UMLS:C0011570 - FACTA Search

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Query: UMLS:C0011570 (depression)
172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Some properties of succinate dehydrogenase [succinate-(acceptor) oxidoreductase, EC 1.3.99.1] in membrane preparations from Micrococcus lysodeikticus (N.C.T.C. 2665) were investigated. 2. In the spectrophotometric assay system adopted the reaction velocity was shown to be proportional to the amount of membrane added. Dichlorophenol-indophenol, reduced photochemically in the presence of phenazine methosulphate, or enzymically by the membrane-bound enzyme, was shown to undergo reoxidation in the dark. 3. The membrane-bound enzyme was found to be inactivated at temperatures above 10 degrees C. 4. The specific activity of membrane-bound succinate dehydrogenase was found to increase between two- and three-fold in diluted membrane preparations equilibrated at 0 degrees C for 6h. Membranes treated with sodium deoxycholate showed no enzyme activation on dilution but displayed maximal activity, all activity being sedimentable at 103000g. The increase in specific activity observed on dilution could be partially inhibited by fixation with glutaraldehyde, or by the presence of bovine serum albumin. 5. The addition of Mg(2+) or Ca(2+) ions to membrane suspensions caused an overall depression of enzyme activity. 6. The results suggest the presence of an ;inhibitor' that affects the expression of membrane bound succinate dehydrogenase activity.
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PMID:Factors influencing the activity of succinate dehydrogenase in membrane preparations from Micrococcus lysodeikticus. 549 52

The effect of ATP synthesis on delta mu H in rat liver mitochondria has been analyzed by separating the steps of adenine nucleotide translocation and ATP synthesis in the matrix. Either exchange of ATP, synthesized by substrate level phosphorylation in the matrix of oligomycin-treated mitochondria, for external ADP, or activity of the membrane-bound ATP synthase complex results in delta mu H depression with respect to resting state levels. This depression appears to be more pronounced, under strictly comparable conditions, when arsenate is used to stimulate ATP synthase activity than when the ornithine-citrulline conversion reaction is used for the same purpose.
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PMID:Studies on the relationship between ATP synthesis and transport and the proton electrochemical gradient in rat liver mitochondria. 621 98

The 5'-nucleotidase activity of rat liver plasma membranes could be selectively modulated by the anionic drugs phenobarbital and pentobarbital, whereas the corresponding activity of a Lubrol-solubilized preparations remained unaltered. The perturbation in the outer half of the bilayer induced by phenobarbital, which lead to a depression in the high temperature onset of the lipid phase separation occurring in this half of the bilayer, concomitantly lowered the break temperature in Arrhenius plots of 5'-nucleotidase activity from 28 degrees C to 16 degrees C. The stimulation of the membrane-bound activity achieved by low anionic drug concentrations was attributed to a preferential fluidization of the outer half of the bilayer. Contrarily, the cationic drugs prilocaine and carbocaine, when tested over agent concentrations that dramatically increase the fluidity of the inner half of the bilayer, achieved no selective effects on the membrane-bound enzyme. Prilocaine (10 mM) was previously found to induce a lipid phase separation at 11 degrees C that was attributed to the lipids of the internal (cytosol-facing) half of the bilayer, but had no effect on the onset of the lipid phase separation occurring at 28 degrees C. Since Arrhenius plots of 5'-nucleotidase activity in the presence of 10 mM prilocaine concentrations demonstrated only the single break at 28 degrees C, we suggest that prilocaine is unable to selectively perturb the enzyme because this cationic drug preferentially interacts with the acidic phospholipids residing in the inner half of the bilayer. The activity of the ectoenzyme 5'-nucleotidase in rat liver plasma membranes appears to be regulated by the external half of the bilayer only. These results support the view that independent modulation of he fluidity or chemical constituents of each half of the bilayer can distinctly affect the activity of proteins that are themselves asymmetrically orientated within the bilayer.
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PMID:The activity of 5'-nucleotidase in liver plasma membranes is affected by the increase in bilayer fluidity achieved by anionic drugs but not by cationic drugs. 627 99

