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PubMed1998

Understanding and valuing environmental issues: the effects of availability and anchoring on judgment.

This paper addresses the effects of availability and anchoring-and-adjustment on people's beliefs and values concerning environmental issues. The first three studies focus on lay people's perceptions of the causes of large scale environmental risks, the second series of three studies deals with how people value environmental goods and how much they are prepared to pay to mitigate environmental risks. In studies 1-3 we investigate the effects of availability and anchoring-and-adjustment on estimating the contribution of various factors to large scale environmental risks. Highly complex risks such as acid rain and global warming tend to be associated with multiple causes, and our results show that estimating the role of these causes is clearly affected by availability and anchoring-and-adjustment. Both have sizeable effects and persist over time. Moreover, corrective procedures only seem to have a limited effect. Availability and anchoring-and-adjustment not only play a role in judging the possible causes of risks; they also play a role in research attempting to assess the public's willingness to pay (WTP) to protect our environment. The outcomes of WTP surveys are often used as a tool to help policy decision making. In the second part of this article we present three studies on this issue. Results provide further evidence of the impact of the two heuristics on the outcomes of WTP research. Implications for research and practice are briefly discussed.

Acid Rain↗

PubMedDate not supplied

The effect of buffering on oxyphenbutazone absorption kinetics and systemic availability.

A systemic availability study comparing an investigational buffered tablet formulation of oxyphenbutazone and a commercially available product, the efficacy of which has been well established by usage, is reported. The experiment was designed to dissociate formulation factors from all other sources of variation including differences between subjects, sexes, sequences of administration, experimental periods, as well as sex by sequence, sex by period, and sex by formulation interactions. Systemic availability was assessed by conventional pharmacokinetic techniques. Results show that buffering of a tablet formulation consistently increased the rate and degree of absorption. Although the relative magnitude of bioavailability indicators is slightly different according to the method of calculation, the estimates are always higher with the buffered formulation. No statistical difference was observed for plasma concentration-time profiles between sexes. The wide range of observed concentrations over the time interval of this study confirms other reports of individual variations in handling oxyphenbutazone. The differences noted between the two formulations may be attributed to faster dissolution rate characteristics and better dispersion of oxyphenbutazone. Some aspects of the clinical relevance of this situation are discussed briefly.

Biological Availability↗

PubMed2006

Available lysine content in human milk: stability during manipulation prior to ingestion.

UNLABELLED: Available lysine content is an indicator of protein quality and nutritional value of milk. Many studies have examined the effects of extraction, treatment and storage of human milk upon its components, though no references are found regarding the possible changes in milk quality as defined by its content in essential amino acids such as lysine. The present study investigates the available lysine content in human milk and the variations in lysine resulting from milk manipulation as follows: (a) Cold storage (refrigeration at 4 degrees C for 48 hours, and frozen for 15 days at -20 degrees C); (b) Thermal treatment under conditions of low (Holder)(63 degrees C/30 minutes) and high pasteurization (75 degrees C/15 seconds). The results obtained show a decrease in milk lysine concentration after storage in both refrigerated and frozen samples. Pasteurization causes a highly significant loss of available lysine. The lysine losses were greater on applying low pasteurization versus the more gentle conditions of high pasteurization. CONCLUSIONS: While manipulation through cold storage or thermal treatment does not affect the protein content of human milk, its protein quality is modified. When human milk must be subjected to hygienization, it is preferable to apply high temperature treatment (75 degrees C, 15 seconds) than habitual pasteurization (63 degrees C, 30 minutes).

Biological Availability↗

PubMed1986

Drug availability to noneliminating tissues and sites of action following an intravenous dose.

It is shown that for drugs with high clearance, administered as an intravenous (iv) bolus, the amount of drug available to noneliminating tissues may be significantly less than the administered dose. This arises as a result of recirculation and elimination of some drug within an eliminating circuit, without contact of the drug with tissues outside the eliminating circuit. The same effect also influences drug availability to noneliminating tissues following an oral dose. The relative availability of a drug to sites of action and drug toxicity are also discussed and shown to depend on clearance and blood flow to these sites.

Administration, Oral↗

PubMed2003

Influence of aging on metal availability in soils.

