Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.64 (MPP)
 1,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The calcium dependence of spontaneous transmitter release from nerve terminals of different lengths was examined at neuromuscular junctions in frog muscle. Miniature endplate potential (MEPP) frequency was positively correlated with the endplate potential (EPP) quantal content and was dependent on external Ca2+. The higher the resting MEPP frequency in a 0.25 mM-Ca2+ Ringer solution, the greater the dependence on external Ca2+. MEPP frequency in all terminals dropped to approximately the same low level in a Ca2(+)-free Ringer solution containing EGTA. This suggests that terminals with higher release levels have a larger Ca2+ influx at rest. 2. Several tests were done to try to characterize the mode of Ca2+ entry into resting terminals. omega-Conotoxin (omega-CgTx) blocked evoked release and reduced MEPP frequency, but not as effectively as zero Ca2(+)-EGTA Ringer solution. Some component of Ca2+ influx thus appears to enter through channels insensitive to omega-CgTx. Tetrodotoxin (TTX) did not affect MEPP frequency, indicating that the Ca2+ did not enter through TTX-sensitive Na+ channels that might be opening spontaneously at rest. Hyperpolarization of the terminal by reducing the K+ in the Ringer solution caused no consistent differences in MEPP frequency, suggesting that the Ca2+ influx is relatively insensitive to small changes in membrane potential around the resting level. Strong buffering of the Ringer solution with citrate, to overwhelm any differences in Ca2+ buffering within different junctional clefts, had no significant effect on the MEPP frequency. 3. Evidence that the Na(+)-Ca2+ exchanger helps set the internal Ca2+ level was obtained. Reduction of the Na+ concentration in the Ringer solution caused increases in MEPP frequency ranging from 6 to 440%. However, these changes were not correlated with resting MEPP frequency, hence differences in MEPP frequency probably are not the result of differences in Na(+)-Ca2+ exchanger function in terminals having a uniform Ca2+ leak. 4. Although MEPP frequency was generally correlated with quantal content, in subsets of junctions grouped according to their similar quantal contents, there was a positive correlation between MEPP frequency and terminal length. 5. In zero Ca2(+)-EGTA Ringer solution, the low residual MEPP frequency is independent of terminal length, even when MPP frequency is sharply increased by tetanic stimulation.
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PMID:Dependence of spontaneous release at frog junctions on synaptic strength, external calcium and terminal length. 257 68

The tissue distribution of interleukin-2 (IL-2) in normal and 1-methyl-4-phenyl-pyridinium (MPP+)-lesioned brains of rats was investigated. Intrastriatal administration of MPP+ caused visible damage in the vicinity of the injected region two weeks after injection. Autoradiography of the tissue section with anti-IL-2 antibodies plus trace amounts of radiolabeled IL-2 showed that the antibodies treatment elicited a selective radiolabeling of the brain tissues localized at the MPP(+)-lesioned region but not at normal cryo-sliced sections. Addition of radiolabeled IL-2 alone or normal rabbit immunoglobulins did not show any labeling effect. These autoradiographic imaging results suggest that there is an accumulation of cells bearing IL-2-like molecules at the MPP(+)-induced lesion sites.
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PMID:Visualization of interleukin-2-like molecules in MPP(+)-lesioned rat brain. 261 Jun 95

