Does increased hydrostatic pressure enhance ionomycin-protein binding?
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Calcimycin↗
Biomedical subjects
D Ogston
Publications and source records attributed to D Ogston.
Effects of hydrostatic pressure and inert gases on platelet aggregation in vitro.
A novel cuvette was used to subject citrated platelet-rich plasma (PRP) to high hydrostatic pressure with negligible contamination by He (used for compression of the apparatus). Aggregation was induced at pressure by ADP and quantified turbidimetrically. The maximum degree of aggregation (MDA) was reduced from a control level of 82.2 to 53.6% by exposure to 101 ATA. Because decompression bubbles did not form, aggregation was also measured immediately after a compression cycle. After exposure to 101 ATA hydrostatic pressure, platelets responded normally to ADP at 1 ATA. In a matching apparatus, PRP was equilibrated with high partial pressures of inert gases. Normal physiological plasma Po2 and pH were maintained during equilibration. N2O (5 ATA) reduced the MDA from 86.5 (control) to 58.1%. N2 (51 ATA) reduced the MDA from 74.7 (control) to 51.6%, and 101 ATA Pn2 reduced the MDA from 78.0 (control) to 32.3%. He (100 ATA) reduced the MDA from 83.6 to 38.6%. It was concluded that platelet aggregation was relatively sensitive to hydrostatic pressure and less sensitive to inert gases than predicted from their anesthetic potency ratios.
Adenosine Diphosphate↗
Current status of antifibrinolytic drugs.
Antifibrinolytic drugs, in particular, epsilon-aminocaproic acid and tranexamic acid, have been used in the management of a wide range of both bleeding and non-haemorrhagic disorders. Recognition of their side-effects and complications, comparison of their efficacy with other forms of therapy and more critical evaluation of their value has reduced the range of their definitive indications to a limited number of relatively uncommon situations; these comprise primary hyperplasminaemia, menorrhagia in women in whom oestrogens are contraindicated or in those with von Willebrand's disease, severe traumatic hyphaema, dental extraction in haemophiliacs and hereditary angioedema in patients in whom treatment with anabolic steroids is contraindicated. In a few conditions the possible benefit of antifibrinolytic agents, alone or supplementary to other forms of therapy, is unresolved; these include upper gastrointestinal bleeding, recurrent epistaxis and abruptio placentae.
Antifibrinolytic Agents↗
Effects of gas bubbling and other forms of convection on platelets in vitro.
Citrated platelet-rich human plasma was subjected to one of three experimental treatments at 37 degrees C for 15 min: stirring, bubbling (with stirring), and gentle agitation achieved by a rocking motion. The last two were "equiconvective" as judged by equilibration rates with CO2 and O2 but presumably differed in the shear stress they imposed on the cells. Stirring platelets in normal air or 5% CO2-air caused no significant aggregation. Bubbling air through platelet-rich plasma increased its pH and marked aggregation occurred. Bubbling CO2-air caused the platelet-rich plasma pH to attain its physiological level of 7.4 with less aggregation. In both cases, subsequent ADP-induced aggregation was diminished. Rocking (without stirring) in the presence of CO2-air caused negligible aggregation in platelets and an enhanced response to ADP. Because of the marked difference between the two equiconvective treatments, bubbling and rocking, the main factor in activating the human platelets is suggested to be shear stress (potentiated by high pH), with perhaps a lesser contribution from the air-plasma interface.
Adenosine Diphosphate↗
Effects of high pressure on platelet aggregation in vitro.
An apparatus which enables aggregating agents to be added to a stirred suspension of platelets subjected to a pressure of up to 600 ATA is described. The ensuing aggregation reaction is monitored optically. The pressure is applied with helium; data are presented that indicate the effects are mainly attributable to hydrostatic pressure. The aggregation of human platelets induced by ADP was reversibly inhibited by pressure in the 1-270 ATA range. The second phase of aggregation was blocked by 65 ATA; the rate of first phase aggregation was reduced but the time to respond to ADP was not affected. Comparable pressures also affected collagen and arachidonate-induced aggregation. The time to respond to these aggregating agents was prolonged and both the rate and the degree of aggregation were reduced by pressure.
