Neutral Phosphatase Activity Research Articles

Effect of straws from Bt-transgenic rice on selected biological activities in water-flooded soil

The biochemical properties of soil have often been described as early and sensitive indicators of ecological changes in both natural soil and agroecosystem. In the current study, the impacts of the amendment of Bt-transgenic rice (KMD) straw on biological activities in water-flooded soil were investigated under laboratory conditions and compared with non-transgenic rice (Xiushui 11) straw. The results showed that there were some differences in protease, neutral phosphatase and cellulase activities between soil amended with Bt-transgenic rice straw and non-transgenic rice straw at the early stage of incubation, and none of these differences were persistent. However, differences in dehydrogenase activity, methanogenesis, hydrogen production and anaerobic respiration between soil supplemented with Bt-transgenic rice straw and non-transgenic rice straw were persistent over the course of incubation. Dehydrogenase activity, methanogenesis and anaerobic respiration were considerably lower from sample days 7 to 56, but higher after day 56 in soil amended with Bt-transgenic rice straw. In comparison, the H 2-production in soil containing Bt-transgenic rice straw was significantly lower after day 56. The results demonstrated that the amendment of the Bt-transgenic rice straw altered some important biological properties in water-flooded soil, indicating a shift in microbial populations or a change in the metabolic abilities of the microbial community as a result of substrate availability in soil.

Bt-transgenic rice straw affects the culturable microbiota and dehydrogenase and phosphatase activities in a flooded paddy soil

There have been few investigations of the possible effects of genetically engineered plants on the microbiota and enzyme activities in flooded soil. We studied the influence of the transgenic rice KeMingDao (KMD) straw on the culturable microbiota and enzymatic activities in a flooded paddy soil under laboratory conditions. KMD contained a synthetic cry1Ab gene from Bacillus thuringiensis under the control of a maize ubiquitin promoter and linked in tandem with the gusA and hpt genes. The results showed that there were only some occasional significant differences ( P<0.05) in the number of Colony forming units of aerobic bacteria, actinomycetes and fungi and in the number of anaerobic fermentative bacteria, denitrifying bacteria, hydrogen-producing acetogenic bacteria, and methanogenic bacteria between the paddy soil amended with Bt-transgenic rice straw and with the non-Bt parental rice straw during the early stages of incubation. From d14 to d84 there were significant increases ( P<0.05) in soil dehydrogenase and soil neutral phosphatase activity in soils amended with rice straw compared to soil without added straw. The dehydrogenase activity was significantly greatly (almost 1.95-fold) in soil amended with Bt-transgenic straw from d7 to d14 but from d21 to d49 there was significantly greater activity (about 1.47-fold) in the soil amended with non-Bt-straw. There were no apparent differences between the activity of soil neutral phosphatase in the soils to which non-Bt-straw and Bt-straw had been added. However, both soils to which rice straws were added demonstrated significant differences in the number of microorganisms except for aerobic bacteria and enzymatic activities with respect to the control soil throughout the incubation. The above results indicated that the Bt-straw from KMD transgenic rice is not toxic to a variety of culturable microorganisms in the studied flooded paddy soil.

Phosphatase activity and P fractions in soils of an 18-year-old Chinese fir ( Cunninghamia lanceolata) plantation

Chinese fir ( Cunninghamia lanceolata), an important native tree species, has been widely planted in mountainous areas in the tropics and subtropics in China for more than 1000 years and used for a variety of wood products. The rate of phosphorus (P) supply is the most limiting factor to primary productivity in many Chinese fir plantation ecosystems. Soil phosphatase activity can be a good indicator of the organic P mineralization potential and biological activity of soils. Acid and neutral phosphatase activity (APA and NPA, respectively) and P fractions in the soils of an 18-year-old Chinese fir plantation in southwestern China were investigated. APA, 181.2 mg phenol kg −1 h −1, was significantly higher than NPA, 80.7 mg phenol kg −1 h −1, in the rhizosphere and bulk soils. In comparing rhizosphere soils and bulk soils at 20, 40, and 80 cm from the tree stem, phosphatase activity significantly decreased with the distance from the tree stem. APA and NPA decreased with soil depth, highest in the soil A horizon and least in the C horizon. Total and organic P, dilute acid extractable P (DA-P), aluminum bound P (Al-P) and iron bound P (Fe-P) in the rhizosphere were significantly higher than in soils at 20, 40 and 80 cm from the tree stem, whereas calcium bound P (Ca-P) was significantly lower. All P fractions significantly decreased with soil depth except for Ca-P. APA and NPA were significantly correlated to total P, inorganic P, organic P and occluded Fe/Al bound P, Al-P, Fe-P as well as Ca-P. These results suggested that organic P compound is used as a P source in Chinese fir plantations deficient in P in southern China, and that the application of organic phosphate fertilizer is effective around trees and in the soil surface horizons.

