Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

E. coli endotoxin (0.03 mg/ml) added to blood perfusing a heart-lung preparation with a venous return of 600 ml/min produced a significant depression in ventricular function within 4 hours. Fragmented sarcoplasmic reticulum isolated from the myocardium of the endotoxin-perfused heart-lung preparations showed depressed calcium uptake rates and ATPase activity. When venous return was increased to 1,200 ml/min, gram-negative endotoxin had no effect on ventricular function, isolated fragmented sarcoplasmic reticulum calcium uptake, or ATPase activity. These observations suggest that gram-negative endotoxin or a product thereof acts in synergism with low venous return in order to depress myocardial function.
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PMID:The influence of venous return on cardiac mechanical and sarcoplasmic reticulum function during endotoxemia. 14 71

The regulatory mechanism in the aortic actomyosin system was studied. Superprecipitation of desensitized aortic myosin B was not exhibited even in the presence of Ca2+, but was observable only in the presence of native tropomyosin and Ca2+. Reconstituted actomyosin composed of pure aortic myosin and pure skeletal actin did not show superprecipitation. Addition of aortic native tropomyosin and Ca2+ caused a marked superprecipitation. The ATPase of reconstituted actomyosin was enhanced three- or fourfold by aortic native tropomyosin and Ca2+. The extent of superprecipitation of aortic myosin B did not show a biphasic type of response to Mg-ATP concentration. Thus, aortic native tropomyosin induces a real activation of the myosin, actin, and ATP system in the presence of Ca2+, in contrast with the case of skeletal native tropomyosin, which induces the depression of skeletal myosin-actin-ATP interaction in the absence of Ca2+.
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PMID:Regulatory mechanism in arterial smooth muscle contraction. 14 28

Cardiac muscle myosin ATPase activity is depressed and contractile function impaired when the heart is subjected to a chronic pressure overload. Administering digitalis in the presence of chronic pressure overload significantly attenuates the decline in mechanical function. The current study sought to determine if the cardiac muscle myosin ATPase activity of cats treated with digitalis in the presence of pressure overload remains normal in parallel with the mechanical function. Four groups of cats were studied: normal controls (C), animals with pressure-overload hypertrophy with or without failure (HF), normal cats that received treatment with digitalis (D), and animals that received digitalis prior to and together with pressure overload (DHF). Compared to C, the maximum myosin ATPase activity of HF was significantly (P less than 0.05) depressed, but the maximum ATPase activity of D and DHF was not altered significantly (P greater than 0.05) from C. In parallel with the enzyme maximum activity, the papillary muscle isometric rate of force development was significantly (P less than 0.005) depressed in HF compared to C; D and DHF were not significantly (P greater than 0.05) different from C. It is concluded that the depression of myosin ATPase observed in HF is not present when digitalis is administered concomitant with the pressure overload.
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PMID:Normal cardiac myosin ATPase and mechanics in pressure overload with digitalis treatment. 14 32

The ATPase activity of chicken gizzard myosin was studied by varying the KCl concentration in the reaction medium. The following was thus found: (a) A sharp depression of the activity occurred when the KCl concentration was reduced to less than 0.3 M, showing the minimum activity around 0.15 M KCl. (b) The activity depression was removed by addition of urea or bay papain-digestion, but not by addition of p-chloromercuribenzoate. (c) In the KCl concentration where the activity depression occurred, the ATPase reaction proceeded in two distinct phases; the activity was relatively high in the early phase of the reaction and declined into the later phase where the steady state reaction took place. (d) In the KCl concentrations higher than that particular concentration or in the presence of urea, the ATPase reaction proceeded in one phase. (e) The temperature dependence of the ATPase activity in the early phase was of an ordinary magnitude being approximately equal to that of the ATPase activity in 0.6 M KCl. In contrast, the temperature dependence of the activity in the later phase was unusually small. Gizzard myosin in various concentrations of KCl was also examined by measuring the turbidity and the light-scattering intensity, and by observation under an electron microscope. The following was thus found: (a) In the KCl concentration where the activity depression occurred, there was a stagnation in the turbidity decrease as the KCl concentration was gradually increased and also the formation of "thick filaments," each of which was approximately 0.6-0.9 micron in length and 20-30 nm in diameter with no central "bare zone." (b) Addition of ATP induced dissociation of the thick filaments, and the dissociation occurred during the early phase of the ATPaseeaction. (c) Moreover, the temperature dependence of the ATP-induced dissociation rate was approximately equal to that of the ATPase activity in the early phase. On the basis of the findings mentioned above, it is concluded that the activity depression results from the ATP-induced dissociation of myosin filaments. Moreover, since high concentrations of KCl or urea also caused dissociation of myosin filaments and yet did not produce the activity depression, it was strongly suggested that gizzard myosin in the ATP-dissociated form must be different from that in the urea- or KCl-dissociated form, probably in the physical state of some myosin aggregates which were not detectable by the physical methods we used. As a side-observation, gizzard myosin filaments formed in the presence of ADP were found to be unusually long (longer than 2 micron), and they looked very similar to the particular filaments of skeletal myosin that were reported, by Moos, to be formed in the absence of the C protein.
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PMID:Adenosine triphosphatase activity and "thick filament" formation of chicken gizzard myosin in low salt media. 14 68

