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PubMedDate not supplied

Assessment of the delayed neurotoxicity of tributyl phosphate, tributoxyethyl phosphate, and dibutylphenyl phosphate.

There industrial organophosphorus compounds were tested for their ability to cause organophosphorus compound-induced delayed neurotoxicity (OPIDN) in the adult hen. The compounds tested were tributyl phosphate (TBP), tributoxyethyl phosphate (TBEP), and dibutylphenyl phosphate (DBPP). The acute oral LD50 of TBP and DBPP were estimated to be 1,863 and 1,500 mg/kg, respectively, and the dose equal to the LD50 was used as a test dose. The acute oral LD50 of TBEP was greater than 5,000 mg/kg and 5,000 mg/kg was used as a test dose. An oral dose of 750 mg tri-o-cresyl phosphate (TOCP) was used as a positive control. For the acute delayed neurotoxicity test, hens were given two test doses of the test materials 21 days apart and killed 21 days after the second dose. None of the hens given TBP, TBEP, or DBPP exhibited nerve damage or clinical signs which distinguished them from untreated control animals. A single dose of TOCP resulted in paralysis and a histopathological profile typical of a distal neuropathy. For the assay of the inhibition of esterases, hens were killed 24 hours after a single dose equal to the greater of either the LD50 or 5000 mg/kg. TOCP administration resulted in over 90% inhibition of brain neurotoxic esterase (NTE), but none of the other three compounds inhibited NTE to an extent (greater than 70%) which would be expected to result in OPIDN. Administration of TOCP, TBEP, or DBPP resulted in approximately a 70% decrease in plasma butyrylcholinesterase (BuChE) activity. TBP caused a 2-3 fold increase in BuChE activity. TBEP administration resulted in about 45% inhibition of acetycholinesterase (AChE) in brain. These results indicate that TBP, TBEP, and DBPP are all unlikely to cause OPIDN with any single sublethal dose.

Animals↗
PubMed1995

Leaf Phosphate Status, Photosynthesis, and Carbon Partitioning in Sugar Beet (IV. Changes with Time Following Increased Supply of Phosphate to Low-Phosphate Plants).

Changes in photosynthesis, carbon partitioning, and growth following resupply of orthophosphate (Pi) to moderately P-deficient plants (low-P) were determined for sugar beets (Beta vulgaris L. cv F58-554H1) cultured hydroponically in growth chambers. One set of plants was supplied with 1.0 mM Pi in half-strength Hoagland solution (control plants), and a second set (low-P plants) was supplied with 0.05 mM Pi. At the end of 2 weeks, the low-P plants were resupplied with 1.0 mM Pi. Low-P plants rapidly accumulated large amounts of Pi, and the photosynthesis rate increased to control values within 4 to 6 h. The rate of photosynthesis appeared to be controlled by ribulose-1,5-bisphosphate (RuBP); low P reduced photosynthesis and RuBP levels, and P resupply increased photosynthesis and RuBP in a manner parallel with time. Low-P treatment reduced adenylate levels substantially but not nicotinamide nucleotides; adenylate levels recovered to control values over 3 to 6 h. With low P, more photosynthate is allocated to non-P carbon compounds (e.g. starch, sucrose) than to sugar phosphates. When P is resupplied, sugar phosphates increase as starch and sucrose pools decrease; this increase in leaf (chloroplast) sugar phosphates was most likely responsible for the increases in RuBP and photosynthesis and may have increased adenylate levels (through enhanced levels of ribose-5-phosphate).

Journal Article↗
PubMed1990

High-performance reversed-phase ion-pair chromatographic study of myo-inositol phosphates. Separation of myo-inositol phosphates, some common nucleotides and sugar phosphates.

