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PubMed1989

Plasma ammonia, plasma, brain and liver amino acids and urea cycle enzyme activities in rats fed ammonium acetate.

Male Sprague-Dawley rats were trained to eat a 6% casein diet within a 3-h period each day. They were then fed a 6% casein diet for 10-16 d before they were fed either the same 6% casein diet or the 6% casein diet supplemented with 15% ammonium acetate for 1 or 7 d. During the absorptive period, plasma ammonia, plasma amino acids and brain amino acids were measured on d 1 and d 7 after feeding ammonium acetate. Food intake of rats fed 15% ammonium acetate was depressed on d 1 and increased to approximately 75% of the intake of the 6% casein-fed group by d 7. On d 1 plasma ammonia of the rats fed 5% ammonium acetate was 101 microM as compared to 56 microM for the rats fed 6% casein (P less than 0.05). On d 7, plasma ammonia of the rats fed 15% ammonium acetate was 240 microM (P less than 0.05) as compared to 44 microM for the rats fed 6% casein. In rats fed 15% ammonium acetate, after 7 d ornithine transcarbamylase and arginase activities were higher and argininosuccinate synthetase activity was lower (P less than 0.05) while carbamyl phosphate synthetase activity tended to be higher than that of rats fed 6% casein. The results suggest that rats adapt to ingestion of 15% ammonium acetate by some unknown neural mechanism rather than by increases in all urea cycle enzyme activities. Feeding ammonium acetate causes changes in plasma, brain and liver amino acid concentrations.

Acetates↗

PubMed2001

Modification of the ProC Global assay using dilution of patient plasma in factor V-depleted plasma as a screening assay for factor V Leiden mutation.

The activated protein C (APC) resistant-factor V (factor V Leiden) has emerged as the most common inherited risk factor for thrombosis in the Caucasian population. Beside DNA analysis, the laboratory diagnosis is often based on the detection of a poor anticoagulant response to exogenous APC. The ProC Global assay (Dade Behring, Marburg, Germany) is a global clotting assay, which was primarily developed to evaluate the functionality of the protein C anticoagulant pathway. It is based on the ability of endogenous APC, generated by activation of protein C by an extract from Agkistrodon contortrix contortrix venom, to prolong an activated partial thromboplastin time. It was previously found to be highly sensitive for the factor V Leiden mutation and for protein C deficiency, but only moderately sensitivity for protein S deficiency. Here, we evaluated the performance of a modification of the ProC Global assay using a 1 : 5 pre-dilution of patient plasma in factor V-depleted plasma in the screening of the factor V Leiden mutation-related APC resistance. For that purpose, we investigated selected frozen plasma samples from 341 patients with a history of venous thromboembolism. The sensitivity for the factor V Leiden mutation of the modified assay was found to be 100%, as all the carriers of that mutation (five homozygotes and 77 heterozygotes) had a decreased response to the assay, i.e. a normalized ratio below 0.80. Its specificity was also 100% since none of the other tested patients had a decreased response, i.e. isolated protein C (n = 3) or protein S deficiency (n = 50), or without any abnormality of the protein C pathway (n = 143), even those on oral anticoagulant treatment (n = 76). However, it would be preferable that each laboratory defines both its reference range and its cut-off level. Finally, even if larger-scale multicentre studies are needed before definite recommendations could be made, these results suggest that the ProC Global performed using a 1 : 5 pre-dilution of the patient plasma in factor V-depleted plasma could be validly used as a screening assay of the factor V Leiden mutation-related APC resistance in patients with a history of thrombosis.

Activated Protein C Resistance↗

PubMed1985

Binding of human renin to plasma proteins and comparison with plasma active and inactive renin.

Inactive renin was partially purified from normal male plasma. It showed no enzymatic activity at pH 7.4, and its molecular weight by gel filtration was 53 000 compared with 45 000 for partially purified plasma active renin and 41 000 for pure renal renin. After exposure to pH 3.0 the inactive renin became enzymatically active but its molecular weight did not change. The acid-activation could be reversed when the renin was re-adjusted to pH 7.4 and warmed. Pure renal renin labelled with I125 was added to normal male plasma. It had a molecular weight of 40 000 by gel filtration. When the mixture was acidified and neutralized, some I125 label appeared in a high-molecular-weight peak, as might occur if the renin was associated with a binding protein. If the mixture of plasma and labelled renin was treated with guanidine hydrochloride, most of the label appeared in the high-molecular-weight peak. However, after both acid treatment and treatment with guanidine hydrochloride the 'high-molecular-weight' peak appeared in the void volume of the column (Mr 108 000) rather than in the position of inactive renin (Mr 53 000). Also, the I125 label in the peak was neither immunologically nor electrophoretically similar to renin. It may represent denatured renin bound to plasma proteins, e.g. alpha-2 macroglobulins. We conclude that 'inactive renin' is a prorenin-like material rather than a protein-bound form of active renin.

