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PubMed1987

Somatostatin-like immunoreactivity in duck plasma, hypothalamus and neural lobe during post-hatch growth: comparison with plasma and pituitary growth hormone concentrations.

Variations in the concentrations of plasma and pituitary GH were determined in ducks for 66 and 87 days after hatch, and compared with somatostatin-like immunoreactivity (SLI) in the plasma, hypothalamus and neural lobe. Plasma GH levels gradually decreased during growth, while pituitary GH content increased. The concentration of pituitary GH increased during the first 3 weeks of age and remained relatively constant thereafter. The decline in plasma GH concentration was paralleled by a similar fall in the level of plasma SLI. While the content of hypothalamic SLI increased during development, the SLI concentration was maximal at 14 days of age and lowest in adults. The content and concentration of SLI in the neural lobe, in contrast, increased progressively during development. Gel filtration of hypothalamic and neural lobe extracts demonstrated that both young and older birds had two main peaks of SLI, corresponding to somatostatin-14 and somatostatin-28, and a third, larger form. The elution pattern of plasma SLI was similar in young and older birds and was principally composed of a large molecular species ('big' somatostatin), although an additional small peak eluting between somatostatin-28 and somatostatin-14 was eluted from a large pool of plasma from 90-day-old ducks. These results suggest that increased plasma GH levels in young birds do not result from a hypothalamic somatostatin deficiency nor from variations in molecular forms of SLI, and that the age-related decline in plasma GH concentration is not due to a deficiency in pituitary GH content. The decline in the circulating GH level during growth is probably due to an increase in hypothalamic somatostatin release.

Animals↗
PubMed2006

Risk of progression to type 2 diabetes based on relationship between postload plasma glucose and fasting plasma glucose.

OBJECTIVE: We sought to assess the risk of progression to type 2 diabetes in normal glucose tolerance (NGT) subjects based on the relationship between the plasma glucose concentration during oral glucose tolerance tests (OGTTs) and the fasting plasma glucose (FPG) concentration. RESEARCH DESIGN AND METHODS: Subjects with NGT (n = 1,282) from the San Antonio Heart Study received an OGTT with measurement of the plasma glucose concentration at 0, 30, 60, and 120 min at baseline and after 7-8 years of follow-up. Subjects were divided into four groups based on the relationship between the plasma glucose concentration during the OGTT and the FPG concentration on the same day as the OGTT. Insulin resistance was calculated by the homeostasis model assessment of insulin resistance (HOMA-IR) and Matsuda index. Early-phase insulin secretion was calculated as the ratio between the incremental plasma insulin and glucose concentrations during the first 30 min of the OGTT (DeltaI(0-30)/DeltaG(0-30)). Total insulin secretion was calculated as the ratio between the incremental areas under the insulin and glucose curves during the OGTT [DeltaG(AUC)/DeltaI(AUC)]. RESULTS: In 23 subjects (group I), the plasma glucose concentration during the OGTT returned to levels below the FPG concentration at 30 min; in 111 subjects (group II) and in 313 subjects (group III), the plasma glucose concentration during the OGTT returned to levels below the FPG concentration at 60 and 120 min, respectively. In the remaining 835 subjects (group IV), the plasma glucose concentration during the OGTT never fell below the FPG concentration. Insulin resistance, measured by HOMA-IR and the Matsuda index, increased progressively from group I through group IV, while insulin secretion measured by DeltaI(0-30)/DeltaG(0-30) and DeltaG(AUC)/DeltaI(AUC) decreased progressively from group I through group IV. The incidence of type 2 diabetes was 0% in group I and progressively increased to 0.9% in group II, 3.2% in group III, and 6.4% in group IV. CONCLUSIONS: Subjects whose postload plasma glucose concentration returned to baseline (i.e., FPG level) more quickly had greater insulin sensitivity, a higher insulinogenic index, and a lower risk of developing type 2 diabetes after 8 years of follow-up compared with subjects whose postload glucose concentration returned to baseline more slowly.