An overview is given on the literature concerning the effect of long-term processes, called aging, on metal availability, and consequences for risk assessment of metal-contaminated soils are discussed. Experiments with freshly prepared metal oxyhydroxides and calcites overpredict the influence of aging because of the initial transformations occurring in these systems. Also, freshly ground clays are not representative of field soils because the surface area exposed for fixation is unrealistically high. Experiments with field soils confirm the hypothesis that metal availability can decrease as a result of aging, especially for metals with a small ionic radius. Although aging also seems to affect metal uptake, it should be noted that some organisms are able to regulate their internal metal concentrations within a narrow range, especially for essential elements. Deficiency of essential metals as well as metal toxicity to plants and invertebrates seem to be related to the environmental availability of these metals. Unfortunately, aging effects are often confounded by differences in soil properties between freshly spiked and historically contaminated soils. Environmental parameters such as temperature, moisture content, drying and rewetting cycles, and pH affect the rate of aging, whereas pH seems to be the sole important parameter affecting the extent of aging.

Aging↗

PubMed1991

The effect of food processing on phytate hydrolysis and availability of iron and zinc.

Phytate is one of the major inhibiting factor for zinc and iron absorption. When phytate is hydrolyzed during the food process the mineral availability is increased. By activation of the endogenous enzyme phytase which is present in plant foods, or addition of phytase, phytate is degraded to various inositolphosphates containing 1-5 phosphate groups per an inositol molecule. The effects of degradation products of phytate on availability of zinc, calcium and iron have to be further investigated. Food processes including soaking, germination and fermentation were under optimal conditions demonstrated to completely reduce the phytate content of cereals and vegetables. The results were related to in vitro measurements of iron availability and human iron and zinc absorption studies.

6-Phytase↗

PubMed1989

Availability predictions by hepatic elimination models for Michaelis-Menten kinetics.

Numerical methods have been used to compare the availability predictions of a number of hepatic elimination models when Michaelis-Menten kinetics is operative. Propranolol and galactose were used as model compounds. Lower availabilities were predicted by the dispersion model than by a segregated distribution model for both compounds. The differences in the predictions were most pronounced for models corresponding to a large variation in solute residence times in the liver. The predictions of the tank-in-series, dispersion model with mixed boundary conditions and dispersion model with Dankwerts boundary conditions were similar over all concentrations studied. Changes in blood flow and protein binding provided little discrimination between the model predictions. It is concluded that micromixing of blood between sinusoids and the anatomical sites of mixing are important determinants of availability when liver eliminating enzymes are partially saturated.

Biological Availability↗

PubMed1992

Bio-availability of iron from spinach (Spanicia oleracea) cultivated in soil fortified with graded levels of iron.

In vitro availability of iron along with ascorbic acid, oxalic acid and phosphorus contents of two varieties of spinach (Pusa Jyoti and Allgreen) cultivated in soil with different levels of added iron was determined. Addition of graded levels of iron to soil markedly increased the total iron and phosphorus contents and significantly decreased the bio-availability of iron, ascorbic acid and oxalic acid contents of spinach. Ascorbic acid and oxalic acid contents markedly exerted a positive influence while phosphorus exerted a negative influence on the bio-availability of iron.

Ascorbic Acid↗

PubMed1992

The systemic availability of oral glutathione.

When the plasma glutathione concentration is low, such as in patients with HIV infection, alcoholics, and patients with cirrhosis, increasing the availability of circulating glutathione by oral administration might be of therapeutic benefit. To assess the feasibility of supplementing oral glutathione we have determined the systemic availability of glutathione in 7 healthy volunteers. The basal concentrations of glutathione, cysteine, and glutamate in plasma were 6.2, 8.3, and 54 mumol.l-1 respectively. During the 270 min after the administration of glutathione in a dose of 0.15 mmol.kg-1 the concentrations of glutathione, cysteine, and glutamate in plasma did not increase significantly, suggesting that the systemic availability of glutathione is negligible in man. Because of hydrolysis of glutathione by intestinal and hepatic gamma-glutamyltransferase, dietary glutathione is not a major determinant of circulating glutathione, and it is not possible to increase circulating glutathione to a clinically beneficial extent by the oral administration of a single dose of 3 g of glutathione.