A detailed study of all the major chromatographic variables affecting the retention behaviour and separation of myo-inositol phosphates in reversed-phase ion-pair chromatographic systems was carried out. The parameters studied included the eluent concentration of the pairing ion, the eluent concentration of the organic modifier and the buffer salt, the pH of the eluent, the minimum column plate count necessary for the separation of the inositol trisphosphate isomers and isocratic and gradient modes of separation. The retention behaviour of some common nucleotides and sugar phosphates was also investigated as these phosphates present chromatographic interference problems in biochemical studies based on the cellular incorporation of [32P]Pi. The separation methods developed appear to be superior to established anion-exchange separation techniques in terms of separation speed and "mildness" of the chromatographic conditions.

Chromatography, High Pressure Liquid↗
PubMed1976

The reactions of D-glyceraldehyde 3-phosphate with thiols and the holoenzyme of D-glyceraldehyde 3-phosphate dehydrogenase and of inorganic phosphate with the acyl-holoenzyme.

D-Glyceraldehyde 3-phosphate forms adducts with thiols. These adducts, which are presumed to be hemithioacetals, equilibrate rapidly with the unhydrated form of the aldehyde, which is the subtrate for D-glyceraldehyde 3-phosphate dehydrogenase. The adduct provides a substrate buffer system whereby a constant low free aldehyde concentration can be maintained during the oxidation of aldehyde by the enzyme and NAD+. With this system, the kinetics of the association of the aldehyde with the enzyme were examined. The rate profile for this reaction is a single exponential process, showing that all four active sites of the enzyme have equivalent and independent reactivity towards the aldehyde, with an apparent second-order rate constant of 5 X 10(7)M-1-S-1 at pH8.0 and 21 degrees C. The second-order rate constant becomes 8 X 10(7)M-1-S-1 when account is taken of the forward and reverse catalytic rate constants of the dehydrogenase. The pH-dependence of the observed rate constant is consistent with a requirement for the unprotonated form of a group of pK 6.1, which is the pK observed for second ionization of glyceraldehyde 3-phosphate. The rate of phosphorolysis of the acyl-enzyme intermediate during the steady-state oxidative phosphorylation of the aldehyde was studied, and is proportional to the total Pi concentration up to at least 1 mM-Pi at pH 7.5. The pH-dependence of the rate of NADH generation under these conditions can be explained by the rate law d[NADA]/dt = k[acy] holoenzyme][PO4(3-)-A1, where thioester bond, although kinetically indistinguishable rate equations for the reaction are possible. The rates of the phosphorolysis reaction and of the aldehyde-association reaction decrease with increasing ionic strength, suggesting that the active site of the enzyme has cationic groups which are involved in the reaction of the enzyme with anionic substrates.

Chemical Phenomena↗
PubMed1997

In vivo study of calcium phosphate cements: implantation of an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste.

alpha-Tricalcium phosphate (alpha-TCP)/dicalcium phosphate dibasic (DCPD)/tetracalcium phosphate monoxide (TeCP) cement was implanted in paste form into soft tissue (rate subcutaneous sockets) and bone tissue (defects in rabbit mandibles) to evaluate the setting behaviour of the cement and tissue responses to the cement. A histological study of the soft tissue implants revealed thin fibrous capsule formation, the appearance of multinucleated giant cells on and close to the cement surface, and small clusters of the cement near the main part of the set cement which were formed by the migration of the paste while setting. X-ray diffraction (XRD) analysis of the implanted cement showed peaks for hydroxyapatite (HA) which increased as the implant period increased. Histology and microradiography of the bone tissue implants showed well-set cement without migration, active bone formation around the cement and direct bone union to it. However, the cement disappeared from the implant site in 4 of 16 specimens where intense bleeding seemed to wash away the implants while setting. From the results of the present study, we concluded that the cement is well tolerated, especially by bone tissue. This may be related to the fact that the cement sets producing HA. The cement is a promising material as a bone substitute; however, there is a problem of migration while setting in soft tissue and of exclusion from the bone defects by intense bleeding.

Animals↗
PubMed1980

4-Azido-2-nitrophenyl phosphate, a new photoaffinity derivative of inorganic phosphate. Study of its interaction with the inorganic phosphate binding site of beef heart mitochondrial adenosine triphosphatase.

