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PubMed2003

Plasma lactate and plasma volume recovery in adults and children following high-intensity exercises.

AIM: To compare plasma lactate concentration recovery kinetics when measured and corrected for variations in plasma volume between children and adults. METHODS: Nine boys (11.3 +/- 1.1 y) and 8 men (21.9 +/- 1.9 y) performed a maximal and a supramaximal exercise until exhaustion. Plasma lactate concentrations, haemoglobin and haematocrit were measured at rest, immediately on completion of exercise and after the 2nd, 5th, 12th and 30th minute of recovery. The plasma lactate concentrations and the rate of recovery were corrected for variations in plasma volume. RESULTS: The maximal decreases in plasma volume were significantly higher in adults than in children for maximal exercise (-18.7 +/- 2.6% vs -14.5 +/- 3.2%; p < 0.05), but similar for the supramaximal exercise (-16.9 +/- 3.4% vs -15.2 +/- 3.4%). During recovery, measured and corrected plasma lactate concentrations were significantly higher in adults. The rate of plasma lactate recovery was higher in adults for maximal exercise only. The same results were obtained when the rates of plasma lactate decrease were calculated from corrected plasma lactate concentrations. CONCLUSION: The correction of the plasma lactate concentrations for variations in plasma volume did not influence the comparison of the concentrations obtained in adults and children, or their rate of recovery.

Adult↗
PubMed2006

Comparison of biochemical values in serum and plasma, fresh and frozen plasma, and hemolyzed samples from orange-winged Amazon parrots (Amazona amazonica).

BACKGROUND: To the authors' knowledge, on the basis of sample type, storage condition, or hemolysis, differences in serum and plasma biochemical values have not been evaluated in orange-winged Amazon parrots (Amazona amazonica). OBJECTIVES: The purpose of this study was to compare values for biochemical analytes in serum vs plasma, fresh vs frozen plasma, and nonhemolyzed vs hemolyzed samples in orange-winged Amazon parrots. We also compared differences in serum and plasma yield from whole-blood aliquots. METHODS: Fifteen biochemical analytes were evaluated in paired serum and plasma, fresh and frozen plasma, nonhemolyzed and hemolyzed serum and plasma samples from orange-winged Amazon parrots (n = 10) using a wet reagent analyzer. Hemolysis was assessed qualitatively (visually) and quantitatively (hemoglobin [Hgb] measured spectrophotometrically). Serum and plasma yields from 500-microl whole-blood aliquots were determined from centrifuged samples. RESULTS: Analyte values significantly differed among sample groups, but were still within published reference intervals, with the exception of increases in potassium concentration in markedly hemolyzed serum and plasma samples. Clinically important changes in hemolyzed serum and plasma samples included increases in potassium, phosphorus, and albumin concentrations and lactate dehydrogenase activity. The degree of hemolysis assigned qualitatively did not correlate with quantitative Hgb concentration. A significantly greater yield of plasma (288 +/- 13 microL) than serum (241 +/- 44 microL) was obtained. CONCLUSIONS: Significant differences may occur in different sample types, however, only changes in potassium, phosphorus, albumin, and lactate dehydrogenase values in hemolyzed samples were considered clinically relevant. Lack of agreement between qualitative and quantitative Hgb concentration indicates the unreliability of visual estimation. Based on higher sample yield, and lack of clinically relevant differences from serum, plasma is a better sample choice for clinical chemistry analysis in birds.

Amazona↗
PubMed1997

Formation of plasma advanced glycosylation end products (AGEs) has no influence on plasma viscosity.

Plasma viscosity is mainly determined by large non-spherical proteins. In Type 1 diabetes mellitus, plasma viscosity increases with deterioration of diabetic control. Since protein glycation and formation of advanced glycosylation end products (AGEs) alter the structural and functional properties of proteins, AGEs might influence the rheological properties of plasma proteins. Therefore, we investigated the influence of plasma-AGEs on plasma viscosity in 34 normoalbuminuric diabetic patients (17 Type 1, 17 Type 2) with normal renal and liver function. In an additional experiment, 6 ml plasma of 9 healthy volunteers were incubated under sterile conditions for 14 days at 37.5 degrees C in the presence of 5.2 and 32.9 mmol l(-1) glucose. In diabetic patients, plasma-AGE levels were not correlated with plasma viscosity. Plasma-AGE levels in healthy controls (246 +/- 37 U ml[-1], mean +/- SD) were raised significantly (p<0.001) after the incubation at 37.5 degrees C (392 +/- 57 U ml[-1] and 552 +/- 58 U ml[-1], respectively). However, no difference was found in plasma viscosity pre- and post-incubation (pre-incubation: 1.25 +/- 0.04 mPas, post-incubation: 1.23 +/- 0.03 and 1.24 +/- 0.03, respectively). We conclude that there is no influence of plasma-AGEs on plasma viscosity.

