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PubMed1991

An analysis of the activators of single-chain urokinase-type plasminogen activator (scu-PA) in the dextran sulphate euglobulin fraction of normal plasma and of plasmas deficient in factor XII and prekallikrein.

An analysis was made of the various possible activators of single-chain urokinase-type plasminogen activator (scu-PA) in the dextran sulphate euglobulin fraction (DEF) of human plasma. scu-PA activators were detected in an assay system in which the substrate scu-PA, in physiological concentration (50 pM), was immuno-immobilized. After activation of the immobilized scu-PA for a certain period of time the activity of the generated amount of immuno-immobilized two-chain u-PA was determined with plasminogen and the chromogenic substrate S-2251. The scu-PA activator activity (scuPA-AA) in the DEF of plasmas deficient in factor XII or prekallikrein was about half of that in the DEF of normal plasma. Separation of scuPA-AA in the DEF by gel chromatography showed to major peaks, one eluting with an apparent Mr of 500,000 and the other around Mr 100,000. The former peak, which coincided with the activity peak of the kallikrein-kininogen complex, was absent in the DEF of plasma depleted of prekallikrein and therefore was identified as kallikrein. The latter peak was still present in the depleted plasma and most likely represents plasmin, because its scuPA-AA coincided with the activity peak of plasmin and could be fully inhibited by antibodies raised against human plasminogen. It is concluded that plasmin and the contact-activation factor kallikrein each contribute for about 50% to the scuPA-AA in the DEF. Compared on a molar basis, however, plasmin was found to be almost 1,000 times more effective than kallikrein, and we conclude, therefore, that in vivo plasmin is the primary activator of scu-PA and the role of the contact system is of secondary importance.

Chemical Fractionation↗
PubMed1991

Protein composition in human plasma after long-term orbital missions and in rodent plasma after spaceflights on biosatellites "Cosmos-1887" and "Cosmos-2044".

The two-dimensional plasma protein map of crewmembers of long-duration "Mir" expeditions obtained the day after the recovery shows a manifold increase in the content of several proteins normally seen in trace amounts. The emergence of several unusual protein spots occurs as well, some of them probably due to charge shifts provided by the events influencing posttranslational modification processes. By the 8 postflight day these phenomena were disappeared. In the "Cosmos-1887" biosatellite experiment, the plasma samples obtained two days after the landing as well as plasma of synchronous animals exhibited the higher fibrinogen levels when compared to those of vivarium animals. The protein consisting of a number of fractions with molecular weight of 50 to 60 kD and pI 5 to 6 had protein spots of similar size in flight and synchronous animals while in vivarium rats one of the spots was larger in size as opposed to the others. The plasma protein spectrum of flight and synchronous groups of animals in "Cosmos-1887" experiment where plasma samples were prepared in the period of time from 5 to 10 hours after spaceflight coincided with the pattern of vivarium animals. The data suggest that the protein changes described above develop during postflight period and accelerations, vibrations, readaptation to 1 G gravity, emotional stress could be the cause of these alterations.

Animals↗
PubMed1990

Response of plasma immunoreactive active renin, inactive renin, plasma renin activity, and aldosterone to hemodialysis in patients with diabetic nephropathy.