Modulation by ammonium ions of gill microsomal (Na +,K +)-ATPase in the swimming crab Callinectes danae: a possible mechanism for regulation of ammonia excretion

The modulation by Na +, K +, NH 4 + and ATP of the (Na +,K +)-ATPase in a microsomal fraction from Callinectes danae gills was analyzed. ATP was hydrolyzed at high-affinity binding sites at a maximal rate of V=35.4±2.1 U mg −1 and K 0.5=54.0±3.6 nM, obeying cooperative kinetics ( n H=3.6). At low-affinity sites, the enzyme hydrolyzed ATP obeying Michaelis–Menten kinetics with K M=55.0±3.0 μM and V=271.5±17.2 U mg −1. This is the first demonstration of a crustacean (Na +,K +)-ATPase with two ATP hydrolyzing sites. Stimulation by sodium ( K 0.5=5.80±0.30 mM), magnesium ( K 0.5=0.48±0.02 mM) and potassium ions ( K 0.5=1.61±0.06 mM) exhibited site–site interactions, while that by ammonium ions obeyed Michaelis–Menten kinetics ( K M=4.61±0.27 mM). Ouabain ( K I=147.2±7.2 μM) and orthovanadate ( K I=11.2±0.6 μM) completely inhibited ATPase activity, indicating the absence of contaminating ATPase and/or neutral phosphatase activities. Ammonium and potassium ions synergistically stimulated the enzyme, increasing specific activities up to 90%, suggesting that these ions bind to different sites on the molecule. The presence of each ion modulates enzyme stimulation by the other. The modulation of (Na +,K +)-ATPase activity by ammonium ions, and the excretion of NH 4 + in benthic crabs are discussed.

Inhibitory effect of regucalcin on Ca2+/calmodulin-dependent protein phosphatase activity in rat brain cytosol.

The effect of Ca2+-binding protein regucalcin on neutral phosphatase activity in rat brain cytosol was investigated. Phosphatase activity was assayed in a reaction mixture containing the cytosolic protein in the presence of phosphotyrosine, phosphoserine, and phosphothreonine. The presence of calcium chloride (10(-5) and 10(-4) M) in the enzyme reaction mixture caused a significant increase in phosphatase activity toward three phosphoaminoacids. The enzyme activity toward phosphoserine and phosphothreonine was significantly enhanced by the addition of calmodulin (1 or 5 microg/ml) in the presence of calcium (10(-5) M). Such an effect was not seen in the presence of phosphotyrosine. Trifluoperazine (2x10(-5) M), an antagonist of calmodulin, completely inhibited calcium (10(-5) M)-increased phosphatase activity toward phosphoserine and phosphothreonine, whereas it had no effect on the enzyme activity toward phosphotyrosine. Regucalcin (10(-9) M) significantly inhibited phosphatase activity toward three phosphoaminoacids without or with Ca2+ addition. The inhibitory effect of regucalcin (10(-10) and 10(-9) M) was also seen in the presence of Ca2+ (10(-5) M) and calmodulin (5 microg/ml). The presence of anti-regucalcin monoclonal antibody (20 or 50 ng/ml) in the enzyme reaction mixture caused a significant elevation of phosphatase activity toward three phosphoaminoacids; this effect was completely abolished by addition of regucalcin (10(-9) M). The present study suggests that the endogenous regucalcin has an inhibitory effect on Ca2+/calmodulin-dependent protein phosphatase activity in rat brain cytosol.