Adult↗
PubMed1992

Prekallikrein activation in human, bovine, and rabbit plasmas: presence of an inhibitor in bovine plasma.

Contact of human plasma with a negatively charged surface such as dextran sulfate activates prekallikrein to kallikrein, which releases the vasoactive peptide bradykinin from high-molecular-weight kininogen. The dextran sulfate-induced activation of prekallikrein at 0 degree C (assayed by its amidolytic activity on the chromogenic substate S-2302) could not be observed in either bovine or rabbit plasmas when compared to human plasma. Neither bovine nor rabbit plasma inhibited the amidolytic activity of contact-activated human plasma at 0 degrees C. The activation of prekallikrein in human plasma was significantly inhibited by the addition of bovine plasma but not by rabbit plasma. Bovine plasma (0.025 units, 1 unit = 1 ml of plasma) caused 68.8% inhibition of prekallikrein activation. Eighty percent of the inhibitory property of bovine plasma was present in the greater than 30,000-molecular-weight fraction. These results indicate the presence of an inhibitor(s) of prekallikrein activation in bovine plasma.

Animals↗
PubMed2006

The in vitro plasma distribution of a novel cholesteryl ester transfer protein inhibitor, torcetrapib, is influenced by differences in plasma lipid concentrations.

PURPOSE: To determine the lipoprotein distribution of Torcetrapib in normolipidemic or hyperlipidemic human plasma and assess any changes in distribution due to lipid profile. METHODS: Torcetrapib was incubated with human plasma samples, and the distribution was measured across four fractions: triglyceride-rich lipoprotein (TRL), low-density lipoprotein, high-density lipoprotein, and lipoprotein-deficient plasma fraction. Two stocks of human plasma were used, one considered normolipidemic (total cholesterol concentration = 164 mg/dL, triglycerides concentration = 139 mg/dL, protein concentration = 912 mg/dL), the other hyperlipidemic (total cholesterol = 260 mg/dL, triglycerides = 775 mg/dL, protein = 917 mg/dL). The plasma samples were incubated with Torcetrapib at 37 degrees C, and the incubation was stopped with the addition of sodium bromide and cooling to 4 degrees C. The plasma samples were then separated by density gradient ultracentrifugation to their lipoprotein fractions. The resulting lipoprotein fractions and an aliquot of incubated plasma were analyzed by a validated gas chromatography/tandem mass spectrometry analytical method. The distribution of Torcetrapib was determined first with varying incubation times, then with several concentrations. RESULTS: At concentrations of 250 and 500 ng/mL, Torcetrapib distributed evenly across the four fractions in normolipidemic plasma. At the same concentrations in hyperlipidemic plasma, approximately 84% of Torcetrapib was found in the TRL fraction, with the remaining 16% evenly partitioned between the low-density lipoprotein, high-density lipoprotein, and lipoprotein-deficient plasma fractions. CONCLUSIONS: The results suggest that lipid profile affects the distribution of Torcetrapib in hyperlipidemic human plasma lipoprotein fractions. The preferential distribution of Torcetrapib into the TRL fraction in hyperlipidemic plasma needs to be investigated to see if it will affect the pharmacological effect of Torcetrapib in vivo.

Anticholesteremic Agents↗
PubMedDate not supplied

The plasma and tissue turnover and distribution of two radio-iodine-labelled pig plasma low density lipoproteins.

