Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.19 (NOS)
 7,285 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aim of the present study was to establish different immunohistochemical staining patterns for a subsequent comparison with those of primitive neuroectodermal (PNET) subsets, i.e. PNET-NOS (not otherwise specified) or PNET with focal neuronal, astrocytic or ependymal differentiation, to relate neoplastic to embryonal development. Tissue of the developing central nervous system, with special emphasis on the stepwise development of the rhombencephalon, the cerebellar and the retinal anlage, from 20 different human embryos and fetuses ranging from 3 to 30 weeks of gestational age (GA) was examined. Six neuronal markers, synaptophysin, chromogranin A, neuron-specific enolase (NSE), neurofilament protein (NFP; 160 kDa, 200 kDa, 70 and 200 kDa) and six other markers, glial fibrillary acidic protein (GFAP), S-100 protein, vimentin, myoglobin, desmin, cytokeratin, were assessed immunohistochemically. GFAP and S-100 protein appeared at the 6th week of GA in primitive glial cells of the cerebellar anlage, brain stem, rhombencephalon, and developing spinal cord, together with--as first neuronal marker--chromogranin A, then NFP (70 and 200 kDa, and 160 kDa) from the 8th week onward. NSE started in the 11th week and synaptophysin not earlier than the 16th week of GA. Interestingly, the differentiation of the retinal anlage started rather late with NSE positivity beginning from the 16th week and positive reactions to synaptophysin and NFPs only from the 25th and chromogranin A from the 28th week of GA onward.
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PMID:Immunohistochemical characterization of primitive neuroectodermal tumors and their possible relationship to the stepwise ontogenetic development of the central nervous system. 1. Ontogenetic studies. 172 30

Optical absorption and resonance Raman spectra of neuronal nitric oxide synthase (b-NOS) isolated in the absence of tetrahydrobiopterin demonstrate that the enzyme preparation is very unstable. This unstable form of the enzyme has properties analogous to those of cytochrome P-420cam, an inactive form of cytochrome P-450cam. Although cysteine is preserved as the proximal ligand in both the ferric and ferrous forms of unstable b-NOS, the lack of tetrahydrobiopterin significantly increases the hexacoordinate low-spin fraction of the heme content, resulting in a loss of the enzymatic activity. Upon the addition of CO, the unstable b-NOS converts from a species exhibiting a Soret absorption maximum at 443 nm, as reported for the CO adducts of stable b-NOS and cytochrome P-450cam, to a species with a Soret maximum at 421 nm. The resonance Raman spectrum of the 421-nm form is the same as those of CO-bound myoglobin at low pH and CO-bound cytochrome P-420cam. The heme in this form of the enzyme is coordinated by a weaker ligand than thiolate; histidine coordination in the CO-bound form of the P-420-like species of NOS is consistent with all of the available data. A similar unstable form of the macrophage (i-NOS) enzyme was also detected. Not only does the heme pocket of NOS have the same coordination as cytochrome P-450 in its stable form, but the partially denatured form has the same properties as cytochrome P-420, the inactive form of cytochrome P-450. Among other possible roles, tetrahydrobiopterin may play a significant role in the stabilization of the active enzyme.
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PMID:Tetrahydrobiopterin-deficient nitric oxide synthase has a modified heme environment and forms a cytochrome P-420 analogue. 753 91

