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Inorganic Phosphate (inorganic + phosphate)
Terms modified by Inorganic Phosphate Selected AbstractsInorganic phosphate as a signaling molecule in osteoblast differentiation,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2003George R. Beck Jr. Abstract The spatial and temporal coordination of the many events required for osteogenic cells to create a mineralized matrix are only partially understood. The complexity of this process, and the nature of the final product, demand that these cells have mechanisms to carefully monitor events in the extracellular environment and have the ability to respond through cellular and molecular changes. The generation of inorganic phosphate during the process of differentiation may be one such signal. In addition to the requirement of inorganic phosphate as a component of hydroxyapatite mineral, Ca10(PO4)6(OH)2, a number of studies have also suggested it is required in the events preceding mineralization. However, contrasting results, physiological relevance, and the lack of a clear mechanism(s) have created some debate as to the significance of elevated phosphate in the differentiation process. More recently, a number of studies have begun to shed light on possible cellular and molecular consequences of elevated intracellular inorganic phosphate. These results suggest a model in which the generation of inorganic phosphate during osteoblast differentiation may in and of itself represent a signal capable of facilitating the temporal coordination of expression and regulation of multiple factors necessary for mineralization. The regulation of protein function and gene expression by elevated inorganic phosphate during osteoblast differentiation may represent a mechanism by which mineralizing cells monitor and respond to the changing extracellular environment. J. Cell. Biochem. 90: 234,243, 2003. Published 2003 Wiley-Liss, Inc. [source] Inorganic phosphate has a crucial effect on Cry3Aa , -endotoxin productionLETTERS IN APPLIED MICROBIOLOGY, Issue 4 2005A. Kurt Abstract Aims:, The study aimed at increasing Cry3Aa , -endotoxin production by a local isolate of Bacillus thuringiensis (B.t. strain Mm2). To this end, different nutritional conditions were tested for their effects on Cry3Aa yields. Methods and Results:,Bacillus thuringiensis Mm2 was grown by shaking at 30°C in different media. Samples were taken from the cultures at intervals and used for protein extraction. SDS-PAGE was performed for toxin analysis. Inclusion of inorganic phosphate (Pi) into the Difco's sporulation medium at an increased level of 200 mmol l,1 caused a fivefold increase (from 3 to 15·6 ,g ml,1) in toxin production. Omission of FeSO4 from the medium decreased this yield by half. Resuspension experiments suggested catabolite repression of toxin biosynthesis by glucose. The inclusion of high Pi invariably increased toxin synthesis, even in the absence of sugars. Conclusions:, Inorganic phosphate had the most striking effect on toxin biosynthesis. Iron effect was found to be unique to our isolate whereas Pi effect seemed to be common to the biosynthesis of Cry3Aa-type toxins. Stimulation of toxin synthesis by Pi did not seem to represent a relief from glucose repression. Significance and Impact of the Study:,Bacillus thuringiensis is the most versatile biopesticide for use in pest management. Regarding cost-effectiveness of related fermentations, high Pi supplement drastically increases Coleoptera-specific toxin synthesis. [source] Biliary inorganic phosphate as a tool for assessing cold preservation-reperfusion injury: A study in the isolated perfused rat liver modelLIVER TRANSPLANTATION, Issue 2 2003Luciana L. Almada Ischemia-reperfusion injury is a major cause of early graft dysfunction after liver transplantation. The bile flow has been suggested as an index of ischemic damage, and severely impaired bile flow seems to be predictive of poor survival in experimental studies. Looking for injury markers, biliary inorganic phosphate has the potential of being a useful endogenous marker of diminished hepatobiliary function because this anion is excreted in the bile by a paracellular pathway and it can detect changes in permeability. The goal of this study was to evaluate the effects of cold preservation-reperfusion of the liver on bile flow and bile inorganic phosphate and their relationship with storage-related graft failure. The isolated and perfused rat liver was used to evaluate the injury for ischemia-reperfusion. The intrahepatic resistance, lactate dehydrogenase release, and potassium and biliary inorganic phosphate concentration were used to estimate viability and function of freshly isolated or cold-preserved livers. The intrahepatic resistance and the bile flow were consistent and significantly decreased throughout the perfusion time in relation to the increment in storage. Inorganic phosphate is more concentrated in bile from preserved livers, showing an alteration in paracellular pathway, confirmed by the biliary excretion of horseradish peroxidase. After preservation, concentration and excretion of the paracellular marker were increased during the first peak. The second peak appears earlier in preserved livers (10 minutes) with a different shape but without changes in concentration. In conclusion, inorganic phosphate in bile shows changes in paracellular permeability as occurs in livers after 48 hours of cold preservation. [source] The regulation and function of phosphate in the human bodyBIOFACTORS, Issue 1-4 2004Eiji Takeda Abstract Inorganic phosphate (Pi) is required for cellular function and skeletal mineralization. Serum Pi level is maintained within a narrow range through a complex interplay between intestinal absorption, exchange with intracellular and bone storage pools, and renal tubular reabsorption. Pi is abundant in the diet, and intestinal absorption of Pi is efficient and minimally regulated. The kidney is a major regulator of Pi homeostasis and can increase or decrease its Pi reabsorptive capacity to accommodate Pi need. The crucial regulated step in Pi homeostasis