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At least 199 records · Page 11Linked to original sources
PubMed1990

Modulation of type X collagen gene expression by calcium beta-glycerophosphate and levamisole: implications for a possible role for type X collagen in endochondral bone formation.

Chondrocytes from the cephalic region of 18-day chick embryo sterna were cultured within type I collagen gels in the presence of increasing concentrations of calcium beta-glycerophosphate (Ca beta GP) (2.5 mM, 5 mM and 10 mM) or 2 mM levamisole. Addition of Ca beta GP produced an increase in type X collagen synthesis and when 10 mM Ca beta GP was used, mineral deposits were observed in the matrix elaborated by the chondrocytes. Measurement of mRNA levels of type II and type X collagen microgram-1 total RNA revealed that the level of alpha 1(II) mRNA decreased whereas the level of alpha 1(X) mRNA remained relatively constant in the presence of Ca beta GP. Thus, Ca beta GP appears to increase type X collagen synthesis by enhancing the rate of collagen type X mRNA translation. In levamisole-treated cultures the synthesis of type X collagen and its deposition within the matrix were inhibited. Measurement of mRNA levels micrograms-1 total RNA revealed that the level of alpha 1(II) mRNA increased whereas the level of alpha 1(X) mRNA was markedly decreased in the presence of levamisole. Consequently, it must be concluded that levamisole inhibits type X collagen synthesis by inhibiting type X collagen gene transcription. These results add support for type X collagen having an important role in the mineralization process and have demonstrated that type X collagen synthesis is probably regulated at the mRNA translational stage during chondrocyte hypertrophy.

Alkaline Phosphatase↗
PubMed2002

Irradiating or autoclaving chitosan/polyol solutions: effect on thermogelling chitosan-beta-glycerophosphate systems.

The effects of steam sterilization and gamma-irradiation on chitosan and thermogelling chitosan-beta-glycerophosphate (GP) solutions containing polyol additives were investigated. The selected polyols were triethylene glycol, glycerol, sorbitol, glucose and poly(ethylene glycol) (PEG). They were incorporated to chitosan solutions prior to sterilization in a proportion ranging from 1 to 5% (w/v). The solutions were characterized with respect to their viscosity, thermogelling properties, compressive stress relaxation behavior and chitosan degradation. All polyols reduced the autoclaving-induced viscosity loss and had a positive impact on the solution thermogelling properties and compressive performance of the gels. Steam sterilization in the presence of glucose resulted in a substantial increase in the solution viscosity and gel strength. This was associated with a strong discoloration suggesting chemical alteration of the system. PEG was the most effective agent in preventing hydrolytic degradation of chitosan chains. Gamma-irradiation strongly decreased the chitosan solution viscosity regardless of the presence of additives, even when sterilization was carried out at -80 degrees C. Moreover, the thermogelling properties were dramatically altered, and thus, gamma-irradiation would not be an appropriate method to sterilize chitosan solutions. In conclusion, polyols are potentially useful additive to maximise the viscoelastic and mechanical properties of chitosan-GP after steam sterilization.

Chitin↗
PubMed1976

Suppression of the mitochondrial oxidation of (-)-palmitylcarnitine by the malate-aspartate and alpha-glycerophosphate shuttles.