Enhancement of neutral phosphatase activity in the cytosol and nuclei of regenerating rat liver: Role of endogenous regucalcin

The role of endogenous regucalcin (RC) in the regulation of neutral phosphatase activity in regenerating rat liver was investigated. The liver weight reduced by a partial hepatectomy (about 70%) was completely restored at 72 h after surgery. Phosphotyrosine, phosphoserine, and phosphothreonine were used as the substrate for the assay of phosphatase activity. Phosphatase activity toward phosphotyrosine in the hepatic cytosol and nuclei was significantly increased at 24-72 h after hepatectomy. Such an increase was not seen in the case of phosphoserine and phosphothreonine. However, the presence of anti-RC monoclonal antibody (200 ng/ml) in the enzyme reaction mixture caused a remarkable elevation of phosphatase activity toward three phosphoaminoacids in the hepatic cytosol at 24 and 48 h after hepatectomy. In the liver nuclei after sham operation or hepatectomy, phosphatase activity toward three phosphoaminoacids was significantly raised by the addition of anti-RC antibody (150 ng/ml). The nuclear phosphatase activity toward phosphothreonine in regenerating liver was significantly enhanced in the presence of anti-RC antibody (100 and 150 ng/ml). The effect of anti-RC antibody to increase phosphatase activity toward three phosphoaminoacids in the cytosol and nuclei of regenerating liver was completely blocked by the addition of exogenous RC (1.0 microM). The present study demonstrates that protein phosphatase activity in the cytoplasm and nuclei is enhanced in regenerating rat liver. This enhancement may be suppressed by endogenous RC.

Enhancement of neutral phosphatase activity in the cytosol and nuclei of regenerating rat liver: Role of endogenous regucalcin

Enhancement of neutral phosphatase activity in the cytosol and nuclei of regenerating rat liver: Role of endogenous regucalcin

Effect of anti-regucalcin antibody on neutral phosphatase activity in rat liver cytosol: involvement of endogenous regucalcin.

The effect of anti-regucalcin monoclonal antibody on neutral phoshatase activity in rat liver cytosol was investigated. Phosphotyrosine, phosphoserine, and phosphothreonine were used as the substrate toward phosphatase assay. Liver cytosolic phosphatase activity with three phosphoaminoacids was significantly increased in the presence of anti-regucalcin antibody (100 and 200 ng/ml) in the enzyme reaction mixture with calcium chloride (0.1 mM) or EGTA (1.0 mM). The effect of anti-regucalcin antibody was completely abolished in the presence of exogenous regucalcin (1.0 microM), indicating the involvement of endogenous regucalcin. The anti-regucalcin anti body- increased phosphatase activity was not significantly altered in the presence of trifluoperazine (20 microM), an antagonist of calmodulin, or akadaic acid ( 10 microM), an inhibitor of protein phosphatase, although these inhibitors caused a slight decrease in liver cytosolic phosphatase activity. The effect of endogenous regucalcin might be not related to calmodulin, and it was insensitive to okadaic acid. The present findings suggest that endogenous regucalcin is involved in the regulation of protein phasphatase in rat liver cytoplasm.

Use of the ARG7 gene as an insertional mutagen to clone PHON24, a gene required for derepressible neutral phosphatase activity in Chlamydomonas reinhardtii.

In Chlamydomonas reinhardtii, transforming DNA apparently integrates at random locations in the nuclear genome and generates a high number of mutants by gene inactivation. Twenty-four phoN mutants lacking the derepressible neutral (DN) phosphatase activity were isolated following transformation of the cw15arg7 strain with plasmid pASL harbouring the ARG7 gene encoding argininosuccinate lyase. In all mutants resulting from the transformation with linearised pASL, a functional ARG7 copy was found to be closely linked to a phoN mutation but additional ARG7 copies were present elsewhere in the genome. Of the 13 mutants submitted to allelism analysis, four were allelic or tightly linked to the previously isolated MNNG-induced phoN mutants (phoN2, phoN3, phoN24), the remaining mutants were distributed among seven additional loci. To learn more about the function of the genes involved in DN phosphatase production, we cloned PHON24 by plasmid rescue and screening of a wild-type genomic library. One clone complemented the phoN24 mutation in cotransformation experiments, as did several subcloned fragments. In all phoN24+ transformants, the DN phosphatase activity was 2-3 times lower than in the wild-type strain but about 10 times higher than in the untransformed control. In wild-type, PHON24 transcript accumulation was independent of inorganic phosphate deficiency. The transcripts were present in the MNNG-induced phoN24 mutant but were lacking in the two insertional phoN24 mutants. Insertional mutagenesis has thus permitted the isolation of novel mutants which were missing after induction with a chemical mutagen and the cloning of a gene which is probably involved in the regulation of the DN phosphatase.

Inhibitory effect of zinc and copper on phosphatase activity in the brain cytosol of rats: involvement of SH groups.