Administration, Oral↗

PubMed1987

Pharmacokinetics and systemic availability of the antihypertensive agent indoramin and its metabolite 6-hydroxyindoramin in healthy subjects.

We have studied the pharmacokinetics and absolute systemic availability of indoramin (50 mg) given orally in solution or as a tablet with reference to intravenously administered drug (0.15 mg/kg) in 9 healthy volunteers. After intravenous administration the median apparent volume of distribution was 6.3 l X kg-1, plasma clearance was 20.0 ml X min-1 X kg-1, and terminal half-time was 4.1 h. When given by tablet indoramin was absorbed with moderate rapidity, with a median tmax of 1.5 h. The median systemic availability was 24%. After oral administration in solution the drug was more rapidly absorbed, with a median tmax of 1.0 h (p less than 0.01). The median systemic availability was 43% (15-85%). Plasma concentrations of an active metabolite, 6-hydroxyindoramin, after single oral doses in either dosage form, were of a similar order to those of unchanged drug and fell with similar rapidity. After intravenous administration, however, concentrations of the metabolite were negligible.

Absorption↗

PubMed2006

Effect of altered pre-exercise carbohydrate availability on selection and perception of effort during prolonged cycling.

This study assessed the effect of altered carbohydrate (CHO) availability on self-selected work rate during prolonged time-trial cycling. Eight endurance-trained men undertook two experimental cycling time-trials after glycogen-depleting exercise and 2 days of: (a) high (9.3 +/- 0 g CHO kg(-1) day(-1)) (HC) and (b) low CHO intakes (0.6 +/- 0.1 g CHO kg(-1) day(-1)) (LC), via a double-blinded crossover design. All feedback regarding performance was removed during both exercise trials. Self-selected external power output was not different during the first 2 h of exercise between experimental conditions (P > 0.05), despite reported sensations of increased tiredness before and during exercise, significantly reduced whole body CHO oxidation (P < 0.05), plasma lactate concentrations (P < 0.05) and earlier onset of fatigue during exercise in LC versus HC. Perceived exertion was not different throughout exercise between conditions (P > 0.05). Mean power output declined significantly in LC versus HC (P < 0.05) after approximately 2 h of exercise, and was associated with significant reductions in cadence, heart rate and plasma glucose concentration (P < 0.05). These results demonstrate that when compared with time-trial cycling performed after a HC diet, reduced CHO availability does not initially alter self-selected work rate in endurance athletes who are deceived of their CHO status prior to exercise. This finding suggests that reduced work rate during exercise following lowered CHO intake may, in part, be a consequence of the subject's awareness of dietary CHO restriction rather than solely a physiologically mediated action. Further research is required to distinguish the influence of circulating glucose and peripheral glycogen availability on pacing strategy during prolonged exercise.

Adaptation, Physiological↗

PubMed1994

Measurement of palmitate availability in serum samples: method and utility.

Palmitic acid shows a very low and unknown solubility at neutral pH. Binding equilibria of palmitate to human serum albumin accordingly cannot be investigated by measuring free and bound ligand concentrations as in conventional binding studies. It is feasible, on the other hand, to describe the binding equilibria in relative terms, by measuring the concentration, p, of reserve albumin, previously defined as the concentration of a purified standard albumin preparation which in buffered solution binds a trace amount of palmitate as tight as it is bound in the sample. Palmitate availability is calculated as C/p, when C is the concentration of bound palmitate. The general binding equation is modified to contain the availability beside relative binding constants, Li = Ki/K1,St, where K1,St is the first stoichiometric binding constant for palmitate to the standard albumin preparation. Availabilities and relative binding constants can replace free concentrations and usual binding constants in considerations of biochemical transport and enzymatic mechanisms. A method is described for measuring the concentration of reserve albumin for binding of palmitate, based upon determination of dialytic exchange rates for palmitate among identical equilibrium samples. A technique for reproducibly adding radiolabelled palmitate to the samples is given.

Adult↗

PubMed1994

Aluminum inhibition of hexokinase activity in vitro: a study in biological availability.