Blood Proteins↗

PubMed1989

Solution of methodological problems in measurement of inactive renin in rat plasma using trypsin activation, and the effect of nephrectomy and sialo-adenectomy on inactive plasma renin.

Trypsin activation of rat plasma destroys angiotensinogen and generates a tetradecapeptide-like material, verified by high performance liquid chromatography, which interferes with the measurement of inactive renin. Using an assay based on removal of the material by a cation-exchange resin and the addition of exogenous angiotensinogen, the plasma concentration of inactive renin in intact conscious male rat was 0.48 GU/l (range 0.28-0.67 GU/l, n = 20). Inactive renin comprised about 70% of the total plasma renin. The level of inactive renin was unchanged 24 h after bilateral nephrectomy and 7 days after submandibular sialo-adenectomy. Bilateral nephrectomy of previously sialo-adenectomized rats decreased the level of inactive renin significantly. Our findings are in contrast to the marked increase, reported by several other investigators, in inactive plasma renin in rats following bilateral nephrectomy, and do not support the previously suggested, mainly extrarenal, origin of inactive plasma renin.

Animals↗

PubMed1995

Increased plasma glucose clearance in sepsis is due to increased exchange between plasma and interstitial fluid.

It has long been unclear why plasma glucose clearance is increased during sepsis, an insulin-resistant state. To address this issue, we studied sheep given a constant infusion of endotoxin for at least 24 h (n = 5). We gave a bolus of 6,6 d2 glucose and determined the fractional exchange of glucose between plasma and interstitial fluid using compartmental modeling techniques. We found that exchange of glucose between plasma and interstitial fluid was significantly increased in sepsis, but the fractional clearance of glucose from interstitial fluid was not significantly altered. Thus the observed increased plasma glucose clearance was solely due to alterations in glucose exchange between plasma and interstitial fluid and was unrelated to glucose transport into cells.

Animals↗

PubMed2001

Interaction potential of microparticles in a plasma: role of collisions with plasma particles.

The interaction potential of two charged microparticles in a plasma is studied. Violation of the plasma equilibrium around the dust particles due to plasma-particle inelastic collisions results in three effects: long-range (non-Yukawa) electrostatic repulsion, attraction due to ion shadowing, and attraction or repulsion due to neutral shadowing (depending on the sign of the temperature difference between the particle surface and neutral gas). An analytical expression for the total potential is obtained and compared with previous theoretical results. The relative contribution of these effects is studied in two limiting cases-an isotropic bulk plasma and the plasma sheath region. The results obtained are compared with existing experimental results on pair particle interaction. The possibility of the so-called dust molecule formation is discussed.

Journal Article↗

PubMed2005

Electromagnetic instabilities for relativistic beam-plasma interaction in whole k space: nonrelativistic beam and plasma temperature effects.

For the system formed by a relativistic electron beam and its plasma return current, we investigate the effects of both transverse and parallel beam and plasma temperatures on the linear stability of collective electromagnetic modes. We focus on nonrelativistic temperatures and wave-vector orientations ranging from two-stream to filamentation instabilities. Water-bag distributions are used to model temperature effects and we discuss their relevance. Labeling Theta(k) the angle between the beam and the wave vector, one or two critical angles Theta(c,i) are determined exactly and separate the k space into two parts. Modes with Theta(k) < Theta(c) =min ( Theta(c,i)) are quasilongitudinal and poorly affected by any kind of temperature. Modes having Theta(k) > Theta(c) are very sensitive to transverse beam and plasma parallel temperatures. Also, parallel plasma temperature can trigger a transition between the beam-dependent filamentation instability (Theta(k) =pi/2) and the plasma-temperature-dependent Weibel instability so that two-stream, filamentation, and Weibel instabilities are eventually closely connected to each other. The maximum growth rate being reached for a mode with Theta(k) < Theta(c), no temperature of any kind can significantly reduce it in the nonrelativistic temperature regime.

Journal Article↗

PubMed2000

Plasma line emission from short pulse laser interactions with dense plasmas

Plasma line emission is observed in simulations of dense plasma irradiated by moderately intense light pulses of duration some tens of femtoseconds, and its scaling with density and with laser intensity is studied. Plasma emission is recorded both during the pulse where it is observed against the background spectrum of harmonics of the laser frequency as well as postpulse. Harmonics of the plasma line up to the fifth have been observed. An unexpected feature present in most of the reflected light spectra appears on the blue side of the plasma line with a central frequency omega approximately 1.5omega(p).