Adult↗
PubMed2002

Plasma adiponectin concentration is associated with skeletal muscle insulin receptor tyrosine phosphorylation, and low plasma concentration precedes a decrease in whole-body insulin sensitivity in humans.

Adiponectin, the most abundant adipose-specific protein, has been found to be negatively associated with degree of adiposity and positively associated with insulin sensitivity in Pima Indians and other populations. Moreover, adiponectin administration to rodents has been shown to increase insulin-induced tyrosine phosphorylation of the insulin receptor (IR) and also increase whole-body insulin sensitivity. To further characterize the relationship between plasma adiponectin concentration and insulin sensitivity in humans, we examined 1) the cross-sectional association between plasma adiponectin concentration and skeletal muscle IR tyrosine phosphorylation and 2) the prospective effect of plasma adiponectin concentration at baseline on change in insulin sensitivity. Fasting plasma adiponectin concentration, body composition (hydrodensitometry or dual energy X-ray absorptiometry), insulin sensitivity (insulin-stimulated glucose disposal, hyperinsulinemic clamp), and glucose tolerance (75-g oral glucose tolerance test) were measured in 55 Pima Indians (47 men and 8 women, aged 31 +/- 8 years, body fat 29 +/- 8% [mean +/- SD]; 50 with normal glucose tolerance, 3 with impaired glucose tolerance, and 2 with diabetes). Group 1 (19 subjects) underwent skeletal muscle biopsies for the measurement of basal and insulin-stimulated tyrosine phosphorylation of the IR (stimulated by 100 nmol/l insulin). The fold increase after insulin stimulation was calculated as the ratio between maximal and basal phosphorylation. Group 2 (38 subjects) had follow-up measurements of insulin-stimulated glucose disposal. Cross-sectionally, plasma adiponectin concentration was positively associated with insulin-stimulated glucose disposal (r = 0.58, P < 0.0001) and negatively associated with percent body fat (r = -0.62, P < 0.0001) in the whole group. In group 1 plasma adiponectin was negatively associated with the basal (r = -0.65, P = 0.003) and positively associated with the fold increase in IR tyrosine phosphorylation (r = 0.69, P = 0.001) before and after the adjustment for percent body fat (r = -0.58, P = 0.01 and r = 0.54, P = 0.02, respectively). Longitudinally, after adjustment for age, sex, and percent body fat, low plasma adiponectin concentration at baseline was associated with a decrease in insulin sensitivity (P = 0.04). In conclusion, our cross-sectional data suggest a role of physiological concentration of fasting plasma adiponectin in the regulation of skeletal muscle IR tyrosine phosphorylation. Prospectively, low plasma adiponectin concentration at baseline precedes a decrease in insulin sensitivity. Our data indicate that adiponectin plays an important role in regulation of insulin sensitivity in humans.

Adiponectin↗
PubMed2003

Contribution of fatty acids released from lipolysis of plasma triglycerides to total plasma fatty acid flux and tissue-specific fatty acid uptake.

There is controversy over the extent to which fatty acids (FAs) derived from plasma free FAs (FFAs) or from hydrolysis of plasma triglycerides (TGFAs) form communal or separate pools and what the contribution of each FA source is to cellular FA metabolism. Chylomicrons and lipid emulsions were labeled with [(3)H]triolein, injected into mice, and appearance in plasma of [(3)H]oleic acid was estimated, either through a steady-state approach or by compartmental modeling. [(14)C]oleic acid was included to trace plasma FFA. Eighty to 90% of triglyceride (TG) label was recovered in plasma, irrespective of tracer method or TG source. The contribution of TG lipolysis to total plasma FA turnover was 10-20%. After infusion of [(3)H]TG and [(14)C]FA, the retention of these labels varied substantially among liver, adipose tissue, and skeletal and heart muscle. Retention of TG label changed during fasting in the same direction as lipoprotein lipase (LPL) activity is regulated. We propose a model that reconciles the paradoxical 80-90% loss of TG label into plasma with LPL-directed differential uptake of TGFA in tissues. In this model, TGFAs mix locally at the capillaries with plasma FFAs, where they would lead to an increase in the local FA concentration, and hence, FA uptake. Our data indicate that a distinction between TG-derived FA and plasma FFA cannot be made.