The kinetic mechanism of yeast inorganic pyrophosphatase (PPase) was examined by carrying out initial velocity studies. Ca2+ and Rh(H2O)4(methylenediphosphonate) (Rh(H2O)4PCP) were used as dead-end inhibitors to study the order of binding of Cr(H2O)4PP to the substrate site and Mg2+ to the "low affinity" activator site on the enzyme. Competitive inhibition was observed for Ca2+ vs Mg2+ (Kis = 0.93 +/- 0.03 mM), for Rh(H2O)4PCP vs Cr(H2O)4PP (Kis = 0.25 +/- 0.07 mM), and for RH(H2O)4PCP vs Mg2+ (Kis = 0.38 +/- 0.03 mM). Uncompetitive inhibition was observed for Ca2+ vs Cr(H2O)4PP (Kii = 0.49 +/- 0.01). On the basis of these results a rapid equilibrium ordered mechanism in which Cr(H2O)4PP binding precedes Mg2+ ion binding is proposed. The inert substrate analog, Mg(imidodiphosphate) (MgPNP) was shown to induce Mg2+ inhibition of the PPase-catalyzed hydrolysis of MgPP. The Mg2+ inhibition observed was competitive vs MgPP and partial. These results suggest that Mg2+/MgPNP release from the enzyme occurs in preferred rather than strict order and that the Mg2+/MgPP-binding steps are at steady state. Zn2+, Co2+, and Mn2+ (but not Mg2+) displayed activator inhibition of the PPase-catalyzed hydrolysis of PPi (this study) and of Cr(H2O)4PP (W.B. Knight, S. Fitts, and D. Dunaway-Mariano, (1981) Biochemistry 20, 4079). These findings suggest that cofactor release from the low affinity cofactor site on the enzyme must precede product release and that Zn2+, Mn2+, and Co2+ (but not Mg2+) have high affinities for the cofactor sites on both the PPase.M.MPP and PPase.M.M(P)2 complexes. The role of the metal cofactor in determining PPase substrate specificity was briefly explored by testing the ability of the Mg2+ complex of tripolyphosphate (PPPi) (a substrate for the Zn2+-activated enzyme but not the Mg2+-activated enzyme) to induce Mg2+ inhibition of PPase-catalyzed hydrolysis of MgPP. MgPPP was shown to be as effective as MgPNP in inducing competitive Mg2+ inhibition (vs MgPP). This result suggests that the low affinity Mg2+ cofactor-binding site present in the enzyme-MgPP complex is maintained in the enzyme-MgPPP complex. Thus, failure of Mg2+ to bind to the enzyme-MgPPP complex was ruled out as a possible explanation for the failure of the Mg2+-activated enzyme to catalyze the hydrolysis of MgPPP.
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PMID:The kinetic mechanism of yeast inorganic pyrophosphatase. 282 96

The efficiency of various dust respirators for eliminating mouse allergens [mouse urine proteins (MUP), pelts proteins (MPP) and serum albumin (MSA)] were evaluated with use of low-volume air samplers and immunochemical methods. Three kinds of dust respirators from one manufacturer which have different efficacy in the exclusion of dust particles were put on the fiber glass filter in each air sampler. Then the air in a mouse housing room was sampled. The allergens passed through the respirators, were trapped in the fiber glass filters, and then extracted from the filters. The allergens of MUP and MPP in the extract were measured by an inhibition method of fluorometric enzyme-linked immunosorbent assay (ELISA) for IgE antibody and those of MSA measured by a fluorometric sandwich ELISA. The respirator with the lowest capability of exclusion was found to eliminate 65-86% of respective allergens. The other two respirators with higher powers eliminated 98% of MUP. MPP and MSA were eliminated to undetectable levels through these respirators. This study provided a means for the evaluation of dust respirators for animal aeroallergens.
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PMID:Evaluation of dust respirators for elimination of mouse aeroallergens. 291 88

Transport of nuclear-encoded precursor proteins into mitochondria includes proteolytic cleavage of amino-terminal targeting sequences in the mitochondrial matrix. We have isolated the processing activity from Neurospora crassa. The final preparation (enriched ca. 10,000-fold over cell extracts) consists of two proteins, the matrix processing peptidase (MPP, 57 kd) and a processing enhancing protein (PEP, 52 kd). The two components were isolated as monomers. PEP is about 15-fold more abundant in mitochondria than MPP. It is partly associated with the inner membrane, while MPP is soluble in the matrix. MPP alone has a low processing activity whereas PEP alone has no apparent activity. Upon recombining both, full processing activity is restored. Our data indicate that MPP contains the catalytic site and that PEP has an enhancing function. The mitochondrial processing enzyme appears to represent a new type of "signal peptidase," different from the bacterial leader peptidase and the signal peptidase of the endoplasmic reticulum.
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PMID:Mitochondrial protein import: identification of processing peptidase and of PEP, a processing enhancing protein. 296 9

Fatigue, polarization level and excitability of striated muscle fibers from ischemia zone were studied on experimental rats under the tourniquet shock. It was established that violation-mediated contraction and fatigue of skeletal muscle was associated with a decrease in a number of muscle fibers with high level of MPP. The article discussed the mechanisms of fatigue and depolarization of muscle fibres in tourniquet shock.
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PMID:[Dependence of skeletal muscle fatigue on the membrane polarization of the different types of muscle fibers in tourniquet shock]. 334 40

