Phosphate Fractions Research Articles

Overexpression of Phosphatidylinositol Transfer Protein α in NIH3T3 Cells Activates a Phospholipase A

In order to investigate the cellular function of the mammalian phosphatidylinositol transfer protein alpha (PI-TPalpha), NIH3T3 fibroblast cells were transfected with the cDNA encoding mouse PI-TPalpha. Two stable cell lines, i.e. SPI6 and SPI8, were isolated, which showed a 2- and 3-fold increase, respectively, in the level of PI-TPalpha. Overexpression of PI-TPalpha resulted in a decrease in the duration of the cell cycle from 21 h for the wild type (nontransfected) NIH3T3 (wtNIH3T3) cells and mock-transfected cells to 13-14 h for SPI6 and SPI8 cells. Analysis of exponentially growing cultures by fluorescence-activated cell sorting showed that a shorter G(1) phase is mainly responsible for this decrease. The saturation density of the cells increased from 0.20 x 10(5) cells/cm(2) for wtNIH3T3 cells to 0.53 x 10(5) cells/cm(2) for SPI6 and SPI8 cells. However, anchorage-dependent growth was maintained as shown by the inability of the cells to grow in soft agar. Upon equilibrium labeling of the cells with myo-[(3)H] inositol, the relative incorporation of radioactivity in the total inositol phosphate fraction was 2-3-fold increased in SPI6 and SPI8 cells when compared with wtNIH3T3 cells. A detailed analysis of the inositol metabolites showed increased levels of glycerophosphoinositol, Ins(1)P, Ins(2)P, and lysophosphatidylinositol (lyso-PtdIns) in SPI8 cells, whereas the levels of phosphatidylinositol (PtdIns) and phosphatidylinositol 4, 5-bisphosphate were the same as those in control cells. The addition of PI-TPalpha to a total lysate of myo-[(3)H]inositol-labeled wtNIH3T3 cells stimulated the formation of lyso-PtdIns. The addition of Ca(2+) further increased this formation. Based on these observations, we propose that PI-TPalpha is involved in the production of lyso-PtdIns by activating a phospholipase A acting on PtdIns. The increased level of lyso-PtdIns that is produced in this reaction could be responsible for the increased growth rate and the partial loss of contact inhibition in SPI8 and SPI6 cells. The addition of growth factors (platelet-derived growth factor, bombesin) to these overexpressers did not activate the phospholipase C-dependent degradation of phosphatidylinositol 4,5-bisphosphate.

Effects of Stone Terracing on Available Phosphorus and Yields on Highly Eroded Slopes in Tigray, Ethiopia

ABSTRACT Stone terraces have been widely constructed in the Tigray region of Ethiopia as a response to the severe soil erosion and land degradation of the area. In order to study the effects of stone terracing on plant available phosphorus 42 composite soil samples from 210 test plots were collected and analysed. The results showed increases in plant available P on terrace benches compared to the soil loss zone of terraces and non-terraced land. Mean Olsen-P values were 14.07 mg/kg, 10.35 mg/kg and 10.69 mg/kg from terrace benches, soil loss zone of terraces and non-terraced land, respectively. Calcium phosphate was by far the most dominant P fraction, but it was relatively insoluble in that it did not seem to contribute to plant available P. The iron phosphate fraction was active or labile, however, and seemed to contribute to available P in the soils of the study. The clay and silt textural classes also showed positive correlations with Olsen extract-able P. Grain yield for wheat (Triticum durum) was highest on the terrace benches. It correlated with available P concentrations and silt content only.

New method of phosphorus determination with improved pretreatment of occluded iron phosphate fraction in soils

In the sequential fractionation of phosphorus (P), a modified approach in the oxidation process of the occluded fraction of P (in iron oxides in soils) using redox titration in nitric acid (HNO3) medium is presented. Also a new spectrophotometric method to determine that P fraction as the phosphomolybdate complex using a mixture of isobutyl acetate and methyl isobutyl ketone to extract the formed complex into the organic phase. Radioactive tracer (32P) and sequential extraction is used to state the yield of extraction of the phosphomolybdate complex. Accuracy, precision, detection limit, and the linearity of the present method are 1.04%, 0.0322 μg mL‐1, 0.0038 ug mL‐1, and 0–15 ug mL‐1, respectively. The results correlate significantly with the results of the standard method of Petersen and Corey (1966), and the procedure saves time (50 min) and chemicals.

