Effects of salinity on the transcriptome of growing maize leaf cells point at cell-age specificity in the involvement of the antioxidative response in cell growth restriction

BACKGROUND: Salinity inhibits growth and development of most plants. The response to salinity is complex and varies between plant organs and stages of development. It involves challenges of ion toxicities and deficiencies as well as osmotic and oxidative stresses. The range of functions affected by the stress is reflected in elaborate changes to the transcriptome. The mechanisms involved in the developmental-stage specificity of the inhibitory responses are not fully understood. The present study took advantage of the well characterized developmental progression that exists along the maize leaf, for identification of salinity induced, developmentally-associated changes to the transcriptome. Differential subtraction screening was conducted for cells of two developmental stages: from the center of the growth zone where the expansion rate is highest, and from older cells at a more distal location of the growing zone where the expansion rate is lower and the salinity restrictive effects are more pronounced. Real-Time PCR analysis was used for validation of the expression of selected genes. RESULTS: The salinity-induced changes demonstrated an age-related response of the growing tissue, with elevation of salinity-damages with increased age. Growth reduction, similar to the elevation of percentage dry matter (%DM), and Na and Cl concentrations were more pronounced in the older cells. The differential subtraction screening identified genes encoding to proteins involved in antioxidant defense, electron transfer and energy, structural proteins, transcription factors and photosynthesis proteins. Of special interest is the higher induced expression of genes involved in antioxidant protection in the young compared to older cells, which was accompanied by suppressed levels of reactive oxygen species (H(2)O(2) and O(2)(-)). This was coupled with heightened expression in the older cells of genes that enhance cell-wall rigidity, which points at reduced potential for cell expansion. CONCLUSIONS: The results demonstrate a cell-age specificity in the salinity response of growing cells, and point at involvement of the antioxidative response in cell growth restriction. Processes involved in reactive oxygen species (ROS) scavenging are more pronounced in the young cells, while the higher growth sensitivity of older cells is suggested to involve effects on cell-wall rigidity and lower protein protection

Field-Induced Electron Emission from Nanoporous Carbons

Influence of fabrication technology on field electron emission properties of nanoporous carbon (NPC) was investigated. Samples of NPC derived from different carbides via chlorination at different temperatures demonstrated similar low-field emission ability with threshold electric field 2-3 V/μm. This property correlated with presence of nanopores with characteristic size 0.5–1.2 nm, determining high values of specific surface area (>800 m2/g) of the material. In most cases, current characteristics of emission were approximately linear in Fowler-Nordheim coordinates (excluding a low-current part near the emission threshold), but the plots’ slope angles were in notable disagreement with the known material morphology and electronic properties, unexplainable within the frames of the classical emission theory. We suggest that the actual emission mechanism for NPC involves generation of hot electrons at internal boundaries and that emission centers may be associated with relatively large (20–100 nm) onion-like particles observed in many microscopic images. Such particles can serve two functions: to provide additional “internal” enhancement of the electric field and to inhibit relaxation of hot charge carriers due to the “phonon bottleneck” effect

Электронная микроскопия трабекулярного аппарата человека в норме и при глаукоме

Aqueous humor (AH) outflow resistance is one of the main causes of elevated intraocular pressure (IOP). The ultrastructural trabecular changes are evaluated by means of scanning electron microscopy (SEM) and transmission microscopy (TEM). The trabecular meshwork (TM) consists of the uveal trabecula, the corneoscleral trabecula and the juxtacanalicular tissue, which is attached to the endothelium of the Schlemm’s canal (SC). In primary open-angle glaucoma (POAG), the juxtacanalicular tissue disintegrates, and disorganization of collagen fibers occurs; a homogeneous electron dense material accumulates, which causes obstruction of the SC’s inner wall. It has been suggested that the extracellular matrix of the juxtacanalicular layer plays an important role in AH retention. In patients with pseudoexfoliation glaucoma (PEG), an irregular networklike pseudoexfoliation is formed between the TC fibers, and pigment granules accumulate in the trabecula. In closedangle glaucoma (CAG) the damage occurs in the uveal tract. Also, the role of cell-inflammatory response is significant. Currently, there is no data on what proportion of pathological material in TM can be attributed to electron microscopy artifacts, which appear under extreme conditions. Further research is needed.Сопротивление оттоку внутриглазной жидкости (ВГЖ) является одной из распространенных причин повышения внутриглазного давления (ВГД). Ультраструктурное изменение трабекулярного аппарата изучается при помощи сканирующей электронной микроскопии (СЭМ) и трансмиссионной микроскопии (ТЭМ). Трабекулярная сеть (ТС) состоит из увеальной трабекулы, корнеосклеральной трабекулы и юкстаканаликулярного слоя, прилежащего к эндотелию шлеммова канала (ШК). При первичной открытоугольной глаукоме (ПОУГ) происходит поражение юкстаканаликулярной ткани и дезорганизация коллагеновых волокон; накапливается гомогенный материал повышенной электронной плотности, который вызывает обструкцию пор внутренней стенки ШК. Выдвинуто предположение о существенной роли внеклеточного вещества юкстаканаликулярного слоя ТС в ретенции ВГЖ. При псевдоэксфолиативной глаукоме (ПЭС) между волокнами ТС формируется иррегулярный сетевидный псевдоэксфолиативный материал, накапливаются гранулы пигмента. При закрытоугольной глаукоме (ЗУГ) повреждение с элементами клеточновоспалительной реакции распространяется со стороны увеального тракта. Несмотря на большое количество данных о патологическом материале, присутствующем в ТС при глаукоме, остается неизвестным, какая доля этих находок может быть объяснена артефактами, возникающими под воздействием экстремальных условий на биологические образцы при электронной микроскопии, что требует дальнейших исследований в этой области