Several alterations in plasma active renin, inactive renin (prorenin), and aldosterone have been described in patients with diabetes mellitus. Such changes could be of some importance for patients on hemodialysis treatment, who must undergo severe changes in fluid and electrolyte status during each dialysis session. Therefore we studied the response of renin and aldosterone to hemodialysis in uremic diabetic nephropathy patients, using direct immunometric assays to measure plasma active renin concentration (ARC), inactive renin concentration (IRC), total renin concentration (TRC), plasma renin activity (PRA), and plasma aldosterone concentration (PAC) in 11 male patients aged 39-69 (mean 53 +/- 2) with diabetic nephropathy and 11 male age-matched non-diabetics who had been on maintenance hemodialysis for 1-10 years. Although baseline values of IRC were slightly higher, and values of PAC lower in diabetics compared to non-diabetics, the results did not reach statistical significance. During hemodialysis, significant increases in ARC (p less than 0.01), TRC (p less than 0.05), and PRA (p less than 0.01), and a significant decrease (p less than 0.05) in PAC were seen in non-diabetic patients but no significant changes were observed in patients with diabetic nephropathy. IRC did not change during hemodialysis in either group of patients. There were no significant differences in body weight, blood pressure, or electrolyte changes in the two groups. These results suggest an altered response of plasma renin and aldosterone to hemodialysis in patients with diabetic nephropathy compared to non-diabetics. The reduced renin response could not be explained by a defect in conversion from inactive renin, but may be caused by decreased secretion of active renin in these patients.

Adult↗
PubMed1989

Phase I and pharmacokinetic evaluation of thiotepa in the cerebrospinal fluid and plasma of pediatric patients: evidence for dose-dependent plasma clearance of thiotepa.

A Phase I trial of thiotepa (TT) administered as an i.v. bolus was performed in 19 children with refractory malignancies. The starting dose was 25 mg/m2 with escalations to 50, 65, and 75 mg/m2. Seven additional patients were treated with 8-h infusions at 50 or 65 mg/m2. The maximum tolerated bolus dose was 65 mg/m2. Reversible myelosuppression was the dose-limiting toxicity. The plasma and cerebrospinal fluid (CSF) pharmacokinetic parameters of TT and its major active metabolite tepa (TP) were also evaluated. When the bolus or infusion methods of TT administration were compared, there was little difference observed in any pharmacokinetic parameter for either TT or TP. The plasma disappearance of TT was rapid and biphasic with half-lives of 0.14 to 0.32 and 1.34 to 2.0 h. Dose-dependent pharmacokinetics was demonstrated by steadily declining plasma clearance with increasing TT dose. Clearance values declined from 28.6 liters/m2/h at the 25-mg/m2 dose to 11.9 liters/m2/h at the 75-mg/m2 dose. The half-life of TP was longer than that of TT and ranged between 4.3 and 5.6 h. There was evidence of the saturation of TP production. TT and TP both exhibited excellent penetration into the CSF, producing lumbar and ventricular concentrations which were nearly identical to simultaneous plasma concentrations. In one patient with a Rickham reservoir, the CSF:plasma area under the (concentration x time) curve ratios for TT and TP were 1.01 and 0.95, respectively. The above data indicate that TT can be safely administered to pediatric patients at doses higher than conventionally used. The favorable CSF penetration of TT and TP suggests that Phase II studies of TT be considered in patients with central nervous system tumors.

Adolescent↗
PubMed1989

Plasma lipids in patients with type I diabetes mellitus. Influence of race, gender, and plasma glucose control: lipids do not correlate with glucose control in black women.

Plasma lipids and hemoglobin A1 were measured in 544 type I diabetic patients. Hemoglobin A1 was positively correlated with the levels of total plasma cholesterol, total triglycerides, and low-density lipoprotein cholesterol and negatively correlated with the level of high-density lipoprotein cholesterol in the entire biracial group. These relationships between plasma lipids and hemoglobin A1 were not present in black women. In the white diabetic population a reduction in hemoglobin A1 of one percentage point was statistically associated with a decrease of 0.16 to 0.17 mmol/L in total plasma cholesterol, a decrease of 0.10 to 0.13 mmol/L in low-density lipoprotein cholesterol, and a reduction of 0.12 to 0.14 mmol/L in triglycerides. These findings suggest that race and gender are important determinants of the response of plasma lipids to glucose control in type I diabetes mellitus.

Adolescent↗
PubMed1987

Plasma endogenous ACTH concentrations and plasma cortisol responses to synthetic ACTH and dexamethasone sodium phosphate in healthy cats.

