Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polyhydroxy acids [poly(L-lactic acid) (L-PLA), poly(D,L-lactic acid) (DL-PLA), and poly-(glycolic acid) (PGA)], biocompatible and bioerodible polymers that are being investigated for controlled delivery of pharmaceuticals and are approved by the Food and Drug Administration for in vivo sutures and bone repair implants, have been dissolved in supercritical CO2 and precipitated by rapid expansion of the resulting supercritical solutions (RESS). The formation of these microparticles and microspheres is a first step toward the goal of producing, in a single processing step, drug-loaded polymeric microspheres for use in controlled release applications. Nucleation of poly(L-lactic acid) from CO2 and CO2-acetone mixtures produced microparticles and microspheres ranging from 4 to 25 microns. Microspheres (2-20 microns) were also obtained with chlorotrifluoromethane as solvent. Commercial L-PLA precipitated after extraction of low molecular weight oligomers showed degradation kinetics similar to that of the starting material. The precipitation of DL-PLA from CO2 produced irregular-sized particles (10-20 microns). PGA, a polymer insoluble in most organic solvents, was found to be soluble in supercritical CO2. Nucleation of PGA from CO2 produced both regular-sized particles and needles of 10-40-microns length. The total solubility of commercial L-PLA in supercritical CO2 at 250 bar and 55 degrees C decreased from 0.14 wt % to less than 0.05 wt % and then leveled off as the cumulative flow of CO2 per unit mass of L-PLA loaded in the extractor increased beyond 20 standard L of CO2/g of L-PLA. Use of acetone (1 wt %) as a cosolvent increased L-PLA solubility by approximately 500%.
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PMID:Formation of bioerodible polymeric microspheres and microparticles by rapid expansion of supercritical solutions. 136 63

It has been recognized in the experiments of animals, that high dose of administration of IgG suppresses the immunoglobulin production in vitro, because of masking of antigen determinants. The study evaluated the effect of several gammaglobulin preparations on in vitro immunoglobulin production induced by pokeweed mitogen. And the effect of these preparations was estimated by following system. Mononuclear cells (5 X 10(5)/ml) were incubated (37 degrees C, 5% CO2) in the presence of gammaglobulin preparations (0.01 mg/ml-1.0 mg/ml). On the sixth day of culture, the cells were spun down, washed three times, resuspended in MEM without L-4,5 [3H]-leucine. After 24 hours, supernatants were harvested, and the concentration of immunoglobulin produced by mononuclear cells was analyzed by solid-phase RIA. And the results which have been obtained as follows. PWM induced immunoglobulin production (IgG) was analyzed in the presence of immunoglobulin preparations. Among these preparations, the suppressive effect of ISG was most significant, and the effect was dose dependent. S-sulfonated and PEG-treated preparations also suppressed the IgG production, but not so strong as ISG. In the suppressive effect between S-sulfonation and PEG treatment, no significant difference was found. Pepsin treated preparation had no suppressive effect. Not only IgG production, but also IgA, IgM production were suppressed by the co-culture of ISG, S-sulfonated, and PEG treated IgG. ISG inhibits directly the differentiation of B cells, and also induces the activation of suppressor T cells. ISG was considered to suppress immunoglobulin production in vitro by these both pathways. The suppressor T cells, which are induced by ISG, are radiation resistant, hydrocortisone resistant and same population with OKT 8 positive cells.
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PMID:[The effect of gammaglobulin preparations on in vitro immunoglobulin production induced by pokeweed mitogen]. 620 26

Two analytical methods without an extraction step were developed using capillary electrophoresis and supercritical fluid chromatography in order to determine phenylglyoxylic (PGA) and mandelic (MA) acids in urine, with minimum treatment and manipulation of biological samples. The urine was diluted ten-fold in acetonitrile and directly injected into the analytical systems after centrifugation. Analysis was performed by capillary electrophoresis on alkyl bonded phase capillary columns with sodium formiate (4 x 10(-2) M)-isopropanol (9:1, v/v) as a buffer, and by supercritical fluid chromatography on a Diol bonded phase silica column with ethanol-water-methanesulphonic acid (97.5:2.4:0.1, v/v) as coeluent of CO2. Detection of PGA and MA was performed by ultraviolet detection at 255 and 210 nm, respectively. The methods are in agreement, and are easily able to detect 5 mg/g creatinine for PGA, and 15 mg/g creatinine for MA, which are one twentieth of the lowest biological exposure index values.
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PMID:Capillary electrophoresis and supercritical chromatography, complementary and alternative techniques for the determination of urinary metabolites of styrene. 899 48

