Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0031511 (pheochromocytoma)
 14,622 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ascorbate peroxidase active component (APAC) was purified and characterized in Synechococcus PCC 9742 (R2) cells. APAC was isolated from freshly harvested cells, by ion exchange chromatography on DEAE cellulose, ultrafiltration through a 3000 dalton cut off filter and high pressure liquid chromatography through a reversed phase C-18 column. APAC was found to be extremely stable to harsh treatments of boiling water for 30 min, acidification to pH 2.0 and proteolytic digestion. A close correlation between activity and iron content of APAC was observed throughout the purification steps. E.S.R. spectrum of APAC showed a resonance line at g = 4.3 in the oxidized from. Peroxide reduction by ascorbate decreased the E.S.R. signal, which reappeared upon reoxidation by H2O2. The affinities of APAC to H2O2 and ascorbate were high (0.38 mM and 0.2 mM, respectively). Amino acid composition analysis of APAC revealed the presence of glutamic acid:glycine:cysteine residues at 2:1:1 ratio.
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PMID:A unique ascorbate peroxidase active component in the cyanobacterium Synechococcus PCC 7942 (R2). 133 15

This study aimed to determine the kinetics of albumin resorption from and the healing of two types of albumin impregnated Vasculour II (Bard Cardiovascular) Dacron grafts (ACG-A and ACG-B) using whole blood preclotted Vasculour II Dacron grafts (without albumin) as controls (PCC). Prostheses measuring 4 mm ID x 50 mm length were implanted in the aortoiliac position in 24 dogs (ACG-A n = 12, ACG-B n = 24, PCC n = 12) and explanted after 1, 2 4, and 6 months. Platelet count, platelet aggregometry to 10(-5) M ADP, prothrombin time (PT), and partial thromboplastin time (PTT) were determined preoperatively and at explantation. Sections of the explanted grafts were assayed for human albumin by immunohistochemical techniques utilizing a rabbit polyclonal mono-specific antibody for human albumin followed by the addition of a biotinylated goat anti-rabbit IgG. Immunoperoxidase staining was then performed using Avidin D horse-radish peroxidase. Histology of the grafts (light microscopy, scanning electron microscopy, and transmission electron microscopy) as well as percent thrombus free surface area (TFSA) by computerized planimetry were also determined. Seven of 48 grafts were occluded (85.4% patency) with no difference among the three groups. Platelet aggregometry was not predictive of graft patency. No change in PT or PTT occurred nor was there any difference among the three groups. Retained albumin was detected in every one-month explant but not beyond that time, with the sensitivity for detecting human albumin in this assay being 20 mg albumin per gram of Dacron. All ACG explants at one month revealed inner capsular fibrin coagula not present in PCC specimens.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Albumin impregnated vascular grafts: albumin resorption and tissue reactions. 138 74

Oxidative stress responses were tested in the unicellular cyanobacterium synechococcus PCC 7942 (R-2). Cells were exposed to hydrogen peroxide, cumene hydroperoxide and high light intensities. The extent and time course of oxidative stress were related to the activities of ascorbate peroxidase and catalase. Ascorbate peroxidase was found to be the major enzyme involved in the removal of hydrogen peroxide under the tested oxidative stress. Catalase activity was inhibited in cells, treated with high H2O2 concentrations, and was not induced under photooxidative stress. Catalase was specifically induced in cells treated with cumene hydroperoxide. Superoxide dismutase activity increased under conditions generating superoxide, such as high light intensities. The induction of the antioxidative enzymes was light dependent and was inhibited by chloramphenicol.
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PMID:Oxidative stress responses in the unicellular cyanobacterium Synechococcus PCC 7942. 190 71