Plasma cortisol responses of 19 healthy cats to synthetic ACTH and dexamethasone sodium phosphate (DSP) were evaluated. After administration of 0.125 mg (n = 5) or 0.25 mg (n = 6) of synthetic ACTH, IM, mean plasma cortisol concentrations increased significantly (P less than 0.05) at 15 minutes, reached a peak at 30 minutes, and decreased progressively to base-line values by 120 minutes. There was no significant difference (P greater than 0.05) between responses resulting from the 2 dosage rates. After administration of 1 mg of DSP/kg of body weight, IV (n = 7), mean plasma cortisol concentrations decreased at postadministration hour (PAH) 1, and were significantly lower than control cortisol concentrations at PAH 4, 6, 8, 10, and 12 (P less than 0.01). Administration of 0.1 mg of DSP/kg, IV (n = 8) or 0.01 mg of DSP/kg, IV (n = 14) induced results that were similar, but less consistent than those after the 1 mg of DSP/kg dosage. Mean plasma cortisol concentrations returned to base-line values by PAH 24. There was not a significant difference between the 3 doses (P greater than 0.05) at most times. Measurement of endogenous ACTH in 16 healthy cats revealed plasma ACTH of less than 20 to 61 pg/ml. Seemingly, administration of synthetic ACTH consistently induced a significant (P less than 0.05) adrenocortical response in healthy cats. On the basis of time-response studies, post-ACTH stimulation cortisol samples should be collected at 30 minutes after ACTH administration to ensure detection of peak adrenocortical response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Function Tests↗
PubMed1986

The influence of hepatic plasma flow on alfentanil plasma concentration plateaus achieved with an infusion model in humans: measurement of alfentanil hepatic extraction coefficient.

In a group of seven patients undergoing intracranial surgery under neurolept anesthesia, an alfentanil infusion was initiated with a loading dose of 235 micrograms/kg over 5 min, followed by a maintenance infusion rate of 1.8 microgram X kg-1 X min-1 in order to obtain a steady state plasma concentration (Css) of 400 ng/ml-1 according to an infusion model. The mean values of Css (446 +/- 209 ng/ml) were close to the predicted ones. Nevertheless, an important intersubject variability in Css values was observed. A positive linear correlation existed between alfentanil steady state clearance and indocyanine green clearance (r = 0.88) and between alfentanil steady state clearance and cardiac index (r = 0.93). In three patients, a catheter was inserted into an hepatic vein to determine the alfentanil hepatic extraction coefficient. Alfentanil plasma clearance did not differ from alfentanil hepatic clearance and alfentanil hepatic extraction coefficient values ranged from 0.32-0.53. We conclude that alfentanil is a drug with an intermediate hepatic extraction coefficient and that alfentanil plasma clearance depends on hepatic plasma flow, which is thus one of the factors accounting for individual variability in plasma concentration plateaus achieved with an infusion model.

Adult↗
PubMedDate not supplied

Plasma renin activity and plasma aldosterone concentrations in normotensive pregnant Nigerians.

Plasma renin activity (PRA) and plasma aldosterone concentrations were determined in thirty-four normotensive pregnant subjects, sixteen subjects who were examined 6 weeks post-partum and sixteen non-pregnant controls. Plasma renin activity and plasma aldosterone concentrations increased sequentially in pregnancy i.e. there were progressive significant increases when the values of the first, second and third trimesters were compared. The values for the post-partum subjects and the non-pregnant controls were not significantly different. There was no significant correlation between any pair of the following indices: mean arterial pressure (MAP), PRA and plasma aldosterone. The results are discussed in the light of the present state of knowledge of the pathogenesis of pregnancy-induced hypertension (PIH).

Aldosterone↗
PubMed1977

Rapid loss of factor XII and XI activity in ellagic acid-activated normal plasma: role of plasma inhibitors and implications for automated activated partial thromboplastin time recording.

