Considerations in measuring Potassium efflux from plant cells using 87Rb magnetic resonance.

In order to stay metabolically active, plant cells must transport Potassium ions across their plasmalemma. Ion transport is subject to many complex metabolic regulatory processes. Information on Potassium metabolism can be obtained with 87Rb NMR spectroscopy, using Rubidium as a congener for Potassium. However, due to the presence of the vacuole, another non-metabolic mechanism for ion flux regulation exists. Using simple biophysical arguments, it is shown that an increase in vacuole size, without a change in total cell volume, could initiate a change in Potassium efflux. This change in efflux can be significant, especially for large vacuoles.     

Considerations in measuring Potassium efflux from plant cells using 87 Rb magnetic resonance

In order to stay metabolically active, plant cells must transport Potassium ions across their plasmalemma. Ion transport is subject to many complex metabolic regulatory processes. Information on Potassium metabolism can be obtained with 87 Rb NMR spectroscopy, using Rubidium as a congener for Potassium. However, due to the presence of the vacuole, another non-metabolic mechanism for ion flux regulation exists. Using simple biophysical arguments, it is shown that an increase in vacuole size, without a change in total cell volume, could initiate a change in Potassium efflux. This change in efflux can be significant, especially for large vacuoles.     

Potassium induces positive changes in nitrogen metabolism and antioxidant system of oat (Avena sativa L cultivar Kent)

Potassium is actively involved in many functions such as enzyme activation, osmotic adjustment and uptake of deleterious ions like Na. Present report analyses the effectivity of different potassium salts on growth and certain components of nitrogen metabolism and antioxidant system in oat and their possible role in amelioration of water stress. Potassium induced enhancement in the activities of nitrate reductase and aminotransferases was evident indicating a positive role of potassium in nitrogen metabolism. Potassium supplementation enhanced activities of antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase) and contents of total phenols and tannins, probably strengthening both the enzymatic as well as non enzymatic antioxidant system. Free amino acids, proline and free sugars also exhibited the same trend in treated plants ensuring better plant growth.     

Effect of osmolarity on potassium transport in isolated cerebral microvessels

Potassium transport in microvessels isolated from rat brain by a technique involving density gradient centrifugation was studied in HEPES buffer solutions of varying osmolarity from 200 to 420 mosmols, containing different concentration of sodium chloride, choline chloride, or sodium nitrate. The flux of 86Rb (as a tracer for K) into and out of the endothelial cells was estimated. Potassium influx was very sensitive to the osmolarity of the medium. Ouabain-insensitive K-component was reduced in hypotonic medium and was increased in medium made hypertonic with sodium chloride or mannitol. Choline chloride replacement caused a large reduction in K influx. Potassium influx was significant decrease when nitrate is substituted for chloride ion in isotonic and hypertonic media, whereas a slight decrease was found in hypotonic medium. The decrease of K influx in the ion-replacement medium is due to a decrement of the ouabain-insensitive component. Potassium efflux was unchanged in hypotonic medium but was somewhat reduced in hypertonic medium. The marked effect of medium osmolarity on K fluxes suggests that these fluxes may be responsible for the volume regulatory K movements. The possible mechanism of changes of K flux under anisotonic media is also discussed.     

宝乐安（酪酸梭菌散剂）治疗婴幼儿轮状病毒性肠炎96例疗效观察

目的观察和评价宝乐安（酪酸梭菌CGMCC0313.1散剂）治疗小儿轮状病毒性肠炎的临床疗效。方法将184例轮状病毒性肠炎患儿随机分为观察组和对照组,观察组96例,宝乐安联合炎琥宁进行治疗,对照组88例,单独应用炎琥宁治疗,观察疗效和不良反应。结果观察组总有效率为86.46%,对照组总有效为62.50%,差异有显著性（P〈0.01）。结论宝乐安联合抗病毒药物炎琥宁治疗小儿轮状病毒性肠炎疗效显著,且未见不良反应,值得临床推广应用。     

Stimulation of sugar loading into sieve elements of willow by potassium and sodium salts

Potassium as the chloride, nitrate or sulphate or sodium as the chloride, were applied at a concentration of 50 mM either to the xylem of stem segments or to the cambial surface of bark strips of willow. Potassium chloride increased the concentration of sucrose in sieve tube exudate collected via severed aphid stylets, without significantly affecting the volume flow rate, or the concentration of potassium in the exudate. The increase in the sucrose level in the sieve tube sap was shown to be due to a stimulation of loading, rather than to an enhancement of longitudinal transport. Potassium nitrate and sulphate or sodium chloride, were not as effective as potassium chloride in stimulating the loading of sucrose. It is suggested that uptake of the cation into cells supplying sugars to the sieve tube is linked to the rate of release of sugars by the supplying cells.     

