Estimation of in-canopy ammonia sources and sinks in a fertilized Zea mays field.

An analytical model was developed to describe in-canopy vertical distribution of ammonia (NH(3)) sources and sinks and vertical fluxes in a fertilized agricultural setting using measured in-canopy mean NH(3) concentration and wind speed profiles. This model was applied to quantify in-canopy air-surface exchange rates and above-canopy NH(3) fluxes in a fertilized corn (Zea mays) field. Modeled air-canopy NH(3) fluxes agreed well with independent above-canopy flux estimates. Based on the model results, the urea fertilized soil surface was a consistent source of NH(3) one month following the fertilizer application, whereas the vegetation canopy was typically a net NH(3) sink with the lower portion of the canopy being a constant sink. The model results suggested that the canopy was a sink for some 70% of the estimated soil NH(3) emissions. A logical conclusion is that parametrization of within-canopy processes in air quality models are necessary to explore the impact of agricultural field level management practices on regional air quality. Moreover, there are agronomic and environmental benefits to timing liquid fertilizer applications as close to canopy closure as possible. Finally, given the large within-canopy mean NH(3) concentration gradients in such agricultural settings, a discussion about the suitability of the proposed model is also presented.

Association of a peripheral blood metabolic profile with coronary artery disease and risk of subsequent cardiovascular events.

BACKGROUND: Molecular tools may provide insight into cardiovascular risk. We assessed whether metabolites discriminate coronary artery disease (CAD) and predict risk of cardiovascular events. METHODS AND RESULTS: We performed mass-spectrometry-based profiling of 69 metabolites in subjects from the CATHGEN biorepository. To evaluate discriminative capabilities of metabolites for CAD, 2 groups were profiled: 174 CAD cases and 174 sex/race-matched controls ("initial"), and 140 CAD cases and 140 controls ("replication"). To evaluate the capability of metabolites to predict cardiovascular events, cases were combined ("event" group); of these, 74 experienced death/myocardial infarction during follow-up. A third independent group was profiled ("event-replication" group; n=63 cases with cardiovascular events, 66 controls). Analysis included principal-components analysis, linear regression, and Cox proportional hazards. Two principal components analysis-derived factors were associated with CAD: 1 comprising branched-chain amino acid metabolites (factor 4, initial P=0.002, replication P=0.01), and 1 comprising urea cycle metabolites (factor 9, initial P=0.0004, replication P=0.01). In multivariable regression, these factors were independently associated with CAD in initial (factor 4, odds ratio [OR], 1.36; 95% CI, 1.06 to 1.74; P=0.02; factor 9, OR, 0.67; 95% CI, 0.52 to 0.87; P=0.003) and replication (factor 4, OR, 1.43; 95% CI, 1.07 to 1.91; P=0.02; factor 9, OR, 0.66; 95% CI, 0.48 to 0.91; P=0.01) groups. A factor composed of dicarboxylacylcarnitines predicted death/myocardial infarction (event group hazard ratio 2.17; 95% CI, 1.23 to 3.84; P=0.007) and was associated with cardiovascular events in the event-replication group (OR, 1.52; 95% CI, 1.08 to 2.14; P=0.01). CONCLUSIONS: Metabolite profiles are associated with CAD and subsequent cardiovascular events.

Intake, digestibility, and passage of a commercially designed diet by two Propithecus species.

The digestibility and passage of an experimental diet was used to compare the digestive physiology of two Propithecus species: P. verreauxi and P. tattersalli. Though both animals have a similar feeding ecology, the captive status of P. verreauxi is considered more stable than that of P. tattersalli. The test diet included a local tree species, Rhus copallina, at 15% of dry matter intake (DMI) and Mazuri Leafeater Primate Diet at 85% of DMI. The chemical composition of the diet (dry matter basis) was 25% crude protein, 34% neutral detergent fiber (NDF), and 22% acid detergent fiber (ADF) with a gross energy of 4.52 kcal/g. After a 6 week acclimation to the experimental diet, animals were placed in research caging. After a 7 day adjustment period, animals were dosed with chromium mordant and Co-EDTA as markers for digesta passage and all feed refusals and feces were collected at timed intervals for 7 days. Digestibility values, similar for both species, were approximately 65% for dry matter, crude protein, and energy, and 40% and 35% respectively, for NDF and ADF. Transit times (17-18.5 hr) and mean retention times (31-34 hr) were not significantly different between species, and there was no difference between the chromium mordant and Co-EDTA. Serum values for glucose, urea, and non-esterified fatty acids (NEFA) were obtained during four different time periods to monitor nutritional status. While there was no change in serum glucose, serum urea increased over time. The NEFAs increased across all four time periods for P. verreauxi and increased for the first three periods then decreased in the last period for P. tattersalli. Results obtained indicate no difference in digestibility nor digesta passage between species, and that both Propithecus species were similar to other post-gastric folivores.