Fractionation of phosphate in sediments of four representative mangrove stages (French Guiana)

Phosphate was fractionated in Guianese mangrove sediments. Fe(OOH)≈P was extracted using a Ca-EDTA + Na-dithionite solution buffered at pH 8. CaCO3≈P was extracted using Na2-EDTA solution at pH 4.5. Next, Acid Soluble Organic Phosphate (ASOP) was extracted by H2SO4 0.5 N. Finally, Residual Organic Phosphate (ROP) was digested with H2SO4 + H2O2. Four representative mangrove stages have been studied: sea edge pioneer mangroves, mature coastal mangroves, mixed riverine mangroves, and declining to dead mangroves. The sum of the P-fractions varied between 638 to 804 μg g-1 in pioneer and mixed mangroves respectively. In all the stages, the percentage of inorganic phosphate was larger than 50% of the total P. Fe(OOH)≈P varied between 221 (pioneer mangrove) to 426 μg g-1 (dead mangrove). CaCO3≈P varied between 75 to 102 μg g-1 in mixed, dead or mature mangroves and attained 125 μg g-1 in pioneer mangrove. The sum of the concentrations of organic phosphate (ASOP + ROP) increased markedly from the dead mangrove (189 μg g-1) to the mixed mangrove (380 μg g-1). Guianese mangroves, are relatively rich in total phosphate, possibly because they are narrowly related to the 'Amazon dispersal system′. Each mangrove stage can be characterised by a prevailing form of phosphate. The concentrations of these different forms were ascribed to the marked relations with the seawater which controls import or export of suspended matters and to the wave action which controls the resuspension of the sediments and subsequently exchange of phosphate between the suspended matter and the water column.

Characterization of the denitrifying fraction of phosphate accumulating organisms in biological phosphate removal

Research Article| January 01 1999 Characterization of the denitrifying fraction of phosphate accumulating organisms in biological phosphate removal Jens Meinhold; Jens Meinhold *Department of Chemical Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark Search for other works by this author on: This Site PubMed Google Scholar Carlos D. M. Filipe; Carlos D. M. Filipe **Environmental Systems Engineering, Clemson University, Clemson, SC 29634-0919, USA Search for other works by this author on: This Site PubMed Google Scholar Glen T. Daigger; Glen T. Daigger ***CH2M HILL, 100 Inverness Terrace East, Englewood, CO 80122, USA Search for other works by this author on: This Site PubMed Google Scholar Steven Isaacs Steven Isaacs †Krüger A/S, Gladsaxevej 363, DK-2860 Soeborg, Denmark Search for other works by this author on: This Site PubMed Google Scholar Water Sci Technol (1999) 39 (1): 31–42. https://doi.org/10.2166/wst.1999.0007 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search nav search search input Search input auto suggest search filter All ContentAll JournalsThis Journal Search Advanced Search Citation Jens Meinhold, Carlos D. M. Filipe, Glen T. Daigger, Steven Isaacs; Characterization of the denitrifying fraction of phosphate accumulating organisms in biological phosphate removal. Water Sci Technol 1 January 1999; 39 (1): 31–42. doi: https://doi.org/10.2166/wst.1999.0007 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Results of experimental investigations are presented that strongly support the hypothesis that PAO from activated sludge systems consist of two groups: a) denitrifying PAO (DNPAO) capable of using oxygen and nitrate and b) non-denitrifying PAO (non-DNPAO) only able to use oxygen. Batch experiments were performed in which activated sludge obtained from a pilot scale BiodeniphoTM was submitted to a sequence of anaerobic/anoxic/aerobic, anaerobic/aerobic or anaerobic/anoxic conditions while monitoring the course of NOx-N, NH4-N, PO4-P, PHB and PHV. Several methods for the determination of the two fractions of PAO are performed and compared.This study extends on previously reported results (Kern-Jespersen and Henze, 1993) in that the pH was controlled to around pH 7 to assure that phosphate precipitation was minimal, and in the measurement of PHB and PHV. With regards to the latter, the paper also examines the influence of the size of the internal PHA pool on the anoxic phosphorus uptake rate. Simulations implementing existing models for the growth of non-DNPAO and DNPAO are used to confirm the experimental results and to gain a better understanding of some of the observations. Phosphorus removal, denitrification, DNPAO, non-DNPAO, activated sludge, simulation, saturation kinetics, PHB This content is only available as a PDF. © IWA Publishing 1999 You do not currently have access to this content.