is the transport of Pi across the renal proximal tubule. Type II sodium-dependent phosphate (Na/Pi) cotransporter (NPT2) is the major molecule in the renal proximal tubule and is regulated by hormones and nonhormonal factors. Recent studies of inherited and acquired hypophosphatemia which exhibit similar biochemical and clinical features, have led to the identification of novel genes, phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and fibroblast growth factor-23 (FGF-23), that play a role in the regulation of Pi homeostasis. The PHEX gene encodes an endopeptidase, predominantly expressed in bone and teeth but not in kidney. FGF-23 may be a substrate of this endopeptidase and inhibit renal Pi reabsorption. In a survey in the United States and in Japan, the amount of phosphorus from food is gradually increasing. It is thought that excess amounts of phosphorus intake for long periods are a strong factor in bone impairment and ageing. The restriction of phosphorus intake seems to be important under low calcium intake to keep QOL on high level. [source] Renal phosphate handling in human , what can we learn from hereditary hypophosphataemias?EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 6 2010Stefan Amatschek Eur J Clin Invest 2010; 40 (6): 552,560 Abstract Background, Renal reabsorption of inorganic phosphate is critical for the maintenance of phosphate homeostasis. The sodium dependent phosphate cotransporters NaPi-IIa and NaPi-IIc have been identified to fulfill this task at the brush border membrane of proximal tubule cells. Various factors including dietary phosphate intake, parathyroid hormone, or the so called phosphatonins such as FGF23 have been shown to regulate activity of these transporters. Design, This review seeks to give an update on our current knowledge about regulatory mechanisms involved in human renal phosphate reabsorption. Results, Recently, an increasing number of genes have been identified that are directly associated with inherited phosphate wasting disorders (Klotho, PHEX, DMP1 and NHERF1). Several of these genes are predominantly expressed by osteocytes and osteoclasts in the bone suggesting indispensable signalling pathways between kidneys and the skeleton. Conclusion, In this review, the affected gene products in these inherited hypophosphataemias and their contribution to phosphate homeostasis are discussed. [source] Expression of Pit2 sodium-phosphate cotransporter during murine odontogenesis is developmentally regulatedEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2006Dawei Zhao Different sodium-dependent inorganic phosphate (Pi) uptake mechanisms play a major role in cellular Pi homeostasis. The function and detailed distribution patterns of the type III Na+ -phosphate cotransporter, PiT-2, in different organs during development are still largely unknown. We therefore examined the temporospatial expression patterns of Pit2 during murine odontogenesis. Odontoblasts were always devoid of Pit2 expression, whereas a transient, but strong, expression was detected in young secretory ameloblasts. However, the stratum intermedium and, later on, the papillary layer and cells of the subodontoblastic layer, exhibited high levels of Pit2 mRNA, which increased gradually as the tooth matured. Hormonal treatment or Pi starvation of tooth germs in vitro did not alter Pit2 levels or patterns of expression, indicating mechanisms of regulation different from those of PiT-1 or other cell types. PiT-2 also functions as a retroviral receptor, and functional membrane-localized protein was confirmed throughout the dental papilla/pulp by demonstrating cellular permissiveness to infection by a gammaretrovirus that uses PiT-2 as a receptor. The distinct pattern of Pit2 expression during odontogenesis suggests that its Pi -transporter function may be important for homeostasis of dental cells and not specifically for mineralization of the dental extracellular matrices. The expression of viral receptors in enamel-forming cells and the dental pulp may be of pathological significance. [source] Casein phosphopeptide promotion of calcium uptake in HT-29 cells , relationship between biological activity and supramolecular structureFEBS JOURNAL, Issue 19 2007Claudia Gravaghi Casein phosphopeptides (CPPs) form aggregated complexes with calcium phosphate and induce Ca2+ influx into HT-29 cells that have been shown to be differentiated in culture. The relationship between the aggregation of CPPs assessed by laser light scattering and their biological effect was studied using the CPPs ,-CN(1,25)4P and ,s1 -CN(59,79)5P, the commercial mixture CPP DMV, the ,cluster sequence' pentapeptide, typical of CPPs, and dephosphorylated ,-CN(1,25)4P, [,-CN(1,25)0P]. The biological effect was found to be: (a) maximal with ,-CN(1,25)4P and null with the ,cluster sequence'; (b) independent of the presence of inorganic phosphate; and (c) maximal at 4 mmol·L,1 Ca2+. The aggregation of CPP had the following features: (a) rapid occurrence; (b) maximal aggregation by ,-CN(1,25)4P with aggregates of 60 nm hydrodynamic radius; (c) need for the concomitant presence of Ca2+ and CPP for optimal aggregation; (d) lower aggregation in Ca2+ -free Krebs/Ringer/Hepes; (e) formation of bigger aggregates (150 nm radius) with ,-CN(1,25)0P. With both ,-CN(1,25)4P and CPP DMV, the maximum biological activity and degree of aggregation were reached at 4 mmol·L,1 Ca2+. [source] Purification and characterization of the single-strand-specific and guanylic-acid-preferential deoxyribonuclease activity of the extracellular nuclease from Basidiobolus haptosporusFEBS JOURNAL, Issue 16 2000Neelam A. Desai An extracellular nuclease from Basidiobolus haptosporus (designated as nuclease Bh1) was purified to homogeneity by ammonium sulfate precipitation, heat treatment, negative adsorption on DEAE-cellulose, and chromatography on phenyl-Sepharose followed by FPLC on phenyl-Superose. The overall yield was 26%. The Mr of the purified enzyme, determined by gel filtration, was 41 000 whereas by SDS/PAGE (after deglycosylation) it was 30 000. It is a glycoprotein with a pI of 6.8. The optimum pH and temperature for DNA hydrolysis were 8.5 and 60 °C, respectively. Nuclease Bh1 is a metalloprotein but has no obligate requirement for metal ions to be active, nor is its activity stimulated in the presence of metal ions. The enzyme was inhibited by Zn2+, Ag2+, Hg2+, Fe3+ and Al3+, inorganic phosphate, pyrophosphate, dithiothreitol, 2-mercaptoethanol, NaCl and KCl. It was stable to high concentrations of organic solvents and urea but susceptible to low concentrations of SDS and guanidine hydrochloride. Nuclease Bh1 is a multifunctional enzyme and its substrate specificity is in the order of ssDNA , 3,AMP , RNA > dsDNA. Studies on its mode of action showed that it cleaved supercoiled pUC 18 DNA and phage M13 DNA, endonucleolytically, generating single base nicks. The enzyme hydrolyzed DNA with preferential liberation of 5,dGMP, suggesting it to be a guanylic acid preferential endoexonuclease. 