These observations clearly indicate that NO inhibits NOS activity and that nNOS and eNOS are more sensitive than iNOS to the inhibitory action of NO. Not only exogenously added NO but also enzymatically generated NO inhibits the activity of nNOS and eNOS. The mechanism by which NO inhibits NOS appears to involve the heme iron prosthetic group of NOS. Moreover, the oxidation state of the heme iron is critical in determining the magnitude of inhibition of NOS by NO. Conditions that favor the higher oxidation state of FeIII markedly increase the inhibitory action of NO, whereas conditions that favor the lower oxidation state of FeII markedly decrease the inhibitory action of NO. One of the cofactor roles of tetrahydrobiopterin may be to reduce the negative-feedback effect of NO on NOS by favoring the formation of the ferrous heme state in NOS. The inhibitory influence of NO on eNOS, albeit indirectly, was also observed in vascular endothelial cells, arterial rings, and in vivo in the perfused rabbit hindquarters vascular bed. Excess NO in the form of NO donor compounds inhibited the endothelium-dependent formation of EDRF/NO in response to endothelium-dependent vasorelaxants such as acetylcholine and bradykinin without influencing the relaxant effect of NO itself. These studies are consistent with the view that enzymatically generated NO may play an important negative-feedback regulatory role on eNOS, and therefore on vascular endothelial cell function. Several biological implications of a negative-feedback modulatory effect by NO on constitutive isoforms of NOS are evident. In nonadrenergic-noncholinergic transmission, in which NO is believed to be the principal inhibitory neurotransmitter (Sanders and Ward, 1992; Rand, 1992; Rajfer et al., 1992), NO may regulate its own synthesis, and therefore the neurotransmission process. Excess NO production may be undesirable because of the potential of NO or a reaction product of NO to elicit cytotoxic effects. Many extraneuronal factors could also contribute to decreasing the potentially cytotoxic actions of NO. For example, reduced hemoproteins such as hemoglobin, myoglobin, and/or their oxygen adducts could inactivate NO, as could superoxide anion generated in the vicinity of NO. In vascular endothelial cells either enzymatically generated NO or the presence of exogenously added NO in the form of nitrovasodilator drugs could diminish the vasodilator responses to endothelium-dependent relaxants and flow or shear stress. Although iNOS is less sensitive than either eNOS or nNOS to inhibition by NO, the generation of relatively large quantities of NO by iNOS within the confines of a cell may lead to a negative-feedback effect. The concomitant generation of superoxide anion by the same or adjacent cells could result in a diminished negative-feedback effect because of the rapid reaction between NO and superoxide anion to form peroxynitrite. Thus, NO production would increase and there would be increased peroxynitrite formation as well, which would result in enhanced cytotoxicity, provided that peroxynitrite is a cytotoxic species. Alternatively, iNOS may be conveniently insensitive to NO in order to allow for the generation of large quantities of NO for the purpose of producing cytotoxic effects.
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PMID:Negative modulation of nitric oxide synthase by nitric oxide and nitroso compounds. 856 36

The ability of hemoglobin and myoglobin to bind nitric oxide (NO) produced by other cells and circulating vasodilators is well known. To characterize erythrocytes (RBCs), we used NADPH diaphorase labeling, as well as antibodies to the three known types of NO synthase (NOS 1, 2, and 3), and to a molecule usually associated with NOS, calmodulin. We show that the NADPH-diaphorase label labels myenteric neurons, endothelial cells, and the blood cells trapped in the lumen of the blood vessels running through the intestinal wall. The myenteric neurons are also positive for neuronal NOS (NOS1), calmodulin, and neuropeptide Y, indicating that they are NO-producing neurons. Endothelial cells are positive for NOS3 (a constitutive form of NOS), while macrophages and lymphocytes are positive for NOS2 (an inducible form of NOS). All are positive for calmodulin. Surprisingly, the RBCs are positive for NOS2 and 3, as well as calmodulin. Thus the RBCs possess all the cellular machinery to synthesize their own NO. We suggest that erythrocytes would synthesize and use NO to modulate their own physiology.
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PMID:Erythrocytes may synthesize their own nitric oxide. 897 93

Transgenic mice have turned out to be important in the analysis of cardiovascular physiology and pathology. A large number of gene knockout and overexpression models have been generated, including genes involved in blood pressure regulation, cardiac function and hemostasis. In this review we concentrate on two models, the endothelial NO synthase and the myoglobin knockout mice. It will be shown that the genetic approach of gene function analysis in mice not only provides new insight into the actual role of the encoded gene product, but also uncovers possible secondary alterations which compensate for the induced change. In the case of NOS knockout mice, upregulation of other NOS isoforms, induction of signal molecules such as prostaglandins or endothelium-derived hyperpolarizing factor may conserve the vasodilatory potential of NOS deficient vessels. In the case of myoglobin knockout mice, even structural changes may contribute to compensate a loss of gene function as shown by the elevated capillary density, which may enhance the oxygen supply to mitochondria. Thus, results obtained by the analysis of gene function in transgenic animals may differ from acute pharmacological interventions in that they reveal the striking ability of an intact organism to effectively adapt to chronic changes in gene expression.
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PMID:Adaptive mechanisms of the cardiovascular system in transgenic mice--lessons from eNOS and myoglobin knockout mice. 1119 71