Characterization of the denitrifying fraction of phosphate accumulating organisms in biological phosphate removal

Results of experimental investigations are presented that strongly support the hypothesis that PAO from activated sludge systems consist of two groups: a) denitrifying PAO (DNPAO) capable of using oxygen and nitrate and b) non-denitrifying PAO (non-DNPAO) only able to use oxygen. Batch experiments were performed in which activated sludge obtained from a pilot scale BlODENIPHO™ was submitted to a sequence of anaerobic/anoxic/aerobic, anaerobic/aerobic or anaerobic/anoxic conditions while monitoring the course of NOx-N, NH4-N, PO4-P, PHB and PHV. Several methods for the determination of the two fractions of PAO are performed and compared.This study extends on previously reported results (Kerrn-Jespersen and Henze, 1993) in that the pH was controlled to around pH 7 to assure that phosphate precipitation was minimal, and in the measurement of PHB and PHV. With regards to the latter, the paper also examines the influence of the size of the internal PHA pool on the anoxic phosphorus uptake rate. Simulations implementing existing models for the growth of non-DNPAO and DNPAO are used to confirm the experimental results and to gain a better understanding of some of the observations.

Phosphorus utilisation efficiency and depletion of phosphate fractions in the rhizosphere of three tea (Camellia sinensis L.) clones

Tea (Camellia sinensis L.) is mostly grown on highly weathered acidic Ultisols in the humid and sub-humid tropics. Phosphorus (P) availability in Ultisols is naturally low due to it's low diffusivity caused by high P-fixation of Fe and Al oxides. Tea is generally fertilised with low-cost reactive phosphate rocks (RPR) because of enhanced solubility of RPR under acidic conditions. In many countries, new tea clones have been developed to improve yield, drought tolerance and resistance to pest and diseases, but the effectiveness of these clones in utilising P from RPR and native soil P forms has not been studied. A study was conducted to investigate the effects of triple superphosphate (TSP) and a sparingly soluble phosphate rock (Eppawala phosphate rock, EPR) on plant P uptake and soil P fractions in the rhizosphere of three tea clones developed in Sri Lanka (S 106, TRI 2023 and TRI 2025). Phosphate uptake by TRI 2023 (3.3 ± 0.02 mg P plant-1) and TRI 2025 (2.6 ± 0.08 mg P plant-1) was significantly greater than S 106 (1.1 ± 0.01 mg P plant-1) for both P treatments. However the type of P fertiliser did not show any significant difference in P uptake by any of the clones. In all tea clones, the rhizosphere soil pH decreased significantly compared to that of the bulk soil in both P fertiliser treatments. The decrease of pH near the rhizoplane (0–0.5 mm) for TRI 2023, TRI 2025 and S 106 were 0.30 ± 0.02, 0.19 ± 0.03 and 0.17 ± 0.05 respectively. Dissolution of EPR in the rhizosphere of TRI 2023 and TRI 2025 was greater than S 106, which could be attributed to enhanced H+ efflux. TRI 2023 and TRI 2025 depleted more resin-P, NaOH–Piand H2SO4–Piin the rhizosphere compared to S 106, which is consistent with the P uptake results. NaOH–Po accumulated in the rhizosphere of all clones suggesting that soluble inorganic P was transformed into organic P forms possibly as a result of increased microbial activity in the rhizosphere. TRI 2023 and TRI 2025 showed a higher external P efficiency (total P uptake) compared to S 106 due to higher root surface area and higher P uptake per unit root surface area. The higher P uptake per unit root surface area in TRI 2023 and TRI 2025 compared to S 106 may be due to higher rhizosphere acidification, root exudation and mycorrhizal associations. Between TRI 2023 and TRI 2025, the former had higher external P efficiency due to greater root surface area. S 106 had higher internal P efficiency (shoot dry matter production per unit plant P) compared to the other two clones. In future tea breeding programmes, attempts should be made to combine these two traits to maximise P utilisation efficiency from tea clones.

Functional and Evolutionary Implications of the Distribution of Phosphagens in Primitive-Type Spermatozoa.

