Plasma appearance

Similarly to fecal balance studies, assessment of element absorption by plasma deconvolution is an approach adopted from non-isotopic measurements. After feeding the test meal containing the isotopic label, serum samples are taken at regular intervals over several hours. Samples are analyzed for the isotopic label to assess the appearance and disappearance of the label over time in blood. TTie area under the resulting curve for label concentration is then proportional to the fraction of label absorbed. The larger the area, the more of the label has passed the intestinal mucosa [29]. 

When a single isotopic label is used for this purpose, the basic limitation is that the absorbed amount of isotopic label cannot be assessed, as also holds true for non-iso-topic deconvolution tests. In single isotope tests, comparisons between test meals can only be made in a relative manner by comparing areas under the curves obtained for different meals. This can be changed by giving a known amount of a second isotopic label in parallel by infusion. The second label enters circulation directly, which would compare to 100% absorption of the element via the intestinal mucosa. As the area under the curve for the intravenous isotopic label corresponds to the intravenous dose, the area under the curve for the oral label can be transformed into the amount of oral label that has been absorbed [30]. The ratio of the area under the curve for the oral and intravenous label equals the amount ratio of the two labels in the body. 

When plasma deconvolution techniques are applied, the isotopic label should be infused slowly and doses for the intravenous label should be kept as low as possible in order not to disturb element homeostasis. Plasma deconvolution is rather invasive and more labor-intensive as it involves the analysis of a dozen or more plasma samples per subject, as opposed to a single sample in most other 

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An approximate equilibrium is set up in the plasma, with the electrons, ions, and atoms having velocity distributions similar to those of a gas that has been heated to temperatures of 7,000 to 10,000°C. Since the plasma is ignited toward the end of the concentric tubes from which argon gas is issuing, the plasma appears as a pale-blue-to-lilac flame coming out of the end of the tube, which is why the system is referred to as a torch, as in a welding torch. 

The relevant pAj for carbonic acid, has a value far removed from the normal pH of blood plasma (pH 7.4). (The pAlj for HgCOj at 25°C is 3.77 (Table 2.4), but at 37°C, pAli is 3.57.) At pH 7.4, the concentration of HgCOj is a minuscule fraction of the HCO3 concentration, and thus the plasma appears to be poorly protected against an influx of OH ions. 

Novotny, J.A. et al.. Plasma appearance of labeled -carotene, lutein, and retinol in humans after consumption of isotopicaUy labeled kale, J. Lipid Res., 46, 1896, 2005. 

ET measured in the plasma appears to be a spillover of the ET that is (locally) released by the endothelium. It is known that low levels of ET (ranging from 0.25 to 5.0 pg/ml) are normally present in the circulation (B8, P12). These levels are increased by 3-10 times in patients with renal failure (S30), diabetes (V3), hypertension, bums (H32), myocardial infarction, primary pulmonary hypertension (N8), and cardiogenic shock (LI, L9, L10, PI, W8). ET is assumed to be released... 

The plasma appears in front of the nozzles and shows a flame-like pattern (Figure 12.4b [56]). It consists of streamers, which propagate from the tip of the nozzles to the planar electrodes (Figure 12.4c [57]). The velocity of the streamer head was estimated to about 2.5 x 105m/s [57],... 

Coral-Hinostroza, GN, Ytrestoyl, T, Ruyter, B, and Bjerkeng, B, 2004. Plasma appearance of unesterified astax-anthin geometrical E/Z and optical R/S isomers in men given single doses of a mixture of optical 3 and 3 R/S isomers of astaxanthin fatty acyl diesters. Comp Biochem Physiol C-Toxicol Pharmacol 139, 99-110. 

Enzymes activities are particularly sensitive to the anticoagulant used in collecting the specimen. Heparin inhibits acid phosphatase (W16) and muramidase (Z5). Amylase activity is inhibited by oxalate or citrate (MIO), and lactic dehydrogenase and acid phosphatase lose activity in oxalate (C2). Alkaline phosphatase is stable in oxalate, oxalate-fluoride, or heparin, but 25 mAf citrate inhibits 50% of the activity, and as little as 50 mlf EDTA is completely inhibitory (B19). Leucine aminopeptidase is inhibited by EDTA, as is creatine phosphokinase (F3). Amylase activity has been reported to be only 83% of that in serum when oxalate or citrate-plasma is used (MIO). Heparin plasma appears to have no inhibitory effect. Despite the fact that clotting factor V is not stable in oxalate or EDTA, these are often used as anticoagulants to obtain plasma for prothrombin determinations (Z2, Z4). 

