The Contribution of an Apoplastic Pathway to Sodium Uptake by Rice Roots in Saline Conditions

An apoplastic pathway, the so-called bypass-flow, across riceroots to the xylem has been investigated and approximately quantifiedusing the apoplastic tracer dye 8-hydroxy-l,3,6-pyrenetrisulphonicacid (PTS); former nomenclature 3-hydroxy-5,8,10-pyrenetrisulphonicacid. It was confirmed that PTS was confined to a compartmentno greater than the apparent free space in living rice roots.Experimental handling did not contribute to bypass-flow. Riceroots recovered rapidly from severe damage: following root pruning,sodium and calcium uptake returned to steady values in about6 h. Apoplastic flow declined after damage as a first-orderkinetic with a half time of 75 min. Analysis of the pattern of elution of PTS from preloaded roots(intact, excised and heat-killed), and from cellulose, was followedto compare PTS movement in the extracellular compartment withthat of water and small hydrated ions. Consideration is givento the factor by which the bypass-flow estimated with the dyewould need to be corrected to reflect the proportion of thetranspiration stream flowing in the apoplastic pathway. Thedata suggest that this factor would be at least 10 for transpiringrice plants. There was large individual variation in the transport both ofsodium and of the apoplastic tracer PTS to the shoot. Plantswith high sodium transport also had high PTS transport and itis concluded that some proportion of the sodium reaching thexylem in rice does so by a pathway which is also available toPTS, presumably direct apoplastic contact across the endodermis.A median value for the bypass-flow of water (corrected fromPTS) would be 0.5 to 1.0 percent of the transpirational volumeflow, but individuals with the highest sodium transport wouldhave bypass-flow values of several percent. Evidence is discussedwhich suggests that apoplastic transport may increase in stressconditions, and it is argued that bypass-flow is a major contributionto sodium uptake in rice in saline conditions. Key words: Oryza saliva, salinity, roots, radial ion transport, apoplast, bypass-flow     

A Comparison of the Methods of X-ray Microanalysis, Compartmental Analysis and Longitudional Ion Profiles to Estimate Cytoplasmic Ion Concentrations in Two Maize Varieties

Hajibagheri, M. A., Flowers, T. J., Collins, J. C. and Yeo,A. R. 1988. A comparison of the methods of X-ray microanalysis,compartmental analysis and longitudinal ion profiles to estimatecytoplasnuc ion concentrations in two maize varieties.—J.exp. Bot. 39: 279-290. The ion content of compartments within plant root cells hasbeen studied by three different methods; flux analysis usingradioactive isotopes, longitudinal ion profiles and X-ray microanalysis.The data provide estimates of the concentrations of K⁺ and CI^–in the cytoplasm of roots of culture solution and salt grownmaize by three independent methods. In the cultivar LG₁₁ grown in 50 mol m^–3 NaCl X-ray microanalysis,compartmental analysis and longitudinal profiles yielded approximatelyagreeing values for cytoplasmic K⁺ of 90, 70 and 62 mol m^–33of tissue volume respectively. However, the methods disagreedon cytoplasmic Cl^– where the value obtained by compartmentalanalysis was about four times that from X-ray microanalysisand longitudinal profiles. Possible reasons for this are discussed. Key words: X-ray microanalysis, longitudinal ion profiles, compartmental analysis, salt-tolerance.     

Ion accumulation in the cell walls of rice plants growing under saline conditions: evidence for the Oertli hypothesis

Abstract. When plants of rice ( Oryza saliva L.) are subjected to mildly saline (50mol m⁻³ NaCl) conditions, the leaves show symptoms of water deficit, even though ion accumulation has been more than sufficient to adjust to the decrease in external water potential. After a few days of exposure to salt, there is a negative correlation, in a population of leaves, between the leaf water concentration (g water per g dry weight) and their sodium concentration (mmol Na per g dry weight). Ion concentrations in the cell walls and the cytoplasm of cells of plants grown in low salinity were measured by X-ray microanalysis. The NaCl concentration in solution in the apoplast was calculated to be around 600mol m⁻³ in leaves of plants whose roots were exposed to only 50 mol m⁻³ NaCl. This constitutes strong evidence that an important factor in salt damage in rice is dehydration due to the extracellular accumulation of salt as suggested in the Oertli hypothesis. The implication, that changes in tissue ion concentration and solute potentials equivalent to the external medium is not evidence of plant osmotic adjustment to salinity, is discussed.     

线粒体DNA缺失与神经肌肉性疾病的研究

应用PCR技术对13例神经肌肉疾病患者的线粒体DNA缺失进行了研究。结果表明,其中二例肢带型肌营养不良症患者骨骼肌组织和一例帕金森氏病患者的血细胞线粒体DNA中存在至少526bp的缺失。提示线粒体突变在一些神经肌肉性疾病的发生中起一定的作用。 Abstract: Using PCR technique,we analysed the skeletal muscle and blood of 13 patients with neuromuscular disaeases.The results show that a mutant mitochondrial DNA with at least 526bp deletion exits in the skeletal muscles of 2 patients with Erb muscular dystrophy and in the blood of a patients with Parkinson’s disease.From our results,mitochondrial DNA mutations could be an important contributory factor to neuromuscular diseases.     