Adipose Tissue↗
PubMed1997

Divergent concentrations of plasma metabolites in swine selected for seven generations for high or low plasma total cholesterol.

It was reported previously that selection for high (HG) or low (LG) plasma total cholesterol (TC) at 8 wk of age in a composite four-breed swine population resulted after four generations in divergent mean concentrations in the selected lines. The data revealed a significant positive correlation between body weight (BW) and TC concentration at 8 wk of age and differential responses in litter size, backfat depth, and carcass length at 6 mo of age. We report here the relationship between plasma TC concentration and other plasma traits related to growth and metabolism in the seventh generation of selection in these two lines of pigs. We measured plasma concentrations of TC, HDL cholesterol (HDL-C), triglycerides (TG), alkaline phosphatase (ALP), total protein (TP), albumin (ALB), urea nitrogen (urea N), and three transaminases (alanine aminotransferase, ALT; aspartate aminotransferase, AST; gamma glutamyltransferase, GGT) in seventh-generation male and female pigs at 8 wk of age. Birth weight (1.48 vs 1.38 kg), 8 wk BW (14.85 vs 12.00 kg), TC (116.8 vs 63.6 mg/dL), HDL-C (43.9 vs 25.5 mg/dL), TG (50.5 vs 33.0 mg/dL), and ALP (78.3 vs 44.9 units/L) were higher (P < .01) in HG than in LG pigs, whereas ALB (3.2 vs 3.4 g/dL), ALT (43.0 vs 45.9 units/L), and AST (53.0 vs 62.2 units/L) were lower in HG than in LG pigs (P < .05). At 8 wk, overall plasma TC concentration was correlated with BW (r = .34, P < .01) and with ALP (r = .23, P < .05) but was not related to ALT, AST, or GGT. Plasma TP urea N, and GGT were unaffected by genetic line on sex. We conclude that the difference between HG and LG pigs in TC concentration in generation 4 at 8 wk of age has persisted but not broadened in pigs of generation 7, that changes in plasma ALP, ALT, and AST may have occurred in response to selection for high or low plasma TC, and that ALP is correlated with plasma TC concentration.

Alanine Transaminase↗
PubMed1986

Effect of haemorrhagic shock and duodenal instillation of blood on the plasma profiles of somatostatin and motilin in pigs. A study of molecular plasma components.

A severe haemorrhage inducing a deep hypovolaemic shock in six anaesthetized pigs effected a plasma somatostatin increase in the superior caval and the portal vein together with a plasma motilin decrease in the portal vein (p less than 0.05). In contrast, the shed blood volume simultaneously instilled intraduodenally in another six anaesthetized pigs in haemodynamic balance induced only an insignificant bimodal somatostatin increase and a modest but significant motilin decrease in plasma from the portal vein (p less than 0.05). Plasma somatostatin immunoreactivity was eluted in four peaks from a Sephadex G-50 Fine column, of which the first peak probably represents somatostatin bound to plasma proteins; the second peak, aggregates of somatostatin-14 and somatostatin degradation products; the third peak, somatostatin-28; and the fourth peak, somatostatin-14. Plasma motilin immunoreactivity eluted in two peaks, of which the first peak possibly represents motilin bound to plasma proteins, and the second peak free plasma motilin. The major changes in portal vein plasma somatostatin and motilin concentrations during the haemorrhagic shock occurred in their free molecular fractions.

Animals↗
PubMed2001

Relationship between the concentrations of plasma phospholipid stearic acid and plasma lipoprotein lipids in healthy men.