5,dGMP, the end product of hydrolysis, was a competitive inhibitor of the enzyme. The absence of 5,dCMP as a hydrolytic product, coupled with the resistance of (dC)10 and deoxyribodinucleoside monophosphates having cytosine either at the 3, or the 5, end, indicates that C-linkages are resistant to cleavage by nuclease Bh1. [source] Phytase activity in Cryptococcus laurentii ABO 510FEMS YEAST RESEARCH, Issue 3 2007Jason Van Staden Abstract Ten Cryptococcus strains were screened for phytase activity, of which the Cryptococcus laurentii ABO 510 strain showed the highest level of activity. The cell wall-associated enzyme displayed temperature and pH optima of 62°C and 5.0, respectively. The enzyme was thermostable at 70°C, with a loss of 40% of its original activity after 3 h. The enzyme was active on a broad range of substrates, including ATP, d -glucose 6-phosphate, d -fructose 1,6-diphosphate and p -nitrophenyl phosphate (p -NPP), but its preferred substrate was phytic acid (Km of 21 ,M). The enzyme activity was completely inhibited by 0.5 mM inorganic phosphate or 5 mM phytic acid, and moderately inhibited in the presence of Hg2+, Zn2+, Cd2+ and Ca2+. These characteristics suggest that the Cry. laurentii ABO 510 phytase may be considered for application as an animal feed additive to assist in the hydrolysis of phytate complexes to improve the bioavailability of phosphorus in plant feedstuff. [source] Fibroblast growth factor 23 reduces expression of type IIa Na+/Pi co-transporter by signaling through a receptor functionally distinct from the known FGFRs in opossum kidney cellsGENES TO CELLS, Issue 5 2005Xiaomei Yan Fibroblast growth factor (FGF) 23 is an important phosphaturic factor that inhibits inorganic phosphate (Pi) reabsorption from the renal proximal tubule. Its overproduction and proteolysis-resistant mutation such as R179Q cause tumor-induced osteomalacia and autosomal dominant hypophosphatemic rickets, respectively. To clarify the signaling mechanisms of FGF23 that mediate the reduction of Pi reabsorption, we inhibited the function of the known FGFRs in opossum kidney (OK-E) cells by expressing a dominant-negative (DN) form of FGFR. OK-E cells, which represent the renal proximal tubular cells, expressed all four known FGFRs. FGF23(R179Q) bound to and activated FGFR2, a prominent FGFR expressed in OK-E cells. The activated receptor transmitted a signal to increase the expression of type IIa Na+/Pi co-transporter and the Pi uptake. Expression of FGFR2(DN), which suppresses the major FGFR-mediated signal through the FRS2,-ERK pathway, reversed the function of FGF23(R179Q). When FGF23(R179Q) was applied to the basolateral side of polarized OK-E cells, regardless of the FGFR2(DN) expression, the apical Pi uptake decreased significantly. The apical application of FGF23(R179Q) in the polarized cells did not show such decrease but increase. The exogenously expressed FGFR2 was detectable only at the apical membrane. These results suggest that an FGF23 receptor, which is functionally distinct from the known FGFRs, is expressed at the basolateral membrane of OK-E cells. [source] Biogeochemical changes induced in uranium mining waste pile samples by uranyl nitrate treatments under anaerobic conditionsGEOBIOLOGY, Issue 3 2009A. GEISSLER Response of the subsurface soil bacterial community of a uranium mining waste pile to treatments with uranyl nitrate over different periods of time was studied under anaerobic conditions. The fate of the added U(VI) without supplementation with electron donors was investigated as well. By using 16S rRNA gene retrieval, we demonstrated that incubation with uranyl nitrate for 4 weeks resulted in a strong reduction in and even disappearance of some of the most predominant bacterial groups of the original sample. Instead, a strong proliferation of denitrifying and uranium-resistant populations of Rahnella spp. from Gammaproteobacteria and of Firmicutes occurred. After longer incubations for 14 weeks with uranyl nitrate, bacterial diversity increased and populations intrinsic to the untreated samples such as Bacteroidetes and Deltaproteobacteria propagated and replaced the above-mentioned uranium-resistant groups. This indicated that U(VI) was immobilized. Mössbauer spectroscopic analysis revealed an increased Fe(III) reduction by increasing the incubation time from four to 14 weeks. This result signified that Fe(III) was used as an electron acceptor by the bacterial community established at the later stages of the treatment. X-ray absorption spectroscopic analysis demonstrated that no detectable amounts of U(VI) were reduced to U(IV) in the time frames of the performed experiments. The reason for this observation is possibly due to the low level of electron donors in the studied oligotrophic environment. Time-resolved laser-induced fluorescence spectroscopic analysis demonstrated that most of the added U(VI) was bound by organic or inorganic phosphate phases both of biotic origin. [source] Redox control of N:P ratios in aquatic ecosystemsGEOBIOLOGY, Issue 2 2009T. M. QUAN ABSTRACT The ratio of dissolved fixed inorganic nitrogen to soluble inorganic phosphate (N:P) in the ocean interior is relatively constant, averaging ~16 : 1 by atoms. In contrast, the ratio of these two elements spans more than six orders of magnitude in lakes and other aquatic environments. To understand the factors influencing N:P ratios in aquatic environments, we analyzed 111 observational datasets derived from 35 water bodies, ranging from small lakes to ocean basins. Our results reveal that N:P ratios are highly correlated with the concentration of dissolved O2 below ~100 µmol L,1. At higher concentrations of O2, N:P ratios are highly variable and not correlated with O2; however, the coefficient of variation in N:P ratios is strongly related to the size of the water body. Hence, classical Redfield ratios observed in the ocean are anomalous; this specific elemental stoichiometry emerges not only as a consequence of the elemental ratio of the sinking flux of organic matter, but also as a result of the size of the basins and their ventilation. We propose that the link between N:P ratios, basin size and oxygen levels, along with the previously determined relationship between sedimentary ,15N and oxygen, can be used to infer historical N:P ratios for any water body. [source] Sucrose phosphorylase of the rumen bacterium Pseudobutyrivibrio ruminis strain AJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2009A. Kasperowicz Abstract Aims:, To verify the taxonomic affiliation of bacterium Butyrivibrio fibrisolvens strain A from our collection and to characterize its enzyme(s) responsible for digestion of sucrose. Methods and Results:, Comparison of the 16S rRNA gene of the bacterium with GenBank showed over 99% sequence identity to the species Pseudobutyrivibrio ruminis. Molecular filtration, native electrophoresis on polyacrylamide gel, zymography and thin layer chromatography were used to identify and characterize the relevant enzyme. An intracellular sucrose phosphorylase with an approximate molecular mass of 52 kDa exhibiting maximum activity at pH 6·0 and temperature 45°C was identified. The enzyme was of inducible character and catalysed the reversible conversion of sucrose to fructose and glucose-1-P. The reaction required inorganic phosphate. The Km for glucose-1-P formation and fructose release were 3·88 × 10,3 and 5·56 × 10,3 mol l,1 sucrose, respectively , while the Vmax of the reactions were ,0·579 and 0·9 ,mol mg protein,1 min,1. The enzyme also released free glucose from glucose phosphate. Conclusion:,Pseudobutyrivibrio ruminis strain A utilized sucrose by phosphorolytic cleavage. Significance and Impact of the Study:, Bacterium P. ruminis strain A probably participates in the transfer of energy from dietetary sucrose to the host animal. [source] The Assembly and Remodeling of the Extracellular Matrix in the Growth Plate in Relationship to Mineral Deposition and Cellular Hypertrophy: An In Situ Study of Collagens II and IX and Proteoglycan,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2002Fackson Mwale Abstract The recent development of new specific immunoassays has provided an opportunity to study the assembly and resorption of type II and IX collagens of the extracellular matrix in relationship to endochondral calcification in situ. Here, we describe how in the bovine fetal physis prehypertrophic chondrocytes deposit an extensive extracellular matrix that, initially, is rich in both type II and type IX collagens and proteoglycan (PG; principally, aggrecan). The majority of the ,1(IX)-chains lack the NC4 domain consistent with our previous studies with cultured chondrocytes. During assembly, the molar ratio of type II/COL2 domain of the ,1(IX)-chain varied from 8:1 to 25:1. An increase in the content of Ca2+ and inorganic phosphate (Pi) was initiated in the prehypertrophic zone when the NC4 domain was removed selectively from the ,1(IX)-chain. This was followed by the progressive loss of the ,1(IX) COL2 domain and type II collagen. In the hypertrophic zone, the Ca2+/Pi molar ratio ranged from 1.56 to a maximum of 1.74, closely corresponding to that of mature hydroxyapatite (1.67). The prehypertrophic zone had an average ratio Ca2+/Pi ranging from 0.25 to 1, suggesting a phase transformation. At hypertrophy, when mineral content was maximal, type II collagen was reduced maximally in content coincident with a peak of cleavage of this molecule by collagenase when matrix metalloproteinase 13 (MMP-13) expression was maximal. In contrast, PG (principally aggrecan) was retained when hydroxyapatite was formed consistent with the view that this PG does not inhibit and might promote calcification in vivo. Taken together with earlier studies, these findings show that matrix remodeling after assembly is linked closely to initial changes in Ca2+ and Pi to subsequent cellular hypertrophy and mineralization. These changes involve a progressive and selective removal of types II and IX collagens with the retention of the PG aggrecan. [source] Inorganic phosphate as a signaling molecule in osteoblast differentiation,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2003George R. Beck Jr. Abstract The spatial and temporal coordination of the many events required for osteogenic cells to create a mineralized matrix are only partially understood. The complexity of this process, and the nature of the final product, demand that these cells have mechanisms to carefully monitor events in the extracellular environment and have the ability to respond through cellular and molecular changes. The generation of inorganic phosphate during the process of differentiation may be one such signal. In addition to the requirement of inorganic phosphate as a component of hydroxyapatite mineral, Ca10(PO4)6(OH)2, a number of studies have also suggested it is required in the events preceding mineralization. However, contrasting results, physiological relevance, and the lack of a clear mechanism(s) have created some debate as to the significance of elevated phosphate in the differentiation process. More recently, a number of studies have begun to shed light on possible cellular and molecular consequences of elevated intracellular inorganic phosphate. These results suggest a model in which the generation of inorganic phosphate during osteoblast differentiation may in and of itself represent a signal capable of facilitating the temporal coordination of expression and regulation of multiple factors necessary for mineralization. The regulation of protein function and gene expression by elevated inorganic phosphate during osteoblast differentiation may represent a mechanism by which mineralizing cells monitor and respond to the changing extracellular environment. J. Cell. Biochem. 