Sodium Chloride Compartmentation in Leaf Vacuoles of the Halophyte Suaeda maritima (L.) Dum. and its Relation to Tonoplast Permeability

Single channel properties, whole vacuole currents and protonpumping capacity were investigated in the intact vacuoles andmembrane patches of leaf tonoplast from the halophyte Suaedamaritima. ATP-dependent proton pumping capacity was similarto non-halophytes whether the plants were or were not grownwith added sodium chloride (200 mM). The most abundant ion channelwas inward rectifying and had a single channel conductance of58 pS in symmetrical KCl solutions (100 mM) to 170 pS usingphysiological conditions (50/150 mM KCl/NaCl cytoplasmic side,50/450 mM KCl/NaCl vacuolar side). The channel showed all thecharacteristics of the SV type channel described in many otherspecies. In the open state these channels caused tonoplast conductancesin excess of 0.5 nS m²– but conductances were much lowerusing physiological ion concentrations and membrane potentials.In spite of the poor selectivity and the potentially large tonoplastconductance it is calculated that compartmentation of NaCl inleaf vacuoles can be sustained by about 30% of ATP-dependentproton pumping capacity. The results do not indicate any specialadaptation of the tonoplast ion channels in the halophyte. Key words: Ion-channels, patch-clamp, salt-tolerance, vacuole     

Two new dihydrobenzofuran-type neolignans from Breynia fruticosa

(7S,8R,7′S)-9,7′,9′-Trihydroxy-3,4-methylenedioxy-3′-methoxy [7-O-4′,8-5′] neolignan (1) and (7S,8R,7′S)-9,9′-dihydroxy-3,4-methylenedioxy-3′,7′-dimethoxy [7-O-4′,8-5′] neolignan (2), two new natural dihydrobenzofuran-type neolignans, along with 9,9′-dihydroxy-3,4-methylenedioxy-3′-methoxy [7-O-4′,8-5′] neolignan (3) and (-)-machicendiol (4), were isolated from the whole plants of Breynia fruticosa. The structures of 1 and 2, including the absolute configurations, were determined by spectroscopic methods and circular dichroism (CD) techniques. The absolute configuration of 4 was confirmed by calculations of the OR spectrum, together with OR and ECD spectra of its p-bromobenzoate ester (4a).     

Associations of plasma high-sensitivity C-reactive protein concentrations with all-cause and cause-specific mortality among middle-aged and elderly individuals

Background

The plasma level of the inflammatory biomarker soluble urokinase plasminogen activator receptor (suPAR) is a strong predictor of disease development and premature mortality in the general population. Unhealthy lifestyle habits such as smoking or unhealthy eating is known to elevate the suPAR level. We aimed to investigate whether change in lifestyle habits impact on the suPAR level, and whether the resultant levels are associated with mortality.

Results

Paired suPAR measurements from baseline- and the 5-year visit of the population-based Inter99 study were compared with the habits of diet, smoking, alcohol consumption, and physical activity. Paired suPAR measurements for 3225 individuals were analyzed by linear regression, adjusted for demographics and lifestyle habits. Compared to individuals with a healthy lifestyle, an unhealthy diet, low physical activity, and daily smoking were associated with a 5.9, 12.8, and 17.6% higher 5-year suPAR, respectively. During 6.1 years of follow-up after the 5-year visit, 1.6% of those with a low suPAR (mean 2.93 ng/ml) died compared with 3.8% of individuals with a high suPAR (mean 4.73 ng/ml), P <  0.001. In Cox regression analysis, adjusted for demographics and lifestyle, the hazard ratio for mortality per 5-year suPAR doubling was 2.03 (95% CI: 1.22–3.37).

Conclusion

Lifestyle has a considerable impact on suPAR levels; the combination of unhealthy habits was associated with 44% higher 5-year suPAR values and the 5-year suPAR was a strong predictor of mortality. We propose suPAR as a candidate biomarker for lifestyle changes as well as the subsequent risk of mortality.

     

A re-evaluation of biomedical named entity-term relations

Text mining can support the interpretation of the enormous quantity of textual data produced in biomedical field. Recent developments in biomedical text mining include advances in the reliability of the recognition of named entities (NEs) such as specific genes and proteins, as well as movement toward richer representations of the associations of NEs. We argue that this shift in representation should be accompanied by the adoption of a more detailed model of the relations holding between NEs and other relevant domain terms. As a step toward this goal, we study NE-term relations with the aim of defining a detailed, broadly applicable set of relation types based on accepted domain standard concepts for use in corpus annotation and domain information extraction approaches.