This study investigated the correlation between the plasma phospholipid (PL) saturated fatty acid (SFA) concentration (as a surrogate marker of SFA intake) and plasma lipid and lipoprotein lipid concentrations in 139 healthy Australian men aged 20-55 years old with widely varying intakes of saturated fat (vegans, n=18; ovolacto vegetarians, n=43; moderate meat eaters, n=60; high meat eaters, n=18). Both the ovolacto vegetarian and vegan groups demonstrated significant decreases in plasma total cholesterol (TC), low-density-lipoprotein cholesterol (LDL-C) and triacylglycerol concentrations compared with both the high-meat-eater and moderate-meat-eater groups. Total SFA and individual SFA [palmitic acid (16:0), stearic acid (18:0) and arachidic acid (20:0)] in the plasma PL were significantly lower in both the ovolacto vegetarian and vegan groups than in both the high- and moderate-meat-eater groups, while myristic acid (14:0) was significantly lower in the vegans than in the high-meat-eaters. Bivariate analysis of the results showed that the plasma PL stearic acid concentration was strongly positively correlated with plasma TC (P<0.0001), LDL-C (P<0.0001) and triacylglycerol (P<0.0001), with r(2) values of 0.655, 0.518 and 0.43 respectively. In multiple linear regression, after controlling for potential confounding factors (such as exercise, dietary group, age, body mass index, plasma PL myristic acid, palmitic acid and arachidic acid, and dietary total fat, saturated fat, cholesterol, carbohydrate and fibre intake), the plasma PL stearic acid concentration was still strongly positively correlated with plasma TC (P<0.0001) and LDL-C (P=0.006) concentrations. Based on the present data, it would seem appropriate for the population to reduce their dietary total SFA intake rather than to replace other SFA with stearic acid.

Adult↗
PubMed1992

Concentration of plasma and milk vitamin E and plasma beta-carotene of mastitic and healthy cows.

Variation of vitamin E in blood plasma and milk and beta-carotene in blood plasma of 38 healthy and 38 mastitic cows was studied. Cows were assigned to one of the two treatment groups: control and vitamin E supplemented. Vitamin E supplementation was started when cows were dried-off at the end of lactation and continued until 3 months post partum at the rate of 1000 IU per cow daily and then reduced to 500 IU for the remaining lactation. A cow was considered mastitic when somatic cell count of milk was greater than 500 x 10(3) cells/ml. Milk samples with somatic cell counts below 100 x 10(3) cells/ml were from healthy cows. Data on vitamin E concentration of plasma and milk and beta-carotene in plasma were analyzed by a least squares procedure. The model included the effects of treatment, mastitis status, stage of lactation, and all first order interactions. Mean vitamin E levels in plasma and milk of supplemented cows were significantly higher than of the non-supplemented cows. Plasma and milk levels of vitamin E as well as beta-carotene in plasma were significantly lower in mastitic than healthy cows. When data were analyzed with loge, of somatic cell count in milk as an independent regression variable, results were similar. There was a negative correlation of mastitis status with vitamin E levels in plasma (-0.48), milk (-0.24), and beta-carotene in plasma (-0.38).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Plasma-vitamin E and low plasma lipoprotein levels in sickle cell anemia patients.

Increasing evidence suggests that in vivo lipid peroxidation may be an important factor in sickle cell anemia (HbSS). Vitamin E is the major lipid-soluble antioxidant in plasma, and this vitamin, as well as cholesterol, is transported in plasma almost exclusively by lipoproteins. The purpose of this investigation was to determine if vitamin E and plasma lipoprotein-cholesterol levels in sickle cell anemia (SCA) patients are interrelated. We found that low plasma-vitamin E levels in SCA patients were accompanied by low levels of plasma-cholesterol. The mean plasma-vitamin E/plasma-cholesterol ratio was similar in 12 SCA patients (6.1 +/- 0.7 micrograms vitamin E per mg plasma-cholesterol) and 21 controls (6.5 +/- 0.7 micrograms/mg). Our results suggest that the low levels of plasma-vitamin E in SCA patients may be related to decreased levels of lipoprotein carriers. The low plasma-cholesterol levels in SCA patients (139.1 +/- 9.9 mg/dL) were due to low levels of both high density lipoprotein-cholesterol (HDL-cholesterol of 35.0 +/- 1.0 mg/dL) and low density lipoprotein-cholesterol (LDL-cholesterol of 97.8 +/- 9.2 mg/dL). The "atherogenic index," defined as LDL-cholesterol/HDL-cholesterol, was similar in the SCA patients (2.9 +/- 0.2) and the controls (3.0 +/- 0.4).