Prazosin is readily absorbed after oral administration, peak serum levels occur approximately 2 hours after a single oral dose, and the antihypertensive effect of prazosin persists for up to 10 hours. Its half-life in plasma ranges from 2.5 to 4 hours, and elimination from plasma appears to follow first-order kinetics. The drug is extensively (perhaps as high as 97%) bound to plasma proteins this observation partially explains the lack of correlation between plasma drug levels and persistence of antihypertensive effect. 

DMHP in plasma appears to have a half-life of 20 h in both rat and rabbit the half-life of total radioactivity ([ C]DMHP plus C-labeled metabolites) in the slower phase of elimination was approximately 24 h. In the rat, 70% of the total radioactivity of the intravenous dose was recovered in urine and feces during 72 h 4% was excreted in urine and 66% was found in feces. A 7-d collection of urine and feces of rabbits given [1 C]DMHP resulted in recovery of 87% of the total radioactivity—24% in urine and 63% in feces. In mouse brain,29 the half-life of [ H]A-9-DMHP appeared to be about 20 h, whereas 11-hydroxy-DMHP and the "polar metabolite" seem to have (by extrapolation) half-lives in excess of 48 h. All three values were calculated on the basis of the slower phase of elimination. 

Knowledge of the pharmacokinetics of isoflavones in soy foods is essential for making recommendations regarding efficacy in clinical studies. Die plasma half-life of daidzein and genistein, measured from their plasma appearance and disappearance curves, is 7.9 h in adults peak concentrations occur 6-8 h after administration of the pure compounds [93] with peak concentrations ranging from 80 to 800 ng/ml (after a single oral dose of 50 mg of pure isoflavones). 

Although elevated levels of cholesterol and LDL in human plasma are linked to an increased incidence of cardiovascular disease, recent data have shown that an increase in concentration of HDL in plasma is correlated with a lowered risk of coronary artery disease. Why does an elevated HDL level in plasma appear to protect against cardiovascular disease, whereas an elevated LDL level seems to cause this disease The answer to this question is not known. An explanation currently favored is that HDL functions in the removal of cholesterol from nonhepatic tissues and the return of cholesterol to the liver, where it is metabolized and secreted. The net effect would be a decrease in the amount of plasma cholesterol available for deposit in arteries (see... 

This particular calculation due to Ray [180] gives a new insight into the problem, as the ordering and spacing between the fine structure multiplet components in high density plasma appear to be completely different from that observed for a free system. 

The absorption of orally administered bromelain in humans was proven by means of measurement of proteolytic activities using the fluorogenic substrate Z-Arg-coumarin ana by immunopreciphaiion followed by electrophoresis and immunodetection. The results showed that orally administered bromelain is found In plasma of human volunteers at low, but clearly measurable, concentrations as a full-size proteolytically active protein. Die bromelain circulating in plasma appears to be partially bound to certain plasma proteins, two of which were identified as oc-macroglobulin and ai-antitrypsin [86],... 

The plasma appearance rate of both T, and rT3 in healthy humans amounts to approximately 40-45 nmol/day, which is roughly 5 (T3) and 20 (rT3) times the thyroidal secretion rates of these compounds [2,3], Consequently, 80% of circulating... 

Besides modifications of time and concentrations incubations in serum or plasma appear to be rather simple and reliable in predicting the in vivo relevance of the in vitro data. 

As metabolic balance techniques cannot separate the contribution of malabsorption from that of endogenous loss, collaborators at the Division of Nutrition, University of Sao Paolo Medical School at Rlbeirao Preto, Brazil and I undertook to assess Sn Zn interaction using the change-in-plasma-zinc approach. Healthy volunteers received 12.5 mg of zinc as 55 mg of zinc sulfate in 100 ml of CocaCola either alone (control) or with 25, 50 or 100 mg of tin as stannous chloride to constitute 2 1, 4 1 and 8 1 Sn/Fe ratios. We measured the change in plasma zinc concentration at hourly Intervals over a 4-h period. None of the treatments produced any significant decrement in the uptake of zinc in plasma (61) (Table V). Thus, unlike the dramatic effect of even lesser ratios of Fe/Zn (above), the plasma appearance of zinc was unaffected by soluble, inorganic, divalent tin ions. 