We reported previously that, following phosphorylation by cyclic AMP-dependent protein kinase, tyrosine hydroxylase in rat corpus striatal extracts is inactivated in a time-dependent and apparently irreversible fashion. Removal of low molecular weight substances from these extracts by gel filtration attenuates this inactivation. We tried to determine the identity of endogenous metabolites that promote inactivation of tyrosine hydroxylase under our experimental conditions. In the present study, we report that the reducing co-substrate tetrahydrobiopterin and its analogues promoted this irreversible inactivation. The concentration that produced a 50% loss of activity (at 20 min) of the phosphorylated enzyme was 0.7 microM and that for the unphosphorylated enzyme was 420 microM. Using enzyme purified from a rat pheochromocytoma, we found that tyrosine, alpha-methyl-p-tyrosine, and a 3-iodotyrosine protected the phosphorylated enzyme against the inactivation produced by tetrahydrobiopterin. Catecholamines (dopamine, norepinephrine, epinephrine, and some of their analogues) also nullified inactivation. In contrast, the product of the reaction, dihydroxyphenylalanine, failed to attenuate the inactivation process. We performed several studies to ascertain the mechanism of inhibition by tetrahydrobiopterin. We considered the possibility that it formed reactive free radicals that produced inhibition. Free radical scavengers, however, failed to block the inhibition produced by tetrahydrobiopterin. Superoxide dismutase, catalase, and peroxidase also failed to protect tyrosine hydroxylase against inactivation. Moreover, when the experiments were performed under anaerobic conditions, the inactivation process was unaffected. These results suggest that reactive oxygenated species were not required for inactivation by tetrahydrobiopterin.
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PMID:Inactivation of tyrosine hydroxylase by pterin substrates following phosphorylation by cyclic AMP-dependent protein kinase. 197 41

By monitoring dopamine metabolism in rat pheochromocytoma derived PC12 cell cultures during extended treatment with manganese chloride, we assessed the functional changes occurring in a dopaminergic system during the development of manganese-induced damage. Besides eliciting a specific toxic effect on PC12 cells, manganese induced the complete disappearance of extracellular (free) but not intracellular (vesicle stored) dopamine and its metabolite 3,4-dihydroxyphenylacetic acid. This effect was observed also using low manganese concentrations (1 microM) and mainly occurred by non-enzymatic catechol oxidation since it was still evident in a cell free medium and it was fully prevented by ascorbic acid but not by reduced glutathione. The possibility of a mere "non-biological" action was ruled out by the observation of an irreversible effect of manganese as manifested by the cells' apparent inability to release dopamine or 3,4-dihydroxyphenylacetic acid into the culture medium even after complete manganese removal (post-manganese incubation). That a free radical mechanism was not involved in the genesis of this irreversible effect was shown by the fact that neither ascorbic acid, catalase, superoxide dismutase nor glutathione-peroxidase were able to prevent the decrease in catecholamine levels in the "post-manganese" incubation medium when added at the same time as the manganese. The results establish this PC12 cell system as an in vitro model for studying interactions between manganese and catechols and provide a detailed description of the nature of the neurochemical alterations that this heavy metal can induce in a dopaminergic system.
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PMID:Dopamine metabolism alterations in a manganese-treated pheochromocytoma cell line (PC12). 203 Dec 48

Rat pheochromocytoma PC 12 cells are susceptible to the oxidative toxicity caused by H2O2, nitrofurantoin, dopamine, and xanthine/xanthine oxidase reaction. The cytotoxicities of these agents are greatly reduced by the simultaneous presence of 0.1 mM tetrahydrobiopterin (BH4), 3 units/ml horseradish peroxidase, 0.2 mM NADH, and 0.1 units/ml sheep liver dihydropteridine reductase (DHPR). Individually, BH4, NADH and DHPR have no protection against H2O2 toxicity in PC 12 cells. Peroxidase alone offers 58% of protection if cells are incubated in the medium but only 3% in Dulbecco's phosphate buffered saline. The efficiency of the BH4-mediated antioxidation system in PC 12 cells is equal to or better than ascorbic acid and catalase, depending on the source of the reactive O2 species (ROS). The reactions responsible for the BH4-antioxidation system may consist of the non-enzymatic and the peroxidase-catalyzed reduction of H2O2 to H2O by BH4 and the regeneration of BH4 by DHPR using NADH as the cofactor. The components of this defence mechanism against ROS are all normal cellular constituents and are ubiquitous in nature. This DHPR-catalyzed redox cycling of BH4 may constitute an as yet little-known antioxidation system in mammalian cells.
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PMID:Antioxidation activity of tetrahydrobiopterin in pheochromocytoma PC 12 cells. 207 Apr 35