90: 234,243, 2003. Published 2003 Wiley-Liss, Inc. [source] Extension of the Pre-rigor Period in Ischemic White Muscle from Yellow-eye Mullet Aldrichetta forsteri) and New Zealand Snapper (Pagrus auratus) as Affected by Hyperbaric Oxygen TreatmentJOURNAL OF FOOD SCIENCE, Issue 4 2004S. E. Black ABSTRACT: Chemical anesthesia (AQUI-STM Plus) was used to harvest tank-rested yellow-eye mullet (Aldrichetta forsteri) and snapper (Pagrus auratus) in a "rested" state. Fillets were stored at half the acclimated temperature under hyperbaric, hyperoxic conditions and compared with fillets stored under normobaric, hyperoxic conditions. Postmortem (PM) changes in white muscle (WM) cut-surface pH and key metabolites (lactate, adenosine triphosphate [ATP], and inorganic phosphate [Pi]) were measured. Hyperbaric, hyperoxic storage extended the pre-rigor period in the rested WM by delaying PM changes. Prolongation of pre-rigor was greatest in rested snapper WM. This was attributed to an extended period of aerobic metabolism in PM rested WM. [source] Inorganic phosphate has a crucial effect on Cry3Aa , -endotoxin productionLETTERS IN APPLIED MICROBIOLOGY, Issue 4 2005A. Kurt Abstract Aims:, The study aimed at increasing Cry3Aa , -endotoxin production by a local isolate of Bacillus thuringiensis (B.t. strain Mm2). To this end, different nutritional conditions were tested for their effects on Cry3Aa yields. Methods and Results:,Bacillus thuringiensis Mm2 was grown by shaking at 30°C in different media. Samples were taken from the cultures at intervals and used for protein extraction. SDS-PAGE was performed for toxin analysis. Inclusion of inorganic phosphate (Pi) into the Difco's sporulation medium at an increased level of 200 mmol l,1 caused a fivefold increase (from 3 to 15·6 ,g ml,1) in toxin production. Omission of FeSO4 from the medium decreased this yield by half. Resuspension experiments suggested catabolite repression of toxin biosynthesis by glucose. The inclusion of high Pi invariably increased toxin synthesis, even in the absence of sugars. Conclusions:, Inorganic phosphate had the most striking effect on toxin biosynthesis. Iron effect was found to be unique to our isolate whereas Pi effect seemed to be common to the biosynthesis of Cry3Aa-type toxins. Stimulation of toxin synthesis by Pi did not seem to represent a relief from glucose repression. Significance and Impact of the Study:,Bacillus thuringiensis is the most versatile biopesticide for use in pest management. Regarding cost-effectiveness of related fermentations, high Pi supplement drastically increases Coleoptera-specific toxin synthesis. [source] Biliary inorganic phosphate as a tool for assessing cold preservation-reperfusion injury: A study in the isolated perfused rat liver modelLIVER TRANSPLANTATION, Issue 2 2003Luciana L. Almada Ischemia-reperfusion injury is a major cause of early graft dysfunction after liver transplantation. The bile flow has been suggested as an index of ischemic damage, and severely impaired bile flow seems to be predictive of poor survival in experimental studies. Looking for injury markers, biliary inorganic phosphate has the potential of being a useful endogenous marker of diminished hepatobiliary function because this anion is excreted in the bile by a paracellular pathway and it can detect changes in permeability. The goal of this study was to evaluate the effects of cold preservation-reperfusion of the liver on bile flow and bile inorganic phosphate and their relationship with storage-related graft failure. The isolated and perfused rat liver was used to evaluate the injury for ischemia-reperfusion. The intrahepatic resistance, lactate dehydrogenase release, and potassium and biliary inorganic phosphate concentration were used to estimate viability and function of freshly isolated or cold-preserved livers. The intrahepatic resistance and the bile flow were consistent and significantly decreased throughout the perfusion time in relation to the increment in storage. Inorganic phosphate is more concentrated in bile from preserved livers, showing an alteration in paracellular pathway, confirmed by the biliary excretion of horseradish peroxidase. After preservation, concentration and excretion of the paracellular marker were increased during the first peak. The second peak appears earlier in preserved livers (10 minutes) with a different shape but without changes in concentration. In conclusion, inorganic phosphate in bile shows changes in paracellular permeability as occurs in livers after 48 hours of cold preservation. [source] Measurement of spin-lattice relaxation times and chemical exchange rates in multiple-site systems using progressive saturationMAGNETIC RESONANCE IN MEDICINE, Issue 1 2007Craig J. Galbán Abstract A new method for measuring spin-lattice relaxation times and chemical exchange (CE) rate constants in multiple-site exchanging systems is described. The method, chemical exchange and T1 measurement using progressive saturation (CUPS), was applied to determine T1s and analyze phosphorus exchange among phosphocreatine (PCr), ATP, and inorganic phosphate (Pi), mediated by creatine kinase (CK) and ATP synthase, using 31P-MRS. Two-site exchange was analyzed in vitro and in the rat leg, and three-site exchange was analyzed in the rat heart. Data were fitted to a model of progressive saturation incorporating T1 relaxation and CE. For the in vitro system at 8.45T, we found T1(PCr) = 2.86 s and T1(,-ATP) = 1.72 s. For the rat gastrocnemius at 1.9T, we found T1(PCr) = 6.60 s and T1(,-ATP) = 2.06 s. For the rat heart at 9.4T, we found T1(PCr) = 3.35 s, T1(,-ATP) = 0.69 s, and T1(Pi) = 1.83 s. All of