Rapid prolongation of the aPTT of normal plasma upon incubation with ellagic acid containing aPTT reagents was observed. The aPTT prolongation was not due to time-dependent changes in pH in the incubation mixture or loss of activity of the labile coagulation factors VIII and V but occurred as a result of rapid progressive inactivation of ellagic acid-activated factors XII and XI. Prolongation of the aPTT and loss of contact factor activities was not observed in plasma incubated with particulate activator reagents. This finding seemed to indicate that adsorption of factors XII and XI to larger particles during the activation process might protect these factors from inactivation by naturally occurring plasma inhibitors. Evidence is presented which supports previous findings that C1-INH, alpha1-AT, and antithrombin (in the presence of heparin) contribute to factor XIIa and XI a inactivation in ellagic acid-activated plasma and that plasma albumin may compete with factor XII for ellagic acid binding. The data indicate that ellagic acid-containing aPTT reagents have unfavorable properties which seriously limit their usefulness in the clinical laboratory, particularly in respect to recording of the aPTT with certain fully automated clot timers.

Antithrombins↗
PubMed1986

The fast-acting inhibitor of tissue-type plasminogen activator in plasma is also the primary plasma inhibitor of urokinase.

We have compared the ability of a plasminogen activator inhibitor (PA-inhibitor) in human plasma, to form complexes with radioiodinated tissue-type plasminogen activator (t-PA) and high molecular weight urokinase (HMr-UK). Addition of 125I-t-PA (final concentration 10 IU/ml) or of 125I-HMr-UK (2 IU/ml) to a plasma containing 33 U/ml of PA-inhibitor resulted in the rapid formation of a 110,000 Mr complex of 125I-t-PA or a 95,000 Mr complex of 125I-HMr-UK with PA-inhibitor. Upon prolonged incubation of the plasma with 125I-HMr-UK a secondary complex of a Mr of 88,000 was observed, which probably derives from limited degradation of the 95,000 complex. Preincubation of the plasma with unlabelled t-PA, HMr-UK or LMr-UK at higher concentrations prevented the subsequent formation of complexes between radiolabelled PAs and the PA-inhibitor. These results thus demonstrate that t-PA and UK form complexes with the same PA-inhibitor. The rate of complex formation of 125I-t-PA or of 125I-HMr-UK with the plasma PA-inhibitor was similar (second order rate constant of association with PA-inhibitor in the order of 10(7) M-1s-1).

Glycoproteins↗
PubMedDate not supplied

Plasma renin activity and plasma aldosterone concentrations in untreated Nigerians with essential hypertension.

On the basis of existing information we set out to test an hypothesis that 'the blood volume and more specifically total body sodium and sodium disposition in the body play a more important role in blood-pressure regulation and the pathophysiology of hypertension than other regulatory mechanisms in the indigenous African'. To achieve our objective, ninety-eight newly diagnosed unmedicated hypertensives with adequate renal function were admitted to the study. Fifty-one (52%) of the subjects were males while forty-seven (48%) were females. Their ages ranged between 21 and 70 years. All grades of the disease were adequately represented with thirty (31%) being mild, fifty (51%) moderate and eighteen (18.4%) in severe phase of the disease. Blood-pressure measurements and blood samples were obtained in the supine position in all the patients after adequate preparation. Plasma renin activity (PRA) and plasma aldosterone concentrations were measured by specific radioimmunoassays. Contrary to what obtains elsewhere, seventy-six (77%) of our patients were of the low renin status, twelve (12%) of whom had undetectable levels by our assay system. Eighteen (18.4%) had PRA levels in the medium range and five (5.1%) in the high range. In a cohort, forty-two (43%) of our ninety-eight patients, we estimated plasma aldosterone levels. The results obtained showed that the plasma aldosterone concentrations were significantly higher in hypertensives than in our normal controls (P less than 0.01). There was lack of correlation between PRA or plasma aldosterone when compared to mean arterial pressure or serum Na+. These results are discussed in relation to the management of hypertension in our environment.