We have used the HK/G6PDH coupled enzyme assay to determine the biological availability of aluminum in mixed-ligand media of biological interest. The biological availability of aluminum was measured as the inhibition of the activity rate of the assay and was shown to be dependent upon the equilibration state of the aluminum stock solutions (prior to their addition to the assay) and the comparative reaction kinetics of competitive aluminum equilibria in the assays. Aluminum was found to inhibit the assay, however, the inhibition by aluminum was abolished when silicic acid was present in both the aluminum stock solution and the assay medium. The assay is proposed as a model system for investigating the biological availability of aluminum in heterogenous media of biochemical significance.

Aluminum↗

PubMed2005

Influence of ageing of residues on the availability of herbicides for leaching.

Losses by leaching of chlorotoluron, isoproturon and triasulfuron from small intact columns of a structured clay loam and an unstructured sandy loam soil were measured in five separate field experiments. In general, losses of all three herbicides were greater from the clay loam than from the sandy loam soil and the order between herbicides was always triasulfuron >> isoproturon > chlorotoluron. Differences between experiments were also consistent for every soil/herbicide combination. There was no relationship between total loss and either total rainfall or cumulative leachate volume. When weighting factors were applied to the rainfall data to make early rainfall more important than later rainfall, there were significant positive relationships between cumulative weighted rainfall and total losses. Also, there were significant negative correlations between total losses and the delay to accumulation of 25 mm rainfall (equivalent to one pore volume of available water) in the different experiments. In laboratory incubations, there was a more rapid decline in aqueous (0.01 M calcium chloride) extractable residues than in total solvent extractable residues indicating increasing sorption with residence time. However, the rate of change in water extractable residues could not completely explain the decrease in leachability with ageing of residues in the field. Short-term sorption studies with aggregates of the two soils indicated slower sorption by those of the clay loam than by those of the sandy loam suggesting that diffusion into and out of aggregates may affect availability for leaching in the more structured soil. Small scale leaching studies with aggregates of the soils also demonstrated reductions in availability for leaching as residence time in soil was increased, which could not be explained by degradation. These results therefore indicate that time-dependent sorption processes are important in controlling pesticide movement in soils, although the data do not give a mechanistic explanation of the changes in leaching with ageing of residues.

Adsorption↗

PubMed2006

Enhancement of pyruvate productivity in Torulopsis glabrata: Increase of NAD+ availability.

This study aimed at increasing the pyruvate productivity from a multi-vitamin auxotrophic yeast Torulopsis glabrata, by increasing the availability of NAD+. We examined two strategies for increasing availability of NAD+. To supplement nicotinic acid (NA), the precursor of NAD+; and to increase the activity of alcohol dehydrogenase integrating with addition acetaldehyde as exterior electron acceptor. The addition of 8 mg l(-1) NA to the fermentation medium resulted in a significant increase in the glucose consumption rate (48.4%) and the pyruvate concentration (29%). An ethanol-utilizing mutant WSH-13 was screened and selected after nitrosoguanidine mutagenesis of the parent strain T. glabrata CCTCC M202019. Compared with the parent strain, the alcohol dehydrogenase activity of the mutant WSH-13 increased about 110% and the mutant could utilize ethanol as the sole carbon source for growth (1.8 g l(-1) dry cell weight). When growing with glucose, the addition of 4 mg l(-1) acetaldehyde to the mutant WSH-13 culture broth led to a significant increase in the glucose consumption rate (26.3%) and pyruvate production (22.5%), but the ratio of NADH/NAD+ decreased to 0.22. Acetaldehyde did not affect the glucose and energy metabolism at high dissolved oxygen (DO) concentration. However, at lower DO concentration (20%), maintaining the acetaldehyde concentration in the mutant culture broth at 4 mg l(-1) caused an increased NAD+ concentration but a decreased NADH concentration. As a consequence, the pyruvate production rate, the pyruvate yield on glucose and the pyruvate concentration were 68, 44 and 45% higher, respectively, than the corresponding values of the control (without acetaldehyde). The strategy for increasing the glycolytic flux and the pyruvate productivity in T. glabrata by increasing the availability of NAD+ may provide an alternative approach to enhance the metabolites productivity in yeast.

Biological Availability↗

PubMed2003

Potential availability of heavy metals to phytoextraction from contaminated soils induced by exogenous humic substances.