Palmitylcarnitine oxidation by isolated liver mitochondria has been used to investigate the interaction of fatty acid oxidation with malate, glutamate, succinate, and the malate-aspartate shuttle. Mitochondria preincubated with fluorocitrate were added to a medium containing 2mM ATP and ATPase. This system, characterized by a high energy change, allowed titration of respiration to any desired rate between States 4 and 3 (Chance, B., and Williams, G. R. (1956) Adv. Enzymol. Relat. Areas Mol. Biol. 17, 65-134). When respiration (reference, with palmitylcarnitine and malate as substrates) was set at 75% of State 3, the oxidation of palmitylcarnitine was limited by acetoacetate formation. The addition of malate or glutamate approximately doubled the rate of beta oxidation. Malate circumvented this limitation by citrate formation, but the effect of glutamate apparently was due to enhancement of the capacity for ketogenesis. The rate of beta oxidation was curtailed when malate and glutamate were both present. This curtailment was more pronounced when the malate-aspartate shuttle was fully reconstituted. Among the oxidizable substrates examined, succinate was most effective in inhibiting palmitylcarnitine oxidation. Mitochondrial NADH/NAD+ ratios were correlated positively with suppression of beta oxidation. The degree of suppression of beta oxidation by the malate-aspartate shuttle (NADH oxidation) or by succinate oxidation was dependent on the respiratory state. Both substrates extensively reduced mitochondrial NAD+ and markedly suppressed beta oxidation as respiration approached State 4. Calculations of the rates of flux of hydrogen equivalents through beta oxidation show that the suppression of beta oxidation by glutamate or by the malate-aspartate shuttle is accounted for by increased flux of reducing equivalents through mitochondrial malic dehydrogenase. This increased Flux is accompanied by an increase in the steady state NADH/NAD+ ratio and a marked decrease in the synthesis of citrate. The alpha-glycerophosphate shuttle was reconstituted with mitochondria isolated from rats treated with L-thyroxine. This shuttle was about equal to the reconstructed malate-aspartate shuttle in supression of palmitylcarnitine oxidation. This interaction could not be demonstrated in euthyroid animals owing to the low activity of the mitochondrial alpha-glycerol phosphate dehydrogenase. It is concluded that beta oxidation can be regulated by the NADH/NAD+ ratio. The observed stimulation of flux through malate dehydrogenase both by glutamate and by the malate-aspartate shuttle results in an increased steady state NADH/NAD+ ratio, and is linked to a stoichiometric outward transport of aspartate. We suggest, therefore, that some of the reducing pressure exerted by the malate-aspartate shuttle and by glutamate plus malate is provided through the energy-linked, electrogenic transport of aspartate out of the mitochondria. These results are discussed with respect to the mechanism of the genesis of ethanol-induced fatty liver.

Animals↗
PubMedDate not supplied

[The effect of alpha-ketoglutarate, malate and alpha-glycerophosphate on bioenergetic processes in ischemic myocardium].

Anti-ischemic action of exogenous natural metabolites and their effect on biological combustion processes indexes in cardiac muscle has been investigated on white rats with the experimental myocardial infarction. It has been established that the marked cardioprotective effect of malate and alpha-ketoglutarate is associated with the glycolysis and enzymes activation of creatine kinase system of energy transport. At the same time malate activates pentose-phosphate cycle and tissue respiration enzymes. alpha-glycerophosphate displays definite anti-ischemic properties not associated with the intervention into biological combustion processes.

Animals↗
PubMedDate not supplied

[The effect of calcium glycerophosphate and Remodent on the dental enamel permeability in dogs with fluorosis].

In 14 dogs aged 6 months with severe fluorosis, the authors studied the effects of intake of calcium glycerophosphate and local remodent application on 45Ca enamel incorporation and the depth of its penetration into the dental hard tissues. The treatment led to a substantial decrease in both enamel 45Ca accumulation and the depth of its penetration under severe fluorosis. Combined use of the drugs was more beneficial in terms of enamel 45Ca permeability.

Animals↗
PubMed1989

In vitro solubility of calcium glycerophosphate versus conventional mineral salts in pediatric parenteral nutrition solutions.

Low-birth-weight infants requiring total parenteral nutrition receive inadequate intakes of calcium (Ca) and phosphorus (P) due to poor solubility of available mineral salts. To optimize Ca/P delivery, we tested the effects on in vitro solubility of mineral salt:calcium glycerophosphate (CaGP) versus calcium gluconate and K2HPO4 (CG + P); Ca:P ratios of 1:1 (at 12.5 and 25 mmol/L of Ca and P) and 2:1 (25:12.5 mmol/L); amino acid (AA) formulation: Aminosyn (A), Aminosyn-PF (A-PF), TrophAmine (T) or Vaminolac (V); and AA concentration (25 versus 8.3 g/L). Parenteral nutrition solutions contained 10% dextrose and vitamins and minerals typical of a neonatal prescription. Solutions were sampled at preparation, after 24 h in the neonatal unit (25 degrees C), and from before and after a 0.22-micron filter in extension tubing through which solutions were pumped at 5 ml/h within an incubator at 37 degrees C. Samples were analyzed for Ca and pH, and precipitation by spectrophotometry at 600 nm and light microscopy at x 100 magnification. The Ca concentration was unaffected by filtration. While spectrophotometry detected only gross precipitation, with light microscopy crystal formation was evident with 25 mmol/L of Ca and P as CG + P in A and T at 25 g of AA/L and in A, V, T, and A-PF at 8.3 g of AA/L. Precipitation did not occur with CaGP or CG + P at 12.5 mmol/L of Ca and P. Under in vitro conditions mimicking the neonatal unit, CaGP versus CG + P resulted in greater mineral solubility even at low AA concentrations.