Reactive molecules O(-)(2), H(2)O(2), and nitrogen monoxide (NO) are produced from macrophages following exposure to lipopolysaccharide (LPS) and involved in cellular signaling for gene expression. Experiments were carried out to determine whether these molecules regulate inducible nitric oxide synthase (iNOS) gene expression in RAW264.7 macrophages exposed to LPS. NO production was inhibited by the antioxidative enzymes catalase, horseradish peroxidase, and myeloperoxidase but not by superoxide dismutase (SOD). In contrast, the NO-producing activity of LPS-stimulated RAW264.7 cells was enhanced by the NO scavengers hemoglobin (Hb) and myoglobin. The antioxidant enzymes decreased levels of iNOS mRNA and protein in LPS-stimulated RAW264.7 cells, whereas the NOS inhibitor N(G)-monomethyl-L-arginine as well as Hb increased the level of iNOS protein but not mRNA, indicating that NO inhibits iNOS protein expression. NF-kappa B was activated in LPS-stimulated RAW264.7 cells and the activation was significantly inhibited by antioxidant enzymes, but not by Hb. Similar results were obtained using LPS-stimulated rodent peritoneal macrophages. Extracellular O(-)(2) generation by LPS-stimulated macrophages was suppressed by SOD, but not by antioxidative enzymes, while accumulation of intracellular reactive oxygen species was inhibited by antioxidative enzymes, but not by SOD. Exogenous H(2)O(2) induced NF-kappa B activation in macrophages, which was inhibited by catalase and pyrroline dithiocarbamate (PDTC). H(2)O(2) enhanced iNOS expression and NO production in peritoneal macrophages when added with interferon-gamma, and the effect of H(2)O(2) was inhibited by catalase and PDTC. These findings suggest that H(2)O(2) production from LPS-stimulated macrophages participates in the upregulation of iNOS expression via NF-kappa B activation and that NO is a negative feedback inhibitor of iNOS protein expression.
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PMID:Antioxidant enzymes suppress nitric oxide production through the inhibition of NF-kappa B activation: role of H(2)O(2) and nitric oxide in inducible nitric oxide synthase expression in macrophages. 1158 65

In the heart, in situ local myocardial blood flow (MBF) varies greater than 10-fold between individual areas and displays a spatially heterogeneous pattern. To analyze its molecular basis, we analyzed protein expression of low and high flow samples (300 mg, <50% or >150% of mean MBF, each n=30) of six beagle dogs by 2-D polyacrylamide gel electrophoresis (380 +/- 78 spots/gel). In low flow samples, dimethylarginine dimethylaminohydrolase (DDAH1) was increased greatly (+377%, compared with high flow samples). This increase resulted in a 75% reduction of asymmetric dimethylarginine (ADMA), the potent endogenous inhibitor of NO synthase, whereas eNOS showed no difference. Low flow samples exhibited enhanced expression of GAPDH (+89%) and phosphoglycerate kinase (+100%), whereas hydroxyacyl-CoA dehydrogenase, electron transfer flavoprotein, myoglobin, and desmin were decreased. Assessing local MBF on different days within 2 weeks revealed a high degree of MBF stability (r2 > 0.79). Thus, stable differences in local MBF are associated with significant differences in local gene and protein expression. In low flow areas, the increased DDAH1 reduces ADMA concentration and NOS inhibition, which strongly suggests enhanced NO formation. Low flow areas are also characterized by a higher glycolytic and a lower fatty acid oxidation capacity. Both the shift in substrate utilization and the rise in NO may contribute to the known lower oxygen consumption in these areas.
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PMID:Myocardial proteome analysis reveals reduced NOS inhibition and enhanced glycolytic capacity in areas of low local blood flow. 1191 76

