Lipids in xylem sap of woody plants across the angiosperm phylogeny.

Lipids have been observed attached to lumen-facing surfaces of mature xylem conduits of several plant species, but there has been little research on their functions or effects on water transport, and only one lipidomic study of the xylem apoplast. Therefore, we conducted lipidomic analyses of xylem sap from woody stems of seven plants representing six major angiosperm clades, including basal magnoliids, monocots and eudicots, to characterize and quantify phospholipids, galactolipids and sulfolipids in sap using mass spectrometry. Locations of lipids in vessels of Laurus nobilis were imaged using transmission electron microscopy and confocal microscopy. Xylem sap contained the galactolipids di- and monogalactosyldiacylglycerol, as well as all common plant phospholipids, but only traces of sulfolipids, with total lipid concentrations in extracted sap ranging from 0.18 to 0.63 nmol ml-1 across all seven species. Contamination of extracted sap from lipids in cut living cells was found to be negligible. Lipid composition of sap was compared with wood in two species and was largely similar, suggesting that sap lipids, including galactolipids, originate from cell content of living vessels. Seasonal changes in lipid composition of sap were observed for one species. Lipid layers coated all lumen-facing vessel surfaces of L. nobilis, and lipids were highly concentrated in inter-vessel pits. The findings suggest that apoplastic, amphiphilic xylem lipids are a universal feature of angiosperms. The findings require a reinterpretation of the cohesion-tension theory of water transport to account for the effects of apoplastic lipids on dynamic surface tension and hydraulic conductance in xylem.

Xylem Surfactants Introduce a New Element to the Cohesion-Tension Theory.

Vascular plants transport water under negative pressure without constantly creating gas bubbles that would disable their hydraulic systems. Attempts to replicate this feat in artificial systems almost invariably result in bubble formation, except under highly controlled conditions with pure water and only hydrophilic surfaces present. In theory, conditions in the xylem should favor bubble nucleation even more: there are millions of conduits with at least some hydrophobic surfaces, and xylem sap is saturated or sometimes supersaturated with atmospheric gas and may contain surface-active molecules that can lower surface tension. So how do plants transport water under negative pressure? Here, we show that angiosperm xylem contains abundant hydrophobic surfaces as well as insoluble lipid surfactants, including phospholipids, and proteins, a composition similar to pulmonary surfactants. Lipid surfactants were found in xylem sap and as nanoparticles under transmission electron microscopy in pores of intervessel pit membranes and deposited on vessel wall surfaces. Nanoparticles observed in xylem sap via nanoparticle-tracking analysis included surfactant-coated nanobubbles when examined by freeze-fracture electron microscopy. Based on their fracture behavior, this technique is able to distinguish between dense-core particles, liquid-filled, bilayer-coated vesicles/liposomes, and gas-filled bubbles. Xylem surfactants showed strong surface activity that reduces surface tension to low values when concentrated as they are in pit membrane pores. We hypothesize that xylem surfactants support water transport under negative pressure as explained by the cohesion-tension theory by coating hydrophobic surfaces and nanobubbles, thereby keeping the latter below the critical size at which bubbles would expand to form embolisms.

From the sap's perspective: The nature of vessel surfaces in angiosperm xylem.

PREMISE OF THE STUDY: Xylem sap in angiosperms moves under negative pressure in conduits and cell wall pores that are nanometers to micrometers in diameter, so sap is always very close to surfaces. Surfaces matter for water transport because hydrophobic ones favor nucleation of bubbles, and surface chemistry can have strong effects on flow. Vessel walls contain cellulose, hemicellulose, lignin, pectins, proteins, and possibly lipids, but what is the nature of the inner, lumen-facing surface that is in contact with sap? METHODS: Vessel lumen surfaces of five angiosperms from different lineages were examined via transmission electron microscopy and confocal and fluorescence microscopy, using fluorophores and autofluorescence to detect cell wall components. Elemental composition was studied by energy-dispersive X-ray spectroscopy, and treatments with phospholipase C (PLC) were used to test for phospholipids. KEY RESULTS: Vessel surfaces consisted mainly of lignin, with strong cellulose signals confined to pit membranes. Proteins were found mainly in inter-vessel pits and pectins only on outer rims of pit membranes and in vessel-parenchyma pits. Continuous layers of lipids were detected on most vessel surfaces and on most pit membranes and were shown by PLC treatment to consist at least partly of phospholipids. CONCLUSIONS: Vessel surfaces appear to be wettable because lignin is not strongly hydrophobic and a coating with amphiphilic lipids would render any surface hydrophilic. New questions arise about these lipids and their possible origins from living xylem cells, especially about their effects on surface tension, surface bubble nucleation, and pit membrane function.

Dissolved atmospheric gas in xylem sap measured with membrane inlet mass spectrometry.