External fertilization is considered to be the primitive condition in metazoans. The spermatozoa of such organisms typically display a common primitive-type morphology that is present in a range of phyla. These spermatozoa are extremely polarized cells in that the site of ATP synthesis (mitochondria in midpiece) is located at large diffusion distances from the ATP sink (dynein ATPases in the flagellum). Spermatozoa of polychaetes, sipunculids, echiuroids, echinoderms, and tunicates contain the phosphagen creatine phosphate or express the corresponding phosphagen kinase creatine kinase (or both), even when other phosphagens/phosphagen kinases are present in somatic tissues and eggs. The selective expression of the creatine kinase system in these spermatozoa may be related to potential advantages in the cellular transport of energy. To evaluate this possibility, we compared the efficacy of the major phosphagen systems for cellular transport of energy. We used a facilitated diffusion model for spatial ATP buffering, taking into account relative differences in diffusivity and thermodynamic poise. At low ratios of [total phosphagen pool]/ [total adenine nucleotide pool] (CG+P/CAd ratio), creatine phosphate carried a higher fraction of total high-energy phosphate (J) than the other phosphagens. However, J values for all phosphagens were greater than 0.9, and these differences disappeared as the CG+P/CAd ratio was increased. Thus, the functional benefit of using CP, rather than other phosphagens, in energy transport is quite limited. The creatine kinase system became associated with primitive-type spermatozoa early in metazoan evolution. This association is not necessarily related to inherent advantages of this phosphagen system for buffering of ATP, but may be linked to historical events in the evolution of the cell phenotype.

Soil constraints on Northwest Yucatán, Mexico: Pedoarchaeology and Maya subsistence at Chunchucmil

The soils and subsistence of ancient Maya Chunchucmil in northwestern Yucatan are the focus of this paper. Today and historically, the population and crop yields here have been very low. Archaeological field work, however, has shown the Late Classic site to be highly populated with densely packed walled mound and field groups. It is enigmatic that this high ancient Maya population existed in a region of meager crop and soil potential. This enigma is addressed by investigating contemporary Maya agriculture, geoarchaeological evidence, and soil potential for intensive agriculture. The local Maya soil classification of kancab and boxluum synthesizes the Alfisols, Inceptisols, and Mollisols described here. The major soil limitations are shallowness, broad areas with no soil, insufficient water holding capacity, and variable deficiencies in phosphorous, potassium, and zinc. Evidence for intensive agriculture and alternative crops can be seen in widespread field walls compartmentalizing the landscape, sascaberas, and preliminary phosphate fractionation signatures. q 1998 John Wiley & Sons, Inc. INTRODUCTION Studying potential agricultural productivity and forms of intensification to ad- dress the riddle of high ancient Maya populations is keenly important to both ar- chaeology and tropical agricultural development. In the Maya Lowlands historical populations have been very low and agricultural methods very extensive, but some prehistoric populations are estimated to have been very high for hundreds of years. The conditions for agriculture in these tropical lowlands present many challenges, and this poses the basic question of how did ancient Maya high populations feed themselves. This article approaches this question by analyzing the soil potential around the current village of Chunchucmil, Yucatan (Figure 1), Mexico, which lies in the midst of a large site dating mainly from the Maya Late Classic (A.D. 550 - 830). Ironically, this site must have been both very densely populated and also one of the Maya world's most limited agricultural environments. This article first re- views the archaeological landscape and environmental and agricultural history of the region. Second, based on field and laboratory testing, the article describes soil diversity and fertility in the geoarchaeological context of each environmental zone. Lastly, it explores the potential for alternative crops and intensive agriculture.

Surface Complexation Modeling of Phosphate Adsorption by Water Treatment Residual

AbstractUse of water treatment plant residuals (WTR), as a soil amendment is a promising alternative to landfill disposal. Unfortunately, WTR has a propensity to bind with phosphate, which is an important plant nutrient. Phosphate may be added to WTR prior to soil application. This type of pretreatment may convert WTR from a phosphate consumer to a phosphate supplier. The binding of phosphate to WTR is typically attributed to surface complexation with metal oxides. However, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) data and phosphate‐WTR adsorption equilibrium data indicate that phosphate also binds to a cationic polyelectrolyte that is added during water treatment processes. Using the FITEQL optimization program, equilibrium constants and total number of surface sites were determined for the polymer. Results from the FITEQL optimization were used to model binding of phosphate by cationic polymer. Binding of phosphate by hydrous ferric oxide was modeled using a diffuse double layer model, which included surface precipitation (MICROQL). The model was validated through the use of phosphate equilibrium partitioning data at pH values of 6 and 8. The model predicted that a significant fraction of phosphate adsorbed onto WTR is associated with the cationic polymer.