There are several potential resolutions of the apparent disagreement between the metabolic balance data (62) and that seen with plasma appearance (61). First, the setting of a mixed diet might have provided additional factors necessary for the expression of the Sn Fe interaction, or the meal-stimulation of... 

Table V. Effect of Tin on the Plasma Appearance of Zinc in Healthy Subjects...

The decrease of Si due to F-containing contaminants and the role of the oxygen plasma treatment can be explained by the principle of CAP. The key factor to explain the change of elementary composition at the interface is the plasma sensitivity of elements involved on the surface and in the plasma phase. The ablation of materials exposed to plasmas appears to follow the plasma sensitivity series of the elements involved, which is in the order of the electronegativity of the elements, i.e., elements with higher electronegativity in the condensed phase are more prone to ablate in plasma that contains elements with lower electronegativity [5]. 

In islets, A-4166 causes a steep rise in insulin release followed by a slow sustained rise to twice the basal level. The insulinotropic effect is not glucose-dependent and takes place in the absence of glucose [191, 192]. The in vivo pharmacodynamic profile (rapid and short-term action) appears to result from a rapid plasma appearance and disappearance of the compound rather than an intrinsic feature of the mechanism [191]. A-4166 may be useful as therapy for NIDDM patients with secondary failure to sulphonylureas [190]. 

Pharmacokinetics. Heparin is poorly absorbed from the gastrointestinal tract and is given i.v. or S.C. once in the blood its effect is immediate. Heparin binds to several plasma proteins and to sites on endothelial cells it is also taken up by cells of the reticuloendothelial system and some is cleared by the kidney. Due to these factors, elimination of heparin from the plasma appears to involve a combination of zero-order and first-order processes, the effect of which is that the plasma biological effect alters disproportionately with dose, being 60 min after 75 units per kg and 150 min after 400 units per kg. 

Reports concerning metallothionein in plasma and urine of Cd-exposed persons are limited [47-49]. This is at least in part due to the fact that the accurate measurement of Cd and metallothionein levels in plasma appears to be difficult [50]. The concentration of metallothionein in urine and blood has to be measured using the Onosaka saturation method, radio-immunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA). The detection limits in human serum and urine for metallothionein by RIA is 1 pg [50]. For ELISA the detection limits are higher. Normal values range between 0.01-1 ng/ml for serum and between 1-10 ng/ml for urine. Metallothionein concentrations in Cd-exposed workers are reported to vary between 2-11 ng/ml in plasma and 2-155 ng/ml in urine [47]. 

Fig. 3.1 Apparatus used for producing a gradient with radio frequency plasma discharge (RFPD). The RF plasma appears between the RF hot plate and the grounded plate. The plasma is exposed to the polymer surface at various lengths of time as regulated by the movable cover30,55...

Plasma Appearance and Spectra The typical plasma has a very intense, brilliant white opaque core topped by a flame-like tail. The core, which extends a few millimeters above the tube, produces a spectral continuum with the atomic spectrum of argon superimposed. The continuum is typical of ion-electron recombination reactions and bremsstrahlung, which is continuum radiation produced when charged particles are slowed or stopped. 

The heat conductance through the sample and in the plasma is responsible for the fact that with the Nd YAG lasers available today, the crater diameters are still much wider than the values determined by the diffraction limitations. When using conventional lasers with pulses in the ns and ps range the plasma shields the radiation, whereas with the femtosecond lasers that are now available a free expanding plasma is obtained, where the heating of the plasma appears to be less supplemented by the laser radiation. This leads to less fractionated volatilization of the solid sample and differences in crater shape, which need to be investigated further [229]. 

The primary determinant of HDL cholesterol levels in human plasma appears to be the cholesterol efflux mediated by ABCl-transporter (also called cholesterol efflux regulatory protein). A defect in this protein causes Tangier... 

Binding of aromatic amino acids to blood plasma appears to occur by both non-polar and electrostatic interactions, but electrostatic interactions only are important for the binding of lactate, - citrate and acetate." These examples appear to be nonspecific at mmol 1" concentration levels and do not appear to be stereochemically selected" and so this would appear to preclude specific molecular recognition. 

Plasma Stability. Over the entire range of experimental variables the plasma was stable and brightly luminous. The luminous region of the plasma appeared to fill about 90% of the cross-sectional area of the cooled quartz tube and extended from the bottom to about 3 inches above the RF. load coil. With high hydrocarbon flow rates a gradual build up of soot occurred on the quartz tube walls. 

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