Amino Acids↗
PubMed1987

Levamisole and inorganic pyrophosphate inhibit beta-glycerophosphate induced mineralization of bone formed in vitro.

The addition of the organic phosphate, beta-glycerophosphate, to the culture media of osteoid forming cells or tissues will induce formation of mineralized bone. The mechanisms behind this phenomenon are not clearly understood. In order to gain new understanding of organic phosphate induced mineralization of bone it was decided to attempt to inhibit this process in two fundamentally different ways. Firstly, the reversible inhibitor of alkaline phosphatase, Levamisole, was used to help define the role of alkaline phosphatase in mineralization in vitro. Secondly, inorganic pyrophosphate, a known inhibitor of hydroxyapatite (HA) formation was also used. It was hypothesized that inorganic pyrophosphate, in addition to its ability to block HA formation, might also interfere with organic phosphate access to alkaline phosphatase and thereby prevent mineralization. The data show that mineralization is blocked when alkaline phosphatase activity is inhibited by Levamisole prior to but not after osteoid maturation. Inorganic pyrophosphate blocks organic phosphate induced mineralization whether added before or after osteoid formation. Organic phosphate effects on alkaline phosphatase activity are reversed by the addition of inorganic pyrophosphate either before or after osteoid formation. These findings suggest a role for alkaline phosphatase in organic phosphate induced mineralization. The data show further that inorganic pyrophosphate may effect mineralization of bone not only by blocking apatite formation but possibly by modulating organic phosphate metabolism.

Animals↗
PubMed1985

Comparison of the effects of calcium alpha-glycerophosphate and Ca2+ on prostaglandin synthesis in rabbit kidney medulla slices.

The stimulatory effects of calcium alpha-glycerophosphate (CaG) and Ca2+ on the generation of medullary prostaglandin E2 have been compared. CaG (4mM) was significantly more effective than Ca2+ (4 mM) as a stimulus for prostaglandin E2 release. This effect of CaG was most pronounced in the presence of exogenous phospholipase A2 (0.1 unit/ml). These results suggest that CaG has a more powerful stimulatory effect on prostaglandin E2 formation than Ca2+ because of its high affinity for phospholipase A2.

Animals↗
PubMed1985

[Enzyme activity and content of glycerophosphate shuttle metabolites in the cortex and medulla oblongata during hyperbaric oxygenation therapy of acute hemorrhage].

The experiments on cats have demonstrated that hyperbaric oxygenation (303.9 kPa, 60 min) in acute blood loss (24.0 +/- 0.8 ml/kg) has an essential effect on glycerophosphate shuttle mechanism: it stimulates mitochondrial glycerol-3-phosphate dehydrogenase in the sensorimotor cortex and medulla oblongata, providing glycerol-3-phosphate dehydrogenation, activates cytoplasm hydrogen delivery to mitochondrial respiratory chain, prevents glycerol-3-phosphate and NADH level increase and cytoplasm glycerol-3-phosphate dehydrogenase inhibition, limiting lactate production.

Animals↗
PubMed1967

Biosynthesis of phosphatidyl glycerophosphate in Escherichia coli.

An enzyme (L-glycerol 3-phosphate: CMP phosphatidyltransferase) catalyzing the synthesis of phosphatidyl glycerophosphate from CDP-diglyceride and L-glycerol 3-phosphate has been rendered soluble by treatment of the particulate, membrane-containing fraction of E. coli with Triton X-100 and has been partially purified. The enzyme, devoid of phosphatidyl glycerophosphatase activity, is specific for L-glycerol 3-phosphate and is completely dependent upon added Mg(++) or Mn(++) for activity. It has high affinity for CDP-diglyceride and can be used for the assay of this nucleotide. Other properties of the enzyme are also described.

Chemical Phenomena↗
PubMedDate not supplied

[Effect of alpha-glycerophosphate on intracellular distribution of hexokinase in the tissue of fetal rabbits during acute hypoxia].

In experiments with 40 rabbit fetuses acute intrauterine hypoxia caused a redistribution of the hexokinase activity in brain and liver tissues towards an increase in the amount of the enzyme associated with mitochondria. Previous administration of alpha-glycerophosphate into rabbit female (at a dose of 1.3 g/kg of body weight) was accompanied by an increase in the hexokinase activity in liver mitochondria and in brain cytoplasmic fraction of fetus as well as in the total homogenate of both tissue. The phenomenon might be considered as a positive pattern in adaptation to hypoxia.