Adult↗
PubMed1983

Isolation of human complex-forming glycoprotein, heterogeneous in charge (protein HC), and its IgA complex from plasma. Physiochemical and immunochemical properties, normal plasma concentration.

Human complex-forming glycoprotein, heterogeneous in charge (protein HC) has previously been isolated from urine and immunochemically shown to be present in low and high molecular weight forms in blood plasma (Tejler, L., and Grubb, A. O. (1976) Biochim. Biophys. Acta 439, 82-94). In the present work, the major low and high molecular weight forms of the protein were isolated from plasma by immunosorption followed by gel chromatography. The plasma low molecular weight protein HC and the urinary protein had similar, if not identical, molecular weight, amino acid composition, NH2-terminal and carboxyl-terminal amino acid sequences and electrophoretic mobility. The low molecular weight plasma protein HC carried a yellow chromophore like the urinary protein, but its molar extinction coefficient at 280 nm was lower and its charge heterogeneity less pronounced than that of urinary protein HC. The plasma high molecular weight protein HC had a hydrodynamic volume which was greater than that of monomeric IgA but smaller than that of dimeric IgA. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the isolated high molecular weight protein followed by electrophoretic blotting and immunochemical analysis demonstrated that the protein contained four polypeptide chains: two light immunoglobulin chains (Mr = 23,000), one IgA alpha-chain (Mr = 54,000), and one chain with Mr approximately 90,000 which carried both alpha-chain and protein HC antigenic determinants. Whether the protein HC X IgA complex is a functionally significant part of the humoral immune system cannot be decided without further experimentation, but the complex was found to be completely absent from the blood plasma of patients with a selective deficiency of IgA-secreting immunocytes. The isolated low and high molecular weight plasma protein HC components were used as standard proteins in the construction of a quantitative crossed immunoelectrophoretic assay for the simultaneous quantitation of the two major protein HC components in blood plasma. The plasma concentrations of the low and high molecular weight protein HC components were measured by this method in 13 healthy Caucasians. The results for the low molecular weight protein HC were: mean, 20.3 mg/liter, S.D., 3.2 mg/liter, range, 13.6-26.0 mg/liter; and for the protein HC X IgA complex: mean, 293 mg/liter, S.D., 176 mg/liter, range, 36-620 mg/liter.

Adult↗
PubMed1984

Prorenin-renin conversion by the contact activation system in human plasma: role of plasma protease inhibitors.

Acid-pretreated normal human plasma generates renin activity at 0 degree C and neutral pH by the activation of prorenin. The activation is caused by kallikrein generated from prekallikrein by activated factor XII. Nonacidified plasma also generates renin at 0 degree C, but at a lower rate (cold-promoted activation). In normal plasma, 14% +/- 1% of prorenin (mean +/- SEM, n = 30) was activated during incubation at 0 degree C for 7 days (range 6% to 26%). Cold-promoted activation of prorenin was within the normal range in plasma deficient in factor XI, X, IX, VIIIC, VII, V, prothrombin, or high mol wt kininogen. Cold-promoted activation of prorenin was less than or equal to 1% in plasma deficient in factor XII or prekallikrein. Reconstitution of these plasmas with highly purified factor XII or prekallikrein restored normal prorenin activation. Correction of high mol wt kininogen deficiency had no effect. Thus cold-promoted activation of prorenin depends on the presence of factor XII and prekallikrein, whereas the other clotting factors are not essential. The influence of the inhibitors C1 esterase-inhibitor, alpha 2-macroglobulin, antithrombin III, and alpha 1-antitrypsin on the activation of prorenin was studied in factor XII-deficient plasma from which one or more of these inhibitors had been selectively removed by immunoadsorption. Factor XII was subsequently added, and the generation of renin at 37 degrees C was observed after complete factor XII-high mol wt kininogen-mediated activation of prekallikrein induced by dextran sulfate. No activation of prorenin was observed at 37 degrees C after depletion of C1 esterase inhibitor, alpha 2-macroglobulin, antithrombin III, or alpha 1-antitrypsin. When prekallikrein was activated in plasma depleted of both C1 esterase-inhibitor and alpha 2-macroglobulin, 6% of prorenin was activated in 2 hours at 37 degrees C. After additional depletion of antithrombin III, the activation increased to 47%. These results indicate that the contact activation system is capable of activating prorenin in plasma at physiologic pH and temperature when the three most important kallikrein inhibitors, C1 esterase-inhibitor, alpha 2-macroglobulin, and antithrombin III, are absent.