Eficiencia agronómica de la fertilización nitrogenada del cultivo de trigo, con dos fuentes y en dos zonas del sur bonarense

La eficiencia de uso de nitrógeno (EUN) aplicado con el fertilizante es un dato importante para maximizar la inversión de esta práctica. Existen opiniones encontradas en cuanto a que las diferentes fuentes presentarían diferencias respecto de este parámetro. El objetivo del presente trabajo fue determinar la EUN de dos fertilizantes nitrogenados (urea y nitrato de amonio calcáreo-CAN) aplicados en el cultivo de trigo en dos zonas del sudeste bonaerense, Necochea y Pigüé. Para ello, se realizó un ensayo de fertilización nitrogenada aplicado en cobertura con dosis crecientes de ambos fertilizantes (100, 150 y 250 kg ha-1 en Necochea y 50, 100, 150 y 200 kg ha-1.en Pigüé). Las dosis de fertilizantes se fijaron tomando como referencia las dosis más utilizadas en cada zona. Los resultados evidenciaron diferencias en EUN de los dos fertilizantes evaluados, siendo de 36.2, 37 y 20.7 kg de trigo kg N aplicado-1 para las dosis de 100, 150 y 250 kg ha-1 de CAN y 16.3, 15.1 y 12.2 de trigo kg N aplicado-1 para las dosis de 100, 150 y 250 kg ha-1 de urea respectivamente. Para la localidad de Pigüe se obtuvieron 22.7, 19.2, 19.2, 21.8 kg de trigo kg N apliacado-1 para las dosis de 50, 100, 150 y 200 kg ha-1 de CAN y 6.7, 14.4, 10.4 y 11.7 de trigo kg N aplicado-1 para las dosis de 50, 100, 150 y 200 kg ha-1 de urea respectivamente. En base a los resultados obtenidos se aceptaría la hipótesis de que en ambos ambientes existirán diferencias a favor del CAN en la EUN en fertilizaciones de trigo en cobertura.

Densidad de siembra y fertilización nitrogenada en trigo : 1-cultivares Marcos Juárez INTA y Norkinpan 70

p.9-16

Uniformidad de distribución transversal de una fertililizadora pendular

p.37-41

Empleo de las lluvias en el período vegetativo del trigo como predictoras de la respuesta a la fertilización

p.133-142

Incidencia de la suplementación lumínica y el uso de una enmienda de bajo impacto ambiental sobre la producción y calidad de lechuga (Lactuca sativa)

p.63-67

Evaluación de la respuesta a la fertilización con nitrógeno en girasol, en un hapludol típico del partido de Vedia, Provincia de Buenos Aires

p.289-296

Distribución de fertilizantes marcados con 15 N en la rotación ajo - moha

p.105-110

Análisis foliar en plantas de maíz de cultivo, I : macroelementos

p.23-30

Proporciones en poesía. Versos aúreos

La sección áurea puede ser un tema al que hacer referencia en distintos momentos y etapas del currículo escolar. Es idóneo para mostrar la relación entre las matemáticas y otras asignaturas del ámbito de humanidades y, de esta forma, contribuir a destruir el muro que tradicionalmente separa a los alumnos en «de letras» y «de ciencias». En este articulo, estudiando el ritmo de intensidad de la poesía clásica española, descubrimos cómo en los metros fundamentales y más utilizados por los autores de todos los tiempos podemos encontrar bien razones áureas, bien otras no menos bellas.

Structure and denaturation of 4-chlorobenzoyl coenzyme A dehalogenase from Arthrobacter sp. strain TM-1

The secondary structure of the trimeric protein 4-chlorobenzoyl coenzyme A dehalogenase from Arthrobacter sp. strain TM-1, the second of three enzymes involved in the dechlorination of 4-chlorobenzoate to form 4-hydroxybenzoate, has been examined. E(mM) for the enzyme was 12.59. Analysis by circular dichroism spectrometry in the far uv indicated that 4-chlorobenzoyl coenzyme A dehalogenase was composed mostly of alpha-helix (56%) with lesser amounts of random coil (21%), beta-turn (13%) and beta-sheet (9%). These data are in close agreement with a computational prediction of secondary structure from the primary amino acid sequence, which indicated 55.8% alpha-helix, 33.7% random coil and 10.5% beta-sheet; the enzyme is, therefore, similar to the 4-chlorobenzoyl coenzyme A dehalogenase from Pseudomonas sp. CBS-3. The three-dimensional structure, including that of the presumed active site, predicted by computational analysis, is also closely similar to that of the Pseudomonas dehalogenase. Study of the stability and physicochemical properties revealed that at room temperature, the enzyme was stable for 24 h but was completely inactivated by heating to 60 degrees C for 5 min; thereafter by cooling at 1 degrees C min(-1) to 45 degrees C, 20.6% of the activity could be recovered. Mildly acidic (pH 5.2) or alkaline (pH 10.1) conditions caused complete inactivation, but activity was fully recovered on returning the enzyme to pH 7.4. Circular dichroism studies also indicated that secondary structure was little altered by heating to 60 degrees C, or by changing the pH from 7.4 to 6.0 or 9.2. Complete, irreversible destruction of, and maximal decrease in the fluorescence yield of the protein at 330-350 nm were brought about by 4.5 M urea or 1.1 M guanidinium chloride. Evidence was obtained to support the hypothetical three-dimensional model, that residues W140 and W167 are buried in a non-polar environment, whereas W182 appears at or close to the surface of the protein. At least one of the enzymes of the dehalogenase system (the combined 4-chlorobenzoate:CoA ligase, the dehalogenase and 4-hydroxybenzoyl coenzyme A thioesterase) appears to be capable of association with the cell membrane.