Passively Q-switched diode-pumped Yb : YAG laser using Cr4+-doped garnets

We investigate the repetitive modulation in the kHz frequency domain of a passively Q-switched, diode-pumped Yb:YAG laser, by Cr4+ :YAG, Cr4+ LuAG, and Cr4+:GSGG saturable absorbers. The results presented here are focused towards the design of a passively Q-switched Yb:YAG microlaser. The free-running performance of both rod and a disk Yb:YAG is characterized and experimental parameters such as gain and loss are evaluated. These values, together with the value of the stimulated emission cross-section, e.g. sigma(cm) = 3.3 x 10(-20) cm(2) were found to fit between our experimental results and an existing numerical model which relates the experimental and physical parameters to the minimal threshold pumping power. Q-switched pulses with maximum peak power of approximate to10.4 kW, with energy of approximate to0.5 mJ/pulse, were extracted with 30% extraction efficiency. (C) 2002 Elsevier Science B.V. All rights reserved

Взаимосвязь спектроскопических и структурных свойств j-агрегатов индоцианина зеленого

Indocyanine green (ICG), when in free form in a liquid, can form stable nanoparticle structures or colloidal solution, while changing its spectroscopic properties. In the work, the aggregation degree and the average size of nanoparticles depending on the concentration of a colloidal solution of indocyanine green (ICG NPs) in the form of J-aggregates were investigated by various methods based on light scattering. The size of nanoparticles is an important parameter from the point of view of clinical application, because the technique of intravenous administration of drugs, in order to avoid microvascular thrombosis and embolism, provides dosage forms with inclusions of individual molecules or their clusters, not exceeding 500 nm diameter. In turn, small nanoparticles less than 30 nm lead to prolonged circulation of the drug in the body with an increased possibility of permeation into cells of healthy tissue. In the course of studies, it was found that an increase in the concentration of ICG NPs in the solution leads to an increase in the average size of spontaneously formed J-aggregates, which, in turn, leads to a decrease in the absorption coefficient in the aggregates. Presumably, this phenomenon, i.e. the established nonlinear dependence of the J-aggregate absorption on its size, can be explained by the formation of absorption centers on the J-aggregate surface in the form of mobile surface molecules. The threshold range of ICG molecule concentration was determined, at which there is a transition from aggregation with an increase in size with a slow addition of ICG J-aggregate molecules in height to a rapid addition in width.Индоцианин зеленый (ICG), находясь в растворе, способен образовывать стабильные структуры наночастиц или коллоидный раствор, изменяя при этом свои спектроскопические свойства. В работе различными методами, основанными на светорассеянии, были исследованы степень агрегации и средний размер наночастиц в зависимости от концентрации коллоидного раствора наночастиц индоцианина зеленого (ICG NPs) в форме J-агрегатов. Размер наночастиц представляет собой важный параметр с точки зрения клинического применения, так как техника внутривенного введения препаратов, с целью избежания тромбозов микрососудов и эмболии, предусматривает лекарственные формы с включениями, в виде отдельных молекул или их кластеров, не превышающими в диаметре 500 нм. С другой стороны, наночастицы размером менее 30 нм длительно циркулируют в организме и могут проникать в клетки здоровой ткани. В ходе исследований, было установлено, что увеличение концентрации ICG NPs в растворе ведет к увеличению среднего размера спонтанно формируемых J-агрегатов, что в свою очередь ведет к уменьшению коэффициента поглощения в агрегатах. Предположительно, нелинейная зависимость поглощения J-агрегата от его размера, может быть объяснен формированием центров поглощения на поверхности J-агрегата в виде подвижных поверхностных молекул. Был определен пороговый диапазон концентрации молекул ICG, при котором происходит переход от агрегации с увеличением размера с медленным прибавлением молекул J-агрегата ICG в высоту, но с быстрым прибавлением в ширину

Influence of spark ignition in the determination of Markstein lengths using spherically expanding flames

Constant pressure outwardly propagating flame experiments in a spherical bomb are performed to examine the duration and radius over which spark ignition effects persist. This is motivated by the need to properly account for such effects in the measurement of laminar burning velocity and Markstein length using the spark ignited expanding flame technique. Ignition energy was varied and its effects on flame propagation in methane-air and isooctane-air mixtures were studied. The Markstein length of the mixture proved critical in the ignition energy dependency of flame propagation. For relatively high values, an underlying common variation of self-sustaining flame speed with radius can be identified by the rapid convergence of curves for different ignition energies. As the Markstein length decreases, low energy spark ignition is found to give rise to a distorted and wrinkled flame kernel. For such mixtures, due to the weak effect of stretch, the kernel subsequently develops into a non-spherically propagating flame. In these cases the spark ignition effect persists up to large radius. It is shown that using low ignition energy leads to a flame speed, during the development phase, which is higher than that of a self-sustaining spherical flame. It is further shown that if this effect is not accounted for, measurements of Markstein length using standard fitting techniques results in a large error. This problem is found to worsen as the Markstein length decreases, such that its apparent measured value becomes increasingly influenced by any distortions of the flame kernel produced by the spark