ATIVIDADE DA ENZIMA NITRATO REDUTASE EM ARROZ DE TERRAS ALTAS SOB CONDIÇÕES DE ESTRESSE HÍDRICOS

A assimilação de nitrogênio é um processo vital que controla o crescimento e desenvolvimento da planta, garantindo bons níveis de produtividade de grãos. A enzima nitrato redutase (NR) catalisa o primeiro passo enzimático da assimilação de nitrogênio pelas plantas superiores por meio da redução do nitrato (NO3-) a nitrito (NO2-). Assim, objetivou-se estudar a atividade da enzima redutase do nitrato em genótipos de arroz de terras altas e correlacioná-la com os demais caracteres agronômicos. O experimento foi conduzido em dois ambientes distintos, com e sem irrigação suplementar. As análises de atividade enzimática foram realizadas em laboratório. Foram avaliados 20 genótipos de um experimento de VCU na safra 2014/2015. O delineamento experimental foi em blocos casualizados com três repetições. Foi obtida a quantidade de nitrito liberado pelos tecidos vegetais na solução de incubação (µmoles NO2- gmf -1 h-1) em sete coletas realizadas aos 7, 14, 21, 28, 45, 75 e 100 dias após emergência (DAE), sempre no período da manhã, em todas as parcelas. Diante dos resultados, observou-se que a atividade da enzima NR, na cultura do arroz, é dependente do genótipo, do período de desenvolvimento vegetal e das condições ambientais, sendo de maior expressão no início do ciclo da cultura e em ambientes sem a ocorrência de estresse hídrico. A atividade da enzima RN não deve ser utilizada isoladamente para seleção indireta no caráter produtividade na cultura do arroz de terras altas, é necessário avaliar outras características que complementem à seleção.Palavras-chave: Oryza sativa; nitrogênio; melhoramento de plantas; expressão enzimática. ACTIVITY OF THE NITRATE REDUCTASE ENZYME IN UPLAND RICE UNDER WATER STRESS CONDITIONS ABSTRACT:Nitrogen uptake is a vital process that controls plant growth and development, ensuring great grain yield levels. The enzyme nitrate reductase (NR) catalyzes the first enzymatic step of nitrogen uptake by higher plants by reducing nitrate (NO3-) to nitrite (NO2-). Thus, the objective was to study the activity of nitrate reductase enzyme in upland rice genotypes and to correlate it with other agronomic traits. The experiment was conducted in two distinct environments, with and without supplemental irrigation. The enzymatic activity assays were performed in the laboratory. Twenty genotypes of a VCU experiment in the 2014/2015 crop were evaluated. The experimental design was in randomized blocks with three replications. The amount of nitrite released by the plant tissues in the incubation solution (µmoles NO2-gmf -1 h-1) was obtained in seven collections performed at 7, 14, 21, 28, 45, 75 and 100 days after emergence (DAE). always in the mornings, in all installments. Given the results, it was observed that the activity of NR enzyme in rice culture is dependent on genotype, plant development period and environmental conditions, being more expressive at the beginning of the crop cycle and in environments without occurrence of water stress. The activity of the RN enzyme should not be used alone for indirect selection in the productivity character in the upland rice crop, it is necessary to evaluate other characteristics that complement the selection.Keywords: Oryza sativa; nitrogen; plant breeding; enzymatic expression.

ROLE OF NA+, K+, 2CL- - COTRANSPORT IN REGULATION OF THE PULMONARY ARTERY TONE

Purpose. We studied the role of Na+, K+, 2Cl- cotransport (NKCC) in contractile activity of pulmonary artery seg- ments with intact endothelium induced by incubation in nonisosmotic solutions. Materials and methods. The influence of nonisosmotic solutions and blocker of NKCC on vascular segments mechanical tension was studied in isometric regime with organ bath technique performed with the 4-channel Myobath II and software complex LAB-TRAX-4/16 (Germany). Hyperosmotic shrinkage was induced by adding 50-300 mM su- crose to the Krebs solution, the hypoosmotic environment was created by reducing the concentration of NaCl from 70 mM to 40 mM. Bumetanide was used as an NKCC blocker. The amplitude of the contractile responses was evaluated as a percentage of the control contraction in highpotassium solution. Results. The addition of 50-300 mM sucrose to the Krebs incubation solution caused a development of dose- dependent of sustained contractile responses. The amplitude of hyperosmotic striction increased with inhibition of NKCC. Incubation of segments in hypoosmotic solution caused the development of transient contractile responses, the amplitude of which decreased in the presence of NKCC inhibitor. Conclusion. Iincubation of pulmonary artery vascular segments in hyper- and hyposmotic solutions induces con- tractile responses, the amplitude of which depends on the NKCC activity.