Two classes of pig plasma low density lipoprotein (LDL1 and LDL2) with different densities and molecular sizes were isolated by zonal ultracentrifugation and were further purified by flotation. The peptide component was iodinated with 125I, and the labelled lipoprotein was injected intravenously. 125I-LDL1 turnover studies were performed on 22 3-4 month old female Large White pigs, and 125I-LDL2 turnover studies on 4 similar pigs. A biological screening experiment confirmed that the shape of the plasma activity curve was not a function of protein denaturation. The pattern of radioactivity decline in plasma was not affected by the degree of LDL iodination. 125I-LDL1 turnover: The curve of plasma radioactivity plotted against time over the first 5 days after injection could be resolved into two exponentials. The plasma biological half-life (T 1/2) was calculated from the slower exponential predominant from the second day. The mean T 1/2 over 2-5 days was 22.9 hr (range 17.2-28.5 hr). Multicompartmental analysis of the plasma decay curve using an open mammillary model gave a mean fractional catabolic rate per day for LDL1 of 1.4 (range 0.9-1.9). The mean T 1/2 was 0.26-0.31 times and the fractional catabolic rate 3.0-3.9 times those values found in two studies on adult humans. The tissue distribution of 125I was analysed in a series of 20 animals killed from 1.0 to 33.8 days after 125I-LDL1 injection. Most tissue 125I (86-89%) was protein bound. An appropriate correction was made to the 125I counts for retained plasma in liver and spleen (using 131I-albumin); retained plasma in other tissues was negligible. Highest 125I tissue levels were found in the liver, supporting other evidence that the liver may be the major site of LDL1 catabolism. After 2.06 and 4.06 days the livers in two animals contained 1.6% and 0.7% respectively of the total injected 125I, equal to 33% and 54% of the total plasma 125I at those times. The skin contained about one-third to one-ninth the 125I in the liver at various times. Distribution in other organs was quantitatively minimal. Higher levels of radioactivity were found in the intima and inner media of the aorta than in the outer media. These results suggest that plasma LDL in the pig diffuses through the endothelial surface into the arterial wall. These findings are confirmed by autoradiography. 125I-LDL2 turnover: Parallel studies of plasma 125I-LDL2 turnover and tissue distribution were performed. The plasma biological decay curve was multi-exponential, suggesting that LDL2 metabolism is complex, and possibly more rapid than that of LDL1 (LDL2 is smaller and denser than LDL1). The tissue distribution of 125I-LDL2 in these pigs was very similar to that of 125I-LDL1. As LDL1 and LDL2 differ in the amount of lipid they contain, they may have different roles to play in lipid transport, and there may be interconversion of one into the other at different sites. This hypothesis remains conjectural.

Animals↗
PubMed2004

Association of plasma folate, plasma total homocysteine, but not methylenetetrahydrofolate reductase C667T polymorphism, with bone mineral density in postmenopausal Iranian women: a cross-sectional study.

Polymorphisms of methylenetetrahydrofolate reductase (MTHFR) have been well documented to cause hyperhomocysteinemia, and recent studies suggest an association of C677T mutation of methylenetetrahydrofolate reductase with low bone mineral density (BMD). In this study, the association of plasma total homocysteine (Hcy), plasma folate, and vitamin B12 as well as methylenetetrahydrofolate reductase C667T polymorphism with bone mineral density at neck of femur and lumbar spine in 271 postmenopausal Iranian women was investigated. Bone mineral density was measured by dual-energy X-ray absorptiometry. Restriction fragment length polymorphism was used for genotyping the methylenetetrahydrofolate reductase polymorphism. Plasma total homocysteine, plasma folate, and vitamin B12 were also determined. The bone mineral densities at the neck of femur and lumbar spine together with other clinical characteristics among methylenetetrahydrofolate reductase genotypes (CC, CT, and TT) were examined. Bone mineral densities at both neck of femur (r = -0.18, P = 0.003) and lumbar spine (r = -0.16, P = 0.01) were significantly and negatively correlated with the logarithm of plasma total homocysteine. Bone mineral density at the lumbar spine was also significantly and positively associated with plasma folate (r = 0.14, P = 0.02). However, no correlation between methylenetetrahydrofolate reductase polymorphism with bone mineral density at neck of femur (r = -0.01, P = 0.81) and lumbar spine (r = -0.04, P = 0.51) was observed. The negative association of plasma total homocysteine with bone mineral density was no longer significant when adjusted for folate and vitamin B12. Plasma folate and age were the main predictors of plasma total homocysteine explaining 15.3% and 5.2% of the variance of plasma total homocysteine, respectively. Methylenetetrahydrofolate reductase polymorphism, however, was not associated with plasma folate (r = 0.086, P = 0.17) or vitamin B12 (r = 0.05, P = 0.4). Plasma folate was one of the main predictors explaining 3.0% and 1.7% of variance of the bone mineral density at femoral neck and lumbar spine, respectively. Results from this study suggest hyperhomocysteinemia as a result of folate deficiency, but not methylenetetrahydrofolate reductase polymorphism, is independently associated with low bone mineral density and may contribute to the pathogenicity of osteoporosis in postmenopausal Iranian women.