4-Azido-2-nitrophenyl phosphate (ANPP) was synthesized and characterized. ANPP, unlabeled or labeled by 32P, was used as a photoreactive analogue of Pi to study the Pi binding site(s) in isolated F1-ATPase and inside-out particles from beef heart mitochondria. In the dark, the phosphate bond of ANPP was cleaved by alkaline phosphatase but not by mitochondrial F1-ATPase. ANPP bound reversibly to the phosphate site of F1-ATPase as shown by competitive inhibition of binding of Pi to F1-ATPase by ANPP in the dark; the Ki value was 60 microM. Upon photoirradiation with visible light, [32P]ANPP bound covalently to F1-ATPase and inactivated the enzyme. Part of the added ANPP was, however, photolyzed with release of Pi. By extrapolation, it could be calculated that complete inactivatin of F1-ATPase was accompanied by incorporation of 32P radioactivity corresponding to 1 mol of [32P]ANPP per mol of F1-ATPase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [32P]-ANPP-labeled F1-ATPase revealed only one radioactive peptide with a Mr of 50000. This peptide was characterized as the beta subunit of F1-ATPase by specific labeling with [14C]dicyclohexylcarbodiimide [Pougeois, R., Satre, M., & Vignais, P. V. (1979) Biochemistry 18, 1408-1413]. Photoirradiation of inside-out submitochondrial particles with [32P]ANPP resulted in the labeling of two peptides with a Mr of 50000 and 30000-32000; both labelings were significantly decreased by incubation of the particles with Pi prior to photoirradiation. The Mr 50000 peptide is most probably the beta subunit of F1-ATPase; the other peptide might be the Pi carrier protein.

Adenosine Triphosphatases↗
PubMed1998

Evaluation of cytotoxicity of calcium phosphate cement consisting of alpha-tricalcium phosphate and dicalcium phosphate dihydrate.

A newly developed calcium phosphate cement, MM, was evaluated for tissue irritability by means of cell cultures. In this study, MM showed extensive mild cytotoxicity compared with other cements before setting. Inhibition of adhesion of L-929 cells was not observed after contact with MM for 24 hours. The influence of MM on colony formation was approximately the same as that of another calcium phosphate cement and less than that of a glass ionomer cement. Toxicity of MM after setting was compared with four cements; another calcium phosphate cement, glass ionomer cement, silicate cement and zinc oxide eugenol cement, but MM showed the least influence on cell morphology. Judging from these results, MM appears to be less cytotoxic than the cements in current use.

Animals↗
PubMed1992

Delayed neurotoxicity of trixylenyl phosphate and a trialkyl/aryl phosphate mixture, and the modulating effect of atropine on tri-o-tolyl phosphate-induced neurotoxicity.

Two hydraulic fluids, Fyrquel EHC (trixylenyl phosphate) and Reofos 65 (trialkyl/aryl phosphate mixture), were examined for effects of organophosphorus-induced delayed neurotoxicity (OPIDN) in hens using the OECD Test Guideline (1984). Furthermore, the influence of atropine and the concentration of tri-o-tolyl phosphate (TOTP) in the oil vehicle on the development of OPIDN were investigated. For Fyrquel EHC a neurotoxic effect was demonstrated with single oral doses of 5, 10 and 15 g/kg. Reofos 65 caused no clinical neurotoxic effect after single oral doses of 5, 10 and 15 g/kg. Redosing at day 22 with Reofos 65 did not result in clinical delayed neurotoxicity, but minor histopathological changes were found in the spinal cord and peripheral nerves. Atropine 10 mg/kg im delayed the onset of OPIDN caused by TOTP 1 g/kg po without affecting the final neurotoxic effect. Dilution of TOTP in large amounts of soybean oil vehicle reduced its neurotoxic effect. In conclusion, the neurotoxic potential of the hydraulic fluids was very low. The effect of atropine and the concentration of the test compound in oil vehicle should be taken into consideration when designing experiments on OPIDN.