Adult↗
PubMed1980

Biogenesis of plasma membrane glycoproteins. Tracer kinetic study of two rat liver plasma membrane glycoproteins in vivo.

Antibodies to purified nucleotide pyrophosphatase (NPPase) and dipeptidyl peptidase IV (DPP IV) were used to study the biogenesis of these rat liver plasma membrane glycoproteins in vivo. Following injection of tritiated leucine, the radioactivity in NPPase and DPP IV decayed at markedly different rates in the plasma membrane, with apparent half-lives of about 1 and 5 days, respectively. In short term experiments, labeling of total plasma membrane proteins was rapid and insensitive to colchicine, while labeling of both NPPase and DPP IV showed a lag of about 15 min, followed by colchcine-sensitive/cycloheximide-insensitive increases to half-maximal and maximal values at about 1 and 2 h, respectively. A peak of labeled DPP IV in rough microsomes at 15 min showed increased mobility on polyacrylamide gels and was largely inaccessible to antibodies in intact microsomes, consistent with its being an underglycosylated precursor, exposed on the cisternal side of the rough endoplasmic reticulum. In contrast, the behavior of unlabeled DPP IV in preparations of rough microsomes and Golgi was consistent with its being contributed by contaminating right-side-out plasma membrane vesicles. This conclusion was also necessary to fit the tracer kinetic data to a simple membrane-flow model, which gave precursor pools (1 microgram/g of liver) and fluxes (1 microgram/h/g of liver) for both DPP IV and NPPase which were about 3 orders of magnitude less than those for the synthesis of rat serum albumin. Thus, unlike hepatoma tissue culture cells (Doyle, D., Baumann, H., England, B., Friedman, E., Hou, E., and Tweto, J. (1978) J. Biol. Chem. 253, 967-973), normal rat liver does not contain large amounts of preformed intracellular plasma membrane precursors.

Animals↗
PubMed1980

Studies on components of the plasma kallikrein-kinin system in plasma samples from normal individuals and patients with septic shock.

Components of the plasma kallikrein-kinin system were determined in plasma samples from ten healthy subjects and eight patients with septic shock. Five of the patients died. Low levels of Hageman factor, prekallikrein, and high molecular weight kininogen, together with significantly reduced concentrations of alpha 2-macroglobulin, were observed during septic shock both in patients who died and in the survivors. The patients who died also revealed a pronounced reduction of functional kallikrein inhibition determined by a chromogenic peptide substrate assay. In the survivors, however, functional kallikrein inhibition was very well preserved during septic shock, being within the range of values found in normals. Also plasma prekallikrein and C1-esterase inhibitor levels were slightly higher in the survivors than in those who died. Our results confirm that the plasma kallikrein-kinin system becomes activated during septicemia and that consumption of components of this protease system occurs. Because both C1-esterase inhibitor concentrations and functional kallikrein inhibitory activities were higher in patients who survived septic shock than in the fatal cases, our results suggest that functional inhibition of plasma kallikrein appears to play a major role in the outcome of this condition.

Complement C1 Inactivator Proteins↗
PubMed1982

Studies on the inhibition of human thrombin: effects of plasma and plasma constituents.

The effects of blood plasma and some plasma constituents on several types of thrombin inhibitors were quite varied. Two active esters were rapidly destroyed by serum albumin; one of these reacted initially with Lys-199, the residue that is also acylated by aspirin. Of two sulfonyl fluorides one was unaffected by albumin, and the other bound reversibly to albumin; this binding was greater with albumin acetylated at Tyr-411 near the binding site for medium-chain fatty acids. The effects of a chloromethyl ketone were inhibited, apparently reversibly, by albumin but were practically abolished by glutathione. Of two potent reversible inhibitors one was unaffected by plasma constituents, while the other was over 10-fold less potent in plasma than in fibrinogen. The effect of plasma could be partially explained by binding to albumin and lipoproteins.

Benzoates↗
PubMed1980

Effect of dithiothreitol on plasma membrane intramembranous particle topography in BALB/c 3T3 and simian virus-transformed 3T3 cells and plasma membrane vesicles.

