Técnicas de aspirado endotraqueal en neonatos: una revisión de la literatura / Endotracheal aspiration techniques in neonates: a literature review / Técnicas de aspirado endotraqueal em neonatos: uma revisão da literatura

Introducción: Para el neonato con ventilación mecánica asistida la técnica de aspiración a través del tubo endotraqueal se hace indispensable para conservarlo libre de secreciones, de esta forma, se mantiene la vía aérea permeable. En el área hospitalaria, la práctica para realizar este procedimiento contempla una técnica cerrada y otra abierta. Ambas son indispensables en el manejo correcto del paciente, cuando se usan adecuadamente. Objetivo: Analizar a través de la evidencia científica disponible, las ventajas y/o desventajas de las técnicas cerrada y abierta en el paciente neonato intubado. Metodología: Se llevó a cabo una revisión bibliográfica en las bases de datos de Pubmed, CUIDEN, Cochrane y LILACS. Además, se examinaron las listas de referencias de los artículos seleccionados. Desarrollo: Tras la revisión de los resultados y la aplicación de los criterios de inclusión fueron seleccionados seis artículos para el análisis en profundidad de los mismos. Resultados y conclusiones: En el recién nacido que está intubado, la literatura establece que la técnica cerrada ofrece mayores ventajas a los neonatos. Los autores concluyen esto, debido a que la técnica cerrada mantiene el volumen pulmonar y la presión intracraneana en parámetros estables, asimismo, mediante esta técnica se previene la hipoxia e hipoxemia por lo cual se conserva adecuadamente la saturación de oxígeno, el llenado capilar y la frecuencia cardiaca durante el procedimiento.

Introduction: In neonates under assisted ventilation, the endotracheal aspiration techniques become necessary in order to maintain the baby's airway free of secretions. Within the hospital area, the practice of these procedures includes a closed and an open technique. Both are crucial for the correct management of these patients and should always be properly performed. Objective: To analyze, through available scientific evidence, the advantages and disadvantages of the open and closed endotracheal aspiration techniques in the neonatal patient under assisted ventilation. Methodology: A bibliographical review was conducted on the PubMed, CUIDEN, Cochrane, and LILACS databases. In addition, the reference lists of the selected articles were also examined. Development: After the review and application of the inclusion criteria, a total of six articles were selected for in-depth analysis. Results and conclusions: The literature on the neonate under assisted ventilation suggests that the closed endotracheal aspiration technique offers more advantages because it maintains the pulmonary volume and the intracranial pressure within stable ranges, and also, it prevents hypoxia and hypoxemia, adequately maintaining the oxygen saturation, the capillary refill, and the cardiac frequency during the procedure.

Introdução: Para o neonato com ventilação mecânica assistida a técnica de aspiração através do tubo endotraqueal se faz indispensável para conservá-lo livre de secreções, mantendo assim, a via aérea permeável. Na área hospitalar, a prática para realizar este procedimento contempla uma técnica fechada e outra aberta. Ambas são indispensáveis no funcionamento correto do paciente, quando se usam adequadamente. Objetivo: Analisar através da evidencia científica disponível, as vantagens e/ou desvantagens das técnicas técnica fechada e aberta no paciente neonato intubado. Metodologia: Levou-se a cabo uma revisão bibliográfica nas bases de dados de Pubmed, CUIDEN, Cochrane e LILACS. Além disso, examinaram-se nas listas de referências dos artigos selecionados. Desenvolvimento: Após da revisão dos resultados e da aplicação dos critérios de inclusão, foram selecionados seis artigos para a análise exaustiva dos mesmos. Resultados e conclusões: No recém-nascido que está intubado, a literatura estabelece que a técnica fechada oferece maiores vantagens nos neonatos. Os autores concluem isto, devido a que a técnica fechada mantem o volume pulmonar e a pressão ointracraneana em parâmetros estáveis, assim mesmo, mediante esta técnica previne-se a hipóxia e hipoxemia, conservando adequadamente a saturação do oxigênio, o enchimento capilar e a frequência cardíaca durante o procedimento.

Over-expression of cytosolic glutamine synthetase increases photosynthesis and growth at low nitrogen concentrations.