A new method is described for measuring dissolved gas concentrations in small volumes of xylem sap using membrane inlet mass spectrometry. The technique can be used to determine concentrations of atmospheric gases, such as argon, as reported here, or for any dissolved gases and their isotopes for a variety of applications, such as rapid detection of trace gases from groundwater only hours after they were taken up by trees and rooting depth estimation. Atmospheric gas content in xylem sap directly affects the conditions and mechanisms that allow for gas removal from xylem embolisms, because gas can dissolve into saturated or supersaturated sap only under gas pressure that is above atmospheric pressure. The method was tested for red trumpet vine, Distictis buccinatoria (Bignoniaceae), by measuring atmospheric gas concentrations in sap collected at times of minimum and maximum daily temperature and during temperature increase and decline. Mean argon concentration in xylem sap did not differ significantly from saturation levels for the temperature and pressure conditions at any time of collection, but more than 40% of all samples were supersaturated, especially during the warm parts of day. There was no significant diurnal pattern, due to high variability between samples.

Mind the bubbles: achieving stable measurements of maximum hydraulic conductivity through woody plant samples.

The maximum specific hydraulic conductivity (k(max)) of a plant sample is a measure of the ability of a plants' vascular system to transport water and dissolved nutrients under optimum conditions. Precise measurements of k(max) are needed in comparative studies of hydraulic conductivity, as well as for measuring the formation and repair of xylem embolisms. Unstable measurements of k(max) are a common problem when measuring woody plant samples and it is commonly observed that k(max) declines from initially high values, especially when positive water pressure is used to flush out embolisms. This study was designed to test five hypotheses that could potentially explain declines in k(max) under positive pressure: (i) non-steady-state flow; (ii) swelling of pectin hydrogels in inter-vessel pit membranes; (iii) nucleation and coalescence of bubbles at constrictions in the xylem; (iv) physiological wounding responses; and (v) passive wounding responses, such as clogging of the xylem by debris. Prehydrated woody stems from Laurus nobilis (Lauraceae) and Encelia farinosa (Asteraceae) collected from plants grown in the Fullerton Arboretum in Southern California, were used to test these hypotheses using a xylem embolism meter (XYL'EM). Treatments included simultaneous measurements of stem inflow and outflow, enzyme inhibitors, stem-debarking, low water temperatures, different water degassing techniques, and varied concentrations of calcium, potassium, magnesium, and copper salts in aqueous measurement solutions. Stable measurements of k(max) were observed at concentrations of calcium, potassium, and magnesium salts high enough to suppress bubble coalescence, as well as with deionized water that was degassed using a membrane contactor under strong vacuum. Bubble formation and coalescence under positive pressure in the xylem therefore appear to be the main cause for declining k(max) values. Our findings suggest that degassing of water is essential for achieving stable and precise measurements of k(max) through woody plant samples. For complete rehydration of woody samples, incubation in water under vacuum for 24 h is suggested as a reliable technique that avoids bubble problems associated with flushing under high positive pressure.

Hydraulic integration and shrub growth form linked across continental aridity gradients.

Both engineered hydraulic systems and plant hydraulic systems are protected against failure by resistance, reparability, and redundancy. A basic rule of reliability engineering is that the level of independent redundancy should increase with increasing risk of fatal system failure. Here we show that hydraulic systems of plants function as predicted by this engineering rule. Hydraulic systems of shrubs sampled along two transcontinental aridity gradients changed with increasing aridity from highly integrated to independently redundant modular designs. Shrubs in humid environments tend to be hydraulically integrated, with single, round basal stems, whereas dryland shrubs typically have modular hydraulic systems and multiple, segmented basal stems. Modularity is achieved anatomically at the vessel-network scale or developmentally at the whole-plant scale through asymmetric secondary growth, which results in a semiclonal or clonal shrub growth form that appears to be ubiquitous in global deserts.

Hydraulically integrated or modular? Comparing whole-plant-level hydraulic systems between two desert shrub species with different growth forms.

* Hydraulic systems of shrubs vary between hydraulically integrated and modular architectures; the latter divide the shrub into independent hydraulic units. Hydraulic systems of two common North American desert shrub species, the multi-branched Ambrosia dumosa and the single-stemmed Encelia farinosa (both Asteraceae), were compared to test for division into independent hydraulic units and the implications of such a division for water loss through leaves and roots. * Hydraulic systems of mature shrubs in the field were characterized using dye tracers and by documenting the degree of stem segmentation. Young pot-grown shrubs were subjected to heterogeneous and homogeneous watering. Spatial within-canopy variation of leaf water potentials and stomatal conductances, as well as soil water contents, were measured in response to manipulated soil water heterogeneity. * Results show that young Ambrosia shrubs are divided into independent hydraulic units long before they physically split into separate ramets as mature shrubs, and that young and mature Encelia shrubs possess integrated hydraulic systems. No hydraulic redistribution was detected for eitherspecies. * Our study shows that functional segmentation into independent hydraulic units precedes physical axis splitting, rather than being the consequence of split axes, and suggests that mature shrubs with round basal stems are likely to be hydraulically integrated.

Wood anatomy and wood density in shrubs: Responses to varying aridity along transcontinental transects.