The influence of endotoxin shock and of experimentally increased venous return during endotoxin shock on myocardial vesicular calcium uptake and calcium stimulated ATPase activity was investigated. Vesicular calcium uptake was depressed (p less than 0.01) from 0.9 mumoles/mg protein/min to 0.3 mumoles/mg/min after 5 hr of endotoxin shock. Control ATPase did not differ between endocardial surface and epicardial surface. This was accompanied by a depressed (p less than 0.01) ATPase activity from 1.2 mumoles Pi/mg/min at the endocardial surface, and to 0.9 mumoles Pi/mg/min at the epicardial surface. A femoral arteriovenous shunt was used to increase venous return by 313 +/- 71 ml/min (approximately 17 ml/kg) during the shock period. Vesicles from AV shunted animals after endotoxin were capable of normal calcium uptake and normal ATPase activity. Results suggest that myocardial depression during endotoxin shock is more severe on the endocardial surface and is caused by depressed vesicular calcium uptake secondary to depressed ATPase activity. Furthermore, this depression may be avoided by maintenance of an adequate venous return.
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PMID:Influence of endotoxin on myocardial calcium transport and the effect of augmented venous return. 14 34

The understanding of the effects of cannabinoids in human subjects has been obscured by a lack of knowledge about how the various active principles from marijuana act at the cellular level in the brain. For this reason the present study was undertaken to determine the effects of cannabinoids on the enzymes associated with the synaptic membranes. Electron micrographic analysis was performed to determine the purity of synaptic membrane preparations from rat brain, and subsequently such preparations were subjected to additions of ethanol, Tween-80, 80% glycerol, and either delta-tetrahydrocannabinol, 11-hydroxy-delta-tetrahydrocannabinol, or cannabinol. Both sodium and potassium activated ATPase (Na, K-ATPase), and Mg-ATPase were measured as the micrometer orthophosphate (P) released per minute per microgram membrane protein and these specific activities of the enzymes expressed as absolute values and as the percentage depression brought about by the cannabinoids. The ATPase spcific activities are taken from the rate curve over a 30-min incubation time. Additionally, synaptic membrane acetylcholineesterase specific activity was measured by continuous rate enzyme assay. While as low as 10 M delta-tetrahydrocannabinol showed appreciable decrements in both the membrane-bound ATPases, the other cannabinoids did not show such a great depression in enzyme activity. The specific activity of acetylcholinesterase, which is weakly bound to the membrane, showed only slight or no changes in activity with the various cannabinoids. It was additionally shown that the cannabinoids, delta-tetrahydrocannabinol in particular, bound to the synaptic membranes almost irreversibly in the in vitro system, and that the vehicle for dissolving the cannabinoids, while used as background control values when calculating the percentage decrements in enzyme specific activity, did vary the effects on the ATPase enzymes in particular. These data are discussed in relation to psychotomimetic activity of the cannabinoids.
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PMID:Effects of cannabinoids on synaptic membrane enzymes. I. In vitro studies on synaptic membranes isolated from rat brain. 14 40

Myosin and subfragment-1 were prepared from rabbit hearts hypertrophied secondary to pulmonary artery constriction. The Ca2+ -stimulated ATPase activity was reduced while the potassium/EDTA-stimulated ATPase activity was unchanged in both the myosin and subfragment 1 (S-1) from hypertrophied hearts. When hypertrophy myosin was mixed with an equal quantity of control myosin, the ATPase activity of the mixed protein fell halfway between control and hypertrophy values. Similar results were obtained with control and hypertrophy S-1. The actin-stimulated ATPase activity of hypertrophy S-1 was slightly depressed but unlike hypertrophy myosin this depression was not significant when compared to normal S-1. This suggests that papain cleavage may have removed part of the conformational difference that exists between control and hypertrophy myosins.
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PMID:The ATPase activity of subfragment-1 from the hypertrophied heart. 14 12