Nitrogen, which is a major limiting nutrient for plant growth, is assimilated as ammonium by the concerted action of glutamine synthetase (GS) and glutamate synthase (GOGAT). GS catalyses the critical incorporation of inorganic ammonium into the amino acid glutamine. Two types of GS isozymes, located in the cytosol (GS1) and in the chloroplast (GS2) have been identified in plants. Tobacco (Nicotiana tabacum) transformants, over-expressing GS1 driven by the constitutive CaMV 35S promoter were analysed. GS in leaves of GS-5 and GS-8 plants was up-regulated, at the level of RNA and proteins. These transgenic plants had six times higher leaf GS activity than controls. Under optimum nitrogen fertilization conditions there was no effect of GS over-expression on photosynthesis or growth. However, under nitrogen starvation the GS transgenics had c. 70% higher shoot and c. 100% greater root dry weight as well as 50% more leaf area than low nitrogen controls. This was achieved by the maintenance of photosynthesis at rates indistinguishable from plants under high nitrogen, while photosynthesis in control plants was inhibited by 40-50% by nitrogen deprivation. It was demonstrated that manipulation of GS activity has the potential to maintain crop photosynthetic productivity while reducing nitrogen fertilization and the concomitant pollution.

ANT1, an aromatic and neutral amino acid transporter in Arabidopsis.

A new amino acid transporter was identified from the Arabidopsis expressed sequence tag cDNAs by expressing the cDNA in a yeast amino acid transport mutant. Transport analysis of the expressed protein in yeast showed that it transports aromatic and neutral amino acids, as well as arginine. This transporter (ANT1, aromatic and neutral transporter) also transports indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid. The cDNA is 1.6 kb in length with an open reading frame that codes for a protein with 432 amino acids and a calculated molecular mass of 50 kD. Hydropathy analysis showed ANT1 is an integral membrane protein with 11 putative membrane-spanning domains. Southern analysis and a BLAST search of the Arabidopsis genome database suggests that ANT1 is part of a small gene family containing at least five members. Phylogenetic comparisons with other known amino acid transporters in plants suggests that ANT1 represents a new class of amino acid transporter. RNA gel-blot analysis showed that this transporter is expressed in all organs with highest abundance in flowers and cauline leaves.

Amino acid transporters in plants.

Amino acid transporters are essential participants in the resource allocation processes that support plant growth and development. Recent results have identified several new transporters that contribute to a wide array of physiological activities, and detailed molecular analysis has provided fundamental insights into the structure, function and regulation of these integral membrane proteins.

Ribonucleoprotein particles of quiescent maize embryonic axes.

Certain RNA molecules are known to be sequestered and stored as ribonucleoprotein particles (RNPs) in many different tissues, particularly at some stages of metabolic quiescence. In this research RNPs from embryonic axes of mature maize seeds were isolated by sucrose and CsCl gradient centrifugation and characterized based on their RNA and protein contents. Two types of RNP particles of non-ribosomal nature were identified by northern blot analysis with specific probes: the 7S RNP and the signal recognition particle (SRP) particles which contain 5S rRNA and 7S RNA respectively. The proteins associated to these RNA molecules were the transcription factor TFIIIA-homologous protein associated to 7S RNP, and the p72, p68 and p54-GTPase proteins associated to SRP.

Synthesis of ribosomal proteins from stored mRNAs early in seed germination.

In several eukaryotic organisms the mRNA expression for ribosomal proteins (RPs) is highly regulated at the translational level. The present work addresses the synthesis of RPs early in germination and particularly the origin of their transcripts. Excised maize axes were labeled with [35S]methionine for 6 h, and both cytoplasmic and ribosomal proteins were analyzed by electrophoresis and fluorography. It was found that some RPs are newly synthesized and already incorporated into ribosomes during this period. Synthesis of RPs was also observed under conditions of transcription inhibition, suggesting the presence of stored-RP transcripts in the embryonic axes. In vitro translation of polysomes isolated from alpha-amanitin-treated axes early in germination (3 and 9 h) was performed. Immunoprecipitation of the products revealed the synthesis of rps. Four heterologous probes two each of the small subunit (S4 and S6) and large (L3, L16) subunit rps were used to detect the correspondent transcripts within the stored mRNA stock of the embryonic axes. Both, by slot blot and northern analysis, a positive cross-reaction occurred for all the tested samples. Although only two of them (S4 and S6) seem to be stored as mature mRNA.

Spatial Distribution of Photosynthesis during Drought in Field-Grown and Acclimated and Nonacclimated Growth Chamber-Grown Cotton.