Animals↗
PubMed1987

Studies on the interaction with thymidylate synthase of analogues of 2'-deoxyuridine-5'-phosphate and 5-fluoro-2'-deoxyuridine-5'-phosphate with modified phosphate groups.

The role of the phosphate moiety of dUMP, and some analogues, in their interaction with mammalian thymidylate synthase, has been investigated. Substrate and inhibitor activities, and the pH-dependence of these activities, of dUMP and 5-FdUMP, as well as analogues with modified phosphate groups, were compared. The methyl ester of dUMP was neither a substrate nor an inhibitor. By contrast, the methyl ester of 5-FdUMP was a slow-binding inhibitor of the enzyme from L1210, Ehrlich ascites carcinoma and CCRF-CEM cells, with Ki values in the micromolar range. Both 5-FdUrd and the newly synthesized 5'-methylphosphonate of 5-FdUrd were also slow-binding inhibitors of the Ehrlich carcinoma enzyme, but with Ki values in the millimolar range. The interaction of dUMP, 5-FdUMP, and the methyl ester of the latter decreased with increase in pH, whereas that of the 5'-methyl-phosphonate of 5-FdUrd remained unchanged. The results are discussed in relation to the role of the phosphate hydroxyls of dUMP in binding to the enzyme. 5-FdUMP and its analogues exhibited differing interactions with two binding sites on the enzyme molecule, consistent with cooperativity of binding. A convenient procedure is described for the synthesis of 5-fluoro-2'-deoxyuridine-5'-methylphosphonate, applicable also to the preparation of other 5'-methylphosphonate analogues.

Animals↗
PubMed2005

Evaluation of the safety of mixed tocopheryl phosphates (MTP) -- a formulation of alpha-tocopheryl phosphate plus alpha-di-tocopheryl phosphate.

The safety of a formulation of mixed tocopheryl phosphates, (MTP) was evaluated in a series of toxicological tests in vivo using rats, mice and rabbits and in vitro using bacterial and mammalian cell cultures. The tests conducted included an oral LD(50) study, three 28-day oral repeat-dose studies, two dermal toxicity tests, an ocular irritation test, mutagenic potential tests, and chromosomal aberrations tests. MTP consists of mono alpha-tocopheryl phosphate (TP) and di-tocopheryl phosphate (T(2)P) and is intended for use as a dietary supplement and for dermal applications in humans and animals. The dermal and oral LD(50) values of MTP were determined to be >1130 mg/kg bw (918 mg tocopherol equivalents/kg bw) in rabbits and rats, respectively. MTP was not a dermal or eye irritant in rabbits and showed no allergenic potential in mice. In the mutagenicity and genotoxicity studies, MTP did not increased the number of revertants in Salmonella typhimurium or Escherichia coli and did not induce chromosomal aberrations in cultured Chinese hamster ovary (CHO) cells. When administered daily for 28 days by gavage at doses up to 955 mg/kg bw/day (780 mg tocopherol equivalents/kg bw/day), MTP produced no consistent, dose-dependent adverse effects in rats.

Animals↗
PubMed1968

Genetic mapping of loci for glucose-6-phosphate dehydrogenase, gluconate-6-phosphate dehydrogenase, and gluconate-6-phosphate dehydrase in Escherichia coli.

The loci on the Escherichia coli genome of mutations affecting the constitutive enzymes glucose-6-phosphate dehydrogenase (zwf) and gluconate-6-phosphate dehydrogenase (gnd), and the inducible enzyme gluconate-6-phosphate dehydrase (edd), were determined by conjugation and transduction experiments, chiefly by three-factor crosses. They are in the same region of the chromosome, and their order is gnd-his-(edd, zwf)-aroD; gnd and his are cotransduceable, as are zwf and edd. The position of gnd in Salmonella typhimurium was shown to be similar to that in E. coli.