Adenosine Diphosphate↗
Nutritional influences on the fibrinolytic system.
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Alcoholic Beverages↗
The influence of the polyphenols of cider on plasmin and plasminogen activators.
Preliminary findings suggested that the inhibitory activity on fibrinolysis produced by most varieties of cider is due to their content of polyphenols. In particular, the inhibitory activity co-eluted with the brown coloration on gel filtration, was removed by adsorption with polyvinylpyrrolidine, and was greatly reduced in a type of cider with a low concentration of phenolic compounds. The individual polyphenols of apple juice and ciders were examined for their ability to inhibit tissue activator, urokinase and plasmin. Neither phloridzin nor chlorogenic acid had any inhibitory activity at concentrations of 500 micrograms/ml while epicatechin had only a slight inhibitory effect at this concentration. The procyanidin fractions were markedly inhibitory on urokinase-induced clot lysis, the amidolytic activity of plasmin and on the fibrinolytic activities of plasmin, urokinase and tissue activator on fibrin plates: inhibition was noted at concentrations as low as 0.25 micrograms/ml. The order of inhibition was polymer greater than oligomer greater than trimer greater than dimer.
Alcoholic Beverages↗
The fibrinolytic system in pre-eclampsia.
Plasma fibrinolytic activity and plasma inhibitory activity against urokinase and tissue activator were measured in primigravidae with moderate or severe pre-eclampsia and in gestation-matched primigravidae with uncomplicated pregnancy. The mean levels of fibrinolytic activity and inhibitory activity against urokinase and tissue activator did not differ significantly between the pre-eclampsia and uncomplicated pregnancy groups. The pattern of inhibitory fractions of plasminogen-depleted plasma from pre-eclamptic and uncomplicated primigravidae after gel filtration on sephadex G-100 was similar.
Adolescent↗
Recent trends in the award of postgraduate medical degrees by the University of Aberdeen.
Recent trends in the award of higher medical degrees by the University of Aberdeen are reported. The proportion of graduates proceeding to a higher degree has remained relatively stable over recent decades. The numbers taking the Ch.M. or Ph.D. has increased while the number taking the M.D. has declined. The proportion of M.D.'s awarded with 'Honours' has fallen progressively.
Education, Medical, Graduate↗
The inhibition by plasma of urokinase and tissue activator-induced fibrinolysis in pregnancy and the puerperium.
The activity of urokinase and tissue activator on fibrin plates was inhibited by plasma from women in the third trimester of pregnancy to a greater extent than by non-pregnant plasma. Pregnancy also inhibited the amidolytic activity of urokinase. The high molecular weight fractions of pregnancy plasma gel filtered on Sephadex G-200 showed comparable inhibitory activity against urokinase as fractions for non-pregnant plasma; in contrast with non-pregnant plasma, the lower molecular weight fractions of pregnancy plasma were markedly inhibitory against urokinase. Plasma exposed to lysine-Sepharose to remove plasminogen and then fractionated on Sephadex G-100 provided a pattern of three areas of inhibition against tissue activator similar to that seen in non-pregnant plasma. The urokinase-inhibitory activity of lower molecular weight fractions of plasma separated on Sephadex G-200 fell within 1 hr of delivery and fell further over the following 18 to 30 hr.
Blood Physiological Phenomena↗
Blood levels of proteinase inhibitors in pre-eclampsia.
The blood levels of alpha 2-macroglobulin, alpha 1-antitrypsin, CT inactivator, antithrombin III and alpha 2-antiplasmin were measured in 18 primigravidae with moderate or severe pre-eclampsia and in 18 gestation-matched primigravidae with uncomplicated pregnancy. The mean levels of the proteinase inhibitors did not differ between the pre-eclampsia and uncomplicated pregnancy groups.