these values were within 20% of literature values. Similarly, the determined exchange rates were in the same range as published values. Using simulations, we compared CUPS with transient saturation transfer as a method for measuring T1s and rates. The two methods showed similar sensitivity to noise. We conclude that CUPS is a viable alternative for measuring T1s and CE rates in exchanging systems. Magn Reson Med 58:8,18, 2007. © 2007 Wiley-Liss, Inc. [source] An efflux transporter PbrA and a phosphatase PbrB cooperate in a lead-resistance mechanism in bacteriaMOLECULAR MICROBIOLOGY, Issue 2 2009Anu Hynninen Summary The gene cluster pbrTRABCD from Cupriavidus metallidurans CH34 is thought to encode a unique, specific resistance mechanism for lead. However, the exact functions of these genes are unknown. In this study we examine the metal specificity and functions of pbrABCD by expressing these genes in different combinations and comparing their ability to restore Pb2+, Zn2+ and Cd2+ resistance in a metal-sensitive C. metallidurans strain DN440. We show that lead resistance in C. metallidurans is achieved through the cooperation of the Zn/Cd/Pb-translocating ATPase PbrA and the undecaprenyl pyrophosphate phosphatase PbrB. While PbrA non-specifically exported Pb2+, Zn2+ and Cd2+, a specific increase in lead resistance was observed when PbrA and PbrB were coexpressed. As a model of action for PbrA and PbrB we propose a mechanism where Pb2+ is exported from the cytoplasm by PbrA and then sequestered as a phosphate salt with the inorganic phosphate produced by PbrB. Similar operons containing genes for heavy metal translocating ATPases and phosphatases were found in several different bacterial species, suggesting that lead detoxification through active efflux and sequestration is a common lead-resistance mechanism. [source] Expression of the Pho regulon negatively regulates biofilm formation by Pseudomonas aureofaciens PA147-2MOLECULAR MICROBIOLOGY, Issue 2 2001Russell D. Monds We report the isolation of insertional mutations to the pstC and pstA genes of the phosphate-specific transport (pst) operon that results in loss of biofilm formation by Pseudomonas aureofaciens PA147-2. Consistent with the known roles of the Pst system in Escherichia coli and Pseudomonas aeruginosa, both P. aureofaciens pst mutants were demonstrated to have defects in inorganic phosphate (Pi) transport and repression of Pho regulon expression. Subsequently, biofilm formation by the wild type was shown to require a threshold concentration of extracellular Pi. The two-component regulatory pair PhoR/PhoB is responsible for upregulation of Pho regulon expression in response to Pi -limiting environments. By generating phoR mutants that were unable to express the Pho regulon, we were able to restore biofilm formation by P. aureofaciens in Pi -limiting conditions. This result suggests that gene(s) within the Pho regulon act to regulate biofilm formation negatively in low-Pi environments, and that phoR mutations uncouple PA147-2 from such regulatory constraints. Furthermore, the inability of pst mutants to repress Pho regulon expression accounts for their inability to form biofilms in non-limiting Pi environments. Preliminary evidence suggests that the Pst system is also required for antifungal activity by PA147-2. During phenotypic analysis of pst mutants, we also uncovered novelties in relation to Pi assimilation and Pho regulon control in P. aureofaciens. [source] Caffeine impairs intramuscular energy balance in patients susceptible to malignant hyperthermiaMUSCLE AND NERVE, Issue 3 2003Zoran Textor MD Abstract Malignant hyperthermia (MH) is a metabolic myopathy with an abnormal release of calcium by the sarcoplasmic reticulum (SR), triggered by volatile anesthetics and succinylcholine. Similarly, caffeine enhances Ca2+release by the SR in vitro. In a prospective, randomized study, high-energy phosphates were studied by intramuscular 31-phosphorus magnetic resonance spectroscopy (31P-MRS) in 10 MH-susceptible (MHS) and 7 MH-nonsusceptible (MHN) subjects before and after injection of 0.5 ml caffeine (20 mM). Intramuscular energy balance, measured by the ratios of Pi/PCr and Pi/,-ATP, did not differ between MHS and MHN patients before and after intramuscular caffeine injection. However, within each group, Pi/PCr and Pi/,-ATP increased significantly only in the MHS group. Intramuscular caffeine injection seemed to impair the metabolic balance in MHS individuals. This may reflect a local calcium overload leading to consumption of high-energy phosphates and increase of inorganic phosphate. Intramuscular stimulation by caffeine and 31P-MRS may provide a valuable tool to investigate MH-related metabolic disturbances. Muscle Nerve 28: 353,358, 2003 [source] In vivo31P MRS detection of an alkaline inorganic phosphate pool with short T1 in human resting skeletal muscleNMR IN BIOMEDICINE, Issue 8 2010H. E. Kan Abstract Non-invasive determination of mitochondrial content is an important objective in clinical and sports medicine. 31P MRS approaches to obtain information on this parameter at low field strength typically require in-magnet exercise. Direct observation of the intra-mitochondrial inorganic phosphate (Pi) pool in resting muscle would constitute an alternative, simpler method. In this study, we exploited the higher spectral resolution and signal-to-noise at 7T to investigate the MR visibility of this metabolite pool. 31P in vivo MR spectra of the resting soleus (SOL) muscle were obtained with 1H MR image-guided surface coil localization (six volunteers) and of the SOL and tibialis anterior (TA) muscle using 2D CSI (five volunteers). A resonance at a frequency 0.38,ppm downfield from the cytosolic Pi resonance (Pi1; pH 7.0,±,0.04) was reproducibly detected in the SOL muscle in all subjects and conditionally attributed to the intra-mitochondrial Pi pool (Pi2; pH 7.3,±,0.07). In the SOL muscle, the Pi2/Pi1 ratio was 1.6 times higher compared to the TA muscle in the same individual. Localized 3D CSI results showed that the Pi2 peak was present in voxels well away from blood vessels. Determination