Aged↗
PubMed2000

Plasma insulin concentration is more tightly linked to plasma leptin concentration than is the body mass index.

This study tested the hypothesis that the integrated plasma insulin response to oral glucose is a more sensitive predictor of the fasting plasma leptin concentration than the body mass index (BMI) or waist to hip ratio (WHR). For this purpose, we determined the fasting plasma leptin concentration and plasma insulin response to a 75-g oral glucose challenge in 76 healthy female subjects, with a BMI of 19.1 to 36.6 kg/m2 and a WHR of 0.57 to 1.1. The results demonstrated that fasting plasma leptin concentrations were significantly correlated with both the BMI (r = .64, P < .001) and the plasma insulin response to glucose (r = .61, P < .001), but not with the WHR (r = .27). Since the BMI and the insulin response were also significantly related (r = .34, P = .003), multivariate analysis was performed to determine if the BMI and insulin response were independent determinants of the fasting leptin concentration. This analysis indicated that both the BMI and insulin response were significantly related to plasma leptin (P < .001). To pursue this issue further, the population was divided into tertiles on the basis of the (1) plasma leptin concentration, (2) BMI, and (3) integrated insulin response. The two variables that were most closely linked to each other were the leptin concentration and insulin response. In contrast, the BMI was relatively easily disassociated from the other two variables. These results indicate that while both the plasma insulin response to glucose and the BMI are significantly associated with the fasting plasma leptin concentration, the plasma insulin response appears more closely associated with the plasma leptin concentration.

Administration, Oral↗
PubMed1992

Atrial natriuretic peptide (ANP) in chronic obstructive pulmonary disease (COPD): the relationship between plasma ANP and lung function. Effects of exercise and of the calcium antagonist, isradipine, on plasma ANP. A randomised, double-blind, placebo-controlled study.

In patients with severe chronic obstructive pulmonary disease (COPD) an increased pulmonary arterial pressure (PAP), a raised plasma level of atrial natriuretic peptide (ANP) and a correlation between increasing PAP and increasing plasma ANP have been shown. Furthermore, a negative correlation between lung function and PAP has been reported, and calcium antagonists have been claimed to decrease PAP. The purpose of the present study was to investigate whether 1) a negative correlation between lung function and plasma ANP could be demonstrated, whether 2) plasma ANP would increase during exercise in patients with COPD, and whether (3), in a randomised, placebo-controlled, double-blind design, a calcium antagonist was able to decrease plasma ANP at rest and modify the expected increase in plasma ANP during exercise. Eighteen patients with severe COPD were investigated. Plasma ANP was measured at rest and during exercise before and two hours after ingestion of either a single dose of 5 mg of isradipine, or a single dose of placebo. At rest, a correlation between lung function (forced vital capacity) and plasma ANP was found (rho = -0.49, P = 0.05). During the first exercise period, before ingestion of isradipine or placebo, the median level of ANP increased from 74 pg/ml at rest to 97 pg/ml at exhaustion (P less than 0.0002) (all patients). Administration of isradipine did not alter resting levels or exercise induced increases in plasma ANP. It is concluded, that in patients with severe COPD plasma ANP tends to be higher the more severely FVC is reduced. Plasma ANP increases during exercise. The calcium antagonist, isradipine, does not alter resting levels or exercise induced levels of plasma ANP.

Atrial Natriuretic Factor↗
PubMed1999

In Zucker diabetic fatty rats plasma leptin levels are correlated with plasma insulin levels rather than with body weight.

The obese (ob) gene product leptin, secreted from adipose tissue, acts in the hypothalamus to regulate body energy stores. In vitro experiments showed that insulin increases both leptin mRNA expression and leptin secretion by adipocytes. Here, we report on the relationship between plasma insulin and plasma leptin in a longitudinal in vivo study. In Zucker diabetic fatty (ZDF) rats, an animal model for non-insulin-dependent diabetes mellitus (NIDDM), and in ZDF control rats, blood glucose, body weight, plasma insulin and plasma leptin levels were measured from 10 to 25 weeks of age. In ZDF control rats, body weight, plasma leptin and plasma insulin levels increased gradually during the study period. In ZDF rats, the time course of plasma leptin was similar to that of plasma insulin, but did not parallel that of body weight. Calculation of partial correlation coefficients revealed that in ZDF control rats plasma leptin correlated with body weight rather than with plasma insulin. However, in ZDF rats, plasma leptin correlated with plasma insulin rather than with body weight, suggesting an important role for insulin in the modulation of leptin secretion in this animal model for NIDDM.