Nitrogen uptake of phytoplankton assemblages under contrasting upwelling and downwelling conditions: The Ría de Vigo, NW Iberia

Regenerated production (including organic nitrogen) is shown here to be important in the Ria de Vigo (Galicia, NW Iberia) in supporting both harmful algal bloom communities during the downwelling season, but also (to a lesser extent) diatom communities during stratified periods of weak to moderate upwelling. The Galician Rias, situated in the Iberian upwelling system, are regularly affected by blooms of toxic dinoflagellates, which pose serious threats to the local mussel farming industry. These tend to occur towards the end of summer, during the transition from upwelling to downwelling favourable seasons, when cold bottom shelf waters in the rias are replaced by warm surface shelf waters. Nitrate, ammonium and urea uptake rates were measured in the Ria de Vigo during a downwelling event in September 2006 and during an upwelling event in June 2007. In September the ria was well mixed, with a downwelling front observed towards the middle of the ria and relatively high nutrient concentrations (1.0-2.6 mu mol L-1 nitrate; 1.0-5.6 mu mol L-1 ammonium; 0.1-0.8 mu mol L-1 phosphate; 2.0-9.0 mu mol L-1 silicic acid) were present throughout the water column. Ammonium represented more than 80% of the nitrogenous nutrients, and the phytoplankton assemblage was dominated by dinoflagellates and small flagellates. In June the water column was stratified, with nutrient-rich, upwelled water below the thermocline and warm, nutrient-depleted water in the surface. At this time, nitrate represented more than 80% of the nitrogenous nutrients, and a mixed diatom assemblage was present. Primary phytoplankton production during both events was mainly sustained by regenerated nitrogen, with ammonium uptake rates of 0.035-0.063 mu mol N L-1 h(-1) in September and 0.078-0.188 mu mol N L-1 h(-1) in June. Although f-ratios were generally low (<0.2) in both June and September, a maximum of 0.61 was reached in June due to higher nitrate uptake (0.225 mu mol N L-1 h(-1)). Total nitrogen uptake was also higher during the upwelling event (0.153-0.366 in June and 0.053-0.096 mu mol N L-1 h(-1) in September). Nitrogen uptake kinetics demonstrated a strong preference for ammonium and urea over nitrate in June.

CYSTATIN RELATED EPIDIDYMAL SPERMATOGENIC PROTEIN RESIDES IN THE OUTER DENSE FIBRES AND LIKELY TRANSIENTLY ASSOCIATES WITH THE SURFACE OF EPIDIDYMAL MOUSE SPERMATOZOA

Cystatin Related Epididymal Spermatogenic protein (CRES) is expressed in both the testis and epididymis and found associated with spermatozoa. It appears as non-glycosylated (14 and 12 kDa) and glycosylated isoforms (19 and 17 kDa). The role of CRES is enigmatic and dependent on localization of its isoforms, which is the objective of this study. The initial approach was to investigate testicular and epididymal origins of these isoforms by immunohistochemistry and immunogold cytochemistry. To further pinpoint CRES localization we then selectively extracted and fractionated epididymal spermatozoa in order to find by immunoblotting which sperm fractions contained CRES isoforms. Immunohistochemical analysis of mouse spermatogenesis showed that CRES was expressed in the tail cytoplasm of elongating spermatids from step 9-16, with a pattern reminiscent of outer dense fibre (ODF) proteins. Ultrastructural immunocytochemistry revealed that the immunogold label was concentrated over growing ODFs and mitochondrial sheath in the testes which persisted in spermatozoa through the epididymis. Sequential extractions of isolated sperm tails with Triton X-100-dithiothreitol (DTT) to remove the mitochondrial sheath, whose extract contained an unrelated 66 kDa immunoreactive band, followed by either sodium dodecyl sulfate (SDS)-DTT or urea-DTT to solubilise accessory fibres of the tail revealed a 14 kDa immunoreactive band associated with the ODF. In addition, Western blots revealed glycosylated and non-glycosylated CRES isoforms in nonyl phenoxylpolyethoxylethanol (NP40) extracts of the caput, but not cauda, sperm. Immunohistochemical analysis of the caput and cauda epithelium showed that CRES is secreted by the Golgi apparatus of the ii initial segment, fills the proximal caput lumen, and disappears by mid caput. Western blots of caput and cauda tissue and luminal fluid revealed 14 and 19 kDa immunoreactive bands in caput tissues and luminal fluid, but not in the cauda. This study concludes that there are two origins of CRES, one arising in the testis and the other in the epididymis. Testicular CRES is ionically and covalently associated with the ODF while epididymal CRES is detergent soluble and is most likely associated temporarily with the surface of caput epididymal sperm.