Effective phytoremediation of soils contaminated by heavy metals depends on their availability to plant uptake that, in turn, may be influenced by either the existing soil humus or an exogenous humic matter. We amended an organic and a mineral soil with an exogenous humic acid (HA) in order to enhance the soil organic carbon (SOC) content by 1% and 2%. The treated soils were further enriched with heavy metals (Cu, Pb, Cd, Zn, Ni) to a concentration of 0, 10, 20, and 40 microg/g for each metal and allowed to age at room temperature for 1 and 2 months. After each period, they were extracted for readily soluble and exchangeable (2.5% acetic acid), plant-available (DTPA, Diethylentriaminepentaacetic acid), and occluded (1 N HNO(3)) metal species. Addition of HA generally reduced the extractability of the soluble and exchangeable forms of metals. This effect was directly related to the amount of added HA and increased with ageing time. Conversely, the potentially plant-available metals extracted with DTPA were generally larger with increasing additions of exogenous HA solutions. This was attributed to the formation of metal-humic complexes, which ensured a temporary bioavailability of metals and prevented their rapid transformation into insoluble species. Extractions with 1 N HNO(3) further indicated that the added metals were present in complexes with HA. The observed effects appeared to also depend on the amount of native SOC and its structural changes with ageing. The results suggest that soil amendments with exogenous humic matter may accelerate the phytoremediation of heavy metals from contaminated soil, while concomitantly prevent their environmental mobility.

Biodegradation, Environmental↗

PubMed2003

Soil availability, plant uptake and soil to plant transfer of 99Tc--a review.

The fission yield of 99Tc from 239Pu and 235U is similar to that of 137Cs or 90Sr and it is therefore an important component of nuclear weapons fall-out, nuclear waste and releases from nuclear facilities. There is particular current interest in 99Tc transfer from soil to plants for: (a) environmental impact assessments for terrestrial nuclear waste repositories, and (b) assessments of the potential for phytoextraction of radionuclides from contaminated effluent and soil. Vascular plants have a high 99Tc uptake capacity, a strong tendency to transport it to shoot material and accumulate it in vegetative rather than reproductive structures. The mechanisms that control 99Tc entry to plants have not been identified and there has been little discussion of the potential for phytoextraction of 99Tc contaminated effluents or soil. Here we review soil availability, plant uptake mechanisms and soil to plant transfer of 99Tc in the light of recent advances in soil science, plant molecular biology and phytoextraction technologies. We conclude that 99Tc might not be highly available in the long term from up to 50% of soils worldwide, and that no single mechanism that might be easily targeted by recombinant DNA technologies controls 99Tc uptake by plants. Overall, we suggest that Tc might be less available in terrestrial ecosystems than is often assumed but that nevertheless the potential of phytoextraction as a decontamination strategy is probably greater for 99Tc than for any other nuclide of radioecological interest.

Biological Availability↗

PubMed2002

Impact of protein binding on the availability and cytotoxic potency of organochlorine pesticides and chlorophenols in vitro.

In vitro toxicity data are generally based on nominal concentrations and thus depend on both activity and availability of a compound. The aims of the present study were to examine the influence of protein binding on the cytotoxicity of selected organochlorine pesticides and chlorophenols in Balb/c 3T3 cell cultures and to determine parameters of protein binding which can be used to estimate protein bound fractions and to model distribution in vitro. EC(50)-values derived from concentration-effect relationships determined in the presence of various concentrations of bovine serum albumin (BSA) were linearly correlated to BSA concentration. Increasing the BSA concentration from about 1.2 to 40 mg/ml increased the EC(50)-values by factors between 3.4 and 34.4. Molar ratios of substance bound to albumin ranged from 0.11 to 2.42. Calculated fractions bound to albumin in the normal growth medium were 0.075-0.17 (p,p'-DDT, p,p'-DDE, dieldrin, lindane), 0.09-0.1 (4-mono- and 2,4-dichlorophenol), 0.68 (2,4,5-trichlorphenol) and almost 1.0 (pentachlorophenol). At 40 mg/ml BSA any compound was largely bound to albumin (fractions bound > or = 0.74). Distribution modelling revealed that the availability of the highly hydrophobic organochlorines additionally was significantly reduced by partitioning into lipids. The results clearly demonstrate that nominal and relative toxic potencies of organochlorine pesticides and chlorophenols determined in vitro are substantially influenced by effects of protein binding on availability.

3T3 Cells↗