With this tissue engineering (TE) technique, the peripheral pulmonary artery was successfully reconstructed, using the patient's own venous cells in a 4-year-old girl, 2 years after Fontan procedure. A 4-year-old girl was given a diagnosis of single right ventricle, double-outlet right ventricle and pulmonary atresia. She underwent left modified Blalock-Taussig shunt at a month old, pulmonary artery angioplasty at a year and 3 months old, and bidirectional cavopulmonary shunt at 2 years and a month old. She underwent again pulmonary artery angioplasty and Fontan operation at 3 years and 3 months. An angiographical examination 7 months after the operation revealed total occlusion of the right intermediate pulmonary artery. TE technique using autologous cells was indicated. The application of this procedure was approved by the ethical committee in Tokyo Women's Medical University. The patient's parents were thoroughly informed and signed a consent form. Approximately 2 cm of the peripheral vein was explanted under sterile conditions. The tissue was minced, placed in tissue culture dishes and cultured at 37 degrees C, 100% humidity and a 5% CO2 atmosphere for almost a month. The number of cells substantially increased to reach 12 millions for almost a month. The culture medium was changed every 3 days. The polymer tube that served as a scaffold for cells was composed of the copolymer of PCL-PLA (50:50) with reinforcement by woven PGA. The polymer conduit, 10 mm in diameter, 20 mm in length and 1 mm in thickness, was designated to biodegradate within 8 weeks. The number of seeded cells was approximately a million/cm2. The graft transplantation was performed 10 days after seeding cells. The occlusive right intermediate pulmonary artery was reconstructed with the TE vessel graft under extracorporeal circulation with a pump-oxygenator. The patient followed a satisfactory postoperative course. The postoperative angiography demonstrated that the graft was not constricted and dilated but that it preserved good patency. Long-term follow-up are necessary. We plan to continue to use the TE technique using autologous cells in the low pressure system like venous or pulmonary circulation. Because our results even in early experimental phase were valuable and promising, we believe that the TE approach may play an important role in the near future as an another alternative, together with transplantation and artificial organ, especially in the field of cardiovascular surgery that mostly needs replants.
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PMID:[First successful clinical application of tissue engineered blood vessel]. 1199 17

The light activation of fructose-1,6-bisphosphatase (EC 3.1.3.11) and sedoheptulose-1,7-bisphosphatase (EC 3.1.3.37) was inhibited in isolated intact spinach (Spinacia oleracea L.) chloroplasts exposed to reduced osmotic potentials. Decreases in the velocity and magnitude of light activation correlated with the overall reduction in CO2 fixation rates. Responses of osmotically stressed chloroplasts to both varying pH and exogeous dihydroxyacetone phosphate (DHAP) or 3-phosphoglycerete (PGA) were examined. In the presence of DHAP, the absolute rate of CO2 fixation was increased and this increase was most pronounced at alkaline pH. Enhanced light activation of these enzymes was also observed under these conditions. However, in the presence of PGA, similar increases in photosynthetic rate and enzyme activation were not evident. Light-dependent stromal alkalization was unaffected by the stress treatments. Inhibition of light activation under hypertonic conditions is discussed in terms of substrate availability, possible alterations of the redox state of ferredoxin and associated electron carriers, and inhibited enzyme-enzyme or enzyme-substrate interactions involved in the light activation process.
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PMID:Inhibited light activation of fructose and sedoheptulose bisphosphatase in spinach chloroplasts exposed to osmotic stress. 2425 69

Sugar-derived reactive carbonyls (RCs), including methylglyoxal (MG), are aggressive by-products of oxidative stress known to impair the functions of multiple proteins. These advanced glycation end-products accumulate in patients with diabetes mellitus and cause major complications, including arteriosclerosis and cardiac insufficiency. In the glycolytic pathway, the equilibration reactions between dihydroxyacetone phosphate and glyceraldehyde 3-phosphate (GAP) have recently been shown to generate MG as a by-product. Because plants produce vast amounts of sugars and support the same reaction in the Calvin cycle, we hypothesized that MG also accumulates in chloroplasts. Incubating isolated chloroplasts with excess 3-phosphoglycerate (3-PGA) as the GAP precursor drove the equilibration reaction toward MG production. The rate of oxygen (O2) evolution was used as an index of 3-PGA-mediated photosynthesis. The 3-PGA- and time-dependent accumulation of MG in chloroplasts was confirmed by HPLC. In addition, MG production increased with an increase in light intensity. We also observed a positive linear relationship between the rates of MG production and O2 evolution (R = 0.88; P < 0.0001). These data provide evidence that MG is produced by the Calvin cycle and that sugar-derived RC production is inevitable during photosynthesis. Furthermore, we found that MG production is enhanced under high-CO2 conditions in illuminated wheat leaves.
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PMID:The Calvin cycle inevitably produces sugar-derived reactive carbonyl methylglyoxal during photosynthesis: a potential cause of plant diabetes. 2440 31