Binding of Cu2+, Zn2+, and Cd2+to Inositol Tri-, Tetra-, Penta-, and Hexaphosphates

myo-Inositol hexaphosphate, the salt of myo-inositol hexaphosphoric acid (IP6), is a common constituent of many plant foods, such as cereals and legumes. IP6 interacts with mineral elements, influencing their bioavailability. Processed foods contain a mixture of different inositol phosphates, i.e., IP6 and its degradation products with five or less phosphate groups (IP5-IP1). The interaction of the lower inositol phosphates with mineral elements is not well-known. In this study, the interaction between metal ions (Cu2+, Zn2+, and Cd2+) and isolated fractions of inositol phosphates with 6, 5, 4 and 3 phosphate groups (IP6-IP3) was investigated by using a potentiometric technique. The study was performed at pH 3-7, which is the pH range in the upper part of the duodenum, where mineral absorption takes place. The inositol phosphate fractions studied had a pronounced binding capacity between pH 5 and 7. Thus, mineral complex formation with lower inositol phosphates is likely to occur in the duodenum, which would be important from a nutritional point of view. The mineral binding capacity as calculated per phosphate group was similar for IP6, IP5, IP4, and IP3, but the binding strength was lower for the lower inositol phosphates (IP4 and IP3). At increasing pH, within the range (pH 3-7), the metal complex formation generally began in the order copper, zinc, cadmium for all inositol phosphates indicating the same order of binding strength, i.e., Cu>Zn>Cd. For IP6 the difference was small between Cu and Zn. (Less)

Frações fosfatadas em mudas de Eucalyptus

Com o objetivo de avaliar os teores e o efeito do tempo de omissão de fósforo nas frações de P em diferentes espécies de eucalipto, instalou-se um experimento em condições controladas no Departamento de Solos da Universidade Federal de Viçosa - UFV, no período de fevereiro a julho de 1993. Avaliou-se, em câmara de crescimento, o comportamento das frações fosfatadas em mudas das seguintes espécies de eucalipto: E. clöeziana ,E. grandis ,E. pellita ,E. pilularis e E. urophylla, quando submetidas à omissão de P. Foi fornecida às plantas uma solução nutritiva com elevado teor de P (8 mg L-1 de P) por vinte e quatro horas. Após esse período, eliminou-se o P da solução nutritiva e analisaram-se as frações de P total solúvel em ácido (Pts), fósforo inorgânico (Pi) e fósforo orgânico (Po), nos tempos de 0, 10 e 20 dias após a omissão do nutriente. Os compartimentos analisados foram as partes apicais e basais de folhas e raízes. A omissão do P da solução nutritiva causou queda no conteúdo de Pts e Pi em todas as espécies, embora em diferente magnitude. E. clöeziana apresentou o maior conteúdo de Pts. Com o aumento do tempo de omissão, as espécies de eucalipto apresentaram redução no percentual de participação do Pi em relação ao Pts, seguido de maior participação relativa do Po nos diversos compartimentos analisados. E. pellita e E. grandis apresentaram um padrão mais homogêneo de comportamento das frações fosfatadas com o tempo de omissão, quando comparadas às outras espécies. Entretanto, essas espécies apresentaram baixos teores de Pi já aos 10 dias de omissão de P, indicativo de um baixo "poder tampão interno de Pi" em relação às outras espécies avaliadas.

Plant availability of phosphorus in the neutral ammonium citrate fraction of brazilian acidulated phosphates