Wood density plays a key role in ecological strategies and life history variation in woody plants, but little is known about its anatomical basis in shrubs. We quantified the relationships between wood density, anatomy, and climate in 61 shrub species from eight field sites along latitudinal belts between 31° and 35° in North and South America. Measurements included cell dimensions, transverse areas of each xylem cell type and percentage contact between different cell types and vessels. Wood density was more significantly correlated with precipitation and aridity than with temperature. High wood density was achieved through reductions in cell size and increases in the proportion of wall relative to lumen. Wood density was independent of vessel traits, suggesting that this trait does not impose conduction limitations in shrubs. The proportion of fibers in direct contact with vessels decreased with and was independent of wood density, indicating that the number of fiber-vessel contacts does not explain the previously observed correlation between wood density and implosion resistance. Axial and radial parenchyma each had a significant but opposite association with wood density. Fiber size and wall thickness link wood density, life history, and ecological strategies by controlling the proportion of carbon invested per unit stem volume.

[Administration of budesonide (inhaled steroid) to children to control intermittent asthma]. / Administración de budesonida (esteroide inhalado) a niños para el control del asma intermitente.

BACKGROUND: Intermittent asthma in children is often treated only with short-action beta-agonists; however, most cases do not control totally the disease. OBJECTIVE: To assess the effect of salbutamol, as rescue drug, associated with other drugs for controlling asthma. PATIENTS AND METHODS: Fifty children, from 1 to 14 years old, with intermittent asthma, who were assisted at Out-Patient Consultation of Pediatric Allergy, Children Hospital Eva Samano de Lopez Mateos, from January to October, 2004, were selected. Treatment consisted of the following regimens: (1) salbutamol, (2) salbutamol and budesonide, (3) salbutamol and montelukast and (4) salbutamol, budesonide and montelukast. After three months of treatment asthma control degree was measured by disappearing of symptoms (total control) or decrease of symptoms in more than 70% a week (partial control). RESULTS: A better control was observed in patients receiving budesonide (inhaled steroid) and salbutamol (p < 0.05), compared to those who were not treated with inhaled steroid. This regimen achieved in 44% the disappearing of symptoms (total control) and in 56% reduced the symptoms in more than 70% (partial control). Group receiving salbutamol, budesonide and montelukast reached a total and partial control in 47.1% and 52.9%, respectively. CONCLUSIONS: Inhaled steroids are a choice to better control and avoid the progression of intermittent asthma. The use of new progression markers of asthma should be evaluated, in order to determine which children may receive early inhaled steroids and how long.

Mejorando la calidad de la atención de salud en el Perú: El Programa de Capacitación Materno-Infantil (PCMI) en su primera etapa ¿Cómo se hizo? y ¿A qué se debió su éxito? / Improving the quality of health care in Peru: Maternal and Child Training Program in its first stage, how was it made? and why it succeeded?

Contiene: Situación de los servicios de salud al iniciarse el PCMI; La propuesta técnica dle PCMI; El proceso de intervención del PCMI; ¿A qué se debió el cambio logrado por el PCMI? Futuro del PCMI; El PCMI en el contexto mundial. Anexos: Formatos de supervisión de establecimientos candidatos a HC y CC del PCMI; Guía base para las entrevistas del estudio cualitativo de establecimientos de salud

Mejorando la calidad de la atención de salud en el Perú. El programa de capacitación de materno infantil (PCMI). En su primera etapa. ¿Cómo se hizo? y ¿A que se debió su éxito? / Improving the quality of the attention of health in Peru. The program of maternal qualification of infantile (PCMI). In his first stage. How it was made? and To that it had its success?

Este libro presenta la descripción de cómo se diseño y ejecutó, cuales fueron sus resultados y a qué se debió el éxito del Programa de Capacitación Materno Infantil - PCMI - del proyecto 2000, un proyecto del Ministerio de Salud del Perú y la Agencia para el Desarrollo Internacional del Gobierno Norteamericano - USAID.

Proyecto regional de educación permanente de personal auxiliar de enfermería en emergencias obstétricas / Regional project for permanent education of nursing auxiliary personnel in obstetric emergencies

Se presenta el Proyecto Regional de Educación Permanente de Personal Auxiliar de Enfermería en Emergencias Obstétricas, en el marco del los Programas de Salud Reproductiva de la OPS y se propone la metodología de trabajo-estudio que toma la propia práctica como objeto de estudio y transformación, la confronta teóricamente, la analiza ética, social y técnicamente y propone estrategias de transformación para el abordaje integral de los problemas de emergencia obstétrica

Proyecto regional de educación permanente de personal auxiliar de enfermería en emergencias obstétricas / Regional project for permanent education of nursing auxiliary personnel in obstetric emergencies

Se presenta el Proyecto Regional de Educación Permanente de Personal Auxiliar de Enfermería en Emergencias Obstétricas, en el marco del los Programas de Salud Reproductiva de la OPS y se propone la metodología de trabajo-estudio que toma la propia práctica como objeto de estudio y transformación, la confronta teóricamente, la analiza ética, social y técnicamente y propone estrategias de transformación para el abordaje integral de los problemas de emergencia obstétrica