Current models of C3 photosynthesis incorporate a phosphate limitation to carboxylation which arises when the capacity for starch and sucrose synthesis fails to match the capacity for the production of triose phosphates in the Calvin cycle. As a result, the release of inorganic phosphate in the chloroplast stroma fails to keep pace with its rate of sequestration into triose phosphate, and phosphate becomes limiting to photosynthesis. Such a model predicts that when phosphate is limiting, assimilation becomes insensitive to both CO2 and O2, and is thus incapable of explaining the experimental observation that assimilation, under phosphate-limited conditions, frequently exhibits reversed sensitivity to both CO2 and O2, i.e., increasing O2 stimulates assimilation and increasing CO2 inhibits assimilation. We propose a model which explains reversed sensitivity to CO2 and O2 by invoking the net release of phosphate in the photorespiratory oxidation cycle. In order for this to occur, some fraction of the glycollate carbon which leaves the stroma and which is recycled to the chloroplast by the photorespiratory pathway as glycerate must remain in the cytosol, perhaps in the form of amino acids. In that case, phosphate normally used in the stromal glycerate kinase reaction to generate PGA from glycerate is made available for photophosphorylation, stimulating RuBP regeneration and assimilation. The model is parameterized for data obtained on soybean and cotton, and model behavior in response to CO2, O2, and light is demonstrated.
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PMID:An improved model of C3 photosynthesis at high CO2: Reversed O 2 sensitivity explained by lack of glycerate reentry into the chloroplast. 2441 89

Isolated epidermes of Tulipa gesneriana L. and Commelian communis L. were exposed to (14)CO2 in the light and in darkness, when stomata were either closed or open. The labelling patterns did not differ: the main products of CO2 fixation were malate and aspartate. Small amounts of radioactivity appeared also in acids of the tricarboxylic-acid cycle and their transamination products. Since the capacity of epidermis to assimilate CO2 is known to reside in the guard cells, we can state that guard cells continuously take up CO2 if present, and are thus able to recognize the presence of CO2 in their environment at all times. Epidermal samples exposed to (14)CO2 in the light contained only small amounts of radioactive 3-phosphoglyceric acid (3-PGA) and sugar phosphates, or none at all. Epidermal samples from Commelina communis did not contain labelled 3-PGA if all adhering mesophyll cells had been removed before exposure to (14)CO2. Homogenates of clean epidermal strips of Commelina communis were able to convert exogenous ribulose diphosphate to 3-PGA at a low rate, but could not catalyze the conversion of exogenous ribulose-5-phosphate to ribulose diphosphate. Guard cells of Commelina communis, and probably also those of Tulipa gesneriana, appear not to possess the reductive pentosephosphate pathway, despite the presence of chloroplasts. In such species, the guard cells will have to rely on import in order to maintain their carbon balance. Earlier findings of photosynthetic reduction of CO2 by epidermal tissues were probably obtained with samples that were contaminated with mesophyll cells.
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PMID:[(14)C]Carbon-dioxide fixation by isolated leaf epidermes with stomata closed or open. 2441 82

Cassava, bean and maize leaves were fed with(14)CO2 in light and the primary products of photosynthesis identified 5 and 10 seconds after assimilation. In maize, approximately three quarters of the labelled carbon was incorporated in C4 acids, in beans about two thirds in PGA, and in cassava approximately 40-60% in C4 acids with 30-50% in PGA. These data indicate that cassava possesses the C4 photosynthetic cycle, however due to the lack of typical Kranz anatomy appreciable carbon assimilation takes place directly through the Calvin-Benson-Bassham cycle.
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PMID:C3-C 4 intermediate photosynthetic characteristics of cassava (Manihot esculenta Crantz) : II. Initial products of(14)CO 2 fixation. 2443 90

The amino acid permeability of the envelope of intact, functional spinach (Spinacia oleracea L.) chloroplasts was investigated by light scattering, volumetry and uptake of (14)C-labelled amino acids. The criterion for the functionally of the chloroplasts was their ability to reduce CO2, PGA and oxaloacetate in the light at high rates.Net uptake into the chloroplast interior of neutral amino acids such as alanine, glycine, serine, proline, threonine or valine occurred only at very low rates. The uptake was concentration dependent, indicating unspecific diffusion rather than carrier-mediated transport. The slowness of uptake is emphasized by the capability of neutral amino acids to provide osmotic support for intact chloroplasts during a considerable length of time. Back-exchange experiments also failed to indicate the existence of specific exchange carriers for the transport of neutral amino acids such as alanine or glycine through the envelope of intact chloroplasts. Dicarboxylic amino-acids are known to be taken up by the so-called dicarboxylate translocator. The same carrier was found to catalyze also the transfer of asparagine and glutamine.The data do not support current assumptions concerning fast carrier-mediated transport of neutral amino acids and their role in the transfer of carbon during photosynthesis.
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PMID:Amino acid permeability of the chloroplast envelope as measured by light scattering, volumetry and amino acid uptake. 2444 17


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