In Brazil, where the rock phosphates are high in impurities, no attempthas been made to evaluate the P supplying efficiency of the neutral ammoniumcitrate fraction (NAC) of P fertilizers, or to verify if the NAC +H2O extraction solution (AOAC) is satisfactory for estimatingthe P availability. To attain these objectives, a greenhouse experiment wascarried out with samples of a Typic Hapludox soil. Four acidulatedphosphates obtained from Brazilian raw materials were studied; monocalciumphosphate p.a.[Ca(H2PO4)2·H2O]was included as a standard source of P, as well as leached samplescontaining no water-soluble P. The fertilizers were thoroughly mixed withthe whole soil in the pots or with only 1% of its volume, at the rateof 50 mg kg-1 of P, soluble in NAC + H2O. Cornplants (Zea mays, L.) were grown for 35 days and the amounts of dry matterand P accumulated in plant tops were determined. Increasing the amount ofcationic impurities in the raw materials decreased the concentration ofwater-soluble P, NAC + H2O-soluble P and water-soluble P/NAC+H2O soluble P ratio of the fertilizers obtained. The P in theNAC fraction was not as much available to plants as in the NAC +H2O fraction or in pure MCP. The great variation found in drymatter (5.4 to 17.1 g pot-1) and in P uptake (6.3 to 22.2 mgpot-1) indicates that the AOAC method is not an adequate indexfor evaluating the P availability of fertilizers with high amounts ofcationic impurities.

Exploration of mesoporous structure of tunisian raw and acid‐leached phosphate ore particles

AbstractRock phosphate fractions were examined for their porous structure by nitrogen adsorption. The pore size distribution and the shape of pores does not seem to depend on the particle size. The specific surface area values present two regions, one above and one below that of the particles with 125 μrn diameter. Particles of a given size were leached with dilute phosphoric acid (1.5 mass% P2O5) at 25°C. It was observed that there is a widening of the initial pores during leaching. The particles collected at the initial period of the reaction are pitted and those collected at the final period are disintegrated.

First Evidence of Poly(ethylene oxide)-Mixed Sodium Dodecyl Sulfate/Sodium Decyl Phosphate Complexes

Polymer-mixed surfactant complex formation among poly(ethylene oxide), sodium dodecyl sulfate, and sodium decyl phosphate was identified using conductivity measurements and following the kinetics of the acid-catalyzed hydrolyses of di-tert-butyl and di-n-butyl benzaldehyde acetals. By conductivity, the onset of the mixed complexation, the critical aggregation concentration, follows an ideal mixing behavior in the same way as takes place in the absence of polymer, previously investigated. The reaction of di-tert-butyl benzaldehyde acetal is generally acid catalyzed, and the first-order rate constant increases linearly up to ca. 0.5 mole fraction of sodium decyl phosphate; however, as the hydrolysis of di-n-butyl benzaldehyde acetal is specifically hydrogen ion catalyzed, the rate constant is independent of the mole fraction of the phosphate surfactant.

Polyphosphates in the red macroalga Chondrus crispus (Rhodophyceae)

SUMMARYPlants of Chondrus crispus Stackhouse, collected from mid‐littoral tidepools, were treated as follows. Some plants were kept for a few weeks under controlled starvation conditions in order to decrease their initial content of total tissue phosphorus, then incubated for up to 48 h in phosphorus (15 μm) and nitrogen (25 μM)enriched sea water. Other plants were directly incubated in enriched sea water. Chemical analyses showed that the total phosphorus content of fresh and starved plants remained stable, reflecting the nutritional status of the plants. The predominant acid‐soluble phosphate fraction was larger in fresh than in starved plants. The content of acid–soluble polyphosphates, similar in both types of plants at the beginning of the experiment, doubled in starved plants, and increased by a factor of 2′7 in fresh plants, over 48 h. The content of acid‐insoluble polyphosphates was lower than that of acid‐soluble polyphosphates.Transmission electron microscopy and energy dispersive X–ray microanalysis confirmed the presence, mostly in medullary cells, of acid‐insoluble polyphosphates in the form of cytoplasmic granules and precipitates along the plasmalemma, particularly near pit plugs. This is the first report of such phosphorus storage structures in a red macroalgal species.

Fractionation of sediment phosphate with chelating compounds: a simplification, and comparison with other methods

The NTA/EDTA fractionation of sediment-bound, inorganic phosphate was improved and made more effective. The iron-bound phosphate is now extracted with Ca-EDTA plus dithionite and followed by an extraction of calcium-bound phosphate by Nat-EDTA at pH = 4.5. A comparison is made with two other sequential extraction procedures: the SEDEX and the Hieltjes & Lijklema extractions. The EDTA extractions have an advantage over the other two methods.