Mitochondria incubated aerobically in the presence of tetrapropylammonium and weak acids and in the presence of trace amounts of tetraphenylboron undergo a series of damped oscillations reflecting cycles of osmotic swelling and shrinkage. The matrix volume changes are consequent to transport of tetrapropylammonium catalytically stimulated by tetraphenylboron. The amplitude and frequency of the oscillations increase with the concentration of tetrapropylammonium, as required for critical rates and extents of ion influx. Addition of bovine serum albumin abolishes both the uptake of tetrapropylammonium and the oscillations. Volume oscillations are paralleled by cyclic activation and depression of the respiratory rate. Two lines of evidence suggest that the train of damped oscillations depends on the cyclic activation of an electroneutral exchange of H+ with organic cations rather than on cyclic uncoupling. First, further increase of cation permeability due to a pulse of tetraphenylboron, after initiation of cation efflux, restores cation influx. Second, addition of Mg2+, which abolishes the oscillations, has a much more marked inhibitory effect on the process of cation efflux than on cation influx. Conversely, addition of A23187, which removes membrane-bound Mg2+, promotes cation efflux and thus the oscillations. It is suggested that, in the present system, stretching of the inner membrane and Mg2+ depletion result in activation of an electroneutral H+/organic cation exchange, and that cyclic activation of this reaction results in damped oscillations.
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PMID:Mitochondrial oscillation and activation of H+/cation exchange. 629 97

Albumin synthesis was studied in the isolated perfused rabbit liver under the influence of the stresses of fasting and acute alcohol and acetaldehyde exposure. Fasting clearly depressed albumin production and disaggregated the endoplasmic membrane-bound polysomes. Acute exposure to alcohol produced the same results. Acetaldehyde 2 mg% resulted in a depression of albumin synthesis but the polysomes were not disaggregated. The metabolism of alcohol was necessary for polysome disaggregation. The acute effects of ethanol and fasting were quite similar and it might be considered that the alcohol was acting like a pharmacologic fast. Employing the liver from a fasted donor specific amino acids infused into the liver at levels of 10 mM reversed the acute effects of fasting and the acute effects of exposure to ethanol. However when the two stresses of fasting and alcohol were combined the same amino acids were not effective. In studying albumin synthesis and/or secretion it is necessary to carefully define the nutritional status of the experimental model.
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PMID:Effects of nutrition and alcohol on albumin synthesis. 634 44

The simultaneous injection of carbaryl and colloidal carbon phagocytized by the reticuloendothelial cells results in competition between the two substances in favor of the carbon particles. Experiments with opsonized carbaryl suggest that the decrease in carbaryl blood clearance by the colloid is mediated by a depletion of serum opsonins. Following blockade, the liver carbaryl uptake was depressed in the control group (17%), while it was increased in the opsonized group (12%). With all preparations of carbaryl, opsonized or non-opsonized, colloidal carbon produced a slight and variable increase in carbaryl uptake by the spleen and lungs. These results indicate that, besides the uptake of carbaryl by the hepatocytes, other clearance sites must also be considered such as the Kupffer cells and other liver sinusoidal cells. Moreover our results show that intravenous administration of carbaryl induces a state of phagocytic depression as indicated by impaired intravascular phagocytosis and depressed hepatic uptake of the reticuloendothelial (RE)-test colloidal suspension. The results obtained from injection of opsonized colloidal particles during carbaryl-induced RE-depression, and the fact that carbaryl and carbon are both opsonized by the same serum factor, suggest that the mechanisms of RE-blockade involve selective hepatic and splenic macrophage failure and depletion of serum opsonins. According to our enzymatic investigation, this failure of the RE system to incorporate colloids during carbaryl--RE-blockade could be due to a defect in the activity of macrophage membrane-bound serine esterase.
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PMID:Evaluation of cellular and humoral mechanisms of carbaryl-induced reticuloendothelial phagocytic depression. 641 30