The purpose of the present study was to investigate whether damage to the medial (MPP) or lateral hippocampal perforant path (LPP) may differentially affect rats' ability to react to novelty or environmental change. Three different types of task were used based on various sets of stimuli; visual/tactile, olfactory, or visual only. The results showed that the lesions produced different responses to different novel stimuli. In contrast to control and MPP animals, LPP rats displayed excessive exploration of the test cage. The results are discussed in terms of impoverished cognitive structure following perforant path disruptions and functional differentiation between MPP and LPP.
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PMID:The role of medial and lateral hippocampal perforant path lesions and object distinctiveness in rats' reaction to novelty. 338 91

1. Protein kinase C (PKC) stimulators, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or cis-unsaturated fatty acid (UFA), have been shown to prolong synaptic enhancement induced by long-term potentiation (LTP). This observation suggests a role for PKC in the biochemical mechanisms underlying maintained enhancement. 2. To determine if PKC stimulators prolong LTP by acting selectively at synapses given high-frequency stimulation or by actions that are not synapse-specific (e.g. increased postsynaptic excitability) we examined the effect of TPA or UFA on input-selective enhancement. Population EPSPs, evoked in the same granule cell population by either the medial (MPP) or lateral (LPP) perforant path, can be selectively enhanced leaving the other perforant path input which receives only low-frequency stimulation as an internal control for PKC stimulator effects not specific to enhanced synapses. 3. Synapse-specific effects were in fact observed, as UFA or TPA selectively prolonged MPP enhancement following two trains of high-frequency MPP stimulation, without affecting responses evoked by the LPP. A similar synapse selectivity of PKC stimulator action was seen following high-frequency LPP stimulation. 4. These findings suggest that PKC stimulators prolong enhancement by acting specifically at high-frequency-stimulated synapses. PKC stimulators do not appear to affect either postsynaptic neurone excitability or synapses given only low-frequency stimulation. This provides further evidence that PKC acts synergistically with the consequences of repetitive synaptic activation to maintain enhancement.
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PMID:Synapse-specific protein kinase C activation enhances maintenance of long-term potentiation in rat hippocampus. 341 28

The binding of a series of phenylpiperazines (3) and benzoylpiperazines (4) to central serotonin (5-HT) sites was investigated. Several derivatives of 3 displayed nanomolar affinities for 5-HT1 sites, whereas derivatives of 4 were essentially inactive both at 5-HT1 and 5-HT2 sites. 1-(2-Methoxyphenyl)piperazine (2-MPP, 3a) was found to possess an affinity (Ki = 35 nM) for 5-HT1 sites comparable to that of the recognized 5-HT agonist 1-[3-(trifluoromethyl)phenyl]piperazine (TFMPP) (Ki = 20 nM); 3a also displayed a 100-fold selectivity for 5-HT1 sites (as compared to 8-fold for TFMPP). In tests of stimulus generalization using rats trained to discriminate TFMPP (ED50 = 0.17 mg/kg) from saline, 3a was found to be nearly equipotent (ED50 = 0.22 mg/kg) with the training drug. These results suggest that 3a may be a novel and more selective 5-HT1 agonist than TFMPP.
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PMID:Synthesis and evaluation of phenyl- and benzoylpiperazines as potential serotonergic agents. 370 81

The significance of pulmonary pressure-flow relation and its correlation to alveolar dead space and histological lesions of the lung were evaluated in ten mongrel dogs, which were subjected to standardized bone trauma and hemorrhagic hypotension at 40 mm Hg for 3h. These results were compared with those of 5 control dogs without trauma and shock. Two different pressure-flow curves were obtained by consecutive measurements of cardiac output and mean pulmonary artery pressure during stepwise arterial hemorrhage and reinfusion. In each experiment, the difference between the two curves at CO of 100 ml/kg min was obtained and represents an increase in pulmonary artery pressure (delta MPP). This increase in pulmonary artery pressure is flow-independent and, therefore, can be used as a quantitative indicator of pulmonary vasoconstriction or vascular obstruction. Severity of shock (uptake) as well as grade of early histological lesions of the lung (microthrombi, edema, hemorrhage) and increased alveolar dead space after reinfusion were associated with a more pronounced shift of the pulmonary pressure-flow curve. In severe experimental shock, therefore, a consistent pattern of pulmonary hemodynamics, lung histology, and respiratory function was demonstrated by the pulmonary pressure-flow relation. This approach permits estimation of the effects of therapeutic interventions and may be suitable for assessing postshock pulmonary impairment.
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PMID:Pulmonary pressure-flow relation after trauma and hemorrhagic shock. 379 20


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