Binding Sites↗
PubMed1984

Plasma therapy of primary rat mammary carcinoma: antitumor activity of tumor-bearer plasma adsorbed against inactivated CNBr sepharose or protein A-sepharose.

We evaluated the ability of plasma adsorbed against Sepharose, inactivated CNBr Sepharose, or protein A-Sepharose to inhibit the growth of primary mammary carcinomas in Buffalo/N rats. Mammary adenocarcinomas were induced by a single intravenous injection of N-nitroso N-methylurea. When palpable mammary tumors were detected, rats were treated by infusion of plasma obtained from normal or tumor-bearing rats. Animals were killed 50 days after entry into the experiment; the index mammary tumor and any subsequently arising tumors were weighed and examined histologically. Unadsorbed plasma obtained from normal or tumor-bearing rats had no detectable antitumor effect. Normal plasma adsorbed against Sepharose or Sepharose derivatives had no significant antitumor effect. Weight (median) of index mammary tumors in groups of rats treated with normal plasma adsorbed against Sepharose alone, inactivated CNBr Sepharose alone, or protein A--Sepharose alone was not significantly different from weight of tumors of untreated, control animals. Tumor-bearer plasma adsorbed against either inactivated CNBr Sepharose or protein A-Sepharose had significant antitumor effect. Weight of index mammary tumors in groups of rats treated with tumor-bearer plasma adsorbed to inactivated CNBr Sepharose alone or against protein A-Sepharose alone was significantly less than weight of tumors in control rats. Tumor-bearer plasma adsorbed against Sepharose alone inhibited tumor growth in one experiment but not in a second experiment. Tests for endotoxin in CNBr Sepharose indicated the presence of approximately 1 ng endotoxin/g Sepharose. Administration of nanogram quantities of Salmonella enteritidis endotoxin in saline did not inhibit growth of primary mammary tumors. These experiments describe a rodent model that may be useful in the analysis of the basis of the inhibition of tumor growth that occurs following administration of adsorbed plasma.

Animals↗
PubMed1984

A unique precipitating autoantibody against plasma thromboplastin antecedent associated with multiple apparent plasma clotting factor deficiencies in a patient with systemic lupus erythematosus.

A 42-yr-old woman with systemic lupus erythematosus without bleeding diathesis developed a prolonged activated partial thromboplastin time that was not corrected by normal plasma. An inhibitor that acted rapidly and inactivated 0.5 U/ml plasma thromboplastin antecedent (PTA, factor XI) at a 1:200 plasma dilution was demonstrated. In addition to a low titer of PTA (less than 0.01 U/ml), plasma assayed at 20-fold dilution also showed low titers of Hageman (factor XII, 0.02 U/ml), Fletcher (plasma prekallikrein, 0.02 U/ml), and Fitzgerald (high molecular weight kininogen, less than 0.01 U/ml) factors. The titer of these factors, except PTA, returned to normal upon further plasma dilution or upon removal of the inhibitor by protein A adsorption. Thus, the inhibitor appeared to interfere with these clotting factor assays, possibly by inactivating PTA in the substrate plasmas in the test system. Its specificity was further confirmed. The inhibitor did not interfere with surface-induced proteolytic cleavage of Hageman factor. Surface-induced generation of plasma kallikrein activity (amidolysis of H-D-pro-phe-arg-pNa and cold-promoted factor VII activity enhancement) requires only Hageman, Fletcher, and Fitzgerald factors and was normal. Reactions requiring all 4 contact phase factors, including PTA, such as surface-induced generation of plasmin activity (amidolysis of H-D-val-leu-lys-pNa) and activated Christmas factor (factor IXa) activity, were defective. Furthermore, the inhibitor bound to agarose-protein A inactivated and removed PTA selectively from normal plasma. The inhibitor was an IgG-lambda autoantibody that precipitated PTA. The inactivated activated PTA (factor XIa) without the requirement for an additional cofactor. Furthermore, it inhibited surface-induced activation of PTA by interfering with its proteolytic cleavage upon glass surface exposure and with its binding onto the reactive surfaces.