Chromosome Mapping↗
PubMed1986

5-Iodoribose 1-phosphate, an analog of ribose 1-phosphate. Enzymatic synthesis and kinetic studies with enzymes of purine, pyrimidine, and sugar phosphate metabolism.

The 5'-deoxy-5'-iodo-substituted analogs of adenosine and inosine are cytotoxic to tumor cells that have high activities of 5'-methylthioadenosine phosphorylase and purine nucleoside phosphorylase, respectively (Savarese, T.M., Chu, S-H., Chu, M.Y., and Parks, R. E., Jr. (1984) Biochem. Pharmacol. 34, 361-367). 5-Iodoribose 1-phosphate (5-IRib-1-P), the common intracellular metabolite of these 5'-iodonucleosides, has been synthesized enzymatically from 5'-deoxy-5'-iodoadenosine via adenosine deaminase from Aspergillus oryzae and human erythrocytic purine nucleoside phosphorylase. The purification and chemical properties of 5-IRib-1-P are described. The analog sugar phosphate inhibited purine nucleoside phosphorylase from human erythrocytes, phosphoglucomutase from rabbit muscle, and 5'-methylthioadenosine phosphorylase from Sarcoma 180 cells with Ki values of 26, 100, and 9 microM, respectively. Enzymes that react with 5-phosphoribosyl 1-pyrophosphate (P-Rib-PP), P-Rib-PP amidotransferase, hypoxanthine-guanine phosphoribosyltransferase, adenine phosphoribosyltransferase, and orotate phosphoribosyltransferase-orotidylate decarboxylase from extracts of Sarcoma 180 cells, were inhibited with Ki values of 49, 465, 307, and 275 microM, respectively. 5-IRib-1-P had no effect on P-Rib-PP synthetase. Since the Ki values of the analog sugar phosphate for 5'-methylthioadenosine phosphorylase and P-Rib-PP amidotransferase are much lower than the Km values of the natural substrates, Pi or P-Rib-PP which are reported to be present at nonsaturating concentrations under physiological conditions, these enzymes could be significantly inhibited by 5-IRib-1-P in intact cells.

Adenosine Deaminase↗
PubMed1999

Mediated, amperometric biosensor for glucose-6-phosphate monitoring based on entrapped glucose-6-phosphate dehydrogenase, Mg2+ ions, tetracyanoquinodimethane, and nicotinamide adenine dinucleotide phosphate in carbon paste.

In this study, an amperometric carbon paste biosensor is developed for glucose-6-phosphate (G6P) monitoring which is based on entrapped Mg2+ ions, G6P dehydrogenase, NADP+ polyethylenimine (PEI) and the electroactive mediator, tetracyanoquinodimethane (TCNQ). The calibration line had a slope of 1.55 x 10(-5) A. M-1 with a correlation coefficient of 0.9965. The limit of detection (defined as three times the standard deviation of the response of the electrode to blank phosphate buffer injections (noise)) of the G6P biosensor was 5.0 x 10(-5) M. The application of this biosensor for monitoring G6P in human blood using the standard addition method is also demonstrated. A two-parameter empirical equation which adequately describes the deactivation of the biosensor steady-state response with time is also proposed.

Biosensing Techniques↗
PubMed1989

Calcium phosphate cements: action of setting regulators on the properties of the beta-tricalcium phosphate-monocalcium phosphate cements.

Various additives were tested as setting retarders of the beta-tricalcium phosphate-monocalcium phosphate monohydrate (beta-TCP-MCPM) cements. Calcium pyrophosphate (CPP), calcium sulphate dihydrate (CSD) and calcium sulphate hemihydrate (CSH) were found to increase the setting time from 30 s to about 10 min. Moreover, the use of CSH resulted in a marked increase of the final diametral strength of the cement, which could be raised from 1 MPa to about 3 MPa. The best results were obtained when CSH and CPP were added together to the cement, while the addition of CSD and CPP alone only retarded the setting, without improving the final strength. A particular cement composition (64 wt% beta-TCP, 16 wt% MCPM, 15 wt% CSH and 5 wt% CPP), selected for its optimum final strength, was aged in vitro for 8 d at 37 degrees C in saline solution (0.9 wt% NaCl in water). After a moderate decrease, the diametral strength of the specimen was found to level off at about 60% of its initial value (3.2 MPa), for ageing times beyond 1 d. This behaviour has been ascribed to the progressive dissolution of the CSD fraction of the hardened cement, compensated by the crystallization of further amounts of DCPD.

