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PubMed1977

Enzyme induction in Streptomyces hydrogenas, VII. Short-term accumulation of guanosine polyphosphates.

Cells of Streptomyces hydrogenans (ATCC 19631) synthesize guanosine 3'(2')-diphosphate 5'-triphosphate (pppGpp) and guanosine 3'(2')-diphosphate 5'-diphosphate (ppGpp). 10 to 20 min after addition of steroids to the culture medium, the amount of pppGpp and ppGpp increases 2- to 3-fold. At the same time, the cellular amount of both ATP and GTP has been found to increase. While "shift down" experiments arrest growth of the cells temporarily, steroids do not impair cell division of Streptomyces hydrogenans. It is suggested that ppGpp and pppGpp mediate the regulatory shut off of nucleic acid synthesis or control their increased turnover triggered by the steroids.

Adenosine Triphosphate↗
PubMed2003

Polyphosphates and other phosphorus-containing polymers for drug delivery applications.

Poly(phosphate ester)s, polyphosphonates, and polyphosphazenes are three classes of phosphorus-containing polymers that have received wide attention over the past decade for their utility in biomedicine and tissue engineering. These three families of polymers can lead to a number of subclasses of polymers with varied properties. Significant research in this area has led to niche polymers with morphologies ranging from viscous gels to amorphous microparticles for utility in drug delivery. Furthermore, the pentavalency of phosphorus offers the potential for covalent linking of the drug. The classes of polymers discussed in this review are being explored in human clinical trials for vaccine delivery as well as delivery of oncolytic and CNS therapeutics. More applications in the areas of DNA delivery and tissue engineering are also being explored.

Delayed-Action Preparations↗
PubMed1974

Pitfalls in Tc99m polyphosphate skeletal imaging.

The quality of Tc-PP scans is best in younger patients. In all age groups quality is adversely affected by free TcO4-. This should be suspected if excessive background is present or marked accumulation is noted in the thyroid gland. Direct physician supervision of all studies is recommended. Symptomatic and roentgenographically positive areas may then be determined for special interpretative attention. Objects which attenuate activity should be removed or noted. Potential sources of superficial contamination (product spill, urine, saliva) must be known and considered when extraneous activity does not correlate with skeletal structures or clinical findings. Normal variations in skeletal uptake of Tc-PP include asymmetries between periarticular areas on the right and left, local increases due to physiologic calvarial thickening and uptake in persistently visualized sternal ossification centers. Apparent variations in the vertebral activity may be due to focal plane effects of rectilinear scanners. Hyperemia can cause diffusely increased Tc-PP localization in an entire extremity. This effect may completely obscure a lesion or obscure the extent of a lesion. Tc-PP excretion through the kidneys occasionally provides useful morphologic or functional information concerning the urinary tract which should be inspected on all scans. Abnormal soft tissue uptake occurs in a variety of conditions including healing wounds and some malignant tumors. A large percentage of patients over 40 years of age demonstrate localization of Tc-PP in the walls of the femoral vessels.

Adolescent↗
PubMed1985

Metabolism of phosphoinositides and inositol polyphosphates in rabbit corneal epithelium.

The synthesis of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2) was studied in the rabbit cornea using 32P and [3H]myo-inositol as precursors. Also, the formation of water-soluble products of the degradation of inositol lipids, inositol-1-phosphate, -1,4-bisphosphate and -1,4,5-trisphosphate, was shown. Corneal epithelium displayed the most active inositol lipid metabolism and endothelium the least when the cornea layers were separately incubated (stroma had intermediate values). In corneal epithelium incubated with [3H]myo-inositol, tritiated glycerophosphorylinositol and water-soluble inositol phosphates were formed. 10 mM LiCl promotes an increase in the inositol phosphates consistent with an inhibitory effect on inositol phosphatase. Cell-free preparations of epithelium incubated with [gamma-32P]ATP detected the presence of diacylglycerol kinase, PI kinase and PIP kinase. Endogenous PI was rapidly phosphorylated to PIP within 1 min of incubation, whereas PIP was phosphorylated more slowly. In conclusion, the components of the inositol lipid cycle are present in the cornea, particularly in the epithelium. It is proposed that the control of these pathways may be involved in the transduction of cell signals through the plasma membrane, intracellular calcium ionization and epithelial cell proliferation and differentiation, particularly in wound healing.

Animals↗
PubMed1989

Separation of three commercial forms of vitamin C (ascorbic acid, ascorbic-2-sulfate and ascorbate-2-polyphosphate) by HPLC.

A modification of an existing separation technique by this laboratory is described for the separation and quantification of the three commercially available forms of ascorbic acid. The technique has the potential for identifying the various metabolic and degradation products resulting from vitamins C2 and C3 metabolism. A microwave technique is used for tissue heat denaturation and extraction.

Animals↗
PubMed2001

SH2 domain-containing inositol polyphosphate 5'-phosphatase is the main mediator of the inhibitory action of the mast cell function-associated antigen.

The mast cell function-associated Ag (MAFA) is a type II membrane glycoprotein originally found on the plasma membrane of rat mucosal-type mast cells (RBL-2H3 line). A C-type lectin domain and an immunoreceptor tyrosine-based inhibitory motif (ITIM) are located in the extracellular and intracellular domains of MAFA, respectively. MAFA clustering has previously been shown to suppress the secretory response of these cells to the FcepsilonRI stimulus. Here we show that the tyrosine of the ITIM undergoes phosphorylation, on MAFA clustering, that is markedly enhanced on pervanadate treatment of the cells. Furthermore, the Src homology 3 domain of the protein tyrosine kinase Lyn binds directly to a peptide containing nonphosphorylated MAFA ITIM and PAAP motif. Results of both in vitro and in vivo experiments suggest that Lyn is probably responsible for this ITIM phosphorylation, which increases the Src homology domain 2 (SH2) affinity of Lyn for the peptide. In vitro measurements established that tyrosine-phosphorylated MAFA ITIM peptides also bind the SH2 domains of inositol 5'-phosphatase (SHIP) as well as protein tyrosine phosphatase-2. However, the former single domain is bound 8-fold stronger than both of the latter. Further support for the role of SHIP in the action of MAFA stems from in vivo experiments in which tyrosine-phosphorylated MAFA was found to bind primarily SHIP. In RBL-2H3 cells overexpressing wild-type SHIP, MAFA clustering causes markedly stronger inhibition of the secretory response than in control cells expressing normal SHIP levels or cells overexpressing either wild-type protein tyrosine phosphatase-2 or its dominant negative form. In contrast, on overexpression of the SH2 domain of SHIP, the inhibitory action of MAFA is essentially abolished. Taken together, these results suggest that SHIP is the primary enzyme responsible for mediating the inhibition by MAFA of RBL-2H3 cell response to the FcepsilonRI stimulus.

Amino Acid Sequence↗