Acute Disease↗
PubMed1996

Pancreatic islet mitochondrial glycerophosphate dehydrogenase deficiency in two animal models of non-insulin-dependent diabetes mellitus.

Western blotting of pancreatic islet extracts from either hereditarily diabetic Goto-Kakizaki rats (GK rats) or animals injected with streptozotocin during the neonatal period (STZ rats) demonstrated a pronounced decrease of immunoreactive mitochondrial glycerophosphate dehydrogenase (m-GDH), when compared to results obtained in islets from control rats. By contrast, the islet glucokinase protein content was either unaffected (GK rats) or much less severely decreased than that of m-GDH (STZ rats). These findings indicate that the impaired activity of m-GDH previously documented in islet homogenates from diabetic rats coincides with a decreased content of this enzyme in the endocrine pancreas.

Animals↗
PubMed1996

Molecular cloning of human mitochondrial glycerophosphate dehydrogenase gene: genomic structure, chromosomal localization, and existence of a pseudogene.

cDNA of mitochondrial glycerophosphate dehydrogenase (mGPDH), a defect of which is a possible cause of non-insulin dependent diabetes mellitus, was cloned from a human insulinoma cDNA library. The deduced amino acid sequence showed 91% and 92% homology with those of rat and mouse mGPDH, respectively. The mGPDH gene was mapped to chromosome 2q23 by FISH analysis. Genomic clones for mGPDH were then isolated using mouse mGPDH cDNA and PCR products of human mGPDH cDNA as probes. Genomic structure was studied by sequencing the exon-intron boundaries and by PCR amplification of intronic regions using genomic clones as templates. The human mGPDH gene was shown to be composed of 15 coding exons, containing a (CA)n repeat region inside the gene, which was not polymorphic in the Japanese population. Genomic cloning also identified a pseudogene located on chromosome 19q13.4. These results provide information useful for analyzing the mGPDH gene in patients with non-insulin dependent diabetes mellitus.

Amino Acid Sequence↗
PubMed1997

Mutation in the calcium-binding domain of the mitochondrial glycerophosphate dehydrogenase gene in a family of diabetic subjects.

The Ca(2+)-sensitive and mitochondrial enzyme FAD-linked glycerophosphate dehydrogenase (m-GDH) represents an essential component of the pancreatic B-cell glucose-sensing device. This report deals with the first identified case of mutation in the calcium-binding domain of the m-GDH gene in a patient with type-2 diabetes and his glucose-intolerant half sister. Single strand conformation polymorphism analysis indeed revealed an abnormal mobility of the 32P-labelled polymerase chain reaction product in these two subjects. The corresponding base pair mutations and amino acid changes were documented. In the diabetic proband, the relative extent of the Ca(2+)-induced activation of m-GDH in CD3+ T-lymphocytes was lower than in his brother with a normal m-GDH gene sequence.

Base Sequence↗
PubMed1998

Site-directed mutations of the FAD-linked glycerophosphate dehydrogenase gene impairs the mitochondrial anchoring of the enzyme in transfected COS-7 cells.

COS-7 cells were transfected with the green fluorescent protein (GFP) of Aequorea victoria, human mitochondrial FAD-linked glycerophosphate dehydrogenase (mGDH), a mGDHwt-EGFP construct, or two mutant mGDH-proteins fused with EGFP. The site of mutation was selected to affect cationic amino acids in the peptide signal sequence currently believed to play a key role in the subcellular distribution of mitochondrial proteins. All proteins were suitably expressed in the COS-7 cells. However, an increase in mGDH enzymatic activity above the control value in non-transfected COS-7 cell homogenates was only observed in cells transfected with mGDH, indicating that the catalytic activity of mGDH was masked in fused proteins. Confocal microscopy documented that, in the cells transfected with the mGDHwt-EGFP construct, the fusion protein was located exclusively in mitochondria, this contrasting with the nuclear labelling of cells expressing the green fluorescent protein alone. The mitochondrial anchoring of the mutated mGDH fused protein was altered, this alteration being most obvious in the mGDH313233-EGFP mutant. These findings raise the idea that a conformation change of the mGDH protein, as resulting from either an inherited or acquired alteration of its amino acid sequence, may affect its subcellular distribution and, hence, modify its immunogenic potential.

Amino Acid Sequence↗