Adult↗
PubMedDate not supplied

Seminal plasma biochemistry. I. Preliminary report: a possible mechanism for the liquefaction of human seminal plasma and its relationship to spermatozoal motility.

Based on indirect evidence it has been suggested that the liquefaction of human seminal plasma involves fibrinolytic and proteolytic enzymes and that the coagulum is formed by proteins. In this preliminary investigation evidence is presented for the involvement of seminal plasma sialyltransferase in liquefaction which suggests that the coagulum may be composed of glycoproteins. It is proposed that the glycoproteins form a polymer by the chelation of divalent metal ions via the carboxylic acid moieties of the sialic acid groups of the glycoproteins. The glycoprotein polymer may then be dismantled by the reduction of the meal ions by the oxidation of L-ascorbic acid, possibly allowing enzymes to complete the liquefaction process. A total of 100 semen samples from 30 male subjects whose semen profiles were considered "normal" by an independent assessor, were examined for the following: (i) liquefaction time of the seminal plasma; (ii) seminal plasma sialyltransferase activity; (iii) spermatozoal motility, defined as directional or nondirectional; (iv) spermatozoal count, and (v) seminal plasma content of free L-ascorbic acid, dehydroascorbic acid and glutathione. Linear regression analysis showed a significant correlation between sialyltransferase activity and the liquefaction time for seminal plasma. Similarly, multilinear regression analysis of the data showed that as the seminal plasma levels of L-ascorbic acid, total dehydroascorbic acid and glutathione increase, there is a decrease in spermatozoal motility and a decrease in the liquefaction time of the seminal plasma. The possible metabolic relationship of seminal plasma L-ascorbic acid and glutathione is discussed and a metabolic pathway is suggested.

Ascorbic Acid↗
PubMed1981

The relationship between plasma iron and plasma iron turnover in the rat.

Plasma iron turnover has been evaluated in the growing rat. Consistent data were obtained with the intravenous injection of radioiron in the form of ferrous sulfate or ferric citrate. Plasma iron turnover changed as a function of plasma iron concentration. Only part of this effect in the rat was due to the different rates of clearance of mono-and differic transferrin, the latter having a higher iron delivery rate in vivo. An additional effect was shown to relate to the rate of red cell production. With decreased production, the effect of plasma iron on plasma iron turnover was reduced, whereas with increased erythropoiesis there was an additional increment in plasma iron turnover for any increase in plasma iron. Since this effect was observed when increased iron demands were due to an increase in erythroid precursors in the marrow but not in the circulating blood, it is attributed to limitations in iron flow to the marrow. This suggests that erythroid marrow activity and the adequacy of iron supply when studied by ferrokinetic techniques can best be defined by the response curve relating plasma iron concentration to plasma iron turnover.

Animals↗
PubMed1995

Increased prothrombin activation in protein S-deficient plasma under flow conditions on endothelial cell matrix: an independent anticoagulant function of protein S in plasma.