The effect of various metal ions on neutral phosphatase activity in the brain cytosol of rats was investigated. p-Nitrophenylphosphate was used as the substrate for the enzyme assay. Brain cytosolic phosphatase activity was significantly decreased by the presence of zinc or copper in the range of 10(-5) to 10(-3) M in the enzyme reaction mixture, while it was significantly increased by manganese, nickel or cobalt (10(-5) to 10(-3) M). Calcium (10(-5) to 10(-3) M) did not have an appreciable effect on brain cytosolic phosphatase activity. The inhibitory effect of zinc (10(-5) M) or copper (10(-5) M) on phosphatase activity was seen in the presence of manganese, nickel or cobalt with 10(-4) M concentration, indicating a potent inhibitory effect of these metals. Zinc or copper-decreased phosphatase activity was clearly prevented by dithiothreitol (5 mM), although the effect of each metal was further enhanced by N-ethylmaleimide (5 mM), suggesting that the metals act on the SH-groups of enzyme. Moreover, the inhibitory effect of zinc (10(-5) M) was significantly enhanced by S-100A (10(-6) M) or calbindin (10(-7) M), although neither protein had any effect in the presence of calcium (10(-5) M) or copper (10(-5) M). These results suggests that zinc has an unique role in the regulation of neutral phosphatase activity in rat brain cytosol.

Use of human and rat keratinocyte cultures to assess skin irritation potential

An in vitro cell culture approach was evaluated for its ability to provide data pertinent to the assessment of skin irritation potential. The hypothesis of this approach is that a direct toxic insult to the epidermal keratinocyte in vivo may lead to release of inflammatory mediators, which are responsible for initiation of a local primary skin irritant reaction. This paper presents data on the cytotoxic potential of a number of structurally unrelated chemicals (chloroform, 2-methoxyethanol, 2-butoxyethylacetate, toluene, 1-butanol, acetaldehyde, n-hexane, sodium dodecyl sulfate, benzalkonium chloride, silver nitrate, dibutyltin dichloride and tributyltin chloride). Cytotoxicity (neutral red uptake and intracellular acid phosphatase activity) of a number of structurally unrelated chemicals, representative of a wide range of skin irritation potential, was evaluated in cultures of rat and human epidermal keratinocytes. The sensitivity of human and rat keratinocytes to the test chemicals was very similar, irrespective of the endpoint of cytotoxicity. The neutral red uptake assay appeared more generally applicable to the diverse range of chemical structures represented in this study, since not all test chemicals elicited an early increase in intracellular acid phosphatase activity. The results were very encouraging, as a good correlation was evident between cytotoxicity in rat keratinocytes and the degree of erythema and oedema associated with an in vivo skin irritant response in rabbits. Keratinocyte cytotoxicity data may provide an indication of the potential of a chemical to induce a severe skin irritant reaction, or if a chemical is more likely to be a marginal or non-irritant. However, the data illustrate that such assays appear unable to discriminate correctly between more subtle classes of irritancy, such as non-irritant, mild, moderate or severe. Available human in vivo skin irritation data were insufficient to conclude which cell type is preferable for evaluation of human skin irritation potential.

Cloning and expression of a neutral phosphatase gene from Treponema denticola

We have isolated and characterized a neutral phosphatase gene, phoN, from Treponema denticola ATCC 35405. The gene was isolated from a T. denticola clone bank constructed in the medium-copy-number plasmid vector pMCL19. Subcloning and nucleotide sequencing of the DNA insert from one phosphatase clone, pTph14, revealed that the activity corresponded to an open reading frame consisting of 1,027 bp coding for a 37.9-kDa protein. Hydrophobicity analysis indicated that the protein exhibits some hydrophobic regions. Indeed, partial purification of the phosphatase suggested that the enzyme was membrane associated both in T. denticola and in the Escherichia coli clone. The pH optimum of the enzyme, approximately pH 6.4, indicated that it corresponded to a neutral phosphatase activity from T. denticola. An examination of possible natural substrates for the enzyme suggested that this enzyme hydrolyzes nucleoside di- and triphosphates. Northern (RNA) blot analysis revealed that this phosphatase gene is not likely to be present in an operon structure.

Islet lysosomal enzyme activities and glucose-induced insulin secretion: effects of mannoheptulose, 2-deoxyglucose and clonidine.