Age Factors↗
PubMed1999

Plasma lycopene concentrations in humans are determined by lycopene intake, plasma cholesterol concentrations and selected demographic factors.

Higher plasma lycopene concentrations have been associated with a reduced risk of several chronic diseases. Determinants of lycopene concentrations in humans have received limited attention. We had blood lycopene concentrations and lycopene consumption data available from 111 participants in a two-center cancer prevention trial involving beta-carotene and examined determinants of plasma lycopene levels cross-sectionally. The median plasma lycopene level was 0.59 micromol/L (range 0.07-1.79). Low plasma concentrations of lycopene were associated with the following variables in univariate analyses: study site (Florida lower than Connecticut, P = 0.001), being nonmarried (P = 0.02), having lower income (P = 0.003), being nonwhite race/ethnicity (P = 0.03), having lower dietary lycopene intake (r = 0.29, P = 0.002), having lower plasma cholesterol (r = 0. 43, P = 0.0001) and triglyceride levels (r = 0.26, P = 0.005), and consuming less vitamin C (r = 0.20, P = 0.03). Women had slightly higher plasma lycopene levels than men (0.65 vs. 0.58 micromol/L; P = 0.31), despite lower dietary intake of lycopene (1,040 vs. 1,320 microg/d; P = 0.50). Plasma lycopene levels did not differ in smokers and nonsmokers. In stepwise regression analyses, the determinants of plasma lycopene were plasma cholesterol, dietary lycopene, and marital status; these three variables explained 26% of the variance in plasma lycopene. Relatively few lifestyle and demographic factors were important determinants of plasma lycopene levels, with plasma cholesterol, marital status, and lycopene intake being of greatest importance.

Adult↗
PubMed1984

Determination of pemoline in plasma, plasma water, mixed saliva, and urine by high-performance liquid chromatography.

A new determination method of pemoline in plasma, plasma water, mixed saliva, and urine using high-performance liquid chromatography was developed. The detection limit of pemoline using 0.2 ml of the sample was 0.02 microgram/ml in plasma, plasma water, saliva, and urine. The recoveries of pemoline added to plasma, saliva, and urine (each 6 micrograms/ml) were more than 98%. The coefficients of variation of within-run and between-run precisions for 5 concentrations of pemoline in plasma were less than 5 and 6%, respectively. The elimination half-lives of pemoline obtained from the plasma concentration-time curves after a single oral administration of pemoline in two subjects were 6.7 and 10.3 h. Mean values of the ratio between saliva and plasma total concentration in two subjects were 0.55 and 0.64, and mean values of plasma protein binding percent were 35.7 and 25.2%, respectively. The saliva concentrations were in proportion to the plasma unbound pemoline concentrations at simultaneous samplings, and the ratios between saliva and plasma unbound concentration were about 0.9 in two subjects. Usefulness of saliva in the estimation of plasma protein-unbound pemoline concentration was noted.

Adult↗
PubMed1986

Activation of factor XII in acetone-treated human plasma: significance of the functional state of plasma kallikrein for the extent of activation.

The kaolin-induced activation of factor XII (XII) to XIIa was studied in plasminogen-free human citrated plasma treated with acetone in the presence of benzamidine 7.5 mM. XIIa was assayed as prekallikrein (PK) activator. The significance of the concentrations of XII, PK and high molecular weight kininogen (HMrK) was examined using mixtures of normal plasma and plasma genetically deficient in these factors. At the high plasma dilution used (1 + 23 v/v in the kaolin incubate) a joint estimation of the factors was obtained. A reduction in amount of XII, PK or HMrK resulted in a correspondingly reduced yield of XIIa. Plasma kallikrein present was assayed as S-2302 amidase. The concentration of PK in XII-deficient plasma was normal, in HMrK-deficient plasma about 30% of normal. The activation of XII was studied in fresh plasma as well as in plasma stored for 3-6 months at -70 degrees, and the activation with acetone was carried out in the presence and in the absence of benzamidine, EDTA or purified HMrK. In previous work benzamidine was found to protect the cofactor function of purified HMrK in the assay system used, and EDTA was found to inhibit purified human plasma kallikrein assayed as plasminogen activator. The present results support the previous observations, and indicate that acetone treatment of fresh human plasma (benzamidine present) results in the activation of plasma kallikrein in a functional state that requires kinin-free, but otherwise native HMrK as a cofactor for the activation of XII.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetone↗
PubMed1997

Blood and plasma lipoprotein distribution and gender differences in the plasma pharmacokinetics of lipid-associated annamycin.