Journal Article↗

PubMed2001

Plasma electron trapping and acceleration in a plasma wake field using a density transition.

A new scheme for plasma electron injection into an acceleration phase of a plasma wake field is presented. In this scheme, a single, short electron pulse travels through an underdense plasma with a sharp, localized, downward density transition. Near this transition, a number of background plasma electrons are trapped in the plasma wake field, due to the rapid wavelength increase of the induced wake wave in this region. The viability of this scheme is verified using two-dimensional particle-in-cell simulations. To investigate the trapping and acceleration mechanisms further, a 1D Hamiltonian analysis, as well as 1D simulations, has been performed, with the results presented and compared.

Journal Article↗

PubMed1988

Plant Plasma Membrane Proteins : II. Biotinylation of Daucus Carota Protoplasts and Detection of Plasma Membrane Polypeptides after Sds-Page.

The ability of two biotinylating reagents, sulfosuccinimidobiotin and sulfosuccinimidyl 2-(biotinamido)ethyl-1,3'-dithiopropionate, to label plasma membrane proteins was examined. These compounds form covalent bonds with the free amino groups of proteins and label the proteins with biotin. Biotinylated proteins can be detected with avidin-peroxidase staining. Protoplasts isolated from embryogenic Daucus carota suspension cells were labeled with biotin and the membranes were separated on linear sucrose gradients. The conditions used for labeling the protoplasts did not cause protoplast rupture or loss of viability. The distribution of the biotin label in these linear sucrose gradients was analyzed and compared to the distribution of vanadate-sensitive ATPase activity, a marker for the plasma membrane. Both the biotin label and the vanadate-sensitive ATPase activity were strongly localized in the gradient at peak density of 1.16 gram per cubic centimeter. When the protoplast surface was labeled, biotinylated polypeptides were detected after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and polypeptides of 153, 94, 51, 30, 20, 17, and 14 kilodaltons were shown to be plasma membrane in origin. When a crude membrane pellet was labeled, numerous biotinylated polypeptides were distributed throughout the gradient. Because the position of the biotin label in the gradient is strongly correlated with the distribution of vanadate-sensitive ATPase, it is concluded that these biotinylating reagents are effective and reliable labels for proteins of the plant plasma membrane. Furthermore, these labels permit the positive identification of plasma membrane proteins after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and can serve as convenient markers for solubilization and purification of these proteins.

Journal Article↗

PubMed1995

C-terminal deletion analysis of plant plasma membrane H(+)-ATPase: yeast as a model system for solute transport across the plant plasma membrane.

The plasma membrane proton pump (H(+)-ATPase) energizes solute uptake by secondary transporters. Wild-type Arabidopsis plasma membrane H(+)-ATPase (AHA2) and truncated H(+)-ATPase lacking 38, 51, 61, 66, 77, 92, 96, and 104 C-terminal amino acids were produced in yeast. All AHA2 species were correctly targeted to the yeast plasma membrane and, in addition, accumulated in internal membranes. Removal of 38 C-terminal residues from AHA2 produced a high-affinity state of plant H(+)-ATPase with a low Km value (0.1 mM) for ATP. Removal of an additional 12 amino acids from the C terminus resulted in a significant increase in molecular activity of the enzyme. There was a close correlation between molecular activity of the various plant H(+)-ATPase species and their ability to complement mutants of the endogenous yeast plasma membrane H(+)-ATPase (pma1). This correlation demonstrates that, at least in this heterologous host, activation of H(+)-ATPase is a prerequisite for proper energization of the plasma membrane.

Amino Acid Sequence↗

PubMed1975

The effect of norepinephrine and theophylline on blood glucose, plasms FFA, plasma glycerol and plasma insulin in normal subjects.

The plasma concentrations of free fatty acids (FFA), glycerol and insulin as well as the blood glucose concentration have been followed in two groups of subjects after infusions of theophyllamine. Each individual was examined twice. The 5 subjects in group 2 were given an infusion of norepinephrine before the theophyllamine at one of the examinations and saline at the other. The 6 subjects in group II were given an infusion of norephinephrine at both examinations, followed by theophyllamine on one occasion and by saline on the other. Thus, the subjects in both groups served as their own controls. It was found that theophyllamine caused lipid mobilization, as measured by the plasma FFA and plasma glycerol concentrations, both when given as the only active drug and when given after norepinephrine. The blood glucose concentration rose slightly after norepinephrine and the plasma insulin level increased concomittantly. When theophylline was given as the only active drug, there was no increase in the blood glucose but the plasma insulin concentration rose slightly.

