. Greater tumors usually have worst outcome because of greater chance of tumor resistance. In order to assess the relation between tumor size and prognosis in high-grade osteosarcoma, we performed the following analysis.METHODS: Retrospectively, tumor volume was determined pre and post chemotherapy in 40 patients with histological diagnosis of high-grade osteosarcoma stage IIb. All of them received neo-adjuvant chemotherapy (ifosfamide + doxorrubicin + high dose methotrexate). Tumor size was determined in plain radiography (RX) (2 dimensions) and magnetic resonance imaging (MRI) (3 dimensions), according to RECIST criteria. Tumor calcifications, pathological fracture and skip metastasis were evaluated.RESULTS: 22 men/18 women. Median age 17 years (range 11-47). Localizations: femur (25), tibia (9), fibula (3), humerus (2) and pelvis (1). Six patients presented pathological fracture and only one skip metastasis. 14 patients had systemic progression. Median survival was 96 months (IC 95%: 80-109) and median disease free survival was 84 months (IC 95%: 69-100). Tumor volume pre chemotherapy greater than &gt;1500 cm3 (MRI) was the variable most predictor of mortality (p=0.02). Median survival was 48 months (IC 95%: 27-70) in tumors greater than 1500 cm3 versus 104 months (IC 95%: 91-118) in those tumors smaller than 1500cm3 (p=0.001). Intensification of radiological calcification, pathological fracture and changes in size pre and post chemotherapy did not have prognostic value.CONCLUSIONS: tumor measurement at diagnosis can distinguish high-risk populations. MRI is superior to RX to estimate prognostic size value. MRI does not sub estimate soft parts of the tumor and allows delimiting better tumor margins. No significant financial relationships to disclose.</p

Inadequate medical intervention as prognostic factor in osteosarcoma

9041 Background: Osteosarcoma is an aggressive disease. Survival has been improved to greater than 75% in most of the last trials. This is due to progress in surgical technique, polychemotherapy and fundamentally because of the multidisciplinary work. Inadequate medical intervention (IMI) (mistakes in the biopsy planning, pathological interpretation or surgery) could impair the osteosarcoma evolution. We compare two groups of patients managed with the same standard of care in our multidisciplinary group; one had a previous IMI and the other did not (control group).METHODS: Since 11/1989 until 9/2002, 15 patients with diagnosis of osteosarcoma that had initiated treatment in other institutions and had IMI were evaluated. Nine men, median age 21,1 years (SD: 9,36), two with central localization. Overall survival (OS), disease free survival (DFS), limb sparing and relapses of these patients were evaluated.RESULTS: erroneous diagnoses were: aneurysmal bone cist (N=4), giant cell tumor (N=2), osteochondroma (N=2), osteoblastoma (N=2), fibrous dysplasia (N=1), osteomyelitis (N=1). Histological revision made by an experienced pathologist showed high-grade osteosarcoma in 11 patients and low grade in the rest. Erroneous initial diagnosis leaded to insufficient surgeries (intralesional) in 14 patients in other institutions. Limb sparing rate was lower versus our control population (p= 0.03). In the IMI group the local and systemic relapse rates were worse (40% versus 15%, p=0.000; and 60 versus 28.3%, p=0.04 respectively). Five year SV of patients with IMI was 24.9% versus 65.3% of control group (p= 0.02). DFS was lower in the IMI group: 18.5 vs. 72.2 months (p= 0.01).CONCLUSIONS: IMI modified evolution of patients with osteosarcoma dramatically. IMI reduces OS, DFS and decreases conservational possibilities. Specialized multidisciplinary teams should treat every patient with osteosarcoma suspicion. No significant financial relationships to disclose.</p