Adolescent↗
An artificial circulation for the study of thrombolysis. The influence of flow rate and pressure on thrombolysis and a comparison between urokinase and tissue activator as thrombolytic agents.
The construction of an artificial circulation for the study of thrombolysis allowing variation in fluid pressure and flow rate is described. The lysis of 125I-fibrin was not influenced by variation in pressure between 10 and 30 cm H2O, but was significantly faster at a flow rate of 25 ml/min than at 40 ml/min or 10 ml/min. At equivalent concentrations as assessed on fibrin plates tissue activator induced greater thrombolysis than urokinase. Thrombolysis by both activators was diminished in the presence of plasma.
Animals↗
Influence of cider on the fibrinolytic enzyme system.
Ingestion of 750 ml cider inhibited plasma fibrinolytic activity: unfermented apple juice appeared to have some inhibitory effect, but this did not reach statistical significance. Cider inhibited urokinase-induced clot lysis in a concentration-dependent manner; the inhibitory activity was heat-stable and non-dialysable. The fibrinolytic activities of plasmin, urokinase and, more markedly, tissue activator on fibrin plates were inhibited by cider in a concentration-dependent manner. The amidolytic activity of plasmin was also inhibited in the presence of cider.
Adult↗
The inhibition of tissue activator and urokinase by human plasma.
Plasma reduced the activity of urokinase and, to a lesser extent, tissue activator on unheated fibrin plates. After depletion of plasminogen by lysine-Sepharose the inhibitory effect of plasma was increased. Normal plasma separated on DEAE-Sepharose or, after passage through lysine-Sepharose, on Sephadex G-100 provided fractions in three regions capable of inhibiting tissue activator. The high molecular weight fractions inhibited both activators, but after plasma fractionation on Sephadex 4B the inhibitory activities against tissue activator and urokinase eluted separately. Urokinase inhibition eluted with alpha 2-macroglobulin: the inhibition of tissue activator was of higher molecular weight and of greater lability. Inhibition of tissue activator was found in two lower molecular weight regions: the fractions of one region inhibited tissue activator and coincided with the elution of fast-acting antiplasmin activity. The other region inhibited both tissue activator and urokinase. Alpha1-antitrypsin and antithrombin III eluted after both inhibitory regions.
Animals↗
Blood levels of proteinase inhibitors in pregnancy.
Plasma volume, serum alpha 2-macroglobulin, alpha 1-antitrypsin, C1 inactivator and alpha 2-antiplasmin, and plasma antithrombin III were measured in 10 pregnant women at gestation periods of 12-14 and 37-38 weeks. The proteinase inhibitors were also measured in 10 non-pregnant healthy women. There was a significant increase in the alpha 1-antitrypsin concentration and significant decreases in alpha 2-macroglobulin and C1 inactivator, but the total circulating quantity of all the proteinase inhibitors was significantly increased.
Adult↗
Inhibition of the plasminogen activator urokinase by alpha-tocopherol.
alpha-Tocopherol (vitamin E) inhibited the activity of urokinase on fibrin plates and on the amidolytic substrate S-2444 in a concentration- and time-dependent manner. Inhibition was not removed by dialysis. In the presence of dilutions of plasma, protein-containing fractions of gel-filtered plasma, or bovine serum albumin, the inhibition of urokinase by alpha-tocopherol was abolished. Urokinase activity was not inhibited by phytol, menadione or hydroquinone.
Animals↗
Inhibitors of fibrinolysis in amniotic fluid.
Amniotic fluid inhibited the fibrinolytic, amidolytic and esterolytic activity of urokinase. Kinetic studies with AGLMe demonstrated non-competitive inhibition. A major part of the inhibitory activity could be separated from alpha 1-antitrypsin by ion-exchange chromatography on DEAE-Sephadex A-50. Plasminogen activator prepared from porcine heart was not inhibited by amniotic fluid. Amniotic fluid also inhibited the caseinolytic and amidolytic activities of plasmin.
Amniotic Fluid↗
Biochemistry of the plasmin system.
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Chemical Phenomena↗