Bone Cements↗
PubMed2002

Phosphate measurements during hypokinesia and phosphate supplements in disclosing phosphate changes in hypokinetic subjects.

BACKGROUND: Hypokinesia (diminished movement) induces significant phosphate (P) change, however, little is known about P retention and P depletion during hypokinesia (HK). Measuring P retention and P balance during HK and P supplementation, the objective of this work was to disclose whether HK could contribute to the decreased P retention and consequently to P depletion in normal subjects. METHODS: Studies were done during 30 days pre-HK period and 364 days HK period. Forty normal male individuals aged, 25.3+/-6.4 years were chosen as subjects. They were divided equally into 4 groups: unsupplemented active control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented active control subjects (SACS) and supplemented hypokinetic subjects (SHKS). Hypokinetic subjects were limited to an average walking distance of 0.5 km day-l, while active control subjects were kept on an average running distance of 9.6 km day-l. Both, SHKS and SACS received daily 14 mmol dicalcium phosphate per kg body weight. RESULTS: Negative P balance, fecal P, urinary calcium (Ca) and P excretion, serum P and total (Cat) level increased significantly (p<0.05) while P retention, serum intact parathyroid hormone (iPTH), 1,25 dihydroxyvitamin D (1,25 (OH)2 D3) and thyrocalcitonin (TC) decreased significantly (p<0.05) in SHKS and UHKS compared with their pre-HK values and their respective active controls (SACS and UACS). However, negative P balance, P retention incapacity, serum, fecal and urinary P level increased significantly (p<0.05) more in SHKS compared with UHKS. Fecal P loss, urinary P and Ca loss, serum P and Cat level, iPTH, TC and 1,25 (OH)2 D3 level, P retention and P balance change insignificantly (p>0.05) in SACS and UACS compared with their pre-HK level. CONCLUSIONS: It was concluded that a significant P excretion in urine and feces in spite of negative P balance and P supplementation may demonstrate reduced P retention, while a significant increase of negative P balance may demonstrate P depletion. Clearly, P intake, regardless of its low or higher dose, was significantly wasted during HK probably due to the decreased ability of the body to retain P.

Adult↗
PubMed1990

Calcium phosphate cements: study of the beta-tricalcium phosphate--dicalcium phosphate--calcite cements.

The setting and strengthening properties of beta-tricalcium phosphate (beta-TCP)--dicalcium phosphate dihydrate (DCPD)--calcite blends upon admixture with water were investigated at 25 and 37 degrees C. Setting was accelerated by seeding the system with hydroxyapatite (HAp), and strengthening improved when the solids were mixed with a solution saturated with DCPD and HAp. The relationship strength versus ageing time in wet conditions was correlated with mineralogical changes of the material. X-Ray diffraction, thermal analysis and scanning electron microscopy observations showed that DCPD and calcite react together to form small HAp crystals acting as bridges between the beta-TCP aggregates present in the paste. Both gaseous CO2 released by the reaction of calcite and the conversion of lower (DCPD, calcite) to higher-density phases (HAp) contributed to increase the porosity of the material. Nevertheless, quite acceptable diametral strengths (around 1.5 MPa) could be achieved, despite the high porosity of the hardened product (up to 54 vol%). After exhaustion of DCPD, calcite can react with beta-TCP to form further HAp, but this process is detrimental to the strength of the material. Both the mineralogical transformations, and the strengthening of the material were accelerated considerably upon increasing the ageing temperature.

Adhesives↗