Relation between algal available phosphate in the sediments of the River Garonne and chemically-determined phosphate fractions

Concentrations of total and inorganic phosphate were measured in forty-seven sediments of the River Garonne (France) using an anion resin, NaOH 0.1 M, Ca-NTA and Na-EDTA. Algal available P was measured using Scenedesmus crassus. The sediments presented a wide range of Tot-P concentrations (226 to 923 µg g−1). Resin P varied between 1.1 to 55.5 µg g−1 and NaOH-P between 3.5 to 262 µg g−1. NTA-P and EDTA-P varied between 13.9 and 178 µg g−1 and between 14.4 to 261 µg g−1 respectively. Algal available P varied between 8.8 to 262 µg g−1/ All forms of P are highly correlated and specially with algal available P (r = 0.70, 0.77, 0.88 and 0.77 for resin-P, NaOH-P, NTA-P and EDTA-P respectively). Nevertheless the partial correlation between EDTA-P and algal available P dropped to 0.05 when the concentration of NTA-P was considered as constant, indicating a spurious correlation with apatitic phosphate (extracted by Na-EDTA). Because of the strongest R2 and the lowest standard error of estimate, phosphate extracted by Ca-NTA can be considered as the best predictor of algal available phosphate.

Renal fibrosis in cyclosporin A-treated renal allograft recipients: morphological findings in relation to renal hemodynamics

Abstract Nineteen nondiabetic kidney graft patients treated with cyclosporin A for 2 years underwent percutaneous renal allograft biopsy as well as renal hemodynamic examination. Renal allograft fibrosis was quantitatively evaluated as the relative volume of the renal cortical interstitium (Vv%) and as the interstitium/tubuli ratio (I/T ratio). The histological changes were then classified into four groups, depending on the degree of interstitial fibrosis. The glomerular filtration rate (GFR), renal plasma flow (RPF), renal blood flow (RBF), filtration fraction (FF), and fractional clearance of sodium, potassium, phosphate, chloride, osmoles, and free water clearance were determined in all patients and in 13 healthy controls. Kidney graft recipients had significantly lower GFR, lower RPF, and lower RBF than the healthy controls (P < 0.001 for all comparisons) while FF was similar in patients and controls. Transplant recipients had a significantly higher fractional excretion of sodium, potassium, chloride, and phosphate than controls. All except one patient had clearly increased Vv values, indicating increased interstitial fibrosis. The mean V, in renal allograft patients was 35 %±10 % (normal < 16%± 5%)andtheI/T ratio was 1.07 ± 0.60 (normal < 0.24 ± 0.08). No correlation was found between the quantitative or semiquantitative biopsy analysis and any renal heniodynamic parameter measured. We conclude that renal function is significantly decreased in kidney graft recipients, but that adaptive tubular changes occur in the graft. Interstitial renal fibrosis was common but did not correlate to any renal functional parameter.

Renal fibrosis in cyclosporin A-treated renal allograft recipients: morphological findings in relation to renal hemodynamics.

Nineteen nondiabetic kidney graft patients treated with cyclosporin A for 2 years underwent percutaneous renal allograft biopsy as well as renal hemodynamic examination. Renal allograft fibrosis was quantitatively evaluated as the relative volume of the renal cortical interstitium (VV %) and as the interstitium/tubuli ratio (I/T ratio). The histological changes were then classified into four groups, depending on the degree of interstitial fibrosis. The glomerular filtration rate (GFR), renal plasma flow (RPF), renal blood flow (RBF), filtration fraction (FF), and fractional clearance of sodium, potassium, phosphate, chloride, osmoles, and free water clearance were determined in all patients and in 13 healthy controls. Kidney graft recipients had significantly lower GFR, lower RPF, and lower RBF than the healthy controls (P < 0.001 for all comparisons) while FF was similar in patients and controls. Transplant recipients had a significantly higher fractional excretion of sodium, potassium, chloride, and phosphate than controls. All except one patient had clearly increased VV values, indicating increased interstitial fibrosis. The mean VV in renal allograft patients was 35% +/- 10% (normal < 16% +/- 5%) and the I/T ratio was 1.07 +/- 0.60 (normal < 0.24 +/- 0.08). No correlation was found between the quantitative or semiquantitative biopsy analysis and any renal hemodynamic parameter measured. We conclude that renal function is significantly decreased in kidney graft recipients, but that adaptive tubular changes occur in the graft. Interstitial renal fibrosis was common but did not correlate to any renal functional parameter.