The effects of gramnegative endotoxin-induced myocardial failure in the pentobarbital-anesthetized dog were examined by monitoring its influence on cardiac myofibrillar ATPase activity. Myofibrils were isolated from endo- and epicardial portions of the left ventricular wall. ATPase activities were determined in animals treated with 4 mg/kg endotoxin and monitored 5 h, in animals monitored for 5 h without endotoxin (controls), and in animals implanted with a unilateral femoral shunt and given endotoxin. No differences were seen in the activities between the endo- and epicardial portions of any preparation. Activity was significantly depressed in endotoxemic animals. Increasing venous return by 313 +/- 71 ml/min significantly increased coronary flow by reducing coronary vascular resistance and prevented any observed depression of myofibrillar ATPase activity. In in vitro studies, adding endotoxin directly to a myofibril preparation did not modify normal activity. It appears that the mechanical and myofibrillar dysfunctions are due to the action of endotoxin at sites not associated with the actomyosin ATPase, but may be due to the production of an intermediary agent in concert with a decreased venous return.
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PMID:Endotoxin and myocardial failure: role of the myofibril and venous return. 15 Jul 99

1. The oxidation of linoleate by rat-liver mitochondria has been studied as a function of substrate concentration. The oxidation of other long-chain unsaturated fatty acids shows similar characteristics. 2. At low concentrations, linoleate is readily oxidized in the absence of carnitine. Its rate of activation by the intramitochondrial acyl-CoA synthetase (EC 6.2.1.2) and subsequent oxidation is limited by the availability of intra-mitochondrial ATP. 3. A gradual increase of the linoleate concentration leads to (i) a strong depression of the rate of linoleate oxidation, and (ii) uncoupling of respiratory-chain phosphorylation together with induction of a mitochondrial ATPase activity. At still higher linoleate concentrations this ATPase activity is lowered rather than further stimulated and, concomitantly, the rate of linoleate oxidation increases again. 4. Evidence is presented that the inhibition by linoleate of the ATPase activity occurs at the level of the ATPase complex itself. This oligomycin-like effect of linoleate allows intramitochondrial linoleate activation to take place at the expense of ATP derived from substrate-level phosphorylation. 5. At very high concentrations of linoleate, its detergent action predominates and causes a complete inhibition of respiration as well as an extensive stimulation of an oligomycin-insensitive, Mg2+-dependent ATPase activity. 6. Measurement of the binding of radioactively labelled linoleate by isolated mitochondria shows that, at a given ratio of linoleate to mitochondrial protein, the ratio of bound to added linoleate is dependent on the concentration of the mitochondria.
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PMID:The oxidation of long-chain unsaturated fatty acids by isolated rat liver mitochondria as a function of substrate concentration. 15 Aug 57

In our previous study (Onishi, H., Susuki, H., Nakamura, k., and Watanabe, S. J. Biochem. 83, 835-847, 1978), we found it to be characteristic of chicken gizzard myosin that thick filaments of gizzard myosin are readily disassembled by a stoichiometric amount of ATP (3 mol of ATP per mol of myosin), and that the ATPase activity of gizzard myosin in the ATP-disassembled state is much lower than that of gizzard myosin disassembled by a high concentration of KCl. We now report the following findings: (1) Thick filaments of (unphosphorylated) gizzard myosin can be in a bipolar structure or in a non-polar structure, depending on the method of preparing the thick filaments. (2) Thick filaments of (unphosphorylated) gizzard myosin in either the bioplar or the non-polar structure are readily disassembled by ATP. (3) Addition of rabbit skeletal C-protein does not confer ATP resistance on thick filaments of (unphosphorylated) gizzard myosin. (4) Unphosphorylated) gizzard myosin in the ATP-disassembled state is in a dimeric form as determined by ultracentrifugation. Moreover, 0.2 M KCl-dissociated gizzard myosin in monomeric form is converted to a dimeric form by ATP. (5) The Mg-ATPase activity of (unphosphorylated) gizzard myosin is much lower in its dimeric form (less than one-tenth) than in its monomeric form. The activity depression observed around 0.15 M KCl is therefore due to the formation of myosin dimers. (6) Skeletal L-meromyosin can increase the very low activity of (unphosphorylated) gizzard myosin ATPase at low ionic strength (0.13 M KCl) by forming ATP-resistant hybrid filaments with (unphosphorylated) gizzard myosin, preventing the formation of myosin dimers. (7) Gizzard myosin in which one of the light-chain components is phosphorylated by myosin light-chain kinase can form thick filaments which are resistant to the disassembling action of ATP. (8) Even in the presence of ATP, thick filaments of phosphorylated gizzard myosin do not disassembled into myosin dimers. Accordingly, the ATPase activity of phosphorylated gizzard myosin does not show activity depression at low ionic strength.
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PMID:Structure and function of chicken gizzard myosin. 15 5


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