Protein S is a vitamin K-dependent nonenzymatic coagulation factor involved in the regulation of activated protein C (aPC). In this study, we report an aPC-independent anticoagulant function of protein S in plasma under flow conditions. Plasma, anticoagulated with low-molecular-weight heparin allowing tissue factor-dependent prothrombin activation, was perfused at a wall shear rate of 100 s-1 over tissue factor containing matrices of stimulated endothelial cells placed in a perfusion chamber. Fractions were collected in time at the outlet and prothrombin activation was determined by measuring the activation fragment F1+2 of prothrombin. In normal plasma, a time-dependent prothrombin activation was detected by the generation of fragment1+2. Prothrombin activation had ceased after 12 minutes perfusion, independent of the amount of tissue factor present in the matrix. Depletion of protein S from plasma or inhibition of protein S in plasma by monoclonal antibodies induced a 5- to 25-fold increase of prothrombin activation on the procoagulant endothelial cell matrix. A prolonged prothrombin activation was detected in protein S-depleted plasma up to 20 minutes after onset of the thrombin generation. The increased prothrombin activation in protein S-depleted plasma could not be explained by the absence of the cofactor function of protein S for aPC because depletion of protein C from plasma did not result in increased prothrombin activation. These data provide further evidence for a strong anticoagulant function of protein S in plasma independent from activated protein C.

Antibodies, Monoclonal↗
PubMed1997

Comparison of mean normal prothrombin time (PT) with PT of fresh normal pooled plasma or of a lyophilized control plasma (R82A) as denominator to express PT results: collaborative study of the International Federation of Clinical Chemistry. IFCC Working Group Standardization of Coagulation Tests.

The mean normal prothrombin time (MNPT) is currently recommended as the denominator term in the expression of PT ratio or International Normalized Ratio (INR) values. The PT of lyophilized normal control plasmas might also be used in calculating PT ratios, but the overall accuracy of this approach and its dependence on reagents and endpoint detectors have not been evaluated in detail. In an IFCC collaborative study involving 15 expert laboratories and 58 PT systems, the PT ratios of 30 apparently healthy subjects were expressed with the use of the MNPT, the PT of fresh normal pooled plasma (FNPP) obtained from the same apparently healthy subjects, or the PT of plasma R82A--a lyophilized normal pooled plasma prepared by the Verband der Deutschen Geräte-Hersteller for in-house calibration of a large amount of control plasma--as the denominator term. The total imprecision of the PT of plasma R82A averaged 2.16%. Mean PT ratios did not differ from 1.00 (mean 1.00, range 1.00-1.01) with the use of the MNPT as the denominator term. Mean PT ratios were > 1.00 with the FNPP-PT as the denominator term (1.02, 0.96-1.05), and differed according to endpoint detectors (P = 0.024). Mean PT ratios with plasma R82A-PT as the denominator term averaged 0.98 (range 0.91-1.06) with plain thromboplastins (n = 11), 1.02 (0.98-1.06) with combined thromboplastins (n = 3), and 0.93 (0.87-0.97) with recombinant thromboplastins (n = 2), but they differed according to the brand of plain or recombinant reagents (P = 0.00001), the endpoint detector (P < 0.0025), and the plasma citrate concentration (P < 0.0025). These findings underline the differences in the PT of lyophilized plasma R82A and the MNPT and PT of FNPP obtained from the same individuals and support the recommendation that the system-specific MNPT should be used as the ideal index of the normal PT in the calculation of INR values.

Female↗
PubMed1980

Effect of lipoprotein-free plasma on the interaction of human plasma high density lipoprotein with egg yolk phosphatidylcholine liposomes.

Liposomes consisting of 14C-labeled egg yolk phosphatidylcholine were incubated with whole human plasma or plasma subfractions. The transfer of liposomal phospholipid to plasma high density lipoprotein was determined by gel filtration. Whole plasma degraded the liposomes considerably faster than isolated high density lipoprotein. The phospholipid-transferring activity of whole plasma could be recovered in an equivalent mixture of isolated high density lipoprotein and lipoprotein-free plasma. The transfer stimulating activity in lipoprotein-free plasma was not associated with albumin but with a component of higher molecular weight. Upon incubation of lipoprotein-free plasma with liposomes this component appeared to be adsorbed to the liposomes and could thus be separated from the bulk protein by gel filtration. This binding to liposomes is taken as an indication that the component acts by modifying the lipid-water interface thus facilitating the insertion of the lipoprotein into the liposomal bilayer.

Biological Transport↗