K肥对假俭草草坪绿度和品质的影响

施K对改善假俭草草坪颜色、延长青绿期、提高品质有一定的作用。适时适量施K,可增加假俭草叶绿素含量;K肥有利于延长青绿期,尤其是4.5g/m² K₂O分三次施用效果更好;施K可增加草坪密度,增强草坪抗性,减轻草坪在不良环境条件下颜色异常现象,从而提高不同时期草坪的品质。等量K肥分次施用的效果好于一次施用,每次施肥量不得高于2.0g/m² K₂O,年总施肥量不得高于6.0g/m²K₂O。假俭草在不同的生长时期都需要K肥,但在高温和低温条件下,施K的效果较好,这与K可提高抗逆性有关。     

Effect of Sorbed Water on Disintegrant Performance of Four Brands of Polacrilin Potassium NF

Polacrilin Potassium NF is a commonly used weak cation exchange resin disintegrant in pharmaceutical tablets. The objective of this research was to evaluate the effects of sorbed moisture on physical characteristics and disintegrant performance of four brands of Polacrilin Potassium NF. The disintegrants were stored in five different relative humidity chambers and their dynamic vapor adsorption–desorption analysis, effect of moisture on their compressibility, compactability, particle size, morphology, water uptake rate, and disintegration ability were studied. Moisture seemed to plasticize the disintegrants, reducing their yield pressures. However, certain optimum amount of moisture was found to be useful in increasing the compactablity of the tablets containing disintegrants. The tablets, however, lost their tensile strengths beyond this optimum moisture content. Moisture caused two brands of the disintegrants to swell; however, two other brands aggregated upon exposure to moisture. Swelling without aggregation increased the water uptake, and in turn the disintegrant performance. However, aggregation probably reduced the porosities of the disintegrants, reducing their water uptake rate and disintegrant performance. Different brands of Polacrilin Potassium NF differed in the abilities to withstand the effects of moisture on their functionality. Effect of moisture on disintegrant performance of Polacrilin Potassium NF needs to be considered before its use in tablets made by wet granulation.     

Oral potassium iodide for the treatment of sporotrichosis

Potassium Iodide is the antimycotic of choice for the treatment of cutaneous sporotrichosis, because of its efficacy, safety and low cost. We carried out a review of published studies on the benefits and adverse reactions of using SSKI (Saturated Solution Potassium Iodide) as treatment for sporotrichosis, but could not identify any well-designed clinical trails. There is an urgent need to conduct randomized double-blind placebo-controlled trials and critically assess usefulness of SSKI by using a standardize monitoring or an effective self-report system.     

Glutamate efflux from rat brain slices and cultures: A comparison of the depolarizing agents potassium, 4-aminopyridine,and veratrine

The major excitatory amino acid neurotransmitter in the mammalian brain is glutamate (GLU). GLU release from nerve terminals is both calcium-dependent and-independent, yet these mechanisms of release are not fully understood. Potassium, 4-aminopyridine (4-AP) and veratrine are commonly used depolarizing agents that were studied for their ability to stimulate GLU efflux from brain slices. These agents produced significant regional variations in GLU efflux from rat brain slices. Potassium was the most potent of the three secretogogues tested. 4-AP produced a significant GLU efflux only in the cerebellum. Veratrine produced consistent stimulation of GLU efflux from all brain regions tested. Potassium was the only depolarizing agent tested that stimulated GLU release from primary astroglial cultures of rat cerebral cortex. All three agents also demonstrated an ability to inhibit GLU reuptake in brain slice preparations. This data suggest that both GLU release and uptake are modulated in a regionally selective manner, and that commonly used depolarizing agents affect not only calcium-dependent neuronal release, but also uptake and glial responses.     

New insights into the structure and function of potassium channels.

Potassium channels are surprisingly modular proteins. Well-defined regions that determine functional properties such as ion conduction and gating have recently been identified.     

施水和钾素添加对元宝枫和女贞木质部栓塞的影响

通过干旱胁迫处理(土壤含水量为田间持水量的30%~40%)和正常水分供给(土壤含水量为田间持水量的70%~80%)两种盆栽控制试验, 研究了耐旱树种元宝枫(Acer truncatum)和中生树种女贞(Ligustrum lucidum)枝条木质部栓塞(以导水率损失百分数(Percentage loss of hydraulic conductivity, PLC)衡量)和水势(Water potential, WP)对钾(K)素添加的响应。结果表明: 两个树种PLC的日变化均呈现先升后降的规律, 而WP呈现相反的变化趋势; 添加K素显著提高了两个树种的PLC, 除了干旱胁迫下的元宝枫, 其他树种和处理的PLC随K素含量的增加而增加; K素显著降低了干旱胁迫下元宝枫和女贞的WP,但对正常水分供给下两个树种的WP无显著影响; 元宝枫的平均PLC高于女贞, 平均WP低于女贞。以上结果表明, K素可能通过降低枝条的WP, 促进树种木质部栓塞的形成, 达到限制水分进一步丧失的目的。K素在调节气孔运动、渗透作用等方面的作用, 可能是树种木质部栓塞形成的诱 因。     