The objectives of this study were to determine the lipoprotein distribution of unbound annamycin and liposomal annamycin within human and rabbit blood and plasma and to evaluate the plasma pharmacokinetics of liposomal annamycin in male and female rabbits following a single intravenous bolus of the compound. Annamycin and liposomal annamycin were incubated in human and rabbit blood and plasma for 60 min. at 37 degrees C. Following incubation blood and plasma samples were assayed by HPLC for drug in each of the lipoprotein and lipoprotein-deficient plasma fractions. To evaluate the plasma pharmacokinetics of liposomal annamycin in male versus female rabbits, a single intravenous bolus dose (5 mg/kg) of liposomal annamycin was administered to male and female rabbits. Sequential blood samples were obtained from the animals following the dose, analyzed for drug, and the pharmacokinetics determined using multicompartmental methods. The incorporation of annamycin into liposomes composed of dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol resulted in no significant differences in blood versus plasma lipoprotein drug distribution. Furthermore, no differences in the plasma distribution of liposomal annamycin were observed when the drug was either incubated in vitro for 1 hr or 1 hr following intravenous administration into New Zealand male white rabbits. The plasma clearance and volume of distribution of liposomal annamycin were decreased and a increase in plasma AUC in female as compared to male rabbits following a single intravenous bolus of liposomal annamycin was observed. These findings suggest that the lipoprotein distribution of liposomal annamycin is not different when incubated in blood or plasma and that in vitro liposomal annamycin plasma distribution is similar to in vivo. Furthermore, it appears that the pharmacokinetics of liposomal annamycin are different following administration to male versus female rabbits.

Animals↗
PubMed1980

Radioimmunoassay of plasma gastric inhibitory polypeptide (GIP), release of GIP after a test meal and duodenal infusion of bile, and immunoreactive plasma GIP components in man.

A sensitive, precise and specific radioimmunoassay method for measuring plasma gastric inhibitory polypeptide (GIP) is described. The present assay system, using a label purified on a Sephadex G-15 and a SP Sephadex C-25 column as well as careful corrections for nonspecific plasma effects, allows measurements of fasting plasma GIP in the lower picomole per liter range, and the significant rise in plasma GIP subsequent to a test meal and duodenal infusion of cattle bile. Apparent immunoreactive fasting plasma GIP was eluted from a Sephadex G-150 Fine column in one peak probably representing plasma GIP bound to plasma proteins and nonspecific plasma effects. Apparent immunoreactive meal-stimulated plasma GIP was eluted from a Sephadex G-50 Fine column in two large and one diminutive peak. The first peak probably represents plasma GIP bound to plasma proteins and nonspecific plasma effects, the almost negligible second peak probably represents big GIP with a molecular weight of some 9,000, and the third and major peak, little GIP with a molecular weight of about 5,000.

Bile↗
PubMed1969

Studies on the prekallikrein (kallikreinogen)--kallikrein enzyme system of human plasma. II. Evidence relating the kaolin-activated arginine esterase to plasma kallikrein.

Evidence is presented in this paper that the kaolin-activated arginine esterase of plasma is related to plasma kallikrein activity. Such a relationship is based on studies that (1) establish a constant ratio of esterase activity on various synthetic substrates for the kaolin-activated arginine esterase, purified kallikrein(s), and preparations obtained during the fractionation procedure; (2) exclude other known plasma and tissue arginine esterases; (3) confirm the requirement for factor XII in the activation of the enzyme precursor; and (4) show similarities in behavior between the plasma esterase and purified kallikrein(s) toward a variety of inhibitors. Based on this probable identification, evidence is provided that the concentration of active factor XII determines the rate of activation of plasma kallikreinogen, and that the activation may be blocked by polybrene. Once activated, plasma kallikrein is rapidly inactivated by the naturally occurring plasma inhibitor, but the inhibition is incomplete. Acid or chloroform treatment of plasma rapidly inactivates the plasma inhibitor without affecting the concentration of plasma kallikreinogen. Another plasma arginine esterase with properties suggestive of permeability factor is activated by factor XII in the presence of synthetic substrates, but only at low ionic strength. The data suggest that this enzyme is closely related to plasma kallikrein and that it arises from a common precursor.