of the T1 of the two Pi pools in a single individual using adiabatic excitation of the spectral region around 5,ppm yielded estimates of 4.3,±,0.4 s vs 1.4,±,0.5 s for Pi1 and Pi2, respectively. Together, these results suggest that the intra-mitochondrial Pi pool in resting human skeletal muscle may be visible with 31P MRS at high field. Copyright © 2010 John Wiley & Sons, Ltd. [source] Brain temperature and pH measured by 1H chemical shift imaging of a thulium agentNMR IN BIOMEDICINE, Issue 2 2009Daniel Coman Abstract Temperature and pH are two of the most important physiological parameters and are believed to be tightly regulated because they are intricately related to energy metabolism in living organisms. Temperature and/or pH data in mammalian brain are scarce, however, mainly because of lack of precise and non-invasive methods. At 11.7,T, we demonstrate that a thulium-based macrocyclic complex infused through the bloodstream can be used to obtain temperature and pH maps of rat brain in vivo by 1H chemical shift imaging (CSI) of the sensor itself in conjunction with a multi-parametric model that depends on several proton resonances of the sensor. Accuracies of temperature and pH determination with the thulium sensor , which has a predominantly extracellular presence , depend on stable signals during the course of the CSI experiment as well as redundancy for temperature and pH sensitivities contained within the observed signals. The thulium-based method compared well with other methods for temperature (1H MRS of N -acetylaspartate and water; copper,constantan thermocouple wire) and pH (31P MRS of inorganic phosphate and phosphocreatine) assessment, as established by in vitro and in vivo studies. In vitro studies in phantoms with two compartments of different pH value observed under different ambient temperature conditions generated precise temperature and pH distribution maps. In vivo studies in , -chloralose-anesthetized and renal-ligated rats revealed temperature (33,34°C) and pH (7.3,7.4) distributions in the cerebral cortex that are in agreement with observations by other methods. These results show that the thulium sensor can be used to measure temperature and pH distributions in rat brain in vivo simultaneously and accurately with using biosensor imaging of redundant. Copyright © 2008 John Wiley & Sons, Ltd. [source] Alterations in inorganic phosphate in mouse hindlimb muscles during limb disuse,NMR IN BIOMEDICINE, Issue 2 2008Neeti Pathare Abstract Muscle disuse induces a wide array of structural, biochemical, and neural adaptations in skeletal muscle, which can affect its function. We recently demonstrated in patients with an orthopedic injury that cast immobilization alters the resting Pi content of skeletal muscle, which may contribute to loss of specific force. The goal of this study was to determine the direct effect of disuse on the basal phosphate content in skeletal muscle in an animal model, avoiding the confounding effects of injury/surgery. 31P and 1H MRS data were acquired from the gastrocnemius muscle of young adult mice (C57BL6 female, n,=,8), at rest and during a reversible ischemia experiment, before and after 2 weeks of cast immobilization. Cast immobilization resulted in an increase in resting Pi content (75%; p,<,0.001) and the Pi to phosphocreatine (PCr) ratio (Pi/PCr; 80%, p,<,0.001). The resting concentrations of ATP, PCr and total creatine (PCr,+,creatine) and the intracellular pH were not significantly different after immobilization. During ischemia (30,min), PCr concentrations decreased to 54,±,2% and 52,±,6% of the resting values in pre-immobilized and immobilized muscles, respectively, but there were no detectable differences in the rates of Pi increase or PCr depletion (0.55,±,0.01,mM min,1 and 0.52,±,0.03,mM min,1 before and after immobilization, respectively; p,=,0.78). At the end of ischemia, immobilized muscles had a twofold higher phosphorylation potential ([ADP][Pi]/[ATP]) and intracellular buffering capacity (3.38,±,0.54 slykes vs 6.18,±,0.57 slykes). However, the rate of PCr resynthesis (kPCr) after ischemia, a measure of in vivo mitochondrial function, was significantly lower in the immobilized muscles (0.31,±,0.04,min,1) than in pre-immobilized muscles (0.43,±,0.04,min,1). In conclusion, our findings indicate that 2 weeks of cast immobilization, independent of injury-related alterations, leads to a significant increase in the resting Pi content of mouse skeletal muscle. The increase in Pi with muscle disuse has a significant effect on the cytosolic phosphorylation potential during transient ischemia and increases the intracellular buffering capacity of skeletal muscle. Copyright © 2007 John Wiley & Sons, Ltd. [source] Kinetics of PME/Pi in pig kidneys during cold ischemiaNMR IN BIOMEDICINE, Issue 7 2007Dominik von Elverfeldt Abstract Quality assessment of renal grafts via 31P magnetic resonance spectroscopy (MRS) has been investigated since 1986. As ATP concentrations decay rapidly during cold ischemia, the ratio of phosphomonoesters (PME) to inorganic phosphate (PiO) within the organ (PME/PiO) is commonly used as a quality marker and is considered to be the most reliable parameter. MRS did not lead to any delay in the transplantation procedure since it was performed during the time necessary for immunological matching (cross-match). Differences in the time period until transplantation call for extrapolation of the measured ratio to the end of cold ischemia before correlating with graft performance after transplantation. Therefore, quantitative determination of PME/PiO kinetics is essential. As a model for metabolite decay in human renal grafts, pig kidneys obtained from a slaughterhouse were monitored for up to 80,h via 31P MRS at 2,T. By employing chemical shift imaging (CSI) with a spatial resolution of approximately 1,×,1,×,4,cm3, it was possible to reduce partial volume effects significantly. The improved spectral resolution gained through CSI enabled reliable PME/PiO ratios to be determined only from those voxels containing renal tissue. Spectra were fitted automatically using the magnetic