Adult↗

PubMed1990

Tianeptine binding to human plasma proteins and plasma from patients with hepatic cirrhosis or renal failure.

1. The binding of tianeptine to human plasma, isolated plasma proteins, red blood cells and to plasma from patients with cirrhosis or renal failure was studied in vitro by equilibrium dialysis. 2. Tianeptine is highly bound to plasma (95%) at therapeutic concentrations (0.3-1 microM). No saturation of the binding sites was seen. 3. Human serum albumin (HSA) was shown to be mainly responsible for this binding (94%) with a saturable process characterized by one binding site with a moderate affinity (Ka = 4.2 x 10(4) M-1) and a non-saturable process with a low total affinity (nKa = 1.2 x 10(4) M-1). 4. Like many basic and amphoteric drugs, tianeptine showed a saturable binding to alpha 1-acid glycoprotein (AAG) with one site and a moderate affinity (Ka = 3.7 x 10(4) M-1). Its binding to lipoproteins and red blood cells (RBC) was weak and non-saturable. Over the range of therapeutic drug concentrations (0.3-1 microM), the unbound fraction in blood remains constant (4.5%). 5. Interactions were studied using non-esterified fatty acids (NEFA) at pathological concentrations; they altered tianeptine binding to plasma and to isolated HSA. Tianeptine seems to bind to a HSA site different from sites I (warfarin) and II (diazepam), but close to site II. It also shares the only basic-site on AAG. However, at therapeutic drug concentrations (0.3-1 microM), not all of these interactions occur. 6. The binding of tianeptine varied according to HSA, AAG and NEFA concentrations both in patients and healthy subjects. In patients with chronic renal failure having high NEFA concentrations the unbound fraction of tianeptine (fu) increased from 0.045 to 0.153 compared with normal (P less than 0.001). In cirrhotic patients, with relatively low HSA concentrations, the fu of tianeptine increased from 0.045 to 0.088 compared with normal (P less than 0.01). 7. Multiple regression analysis of all of the data indicated that the fu of tianeptine was related significantly to HSA, NEFA and AAG concentrations, with a particularly strong correlation with NEFA concentrations. Therefore, variation of HSA and NEFA concentrations in patients on maintenance therapy may cause an increase of tianeptine fu.

Adult↗

PubMed1992

The effect of ageing on plasma albumin and plasma protein binding of diazepam, salicylic acid and digitoxin in healthy subjects and patients with renal impairment.

1. Plasma albumin concentration was measured in 118 healthy subjects (aged between 18 and 87 years), in 95 renal patients with creatinine clearances between 15 and 50 ml min-1 (aged between 14 and 79 years) and in 101 uraemic patients maintained on chronic haemodialysis (aged between 27 and 83 years). 2. There was a significant (P less than 0.001) negative correlation between albumin concentration and age in healthy subjects, but no correlation in patients with low creatinine clearance or in uraemic patients. 3. The ex vivo plasma binding of diazepam (1 microM), salicylic acid (2 mM) and digitoxin (37 nM) was studied in groups of age-selected young and aged healthy subjects in patients with low creatinine clearance and in patients with uraemia. The unbound fractions of diazepam and salicylic acid were about double in old compared with young healthy subjects whereas they were similar in young and old patients with lowered creatinine clearance. In uraemic patients, ageing did not affect the binding of salicylic acid whereas the unbound fraction of diazepam was slightly but significantly greater in elderly subjects. The unbound fraction of digitoxin was independent of age in both healthy subjects and in those with renal disease. 4. Decreased plasma binding of diazepam and salicylic acid was partially corrected by extensive dialysis of plasma. The lower plasma binding of diazepam and salicylic acid associated with ageing may be ascribed to the effects of endogenous displacers and to hypoalbuminaemia. The influence of these two factors appears to be drug-dependent.

Adolescent↗

PubMed1984

Simultaneous assay of noradrenaline and its deaminated metabolite, dihydroxyphenylglycol, in plasma: a simplified approach to the exclusion of phaeochromocytoma in patients with borderline elevation of plasma noradrenaline concentration.