Ruminal microbes of adult steers do not degrade extracellular L-citrulline and have a limited ability to metabolize extracellular L-glutamate1,2

The microbial population within the rumen has long been considered to have the capability of extensively degrading all dietary AA. Results from our feeding trials revealed that this dogma is not correct. In vitro studies were conducted to test the hypothesis that certain AA undergo little degradation by ruminal microbes. Whole ruminal fluid (3 mL, containing microorganisms) from cannulated adult steers (~500 kg, n = 6) was incubated at 37 °C with 5 mM l-glutamine, l-glutamate, l-arginine, or l-citrulline for 0, 0.5, 1, and 2 h to determine time-dependent changes in the metabolism of these AA. Additional ruminal fluid was incubated with 0, 0.5, 2 or 5 mM l-glutamine, l-glutamate, l-arginine, or l-citrulline for 2 h to determine dose-dependent changes in their metabolism. An aliquot (50 µL) of the incubation solution was collected at the predetermined time points for AA analyses. There was extensive hydrolysis of l-glutamine into l-glutamate and ammonia, and l-arginine into l-ornithine, l-proline, and ammonia, but the near absence of catabolism of extracellular l-glutamate and no degradation of extracellular l-citrulline by ruminal microbes. There was little uptake of 14C-labeled l-glutamate and no detectable uptake of 14C-labeled l-citrulline by the cells. These results indicate, for the first time, that ruminal microbes of adult steers do not degrade extracellular l-citrulline and that metabolism of extracellular l-glutamate is negligible compared with their ability to extensively catabolize extracellular l-arginine and l-glutamine.

Fitting of pH conditions for the study of concentrate feeds fermentation by the in vitro gas-production technique

Two experiments were conducted to simulate in vitro the fermentation conditions under high-concentrate feeding. The concentration of bicarbonate ion in the buffer of the incubation solution was assayed in Experiment 1, by adjusting medium pH to 6.50, 6.25, 6.00, 5.75 and 5.50, in two incubation series of 12 h, using barley as the reference substrate. The pH diminished linearly (P < 0001) by lowering the buffer, and remained constant throughout 12 h, except for treatments 5.75 and 5.50, where pH dropped to 5.51 and 5.31 at 12 h. Gas production decreased linearly with a decreasing medium pH (P < 0.001), with the total volume of gas produced after 12 h being highly dependent (P < 0.01) on pH at 12 h (R2 = 0.629), thus demonstrating the importance of the incubation pH for estimation of fermentation of concentrate feeds. In Experiment 2, the effect of pH on direct and indirect proportion of gas was studied by adding 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 mmol of acetic acid, either with or without (water added instead) rumen inoculum, to the media. Linear multiple regressions established between the volume of gas produced and the addition of acetic acid, and the bicarbonate ion concentration showed high determination coefficients for water (R2 = 0.929) and rumen inoculum (R2 = 0.851). Without inoculum, indirect gas production ranged from 9.4 to 12.4 mL/mmol of acid for medium pH of 5.50–6.50. With rumen inoculum, indirect gas was 20.8 mL/mmol acid, although this may have been biased by the contribution of inoculum itself to direct fermentation.

Degradation of Resin Restorative Materials by Streptococcus Mutans: A Pilot Study

Objective: To evaluate the degradation of three resin based restorative materials by S Mutans. Study design: Class I cavity was prepared in extracted premolars and were randomly divided into 3 groups (Group I – Conventional composite (CC), Group II – Resin Modified GIC and Group III–Giomer). Teeth were then restored by respective restorative material and equally divided in two subgroups (Control and Experimental). Experiment subgroup samples were then incubated in 2 ml of BHI with 1:10 dilution of SM (MTCC-497) grown overnight in BHI whereas control subgroup samples were incubated in BHI without SM. The incubation solution was collected at 2,14 and 30 days interval, and the analysis for identification and quantification of Bis-HPPP was done by High performance Liquid Chromatography. Results: Statistical analysis of the collected data revealed a statistically increased Bis HPPP production in the presence of SM in all the tested materials, with minimum in Resin Modified GIC and a maximum in Conventional Composite (CC). Conclusion: SM degrades the resin based restorative materials & among the tested materials Resin Modified GIC appears to be most Biostable.

Changes in some nitrogen fractions, protease and RNA depolymerase activity during induction by auxin of adventitious roots in tomato leaves cuttings

On tomato leaf cuttings treated with 10^-4 M IAA for 24 h and then placed for 24 h in an incubation solution induces after 4 days the appearance of adventitious roots. Experiments with actinomycin D and chloramfenicol indicate that a period of 2-3 days is essential for the synthesis of protein specific for rooting. It was found that in this period a number of characteristic changes in metabolism occurs in cuttings treated in this way. A decrease of insoluble nitrogen (Np) in the leaf blades was noted with simultaneous synthesis of this fraction and an increase of the soluble nitrogen fraction amount (Ns) in the basal pant of the petiole. In this period an enhanced activity of proteolytic enzymes is observed in the blades of leaf cuttings treated with IAA, and a decrease of activity of these enzymes and of RNA depolymerases in the basal part of the petiole. It is suggested that treatment of the cuttings with IAA solution elicits in them a number of changes in metabolic processes, leading as consequence to initiation of adventitious roots.