Elevated cardiac levels of nitric oxide (NO) generated by inducible nitric oxide synthase (iNOS) have been implicated in the development of heart failure. The surprisingly benign phenotype of recently generated mice with cardiac-specific iNOS overexpression (TGiNOS) provided the rationale to investigate whether NO scavenging by oxymyoglobin (MbO2) yielding nitrate and metmyoglobin (metMb) is involved in preservation of myocardial function in TGiNOS mice. 1H nuclear magnetic resonance (NMR) spectroscopy was used to monitor changes of cardiac myoglobin (Mb) metabolism in isolated hearts of wild-type (WT) and TGiNOS mice. NO formation by iNOS resulted in a significant decrease of the MbO2 signal and a concomitantly emerging metMb signal in spectra of TGiNOS hearts only (DeltaMbO2: -46.3+/-38.4 micromol/kg, DeltametMb: +41.4+/-17.6 micromol/kg, n=6; P<0.05) leaving contractility and energetics unaffected. Inhibition of the Mb-mediated NO degradation by carbon monoxide (20%) led to a deterioration of myocardial contractility in TGiNOS hearts (left ventricular developed pressure: 78.2+/-8.2% versus 96.7+/-4.6% of baseline, n=6; P<0.005), which was associated with a profound pertubation of cardiac energy state as assessed by 31P NMR spectroscopy (eg, phosphocreatine: 13.3+/-1.3 mmol/L (TGiNOS) versus 15.9+/-0.7 mmol/L (WT), n=6; P<0.005). These alterations could be fully antagonized by the NOS inhibitor S-ethylisothiourea. Our findings demonstrate that myoglobin serves as an important cytoplasmic buffer of iNOS-derived NO, which determines the functional consequences of iNOS overexpression.
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PMID:Acute inhibition of myoglobin impairs contractility and energy state of iNOS-overexpressing hearts. 1452 22

Nitric oxide (NO) plays an important role in autocrine and paracrine manner in numerous physiological processes, including regulation of blood pressure and blood flow, platelet aggregation, and leukocyte adhesion. In vascular wall, most of the bioavailable NO is believed to derive from endothelial cell NO synthase (eNOS). Recently, neuronal NOS (nNOS) has been identified as a source of NO in the vicinity of microvessels and has been shown to participate in vascular function. Thus NO can be produced and transported to the vascular smooth muscle cells from 1). endothelial cells and 2). perivascular nerve fibers, mast cells, and other nNOS-containing sources. In this study, a mathematical model of NO diffusion-reaction in a cylindrical arteriolar segment was formulated. The model quantifies the relative contribution of these NO sources and the smooth muscle availability of NO in a tissue containing an arteriolar blood vessel. The results indicate that a source of NO derived through nNOS in the perivascular region can be a significant contributor to smooth muscle NO. Predicted smooth muscle NO concentrations are as high as 430 nM, which is consistent with reported experimental measurements ( approximately 400 nM). In addition, we used the model to analyze the smooth muscle NO availability in 1). eNOS and nNOS knockout experiments, 2). the presence of myoglobin, and 3). the presence of cell-free Hb, e.g., Hb-based oxygen carriers. The results show that NO release by nNOS would significantly affect available smooth muscle NO. Further experimental and theoretical studies are required to account for distribution of NOS isoforms and determine NO availability in vasculatures of different tissues.
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PMID:Contribution of nNOS- and eNOS-derived NO to microvascular smooth muscle NO exposure. 1503 59

Recent studies of myoglobin (Mb) knockout (myo-/-) mice have extended our understanding of Mb's diverse functions and have demonstrated a complex array of compensatory mechanisms. The present study was aimed at detailed analysis of cardiac function and exercise endurance in myo-/- mice and at providing evidence for Mb's functional relevance. Myo-/- isolated working hearts display decreased contractility (dP/dtmax 3883+/-351 vs. 4618+/-268 mmHg/sec, myo-/- vs. WT, P<0.005). Due to a shift in sympathetic/parasympathetic tone, heart rate is reduced in conscious myo mice-/- (615+/-33 vs. 645+/-27 bpm, myo-/- vs. WT, P<0.001). Oxygen consumption (VO2) under resting conditions (3082+/-413 vs. 4452+/-552 ml x kg(-1) x h(-1), myo-/- vs. WT, P<0.001) and exercise endurance, as determined by spiroergometry, are decreased (466+/-113 vs. 585+/-153 m, myo-/- vs. WT, P<0.01). Conscious myo-/- mice evaluated by echocardiography display lowered cardiac output (0.64+/-0.06 vs. 0.75+/-0.09 ml x min(-1) x g(-1), myo-/- vs. WT, P<0.001), impaired systolic shortening (60+/-3.5 vs. 65+/-4%, myo-/- vs. WT, P<0.001) and fail to respond to beta1-stimulation. Strikingly, the latter cardiac effects of Mb deficiency can be partially attenuated by NOS inhibition. Loss of Mb results in a distinct phenotype, even under resting conditions, and the importance of oxygen supply and nitric oxide scavenging by Mb is clearly demonstrated at the conscious animal level.
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PMID:Oxygen supply and nitric oxide scavenging by myoglobin contribute to exercise endurance and cardiac function. 1581 40


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