A statistical analysis of plasma membrane intramembranous particle topography was performed on purified 3T3 and simian virus (SV)-transformed 3T3 plasma membrane vesicles and on intact 3T3 and SV3T3 cells. The results show that intramembranous particles were more aggregated in intact 3T3 cells than in intact SV3T3 cells. By contrast, in purified plasma membrane vesicles intramembranous particles were significantly more aggregated in SV3T3 than in 3T3 preparations. These unexpected results suggest that intramembranous particle topography is selectively altered in SV3T3 plasma membranes during the membrane vesicle isolation procedure. Inasmuch as the disulfide-reducing agent dithothreitol (DTT) was used to isolate membranes, tests were done to determine if DTT would preferentially affect particle topography in intact SV3T3 cells. Exposure of intact SV3T3 cells to 10 or 50 mM DTT induced intramembranous particle aggregation but had no effect on intact 3T3 cells. Preliminary studies also showed that other sulfhydrylreactive compounds preferentially induced particle aggregation in SV3T3 specimens. These observations suggest that the state of cross-linking of membrane-associated proteins by disulfide bonding influences intramembranous particle topography and that differences exist in plasma membrane-associated sulfhydryl proteins in nontransformed and transformed cells.

Animals↗
PubMed1984

Relationship between paired plasma and serum viscosity and plasma proteins in the horse.

The relationship between paired plasma and serum viscosity measurements and plasma proteins, including fibrinogen, were compared in 106 horses with both normal and abnormal serum protein levels. There is a highly significant positive correlation between serum viscosity and total serum proteins and total globulin levels. The difference between plasma and serum viscosity correlated well with clottable fibrinogen concentration. Albumin levels showed a negative correlation with plasma and serum viscosity, globulins and fibrinogen. Simultaneous estimation of serum and plasma viscosity improves the diagnostic value of the latter test without appreciable increase in cost or time and should prove useful for screening large numbers of samples for the presence or absence of abnormal levels of globulins and, or, fibrinogen.

Animals↗
PubMed1984

[Incorporation of 1-0-alkyl-2-acetyl-sn-glycerol-3-phosphocholine into human plasma lipoproteins in vitro. Effect of the lecithin:cholesterol acyltransferase activity of plasma].

The binding of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, a platelet activating factor (PAF), to individual classes of human plasma lipoproteins was studied. It was found that PAF is rapidly incorporated into plasma lipoproteins. The degree of PAF binding to the lipoproteins depends on their type. Analysis of PAF binding in Scatchard plots revealed that HDL2 contain high affinity binding sites for PAF. On the other hand, LDL bind PAF in a nonspecific manner. Incubation of PAF with human plasma results in inhibition of lecithin: cholesterol acyltransferase (LCAT)-catalyzed cholesterol esterification. On the contrary, prostaglandin E1 stimulates LCAT activity in human plasma. PAF and prostaglandin E1 do not compete with each other for the binding sites in HDL2. It is concluded that incorporation of PAF into plasma lipoproteins may influence the LCAT activity in vivo.

Alprostadil↗
PubMed1980

Relationship between plasma catecholamines, plasma renin activity, aldosterone, and arterial pressure during postural stress in normal subjects.

The relationship between plasma catecholamines, PRA, aldosterone, and MBP in the supine and upright positions and after furosemide were studied in 44 normal subjects. Supine plasma NE correlated with MBP (r = 0.52, p greater than 0.01) and with age (r = 0.57, p greater than 0.01). The partial correlation coefficient of plasma NE with MBP controlling for age was r = 0.40, p greater than 0.025. These data suggest that the sympathetic nervous system plays an important role in the maintenance of blood pressure during the supine position. With upright posture, plasma NE and E, PRA, and plasma aldosterone increased significantly, whereas urinary sodium excretion decreased and urinary excretion of NE did not change.

Adolescent↗