Passive electrical parameters of bullfrog atrial trabeculae were measured in a single gap arrangement. Attention was focussed on the resistance of internal longitudinal pathway. The influence of external Ca2+ depletion was tested using EGTA as chelating agent. Morphometry of trabeculae, fine structure of junctional complexes, and distribution of membrane-bound Ca were investigated by light and electron microscopic methods. The specific internal resistance to longitudinal current flow was 523 omega cm with normal Ringer as perfusing fluid and 1140 omega cm in EGTA-containing solution. These values are considered to represent the sum of myoplasmic and junctional resistivity. Morphometrical studies indicated an interstitial space of 12%, a mean cell length of 358 micron, and a mean cell diameter of 3.2 micron. In freeze-fractured preparations junctional structures were observed in the form of "atypical gap junctions" consisting of 10 nm particles arranged in a circular or linear array. The number of gap junctions was estimated to range between 20 and 50/cell which is equivalent to a junctional area of 0.01 or 0.03% of total surface area. A mean number of 55 particles/gap junction was calculated. After 20 min of exposure to EGTA the majority of junctional complexes were converted to clusters; the number of particles/gap junction was not significantly altered. The fluorescent dye CTC was used as a probe for membrane-bound Ca of isolated living cells. In normal Ringer a strong fluorescence was seen at the cell surface and in different intracellular compartments. With EGTA both superficial and internal fluorescence disappeared completely. From a combination of electrical and morphometrical data the resistance of intercellular junctions was calculated. Under normal conditions the specific resistance of junctional membrane amounted to 0.4 omega cm2 and the resistance of an individual connection was of the order of 10(11) omega. With EGTA, the respective values were increased by about 230%. The mechanism underlying this depression of junctional conductance is not clear. It seems not related to a rise of cytoplasmic free Ca2+. The EGTA-induced increase in internal resistance was reflected by a decrease of the length constant of a bundle. The nature of "atypical gap junctions" and their relation to tight junctions are discussed. It is concluded that the junctions observed in frog atrial muscle are analogous to gap junctions of insect or mammalian cells in spite of the different size and arrangement of the particles. A theoretical model is presented for the electrical behaviour of a bundle in a single gap arrangement.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Intercellular coupling in frog heart muscle. Electrophysiological and morphological aspects. 660 56

Heart sarcolemma from different animals was isolated for studying the effect of NaF on membrane-bound adenylate cyclase activity. Unlike dog and rabbit heart, a depression of adenylate cyclase by NaF was observed in sarcolemma from rat heart. There was a progressive attenuation of the NaF ability to stimulate the enzyme at different steps of the sarcolemmal isolation procedure. The activation by epinephrine in the presence of Gpp(NH)p also decreased progressively but unlike NaF, this agent did not show an inhibition of the enzyme. The inhibitory action of NaF was not reversed upon the treatment of heart membranes with deoxycholate or by Ca2+. Lubrol extract (supernatant) of a particulate fraction from rat heart, which showed NaF activation, returned the stimulatory response of the sarcolemmal adenylate cyclase to NaF. These results suggest that some regulatory factor is required for the stimulation of adenylate cyclase by NaF in myocardium and rat heart is susceptible for the loss of such a factor during the sarcolemmal isolation by the hypotonic shock-LiBr treatment method.
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PMID:Association of adenylate cyclase inhibition by NaF with loss of a factor in rat heart sarcolemma. 662 5

During chronic intoxication by diisopropyl fluorophosphate (Isoflurophate, DFP; s.c. treatment on alternate days - first dose of 1.1 mg/kg, subsequent doses of 0.7 mg/kg each until the 23rd day) a partial recovery of enzymatic activity was found at 24 h after each DFP administration. Relative to maximal AChE depression at 90 min, these rises were more pronounced in the soluble portion of the enzyme than in total enzyme preparation, i.e., that containing mainly membrane-bound AChE. Moreover, from the 2nd DFP administration on, there was a persistent increase of medium-molecular-weight forms both in soluble and in total AChE. The results suggest an important role of the soluble portion of AChE and of medium forms in the process of recovery of enzymatic activity.
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PMID:Mechanisms of recovery of brain acetylcholinesterase in rats during chronic intoxication by isoflurophate. 695 89

The number of leukocytes and the percentage of cells in various mononuclear subpopulations were determined in 22 patients with epilepsy. The lymphocyte response to PHA were examined in the patients and in selected controls. The patients were grouped according to phenytoin treatment at present or previously, and according to the presence or absence of serum IgA depression. Patients taking phenytoin demonstrated reduced leukocyte counts. The lowest counts were found in phenytoin-treated patients with markedly reduced IgA concentrations. The number of lymphocytes were reduced more than the total leukocyte count in the patients. No significant differences were observed between patients and controls regarding percentage of cells with membrane-bound immunoglobulins, active E-rosetting cells, AET-rosetting cells, EA-rosetting cells, EAC-rosetting cells, and cells with a capacity of phagocytosis. The mean response to PHA stimulation (PHA concentration 0.6 micrograms/ml) was 4634 counts per minute in the patients and 6132 counts per minute in the controls. However, the response to this stimulation varied considerably between individuals in both groups, and the difference between the 2 groups was not statistically significant.
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PMID:Lymphocyte subpopulations and lymphocyte function in phenytoin-treated patients with epilepsy. 697 23

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