Inhomogeneous photosynthetic activity has been reported to occur in drought-stressed leaves. In addition, it has been suggested that these water stress-induced nonuniformities in photosynthesis are caused by "patchy" stomatal closure and that the phenomenon may have created the illusion of a nonstomatal component to the inhibition of photosynthesis. Because these earlier studies were performed with nonacclimated growth chamber-grown plants, we sought to determine whether such "patches" existed in drought-treated, field-grown plants or in chamber-grown plants that had been acclimated to low leaf water potentials (psi(leaf)). Cotton (Gossypium hirsutum L.) was grown in the field and subjected to drought by withholding irrigation and rain from 24 d after planting. The distribution of photosynthesis, which may reflect the stomatal aperture distribution in a heterobaric species such as cotton, was assayed by autoradiography after briefly exposing attached leaves of field-grown plants to (14)CO(2). A homogeneous distribution of radioactive photosynthate was evident even at the lowest psi(leaf) of -1.34 MPa. "Patchiness" could, however, be induced by uprooting the plant and allowing the shoot to air dry for 6 to 8 min. In parallel studies, growth chamber-grown plants were acclimated to drought by withholding irrigation for three 5-d drought cycles interspersed with irrigation. This drought acclimation lowered the psi(leaf) value at which control rates of photosynthesis could be sustained by approximately 0.7 MPa and was accompanied by a similar decline in the psi(leaf) at which patchiness first appeared. Photosynthetic inhomogeneities in chamber-grown plants that were visible during moderate water stress and ambient levels of CO(2) could be largely removed with elevated CO(2) levels (3000 muL L(-1)), suggesting that they were stomatal in nature. However, advanced dehydration (less than approximately 2.0 MPa) resulted in "patches" that could not be so removed and were probably caused by nonstomatal factors. The demonstration that patches do not exist in drought-treated, field-grown cotton and that the presence of patches in chamber-grown plants can be altered by treatments that cause an acclimation of photosynthesis leads us to conclude that spatial heterogeneities in photosynthesis probably do not occur frequently under natural drought conditions.

Photophosphorylation in Attached Leaves of Helianthus annuus at Low Water Potentials.

The in situ response of photophosphorylation and coupling factor activity to low leaf water potential (psi(L)) was investigated using kinetic spectroscopy to measure the flash-induced electrochromic absorption change in attached sunflower (Helianthus annuus L. cv IS894) leaves. The electrochromic change is caused by the formation of an electric potential across the thylakoid membrane associated with proton uptake. Since depolarization of the thylakoid membrane following flash excitation is normally dominated by proton efflux through the coupling factor during ATP formation, this measurement can provide direct information about the catalytic activity of the coupling factor. Under low psi(L) conditions in which a clear nonstomatal limitation of net photosynthesis could be demonstrated, we found a strong inhibition of coupling factor activity in dark-adapted leaves which was probably caused by an increase in the energetic threshold for the activation of the enzyme at low psi(L). While this result supported earlier in vitro findings, we further discovered that the light-dependent reduction of coupling factor reversed any observable effect of low psi(L) on the energetics of activation or on photophosphorylation competence. Furthermore, coupling factor was reduced, even in severely droughted sunflower, almost immediately upon illumination. Based on these measurements, we conclude that the nonstomatal limitation of photosynthesis observed by us and others in droughted plants cannot be explained by impaired coupling factor activity.

The involvement of the photoinhibition of photosystem II and impaired membrane energization in the reduced quantum yield of carbon assimilation in chilled maize.

In this study we investigated the basis for the reduction in the quantum yield of carbon assimilation in maize (Zea mays L. cv. LG11) caused by chilling in high light. After chilling attached maize leaves at 5° C for 6 h at high irradiance (1000 µmol photons·m(-2)·s(-1)) chlorophyll fluorescence measurements indicated a serious effect on the efficiency of photochemical conversion by photosystem II (PSII) and measurements of [(14)C]atrazine binding showed that the plastoquinone binding site was altered in more than half of the PSII reaction centres. Although there were no direct effects of the chilling treatment on coupling-factor activity, ATP-formation capacity was affected because the photoinhibition of PSII led to a reduced capacity to energize the thylakoid membranes. In contrast to chilling at high irradiance, no photoinhibition of PSII accompanied the 20% decrease in the quantum yield of carbon assimilation when attached maize leaves were chilled in low light (50 µmol photons·m(-2)·s(-1)). Thus it is clear that photoinhibition of PSII is not the sole cause of the light-dependent, chillinduced decrease in the quantum yield of carbon assimilation. During the recovery of photosynthesis from the chilling treatment it was observed that full [(14)C]atrazinebinding capacity and membrane-energization capacity recovered significantly more slowly than the quantum yield of carbon assimilation. Thus, not only is photoinhibition of PSII not the sole cause for the decreased quantum yield of carbon assimilation, apparently an appreciable population of photoinhibited PSII centres can be tolerated without any reduction in the quantum yield of carbon assimilation.