In previous investigations we have shown a striking relationship between the activity of glycogenolytic glucose producing acid hydrolases in pancreatic islet tissue and certain insulin-releasing processes. In the present investigation we have studied the relation between islet lysosomal enzyme activities and glucose-induced insulin secretion in vitro in the presence of various insulin secretory inhibitors. It was observed that the nonmetabolizable glucose analogue, mannoheptulose (5 mmol/l) did induce a 2-fold increase in insulin release at low (1 mmol/l) glucose, and a total suppression of insulin release at high (16.7 mmol/l) glucose. These changes in the insulin-secretory pattern were accompanied by similar changes in the activity of islet acid alpha-glucosidase. The activities of neutral alpha-glucosidase (endoplasmic reticulum) or acid phosphatase and N-acetyl-beta-D-glucosaminidase (lysosomes) were not affected by mannoheptulose. 2-Deoxyglucose (5 mmol/l), another glucose analogue, did not increase insulin secretion or acid alpha-glucosidase activity at low glucose. At high glucose, however, a partial inhibition of both insulin release (approximately 50%) and acid alpha-glucosidase activity was seen. 2-Deoxyglucose slightly suppressed acid phosphatase activity but did not influence the activities of neutral alpha-glucosidase or N-acetyl-beta-D- glucosaminidase. Direct addition of glucose to islet homogenates showed a suppressive effect on alpha-glucosidase activity at pH 4.0 and 5.0. The glucose analogues displayed only marginal (-10%) inhibition of alpha-glucosidase activity at pH 5.0. No effect of the analogues was seen at pH 4.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential changes in CNS phosphatase activities during seizures

Neutral and alkaline phosphatase activities were studied in small synaptosomes isolated from rat brain and cerebellum after administration of the convulsant 3-mercaptopropionic acid (MP). Cerebral cortex phosphatase activity assayed at pH 7.2 in the presence of K+ increased both during and after seizures; when it was assayed at pH 7.2 in the absence of K+ it decreased at both stages. The enzyme activity determined in cortical fractions at pH 9.0 with or without K+ decreased in seizure and postseizure states. After MP treatment, cerebellum enzyme activity assay at pH 7.2 was higher than in controls throughout; phosphatase activity assayed at pH 9.0 decreased following MP administration except during seizures when the enzyme was assayed in the presence of K+. Such changes following MP treatment may well be related to seizure-induced alteration of phosphate ester levels or protein-kinase activities.

Erythrocytes, erythrocyte membranes, neutrophils and platelets as biopsy materials for the assessment of zinc status in humans.

During a controlled zinc depletion-repletion study, fifteen men aged 25.3 (SD 3.3) years were fed on a low-Zn diet with high phytate:Zn and phytate x calcium:Zn molar ratios for 7 weeks, followed by a 2 week repletion period when 30 mg supplemental Zn/d was given. Changes in plasma, urine, and hair Zn concentrations, taste acuity, and cellular immune response confirmed the development of mild Zn deficiency. Zn concentrations in neutrophils, platelets, erythrocytes and erythrocyte membranes, mean platelet volume, and activities of alkaline phosphatase (EC 3.1.3.1) and alpha-D-mannosidase (EC 3.2.1.24) in neutrophils did not respond to changes in Zn status. In contrast, alkaline phosphatase activity in erythrocyte membranes showed a significant decline which was consistent in all subjects (nmol product formed/min per mg protein; baseline v. 7-week Zn depletion, 0.656 (SD 0.279) v. 0.506 (SD 0.230), at 7 weeks; P < 0.05); neutral phosphatase activity remained unchanged. Alkaline phosphatase activity in erythrocyte membranes may be a potential index of Zn status in humans.

New polypeptides and in-vitro-translatable mRNAs are produced by phosphate-starved cells of the unicellular algaChlamydomonas reinhardtii

Cells of the unicellular algaChlamydomonas reinhardtii Dang. deprived of inorganic phosphate (Pi) secrete into the culture medium large amounts of glycoproteins which are not produced by cells grown in the presence of Pi. One of the polypeptides (P6: Mr 73000 ± 2 000) resolved by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) is absent from a mutant lacking neutral-phosphatase activity, and probably corresponds to a subunit of this enzyme. The antibodies raised to P6, however, were able to cross-react on Western blots with most of the secreted proteins which indicates that they recognize oligosaccharide epitopes common to all of these de-novo-formed molecules. In order to verify whether the response to Pi deprivation takes place at the transcriptional level, the in-vitro translation products directed by poly(A)(+) RNA preparations obtained from cells grown with or without Pi were analyzed by two-dimensional SDS-PAGE. Three polypeptides specific to Pi-starved cells were detected but were considered unlikely to correspond to subunits of the neutral phosphatase. Whereas in-vivo-labelled proteins (notably P6) were precipitable by our antibodies, all attempts at precipitating in-vitro translation products have failed. This result is in agreement with the hypothesis that the antibodies recognize the oligosaccharide side chains but not the polypeptide backbone of the glycoproteins, a situation already described for monoclonal antibodies to the major structural glycoprotein of theChlamydomonas cell wall.