Alzheimer's neurofibrillary tangles (NFT) and paired helical filaments (PHF) were found in the pheochromocytoma cells of the adrenal gland removed from a 54-year-old female. By electron microscopy they were identical to those found in the brains affected by dementia of Alzheimer type. In the tumor cells, most of the PHF were found dispersed loosely in the cytoplasm, while typical NFT were infrequent. By immunoelectron microscopy using peroxidase-antiperoxidase method, both NFT and dispersed PHF were stained positively with a polyclonal antiserum to human tau protein. This is the first observation of NFT and PHF in paraneuronal tumor cells. The patient has no obvious Alzheimer's disease.
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PMID:Alzheimer's neurofibrillary tangles and paired helical filaments in the pheochromocytoma cells of the adrenal medulla--electron microscopic and immunoelectron microscopic observations. 212 83

The presence of somatostatin-immunoreactivity in tumor tissue of adrenal pheochromocytoma and thyroid medullary carcinoma identified by peroxidase-antiperoxidase technique is reported in one case of Sipple syndrome. This patient was found to have a high concentration of somatostatin-immunoreactivity in the peripheral blood (40 ng/l, normal 0-20 ng/l). After removal of the tumors, the plasma somatostatin-immunoreactivity fell within normal range (12.5 ng/l). This seems to be the first report of Sipple syndrome that produces somatostatin-immunoreactivity in both: pheochromocytoma and thyroid medullary carcinoma.
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PMID:Coexistence of somatostatin-immunoreactivity in an adrenal pheochromocytoma and a thyroid medullary carcinoma (Sipple syndrome). 290 Jul 71

Tyrosine hydroxylase activity is reversibly modulated by the actions of a number of protein kinases and phosphoprotein phosphatases. A previous report from this laboratory showed that low-molecular-weight substances present in striatal extracts lead to an irreversible loss of tyrosine hydroxylase activity under cyclic AMP-dependent phosphorylation conditions. We report here that ascorbate is one agent that inactivates striatal tyrosine hydroxylase activity with an EC50 of 5.9 microM under phosphorylating conditions. Much higher concentrations (100 mM) fail to inactivate the enzyme under nonphosphorylating conditions. Isoascorbate (EC50, 11 microM) and dehydroascorbate (EC50, 970 microM) also inactivated tyrosine hydroxylase under phosphorylating but not under nonphosphorylating conditions. In contrast, ascorbate sulfate was inactive under phosphorylating conditions at concentrations up to 100 mM. Since the reduced compounds generate several reactive species in the presence of oxygen, the possible protecting effects of catalase, peroxidase, and superoxide dismutase were examined. None of these three enzymes, however, afforded any protection against inactivation. We also examined the effects of ascorbate and its congeners on the activity of tyrosine hydroxylase purified to near homogeneity from a rat pheochromocytoma. This purified enzyme was also inactivated by the same agents that inactivated the impure corpus striatal enzyme. Under conditions in which ascorbate almost completely abolished enzyme activity, we found no indication for significant proteolysis of the purified enzyme as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We also found that pretreatment of PC12 cells in culture for 4 h with 1 mM ascorbate, dehydroascorbate, or isoascorbate (but not ascorbate sulfate) also decreased tyrosine hydroxylase activity 25-50%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inactivation of tyrosine hydroxylase activity by ascorbate in vitro and in rat PC12 cells. 290 63

A procedure is described for assay of GM1 and other gangliotetraose-type gangliosides at the picomole level. The gangliosides are absorbed onto polystyrene microwells and treated with neuraminidase and then with cholera toxin B subunits conjugated to horseradish peroxidase. Color is developed and quantified spectrophotometrically. Omission of neuraminidase gives a measure of GM1 alone. Linearity was obtained between 0.5 and 3 pmol. This procedure was applied to ganglioside mixtures isolated fron neuro-2A neuroblastoma and PC12 pheochromocytoma cells. For the latter, an additional step involving reaction with fucosidase increased the yield of GM1 due to the presence of fucosylated gangliosides. Application of the same reagents as a TLC overlay procedure to the gangliosides from neuro-2A cells revealed the presence of GD1a, GD1b, and GT1b in addition to GM1, thus confirming the presence of a family of gangliotetraose gangliosides.
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PMID:Quantification of gangliotetraose gangliosides with cholera toxin. 318 15


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