resonance user interface (MRUI), with prior knowledge obtained from unlocalized spectra when necessary. A monoexponential time dependence of PME/PiO for histidine,tryptophane,alpha-ketoglutarate (HTK)-perfused kidneys during cold ischemia was observed, and the determined value of the decay constant , was 0.0099,±,0.0012,h,1. In University of Wisconsin solution (UW)-perfused kidneys, an , of 0.0183,±,0.0053,h,1 was determined. Determination of the decay constant enables a usable extrapolation of PME/PiO for quality assessment of UW perfusion and a reliable extrapolation for HTK-perfused human renal grafts. Copyright © 2007 John Wiley & Sons, Ltd. [source] Monitoring acute inflammatory processes in mouse muscle by MR imaging and spectroscopy: a comparison with pathological resultsNMR IN BIOMEDICINE, Issue 3 2002Jesús Ruiz-Cabello Abstract We have studied an animal model of acute local inflammation in muscle induced by Aspergillus fumigatus by using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). We have compared our data to those found using histopathology and segmentation maps obtained by the mathematical processing of three-dimensional T2 -weighted MRI data via a neural network. The MRI patterns agreed satisfactorily with the clinical and biological evidence of the phases of acute local infection and its evolution towards chronicity. The MRS results show a statistically significant increase in inorganic phosphate and a significant decrease in phosphocreatine levels in the inflamed region. Image segmentation made with a self-organizing, neural-network map yielded a set of ordered representatives that remained constant for all animals during the inflammatory process, allowing a non-invasive, three-dimensional identification and quantification of the inflamed infected regions by MRI. Copyright © 2002 John Wiley & Sons, Ltd. [source] Stimulated whole salivary flow rate and composition in menopausal women with oral dryness feelingORAL DISEASES, Issue 3 2007F Agha-Hosseini The aim of this study was to compare stimulated whole saliva flow rate and composition of menopausal women with/without oral dryness (OD) feeling. A case,control study was carried out in 42 selected menopausal women aged 52,73 years with or without OD feeling (21 as case and 21 as control) conducted at the Clinic of Oral Medicine, Tehran University of Medical Sciences. Paraffin-stimulated saliva samples were obtained by expectoration. The stimulated whole saliva composition was measured by a spectrophotometer [magnesium (Mg+2), calcium (Ca+2), chloride (Cl,), inorganic phosphate (Pi) and total protein], flame-photometry [sodium (Na+)] and ion selective electrode (ISE) [potassium (K+)] methods. No significant differences were found in stimulated whole saliva flow rate, Mg+2, Cl,, Pi, Na+, K+ and total protein concentrations between the two groups, but the mean calcium concentration was significantly higher in cases than in controls (P = 0.003). It seems that the level of salivary calcium concentration may be higher in menopausal women with OD feeling than in the control group. [source] Functional genomics of phosphate antiport systems of plastidsPHYSIOLOGIA PLANTARUM, Issue 4 2003Ulf-Ingo Flügge Plant cells require a co-ordination of metabolism between their major compartments, the plastids and the cytosol, in particular as certain metabolic pathways are confined to either compartments. The inner envelope membrane of the plastids forms the major barrier for metabolite exchange and is the site for numerous transport proteins, which selectively catalyse metabolite exchanges characteristic for green and/or non-green tissues. This report is focused on the molecular biology, evolution and physiological function of the family of phosphate translocators (PT) from plastids. Until now, four distinct subfamilies have been identified and characterized, which all share inorganic phosphate as common substrate, but have different spectra of counter exchange substrates to fulfil the metabolic needs of individual cells and tissues. The PTs are named after their main transported substrate, triose phosphate (TPT), phosphoenolpyruvate (PPT), glucose 6-phosphate (GPT) and xylulose 5-P (XPT). All PTs belong to the TPT/nucleotide sugar transporter (NST) superfamily, which includes yet uncharacterized PT homologues from plants and other eukaryotes. Transgenic plants or mutants with altered transport activity of some of the PTs have been generated or isolated. The analysis of these plant lines revealed new insights in the co-ordination and flexibility of plant metabolism. [source] Neural damage due to temporal lobe epilepsy: Dual-nuclei (proton and phosphorus) magnetic resonance spectroscopy studyPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 1 2004TAKAYUKI OBATA md Abstract, The aim of this study was to evaluate the usefulness of proton and phosphorus (1H and 31P) magnetic resonance spectroscopy (MRS) for temporal lobe epilepsy (TLE) patients, and to evaluate neural damage and metabolite dysfunction in the TLE patient brain. We performed 1H and 31P MRS of medial temporal lobes (MTL) in the same TLE patients (n = 14) with a relatively wide range of severity from almost seizure-free to intractable, and calculated the ratio of N-acetylasparate to choline-containing compounds and creatine + phosphocreatine (NAA/Cho + Cr) in 1H MRS and inorganic phosphate to all main peaks (%Pi) in 31P MRS. There was no significant correlation between NAA/(Cho + Cr) and %Pi ,in ,each ,side ,(ipsilateral, ,r = ,0.20; ,contralateral, ,r =,0.19). The values of NAA/(Cho + Cr) showed a significant difference between ipsilateral and contralateral MTLs to the focus of TLE patients (P < 0.01, paired t -test). Although %Pi also had a tendency to show the laterality of TLE, there was no significance. Ipsilateral (r = ,0.90, P < 0.0001) and contralateral (r = ,0.70, P < 0.005) NAA/(Cho + Cr) decreases and contralateral %Pi increase (r = 0.81, P < 0.001) had significant correlation with seizure frequency. 1H MRS provides more important information concerning neuronal dysfunction in MTL of TLE patients than 31P MRS. [source] |