Alkaline, acid, and neutral phosphatase activities are induced during development in Myxococcus xanthus

One of the signals that has been reported to be important in stimulating fruiting body formation of Myxococcus xanthus is starvation for phosphate. We therefore chose to study phosphatase activity during M. xanthus development. Many phosphatases can cleave the substrate p-nitrophenol phosphate. Using this substrate in buffers at various pHs, we obtained a profile of phosphatase activities during development and germination of M. xanthus. These experiments indicated that there are five patterns of phosphatase activity in M. xanthus: two vegetative and three developmental. The two uniquely vegetative activities have pH optima at 7.2 and 8.5. Both require magnesium and both are inhibited by the reducing agent dithiothreitol. The developmental (spores) patterns of activity have pH optima of 5.2, 7.2, and 8.5. All three activities are Mg independent. Only the alkaline phosphatase activity is inhibited by dithiothreitol. The acid phosphatase activity is induced very early in development, within the first 2 to 4 h. Both the neutral and alkaline phosphatase Mg-independent activities are induced much later, about the time that myxospores become evident (24 to 30 h). The three activities are greatly diminished upon germination; however, the kinetics of loss differ for all three. The acid phosphatase activity declines very rapidly, the neutral activity begins to decline only after spores begin to convert to rods, and the alkaline phosphatase activity remains high until the time the cells begin to divide. All three developmental activities were measured in the developmental signalling mutants carrying asg, csg, and dsg. The pattern of expression obtained in the mutants was consistent with that of other developmentally regulated genes which exhibit similar patterns of expression during development. The ease with which phosphatases can be assayed should make the activities described in this report useful biochemical markers of stages of both fruiting body formation and germination.

Vitamin B-6 Metabolic Enzymes in Blood and Placenta of Pregnant Mice

Plasma pyridoxal 5'-phosphate (PLP) concentrations decrease 50% in pregnant mice and erythrocyte PLP levels increase threefold over nonpregnant levels. These studies were designed to determine whether changes in the enzymes involved in synthesis and degradation of PLP in blood are altered during pregnancy. We measured net synthesis of PLP in erythrocytes and the activity of enzymes involved in the regulation of plasma and erythrocyte PLP concentration: erythrocyte pyridoxal kinase (PLK) and neutral phosphatase, and plasma and tissue alkaline phosphatase (ALP). Net synthesis of PLP and activities of erythrocyte PLK and neutral phosphatase in erythrocytes remained unchanged during pregnancy. We were unable to detect any dephosphorylation of PLP in erythrocytes of pregnant or nonpregnant mice. Mouse erythrocytes were devoid of ALP activity; neutral phosphatase was inactive with PLP and PLP was an uncompetitive inhibitor of the enzyme. Plasma ALP activity decreased 50% in the pregnant mice; therefore, it likely does not participate in the reduction of plasma PLP levels during pregnancy. Placenta had high levels of PLP-phosphatase activity (ALP) and, if it is active as an ectoenzyme in this tissue as it is in others, it may be the most important mediator of plasma PLP levels in pregnancy.

Effect of Vesicular-arbuscular Mycorrhizal Infection on the Distribution of Neutral Phosphatase Activities in Root Cortical Cells

Summary Neutral phosphatase activities are present along the elongating plasmalemma in differentiating root cells where cell wall synthesis is actively occurring, whilst they cannot be detected along this membrane in cortical cells that have completed elongation and differentiation; here they are associated with the endoplasmic reticulum and tonoplast. When differentiated cortical cells are infected by a vesicular-arbuscular mycorrhizal fungus, plasmalemma-bound neutral phosphatase activities reappear and are localized along the host membrane extending around the arbuscular hyphae. These observations are discussed in relation to host-fungus interactions occurring in the mycorrhizal associations.

An examination of the factors involved in determining phosphatase activities in estuarine waters. 2: Sampling procedures

Sampling procedures which are significant in the assessment of phosphatase activities in water bodies have been studied. Variations in neutral phosphatase activities among sampling stations and over depth profiles were considered, as well as seasonal and diurnal variations.