白术提取物对六价铬致人外周血淋巴细胞 抗突变作用研究

目的：探讨白术提取物抗六价铬的致突变作用。方法：采用人外周血淋巴细胞程序外DNA合成（UDS）试验检测了0．03g、0．015g和0．0075／ml白术提取物对重铬酸钾（含Cr^6＋0．31ug/ml）所致淋巴细胞程序外DNA合成的影响。同时检测白术提取物与重铬酸钾的加入顺序对UDS的影响。结果：阳性对照（重铬酸钾,含CCr^6＋0.31ug/ml）组CPM值显著高于阴性对照（蒸馏水）组,P〈0．01。白术提取物与重铬酸钾同时加入以及两者间隔2h先后加入均显示白术提取物浓度与CPM值呈显著负相关（P〈0.05）,在上述不同加入方法中,白术提取物的各浓度均显示CPM值显著低于阳性对照。结论：白术提取物具有抑制Cr^6＋的致突变作用。     

Accumulation of high levels of potassium in the developing xylem elements in roots of soybean and some other dicotyledons

Summary Potassium concentrations have been determined by cryo-analytical scanning microscopy in vacuoles of cells of the roots of soybean and six other dicotyledons. Developing vessel elements accumulate the highest concentration of potassium in any cell type in these roots, and those of the secondary xylem have more (median 190 mM normalized to 120%) than those of either the early (median 100 mM, normalized 80%) or late metaxylem (median 110 mM, normalized 100%). Potassium concentration in these developing vessels always exceeds those of their adjacent parenchyma (60–80%), which in turn are higher than those in cells of the cortex (30–40%), including the endodermis. Potassium concentration in the vessels increases during their development until cell death and maturation when it drops dramatically (normalized 4–12%). Developing vessel elements are clearly major sites of potassium accumulation in roots and need to be considered in any models of ion uptake, accumulation, circulation, or exudation.Abbreviations EDX energy dispersive X-ray microanalysis - EMX early metaxylem - K elemental potassium - LMX late metaxylem - CSEM cryo-scanning electron microscopy - SX secondary xylem Dedicated to the memory of Professor John G. Torrey     

Uncovering expression and functional analysis of newly discovered high-affinity K+ transporter family members from sugarcane

Journal of Plant Biochemistry and Biotechnology - Potassium ions are widely involved in a series of physiological and biochemical processes of plants, which is of great significance to plant...     

Functional Characterization of ZmHAK1 Promoter and Its Regulatory Transcription Factors in Maize

Molecular Biology - Potassium (K+) deficiency in the soil may seriously affect the yield and quality of plants, which usually satisfy their potassium requirements by engaging their K+ transporters...     

Building blocks for polyamide nucleic acids: facile synthesis using potassium fluoride doped natural phosphate as basic catalyst

Potassium fluoride doped natural phosphate, inexpensive and environmentally friendly catalyst, is shown to be an efficient basic catalyst for the N1/N9 alkylation of different nucleobases as synthons for PNAs.     

Transcriptome analysis reveals dynamic changes in the gene expression of tobacco seedlings under low potassium stress

Journal of Genetics - Potassium plays a key role in plant development and reproduction. In agricultural practice, potassium deficiency is common worldwide, and leads to crop growth inhibition and...     

Potassium channels in plant cells

Potassium (K(+) ) is the most abundant inorganic cation in plant cells. Unlike animals, plants lack sodium/potassium exchangers. Instead, plant cells have developed unique transport systems for K(+) accumulation and release. An essential role in potassium uptake and efflux is played by potassium channels. Since the first molecular characterization of K(+) channels from Arabidopsis thaliana in 1992, a large number of studies on plant potassium channels have been conducted. Potassium channels are considered to be one of the best characterized class of membrane proteins in plants. Nevertheless, knowledge on plant potassium channels is still incomplete. This minireview focuses on recent developments in the research of potassium transport in plants with a strong focus on voltage-gated potassium channels.     

OsJAZ9 overexpression modulates jasmonic acid biosynthesis and potassium deficiency responses in rice

Plant Molecular Biology - Enhanced bioactive JA (JA-Ile) accumulation in OsJAZ9 overexpressing rice helps plants tolerate K deficiency. Potassium (K) represents up to 10% of the...