Aprotinin↗
PubMed1985

Long-term control of plasma calcitriol concentration in dogs and humans. Dominant role of plasma calcium concentration in experimental hyperparathyroidism.

Despite great interest in the elevated circulating levels of calcitriol (1,25-[OH]2D) associated with the clinical syndrome of human primary hyperparathyroidism, the relative potencies of known and potential stimuli/suppressors of long-term calcitriol levels have not been evaluated in either clinical or experimentally induced hyperparathyroid states. Based on reports that aparathyroid animals exhibit suppressed plasma calcitriol concentration and that acute administration of parathyroid hormone (PTH) to both humans and experimental animals or to renal slices in vitro results in increased plasma calcitriol concentration/production rate, it might be predicted that a chronic experimental model of either hypercalcemic primary hyperparathyroidism or hypocalcemic secondary hyperparathyroidism would show increased plasma calcitriol concentration. Chronic alterations in plasma calcium concentration have not been implicated as modulating calcitriol levels in any species. Accordingly, we investigated the long-term response of plasma calcitriol concentration in states of sustained experimental primary and secondary hyperparathyroidism. Intact dogs (group I) undergoing continuous intravenous PTH infusion for 12 d developed sustained hypercalcemia and hypophosphatemia, and plasma calcitriol concentration decreased from 23 +/- 3 to 14 +/- 3 pg/ml (P less than 0.01). Subsequent chelator (EGTA)-induced chronic normalization of hypercalcemia during ongoing PTH infusion resulted in a large and sustained increase in plasma calcitriol concentration to supernormal levels, reversible during subsequent cessation of chelator infusion. In additional intact dogs (group II), chronic chelator-induced hypocalcemic secondary hyperparathyroidism resulted in a sustained increase in plasma calcitriol concentration despite hyperphosphatemia. In normal human subjects undergoing a 12-13-d continuous intravenous PTH infusion to result in sustained moderate hypercalcemia (12.0 +/- 0.2 mg/100 ml) and hypophosphatemia, plasma calcitriol concentration decreased significantly (P less than 0.01) as in group I dogs and was followed by reversal to normal levels in a recovery period. The present results provide strong evidence in both humans and dogs that during experimentally induced chronic PTH excess, alterations in plasma calcium concentration dictate the directional response of circulating calcitriol concentrations. The long-term potency of plasma calcium concentration as a modulator of calcitriol metabolism is sufficient to override opposing modulation by plasma phosphorus concentration and PTH.

25-Hydroxyvitamin D 2↗
PubMed2005

Higher concentrations of heparin and hirudin are required to inhibit thrombin generation in tissue factor-activated cord plasma than in adult plasma.

Neonatal plasma clots slower than adult plasma, and only 30-50% of peak adult thrombin activity can be produced in neonatal plasma when high amounts of tissue factor (TF) are added to trigger clotting, as used in standard clotting assays. Plasma activation by addition of low amounts of TF probably better reflects conditions in vivo. Under these conditions, cord plasma clots faster than adult plasma. In the present study, we show that after activation with low amounts of TF, higher amounts of the anticoagulants heparin and hirudin are required in cord plasma for effective inhibition of thrombin generation compared with adult plasma. After strong activation with high amounts of TF (30 microM), the thrombin potential was significantly more suppressed in cord plasma compared with adult plasma in the presence of 0.4 IE/mL heparin (-92 versus -75%; p < 0.01) and in the presence of 2 IE/mL hirudin (-18 versus -8%; p < 0.01). In contrast, after weak activation with low amounts of TF (30 pM), the thrombin potential was significantly more suppressed in adult plasma compared with neonatal plasma in the presence of 0.025 IE/mL heparin (-93 versus -8%; p < 0.01) and in the presence of 2 IE/mL hirudin (-89 versus -48%; p < 0.01). Our results show that in neonates, effects of anticoagulants very much depend on the type of activation used to initiate clotting, and doses of anticoagulants should not be derived from studies done in adults, because potentially higher doses of anticoagulants may be required.

Adult↗