The fate of noradrenaline released from sympathetic endings differs from that of noradrenaline secreted directly into the bloodstream. This has been used to establish a single sample test for the exclusion of phaeochromocytoma in patients with borderline elevation of plasma noradrenaline concentration. This test is based on the measurement of the ratio in plasma of noradrenaline to its deaminated metabolite, dihydroxyphenylglycol (DHPG). The latter was shown to reflect mainly nervous release of noradrenaline and its plasma concentration was not increased during intravenous noradrenaline infusion. In seventeen phaeochromocytoma patients the ratio in plasma of noradrenaline to DHPG was greater than 2 (range 2.05-3.57); in nineteen non-phaeochromocytoma patients the reverse was found, the ratio of DHPG to noradrenaline being greater than 2 (range 2.08-2.74). Since DHPG can be measured simultaneously with noradrenaline, measurement of the plasma ratio of these two catechols may prove a simple method of differentiating phaeochromocytoma from nonphaeochromocytoma patients.

Adrenal Gland Neoplasms↗

PubMed1986

The isolation of plasma membrane and characterisation of the plasma membrane ATPase from the yeast Candida albicans.

Plasma membrane ghosts were isolated from Candida albicans ATCC 10261 yeast cells following stabilisation of spheroplasts with concanavalin A, osmotic lysis and Percoll density gradient centrifugation. Removal of extrinsic proteins with NaCl and methyl alpha-mannoside gave increased ATPase and chitin synthase specific activities in the resultant plasma membrane fraction. Sonication of this fraction yielded unilamellar plasma membrane vesicles which exhibited ATPase and chitin synthase specific activities of 4.5-fold and 3.0-fold, respectively, over those of the plasma membrane ghosts. ATPase activity in the membrane ghosts was optimal at pH 6.4, showed high substrate specificity (for Mg X ATP) and was inhibited 80% by sodium vanadate but less than 4% by oligomycin and azide. The effects of a range of other inhibitors were also characterised. Temperature effects of ATPase activity were marked, with a maximum at 35 degrees C. Breaks in the Arrhenius plot, at 12.2 degrees C and 28.9 degrees C, coincided with endothermic heat flow peaks detected by differential scanning calorimetry. ATPase was solubilised from the plasma membranes with Zwittergent in the presence of glycerol and phenylmethylsulphonyl fluoride and partially purified by glycerol density gradient centrifugation. The solubilised enzyme hydrolysed Mg X ATP at Vmax = 20 mumol X min-1 X mg-1 in the presence of phospholipids, with optimal activity at pH 6.0--6.5.

Adenosine Triphosphatases↗

PubMedDate not supplied

Plasma noradrenaline and its relationship to plasma oestradiol in normal women during the menstrual cycle.

In order to investigate a possible relationship between sympatho-adrenal neuronal activity and the endocrine changes during the menstrual cycle, free and sulphate-conjugated plasma catecholamines and oestradiol were measured under carefully controlled conditions in 26 normal menstruating women. Plasma oestradiol levels were generally higher during the luteal compared with the follicular phase which corresponded to the self-reported day of the cycle. Free plasma noradrenaline concentration was higher during the luteal phase (P = 0.02) and was positively correlated with plasma oestradiol concentration (r = 0.40, P = 0.023). These relationships were not present for plasma adrenaline. It is conceivable that the higher luteal phase noradrenaline is causally related to the higher oestradiol levels, leading to incomplete inactivation by reducing tissue uptake or competitive inhibition of catechol-O-methyl transferase. As sulphated noradrenaline was not significantly different between the follicular and luteal phases, competitive inhibition of phenolsulphotransferase by oestradiol was considered unlikely.

Adult↗

PubMed2005

Elevated plasma adiponectin concentrations in patients with liver cirrhosis correlate with plasma insulin levels.

BACKGROUND: Adiponectin is a hormone secreted by adipocytes and has anti-diabetic and anti-atherogenic properties. Hypoadiponectinemia is associated with insulin-resistant diabetes and liver dysfunction. The aim of this study was to determine plasma adiponectin and insulin levels in patients with liver cirrhosis. METHODS: Adiponectin and insulin levels were determined in 38 patients with cirrhosis and 30 healthy controls, and were correlated with various clinical and biochemical parameters. Patients included 21 with Child A, eight Child B, and nine with Child C liver cirrhosis. RESULTS: Log adiponectin and insulin levels were significantly elevated in patients with cirrhosis compared with the control. In liver cirrhosis, the level of adiponectin increased proportionately with the Child's classification score. In control subjects, plasma adiponectin correlated inversely with insulin levels. In contrast, plasma adiponectin correlated positively with insulin levels in patients with liver cirrhosis. Plasma adiponectin levels did not correlate with age, sex, body mass index, total bilirubin, aspartate aminotransferase, and fasting blood sugar levels in both groups, while alanine aminotransferase correlated negatively with adiponectin in control subjects as reported previously. CONCLUSION: Our results of high plasma adiponectin in patients with liver cirrhosis could reflect an imbalance between its production by adipocytes and metabolism in the liver.

Adiponectin↗